Onium salt, chemically amplified positive-type resist composition, and method for forming a resist pattern

Abstract

To provide an onium salt that has adequate acid strength and is capable of generating an acid with low diffusion, a chemically amplified positive resist composition comprising the onium salt, and a resist pattern forming process using the resist composition.SOLUTION: The present invention provides an onium salt represented by the formula (A).SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to an onium salt, a chemically amplified positive-type resist composition, and a resist pattern formation method. [Background technology]

[0002] In recent years, with the increasing integration of integrated circuits, there has been a demand for the formation of finer patterns, and chemically amplified resist compositions using acids as catalysts are primarily used for processing patterns of 0.2 μm or less. High-energy beams such as ultraviolet light, far ultraviolet light, and electron beams (EB) are used as exposure sources in this process, and EB lithography, in particular, which is used as an ultrafine processing technology, has become indispensable as a method for processing photomask blanks when creating photomasks for semiconductor manufacturing. As for the resist compositions used in such photolithography, there are positive types that form patterns by dissolving the exposed areas and negative types that form patterns by leaving the exposed areas intact, and the one that is easier to use is selected depending on the desired form of the resist pattern.

[0003] Generally, EB (electroluminescent) lithography does not use a mask. In the case of positive-type lithography, the area other than the region where the resist film is to be preserved is sequentially irradiated with a micro-area EB. In the case of negative-type lithography, the area where the resist film is to be preserved is sequentially irradiated. This process involves sweeping across the entire area of ​​the processed surface, which takes longer than batch exposure using a photomask. To maintain throughput, the resist film must be highly sensitive. Also, because the lithography time is long, differences tend to occur between the areas lithographed early and those lithographed later. Therefore, the temporal stability of the exposed area in a vacuum is an important performance requirement. Furthermore, in the processing of photomask blanks, which is a particularly important application, some photomask substrates have surface materials such as chromium oxide and other chromium compound films that can easily affect the pattern shape of the chemically amplified resist film. To maintain high resolution and the shape after etching, it is important to maintain a rectangular pattern profile of the resist film regardless of the substrate type.

[0004] The control of the sensitivity and pattern profile of the resist film mentioned above has been improved through various means, including the selection and combination of materials used in the resist composition and process conditions. One such improvement addresses the issue of acid diffusion, which has a significant impact on the resolution of chemically amplified resist films. In photomask processing, it is required that the shape of the resulting resist pattern does not change depending on the time until post-exposure heating (PEB). A major cause of this time-dependent change is the diffusion of acid generated by exposure. This acid diffusion problem has been extensively studied not only in photomask processing but also in general resist compositions, as it significantly affects sensitivity and resolution.

[0005] Patent documents 1 and 2 describe examples of reducing roughness by increasing the bulk of the acid generated from an acid generator to suppress acid diffusion. However, such acid generators are still insufficient in suppressing acid diffusion, so there has been a need for the development of acid generators with even lower diffusion.

[0006] Furthermore, Patent Document 3 describes an example of controlling acid diffusion by bonding sulfonic acid generated by exposure to the resin used in the resist composition. This method of suppressing acid diffusion by bonding repeating units that generate acid upon exposure to a base polymer is effective in obtaining patterns with low line edge roughness (LER). However, depending on the structure and introduction rate of such repeating units, there have been cases where problems arose with the solubility of the base polymer to which the repeating units that generate acid upon exposure are bonded in organic solvents.

[0007] Incidentally, polymers containing a large amount of aromatic skeletons with acidic side chains, such as polyhydroxystyrene, have been usefully used as resist compositions for KrF lithography. However, because they exhibit significant absorption of light around 200 nm, they have not been used as materials for resist compositions for ArF lithography. Nevertheless, they are important materials for resist compositions for EB lithography and extreme ultraviolet (EUV) lithography, which are promising techniques for forming patterns smaller than the processing limit of ArF lithography, due to their high etching resistance.

[0008] For positive-type EB lithography resist compositions and EUV lithography resist compositions, the base polymers mainly used are those that, when irradiated with high-energy rays, use the acid generated from a photoacid generator as a catalyst to deprotect the acid-unstable groups (acid-degradable protecting groups) that mask the acidic functional groups of the phenol side chains of the base polymer, thereby making them solubilizable in an alkaline developer. In addition, tertiary alkyl groups, tert-butoxycarbonyl groups, and acetal groups have been mainly used as the acid-unstable groups. While using protecting groups such as acetal groups, which require relatively low activation energy for deprotection, has the advantage of obtaining highly sensitive resist films, if the diffusion of the generated acid is not sufficiently suppressed, the deprotection reaction can occur even in unexposed areas of the resist film, leading to problems such as degradation of the LER and a decrease in the in-plane uniformity of pattern line width (CDU).

[0009] Furthermore, when using a sulfonium salt that generates a low pKa and strong acid, such as the fluorinated alkanesulfonic acid described in Patent Document 4, and a resin having repeating units with acetal groups, there was a problem in that a large LER pattern was formed. In other words, for the deprotection of acetal groups, which require a relatively low activation energy for deprotection, the acid strength of the fluorinated alkanesulfonic acid is too high, so even if acid diffusion is suppressed, the deprotection reaction proceeds due to trace amounts of acid diffused into the unexposed areas.

[0010] Furthermore, Patent Documents 5 and 6 propose photoacid generators that produce non-fluorinated aromatic sulfonic acids having multiple bulky alkyl substituents. While the multiple alkyl substituents increase the molecular weight of the generated acid, thereby reducing acid diffusion, the suppression of acid diffusion is still insufficient when the goal is to form fine patterns, leaving room for further improvement. [Prior art documents] [Patent Documents]

[0011] [Patent Document 1] Japanese Patent Publication No. 2009-053518 [Patent Document 2] Japanese Patent Publication No. 2010-100604 [Patent Document 3] Japanese Patent Publication No. 2011-22564 [Patent Document 4] Patent No. 5083528 [Patent Document 5] Patent No. 6248882 [Patent Document 6] Japanese Patent Publication No. 2019-202974 [Overview of the Initiative] [Problems that the invention aims to solve]

[0012] In recent years, there has been a demand for resist compositions that excel not only in line-and-space (LS), isoline (IL), and isospace (IS) patterns, but also in hole pattern shape. While the acid generator described in Patent Document 5, which generates a bulky acid and suppresses acid diffusion, produced patterns with good resolution and roughness, it had the problem of corner rounding occurring in hole patterns.

[0013] The present invention has been made in view of the above circumstances, and aims to provide an onium salt that has appropriate acid strength and can generate an acid with low diffusion, a chemically amplified positive resist composition containing the same, and a method for forming a resist pattern using the resist composition. [Means for solving the problem]

[0014] As a result of diligent research to achieve the above objective, the present inventors have developed an alkanesulfone having a bulky substituent at the α-position of the sulfo group of the anion and having a bulky aromatic ring structure. acid We discovered that when a type of onium salt is introduced into a resist composition as an acid generator, the generated acid has an appropriate acidity, and the anionic structure is bulky, which suppresses the rotation of the linking groups, thereby suppressing excessive diffusion of the acid. This results in a pattern with good resolution and a small LER, and furthermore, due to its appropriate dissolution inhibition, a pattern with good rectangular shape can be obtained. Based on these findings, we have come to the present invention.

[0015] In other words, the present invention provides the following onium salt, chemically amplified positive resist composition, and resist pattern formation method. 1. An onium salt represented by the following formula (A). [ka] (In the formula, n1 is an integer between 0 and 2. When n1=0, n2 is an integer between 2 and 5; when n1=1, n2 is an integer between 2 and 7; and when n1=2, n2 is an integer between 2 and 9.) L is a single bond, ether bond, ester bond, sulfonic acid ester bond, carbonate bond, or carbamate bond. R 1 and R 2 These are branched and cyclic hydrocarbyl groups with 3 to 20 carbon atoms, which may each independently contain a hydrogen atom or a heteroatom, but neither can be a hydrogen atom. Also, R 1 and R 2 These elements may bond with each other to form a ring with the carbon atoms to which they are bonded. R 3 Each is independently a branched and cyclic hydrocarbyl group having 3 to 20 carbon atoms, which may contain an iodine atom or a heteroatom, and at least one R 3 L is bonded to a carbon atom adjacent to the carbon atom to which it is bonded. Z + is an onium cation.) 2. The onium salt of 1 represented by the following formula (A1).

Chemical formula

Chemical formula

Chemical formula

Chemical formula

[0016] The chemically amplified positive resist composition containing the onium salt of the present invention as a photoacid generator exhibits extremely high resolution and can produce patterns with low LER in microfabrication techniques, particularly EB lithography and EUV lithography. Furthermore, it is suitable as a chemically amplified positive resist material because it can produce patterns with good rectangular shape due to its appropriate dissolution inhibition properties. [Modes for carrying out the invention]

[0017] The present invention will be described in detail below. In the following description, depending on the structure represented by the chemical formula, an asymmetric carbon may be present, and enantiomers or diastereomers may exist. In such cases, one formula will represent all of these isomers. These isomers may be used individually or as a mixture of two or more.

[0018] [Onium salt] The onium salt of the present invention is represented by the following formula (A). [ka]

[0019] In formula (A), n1 is an integer from 0 to 2. When n1 = 0, it represents a benzene ring; when n1 = 1, it represents a naphthalene ring; when n1 = 2 , it represents an anthracene ring. From the perspective of solvent solubility, it is preferably a benzene ring with n1 = 0. n2 is an integer from 2 to 5 when n1 = 0, an integer from 2 to 7 when n1 = 1, and an integer from 2 to 9 when n1 = 2.

[0020] In formula (A), L is a single bond, an ether bond, an ester bond, a sulfonic acid ester bond, a carbonate bond or a carbamate bond. Among these, an ester bond or a sulfonic acid ester bond is preferred, and a sulfonic acid ester bond is more preferred.

[0021] In formula (A), R 1 and R 2 are each independently a hydrogen atom or a branched and cyclic hydrocarbyl group having 3 to 20 carbon atoms which may contain heteroatoms, but they do not both become hydrogen atoms. When both R 1 and R 2 are hydrogen atoms or linear hydrocarbyl groups, the apparent acid diffusion is not suppressed due to the lack of steric bulk near the -SO3 - group, and the lithography performance deteriorates.

[0022] R 1 and R 2 The hydrocarbyl group represented by may be saturated or unsaturated. Specific examples thereof include branched alkyl groups having 3 to 20 carbon atoms such as isopropyl group, sec-butyl group, tert-butyl group, tert-pentyl group, 2-ethylhexyl group; cyclopentyl group, cyclohexyl group, cyclopentylmethyl group, cyclopentylethyl group, cyclopentylbutyl group, cyclohexylmethyl group, cyclohexylethyl group, cyclohexylbutyl group, norbornyl group, oxanorbornyl group, tricyclo[5.2.1.0 2,6Examples include, but are not limited to, cyclic aliphatic hydrocarbyl groups having 3 to 20 carbon atoms, such as decyl groups and adamantyl groups; aryl groups having 6 to 20 carbon atoms, such as phenyl groups, naphthyl groups and anthracenyl groups; 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, sulfur atom, nitrogen atom, or halogen atom, and some of the -CH2- of the hydrocarbyl group may be substituted with a group containing a heteroatom such as an oxygen atom, sulfur atom, or nitrogen atom, and as a result, the group may contain a hydroxyl 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 sulfonic acid ester bond, a carbonate bond, a lactone ring, a sultone ring, a carboxylic acid anhydride (-C(=O)-OC(=O)-), a haloalkyl group, etc. Examples of the halogen atoms include fluorine atoms, chlorine atoms, bromine atoms, and iodine atoms, but among these, fluorine atoms and iodine atoms are preferred.

[0023] Also, R 1 and R 2 These may bond with each other to form a ring with the carbon atoms to which they are bonded. Examples of rings formed in this case include cyclopropane rings, cyclobutane rings, cyclopentane rings, cyclohexane rings, norbornane rings, adamantane rings, etc. Furthermore, some or all of the hydrogen atoms in the ring may be substituted with groups containing heteroatoms such as oxygen atoms, sulfur atoms, nitrogen atoms, halogen atoms, etc., and some of the -CH2- in the ring may be substituted with groups containing heteroatoms such as oxygen atoms, sulfur atoms, nitrogen atoms, etc. As a result, the ring may contain hydroxyl groups, cyano groups, fluorine atoms, chlorine atoms, bromine atoms, iodine atoms, carbonyl groups, ether bonds, ester bonds, sulfonic acid ester bonds, carbonate bonds, lactone rings, sultone rings, carboxylic acid anhydrides (-C(=O)-OC(=O)-), haloalkyl groups, etc.

[0024] In formula (A), R 3Each is independently a branched and cyclic hydrocarbyl group having 3 to 20 carbon atoms, which may contain an iodine atom or a heteroatom, and at least one R 3 It is bonded to a carbon atom adjacent to the carbon atom to which L is bonded. A specific example of the hydrocarbyl group is R 1 and R 2 Examples of hydrocarbyl groups represented by the same formula as those exemplified above include those shown.

[0025] R in equation (A) 3 The following are examples of structures in which the aromatic ring is bonded, but are not limited to these. In the following formulas, the dashed lines represent bonds with L. [ka]

[0026] [ka]

[0027] [ka]

[0028] [ka]

[0029] [ka]

[0030] [ka]

[0031] The onium salt represented by formula (A) is preferably the one represented by formula (A1) below. [ka] (In the formula, L, R 1 , R 2 , R 3 and Z + (The same as above. n3 is an integer between 1 and 4.)

[0032] The onium salt represented by formula (A1) is preferably the one represented by formula (A2) below. [ka] (In the formula, n3, R 1 , R 2 , R 3 and Z + (This is the same as above.)

[0033] Particularly preferred examples of anions of onium salts represented by formula (A) include, but are not limited to, those listed below. [ka]

[0034] [ka]

[0035] [ka]

[0036] [ka]

[0037] [ka]

[0038] [ka]

[0039]

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[0093] [ka]

[0094] In formula (A), Z + This is an onium cation. The onium cation is preferably a sulfonium cation represented by the following formula (cation-1) or an iodonium cation represented by the following formula (cation-2). [ka]

[0095] In formulas (cation-1) and (cation-2), R ct1 ~R ct5 Each of these is independently a hydrocarbyl group having 1 to 30 carbon atoms, which may contain a halogen atom or a heteroatom.

[0096] Examples of the halogen atoms mentioned above include fluorine atoms, chlorine atoms, bromine atoms, and iodine atoms.

[0097] The hydrocarbyl group may be saturated or unsaturated, and may be linear, branched, or cyclic. Specific examples include C1-C30 alkyl groups such as methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, and tert-butyl groups; C3-C30 cyclic saturated hydrocarbyl groups such as cyclopropyl, cyclopentyl, cyclohexyl, cyclopropylmethyl, 4-methylcyclohexyl, cyclohexylmethyl, norbornyl, and adamantyl groups; C2-C30 alkenyl groups such as vinyl, allyl, propenyl, butenyl, and hexenyl groups; C3-C30 cyclic unsaturated hydrocarbyl groups such as cyclohexenyl groups; C6-C30 aryl groups such as phenyl, naphthyl, and thienyl groups; C7-C30 aralkyl groups such as benzyl, 1-phenylethyl, and 2-phenylethyl groups; and groups obtained by combining these, but aryl groups are preferred. Furthermore, some or all of the hydrogen atoms of the hydrocarbyl group may be substituted with a group containing heteroatoms such as oxygen, sulfur, nitrogen, or halogen atoms, and some of the -CH2- groups of the hydrocarbyl group may be substituted with a group containing heteroatoms such as oxygen, sulfur, or nitrogen atoms, and as a result, the material may contain hydroxyl groups, cyano groups, fluorine atoms, chlorine atoms, bromine atoms, iodine atoms, carbonyl groups, ether bonds, ester bonds, sulfonic acid ester bonds, carbonate bonds, lactone rings, sultone rings, carboxylic acid anhydrides (-C(=O)-OC(=O)-), haloalkyl groups, etc.

[0098] Also, R ct1 and R ct2 However, they may bond with each other to form a ring with the sulfur atom to which they are bonded. In this case, examples of sulfonium cations represented by formula (cation-1) include those represented by the following formula. [ka] (In the formula, the dashed line represents R ct3 (This is a combination of the two.)

[0099] Examples of sulfonium cations represented by formula (cation-1) include, but are not limited to, those listed below. [ka]

[0100] [ka]

[0101] [ka]

[0102] [ka]

[0103] [ka]

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[0125] The iodonium cations represented by formula (cation-2) are as follows: These are some examples, but are not limited to them. [ka]

[0126] [ka]

[0127] Specific examples of the onium salt of the present invention include any combination of the anion and cation described above.

[0128] The onium salts of the present invention can be synthesized by known methods. For example, the case in formula (A) where L is a sulfonic acid ester bond is shown below, but is not limited thereto. [ka] (In the formula, n1, n2, R 1 , R 2 , R 3 and Z + This is the same as above. M + X is a lithium ion, a sodium ion, or a potassium ion. - (These are halide ions or methyl sulfate ions.)

[0129] The first step is to obtain sulfonate (S-3) by the reaction of sulfonate (S-1) and hydroxysulfonate (S-2). The reaction can be carried out according to conventional methods, and it is preferable to add sulfonate (S-1), hydroxysulfonate (S-2), and base sequentially or simultaneously in a solvent, and to cool or heat as necessary.

[0130] Solvents that can be used in the first step of the reaction include water, tetrahydrofuran (THF), ethers such as diethyl ether, diisopropyl ether, di-n-butyl ether, and 1,4-dioxane, hydrocarbons such as n-hexane, n-heptane, benzene, toluene, and xylene, aprotic polar solvents such as acetonitrile, dimethyl sulfoxide (DMSO), and N,N-dimethylformamide (DMF), and chlorinated organic solvents such as methylene chloride, chloroform, and carbon tetrachloride. These solvents may be selected and used as appropriate depending on the reaction conditions, and may be used individually or in mixtures of two or more.

[0131] Furthermore, examples of bases that can be used in the first step of the reaction include ammonia, triethylamine, pyridine, lutidine, colidine, N,N-dimethylaniline and other amines, hydroxides such as sodium hydroxide, potassium hydroxide, and tetramethylammonium hydroxide, and carbonates such as potassium carbonate and sodium bicarbonate. These bases may be used individually or in combination of two or more.

[0132] The second step involves obtaining the onium salt (A') through an ion exchange reaction between the sulfonate (S-3) and the onium salt (S-4). The sulfonate (S-3) may be isolated after the reaction in the first step through a normal aqueous work-up, or it may be used without any special work-up after the reaction has been stopped.

[0133] When using isolated sulfonate (S-3), dissolve the sulfonate (S-3) in water, ethers such as THF, diethyl ether, diisopropyl ether, di-n-butyl ether, and 1,4-dioxane, hydrocarbons such as n-hexane, n-heptane, benzene, toluene, and xylene, aprotic polar solvents such as acetonitrile, DMSO, and DMF, or chlorinated organic solvents such as methylene chloride, chloroform, and carbon tetrachloride, mix with onium salt (S-4), and obtain a reaction mixture by cooling or heating as necessary. Then, the onium salt (A) is obtained from the reaction mixture by normal aqueous post-treatment. ' ) can be obtained. If necessary, it may be purified by conventional methods such as distillation, recrystallization, and chromatography.

[0134] If the reaction to synthesize the sulfonate (S-3) has been stopped and no special work-up is to be used, the onium salt (S-4) can be added to the mixture from which the sulfonate (S-3) synthesis reaction has been stopped, and the mixture can be cooled or heated as needed to obtain the onium salt (A'). In this case, water, THF, ethers such as diethyl ether, diisopropyl ether, di-n-butyl ether, and 1,4-dioxane, hydrocarbons such as n-hexane, n-heptane, benzene, toluene, and xylene, aprotic polar solvents such as acetonitrile, DMSO, and DMF, and chlorinated organic solvents such as methylene chloride, chloroform, and carbon tetrachloride can be added as needed. The onium salt (A') can be obtained from the reaction mixture by conventional aqueous work-up. If necessary, the mixture can be purified by conventional methods such as recrystallization and chromatography.

[0135] The onium salt represented by formula (A) has an onium salt structure of sulfonic acid that is not substituted with fluorine atoms, and therefore can generate an acid of appropriate intensity by high-energy ray irradiation. - The presence of a bulky substituent at the α-position shields the vicinity of the generated sulfonic acid, and the presence of a bulky substituent at the α-position and another bulky substituent on the aromatic ring suppresses the rotation of the L bond axis connecting them due to steric hindrance, thereby suppressing excessive acid diffusion of the generated acid. Due to these synergistic effects, the contrast between the exposed and unexposed areas is good, and even in the formation of fine patterns, it is possible to form patterns with low roughness. Furthermore, since the onium salt of the present invention has sufficient lipophilicity, it is easy to manufacture and handle, and it also exhibits appropriate dissolution inhibition ability in the unexposed areas.

[0136] The onium salt of the present invention can be suitably used as a photoacid generator.

[0137] [Chemically amplified positive-type resist composition] [(A) Photoacid Generator] The chemically amplified positive resist composition of the present invention contains, as component (A), a photoacid generator consisting of an onium salt represented by formula (A) as an essential component.

[0138] In the chemically amplified positive resist composition of the present invention, the content of (A) photoacid generator 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 (B) base polymer, as described later. When the content of the photoacid generator is within the above range, the amount of acid necessary for deprotection of acid-unstable groups is generated, and storage stability is also good. (A) photoacid generator may be used alone or in combination of two or more types.

[0139] [(B) Base polymer] The resist composition of the present invention includes a base polymer as component (B) which is decomposed by the action of an acid and whose solubility in an alkaline developer increases.

[0140] The polymer is preferably a polymer containing a repeating unit represented by the following formula (B1) (hereinafter also referred to as repeating unit B1). [ka]

[0141] In formula (B1), a1 is 0 or 1. a2 is an integer between 0 and 2, where 0 represents the benzene skeleton, 1 represents the naphthalene skeleton, and 2 represents the anthracene skeleton. a3 is an integer satisfying 0 ≤ a3 ≤ 5 + 2(a2) - a4. a4 is an integer between 1 and 3. When a2 is 0, preferably a3 is an integer between 0 and 3 and a4 is an integer between 1 and 3. When a2 is 1 or 2, preferably a3 is an integer between 0 and 4 and a4 is an integer between 1 and 3.

[0142] In formula (B1), R A These are a hydrogen atom, a fluorine atom, a methyl group, or a trifluoromethyl group.

[0143] In formula (B1), R 11 This is a halogen atom, a saturated hydrocarbyl carbonyloxy group having 2 to 8 carbon atoms that may be substituted with a halogen atom, a saturated hydrocarbyl group having 1 to 6 carbon atoms that may be substituted with a halogen atom, or a saturated hydrocarbyloxy group having 1 to 6 carbon atoms that may be substituted with a halogen atom. The saturated hydrocarbyl group, and the saturated hydrocarbyl portion of the saturated hydrocarbyl carbonyloxy group and saturated hydrocarbyloxy group may be linear, branched, or cyclic. Specific examples include alkyl groups such as methyl, ethyl, n-propyl, isopropyl, butyl, pentyl, hexyl, and their structural isomers; cycloalkyl groups such as cyclopropyl, cyclobutyl, cyclopentyl, and cyclohexyl; and groups obtained by combining these. If the number of carbon atoms is below the upper limit, solubility in alkaline developer is good. When a3 is 2 or more, each R 11 They may be the same as or different from each other.

[0144] In formula (B1), A 1 This is a single bond or a saturated hydrocarbylene group having 1 to 10 carbon atoms, and some of the -CH2- in the saturated hydrocarbylene group may be substituted with -O-. The saturated hydrocarbylene group may be linear, branched, or cyclic, and specific examples include alkanediyl groups having 1 to 10 carbon atoms such as methylene 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, and structural isomers thereof; cyclic saturated hydrocarbylene groups having 3 to 10 carbon atoms such as cyclopropanediyl group, cyclobutanediyl group, cyclopentanediyl group, and cyclohexanediyl group; and groups obtained by combining these. If the saturated hydrocarbylene group contains an ether bond, when a1 in formula (B1) is 1, it may be placed at any position other than between the α-carbon atom and the β-carbon atom with respect to the ester oxygen atom. Furthermore, when a1 is 0, the atom bonded to the main chain becomes an etheric oxygen atom, and the second ether bond may be inserted at any position other than between the α-carbon and β-carbon atoms relative to the etheric oxygen atom. It is preferable that the saturated hydrocarbylene group has 10 or fewer carbon atoms, as this allows for sufficient solubility in alkaline developing solutions.

[0145] a1 is 0 and A 1 When it is a single bond, that is, the aromatic ring is directly bonded to the main chain of the polymer (i.e., a linker (-C(=O)-OA) 1 If the repeating unit B1 does not have the -), preferred examples of the repeating unit B1 include units derived from 3-hydroxystyrene, 4-hydroxystyrene, 5-hydroxy-2-vinylnaphthalene, 6-hydroxy-2-vinylnaphthalene, etc. In particular, the repeating unit represented by the following formula (B1-1) is preferred. [ka] (In the formula, R A (and a4 are the same as above.)

[0146] a1 is 1 (i.e., -C(=O)-OA as the linker) 1 When R has -, preferred examples of repeating unit B1 are, but are not limited to, those shown below. Note that in the following formula, A This is the same as described above. [ka]

[0147] The content of repeating unit B1 is preferably 30 to 90 mol%, and more preferably 40 to 85 mol%, of the total repeating units constituting the polymer. However, if the polymer described later provides high etching resistance and includes at least one of the repeating units represented by formula (B3) and formula (B4), and the unit has a phenolic hydroxyl group as a substituent, it is preferable to include the ratio of the repeating unit in addition to the above range. Repeating unit B1 may be used alone or in combination of two or more types.

[0148] The polymer preferably contains repeating units having acidic functional groups protected by acid-unstable groups, i.e., repeating units protected by acid-unstable groups that become alkali-soluble by the action of acid (hereinafter also referred to as repeating unit B2), in order to provide the positive-type resist composition with the property that the exposed area dissolves in an alkaline developer.

[0149] The most preferred repeating unit B2 is the one represented by the following formula (B2-1) (hereinafter also referred to as repeating unit B2-1). [ka]

[0150] In formula (B2-1), b1 is 0 or 1. b2 is an integer between 0 and 2, where 0 represents the benzene skeleton, 1 represents the naphthalene skeleton, and 2 represents the anthracene skeleton. b3 is an integer satisfying 0 ≤ b3 ≤ 5 + 2(b2) - b4. b4 is an integer between 1 and 3. b5 is 0 or 1. When b2 is 0, preferably b3 is an integer between 0 and 3 and b4 is an integer between 1 and 3. When b2 is 1 or 2, preferably b3 is an integer between 0 and 4 and b4 is an integer between 1 and 3.

[0151] In formula (B2-1), R A These are a hydrogen atom, a fluorine atom, a methyl group, or a trifluoromethyl group.

[0152] In formula (B2-1), R 12 This is a halogen atom, a saturated hydrocarbyl carbonyloxy group having 2 to 8 carbon atoms that may be substituted with a halogen atom, a saturated hydrocarbyl group having 1 to 6 carbon atoms that may be substituted with a halogen atom, or a saturated hydrocarbyloxy group having 1 to 6 carbon atoms that may be substituted with a halogen atom. The saturated hydrocarbyl group, and the saturated hydrocarbyl portion of the saturated hydrocarbyl carbonyloxy group and saturated hydrocarbyloxy group may be linear, branched, or cyclic. Specific examples include alkyl groups such as methyl, ethyl, n-propyl, isopropyl, butyl, pentyl, hexyl, and their structural isomers; cycloalkyl groups such as cyclopropyl, cyclobutyl, cyclopentyl, and cyclohexyl; and groups obtained by combining these. If the number of carbon atoms is below the upper limit, solubility in alkaline developer is good. When b3 is 2 or more, each R 12 They may be the same as or different from each other.

[0153] In formula (B2-1), A 2This is a single bond or a saturated hydrocarbylene group having 1 to 10 carbon atoms, and some of the -CH2- in the saturated hydrocarbylene group may be substituted with -O-. The saturated hydrocarbylene group may be linear, branched, or cyclic, and specific examples include alkanediyl groups having 1 to 10 carbon atoms such as methylene 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, and structural isomers thereof; cyclic saturated hydrocarbylene groups having 3 to 10 carbon atoms such as cyclopropanediyl group, cyclobutanediyl group, cyclopentanediyl group, and cyclohexanediyl group; and groups obtained by combining these. When the saturated hydrocarbylene group contains an ether bond, when b1 in formula (B2-1) is 1, it may be placed at any position other than between the α-carbon and β-carbon atoms relative to the ester oxygen atom. Furthermore, when b1 is 0, the atom bonded to the main chain becomes an etheric oxygen atom, and the second ether bond may be inserted at any position other than between the α-carbon and β-carbon atoms relative to the etheric oxygen atom. It is preferable that the saturated hydrocarbylene group has 10 or fewer carbon atoms, as this allows for sufficient solubility in alkaline developing solutions.

[0154] In formula (B2-1), when b4 is 1, X is an acid-unstable group. When b4 is 2 or 3, X is independently either a hydrogen atom or an acid-unstable group, but at least one is an acid-unstable group. That is, the repeating unit B2-1 is a configuration in which at least one phenolic hydroxyl group attached to an aromatic ring is protected by an acid-unstable group, or a carboxyl group attached to an aromatic ring is protected by an acid-unstable group. The acid-unstable group can be any that is removed by acid to yield an acidic group, as has been used in many known chemically amplified positive resist compositions, and is not particularly limited.

[0155] Examples of the acid-unstable group include tertiary saturated hydrocarbyl groups. The tertiary saturated hydrocarbyl group is preferably one having 4 to 18 carbon atoms, in order to obtain the resulting polymerization monomer by distillation.

[0156] The saturated hydrocarbyl group bonded to the tertiary carbon atom of the tertiary saturated hydrocarbyl group is preferably one having 1 to 15 carbon atoms. The saturated hydrocarbyl group having 1 to 15 carbon atoms may be linear, branched, or cyclic, and may contain oxygen atom-containing functional groups such as ether bonds or carbonyl groups between its carbon-carbon bonds. Furthermore, saturated hydrocarbyl groups bonded to tertiary carbon atoms may bond to each other, forming a ring together with the tertiary carbon atom to which they are bonded.

[0157] The alkyl substituents include methyl, ethyl, propyl, adamantyl, norbornyl, tetrahydrofuran-2-yl, 7-oxanorbornan-2-yl, cyclopentyl, 2-tetrahydrofuryl, and tricyclo[5.2.1.0 2,6 ]decyl group, 8-ethyl-8-tricyclo[5.2.1.0 2,6 ]decyl group, 3-methyl-3-tetracyclo[4.4.0.1 2,5 .1 7,10 ]dodecyl group, tetracyclo[4.4.0.1 2,5 .1 7,10 Examples include a dodecyl group and a 3-oxo-1-cyclohexyl group.

[0158] The tertiary saturated hydrocarbyl groups include tert-butyl group, tert-pentyl group, 1-ethyl-1-methylpropyl group, 1,1-diethylpropyl group, 1,1,2-trimethylpropyl group, 1-adamantyl-1-methylethyl group, 1-methyl-1-(2-norbornyl)ethyl group, 1-methyl-1-(tetrahydrofuran-2-yl)ethyl group, 1-methyl-1-(7-oxanorbornan-2-yl)ethyl group, 1-methylcyclopentyl group, 1-ethylcyclopentyl group, 1-Propylcyclopentyl group, 1-Cyclopentylcyclopentyl group, 1-Cyclohexylcyclopentyl group, 1-(2-tetrahydrofuryl)cyclopentyl group, 1-(7-oxanorbornan-2-yl)cyclopentyl group, 1-Methylcyclohexyl group, 1-Ethylcyclohexyl group, 1-Cyclopentylcyclohexyl group, 1-Cyclohexylcyclohexyl group, 2-Methyl-2-norbonyl group, 2-Ethyl-2-norbonyl group, 8-Methyl-8-Tricyclo[5.2.1.0 2,6 ]decyl group, 8-ethyl-8-tricyclo[5.2.1.0 2,6 ]decyl group, 3-methyl-3-tetracyclo[4.4.0.1 2,5 .1 7,10 ]dodecyl group, 3-ethyl-3-tetracyclo[4.4.0.1 2,5 .1 7,10 Examples include, but are not limited to, the dodecyl group, 2-methyl-2-adamantyl group, 2-ethyl-2-adamantyl group, 1-methyl-3-oxo-1-cyclohexyl group, 1-methyl-1-(tetrahydrofuran-2-yl)ethyl group, 5-hydroxy-2-methyl-2-adamantyl group, and 5-hydroxy-2-ethyl-2-adamantyl group.

[0159] Furthermore, the group represented by the following formula (B2-1-1) can be cited as the acid-unstable group. The group represented by formula (B2-1-1) is commonly used as an acid-unstable group and is a useful choice as an acid-unstable group that stably gives patterns where the interface between the pattern and the substrate is relatively rectangular. When X is the group represented by formula (B2-1-1), an acetal structure is formed. [ka] (In the equation, dashed lines represent connections.)

[0160] In formula (B2-1-1), R L1 This is a hydrogen atom or a saturated hydrocarbyl group having 1 to 10 carbon atoms. The saturated hydrocarbyl group may be linear, branched, or cyclic.

[0161] R L1 The group is appropriately selected according to the design of the sensitivity of the decomposition group to acid. For example, if the design is to decompose with a strong acid while ensuring relatively high stability, a hydrogen atom is preferred, and if the design is to achieve high sensitivity to pH changes using relatively high reactivity, a linear alkyl group is preferred. Depending on the combination with the acid generator or quencher incorporated into the resist composition, R L2 If a relatively large alkyl group is selected at the terminal and the change in solubility due to decomposition is designed to be significant, then R L1 Preferably, the carbon atom bonded to the acetal carbon is a secondary carbon atom. L1 Examples include, but are not limited to, isopropyl groups, sec-butyl groups, cyclopentyl groups, and cyclohexyl groups.

[0162] In formula (B2-1-1), R L2 This is a hydrocarbyl group having 1 to 30 carbon atoms. The hydrocarbyl group may be saturated or unsaturated, and may be linear, branched, or cyclic. Specific examples include saturated hydrocarbyl groups having 1 to 30 carbon atoms and aryl groups having 6 to 30 carbon atoms. In particular, to obtain higher resolution in fine pattern formation, R L2 It is preferably a hydrocarbyl group having 1 to 6 carbon atoms. L2 When the group is a hydrocarbyl group with 1 to 6 carbon atoms, the alcohol produced after the deprotection reaction with acid is water-soluble. Therefore, it dissolves in the developer when forming a positive pattern with an alkaline developer, thus suppressing residual defects in the exposed areas.

[0163] Preferred examples of the base represented by formula (B2-1-1) are, but are not limited to, those listed below. Note that in the following formula, R L1 The same as above, and the dashed lines represent connections. [ka]

[0164] [ka]

[0165] Other acid-unstable groups can also be used in which the hydrogen atom of a phenolic hydroxyl group is substituted with -CH2COO- (tertiary saturated hydrocarbyl group). In this case, the same tertiary saturated hydrocarbyl group used for protecting the phenolic hydroxyl group as described above can be used.

[0166] Furthermore, as a repeating unit B2, a repeating unit represented by the following formula (B2-2) (hereinafter also referred to as repeating unit B2-2) can be mentioned. Repeating unit B2-2 is a useful option as an acid-unstable group-containing unit that provides good performance against line width fluctuations during development loading because it increases the dissolution rate of the exposed area. [ka]

[0167] In equation (B2-2), c1 is an integer between 0 and 2. c2 is an integer between 0 and 2. c3 is an integer between 0 and 5. c4 is an integer between 0 and 2.

[0168] In formula (B2-2), R A These are a hydrogen atom, a fluorine atom, a methyl group, or a trifluoromethyl group.

[0169] In formula (B2-2), R 13 and R 14Each of these is independently a hydrocarbyl group having 1 to 10 carbon atoms, which may contain heteroatoms, and R 13 and R 14 These elements may bond with each other to form a ring with the carbon atoms to which they are bonded.

[0170] In formula (B2-2), R 15 Each of these is independently a fluorine atom, a fluorinated alkyl group having 1 to 5 carbon atoms, or a fluorinated alkoxy group having 1 to 5 carbon atoms.

[0171] In formula (B2-2), R 16 Each of these is independently a hydrocarbyl group having 1 to 10 carbon atoms, which may contain heteroatoms.

[0172] In formula (B2-2), A 3 This refers to a single bond, a phenylene group, a naphthylene group, or *-C(=O)-OA 31 - is A 31 This is an aliphatic hydrocarbylene group having 1 to 20 carbon atoms, which may contain a hydroxyl group, an ether bond, an ester bond, or a lactone ring, or a phenylene group or naphthylene group. * indicates a bond with a carbon atom of the main chain.

[0173] Preferred examples of repeating unit B2-2 are, but are not limited to, those shown below. Note that in the following formula, R A This is the same as described above. [ka]

[0174] The content of repeating unit B2 is preferably 5 to 95 mol%, and more preferably 20 to 80 mol%, of the total repeating units constituting the polymer. Repeating unit B2 may be used alone or in combination of two or more types.

[0175] The polymer may contain at least one repeating unit selected from the following: a repeating unit represented by formula (B3) (hereinafter also referred to as repeating unit B3), a repeating unit represented by formula (B4) (hereinafter also referred to as repeating unit B4), and a repeating unit represented by formula (B5) (hereinafter also referred to as repeating unit B5). [ka]

[0176] In equations (B3) and (B4), d is an integer between 0 and 6, and e is an integer between 0 and 4.

[0177] In formulas (B3) and (B4), R 17 and R 18 Each of these is independently a hydroxyl group, a halogen atom, a saturated hydrocarbyl group having 1 to 6 carbon atoms that may be substituted with a halogen atom, a saturated hydrocarbyloxy group having 1 to 6 carbon atoms that may be substituted with a halogen atom, or a saturated hydrocarbylcarbonyloxy group having 2 to 8 carbon atoms that may be substituted with a halogen atom. The saturated hydrocarbyl group, saturated hydrocarbyloxy group, and saturated hydrocarbylcarbonyloxy group may be linear, branched, or cyclic. When d is 2 or more, each R 17 They may be the same or different from each other. When e is 2 or greater, each R 18 They may be the same as or different from each other.

[0178] In formula (B5), f1 is 0 or 1. f2 is an integer between 0 and 2, where 0 represents a benzene skeleton, 1 represents a naphthalene skeleton, and 2 represents an anthracene skeleton. f3 is an integer between 0 and 5. When f2 is 0, f3 is preferably an integer between 0 and 3, and when f2 is 1 or 2, f3 is preferably an integer between 0 and 4.

[0179] In formula (B5), R A These are a hydrogen atom, a fluorine atom, a methyl group, or a trifluoromethyl group.

[0180] In formula (B5), R 19 This is a saturated hydrocarbyl group having 1 to 20 carbon atoms, a saturated hydrocarbyloxy group having 1 to 20 carbon atoms, a saturated hydrocarbylcarbonyloxy group having 2 to 20 carbon atoms, a saturated hydrocarbyloxyhydrocarbyl group having 2 to 20 carbon atoms, a saturated hydrocarbylthiohydrocarbyl group having 2 to 20 carbon atoms, a halogen atom, a nitro group, or a cyano group, and when f2 is 1 or 2, it may also be a hydroxyl group. The saturated hydrocarbyl group, saturated hydrocarbyloxy group, saturated hydrocarbylcarbonyloxy group, saturated hydrocarbyloxyhydrocarbyl group, and saturated hydrocarbylthiohydrocarbyl group may be linear, branched, or cyclic. When f3 is 2 or more, each R 19 They may be the same as or different from each other.

[0181] In formula (B5), A 4 A is a single bond or a saturated hydrocarbylene group having 1 to 10 carbon atoms, and some of the -CH2- in the saturated hydrocarbylene group may be substituted with -O-. The saturated hydrocarbylene group may be linear, branched, or cyclic, and a specific example thereof is A in formula (B1). 1 Examples similar to those given in the explanation can be cited.

[0182] When at least one of the repeating units B3 to B5 is used as a constituent unit of the polymer, in addition to the etching resistance of the aromatic ring, the addition of a ring structure to the main chain enhances etching resistance and EB irradiation resistance during pattern inspection.

[0183] To obtain the effect of improving etching resistance, the content of repeating units B3 to B5 is preferably 5 mol% or more of the total repeating units constituting the polymer. Furthermore, the content of repeating units B3 to B5 is preferably 25 mol% or less, and more preferably 20 mol% or less of the total repeating units constituting the polymer. If the amount introduced when there is no functional group or when the functional group is not a hydroxyl group is 25 mol% or less, it is preferable because there is no risk of development defects occurring. Repeating units B3 to B5 may be used individually or in combination of two or more types.

[0184] The polymer preferably contains at least one repeating unit selected from repeating units B1, B2, and B3 to B5, as this is excellent in achieving both high etching resistance and resolution. In this case, it is preferable that these repeating units make up 60 mol% or more of the total repeating units constituting the polymer, more preferably 70 mol% or more, even more preferably 80 mol% or more, and even more preferably 90 mol% or more.

[0185] The polymer may contain at least one selected from the following repeating units: repeating unit (B6) (hereinafter also referred to as repeating unit B6), repeating unit (B7) (hereinafter also referred to as repeating unit B7), repeating unit (B8) (hereinafter also referred to as repeating unit B8), repeating unit (B9) (hereinafter also referred to as repeating unit B9), repeating unit (B10) (hereinafter also referred to as repeating unit B10), repeating unit (B11) (hereinafter also referred to as repeating unit B11), repeating unit (B12) (hereinafter also referred to as repeating unit B12), and repeating unit (B13) (hereinafter also referred to as repeating unit B13). [ka]

[0186] In formulas (B6) to (B13), RA These are, independently, a hydrogen atom, a fluorine atom, a methyl group, or a trifluoromethyl group. 1 This refers to a single bond, an aliphatic hydrocarbylene group having 1 to 6 carbon atoms, a phenylene group, a naphthylene group, or a group having 7 to 18 carbon atoms obtained by combining these, or *-OY 11 -, *-C(=O)-OY 11 -or *-C(=O)-NH-Y 11 - and Y 11 This is an aliphatic hydrocarbylene group having 1 to 6 carbon atoms, a phenylene group, a naphthylene group, or a group having 7 to 18 carbon atoms obtained by combining these, and may contain a carbonyl group, an ester bond, an ether bond, or a hydroxyl group. 2 is a single bond or **-Y 21 -C(=O)-O- and Y 21 This is a hydroxylene group having 1 to 20 carbon atoms, which may contain heteroatoms. 3 This includes single bonds, methylene groups, ethylene groups, phenylene groups, fluorinated phenylene groups, trifluoromethyl groups, and phenylene groups substituted with *-OY 31 -, *-C(=O)-OY 31 -or *-C(=O)-NH-Y 31 - is Y 31 This is a C1-C6 aliphatic hydrocarbylene group, phenylene group, fluorinated phenylene group, phenylene group substituted with a trifluoromethyl group, or a C7-C20 group obtained by combining these, and may contain a carbonyl group, ester bond, ether bond, or hydroxyl group. * represents a bond with a carbon atom of the main chain, and ** represents a bond with an oxygen atom in the formula. Y 4 This is a hydroxylene group having 1 to 30 carbon atoms, which may contain single bonds or heteroatoms. g1 and g2 are independently 0 or 1, but Y 4 When it is a single bond, g1 and g2 are 0.

[0187] In equations (B6) and (B10), Xa - Xa is a non-nucleophilic counterion. -Examples of non-nucleophilic counterions represented by include those described in Japanese Patent Publication No. 2010-113209 and Japanese Patent Publication No. 2007-145797.

[0188] In formulas (B7) and (B11), Y 2 ga-Y 21 When -C(=O)-O-, Y 21 Examples of hydrocarbylene groups that may contain a heteroatom represented by the following are, but are not limited to, those listed below. [ka] (In the equation, dashed lines represent connections.)

[0189] In formulas (B7) and (B11), R HF is a hydrogen atom or a trifluoromethyl group. In repeating units B7 and B11, R HF A specific example of the case where is a hydrogen atom is described in Japanese Patent Publication No. 2010-116550, and R HF Specific examples of cases where is a trifluoromethyl group include those described in Japanese Patent Publication No. 2010-77404. Examples of repeating units B7 and B11 include those described in Japanese Patent Publication No. 2012-246265 and Japanese Patent Publication No. 2012-246426.

[0190] Y 4The 1-30 carbon dioxide hydrocarbylene group, which may contain a heteroatom represented by , may be saturated or unsaturated, and may be linear, branched, or cyclic. Specific examples include alkane diyl groups with 1 to 30 carbon atoms, such as methylene 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, heptadecane-1,17-diyl group, etc.; cyclopentanediyl group, cyclohexanediyl group, Examples include cyclic saturated hydrocarbylene groups having 3 to 30 carbon atoms, such as norbornanediyl group and adamantanediyl group; arylene groups having 6 to 30 carbon atoms, such as phenylene group, methylphenylene group, ethylphenylene group, n-propylphenylene group, isopropylphenylene group, n-butylphenylene group, isobutylphenylene group, sec-butylphenylene group, tert-butylphenylene group, naphthylene group, methylnaphthylene group, ethylnaphthylene group, n-propylnaphthylene group, isopropylnaphthylene group, n-butylnaphthylene group, isobutylnaphthylene group, sec-butylnaphthylene group, and tert-butylnaphthylene group; and groups obtained by combining these.

[0191] Furthermore, 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, sulfur atom, nitrogen atom, or halogen atom, and some of the -CH2- of the hydrocarbylene group may be substituted with a group containing a heteroatom such as an oxygen atom, sulfur atom, or nitrogen atom, and as a result, it may contain a hydroxyl 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 sulfonic acid ester bond, a carbonate bond, a lactone ring, a sultone ring, a carboxylic acid anhydride (-C(=O)-OC(=O)-), a haloalkyl group, etc.

[0192] Repeating units B9 and B13 are repeating units that generate an acid in which the β-position of the sulfonyl group is difluoromethylated when irradiated with high-energy rays such as ultraviolet, far-ultraviolet, EB, EUV, X-rays, gamma rays, and synchrotron radiation. The acid has an acid strength suitable for deprotecting polymers containing repeating unit A2. Furthermore, by using a polymer containing repeating unit B9 or B13 as the base polymer of a resist composition, it is possible to appropriately control the movement and diffusion of the generated acid.

[0193] Photoacid generators that produce arene sulfonic acid by irradiation with high-energy rays are commonly used to deprotect polymers containing units protected by acetal groups, tertiary alkyl groups, or tert-butoxycarbonyl groups. However, even when arene sulfonic acid generating units are introduced as repeating units of the base polymer to obtain the effects of the present invention, the base polymer sometimes does not dissolve in the solvent due to its low solvent solubility. On the other hand, polymers containing repeating units B9 or B13 have sufficient lipophilicity, making them easy to manufacture and handle, and thus easy to prepare resist compositions.

[0194] Preferred examples of monomer anions that give repeating units B9 or B13 include, but are not limited to, those listed below. [ka]

[0195] [ka]

[0196] In formulas (B6) to (B13), R 21 ~R 38 Each of these is independently a C1-C20 hydrocarbyl group which may contain a halogen atom or a heteroatom.

[0197] Examples of the halogen atoms mentioned above include fluorine atoms, chlorine atoms, bromine atoms, and iodine atoms.

[0198] The C1-C20 hydrocarbyl group may be saturated or unsaturated, and may be linear, branched, or cyclic. Specific examples include C1-C20 alkyl groups such as methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, n-pentyl, tert-pentyl, n-hexyl, n-octyl, 2-ethylhexyl, n-nonyl, and n-decyl; cyclopentyl, cyclohexyl, cyclopentylmethyl, cyclopentylethyl, cyclopentylbutyl, cyclohexylmethyl, cyclohexylethyl, cyclohexylbutyl, norbornyl, and tricyclo[5.2.1.0 2,6 Examples include cyclic saturated hydrocarbyl groups having 3 to 20 carbon atoms, such as decyl groups, adamantyl groups, and adamantylmethyl groups; and aryl groups having 6 to 20 carbon atoms, such as phenyl groups, naphthyl groups, and anthracenyl groups. Furthermore, some or all of the hydrogen atoms of the hydrocarbyl group may be substituted with groups containing heteroatoms such as oxygen atoms, sulfur atoms, nitrogen atoms, and halogen atoms, and some of the -CH2- groups of the hydrocarbyl group may be substituted with groups containing heteroatoms such as oxygen atoms, sulfur atoms, and nitrogen atoms. As a result, the group may contain hydroxyl groups, fluorine atoms, chlorine atoms, bromine atoms, iodine atoms, cyano groups, carbonyl groups, ether bonds, ester bonds, sulfonic acid ester bonds, carbonate bonds, lactone rings, sultone rings, carboxylic acid anhydrides (-C(=O)-OC(=O)-), haloalkyl groups, etc.

[0199] Also, R 21 and R 22 However, they may bond to each other and form a ring with the sulfur atom to which they are bonded, R 23 and R 24 , R 26 and R 27 , or R 29 and R 30 However, they may bond with each other to form a ring with the sulfur atom to which they are bonded. In this case, the ring formed is as described in the explanation of formula (cation-1), R ct1 and Rct2 Examples similar to those exemplified include rings that can be formed when these elements bond to each other, together with the sulfur atoms to which they bond.

[0200] In formulas (B7) to (B9), specific examples of sulfonium cations include, but are not limited to, those exemplified as the sulfonium cation represented by formula (cation-1). Similarly, in formulas (B11) to (B13), specific examples of iodonium cations include, but are not limited to, those exemplified as the iodonium cation represented by formula (cation-2).

[0201] Among the repeating units B6 to B13, repeating unit B9 is preferred for processing photomask blanks because its acid strength is optimal for designing acid-unstable groups in polymers.

[0202] Repeating units B6 to B13 are units that generate acid when irradiated with high-energy rays. It is believed that the inclusion of these units in the polymer moderately suppresses acid diffusion, resulting in a pattern with reduced LER. Furthermore, the inclusion of these units in the polymer suppresses the phenomenon of acid volatilizing from the exposed areas and reattaching to the unexposed areas during baking in a vacuum, which is thought to be effective in reducing LER and minimizing shape degradation due to unwanted film loss in the unexposed areas.

[0203] Repeating units B6 to B13 are preferably introduced in an amount of 0.1 to 30 mol%, and more preferably in an amount of 0.5 to 20 mol%, of the total repeating units constituting the polymer. Repeating units B6 to B13 may be used individually or in combination of two or more types.

[0204] The content of repeating units having an aromatic ring skeleton among all repeating units constituting the polymer is preferably 65 mol% or more, more preferably 75 mol% or more, and even more preferably 85 mol% or more. If repeating units B6 to B13 are not included, it is preferable that all units have an aromatic ring skeleton.

[0205] The polymer may contain commonly used (meth)acrylic acid ester units protected by acid-unstable groups, or (meth)acrylic acid ester units having adhesive groups such as lactone structures or hydroxyl groups other than phenolic hydroxyl groups. While these repeating units allow for fine-tuning of the properties of the resist film, they are not required to be included.

[0206] Examples of (meth)acrylic acid ester units having the aforementioned adhesive group include the repeating unit represented by the following formula (B14) (hereinafter also referred to as repeating unit B14), the repeating unit represented by the following formula (B15) (hereinafter also referred to as repeating unit B15), and the repeating unit represented by the following formula (B16) (hereinafter also referred to as repeating unit B16). These units do not exhibit acidity and can be used auxiliaryly as units that provide adhesion to the substrate or as units that adjust solubility. [ka]

[0207] In formulas (B14) to (B16), R A These are, independently, a hydrogen atom, a fluorine atom, a methyl group, or a trifluoromethyl group. 41 R is either an -O- or a methylene group. 42 R is a hydrogen atom or a hydroxyl group. 43 k is a saturated hydrocarbyl group having 1 to 4 carbon atoms. k is an integer from 0 to 3.

[0208] When repeating units B14 to B16 are included, their content is preferably 0 to 20 mol%, and more preferably 0 to 10 mol%, of the total repeating units constituting the polymer. Repeating units B14 to B16 may be used individually or in combination of two or more types.

[0209] The aforementioned polymer can be synthesized by copolymerizing each monomer, which is optionally protected with a protecting group, using known methods, and then performing a deprotection reaction as necessary. The copolymerization reaction is not particularly limited, but radical polymerization and anionic polymerization are preferred. For these methods, refer to Japanese Patent Application Publication No. 2004-115630.

[0210] The polymer preferably has a weight-average molecular weight (Mw) of 1,000 to 50,000, and more preferably 2,000 to 20,000. If Mw is 1,000 or more, there is no risk of phenomena such as the pattern heads becoming rounded, reducing resolution, and LER degradation, as is conventionally known. On the other hand, if Mw is 50,000 or less, there is no risk of LER degradation, especially when forming patterns with a pattern line width of 100 nm or less. In this invention, Mw is a polystyrene-converted measurement value obtained by gel permeation chromatography (GPC) using tetrahydrofuran (THF) or dimethylformamide (DMF) as a solvent.

[0211] The polymer preferably has a narrow dispersion with a molecular weight distribution (Mw / Mn) of 1.0 to 2.0, preferably 1.0 to 1.9, and more preferably 1.0 to 1.8. When the dispersion is narrow in this way, after development, no foreign matter will be generated on the pattern, and the shape of the pattern will not deteriorate.

[0212] Furthermore, regarding the base polymer design, the dissolution rate in alkaline developer is preferably 10 nm / min or less, more preferably 7 nm / min or less, and even more preferably 5 nm / min or less. In advanced generations, when the coated film on the substrate is in the thin film region (100 nm or less), the effect of pattern film reduction on alkaline development becomes significant, and if the alkali dissolution rate of the polymer is greater than 10 nm / min, the pattern collapses, making it impossible to form fine patterns. This is particularly noticeable in the fabrication of photomasks, where defect-free conditions are required, as the development process tends to be strong. In this invention, the dissolution rate of the base polymer in alkaline developer is calculated from the amount of film reduction when a polymer solution (polymer concentration: 16.7% by mass, solvent: propylene glycol monomethyl ether acetate (PGMEA)) is spin-coated onto an 8-inch silicon wafer, baked at 100°C for 90 seconds to form a film with a thickness of 1000 nm, and then developed with a 2.38% by mass aqueous solution of tetramethylammonium hydroxide (TMAH) at 23°C for 100 seconds.

[0213] The base polymer of component (B) may include other polymers other than the polymer mentioned above. Other polymers that are conventionally known as base polymers for resist compositions can be used. The content of other polymers is not particularly limited, as long as it does not impair the effects of the present invention.

[0214] [(C) Organic Solvents] The resist composition of the present invention may contain an organic solvent as component (C). The organic solvent is not particularly limited as long as it is capable of dissolving each component. Examples of such organic solvents include ketones such as cyclohexanone and methyl-2-n-pentyl ketone, as described in paragraphs

[0144] to

[0145] of Japanese Patent Application Publication No. 2008-111103; alcohols such as 3-methoxybutanol, 3-methyl-3-methoxybutanol, 1-methoxy-2-propanol, 1-ethoxy-2-propanol, and diacetone alcohol; propylene glycol monomethyl ether (PGME), ethylene glycol monomethyl ether, propylene glycol monoethyl ether, and ethylene glycol Examples include ethers such as monoethyl ether, propylene glycol dimethyl ether, and diethylene glycol dimethyl ether; esters such as PGMEA, propylene glycol monoethyl ether acetate, ethyl lactate (EL), ethyl pyruvate, butyl acetate, methyl 3-methoxypropionate, ethyl 3-ethoxypropionate, tert-butyl acetate, tert-butyl propionate, and propylene glycol monotert-butyl ether acetate; lactones such as γ-butyrolactone; and mixed solvents thereof. When using acetal-based acid-unstable groups, high-boiling point alcohol-based solvents, specifically diethylene glycol, propylene glycol, glycerin, 1,4-butanediol, and 1,3-butanediol, can be added to accelerate the deprotection reaction of the acetal.

[0215] Among these organic solvents, 1-ethoxy-2-propanol, PGMEA, PGME, cyclohexanone, EL, γ-butyrolactone, and mixtures thereof are preferred.

[0216] If the chemically amplified positive resist composition of the present invention contains (C) an organic solvent, its content is preferably 200 to 10,000 parts by mass, and more preferably 400 to 5,000 parts by mass, per 80 parts by mass of (B) the base polymer. The (C) organic solvent may be used alone or as a mixture of two or more types.

[0217] [(D) Fluorine atom-containing polymer] The chemically amplified positive resist composition of the present invention may contain a fluorine atom-containing polymer as component (D) for the purpose of increasing contrast, suppressing the chemical flare phenomenon of acids during high-energy ray irradiation, and shielding against the mixing of acids from the antistatic film during the process of coating the antistatic film material onto the resist film, thereby suppressing unexpected and unwanted pattern degradation. This polymer may further contain at least one selected from the following repeating units: a repeating unit represented by the following formula (D1) (hereinafter also referred to as repeating unit D1), a repeating unit represented by the following formula (D2) (hereinafter also referred to as repeating unit D2), a repeating unit represented by the following formula (D3) (hereinafter also referred to as repeating unit D3), and a repeating unit represented by the following formula (D4) (hereinafter also referred to as repeating unit D4), and may further contain at least one selected from the following repeating units: a repeating unit represented by the following formula (D5) (hereinafter also referred to as repeating unit D5) and a repeating unit represented by the following formula (D6) (hereinafter also referred to as repeating unit D6). Since the fluorine atom-containing polymer also functions as a surfactant, it can prevent the re-adhesion of insoluble substances to the substrate that may occur during the development process, thus also exhibiting an effect against development defects. [ka]

[0218] In equations (D1) to (D6), x is an integer between 1 and 3. y is an integer satisfying 0 ≤ y ≤ 5 + 2z - x. z is either 0 or 1. h is an integer between 1 and 3. R B These are, independently, a hydrogen atom, a fluorine atom, a methyl group, or a trifluoromethyl group. C Each of these is independently either a hydrogen atom or a methyl group. 101 , R 102 , R 104 and R 105 Each of these is independently a hydrogen atom or a saturated hydrocarbyl group having 1 to 10 carbon atoms. 103 , R 106 , R 107 and R 108Each of these is independently a hydrogen atom, a C1-C15 hydrocarbyl group, a C1-C15 fluorinated hydrocarbyl group, or an acid-unstable group, and R 103 , R 106 , R 107 and R 108 When is a hydrocarbyl group or a fluorinated hydrocarbyl group, an ether bond or a carbonyl group may be interposed between the carbon-carbon bonds. 109 This is a linear or branched hydrocarbyl group having 1 to 5 carbon atoms, which may have a hydrogen atom or a group containing a heteroatom between the carbon-carbon bonds. 110 This is a linear or branched hydrocarbyl group having 1 to 5 carbon atoms, which may have a heteroatom interposed between the carbon-carbon bonds. 111 This is a saturated hydrocarbyl group having 1 to 20 carbon atoms in which at least one hydrogen atom is substituted with a fluorine atom, and a portion of the -CH2- of the saturated hydrocarbyl group may be substituted with an ester bond or an ether bond. 1 This is a (h+1) valent hydrocarbon group having 1 to 20 carbon atoms or a (h+1) valent fluorinated hydrocarbon group having 1 to 20 carbon atoms. 2 The bond is a single bond, *-C(=O)-O- or *-C(=O)-NH-. * represents a bond with a carbon atom in the main chain. 3 This is a single bond, -O-, *-C(=O)-OZ 31 -Z 32 -or *-C(=O)-NH-Z 31 -Z 32 - is Z 31 This is a single bond or a saturated hydrocarbylene group having 1 to 10 carbon atoms. 32 A is a single bond, ester bond, ether bond, or sulfonamide bond. * indicates a bond with a carbon atom of the main chain.

[0219] In equations (D1) and (D2), R 101 , R 102 , R 104 and R 105The saturated hydrocarbyl group having 1 to 10 carbon atoms, represented by , may be linear, branched, or cyclic. Specific examples include alkyl groups having 1 to 10 carbon atoms 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 groups; and cyclic saturated hydrocarbyl groups having 3 to 10 carbon atoms such as cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl, adamantyl, and norbornyl groups. Of these, saturated hydrocarbyl groups having 1 to 6 carbon atoms are preferred.

[0220] In formulas (D1) to (D4), R 103 , R 106 , R 107 and R 108 The C1-C15 hydrocarbyl group represented by can be linear, branched, or cyclic. Specific examples include C1-C15 alkyl groups, C2-C15 alkenyl groups, and C2-C15 alkynyl groups, but C1-C15 alkyl groups are preferred. Examples of alkyl groups include, in addition to those mentioned above, methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, n-pentyl, n-hexyl, n-heptyl, n-octyl, n-nonyl, n-decyl, n-undecyl, n-dodecyl, n-tridecyl, n-tetradecyl, and n-pentadecyl groups. Fluorinated hydrocarbyl groups include groups in which some or all of the hydrogen atoms bonded to the carbon atoms of the hydrocarbyl group mentioned above are substituted with fluorine atoms.

[0221] In formula (D4), Z 1 Examples of (h+1) valent hydrocarbon groups having 1 to 20 carbon atoms, represented by , include alkyl groups having 1 to 20 carbon atoms or cyclic saturated hydrocarbyl groups having 3 to 20 carbon atoms from which h hydrogen atoms have been removed. Also, Z 1Examples of (h+1) valent fluorinated hydrocarbon groups having 1 to 20 carbon atoms, as represented by the formula, include groups in which at least one hydrogen atom of the aforementioned (h+1) valent hydrocarbon group is substituted with a fluorine atom.

[0222] Specific examples of repeating units D1 to D4 are shown below, but are not limited to these. Note that in the following formula, R B This is the same as described above. [ka]

[0223] [ka]

[0224] [ka]

[0225] In formula (D5), R 109 and R 110 Examples of C1-C5 hydrocarbyl groups represented by include alkyl groups, alkenyl groups, and alkynyl groups, but alkyl groups are preferred. Examples of alkyl groups include methyl groups, ethyl groups, n-propyl groups, isopropyl groups, n-butyl groups, isobutyl groups, sec-butyl groups, and n-pentyl groups. In addition, a group containing a heteroatom such as an oxygen atom, a sulfur atom, or a nitrogen atom may be interposed between the carbon-carbon bonds of the hydrocarbyl group.

[0226] In formula (D5), -OR 109 It is preferable that R is a hydrophilic group. In this case, R 109 Preferred elements include hydrogen atoms, C1-C5 alkyl groups with oxygen atoms interposed between carbon-carbon bonds, etc.

[0227] In formula (D5), Z 2 It is preferable that *-C(=O)-O- or *-C(=O)-NH-. Furthermore, R CIt is preferable that it is a methyl group. 2 The presence of a carbonyl group improves the acid trapping ability derived from the antistatic film. Also, R C When the group is a methyl group, a more rigid polymer with a higher glass transition temperature (Tg) is formed, thus suppressing acid diffusion. This results in good temporal stability of the resist film, and the resolution and pattern shape do not deteriorate.

[0228] The repeating unit D5 can be, but is not limited to, the following. Note that in the following formula, R C This is the same as described above. [ka]

[0229] [ka]

[0230] In formula (D6), Z 3 The saturated hydrocarbylene group having 1 to 10 carbon atoms, represented by , may be linear, branched, or cyclic. Specific examples include methanediyl group, ethane-1,1-diyl group, ethane-1,2-diyl group, propane-1,1-diyl group, propane-1,2-diyl group, propane-1,3-diyl group, propane-2,2-diyl group, butane-1,1-diyl group, butane-1,2-diyl group, butane-1,3-diyl group, butane-2,3-diyl group, butane-1,4-diyl group, and 1,1-dimethylethane-1,2-diyl group.

[0231] In formula (D6), R 111 A saturated hydrocarbyl group having 1 to 20 carbon atoms, represented by , in which at least one hydrogen atom is substituted with a fluorine atom, may be linear, branched, or cyclic. Specific examples include alkyl groups having 1 to 20 carbon atoms or cyclic saturated hydrocarbyl groups having 3 to 20 carbon atoms in which at least one hydrogen atom is substituted with a fluorine atom.

[0232] The repeating unit D6 can be, but is not limited to, the following. Note that in the following formula, R C This is the same as described above. [ka]

[0233] [ka]

[0234] [ka]

[0235] [ka]

[0236] The content of repeating units D1 to D4 is preferably 15 to 95 mol%, and more preferably 20 to 85 mol%, of the total repeating units of the fluorine atom-containing polymer. The content of repeating units D5 and / or D6 is preferably 5 to 85 mol%, and more preferably 15 to 80 mol%, of the total repeating units of the fluorine atom-containing polymer. Repeating units D1 to D6 may be used individually or in combination of two or more types.

[0237] (D) The fluorine atom-containing polymer may contain other repeating units besides those described above. Examples of such repeating units include those described in paragraphs

[0046] to

[0078] of Japanese Patent Application Publication No. 2014-177407. (D) If the fluorine atom-containing polymer contains other repeating units, the content thereof is preferably 50 mol% or less of the total repeating units of the fluorine atom-containing polymer.

[0238] (D) Fluorine atom-containing polymers can be synthesized by copolymerizing each monomer, which is optionally protected with a protecting group, using known methods, and then performing a deprotection reaction as necessary. The copolymerization reaction is not particularly limited, but radical polymerization and anionic polymerization are preferred. For these methods, refer to Japanese Patent Application Publication No. 2004-115630.

[0239] (D) The Mw of the fluorine atom-containing polymer is preferably 2000 to 50000, and more preferably 3000 to 20000. If the Mw is less than 2000, it may promote acid diffusion, leading to a deterioration in resolution and impaired stability over time. If the Mw is too high, the solubility in the solvent will decrease, potentially causing coating defects. Furthermore, the Mw / Mn of the (D) fluorine atom-containing polymer is preferably 1.0 to 2.2, and more preferably 1.0 to 1.7.

[0240] When the chemically amplified positive resist composition of the present invention contains (D) a fluorine atom-containing polymer, its content is preferably 0.01 to 30 parts by mass, and more preferably 0.1 to 20 parts by mass, per 80 parts by mass of (B) the base polymer. (D) The fluorine atom-containing polymer may be used alone or in combination of two or more types.

[0241] [(E) Quencher] The chemically amplified positive resist composition of the present invention may optionally contain a quencher as component (E). In this invention, a quencher refers to a compound that traps the acid generated from the acid generator. This suppresses the diffusion rate of the acid generated from the acid generator when it diffuses into the resist film, and even when a substrate with a chromium-containing material on its outermost surface is used, the influence of the acid generated in the resist film on the chromium-containing material can be suppressed.

[0242] A suitable example of a quencher in the present invention is an onium carboxylate represented by the following formula (E1). [ka]

[0243] In formula (E1), R 201 This is a C1-C40 hydrocarbyl group, which may contain heteroatoms. The hydrocarbyl group may be saturated or unsaturated, and may be linear, branched, or cyclic. Specific examples include C1-C40 alkyl groups, C3-C40 cyclic saturated hydrocarbyl groups, C2-C40 alkenyl groups, C2-C40 alkynyl groups, C3-C40 cyclic unsaturated aliphatic hydrocarbyl groups, C6-C40 aryl groups, C7-C40 aralkyl groups, and groups obtained by combining these. Furthermore, some or all of the hydrogen atoms of the hydrocarbyl group may be substituted with a hydroxyl group, carboxyl group, halogen atom, cyano group, amide group, nitro group, mercapto group, sultone group, sulfone group, or sulfonium salt-containing group, and some of the -CH2- of the hydrocarbyl group may be substituted with an ether bond, ester bond, carbonyl group, carbonate group, or sulfonic acid ester bond.

[0244] In formula (E1), Mq + This is an onium cation. Examples of the onium cation include sulfonium cations, iodonium cations, and ammonium cations, but sulfonium cations are preferred. Preferred sulfonium cations are the same as those exemplified as the sulfonium cation represented by formula (cation-1).

[0245] When the chemically amplified positive resist composition of the present invention contains an onium carboxylate salt represented by formula (E1) as a quencher, the content is preferably 0.1 to 40 parts by mass, and more preferably 0.1 to 20 parts by mass, per 80 parts by mass of the (B) base polymer.

[0246] Other examples of the quencher include onium carboxylates represented by the following formulas (E2) or (E3). [ka] (In the formula, Mq + (This is the same as above.)

[0247] In formula (E2), R 211 ~R 214 These are, independently, hydrogen atoms and -L A -CO2 - or a hydrocarbyl group having 1 to 20 carbon atoms, which may contain heteroatoms. 211 and R 212 And, R 212 and R 213 or R 213 and R 214 These may bond with each other to form a ring with the carbon atoms to which they are bonded. A This is a hydroxylene group having 1 to 20 carbon atoms, which may contain single bonds or heteroatoms. 215 This is a hydrocarbyl group having 1 to 20 carbon atoms, which may contain a hydrogen atom or a heteroatom.

[0248] In formula (E2), ring R is a ring having 2 to 6 carbon atoms, including the carbon and nitrogen atoms in the formula, and some or all of the hydrogen atoms bonded to the carbon atoms of the ring are a hydrocarbyl group having 1 to 20 carbon atoms, or -L A -CO2 - The ring may be substituted with a divalent group containing a sulfur atom, an oxygen atom, or a nitrogen atom. The ring may be an alicyclic or aromatic ring. The ring is preferably a five-membered or six-membered ring, and specific examples include pyridine rings, pyrrole rings, pyrrolidine rings, piperidine rings, pyrazole rings, imidazoline rings, pyridazine rings, pyrimidine rings, pyrazine rings, imidazoline rings, oxazole rings, thiazole rings, morpholine rings, thiazine rings, triazole rings, and the like.

[0249] The onium carboxylate salt represented by formula (E2) contains at least one -L A -CO2 - It has a group. That is, R 211 ~R 214At least one of them is -L A -CO2 - is and / or at least one hydrogen atom bonded to a carbon atom of ring R is -L A -CO2 - It has been replaced with this.

[0250] In formula (E3), R 221 ~R 226 Each of these is independently a hydrocarbyl group having 1 to 20 carbon atoms, which may contain a hydrogen atom or a heteroatom. 221 and R 222 or R 223 and R 226 These may bond with each other to form a ring with the carbon atoms to which they are bonded, R 224 and R 225 These elements may bond with each other to form a ring with the nitrogen atom to which they are bonded. k1 is either 0 or 1. When k1=0, k2 is either 0 or 1, and when k1=1, k2 is an integer between 0 and 3.

[0251] When the chemically amplified positive resist composition of the present invention contains an onium carboxylate salt represented by formula (E2) or (E3) as a quencher, the content is preferably 0.1 to 50 parts by mass, and more preferably 0.5 to 30 parts by mass, per 80 parts by mass of the (B) base polymer.

[0252] Another example of the aforementioned quencher is a sulfonium compound represented by the following formula (E4). [ka]

[0253] In formula (E4), R 231 , R 232 and R 233Each of these is independently a C1-C20 hydrocarbyl group which may contain heteroatoms. Furthermore, some of the hydrogen atoms of the hydrocarbyl group may be substituted with groups containing heteroatoms such as oxygen, sulfur, nitrogen, and halogen atoms, and some of the -CH2- of the hydrocarbyl group may be substituted with groups containing heteroatoms such as oxygen, sulfur, and nitrogen atoms, resulting in the inclusion of hydroxyl groups, cyano groups, carbonyl groups, ether bonds, thioether bonds, ester bonds, sulfonic acid ester bonds, carbonate bonds, carbamate bonds, lactone rings, sultone rings, carboxylic acid anhydrides (-C(=O)-OC(=O)-), haloalkyl groups, etc. Note that the -CH2- of the hydrocarbyl group may be a carbon atom bonded to the benzene ring in the formula.

[0254] In formula (E4), z1 and z2 are each an integer between 0 and 5, and z3 is an integer between 0 and 4. From the viewpoint of ease of synthesis and availability of raw materials, z1, z2, and z3 are preferably 0, 1, or 2, respectively.

[0255] When z1 is between 2 and 5, two adjacent R 231 However, they may bond with each other and form a ring with the carbon atoms to which they are bonded. When z2 is 2 to 5, two adjacent R 232 However, they may bond to each other and form a ring with the carbon atoms to which they are bonded. When z3 is 2 to 4, two adjacent R 233 However, they may bond with each other to form a ring with the carbon atoms to which they are bonded.

[0256] When the chemically amplified positive resist composition of the present invention contains a sulfonium compound represented by formula (E4) as a quencher, the content thereof is preferably 0.1 to 40 parts by mass, and more preferably 1 to 20 parts by mass, per 80 parts by mass of the (B) base polymer.

[0257] As a quencher, in addition to the onium salt compounds described above, a photodegradable onium salt having a nitrogen-containing substituent may be used in combination as needed. Such compounds function as a quencher in the unexposed areas and lose their quenching ability in the exposed areas through neutralization with the acid they generate, functioning as a so-called photodecayable base. By using a photodecayable base, the contrast between the exposed and unexposed areas can be further enhanced. Examples of photodecayable bases include those described in Japanese Patent Publication No. 2009-109595, Japanese Patent Publication No. 2012-46501, Japanese Patent Publication No. 2013-209360, etc. When the chemically amplified positive resist composition of the present invention contains the photodecayable base as a quencher, its content is preferably 0.1 to 40 parts by mass, and more preferably 0.1 to 20 parts by mass, per 80 parts by mass of the (B) base polymer.

[0258] As a quencher, an amine compound can also be used. Examples of such amine compounds include primary, secondary, or tertiary amine compounds described in paragraphs

[0146] to

[0164] of Japanese Patent Publication No. 2008-111103, particularly amine compounds having a hydroxyl group, an ether bond, an ester bond, a lactone ring, a cyano group, or a sulfonic acid ester bond. Also, as described in Japanese Patent Publication No. 3790649, compounds in which a primary or secondary amine is protected with a carbamate group can also be used. When the chemically amplified positive resist composition of the present invention contains the amine compound as a quencher, its content is preferably 0.001 to 12 parts by mass, and more preferably 0.01 to 8 parts by mass, per 80 parts by mass of the (B) base polymer.

[0259] [(F) Other photoacid generators] The chemically amplified positive resist composition of the present invention may contain photoacid generators other than the photoacid generator comprising an onium salt represented by formula (A). The other photoacid generators are not particularly limited as long as they are compounds that generate acid upon irradiation with high-energy rays. Suitable photoacid generators include sulfonium salts, iodonium salts, sulfonyldiazomethane, N-sulfonyloxiimide, oxime-O-sulfonate type acid generators, and the like.

[0260] Specific examples of the aforementioned other photoacid generators include nonafluorobutanesulfonate, partially fluorinated sulfonates described in paragraphs

[0247] to

[0251] of Japanese Patent Publication No. 2012-189977, and paragraph

[0247] to

[0251] of Japanese Patent Publication No. 2013-101271.

[0261] Examples include the partially fluorinated sulfonates described in

[0265] , paragraphs

[0122] to

[0142] of Japanese Patent Publication No. 2008-111103, and paragraphs

[0080] to

[0081] of Japanese Patent Publication No. 2010-215608. Among the above specific examples, aryl sulfonate type or alkane sulfonate type photoacid generators are preferred because they generate an acid of appropriate strength for deprotecting the acid-unstable group of repeating unit B2.

[0261] A preferred example of the photoacid generator is a salt compound containing an anion having the structure shown below. [ka]

[0262] [ka]

[0263] [ka]

[0264] [ka]

[0265] [ka]

[0266] [ka]

[0267] [ka]

[0268] [ka]

[0269] [ka]

[0270] Other preferred examples of the photoacid generator include salt compounds containing an anion represented by the following formula (F1). [ka]

[0271] In equation (F1), m1 is either 0 or 1. p is an integer between 1 and 3. q is an integer between 1 and 5. r is an integer between 0 and 3.

[0272] In formula (F1), L 1 These are single bonds, ether bonds, ester bonds, sulfonic acid ester bonds, carbonate bonds, or carbamate bonds.

[0273] In formula (F1), L 2 These are ether bonds, ester bonds, sulfonic acid ester bonds, carbonate bonds, or carbamate bonds.

[0274] In formula (F1), L B When p is 1, it is a single bond or a hydroxylene group having 1 to 20 carbon atoms, and when p is 2 or 3, it is a (p+1) valent hydrocarbon group having 1 to 20 carbon atoms. The hydroxylene group and the (p+1) valent hydrocarbon group may contain at least one selected from an ether bond, a carbonyl group, an ester bond, an amide bond, a sultone ring, a lactam ring, a carbonate bond, a halogen atom, a hydroxyl group, and a carboxyl group.

[0275] L BThe hydroxylene group, represented by , having 1 to 20 carbon atoms, may be saturated or unsaturated, and may be linear, branched, or cyclic. Specific examples include the methylene 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, etc. Examples include alkanediyl groups with 1 to 20 carbon atoms; cyclic saturated hydrocarbylene groups with 3 to 20 carbon atoms such as cyclopentanediyl, cyclohexanediyl, norbornanediyl, and adamantanediyl; unsaturated aliphatic hydrocarbylene groups with 2 to 20 carbon atoms such as vinylene and propene-1,3-diyl; arylene groups with 6 to 20 carbon atoms such as phenylene and naphthylene; and groups obtained by combining these. Also, L B The (p+1) valent hydrocarbon group having 1 to 20 carbon atoms, represented by , may be saturated or unsaturated, and may be linear, branched, or cyclic. Specific examples include groups obtained by removing one or two hydrogen atoms from the aforementioned specific examples of the 1 to 20 carbon atom hydrocarbylene group.

[0276] In formula (F1), Rf 1 and Rf 2 Each of these is independently a hydrogen atom, a fluorine atom, or a trifluoromethyl group, but at least one is either a fluorine atom or a trifluoromethyl group.

[0277] In formula (F1), R 301 This includes a hydroxyl group, a carboxyl group, a saturated hydrocarbyl group having 1 to 6 carbon atoms, a saturated hydrocarbyloxy group having 1 to 6 carbon atoms, a saturated hydrocarbylcarbonyloxy group having 2 to 6 carbon atoms, a fluorine atom, a chlorine atom, a bromine atom, an amino group, and -N(R 301A )-C(=O)-R 301B or -N(R 301A )-C(=O)-OR 301B And R 301A R is a hydrogen atom or a saturated hydrocarbyl group having 1 to 6 carbon atoms.301B This is a saturated hydrocarbyl group having 1 to 6 carbon atoms or an unsaturated aliphatic hydrocarbyl group having 2 to 8 carbon atoms.

[0278] R 301 , R 301A and R 301B The saturated hydrocarbyl group having 1 to 6 carbon atoms, represented by R, may be linear, branched, or cyclic. Specific examples include alkyl groups having 1 to 6 carbon atoms such as methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, n-pentyl, and n-hexyl groups; and cyclic saturated hydrocarbyl groups having 3 to 6 carbon atoms such as cyclopropyl, cyclobutyl, cyclopentyl, and cyclohexyl groups. 301 The saturated hydrocarbyl portion of the saturated hydrocarbyloxy group having 1 to 6 carbon atoms, as represented by R, is the same as the specific examples of saturated hydrocarbyl groups mentioned above. 301 Examples of the saturated hydrocarbyl portion of the saturated hydrocarbyl carbonyloxy group having 2 to 6 carbon atoms, as described above, include those having 1 to 5 carbon atoms.

[0279] R 301B The carbon-2-carbon unsaturated aliphatic hydrocarbyl groups represented by can be linear, branched, or cyclic. Specific examples include carbon-2-carbon alkenyl groups such as vinyl, propenyl, butenyl, and hexenyl groups; carbon-2-carbon alkynyl groups such as ethynyl, propynyl, and butynyl groups; and carbon-3-carbon cyclic unsaturated aliphatic hydrocarbyl groups such as cyclohexenyl and norbornenyl groups.

[0280] In formula (F1), R 302This is a saturated hydrocarbylene group having 1 to 20 carbon atoms or an arylene group having 6 to 14 carbon atoms, wherein some or all of the hydrogen atoms of the saturated hydrocarbylene group may be substituted with halogen atoms other than fluorine atoms, and some or all of the hydrogen atoms of the arylene group may be substituted with substituents selected from a saturated hydrocarbyl group having 1 to 20 carbon atoms, a saturated hydrocarbyloxy group having 1 to 20 carbon atoms, an aryl group having 6 to 14 carbon atoms, a halogen atom, and a hydroxyl group.

[0281] R 302 The saturated hydrocarbylene groups having 1 to 20 carbon atoms, represented by , may be linear, branched, or cyclic. Specific examples include alkane diyl groups having 1 to 20 carbon atoms, such as methylene, ethane-1,1-diyl, ethane-1,2-diyl, propane-1,3-diyl, butane-1,4-diyl, pentane-1,5-diyl, hexane-1,6-diyl, heptane-1,7-diyl, octane-1,8-diyl, nonane-1,9-diyl, decane-1,10-diyl, undecane-1,11-diyl, and dodecane-1,12-diyl; and cyclic saturated hydrocarbylene groups having 3 to 20 carbon atoms, such as cyclopentanediyl, cyclohexanediyl, norbornanediyl, and adamantanediyl.

[0282] R 302Specific examples of arylene groups with 6 to 14 carbon atoms, represented by , include phenylene groups, naphthylene groups, phenanthrendiyl groups, and anthracenediyl groups. The hydrocarbyl portion of the saturated hydrocarbyl group having 1 to 20 carbon atoms and the hydrocarbyloxy group having 1 to 20 carbon atoms, which are substituents on the arylene group, may be linear, branched, or cyclic. Specific examples 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 eicosyl groups; and cyclic saturated hydrocarbyl groups having 3 to 20 carbon atoms such as cyclopropyl, cyclopentyl, cyclohexyl, cyclopropylmethyl, 4-methylcyclohexyl, cyclohexylmethyl, norbornyl, and adamantyl groups. Specific examples of arylene groups having 6 to 14 carbon atoms that are substituents on the aforementioned arylene group include phenylene group, naphthylene group, phenanthrendiyl group, anthracenediyl group, and the like.

[0283] The anion represented by formula (F1) is preferably the anion represented by the following formula (F2). [ka]

[0284] In formula (F2), p, q, r, L 1 , L B and R 301 The same as above. m2 is an integer from 1 to 4. R 302A These are saturated hydrocarbyl groups with 1 to 20 carbon atoms, saturated hydrocarbyloxy groups with 1 to 20 carbon atoms, aryl groups with 6 to 14 carbon atoms, halogen atoms, or hydroxyl groups. When m2 is 2 to 4, each R 302A They may be the same as or different from each other.

[0285] The anions represented by formula (F1) include, but are not limited to, those listed below. [ka]

[0286] [ka]

[0287] [ka]

[0288] [ka]

[0289] [ka]

[0290] [ka]

[0291] [ka]

[0292] [ka]

[0293] [ka]

[0294] [ka]

[0295]

change

[0296]

change

[0297]

change

[0298]

change

[0299]

change

[0300]

change

[0301]

change

[0302]

change

[0303]

change

[0304]

change

[0305]

change

[0306] [ka]

[0307] [ka]

[0308] [ka]

[0309] [ka]

[0310] [ka]

[0311] [ka]

[0312] [ka]

[0313] (F) In other photoacid generators, a sulfonium cation or an iodonium cation is preferred as the cation paired with the anion described above. Specific examples of the sulfonium cation include, but are not limited to, those exemplified as the sulfonium cation represented by formula (cation-1). Specific examples of the iodonium cation include, but are not limited to, those exemplified as the sulfonium cation represented by formula (cation-2).

[0314] The acid generated by the aforementioned other photoacid generators is preferably of a pKa of -2.0 or higher, and more preferably of -1.0 or higher. Furthermore, the upper limit of the pKa is preferably 2.0. The pKa values ​​were calculated using the pKa DB in the ACD / Chemsketch ver:9.04 software from Advanced Chemistry Development, Inc.

[0315] If the chemically amplified positive resist composition of the present invention contains (F) other photoacid generators, the content thereof is preferably 1 to 10 parts by mass, and more preferably 1 to 5 parts by mass, per 80 parts by mass of the base polymer. (F) Other photoacid generators may be used alone or in combination of two or more. By including other photoacid generators, the amount of acid generated in the exposed areas and the dissolution inhibition in the unexposed areas can be appropriately adjusted.

[0316] [(G) Surfactants] The chemically amplified positive resist composition of the present invention may contain a commonly used surfactant as component (G) to improve its applicability to substrates. Numerous surfactants are known, as described in International Publication No. 2006 / 121096, Japanese Patent Publication No. 2008-102383, Japanese Patent Publication No. 2008-304590, Japanese Patent Publication No. 2004-115630, and Japanese Patent Publication No. 2005-8766, and can be selected by reference thereto.

[0317] If the chemically amplified positive resist composition of the present invention contains (G) a surfactant, its content is preferably 2 parts by mass or less, more preferably 1 part by mass or less, and preferably 0.01 parts by mass or more, per 80 parts by mass of the (B) base polymer. The (G) surfactant may be used alone or in combination of two or more types.

[0318] [Method for forming a resist pattern] The resist pattern formation method of the present invention includes the steps of forming a resist film on a substrate using the chemically amplified positive-type resist composition described above, exposing the resist film using high-energy rays, and developing the resist film irradiated with the pattern using an alkaline developer to obtain a resist pattern.

[0319] As the substrate, for example, substrates for integrated circuit manufacturing (Si, SiO, SiO2, SiN, SiON, TiN, WSi, BPSG, SOG, organic anti-reflective coatings, etc.) or substrates for mask circuit manufacturing (Cr, CrO, CrON, MoSi2, Si, SiO, SiO2, etc.) can be used. The chemically amplified positive resist composition is applied to the substrate by a method such as spin coating to a film thickness of 0.03 to 2 μm, and this is pre-baked on a hot plate, preferably at 60 to 150°C for 1 to 20 minutes, more preferably at 80 to 140°C for 1 to 10 minutes, to form a resist film.

[0320] Next, the resist film is exposed using high-energy rays to irradiate a pattern. Examples of such high-energy rays include ultraviolet rays, far-ultraviolet rays, excimer laser light (KrF, ArF, etc.), EB, EUV, X-rays, gamma rays, and synchrotron radiation.

[0321] When using ultraviolet light, far ultraviolet light, excimer laser light, EUV, X-rays, gamma rays, or synchrotron radiation as the high-energy rays, a mask is used to form the desired pattern, and the exposure amount is preferably 1 to 300 mJ / cm². 2 More preferably 10-200 mJ / cm² 2 Irradiate in such a manner. When using EB as the high-energy beam, the exposure dose is preferably 1 to 300 μC / cm². 2 More preferably 10-200 μC / cm 2 The image is drawn directly in this manner. Furthermore, the chemically amplified positive resist composition of the present invention is particularly useful for EUV or EB lithography.

[0322] In addition to conventional exposure methods, immersion exposure, which involves inserting a liquid between the mask and the resist film, can also be used in some cases. In such cases, a water-insoluble protective film can be used.

[0323] Next, post-exposure baking (PEB) is performed on a hot plate, preferably at 60-150°C for 1-20 minutes, more preferably at 80-140°C for 1-10 minutes.

[0324] Subsequently, the substrate is developed using a developer solution of an alkaline aqueous solution such as tetramethylammonium hydroxide (TMAH) in a concentration of preferably 0.1 to 5% by mass, more preferably 2 to 3% by mass, for 0.1 to 3 minutes, preferably 0.5 to 2 minutes, by a conventional method such as the dip method, puddle method, or spray method, thereby forming the desired pattern on the substrate.

[0325] The chemically amplified positive resist composition of the present invention is particularly useful when used under conditions requiring high etching resistance, minimal change in pattern line width even when the time from exposure to PEB is extended, and a low LER (Low Emission Rate). Furthermore, the resist composition of the present invention is particularly useful for application to substrates with surfaces that are prone to pattern peeling or collapse due to difficulty in achieving good adhesion of the resist pattern. Examples of such substrates include substrates in which a chromium compound containing metallic chromium or one or more light elements selected from oxygen, nitrogen, and carbon is deposited by sputtering. The chemically amplified positive resist composition of the present invention is particularly useful for pattern formation using a photomask blank as the substrate. [Examples]

[0326] The present invention will be specifically described below with reference to synthesis examples, examples, and comparative examples, but the present invention is not limited to the following examples. The apparatus used is as follows. • MALDI TOF-MS: S3000 manufactured by JEOL Ltd.

[0327] [1] Synthesis of onium salts [Example 1-1] Synthesis of PAG-1 [ka]

[0328] Under a nitrogen atmosphere, SM-1 (10.6g), SM-2 (6.3g), and 4-dimethylaminopyridine (0.3g) were suspended in THF (50g) and cooled in an ice bath. Triethylamine (3.5g) was added dropwise, and the mixture was stirred at room temperature for 10 hours. After maturation, the reaction mixture was cooled, and water (50g) was added to stop the reaction. Subsequently, SM-3 (9.4g) was added, the target product was extracted with methylene chloride (100g), and a normal aqueous work-up was performed to remove the solvent by distillation, yielding 15.5g of PAG-1 as an oily substance (yield 73%).

[0329] The TOF-MS results for PAG-1 are shown below. MALDI TOF-MS: POSITIVE M + 277(C 18 H 13 OS + equivalent) NEGATIVE M - 573(C 31 H 41 O6S - equivalent)

[0330] [Examples 1-2 to 1-7] Synthesis of PAG-2 to PAG-7 Using corresponding raw materials and known organic synthesis reactions, onium salts PAG-2 to PAG-7, represented by the following formulas, were synthesized. [ka]

[0331] [2] Synthesis of base polymers [Synthesis Example 1] Synthesis of Polymer P-1 20 g of polyhydroxystyrene-acenaphthylene copolymer and 46.7 g of tetrahydrofuran as solvent were added to a 100 mL flask. Then, under a nitrogen atmosphere at approximately 25°C, 0.5 g of methanesulfonic acid was added, followed by the dropwise addition of 4.4 g of 1-methoxy-2-methylpropene, and the mixture was allowed to react at room temperature for 4.5 hours. After the reaction was complete, 1.0 g of triethylamine was added, and the resulting reaction solution was added dropwise to 500 g of hexane. The precipitated solid was filtered off. The filtered solid was washed twice with 120 g of hexane. The obtained solid was dissolved in a mixed solvent of 60 g of ethyl acetate and 20 g of water. The resulting solution was transferred to a separatory funnel, 0.7 g of acetic acid was added, and the liquid-liquid extraction was performed. The lower layer was removed by distillation, and 20 g of water and 0.9 g of pyridine were added to the resulting organic layer, and the liquid-liquid extraction was performed. The lower layer was removed by distillation, and 20 g of water was added to the obtained organic layer for water washing and separation (water washing and separation was performed a total of 5 times). After separation, the organic layer was concentrated and dissolved in 40 g of PGME. The resulting solution was added dropwise to 600 g of water, and the precipitated solid was filtered off. The obtained solid was washed with water and dried to obtain 20.3 g of the target polymer P-1, which is a white polymer. 1 H-NMR, 13 The following analysis results were obtained by measuring using 1C-NMR and GPC. [ka]

[0332] [Synthesis Examples 2-9] Synthesis of Polymers P-2-P-9 Except for changing the types and mixing ratios of each monomer, polymers P-2 to P-9 shown below were synthesized with reference to Synthesis Example 1 and known methods. [ka]

[0333] [3] Preparation of chemically amplified positive resist compositions [Examples 2-1 to 2-32, Comparative Examples 1-1 to 1-21] Chemically amplified positive resist compositions were prepared by dissolving each component in an organic solvent with the compositions shown in Tables 1 to 3 below, and filtering the resulting solutions through a 5 nm nylon filter and a 1 nm UPE filter. The organic solvent was a mixed solvent consisting of 940 parts by mass of PGMEA, 1870 parts by mass of EL, and 1870 parts by mass of PGME.

[0334] [Table 1]

[0335] [Table 2]

[0336] [Table 3]

[0337] In Tables 1-3, the comparative photoacid generators cPAG-1 to cPAG-4, photoacid generators PAG-A and PAG-B, quenchers Q-1 to Q-4, and fluorine atom-containing polymers D-1 to D-5 are as follows.

[0338] [ka]

[0339] [ka]

[0340] [ka]

[0341] [ka]

[0342] [4] EB lithography evaluation [Examples 3-1 to 3-32, Comparative Examples 2-1 to 2-21] Each chemically amplified positive resist composition (R-1 to R-32, CR-1 to CR-21) was spin-coated onto a reflective mask blank for EUV exposure using ACT-M (manufactured by Tokyo Electron Ltd.). The blank consisted of a 284 nm thick Mo / Si 40-layer multilayer reflective film, a 3.5 nm thick Ru film as a protective layer, a 70 nm thick TaN film as an absorption layer, and a 6 nm thick CrN film as a hard mask. The mask blank was then pre-baked on a hot plate at 110°C for 600 seconds to produce an 80 nm thick resist film. The thickness of the obtained resist film was measured using an optical measuring instrument, NanoSpec (manufactured by Nanometrics). Measurements were taken at 81 locations within the plane of the blank substrate, excluding the outer edge portion up to 10 mm inward from the outer edge, and the average thickness and thickness range were calculated.

[0343] Furthermore, the resist film was exposed using an electron beam lithography system (EBM-5000plus, manufactured by Newflare Technology Co., Ltd., accelerating voltage 50kV), subjected to PEB at 110°C for 600 seconds, and developed with a 2.38 mass% TMAH aqueous solution to obtain a positive type pattern.

[0344] The obtained resist patterns were evaluated as follows: The fabricated patterned mask blanks were observed using an overhead SEM (scanning electron microscope), and the optimal exposure amount (μC / cm²) was determined to resolve 200 nm 1:1 line-and-space (LS) lines at a 1:1 ratio. 2 The resolution (limiting IS resolution) was defined as the minimum dimension at the exposure dose that resolves a 200nm isolated space at a 9:1 ratio, and the LER of a 200nm LS was measured by SEM. For development loading evaluation, the exposure dose (μC / cm²) that resolves a 200nm 1:1 LS at a 1:1 ratio within the substrate surface was defined. 2The dimensions of the space between a 200nm LS pattern formed using ( ) and a 200nm LS pattern with dummy patterns of densities of 15%, 25%, 33%, 45%, 50%, 55%, 66%, 75%, 85%, and 95% placed around the pattern were measured by SEM, and the difference in dimensional differences between the dense and sparse patterns was compared. The pattern shape was determined visually to determine whether it was rectangular or not.

[0345] The dissolution rate of the exposed area is determined by spin-coating a resist solution onto an 8-inch silicon wafer, baking it at 110°C for 60 seconds to form a resist film with a thickness of 90 nm, and then applying an exposure dose (mJ / cm²) that resolves a 200 nm 1:1 line and space (LS) at a 1:1 ratio. 2 Exposure was performed using KrF excimer laser light, followed by baking at 110°C for 60 seconds. Then, the resist was developed using a resist development analyzer (RDA-800, manufactured by Lithotech Japan Co., Ltd.) with a 2.38 mass% TMAH aqueous solution at 23°C, and the results were calculated. The results are shown in Tables 4 and 5.

[0346] [Table 4]

[0347] [Table 5]

[0348] The results shown in Tables 4 and 5 demonstrate that the photoacid generator of the present invention, the chemically amplified positive resist composition using the same, and the resist pattern formation method are useful for semiconductor device manufacturing, particularly for photolithography in the processing of transmissive and reflective photomask blanks.

Claims

1. An onium salt represented by the following formula (A). 【Chemistry 1】 (In the formula, n1 is an integer between 0 and 2. When n1=0, n2 is an integer between 2 and 5; when n1=1, n2 is an integer between 2 and 7; and when n1=2, n2 is an integer between 2 and 9.) L is a single bond, ether bond, ester bond, sulfonic acid ester bond, carbonate bond, or carbamate bond. R1 is a branched and cyclic hydrocarbyl group having 3 to 20 carbon atoms, which may contain a hydrogen atom or a heteroatom. R2 is a hydrocarbyl group having 6 to 20 carbon atoms, which may contain a heteroatom and contain an aromatic ring. R 3 Each is independently a branched and cyclic hydrocarbyl group having 3 to 20 carbon atoms, which may contain an iodine atom or a heteroatom, and at least one R 3 L is bonded to a carbon atom adjacent to the carbon atom to which it is bonded. Z + (This is an onium cation.)

2. The onium salt according to claim 1, wherein R2 is an aryl group having 6 to 20 carbon atoms, which may contain a heteroatom.

3. The onium salt according to claim 1, represented by the following formula (A1). 【Chemistry 2】 (In the formula, L, R 1 , R 2 , R 3 and Z + (The same as above. n3 is an integer between 1 and 4.)

4. The onium salt according to claim 3, represented by the following formula (A2). 【Transformation 3】 (where n3, R 1 , R 2 , R 3 and Z + are the same as described above.)

5. Z + The onium salt according to claim 1, wherein the onium cation is represented by the following formula (caten-1) or (caten-2). 【Chemistry 4】 (In the formula, R ct1 ~R ct5 Each of these is independently a hydrocarbyl group having 1 to 30 carbon atoms, which may contain heteroatoms. Also, R ct1 and R ct2 However, they may bond with each other to form a ring with the sulfur atom to which they are bonded.

6. A photoacid generator comprising the onium salt described in claim 1.

7. A chemically amplified positive resist composition comprising the photoacid generator described in claim 6.

8. Furthermore, the chemically amplified positive-type resist composition according to claim 7, further comprising a base polymer containing a polymer that decomposes under the action of an acid, thereby increasing its solubility in an alkaline developer.

9. The chemically amplified positive resist composition according to claim 8, wherein the polymer contains repeating units represented by the following formula (B1). 【Transformation 5】 (In the formula, a1 is 0 or 1. a2 is an integer between 0 and 2. a3 is an integer satisfying 0 ≤ a3 ≤ 5 + 2(a2) - a4. a4 is an integer between 1 and 3.) R A These are a hydrogen atom, a fluorine atom, a methyl group, or a trifluoromethyl group. R 11 This is a halogen atom, a saturated hydrocarbyl carbonyloxy group having 2 to 8 carbon atoms that may be substituted with a halogen atom, a saturated hydrocarbyl group having 1 to 6 carbon atoms that may be substituted with a halogen atom, or a saturated hydrocarbyloxy group having 1 to 6 carbon atoms that may be substituted with a halogen atom. A 1 This is a single bond or a saturated hydrocarbylene group having 1 to 10 carbon atoms, and the saturated hydrocarbylene group is -CH 2 (The - may be replaced by -O-.)

10. The chemically amplified positive resist composition according to claim 8, wherein the polymer contains repeating units represented by the following formula (B2). 【Transformation 6】 (In the formula, b1 is 0 or 1. b2 is an integer between 0 and 2. b3 is an integer satisfying 0 ≤ b3 ≤ 5 + 2(b2) - b4. b4 is an integer between 1 and 3. b5 is 0 or 1.) R A These are a hydrogen atom, a fluorine atom, a methyl group, or a trifluoromethyl group. R 12 This is a halogen atom, a saturated hydrocarbyl carbonyloxy group having 2 to 8 carbon atoms that may be substituted with a halogen atom, a saturated hydrocarbyl group having 1 to 6 carbon atoms that may be substituted with a halogen atom, or a saturated hydrocarbyloxy group having 1 to 6 carbon atoms that may be substituted with a halogen atom. A 2 This is a single bond or a saturated hydrocarbylene group having 1 to 10 carbon atoms, and the saturated hydrocarbylene group is -CH 2 The minus sign may be replaced by -O-. When b4 is 1, X is an acid-unstable group. When b4 is 2 or 3, X is independently either a hydrogen atom or an acid-unstable group, but at least one of them is an acid-unstable group.

11. The chemically amplified positive resist composition according to claim 8, wherein the polymer contains repeating units represented by the following formula (B2-2). 【Transformation 7】 (In the formula, c1 is an integer between 0 and 2. c2 is an integer between 0 and 2. c3 is an integer between 0 and 5. c4 is an integer between 0 and 2.) R A These are a hydrogen atom, a fluorine atom, a methyl group, or a trifluoromethyl group. R 13 and R 14 Each of these is independently a hydrocarbyl group having 1 to 10 carbon atoms, which may contain heteroatoms, and R 13 and R 14 These elements may bond with each other to form a ring with the carbon atoms to which they are bonded. R 15 Each of these is independently a fluorine atom, a fluorinated alkyl group having 1 to 5 carbon atoms, or a fluorinated alkoxy group having 1 to 5 carbon atoms. R 16 Each of these is independently a hydrocarbyl group having 1 to 10 carbon atoms, which may contain heteroatoms. A 3 This refers to a single bond, a phenylene group, a naphthylene group, or *-C(=O)-O-A 31 - is true. A 31 This is an aliphatic hydrocarbylene group having 1 to 20 carbon atoms, which may contain a hydroxyl group, an ether bond, an ester bond, or a lactone ring, or a phenylene group or naphthylene group. * indicates a bond with a carbon atom of the main chain.

12. The chemically amplified positive resist composition according to claim 8, wherein the polymer comprises at least one selected from repeating units represented by the following formula (B3), repeating units represented by the following formula (B4), and repeating units represented by the following formula (B5). 【Transformation 8】 (In the formula, d is an integer from 0 to 6. e is an integer from 0 to 4. f1 is 0 or 1. f2 is an integer from 0 to 2. f3 is an integer from 0 to 5.) R A These are a hydrogen atom, a fluorine atom, a methyl group, or a trifluoromethyl group. R 17 and R 18 These are, independently, a hydroxyl group, a halogen atom, a saturated hydrocarbyl group having 1 to 6 carbon atoms that may be substituted with a halogen atom, a saturated hydrocarbyloxy group having 1 to 6 carbon atoms that may be substituted with a halogen atom, or a saturated hydrocarbylcarbonyloxy group having 2 to 8 carbon atoms that may be substituted with a halogen atom. R 19 This is a saturated hydrocarbyl group having 1 to 20 carbon atoms, a saturated hydrocarbyloxy group having 1 to 20 carbon atoms, a saturated hydrocarbylcarbonyloxy group having 2 to 20 carbon atoms, a saturated hydrocarbyloxyhydrocarbyl group having 2 to 20 carbon atoms, a saturated hydrocarbylthiohydrocarbyl group having 2 to 20 carbon atoms, a halogen atom, a nitro group, or a cyano group, and may also be a hydroxyl group when f2 is 1 or 2. A 4 This is a single bond or a saturated hydrocarbylene group having 1 to 10 carbon atoms, and the saturated hydrocarbylene group is -CH 2 (The - may be replaced by -O-.)

13. The chemically amplified positive resist composition according to claim 8, wherein the polymer comprises at least one selected from repeating units represented by the following formula (B6), repeating units represented by the following formula (B7), repeating units represented by the following formula (B8), repeating units represented by the following formula (B9), repeating units represented by the following formula (B10), repeating units represented by the following formula (B11), repeating units represented by the following formula (B12), and repeating units represented by the following formula (B13). 【Chemistry 9】 (In the formula, R A These are, independently, a hydrogen atom, a fluorine atom, a methyl group, or a trifluoromethyl group. Y 1 This includes single bonds, aliphatic hydrocarbylene groups having 1 to 6 carbon atoms, phenylene groups, naphthylene groups, or groups having 7 to 18 carbon atoms obtained by combining these, or *-O-Y 11 -, *-C(=O)-O-Y 11 - or * - C (= O) - NH - Y 11 - and Y 11 This refers to an aliphatic hydrocarbylene group having 1 to 6 carbon atoms, a phenylene group, a naphthylene group, or a group having 7 to 18 carbon atoms obtained by combining these, and may contain a carbonyl group, an ester bond, an ether bond, or a hydroxyl group. Y 2 is a single bond or **-Y 21 -C(=O)-O- and Y 21 This is a hydrocarbylene group having 1 to 20 carbon atoms, which may contain heteroatoms. Y 3 This includes single bonds, methylene groups, ethylene groups, phenylene groups, fluorinated phenylene groups, trifluoromethyl groups, and phenylene groups substituted with *-O-Y. 31 -, *-C(=O)-O-Y 31 - or * - C (= O) - NH - Y 31 - is Y 31 This refers to a C1-C6 aliphatic hydrocarbylene group, phenylene group, fluorinated phenylene group, phenylene group substituted with a trifluoromethyl group, or a C7-C20 group obtained by combining these, which may contain a carbonyl group, ester bond, ether bond, or hydroxyl group. * represents a bond with a carbon atom in the main chain, and ** represents a bond with an oxygen atom in the formula. Y 4 This is a hydrocarbylene group having 1 to 30 carbon atoms, which may contain single bonds or heteroatoms. g1 and g2 are independently either 0 or 1, but Y 4 When it is a single bond, g1 and g2 are 0. R 21 ~R 38 Each of these is independently a C1-C20 hydrocarbyl group which may contain a halogen atom or a heteroatom. 21 and R 22 However, they may bond to each other and form a ring with the sulfur atom to which they are bonded, R 23 and R 24 , R 26 and R 27 , or R 29 and R 30 However, they may bond with each other to form a ring with the sulfur atom to which they are bonded. R HF This is either a hydrogen atom or a trifluoromethyl group. Xa - (It is a non-nucleophilic counterion.)

14. Furthermore, the chemically amplified positive resist composition according to claim 8, further comprising an organic solvent.

15. The chemically amplified positive resist composition according to claim 8, further comprising a fluorine atom-containing polymer that further includes at least one selected from repeating units represented by the following formula (D1), repeating units represented by the following formula (D2), repeating units represented by the following formula (D3), and repeating units represented by the following formula (D4), and which may further include at least one selected from repeating units represented by the following formula (D5) and repeating units represented by the following formula (D6). 【Chemistry 10】 (In the formula, x is an integer between 1 and 3. y is an integer satisfying 0 ≤ y ≤ 5 + 2z - x. z is 0 or 1. h is an integer between 1 and 3.) R B These are, independently, a hydrogen atom, a fluorine atom, a methyl group, or a trifluoromethyl group. R C Each of these is independently either a hydrogen atom or a methyl group. R 101 , R 102 , R 104 and R 105 Each of these is independently either a hydrogen atom or a saturated hydrocarbyl group having 1 to 10 carbon atoms. R 103 , R 106 , R 107 and R 108 Each of these is independently a hydrogen atom, a C1-C15 hydrocarbyl group, a C1-C15 fluorinated hydrocarbyl group, or an acid-unstable group, R 103 , R 106 , R 107 and R 108 When the group is a hydrocarbyl group or a fluorinated hydrocarbyl group, an ether bond or a carbonyl group may be interposed between the carbon-carbon bonds. R 109 This is a linear or branched hydrocarbyl group having 1 to 5 carbon atoms, which may have a hydrogen atom or a group containing a heteroatom between the carbon-carbon bonds. R 110 This is a linear or branched hydrocarbyl group having 1 to 5 carbon atoms, which may have a heteroatom interposed between the carbon-carbon bonds. R 111 This is a saturated hydrocarbyl group having 1 to 20 carbon atoms in which at least one hydrogen atom is substituted with a fluorine atom, and the saturated hydrocarbyl group is -CH 2 A portion of the - may be substituted with an ester bond or an ether bond. Z 1 This is a (h+1) valent hydrocarbon group having 1 to 20 carbon atoms or a (h+1) valent fluorinated hydrocarbon group having 1 to 20 carbon atoms. Z 2 The bond is a single bond, *-C(=O)-O-, or *-C(=O)-NH-. The asterisk (*) is a bond to a carbon atom in the main chain. Z 3 is a single bond, -O-, *-C(=O)-O-Z 31 -Z 32 - or *-C(=O)-NH-Z 31 -Z 32 -. Z 31 is a single bond or a saturated hydrocarbylene group having 1 to 10 carbon atoms. Z 32 is a single bond, an ester bond, an ether bond or a sulfonamide bond. * is a bond to a carbon atom in the main chain.)

16. Furthermore, the chemically amplified positive resist composition according to claim 8, further comprising a quencher.

17. Furthermore, the chemically amplified positive resist composition according to claim 8, comprising a photoacid generator other than the photoacid generator described in claim 6.

18. A method for forming a resist pattern, comprising the steps of: forming a resist film on a substrate using a chemically amplified positive-type resist composition according to any one of claims 8 to 17; exposing the resist film using a high-energy beam; and developing the exposed resist film using an alkaline developer to obtain a resist pattern.

19. The resist pattern formation method according to claim 18, wherein the high-energy ray is an extreme ultraviolet ray or an electron ray.

20. The resist pattern forming method according to claim 18, wherein the outermost surface of the substrate is made of a chromium-containing material.

21. The resist pattern formation method according to claim 18, wherein the substrate is a photomask blank.

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