JP7777979B2 - Negative photosensitive composition, photosensitive film, and pattern forming method - Google Patents

Description

The present invention relates to a negative-type photosensitive composition and a pattern formation method.

In recent years, as electronic components have become smaller and denser, there has been a growing demand for photosensitive compositions that can be used in electronic components with hollow sealing structures, such as surface acoustic wave (SAW) filters. To form hollow sealing structures for these electronic components, the cured film formed from the photosensitive composition must be thin and strong.

Photosensitive compositions are also used as spacers (wall materials) between semiconductor wafers and transparent substrates. For example, a negative-tone photosensitive composition is used to form a photosensitive film on the surface of a semiconductor wafer or the like. The photosensitive film is then selectively exposed to radiation such as light or electron beams, and developed to form a pattern. The film is then pressed against a transparent substrate (e.g., a glass substrate) to form a spacer. When this photosensitive film is developed using photolithography, it must be formed to the required thickness for the spacer, have a good shape, be free of residue, enable high-resolution patterning, and have good adhesion to the transparent substrate. One known method for improving adhesion between a photosensitive film and a transparent substrate is to reduce the stress in the cured film when the photosensitive film is cured.

As a photosensitive material for forming the photosensitive film, a photosensitive resin composition containing an epoxy resin having two or more epoxy groups per molecule, an alkali-soluble resin, and a cationic polymerization initiator has been disclosed (see Patent Document 1).

International Publication No. 2012/176750

As electronic components having hollow sealing structures become increasingly smaller and denser, it is important to form thick films and fine patterns in the formation of hollow sealing structures.
However, with conventional photosensitive compositions such as those described in Patent Document 1, when attempting to miniaturize the pattern serving as the wall material of the hollow sealing structure, poor adhesion between the photosensitive film and the transparent substrate becomes a problem. Furthermore, there is a trade-off between reducing the stress of the cured film to improve adhesion between the photosensitive film and the transparent substrate, which tends to reduce the elastic modulus of the cured film at high temperatures. Furthermore, with conventional photosensitive compositions, when a negative pattern is formed on the surface of a wafer, the peripheral portion of the negative pattern image (residual film) in contact with the wafer at the interface between the two is likely to be cut, resulting in so-called undercuts, which can cause defects in the pattern shape. This undercutting can potentially lead to poor plating after structure formation, reduced mold resistance, and the like.

The present invention was made in consideration of the above circumstances, and aims to provide a negative-tone photosensitive composition that can reduce stress in the cured film, maintain a high elastic modulus, and is less likely to cause undercut and produces excellent pattern shapes, as well as a pattern formation method using the same.

In order to solve the above problems, the present invention employs the following configuration.
That is, a first aspect of the present invention is a negative-tone photosensitive composition containing an epoxy group-containing compound (A) and a cationic polymerization initiator (I), wherein the epoxy group-containing compound (A) includes an epoxy group-containing compound (AS) that is solid at 25°C and an epoxy group-containing compound (AL) that is liquid at 25°C, and the cationic polymerization initiator (I) includes a borate salt (IO) that includes a cation moiety having a thioxanthene skeleton and an anion moiety that is a borate anion.

A second aspect of the present invention is a pattern formation method comprising the steps of forming a photosensitive film on a support using the negative-tone photosensitive composition according to the first aspect, exposing the photosensitive film to light, and developing the exposed photosensitive film with a developer containing an organic solvent to form a negative-tone pattern.

The present invention provides a negative-tone photosensitive composition that can reduce stress in the cured film, maintain a high elastic modulus, and is less likely to cause undercuts, resulting in excellent pattern shapes, as well as a pattern formation method using the same.

In this specification and claims, the term "aliphatic" is a relative concept to aromatic, and is defined to mean a group or compound that does not have aromaticity.
Unless otherwise specified, the term "alkyl group" includes linear, branched, and cyclic monovalent saturated hydrocarbon groups. The same applies to alkyl groups in alkoxy groups.
Unless otherwise specified, the term "alkylene group" includes linear, branched and cyclic divalent saturated hydrocarbon groups.
A "halogenated alkyl group" is an alkyl group in which some or all of the hydrogen atoms have been substituted with halogen atoms, and examples of such halogen atoms include fluorine, chlorine, bromine, and iodine atoms.
The term "fluorinated alkyl group" refers to an alkyl group in which some or all of the hydrogen atoms have been substituted with fluorine atoms.
The term "structural unit" refers to a monomer unit that constitutes a polymeric compound (resin, polymer, copolymer).
The phrase "optionally substituted" includes both the case where a hydrogen atom (--H) is substituted with a monovalent group and the case where a methylene group (--CH ₂ -) is substituted with a divalent group.
The term "exposure" is a general concept that includes irradiation with radiation.

(Negative Photosensitive Composition)
The negative photosensitive composition of this embodiment contains an epoxy group-containing compound (A) and a cationic polymerization initiator (I). Hereinafter, these components are also referred to as component (A) and component (I), respectively. The component (A) contains an epoxy group-containing compound (AS) that is solid at 25°C and an epoxy group-containing compound (AL) that is liquid at 25°C. The component (I) contains a borate salt (IO).
When a photosensitive film is formed using such a negative photosensitive composition and the photosensitive film is selectively exposed to light, the cationic moiety of component (I) decomposes in the exposed areas of the photosensitive film to generate an acid, and the epoxy groups in component (A) undergo ring-opening polymerization under the action of the acid, reducing the solubility of component (A) in a developer containing an organic solvent. Meanwhile, the solubility of component (A) in a developer containing an organic solvent remains unchanged in the unexposed areas of the photosensitive film, resulting in a difference in solubility in a developer containing an organic solvent between the exposed and unexposed areas of the photosensitive film. Therefore, when the photosensitive film is developed with a developer containing an organic solvent, the unexposed areas of the photosensitive film are dissolved and removed, forming a negative pattern.

<Epoxy Group-Containing Compound (A)>
The epoxy group-containing compound (component (A)) in this embodiment includes an epoxy group-containing compound (AS) that is solid at 25° C. and an epoxy group-containing compound (AL) that is liquid at 25° C. Hereinafter, these components will also be referred to as component (AS) and component (AL), respectively.
The total content of the (AS) component and the (AL) component in the (A) component may be 50% by mass or more, 70% by mass or more, 90% by mass or more, or 100% by mass, and is preferably 100% by mass, based on the total mass (% by mass) of the (A) component.
Component (A) may be any resin having a sufficient number of epoxy groups per molecule to form a pattern upon exposure, and may be, for example, a resin having a glycidyl ether group in its structure.

<Epoxy group-containing compound (AS) that is solid at 25°C>
Component (AS) is an epoxy group-containing compound that is solid at 25°C.
The epoxy equivalent of component (AS) is, for example, 180 g/eq. or more, preferably 180 g/eq. or more and 600 g/eq. or less, more preferably 180 g/eq. or more and 400 g/eq. or less, and even more preferably 180 g/eq. or more and 250 g/eq. or less.
As used herein, the term "epoxy equivalent" refers to the number of grams of a compound containing one gram equivalent of epoxy groups.

The softening point of the (AS) component is, for example, 60°C or higher, preferably 60°C or higher and 80°C or lower, and more preferably 65°C or higher and 75°C or lower.
The softening point of component (A) is a value measured by the ring and ball method.

Examples of the (AS) component include novolac-type epoxy resin (Anv) that is solid at 25°C and bisphenol-type epoxy resin (Abp) that is solid at 25°C.

Regarding novolac epoxy resin (Anv):
Suitable examples of the novolac epoxy resin (Anv) include resin (A1) (hereinafter also referred to as "component (A1)") represented by the following general formula (A1).

[In the formula, R ^p1 and R ^p2 each independently represent a hydrogen atom or an alkyl group having 1 to 5 carbon atoms. Multiple R ^p1s may be the same as or different from one another. Multiple R ^p2s may be the same as or different from one another. _n1 is an integer of 1 to 5. R ^EP is an epoxy group-containing group. Multiple R ^EPs may be the same as or different from one another.]

In the formula (A1), the alkyl group having 1 to 5 carbon atoms for R ^p1 and R ^p2 is, for example, a linear, branched, or cyclic alkyl group having 1 to 5 carbon atoms. Examples of the linear or branched alkyl group include a methyl group, an ethyl group, a propyl group, an isopropyl group, an n-butyl group, an isobutyl group, a tert-butyl group, a pentyl group, an isopentyl group, and a neopentyl group, and examples of the cyclic alkyl group include a cyclobutyl group and a cyclopentyl group.
Among these, R ^p1 and R ^p2 are preferably a hydrogen atom or a linear or branched alkyl group, more preferably a hydrogen atom or a linear alkyl group, and particularly preferably a hydrogen atom or a methyl group.
In formula (A1), multiple R ^p1s may be the same as or different from each other, and multiple R ^p2s may be the same as or different from each other.

In formula (A1), _n1 is an integer of 1 to 5, preferably 2 or 3, and more preferably 2.

In formula (A1), R ^EP is an epoxy group-containing group.
The epoxy group-containing group of ^REP is not particularly limited, and examples thereof include a group consisting of only epoxy groups; a group consisting of only alicyclic epoxy groups; and a group having an epoxy group or alicyclic epoxy group and a divalent linking group.
The alicyclic epoxy group is an alicyclic group having an oxacyclopropane structure, which is a three-membered ring ether, and specifically, a group having an alicyclic group and an oxacyclopropane structure.
The alicyclic group that forms the basic skeleton of the alicyclic epoxy group may be monocyclic or polycyclic. Examples of monocyclic alicyclic groups include cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl, cycloheptyl, and cyclooctyl groups. Examples of polycyclic alicyclic groups include norbornyl, isobornyl, tricyclononyl, tricyclodecyl, and tetracyclododecyl groups. The hydrogen atoms of these alicyclic groups may be substituted with alkyl, alkoxy, or hydroxyl groups.
In the case of a group having an epoxy group or an alicyclic epoxy group and a divalent linking group, it is preferable that the epoxy group or the alicyclic epoxy group is bonded via the divalent linking group bonded to an oxygen atom (—O—) in the formula.

Here, the divalent linking group is not particularly limited, but suitable examples include a divalent hydrocarbon group which may have a substituent, a divalent linking group containing a heteroatom, etc.

Regarding the optionally substituted divalent hydrocarbon group:
Such a divalent hydrocarbon group may be an aliphatic hydrocarbon group or an aromatic hydrocarbon group.
The aliphatic hydrocarbon group in the divalent hydrocarbon group may be saturated or unsaturated, and is usually preferably saturated.
More specifically, the aliphatic hydrocarbon group may be a straight-chain or branched-chain aliphatic hydrocarbon group, or an aliphatic hydrocarbon group containing a ring in its structure.

The linear aliphatic hydrocarbon group preferably has 1 to 10 carbon atoms, more preferably 1 to 6, even more preferably 1 to 4, and most preferably 1 to 3. The linear aliphatic hydrocarbon group is preferably a linear alkylene group, and specific examples thereof include a methylene group [-CH ₂ -], an ethylene group [-(CH ₂ ) ₂ -], a trimethylene group [-(CH ₂ ) ₃ -], a tetramethylene group [-(CH ₂ ) ₄ -], and a pentamethylene group [-(CH ₂ ) ₅ -].
The branched aliphatic hydrocarbon group preferably has 2 to 10 carbon atoms, more preferably 2 to 6 carbon atoms, even more preferably 2 to 4 carbon atoms, and most preferably 2 or 3 carbon atoms. The branched aliphatic hydrocarbon group is preferably a branched alkylene group, and specific examples thereof include alkylmethylene groups such as -CH( _CH3 )-, -CH( _CH2CH3 )-, -C( _CH3 ) _2- , -C( _CH3 ) _{( CH2CH3} )-, -C( _CH3 ) _{( CH2CH2CH3} )-, _{and -C(CH2CH3)2- ; alkylethylene} groups such as -CH( _CH3 ) _CH2- , -CH( _CH3 )CH( _CH3 ) _- , _-C ( _CH3 ) _{2CH2- , -CH( CH2CH3 ) CH2-} , _and -C( _{CH2CH3 ) 2 - CH2- ;} alkyltrimethylene groups such as -CH( _CH3 ) _CH2CH2CH2- , -CH2CH( _CH3 ) _{CH2CH2- ,} etc.; and alkylalkylene groups such as alkyltetramethylene groups such as _-CH (CH3) _{CH2CH2CH2- , -CH2CH} ( _CH3 ) _CH2CH2- , etc. The alkyl group in the alkylalkylene group is preferably a linear alkyl group having 1 to 5 carbon atoms.

Examples of the aliphatic hydrocarbon group containing a ring in its structure include alicyclic hydrocarbon groups (groups in which two hydrogen atoms have been removed from an aliphatic hydrocarbon ring), groups in which an alicyclic hydrocarbon group is bonded to the end of a straight-chain or branched-chain aliphatic hydrocarbon group, and groups in which an alicyclic hydrocarbon group is interposed in the middle of a straight-chain or branched-chain aliphatic hydrocarbon group. Examples of the straight-chain or branched-chain aliphatic hydrocarbon group include the same as those described above.
The alicyclic hydrocarbon group preferably has 3 to 20 carbon atoms, and more preferably has 3 to 12 carbon atoms.
The alicyclic hydrocarbon group may be a polycyclic group or a monocyclic group. The monocyclic alicyclic hydrocarbon group is preferably a group in which two hydrogen atoms have been removed from a monocycloalkane. The monocycloalkane preferably has 3 to 6 carbon atoms, and specific examples include cyclopentane and cyclohexane.
The polycyclic alicyclic hydrocarbon group is preferably a group in which two hydrogen atoms have been removed from a polycycloalkane, and the polycycloalkane preferably has 7 to 12 carbon atoms, and specific examples thereof include adamantane, norbornane, isobornane, tricyclodecane, and tetracyclododecane.

The aromatic hydrocarbon group in the divalent hydrocarbon group is a hydrocarbon group having at least one aromatic ring. This aromatic ring is not particularly limited as long as it is a cyclic conjugated system having (4n+2) π electrons, and may be monocyclic or polycyclic. The number of carbon atoms in the aromatic ring is preferably 5 to 30, more preferably 5 to 20, even more preferably 6 to 15, and particularly preferably 6 to 12. Specific examples of aromatic rings include aromatic hydrocarbon rings such as benzene, naphthalene, anthracene, and phenanthrene; and aromatic heterocycles in which some of the carbon atoms constituting the aromatic hydrocarbon ring are substituted with heteroatoms. Examples of heteroatoms in aromatic heterocycles include oxygen atoms, sulfur atoms, and nitrogen atoms. Specific examples of aromatic heterocycles include pyridine rings and thiophene rings.
Specific examples of the aromatic hydrocarbon group include groups in which two hydrogen atoms have been removed from the aromatic hydrocarbon ring or aromatic heterocycle (arylene groups or heteroarylene groups); groups in which two hydrogen atoms have been removed from an aromatic compound containing two or more aromatic rings (e.g., biphenyl, fluorene, etc.); and groups in which one hydrogen atom of a group in which one hydrogen atom has been removed from the aromatic hydrocarbon ring or aromatic heterocycle (aryl group or heteroaryl group) has been substituted with an alkylene group (e.g., groups in which one further hydrogen atom has been removed from the aryl group in an arylalkyl group such as a benzyl group, phenethyl group, 1-naphthylmethyl group, 2-naphthylmethyl group, 1-naphthylethyl group, or 2-naphthylethyl group). The alkylene group bonded to the aryl group or heteroaryl group preferably has 1 to 4 carbon atoms, more preferably 1 or 2, and particularly preferably 1 carbon atom.

The divalent hydrocarbon group may have a substituent.
The linear or branched aliphatic hydrocarbon group as the divalent hydrocarbon group may or may not have a substituent, such as a fluorine atom, a fluorinated alkyl group having 1 to 5 carbon atoms and substituted with a fluorine atom, or a carbonyl group.

The alicyclic hydrocarbon group in the aliphatic hydrocarbon group containing a ring in its structure as a divalent hydrocarbon group may or may not have a substituent, such as an alkyl group, an alkoxy group, a halogen atom, a halogenated alkyl group, a hydroxyl group, or a carbonyl group.
The alkyl group as the substituent is preferably an alkyl group having 1 to 5 carbon atoms, and most preferably a methyl group, an ethyl group, a propyl group, an n-butyl group, or a tert-butyl group.
The alkoxy group as the substituent is preferably an alkoxy group having 1 to 5 carbon atoms, more preferably a methoxy group, an ethoxy group, an n-propoxy group, an iso-propoxy group, an n-butoxy group, or a tert-butoxy group, and most preferably a methoxy group or an ethoxy group.
Examples of the halogen atom as the substituent include a fluorine atom, a chlorine atom, a bromine atom, and an iodine atom, with a fluorine atom being preferred.
Examples of the halogenated alkyl group as the substituent include groups in which some or all of the hydrogen atoms of the alkyl group have been substituted with the halogen atoms.
In the alicyclic hydrocarbon group, some of the carbon atoms constituting the ring structure may be substituted with a substituent containing a heteroatom. Preferred examples of the substituent containing a heteroatom include -O-, -C(=O)-O-, -S-, -S(=O) ₂ -, and -S(=O) ₂ -O-.

In the aromatic hydrocarbon group as a divalent hydrocarbon group, a hydrogen atom of the aromatic hydrocarbon group may be substituted with a substituent. For example, a hydrogen atom bonded to an aromatic ring in the aromatic hydrocarbon group may be substituted with a substituent. Examples of the substituent include an alkyl group, an alkoxy group, a halogen atom, a halogenated alkyl group, and a hydroxyl group.
The alkyl group as the substituent is preferably an alkyl group having 1 to 5 carbon atoms, and most preferably a methyl group, an ethyl group, a propyl group, an n-butyl group, or a tert-butyl group.
Examples of the alkoxy group, halogen atom and halogenated alkyl group as the substituent include those exemplified as the substituent substituting the hydrogen atom of the alicyclic hydrocarbon group.

Regarding divalent linking groups containing heteroatoms:
The heteroatom in the divalent linking group containing a heteroatom is an atom other than a carbon atom or a hydrogen atom, and examples thereof include an oxygen atom, a nitrogen atom, a sulfur atom, and a halogen atom.

In the divalent linking group containing a hetero atom, preferred examples of the linking group include -O-, -C(=O)-O-, -C(=O)-, -O-C(=O)-O-; -C(=O)-NH-, -NH-, -NH-C(=O)-O-, -NH-C(=NH)- (H may be substituted by a substituent such as an alkyl group or an acyl group); -S-, -S(=O) ₂ -, -S(=O) ₂ -O-, the general formula -Y ²¹ -O-Y ²² -, -Y ²¹ -O-, -Y ²¹ -C(=O)-O-, -C(=O)-O-Y ²¹ , -[Y ²¹ -C(=O)-O] _m" -Y ²² - or -Y ²¹ -O-C(=O)-Y ²² - (wherein Y ²¹ and Y ²² each independently represent a divalent hydrocarbon group which may have a substituent, O represents an oxygen atom, and m″ represents an integer of 0 to 3).
When the divalent linking group containing a hetero atom is -C(=O)-NH-, -NH-, -NH-C(=O)-O-, or -NH-C(=NH)-, the H may be substituted with a substituent such as an alkyl group, acyl, etc. The substituent (alkyl group, acyl group, etc.) preferably has 1 to 10 carbon atoms, more preferably 1 to 8 carbon atoms, and particularly preferably 1 to 5 carbon atoms.
In the formula -Y ²¹ -O-Y ²² -, -Y ²¹ -O-, -Y ²¹ -C(═O)-O-, -C(═O)-O-Y ²¹ -, -[Y ²¹ -C(═O)-O] _m" -Y ²² - or -Y ²¹ -O-C(═O)-Y ²² -, Y ²¹ and Y ²² each independently represent a divalent hydrocarbon group which may have a substituent. Examples of the divalent hydrocarbon group include the same as the "divalent hydrocarbon group which may have a substituent" listed above in the description of the divalent linking group.
Y ²¹ is preferably a linear aliphatic hydrocarbon group, more preferably a linear alkylene group, still more preferably a linear alkylene group having 1 to 5 carbon atoms, and particularly preferably a methylene group or ethylene group.
Y ²² is preferably a linear or branched aliphatic hydrocarbon group, more preferably a methylene group, an ethylene group, or an alkylmethylene group. The alkyl group in the alkylmethylene group is preferably a linear alkyl group having 1 to 5 carbon atoms, more preferably a linear alkyl group having 1 to 3 carbon atoms, and most preferably a methyl group.
In the group represented by the formula -[Y ²¹ -C(═O)-O] _m" -Y ²² -, m" represents an integer of 0 to 3, preferably an integer of 0 to 2, more preferably 0 or 1, and particularly preferably 1. That is, as the group represented by the formula -[Y ²¹ -C(═O)-O] _m" -Y ²² -, a group represented by the formula -Y ²¹ -C(═O)-O-Y ²² - is particularly preferred. Of these, a group represented by the formula -(CH ₂ ) _a' -C(═O)-O-(CH ₂ ) _b' - is preferred. In the formula, a' represents an integer of 1 to 10, preferably an integer of 1 to 8, more preferably an integer of 1 to 5, even more preferably 1 or 2, and most preferably 1. b' represents an integer of 1 to 10, preferably an integer of 1 to 8, more preferably an integer of 1 to 5, even more preferably 1 or 2, and most preferably 1.

Among these, the epoxy group-containing group in ^REP is preferably a glycidyl group.

Furthermore, suitable examples of novolac-type epoxy resins (Anv) include resins having a structural unit represented by the following general formula (anv1):

[In the formula, R ^EP represents an epoxy group-containing group, and R ^a22 and R ^a23 each independently represent a hydrogen atom, an alkyl group having 1 to 5 carbon atoms, or a halogen atom.]

In formula (anv1), the alkyl group having 1 to 5 carbon atoms for R ^a22 and R ^a23 is the same as the alkyl group having 1 to 5 carbon atoms for R ^p1 and R ^p2 in formula (A1). The halogen atoms for ^{R a22} and R ^a23 are preferably chlorine atoms or bromine atoms.
In formula (anv1), ^REP is the same as ^REP in formula (A1), and is preferably a glycidyl group.

Specific examples of the structural unit represented by formula (anv1) are shown below.

The novolac epoxy resin (Anv) may be a resin consisting solely of the structural unit (anv1), or may be a resin containing the structural unit (anv1) and other structural units. Examples of these other structural units include the structural units represented by the following general formulas (anv2) to (anv3).

[In the formula, R ^a24 represents a hydrocarbon group which may have a substituent. R ^a25 to R ^a26 and R ^a28 to R ^a30 each independently represent a hydrogen atom, an alkyl group having 1 to 5 carbon atoms, or a halogen atom. R ^a27 represents an epoxy group-containing group or a hydrocarbon group which may have a substituent.]

In formula (anv2), R ^a24 represents a hydrocarbon group which may have a substituent. Examples of the hydrocarbon group which may have a substituent include a linear or branched alkyl group, and a cyclic hydrocarbon group.
The linear alkyl group preferably has 1 to 5 carbon atoms, more preferably 1 to 4 carbon atoms, and even more preferably 1 or 2 carbon atoms. Specific examples include a methyl group, an ethyl group, an n-propyl group, an n-butyl group, and an n-pentyl group. Of these, a methyl group, an ethyl group, or an n-butyl group is preferred, and a methyl group or an ethyl group is more preferred.

The branched alkyl group preferably has 3 to 10 carbon atoms, and more preferably 3 to 5. Specific examples include an isopropyl group, an isobutyl group, a tert-butyl group, an isopentyl group, a neopentyl group, a 1,1-diethylpropyl group, and a 2,2-dimethylbutyl group, with an isopropyl group being preferred.

When R ^a24 is a cyclic hydrocarbon group, the hydrocarbon group may be an aliphatic hydrocarbon group or an aromatic hydrocarbon group, and may be a polycyclic group or a monocyclic group.
The monocyclic aliphatic hydrocarbon group is preferably a group in which one hydrogen atom has been removed from a monocycloalkane. The monocycloalkane preferably has 3 to 6 carbon atoms, and specific examples include cyclopentane and cyclohexane.
The aliphatic hydrocarbon group that is a polycyclic group is preferably a group in which one hydrogen atom has been removed from a polycycloalkane, and the polycycloalkane is preferably one having 7 to 12 carbon atoms, and specific examples thereof include adamantane, norbornane, isobornane, tricyclodecane, and tetracyclododecane.

When the cyclic hydrocarbon group of R ^a24 is an aromatic hydrocarbon group, the aromatic hydrocarbon group is a hydrocarbon group having at least one aromatic ring.
This aromatic ring is not particularly limited as long as it is a cyclic conjugated system having 4n+2 π electrons, and may be monocyclic or polycyclic. The number of carbon atoms in the aromatic ring is preferably 5 to 30, more preferably 5 to 20, even more preferably 6 to 15, and particularly preferably 6 to 12. Specific examples of the aromatic ring include aromatic hydrocarbon rings such as benzene, naphthalene, anthracene, and phenanthrene; and aromatic heterocycles in which a portion of the carbon atoms constituting the aromatic hydrocarbon ring is substituted with a heteroatom. Examples of heteroatoms in the aromatic heterocycle include an oxygen atom, a sulfur atom, and a nitrogen atom. Specific examples of the aromatic heterocycle include a pyridine ring and a thiophene ring.
Specific examples of the aromatic hydrocarbon group for R ^a24 include groups in which one hydrogen atom has been removed from the aromatic hydrocarbon ring or aromatic heterocycle (aryl groups or heteroaryl groups); groups in which one hydrogen atom has been removed from an aromatic compound containing two or more aromatic rings (e.g., biphenyl, fluorene, etc.); and groups in which one hydrogen atom of the aromatic hydrocarbon ring or aromatic heterocycle has been substituted with an alkylene group (e.g., arylalkyl groups such as benzyl group, phenethyl group, 1-naphthylmethyl group, 2-naphthylmethyl group, 1-naphthylethyl group, 2-naphthylethyl group, etc.). The alkylene group bonded to the aromatic hydrocarbon ring or aromatic heterocycle preferably has 1 to 4 carbon atoms, more preferably 1 or 2, and particularly preferably 1 carbon atom.

In formulae (anv2) and (anv3), R ^a25 to R ^a26 and R ^a28 to R ^a30 each independently represent a hydrogen atom, an alkyl group having 1 to 5 carbon atoms, or a halogen atom, and the alkyl group having 1 to 5 carbon atoms and the halogen atom are the same as those defined above for R ^a22 and R ^a23 , respectively.

In formula (anv3), R ^a27 represents an epoxy group-containing group or a hydrocarbon group which may have a substituent. The epoxy group-containing group of ^{R a27} is the same as R ^EP in formula (A1), and the hydrocarbon group which may have a substituent of R ^a27 is the same as R ^a24 .

Specific examples of the structural units represented by the formulas (anv2) to (anv3) are shown below.

When the novolac epoxy resin (Anv) has other structural units in addition to the structural unit (anv1), the proportion of each structural unit in the resin (Anv) is not particularly limited, but the total amount of structural units having epoxy groups relative to the total amount of all structural units constituting the resin (Anv) is preferably 10 to 90 mol%, more preferably 20 to 80 mol%, and even more preferably 30 to 70 mol%.

Regarding bisphenol epoxy resin (Abp):
Suitable examples of the bisphenol-type epoxy resin (Abp) include epoxy resins represented by the following general formula (abp1).

[In the formula, R ^EP represents an epoxy group-containing group, R ^a31 and R ^a32 each independently represent a hydrogen atom, an alkyl group having 1 to 5 carbon atoms, or a fluorinated alkyl group having 1 to 5 carbon atoms, and na ³¹ represents an integer of 1 to 50.]

In the formula (abp1), ^REP is the same as ^REP in the formula (A1), and is preferably a glycidyl group.
In the formula (abp1), the alkyl group having 1 to 5 carbon atoms in R ^a31 and R ^a32 is the same as the alkyl group having 1 to 5 carbon atoms in R ^p1 and R ^p2 in the formula (A1). Of these, R ^a31 and R ^a32 are preferably each a hydrogen atom or a methyl group.
Examples of the fluorinated alkyl group having 1 to 5 carbon atoms for R ^a31 and R ^a32 include groups in which some or all of the hydrogen atoms of the alkyl group having 1 to 5 carbon atoms for R ^a31 and R ^a32 have been substituted with fluorine atoms.
In the formula (abp1), na ³¹ represents an integer of 1 to 50, preferably an integer of 4 to 15, and more preferably an integer of 5 to 8.

In the negative photosensitive composition of this embodiment, the component (AS) may be used alone or in combination of two or more types.
As the component (AS), particularly from the viewpoint of the elastic modulus of the cured film, a polyfunctional epoxy resin having three or more epoxy groups is preferred, and among these, novolac type epoxy resin (Anv) is more preferred.

Commercially available products of the (AS) component include novolac epoxy resins such as jER-152, jER-154, jER-157S70, and jER-157S65 (all manufactured by Mitsubishi Chemical Corporation); EPICLON N-740, EPICLON N-740, EPICLON N-770, EPICLON N-775, EPICLON N-660, EPICLON N-665, EPICLON N-670, EPICLON N-673, EPICLON N-680, EPICLON N-690, EPICLON N-695, and EPICLON N-740. Examples include HP5000 (both manufactured by DIC Corporation); EOCN-1020 (both manufactured by Nippon Kayaku Co., Ltd.).

Commercially available products of the (AS) component include bisphenol-type epoxy resins such as jER-4005, jER-4007, and jER-4010 (all manufactured by Mitsubishi Chemical Corporation); jER-827, jER-828, jER-834, jER-1001, jER-1002, jER-1003, jER-1055, jER-1007, jER-1009, and jER-1010 (all manufactured by Mitsubishi Chemical Corporation); and EPICLON 860, EPICLON 1050, EPICLON 1051, and EPICLON 1055 (all manufactured by DIC Corporation).

The polystyrene-equivalent weight average molecular weight of component (AS) is preferably 100 to 300,000, more preferably 200 to 200,000, and even more preferably 300 to 200,000. By achieving such a weight average molecular weight, peeling from the support is less likely to occur, and the strength of the cured film that is formed is sufficiently increased.

The component (AS) preferably has a dispersity of at least 1.05, which further improves lithography properties during pattern formation.
The degree of dispersion referred to here means the value obtained by dividing the mass average molecular weight by the number average molecular weight.

The content of the (AS) component in the negative-type photosensitive composition of this embodiment can be adjusted depending on the film thickness of the photosensitive film to be formed, etc.

<Epoxy group-containing compound (AL) that is liquid at 25°C>
The component (AL) is an epoxy group-containing compound that is liquid at 25°C.
The epoxy equivalent of the (AL) component is, for example, less than 180 g/eq., preferably 90 g/eq. to 180 g/eq., and more preferably 120 g/eq. to 150 g/eq.

Examples of the component (AL) include aliphatic epoxy resins that are liquid at 25°C.
Examples of the aliphatic epoxy resin include a compound containing a partial structure represented by the following general formula (m1) (hereinafter also referred to as "component (m1)").

[In the formula, _n2 is an integer of 1 to 4. * indicates a bond.]

In formula (m1), _n2 is an integer of 1 to 4, preferably an integer of 1 to 3, and more preferably 2.

Examples of the component (m1) include compounds in which a plurality of partial structures represented by the general formula (m1) are bonded via a divalent linking group or a single bond. Among these, compounds in which a plurality of partial structures represented by the general formula (m1) are bonded via a divalent linking group are preferred.
The divalent linking group here is not particularly limited, but suitable examples include a divalent hydrocarbon group which may have a substituent and a divalent linking group which contains a heteroatom. The divalent hydrocarbon group which may have a substituent and the divalent linking group which contains a heteroatom are the same as the divalent hydrocarbon group which may have a substituent and the divalent linking group which contains a heteroatom explained in relation to R ^EP (epoxy group-containing group) in formula (A1) above, and among these, a divalent linking group which contains a heteroatom is preferred, and a group represented by -Y ²¹ -C(═O)-O- and a group represented by -C(═O)-O-Y ²¹ - are more preferred. Y ²¹ is preferably a linear aliphatic hydrocarbon group, more preferably a linear alkylene group, even more preferably a linear alkylene group having 1 to 5 carbon atoms, and particularly preferably a methylene group or an ethylene group.

Furthermore, suitable aliphatic epoxy resins include compounds represented by the following general formula (AL1) (hereinafter also referred to as "component (AL1)"):

[In the formula, ^REP is an epoxy group-containing group. Multiple ^REPs may be the same or different.]

In the formula (AL1), ^REP is an epoxy group-containing group and is the same as ^REP in the formula (A1).

In the negative photosensitive composition of this embodiment, the component (AL) may be used alone or in combination of two or more types.
The component (AL) preferably contains at least one selected from the group consisting of the component (m1) and the component (AL1), and among these, the component (AL1) is more preferred.

Commercially available products containing the (AL) component include, for example, ADEKA RESIN EP-4080S, EP-4085S, and EP-4088S (all manufactured by ADEKA Corporation); CELLOXIDE 2021P, CELLOXIDE 2081, CELLOXIDE 2083, CELLOXIDE 2085, CELLOXIDE 8000, CELLOXIDE 8010, EHPE-3150, EPOLEAD PB 3600, and EPOLEAD PB 4700 (all manufactured by Daicel Corporation); and DENACOL Examples include EX-211L, EX-212L, EX-214L, EX-216L, EX-321L, and EX-850L (manufactured by Nagase ChemteX Corporation); the TEPIC series, such as TEPIC, TEPIC-VL, TEPIC-PAS, TEPIC-G, TEPIC-S, TEPIC-SP, TEPIC-SS, TEPIC-HP, TEPIC-L, TEPIC-FL, and TEPIC-UC (manufactured by Nissan Chemical Industries, Ltd.); MA-DGIC, DA-MGIC, and TOIC (manufactured by Shikoku Chemical Industry Co., Ltd.).

In the negative photosensitive composition of this embodiment, the amount of the component (AL) relative to 100 parts by mass of the component (AS) is preferably 1 to 10 parts by mass, more preferably 1.5 to 9 parts by mass, and even more preferably 2 to 8 parts by mass.
When the content of the (AL) component is equal to or greater than the lower limit of the above-mentioned preferred range, undercutting is less likely to occur during pattern formation, resulting in an improved pattern shape, whereas when the content is equal to or less than the upper limit of the above-mentioned preferred range, sensitivity is appropriately controlled, making it easier to obtain a pattern with a good shape.

<Epoxy Group-Containing Compound Other than Component (AS) and Component (AL)>
In the negative photosensitive composition of this embodiment, the component (A) may further include an epoxy group-containing compound other than the components (AS) and (AL).
Examples of epoxy group-containing compounds other than those mentioned above include acrylic resins having epoxy group-containing units and polyfunctional aromatic epoxy compounds other than those mentioned above.
Examples of polyfunctional aromatic epoxy compounds other than those mentioned above include trimethylolpropane triglycidyl ether, glycerin triglycidyl ether; pentaerythritol tetraglycidyl ether, ditrimethylolpropane tetraglycidyl ether, diglycerin tetraglycidyl ether, erythritol tetraglycidyl ether; xylitol pentaglycidyl ether, dipentaerythritol pentaglycidyl ether, inositol pentaglycidyl ether; dipentaerythritol hexaglycidyl ether, sorbitol hexaglycidyl ether, and inositol hexaglycidyl ether.

<Cationic Polymerization Initiator (I)>
The cationic polymerization initiator (component (I)) contains a borate salt (I0) (hereinafter also referred to as “component (I0)”) that is composed of a cationic moiety having a thioxanthene skeleton and an anionic moiety that is a borate anion.
The content of component (I0) in component (I) relative to the total mass (mass%) of component (I) may be 50 mass% or more, 70 mass% or more, 90 mass% or more, or 100 mass%, and is preferably 100 mass%.

<Borate salt (IO)>
The component (I0) in this embodiment is composed of a cation moiety having a thioxanthene skeleton and an anion moiety that is a borate anion.

The thioxanthene skeleton possessed by the cation portion of component (I0) refers to a structure represented by the following chemical formula (Th).

Sulfonium cations and iodonium cations are suitable as the cation moiety in component (I0), and organic cations represented by the following general formulas (ca-1) to (ca-5) are particularly preferred.

[In the formula, R ²⁰¹ to R ²⁰⁷ and R ²¹¹ to R ²¹² each independently represent an aryl group, heteroaryl group, alkyl group, or alkenyl group, which may have a substituent. R ²⁰¹ to R ²⁰³ , R ²⁰⁶ to R ²⁰⁷ , and R ²¹¹ to R ²¹² may be bonded to each other to form a ring together with the sulfur atom in the formula. R ²⁰⁸ to R ²⁰⁹ each independently represent a hydrogen atom or an alkyl group of 1 to 5 carbon atoms. R ²¹⁰ is an aryl group which may have a substituent, an alkyl group which may have a substituent, an alkenyl group which may have a substituent, or an —SO ₂ — containing cyclic group which may have a substituent. L ²⁰¹ represents —C(═O)— or —C(═O)—O—. Y ²⁰¹ each independently represent an arylene group, an alkylene group, or an alkenylene group. x is 1 or 2.] W ²⁰¹ represents a (x+1)-valent linking group, provided that the cation structure has one or more thioxanthene skeletons.

The aryl group for R ²⁰¹ to R ²⁰⁷ and R ²¹¹ to R ²¹² includes an unsubstituted aryl group having 6 to 20 carbon atoms, and a phenyl group or a naphthyl group is preferred.
The heteroaryl groups represented by R ²⁰¹ to R ²⁰⁷ and R ²¹¹ to R ²¹² include those in which some of the carbon atoms constituting the aryl group have been substituted with heteroatoms. Examples of heteroatoms include oxygen atoms, sulfur atoms, and nitrogen atoms. Examples of this heteroaryl group include a group in which one hydrogen atom has been removed from 9H-thioxanthene; and examples of the substituted heteroaryl group include a group in which one hydrogen atom has been removed from 9H-thioxanthen-9-one.
The alkyl groups for R ²⁰¹ to R ²⁰⁷ and R ²¹¹ to R ²¹² are preferably chain or cyclic alkyl groups having 1 to 30 carbon atoms.
The alkenyl groups for R ²⁰¹ to R ²⁰⁷ and R ²¹¹ to R ²¹² preferably have 2 to 10 carbon atoms.
Examples of the substituent that R ²⁰¹ to R ²⁰⁷ and R ²¹⁰ to R ²¹² may have include an alkyl group, a halogen atom, a halogenated alkyl group, a carbonyl group, a cyano group, an amino group, an oxo group (═O), an aryl group, and groups represented by the following formulas (ca-r-1) to (ca-r-10), respectively.

[In the formula, each ^R'201 independently represents a hydrogen atom, an optionally substituted cyclic group, an optionally substituted chain alkyl group, or an optionally substituted chain alkenyl group.]

In the above formulas (car-r-1) to (car-r-10), R' ²⁰¹ each independently represents a hydrogen atom, a cyclic group which may have a substituent, a chain alkyl group which may have a substituent, or a chain alkenyl group which may have a substituent.

Optionally substituted cyclic group:
The cyclic group is preferably a cyclic hydrocarbon group, and the cyclic hydrocarbon group may be an aromatic hydrocarbon group or a cyclic aliphatic hydrocarbon group. An aliphatic hydrocarbon group means a hydrocarbon group that does not have aromaticity. Furthermore, the aliphatic hydrocarbon group may be saturated or unsaturated, and is usually preferably saturated.

The aromatic hydrocarbon group for ^R'201 is a hydrocarbon group having an aromatic ring. The number of carbon atoms in the aromatic hydrocarbon group is preferably 3 to 30, more preferably 5 to 30, even more preferably 5 to 20, particularly preferably 6 to 15, and most preferably 6 to 10. However, this number of carbon atoms does not include the number of carbon atoms in the substituent.
Specific examples of the aromatic ring contained in the aromatic hydrocarbon group of R' ²⁰¹ include benzene, fluorene, naphthalene, anthracene, phenanthrene, biphenyl, and aromatic heterocycles in which some of the carbon atoms constituting these aromatic rings have been substituted with heteroatoms, as well as rings in which some of the hydrogen atoms constituting these aromatic rings or aromatic heterocycles have been substituted with oxo groups, etc. Examples of the heteroatom in the aromatic heterocycle include an oxygen atom, a sulfur atom, and a nitrogen atom.
Specific examples of the aromatic hydrocarbon group for R' ²⁰¹ include groups in which one hydrogen atom has been removed from the aromatic ring (aryl groups: for example, phenyl, naphthyl, and anthracenyl), groups in which one hydrogen atom of the aromatic ring has been substituted with an alkylene group (for example, arylalkyl groups such as benzyl, phenethyl, 1-naphthylmethyl, 2-naphthylmethyl, 1-naphthylethyl, and 2-naphthylethyl), groups in which one hydrogen atom has been removed from a ring in which some of the hydrogen atoms constituting the aromatic ring have been substituted with an oxo group or the like (for example, anthraquinone), and groups in which one hydrogen atom has been removed from an aromatic heterocycle (for example, 9H-thioxanthene and 9H-thioxanthen-9-one). The number of carbon atoms in the alkylene group (the alkyl chain in the arylalkyl group) is preferably 1 to 4, more preferably 1 or 2, and particularly preferably 1.

The cyclic aliphatic hydrocarbon group for R' ²⁰¹ includes an aliphatic hydrocarbon group containing a ring in the structure.
Examples of the aliphatic hydrocarbon group containing a ring in its structure include alicyclic hydrocarbon groups (groups in which one hydrogen atom has been removed from an aliphatic hydrocarbon ring), groups in which an alicyclic hydrocarbon group is bonded to the end of a straight-chain or branched-chain aliphatic hydrocarbon group, and groups in which an alicyclic hydrocarbon group is present in the middle of a straight-chain or branched-chain aliphatic hydrocarbon group.
The alicyclic hydrocarbon group preferably has 3 to 20 carbon atoms, and more preferably 3 to 12 carbon atoms.
The alicyclic hydrocarbon group may be a polycyclic group or a monocyclic group. The monocyclic alicyclic hydrocarbon group is preferably a group obtained by removing one or more hydrogen atoms from a monocycloalkane. The monocycloalkane preferably has 3 to 6 carbon atoms, and specific examples include cyclopentane and cyclohexane. The polycyclic alicyclic hydrocarbon group is preferably a group obtained by removing one or more hydrogen atoms from a polycycloalkane, and the polycycloalkane preferably has 7 to 30 carbon atoms. Among these, the polycycloalkane is more preferably a polycycloalkane having a bridged ring polycyclic skeleton, such as adamantane, norbornane, isobornane, tricyclodecane, or tetracyclododecane; or a polycycloalkane having a fused ring polycyclic skeleton, such as a cyclic group having a steroid skeleton.

Among these, the cyclic aliphatic hydrocarbon group for ^R'201 is preferably a group in which one or more hydrogen atoms have been removed from a monocycloalkane or polycycloalkane, more preferably a group in which one hydrogen atom has been removed from a polycycloalkane, particularly preferably an adamantyl group or a norbornyl group, and most preferably an adamantyl group.

The linear or branched aliphatic hydrocarbon group which may be bonded to the alicyclic hydrocarbon group preferably has 1 to 10 carbon atoms, more preferably 1 to 6 carbon atoms, even more preferably 1 to 4 carbon atoms, and most preferably 1 to 3 carbon atoms.
As the straight-chain aliphatic hydrocarbon group, a straight-chain alkylene group is preferred, and specific examples thereof include a methylene group [-CH ₂ -], an ethylene group [-(CH ₂ ) ₂ -], a trimethylene group [-(CH ₂ ) ₃ -], a tetramethylene group [-(CH ₂ ) ₄ -], and a pentamethylene group [-(CH ₂ ) ₅ -].
The branched aliphatic hydrocarbon group is preferably a branched alkylene group, and specific examples thereof include alkylmethylene groups such as -CH( _CH3 )-, -CH( _CH2CH3 )-, -C( _CH3 ) _2- , -C( _CH3 ) _{( CH2CH3} )-, -C( _CH3 ) _{( CH2CH2CH3} )-, _{and -C(CH2CH3)2- ; alkylethylene} groups such as -CH( _CH3 ) _CH2- , -CH( _CH3 )CH( _CH3 ) _- , _-C ( _CH3 ) _{2CH2- , -CH( CH2CH3 ) CH2-} , _and -C( _{CH2CH3 ) 2 - CH2- ;} alkyltrimethylene groups such as -CH( _CH3 ) _CH2CH2CH2- , -CH2CH( _CH3 ) _{CH2CH2- ,} etc.; and alkylalkylene groups such as alkyltetramethylene groups such as _-CH (CH3) _{CH2CH2CH2- , -CH2CH} ( _CH3 ) _CH2CH2- , etc. The alkyl group in the alkylalkylene group is preferably a linear alkyl group having 1 to 5 carbon atoms.

A chain alkyl group which may have a substituent:
The chain alkyl group of R' ²⁰¹ may be either a straight chain or a branched chain.
The linear alkyl group preferably has 1 to 20 carbon atoms, more preferably 1 to 15 carbon atoms, and most preferably 1 to 10 carbon atoms. Specific examples include a methyl group, an ethyl group, a propyl group, a butyl group, a pentyl group, a hexyl group, a heptyl group, an octyl group, a nonyl group, a decanyl group, an undecyl group, a dodecyl group, a tridecyl group, an isotridecyl group, a tetradecyl group, a pentadecyl group, a hexadecyl group, an isohexadecyl group, a heptadecyl group, an octadecyl group, a nonadecyl group, an icosyl group, a heneicosyl group, and a docosyl group.
The branched alkyl group preferably has 3 to 20 carbon atoms, more preferably 3 to 15 carbon atoms, and most preferably 3 to 10 carbon atoms. Specific examples include a 1-methylethyl group, a 1-methylpropyl group, a 2-methylpropyl group, a 1-methylbutyl group, a 2-methylbutyl group, a 3-methylbutyl group, a 1-ethylbutyl group, a 2-ethylbutyl group, a 1-methylpentyl group, a 2-methylpentyl group, a 3-methylpentyl group, and a 4-methylpentyl group.

An optionally substituted chain alkenyl group:
The chain alkenyl group for ^R'201 may be either linear or branched, and preferably has 2 to 10 carbon atoms, more preferably 2 to 5, even more preferably 2 to 4, and particularly preferably 3. Examples of linear alkenyl groups include vinyl, propenyl (allyl), and butynyl groups. Examples of branched alkenyl groups include 1-methylvinyl, 2-methylvinyl, 1-methylpropenyl, and 2-methylpropenyl groups.
Of the chain alkenyl groups mentioned above, linear alkenyl groups are preferred, vinyl groups and propenyl groups are more preferred, and vinyl groups are particularly preferred.

Examples of the substituent in the cyclic group, chain alkyl group or alkenyl group of ^R'201 include an alkoxy group, a halogen atom, a halogenated alkyl group, a hydroxyl group, a carbonyl group, a nitro group, an amino group, an oxo group, the cyclic group in ^R'201 above, an alkylcarbonyl group, a thienylcarbonyl group, etc.

Among these, R' ²⁰¹ is preferably a cyclic group which may have a substituent, or a chain alkyl group which may have a substituent.

When R ²⁰¹ to R ²⁰³ , R ²⁰⁶ to R ²⁰⁷ , and R ²¹¹ to R ²¹² bond to each other to form a ring together with the sulfur atom in the formula, they may be bonded via a heteroatom such as a sulfur atom, an oxygen atom, or a nitrogen atom, or a functional group such as a carbonyl group, -SO-, -SO ₂ -, -SO ₃ -, -COO-, -CONH-, or -N(R _N )- (wherein R _N is an alkyl group having 1 to 5 carbon atoms). As the ring formed, one ring containing the sulfur atom in the ring skeleton is preferably a 3- to 10-membered ring, including the sulfur atom, and particularly preferably a 5- to 7-membered ring. Specific examples of the ring formed include a thiophene ring, a thiazole ring, a benzothiophene ring, a thianthrene ring, a benzothiophene ring, a dibenzothiophene ring, a 9H-thioxanthene ring, a thioxanthone ring, a thianthrene ring, a phenoxathiin ring, a tetrahydrothiophenium ring, and a tetrahydrothiopyranium ring.

In the formula (ca-3), R ²⁰⁸ to R ²⁰⁹ each independently represent a hydrogen atom or an alkyl group having 1 to 5 carbon atoms, preferably a hydrogen atom or an alkyl group having 1 to 3 carbon atoms, and when they are alkyl groups, they may be bonded to each other to form a ring.

In the formula (ca-3), R ²¹⁰ represents an aryl group which may have a substituent, an alkyl group which may have a substituent, an alkenyl group which may have a substituent, or an —SO ₂ —-containing cyclic group which may have a substituent.
The aryl group for R ²¹⁰ includes an unsubstituted aryl group having 6 to 20 carbon atoms, and a phenyl group or a naphthyl group is preferred.
The alkyl group for R ²¹⁰ is preferably a chain or cyclic alkyl group having 1 to 30 carbon atoms.
The alkenyl group for R ²¹⁰ preferably has 2 to 10 carbon atoms.

In the formulae (ca-4) and (ca-5), Y ²⁰¹ each independently represents an arylene group, an alkylene group, or an alkenylene group.
Examples of the arylene group for Y ²⁰¹ include groups in which one hydrogen atom has been removed from the aryl groups exemplified as the aromatic hydrocarbon group for R′ ²⁰¹ .
Examples of the alkylene group and alkenylene group for Y ²⁰¹ include groups in which one hydrogen atom has been removed from the groups exemplified as the chain alkyl group and chain alkenyl group for R′ ²⁰¹ .

In the formulas (ca-4) and (ca-5), x is 1 or 2.
W ²⁰¹ is an (x+1)-valent linking group, that is, a divalent or trivalent linking group.
The divalent linking group in W ²⁰¹ is preferably a divalent hydrocarbon group which may have a substituent, and is preferably the same as the divalent hydrocarbon group which may have a substituent exemplified in the above-mentioned "epoxy group-containing group". The divalent linking group in ^{W 201} may be linear, branched, or cyclic, and is preferably cyclic. Among them, a group in which two carbonyl groups are combined at both ends of an arylene group, or a group consisting of only an arylene group is preferred. Examples of the arylene group include a phenylene group and a naphthylene group, and a phenylene group is particularly preferred.
Examples of the trivalent linking group for W ²⁰¹ include a group in which one hydrogen atom has been removed from the divalent linking group for W ²⁰¹ , and a group in which the divalent linking group is further bonded to the divalent linking group. As the trivalent linking group for ^{W 201} , a group in which two carbonyl groups are bonded to an arylene group is preferred.

Of the above, the cation moiety in component (I0) is preferably a cation represented by general formula (ca-1), and specific examples include the cations represented by the following formulas (I0-ca-1) to (I0-ca-10).

The borate anion in the anion portion of component (I0) is preferably, for example, an anion represented by the following general formula (I0-an):

[In the formula, R ^b01 to R ^b04 each independently represent an aryl group which may have a substituent, or a fluorine atom.]

In the formula (I0-an), the aryl group for R ^b01 to R ^b04 preferably has 5 to 30 carbon atoms, more preferably 5 to 20, still more preferably 6 to 15, and particularly preferably 6 to 12. Specific examples include a naphthyl group, a phenyl group, and an anthracenyl group, with a phenyl group being preferred because of its easy availability.
The aryl group in R ^b01 to R ^b04 may have a substituent. The substituent is not particularly limited, but is preferably a halogen atom, a hydroxyl group, an alkyl group (preferably a linear or branched alkyl group, preferably having 1 to 5 carbon atoms), or a halogenated alkyl group, more preferably a halogen atom or a halogenated alkyl group having 1 to 5 carbon atoms, and particularly preferably a fluorine atom or a fluorinated alkyl group having 1 to 5 carbon atoms. When the aryl group has a fluorine atom, the polarity of the anion moiety is enhanced, and this is preferable.
Of these, R ^b01 to R ^b04 in formula (I0-an) are each preferably a fluorinated phenyl group, and particularly preferably a perfluorophenyl group.

Specific preferred examples of the anion represented by formula (I0-an) include tetrakis(pentafluorophenyl)borate ([B(C ₆ F ₅ ) ₄ ] ⁻ ); tetrakis[(trifluoromethyl)phenyl]borate ([B(C ₆ H ₄ CF ₃ ) ₄ ] ⁻ ); difluorobis(pentafluorophenyl)borate ([(C ₆ F ₅ ) ₂ BF ₂ ] ⁻ ); trifluoro(pentafluorophenyl)borate ([(C ₆ F ₅ )BF ₃ ] ⁻ ); tetrakis(difluorophenyl)borate ([B(C ₆ H ₃ F ₂ ) ₄ ] ⁻ ); and the like.
Among these, tetrakis(pentafluorophenyl)borate ([B(C ₆ F ₅ ) ₄ ] ⁻ ) is particularly preferred.

The borate salt (I0) preferably includes, for example, a sulfonium salt represented by the following general formula (I0-1):

In formula (I0-1), R ^b01 to R ^b04 each independently represent an aryl group which may have a substituent, or a fluorine atom.
R1 and R2 each represent an aryl group having 6 to 30 carbon atoms, a heterocyclic hydrocarbon group having 4 to 30 carbon atoms, or an alkyl group having 1 to 30 carbon atoms, and some of the hydrogen atoms of these aryl groups, heterocyclic hydrocarbon groups, or alkyl groups may be substituted with a substituent (t). This substituent (t) is an alkyl group having 1 to 18 carbon atoms, a hydroxy group, an alkoxy group having 1 to 18 carbon atoms, an alkylcarbonyl group having 2 to 18 carbon atoms, an arylcarbonyl group having 7 to 11 carbon atoms, an acyloxy group having 2 to 19 carbon atoms, an arylthio group having 6 to 20 carbon atoms, an alkylthio group having 1 to 18 carbon atoms, an aryl group having 6 to 10 carbon atoms, a heterocyclic hydrocarbon group having 4 to 20 carbon atoms, an aryloxy group having 6 to 10 carbon atoms, or HO(—R ^X O) q —(where R ^X O represents an ethyleneoxy group and/or a propyleneoxy group, and q represents an integer of 1 to 5). and at least one selected from the group consisting of a hydroxy(poly)alkyleneoxy group represented by the formula {} and a halogen atom. R3 to R5 each represent an alkyl group, a hydroxy group, an alkoxy group, an alkylcarbonyl group, an arylcarbonyl group, an acyloxy group, an arylthio group, an alkylthio group, an aryl group, a heterocyclic hydrocarbon group, an aryloxy group, a hydroxy(poly)alkyleneoxy group, or a halogen atom. k, m, and n represent the number of R3, R4, and R5, respectively, where k is an integer of 0 to 4, m is an integer of 0 to 3, and n is an integer of 0 to 4. When k, m, and n are each 2 or more, multiple R3s, R4s, and R5s may be the same or different. A is a group represented by -S-, -O-, -SO-, -SO ₂ -, or -CO-. B is a boron atom, O is an oxygen atom, and S is a sulfur atom.]

In the formula (I0-1), the explanation of R ^b01 to R ^b04 is the same as the explanation of R ^b01 to R ^b04 in the general formula (I0-an) above.

In formula (I0-1), among R3 to R5, examples of the alkyl group include linear alkyl groups having 1 to 18 carbon atoms (methyl, ethyl, n-propyl, n-butyl, n-pentyl, n-octyl, n-decyl, n-dodecyl, n-tetradecyl, n-hexadecyl, and n-octadecyl, etc.), branched alkyl groups having 1 to 18 carbon atoms (isopropyl, isobutyl, sec-butyl, tert-butyl, isopentyl, neopentyl, tert-pentyl, isohexyl, and isooctadecyl), and cycloalkyl groups having 3 to 18 carbon atoms (cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl, and 4-decylcyclohexyl, etc.).

Among R3 to R5, the alkoxy group includes linear or branched alkoxy groups having 1 to 18 carbon atoms (such as methoxy, ethoxy, propoxy, isopropoxy, butoxy, isobutoxy, sec-butoxy, tert-butoxy, hexyloxy, decyloxy, dodecyloxy, and octadecyloxy).

Of R3 to R5, the alkylcarbonyl group includes linear or branched alkylcarbonyl groups having 2 to 18 carbon atoms (acetyl, propionyl, butanoyl, 2-methylpropionyl, heptanoyl, 2-methylbutanoyl, 3-methylbutanoyl, octanoyl, decanoyl, dodecanoyl, octadecanoyl, etc.).

Among R3 to R5, the arylcarbonyl group includes arylcarbonyl groups having 7 to 11 carbon atoms (such as benzoyl and naphthoyl).

Of R3 to R5, examples of the acyloxy group include linear or branched acyloxy groups having 2 to 19 carbon atoms (e.g., acetoxy, ethylcarbonyloxy, propylcarbonyloxy, isopropylcarbonyloxy, butylcarbonyloxy, isobutylcarbonyloxy, sec-butylcarbonyloxy, tert-butylcarbonyloxy, octylcarbonyloxy, tetradecylcarbonyloxy, and octadecylcarbonyloxy).

Among R3 to R5, the arylthio group is an arylthio group having 6 to 20 carbon atoms (phenylthio, 2-methylphenylthio, 3-methylphenylthio, 4-methylphenylthio, 2-chlorophenylthio, 3-chlorophenylthio, 4-chlorophenylthio, 2-bromophenylthio, 3-bromophenylthio, 4-bromophenylthio, 2-fluorophenylthio, 3-fluorophenylthio, 4-fluorophenylthio, 2-hydroxyphenylthio, 4-hydroxyphenylthio, 2-methoxyphenylthio, 4-methoxyphenylthio, 1-naphthylthio, 2-naphthylthio, 4-[4-(phenylthio)benzoyl]phenylthio, 4-[4-(phenylthio)benzoyl]phenylthio, )phenoxy]phenylthio, 4-[4-(phenylthio)phenyl]phenylthio, 4-(phenylthio)phenylthio, 4-benzoylphenylthio, 4-benzoyl-2-chlorophenylthio, 4-benzoyl-3-chlorophenylthio, 4-benzoyl-3-methylthiophenylthio, 4-benzoyl-2-methylthiophenylthio, 4-(4-methylthiobenzoyl)phenylthio, 4-(2-methylthiobenzoyl)phenylthio, 4-(p-methylbenzoyl)phenylthio, 4-(p-ethylbenzoyl)phenylthio, 4-(p-isopropylbenzoyl)phenylthio, and 4-(p-tert-butylbenzoyl)phenylthio, etc.

Of R3 to R5, the alkylthio group includes linear or branched alkylthio groups having 1 to 18 carbon atoms (such as methylthio, ethylthio, propylthio, isopropylthio, butylthio, isobutylthio, sec-butylthio, tert-butylthio, pentylthio, isopentylthio, neopentylthio, tert-pentylthio, octylthio, decylthio, dodecylthio, and isooctadecylthio).

Among R3 to R5, the aryl group includes aryl groups having 6 to 10 carbon atoms (such as phenyl, tolyl, dimethylphenyl, and naphthyl).

Of R3 to R5, examples of heterocyclic hydrocarbon groups include heterocyclic hydrocarbon groups having 4 to 20 carbon atoms (such as thienyl, furanyl, pyranyl, pyrrolyl, oxazolyl, thiazolyl, pyridyl, pyrimidyl, pyrazinyl, indolyl, benzofuranyl, benzothienyl, quinolyl, isoquinolyl, quinoxalinyl, quinazolinyl, carbazolyl, acridinyl, phenothiazinyl, phenazinyl, xanthenyl, thianthrenyl, phenoxazinyl, phenoxathiinyl, chromanyl, isochromanyl, dibenzothienyl, xanthonyl, thioxanthonyl, and dibenzofuranyl).

Among R3 to R5, the aryloxy group includes aryloxy groups having 6 to 10 carbon atoms (such as phenoxy and naphthyloxy).

Among R3 to R5, the hydroxy(poly)alkyleneoxy group includes a hydroxy(poly)alkyleneoxy group represented by formula (2).
HO(-R ^X O)q- (2)
R ^X O represents an ethyleneoxy group and/or a propyleneoxy group; q represents an integer of 1 to 5;

Among R3 to R5, halogen atoms include fluorine atoms, chlorine atoms, bromine atoms, and iodine atoms.

R3 to R5 may be the same or different, or may be partially different. When k, m, and n, described below, are each 2 or greater, multiple R3s may be the same or different. Multiple R4s may be the same or different. Multiple R5s may be the same or different.

k represents the number of R3 and is an integer of 0 to 4, preferably 0 to 2, more preferably 0 or 1, and particularly preferably 0.
Furthermore, m represents the number of R4 and is an integer of 0 to 3, preferably 0 or 1, and particularly preferably 0.
Furthermore, n represents the number of R5 and is an integer of 0 to 4, preferably 1 or 2 from the viewpoint of industrial raw material availability, and particularly preferably 2 from the viewpoint of solubility.

There are no limitations on the bonding position of R5, but if it is at the ortho position relative to the C-- ^S bond, the photosensitivity of the sulfonium salt will be better.

In the formula (I0-1), A is a group represented by —O—, —S—, —SO—, —SO ₂ —, or —CO—, and is preferably —S—.

In the formula (I0-1), R1 and R2 are each selected from an aryl group having 6 to 30 carbon atoms, a heterocyclic hydrocarbon group having 4 to 30 carbon atoms, and an alkyl group having 1 to 30 carbon atoms, and some of the hydrogen atoms of these aryl groups, heterocyclic hydrocarbon groups, and alkyl groups may be substituted with a substituent (t).
The substituent (t) is at least one selected from the group consisting of an alkyl group having 1 to 18 carbon atoms, a hydroxy group, an alkoxy group having 1 to 18 carbon atoms, an alkylcarbonyl group having 2 to 18 carbon atoms, an arylcarbonyl group having 7 to 11 carbon atoms, an acyloxy group having 2 to 19 carbon atoms, an arylthio group having 6 to 20 carbon atoms, an alkylthio group having 1 to 18 carbon atoms, an aryl group having 6 to 10 carbon atoms, a heterocyclic hydrocarbon group having 4 to 20 carbon atoms, an aryloxy group having 6 to 10 carbon atoms, a hydroxy(poly)alkyleneoxy group, and a halogen atom. The substituent (t) is the same as the substituents described for R3 to R5.

Of R1 and R2, the aryl group having 6 to 30 carbon atoms includes a monocyclic aryl group and a fused polycyclic aryl group.
Examples of the monocyclic aryl group include phenyl, hydroxyphenyl, toluyl, dimethylphenyl, trimethylphenyl, ethylphenyl, diethylphenyl, triethylphenyl, n-propylphenyl, isopropylphenyl, n-butylphenyl, isobutylphenyl, sec-butylphenyl, tert-butylphenyl, methoxyphenyl, ethoxyphenyl, n-propoxyphenyl, isopropoxyphenyl, n-butoxyphenyl, isobutoxyphenyl, sec-butoxyphenyl, tert-butoxyphenyl, acetylphenyl, benzoylphenyl, naphthoylphenyl, phenylthiophenyl, naphthylthiophenyl, biphenylyl, phenoxyphenyl, naphthoxyphenyl, nitrophenyl, fluorophenyl, chlorophenyl, and bromophenyl.

Fused polycyclic aryl groups include naphthyl, anthracenyl, phenanthrenyl, pyrenyl, chrysenyl, naphthacenyl, benzanthracenyl, anthraquinolyl, fluorenyl, naphthoquinolyl, hydroxynaphthyl, methylnaphthyl, ethylnaphthyl, methoxynaphthyl, ethoxynaphthyl, acetylnaphthyl, benzoylnaphthyl, phenylthionaphthyl, phenylnaphthyl, phenoxynaphthyl, nitronaphthyl, fluoronaphthyl, chloronaphthyl, bromonaphthyl, hydroxyanthracenyl, methylanthracenyl, ethylanthracenyl, methoxyanthracenyl, ethoxyanthracenyl, acetylanthracenyl, benzoylanthracenyl, phenylthioanthracenyl, phenoxyanthracenyl, nitroanthracenyl, fluoroanthracenyl, chloroanthracenyl, and bromoanthracenyl.

Of R1 and R2, heterocyclic hydrocarbon groups having 4 to 30 carbon atoms include cyclic hydrocarbon groups containing 1 to 3 heteroatoms (such as oxygen atoms, nitrogen atoms, and sulfur atoms) in the ring, and include monocyclic heterocyclic hydrocarbon groups and condensed polycyclic heterocyclic hydrocarbon groups.

Examples of monocyclic heterocyclic hydrocarbon groups include thienyl, furanyl, pyranyl, pyrrolyl, oxazolyl, thiazolyl, pyridyl, pyrimidyl, pyrazinyl, hydroxythienyl, methylthienyl, ethylthienyl, methoxythienyl, acetylthienyl, benzoylthienyl, phenylthiothienyl, phenoxythienyl, nitrothienyl, fluorothienyl, chlorothienyl, bromothienyl, hydroxyfuranyl, methylfuranyl, ethylfuranyl, methoxyfuranyl, acetylfuranyl, benzoylfuranyl, phenylthiofuranyl, phenoxyfuranyl, nitrofuranyl, fluorofuranyl, chlorofuranyl, and bromofuranyl.

Fused polycyclic heterocyclic hydrocarbon groups include indolyl, benzofuranyl, isobenzofuranyl, benzothienyl, isobenzothienyl, quinolyl, isoquinolyl, quinoxalinyl, quinazolinyl, carbazolyl, acridinyl, phenothiazinyl, phenazinyl, xanthenyl, thianthrenyl, phenoxazinyl, phenoxathiinyl, chromanyl, isochromanyl, dibenzothienyl, xanthonyl, thioxanthonyl, dibenzofuranyl, hydroxyxanthenyl, and methylxanthenyl. thianthrenyl, ethylxanthenyl, methoxyxanthenyl, acetylxanthenyl, benzoylxanthenyl, phenylthioxanthenyl, phenoxyxanthenyl, nitroxanthenyl, fluoroxanthenyl, chloroxanthenyl, bromoxanthenyl, hydroxythianthrenyl, methylthianthrenyl, ethylthianthrenyl, methoxythianthrenyl, benzoylthianthrenyl, phenylthiothianthrenyl, phenoxythianthrenyl, nitrothianthrenyl, fluorothianthrenyl Examples include thioxanthonyl, chlorothianthrenyl, bromothianthrenyl, hydroxyxanthonyl, methylxanthonyl, dimethylxanthonyl, ethylxanthonyl, diethylxanthonyl, n-propylxanthonyl, isopropylxanthonyl, methoxyxanthonyl, acetylxanthonyl, benzoylxanthonyl, phenylthioxanthonyl, phenoxyxanthonyl, acetoxyxanthonyl, nitroxanthonyl, fluoroxanthonyl, chloroxanthonyl, hydroxythioxanthonyl, methylthioxanthonyl, dimethylthioxanthonyl, ethylthioxanthonyl, diethylthioxanthonyl, n-propylthioxanthonyl, isopropylthioxanthonyl, methoxythioxanthonyl, acetylthioxanthonyl, benzoylthioxanthonyl, phenylthiothioxanthonyl, phenoxythioxanthonyl, acetoxythioxanthonyl, nitrothioxanthonyl, fluorothioxanthonyl, chlorothioxanthonyl, and bromothioxanthonyl.

Among R1 and R2, examples of the alkyl group having 1 to 30 carbon atoms include linear alkyl groups (methyl, ethyl, propyl, butyl, pentyl, octyl, decyl, dodecyl, tetradecyl, hexadecyl, octadecyl, benzyl, diphenylmethyl, naphthylmethyl, anthracenylmethyl, phenacyl (—CH ₂ COC ₆ H ₅ ), naphthoylmethyl, anthoylmethyl, etc.), branched alkyl groups (isopropyl, isobutyl, sec-butyl, tert-butyl, isopentyl, neopentyl, tert-pentyl, isohexyl, etc.), and cycloalkyl groups (cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl, etc.).

R1 and R2 are preferably an aryl group having 6 to 30 carbon atoms, some of whose hydrogen atoms may be substituted with a substituent (t), or a heterocyclic hydrocarbon group having 4 to 30 carbon atoms, some of whose hydrogen atoms may be substituted with a substituent (t). It is more preferable that at least one of R1 or R2 is a heterocyclic hydrocarbon group having 4 to 30 carbon atoms. From the viewpoint of photosensitivity and solubility, it is particularly preferable that R1 is a thioxanthonyl group and R2 is an aryl group having 6 to 30 carbon atoms, some of whose hydrogen atoms may be substituted with a substituent (t).

The substituent (t) is preferably an alkyl group having 1 to 18 carbon atoms, a hydroxy group, an alkoxy group having 1 to 18 carbon atoms, an alkylcarbonyl group having 2 to 18 carbon atoms, or an arylcarbonyl group having 7 to 11 carbon atoms, more preferably an alkyl group or an alkoxy group, and particularly preferably a methyl group, an ethyl group, a propyl group (n-propyl, isopropyl), a butyl group (n-butyl, isobutyl, sec-butyl, tert-butyl), a methoxy group, or an ethoxy group.

The cationic moiety in the component (I0) is preferably a cation in which A in the general formula (I0-1) is a group represented by —S— or —O—, k and m are each 0, and n is an integer of 1 to 4.
Alternatively, the cation moiety in the component (I0) is preferably a cation in which R1 or R2 in the general formula (I0-1) is an aryl group having 6 to 30 carbon atoms or a heterocyclic hydrocarbon group having 4 to 30 carbon atoms (some of the hydrogen atoms of these aryl groups or heterocyclic hydrocarbon groups may be substituted with the substituent (t)).
Alternatively, the cationic moiety in the component (I0) is preferably a cation in which R1 or R2 in general formula (I0-1) is a thioxanthonyl group in which some of the hydrogen atoms may be substituted with the substituent (t), k and m are each 0, n is 1 or 2, and A is a group represented by -S-.

Specific examples of suitable components (I0) are listed below.
The compound represented by chemical formula (I0-1-1) is referred to as "compound (I0-1-1)." The compound represented by chemical formula (I0-1-2) is referred to as "compound (I0-1-2)." The compound represented by chemical formula (I0-1-3) is referred to as "compound (I0-1-3)."

In the negative photosensitive composition of this embodiment, the component (I0) may be used alone or in combination of two or more different compounds.
As the component (I0), at least one selected from the group consisting of the above-mentioned compounds (I0-1-1), (I0-1-2), and (I0-1-3) is preferred, and among these, at least one selected from the group consisting of the compounds (I0-1-1) and (I0-1-2) is more preferred, with the compound (I0-1-1) being even more preferred.
In the negative photosensitive composition of this embodiment, the amount of the component (I0) relative to 100 parts by mass of the component (AS) is preferably 0.1 to 5 parts by mass, more preferably 0.2 to 4 parts by mass, and even more preferably 0.3 to 2 parts by mass.
When the content of the component (I0) is at least the lower limit of the above-mentioned preferred range, stress in the cured film is easily reduced and adhesion to the substrate, etc. is further improved. On the other hand, when the content is at most the upper limit of the above-mentioned preferred range, sensitivity is appropriately controlled and a pattern with a good shape is easily obtained.

[Method for producing borate salt (I0)]
The borate salt (I0) in this embodiment can be produced, for example, by using the method described in "Experimental Chemistry Lectures, 4th Edition, Vol. 24, 1992, published by Maruzen Co., Ltd., p. 376," JP-A Nos. 7-329399, 8-165290, 10-212286, and 10-7680.

<Cationic Polymerization Initiators Other than Borate Salts (IO)>
In the negative photosensitive composition of this embodiment, the component (I) may further contain, in addition to the component (I0), a cationic polymerization initiator other than the component (I0).
Examples of cationic polymerization initiators other than the component (I0) include cationic polymerization initiator (I1) (hereinafter referred to as "component (I1)"), which has a different cationic moiety from the component (I0), a compound represented by the following general formula (I2) (hereinafter referred to as "component (I2)"), and a compound represented by the following general formula (I3-1) or (I3-2) (hereinafter referred to as "component (I3)"):

Regarding component (I1):
The component (I1) is a cationic polymerization initiator having a different cationic moiety from the component (I0).
The anion moiety of the component (I1) is a borate anion, and suitable examples thereof include the anion represented by the above general formula (I0-an).
Suitable examples of the cation moiety of component (I1) include sulfonium cations and iodonium cations, and include organic cations (not having a thioxanthene skeleton) represented by the above general formulas (ca-1) to (ca-5). Of these, the cation moiety is preferably a cation represented by general formula (ca-1).

Specific examples of suitable cations represented by formula (ca-1) include those represented by the following formulas (ca-1-1) to (ca-1-24):

[In the formula, R″ ²⁰¹ is a hydrogen atom or a substituent. Examples of the substituent are the same as those exemplified as the substituents that may be possessed by R ²⁰¹ to R ²⁰⁷ and R ²¹⁰ to R ^212. ]

Furthermore, as the cation represented by formula (ca-1), cations represented by the following general formulas (ca-1-25) to (ca-1-34) are also preferred.

[In the formula, ^R'211 is an alkyl group, and ^Rhal is a hydrogen atom or a halogen atom.]

Furthermore, as the cation represented by formula (ca-1), cations represented by the following chemical formulas (ca-1-36) to (ca-1-46) are also preferred.

Specific examples of suitable cations represented by formula (ca-2) include diphenyliodonium cation and bis(4-tert-butylphenyl)iodonium cation.

Specific examples of suitable cations represented by formula (ca-3) include the cations represented by the following formulas (ca-3-1) to (ca-3-6).

Specific examples of suitable cations represented by formula (ca-4) include the cations represented by the following formulas (ca-4-1) to (ca-4-2).

Furthermore, as the cation represented by formula (ca-5), cations represented by the following general formulas (ca-5-1) to (ca-5-3) are also preferred.

[In the formula, ^R'212 is an alkyl group or a hydrogen atom, and ^R'211 is an alkyl group.]

Regarding component (I2):
The component (I2) is a compound represented by the following general formula (I2-1) or (I2-2).
The component (I2) generates a relatively strong acid upon exposure, and therefore, when a negative-working photosensitive composition containing the component (I) is used to form a pattern, sufficient sensitivity is obtained, resulting in the formation of a good pattern.

[In the formula, R ^b05 represents a fluorine atom or a fluorine atom, and R ^b05 may be the same or different from one another. q represents an integer of 1 or greater, and Q ^q+ represents a q-valent organic cation.]

[In the formula, R ^b06 represents a fluorinated alkyl group which may have a substituent, or a fluorine atom. Multiple R ^b06 may be the same or different. q represents an integer of 1 or greater, and Q ^q+ represents a q-valent organic cation.]

Anion Moiety In the formula (I2-1), R ^b05 represents a fluorine atom or a fluorinated alkyl group which may have a substituent. Multiple R ^b05 may be the same or different.
The fluorinated alkyl group for R ^b05 preferably has 1 to 10 carbon atoms, more preferably 1 to 8 carbon atoms, and even more preferably 1 to 5 carbon atoms. Specific examples include alkyl groups having 1 to 5 carbon atoms in which some or all of the hydrogen atoms have been substituted with fluorine atoms.
Among these, R ^b05 is preferably a fluorine atom or a fluorinated alkyl group having 1 to 5 carbon atoms, more preferably a fluorine atom or a perfluoroalkyl group having 1 to 5 carbon atoms, and even more preferably a fluorine atom, a trifluoromethyl group or a pentafluoroethyl group.

The anion portion of the compound represented by formula (I2-1) is preferably represented by the following general formula (I2-an1):

[In the formula, R ^bf05 represents a fluorinated alkyl group which may have a substituent, and nb ¹ represents an integer of 1 to 5.]

In formula (I2-an1), the optionally substituted fluorinated alkyl group in R ^bf05 is the same as the optionally substituted fluorinated alkyl group exemplified above for R ^b05 .
In formula (I2-an1), nb ¹ is preferably an integer of 1 to 4, more preferably an integer of 2 to 4, and most preferably 3.

In the formula (I2-2), R ^b06 represents a fluorine atom or a fluorinated alkyl group which may have a substituent. Multiple R ^b06 may be the same or different.
The fluorinated alkyl group for R ^b06 preferably has 1 to 10 carbon atoms, more preferably 1 to 8 carbon atoms, and even more preferably 1 to 5 carbon atoms. Specific examples include alkyl groups having 1 to 5 carbon atoms in which some or all of the hydrogen atoms have been substituted with fluorine atoms.
Among these, R ^b06 is preferably a fluorine atom or a fluorinated alkyl group having 1 to 5 carbon atoms, more preferably a fluorine atom or a perfluoroalkyl group having 1 to 5 carbon atoms, and even more preferably a fluorine atom.

Cation Moiety In formula (I2-1) and formula (I2-2), q is an integer of 1 or more, and Q ^q+ is a q-valent organic cation.
Examples of Q ^q+ include the same cations as those in the cation moiety of component (I1).

Regarding component (I3):
The component (I3) is a compound represented by the following general formula (I3-1) or (I3-2).

[In the formula, R ^b11 to R ^b12 are cyclic groups which may have a substituent other than a halogen atom, chain alkyl groups which may have a substituent other than a halogen atom, or chain alkenyl groups which may have a substituent other than a halogen atom, m is an integer of 1 or more, and M ^m+ are each independently an m-valent organic cation.]

{Component (I3-1)}
Anion Moiety In formula (I3-1), R ^b12 is a cyclic group which may have a substituent other than a halogen atom, a chain alkyl group which may have a substituent other than a halogen atom, or a chain alkenyl group which may have a substituent other than a halogen atom, and examples thereof include the cyclic groups, chain alkyl groups, and chain alkenyl groups in the description of R' ²⁰¹ above which have no substituent or which have a substituent other than a halogen atom.
R ^b12 is preferably a chain alkyl group which may have a substituent other than a halogen atom, or an aliphatic cyclic group which may have a substituent other than a halogen atom.
The chain alkyl group preferably has 1 to 10 carbon atoms, and more preferably 3 to 10. The aliphatic cyclic group is more preferably a group in which one or more hydrogen atoms have been removed from adamantane, norbornane, isobornane, tricyclodecane, tetracyclododecane, or the like (which may have a substituent other than a halogen atom); or a group in which one or more hydrogen atoms have been removed from camphor, or the like.
The hydrocarbon group of R ^b12 may have a substituent other than a halogen atom, and examples of the substituent include the same as the substituent other than a halogen atom that may be had by the hydrocarbon group (aromatic hydrocarbon group, aliphatic cyclic group, chain alkyl group) in R ^b11 of formula (I3-2) above.
The phrase "may have a substituent other than a halogen atom" as used herein not only excludes cases where a substituent consisting of only halogen atoms is present, but also excludes cases where a substituent containing at least one halogen atom is present (for example, cases where the substituent is a fluorinated alkyl group, etc.).

Specific examples of preferred anion moieties of component (I3-1) are shown below.

Cation Moiety In formula (I3-1), M ^m+ is an m-valent organic cation.
Suitable examples of the organic cation of M ^m+ include the same cations as those represented by the above general formulae (ca-1) to (ca-5), and among these, the cation represented by the above general formula (ca-1) is more preferred. Among these, sulfonium cations in which at least one of R ²⁰¹ , R ²⁰² , and R ²⁰³ in the above general formula (ca-1) is an organic group having 16 or more carbon atoms (an aryl group, a heteroaryl group, an alkyl group, or an alkenyl group) which may have a substituent are particularly preferred, as they improve resolution and roughness characteristics.
The substituent that the organic group may have is the same as described above, and examples thereof include an alkyl group, a halogen atom, a halogenated alkyl group, a carbonyl group, a cyano group, an amino group, an oxo group (═O), an aryl group, and groups represented by the above formulas (ca-r-1) to (ca-r-10), respectively.
The number of carbon atoms in the organic group (aryl group, heteroaryl group, alkyl group, or alkenyl group) is preferably 16 to 25, more preferably 16 to 20, and particularly preferably 16 to 18. Suitable examples of the organic cation of M ^m+ include the cations represented by the above formulas (ca-1-25), (ca-1-26), (ca-1-28) to (ca-1-34), (ca-1-36), (ca-1-38), and (ca-1-46), and of these, the cation represented by the above formula (ca-1-29) is particularly preferred.

{Component (I3-2)}
Anion Moiety In formula (I3-2), R ^b11 is a cyclic group which may have a substituent other than a halogen atom, a chain alkyl group which may have a substituent other than a halogen atom, or a chain alkenyl group which may have a substituent other than a halogen atom, and examples thereof include the cyclic groups, chain alkyl groups, and chain alkenyl groups in the description of R' ²⁰¹ above which have no substituent or which have a substituent other than a halogen atom.

Among these, R ^b11 is preferably an aromatic hydrocarbon group which may have a substituent other than a halogen atom, an aliphatic cyclic group which may have a substituent other than a halogen atom, or a chain alkyl group which may have a substituent other than a halogen atom. Examples of the substituent which these groups may have include a hydroxyl group, an oxo group, an alkyl group, an aryl group, a lactone-containing cyclic group, an ether bond, an ester bond, or a combination thereof.
When an ether bond or an ester bond is contained as a substituent, it may be connected via an alkylene group, and in this case, the substituent is preferably a linking group represented by each of the following general formulas (y-al-1) to (y-al-7).
In the following general formulae (y-al-1) to (y-al-7), it is V' ¹⁰¹ in the following general formulae (y-al-1) to (y-al-7) that bonds to R ^b11 in the above formula (I3-2).

[In the formula, V' ¹⁰¹ is a single bond or an alkylene group having 1 to 5 carbon atoms, and V' ¹⁰² is a divalent saturated hydrocarbon group having 1 to 30 carbon atoms.]

The divalent saturated hydrocarbon group for V' ¹⁰² is preferably an alkylene group having 1 to 30 carbon atoms, more preferably an alkylene group having 1 to 10 carbon atoms, and even more preferably an alkylene group having 1 to 5 carbon atoms.

The alkylene group in V' ¹⁰¹ and V' ¹⁰² may be a straight-chain alkylene group or a branched-chain alkylene group, with a straight-chain alkylene group being preferred.
Specific examples of the alkylene group in V' ¹⁰¹ and V' ¹⁰² include a methylene group [-CH ₂ -]; alkylmethylene groups such as -CH(CH ₃ )-, -CH(CH ₂ CH ₃ )-, -C(CH ₃ ) ₂ -, -C(CH ₃ )(CH ₂ CH ₃ )-, -C(CH ₃ )(CH ₂ CH ₂ CH ₃ )-, and -C(CH ₂ CH ₃ ) ₂ -; an ethylene group [-CH ₂ CH ₂ -]; alkylethylene groups such as -CH(CH ₃ )CH ₂ -, -CH(CH ₃ )CH(CH ₃ )-, -C(CH ₃ ) ₂ CH ₂ -, and -CH(CH ₂ CH ₃ )CH ₂ -; a trimethylene group (n-propylene group) [-CH ₂ CH _2CH2- ]; alkyltrimethylene groups such as -CH( _CH3 ) _CH2CH2- and _-CH2CH (CH3) _CH2- ; _{tetramethylene} group _{[ -CH2CH2CH2CH2CH2- ]} ; alkyltetramethylene _groups such as -CH( _{CH3 ) CH2CH2CH2CH2- and -CH2CH ( CH3 ) CH2CH2- ;} and _{pentamethylene} group _{[ -CH2CH2CH2CH2CH2CH2- ] .}
In addition, some methylene groups in the alkylene group in V' ¹⁰¹ or V' ¹⁰² may be substituted with a divalent aliphatic cyclic group having 5 to 10 carbon atoms. The aliphatic cyclic group is preferably a divalent group in which one hydrogen atom has been further removed from the cyclic aliphatic hydrocarbon group of R' ²⁰¹ (a monocyclic alicyclic hydrocarbon group, a polycyclic alicyclic hydrocarbon group), and more preferably a cyclohexylene group, a 1,5-adamantylene group, or a 2,6-adamantylene group.

The aromatic hydrocarbon group is more preferably a phenyl group or a naphthyl group.
The aliphatic cyclic group is more preferably a group in which one or more hydrogen atoms have been removed from a polycycloalkane such as adamantane, norbornane, isobornane, tricyclodecane, or tetracyclododecane.
The chain alkyl group preferably has 1 to 10 carbon atoms, and specific examples thereof include straight-chain alkyl groups such as a methyl group, an ethyl group, a propyl group, a butyl group, a pentyl group, a hexyl group, a heptyl group, an octyl group, a nonyl group, and a decyl group; and branched-chain alkyl groups such as a 1-methylethyl group, a 1-methylpropyl group, a 2-methylpropyl group, a 1-methylbutyl group, a 2-methylbutyl group, a 3-methylbutyl group, a 1-ethylbutyl group, a 2-ethylbutyl group, a 1-methylpentyl group, a 2-methylpentyl group, a 3-methylpentyl group, and a 4-methylpentyl group.

R ^b11 is preferably a cyclic group which may have a substituent other than a halogen atom.
Specific examples of preferred anion moieties of the component (I3-2) are shown below.

Cation Moiety In formula (I3-2), M ^m+ is an m-valent organic cation and is the same as M ^m+ in formula (I3-1).

Specific examples of suitable (I3) components are listed below.

In the negative photosensitive composition of this embodiment, the component (I) preferably includes, in addition to the component (I0), at least one selected from the group consisting of the component (I1), the component (I2), and the component (I3), and it is more preferable to use the component (I0) and the component (I3) in combination.
By using the component (I0) and the component (I3) in combination, a pattern with a good shape is more likely to be formed.
When the component (I0) and the component (I3) are used in combination, the content of the component (I0) is preferably 0.1 to 5 parts by mass, more preferably 0.2 to 4 parts by mass, and even more preferably 0.3 to 2 parts by mass, per 100 parts by mass of the component (AS); and the content of the component (I3) is preferably 0.001 to 0.5 parts by mass, more preferably 0.002 to 0.1 parts by mass, and even more preferably 0.005 to 0.05 parts by mass, per 100 parts by mass of the component (AS).
The mixing ratio of the component (I0) to the component (I3), expressed as a mass ratio of the component (I0)/the component (I3), is preferably 30 to 90, more preferably 40 to 80, and even more preferably 50 to 70.

<Other ingredients>
The negative photosensitive composition of this embodiment may contain other components (optional components) as needed, in addition to the components (A) and (I) described above.
If desired, the negative photosensitive composition of the present embodiment may appropriately contain miscible additives such as a metal oxide (M), a silane coupling agent, a sensitizer component, a solvent, an additional resin for improving the performance of the film, a dissolution inhibitor, a basic compound, a plasticizer, a stabilizer, a colorant, and an antihalation agent.

<Metal oxide (M)>
In addition to the component (A) and the component (I), the negative photosensitive composition of this embodiment may further contain a metal oxide (M) (hereinafter also referred to as "component (M)"), because this makes it easier to obtain a cured film with increased strength. By including the component (M), a high-resolution pattern with a good shape can be formed.
Examples of the component (M) include oxides of metals such as silicon (metallic silicon), titanium, zirconium, and hafnium. Of these, silicon oxide is preferred, and among these, silica is particularly preferred.
The component (M) is preferably in the form of particles. Such a particulate component (M) is preferably composed of particles having a volume average particle diameter of 5 to 40 nm, more preferably 5 to 30 nm, and even more preferably 10 to 20 nm.

<Silane coupling agents>
The negative photosensitive composition of this embodiment may further contain an adhesion promoter to improve adhesion between the cured film and the substrate. The adhesion promoter is preferably a silane coupling agent.
Examples of the silane coupling agent include silane coupling agents having a reactive substituent such as a carboxy group, a methacryloyl group, an isocyanate group, an epoxy group, etc. Specific examples include trimethoxysilylbenzoic acid, γ-methacryloxypropyltrimethoxysilane, vinyltriacetoxysilane, vinyltrimethoxysilane, γ-glycidoxypropyltrimethoxysilane, and β-(3,4-epoxycyclohexyl)ethyltrimethoxysilane.
The silane coupling agents may be used alone or in combination of two or more.
When a silane coupling agent is contained, the content of the silane coupling agent is preferably 0.5 to 7 parts by mass, more preferably 0.75 to 5 parts by mass, and even more preferably 1 to 3 parts by mass, per 100 parts by mass of the component (AS).
When the content of the silane coupling agent is within the above-mentioned preferred range, the strength of the cured film is further increased, and in addition, the adhesion between the cured film and the substrate is further strengthened.

<Sensitizer ingredient>
The negative photosensitive composition of this embodiment may further contain a sensitizer component.
The sensitizer component is not particularly limited as long as it can absorb energy from exposure and transfer that energy to another substance.
Specific examples of the sensitizer component that can be used include benzophenone-based photosensitizers such as benzophenone and p,p'-tetramethyldiaminobenzophenone, carbazole-based photosensitizers, acetophenone-based photosensitizers, naphthalene-based photosensitizers such as 1,5-dihydroxynaphthalene, phenol-based photosensitizers, anthracene-based photosensitizers such as 9-ethoxyanthracene, and known photosensitizers such as biacetyl, eosin, rose bengal, pyrene, phenothiazine, and anthrone.

<Solvent>
The negative photosensitive composition of this embodiment may further contain a solvent (hereinafter sometimes referred to as "component (S)").
Examples of the component (S) include lactones such as γ-butyrolactone; ketones such as acetone, methyl ethyl ketone (MEK), cyclohexanone, methyl-n-pentyl ketone, methyl isopentyl ketone, and 2-heptanone; polyhydric alcohols such as ethylene glycol, diethylene glycol, propylene glycol, and dipropylene glycol; compounds having an ester bond such as 2-methoxybutyl acetate, 3-methoxybutyl acetate, 4-methoxybutyl acetate, ethylene glycol monoacetate, diethylene glycol monoacetate, propylene glycol monoacetate, and dipropylene glycol monoacetate; monoalkyl ethers or monoalkyl ethers of the polyhydric alcohols or the compounds having an ester bond such as monomethyl ether, monoethyl ether, monopropyl ether, and monobutyl ether; derivatives of polyhydric alcohols such as compounds having an ether bond, such as propylene glycol monomethyl ether acetate (PGMEA) and propylene glycol monomethyl ether (PGME) are preferred among these; cyclic ethers such as dioxane; esters such as methyl lactate, ethyl lactate (EL), methyl acetate, ethyl acetate, butyl acetate, methyl pyruvate, ethyl pyruvate, methyl methoxypropionate, and ethyl ethoxypropionate; aromatic organic solvents such as anisole, ethyl benzyl ether, cresyl methyl ether, diphenyl ether, dibenzyl ether, phenetole, butyl phenyl ether, ethylbenzene, diethylbenzene, pentylbenzene, isopropylbenzene, toluene, xylene, cymene, and mesitylene; and dimethyl sulfoxide (DMSO).

Component (S) may be used alone or as a mixed solvent of two or more types.

When component (S) is contained, the amount used is not particularly limited, and is set appropriately depending on the coating film thickness at a concentration that allows the negative photosensitive composition to be applied to a substrate or the like without dripping.
For example, the component (S) can be used so that the solids concentration is 50% by mass or more, or the component (S) can be used so that the solids concentration is 60% by mass or more.
Furthermore, an embodiment in which the component (S) is substantially not contained (i.e., an embodiment in which the solid content concentration is 100% by mass) can also be employed.

The negative-type photosensitive composition of this embodiment has a viscosity at 23°C of, for example, 10 to 5000 mPa·s, or may have a viscosity of 30 to 3000 mPa·s, or may have a viscosity of 50 to 2000 mPa·s.

The negative-tone photosensitive composition of this embodiment described above contains an epoxy group-containing compound (AS) that is solid at 25°C, an epoxy group-containing compound (AL) that is liquid at 25°C, and a specific borate salt (I1). By using a borate salt having a cation moiety with a thioxanthene skeleton together with the (AS) and (AL) components, the elastic modulus of the cured film can be maintained high while the stress of the cured film can be reduced. In addition, the inclusion of the (AL) component makes it less likely for undercut to occur during pattern formation, allowing for the formation of a well-shaped pattern.

The negative photosensitive composition of this embodiment is useful as a material for producing hollow encapsulating structures in electronic components.
Furthermore, the negative photosensitive composition of this embodiment can form a film with a thickness required for a spacer in the production of a hollow sealing structure, and can achieve high-resolution patterning with a good shape and no residue.

(Pattern Forming Method)
The pattern formation method of this embodiment includes a step of forming a photosensitive film on a support using the negative photosensitive composition of the above-described embodiment (hereinafter referred to as a "film formation step"), a step of exposing the photosensitive film to light (hereinafter referred to as an "exposure step"), and a step of developing the exposed photosensitive film with a developer containing an organic solvent to form a negative pattern (hereinafter referred to as a "development step").
The pattern forming method of this embodiment can be carried out, for example, as follows.

[Film formation process]
First, the negative photosensitive composition of the above-described embodiment is applied onto a support by a known method such as spin coating, roll coating, or screen printing, and then baked (post-applied bake (PAB)) for 2 to 60 minutes at a temperature of 50 to 150° C., for example, to form a photosensitive film.
The film forming step can also be carried out by disposing the photosensitive composition layer of the aforementioned laminated film on a support.

The support is not particularly limited, and conventionally known supports can be used, such as substrates for electronic components and those on which a predetermined wiring pattern is formed. More specifically, examples include substrates made of metals such as silicon, silicon nitride, titanium, tantalum, lithium tantalate (LiTaO ₃ ), niobium, lithium niobate (LiNbO ₃ ), palladium, tungsten, titanium tungsten, copper, chromium, iron, and aluminum, as well as glass substrates. Examples of materials that can be used for the wiring pattern include copper, aluminum, nickel, and gold.

The pattern forming method of this embodiment is particularly useful for lithium tantalate (LiTaO ₃ ) substrates and lithium niobate (LiNbO ₃ ) substrates used for SAW devices mounted on communication terminals.

The thickness of the photosensitive film formed from the negative-type photosensitive composition is not particularly limited, but is preferably approximately 10 to 100 μm. The negative-type photosensitive composition of the above-described embodiment provides good properties even when a thick film is formed.

[Exposure process]
Next, the formed photosensitive film is selectively exposed using a known exposure device, for example, by exposure through a mask (mask pattern) on which a predetermined pattern has been formed, or by drawing by direct irradiation with an electron beam without using a mask pattern, and then baked (post-exposure bake (PEB)) as needed, for example, at a temperature of 80 to 150° C. for 40 to 1200 seconds, preferably 40 to 1000 seconds, and more preferably 60 to 900 seconds.

The wavelength used for exposure is not particularly limited, and radiation such as ultraviolet light having a wavelength of 300 to 500 nm, i-rays (wavelength 365 nm), or visible light is selectively irradiated (exposed). Examples of radiation sources that can be used include low-pressure mercury lamps, high-pressure mercury lamps, ultra-high-pressure mercury lamps, metal halide lamps, and argon gas lasers.
Here, radiation means ultraviolet light, visible light, far ultraviolet light, X-rays, electron beams, etc. The radiation dose varies depending on the type and amount of each component in the composition, the thickness of the coating film, etc., but for example, when an ultra-high pressure mercury lamp is used, it is 100 to 2000 mJ/ ^cm2 .

The exposure method for the photosensitive film may be normal exposure (dry exposure) performed in air or an inert gas such as nitrogen, or liquid immersion exposure (liquid immersion lithography).

The photosensitive film after the exposure step has high transparency, and for example, the haze value when irradiated with i-line (wavelength 365 nm) is preferably 3% or less, more preferably 1.0 to 2.7%.
As described above, the photosensitive film formed using the negative photosensitive composition of the above-described embodiment has high transparency, which increases light transmittance during exposure in pattern formation, making it easier to obtain a negative pattern with good lithography properties.
The haze value of the photosensitive film after such an exposure step is measured using a method in accordance with JIS K 7136 (2000).

[Development process]
Next, the exposed photosensitive film is developed with a developer containing an organic solvent (organic developer). After development, a rinse treatment is preferably performed. If necessary, a bake treatment (post-bake) may be performed.

The organic solvent contained in the organic developer may be any solvent capable of dissolving component (A) (component (A) before exposure), and may be appropriately selected from known organic solvents. Specific examples include polar solvents such as ketone solvents, ester solvents, alcohol solvents, nitrile solvents, amide solvents, and ether solvents, as well as hydrocarbon solvents.

Examples of ketone solvents include 1-octanone, 2-octanone, 1-nonanone, 2-nonanone, acetone, 4-heptanone, 1-hexanone, 2-hexanone, diisobutyl ketone, cyclohexanone, methylcyclohexanone, phenylacetone, methyl ethyl ketone, methyl isobutyl ketone, acetylacetone, acetonylacetone, ionone, diacetonyl alcohol, acetylcarbinol, acetophenone, methyl naphthyl ketone, isophorone, propylene carbonate, γ-butyrolactone, and methyl amyl ketone (2-heptanone). Among these, methyl amyl ketone (2-heptanone) is preferred as a ketone solvent.

Examples of ester solvents include methyl acetate, butyl acetate, ethyl acetate, isopropyl acetate, amyl acetate, isoamyl acetate, ethyl methoxyacetate, ethyl ethoxyacetate, propylene glycol monomethyl ether acetate (PGMEA), ethylene glycol monoethyl ether acetate, ethylene glycol monopropyl ether acetate, ethylene glycol monobutyl ether acetate, ethylene glycol monophenyl ether acetate, diethylene glycol monomethyl ether acetate, diethylene glycol monopropyl ether acetate, diethylene glycol monoethyl ether acetate, diethylene glycol monophenyl ether acetate, diethylene glycol monobutyl ether acetate, diethylene glycol monoethyl ether acetate, 2-methoxybutyl acetate, 3-methoxybutyl acetate, 4-methoxybutyl acetate, 3-methyl-3-methoxybutyl acetate, 3-ethyl-3-methoxybutyl acetate, propylene glycol monomethyl ether acetate, propylene glycol monoethyl ether acetate, and propylene glycol monomethyl ether acetate. Pyrene glycol monopropyl ether acetate, 2-ethoxybutyl acetate, 4-ethoxybutyl acetate, 4-propoxybutyl acetate, 2-methoxypentyl acetate, 3-methoxypentyl acetate, 4-methoxypentyl acetate, 2-methyl-3-methoxypentyl acetate, 3-methyl-3-methoxypentyl acetate, 3-methyl-4-methoxypentyl acetate, 4-methyl-4-methoxypentyl acetate, propylene glycol diacetate, methyl formate, ethyl formate, butyl formate, propyl formate, milk Examples of suitable ester solvents include ethyl acetate, butyl lactate, propyl lactate, ethyl carbonate, propyl carbonate, butyl carbonate, methyl pyruvate, ethyl pyruvate, propyl pyruvate, butyl pyruvate, methyl acetoacetate, ethyl acetoacetate, methyl propionate, ethyl propionate, propyl propionate, isopropyl propionate, methyl 2-hydroxypropionate, ethyl 2-hydroxypropionate, methyl 3-methoxypropionate, ethyl 3-methoxypropionate, ethyl 3-ethoxypropionate, and propyl 3-methoxypropionate. Among these, butyl acetate or PGMEA is preferred as the ester solvent.

Examples of nitrile solvents include acetonitrile, propionitrile, valeronitrile, and butyronitrile.

The content of organic solvent in the organic developer is typically 90% by mass or more, or may be 95% by mass or more, 98% by mass or more, or 100% by mass, based on the total amount of the organic developer, and is preferably 100% by mass.

The organic developer may contain known additives as needed. Examples of such additives include surfactants. The surfactants are not particularly limited, but may include, for example, ionic or nonionic fluorine-based and/or silicon-based surfactants.
The surfactant is preferably a nonionic surfactant, and more preferably a nonionic fluorine-based surfactant or a nonionic silicon-based surfactant.
When a surfactant is added, the amount added is usually 0.001 to 5% by mass, preferably 0.005 to 2% by mass, and more preferably 0.01 to 0.5% by mass, based on the total amount of the organic developer.

Development can be carried out by known development methods, such as immersing the support in a developer for a certain period of time (dip method), puddling the developer on the support surface using surface tension and leaving it there for a certain period of time (puddle method), spraying the developer onto the support surface (spray method), or continuously dispensing the developer by scanning a developer dispensing nozzle at a constant speed onto a support rotating at a constant speed (dynamic dispense method).

The rinse treatment (cleaning treatment) using a rinse solution can be carried out by a known rinse method, such as a method in which the rinse solution is continuously applied onto a support rotating at a constant speed (spin coating method), a method in which the support is immersed in the rinse solution for a certain period of time (dipping method), or a method in which the rinse solution is sprayed onto the surface of the support (spray method).
The rinsing treatment is preferably carried out using a rinsing liquid containing an organic solvent.

A pattern can be formed through the film formation process, exposure process, and development process described above.

The pattern formation method of the above-described embodiment uses the negative photosensitive composition of the first aspect described above, which makes it less likely to develop undercuts, which are a problem at the interface between the support and the negative pattern, and allows for the formation of patterns with good shapes, for example, highly rectangular shapes. This helps to improve plating defects and reduced mold resistance after structure formation. In addition, the pattern formation method of the embodiment achieves high sensitivity and reduces residue, allowing for the formation of good-shaped patterns.

(cured film)
The cured film of this embodiment is obtained by curing the negative-type photosensitive composition of the above-described embodiment. Since the negative-type photosensitive composition of the first aspect described above is used in this cured film, the stress of the cured film is kept low, peeling from the substrate during reliability testing is unlikely to occur, and adhesion is improved. Additionally, the cured film maintains a high elastic modulus, allowing for the required stress and elastic modulus to be compatible.

(Method for producing cured film)
The method for producing a cured film of the present embodiment includes a step (i) of forming a photosensitive film on a support using the negative photosensitive composition of the above-described embodiment, and a step (ii) of curing the photosensitive film to obtain a cured film.
The operation of step (i) can be performed in the same manner as in the above-mentioned [film formation step]. The baking treatment can be performed, for example, at a temperature of 80 to 150° C. for 40 to 600 seconds.
The curing treatment in step (ii) can be carried out, for example, at a temperature of 100 to 250° C. for 0.5 to 2 hours.
The method for producing a cured film according to the embodiment may include other steps in addition to steps (i) and (ii). For example, the above-described [exposure step] may be included between steps (i) and (ii). In this case, the photosensitive film formed in step (i) may be selectively exposed to light, and the photosensitive film (pre-cured film) may be cured after being subjected to post-exposure bake (PEB) treatment as necessary to obtain a cured film.
According to the method for producing a cured film of the embodiment described above, a cured film that faithfully reproduces a mask pattern can be easily produced.

The present invention will be explained in more detail below using examples, but the present invention is not limited to these examples.

<Preparation of negative photosensitive composition>
(Examples 1 to 6, Comparative Examples 1 to 5)
The components shown in Table 1 were mixed and dissolved, and the mixture was filtered using a PTFE filter (pore size 1 μm, manufactured by PALL Corporation) to prepare negative-type photosensitive compositions (solutions with a solids content of 78% by mass) for each example.

In Table 1, the abbreviations have the following meanings: The numbers in brackets [ ] are the amounts of each component blended (parts by mass; solid content equivalent).
(A)-1: Novolac epoxy resin represented by the following chemical formula (A1-1), product name "jER157S70", manufactured by Mitsubishi Chemical Corporation, softening point 70°C, epoxy equivalent 200 to 220 g/eq.

(A)-2: Phenol novolac epoxy resin. Product name: "EPICLON N770", manufactured by DIC Corporation. Softening point: 65-75°C, epoxy equivalent: 180-200g/eq.

(A)-3: Bisphenol A epoxy resin represented by the following chemical formula (abp1-1). Product name: "EPICLON 1055," manufactured by DIC Corporation. In formula (abp1-1), n is the number of repeating units of the structure in parentheses. Softening point: 62-73°C, epoxy equivalent: 450-500 g/eq.

(A)-4: A liquid epoxy-containing compound represented by the following chemical formula (AL1-1). Product name: "TEPIC-VL," manufactured by Nissan Chemical Industries, Ltd. Epoxy equivalent: 125-145 g/eq.

(I)-1: The following compound (I0-1-1).
(I)-2: The following compound (I0-1-2).

(I)-3: A cationic polymerization initiator represented by the following chemical formula (I2-1-1).
(I)-4: A cationic polymerization initiator represented by the following chemical formula (I2-1-2).
(I)-5: A cationic polymerization initiator represented by the following chemical formula (I1-1).
(I)-6: A cationic polymerization initiator represented by the following chemical formula (I3-1-1).

Add-1: A compound represented by the following chemical formula (SC-1).
(S)-1: Methyl ethyl ketone.

<Evaluation>
The negative photosensitive composition of each example was evaluated for stress when formed into a cured film.
Furthermore, a reliability test was carried out on the hollow structure produced using the negative photosensitive composition of each example, and the presence or absence of peeling between the hollow structure and the substrate was evaluated.
Furthermore, the elastic modulus of each negative photosensitive composition when formed into a cured film was evaluated.
Furthermore, a hole pattern was formed using the negative photosensitive composition of each example, and the state of undercut occurrence at the wafer interface was observed to evaluate the pattern shape.

[Evaluation of stress of cured film]
The "warpage amount" of a 6-inch silicon wafer having a thickness of 625 μm±25 μm was measured in advance using a residual stress measuring device (manufactured by Tencor Corporation, model name FLX3300-T).
The negative photosensitive composition of each example was uniformly applied onto the 6-inch silicon wafer using an applicator, and then subjected to baking treatment (PAB) at a heating temperature of 115°C for 5 minutes to form a photosensitive film (film thickness 20 μm).
Next, the photosensitive film was exposed to an exposure dose of 200 mJ/cm ² (ghi broadband).
Next, the exposed photosensitive film was post-exposure baked on a hot plate at 90° C. for 5 minutes to obtain a pre-cured film.
The resulting pre-cured film was then cured by heating at 200° C. for 1 hour in a nitrogen atmosphere to obtain the desired cured film.

The amount of warpage of the 6-inch silicon wafer on which the cured film was formed was measured using the residual stress measuring device, and the stress [MPa] generated between the silicon wafer and the cured film was evaluated. The evaluation results are shown in Table 2.
In the evaluation of the stress of the cured film, those rated as "◯" had a stress of 24 MPa or less, and those rated as "×" had a stress of more than 24 MPa.

[Reliability test]
The negative photosensitive compositions of each example were used for the wall and roof materials, and hollow structures were fabricated as follows. A Si substrate was used as the substrate. A reliability test was then conducted on the hollow structures.

<Manufacturing of hollow structures>
Each negative photosensitive composition of each example was uniformly applied onto a Si substrate using an applicator, and then baked (PAB) at a heating temperature of 115° C. for 5 minutes to form a photosensitive film (film thickness 20 μm).
The photosensitive film was then exposed to a Suss MABA8 Gen4 pro aligner at a dose of 200 mJ/cm ² (ghi broadband).
Next, the exposed photosensitive film was post-exposure baked on a hot plate at 90° C. for 5 minutes to obtain a pre-cured film.
Next, puddle development was carried out at 23° C. for 120 seconds using PGMEA as a developer, and after shaking off and drying, the film was heated at 200° C. for 1 hour in a nitrogen atmosphere to be cured.
As a result, a walled substrate was obtained in which a recess pattern was formed on the Si substrate, with the periphery of a square measuring 1170 μm in length and 1500 μm in width being surrounded by a 50 μm-wide sidewall made of the cured film.

Next, a photosensitive resist film adjusted to a film thickness of 30 μm corresponding to the negative photosensitive composition of each example was arranged (laminated) so as to cover the opening of the recess in the walled substrate. That is, the same negative photosensitive composition was used for the side walls (Wall) and the top plate part (Roof (Roof) covering the opening of the recess) of the hollow structure.
Next, the photosensitive resist film was prepared using a Suss MABA8 Gen4 pro aligner, and exposed to 200 mJ/cm ² (i-line equivalent) through a predetermined mask pattern.
Next, the photosensitive resist film after the exposure was subjected to post-exposure heating on a hot plate at a temperature of 90° C. for 5 minutes.
Next, the photosensitive resist film after exposure and baking was subjected to puddle development at 23°C for 120 seconds using PGMEA as a developer, thereby forming a roof pattern that would become the top plate portion (the roof that covers the opening surface of the recess).
The roof pattern was further cured by heat treatment in an oven at 200° C. for 60 minutes to produce a hollow structure (cavity size: length 1170 μm×width 1500 μm×height 50 μm).

[Reliability test]
The hollow structures produced using the negative photosensitive compositions of each example were placed in a thermostatic chamber, and a heat cycle test was carried out in which the temperature in the thermostatic chamber in which the hollow structures were placed was increased from room temperature to 125°C, maintained at 125°C for 15 minutes, cooled to -55°C, maintained at -55°C for 15 minutes, and then returned to room temperature, repeating this cycle 100 times.
After the heat cycle test of 100 cycles was completed, the hollow structure was observed, and the reliability was evaluated by a microscope to see whether or not there was any peeling between the Si substrate and the hollow structure.
Those in which no peeling occurred between the Si substrate and the hollow structure were evaluated as "good", and those in which peeling occurred were evaluated as "poor".

[Evaluation of Elastic Modulus of Cured Film]
Each of the negative photosensitive compositions of the examples was uniformly applied onto a 6-inch silicon wafer using an applicator, and then subjected to baking treatment (PAB) at a heating temperature of 115°C for 5 minutes to form a photosensitive film (film thickness 20 µm).
Next, the photosensitive film was exposed to an exposure dose of 200 mJ/cm ² (ghi broadband).
Next, the exposed photosensitive film was post-exposure baked on a hot plate at 90° C. for 5 minutes to obtain a pre-cured film.
Next, puddle development was carried out at 23°C for 120 seconds using propylene glycol monomethyl ether acetate (PGMEA) as a developer, and after shaking off and drying, the film was heated in a nitrogen atmosphere at 200°C for 1 hour to be cured, thereby obtaining a square cured film of 5 mm x 10 mm.
The strength of the resulting cured film was evaluated using the hot elastic modulus as an index. The hot elastic modulus was measured as follows. The measurement results are shown in Table 2.
The resulting cured film was peeled off from the silicon wafer, and the hot elastic modulus (E*/GPa) of the cured film at 175° C. was measured using the following evaluation device and measurement conditions.
Evaluation device: Reogel E-4000 (manufactured by UBM)
Measurement conditions: tension mode, frequency 1 MHz, chuck distance 10 mm
In the evaluation of the elastic modulus of the cured film, those rated as "○" had an elastic modulus of 1.5 GPa or more when hot, and those rated as "×" had an elastic modulus of less than 1.5 GPa when hot.

[Evaluation of Pattern Shape]
Using the negative photosensitive compositions of the respective examples, attempts were made to form negative patterns as follows.

Film formation process:
Each of the negative photosensitive compositions of the examples was applied onto a silicon substrate using a spinner, and the applied photosensitive composition was pre-baked (PAB) on a hot plate at a temperature of 115°C for 5 minutes, followed by drying to form a photosensitive film having a thickness of 20 µm.

Exposure process:
Next, the photosensitive film was irradiated with ghi rays with a gap of 30 μm.
Thereafter, post-exposure baking was carried out on a hot plate at 90° C. for 5 minutes.

Development process:
Next, development was carried out for 120 seconds using propylene glycol monomethyl ether acetate (PGMEA) to attempt to form a negative pattern, resulting in the formation of a hole pattern with a diameter of 60 μm.

The cross-sectional shape of the hole pattern formed by the above-mentioned film formation step, exposure step, and development step was observed with a scanning electron microscope (product name: S4500; manufactured by Hitachi, Ltd.), and the occurrence of undercuts (notches at the periphery of the negative pattern image (residual film) in contact with the silicon substrate) was evaluated based on the following evaluation criteria. The results are shown in Table 2.
Undercut evaluation criteria:
The notch state of the peripheral portion of the negative pattern image (residual film) in contact with the silicon substrate was evaluated as "Good" when the angle between the silicon substrate surface and the notch surface of the residual film was 80° or more, and the angle was evaluated as "Poor" when the angle was less than 80°.

The results shown in Table 2 confirm that the negative photosensitive compositions of Examples 1 to 6 to which the present invention is applied can suppress the stress of the cured film when formed into a cured film, and in a reliability test, no peeling occurred between the Si substrate and the hollow structure, making it possible to form a highly reliable cured film.
In addition, it can be confirmed that the cured films formed from the negative photosensitive compositions of Examples 1 to 6 maintain a high modulus of elasticity, are less likely to develop undercuts, and have excellent pattern shapes.
On the other hand, the negative photosensitive compositions of Comparative Examples 1 to 5, which are outside the scope of the present invention, showed poor evaluation results in any of the stress and reliability tests, elastic modulus, and pattern shape.

Claims (4)

A negative photosensitive composition containing an epoxy group-containing compound (A) and a cationic polymerization initiator (I),
The epoxy group-containing compound (A) includes an epoxy group-containing compound (AS) that is solid at 25°C and an epoxy group-containing compound (AL) that is liquid at 25°C,
the epoxy group-containing compound (AS) contains a novolac epoxy resin,
The epoxy group-containing compound (AL) includes a compound represented by the following general formula (AL1):
The cationic polymerization initiator (I) contains a sulfonium salt represented by the following general formula (I0-1) and a compound represented by the following general formula (I3-1) :
A negative photosensitive composition, wherein the bonding position of at least one R5 in the general formula (I0-1) is the ortho position relative to the C—S ⁺ bond .
[In the formula, ^REP is an epoxy group-containing group. Multiple ^REPs may be the same or different.]
In formula (I0-1), R ^b01 to R ^b04 each independently represent an aryl group which may have a substituent, or a fluorine atom.
R1 represents a thioxanthonyl group and R2 represents an aryl group having 6 to 30 carbon atoms, and some of the hydrogen atoms of the thioxanthonyl group or aryl group may be substituted with a substituent (t). The substituent (t) is an alkyl group having 1 to 18 carbon atoms. R3 to R5 each independently represent an alkyl group . k, m, and n represent the number of R3, R4, and R5, respectively, where k is an integer of 0 to 4, m is an integer of 0 to 3, and n is 2. When k and m are each 2 or greater, multiple R3s and multiple R4s may be the same or different. Two R5s may be the same or different. A is a group represented by -S-, -O-, -SO-, -SO ₂ -, or -CO-. B is a boron atom, O is an oxygen atom, and S is a sulfur atom.]
[In the formula, R ^b12 represents a cyclic group which may have a substituent other than a halogen atom, a chain alkyl group which may have a substituent other than a halogen atom, or a chain alkenyl group which may have a substituent other than a halogen atom, m represents an integer of 1 or more, and M ^m+ represents an m-valent organic cation.] 2. The negative photosensitive composition according to claim 1 , wherein the novolac epoxy resin comprises a resin represented by the following general formula (A1):
[In the formula, R ^p1 and R ^p2 each independently represent a hydrogen atom or an alkyl group having 1 to 5 carbon atoms. Multiple R ^p1s may be the same as or different from one another. Multiple R ^p2s may be the same as or different from one another. _n1 is an integer of 1 to 5. R ^EP is an epoxy group-containing group. Multiple R ^EPs may be the same as or different from one another.] 3. A pattern forming method comprising the steps of: forming a photosensitive film on a support using the negative photosensitive composition according to claim 1 ; exposing the photosensitive film; and developing the exposed photosensitive film with a developer containing an organic solvent to form a negative pattern. A photosensitive film formed using the negative photosensitive composition according to claim 1 or 2 .