Chemically amplified positive resist composition and method for forming resist pattern

Abstract

To provide a chemically amplified positive resist composition which improves resolution in pattern formation and can give a resist pattern improved in LER and resolution, pattern fidelity, and dose margin, and to provide a resist pattern forming method.SOLUTION: The chemically amplified positive resist composition contains: (A) a quencher containing a sulfonium salt represented by formula (A1); and (B) a base polymer containing a polymer which contains a repeating unit having a phenol structure, is decomposed by the action of an acid, and increases its solubility in an alkali developer.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a chemically amplified positive resist composition and a method of forming a resist pattern. [Background technology]

[0002] In recent years, with the increasing integration and speed of LSIs, pattern rules have been rapidly becoming finer. Chemically amplified resist compositions using acid as a catalyst are used exclusively for processing patterns of 0.2 μm or less. High-energy beams such as ultraviolet, far ultraviolet, and electron beams (EB) are used as exposure sources. EB lithography, which is used as an ultrafine processing technology, is also indispensable as a method for processing photomask blanks when producing photomasks for semiconductor manufacturing.

[0003] Polymers containing a large amount of aromatic skeletons with acidic side chains, such as polyhydroxystyrene, are useful as materials for resist compositions for KrF lithography, which uses a KrF excimer laser, but because they exhibit high absorption of light with wavelengths around 200 nm, they have not been used as materials for resist compositions for ArF lithography, which uses an ArF excimer laser.However, they are important materials for resist compositions for EB lithography, a powerful technology for forming patterns smaller than the processing limit of ArF excimer lasers, and for extreme ultraviolet (EUV) lithography, because they provide high etching resistance.

[0004] Typically, the base polymer used in positive resist compositions for EB lithography and EUV lithography is a material that is soluble in an alkaline developer and that uses an acid generated from a photoacid generator upon exposure to high-energy rays as a catalyst to deprotect the acid-labile protecting groups (acid-labile groups) that mask the acidic functional groups on the phenol side chains of the base polymer.

[0005] Tertiary alkyl groups, tert-butoxycarbonyl groups, acetal groups, and other groups have been used as acid-labile protecting groups. While the use of 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 acid diffusion can lead to deprotection reactions in unexposed areas of the resist film, resulting in poor line edge roughness (LER) and reduced dimensional uniformity (CDU). Furthermore, in the processing of photomask blanks, a particularly important application, photomask substrates often contain surface materials, such as chromium oxide and other chromium compounds, that can easily affect the pattern profile of chemically amplified resist films. Maintaining a rectangular resist profile, regardless of the type of substrate, is crucial for maintaining high resolution and post-etching shape. In recent years, in order to achieve miniaturization, the MBMW (multi-beam mask writing) writing process is sometimes used to process mask blanks. In this case, a low-sensitivity resist composition (high dose region) that is advantageous for roughness is used as the resist composition, and optimization of the resist composition in this high dose region has also been attracting attention.

[0006] Various improvements have been made to control sensitivity and pattern profile by selecting and combining materials used in resist compositions, process conditions, etc. One of these improvements addresses the issue of acid diffusion. Acid diffusion has a significant impact on the sensitivity and resolution of chemically amplified resist compositions, and has therefore been the subject of extensive research.

[0007] Patent Documents 1 and 2 describe examples in which acid diffusion is suppressed and roughness is reduced by increasing the bulkiness of benzenesulfonic acid generated from a photoacid generator upon exposure. However, the acid diffusion suppression by these acid generators is still insufficient, and therefore, the development of an acid generator with even smaller diffusion has been desired.

[0008] Patent Document 3 describes an example of controlling acid diffusion by binding sulfonic acid generated upon exposure to a polymer used in a resist composition to suppress diffusion. This method of suppressing acid diffusion by incorporating a repeating unit that generates acid upon exposure into a base polymer is effective for obtaining patterns with small LER. However, depending on the structure and incorporation rate of such repeating units, problems may arise with the solubility of base polymers bound to repeating units that generate acid upon exposure in organic solvents.

[0009] Furthermore, when a sulfonium salt that generates an acid with high acid strength, such as a fluorinated alkane sulfonic acid, as described in Patent Document 4, is used with a polymer containing a repeating unit having an acetal group, a problem occurs in that a pattern with large LER is formed. Because the acid strength of a fluorinated alkane sulfonic acid is too high for deprotection of an acetal group, which has a relatively small activation energy for deprotection, 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. This is also true for the sulfonium salts that generate benzenesulfonic acid, as described in Patent Documents 1 and 2. Therefore, there is a need for the development of an acid generator that generates an acid with a strength more suitable for deprotection of an acetal group.

[0010] In addition to the aforementioned method of increasing the bulk of the generated acid, improving the quencher (acid diffusion controller) is another possible method for suppressing acid diffusion. Quenchers suppress acid diffusion and are essentially essential components for improving the performance of resist compositions. Various quenchers have been investigated, with amines and weak acid onium salts typically being used. Patent Document 5 describes, as an example of a weak acid onium salt, the addition of triphenylsulfonium acetate, which enables the formation of a good resist pattern free of T-top formation, linewidth differences between isolated and dense patterns, and standing waves. Patent Document 6 describes the addition of an ammonium sulfonate salt or an ammonium carboxylate salt, which improves sensitivity, resolution, and exposure margin. Patent Document 7 also describes the use of a resist composition for KrF lithography and EB lithography containing a photoacid generator that generates a fluorine-containing carboxylic acid, which exhibits excellent resolution and improved process tolerances, such as exposure margin and depth of focus. These are used in KrF lithography, EB lithography or F2 lithography.

[0011] Patent Document 8 describes a positive-tone photosensitive composition for ArF lithography containing a carboxylic acid onium salt. In this composition, a strong acid (sulfonic acid) generated from a photoacid generator upon exposure is exchanged with a weak acid onium salt to form a weak acid and a strong acid onium salt, thereby replacing a highly acidic strong acid (sulfonic acid) with a weak acid (carboxylic acid), thereby suppressing the acid decomposition reaction of acid-labile groups and reducing (controlling) the acid diffusion distance, and apparently functioning as a quencher.

[0012] Patent Document 9 describes the use of a sulfonium salt of a carboxylic acid containing a nitrogen-containing heterocycle as a quencher, but no detailed investigation has been conducted into low-sensitivity resist compositions (high dose range) of 50 μC or more.

[0013] However, when patterning is performed using a resist composition containing the above-mentioned onium carboxylate salt or onium fluorocarboxylate salt, LER and resolution are still insufficient despite the recent advances in miniaturization. Therefore, there has been a demand for the development of a quencher that can further reduce LER and improve resolution, pattern fidelity, and dose margin. [Prior art documents] [Patent documents]

[0014] [Patent Document 1] Japanese Patent Application Laid-Open No. 2009-53518 [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. 3955384 [Patent Document 6] Japanese Patent Application Publication No. 11-327143 [Patent Document 7] Patent No. 4231622 [Patent Document 8] Patent No. 4226803 [Patent Document 9] Patent No. 6512049 Summary of the Invention [Problem to be solved by the invention]

[0015] The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a chemically amplified positive resist composition that improves resolution during pattern formation and that is capable of obtaining a resist pattern that has improved LER, resolution, pattern fidelity, and dose margin, and a method of forming a resist pattern. [Means for solving the problem]

[0016] As a result of extensive investigations into achieving the above-mentioned object, the present inventors have found that when a quencher comprising a sulfonium salt of a carboxylic acid having a specific nitrogen-containing heterocycle is incorporated into a resist composition, it is possible to obtain patterns that exhibit good resolution and pattern shape, as well as improved LER, pattern fidelity, and dose margin, and have thereby completed the present invention.

[0017] That is, the present invention provides the following chemically amplified positive resist composition and method of forming a resist pattern. 1. A chemically amplified positive resist composition comprising: (A) a quencher containing a sulfonium salt represented by the following formula (A1); and (B) a base polymer containing a polymer that contains a repeating unit represented by the following formula (B1), and that decomposes under the action of an acid and has increased solubility in an alkaline developer. [ka] (In the formula, m is an integer of 0 to 2. The ring R in the formula is a saturated heterocyclic ring containing a nitrogen atom and having 2 to 12 carbon atoms, and the ring may have at least one bond selected from an ether bond, an ester bond, a thioether bond and a sulfonyl group. R 1 is an acid labile group. R 2 is a halogen atom or a saturated hydrocarbyl group having 1 to 6 carbon atoms which may contain a halogen atom. R 3 is a saturated hydrocarbylene group having 1 to 10 carbon atoms which may contain a single bond, or an ether bond, an ester bond or a thioether bond. R 4 , R 5 and R 6 are each independently a halogen atom or a hydrocarbyl group having 1 to 20 carbon atoms which may contain a heteroatom. 4 and R 5 and may be bonded to each other to form a ring together with the sulfur atom to which they are attached. [ka] (In the formula, a1 is 0 or 1. a2 is an integer of 0 to 2. a3 is an integer that satisfies 0≦a3≦5+2a2−a4. a4 is an integer of 1 to 3.) R A is a hydrogen atom, a fluorine atom, a methyl group, or a trifluoromethyl group. R 11 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 1 represents a single bond or a saturated hydrocarbylene group having 1 to 10 carbon atoms, and —CH2— of the saturated hydrocarbylene group may be substituted with —O—. 2. The chemically amplified positive resist composition of 1, wherein the polymer further 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 an integer of 0 to 2. b3 is an integer that satisfies 0≦b3≦5+2b2−b4. b4 is an integer of 1 to 3. b5 is 0 or 1. R 12 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 2 is a single bond or a saturated hydrocarbylene group having 1 to 10 carbon atoms, and -CH2- of the saturated hydrocarbylene group may be substituted with -O-. When b4 is 1, X is an acid labile group, and when b4 is 2 or more, X is a hydrogen atom or an acid labile group, provided that at least one X is an acid labile group. 3. The chemically amplified positive resist composition of 1 or 2, wherein the polymer further contains a repeating unit represented by the following formula (B2-2): [ka] (In the formula, c1 is an integer of 0 to 2. c2 is an integer of 0 to 2. c3 is an integer of 0 to 5. c4 is an integer of 0 to 2. R A is a hydrogen atom, a fluorine atom, a methyl group, or a trifluoromethyl group. 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. R 13 and R 14 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. R 15 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 16 are each independently a hydrocarbyl group having 1 to 10 carbon atoms which may contain a heteroatom. 4. The chemically amplified positive resist composition according to any one of 1 to 3, wherein the polymer further 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): [ka] (In the formula, d and e each independently represent an integer of 0 to 4. f1 is 0 or 1. f2 is an integer of 0 to 5. f3 is an integer of 0 to 2.) R A is a hydrogen atom, a fluorine atom, a methyl group, or a trifluoromethyl group. R 21 and R 22 are each independently a hydroxy group, a halogen atom, a saturated hydrocarbyl group having 1 to 8 carbon atoms which may be substituted with a halogen atom, a saturated hydrocarbyloxy group having 1 to 8 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 23 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, a cyano group, a sulfinyl group, or a sulfonyl group. A 4 represents a single bond or a saturated hydrocarbylene group having 1 to 10 carbon atoms, and —CH2— of the saturated hydrocarbylene group may be substituted with —O—. 5. The chemically amplified positive resist composition of any one of 1 to 4, wherein the polymer further comprises at least one repeating unit selected from the group consisting of repeating units represented by the following formulas (B6) to (B13): [ka] (In the formula, R B are each independently a hydrogen atom or a methyl group. Y 1 represents a single bond, an aliphatic hydrocarbylene group having 1 to 6 carbon atoms, a phenylene group, a naphthylene group, or a group having 7 to 18 carbon atoms obtained by combining these groups; -OY 11 -, -C(=O)-OY 11 - or -C(=O)-NH-Y 11 - and Y 11represents an aliphatic hydrocarbylene group having 1 to 6 carbon atoms, a phenylene group, a naphthylene group, or a group having 7 to 18 carbon atoms obtained by combining these, and may contain a carbonyl group, an ester bond, an ether bond, or a hydroxy group. Y 2 is a single bond or -Y 21 -C(=O)-O-, and Y 21 is a hydrocarbylene group having 1 to 20 carbon atoms which may contain a heteroatom. Y 3 represents a single bond, a methylene group, an ethylene group, a phenylene group, a fluorinated phenylene group, a phenylene group substituted with a trifluoromethyl group, -OY 31 -, -C(=O)-OY 31 - or -C(=O)-NH-Y 31 - and Y 31 represents an aliphatic hydrocarbylene group having 1 to 6 carbon atoms, a phenylene group, a fluorinated phenylene group, a phenylene group substituted with a trifluoromethyl group, or a group having 7 to 20 carbon atoms obtained by combining these, and may contain a carbonyl group, an ester bond, an ether bond, or a hydroxy group. Y 4 represents a single bond or a hydrocarbylene group having 1 to 30 carbon atoms which may contain a heteroatom. g1 and g2 each independently represent 0 or 1, but Y 4 When is a single bond, g1 and g2 are 0. R 31 ~R 48 are each independently a hydrocarbyl group having 1 to 20 carbon atoms which may contain a heteroatom. 31 and R 32 may be bonded to each other to form a ring together with the sulfur atom to which they are attached, and R 33 and R 34 , R 36 and R 37 , or R 39 and R 40 may be bonded to each other to form a ring together with the sulfur atom to which they are attached. R HF is a hydrogen atom or a trifluoromethyl group. Xa- is a non-nucleophilic counterion. 6. The chemically amplified positive resist composition of any one of 1 to 5, 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. 7. The chemically amplified positive resist composition according to any one of 1 to 6, further comprising (C) a photoacid generator. 8. The chemically amplified positive resist composition of 7, wherein the acid strength (pKa) of the anion of the photoacid generator is −3.0 or higher. 9. The chemically amplified positive resist composition of 7 or 8, wherein the content ratio of the photoacid generator (C) to the quencher (A) is less than 6 in mass ratio. 10. The chemically amplified positive resist composition of any of 1 to 9, further comprising (D) a fluorine atom-containing polymer that contains at least one repeating unit selected from the group consisting of a repeating unit represented by the following formula (D1), a repeating unit represented by the following formula (D2), a repeating unit represented by the following formula (D3), and a repeating unit represented by the following formula (D4), and that may further contain at least one repeating unit selected from the group consisting of a repeating unit represented by the following formula (D5) and a repeating unit represented by the following formula (D6). [ka] (In the formula, R C are each independently a hydrogen atom, a fluorine atom, a methyl group, or a trifluoromethyl group. R D are each independently a hydrogen atom or a methyl group. R 101 , R 102 , R 104 and R 105 are each independently a hydrogen atom or a saturated hydrocarbyl group having 1 to 10 carbon atoms. R 103 , R 106 , R 107 and R 108 are each independently a hydrogen atom, a hydrocarbyl group having 1 to 15 carbon atoms, a fluorinated hydrocarbyl group having 1 to 15 carbon atoms, or an acid labile group, and R 103 , R 106 , R 107 and R108 When is a hydrocarbyl group or a fluorinated hydrocarbyl group, an ether bond or a carbonyl group may be present between the carbon-carbon bonds. R 109 is a hydrogen atom or a linear or branched hydrocarbyl group having 1 to 5 carbon atoms which may have a group containing a heteroatom interposed between its carbon-carbon bond. R 110 is 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 111 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 is an integer of 1 to 3. y is an integer that satisfies 0≦y≦5+2z−x. z is 0 or 1. h is an integer of 1 to 3. Z 1 is a (h+1)-valent hydrocarbon group having 1 to 20 carbon atoms or a (h+1)-valent fluorinated hydrocarbon group having 1 to 20 carbon atoms. Z 2 is a single bond, *-C(=O)-O-, or *-C(=O)-NH-. * is a bond to a carbon atom in the main chain. Z 3 is a single bond, -O-, *-C(=O)-OZ 31 -Z 32 -or*-C(=O)-NH-Z 31 -Z 32 -It is. Z 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. 11. The chemically amplified positive resist composition according to any one of 1 to 10, further comprising (E) an organic solvent. 12. A method for forming a resist pattern, comprising the steps of: forming a resist film on a substrate using the chemically amplified positive resist composition according to any one of 1 to 11; irradiating the resist film with a pattern using high-energy rays; and developing the resist film irradiated with the pattern using an alkaline developer. 13. The method for forming a resist pattern according to 12, wherein the high-energy radiation is extreme ultraviolet radiation or an electron beam. 14. The method for forming a resist pattern according to 12 or 13, wherein the outermost surface of the substrate is made of a material containing at least one element selected from the group consisting of chromium, silicon, tantalum, molybdenum, cobalt, nickel, tungsten, and tin. 15. The method for forming a resist pattern according to any one of 12 to 14, wherein the substrate is a transmission or reflection mask blank. 16. A transmission or reflection mask blank coated with any one of the chemically amplified positive resist compositions set forth in any one of 1 to 11. [Effects of the Invention]

[0018] The chemically amplified positive resist composition of the present invention, due to the action of the sulfonium salt represented by formula (A1), can effectively control acid diffusion due to exposure during pattern formation, and when formed into a resist film to form a pattern, can obtain a pattern that has extremely high resolution and pattern fidelity and is improved in LER and dose margin. Furthermore, due to the action of the repeating unit represented by formula (B1), the composition exhibits good solubility in alkaline developers and can also improve adhesion to substrates during resist film formation.

[0019] A resist pattern forming method using the chemically amplified positive resist composition of the present invention can form a pattern that has high resolution and pattern fidelity, while also improving LER and dose margin, and therefore can be suitably used in microfabrication techniques, in particular EUV lithography and EB lithography. DETAILED DESCRIPTION OF THE INVENTION

[0020] 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 alone or as a mixture.

[0021] [Chemically amplified positive resist composition] The chemically amplified positive resist composition of the present invention is characterized by comprising (A) a quencher containing a sulfonium salt of a carboxylic acid containing a predetermined nitrogen-containing heterocycle, and (B) a base polymer containing a predetermined polymer.

[0022] [(A) Quencher] The quencher of the component (A) contains a sulfonium salt represented by the following formula (A1). [ka]

[0023] In formula (A1), m is an integer of 0 to 2.

[0024] The ring R in the formula is a saturated heterocyclic ring containing a nitrogen atom and having 2 to 12 carbon atoms, and the ring may have at least one bond selected from an ether bond, an ester bond, a thioether bond and a sulfonyl group.

[0025] The saturated heterocyclic ring containing a nitrogen atom and having 2 to 12 carbon atoms may be a monocyclic ring or a polycyclic ring. In the case of a polycyclic ring, a fused ring or a bridged ring is preferable. Specific examples of the ring R include an aziridine ring, an azetidine ring, a pyrrolidine ring, a piperidine ring, an azepane ring, an azocane ring, an azaadamantane ring, a nortropane ring, an oxazolidine ring, a thiazolidine ring, a morpholine ring, a thiomorpholine ring, an octahydroindole ring, an octahydroisoindole ring, a decahydroquinoline ring, a decahydroisoquinoline ring, a 3-azatricyclo[7.3.1.0] ... 5,13 ]tridecane ring, 1-azaspiro[4.4]nonane ring, 1-azaspiro[4.5]decane ring, carbazole ring, and the like are preferred.

[0026] In formula (A1), R 1 is an acid labile group. As the acid labile group, those represented by the following formulae (AL-1) to (AL-19) are preferred. [ka] (In the formula, the dashed lines represent bonds.)

[0027] In formulas (AL-1) to (AL-19), R L1 are each independently a saturated hydrocarbyl group or an aryl group having 6 to 20 carbon atoms. L2 and R L4 are each independently a hydrogen atom or a saturated hydrocarbyl group having 1 to 20 carbon atoms. L3 is an aryl group having 6 to 20 carbon atoms. The saturated hydrocarbyl group may be linear, branched, or cyclic. The aryl group is preferably a phenyl group. R F is a fluorine atom or a trifluoromethyl group, and n is an integer of 1 to 5.

[0028] Selecting a tertiary hydrocarbyl group as the acid labile group is preferable because it provides a pattern with a small LER even when the resist film is formed to a thickness of, for example, 10 to 100 nm and a fine pattern with a line width of 45 nm or less is formed. The tertiary hydrocarbyl group preferably has 4 to 18 carbon atoms so that the resulting polymerization monomer can be obtained by distillation. Furthermore, the group bonded to the tertiary carbon atom of the tertiary hydrocarbyl group may be a saturated hydrocarbyl group having 1 to 15 carbon atoms, which may contain an ether bond or an oxygen-containing functional group such as a carbonyl group, and the groups bonded to the tertiary carbon atom may bond to each other to form a ring.

[0029] Specific examples of the group bonded to the tertiary carbon atom 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, tetracyclo[4.4.0.1 2,5 .1 7,10 ]dodecyl group, and 3-oxo-1-cyclohexyl group.

[0030] Examples of the tertiary 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, a 1-propylcyclopentyl group, a 1-iso ... 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-isopropylcyclohexyl 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, 3-isopropyl-3-tetracyclo[4.4.0.1 2,5 .1 7,10]dodecyl group, 2-methyl-2-adamantyl group, 2-ethyl-2-adamantyl group, 2-isopropyl-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, 5-hydroxy-2-ethyl-2-adamantyl group, 2-(4-fluorophenyl)-2-propyl group, and the like.

[0031] Furthermore, an acetal group represented by the following formula (AL-20) 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. [ka]

[0032] In formula (AL-20), R L5 is a hydrogen atom or a saturated hydrocarbyl group having 1 to 10 carbon atoms. L6 is a saturated hydrocarbyl group having a carbon number of 1 to 30. The saturated hydrocarbyl group may be linear, branched, or cyclic.

[0033] R L5 is selected appropriately 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 being decomposed by strong acid, a hydrogen atom is selected, and if the design is to use relatively high reactivity to increase sensitivity to pH changes, a linear alkyl group is selected. Depending on the combination with the acid generator and basic compound to be compounded in the resist composition, R L6 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 L5 As for R, the carbon atom bonded to the acetal carbon is preferably a secondary carbon atom. L5 Examples of the alkyl group include an isopropyl group, a sec-butyl group, a cyclopentyl group, and a cyclohexyl group.

[0034] Among the acetal groups, R L6 is preferably a polycyclic alkyl group having 7 to 30 carbon atoms. L6 When R is a polycyclic alkyl group, it is preferable that a bond is formed between the secondary carbon atom constituting the polycyclic ring structure and the acetal oxygen. When R is bonded on the secondary carbon atom of the ring structure, the polymer becomes a stable compound compared to when R is bonded on the tertiary carbon atom, and the storage stability of the resist composition is improved, and there is no deterioration in resolution. In addition, when R is bonded on the secondary carbon atom of the ring structure, the polymer becomes a stable compound compared to when R is bonded on the tertiary carbon atom. L6 is bonded to a primary carbon atom via a linear alkyl group having one or more carbon atoms, the polymer has a good glass transition temperature (Tg), and the developed resist pattern does not suffer from shape defects due to baking.

[0035] Preferred examples of the group represented by formula (AL-20) include, but are not limited to, the following: L5 is the same as above. [ka]

[0036] In formula (A1), R 2 is a halogen atom or a saturated hydrocarbyl group having 1 to 6 carbon atoms which may contain a halogen atom. Examples of the halogen atom include a fluorine atom, a chlorine atom, a bromine atom, and an iodine atom. The saturated hydrocarbyl group having 1 to 6 carbon atoms may be linear, branched, or cyclic, and specific examples thereof include alkyl groups having 1 to 6 carbon atoms such as a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, an isobutyl group, a sec-butyl group, a tert-butyl group, an n-pentyl group, and an n-hexyl group; cyclic saturated hydrocarbyl groups having 3 to 6 carbon atoms such as a cyclopropyl group, a cyclobutyl group, a cyclopentyl group, and a cyclohexyl group; and groups obtained by combining these groups.

[0037] In formula (A1), R 3is a single bond or a saturated hydrocarbylene group having 1 to 10 carbon atoms which may contain an ether bond, an ester bond or a thioether bond. The saturated hydrocarbylene group having 1 to 10 carbon atoms may be linear, branched or cyclic, and specific examples thereof include alkanediyl groups such as a methylene group, an ethane-1,2-diyl group, a propane-1,3-diyl group, a butane-1,4-diyl group, a pentane-1,5-diyl group, a hexane-1,6-diyl group, and structural isomers thereof; cyclic saturated hydrocarbylene groups such as a cyclopropanediyl group, a cyclobutanediyl group, a cyclopentanediyl group, and a cyclohexanediyl group; and groups obtained by combining these groups.

[0038] Examples of the anion of the sulfonium salt represented by formula (A1) include, but are not limited to, those shown below. [ka]

[0039] [ka]

[0040] [ka]

[0041] [ka]

[0042] [ka]

[0043] [ka]

[0044] [ka]

[0045] [ka]

[0046] [ka]

[0047] [ka]

[0048] [ka]

[0049] [ka]

[0050] In formula (A1), R 4 , R 5 and R 6are each independently a halogen atom or a hydrocarbyl 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. The hydrocarbyl group may be saturated or unsaturated, and may be linear, branched, or cyclic. Specific examples thereof include alkyl groups having 1 to 20 carbon atoms, such as methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, n-pentyl, n-hexyl, n-octyl, n-nonyl, n-decyl, undecyl, dodecyl, tridecyl, tetradecyl, pentadecyl, heptadecyl, octadecyl, nonadecyl, and icosyl groups; cyclic saturated hydrocarbyl groups having 3 to 20 carbon atoms, such as cyclopropyl, cyclopentyl, cyclohexyl, cyclopropylmethyl, 4-methylcyclohexyl, cyclohexylmethyl, norbornyl, and adamantyl groups; alkenyl groups having 2 to 20 carbon atoms, such as vinyl, propenyl, butenyl, and hexenyl groups; and cyclohexyl. Examples of such alkyl groups include cyclic unsaturated aliphatic hydrocarbyl groups having 3 to 20 carbon atoms, such as phenyl, propynyl, and norbornenyl; alkynyl groups having 2 to 20 carbon atoms, such as ethynyl, propynyl, and butynyl; aryl groups having 6 to 20 carbon atoms, such as phenyl, methylphenyl, ethylphenyl, n-propylphenyl, isopropylphenyl, n-butylphenyl, isobutylphenyl, sec-butylphenyl, tert-butylphenyl, naphthyl, methylnaphthyl, ethylnaphthyl, n-propylnaphthyl, isopropylnaphthyl, n-butylnaphthyl, isobutylnaphthyl, sec-butylnaphthyl, and tert-butylnaphthyl; aralkyl groups having 7 to 20 carbon atoms, such as benzyl and phenethyl; and groups obtained by combining these groups.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.

[0051] Also, R 4 and R 5 and may be bonded to each other to form a ring together with the sulfur atom to which they are bonded. Examples of the ring formed in this case include the rings shown below. [ka] (In the formula, the dashed lines represent bonds.)

[0052] Examples of the cation of the sulfonium salt represented by formula (A1) include, but are not limited to, those shown below. [ka]

[0053] [ka]

[0054] [ka]

[0055] [ka]

[0056] [ka]

[0057]

change

[0058]

change

[0059]

change

[0060]

change

[0061]

change

[0062]

change

[0063]

change

[0064]

change

[0065]

change

[0066]

change

[0067] [ka]

[0068] [ka]

[0069] [ka]

[0070] [ka]

[0071] [ka]

[0072] [ka]

[0073] [ka]

[0074] The sulfonium salt represented by formula (A1) can be synthesized by ion-exchanging a carboxylic acid having the anion represented by formula (A1) with a sulfonium salt of a weaker acid than the carboxylic acid. An example of such an acid weaker than the carboxylic acid is carbonic acid. Alternatively, the sulfonium salt can be synthesized by ion-exchanging a sodium salt of a carboxylic acid having the anion represented by formula (A1) with a sulfonium chloride.

[0075] When applied to a chemically amplified positive resist composition, the sulfonium salt represented by formula (A1) functions extremely effectively as an optimal quencher.

[0076] In the chemically amplified positive resist composition of the present invention, the content of the sulfonium salt represented by formula (A1) is preferably 0.1 to 100 parts by mass, and more preferably 1 to 50 parts by mass, relative to 80 parts by mass of the (B) base polymer described below. When the content of the sulfonium salt represented by formula (A1) is within the above range, it functions satisfactorily as a quencher, and there is no risk of performance degradation such as reduced sensitivity or generation of foreign matter due to insufficient solubility. The sulfonium salt represented by formula (A1) may be used singly or in combination of two or more types.

[0077] [(B) Base polymer] The base polymer of component (B) contains a repeating unit represented by the following formula (B1) (hereinafter also referred to as repeating unit B1), and contains a polymer that decomposes under the action of an acid and has increased solubility in an alkaline developer. [ka]

[0078] In formula (B1), a1 is 0 or 1. a2 is an integer of 0 to 2, and when it is 0, it represents a benzene skeleton, when it is 1, it represents a naphthalene skeleton, and when it is 2, it represents an anthracene skeleton. a3 is an integer that satisfies 0≦a3≦5+2a2−a4, and a4 is an integer of 1 to 3. When a2 is 0, a3 is preferably an integer of 0 to 3 and a4 is an integer of 1 to 3, and when a2 is 1 or 2, a3 is preferably an integer of 0 to 4 and a4 is an integer of 1 to 3.

[0079] In formula (B1), R A is a hydrogen atom, a fluorine atom, a methyl group, or a trifluoromethyl group.

[0080] In formula (B1), R 11is 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 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, propyl, isopropyl, butyl, pentyl, and hexyl; 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 an alkaline developer is good. When a3 is 2 or more, each R 11 may be the same as or different from each other.

[0081] In formula (B1), A 1is a single bond or a saturated hydrocarbylene group having 1 to 10 carbon atoms, and -CH2- of the saturated hydrocarbylene group may be replaced with -O-. The saturated hydrocarbylene group may be linear, branched, or cyclic, and specific examples thereof include alkanediyl groups 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 such as cyclopropanediyl, cyclobutanediyl, cyclopentanediyl, and cyclohexanediyl; and groups obtained by combining these. When the saturated hydrocarbylene group contains an ether bond, when a1 in formula (B1) is 1, it may be located 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.

[0082] 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. In particular, the repeating unit represented by the following formula (B1-1) is preferred. [ka] (In the formula, R A and a4 are the same as above.)

[0083] Also, a1 is 1 (i.e., -C(=O)-OA as a linker). 1-), preferred examples of repeating unit B1 include, but are not limited to, those shown below. [ka] (In the formula, R A is the same as above.)

[0084] The content of the repeating unit B1 is preferably 10 to 95 mol %, more preferably 40 to 90 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 impart high etching resistance to the polymer used in the present invention described below, and when this unit has a phenolic hydroxy group as a substituent, the proportion of this unit is also preferably included within the above range. The repeating unit B1 may be used alone or in combination of two or more types.

[0085] In order to provide the polymer as a positive resist composition with the property that the exposed area is soluble in an alkaline aqueous solution, it is preferable that the polymer contains a repeating unit having an acidic functional group protected by an acid labile group (a repeating unit that is protected by an acid labile group and becomes alkaline-soluble by the action of acid). In this case, the acid labile group (protecting group) in the repeating unit undergoes a deprotection reaction by the action of acid, so that the polymer exhibits better solubility in an alkaline developer.

[0086] The most preferred repeating unit is one represented by the following formula (B2-1) (hereinafter also referred to as repeating unit B2-1). [ka]

[0087] In formula (B2-1), R Aare the same as above. b1 is 0 or 1. b2 is an integer of 0 to 2, and when it is 0, it represents a benzene skeleton, when it is 1, it represents a naphthalene skeleton, and when it is 2, it represents an anthracene skeleton. b3 is an integer that satisfies 0≦b3≦5+2b2−b4. b4 is an integer of 1 to 3. b5 is 0 or 1. When b2 is 0, preferably b3 is an integer of 0 to 3 and b4 is an integer of 1 to 3, and when b2 is 1 or 2, preferably b3 is an integer of 0 to 4 and b4 is an integer of 1 to 3.

[0088] In formula (B2-1), R A is a hydrogen atom, a fluorine atom, a methyl group, or a trifluoromethyl group.

[0089] In formula (B2-1), R 12 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. 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, propyl, isopropyl, butyl, pentyl, and hexyl; 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 an alkaline developer is good. When b3 is 2 or more, each R 12 may be the same as or different from each other.

[0090] In formula (B2-1), A 2is a single bond or a saturated hydrocarbylene group having 1 to 10 carbon atoms, and -CH2- of the saturated hydrocarbylene group may be replaced with -O-. The saturated hydrocarbylene group may be linear, branched, or cyclic, and specific examples thereof include alkanediyl groups 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 such as cyclopropanediyl, cyclobutanediyl, cyclopentanediyl, and cyclohexanediyl; and groups obtained by combining these. When the saturated hydrocarbylene group contains an ether bond, when b1 in formula (B2-1) is 1, it may be located 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 b1 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.

[0091] In formula (B2-1), X is an acid labile group when b4 is 1, and is a hydrogen atom or an acid labile group when b4 is 2 or more, 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. Such an acid labile group is not particularly limited, and any of those already used in many known chemically amplified resist compositions can be used as long as they are released by an acid to give an acidic group. Specific examples of the acid labile group include R 1 Examples of the acid labile group represented by the formula (I) include the same as those exemplified above.

[0092] Further, examples of the repeating unit having an acidic functional group protected by the acid labile group include a repeating unit represented by the following formula (B2-2) (hereinafter also referred to as repeating unit B2-2): The repeating unit represented by formula (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]

[0093] In formula (B2-2), c1 is an integer of 0 to 2. c2 is an integer of 0 to 2. c3 is an integer of 0 to 5. c4 is an integer of 0 to 2.

[0094] In formula (B2-2), R A is a hydrogen atom, a fluorine atom, a methyl group, or a trifluoromethyl group.

[0095] In formula (B2-2), 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.

[0096] In formula (B2-2), R 13 and R 14 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.

[0097] In formula (B2-2), R 15 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.

[0098] In formula (B2-2), R16 are each independently a hydrocarbyl group having 1 to 10 carbon atoms which may contain a heteroatom.

[0099] Preferred examples of the repeating unit B2-2 include, but are not limited to, the following: A is the same as above. [ka]

[0100] 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.

[0101] The content of the repeating units B2-1 and B2-2 is preferably 5 to 50 mol % of all the repeating units constituting the polymer. The repeating units B2-1 and B2-2 may each be used alone or in combination of two or more.

[0102] The polymer may further contain at least one repeating unit selected from the group consisting of a repeating unit represented by the following formula (B3) (hereinafter also referred to as repeating unit B3), a repeating unit represented by the following formula (B4) (hereinafter also referred to as repeating unit B4), and a repeating unit represented by the following formula (B5) (hereinafter also referred to as repeating unit B5). [ka]

[0103] In the formulae (B3) and (B4), d and e each independently represent an integer of 0 to 4.

[0104] In formulas (B3) and (B4), R 21 and R 22are each independently a hydroxy group, a halogen atom, a saturated hydrocarbyl group having 1 to 8 carbon atoms which may be substituted with a halogen atom, a saturated hydrocarbyloxy group having 1 to 8 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 21 may be the same or different. When e is 2 or more, each R 22 may be the same as or different from each other.

[0105] In formula (B5), f1 is 0 or 1. f2 is an integer of 0 to 5. f3 is an integer of 0 to 2, and when f3 is 0, it represents a benzene skeleton, when f3 is 1, it represents a naphthalene skeleton, and when f3 is 2, it represents an anthracene skeleton. When f3 is 0, f2 is preferably an integer of 0 to 3, and when f3 is 1 or 2, f2 is preferably an integer of 0 to 4.

[0106] In formula (B5), R A is the same as above. R 23 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, a cyano group, a sulfinyl group, or a sulfonyl 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 f2 is 2 or more, each R 23 may be the same as or different from each other.

[0107] R 23Preferred examples of the alkyl group include halogen atoms such as chlorine, bromine, and iodine; saturated hydrocarbyl groups such as methyl, ethyl, propyl, butyl, pentyl, hexyl, cyclopentyl, and cyclohexyl groups, and structural isomers thereof; and saturated hydrocarbyloxy groups such as methoxy, ethoxy, propoxy, butoxy, pentyloxy, hexyloxy, cyclopentyloxy, and cyclohexyloxy groups, and structural isomers of the hydrocarbon moiety thereof. Of these, methoxy and ethoxy groups are particularly useful.

[0108] Furthermore, saturated hydrocarbyl carbonyloxy groups can be easily introduced by chemical modification even after polymer polymerization and can be used to finely adjust the solubility of the base polymer in alkaline developers. Examples of the saturated hydrocarbyl carbonyloxy group include methyl carbonyloxy groups, ethyl carbonyloxy groups, propyl carbonyloxy groups, butyl carbonyloxy groups, pentyl carbonyloxy groups, hexyl carbonyloxy groups, cyclopentyl carbonyloxy groups, cyclohexyl carbonyloxy groups, benzoyloxy groups, and structural isomers of the hydrocarbon moieties thereof. If the number of carbon atoms is 20 or less, the effect of controlling and adjusting (mainly the effect of reducing) the solubility of the base polymer in alkaline developers can be made appropriate, and the occurrence of scum (development defects) can be suppressed.

[0109] Among the above-mentioned preferred substituents, examples of substituents that are particularly easy to prepare as a monomer and are usefully used include a chlorine atom, a bromine atom, an iodine atom, a methyl group, an ethyl group, and a methoxy group.

[0110] In formula (B5), A 4is a single bond or a saturated hydrocarbylene group having 1 to 10 carbon atoms, and -CH2- of the saturated hydrocarbylene group may be replaced with -O-. The saturated hydrocarbylene group may be linear, branched, or cyclic, and specific examples thereof include alkanediyl groups 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 such as cyclopropanediyl, cyclobutanediyl, cyclopentanediyl, and cyclohexanediyl; and groups obtained by combining these. When the saturated hydrocarbylene group contains an ether bond, when f1 in formula (B5) is 1, it 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 f1 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.

[0111] f1 is 0 and A 4 is a single bond, that is, the aromatic ring is directly bonded to the main chain of the polymer (i.e., the linker (-C(=O)-OA 4 When the repeating unit B5 does not have -), preferred examples of the repeating unit B5 include units derived from styrene, 4-chlorostyrene, 4-methylstyrene, 4-methoxystyrene, 4-bromostyrene, 4-acetoxystyrene, 2-hydroxypropylstyrene, 2-vinylnaphthalene, 3-vinylnaphthalene, etc.

[0112] Also, when f1 is 1 (i.e., -C(=O)-OA as a linker 4 In the case where R A is the same as above. [ka]

[0113] [ka]

[0114] When at least one of the repeating units B3 to B5 is used as a structural unit, the addition of a ring structure to the main chain provides the effect of improving the etching resistance of the aromatic ring as well as the resistance to EB irradiation during pattern inspection.

[0115] 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 35 mol % or less, more preferably 30 mol % or less, of all repeating units constituting the polymer. When no functional group is present or when the functional group is neither, it is preferable that the amount introduced is 35 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.

[0116] The polymer preferably contains, as structural units, repeating unit B1, repeating unit B2-1 and / or B2-2, and at least one selected from repeating units B3 to B5, from the viewpoint of achieving both high etching resistance and excellent resolution. In this case, these repeating units preferably account for 60 mol % or more, more preferably 70 mol % or more, and even more preferably 80 mol % or more of all repeating units.

[0117] The polymer may further contain at least one repeating unit selected from the group consisting of a repeating unit represented by the following formula (B6) (hereinafter also referred to as repeating unit B6), a repeating unit represented by the following formula (B7) (hereinafter also referred to as repeating unit B7), a repeating unit represented by the following formula (B8) (hereinafter also referred to as repeating unit B8), a repeating unit represented by the following formula (B9) (hereinafter also referred to as repeating unit B9), a repeating unit represented by the following formula (B10) (hereinafter also referred to as repeating unit B10), a repeating unit represented by the following formula (B11) (hereinafter also referred to as repeating unit B11), a repeating unit represented by the following formula (B12) (hereinafter also referred to as repeating unit B12), and a repeating unit represented by the following formula (B13) (hereinafter also referred to as repeating unit B13). In this case, acid diffusion can be effectively suppressed, improving resolution and enabling the production of a pattern with reduced LER. [ka]

[0118] In formulas (B6) to (B13), R B are each independently a hydrogen atom or a methyl group. 1 represents a single bond, an aliphatic hydrocarbylene group having 1 to 6 carbon atoms, a phenylene group, a naphthylene group, or a group having 7 to 18 carbon atoms obtained by combining these groups; -OY 11 -, -C(=O)-OY 11 - or -C(=O)-NH-Y 11 - and Y 11 Y is an aliphatic hydrocarbylene group having 1 to 6 carbon atoms, a phenylene group, a naphthylene group, or a group having 7 to 18 carbon atoms obtained by combining these, and may contain a carbonyl group, an ester bond, an ether bond, or a hydroxy group. 2 is a single bond or -Y 21 -C(=O)-O-, and Y 21 Y is a hydrocarbylene group having 1 to 20 carbon atoms which may contain a heteroatom. 3 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, -OY31 -, -C(=O)-OY 31 - or -C(=O)-NH-Y 31 - and Y 31 Y is an aliphatic hydrocarbylene group having 1 to 6 carbon atoms, a phenylene group, a fluorinated phenylene group, a phenylene group substituted with a trifluoromethyl group, or a group having 7 to 20 carbon atoms obtained by combining these, and may contain a carbonyl group, an ester bond, an ether bond, or a hydroxy group. 4 represents a single bond or a hydrocarbylene group having 1 to 30 carbon atoms which may contain a heteroatom. g1 and g2 each independently represent 0 or 1, but Y 4 When is a single bond, g1 and g2 are 0.

[0119] In formulas (B7) and (B11), Y 2 Ga-Y 21 -C(=O)-O-, Y 21 Examples of the hydrocarbylene group represented by the formula (I) which may contain a heteroatom include, but are not limited to, those shown below. [ka] (In the formula, the dashed lines represent bonds.)

[0120] In formulas (B7) and (B11), R HF is a hydrogen atom or a trifluoromethyl group. HF Specific examples of when R is a hydrogen atom include those described in JP-A-2010-116550. HF Specific examples of repeating units B8 and B12 in which is a trifluoromethyl group include those described in JP-A-2010-77404. Examples of repeating units B8 and B12 include those described in JP-A-2012-246265 and JP-A-2012-246426.

[0121] In formulas (B6) and (B10), Xa - is a non-nucleophilic counterion. -Examples of non-nucleophilic counter ions represented by the formula (I) include those described in JP-A-2010-113209 and JP-A-2007-145797.

[0122] Preferred examples of the anion of the monomer that provides the repeating units B9 and B13 include, but are not limited to, those shown below. [ka]

[0123] [ka]

[0124] In formulas (B6) to (B13), R 31 ~R 48 are each independently a hydrocarbyl group having 1 to 20 carbon atoms which may contain a heteroatom. The hydrocarbyl group may be saturated or unsaturated, and may be linear, branched, or cyclic. Specific examples thereof include R 4 , R 5 and R 6 Examples include the same as those exemplified as the hydrocarbyl group represented by the formula: 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- 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 acid anhydride (-C(=O)-OC(=O)-), a haloalkyl group, etc.

[0125] Also, R 31 and R 32 may be bonded to each other to form a ring together with the sulfur atom to which they are attached, and R 33 and R34 , R 36 and R 37 , or R 39 and R 40 may be bonded to each other to form a ring together with the sulfur atom to which they are bonded. In this case, the ring formed is the same as that of R 3 and R 4 are bonded to each other to form a ring together with the sulfur atom to which they are bonded, the same as those exemplified above.

[0126] Specific examples of the sulfonium cations in the repeating units B7 to B9 include the same as those exemplified as the cations in the sulfonium salt represented by formula (A1). Specific examples of the iodonium cations in the repeating units B11 to B13 include, but are not limited to, the following: [ka]

[0127] [ka]

[0128] The repeating units B6 to B13 are units that generate acid upon irradiation with high-energy rays. It is believed that the inclusion of these units in the polymer moderately suppresses acid diffusion, resulting in a pattern with improved LER and CDU. Furthermore, the inclusion of these units in the polymer suppresses the phenomenon in which acid volatilizes from exposed areas and reattaches to unexposed areas during baking in a vacuum, which is believed to be effective in improving LER and CDU and reducing pattern defects due to the suppression of undesired deprotection reactions in unexposed areas. When repeating units B6 to B13 are included, their content is preferably 0.5 to 30 mol % of the total repeating units constituting the polymer. The repeating units B6 to B13 may be used singly or in combination of two or more.

[0129] The base polymer (B) may be a mixture of a polymer containing at least one repeating unit selected from B6 to B13 in addition to the repeating unit B1, and a polymer containing the repeating unit B1 but not B6 to B13. In this case, the content of the polymer not containing B6 to B13 is preferably 2 to 5,000 parts by mass, more preferably 10 to 1,000 parts by mass, per 100 parts by mass of the polymer containing B6 to B13.

[0130] 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.

[0131] Examples of the (meth)acrylic acid ester unit having the adhesive group include a repeating unit represented by the following formula (B14) (hereinafter also referred to as repeating unit B14), a repeating unit represented by the following formula (B15) (hereinafter also referred to as repeating unit B15), and a repeating unit represented by the following formula (B16) (hereinafter also referred to as repeating unit B16). These units do not exhibit acidity and can be used auxiliary as units that impart adhesion to substrates or units that adjust solubility. [ka]

[0132] In formulas (B14) to (B16), R A is the same as above. R 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. k is an integer of 0 to 3.

[0133] When repeating units B14 to B16 are contained, the content thereof is preferably 0 to 30 mol %, more preferably 0 to 20 mol %, of all repeating units constituting the polymer. The repeating units B14 to B16 may be used alone or in combination of two or more.

[0134] 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.

[0135] 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, resulting in reduced resolution and deterioration of LER and CDU. On the other hand, when Mw is 50,000 or less, there is no risk of deterioration of LER and CDU, particularly when forming a pattern with a line width of 100 nm or less. In the present invention, Mw is a value measured in terms of polystyrene by gel permeation chromatography (GPC) using tetrahydrofuran (THF) or dimethylformamide (DMF) as a solvent.

[0136] The polymer preferably has a narrow molecular weight distribution (Mw / Mn) of 1.0 to 2.0, particularly 1.0 to 1.8, such that foreign matter does not appear on the pattern after development and the pattern shape does not deteriorate.

[0137] [(C) Photoacid generator] The chemically amplified positive resist composition of the present invention may contain a photoacid generator as component (C). There are no particular limitations on the photoacid generator, as long as it is a compound that generates an 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.

[0138] Specific examples of the photoacid generator include nonafluorobutanesulfonate, the partially fluorinated sulfonates described in paragraphs

[0247] to

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

[0261] to

[0265] of JP-A 2013-101271, the partially fluorinated sulfonates described in paragraphs

[0122] to

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

[0080] to

[0081] of JP-A 2010-215608, etc. Among these, arylsulfonate- or alkane sulfonate-type photoacid generators are preferred because they generate an acid of suitable strength for deprotecting the acid labile groups in the repeating units B2-1 and B2-2.

[0139] Furthermore, in order to obtain the effect of improving LER by combining the photoacid generator with the quencher of component (A), the pKa of the acid generated from the photoacid generator is -3.0 or higher, preferably in the range of -3.0 to 2.0, and more preferably in the range of -2.0 to 1.5. As such a photoacid generator, a compound having an anion with the structure shown below is preferred. Examples of the counter cation include those previously mentioned as specific examples of the sulfonium cation in formula (A1) and formulas (B7) to (B9) and those previously mentioned as specific examples of the iodonium cation in formulas (B11) to (B13). [ka]

[0140] [ka]

[0141] [ka]

[0142] [ka]

[0143] [ka]

[0144] [ka]

[0145] [ka]

[0146] When the chemically amplified positive resist composition of the present invention contains a photoacid generator (C), the content thereof is preferably 1 to 30 parts by mass, more preferably 2 to 20 parts by mass, relative to 80 parts by mass of the base polymer (B). When the base polymer contains repeating units B6 to B13 (i.e., when the base polymer is a polymer-bound acid generator), the incorporation of the photoacid generator (C) may be omitted. The photoacid generators (C) may be used singly or in combination of two or more.

[0147] When the chemically amplified positive resist composition of the present invention contains a quencher as component (A) and a photoacid generator as component (C), the content ratio of the photoacid generator to the quencher ((C) / (A)) is preferably less than 6 by mass, more preferably less than 5, and even more preferably less than 4. When the content ratio of the photoacid generator to the quencher in the chemically amplified positive resist composition is within the above range, acid diffusion can be sufficiently suppressed, and excellent resolution and dimensional uniformity can be obtained.

[0148] [(D) Fluorine atom-containing polymer] The chemically amplified positive resist composition of the present invention aims to achieve high contrast, shield the chemical flare of acids during high-energy radiation exposure and the mixing of acids from the antistatic coating during the process of applying an antistatic coating material to the resist film, and suppress unexpected and unnecessary pattern degradation. To this end, the resist composition of the present invention may contain, as component (D), a fluorine-containing polymer that contains at least one repeating unit selected from the group consisting of repeating units represented by formula (D1), (D2), (D3), and (D4) (hereinafter also referred to as repeating units D1, D2, D3, and D4, respectively), and that may further contain at least one repeating unit selected from the group consisting of repeating units represented by formula (D5) and (D6) (hereinafter also referred to as repeating units D5 and D6, respectively). The fluorine-containing polymer also functions as a surfactant, preventing redeposition of insoluble matter onto the substrate during the development process and thereby reducing development defects. [ka]

[0149] In formulas (D1) to (D6), R C are each independently a hydrogen atom, a fluorine atom, a methyl group, or a trifluoromethyl group. D are each independently a hydrogen atom or a methyl group. 101 , R 102 , R 104 and R 105 are each independently a hydrogen atom or a saturated hydrocarbyl group having 1 to 10 carbon atoms. 103 , R 106 , R 107 and R 108 are each independently a hydrogen atom, a hydrocarbyl group having 1 to 15 carbon atoms, a fluorinated hydrocarbyl group having 1 to 15 carbon atoms, or an acid labile group, and R 103 , R 106 , R 107 and R 108When 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. 109 R is a hydrogen atom or a linear or branched hydrocarbyl group having 1 to 5 carbon atoms which may have a heteroatom-containing group interposed between its carbon-carbon bond. 110 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. 111 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 is an integer of 1 to 3. y is an integer that satisfies 0≦y≦5+2z-x. z is 0 or 1. h is an integer of 1 to 3. Z 1 is a (h+1)-valent hydrocarbon group having 1 to 20 carbon atoms or a (h+1)-valent fluorinated hydrocarbon group having 1 to 20 carbon atoms. 2 is a single bond, *-C(=O)-O-, or *-C(=O)-NH-. * is a bond to a carbon atom in the main chain. Z 3 is a single bond, -O-, *-C(=O)-OZ 31 -Z 32 -or*-C(=O)-NH-Z 31 -Z 32 -It is. Z 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.

[0150] In formulas (D1) and (D2), R 101 , R 102 , R 104 and R 105Examples of saturated hydrocarbyl groups having 1 to 10 carbon atoms represented by the formula (I) 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.

[0151] In formulas (D1) to (D4), R 103 , R 106 , R 107 and R 108 Examples of the hydrocarbyl group having 1 to 15 carbon atoms represented by the formula (I) 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. In addition to the alkyl groups mentioned above, examples of the alkyl group include a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, an isobutyl group, a sec-butyl group, an n-pentyl group, an n-hexyl group, an n-heptyl group, an n-octyl group, an n-nonyl group, an n-decyl group, an n-undecyl group, an n-dodecyl group, an n-tridecyl group, an n-tetradecyl group, and an n-pentadecyl group. Examples of the fluorinated hydrocarbyl group include groups in which some or all of the hydrogen atoms bonded to the carbon atoms of the hydrocarbyl group mentioned above have been substituted with fluorine atoms.

[0152] In formula (D4), Z 1 Examples of the (h+1)-valent hydrocarbon group having 1 to 20 carbon atoms and represented by the formula (I) include a group in which h 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. 1 Examples of the (mh+1)-valent fluorinated hydrocarbon group having 1 to 20 carbon atoms and represented by the formula below include groups in which at least one hydrogen atom of the aforementioned (h+1)-valent hydrocarbon group has been substituted with a fluorine atom.

[0153] Specific examples of the repeating units D1 to D4 include, but are not limited to, the following: C is the same as above. [ka]

[0154] [ka]

[0155] [ka]

[0156] In formula (D5), 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.

[0157] In formula (D5), -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.

[0158] In formula (D5), Z 2 is preferably *-C(=O)-O- or *-C(=O)-NH-. D is preferably a methyl group. 2 The presence of a carbonyl group in R improves the acid trapping ability of the antistatic film. DWhen 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.

[0159] Examples of the repeating unit D5 include, but are not limited to, those shown below. D is the same as above. [ka]

[0160] [ka]

[0161] In formula (D6), Z 3 The saturated hydrocarbylene group having 1 to 10 carbon atoms represented by the formula (I) may be linear, branched, or cyclic, and specific examples thereof include a methanediyl group, an ethane-1,1-diyl group, an ethane-1,2-diyl group, a propane-1,1-diyl group, a propane-1,2-diyl group, a propane-1,3-diyl group, a propane-2,2-diyl group, a butane-1,1-diyl group, a butane-1,2-diyl group, a butane-1,3-diyl group, a butane-2,3-diyl group, a butane-1,4-diyl group, and a 1,1-dimethylethane-1,2-diyl group.

[0162] In formula (D6), R 111 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.

[0163] Examples of the repeating unit D6 include, but are not limited to, those shown below. D is the same as above. [ka]

[0164] [ka]

[0165] [ka]

[0166] [ka]

[0167] The content of repeating units D1 to D4 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 D5 and / or D6 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 D1 to D6 may be used alone or in combination of two or more.

[0168] The 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 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.

[0169] The 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 2004-115630 A.

[0170] The Mw of the fluorine atom-containing polymer is preferably 2000 to 50000, more preferably 3000 to 20000. If the Mw is less than 2000, the diffusion of the acid is promoted, which may result in a deterioration in resolution and a loss of stability over time. If the Mw is too large, the solubility in the solvent decreases, which may cause coating defects. Furthermore, the fluorine atom-containing polymer preferably has an Mw / Mn ratio of 1.0 to 2.2, more preferably 1.0 to 1.7.

[0171] When the chemically amplified positive resist composition of the present invention contains (D) a fluorine atom-containing polymer, the content thereof is preferably from 0.01 to 30 parts by mass, more preferably from 0.1 to 20 parts by mass, and even more preferably from 0.5 to 10 parts by mass, relative to 80 parts by mass of (B) base polymer. The (D) fluorine atom-containing polymer may be used alone, or two or more types may be used in combination.

[0172] [(E) Organic solvent] The chemically amplified positive resist composition of the present invention may contain an organic solvent as component (E). There are no particular restrictions on the organic solvent as 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; propylene glycol monomethyl ether (PGME), ethylene glycol monomethyl ether, propylene glycol monoethyl ether, and ethylene glycol monoethyl ether. Examples of suitable solvents include ethers such as propylene glycol monomethyl ether acetate (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.

[0173] Among these organic solvents, 1-ethoxy-2-propanol, PGMEA, PGME, cyclohexanone, EL, γ-butyrolactone, and mixed solvents thereof are preferred.

[0174] In the chemically amplified positive resist composition of the present invention, the content of (E) organic solvent 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 (B) base polymer. (E) The organic solvent may be used alone, or two or more types may be mixed and used.

[0175] [(F) Basic compounds] The chemically amplified positive resist composition of the present invention may also contain (F) a basic compound as a quencher in addition to the component (A) for the purpose of correcting the shape of a pattern, etc. By adding a basic compound, acid diffusion can be effectively controlled, and even in cases where the outermost surface of a substrate is made of a material containing chromium, tantalum, or silicon, the effects of acid generated within the resist film on the substrate can be suppressed.

[0176] Many basic compounds are known, including primary, secondary, or 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, carbamates, and ammonium salts. Many specific examples of these compounds are listed in Patent Document 9, and essentially all of these compounds can be used. Particularly preferred compounds include tris[2-(methoxymethoxy)ethyl]amine, tris[2-(methoxymethoxy)ethyl]amine-N-oxide, dibutylaminobenzoic acid, morpholine derivatives, and imidazole derivatives.

[0177] In the chemically amplified positive resist composition of the present invention, the content of the (F) basic compound is preferably 0 to 10 parts by mass, and more preferably 0 to 5 parts by mass, relative to 80 parts by mass of the (B) base polymer. The (F) basic compound may be used alone, or two or more types may be used in combination.

[0178] [(G) Surfactant] The chemically amplified positive resist composition of the present invention may contain a commonly used surfactant to improve its coatability onto a substrate. Many surfactants are known, as described in JP-A-2004-115630, and the surfactant can be selected with reference to these examples. In the chemically amplified positive resist composition of the present invention, the content of the (G) surfactant is preferably 0 to 5 parts by mass per 80 parts by mass of the (B) base polymer. The (G) surfactant may be used alone, or two or more types may be used in combination.

[0179] [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.

[0180] The substrate may be, for example, a substrate used for manufacturing integrated circuits (Si, SiO, SiO2, SiN, SiON, TiN, WSi, BPSG, SOG, organic anti-reflective coating, etc.), or a substrate used for manufacturing transmission or reflection mask circuits (Cr, CrO, CrON, MoSi2, Si, SiO, SiO2, SiON, SiONC, CoTa, NiTa, TaBN, SnO2, 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 the composition 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.

[0181] Next, the resist film is exposed to high-energy rays to form a pattern. Examples of the high-energy rays include ultraviolet rays, far ultraviolet rays, excimer laser light (KrF, ArF, etc.), EUV, X-rays, gamma rays, synchrotron radiation, and EB. In the present invention, exposure using EUV or EB is preferred.

[0182] 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 500 mJ / cm. 2 , more preferably 10 to 400 mJ / cm 2 When EB is used, the exposure dose is preferably 1 to 500 μC / cm 2 directly to form the desired pattern. 2 , more preferably 10 to 400 μC / cm 2 Irradiate so that

[0183] The exposure may be performed by a conventional exposure method or, in some cases, by an immersion method in which the space between the mask and the resist film is immersed in liquid. In this case, a water-insoluble protective film may be used.

[0184] 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.

[0185] Thereafter, the substrate is developed using a developer such as an aqueous alkaline solution of 0.1 to 5 mass %, preferably 2 to 3 mass %, tetramethylammonium hydroxide (TMAH) or the like, preferably for 0.1 to 3 minutes, more preferably for 0.5 to 2 minutes, by a conventional method such as dipping, puddling, or spraying, to form a desired pattern on the substrate.

[0186] The chemically amplified positive resist composition of the present invention is useful because it can form a pattern with particularly good resolution and small LER. Furthermore, the chemically amplified positive resist composition of the present invention is particularly useful for pattern formation on substrates having a surface made of a material that is prone to pattern peeling or pattern collapse, since it is difficult to obtain good resist pattern adhesion. Examples of such substrates include substrates having a sputtering film formed on the outermost surface by sputtering a film of metallic chromium or a chromium compound containing one or more light elements selected from oxygen, nitrogen, and carbon, SiO , SiO x, a tantalum compound, a molybdenum compound, a cobalt compound, a nickel compound, a tungsten compound, or a tin compound in the outermost layer. The chemically amplified positive resist composition of the present invention is particularly useful for pattern formation using a photomask blank as the substrate. In this case, the photomask blank may be either a transmissive or reflective type.

[0187] As a transmission mask blank, a photomask blank having a light-shielding film made of a chromium-based material may be a photomask blank for a binary mask or a photomask blank for a phase shift mask. In the case of a photomask blank for a binary mask, the light-shielding film may have an antireflection layer and a light-shielding layer made of a chromium-based material, or the entire antireflection film on the surface layer side or only the layer further above the antireflection film on the surface layer side may be made of a chromium-based material, with the remaining portion being made of a silicon-based compound material that may contain, for example, a transition metal. In addition, in the case of a photomask blank for a phase shift mask, the target photomask blank may be a photomask blank for a phase shift mask having a chromium-based light-shielding film on a phase shift film.

[0188] The above-mentioned photomask blank having a chromium-based material in the outermost layer is very well known, as is disclosed in JP-A Nos. 2008-26500 and 2007-302873, or as examples of prior art therein. Therefore, detailed description will be omitted. However, for example, when a light-shielding film having an antireflection layer and a light-shielding layer is formed using a chromium-based material, the following film configuration can be used.

[0189] When a light-shielding film having an anti-reflection layer and a light-shielding layer is formed using a chromium-based material, the layer structure may be such that the anti-reflection layer and the light-shielding layer are laminated in this order from the surface side, or the anti-reflection layer, the light-shielding layer, and the anti-reflection layer are laminated in this order. The anti-reflection layer and the light-shielding layer may each be multi-layered, and the composition between layers with different compositions may change discontinuously or continuously. The chromium-based material used includes metallic chromium and metallic chromium containing light elements such as oxygen, nitrogen, and carbon. Specifically, metallic chromium, chromium oxide, chromium nitride, chromium carbide, chromium oxide nitride, chromium carbide oxide, chromium nitride carbonitride, chromium oxynitride carbonitride, etc. may be used.

[0190] A reflective mask blank includes a substrate, a multilayer reflective film formed on one main surface (front surface) of the substrate, specifically a multilayer reflective film that reflects exposure light such as EUV light, and an absorber film formed on the multilayer reflective film, specifically an absorber film that absorbs exposure light such as EUV light and reduces reflectance. From the reflective mask blank (EUV reflective mask blank), a reflective mask (EUV reflective mask) having an absorber pattern (absorber film pattern) formed by patterning the absorber film is manufactured. The wavelength of EUV light used in EUV lithography is 13 to 14 nm, and is typically light with a wavelength of about 13.5 nm.

[0191] Although the multilayer reflective film is preferably provided in contact with one main surface of the substrate, a base film may be provided between the substrate and the multilayer reflective film as long as the effects of the present invention are not lost. The absorber film may be formed in contact with the multilayer reflective film, but a protective film (protective film for the multilayer reflective film) may be provided between the multilayer reflective film and the absorber film, preferably in contact with the multilayer reflective film, and more preferably in contact with both the multilayer reflective film and the absorber film. The protective film is used to protect the multilayer reflective film during processing such as cleaning and repair. Furthermore, the protective film preferably has the function of protecting the multilayer reflective film when the absorber film is patterned by etching and preventing oxidation of the multilayer reflective film. Meanwhile, a conductive film used for electrostatically chucking the reflective mask to an exposure device may be provided under the other main surface (back surface) of the substrate, which is the surface opposite to the one main surface, preferably in contact with the other main surface. Here, one main surface of the substrate is the front surface and the upper side, and the other main surface is the back surface and the lower side, but the front and back and top and bottom of both are defined for convenience, and the one main surface and the other main surface are either of the two main surfaces (film formation surfaces) of the substrate, and the front and back and top and bottom are interchangeable. More specifically, it can be formed by a method such as that described in JP 2021-139970 A or exemplified as prior art therein.

[0192] According to the method for forming a resist pattern of the present invention, even when a substrate (e.g., a photomask blank) is used whose outermost surface is made of a material that is likely to affect the shape of the resist pattern, such as a material containing chromium or silicon, the chemically amplified positive resist composition of the present invention efficiently controls acid diffusion at the substrate interface, making it possible to form a pattern that has high resolution and pattern fidelity, as well as improved LER and dose margin. [Example]

[0193] The present invention will be specifically described below with reference to examples and comparative examples, but the present invention is not limited to the following examples. The copolymer composition ratio is a molar ratio, and Mw is a polystyrene-equivalent value measured by GPC.

[0194] The structures of quenchers Q-1 to Q-8 used in the chemically amplified positive resist composition of the present invention are shown below. [ka]

[0195] The structures of quenchers cQ-1 to cQ-3 used in the comparative examples are shown below. [ka]

[0196] The structures of polymers A-1 to A-14 and polymers P-1 to P-5 used in the resist composition are shown below. [ka]

[0197] [ka]

[0198] [ka]

[0199] [ka]

[0200] [ka]

[0201] The structures of PAG-A to PAG-D and fluorine atom-containing polymers B-1 to B-5 used in the resist compositions are shown below. [ka]

[0202] [ka]

[0203] [1] Preparation of chemically amplified positive resist composition [Examples 1-1 to 1-40, Comparative Examples 1-1 to 1-4] Chemically amplified positive resist compositions (R-1 to R-40, CR-1 to CR-4) were prepared by dissolving each component in an organic solvent according to the formulations shown in Tables 1 to 3 below, and filtering each resulting solution through a UPE filter and / or nylon filter selected from 10 nm, 5 nm, 3 nm, and 1 nm sizes. The organic solvent was a mixed solvent of 900 parts by mass of PGMEA, 1800 parts by mass of EL, and 1800 parts by mass of PGME.

[0204] [Table 1]

[0205] [Table 2]

[0206] [Table 3]

[0207] [2] EB lithography evaluation [Examples 2-1 to 2-40, Comparative Examples 2-1 to 2-4] Each chemically amplified positive resist composition (R-1 to R-40, CR-1 to CR-4) was spin-coated onto a 152 mm square mask blank with a silicon oxide outer surface that had been vapor primed with hexamethyldisilazane (HMDS) using ACT-M (Tokyo Electron Limited), and the blank 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 extending 10 mm inward from the outer periphery of the blank, and the average thickness and thickness range were calculated. The film was exposed using an electron beam exposure system (EBM-5000plus manufactured by NuFlare Technology, Inc., accelerating voltage 50 kV), subjected to PEB at 120°C for 600 seconds, and developed with a 2.38% by mass TMAH aqueous solution to obtain a positive pattern.

[0208] 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 200 nm 1:1 line and space (LS) at 1:1 was determined as the optimal exposure dose (μC / cm 2 ) and the minimum dimension at the exposure dose that resolves a 200 nm LS at 1:1 was taken as the resolution (limiting resolution). For the 200 nm LS pattern obtained by irradiation at the optimal exposure dose, edge detection was performed at 80 points on each of the 32 edges of the 200 nm LS pattern using an SEM, and the triple value (3σ) of the variation (standard deviation, σ) was calculated and used as the LER (nm). In addition, the CD change per 1 μC when the exposure dose that resolves at 1:1 was used as the standard was calculated from the dose curve. The results are shown in Tables 4 to 6.

[0209] [Table 4]

[0210] [Table 5]

[0211] [Table 6]

[0212] The resist compositions (R-1 to R-40) of the present invention containing the sulfonium salt represented by formula (A1) effectively controlled acid diffusion, and all exhibited good resolution, as well as good LER and dose margin values, compared to the comparative resist compositions (CR-1 to CR-4). Comparing R-39 and R-40 with CR-1, it was confirmed that the effects of the present invention can be best achieved when the optimal exposure dose is 50 μC or higher.

[0213] Furthermore, the sulfonium salt represented by formula (A1) has a high quenching ability, and since only a small amount is used to adjust the resist sensitivity, it has high compatibility with the solvent used and is uniformly dispersed within the film, and therefore exhibits particularly favorable LER values.

[0214] As explained above, by using the chemically amplified positive resist composition of the present invention, it is possible to form a pattern with extremely high resolution and excellent LER and dose margin. The method of forming a resist pattern using the chemically amplified positive resist composition of the present invention is useful for photolithography in the production of semiconductor devices, particularly in the processing of transmission or reflective mask blanks.

Claims

1. A chemically amplified positive resist composition comprising: (A) a quencher containing a sulfonium salt represented by the following formula (A1); (B) a base polymer containing a polymer that contains a repeating unit represented by the following formula (B1), and that decomposes under the action of an acid, thereby increasing its solubility in an alkaline developer; and (C) a photoacid generator, the content of repeating units having an aromatic ring skeleton is 60 mol % or more of all repeating units of the polymer contained in the base polymer, The polymer may further contain at least one repeating unit selected from the repeating units represented by the following formulas (B6) to (B13): The content ratio of the photoacid generator (C) to the quencher (A) is less than 6 by mass ratio. A chemically amplified positive resist composition. 【Chemistry 1】 (In the formula, m is an integer of 0 to 2. The ring R in the formula is a saturated heterocyclic ring containing a nitrogen atom and having 2 to 12 carbon atoms, and the ring may have at least one bond selected from an ether bond, an ester bond, a thioether bond, and a sulfonyl group. R 1 is an acid labile group selected from a tert-pentyl group, a 1-ethyl-1-methylpropyl group, a 1,1-diethylpropyl group, a 1,1,2-trimethylpropyl group, and groups represented by the following formulae (AL-1) to (AL-19). 【Chemistry 2】 (In the formula, each R L1 is independently a saturated hydrocarbyl group or an aryl group having 6 to 20 carbon atoms. Each R L2 and R L4 is independently a hydrogen atom or a saturated hydrocarbyl group having 1 to 20 carbon atoms. R L3 is an aryl group having 6 to 20 carbon atoms. R F is a fluorine atom or a trifluoromethyl group. n is an integer of 1 to 5.) R 2 is a halogen atom or a saturated hydrocarbyl group having 1 to 6 carbon atoms which may contain a halogen atom. R 3 is a saturated hydrocarbylene group having 1 to 10 carbon atoms which may contain a single bond, an ether bond, an ester bond or a thioether bond. R 4 , R 5 and R 6 are each independently a halogen atom or a hydrocarbyl group having 1 to 20 carbon atoms which may contain a heteroatom. 4 and R 5 may be bonded to each other to form a ring together with the sulfur atom to which they are attached. 【Transformation 3】 (In the formula, a1 is 0 or 1. a2 is an integer of 0 to 2. a3 is an integer that satisfies 0≦a3≦5+2a2−a4. a4 is an integer of 1 to 3.) R A is a hydrogen atom, a fluorine atom, a methyl group, or a trifluoromethyl group. R 11 represents a halogen atom, a saturated 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 - may be replaced by -O-. 【Chemistry 4】 (In the formula, R B are each independently a hydrogen atom or a methyl group. Y 1 represents a single bond, an aliphatic hydrocarbylene group having 1 to 6 carbon atoms, a phenylene group, a naphthylene group, or a group having 7 to 18 carbon atoms obtained by combining these groups; -O-Y 11 -, -C(=O)-O-Y 11 - or -C(=O)-NH-Y 11 - and Y 11 represents an aliphatic hydrocarbylene group having 1 to 6 carbon atoms, a phenylene group, a naphthylene group, or a group having 7 to 18 carbon atoms obtained by combining these, and may contain a carbonyl group, an ester bond, an ether bond, or a hydroxy group. Y 2 is a single bond or -Y 21 -C(=O)-O-, and Y 21 is a hydrocarbylene group having 1 to 20 carbon atoms which may contain a heteroatom. Y 3 represents a single bond, a methylene group, an ethylene group, a phenylene group, a fluorinated phenylene group, a phenylene group substituted with a trifluoromethyl group, —O—Y 31 -, -C(=O)-O-Y 31 - or -C(=O)-NH-Y 31 - and Y 31 represents an aliphatic hydrocarbylene group having 1 to 6 carbon atoms, a phenylene group, a fluorinated phenylene group, a phenylene group substituted with a trifluoromethyl group, or a group having 7 to 20 carbon atoms obtained by combining these, and may contain a carbonyl group, an ester bond, an ether bond, or a hydroxy group. Y 4 is a single bond or a hydrocarbylene group having 1 to 30 carbon atoms which may contain a heteroatom. g1 and g2 each independently represent 0 or 1, but Y 4 is a single bond, g1 and g2 are 0. R 31 ~R 48 are each independently a hydrocarbyl group having 1 to 20 carbon atoms which may contain a heteroatom. 31 and R 32 may be bonded to each other to form a ring together with the sulfur atom to which they are attached, and R 33 and R 34 , R 36 and R 37 , or R 39 and R 40 may be bonded to each other to form a ring together with the sulfur atom to which they are attached. R HF is a hydrogen atom or a trifluoromethyl group. Xa - is a non-nucleophilic counterion.)

2. 2. The chemically amplified positive resist composition according to claim 1, wherein the acid labile group is selected from the group consisting of a 1-ethyl-1-methylpropyl group, a 1,1-diethylpropyl group, a 1,1,2-trimethylpropyl group, and groups represented by formulas (AL-1) to (AL-19).

3. 2. The chemically amplified positive resist composition according to claim 1, wherein the polymer further contains a repeating unit represented by the following formula (B2-1): 【Transformation 5】 (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 an integer from 0 to 2. b3 is an integer that satisfies 0≦b3≦5+2b2−b4. b4 is an integer from 1 to 3. b5 is 0 or 1. R 12 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 - may be replaced by -O-. When b4 is 1, X is an acid labile group, and when b4 is 2 or more, X is a hydrogen atom or an acid labile group, provided that at least one X is an acid labile group.

4. 2. The chemically amplified positive resist composition according to claim 1, wherein the polymer further contains a repeating unit represented by the following formula (B2-2): 【Transformation 6】 (In the formula, c1 is an integer of 0 to 2. c2 is an integer of 0 to 2. c3 is an integer of 0 to 5. c4 is an integer of 0 to 2. R A is a hydrogen atom, a fluorine atom, a methyl group, or a trifluoromethyl group. 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 naphthylene group. R 13 and R 14 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. R 15 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 16 are each independently a hydrocarbyl group having 1 to 10 carbon atoms which may contain a heteroatom.

5. 2. The chemically amplified positive resist composition according to claim 1, wherein the polymer further 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): 【Transformation 7】 (In the formula, d and e each independently represent an integer of 0 to 4. f1 is 0 or 1. f2 is an integer of 0 to 5. f3 is an integer of 0 to 2.) R A is a hydrogen atom, a fluorine atom, a methyl group, or a trifluoromethyl group. R 21 and R 22 are each independently a hydroxy group, a halogen atom, a saturated hydrocarbyl group having 1 to 8 carbon atoms which may be substituted with a halogen atom, a saturated hydrocarbyloxy group having 1 to 8 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 23 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, a cyano group, a sulfinyl group, or a sulfonyl group. A 4 is a single bond or a saturated hydrocarbylene group having 1 to 10 carbon atoms, and the —CH 2 - may be replaced by -O-.

6. 2. The chemically amplified positive resist composition according to claim 1, wherein the acid strength (pKa) of the anion of said photoacid generator is −3.0 or higher.

7. 2. The chemically amplified positive resist composition according to claim 1, further comprising (D) a fluorine atom-containing polymer that contains at least one repeating unit selected from the group consisting of a repeating unit represented by the following formula (D1), a repeating unit represented by the following formula (D2), a repeating unit represented by the following formula (D3), and a repeating unit represented by the following formula (D4), and that may further contain at least one repeating unit selected from the group consisting of a repeating unit represented by the following formula (D5) and a repeating unit represented by the following formula (D6): 【Transformation 8】 (In the formula, R C are each independently a hydrogen atom, a fluorine atom, a methyl group, or a trifluoromethyl group. R D are each independently a hydrogen atom or a methyl group. R 101 , R 102 , R 104 and R 105 are each independently a hydrogen atom or a saturated hydrocarbyl group having 1 to 10 carbon atoms. R 103 , R 106 , R 107 and R 108 are each independently a hydrogen atom, a hydrocarbyl group having 1 to 15 carbon atoms, a fluorinated hydrocarbyl group having 1 to 15 carbon atoms, or an acid labile group; R 103 , R 106 , R 107 and R 108 When is a hydrocarbyl group or a fluorinated hydrocarbyl group, an ether bond or a carbonyl group may be present between the carbon-carbon bond. R 109 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 110 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 111 is a saturated hydrocarbyl group having 1 to 20 carbon atoms in which at least one hydrogen atom is substituted with a fluorine atom, and —CH 2 A portion of the - may be substituted with an ester bond or an ether bond. x is an integer of 1 to 3. y is an integer that satisfies 0≦y≦5+2z−x. z is 0 or 1. h is an integer of 1 to 3. Z 1 is a (h+1)-valent hydrocarbon group having 1 to 20 carbon atoms or a (h+1)-valent fluorinated hydrocarbon group having 1 to 20 carbon atoms. Z 2 is a single bond, *-C(=O)-O-, or *-C(=O)-NH-. * is a bond to a carbon atom in the main chain. Z 3 is a single bond, -O-, *-C(=O)-O-Z 31 -Z 32 - or *-C(=O)-NH-Z 31 -Z 32 - is. Z 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.)

8. 2. The chemically amplified positive resist composition according to claim 1, further comprising (E) an organic solvent.

9. 9. A method for forming a resist pattern, comprising: a step of forming a resist film on a substrate using the chemically amplified positive resist composition according to claim 1; a step of irradiating the resist film with a pattern using high-energy rays; and a step of developing the resist film irradiated with the pattern using an alkaline developer.

10. 10. The method for forming a resist pattern according to claim 9, wherein the high-energy radiation is extreme ultraviolet radiation or an electron beam.

11. 10. The method for forming a resist pattern according to claim 9, wherein the outermost surface of the substrate is made of a material containing at least one element selected from the group consisting of chromium, silicon, tantalum, molybdenum, cobalt, nickel, tungsten, and tin.

12. 10. The method for forming a resist pattern according to claim 9, wherein the substrate is a transmission or reflection mask blank.

13. A transmission or reflection mask blank coated with the chemically amplified positive resist composition according to any one of claims 1 to 8.

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