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

Abstract

The present invention provides an onium salt that has an appropriate acid strength and is capable of generating an acid with little diffusion, a chemically amplified positive resist composition containing the onium salt, and a method of forming a resist pattern using the resist composition. The present invention provides an onium salt represented by the following formula (A): TIFF2026042362000334.tif25127 (In the formula, n1 is 0 or 1, n2 is 0 to 4, n3 is 1 to 4, n4 is 0 or 1, n5 is 0 to 4, and n6 is 0 to 4. However, when n1 is 0, 1≦n2+n3≦5, and when n1 is 1, 1≦n2+n3≦7. R 1 ~R 4 is a hydrocarbyl group having 1 to 20 carbon atoms, etc. A , L B and L C are each independently a single bond, an ether bond, an ester bond, a sulfonate ester bond, an amide bond, a sulfonamide bond, a carbonate bond, or a carbamate bond. L1 is a single bond or a hydrocarbylene group having 1 to 40 carbon atoms which may contain a heteroatom. Z+ is an onium cation.

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 increasing integration density 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. High-energy radiation such as ultraviolet light, far ultraviolet light, and electron beam (EB) radiation are used as exposure sources for this purpose. EB lithography, which is particularly utilized as an ultrafine processing technology, has also become essential as a processing method for photomask blanks when producing photomasks for semiconductor manufacturing. Resist compositions used in this type of photolithography include positive-type resists, which form patterns by dissolving exposed areas, and negative-type resists, which form patterns by leaving exposed areas intact. The most convenient type is selected based on the desired resist pattern.

[0003] Typically, EB lithography is performed without a mask. In the case of positive-tone resists, the EB is sequentially irradiated onto areas other than the desired resist film. In the case of negative-tone resists, the EB is sequentially irradiated onto the desired resist film. This process requires sweeping the EB across the entire finely divided area of ​​the processing surface, which takes longer than one-shot exposure using a photomask. To maintain throughput, the resist film must be highly sensitive. Furthermore, the long lithography time can easily lead to differences between the initial and later lithography regions, making the stability of the exposed area over time in vacuum a key performance requirement. Furthermore, in the processing of photomask blanks, which is a particularly important application, the photomask substrate often contains surface materials, such as chromium oxide and other chromium compounds, that can affect the pattern shape of the chemically amplified resist film. Maintaining a rectangular resist pattern profile, regardless of the type of substrate, is also crucial to maintaining high resolution and post-etching shape.

[0004] Various improvements have been made to the control of the sensitivity and pattern profile of the resist film described above, such as by selecting and combining materials used in the resist composition and by adjusting process conditions. One of these improvements addresses the issue of acid diffusion, which has a significant impact on the resolution of chemically amplified resist films. In photomask processing, it is required that the shape of the resulting resist pattern does not change over time until post-exposure bake (PEB). A major cause of time-dependent changes is the diffusion of acid generated by exposure. This issue of acid diffusion has been extensively investigated, not only in photomask processing but also in general resist compositions, as it has a significant impact 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, these acid generators are still insufficient in suppressing acid diffusion, and therefore, there has been a demand for the development of an acid generator with even smaller diffusion.

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

[0007] Polymers containing a large amount of aromatic skeletons with acidic side chains, such as polyhydroxystyrene, have been useful in resist compositions for KrF lithography, but have not been used as materials for resist compositions for ArF lithography because they exhibit high absorption of light with wavelengths around 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] The base polymers used in positive-tone EB lithography resist compositions and EUV lithography resist compositions are typically made of materials that, upon exposure to high-energy radiation, use an acid generated from a photoacid generator as a catalyst to deprotect the acid-labile groups (acid-labile protecting groups) that mask the acidic functional groups on the phenol side chains of the base polymer, rendering the polymer soluble in alkaline developers. Furthermore, tertiary alkyl groups, tert-butoxycarbonyl groups, acetal groups, and the like have typically been used as the acid-labile groups. While using protecting groups such as acetal groups, which require relatively low activation energy for deprotection, offers the advantage of producing highly sensitive resist films, insufficient suppression of the diffusion of the generated acid can lead to deprotection reactions in unexposed areas of the resist film, resulting in problems such as degradation of LER and reduced linewidth uniformity (CDU).

[0009] Furthermore, when a resin having a repeating unit with an acetal group is used with a sulfonium salt that generates a strong acid with a low pKa, such as the fluorinated alkanesulfonic acid described in Patent Document 4, a pattern with large LER is formed. That is, 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, and therefore, even if the diffusion of the acid is suppressed, the deprotection reaction proceeds due to the trace amount of acid that diffuses into the unexposed area.

[0010] Furthermore, Patent Documents 5 and 6 propose photoacid generators that generate non-fluorinated aromatic sulfonic acids having multiple bulky alkyl substituents, and Patent Document 7 proposes a photoacid generator with a triarylbenzenesulfonate anion structure. Patent Document 8 proposes a photoacid generator that generates non-fluorinated aromatic sulfonic acids into which an iodine-containing aromatic ring has been introduced. Although attempts are made to reduce acid diffusion by increasing the molecular weight of the generated acid through the use of multiple alkyl substituents, aromatic rings, and iodine atoms, the suppression of acid diffusion is still insufficient when the purpose is to form fine patterns, and there is still room for further improvement. [Prior art documents] [Patent documents]

[0011] [Patent Document 1] Japanese Patent Application Laid-Open No. 2009-053518 [Patent Document 2] Japanese Patent Application Laid-Open No. 2010-100604 [Patent Document 3] Japanese Patent Application Laid-Open No. 2011-22564 [Patent Document 4] Patent No. 5083528 [Patent Document 5] Patent No. 6248882 [Patent Document 6] Patent No. 7067271 [Patent Document 7] Patent No. 7032549 [Patent Document 8] Japanese Patent Application Publication No. 2023-177038 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. Patent Document 5 describes an acid generator that generates a bulky acid and suppresses acid diffusion, which yields patterns with excellent resolution and roughness, but which suffers from the problem of corner rounding occurring in hole patterns.

[0013] The present invention has been made in consideration of the above 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 with little diffusion, a chemically amplified positive resist composition containing the same, and a method of forming a resist pattern that uses the resist composition. [Means for solving the problem]

[0014] As a result of intensive research into achieving the above-mentioned object, the present inventors have found that when an onium salt that is a photoacid generator that generates a benzenesulfonic acid derivative, has a substituent on the carbon atom adjacent to the sulfo group of the anion, and further includes a triarylbenzene or diarylbenzene structure, is incorporated into a resist composition as an acid generator, the acid generated thereby has appropriate acidity and is prevented from excessive diffusion, thereby enabling a pattern with good resolution and small LER to be obtained, and furthermore, due to appropriate dissolution inhibition properties, a pattern with good rectangularity can be obtained. This finding 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 0 or 1. n2 is 0, 1, 2, 3, or 4. n3 is 1, 2, 3, or 4. n4 is 0 or 1. n5 is 0, 1, 2, 3, or 4. n6 is 0, 1, 2, 3, or 4. However, when n1 is 0, 1≦n2+n3≦5, and when n1 is 1, 1≦n2+n3≦7. R 1 is a hydrocarbyl group having 1 to 20 carbon atoms. R 2 is a halogen atom, a nitro group, a cyano group, a hydroxy group, a carboxy group, a hydrocarbyl group having 1 to 20 carbon atoms which may contain a heteroatom, a hydrocarbyloxy group having 1 to 20 carbon atoms which may contain a heteroatom, a hydrocarbylthio group having 1 to 20 carbon atoms which may contain a heteroatom, or a hydrocarbyloxycarbonyl group having 1 to 20 carbon atoms which may contain a heteroatom. When n2 is 2, 3, or 4, each R 2 may be the same or different, and multiple R 2 may be bonded to each other to form a ring together with the carbon atoms to which they are attached. R 3 is a halogen atom, a nitro group, a cyano group, a hydroxy group, a carboxy group, a hydrocarbyl group having 1 to 20 carbon atoms which may contain a heteroatom, a hydrocarbyloxy group having 1 to 20 carbon atoms which may contain a heteroatom, a hydrocarbylthio group having 1 to 20 carbon atoms which may contain a heteroatom, a hydrocarbyloxycarbonyl group having 1 to 20 carbon atoms which may contain a heteroatom, or a hydrocarbylcarbonyloxy group having 1 to 20 carbon atoms which may contain a heteroatom. When n5 is 2, 3, or 4, each R 3 may be the same or different, and multiple R 3 may be bonded to each other to form a ring together with the carbon atoms to which they are attached. R 4 is a halogen atom, a nitro group, a cyano group, a hydroxy group, a hydrocarbyl group having 1 to 20 carbon atoms which may contain a heteroatom, a hydrocarbyloxy group having 1 to 20 carbon atoms which may contain a heteroatom, or a hydrocarbylthio group having 1 to 20 carbon atoms which may contain a heteroatom. When n6 is 2, 3, or 4, each R 4 may be the same or different, but multiple R 4 do not bond to each other to form a ring together with the carbon atoms to which they are attached. L A , L B and LC are each independently a single bond, an ether bond, an ester bond, a sulfonate ester bond, an amide bond, a sulfonamide bond, a carbonate bond or a carbamate bond. X L1 is a single bond or a hydrocarbylene group having 1 to 40 carbon atoms which may contain a hetero atom. Z + is an onium cation. 2. An onium salt of formula 1, which is represented by the following formula (A1): [ka] (In the formula, n2, n3, n5, n6, R 1 ~R 4 , L A , L B , L C , X L1 and Z + is the same as above.) 3. An onium salt of 2 represented by the following formula (A2): [ka] (In the formula, n2, n3, n5, n6, R 1 ~R 4 , L A and Z + is the same as above.) 4.Z + is a sulfonium cation represented by the following formula (Z-1) or an iodonium cation represented by the following formula (Z-2). [ka] (In the formula, 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. 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.Z +is a sulfonium cation represented by the following formula (Z-3): [ka] (Wherein, m1 is 0 or 1. m2 is 0 or 1. m3 is 0 or 1. m4 is 0, 1, 2, 3 or 4. m5 is 0, 1, 2, 3 or 4. m6 is 0, 1, 2, 3, 4, 5 or 6. m7 is 0, 1, 2, 3, 4, 5 or 6. m8 is 0, 1 or 2. m9 is 0, 1 or 2. m10 is 0, 1 or 2. m11 is 0 or 1. m12 is 0, 1, 2, 3 or 4. m13 is 0, 1 or 2. m14 is 0, 1 or 2. However, when m1 is 0, 0≦m6+m9≦4, and when m1 is 1, 0≦m6+m9≦6. When m2 is 0, 0≦m7+m10≦4, and when m2 is 1, 0≦m7+m10≦6. When m3 is 0, 1≦m4+m5+m8+m14≦4, and when m3 is 1, 1≦m4+m5+m8+m14≦6. When m11 is 0, 0≦m12+m13≦4, and when m11 is 1, 0≦m12+m13≦6. Also, m4+m12≧1. R F1 ~R F3 are each independently a fluorine atom, a fluorinated saturated hydrocarbyl group having 1 to 6 carbon atoms, a fluorinated saturated hydrocarbyloxy group having 1 to 6 carbon atoms, or a fluorinated saturated hydrocarbylthio group having 1 to 6 carbon atoms. When m5 is 2 or more, each R F1 may be the same or different, and when m6 is 2 or more, each R F2 may be the same or different, and when m7 is 2 or more, each R F3 may be the same or different from each other. R ct6 ~R ct9is a halogen atom other than an iodine atom or a fluorine atom, a nitro group, a cyano group, a hydrocarbyl group having 1 to 20 carbon atoms which may contain a heteroatom, a hydrocarbyloxy group having 1 to 20 carbon atoms which may contain a heteroatom, or a hydrocarbylthio group having 1 to 20 carbon atoms which may contain a heteroatom. When m8 is 2, two R ct6 may be the same or different, and two R ct6 may be bonded to each other to form a ring together with the carbon atoms to which they are attached, and when m9 is 2, two R ct7 may be the same or different, and two R ct7 may be bonded to each other to form a ring together with the carbon atoms to which they are bonded, and when m10 is 2, two R ct8 may be the same or different, and two R ct8 may be bonded to each other to form a ring together with the carbon atoms to which they are bonded, and when m13 is 2, two R ct9 may be the same or different, and two R ct9 may be bonded to each other to form a ring together with the carbon atoms to which they are attached. In addition, S in the sulfonium cation + The aromatic rings directly bonded to S + may form a ring together with L D and L E are each independently a single bond, an ether bond, an ester bond, an amide bond, a sulfonate ester bond, a sulfonamide bond, a carbonate bond or a carbamate bond. X L2 is a single bond or a hydrocarbylene group having 1 to 40 carbon atoms which may contain a heteroatom. 6. A photoacid generator comprising an onium salt according to any one of 1 to 5. 7. A chemically amplified positive resist composition containing a photoacid generator according to claim 6. 8. A chemically amplified positive resist composition according to 7, further comprising a base polymer containing a polymer that decomposes under the action of an acid and has increased solubility in an alkaline developer. 9. The chemically amplified positive resist composition of 8, wherein the polymer contains a repeating unit represented by the following formula (B1): [ka] (In the formula, a1 is 0 or 1. a2 is 0, 1, or 2. a3 is an integer that satisfies 0≦a3≦5+2(a2)−a4. a4 is 1, 2, or 3. R A is a hydrogen atom, a fluorine atom, a methyl group, or a trifluoromethyl group. R 11 represents a halogen atom, a nitro group, a carboxy group, 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. A 1 represents a single bond or a saturated hydrocarbylene group having 1 to 10 carbon atoms, and some of the -CH2- in the saturated hydrocarbylene group may be substituted with -O-. 10. The chemically amplified positive resist composition of 8 or 9, wherein the polymer contains a repeating unit represented by the following formula (B2-1): [ka] (In the formula, R A is a hydrogen atom, a fluorine atom, a methyl group, or a trifluoromethyl group. b1 is 0 or 1. b2 is 0, 1, or 2. b3 is an integer that satisfies 0≦b3≦5+2(b2)−b4. b4 is 1, 2, or 3. b5 is 0 or 1. R 21 is 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. A 2is a single bond or a saturated hydrocarbylene group having 1 to 10 carbon atoms, and some of the -CH2- in the saturated hydrocarbylene group may be substituted with -O-. When b4 is 1, X is an acid labile group, and when b4 is 2 or 3, X is a hydrogen atom or an acid labile group, provided that at least one X is an acid labile group. 11. The chemically amplified positive resist composition of any one of 8 to 10, wherein the polymer contains a repeating unit represented by the following formula (B2-2): [ka] (In the formula, c1 is 0, 1 or 2; c2 is 0, 1 or 2; c3 is 0, 1, 2, 3, 4 or 5; and c4 is 0, 1 or 2. R A is a hydrogen atom, a fluorine atom, a methyl group, or a trifluoromethyl group. R 22 and R 23 are each independently a hydrocarbyl group having 1 to 10 carbon atoms which may contain a heteroatom, and R 22 and R 23 may be bonded to each other to form a ring together with the carbon atoms to which they are attached. R 24 are each independently a fluorine atom, a fluorinated alkyl group having 1 to 5 carbon atoms, or a fluorinated alkoxy group having 1 to 5 carbon atoms. R 25 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. A 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 a naphthylene group. 12. The chemically amplified positive resist composition of any one of 8 to 11, 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 0, 1, 2, 3, 4, 5, or 6. e is 0, 1, 2, 3, or 4. f1 is 0 or 1. f2 is 0, 1, or 2. f3 is 0, 1, 2, 3, 4, or 5. R A is a hydrogen atom, a fluorine atom, a methyl group, or a trifluoromethyl group. R 31 and R 32 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. R 33 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 represents a single bond or a saturated hydrocarbylene group having 1 to 10 carbon atoms, and some of the -CH2- in the saturated hydrocarbylene group may be substituted with -O-. 13. The chemically amplified positive resist composition of any one of 8 to 12, wherein the polymer comprises at least one selected from the group consisting of 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), and a repeating unit represented by the following formula (B10). [ka] (In the formula, g1 and g2 are each independently 0, 1, 2, or 3. h1 is 0 or 1. h2 is 0, 1, 2, 3, or 4. h3 is 0, 1, 2, 3, or 4. However, when h1 is 0, 0≦h2+h3≦4, and when h1 is 1, 0≦h2+h3≦6. R A are each independently a hydrogen atom, a fluorine atom, a methyl group, or a trifluoromethyl group. Z 1 represents a single bond or an optionally substituted phenylene group. Z 2 is a single bond, **-C(=O)-OZ 21 -, **-C(=O)-NH-Z 21 -or **-OZ 21 -It is. Z 21 represents an aliphatic hydrocarbylene group having 1 to 6 carbon atoms, a phenylene group, or a divalent group obtained by combining these, and may contain a halogen atom, a carbonyl group, an ester bond, an ether bond, or a hydroxy group. Z 3 is a single bond, an ether bond, an ester bond, an amide bond, a sulfonate ester bond, a sulfonamide bond, a carbonate bond or a carbamate bond. Z 4 represents a single bond, an aliphatic hydrocarbylene group having 1 to 6 carbon atoms, a phenylene group, or a divalent group obtained by combining these, and may contain a halogen atom, a carbonyl group, an ester bond, an ether bond, or a hydroxy group. Z 5 each independently represents a single bond, an optionally substituted phenylene group, a naphthylene group, or *-C(=O)-OZ 51 -It is. Z 51 is an aliphatic hydrocarbylene group having 1 to 10 carbon atoms, a phenylene group, or a naphthylene group, and the aliphatic hydrocarbylene group may contain a halogen atom, a hydroxy group, an ether bond, an ester bond, or a lactone ring. Z 6is a single bond, an ether bond, an ester bond, an amide bond, a sulfonate ester bond, a sulfonamide bond, a carbonate bond or a carbamate bond. Z 7 are each independently a single bond, ***-Z 71 -C(=O)-O-, ***-C(=O)-NH-Z 71 -or***-OZ 71 -It is. It is. Z 71 is a hydrocarbylene group having 1 to 20 carbon atoms which may contain a heteroatom. Z 8 are each independently a single bond, ****-Z 81 -C(=O)-O-, ****-C(=O)-NH-Z 81 -or ****-OZ 81 -It is. Z 81 is a hydrocarbylene group having 1 to 20 carbon atoms which may contain a heteroatom. Z 9 represents a single bond, a methylene group, an ethylene group, a phenylene group, a fluorinated phenylene group, a phenylene group substituted with a trifluoromethyl group, *-C(=O)-OZ 91 -, *-C(=O)-N(H)-Z 91 -or*-OZ 91 -It is. Z 91 represents an aliphatic hydrocarbylene group having 1 to 6 carbon atoms, a phenylene group, a fluorinated phenylene group, or a phenylene group substituted with a trifluoromethyl group, and may contain a carbonyl group, an ester bond, an ether bond, or a hydroxy group. * represents a bond to a carbon atom in the main chain. ** represents Z 1 *** represents a bond with Z 6 **** represents a bond with Z 7 Represents a bond with . L 1 is a single bond, an ether bond, an ester bond, a carbonyl group, a sulfonate ester bond, a sulfonamide bond, a carbonate bond or a carbamate bond. Rf 1 and Rf 2are each independently a fluorine atom or a fluorinated saturated hydrocarbyl group having 1 to 6 carbon atoms. Rf 3 and Rf 4 are each independently a hydrogen atom, a fluorine atom, or a fluorinated saturated hydrocarbyl group having 1 to 6 carbon atoms. Rf 5 and Rf 6 are each independently a hydrogen atom, a fluorine atom, or a fluorinated saturated hydrocarbyl group having 1 to 6 carbon atoms, provided that all Rf 5 and Rf 6 cannot simultaneously become a hydrogen atom. Rf 7 is a fluorine atom, a fluorinated alkyl group having 1 to 6 carbon atoms, a fluorinated alkoxy group having 1 to 6 carbon atoms, or a fluorinated alkylthio group having 1 to 6 carbon atoms. R 41 and R 42 are each independently a hydrocarbyl group having 1 to 20 carbon atoms which may contain a heteroatom. 41 and R 42 may be bonded to each other to form a ring together with the sulfur atom to which they are attached. R 43 is a hydrocarbyl group having 1 to 20 carbon atoms which may contain a halogen atom other than a fluorine atom or a heteroatom. When h3 is 2, 3, or 4, each R 43 may be the same or different, and multiple R 43 may be bonded to each other to form a ring together with the carbon atoms to which they are attached. M - is a non-nucleophilic counterion. A + is an onium cation. 14. The chemically amplified positive resist composition of any one of 8 to 13, wherein the content of repeating units having an aromatic ring skeleton in all repeating units of the polymer contained in the base polymer is 60 mol % or more. 15. The chemically amplified positive resist composition of any one of 7 to 14, further comprising an organic solvent. 16. The chemically amplified positive resist composition of any one of 7 to 15, further comprising a quencher. 17. The chemically amplified positive resist composition of any of 7 to 16, further comprising a fluorine atom-containing polymer that contains at least one selected from the group consisting of a repeating unit represented by the following formula (E1), a repeating unit represented by the following formula (E2), a repeating unit represented by the following formula (E3), and a repeating unit represented by the following formula (E4), and that may further contain at least one selected from the group consisting of a repeating unit represented by the following formula (E5) and a repeating unit represented by the following formula (E6): [ka] (In the formula, j1 is 1, 2, or 3. j2 is an integer that satisfies 0≦j2≦5+2(j3)−j1. j3 is 0 or 1. k is 1, 2, or 3. R B are each independently 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 201 , R 202 , R 204 and R 205 are each independently a hydrogen atom or a saturated hydrocarbyl group having 1 to 10 carbon atoms. R 203 , R 206 , R 207 and R 208 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, and R 203 , R 206 , R 207 and R 208 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 209 is a hydrogen atom or a linear or branched hydrocarbyl group having 1 to 5 carbon atoms which may have a group containing a hetero atom interposed between its carbon-carbon bond. R 210is a linear or branched hydrocarbyl group having 1 to 5 carbon atoms which may have a group containing a hetero atom interposed between its carbon-carbon bond. R 211 is a saturated hydrocarbyl group having 1 to 20 carbon atoms in which at least one hydrogen atom has been substituted with a fluorine atom, and some of the -CH2- groups in the saturated hydrocarbyl group may be substituted with an ester bond or an ether bond. X 1 is a (k+1)-valent hydrocarbon group having 1 to 20 carbon atoms or a (k+1)-valent fluorinated hydrocarbon group having 1 to 20 carbon atoms. X 2 is a single bond, *-C(=O)-O-, or *-C(=O)-NH-. * is a bond to a carbon atom in the main chain. X 3 is a single bond, -O-, *-C(=O)-OX 31 -X 32 - or *-C(=O)-NH-X 31 -X 32 -X 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. 18. The chemically amplified positive resist composition of any one of 7 to 17, further comprising a photoacid generator other than the photoacid generator of 6. 19. 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 of any one of 7 to 18, irradiating the resist film with a pattern using high-energy rays, and developing the resist film irradiated with the pattern using an alkaline developer. 20. The method for forming a resist pattern according to 19, wherein the high-energy radiation is EUV or EB having a wavelength of 3 to 15 nm. 21. The method for forming a resist pattern according to 19 or 20, wherein the outermost surface of the substrate is made of a material containing chromium. 22. The method for forming a resist pattern according to any one of 19 to 21, wherein the substrate is a photomask blank. [Effects of the Invention]

[0016] A chemically amplified positive resist composition containing the onium salt of the present invention as a photoacid generator exhibits extremely high resolution and can provide patterns with small LER in microfabrication techniques, particularly EB lithography and EUV lithography. Furthermore, due to its moderate dissolution inhibition properties, it can provide patterns with good rectangularity, making it suitable as a chemically amplified positive resist material. [Brief explanation of the drawings]

[0017] [Figure 1] 1 is a nuclear magnetic resonance spectrum (H-NMR / DMSO-d) of the onium salt PAG-1 synthesized in Example 1-1. DETAILED DESCRIPTION OF THE INVENTION

[0018] The present invention will be described in detail below. In the following description, some structures represented by chemical formulas may have asymmetric carbon atoms, and enantiomers or diastereomers may exist. In such cases, a single formula will be used to represent all isomers. These isomers may be used singly or as a mixture of two or more.

[0019] [Onium salts] The onium salt of the present invention is represented by the following formula (A). [ka]

[0020] In formula (A), n1 is 0 or 1. When n1 is 0, it is a benzene ring, and when n1 is 1, it is a naphthalene ring; however, from the viewpoint of solvent solubility, it is preferable that n1 is a benzene ring of 0. n2 is 0, 1, 2, 3, or 4. From the viewpoint of raw material procurement, it is preferable that n2 is 0 or 1. n3 is 1, 2, 3, or 4. From the viewpoint of raw material procurement, it is preferable that n3 is 1, 2, or 3; from the viewpoint of acid diffusion control, it is preferable that n3 is 2 or 3. n4 is 0 or 1. When n4 is 0, it is a benzene ring, and when n4 is 1, it is a naphthalene ring; however, from the viewpoint of solvent solubility, it is preferable that n4 is a benzene ring of 0. n5 is 0, 1, 2, 3, or 4. From the viewpoint of raw material procurement, it is preferable that n5 is 0, 1, 2, or 3. n6 is 0, 1, 2, 3, or 4. From the viewpoint of raw material procurement, it is preferable that n6 is 1 or 2. However, when n1 is 0, 1≦n4+n5≦5, and when n1 is 1, 1≦n4+n5≦7.

[0021] In formula (A), R 1 is a hydrocarbyl group having 1 to 20 carbon atoms. The hydrocarbyl group may be saturated or unsaturated, and may be linear, branched, or cyclic. Specific examples thereof include an isopropyl group, a sec-butyl group, a tert-butyl group, a tert-pentyl group, a 2-ethylhexyl group, Alkyl groups having 1 to 20 carbon atoms, such as methyl, ethyl, n-propyl, isopropyl, n-butyl, sec-butyl, tert-butyl, n-pentyl, tert-pentyl, n-hexyl, n-octyl, 2-ethylhexyl, n-nonyl, and n-decyl groups; cyclopentyl, cyclohexyl, cyclopentylmethyl, cyclopentylethyl, cyclopentylbutyl, cyclohexylmethyl, cyclohexylethyl, cyclohexylbutyl, norbornyl, and tricyclo[5.2.1.0] 2,6 ] aliphatic cyclic hydrocarbyl groups having 3 to 20 carbon atoms such as a decyl group and an adamantyl group; aryl groups having 6 to 20 carbon atoms such as a phenyl group, a naphthyl group and anthracenyl group; and groups obtained by combining these groups, but are not limited to these. 1Preferred examples of the alkyl group 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; aliphatic cyclic hydrocarbyl groups having 3 to 20 carbon atoms, such as a cyclopentyl group and a cyclohexyl group; and aryl groups having 6 to 20 carbon atoms, such as a phenyl group and a naphthyl group.

[0022] In formula (A), R 2is a halogen atom, a nitro group, a cyano group, a hydroxy group, a carboxy group, a hydrocarbyl group having 1 to 20 carbon atoms which may contain a heteroatom, a hydrocarbyloxy group having 1 to 20 carbon atoms which may contain a heteroatom, a hydrocarbylthio group having 1 to 20 carbon atoms which may contain a heteroatom, or a hydrocarbyloxycarbonyl group having 1 to 20 carbon atoms which may contain a heteroatom. Examples of the halogen atom include a fluorine atom, a chlorine atom, a bromine atom, and an iodine atom, with a fluorine atom or an iodine atom being preferred. The hydrocarbyl group may be saturated or unsaturated and may be linear, branched, or cyclic. Specific examples thereof include alkyl groups having 1 to 20 carbon atoms, such as methyl, ethyl, n-propyl, isopropyl, n-butyl, and tert-butyl; saturated cyclic hydrocarbyl groups having 3 to 20 carbon atoms, such as cyclopropyl, cyclopentyl, cyclohexyl, cyclopropylmethyl, 4-methylcyclohexyl, cyclohexylmethyl, norbornyl, and adamantyl; alkenyl groups having 2 to 20 carbon atoms, such as vinyl, allyl, propenyl, butenyl, and hexenyl; unsaturated cyclic hydrocarbyl groups having 3 to 20 carbon atoms, such as cyclohexenyl; aryl groups having 6 to 20 carbon atoms, such as phenyl and naphthyl; aralkyl groups having 7 to 20 carbon atoms, such as benzyl, 1-phenylethyl, and 2-phenylethyl; 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 group containing a heteroatom such as an oxygen atom, a sulfur atom, a nitrogen atom or a halogen atom, and some of the -CH2- constituting the hydrocarbyl group may be substituted with a group containing a heteroatom such as an oxygen atom, a sulfur atom or a nitrogen atom, resulting in the hydrocarbyl group containing a hydroxy group, a cyano group, a fluorine atom, a chlorine atom, a bromine atom, an iodine atom, a carbonyl group, an ether bond, an ester bond, a sulfonate ester bond, a carbonate bond, a lactone ring, a sultone ring, a carboxylic acid anhydride, a haloalkyl group, etc. When n2 is 2, 3 or 4, multiple R 2 may be the same as or different from each other.

[0023] When n2 is 2, 3, or 4, multiple R2 However, they may be bonded to each other to form a ring together with the carbon atoms to which they are bonded. In this case, the ring is preferably a 5- to 8-membered ring.

[0024] In formula (A), R 3 R is a halogen atom, a nitro group, a cyano group, a hydroxy group, a carboxy group, a hydrocarbyl group having 1 to 20 carbon atoms which may contain a heteroatom, a hydrocarbyloxy group having 1 to 20 carbon atoms which may contain a heteroatom, a hydrocarbylthio group having 1 to 20 carbon atoms which may contain a heteroatom, a hydrocarbyloxycarbonyl group having 1 to 20 carbon atoms which may contain a heteroatom, or a hydrocarbylcarbonyloxy group having 1 to 20 carbon atoms which may contain a heteroatom. 3 Specific examples of the halogen atom and the hydrocarbyl moiety of the hydrocarbyl group, hydrocarbyloxy group, hydrocarbylthio group, hydrocarbyloxycarbonyl group and hydrocarbylcarbonyloxy group represented by the formula: 2 Specific examples of the halogen atom and hydrocarbyl group represented by the formula (I) include, but are not limited to, the same as those exemplified above. When n5 is 2, 3 or 4, a plurality of R 3 may be the same as or different from each other.

[0025] Also, when n5 is 2, 3, or 4, multiple R 3 However, they may be bonded to each other to form a ring together with the carbon atoms to which they are bonded. In this case, the ring is preferably a 5- to 8-membered ring.

[0026] In formula (A), R 4 R is a halogen atom, a nitro group, a cyano group, a hydroxy group, a hydrocarbyl group having 1 to 20 carbon atoms which may contain a heteroatom, a hydrocarbyloxy group having 1 to 20 carbon atoms which may contain a heteroatom, or a hydrocarbylthio group having 1 to 20 carbon atoms which may contain a heteroatom. The hydrocarbyl group may be saturated or unsaturated, and may be linear, branched, or cyclic. 4 A specific example of this is R 2Examples include, but are not limited to, the following: 4 is preferably a hydrocarbyl group having 1 to 20 carbon atoms, more preferably an alkyl group having 1 to 20 carbon atoms, an aliphatic cyclic hydrocarbyl group having 3 to 20 carbon atoms, or an aryl group having 6 to 20 carbon atoms. 4 is -SO3 - Preferably, R is bonded to the ortho or meta position of R. 4 Ga-SO3 - If bonded to the ortho position of R 4 As the alkyl group, a branched alkyl group having 3 to 20 carbon atoms, an aliphatic cyclic hydrocarbyl group having 3 to 20 carbon atoms, or an aryl group having 6 to 20 carbon atoms is preferred.

[0027] In formula (A), L A , L B and L C are each independently a single bond, an ether bond, an ester bond, a sulfonate ester bond, an amide bond, a sulfonamide bond, a carbonate bond or a carbamate bond. A is preferably a single bond, an ether bond, an ester bond or a sulfonate ester bond, and more preferably an ester bond or a sulfonate ester bond. B is preferably a single bond, an ether bond, an ester bond or a sulfonate ester bond, and more preferably a single bond, an ester bond or a sulfonate ester bond. C is preferably a single bond, an ether bond, an ester bond or a sulfonate ester bond, and more preferably a single bond, an ester bond or a sulfonate ester bond. B is -SO3 - It is preferred that the bond is at the para position of

[0028] In formula (A), X Lis a single bond or a hydrocarbylene group having 1 to 40 carbon atoms which may contain a heteroatom. The hydrocarbylene group may be linear, branched, or cyclic, and specific examples thereof include an alkanediyl group and a cyclic saturated hydrocarbylene group. Specific examples of the heteroatom include an oxygen atom, a nitrogen atom, and a sulfur atom.

[0029] X L Specific examples of the hydrocarbylene group having 1 to 40 carbon atoms and optionally containing a hetero atom, represented by the formula (I), include, but are not limited to, those shown below. In the formula (I), * represents L A and L B Represents a bond with . [ka]

[0030] [ka]

[0031] [ka]

[0032] [ka]

[0033] Of these, X L -0~X L -22 and X L -47~X L -58 is preferred.

[0034] The onium salt represented by formula (A) is preferably one represented by the following formula (A1). [ka] (In the formula, n2, n3, n5, n6, R 1 ~R 4 , LA , L B , L C , X L1 and Z + is the same as above.)

[0035] The onium salt represented by formula (A1) is preferably one represented by the following formula (A2). [ka] (In the formula, n2, n3, n5, n6, R 1 ~R 4 , L A and Z + is the same as above.)

[0036] Particularly preferred examples of the anion of the onium salt represented by formula (A) include, but are not limited to, those shown below. [ka]

[0037] [ka]

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[0116] In formula (A), Z +is an onium cation. The onium cation is preferably a sulfonium cation represented by the following formula (Z-1) or an iodonium cation represented by the following formula (Z-2). [ka]

[0117] In formulas (Z-1) and (Z-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.

[0118] R ct1 ~R ct5 Specific examples of the halogen atom represented by the formula (I) include a fluorine atom, a chlorine atom, a bromine atom, and an iodine atom.

[0119] R ct1 ~R ct5The hydrocarbyl group represented by the formula (I) may be saturated or unsaturated, and may be linear, branched, or cyclic. Specific examples thereof include alkyl groups having 1 to 30 carbon atoms, such as methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, and tert-butyl; saturated cyclic hydrocarbyl groups having 3 to 30 carbon atoms, such as cyclopropyl, cyclopentyl, cyclohexyl, cyclopropylmethyl, 4-methylcyclohexyl, cyclohexylmethyl, norbornyl, and adamantyl; alkenyl groups having 2 to 30 carbon atoms, such as vinyl, 1-propenyl, 2-propenyl, butenyl, and hexenyl; unsaturated cyclic hydrocarbyl groups having 3 to 30 carbon atoms, such as cyclohexenyl; aryl groups having 6 to 30 carbon atoms, such as phenyl, naphthyl, and thienyl; aralkyl groups having 7 to 30 carbon atoms, such as benzyl, 1-phenylethyl, and 2-phenylethyl; and groups obtained by combining these, with aryl groups being preferred. Furthermore, some or all of the hydrogen atoms of the hydrocarbyl group may be substituted with a group containing a heteroatom such as an oxygen atom, a sulfur atom, a nitrogen atom or a halogen atom, and some of the -CH- groups of the hydrocarbyl group may be substituted with a group containing a heteroatom such as an oxygen atom, a sulfur atom or a nitrogen atom, and as a result, the hydrocarbyl group may contain a hydroxy group, a fluorine atom, a chlorine atom, a bromine atom, an iodine atom, a cyano group, a nitro group, a carbonyl group, an ether bond, an ester bond, a sulfonate ester bond, a carbonate bond, a lactone ring, a sultone ring, a carboxylic anhydride (-C(=O)-OC(=O)-), a haloalkyl group, etc.

[0120] Also, R ct1 and R ct2 However, they may be bonded to each other to form a ring together with the sulfur atom to which they are bonded. In this case, specific examples of the ring structure include those represented by the following formulas. [ka] (In the formula, the dashed line indicates R ct3 )

[0121] Specific examples of the sulfonium cation represented by formula (Z-1) include those described in paragraphs

[0102] to

[0125] of JP-A No. 2024-003744 and those described in paragraphs

[0070] to

[0085] of JP-A No. 2023-169812, but are not limited thereto.

[0122] Specific examples of the iodonium cation represented by formula (Z-2) include, but are not limited to, those described in paragraph

[0181] of JP-A No. 2024-000259.

[0123] Z + As the onium cation represented by the formula (Z-1), a sulfonium cation represented by the following formula (Z-3) is also preferred. [ka]

[0124] In formula (Z-3), m1 is 0 or 1. When m1 is 0, it is a benzene ring, and when m1 is 1, it is a naphthalene ring, but from the viewpoint of solvent solubility, it is preferably a benzene ring with m1 being 0. m2 is 0 or 1. When m2 is 0, it is a benzene ring, and when m2 is 1, it is a naphthalene ring, but from the viewpoint of solvent solubility, it is preferably a benzene ring with m1 being 0. m3 is 0 or 1. When m3 is 0, it is a benzene ring, and when m3 is 1, it is a naphthalene ring, but from the viewpoint of solvent solubility, it is preferably a benzene ring with m3 being 0.

[0125] In formula (Z-3), m4 is 0, 1, 2, 3, or 4. As the number of iodine atoms in the cation structure increases, absorption, particularly of EUV, increases. However, solvent solubility decreases, raising concerns about precipitation in the resist composition. Therefore, m4 is preferably 0, 1, 2, or 3, and more preferably 0, 1, or 2.

[0126] In formula (Z-3), m5 is 0, 1, 2, 3, or 4. From the viewpoint of raw material procurement, m5 is preferably 0, 1, 2, or 3, and more preferably 0, 1, or 2. m6 is 0, 1, 2, 3, 4, 5, or 6. From the viewpoint of raw material procurement, m6 is preferably 0, 1, 2, or 3, and more preferably 0, 1, or 2. m7 is 0, 1, 2, 3, 4, 5, or 6. From the viewpoint of raw material procurement, m7 is preferably 0, 1, 2, or 3, and more preferably 0, 1, or 2.

[0127] In formula (Z-3), m8 is 0, 1, or 2. From the viewpoint of raw material procurement, m8 is preferably 0 or 1. m9 is 0, 1, or 2. From the viewpoint of raw material procurement, m9 is preferably 0 or 1. m10 is 0, 1, or 2. From the viewpoint of raw material procurement, m10 is preferably 0 or 1.

[0128] In formula (Z-3), m11 is 0 or 1. When m11 is 0, it is a benzene ring, and when m11 is 1, it is a naphthalene ring, but from the viewpoint of solvent solubility, it is preferable that m11 is 0 and is a benzene ring.

[0129] In formula (Z-3), m12 is 0, 1, 2, 3, or 4. As the number of iodine atoms in the cation structure increases, absorption, particularly of EUV, increases. However, solvent solubility decreases, raising concerns about precipitation in the resist composition. Therefore, m12 is preferably 0, 1, 2, or 3, and more preferably 0, 1, or 2.

[0130] In formula (Z-3), m13 is 0, 1 or 2. From the viewpoint of raw material procurement, m13 is preferably 0 or 1. m14 is 0, 1 or 2. From the viewpoint of synthesis, m14 is preferably 0 or 1.

[0131] However, when m1 is 0, 0≦m6+m9≦4, and when m1 is 1, 0≦m6+m9≦6. When m2 is 0, 0≦m7+m10≦4, and when m2 is 1, 0≦m7+m10≦6. When m3 is 0, 1≦m4+m5+m8+m14≦4, and when m3 is 1, 1≦m4+m5+m8+m14≦6. When m11 is 0, 0≦m12+m13≦4, and when m11 is 1, 0≦m12+m13≦6. Also, m4+m12≧1.

[0132] In formula (Z-3), R F1 ~R F3 are each independently a fluorine atom, a fluorinated saturated hydrocarbyl group having 1 to 6 carbon atoms, a fluorinated saturated hydrocarbyloxy group having 1 to 6 carbon atoms, or a fluorinated saturated hydrocarbylthio group having 1 to 6 carbon atoms. Among these, a trifluoromethyl group, a trifluoromethoxy group, or a trifluorothiomethoxy group is preferred. When m5 is 2 or more, each R F1 may be the same or different, and when m6 is 2 or more, each R F2 may be the same or different, and when m7 is 2 or more, each R F3 may be the same or different from each other.

[0133] In formula (Z-3), R ct6 ~R ct9 is a halogen atom other than iodine and fluorine atoms, a nitro group, a cyano group, a hydrocarbyl group having 1 to 20 carbon atoms which may contain a heteroatom, a hydrocarbyloxy group having 1 to 20 carbon atoms which may contain a heteroatom, or a hydrocarbylthio group having 1 to 20 carbon atoms which may contain a heteroatom. The hydrocarbyl group and the hydrocarbyl moiety of the hydrocarbyloxy group and hydrocarbylthio group may be saturated or unsaturated, and may be linear, branched, or cyclic. Specific examples thereof include R 1In addition, some or all of the hydrogen atoms in the hydrocarbyl moiety of the hydrocarbyl group, hydrocarbyloxy group, and hydrocarbylthio group may be substituted with a group containing a heteroatom such as an oxygen atom, sulfur atom, nitrogen atom, or halogen atom, and some of the -CH2- in the hydrocarbyl group may be substituted with a group containing a heteroatom such as an oxygen atom, sulfur atom, or nitrogen atom, so that the hydrocarbyl group may contain a hydroxy group, cyano group, fluorine atom, chlorine atom, bromine atom, iodine atom, carbonyl group, ether bond, ester bond, sulfonate ester bond, carbonate bond, lactone ring, sultone ring, carboxylic anhydride (-C(=O)-OC(=O)-), haloalkyl group, etc.

[0134] Also, when m8 is 2, two R ct6 may be the same or different, and two R ct6 may be bonded to each other to form a ring together with the carbon atoms to which they are attached, and when m9 is 2, two R ct7 may be the same or different, and two R ct7 may be bonded to each other to form a ring together with the carbon atoms to which they are bonded, and when m10 is 2, two R ct8 may be the same or different, and two R ct8 may be bonded to each other to form a ring together with the carbon atoms to which they are bonded, and when m13 is 2, two R ct9 may be the same or different, and two R ct9may be bonded to each other to form a ring together with the carbon atoms to which they are bonded. Specific 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. Furthermore, 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 -CH- groups in the ring may be substituted with a group containing a heteroatom such as an oxygen atom, a sulfur atom, or a nitrogen atom, resulting in the ring containing a hydroxy group, a fluorine atom, a chlorine atom, a bromine atom, an iodine atom, a cyano group, a carbonyl group, an ether bond, an ester bond, a sulfonate ester bond, a carbonate bond, a lactone ring, a sultone ring, a carboxylic anhydride (-C(=O)-OC(=O)-), a haloalkyl group, or the like.

[0135] In addition, S in the sulfonium cation represented by formula (Z-3) + The aromatic rings directly bonded to S + In this case, specific examples of the ring structure include those represented by the following formulas: [ka]

[0136] In formula (Z-3), L D and L E are each independently a single bond, an ether bond, an ester bond, an amide bond, a sulfonate ester bond, a sulfonamide bond, a carbonate bond, or a carbamate bond. D is preferably a single bond, an ether bond, an ester bond or a sulfonate ester bond, and more preferably an ester bond or a sulfonate ester bond. E is preferably a single bond, an ether bond or an ester bond, and more preferably a single bond.

[0137] In formula (Z-3), X L2is a single bond or a hydrocarbylene group having 1 to 40 carbon atoms which may contain a hetero atom. Specific examples of the hydrocarbylene group having 1 to 40 carbon atoms which may contain a hetero atom include X L1 Specific examples of the hydrocarbylene group having 1 to 40 carbon atoms and optionally containing a hetero atom, represented by the following formula, include, but are not limited to, the same as those exemplified above.

[0138] The sulfonium cation represented by formula (Z-3) is preferably one represented by the following formula (Z-3-1). [ka] (In the formula, m4~m10, m12~m14, R F1 ~R F3 , R ct6 ~R ct9 , L D , L E and X L is the same as above.)

[0139] The cation represented by formula (Z-3-1) is preferably one represented by the following formula (Z-3-2). [ka] (In the formula, m4~m10, R F1 ~R F3 and R ct6 ~R ct8 is the same as above.)

[0140] Specific examples of the sulfonium cation represented by formula (Z-3) include, but are not limited to, the following: In the following formula, Me is a methyl group. [ka]

[0141] [ka]

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[0167] [ka]

[0168] Specific examples of the onium salt of the present invention include any combination of the above-mentioned anions and cations.

[0169] The onium salt of the present invention can be synthesized by a known method. As an example, a method for producing the onium salt represented by the following formula (PAG-1-ex) will be described. [ka] (In the formula, n1~n6, R 1 ~R 4 , L C and Z + is the same as above. + is an alkali metal cation.

[0170] The first step is to obtain aromatic sulfonate chloride intermediate In-1 by reacting alkali metal salt SM-1 of sulfonate anion, which is commercially available or can be synthesized by a known synthetic method, with oxalyl chloride or thionyl chloride. The reaction can be carried out by a known organic synthesis method. Specifically, starting material SM-1 is dissolved in a halogenated solvent such as methylene chloride or chloroform, and oxalyl chloride or thionyl chloride is added dropwise to the solution. The reaction can be accelerated by adding a catalytic amount of N,N-dimethylformamide. Heating is recommended as needed. The reaction temperature ranges from room temperature to the boiling point of the solvent used, but heating is preferred for smooth reaction progression. The reaction time is typically 2 to 10 hours, although tracking the reaction by silica gel thin-layer chromatography (TLC) to complete the reaction is desirable from the viewpoint of yield. The reaction is then quenched with water, and the target product is extracted from the reaction mixture. Intermediate In-1 can be obtained by conventional aqueous work-up. The resulting intermediate In-1 can be purified, if necessary, by a conventional method such as chromatography or recrystallization.

[0171] The second step is a sulfonate esterification reaction between intermediate In-1 and hydroxyaromatic sulfonate SM-2 to obtain aromatic sulfonate onium salt PAG-1-ex. The reaction can be carried out according to a conventional method. Examples of solvents that can be used in the reaction include water; ethers such as 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 chlorinated organic solvents such as methylene chloride, chloroform, and carbon tetrachloride. These solvents can be selected appropriately depending on the reaction conditions. They may be used alone or in combination. Intermediate In-1, hydroxyaromatic sulfonate SM-2, and a base are added sequentially or simultaneously to these solvents, and the reaction is carried out with cooling or heating as necessary. Examples of bases that can be used in the reaction include ammonia; amines such as triethylamine, pyridine, lutidine, collidine, and N,N-dimethylaniline; hydroxides such as sodium hydroxide, potassium hydroxide, and tetramethylammonium hydroxide; and carbonates such as potassium carbonate and sodium bicarbonate. These bases may be used alone or in combination. It is desirable to monitor the progress of the reaction by TLC in terms of yield. The onium salt PAG-1-ex can be obtained by subjecting the resulting reaction solution to a standard aqueous workup. If necessary, the product can be purified by standard methods such as chromatography and recrystallization.

[0172] The onium salt represented by formula (A) is an onium salt of sulfonic acid that is not substituted with fluorine atoms, and therefore can generate an acid of appropriate strength upon irradiation with high-energy radiation. It also has a triarylbenzene or diarylbenzene structure, and various functional groups can be introduced into the aryl group. Therefore, functional groups are preferred for the aryl group. When the functional group contains a hydrocarbyloxycarbonyl group, the presence of multiple heteroatoms via ester bonds can reduce acid diffusion. Furthermore, when the functional group contains a halogen atom, particularly a fluorine atom, the onium salt itself exhibits increased solvent solubility, improving uniform dispersion. This also increases the acidity of the generated sulfonic acid, thereby accelerating the deprotection reaction of the base polymer's protecting groups and potentially improving resolution. Furthermore, when the onium salt contains a branched alkyl group or an alicyclic group, the excluded volume of the anion increases, resulting in a bulky structure, which generates a low-diffusion acid, thereby improving LER and other issues. Furthermore, the multiple aromatic rings in the anion have improved compatibility with the aromatic rings in the base polymer through mutual (π-π stacking interactions), which is expected to have the effect of suppressing excessive acid diffusion. These effects enable the acid with excessive acid strength and acid diffusion controlled to be uniformly generated in the resist film, resulting in patterns with good resolution and small LER even in fine patterns, and in positive resist compositions using alkaline developers, the moderate dissolution inhibition properties enable patterns with good rectangularity to be obtained.

[0173] The onium salt of the present invention can be suitably used as a photoacid generator.

[0174] [Chemically amplified positive resist composition] [(A) Photoacid generator] The chemically amplified positive resist composition of the present invention contains, as an essential component, component (A), a photoacid generator comprising an onium salt represented by formula (A).

[0175] In the chemically amplified positive resist composition of the present invention, the content of the (A) photoacid generator is preferably 0.1 to 40 parts by mass, and more preferably 1 to 20 parts by mass, relative to 80 parts by mass of the (B) base polymer described below. When the content of the (A) photoacid generator is within the above range, an amount of acid necessary for deprotecting the acid labile groups is generated, and storage stability is also good. The (A) photoacid generators may be used alone, or two or more may be used in combination.

[0176] [(B) Base polymer] The resist composition of the present invention contains, as component (B), a base polymer that contains a polymer that decomposes under the action of an acid and exhibits increased solubility in an alkaline developer.

[0177] 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]

[0178] In formula (B1), a1 is 0 or 1. a2 is 0, 1, or 2; when it is 0, it is a benzene skeleton, when it is 1, it is a naphthalene skeleton, and when it is 2, it is an anthracene skeleton. a3 is an integer that satisfies 0≦a3≦5+2(a2)−a4. a4 is 1, 2, or 3. When a2 is 0, a3 is preferably 0, 1, 2, or 3, and a4 is 1, 2, or 3; when a2 is 1 or 2, a3 is preferably 0, 1, 2, 3, or 4, and a4 is 1, 2, or 3.

[0179] In formula (B1), R A is a hydrogen atom, a fluorine atom, a methyl group, or a trifluoromethyl group.

[0180] In formula (B1), R 11is a halogen atom, a nitro group, a carboxy group, 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 and the saturated hydrocarbyl moiety of the saturated hydrocarbyloxy group and saturated hydrocarbylcarbonyloxy group may be linear, branched, or cyclic. Specific examples 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. When the number of carbon atoms is equal to or less than the upper limit, the solubility in alkaline developers is good. When a3 is 2 or more, each R 11 may be the same as or different from each other.

[0181] In formula (B1), A 1is a single bond or a saturated hydrocarbylene group having 1 to 10 carbon atoms, and a portion of the -CH2- in the saturated hydrocarbylene group may be substituted with -O-. The saturated hydrocarbylene group may be linear, branched, or cyclic, and specific examples 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, and 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, the ether bond may be located anywhere 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 bonding 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 relative to the etheric oxygen atom. Note that 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.

[0182] 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 When 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. Specific examples include, but are not limited to, those shown below. In the following formula, R A is the same as above. [ka]

[0183] [ka]

[0184] [ka]

[0185] a1 is 1 (i.e., -C(=O)-OA as a linker) 1 In the case where R A is the same as above. [ka]

[0186] [ka]

[0187] [ka]

[0188] [ka]

[0189] [ka]

[0190] The content of the repeating unit B1 is preferably 15 to 90 mol %, more preferably 15 to 80 mol %, of all repeating units constituting the polymer. However, when the polymer contains at least one of the repeating units represented by formula (B3) and the repeating unit represented by formula (B4), which will be described later and which impart high etching resistance to the polymer, and this unit has a phenolic hydroxy group as a substituent, it is preferable that the proportion of the repeating unit B1 also be included within the above range. The repeating unit B1 may be used alone or in combination of two or more types.

[0191] 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 through the action of an acid (hereinafter, also referred to as repeating unit B2).

[0192] 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]

[0193] In formula (B2-1), b1 is 0 or 1. b2 is 0, 1, or 2; when 0, it is a benzene skeleton, when 1, it is naphthalene, and when 2, it is anthracene. b3 is an integer satisfying 0≦b3≦5+2(b2)−b4. b4 is 1, 2, or 3. b5 is 0 or 1. When b2 is 0, b3 is preferably 0, 1, 2, or 3, and b4 is 1, 2, or 3; when b2 is 1 or 2, b3 is preferably 0, 1, 2, 3, or 4, and b4 is 1, 2, or 3.

[0194] In formula (B2-1), R A is a hydrogen atom, a fluorine atom, a methyl group, or a trifluoromethyl group.

[0195] In formula (B2-1), R 21is 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 moiety of the saturated hydrocarbylcarbonyloxy group and saturated hydrocarbyloxy group may be linear, branched, or cyclic. Specific examples include alkyl groups such as methyl, ethyl, n-propyl, isopropyl, butyl, pentyl, hexyl, and structural isomers thereof; cycloalkyl groups such as cyclopropyl, cyclobutyl, cyclopentyl, and cyclohexyl; and groups obtained by combining these. When the number of carbon atoms is equal to or less than the upper limit, the solubility in alkaline developers is good. When b3 is 2 or more, each R 21 may be the same as or different from each other.

[0196] In formula (B2-1), A 2is a single bond or a saturated hydrocarbylene group having 1 to 10 carbon atoms, and some of the -CH2- in the saturated hydrocarbylene group may be substituted with -O-. The saturated hydrocarbylene group may be linear, branched, or cyclic, and specific examples 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, and 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, the 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 relative to the ester oxygen atom. When b1 is 0, the atom bonding to the main chain is an ether oxygen atom, and a 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 relative to the ether oxygen atom. Note that 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.

[0197] In formula (B2-1), 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, with at least one being an acid labile group. That is, in the repeating unit B2-1, at least one phenolic hydroxy group bonded to an aromatic ring is protected with an acid labile group, or a carboxy group bonded to an 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 cleaved by an acid to give an acidic group can be used.

[0198] The acid labile group may be, for example, a tertiary saturated hydrocarbyl group. The tertiary saturated hydrocarbyl group preferably has 4 to 18 carbon atoms so that the resulting monomer for polymerization can be obtained by distillation.

[0199] 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 ether bond or an oxygen atom-containing functional group such as a carbonyl group between its carbon-carbon bond. Furthermore, 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 attached.

[0200] 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.

[0201] 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, but are not limited to these.

[0202] Further, examples of the acid labile group include groups 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 in which the interface between the pattern and the substrate is relatively rectangular. 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.)

[0203] 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.

[0204] 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 while decomposing with strong acid, a group in which the carbon atom bonded to the hydrogen atom or acetal carbon is a tertiary carbon atom is preferred. R bonded to the acetal carbon by a tertiary carbon atom L1 Examples of R include, but are not limited to, a tert-butyl group, a tert-pentyl group, and a 1-adamantyl group. If the design is to achieve high sensitivity to pH changes by using relatively high reactivity, a straight-chain alkyl group is preferred. Depending on the combination with the acid generator and quencher to be compounded in the resist composition, R L2 When a relatively large alkyl group is selected at the end of the polymer, and the polymer is designed to have a large change in solubility due to decomposition, R L1 As for R, the carbon atom bonded to the acetal carbon is preferably a secondary carbon atom. L1 Examples of include, but are not limited to, an isopropyl group, a sec-butyl group, a cyclopentyl group, a cyclohexyl group, and the like.

[0205] In formula (B2-1-1), R L2is a hydrocarbyl group having 1 to 30 carbon atoms. The hydrocarbyl group may be saturated or unsaturated, and may be linear, branched, or cyclic. A portion of the -CH2- in the hydrocarbyl group may be substituted with a heteroatom such as an oxygen atom or a sulfur atom, and as a result, the hydrocarbyl group may contain an ether bond, a sulfide bond, or the like. Specific examples of the hydrocarbyl group 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 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.

[0206] 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 line represents a bond. [ka]

[0207] [ka]

[0208] Other acid labile groups that can be used include those in which the hydrogen atom of a phenolic hydroxy group is substituted with -CHCOO- (a tertiary saturated hydrocarbyl group), which can be the same as the tertiary saturated hydrocarbyl groups used to protect the phenolic hydroxy group described above.

[0209] Further, examples of the repeating unit B2 include a repeating unit represented by the following formula (B2-2) (hereinafter also referred to as repeating unit B2-2): The repeating unit B2-2 increases the dissolution rate of the exposed area, and is therefore a useful option as an acid labile group-containing unit that provides good performance against line width fluctuations during development loading. [ka]

[0210] In formula (B2-2), c1 is 0, 1 or 2. c2 is 0, 1 or 2. c3 is 0, 1, 2, 3, 4 or 5. c4 is 0, 1 or 2.

[0211] In formula (B2-2), R A is a hydrogen atom, a fluorine atom, a methyl group, or a trifluoromethyl group.

[0212] In formula (B2-2), R 22 and R 23 are each independently a hydrocarbyl group having 1 to 10 carbon atoms which may contain a heteroatom, and 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.

[0213] In formula (B2-2), R 24 are each independently a fluorine atom, a fluorinated alkyl group having 1 to 5 carbon atoms, or a fluorinated alkoxy group having 1 to 5 carbon atoms.

[0214] In formula (B2-2), R 25 are each independently a hydrocarbyl group having 1 to 10 carbon atoms which may contain a heteroatom.

[0215] In formula (B2-2), A 3 is a single bond, a phenylene group, a naphthylene group, or *-C(=O)-OA 31 -It is. A 31is 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. * represents a bond to a carbon atom in the main chain.

[0216] Preferred examples of the repeating unit B2-2 include, but are not limited to, the following: A is the same as above. [ka]

[0217] [ka]

[0218] 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.

[0219] The polymer may contain at least one selected from 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]

[0220] In the formulae (B3) and (B4), d is 0, 1, 2, 3, 4, 5, or 6. e is 0, 1, 2, 3, or 4.

[0221] In formulas (B3) and (B4), R 31 and R 32are 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 31 may be the same or different. When e is 2 or more, each R 32 may be the same as or different from each other.

[0222] In formula (B5), f1 is 0 or 1. f2 is 0, 1, or 2. When f2 is 0, it is a benzene skeleton, when it is 1, it is a naphthalene skeleton, and when it is 2, it is an anthracene skeleton. f3 is 0, 1, 2, 3, 4, or 5. When f2 is 0, f3 is preferably 0, 1, 2, or 3, and when f2 is 1 or 2, f3 is preferably 0, 1, 2, 3, or 4.

[0223] In formula (B5), R A is a hydrogen atom, a fluorine atom, a methyl group, or a trifluoromethyl group.

[0224] In formula (B5), R 33 is a saturated hydrocarbyl group having 1 to 20 carbon atoms, a saturated hydrocarbyloxy group having 1 to 20 carbon atoms, a saturated hydrocarbylcarbonyloxy group having 2 to 20 carbon atoms, a saturated hydrocarbyloxyhydrocarbyl group having 2 to 20 carbon atoms, a saturated hydrocarbylthiohydrocarbyl group having 2 to 20 carbon atoms, a halogen atom, a nitro group, or a cyano group, and when f2 is 1 or 2, it may be a hydroxy group. The saturated hydrocarbyl group, saturated hydrocarbyloxy group, saturated hydrocarbylcarbonyloxy group, saturated hydrocarbyloxyhydrocarbyl group, and saturated hydrocarbylthiohydrocarbyl group may be linear, branched, or cyclic. When f3 is 2 or more, each R 33 may be the same as or different from each other.

[0225] In formula (B5), A 4 is a single bond or a saturated hydrocarbylene group having 1 to 10 carbon atoms, and a portion 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 above-mentioned examples are the same as those given in the explanation of the above.

[0226] 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 not only the etching resistance of the aromatic ring but also the effect of improving etching resistance and EB irradiation resistance during pattern inspection.

[0227] To obtain the effect of improving etching resistance, the content of repeating units B3 to B5 is preferably 5 mol % or more of all repeating units constituting the polymer. Furthermore, the content of 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 no functional group is present or the functional group is other than a hydroxy group, it is preferable that the amount introduced is 25 mol % or less, since this does not cause development defects. Repeating units B3 to B5 may be used singly or in combination of two or more.

[0228] The polymer preferably contains at least one selected from the group consisting of repeating units B1, B2, and B3 to B5, which are excellent in achieving both high etching resistance and high resolution. These repeating units preferably account for 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 the total repeating units of the polymer.

[0229] 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), and a repeating unit represented by the following formula (B10) (hereinafter also referred to as repeating unit B10). [ka]

[0230] In formulas (B6) to (B10), R A are each independently a hydrogen atom, a fluorine atom, a methyl group, or a trifluoromethyl group. 1 Z is a single bond or an optionally substituted phenylene group. 2 is a single bond, **-C(=O)-OZ 21 -, **-C(=O)-NH-Z 21 -or **-OZ 21 -It is. Z 21 Z is an aliphatic hydrocarbylene group having 1 to 6 carbon atoms, a phenylene group, or a divalent group obtained by combining these, and may contain a halogen atom, a carbonyl group, an ester bond, an ether bond, or a hydroxy group. 3 is a single bond, an ether bond, an ester bond, an amide bond, a sulfonate ester bond, a sulfonamide bond, a carbonate bond or a carbamate bond. 4 Z is a single bond, an aliphatic hydrocarbylene group having 1 to 6 carbon atoms, a phenylene group, or a divalent group obtained by combining these, and may contain a halogen atom, a carbonyl group, an ester bond, an ether bond, or a hydroxy group. 5 each independently represents a single bond, an optionally substituted phenylene group, a naphthylene group, or *-C(=O)-OZ 51 -It is. Z 51is an aliphatic hydrocarbylene group having 1 to 10 carbon atoms, a phenylene group, or a naphthylene group, and the aliphatic hydrocarbylene group may contain a halogen atom, a hydroxy group, an ether bond, an ester bond, or a lactone ring. 6 is a single bond, an ether bond, an ester bond, an amide bond, a sulfonate ester bond, a sulfonamide bond, a carbonate bond or a carbamate bond. 7 are each independently a single bond, ***-Z 71 -C(=O)-O-, ***-C(=O)-NH-Z 71 -or***-OZ 71 -It is. It is. Z 71 is a hydrocarbylene group having 1 to 20 carbon atoms which may contain a heteroatom. 8 are each independently a single bond, ****-Z 81 -C(=O)-O-, ****-C(=O)-NH-Z 81 -or ****-OZ 81 -It is. Z 81 is a hydrocarbylene group having 1 to 20 carbon atoms which may contain a heteroatom. 9 represents a single bond, a methylene group, an ethylene group, a phenylene group, a fluorinated phenylene group, a phenylene group substituted with a trifluoromethyl group, *-C(=O)-OZ 91 -, *-C(=O)-N(H)-Z 91 -or*-OZ 91 -It is. Z 91 is an aliphatic hydrocarbylene group having 1 to 6 carbon atoms, a phenylene group, a fluorinated phenylene group, or a phenylene group substituted with a trifluoromethyl group, and may contain a carbonyl group, an ester bond, an ether bond, or a hydroxy group. * represents a bond to a carbon atom in the main chain. ** represents a bond to a carbon atom in the main chain. Z 1 *** represents a bond with Z 6 **** represents a bond with Z 7 Represents a bond with .

[0231] Z 21 , Z 51 and Z 91The aliphatic hydrocarbylene group represented by the formula (I) may be linear, branched or cyclic, and specific examples thereof include a methanediyl group, an ethane-1,1-diyl group, an ethane-1,2-diyl group, a propane-1,1-diyl group, a propane-1,2-diyl group, a propane-1,3-diyl group, a propane-2,2-diyl group, a butane-1,1-diyl group, a butane-1,2-diyl group, a butane-1,3-diyl group, a butane- Examples of the alkyl group include alkanediyl groups such as a 2,3-diyl group, a butane-1,4-diyl group, a 1,1-dimethylethane-1,2-diyl group, a pentane-1,5-diyl group, a 2-methylbutane-1,2-diyl group, and a hexane-1,6-diyl group; cycloalkanediyl groups such as a cyclopropanediyl group, a cyclobutanediyl group, a cyclopentanediyl group, and a cyclohexanediyl group; and groups obtained by combining these groups.

[0232] Z 71 and Z 81 The hydrocarbylene group optionally containing a heteroatom, represented by the formula (I), may be saturated or unsaturated, and may be linear, branched, or cyclic. Specific examples thereof include, but are not limited to, those shown below. [ka] (In the formula, the dashed lines represent bonds.)

[0233] In formula (B6), R 41 and R 42are each independently a hydrocarbyl group having 1 to 20 carbon atoms which may contain a heteroatom. The hydrocarbyl group may be saturated or unsaturated, and may be linear, branched, or cyclic. Specific examples thereof include alkyl groups having 1 to 20 carbon atoms, such as methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, and tert-butyl; saturated cyclic hydrocarbyl groups having 3 to 20 carbon atoms, such as cyclopropyl, cyclopentyl, cyclohexyl, cyclopropylmethyl, 4-methylcyclohexyl, cyclohexylmethyl, norbornyl, and adamantyl; alkenyl groups having 2 to 20 carbon atoms, such as vinyl, 1-propenyl, 2-propenyl, butenyl, and hexenyl; unsaturated cyclic hydrocarbyl groups having 3 to 20 carbon atoms, such as cyclohexenyl; aryl groups having 6 to 20 carbon atoms, such as phenyl, naphthyl, and thienyl; aralkyl groups having 7 to 20 carbon atoms, such as benzyl, 1-phenylethyl, and 2-phenylethyl; and groups obtained by combining these, with aryl groups being preferred. Furthermore, some or all of the hydrogen atoms of the hydrocarbyl group may be substituted with a group containing a heteroatom such as an oxygen atom, a sulfur atom, a nitrogen atom or a halogen atom, and some of the -CH- groups of the hydrocarbyl group may be substituted with a group containing a heteroatom such as an oxygen atom, a sulfur atom or a nitrogen atom, and as a result, the hydrocarbyl group may contain a hydroxy group, a fluorine atom, a chlorine atom, a bromine atom, an iodine atom, a cyano group, a carbonyl group, an ether bond, an ester bond, a sulfonate ester bond, a carbonate bond, a lactone ring, a sultone ring, a carboxylic anhydride (-C(=O)-OC(=O)-), a haloalkyl group, etc.

[0234] Also, R 41 and R 42 However, they may be bonded to each other to form a ring together with the sulfur atom to which they are bonded. In this case, specific examples of the ring include those represented by the following formulas. [ka] (In the formula, the dashed line represents Z 4 )

[0235] Specific examples of the cation of the repeating unit B6 include, but are not limited to, the following: A is the same as above. [ka]

[0236] [ka]

[0237] [ka]

[0238] [ka]

[0239] [ka]

[0240] [ka]

[0241] [ka]

[0242] [ka]

[0243] [ka]

[0244] [ka]

[0245] In formula (B6), M - is a non-nucleophilic counter ion. Examples of the non-nucleophilic counter ion include halide ions, sulfonate anions, imidate anions, and methide anions. Specific examples of the halide ions include chloride ions and bromide ions. Specific examples of the sulfonate anions (sulfonate ions) include fluoroalkylsulfonate ions such as triflate ions, 1,1,1-trifluoroethanesulfonate ions, and nonafluorobutanesulfonate ions; arylsulfonate ions such as tosylate ions, benzenesulfonate ions, 4-fluorobenzenesulfonate ions, and 1,2,3,4,5-pentafluorobenzenesulfonate ions; and alkylsulfonate ions such as mesylate ions and butanesulfonate ions. Specific examples of the imidate anions (imide ions) include bis(trifluoromethylsulfonyl)imide ions, bis(perfluoroethylsulfonyl)imide ions, and bis(perfluorobutylsulfonyl)imide ions. Specific examples of the methide acid anion (methide ion) include tris(trifluoromethylsulfonyl)methide ion, tris(perfluoroethylsulfonyl)methide ion, and the like.

[0246] Other examples of the non-nucleophilic counter ion include anions represented by any of the following formulae (B6-1) to (B6-4). [ka]

[0247] In formula (B6-1), R fa is a hydrocarbyl group having 1 to 40 carbon atoms which may contain a fluorine atom or a heteroatom. The hydrocarbyl group may be saturated or unsaturated, and may be linear, branched, or cyclic. Specific examples thereof include R in formula (B6-1-1) described later. fa1Examples of the hydrocarbyl group represented by the formula (I) include the same as those exemplified above.

[0248] The anion represented by formula (B6-1) is preferably one represented by the following formula (B6-1-1). [ka]

[0249] In formula (B6-1-1), Q 1 and Q 2 are each independently a hydrogen atom, a fluorine atom, or a fluorinated saturated hydrocarbyl group having 1 to 6 carbon atoms, but in order to improve solvent solubility, it is preferable that at least one of them is a trifluoromethyl group. m is 0, 1, 2, 3, or 4, but is particularly preferably 1. R fa1 is a hydrocarbyl group having 1 to 35 carbon atoms which may contain a heteroatom. The heteroatom is preferably an oxygen atom, a nitrogen atom, a sulfur atom, a halogen atom, or the like, and more preferably an oxygen atom. From the viewpoint of obtaining high resolution in the formation of a fine pattern, the hydrocarbyl group is particularly preferably one having 6 to 30 carbon atoms.

[0250] In formula (B6-1-1), R fa1The hydrocarbyl group having 1 to 35 carbon atoms and represented by the formula (I) may be saturated or unsaturated, and may be linear, branched, or cyclic. Specific examples thereof include alkyl groups having 1 to 35 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, a pentyl group, a neopentyl group, a hexyl group, a heptyl group, a 2-ethylhexyl group, a nonyl group, an undecyl group, a tridecyl group, a pentadecyl group, a heptadecyl group, and an icosyl group; a cyclopentyl group, a cyclohexyl group, a 1-adamantyl group, a 2-adamantyl group, a 1-adamantylmethyl group, a norbornyl group, a norbornyl group, and an alkyl group having 1 to 35 carbon atoms. Examples of such alkyl groups include saturated cyclic hydrocarbyl groups having 3 to 35 carbon atoms, such as a 2-cyclohexylmethyl group, a tricyclodecyl group, a tetracyclododecyl group, a tetracyclododecylmethyl group, and a dicyclohexylmethyl group; unsaturated aliphatic hydrocarbyl groups having 2 to 35 carbon atoms, such as a 2-propenyl group and a 3-cyclohexenyl group; aryl groups having 6 to 35 carbon atoms, such as a phenyl group, a 1-naphthyl group, a 2-naphthyl group, and a 9-fluorenyl group; aralkyl groups having 7 to 35 carbon atoms, such as a benzyl group and a diphenylmethyl group; and groups obtained by combining these groups.

[0251] Furthermore, some or all of the hydrogen atoms of the hydrocarbyl group may be substituted with a group containing a heteroatom such as an oxygen atom, a sulfur atom, a nitrogen atom or a halogen atom, and some of the -CH- groups of the hydrocarbyl group may be substituted with a group containing a heteroatom such as an oxygen atom, a sulfur atom or a nitrogen atom, and as a result, the hydrocarbyl group may contain a hydroxy group, a fluorine atom, a chlorine atom, a bromine atom, an iodine atom, a cyano group, a nitro group, a carbonyl group, an ether bond, an ester bond, a sulfonate ester bond, a carbonate bond, a lactone ring, a sultone ring, a carboxylic anhydride (-C(=O)-OC(=O)-), a haloalkyl group, etc. Specific examples of hydrocarbyl groups containing hetero atoms include tetrahydrofuryl, methoxymethyl, ethoxymethyl, methylthiomethyl, acetamidomethyl, trifluoroethyl, (2-methoxyethoxy)methyl, acetoxymethyl, 2-carboxy-1-cyclohexyl, 2-oxopropyl, 4-oxo-1-adamantyl, and 3-oxocyclohexyl groups.

[0252] In formula (B6-1-1), L a1 is a single bond, an ether bond, an ester bond, a sulfonate ester bond, a carbonate bond or a carbamate bond, but from the viewpoint of synthesis, an ether bond or an ester bond is preferred, and an ester bond is more preferred.

[0253] Specific examples of the anion represented by formula (B6-1) include, but are not limited to, the following: 1 is the same as above, and Ac is an acetyl group. [ka]

[0254] [ka]

[0255] [ka]

[0256] [ka]

[0257] [ka]

[0258] [ka]

[0259] [ka]

[0260] [ka]

[0261] [ka]

[0262] [ka]

[0263] In formula (B6-2), R fb1 and R fb2 are each independently a hydrocarbyl group having 1 to 40 carbon atoms which may contain a fluorine atom or a heteroatom. The hydrocarbyl group may be saturated or unsaturated, and may be linear, branched, or cyclic. Specific examples thereof include R in formula (B6-1-1): fa1 Examples of the hydrocarbyl group represented by R include the same as those exemplified above. fb1 and R fb2 is preferably a fluorine atom or a linear fluorinated alkyl group having 1 to 4 carbon atoms. fb1 and R fb2 are bonded to each other and form the bonded group (-CF2-SO2-N - -SO2-CF2-) together may form a ring, in which case R fb1 and R fb2 The group obtained by bonding together is preferably a fluorinated ethylene group or a fluorinated propylene group.

[0264] In formula (B6-3), R fc1 , R fc2 and R fc3 are each independently a hydrocarbyl group having 1 to 40 carbon atoms which may contain a fluorine atom or a heteroatom. The hydrocarbyl group may be saturated or unsaturated, and may be linear, branched, or cyclic. Specific examples thereof include R in formula (B6-1-1): fa1 Examples of the hydrocarbyl group represented by R include the same as those exemplified above. fc1 , R fc2 and Rfc3 is preferably a fluorine atom or a linear fluorinated alkyl group having 1 to 4 carbon atoms. fc1 and R fc2 are bonded to each other and form the bonded group (-CF2-SO2-C - -SO2-CF2-) together may form a ring, in which case R fc1 and R fc2 The group obtained by bonding together is preferably a fluorinated ethylene group or a fluorinated propylene group.

[0265] In formula (B6-4), R fd 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 R in formula (B6-1-1): fa1 Examples of the hydrocarbyl group represented by the formula (I) include the same as those exemplified above.

[0266] Specific examples of the anion represented by formula (B6-4) include, but are not limited to, the following: [ka]

[0267] [ka]

[0268] Further examples of the non-nucleophilic counter ion include anions having an aromatic ring substituted with an iodine atom or a bromine atom. Specific examples of such anions include those represented by the following formula (B6-5): [ka]

[0269] In formula (B6-5), x is 1, 2, or 3. y is 1, 2, 3, 4, or 5. z is 0, 1, 2, or 3, provided that 1≦y+z≦5. y is preferably 1, 2, or 3, and more preferably 2 or 3. z is preferably 0, 1, or 2.

[0270] In formula (B6-5), X BI is an iodine atom or a bromine atom, and when x and / or y are 2 or more, they may be the same or different.

[0271] In formula (B6-5), L 11 is a single bond, an ether bond, an ester bond, or a saturated hydrocarbylene group having 1 to 6 carbon atoms which may contain an ether bond or an ester bond. The saturated hydrocarbylene group may be linear, branched, or cyclic.

[0272] In formula (B6-5), L 12 represents a single bond or a divalent linking group having 1 to 20 carbon atoms when x is 1, and represents an (x+1)-valent linking group having 1 to 20 carbon atoms when x is 2 or 3, and the linking group may contain an oxygen atom, a sulfur atom, or a nitrogen atom.

[0273] In formula (B6-5), R fe is a hydroxy group, a carboxy group, a fluorine atom, a chlorine atom, a bromine atom or an amino group, or a hydrocarbyl group having 1 to 20 carbon atoms, a hydrocarbyloxy group having 1 to 20 carbon atoms, a hydrocarbylcarbonyl group having 2 to 20 carbon atoms, a hydrocarbyloxycarbonyl group having 2 to 20 carbon atoms, a hydrocarbylcarbonyloxy group having 2 to 20 carbon atoms or a hydrocarbylsulfonyloxy group having 1 to 20 carbon atoms which may contain a fluorine atom, a chlorine atom, a bromine atom, a hydroxy group, an amino group or an ether bond, or feA )(R feB ), -N(R feC )-C(=O)-R feD or -N(R feC )-C(=O)-OR feD R feA and R feBare each independently a hydrogen atom or a saturated hydrocarbyl group having 1 to 6 carbon atoms. feC is a hydrogen atom or a saturated hydrocarbyl group having 1 to 6 carbon atoms, and may contain a halogen atom, a hydroxy group, a saturated hydrocarbyloxy group having 1 to 6 carbon atoms, a saturated hydrocarbylcarbonyl group having 2 to 6 carbon atoms, or a saturated hydrocarbylcarbonyloxy group having 2 to 6 carbon atoms. feD is an aliphatic hydrocarbyl group having 1 to 16 carbon atoms, an aryl group having 6 to 12 carbon atoms, or an aralkyl group having 7 to 15 carbon atoms, and may contain a halogen atom, a hydroxy group, a saturated hydrocarbyloxy group having 1 to 6 carbon atoms, a saturated hydrocarbylcarbonyl group having 2 to 6 carbon atoms, or a saturated hydrocarbylcarbonyloxy group having 2 to 6 carbon atoms. The aliphatic hydrocarbyl group may be saturated or unsaturated and may be linear, branched, or cyclic. The hydrocarbyl group, hydrocarbyloxy group, hydrocarbylcarbonyl group, hydrocarbyloxycarbonyl group, hydrocarbylcarbonyloxy group, and hydrocarbylsulfonyloxy group may be linear, branched, or cyclic. When x and / or z is 2 or more, each R fe may be the same or different from each other.

[0274] Of these, R fe Examples of the hydroxyl group include -N(R feC )-C(=O)-R feD , -N(R feC )-C(=O)-OR feD fluorine atom, chlorine atom, bromine atom, methyl group, methoxy group, etc. are preferred.

[0275] In formula (B6-5), Rf 11 ~Rf 14 are each independently a hydrogen atom, a fluorine atom, or a trifluoromethyl group, and at least one of them is a fluorine atom or a trifluoromethyl group. 11 and Rf 12 may combine to form a carbonyl group. 13 and Rf 14 are preferably both fluorine atoms.

[0276] Specific examples of the anion represented by formula (B6-5) include, but are not limited to, the following: BI is the same as above. [ka]

[0277] [ka]

[0278] [ka]

[0279] [ka]

[0280] [ka]

[0281] [ka]

[0282] [ka]

[0283] [ka]

[0284] [ka]

[0285] [ka]

[0286]

change

[0287]

change

[0288]

change

[0289]

change

[0290]

change

[0291]

change

[0292]

change

[0293]

change

[0294]

change

[0295]

change

[0296] [ka]

[0297] [ka]

[0298] [ka]

[0299] Examples of the non-nucleophilic counter ion include a fluorobenzenesulfonate anion bonded to an aromatic group containing an iodine atom, as described in Japanese Patent No. 6648726, an anion having a mechanism for decomposing with an acid, as described in International Publication No. 2021 / 200056 and Japanese Patent Application Publication No. 2021-70692, an anion having a cyclic ether group, as described in Japanese Patent Application Publication No. 2018-180525 and Japanese Patent Application Publication No. 2021-35935, and an anion described in Japanese Patent Application Publication No. 2018-92159.

[0300] Further examples of the non-nucleophilic counter ion include anions of bulky benzenesulfonic acid derivatives that do not contain fluorine atoms, as described in JP 2006-276759 A, JP 2015-117200 A, JP 2016-65016 A, and JP 2019-202974 A, and benzenesulfonic acid anions and alkylsulfonic acid anions that do not contain fluorine atoms bonded to aromatic groups containing iodine atoms, as described in Japanese Patent No. 6645464 A.

[0301] Further examples of the non-nucleophilic counter ion include anions of bissulfonic acid described in JP 2015-206932 A, anions of sulfonamides or sulfonimides having a sulfonic acid on one side and a different sulfonic acid on the other side described in WO 2020 / 158366 A, and anions of sulfonic acid on one side and carboxylic acid on the other described in JP 2015-24989 A.

[0302] In formulae (B7) and (B8), g1 and g2 each independently represent 0, 1, 2 or 3, with 1 being preferred.

[0303] In formula (B9), h1 is 0 or 1. h2 is 0, 1, 2, 3, or 4. h3 is 0, 1, 2, 3, or 4. However, when g1 is 0, 0≦h2+h3≦4, and when g1 is 1, 0≦h2+h3≦6.

[0304] In formulas (B7), (B8) and (B9), L 1 is a single bond, an ether bond, an ester bond, a carbonyl group, a sulfonate ester bond, a sulfonamide bond, a carbonate bond, or a carbamate bond. Among these, from the viewpoint of synthesis, an ether bond, an ester bond, or a carbonyl group is preferred, and an ester bond or a carbonyl group is more preferred.

[0305] In formula (B7), Rf 1 and Rf 2 are each independently a fluorine atom or a fluorinated saturated hydrocarbyl group having 1 to 6 carbon atoms. 1 and Rf 2 In order to increase the acid strength of the generated acid, it is preferable that Rf be a fluorine atom. 3 and Rf 4 are each independently a hydrogen atom, a fluorine atom, or a fluorinated saturated hydrocarbyl group having 1 to 6 carbon atoms. Of these, Rf 3 and Rf 4 At least one of these is preferably a trifluoromethyl group.

[0306] In formula (B8), Rf 5 and Rf 6 are each independently a hydrogen atom, a fluorine atom, or a fluorinated saturated hydrocarbyl group having 1 to 6 carbon atoms, provided that all Rf 5 and Rf 6 cannot be simultaneously hydrogen atoms. Among these, Rf 5 and Rf 6At least one of these is preferably a trifluoromethyl group.

[0307] In formula (B9), Rf 7 Rf is a fluorine atom, a fluorinated alkyl group having 1 to 6 carbon atoms, a fluorinated alkoxy group having 1 to 6 carbon atoms, or a fluorinated alkylthio group having 1 to 6 carbon atoms. 7 is preferably a fluorine atom, a trifluoromethyl group, a difluoromethyl group, a trifluoromethoxy group, a difluoromethoxy group, a trifluoromethylthio group, or a difluoromethylthio group, and more preferably a fluorine atom, a trifluoromethyl group, or a trifluoromethoxy group. 7 may be the same as or different from each other.

[0308] In formula (B9), R 43 is a hydrocarbyl group having 1 to 20 carbon atoms, which may contain a halogen atom other than a fluorine atom, or a heteroatom. The hydrocarbyl group may be saturated or unsaturated, and may be linear, branched, or cyclic. Specific examples thereof include R 1 Examples of the hydrocarbyl group represented by the formula (I) include, but are not limited to, the same as those exemplified above. When h3 is 2, 3, or 4, each R 43 may be the same as or different from each other.

[0309] Also, when h3 is 2, 3 or 4, multiple R 43may be bonded to each other to form a ring together with the carbon atoms to which they are bonded. Specific 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. Furthermore, 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 -CH- groups in the ring may be substituted with a group containing a heteroatom such as an oxygen atom, a sulfur atom, or a nitrogen atom, resulting in the ring containing a hydroxy group, a fluorine atom, a chlorine atom, a bromine atom, an iodine atom, a cyano group, a carbonyl group, an ether bond, an ester bond, a sulfonate ester bond, a carbonate bond, a lactone ring, a sultone ring, a carboxylic anhydride (-C(=O)-OC(=O)-), a haloalkyl group, or the like.

[0310] Specific examples of the anion of the repeating unit B7 include, but are not limited to, the following: A is the same as above, and Me is a methyl group. [ka]

[0311] [ka]

[0312] [ka]

[0313] [ka]

[0314] [ka]

[0315] [ka]

[0316] [ka]

[0317] [ka]

[0318] [ka]

[0319] [ka]

[0320] [ka]

[0321] [ka]

[0322] [ka]

[0323] Specific examples of the anion of the repeating unit B8 include, but are not limited to, those shown below. A is the same as above. [ka]

[0324] [ka]

[0325] [ka]

[0326] [ka]

[0327] [ka]

[0328] [ka]

[0329] [ka]

[0330] [ka]

[0331] [ka]

[0332] [ka]

[0333] [ka]

[0334] Specific examples of the anion of the repeating unit B9 include, but are not limited to, those shown below. A is the same as above. [ka]

[0335]

change

[0336]

change

[0337]

change

[0338]

change

[0339]

change

[0340]

change

[0341]

change

[0342]

change

[0343]

change

[0344]

change

[0345] [ka]

[0346] [ka]

[0347] [ka]

[0348] [ka]

[0349] [ka]

[0350] [ka]

[0351] Specific examples of the anion of the repeating unit B10 include, but are not limited to, the following: A is the same as above. [ka]

[0352] In formulas (B7) to (B10), A +is an onium cation. The onium cation is preferably a sulfonium cation or an iodonium cation. Specific examples of the sulfonium cation include, but are not limited to, those exemplified as specific examples of the sulfonium cation represented by formula (Z-1) and those exemplified as specific examples of the sulfonium cation represented by formula (Z-3). Specific examples of the iodonium cation include, but are not limited to, those exemplified as specific examples of the iodonium cation represented by formula (Z-2).

[0353] Specific structures of the repeating units B6 to B10 include any combination of the above-mentioned anions and cations.

[0354] The repeating units B6 to B10 are units that generate acid upon irradiation with high-energy rays. It is believed that the inclusion of these units in the polymer appropriately suppresses acid diffusion, resulting in a pattern with reduced LER. Furthermore, the inclusion of these units in the polymer suppresses the phenomenon in which acid volatilizes from the exposed area and reattaches to the unexposed area during baking in a vacuum, which is believed to be effective in reducing LER and reducing shape deterioration due to unwanted film loss in the unexposed area.

[0355] Among the repeating units B6 to B10, the repeating units B7 to B10 are preferred as units suitable for processing photomask blanks, as they have optimal acid strength for suppressing acid diffusion and designing acid labile groups in the polymer, and repeating units B8, B9 and B10 are more preferred.

[0356] The repeating units B6 to B10 are preferably incorporated in an amount of 0.1 to 30 mol %, more preferably 0.5 to 20 mol %, of the total repeating units of the polymer. The repeating units B6 to B10 may be used singly or in combination of two or more.

[0357] The content of repeating units having an aromatic ring skeleton in all repeating units of the polymer is preferably 65 mol % or more, more preferably 75 mol % or more, and even more preferably 85 mol % or more. When repeating units B6 to B10 are not included, it is preferable that all units have an aromatic ring skeleton.

[0358] The polymer may contain commonly used (meth)acrylate units protected with an acid labile group, or (meth)acrylate units having an adhesive group such as a lactone structure or a hydroxy group other than a phenolic hydroxy group. These repeating units allow for fine adjustment of the properties of the resist film, but they do not necessarily have to be included.

[0359] Examples of the (meth)acrylic acid ester unit having the adhesive group include 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). These units do not exhibit acidity and can be used auxiliary as units that impart adhesion to substrates or units that adjust solubility. [ka]

[0360] In formulas (B11) to (B13), R A are each independently a hydrogen atom, a fluorine atom, a methyl group, or a trifluoromethyl group. 51 is —O— or a methylene group. 52 is a hydrogen atom or a hydroxy group. 53 is a saturated hydrocarbyl group having 1 to 4 carbon atoms. i is 0, 1, 2 or 3.

[0361] When repeating units B11 to B13 are contained, the content thereof is preferably 0 to 20 mol %, more preferably 0 to 10 mol %, of all repeating units of the polymer. Repeating units B14 to B16 may be used alone or in combination of two or more.

[0362] The polymer can be synthesized by copolymerizing each monomer, optionally protected with a protecting group, using a known method, followed by a deprotection reaction as needed. The copolymerization reaction is not particularly limited, but is preferably radical polymerization or anionic polymerization. For these methods, see JP 2004-115630 A.

[0363] The polymer preferably has a weight-average molecular weight (Mw) of 1,000 to 50,000, more preferably 2,000 to 20,000. When Mw is 1,000 or more, there is no risk of the conventionally known phenomenon of pattern heads becoming rounded, reducing resolution and deteriorating LER. On the other hand, when Mw is 50,000 or less, there is no risk of LER degradation, particularly when forming a pattern with a line width of 100 nm or less. In the present invention, Mw is a polystyrene-equivalent value measured by gel permeation chromatography (GPC) using THF or DMF as a solvent.

[0364] 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 distribution, foreign matter is not generated on the pattern after development, and the pattern shape is not deteriorated.

[0365] Furthermore, the base polymer is designed to have a dissolution rate in an alkaline developer of preferably 10 nm / min or less, more preferably 7 nm / min or less, and even more preferably 5 nm / min or less. In advanced-generation photomasks, when the coating film on the substrate is thin (100 nm or less), the pattern is significantly affected by pattern film loss during alkaline development. If the polymer's alkaline dissolution rate exceeds 10 nm / min, the pattern collapses, making it impossible to form fine patterns. This is particularly true in the production of photomasks, which require a defect-free design, since the development process tends to be intense. In this invention, the dissolution rate of the base polymer in an alkaline developer was calculated from the film loss observed when an 8-inch silicon wafer was spin-coated with a polymer solution (polymer concentration: 16.7 wt %, solvent: propylene glycol monomethyl ether acetate (PGMEA)), baked at 100°C for 90 seconds to form a 1000 nm-thick film, and then developed at 23°C for 100 seconds with a 2.38 wt % aqueous solution of tetramethylammonium hydroxide (TMAH).

[0366] The base polymer of component (B) may contain a polymer other than the above-mentioned polymer. As the other polymer, a conventionally known base polymer for a resist composition can be used. The content of the other polymer is not particularly limited as long as it does not impair the effects of the present invention.

[0367] [(C) Organic solvent] The resist composition of the present invention may contain an organic solvent as component (C). There are no particular limitations on the organic solvent, so long as it is capable of dissolving each component. Examples of such organic solvents include ketones such as cyclohexanone, cyclopentanone, methyl-2-n-pentyl ketone, and 2-heptanone, as described in paragraphs

[0144] and

[0145] of JP-A No. 2008-111103; alcohols such as 3-methoxybutanol, 3-methyl-3-methoxybutanol, 1-methoxy-2-propanol, 1-ethoxy-2-propanol, and diacetone alcohol; and propylene glycol monomethyl ether (PGME), ethylene glycol monomethyl ether, and propylene glycol monoethyl ether. Examples of suitable solvents include ethers such as ethylene glycol 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, can be added to accelerate the deprotection reaction of the acetal.

[0368] Among these organic solvents, 1-ethoxy-2-propanol, PGMEA, PGME, cyclohexanone, EL, γ-butyrolactone, and mixed solvents thereof are preferred.

[0369] 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 two or more types may be mixed and used.

[0370] [(D) Quencher] The chemically amplified positive resist composition of the present invention may optionally contain a quencher as component (D). In this specification, a quencher refers to a compound that traps the acid generated from the acid generator. This can reduce the rate at which the acid generated from the acid generator diffuses into the resist film. Even when a substrate is used whose outermost surface is made of a material containing chromium, the effect of the acid generated within the resist film on the chromium-containing material can be reduced.

[0371] Examples of the quencher include conventional basic compounds. Examples of conventional basic compounds include primary, secondary, and tertiary aliphatic amines, mixed amines, aromatic amines, heterocyclic amines, nitrogen-containing compounds having a carboxy group, nitrogen-containing compounds having a sulfonyl group, nitrogen-containing compounds having a hydroxy group, nitrogen-containing compounds having a hydroxyphenyl group, alcoholic nitrogen-containing compounds, amides, imides, and carbamates. In particular, the primary, secondary, and tertiary amine compounds described in paragraphs

[0146] to

[0164] of JP 2008-111103 A are preferred, including amine compounds having a hydroxy group, an ether bond, an ester bond, a lactone ring, a cyano group, or a sulfonate ester bond, and compounds having a carbamate group described in JP 3790649 A. Preferred examples include tris[2-(methoxymethoxy)ethyl]amine, tris[2-(methoxymethoxy)ethyl]amine-N-oxide, dibutylaminobenzoic acid, morpholine derivatives, imidazole derivatives, etc. Addition of such basic compounds can, for example, further suppress the diffusion rate of acid in the resist film or correct the shape.

[0372] Further, examples of the quencher include onium salts such as sulfonium salts, iodonium salts, and ammonium salts of carboxylic acids not fluorinated at the α-position, as described in JP-A-2008-158339. Sulfonic acids, imide acids, or methide acids fluorinated at the α-position are necessary for deprotecting acid labile groups, and salt exchange with onium salts not fluorinated at the α-position releases carboxylic acids not fluorinated at the α-position. Carboxylic acids not fluorinated at the α-position hardly undergo deprotection reactions, and therefore function as quenchers.

[0373] Examples of onium salts of carboxylic acids that are not fluorinated at the α-position include those represented by the following formula (D1). [ka]

[0374] In formula (D1), R 101 represents a hydrocarbyl group having 1 to 40 carbon atoms which may contain a hydrogen atom or a heteroatom, but excludes those in which the hydrogen atom bonded to the carbon atom at the α-position of the carboxy group is substituted with a fluorine atom or a fluoroalkyl group.

[0375] R 101 The hydrocarbyl group represented by the formula (I) may be saturated or unsaturated, and may be linear, branched, or cyclic. Specific examples thereof include alkyl groups having 1 to 40 carbon atoms, such as methyl, ethyl, n-propyl, isopropyl, n-butyl, sec-butyl, tert-butyl, n-pentyl, tert-pentyl, n-hexyl, n-octyl, 2-ethylhexyl, n-nonyl, and n-decyl; cyclopentyl, cyclohexyl, cyclopentylmethyl, cyclopentylethyl, cyclopentylbutyl, cyclohexylmethyl, cyclohexylethyl, cyclohexylbutyl, norbornyl, and tricyclo[5.2.1.0]. 2,6]Cyclic saturated hydrocarbyl groups having 3 to 40 carbon atoms such as a decyl group, an adamantyl group, and an adamantylmethyl group; alkenyl groups having 2 to 40 carbon atoms such as a vinyl group, an allyl group, a propenyl group, a butenyl group, and a hexenyl group; cyclic unsaturated aliphatic hydrocarbyl groups having 3 to 40 carbon atoms such as a cyclohexenyl group; phenyl group, naphthyl group, alkylphenyl groups (2-methylphenyl group, 3-methylphenyl group, 4-methylphenyl group, 4-ethylphenyl group, 4-tert-butylphenyl group, Examples of aryl groups include aryl groups having 6 to 40 carbon atoms such as arylphenyl groups (e.g., 2,4-n-butylphenyl group, 4-n-butylphenyl group), di- or trialkylphenyl groups (e.g., 2,4-dimethylphenyl group, 2,4,6-triisopropylphenyl group), alkylnaphthyl groups (e.g., methylnaphthyl group, ethylnaphthyl group), and dialkylnaphthyl groups (e.g., dimethylnaphthyl group, diethylnaphthyl group); and aralkyl groups having 7 to 40 carbon atoms such as benzyl group, 1-phenylethyl group, and 2-phenylethyl group.

[0376] Furthermore, some or all of the hydrogen atoms of the hydrocarbyl group may be substituted with a group containing a heteroatom such as an oxygen atom, a sulfur atom, a nitrogen atom or a halogen atom, and some of the -CH- groups of the hydrocarbyl group may be substituted with a group containing a heteroatom such as an oxygen atom, a sulfur atom or a nitrogen atom, and as a result, the hydrocarbyl group may contain a hydroxy group, a cyano group, a carbonyl group, an ether bond, a thioether 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. Examples of the hydrocarbyl group containing a heteroatom include heteroaryl groups such as a thienyl group; alkoxyphenyl groups such as a 4-hydroxyphenyl group, a 4-methoxyphenyl group, a 3-methoxyphenyl group, a 2-methoxyphenyl group, a 4-ethoxyphenyl group, a 4-tert-butoxyphenyl group, and a 3-tert-butoxyphenyl group; alkoxynaphthyl groups such as a methoxynaphthyl group, an ethoxynaphthyl group, an n-propoxynaphthyl group, and an n-butoxynaphthyl group; dialkoxynaphthyl groups such as a dimethoxynaphthyl group and a diethoxynaphthyl group; and aryloxoalkyl groups such as a 2-aryl-2-oxoethyl group, a 2-(1-naphthyl)-2-oxoethyl group, and a 2-(2-naphthyl)-2-oxoethyl group.

[0377] In formula (D1), Mq A + is an onium cation. The onium cation is preferably a sulfonium cation, an iodonium cation, or an ammonium cation, and more preferably a sulfonium cation or an iodonium cation. Specific examples of the sulfonium cation include those exemplified as specific examples of the sulfonium cation represented by formula (Z-1) and the sulfonium cation represented by formula (Z-3). Specific examples of the iodonium cation include those exemplified as specific examples of the iodonium cation represented by formula (Z-2).

[0378] Examples of the anion of the onium salt represented by formula (D1) include, but are not limited to, those shown below. [ka]

[0379] [ka]

[0380] [ka]

[0381] As the quencher, a sulfonium salt of an iodinated benzene ring-containing carboxylic acid represented by the following formula (D2) can also be suitably used. [ka]

[0382] In formula (D2), s is 1, 2, 3, 4, or 5. t is 0, 1, 2, or 3, provided that 1≦s+t≦5. u is 1, 2, or 3.

[0383] In formula (D2), R 111 is a hydroxy group, a fluorine atom, a chlorine atom, a bromine atom, an amino group, a nitro group, a cyano 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, or a saturated hydrocarbylsulfonyloxy group having 1 to 4 carbon atoms, -N(R 111A )-C(=O)-R 111B or -N(R 111A )-C(=O)-OR 111B and some or all of the hydrogen atoms of the saturated hydrocarbyl group, saturated hydrocarbyloxy group, saturated hydrocarbylcarbonyloxy group or saturated hydrocarbylsulfonyloxy group may be substituted with halogen atoms. 111A is a hydrogen atom or a saturated hydrocarbyl group having 1 to 6 carbon atoms.111B is a saturated hydrocarbyl group having 1 to 6 carbon atoms or an unsaturated aliphatic hydrocarbyl group having 2 to 8 carbon atoms. When t and / or u is 2 or more, each R 111 may be the same or different from each other.

[0384] In formula (D2), L 21 is a single bond or a (u+1)-valent linking group having 1 to 20 carbon atoms, and may contain at least one selected from an ether bond, a carbonyl group, an ester bond, an amide bond, a sultone ring, a lactam ring, a carbonate bond, a halogen atom, a hydroxy group, and a carboxy group. The saturated hydrocarbyl group, saturated hydrocarbyloxy group, saturated hydrocarbylcarbonyloxy group, and saturated hydrocarbylsulfonyloxy group may be linear, branched, or cyclic.

[0385] In formula (D2), R 112 , R 113 and R 114 are each independently a hydrocarbyl group having 1 to 20 carbon atoms which may contain a halogen atom or 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 20 carbon atoms, an alkenyl group having 2 to 20 carbon atoms, an aryl group having 6 to 20 carbon atoms, and an aralkyl group having 7 to 20 carbon atoms. Some or all of the hydrogen atoms in the hydrocarbyl group may be substituted with a hydroxy group, a carboxy group, a halogen atom, an oxo group, a cyano group, a nitro group, a sultone ring, a sulfo group, or a sulfonium salt-containing group. Some of the -CH2- groups in the hydrocarbyl group may be substituted with an ether bond, an ester bond, a carbonyl group, an amide bond, a carbonate bond, or a sulfonate ester bond. Furthermore, R 112 and R 113 may be bonded to each other to form a ring together with the sulfur atom to which they are attached.

[0386] Specific examples of the compound represented by formula (D2) include those described in JP 2017-219836 A. The compound represented by formula (D2) has high absorption, a high sensitizing effect, and a high acid diffusion control effect.

[0387] As the quencher, a nitrogen atom-containing carboxylate compound represented by the following formula (D3) can also be used. [ka]

[0388] In formula (D3), R 121 ~R 124 are each independently a hydrogen atom, -L 22 -CO2 - or a hydrocarbyl group having 1 to 20 carbon atoms which may contain a hetero atom. 121 and R 122 and R 122 and R 123 and, or R 123 and R 124 and may be bonded to each other to form a ring together with the carbon atoms to which they are attached. 22 R is a single bond or a hydrocarbylene group having 1 to 20 carbon atoms which may contain a heteroatom. 125 is a hydrocarbyl group having 1 to 20 carbon atoms which may contain a hydrogen atom or a heteroatom.

[0389] In formula (D3), ring R 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 22 -CO2 -and a portion of -CH2- in the ring may be substituted with a sulfur atom, an oxygen atom, or a nitrogen atom. The ring may be an alicyclic ring or an aromatic ring, and is preferably a 5- or 6-membered ring, specific examples of which 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.

[0390] The onium carboxylic acid salt represented by formula (D3) has at least one -L 22 -CO2 - group, i.e., R 121 ~R 124 At least one of the 22 -CO2 - and / or ring R r At least one of the hydrogen atoms bonded to the carbon atom of 22 -CO2 - is replaced by

[0391] In formula (D3), Mq B + is a sulfonium cation, an iodonium cation, or an ammonium cation, and is preferably a sulfonium cation. Specific examples of the sulfonium cation include the same as those exemplified as specific examples of the sulfonium cation represented by formula (Z-1) and the sulfonium cation represented by formula (Z-3).

[0392] Examples of the anion of the compound represented by formula (D3) include, but are not limited to, those shown below. [ka]

[0393] [ka]

[0394] [ka]

[0395] [ka]

[0396] [ka]

[0397] [ka]

[0398] Furthermore, a weak acid betaine type compound can also be used as the quencher. Specific examples thereof include, but are not limited to, the following: [ka]

[0399] Further examples of the quencher include the polymer-type quencher described in JP 2008-239918 A. This quencher enhances the rectangularity of the resist pattern by orienting on the surface of the resist film. The polymer-type quencher also has the effect of preventing pattern film loss and pattern top rounding when a protective film for immersion lithography is applied.

[0400] When the chemically amplified positive resist composition of the present invention contains a quencher, the content thereof is preferably from 0 to 50 parts by mass, and more preferably from 0.1 to 40 parts by mass, relative to 80 parts by mass of the base polymer. The quenchers may be used singly or in combination of two or more.

[0401] [(E) Fluorine atom-containing polymer] The chemically amplified positive resist composition of the present invention, for the purposes of achieving high contrast, suppressing acid chemical flare upon high-energy radiation irradiation, shielding acid from mixing from the antistatic coating during the process of applying an antistatic coating material onto the resist film, and suppressing unexpected and unnecessary pattern degradation, may comprise, as component (E), a fluorine-containing polymer that includes at least one selected from the group consisting of a repeating unit represented by formula (E1) below (hereinafter also referred to as repeating unit E1), a repeating unit represented by formula (E2) below (hereinafter also referred to as repeating unit E2), a repeating unit represented by formula (E3) below (hereinafter also referred to as repeating unit E3), and a repeating unit represented by formula (E4) below (hereinafter also referred to as repeating unit E4), and that may further include at least one selected from the group consisting of a repeating unit represented by formula (E5) below (hereinafter also referred to as repeating unit E5) and a repeating unit represented by formula (E6) below (hereinafter also referred to as repeating unit E6). The fluorine atom-containing polymer also functions as a surfactant, and is therefore effective in preventing insoluble matter from re-adhering to the substrate during the development process, thereby preventing development defects. [ka]

[0402] In the formulas (E1) to (E6), j1 is 1, 2, or 3. j2 is an integer that satisfies 0≦j2≦5+2(j3)−j1. j3 is 0 or 1. k is 1, 2, or 3. R B are each independently a hydrogen atom, a fluorine atom, a methyl group, or a trifluoromethyl group. C are each independently a hydrogen atom or a methyl group. 201 , R 202 , R 204 and R 205 are each independently a hydrogen atom or a saturated hydrocarbyl group having 1 to 10 carbon atoms. 203 , R 206 , R 207 and R 208 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, and R203 , R 206 , R 207 and R 208 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 bond. 209 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 its carbon-carbon bond. 210 R is a linear or branched hydrocarbyl group having 1 to 5 carbon atoms, which may have a heteroatom-containing group interposed between its carbon-carbon bond. 211 is a saturated hydrocarbyl group having 1 to 20 carbon atoms in which at least one hydrogen atom has been substituted with a fluorine atom, and some of the -CH2- groups in the saturated hydrocarbyl group may be substituted with an ester bond or an ether bond. 1 is a (k+1)-valent hydrocarbon group having 1 to 20 carbon atoms or a (k+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. X 3 is a single bond, -O-, *-C(=O)-OX 31 -X 32 - or *-C(=O)-NH-X 31 -X 32 -X 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.

[0403] In formulas (E1) and (E2), R 201 , R 202 , R 204 and R 205The 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 methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, n-pentyl, n-hexyl, n-heptyl, n-octyl, n-nonyl, and n-decyl; and cyclic saturated hydrocarbyl groups having 3 to 10 carbon atoms, such as cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl, adamantyl, and norbornyl. Of these, saturated hydrocarbyl groups having 1 to 6 carbon atoms are preferred.

[0404] In formulas (E1) to (E4), R 203 , R 206 , R 207 and R 208 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, with an alkyl group having 1 to 15 carbon atoms being preferred. Examples of the alkyl group include those mentioned above, as well as methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, n-pentyl, n-hexyl, n-heptyl, n-octyl, n-nonyl, n-decyl, n-undecyl, n-dodecyl, n-tridecyl, n-tetradecyl, and n-pentadecyl. Examples of the fluorinated hydrocarbyl group include groups in which some or all of the hydrogen atoms bonded to carbon atoms in the hydrocarbyl group mentioned above have been substituted with fluorine atoms.

[0405] In formula (E4), X 1 Examples of the (k+1)-valent hydrocarbon group having 1 to 20 carbon atoms and represented by the formula (1) include a group in which k hydrogen atoms have been further removed from an alkyl group having 1 to 20 carbon atoms or a cyclic saturated hydrocarbyl group having 3 to 20 carbon atoms. 1Examples of the (k+1)-valent fluorinated hydrocarbon group having 1 to 20 carbon atoms and represented by the formula (I) include groups in which at least one hydrogen atom of the aforementioned (k+1)-valent hydrocarbon group has been substituted with a fluorine atom.

[0406] Specific examples of the repeating units E1 to E4 include, but are not limited to, the following: B is the same as above. [ka]

[0407] [ka]

[0408] [ka]

[0409] In formula (E5), R 109 and R 110 Examples of the hydrocarbyl group having 1 to 5 carbon atoms represented by the formula (I) 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.

[0410] In formula (E5), -OR 109 is preferably a hydrophilic group. In this case, R 109 As the alkyl group, a hydrogen atom, an alkyl group having 1 to 5 carbon atoms and an oxygen atom intervening between the carbon-carbon bonds, and the like are preferred.

[0411] In formula (E5), X 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 acid diffusion, resulting in good stability of the resist film over time and preventing degradation of resolution and pattern shape.

[0412] Examples of the repeating unit E5 include, but are not limited to, those shown below. C is the same as above. [ka]

[0413] [ka]

[0414] In formula (E6), X 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.

[0415] In formula (E6), R 211 The saturated hydrocarbyl group having 1 to 20 carbon atoms, represented by the formula (I) above, in which at least one hydrogen atom has been substituted with a fluorine atom, 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 has been substituted with a fluorine atom.

[0416] Examples of the repeating unit E6 include, but are not limited to, those shown below. C is the same as above. [ka]

[0417] [ka]

[0418] [ka]

[0419] [ka]

[0420] The content of repeating units E1 to E4 is preferably 15 to 95 mol %, more preferably 20 to 85 mol %, of all repeating units in the fluorine atom-containing polymer. The content of repeating units E5 and / or E6 is preferably 5 to 85 mol %, more preferably 15 to 80 mol %, of all repeating units in the fluorine atom-containing polymer. The repeating units E1 to E6 may be used alone or in combination of two or more.

[0421] The (E) fluorine atom-containing polymer may contain repeating units other than the repeating units described above. Examples of such repeating units include those described in paragraphs

[0046] to

[0078] of JP 2014-177407 A. When the (E) fluorine atom-containing polymer contains other repeating units, the content of such other repeating units is preferably 50 mol % or less of all repeating units of the fluorine atom-containing polymer.

[0422] The (E) fluorine atom-containing polymer can be synthesized by copolymerizing each monomer, optionally protected with a protecting group, according to a known method, followed by a deprotection reaction as needed. The copolymerization reaction is not particularly limited, but is preferably radical polymerization or anionic polymerization. For these methods, reference can be made to JP-A-2004-115630.

[0423] The Mw of the (E) fluorine atom-containing polymer is preferably 2,000 to 50,000, more preferably 3,000 to 20,000. When the Mw is 2,000 or more, the acid does not diffuse, the resolution does not deteriorate, and the stability over time is not impaired. When the Mw is 50,000 or less, the solubility in solvents is sufficient and coating defects do not occur. Furthermore, the (E) fluorine atom-containing polymer preferably has an Mw / Mn ratio of 1.0 to 2.2, more preferably 1.0 to 1.7.

[0424] When the chemically amplified positive resist composition of the present invention contains (E) a fluorine atom-containing polymer, the content thereof is preferably from 0.01 to 30 parts by mass, and more preferably from 0.1 to 20 parts by mass, relative to 80 parts by mass of (B) the base polymer. The (E) fluorine atom-containing polymer may be used alone, or two or more types may be used in combination.

[0425] [(F) Other Photoacid Generators] The chemically amplified positive resist composition of the present invention may contain, as component (F), a photoacid generator other than the photoacid generator consisting of an onium salt represented by formula (A) (hereinafter also referred to as "other photoacid generators"). The other photoacid generators are not particularly limited as long as they are compounds that generate acid upon exposure to high-energy rays. Suitable photoacid generators include sulfonium salts, iodonium salts, sulfonyldiazomethane, N-sulfonyloxyimide, and oxime-O-sulfonate-type acid generators.

[0426] Specific examples of the other photoacid generators include nonafluorobutanesulfonate, the partially fluorinated sulfonates described in paragraphs

[0247] to

[0251] of JP 2012-189977 A, the partially fluorinated sulfonates described in paragraphs

[0261] to

[0265] of JP 2013-101271 A, and those described in paragraphs

[0122] to

[0142] of JP 2008-111103 A and paragraphs

[0080] to

[0081] of JP 2010-215608 A. Among the specific examples, arenesulfonate- or alkanesulfonate-type photoacid generators are preferred because they generate an acid of appropriate strength for deprotecting the acid labile group in the repeating unit B2.

[0427] The photoacid generator is preferably a salt compound containing an anion having the structure shown below. [ka]

[0428] [ka]

[0429] [ka]

[0430] [ka]

[0431] [ka]

[0432] [ka]

[0433] [ka]

[0434] [ka]

[0435] [ka]

[0436] [ka]

[0437] [ka]

[0438] Furthermore, as the photoacid generator, a salt compound containing an anion represented by the following formula (F1) is also preferred. [ka]

[0439] In formula (F1), p is 1, 2 or 3. q is 1, 2, 3, 4 or 5. r is 0, 1, 2 or 3. s1 is 0 or 1.

[0440] In formula (F1), L 31 is a single bond, an ether bond, an ester bond, a sulfonate ester bond, a carbonate bond or a carbamate bond.

[0441] In formula (F1), L 32 is an ether bond, an ester bond, a sulfonate ester bond, a carbonate bond or a carbamate bond.

[0442] In formula (F1), L Frepresents 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 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.

[0443] L F The hydrocarbylene group having 1 to 20 carbon atoms represented by the formula (I) may be saturated or unsaturated, and may be linear, branched, or cyclic. Specific examples thereof include a methanediyl 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. alkanediyl groups having 1 to 20 carbon atoms; cyclic saturated hydrocarbylene groups having 3 to 20 carbon atoms such as cyclopentanediyl group, cyclohexanediyl group, norbornanediyl group, and adamantanediyl group; unsaturated aliphatic hydrocarbylene groups having 2 to 20 carbon atoms such as vinylene group and propene-1,3-diyl group; arylene groups having 6 to 20 carbon atoms such as phenylene group and naphthylene group; and groups obtained by combining these. F 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.

[0444] In formula (F1), Rf 21 and Rf 22 are each independently a hydrogen atom, a fluorine atom, or a trifluoromethyl group, provided that at least one is a fluorine atom or a trifluoromethyl group.

[0445] In formula (F1), R301 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, -N(R 301A )(R 301B ), -N(R 301C )-C(=O)-R 301D or -N(R 301C )-C(=O)-OR 301D R 301A and R 301B are each independently a hydrogen atom or a saturated hydrocarbyl group having 1 to 6 carbon atoms. 301C is a hydrogen atom or a saturated hydrocarbyl group having 1 to 6 carbon atoms. 301D is a saturated hydrocarbyl group having 1 to 6 carbon atoms or an unsaturated aliphatic hydrocarbyl group having 2 to 8 carbon atoms.

[0446] 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 and 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 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.

[0447] R 301BThe 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 vinyl, propenyl, butenyl, and hexenyl groups; alkynyl groups having 2 to 8 carbon atoms such as ethynyl, propynyl, and butynyl groups; and cyclic unsaturated aliphatic hydrocarbyl groups having 3 to 8 carbon atoms such as cyclohexenyl and norbornenyl groups.

[0448] In formula (F1), R 302 represents a saturated hydrocarbylene group having 1 to 20 carbon atoms or an arylene group having 6 to 20 carbon atoms, and some or all of the hydrogen atoms of the saturated hydrocarbylene group may be substituted with halogen atoms other than fluorine atoms, or 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.

[0449] 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 methanediyl group, ethane-1,1-diyl group, ethane-1,2-diyl group, propane-1,3-diyl group, butane-1,4-diyl group, pentane-1,5-diyl group, hexane-1,6-diyl group, heptane-1,7-diyl group, octane-1,8-diyl group, nonane-1,9-diyl group, decane-1,10-diyl group, undecane-1,11-diyl group, and dodecane-1,12-diyl group; and cyclic saturated hydrocarbylene groups having 3 to 20 carbon atoms such as cyclopentanediyl group, cyclohexanediyl group, norbornanediyl group, and adamantanediyl group.

[0450] R 302Specific examples of the arylene group having 6 to 20 carbon atoms represented by the formula (I) 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 on the arylene group, may be linear, branched, or cyclic, and specific examples thereof include alkyl groups having 1 to 20 carbon atoms, such as a methyl group, ethyl group, n-propyl group, isopropyl group, n-butyl group, isobutyl group, sec-butyl group, tert-butyl group, n-pentyl group, n-hexyl group, n-octyl group, n-nonyl group, n-decyl group, undecyl group, dodecyl group, tridecyl group, tetradecyl group, pentadecyl group, heptadecyl group, octadecyl group, nonadecyl group, and icosyl group; and cyclic saturated hydrocarbyl groups having 3 to 20 carbon atoms, such as a cyclopropyl group, cyclopentyl group, cyclohexyl group, cyclopropylmethyl group, 4-methylcyclohexyl group, cyclohexylmethyl group, norbornyl group, and adamantyl group. Specific examples of the arylene group having 6 to 14 carbon atoms that is the substituent of the arylene group include a phenylene group, a naphthylene group, a phenanthrenediyl group, and an anthracenediyl group.

[0451] The anion represented by formula (F1) is preferably an anion represented by the following formula (F2). [ka]

[0452] In formula (F2), p, q, r, L 31 , L F and R 301 is the same as above. s2 is 1, 2, 3 or 4. R 302A is a saturated hydrocarbyl group having 1 to 14 carbon atoms, a saturated hydrocarbyloxy group having 1 to 14 carbon atoms, an aryl group having 6 to 14 carbon atoms, a halogen atom, or a hydroxy group. When s2 is 2, 3, or 4, each R 302A may be the same as or different from each other.

[0453] Specific examples of the anion represented by formula (F1) include, but are not limited to, those shown below. [ka]

[0454] [ka]

[0455] [ka]

[0456] [ka]

[0457] [ka]

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[0459] [ka]

[0460] [ka]

[0461] [ka]

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[0463]

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[0478] [ka]

[0479] [ka]

[0480] [ka]

[0481] In the (F) other photoacid generators, the cation paired with the anion is preferably a sulfonium cation or an iodonium cation. Specific examples of the sulfonium cation include, but are not limited to, those exemplified as specific examples of the sulfonium cation represented by formula (Z-1) and those exemplified as specific examples of the sulfonium cation represented by formula (Z-3). Specific examples of the iodonium cation include, but are not limited to, those exemplified as specific examples of the iodonium cation represented by formula (Z-2).

[0482] The acid generated by the other photoacid generator preferably has a pKa of -2.0 or higher, more preferably -1.0 or higher. The upper limit of the pKa is preferably 2.0. The pKa value was calculated using the pKa DB in the software ACD / Chemsketch ver. 9.04 manufactured by Advanced Chemistry Development, Inc.

[0483] 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. By including the other photoacid generator, it is possible to appropriately adjust the amount of acid generated in the exposed area and the dissolution inhibition ability of the unexposed area. The (F) other photoacid generator may be used alone or in combination of two or more.

[0484] [(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 its coatability onto a substrate. Many such surfactants are known, as described in WO 2006 / 121096, JP 2008-102383, JP 2008-304590, JP 2004-115630, and JP 2005-8766, and a surfactant can be selected with reference to these publications.

[0485] 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 parts by mass or more, relative to 80 parts by mass of the base polymer (B). The surfactant (G) may be used alone, or two or more types may be used in combination.

[0486] [Method for 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; irradiating the resist film with a pattern using high-energy rays (i.e., exposing the resist film with high-energy rays); and developing the resist film irradiated with the pattern using an alkaline developer to obtain a resist pattern.

[0487] The substrate may be, for example, a substrate for manufacturing integrated circuits (Si, SiO, SiO2, SiN, SiON, TiN, WSi, BPSG, SOG, organic anti-reflective coating, etc.) or a substrate for manufacturing mask circuits (Cr, CrO, CrON, MoSi2, Si, SiO2, SiO2, etc.) The chemically amplified positive resist composition is applied to the substrate by a method such as spin coating to a film thickness of 0.03 to 2 μm, and this is then 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.

[0488] The resist film is then exposed to a pattern using high-energy radiation such as ultraviolet radiation, far ultraviolet radiation, excimer laser light (e.g., KrF or ArF), EB, EUV, X-rays, gamma rays, and synchrotron radiation.

[0489] When ultraviolet rays, far ultraviolet rays, excimer laser light, EUV, X-rays, gamma rays, or synchrotron radiation is used as the high-energy rays, 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.

[0490] Exposure can be performed by conventional exposure methods, or in some cases by immersion, in which a liquid is inserted between the mask and the resist film. In this case, a water-insoluble protective film can be used.

[0491] Next, post-exposure baking (PEB) is carried out 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.

[0492] 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 dipping, puddling, or spraying, to form a desired pattern on the substrate.

[0493] The chemically amplified positive resist composition of the present invention is particularly useful when used under conditions requiring 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 also particularly useful for application to substrates having a surface made of a material that is prone to pattern peeling or pattern collapse due to the difficulty in achieving resist pattern adhesion. Examples of such substrates include substrates on which a film of metallic chromium or a chromium compound containing one or more light elements selected from oxygen, nitrogen, and carbon is sputtered. The chemically amplified positive resist composition of the present invention is particularly useful for pattern formation using a photomask blank as the substrate. [Example]

[0494] The present invention will be specifically explained below by showing synthesis examples, examples, and comparative examples, but the present invention is not limited to the following examples. The apparatuses used are as follows. IR: Thermo Fisher Scientific NICOLET 6700 · 1 H-NMR: ECA-500 manufactured by JEOL Ltd. MALDI TOF-MS: JEOL S3000

[0495] [1] Synthesis of onium salts [Example 1-1] Synthesis of onium salt PAG-1 [ka]

[0496] (1) Synthesis of intermediate In-1 Under a nitrogen atmosphere, raw materials SM-1 (14.5 g) and N,N-dimethylformamide (0.2 g) were dissolved in methylene chloride (100 g) in a reaction vessel, and the temperature inside the reaction vessel was raised to 40°C. Then, oxalyl chloride (9.5 g) was added dropwise. After the dropwise addition, the reaction vessel was aged for 2 hours while maintaining the temperature inside the reaction vessel at 40°C. After aging, the reaction solution was cooled, and water (50 g) was added to quench the reaction. Methylene chloride (50 g) was added to extract the target product, which was then subjected to a standard aqueous work-up. The solvent was evaporated, and hexane was added to recrystallize the product, yielding 13.7 g of intermediate In-1 as white crystals (yield 95%).

[0497] (2) Synthesis of onium salt PAG-1 Under a nitrogen atmosphere, raw material SM-1 (8.7 g) was suspended in a mixed solvent of THF (30 g) and water (30 g) in a reaction vessel. 2.5 g of 25% by mass aqueous sodium hydroxide solution was added dropwise, and the mixture was stirred at room temperature for 5 hours. Subsequently, intermediate In-1 (8.7 g) was added, and the mixture was further aged at room temperature for 3 hours. After aging, water (50 g) was added to quench the reaction. Methylene chloride (60 g) was added to extract the target product, and after standard aqueous work-up, the solvent was evaporated. Diisopropyl ether was added to recrystallize the product, yielding 14.5 g of the onium salt PAG-1 as white crystals (yield 92%).

[0498] The IR spectrum data and TOF-MS results of PAG-1 are shown below. 1 The results of H-NMR / DMSO-d6) are shown in Figure 1. IR(D-ATR): ν= 3062, 2971, 1720, 1610, 1586, 1465, 1438, 1386, 1276, 1224, 1187, 1105, 1082, 1036, 1019, 966, 904, 886, 853, 821, 772, 707, 682, 643, 625, 548, 487 cm -1 . MALDI TOF-MS: POSITIVE M + 277(C 18 H 13 OS + equivalent) NEGATIVE M - 771(C 40 H 35 O 12 S2 + equivalent)

[0499] [Examples 1-2 to 1-10] Synthesis of onium salts PAG-2 to PAG-10 Onium salts PAG-2 to PAG-10 represented by the following formulae were synthesized using the corresponding raw materials and known organic synthesis reactions. [ka]

[0500] [ka]

[0501] [2] Synthesis of base polymer [Synthesis Example] Synthesis of base polymers (P-1 to P-6) Each monomer was combined according to a known recipe and copolymerized in a solvent, the reaction solution was poured into hexane, and the precipitated solid was washed with hexane, isolated, and dried to obtain base polymers (P-1 to P-6) with the following compositions. 1 H-NMR, 13 Mw and Mw / Mn were confirmed by C-NMR and GPC (solvent: THF, standard: polystyrene). [ka]

[0502] [3] Preparation of chemically amplified positive resist composition [Examples 2-1 to 2-50, Comparative Examples 1-1 to 1-42] Chemically amplified positive resist compositions were prepared by dissolving each component in an organic solvent according to the formulations 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.

[0503] [Table 1]

[0504] [Table 2]

[0505] [Table 3]

[0506] In Tables 1 to 3, the comparative photoacid generators PAG-A to PAG-E, the blend photoacid generator PAG-Z, the quenchers SQ-1 to SQ-4, and the fluorine atom-containing polymers FP-1 to FP-5 are as follows.

[0507] [ka]

[0508] [ka]

[0509] [ka]

[0510] [ka]

[0511] [4] EB lithography evaluation [Examples 3-1 to 3-50, Comparative Examples 2-1 to 2-42] Each chemically amplified positive resist composition (R-1 to R-50, CR-1 to CR-42) was spin-coated using ACT-M (Tokyo Electron Limited) onto a 152 mm square reflective mask blank for EUV exposure masks, the outermost surface of which was a chromium compound, and the mask was 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 resulting resist film was measured using an optical measuring device, Nanospec (Nanometrics). Measurements were performed at 81 locations on the surface of the blank substrate, excluding the outer edge portion extending 10 mm inward from the outer periphery, and the average thickness and thickness range were calculated.

[0512] Next, the 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% by mass TMAH aqueous solution to obtain a positive pattern.

[0513] The obtained resist patterns were evaluated as follows: The prepared patterned mask blanks were observed with a top-down SEM (scanning electron microscope), and the exposure dose required to resolve a 200 nm 1:1 line and space (LS) at 1:1 was determined as the optimal exposure dose (μC / cm 2 The minimum dimension at the exposure dose required to resolve a 200 nm line-and-space pattern at a 1:1 ratio was defined as the resolution (limiting resolution), and the LER of the 200 nm line-and-space pattern was measured using an SEM. Regarding the limiting resolution of isolated spaces (IS), the minimum dimension at the exposure dose required to resolve a 200 nm line-and-space pattern at a 9:1 ratio was defined as the limiting resolution. The results are shown in Tables 4 to 6.

[0514] [Table 4]

[0515] [Table 5]

[0516] [Table 6]

[0517] The chemically amplified positive resist compositions of the present invention (R-1 to R-50) all exhibited good resolution, LER, and pattern rectangularity. On the other hand, the comparative resist compositions (CR-1 to CR-42) showed insufficient optimization of acid diffusion, and exhibited degradation in resolution and LER.

[0518] The method of forming a resist pattern using the chemically amplified positive resist composition of the present invention is useful for the production of semiconductor devices, particularly for photolithography in the processing of transmission and reflection photomask blanks.

Claims

1. An onium salt represented by the following formula (A): 【Chemistry 1】 (In the formula, n1 is 0 or 1. n2 is 0, 1, 2, 3, or 4. n3 is 1, 2, 3, or 4. n4 is 0 or 1. n5 is 0, 1, 2, 3, or 4. n6 is 0, 1, 2, 3, or 4. However, when n1 is 0, 1≦n2+n3≦5, and when n1 is 1, 1≦n2+n3≦7. R 1 is a hydrocarbyl group having 1 to 20 carbon atoms. R 2 is a halogen atom, a nitro group, a cyano group, a hydroxy group, a carboxy group, a hydrocarbyl group having 1 to 20 carbon atoms which may contain a heteroatom, a hydrocarbyloxy group having 1 to 20 carbon atoms which may contain a heteroatom, a hydrocarbylthio group having 1 to 20 carbon atoms which may contain a heteroatom, or a hydrocarbyloxycarbonyl group having 1 to 20 carbon atoms which may contain a heteroatom. 2 may be the same or different, and multiple R 2 may be bonded to each other to form a ring together with the carbon atoms to which they are attached. R 3 is a halogen atom, a nitro group, a cyano group, a hydroxy group, a carboxy group, a hydrocarbyl group having 1 to 20 carbon atoms which may contain a heteroatom, a hydrocarbyloxy group having 1 to 20 carbon atoms which may contain a heteroatom, a hydrocarbylthio group having 1 to 20 carbon atoms which may contain a heteroatom, a hydrocarbyloxycarbonyl group having 1 to 20 carbon atoms which may contain a heteroatom, or a hydrocarbylcarbonyloxy group having 1 to 20 carbon atoms which may contain a heteroatom. 3 may be the same or different, and multiple R 3 may be bonded to each other to form a ring together with the carbon atoms to which they are attached. R 4 is a halogen atom, a nitro group, a cyano group, a hydroxy group, a hydrocarbyl group having 1 to 20 carbon atoms which may contain a heteroatom, a hydrocarbyloxy group having 1 to 20 carbon atoms which may contain a heteroatom, or a hydrocarbylthio group having 1 to 20 carbon atoms which may contain a heteroatom. 4 may be the same or different, but multiple R 4 do not bond to each other to form a ring together with the carbon atoms to which they are attached. L A , L B and L C are each independently a single bond, an ether bond, an ester bond, a sulfonate ester bond, an amide bond, a sulfonamide bond, a carbonate bond or a carbamate bond. X L1 is a single bond or a hydrocarbylene group having 1 to 40 carbon atoms which may contain a heteroatom. Z + is an onium cation.

2. 2. The onium salt according to claim 1, which is represented by the following formula (A1): 【Chemistry 2】 (In the formula, n2, n3, n5, n6, R 1 ~R 4 , L A , L B , L C , X L1 and Z + is the same as above.)

3. The onium salt according to claim 2, which is represented by the following formula (A2): 【Transformation 3】 (In the formula, n2, n3, n5, n6, R 1 ~R 4 , L A and Z + is the same as above.)

4. Z + is a sulfonium cation represented by the following formula (Z-1) or an iodonium cation represented by the following formula (Z-2): 【Chemistry 4】 (In the formula, 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. 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. Z + is a sulfonium cation represented by the following formula (Z-3): 【Transformation 5】 (Wherein, m1 is 0 or 1. m2 is 0 or 1. m3 is 0 or 1. m4 is 0, 1, 2, 3 or 4. m5 is 0, 1, 2, 3 or 4. m6 is 0, 1, 2, 3, 4, 5 or 6. m7 is 0, 1, 2, 3, 4, 5 or 6. m8 is 0, 1 or 2. m9 is 0, 1 or 2. m10 is 0, 1 or 2. m11 is 0 or 1. m12 is 0, 1, 2, 3 or 4. m13 is 0, 1 or 2. m14 is 0, 1 or 2. However, when m1 is 0, 0≦m6+m9≦4, and when m1 is 1, 0≦m6+m9≦6. When m2 is 0, 0≦m7+m10≦4, and when m2 is 1, 0≦m7+m10≦6. When m3 is 0, 1≦m4+m5+m8+m14≦4, and when m3 is 1, 1≦m4+m5+m8+m14≦6. When m11 is 0, 0≦m12+m13≦4, and when m11 is 1, 0≦m12+m13≦6. Also, m4+m12≧1. R F1 ~R F3 are each independently a fluorine atom, a fluorinated saturated hydrocarbyl group having 1 to 6 carbon atoms, a fluorinated saturated hydrocarbyloxy group having 1 to 6 carbon atoms, or a fluorinated saturated hydrocarbylthio group having 1 to 6 carbon atoms. F1 may be the same or different, and when m6 is 2 or more, each R F2 may be the same or different, and when m7 is 2 or more, each R F3 may be the same or different from each other. R ct6 ~R ct9 is a halogen atom other than an iodine atom or a fluorine atom, a nitro group, a cyano group, a hydrocarbyl group having 1 to 20 carbon atoms which may contain a heteroatom, a hydrocarbyloxy group having 1 to 20 carbon atoms which may contain a heteroatom, or a hydrocarbylthio group having 1 to 20 carbon atoms which may contain a heteroatom. ct6 may be the same or different, and two R ct6 may be bonded to each other to form a ring together with the carbon atoms to which they are bonded, and when m9 is 2, two R ct7 may be the same or different, and two R ct7 may be bonded to each other to form a ring together with the carbon atoms to which they are bonded, and when m10 is 2, two R ct8 may be the same or different, and two R ct8 may be bonded to each other to form a ring together with the carbon atoms to which they are bonded, and when m13 is 2, two R ct9 may be the same or different, and two R ct9 may be bonded to each other to form a ring together with the carbon atoms to which they are attached. In addition, S in the sulfonium cation + The aromatic rings directly bonded to S + may form a ring together with L D and L E are each independently a single bond, an ether bond, an ester bond, an amide bond, a sulfonate ester bond, a sulfonamide bond, a carbonate bond or a carbamate bond. X L2 is a single bond or a hydrocarbylene group having 1 to 40 carbon atoms which may contain a heteroatom.

6. A photoacid generator comprising the onium salt according to any one of claims 1 to 5.

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

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

9. 9. The chemically amplified positive resist composition according to claim 8, wherein the polymer contains a repeating unit represented by the following formula (B1): 【Transformation 6】 (In the formula, a1 is 0 or 1. a2 is 0, 1, or 2. a3 is an integer that satisfies 0≦a3≦5+2(a2)−a4. a4 is 1, 2, or 3. R A is a hydrogen atom, a fluorine atom, a methyl group, or a trifluoromethyl group. R 11 represents a halogen atom, a nitro group, a carboxy group, 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. A 1 is a single bond or a saturated hydrocarbylene group having 1 to 10 carbon atoms, and the —CH 2 A part of - may be replaced by -O-.)

10. 9. The chemically amplified positive resist composition according to claim 8, wherein the polymer contains a repeating unit represented by the following formula (B2-1): 【Transformation 7】 (In the formula, R A is a hydrogen atom, a fluorine atom, a methyl group, or a trifluoromethyl group. b1 is 0 or 1. b2 is 0, 1, or 2. b3 is an integer that satisfies 0≦b3≦5+2(b2)−b4. b4 is 1, 2, or 3. b5 is 0 or 1. R 21 represents 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. A 2 is a single bond or a saturated hydrocarbylene group having 1 to 10 carbon atoms, and the —CH 2 A part of - may be substituted with -O-. When b4 is 1, X is an acid labile group, and when b4 is 2 or 3, X is a hydrogen atom or an acid labile group, provided that at least one X is an acid labile group.

11. 9. The chemically amplified positive resist composition according to claim 8, wherein the polymer contains a repeating unit represented by the following formula (B2-2): 【Transformation 8】 (Wherein, c1 is 0, 1 or 2; c2 is 0, 1 or 2; c3 is 0, 1, 2, 3, 4 or 5; and c4 is 0, 1 or 2. R A is a hydrogen atom, a fluorine atom, a methyl group, or a trifluoromethyl group. R 22 and R 23 are each independently a hydrocarbyl group having 1 to 10 carbon atoms which may contain a heteroatom, and R 22 and R 23 may be bonded to each other to form a ring together with the carbon atoms to which they are attached. R 24 are each independently a fluorine atom, a fluorinated alkyl group having 1 to 5 carbon atoms, or a fluorinated alkoxy group having 1 to 5 carbon atoms. R 25 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. A 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 a naphthylene group.

12. 9. The chemically amplified positive resist composition according to claim 8, wherein the polymer comprises 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): 【Chemistry 9】 (In the formula, d is 0, 1, 2, 3, 4, 5, or 6. e is 0, 1, 2, 3, or 4. f1 is 0 or 1. f2 is 0, 1, or 2. f3 is 0, 1, 2, 3, 4, or 5. R A is a hydrogen atom, a fluorine atom, a methyl group, or a trifluoromethyl group. R 31 and R 32 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. R 33 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 the —CH 2 A part of - may be replaced by -O-.)

13. 9. The chemically amplified positive resist composition according to claim 8, wherein the polymer comprises at least one selected from the group consisting of 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), and a repeating unit represented by the following formula (B10): 【Chemistry 10】 (In the formula, g1 and g2 are each independently 0, 1, 2, or 3. h1 is 0 or 1. h2 is 0, 1, 2, 3, or 4. h3 is 0, 1, 2, 3, or 4. However, when h1 is 0, 0≦h2+h3≦4, and when h1 is 1, 0≦h2+h3≦6. R A are each independently a hydrogen atom, a fluorine atom, a methyl group, or a trifluoromethyl group. Z 1 represents a single bond or an optionally substituted phenylene group. Z 2 is a single bond, **-C(=O)-O-Z 21 -, **-C(=O)-NH-Z 21 - or **-O-Z 21 - is. Z 21 represents an aliphatic hydrocarbylene group having 1 to 6 carbon atoms, a phenylene group, or a divalent group obtained by combining these, and may contain a halogen atom, a carbonyl group, an ester bond, an ether bond, or a hydroxy group. Z 3 is a single bond, an ether bond, an ester bond, an amide bond, a sulfonate ester bond, a sulfonamide bond, a carbonate bond or a carbamate bond. Z 4 represents a single bond, an aliphatic hydrocarbylene group having 1 to 6 carbon atoms, a phenylene group, or a divalent group obtained by combining these, and may contain a halogen atom, a carbonyl group, an ester bond, an ether bond, or a hydroxy group. Z 5 each independently represents a single bond, an optionally substituted phenylene group, a naphthylene group, or *-C(=O)-O-Z 51 - is. Z 51 is an aliphatic hydrocarbylene group having 1 to 10 carbon atoms, a phenylene group, or a naphthylene group, and the aliphatic hydrocarbylene group may contain a halogen atom, a hydroxy group, an ether bond, an ester bond, or a lactone ring. Z 6 is a single bond, an ether bond, an ester bond, an amide bond, a sulfonate ester bond, a sulfonamide bond, a carbonate bond or a carbamate bond. Z 7 each independently represents a single bond, ***-Z 71 -C(=O)-O-, ***-C(=O)-NH-Z 71 -or***-O-Z 71 -It is. It is. Z 71 is a hydrocarbylene group having 1 to 20 carbon atoms which may contain a heteroatom. Z 8 are each independently a single bond, ****-Z 81 -C(=O)-O-, ****-C(=O)-NH-Z 81 - or ****-O-Z 81 - is. Z 81 is a hydrocarbylene group having 1 to 20 carbon atoms which may contain a heteroatom. Z 9 represents a single bond, a methylene group, an ethylene group, a phenylene group, a fluorinated phenylene group, a phenylene group substituted with a trifluoromethyl group, *-C(=O)-O-Z 91 -, *-C(=O)-N(H)-Z 91 - or *-O-Z 91 - is. Z 91 represents an aliphatic hydrocarbylene group having 1 to 6 carbon atoms, a phenylene group, a fluorinated phenylene group, or a phenylene group substituted with a trifluoromethyl group, and may contain a carbonyl group, an ester bond, an ether bond, or a hydroxy group. * represents a bond to a carbon atom in the main chain. ** represents Z 1 *** represents a bond with Z 6 **** represents a bond with Z. 7 Represents a bond with . L 1 is a single bond, an ether bond, an ester bond, a carbonyl group, a sulfonate ester bond, a sulfonamide bond, a carbonate bond or a carbamate bond. Rf 1 and Rf 2 are each independently a fluorine atom or a fluorinated saturated hydrocarbyl group having 1 to 6 carbon atoms. Rf 3 and Rf 4 are each independently a hydrogen atom, a fluorine atom, or a fluorinated saturated hydrocarbyl group having 1 to 6 carbon atoms. Rf 5 and Rf 6 are each independently a hydrogen atom, a fluorine atom, or a fluorinated saturated hydrocarbyl group having 1 to 6 carbon atoms. 5 and Rf 6 cannot simultaneously become a hydrogen atom. Rf 7 is a fluorine atom, a fluorinated alkyl group having 1 to 6 carbon atoms, a fluorinated alkoxy group having 1 to 6 carbon atoms, or a fluorinated alkylthio group having 1 to 6 carbon atoms. R 41 and R 42 are each independently a hydrocarbyl group having 1 to 20 carbon atoms which may contain a heteroatom. 41 and R 42 may be bonded to each other to form a ring together with the sulfur atom to which they are attached. R 43 is a hydrocarbyl group having 1 to 20 carbon atoms which may contain a halogen atom other than a fluorine atom or a heteroatom. When h3 is 2, 3 or 4, each R 43 may be the same or different, and multiple R 43 may be bonded to each other to form a ring together with the carbon atoms to which they are attached. M - is a non-nucleophilic counterion. A + is an onium cation.

14. 9. The chemically amplified positive resist composition according to claim 8, wherein the content of repeating units having an aromatic ring skeleton in all repeating units of the polymer contained in said base polymer is 60 mol % or more.

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

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

17. 8. The chemically amplified positive resist composition according to claim 7, further comprising a fluorine atom-containing polymer that contains at least one selected from the group consisting of a repeating unit represented by the following formula (E1), a repeating unit represented by the following formula (E2), a repeating unit represented by the following formula (E3), and a repeating unit represented by the following formula (E4), and that may further contain at least one selected from the group consisting of a repeating unit represented by the following formula (E5) and a repeating unit represented by the following formula (E6): 【Chemistry 11】 (In the formula, j1 is 1, 2, or 3. j2 is an integer that satisfies 0≦j2≦5+2(j3)−j1. j3 is 0 or 1. k is 1, 2, or 3. R B are each independently 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 201 , R 202 , R 204 and R 205 are each independently a hydrogen atom or a saturated hydrocarbyl group having 1 to 10 carbon atoms. R 203 , R 206 , R 207 and R 208 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 203 , R 206 , R 207 and R 208 When is a hydrocarbyl group or a fluorinated hydrocarbyl group, an ether bond or a carbonyl group may be present between the carbon-carbon bond. R 209 is 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 its carbon-carbon bonds. R 210 is a linear or branched hydrocarbyl group having 1 to 5 carbon atoms which may have a heteroatom-containing group interposed between its carbon-carbon bonds. R 211 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 —CH 2 A portion of the - may be substituted with an ester bond or an ether bond. X 1 is a (k+1)-valent hydrocarbon group having 1 to 20 carbon atoms or a (k+1)-valent fluorinated hydrocarbon group having 1 to 20 carbon atoms. X 2 is a single bond, *-C(=O)-O-, or *-C(=O)-NH-. * is a bond to a carbon atom in the main chain. X 3 is a single bond, -O-, *-C(=O)-O-X 31 -X 32 - or *-C(=O)-NH-X 31 -X 32 - is. X 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.)

18. 8. The chemically amplified positive resist composition according to claim 7, further comprising a photoacid generator other than the photoacid generator according to claim 6.

19. 10. 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 claim 7; irradiating the resist film with a pattern using high-energy rays; and developing the resist film irradiated with the pattern using an alkaline developer.

20. 20. The method for forming a resist pattern according to claim 19, wherein the high-energy radiation is extreme ultraviolet radiation having a wavelength of 3 to 15 nm or an electron beam.

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

22. 20. The method for forming a resist pattern according to claim 19, wherein the substrate is a photomask blank.

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