JP7795866B2 - Carboxylic acid salt, carboxylic acid generator, resist composition and method for producing resist pattern - Google Patents

Description

The present invention relates to a carboxylic acid salt, a carboxylic acid generator, a resist composition, and a method for producing a resist pattern.

Patent Document 1 describes a resist composition containing a carboxylic acid salt represented by the following formula as a carboxylic acid generator.
Patent Document 2 describes a resist composition containing a salt represented by the following formula as an acid generator.

JP 2011-039502 A Japanese Patent Application Laid-Open No. 2020-015713

The present invention provides a carboxylate salt that forms a resist pattern with a better mask error factor (MEF) than a resist pattern formed using a resist composition containing the above salt.

The present invention includes the following inventions.
[1] A carboxylic acid salt represented by formula (I).
[In formula (I),
R ⁴ , R ⁵ , R ⁶ , R ⁷ , R ⁸ and R ⁹ each independently represent a halogen atom, a fluorinated alkyl group having 1 to 6 carbon atoms or a hydrocarbon group having 1 to 18 carbon atoms, the hydrocarbon group may have a substituent, and -CH ₂ - contained in the hydrocarbon group may be replaced by -O-, -CO-, -S- or -SO ₂ -.
X ¹ , X ² and X ³ each independently represent an oxygen atom or a sulfur atom.
m1 represents an integer of 1 to 5, and when m1 is 2 or more, the groups in the parentheses may be the same or different.
m2 represents an integer of 0 to 5, and when m2 is 2 or more, the groups in the parentheses may be the same or different.
m3 represents an integer of 0 to 5, and when m3 is 2 or more, the groups in the parentheses may be the same or different from each other. When m2 or m3 is 1 or more and there are multiple R ^10s , they may be the same or different from each other.
m4 represents an integer of 0 to 5, and when m4 is 2 or greater, multiple R ^4s may be the same or different.
m5 represents an integer of 0 to 5, and when m5 is 2 or more, the multiple ^R5s may be the same or different.
m6 represents an integer of 0 to 5, and when m6 is 2 or greater, multiple R ^6s may be the same or different.
m7 represents an integer of 0 to 4, and when m7 is 2 or greater, the multiple ^R7s may be the same or different.
m8 represents an integer of 0 to 5, and when m8 is 2 or greater, multiple ^R8s may be the same or different.
m9 represents an integer of 0 to 5, and when m9 is 2 or more, the multiple R ^9s may be the same or different.
However, 1≦m1+m7≦5, 0≦m2+m8≦5, and 0≦m3+m9≦5.
X ⁰ represents a hydrocarbon group having 1 to 72 carbon atoms which may have a substituent, and one —CH ₂ — contained in the hydrocarbon group may be replaced by —O—, —S—, —CO— or —SO ₂ —.]
[2] The carboxylate according to [1], wherein X ¹ , X ² and X ³ are oxygen atoms.
[3] The carboxylate according to [1] or [2], wherein R ⁴ , R ⁵ and R ⁶ are each independently a fluorine atom, an iodine atom or a perfluoroalkyl group having 1 to 4 carbon atoms.
[4] The carboxylate according to any one of [1] to [3], wherein X ⁰ is an aliphatic hydrocarbon group having 1 to 72 carbon atoms which may have a substituent (provided that —CH ₂ — contained in the aliphatic hydrocarbon group may be replaced by —O—, —S—, —CO— or —SO ₂ —), or an aromatic hydrocarbon group having 6 to 36 carbon atoms which may have a substituent.
[5] The carboxylate according to any one of [1] to [4], wherein X ⁰ is an alicyclic hydrocarbon group having 3 to 36 carbon atoms which may have a fluorine atom or a hydroxy group (-CH ₂ - contained in the alicyclic hydrocarbon group may be replaced by -O-, -CO-, -S- or -SO ₂ -), or an aromatic hydrocarbon group having 6 carbon atoms which may have a halogen atom, a hydroxy group or a perfluoroalkyl group having 1 to 4 carbon atoms.
[6] The carboxylate according to [4], wherein X ⁰ is a group represented by (aa).
[In formula (aa),
X ^a and X ^b each independently represent —O— or —S—.
X ^1a represents a hydrocarbon group having 1 to 24 carbon atoms which may have a substituent, and one —CH ₂ — contained in the hydrocarbon group may be replaced by —O—, —S—, —CO— or —SO ₂ —.
X ^2a represents a hydrocarbon group having 1 to 48 carbon atoms which may have a substituent, and one —CH ₂ — contained in the hydrocarbon group may be replaced by —O—, —S—, —CO— or —SO ₂ —.
* indicates the bonding position with the carbon atom of ^—COO— .]
[7] The carboxylate according to [4], wherein X ⁰ is an aromatic hydrocarbon group having 6 to 36 carbon atoms which may have a halogen atom, a hydroxy group, or a perfluoroalkyl group having 1 to 4 carbon atoms.
[8] The carboxylate according to [4], wherein X ⁰ is a group represented by formula (bb):
[In formula (bb),
L 1 ^A represents an alkanediyl group having 1 to 6 carbon atoms which may have a fluorine atom, or an aromatic hydrocarbon group having 6 carbon atoms which may have a halogen atom or a perfluoroalkyl group having 1 to 4 carbon atoms.
L 1 ^B represents a single bond or an alkanediyl group having 1 to 6 carbon atoms, and one —CH ₂ — contained in the alkanediyl group may be replaced by —O—, —S—, —CO— or —SO ₂ —.
R ^A represents a hydrocarbon group having 1 to 36 carbon atoms which may have a substituent, and one —CH ₂ — contained in the hydrocarbon group may be replaced by —O—, —S—, —CO— or —SO ₂ —.
* indicates the bonding position with the carbon atom of ^—COO— .]
[9] A carboxylic acid generator containing the carboxylic acid salt according to any one of [1] to [8].
[10] A resist composition comprising the carboxylic acid generator according to [9], an acid generator other than the carboxylic acid generator, and a resin having an acid labile group.
[11] The resist composition according to [10], wherein the resin having an acid labile group comprises at least one selected from the group consisting of a structural unit represented by formula (a1-1) and a structural unit represented by formula (a1-2):
[In formula (a1-1) and formula (a1-2),
L ^a1 and L ^a2 each independently represent —O— or *-O—(CH ₂ ) _k1 —CO—O—, where k1 represents an integer of 1 to 7, and * represents the bonding position with —CO—.
R ^a4 and R ^a5 each independently represent a hydrogen atom, a halogen atom, or an alkyl group having 1 to 6 carbon atoms which may have a halogen atom.
R ^a6 and R ^a7 each independently represent an alkyl group having 1 to 8 carbon atoms, an alkenyl group having 2 to 8 carbon atoms, an alicyclic hydrocarbon group having 3 to 18 carbon atoms, an aromatic hydrocarbon group having 6 to 18 carbon atoms, or a combination thereof.
m1 represents an integer of 0 to 14.
n1 represents an integer of 0 to 10.
n1′ represents an integer of 0 to 3.
[12] The resist composition according to [10] or [11], further comprising a resin containing a structural unit having a fluorine atom.
[13] (1) A step of applying the resist composition according to any one of [10] to [12] onto a substrate;
(2) a step of drying the applied composition to form a composition layer;
(3) exposing the composition layer to light;
(4) a step of heating the composition layer after exposure; and (5) a step of developing the composition layer after heating.

By using a resist composition that uses the carboxylate salt of the present invention, it is possible to produce resist patterns with a good mask error factor (MEF).

In this specification, "(meth)acrylic monomer" means at least one selected from the group consisting of monomers having a "CH ₂ ═CH—CO—" structure and monomers having a "CH ₂ ═C(CH ₃ )—CO—" structure. Similarly, "(meth)acrylate" and "(meth)acrylic acid" mean "at least one selected from the group consisting of acrylates and methacrylates" and "at least one selected from the group consisting of acrylic acid and methacrylic acid," respectively. When a structural unit having "CH ₂ ═C(CH ₃ )—CO—" or "CH ₂ ═CH—CO—" is exemplified, structural units having both groups are also exemplified. Furthermore, among the groups described in this specification, those that can have both a linear structure and a branched structure may have either. When -CH ₂ - contained in a hydrocarbon group or the like is replaced with -O-, -S-, -CO-, or -SO ₂ -, the same examples apply to each group. A "combined group" refers to a group in which two or more of the exemplified groups are bonded together, and the valence of these groups may be changed appropriately depending on the bonding form. "Derived from" or "derived from" refers to a polymerizable C═C bond contained in the molecule becoming a -C-C- group by polymerization. When stereoisomers exist, all stereoisomers are included.
In this specification, the term "solids content of a resist composition" refers to the sum of all components in the resist composition excluding the solvent (E), which will be described later.

[Salt represented by formula (I)]
The present invention relates to a carboxylate salt represented by formula (I) (hereinafter, sometimes referred to as "salt (I)").
In the salt (I), the negatively charged side is sometimes referred to as the "anion (I)" and the positively charged side is sometimes referred to as the "cation (I)".
[In the formula, all symbols have the same meanings as defined above.]

Examples of the halogen atom for R ⁴ , R ⁵ , R ⁶ , R ⁷ , R ⁸ and R ⁹ include a fluorine atom, a chlorine atom, a bromine atom and an iodine atom.
The fluorinated alkyl group having 1 to 6 carbon atoms for R ⁴ , R ⁵ , R ⁶ , R ⁷ , R ⁸ and R ⁹ represents an alkyl group having 1 to 6 carbon atoms and containing a fluorine atom, and examples thereof include perfluoroalkyl groups having 1 to 6 carbon atoms (trifluoromethyl group, pentafluoroethyl group, heptafluoropropyl group, nonafluorobutyl group), as well as 2,2,2-trifluoroethyl group, 3,3,3-trifluoropropyl group, 4,4,4-trifluorobutyl group, and 3,3,4,4,4-pentafluorobutyl group. The number of carbon atoms in the fluorinated alkyl group is preferably 1 to 4, and more preferably 1 to 3.
Examples of the hydrocarbon group having 1 to 18 carbon atoms for R ⁴ , R ⁵ , R ⁶ , R ⁷ , R ⁸ and R ⁹ include chain hydrocarbon groups such as alkyl groups, alicyclic hydrocarbon groups, aromatic hydrocarbon groups and groups formed by combining these.
Examples of the alkyl group include a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, a sec-butyl group, a tert-butyl group, a pentyl group, a hexyl group, a heptyl group, a 2-ethylhexyl group, an octyl group, a nonyl group, a decyl group, an undecyl group, and a dodecyl group. The number of carbon atoms in the alkyl group is preferably 1 to 12, more preferably 1 to 9, even more preferably 1 to 6, and still more preferably 1 to 4.
The alicyclic hydrocarbon group may be either monocyclic or polycyclic, and examples of the alicyclic hydrocarbon group include the groups shown below. The bonding site can be at any position.
Specifically, examples of monocyclic alicyclic hydrocarbon groups include cycloalkyl groups such as cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl, cycloheptyl, cyclooctyl, and cyclodecyl. Examples of polycyclic alicyclic hydrocarbon groups include decahydronaphthyl, adamantyl, and norbornyl. The number of carbon atoms in the alicyclic hydrocarbon group is preferably 3 to 18, more preferably 3 to 16, and even more preferably 3 to 12.
Examples of the aromatic hydrocarbon group include a phenyl group, a naphthyl group, a biphenyl group, an anthryl group, a phenanthryl group, a binaphthyl group, etc. The aromatic hydrocarbon group preferably has 6 to 18 carbon atoms, more preferably 6 to 14 carbon atoms, and even more preferably 6 to 10 carbon atoms.

Groups formed by combination include groups combining an aromatic hydrocarbon group with a chain hydrocarbon group (for example, aromatic hydrocarbon group-alkanediyl group-*, alkyl group-aromatic hydrocarbon group-*; —CH ₂ — contained in the alkanediyl group and the alkyl group may be replaced with —O—, —CO— or —S—), groups combining an alicyclic hydrocarbon group with a chain hydrocarbon group (for example, alicyclic hydrocarbon group-alkanediyl group-*, alkyl group-alicyclic hydrocarbon group-*; —CH ₂ — contained in the alkanediyl group and the alkyl group may be replaced with —O—, —CO— or —S—), and groups combining an aromatic hydrocarbon group with an alicyclic hydrocarbon group (for example, aromatic hydrocarbon group-alicyclic hydrocarbon group-*, alicyclic hydrocarbon group-aromatic hydrocarbon group-*). * represents a bonding site.
Examples of the aromatic hydrocarbon group -alkanediyl group-* include aralkyl groups such as benzyl and phenethyl.
Examples of the alkyl group-aromatic hydrocarbon group-* include a tolyl group, a xylyl group, and a cumenyl group.
Examples of the alicyclic hydrocarbon group -alkanediyl group-* include cycloalkylalkyl groups such as cyclohexylmethyl group, cyclohexylethyl group, 1-(adamantan-1-yl)methyl group, and 1-(adamantan-1-yl)-1-methylethyl group.
Examples of the alkyl group-alicyclic hydrocarbon group-* include cycloalkyl groups having an alkyl group such as a methylcyclohexyl group, a dimethylcyclohexyl group, and a 2-alkyladamantan-2-yl group.
Examples of the aromatic hydrocarbon group-alicyclic hydrocarbon group-* include a phenylcyclohexyl group.
Examples of the alicyclic hydrocarbon group-aromatic hydrocarbon group-* include a cyclohexylphenyl group.
In addition, two or more types of alicyclic hydrocarbon groups, aromatic hydrocarbon groups, and chain hydrocarbon groups may be combined, and any of the groups may be bonded to a benzene ring.

Examples of groups in which —CH ₂ — in a hydrocarbon group is replaced by —O—, —CO—, —SO ₂ — or —S— include a hydroxy group (a group in which —CH ₂ — in a methyl group is replaced by —O—), a carboxy group (a group in which —CH _{2 —} in an ethyl group is replaced by —O—CO—), a thiol group (a group in which —CH ₂ — in a methyl group is replaced by —S—), an alkoxy group (a group in which —CH ₂ — at any position in an alkyl group is replaced by —O—), an alkoxycarbonyl group (a group in which —CH _{2 —} at any position in an alkyl group is replaced by —O—CO—), an alkylcarbonyl group (a group in which —CH ₂ — at any position in an alkyl group is replaced by —CO—), and an alkylcarbonyloxy group (a group in which —CH _{2 —} Examples of the alkyl group include: an alkylthio group (a group in which -CH ₂ - at any position in an alkyl group is replaced with -S-); an alkylsulfonyl group (a group in which -CH 2 - at any position in an alkyl group is replaced with -SO _{2 -} ); a cycloalkoxy group having 3 to 17 carbon atoms such as a cyclohexyloxy group; a cycloalkylalkoxy group having 4 to 17 carbon atoms such as a cyclohexylmethoxy group; an alkoxycarbonyloxy group having 2 to 16 carbon atoms such as a butoxycarbonyloxy group; and an aromatic hydrocarbon group-carbonyloxy group having 7 to 17 carbon atoms such as a benzoyloxy group.

Examples of the alkoxy group include alkoxy groups having 1 to 17 carbon atoms, such as a methoxy group, an ethoxy group, a propoxy group, a butoxy group, a pentyloxy group, a hexyloxy group, an octyloxy group, a 2-ethylhexyloxy group, a nonyloxy group, a decyloxy group, an undecyloxy group, etc. The number of carbon atoms in the alkoxy group is preferably 1 to 11, more preferably 1 to 6, and even more preferably 1 to 4.
The alkoxycarbonyl group, alkylcarbonyl group and alkylcarbonyloxy group represent groups in which a carbonyl group or carbonyloxy group is bonded to the above-mentioned alkyl group or alkoxy group.
Examples of the alkoxycarbonyl group include alkoxycarbonyl groups having 2 to 17 carbon atoms, such as methoxycarbonyl, ethoxycarbonyl, and butoxycarbonyl. Examples of the alkylcarbonyl group include alkylcarbonyl groups having 2 to 18 carbon atoms, such as acetyl, propionyl, and butyryl. Examples of the alkylcarbonyloxy group include alkylcarbonyloxy groups having 2 to 17 carbon atoms, such as acetyloxy, propionyloxy, and butyryloxy. Examples of the alkylthio group include alkylthio groups having 1 to 17 carbon atoms, such as methylthio, ethylthio, and propylthio. Examples of the alkylsulfonyl group include alkylsulfonyl groups having 1 to 17 carbon atoms, such as methylsulfonyl, ethylsulfonyl, and propylsulfonyl. The number of carbon atoms in the alkoxycarbonyl group is preferably 2 to 11, more preferably 2 to 6, and even more preferably 2 to 4. The number of carbon atoms in the alkylcarbonyl group is preferably 2 to 12, more preferably 2 to 6, and even more preferably 2 to 4. The number of carbon atoms in the alkylcarbonyloxy group is preferably 2 to 11, more preferably 2 to 6, and even more preferably 2 to 4. The number of carbon atoms in the alkylthio group is preferably 2 to 11, more preferably 2 to 6, and even more preferably 2 to 4. The number of carbon atoms in the alkylsulfonyl group is preferably 1 to 11, more preferably 1 to 6, and even more preferably 1 to 4.

Furthermore, examples of groups in which —CH ₂ — contained in an alicyclic hydrocarbon group is replaced by —O—, —CO—, —SO ₂ — or —S— include the groups shown below. In the groups shown below, —O— may be replaced by —S—, and —CO— may be replaced by —SO ₂ —. The bonding site may be at any position.
When a —CH ₂ — contained in the hydrocarbon group is replaced by —O—, —S—, —SO ₂ —, or —CO—, the number of carbon atoms before the replacement is taken as the total number of carbon atoms in the hydrocarbon group.

Substituents that the hydrocarbon groups of R ⁴ , R ⁵ , R ⁶ , R ⁷ , R ⁸ and R ⁹ may have include a halogen atom, a cyano group, and an alkyl group having 1 to 12 carbon atoms (-CH ₂ - contained in the alkyl group may be replaced with -O- or -CO-).
Examples of the halogen atom include the same groups as those mentioned above.
Examples of the alkyl group having 1 to 12 carbon atoms include the same groups as those mentioned above.
When —CH ₂ — contained in an alkyl group as a substituent is replaced with —O— or —CO—, the number of carbon atoms before replacement is counted as the total number of carbon atoms in the alkyl group. Examples of the substituted group include a hydroxy group (a group in which —CH ₂ — in a methyl group is replaced with —O—), a carboxy group (a group in which —CH ₂ —CH ₂ — in an ethyl group is replaced with —O—CO—), an alkoxy group (a group in which —CH ₂ — at any position in an alkyl group is replaced with —O—), an alkoxycarbonyl group (a group in which —CH ₂ —CH ₂ — at any position in an alkyl group is replaced with —O—CO—), an alkylcarbonyl group (a group in which —CH ₂ — at any position in an alkyl group is replaced with —CO—), and an alkylcarbonyloxy group (a group in which —CH ₂ —CH ₂ — at any position in an alkyl group is replaced with —CO—O—).
Examples of the alkoxy group, alkoxycarbonyl group, alkylcarbonyl group and alkylcarbonyloxy group include the same groups as those described above.
The hydrocarbon group may have one or more substituents.

^X1 is preferably an oxygen atom.
^X2 is preferably an oxygen atom.
^X3 is preferably an oxygen atom.
The bonding positions of X ¹ , X ² and X ³ may be any of the o-position, m-position and p-position relative to the bonding position of S ⁺ , and are preferably bonded to the p-position relative to the bonding position of S ⁺ .
m1 is preferably 1 or 2, and more preferably 1.
m2 is preferably 0 or 1.
m3 is preferably 0 or 1, and more preferably 0.
m4 is preferably 0, 1, 2, 3 or 5, and more preferably 0, 1, 2 or 5.
m5 is preferably 0 or 1, and more preferably 0.
m6 is preferably 0 or 1, and more preferably 0.
m7 is preferably 0, 1 or 2, and more preferably 0.
m8 is preferably 0 or 1. When m2 is 0, m8 is preferably 1.
m9 is preferably 0 or 1. When m3 is 0, m9 is preferably 1.
R ⁴ , R ⁵ and R ⁶ are each independently preferably a halogen atom, a fluorinated alkyl group having 1 to 4 carbon atoms or an alkyl group having 1 to 6 carbon atoms (wherein the —CH ₂ — contained in the alkyl group may be replaced with —O— or —CO—), more preferably a halogen atom, a fluorinated alkyl group having 1 to 4 carbon atoms or an alkyl group having 1 to 4 carbon atoms (wherein the —CH ₂ — contained in the alkyl group may be replaced with —O— or —CO—), even more preferably a fluorine atom, an iodine atom, a perfluoroalkyl group having 1 to 4 carbon atoms or an alkyl group having 1 to 4 carbon atoms (wherein the —CH ₂ — contained in the alkyl group may be replaced with —O— or —CO—), and even more preferably a fluorine atom, an iodine atom or a trifluoromethyl group.
The bonding positions of R ⁴ , R ⁵ and R ⁶ may be any of the o-position, m-position and p-position relative to the bonding positions of X ¹ , X ² and X ^3. In particular, it is preferable that they are bonded at least at the p-position relative to the bonding positions of X ¹ , X ² and X ³ .
R ⁷ , R ⁸ and R ⁹ are each independently preferably a halogen atom, a fluorinated alkyl group having 1 to 4 carbon atoms or an alkyl group having 1 to 6 carbon atoms (wherein the —CH ₂ — contained in the alkyl group may be replaced with —O— or —CO—), more preferably a halogen atom, a fluorinated alkyl group having 1 to 4 carbon atoms or an alkyl group having 1 to 4 carbon atoms (wherein the —CH ₂ — contained in the alkyl group may be replaced with —O— or —CO—), still more preferably a fluorine atom, an iodine atom, a perfluoroalkyl group having 1 to 4 carbon atoms or an alkyl group having 1 to 4 carbon atoms (wherein the —CH ₂ — contained in the alkyl group may be replaced with —O— or —CO—), and even more preferably a fluorine atom, an iodine atom or a trifluoromethyl group.

Examples of the cation of the salt (I) include cations represented by the following formulae (I-c-1) to (I-c-44).

In formula (I), examples of the hydrocarbon group represented by ^X0 include aliphatic hydrocarbon groups (chain hydrocarbon groups such as alkyl groups, alkenyl groups, and alkynyl groups, and alicyclic hydrocarbon groups), aromatic hydrocarbon groups, and groups combining these, etc. _-CH2- contained in the aliphatic hydrocarbon group may be replaced by -O-, -S-, -CO-, or _-SO2- .
Examples of the alkyl group include a methyl group, an ethyl group, a propyl group, an isopropyl group, a butyl group, an isobutyl group, a tert-butyl group, a pentyl group, a hexyl group, an octyl group, a nonyl group, etc. The number of carbon atoms in the alkyl group is preferably 1 to 18, more preferably 1 to 12, even more preferably 1 to 9, still more preferably 1 to 6, and even more preferably 1 to 4.
Examples of the alkenyl group include ethenyl, propenyl, isopropenyl, butenyl, isobutenyl, tert-butenyl, pentenyl, hexenyl, heptenyl, octynyl, isooctynyl, and nonenyl groups.
Examples of the alkynyl group include an ethynyl group, a propynyl group, an isopropynyl group, a butynyl group, an isobutynyl group, a tert-butynyl group, a pentynyl group, a hexynyl group, an octynyl group, and a nonynyl group. Examples of groups in which —CH ₂ — in a chain hydrocarbon group is replaced by —O—, —S—, —CO— or —SO ₂ — include a hydroxy group (a group in which —CH ₂ — in a methyl group is replaced by —O—), a carboxy group (a group in which —CH _{2 —} in an ethyl group is replaced by —O—CO—), a thiol group (a group in which —CH ₂ — in a methyl group is replaced by —S—), an alkoxy group (a group in which —CH ₂ — at any position in an alkyl group is replaced by —O—), an alkoxycarbonyl group (a group in which —CH _{2 —} at any position in an alkyl group is replaced by —O—CO—), an alkylcarbonyl group (a group in which —CH ₂ — at any position in an alkyl group is replaced by —CO—), and an alkylcarbonyloxy group (a group in which —CH _{2 —} Examples of such groups include alkyl groups (a group in which any --CH _{2 --} at any position in an alkyl group is replaced with --CO--O--), alkylthio groups (a group in which any --CH 2 -- at any position in an alkyl group is replaced with --S--), and the like.
Examples of the alkoxy group, alkoxycarbonyl group, alkylcarbonyl group, alkylcarbonyloxy group, alkylthio group, and alkylsulfonyl group include the same groups as those mentioned above.
The substitution in the alkenyl group or alkynyl group may be any of the substitutions in the alkyl group exemplified above, as long as it contains a carbon-carbon double bond or a carbon-carbon triple bond at any position.

The alicyclic hydrocarbon group may be monocyclic, polycyclic, or spirocyclic, and may be saturated or unsaturated. Examples of the alicyclic hydrocarbon group include monocyclic cycloalkyl groups such as cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl, cyclooctyl, cyclononyl, cyclodecyl, and cyclododecyl, and polycyclic cycloalkyl groups such as norbornyl and adamantyl.
Specific examples of the alicyclic hydrocarbon group or a group in which —CH ₂ — contained in the alicyclic hydrocarbon group is replaced with —O—, —S—, —CO— or —SO ₂ — include the following groups: The bonding site can be at any position.


The alicyclic hydrocarbon group or a group in which —CH ₂ — contained in the alicyclic hydrocarbon group is replaced with —O—, —S—, —CO— or —SO ₂ — is preferably a group represented by formulas (y1) to (y71), more preferably a group represented by any of formulas (y1) to (y20), (y26), (y27), (y30), (y31), and (y39) to (y71), and even more preferably a group represented by formulas (y3), (y4), (y9), (y11), (y14), (y15), (y16), (y20), (y26), (y27), (y30), (y31), (y39), (y40), (y42), (y43), (y49) to (y58), and (y62) to (y71). The alicyclic hydrocarbon group preferably has 3 to 36 carbon atoms, more preferably 3 to 24 carbon atoms, even more preferably 3 to 18 carbon atoms, still more preferably 3 to 16 carbon atoms, and even more preferably 3 to 12 carbon atoms.

Examples of the aromatic hydrocarbon group include aryl groups such as a phenyl group, a naphthyl group, a biphenyl group, an anthryl group, a phenanthryl group, and a binaphthyl group. The number of carbon atoms in the aromatic hydrocarbon group is preferably 6 to 36, more preferably 6 to 24, even more preferably 6 to 18, still more preferably 6 to 14, and even more preferably 6 to 10.
In the case of a combined group, the above groups may contain groups with different valences (such as an alkanediyl group, an alkanetriyl group, an alkanetetrayl group, a cycloalkanediyl group, a cycloalkanetriyl group, or a cycloalkanetetrayl group).

The combined groups are:
a group combining an alicyclic hydrocarbon group and a chain hydrocarbon group ( _-CH2- contained in the chain hydrocarbon group and the alicyclic hydrocarbon group may be replaced by -O-, -S-, -CO- or _-SO2- );
It represents a group in which a chain hydrocarbon group and an aromatic hydrocarbon group are combined (-CH ₂ - contained in the chain hydrocarbon group may be replaced by -O-, -S-, -CO- or -SO ₂ -), and a group in which an alicyclic hydrocarbon group and an aromatic hydrocarbon group are combined (-CH ₂ - contained in the alicyclic hydrocarbon group may be replaced by -O-, -S-, -CO- or -SO ₂ -).
In addition, in the combination, two or more types of each of the alicyclic hydrocarbon group, the chain hydrocarbon group and the aromatic hydrocarbon group may be combined.
Specifically, the combined groups include:
alicyclic hydrocarbon group-chain hydrocarbon group-* such as an adamantylmethylene group or a cyclohexylmethylene group, (alicyclic hydrocarbon group) ₂ -chain hydrocarbon group-* (wherein —CH ₂ — contained in the chain hydrocarbon group or the alicyclic hydrocarbon group may be replaced by —O—, —S—, —CO— or —SO ₂ —),
chain hydrocarbon group-alicyclic hydrocarbon group-* such as methyladamantyl group and dimethyladamantyl group, (chain hydrocarbon group) ₂ -alicyclic hydrocarbon group-* (-CH ₂ - contained in the chain hydrocarbon group and the alicyclic hydrocarbon group may be replaced by -O-, -S-, -CO- or -SO ₂ -),
a chain hydrocarbon group such as a tolyl group or a xylyl group - an aromatic hydrocarbon group -* (wherein -CH ₂ - contained in the chain hydrocarbon group may be replaced by -O-, -S-, -CO- or -SO ₂ -);
chain hydrocarbon group-alicyclic hydrocarbon group-chain hydrocarbon group-* such as a methylcyclohexylmethylene group, (chain hydrocarbon group) ₂ -alicyclic hydrocarbon group-chain hydrocarbon group-*, (chain hydrocarbon group-alicyclic hydrocarbon group) ₂ -chain hydrocarbon group-* (-CH ₂ - contained in the chain hydrocarbon group and the alicyclic hydrocarbon group may be replaced by -O-, -S-, -CO- or -SO ₂ -),
an aromatic hydrocarbon group such as a benzyl group - a chain hydrocarbon group -* (wherein -CH ₂ - contained in the chain hydrocarbon group may be replaced by -O-, -S-, -CO- or -SO ₂ -);
A chain hydrocarbon group such as a tolylmethyl group - an aromatic hydrocarbon group - a chain hydrocarbon group - * (wherein -CH ₂ - contained in the chain hydrocarbon group may be replaced by -O-, -S-, -CO- or -SO ₂ -)
chain hydrocarbon group-alicyclic hydrocarbon group-chain hydrocarbon group-alicyclic hydrocarbon group-*, (chain hydrocarbon group-alicyclic hydrocarbon group-chain hydrocarbon group) 2 -alicyclic hydrocarbon group-*, (chain hydrocarbon group-alicyclic hydrocarbon group) ₂ -chain hydrocarbon group-alicyclic hydrocarbon group-*, (chain hydrocarbon group-alicyclic hydrocarbon group) ₂ -chain hydrocarbon group-alicyclic hydrocarbon group-*, (chain hydrocarbon group) ₂ -alicyclic hydrocarbon group-chain hydrocarbon group-alicyclic hydrocarbon group-* (-CH ₂ - contained in the chain hydrocarbon group and the alicyclic hydrocarbon group may be replaced by -O-, -S-, -CO- or -SO ₂ -),
Alicyclic hydrocarbon group-chain hydrocarbon group-alicyclic hydrocarbon group-chain hydrocarbon group-*, (alicyclic hydrocarbon group) ₂ -chain hydrocarbon group-alicyclic hydrocarbon group-chain hydrocarbon group-*, (alicyclic hydrocarbon group-chain hydrocarbon group) ₂ -alicyclic hydrocarbon group-chain hydrocarbon group-*, (alicyclic hydrocarbon group-chain hydrocarbon group-alicyclic hydrocarbon group) ₂ -chain hydrocarbon group-* (-CH ₂ - contained in the chain hydrocarbon group and the alicyclic hydrocarbon group may be replaced by -O-, -S-, -CO- or -SO ₂ -),
chain hydrocarbon group-alicyclic hydrocarbon group-chain hydrocarbon group-alicyclic hydrocarbon group-chain hydrocarbon group-*, (chain hydrocarbon group) ₂ -alicyclic hydrocarbon group-chain hydrocarbon group-alicyclic hydrocarbon group-chain hydrocarbon group-*, (chain hydrocarbon group-alicyclic hydrocarbon group) 2 -chain hydrocarbon group-alicyclic hydrocarbon group-chain hydrocarbon group-*, (chain hydrocarbon group-alicyclic hydrocarbon group-chain hydrocarbon group) ₂ -alicyclic hydrocarbon group-chain hydrocarbon group-*, (chain hydrocarbon group-alicyclic hydrocarbon group-chain hydrocarbon group) ₂ -alicyclic hydrocarbon group-chain hydrocarbon group-*, (chain hydrocarbon group-alicyclic hydrocarbon group-chain hydrocarbon group-alicyclic hydrocarbon group) ₂ -chain hydrocarbon group-* (-CH ₂ - contained in the chain hydrocarbon group and the alicyclic hydrocarbon group may be replaced by -O-, -S-, -CO- or -SO ₂ -),
Here, * indicates the bonding position with the carbon atom of the carbonyl group.
When —CH ₂ — contained in the hydrocarbon group represented by X ⁰ is replaced by —O—, —S—, —CO— or —SO ₂ —, the total number of carbon atoms in the hydrocarbon group is the number of carbon atoms before the replacement. When a substituent is bonded to the hydrocarbon group represented by X ⁰ , the total number of carbon atoms in the hydrocarbon group is the number of carbon atoms before the replacement.

The hydrocarbon group represented by X ⁰ may have one or more substituents.
Examples of the substituent include a hydroxy group, a halogen atom, a cyano group, an alkyl group having 1 to 12 carbon atoms, an alkoxy group having 1 to 12 carbon atoms, an alkoxycarbonyl group having 2 to 13 carbon atoms, an alkylcarbonyl group having 2 to 13 carbon atoms, an alkylcarbonyloxy group having 2 to 13 carbon atoms, an alicyclic hydrocarbon group having 3 to 12 carbon atoms, an aromatic hydrocarbon group having 6 to 10 carbon atoms, or a group combining these.
Examples of the halogen atom include a fluorine atom, a chlorine atom, a bromine atom, and an iodine atom.
Examples of the alkyl group having 1 to 12 carbon atoms include a methyl group, an ethyl group, a propyl group, an isopropyl group, a butyl group, an isobutyl group, a tert-butyl group, a pentyl group, a hexyl group, an octyl group, and a nonyl group.
Examples of the alkoxy group having 1 to 12 carbon atoms include a methoxy group, an ethoxy group, a propoxy group, a butoxy group, a pentyloxy group, a hexyloxy group, an octyloxy group, a 2-ethylhexyloxy group, a nonyloxy group, a decyloxy group, an undecyloxy group, and a dodecyloxy group.
The alkoxycarbonyl group having 2 to 13 carbon atoms, the alkylcarbonyl group having 2 to 13 carbon atoms, and the alkylcarbonyloxy group having 2 to 13 carbon atoms represent groups in which a carbonyl group or a carbonyloxy group is bonded to the above-mentioned alkyl group or alkoxy group.
Examples of the alkoxycarbonyl group having 2 to 13 carbon atoms include a methoxycarbonyl group, an ethoxycarbonyl group, and a butoxycarbonyl group. Examples of the alkylcarbonyl group having 2 to 13 carbon atoms include an acetyl group, a propionyl group, and a butyryl group. Examples of the alkylcarbonyloxy group having 2 to 13 carbon atoms include an acetyloxy group, a propionyloxy group, and a butyryloxy group.
Examples of the alicyclic hydrocarbon group having 3 to 12 carbon atoms include the groups shown below, where ** represents the bonding position with ^X0 .
Examples of the aromatic hydrocarbon group having 6 to 10 carbon atoms include aryl groups such as phenyl and naphthyl groups.
Examples of the combined group include a group in which a hydroxy group is combined with an alkyl group having 1 to 12 carbon atoms, a group in which an alkyl group having 1 to 12 carbon atoms is combined with an aromatic hydrocarbon group having 6 to 10 carbon atoms, and a group in which an alicyclic hydrocarbon group having 3 to 12 carbon atoms is combined with an aromatic hydrocarbon group having 6 to 10 carbon atoms.
Examples of the group combining a hydroxy group with an alkyl group having 1 to 12 carbon atoms include hydroxyalkyl groups having 1 to 12 carbon atoms, such as a hydroxymethyl group and a hydroxyethyl group.
Examples of the group formed by combining an alkyl group having 1 to 12 carbon atoms with an aromatic hydrocarbon group having 6 to 10 carbon atoms include aralkyl groups having 7 to 22 carbon atoms, such as a benzyl group, and alkylaryl groups having 7 to 22 carbon atoms, such as a tolyl group and a xylyl group.
Examples of groups formed by combining an alicyclic hydrocarbon group having 3 to 12 carbon atoms with an aromatic hydrocarbon group having 6 to 10 carbon atoms include a cyclohexylphenyl group.

The hydrocarbon group represented by ^X0 is preferably an aliphatic hydrocarbon group having 1 to 72 carbon atoms which may have a substituent ( _-CH2- contained in the aliphatic hydrocarbon group may be replaced by -O-, -S-, -CO- or _-SO2- ), or an aromatic hydrocarbon group having 6 to 36 carbon atoms which may have a substituent;
More preferred are alicyclic hydrocarbon groups having 3 to 36 carbon atoms which may have a hydroxy group or a fluorine atom (provided that —CH ₂ — contained in the alicyclic hydrocarbon group may be replaced by —O—, —S—, —CO— or —SO ₂ —), groups which combine an alicyclic hydrocarbon group having 3 to 36 carbon atoms with a chain hydrocarbon group having 1 to 18 carbon atoms (—CH ₂ — contained in the alicyclic hydrocarbon group may be replaced by —O—, —S—, —CO— or —SO ₂ —, and —CH ₂ — contained in the chain hydrocarbon group may be replaced by —O— or —CO—, and the alicyclic hydrocarbon group and the chain hydrocarbon group may have a fluorine atom or a hydroxy group), aromatic hydrocarbon groups having 6 to 36 carbon atoms which may have a fluorine atom or a hydroxy group, groups represented by formula (aa) or groups represented by formula (bb),
More preferred are *-alicyclic hydrocarbon group (wherein —CH ₂ — contained in the alicyclic hydrocarbon group may be replaced by —O—, —S—, —CO— or —SO ₂ —, and the alicyclic hydrocarbon group may have a hydroxy group or a fluorine atom. * represents the bonding position of —COO— to the carbon atom), *-alicyclic hydrocarbon group-chain hydrocarbon group (wherein —CH 2 ^— contained in the alicyclic hydrocarbon group may be replaced by —O—, —S—, —CO— or —SO 2 —, and the —CH ₂ — contained in the chain hydrocarbon group may be replaced by —O— or —CO—, and the alicyclic hydrocarbon group and the chain hydrocarbon group may have a fluorine atom or a hydroxy group. * represents the bonding position of —COO— to the carbon atom), *-chain hydrocarbon group-alicyclic hydrocarbon group (wherein —CH ₂ — contained in the chain hydrocarbon group may be replaced by —O—, —S—, —CO— or —SO ₂ —, and the —CH 2 ^— contained in the chain hydrocarbon group may be replaced by —O— or —CO—, and the alicyclic hydrocarbon group and the chain hydrocarbon group may have a fluorine atom or a hydroxy group. * represents the bonding position of —COO— to the carbon atom ₎ . - may be replaced by -O- or -CO-, -CH ₂ - contained in the alicyclic hydrocarbon group may be replaced by -O-, -S-, -CO- or -SO ₂ -, and the chain hydrocarbon group and the alicyclic hydrocarbon group may have a fluorine atom or a hydroxy group. * represents the bonding position of ^-COO- to the carbon atom.), an aromatic hydrocarbon group which may have a fluorine atom or a hydroxy group, a group represented by formula (aa) or a group represented by formula (bb),
More preferably, the following are listed: *-polycyclic alicyclic hydrocarbon group (wherein —CH ₂ — contained in the polycyclic alicyclic hydrocarbon group may be replaced by —O—, —S—, —CO— or —SO ₂ —, and the polycyclic alicyclic hydrocarbon group may have a hydroxy group or a fluorine atom. * represents the bonding position of ^—COO— to the carbon atom); *-polycyclic alicyclic hydrocarbon group-chain hydrocarbon group (wherein —CH ₂ — contained in the polycyclic alicyclic hydrocarbon group may be replaced by —O—, —S—, —CO— or —SO ₂ —, and the —CH ₂ — contained in the chain hydrocarbon group may be replaced by —O— or —CO—, and the polycyclic alicyclic hydrocarbon group and the chain hydrocarbon group may have a fluorine atom or a hydroxy group. * represents the bonding position of ^—COO— to the carbon atom); *-chain hydrocarbon group-polycyclic alicyclic hydrocarbon group (wherein —CH ₂ — contained in the chain hydrocarbon group - may be replaced by -O- or -CO-, -CH ₂ - contained in the polycyclic alicyclic hydrocarbon group may be replaced by -O-, -S-, -CO- or -SO ₂ -, and the chain hydrocarbon group and the polycyclic alicyclic hydrocarbon group may have a fluorine atom or a hydroxy group. * represents the bonding position with the carbon atom of ^-COO- ), an aromatic hydrocarbon group which may have a fluorine atom or a hydroxy group, a group represented by formula (aa) or a group represented by formula (bb),
Particularly preferred are an adamantanone group, a hydroxyadamantyl group, a group combining an adamantyl group with an alkyl group (wherein the —CH ₂ — contained in the alkyl group may be replaced with —O— or —CO—), a group represented by formula (Y30F), or a phenyl group having a hydroxy group.
In the above groups, the number of carbon atoms in the alicyclic hydrocarbon group is preferably 3 to 36, more preferably 3 to 24, even more preferably 3 to 18, still more preferably 3 to 16, and even more preferably 3 to 12. The number of carbon atoms in the chain hydrocarbon group is preferably 1 to 18, more preferably 1 to 12, even more preferably 1 to 9, still more preferably 1 to 6, and even more preferably 1 to 4. The number of carbon atoms in the aromatic hydrocarbon group is preferably 6 to 36, more preferably 6 to 24, even more preferably 6 to 18, still more preferably 6 to 14, and even more preferably 6 to 10.
[In formula (aa),
X ^a and X ^b each independently represent —O— or —S—.
X ^1a represents a hydrocarbon group having 1 to 24 carbon atoms which may have a substituent, and one —CH ₂ — contained in the hydrocarbon group may be replaced by —O—, —S—, —CO— or —SO ₂ —.
X ^2a represents a hydrocarbon group having 1 to 48 carbon atoms which may have a substituent, and one —CH ₂ — contained in the hydrocarbon group may be replaced by —O—, —S—, —CO— or —SO ₂ —.
* indicates the bonding position with the carbon atom of ^—COO— .]
[In formula (bb),
L 1 ^A represents an alkanediyl group having 1 to 6 carbon atoms which may have a fluorine atom, or an aromatic hydrocarbon group having 6 carbon atoms which may have a halogen atom or a perfluoroalkyl group having 1 to 4 carbon atoms.
L 1 ^B represents a single bond or an alkanediyl group having 1 to 6 carbon atoms, and one —CH ₂ — contained in the alkanediyl group may be replaced by —O—, —S—, —CO— or —SO ₂ —.
R ^A represents a hydrocarbon group having 1 to 36 carbon atoms which may have a substituent, and one —CH ₂ — contained in the hydrocarbon group may be replaced by —O—, —S—, —CO— or —SO ₂ —.
* indicates the bonding position with the carbon atom of ^—COO— .]

X ^a and X ^b are preferably the same atom, and more preferably both are oxygen atoms.

Examples of hydrocarbon groups represented by X ^1a and X ^2a include aliphatic hydrocarbon groups, aromatic hydrocarbon groups, and groups combining two or more of these. These hydrocarbon groups may have a substituent. Furthermore, —CH ₂ — contained in these hydrocarbon groups may be replaced by —O—, —S—, —CO—, or —SO ₂ —. Here, the number of carbon atoms in the hydrocarbon group means the number of carbon atoms in an unsubstituted hydrocarbon group that does not have a substituent.

Examples of the aliphatic hydrocarbon group for X ^1a include chain hydrocarbon groups such as alkanetriyl groups, alicyclic hydrocarbon groups, and groups formed by combining these groups.
Specific examples of the alkanetriyl group include a methine group, an ethanetriyl group, a propanetriyl group, a butanetriyl group, a pentanetriyl group, a hexanetriyl group, a heptanetriyl group, an octanetriyl group, a nonanetriyl group, a decanetriyl group, an undecanetriyl group, and a dodecanetriyl group.

The alicyclic hydrocarbon group may be either monocyclic or polycyclic.
Examples of the monocyclic alicyclic hydrocarbon group include a cyclobutanetriyl group, a cyclopentanetriyl group, a cyclohexanetriyl group, and a cyclooctanetriyl group.
Examples of the polycyclic alicyclic hydrocarbon group include a norbornanetriyl group and an adamantanetriyl group.
Examples of the aromatic hydrocarbon group include a benzenetriyl group, a naphthalenetriyl group, and an anthracenetriyl group.
In the case of a combined group, the above groups may contain groups with different valences (such as an alkyl group, an alkanediyl group, an alkanetetrayl group, a cycloalkyl group, a cycloalkanediyl group, or a cycloalkanetetrayl group).

The hydrocarbon group represented by X ^1a has 1 to 24 carbon atoms and may further have one or more substituents. Examples of the substituents include a hydroxy group, a halogen atom, a cyano group, an alkyl group having 1 to 12 carbon atoms, an alkoxy group having 1 to 12 carbon atoms, an alkoxycarbonyl group having 2 to 13 carbon atoms, an alkylcarbonyl group having 2 to 13 carbon atoms, an alkylcarbonyloxy group having 2 to 13 carbon atoms, an alicyclic hydrocarbon group having 3 to 12 carbon atoms, an aromatic hydrocarbon group having 6 to 10 carbon atoms, or a group combining these.
Examples of the halogen atom, alkyl group, alkoxy group, alkoxycarbonyl group, alkylcarbonyl group, alkylcarbonyloxy group, alicyclic hydrocarbon group, aromatic hydrocarbon group, and combinations thereof include the same groups as those described above.

The hydrocarbon group represented by X ^1a is preferably an alkanetriyl group having 1 to 6 carbon atoms which may have a substituent or an alicyclic hydrocarbon group having 3 to 18 carbon atoms which may have a substituent, more preferably an alkanetriyl group having 1 to 6 carbon atoms or a group represented by formula (w1-1) to formula (w1-11), and even more preferably an alkanetriyl group having 1 to 6 carbon atoms, a polycyclic hydrocarbon group such as a group represented by formula (w1-1) or a group represented by formula (w1-3), or a monocyclic hydrocarbon group such as a group represented by formula (w1-2) or a group represented by formula (w1-6).
[In formulas (w1-1) to (w1-11),
The ring may have a hydroxy group, a halogen atom, a cyano group, an alkyl group having 1 to 12 carbon atoms, an alkoxy group having 1 to 12 carbon atoms, an alkoxycarbonyl group having 2 to 13 carbon atoms, an alkylcarbonyl group having 2 to 13 carbon atoms, an alkylcarbonyloxy group having 2 to 13 carbon atoms, an alicyclic hydrocarbon group having 3 to 12 carbon atoms, an aromatic hydrocarbon group having 6 to 10 carbon atoms, or a combination thereof.
* indicates the bond position.

The hydrocarbon group represented by ^X2a preferably has 2 to 48 carbon atoms, more preferably 4 to 48 carbon atoms, even more preferably 6 to 44 carbon atoms, even more preferably 8 to 40 carbon atoms, and even more preferably 10 to 38 carbon atoms.

Examples of the substituent that the hydrocarbon group for X ^2a may have include a hydroxy group, a halogen atom, a cyano group, an alkyl group having 1 to 12 carbon atoms, an alkoxy group having 1 to 12 carbon atoms, an alkoxycarbonyl group having 2 to 13 carbon atoms, an alkylcarbonyl group having 2 to 13 carbon atoms, an alkylcarbonyloxy group having 2 to 13 carbon atoms, an alicyclic hydrocarbon group having 3 to 12 carbon atoms, an aromatic hydrocarbon group having 6 to 10 carbon atoms, or a group combining these.
Examples of the halogen atom, alkyl group, alkoxy group, alkoxycarbonyl group, alkylcarbonyl group, alkylcarbonyloxy group, alicyclic hydrocarbon group, aromatic hydrocarbon group, and combinations thereof include the same groups as those described above.
The hydrocarbon group having 1 to 48 carbon atoms represented by X ^2a may have one or more substituents.

Examples of the hydrocarbon group for ^X2a include linear or branched chain hydrocarbon groups (e.g., alkanediyl groups, etc.), monocyclic or polycyclic alicyclic hydrocarbon groups, and aromatic hydrocarbon groups, and may be a combination of two or more of these groups.
Specific examples include linear alkanediyl groups such as a methylene group, an ethylene group, a propane-1,3-diyl group, a butane-1,4-diyl group, a pentane-1,5-diyl group, a hexane-1,6-diyl group, a heptane-1,7-diyl group, and an octane-1,8-diyl group;
branched alkanediyl groups such as an ethane-1,1-diyl group, a propane-1,1-diyl group, a propane-1,2-diyl group, a propane-2,2-diyl group, a pentane-2,4-diyl group, a 2-methylpropane-1,3-diyl group, a 2-methylpropane-1,2-diyl group, a pentane-1,4-diyl group, and a 2-methylbutane-1,4-diyl group;
monocyclic alicyclic hydrocarbon groups such as monocyclic cycloalkanediyl groups, such as cyclobutane-1,3-diyl, cyclopentane-1,3-diyl, cyclohexane-1,4-diyl, and cyclooctane-1,5-diyl;
polycyclic alicyclic hydrocarbon groups such as polycyclic cycloalkanediyl groups, such as norbornane-1,4-diyl group, norbornane-2,5-diyl group, adamantane-1,5-diyl group, and adamantane-2,6-diyl group;
Examples of the aromatic hydrocarbon groups include a phenylene group, a naphthylene group, a biphenylene group, an anthrylene group, a phenanthrylene group, and a binaphthylene group.
In the case of a combined group, the above groups may contain groups with different valences (such as an alkyl group, an alkanetriyl group, an alkanetetrayl group, a cycloalkyl group, a cycloalkanetriyl group, or a cycloalkanetetrayl group).
Examples of the combined group include a group in which a chain hydrocarbon group and an alicyclic hydrocarbon group are combined, a group in which a chain hydrocarbon group and an aromatic hydrocarbon group are combined, and a group in which an alicyclic hydrocarbon group and an aromatic hydrocarbon group are combined. Specific examples include a group in which one or more alicyclic hydrocarbon groups are bonded to a chain hydrocarbon group (e.g., -chain hydrocarbon group-alicyclic hydrocarbon group, -chain hydrocarbon group-(alicyclic hydrocarbon group) ₂ , etc.), a group in which one or more chain hydrocarbon groups are bonded to an alicyclic hydrocarbon group (e.g., -alicyclic hydrocarbon group-chain hydrocarbon group, -alicyclic hydrocarbon group-(chain hydrocarbon group) ₂ , etc.), and a group in which one or more alicyclic hydrocarbon groups and chain hydrocarbon groups are bonded to a chain hydrocarbon group (e.g., -chain hydrocarbon group-alicyclic hydrocarbon group-chain hydrocarbon group, -chain hydrocarbon group-(alicyclic hydrocarbon group-chain hydrocarbon group) ₂ , etc.).

Examples of the hydrocarbon group for ^X2a include:
a chain hydrocarbon group having 2 to 18 carbon atoms ( _-CH2- contained in the chain hydrocarbon group may be replaced by -O- or -CO-, and the chain hydrocarbon group may have a substituent);
an alicyclic hydrocarbon group having 3 to 18 carbon atoms ( _-CH2- contained in the alicyclic hydrocarbon group may be replaced by -O-, -S-, -CO- or _-SO2- , and the alicyclic hydrocarbon group may have a substituent), or
It is preferably a group (which may have a substituent) that combines a chain hydrocarbon group having 1 to 12 carbon atoms ( _-CH2- in the chain hydrocarbon group may be replaced by -O- or -CO-) with an alicyclic hydrocarbon group having 3 to ₁₈ carbon atoms ( _-CH2- in the alicyclic hydrocarbon group may be replaced by -O-, -S-, -CO- or -SO2-),
a chain hydrocarbon group having 4 to 18 carbon atoms ( _-CH2- contained in the chain hydrocarbon group may be replaced by -O- or -CO-, and the chain hydrocarbon group may have a substituent), or
More preferably, it is a group (which may have a substituent) that combines a chain hydrocarbon group having 1 to 12 carbon atoms ( _-CH2- in the chain hydrocarbon group may be replaced by -O- or -CO-) with an alicyclic hydrocarbon group having ₃ to 16 carbon atoms ( _-CH2- in the alicyclic hydrocarbon group may be replaced by -O-, -S-, -CO- or -SO2-),
a chain hydrocarbon group having 6 to 14 carbon atoms ( _-CH2- contained in the chain hydrocarbon group may be replaced by -O- or -CO-, and the chain hydrocarbon group may have a substituent), or
More preferably, it is a group (which may have a substituent) that combines a chain hydrocarbon group having 1 to 12 carbon atoms (-CH ₂ - contained in the chain hydrocarbon group may be replaced by -O- or -CO-) with an alicyclic hydrocarbon group having 5 to 14 carbon atoms (-CH ₂ - contained in the alicyclic hydrocarbon group may be replaced by -O-, -S-, -CO- or -SO ₂ -).

Specific examples of the hydrocarbon group for X ^2a include:
an alkanediyl group having 2 to 18 carbon atoms ( _-CH2- contained in the alkanediyl group may be replaced by -O- or -CO-, and the alkanediyl group may have a substituent);
an alicyclic hydrocarbon group having 3 to 18 carbon atoms (-CH ₂ - contained in the alicyclic hydrocarbon group may be replaced by -O-, -S-, -CO- or -SO ₂ -, and the alicyclic hydrocarbon group may have a substituent); a group consisting of an alkanediyl group having 1 to 12 carbon atoms (-CH ₂ - contained in the alkanediyl group may be replaced by -O- or -CO-) and an alicyclic hydrocarbon group having 3 to 18 carbon atoms (-CH ₂ - contained in the alicyclic hydrocarbon group may be replaced by -O-, -S-, -CO- or -SO 2 -), which may have a substituent; or an alkanediyl group having 1 to 12 carbon atoms (-CH ₂ - contained in the alkanediyl group may be replaced by -O-, -S-, -CO- or -SO ₂ -), which may have a substituent. and a group (which may have a substituent) consisting of an alicyclic hydrocarbon group having 3 to 18 carbon atoms and an alkyl group having 1 to 12 carbon atoms (wherein —CH ₂ — contained in the alkyl group may be replaced by —O— or —CO—),
an alkanediyl group having 4 to 18 carbon atoms ( _-CH2- contained in the alkanediyl group may be replaced by -O- or -CO-, and the alkanediyl group may have a substituent);
and more preferably a group consisting of an alkanediyl group having 1 to 12 carbon atoms (-CH ₂ - contained in the alkanediyl group may be replaced with -O- or -CO-) and an alicyclic hydrocarbon group having 3 to 16 carbon atoms (-CH ₂ - contained in the alicyclic hydrocarbon group may be replaced with -O-, -S-, -CO- or -SO ₂ -), which may have a substituent; or a group consisting of an alkanediyl group having 1 to 12 carbon atoms (-CH ₂ - contained in the alkanediyl group may be replaced with -O- or -CO-), an alicyclic hydrocarbon group having 3 to 16 carbon atoms and an alkyl group having 1 to 12 carbon atoms (-CH ₂ - contained in the alkyl group may be replaced with -O- or -CO-), which may have a substituent.
an alkanediyl group having 6 to 14 carbon atoms ( _-CH2- contained in the alkanediyl group may be replaced by -O- or -CO-, and the alkanediyl group may have a substituent);
More preferably, the group is an optionally substituted group consisting of an alkanediyl group having 1 to 12 carbon atoms (-CH ₂ - contained in the alkanediyl group may be replaced by -O- or -CO-) and an adamantanediyl group (-CH ₂ - contained in the adamantanediyl group may be replaced by -O- or -CO-), or an optionally substituted group consisting of an alkanediyl group having 1 to 12 carbon atoms (-CH ₂ - contained in the alkanediyl group may be replaced by -O- or -CO-), an adamantanediyl group, and an alkyl group having 1 to 12 carbon atoms (-CH ₂ - contained in the alkyl group may be replaced by -O- or -CO-).

Specifically, X ^2a is preferably a group represented by formula (X ² -1), a group represented by formula (X ² -2), a group represented by formula (X ² -3) or a group represented by formula (X ² -4).
[In the formula,
R ^1x , R ^2x , R ^3x , R ^4x , R ^5x and R ^6x each independently represent an alkyl group having 1 to 6 carbon atoms, an alicyclic hydrocarbon group having 5 to 12 carbon atoms or a group combining two or more of these groups, and —CH ₂ — contained in the alkyl group and the alicyclic hydrocarbon group may be replaced by —O—, —S—, —CO— or —SO ₂ —, and the alkyl group and the alicyclic hydrocarbon group may have a substituent.
* represents the bonding position with X ^a and X ^b .]
The combined group may be a combination of one alkyl group and one alicyclic hydrocarbon group, or two or more of either one or two or more of both. In this case, the number of carbon atoms in the combined group is 39 or less, and preferably 37 or less.

Among these, R ^1x , R ^2x , R ^3x , R ^4x , R ^5x and R ^6x are preferably an alkyl group having 1 to 6 carbon atoms (wherein —CH ₂ — contained in the alkyl group may be replaced by —O— or —CO—, and the alkyl group may have a substituent), an alicyclic hydrocarbon group having 5 to 12 carbon atoms (wherein —CH ₂ — contained in the alicyclic hydrocarbon group may be replaced by —O—, —S—, —CO— or —SO ₂ —, and the alicyclic hydrocarbon group may have a substituent), or a combination of an alkyl group having 1 to 6 carbon atoms (wherein —CH ₂ — contained in the alkyl group may be replaced by —O— or —CO—) and an alicyclic hydrocarbon group having 5 to 12 carbon atoms (wherein —CH ₂ — contained in the alicyclic hydrocarbon group is —O—, —S—, —CO— or —SO ₂ —). - may be replaced by -.) and the group (which may have a substituent) is preferred, and a methoxy group, an adamantyl group (wherein -CH ₂ - contained in the adamantyl group may be replaced by -O- or -CO-, and the adamantyl group may have a substituent), or a group (which may have a substituent) combining an alkyl group having 1 to 6 carbon atoms (wherein -CH ₂ - contained in the alkyl group may be replaced by -O- or -CO-) and an adamantyl group is more preferred.

In formula (bb), examples of the alkanediyl group having 1 to 6 carbon atoms in L 1 ^A and L 2 ^B include linear alkanediyl groups such as methylene, ethylene, propane-1,3-diyl, butane-1,4-diyl, pentane-1,5-diyl, and hexane-1,6-diyl; and branched alkanediyl groups such as propane-1,2-diyl, 1-methylpropane-1,3-diyl, 2-methylpropane-1,3-diyl, 2-methylpropane-1,2-diyl, 1-methylbutane-1,4-diyl, and 2-methylbutane-1,4-diyl. The number of carbon atoms in the alkanediyl group is preferably 1 to 4, and more preferably 1 to 3.
Examples of the alkanediyl group which may have a fluorine atom include perfluoroalkanediyl groups such as a difluoromethylene group, a perfluoroethylene group, a perfluoropropanediyl group, a perfluorobutanediyl group, and a perfluoropentanediyl group.
When --CH ₂ -- contained in the alkanediyl group is replaced by --O-- or --CO--, the number of carbon atoms before the replacement is regarded as the total number of carbon atoms in the alkanediyl group. The alkanediyl group includes a hydroxy group (a group in which —CH ₂ — in a methyl group is replaced with —O—), a carboxy group (a group in which —CH _{2 —} in an ethyl group is replaced with —O—CO—), an alkoxy group (a group in which —CH ₂ — at any position in an alkyl group is replaced with —O—), an alkoxycarbonyl group (a group in which —CH _{2 —} in any position in an alkyl group is replaced with —O—CO—), an alkylcarbonyl group (a group in which —CH ₂ — in any position in an alkyl group is replaced with —CO—), an alkylcarbonyloxy group (a group in which —CH _{2 —} in any position in an alkyl group is replaced with —CO—O—), an alkanediyloxy group (a group in which —CH _{2 —} in any position in an alkanediyl ... It may have an alkanediyloxycarbonyl group (a group in which -CH ₂ -CH ₂ - at any position in an alkanediyl group is replaced with -O-), an alkanediylcarbonyl group (a group in which -CH ₂ - at any position in an alkanediyl group is replaced with -CO-), or an alkanediylcarbonyloxy group (a group in which -CH ₂ -CH ₂ - at any position in an alkanediyl group is replaced with -CO-O-).
Examples of the alkanediyloxy group include a methyleneoxy group, an ethyleneoxy group, a propanediyloxy group, a butanediyloxy group, and a pentanediyloxy group.
Examples of the alkanediyloxycarbonyl group include a methyleneoxycarbonyl group, an ethyleneoxycarbonyl group, a propanediyloxycarbonyl group, and a butanediyloxycarbonyl group.
Examples of the alkanediylcarbonyl group include a methylenecarbonyl group, an ethylenecarbonyl group, a propanediylcarbonyl group, a butanediylcarbonyl group, and a pentanediylcarbonyl group.
Examples of the alkanediylcarbonyloxy group include a methylenecarbonyloxy group, an ethylenecarbonyloxy group, a propanediylcarbonyloxy group, and a butanediylcarbonyloxy group.
L ^A is preferably an alkanediyl group having 1 to 4 carbon atoms which may have a fluorine atom, or an aromatic hydrocarbon group having 6 carbon atoms which may have a halogen atom or a perfluoroalkyl group having 1 to 4 carbon atoms, and more preferably an alkanediyl group having 1 to 3 carbon atoms which may have a fluorine atom, or an aromatic hydrocarbon group having 6 carbon atoms which may have a fluorine atom, an iodine atom, or a perfluoroalkyl group having 1 to 4 carbon atoms.
L 3 ^B is preferably a single bond or an alkanediyl group having 1 to 3 carbon atoms (wherein —CH ₂ — contained in the alkanediyl group may be replaced by —O— or —CO—), and more preferably a single bond, a methylene group or an ethylene group.

Examples of the hydrocarbon group in R ^A include aliphatic hydrocarbon groups (chain hydrocarbon groups such as alkyl groups, alkenyl groups, and alkynyl groups, and alicyclic hydrocarbon groups), aromatic hydrocarbon groups, and groups formed by combining these.
Examples of the alkyl group include a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, a sec-butyl group, a tert-butyl group, an n-pentyl group, an n-hexyl group, an n-heptyl group, a 2-ethylhexyl group, an n-octyl group, an n-nonyl group, an n-decyl group, an n-undecyl group, an n-dodecyl group, etc. The number of carbon atoms in the alkyl group is preferably 1 to 18, more preferably 1 to 12, even more preferably 1 to 9, still more preferably 1 to 6, and even more preferably 1 to 4.
Examples of the alkenyl group include ethenyl, propenyl, isopropenyl, butenyl, isobutenyl, tert-butenyl, pentenyl, hexenyl, heptenyl, octynyl, isooctynyl, and nonenyl groups.
Examples of the alkynyl group include an ethynyl group, a propynyl group, an isopropynyl group, a butynyl group, an isobutynyl group, a tert-butynyl group, a pentynyl group, a hexynyl group, an octynyl group, and a nonynyl group.
Examples of groups in which —CH ₂ — contained in a chain hydrocarbon group is replaced with —O—, —S—, —CO— or —SO ₂ — include a hydroxy group, a carboxy group, an alkoxy group, an alkoxycarbonyl group, an alkylcarbonyl group, an alkylcarbonyloxy group, and an alkylthio group.
Examples of the alkoxy group, alkoxycarbonyl group, alkylcarbonyl group, alkylcarbonyloxy group and alkylthio group include an alkoxy group having 1 to 17 carbon atoms, an alkoxycarbonyl group having 2 to 17 carbon atoms, an alkylcarbonyl group having 2 to 18 carbon atoms, an alkylcarbonyloxy group having 2 to 17 carbon atoms and an alkylthio group having 1 to 17 carbon atoms, and examples thereof include the same groups as those described above.

The alicyclic hydrocarbon group may be monocyclic, polycyclic, or spirocyclic, and may be saturated or unsaturated. Examples of the monocyclic alicyclic hydrocarbon group include monocyclic cycloalkyl groups such as cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl, cycloheptyl, cyclooctyl, cyclononyl, cyclodecyl, and cyclododecyl. Examples of the polycyclic alicyclic hydrocarbon group include polycyclic cycloalkyl groups such as decahydronaphthyl, adamantyl, and norbornyl.
Specific examples of the group in which —CH ₂ — contained in the alicyclic hydrocarbon group is replaced by —O—, —S—, —CO— or —SO ₂ — include the groups represented by the above formulas (y1) to (y71). The number of carbon atoms in the alicyclic hydrocarbon group is preferably 3 to 36, more preferably 3 to 24, even more preferably 3 to 18, still more preferably 3 to 16, and even more preferably 3 to 12.
Examples of the aromatic hydrocarbon group include aryl groups such as a phenyl group, a naphthyl group, a biphenyl group, an anthryl group, a phenanthryl group, and a binaphthyl group. The number of carbon atoms in the aromatic hydrocarbon group is preferably 6 to 36, more preferably 6 to 24, even more preferably 6 to 18, still more preferably 6 to 14, and even more preferably 6 to 10.

In the case of a combined group, the above groups may contain groups with different valences (such as an alkanediyl group, an alkanetriyl group, a cycloalkanediyl group, or a cycloalkanetriyl group).
Groups formed by combination include groups formed by combining an aromatic hydrocarbon group with a chain hydrocarbon group (for example, aromatic hydrocarbon group-alkanediyl group-*, alkyl group-aromatic hydrocarbon group-*), groups formed by combining an alicyclic hydrocarbon group with a chain hydrocarbon group (for example, alicyclic hydrocarbon group-alkanediyl group-*, alkyl group-alicyclic hydrocarbon group-*), and groups formed by combining an aromatic hydrocarbon group with a alicyclic hydrocarbon group (for example, aromatic hydrocarbon group-alicyclic hydrocarbon group-*, alicyclic hydrocarbon group-aromatic hydrocarbon group-*). * represents a bonding site.
Examples of the aromatic hydrocarbon group -alkanediyl group-* include aralkyl groups such as benzyl and phenethyl.
Examples of the alkyl group-aromatic hydrocarbon group-* include a tolyl group, a xylyl group, and a cumenyl group.
Examples of the alicyclic hydrocarbon group -alkanediyl group-* include cycloalkylalkyl groups such as cyclohexylmethyl group, cyclohexylethyl group, 1-(adamantan-1-yl)methyl group, and 1-(adamantan-1-yl)-1-methylethyl group.
Examples of the alkyl group-alicyclic hydrocarbon group-* include cycloalkyl groups having an alkyl group such as a methylcyclohexyl group, a dimethylcyclohexyl group, and a 2-alkyladamantan-2-yl group.
Examples of the aromatic hydrocarbon group-alicyclic hydrocarbon group-* include a phenyladamantyl group.
Examples of the alicyclic hydrocarbon group-aromatic hydrocarbon group-* include an adamantylphenyl group.
In addition, two or more types of alicyclic hydrocarbon groups, aromatic hydrocarbon groups, and chain hydrocarbon groups may be combined, and any of the groups may be bonded to L 1 ^B.

In addition to the above-mentioned groups, examples of groups in which —CH ₂ — contained in a hydrocarbon group is replaced with —O—, —S—, —CO— or —SO ₂ — include cycloalkoxy groups, cycloalkylalkoxy groups, alkoxycarbonyloxy groups, aromatic hydrocarbon group-carbonyloxy groups, and groups in which two or more of these groups are combined.
Examples of cycloalkoxy groups include cycloalkoxy groups having 3 to 17 carbon atoms, such as a cyclohexyloxy group. Examples of cycloalkylalkoxy groups include cycloalkylalkoxy groups having 4 to 17 carbon atoms, such as a cyclohexylmethoxy group. Examples of alkoxycarbonyloxy groups include alkoxycarbonyloxy groups having 2 to 16 carbon atoms, such as a butoxycarbonyloxy group. Examples of aromatic hydrocarbon group-carbonyloxy groups include aromatic hydrocarbon group-carbonyloxy groups having 7 to 17 carbon atoms, such as a benzoyloxy group.
When a —CH ₂ — contained in the hydrocarbon group is replaced by —O—, —S—, —SO ₂ —, or —CO—, the total number of carbon atoms in the hydrocarbon group is the number of carbon atoms before the replacement, and the number may be one or two or more.

Substituents that the hydrocarbon group of R ^A may have include a halogen atom, a cyano group, and an alkyl group having 1 to 12 carbon atoms (-CH ₂ - contained in the alkyl group may be replaced by -O-, -S-, -CO- or -SO ₂ -).
Examples of the halogen atom include the same groups as those mentioned above.
Examples of the alkyl group having 1 to 12 carbon atoms include the same groups as those mentioned above.
Examples of groups in which --CH ₂ -- in an alkyl group is replaced with --O-- or --CO-- include a hydroxy group, a carboxy group, an alkoxy group, an alkoxycarbonyl group, an alkylcarbonyl group, and an alkylcarbonyloxy group.
Examples of the alkoxy group, alkoxycarbonyl group, alkylcarbonyl group, and alkylcarbonyloxy group include an alkoxy group having 1 to 11 carbon atoms, an alkoxycarbonyl group having 2 to 11 carbon atoms, an alkylcarbonyl group having 2 to 12 carbon atoms, and an alkylcarbonyloxy group having 2 to 11 carbon atoms, and examples thereof include the same groups as those described above.
The hydrocarbon group in R ^A may have one or more substituents.

The hydrocarbon group in R ^A is preferably an alkyl group having 1 to 12 carbon atoms which may have a substituent (provided that -CH ₂ - contained in the alkyl group may be replaced with -O-, -S-, -CO- or -SO ₂ -), or a cyclic hydrocarbon group having 3 to 18 carbon atoms which may have a substituent (provided that -CH ₂ - contained in the cyclic hydrocarbon group may be replaced with -O-, -S-, -CO- or -SO ₂ -), and more preferably a cyclic hydrocarbon group having 3 to 18 carbon atoms which may have a fluorine atom, a hydroxy group, or an alkyl group having 1 to 6 carbon atoms (provided that -CH ₂ - contained in the cyclic hydrocarbon group may be replaced with -O-, -S-, -CO- or -SO ₂ -).

Examples of the cyclic hydrocarbon group include monocyclic or polycyclic alicyclic hydrocarbon groups having 3 to 18 carbon atoms and aromatic hydrocarbon groups having 6 to 18 carbon atoms, as well as combinations of these groups.
Examples of the alicyclic hydrocarbon group, aromatic hydrocarbon group, and combined group include the same groups as those described above.
In addition, two or more types of alicyclic hydrocarbon groups and two or more types of aromatic hydrocarbon groups may be combined, and either group may be bonded to L 1 ^B.

A cyclic hydrocarbon group having 3 to 18 carbon atoms (the cyclic hydrocarbon group may have a fluorine atom, a hydroxy group, or an alkyl group having 1 to 6 carbon atoms, and —CH ₂ — contained in the cyclic hydrocarbon group may be replaced by —O—, —S—, —CO—, or —SO ₂ —) is
an alicyclic hydrocarbon group having 3 to 18 carbon atoms which may have a fluorine atom, a hydroxy group or an alkyl group having 1 to 4 carbon atoms ( _-CH2- contained in the alicyclic hydrocarbon group may be replaced by -O-, -S-, -CO- or _-SO2- ), or
It is preferably an aromatic hydrocarbon group having 6 to 18 carbon atoms which may have a fluorine atom, a hydroxy group, or an alkyl group having 1 to 4 carbon atoms,
It is more preferably an alicyclic hydrocarbon group having 3 to 18 carbon atoms which may have a fluorine atom, a hydroxy group or an alkyl group having 1 to 4 carbon atoms ( _-CH2- contained in the alicyclic hydrocarbon group may be replaced by -O- or -CO-).
Preferred alicyclic hydrocarbon groups include cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl, norbornyl, adamantyl, and the following groups (the bonding site may be any position): and preferred aromatic hydrocarbon groups include phenyl and naphthyl groups.

Examples of the carboxylate anion in the carboxylate salt represented by formula (I) include the carboxylate anions described below.

Specific examples of the carboxylate (I) include salts of any combination of the above-mentioned cations and anions. Specific examples of the carboxylate (I) are shown in the table below.
In the table below, each symbol represents the symbol attached to the structure representing the anion and cation described above, and "to" indicates that the carboxylate (I) corresponds to the anion (I). For example, carboxylate (I-1) is a salt consisting of an anion represented by formula (I-a-1) and a cation represented by formula (I-c-1), carboxylate (I-2) is a salt consisting of an anion represented by formula (I-a-2) and a cation represented by formula (I-c-1), and carboxylate (I-55) is a salt consisting of an anion represented by formula (I-a-1) and a cation represented by formula (I-c-2).

Among these, carboxylates (I) include carboxylates (I-1) to (I-5), carboxylates (I-55) to (I-59), carboxylates (I-109) to (I-113), carboxylates (I-163) to (I-167), carboxylates (I-217) to (I-221), carboxylates (I-271) to (I-275), carboxylates (I-325) to (I-329), carboxylates (I-379) to (I-383), carboxylates (I-433) to (I-437), carboxylates (I-487) to (I-491), carboxylates (I-541) to (I-545), and carboxylates (I-5 95) to Carboxylic Acid Salt (I-599), Carboxylic Acid Salt (I-649) to Carboxylic Acid Salt (I-653), Carboxylic Acid Salt (I-703) to Carboxylic Acid Salt (I-707), Carboxylic Acid Salt (I-757) to Carboxylic Acid Salt (I-761), Carboxylic Acid Salt (I-811) to Carboxylic Acid Salt (I-815), Carboxylic Acid Salt (I-865) to Carboxylic Acid Salt (I-869), Carboxylic Acid Salt (I-919) to Carboxylic Acid Salt (I-923), Carboxylic Acid Salt (I-973) to Carboxylic Acid Salt (I-977), Carboxylic Acid Salt (I-1027) to Carboxylic Acid Salt (I-1031), Carboxylic Acid Salt (I-1081) to Carboxylic Acid Salt (I-1085), Carboxylic Acid Salt (I-1135) to Carboxylic Acid Salt (I-1139), Carboxylic Acid Salt (I-1189) to Carboxylic Acid Salt (I-119) 3), Carboxylate (I-1243) to Carboxylate (I-1247), Carboxylate (I-1297) to Carboxylate (I-1301), Carboxylate (I-1351) to Carboxylate (I-1355), Carboxylate (I-1405) to Carboxylate (I-1409), Carboxylate (I-1459) to Carboxylate (I-1463), Carboxylate (I-1513) to Carboxylate (I-1517), Carboxylate (I-1567) to Carboxylate (I-1571), Carboxylate (I-1621) to Carboxylate (I-1625), Carboxylate (I-1675) to Carboxylate (I-1679), Carboxylate (I-1729) to Carboxylate (I-1733), Carboxylate (I-1783) to Carboxylate (I-1787) ), Carboxylate (I-1837) to Carboxylate (I-1841), Carboxylate (I-1891) to Carboxylate (I-1895), Carboxylate (I-1945) to Carboxylate (I-1949), Carboxylate (I-1999) to Carboxylate (I-2003), Carboxylate (I-2053) to Carboxylate (I-2057), Carboxylate (I-2107) to Carboxylate (I-2111), Carboxylate (I-2161) to Carboxylate (I-2165), Carboxylate (I-2215) to Carboxylate (I-2219), Carboxylate (I-2269) to Carboxylate (I-2273), Carboxylate (I-2323) to Carboxylate (I-2327), Carboxylate (I-2377) to Carboxylate (I-2394), Carboxylate (I-2416) to Carboxylate (I-2433), Carboxylate (I-2455) to Carboxylate (I-2472), Carboxylate (I-2494) to Carboxylate (I-2511), Carboxylate (I-2533) to Carboxylate (I-2550), Carboxylate (I-2572) to Carboxylate (I-2589), Carboxylate (I-2611) to Carboxylate (I-2628), Carboxylate (I-2650) to Carboxylate (I-2667), Carboxylate (I-2689) to Carboxylate (I-2706), Carboxylate (I-2728) to Carboxylate (I-2745), Carboxylate (I-2767) to Carboxylate (I-2784), Carboxylate (I-2806) to Carboxylate (I-2823), Carboxylate (I-2845) to Carboxylate (I-2862), Carboxylate (I-2884) to Carboxylate (I-2901), Carboxylate (I-2923) to Carboxylate (I-2940), Carboxylate (I-2962) to Carboxylate (I-2979), Carboxylate (I-3001) to Carboxylate (I-3018), Carboxylate (I-3040) to Carboxylate (I-3057), Carboxylate (I-3079) to Carboxylate (I-3096), Carboxylate (I-3118) to Carboxylate (I-3135), Carboxylate (I-3157) to Carboxylate (I-3174), Carboxylate (I-3196) to Carboxylate (I-3213), Carboxylate (I-3235) to Carboxylate (I-3252), Carboxylate Carboxylic acid salt (I-3274) to carboxylate (I-3291), carboxylate (I-3313) to carboxylate (I-3330), carboxylate (I-3352) to carboxylate (I-3369), carboxylate (I-3391) to carboxylate (I-3408), carboxylate (I-3430) to carboxylate (I-3447), carboxylate (I-3469) to carboxylate (I-3486), carboxylate (I-3508) to carboxylate (I-3525), carboxylate (I-3547) to carboxylate (I-3564), carboxylate (I-3586) to carboxylate (I-3603), carboxylate (I-3625) to carboxylate (I-3642), carboxylate (I-3664) to carboxylate (I-3681), carboxylate Preferred are carboxylate (I-3703) to carboxylate (I-3720), carboxylate (I-3742) to carboxylate (I-3759), carboxylate (I-3781) to carboxylate (I-3798), carboxylate (I-3820) to carboxylate (I-3837), carboxylate (I-3859) to carboxylate (I-3876), carboxylate (I-3898) to carboxylate (I-3915), carboxylate (I-3937) to carboxylate (I-3954), carboxylate (I-3976) to carboxylate (I-3993), carboxylate (I-4015) to carboxylate (I-4032), carboxylate (I-4054) to carboxylate (I-4071), and carboxylate (I-4093) to carboxylate (I-4102).

<Method for producing salt (I)>
The salt (I) can be produced by reacting a salt represented by formula (Ia) with a salt represented by formula (Ib) in a solvent.
wherein all symbols have the same meanings as defined above.
R ^A , R ^B and R ^C each independently represent a hydrocarbon group having 1 to 12 carbon atoms, or R ^A , R ^B and R ^C may combine to form an aromatic ring. R ^D represents a hydrogen atom or a hydrocarbon group having 1 to 12 carbon atoms.]
Examples of solvents used in this reaction include chloroform, acetonitrile, and ion-exchanged water.
The reaction temperature is usually 15° C. to 80° C., and the reaction time is usually 0.5 to 24 hours.

The salt represented by formula (I-b) can be synthesized with reference to the methods described in JP-A-2011-39502 and JP-A-2014-88367, and examples thereof include salts represented by the following formulas:

The salt represented by formula (I-a) can be produced by reacting the salt represented by formula (I-c), a compound represented by formula (I-d1), a compound represented by formula (I-d2), and a compound represented by formula (I-d3) in a solvent in the presence of a catalyst.
[In the formula, all symbols have the same meanings as defined above.]
Examples of the catalyst include potassium carbonate and sodium hydride.
Examples of the solvent include chloroform, monochlorobenzene, acetonitrile, and water.
The reaction temperature is usually 15° C. to 100° C., and the reaction time is usually 0.5 to 24 hours.

Examples of the salt represented by formula (Ie) include salts represented by the following formula, which are readily available on the market.

Examples of the compound represented by formula (I-d1), the compound represented by formula (I-d2), and the compound represented by formula (I-d3) include the compounds represented below, which are easily available on the market.

The salt represented by formula (I-a) can be produced by reacting the salt represented by formula (I-e), a compound represented by formula (I-f1), a compound represented by formula (I-f2), and a compound represented by formula (I-f3) in a solvent in the presence of a base.
[In the formula, all symbols have the same meanings as defined above.]
Examples of the base include potassium hydroxide and sodium hydride.
Examples of the solvent include chloroform, monochlorobenzene, acetonitrile, and water.
The reaction temperature is usually 15° C. to 100° C., and the reaction time is usually 0.5 to 24 hours.

Examples of the salt represented by formula (Ie) include salts represented by the following formula, which are readily available on the market.

Examples of the compound represented by formula (I-f1), the compound represented by formula (I-f2), and the compound represented by formula (I-f3) include the compounds represented below, which are easily available on the market.

[Carboxylic Acid Generator]
The carboxylic acid generator of the present invention is an acid generator containing a carboxylic acid salt (I). The carboxylic acid salt (I) of the present invention can act as an acid generator in a resist composition. When the carboxylic acid salt (I) is used as an acid generator in a resist composition, the acid generator may contain only one type of carboxylic acid salt (I) or two or more types of carboxylic acid salts (I).
Furthermore, as will be described later, the acid generator of the present invention may further contain an acid generator other than the carboxylate (I) that is known in the resist field (hereinafter, this may be referred to as "acid generator (B)") and/or a carboxylic acid generator other than the carboxylate (I) that is known in the resist field. The acid generator (B) may be used alone or in combination of two or more kinds.
When the carboxylic acid generator of the present invention contains an acid generator (B) or the like, the ratio of the contents of the carboxylic acid salt (I) to the acid generator (B) or the like (mass ratio; carboxylic acid salt (I):acid generator (B)) is usually 1:99 to 100:0, preferably 1:99 to 99:1, more preferably 2:98 to 98:2, and even more preferably 5:95 to 95:5.

[Resist Composition]
The resist composition contains a carboxylic acid generator containing the carboxylic acid salt (I) of the present invention, an acid generator (B) other than the carboxylic acid salt (I), and a resin having an acid labile group (hereinafter may be referred to as "resin (A)"). Here, the "acid labile group" refers to a group that has a leaving group and that is eliminated upon contact with an acid to form a hydrophilic group (e.g., a hydroxy group or a carboxy group).
The resist composition preferably further contains a quencher (hereinafter sometimes referred to as "quencher (C)") and/or a solvent (hereinafter sometimes referred to as "solvent (E)").
In the resist composition of the present invention, the content of the carboxylate (I) is preferably from 0.1 to 35% by mass, more preferably from 0.5 to 30% by mass, and even more preferably from 1 to 25% by mass, relative to the solid content of the resist composition.

<Acid Generator (B)>
The acid generator (B) may be either nonionic or ionic. Examples of nonionic acid generators include sulfonate esters (e.g., 2-nitrobenzyl ester, aromatic sulfonate, oxime sulfonate, N-sulfonyloxyimide, sulfonyloxyketone, diazonaphthoquinone 4-sulfonate), sulfones (e.g., disulfone, ketosulfone, sulfonyldiazomethane), and the like. Examples of ionic acid generators include onium salts containing onium cations (e.g., diazonium salts, phosphonium salts, sulfonium salts, iodonium salts). Examples of the anion of the onium salt include a sulfonate anion, a sulfonylimide anion, and a sulfonylmethide anion.

The acid generator (B) may be a compound that generates an acid when exposed to radiation, as described in JP-A Nos. 63-26653, 55-164824, 62-69263, 63-146038, 63-163452, 62-153853, 63-146029, U.S. Pat. No. 3,779,778, 3,849,137, German Patent No. 3,914,407, or European Patent No. 126,712. Compounds produced by known methods may also be used. Two or more types of acid generator (B) may be used in combination.

The acid generator (B) is preferably a fluorine-containing acid generator, and more preferably a salt represented by formula (B1) (hereinafter, sometimes referred to as "acid generator (B1)").
[In formula (B1),
Q ^b1 and Q ^b2 each independently represent a fluorine atom or a perfluoroalkyl group having 1 to 6 carbon atoms.
L ^b1 represents a divalent saturated hydrocarbon group having 1 to 24 carbon atoms, wherein —CH ₂ — contained in the divalent saturated hydrocarbon group may be replaced by —O— or —CO—, and wherein a hydrogen atom contained in the divalent saturated hydrocarbon group may be substituted by a fluorine atom or a hydroxy group.
Y represents an optionally substituted methyl group or an optionally substituted alicyclic hydrocarbon group having 3 to 24 carbon atoms, and one —CH ₂ — contained in the alicyclic hydrocarbon group may be replaced by —O—, —SO ₂ — or —CO—.
Z ⁺ represents an organic cation.

Examples of the perfluoroalkyl group represented by Q ^b1 and Q ^b2 include a trifluoromethyl group, a perfluoroethyl group, a perfluoropropyl group, a perfluoroisopropyl group, a perfluorobutyl group, a perfluorosec-butyl group, a perfluorotert-butyl group, a perfluoropentyl group, and a perfluorohexyl group.
Q ^b1 and Q ^b2 each independently preferably represent a fluorine atom or a trifluoromethyl group, and more preferably represent both a fluorine atom.

Examples of the divalent saturated hydrocarbon group for L ^b1 include a linear alkanediyl group, a branched alkanediyl group, and a monocyclic or polycyclic divalent alicyclic saturated hydrocarbon group, and may be a group formed by combining two or more of these groups.
Specific examples thereof include linear alkanediyl groups such as a methylene group, an ethylene group, a propane-1,3-diyl group, a butane-1,4-diyl group, a pentane-1,5-diyl group, a hexane-1,6-diyl group, a heptane-1,7-diyl group, an octane-1,8-diyl group, a nonane-1,9-diyl group, a decane-1,10-diyl group, an undecane-1,11-diyl group, a dodecane-1,12-diyl group, a tridecane-1,13-diyl group, a tetradecane-1,14-diyl group, a pentadecane-1,15-diyl group, a hexadecane-1,16-diyl group, and a heptadecane-1,17-diyl group;
branched alkanediyl groups such as an ethane-1,1-diyl group, a propane-1,1-diyl group, a propane-1,2-diyl group, a propane-2,2-diyl group, a pentane-2,4-diyl group, a 2-methylpropane-1,3-diyl group, a 2-methylpropane-1,2-diyl group, a pentane-1,4-diyl group, and a 2-methylbutane-1,4-diyl group;
a monocyclic divalent alicyclic saturated hydrocarbon group such as a cycloalkanediyl group, such as a cyclobutane-1,3-diyl group, a cyclopentane-1,3-diyl group, a cyclohexane-1,4-diyl group, or a cyclooctane-1,5-diyl group;
Examples include polycyclic divalent alicyclic saturated hydrocarbon groups such as norbornane-1,4-diyl group, norbornane-2,5-diyl group, adamantane-1,5-diyl group, and adamantane-2,6-diyl group.

Examples of the divalent saturated hydrocarbon group represented by L ^b1 in which one —CH ₂ — group is replaced by —O— or —CO— include groups represented by any of formulas (b1-1) to (b1-3). In the groups represented by formulas (b1-1) to (b1-3) and specific examples thereof, groups represented by formulas (b1-4) to (b1-11), * and ** represent bonding positions, and * represents the bonding position to —Y.

[In formula (b1-1),
L ^b2 represents a single bond or a divalent saturated hydrocarbon group having 1 to 22 carbon atoms, and a hydrogen atom contained in the saturated hydrocarbon group may be substituted with a fluorine atom.
L ^b3 represents a single bond or a divalent saturated hydrocarbon group having 1 to 22 carbon atoms, and a hydrogen atom contained in the saturated hydrocarbon group may be substituted with a fluorine atom or a hydroxy group, and a —CH ₂ — contained in the saturated hydrocarbon group may be substituted with —O— or —CO—.
However, the total number of carbon atoms in L ^b2 and L ^b3 is 22 or less.
In formula (b1-2),
L ^b4 represents a single bond or a divalent saturated hydrocarbon group having 1 to 22 carbon atoms, and a hydrogen atom contained in the saturated hydrocarbon group may be substituted with a fluorine atom.
L ^b5 represents a single bond or a divalent saturated hydrocarbon group having 1 to 22 carbon atoms, wherein a hydrogen atom contained in the saturated hydrocarbon group may be substituted with a fluorine atom or a hydroxy group, and wherein a —CH ₂ — contained in the saturated hydrocarbon group may be substituted with —O— or —CO—.
However, the total number of carbon atoms in L ^b4 and L ^b5 is 22 or less.
In formula (b1-3),
L ^b6 represents a single bond or a divalent saturated hydrocarbon group having 1 to 23 carbon atoms, and a hydrogen atom contained in the saturated hydrocarbon group may be substituted with a fluorine atom or a hydroxy group.
L ^b7 represents a single bond or a divalent saturated hydrocarbon group having 1 to 23 carbon atoms, wherein a hydrogen atom contained in the saturated hydrocarbon group may be substituted with a fluorine atom or a hydroxy group, and wherein a —CH ₂ — contained in the saturated hydrocarbon group may be substituted with —O— or —CO—.
However, the total number of carbon atoms in L ^b6 and L ^b7 is 23 or less.]

In the groups represented by formulae (b1-1) to (b1-3), when —CH ₂ — contained in the saturated hydrocarbon group is replaced with —O— or —CO—, the number of carbon atoms before replacement is regarded as the number of carbon atoms of the saturated hydrocarbon group.
Examples of the divalent saturated hydrocarbon group include the same divalent saturated hydrocarbon groups as those for L ^b1 .

L ^b2 is preferably a single bond.
L ^b3 is preferably a divalent saturated hydrocarbon group having 1 to 4 carbon atoms.
L ^b4 is preferably a divalent saturated hydrocarbon group having 1 to 8 carbon atoms, and a hydrogen atom contained in the divalent saturated hydrocarbon group may be substituted with a fluorine atom.
L ^b5 is preferably a single bond or a divalent saturated hydrocarbon group having 1 to 8 carbon atoms.
L ^b6 is preferably a single bond or a divalent saturated hydrocarbon group having 1 to 4 carbon atoms, and a hydrogen atom contained in the saturated hydrocarbon group may be substituted with a fluorine atom.
L ^b7 is preferably a single bond or a divalent saturated hydrocarbon group having 1 to 18 carbon atoms, in which a hydrogen atom contained in the saturated hydrocarbon group may be substituted with a fluorine atom or a hydroxy group, and a —CH ₂ — contained in the divalent saturated hydrocarbon group may be substituted with —O— or —CO—.

As the divalent saturated hydrocarbon group represented by L ^b1 in which one —CH ₂ — group is replaced by —O— or —CO—, a group represented by formula (b1-1) or formula (b1-3) is preferred.

Examples of the group represented by formula (b1-1) include groups represented by formulas (b1-4) to (b1-8).
[In formula (b1-4),
L ^b8 represents a single bond or a divalent saturated hydrocarbon group having 1 to 22 carbon atoms, and a hydrogen atom contained in the saturated hydrocarbon group may be substituted with a fluorine atom or a hydroxy group.
In formula (b1-5),
L ^b9 represents a divalent saturated hydrocarbon group having 1 to 20 carbon atoms, and one —CH ₂ — contained in the divalent saturated hydrocarbon group may be replaced by —O— or —CO—.
L ^b10 represents a single bond or a divalent saturated hydrocarbon group having 1 to 19 carbon atoms, and a hydrogen atom contained in the divalent saturated hydrocarbon group may be substituted with a fluorine atom or a hydroxy group.
However, the total number of carbon atoms in L ^b9 and L ^b10 is 20 or less.
In formula (b1-6),
L ^b11 represents a divalent saturated hydrocarbon group having 1 to 21 carbon atoms.
L ^b12 represents a single bond or a divalent saturated hydrocarbon group having 1 to 20 carbon atoms, and a hydrogen atom contained in the divalent saturated hydrocarbon group may be substituted with a fluorine atom or a hydroxy group.
However, the total number of carbon atoms in L ^b11 and L ^b12 is 21 or less.
In formula (b1-7),
L ^b13 represents a divalent saturated hydrocarbon group having 1 to 19 carbon atoms.
L ^b14 represents a single bond or a divalent saturated hydrocarbon group having 1 to 18 carbon atoms, and one --CH ₂ -- contained in the divalent saturated hydrocarbon group may be replaced with --O-- or --CO--.
L ^b15 represents a single bond or a divalent saturated hydrocarbon group having 1 to 18 carbon atoms, and a hydrogen atom contained in the divalent saturated hydrocarbon group may be substituted with a fluorine atom or a hydroxy group.
However, the total number of carbon atoms of L ^b13 to L ^b15 is 19 or less.
In formula (b1-8),
L ^b16 represents a divalent saturated hydrocarbon group having 1 to 18 carbon atoms, and one --CH ₂ -- contained in the divalent saturated hydrocarbon group may be replaced by --O-- or --CO--.
L ^b17 represents a divalent saturated hydrocarbon group having 1 to 18 carbon atoms.
L ^b18 represents a single bond or a divalent saturated hydrocarbon group having 1 to 17 carbon atoms, and a hydrogen atom contained in the divalent saturated hydrocarbon group may be substituted with a fluorine atom or a hydroxy group.
However, the total number of carbon atoms of L ^b16 to L ^b18 is 19 or less.]

L ^b8 is preferably a divalent saturated hydrocarbon group having 1 to 4 carbon atoms.
L ^b9 is preferably a divalent saturated hydrocarbon group having 1 to 8 carbon atoms.
L ^b10 is preferably a single bond or a divalent saturated hydrocarbon group having 1 to 19 carbon atoms, and more preferably a single bond or a divalent saturated hydrocarbon group having 1 to 8 carbon atoms.
L ^b11 is preferably a divalent saturated hydrocarbon group having 1 to 8 carbon atoms.
L ^b12 is preferably a single bond or a divalent saturated hydrocarbon group having 1 to 8 carbon atoms.
L ^b13 is preferably a divalent saturated hydrocarbon group having 1 to 12 carbon atoms.
L ^b14 is preferably a single bond or a divalent saturated hydrocarbon group having 1 to 6 carbon atoms.
L ^b15 is preferably a single bond or a divalent saturated hydrocarbon group having 1 to 18 carbon atoms, and more preferably a single bond or a divalent saturated hydrocarbon group having 1 to 8 carbon atoms.
L ^b16 is preferably a divalent saturated hydrocarbon group having 1 to 12 carbon atoms.
L ^b17 is preferably a divalent saturated hydrocarbon group having 1 to 6 carbon atoms.
L ^b18 is preferably a single bond or a divalent saturated hydrocarbon group having 1 to 17 carbon atoms, and more preferably a single bond or a divalent saturated hydrocarbon group having 1 to 4 carbon atoms.

Examples of the group represented by formula (b1-3) include groups represented by formulas (b1-9) to (b1-11).
[In formula (b1-9),
L ^b19 represents a single bond or a divalent saturated hydrocarbon group having 1 to 23 carbon atoms, and a hydrogen atom contained in the saturated hydrocarbon group may be substituted with a fluorine atom.
L ^b20 represents a single bond or a divalent saturated hydrocarbon group having 1 to 23 carbon atoms, wherein a hydrogen atom contained in the saturated hydrocarbon group may be substituted with a fluorine atom, a hydroxy group, or an alkylcarbonyloxy group, wherein a —CH ₂ — contained in the alkylcarbonyloxy group may be replaced with —O— or —CO—, and a hydrogen atom contained in the alkylcarbonyloxy group may be substituted with a hydroxy group.
However, the total number of carbon atoms in L ^b19 and L ^b20 is 23 or less.
In formula (b1-10),
L ^b21 represents a single bond or a divalent saturated hydrocarbon group having 1 to 21 carbon atoms, and a hydrogen atom contained in the saturated hydrocarbon group may be substituted with a fluorine atom.
L ^b22 represents a single bond or a divalent saturated hydrocarbon group having 1 to 21 carbon atoms.
L ^b23 represents a single bond or a divalent saturated hydrocarbon group having 1 to 21 carbon atoms, and a hydrogen atom contained in the saturated hydrocarbon group may be substituted with a fluorine atom, a hydroxy group, or an alkylcarbonyloxy group. A —CH ₂ — contained in the alkylcarbonyloxy group may be replaced with —O— or —CO—, and a hydrogen atom contained in the alkylcarbonyloxy group may be substituted with a hydroxy group.
However, the total number of carbon atoms of L ^b21 , L ^b22 and L ^b23 is 21 or less.
In formula (b1-11),
L ^b24 represents a single bond or a divalent saturated hydrocarbon group having 1 to 20 carbon atoms, and a hydrogen atom contained in the saturated hydrocarbon group may be substituted with a fluorine atom.
L ^b25 represents a divalent saturated hydrocarbon group having 1 to 21 carbon atoms.
L ^b26 represents a single bond or a divalent saturated hydrocarbon group having 1 to 20 carbon atoms, and a hydrogen atom contained in the saturated hydrocarbon group may be substituted with a fluorine atom, a hydroxy group, or an alkylcarbonyloxy group. A —CH ₂ — contained in the alkylcarbonyloxy group may be replaced with —O— or —CO—, and a hydrogen atom contained in the alkylcarbonyloxy group may be substituted with a hydroxy group.
However, the total number of carbon atoms in L ^b24 , L ^b25 and L ^b26 is 21 or less.]

In addition, in the groups represented by formulas (b1-9) to (b1-11), when a hydrogen atom contained in the saturated hydrocarbon group is substituted with an alkylcarbonyloxy group, the number of carbon atoms before substitution is regarded as the number of carbon atoms in the saturated hydrocarbon group.

Examples of alkylcarbonyloxy groups include acetyloxy groups, propionyloxy groups, butyryloxy groups, cyclohexylcarbonyloxy groups, and adamantylcarbonyloxy groups.

Examples of the group represented by formula (b1-4) include the following.

Examples of the group represented by formula (b1-5) include the following.

Examples of the group represented by formula (b1-6) include the following.

Examples of the group represented by formula (b1-7) include the following.

Examples of the group represented by formula (b1-8) include the following.

Examples of the group represented by formula (b1-2) include the following.

Examples of the group represented by formula (b1-9) include the following.

Examples of the group represented by formula (b1-10) include the following.

Examples of the group represented by formula (b1-11) include the following.

Examples of the alicyclic hydrocarbon group represented by Y include groups represented by formulae (Y1) to (Y11) and (Y36) to (Y38).
When a —CH ₂ — contained in the alicyclic hydrocarbon group represented by Y is replaced by —O—, —SO ₂ — or —CO—, the number may be 1 or 2 or more. Examples of such groups include groups represented by formulae (Y12) to (Y35) and formulae (Y39) to (Y43). * represents the bonding site with ^L1 .

The alicyclic hydrocarbon group represented by Y is preferably a group represented by any one of formulas (Y1) to (Y20), (Y26), (Y27), (Y30), (Y31), and (Y39) to (Y43), more preferably a group represented by formula (Y11), (Y15), (Y16), (Y20), (Y26), (Y27), (Y30), (Y31), (Y39), (Y40), (Y42), or (Y43), and even more preferably a group represented by formula (Y11), (Y15), (Y20), (Y26), (Y27), (Y30), (Y31), (Y39), (Y40), (Y42), or (Y43).
When the alicyclic hydrocarbon group represented by Y is a spiro ring such as those of formulae (Y28) to (Y35), (Y39) to (Y40), (Y42) or (Y43), the alkanediyl group between the two oxygen atoms preferably has one or more fluorine atoms. Furthermore, among the alkanediyl groups contained in the ketal structure, it is preferred that the methylene group adjacent to the oxygen atom is not substituted with a fluorine atom.

Examples of the substituent on the methyl group represented by ^Y1 include a halogen atom, a hydroxy group, an alicyclic hydrocarbon group having 3 to 16 carbon atoms, an aromatic hydrocarbon group having 6 to 18 carbon atoms, a glycidyloxy group, a -(CH ₂ ) _ja -CO-O-R ^b1 group, or a -(CH ₂ ) _ja -O-CO-R ^b1 group (wherein R ^b1 represents an alkyl group having 1 to 16 carbon atoms, an alicyclic hydrocarbon group having 3 to 16 carbon atoms, an aromatic hydrocarbon group having 6 to 18 carbon atoms, or a group formed by combining these; ja represents an integer of 0 to 4; -CH ₂ - contained in the alkyl group and the alicyclic hydrocarbon group may be replaced by -O-, -SO ₂ - or -CO-; and a hydrogen atom contained in the alkyl group, the alicyclic hydrocarbon group, and the aromatic hydrocarbon group may be replaced by a hydroxy group or a fluorine atom).
Substituents for the alicyclic hydrocarbon group represented by ^Y1 include a halogen atom, a hydroxy group, an alkyl group having 1 to 16 carbon atoms which may be substituted with a hydroxy group (wherein —CH ₂ — contained in the alkyl group may be replaced with —O— or —CO—), an alicyclic hydrocarbon group having 3 to 16 carbon atoms, an aromatic hydrocarbon group having 6 to 18 carbon atoms, an aralkyl group having 7 to 21 carbon atoms, a glycidyloxy group, a —(CH ₂ ) _ja -CO-O-R ^b1 group, or a —(CH ₂ ) _ja -O-CO-R ^b1 group (wherein R ^b1 represents an alkyl group having 1 to 16 carbon atoms, an alicyclic hydrocarbon group having 3 to 16 carbon atoms, an aromatic hydrocarbon group having 6 to 18 carbon atoms, or a group combining these; ja represents an integer of 0 to 4. The —CH ₂ — contained in the alkyl group and the alicyclic hydrocarbon group may be replaced with —O—, —SO ₂ - or -CO-, and a hydrogen atom contained in the alkyl group, the alicyclic hydrocarbon group, and the aromatic hydrocarbon group may be replaced by a hydroxy group or a fluorine atom.

Examples of the halogen atom include a fluorine atom, a chlorine atom, a bromine atom, and an iodine atom.
Examples of the alicyclic hydrocarbon group include a cyclopentyl group, a cyclohexyl group, a methylcyclohexyl group, a dimethylcyclohexyl group, a cycloheptyl group, a cyclooctyl group, a norbornyl group, and an adamantyl group. The alicyclic hydrocarbon group may have a chain hydrocarbon group, such as a methylcyclohexyl group or a dimethylcyclohexyl group. The number of carbon atoms in the alicyclic hydrocarbon group is preferably 3 to 12, and more preferably 3 to 10.
Examples of aromatic hydrocarbon groups include aryl groups such as phenyl, naphthyl, anthryl, biphenyl, and phenanthryl. The aromatic hydrocarbon group may have a chain hydrocarbon group or an alicyclic hydrocarbon group, and examples include aromatic hydrocarbon groups having a chain hydrocarbon group of 1 to 18 carbon atoms (such as tolyl, xylyl, cumenyl, mesityl, p-methylphenyl, p-ethylphenyl, p-tert-butylphenyl, 2,6-diethylphenyl, and 2-methyl-6-ethylphenyl), and aromatic hydrocarbon groups having an alicyclic hydrocarbon group of 3 to 18 carbon atoms (such as p-cyclohexylphenyl and p-adamantylphenyl). The aromatic hydrocarbon group preferably has 6 to 14 carbon atoms, and more preferably 6 to 10 carbon atoms.
Examples of the alkyl group include a methyl group, an ethyl group, a propyl group, an isopropyl group, a butyl group, a sec-butyl group, a tert-butyl group, a pentyl group, a hexyl group, a heptyl group, a 2-ethylhexyl group, an octyl group, a nonyl group, a decyl group, an undecyl group, a dodecyl group, etc. The number of carbon atoms in the alkyl group is preferably 1 to 12, more preferably 1 to 6, and even more preferably 1 to 4.
Examples of the alkyl group substituted with a hydroxy group include hydroxyalkyl groups such as a hydroxymethyl group and a hydroxyethyl group.
Examples of the aralkyl group include a benzyl group, a phenethyl group, a phenylpropyl group, a naphthylmethyl group, and a naphthylethyl group.
Examples of the alkyl group in which --CH ₂ -- is replaced by --O--, --SO ₂ --, --CO-- or the like include an alkoxy group, an alkoxycarbonyl group, an alkylcarbonyl group, an alkylcarbonyloxy group, or a combination thereof.
Examples of the alkoxy group include a methoxy group, an ethoxy group, a propoxy group, a butoxy group, a pentyloxy group, a hexyloxy group, a heptyloxy group, an octyloxy group, a decyloxy group, and a dodecyloxy group. The number of carbon atoms in the alkoxy group is preferably 1 to 12, more preferably 1 to 6, and even more preferably 1 to 4.
Examples of the alkoxycarbonyl group include a methoxycarbonyl group, an ethoxycarbonyl group, a butoxycarbonyl group, etc. The number of carbon atoms in the alkoxycarbonyl group is preferably 2 to 12, more preferably 2 to 6, and even more preferably 2 to 4.
Examples of the alkylcarbonyl group include an acetyl group, a propionyl group, and a butyryl group. The alkylcarbonyl group preferably has 2 to 12 carbon atoms, more preferably 2 to 6 carbon atoms, and even more preferably 2 to 4 carbon atoms.
Examples of the alkylcarbonyloxy group include an acetyloxy group, a propionyloxy group, a butyryloxy group, etc. The number of carbon atoms in the alkylcarbonyloxy group is preferably 2 to 12, more preferably 2 to 6, and even more preferably 2 to 4.
Examples of the combined group include a group combining an alkoxy group and an alkyl group, a group combining an alkoxy group and an alkoxy group, a group combining an alkoxy group and an alkylcarbonyl group, and a group combining an alkoxy group and an alkylcarbonyloxy group.
Examples of the group combining an alkoxy group and an alkyl group include alkoxyalkyl groups such as a methoxymethyl group, a methoxyethyl group, an ethoxyethyl group, an ethoxymethyl group, etc. The number of carbon atoms in the alkoxyalkyl group is preferably 2 to 12, more preferably 2 to 6, and even more preferably 2 to 4.
Examples of a group formed by combining an alkoxy group with another alkoxy group include alkoxyalkoxy groups such as a methoxymethoxy group, a methoxyethoxy group, an ethoxymethoxy group, and an ethoxyethoxy group. The number of carbon atoms in the alkoxyalkoxy group is preferably 2 to 12, more preferably 2 to 6, and even more preferably 2 to 4.
Examples of the group combining an alkoxy group and an alkylcarbonyl group include alkoxyalkylcarbonyl groups such as a methoxyacetyl group, a methoxypropionyl group, an ethoxyacetyl group, an ethoxypropionyl group, etc. The number of carbon atoms in the alkoxyalkylcarbonyl group is preferably 3 to 13, more preferably 3 to 7, and even more preferably 3 to 5.
Examples of a group combining an alkoxy group and an alkylcarbonyloxy group include alkoxyalkylcarbonyloxy groups such as a methoxyacetyloxy group, a methoxypropionyloxy group, an ethoxyacetyloxy group, an ethoxypropionyloxy group, etc. The number of carbon atoms in the alkoxyalkylcarbonyloxy group is preferably 3 to 13, more preferably 3 to 7, and even more preferably 3 to 5.
Examples of the alicyclic hydrocarbon group in which —CH ₂ — is replaced by —O—, —SO ₂ —, —CO— or the like include groups represented by formulae (Y12) to (Y35) and formulae (Y39) to (Y43).

Examples of ^Y1 include the following.

Y is preferably an alicyclic hydrocarbon group of 3 to 24 carbon atoms which may have a substituent, more preferably an alicyclic hydrocarbon group of 3 to 20 carbon atoms which may have a substituent, even more preferably an alicyclic hydrocarbon group of 3 to 18 carbon atoms which may have a substituent, and even more preferably an adamantyl group which may have a substituent, wherein —CH ₂ — constituting the alicyclic hydrocarbon group or the adamantyl group may be replaced by —CO—, —SO ₂ — or —CO—. Specifically, Y is preferably an adamantyl group, a hydroxyadamantyl group, an oxoadamantyl group, or a group represented by formula (Y42), or a group represented by formula (Y100) to formula (Y114).

The anion in the salt represented by formula (B1) is preferably an anion represented by formula (B1-A-1) to formula (B1-A-59) (hereinafter, these may be referred to as "anion (B1-A-1)" or the like depending on the formula number). An anion represented by any of formulas (B1-A-1) to (B1-A-4), (B1-A-9), (B1-A-10), (B1-A-24) to (B1-A-33), (B1-A-36) to (B1-A-40), and (B1-A-47) to (B1-A-59) is more preferred.

Here, R ⁱ² to R ⁱ⁷ are each independently, for example, an alkyl group having 1 to 4 carbon atoms, preferably a methyl group or an ethyl group. ^{R i8} is, for example, an open-chain hydrocarbon group having 1 to 12 carbon atoms, preferably an alkyl group having 1 to 4 carbon atoms, an alicyclic hydrocarbon group having 5 to 12 carbon atoms, or a group formed by combining these, more preferably a methyl group, an ethyl group, a cyclohexyl group, or an adamantyl group. ^{L A4} is a single bond or an alkanediyl group having 1 to 4 carbon atoms. ^{Q 1} and Q ² have the same meaning as above.
Specific examples of the anion represented by formula (IA) include the anions described in JP-A-2010-204646.

Preferable anions in the salt represented by formula (B1) include anions represented by formulas (B1a-1) to (B1a-38).

Among these, anions represented by any of formulas (B1a-1) to (B1a-3), (B1a-7) to (B1a-16), (B1a-18), (B1a-19), and (B1a-22) to (B1a-38) are preferred.

Examples of the organic cation for Z1 ⁺ include organic onium cations, organic sulfonium cations, organic iodonium cations, organic ammonium cations, benzothiazolium cations, and organic phosphonium cations. Among these, organic sulfonium cations and organic iodonium cations are preferred, and arylsulfonium cations are more preferred. Specific examples include cations represented by any of formulas (b2-1) to (b2-4) (hereinafter, these may be referred to as "cation (b2-1)" or the like depending on the formula number).
In formulas (b2-1) to (b2-4),
R ^b4 to R ^b6 each independently represent a chain hydrocarbon group having 1 to 30 carbon atoms, an alicyclic hydrocarbon group having 3 to 36 carbon atoms, or an aromatic hydrocarbon group having 6 to 36 carbon atoms, a hydrogen atom contained in the chain hydrocarbon group may be substituted with a hydroxy group, an alkoxy group having 1 to 12 carbon atoms, an alicyclic hydrocarbon group having 3 to 12 carbon atoms, or an aromatic hydrocarbon group having 6 to 18 carbon atoms, a hydrogen atom contained in the alicyclic hydrocarbon group may be substituted with a halogen atom, an aliphatic hydrocarbon group having 1 to 18 carbon atoms, an alkylcarbonyl group having 2 to 4 carbon atoms, or a glycidyloxy group, and a hydrogen atom contained in the aromatic hydrocarbon group may be substituted with a halogen atom, a hydroxy group, an aliphatic hydrocarbon group having 1 to 18 carbon atoms, a fluorinated alkyl group having 1 to 12 carbon atoms, or an alkoxy group having 1 to 12 carbon atoms.
R ^b4 and R ^b5 may be bonded to each other to form a ring together with the sulfur atom to which they are bonded, and —CH ₂ — contained in the ring may be replaced by —O—, —S— or —CO—.
R ^b7 and R ^b8 each independently represent a halogen atom, a hydroxy group, an aliphatic hydrocarbon group having 1 to 12 carbon atoms, or an alkoxy group having 1 to 12 carbon atoms.
m2 and n2 each independently represent an integer of 0 to 5.
When m2 is 2 or more, multiple R ^b7s may be the same or different, and when n2 is 2 or more, multiple R ^b8s may be the same or different.
R ^b9 and R ^b10 each independently represent a chain hydrocarbon group having 1 to 36 carbon atoms or an alicyclic hydrocarbon group having 3 to 36 carbon atoms.
R ^b9 and R ^b10 may be bonded to each other to form a ring together with the sulfur atom to which they are bonded, and --CH ₂ -- contained in the ring may be replaced with --O--, --S-- or --CO--.
R ^b11 represents a hydrogen atom, a chain hydrocarbon group having 1 to 36 carbon atoms, an alicyclic hydrocarbon group having 3 to 36 carbon atoms, or an aromatic hydrocarbon group having 6 to 18 carbon atoms.
R ^b12 represents a chain hydrocarbon group having 1 to 12 carbon atoms, an alicyclic hydrocarbon group having 3 to 18 carbon atoms, or an aromatic hydrocarbon group having 6 to 18 carbon atoms, and a hydrogen atom contained in the chain hydrocarbon group may be substituted with an aromatic hydrocarbon group having 6 to 18 carbon atoms, or a hydrogen atom contained in the aromatic hydrocarbon group may be substituted with an alkoxy group having 1 to 12 carbon atoms or an alkylcarbonyloxy group having 1 to 12 carbon atoms.
R ^b11 and R ^b12 may be bonded to each other to form a ring including the —CH—CO— to which they are bonded, and —CH ₂ — contained in the ring may be replaced by —O—, —S— or —CO—.
R ^b13 to R ^b18 each independently represent a halogen atom, a hydroxy group, an aliphatic hydrocarbon group having 1 to 12 carbon atoms, or an alkoxy group having 1 to 12 carbon atoms.
L ^b31 represents a sulfur atom or an oxygen atom.
o2, p2, s2, and t2 each independently represent an integer of 0 to 5.
q2 and r2 each independently represent an integer of 0 to 4.
u2 represents 0 or 1;
When o2 is 2 or more, multiple R ^b13s are the same or different; when p2 is 2 or more, multiple R ^b14s are the same or different; when q2 is 2 or more, multiple R ^b15s are the same or different; when r2 is 2 or more, multiple R ^b16s are the same or different; when s2 is 2 or more, multiple R ^b17s are the same or different; and when t2 is 2 or more, multiple R ^b18s are the same or different.
The aliphatic hydrocarbon group refers to a chain hydrocarbon group and an alicyclic hydrocarbon group.
Examples of the chain hydrocarbon group include alkyl groups such as methyl, ethyl, propyl, isopropyl, butyl, sec-butyl, tert-butyl, pentyl, hexyl, octyl, and 2-ethylhexyl.
In particular, the chain hydrocarbon groups of R ^b9 to R ^b12 preferably have 1 to 12 carbon atoms.
The alicyclic hydrocarbon group may be either monocyclic or polycyclic, and examples of the monocyclic alicyclic hydrocarbon group include cycloalkyl groups such as cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl, cycloheptyl, cyclooctyl, and cyclodecyl. Examples of the polycyclic alicyclic hydrocarbon group include decahydronaphthyl, adamantyl, and norbornyl groups, as well as the following groups:
In particular, the alicyclic hydrocarbon groups of R ^b9 to R ^b12 preferably have 3 to 18 carbon atoms, and more preferably have 4 to 12 carbon atoms.
Examples of the alicyclic hydrocarbon group in which a hydrogen atom is substituted with an aliphatic hydrocarbon group include a methylcyclohexyl group, a dimethylcyclohexyl group, a 2-methyladamantan-2-yl group, a 2-ethyladamantan-2-yl group, a 2-isopropyladamantan-2-yl group, a methylnorbornyl group, an isobornyl group, etc. In the alicyclic hydrocarbon group in which a hydrogen atom is substituted with an aliphatic hydrocarbon group, the total number of carbon atoms in the alicyclic hydrocarbon group and the aliphatic hydrocarbon group is preferably 20 or less.
The fluorinated alkyl group refers to an alkyl group having 1 to 12 carbon atoms and a fluorine atom, and examples thereof include a fluoromethyl group, a difluoromethyl group, a trifluoromethyl group, a perfluorobutyl group, etc. The number of carbon atoms in the fluorinated alkyl group is preferably 1 to 9, more preferably 1 to 6, and even more preferably 1 to 4.
Examples of aromatic hydrocarbon groups include aryl groups such as a phenyl group, a biphenyl group, a naphthyl group, and a phenanthryl group. The aromatic hydrocarbon group may have a chain hydrocarbon group or an alicyclic hydrocarbon group, and examples thereof include aromatic hydrocarbon groups having a chain hydrocarbon group of 1 to 18 carbon atoms (such as a tolyl group, a xylyl group, a cumenyl group, a mesityl group, a p-ethylphenyl group, a p-tert-butylphenyl group, a 2,6-diethylphenyl group, and a 2-methyl-6-ethylphenyl group), and aromatic hydrocarbon groups having an alicyclic hydrocarbon group of 3 to 18 carbon atoms (such as a p-cyclohexylphenyl group and a p-adamantylphenyl group).
When the aromatic hydrocarbon group has a chain hydrocarbon group or an alicyclic hydrocarbon group, a chain hydrocarbon group having 1 to 18 carbon atoms and an alicyclic hydrocarbon group having 3 to 18 carbon atoms are preferred.
Examples of aromatic hydrocarbon groups in which hydrogen atoms are substituted with alkoxy groups include p-methoxyphenyl groups.
Examples of the chain hydrocarbon group in which a hydrogen atom is substituted with an aromatic hydrocarbon group include aralkyl groups such as a benzyl group, a phenethyl group, a phenylpropyl group, a trityl group, a naphthylmethyl group, and a naphthylethyl group.
Examples of the alkoxy group include a methoxy group, an ethoxy group, a propoxy group, a butoxy group, a pentyloxy group, a hexyloxy group, a heptyloxy group, an octyloxy group, a decyloxy group, and a dodecyloxy group.
Examples of the alkylcarbonyl group include an acetyl group, a propionyl group, and a butyryl group.
Examples of the halogen atom include a fluorine atom, a chlorine atom, a bromine atom, and an iodine atom.
Examples of the alkylcarbonyloxy group include a methylcarbonyloxy group, an ethylcarbonyloxy group, a propylcarbonyloxy group, an isopropylcarbonyloxy group, a butylcarbonyloxy group, a sec-butylcarbonyloxy group, a tert-butylcarbonyloxy group, a pentylcarbonyloxy group, a hexylcarbonyloxy group, an octylcarbonyloxy group, and a 2-ethylhexylcarbonyloxy group.
The ring formed by R ^b4 and R ^b5 bonding to each other and together with the sulfur atom to which they are bonded may be any of a monocyclic, polycyclic, aromatic, non-aromatic, saturated, and unsaturated ring. This ring may be a ring having 3 to 18 carbon atoms, and preferably a ring having 4 to 18 carbon atoms. Furthermore, the ring containing a sulfur atom may be a 3- to 12-membered ring, and preferably a 3- to 7-membered ring, and examples thereof include the rings shown below. * represents a bonding position.
The ring formed by R ^b9 and R ^b10 together may be any of monocyclic, polycyclic, aromatic, non-aromatic, saturated and unsaturated rings. This ring may be a 3- to 12-membered ring, preferably a 3- to 7-membered ring. Examples of this ring include a thiolan-1-ium ring (tetrahydrothiophenium ring), a thian-1-ium ring, and a 1,4-oxathian-4-ium ring.
The ring formed by R ^b11 and R ^b12 together may be any of monocyclic, polycyclic, aromatic, non-aromatic, saturated and unsaturated rings. This ring may be a 3- to 12-membered ring, preferably a 3- to 7-membered ring. Examples of the ring include an oxocycloheptane ring, an oxocyclohexane ring, an oxonorbornane ring, and an oxoadamantane ring.

Among the cations (b2-1) to (b2-4), the cation (b2-1) is preferred.
Examples of the cation (b2-1) include the following cations.

Examples of the cation (b2-2) include the following cations.

Examples of the cation (b2-3) include the following cations.

Examples of the cation (b2-4) include the following cations.

Acid generator (B) is a combination of the above-mentioned anions and the above-mentioned organic cations, and these can be combined in any desired manner. Acid generator (B) is preferably a combination of an anion represented by any of formulas (B1a-1) to (B1a-3), (B1a-7) to (B1a-16), (B1a-18), (B1a-19), and (B1a-22) to (B1a-38) with cation (b2-1), cation (b2-3), or cation (b2-4).

Preferred examples of the acid generator (B) include those represented by formulas (B1-1) to (B1-56). Among these, those containing an arylsulfonium cation are preferred, and those represented by formulas (B1-1) to (B1-3), (B1-5) to (B1-7), (B1-11) to (B1-14), (B1-20) to (B1-26), (B1-29), and (B1-31) to (B1-56) are particularly preferred.

In the resist composition of the present invention, the content of the acid generator (B) is preferably 1 part by mass or more and 45 parts by mass or less, more preferably 1 part by mass or more and 40 parts by mass or less, and even more preferably 3 parts by mass or more and 35 parts by mass or less, per 100 parts by mass of the resin (A). The resist composition of the present invention may contain one type of acid generator (B) alone, or may contain multiple types.

<Resin (A)>
Resin (A) has a structural unit having an acid labile group (hereinafter may be referred to as "structural unit (a1)"). Resin (A) preferably further contains a structural unit other than the structural unit (a1). Examples of structural units other than the structural unit (a1) include a structural unit not having an acid labile group (hereinafter may be referred to as "structural unit (s)"), structural units other than the structural unit (a1) and the structural unit (s) (for example, a structural unit having a halogen atom (hereinafter may be referred to as "structural unit (a4)") described below, a structural unit having a non-leaving hydrocarbon group (hereinafter may be referred to as "structural unit (a5)") described below), and other structural units derived from monomers known in the art.

<Structural Unit (a1)>
The structural unit (a1) is derived from a monomer having an acid labile group (hereinafter, sometimes referred to as "monomer (a1)").
The acid labile group contained in the resin (A) is preferably a group represented by formula (1) (hereinafter also referred to as group (1)) and/or a group represented by formula (2) (hereinafter also referred to as group (2)).
[In formula (1), R ^a1 , R ^a2 and R ^a3 each independently represent an alkyl group having 1 to 8 carbon atoms, an alkenyl group having 2 to 8 carbon atoms, an alicyclic hydrocarbon group having 3 to 20 carbon atoms, an aromatic hydrocarbon group having 6 to 18 carbon atoms, or a group combining these, or R ^a1 and R ^a2 bond to each other to form an alicyclic hydrocarbon group having 3 to 20 carbon atoms together with the carbon atom to which they are bonded.]
ma and na each independently represent 0 or 1, and at least one of ma and na represents 1.
* indicates the bond position.
[In formula (2), R ^a1' and R ^a2' each independently represent a hydrogen atom or a hydrocarbon group having 1 to 12 carbon atoms; R ^a3' represents a hydrocarbon group having 1 to 20 carbon atoms; or R ^a2' and R ^a3' are bonded to each other to form, together with the carbon atom to which they are bonded and X, a heterocyclic group having 3 to 20 carbon atoms, and —CH ₂ — contained in the hydrocarbon group and the heterocyclic group may be replaced by —O— or —S—.]
X represents an oxygen atom or a sulfur atom.
na' represents 0 or 1.
* represents a bond.

Examples of the alkyl group in R ^a1 , R ^a2 and R ^a3 include a methyl group, an ethyl group, a propyl group, a butyl group, a pentyl group, a hexyl group, a heptyl group and an octyl group.
Examples of the alkenyl group for R ^a1 , R ^a2 and R ^a3 include an ethenyl group, a propenyl group, an isopropenyl group, a butenyl group, an isobutenyl group, a tert-butenyl group, a pentenyl group, a hexenyl group, a heptenyl group, an octynyl group, an isooctynyl group and a nonenyl group.
The alicyclic hydrocarbon groups in R ^a1 , R ^a2 and R ^a3 may be either monocyclic or polycyclic. Examples of monocyclic alicyclic hydrocarbon groups include cycloalkyl groups such as cyclopentyl, cyclohexyl, cycloheptyl and cyclooctyl. Examples of polycyclic alicyclic hydrocarbon groups include decahydronaphthyl, adamantyl, norbornyl and the following groups (* represents a bond): The number of carbon atoms in the alicyclic hydrocarbon groups in R ^a1 , R ^a2 and R ^a3 is preferably 3 to 16.
Examples of the aromatic hydrocarbon group for R ^a1 , R ^a2 and R ^a3 include aryl groups such as a phenyl group, a naphthyl group, an anthryl group, a biphenyl group and a phenanthryl group.
Examples of the combined group include a group combining the above-mentioned alkyl group with an alicyclic hydrocarbon group (for example, an alkylcycloalkyl group or a cycloalkylalkyl group), an aralkyl group such as a benzyl group, an aromatic hydrocarbon group having an alkyl group (for example, a p-methylphenyl group, a p-tert-butylphenyl group, a tolyl group, a xylyl group, a cumenyl group, a mesityl group, a 2,6-diethylphenyl group, a 2-methyl-6-ethylphenyl group, etc.), an aromatic hydrocarbon group having an alicyclic hydrocarbon group (for example, a p-cyclohexylphenyl group, a p-adamantylphenyl group, etc.), and an aryl-cycloalkyl group such as a phenylcyclohexyl group. Preferably, ma is 0 and na is 1.
When R ^a1 and R ^a2 bond to each other to form an alicyclic hydrocarbon group, examples of -C(R ^a1 )(R ^a2 )(R ^a3 ) include the following groups. The alicyclic hydrocarbon group preferably has 3 to 12 carbon atoms. * represents the bonding position with -O-.

Examples of the hydrocarbon group in R ^a1′ , R ^a2′ and R ^a3′ include an alkyl group, an alicyclic hydrocarbon group, an aromatic hydrocarbon group and a group formed by combining these groups.
Examples of the alkyl group and alicyclic hydrocarbon group include the same groups as those listed for R ^a1 , R ^a2 and R ^a3 .
Examples of the aromatic hydrocarbon group include aryl groups such as a phenyl group, a naphthyl group, an anthryl group, a biphenyl group, and a phenanthryl group.
Examples of the combined group include a group in which the above-mentioned alkyl group and alicyclic hydrocarbon group are combined (for example, an alkylcycloalkyl group or a cycloalkylalkyl group), an aralkyl group (benzyl group, etc.), an aromatic hydrocarbon group having an alkyl group (p-methylphenyl group, p-tert-butylphenyl group, tolyl group, xylyl group, cumenyl group, mesityl group, 2,6-diethylphenyl group, 2-methyl-6-ethylphenyl group, etc.), an aromatic hydrocarbon group having an alicyclic hydrocarbon group (p-cyclohexylphenyl group, p-adamantylphenyl group, etc.), an alicyclic hydrocarbon group having an aromatic hydrocarbon group (phenylcyclohexyl group, etc.), and the like.
When R ^a2′ and R ^a3′ are bonded to each other to form a heterocyclic group together with the carbon atom to which they are bonded and X, examples of —C(R ^a1′ )(R ^a2′ )—X—R ^a3′ include the following groups: * represents the bonding position.
At least one of R ^a1′ and R ^a2′ is preferably a hydrogen atom.
na' is preferably 0.

Examples of the group (1) include the following groups.
A group in which R ^a1 , R ^a2 and R ^a3 are alkyl groups, ma = 0 and na = 1 in formula (1). The group is preferably a tert-butoxycarbonyl group.
A group in which, in formula (1), R ^a1 and R ^a2 together with the carbon atom to which they are bonded form an adamantyl group, R ^a3 is an alkyl group, ma=0, and na=1.
A group represented by formula (1), in which R ^a1 and R ^a2 each independently represent an alkyl group, R ^a3 represents an adamantyl group, ma=0, and na=1.
Specific examples of the group (1) include the following groups: * represents a bond.

Specific examples of group (2) include the following groups: * indicates the bonding position.

Monomer (a1) is preferably a monomer having an acid labile group and an ethylenically unsaturated bond, more preferably a (meth)acrylic monomer having an acid labile group.

Among (meth)acrylic monomers having an acid labile group, those having an alicyclic hydrocarbon group having 5 to 20 carbon atoms are preferred. The use of a resin (A) having structural units derived from a monomer (a1) having a bulky structure such as an alicyclic hydrocarbon group in a resist composition can improve the resolution of the resist pattern.

Examples of structural units derived from a (meth)acrylic monomer having group (1) include a structural unit represented by formula (a1-0) (hereinafter, sometimes referred to as structural unit (a1-0)), a structural unit represented by formula (a1-1) (hereinafter, sometimes referred to as structural unit (a1-1)), or a structural unit represented by formula (a1-2) (hereinafter, sometimes referred to as structural unit (a1-2)). Preferably, at least one structural unit selected from the group consisting of structural unit (a1-1) and structural unit (a1-2). These may be used alone or in combination of two or more.
[In formula (a1-0), formula (a1-1) and formula (a1-2),
L ^a01 , L ^a1 and L ^a2 each independently represent —O— or ^* —O—(CH ₂ ) _k1 —CO—O—, where k1 represents an integer of 1 to 7, and * represents a bond to —CO—.
R ^a01 , R ^a4 and R ^a5 each independently represent a hydrogen atom, a halogen atom or an alkyl group having 1 to 6 carbon atoms which may have a halogen atom.
R ^a02 , R ^a03 and R ^a04 each independently represent an alkyl group having 1 to 8 carbon atoms, an alicyclic hydrocarbon group having 3 to 18 carbon atoms, an aromatic hydrocarbon group having 6 to 18 carbon atoms or a combination thereof.
R ^a6 and R ^a7 each independently represent an alkyl group having 1 to 8 carbon atoms, an alkenyl group having 2 to 8 carbon atoms, an alicyclic hydrocarbon group having 3 to 18 carbon atoms, an aromatic hydrocarbon group having 6 to 18 carbon atoms, or a group formed by combining these.
m1 represents an integer of 0 to 14.
n1 represents an integer of 0 to 10.
n1′ represents an integer of 0 to 3.]

R ^a01 , R ^a4 and R ^a5 are preferably a hydrogen atom or a methyl group, more preferably a methyl group.
L ^a01 , L ^a1 and L ^a2 are preferably an oxygen atom or *-O-(CH ₂ ) _k01 -CO-O- (wherein k01 is preferably an integer of 1 to 4, more preferably 1), and more preferably an oxygen atom.
Examples of the alkyl group, alkenyl group, alicyclic hydrocarbon group, aromatic hydrocarbon group, and combinations thereof in R ^a02 , R ^a03 , R ^a04 , R ^a6 , and R ^a7 include the same groups as those exemplified for R ^a1 to R ^a3 in formula (1).
The alkyl group in R ^a02 , R ^a03 , and R ^a04 is preferably an alkyl group having 1 to 6 carbon atoms, more preferably a methyl group or an ethyl group, and even more preferably a methyl group.
The alkyl group in R ^a6 and R ^a7 is preferably an alkyl group having 1 to 6 carbon atoms, more preferably a methyl group, an ethyl group, an isopropyl group, or a t-butyl group, and even more preferably an ethyl group, an isopropyl group, or a t-butyl group.
The alkenyl group in R ^a6 and R ^a7 is preferably an alkenyl group having 2 to 6 carbon atoms, and more preferably an ethenyl group, a propenyl group, an isopropenyl group, or a butenyl group.
The alicyclic hydrocarbon groups of R ^a02 , R ^a03 and R ^a04 preferably have 5 to 12 carbon atoms, and more preferably 5 to 10 carbon atoms.
The aromatic hydrocarbon groups of R ^a02 , R ^a03 , R ^a04 , R ^a6 and R ^a7 preferably have 6 to 12 carbon atoms, and more preferably 6 to 10 carbon atoms.
In the group in which an alkyl group and an alicyclic hydrocarbon group are combined, the total number of carbon atoms in the combination of the alkyl group and the alicyclic hydrocarbon group is preferably 18 or less.
In the group in which an alkyl group and an aromatic hydrocarbon group are combined, the total number of carbon atoms in the combination of the alkyl group and the aromatic hydrocarbon group is preferably 18 or less.
R ^a02 and R ^a03 are preferably alkyl groups having 1 to 6 carbon atoms or aromatic hydrocarbon groups having 6 to 12 carbon atoms, and more preferably methyl, ethyl, phenyl or naphthyl groups.
R ^a04 is preferably an alkyl group having 1 to 6 carbon atoms or an alicyclic hydrocarbon group having 5 to 12 carbon atoms, and more preferably a methyl group, an ethyl group, a cyclohexyl group or an adamantyl group.
R ^a6 and R ^a7 are preferably an alkyl group having 1 to 6 carbon atoms, an alkenyl group having 2 to 6 carbon atoms, or an aromatic hydrocarbon group having 6 to 12 carbon atoms, more preferably a methyl group, an ethyl group, an isopropyl group, a t-butyl group, an ethenyl group, a phenyl group, or a naphthyl group, and even more preferably an ethyl group, an isopropyl group, a t-butyl group, an ethenyl group, or a phenyl group.
m1 is preferably an integer of 0 to 3, and more preferably 0 or 1.
n1 is preferably an integer of 0 to 3, and more preferably 0 or 1.
n1' is preferably 0 or 1.

Examples of the structural unit (a1-0) include structural units represented by any one of formulas (a1-0-1) to (a1-0-18) and structural units in which the methyl group corresponding to R ^a01 in the structural unit (a1-0) has been replaced with a hydrogen atom, a halogen atom, a haloalkyl group, or another alkyl group, and structural units represented by any one of formulas (a1-0-1) to (a1-0-10), (a1-0-13), and (a1-0-14) are preferred.

Examples of the structural unit (a1-1) include structural units derived from monomers described in JP 2010-204646 A. Among these, structural units represented by any one of formulas (a1-1-1) to (a1-1-7) and structural units in which the methyl group corresponding to R ^a4 in the structural unit (a1-1) has been replaced with a hydrogen atom, a halogen atom, a haloalkyl group, or another alkyl group are preferred, and structural units represented by any one of formulas (a1-1-1) to (a1-1-4) are more preferred.

Examples of the structural unit (a1-2) include structural units represented by any one of formulas (a1-2-1) to (a1-2-12) and structural units in which the methyl group corresponding to R ^a5 in the structural unit (a1-2) has been replaced with a hydrogen atom, a halogen atom, a haloalkyl group, or another alkyl group, and structural units represented by any one of formulas (a1-2-2), (a1-2-5), (a1-2-6), and (a1-2-10) to (a1-2-12) are preferred.

When the resin (A) contains the structural unit (a1-0), the content thereof is usually 5 to 60 mol %, preferably 5 to 50 mol %, and more preferably 10 to 40 mol %, based on all structural units of the resin (A).
When the resin (A) contains the structural unit (a1-1) and/or the structural unit (a1-2), the total content thereof is usually 10 to 95 mol %, preferably 15 to 85 mol %, more preferably 15 to 80 mol %, even more preferably 20 to 80 mol %, and still more preferably 20 to 75 mol %, based on all structural units in the resin (A).

The structural unit (a1) having the group (2) includes a structural unit represented by formula (a1-4) (hereinafter, sometimes referred to as "structural unit (a1-4)").
[In formula (a1-4),
R ^a32 represents a hydrogen atom, a halogen atom, or an alkyl group having 1 to 6 carbon atoms which may have a halogen atom.
R ^a33 represents a halogen atom, a hydroxy group, an alkyl group having 1 to 6 carbon atoms, an alkoxy group having 1 to 6 carbon atoms, an alkoxyalkyl group having 2 to 12 carbon atoms, an alkoxyalkoxy group having 2 to 12 carbon atoms, an alkylcarbonyl group having 2 to 4 carbon atoms, an alkylcarbonyloxy group having 2 to 4 carbon atoms, an acryloyloxy group, or a methacryloyloxy group.
A ^a30 represents a single bond or ^* -X ^a31 -(A ^a32 -X ^a32 ) _nc -, where * represents the bonding site with the carbon atom to which -R ^a32 is bonded.
A ^a32 represents an alkanediyl group having 1 to 6 carbon atoms.
X ^a31 and X ^a32 each independently represent —O—, —CO—O—, or —O—CO—.
nc represents 0 or 1.
Ia represents an integer of 0 to 4. When Ia is an integer of 2 or more, multiple R ^a33s may be the same or different.
R ^a34 and R ^a35 each independently represent a hydrogen atom or a hydrocarbon group having 1 to 12 carbon atoms, R ^a36 represents a hydrocarbon group having 1 to 20 carbon atoms, or R ^a35 and R ^a36 are bonded to each other to form a divalent hydrocarbon group having 2 to 20 carbon atoms together with the —C—O— to which they are bonded, and —CH ₂ — contained in the hydrocarbon group and the divalent hydrocarbon group may be replaced by —O— or —S—.]

Examples of the halogen atom in R ^a32 and R ^a33 include a fluorine atom, a chlorine atom, and a bromine atom.
Examples of the alkyl group having 1 to 6 carbon atoms which may have a halogen atom for R ^a32 include a trifluoromethyl group, a difluoromethyl group, a methyl group, a perfluoroethyl group, a 2,2,2-trifluoroethyl group, a 1,1,2,2-tetrafluoroethyl group, an ethyl group, a perfluoropropyl group, a 2,2,3,3,3-pentafluoropropyl group, a propyl group, a perfluorobutyl group, a 1,1,2,2,3,3,4,4-octafluorobutyl group, a butyl group, a perfluoropentyl group, a 2,2,3,3,4,4,5,5,5-nonafluoropentyl group, a pentyl group, a hexyl group, and a perfluorohexyl group.
R ^a32 is preferably a hydrogen atom or an alkyl group having 1 to 4 carbon atoms, more preferably a hydrogen atom, a methyl group or an ethyl group, and even more preferably a hydrogen atom or a methyl group.
Examples of the alkyl group for R ^a33 include a methyl group, an ethyl group, a propyl group, an isopropyl group, a butyl group, a sec-butyl group, a tert-butyl group, a pentyl group, and a hexyl group.
Examples of the alkoxy group for R ^a33 include a methoxy group, an ethoxy group, a propoxy group, an isopropoxy group, a butoxy group, a sec-butoxy group, a tert-butoxy group, a pentyloxy group, and a hexyloxy group. The alkoxy group is preferably an alkoxy group having 1 to 4 carbon atoms, more preferably a methoxy group or an ethoxy group, and even more preferably a methoxy group.
Examples of the alkoxyalkyl group for R ^a33 include a methoxymethyl group, an ethoxyethyl group, a propoxymethyl group, an isopropoxymethyl group, a butoxymethyl group, a sec-butoxymethyl group, and a tert-butoxymethyl group. The alkoxyalkyl group is preferably an alkoxyalkyl group having 2 to 8 carbon atoms, more preferably a methoxymethyl group or an ethoxyethyl group, and even more preferably a methoxymethyl group.
Examples of the alkoxyalkoxy group for R ^a33 include a methoxymethoxy group, a methoxyethoxy group, an ethoxymethoxy group, an ethoxyethoxy group, a propoxymethoxy group, an isopropoxymethoxy group, a butoxymethoxy group, a sec-butoxymethoxy group, and a tert-butoxymethoxy group. The alkoxyalkoxy group is preferably an alkoxyalkoxy group having 2 to 8 carbon atoms, and more preferably a methoxyethyl group or an ethoxyethyl group.
Examples of the alkylcarbonyl group for R ^a33 include an acetyl group, a propionyl group, a butyryl group, etc. The alkylcarbonyl group is preferably an alkylcarbonyl group having 2 to 3 carbon atoms, and more preferably an acetyl group.
Examples of the alkylcarbonyloxy group for R ^a33 include an acetyloxy group, a propionyloxy group, and a butyryloxy group. The alkylcarbonyloxy group is preferably an alkylcarbonyloxy group having 2 to 3 carbon atoms, and more preferably an acetyloxy group.
R ^a33 is preferably a halogen atom, a hydroxy group, an alkyl group having 1 to 4 carbon atoms, an alkoxy group having 1 to 4 carbon atoms, or an alkoxyalkoxy group having 2 to 8 carbon atoms, more preferably a fluorine atom, an iodine atom, a hydroxy group, a methyl group, a methoxy group, an ethoxy group, an ethoxyethoxy group, or an ethoxymethoxy group, and even more preferably a fluorine atom, an iodine atom, a hydroxy group, a methyl group, a methoxy group, or an ethoxyethoxy group.

Examples of *-X ^a31 -(A ^a32 -X ^a32 ) _nc - include *-O-, *-CO-O-, *-O-CO-, *-CO-O-A ^a32 -CO-O-, *-O-CO-A ^a32 -O-, *-O-A ^a32 -CO-O-, *-CO-O-A ^a32 -O-CO-, *-O-CO-A ^a32 -O-CO-. Of these, *-CO-O-, *-CO-O-A ^a32 -CO-O- or *-O-A ^a32 -CO-O- are preferred.

Examples of the alkanediyl group include a methylene group, an ethylene group, a propane-1,3-diyl group, a propane-1,2-diyl group, a butane-1,4-diyl group, a pentane-1,5-diyl group, a hexane-1,6-diyl group, a butane-1,3-diyl group, a 2-methylpropane-1,3-diyl group, a 2-methylpropane-1,2-diyl group, a pentane-1,4-diyl group, and a 2-methylbutane-1,4-diyl group.
A ^a32 is preferably a methylene group or an ethylene group.

A ^a30 is preferably a single bond, *-CO-O-, or *-CO-O-A ^a32 -CO-O-, more preferably a single bond, *-CO-O-, or *-CO-O-CH ₂ -CO-O-, and even more preferably a single bond or *-CO-O-.

Ia is preferably 0, 1 or 2, more preferably 0 or 1, and even more preferably 0.
Examples of the hydrocarbon group for R ^a34 , R ^a35 and R ^a36 include an alkyl group, an alicyclic hydrocarbon group, an aromatic hydrocarbon group and a group formed by combining these groups.
Examples of the alkyl group include a methyl group, an ethyl group, a propyl group, a butyl group, a pentyl group, a hexyl group, a heptyl group, and an octyl group.
The alicyclic hydrocarbon group may be either monocyclic or polycyclic. Examples of monocyclic alicyclic hydrocarbon groups include cycloalkyl groups such as cyclopentyl, cyclohexyl, cycloheptyl, and cyclooctyl. Examples of polycyclic alicyclic hydrocarbon groups include decahydronaphthyl, adamantyl, and norbornyl groups, as well as the following groups (* indicates a bonding site):
Examples of the aromatic hydrocarbon group include aryl groups such as a phenyl group, a naphthyl group, an anthryl group, a biphenyl group, and a phenanthryl group.
Examples of the combined group include a group combining the above-mentioned alkyl group and alicyclic hydrocarbon group (for example, a cycloalkylalkyl group), aralkyl groups such as a benzyl group, aromatic hydrocarbon groups having an alkyl group (e.g., a p-methylphenyl group, a p-tert-butylphenyl group, a tolyl group, a xylyl group, a cumenyl group, a mesityl group, a 2,6-diethylphenyl group, a 2-methyl-6-ethylphenyl group, etc.), aromatic hydrocarbon groups having an alicyclic hydrocarbon group (e.g., a p-cyclohexylphenyl group, a p-adamantylphenyl group, etc.), and aryl-cycloalkyl groups such as a phenylcyclohexyl group. In particular, R ^a36 may be an alkyl group having 1 to 18 carbon atoms, an alicyclic hydrocarbon group having 3 to 18 carbon atoms, an aromatic hydrocarbon group having 6 to 18 carbon atoms, or a group formed by combining these.

R ^a34 is preferably a hydrogen atom.
R ^a35 is preferably a hydrogen atom, an alkyl group having 1 to 12 carbon atoms, or an alicyclic hydrocarbon group having 3 to 12 carbon atoms, and more preferably a methyl group or an ethyl group.
The hydrocarbon group for R ^a36 is preferably an alkyl group having 1 to 18 carbon atoms, an alicyclic hydrocarbon group having 3 to 18 carbon atoms, an aromatic hydrocarbon group having 6 to 18 carbon atoms, or a group formed by combining these, and more preferably an alkyl group having 1 to 18 carbon atoms, an alicyclic hydrocarbon group having 3 to 18 carbon atoms, or an aralkyl group having 7 to 18 carbon atoms. The alkyl group and alicyclic hydrocarbon group for ^{R a36} are preferably unsubstituted. The aromatic hydrocarbon group for ^{R a36} is preferably an aromatic ring having an aryloxy group having 6 to 10 carbon atoms.

The —OC(R ^a34 )(R ^a35 )—O—R ^a36 in the structural unit (a1-4) is eliminated upon contact with an acid (for example, p-toluenesulfonic acid) to form a hydroxy group.
--OC(R ^a34 )(R ^a35 )--O--R ^a36 is preferably bonded to the o-position or p-position of the benzene ring, and more preferably bonded to the p-position.

Examples of the structural unit (a1-4) include structural units derived from monomers described in JP 2010-204646 A. Preferred examples include structural units represented by formulas (a1-4-1) to (a1-4-18) and structural units in which the hydrogen atom corresponding to ^R in the structural unit (a1-4) is replaced with a halogen atom, a haloalkyl group, or an alkyl group, and more preferred examples include structural units represented by formulas (a1-4-1) to (a1-4-5), (a1-4-10), (a1-4-13), and (a1-4-14).
When the resin (A) has the structural unit (a1-4), the content thereof is preferably 5 to 60 mol %, more preferably 5 to 50 mol %, and even more preferably 10 to 40 mol %, based on the total amount of all structural units in the resin (A).

Examples of the structural unit derived from a (meth)acrylic monomer having the group (2) include a structural unit represented by formula (a1-5) (hereinafter, sometimes referred to as "structural unit (a1-5)").
In formula (a1-5),
R ^a8 represents an alkyl group having 1 to 6 carbon atoms which may have one or more halogen atoms, a hydrogen atom, or a halogen atom.
Z ^a1 represents a single bond or *-(CH ₂ ) _h3 -CO-L ⁵⁴ -, where h3 represents an integer of 1 to 4, and * represents the bonding position with L ⁵¹ .
L ⁵¹ , L ⁵² , L ⁵³ and L ⁵⁴ each independently represent —O— or —S—.
s1 represents an integer of 1 to 3.
s1' represents an integer of 0 to 3.

Examples of halogen atoms include fluorine atoms and chlorine atoms, with fluorine atoms being preferred.
Examples of the alkyl group having 1 to 6 carbon atoms which may have a halogen atom include a methyl group, an ethyl group, a propyl group, a butyl group, a pentyl group, a hexyl group, a heptyl group, an octyl group, a fluoromethyl group, and a trifluoromethyl group.
In formula (a1-5), R ^a8 is preferably a hydrogen atom, a methyl group or a trifluoromethyl group.
L ⁵¹ is preferably an oxygen atom.
It is preferred that one of L ⁵² and L ⁵³ is —O— and the other is —S—.
s1 is preferably 1.
s1' is preferably an integer of 0 to 2.
Z ^a1 is preferably a single bond or *-CH ₂ -CO-O-.

Examples of the structural unit (a1-5) include structural units derived from monomers described in JP-A-2010-61117. Among these, structural units represented by formulas (a1-5-1) to (a1-5-4) are preferred, and structural units represented by formula (a1-5-1) or (a1-5-2) are more preferred.
When the resin (A) has the structural unit (a1-5), the content thereof is preferably 1 to 50 mol %, more preferably 3 to 45 mol %, even more preferably 5 to 40 mol %, and still more preferably 5 to 30 mol %, based on all structural units of the resin (A).

Further, examples of the structural unit (a1) include the following structural units.
When the resin (A) contains the above structural unit, the content thereof is preferably 5 to 60 mol %, more preferably 5 to 50 mol %, and even more preferably 10 to 40 mol %, based on the total structural units of the resin (A).

<Structural unit (s)>
The structural unit (s) is derived from a monomer having no acid labile group (hereinafter, may be referred to as "monomer (s)"). As the monomer from which the structural unit (s) is derived, a monomer having no acid labile group known in the resist field can be used.
The structural unit (s) preferably has a hydroxy group or a lactone ring. By using a resin having a structural unit that has a hydroxy group but no acid labile group (hereinafter sometimes referred to as "structural unit (a2)") and/or a structural unit that has a lactone ring but no acid labile group (hereinafter sometimes referred to as "structural unit (a3)") in the resist composition of the present invention, the resolution of the resist pattern and adhesion to the substrate can be improved.

<Structural Unit (a2)>
The hydroxy group contained in the structural unit (a2) may be an alcoholic hydroxy group or a phenolic hydroxy group.
When producing a resist pattern from the resist composition of the present invention, if a high-energy ray such as a KrF excimer laser (248 nm), an electron beam, or EUV (extreme ultraviolet) is used as an exposure light source, the structural unit (a2) preferably has a phenolic hydroxy group, and it is more preferable to use the structural unit (a2-A) described below. Furthermore, if an ArF excimer laser (193 nm) or the like is used, the structural unit (a2) preferably has an alcoholic hydroxy group, and it is more preferable to use the structural unit (a2-1) described below. The structural unit (a2) may contain one type alone, or two or more types.

The structural unit (a2) having a phenolic hydroxy group includes a structural unit represented by formula (a2-A) (hereinafter, sometimes referred to as "structural unit (a2-A)").
[In formula (a2-A),
R ^a50 represents a hydrogen atom, a halogen atom or an alkyl group having 1 to 6 carbon atoms which may have a halogen atom.
R ^a51 represents a halogen atom, a hydroxy group, an alkyl group having 1 to 6 carbon atoms, an alkoxy group having 1 to 6 carbon atoms, an alkoxyalkyl group having 2 to 12 carbon atoms, an alkoxyalkoxy group having 2 to 12 carbon atoms, an alkylcarbonyl group having 2 to 4 carbon atoms, an alkylcarbonyloxy group having 2 to 4 carbon atoms, an acryloyloxy group, or a methacryloyloxy group.
A ^a50 represents a single bond or *-X ^a51 -(A ^a52 -X ^a52 ) _nb -, where * represents the bonding position with the carbon atom to which -R ^a50 is bonded.
Each A ^a52 independently represents an alkanediyl group having 1 to 6 carbon atoms.
X ^a51 and X ^a52 each independently represent —O—, —CO—O—, or —O—CO—.
nb represents 0 or 1.
mb represents an integer of 0 to 4. When mb is an integer of 2 or more, multiple R ^a51 may be the same or different.]

Examples of the halogen atom in R ^a50 and R ^a51 include a fluorine atom, a chlorine atom, and a bromine atom.
Examples of the alkyl group having 1 to 6 carbon atoms which may have a halogen atom for R ^a50 include a trifluoromethyl group, a difluoromethyl group, a methyl group, a perfluoroethyl group, a 2,2,2-trifluoroethyl group, a 1,1,2,2-tetrafluoroethyl group, an ethyl group, a perfluoropropyl group, a 2,2,3,3,3-pentafluoropropyl group, a propyl group, a perfluorobutyl group, a 1,1,2,2,3,3,4,4-octafluorobutyl group, a butyl group, a perfluoropentyl group, a 2,2,3,3,4,4,5,5,5-nonafluoropentyl group, a pentyl group, a hexyl group, and a perfluorohexyl group.
R ^a50 is preferably a hydrogen atom or an alkyl group having 1 to 4 carbon atoms, more preferably a hydrogen atom, a methyl group or an ethyl group, and even more preferably a hydrogen atom or a methyl group.
Examples of the alkyl group for R ^a51 include a methyl group, an ethyl group, a propyl group, an isopropyl group, a butyl group, a sec-butyl group, a tert-butyl group, a pentyl group, and a hexyl group. The alkyl group is preferably an alkyl group having 1 to 4 carbon atoms, more preferably a methyl group or an ethyl group, and even more preferably a methyl group.
Examples of the alkoxy group for R ^a51 include a methoxy group, an ethoxy group, a propoxy group, an isopropoxy group, a butoxy group, a sec-butoxy group, and a tert-butoxy group. The alkoxy group is preferably an alkoxy group having 1 to 4 carbon atoms, more preferably a methoxy group or an ethoxy group, and even more preferably a methoxy group.
Examples of the alkoxyalkyl group for R ^a51 include a methoxymethyl group, an ethoxyethyl group, a propoxymethyl group, an isopropoxymethyl group, a butoxymethyl group, a sec-butoxymethyl group, and a tert-butoxymethyl group. The alkoxyalkyl group is preferably an alkoxyalkyl group having 2 to 8 carbon atoms, more preferably a methoxymethyl group or an ethoxyethyl group, and even more preferably a methoxymethyl group.
Examples of the alkoxyalkoxy group for R ^a51 include a methoxymethoxy group, a methoxyethoxy group, an ethoxymethoxy group, an ethoxyethoxy group, a propoxymethoxy group, an isopropoxymethoxy group, a butoxymethoxy group, a sec-butoxymethoxy group, and a tert-butoxymethoxy group. The alkoxyalkoxy group is preferably an alkoxyalkoxy group having 2 to 8 carbon atoms, and more preferably a methoxyethoxy group or an ethoxyethoxy group.
Examples of the alkylcarbonyl group for R ^a51 include an acetyl group, a propionyl group, a butyryl group, etc. The alkylcarbonyl group is preferably an alkylcarbonyl group having 2 to 3 carbon atoms, and more preferably an acetyl group.
Examples of the alkylcarbonyloxy group for R ^a51 include an acetyloxy group, a propionyloxy group, and a butyryloxy group. The alkylcarbonyloxy group is preferably an alkylcarbonyloxy group having 2 to 3 carbon atoms, and more preferably an acetyloxy group.
R ^a51 is preferably a halogen atom, a hydroxy group, an alkyl group having 1 to 4 carbon atoms, an alkoxy group having 1 to 4 carbon atoms, or an alkoxyalkoxy group having 2 to 8 carbon atoms, more preferably a fluorine atom, an iodine atom, a hydroxy group, a methyl group, a methoxy group, an ethoxy group, an ethoxyethoxy group, or an ethoxymethoxy group, and still more preferably a fluorine atom, an iodine atom, a hydroxy group, a methyl group, a methoxy group, or an ethoxyethoxy group.

Examples of *-X ^a51 -(A ^a52 -X ^a52 ) _nb - include *-O-, *-CO-O-, *-O-CO-, *-CO-O-A ^a52 -CO-O-, *-O-CO-A ^a52 -O-, *-O-A ^a52 -CO-O-, *-CO-O-A ^a52 -O-CO-, *-O-CO-A ^a52 -O-CO-. Of these, *-CO-O-, *-CO-O-A ^a52 -CO-O- or *-O-A ^a52 -CO-O- are preferred.
Examples of the alkanediyl group include a methylene group, an ethylene group, a propane-1,3-diyl group, a propane-1,2-diyl group, a butane-1,4-diyl group, a pentane-1,5-diyl group, a hexane-1,6-diyl group, a butane-1,3-diyl group, a 2-methylpropane-1,3-diyl group, a 2-methylpropane-1,2-diyl group, a pentane-1,4-diyl group, and a 2-methylbutane-1,4-diyl group.
A ^a52 is preferably a methylene group or an ethylene group.
A ^a50 is preferably a single bond, *-CO-O- or *-CO-O-A ^a52 -CO-O-, more preferably a single bond, *-CO-O- or *-CO-O-CH ₂ -CO-O-, and even more preferably a single bond or *-CO-O-.
mb is preferably 0, 1 or 2, more preferably 0 or 1, and particularly preferably 0.
The hydroxy group is preferably bonded to the ortho- or para-position of the benzene ring, more preferably to the para-position.

Examples of the structural unit (a2-A) include structural units derived from monomers described in JP-A Nos. 2010-204634 and 2012-12577.
Examples of the structural unit (a2-A) include structural units represented by formulas (a2-2-1) to (a2-2-16) and structural units in which the methyl group corresponding to R in the structural unit (a2-A) in the structural units represented by formulas ( ^a2-2-1 ) to (a2-2-16) is replaced with a hydrogen atom, a halogen atom, a haloalkyl group, or another alkyl group. The structural unit (a2-A) is a structural unit represented by formula (a2-2-1), a structural unit represented by formula (a2-2-3), a structural unit represented by formula (a2-2-6), a structural unit represented by formula (a2-2-8), a structural unit represented by formulas (a2-2-12) to (a2-2-14), and a structural unit represented by formula (a2-2-1), a structural unit represented by formula (a2-2-3), a structural unit represented by formula (a2-2-6), a structural unit represented by formula (a2-2-8), and a structural unit represented by formulas (a2-2-12) to (a2-2-14). In these structural units, R The structural unit is preferably a structural unit in which a methyl group corresponding to ^a50 in the structural unit (a2-A) is replaced with a hydrogen atom, and is more preferably a structural unit represented by formula (a2-2-3), a structural unit represented by formula (a2-2-8), a structural unit represented by formulas (a2-2-12) to (a2-2-14), and a structural unit represented by formula (a2-2-3) or a structural unit represented by formula (a2-2-8), and a structural unit represented by formulas (a2-2-12) to (a2-2-14), in which a methyl group corresponding to R ^a50 in the structural unit (a2-A) is replaced with a hydrogen atom, and is even more preferably a structural unit represented by formula (a2-2-8) and a structural unit represented by formula (a2-2-8), in which a methyl group corresponding to R ^a50 in the structural unit (a2-A) is replaced with a hydrogen atom.
When the structural unit (a2-A) is contained in the resin (A), the content of the structural unit (a2-A) is preferably 5 to 80 mol %, more preferably 10 to 70 mol %, even more preferably 15 to 65 mol %, and still more preferably 20 to 65 mol %, based on all structural units.
The structural unit (a2-A) can be incorporated into the resin (A) by, for example, polymerizing the structural unit (a1-4) and then treating with an acid such as p-toluenesulfonic acid. Alternatively, the structural unit (a2-A) can be incorporated into the resin (A) by polymerizing the structural unit (a1-4) and then treating with an alkali such as tetramethylammonium hydroxide.

The structural unit (a2) having an alcoholic hydroxy group includes a structural unit represented by formula (a2-1) (hereinafter, sometimes referred to as "structural unit (a2-1)").
In formula (a2-1),
L ^a3 represents —O— or ^* —O—(CH ₂ ) _k2 —CO—O—;
k2 represents an integer of 1 to 7. * represents the bonding position with —CO—.
R ^a14 represents a hydrogen atom or a methyl group.
R ^a15 and R ^a16 each independently represent a hydrogen atom, a methyl group or a hydroxy group.
o1 represents an integer of 0 to 10.

In formula (a2-1), L ^a3 is preferably —O— or —O—(CH ₂ ) _f1 —CO—O— (wherein f1 represents an integer of 1 to 4), and more preferably —O—.
R ^a14 is preferably a methyl group.
R ^a15 is preferably a hydrogen atom.
R ^a16 is preferably a hydrogen atom or a hydroxy group.
o1 is preferably an integer of 0 to 3, more preferably 0 or 1.

Examples of the structural unit (a2-1) include structural units derived from monomers described in JP 2010-204646 A. A structural unit represented by any one of formulas (a2-1-1) to (a2-1-6) is preferred, a structural unit represented by any one of formulas (a2-1-1) to (a2-1-4) is more preferred, and a structural unit represented by formula (a2-1-1) or formula (a2-1-3) is even more preferred.
When the resin (A) contains the structural unit (a2-1), the content thereof is usually 1 to 45 mol %, preferably 1 to 40 mol %, more preferably 1 to 35 mol %, even more preferably 2 to 20 mol %, and still more preferably 2 to 10 mol %, based on all structural units of the resin (A).

<Structural Unit (a3)>
The lactone ring contained in the structural unit (a3) may be a monocyclic ring such as a β-propiolactone ring, a γ-butyrolactone ring, or a δ-valerolactone ring, or may be a condensed ring of a monocyclic lactone ring with another ring. Preferred examples include a γ-butyrolactone ring, an adamantane lactone ring, or a bridged ring containing a γ-butyrolactone ring structure (for example, a structural unit represented by the following formula (a3-2)).
The structural unit (a3) is preferably a structural unit represented by formula (a3-1), formula (a3-2), formula (a3-3), or formula (a3-4). One of these may be contained alone, or two or more may be contained.
[In formula (a3-1), formula (a3-2), formula (a3-3) and formula (a3-4),
L ^a4 , L ^a5 and L ^a6 each independently represent a group represented by —O— or *-O—(CH ₂ ) _k3 —CO—O— (k3 represents an integer of 1 to 7).
L ^a7 represents -O-, *-OL ^a8 -O-, *-OL ^a8 -CO-O-, *-OL ^a8 -CO-O-L ^a9 -CO-O-, or *-OL ^a8 -O-CO-L ^a9 -O-.
L ^a8 and L ^a9 each independently represent an alkanediyl group having 1 to 6 carbon atoms.
* indicates the bonding site with the carbonyl group.
R ^a18 , R ^a19 and R ^a20 each independently represent a hydrogen atom or a methyl group.
R ^a24 represents an alkyl group having 1 to 6 carbon atoms which may have a halogen atom, a hydrogen atom or a halogen atom.
X ^a3 represents —CH ₂ — or an oxygen atom.
R ^a21 represents an aliphatic hydrocarbon group having 1 to 4 carbon atoms.
R ^a22 , R ^a23 and R ^a25 each independently represent a carboxy group, a cyano group or an aliphatic hydrocarbon group having 1 to 4 carbon atoms.
p1 represents an integer of 0 to 5.
q1 represents an integer of 0 to 3.
r1 represents an integer of 0 to 3.
w1 represents an integer of 0 to 8.
When p1, q1, r1 and/or w1 is 2 or more, multiple R ^a21 , R ^a22 , R ^a23 and/or R ^a25 may be the same or different from each other.]

Examples of the aliphatic hydrocarbon group for R ^a21 , R ^a22 , R ^a23 and R ^a25 include alkyl groups such as a methyl group, an ethyl group, a propyl group, an isopropyl group, a butyl group, a sec-butyl group and a tert-butyl group.
The halogen atom in R ^a24 includes a fluorine atom, a chlorine atom, a bromine atom and an iodine atom.
Examples of the alkyl group for R ^a24 include a methyl group, an ethyl group, a propyl group, an isopropyl group, a butyl group, a sec-butyl group, a tert-butyl group, a pentyl group, and a hexyl group, and are preferably alkyl groups having 1 to 4 carbon atoms, and more preferably a methyl group or an ethyl group.
Examples of the alkyl group having a halogen atom for R ^a24 include a trifluoromethyl group, a perfluoroethyl group, a perfluoropropyl group, a perfluoroisopropyl group, a perfluorobutyl group, a perfluorosec-butyl group, a perfluorotert-butyl group, a perfluoropentyl group, a perfluorohexyl group, a trichloromethyl group, a tribromomethyl group, and a triiodomethyl group.

Examples of the alkanediyl group in L ^a8 and L ^a9 include a methylene group, an ethylene group, a propane-1,3-diyl group, a propane-1,2-diyl group, a butane-1,4-diyl group, a pentane-1,5-diyl group, a hexane-1,6-diyl group, a butane-1,3-diyl group, a 2-methylpropane-1,3-diyl group, a 2-methylpropane-1,2-diyl group, a pentane-1,4-diyl group, and a 2-methylbutane-1,4-diyl group.

In formulae (a3-1) to (a3-3), L ^a4 to L ^a6 each independently represent preferably —O— or *-O-(CH ₂ ) _k3 -CO-O-, where k3 is an integer of 1 to 4, more preferably —O— and *-O-CH ₂ -CO-O-, and even more preferably an oxygen atom.
R ^a18 to R ^a21 are preferably methyl groups.
R ^a22 and R ^a23 each independently represent preferably a carboxy group, a cyano group, or a methyl group.
p1, q1 and r1 each independently represent an integer of preferably 0 to 2, and more preferably 0 or 1.

In formula (a3-4), R ^a24 is preferably a hydrogen atom or an alkyl group having 1 to 4 carbon atoms, more preferably a hydrogen atom, a methyl group or an ethyl group, and even more preferably a hydrogen atom or a methyl group.
R ^a25 is preferably a carboxy group, a cyano group or a methyl group.
L ^a7 is preferably —O— or *-OL ^a8 —CO—O—, and more preferably —O—, —O—CH ₂ —CO—O— or —OC ₂ H ₄ —CO—O—.
w1 is preferably an integer of 0 to 2, and more preferably 0 or 1.
In particular, the formula (a3-4) is preferably the formula (a3-4)'.
(In the formula, R ^a24 and L ^a7 have the same meanings as above.)

Examples of the structural unit (a3) include structural units derived from the monomers described in JP-A No. 2010-204646, JP-A No. 2000-122294, and JP-A No. 2012-41274. Preferred structural units (a3) are structural units represented by any one of formulas (a3-1-1), (a3-1-2), (a3-2-1), (a3-2-2), (a3-3-1), (a3-3-2), and (a3-4-1) to (a3-4-12), and structural units in which the methyl groups corresponding to R ^a18 , R ^a19 , R ^a20 , and R ^a24 in formulas (a3-1) to (a3-4) in the structural units are replaced with hydrogen atoms.
When the resin (A) contains the structural unit (a3), the total content thereof is usually 1 to 70 mol %, preferably 1 to 65 mol %, and more preferably 1 to 60 mol %, based on all structural units of the resin (A).
Furthermore, the content of the structural unit (a3-1), the structural unit (a3-2), the structural unit (a3-3), or the structural unit (a3-4) is preferably 1 to 60 mol%, more preferably 1 to 50 mol%, and even more preferably 1 to 50 mol%, based on all structural units in the resin (A).

<Structural unit (a4)>
Examples of the structural unit (a4) include the following structural units.
[In formula (a4),
R ⁴¹ represents a hydrogen atom or a methyl group.
R ⁴² represents a saturated hydrocarbon group having 1 to 24 carbon atoms and containing a fluorine atom, and —CH ₂ — contained in the saturated hydrocarbon group may be replaced by —O— or —CO—.]
Examples of the saturated hydrocarbon group represented by R ⁴² include chain hydrocarbon groups, monocyclic or polycyclic alicyclic hydrocarbon groups, and groups formed by combining these groups.

Examples of the chain hydrocarbon group include a methyl group, an ethyl group, a propyl group, a butyl group, a pentyl group, a hexyl group, a heptyl group, an octyl group, a decyl group, a dodecyl group, a pentadecyl group, a hexadecyl group, a heptadecyl group, and an octadecyl group.
Examples of the monocyclic or polycyclic alicyclic hydrocarbon group include cycloalkyl groups such as a cyclopentyl group, a cyclohexyl group, a cycloheptyl group, and a cyclooctyl group; and polycyclic alicyclic hydrocarbon groups such as a decahydronaphthyl group, an adamantyl group, a norbornyl group, and the following groups (* indicates a bonding position):
Examples of groups formed by combination include groups formed by combining one or more alkyl groups or one or more alkanediyl groups with one or more alicyclic hydrocarbon groups, such as -alkanediyl group-alicyclic hydrocarbon group, -alicyclic hydrocarbon group-alkyl group, and -alkanediyl group-alicyclic hydrocarbon group-alkyl group.

Examples of the structural unit (a4) include at least one structural unit selected from the group consisting of formula (a4-0), formula (a4-1), formula (a4-2), formula (a4-3), and formula (a4-4).
[In formula (a4-0),
R ^5a represents a hydrogen atom or a methyl group.
L ^4a represents a single bond or an alkanediyl group having 1 to 4 carbon atoms.
^L3a represents a perfluoroalkanediyl group having 1 to 8 carbon atoms or a perfluorocycloalkanediyl group having 3 to 12 carbon atoms.
^R6a represents a hydrogen atom or a fluorine atom.

Examples of the alkanediyl group for ^L4a include linear alkanediyl groups such as a methylene group, an ethylene group, a propane-1,3-diyl group, and a butane-1,4-diyl group, and branched alkanediyl groups such as an ethane-1,1-diyl group, a propane-1,2-diyl group, a butane-1,3-diyl group, a 2-methylpropane-1,3-diyl group, and a 2-methylpropane-1,2-diyl group.

Examples of the perfluoroalkanediyl group in ^L3a include a difluoromethylene group, a perfluoroethylene group, a perfluoropropane-1,1-diyl group, a perfluoropropane-1,3-diyl group, a perfluoropropane-1,2-diyl group, a perfluoropropane-2,2-diyl group, a perfluorobutane-1,4-diyl group, a perfluorobutane-2,2-diyl group, a perfluorobutane-1,2-diyl group, a perfluoropentane-1,5-diyl group, a perfluoropentane-2,2-diyl group, a perfluoropentane- perfluorohexane-3,3-diyl group, perfluorohexane-1,6-diyl group, perfluorohexane-2,2-diyl group, perfluorohexane-3,3-diyl group, perfluoroheptane-1,7-diyl group, perfluoroheptane-2,2-diyl group, perfluoroheptane-3,4-diyl group, perfluoroheptane-4,4-diyl group, perfluorooctane-1,8-diyl group, perfluorooctane-2,2-diyl group, perfluorooctane-3,3-diyl group, and perfluorooctane-4,4-diyl group.
Examples of the perfluorocycloalkanediyl group in ^L3a include a perfluorocyclohexanediyl group, a perfluorocyclopentanediyl group, a perfluorocycloheptanediyl group, and a perfluoroadamantanediyl group.

L ^4a is preferably a single bond, a methylene group or an ethylene group, more preferably a single bond or a methylene group.
^L3a is preferably a perfluoroalkanediyl group having 1 to 6 carbon atoms, and more preferably a perfluoroalkanediyl group having 1 to 3 carbon atoms.

Examples of the structural unit (a4-0) include the structural units shown below and structural units in which the methyl group corresponding to R ^5a in the structural unit (a4-0) has been replaced with a hydrogen atom.

[In formula (a4-1),
R ^a41 represents a hydrogen atom or a methyl group.
R ^a42 represents a saturated hydrocarbon group having 1 to 20 carbon atoms which may have a substituent, and one --CH ₂ -- contained in the saturated hydrocarbon group may be replaced by --O-- or --CO--.
A ^a41 represents an alkanediyl group having 1 to 6 carbon atoms which may have a substituent or a group represented by formula (a-g1), provided that at least one of A ^a41 and R ^a42 has a halogen atom (preferably a fluorine atom) as a substituent.
[In formula (a-g1),
s represents 0 or 1.
A ^a42 and A ^a44 each independently represent a divalent saturated hydrocarbon group having 1 to 5 carbon atoms which may have a substituent.
A ^a43 represents a single bond or a divalent aliphatic hydrocarbon group having 1 to 5 carbon atoms which may have a substituent.
X ^a41 and X ^a42 each independently represent —O—, —CO—, —CO—O— or —O—CO—.
However, the total number of carbon atoms of A ^a42 , A ^a43 , A ^a44 , X ^a41 and X ^a42 is 7 or less.]
* indicates the bonding position, and the * on the right side indicates the bonding position with —O—CO—R ^a42 .]

Examples of the saturated hydrocarbon group for R ^a42 include a chain saturated hydrocarbon group, a monocyclic or polycyclic alicyclic saturated hydrocarbon group, and groups formed by combining these groups.

Examples of the chain saturated hydrocarbon group include a methyl group, an ethyl group, a propyl group, a butyl group, a pentyl group, a hexyl group, a heptyl group, an octyl group, a decyl group, a dodecyl group, a pentadecyl group, a hexadecyl group, a heptadecyl group, and an octadecyl group.
Examples of the monocyclic or polycyclic alicyclic saturated hydrocarbon group include cycloalkyl groups such as a cyclopentyl group, a cyclohexyl group, a cycloheptyl group, and a cyclooctyl group; and polycyclic alicyclic saturated hydrocarbon groups such as a decahydronaphthyl group, an adamantyl group, a norbornyl group, and the following groups (* indicates a bonding position):
Examples of groups formed by this combination include groups formed by combining one or more alkyl groups or one or more alkanediyl groups with one or more alicyclic saturated hydrocarbon groups, such as -alkanediyl group-alicyclic saturated hydrocarbon group, -alicyclic saturated hydrocarbon group-alkyl group, and -alkanediyl group-alicyclic saturated hydrocarbon group-alkyl group.

Examples of the substituent that R ^a42 has include at least one selected from the group consisting of a halogen atom and a group represented by formula (a-g3): Examples of the halogen atom include a fluorine atom, a chlorine atom, a bromine atom, and an iodine atom, and a fluorine atom is preferred.
[In formula (a-g3),
X ^a43 represents an oxygen atom, a carbonyl group, *-O-CO- or *-CO-O-.
A ^a45 represents an aliphatic hydrocarbon group having 1 to 17 carbon atoms which may have a halogen atom.
* indicates the bonding position with R ^a42 .]
However, in R ^a42 -X ^a43 -A ^a45 , when R ^a42 does not have a halogen atom, A ^a45 represents an aliphatic hydrocarbon group having 1 to 17 carbon atoms and at least one halogen atom.

Examples of the aliphatic hydrocarbon group for A ^a45 include alkyl groups such as a methyl group, an ethyl group, a propyl group, a butyl group, a pentyl group, a hexyl group, a heptyl group, an octyl group, a decyl group, a dodecyl group, a pentadecyl group, a hexadecyl group, a heptadecyl group, and an octadecyl group;
Examples include monocyclic alicyclic hydrocarbon groups such as a cyclopentyl group, a cyclohexyl group, a cycloheptyl group, and a cyclooctyl group; and polycyclic alicyclic hydrocarbon groups such as a decahydronaphthyl group, an adamantyl group, a norbornyl group, and the following groups (* indicates a bonding position):

R ^a42 is preferably a saturated hydrocarbon group which may have a halogen atom, and more preferably a saturated hydrocarbon group having an alkyl group having a halogen atom and/or a group represented by formula (a-g3).
When R ^a42 is a saturated hydrocarbon group having a halogen atom, it is preferably a saturated hydrocarbon group having a fluorine atom, more preferably a perfluoroalkyl group or a perfluorocycloalkyl group, still more preferably a perfluoroalkyl group having 1 to 6 carbon atoms, and particularly preferably a perfluoroalkyl group having 1 to 3 carbon atoms. Examples of perfluoroalkyl groups include a perfluoromethyl group, a perfluoroethyl group, a perfluoropropyl group, a perfluorobutyl group, a perfluoropentyl group, a perfluorohexyl group, a perfluoroheptyl group, and a perfluorooctyl group. Examples of perfluorocycloalkyl groups include a perfluorocyclohexyl group.
When R ^a42 is a saturated hydrocarbon group having a group represented by formula (a-g3), the total number of carbon atoms in R ^a42 , including the number of carbon atoms contained in the group represented by formula (a-g3), is preferably 15 or less, and more preferably 12 or less. When R a42 has a group represented by formula (a-g3) as a substituent, the number thereof is preferably 1.

When R ^a42 is a saturated hydrocarbon group having a group represented by formula (a-g3), R ^a42 is more preferably a group represented by formula (a-g2).
[In formula (a-g2),
A ^a46 represents a divalent saturated hydrocarbon group having 1 to 17 carbon atoms which may have a halogen atom.
X ^a44 represents **-O-CO- or **-CO-O- (** represents the bonding position with A ^a46 ).
A ^a47 represents an aliphatic hydrocarbon group having 1 to 17 carbon atoms which may have a halogen atom.
However, the total number of carbon atoms of A ^a46 , A ^a47 and X ^a44 is 18 or less, and at least one of A ^a46 and A ^a47 has at least one halogen atom.
* indicates the bonding position with the carbonyl group.

The saturated hydrocarbon group of A ^a46 preferably has 1 to 6 carbon atoms, and more preferably 1 to 3 carbon atoms.
The aliphatic hydrocarbon group of A ^a47 preferably has 4 to 15 carbon atoms, more preferably 5 to 12 carbon atoms, and A ^a47 is even more preferably a cyclohexyl group or an adamantyl group.

A preferred structure of the group represented by formula (a-g2) is the following structure (* indicates the bonding position with the carbonyl group):

Examples of the alkanediyl group for A ^a41 include linear alkanediyl groups such as a methylene group, an ethylene group, a propane-1,3-diyl group, a butane-1,4-diyl group, a pentane-1,5-diyl group, and a hexane-1,6-diyl group; and branched alkanediyl groups such as a propane-1,2-diyl group, a butane-1,3-diyl group, a 2-methylpropane-1,2-diyl group, a 1-methylbutane-1,4-diyl group, and a 2-methylbutane-1,4-diyl group.
Examples of the substituent in the alkanediyl group represented by A ^a41 include a hydroxy group and an alkoxy group having 1 to 6 carbon atoms.
A ^a41 is preferably an alkanediyl group having 1 to 4 carbon atoms, more preferably an alkanediyl group having 2 to 4 carbon atoms, and even more preferably an ethylene group.

Examples of the divalent saturated hydrocarbon group represented by A ^a42 , A ^a43 , and A ^a44 in the group represented by formula (a-g1) include a linear or branched alkanediyl group, a monocyclic or polycyclic divalent alicyclic hydrocarbon group, and a group formed by combining an alkanediyl group and a divalent alicyclic hydrocarbon group. Specific examples include a methylene group, an ethylene group, a propane-1,3-diyl group, a propane-1,2-diyl group, a butane-1,4-diyl group, a 1-methylpropane-1,3-diyl group, a 2-methylpropane-1,3-diyl group, and a 2-methylpropane-1,2-diyl group.
Examples of the substituent of the divalent saturated hydrocarbon group represented by A ^a42 , A ^a43 and A ^a44 include a hydroxy group and an alkoxy group having 1 to 6 carbon atoms.
Preferably, s is 0.

In the group represented by formula (a-g1), examples of the group in which X ^a42 is —O—, —CO—, —CO—O—, or —O—CO— include the following groups: In the following examples, * and ** each represent a bonding position, and ** is the bonding position with —O—CO—R ^a42 .

Examples of the structural unit represented by formula (a4-1) include the structural units shown below and structural units in which the methyl group corresponding to R ^a41 in the structural unit represented by formula (a4-1) in the following structural units is replaced with a hydrogen atom.

The structural unit represented by formula (a4-1) is preferably a structural unit represented by formula (a4-2).
[In formula (a4-2),
R ^f5 represents a hydrogen atom or a methyl group.
L ⁴⁴ represents an alkanediyl group having 1 to 6 carbon atoms, and one --CH ₂ -- contained in the alkanediyl group may be replaced by --O-- or --CO--.
R ^f6 represents a saturated hydrocarbon group having 1 to 20 carbon atoms and containing a fluorine atom.
However, the upper limit of the total number of carbon atoms in L ⁴⁴ and R ^f6 is 21.]

Examples of the alkanediyl group of L ⁴⁴ include the same groups as those exemplified for A ^a41 .
Examples of the saturated hydrocarbon group of R ^f6 include the same groups as those exemplified for R ^a42 .
The alkanediyl group in L ⁴⁴ is preferably an alkanediyl group having 2 to 4 carbon atoms, more preferably an ethylene group.

Examples of the structural unit represented by formula (a4-2) include structural units represented by formulas (a4-1-1) to (a4-1-11). Examples of the structural unit represented by formula (a4-2) include a structural unit in which the methyl group corresponding to R ^f5 in the structural unit (a4-2) is replaced with a hydrogen atom.

[In formula (a4-3),
R ^f7 represents a hydrogen atom or a methyl group.
^L5 represents an alkanediyl group having 1 to 6 carbon atoms.
A ^f13 represents a divalent saturated hydrocarbon group having 1 to 18 carbon atoms which may have a fluorine atom.
X ^f12 represents *-O-CO- or *-CO-O- (* represents the bonding position to A ^f13 ).
A ^f14 represents a saturated hydrocarbon group having 1 to 17 carbon atoms which may have a fluorine atom.
However, at least one of A ^f13 and A ^f14 has a fluorine atom, and the upper limit of the total number of carbon atoms of L ⁵ , A ^f13 and A ^f14 is 20.]

Examples of the alkanediyl group in ^L5 include the same groups as those exemplified as the alkanediyl group in ^Aa41 .
The divalent saturated hydrocarbon group for A ^f13 which may have a fluorine atom is preferably a divalent chain saturated hydrocarbon group which may have a fluorine atom and a divalent alicyclic saturated hydrocarbon group which may have a fluorine atom, and more preferably a perfluoroalkanediyl group.
Examples of the divalent chain hydrocarbon group which may have a fluorine atom include alkanediyl groups such as a methylene group, an ethylene group, a propanediyl group, a butanediyl group, and a pentanediyl group; and perfluoroalkanediyl groups such as a difluoromethylene group, a perfluoroethylene group, a perfluoropropanediyl group, a perfluorobutanediyl group, and a perfluoropentanediyl group.
The divalent alicyclic hydrocarbon group optionally having a fluorine atom may be either monocyclic or polycyclic. Examples of the monocyclic group include a cyclohexanediyl group and a perfluorocyclohexanediyl group. Examples of the polycyclic group include an adamantanediyl group, a norbornanediyl group, and a perfluoroadamantanediyl group.

Examples of the saturated hydrocarbon group and the saturated hydrocarbon group which may have a fluorine atom of A ^f14 include the same groups as those exemplified for R ^a42 . Among them, a trifluoromethyl group, a difluoromethyl group, a methyl group, a perfluoroethyl group, a 2,2,2-trifluoroethyl group, a 1,1,2,2-tetrafluoroethyl group, an ethyl group, a perfluoropropyl group, a 2,2,3,3,3-pentafluoropropyl group, a propyl group, a perfluorobutyl group, a 1,1,2,2,3,3,4,4-octafluorobutyl group, a butyl group, a perfluoropentyl group, a 2,2,3,3,4,4,5,5,5-nonafluoropentyl group, a pentyl group, Preferred are fluorinated alkyl groups such as a hexyl group, a perfluorohexyl group, a heptyl group, a perfluoroheptyl group, an octyl group, and a perfluorooctyl group, a cyclopropylmethyl group, a cyclopropyl group, a cyclobutylmethyl group, a cyclopentyl group, a cyclohexyl group, a perfluorocyclohexyl group, an adamantyl group, an adamantylmethyl group, an adamantyldimethyl group, a norbornyl group, a norbornylmethyl group, a perfluoroadamantyl group, and a perfluoroadamantylmethyl group.

In formula (a4-3), L ⁵ is preferably an ethylene group.
The divalent saturated hydrocarbon group for A ^f13 is preferably a group containing a divalent chain hydrocarbon group having 1 to 6 carbon atoms and a divalent alicyclic hydrocarbon group having 3 to 12 carbon atoms, more preferably a divalent chain hydrocarbon group having 2 to 3 carbon atoms.
The saturated hydrocarbon group of A ^f14 is preferably a group containing a chain hydrocarbon group having 3 to 12 carbon atoms and an alicyclic hydrocarbon group having 3 to 12 carbon atoms, and more preferably a group containing a chain hydrocarbon group having 3 to 10 carbon atoms and an alicyclic hydrocarbon group having 3 to 10 carbon atoms. Of these, A ^f14 is preferably a group containing an alicyclic hydrocarbon group having 3 to 12 carbon atoms, and more preferably a cyclopropylmethyl group, a cyclopentyl group, a cyclohexyl group, a norbornyl group, or an adamantyl group.

Examples of the structural unit represented by formula (a4-3) include structural units represented by formulas (a4-1'-1) to (a4-1'-11). Examples of the structural unit represented by formula (a4-3) include a structural unit in which the methyl group corresponding to ^Rf7 in the structural unit (a4-3) is replaced with a hydrogen atom.

The structural unit (a4) also includes a structural unit represented by formula (a4-4).
[In formula (a4-4),
R ^f21 represents a hydrogen atom or a methyl group.
A ^f21 represents --(CH ₂ ) _j1 --, --(CH ₂ ) _j2 --O--(CH ₂ ) _j3 --, or --(CH ₂ ) _j4 --CO--O--(CH ₂ ) _j5 --.
j1 to j5 each independently represent an integer of 1 to 6.
R ^f22 represents a saturated hydrocarbon group having 1 to 10 carbon atoms and a fluorine atom.]

Examples of the saturated hydrocarbon group for R ^f22 include the same as the saturated hydrocarbon group represented by R ^a42 . ^{R f22} is preferably an alkyl group having 1 to 10 carbon atoms and containing a fluorine atom or an alicyclic hydrocarbon group having 1 to 10 carbon atoms and containing a fluorine atom, more preferably an alkyl group having 1 to 10 carbon atoms and containing a fluorine atom, and even more preferably an alkyl group having 1 to 6 carbon atoms and containing a fluorine atom.
In formula (a4-4), A ^f21 is preferably —(CH ₂ ) _j1 —, more preferably an ethylene group or a methylene group, and even more preferably a methylene group.

Examples of the structural unit represented by formula (a4-4) include the following structural units and structural units represented by the following formulas in which a methyl group corresponding to R ^f21 in the structural unit (a4-4) is replaced with a hydrogen atom:
When the resin (A) has the structural unit (a4), the content thereof is preferably 1 to 20 mol %, more preferably 2 to 15 mol %, and even more preferably 3 to 10 mol %, based on all structural units of the resin (A).

<Structural unit (a5)>
The non-leaving hydrocarbon group contained in the structural unit (a5) may be a group containing a linear, branched, or cyclic hydrocarbon group. Among these, the structural unit (a5) is preferably a group containing an alicyclic hydrocarbon group.
Examples of the structural unit (a5) include a structural unit represented by formula (a5-1).
[In formula (a5-1),
R ⁵¹ represents a hydrogen atom or a methyl group.
R ⁵² represents an alicyclic hydrocarbon group having 3 to 18 carbon atoms, and a hydrogen atom contained in the alicyclic hydrocarbon group may be substituted with an aliphatic hydrocarbon group having 1 to 8 carbon atoms.
L ⁵⁵ represents a single bond or a divalent saturated hydrocarbon group having 1 to 18 carbon atoms, and one —CH ₂ — contained in the saturated hydrocarbon group may be replaced by —O— or —CO—.]

The alicyclic hydrocarbon group for ^R52 may be either monocyclic or polycyclic. Examples of monocyclic alicyclic hydrocarbon groups include cyclopropyl, cyclobutyl, cyclopentyl, and cyclohexyl. Examples of polycyclic alicyclic hydrocarbon groups include adamantyl and norbornyl.
Examples of the aliphatic hydrocarbon group having 1 to 8 carbon atoms include alkyl groups such as a methyl group, an ethyl group, a propyl group, an isopropyl group, a butyl group, a sec-butyl group, a tert-butyl group, a pentyl group, a hexyl group, an octyl group, and a 2-ethylhexyl group.
Examples of the alicyclic hydrocarbon group having a substituent include a 3-methyladamantyl group.
R ⁵² is preferably an unsubstituted alicyclic hydrocarbon group having 3 to 18 carbon atoms, and more preferably an adamantyl group, a norbornyl group, or a cyclohexyl group.

The divalent saturated hydrocarbon group for L ⁵⁵ includes a divalent chain saturated hydrocarbon group and a divalent alicyclic saturated hydrocarbon group, and is preferably a divalent chain saturated hydrocarbon group.
Examples of the divalent chain saturated hydrocarbon group include a methylene group, an ethylene group, and an alkanediyl group such as a propanediyl group, a butanediyl group, and a pentanediyl group.
The divalent alicyclic saturated hydrocarbon group may be either monocyclic or polycyclic. Examples of the monocyclic alicyclic saturated hydrocarbon group include cycloalkanediyl groups such as cyclopentanediyl and cyclohexanediyl. Examples of the polycyclic divalent alicyclic saturated hydrocarbon group include adamantanediyl and norbornanediyl.

Examples of the divalent saturated hydrocarbon group represented by L ⁵⁵ in which —CH ₂ — is replaced by —O— or —CO— include groups represented by formulae (L1-1) to (L1-4). In the following formulae, * and ** represent bonding positions, and * represents the bonding position with an oxygen atom.
In formula (L1-1),
X ^x1 represents *-O-CO- or *-CO-O- (* represents the bonding position with L ^x1 ).
L ^x1 represents a divalent aliphatic saturated hydrocarbon group having 1 to 16 carbon atoms.
L ^x2 represents a single bond or a divalent aliphatic saturated hydrocarbon group having 1 to 15 carbon atoms.
However, the total number of carbon atoms in L ^x1 and L ^x2 is 16 or less.
In formula (L1-2),
L ^x3 represents a divalent aliphatic saturated hydrocarbon group having 1 to 17 carbon atoms.
L ^x4 represents a single bond or a divalent aliphatic saturated hydrocarbon group having 1 to 16 carbon atoms.
However, the total number of carbon atoms in L ^x3 and L ^x4 is 17 or less.
In formula (L1-3),
L ^x5 represents a divalent aliphatic saturated hydrocarbon group having 1 to 15 carbon atoms.
L ^x6 and L ^x7 each independently represent a single bond or a divalent aliphatic saturated hydrocarbon group having 1 to 14 carbon atoms.
However, the total number of carbon atoms in L ^x5 , L ^x6 and L ^x7 is 15 or less.
In formula (L1-4),
L ^x8 and L ^x9 each represent a single bond or a divalent aliphatic saturated hydrocarbon group having 1 to 12 carbon atoms.
W ^x1 represents a divalent alicyclic saturated hydrocarbon group having 3 to 15 carbon atoms.
However, the total number of carbon atoms in L ^x8 , L ^x9 and W ^x1 is 15 or less.

L ^x1 is preferably a divalent aliphatic saturated hydrocarbon group having 1 to 8 carbon atoms, more preferably a methylene group or an ethylene group.
L ^x2 is preferably a single bond or a divalent aliphatic saturated hydrocarbon group having 1 to 8 carbon atoms, more preferably a single bond.
L ^x3 is preferably a divalent aliphatic saturated hydrocarbon group having 1 to 8 carbon atoms.
L ^x4 is preferably a single bond or a divalent aliphatic saturated hydrocarbon group having 1 to 8 carbon atoms.
L ^x5 is preferably a divalent aliphatic saturated hydrocarbon group having 1 to 8 carbon atoms, more preferably a methylene group or an ethylene group.
L ^x6 is preferably a single bond or a divalent aliphatic saturated hydrocarbon group having 1 to 8 carbon atoms, more preferably a methylene group or an ethylene group.
L ^x7 is preferably a single bond or a divalent aliphatic saturated hydrocarbon group having 1 to 8 carbon atoms.
L ^x8 is preferably a single bond or a divalent aliphatic saturated hydrocarbon group having 1 to 8 carbon atoms, more preferably a single bond or a methylene group.
L ^x9 is preferably a single bond or a divalent aliphatic saturated hydrocarbon group having 1 to 8 carbon atoms, more preferably a single bond or a methylene group.
W ^x1 is preferably a divalent alicyclic saturated hydrocarbon group having 3 to 10 carbon atoms, more preferably a cyclohexanediyl group or an adamantanediyl group.

Examples of the group represented by formula (L1-1) include the divalent groups shown below.

Examples of the group represented by formula (L1-2) include the divalent groups shown below.

Examples of the group represented by formula (L1-3) include the divalent groups shown below.

Examples of the group represented by formula (L1-4) include the divalent groups shown below.
L ⁵⁵ is preferably a single bond or a group represented by formula (L1-1).

Examples of the structural unit (a5-1) include the structural units shown below and structural units in which the methyl group corresponding to R ⁵¹ in the structural unit (a5-1) has been replaced with a hydrogen atom.
When the resin (A) has the structural unit (a5), the content thereof is preferably 1 to 30 mol %, more preferably 2 to 20 mol %, and even more preferably 3 to 15 mol %, based on all structural units of the resin (A).

<Structural Unit (II)>
Resin (A) may further contain a structural unit that decomposes upon exposure to generate an acid (hereinafter, sometimes referred to as "structural unit (II)"). Specific examples of structural unit (II) include the structural units described in JP-A-2016-79235, and are preferably structural units having a sulfonate group or carboxylate group and an organic cation in the side chain, or a structural unit having a sulfonio group and an organic anion in the side chain.

The structural unit having a sulfonate group or carboxylate group and an organic cation in the side chain is preferably a structural unit represented by formula (II-2-A').
[In formula (II-2-A'),
X ^III3 represents a divalent saturated hydrocarbon group having 1 to 18 carbon atoms, in which —CH ₂ — contained in the saturated hydrocarbon group may be replaced by —O—, —S— or —CO—, and a hydrogen atom contained in the saturated hydrocarbon group may be replaced by a halogen atom, an alkyl group having 1 to 6 carbon atoms which may have a halogen atom, or a hydroxy group.
A ^x1 represents an alkanediyl group having 1 to 8 carbon atoms, and a hydrogen atom contained in the alkanediyl group may be substituted with a fluorine atom or a perfluoroalkyl group having 1 to 6 carbon atoms.
RA ^- represents a sulfonate group or a carboxylate group.
R ^III3 represents a hydrogen atom, a halogen atom or an alkyl group having 1 to 6 carbon atoms which may have a halogen atom.
ZA ⁺ represents an organic cation.

Examples of the halogen atom represented by R ^III3 include a fluorine atom, a chlorine atom, a bromine atom, and an iodine atom.
Examples of the alkyl group having 1 to 6 carbon atoms which may have a halogen atom and which is represented by R ^III3 include the same as the alkyl group having 1 to 6 carbon atoms which may have a halogen atom and which is represented by R ^a8 .
Examples of the alkanediyl group having 1 to 8 carbon atoms represented by A ^x1 include a methylene group, an ethylene group, a propane-1,3-diyl group, a butane-1,4-diyl group, a pentane-1,5-diyl group, a hexane-1,6-diyl group, an ethane-1,1-diyl group, a propane-1,1-diyl group, a propane-1,2-diyl group, a propane-2,2-diyl group, a pentane-2,4-diyl group, a 2-methylpropane-1,3-diyl group, a 2-methylpropane-1,2-diyl group, a pentane-1,4-diyl group, and a 2-methylbutane-1,4-diyl group.
Examples of the perfluoroalkyl group having 1 to 6 carbon atoms which may be substituted by A ^x1 include a trifluoromethyl group, a perfluoroethyl group, a perfluoropropyl group, a perfluoroisopropyl group, a perfluorobutyl group, a perfluorosec-butyl group, a perfluorotert-butyl group, a perfluoropentyl group, and a perfluorohexyl group.
Examples of the divalent saturated hydrocarbon group having 1 to 18 carbon atoms represented by X ^III3 include linear or branched alkanediyl groups, and monocyclic or polycyclic divalent alicyclic saturated hydrocarbon groups, and combinations of these may also be used.
Specific examples thereof include linear alkanediyl groups such as methylene, ethylene, propane-1,3-diyl, propane-1,2-diyl, butane-1,4-diyl, pentane-1,5-diyl, hexane-1,6-diyl, heptane-1,7-diyl, octane-1,8-diyl, nonane-1,9-diyl, decane-1,10-diyl, undecane-1,11-diyl, and dodecane-1,12-diyl; butane-1,3-diyl, 2-methylpropane-1,3-diyl, and 2-methylpropane-1,3-diyl; Examples thereof include branched alkanediyl groups such as pentane-1,2-diyl group, pentane-1,4-diyl group, and 2-methylbutane-1,4-diyl group; cycloalkanediyl groups such as cyclobutane-1,3-diyl group, cyclopentane-1,3-diyl group, cyclohexane-1,4-diyl group, and cyclooctane-1,5-diyl group; and divalent polycyclic alicyclic saturated hydrocarbon groups such as norbornane-1,4-diyl group, norbornane-2,5-diyl group, adamantane-1,5-diyl group, and adamantane-2,6-diyl group.
Examples of saturated hydrocarbon groups in which —CH ₂ — is replaced by —O—, —S— or —CO— include divalent groups represented by formulae (X1) to (X53). However, the number of carbon atoms before —CH ₂ — is replaced by —O—, —S— or —CO— is 17 or less. In the following formulae, * represents a bond to A ^x1 .

^X3 represents a divalent saturated hydrocarbon group having 1 to 16 carbon atoms.
X ⁴ represents a divalent saturated hydrocarbon group having 1 to 15 carbon atoms.
^X5 represents a divalent saturated hydrocarbon group having 1 to 13 carbon atoms.
^X6 represents a divalent saturated hydrocarbon group having 1 to 14 carbon atoms.
^X7 represents a trivalent saturated hydrocarbon group having 1 to 14 carbon atoms.
^X8 represents a divalent saturated hydrocarbon group having 1 to 13 carbon atoms.

ZA ⁺ in formula (II-2-A') may be the same as the cation Z1 ⁺ in the acid generator (B1).

The structural unit represented by formula (II-2-A') is preferably a structural unit represented by formula (II-2-A).
[In formula (II-2-A),
R ^III3 , X ^III3 and ZA ⁺ have the same meanings as above.
z2A represents an integer of 0 to 6.
R ^III2 and R ^III4 each independently represent a hydrogen atom, a fluorine atom, or a perfluoroalkyl group having 1 to 6 carbon atoms, and when z2A is 2 or greater, a plurality of R ^III2s and R ^III4s may be the same or different.
Q ^a and Q ^b each independently represent a fluorine atom or a perfluoroalkyl group having 1 to 6 carbon atoms.]
Examples of the perfluoroalkyl group having 1 to 6 carbon atoms represented by R ^III2 , R ^III4 , Q ^a and Q ^b include the same perfluoroalkyl groups having 1 to 6 carbon atoms as those represented by Q ^b1 above.

The structural unit represented by formula (II-2-A) is preferably a structural unit represented by formula (II-2-A-1).
[In formula (II-2-A-1),
R ^III2 , R ^III3 , R ^III4 , Q ^a , Q ^b and ZA ⁺ have the same meanings as above.
R ^III5 represents a saturated hydrocarbon group having 1 to 12 carbon atoms.
z2A1 represents an integer of 0 to 6.
X ^I2 represents a divalent saturated hydrocarbon group having 1 to 11 carbon atoms, in which —CH ₂ — contained in the saturated hydrocarbon group may be replaced by —O—, —S—, or —CO—, and in which a hydrogen atom contained in the saturated hydrocarbon group may be substituted by a halogen atom or a hydroxy group.]
Examples of saturated hydrocarbon groups having 1 to 12 carbon atoms represented by R ^III5 include linear or branched alkyl groups such as methyl, ethyl, propyl, isopropyl, butyl, sec-butyl, tert-butyl, pentyl, hexyl, heptyl, octyl, nonyl, decyl, undecyl, and dodecyl groups.
Examples of the divalent saturated hydrocarbon group represented by X ^I2 include the same as the divalent saturated hydrocarbon group represented by X ^III3 .

As the structural unit represented by formula (II-2-A-1), a structural unit represented by formula (II-2-A-2) is more preferred.
[In formula (II-2-A-2),
R ^III3 , R ^III5 and ZA ⁺ have the same meanings as above.
mA and nA each independently represent 1 or 2.

Examples of the structural unit represented by formula (II-2-A') include the following structural units, structural units in which the group corresponding to the methyl group in R ^III3 is replaced with a hydrogen atom, a halogen atom (e.g., a fluorine atom), or an alkyl group having 1 to 6 carbon atoms which may have a halogen atom (e.g., a trifluoromethyl group), and structural units described in WO 2012/050015. ZA ⁺ represents an organic cation.

The structural unit having a sulfonio group and an organic anion on the side chain is preferably a structural unit represented by formula (II-1-1).
[In formula (II-1-1),
A ^II1 represents a single bond or a divalent linking group.
R ^II1 represents a divalent aromatic hydrocarbon group having 6 to 18 carbon atoms.
R ^II2 and R ^II3 each independently represent a hydrocarbon group having 1 to 18 carbon atoms, and R ^II2 and R ^II3 may be bonded to each other to form a ring together with the sulfur atom to which they are bonded.
R ^II4 represents a hydrogen atom, a halogen atom or an alkyl group having 1 to 6 carbon atoms which may have a halogen atom.
A ⁻ represents an organic anion.
Examples of the divalent aromatic hydrocarbon group having 6 to 18 carbon atoms represented by R ^II1 include a phenylene group and a naphthylene group.
Examples of the hydrocarbon group represented by R ^II2 and R ^II3 include an alkyl group, an alicyclic hydrocarbon group, an aromatic hydrocarbon group, and a group formed by combining these groups.
Examples of the halogen atom represented by R ^II4 include a fluorine atom, a chlorine atom, a bromine atom, and an iodine atom.
Examples of the alkyl group having 1 to 6 carbon atoms which may have a halogen atom and which is represented by R ^II4 include the same as the alkyl group having 1 to 6 carbon atoms which may have a halogen atom and which is represented by R ^a8 .
Examples of the divalent linking group represented by A ^II1 include divalent saturated hydrocarbon groups having 1 to 18 carbon atoms, in which —CH ₂ — may be replaced by —O—, —S—, or —CO—. Specific examples include the same as the divalent saturated hydrocarbon groups having 1 to 18 carbon atoms represented by X ^III3 .

Examples of the cation-containing structural unit in formula (II-1-1) include structural units represented by the following formulas and structural units in which the group corresponding to the methyl group in R ^II4 is replaced with a hydrogen atom, a fluorine atom, a trifluoromethyl group, or the like.

Examples of the organic anion represented by ^A- include a sulfonate anion, a sulfonylimide anion, a sulfonylmethide anion, and a carboxylate anion. The organic anion represented by ^A- is preferably a sulfonate anion, and the sulfonate anion is more preferably an anion contained in the salt represented by the above formula (B1).

Examples of the sulfonylimide anion represented by A 1 ^- include the following.

Examples of sulfonylmethide anions include the following:

Examples of carboxylate anions include the following:

Examples of the structural unit represented by formula (II-1-1) include structural units represented by the following formulas:
When the resin (A) contains the structural unit (II), the content of the structural unit (II) is preferably 1 to 20 mol %, more preferably 2 to 15 mol %, and even more preferably 3 to 10 mol %, based on the total structural units of the resin (A).

Resin (A) may contain structural units other than those described above, including structural units well known in the art.

The resin (A) is preferably a resin composed of the structural unit (a1) and the structural unit (s).
The structural unit (a1) is preferably at least one selected from the group consisting of the structural unit (a1-0), the structural unit (a1-1), and the structural unit (a1-2) (preferably the structural unit having a cyclohexyl group and a cyclopentyl group), more preferably at least two selected from the group consisting of the structural unit (a1-0), the structural unit (a1-1), and the structural unit (a1-2), and even more preferably the structural unit (a1-1) and/or the structural unit (a1-2).
The structural unit (s) is preferably at least one selected from the group consisting of the structural unit (a2) and the structural unit (a3). The structural unit (a2) is preferably a structural unit represented by formula (a2-A) or a structural unit represented by formula (a2-1). The structural unit (a3) is preferably at least one selected from the group consisting of a structural unit represented by formula (a3-1), a structural unit represented by formula (a3-2), and a structural unit represented by formula (a3-4).

The structural units constituting the resin (A) may be used singly or in combination of two or more, and can be produced by a known polymerization method (e.g., radical polymerization) using monomers that lead to these structural units. The content of each structural unit in the resin (A) can be adjusted by the amount of monomer used in the polymerization.
The weight average molecular weight of the resin (A) is preferably 2,000 or more (more preferably 2,500 or more, even more preferably 3,000 or more) and 50,000 or less (more preferably 30,000 or less, even more preferably 15,000 or less). In this specification, the weight average molecular weight is a value determined by gel permeation chromatography under the conditions described in the Examples.

<Resins other than resin (A)>
The resist composition of the present invention may contain a resin other than the resin (A) in combination.
Examples of resins other than resin (A) include resins containing the structural unit (a4) or the structural unit (a5) (hereinafter, sometimes referred to as resin (X)).
Of these, the resin (X) is preferably a resin containing the structural unit (a4).
In the resin (X), the content of the structural unit (a4) is preferably 30 mol % or more, more preferably 40 mol % or more, and even more preferably 45 mol % or more, based on the total amount of all structural units in the resin (X).
Examples of structural units that the resin (X) may further have include the structural unit (a2), the structural unit (a3), and structural units derived from other known monomers. Among these, the resin (X) is preferably a resin consisting only of the structural unit (a4) and/or the structural unit (a5), and more preferably a resin consisting only of the structural unit (a4).
The structural units constituting the resin (X) may be used singly or in combination of two or more, and can be produced by a known polymerization method (e.g., radical polymerization) using monomers that derive these structural units. The content of each structural unit in the resin (X) can be adjusted by the amount of monomer used in the polymerization.
The weight average molecular weight of resin (X) is preferably 6,000 or more (more preferably 7,000 or more) and 80,000 or less (more preferably 60,000 or less). The method for measuring the weight average molecular weight of resin (X) is the same as that for resin (A).
Furthermore, when the resist composition contains resin (X), the content thereof is preferably 1 to 60 parts by mass, more preferably 1 to 50 parts by mass, even more preferably 1 to 40 parts by mass, still more preferably 1 to 30 parts by mass, and particularly preferably 1 to 8 parts by mass, relative to 100 parts by mass of resin (A).

The content of resin (A) in the resist composition is preferably 80% by mass or more and 99% by mass or less, and more preferably 90% by mass or more and 99% by mass or less, based on the solid content of the resist composition. Furthermore, when resins other than resin (A) are contained, the total content of resin (A) and the resins other than resin (A) is preferably 80% by mass or more and 99% by mass or less, and more preferably 90% by mass or more and 99% by mass or less, based on the solid content of the resist composition. The solid content of the resist composition and the resin content relative to the solid content can be measured using known analytical methods such as liquid chromatography or gas chromatography.

<Solvent (E)>
The content of the solvent (E) in the resist composition is usually from 90% by mass to 99.9% by mass, preferably from 92% by mass to 99% by mass, and more preferably from 94% by mass to 99% by mass. The content of the solvent (E) can be measured by known analytical means such as liquid chromatography or gas chromatography.
Examples of the solvent (E) include glycol ether esters such as ethyl cellosolve acetate, methyl cellosolve acetate, and propylene glycol monomethyl ether acetate; glycol ethers such as propylene glycol monomethyl ether; esters such as ethyl lactate, butyl acetate, amyl acetate, and ethyl pyruvate; ketones such as acetone, methyl isobutyl ketone, 2-heptanone, and cyclohexanone; cyclic esters such as γ-butyrolactone; etc. One type of solvent (E) may be used alone, or two or more types may be used.

<Quencher (C)>
Examples of the quencher (C) include a basic nitrogen-containing organic compound or a salt that generates an acid with a weaker acidity than the acid generated from the acid generator (B) (however, excluding the carboxylate salt represented by formula (I)). When the resist composition contains the quencher (C), the content of the quencher (C) is preferably from about 0.01 to 15 mass%, more preferably from about 0.01 to 10 mass%, even more preferably from about 0.1 to 5 mass%, and even more preferably from about 0.1 to 3 mass%, based on the solids content of the resist composition.
The basic nitrogen-containing organic compound includes amines and ammonium salts. The amines include aliphatic amines and aromatic amines. The aliphatic amines include primary amines, secondary amines, and tertiary amines.
Examples of amines include 1-naphthylamine, 2-naphthylamine, aniline, diisopropylaniline, 2-, 3-, or 4-methylaniline, 4-nitroaniline, N-methylaniline, N,N-dimethylaniline, diphenylamine, hexylamine, heptylamine, octylamine, nonylamine, decylamine, dibutylamine, dipentylamine, dihexylamine, diheptylamine, dioctylamine, dinonylamine, didecylamine, triethylamine, trimethylamine, tripropylamine, and tributylamine. Amine, tripentylamine, trihexylamine, triheptylamine, trioctylamine, trinonylamine, tridecylamine, methyldibutylamine, methyldipentylamine, methyldihexylamine, methyldicyclohexylamine, methyldiheptylamine, methyldioctylamine, methyldinonylamine, methyldidecylamine, ethyldibutylamine, ethyldipentylamine, ethyldihexylamine, ethyldiheptylamine, ethyldioctylamine, ethyldinonylamine, ethyldidecylamine amine, dicyclohexylmethylamine, tris[2-(2-methoxyethoxy)ethyl]amine, triisopropanolamine, ethylenediamine, tetramethylenediamine, hexamethylenediamine, 4,4'-diamino-1,2-diphenylethane, 4,4'-diamino-3,3'-dimethyldiphenylmethane, 4,4'-diamino-3,3'-diethyldiphenylmethane, 2,2'-methylenebisaniline, imidazole, 4-methylimidazole, pyridine, 4-methylpyridine, 1,2-di(2-pyridyl)ethane Examples of the amines include 4,4'-dipyridyl ethane, 1,2-di(2-pyridyl)ethene, 1,2-di(4-pyridyl)ethene, 1,3-di(4-pyridyl)propane, 1,2-di(4-pyridyloxy)ethane, di(2-pyridyl)ketone, 4,4'-dipyridyl sulfide, 4,4'-dipyridyl disulfide, 2,2'-dipyridylamine, 2,2'-dipicolylamine, and bipyridine. Preferred are aromatic amines such as diisopropylaniline, and more preferred is 2,6-diisopropylaniline.
Examples of ammonium salts include tetramethylammonium hydroxide, tetraisopropylammonium hydroxide, tetrabutylammonium hydroxide, tetrahexylammonium hydroxide, tetraoctylammonium hydroxide, phenyltrimethylammonium hydroxide, 3-(trifluoromethyl)phenyltrimethylammonium hydroxide, tetra-n-butylammonium salicylate, and choline.

The acidity of a salt that generates an acid weaker than the acid generated from the acid generator (B) is indicated by its acid dissociation constant (pKa). A salt that generates an acid weaker than the acid generated from the acid generator (B) is a salt whose acid dissociation constant of the acid generated from the salt is usually −3<pKa, preferably −1<pKa<7, and more preferably 0<pKa<5.
Examples of salts that generate an acid that is weaker in acidity than the acid generated from acid generator (B) include salts represented by the following formula, salts represented by formula (D) described in JP 2015-147926 A (hereinafter, sometimes referred to as "weak acid inner salt (D)"), and salts described in JP 2012-229206 A, JP 2012-6908 A, JP 2012-72109 A, JP 2011-39502 A, and JP 2011-191745 A. The salt that generates an acid that is weaker in acidity than the acid generated from acid generator (B) is preferably a salt that generates a carboxylic acid that is weaker in acidity than the acid generated from acid generator (B) (salt having a carboxylic acid anion), and more preferably a weak acid inner salt (D).

Examples of the weak acid inner salt (D) include the following salts.

<Other ingredients>
The resist composition of the present invention may optionally contain components other than those described above (hereinafter, these may be referred to as "other components (F)"). There are no particular limitations on the other components (F), and additives known in the resist field, such as sensitizers, dissolution inhibitors, surfactants, stabilizers, and dyes, can be used.

<Preparation of Resist Composition>
The resist composition of the present invention can be prepared by mixing the carboxylate (I) and resin (A), the acid generator (B), and, if necessary, a resin other than the resin (A), the solvent (E), the quencher (C), and other components (F). The order of mixing is arbitrary and is not particularly limited. The temperature during mixing can be selected from 10 to 40°C, depending on the type of resin, the solubility of the resin in the solvent (E), and other factors. The mixing time can be selected from 0.5 to 24 hours, depending on the mixing temperature. The mixing means is also not particularly limited, and stirring and mixing can be used.
After mixing the components, it is preferable to filter the mixture using a filter with a pore size of about 0.003 to 0.2 μm.

<Method for producing a resist pattern>
The method for producing a resist pattern of the present invention comprises:
(1) applying the resist composition of the present invention onto a substrate;
(2) a step of drying the applied composition to form a composition layer;
(3) exposing the composition layer to light;
(4) a step of heating the composition layer after exposure; and (5) a step of developing the composition layer after heating.
The resist composition can be applied to a substrate using a commonly used device such as a spin coater. Examples of the substrate include inorganic substrates such as silicon wafers. Before applying the resist composition, the substrate may be cleaned, and an anti-reflective film or the like may be formed on the substrate.
The composition after coating is dried to remove the solvent and form a composition layer. Drying is carried out, for example, by evaporating the solvent using a heating device such as a hot plate (so-called pre-baking), or by using a vacuum device. The heating temperature is preferably 50 to 200°C, and the heating time is preferably 10 to 180 seconds. The pressure during vacuum drying is preferably about 1 to 1.0 x ¹⁰⁵ Pa.
The obtained composition layer is usually exposed using an exposure machine. The exposure machine may be an immersion exposure machine. As the exposure light source, various types can be used, such as those that emit ultraviolet laser light such as KrF excimer laser (wavelength 248 nm), ArF excimer laser (wavelength 193 nm), and _F2 excimer laser (wavelength 157 nm), those that emit harmonic laser light in the far ultraviolet or vacuum ultraviolet region by wavelength conversion of laser light from a solid laser light source (YAG or semiconductor laser, etc.), and those that irradiate electron beams or extreme ultraviolet light (EUV). In this specification, irradiation with these types of radiation may be collectively referred to as "exposure". During exposure, exposure is usually performed through a mask corresponding to the desired pattern. When the exposure light source is an electron beam, exposure may be performed by direct writing without using a mask.
The composition layer after exposure is subjected to a heat treatment (so-called post-exposure bake) to promote the deprotection reaction of the acid labile groups. The heating temperature is usually about 50 to 200°C, preferably about 70 to 150°C.
The heated composition layer is usually developed using a developer in a developing device. Development methods include dipping, puddling, spraying, and dynamic dispensing. The development temperature is preferably, for example, 5 to 60°C, and the development time is preferably, for example, 5 to 300 seconds. By selecting the type of developer as follows, a positive resist pattern or a negative resist pattern can be produced.
When producing a positive resist pattern from the resist composition of the present invention, an alkaline developer is used as the developer. The alkaline developer may be any of various alkaline aqueous solutions used in this field. Examples include aqueous solutions of tetramethylammonium hydroxide and (2-hydroxyethyl)trimethylammonium hydroxide (commonly known as choline). The alkaline developer may also contain a surfactant.
After development, the resist pattern is preferably washed with ultrapure water, and then water remaining on the substrate and pattern is removed.
When a negative resist pattern is produced from the resist composition of the present invention, a developer containing an organic solvent (hereinafter sometimes referred to as an "organic developer") is used as the developer.
Examples of the organic solvent contained in the organic developer include ketone solvents such as 2-hexanone and 2-heptanone; glycol ether ester solvents such as propylene glycol monomethyl ether acetate; ester solvents such as butyl acetate; glycol ether solvents such as propylene glycol monomethyl ether; amide solvents such as N,N-dimethylacetamide; and aromatic hydrocarbon solvents such as anisole.
The content of the organic solvent in the organic developer is preferably from 90% by mass to 100% by mass, more preferably from 95% by mass to 100% by mass, and even more preferably substantially from the organic solvent alone.
Among these, the organic developer is preferably a developer containing butyl acetate and/or 2-heptanone. The total content of butyl acetate and 2-heptanone in the organic developer is preferably 50% by mass or more and 100% by mass or less, more preferably 90% by mass or more and 100% by mass or less, and even more preferably the organic developer contains substantially only butyl acetate and/or 2-heptanone.
The organic developer may contain a surfactant and a small amount of water.
During development, development may be stopped by replacing the organic developer with a different type of solvent.
The developed resist pattern is preferably washed with a rinse solution. There are no particular limitations on the rinse solution as long as it does not dissolve the resist pattern, and a solution containing a general organic solvent can be used, preferably an alcohol solvent or an ester solvent.
After cleaning, it is preferable to remove the rinse liquid remaining on the substrate and the pattern.

<Application>
The resist composition of the present invention is suitable as a resist composition for KrF excimer laser exposure, a resist composition for ArF excimer laser exposure, a resist composition for electron beam (EB) exposure, or a resist composition for EUV exposure, and is particularly suitable as a resist composition for electron beam (EB) exposure or a resist composition for EUV exposure, and is useful for semiconductor microfabrication.

The present invention will be explained in more detail with reference to examples. In the examples, "%" and "parts" representing the content or amount used are by mass unless otherwise specified.
The weight-average molecular weight is a value determined by gel permeation chromatography under the following analytical conditions:
Column: TSKgel Multipore HXL-M x 3 + guard column (Tosoh Corporation)
Eluent: tetrahydrofuran Flow rate: 1.0 mL/min
Detector: RI detector Column temperature: 40°C
Injection volume: 100μl
Molecular weight standard: Standard polystyrene (Tosoh Corporation)
The structure of the compound was confirmed by measuring the molecular ion peak using mass spectrometry (LC: Agilent 1100 model, MASS: Agilent LC/MSD model). In the following examples, the value of this molecular ion peak is indicated by "MASS".

Example 1: Synthesis of salt represented by formula (I-2)
1.58 parts of the salt represented by formula (I-2-a), 0.47 parts of the compound represented by formula (I-2-b), and 10 parts of dimethylformamide were mixed and stirred at 23°C for 30 minutes. 0.44 parts of potassium carbonate was added to the resulting mixture, and the mixture was stirred at 23°C for 30 minutes, followed by further stirring at 90°C for 3 hours, thereby obtaining a mixture containing the salt represented by formula (I-2-c). The resulting mixture was cooled to 23°C, and 12 parts of a 5% aqueous oxalic acid solution was added and stirred at 23°C for 30 minutes. 1.48 parts of the salt represented by formula (I-2-d) was then added and stirred at 23°C for 7 hours. 30 parts of chloroform and 30 parts of ion-exchanged water were added to the resulting reaction mixture, and the mixture was stirred at 23°C for 30 minutes, followed by separation to isolate the organic layer. 30 parts of ion-exchanged water was added to the resulting organic layer, and the mixture was stirred at 23°C for 30 minutes, followed by separation to isolate the organic layer. This water-washing procedure was repeated 7 times. The obtained organic layer was concentrated to obtain 2.43 parts of the salt represented by formula (I-2).
MASS (ESI (+) Spectrum): M ⁺ 355.1
MASS (ESI(-)Spectrum): M ^- 193.1

Example 2: Synthesis of salt represented by formula (I-380)
1.58 parts of the salt represented by formula (I-2-a), 1.10 parts of the compound represented by formula (I-380-b), and 10 parts of dimethylformamide were mixed and stirred at 23°C for 30 minutes. 0.44 parts of potassium carbonate was added to the resulting mixture, and the mixture was stirred at 23°C for 30 minutes, followed by further stirring at 90°C for 3 hours, thereby obtaining a mixture containing the salt represented by formula (I-380-c). The resulting mixture was cooled to 23°C, and 12 parts of a 5% aqueous oxalic acid solution was added and stirred at 23°C for 30 minutes. 1.48 parts of the salt represented by formula (I-2-d) was then added and stirred at 23°C for 7 hours. 30 parts of chloroform and 30 parts of ion-exchanged water were added to the resulting reaction mixture, and the mixture was stirred at 23°C for 30 minutes, followed by separation to isolate the organic layer. 30 parts of ion-exchanged water was added to the resulting organic layer, and the mixture was stirred at 23°C for 30 minutes, followed by separation to isolate the organic layer. This water-washing procedure was repeated 7 times. The obtained organic layer was concentrated to obtain 2.02 parts of the salt represented by formula (I-380).
MASS (ESI (+) Spectrum): M ⁺ 481.0
MASS (ESI(-)Spectrum): M ^- 193.1

Example 3: Synthesis of salt represented by formula (I-1352)
1.19 parts of the compound represented by formula (I-1352-b) and 10 parts of tetrahydrofuran were mixed and stirred at 23°C for 30 minutes, then cooled to 5°C, and 0.14 parts of sodium hydride was added. To the resulting mixture, 1.58 parts of the salt represented by formula (I-2-a) was added, and the mixture was stirred at 5°C for 3 hours. To the resulting mixture, 6.30 parts of 1N hydrochloric acid was added, and the mixture was heated to 23°C and stirred at 23°C for 30 minutes. To the resulting mixture, 30 parts of chloroform and 15 parts of ion-exchanged water were added, and the mixture was stirred at 23°C for 30 minutes, followed by separation and isolation of the organic layer. The resulting organic layer was concentrated, and then 1.5 parts of acetonitrile and 30 parts of tert-butyl methyl ether were added to the concentrated residue, and the mixture was stirred at 23°C for 30 minutes. The supernatant was removed and the mixture was concentrated to obtain 2.49 parts of the salt represented by formula (I-1352-c). 2.49 parts of the salt represented by formula (I-1352-c), 1.38 parts of the salt represented by formula (I-2-d), and 20 parts of chloroform were added and stirred at 23°C for 3 hours. 15 parts of ion-exchanged water was added to the obtained reaction mixture, and the mixture was stirred at 23°C for 30 minutes, followed by separation to separate the organic layer. 15 parts of ion-exchanged water was added to the obtained organic layer, and the mixture was stirred at 23°C for 30 minutes, followed by separation to separate the organic layer. This water washing operation was repeated five times. The obtained organic layer was concentrated to obtain 2.79 parts of the salt represented by formula (I-1352).
MASS (ESI (+) Spectrum): M ⁺ 499.0
MASS (ESI(-)Spectrum): M ^- 193.1

Example 4: Synthesis of salt represented by formula (I-434)
0.92 parts of the compound represented by formula (I-434-b) and 10 parts of tetrahydrofuran were mixed and stirred at 23°C for 30 minutes, then cooled to 5°C, and 0.14 parts of sodium hydride was added. To the resulting mixture, 1.58 parts of the salt represented by formula (I-2-a) was added, and the mixture was stirred at 5°C for 3 hours. To the resulting mixture, 6.30 parts of 1N hydrochloric acid was added, and the mixture was heated to 23°C and stirred at 23°C for 30 minutes. To the resulting mixture, 30 parts of chloroform and 15 parts of ion-exchanged water were added, and the mixture was stirred at 23°C for 30 minutes, followed by separation and isolation of the organic layer. The resulting organic layer was concentrated, and then 1.5 parts of acetonitrile and 30 parts of tert-butyl methyl ether were added to the concentrated residue, and the mixture was stirred at 23°C for 30 minutes. The supernatant was removed and the mixture was concentrated to obtain 2.19 parts of the salt represented by formula (I-434-c). 2.19 parts of the salt represented by formula (I-434-c), 1.35 parts of the salt represented by formula (I-2-d), and 20 parts of chloroform were added and stirred at 23°C for 3 hours. 15 parts of ion-exchanged water was added to the obtained reaction mixture, and the mixture was stirred at 23°C for 30 minutes, followed by separation to separate the organic layer. 15 parts of ion-exchanged water was added to the obtained organic layer, and the mixture was stirred at 23°C for 30 minutes, followed by separation to separate the organic layer. This water washing operation was repeated five times. The obtained organic layer was concentrated to obtain 2.49 parts of the salt represented by formula (I-434).
MASS (ESI (+) Spectrum): M ⁺ 445.1
MASS (ESI(-)Spectrum): M ^- 193.1

Example 5: Synthesis of salt represented by formula (I-436)
0.92 parts of the compound represented by formula (I-434-b) and 10 parts of tetrahydrofuran were mixed and stirred at 23°C for 30 minutes, then cooled to 5°C, and 0.14 parts of sodium hydride was added. To the resulting mixture, 1.58 parts of the salt represented by formula (I-2-a) was added, and the mixture was stirred at 5°C for 3 hours. To the resulting mixture, 6.30 parts of 1N hydrochloric acid was added, and the mixture was heated to 23°C and stirred at 23°C for 30 minutes. To the resulting mixture, 30 parts of chloroform and 15 parts of ion-exchanged water were added, and the mixture was stirred at 23°C for 30 minutes, followed by separation and isolation of the organic layer. The resulting organic layer was concentrated, and then 1.5 parts of acetonitrile and 30 parts of tert-butyl methyl ether were added to the concentrated residue, and the mixture was stirred at 23°C for 30 minutes. The supernatant was removed and the mixture was concentrated to obtain 2.19 parts of the salt represented by formula (I-434-c). 2.19 parts of the salt represented by formula (I-434-c), 2.00 parts of the salt represented by formula (I-436-d), and 20 parts of chloroform were added and stirred at 23°C for 3 hours. 15 parts of ion-exchanged water was added to the obtained reaction mixture, and the mixture was stirred at 23°C for 30 minutes, followed by separation to separate the organic layer. 15 parts of ion-exchanged water was added to the obtained organic layer, and the mixture was stirred at 23°C for 30 minutes, followed by separation to separate the organic layer. This water washing operation was repeated five times. The obtained organic layer was concentrated to obtain 3.38 parts of the salt represented by formula (I-436).
MASS (ESI (+) Spectrum): M ⁺ 445.1
MASS (ESI(-)Spectrum): M ^- 337.1

Example 6: Synthesis of salt represented by formula (I-4100)
50 parts of the salt represented by formula (I-2-a), 30.34 parts of the compound represented by formula (I-380-b), and 250 parts of dimethylformamide were mixed and stirred at 23°C for 30 minutes. To the resulting mixture, 13.34 parts of potassium carbonate was added, and the mixture was stirred at 23°C for 30 minutes, and then further stirred at 80°C for 2 hours. The resulting reaction mixture was cooled to 23°C, and then 350 parts of chloroform and 210 parts of a 5% aqueous oxalic acid solution were added. The mixture was stirred at 23°C for 30 minutes, and then separated to separate the organic layer. To the resulting organic layer, 350 parts of ion-exchanged water was added, and the mixture was stirred at 23°C for 30 minutes, and then separated to separate the organic layer. This water washing operation was repeated five times. The obtained organic layer was concentrated, and then 250 parts of chloroform, 250 parts of ethyl acetate, and 250 parts of tert-butyl methyl ether were added to the concentrated residue. The mixture was stirred at 23°C for 30 minutes, and the supernatant was removed. The mixture was then concentrated, thereby obtaining 52.97 parts of the salt represented by formula (I-380-c).
25.29 parts of the salt represented by formula (I-380-c) and 90 parts of methanol were mixed and stirred at 23°C for 30 minutes. To the resulting mixture, 73.35 parts of sodium iodide and 370 parts of ion-exchanged water were added, and the mixture was stirred at 23°C for 30 minutes, followed by further stirring for 16 hours. 600 parts of chloroform was added to the resulting reaction mixture, and the mixture was stirred at 23°C for 30 minutes, followed by separation to separate the organic layer. 300 parts of ion-exchanged water was added to the resulting organic layer, and the mixture was stirred at 23°C for 30 minutes, followed by separation to separate the organic layer. This water washing operation was repeated three times. The resulting organic layer was concentrated, and then 20 parts of acetonitrile and 350 parts of tert-butyl methyl ether were added to the concentrated residue, followed by stirring at 23°C for 30 minutes, followed by filtration to obtain 28.08 parts of the salt represented by formula (I-380-d).
3.92 parts of the compound represented by formula (I-4100-a), 80 parts of methanol, and 1.78 parts of silver oxide were mixed and stirred at 23°C for 30 minutes. To the resulting mixture, 9.42 parts of the salt represented by formula (I-380-d) was added, and the mixture was stirred at 23°C for 16 hours and then filtered. The recovered filtrate was concentrated, and then 100 parts of n-heptane was added to the concentrated residue. The mixture was stirred at 23°C for 30 minutes, after which the supernatant was removed and the mixture was concentrated to obtain 11.11 parts of the salt represented by formula (I-4100).
MASS (ESI (+) Spectrum): M ⁺ 481.0
MASS (ESI (-) Spectrum): M ^- 257.0

Example 7: Synthesis of salt represented by formula (I-4144)
200 parts of the compound represented by formula (I-4144-a), 187.13 parts of the compound represented by formula (I-4144-b), and 400 parts of acetonitrile were mixed and stirred at 23°C for 30 minutes, and then the temperature was raised to 70°C. 154.35 parts of dimethylaminopyridine was added to the resulting mixture, and the mixture was stirred at 70°C for 3 hours and then cooled to 23°C. 1200 parts of tert-butyl methyl ether was added to the resulting reaction mixture, and the mixture was stirred at 23°C for 30 minutes and then filtered. 1200 parts of chloroform and 1200 parts of 1N hydrochloric acid were added to the resulting residue, and the mixture was stirred at 23°C for 30 minutes, and then the organic layer was separated and isolated. 1200 parts of ion-exchanged water was added to the resulting organic layer, and the mixture was stirred at 23°C for 30 minutes, and then the organic layer was separated and isolated. This water washing operation was repeated three times. The obtained organic layer was concentrated, and the concentrated mixture was separated using a column (silica gel 60N (spherical, neutral) 100-210 μm; manufactured by Kanto Chemical Co., Inc., developing solvent: n-heptane/ethyl acetate=1/1) to obtain 189.21 parts of the salt represented by formula (I-4144-d).
4.77 parts of the compound represented by formula (I-4144-d), 80 parts of methanol, and 1.78 parts of silver oxide were mixed and stirred at 23°C for 30 minutes. To the resulting mixture, 9.42 parts of the salt represented by formula (I-380-d) was added, and the mixture was stirred at 23°C for 16 hours and then filtered. The recovered filtrate was concentrated, and then 100 parts of tert-butyl methyl ether was added to the concentrated residue. The mixture was stirred at 23°C for 30 minutes, after which the supernatant was removed and the mixture was concentrated to obtain 10.66 parts of the salt represented by formula (I-4144).
MASS (ESI (+) Spectrum): M ⁺ 481.0
MASS (ESI(-)Spectrum): M ^- 313.1

Example 8: Synthesis of salt represented by formula (I-382)
1.58 parts of the salt represented by formula (I-2-a), 1.10 parts of the compound represented by formula (I-380-b), and 10 parts of dimethylformamide were mixed and stirred at 23°C for 30 minutes. 0.44 parts of potassium carbonate was added to the resulting mixture, and the mixture was stirred at 23°C for 30 minutes, followed by further stirring at 90°C for 3 hours, thereby obtaining a mixture containing the salt represented by formula (I-380-c). The resulting mixture was cooled to 23°C, and 12 parts of a 5% aqueous oxalic acid solution was added and stirred at 23°C for 30 minutes. 2.20 parts of the salt represented by formula (I-436-d) was then added and stirred at 23°C for 7 hours. 30 parts of chloroform and 30 parts of ion-exchanged water were added to the resulting reaction mixture, and the mixture was stirred at 23°C for 30 minutes, followed by separation to isolate the organic layer. 30 parts of ion-exchanged water was added to the resulting organic layer, and the mixture was stirred at 23°C for 30 minutes, followed by separation to isolate the organic layer. This water-washing procedure was repeated 7 times. The obtained organic layer was concentrated to obtain 2.69 parts of the salt represented by formula (I-382).
MASS (ESI (+) Spectrum): M ⁺ 481.0
MASS (ESI(-)Spectrum): M ^- 337.1

Example 9: Synthesis of salt represented by formula (I-1894)
2.26 parts of the salt represented by formula (I-1894-a), 1.10 parts of the compound represented by formula (I-380-b), and 10 parts of dimethylformamide were mixed and stirred at 23°C for 30 minutes. 0.44 parts of potassium carbonate was added to the resulting mixture, and the mixture was stirred at 23°C for 30 minutes, followed by further stirring at 90°C for 3 hours, thereby obtaining a mixture containing the salt represented by formula (I-1894-c). The resulting mixture was cooled to 23°C, and 12 parts of a 5% aqueous oxalic acid solution was added and stirred at 23°C for 30 minutes. 2.20 parts of the salt represented by formula (I-436-d) was then added and stirred at 23°C for 7 hours. 30 parts of chloroform and 30 parts of ion-exchanged water were added to the resulting reaction mixture, and the mixture was stirred at 23°C for 30 minutes, followed by separation to separate the organic layer. 30 parts of ion-exchanged water was added to the resulting organic layer, and the mixture was stirred at 23°C for 30 minutes, followed by separation to separate the organic layer. This water washing procedure was repeated seven times, and the resulting organic layer was concentrated to obtain 3.49 parts of the salt represented by formula (I-1894).
MASS (ESI (+) Spectrum): M ⁺ 617.0
MASS (ESI(-)Spectrum): M ^- 337.1

Example 10: Synthesis of salt represented by formula (I-2218)
2.30 parts of the salt represented by formula (I-2218-a), 2.20 parts of the compound represented by formula (I-380-b), and 20 parts of dimethylformamide were mixed and stirred at 23°C for 30 minutes. 0.88 parts of potassium carbonate was added to the resulting mixture, and the mixture was stirred at 23°C for 30 minutes, followed by further stirring at 90°C for 3 hours, thereby obtaining a mixture containing the salt represented by formula (I-2218-c). The resulting mixture was cooled to 23°C, and 12 parts of a 5% aqueous oxalic acid solution was added and stirred at 23°C for 30 minutes. 2.20 parts of the salt represented by formula (I-436-d) was then added and stirred at 23°C for 7 hours. 30 parts of chloroform and 30 parts of ion-exchanged water were added to the resulting reaction mixture, and the mixture was stirred at 23°C for 30 minutes, followed by separation to remove the organic layer. 30 parts of ion-exchanged water was added to the resulting organic layer, and the mixture was stirred at 23°C for 30 minutes, followed by separation to remove the organic layer. This water washing procedure was repeated five times, and the resulting organic layer was concentrated to obtain 4.98 parts of the salt represented by formula (I-2218).
MASS (ESI (+) Spectrum): M ⁺ 824.8
MASS (ESI(-)Spectrum): M ^- 337.1

Synthesis of Resin The compounds (monomers) used in the synthesis of Resin (A) are shown below. Hereinafter, these compounds will be referred to as "monomers (a1-1-3)" etc. according to their formula numbers.

Synthesis Example 1: Synthesis of Resin A1 Monomers were used: Monomer (a1-1-3), Monomer (a1-2-6), Monomer (a2-1-1), and Monomer (a3-4-2), and the molar ratio [monomer (a1-1-3): Monomer (a1-2-6): Monomer (a2-1-1): Monomer (a3-4-2)] was mixed to a ratio of 45:14:2.5:38.5, and propylene glycol monomethyl ether acetate was added in an amount 1.5 times the total amount of monomers to form a solution. To this solution, azobisisobutyronitrile and azobis(2,4-dimethylvaleronitrile) were added as initiators in amounts of 1 mol% and 3 mol%, respectively, relative to the total amount of monomers, and the mixture was heated at 73 ° C. for approximately 5 hours. The resulting reaction mixture was poured into a large amount of methanol/water mixed solvent to precipitate a resin, which was then filtered. The resulting resin was again dissolved in propylene glycol monomethyl ether acetate, and the resulting solution was poured into a methanol/water mixed solvent to precipitate the resin. This resin was then filtered. This reprecipitation procedure was repeated twice to obtain Resin A1 with a weight-average molecular weight of 7.8 × 10 ³ in a yield of 69%. Resin A1 has the following structural units:

Synthesis Example 2: Synthesis of Resin X1 Monomer (a5-1-1) and monomer (a4-0-12) were used as monomers, and the molar ratio [monomer (a5-1-1):monomer (a4-0-12)] was mixed to a 50:50 ratio. Methyl isobutyl ketone was added in an amount 1.2 times the total amount of monomers by mass to form a solution. Azobis(2,4-dimethylvaleronitrile) was added as an initiator at 3 mol% relative to the total amount of monomers to this solution, and the mixture was heated at 70°C for approximately 5 hours. The resulting reaction mixture was poured into a large amount of a methanol/water mixed solvent to precipitate the resin. The resin was filtered, and Resin X with a weight average molecular weight of 1.0 x ¹⁰⁴ was obtained in a 91% yield. Resin X1 has the following structural units:

<Preparation of Resist Composition>
As shown in Table 2, the following components were mixed and the resulting mixture was filtered through a fluororesin filter with a pore size of 0.2 μm to prepare a resist composition.

<Resin>
A1, X1: Resin A1, Resin X1
<Acid Generator (B)>
B1-21: A salt represented by formula (B1-21) B1-22: A salt represented by formula (B1-22)
<Carboxylate (I)>
I-2: a salt represented by formula (I-2) I-380: a salt represented by formula (I-380) I-382: a salt represented by formula (I-382) I-434: a salt represented by formula (I-434) I-436: a salt represented by formula (I-436) I-1352: a salt represented by formula (I-1352) I-1894: a salt represented by formula (I-1894) I-2218: a salt represented by formula (I-2218) I-4100: a salt represented by formula (I-4100) I-4144: a salt represented by formula (I-4144) <Quencher (C)>
IX-1:
IX-2:
<Solvent>
Propylene glycol monomethyl ether acetate 265 parts Propylene glycol monomethyl ether 20 parts 2-heptanone 20 parts γ-butyrolactone 3.5 parts

<Production of Resist Pattern and Its Evaluation>
A silicon wafer was coated with an organic antireflective coating composition (ARC-29; manufactured by Nissan Chemical Industries, Ltd.) and baked at 205°C for 60 seconds to form an organic antireflective coating with a thickness of 78 nm on the wafer. The resist composition described above was then coated (spin coated) onto the organic antireflective coating to a dry thickness of 85 nm. After coating, the silicon wafer was prebaked on a direct hot plate for 60 seconds at the temperature listed in the "PB" column of Table 2 to form a composition layer. The silicon wafer with the composition layer formed thereon was exposed to light using an ArF excimer stepper for immersion lithography (XT: 1900 Gi; manufactured by ASML, NA = 1.35, 3/4 Annular X-Y polarization) with a mask for forming a contact hole pattern (hole pitch 90 nm/hole diameter 55 nm) while gradually changing the exposure dose. Ultrapure water was used as the immersion medium.
After exposure, post-exposure baking was performed on a hot plate for 60 seconds at the temperature shown in the "PEB" column in Table 2. Next, the composition layer on this silicon wafer was developed by a dynamic dispensing method at 23°C for 20 seconds using butyl acetate (manufactured by Tokyo Chemical Industry Co., Ltd.) as a developer, thereby producing a negative resist pattern.

In the resist pattern obtained after development, the exposure dose at which the hole diameter formed using the mask was 45 nm was defined as the effective sensitivity.

<Mask Error Factor (MEF) Evaluation>
Resist patterns were formed using masks with effective sensitivity having mask hole diameters (hole diameters of the light-transmitting portions of the mask) of 57 nm, 56 nm, 55 nm, 54 nm, and 53 nm (hole pitch of 90 nm in each case). The mask hole diameter was plotted on the horizontal axis against the hole diameter of the resist pattern formed (transferred) on the substrate by exposure on the vertical axis, and the slope of the regression line was calculated as the MEF value.
The results are shown in Table 3. The values in the table indicate MEF values.

Compared with the comparative compositions 1 and 2, the slope of the regression line was small for compositions 1 to 10, and the mask error factor (MEF) evaluation was good.

The carboxylate salt of the present invention and the resist composition containing the carboxylate salt can produce resist patterns with a good mask error factor (MEF), making them suitable for semiconductor microfabrication and extremely useful industrially.

Claims (9)

A carboxylic acid salt represented by formula (I):
[In formula (I),
R ⁴ , R ⁵ , R ⁶ , R ⁷ , R ⁸ and R ⁹ each independently represent a halogen atom, a fluorinated alkyl group having 1 to 6 carbon atoms or a hydrocarbon group having 1 to 18 carbon atoms, the hydrocarbon group may have a substituent, and -CH ₂ - contained in the hydrocarbon group may be replaced by -O-, -CO-, -S- or -SO ₂ -.
X ¹ , X ² and X ³ each independently represent an oxygen atom.
m1 represents an integer of 1 to 5, and when m1 is 2 or more, the groups in the parentheses may be the same or different.
m2 represents an integer of 0 to 5, and when m2 is 2 or more, the groups in the parentheses may be the same or different.
m3 represents an integer of 0 to 5, and when m3 is 2 or more, the groups in the parentheses may be the same or different from each other. When m2 or m3 is 1 or more and there are multiple R ^10s , they may be the same or different from each other .
m4 represents an integer of 0 to 5, and when m4 is 2 or greater, multiple R ^4s may be the same or different.
m5 represents an integer of 0 to 5, and when m5 is 2 or more, the multiple ^R5s may be the same or different.
m6 represents an integer of 0 to 5, and when m6 is 2 or greater, multiple R ^6s may be the same or different.
m7 represents an integer of 0 to 4, and when m7 is 2 or greater, the multiple ^R7s may be the same or different.
m8 represents an integer of 0 to 5, and when m8 is 2 or greater, multiple ^R8s may be the same or different.
m9 represents an integer of 0 to 5, and when m9 is 2 or more, the multiple R ^9s may be the same or different.
However, 1≦m1+m7≦5, 0≦m2+m8≦5, and 0≦m3+m9≦5.
X ⁰ represents a group represented by formula (bb).
(In formula (bb),
L 1 ^A represents an alkanediyl group having 1 to 6 carbon atoms which may have a fluorine atom, or an aromatic hydrocarbon group having 6 carbon atoms which may have a halogen atom or a perfluoroalkyl group having 1 to 4 carbon atoms.
L 1 ^B represents a single bond or an alkanediyl group having 1 to 6 carbon atoms, and one —CH ₂ — contained in the alkanediyl group may be replaced by —O—, —S—, —CO— or —SO ₂ —.
R ^A represents a hydrocarbon group having 1 to 36 carbon atoms which may have a substituent, and one —CH ₂ — contained in the hydrocarbon group may be replaced by —O—, —S—, —CO— or —SO ₂ —.
* indicates the bonding position of —COO— ^to the carbon atom.) A carboxylic acid salt represented by formula (I ¹ ):
[In formula (I ¹ ),
R ⁴ , R ⁵ , R ⁶ , R ⁷ , R ⁸ and R ⁹ each independently represent a halogen atom, a fluorinated alkyl group having 1 to 6 carbon atoms or a hydrocarbon group having 1 to 18 carbon atoms, the hydrocarbon group may have a substituent, and -CH ₂ - contained in the hydrocarbon group may be replaced by -O-, -CO-, -S- or -SO ₂ -.
X ¹ , X ² and X ³ each independently represent an oxygen atom.
m1 represents an integer of 1 to 5, and when m1 is 2 or more, the groups in the parentheses may be the same or different.
m2 represents an integer of 0 to 5, and when m2 is 2 or more, the groups in the parentheses may be the same or different.
m3 represents an integer of 0 to 5, and when m3 is 2 or more, the groups in the parentheses may be the same or different from each other. When m2 or m3 is 1 or more and there are multiple R ^10s , they may be the same or different from each other.
m4 represents an integer of 0 to 5, and when m4 is 2 or greater, multiple R ^4s may be the same or different.
m5 represents an integer of 0 to 5, and when m5 is 2 or more, the multiple R5s ^may be the same or different.
m6 represents an integer of 0 to 5, and when m6 is 2 or greater, multiple R ^6s may be the same or different.
m7 represents an integer of 0 to 4, and when m7 is 2 or greater, the multiple R7s ^may be the same or different.
m8 represents an integer of 0 to 5, and when m8 is 2 or greater, multiple R8s ^may be the same or different.
m9 represents an integer of 0 to 5, and when m9 is 2 or more, the multiple R ^9s may be the same or different.
However, 1≦m1+m7≦5, 0≦m2+m8≦5, and 0≦m3+m9≦5.
X01 represents a halogen atom, a hydroxy group, or an aromatic hydrocarbon group having 6 carbon atoms and a perfluoroalkyl group having 1 to 4 carbon atoms. ^] A carboxylic acid salt represented by formula (I ² ):
[In formula (I ² ),
R ⁴ , R ⁵ , R ⁶ , R ⁷ , R ⁸ and R ⁹ each independently represent a halogen atom, a fluorinated alkyl group having 1 to 6 carbon atoms or a hydrocarbon group having 1 to 18 carbon atoms, the hydrocarbon group may have a substituent, and -CH ₂ - contained in the hydrocarbon group may be replaced by -O-, -CO-, -S- or -SO ₂ -.
X ¹ , X ² and X ³ each independently represent an oxygen atom.
m1 represents an integer of 1 to 5, and when m1 is 2 or more, the groups in the parentheses may be the same or different.
m2 represents an integer of 0 to 5, and when m2 is 2 or more, the groups in the parentheses may be the same or different.
m3 represents an integer of 0 to 5, and when m3 is 2 or more, the groups in the parentheses may be the same or different from each other. When m2 or m3 is 1 or more and there are multiple R ^10s , they may be the same or different from each other.
m4 represents an integer of 0 to 5, and when m4 is 2 or greater, multiple R ^4s may be the same or different.
m5 represents an integer of 0 to 5, and when m5 is 2 or more, the multiple R5s ^may be the same or different.
m6 represents an integer of 0 to 5, and when m6 is 2 or greater, multiple R ^6s may be the same or different.
m7 represents an integer of 0 to 4, and when m7 is 2 or greater, the multiple R7s ^may be the same or different.
m8 represents an integer of 0 to 5, and when m8 is 2 or greater, multiple R8s ^may be the same or different.
m9 represents an integer of 0 to 5, and when m9 is 2 or more, the multiple R ^9s may be the same or different.
However, 1≦m1+m7≦5, 0≦m2+m8≦5, and 0≦m3+m9≦5.
X ⁰² represents a group represented by formula (aa).
(In formula (aa),
X ^a and X ^b each independently represent —O— or —S—.
X ^1a represents an alkanetriyl group having 1 to 6 carbon atoms which may have a substituent, or an alicyclic hydrocarbon group having 3 to 18 carbon atoms which may have a substituent, and one —CH ₂ — contained in the alicyclic hydrocarbon group may be replaced by —O—, —S—, —CO— or —SO ₂ —.
X ^2a represents a group represented by formula (X ² -1), formula (X ² -2), formula (X ² -3) or formula (X ² -4).
During the ceremony,
R ^1x , R ^2x , R ^3x , R ^4x , R ^5x and R ^6x each independently represent an alkyl group having 1 to 6 carbon atoms, an alicyclic hydrocarbon group having 5 to 12 carbon atoms or a group combining two or more of these groups, and —CH ₂ — contained in the alkyl group and the alicyclic hydrocarbon group may be replaced by —O—, —S—, —CO— or —SO ₂ —, and the alkyl group and the alicyclic hydrocarbon group may have a substituent.) 4. The carboxylate salt according to claim 1, wherein R ⁴ , R ⁵ and R ⁶ are each independently a fluorine atom, an iodine atom or a perfluoroalkyl group having 1 to 4 carbon atoms. A carboxylic acid generator comprising the carboxylic acid salt according to any one of claims 1 to 4 . 6. A resist composition comprising the carboxylic acid generator according to claim 5 , an acid generator other than said carboxylic acid generator, and a resin having an acid labile group. 7. The resist composition according to claim 6 , wherein the resin having an acid labile group comprises at least one structural unit selected from the group consisting of structural units represented by formula (a1-1) and structural units represented by formula (a1-2):
[In formula (a1-1) and formula (a1-2),
L ^a1 and L ^a2 each independently represent —O— or *-O—(CH ₂ ) _k1 —CO—O—, where k1 represents an integer of 1 to 7, and * represents a bond to —CO—.
R ^a4 and R ^a5 each independently represent a hydrogen atom, a halogen atom, or an alkyl group having 1 to 6 carbon atoms which may have a halogen atom.
R ^a6 and R ^a7 each independently represent an alkyl group having 1 to 8 carbon atoms, an alkenyl group having 2 to 8 carbon atoms, an alicyclic hydrocarbon group having 3 to 18 carbon atoms, an aromatic hydrocarbon group having 6 to 18 carbon atoms, or a combination thereof.
m1 represents an integer of 0 to 14.
n1 represents an integer of 0 to 10.
n1′ represents an integer of 0 to 3. 8. The resist composition according to claim 6 , further comprising a resin containing a structural unit having a fluorine atom. (1) a step of applying the resist composition according to any one of claims 6 to 8 onto a substrate;
(2) a step of drying the applied composition to form a composition layer;
(3) exposing the composition layer to light;
(4) a step of heating the composition layer after exposure; and (5) a step of developing the composition layer after heating.
A method for producing a resist pattern comprising: