JP7768069B2 - Chemically amplified positive resist material and pattern formation method - Google Patents

Description

The present invention relates to a positive resist material and a pattern formation method.

As LSIs become more highly integrated and faster, pattern rules are becoming increasingly miniaturized. This is because the widespread adoption of 5G high-speed communications and artificial intelligence (AI) requires high-performance devices to process these technologies. The most advanced miniaturization technology is extreme ultraviolet (EUV) lithography with a wavelength of 13.5 nm, which is currently being used to mass-produce 5 nm node devices. Furthermore, the use of EUV lithography is also being considered for next-generation 3 nm node and next-generation 2 nm node devices.

As miniaturization progresses, image blurring due to acid diffusion has become a problem. To ensure resolution in fine patterns with dimensions of 45 nm and smaller, it has been suggested that controlling acid diffusion is important, in addition to improving dissolution contrast, as has been proposed previously (Non-Patent Document 1). However, because chemically amplified resist materials increase sensitivity and contrast through acid diffusion, attempts to minimize acid diffusion by lowering the post-exposure bake (PEB) temperature or shortening the time result in a significant decrease in sensitivity and contrast.

Adding an acid generator that generates bulky acid is effective in suppressing acid diffusion. Therefore, it has been proposed to incorporate repeating units derived from onium salts with polymerizable unsaturated bonds into the polymer. In this case, the polymer also functions as an acid generator (polymer-bound acid generator). Patent Document 1 proposes sulfonium salts and iodonium salts with polymerizable unsaturated bonds that generate specific sulfonic acids. Patent Document 2 proposes sulfonium salts in which sulfonic acids are directly linked to the main chain.

Resist materials with modified polymer terminals have been proposed. These include a resist material in which an acid-labile group is attached to the terminal of a living anionic polymerization using alkyllithium as an initiator (Patent Document 3), a resist material in which a sulfonium salt acting as an acid generator for fluorosulfonic acid is attached to the polymer terminal in living radical polymerization (RAFT) (Patent Document 4), and a resist material in which an acid generator is attached to both terminals of a polymer polymerized using an azo-based polymerization initiator with sulfonium salts acting as acid generators for fluorosulfonic acid attached to both ends (Patent Document 5). However, polymers with acid generators attached to the terminals, in particular, have the disadvantage of increased acid diffusion due to the easily mobile terminals.

Japanese Patent Application Laid-Open No. 2006-45311 Japanese Patent Application Laid-Open No. 2006-178317 Patent No. 4132783 JP 2014-65896 A JP 2013-1850 A

SPIE Vol. 3331 p531 (1998)

The present invention has been made in consideration of the above circumstances, and aims to provide a positive resist material and pattern formation method that controls acid diffusion, has resolution superior to conventional positive resist materials, has minimal edge roughness and dimensional variation, and produces a good pattern shape after exposure.

The inventors of the present invention have conducted extensive research to develop a positive resist material that meets the recent demand for high resolution and has minimal edge roughness and dimensional variation. As a result, they discovered that to achieve this, it is necessary to minimize the acid diffusion distance and to suppress swelling in alkaline developers. They also discovered that by attaching a sulfonium salt containing a carboxylic acid anion, which acts as a quencher, to the end of the polymer, acid diffusion can be minimized and swelling can be reduced, and that this is particularly effective when used as the base polymer for chemically amplified positive resist materials.

Furthermore, in order to improve dissolution contrast, the inventors discovered that by introducing into the base polymer repeating units in which the hydrogen atoms of the carboxyl or phenolic hydroxyl groups are substituted with acid labile groups, the alkaline dissolution rate contrast before and after exposure is significantly higher, acid diffusion is more effectively suppressed, high resolution is achieved, and the pattern shape, edge roughness, and dimensional uniformity (CDU) after exposure are excellent. This positive resist material is particularly suitable as a material for forming fine patterns in VLSI manufacturing or photomasks, and thus the present invention was completed.

That is, the present invention provides the following positive resist material and pattern forming method.
1. A positive resist material comprising a base polymer end-capped with a sulfonium salt containing a carboxylate anion linked to a sulfide group.
2. The positive resist material of 1, wherein the terminal structure is represented by the following formula (a):
(In the formula, ^X1 is a hydrocarbylene group having 1 to 20 carbon atoms, and the hydrocarbylene group may contain at least one bond selected from a hydroxy group, an ether bond, a sulfide group, an ester bond, a carbonate bond, a urethane bond, a lactone ring, a sultone ring, and a halogen atom.
^R1 to ^R3 are each independently a hydrocarbyl group having 1 to 20 carbon atoms, and may contain at least one atom selected from an oxygen atom, a sulfur atom, a nitrogen atom, and a halogen atom. ^R1 and ^R2 may be bonded to each other to form a ring together with the sulfur atom to which they are bonded.
The dashed lines represent bonds.)
3. The positive resist material of 1 or 2, wherein the base polymer comprises a repeating unit b1 in which a hydrogen atom of a carboxy group is substituted with an acid labile group or a repeating unit b2 in which a hydrogen atom of a phenolic hydroxy group is substituted with an acid labile group.
4. The positive resist material of 3, wherein the repeating unit b1 is represented by the following formula (b1), and the repeating unit b2 is represented by the following formula (b2).
(In the formula, each R ^A is independently a hydrogen atom or a methyl group.
Y ¹ is a single bond, a phenylene group, a naphthylene group, or a linking group having 1 to 12 carbon atoms and containing at least one bond selected from an ester bond, an ether bond, and a lactone ring.
^Y2 is a single bond, an ester bond or an amide bond.
^Y3 is a single bond, an ether bond or an ester bond.
R ¹¹ and R ¹² are each independently an acid labile group.
R ¹³ is a fluorine atom, a trifluoromethyl group, a cyano group or a saturated hydrocarbyl group having 1 to 6 carbon atoms.
R ¹⁴ is a single bond or an alkanediyl group having 1 to 6 carbon atoms, and the alkanediyl group may contain an ether bond or an ester bond.
a is 1 or 2, and b is an integer from 0 to 4, provided that 1≦a+b≦5.
5. The positive resist material of any one of 1 to 4, wherein the base polymer further contains a repeating unit c containing an adhesive group selected from a hydroxy group, a carboxy group, a lactone ring, a carbonate bond, a thiocarbonate bond, a carbonyl group, a cyclic acetal group, an ether bond, an ester bond, a sulfonate ester bond, a cyano group, an amide bond, —O—C(═O)—S—, and —O—C(═O)—NH—.
6. The positive resist material of any one of 1 to 5, wherein the base polymer further contains a repeating unit represented by any one of the following formulas (d1) to (d3):
(In the formula, each R ^A is independently a hydrogen atom or a methyl group.
Z ¹ is a single bond, an aliphatic hydrocarbylene group having 1 to 6 carbon atoms, a phenylene group, a naphthylene group, or a group having 7 to 18 carbon atoms obtained by combining these, or -O-Z ¹¹ -, -C(═O)-O-Z ¹¹ -, or -C(═O)-NH-Z ¹¹ -. ^{Z 11} is an aliphatic hydrocarbylene group having 1 to 6 carbon atoms, a phenylene group, a naphthylene group, or a group having 7 to 18 carbon atoms obtained by combining these, and may contain a carbonyl group, an ester bond, an ether bond, or a hydroxy group.
^Z2 is a single bond or an ester bond.
Z ³ is a single bond, -Z ³¹ -C(═O)-O-, -Z ³¹ -O-, or -Z ³¹ -O-C(═O)-. Z ³¹ is an aliphatic hydrocarbylene group having 1 to 12 carbon atoms, a phenylene group, or a group having 7 to 18 carbon atoms obtained by combining these, and may contain a carbonyl group, an ester bond, an ether bond, a bromine atom, or an iodine atom.
^Z4 is a methylene group, a 2,2,2-trifluoro-1,1-ethanediyl group, or a carbonyl group.
^Z5 is a single bond, a methylene group, an ethylene group, a phenylene group, a fluorinated phenylene group, a phenylene group substituted with a trifluoromethyl group, -O- ^Z51- , -C(=O)-O- ^Z51- or -C(=O)-NH- ^Z51- . ^Z51 is an aliphatic hydrocarbylene group having 1 to 6 carbon atoms, a phenylene group, a fluorinated phenylene group or a phenylene group substituted with a trifluoromethyl group, and may contain a carbonyl group, an ester bond, an ether bond, a halogen atom or a hydroxy group.
R ²¹ to R ²⁸ are each independently a halogen atom or a hydrocarbyl group having 1 to 20 carbon atoms which may contain a heteroatom. R ²³ and R ²⁴ or R ²⁶ and R ²⁷ may be bonded to each other to form a ring together with the sulfur atom to which they are bonded.
M ⁻ is a non-nucleophilic counter ion.
7. The positive resist material according to any one of 1 to 6, further comprising an acid generator.
8. The positive resist material according to any one of 1 to 7, further comprising an organic solvent.
9. The positive resist material according to any one of 1 to 8, further comprising a quencher.
10. The positive resist material according to any one of 1 to 9, further comprising a surfactant.
11. A pattern formation method comprising the steps of: forming a resist film on a substrate using the positive resist material of any one of 1 to 10; exposing the resist film to high-energy rays; and developing the exposed resist film using a developer.
12. The pattern formation method according to 11, wherein the high-energy beam is i-line, KrF excimer laser light, ArF excimer laser light, electron beam (EB), or EUV light having a wavelength of 3 to 15 nm.

The positive resist material of the present invention is highly effective in suppressing acid diffusion, and when formed into a resist film, it exhibits a high contrast in alkali dissolution rate before and after exposure, high resolution, and good pattern shape, edge roughness, and CDU after exposure. Therefore, due to these excellent properties, it is highly practical and is particularly useful as a fine pattern formation material for photomasks used in VLSI manufacturing or EB writing, and as a pattern formation material for EB or EUV exposure. The positive resist material of the present invention can be applied, for example, not only to lithography in semiconductor circuit formation, but also to the formation of mask circuit patterns, micromachines, and thin-film magnetic head circuits.

[Base polymer]
The positive resist material of the present invention is characterized by comprising a base polymer end-capped with a sulfonium salt containing a carboxylate anion linked to a sulfide group.

The terminal structure (hereinafter also referred to as terminal structure a) is preferably a structure represented by the following formula (a).
(In the formula, the dashed lines represent bonds.)

In formula (a), ^X1 is a hydrocarbylene group having 1 to 20 carbon atoms, and the hydrocarbylene group may contain at least one bond selected from a hydroxy group, an ether bond, a sulfide group, an ester bond, a carbonate bond, a urethane bond, a lactone ring, a sultone ring, and a halogen atom. The hydrocarbylene group may be saturated or unsaturated, and may be linear, branched, or cyclic. Specific examples thereof include alkanediyl groups having 1 to 20 carbon atoms, such as methanediyl group, ethane-1,1-diyl group, ethane-1,2-diyl group, propane-1,3-diyl group, butane-1,4-diyl group, pentane-1,5-diyl group, hexane-1,6-diyl group, heptane-1,7-diyl group, octane-1,8-diyl group, nonane-1,9-diyl group, decane-1,10-diyl group, undecane-1,11-diyl group, and dodecane-1,12-diyl group; cyclopentanediyl group, cyclohexanediyl group, and the like. Examples of such hydrocarbyl groups include cyclic saturated hydrocarbylene groups having 3 to 20 carbon atoms, such as vinylene, propene-1,3-diyl, ethyne-1,2-diyl, and propyne-1,3-diyl; unsaturated aliphatic hydrocarbylene groups having 2 to 20 carbon atoms, such as vinylene, propene-1,3-diyl, ethyne-1,2-diyl, and propyne-1,3-diyl; arylene groups having 6 to 20 carbon atoms, such as phenylene, naphthylene, and biphenylylene; groups in which some or all of the hydrogen atoms of these groups have been substituted with hydrocarbyl groups having 1 to 12 carbon atoms; and groups obtained by combining these. The hydrocarbyl groups may be saturated or unsaturated and may be linear, branched, or cyclic. Specific examples thereof include those having 1 to 12 carbon atoms, among those exemplified as hydrocarbyl groups having 1 to 20 carbon atoms represented by R ¹⁰¹ to R ¹⁰⁵ in the description of formulas (1-1) and (1-2) below.

In formula (a), R ¹ to R ³ are each independently a hydrocarbyl group having 1 to 20 carbon atoms, and may contain at least one atom selected from an oxygen atom, a sulfur atom, a nitrogen atom, and a halogen atom. The hydrocarbyl group may be saturated or unsaturated, and may be linear, branched, or cyclic. Specific examples thereof include the same groups as those exemplified as hydrocarbyl groups having 1 to 20 carbon atoms represented by R ¹⁰¹ to R ¹⁰⁵ in the description of formulas (1-1) and (1-2) below. R ¹ and R ² may be bonded to each other to form a ring together with the sulfur atom to which they are bonded. In this case, examples of the ring include the same groups as those exemplified as rings that may be formed when R ¹⁰¹ and R ¹⁰² are bonded to each other and together with the sulfur atom to which they are bonded in the description of formula (1-1) below.

To attach a sulfonium salt containing a carboxylate anion linked to a sulfide group to a polymer terminal, a compound represented by the following formula (a1) is used as a chain transfer agent, which is added to a polymerization solution before or during polymerization to carry out the polymerization reaction. Radicals are generated by decomposition of the polymerization initiator, and polymerization begins with chain transfer of the radicals to the thiol, producing a polymer whose terminals are capped with the sulfonium salt.
(wherein ^X1 and ^R1 to ^R3 are the same as above.)

Examples of the anion of the compound represented by formula (a1) include, but are not limited to, those shown below.

Specific examples of the cation of the terminal structure a and the cation of the compound represented by formula (a1) include the same as those exemplified as specific examples of the cation of the sulfonium salt represented by formula (1-1) described below.

The compound represented by formula (a1) can be synthesized, for example, by an ion exchange reaction between a carboxylic acid linked to a sulfide group and a carbonate or hydrochloride salt of a sulfonium salt.

The base polymer preferably contains a repeating unit b1 in which the hydrogen atom of a carboxy group is substituted with an acid labile group, or a repeating unit b2 in which the hydrogen atom of a phenolic hydroxy group is substituted with an acid labile group.

Examples of the repeating units b1 and b2 include those represented by the following formulae (b1) and (b2), respectively.

In formulas (b1) and (b2), ^R is each independently a hydrogen atom or a methyl group, and ^Y is a single bond, a phenylene group, a naphthylene group, or a linking group having 1 to 12 carbon atoms and containing at least one bond selected from the group consisting of an ester bond, an ether bond, and a lactone ring.
^Y2 is a single bond, an ester bond, or an amide bond. ^Y3 is a single bond, an ether bond, or an ester bond. ^R11 and ^R12 are each independently an acid labile group. ^R13 is a fluorine atom, a trifluoromethyl group, a cyano group, or a saturated hydrocarbyl group having 1 to 6 carbon atoms. ^R14 is a single bond or an alkanediyl group having 1 to 6 carbon atoms, and the alkanediyl group may contain an ether bond or an ester bond. a is 1 or 2. b is an integer from 0 to 4, with the proviso that 1≦a+b≦5.

Examples of monomers that provide the repeating unit b1 include, but are not limited to, the following: In the following formula, R ^A and R ¹¹ are the same as defined above.

Examples of monomers that provide the repeating unit b2 include, but are not limited to, the following: In the following formula, R ^A and R ¹² are the same as defined above.

The acid labile group represented by R ¹¹ or R ¹² may be selected from a variety of groups, and examples thereof include those represented by the following formulae (AL-1) to (AL-3).
(In the formula, the dashed lines represent bonds.)

In formula (AL-1), c is an integer of 0 to 6. ^{R L1} is a tertiary hydrocarbyl group having 4 to 20 carbon atoms, preferably 4 to 15 carbon atoms, a trihydrocarbylsilyl group in which each hydrocarbyl group is a saturated hydrocarbyl group having 1 to 6 carbon atoms, a carbonyl group, or a saturated hydrocarbyl group having 4 to 20 carbon atoms containing an ether bond or an ester bond, or a group represented by formula (AL-3). The tertiary hydrocarbyl group refers to a group obtained by eliminating a hydrogen atom from a tertiary carbon atom of a hydrocarbon.

The tertiary hydrocarbyl group represented by ^R may be saturated or unsaturated, branched or cyclic. Specific examples include tert-butyl, tert-pentyl, 1,1-diethylpropyl, 1-ethylcyclopentyl, 1-butylcyclopentyl, 1-ethylcyclohexyl, 1-butylcyclohexyl, 1-ethyl-2-cyclopentenyl, 1-ethyl-2-cyclohexenyl, and 2-methyl-2-adamantyl. Examples of the trihydrocarbylsilyl group include trimethylsilyl, triethylsilyl, and dimethyl-tert-butylsilyl. The saturated hydrocarbyl group containing a carbonyl group, an ether bond, or an ester bond may be linear, branched, or cyclic, but is preferably cyclic. Specific examples thereof include a 3-oxocyclohexyl group, a 4-methyl-2-oxooxan-4-yl group, a 5-methyl-2-oxoxolan-5-yl group, a 2-tetrahydropyranyl group, and a 2-tetrahydrofuranyl group.

Examples of acid labile groups represented by formula (AL-1) include tert-butoxycarbonyl, tert-butoxycarbonylmethyl, tert-pentyloxycarbonyl, tert-pentyloxycarbonylmethyl, 1,1-diethylpropyloxycarbonyl, 1,1-diethylpropyloxycarbonylmethyl, 1-ethylcyclopentyloxycarbonyl, 1-ethylcyclopentyloxycarbonylmethyl, 1-ethyl-2-cyclopentenyloxycarbonyl, 1-ethyl-2-cyclopentenyloxycarbonylmethyl, 1-ethoxyethoxycarbonylmethyl, 2-tetrahydropyranyloxycarbonylmethyl, and 2-tetrahydrofuranyloxycarbonylmethyl.

Further, examples of the acid labile group represented by formula (AL-1) include groups represented by the following formulae (AL-1)-1 to (AL-1)-10.
(In the formula, the dashed lines represent bonds.)

In formulas (AL-1)-1 to (AL-1)-10, c is the same as defined above. Each ^{R L8} is independently a saturated hydrocarbyl group having 1 to 10 carbon atoms or an aryl group having 6 to 20 carbon atoms. R ^L9 is a hydrogen atom or a saturated hydrocarbyl group having 1 to 10 carbon atoms. ^{R L10} is a saturated hydrocarbyl group having 2 to 10 carbon atoms or an aryl group having 6 to 20 carbon atoms. The saturated hydrocarbyl group may be linear, branched, or cyclic.

In formula (AL-2), R ^L2 and R ^L3 each independently represent a hydrogen atom or a saturated hydrocarbyl group having 1 to 18 carbon atoms, preferably 1 to 10. The saturated hydrocarbyl group may be linear, branched, or cyclic, and specific examples thereof include a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, an isobutyl group, a sec-butyl group, a tert-butyl group, a cyclopentyl group, a cyclohexyl group, a 2-ethylhexyl group, and an n-octyl group.

In formula (AL-2), R ^L4 is a hydrocarbyl group having 1 to 18 carbon atoms, preferably 1 to 10, which may contain a heteroatom. The hydrocarbyl group may be saturated or unsaturated, and may be linear, branched, or cyclic. Examples of the hydrocarbyl group include saturated hydrocarbyl groups having 1 to 18 carbon atoms, and some of the hydrogen atoms may be substituted with hydroxy groups, alkoxy groups, oxo groups, amino groups, alkylamino groups, or the like. Examples of such substituted saturated hydrocarbyl groups include those shown below.
(In the formula, the dashed lines represent bonds.)

R and ^R , ^R and ^R , or R and ^R may be bonded to each other to form a ring together with the carbon atom to which they are bonded, or together with the carbon ^atom and oxygen atom, and in this ^case , ^R and ^R , ^R and ^R participating in the formation of the ^ring are each independently an ^alkanediyl group having 1 to 18 carbon atoms, preferably 1 to 10. The number of carbon atoms in the ring obtained by bonding these is preferably 3 to 10, more preferably 4 to 10.

Among the acid labile groups represented by formula (AL-2), linear or branched groups include, but are not limited to, those represented by the following formulae (AL-2)-1 to (AL-2)-69, in which the dashed lines represent bonds.

Among the acid labile groups represented by formula (AL-2), cyclic groups include tetrahydrofuran-2-yl, 2-methyltetrahydrofuran-2-yl, tetrahydropyran-2-yl, and 2-methyltetrahydropyran-2-yl groups.

Further, examples of the acid labile group include groups represented by the following formula (AL-2a) or (AL-2b): The base polymer may be inter- or intramolecularly crosslinked by the acid labile group.
(In the formula, the dashed lines represent bonds.)

In formula (AL-2a) or (AL-2b), R ^L11 and R ^L12 each independently represent a hydrogen atom or a saturated hydrocarbyl group having 1 to 8 carbon atoms. The saturated hydrocarbyl group may be linear, branched, or cyclic. R ^L11 and R ^L12 may be bonded to each other to form a ring together with the carbon atom to which they are attached. In this case, R ^L11 and R ^L12 each independently represent an alkanediyl group having 1 to 8 carbon atoms. R ^L13 each independently represents a saturated hydrocarbylene group having 1 to 10 carbon atoms. The saturated hydrocarbylene group may be linear, branched, or cyclic. d and e each independently represent an integer of 0 to 10, preferably an integer of 0 to 5, and f is an integer of 1 to 7, preferably an integer of 1 to 3.

In formula (AL-2a) or (AL-2b), L ^A is an (f+1)-valent aliphatic saturated hydrocarbon group having 1 to 50 carbon atoms, an (f+1)-valent alicyclic saturated hydrocarbon group having 3 to 50 carbon atoms, an (f+1)-valent aromatic hydrocarbon group having 6 to 50 carbon atoms, or an (f+1)-valent heterocyclic group having 3 to 50 carbon atoms. Some of the —CH ₂ — groups in these groups may be substituted with a group containing a heteroatom, and some of the hydrogen atoms in these groups may be substituted with a hydroxy group, a carboxy group, an acyl group, or a fluorine atom. ^{L A} is preferably a saturated hydrocarbon group such as a saturated hydrocarbylene group having 1 to 20 carbon atoms, a trivalent saturated hydrocarbon group, or a tetravalent saturated hydrocarbon group, or an arylene group having 6 to 30 carbon atoms. The saturated hydrocarbon group may be linear, branched, or cyclic. L ^B is —C(═O)—O—, —NH—C(═O)—O— or —NH—C(═O)—NH—.

Examples of the crosslinked acetal group represented by formula (AL-2a) or (AL-2b) include groups represented by the following formulae (AL-2)-70 to (AL-2)-77.
(In the formula, the dashed lines represent bonds.)

In formula (AL-3), R ^L5 , R ^L6 , and R ^L7 are each independently a hydrocarbyl group having 1 to 20 carbon atoms, which may contain a heteroatom such as an oxygen atom, a sulfur atom, a nitrogen atom, or a fluorine atom. The hydrocarbyl group may be saturated or unsaturated, and may be linear, branched, or cyclic. Specific examples include alkyl groups having 1 to 20 carbon atoms, cyclic saturated hydrocarbyl groups having 3 to 20 carbon atoms, alkenyl groups having 2 to 20 carbon atoms, cyclic unsaturated hydrocarbyl groups having 3 to 20 carbon atoms, and aryl groups having 6 to 10 carbon atoms. R ^L5 and R ^L6 , R ^L5 and R ^L7 , or R ^L6 and R ^L7 may bond to each other to form an alicyclic ring having 3 to 20 carbon atoms together with the carbon atoms to which they are bonded.

Examples of the group represented by formula (AL-3) include a tert-butyl group, a 1,1-diethylpropyl group, a 1-ethylnorbornyl group, a 1-methylcyclopentyl group, a 1-ethylcyclopentyl group, a 1-isopropylcyclopentyl group, a 1-methylcyclohexyl group, a 2-(2-methyl)adamantyl group, a 2-(2-ethyl)adamantyl group, and a tert-pentyl group.

Further, examples of the group represented by formula (AL-3) include groups represented by the following formulae (AL-3)-1 to (AL-3)-19.
(In the formula, the dashed lines represent bonds.)

In formulas (AL-3)-1 to (AL-3)-19, R ^L14 each independently represents a saturated hydrocarbyl group having 1 to 8 carbon atoms or an aryl group having 6 to 20 carbon atoms. R ^L15 and R ^L17 each independently represent a hydrogen atom or a saturated hydrocarbyl group having 1 to 20 carbon atoms. R ^L16 is an aryl group having 6 to 20 carbon atoms. The saturated hydrocarbyl group may be linear, branched, or cyclic. Furthermore, the aryl group is preferably a phenyl group. R ^F is a fluorine atom, a trifluoromethyl group, or a nitro group. g is an integer from 1 to 5.

Further examples of the acid labile group include groups represented by the following formula (AL-3)-20 or (AL-3)-21: The polymer may be intramolecularly or intermolecularly crosslinked by the acid labile group.
(In the formula, the dashed lines represent bonds.)

In formulas (AL-3)-20 and (AL-3)-21, R ^L14 is the same as defined above. ^{R L18} is a (h+1)-valent saturated hydrocarbylene group having 1 to 20 carbon atoms or a (h+1)-valent arylene group having 6 to 20 carbon atoms, and may contain a heteroatom such as an oxygen atom, a sulfur atom, or a nitrogen atom. The saturated hydrocarbylene group may be linear, branched, or cyclic. h is an integer of 1 to 3.

Examples of monomers that provide repeating units containing an acid labile group represented by formula (AL-3) include (meth)acrylates containing an exo structure represented by formula (AL-3)-22 below.

In formula (AL-3)-22, R ^A is the same as defined above. R ^Lc1 is a saturated hydrocarbyl group having 1 to 8 carbon atoms or an optionally substituted aryl group having 6 to 20 carbon atoms. The saturated hydrocarbyl group may be linear, branched, or cyclic. ^{R Lc2} to R ^Lc11 are each independently a hydrocarbyl group having 1 to 15 carbon atoms which may contain a hydrogen atom or a heteroatom. Examples of the heteroatom include an oxygen atom. Examples of the hydrocarbyl group include an alkyl group having 1 to 15 carbon atoms and an aryl group having 6 to 15 carbon atoms. R ^Lc2 and R ^Lc3 , R ^Lc4 and R ^Lc6 , R ^Lc4 and R ^Lc7 , R ^Lc5 and R ^Lc7 , R ^Lc5 and R ^Lc11 , R ^Lc6 and R ^Lc10 , R ^Lc8 and R ^Lc9 , or R ^Lc9 and R ^Lc10 may be bonded to each other to form a ring together with the carbon atoms to which they are bonded, in which case the group participating in the bond is a hydrocarbylene group having 1 to 15 carbon atoms which may contain a heteroatom. Furthermore, R ^Lc2 and R ^Lc11 , R ^Lc8 and R ^Lc11 , or R ^Lc4 and R ^Lc6 may be bonded to adjacent carbon atoms without any intervening group to form a double bond. Note that this formula also represents enantiomers.

Here, examples of the monomer represented by formula (AL-3)-22 include those described in JP-A-2000-327633. Specific examples include, but are not limited to, those shown below. In the following formula, R ^A is the same as defined above.

Examples of monomers that provide repeating units containing an acid labile group represented by formula (AL-3) include (meth)acrylic acid esters containing a furandiyl group, a tetrahydrofurandiyl group, or an oxanorbornanediyl group represented by the following formula (AL-3)-23:

In formula (AL-3)-23, R ^A is the same as defined above. R ^Lc12 and R ^Lc13 each independently represent a hydrocarbyl group having 1 to 10 carbon atoms. R ^Lc12 and R ^Lc13 may be bonded to each other to form an alicyclic ring together with the carbon atom to which they are attached. R ^Lc14 is a furandiyl group, a tetrahydrofurandiyl group, or an oxanorbornanediyl group. R ^Lc15 is a hydrocarbyl group having 1 to 10 carbon atoms which may contain a hydrogen atom or a heteroatom. The hydrocarbyl group may be linear, branched, or cyclic. Specific examples include saturated hydrocarbyl groups having 1 to 10 carbon atoms.

Examples of the monomer represented by formula (AL-3)-23 include, but are not limited to, the following: In the following formula, R ^A is the same as above, Ac is an acetyl group, and Me is a methyl group.

In addition to the above-mentioned acid labile groups, acid labile groups containing aromatic groups as described in Japanese Patent Nos. 5,565,293, 5,434,983, 5,407,941, 5,655,756, and 5,655,755 can also be used.

The base polymer may further contain a repeating unit c containing an adhesive group selected from a hydroxy group, a carboxy group, a lactone ring, a carbonate bond, a thiocarbonate bond, a carbonyl group, a cyclic acetal group, an ether bond, an ester bond, a sulfonate ester bond, a cyano group, an amide bond, -O-C(=O)-S-, and -O-C(=O)-NH-.

Examples of monomers that provide the repeating unit c include, but are not limited to, the following: In the following formula, R ^A is the same as defined above.

The base polymer may further contain at least one repeating unit selected from the group consisting of a repeating unit represented by the following formula (d1) (hereinafter also referred to as repeating unit d1), a repeating unit represented by the following formula (d2) (hereinafter also referred to as repeating unit d2), and a repeating unit represented by the following formula (d3) (hereinafter also referred to as repeating unit d3):

In formulas (d1) to (d3), R ^A is each independently a hydrogen atom or a methyl group. Z ¹ is a single bond, an aliphatic hydrocarbylene group having 1 to 6 carbon atoms, a phenylene group, a naphthylene group, or a group having 7 to 18 carbon atoms obtained by combining these, or -O-Z ¹¹ -, -C(═O)-O-Z ¹¹ -, or -C(═O)-NH-Z ¹¹ -. ^{Z 11} is an aliphatic hydrocarbylene group having 1 to 6 carbon atoms, a phenylene group, a naphthylene group, or a group having 7 to 18 carbon atoms obtained by combining these, and may contain a carbonyl group, an ester bond, an ether bond, or a hydroxy group. Z ² is a single bond or an ester bond. Z ³ is a single bond, -Z ³¹ -C(═O)-O-, -Z ³¹ -O-, or -Z ³¹ -O-C(═O)-. Z ³¹ is an aliphatic hydrocarbylene group having 1 to 12 carbon atoms, a phenylene group, or a group obtained by combining these and having 7 to 18 carbon atoms, and may contain a carbonyl group, an ester bond, an ether bond, a bromine atom, or an iodine atom. Z ⁴ is a methylene group, a 2,2,2-trifluoro-1,1-ethanediyl group, or a carbonyl group. Z ⁵ is a single bond, a methylene group, an ethylene group, a phenylene group, a fluorinated phenylene group, a phenylene group substituted with a trifluoromethyl group, -O-Z ⁵¹ -, -C(═O)-O-Z ⁵¹ -, or -C(═O)-NH-Z ⁵¹ -. Z ⁵¹ is an aliphatic hydrocarbylene group having 1 to 6 carbon atoms, a phenylene group, a fluorinated phenylene group, or a phenylene group substituted with a trifluoromethyl group, and may contain a carbonyl group, an ester bond, an ether bond, a halogen atom, or a hydroxy group. The aliphatic hydrocarbylene groups represented by Z ¹ , Z ¹¹ , Z ³¹ , and Z ⁵¹ may be saturated or unsaturated, and may be linear, branched, or cyclic.

In formulas (d1) to (d3), R ²¹ to R ²⁸ are each independently a halogen atom or a hydrocarbyl group having 1 to 20 carbon atoms which may contain a heteroatom. Examples of the halogen atom include a fluorine atom, a chlorine atom, a bromine atom, and an iodine atom. The hydrocarbyl group may be saturated or unsaturated and may be linear, branched, or cyclic. Specific examples thereof include the same groups as those exemplified in the description of R ¹⁰¹ to R ¹⁰⁵ in formulas (1-1) and (1-2) below.

Furthermore, R ²³ and R ²⁴ or R ²⁶ and R ²⁷ may be bonded to each other to form a ring together with the sulfur atom to which they are bonded. In this case, examples of the ring include the same rings as those exemplified as the ring that can be formed by R ¹⁰¹ and R ¹⁰² being bonded to each other together with the sulfur atom to which they are bonded in the description of formula (1-1) below.

In formula (d1), M ⁻ represents a non-nucleophilic counter ion. Examples of the non-nucleophilic counter ion include halide ions such as chloride ion and bromide ion, fluoroalkylsulfonate ions such as triflate ion, 1,1,1-trifluoroethanesulfonate ion and nonafluorobutanesulfonate ion, arylsulfonate ions such as tosylate ion, benzenesulfonate ion, 4-fluorobenzenesulfonate ion and 1,2,3,4,5-pentafluorobenzenesulfonate ion, alkylsulfonate ions such as mesylate ion and butanesulfonate ion, imide ions such as bis(trifluoromethylsulfonyl)imide ion, bis(perfluoroethylsulfonyl)imide ion and bis(perfluorobutylsulfonyl)imide ion, and methide ions such as tris(trifluoromethylsulfonyl)methide ion and tris(perfluoroethylsulfonyl)methide ion.

Further examples of the non-nucleophilic counter ion include a sulfonate ion represented by the following formula (d1-1) in which the α-position is substituted with a fluorine atom, and a sulfonate ion represented by the following formula (d1-2) in which the α-position is substituted with a fluorine atom and the β-position is substituted with a trifluoromethyl group.

In formula (d1-1), R ³¹ is a hydrogen atom or a hydrocarbyl group having 1 to 20 carbon atoms, and the hydrocarbyl group may contain an ether bond, an ester bond, a carbonyl group, a lactone ring, or a fluorine atom. The hydrocarbyl group may be saturated or unsaturated, and may be linear, branched, or cyclic. Specific examples thereof include the same groups as those exemplified as the hydrocarbyl group represented by R ¹¹¹ in formula (1A') described below.

In formula (d1-2), R ³² represents a hydrogen atom, a hydrocarbyl group having 1 to 30 carbon atoms, or a hydrocarbyl carbonyl group having 2 to 30 carbon atoms, and the hydrocarbyl group and hydrocarbyl carbonyl group may contain an ether bond, an ester bond, a carbonyl group, or a lactone ring. The hydrocarbyl moiety of the hydrocarbyl group and hydrocarbyl carbonyl group may be saturated or unsaturated and may be linear, branched, or cyclic. Specific examples thereof include the same as those exemplified as the hydrocarbyl group represented by R ¹¹¹ in formula (1A') described below.

Examples of the cation of the monomer that gives the repeating unit d1 include, but are not limited to, the following: In the following formula, R ^A is the same as defined above.

Specific examples of the cation of the monomer that gives the repeating unit d2 or d3 include the same as those exemplified as the cation of the sulfonium salt represented by formula (1-1) described below.

Examples of the anion of the monomer that gives the repeating unit d2 include, but are not limited to, the following: In the following formula, R ^A is the same as defined above.

Examples of the anion of the monomer that gives the repeating unit d3 include, but are not limited to, the following: In the following formula, R ^A is the same as defined above.

Repeating units d1 to d3 function as an acid generator. By binding the acid generator to the polymer main chain, acid diffusion is reduced, preventing a decrease in resolution due to blurring caused by acid diffusion. Furthermore, uniform dispersion of the acid generator improves edge roughness and CDU. Note that when using a base polymer containing repeating units d1 to d3 (i.e., a polymer-bound acid generator), the addition of the additive acid generator described below can be omitted.

The base polymer may contain a repeating unit e containing an iodine atom. Examples of monomers that provide the repeating unit e include, but are not limited to, the following: In the following formula, R ^A is the same as defined above.

The base polymer may contain a repeating unit f other than the repeating units described above. Examples of repeating unit f include those derived from styrene, vinylnaphthalene, indene, acenaphthylene, coumarin, and coumarone.

In the base polymer, the content ratios of repeating units b1, b2, c, d1, d2, d3, e, and f are preferably 0≦b1≦0.9, 0≦b2≦0.9, 0.1≦b1+b2≦0.9, 0≦c≦0.9, 0≦d1≦0.5, 0≦d2≦0.5, 0≦d3≦0.5, 0≦d1+d2+d3≦0.5, 0≦e≦0.5, and 0≦f≦0.5, and are preferably 0≦b1≦0.8, 0≦b2≦0.8, 0.2≦b1+b2≦0. 8, 0≦c≦0.8, 0≦d1≦0.4, 0≦d2≦0.4, 0≦d3≦0.4, 0≦d1+d2+d3≦0.4, 0≦e≦0.4, and 0≦f≦0.4 are more preferred, and 0≦b1≦0.7, 0≦b2≦0.7, 0.25≦b1+b2≦0.7, 0≦c≦0.7, 0≦d1≦0.3, 0≦d2≦0.3, 0≦d3≦0.3, 0≦d1+d2+d3≦0.3, 0≦e≦0.3, and 0≦f≦0.3 are even more preferred, with the proviso that b1+b2+c+d1+d2+d3+e+f=1.0.

To synthesize the base polymer, for example, a monomer that provides the repeating unit described above is polymerized by heating in an organic solvent with the addition of a radical polymerization initiator and a chain transfer agent, which is a sulfonium salt containing a carboxylate anion linked to a thiol group. By using the chain transfer agent, the ends of the base polymer can be capped with a sulfonium salt containing a carboxylate anion linked to a sulfide group. The polymerization initiator and chain transfer agent may be added at the start of polymerization, during polymerization, or gradually during polymerization.

Chain transfer agents are generally used to reduce the molecular weight of polymers. Polymerization is carried out by radicals generated from a polymerization initiator, and the activated radicals move to the sulfonium salt containing a carboxylate anion linked to a thiol group of the present invention, starting polymerization. In this way, the sulfonium salt containing a carboxylate anion linked to a thiol group of the present invention bonds to the end of the polymer.

A smaller molecular weight has the advantage of reducing swelling in the developer. However, a lower glass transition temperature (Tg) of the polymer has the disadvantage of increasing acid diffusion during PEB. Polymer-type quenchers are highly effective at suppressing acid diffusion, and this effect can be maintained even when the molecular weight of the polymer is reduced. In particular, by placing a quencher at the polymer end, as in the present invention, the acid capture ability can be enhanced. The aim of the present invention is to develop a material that can achieve both reduced swelling in the developer through lower molecular weight and low acid diffusion.

The amount of the chain transfer agent used can be selected depending on the target molecular weight, the raw material monomers, and production conditions such as polymerization temperature and polymerization method.

Commercially available radical polymerization initiators can be used as the polymerization initiator. Radical polymerization initiators such as azo initiators and peroxide initiators are preferred. Polymerization initiators can be used alone or in combination. The amount of polymerization initiator used can be selected depending on the target molecular weight, the raw material monomers, and production conditions such as polymerization temperature and polymerization method. Specific examples of polymerization initiators are listed below.

Specific examples of azo initiators include 2,2'-azobisisobutyronitrile, 2,2'-azobis(2,4-dimethylvaleronitrile), 2,2'-azobis(2-methylpropionate)dimethyl, 2,2'-azobis(4-methoxy-2,4-dimethylvaleronitrile), 2,2'-azobis(cyclohexane-1-carbonitrile), 4,4'-azobis(4-cyanovaleric acid), and 2,2'-azobis(isobutyrate)dimethyl. Specific examples of peroxide initiators include benzoyl peroxide, decanoyl peroxide, lauroyl peroxide, succinic acid peroxide, tert-butylperoxy-2-ethylhexanoate, tert-butylperoxypivaloate, and 1,1,3,3-tetramethylbutylperoxy-2-ethylhexanoate.

Examples of organic solvents used during polymerization include toluene, benzene, tetrahydrofuran (THF), diethyl ether, and dioxane . The temperature during polymerization is preferably 50 to 80° C. The reaction time is preferably 2 to 100 hours, and more preferably 5 to 20 hours.

When copolymerizing monomers containing hydroxy groups, the hydroxy groups can be substituted with acetal groups, such as ethoxyethoxy groups, which are easily deprotected by acid during polymerization, and then deprotected using a weak acid and water after polymerization. Alternatively, the hydroxy groups can be substituted with acetyl groups, formyl groups, pivaloyl groups, etc., and then subjected to alkaline hydrolysis after polymerization.

When copolymerizing hydroxystyrene or hydroxyvinylnaphthalene, acetoxystyrene or acetoxyvinylnaphthalene can be used instead of hydroxystyrene or hydroxyvinylnaphthalene, and after polymerization, the acetoxy groups can be deprotected by alkaline hydrolysis to yield hydroxystyrene or hydroxyvinylnaphthalene.

Ammonia water, triethylamine, etc. can be used as the base for alkaline hydrolysis. The reaction temperature is preferably -20 to 100°C, more preferably 0 to 60°C. The reaction time is preferably 0.2 to 100 hours, more preferably 0.5 to 20 hours.

The base polymer preferably has a weight average molecular weight (Mw) in terms of polystyrene measured by gel permeation chromatography (GPC) using THF as a solvent of 1,000 to 500,000, and more preferably 2,000 to 30,000. If the Mw is too small, the resist material will have poor heat resistance, while if it is too large, it will have poor alkali solubility and be more likely to experience a footing phenomenon after pattern formation.

Furthermore, if the base polymer has a broad molecular weight distribution (Mw/Mn), the presence of low-molecular-weight and high-molecular-weight polymers may result in foreign matter appearing on the pattern after exposure, or the pattern shape may be degraded. As pattern rules become finer, the effects of Mw and Mw/Mn tend to become greater. Therefore, to obtain a resist material suitable for fine pattern dimensions, it is preferable that the base polymer have a narrow Mw/Mn distribution of 1.0 to 2.0, and particularly 1.0 to 1.5.

The base polymer may contain two or more polymers with different composition ratios, Mw, or Mw/Mn. Polymers containing different terminal structures a may also be blended, or a polymer containing terminal structure a may be blended with a polymer not containing terminal structure a.

[Acid Generator]
The positive resist composition of the present invention may contain an acid generator that generates a strong acid (hereinafter also referred to as an additive-type acid generator). The strong acid here refers to a compound that has sufficient acidity to cause a deprotection reaction of the acid labile groups in the base polymer.

Examples of the acid generator include compounds (photoacid generators) that generate acid in response to actinic rays or radiation. The photoacid generator may be any compound that generates acid upon exposure to high-energy rays, but those that generate sulfonic acid, imide acid, or methide acid are preferred. Suitable photoacid generators include sulfonium salts, iodonium salts, sulfonyldiazomethane, N-sulfonyloxyimide, and oxime-O-sulfonate-type acid generators. Specific examples of photoacid generators include those described in paragraphs [0122] to [0142] of JP 2008-111103 A.

Furthermore, as the photoacid generator, a sulfonium salt represented by the following formula (1-1) or an iodonium salt represented by the following formula (1-2) can also be suitably used.

In formulas (1-1) and (1-2), R ¹⁰¹ to R ¹⁰⁵ each independently represent a halogen atom or a hydrocarbyl group having 1 to 20 carbon atoms which may contain a heteroatom.

Examples of the halogen atom include a fluorine atom, a chlorine atom, a bromine atom, and an iodine atom.

The hydrocarbyl groups having 1 to 20 carbon atoms represented by R ¹⁰¹ to R ¹⁰⁵ may be saturated or unsaturated, and may be straight-chain, branched, or cyclic. Specific examples thereof include alkyl groups having 1 to 20 carbon atoms, such as methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, n-pentyl, n-hexyl, n-octyl, n-nonyl, n-decyl, undecyl, dodecyl, tridecyl, tetradecyl, pentadecyl, heptadecyl, octadecyl, nonadecyl, and icosyl groups; cyclic saturated hydrocarbyl groups having 3 to 20 carbon atoms, such as cyclopropyl, cyclopentyl, cyclohexyl, cyclopropylmethyl, 4-methylcyclohexyl, cyclohexylmethyl, norbornyl, and adamantyl groups; alkenyl groups having 2 to 20 carbon atoms, such as vinyl, propenyl, butenyl, and hexenyl groups; and ethynyl groups. alkynyl groups having 2 to 20 carbon atoms such as a propynyl group or a butynyl group; cyclic unsaturated aliphatic hydrocarbyl groups having 3 to 20 carbon atoms such as a cyclohexenyl group or a norbornenyl group; aryl groups having 6 to 20 carbon atoms such as a phenyl group, a methylphenyl group, an ethylphenyl group, an n-propylphenyl group, an isopropylphenyl group, an n-butylphenyl group, an isobutylphenyl group, a sec-butylphenyl group, a tert-butylphenyl group, a naphthyl group, a methylnaphthyl group, an ethylnaphthyl group, an n-propylnaphthyl group, an isopropylnaphthyl group, an n-butylnaphthyl group, an isobutylnaphthyl group, a sec-butylnaphthyl group or a tert-butylnaphthyl group; aralkyl groups having 7 to 20 carbon atoms such as a benzyl group or a phenethyl group; and groups obtained by combining these.

In addition, some or all of the hydrogen atoms in these groups may be substituted with groups containing heteroatoms such as oxygen atoms, sulfur atoms, nitrogen atoms, and halogen atoms, and some of the -CH ₂ - groups in these groups may be substituted with groups containing heteroatoms such as oxygen atoms, sulfur atoms, and nitrogen atoms, resulting in the group containing a hydroxy group, a fluorine atom, a chlorine atom, a bromine atom, an iodine atom, a cyano group, a nitro group, a carbonyl group, an ether bond, an ester bond, a sulfonate ester bond, a carbonate bond, a lactone ring, a sultone ring, a carboxylic acid anhydride, a haloalkyl group, etc.

Furthermore, R ¹⁰¹ and R ¹⁰² may be bonded to each other to form a ring together with the sulfur atom to which they are bonded. In this case, the ring preferably has the following structure.
(In the formula, the dashed line represents a bond to R ^103. )

Examples of the cation of the sulfonium salt represented by formula (1-1) include, but are not limited to, those shown below.

Examples of the cation of the iodonium salt represented by formula (1-2) include, but are not limited to, those shown below.

In formulas (1-1) and (1-2), Xa ⁻ is an anion selected from the following formulas (1A) to (1D).

In formula (1A), R ^fa represents a hydrocarbyl group having 1 to 40 carbon atoms which may contain a fluorine atom or a heteroatom. The hydrocarbyl group may be saturated or unsaturated and may be linear, branched, or cyclic. Specific examples thereof include the same groups as those exemplified as the hydrocarbyl group represented by R ¹¹¹ in formula (1A') described below.

The anion represented by formula (1A) is preferably an anion represented by the following formula (1A').

In formula (1A'), R ^HF represents a hydrogen atom or a trifluoromethyl group, preferably a trifluoromethyl group. R ¹¹¹ represents a hydrocarbyl group having 1 to 38 carbon atoms which may contain a heteroatom. The heteroatom is preferably an oxygen atom, a nitrogen atom, a sulfur atom, a halogen atom, or the like, more preferably an oxygen atom. From the viewpoint of obtaining high resolution in fine pattern formation, the hydrocarbyl group is preferably one having 6 to 30 carbon atoms.

The hydrocarbyl group represented by R ¹¹¹ may be saturated or unsaturated, and may be linear, branched, or cyclic. Specific examples thereof include alkyl groups having 1 to 38 carbon atoms, such as a methyl group, an ethyl group, an n-propyl group, an isopropyl group, a butyl group, an isobutyl group, a sec-butyl group, a tert-butyl group, a pentyl group, a neopentyl group, a hexyl group, a heptyl group, a 2-ethylhexyl group, a nonyl group, an undecyl group, a tridecyl group, a pentadecyl group, a heptadecyl group, and an icosyl group; a cyclopentyl group, a cyclohexyl group, a 1-adamantyl group, a 2-adamantyl group, a 1-adamantylmethyl group, a norbornyl group, Examples include cyclic saturated hydrocarbyl groups having 3 to 38 carbon atoms, such as norbornylmethyl, tricyclodecanyl, tetracyclododecanyl, tetracyclododecanylmethyl, and dicyclohexylmethyl; unsaturated aliphatic hydrocarbyl groups having 2 to 38 carbon atoms, such as allyl and 3-cyclohexenyl; aryl groups having 6 to 38 carbon atoms, such as phenyl, 1-naphthyl, and 2-naphthyl; aralkyl groups having 7 to 38 carbon atoms, such as benzyl and diphenylmethyl; and groups obtained by combining these.

In addition, some or all of the hydrogen atoms in these groups may be substituted with a group containing a heteroatom such as an oxygen atom, a sulfur atom, a nitrogen atom or a halogen atom, and some of the —CH ₂ — groups in these groups may be substituted with a group containing a heteroatom such as an oxygen atom, a sulfur atom or a nitrogen atom, resulting in the group containing a hydroxy group, a fluorine atom, a chlorine atom, a bromine atom, an iodine atom, a cyano group, a nitro group, a carbonyl group, an ether bond, an ester bond, a sulfonate ester bond, a carbonate bond, a lactone ring, a sultone ring, a carboxylic acid anhydride, a haloalkyl group, etc. Examples of hydrocarbyl groups containing a heteroatom include a tetrahydrofuryl group, a methoxymethyl group, an ethoxymethyl group, a methylthiomethyl group, an acetamidomethyl group, a trifluoroethyl group, a (2-methoxyethoxy)methyl group, an acetoxymethyl group, a 2-carboxy-1-cyclohexyl group, a 2-oxopropyl group, a 4-oxo-1-adamantyl group, and a 3-oxocyclohexyl group.

The synthesis of sulfonium salts containing the anion represented by formula (1A') is described in detail in JP-A Nos. 2007-145797, 2008-106045, 2009-7327, and 2009-258695. Sulfonium salts described in JP-A Nos. 2010-215608, 2012-41320, 2012-106986, and 2012-153644 are also suitable.

Examples of the anion represented by formula (1A) include the same anions as those exemplified as the anion represented by formula (1A) in JP 2018-197853 A.

In formula (1B), R ^fb1 and R ^fb2 each independently represent a fluorine atom or a hydrocarbyl group having 1 to 40 carbon atoms which may contain a heteroatom. The hydrocarbyl group may be saturated or unsaturated and may be linear, branched, or cyclic. Specific examples thereof include the same groups as those exemplified as the hydrocarbyl group represented by R ¹¹¹ in formula (1A'). R ^fb1 and R ^fb2 are preferably a fluorine atom or a linear fluorinated alkyl group having 1 to 4 carbon atoms. R ^fb1 and R ^fb2 may be bonded to each other to form a ring together with the group to which they are bonded (-CF ₂ -SO ₂ -N ^- -SO ₂ -CF ₂ -), and in this case, the group obtained by bonding R ^fb1 and R ^fb2 to each other is preferably a fluorinated ethylene group or a fluorinated propylene group.

In formula (1C), ^Rfc1 , ^Rfc2 , and ^Rfc3 each independently represent a fluorine atom or a hydrocarbyl group having 1 to 40 carbon atoms which may contain a heteroatom. The hydrocarbyl group may be saturated or unsaturated and may be linear, branched, or cyclic. Specific examples thereof include the same groups as those exemplified as the hydrocarbyl group represented by ^R111 in formula (1A'). ^Rfc1 , ^Rfc2 , and ^Rfc3 are preferably a fluorine atom or a linear fluorinated alkyl group having 1 to 4 carbon atoms. ^Rfc1 and ^Rfc2 may bond to each other to form a ring together with the group to which they are bonded ( _-CF2 - _SO2 -C ^-- _SO2 - _CF2- ), and in this case, the group obtained by bonding ^Rfc1 and ^Rfc2 to each other is preferably a fluorinated ethylene group or a fluorinated propylene group.

In formula (1D), R ^fd is a hydrocarbyl group having 1 to 40 carbon atoms which may contain a heteroatom. The hydrocarbyl group may be saturated or unsaturated, and may be linear, branched, or cyclic. Specific examples thereof include the same groups as those exemplified as the hydrocarbyl group represented by R ¹¹¹ in formula (1A').

Details on the synthesis of sulfonium salts containing the anion represented by formula (1D) are found in JP-A-2010-215608 and JP-A-2014-133723.

Examples of the anion represented by formula (1D) include the same anions as those exemplified as the anion represented by formula (1D) in JP 2018-197853 A.

Note that photoacid generators containing the anion represented by formula (1D) do not have a fluorine atom at the α-position of the sulfo group, but because they have two trifluoromethyl groups at the β-position, they have sufficient acidity to cleave acid-labile groups in the base polymer. Therefore, they can be used as photoacid generators.

As the photoacid generator, a compound represented by the following formula (2) can also be suitably used.

In formula (2), R ²⁰¹ and R ²⁰² are each independently a halogen atom or a hydrocarbyl group having 1 to 30 carbon atoms which may contain a heteroatom. R ²⁰³ is a hydrocarbylene group having 1 to 30 carbon atoms which may contain a heteroatom. Any two of R ²⁰¹ , R ²⁰² , and R ²⁰³ may be bonded to each other to form a ring together with the sulfur atom to which they are bonded. In this case, examples of the ring include those exemplified in the description of formula (1-1) as the ring that can be formed by R ¹⁰¹ and R ¹⁰² bonding together with the sulfur atom to which they are bonded.

The hydrocarbyl groups represented by R ²⁰¹ and R ²⁰² may be saturated or unsaturated and may be linear, branched, or cyclic. Specific examples thereof include alkyl groups having 1 to 30 carbon atoms, such as methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, n-pentyl, tert-pentyl, n-hexyl, n-octyl, 2-ethylhexyl, n-nonyl, and n-decyl; cyclopentyl, cyclohexyl, cyclopentylmethyl, cyclopentylethyl, cyclopentylbutyl, cyclohexylmethyl, cyclohexylethyl, cyclohexylbutyl, norbornyl, and tricyclo[5.2.1.0 ^2,6 cyclic saturated hydrocarbyl groups having 3 to 30 carbon atoms such as a phenyl group, a methylphenyl group, an ethylphenyl group, an n-propylphenyl group, an isopropylphenyl group, an n-butylphenyl group, an isobutylphenyl group, a sec-butylphenyl group, a tert-butylphenyl group, a naphthyl group, a methylnaphthyl group, an ethylnaphthyl group, an n-propylnaphthyl group, an isopropylnaphthyl group, an n-butylnaphthyl group, an isobutylnaphthyl group, a sec-butylnaphthyl group, a tert-butylnaphthyl group, an anthracenyl group, and the like; and groups obtained by combining these. In addition, some or all of the hydrogen atoms in these groups may be substituted with groups containing heteroatoms such as oxygen atoms, sulfur atoms, nitrogen atoms, and halogen atoms, and some of the -CH ₂ - groups in these groups may be substituted with groups containing heteroatoms such as oxygen atoms, sulfur atoms, and nitrogen atoms, resulting in the group containing a hydroxy group, a fluorine atom, a chlorine atom, a bromine atom, an iodine atom, a cyano group, a nitro group, a carbonyl group, an ether bond, an ester bond, a sulfonate ester bond, a carbonate bond, a lactone ring, a sultone ring, a carboxylic acid anhydride, a haloalkyl group, etc.

The hydrocarbylene group represented by R ²⁰³ may be saturated or unsaturated, and may be straight-chain, branched, or cyclic. Specific examples thereof include alkanediyl groups having 1 to 30 carbon atoms, such as methanediyl group, ethane-1,1-diyl group, ethane-1,2-diyl group, propane-1,3-diyl group, butane-1,4-diyl group, pentane-1,5-diyl group, hexane-1,6-diyl group, heptane-1,7-diyl group, octane-1,8-diyl group, nonane-1,9-diyl group, decane-1,10-diyl group, undecane-1,11-diyl group, dodecane-1,12-diyl group, tridecane-1,13-diyl group, tetradecane-1,14-diyl group, pentadecane-1,15-diyl group, hexadecane-1,16-diyl group, and heptadecane-1,17-diyl group; cyclopentanediyl group, cyclohexanediyl group, and the like. Examples of the alkylene group include cyclic saturated hydrocarbylene groups having 3 to 30 carbon atoms, such as xanediyl, norbornanediyl, and adamantanediyl; arylene groups having 6 to 30 carbon atoms, such as phenylene, methylphenylene, ethylphenylene, n-propylphenylene, isopropylphenylene, n-butylphenylene, isobutylphenylene, sec-butylphenylene, tert-butylphenylene, naphthylene, methylnaphthylene, ethylnaphthylene, n-propylnaphthylene, isopropylnaphthylene, n-butylnaphthylene, isobutylnaphthylene, sec-butylnaphthylene, and tert-butylnaphthylene; and groups obtained by combining these groups. In addition, some or all of the hydrogen atoms in these groups may be substituted with a group containing a heteroatom such as an oxygen atom, a sulfur atom, a nitrogen atom or a halogen atom, and some of the —CH ₂ — groups in these groups may be substituted with a group containing a heteroatom such as an oxygen atom, a sulfur atom or a nitrogen atom, resulting in the group containing a hydroxy group, a fluorine atom, a chlorine atom, a bromine atom, an iodine atom, a cyano group, a nitro group, a carbonyl group, an ether bond, an ester bond, a sulfonate ester bond, a carbonate bond, a lactone ring, a sultone ring, a carboxylic acid anhydride, a haloalkyl group, etc. As the heteroatom, an oxygen atom is preferred.

In formula (2), ^L represents a single bond, an ether bond, or a hydrocarbylene group having 1 to 20 carbon atoms which may contain a heteroatom. The hydrocarbylene group may be saturated or unsaturated and may be linear, branched, or cyclic. Specific examples thereof include the same groups as those exemplified as the hydrocarbylene group represented by ^R.

In formula (2), ^XA , ^XB , ^XC, and ^XD each independently represent a hydrogen atom, a fluorine atom, or a trifluoromethyl group, provided that at least one of ^XA , ^XB , ^XC , and ^XD is a fluorine atom or a trifluoromethyl group.

In formula (2), t is an integer from 0 to 3.

The photoacid generator represented by formula (2) is preferably one represented by the following formula (2').

In formula (2'), ^L is the same as defined above. R ^HF is a hydrogen atom or a trifluoromethyl group, preferably a trifluoromethyl group. R ³⁰¹ , R ³⁰² , and R ³⁰³ are each independently a hydrogen atom or a hydrocarbyl group having 1 to 20 carbon atoms which may contain a heteroatom. The hydrocarbyl group may be saturated or unsaturated, and may be linear, branched, or cyclic. Specific examples include the same groups as those exemplified as the hydrocarbyl group represented by R ¹¹¹ in formula (1A'). x and y are each independently an integer of 0 to 5, and z is an integer of 0 to 4.

Examples of photoacid generators represented by formula (2) include those exemplified as photoacid generators represented by formula (2) in JP 2017-26980 A.

Among the above photoacid generators, those containing anions represented by formula (1A') or (1D) are particularly preferred, as they have low acid diffusion and excellent solubility in solvents. Furthermore, those represented by formula (2') are particularly preferred, as they have extremely low acid diffusion.

The photoacid generator may also be a sulfonium salt or iodonium salt containing an anion having an aromatic ring substituted with an iodine atom or a bromine atom, such as those represented by the following formula (3-1) or (3-2):

In formulas (3-1) and (3-2), p is an integer that satisfies 1≦p≦3. q and r are integers that satisfy 1≦q≦5, 0≦r≦3, and 1≦q+r≦5. q is preferably an integer that satisfies 1≦q≦3, more preferably 2 or 3. r is preferably an integer that satisfies 0≦r≦2.

In formulas (3-1) and (3-2), X ^BI represents an iodine atom or a bromine atom, and when p and/or q is 2 or more, they may be the same or different.

In formulas (3-1) and (3-2), ^L1 is a single bond, an ether bond, an ester bond, or a saturated hydrocarbylene group having 1 to 6 carbon atoms which may contain an ether bond or an ester bond. The saturated hydrocarbylene group may be linear, branched, or cyclic.

In formulas (3-1) and (3-2), ^L2 is a single bond or a divalent linking group having 1 to 20 carbon atoms when p is 1, and is a (p+1)-valent linking group having 1 to 20 carbon atoms when p is 2 or 3, and the linking group may contain an oxygen atom, a sulfur atom, or a nitrogen atom.

In formulas (3-1) and (3-2), R ⁴⁰¹ is a hydroxy group, a carboxy group, a fluorine atom, a chlorine atom, a bromine atom, or an amino group, or a hydrocarbyl group having 1 to 20 carbon atoms, a hydrocarbyloxy group having 1 to 20 carbon atoms, a hydrocarbylcarbonyl group having 2 to 20 carbon atoms, a hydrocarbyloxycarbonyl group having 2 to 20 carbon atoms, a hydrocarbylcarbonyloxy group having 2 to 20 carbon atoms, or a hydrocarbylsulfonyloxy group having 1 to 20 carbon atoms, each of which may contain a fluorine atom, a chlorine atom, a bromine atom, a hydroxy group, an amino group, or an ether bond, or -N(R ^401A )(R ^401B ), -N( ^{R 401C} )-C(═O)-R 401D or -N(R ^401C )-C(═O)-O-R ^401D . R ^401A and R ^401B are each independently a hydrogen atom or a saturated hydrocarbyl group having 1 to 6 carbon atoms. R ^401C is a hydrogen atom or a saturated hydrocarbyl group having 1 to 6 carbon atoms, and may contain a halogen atom, a hydroxy group, a saturated hydrocarbyloxy group having 1 to 6 carbon atoms, a saturated hydrocarbylcarbonyl group having 2 to 6 carbon atoms, or a saturated hydrocarbylcarbonyloxy group having 2 to 6 carbon atoms. R ^401D is an aliphatic hydrocarbyl group having 1 to 16 carbon atoms, an aryl group having 6 to 12 carbon atoms, or an aralkyl group having 7 to 15 carbon atoms, and may contain a halogen atom, a hydroxy group, a saturated hydrocarbyloxy group having 1 to 6 carbon atoms, a saturated hydrocarbylcarbonyl group having 2 to 6 carbon atoms, or a saturated hydrocarbylcarbonyloxy group having 2 to 6 carbon atoms. The aliphatic hydrocarbyl group may be saturated or unsaturated, and may be linear, branched, or cyclic. The hydrocarbyl group, hydrocarbyloxy group, hydrocarbylcarbonyl group, hydrocarbyloxycarbonyl group, hydrocarbylcarbonyloxy group, and hydrocarbylsulfonyloxy group may be linear, branched, or cyclic. When p and/or r is 2 or more, each ^R may be the same or different.

Of these, preferred as R ⁴⁰¹ are a hydroxy group, —N(R ^401C )—C(═O)—R ^401D , —N(R ^401C )—C(═O)—O—R ^401D , a fluorine atom, a chlorine atom, a bromine atom, a methyl group, a methoxy group, and the like.

In formulas (3-1) and (3-2), Rf ¹ to Rf ⁴ are each independently a hydrogen atom, a fluorine atom, or a trifluoromethyl group, with at least one of them being a fluorine atom or a trifluoromethyl group. Rf ¹ and Rf ² may combine to form a carbonyl group. It is particularly preferred that Rf ³ and Rf ⁴ are both fluorine atoms.

In formulas (3-1) and (3-2), R ⁴⁰² to R ⁴⁰⁶ each independently represent a hydrocarbyl group having 1 to 20 carbon atoms, which may contain a halogen atom or a heteroatom. The hydrocarbyl group may be saturated or unsaturated and may be linear, branched, or cyclic. Specific examples include the same groups as those exemplified as the hydrocarbyl groups represented by R ¹⁰¹ to R ¹⁰⁵ in the description of formulas (1-1) and (1-2). Some or all of the hydrogen atoms in these groups may be substituted with a hydroxy group, a carboxy group, a halogen atom, a cyano group, a nitro group, a mercapto group, a sultone ring, a sulfo group, or a sulfonium salt-containing group, and some of the —CH ₂ — groups in these groups may be substituted with an ether bond, an ester bond, a carbonyl group, an amide bond, a carbonate bond, or a sulfonate ester bond. R ⁴⁰² and R ⁴⁰³ may also bond to each other to form a ring together with the sulfur atom to which they are bonded. In this case, examples of the ring include the same rings as those exemplified in the explanation of formula (1-1) as rings that can be formed by combining R ¹⁰¹ and R ¹⁰² together with the sulfur atom to which they are bonded.

Cations of the sulfonium salt represented by formula (3-1) include the same as those exemplified as cations of the sulfonium salt represented by formula (1-1). Furthermore, cations of the iodonium salt represented by formula (3-2) include the same as those exemplified as cations of the iodonium salt represented by formula (1-2).

Examples of the anion of the onium salt represented by formula (3-1) or (3-2) include, but are not limited to, those shown below: In the following formula, X ^BI is the same as defined above.

When the positive resist material of the present invention contains an additive acid generator, the content thereof is preferably 0.1 to 50 parts by mass, and more preferably 1 to 40 parts by mass, per 100 parts by mass of the base polymer. The additive acid generators may be used alone or in combination of two or more types. By including repeating units d1 to d3 in the base polymer and/or by including an additive acid generator, the positive resist material of the present invention can function as a chemically amplified positive resist material.

[Organic solvent]
The positive resist material of the present invention may contain an organic solvent. There are no particular limitations on the organic solvent, so long as it can dissolve the components described above and below. Examples of the organic solvent include ketones such as cyclohexanone, cyclopentanone, methyl-2-n-pentyl ketone, and 2-heptanone, as described in paragraphs [0144] and [0145] of JP-A No. 2008-111103; alcohols such as 3-methoxybutanol, 3-methyl-3-methoxybutanol, 1-methoxy-2-propanol, 1-ethoxy-2-propanol, and diacetone alcohol; propylene glycol monomethyl ether, ethylene glycol monomethyl ether, propylene glycol monoethyl ether, ethylene glycol monoethyl ether, and propylene glycol monomethyl ether. Examples of suitable esters include ethers such as pyrene glycol dimethyl ether and diethylene glycol dimethyl ether; esters such as propylene glycol monomethyl ether acetate, propylene glycol monoethyl ether acetate, ethyl lactate (L-form), ethyl lactate (D-form), ethyl lactate (DL-form), ethyl pyruvate, butyl acetate, methyl 3-methoxypropionate, ethyl 3-ethoxypropionate, tert-butyl acetate, tert-butyl propionate, and propylene glycol mono-tert-butyl ether acetate; and lactones such as γ-butyrolactone.

In the positive resist material of the present invention, the content of the organic solvent is preferably 100 to 10,000 parts by mass, and more preferably 200 to 8,000 parts by mass, per 100 parts by mass of the base polymer. The organic solvent may be used alone or in combination of two or more types.

[Quencher]
The positive resist material of the present invention has a sulfonium salt-type quencher at the polymer terminal, but may also contain a separate quencher. The quencher refers to a compound that can trap the acid generated by the acid generator in the resist material, thereby preventing it from diffusing into unexposed areas.

Examples of the quencher include conventional basic compounds. Examples of conventional basic compounds include primary, secondary, and tertiary aliphatic amines, mixed amines, aromatic amines, heterocyclic amines, nitrogen-containing compounds having a carboxy group, nitrogen-containing compounds having a sulfonyl group, nitrogen-containing compounds having a hydroxy group, nitrogen-containing compounds having a hydroxyphenyl group, alcoholic nitrogen-containing compounds, amides, imides, and carbamates. Particularly preferred are the primary, secondary, and tertiary amine compounds described in paragraphs [0146] to [0164] of JP 2008-111103 A, particularly amine compounds having a hydroxy group, an ether bond, an ester bond, a lactone ring, a cyano group, or a sulfonate ester bond, and compounds having a carbamate group described in Japanese Patent No. 3790649 A. Addition of such basic compounds can, for example, further suppress the diffusion rate of acid in the resist film or correct the shape.

Further examples of the quencher include onium salts such as sulfonium salts, iodonium salts, and ammonium salts of sulfonic acids, carboxylic acids, or fluorinated alkoxides that are not fluorinated at the α-position, as described in JP 2008-158339 A. Sulfonic acids, imide acids, or methide acids that are fluorinated at the α-position are necessary to deprotect the acid labile group of a carboxylic acid ester, and salt exchange with an onium salt that is not fluorinated at the α-position releases sulfonic acids, carboxylic acids, or fluorinated alcohols that are not fluorinated at the α-position. Sulfonic acids, carboxylic acids, and fluorinated alcohols that are not fluorinated at the α-position do not undergo deprotection reactions, and therefore function as quenchers.

Examples of such quenchers include compounds represented by the following formula (4) (onium salts of sulfonic acids not fluorinated at the α-position), compounds represented by the following formula (5) (onium salts of carboxylic acids), and compounds represented by the following formula (6) (onium salts of alkoxides).

In formula (4), R ⁵⁰¹ is a hydrocarbyl group having 1 to 40 carbon atoms which may contain a hydrogen atom or a heteroatom, but excludes those in which the hydrogen atom bonded to the carbon atom at the α-position of the sulfo group is substituted with a fluorine atom or a fluoroalkyl group.

The hydrocarbyl group may be saturated or unsaturated, and may be linear, branched, or cyclic. Specific examples thereof include alkyl groups having 1 to 40 carbon atoms, such as methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, tert-pentyl, n-pentyl, n-hexyl, n-octyl, 2-ethylhexyl, n-nonyl, and n-decyl; cyclopentyl, cyclohexyl, cyclopentylmethyl, cyclopentylethyl, cyclopentylbutyl, cyclohexylmethyl, cyclohexylethyl, cyclohexylbutyl, norbornyl, and tricyclo[5.2.1.0 ^2,6 ]Cyclic saturated hydrocarbyl groups having 3 to 40 carbon atoms such as decanyl group, adamantyl group, and adamantylmethyl group; C2 to 40 alkenyl groups such as vinyl group, allyl group, propenyl group, butenyl group, and hexenyl group; C3 to 40 unsaturated aliphatic hydrocarbyl groups such as cyclohexenyl group; phenyl group, naphthyl group, alkylphenyl groups (2-methylphenyl group, 3-methylphenyl group, 4-methylphenyl group, 4-ethylphenyl group, 4-tert-butylphenyl group, 4-n-butylphenyl group, etc.), dialkylphenyl groups (2,4-dimethylphenyl group, etc.) aryl groups having 6 to 40 carbon atoms such as a 2,4,6-triisopropylphenyl group, an alkylnaphthyl group (e.g., a methylnaphthyl group, an ethylnaphthyl group), and a dialkylnaphthyl group (e.g., a dimethylnaphthyl group, a diethylnaphthyl group); and aralkyl groups having 7 to 40 carbon atoms such as a benzyl group, a 1-phenylethyl group, and a 2-phenylethyl group.

In addition, some of the hydrogen atoms in the hydrocarbyl group may be substituted with groups containing heteroatoms such as oxygen atoms, sulfur atoms, nitrogen atoms, and halogen atoms, and some of the -CH ₂ - groups in the hydrocarbyl group may be substituted with groups containing heteroatoms such as oxygen atoms, sulfur atoms, and nitrogen atoms, and as a result, the hydrocarbyl group may contain a hydroxy group, a cyano group, a carbonyl group, an ether bond, an ester bond, a sulfonate ester bond, a carbonate bond, a lactone ring, a sultone ring, a carboxylic acid anhydride, a haloalkyl group, etc. Examples of the hydrocarbyl group containing a heteroatom include heteroaryl groups such as a thienyl group and an indolyl group; alkoxyphenyl groups such as a 4-hydroxyphenyl group, a 4-methoxyphenyl group, a 3-methoxyphenyl group, a 2-methoxyphenyl group, a 4-ethoxyphenyl group, a 4-tert-butoxyphenyl group, and a 3-tert-butoxyphenyl group; alkoxynaphthyl groups such as a methoxynaphthyl group, an ethoxynaphthyl group, an n-propoxynaphthyl group, and an n-butoxynaphthyl group; dialkoxynaphthyl groups such as a dimethoxynaphthyl group and a diethoxynaphthyl group; and aryloxoalkyl groups such as a 2-aryl-2-oxoethyl group, a 2-(1-naphthyl)-2-oxoethyl group, and a 2-(2-naphthyl)-2-oxoethyl group.

In formula (5), R ⁵⁰² is a hydrocarbyl group having 1 to 40 carbon atoms which may contain a heteroatom. Examples of the hydrocarbyl group represented by R ⁵⁰² include the same groups as those exemplified as the hydrocarbyl group represented by R ^501. Other specific examples include fluorine-containing alkyl groups such as a trifluoromethyl group, a trifluoroethyl group, a 2,2,2-trifluoro-1-methyl-1-hydroxyethyl group, and a 2,2,2-trifluoro-1-(trifluoromethyl)-1-hydroxyethyl group; and fluorine-containing aryl groups such as a pentafluorophenyl group and a 4-trifluoromethylphenyl group.

In formula (6), R ⁵⁰³ is a saturated hydrocarbyl group having 1 to 8 carbon atoms and at least three fluorine atoms, or an aryl group having 6 to 10 carbon atoms and at least three fluorine atoms, which may have a nitro group.

In formulas (4) to (6), Mq ⁺ represents an onium cation. The onium cation is preferably a sulfonium cation, an iodonium cation, or an ammonium cation, and more preferably a sulfonium cation or an iodonium cation. Examples of the sulfonium cation include the same cations as those exemplified as the cations of the sulfonium salt represented by formula (1-1). Examples of the iodonium cation include the same cations as those exemplified as the cations of the iodonium salt represented by formula (1-2).

As the quencher, a sulfonium salt of an iodinated benzene ring-containing carboxylic acid represented by the following formula (7) can also be suitably used.

In formula (7), R ⁶⁰¹ represents a hydroxy group, a fluorine atom, a chlorine atom, a bromine atom, an amino group, a nitro group, a cyano group, or a saturated hydrocarbyl group having 1 to 6 carbon atoms, a saturated hydrocarbyloxy group having 1 to 6 carbon atoms, a saturated hydrocarbylcarbonyloxy group having 2 to 6 carbon atoms, or a saturated hydrocarbylsulfonyloxy group having 1 to 4 carbon atoms, in which some or all of the hydrogen atoms may be substituted with halogen atoms, or -N(R ^601A )-C(═O)-R ^601B or -N(R ^601A )-C(═O)-O-R ^601B . R ^601A represents a hydrogen atom or a saturated hydrocarbyl group having 1 to 6 carbon atoms. R ^601B represents a saturated hydrocarbyl group having 1 to 6 carbon atoms or an unsaturated aliphatic hydrocarbyl group having 2 to 8 carbon atoms.

In formula (7), x' is an integer of 1 to 5. y' is an integer of 0 to 3. z' is an integer of 1 to 3. ^{L 11} is a single bond or a (z'+1)-valent linking group having 1 to 20 carbon atoms, and may contain at least one selected from an ether bond, a carbonyl group, an ester bond, an amide bond, a sultone ring, a lactam ring, a carbonate bond, a halogen atom, a hydroxy group, and a carboxy group. The saturated hydrocarbyl group, saturated hydrocarbyloxy group, saturated hydrocarbylcarbonyloxy group, and saturated hydrocarbylsulfonyloxy group may be linear, branched, or cyclic. When y' and/or z' is 2 or greater, each R ⁶⁰¹ may be the same or different.

In formula (7), R ⁶⁰² , R ⁶⁰³ , and R ⁶⁰⁴ each independently represent a hydrocarbyl group having 1 to 20 carbon atoms which may contain a halogen atom or a heteroatom. The hydrocarbyl group may be saturated or unsaturated and may be linear, branched, or cyclic. Specific examples thereof include the same groups as those exemplified as the hydrocarbyl groups represented by R ¹⁰¹ to R ¹⁰⁵ in formulas (1-1) and (1-2). In addition, some or all of the hydrogen atoms in the hydrocarbyl group may be substituted with a hydroxy group, a carboxy group, a halogen atom, an oxo group, a cyano group, a nitro group, a sultone ring, a sulfo group, or a sulfonium salt-containing group, and some of the —CH ₂ — groups in the hydrocarbyl group may be substituted with an ether bond, an ester bond, a carbonyl group, an amide bond, a carbonate bond, or a sulfonate ester bond. Furthermore, R ⁶⁰² and R ⁶⁰³ may be bonded to each other to form a ring together with the sulfur atom to which they are bonded.

Specific examples of compounds represented by formula (7) include those described in JP 2017-219836 A.

Another example of the quencher is the polymer-type quencher described in JP 2008-239918 A. This enhances the rectangularity of the resist pattern by orienting on the surface of the resist film. Polymer-type quenchers also have the effect of preventing pattern film loss and rounding of the pattern top when a protective film for immersion lithography is applied.

When the positive resist material of the present invention contains the quencher, the content thereof is preferably 0 to 5 parts by mass, and more preferably 0 to 4 parts by mass, per 100 parts by mass of the base polymer. The quencher may be used alone or in combination of two or more types.

[Other ingredients]
The positive resist composition of the present invention may contain, in addition to the above-mentioned components, surfactants, dissolution inhibitors, water repellency improvers, acetylene alcohols, and the like.

Examples of the surfactant include those described in paragraphs [0165] to [0166] of JP 2008-111103 A. Adding a surfactant can further improve or control the coatability of the resist material. When the positive resist material of the present invention contains the surfactant, the content is preferably 0.0001 to 10 parts by mass per 100 parts by mass of the base polymer. The surfactant may be used alone or in combination of two or more types.

By incorporating a dissolution inhibitor into the positive resist material of the present invention, the difference in dissolution rate between exposed and unexposed areas can be further increased, resulting in improved resolution. Examples of dissolution inhibitors include compounds with a molecular weight of preferably 100 to 1,000, more preferably 150 to 800, containing two or more phenolic hydroxy groups in the molecule, in which the hydrogen atoms of the phenolic hydroxy groups have been substituted with acid labile groups in an overall ratio of 0 to 100 mol %, and compounds containing carboxy groups in the molecule, in which the hydrogen atoms of the carboxy groups have been substituted with acid labile groups in an overall average ratio of 50 to 100 mol %. Specific examples include compounds in which the hydrogen atoms of the hydroxyl groups and carboxyl groups of bisphenol A, trisphenol, phenolphthalein, cresol novolak, naphthalenecarboxylic acid, adamantanecarboxylic acid, and cholic acid have been substituted with acid labile groups. These compounds are described, for example, in paragraphs [0155] to [0178] of JP 2008-122932 A.

When the positive resist material of the present invention contains the dissolution inhibitor, the content thereof is preferably 0 to 50 parts by mass, and more preferably 5 to 40 parts by mass, per 100 parts by mass of the base polymer. The dissolution inhibitor may be used alone or in combination of two or more types.

The water-repellency improver improves the water-repellency of the resist film surface and can be used in immersion lithography without a topcoat. Preferred examples of the water-repellency improver include polymers containing fluorinated alkyl groups and polymers containing a specific 1,1,1,3,3,3-hexafluoro-2-propanol residue structure, with those exemplified in JP 2007-297590 A and JP 2008-111103 A being more preferred. The water-repellency improver must be soluble in an alkaline developer or an organic solvent developer. The water-repellency improver containing the specific 1,1,1,3,3,3-hexafluoro-2-propanol residue described above has good solubility in the developer. As a water-repellency improver, polymers containing repeating units containing amino groups or amine salts are highly effective in preventing acid evaporation during PEB and preventing poor hole pattern opening after development. When the positive resist material of the present invention contains a water repellency improver, the content thereof is preferably 0 to 20 parts by mass, and more preferably 0.5 to 10 parts by mass, per 100 parts by mass of the base polymer. The water repellency improver may be used alone or in combination of two or more types.

Examples of the acetylene alcohols include those described in paragraphs [0179] to [0182] of JP 2008-122932 A. When the positive resist material of the present invention contains an acetylene alcohol, the content is preferably 0 to 5 parts by mass per 100 parts by mass of the base polymer. The acetylene alcohols may be used alone or in combination of two or more types.

[Pattern formation method]
When the positive resist material of the present invention is used in the manufacture of various integrated circuits, known lithography techniques can be applied. For example, a pattern formation method can include a method comprising the steps of forming a resist film on a substrate using the above-mentioned positive resist material, exposing the resist film to high-energy rays, and developing the exposed resist film using a developer.

First, the positive resist material of the present invention is applied to a substrate for integrated circuit production (Si, _SiO2 , SiN, SiON, TiN, WSi, BPSG, SOG, organic antireflective coating, etc.) or a substrate for mask circuit production (Cr, CrO, CrON, _MoSi2 , _SiO2 , etc.) by a suitable coating method such as spin coating, roll coating, flow coating, dip coating, spray coating, doctor coating, etc., to a coating thickness of 0.01 to 2 μm. This is then prebaked on a hot plate, preferably at 60 to 150°C for 10 seconds to 30 minutes, more preferably at 80 to 120°C for 30 seconds to 20 minutes, to form a resist film.

Next, the resist film is exposed to high-energy radiation. Examples of such high-energy radiation include ultraviolet radiation, far ultraviolet radiation, EB, EUV radiation with a wavelength of 3 to 15 nm, X-rays, soft X-rays, excimer laser light, gamma rays, and synchrotron radiation. When ultraviolet radiation, far ultraviolet radiation, EUV, X-rays, soft X-rays, excimer laser light, gamma rays, and synchrotron radiation are used as the high-energy radiation, the radiation is applied directly or using a mask for forming the desired pattern, with an exposure dose of preferably about 1 to 200 mJ/ ^cm2 , more preferably about 10 to 100 mJ/ ^cm2 . When EB is used as the high-energy radiation, the radiation is applied directly or using a mask for forming the desired pattern, with an exposure dose of preferably about 0.1 to 100 μC/ ^cm2 , more preferably about 0.5 to 50 μC/ ^cm2 . The positive resist material of the present invention is particularly suitable for fine patterning using high-energy rays such as KrF excimer laser light, ArF excimer laser light, EB, EUV, i-rays, X-rays, soft X-rays, γ-rays, and synchrotron radiation, and is particularly suitable for fine patterning using EB or EUV.

After exposure, PEB may be performed on a hot plate or in an oven, preferably at 50 to 150°C for 10 seconds to 30 minutes, more preferably at 60 to 120°C for 30 seconds to 20 minutes.

After exposure or PEB, the exposed resist film is developed using a developer, preferably an aqueous alkaline solution of 0.1 to 10% by weight, more preferably 2 to 5% by weight, such as tetramethylammonium hydroxide (TMAH), tetraethylammonium hydroxide (TEAH), tetrapropylammonium hydroxide (TPAH), or tetrabutylammonium hydroxide (TBAH), for 3 seconds to 3 minutes, preferably 5 seconds to 2 minutes, by a standard method such as dipping, puddling, or spraying. The irradiated areas dissolve in the developer, while the unexposed areas do not, forming the desired positive-tone pattern on the substrate.

The positive resist material can also be used for negative development, which produces a negative pattern by organic solvent development. Developers used in this case include 2-octanone, 2-nonanone, 2-heptanone, 3-heptanone, 4-heptanone, 2-hexanone, 3-hexanone, diisobutyl ketone, methylcyclohexanone, acetophenone, methylacetophenone, propyl acetate, butyl acetate, isobutyl acetate, pentyl acetate, butenyl acetate, isopentyl acetate, propyl formate, butyl formate, isobutyl formate, pentyl formate, isopentyl formate, methyl valerate, methyl pentenoate, methyl crotonate, ethyl crotonate, Examples of organic solvents include methyl propionate, ethyl propionate, ethyl 3-ethoxypropionate, methyl lactate, ethyl lactate, propyl lactate, butyl lactate, isobutyl lactate, pentyl lactate, isopentyl lactate, methyl 2-hydroxyisobutyrate, ethyl 2-hydroxyisobutyrate, methyl benzoate, ethyl benzoate, phenyl acetate, benzyl acetate, methyl phenylacetate, benzyl formate, phenylethyl formate, methyl 3-phenylpropionate, benzyl propionate, ethyl phenylacetate, and 2-phenylethyl acetate. These organic solvents may be used alone or in combination of two or more.

After development is complete, the resist film is rinsed. A preferred rinse solution is a solvent that is miscible with the developer but does not dissolve the resist film. Preferred solvents include alcohols with 3 to 10 carbon atoms, ether compounds with 8 to 12 carbon atoms, alkanes, alkenes, alkynes, and aromatic solvents with 6 to 12 carbon atoms.

Specific examples of alcohols having 3 to 10 carbon atoms include n-propyl alcohol, isopropyl alcohol, 1-butyl alcohol, 2-butyl alcohol, isobutyl alcohol, tert-butyl alcohol, 1-pentanol, 2-pentanol, 3-pentanol, tert-pentyl alcohol, neopentyl alcohol, 2-methyl-1-butanol, 3-methyl-1-butanol, 3-methyl-3-pentanol, cyclopentanol, 1-hexanol, 2-hexanol, and 3-hexanol. , 2,3-dimethyl-2-butanol, 3,3-dimethyl-1-butanol, 3,3-dimethyl-2-butanol, 2-ethyl-1-butanol, 2-methyl-1-pentanol, 2-methyl-2-pentanol, 2-methyl-3-pentanol, 3-methyl-1-pentanol, 3-methyl-2-pentanol, 3-methyl-3-pentanol, 4-methyl-1-pentanol, 4-methyl-2-pentanol, 4-methyl-3-pentanol, cyclohexanol, 1-octanol, etc.

Examples of ether compounds having 8 to 12 carbon atoms include di-n-butyl ether, diisobutyl ether, di-sec-butyl ether, di-n-pentyl ether, diisopentyl ether, di-sec-pentyl ether, di-tert-pentyl ether, and di-n-hexyl ether.

Examples of alkanes having 6 to 12 carbon atoms include hexane, heptane, octane, nonane, decane, undecane, dodecane, methylcyclopentane, dimethylcyclopentane, cyclohexane, methylcyclohexane, dimethylcyclohexane, cycloheptane, cyclooctane, and cyclononane. Examples of alkenes having 6 to 12 carbon atoms include hexene, heptene, octene, cyclohexene, methylcyclohexene, dimethylcyclohexene, cycloheptene, and cyclooctene. Examples of alkynes having 6 to 12 carbon atoms include hexyne, heptine, and octyne.

Aromatic solvents include toluene, xylene, ethylbenzene, isopropylbenzene, tert-butylbenzene, and mesitylene.

Rinsing can reduce the occurrence of resist pattern collapse and defects. Rinsing is not always necessary, and eliminating rinsing can reduce the amount of solvent used.

After development, hole or trench patterns can also be shrunk using thermal flow, RELACS, or DSA techniques. A shrink agent is applied to the hole pattern, and the diffusion of acid catalyst from the resist film during baking causes crosslinking of the shrink agent on the surface of the resist film, resulting in the shrink agent adhering to the sidewalls of the hole pattern. The bake temperature is preferably 70 to 180°C, more preferably 80 to 170°C, and the bake time is preferably 10 to 300 seconds. Excess shrink agent is removed, and the hole pattern is shrunk.

The present invention will be specifically explained below using synthesis examples, working examples, and comparative examples, but the present invention is not limited to the following examples.

The chain transfer agents CTA-1 to CTA-16 used in the synthesis of the base polymer are as follows:

[1] Synthesis of Base Polymer The monomers PM-1 to PM-3, AM-1 to AM-10, FM-1, and FM-2 used in the synthesis of the base polymer are as follows. The Mw of the polymer is a polystyrene-equivalent value measured by GPC using THF as the solvent.

Synthesis Example 1 Synthesis of Polymer P-1 8.4 g of 1-methyl-1-cyclopentyl methacrylate, 6.0 g of 4-hydroxystyrene, and 40 g of THF as a solvent were added to a 2 L flask. The reaction vessel was cooled to -70°C under a nitrogen atmosphere, and degassing under reduced pressure and nitrogen blowing were repeated three times. After warming to room temperature, 1.2 g of dimethyl 2,2'-azobis(isobutyrate) as a polymerization initiator and 2.2 g of CTA-1 were added, and the temperature was raised to 60°C and the reaction was carried out for 15 hours. This reaction solution was added to ¹ L of isopropyl alcohol, and the precipitated white solid was filtered off. The resulting white solid was dried under reduced pressure at 60 ^° C to obtain Polymer P-1. The composition of Polymer P-1 was confirmed by C-NMR and H-NMR, and the Mw and Mw/Mn were confirmed by GPC.

Synthesis Example 2: Synthesis of Polymer P-2: A 2-L flask was charged with 8.4 g of 1-methyl-1-cyclopentyl methacrylate, 4.2 g of 4-hydroxystyrene, 11.9 g of monomer PM-1, and 40 g of THF as a solvent. The reaction vessel was cooled to -70°C under a nitrogen atmosphere, and degassing under reduced pressure and nitrogen blowing were repeated three times. After warming to room temperature, 1.2 g of 2,2'-azobis(isobutyrate)dimethyl as a polymerization initiator and 2.5 g of CTA-2 were added, and the mixture was heated to 60°C and reacted for 15 ^hours . This reaction solution was added to 1 L of isopropyl alcohol, and the precipitated white solid was filtered off. The resulting white solid was dried under reduced pressure at 60°C to obtain Polymer P-2. The composition of Polymer P-2 was confirmed by C-NMR and ^H -NMR, and the Mw and Mw/Mn were confirmed by GPC.

Synthesis Example 3: Synthesis of Polymer P-3 A 2-L flask was charged with 8.4 g of 1-methyl-1-cyclopentyl methacrylate, 4.2 g of 3-hydroxystyrene, 11.0 g of Monomer PM-2, and 40 g of THF as a solvent. The reaction vessel was cooled to -70°C under a nitrogen atmosphere, and degassing under reduced pressure and nitrogen blowing were repeated three times. After warming to room temperature, 1.2 g of 2,2'-azobis(isobutyrate)dimethyl as a polymerization initiator and 3.0 g of CTA-3 were added, and the temperature was raised to 60°C and the reaction was carried out for ¹⁵ hours. This reaction solution was added to 1 L of isopropyl alcohol, and the precipitated white solid was filtered off. The resulting white solid was dried under reduced pressure at 60°C to obtain Polymer P-3. The composition of Polymer P-3 was confirmed by C-NMR and ^H -NMR, and the Mw and Mw/Mn were confirmed by GPC.

Synthesis Example 4: Synthesis of Polymer P-4 To a 2-L flask were added 8.4 g of 1-methyl-1-cyclopentyl methacrylate, 4.8 g of 3-hydroxystyrene, 8.2 g of Monomer PM-3, and 40 g of THF as a solvent. The reaction vessel was cooled to -70°C under a nitrogen atmosphere, and degassing under reduced pressure and nitrogen blowing were repeated three times. After warming to room temperature, 1.2 g of 2,2'-azobis(isobutyrate)dimethyl as a polymerization initiator and 3.1 g of CTA-6 were added, and the mixture was heated to 60°C and reacted for 15 hours. This reaction solution was added to 1 L of isopropyl alcohol, and the precipitated white solid was filtered off. The resulting white solid was dried under reduced pressure at 60°C to obtain Polymer P-4. The composition of Polymer P-4 was confirmed by ^C -NMR and ^H -NMR, and the Mw and Mw/Mn were confirmed by GPC.

Synthesis Example 5 Synthesis of Polymer P-5 To a 2-L flask were added 11.1 g of Monomer AM-1, 4.2 g of 3-hydroxystyrene, 11.0 g of Monomer PM-2, and 40 g of THF as a solvent. The reaction vessel was cooled to -70°C under a nitrogen atmosphere, and degassing under reduced pressure and nitrogen blowing were repeated three times. After warming to room temperature, 1.2 g of 2,2'-azobis(isobutyrate)dimethyl as a polymerization initiator and 2.2 g of CTA-5 were added, and the mixture was heated to 60°C and reacted for 15 hours. This reaction solution was added to 1 L of isopropyl alcohol, and the precipitated white solid was filtered off. The resulting white solid was dried under reduced pressure at 60°C to obtain Polymer P-5. The composition of Polymer P-5 was confirmed by ^C -NMR and ^H -NMR, and the Mw and Mw/Mn were confirmed by GPC.

Synthesis Example 6: Synthesis of Polymer P-6 To a 2-L flask were added 8.2 g of Monomer AM-2, 4.0 g of Monomer AM-3, 4.2 g of 3-hydroxystyrene, 11.0 g of Monomer PM-2, and 40 g of THF as a solvent. The reaction vessel was cooled to -70°C under a nitrogen atmosphere, and degassing under reduced pressure and nitrogen blowing were repeated three times. After warming to room temperature, 1.2 g of 2,2'-azobis(isobutyrate)dimethyl as a polymerization initiator and 3.3 g of CTA-4 were added, and the mixture was heated to 60°C and reacted for 15 hours. This reaction solution was added to 1 L of isopropyl alcohol, and the precipitated white solid was filtered off. The resulting white solid was dried under reduced pressure at 60°C to obtain Polymer P-6. The composition of Polymer P-6 was confirmed by ^C -NMR and ^H -NMR, and the Mw and Mw/Mn were confirmed by GPC.

Synthesis Example 7 Synthesis of Polymer P-7 To a 2-L flask were added 6.7 g of Monomer AM-1, 3.8 g of Monomer AM-4, 4.2 g of 3-hydroxystyrene, 11.9 g of Monomer PM-1, and 40 g of THF as a solvent. The reaction vessel was cooled to -70°C under a nitrogen atmosphere, and degassing under reduced pressure and nitrogen blowing were repeated three times. After warming to room temperature, 1.2 g of 2,2'-azobis(isobutyrate)dimethyl as a polymerization initiator and 2.5 g of CTA-7 were added, and the temperature was raised to 60°C and the reaction was carried out for 15 hours. This reaction solution was added to 1 L of isopropyl alcohol, and the precipitated white solid was filtered off. The resulting white solid was dried under reduced pressure at 60°C to obtain Polymer P-7. The composition of Polymer P-7 was confirmed by ^C -NMR and ^H -NMR, and the Mw and Mw/Mn were confirmed by GPC.

Synthesis Example 8 Synthesis of Polymer P-8 To a 2-L flask were added 9.0 g of Monomer AM-5, 4.2 g of 3-hydroxystyrene, 11.9 g of Monomer PM-1, and 40 g of THF as a solvent. The reaction vessel was cooled to -70°C under a nitrogen atmosphere, and degassing under reduced pressure and nitrogen blowing were repeated three times. After warming to room temperature, 1.2 g of 2,2'-azobis(isobutyrate)dimethyl as a polymerization initiator and 4.8 g of CTA-8 were added, and the temperature was raised to 60°C and the reaction was carried out for 15 hours. This reaction solution was added to 1 L of isopropyl alcohol, and the precipitated white solid was filtered off. The resulting white solid was dried under reduced pressure at 60°C to obtain Polymer P-8. The composition of Polymer P-8 was confirmed by ^C -NMR and ^H -NMR, and the Mw and Mw/Mn were confirmed by GPC.

Synthesis Example 9 Synthesis of Polymer P-9 To a 2-L flask were added 10.8 g of Monomer AM-6, 4.2 g of 3-hydroxystyrene, 11.0 g of Monomer PM-2, and 40 g of THF as a solvent. The reaction vessel was cooled to -70°C under a nitrogen atmosphere, and degassing under reduced pressure and nitrogen blowing were repeated three times. After warming to room temperature, 1.2 g of 2,2'-azobis(isobutyrate)dimethyl as a polymerization initiator and 3.1 g of CTA-9 were added, and the temperature was raised to 60°C and the reaction was carried out for 15 hours. This reaction solution was added to 1 L of isopropyl alcohol, and the precipitated white solid was filtered off. The resulting white solid was dried under reduced pressure at 60°C to obtain Polymer P-9. The composition of Polymer P-9 was confirmed by ^C -NMR and ^H -NMR, and the Mw and Mw/Mn were confirmed by GPC.

Synthesis Example 10: Synthesis of Polymer P-10 To a 2 L flask were added 8.4 g of 1-methyl-1-cyclopentyl methacrylate, 3.0 g of 3-hydroxystyrene, 3.2 g of Monomer FM-1, 11.0 g of Monomer PM-2, and 40 g of THF as a solvent. The reaction vessel was cooled to -70°C under a nitrogen atmosphere, and degassing under reduced pressure and nitrogen blowing were repeated three times. After warming to room temperature, 1.2 g of 2,2'-azobis(isobutyrate)dimethyl as a polymerization initiator and 2.2 g of CTA-5 were added, and the mixture was heated to 60°C and reacted for 15 hours. This reaction solution was added to 1 L of isopropyl alcohol, and the precipitated white solid was filtered off. The resulting white solid was dried under reduced pressure at 60°C to obtain Polymer P-10. The composition of polymer P-10 was confirmed by ¹³ C-NMR and ¹ H-NMR, and Mw and Mw/Mn were confirmed by GPC.

Synthesis Example 11 Synthesis of Polymer P-11 To a 2 L flask were added 8.4 g of 1-methyl-1-cyclopentyl methacrylate, 3.0 g of 3-hydroxystyrene, 2.7 g of Monomer FM-2, 11.0 g of Monomer PM-2, and 40 g of THF as a solvent. The reaction vessel was cooled to -70 °C under a nitrogen atmosphere, and degassing under reduced pressure and nitrogen blowing were repeated three times. After warming to room temperature, 1.2 g of 2,2'-azobis(isobutyrate)dimethyl as a polymerization initiator and 2.2 g of CTA-5 were added, and the mixture was heated to 60 °C and reacted for 15 hours. This reaction solution was added to 1 L of isopropyl alcohol, and the precipitated white solid was filtered off. The resulting white solid was dried under reduced pressure at 60 °C to obtain Polymer P-11. The composition of polymer P-11 was confirmed by ¹³ C-NMR and ¹ H-NMR, and Mw and Mw/Mn were confirmed by GPC.

Synthesis Example 12: Synthesis of Polymer P-12: A 2-L flask was charged with 8.4 g of 1-methyl-1-cyclopentyl methacrylate, 4.2 g of 3-hydroxystyrene, 11.9 g of monomer PM-1, and 40 g of THF as a solvent. The reaction vessel was cooled to -70°C under a nitrogen atmosphere, and degassing under reduced pressure and nitrogen blowing were repeated three times. After warming to room temperature, 1.2 g of dimethyl 2,2'-azobis(isobutyrate) as a polymerization initiator and 3.3 g of CTA-10 were added, and the mixture was heated to 60°C and reacted for 15 ^hours . This reaction solution was added to 1 L of isopropyl alcohol, and the precipitated white solid was filtered off. The resulting white solid was dried under reduced pressure at 60°C to obtain Polymer P-12. The composition of Polymer P-12 was confirmed by C-NMR and ^H -NMR, and the Mw and Mw/Mn were confirmed by GPC.

Synthesis Example 13: Synthesis of Polymer P-13 To a 2-L flask were added 8.4 g of 1-methyl-1-cyclopentyl methacrylate, 4.2 g of 3-hydroxystyrene, 11.9 g of monomer PM-1, and 40 g of THF as a solvent. The reaction vessel was cooled to -70°C under a nitrogen atmosphere, and degassing under reduced pressure and nitrogen blowing were repeated three times. After warming to room temperature, 1.2 g of dimethyl 2,2'-azobis(isobutyrate) as a polymerization initiator and 4.5 g of CTA-11 were added, and the mixture was heated to 60°C and reacted for 15 hours. This reaction solution was added to 1 L of isopropyl alcohol, and the precipitated white solid was filtered off. The resulting white solid was dried under reduced pressure at 60°C to obtain Polymer P-13. The composition of Polymer P-13 was confirmed by ^C -NMR and ^H -NMR, and the Mw and Mw/Mn were confirmed by GPC.

Synthesis Example 14: Synthesis of Polymer P-14 To a 2-L flask were added 8.4 g of 1-methyl-1-cyclopentyl methacrylate, 4.2 g of 3-hydroxystyrene, 11.9 g of monomer PM-1, and 40 g of THF as a solvent. The reaction vessel was cooled to -70°C under a nitrogen atmosphere, and degassing under reduced pressure and nitrogen blowing were repeated three times. After warming to room temperature, 1.2 g of 2,2'-azobis(isobutyrate)dimethyl as a polymerization initiator and 3.3 g of CTA-12 were added, and the mixture was heated to 60°C and reacted for 15 hours. This reaction solution was added to 1 L of isopropyl alcohol, and the precipitated white solid was filtered off. The resulting white solid was dried under reduced pressure at 60°C to obtain Polymer P-14. The composition of Polymer P-14 was confirmed by ^C -NMR and ^H -NMR, and the Mw and Mw/Mn were confirmed by GPC.

Synthesis Example 15: Synthesis of Polymer P-15: A 2-L flask was charged with 8.4 g of 1-methyl-1-cyclopentyl methacrylate, 4.2 g of 3-hydroxystyrene, 11.9 g of monomer PM-1, and 40 g of THF as a solvent. The reaction vessel was cooled to -70°C under a nitrogen atmosphere, and degassing under reduced pressure and nitrogen blowing were repeated three times. After warming to room temperature, 1.2 g of dimethyl 2,2'-azobis(isobutyrate) as a polymerization initiator and 1.9 g of CTA-13 were added, and the mixture was heated to 60°C and reacted for 15 ^hours . This reaction solution was added to 1 L of isopropyl alcohol, and the precipitated white solid was filtered off. The resulting white solid was dried under reduced pressure at 60°C to obtain Polymer P-15. The composition of Polymer P-15 was confirmed by C-NMR and ^H -NMR, and the Mw and Mw/Mn were confirmed by GPC.

Synthesis Example 16: Synthesis of Polymer P-16 To a 2-L flask were added 13.2 g of Monomer AM-7, 4.2 g of 3-hydroxystyrene, 11.9 g of Monomer PM-1, and 40 g of THF as a solvent. The reaction vessel was cooled to -70°C under a nitrogen atmosphere, and degassing under reduced pressure and nitrogen blowing were repeated three times. After warming to room temperature, 1.2 g of 2,2'-azobis(isobutyrate)dimethyl as a polymerization initiator and 2.2 g of CTA-14 were added, and the temperature was raised to 60°C and the reaction was carried out for 15 hours. This reaction solution was added to 1 L of isopropyl alcohol, and the precipitated white solid was filtered off. The resulting white solid was dried under reduced pressure at 60°C to obtain Polymer P-16. The composition of Polymer P-16 was confirmed by ^C -NMR and ^H -NMR, and the Mw and Mw/Mn were confirmed by GPC.

Synthesis Example 17 Synthesis of Polymer P-17 To a 2-L flask were added 12.4 g of Monomer AM-8, 4.2 g of 3-hydroxystyrene, 11.9 g of Monomer PM-1, and 40 g of THF as a solvent. The reaction vessel was cooled to -70°C under a nitrogen atmosphere, and degassing under reduced pressure and nitrogen blowing were repeated three times. After warming to room temperature, 1.2 g of 2,2'-azobis(isobutyrate)dimethyl as a polymerization initiator and 4.4 g of CTA-15 were added, and the mixture was heated to 60°C and reacted for 15 hours. This reaction solution was added to ¹ L of isopropyl alcohol, and the precipitated white solid was filtered off. The resulting white solid was dried under reduced pressure at 60°C to obtain Polymer P-17. The composition of Polymer P-17 was confirmed by ^C -NMR and H-NMR, and the Mw and Mw/Mn were confirmed by GPC.

Synthesis Example 18 Synthesis of Polymer P-18 To a 2 L flask were added 3.6 g of 1-methyl-1-cyclopentyl methacrylate, 5.8 g of Monomer AM-4, 3.6 g of 3-hydroxystyrene, 2.4 g of 2-hydroxystyrene, and 40 g of THF as a solvent. The reaction vessel was cooled to -70°C under a nitrogen atmosphere, and degassing under reduced pressure and nitrogen blowing were repeated three times. After warming to room temperature, 1.2 g of 2,2'-azobis(isobutyrate)dimethyl as a polymerization initiator and 1.9 g of CTA-14 were added, and the mixture was heated to 60°C and reacted for 15 hours. This reaction solution was added to 1 L of isopropyl alcohol, and the precipitated white solid was filtered off. The resulting white solid was dried under reduced pressure at 60°C to obtain Polymer P-18. The composition of polymer P-18 was confirmed by ¹³ C-NMR and ¹ H-NMR, and Mw and Mw/Mn were confirmed by GPC.

Synthesis Example 19 Synthesis of Polymer P-19 To a 2 L flask were added 3.6 g of 1-methyl-1-cyclopentyl methacrylate, 5.3 g of Monomer AM-9, 4.8 g of 4-hydroxystyrene, 1.0 g of styrene, and 40 g of THF as a solvent. The reaction vessel was cooled to -70°C under a nitrogen atmosphere, and degassing under reduced pressure and nitrogen blowing were repeated three times. After warming to room temperature, 1.2 g of dimethyl 2,2'-azobis(isobutyrate) and 1.9 g of CTA-14 were added as a polymerization initiator, and the mixture was heated to 60°C and reacted for 15 hours. This reaction solution was added to 1 L of isopropyl alcohol, and the precipitated white solid was filtered off. The resulting white solid was dried under reduced pressure at 60°C to obtain Polymer P-19. The composition of polymer P-19 was confirmed by ¹³ C-NMR and ¹ H-NMR, and Mw and Mw/Mn were confirmed by GPC.

Synthesis Example 20: Synthesis of Polymer P-20 To a 2-L flask were added 3.6 g of 1-methyl-1-cyclopentyl methacrylate, 5.4 g of Monomer AM-10, 3.0 g of 3-hydroxystyrene, 3.0 g of 2-hydroxystyrene, and 40 g of THF as a solvent. The reaction vessel was cooled to -70°C under a nitrogen atmosphere, and degassing under reduced pressure and nitrogen blowing were repeated three times. After warming to room temperature, 1.2 g of 2,2'-azobis(isobutyrate)dimethyl as a polymerization initiator and 2.7 g of CTA-16 were added, and the mixture was heated to 60°C and reacted for 15 hours. This reaction solution was added to 1 L of isopropyl alcohol, and the precipitated white solid was filtered off. The resulting white solid was dried under reduced pressure at 60°C to obtain Polymer P-20. The composition of polymer P-20 was confirmed by ¹³ C-NMR and ¹ H-NMR, and Mw and Mw/Mn were confirmed by GPC.

Comparative Synthesis Example 1 Synthesis of Comparative Polymer cP-1 Comparative polymer cP-1 was obtained in the same manner as in Synthesis Example 1, without using CTA-1. The composition of comparative polymer cP-1 was confirmed by ^C -NMR and ^H -NMR, and Mw and Mw/Mn were confirmed by GPC.

Comparative Synthesis Example 2 Synthesis of Comparative Polymer cP-2 Comparative polymer cP-2 was obtained in the same manner as in Synthesis Example 1, except that ² -mercaptoethanol was used as a chain transfer agent instead of CTA-1. The composition of comparative polymer cP-2 was confirmed by C-NMR and ^H -NMR, and Mw and Mw/Mn were confirmed by GPC.

Comparative Synthesis Example 3 Synthesis of Comparative Polymer cP-3 Comparative polymer cP-3 was obtained in the same manner as in Synthesis Example 2, without using CTA-2. The composition of comparative polymer cP-3 was confirmed by ^C -NMR and ^H -NMR, and Mw and Mw/Mn were confirmed by GPC.

[2] Preparation and evaluation of positive resist materials [Examples 1 to 22, Comparative Examples 1 to 3]
(1) Preparation of Positive Resist Material A solution of the components shown in Table 1 dissolved in a solvent containing 50 ppm of Omnova surfactant PolyFox PF-636 was filtered through a 0.02 μm high-density polyethylene filter to prepare a positive resist material.

In Table 1, the components are as follows:
Organic solvent: PGMEA (propylene glycol monomethyl ether acetate)
DAA (diacetone alcohol)
EL (L-ethyl lactate)

Acid generator: PAG-1, PAG-2

Quencher: Q-1 to Q-3

(2) EUV Lithography Evaluation Each positive resist material shown in Table 1 was spin-coated onto a Si substrate with a 20 nm thick silicon-containing spin-on hard mask SHB-A940 (silicon content: 43% by mass) manufactured by Shin-Etsu Chemical Co., Ltd., and pre-baked at 105 ° C. for 60 seconds using a hot plate to produce a 60 nm thick resist film. The resist film was exposed using an ASML EUV scanner NXE3400 (NA 0.33, σ 0.9/0.6, quadruple pole illumination, wafer dimensions with a pitch of 46 nm and a hole pattern mask with a +20% bias), and then subjected to PEB on a hot plate at the temperature shown in Table 1 for 60 seconds. Development was performed for 30 seconds with a 2.38% by mass TMAH aqueous solution to obtain a hole pattern with a dimension of 23 nm.
The exposure dose when each hole dimension was 23 nm was measured and used as the sensitivity. The dimensions of 50 holes were measured using a Hitachi High-Technologies Corporation critical dimension SEM (CG6300), and the CDU was calculated as three times the standard deviation (σ) (3σ). The results are also shown in Table 1.

The results shown in Table 1 show that the positive resist material of the present invention, which uses a base polymer end-capped with a sulfonium salt containing a carboxylic acid anion linked to a sulfide group, exhibited good CDU.

Claims (10)

1. A chemically amplified positive resist material comprising a base polymer end-capped with a sulfonium salt comprising a carboxylate anion linked to a sulfide group ,
The positive resist material further comprises a photoacid generator, or the base polymer comprises a repeating unit represented by any one of the following formulas (d1) to (d3) :
(In the formula, each R ^A is independently a hydrogen atom or a methyl group.
Z ¹ is a single bond, an aliphatic hydrocarbylene group having 1 to 6 carbon atoms, a phenylene group, a naphthylene group, or a group having 7 to 18 carbon atoms obtained by combining these, or -O-Z ¹¹ -, -C(═O)-O-Z ¹¹ -, or -C(═O)-NH-Z ¹¹ -. ^{Z 11} is an aliphatic hydrocarbylene group having 1 to 6 carbon atoms, a phenylene group, a naphthylene group, or a group having 7 to 18 carbon atoms obtained by combining these, and may contain a carbonyl group, an ester bond, an ether bond, or a hydroxy group.
Z2 is a single bond or an ester bond ^.
Z ³ is a single bond, -Z ³¹ -C(═O)-O-, -Z ³¹ -O-, or -Z ³¹ -O-C(═O)-. Z ³¹ is an aliphatic hydrocarbylene group having 1 to 12 carbon atoms, a phenylene group, or a group having 7 to 18 carbon atoms obtained by combining these, and may contain a carbonyl group, an ester bond, an ether bond, a bromine atom, or an iodine atom.
Z4 is a methylene group, a 2,2,2-trifluoro-1,1-ethanediyl group, or a carbonyl group ^.
Z5 ^is a single bond, a methylene group, an ethylene group, a phenylene group, a fluorinated phenylene group, a phenylene group substituted with a trifluoromethyl group, -O-Z51- ^, -C(=O)-O-Z51- ^or -C(=O)-NH-Z51- ^. Z51 is an aliphatic hydrocarbylene group having 1 to 6 carbon atoms, a phenylene group, a fluorinated phenylene group or a phenylene group substituted with a trifluoromethyl group, and may contain ^a carbonyl group, an ester bond, an ether bond, a halogen atom or a hydroxy group.
R ²¹ to R ²⁸ are each independently a halogen atom or a hydrocarbyl group having 1 to 20 carbon atoms which may contain a heteroatom. R ²³ and R ²⁴ or R ²⁶ and R ²⁷ may be bonded to each other to form a ring together with the sulfur atom to which they are bonded.
M ⁻ is a non-nucleophilic counter ion. 2. The chemically amplified positive resist material according to claim 1, wherein the terminal structure is represented by the following formula (a):
(In the formula, ^X1 is a hydrocarbylene group having 1 to 20 carbon atoms, and the hydrocarbylene group may contain at least one bond selected from a hydroxy group, an ether bond, a sulfide group, an ester bond, a carbonate bond, a urethane bond, a lactone ring, a sultone ring, and a halogen atom.
^R1 to ^R3 are each independently a hydrocarbyl group having 1 to 20 carbon atoms, and may contain at least one atom selected from an oxygen atom, a sulfur atom, a nitrogen atom, and a halogen atom. ^R1 and ^R2 may be bonded to each other to form a ring together with the sulfur atom to which they are bonded.
The dashed lines represent bonds.) 2. The chemically amplified positive resist material according to claim 1, wherein the base polymer comprises a repeating unit b1 in which a hydrogen atom of a carboxy group is substituted with an acid labile group or a repeating unit b2 in which a hydrogen atom of a phenolic hydroxy group is substituted with an acid labile group. 4. The chemically amplified positive resist material according to claim 3, wherein the repeating unit b1 is represented by the following formula (b1), and the repeating unit b2 is represented by the following formula (b2).
(In the formula, each R ^A is independently a hydrogen atom or a methyl group.
Y ¹ is a single bond, a phenylene group, a naphthylene group, or a linking group having 1 to 12 carbon atoms and containing at least one bond selected from an ester bond, an ether bond, and a lactone ring.
^Y2 is a single bond, an ester bond or an amide bond.
^Y3 is a single bond, an ether bond or an ester bond.
R ¹¹ and R ¹² are each independently an acid labile group.
R ¹³ is a fluorine atom, a trifluoromethyl group, a cyano group or a saturated hydrocarbyl group having 1 to 6 carbon atoms.
R ¹⁴ is a single bond or an alkanediyl group having 1 to 6 carbon atoms, and the alkanediyl group may contain an ether bond or an ester bond.
a is 1 or 2, and b is an integer from 0 to 4, provided that 1≦a+b≦5. 2. The chemically amplified positive resist material according to claim 1, wherein the base polymer further comprises a repeating unit c containing an adhesive group selected from the group consisting of a hydroxy group, a carboxy group, a lactone ring, a carbonate bond, a thiocarbonate bond, a carbonyl group, a cyclic acetal group, an ether bond, an ester bond, a sulfonate ester bond, a cyano group, an amide bond, —O—C(═O)—S—, and —O—C(═O)—NH—. 2. The chemically amplified positive resist composition according to claim 1, further comprising an organic solvent. 2. The chemically amplified positive resist material according to claim 1, further comprising a quencher. 2. The chemically amplified positive resist material according to claim 1, further comprising a surfactant. A pattern formation method comprising the steps of: forming a resist film on a substrate using the chemically amplified positive resist material according to any one of claims 1 to 8 ; exposing the resist film to high-energy radiation; and developing the exposed resist film using a developer. 10. The pattern forming method according to claim 9 , wherein the high-energy beam is i-ray, KrF excimer laser light, ArF excimer laser light, electron beam, or extreme ultraviolet light having a wavelength of 3 to 15 nm.