Onium salt, resist composition, and pattern forming method

Abstract

To provide a resist composition that exhibits improved LWR and resolution and prevents a resist pattern from collapsing in deep-UV, EB or EUV lithography, an onium salt for use in the resist composition, and a patterning method using the resist composition.SOLUTION: An onium salt has an anion moiety whose conjugate acid decomposes into carbon dioxide and an organic compound of up to 12 carbon atoms under the action of acid and heat.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to an onium salt, a resist composition containing the same, and a pattern forming method using the resist composition. [Background technology]

[0002] As LSIs become more highly integrated and faster, pattern rules are becoming increasingly miniaturized. This is due to the increasing popularity of 5G high-speed communications and artificial intelligence (AI), which require high-performance devices to process these. The most advanced miniaturization technology is extreme ultraviolet (EUV) lithography with a wavelength of 13.5 nm, which is currently used to mass-produce 5 nm node devices. Furthermore, the use of EUV lithography is being considered for next-generation 3 nm node devices and the next-generation 2 nm node devices.

[0003] As miniaturization progresses, image blurring due to acid diffusion has become a problem. To ensure resolution in fine patterns with dimensions of 45 nm and smaller, it has been suggested that controlling acid diffusion is important, in addition to improving dissolution contrast, as has been proposed previously (Non-Patent Document 1). However, because chemically amplified resist compositions increase sensitivity and contrast through acid diffusion, attempts to minimize acid diffusion by lowering the post-exposure bake (PEB) temperature or shortening the time result in significant decreases in sensitivity and contrast.

[0004] The triangle trade-off relationship between sensitivity, resolution, and edge roughness (LER, LWR) is shown. To improve resolution, it is necessary to suppress acid diffusion, but as the acid diffusion distance becomes shorter, sensitivity decreases.

[0005] It is effective to suppress acid diffusion by adding an acid generator that generates bulky acid. Therefore, it has been proposed to incorporate repeating units derived from onium salts having polymerizable unsaturated bonds into a polymer. In this case, the polymer also functions as an acid generator (polymer-bound acid generator). Patent Document 1 proposes sulfonium salts and iodonium salts having polymerizable unsaturated bonds that generate specific sulfonic acids. Patent Document 2 proposes sulfonium salts in which sulfonic acids are directly linked to the main chain.

[0007] Quenchers (acid diffusion controllers) have also been extensively studied. While various amines are primarily used as quenchers, many issues remain to be addressed, such as line width roughness (LWR), an indicator of pattern roughness, and pattern shape. Studies using weak acid onium salts as quenchers have also been reported. For example, Patent Document 1 describes that patterns with minimal roughness can be formed by using a compound that generates a carboxylic acid with a boiling point of 150°C or higher. Patent Document 2 describes that the addition of an ammonium sulfonate salt or an ammonium carboxylate salt improves sensitivity, resolution, and exposure margin. Patent Document 3 describes that a resist composition for KrF or electron beam (EB) lithography containing a photoacid generator that generates a fluorine-containing carboxylic acid exhibits excellent resolution and improved process tolerances, such as exposure margin and depth of focus (DOF). Patent Document 4 describes a positive-tone photosensitive composition for ArF excimer laser exposure containing a carboxylic acid onium salt. Patent Document 5 describes a fluoroalkanesulfonamide onium salt that functions as a weak acid onium salt. However, even when this salt is used, the LWR (Linear Write Limit) and resolution (indicating pattern roughness) of the pattern are insufficient for the generation requiring ultrafine processing using ArF lithography or ArF immersion lithography. Therefore, further development of a weak acid onium salt with excellent quencher function is desired. Patent Documents 6 to 8 also describe α,α-difluorocarboxylic acid onium salts and onium salts having an oxalic acid structure as carboxylic acid onium salts. Even when these salts are used, the acidity of the carboxylic acid after proton exchange with a strong acid is not sufficiently low, and in some cases they may also function as acid generators. As a result, the quencher function is low, and the LWR and resolution are unsatisfactory. Patent Document 9 also reports an example of the use of aromatic carboxylic acid onium salts, which have not been actively used in ArF lithography, in EUV lithography, which has seen rapid development in recent years.

[0008] These weak acid onium salts function as quenchers because, upon exposure, the strong acid (sulfonic acid) generated from other photoacid generators is exchanged with the weak acid onium salt, forming a weak acid and a strong acid onium salt, which replaces a highly acidic strong acid (α,α-difluorosulfonic acid) with a weak acid (alkanesulfonic acid, carboxylic acid, etc.). This suppresses the acid elimination reaction of acid-labile groups and reduces (controls) the acid diffusion distance. However, with the recent advances in miniaturization, particularly in EUV lithography, even resist compositions using these weak acid onium salts have not been able to achieve satisfactory resolution, roughness, DOF, etc. In the case of alkanesulfonates, their acidity is insufficient, resulting in poor quenching ability. In contrast, carboxylic acid salts not only lack the above-mentioned properties, but also have a high affinity for alkaline developers due to their high hydrophilicity, which attracts the developer to exposed areas, causing swelling. This swelling, in particular, can cause resist pattern collapse, particularly in the formation of fine line patterns. To meet the demand for further miniaturization, there is a need to develop a quencher that has sufficiently low acidity, excellent quenching performance, and can suppress collapse of the resist pattern due to swelling caused by alkaline developers. [Prior art documents] [Patent documents]

[0009] [Patent Document 1] Japanese Patent Application Publication No. 11-125907 [Patent Document 2] Japanese Patent Application Publication No. 11-327143 [Patent Document 3] Japanese Patent Application Laid-Open No. 2001-281849 [Patent Document 4] Patent No. 4226803 [Patent Document 5] Japanese Patent Application Laid-Open No. 2012-108447 [Patent Document 6] Japanese Patent Application Laid-Open No. 2015-54833 [Patent Document 7] International Publication No. 2021-199789 [Patent Document 8] Patent No. 6304246 [Patent Document 9] Patent No. 6561731 [Non-patent literature]

[0010] [Non-Patent Document 1] SPIE Vol. 6520 65203L-1 (2007) Summary of the Invention [Problem to be solved by the invention]

[0011] The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a resist composition that exhibits excellent LWR and resolution and is also capable of suppressing resist pattern collapse in deep-UV lithography, EB lithography, and EUV lithography; an onium salt for use in the resist composition; and a pattern formation method that uses the resist composition. [Means for solving the problem]

[0012] As a result of extensive research into achieving the above-mentioned object, the inventors of the present invention have discovered that a resist composition containing, as a quencher, an onium salt in which the conjugated acid of the anion moiety is decomposed by the action of acid and heat to carbon dioxide and an organic compound having 12 or less carbon atoms, can produce resist films with excellent resolution and small LWR, and furthermore, can suppress swelling during development, making it extremely effective for precise microfabrication, thereby achieving the present invention.

[0013] That is, the present invention provides the following onium salt, resist composition, and pattern forming method. 1. An onium salt in which the conjugate acid of the anion part decomposes into carbon dioxide and organic compounds with 12 or less carbon atoms under the action of acid and heat. 2. An onium salt of formula 1, which is represented by the following formula (1): [ka] (In the formula, X is a single bond, —O—, or —S—. R 1 and R 2 are each independently a hydrogen atom or a hydrocarbyl group having 1 to 10 carbon atoms, and some of the -CH2- in the hydrocarbyl group may be substituted with -O- or -C(=O)-. 1 and R 2 may be bonded to each other to form a ring together with the carbon atoms to which they are attached. R 3 represents a hydrogen atom or a hydrocarbyl group having 1 to 10 carbon atoms when X is a single bond or -S-; represents a hydrogen atom, a hydrocarbyl group having 1 to 10 carbon atoms other than an acid labile group, or an acid labile group when X is -O-; some or all of the hydrogen atoms of the hydrocarbyl group may be substituted with halogen atoms, and some of the -CH2- of the hydrocarbyl group may be substituted with -O- or -C(=O)-; R 1 and R 3 may be bonded to each other to form a ring together with the atoms to which they are bonded and the atoms between them. 3 is other than an acid labile group, R 1 ~R 3 The maximum number of carbon atoms contained in the Z + is an onium cation. 3. Onium salts of 2 where X is -O-. 4.R 3 Onium salt of 3, which is an acid labile group. 5. The onium salt of 4, wherein the acid labile group is represented by the following formula (AL-1) or (AL-2): [ka] (In the formula, X a is —O— or —S—. R 4 , R 5 and R 6are each independently a hydrocarbyl group having 1 to 12 carbon atoms, in which some of the -CH2- groups in the hydrocarbyl group may be substituted with -O- or -S-, and when the hydrocarbyl group contains an aromatic ring, some or all of the hydrogen atoms in the aromatic ring may be substituted with a halogen atom, a cyano group, a nitro group, an alkyl group having 1 to 4 carbon atoms which may contain a halogen atom, or an alkoxy group having 1 to 4 carbon atoms which may contain a halogen atom. 4 , R 5 and R 6 Any two of these may be bonded to each other to form a ring, and some of the -CH2- in the ring may be substituted with -O- or -S-. R 7 and R 8 are each independently a hydrogen atom or a hydrocarbyl group having 1 to 10 carbon atoms. 9 is a hydrocarbyl group having 1 to 20 carbon atoms, and some of the -CH2- in the hydrocarbyl group may be substituted with -O- or -S-. 8 and R 9 and are bonded to each other, and the carbon atoms to which they are bonded and X a may form a heterocyclic group having 3 to 20 carbon atoms together, and some of the -CH2- in the heterocyclic group may be substituted with -O- or -S-. n1 and n2 each independently represent 0 or 1. * represents a bond to the adjacent -O-.) 6.Z + is an onium cation represented by any one of the following formulae (cation-1) to (cation-3): [ka] (In the formula, R 11 ~R 19 are each independently a hydrocarbyl group having 1 to 30 carbon atoms which may contain a heteroatom. 11 and R 12 may be bonded to each other to form a ring together with the sulfur atom to which they are attached. 7. A quencher comprising any one of the onium salts of 1 to 6. 8.7 A resist composition containing a quencher. 9. The resist composition of 8, further comprising an organic solvent. 10. A polymer comprising a base polymer containing a repeating unit represented by the following formula (a1): Mu8 10. The resist composition according to claim 9. [ka] (In the formula, R A is a hydrogen atom, a fluorine atom, a methyl group, or a trifluoromethyl group. X 1 is a single bond, a phenylene group, a naphthylene group, or *-C(=O)-OX 11 -, and the phenylene group or naphthylene group may be substituted with a halogen atom or an alkoxy group having 1 to 10 carbon atoms which may contain a fluorine atom. 11 is a saturated hydrocarbylene group having 1 to 10 carbon atoms, which may contain a hydroxy group, an ether bond, an ester bond or a lactone ring, a phenylene group or a naphthylene group. R * indicates a bond to a carbon atom in the main chain. AL 1 is an acid labile group. 11. The resist composition of 10, wherein the base polymer further contains a repeating unit represented by the following formula (a2): [ka] (In the formula, R A is a hydrogen atom, a fluorine atom, a methyl group, or a trifluoromethyl group. X 2 is a single bond or *-C(=O)-O-. * represents a bond to a carbon atom in the main chain. R 21represents a halogen atom, a cyano group, a hydrocarbyl group having 1 to 20 carbon atoms which may contain a heteroatom, a hydrocarbyloxy group having 1 to 20 carbon atoms which may contain a heteroatom, a hydrocarbylcarbonyl group having 2 to 20 carbon atoms which may contain a heteroatom, a hydrocarbylcarbonyloxy group having 2 to 20 carbon atoms which may contain a heteroatom, or a hydrocarbyloxycarbonyl group having 2 to 20 carbon atoms which may contain a heteroatom. AL 2 is an acid labile group. a is an integer from 0 to 4. 12. The resist composition of 10 or 11, wherein the base polymer further contains a repeating unit represented by the following formula (b1) or (b2): [ka] (In the formula, R A are each independently a hydrogen atom, a fluorine atom, a methyl group, or a trifluoromethyl group. Y 1 is a single bond or *-C(=O)-O-. R 22 is a group having 1 to 20 carbon atoms and containing at least one structure selected from a hydrogen atom, a hydroxy group other than a phenolic hydroxy group, a cyano group, a carbonyl group, a carboxy group, an ether bond, an ester bond, a sulfonate ester bond, a carbonate bond, a lactone ring, a sultone ring, and a carboxylic anhydride (-C(=O)-OC(=O)-). R 23 represents a halogen atom, a hydroxy group, a nitro group, a hydrocarbyl group having 1 to 20 carbon atoms which may contain a heteroatom, a hydrocarbyloxy group having 1 to 20 carbon atoms which may contain a heteroatom, a hydrocarbylcarbonyl group having 2 to 20 carbon atoms which may contain a heteroatom, a hydrocarbylcarbonyloxy group having 2 to 20 carbon atoms which may contain a heteroatom, or a hydrocarbyloxycarbonyl group having 2 to 20 carbon atoms which may contain a heteroatom. b is an integer from 1 to 4, and c is an integer from 0 to 4, provided that 1≦b+c≦5. 13. The resist composition of any one of 10 to 12, wherein the base polymer further comprises at least one repeating unit selected from the repeating units represented by the following formulae (c1) to (c4): [ka] (In the formula, R A are each independently a hydrogen atom, a fluorine atom, a methyl group, or a trifluoromethyl group. Z 1 is a single bond or a phenylene group. Z 2 is *-C(=O)-OZ 21 -, *-C(=O)-NH-Z 21 -or*-OZ 21 -It is. Z 21 represents an aliphatic hydrocarbylene group having 1 to 6 carbon atoms, a phenylene group, or a divalent group obtained by combining these, and may contain a carbonyl group, an ester bond, an ether bond, or a hydroxy group. Z 3 is a single bond, a phenylene group, a naphthylene group, or *-C(=O)-OZ 31 -It is. Z 31 is an aliphatic hydrocarbylene group having 1 to 10 carbon atoms, a phenylene group, or a naphthylene group, and the aliphatic hydrocarbylene group may contain a hydroxy group, an ether bond, an ester bond, or a lactone ring. Z 4 is a single bond or *-Z 41 -C(=O)-O-. Z 41 is a hydrocarbylene group having 1 to 20 carbon atoms which may contain a heteroatom. 5 represents a single bond, a methylene group, an ethylene group, a phenylene group, a fluorinated phenylene group, a phenylene group substituted with a trifluoromethyl group, *-C(=O)-OZ 51 -, *-C(=O)-N(H)-Z 51 -or*-OZ 51 -It is. Z 51represents an aliphatic hydrocarbylene group having 1 to 6 carbon atoms, a phenylene group, a fluorinated phenylene group, or a phenylene group substituted with a trifluoromethyl group, and may contain a carbonyl group, an ester bond, an ether bond, or a hydroxy group. * indicates a bond to a carbon atom in the main chain. R 31 and R 32 are each independently a hydrocarbyl group having 1 to 20 carbon atoms which may contain a heteroatom. 31 and R 32 and may be bonded to each other to form a ring together with the sulfur atom to which they are attached. L 1 is a single bond, an ether bond, an ester bond, a carbonyl group, a sulfonate ester bond, a carbonate bond or a carbamate bond. Rf 1 and Rf 2 are each independently a fluorine atom or a fluorinated alkyl group having 1 to 6 carbon atoms. Rf 3 and Rf 4 are each independently a hydrogen atom, a fluorine atom or a fluorinated alkyl group having 1 to 6 carbon atoms. Rf 5 and Rf 6 are each independently a hydrogen atom, a fluorine atom, or a fluorinated alkyl group having 1 to 6 carbon atoms, provided that all Rf 5 and Rf 6 cannot simultaneously become a hydrogen atom. M - is a non-nucleophilic counterion. A + is an onium cation. d is an integer from 0 to 3. 14. The resist composition of any one of 8 to 13, further comprising a photoacid generator. 15. The resist composition of any one of 8 to 14, further comprising an amine compound. 16. The resist composition of any one of 8 to 15, further comprising a surfactant. 17. A pattern forming method comprising the steps of forming a resist film on a substrate using a resist composition according to any one of claims 8 to 16, exposing the resist film to high-energy rays, performing PEB, and developing the PEB-treated resist film using a developer. 18. The pattern formation method of 17, wherein the high-energy radiation is KrF excimer laser light, ArF excimer laser light, EB, or EUV having a wavelength of 3 to 15 nm. [Effects of the Invention]

[0014] The onium salt of the present invention functions well as a quencher in a resist composition, thereby enabling the construction of a high-resolution pattern profile with small LWR and excellent rectangularity. Furthermore, the present invention provides a resist composition that suppresses swelling of the resist pattern during alkaline development, enabling the formation of a pattern that is resistant to collapse and is excellent for the formation of fine patterns. DETAILED DESCRIPTION OF THE INVENTION

[0015] [Onium salts] The onium salt of the present invention is characterized in that the conjugate acid of the anion moiety decomposes into carbon dioxide and an organic compound having 12 or less carbon atoms under the action of acid and heat. Specifically, it is represented by the following formula (1): [ka]

[0016] In formula (1), X represents a single bond, -O-, or -S-. Of these, a single bond or -O- is preferred, and -O- is more preferred.

[0017] In formula (1), R 1 and R 2are each independently a hydrogen atom or a hydrocarbyl group having 1 to 10 carbon atoms, and some of the -CH2- groups in the hydrocarbyl group may be substituted with -O- or -C(=O)-. The hydrocarbyl group may be saturated or unsaturated, and may be linear, branched, or cyclic. Specific examples thereof include alkyl groups having 1 to 10 carbon atoms, such as methyl, ethyl, n-propyl, isopropyl, n-butyl, and tert-butyl; saturated cyclic hydrocarbyl groups having 3 to 10 carbon atoms, such as cyclopropyl, cyclopentyl, cyclohexyl, cyclopropylmethyl, 4-methylcyclohexyl, cyclohexylmethyl, norbornyl, and adamantyl; alkenyl groups having 2 to 10 carbon atoms, such as vinyl, allyl, propenyl, butenyl, and hexenyl; unsaturated cyclic hydrocarbyl groups having 3 to 10 carbon atoms, such as cyclohexenyl; and unsaturated cyclic hydrocarbyl groups having 3 to 10 carbon atoms, such as phenyl and naphthyl. 6 aryl groups having 7 to 10 carbon atoms, such as benzyl, 1-phenylethyl, and 2-phenylethyl; and groups obtained by combining these. In addition, some of the -CH2- in the hydrocarbyl groups may be substituted with -O- or -C(=O)-.

[0018] Also, R 1 and R 2 may be bonded to each other to form a ring together with the carbon atoms to which they are bonded. In this case, the ring is preferably a ring having 3 to 10 carbon atoms, and more preferably a saturated ring. Specifically, a cyclopropane ring, a cyclobutane ring, a cyclopentane ring, a cyclohexane ring, a norbornane ring, an adamantane ring, etc. are preferred. In addition, a portion of -CH2- in the ring may be substituted with -O- or -C(=O)-.

[0019] R 1 and R 2 is a hydrogen atom, a saturated hydrocarbyl group having 1 to 6 carbon atoms, or R 1 and R 2 are bonded to each other to form a saturated ring having 3 to 8 carbon atoms together with the carbon atoms to which they are bonded, and R1 and R 2 are more preferably bonded to each other to form a saturated ring having 3 to 6 carbon atoms together with the carbon atoms to which they are bonded.

[0020] In formula (1), R 3 represents a hydrogen atom or a hydrocarbyl group having 1 to 10 carbon atoms when X is a single bond or -S-, and represents a hydrogen atom, a hydrocarbyl group having 1 to 10 carbon atoms other than an acid labile group, or an acid labile group when X is -O-. The hydrocarbyl group may be saturated or unsaturated, and may be linear, branched, or cyclic. Specific examples thereof include alkyl groups having 1 to 10 carbon atoms, such as methyl, ethyl, n-propyl, isopropyl, n-butyl, and tert-butyl; saturated cyclic hydrocarbyl groups having 3 to 10 carbon atoms, such as cyclopropyl, cyclopentyl, cyclohexyl, cyclopropylmethyl, 4-methylcyclohexyl, cyclohexylmethyl, norbornyl, and adamantyl; alkenyl groups having 2 to 10 carbon atoms, such as vinyl, allyl, propenyl, butenyl, and hexenyl; unsaturated cyclic hydrocarbyl groups having 3 to 10 carbon atoms, such as cyclohexenyl; and unsaturated cyclic hydrocarbyl groups having 3 to 10 carbon atoms, such as phenyl and naphthyl. 6 aryl groups having 7 to 10 carbon atoms, such as benzyl, 1-phenylethyl, and 2-phenylethyl; and groups obtained by combining these. Some or all of the hydrogen atoms in the hydrocarbyl groups may be substituted with halogen atoms such as fluorine, chlorine, bromine, and iodine, and some of the -CH2- in the hydrocarbyl groups may be substituted with -O- or -C(=O)-.

[0021] Also, R 1 and R 3 are combined with each other and Atoms and atoms in betweenand may form a ring together with X. The ring formed is a corresponding cycloalkyl ketone when X is a single bond, a corresponding lactone ring when X is -O-, and a corresponding thiolactone ring when X is -S-. The ring is preferably a 3- to 8-membered ring, and more preferably a 5- to 7-membered ring. Some or all of the hydrogen atoms in the ring may be substituted with halogen atoms, and some of the -CH2- groups in the ring may be substituted with -O- or -C(=O)-.

[0022] In addition, R 3 is other than an acid labile group, R 1 ~R 3 The maximum number of carbon atoms contained in the

[0023] R 3 The acid labile group represented by the formula (AL-1) or (AL-2) below is preferred. [ka]

[0024] In formula (AL-1), R 4 , R 5 and R 6 are each independently a hydrocarbyl group having 1 to 12 carbon atoms, in which some of the -CH2- groups in the hydrocarbyl group may be substituted with -O- or -S-, and if the hydrocarbyl group contains an aromatic ring, some or all of the hydrogen atoms in the aromatic ring may be substituted with a halogen atom, a cyano group, a nitro group, an alkyl group having 1 to 4 carbon atoms which may contain a halogen atom, or an alkoxy group having 1 to 4 carbon atoms which may contain a halogen atom. n1 is 0 or 1. * represents a bond to the adjacent -O-.

[0025] R 4 , R 5 and R 6The hydrocarbyl group having 1 to 12 carbon atoms represented by the formula (I) may be saturated or unsaturated, and may be linear, branched, or cyclic. Specific examples thereof include alkyl groups having 1 to 12 carbon atoms such as methyl, ethyl, n-propyl, isopropyl, n-butyl, sec-butyl, tert-butyl, n-pentyl, tert-pentyl, n-hexyl, n-octyl, 2-ethylhexyl, n-nonyl, n-decyl, n-undecyl, and n-dodecyl; cyclopentyl, cyclohexyl, cyclopentylmethyl, cyclopentylethyl, cyclopentylbutyl, cyclohexylmethyl, cyclohexylethyl, cyclohexylbutyl, norbornyl, norbornylmethyl, adamantyl, adamantylmethyl, and tricyclo[5.2.1.0]. 2,6 ]decyl group, tetracyclo[6.2.1.1 3,6 .0 2,7 cyclic saturated hydrocarbyl groups having 3 to 12 carbon atoms, such as a dodecyl group; alkenyl groups having 2 to 12 carbon atoms, such as a vinyl group, allyl group, propenyl group, butenyl group, pentenyl group, and hexenyl group; alkynyl groups having 2 to 12 carbon atoms, such as an ethynyl group, propynyl group, butynyl group, pentynyl group, and hexynyl group; cyclic unsaturated aliphatic hydrocarbyl groups having 3 to 12 carbon atoms, such as a cyclopentenyl group and cyclohexenyl group; aryl groups having 6 to 12 carbon atoms, such as a phenyl group, naphthyl group, and indanyl group; aralkyl groups having 7 to 12 carbon atoms, such as a benzyl group, 1-phenylethyl group, and 2-phenylethyl group; and groups obtained by combining these.

[0026] Also, R 4 , R 5 and R 6 Any two of these may be bonded to each other to form a ring. Examples of the ring formed in this case include a cyclopropane ring, a cyclobutane ring, a cyclopentane ring, a cyclohexane ring, a cycloheptane ring, a cyclooctane ring, a norbornane ring, an adamantane ring, a tricyclo[5.2.1.0 2,6 ] decane ring, tetracyclo[6.2.1.1 3,6 .0 2,7]dodecane ring, etc. In addition, some of the -CH2- groups in the ring may be substituted with -O- or -S-.

[0027] In formula (AL-2), X a is -O- or -S-. 7 and R 8 are each independently a hydrogen atom or a hydrocarbyl group having 1 to 10 carbon atoms. 7 and R 8 The hydrocarbyl group having 1 to 10 carbon atoms represented by the formula (I) may be saturated or unsaturated, and may be linear, branched, or cyclic. Specific examples thereof include R 1 and R 2 Examples of the hydrocarbyl group having 1 to 10 carbon atoms represented by the following formula include the same as those exemplified above.

[0028] In formula (AL-2), R 9 is a hydrocarbyl group having 1 to 20 carbon atoms, and some of the -CH2- groups in the hydrocarbyl group may be substituted with -O- or -S-. The hydrocarbyl group may be saturated or unsaturated, and may be linear, branched, or cyclic. Specific examples thereof include alkyl groups having 1 to 20 carbon atoms such as methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, n-pentyl, n-hexyl, n-octyl, n-nonyl, n-decyl, undecyl, dodecyl, tridecyl, tetradecyl, pentadecyl, heptadecyl, octadecyl, nonadecyl, and icosyl groups; cyclopropyl, cyclopentyl, cyclohexyl, cyclopropylmethyl, 4-methylcyclohexyl, cyclohexylmethyl, norbornyl, norbornylmethyl, adamantyl, adamantylmethyl, and tricyclo[5.2.1.0] groups. 2,6 ]decyl group, tetracyclo[6.2.1.1 3,6 .0 2,7]Cyclic saturated hydrocarbyl groups having 3 to 20 carbon atoms, such as a dodecyl group; alkenyl groups having 2 to 20 carbon atoms, such as a vinyl group, a propenyl group, a butenyl group, a pentenyl group, or a hexenyl group; alkynyl groups having 2 to 20 carbon atoms, such as an ethynyl group, a propynyl group, a butynyl group, a pentynyl group, or a hexynyl group; cyclic unsaturated aliphatic hydrocarbyl groups having 3 to 20 carbon atoms, such as a cyclopentenyl group, a cyclohexenyl group, or a norbornenyl group; phenyl group, a methylphenyl group, an ethylphenyl group, an n-propylphenyl group, an isopropyl Examples include aryl groups having 6 to 20 carbon atoms such as a phenyl group, an n-butylphenyl group, an isobutylphenyl group, a sec-butylphenyl group, a tert-butylphenyl group, a naphthyl group, a methylnaphthyl group, an ethylnaphthyl group, an n-propylnaphthyl group, an isopropylnaphthyl group, an n-butylnaphthyl group, an isobutylnaphthyl group, a sec-butylnaphthyl group, and a tert-butylnaphthyl group; aralkyl groups having 7 to 20 carbon atoms such as a benzyl group and a phenethyl group; and groups obtained by combining these. 8 and R 9 and are bonded to each other, and the carbon atoms to which they are bonded and X a may form a heterocyclic group having 3 to 20 carbon atoms together with -, and some of the -CH2- in the heterocyclic group may be substituted with -O- or -S-. n2 is 0 or 1. * represents a bond to the adjacent -O-.

[0029] Examples of the acid labile group represented by formula (AL-1) include, but are not limited to, the following: In the following formula, * represents a bond to the adjacent —O—. [ka]

[0030] [ka]

[0031] [ka]

[0032] [ka]

[0033] [ka]

[0034] [ka]

[0035] [ka]

[0036] [ka]

[0037] [ka]

[0038] [ka]

[0039] [ka]

[0040] Examples of the acid labile group represented by formula (AL-2) include, but are not limited to, the following: In the following formula, * represents a bond to the adjacent —O—. [ka]

[0041] [ka]

[0042] R 3 When X is a single bond or -S-, a hydrogen atom, an alkyl group of 1 to 4 carbon atoms, an alkyl group of 1 to 4 carbon atoms substituted with a halogen atom, or a cyclic saturated hydrocarbyl group of 3 to 6 carbon atoms is preferred, and a hydrogen atom, an alkyl group of 1 to 3 carbon atoms, an alkyl group of 1 to 3 carbon atoms substituted with a halogen atom, or a cyclic saturated hydrocarbyl group of 3 to 6 carbon atoms is more preferred.When X is -O-, a hydrogen atom, an alkyl group of 1 to 4 carbon atoms other than acid labile groups, an alkyl group of 1 to 4 carbon atoms other than acid labile groups substituted with a halogen atom, or an acid labile group represented by formula (AL-1) or (AL-2) is preferred, and a hydrogen atom, a hydrocarbyl group of 1 to 3 carbon atoms other than acid labile groups, an alkyl group of 1 to 3 carbon atoms other than acid labile groups substituted with a halogen atom, or an acid labile group represented by formula (AL-1) or (AL-2) is more preferred.

[0043] Preferred examples of the anion of the onium salt represented by formula (1) include, but are not limited to, those shown below. [ka]

[0044] [ka]

[0045] [ka]

[0046] [ka]

[0047] [ka]

[0048]

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[0049]

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[0050]

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[0080] [ka]

[0081] [ka]

[0082] [ka]

[0083] [ka]

[0084] In formula (1), Z + is an onium cation represented by any one of the following formulas (cation-1) to (cation-3): [ka]

[0085] In formulas (cation-1)~(cation-3), R 11 ~R 19are each independently a hydrocarbyl group having 1 to 30 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 having 1 to 30 carbon atoms, such as methyl, ethyl, n-propyl, isopropyl, n-butyl, and tert-butyl; saturated cyclic hydrocarbyl groups having 3 to 30 carbon atoms, such as cyclopropyl, cyclopentyl, cyclohexyl, cyclopropylmethyl, 4-methylcyclohexyl, cyclohexylmethyl, norbornyl, and adamantyl; alkenyl groups having 2 to 30 carbon atoms, such as vinyl, allyl, propenyl, butenyl, and hexenyl; unsaturated cyclic hydrocarbyl groups having 3 to 30 carbon atoms, such as cyclohexenyl; aryl groups having 6 to 30 carbon atoms, such as phenyl, naphthyl, and thienyl; aralkyl groups having 7 to 30 carbon atoms, such as benzyl, 1-phenylethyl, and 2-phenylethyl; and groups obtained by combining these, with aryl groups being preferred. Furthermore, some or all of the hydrogen atoms of the hydrocarbyl group may be substituted with a group containing a heteroatom such as an oxygen atom, a sulfur atom, a nitrogen atom or a halogen atom, and some of the -CH- groups of these groups may be substituted with a group containing a heteroatom such as an oxygen atom, a sulfur atom or a nitrogen atom, resulting in the hydrocarbyl group containing a hydroxy group, a cyano group, a carbonyl group, an ether bond, an ester bond, a sulfonate ester bond, a carbonate bond, a lactone ring, a sultone ring, a carboxylic anhydride (-C(=O)-OC(=O)-), a haloalkyl group, etc.

[0086] Also, R 11 and R 12 However, they may be bonded to each other to form a ring together with the sulfur atom to which they are bonded. In this case, examples of the sulfonium cation represented by formula (cation-1) include those represented by the following formula: [ka] (In the formula, the dashed line indicates R 13 )

[0087] Examples of the sulfonium cation represented by formula (cation-1) include, but are not limited to, those shown below. [ka]

[0088] [ka]

[0089] [ka]

[0090] [ka]

[0091] [ka]

[0092] [ka]

[0093] [ka]

[0094] [ka]

[0095] [ka]

[0096] [ka]

[0097]

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[0098]

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[0099]

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[0100]

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[0101]

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[0102]

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[0103]

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[0104]

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[0105]

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[0106]

change

[0107]

change

[0108] Examples of the iodonium cation represented by formula (cation-2) include, but are not limited to, those shown below. [ka]

[0109] Examples of the ammonium cation represented by formula (cation-3) include, but are not limited to, those shown below. [ka]

[0110] Specific structures of the onium salt of the present invention include any combination of the above-mentioned anions and cations.

[0111] The onium salt of the present invention can be produced, for example, according to the following scheme: As an example, synthesis of onium salt (1') in which X is an oxygen atom will be described below, but the synthesis method is not limited to this. [ka] (In the formula, R 1 ~R 3 and Z + is the same as above. Et is an ethyl group. M + is a metal cation. - is an anion.)

[0112] First, the starting alcohol (SM-A) is reacted with the acid chloride (SM-B) to perform esterification. The starting alcohol (SM-A) is dissolved in a solvent such as tetrahydrofuran (THF) or acetonitrile, and the acid chloride (SM-B) is added dropwise in the presence of a base such as pyridine or 2,6-lutidine. The reaction can be carried out with heating, if necessary. From the perspective of yield, it is desirable to monitor the reaction by gas chromatography (GC) or silica gel thin-layer chromatography (TLC) to ensure completion, but the reaction time is usually about 2 to 24 hours. The intermediate (In-A) can be obtained from the reaction mixture by conventional aqueous workup, and if necessary, it can be purified by conventional methods such as distillation, chromatography, or recrystallization.

[0113] Next, the obtained intermediate (In-A) is subjected to alkaline hydrolysis using a metal hydroxide represented by M-OH to synthesize intermediate (In-B). The intermediate is dissolved in a solvent such as THF or acetonitrile, and an aqueous solution of the metal hydroxide represented by M-OH is added dropwise to perform alkaline hydrolysis. Examples of metal hydroxides that can be used include sodium hydroxide, potassium hydroxide, and lithium hydroxide. The reaction can be carried out by heating, if necessary. The reaction time is usually about 2 to 24 hours, although it is desirable to monitor the reaction by silica gel thin-layer chromatography (TLC) to complete the reaction from the viewpoint of yield. The intermediate (In-B) can be obtained from the reaction mixture by conventional aqueous work-up, and if necessary, it can be purified by conventional methods such as chromatography and recrystallization.

[0114] The final step is to convert the obtained intermediate (In-B) into Z + X - By salt exchange with an onium salt represented by the formula: - As the ions, hydrogen carbonate ions, chloride ions and bromide ions are preferred because the exchange reaction easily proceeds quantitatively.

[0115] In the above scheme, the third step, ion exchange, can be easily carried out by a known method, for example, JP-A No. 2007-145797.

[0116] The production method according to the above scheme is merely an example, and the production method of the onium salt of the present invention is not limited to this.

[0117] [Quencher] The onium salt of the present invention is useful as a quencher. In the present invention, a quencher is a material that traps the acid generated from a photoacid generator in a resist composition, thereby preventing the acid from diffusing to unexposed areas and allowing the formation of a desired pattern.

[0118] When the onium salt of the present invention is coexisted with an onium salt that generates a strong acid, such as a sulfonic acid, imide acid, or methide acid fluorinated at the α-position, the corresponding carboxylic acid and strong acid are generated upon irradiation with light. Meanwhile, in areas with low exposure, a large amount of undecomposed onium salt remains. While the strong acid functions as a catalyst to induce the deprotection reaction of the base polymer, the onium salt of the present invention hardly induces the deprotection reaction. The strong acid undergoes ion exchange with the remaining carboxylic acid sulfonium salt to form an onium salt of the strong acid, which releases a carboxylic acid instead. In other words, the strong acid is neutralized by the carboxylic acid onium salt through ion exchange. That is, the onium salt of the present invention functions as a quencher. This onium salt-type quencher generally tends to produce a smaller LWR of the resist pattern than quenchers using amine compounds.

[0119] The salt exchange between the strong acid and the carboxylic acid onium salt is repeated countless times. The location where the strong acid is generated at the end of exposure is different from the location where the strong acid-generating onium salt was initially present. It is presumed that the repeated cycle of acid generation by light and salt exchange averages out the acid generation points, thereby reducing the LWR of the resist pattern after development.

[0120] Materials that exhibit a quencher effect through a similar mechanism include, for example, carboxylic acid onium salts, alkane sulfonic acid onium salts, arenesulfonic acid onium salts, and α,α-difluorocarboxylic acid onium salts, as described in Patent Documents 1 to 6. Examples of onium salts include sulfonium salts, iodonium salts, and ammonium salts. When using alkane sulfonic acid onium salts or arenesulfonic acid onium salts, the acid strength of the generated acid is relatively high, so some of the acid acts as an acid generator rather than a quencher, causing deprotection reactions. This results in reduced resolution and increased acid diffusion, degrading resist performance such as exposure margin (EL) and mask error factor (MEF). Furthermore, the α,α-difluorocarboxylic acid onium salts described in Patent Document 6 are carboxylic acid onium salts, but have a fluorine atom at the α-position of the carboxylate anion. This means that, like the sulfonic acid onium salts, the acidity of the generated acid is relatively high, potentially causing deprotection reactions depending on the acid-labile group selected in the base polymer. Fluorocarboxylic acid onium salts with simply elongated linear chains also exhibit high acid diffusion, leading to salt exchange with strong acids in unexposed areas, which is thought to result in reduced resolution, EL, and MEF. Furthermore, while alkanecarboxylic acids function as quenchers, they are highly hydrophilic. While fluoroalkanecarboxylic acid onium salts such as those described in Patent Document 3 can control hydrophilicity to a certain extent compared to non-fluorinated types, hydrophilicity control is still insufficient when the carbon number is low. While perfluoroalkanecarboxylic acid onium salts with a high carbon number are also exemplified, in this case the carboxylic acid exhibits surfactant-like properties and is thought to have poor compatibility with resist compositions. Poor compatibility with resist compositions can lead to defects. Furthermore, perfluoroalkanecarboxylic acids are undesirable from the perspective of biology and the environment.

[0121] The onium salt of the present invention can solve the above-mentioned problems. Onium salts having these structures as anions act as quenchers and effectively trap the strong acid generated from the acid generator, thereby forming a 1,3-dicarboxylic acid monoester or 1,3-ketocarboxylic acid structure. In formula (1), R 3 When the 1,3-dicarboxylic acid monoester, 1,3-ketocarboxylic acid, and 1,3-dicarboxylic acid form an acid-labile group with the adjacent oxygen atom, the acid-labile group reacts with a strong acid to eliminate the acid-labile group, improving resist sensitivity and forming a 1,3-dicarboxylic acid (e.g., malonic acid) structure. In the subsequent PEB process, the 1,3-dicarboxylic acid monoester, 1,3-ketocarboxylic acid, and 1,3-dicarboxylic acid undergo a thermal decarboxylation reaction, decomposing into carbon dioxide and the corresponding acetic acid derivative or ketone derivative, which then volatilizes from the film. During subsequent development with an alkaline developer, the absence of carboxylic acid, which has a high affinity for the alkaline developer, suppresses swelling and prevents resist pattern collapse, a problem that has been a problem in fine pattern formation.

[0122] [Resist composition] The resist composition of the present invention contains, as an essential component, (A) a quencher made of an onium salt represented by formula (1).

[0123] In the resist composition of the present invention, the content of the quencher (A) is preferably 0.1 to 40 parts by mass, and more preferably 1 to 20 parts by mass, relative to 80 parts by mass of the base polymer (C) described below. When the content of the quencher (A) is within this range, the quencher functions satisfactorily and there is no risk of performance degradation such as reduced sensitivity or generation of foreign matter due to insufficient solubility.

[0124] [(B) Organic solvent] The resist composition of the present invention may contain an organic solvent as component (B). There are no particular limitations on the organic solvent (B) as long as it is capable of dissolving component (A) and the components described below. Examples of such organic solvents include ketones such as cyclopentanone, cyclohexanone, and methyl-2-n-pentyl ketone; alcohols such as 3-methoxybutanol, 3-methyl-3-methoxybutanol, 1-methoxy-2-propanol, and 1-ethoxy-2-propanol; ketoalcohols such as diacetone alcohol (DAA); propylene glycol monomethyl ether (PGME), ethylene glycol monomethyl ether, propylene glycol monoethyl ether, ethylene glycol monoethyl ether, and propylene glycol diethyl ether. Examples of suitable solvents include ethers such as methyl ether and diethylene glycol dimethyl ether; esters such as propylene glycol monomethyl ether acetate (PGMEA), propylene glycol monoethyl ether acetate, ethyl lactate, ethyl pyruvate, butyl acetate, methyl 3-methoxypropionate, ethyl 3-ethoxypropionate, tert-butyl acetate, tert-butyl propionate, and propylene glycol mono-tert-butyl ether acetate; lactones such as γ-butyrolactone (GBL), and mixed solvents thereof.

[0125] Among these organic solvents, PGME, PGMEA, cyclohexanone, GBL, DAA, ethyl lactate, and mixed solvents thereof are preferred because they have particularly excellent solubility for the base polymer of component (C).

[0126] In the resist composition of the present invention, the content of (B) organic solvent is preferably 200 to 5000 parts by mass, and more preferably 400 to 3500 parts by mass, relative to 80 parts by mass of (C) base polymer (described below). (B) organic solvent may be used alone or in combination of two or more types.

[0127] [(C) Base polymer] The resist composition of the present invention may contain a base polymer as component (C). The base polymer (C) contains a repeating unit represented by the following formula (a1) (hereinafter also referred to as repeating unit a1): [ka]

[0128] In formula (a1), R A is a hydrogen atom, a fluorine atom, a methyl group, or a trifluoromethyl group. 1 is a single bond, a phenylene group, a naphthylene group, or *-C(=O)-OX 11 -, and the phenylene group or naphthylene group may be substituted with a halogen atom or an alkoxy group having 1 to 10 carbon atoms which may contain a fluorine atom. 11 is a saturated hydrocarbylene group having 1 to 10 carbon atoms, which may contain a hydroxy group, an ether bond, an ester bond or a lactone ring, a phenylene group or a naphthylene group, and the saturated hydrocarbylene group may contain a hydroxy group, an ether bond, an ester bond or a lactone ring. * represents a bond to a carbon atom in the main chain. AL 1 is an acid labile group.

[0129] In formula (a1), AL 1 is an acid labile group. Examples of the acid labile group include those described in JP-A Nos. 2013-80033 and 2013-83821.

[0130] Typical examples of the acid labile group include those represented by the following formulae (AL-3) to (AL-5). [ka] (In the formula, the dashed lines represent bonds.)

[0131] In formulas (AL-3) and (AL-4), R L1 and R L2are each independently a saturated hydrocarbyl group having 1 to 40 carbon atoms, which may contain a heteroatom such as an oxygen atom, a sulfur atom, a nitrogen atom, or a fluorine atom. The saturated hydrocarbyl group may be linear, branched, or cyclic. The saturated hydrocarbyl group preferably has 1 to 20 carbon atoms.

[0132] In formula (AL-3), k is an integer of 0 to 10, and an integer of 1 to 5 is preferred.

[0133] In formula (AL-4), R L3 and R L4 are each independently a hydrogen atom or a saturated hydrocarbyl group having 1 to 20 carbon atoms, and may contain a heteroatom such as an oxygen atom, a sulfur atom, a nitrogen atom, or a fluorine atom. The hydrocarbyl group may be linear, branched, or cyclic. L2 , R L3 and R L4 Any two of these may be bonded to each other to form a ring having 3 to 20 carbon atoms together with the carbon atom or the carbon atom and oxygen atom to which they are bonded. As the ring, a ring having 4 to 16 carbon atoms is preferred, and an alicyclic ring is particularly preferred.

[0134] In formula (AL-5), R L5 , R L6 and R L7 are each independently a saturated hydrocarbyl group having 1 to 20 carbon atoms, which may contain a heteroatom such as an oxygen atom, a sulfur atom, a nitrogen atom, or a fluorine atom. The hydrocarbyl group may be linear, branched, or cyclic. L5 , R L6 and R L7 Any two of these may be bonded to each other together with the carbon atoms to which they are bonded to form a ring having 3 to 20 carbon atoms. As the ring, a ring having 4 to 16 carbon atoms is preferred, and an alicyclic ring is particularly preferred.

[0135] Examples of the repeating unit a1 include, but are not limited to, those shown below. A and AL 1 is the same as above. [ka]

[0136] [ka]

[0137] [ka]

[0138] The base polymer may further contain a repeating unit represented by the following formula (a2) (hereinafter also referred to as repeating unit a2). [ka]

[0139] In formula (a2), R A is a hydrogen atom, a fluorine atom, a methyl group, or a trifluoromethyl group. 2 is a single bond or *-C(=O)-O-. * represents a bond to a carbon atom in the main chain. R 21 is a halogen atom, a cyano group, a hydrocarbyl group having 1 to 20 carbon atoms which may contain a heteroatom, a hydrocarbyloxy group having 1 to 20 carbon atoms which may contain a heteroatom, a hydrocarbylcarbonyl group having 2 to 20 carbon atoms which may contain a heteroatom, a hydrocarbylcarbonyloxy group having 2 to 20 carbon atoms which may contain a heteroatom, or a hydrocarbyloxycarbonyl group having 2 to 20 carbon atoms which may contain a heteroatom. a is an integer of 0 to 4, preferably 0 or 1. AL 2 is an acid labile group. The acid labile group may be AL 1 Examples of the acid labile group represented by the formula (I) include the same as those exemplified above.

[0140] Examples of the repeating unit a2 include, but are not limited to, those shown below. A and AL 2is the same as above. [ka]

[0141] The base polymer preferably further contains a repeating unit represented by the following formula (b1) (hereinafter also referred to as repeating unit b1) or a repeating unit represented by the following formula (b2) (hereinafter also referred to as repeating unit b2). [ka]

[0142] In formulas (b1) and (b2), R A are each independently a hydrogen atom, a fluorine atom, a methyl group, or a trifluoromethyl group. 1 is a single bond or *-C(=O)-O-. 22 R is a group having 1 to 20 carbon atoms and containing at least one structure selected from a hydrogen atom, a hydroxy group other than a phenolic hydroxy group, a cyano group, a carbonyl group, a carboxy group, an ether bond, an ester bond, a sulfonate ester bond, a carbonate bond, a lactone ring, a sultone ring, and a carboxylic anhydride (-C(=O)-OC(=O)-). 23 is a halogen atom, a hydroxy group, a nitro group, a hydrocarbyl group having 1 to 20 carbon atoms which may contain a heteroatom, a hydrocarbyloxy group having 1 to 20 carbon atoms which may contain a heteroatom, a hydrocarbylcarbonyl group having 2 to 20 carbon atoms which may contain a heteroatom, a hydrocarbylcarbonyloxy group having 2 to 20 carbon atoms which may contain a heteroatom, or a hydrocarbyloxycarbonyl group having 2 to 20 carbon atoms which may contain a heteroatom. b is an integer of 1 to 4. c is an integer of 0 to 4, provided that 1≦b+c≦5.

[0143] Examples of the repeating unit b1 include, but are not limited to, those shown below. A is the same as above. [ka]

[0144]

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[0145]

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[0146]

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[0147]

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[0148]

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[0149]

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[0150]

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[0151]

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[0152]

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[0153]

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[0154] [ka]

[0155] [ka]

[0156] [ka]

[0157] [ka]

[0158] [ka]

[0159] Examples of the repeating unit b2 include, but are not limited to, those shown below. A is the same as above. [ka]

[0160] [ka]

[0161] [ka]

[0162] [ka]

[0163] [ka]

[0164] As the repeating unit b1 or b2, those having a lactone ring as a polar group are particularly preferred for ArF lithography, and those having a phenol moiety are preferred for KrF lithography, EB lithography and EUV lithography.

[0165] The base polymer may further contain a repeating unit represented by any one of the following formulas (c1) to (c4) (hereinafter also referred to as repeating units c1 to c4, respectively). [ka]

[0166] In formulas (c1) to (c4), R A are each independently a hydrogen atom, a fluorine atom, a methyl group, or a trifluoromethyl group. 1 is a single bond or a phenylene group. 2 is *-C(=O)-OZ 21 -, *-C(=O)-NH-Z 21 -or*-OZ 21 -It is. Z 21 Z is an aliphatic hydrocarbylene group having 1 to 6 carbon atoms, a phenylene group, or a divalent group obtained by combining these, and may contain a carbonyl group, an ester bond, an ether bond, or a hydroxy group. 3 is a single bond, a phenylene group, a naphthylene group, or *-C(=O)-OZ 31 -It is. Z 31 is an aliphatic hydrocarbylene group having 1 to 10 carbon atoms, a phenylene group, or a naphthylene group, and the aliphatic hydrocarbylene group may contain a hydroxy group, an ether bond, an ester bond, or a lactone ring. 4 is a single bond or *-Z 41 -C(=O)-O-. Z 41 is a hydrocarbylene group having 1 to 20 carbon atoms which may contain a heteroatom. 5represents a single bond, a methylene group, an ethylene group, a phenylene group, a fluorinated phenylene group, a phenylene group substituted with a trifluoromethyl group, *-C(=O)-OZ 51 -, *-C(=O)-N(H)-Z 51 -or*-OZ 51 -It is. Z 51 represents an aliphatic hydrocarbylene group having 1 to 6 carbon atoms, a phenylene group, a fluorinated phenylene group, or a phenylene group substituted with a trifluoromethyl group, and may contain a carbonyl group, an ester bond, an ether bond, or a hydroxy group. * represents a bond to a carbon atom in the main chain.

[0167] Z 21 , Z 31 and Z 51 The aliphatic hydrocarbylene group represented by the formula (I) may be linear, branched or cyclic, and specific examples thereof include a methanediyl group, an ethane-1,1-diyl group, an ethane-1,2-diyl group, a propane-1,1-diyl group, a propane-1,2-diyl group, a propane-1,3-diyl group, a propane-2,2-diyl group, a butane-1,1-diyl group, a butane-1,2-diyl group, a butane-1,3-diyl group, a butane- Examples of the alkyl group include alkanediyl groups such as a 2,3-diyl group, a butane-1,4-diyl group, a 1,1-dimethylethane-1,2-diyl group, a pentane-1,5-diyl group, a 2-methylbutane-1,2-diyl group, and a hexane-1,6-diyl group; cycloalkanediyl groups such as a cyclopropanediyl group, a cyclobutanediyl group, a cyclopentanediyl group, and a cyclohexanediyl group; and groups obtained by combining these groups.

[0168] Z 41 The hydrocarbylene group represented by the formula (I) may be saturated or unsaturated, and may be linear, branched, or cyclic. Specific examples thereof include, but are not limited to, those shown below. [ka] (In the formula, the dashed lines represent bonds.)

[0169] In formula (c1), R 31and R 32 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 having 1 to 20 carbon atoms, such as methyl, ethyl, n-propyl, isopropyl, n-butyl, and tert-butyl; saturated cyclic hydrocarbyl groups having 3 to 20 carbon atoms, such as cyclopropyl, cyclopentyl, cyclohexyl, cyclopropylmethyl, 4-methylcyclohexyl, cyclohexylmethyl, norbornyl, and adamantyl; alkenyl groups having 2 to 20 carbon atoms, such as vinyl, allyl, propenyl, butenyl, and hexenyl; unsaturated cyclic hydrocarbyl groups having 3 to 20 carbon atoms, such as cyclohexenyl; aryl groups having 6 to 20 carbon atoms, such as phenyl, naphthyl, and thienyl; aralkyl groups, such as benzyl, 1-phenylethyl, and 2-phenylethyl; and groups obtained by combining these, with aryl groups being preferred. Furthermore, some or all of the hydrogen atoms of the hydrocarbyl group may be substituted with a group containing a heteroatom such as an oxygen atom, a sulfur atom, a nitrogen atom or a halogen atom, and some of the -CH- groups of the hydrocarbyl group may be substituted with a group containing a heteroatom such as an oxygen atom, a sulfur atom or a nitrogen atom, and as a result, the hydrocarbyl group may contain a hydroxy group, a fluorine atom, a chlorine atom, a bromine atom, an iodine atom, a cyano group, a carbonyl group, an ether bond, an ester bond, a sulfonate ester bond, a carbonate bond, a lactone ring, a sultone ring, a carboxylic anhydride (-C(=O)-OC(=O)-), a haloalkyl group, etc.

[0170] Also, R 31 and R 32 and may be bonded to each other to form a ring together with the sulfur atom to which they are bonded. In this case, the ring is the same as that described in the explanation of formula (cation-1) as R 11 and R 12 Examples of the ring that can be formed by bonding these together with the sulfur atom to which they are bonded are the same as those exemplified above.

[0171] Examples of the cation of the repeating unit c1 include, but are not limited to, the following: A is the same as above. [ka]

[0172] [ka]

[0173] [ka]

[0174] [ka]

[0175] [ka]

[0176] [ka]

[0177] [ka]

[0178] In formula (c1), M -is a non-nucleophilic counter ion. Examples of the non-nucleophilic counter ion include halide ions such as chloride ion and bromide ion; fluoroalkylsulfonate ions such as triflate ion, 1,1,1-trifluoroethanesulfonate ion and nonafluorobutanesulfonate ion; arylsulfonate ions such as tosylate ion, benzenesulfonate ion, 4-fluorobenzenesulfonate ion and 1,2,3,4,5-pentafluorobenzenesulfonate ion; alkylsulfonate ions such as mesylate ion and butanesulfonate ion; imide ions such as bis(trifluoromethylsulfonyl)imide ion, bis(perfluoroethylsulfonyl)imide ion and bis(perfluorobutylsulfonyl)imide ion; and methide ions such as tris(trifluoromethylsulfonyl)methide ion and tris(perfluoroethylsulfonyl)methide ion.

[0179] Further examples of the non-nucleophilic counter ion include a sulfonate anion represented by the following formula (c1-1) in which the α-position is substituted with a fluorine atom, and a sulfonate anion represented by the following formula (c1-2) in which the α-position is substituted with a fluorine atom and the β-position is substituted with a trifluoromethyl group. [ka]

[0180] In formula (c1-1), R 33 is a hydrogen atom, a hydrocarbyl group having 1 to 30 carbon atoms, a hydrocarbylcarbonyloxy group having 2 to 30 carbon atoms, or a hydrocarbyloxycarbonyl group having 2 to 30 carbon atoms, and the hydrocarbyl group may contain a halogen atom, an ether bond, an ester bond, a carbonyl group, or a lactone ring. The hydrocarbyl group and the hydrocarbyl moiety of the hydrocarbylcarbonyloxy group and hydrocarbyloxycarbonyl group may be saturated or unsaturated, and may be linear, branched, or cyclic. Specific examples thereof include R in formula (2A') described below. fa1 Examples of the hydrocarbyl group represented by the formula (I) include the same as those exemplified above.

[0181] In formula (c1-2), R 34 R is a hydrogen atom, a hydrocarbyl group having 1 to 30 carbon atoms, or a hydrocarbylcarbonyl group having 2 to 30 carbon atoms, and the hydrocarbyl group and hydrocarbylcarbonyl group may contain a halogen atom, an ether bond, an ester bond, a carbonyl group, or a lactone ring. 35 is a hydrogen atom, a fluorine atom, or a fluorinated alkyl group having 1 to 6 carbon atoms. The hydrocarbyl moiety of the hydrocarbyl group and the hydrocarbyl carbonyl group may be saturated or unsaturated, and may be linear, branched, or cyclic. Specific examples thereof include R in formula (2A') described below. fa1 Examples of the hydrocarbyl group represented by R include the same as those exemplified above. 35 As the aryl group, a trifluoromethyl group is preferred.

[0182] Specific examples of the sulfonate anion represented by formula (c1-1) or (c1-2) include, but are not limited to, the following: 35 is the same as above, and Ac is an acetyl group. [ka]

[0183] [ka]

[0184] [ka]

[0185] [ka]

[0186] [ka]

[0187] [ka]

[0188] [ka]

[0189] [ka]

[0190] [ka]

[0191] [ka]

[0192] In formulas (c2) and (c3), L 1 is a single bond, an ether bond, an ester bond, a carbonyl group, a sulfonate ester bond, a carbonate bond, or a carbamate bond. Among these, from the viewpoint of synthesis, an ether bond, an ester bond, or a carbonyl group is preferred, and an ester bond or a carbonyl group is more preferred.

[0193] In formula (c2), Rf 1 and Rf 2 are each independently a fluorine atom or a fluorinated alkyl group having 1 to 6 carbon atoms. 1 and Rf 2 In order to increase the acid strength of the generated acid, it is preferable that Rf be a fluorine atom. 3 and Rf 4 are each independently a hydrogen atom, a fluorine atom, or a fluorinated alkyl group having 1 to 6 carbon atoms. Of these, Rf 3 and Rf 4 At least one of these is preferably a trifluoromethyl group.

[0194] In formula (c3), Rf 5 and Rf 6 are each independently a hydrogen atom, a fluorine atom, or a fluorinated alkyl group having 1 to 6 carbon atoms, provided that all Rf 5 and Rf 6 cannot be simultaneously hydrogen atoms. Among these, Rf 5 and Rf 6 At least one of these is preferably a trifluoromethyl group.

[0195] In the formulae (c2) and (c3), d is an integer of 0 to 3, with 1 being preferred.

[0196] Examples of the anion of the repeating unit c2 include, but are not limited to, those shown below. A is the same as above. [ka]

[0197] [ka]

[0198] [ka]

[0199] [ka]

[0200] [ka]

[0201] [ka]

[0202] Examples of the anion of the repeating unit c3 include, but are not limited to, those shown below. A is the same as above. [ka]

[0203] [ka]

[0204] [ka]

[0205] Specific examples of the anion of the repeating unit c4 include, but are not limited to, those shown below. A is the same as above. [ka]

[0206] In formulas (c2) to (c4), A + is an onium cation. Examples of the onium cation include a sulfonium cation, an iodonium cation, and an ammonium cation, and the sulfonium cation and the iodonium cation are preferred. Specific structures of these cations include those exemplified as the cations represented by formulas (cation-1) to (cation-3).

[0207] The repeating units c1 to c4 function as a photoacid generator. When a base polymer containing repeating units c1 to c4 (i.e., a polymer-bound acid generator) is used, the resist composition of the present invention may or may not contain a photoacid generator (D) described below.

[0208] The base polymer may further contain a repeating unit having a structure in which a hydroxy group is protected by an acid labile group (hereinafter also referred to as repeating unit d). The repeating unit d is not particularly limited as long as it has one or more structures in which a hydroxy group is protected and the protecting group is decomposed by the action of an acid to generate a hydroxy group, but is preferably one represented by the following formula (d1): [ka]

[0209] In formula (d1), R A is the same as above. R 41 R is a (d+1)-valent hydrocarbon group having 1 to 30 carbon atoms which may contain a heteroatom. 42 is an acid labile group. e is an integer of 1 to 4.

[0210] In formula (d1), R 42 The acid labile group represented by R may be any group that can be deprotected by the action of an acid to generate a hydroxy group. 42 Although the structure is not particularly limited, an acetal structure, a ketal structure, an alkoxycarbonyl group, an alkoxymethyl group represented by the following formula (d2), and the like are preferred, and an alkoxymethyl group represented by the following formula (d2) is particularly preferred. [ka] (In the formula, * represents a bond. R 43 is a hydrocarbyl group having 1 to 15 carbon atoms.

[0211] R 42 Specific examples of the acid labile group represented by the formula (d2), the alkoxymethyl group represented by the formula (d3), and the repeating unit d are the same as those exemplified in the description of the repeating unit d described in JP-A-2020-111564.

[0212] The base polymer may further contain a repeating unit e derived from indene, benzofuran, benzothiophene, acenaphthylene, chromone, coumarin, norbornadiene or derivatives thereof. Examples of the monomer that gives the repeating unit e include, but are not limited to, those shown below. [Chemical formula]

[0213] The base polymer may further contain a repeating unit f derived from indane, vinyl pyridine or vinyl carbazole. <​​​​​​​​​Furthermore, since the influence of Mw / Mn on the molecular weight distribution of the polymer tends to become greater as the pattern rule becomes finer, in order to obtain a resist composition that is suitable for use with fine pattern dimensions, it is preferable that Mw / Mn be a narrow dispersity of 1.0 to 2.0. If it is within this range, there will be little low-molecular-weight or high-molecular-weight polymer, and there will be no risk of foreign matter being observed on the pattern or deterioration of the pattern shape after exposure.

[0217] To synthesize the polymer, for example, a monomer that provides the repeating unit described above may be polymerized by heating in an organic solvent with the addition of a radical polymerization initiator.

[0218] Examples of organic solvents used during polymerization include toluene, benzene, THF, diethyl ether, dioxane, cyclohexane, cyclopentane, methyl ethyl ketone (MEK), PGMEA, and GBL. Examples of the polymerization initiator include 2,2'-azobisisobutyronitrile (AIBN), 2,2'-azobis(2,4-dimethylvaleronitrile), dimethyl-2,2-azobis(2-methylpropionate), 1,1'-azobis(1-acetoxy-1-phenylethane), benzoyl peroxide, and lauroyl peroxide. The amount of these initiators added is preferably 0.01 to 25 mol% based on the total amount of monomers to be polymerized. The reaction temperature is preferably 50 to 150°C, more preferably 60 to 100°C. The reaction time is preferably 2 to 24 hours, and more preferably 2 to 12 hours from the viewpoint of production efficiency.

[0219] The polymerization initiator may be added to the monomer solution and then fed to the reaction vessel. Alternatively, an initiator solution may be prepared separately from the monomer solution and then fed to the reaction vessel independently. From the perspective of quality control, it is preferable to prepare the monomer solution and the initiator solution independently and then add them dropwise, since radicals generated from the initiator during the waiting time may cause the polymerization reaction to proceed, resulting in the formation of ultra-high molecular weight polymers. The acid labile group may be used as is after being introduced into the monomer, or may be protected or partially protected after polymerization. Furthermore, known chain transfer agents such as dodecyl mercaptan and 2-mercaptoethanol may be used in combination to adjust the molecular weight. In this case, the amount of the chain transfer agent added is preferably 0.01 to 20 mol % of the total amount of monomers to be polymerized.

[0220] In the case of a monomer containing a hydroxy group, the hydroxy group may be substituted with an acetal group, such as an ethoxyethoxy group, which is easily deprotected by an acid, during polymerization, and then deprotected with a weak acid and water after polymerization. Alternatively, the hydroxy group may be substituted with an acetyl group, a formyl group, a pivaloyl group, or the like, and then subjected to alkaline hydrolysis after polymerization.

[0221] When copolymerizing hydroxystyrene or hydroxyvinylnaphthalene, hydroxystyrene or hydroxyvinylnaphthalene and other monomers may be polymerized by heating in an organic solvent with the addition of a radical polymerization initiator. Alternatively, acetoxystyrene or acetoxyvinylnaphthalene may be used, and the acetoxy group may be deprotected by alkaline hydrolysis after polymerization to produce polyhydroxystyrene or Poly Hydroxy Shibi It may also be converted to phenylnaphthalene.

[0222] The base that can be used in alkaline hydrolysis includes aqueous ammonia, triethylamine, etc. The reaction temperature is preferably −20 to 100° C., more preferably 0 to 60° C. The reaction time is preferably 0.2 to 100 hours, more preferably 0.5 to 20 hours.

[0223] The amount of each monomer in the monomer solution may be appropriately set so as to achieve the preferred content ratio of the repeating units described above.

[0224] The polymer obtained by the above-described production method may be a reaction solution obtained by a polymerization reaction as a final product, or a powder obtained through a purification step such as a reprecipitation method in which a polymerization solution is added to a poor solvent to obtain a powder, and the resulting powder may be handled as a final product. However, from the viewpoint of work efficiency and quality stability, it is preferable to handle a polymer solution obtained by dissolving the powder obtained through the purification step in a solvent as a final product.

[0225] Specific examples of the solvent used in this case include ketones such as cyclohexanone and methyl-2-n-pentyl ketone; alcohols such as 3-methoxybutanol, 3-methyl-3-methoxybutanol, 1-methoxy-2-propanol, and 1-ethoxy-2-propanol; and alcohols such as PGME, ethylene glycol monomethyl ether, propylene glycol monoethyl ether, ethylene glycol monoethyl ether, propylene glycol dimethyl ether, and diethylene glycol dimethyl ether, as described in paragraphs

[0144] and

[0145] of JP-A-2008-111103. ethers; esters such as PGMEA, propylene glycol monoethyl ether acetate, ethyl lactate, ethyl pyruvate, butyl acetate, methyl 3-methoxypropionate, ethyl 3-ethoxypropionate, tert-butyl acetate, tert-butyl propionate, and propylene glycol mono tert-butyl ether acetate; lactones such as GBL; alcohols such as DAA; high-boiling alcohol solvents such as diethylene glycol, propylene glycol, glycerin, 1,4-butanediol, and 1,3-butanediol; and mixed solvents thereof.

[0226] The concentration of the polymer in the polymer solution is preferably 0.01 to 30% by mass, more preferably 0.1 to 20% by mass.

[0227] The reaction solution and polymer solution are preferably filtered through a filter, which is effective in stabilizing quality by removing foreign matter and gels that may cause defects.

[0228] Examples of filter materials used in the filter filtration include fluorocarbon, cellulose, nylon, polyester, and hydrocarbon-based materials. However, in the filtration process of resist compositions, filters made of fluorocarbons, such as Teflon (registered trademark), hydrocarbons such as polyethylene and polypropylene, or nylon are preferred. The pore size of the filter can be selected appropriately depending on the target cleanliness, but is preferably 100 nm or less, more preferably 20 nm or less. These filters may be used alone or in combination. The filtration method may involve passing the solution through the filter only once, but it is more preferable to circulate the solution and filter it multiple times. The filtration process can be performed in any order and any number of times in the polymer production process. However, it is preferable to filter the reaction solution after the polymerization reaction, the polymer solution, or both.

[0229] The base polymer (C) may be used singly or in combination of two or more different polymers with different composition ratios, Mw, and / or Mw / Mn. The base polymer (C) may also contain, in addition to the above-mentioned polymer, a hydrogenated ring-opening metathesis polymer, and the polymers described in JP-A-2003-66612 can be used.

[0230] [(D) Photoacid generator] The resist composition of the present invention may contain a photoacid generator as component (D). The photoacid generator for component (D) is not particularly limited as long as it is a compound that generates an acid upon exposure to high-energy rays. Suitable photoacid generators include those represented by the following formula (2): [ka]

[0231] In formula (2), R 101 , R 102 and R 103 are each independently a hydrocarbyl group having 1 to 20 carbon atoms which may contain a heteroatom. 101 , R 102 and R 103 Any two of these may be bonded to each other to form a ring together with the sulfur atom to which they are bonded. 11 ~R 13 Examples of the hydrocarbyl group represented by formula (2) include the same as those exemplified above. Examples of the cation of the sulfonium salt represented by formula (2) include the same as those exemplified above as the sulfonium cation represented by formula (cation-1).

[0232] In formula (2), Xa - is an anion selected from the following formulae (2A) to (2D). [ka]

[0233] In formula (2A), R fa is a hydrocarbyl group having 1 to 40 carbon atoms which may contain a fluorine atom or a heteroatom. The hydrocarbyl group may be saturated or unsaturated, and may be linear, branched, or cyclic. Specific examples thereof include R in formula (2A') described below. fa1 Examples of the hydrocarbyl group represented by the formula (I) include the same as those exemplified above.

[0234] The anion represented by formula (2A) is preferably one represented by the following formula (2A'). TIFF0007760962000154.tif1679

[0235] In formula (2A'), R HF is a hydrogen atom or a trifluoromethyl group, preferably a trifluoromethyl group.

[0236] R fa1 is a hydrocarbyl group having 1 to 38 carbon atoms which may contain a heteroatom. The heteroatom is preferably an oxygen atom, a nitrogen atom, a sulfur atom, a halogen atom, or the like, and more preferably an oxygen atom. In order to obtain high resolution in the formation of a fine pattern, the hydrocarbyl group is particularly preferably one having 6 to 30 carbon atoms.

[0237] R fa1 The hydrocarbyl group having 1 to 38 carbon atoms and represented by the formula (I) may be saturated or unsaturated, and may be linear, branched, or cyclic. Specific examples thereof include alkyl groups having 1 to 30 carbon atoms, such as methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, pentyl, neopentyl, hexyl, heptyl, octyl, 2-ethylhexyl, nonyl, decyl, undecyl, dodecyl, tridecyl, pentadecyl, heptadecyl, and icosyl groups; cyclopentyl, cyclohexyl, 1-adamantyl, 2-adamantyl, and 1-adamantylmethyl. saturated cyclic hydrocarbyl groups having 3 to 30 carbon atoms such as a norbornyl group, a norbornylmethyl group, a tricyclodecanyl group, a tetracyclododecanyl group, a tetracyclododecanylmethyl group, or a dicyclohexylmethyl group; unsaturated aliphatic hydrocarbyl groups having 2 to 30 carbon atoms such as an allyl group or a 3-cyclohexenyl group; aryl groups having 6 to 30 carbon atoms such as a phenyl group, a 1-naphthyl group, or a 2-naphthyl group; aralkyl groups having 7 to 38 carbon atoms such as a benzyl group or a diphenylmethyl group; and groups obtained by combining these.

[0238] Furthermore, some or all of the hydrogen atoms of the hydrocarbyl group may be substituted with a group containing a heteroatom such as an oxygen atom, a sulfur atom, a nitrogen atom or a halogen atom, and some of the -CH- groups of the hydrocarbyl group may be substituted with a group containing a heteroatom such as an oxygen atom, a sulfur atom or a nitrogen atom, and as a result, the hydrocarbyl group may contain a hydroxy group, a fluorine atom, a chlorine atom, a bromine atom, an iodine atom, a cyano group, a carbonyl group, an ether bond, an ester bond, a sulfonate ester bond, a carbonate bond, a lactone ring, a sultone ring, a carboxylic anhydride (-C(=O)-OC(=O)-), a haloalkyl group, etc. Examples of hydrocarbyl groups containing heteroatoms include tetrahydrofuryl, methoxymethyl, ethoxymethyl, methylthiomethyl, acetamidomethyl, trifluoroethyl, (2-methoxyethoxy)methyl, acetoxymethyl, 2-carboxy-1-cyclohexyl, 2-oxopropyl, 4-oxo-1-adamantyl, 5-hydroxy-1-adamantyl, 5-tert-butylcarbonyloxy-1-adamantyl, 4-oxatricyclo[4.2.1.0]. 3,7 ]nonan-5-on-2-yl group, 3-oxocyclohexyl group, and the like.

[0239] Synthesis of sulfonium salts containing anions represented by formula (2A') is described in detail in JP-A Nos. 2007-145797, 2008-106045, 2009-7327, and 2009-258695. Sulfonium salts described in JP-A Nos. 2010-215608, 2012-41320, 2012-106986, and 2012-153644 are also suitable.

[0240] Examples of the anion represented by formula (2A) include the same anions as those exemplified as the anions represented by formulae (c1-1) and (c1-2).

[0241] In formula (2B), R fb1 and R fb2are each independently a hydrocarbyl group having 1 to 40 carbon atoms which may contain a fluorine atom or a heteroatom. The hydrocarbyl group may be saturated or unsaturated, and may be linear, branched, or cyclic. Specific examples thereof include R in formula (2A'). fa1 Examples of the hydrocarbyl group represented by R include the same as those exemplified above. fb1 and R fb2 is preferably a fluorine atom or a linear fluorinated alkyl group having 1 to 4 carbon atoms. fb1 and R fb2 are bonded to each other and form the bonded group (-CF2-SO2-N - -SO2-CF2-) together may form a ring, in which case R fb1 and R fb2 The group obtained by bonding together is preferably a fluorinated ethylene group or a fluorinated propylene group.

[0242] In formula (2C), R fc1 , R fc2 and R fc3 are each independently a hydrocarbyl group having 1 to 40 carbon atoms which may contain a fluorine atom or a heteroatom. The hydrocarbyl group may be saturated or unsaturated, and may be linear, branched, or cyclic. Specific examples thereof include R in formula (2A'). fa1 Examples of the hydrocarbyl group represented by R include the same as those exemplified above. fc1 , R fc2 and R fc3 is preferably a fluorine atom or a linear fluorinated alkyl group having 1 to 4 carbon atoms. fc1 and R fc2 are bonded to each other and form the bonded group (-CF2-SO2-C - -SO2-CF2-) together may form a ring, in which case R fc1 and R fc2 The group obtained by bonding together is preferably a fluorinated ethylene group or a fluorinated propylene group.

[0243] In formula (2D), R fdis a hydrocarbyl group having 1 to 40 carbon atoms which may contain a heteroatom. The hydrocarbyl group may be saturated or unsaturated, and may be linear, branched, or cyclic. Specific examples thereof include R in formula (2A'). fa1 Examples of the hydrocarbyl group represented by the formula (I) include the same as those exemplified above.

[0244] The synthesis of sulfonium salts containing anions represented by formula (2D) is described in detail in JP-A-2010-215608 and JP-A-2014-133723.

[0245] Examples of the anion represented by formula (2D) include, but are not limited to, those shown below. [ka]

[0246] [ka]

[0247] Further examples of the non-nucleophilic counter ion include anions having an aromatic ring substituted with an iodine atom or a bromine atom, such as those represented by the following formula (2E): [ka]

[0248] In formula (2E), x is an integer that satisfies 1≦x≦3. y and z are integers that satisfy 1≦y≦5, 0≦z≦3, and 1≦y+z≦5. y is preferably an integer that satisfies 1≦y≦3, more preferably 2 or 3. z is preferably an integer that satisfies 0≦z≦2.

[0249] In formula (2E), X BI is an iodine atom or a bromine atom, and when x and / or y are 2 or more, they may be the same or different.

[0250] In formula (2E), L 11 is a single bond, an ether bond, an ester bond, or a saturated hydrocarbylene group having 1 to 6 carbon atoms which may contain an ether bond or an ester bond. The saturated hydrocarbylene group may be linear, branched, or cyclic.

[0251] In formula (2E), L 12 represents a single bond or a divalent linking group having 1 to 20 carbon atoms when x is 1, and represents an (x+1)-valent linking group having 1 to 20 carbon atoms when x is 2 or 3, and the linking group may contain an oxygen atom, a sulfur atom, or a nitrogen atom.

[0252] In formula (2E), R fe is a hydroxy group, a carboxy group, a fluorine atom, a chlorine atom, a bromine atom or an amino group, or a hydrocarbyl group having 1 to 20 carbon atoms, a hydrocarbyloxy group having 1 to 20 carbon atoms, a hydrocarbylcarbonyl group having 2 to 20 carbon atoms, a hydrocarbyloxycarbonyl group having 2 to 20 carbon atoms, a hydrocarbylcarbonyloxy group having 2 to 20 carbon atoms or a hydrocarbylsulfonyloxy group having 1 to 20 carbon atoms which may contain a fluorine atom, a chlorine atom, a bromine atom, a hydroxy group, an amino group or an ether bond, or feA )(R feB ), -N(R feC )-C(=O)-R feD or -N(R feC )-C(=O)-OR feD R feA and R feB are each independently a hydrogen atom or a saturated hydrocarbyl group having 1 to 6 carbon atoms. feC is a hydrogen atom or a saturated hydrocarbyl group having 1 to 6 carbon atoms, and may contain a halogen atom, a hydroxy group, a saturated hydrocarbyloxy group having 1 to 6 carbon atoms, a saturated hydrocarbylcarbonyl group having 2 to 6 carbon atoms, or a saturated hydrocarbylcarbonyloxy group having 2 to 6 carbon atoms. feDis an aliphatic hydrocarbyl group having 1 to 16 carbon atoms, an aryl group having 6 to 12 carbon atoms, or an aralkyl group having 7 to 15 carbon atoms, and may contain a halogen atom, a hydroxy group, a saturated hydrocarbyloxy group having 1 to 6 carbon atoms, a saturated hydrocarbylcarbonyl group having 2 to 6 carbon atoms, or a saturated hydrocarbylcarbonyloxy group having 2 to 6 carbon atoms. The aliphatic hydrocarbyl group may be saturated or unsaturated and may be linear, branched, or cyclic. The hydrocarbyl group, hydrocarbyloxy group, hydrocarbylcarbonyl group, hydrocarbyloxycarbonyl group, hydrocarbylcarbonyloxy group, and hydrocarbylsulfonyloxy group may be linear, branched, or cyclic. When x and / or z is 2 or more, each R fe may be the same or different from each other.

[0253] Of these, R fe Examples of the hydroxyl group include -N(R feC )-C(=O)-R feD , -N(R feC )-C(=O)-OR feD fluorine atom, chlorine atom, bromine atom, methyl group, methoxy group, etc. are preferred.

[0254] In formula (2E), Rf 11 ~Rf 14 are each independently a hydrogen atom, a fluorine atom, or a trifluoromethyl group, and at least one of them is a fluorine atom or a trifluoromethyl group. 11 and Rf 12 may combine to form a carbonyl group. 13 and Rf 14 are preferably both fluorine atoms.

[0255] Examples of the anion of the onium salt represented by formula (2E) include, but are not limited to, those shown below. BI is the same as above. [ka]

[0256]

change

[0257]

change

[0258]

change

[0259]

change

[0260]

change

[0261]

change

[0262]

change

[0263]

change

[0264]

change

[0265]

change

[0266]

change

[0267]

change

[0268]

change

[0269]

change

[0270]

change

[0271]

change

[0272]

change

[0273]

change

[0274]

change

[0275]

change

[0276]

change

[0277] [ka]

[0278] Examples of the non-nucleophilic counter ion include a fluorobenzenesulfonate anion bonded to an aromatic group containing an iodine atom as described in Japanese Patent No. 6648726, an anion having a mechanism for decomposing with an acid as described in International Publication No. 2021 / 200056 and Japanese Patent Application Publication No. 2021-70692, an anion having a cyclic ether group as described in Japanese Patent Application Publication No. 2018-180525 and Japanese Patent Application Publication No. 2021-35935, and an anion as described in Japanese Patent Application Publication No. 2018-92159.

[0279] Further examples of the non-nucleophilic counter ion include anions of bulky benzenesulfonic acid derivatives that do not contain fluorine atoms, as described in JP 2006-276759 A, JP 2015-117200 A, JP 2016-65016 A, and JP 2019-202974 A, and benzenesulfonic acid anions and alkylsulfonic acid anions that do not contain fluorine atoms bonded to aromatic groups containing iodine atoms, as described in Japanese Patent No. 6645464 A.

[0280] Further examples of the non-nucleophilic counter ion include anions of bissulfonic acid described in JP 2015-206932 A, anions of sulfonamides or sulfonimides having a sulfonic acid on one side and a different sulfonic acid on the other side described in WO 2020 / 158366 A, and anions of sulfonic acid on one side and carboxylic acid on the other described in JP 2015-24989 A.

[0281] Furthermore, the photoacid generator of the component (D) is preferably one represented by the following formula (3). [ka]

[0282] In formula (3), R 201 and R 202R are each independently a hydrocarbyl group having 1 to 30 carbon atoms which may contain a heteroatom. 203 is a hydrocarbylene group having 1 to 30 carbon atoms which may contain a heteroatom. 201 , R 202 and R 203 Any two of may be bonded to each other to form a ring together with the sulfur atom to which they are attached.

[0283] R 201 and R 202 The hydrocarbyl group having 1 to 30 carbon atoms represented by the formula (I) may be saturated or unsaturated, and may be linear, branched, or cyclic. Specific examples thereof include alkyl groups having 1 to 30 carbon atoms such as methyl, ethyl, n-propyl, isopropyl, n-butyl, sec-butyl, tert-butyl, n-pentyl, tert-pentyl, n-hexyl, n-octyl, 2-ethylhexyl, n-nonyl, and n-decyl; cyclopentyl, cyclohexyl, cyclopentylmethyl, cyclopentylethyl, cyclopentylbutyl, cyclohexylmethyl, cyclohexylethyl, cyclohexylbutyl, norbornyl, oxanorbornyl, and tricyclo[5.2.1.0]. 2,6cyclic saturated hydrocarbyl groups having 3 to 30 carbon atoms such as a phenyl group, a methylphenyl group, an ethylphenyl group, an n-propylphenyl group, an isopropylphenyl group, an n-butylphenyl group, an isobutylphenyl group, a sec-butylphenyl group, a tert-butylphenyl group, a naphthyl group, a methylnaphthyl group, an ethylnaphthyl group, an n-propylnaphthyl group, an isopropylnaphthyl group, an n-butylnaphthyl group, an isobutylnaphthyl group, a sec-butylnaphthyl group, a tert-butylnaphthyl group, an anthracenyl group, and the like; and groups obtained by combining these. Furthermore, some or all of the hydrogen atoms of the hydrocarbyl group may be substituted with a group containing a heteroatom such as an oxygen atom, a sulfur atom, a nitrogen atom or a halogen atom, and some of the -CH- groups of the hydrocarbyl group may be substituted with a group containing a heteroatom such as an oxygen atom, a sulfur atom or a nitrogen atom, and as a result, the hydrocarbyl group may contain a hydroxy group, a cyano group, a fluorine atom, a chlorine atom, a bromine atom, an iodine atom, a carbonyl group, an ether bond, an ester bond, a sulfonate ester bond, a carbonate bond, a lactone ring, a sultone ring, a carboxylic anhydride (-C(=O)-OC(=O)-), a haloalkyl group, or the like.

[0284] R 203The hydrocarbylene group having 1 to 30 carbon atoms represented by the formula (I) may be saturated or unsaturated, and may be linear, branched, or cyclic. Specific examples thereof include alkanediyl groups having 1 to 30 carbon atoms, such as methanediyl group, ethane-1,1-diyl group, ethane-1,2-diyl group, propane-1,3-diyl group, butane-1,4-diyl group, pentane-1,5-diyl group, hexane-1,6-diyl group, heptane-1,7-diyl group, octane-1,8-diyl group, nonane-1,9-diyl group, decane-1,10-diyl group, undecane-1,11-diyl group, dodecane-1,12-diyl group, tridecane-1,13-diyl group, tetradecane-1,14-diyl group, pentadecane-1,15-diyl group, hexadecane-1,16-diyl group, and heptadecane-1,17-diyl group; cyclopentanediyl group, cyclohexene-1,18-diyl group, and the like. Examples of the alkylene groups include cyclic saturated hydrocarbylene groups having 3 to 30 carbon atoms, such as xanediyl, norbornanediyl, and adamantanediyl; arylene groups having 6 to 30 carbon atoms, such as phenylene, methylphenylene, ethylphenylene, n-propylphenylene, isopropylphenylene, n-butylphenylene, isobutylphenylene, sec-butylphenylene, tert-butylphenylene, naphthylene, methylnaphthylene, ethylnaphthylene, n-propylnaphthylene, isopropylnaphthylene, n-butylnaphthylene, isobutylnaphthylene, sec-butylnaphthylene, and tert-butylnaphthylene; and groups obtained by combining these groups. In addition, some or all of the hydrogen atoms of the hydrocarbylene group may be substituted with a group containing a heteroatom such as an oxygen atom, a sulfur atom, a nitrogen atom, or a halogen atom, and some of the -CH- groups of the hydrocarbylene group may be substituted with a group containing a heteroatom such as an oxygen atom, a sulfur atom, or a nitrogen atom, resulting in the hydrocarbylene group containing a hydroxy group, a cyano group, a fluorine atom, a chlorine atom, a bromine atom, an iodine atom, a carbonyl group, an ether bond, an ester bond, a sulfonate ester bond, a carbonate bond, a lactone ring, a sultone ring, a carboxylic anhydride (-C(=O)-OC(=O)-), a haloalkyl group, etc. As the heteroatom, an oxygen atom is preferred.

[0285] In formula (3), LA is a single bond, an ether bond, or a hydrocarbylene group having 1 to 20 carbon atoms which may contain a heteroatom. The hydrocarbylene group may be saturated or unsaturated, and may be linear, branched, or cyclic. Specific examples thereof include R 203 Examples of the hydrocarbylene group represented by the formula (I) include the same as those exemplified above.

[0286] In formula (3), X a , X b , X c and X d are each independently a hydrogen atom, a fluorine atom, or a trifluoromethyl group, provided that X a , X b , X c and X d At least one of the groups is a fluorine atom or a trifluoromethyl group.

[0287] The photoacid generator represented by formula (3) is preferably one represented by the following formula (3'). [ka]

[0288] In formula (3'), L A is the same as above. X e is a hydrogen atom or a trifluoromethyl group, preferably a trifluoromethyl group. 301 , R 302 and R 303 are each independently a hydrogen atom or a hydrocarbyl group having 1 to 20 carbon atoms which may contain a heteroatom. The hydrocarbyl group may be saturated or unsaturated, and may be linear, branched, or cyclic. Specific examples thereof include R in formula (2A'). fa1 Examples of the hydrocarbyl group represented by m include the same as those exemplified above. 1 and m 2 are each independently an integer of 0 to 5, and m 3 is an integer from 0 to 4.

[0289] Examples of the photoacid generator represented by formula (3) include the same compounds as those exemplified as the photoacid generator represented by formula (2) in JP-A-2017-26980.

[0290] Among the photoacid generators, those containing an anion represented by formula (2A') or (2D) are particularly preferred because of their small acid diffusion and excellent solubility in solvents. Also, those represented by formula (3') are particularly preferred because of their extremely small acid diffusion.

[0291] When the resist composition of the present invention contains a photoacid generator (D), the content thereof is preferably 0.1 to 40 parts by mass, more preferably 0.5 to 20 parts by mass, relative to 80 parts by mass of the base polymer (C). When the amount of the photoacid generator (D) added is within the above range, the resolution is good and there is no risk of problems with foreign matter occurring after development of the resist film or during stripping, which is preferable. The photoacid generator (D) may be used alone, or two or more different types may be used in combination. When the base polymer contains any of the repeating units c1 to c4 and / or when the resist composition contains a photoacid generator (D), the resist composition of the present invention can function as a chemically amplified resist composition.

[0292] [(E) Nitrogen-containing compounds] The resist composition of the present invention requires a quencher (component (A)), but may also contain a nitrogen-containing compound as another quencher. Examples of such nitrogen-containing compounds include primary, secondary, or tertiary amine compounds described in paragraphs

[0146] to

[0164] of JP 2008-111103 A, particularly amine compounds having a hydroxy group, an ether bond, an ester bond, a lactone ring, a cyano group, or a sulfonate ester bond. Other examples include compounds in which a primary or secondary amine is protected with a carbamate group, such as those described in JP 3790649 A.

[0293] Alternatively, a sulfonate sulfonium salt having a nitrogen-containing substituent may be used as the nitrogen-containing compound. Such a compound functions as a quencher in the unexposed area and loses its quenching ability in the exposed area by neutralizing with the acid generated by the compound itself, functioning as a so-called photodegradable base. The use of a photodegradable base can further enhance the contrast between the exposed and unexposed areas. For example, JP-A Nos. 2009-109595 and 2012-46501 can be used as references for the photodegradable base.

[0294] When the resist composition of the present invention contains a nitrogen-containing compound (E), the content thereof is preferably from 0.001 to 12 parts by mass, and more preferably from 0.01 to 8 parts by mass, relative to 80 parts by mass of the base polymer (C). The nitrogen-containing compounds (E) may be used alone or in combination of two or more.

[0295] [(F) Surfactant] The resist composition of the present invention may further comprise a surfactant (F). The surfactant (F) is preferably a surfactant that is insoluble or slightly soluble in water but soluble in an alkaline developer, or a surfactant that is insoluble or slightly soluble in both water and an alkaline developer. Examples of such surfactants include those described in JP-A-2010-215608 and JP-A-2011-16746.

[0296] Among the surfactants described in the above publications, preferred surfactants that are insoluble or slightly soluble in water and alkaline developers include FC-4430 (manufactured by 3M), Surflon (registered trademark) S-381 (manufactured by AGC Seimi Chemical Co., Ltd.), Olfine (registered trademark) E1004 (manufactured by Nissin Chemical Industry Co., Ltd.), KH-20, KH-30 (manufactured by AGC Seimi Chemical Co., Ltd.), and oxetane ring-opening polymers represented by the following formula (surf-1): [ka]

[0297] Here, R, Rf, A, B, C, m, and n apply only to formula (surf-1), regardless of the above descriptions. R is a divalent to tetravalent aliphatic group having 2 to 5 carbon atoms. Examples of the divalent aliphatic group include an ethylene group, a 1,4-butylene group, a 1,2-propylene group, a 2,2-dimethyl-1,3-propylene group, and a 1,5-pentylene group, and examples of the trivalent or tetravalent aliphatic group include the following: [ka] (In the formula, the dashed lines represent bonds and are partial structures derived from glycerol, trimethylolethane, trimethylolpropane, and pentaerythritol, respectively.)

[0298] Among these, a 1,4-butylene group, a 2,2-dimethyl-1,3-propylene group, and the like are preferred.

[0299] Rf is a trifluoromethyl group or a pentafluoroethyl group, preferably a trifluoromethyl group. m is an integer of 0 to 3, n is an integer of 1 to 4, and the sum of n and m is the valence of R, which is an integer of 2 to 4. A is 1. B is an integer of 2 to 25, preferably an integer of 4 to 20. C is an integer of 0 to 10, preferably 0 or 1. The order of the structural units in formula (surf-1) is not specified, and they may be bonded in blocks or randomly. The production of surfactants based on partially fluorinated oxetane ring-opening polymers is described in detail in the specification of U.S. Pat. No. 5,650,483, etc.

[0300] Surfactants that are insoluble or slightly soluble in water but soluble in alkaline developers have the function of reducing water penetration and leaching by orienting themselves on the surface of the resist film when a resist protective film is not used in ArF immersion lithography. Therefore, they are useful for suppressing the elution of water-soluble components from the resist film and reducing damage to the exposure equipment. They are also useful because they become soluble during alkaline aqueous development after exposure or PEB, making them less likely to become contaminants that could cause defects. Such surfactants are insoluble or slightly soluble in water but soluble in alkaline developers. They are polymeric surfactants, also known as hydrophobic resins, and are particularly preferred because they have high water repellency and improve water slippage. Such polymer surfactants include those containing at least one repeating unit selected from the repeating units represented by the following formulas (4A) to (4E). [ka]

[0301] In formulas (4A) to (4E), R B is a hydrogen atom, a fluorine atom, a methyl group, or a trifluoromethyl group. 1 is -CH2-, -CH2CH2-, -O- or two -H groups separated from each other. s1 are each independently a hydrogen atom or a hydrocarbyl group having 1 to 10 carbon atoms. s2 R is a single bond or a linear or branched hydrocarbylene group having 1 to 5 carbon atoms. s3 R are each independently a hydrogen atom, a hydrocarbyl group or a fluorinated hydrocarbyl group having 1 to 15 carbon atoms, or an acid labile group. s3 When R is a hydrocarbyl group or a fluorinated hydrocarbyl group, an ether bond or a carbonyl group may be present between the carbon-carbon bonds. s4 is a hydrocarbon group or a fluorinated hydrocarbon group having 1 to 20 carbon atoms and a valence of (u+1). u is an integer of 1 to 3. R s5 are each independently a hydrogen atom or a group of the formula -C(=O)-OR sa is a group represented by R sais a fluorinated hydrocarbyl group having 1 to 20 carbon atoms. s6 is a hydrocarbyl group or a fluorinated hydrocarbyl group having 1 to 15 carbon atoms, and an ether bond or a carbonyl group may be present between the carbon-carbon bonds.

[0302] R s1 The hydrocarbyl group represented by the formula (I) is preferably a saturated hydrocarbyl group, and may be linear, branched, or cyclic. Specific examples thereof include alkyl groups such as methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, n-pentyl, n-hexyl, n-heptyl, n-octyl, n-nonyl, and n-decyl; and cyclic saturated hydrocarbyl groups such as cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl, adamantyl, and norbornyl. Among these, those having 1 to 6 carbon atoms are preferred.

[0303] R s2 The hydrocarbylene group represented by the formula (I) is preferably a saturated hydrocarbylene group, which may be linear, branched, or cyclic. Specific examples thereof include a methylene group, an ethylene group, a propylene group, a butylene group, and a pentylene group.

[0304] R s3 or R s6 The hydrocarbyl group represented by the formula (I) may be saturated or unsaturated, and may be linear, branched, or cyclic. Specific examples thereof include saturated hydrocarbyl groups, and aliphatic unsaturated hydrocarbyl groups such as alkenyl groups and alkynyl groups, with saturated hydrocarbyl groups being preferred. As the saturated hydrocarbyl group, R s1 In addition to the examples of the hydrocarbyl group represented by the formula (R), examples include an n-undecyl group, an n-dodecyl group, a tridecyl group, a tetradecyl group, and a pentadecyl group. s3 or R s6Examples of the fluorinated hydrocarbyl group represented by the formula (I) include groups in which some or all of the hydrogen atoms bonded to the carbon atoms of the aforementioned hydrocarbyl group have been substituted with fluorine atoms. As mentioned above, an ether bond or a carbonyl group may be present between these carbon-carbon bonds.

[0305] R s3 Examples of the acid labile group represented by the formula (AL-3) to (AL-5) include the groups represented by the formulas (AL-3) to (AL-5) above, trialkylsilyl groups in which each alkyl group has 1 to 6 carbon atoms, and oxo group-containing alkyl groups having 4 to 20 carbon atoms.

[0306] R s4 The (u+1)-valent hydrocarbon group or fluorinated hydrocarbon group represented by the formula (I) may be linear, branched, or cyclic, and specific examples thereof include groups in which u hydrogen atoms have been further removed from the aforementioned hydrocarbyl group or fluorinated hydrocarbyl group.

[0307] R sa The fluorinated hydrocarbyl group represented by the formula (I) is preferably saturated, and may be linear, branched, or cyclic. Specific examples thereof include those in which some or all of the hydrogen atoms of the hydrocarbyl groups have been substituted with fluorine atoms, such as a trifluoromethyl group, a 2,2,2-trifluoroethyl group, a 3,3,3-trifluoro-1-propyl group, a 3,3,3-trifluoro-2-propyl group, a 2,2,3,3-tetrafluoropropyl group, a 1,1,1,3,3,3-hexafluoroisopropyl group, a 2,2,3,3,4,4,4-heptafluorobutyl group, a 2,2,3,3,4,4,5,5-octafluoropentyl group, a 2,2,3,3,4,4,5,5,6,6,7,7-dodecafluoroheptyl group, a 2-(perfluorobutyl)ethyl group, a 2-(perfluorohexyl)ethyl group, a 2-(perfluorooctyl)ethyl group, and a 2-(perfluorodecyl)ethyl group.

[0308] Examples of the repeating units represented by formulae (4A) to (4E) include, but are not limited to, those shown below.B is the same as above. [ka]

[0309] [ka]

[0310] [ka]

[0311] [ka]

[0312] [ka]

[0313] The polymer surfactant may further contain other repeating units in addition to the repeating units represented by formulae (4A) to (4E). Examples of such other repeating units include repeating units obtained from methacrylic acid and α-trifluoromethylacrylic acid derivatives. In the polymer surfactant, the content of the repeating units represented by formulae (4A) to (4E) is preferably 20 mol % or more, more preferably 60 mol % or more, and even more preferably 100 mol %, of all repeating units.

[0314] The Mw of the polymer surfactant is preferably from 1,000 to 500,000, and more preferably from 3,000 to 100,000. The Mw / Mn is preferably from 1.0 to 2.0, and more preferably from 1.0 to 1.6.

[0315] The polymer surfactant can be synthesized by heating a monomer containing an unsaturated bond that provides the repeating units represented by formulas (4A) to (4E) and, if necessary, other repeating units, in an organic solvent with the addition of a radical initiator to polymerize the monomer. Examples of organic solvents used in polymerization include toluene, benzene, THF, diethyl ether, and dioxane. Examples of polymerization initiators include AIBN, 2,2'-azobis(2,4-dimethylvaleronitrile), dimethyl 2,2-azobis(2-methylpropionate), benzoyl peroxide, and lauroyl peroxide. The reaction temperature is preferably 50 to 100°C. The reaction time is preferably 4 to 24 hours. The acid labile group introduced into the monomer may be used as is, or may be protected or partially protected after polymerization.

[0316] When synthesizing the polymer surfactant, a known chain transfer agent such as dodecyl mercaptan or 2-mercaptoethanol may be used to adjust the molecular weight. In this case, the amount of the chain transfer agent added is preferably 0.01 to 10 mol % based on the total number of moles of the monomers to be polymerized.

[0317] When the resist composition of the present invention contains a surfactant (F), the content thereof is preferably 0.1 to 50 parts by mass, and more preferably 0.5 to 10 parts by mass, relative to 80 parts by mass of the base polymer (C). When the surfactant (F) content is 0.1 part by mass or more, the receding contact angle between the resist film surface and water is sufficiently improved, while when the surfactant content is 50 parts by mass or less, the dissolution rate of the resist film surface in the developer is low, and the height of the formed fine pattern is sufficiently maintained. The surfactant (F) may be used alone or in combination of two or more types.

[0318] [(G) Other ingredients] The resist composition of the present invention may contain, as other components (G), a compound that decomposes in the presence of acid to generate acid (acid amplifying compound), an organic acid derivative, a fluorine-substituted alcohol, or a compound with a Mw of 3000 or less whose solubility in a developer changes upon the action of acid (dissolution inhibitor). Examples of the acid amplifying compound include the compounds described in JP-A-2009-269953 and JP-A-2010-215608. When the acid amplifying compound is contained, its content is preferably 0 to 5 parts by mass, more preferably 0 to 3 parts by mass, relative to 80 parts by mass of the base polymer (C). If the content is too high, it may be difficult to control acid diffusion, resulting in degradation of resolution and pattern shape. Examples of the organic acid derivative, fluorine-substituted alcohol, and dissolution inhibitor include the compounds described in JP-A-2009-269953 and JP-A-2010-215608.

[0319] [Pattern formation method] The pattern formation method of the present invention includes the steps of forming a resist film on a substrate using the above-described resist composition, exposing the resist film to high-energy rays, performing PEB, and developing the PEB-treated resist film using a developer.

[0320] The substrate may be, for example, a substrate for integrated circuit manufacturing (Si, SiO2, SiN, SiON, TiN, WSi, BPSG, SOG, organic anti-reflective coating, etc.) or a substrate for mask circuit manufacturing (Cr, CrO, CrON, MoSi2, SiO2, etc.).

[0321] The resist film can be formed, for example, by applying the resist composition by a method such as spin coating so that the film thickness is preferably 0.05 to 2 μm, and then pre-baking the applied resist composition on a hot plate preferably at 60 to 150°C for 1 to 10 minutes, more preferably at 80 to 140°C for 1 to 5 minutes.

[0322] Examples of high-energy rays used to expose the resist film include KrF excimer laser light, ArF excimer laser light, EB, EUV, etc. When KrF excimer laser light, ArF excimer laser light, or EUV is used for exposure, a mask for forming a desired pattern is used, and the exposure dose is preferably 1 to 200 mJ / cm. 2 , more preferably 10 to 100 mJ / cm 2 When EB is used, the exposure dose is preferably 1 to 300 μC / cm 2 , either directly or through a mask for forming a desired pattern. 2 , more preferably 10 to 200 μC / cm 2 Irradiate so that

[0323] In addition to the usual exposure method, the immersion method can also be used, in which a liquid with a refractive index of 1.0 or higher is placed between the resist film and the projection lens. In this case, a water-insoluble protective film can also be used.

[0324] The water-insoluble protective film is used to prevent substances from eluting from the resist film and increase the water sliding property of the film surface, and can be broadly divided into two types. One is an organic solvent-removable type that needs to be stripped off before alkaline aqueous development using an organic solvent that does not dissolve the resist film. The other is an alkaline aqueous solution-soluble type that is soluble in alkaline developer and removes the protective film along with removing the soluble part of the resist film. The latter is based on a polymer containing 1,1,1,3,3,3-hexafluoro-2-propanol residue, which is insoluble in water but soluble in alkaline developer, and is suitable for use in alcohol-based solvents with 4 or more carbon atoms, ether-based solvents with 8 to 12 carbon atoms, or A material dissolved in these mixed solvents is preferred. A material obtained by dissolving the above-mentioned surfactant that is insoluble in water but soluble in an alkaline developer 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 may also be used.

[0325] After the exposure, PEB is performed, which can be performed, for example, by heating on a hot plate at preferably 60 to 150° C. for 1 to 5 minutes, more preferably 80 to 140° C. for 1 to 3 minutes.

[0326] The development is carried out using a developer, for example, an alkaline aqueous solution of tetramethylammonium hydroxide (TMAH) or the like, preferably at 0.1 to 5 mass %, more preferably 2 to 3 mass %, for preferably 0.1 to 3 minutes, more preferably 0.5 to 2 minutes, by a conventional method such as dipping, puddling, or spraying, whereby the exposed areas are dissolved and the desired pattern is formed on the substrate.

[0327] After forming the resist film, the resist film may be rinsed with pure water to extract the acid generator and the like from the film surface or to wash away particles, or the resist film may be rinsed after exposure to remove water remaining on the film.

[0328] Furthermore, the pattern may be formed by a double patterning method, such as a trench method in which a first exposure and etching process is performed to process an underlayer with a 1:3 trench pattern, and then a second exposure process is performed with a shifted position to form a 1:3 trench pattern, thereby forming a 1:1 pattern, or a line method in which a first underlayer with a 1:3 isolated leave pattern is processed by a first exposure and etching process, and then a second exposure process is performed with a shifted position to process a second underlayer with a 1:3 isolated leave pattern formed below the first underlayer, thereby forming a 1:1 pattern with half the pitch.

[0329] In the pattern forming method of the present invention, a negative tone development method may be used in which an organic solvent is used as a developer instead of the alkaline aqueous solution to dissolve unexposed areas. For the organic solvent development, the developer may be 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, propyl cyclohexanone ... Examples of organic solvents that can be used include methyl propionate, ethyl propionate, ethyl 3-ethoxypropionate, methyl lactate, ethyl lactate, propyl lactate, butyl lactate, isobutyl lactate, pentyl lactate, isopentyl lactate, methyl 2-hydroxyisobutyrate, ethyl 2-hydroxyisobutyrate, methyl benzoate, ethyl benzoate, phenyl acetate, benzyl acetate, methyl phenylacetate, ethyl phenylacetate, benzyl formate, phenylethyl formate, methyl 3-phenylpropionate, benzyl propionate, and 2-phenylethyl acetate. These organic solvents may be used alone or in combination of two or more. [Example]

[0330] The present invention will be specifically explained below by showing synthesis examples, examples, and comparative examples, but the present invention is not limited to the following examples. The apparatuses used are as follows. IR: Thermo Fisher Scientific NICOLET 6700 · 1 H-NMR: ECA-500 manufactured by JEOL Ltd. MALDI TOF-MS: JEOL S3000

[0331] [1] Synthesis of onium salts [Example 1-1] Synthesis of onium salt SQ-1 [ka]

[0332] (1) Synthesis of intermediate In-1 Under a nitrogen atmosphere, compound SM-1 (57.8 g) and pyridine (42.7 g) were dissolved in THF (400 mL) in a reaction vessel and cooled in an ice bath. Subsequently, compound SM-2 (81.3 g) was added dropwise while maintaining the internal temperature at 20°C or below. After the dropwise addition, the reaction temperature was returned to room temperature and aged for 12 hours. The reaction solution was cooled in an ice bath, and water (300 mL) was added to quench the reaction. The target product was extracted twice with ethyl acetate (500 g), followed by standard aqueous work-up. The solvent was removed by distillation, and the resulting mixture was purified by distillation to obtain 102.9 g of intermediate In-1 as a colorless oil (yield 94%).

[0333] (2) Synthesis of intermediate In-2 Under a nitrogen atmosphere, intermediate In-1 (24.2 g) was dissolved in THF (120 g). Then, 25% by mass aqueous sodium hydroxide solution (17.6 g) was added dropwise. After the dropwise addition, the reaction solution was heated to 40°C and aged for 4 hours. After aging, the reaction system was cooled to below 10°C, and diisopropyl ether (100 g) and water (100 g) were added to wash the aqueous layer. The aqueous layer was then separated to obtain an aqueous solution containing intermediate In-2. The separated aqueous layer was used in the next step without further purification.

[0334] (3) Onium Salt S Synthesis of Q-1 Under a nitrogen atmosphere, an aqueous solution containing intermediate In-2, triphenylsulfonium chloride (29.9 g), and methylene chloride (100 g) were mixed and stirred at room temperature for 2 hours. After stirring, the mixture was subjected to a standard aqueous work-up and the solvent was distilled off, yielding 34.8 g of onium salt SQ-1 as an oil (73% yield).

[0335] The results of TOF-MS of the onium salt SQ-1 are shown below. MALDI TOF-MS: POSITIVE M + 263(C 18 H 15 S+ equivalent) NEGATIVE M - 213 (C 11 H 17 O4 - equivalent)

[0336] [Example 1-2] Synthesis of onium salt SQ-2 [ka]

[0337] 7.7 g of onium salt SQ-2 was obtained as an oily product (yield 67%) in the same manner as in Example 1-1(3), except that compound SM-3 was used instead of intermediate In-2.

[0338] The results of TOF-MS of the onium salt SQ-2 are shown below. MALDI TOF-MS: POSITIVE M + 263(C 18 H 15 S + equivalent) NEGATIVE M - 131(C5H7O4 - equivalent)

[0339] [Examples 1-3 to 1-10] Synthesis of onium salts SQ-3 to SQ-10 Using the corresponding raw materials and known organic chemical reactions, onium salts SQ-3 to SQ-10 represented by the following formulas were synthesized. [ka]

[0340] [2] Synthesis of base polymer The monomers used in the synthesis of the base polymer are as follows: [ka]

[0341] [ka]

[0342] [ka]

[0343] [ka]

[0344] [ka]

[0345] [Synthesis Example 1] Synthesis of base polymer P-1 Under a nitrogen atmosphere, a flask was charged with 50.1 g of monomer a1-1, 24.8 g of monomer b2-1, 38.0 g of monomer c1, 3.96 g of V-601 (Fujifilm Wako Pure Chemical Industries, Ltd.), and 127 g of MEK to prepare a monomer-polymerization initiator solution. 46 g of MEK was charged to a separate flask under a nitrogen atmosphere and heated to 80°C with stirring. The monomer-polymerization initiator solution was then added dropwise over 4 hours. After the addition was complete, the polymerization solution was stirred for 2 hours while maintaining the temperature at 80°C, and then cooled to room temperature. The resulting polymerization solution was added dropwise to 2000 g of vigorously stirred hexane, and the precipitated polymer was filtered off. The resulting polymer was then washed twice with 600 g of hexane and vacuum-dried at 50°C for 20 hours to obtain a white powdery base polymer P-1 (yield: 98.1 g, 98%). The base polymer P-1 had an Mw of 10,900 and an Mw / Mn of 1.82. The Mw was measured in terms of polystyrene by GPC using DMF as a solvent.

[0346] [ka]

[0347] [Synthesis Examples 2 to 18] Synthesis of base polymers P-2 to P-18 The base polymers shown in Table 1 below were synthesized in the same manner as in Synthesis Example 1, except that the types and blending ratios of the respective monomers were changed.

[0348] [Table 1]

[0349] [3] Preparation of resist composition [Examples 2-1 to 2-30, Comparative Examples 1-1 to 1-30] Resist compositions were prepared by dissolving the onium salts of the present invention (SQ-1 to SQ-10), comparative quenchers (SQ-A to SQ-H, AQ-A to AQ-B), base polymers (P-1 to P-18), and photoacid generators (PAG-X, PAG-Y) in the compositions shown in Tables 2 to 5 below in 100 ppm of FC-4430 (manufactured by 3M) as a surfactant. The solutions were then filtered through a 0.2 μm Teflon (registered trademark) filter.

[0350] In Tables 2 to 5, the components are as follows. Organic solvent: PGMEA (propylene glycol monomethyl ether acetate) DAA (diacetone alcohol)

[0351] Photoacid generator: PAG-X, PAG-Y [ka]

[0352] Comparison quenchers: SQ-A to SQ-H, AQ-A to AQ-B [ka]

[0353] [ka]

[0354] [Table 2]

[0355] [Table 3]

[0356] [Table 4]

[0357] [Table 5]

[0358] [4] EUV lithography evaluation Price [Examples 3-1 to 3-30, Comparative Examples 2-1 to 2-30] Each resist composition (R-1 to R-30, CR-1 to CR-30) was spin-coated onto a Si substrate on which a 20 nm thick silicon-containing spin-on hard mask SHB-A940 (43% silicon by mass) manufactured by Shin-Etsu Chemical Co., Ltd. had been formed, and the substrate was pre-baked at 100°C for 60 seconds using a hot plate to produce a 50 nm thick resist film. An ASML EUV scanner NXE3300 (NA 0.33, σ 0.9 / 0.6, dipole illumination) was used to expose an LS pattern with an on-wafer dimension of 18 nm and a pitch of 36 nm, varying the exposure dose and focus (exposure dose pitch: 1 mJ / cm). 2 The resist film was exposed to light while being scanned with a focus pitch of 0.020 μm. After exposure, PEB was performed for 60 seconds at the temperatures shown in Tables 6 and 7 below. Paddle development was then performed for 30 seconds with a 2.38% by mass aqueous solution of TMAH, followed by rinsing with a surfactant-containing rinse solution and spin drying to obtain a positive pattern. The developed LS pattern was observed with a Hitachi High-Technologies Corporation critical dimension SEM (CG6300), and the sensitivity, EL, LWR, DOF, and collapse limit were evaluated according to the methods described below. The results are shown in Tables 6 and 7.

[0359] [Sensitivity evaluation] The optimum exposure dose E for obtaining an LS pattern with a line width of 18 nm and a pitch of 36 nm op (mJ / cm 2 ) was calculated and used as the sensitivity.

[0360] [EL Rating] EL (unit: %) was calculated from the exposure amount formed within a range of ±10% (16.2 to 19.8 nm) of the 18 nm space width in the LS pattern using the following formula: The larger this value, the better the performance. EL(%)=(|E1-E2| / E op ) x 100 E1: Optimal exposure dose for LS pattern with line width of 16.2 nm and pitch of 36 nm E2: Optimal exposure dose for LS pattern with line width of 19.8 nm and pitch of 36 nm E op : Optimal exposure dose to produce LS pattern with line width of 18nm and pitch of 36nm

[0361] [LWR rating] E op The dimensions of the LS pattern obtained by irradiation at 10 points in the longitudinal direction of the line were measured, and the LWR was calculated as three times the standard deviation (σ) (3σ). The smaller this value, the less roughness and the more uniform the line width pattern obtained.

[0362] [DOF evaluation] For the DOF evaluation, the focus range formed within a range of ±10% (16.2 to 19.8 nm) of the 18 nm dimension in the LS pattern was determined. The larger this value, the wider the depth of focus.

[0363] [Line pattern collapse limit evaluation] The line dimension of the LS pattern at each exposure dose at the optimum focus was measured at 10 points in the longitudinal direction. The thinnest line dimension obtained without collapse was defined as the collapse limit dimension. The smaller this value, the better the collapse limit.

[0364] [Table 6]

[0365] [Table 7]

[0366] The results shown in Tables 6 and 7 confirm that the resist composition of the present invention has good sensitivity, is excellent in various lithography performances, and exhibits resistance to pattern collapse.

Claims

1. An onium salt represented by the following formula (1), in which the conjugate acid of the anion moiety decomposes into carbon dioxide and an organic compound having 12 or less carbon atoms under the action of acid and heat. 【Chemistry 1】 (In the formula, X is a single bond, —O—, or —S—. R 1 and R 2 are each independently a hydrogen atom or a hydrocarbyl group having 1 to 10 carbon atoms, and some of the —CH 2 — groups in the hydrocarbyl group may be substituted with —O— or —C(═O)—. R 1 and R 2 may also be bonded to each other to form a ring together with the carbon atoms to which they are attached. When X is a single bond or -S-, R 3 is a hydrogen atom or a hydrocarbyl group having 1 to 10 carbon atoms, and when X is -O-, R 3 is an acid labile group in which some or all of the hydrogen atoms of the hydrocarbyl group may be substituted with halogen atoms, and R 1 and R 3 may be bonded to each other to form a ring together with the atoms to which they are bonded and the atoms between them. However, when R 3 is other than an acid labile group, the upper limit of the number of carbon atoms contained in R 1 to R 3 is 10. Z + is an onium cation.

2. The onium salt according to claim 1, wherein R 1 and R 2 are each independently a hydrogen atom, a saturated hydrocarbyl group having 1 to 6 carbon atoms, or a saturated ring having 3 to 8 carbon atoms formed by R 1 and R 2 bonding to each other and the carbon atoms to which they are bonded.

3. The onium salt according to claim 1, wherein when X is a single bond or -S-, R 3 is a hydrogen atom, an alkyl group having 1 to 4 carbon atoms, an alkyl group having 1 to 4 carbon atoms substituted with a halogen atom, or a cyclic saturated hydrocarbyl group having 3 to 6 carbon atoms.

4. 2. The onium salt according to claim 1, wherein X is —O—.

5. 5. The onium salt according to claim 4, wherein the acid labile group is represented by the following formula (AL-1) or (AL-2): 【Chemistry 2】 (In the formula, X a is —O— or —S—. R 4 , R 5 and R 6 are each independently a hydrocarbyl group having 1 to 12 carbon atoms, and the —CH 2 A part of - may be substituted with -O- or -S-, and when the hydrocarbyl group contains an aromatic ring, a part or all of the hydrogen atoms of the aromatic ring may be substituted with a halogen atom, a cyano group, a nitro group, an alkyl group having 1 to 4 carbon atoms which may contain a halogen atom, or an alkoxy group having 1 to 4 carbon atoms which may contain a halogen atom. 4 , R 5 and R 6 may be bonded to each other to form a ring, and —CH 2 A portion of - may be substituted with -O- or -S-. R 7 and R 8 are each independently a hydrogen atom or a hydrocarbyl group having 1 to 10 carbon atoms. 9 is a hydrocarbyl group having 1 to 20 carbon atoms, and the —CH 2 A part of - may be substituted with -O- or -S-. 8 and R 9 and are bonded to each other, and the carbon atom and X to which they are bonded a may form a heterocyclic group having 3 to 20 carbon atoms together with the —CH 2 A portion of - may be substituted with -O- or -S-. n1 and n2 each independently represent 0 or 1. * represents a bond to the adjacent —O—.)

6. Z + is an onium cation represented by any one of the following formulas (cation-1) to (cation-3): 【Transformation 3】 (In the formula, R 11 ~R 19 are each independently a hydrocarbyl group having 1 to 30 carbon atoms which may contain a heteroatom. 11 and R 12 may be bonded to each other to form a ring together with the sulfur atom to which they are attached.)

7. A quencher comprising the onium salt according to any one of claims 1 to 6.

8. A resist composition comprising the quencher according to claim 7.

9. 9. The resist composition according to claim 8, further comprising an organic solvent.

10. 9. The resist composition according to claim 8, which comprises a base polymer containing a repeating unit represented by the following formula (a1): 【Chemistry 4】 (In the formula, R A is a hydrogen atom, a fluorine atom, a methyl group, or a trifluoromethyl group. X 1 is a single bond, a phenylene group, a naphthylene group, or *-C(=O)-O-X 11 -, and the phenylene group or naphthylene group may be substituted with a halogen atom or an alkoxy group having 1 to 10 carbon atoms which may contain a fluorine atom. 11 represents a saturated hydrocarbylene group having 1 to 10 carbon atoms, which may contain a hydroxy group, an ether bond, an ester bond, or a lactone ring, a phenylene group, or a naphthylene group, and the saturated hydrocarbylene group may contain a hydroxy group, an ether bond, an ester bond, or a lactone ring. * represents a bond to a carbon atom in the main chain. AL 1 is an acid labile group.

11. 11. The resist composition according to claim 10, wherein the base polymer further comprises a repeating unit represented by the following formula (a2): 【Transformation 5】 (In the formula, R A is a hydrogen atom, a fluorine atom, a methyl group, or a trifluoromethyl group. X 2 is a single bond or *-C(=O)-O-. * represents a bond to a carbon atom in the main chain. R 21 represents a halogen atom, a cyano group, a hydrocarbyl group having 1 to 20 carbon atoms which may contain a heteroatom, a hydrocarbyloxy group having 1 to 20 carbon atoms which may contain a heteroatom, a hydrocarbylcarbonyl group having 2 to 20 carbon atoms which may contain a heteroatom, a hydrocarbylcarbonyloxy group having 2 to 20 carbon atoms which may contain a heteroatom, or a hydrocarbyloxycarbonyl group having 2 to 20 carbon atoms which may contain a heteroatom. AL 2 is an acid labile group. a is an integer from 0 to 4.

12. 11. The resist composition according to claim 10, wherein the base polymer further comprises a repeating unit represented by the following formula (b1) or (b2): 【Transformation 6】 (In the formula, R A are each independently a hydrogen atom, a fluorine atom, a methyl group, or a trifluoromethyl group. Y 1 is a single bond or *-C(=O)-O-. R 22 is a group having 1 to 20 carbon atoms and containing at least one structure selected from a hydrogen atom, a hydroxy group other than a phenolic hydroxy group, a cyano group, a carbonyl group, a carboxy group, an ether bond, an ester bond, a sulfonate ester bond, a carbonate bond, a lactone ring, a sultone ring, and a carboxylic acid anhydride (-C(=O)-O-C(=O)-). R 23 represents a halogen atom, a hydroxy group, a nitro group, a hydrocarbyl group having 1 to 20 carbon atoms which may contain a heteroatom, a hydrocarbyloxy group having 1 to 20 carbon atoms which may contain a heteroatom, a hydrocarbylcarbonyl group having 2 to 20 carbon atoms which may contain a heteroatom, a hydrocarbylcarbonyloxy group having 2 to 20 carbon atoms which may contain a heteroatom, or a hydrocarbyloxycarbonyl group having 2 to 20 carbon atoms which may contain a heteroatom. b is an integer from 1 to 4, and c is an integer from 0 to 4, provided that 1≦b+c≦5.

13. 11. The resist composition according to claim 10, wherein the base polymer further comprises at least one repeating unit selected from the group consisting of repeating units represented by the following formulas (c1) to (c4): 【Transformation 7】 (In the formula, R A are each independently a hydrogen atom, a fluorine atom, a methyl group, or a trifluoromethyl group. Z 1 is a single bond or a phenylene group. Z 2 is *-C(=O)-O-Z 21 -, *-C(=O)-NH-Z 21 - or *-O-Z 21 - is. Z 21 represents an aliphatic hydrocarbylene group having 1 to 6 carbon atoms, a phenylene group, or a divalent group obtained by combining these, and may contain a carbonyl group, an ester bond, an ether bond, or a hydroxy group. Z 3 represents a single bond, a phenylene group, a naphthylene group, or *-C(=O)-O-Z 31 - is. Z 31 is an aliphatic hydrocarbylene group having 1 to 10 carbon atoms, a phenylene group, or a naphthylene group, and the aliphatic hydrocarbylene group may contain a hydroxy group, an ether bond, an ester bond, or a lactone ring. Z 4 is a single bond or *-Z 41 -C(=O)-O-. Z 41 is a hydrocarbylene group having 1 to 20 carbon atoms which may contain a heteroatom. 5 represents a single bond, a methylene group, an ethylene group, a phenylene group, a fluorinated phenylene group, a phenylene group substituted with a trifluoromethyl group, *-C(=O)-O-Z 51 -, *-C(=O)-N(H)-Z 51 - or *-O-Z 51 - is. Z 51 represents an aliphatic hydrocarbylene group having 1 to 6 carbon atoms, a phenylene group, a fluorinated phenylene group, or a phenylene group substituted with a trifluoromethyl group, and may contain a carbonyl group, an ester bond, an ether bond, or a hydroxy group. * indicates a bond to a carbon atom in the main chain. R 31 and R 32 are each independently a hydrocarbyl group having 1 to 20 carbon atoms which may contain a heteroatom. 31 and R 32 and may be bonded to each other to form a ring together with the sulfur atom to which they are attached. L 1 is a single bond, an ether bond, an ester bond, a carbonyl group, a sulfonate ester bond, a carbonate bond or a carbamate bond. Rf 1 and Rf 2 are each independently a fluorine atom or a fluorinated alkyl group having 1 to 6 carbon atoms. Rf 3 and Rf 4 are each independently a hydrogen atom, a fluorine atom, or a fluorinated alkyl group having 1 to 6 carbon atoms. Rf 5 and Rf 6 are each independently a hydrogen atom, a fluorine atom, or a fluorinated alkyl group having 1 to 6 carbon atoms. 5 and Rf 6 cannot simultaneously become a hydrogen atom. M - is a non-nucleophilic counterion. A + is an onium cation. d is an integer from 0 to 3.

14. 9. The resist composition according to claim 8, further comprising a photoacid generator.

15. 9. The resist composition according to claim 8, further comprising an amine compound.

16. 9. The resist composition according to claim 8, further comprising a surfactant.

17. 10. A pattern forming method comprising the steps of: forming a resist film on a substrate using the resist composition according to claim 8; exposing the resist film to high-energy rays; performing a post-exposure bake treatment; and developing the post-exposure baked resist film using a developer.

18. 18. The pattern forming method according to claim 17, wherein the high-energy beam is a KrF excimer laser beam, an ArF excimer laser beam, an electron beam, or extreme ultraviolet light having a wavelength of 3 to 15 nm.

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