Salt compound, resist composition and patterning process

Abstract

To provide a resist composition having superior lithographic performance such as CDU and LWR, without impairing sensitivity, in photolithography using high-energy rays; an acid diffusion inhibitor used in the resist composition; and a patterning process using the resist composition.SOLUTION: The present invention provides a salt compound represented by a formula (2), an acid diffusion inhibitor comprising the salt compound, and a resist composition comprising the acid diffusion inhibitor.SELECTED DRAWING: None

Description

Technical Field

[0001] The present invention relates to a salt compound, a resist composition, and a patterning method.

Background Art

[0002] In recent years, with the increasing integration and speed of LSIs, the miniaturization of pattern rules has been required, and as high-resolution resist patterns have been demanded, in addition to lithography characteristics typified by pattern shape, contrast, Mask Error Factor (MEF), Depth of Focus (DOF), Critical Dimension Uniformity (CDU), Line Width Roughness (LWR), etc., improvement of defects in the resist pattern after development has been increasingly required.

[0003] In particular, LWR has been regarded as a problem along with the miniaturization of patterns. The influence of uneven distribution and aggregation of the base polymer and acid generator, and the influence of acid diffusion have been pointed out. Furthermore, LWR tends to increase as the resist film becomes thinner, and the deterioration of LWR due to thinning accompanying the progress of miniaturization has become a serious problem.

[0004] In a resist composition for extreme ultraviolet (EUV) lithography, it is necessary to simultaneously achieve high sensitivity, high resolution, and low LWR. When the acid diffusion distance is shortened, LWR becomes smaller, but the sensitivity decreases. For example, when the post-exposure bake (PEB) temperature is lowered, LWR becomes smaller, but the sensitivity decreases. Even when the addition amount of an acid diffusion inhibitor (quencher) is increased, LWR becomes smaller, but the sensitivity decreases. It is necessary to break the trade-off relationship between sensitivity and LWR.

[0005] In order to break the trade-off relationship between sensitivity and LWR, various additives have been studied. Starting from the structural optimization of photoacid generators and acid diffusion inhibitors such as amines and weak acid onium salts, increasing the sensitivity by adding acid proliferators, and in Patent Documents 1 to 3, studies have been conducted on additives incorporating the shape correction effect by the surface-localized acids, amines, and weak acid onium salt-type acid diffusion inhibitors shown below. However, a resist composition that can satisfy all of sensitivity, LWR, and CDU has not yet been developed. [Chemical formula] [Prior Art Documents] [Patent Documents]

[0006] [Patent Document 1] Japanese Patent Application Laid-Open No. 2019-218340 [Patent Document 2] Japanese Patent Application Laid-Open No. 2019-026637 [Patent Document 3] Japanese Patent Application Laid-Open No. 2019-034931 [Summary of the Invention] [Problems to be Solved by the Invention]

[0007] In response to the requirements for high-resolution resist patterns in recent years, in resist compositions using conventional acid diffusion inhibitors, lithography performance such as CDU and LWR may not always be satisfactory.

[0008] The present invention has been made in view of the above circumstances, and in photolithography using high-energy rays such as KrF excimer laser light, ArF excimer laser light, electron beam (EB), EUV, etc., a resist composition excellent in lithography performance such as CDU and LWR without sacrificing sensitivity, an acid diffusion inhibitor used therein, and a pattern forming method using the resist composition are provided. [Means for Solving the Problems]

[0009] As a result of intensive studies to achieve the above object, the present inventors have found that a resist composition using an onium salt having a predetermined structure as an acid diffusion inhibitor is excellent in lithography performance such as CDU and LWR, and is extremely effective for precise microfabrication, and thus have completed the present invention.

[0010] That is, the present invention provides the following salt compound, resist composition, and pattern forming method. 1. A salt compound represented by the following formula (2). [Chemical formula] [In the formula, n is an integer of 1 to 5. m is an integer of 0 to 4. L is a single bond, an ether bond, or an ester bond. When n is 2 or more, each L may be the same or different. R 1F is a fluorinated alkyl group having 4 to 18 carbon atoms, and -CH2- in the alkyl group may be substituted with an ether bond or a carbonyl group. However, R 1F has at least two groups selected from -CF2- and -CF3. Further, the fluorinated alkyl group may contain a ring structure selected from a cyclopentane ring, a cyclohexane ring, an adamantane ring, a norbornyl ring, and a benzene ring as a partial structure at the terminal or between carbon-carbon bonds. R 2 is a halogen atom, a hydroxy group, or a hydrocarbyl group having 1 to 10 carbon atoms, a hydrogen atom in the hydrocarbyl group may be substituted with a halogen atom, and -CH2- in the hydrocarbyl group may be substituted with an ether bond or a carbonyl group. M + is a sulfonium cation or an iodonium cation. A - is an anion represented by any one of the following formulas (A1) to (A4). However, when A - is an anion represented by the following formula (A2), R in formula (2) 1FThe partial structure represented by -L- and the benzene ring are bonded via -CH2- or -O-. [Chemical formula] (In the formula, R f1 is a hydrogen atom or a fluorine atom. R f2 and R f3 are each independently a methyl group, a phenyl group, a tolyl group, or a C1-C4 perfluoroalkyl group. The dashed line represents a bond.) 2. A - is a salt compound of 1, which is an anion represented by formula (A1) or (A2). 3. In 1 or 2, m is 1 or more, and at least one of R 2 is an iodine atom. 4. M + is a salt compound of any one of 1 to 3, which is a cation represented by any one of the following formulas (M-1) to (M-3). [Chemical formula] (In the formula, R M1 , R M2 , R M3 , R M4 and R M5 are each independently a hydroxy group, a halogen atom, or a C1-C15 hydrocarbyl group, and some or all of the hydrogen atoms in the hydrocarbyl group may be substituted with a group containing a heteroatom, and -CH2- in the hydrocarbyl group may be substituted with -O-, -C(=O)-, -S-, -S(=O)-, -S(=O)2- or -N(H)-. k 1 , k 2 , k 3 , k 4 and k 5 are each independently an integer from 0 to 5. When k 1 is 2 or more, each R M1 may be the same or different, and two R M1 may combine with each other to form a ring together with the carbon atom on the benzene ring to which they are attached. When k 2 is 2 or more, each RM2 may be the same or different, and two Rs M2 may combine with each other to form a ring together with the carbon atom on the benzene ring to which they are attached. k 3 When k is 2 or more, each R M3 may be the same or different, and two Rs M3 may combine with each other to form a ring together with the carbon atom on the benzene ring to which they are attached. k 4 When k is 2 or more, each R M4 may be the same or different, and two Rs M4 may combine with each other to form a ring together with the carbon atom on the benzene ring to which they are attached. k 5 When k is 2 or more, each R M5 may be the same or different, and two Rs M5 may combine with each other to form a ring together with the carbon atom on the benzene ring to which they are attached. X is a single bond, -CH2-, -O-, -C(=O)-, -S-, -S(=O)-, -S(=O)2- or -N(H)-.) 5. The salt compound according to claim 4, comprising an anion represented by the following formula (2-I) and a cation represented by the formula (M-1) or (M-2).

Chemical formula

Chemical formula

Chemical formula

Chemical formula

Advantages of the Invention

[0011] When pattern formation is performed using the resist composition containing the salt compound of the present invention as an acid diffusion inhibitor, it becomes possible to form a pattern excellent in lithography performance such as CDU, LWR, and DOF.

Brief Description of the Drawings

[0012]

Figure 1

Figure 2

Figure 3

[0013] The present invention will be described in detail below. In the following description, depending on the structure represented by the chemical formula, there may be asymmetric carbons and enantiomers or diastereomers may exist. In such cases, these isomers are represented by one formula on behalf of them. These isomers may be used alone or in combination of two or more.

[0014] [Salt compound] The salt compound of the present invention is represented by the following formula (1) or (2). [Chemical formula]

[0015] In formulas (1) and (2), n is an integer from 1 to 5, preferably 1 or 2. m is an integer from 0 to 4, preferably from 0 to 2.

[0016] In formulas (1) and (2), L is a single bond, an ether bond or an ester bond. When n is 2 or more, each L may be the same or different. As L, an ether bond is preferred.

[0017] In formula (1), R 1 is an alkyl group having 6 to 18 carbon atoms, and -CH2- in the alkyl group may be substituted with an ether bond or a carbonyl group. However, R 1 has at least one linear structure having 6 or more carbon atoms. When n is 2 or more, each R 1 may be the same or different.

[0018] R 1Examples of the alkyl group having 6 to 18 carbon atoms represented by include 1-hexyl group, 1-heptyl group, 1-octyl group, 1-nonyl group, 1-decyl group, 1-undecyl group, 1-dodecyl group, 1-tridecyl group, 1-tetradecyl group, 1-hexadecyl group, 1-octadecyl group, octan-2-yl group, decan-2-yl group, decan-4-yl group, octadecane-8-yl group, 7,7-dimethyloctyl group, 7,7-diethylnonyl group, 4-butyldodecyl group, and the like. Further, as a partial structure, the alkyl group may have a cyclic group, such as a cyclopentane ring, a cyclohexane ring, an adamantane ring, a norbornane ring or a benzene ring, between the terminal or the chain structure. Further, -CH2- in the group may be substituted with an ether bond or a carbonyl group, and as a result, an ester bond or a lactone ring may be formed. R 1 is preferably a linear alkyl group or a linear glyme chain.

[0019] In formula (2), R 1F is a fluorinated alkyl group having 4 to 18 carbon atoms, and -CH2- in the alkyl group may be substituted with an ether bond or a carbonyl group. However, R 1F has at least two groups selected from -CF2- and -CF3.

[0020] R 1FExamples of the fluorinated alkyl group having 4 to 18 carbon atoms represented by [the formula] include groups in which some or all of the hydrogen atoms of, for example, a 1-butyl group, 1-pentyl group, 1-hexyl group, 1-heptyl group, 1-octyl group, 1-nonyl group, 1-decyl group, 1-undecyl group, 1-dodecyl group, 1-tridecyl group, 1-tetradecyl group, 1-hexadecyl group, 1-octadecyl group, octan-2-yl group, decan-2-yl group, decan-4-yl group, octadecane-8-yl group, 7,7-dimethyloctyl group, 7,7-diethylnonyl group, 4-butyldodecyl group, etc. are substituted with fluorine atoms. Further, as a partial structure, the fluorinated alkyl group may have a cyclic group, for example, a cyclopentane ring, cyclohexane ring, adamantane ring, norbornyl ring or benzene ring, between the terminal or the chain structure. Further, -CH2- in the group may be substituted with an ether bond or a carbonyl group, and as a result, an ester bond or a lactone ring may be formed.

[0021] R 1F The following are preferred. In the following formulas, the dashed line represents a bond.

Chemical formula

[0022] In formulas (1) and (2), R 2 is a halogen atom, a hydroxy group or a hydrocarbyl group having 1 to 10 carbon atoms, and the hydrogen atom in the hydrocarbyl group may be substituted with a halogen atom, and -CH2- in the hydrocarbyl group may be substituted with an ether bond or a carbonyl group. R 2Examples include a fluorine atom, an iodine atom, a hydroxy group, a methyl group, a trifluoromethyl group, a methoxy group, a trifluoromethoxy group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, a sec-butyl group, a tert-butyl group, a cyclohexyl group, a phenyl group, an adamantyl group, a 2,2,2-trifluoroethoxy group, a 2-methoxyethoxy group, a 2-hydroxy-2-trifluoromethyl-3,3,3-trifluoropropoxy group, an acetyl group, an acetoxy group, and the like. Among these, a hydroxy group, a fluorine atom, an iodine atom, a trifluoromethyl group, a methyl group, a tert-butyl group, and the like are preferable.

[0023] In formulas (1) and (2), A - is an anion represented by any of the following formulas (A1) to (A4). However, when A - is an anion represented by the following formula (A2), the partial structure represented by R 1 -L- or R 1F -L- and the benzene ring are bonded via -CH2- or -O-.

Chemical formula

[0024] In formulas (A1) to (A4), R f1 is a hydrogen atom or a fluorine atom, preferably a fluorine atom. R f2 and R f3 are each independently a methyl group, a phenyl group, a tolyl group, or a C1-C4 perfluoroalkyl group, preferably a perfluoromethyl group.

[0025] A - is preferably an anion represented by formula (A1) or (A2), more preferably an anion represented by formula (A1).

[0026] Specific examples of the anion of the salt compound represented by formula (1) include, but are not limited to, those shown below. [Chemistry]

[0027] [Chemistry]

[0028] [Chemistry]

[0029] [Chemistry]

[0030] Specific examples of the anion of the salt compound represented by formula (2) include, but are not limited to, those shown below. [Chemistry]

[0031] [Chemistry]

[0032] [Chemistry]

[0033] In formulas (1) and (2), M + is a sulfonium cation or an iodonium cation. As M + , a cation having one or more benzene rings bonded to the cation center is preferred, and a cation represented by any of the following formulas (M-1) to (M-3) is more preferred. [Chemistry]

[0034] In formulas (M-1) to (M-3), R M1 , RM2 、 R M3 、 R M4 and R M5 are each independently a hydroxy group, a halogen atom, or a hydrocarbyl group having 1 to 15 carbon atoms.

[0035] Examples of the halogen atom include a fluorine atom, a chlorine atom, a bromine atom, and an iodine atom. The hydrocarbyl group having 1 to 15 carbon atoms may be saturated or unsaturated, and may be linear, branched, or cyclic. Specific examples thereof include alkyl groups such as a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, a sec-butyl group, a tert-butyl group, an n-pentyl group, an n-hexyl group, an n-octyl group, an n-nonyl group, and an n-decyl group; cycloaliphatic hydrocarbyl groups such as a cyclopentyl group, a cyclohexyl group, and an adamantyl group; aromatic hydrocarbyl groups such as a phenyl group; groups obtained by combining these; and the like. Further, some or all of the hydrogen atoms in the hydrocarbyl group may be substituted with a group containing a hetero atom such as an oxygen atom, a sulfur atom, a nitrogen atom, or a halogen atom, and -CH2- in the hydrocarbyl group may be substituted with -O-, -C(=O)-, -S-, -S(=O)-, -S(=O)2-, or -N(H)-. That is, the hydrocarbyl group may contain a hydroxy group, a cyano group, a carbonyl group, an ether bond, an ester bond, an amide bond, a thioether bond, a sulfonate ester bond, a carbonate bond, a lactone ring, a sultone ring, a carboxylic acid anhydride (-C(=O)-O-C(=O)-), a haloalkyl group, or the like. Note that -CH2- in the hydrocarbyl group may be bonded to a carbon atom of the benzene ring in formulas (M-1) to (M-3). At this time, R M1 ~R M5 may be a hydrocarbyloxy group, a hydrocarbylcarbonyloxy group, a hydrocarbylthio group, a hydrocarbylcarbonyl group, a hydrocarbylsulfonyl group, a hydrocarbylamino group, or the like.

[0036] In formulas (M-1) to (M-3), k 1 、 k 2 、 k 3 、 k4 and k 5 is, independently of one another, an integer from 0 to 5. When k 1 is 2 or more, each R M1 may be the same or different, and two R M1 may be bonded to each other to form a ring together with the carbon atoms on the benzene ring to which they are bonded. When k 2 is 2 or more, each R M2 may be the same or different, and two R M2 may be bonded to each other to form a ring together with the carbon atoms on the benzene ring to which they are bonded. When k 3 is 2 or more, each R M3 may be the same or different, and two R M3 may be bonded to each other to form a ring together with the carbon atoms on the benzene ring to which they are bonded. When k 4 is 2 or more, each R M4 may be the same or different, and two R M4 may be bonded to each other to form a ring together with the carbon atoms on the benzene ring to which they are bonded. When k 5 is 2 or more, each R M5 may be the same or different, and two R M5 may be bonded to each other to form a ring together with the carbon atoms on the benzene ring to which they are bonded.

[0037] In formula (M-2), X is a single bond, -CH2-, -O-, -C(=O)-, -S-, -S(=O)-, -S(=O)2- or -N(H)-.

[0038] M + Specific examples of the sulfonium cation represented by include, but are not limited to, those shown below. In the following formulas, Me is a methyl group and tBu is a tert-butyl group.

Chemical formula

[0039]

Chemical formula

[0040]

Chem.

[0041]

Chem.

[0042] M + Specific examples of the iodonium cation represented by M include, but are not limited to, those shown below. In the following formulas, Me is a methyl group and tBu is a tert-butyl group.

Chem.

[0043] As the salt compound represented by formula (1) or (2), a salt composed of a combination of an anion represented by the following formula (1-I) or (2-I) and a cation represented by formula (M-1) or (M-2) is preferred.

Chem.

[0044] As the salt compound represented by formula (1) or (2), a salt composed of a combination of the following anions and cations is particularly preferred. [Chemistry]

[0045] [Chemistry]

[0046] The salt compound of the present invention can be synthesized, for example, according to the method shown below. [Chemistry] (In the formula, R 1 , R 2 , M + , m and n are the same as described above. R is a hydrogen atom, a methyl group, or a 2,2,2-trifluoroethyl group. L a is an ether bond or an ester bond. X A is a chlorine atom, a bromine atom, or an iodine atom when L a is an ether bond, and is -C(=O)-Cl when L a is an ester bond. M B + is a monovalent metal ion or a tetramethylammonium cation. X B - is an anion.)

[0047] In the first step, the phenol derivative (A) is reacted with a halide (R 1 -X A ) under basic conditions to perform etherification, thereby synthesizing the intermediate (B). Also, the halide (R 1 -X A) When using acid chloride, esterification can be carried out by reacting with the phenol derivative (A) under basic conditions in the same manner to synthesize the intermediate (B). The etherification reaction can be carried out using a base such as sodium carbonate, potassium carbonate, cesium carbonate, sodium hydroxide, etc. in a polar solvent such as N-methylpyrrolidone, N,N-dimethylformamide, acetonitrile, etc. The esterification reaction can be carried out by reacting with a base such as triethylamine, diisopropylethylamine, pyridine, N,N-dimethylaminopyridine, etc. in a solvent such as methylene chloride, acetonitrile, etc.

[0048] In the second step, the intermediate (B) is hydrolyzed with a hydroxide salt (M B + OH - ) to obtain the intermediate (C). Examples of the hydroxide salt (M B + OH - ) include lithium hydroxide, sodium hydroxide, potassium hydroxide, and tetramethylammonium hydroxide. Examples of the reaction solvent include tetrahydrofuran (THF), dioxane, water, or a mixed solvent thereof.

[0049] In the third step, the target compound (D) is obtained by ion exchange using the intermediate (C) having the target anion structure and the salt (M + X B - ) having the target cation structure. This ion exchange reaction can be easily achieved by a known method, and for example, JP-A-2007-145797 can be referred to.

[0050] Note that the above-described synthesis method is merely an example, and the present invention is not limited thereto.

[0051] The resist composition using the salt compound represented by the formula (1) or (2) as an acid diffusion inhibitor is excellent in LWR and CDU. The reason for this is presumed as follows, although the details are unclear.

[0052] In the salt compound of the present invention, the anion has a linear structure with 6 or more carbon atoms or a fluorine atom-containing chain structure with 4 or more carbon atoms. By having these groups, it is considered that the acid diffusion inhibitor composed of the salt compound of the present invention is unevenly distributed in the surface layer of the resist film, so that the quencher concentration increases toward the surface layer and the concentration of the acid diffusion inhibitor decreases toward the lower layer. Also, since the light absorption due to exposure becomes stronger toward the upper layer, the concentration of the generated acid generated by photolysis also becomes higher in the upper layer (surface layer). As a result, a large amount of the acid diffusion inhibitor is present in the upper layer with a high acid concentration, and a small amount of the acid diffusion inhibitor is present in the lower layer with a low acid concentration. Therefore, it is considered that the acid diffusion of the generated acid is efficiently suppressed, the pattern shape is improved, and the lithography performance such as LWR and CDU is improved.

[0053] Patent Document 2 discloses a compound represented by the following formula as a carboxylate-type acid diffusion inhibitor containing a fluoroalkyl chain.

Chemical formula

[0054] Regarding this compound, although an uneven distribution effect on the surface layer is suggested, it is inferior to the acid diffusion inhibitor of the present invention in lithography performance.

[0055] Although the details are unknown, it is considered as follows. The compound represented by the above formula has a structure in which the anion site and the main skeleton of the anion are bonded via an ester bond. Furthermore, since the ester structure is a fluorine-containing alkyl carboxylic acid ester, it is expected to be weak against an alkaline developer and may be decomposed during development. It is considered that the decomposition product by alkaline development has an adverse effect on the dissolution contrast, and the resist film surface layer in the unexposed portion dissolves due to the polarity change by alkaline development, resulting in deterioration of lithography performance. On the other hand, the anion site of the acid diffusion inhibitor of the present invention is directly bonded to the benzene ring which is the anion main skeleton and is bonded via an ether bond or an amide bond, and these bonds are not decomposed by an alkaline developer. Therefore, it is possible to obtain good lithography performance without lowering the dissolution contrast during development.

[0056] Patent Document 3 discloses a compound represented by the following formula as an amine type acid diffusion inhibitor containing a fluoroalkyl chain.

Chemical Formula

[0057] Regarding the compound represented by the above formula, although a tendency of uneven distribution on the surface layer is suggested, compared with the photodegradable salt compound of the present invention, the dissolution contrast between the exposed portion and the unexposed portion is lowered. That is, in the salt compound of the present invention, the cation in the exposed portion is decomposed by the generated acid and the quenching ability is deactivated, and it acts only as an acid diffusion inhibitor in the unexposed portion, whereas the amine type quencher suppresses acid diffusion regardless of the exposed portion and the unexposed portion, resulting in a decrease in sensitivity and a decrease in dissolution contrast. As a result, it is considered that better lithography performance can be obtained by using the acid diffusion inhibitor of the present invention.

[0058] In addition, when a salt compound having an anion represented by the formula (1-I) or (2-I) in which an iodine atom is introduced into the anion is used as an acid diffusion inhibitor, it can be expected to have high sensitivity because the iodine atom efficiently absorbs EUV light.

[0059] [Resist composition] The resist composition of the present invention (A) A base polymer whose solubility in a developer changes by the action of an acid, (B) A photoacid generator, (C-1) An acid diffusion inhibitor comprising the salt compound of the present invention, and (D) An organic solvent are included as essential components, and, if necessary, (C-2) An acid diffusion inhibitor other than the salt compound of the present invention, (E) A surfactant, and (F) Other components may be included.

[0060] Or, (A') A base polymer that changes its solubility in a developer by the action of an acid and contains a photoacid generating site having a function of generating an acid upon exposure as a structural unit, (C-1) An acid diffusion inhibitor comprising the salt compound of the present invention, and (D) An organic solvent are included as essential components, and, if necessary, (B) A photoacid generator, (C-2) An acid diffusion inhibitor other than the salt compound of the present invention, (E) A surfactant, and (F) Other components may be included.

[0061] [(A) Base polymer] As the base polymer of the component (A), a polymer containing a repeating unit represented by the following formula (a) (hereinafter also referred to as repeating unit a) or a repeating unit represented by the following formula (b) (hereinafter also referred to as repeating unit b) is preferable. [Chemical formula]

[0062] In formulas (a) and (b), R A is a hydrogen atom or a methyl group. X A is a single bond, a phenylene group, a naphthylene group, or *-C(=O)-O-X A1 -. * is a bond to the carbon atom of the main chain. X A1 is a hydrocarbylene group having 1 to 15 carbon atoms, and may contain at least one selected from a hydroxy group, an ether bond, an ester bond, and a lactone ring. X B is a single bond or an ester bond. AL 1 and AL 2 are each independently an acid-labile group. The hydrocarbylene group may be saturated or unsaturated, and may be linear, branched, or cyclic.

[0063] The acid-labile groups AL 1 and AL 2 are not particularly limited, and examples thereof include a tertiary hydrocarbyl group having 4 to 20 carbon atoms, a trihydrocarbylsilyl group in which each hydrocarbyl group is a hydrocarbyl group having 1 to 6 carbon atoms, an oxoalkyl group having 4 to 20 carbon atoms, and the like. For a detailed description of the specific structures of these acid-labile groups, paragraphs

[0016] to

[0035] of JP-A-2014-225005 are detailed.

[0064] The acid-labile groups AL 1 and AL 2 are preferably groups represented by the following formula (L1). [Chemical formula]

[0065] In formula (L1), R 11 is a hydrocarbyl group having 1 to 7 carbon atoms, and -CH2- in the hydrocarbyl group may be substituted with -O-. a is 1 or 2. The dashed line is a bond.

[0066] The acid-labile groups AL 1 and AL 2As for the group, the groups shown below are particularly preferred. [Chemical formula] (In the formula, the dashed line represents a bond.)

[0067] X in formula (a) A Specific examples of the structure in which X is changed include those described in paragraph

[0015] of JP-A-2014-225005, but the following are preferred. In the following formulas, R A and AL 1 are the same as those described above. [Chemical formula]

[0068] Examples of the repeating unit a include, but are not limited to, those shown below. In the following formulas, R A is the same as those described above. [Chemical formula]

[0069] [Chemical formula]

[0070] [Chemical formula]

[0071] [Chemical formula]

[0072] [Chemical formula]

[0073] Examples of the repeating unit b include, but are not limited to, those shown below. In the following formulas, R Ais the same as the above. [Chemical formula]

[0074] [Chemical formula]

[0075] [Chemical formula]

[0076] In addition, in the above specific examples, X A and X B are single bonds. However, even in the case of other than single bonds, it can be combined with the same acid-labile groups. Specific examples when X A is other than a single bond are as described above. Specific examples when X B is an ester bond include those in which the single bond between the main chain and the benzene ring in the above specific examples is replaced with an ester bond.

[0077] The base polymer preferably contains a repeating unit represented by the following formula (c) (hereinafter, also referred to as repeating unit c). [Chemical formula]

[0078] In formula (c), R A is a hydrogen atom or a methyl group. Y A is a single bond or an ester bond.

[0079] In formula (c), R 21is a fluorine atom, an iodine atom, or a hydrocarbyl group having 1 to 10 carbon atoms. The hydrocarbyl group may be saturated or unsaturated, and may be linear, branched, or cyclic. Specific examples thereof include alkyl groups such as methyl group, ethyl group, n-propyl group, isopropyl group, n-butyl group, sec-butyl group, tert-butyl group, n-pentyl group, n-hexyl group, n-octyl group, n-nonyl group, n-decyl group; cyclic saturated hydrocarbyl groups such as cyclopentyl group, cyclohexyl group, adamantyl group; aryl groups such as phenyl group; groups obtained by combining these, and the like.

[0080] Further, -CH2- in the hydrocarbyl group may be substituted with -O- or -C(=O)-. Note that -CH2- in the hydrocarbyl group may be bonded to a carbon atom of the benzene ring in formula (c). Examples of the substituted hydrocarbyl group include methoxy group, ethoxy group, propoxy group, butoxy group, phenoxy group, 2-methoxyethoxy group, acetyl group, ethylcarbonyl group, hexylcarbonyl group, acetoxy group, ethylcarbonyloxy group, propylcarbonyloxy group, pentylcarbonyloxy group, hexylcarbonyloxy group, heptylcarbonyloxy group, methoxymethylcarbonyloxy group, (2-methoxyethoxy)methylcarbonyloxy group, methyloxycarbonyl group, ethyloxycarbonyl group, hexyloxycarbonyl group, phenyloxycarbonyl group, acetoxymethyl group, phenoxymethyl group, methoxycarbonyloxy group, and the like, but are not limited thereto. R 21 is preferably a fluorine atom, an iodine atom, a methyl group, an acetyl group, or a methoxy group.

[0081] In formula (c), b and c are integers satisfying 1 ≤ b ≤ 5, 0 ≤ c ≤ 4, and 1 ≤ b + c ≤ 5. b is preferably 1, 2, or 3, and c is preferably 0, 1, or 2.

[0082] The repeating unit c has the function of improving the adhesion to the substrate and the underlying film. Further, since it has a phenolic hydroxy group with a high acidity, it promotes the action of the acid generated by exposure, contributes to higher sensitivity, and in EUV exposure, it serves as a proton source of the acid generated by exposure, so an improvement in sensitivity can be expected.

[0083] Examples of the repeating unit c include, but are not limited to, those shown below. In the following formulas, R A is the same as described above, and Me is a methyl group.

Chemical formula

[0084]

Chemical formula

[0085]

Chemical formula

[0086] Among these, the following are preferred as the repeating unit c. In the following formulas, R A is the same as described above, and Me is a methyl group.

Chemical formula

[0087] The base polymer may contain a repeating unit represented by any of the following formulas (d1) to (d4).

Chemical formula

[0088] In the formulas (d1) to (d4), R B is a hydrogen atom, a fluorine atom, a methyl group or a trifluoromethyl group. Z A is a single bond, a phenylene group, -O-Z A1-、 -C(=O)-O-Z A1 - or -C(=O)-N(H)-Z A1 - wherein Z A1 is a hydrocarbylene group having 1 to 20 carbon atoms which may contain a heteroatom. Z B and Z C are each independently a single bond or a hydrocarbylene group having 1 to 20 carbon atoms which may contain a heteroatom. Z D is a single bond, a methylene group, an ethylene group, a phenylene group, a fluorinated phenylene group, -O-Z D1 -, -C(=O)-O-Z D1 - or -C(=O)-N(H)-Z D1 - wherein Z D1 is an optionally substituted phenylene group.

[0089] Z A1The hydrocarbylene group represented by may be saturated or unsaturated, and may be linear, branched or cyclic. Specific examples thereof include alkane diyl groups such as methylene group, ethane-1,1-diyl group, ethane-1,2-diyl group, propane-1,2-diyl group, propane-1,3-diyl group, butane-1,3-diyl group, butane-1,4-diyl group, pentane-1,5-diyl group, hexane-1,6-diyl group, heptane-1,7-diyl group, octane-1,8-diyl group, nonane-1,9-diyl group, decane-1,10-diyl group, 2,2-dimethylpropane-1,3-diyl group; cyclic saturated hydrocarbylene groups such as cyclopentane diyl group, cyclohexane diyl group, norbornane diyl group, adamantane diyl group; alkene diyl groups such as ethene-1,2-diyl group, 1-propene-1,3-diyl group, 2-butene-1,4-diyl group, 1-methyl-1-butene-1,4-diyl group; cyclic unsaturated aliphatic hydrocarbylene groups such as 2-cyclohexene-1,4-diyl group; aromatic hydrocarbylene groups such as phenylene group, naphthylene group; and groups obtained by combining these. Further, some or all of the hydrogen atoms in the hydrocarbylene group may be substituted with groups containing heteroatoms such as oxygen atom, sulfur atom, nitrogen atom, halogen atom, and -CH2- in the hydrocarbyl group may be substituted with a group containing a heteroatom such as oxygen atom, sulfur atom, nitrogen atom, and as a result, it may contain a hydroxy group, cyano group, carbonyl group, ether bond, ester bond, sulfonic acid ester bond, carbonate bond, lactone ring, sultone ring, carboxylic acid anhydride (-C(=O)-O-C(=O)-), haloalkyl group, etc.

[0090] Z B and Z C The hydrocarbylene group represented by may be saturated or unsaturated, and may be linear, branched or cyclic. Specific examples thereof include those similar to those exemplified as the hydrocarbylene group represented by A1 Z B and Z C is preferably a single bond, an adamantane diyl group or a phenylene group.

[0091] In formulas (d1) to (d4), R 31 ~R 41 are each independently a hydrocarbyl group having 1 to 20 carbon atoms which may contain a heteroatom. The hydrocarbyl group may be saturated or unsaturated, and may be linear, branched or cyclic. Specific examples thereof include alkyl groups such as methyl group, ethyl group, n-propyl group, isopropyl group, n-butyl group, sec-butyl group, tert-butyl group, n-pentyl group, n-hexyl group, n-octyl group, 2-ethylhexyl group, n-nonyl group, n-decyl group; cyclopentyl group, cyclohexyl group, cyclopentylmethyl group, cyclopentylethyl group, cyclopentylbutyl group, cyclohexylmethyl group, cyclohexylethyl group, cyclohexylbutyl group, norbornyl group, tricyclo[5.2.1.0 2,6Cyclic saturated hydrocarbyl groups such as decanyl group, adamantyl group, adamantylmethyl group; alkenyl groups such as vinyl group, allyl group, propenyl group, butenyl group, hexenyl group; cyclic unsaturated aliphatic hydrocarbyl groups such as cyclohexenyl group; aryl groups such as phenyl group, naphthyl group, thienyl group, 4-hydroxyphenyl group, 4-methoxyphenyl group, 3-methoxyphenyl group, 2-methoxyphenyl group, 4-ethoxyphenyl group, 4-tert-butoxyphenyl group, 3-tert-butoxyphenyl, 2-methylphenyl group, 3-methylphenyl group, 4-methylphenyl group, 4-ethylphenyl group, 4-tert-butylphenyl group, 4-n-butylphenyl group, 2,4-dimethylphenyl group, 2,4,6-triisopropylphenyl group, methylnaphthyl group, ethylnaphthyl group, methoxynaphthyl group, ethoxynaphthyl group, n-propoxynaphthyl group, n-butoxynaphthyl group, dimethylnaphthyl group, diethylnaphthyl group, dimethoxynaphthyl group, diethoxynaphthyl group; aralkyl groups such as benzyl group, 1-phenylethyl group, 2-phenylethyl group; groups obtained by combining these, etc. may be mentioned. Further, some or all of the hydrogen atoms in the hydrocarbyl group may be substituted with groups containing heteroatoms such as oxygen atom, sulfur atom, nitrogen atom, halogen atom, and -CH2- in the hydrocarbyl group may be substituted with groups containing heteroatoms such as oxygen atom, sulfur atom, nitrogen atom, etc. As a result, it may contain a hydroxy group, a cyano group, a carbonyl group, an ether bond, an ester bond, a sulfonic acid ester bond, a carbonate bond, a lactone ring, a sultone ring, a carboxylic acid anhydride (-C(=O)-O-C(=O)-), a haloalkyl group, etc.

[0092] Z A and R 31 ~R 41 contains a phenyl group, and the structure in which the phenyl group is bonded to S in the formula is preferable. + is preferably a structure in which it is bonded to S in the formula.

[0093] Also, Z A , R 31 and R 32Any two or more of them may combine with each other to form a ring together with the sulfur atom to which they are attached, R 33 R 34 and R 35 Any two or more of, R 36 R 37 and R 38 Any two or more of or R 39 R 40 and R 41 Any two or more of may combine with each other to form a ring together with the sulfur atom to which they are attached.

[0094] In formula (d2), R HF is a hydrogen atom or a trifluoromethyl group.

[0095] In formula (d2), n 1 is 0 or 1, provided that it is 0 when Z B is a single bond. In formula (d3), n 2 is 0 or 1, provided that it is 0 when Z C is a single bond.

[0096] In formula (d1), Xa -is a non-nucleophilic counter ion. The non-nucleophilic counter ion is not particularly limited, and examples thereof include halide ions such as chloride ion and bromide ion; fluoroalkyl sulfonate ions such as triflate ion, 1,1,1-trifluoroethanesulfonate ion, and nonafluorobutanesulfonate ion; aryl sulfonate ions such as tosylate ion, benzenesulfonate ion, 4-fluorobenzenesulfonate ion, and 1,2,3,4,5-pentafluorobenzenesulfonate ion; alkyl sulfonate ions such as mesylate ion and butanesulfonate ion; imide ions such as bis(trifluoromethylsulfonyl)imide ion, bis(perfluoroethylsulfonyl)imide ion, and bis(perfluorobutylsulfonyl)imide ion; methide ions such as tris(trifluoromethylsulfonyl)methide ion and tris(perfluoroethylsulfonyl)methide ion, etc. Preferably, it is an anion represented by the following formula (d1-1) or (d1-2).

Chemical formula

[0097] In formula (d1-1) and (d1-2), R 51 and R 52 are each independently a hydrocarbyl group having 1 to 40 carbon atoms which may contain a hetero atom. R HF is a hydrogen atom or a trifluoromethyl group.

[0098] Examples of the anion represented by formula (d1-1) include those described in paragraphs

[0100] to

[0101] of JP-A-2014-177407 and those represented by the following formula, but are not limited thereto. In the following formula, R HF is the same as described above.

Chemical formula

[0099]

Chemical formula

[0100]

Chem.

[0101] Examples of the anion represented by formula (d1-2) include, but are not limited to, those described in paragraphs

[0080] to

[0081] of JP-A-2010-215608 and those represented by the following formula. In the following formula, Ac is an acetyl group.

Chem.

[0102]

Chem.

[0103] Examples of the anion in the repeating unit d2 include those described in paragraphs

[0021] to

[0026] of JP-A-2014-177407. Also, R HF Specific examples of the anion in which is a hydrogen atom include those described in paragraphs

[0021] to

[0028] of JP-A-2010-116550, and when R HF is a trifluoromethyl group, specific examples of the anion include those described in paragraphs

[0021] to

[0027] of JP-A-2010-77404.

[0104] Examples of the anion in the repeating unit d3 include those obtained by replacing the portion of -CH(R HF )CF2SO3 - with -C(CF3)2CH2SO3 - in the specific examples of the anion in the repeating unit d2.

[0105] Preferred examples of the anions of the repeating units d2 to d4 include, but are not limited to, those shown below. In the following formula, R B is the same as described above. [Chemical formula]

[0106] Specific examples of the sulfonium cation in formulas (d2) to (d4) include the cations described in paragraph

[0223] of JP-A-2008-158339 and those similar to the sulfonium cations exemplified for the salt compounds represented by formula (1) or (2). Among these, the following are preferred, but not limited thereto. In the following formulas, Me represents a methyl group and tBu represents a tert-butyl group. [Chemical formula]

[0107] The repeating units d1 to d4 have the function of a photoacid generator. When using a base polymer containing the repeating units d1 to d4, the blending of the additive photoacid generator described later can be omitted.

[0108] The base polymer may further contain, as other adhesion groups, a repeating unit containing a hydroxy group other than a phenolic hydroxy group, a lactone ring, an ether bond, an ester bond, a carbonyl group, a cyano group, or a carboxy group (hereinafter also referred to as repeating unit e).

[0109] Examples of the repeating unit e include, but are not limited to, the following. In the following formulas, R A is the same as described above, and Me represents a methyl group. [Chemical formula]

[0110] [Chemical formula]

[0111] [Chemical formula]

[0112]

Chem.

[0113] As the repeating unit e, in addition to these, those described in paragraphs

[0045] to

[0053] of JP-A-2014-225005 can also be mentioned.

[0114] Among these, as the repeating unit e, those having a hydroxy group or a lactone ring are preferable. For example, those shown below are preferable. In the following formula, R A is the same as described above, and Me is a methyl group.

Chem.

[0115] The base polymer may further contain other repeating units other than those described above. Examples of other repeating units include repeating units having an oxirane ring or an oxetane ring. By including a repeating unit having an oxirane ring or an oxetane ring, the exposed portion is crosslinked, so that the remaining film characteristics and etching resistance of the exposed portion are improved.

[0116] The base polymer may further contain, as other repeating units, substituted acrylic esters such as methyl crotonate, dimethyl maleate, and dimethyl itaconate; unsaturated carboxylic acids such as maleic acid, fumaric acid, and itaconic acid; norbornene, norbornene derivatives, tetracyclo[6.2.1.1 3,6 .0 2,7 dodecene derivatives and other cyclic olefins; unsaturated acid anhydrides such as itaconic anhydride; vinyl aromatics such as styrene, tert-butoxystyrene, vinylnaphthalene, acetoxystyrene, and acenaphthylene; and repeating units obtained from other monomers.

[0117] The weight average molecular weight (Mw) of the base polymer is preferably from 1,000 to 500,000, more preferably from 3,000 to 100,000, and still more preferably from 4,000 to 20,000. If Mw is within the above range, the etching resistance will not extremely decrease, and the difference in dissolution rate before and after exposure can be ensured, so that the resolution is good. In the present invention, Mw is a polystyrene-equivalent measurement value by gel permeation chromatography (GPC). The dispersity (Mw / Mn) is preferably from 1.20 to 2.50, more preferably from 1.30 to 2.00.

[0118] As a method for synthesizing the base polymer, for example, among monomers providing various repeating units, a method of polymerizing one or more desired monomers by adding a radical polymerization initiator and heating in an organic solvent can be mentioned. Such a polymerization method is detailed in paragraphs

[0134] to

[0137] of JP-A-2015-214634. Further, the acid-labile group may be used as it is introduced into the monomer, or may be protected or partially protected after polymerization.

[0119] In the base polymer, the preferred content ratio of each repeating unit can be, for example, in the range (mol%) shown below, but is not limited thereto. (I) One or more selected from repeating units a and b are preferably contained in an amount of 10 to 70 mol%, more preferably 20 to 65 mol%, and still more preferably 30 to 60 mol%. If necessary, (II) One or more of repeating unit c are preferably contained in an amount of 0 to 90 mol%, more preferably 15 to 80 mol%, and still more preferably 30 to 60 mol%. If necessary, (III) One or more selected from repeating units d1 to d4 are preferably contained in an amount of 0 to 30 mol%, more preferably 0 to 20 mol%, and still more preferably 0 to 15 mol%. If necessary, (IV) One or more selected from repeating unit e and other repeating units can be preferably contained in an amount of 0 to 80 mol%, more preferably 0 to 70 mol%, and still more preferably 0 to 50 mol%.

[0120] (A) The base polymer of the component may be used alone, or two or more kinds having different composition ratios, Mw and / or Mw / Mn may be used in combination. Further, as the base polymer of the component (A), in addition to the above polymer, a hydrogenated product of a ring-opening metathesis polymer may be included. As the hydrogenated product of the ring-opening metathesis polymer, those described in JP-A-2003-66612 can be used.

[0121] [(B) Photoacid generator] When the base polymer of the resist composition of the present invention does not contain at least one selected from the repeating units d1 to d4, it contains (B) a photoacid generator (hereinafter also referred to as an additive type photoacid generator) as an essential component. Even when the base polymer contains at least one selected from the repeating units d1 to d4, an additive type photoacid generator may be contained.

[0122] The additive type photoacid generator is not particularly limited as long as it is a compound that generates an acid upon irradiation with high-energy rays. Suitable photoacid generators include photoacid generators such as sulfonium salts, iodonium salts, sulfonyldiazomethane, N-sulfonyloxydicarboximide, O-arylsulfonyloxime, and O-alkylsulfonyloxime. Specifically, for example, the compounds described in paragraphs

[0102] to

[0113] of JP-A-2007-145797, the compounds described in paragraphs

[0122] to

[0142] of JP-A-2008-111103, the compounds described in paragraphs

[0081] to

[0092] of JP-A-2014-001259, the compounds described in JP-A-2012-41320, the compounds described in JP-A-2012-153644, the compounds described in JP-A-2012-106986, the compounds described in JP-A-2016-018007, etc. are included. The partially fluorinated sulfonic acid-generating type photoacid generators described in these publications have appropriate acid strength and diffusion length particularly in ArF lithography and are preferably used.

[0123] Preferred examples of the photoacid generator of component (B) include sulfonium salts represented by the following formula (3) or iodonium salts represented by the following formula (4).

Chemical formula

[0124] In formulas (3) and (4), R 101 , R 102 , R 103 , R 104 and R 105 are each independently a hydrocarbyl group having 1 to 20 carbon atoms which may contain a heteroatom. Examples of the hydrocarbyl group are the same as those exemplified in the description of R 31 to R 41 in formulas (d1) to (d4). Also, any two of R 101 , R 102 and R 103 may be bonded to each other to form a ring together with the sulfur atom to which they are bonded, and R 104 and R 105 may be bonded to each other to form a ring together with the iodine atom to which they are bonded. R 101 to R 105 contain a phenyl group, and a structure in which the phenyl group is bonded to S + or I + in the formula is preferred.

[0125] Regarding the sulfonium cation of the sulfonium salt represented by formula (3), it is detailed in paragraphs

[0082] to

[0085] of JP-A-2014-001259. Specific examples thereof include those described in paragraphs

[0027] to

[0033] of JP-A-2007-145797, those described in paragraph

[0059] of JP-A-2010-113209, those described in JP-A-2012-41320, those described in JP-A-2012-153644, those described in JP-A-2012-106986, and those similar to the sulfonium cations exemplified as the salt compounds represented by formula (1) or (2).

[0126] As the cation of the sulfonium salt represented by the formula (3), the following are preferred, but not limited thereto. In the following formulas, Me represents a methyl group and tBu represents a tert-butyl group.

Chemical formula

[0127] As the cation of the sulfonium salt represented by the formula (3), in particular, a triphenylsulfonium cation, an S-phenyldibenzothiophenium cation, a (4-tert-butylphenyl)diphenylsulfonium cation, a (4-fluorophenyl)diphenylsulfonium cation, a (4-hydroxyphenyl)diphenylsulfonium cation, a tris(4-fluorophenyl)sulfonium cation, etc. are preferred.

[0128] As the cation of the iodonium salt represented by the formula (4), those similar to the iodonium cations exemplified as M in the formula (1) or (2) + are mentioned, and a diphenyliodonium cation or a di-tert-butylphenyliodonium cation is particularly preferred. .

[0129] In the formulas (3) and (4), Xb - is an anion represented by the following formula (5) or (6).

Chemical formula

[0130] In the formulas (5) and (6), R fa is a fluorine atom, a perfluoroalkyl group having 1 to 4 carbon atoms, or a hydrocarbyl group having 1 to 40 carbon atoms which may contain a hetero atom. R fb is a hydrocarbyl group having 1 to 40 carbon atoms which may contain a hetero atom. R fa and R fbThe hydrocarbyl group represented by is saturated or unsaturated and may be linear, branched or cyclic. Specific examples thereof include R in formula (5') described later. 112 The hydrocarbyl group represented by is the same as that exemplified as the hydrocarbyl group represented by .

[0131] As the anion represented by formula (5), a trifluoromethanesulfonate anion, a nonafluorobutanesulfonate anion or an anion represented by the following formula (5') is preferable.

Chemical formula

[0132] In formula (5'), R 111 is a hydrogen atom or a trifluoromethyl group, preferably a trifluoromethyl group.

[0133] In formula (5'), R 112 is a hydrocarbyl group having 1 to 35 carbon atoms which may contain a heteroatom. The hydrocarbyl group may be saturated or unsaturated and may be linear, branched or cyclic. Specific examples thereof include alkyl groups such as methyl group, ethyl group, n-propyl group, isopropyl group, n-butyl group, sec-butyl group, tert-butyl group, n-pentyl group, n-hexyl group, n-octyl group, 2-ethylhexyl group, n-nonyl group, n-decyl group; cyclopentyl group, cyclohexyl group, cyclopentylmethyl group, cyclopentylethyl group, cyclopentylbutyl group, cyclohexylmethyl group, cyclohexylethyl group, cyclohexylbutyl group, norbornyl group, tricyclo[5.2.1.0 2,6Cyclic saturated hydrocarbyl groups such as decanyl group, adamantyl group, adamantylmethyl group; alkenyl groups such as vinyl group, allyl group, propenyl group, butenyl group, hexenyl group; cyclic unsaturated aliphatic hydrocarbyl groups such as cyclohexenyl group; aryl groups such as phenyl group, naphthyl group, thienyl group, 4-hydroxyphenyl group, 4-methoxyphenyl group, 3-methoxyphenyl group, 2-methoxyphenyl group, 4-ethoxyphenyl group, 4-tert-butoxyphenyl group, 3-tert-butoxyphenyl, 2-methylphenyl group, 3-methylphenyl group, 4-methylphenyl group, 4-ethylphenyl group, 4-tert-butylphenyl group, 4-n-butylphenyl group, 2,4-dimethylphenyl group, 2,4,6-triisopropylphenyl group, methylnaphthyl group, ethylnaphthyl group, methoxynaphthyl group, ethoxynaphthyl group, n-propoxynaphthyl group, n-butoxynaphthyl group, dimethylnaphthyl group, diethylnaphthyl group, dimethoxynaphthyl group, diethoxynaphthyl group; aralkyl groups such as benzyl group, 1-phenylethyl group, 2-phenylethyl group; groups obtained by combining these. Further, part or all of the hydrogen atoms in the hydrocarbyl group may be substituted with a group containing a heteroatom such as an oxygen atom, a sulfur atom, a nitrogen atom, a halogen atom, and -CH2- in the hydrocarbyl group may be substituted with a group containing a heteroatom such as an oxygen atom, a sulfur atom, a nitrogen atom, and as a result, it may contain a hydroxy group, a cyano group, a carbonyl group, an ether bond, an ester bond, a sulfonic acid ester bond, a carbonate bond, a lactone ring, a sultone ring, a carboxylic acid anhydride (-C(=O)-O-C(=O)-), a haloalkyl group, etc.

[0134] Regarding the anion represented by formula (5'), it is detailed in JP-A-2007-145797, JP-A-2008-106045, JP-A-2009-007327, JP-A-2009-258695, and JP-A-2012-181306. Specific examples of the anion represented by formula (5) include the anions described in these publications and those similar to the ones exemplified as the anion represented by formula (d1-1).

[0135] Regarding the anion represented by the formula (6), it is detailed in JP-A-2010-215608 and JP-A-2014-133723. Further, specific examples of the anion represented by the formula (6) include those described in these publications and those similar to those exemplified as the anion represented by the formula (d1-2). Note that the photoacid generator having the anion represented by the formula (6) does not have a fluorine atom at the α-position of the sulfo group, but has two trifluoromethyl groups at the β-position, and thus has sufficient acidity to cleave the acid-labile group in the base polymer. Therefore, it can be used as a photoacid generator.

[0136] Xb - As the anion represented by, the following are preferable, but not limited thereto. In the following formula, R HF is a hydrogen atom or a trifluoromethyl group.

Chemical formula

[0137]

Chemical formula

[0138] Specific examples of the structure of the photoacid generator represented by the formula (3) or (4) include, but are not limited to, any combination of the specific examples of the above-mentioned anion and the specific examples of the cation.

[0139] Another preferable example of the photoacid generator of the component (B) includes a compound represented by the following formula (7).

Chemical formula

[0140] In the formula (7), R 201 and R 202 are each independently a hydrocarbyl group having 1 to 30 carbon atoms which may contain a hetero atom. R 203is a hydrocarbylene group having 1 to 30 carbon atoms which may contain a heteroatom. Also, R 201 and R 202 and R 203 any two of them may be bonded to each other to form a ring together with the sulfur atom to which they are bonded.

[0141] R 201 and R 202 The hydrocarbyl groups represented by may be saturated or unsaturated, and may be linear, branched or cyclic. Specific examples thereof include the same ones as those exemplified as the hydrocarbyl group represented by R 112 in formula (5').

[0142] R 203The hydrocarbylene group represented by may be saturated or unsaturated, and may be linear, branched, or cyclic. Specific examples thereof include alkane diyl groups such as methylene group, ethylene group, propane-1,3-diyl group, butane-1,4-diyl group, pentane-1,5-diyl group, hexane-1,6-diyl group, heptane-1,7-diyl group, octane-1,8-diyl group, nonane-1,9-diyl group, decane-1,10-diyl group, undecane-1,11-diyl group, dodecane-1,12-diyl group, tridecane-1,13-diyl group, tetradecane-1,14-diyl group; cyclic saturated hydrocarbylene groups such as cyclopentane diyl group, cyclohexane diyl group, norbornane diyl group, adamantane diyl group; arylene groups such as phenylene group, methylphenylene group, ethylphenylene group, n-propylphenylene group, isopropylphenylene group, n-butylphenylene group, isobutylphenylene group, sec-butylphenylene group, tert-butylphenylene group, naphthylene group, methylnaphthylene group, ethylnaphthylene group, n-propylnaphthylene group, isopropylnaphthylene group, n-butylnaphthylene group, isobutylnaphthylene group, sec-butylnaphthylene group, tert-butylnaphthylene group; groups obtained by combining these, and the like. Further, some or all of the hydrogen atoms in the hydrocarbylene group may be substituted with a group containing a heteroatom such as an oxygen atom, a sulfur atom, a nitrogen atom, a halogen atom, etc., and some of -CH2- in the hydrocarbylene group may be substituted with a group containing a heteroatom such as an oxygen atom, a sulfur atom, a nitrogen atom, etc. As a result, it may contain a hydroxy group, a cyano group, a carbonyl group, an ether bond, an ester bond, a sulfonic acid ester bond, a carbonate bond, a lactone ring, a sultone ring, a carboxylic acid anhydride (-C(=O)-O-C(=O)-), a haloalkyl group, and the like.

[0143] In formula (7), L A is a single bond, an ether bond, an ester bond, or a hydrocarbylene group having 1 to 20 carbon atoms which may contain a heteroatom. Note that -CH2- in the hydrocarbylene group is the carbon atom and / or R in formula (7) 203It may be bonded to. As the hydrocarbylene group, R 203 Examples thereof include the same ones as those exemplified as the hydrocarbylene group represented by

[0144] In formula (7), X 1 , X 2 , X 3 and X 4 are each independently a hydrogen atom, a fluorine atom or a trifluoromethyl group, but at least one is a fluorine atom or a trifluoromethyl group.

[0145] As the compound represented by formula (7), those represented by the following formula (7') are particularly preferable.

Chemical formula

[0146] In formula (7'), R HF is a hydrogen atom or a trifluoromethyl group, preferably a trifluoromethyl group. R 301 , R 302 and R 303 are each independently a hydrocarbyl group having 1 to 20 carbon atoms which may contain a hetero atom. The hydrocarbyl group may be saturated or unsaturated, and may be linear, branched or cyclic. Specific examples thereof include the same ones as those exemplified as the hydrocarbyl group represented by R 112 in formula (5'). x and y are each independently an integer of 0 to 5, and z is an integer of 0 to 4.

[0147] Regarding the photoacid generator represented by formula (7) or (7'), it is detailed in JP-A-2011-16746. Further, specific examples thereof include the compounds described in the above publication and the compounds described in paragraphs

[0149] to

[0150] of JP-A-2015-214634.

[0148] Examples of the photoacid generator represented by formula (7) include, but are not limited to, the following. In the following formulas, RHF is the same as the above, Me is a methyl group, and tBu is a tert-butyl group.

Chemical formula

[0149]

Chemical formula

[0150] In the resist composition of the present invention, the content of component (B) is preferably 1 to 30 parts by mass, more preferably 2 to 25 parts by mass, and still more preferably 4 to 20 parts by mass with respect to 100 parts by mass of component (A) base polymer. If the content is within the above range, there is no possibility of deterioration in resolution or problems with foreign matters during or after resist development or peeling. The photoacid generator of component (B) may be used alone or in combination of two or more.

[0151] [(C) Acid diffusion inhibitor] The resist composition of the present invention contains an acid diffusion inhibitor as component (C). Component (C) contains a salt compound represented by formula (1) as an essential component (C-1), and may also contain an acid diffusion inhibitor (C-2) other than the salt compound represented by formula (1). In the present invention, the acid diffusion inhibitor means a compound that can suppress the diffusion rate when the acid generated from the photoacid generator diffuses in the resist film.

[0152] Examples of the acid diffusion inhibitor (C-2) include amine compounds and weak acid onium salts such as sulfonic acids or carboxylic acids in which the α-position is not fluorinated.

[0153] Examples of the amine compound include primary, secondary or tertiary amine compounds, particularly amine compounds having any one of a hydroxy group, an ether bond, an ester bond, a lactone ring, a cyano group and a sulfonic acid ester bond. In addition, primary or secondary amine compounds protected with a carbamate group can also be mentioned as the acid diffusion inhibitor. Such protected amine compounds are effective when there are components unstable to a base in the resist composition. Examples of such acid diffusion inhibitors include, but are not limited to, the compounds described in paragraphs

[0146] to

[0164] of JP-A-2008-111103, the compounds described in Japanese Patent No. 3790649, and those shown below. [Chemical formula]

[0154] [Chemical formula]

[0155] Examples of the onium salts of sulfonic acids or carboxylic acids in which the α-position is not fluorinated include onium salt compounds represented by the following formula (8) or (9). [Chemical formula]

[0156] In formula (8), R q1 is a hydrogen atom, a methoxy group, or a hydrocarbyl group having 1 to 40 carbon atoms which may contain a hetero atom, provided that the hydrogen atom on the carbon atom at the α-position of the sulfo group is excluded when it is substituted with a fluorine atom or a fluoroalkyl group.

[0157] In formula (9), R q2 is a hydrogen atom, a hydroxy group, or a hydrocarbyl group having 1 to 40 carbon atoms which may contain a hetero atom.

[0158] In formulas (8) and (9), Mq +is an onium cation. As the onium cation, those represented by the following formula (10), (11) or (12) are preferable.

[0159] [Chemical formula]

[0160] In formulas (10) to (12), R 401 ~R 409 are each independently a hydrocarbyl group having 1 to 40 carbon atoms which may contain a heteroatom. Also, R 401 and R 402 , R 404 and R 405 or R 406 and R 407 may combine with each other to form a ring together with the sulfur atom, iodine atom or nitrogen atom to which they are attached.

[0161] The hydrocarbyl group having 1 to 40 carbon atoms which may contain a heteroatom represented by R q1 may be saturated or unsaturated, and may be linear, branched or cyclic. Specific examples thereof include alkyl groups such as methyl group, ethyl group, n-propyl group, isopropyl group, n-butyl group, sec-butyl group, tert-butyl group, tert-pentyl group, n-pentyl group, n-hexyl group, n-octyl group, n-nonyl group, n-decyl group; cyclopentyl group, cyclohexyl group, 2-ethylhexyl group, cyclopentylmethyl group, cyclopentylethyl group, cyclopentylbutyl group, cyclohexylmethyl group, cyclohexylethyl group, cyclohexylbutyl group, norbornyl group, tricyclo[5.2.1.0 2,6Cyclic saturated hydrocarbyl groups such as decanyl group, adamantyl group, adamantylmethyl group; alkenyl groups such as vinyl group, allyl group, propenyl group, butenyl group, hexenyl group; cyclic unsaturated hydrocarbyl groups such as cyclohexenyl group; aryl groups such as phenyl group, naphthyl group; heteroaryl groups such as thienyl group; hydroxyphenyl groups such as 4-hydroxyphenyl group; alkoxyphenyl groups such as 4-methoxyphenyl group, 3-methoxyphenyl group, 2-methoxyphenyl group, 4-ethoxyphenyl group, 4-tert-butoxyphenyl group, 3-tert-butoxyphenyl group; alkylphenyl groups such as 2-methylphenyl group, 3-methylphenyl group, 4-methylphenyl group, 4-ethylphenyl group, 4-tert-butylphenyl group, 4-n-butylphenyl group, 2,4-dimethylphenyl group, 2,4,6-triisopropylphenyl group; alkylnaphthyl groups such as methylnaphthyl group, ethylnaphthyl group; alkoxynaphthyl groups such as methoxynaphthyl group, ethoxynaphthyl group, n-propoxynaphthyl group, n-butoxynaphthyl group; dialkylnaphthyl groups such as dimethylnaphthyl group, diethylnaphthyl group; dialkoxynaphthyl groups such as dimethoxynaphthyl group, diethoxynaphthyl group; aralkyl groups such as benzyl group, 1-phenylethyl group, 2-phenylethyl group; aryloxoalkyl groups such as 2-aryl-2-oxoethyl groups such as 2-phenyl-2-oxoethyl group, 2-(1-naphthyl)-2-oxoethyl group, 2-(2-naphthyl)-2-oxoethyl group, etc. are mentioned. Further, some or all of the hydrogen atoms in the hydrocarbyl group may be substituted with a group containing a heteroatom such as an oxygen atom, a sulfur atom, a nitrogen atom, a halogen atom, etc., and some of -CH2- in the hydrocarbyl group may be substituted with a group containing a heteroatom such as an oxygen atom, a sulfur atom, a nitrogen atom, etc., and as a result, it may contain a hydroxy group, a cyano group, a carbonyl group, an ether bond, an ester bond, a sulfonic acid ester bond, a carbonate bond, a lactone ring, a sultone ring, a carboxylic acid anhydride (-C(=O)-O-C(=O)-), a haloalkyl group, etc.

[0162] R q2The hydrocarbyl group having 1 to 40 carbon atoms which may contain a heteroatom represented by may be saturated or unsaturated, and may be linear, branched or cyclic. Specific examples thereof include R q1 In addition to the substituents exemplified as specific examples of, fluorine-containing alkyl groups such as trifluoromethyl group, trifluoroethyl group, 2,2,2-trifluoro-1-methyl-1-hydroxyethyl group, 2,2,2-trifluoro-1-(trifluoromethyl)-1-hydroxyethyl group, and fluorine-containing aryl groups such as pentafluorophenyl group, 4-trifluoromethylphenyl group and the like can be mentioned.

[0163] Regarding the sulfonium salt represented by formula (8) and the onium carboxylate represented by formula (9), it is detailed in JP-A-2008-158339 and JP-A-2010-155824. Further, specific examples of these compounds include those described in these publications.

[0164] Examples of the anion of the sulfonium salt represented by formula (8) include, but are not limited to, those shown below.

Chemical formula

[0165] Examples of the anion of the onium carboxylate represented by formula (9) include, but are not limited to, those shown below.

Chemical formula

[0166] Examples of the cation represented by formula (10) and the cation represented by formula (11) are M in formula (1) or (2), respectively. +Examples thereof include the same ones as those exemplified as the sulfonium cation and iodonium cation represented by [[ID=]], and examples of the cation represented by formula (12) include, but are not limited to, tetramethylammonium cation, tetraethylammonium cation, tetrabutylammonium cation, trimethylbenzyl cation, and trimethylphenyl cation. Particularly preferred cations include the following. In the following formulas, Me represents a methyl group and tBu represents a tert-butyl group.

Chemical formula

[0167] Specific examples of the sulfonate salt represented by formula (8) and the carboxylate salt represented by formula (9) include any combination of the aforementioned anions and cations. These onium salts can be easily prepared by an ion exchange reaction using known organic chemical methods. For the ion exchange reaction, for example, JP-A-2007-145797 can be referred to.

[0168] The onium salt compound represented by formula (8) or (9) acts as an acid diffusion inhibitor in the present invention. This is due to each counter anion of the onium salt compound being a conjugate base of a weak acid. The weak acid referred to here means an acid having an acidity that cannot deprotect the acid-labile group of the acid-labile group-containing unit contained in the base polymer. When the onium salt compound represented by formula (8) or (9) is used in combination with an onium salt type photoacid generator having a conjugate base of a strong acid such as a sulfonic acid with a fluorinated α-position as a counter anion, it functions as an acid diffusion inhibitor. That is, when an onium salt that generates a strong acid such as a sulfonic acid with a fluorinated α-position is mixed with an onium salt that generates a weak acid such as a non-fluorinated sulfonic acid or a carboxylic acid and used, when the strong acid generated from the photoacid generator by high-energy ray irradiation collides with the onium salt having an unreacted weak acid anion, a weak acid is released by salt exchange to generate an onium salt having a strong acid anion. Since the strong acid is exchanged for a weak acid with lower catalytic ability in this process, seemingly, the acid is deactivated and the acid diffusion can be controlled.

[0169] In the onium salt compound represented by formula (8) or (9), Mq + When the onium salt is a sulfonium cation (10) or an iodonium cation (11), since it is particularly photodegradable, the quenching ability in the part with strong light intensity decreases, and the concentration of the strong acid derived from the photoacid generator increases. Thereby, the contrast of the exposed part is improved, and it becomes possible to form a pattern excellent in LWR and CDU.

[0170] Further, when the acid-labile group is an acetal group that is particularly sensitive to an acid, the acid for detaching the protecting group does not necessarily have to be a sulfonic acid, imidic acid, or methidic acid with a fluorinated α-position, and the deprotection reaction may proceed even with a sulfonic acid with a non-fluorinated α-position. In this case, as the acid diffusion inhibitor, it is preferable to use an amine compound or a carboxylic acid onium salt represented by formula (9).

[0171] In addition to the onium salt, a betaine-type compound of a weak acid can also be used as the acid diffusion inhibitor. Specific examples thereof include, but are not limited to, those shown below. [Chemical formula]

[0172] In addition to the compounds described above, a sulfonium salt or iodonium salt having Cl - , Br - , NO3 - as an anion can also be used as the acid diffusion inhibitor. Specific examples thereof include triphenylsulfonium chloride, diphenyliodonium chloride, triphenylsulfonium bromide, triphenylsulfonium nitrate, and the like. Since these anions have a low boiling point of the conjugate acid, the acid generated after quenching of the strong acid can be easily removed from the resist film by PEB or the like. Since the acid is removed from the resist film to the outside of the system, acid diffusion is highly suppressed and the contrast can be improved.

[0173] A photodegradable onium salt having a nitrogen-containing substituent can also be used as the acid diffusion inhibitor. The photodegradable onium salt functions as an acid diffusion inhibitor in the unexposed portion and loses its acid diffusion inhibitory ability by neutralization with the acid generated from itself in the exposed portion, and functions as a so-called photodecomposable base. By using a photodecomposable base, the contrast between the exposed portion and the unexposed portion can be further enhanced. As the photodecomposable base, for example, JP-A-2009-109595, JP-A-2012-46501, JP-A-2013-209360, etc. can be referred to.

[0174] Specific examples of the anion of the photodegradable onium salt include, but are not limited to, those shown below. In the following formula, R HF is a hydrogen atom or a trifluoromethyl group. [Chemical formula]

[0175] Specific examples of the cation of the photodegradable onium salt include M in formula (1) or (2). + Examples thereof include the same ones as those exemplified as the cation represented by M. Among these, those shown below are preferable, but not limited thereto. In the following formulas, Me represents a methyl group and tBu represents a tert-butyl group.

Chemical formula

[0176] Specific examples of the photodegradable onium salt include, but are not limited to, those obtained by combining the anion and the cation.

[0177] In the resist composition of the present invention, the content of component (C) is preferably 2 to 30 parts by mass, more preferably 2.5 to 20 parts by mass, and still more preferably 4 to 15 parts by mass with respect to 100 parts by mass of component (A) base polymer. By blending the acid diffusion inhibitor within the above range, in addition to facilitating the adjustment of the resist sensitivity, the diffusion rate of the acid in the resist film is suppressed, the resolution is improved, the sensitivity change after exposure is suppressed, the substrate and environmental dependence are reduced, and the exposure margin, pattern profile, etc. can be improved. Further, by adding the acid diffusion inhibitor, the substrate adhesion can also be improved. The content of component (C) means the total content including the content of the acid diffusion inhibitor other than the salt compound represented by formula (1) in addition to the acid diffusion inhibitor composed of the salt compound represented by formula (1). In the acid diffusion inhibitor of component (C), the salt compound represented by formula (1) is preferably contained in an amount of 50 to 100% by mass. The acid diffusion inhibitor of component (C) may be used alone or in combination of two or more.

[0178] [(D) Organic solvent] The resist composition of the present invention may contain an organic solvent as component (D). The organic solvent is not particularly limited as long as it can dissolve each of the above-described components and each of the components described below. Examples of such organic solvents include ketones such as cyclohexanone and methyl-2-n-pentyl ketone described in paragraphs

[0144] to

[0145] of JP-A-2008-111103; alcohols such as 3-methoxybutanol, 3-methyl-3-methoxybutanol, 1-methoxy-2-propanol, 1-ethoxy-2-propanol, and diacetone alcohol; ethers such as propylene glycol monomethyl ether, ethylene glycol monomethyl ether, propylene glycol monoethyl ether, ethylene glycol monoethyl ether, propylene glycol dimethyl ether, and diethylene glycol dimethyl ether; esters such as propylene glycol monomethyl ether acetate, propylene glycol monoethyl ether acetate, ethyl lactate, ethyl pyruvate, butyl acetate, methyl 3-methoxypropionate, ethyl 3-ethoxypropionate, tert-butyl acetate, tert-butyl propionate, methyl 2-hydroxyisobutyrate, and propylene glycol monotert-butyl ether acetate; lactones such as γ-butyrolactone; and mixed solvents thereof. When an acetal-based acid-labile group is used, a high-boiling alcohol-based solvent, specifically, diethylene glycol, propylene glycol, glycerin, 1,4-butanediol, 1,3-butanediol, etc. can also be added to accelerate the deprotection reaction of the acetal.

[0179] Among these organic solvents, 1-ethoxy-2-propanol, propylene glycol monomethyl ether acetate, diacetone alcohol, cyclohexanone, γ-butyrolactone, ethyl lactate, and their mixed solvents, which have particularly excellent solubility of the photoacid generator, are preferred. In particular, a solvent system containing propylene glycol monomethyl ether acetate (X component) and mixing one or two of the four solvents (Y components) of 1-ethoxy-2-propanol, diacetone alcohol, cyclohexanone, and γ-butyrolactone, and having a ratio of X component to Y component in the range of 90:10 to 60:40 is preferred.

[0180] In the resist composition of the present invention, the content of component (D) is preferably 100 to 8,000 parts by mass, more preferably 400 to 6,000 parts by mass, based on 100 parts by mass of the (A) base polymer.

[0181] [(E) Surfactant] In addition to the above components, the resist composition of the present invention may contain, as component (E), a surfactant commonly used to improve coatability.

[0182] The surfactant of component (E) is preferably a surfactant that is insoluble or hardly soluble in water and an alkaline developer, or a surfactant that is insoluble or hardly soluble in water and soluble in an alkaline developer. As such surfactants, those described in JP-A-2010-215608 and JP-A-2011-16746 can be referred to.

[0183] As the surfactant that is insoluble or hardly soluble in water and an alkaline developer, among the surfactants described in the above publication, FC-4430 (manufactured by 3M), Surflon (registered trademark) S-381 (manufactured by AGC Seimi Chemical Co., Ltd.), Orfin (registered trademark) E1004 (manufactured by Nissin Chemical Industry Co., Ltd.), KH-20, KH-30 (manufactured by AGC Seimi Chemical Co., Ltd.), PolyFox PF-636 (manufactured by Omnova), oxetane ring-opening polymers represented by the following formula (surf-1), etc. are preferred.

Chemical formula

[0184] Here, regardless of the above description, R, Rf, A, B, C, m, and n are only applicable to formula (surf-1). R is an aliphatic group having 2 to 4 valences and 2 to 5 carbon atoms. Examples of the aliphatic group include, as a divalent group, an ethylene group, a 1,4-butylene group, a 1,2-propylene group, a 2,2-dimethyl-1,3-propylene group, a 1,5-pentylene group, etc., and examples of the trivalent or tetravalent group include the following.

Chemical formula

[0185] Among these, a 1,4-butylene group, a 2,2-dimethyl-1,3-propylene group, etc. are preferable.

[0186] Rf is a trifluoromethyl group or a pentafluoroethyl group, preferably a trifluoromethyl group. m is an integer from 0 to 3, n is an integer from 1 to 4, the sum of n and m is the valence of R, and is an integer from 2 to 4. A is 1. B is an integer from 2 to 25, preferably an integer from 4 to 20. C is an integer from 0 to 10, preferably 0 or 1. Also, each structural unit in formula (surf-1) does not define its arrangement, and they may be bonded blockwise or randomly. Regarding the production of the surfactant of the partially fluorinated oxetane ring-opening polymer system, it is detailed in, for example, U.S. Patent No. 5650483.

[0187] Surfactants that are insoluble or poorly soluble in water and soluble in an alkaline developer have the function of reducing the penetration and leaching of water by orienting on the surface of the resist film when no resist protective film is used in ArF immersion lithography. Therefore, it is useful for suppressing the elution of water-soluble components from the resist film and reducing damage to the exposure apparatus. Also, after exposure, it solubilizes during development with an alkaline aqueous solution after PEB and is less likely to become foreign matter causing defects, so it is useful. Such a surfactant has the property of being insoluble or poorly soluble in water and soluble in an alkaline developer, and is a polymer-type surfactant, also called a hydrophobic resin, and those having particularly high water repellency and improved lubricity are preferred.

[0188] Examples of such polymer-type surfactants include those containing at least one selected from the repeating units represented by the following formulas (13) to (17).

Chemical formula

[0189] In formulas (13) to (17), R C is a hydrogen atom or a methyl group. W 1 is -CH2-, -CH2CH2- or -O-, or two separated -H's. R s1 is each independently a hydrogen atom or a hydrocarbyl group having 1 to 10 carbon atoms. R s2 is a single bond or an alkanediyl group having 1 to 5 carbon atoms. R s3 is each independently a hydrogen atom, a hydrocarbyl group having 1 to 15 carbon atoms, a fluorinated hydrocarbyl group having 1 to 15 carbon atoms or an acid-labile group. When R s3 is a hydrocarbyl group or a fluorinated hydrocarbyl group, an ether bond or a carbonyl group may be interposed between its carbon-carbon bonds. R s4 is a (u + 1)-valent hydrocarbon group or fluorinated hydrocarbon group having 1 to 20 carbon atoms. u is an integer of 1 to 3. R s5 is each independently a hydrogen atom or the following formula -C(=O)-O-R s5A (In the formula, Rs5A is a fluorinated hydrocarbyl group having 1 to 20 carbon atoms.) is a group represented by R s6 is a hydrocarbyl group having 1 to 15 carbon atoms or a fluorinated hydrocarbyl group having 1 to 15 carbon atoms, and an ether bond or a carbonyl group may be interposed between carbon-carbon bonds.)

[0190] The polymer surfactant may further contain other repeating units other than the repeating units represented by formulas (13) to (17). Examples of the other repeating units include repeating units obtained from methacrylic acid, α-trifluoromethylacrylic acid derivatives, and the like. In the polymer surfactant, the content of the repeating units represented by formulas (13) to (17) is preferably 20 mol% or more, more preferably 60 mol% or more, and still more preferably 100 mol% in all the repeating units.)

[0191] For the surfactant that is insoluble or hardly soluble in water and soluble in an alkaline developer, reference can also be made to JP-A-2008-122932, JP-A-2010-134012, JP-A-2010-107695, JP-A-2009-276363, JP-A-2009-192784, JP-A-2009-191151, JP-A-2009-98638, JP-A-2010-250105, and JP-A-2011-42789.)

[0192] In the resist composition of the present invention, the content of the component (E) is preferably 0 to 20 parts by mass with respect to 100 parts by mass of the (A) base polymer. When the component (E) is included, it is preferably 0.001 to 15 parts by mass, more preferably 0.01 to 10 parts by mass. The surfactant of the component (E) may be used alone or in combination of two or more.)

[0193] [(F) Other components] The resist composition of the present invention may contain, as other components (F), a compound that decomposes by an acid to generate an acid (acid-generating compound), an organic acid derivative, a fluorine-substituted alcohol, a crosslinking agent, a compound having an Mw of 3,000 or less (dissolution inhibitor) whose solubility in a developer changes by the action of an acid, acetylene alcohols, etc. Specifically, regarding the acid-generating compound, it is detailed in JP-A-2009-269953 and JP-A-2010-215608, and its content is preferably 0 to 5 parts by mass, more preferably 0 to 3 parts by mass, with respect to 100 parts by mass of the (A) base polymer. If the content is too large, it is difficult to control acid diffusion, and there is a possibility of causing deterioration of resolution and pattern shape. Regarding other additives, it is detailed in paragraphs

[0155] to

[0182] of JP-A-2008-122932, JP-A-2009-269953, and JP-A-2010-215608.

[0194] If it is the resist composition of the present invention containing the salt compound represented by the formula (1) as an acid diffusion inhibitor, in photolithography using high-energy rays such as KrF excimer laser light, ArF excimer laser light, EB, and EUV, it exhibits high acid diffusion inhibition ability, and high-contrast pattern formation becomes possible, resulting in a chemically amplified resist composition excellent in lithography performance such as CDU, LWR, and sensitivity.

[0195] [Pattern Formation Method] The pattern formation method of the present invention includes a step of forming a resist film on a substrate using the above-described resist composition, a step of exposing the resist film with KrF excimer laser light, ArF excimer laser light, EB, or EUV, and a step of developing the exposed resist film using a developer.

[0196] As the substrate, for example, a substrate for integrated circuit manufacturing (Si, SiO2, SiN, SiON, TiN, WSi, BPSG, SOG, organic antireflection film, etc.) or a substrate for mask circuit manufacturing (Cr, CrO, CrON, MoSi2, SiO2, etc.) can be used.

[0197] The resist film can be formed, for example, by applying a resist composition onto a substrate by a method such as spin coating so that the film thickness is preferably 10 to 2,000 nm, and then pre-baking this on a hot plate at preferably 60 to 180 °C for 10 to 600 seconds, more preferably at 70 to 150 °C for 15 to 300 seconds.

[0198] When exposing the resist film using KrF excimer laser light, ArF excimer laser light, or EUV, a mask for forming the target pattern is used, and the exposure dose is preferably 1 to 200 mJ / cm 2 and more preferably 10 to 100 mJ / cm 2 and the irradiation is performed so as to achieve this. When using EB, a mask for forming the target pattern is used or directly, and the exposure dose is preferably 1 to 300 μC / cm 2 and more preferably 10 to 200 μC / cm 2 and the irradiation is performed so as to achieve this.

[0199] In addition to the normal exposure method, it is also possible to use a liquid immersion method in which a liquid having a refractive index of 1.0 or more is interposed between the resist film and the projection lens for exposure. In that case, it is also possible to use a protective film insoluble in water.

[0200] The protective film insoluble in water is used to prevent elution from the resist film and increase the hydrophilicity of the film surface, and there are roughly two types. One is an organic solvent peelable type that needs to be peeled off before alkali aqueous solution development with an organic solvent that does not dissolve the resist film, and the other is an alkali aqueous solution soluble type that is soluble in an alkali developer and removes both the soluble part of the resist film and the protective film. The latter is particularly based on a polymer having a 1,1,1,3,3,3-hexafluoro-2-propanol residue that is insoluble in water and soluble in an alkali developer, and a material dissolved in an alcohol-based solvent having 4 or more carbon atoms, an ether-based solvent having 8 to 12 carbon atoms, or a mixed solvent thereof is preferred. The surfactant described above that is insoluble in water and soluble in an alkali developer can also be a material dissolved in an alcohol-based solvent having 4 or more carbon atoms, an ether-based solvent having 8 to 12 carbon atoms, or a mixed solvent thereof.

[0201] After exposure, heat treatment (PEB) may be performed as necessary. PEB can be performed, for example, on a hot plate, preferably at 60 to 150 °C for 1 to 5 minutes, more preferably at 80 to 140 °C for 1 to 3 minutes.

[0202] Development can be carried out, for example, using a developer of an alkaline aqueous solution such as preferably 0.1 to 5% by mass, more preferably 2 to 3% by mass of tetramethylammonium hydroxide (TMAH), or an organic solvent developer, preferably for 0.1 to 3 minutes, more preferably for 0.5 to 2 minutes, by a conventional method such as the dip method, the puddle method, or the spray method.

[0203] Regarding the method of forming a positive pattern using an alkaline aqueous solution as a developer, it is detailed in paragraphs

[0138] to

[0146] of JP-A-2011-231312, and regarding the method of forming a negative pattern using an organic solvent as a developer, it is detailed in paragraphs

[0173] to

[0183] of JP-A-2015-214634.

[0204] In addition, as a means of the pattern formation method, after forming the resist film, extraction of an acid generator or the like from the film surface or washing away of particles may be performed by performing pure water rinsing (post soak), or rinsing (post soak) for removing water remaining on the film after exposure may be performed.

[0205] Furthermore, a pattern can also be formed by the double patterning method. Examples of the double patterning method include the trench method in which the base of a 1:3 trench pattern is processed by the first exposure and etching, the position is shifted, and a 1:3 trench pattern is formed by the second exposure to form a 1:1 pattern, and the line method in which the first base of a 1:3 isolated residue pattern is processed by the first exposure and etching, the position is shifted, and a 1:3 isolated residue pattern is formed under the first base by the second exposure to process the second base to form a 1:1 pattern with half the pitch.

[0206] Also, when forming a hole pattern by negative tone development using a developer containing an organic solvent, by performing exposure using dipole illumination of line patterns twice in the X-axis and Y-axis directions, light with the highest contrast can be used. Further, when s-polarized illumination is added to the dipole illumination of line patterns twice in the X-axis and Y-axis directions, the contrast can be further increased. These pattern formation methods are detailed in Japanese Patent Application Laid-Open No. 2011-221513.

[0207] Regarding the developer of the pattern formation method of the present invention, examples of the alkaline aqueous solution developer include the aforementioned TMAH aqueous solution and the alkaline aqueous solution described in paragraphs

[0148] to

[0149] of Japanese Patent Application Laid-Open No. 2015-180748, and preferably a 2 to 3 mass% TMAH aqueous solution.

[0208] Examples of the developer for organic solvent development include 2-octanone, 2-nonanone, 2-heptanone, 3-heptanone, 4-heptanone, 2-hexanone, 3-hexanone, diisobutyl ketone, methylcyclohexanone, acetophenone, methylacetophenone, propyl acetate, butyl acetate, isobutyl acetate, pentyl acetate, butenyl acetate, isopentyl acetate, propyl formate, butyl formate, isobutyl formate, pentyl formate, isopentyl formate, methyl valerate, methyl pentenoate, methyl crotonate, ethyl crotonate, methyl propionate, ethyl propionate, ethyl 3-ethoxypropionate, methyl lactate, ethyl lactate, propyl lactate, butyl lactate, isobutyl lactate, pentyl lactate, isopentyl lactate, methyl 2-hydroxyisobutyrate, ethyl 2-hydroxyisobutyrate, methyl benzoate, ethyl benzoate, phenyl acetate, benzyl acetate, methyl phenylacetate, benzyl formate, phenylethyl formate, methyl 3-phenylpropionate, benzyl propionate, ethyl phenylacetate, 2-phenylethyl acetate, and the like. These solvents may be used alone or in combination of two or more.

[0209] The developed hole pattern or trench pattern can also be shrunk by thermal flow, RELACS (Resolution Enhancement Lithography Assisted by Chemical Shrink) technology, DSA (Directed Self-Assembly) technology, etc. A shrinking agent is applied onto the hole pattern, and crosslinking of the shrinking agent occurs on the surface of the resist film due to diffusion of the acid catalyst from the resist film during baking, and the shrinking agent adheres to the sidewalls of the hole pattern. The baking temperature is preferably 70 to 180°C, more preferably 80 to 170°C, and the baking time is 10 to 300 seconds. Finally, the excess shrinking agent is removed to shrink the hole pattern.

[0210] By using the resist composition containing the salt compound represented by the formula (1) of the present invention as an acid diffusion inhibitor, a fine pattern excellent in lithography performance such as CDU, LWR, and sensitivity can be easily formed.

Example

[0211] Hereinafter, the present invention will be specifically described by showing synthesis examples, examples, and comparative examples, but the present invention is not limited to the following examples and the like. In the following examples, Mw is a polystyrene equivalent measurement value by GPC using THF as a solvent.

[0212] [Example 1-1] Synthesis of Sulfonium Salt (Q-1)

Chemical formula

[0213] 98.2 g of methyl 2,5-diiodobenzoate, 49.3 g of n-octyl bromide, 40.3 g of potassium carbonate and 392.7 g of N,N-dimethylformamide were mixed and stirred at 80 °C for 27 hours. After ice-cooling, 800 g of pure water was added to stop the reaction, 850 g of ethyl acetate was added and stirred, and then the organic layer was separated. The obtained organic layer was washed 4 times with 500 g of pure water. The organic layer was concentrated under reduced pressure at 40 °C to obtain 128.4 g of intermediate (I-1) as an oily substance (yield: 98%).

[0214] 128.2 g of intermediate (I-1), 390 g of THF and 390 g of pure water were mixed, and then 43.8 g of a 25% by mass aqueous sodium hydroxide solution was added dropwise at room temperature, and the mixture was stirred at 40 °C for 24 hours. The reaction solution was concentrated under reduced pressure to remove THF, and then 360 mL of hexane, 95 g of methanol and 50 g of pure water were added and stirred. After stirring, the aqueous layer was separated, 360 mL of hexane and 50 g of methanol were added to the obtained aqueous layer, and after stirring, the aqueous layer was separated. The obtained aqueous layer was washed 2 times with 300 mL of hexane to obtain the target intermediate (I-2) as an aqueous solution. In this step, no further purification was performed and it was used in the next step.

[0215] To the aqueous solution of intermediate (I-2), 108.6 g of triphenylsulfonium methyl sulfate, 584 g of methyl isobutyl ketone and 11.6 g of 1-pentanol were added and stirred for 30 minutes, and then the organic layer was separated. The obtained organic layer was washed 6 times with 100 g of pure water. 20 g of methanol was added to the obtained organic layer, and further 7.5 g of activated carbon was added and stirred overnight. Then, it was washed once with 200 g of 0.7% by mass oxalic acid water, twice with 200 g of pure water, once with 200 g of 1% by mass aqueous ammonia, and 8 times with 200 g of pure water. The organic layer was concentrated under reduced pressure at 50 °C to obtain 165.4 g of the target sulfonium salt (Q-1) as an oily substance (two-step yield: 84%).

[0216] For the sulfonium salt (Q-1) 1 The 1H-NMR (500 MHz, DMSO-d6) spectrum is shown in Figure 1. Also, the IR spectrum data and the results of time-of-flight mass spectrometry are shown below. IR (D-ATR): ν = 3388, 3057, 2952, 2925, 2853, 1708, 1602, 1531, 1476, 1446, 1426, 1378, 1346, 1233, 1102, 1089, 1065, 1022, 996, 861, 749, 696, 685, 503 cm -1 Time-of-flight mass spectrometry (TOFMS; MALDI) POSITIVE M + 263.1 (C 18 H 15 S + equivalent) NEGATIVE M - 500.9 (C 15 H 19 I2O3 - equivalent)

[0217] [Example 1-2] Synthesis of Sulfonium Salt (Q-2)

Chemical Structure

[0218] 8.1 g of methyl 3,5-diiodosalicylate, 6.5 g of 1-bromododecane, 4.4 g of potassium carbonate, and 60 g of N,N-dimethylformamide were mixed and stirred at 80 °C for 16 hours. After ice-cooling, 120 g of hydrochloric acid was added to stop the reaction, and 100 g of methylene chloride was added and stirred. Then, the organic layer was separated. The obtained organic layer was washed 4 times with 60 g of pure water. The organic layer was concentrated under reduced pressure at 50 °C to obtain 12.5 g of intermediate (I-3) as an oily substance (yield: 97%).

[0219] 12.5 g of intermediate (I-3), 50 g of dioxane, and 5 g of pure water were mixed. Then, 3.8 g of a 25% by mass aqueous sodium hydroxide solution was added dropwise at room temperature, and the mixture was stirred at 40 °C for 17.5 hours. The reaction solution was concentrated under reduced pressure to remove dioxane and pure water. Then, 60 g of diisopropyl ether was added and stirred for 20 minutes. The precipitated solid was filtered off to obtain 7.2 g of the target intermediate (I-4) as wet crystals. In this step, vacuum drying was not performed, and it was used in the next step.

[0220] 7.2 g of the wet crystal of intermediate (I-4), 7.5 g of triphenylsulfonium methyl sulfate, 60 g of methyl isobutyl ketone, 5 g of methanol, 20 g of 1-pentanol and 20 g of pure water were mixed and stirred for 50 minutes, and then the organic layer was separated. The obtained organic layer was washed 7 times with 20 g of pure water. The organic layer was concentrated under reduced pressure at 50 °C to obtain 15.7 g of the target sulfonium salt (Q-2) as an oily substance (two-step yield: 76%).

[0221] For the sulfonium salt (Q-2) 1 The 1H-NMR (500 MHz, DMSO-d6) spectrum is shown in Figure 2. Also, the IR spectrum data and the results of time-of-flight mass spectrometry are shown below. IR (D-ATR): ν = 3367, 3056, 2923, 2852, 1603, 1531, 1476, 1446, 1427, 1378, 1345, 1233, 1102, 1088, 1065, 966, 860, 749, 696, 685, 503 cm -1 Time-of-flight mass spectrometry (TOFMS; MALDI) POSITIVE M + 263.1 (C 18 H 15 S + equivalent) NEGATIVE M - 557.0 (C 19 H 27 I2O3 - equivalent)

[0222] [Example 1-3] Synthesis of sulfonium salt (Q-3)

Chemical formula

[0223] 5.0 g of methyl 4-iodosalicylate, 5.8 g of 1-bromododecane, 4.0 g of potassium carbonate and 50 g of N,N-dimethylformamide were mixed and stirred at 80 °C for 16 hours. After cooling in ice, 100 g of hydrochloric acid was added to stop the reaction, and 80 g of methylene chloride was added and stirred. Then, the organic layer was separated. The obtained organic layer was washed 4 times with 50 g of pure water. The organic layer was concentrated under reduced pressure at 50 °C to obtain 9.0 g of intermediate (I-5) as an oily substance (yield: 98%).

[0224] 8.9 g of intermediate (I-5), 36 g of dioxane and 4.5 g of pure water were mixed. Then, 3.4 g of a 25% by mass aqueous sodium hydroxide solution was added dropwise at room temperature, and the mixture was stirred at 40 °C for 17 hours. The reaction solution was concentrated under reduced pressure to remove dioxane and pure water. Then, 50 g of diisopropyl ether was added and stirred for 20 minutes. The precipitated solid was filtered off to obtain 7.3 g of the target intermediate (I-6) as wet crystals. In this step, it was used in the next step without performing vacuum drying.

[0225] 7.3 g of wet crystals of intermediate (I-6), 6.7 g of triphenylsulfonium methyl sulfate, 50 g of methyl isobutyl ketone, 5 g of methanol, 15 g of 1-pentanol and 20 g of pure water were mixed and stirred for 70 minutes. Then, the organic layer was separated. The obtained organic layer was washed 4 times with 20 g of pure water. The organic layer was concentrated under reduced pressure at 50 °C to obtain 12.3 g of the target sulfonium salt (Q-3) as an oily substance (two-step yield: 81%).

[0226] Of the sulfonium salt (Q-3) 1 The 1H-NMR (500 MHz, DMSO-d6) spectrum is shown in Figure 3. Also, the results of time-of-flight mass spectrometry are shown below. Time-of-flight mass spectrometry (TOFMS; MALDI) POSITIVE M + 263.1 (C 18 H 15 S + equivalent) NEGATIVE M - 431.1 (C 19 H 28 IO3 - equivalent)

[0227] [Examples 1-4 to 1-18] Furthermore, with reference to the above-described synthesis examples, the following sulfonium salts (Q-4) to (Q-18) were synthesized. [Chemical formula]

[0228] [Synthesis Example 1] Synthesis of Polymer (P-1) Under a nitrogen atmosphere, 2.8 g of triphenylsulfonium 1,1,3,3,3-pentafluoro-2-methacryloyloxypropane-1-sulfonate, 12.3 g of 3-ethyl-3-exo-tetracyclo 2,5 .1 7,10 dodecyl, 9.0 g of 4,8-dioxatricyclo[[4.2.1.0 3,7 nonan-5-one-2-yl, 2.4 g of 3-hydroxy-1-adamantyl methacrylate and 0.9 g of dimethyl 2,2'-azobis(isobutyrate) were dissolved in 72.8 g of methyl ethyl ketone to prepare a solution. The solution was added dropwise over 4 hours to 20.7 g of methyl ethyl ketone stirred at 80°C under a nitrogen atmosphere. After completion of the dropwise addition, the mixture was stirred for 2 hours while maintaining the temperature at 80°C, cooled to room temperature, and then the polymerization solution was added dropwise to 400 g of hexane. The precipitated solid was filtered off, washed twice with a mixed solvent of 45 g of methyl ethyl ketone and 195 g of hexane, and then vacuum dried at 50°C for 20 hours to obtain a white powdery polymer (P-1). The yield was 25.2 g and the yield rate was 95%. When analyzed by GPC, the Mw of the polymer (P-1) was 8,200 and the Mw / Mn was 1.63. [Chemical formula]

[0229] [Synthesis Examples 2 to 5] Synthesis of Polymers (P-2) to (P-4) Except for changing the types and mixing ratios of the respective monomers, the following polymers (P-2) to (P-4) were produced by the same method as in Synthesis Example 1. [Chemical formula]

[0230] [Examples 2-1 to 2-46, Comparative Examples 1-1 to 1-23] Preparation of Resist Composition Acid diffusion inhibitors (sulfonium salts (Q-1) to (Q-18)), base polymers (polymers (P-1) to (P-4)), and, if necessary, photoacid generators (PAG-1, PAG-2), acid diffusion inhibitors other than the salt compound represented by formula (1), and an alkali-soluble surfactant (SF-1) were dissolved in a solvent containing 0.01% by mass of surfactant PolyFox PF-636 (manufactured by Omnova) to prepare a solution, and the resulting solution was filtered through a 0.2 μm Teflon (registered trademark) filter to prepare a resist composition. Also, for comparison, resist compositions were prepared in the same manner using acid diffusion inhibitors (Q-A to Q-I). The compositions of the prepared resist solutions are shown in Tables 1 to 3 below.

[0231] In Tables 1 to 3, the photoacid generators (PAG-1, PAG-2), solvents, comparative acid diffusion inhibitors (Q-A to Q-I), and alkali-soluble surfactant (SF-1) are as follows. · Photoacid generators (PAG-1, PAG-2) [Chemical formula]

[0232] · Solvents PGMEA: Propylene glycol monomethyl ether acetate GBL: γ-Butyrolactone DAA: Diacetone alcohol

[0233] · Acid diffusion inhibitors (Q-A to Q-I) [Chemical formula]

[0234] · Alkali-soluble surfactant (SF-1): Poly(2,2,3,3,4,4,4-heptafluoro-1-isobutyl-1-butyl methacrylate 9-(2,2,2-trifluoro-1-trifluoromethylethyloxycarbonyl)-4-oxatricyclo 3,7 nonan-5-one-2-yl) Mw = 7,700 Mw / Mn = 1.82 [Chemical formula]

[0235] [Table 1]

[0236] [Table 2]

[0237] [Table 3]

[0238] [Examples 3-1 to 3-6, Comparative Examples 2-1 to 2-6] ArF immersion lithography evaluation An antireflection film solution (ARC-29A manufactured by Nissan Chemical Industries, Ltd.) was applied onto a silicon substrate and baked at 180 °C for 60 seconds to form an antireflection film (film thickness: 100 nm). Each resist composition (R-1 to R-6, CR-1 to CR-6) was spin-coated onto the antireflection film and baked at 100 °C for 60 seconds using a hot plate to form a resist film with a film thickness of 90 nm. Immersion exposure was performed using an ArF excimer laser scanner (NSR-S610C manufactured by Nikon Corporation, NA = 1.30, σ 0.94 / 0.74, Dipole-35deg illumination, 6% halftone phase shift mask). Note that water was used as the immersion liquid. Thereafter, PEB was performed at 90 °C for 60 seconds, and development was performed for 60 seconds with a 2.38 mass% TMAH aqueous solution to form a line and space (LS) pattern.

[0239] The developed LS pattern was observed using a length measuring SEM (CG5000) manufactured by Hitachi High-Tech Corporation, and the sensitivity and LWR were evaluated according to the following methods. The results are shown in Table 4.

[0240] [Sensitivity evaluation] As the sensitivity, the optimum exposure dose E op (mJ / cm 2 ) at which an LS pattern with a line width of 40 nm and a pitch of 80 nm is obtained was determined. The smaller this value, the higher the sensitivity.

[0241] [LWR evaluation] E op The LS pattern obtained by irradiation with E was measured for the dimensions at 10 locations in the longitudinal direction of the line, and from the results, three times the standard deviation (σ) (3σ) was determined as the LWR. The smaller this value, the smaller the roughness and the more uniform the line width pattern can be obtained. In this evaluation, good (○): 2.5 nm or less, poor (×): greater than 2.5 nm was defined.

[0242]

Table 4

[0243] From the results shown in Table 4, it was shown that the resist composition of the present invention is excellent in LWR and suitable as a material for ArF immersion lithography.

[0244] [Examples 4-1 to 4-40, Comparative Examples 3-1 to 3-17] EUV Lithography Evaluation Each resist composition (R-7 to R-46, CR-7 to CR-23) was spin-coated on a silicon substrate on which a silicon-containing spin-on hard mask SHB-A940 (silicon content: 43% by mass) manufactured by Shin-Etsu Chemical Co., Ltd. was formed to a film thickness of 20 nm, and pre-baked at 100 °C for 60 seconds using a hot plate to produce a resist film with a film thickness of 50 nm. The resist film was exposed using an EUV scanner NXE3400 (NA 0.33, σ 0.9 / 0.6, quadrupole illumination, mask for a hole pattern with a wafer size of pitch 46 nm and +20% bias) manufactured by ASML, PEB was performed at 85 °C for 60 seconds on a hot plate, and development was performed for 30 seconds with a 2.38% by mass TMAH aqueous solution to form a hole pattern with a size of 23 nm.

[0245] The hole pattern after development was observed with a length-measuring SEM (CG6300) manufactured by Hitachi High-Tech Corporation, and the sensitivity and CDU were evaluated according to the following methods. The results are shown in Tables 5 to 7.

[0246] [Sensitivity evaluation] As the sensitivity, the optimum exposure dose E op (mJ / cm 2 ) when the hole size was formed to 23 nm was determined. The smaller this value, the higher the sensitivity.

[0247] [CDU evaluation] E op The hole pattern obtained by irradiation with was measured for the dimensions at 50 locations within the same exposure dose shot, and from the results, the triple value (3σ) of the standard deviation (σ) was determined as the CDU. The smaller this value, the better the dimensional uniformity of the hole pattern. In this evaluation, good (○): 3.0 nm or less, poor (×): greater than 3.0 nm was defined.

[0248]

Table 5

[0249]

Table 6

[0250]

Table 7

[0251] From the results shown in Tables 5 to 7, it was shown that the resist composition of the present invention is excellent in CDU and suitable as a material for EUV lithography.

Claims

1. A salt compound represented by the following formula (2). 【Chemical 1】 [In the formula, n is an integer of 1 to 5. m is an integer of 0 to 4. L is a single bond, an ether bond or an ester bond. When n is 2 or more, each L may be the same or different. R 1F is a fluorinated alkyl group having 4 to 18 carbon atoms, and -CH 2 - in the alkyl group may be substituted with an ether bond or a carbonyl group. However, R 1F has at least two groups selected from -CF 2 - and -CF 3 -. Further, the fluorinated alkyl group may contain, as a partial structure, a ring structure selected from a cyclopentane ring, a cyclohexane ring, an adamantane ring, a norbornyl ring, or a benzene ring at the terminal or between carbon-carbon bonds. R 2 is a halogen atom, a hydroxy group or a hydrocarbyl group having 1 to 10 carbon atoms, wherein a hydrogen atom in the hydrocarbyl group may be substituted with a halogen atom, and -CH 2 - in the hydrocarbyl group may be substituted with an ether bond or a carbonyl group. M + is a sulfonium cation or an iodonium cation. A - is an anion represented by any of the following formulas (A1) to (A4). However, when A - is an anion represented by the following formula (A2), the partial structure represented by R 1F -L- and the benzene ring are bonded via -CH 2 - or -O-. 【Chemical 2】 (wherein, R f1 is a hydrogen atom or a fluorine atom. R f2 and R f3 are each independently a methyl group, a phenyl group, a tolyl group or a C1-C4 perfluoroalkyl group. The dashed line is a bond.) ]

2. A - The salt compound according to claim 1, wherein A is an anion represented by formula (A1) or (A2).

3. where m is 1 or more, and R 2 The salt compound according to claim 1 or 2, wherein at least one of them is an iodine atom.

4. M + The salt compound according to any one of claims 1 to 3, wherein M is a cation represented by any one of the following formulas (M-1) to (M-3). [Chemical Formula 3] (wherein R M1 , R M2 , R M3 , R M4 and R M5 are each independently a hydroxy group, a halogen atom, or a hydrocarbyl group having 1 to 15 carbon atoms, and part or all of the hydrogen atoms in the hydrocarbyl group may be substituted with a group containing a hetero atom, and -CH 2 - in the hydrocarbyl group may be substituted with -O-, -C(=O)-, -S-, -S(=O)-, -S(=O) 2 - or -N(H)-. k 1 、 k 2 、 k 3 、 k 4 and k 5 are each independently an integer from 0 to 5. When k 1 is 2 or more, each R M1 may be the same or different, and two Rs M1 may combine with each other to form a ring together with the carbon atoms on the benzene ring to which they are attached. When k 2 is 2 or more, each R M2 may be the same or different, and two Rs M2 may combine with each other to form a ring together with the carbon atoms on the benzene ring to which they are attached. When k 3 is 2 or more, each R M3 may be the same or different, and two Rs M3 may combine with each other to form a ring together with the carbon atoms on the benzene ring to which they are attached. When k 4 is 2 or more, each R M4 may be the same or different, and two Rs M4 may combine with each other to form a ring together with the carbon atoms on the benzene ring to which they are attached. When k 5 is 2 or more, each R M5 may be the same or different, and two Rs M5 may combine with each other to form a ring together with the carbon atoms on the benzene ring to which they are attached. X is a single bond, -CH 2 -, -O-, -C(=O)-, -S-, -S(=O)-, -S(=O) 2 - or -N(H)-.)

5. The salt compound according to claim 4, comprising an anion represented by the following formula (2-I) and a cation represented by formula (M-1) or (M-2). 【Chemical 4】 (wherein, L, R 1F and n are the same as described above. R 2A is a halogen atom other than an iodine atom, a hydroxy group or a hydrocarbyl group having 1 to 10 carbon atoms, wherein a hydrogen atom in the hydrocarbyl group may be substituted with a halogen atom, and -CH 2 - in the hydrocarbyl group may be substituted with an ether bond or a carbonyl group. m 1 is an integer from 1 to 4. m 2 is an integer from 0 to 3. However, 2 ≤ n + m 1 + m 2 ≤ 5. )

6. An acid diffusion inhibitor comprising the salt compound according to any one of claims 1 to 5.

7. A resist composition comprising (A) a base polymer whose solubility in a developer changes by the action of an acid, (B) a photoacid generator, (C) the acid diffusion inhibitor according to claim 6, and (D) an organic solvent.

8. A resist composition comprising (A') a base polymer containing, as a structural unit, a photoacid generating site that changes in solubility in a developer by the action of an acid and has a function of generating an acid upon exposure, (C) the acid diffusion inhibitor according to claim 6, and (D) an organic solvent.

9. The resist composition according to claim 7 or 8, wherein the base polymer is a polymer containing a repeating unit represented by the following formula (a) or a repeating unit represented by the following formula (b). 【Chemical Formula 5】 (wherein, R A is a hydrogen atom or a methyl group.) X A is a single bond, a phenylene group, a naphthylene group or *-C(=O)-O-X A1 -. X A1 is a hydrocarbylene group having 1 to 15 carbon atoms, and may contain at least one selected from a hydroxy group, an ether bond, an ester bond and a lactone ring. * is a bond to a carbon atom of the main chain. X B is a single bond or an ester bond. AL 1 and AL 2 are each independently an acid-labile group.)

10. The resist composition according to claim 9, wherein the acid-labile group is a group represented by the following formula (L1). ​ (In the formula, R 11 is a hydrocarbyl group having 1 to 7 carbon atoms, and -CH 2 - in the hydrocarbyl group may be substituted with -O-. a is 1 or 2. The broken line is a bond.)

11. The resist composition according to any one of claims 7 to 10, wherein the base polymer is a polymer containing a repeating unit represented by the following formula (c). 【Chemical Formula 7】 (wherein R A is a hydrogen atom or a methyl group.) Y A is a single bond or an ester bond. R 21 is a fluorine atom, an iodine atom or a hydrocarbyl group having 1 to 10 carbon atoms, and -CH 2 - in the hydrocarbyl group may be substituted with -O- or -C(=O)-. b and c are integers satisfying 1 ≦ b ≦ 5, 0 ≦ c ≦ 4 and 1 ≦ b + c ≦ 5.)

12. The resist composition according to claim 8, wherein the base polymer contains at least one selected from the repeating units represented by the following formulas (d1) to (d4). 【Chemical Formula 8】 (wherein, R B is a hydrogen atom, a fluorine atom, a methyl group or a trifluoromethyl group.) Z A is a single bond, a phenylene group, -O-Z A1 -, -C(=O)-O-Z A1 - or -C(=O)-N(H)-Z A1 -. Z A1 is a hydrocarbylene group having 1 to 20 carbon atoms which may contain a heteroatom. Z B and Z C each independently is a hydrocarbylene group having 1 to 20 carbon atoms which may contain a single bond or a heteroatom. Z D is a single bond, a methylene group, an ethylene group, a phenylene group, a fluorinated phenylene group, -O-Z D1 -, -C(=O)-O-Z D1 - or -C(=O)-N(H)-Z D1 . Z D1 is an optionally substituted phenylene group. R 31 ~R 41 are each independently a hydrocarbyl group having 1 to 20 carbon atoms which may contain a heteroatom. Also, Z A , R 31 and R 32 any two or more of may be bonded to each other to form a ring together with the sulfur atom to which they are bonded, and R 33 , R 34 and R 35 any two or more of, R 36 , R 37 and R 38 any two or more of or R 39 , R 40 and R 41 any two or more of may be bonded to each other to form a ring together with the sulfur atom to which they are bonded. R HF is a hydrogen atom or a trifluoromethyl group. n 1 is 0 or 1, provided that it is 0 when Z B is a single bond. n 2 is 0 or 1, provided that it is 0 when Z C is a single bond. Xa - is a non-nucleophilic counter ion.)

13. A pattern forming method comprising a step of forming a resist film on a substrate using the resist composition according to any one of claims 7 to 12, a step of exposing the resist film with KrF excimer laser light, ArF excimer laser light, an electron beam or extreme ultraviolet light, and a step of developing the exposed resist film using a developer.

14. The pattern forming method according to claim 13, wherein an alkaline aqueous solution is used as the developer to dissolve the exposed portion and obtain a positive pattern in which the unexposed portion is not dissolved.

15. The pattern forming method according to claim 13, wherein an organic solvent is used as a developer to dissolve an unexposed portion and obtain a negative pattern in which the exposed portion is not dissolved.

16. The pattern forming method according to claim 15, wherein the developer is at least one selected from 2-octanone, 2-nonanone, 2-heptanone, 3-heptanone, 4-heptanone, 2-hexanone, 3-hexanone, diisobutyl ketone, methylcyclohexanone, acetophenone, methylacetophenone, propyl acetate, butyl acetate, isobutyl acetate, pentyl acetate, butenyl acetate, isopentyl acetate, propyl formate, butyl formate, isobutyl formate, pentyl formate, isopentyl formate, methyl valerate, methyl pentenoate, methyl crotonate, ethyl crotonate, methyl propionate, ethyl propionate, ethyl 3-ethoxypropionate, methyl lactate, ethyl lactate, propyl lactate, butyl lactate, isobutyl lactate, pentyl lactate, isopentyl lactate, methyl 2-hydroxyisobutyrate, ethyl 2-hydroxyisobutyrate, methyl benzoate, ethyl benzoate, phenyl acetate, benzyl acetate, methyl phenylacetate, benzyl formate, phenylethyl formate, methyl 3-phenylpropionate, benzyl propionate, ethyl phenylacetate and 2-phenylethyl acetate.

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