Onium salt, chemically amplified positive resist composition, and resist pattern forming process

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 resist composition, and a method of forming a resist pattern. [Background technology]

[0002] In recent years, the high integration of integrated circuits has led to a demand for finer pattern formation, and chemically amplified resist compositions using acid as a catalyst are used exclusively for processing patterns of 0.2 μm or less. In this case, high-energy rays such as ultraviolet rays, far ultraviolet rays, and electron beams (EB) are used as exposure sources, and EB lithography, which is particularly used as an ultrafine processing technology, is also indispensable as a processing method for photomask blanks when producing photomasks for semiconductor manufacturing. Resist compositions used in such photolithography include positive types that form patterns by dissolving exposed areas, and negative types that form patterns by leaving exposed areas, and the one that is easier to use is selected depending on the form of the resist pattern required.

[0003] Generally, EB writing does not use a mask. In the case of a positive type, the areas other than the area where the resist film is to be left are sequentially irradiated with fine-area EB. In the case of a negative type, the areas where the resist film is to be left are sequentially irradiated. This is a process of sweeping over the entire finely divided area of ​​the processing surface, so it takes time compared to one-time exposure using a photomask, and in order to avoid a drop in throughput, the resist film needs to be highly sensitive. In addition, since the writing time is long, differences are likely to occur between the areas written in the early stages and the areas written in the later stages, so the stability of the exposed areas over time in 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 that easily affect the pattern shape of the chemically amplified resist film, such as chromium oxide and other chromium compound films formed on the photomask substrate. In order to maintain high resolution and the shape after etching, it is also important to maintain the rectangular pattern profile of the resist film regardless of the type of substrate.

[0004] The above-mentioned sensitivity and pattern profile of the resist film have been improved in various ways by selecting and combining materials used in the resist composition, process conditions, etc. One of these improvements is the problem of acid diffusion, which has a significant effect on the resolution of chemically amplified resist films. In photomask processing, it is required that the shape of the obtained resist pattern does not change depending on the time until post-exposure bake (PEB), and the main cause of time-dependent changes is the diffusion of acid generated by exposure. This problem of acid diffusion has been extensively studied not only in photomask processing but also in general resist compositions, as it has a significant effect on sensitivity and resolution.

[0005] Patent Documents 1 and 2 describe examples in which acid diffusion is suppressed and roughness is reduced by increasing the bulk of the acid generated from an acid generator. However, such acid generators are still insufficient in suppressing acid diffusion, and therefore, there has been a demand for the development of an acid generator with smaller diffusion.

[0006] Patent Document 3 also describes an example of controlling acid diffusion by binding sulfonic acid generated by exposure to a resin used in a resist composition. This method of suppressing acid diffusion by binding a repeating unit that generates acid by exposure to a base polymer is effective for obtaining a pattern with small line edge roughness (LER). However, depending on the structure and introduction rate of such a repeating unit, there have been cases where a problem has arisen in the solubility of the base polymer bound to the repeating unit that generates acid by exposure in an organic solvent.

[0007] Meanwhile, polymers having a large amount of aromatic skeletons with acidic side chains, such as polyhydroxystyrene, have been usefully used as resist compositions for KrF lithography, but have not been used as materials for resist compositions for ArF lithography because they exhibit high absorption for light with a wavelength of about 200 nm. However, they are important materials for resist compositions for EB lithography, which is a powerful technique for forming patterns smaller than the processing limit of ArF lithography, and for resist compositions for extreme ultraviolet (EUV) lithography, because they provide high etching resistance.

[0008] As the base polymer of a positive resist composition for EB lithography or EUV lithography, a material is mainly used that uses an acid generated from a photoacid generator by irradiation with high energy rays as a catalyst to deprotect an acid labile group (acid decomposable protecting group) that masks an acidic functional group of a phenol side chain of the base polymer, thereby making the base polymer soluble in an alkaline developer. In addition, tertiary alkyl groups, tert-butoxycarbonyl groups, acetal groups, etc. have been mainly used as the acid labile group. Here, the use of a protecting group such as an acetal group that requires a relatively small activation energy for deprotection has the advantage of providing a highly sensitive resist film, but if the diffusion of the generated acid is not sufficiently suppressed, a deprotection reaction will occur even in the unexposed parts of the resist film, leading to problems such as deterioration of LER and reduction in the in-plane uniformity (CDU) of the pattern line width.

[0009] Furthermore, when a sulfonium salt that generates an acid with a low pKa and strong acid strength, such as the fluorinated alkanesulfonic acid described in Patent Document 4, is used with a resin having a repeating unit with an acetal group, there is a problem that a pattern with a large LER is formed. That is, since the acid strength of the fluorinated alkanesulfonic acid is too high for deprotection of an acetal group, which requires a relatively low activation energy for deprotection, the deprotection reaction proceeds due to a small amount of acid diffused into the unexposed area even if the diffusion of the acid is suppressed.

[0010] Furthermore, Patent Documents 5 and 6 propose photoacid generators that generate non-fluorinated aromatic sulfonic acids having multiple bulky alkyl substituents. Although the molecular weight of the generated acid is increased by multiple alkyl substituents, the acid diffusion is reduced, in the case of the purpose of forming fine patterns, the inhibition of acid diffusion is still insufficient, and there is still room for further improvement. [Prior art documents] [Patent documents]

[0011] [Patent Document 1] JP 2009-053518 A [Patent Document 2] JP 2010-100604 A [Patent Document 3] JP 2011-22564 A [Patent Document 4] Patent No. 5083528 [Patent Document 5] Patent No. 6248882 [Patent Document 6] JP 2019-202974 A Summary of the Invention [Problem to be solved by the invention]

[0012] In recent years, there has been a demand for resist compositions that are excellent not only in line and space (LS), isoline (IL), and isospace (IS) patterns, but also in hole pattern shapes. The acid generator described in Patent Document 5 generates a bulky acid and inhibits diffusion of the acid, and a pattern with good resolution and roughness was obtained, but there was a problem in that corner rounding occurred in the hole pattern.

[0013] The present invention has been made in consideration of the above-mentioned circumstances, and an object of the present invention is to provide an onium salt that has appropriate acid strength and is capable of generating an acid that diffuses little, a chemically amplified positive resist composition containing the same, and a method of forming a resist pattern using the resist composition. [Means for solving the problem]

[0014]

[0011] As a result of intensive investigations in order to achieve the above-mentioned object, the present inventors have found that when an alkanesulfone-type onium salt having a bulky substituent at the α-position of the sulfo group of the anion and having a bulky aromatic ring structure is introduced as an acid generator into a resist composition, the generated acid has appropriate acidity, and the anion structure is bulky, and rotation of the linking group is suppressed, thereby suppressing excessive diffusion of the acid, resulting in a pattern with good resolution and small LER, and furthermore, due to appropriate dissolution inhibition, a pattern with good rectangularity can be obtained, which has led to the completion of the present invention.

[0015] That is, the present invention provides the following onium salt, chemically amplified positive resist composition, and method of forming a resist pattern. 1. An onium salt represented by the following formula (A): [ka] (In the formula, n1 is an integer of 0 to 2. When n1=0, n2 is an integer of 2 to 5, when n1=1, n2 is an integer of 2 to 7, and when n1=2, n2 is an integer of 2 to 9. L is a single bond, an ether bond, an ester bond, a sulfonate ester bond, a carbonate bond or a carbamate bond. R 1 and R 2 are each independently a hydrogen atom or a branched or cyclic hydrocarbyl group having 3 to 20 carbon atoms which may contain a heteroatom, but cannot both be hydrogen atoms. 1 and R 2 may be bonded to each other to form a ring together with the carbon atoms to which they are attached. R 3 are each independently an iodine atom or a branched or cyclic hydrocarbyl group having 3 to 20 carbon atoms which may contain a heteroatom, and at least one R 3 is bonded to the carbon atom adjacent to the carbon atom to which L is bonded. Z +is an onium cation. 2. An onium salt of 1 represented by the following formula (A1): [ka] (In the formula, L, R 1 , R 2 , R 3 and Z + is the same as above. n3 is an integer of 1 to 4. 3. An onium salt of 2 represented by the following formula (A2): [ka] (In the formula, n3, R 1 , R 2 , R 3 and Z + is the same as above.) 4.Z + is an onium cation represented by the following formula (cation-1) or (cation-2): [ka] (In the formula, R ct1 ~R ct5 are each independently a hydrocarbyl group having 1 to 30 carbon atoms which may contain a heteroatom. ct1 and R ct2 may be bonded to each other to form a ring together with the sulfur atom to which they are attached. 5. A photoacid generator comprising an onium salt according to any one of 1 to 4. 6.5 A chemically amplified positive resist composition containing a photoacid generator. 7. A chemically amplified positive resist composition according to claim 6, further comprising a base polymer which contains a polymer which decomposes under the action of an acid and has increased solubility in an alkaline developer. 8. The chemically amplified positive resist composition according to 7, wherein the polymer contains a repeating unit represented by the following formula (B1): [ka] (In the formula, a1 is 0 or 1. a2 is an integer of 0 to 2. a3 is an integer that satisfies 0≦a3≦5+2(a2)−a4. a4 is an integer of 1 to 3. R A is a hydrogen atom, a fluorine atom, a methyl group or a trifluoromethyl group. R 11 represents a halogen atom, a saturated hydrocarbylcarbonyloxy group having 2 to 8 carbon atoms which may be substituted with a halogen atom, a saturated hydrocarbyl group having 1 to 6 carbon atoms which may be substituted with a halogen atom, or a saturated hydrocarbyloxy group having 1 to 6 carbon atoms which may be substituted with a halogen atom. A 1 is a single bond or a saturated hydrocarbylene group having 1 to 10 carbon atoms, and -CH2- of the saturated hydrocarbylene group may be substituted with -O-. 9. The chemically amplified positive resist composition according to 7 or 8, wherein the polymer contains a repeating unit represented by the following formula (B2): [ka] (In the formula, b1 is 0 or 1. b2 is an integer of 0 to 2. b3 is an integer satisfying 0≦b3≦5+2(b2)−b4. b4 is an integer of 1 to 3. b5 is 0 or 1. R A is a hydrogen atom, a fluorine atom, a methyl group or a trifluoromethyl group. R 12 represents a halogen atom, a saturated hydrocarbylcarbonyloxy group having 2 to 8 carbon atoms which may be substituted with a halogen atom, a saturated hydrocarbyl group having 1 to 6 carbon atoms which may be substituted with a halogen atom, or a saturated hydrocarbyloxy group having 1 to 6 carbon atoms which may be substituted with a halogen atom. A 2 is a single bond or a saturated hydrocarbylene group having 1 to 10 carbon atoms, and -CH2- of the saturated hydrocarbylene group may be substituted with -O-. When b4 is 1, X is an acid labile group. When b4 is 2 or 3, X is each independently a hydrogen atom or an acid labile group, provided that at least one X is an acid labile group. 10. The chemically amplified positive resist composition according to any one of 7 to 9, wherein the polymer contains a repeating unit represented by the following formula (B2-2): [ka] (In the formula, c1 is an integer of 0 to 2. c2 is an integer of 0 to 2. c3 is an integer of 0 to 5. c4 is an integer of 0 to 2. R A is a hydrogen atom, a fluorine atom, a methyl group or a trifluoromethyl group. R 13 and R 14 are each independently a hydrocarbyl group having 1 to 10 carbon atoms which may contain a heteroatom, R 13 and R 14 may be bonded to each other to form a ring together with the carbon atoms to which they are attached. R 15 each independently represents 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 are each independently a hydrocarbyl group having 1 to 10 carbon atoms which may contain a heteroatom. A 3 is a single bond, a phenylene group, a naphthylene group, or *-C(=O)-OA 31 -It is. 31 is an aliphatic hydrocarbylene group having 1 to 20 carbon atoms which may contain a hydroxy group, an ether bond, an ester bond or a lactone ring, or a phenylene group or naphthylene group. * is a bond to a carbon atom of the main chain.) 11. The chemically amplified positive resist composition of any one of 7 to 10, wherein the polymer contains at least one repeating unit selected from the group consisting of a repeating unit represented by the following formula (B3), a repeating unit represented by the following formula (B4), and a repeating unit represented by the following formula (B5): [ka] (In the formula, d is an integer of 0 to 6. e is an integer of 0 to 4. f1 is 0 or 1. f2 is an integer of 0 to 2. f3 is an integer of 0 to 5.) R A is a hydrogen atom, a fluorine atom, a methyl group or a trifluoromethyl group. R 17 and R 18 each independently represents a hydroxy group, a halogen atom, a saturated hydrocarbyl group having 1 to 6 carbon atoms which may be substituted with a halogen atom, a saturated hydrocarbyloxy group having 1 to 6 carbon atoms which may be substituted with a halogen atom, or a saturated hydrocarbylcarbonyloxy group having 2 to 8 carbon atoms which may be substituted with a halogen atom. R 19 represents 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 be a hydroxy group. A 4 is a single bond or a saturated hydrocarbylene group having 1 to 10 carbon atoms, and -CH2- of the saturated hydrocarbylene group may be substituted with -O-. 12. The chemically amplified positive resist composition according to any one of 7 to 11, wherein the polymer comprises at least one selected from a repeating unit represented by the following formula (B6), a repeating unit represented by the following formula (B7), a repeating unit represented by the following formula (B8), a repeating unit represented by the following formula (B9), a repeating unit represented by the following formula (B10), a repeating unit represented by the following formula (B11), a repeating unit represented by the following formula (B12), and a repeating unit represented by the following formula (B13). [ka] (In the formula, R A each independently represents a hydrogen atom, a fluorine atom, a methyl group, or a trifluoromethyl group. Y 1represents 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 represents an aliphatic hydrocarbylene group having 1 to 6 carbon atoms, a phenylene group, a naphthylene group, or a group obtained by combining these and having 7 to 18 carbon atoms, and may contain a carbonyl group, an ester bond, an ether bond, or a hydroxy group. Y 2 is a single bond or **-Y 21 -C(=O)-O-, and Y 21 is a hydrocarbylene group having 1 to 20 carbon atoms which may contain a heteroatom. Y 3 is a single bond, a methylene group, an ethylene group, a phenylene group, a fluorinated phenylene group, a phenylene group substituted with a trifluoromethyl group, *-OY 31 -, *-C(=O)-OY 31 - or -C(=O)-NH-Y 31 -It is. Y 31 represents an aliphatic hydrocarbylene group having 1 to 6 carbon atoms, a phenylene group, a fluorinated phenylene group, a phenylene group substituted with a trifluoromethyl group, or a group having 7 to 20 carbon atoms obtained by combining these, and may contain a carbonyl group, an ester bond, an ether bond, or a hydroxy group. * represents a bond to a carbon atom in the main chain, and ** represents a bond to an oxygen atom in the formula. Y 4 represents a single bond or a hydrocarbylene group having 1 to 30 carbon atoms which may contain a heteroatom. g1 and g2 are each independently 0 or 1, but Y 4 When is a single bond, g1 and g2 are 0. R 21 ~R 38 are each independently a halogen atom or a hydrocarbyl group having 1 to 20 carbon atoms which may contain a heteroatom. 21 and R22 may be bonded to each other to form a ring together with the sulfur atom to which they are attached, R 23 and R 24 , R 26 and R 27 , or R 29 and R 30 may be bonded to each other to form a ring together with the sulfur atom to which they are attached. R HF is a hydrogen atom or a trifluoromethyl group. Xa - is a non-nucleophilic counterion. 13. Any one of the chemically amplified positive resist compositions of 7 to 12, further comprising an organic solvent. 14. The chemically amplified positive resist composition according to any one of 7 to 13, further comprising a fluorine atom-containing polymer which contains at least one selected from the group consisting of a repeating unit represented by the following formula (D1), a repeating unit represented by the following formula (D2), a repeating unit represented by the following formula (D3), and a repeating unit represented by the following formula (D4), and which may further contain at least one selected from the group consisting of a repeating unit represented by the following formula (D5) and a repeating unit represented by the following formula (D6). [ka] (In the formula, x is an integer of 1 to 3. y is an integer that satisfies 0≦y≦5+2z−x. z is 0 or 1. h is an integer of 1 to 3. R B each independently represents a hydrogen atom, a fluorine atom, a methyl group, or a trifluoromethyl group. R C are each independently a hydrogen atom or a methyl group. R 101 , R 102 , R 104 and R 105 are each independently a hydrogen atom or a saturated hydrocarbyl group having 1 to 10 carbon atoms. R 103 , R 106 , R 107 and R 108each independently represents a hydrogen atom, a hydrocarbyl group having 1 to 15 carbon atoms, a fluorinated hydrocarbyl group having 1 to 15 carbon atoms, or an acid labile group; 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 present between the carbon-carbon bonds. R 109 represents a hydrogen atom or a linear or branched hydrocarbyl group having 1 to 5 carbon atoms which may have a group containing a heteroatom interposed between the carbon-carbon bonds. R 110 is a linear or branched hydrocarbyl group having 1 to 5 carbon atoms which may have a group containing a heteroatom interposed between the carbon-carbon bonds. R 111 represents 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- in the saturated hydrocarbyl group may be substituted with an ester bond or an ether bond. Z 1 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 is a single bond, *-C(=O)-O-, or *-C(=O)-NH-. * is a bond to a carbon atom in the main chain. Z 3 is a single bond, -O-, *-C(=O)-OZ 31 -Z 32 - or -C(=O)-NH-Z 31 -Z 32 -It is. 31 is a single bond or a saturated hydrocarbylene group having 1 to 10 carbon atoms. 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.) 15. Any one of the chemically amplified positive resist compositions 7 to 14, further comprising a quencher. 16. A chemically amplified positive resist composition according to any one of 7 to 15, further comprising a photoacid generator other than the photoacid generator according to 5. 17. A method for forming a resist pattern, comprising the steps of forming a resist film on a substrate using the chemically amplified positive resist composition according to any one of claims 7 to 16, exposing the resist film to high-energy rays, and developing the exposed resist film using an alkaline developer to obtain a resist pattern. 18. The method for forming a resist pattern according to claim 17, wherein the high energy beam is EUV or an electron beam. 19. The method for forming a resist pattern according to claim 17 or 18, wherein the outermost surface of the substrate is made of a material containing chromium. 20. The method for forming a resist pattern according to any one of 17 to 19, wherein the substrate is a photomask blank. Effect of the Invention

[0016] The chemically amplified positive resist composition containing the onium salt of the present invention as a photoacid generator has extremely high resolution and can provide a pattern with small LER in microfabrication techniques, particularly EB lithography and EUV lithography. In addition, since it has a suitable dissolution inhibition property and can provide a pattern with good rectangularity, it is suitable as a chemically amplified positive resist material. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0017] The present invention will be described in detail below. In the following description, some structures represented by chemical formulas may have asymmetric carbons and may have enantiomers or diastereomers, but in such cases, one formula will be used to represent these isomers. These isomers may be used alone or as a mixture of two or more.

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

[0019] In formula (A), n1 is an integer of 0 to 2. When n1=0, it represents a benzene ring, when n1=1, it represents a naphthalene ring, and when n1=3, it represents an anthracene ring, but from the viewpoint of solvent solubility, it is preferable that n1=0 is a benzene ring. When n1=0, n2 is an integer of 2 to 5, when n1=1, it is an integer of 2 to 7, and when n1=2, it is an integer of 2 to 9.

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

[0021] In formula (A), R 1 and R 2 R are each independently a hydrogen atom or a branched or cyclic hydrocarbyl group having 3 to 20 carbon atoms which may contain a heteroatom, but cannot both be hydrogen atoms. 1 and R 2 When both are hydrogen atoms or linear hydrocarbyl groups, -SO3 - When the bulkiness in the vicinity of the group is reduced, the apparent acid diffusion is not suppressed, and the lithography performance is deteriorated.

[0022] R 1 and R 2 The hydrocarbyl group represented by the formula (I) may be saturated or unsaturated, and specific examples thereof include branched alkyl groups having 3 to 20 carbon atoms, such as an isopropyl group, a sec-butyl group, a tert-butyl group, a tert-pentyl group, and a 2-ethylhexyl group; a cyclopentyl group, a cyclohexyl group, a cyclopentylmethyl group, a cyclopentylethyl group, a cyclopentylbutyl group, a cyclohexylmethyl group, a cyclohexylethyl group, a cyclohexylbutyl group, a norbornyl group, an oxanorbornyl group, a tricyclo[5.2.1.0 2,6] cycloaliphatic hydrocarbyl groups having 3 to 20 carbon atoms, such as decyl group and adamantyl group; aryl groups having 6 to 20 carbon atoms, such as phenyl group, naphthyl group and anthracenyl group; and groups obtained by combining these groups, but are not limited thereto. In addition, some or all of the hydrogen atoms of the hydrocarbyl groups may be substituted with groups containing heteroatoms, such as oxygen atoms, sulfur atoms, nitrogen atoms and halogen atoms, and some of -CH2- of the hydrocarbyl groups may be substituted with groups containing heteroatoms, such as oxygen atoms, sulfur atoms and nitrogen atoms, and as a result, the hydrocarbyl groups may contain hydroxyl groups, cyano groups, fluorine atoms, chlorine atoms, bromine atoms, iodine atoms, carbonyl groups, ether bonds, ester bonds, sulfonate ester bonds, carbonate bonds, lactone rings, sultone rings, carboxylic anhydrides (-C(=O)-OC(=O)-), haloalkyl groups and the like. The halogen atom includes a fluorine atom, a chlorine atom, a bromine atom, and an iodine atom, and among these, a fluorine atom and an iodine atom are preferable.

[0023] Also, R 1 and R 2 may be bonded to each other to form a ring together with the carbon atom to which they are bonded. Examples of the ring formed in this case include a cyclopropane ring, a cyclobutane ring, a cyclopentane ring, a cyclohexane ring, a norbornane ring, and an adamantane ring. In addition, some or all of the hydrogen atoms in the ring may be substituted with a group containing a heteroatom such as an oxygen atom, a sulfur atom, a nitrogen atom, or a halogen atom, and some of the -CH2- in the ring may be substituted with a group containing a heteroatom such as an oxygen atom, a sulfur atom, or a nitrogen atom, and as a result, the ring may contain a hydroxy group, a cyano group, a fluorine atom, a chlorine atom, a bromine atom, an iodine atom, a carbonyl group, an ether bond, an ester bond, a sulfonate ester bond, a carbonate bond, a lactone ring, a sultone ring, a carboxylic anhydride (-C(=O)-OC(=O)-), a haloalkyl group, or the like.

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

[0025] R in formula (A) 3 Examples of the structure in which an aromatic ring is bonded to an aromatic ring include, but are not limited to, those shown below. In the following formula, the dashed line represents a bond to L. [ka]

[0026] [ka]

[0027] [ka]

[0028] [ka]

[0029] [ka]

[0030] [ka]

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

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

[0033] Particularly preferred examples of the anion of the onium salt represented by formula (A) include those shown below, but are not limited to these. [ka]

[0034] [ka]

[0035] [ka]

[0036] [ka]

[0037] [ka]

[0038] [ka]

[0039]

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[0040]

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[0093] [ka]

[0094] In formula (A), Z + 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 are each independently a halogen atom or a hydrocarbyl group having 1 to 30 carbon atoms which may contain a heteroatom.

[0096] Examples of the halogen atom include a fluorine atom, a chlorine atom, a bromine atom, and an iodine atom.

[0097] The hydrocarbyl groups may be saturated or unsaturated and may be linear, branched or cyclic. Specific examples thereof include alkyl groups having 1 to 30 carbon atoms, such as methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, and tert-butyl groups; cyclic saturated hydrocarbyl groups having 3 to 30 carbon atoms, such as cyclopropyl, cyclopentyl, cyclohexyl, cyclopropylmethyl, 4-methylcyclohexyl, cyclohexylmethyl, norbornyl, and adamantyl groups; alkenyl groups having 2 to 30 carbon atoms, such as vinyl, allyl, propenyl, butenyl, and hexenyl groups; cyclic unsaturated hydrocarbyl groups having 3 to 30 carbon atoms, such as cyclohexenyl groups; aryl groups having 6 to 30 carbon atoms, such as phenyl, naphthyl, and thienyl groups; aralkyl groups having 7 to 30 carbon atoms, such as benzyl, 1-phenylethyl, and 2-phenylethyl groups; and groups obtained by combining these, with aryl groups being preferred. In addition, some or all of the hydrogen atoms of the hydrocarbyl group may be substituted with a group containing a heteroatom such as an oxygen atom, a sulfur atom, a nitrogen atom or a halogen atom, and some of the -CH2- of the hydrocarbyl group may be substituted with a group containing a heteroatom such as an oxygen atom, a sulfur atom or a nitrogen atom, and as a result, the hydrocarbyl group may contain a hydroxy group, a cyano group, a fluorine atom, a chlorine atom, a bromine atom, an iodine atom, a carbonyl group, an ether bond, an ester bond, a sulfonate ester bond, a carbonate bond, a lactone ring, a sultone ring, a carboxylic anhydride (-C(=O)-OC(=O)-), a haloalkyl group, or the like.

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

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

[0100] [ka]

[0101] [ka]

[0102] [ka]

[0103] [ka]

[0104] [ka]

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[0123] [ka]

[0124] [ka]

[0125] The iodonium cation represented by formula (cation-2) is shown below. These include, but are not limited to: [ka]

[0126] [ka]

[0127] Specific examples of the onium salt of the present invention include any combination of the above-mentioned anions and cations.

[0128] The onium salt of the present invention can be synthesized by a known method. As an example, the case where L in formula (A) is a sulfonate ester bond is shown below, but is not limited thereto. [ka] (In the formula, n1, n2, R 1 , R 2 , R 3 and Z + is the same as above. + is a lithium ion, a sodium ion, or a potassium ion. - is a halide ion or a methyl sulfate ion.

[0129] The first step is a step of obtaining a sulfonate (S-3) by reacting a sulfonate chloride (S-1) with a hydroxysulfonate (S-2). The reaction can be carried out according to a conventional method, and is preferably carried out by adding the sulfonate chloride (S-1), the hydroxysulfonate (S-2) and a base in a solvent in sequence or simultaneously, and cooling or heating as necessary.

[0130] Examples of the solvent that can be used in the reaction of the first step include ethers such as water, tetrahydrofuran (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, dimethyl sulfoxide (DMSO), and N,N-dimethylformamide (DMF), and chlorine-based organic solvents such as methylene chloride, chloroform, and carbon tetrachloride. These solvents may be appropriately selected depending on the reaction conditions, and may be used alone or in combination of two or more.

[0131] Examples of the base that can be used in the reaction of the first step include amines such as ammonia, triethylamine, pyridine, lutidine, collidine, and N,N-dimethylaniline, hydroxides such as sodium hydroxide, potassium hydroxide, and tetramethylammonium hydroxide, carbonates such as potassium carbonate, sodium hydrogen carbonate, etc. These bases may be used alone or in combination of two or more.

[0132] The second step is a step of obtaining an onium salt (A') by 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 of the first step through a normal aqueous work-up, or may be used without any particular work-up after the reaction is stopped.

[0133] When using the isolated sulfonate (S-3), the sulfonate (S-3) is dissolved in water, THF, diethyl ether, diisopropyl ether, di-n-butyl ether, 1,4-dioxane and other ethers, n-hexane, n-heptane, benzene, toluene, xylene and other hydrocarbons, acetonitrile, DMSO, DMF and other aprotic polar solvents, methylene chloride, chloroform, carbon tetrachloride and other chlorine-based organic solvents, etc., mixed with the onium salt (S-4), and cooled or heated as necessary to obtain a reaction mixture, after which the onium salt (A) can be obtained from the reaction mixture by a conventional aqueous post-treatment. If necessary, the reaction mixture may be purified according to conventional methods such as distillation, recrystallization, and chromatography.

[0134] When the reaction for synthesizing the sulfonate (S-3) is stopped and no particular post-treatment is performed, the onium salt (S-4) can be added to the mixture in which the synthesis reaction of the sulfonate (S-3) is stopped, and the mixture can be cooled or heated as necessary to obtain the onium salt (A'). In this case, ethers such as water, 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, and chlorine-based organic solvents such as methylene chloride, chloroform, and carbon tetrachloride can be added as necessary. The onium salt (A') can be obtained from the reaction mixture by a normal aqueous post-treatment. If necessary, the mixture can be purified according to a conventional method such as recrystallization or 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 strength when irradiated with high-energy rays. - The presence of a bulky substituent at the α-position of the α-position shields the vicinity of the generated sulfonic acid, and the presence of a bulky substituent at the α-position and a bulky substituent on another aromatic ring inhibits the rotation of the bond axis of L 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 it is possible to form a pattern with small roughness even in the formation of a fine pattern. In addition, since the onium salt of the present invention has sufficient liposolubility, it is easy to manufacture and handle, and also exhibits a moderate dissolution inhibition ability in the unexposed area.

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

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

[0138] In the chemically amplified positive resist composition of the present invention, the content of the photoacid generator (A) is preferably 0.1 to 40 parts by mass, more preferably 1 to 20 parts by mass, relative to 80 parts by mass of the base polymer (B) described below. If the content of the photoacid generator is within the above range, an amount of acid required for deprotection of the acid labile group is generated, and the storage stability is also good. The photoacid generator (A) may be used alone or in combination of two or more kinds.

[0139] [(B) Base polymer] The resist composition of the present invention contains, as the component (B), a base polymer which contains a polymer that decomposes under the action of an acid and has increased solubility in an alkaline developer.

[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 of 0 to 2, and when a2 is 0, it represents a benzene skeleton, when a2 is 1, it represents a naphthalene skeleton, and when a2 is 2, it represents an anthracene skeleton. a3 is an integer that satisfies 0≦a3≦5+2(a2)-a4. a4 is an integer of 1 to 3. When a2 is 0, a3 is preferably an integer of 0 to 3 and a4 is preferably an integer of 1 to 3, and when a2 is 1 or 2, a3 is preferably an integer of 0 to 4 and a4 is preferably an integer of 1 to 3.

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

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

[0144] In formula (B1), A 1 is a single bond or a saturated hydrocarbylene group having 1 to 10 carbon atoms, and a part of -CH2- of the saturated hydrocarbylene group may be replaced by -O-. The saturated hydrocarbylene group may be linear, branched, or cyclic, and specific examples thereof include alkanediyl groups having 1 to 10 carbon atoms, such as methylene, ethane-1,2-diyl, propane-1,3-diyl, butane-1,4-diyl, pentane-1,5-diyl, hexane-1,6-diyl, and structural isomers thereof; cyclic saturated hydrocarbylene groups having 3 to 10 carbon atoms, such as cyclopropanediyl, cyclobutanediyl, cyclopentanediyl, and cyclohexanediyl; and groups obtained by combining these. When the saturated hydrocarbylene group contains an ether bond, when a1 in formula (B1) is 1, it may be located at any position except between the carbon atom at the α-position and the carbon atom at the β-position relative to the ester oxygen atom. When a1 is 0, the atom bonded to the main chain is an etheric oxygen atom, and the second ether bond may be inserted at any position except between the carbon atom at the α-position and the carbon atom at the β-position with respect to the etheric oxygen atom. If the number of carbon atoms in the saturated hydrocarbylene group is 10 or less, sufficient solubility in an alkaline developer can be obtained, which is preferable.

[0145] a1 is 0 and A 1 is a single bond, i.e., the aromatic ring is directly attached to the polymer backbone (i.e., the linker (-C(=O)-OA 1 In the case where the repeating unit B1 does not have -), 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 a linker 1 In the case where R A is the same as above. [ka]

[0147] The content of the repeating unit B1 is preferably 30 to 90 mol %, more preferably 40 to 85 mol %, of all repeating units constituting the polymer. However, when the repeating unit contains at least one of the repeating units represented by formula (B3) and the repeating unit represented by formula (B4), which give the polymer higher etching resistance as described below, and the unit has a phenolic hydroxyl group as a substituent, it is preferable that the ratio of the unit is also within the above range. The repeating unit B1 may be used alone or in combination of two or more kinds.

[0148] In order to provide the polymer as a positive resist composition with the property that the exposed area dissolves in an alkaline developer, it is preferable that the polymer contains a repeating unit having an acidic functional group protected by an acid labile group, i.e., a repeating unit that is protected by an acid labile group and becomes alkali-soluble by the action of acid (hereinafter, also referred to as repeating unit B2).

[0149] The most preferred repeating unit B2 is 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 of 0 to 2, and when it is 0, it represents a benzene skeleton, when it is 1, it represents a naphthalene skeleton, and when it is 2, it represents an anthracene skeleton. b3 is an integer that satisfies 0≦b3≦5+2(b2)-b4. b4 is an integer of 1 to 3. b5 is 0 or 1. When b2 is 0, b3 is preferably an integer of 0 to 3 and b4 is an integer of 1 to 3, and when b2 is 1 or 2, b3 is preferably an integer of 0 to 4 and b4 is an integer of 1 to 3.

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

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

[0153] In formula (B2-1), A 2is a single bond or a saturated hydrocarbylene group having 1 to 10 carbon atoms, and a part of -CH2- of the saturated hydrocarbylene group may be replaced by -O-. The saturated hydrocarbylene group may be linear, branched, or cyclic, and specific examples thereof include alkanediyl groups having 1 to 10 carbon atoms, such as methylene, ethane-1,2-diyl, propane-1,3-diyl, butane-1,4-diyl, pentane-1,5-diyl, hexane-1,6-diyl, and structural isomers thereof; cyclic saturated hydrocarbylene groups having 3 to 10 carbon atoms, such as cyclopropanediyl, cyclobutanediyl, cyclopentanediyl, and cyclohexanediyl; 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 located at any position except between the carbon atom at the α position and the carbon atom at the β position relative to the ester oxygen atom. When b1 is 0, the atom bonded to the main chain is an ether oxygen atom, and the second ether bond may be inserted at any position except between the carbon atom at the α-position and the carbon atom at the β-position with respect to the ether oxygen atom. If the number of carbon atoms in the saturated hydrocarbylene group is 10 or less, sufficient solubility in an alkaline developer can be obtained, which is preferable.

[0154] In formula (B2-1), when b4 is 1, X is an acid labile group. When b4 is 2 or 3, each X is independently a hydrogen atom or an acid labile group, and at least one of them is an acid labile group. That is, in the repeating unit B2-1, at least one of the phenolic hydroxyl groups bonded to the aromatic ring is protected with an acid labile group, or the carboxyl group bonded to the aromatic ring is protected with an acid labile group. The acid labile group is not particularly limited and any of those that have been used in many known chemically amplified positive resist compositions and that are detached by an acid to give an acidic group can be used.

[0155] The acid labile group may, for example, be a tertiary saturated hydrocarbyl group. The tertiary saturated hydrocarbyl group preferably has 4 to 18 carbon atoms so that the resulting monomer for polymerization is obtained by distillation.

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

[0157] Examples of the alkyl substituent include a methyl group, an ethyl group, a propyl group, an adamantyl group, a norbornyl group, a tetrahydrofuran-2-yl group, a 7-oxanorbornan-2-yl group, a cyclopentyl group, a 2-tetrahydrofuryl group, a 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 ]dodecyl group, 3-oxo-1-cyclohexyl group, and the like.

[0158] Examples of the tertiary saturated hydrocarbyl group include a tert-butyl group, a tert-pentyl group, a 1-ethyl-1-methylpropyl group, a 1,1-diethylpropyl group, a 1,1,2-trimethylpropyl group, a 1-adamantyl-1-methylethyl group, a 1-methyl-1-(2-norbornyl)ethyl group, a 1-methyl-1-(tetrahydrofuran-2-yl)ethyl group, a 1-methyl-1-(7-oxanorbornan-2-yl)ethyl group, a 1-methylcyclopentyl group, a 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-norbornyl group, 2-ethyl-2-norbornyl 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 ]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] The acid labile group may be a group represented by the following formula (B2-1-1). The group represented by formula (B2-1-1) is often used as an acid labile group, and is a useful option as an acid labile group that stably gives a pattern with a relatively rectangular interface between the pattern and the substrate. When X is a group represented by formula (B2-1-1), an acetal structure is formed. [ka] (In the formula, the dashed lines represent bonds.)

[0160] In formula (B2-1-1), R L1 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 is appropriately selected depending on the design of the sensitivity of the decomposable group to acid. For example, if the design is to ensure relatively high stability and to decompose with strong acid, a hydrogen atom is preferred, whereas if the design is to use relatively high reactivity to increase sensitivity to pH changes, a straight-chain alkyl group is preferred. Depending on the combination with the acid generator and quencher to be incorporated in the resist composition, R L2 In the case where a relatively large alkyl group is selected at the end of the alkyl group, and the solubility change due to decomposition is large, R L1 As for R, the carbon atom bonded to the acetal carbon is preferably a secondary carbon atom. L1 Examples of the aryl group include, but are not limited to, an isopropyl group, a sec-butyl group, a cyclopentyl group, a cyclohexyl group, and the like.

[0162] In formula (B2-1-1), R L2 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 thereof include saturated hydrocarbyl groups having 1 to 30 carbon atoms and aryl groups having 6 to 30 carbon atoms. In particular, in order to obtain higher resolution in the formation of fine patterns, R L2 R is preferably a hydrocarbyl group having 1 to 6 carbon atoms. L2 When is a hydrocarbyl group having 1 to 6 carbon atoms, the alcohol generated after the deprotection reaction with an acid proceeds is water-soluble, and therefore dissolves in an alkaline developer when a positive pattern is formed using the developer, thereby making it possible to suppress residual defects in exposed areas.

[0163] Preferred examples of the group represented by formula (B2-1-1) include, but are not limited to, the following: L1 is the same as above, and the dashed lines represent bonds. [ka]

[0164] [ka]

[0165] As another acid labile group, a phenolic hydroxyl group in which a hydrogen atom is replaced with -CH2COO- (a tertiary saturated hydrocarbyl group) can be used. In this case, the tertiary saturated hydrocarbyl group can be the same as the tertiary saturated hydrocarbyl group used for protecting the phenolic hydroxyl group described above.

[0166] Further, the repeating unit B2 may be a repeating unit represented by the following formula (B2-2) (hereinafter, also referred to as repeating unit B2-2). The repeating unit B2-2 is a useful option as an acid labile group-containing unit that provides good performance against line width fluctuation in development loading because it increases the dissolution rate of the exposed area. [ka]

[0167] In formula (B2-2), c1 is an integer of 0 to 2. c2 is an integer of 0 to 2. c3 is an integer of 0 to 5. c4 is an integer of 0 to 2.

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

[0169] In formula (B2-2), R 13 and R 14are each independently a hydrocarbyl group having 1 to 10 carbon atoms which may contain a heteroatom, R 13 and R 14 may be bonded to each other to form a ring together with the carbon atoms to which they are attached.

[0170] In formula (B2-2), R 15 each independently represents 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 are each independently a hydrocarbyl group having 1 to 10 carbon atoms which may contain a heteroatom.

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

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

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

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

[0176] In the formulas (B3) and (B4), d is an integer of 0 to 6. e is an integer of 0 to 4.

[0177] In formulas (B3) and (B4), R 17 and R 18 are each independently a hydroxy group, a halogen atom, a saturated hydrocarbyl group having 1 to 6 carbon atoms which may be substituted with a halogen atom, a saturated hydrocarbyloxy group having 1 to 6 carbon atoms which may be substituted with a halogen atom, or a saturated hydrocarbylcarbonyloxy group having 2 to 8 carbon atoms which 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 may be the same or different. When e is 2 or more, each R 18 may be the same as or different from each other.

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

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

[0180] In formula (B5), R 19 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 be a hydroxy group when f2 is 1 or 2. 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 may be the same as or different from each other.

[0181] In formula (B5), A 4 is a single bond or a saturated hydrocarbylene group having 1 to 10 carbon atoms, and a part of -CH2- in the saturated hydrocarbylene group may be substituted with -O-. The saturated hydrocarbylene group may be linear, branched, or cyclic. Specific examples thereof include A in formula (B1): 1 Examples of the examples are similar to those given in the description of .

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

[0183] The content of the repeating units B3 to B5 is preferably 5 mol % or more of all repeating units constituting the polymer in order to obtain the effect of improving etching resistance. The content of the repeating units B3 to B5 is preferably 25 mol % or less, more preferably 20 mol % or less of all repeating units constituting the polymer. When there is no functional group or when the functional group is other than a hydroxy group, it is preferable that the amount of introduction is 25 mol % or less, since there is no risk of development defects occurring. The repeating units B3 to B5 may be used alone or in combination of two or more.

[0184] The polymer preferably contains at least one selected from the group consisting of repeating units B1, B2, and B3 to B5, in that it is excellent in achieving both high etching resistance and high resolution. In this case, these repeating units are preferably contained in an amount of 60 mol % or more, more preferably 70 mol % or more, even more preferably 80 mol % or more, and even more preferably 90 mol % or more of all repeating units constituting the polymer.

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

[0186] In formulas (B6) to (B13), RA Y each independently represents a hydrogen atom, a fluorine atom, a methyl group, or a trifluoromethyl group. 1 represents 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 Y 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 Y is a hydrocarbylene group having 1 to 20 carbon atoms which may contain a heteroatom. 3 is a single bond, a methylene group, an ethylene group, a phenylene group, a fluorinated phenylene group, a phenylene group substituted with a trifluoromethyl group, *-OY 31 -, *-C(=O)-OY 31 - or -C(=O)-NH-Y 31 -It is. Y 31 represents an aliphatic hydrocarbylene group having 1 to 6 carbon atoms, a phenylene group, a fluorinated phenylene group, a phenylene group substituted with a trifluoromethyl group, or a group having 7 to 20 carbon atoms obtained by combining these, and may contain a carbonyl group, an ester bond, an ether bond, or a hydroxyl group. * represents a bond to a carbon atom in the main chain, and ** represents a bond to an oxygen atom in the formula. Y 4 is a single bond or a hydrocarbylene group having 1 to 30 carbon atoms which may contain a heteroatom. g1 and g2 each independently represent 0 or 1, but Y 4 When is a single bond, g1 and g2 are 0.

[0187] In formulae (B6) and (B10), Xa - is a non-nucleophilic counterion. -Examples of the non-nucleophilic counter ion represented by the formula (I) include those described in JP-A-2010-113209 and JP-A-2007-145797.

[0188] In formulas (B7) and (B11), Y 2 -Y 21 -C(=O)-O-, Y 21 Examples of the hydrocarbylene group which may contain a heteroatom and is represented by the following formula (I) include, but are not limited to, the following groups: [ka] (In the formula, the dashed lines represent bonds.)

[0189] In formulas (B7) and (B11), R HF is a hydrogen atom or a trifluoromethyl group. In the repeating units B7 and B11, R HF Specific examples of when R is a hydrogen atom include those described in JP 2010-116550 A. HF Specific examples of the repeating units B7 and B11 in which is a trifluoromethyl group include those described in JP-A-2010-77404. Examples of the repeating units B7 and B11 in which is a trifluoromethyl group include those described in JP-A-2012-246265 and JP-A-2012-246426.

[0190] Y 4The hydrocarbylene group having 1 to 30 carbon atoms and optionally containing a heteroatom, represented by the following formula, may be saturated or unsaturated, and may be linear, branched, or cyclic. Specific examples thereof include alkanediyl groups having 1 to 30 carbon atoms, such as a methylene group, an ethane-1,2-diyl group, a propane-1,3-diyl group, a butane-1,4-diyl group, a pentane-1,5-diyl group, a hexane-1,6-diyl group, a heptane-1,7-diyl group, an octane-1,8-diyl group, a nonane-1,9-diyl group, a decane-1,10-diyl group, an undecane-1,11-diyl group, a dodecane-1,12-diyl group, a tridecane-1,13-diyl group, a tetradecane-1,14-diyl group, a pentadecane-1,15-diyl group, a hexadecane-1,16-diyl group, and a heptadecane-1,17-diyl group; a cyclopentanediyl group, a cyclohexanediyl group, Examples of the alkylene groups include cyclic saturated hydrocarbylene groups having 3 to 30 carbon atoms, such as a norbornanediyl group and an adamantanediyl group; arylene groups having 6 to 30 carbon atoms, such as a phenylene group, a methylphenylene group, an ethylphenylene group, an n-propylphenylene group, an isopropylphenylene group, an n-butylphenylene group, an isobutylphenylene group, a sec-butylphenylene group, a tert-butylphenylene group, a naphthylene group, a methylnaphthylene group, an ethylnaphthylene group, an n-propylnaphthylene group, an isopropylnaphthylene group, an n-butylnaphthylene group, an isobutylnaphthylene group, a sec-butylnaphthylene group, and a tert-butylnaphthylene group; and groups obtained by combining these groups.

[0191] In addition, some or all of the hydrogen atoms of the hydrocarbylene group may be substituted with a group containing a heteroatom such as an oxygen atom, a sulfur atom, a nitrogen atom or a halogen atom, and some of the -CH2- of the hydrocarbylene group may be substituted with a group containing a heteroatom such as an oxygen atom, a sulfur atom or a nitrogen atom, and as a result, the hydrocarbylene group may contain a hydroxy group, a cyano group, a fluorine atom, a chlorine atom, a bromine atom, an iodine atom, a carbonyl group, an ether bond, an ester bond, a sulfonate ester bond, a carbonate bond, a lactone ring, a sultone ring, a carboxylic anhydride (-C(=O)-OC(=O)-), a haloalkyl group, or the like.

[0192] The 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 rays, far ultraviolet rays, EB, EUV, X-rays, gamma rays, and synchrotron radiation. The acid has an acid strength suitable for deprotection of a polymer containing the repeating unit A2. In addition, when a polymer containing the repeating unit B9 or B13 is used as a base polymer of a resist composition, it is possible to appropriately control the movement and diffusion of the generated acid.

[0193] Photoacid generators that generate arenesulfonic acid by irradiation with high energy rays are also commonly used to deprotect polymers containing units protected by acetal groups, tertiary alkyl groups, or tert-butoxycarbonyl groups. However, even if arenesulfonic acid generating units are introduced as repeating units of a base polymer to obtain the effects of the present invention, the base polymer may not dissolve in a solvent due to its low solvent solubility. On the other hand, polymers containing repeating units B9 or B13 have sufficient liposolubility, so that they are easy to manufacture and handle, and the resist composition can also be easily prepared.

[0194] Preferred examples of the anion of the monomer that provides the repeating unit B9 or B13 include, but are not limited to, those shown below. [ka]

[0195] [ka]

[0196] In formulas (B6) to (B13), R 21 ~R 38 are each independently a halogen atom or a hydrocarbyl group having 1 to 20 carbon atoms which may contain a heteroatom.

[0197] Examples of the halogen atom include a fluorine atom, a chlorine atom, a bromine atom, and an iodine atom.

[0198] The hydrocarbyl group having 1 to 20 carbon atoms may be saturated or unsaturated, and may be linear, branched or cyclic. Specific examples thereof include alkyl groups having 1 to 20 carbon atoms, such as methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, n-pentyl, tert-pentyl, n-hexyl, n-octyl, 2-ethylhexyl, n-nonyl and n-decyl groups; cyclopentyl, cyclohexyl, cyclopentylmethyl, cyclopentylethyl, cyclopentylbutyl, cyclohexylmethyl, cyclohexylethyl, cyclohexylbutyl, norbornyl and tricyclo[5.2.1.0] 2,6 ] cyclic saturated hydrocarbyl groups having 3 to 20 carbon atoms, such as a decyl group, an adamantyl group, and an adamantylmethyl group; and aryl groups having 6 to 20 carbon atoms, such as a phenyl group, a naphthyl group, and an anthracenyl group. In addition, some or all of the hydrogen atoms of the hydrocarbyl groups may be substituted with groups containing heteroatoms, such as oxygen atoms, sulfur atoms, nitrogen atoms, and halogen atoms, and some of the -CH2- of the hydrocarbyl groups may be substituted with groups containing heteroatoms, such as oxygen atoms, sulfur atoms, and nitrogen atoms, so that the hydrocarbyl groups may contain hydroxyl groups, fluorine atoms, chlorine atoms, bromine atoms, iodine atoms, cyano groups, carbonyl groups, ether bonds, ester bonds, sulfonate ester bonds, carbonate bonds, lactone rings, sultone rings, carboxylic anhydrides (-C(=O)-OC(=O)-), haloalkyl groups, and the like.

[0199] Also, R 21 and R 22 may be bonded to each other to form a ring together with the sulfur atom to which they are attached, R 23 and R 24 , R 26 and R 27 , or R 29 and R 30 may be bonded to each other to form a ring together with the sulfur atom to which they are bonded. In this case, the ring formed is as shown in the formula (cation-1) in the description of R ct1 and Rct2 may be bonded to each other to form a ring together with the sulfur atom to which they are bonded, similar to those exemplified above.

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

[0201] Of the repeating units B6 to B13, the repeating unit B9 is preferred for processing the photomask blank because it has the optimum acid strength in designing the acid labile groups of the polymer.

[0202] The repeating units B6 to B13 are units that generate acid by irradiation with high energy rays. It is believed that the inclusion of these units in the polymer appropriately suppresses acid diffusion, and thus makes it possible to obtain a pattern with reduced LER. In addition, the inclusion of these units in the polymer suppresses the phenomenon in which acid volatilizes from the exposed area during baking in a vacuum and reattaches to the unexposed area, and is therefore believed to be effective in reducing LER and reducing shape deterioration due to unwanted film loss in the unexposed area.

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

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

[0205] The polymer may contain a commonly used (meth)acrylic acid ester unit protected by an acid labile group, or a (meth)acrylic acid ester unit having an adhesive group such as a lactone structure or a hydroxy group other than a phenolic hydroxy group. Although these repeating units allow fine adjustment of the properties of the resist film, they may not be included.

[0206] Examples of the (meth)acrylic acid ester unit having the adhesive group include a repeating unit represented by the following formula (B14) (hereinafter also referred to as repeating unit B14), a repeating unit represented by the following formula (B15) (hereinafter also referred to as repeating unit B15), and a 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 auxiliary as units that impart adhesion to a substrate or units that adjust solubility. [ka]

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

[0208] When the repeating units B14 to B16 are contained, the content thereof is preferably 0 to 20 mol %, more preferably 0 to 10 mol %, of all the repeating units constituting the polymer. The repeating units B14 to B16 may be used alone or in combination of two or more kinds.

[0209] The polymer can be synthesized by copolymerizing each monomer protected by a protecting group as necessary by a known method, and then carrying out a deprotection reaction as necessary. The copolymerization reaction is not particularly limited, but is preferably radical polymerization or anionic polymerization. For these methods, JP-A-2004-115630 can be referred to.

[0210] The polymer preferably has a weight average molecular weight (Mw) of 1000 to 50000, more preferably 2000 to 20000. If Mw is 1000 or more, there is no risk of the phenomenon that the head of the pattern becomes rounded, the resolution decreases, and the LER deteriorates, as has been known in the past. On the other hand, if Mw is 50000 or less, there is no risk of the LER deteriorates, especially when a pattern having a pattern line width of 100 nm or less is formed. In the present invention, Mw is a value measured in terms of polystyrene by gel permeation chromatography (GPC) using tetrahydrofuran (THF) or dimethylformamide (DMF) as a solvent.

[0211] The polymer preferably has a narrow 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 polymer has such a narrow molecular weight distribution, no foreign matter is generated on the pattern after development, and the shape of the pattern is not deteriorated.

[0212] In addition, as the base polymer design, the dissolution rate in an 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 the advanced generation, when the coating film on the substrate is in the thin film region (100 nm or less), the effect of pattern film loss due to alkaline development becomes large, and when the alkaline dissolution rate of the polymer is more than 10 nm / min, the pattern collapses and fine patterns cannot be formed. This is particularly noticeable in photomask production, which requires no defects, because the development process tends to be strong. In addition, in the present invention, the dissolution rate of the base polymer in an alkaline developer is a value calculated from the amount of film loss when a polymer solution (polymer concentration: 16.7 mass%, solvent: propylene glycol monomethyl ether acetate (PGMEA)) is spin-coated on 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 at 23°C for 100 seconds with a 2.38 mass% aqueous solution of tetramethylammonium hydroxide (TMAH).

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

[0214] [(C) Organic solvent] 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 can dissolve 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 JP-A-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 of suitable solvents 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 an acetal-based acid labile group is used, a high-boiling alcohol solvent, specifically diethylene glycol, propylene glycol, glycerin, 1,4-butanediol, 1,3-butanediol, or the like, may 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 mixed solvents thereof are preferable.

[0216] When the chemically amplified positive resist composition of the present invention contains an organic solvent (C), the content thereof is preferably 200 to 10,000 parts by mass, and more preferably 400 to 5,000 parts by mass, relative to 80 parts by mass of the base polymer (B). The organic solvent (C) may be used alone or in combination of two or more kinds.

[0217] [(D) Fluorine atom-containing polymer] The chemically amplified positive resist composition of the present invention, for the purposes of increasing contrast, suppressing the chemical flare phenomenon of acid when irradiated with high-energy rays, and shielding acid mixing from the antistatic film in the process of applying an antistatic film material onto the resist film, thereby suppressing unexpected and unnecessary pattern degradation, may contain, as component (D), a fluorine-containing polymer that contains at least one selected from the group consisting of a repeating unit represented by formula (D1) below (hereinafter also referred to as repeating unit D1), a repeating unit represented by formula (D2) below (hereinafter also referred to as repeating unit D2), a repeating unit represented by formula (D3) below (hereinafter also referred to as repeating unit D3), and a repeating unit represented by formula (D4) below (hereinafter also referred to as repeating unit D4), and that may further contain at least one selected from the group consisting of a repeating unit represented by formula (D5) below (hereinafter also referred to as repeating unit D5) and a repeating unit represented by formula (D6) below (hereinafter also referred to as repeating unit D6). The fluorine atom-containing polymer also functions as a surfactant, and is therefore effective against development defects since it can prevent insoluble matter from re-adhering to the substrate during the development process. [ka]

[0218] In the formulas (D1) to (D6), x is an integer of 1 to 3. y is an integer satisfying 0≦y≦5+2z−x. z is 0 or 1. h is an integer of 1 to 3. R B R are each independently a hydrogen atom, a fluorine atom, a methyl group, or a trifluoromethyl group. C R is each independently a hydrogen atom or a methyl group. 101 , R 102 , R 104 and R 105 R are each independently a hydrogen atom or a saturated hydrocarbyl group having 1 to 10 carbon atoms. 103 , R 106 , R 107 and R 108each independently represents a hydrogen atom, a hydrocarbyl group having 1 to 15 carbon atoms, a fluorinated hydrocarbyl group having 1 to 15 carbon atoms, or an acid labile group; R 103 , R 106 , R 107 and R 108 When R is a hydrocarbyl group or a fluorinated hydrocarbyl group, an ether bond or a carbonyl group may be present between the carbon-carbon bonds. 109 R is a hydrogen atom or a linear or branched hydrocarbyl group having 1 to 5 carbon atoms which may have a heteroatom-containing group interposed between the carbon-carbon bonds. 110 R is a linear or branched hydrocarbyl group having 1 to 5 carbon atoms which may have a heteroatom-containing group between its carbon-carbon bonds. 111 Z 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 part of the -CH2- in the saturated hydrocarbyl group may be substituted with an ester bond or an ether bond. 1 Z 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 is a single bond, *-C(=O)-O-, or *-C(=O)-NH-. * is a bond to a carbon atom in the main chain. Z 3 is a single bond, -O-, *-C(=O)-OZ 31 -Z 32 - or -C(=O)-NH-Z 31 -Z 32 -It is. 31 is a single bond or a saturated hydrocarbylene group having 1 to 10 carbon atoms. 32 is a single bond, an ester bond, an ether bond or a sulfonamide bond. * is a bond to a carbon atom of the main chain.

[0219] In formulas (D1) and (D2), R 101 , R 102 , R 104 and R 105The saturated hydrocarbyl group having 1 to 10 carbon atoms represented by the formula (I) may be linear, branched or cyclic, and specific examples thereof include alkyl groups having 1 to 10 carbon atoms, such as a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, an isobutyl group, a sec-butyl group, a tert-butyl group, an n-pentyl group, an n-hexyl group, an n-heptyl group, an n-octyl group, an n-nonyl group or an n-decyl group; and cyclic saturated hydrocarbyl groups having 3 to 10 carbon atoms, such as a cyclopropyl group, a cyclobutyl group, a cyclopentyl group, a cyclohexyl group, an adamantyl group or a norbornyl group. 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 hydrocarbyl group having 1 to 15 carbon atoms represented by the formula (I) may be linear, branched, or cyclic, and specific examples thereof include an alkyl group having 1 to 15 carbon atoms, an alkenyl group having 2 to 15 carbon atoms, and an alkynyl group having 2 to 15 carbon atoms, and an alkyl group having 1 to 15 carbon atoms is preferred. In addition to the above, examples of the alkyl group include a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, an isobutyl group, a sec-butyl group, an n-pentyl group, an n-hexyl group, an n-heptyl group, an n-octyl group, an n-nonyl group, an n-decyl group, an n-undecyl group, an n-dodecyl group, an n-tridecyl group, an n-tetradecyl group, and an n-pentadecyl group. Examples of the fluorinated hydrocarbyl group include a group in which some or all of the hydrogen atoms bonded to the carbon atoms of the above-mentioned hydrocarbyl group are substituted with fluorine atoms.

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

[0222] Specific examples of the repeating units D1 to D4 include, but are not limited to, those shown below. B is the same as above. [ka]

[0223] [ka]

[0224] [ka]

[0225] In formula (D5), R 109 and R 110 Examples of the hydrocarbyl group having 1 to 5 carbon atoms represented by the formula (1) include an alkyl group, an alkenyl group, and an alkynyl group, with an alkyl group being preferred. Examples of the alkyl group include a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, an isobutyl group, a sec-butyl group, and an n-pentyl group. In addition, a group containing a heteroatom such as an oxygen atom, a sulfur atom, or a nitrogen atom may be present between the carbon-carbon bonds of the hydrocarbyl group.

[0226] In formula (D5), -OR 109 is preferably a hydrophilic group. In this case, R 109 is preferably a hydrogen atom, an alkyl group having 1 to 5 carbon atoms and an oxygen atom intervening between the carbon-carbon bonds, or the like.

[0227] In formula (D5), Z 2 is preferably *-C(=O)-O- or *-C(=O)-NH-. Cis preferably a methyl group. 2 The presence of a carbonyl group in R improves the acid trapping ability of the antistatic film. C When the methyl group is used, the polymer becomes more rigid with a higher glass transition temperature (Tg), which suppresses the diffusion of acid. This improves the stability of the resist film over time, and the resolution and pattern shape do not deteriorate.

[0228] Examples of the repeating unit D5 include, but are not limited to, those shown below. In the following formula, R C is the same as above. [ka]

[0229] [ka]

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

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

[0232] Examples of the repeating unit D6 include, but are not limited to, those shown below. In the following formula, R C is the same as above. [ka]

[0233] [ka]

[0234] [ka]

[0235] [ka]

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

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

[0046] to

[0078] of JP2014-177407A. When the fluorine atom-containing polymer (D) contains other repeating units, the content of such units is preferably 50 mol% or less of the total repeating units of the fluorine atom-containing polymer.

[0238] (D) The fluorine atom-containing polymer can be synthesized by copolymerizing each monomer protected by a protecting group as necessary by a known method, and then carrying out a deprotection reaction as necessary. The copolymerization reaction is not particularly limited, but is preferably radical polymerization or anionic polymerization. For these methods, JP-A-2004-115630 can be referred to.

[0239] The Mw of the fluorine atom-containing polymer (D) is preferably 2000 to 50000, more preferably 3000 to 20000. If the Mw is less than 2000, the diffusion of the acid is promoted, which may result in deterioration of the resolution and deterioration of the stability over time. If the Mw is too large, the solubility in the solvent may decrease, which may cause coating defects. In addition, the Mw / Mn of the fluorine atom-containing polymer (D) is preferably 1.0 to 2.2, more preferably 1.0 to 1.7.

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

[0241] [(E) Quencher] The chemically amplified positive resist composition of the present invention may contain a quencher as component (E) as necessary. In the present invention, the quencher means a compound that traps the acid generated from the acid generator. This makes it possible to suppress the diffusion speed of the acid generated from the acid generator when it diffuses into the resist film, and even when a substrate is used whose outermost surface is made of a material containing chromium, it is possible to suppress the effect of the acid generated in the resist film on the material containing chromium.

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

[0243] In formula (E1), R 201 is a hydrocarbyl group having 1 to 40 carbon atoms which may contain a heteroatom. The hydrocarbyl group may be saturated or unsaturated, and may be linear, branched, or cyclic. Specific examples thereof include an alkyl group having 1 to 40 carbon atoms, a cyclic saturated hydrocarbyl group having 3 to 40 carbon atoms, an alkenyl group having 2 to 40 carbon atoms, an alkynyl group having 2 to 40 carbon atoms, a cyclic unsaturated aliphatic hydrocarbyl group having 3 to 40 carbon atoms, an aryl group having 6 to 40 carbon atoms, an aralkyl group having 7 to 40 carbon atoms, and groups obtained by combining these groups. In addition, some or all of the hydrogen atoms of the hydrocarbyl group may be substituted with a hydroxy group, a carboxy group, a halogen atom, a cyano group, an amide group, a nitro group, a mercapto group, a sultone group, a sulfone group, or a sulfonium salt-containing group, and some of the -CH2- of the hydrocarbyl group may be substituted with an ether bond, an ester bond, a carbonyl group, a carbonate group, or a sulfonate ester bond.

[0244] In formula (E1), Mq + is an onium cation. The onium cation may be a sulfonium cation, an iodonium cation, an ammonium cation, or the like, and is preferably a sulfonium cation. Preferred sulfonium cations include those exemplified as the sulfonium cation represented by formula (cation-1).

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

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

[0247] In formula (E2), R 211 ~R 214 Each independently represents a hydrogen atom, -L A -CO2 - or a hydrocarbyl group having 1 to 20 carbon atoms which may contain a heteroatom. 211 and R 212 And, R 212 and R 213 and, or R 213 and R 214 may be bonded to each other to form a ring together with the carbon atoms to which they are attached. A R is a single bond or a hydrocarbylene group having 1 to 20 carbon atoms which may contain a heteroatom. 115 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 containing carbon atoms and nitrogen atoms and having 2 to 6 carbon atoms, and some or all of the hydrogen atoms bonded to the carbon atoms of the ring are hydrocarbyl groups having 1 to 20 carbon atoms, or -L A -CO2 - and a part of -CH2- in 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 ring or an aromatic ring. The ring is preferably a 5-membered or 6-membered ring, and specific examples thereof include a pyridine ring, a pyrrole ring, a pyrrolidine ring, a piperidine ring, a pyrazole ring, an imidazoline ring, a pyridazine ring, a pyrimidine ring, a pyrazine ring, an imidazoline ring, an oxazole ring, a thiazole ring, a morpholine ring, a thiazine ring, and a triazole ring.

[0249] The carboxylic acid onium salt represented by formula (E2) has at least one -L A -CO2 - That is, R 211 ~R 214 At least one of the following is -LA -CO2 - and / or at least one of the hydrogen atoms bonded to the carbon atom of the ring R is -L A -CO2 - is replaced by

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

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

[0252] Other examples of the quencher include sulfonium compounds represented by the following formula (E4). [ka]

[0253] In formula (E4), R 231 , R 232 and R 233are each independently a hydrocarbyl group having 1 to 20 carbon atoms which may contain a heteroatom. A part of the hydrogen atoms of the hydrocarbyl group may be substituted with a group containing a heteroatom such as an oxygen atom, a sulfur atom, a nitrogen atom, or a halogen atom, and a part of -CH2- of the hydrocarbyl group may be substituted with a group containing a heteroatom such as an oxygen atom, a sulfur atom, or a nitrogen atom, and as a result, the hydrocarbyl group may contain a hydroxy group, a cyano group, a carbonyl group, an ether bond, a thioether bond, an ester bond, a sulfonate ester bond, a carbonate bond, a carbamate bond, a lactone ring, a sultone ring, a carboxylic anhydride (-C(=O)-OC(=O)-), a haloalkyl group, or the like. The -CH2- of the hydrocarbyl group may be a carbon atom bonded to a benzene ring in the formula.

[0254] In formula (E4), z1 and z2 each independently represent an integer of 0 to 5. z3 represents an integer of 0 to 4. z1, z2 and z3 are each preferably 0, 1 or 2 from the viewpoints of ease of synthesis and availability of raw materials.

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

[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 from 0.1 to 40 parts by mass, and more preferably from 1 to 20 parts by mass, relative to 80 parts by mass of the (B) base polymer.

[0257] As the quencher, in addition to the onium salt compound described above, a photodecomposable onium salt having a nitrogen-containing substituent may be used in combination as necessary. Such a compound functions as a quencher in the unexposed area, and functions as a so-called photodecomposable base in the exposed area, which loses its quenching ability by neutralization with the acid generated from itself. By using a photodecomposable base, the contrast between the exposed area and the unexposed area can be further enhanced. Examples of the photodecomposable base include those described in JP-A-2009-109595, JP-A-2012-46501, and JP-A-2013-209360. When the chemically amplified positive resist composition of the present invention contains the photodecomposable base as a quencher, the content thereof is preferably 0.1 to 40 parts by mass, more preferably 0.1 to 20 parts by mass, relative to 80 parts by mass of the (B) base polymer.

[0258] As the quencher, an amine compound can also be used. The amine compound includes the primary, secondary, or tertiary amine compounds described in paragraphs

[0146] to

[0164] of JP-A-2008-111103, particularly amine compounds having a hydroxyl group, an ether bond, an ester bond, a lactone ring, a cyano group, or a sulfonate ester bond. In addition, compounds in which a primary or secondary amine is protected with a carbamate group, such as the compounds described in JP-A-3790649, can also be used. When the chemically amplified positive resist composition of the present invention contains the amine compound as a quencher, the content thereof is preferably 0.001 to 12 parts by mass, more preferably 0.01 to 8 parts by mass, relative to 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 a photoacid generator other than the photoacid generator consisting of an onium salt represented by formula (A). The other photoacid generator is not particularly limited as long as it is a compound that generates an acid upon irradiation with high-energy rays. Suitable photoacid generators include sulfonium salts, iodonium salts, sulfonyldiazomethane, N-sulfonyloxyimide, and oxime-O-sulfonate type acid generators.

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

[0247] to

[0251] of JP-A-2012-189977, and the like.

[0261] to

[0265] , those described in JP-A-2008-111103, paragraphs

[0122] to

[0142] , and JP-A-2010-215608, paragraphs

[0080] to

[0081] , etc. Among the above specific examples, arylsulfonate-type or alkane sulfonate-type photoacid generators are preferred because they generate an acid of suitable strength for deprotecting the acid labile group in the repeating unit B2.

[0261] Preferred examples of the photoacid generator include salt compounds containing anions having the structures 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 formula (F1), m1 is 0 or 1. p is an integer of 1 to 3. q is an integer of 1 to 5. r is an integer of 0 to 3.

[0272] In formula (F1), L 1 is a single bond, an ether bond, an ester bond, a sulfonate ester bond, a carbonate bond or a carbamate bond.

[0273] In formula (F1), L 2 is an ether bond, an ester bond, a sulfonate ester bond, a carbonate bond or a carbamate bond.

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

[0275] L BThe hydrocarbylene group having 1 to 20 carbon atoms represented by the formula (1) may be saturated or unsaturated, and may be linear, branched, or cyclic. Specific examples thereof include a methylene group, an ethane-1,1-diyl group, an ethane-1,2-diyl group, a propane-1,3-diyl group, a butane-1,4-diyl group, a pentane-1,5-diyl group, a hexane-1,6-diyl group, a heptane-1,7-diyl group, an octane-1,8-diyl group, a nonane-1,9-diyl group, a decane-1,10-diyl group, an undecane-1,11-diyl group, and a dodecane-1,12-diyl group. Examples of the alkylene groups include alkanediyl groups having 1 to 20 carbon atoms; cyclic saturated hydrocarbylene groups having 3 to 20 carbon atoms, such as cyclopentanediyl groups, cyclohexanediyl groups, norbornanediyl groups, and adamantanediyl groups; unsaturated aliphatic hydrocarbylene groups having 2 to 20 carbon atoms, such as vinylene groups and propene-1,3-diyl groups; arylene groups having 6 to 20 carbon atoms, such as phenylene groups and naphthylene groups; and groups obtained by combining these groups. B The (p+1)-valent hydrocarbon group having 1 to 20 carbon atoms represented by the formula (1) may be saturated or unsaturated, and may be linear, branched, or cyclic. Specific examples thereof include groups obtained by further removing one or two hydrogen atoms from the specific examples of the hydrocarbylene group having 1 to 20 carbon atoms described above.

[0276] In formula (F1), Rf 1 and Rf 2 are each independently a hydrogen atom, a fluorine atom, or a trifluoromethyl group, provided that at least one of them is a fluorine atom or a trifluoromethyl group.

[0277] In formula (F1), R 301 is a hydroxy group, a carboxy 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, -N(R 301A )-C(=O)-R 301B Or -N(R 301A )-C(=O)-OR 301B and R 301A is a hydrogen atom or a saturated hydrocarbyl group having 1 to 6 carbon atoms, R301B 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 the formula (I) may be linear, branched or cyclic, and specific examples thereof 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 Examples of the saturated hydrocarbyl moiety of the saturated hydrocarbyloxy group having 1 to 6 carbon atoms represented by the formula (I) include the same as the specific examples of the saturated hydrocarbyl group described above, and R 301 Examples of the saturated hydrocarbyl moiety of the saturated hydrocarbylcarbonyloxy group having 2 to 6 carbon atoms represented by the following formula include those having 1 to 5 carbon atoms among the specific examples of the saturated hydrocarbyl groups having 1 to 6 carbon atoms mentioned above.

[0279] R 301B The unsaturated aliphatic hydrocarbyl group having 2 to 8 carbon atoms represented by the formula (I) may be linear, branched, or cyclic, and specific examples thereof include alkenyl groups having 2 to 8 carbon atoms, such as a vinyl group, a propenyl group, a butenyl group, or a hexenyl group; alkynyl groups having 2 to 8 carbon atoms, such as an ethynyl group, a propynyl group, or a butynyl group; and cyclic unsaturated aliphatic hydrocarbyl groups having 3 to 8 carbon atoms, such as a cyclohexenyl group or a norbornenyl group.

[0280] In formula (F1), R 302represents a saturated hydrocarbylene group having 1 to 20 carbon atoms or an arylene group having 6 to 14 carbon atoms, 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 a substituent 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 hydroxy group.

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

[0282] R 302Specific examples of the arylene group having 6 to 14 carbon atoms represented by the following formula include a phenylene group, a naphthylene group, a phenanthrenediyl group, and an anthracenediyl group. The hydrocarbyl moiety of the saturated hydrocarbyl group having 1 to 20 carbon atoms and the hydrocarbyloxy group having 1 to 20 carbon atoms, which are substituents of the arylene group, may be any one of linear, branched, and cyclic, and specific examples thereof include alkyl groups having 1 to 20 carbon atoms, such as a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, an isobutyl group, a sec-butyl group, a tert-butyl group, an n-pentyl group, an n-hexyl group, an n-octyl group, an n-nonyl group, an n-decyl group, an undecyl group, a dodecyl group, a tridecyl group, a tetradecyl group, a pentadecyl group, a heptadecyl group, an octadecyl group, a nonadecyl group, and an icosyl group; and cyclic saturated hydrocarbyl groups having 3 to 20 carbon atoms, such as a cyclopropyl group, a cyclopentyl group, a cyclohexyl group, a cyclopropylmethyl group, a 4-methylcyclohexyl group, a cyclohexylmethyl group, a norbornyl group, and an adamantyl group. Specific examples of the arylene group having 6 to 14 carbon atoms which is the substituent of the arylene group include a phenylene group, a naphthylene group, a phenanthrenediyl group, and an anthracenediyl group.

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

[0284] In formula (F2), p, q, r, L 1 , L B and R 301 is the same as above. m2 is an integer of 1 to 4. R 302A is 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, or a hydroxy group. 302A may be the same as or different from each other.

[0285] Examples of the anion represented by formula (F1) include, but are not limited to, those shown 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, the cation paired with the above-mentioned anion is preferably a sulfonium cation or an iodonium cation.Specific examples of the sulfonium cation include, but are not limited to, the same as those exemplified as the sulfonium cation represented by formula (cation-1).Specific examples of the iodonium cation include, but are not limited to, the same as those exemplified as the sulfonium cation represented by formula (cation-2).

[0314] The acid generated by the other photoacid generator preferably has a pKa of -2.0 or more, more preferably -1.0 or more. The upper limit of the pKa is preferably 2.0. The pKa value is calculated using the pKa DB in the software ACD / Chemsketch ver:9.04 manufactured by Advanced Chemistry Development, Inc.

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

[0316] [(G) Surfactant] The chemically amplified positive resist composition of the present invention may contain a commonly used surfactant as component (G) in order to improve the coating properties onto a substrate. Many of the surfactants are known as described in International Publication No. 2006 / 121096, JP-A No. 2008-102383, JP-A No. 2008-304590, JP-A No. 2004-115630, and JP-A No. 2005-8766, and the surfactant can be selected with reference to these.

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

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

[0319] The substrate may be, for example, a substrate for manufacturing integrated circuits (Si, SiO, SiO2, SiN, SiON, TiN, WSi, BPSG, SOG, organic anti-reflective film, etc.) or a substrate for manufacturing mask circuits (Cr, CrO, CrON, MoSi2, Si, SiO, SiO2, etc.) The chemically amplified positive resist composition is applied onto 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] The resist film is then exposed to a pattern using high-energy radiation, such as ultraviolet radiation, far ultraviolet radiation, excimer laser light (KrF, ArF, etc.), EB, EUV, X-rays, gamma rays, and synchrotron radiation.

[0321] When ultraviolet rays, far ultraviolet rays, excimer laser light, EUV, X-rays, gamma rays, or synchrotron radiation is used as the high-energy radiation, a mask for forming a desired pattern is used, and the exposure dose is preferably 1 to 300 mJ / cm. 2 , more preferably 10 to 200 mJ / cm 2 When EB is used as the high energy beam, the exposure dose is preferably 1 to 300 μC / cm 2 , more preferably 10 to 200 μC / cm 2 The chemically amplified positive resist composition of the present invention is particularly useful for EUV or EB lithography.

[0322] The exposure can be performed by a normal exposure method, or in some cases by an immersion method in which a liquid is inserted between the mask and the resist film. In that case, a water-insoluble protective film can be used.

[0323] Next, post-exposure baking (PEB) is performed 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.

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

[0325] The chemically amplified positive resist composition of the present invention is particularly useful when used under conditions that require high etching resistance, small change in pattern line width even when the time until PEB after exposure is extended, and small LER. The resist composition of the present invention is particularly useful for application to a substrate having a surface made of a material that is prone to pattern peeling or pattern collapse because it is difficult to obtain adhesion of the resist pattern. Examples of such substrates include substrates formed by sputtering a film of a chromium compound containing metal chromium or one or more light elements selected from oxygen, nitrogen, and carbon. 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 apparatuses used are as follows. MALDI TOF-MS: JEOL S3000

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

[0328] Under a nitrogen atmosphere, SM-1 (10.6 g), SM-2 (6.3 g) and 4-dimethylaminopyridine (0.3 g) were suspended in THF (50 g) and cooled in an ice bath. Triethylamine (3.5 g) was added dropwise thereto, and the mixture was stirred at room temperature for 10 hours. After aging, the reaction solution was cooled and water (50 g) was added to stop the reaction. Then, SM-3 (9.4 g) was added, and the target product was extracted with methylene chloride (100 g), and the usual aqueous work-up was performed. The solvent was distilled off to obtain 15.5 g of PAG-1 as an oil (yield 73%).

[0329] The TOF-MS results of 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 the 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 polymer [Synthesis Example 1] Synthesis of Polymer P-1 In a 100 mL flask, 20 g of polyhydroxystyrene-acenaphthylene copolymer and 46.7 g of tetrahydrofuran as a solvent were added. 0.5 g of methanesulfonic acid was added thereto at about 25°C under a nitrogen atmosphere, and then 4.4 g of 1-methoxy-2-methylpropene was added dropwise and reacted at room temperature for 4.5 hours. After the reaction was completed, 1.0 g of triethylamine was added, and the resulting reaction solution was dropped into 500 g of hexane, and 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, and the obtained solution was transferred to a separatory funnel, and 0.7 g of acetic acid was added to perform a separation operation. The lower layer was distilled off, and 20 g of water and 0.9 g of pyridine were added to the obtained organic layer, and a separation operation was performed. The lower layer was distilled off, and 20 g of water was added to the obtained organic layer to perform water washing and separation (a total of 5 times of water washing and separation). After separation, the organic layer was concentrated and then dissolved in 40 g of PGME. The obtained solution was dropped into 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. Polymer P-1 was 1 H-NMR, 13 Measurement by C-NMR and GPC gave the following analytical results: [ka]

[0332] [Synthesis Examples 2 to 9] Synthesis of Polymers P-2 to P-9 Polymers P-2 to P-9 shown below were synthesized with reference to Synthesis Example 1 and known methods, except that the types and compounding ratios of each monomer were changed. [ka]

[0333] [3] Preparation of chemically amplified positive resist composition [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 according to the compositions shown in Tables 1 to 3 below, and filtering the resulting solution through a 5 nm nylon filter and a 1 nm UPE filter. The organic solvent was a mixed solvent 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 to 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 using ACT-M (Tokyo Electron Ltd.) onto a mask blank for EUV exposure masks, which was a reflective mask blank consisting of a 284 nm thick Mo / Si 40-layer multilayer reflective film on a 6-inch side low thermal expansion glass substrate, a 3.5 nm thick Ru film as a protective film on top of that, a 70 nm thick TaN film as an absorbing layer on top of that, and a 6 nm thick CrN film as a hard mask on top of that, and pre-baked on a hot plate at 110°C for 600 seconds to produce a resist film with a thickness of 80 nm. The thickness of the obtained resist film was measured using an optical measuring instrument Nanospec (Nanometrics Co., Ltd.). Measurements were performed at 81 points on the surface of the blank substrate, excluding the outer edge portion from the outer periphery to the inside by 10 mm, and the average thickness and thickness range were calculated.

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

[0344] The obtained resist patterns were evaluated as follows. The prepared patterned mask blanks were observed with an overhead SEM (scanning electron microscope), and the exposure dose required to resolve 200 nm 1:1 line and space (LS) at 1:1 was determined as the optimal exposure dose (μC / cm 2 ), and the minimum dimension at the exposure dose that resolves a 200 nm isolated space at a ratio of 9:1 was taken as the resolution (limit IS resolution), and the LER of 200 nm LS was measured using an SEM. For the development loading evaluation, the exposure dose (μC / cm) that resolves a 1:1 LS of the design 200 nm at a ratio of 1:1 was used within the substrate surface. 2The space dimensions of a 200nm LS pattern formed by the 200nm LS pattern with dummy patterns of densities of 15%, 25%, 33%, 45%, 50%, 55%, 66%, 75%, 85%, and 95% were measured by SEM, and the dimensional differences of the dense and sparse patterns were compared. The pattern shape was visually judged to be rectangular or not.

[0345] The dissolution rate of the exposed area was measured 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 measuring the exposure dose (mJ / cm2) required to resolve a 1:1 line and space (LS) of 200 nm at 1:1. 2 ) and exposed to KrF excimer laser light, baked at 110°C for 60 seconds, and then developed at 23°C with a 2.38% by mass TMAH aqueous solution using a resist development analyzer (RDA-800 manufactured by LithoTech Japan Co., Ltd.), and calculations were performed. 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 method of forming a resist pattern are useful for the production of semiconductor devices, in particular for photolithography in the processing of transmissive and reflective photomask blanks.

Claims

1. An onium salt represented by the following formula (A): [Formula 1] (In the formula, n1 is an integer of 0 to 2. When n1=0, n2 is an integer of 2 to 5, when n1=1, n2 is an integer of 2 to 7, and when n1=2, n2 is an integer of 2 to 9. L is a single bond, an ether bond, an ester bond, a sulfonate ester bond, a carbonate bond or a carbamate bond. R 1 and R 2 are each independently a hydrogen atom or a branched or cyclic hydrocarbyl group having 3 to 20 carbon atoms which may contain a heteroatom, but cannot both be hydrogen atoms. 1 and R 2 may be bonded to each other to form a ring together with the carbon atoms to which they are attached. R 3 are each independently an iodine atom or a branched or cyclic hydrocarbyl group having 3 to 20 carbon atoms which may contain a heteroatom, and at least one R 3 is bonded to a carbon atom adjacent to the carbon atom to which L is bonded. Z + is an onium cation.

2. The onium salt according to claim 1, represented by the following formula (A1): [Case 2] (In the formula, L, R 1 , R 2 , R 3 and Z + is the same as above. n3 is an integer of 1 to 4.

3. The onium salt according to claim 2, represented by the following formula (A2): [C3] (In the formula, n3, R 1 , R 2 , R 3 and Z + is the same as above.)

4. Z + The onium salt according to claim 1, wherein is an onium cation represented by the following formula (category-1) or (category-2): [C4] (In the formula, R ct1 ~R ct5 are each independently a hydrocarbyl group having 1 to 30 carbon atoms which may contain a heteroatom. ct1 and R ct2 may be bonded to each other to form a ring together with the sulfur atom to which they are attached.)

5. A photoacid generator comprising the onium salt according to claim 1.

6. A chemically amplified positive resist composition comprising the photoacid generator according to claim 5.

7. 7. The chemically amplified positive resist composition according to claim 6, further comprising a base polymer which contains a polymer which is decomposed by the action of an acid and has increased solubility in an alkaline developer.

8. 8. The chemically amplified positive resist composition according to claim 7, wherein the polymer contains a repeating unit represented by the following formula (B1): [C5] (In the formula, a1 is 0 or 1. a2 is an integer from 0 to 2. a3 is an integer that satisfies 0≦a3≦5+2(a2)−a4. a4 is an integer from 1 to 3. R A is a hydrogen atom, a fluorine atom, a methyl group or a trifluoromethyl group. R 11 represents a halogen atom, a saturated hydrocarbylcarbonyloxy group having 2 to 8 carbon atoms which may be substituted with a halogen atom, a saturated hydrocarbyl group having 1 to 6 carbon atoms which may be substituted with a halogen atom, or a saturated hydrocarbyloxy group having 1 to 6 carbon atoms which may be substituted with a halogen atom. A 1 is a single bond or a saturated hydrocarbylene group having 1 to 10 carbon atoms, and the —CH 2 - may be replaced by -O-.

9. 8. The chemically amplified positive resist composition according to claim 7, wherein the polymer contains a repeating unit represented by the following formula (B2): [C6] (In the formula, b1 is 0 or 1. b2 is an integer from 0 to 2. b3 is an integer satisfying 0≦b3≦5+2(b2)−b4. b4 is an integer from 1 to 3. b5 is 0 or 1. R A is a hydrogen atom, a fluorine atom, a methyl group or a trifluoromethyl group. R 12 represents a halogen atom, a saturated hydrocarbylcarbonyloxy group having 2 to 8 carbon atoms which may be substituted with a halogen atom, a saturated hydrocarbyl group having 1 to 6 carbon atoms which may be substituted with a halogen atom, or a saturated hydrocarbyloxy group having 1 to 6 carbon atoms which may be substituted with a halogen atom. A 2 is a single bond or a saturated hydrocarbylene group having 1 to 10 carbon atoms, and the —CH 2 - may be replaced by -O-. When b4 is 1, X is an acid labile group. When b4 is 2 or 3, X is each independently a hydrogen atom or an acid labile group, provided that at least one X is an acid labile group.

10. 8. The chemically amplified positive resist composition according to claim 7, wherein the polymer contains a repeating unit represented by the following formula (B2-2): [C7] (In the formula, c1 is an integer from 0 to 2. c2 is an integer from 0 to 2. c3 is an integer from 0 to 5. c4 is an integer from 0 to 2. R A is a hydrogen atom, a fluorine atom, a methyl group or a trifluoromethyl group. R 13 and R 14are each independently a hydrocarbyl group having 1 to 10 carbon atoms which may contain a heteroatom; R 13 and R 14 may be bonded to each other to form a ring together with the carbon atoms to which they are attached. R 15 each independently represents 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 are each independently a hydrocarbyl group having 1 to 10 carbon atoms which may contain a heteroatom. A 3 is a single bond, a phenylene group, a naphthylene group, or *-C(=O)-O-A 31 - is. 31 is an aliphatic hydrocarbylene group having 1 to 20 carbon atoms which may contain a hydroxy group, an ether bond, an ester bond, or a lactone ring, or a phenylene group or naphthylene group. * is a bond to a carbon atom of the main chain.)

11. 8. The chemically amplified positive resist composition according to claim 7, wherein the polymer contains at least one repeating unit selected from the group consisting of a repeating unit represented by the following formula (B3), a repeating unit represented by the following formula (B4), and a repeating unit represented by the following formula (B5): [C8] (In the formula, d is an integer of 0 to 6. e is an integer of 0 to 4. f1 is 0 or 1. f2 is an integer of 0 to 2. f3 is an integer of 0 to 5. R A is a hydrogen atom, a fluorine atom, a methyl group or a trifluoromethyl group. R 17 and R 18 each independently represents a hydroxy group, a halogen atom, a saturated hydrocarbyl group having 1 to 6 carbon atoms which may be substituted with a halogen atom, a saturated hydrocarbyloxy group having 1 to 6 carbon atoms which may be substituted with a halogen atom, or a saturated hydrocarbylcarbonyloxy group having 2 to 8 carbon atoms which may be substituted with a halogen atom. R 19represents 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 be a hydroxy group. A 4 is a single bond or a saturated hydrocarbylene group having 1 to 10 carbon atoms, and the —CH 2 - may be replaced by -O-.

12. 8. The chemically amplified positive resist composition according to claim 7, wherein the polymer comprises at least one selected from the group consisting of a repeating unit represented by formula (B6), a repeating unit represented by formula (B7), a repeating unit represented by formula (B8), a repeating unit represented by formula (B9), a repeating unit represented by formula (B10), a repeating unit represented by formula (B11), a repeating unit represented by formula (B12), and a repeating unit represented by formula (B13): [C9] (In the formula, R A each independently represents a hydrogen atom, a fluorine atom, a methyl group, or a trifluoromethyl group. Y 1 represents a single bond, an aliphatic hydrocarbylene group having 1 to 6 carbon atoms, a phenylene group, a naphthylene group, or a group having 7 to 18 carbon atoms obtained by combining these, or *-O-Y 11 -, *-C(=O)-O-Y 11 - or *-C(=O)-NH-Y 11 - and Y 11 represents an aliphatic hydrocarbylene group having 1 to 6 carbon atoms, a phenylene group, a naphthylene group, or a group having 7 to 18 carbon atoms obtained by combining these, and may contain a carbonyl group, an ester bond, an ether bond, or a hydroxy group. Y 2 is a single bond or **-Y 21 -C(=O)-O-, and Y 21is a hydrocarbylene group having 1 to 20 carbon atoms which may contain a heteroatom. Y 3 represents a single bond, a methylene group, an ethylene group, a phenylene group, a fluorinated phenylene group, a phenylene group substituted with a trifluoromethyl group, *-O-Y 31 -, *-C(=O)-O-Y 31 - or *-C(=O)-NH-Y 31 - is. 31 represents an aliphatic hydrocarbylene group having 1 to 6 carbon atoms, a phenylene group, a fluorinated phenylene group, a phenylene group substituted with a trifluoromethyl group, or a group having 7 to 20 carbon atoms obtained by combining these, which may contain a carbonyl group, an ester bond, an ether bond, or a hydroxy group. * represents a bond to a carbon atom in the main chain, and ** represents a bond to an oxygen atom in the formula. Y 4 is a single bond or a hydrocarbylene group having 1 to 30 carbon atoms which may contain a heteroatom. g1 and g2 each independently represent 0 or 1, and Y 4 When is a single bond, g1 and g2 are 0. R 21 ~R 38 are each independently a halogen atom or a hydrocarbyl group having 1 to 20 carbon atoms which may contain a heteroatom. 21 and R 22 may be bonded to each other to form a ring together with the sulfur atom to which they are attached, R 23 and R 24 , R 26 and R 27 , or R 29 and R 30 may be bonded to each other to form a ring together with the sulfur atom to which they are attached. R HF is a hydrogen atom or a trifluoromethyl group. Xa - is a non-nucleophilic counterion.)

13. 8. The chemically amplified positive resist composition according to claim 7, further comprising an organic solvent.

14. The chemically amplified positive resist composition according to claim 7, further comprising a fluorine atom-containing polymer which contains at least one repeating unit selected from the group consisting of a repeating unit represented by the following formula (D1), a repeating unit represented by the following formula (D2), a repeating unit represented by the following formula (D3), and a repeating unit represented by the following formula (D4), and which may further contain at least one repeating unit selected from the group consisting of a repeating unit represented by the following formula (D5) and a repeating unit represented by the following formula (D6): [C10] (In the formula, x is an integer of 1 to 3. y is an integer satisfying 0≦y≦5+2z−x. z is 0 or 1. h is an integer of 1 to 3. R B each independently represents a hydrogen atom, a fluorine atom, a methyl group, or a trifluoromethyl group. R C are each independently a hydrogen atom or a methyl group. R 101 , R 102 , R 104 and R 105 are each independently a hydrogen atom or a saturated hydrocarbyl group having 1 to 10 carbon atoms. R 103 , R 106 , R 107 and R 108 are each independently a hydrogen atom, a hydrocarbyl group having 1 to 15 carbon atoms, a fluorinated hydrocarbyl group having 1 to 15 carbon atoms, or an acid labile group; 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 present between the carbon-carbon bonds. R 109 is a hydrogen atom or a linear or branched hydrocarbyl group having 1 to 5 carbon atoms which may have a heteroatom-containing group interposed between the carbon-carbon bonds. R 110is a linear or branched hydrocarbyl group having 1 to 5 carbon atoms which may have a heteroatom-containing group between its carbon-carbon bonds. R 111 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 —CH 2 A part of the - may be substituted with an ester bond or an ether bond. Z 1 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 is a single bond, *-C(=O)-O-, or *-C(=O)-NH-. * 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 - is. 31 is a single bond or a saturated hydrocarbylene group having 1 to 10 carbon atoms. 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.)

15. 8. The chemically amplified positive resist composition according to claim 7, further comprising a quencher.

16. 8. The chemically amplified positive resist composition according to claim 7, further comprising a photoacid generator other than the photoacid generator according to claim 5.

17. A method for forming a resist pattern, comprising the steps of: forming a resist film on a substrate using the chemically amplified positive resist composition according to any one of claims 7 to 16; exposing the resist film to high-energy rays; and developing the exposed resist film using an alkaline developer to obtain a resist pattern.

18. 18. The method for forming a resist pattern according to claim 17, wherein the high-energy radiation is extreme ultraviolet radiation or an electron beam.

19. 18. The method for forming a resist pattern according to claim 17, wherein the outermost surface of the substrate is made of a material containing chromium.

20. 18. The method of forming a resist pattern according to claim 17, wherein the substrate is a photomask blank.

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