Chemically amplified positive resist composition and method for forming resist pattern

Abstract

To provide a chemically amplified positive resist composition that can improve the resolution during pattern formation, can obtain a resist pattern having improved LER and CDU, has reduced defects, and allows for a defect inspection using short wavelengths of 300 to 400 nm, and a method for forming a resist pattern.SOLUTION: A chemically amplified positive resist composition comprises: (A) an onium salt compound represented by the following formula (A1); (B) a base polymer containing a polymer that contains a repeating unit represented by a specific formula, and is decomposed under the action of an acid to increase its solubility in an alkaline developer (excluding a polymer containing a repeating unit having a lactone ring); and (C) a photoacid generator, each in a predetermined amount.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] 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.

[0006] Patent Documents 1 and 2 describe examples in which acid diffusion is suppressed and roughness (LER) 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.

[0007] 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.

[0008] In addition to the aforementioned method of increasing the bulk of the generated acid, improving the acid diffusion controller (quencher) is another possible method for suppressing acid diffusion. Acid diffusion controllers suppress acid diffusion and are essentially essential components for improving the performance of resist compositions. Various studies have been conducted on acid diffusion controllers, with amines and weak acid onium salts being commonly used. Patent Document 4 describes an example of a weak acid onium salt: the addition of triphenylsulfonium acetate 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 5 describes the addition of an ammonium sulfonate salt or an ammonium carboxylate salt to improve sensitivity, resolution, and exposure margin. Patent Document 6 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.

[0009] Patent Document 7 describes a positive-tone photosensitive composition for ArF lithography containing a carboxylic acid onium salt. These compositions are characterized in that upon exposure, a strong acid (sulfonic acid) generated from a photoacid generator 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 appear to function as an acid diffusion controller.

[0010] However, when patterning is performed using a resist composition containing the above-mentioned onium carboxylate salt or onium fluorocarboxylate salt, significant LER still remains a problem despite the recent advances in miniaturization. Therefore, there has been a demand for the development of an acid diffusion controller that can further reduce LER.

[0011] Furthermore, in order to reduce LER, a method of suppressing acid diffusion by adding a large amount of an acid diffusion controller to an acid generator is also used. However, in this case, since onium salt-type acid diffusion controllers have poor solubility in resist solvents, aggregates are formed, which causes defects.

[0012] Furthermore, as patterns have become finer in recent years, there is a demand for inspection equipment with short inspection wavelengths to detect minute defects. However, inspection light with a wavelength of 400 nm or less is absorbed by resist materials, causing the problem of deterioration of the resist film due to photoexposure.

[0013] Patent Document 8 describes a resist composition containing triphenylsulfonium phenolate. However, in response to recent demands for dimensional uniformity (CDU), the resist composition described in Patent Document 8 suffers from a problem of insufficient CDU. [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. 3955384 [Patent Document 5] Japanese Patent Application Publication No. 11-327143 [Patent Document 6] Patent No. 4231622 [Patent Document 7] Patent No. 4226803 [Patent Document 8] Japanese Patent Application Laid-Open No. 2016-6495 [Patent Document 9] Patent No. 4575479 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 has an object to provide a chemically amplified positive resist composition that improves resolution during pattern formation, is capable of obtaining a resist pattern with improved LER and CDU, has few defects, and allows defect inspection using a short wavelength of 300 to 400 nm, and a method of forming a resist pattern. [Means for solving the problem]

[0016] As a result of extensive research into achieving the above-mentioned object, the inventors of the present invention have found that a resist composition containing an acid diffusion controller comprising an onium salt compound having a specific phenoxide anion exhibits good resolution and pattern shape, produces patterns with improved LER and CDU, has few defects, and does not absorb light with a short wavelength of 300 to 400 nm. This finding led to the completion of 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) an onium salt compound represented by the following formula (A1); (B) a base polymer (excluding polymers containing a repeating unit having a lactone ring) containing a polymer that contains a repeating unit represented by the following formula (B1) and that decomposes under the action of an acid to increase its solubility in an alkaline developer; and (C) a photoacid generator, a chemically amplified positive resist composition in which, of all repeating units of the polymer contained in the base polymer, the content of repeating units having an aromatic ring skeleton is 65 mol % or more; the content ratio of the photoacid generator relative to the onium salt compound represented by formula (A1) is less than 4; the content of the photoacid generator is 5 parts by mass or more relative to 80 parts by mass of the polymer; and the total content of the onium salt compound represented by formula (A1) and the photoacid generator is 10 parts by mass or more relative to 80 parts by mass of the polymer. [ka] [In the formula, R 1 ~R 5 each independently represents a hydrogen atom, a halogen atom, a nitro group, a cyano group, an aldehyde group, a hydrocarbyl group having 1 to 18 carbon atoms which may contain a heteroatom, -C(O)OR 6 , -C(O)R 7 , -OR 8 , -S(O)2R 9 or -S(O)N(R 10 )2. R 6 and R 7 R are each independently a hydrocarbyl group having 1 to 19 carbon atoms which may contain a heteroatom. 8 and R 9 R are each independently a hydrocarbyl group having 1 to 20 carbon atoms which may contain a heteroatom. 10 are each independently a hydrogen atom or a hydrocarbyl group having 1 to 20 carbon atoms which may contain a heteroatom. Q + is a sulfonium cation represented by the following formula (A2) or an iodonium cation represented by the following formula (A3). [ka] (In the formula, R 11 ~R 15 each independently represents a hydrocarbyl group having 1 to 20 carbon atoms which may contain a heteroatom. 11 and R 12 may be bonded to each other to form a ring together with the sulfur atom to which they are attached.)] [ka] (In the formula, R A is a hydrogen atom, a fluorine atom, a methyl group, or a trifluoromethyl group. 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 21is a halogen atom, a saturated hydrocarbylcarbonyloxy group having 2 to 8 carbon atoms which may be substituted with a halogen atom, a saturated hydrocarbyl group having 1 to 6 carbon atoms which may be substituted with a halogen atom, or a saturated hydrocarbyloxy group having 1 to 6 carbon atoms which may be substituted with a halogen atom. A 1 is a single bond or a saturated hydrocarbylene group having 1 to 10 carbon atoms, and one -CH2- constituting the saturated hydrocarbylene group may be substituted with -O-. 2.R 1 ~R 5 3. The chemically amplified positive resist composition of 1, wherein at least one of the groups is a group containing a fluorine atom, a chlorine atom, a bromine atom, or an iodine atom. 3. The chemically amplified positive resist composition of 1 or 2, wherein the repeating unit represented by formula (B1) is represented by the following formula (B1-1): [ka] (In the formula, R A and a4 are the same as above.) 4. The chemically amplified positive resist composition of any one of 1 to 3, wherein the polymer further comprises a repeating unit represented by the following formula (B2): [ka] (In the formula, R A is the same as above. 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 22 is a halogen atom, a saturated hydrocarbylcarbonyloxy group having 2 to 8 carbon atoms which may be substituted with a halogen atom, a saturated hydrocarbyl group having 1 to 6 carbon atoms which may be substituted with a halogen atom, or a saturated hydrocarbyloxy group having 1 to 6 carbon atoms which may be substituted with a halogen atom. A 2is a single bond or a saturated hydrocarbylene group having 1 to 10 carbon atoms, and one of --CH2-- constituting 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. 5. The chemically amplified positive resist composition according to any one of 1 to 4, 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, R A is the same as above. c and d each independently represent an integer of 0 to 4. e1 is 0 or 1. e2 is an integer of 0 to 5. e3 is an integer of 0 to 2. R 23 and R 24 are each independently a hydroxy group, a halogen atom, a saturated hydrocarbylcarbonyloxy group of 2 to 8 carbon atoms which may be substituted with a halogen atom, a saturated hydrocarbyl group of 1 to 8 carbon atoms which may be substituted with a halogen atom, a saturated hydrocarbyloxy group of 1 to 8 carbon atoms which may be substituted with a halogen atom, or a saturated hydrocarbylcarbonyloxy group of 2 to 8 carbon atoms which may be substituted with a halogen atom. R 25 is an acetyl group, 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 3 is a single bond or a saturated hydrocarbylene group having 1 to 10 carbon atoms, and one -CH2- constituting the saturated hydrocarbylene group may be substituted with -O-. 6. The chemically amplified positive resist composition of any one of 1 to 5, 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. Z 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; -OZ 11 -, -C(=O)-OZ 11 - or -C(=O)-NH-Z 11 - and Z 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. Z 2 is a single bond or -Z 21 -C(=O)-O-, and Z 21 is a hydrocarbylene group having 1 to 20 carbon atoms which may contain a heteroatom. Z 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, -OZ 31 -, -C(=O)-OZ 31 - or -C(=O)-NH-Z 31 - and Z 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. Z 4 is a single bond or a hydrocarbylene group having 1 to 30 carbon atoms which may contain a hetero atom. f1 and f2 are each independently 0 or 1, but Z 4When is a single bond, f1 and f2 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. 7. The chemically amplified positive resist composition according to any one of 1 to 6, further comprising (D) a polymer containing at least one repeating unit selected from the group consisting of a repeating unit represented by the following formula (D1) and repeating units represented by formulas (D2) to (D5): [ka] (In the formula, R C are each independently a hydrogen atom or a methyl group. R D are each independently a hydrogen atom, a fluorine atom, a methyl group, or a trifluoromethyl group. R 51 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 52 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 53 , R 54 , R 56 and R 57 are each independently a hydrogen atom or a saturated hydrocarbyl group having 1 to 10 carbon atoms. R 55 , R58 , R 59 and R 60 are each independently a hydrogen atom, a hydrocarbyl group having 1 to 15 carbon atoms, a fluorinated hydrocarbyl group, or an acid labile group, and R 55 , R 58 , R 59 and R 60 When the group is a hydrocarbyl group or a fluorinated hydrocarbyl group, an ether bond or a carbonyl group may be present between the carbon-carbon bonds. k1 is an integer of 1 to 3. k2 is an integer that satisfies 0≦k2≦5+2k3−k1. k3 is 0 or 1. m is an integer of 1 to 3. X 1 is a single bond, —C(═O)—O—, or —C(═O)—NH—. X 2 is a (m+1)-valent hydrocarbon group having 1 to 20 carbon atoms or a (m+1)-valent fluorinated hydrocarbon group having 1 to 20 carbon atoms. 8. The chemically amplified positive resist composition according to any one of 1 to 7, further comprising (E) an organic solvent. 9. A chemically amplified positive resist composition according to any one of 1 to 8, which provides a resist film having an extinction coefficient (k value) of 0.01 or less when exposed to inspection light having a wavelength of 300 to 400 nm. 10. A method for forming a resist pattern, comprising the steps of: forming a resist film on a substrate using the chemically amplified positive resist composition according to any one of 1 to 9; irradiating the resist film with a pattern using high-energy rays; and developing the resist film irradiated with the pattern using an alkaline developer. 11. The method for forming a resist pattern according to claim 10, wherein the high-energy radiation is EUV or EB. 12. The method for forming a resist pattern according to 10 or 11, wherein the outermost surface of the substrate is made of a material containing at least one selected from the group consisting of chromium, silicon, tantalum, molybdenum, cobalt, nickel, tungsten, and tin. 13. The method for forming a resist pattern according to any one of 10 to 12, wherein the substrate is a photomask blank. 14. A photomask blank comprising a resist film obtained from the chemically amplified positive resist composition according to any one of 1 to 9. 15. Further, the photomask blank of 14 is provided with an antistatic film. [Effects of the Invention]

[0018] The chemically amplified positive resist composition of the present invention effectively controls acid diffusion due to exposure during pattern formation due to the action of the onium salt compound represented by formula (A1). When the resist composition is formed into a resist film to form a pattern, it exhibits extremely high resolution and can obtain a pattern with improved LER and CDU. Furthermore, its high solubility in solvents used in the resist composition prevents aggregation of the acid diffusion controller and suppresses the occurrence of defects. Furthermore, its lack of sensitivity to short-wavelength inspection light of 300 to 400 nm enables inspection of minute defects using short-wavelength inspection light. Furthermore, the repeating unit represented by formula (B1) not only provides good solubility in alkaline developers, but also improves 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 improved LER and CDU, suppresses defects, and enables inspection of micro-defects using short wavelengths, and therefore can be suitably used in microfabrication techniques, in particular EUV lithography and EB lithography. [Brief explanation of the drawings]

[0020] [Figure 1] 1 is a 1H-NMR spectrum of compound QA obtained in Synthesis Example 1-1. DETAILED DESCRIPTION OF THE INVENTION

[0021] 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.

[0022] [Chemically amplified positive resist composition] The chemically amplified positive resist composition of the present invention is characterized by comprising (A) a predetermined onium salt compound, (B) a base polymer containing a predetermined polymer, and (C) a photoacid generator.

[0023] [(A) Onium salt compound] The onium salt compound of the component (A) is represented by the following formula (A1). [ka]

[0024] In formula (A1), R 1 ~R 5 each independently represents a hydrogen atom, a halogen atom, a nitro group, a cyano group, an aldehyde group, a hydrocarbyl group having 1 to 18 carbon atoms which may contain a heteroatom, -C(O)OR 6 , -C(O)R 7 , -OR 8 , -S(O)2R 9 or -S(O)N(R 10 )2. R 6 and R 7 R are each independently a hydrocarbyl group having 1 to 19 carbon atoms which may contain a heteroatom. 8 and R 9 R are each independently a hydrocarbyl group having 1 to 20 carbon atoms which may contain a heteroatom. 10 are each independently a hydrogen atom or a hydrocarbyl group having 1 to 20 carbon atoms which may contain a heteroatom.

[0025] R 1 ~R 5Examples of the halogen atom represented by the formula (I) include a fluorine atom, a chlorine atom, a bromine atom, and an iodine atom.

[0026] R 1 ~R 10 The hydrocarbyl group represented by the formula (I) may be saturated or unsaturated, and may be linear, branched, or cyclic. Specific examples thereof include alkyl groups such as methyl, ethyl, n-propyl, isopropyl, n-butyl, sec-butyl, tert-butyl, tert-pentyl, n-pentyl, n-hexyl, n-octyl, 2-ethylhexyl, n-nonyl, and n-decyl; cyclopentyl, cyclohexyl, cyclopentylmethyl, cyclopentylethyl, cyclopentylbutyl, cyclohexylmethyl, cyclohexylethyl, cyclohexylbutyl, norbornyl, and tricyclo[5.2.1.0]. 2,6 ] cyclic saturated hydrocarbyl groups such as decanyl group, adamantyl group, and adamantylmethyl group; alkenyl groups such as vinyl group, allyl group, propenyl group, butenyl group, and hexenyl group; cyclic unsaturated aliphatic hydrocarbyl groups such as cyclohexenyl group, aryl groups having 6 to 20 carbon atoms such as phenyl group, naphthyl group, and anthracenyl group; and groups obtained by combining these. Furthermore, some or all of the hydrogen atoms of the hydrocarbyl group may be substituted with a group containing a heteroatom such as an oxygen atom, a sulfur atom, a nitrogen atom or a halogen atom, and some of the -CH- groups of the hydrocarbyl group may be substituted with a group containing a heteroatom such as an oxygen atom, a sulfur atom or a nitrogen atom, and as a result, the hydrocarbyl group may contain a hydroxy group, a 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.

[0027] R 1 ~R 5Preferred examples of the alkyl group include a halogen atom, an alkyl group having 1 to 6 carbon atoms, a halogenated alkyl group having 1 to 6 carbon atoms, a hydroxyalkyl group having 1 to 6 carbon atoms, an alkyloxy group having 1 to 6 carbon atoms, and a halogenated alkyloxy group having 1 to 6 carbon atoms.

[0028] Specific examples of the anion of the onium salt compound represented by formula (A1) include, but are not limited to, those shown below. [ka]

[0029] [ka]

[0030] [ka]

[0031] In formula (A1), Q + is a sulfonium cation represented by the following formula (A2) or an iodonium cation represented by the following formula (A3). [ka]

[0032] In formulas (A2) and (A3), R 11 ~R 15 are each independently a hydrocarbyl group having 1 to 20 carbon atoms which may contain a heteroatom. 11 and R 12 may be bonded to each other to form a ring together with the sulfur atom to which they are attached.

[0033] R 11 ~R 15 The hydrocarbyl group represented by may be saturated or unsaturated, and may be linear, branched, or cyclic. Specific examples thereof include the group R 1 ~R 10Examples of the hydrocarbyl group represented by R include the same as those exemplified above. 11 ~R 15 As the group, an aryl group is particularly preferred.

[0034] Also, R 11 and R 12 However, they may be bonded to each other to form a ring together with the sulfur atom to which they are bonded. In this case, the ring preferably has the following structure: [ka] (In the formula, the dashed lines represent bonds.)

[0035] Specific examples of the sulfonium cation represented by formula (A2) include, but are not limited to, the following: [ka]

[0036] Specific examples of the iodonium cation represented by formula (A3) include bis(4-methylphenyl)iodonium, bis(4-ethylphenyl)iodonium, bis(4-tert-butylphenyl)iodonium, bis[4-(1,1-dimethylpropyl)phenyl]iodonium, 4-methoxyphenylphenyliodonium, 4-tert-butoxyphenylphenyliodonium, 4-acryloyloxyphenylphenyliodonium, 4-methacryloyloxyphenylphenyliodonium, etc. Among these, bis(4-tert-butylphenyl)iodonium is particularly preferred.

[0037] Specific structures of the onium salt include any combination of the specific anions and specific cations described above.

[0038] The onium salt compound represented by formula (A1) functions extremely effectively as an acid diffusion controller when applied to a chemically amplified positive resist composition. In the present invention, the term "acid diffusion controller" refers to a material that traps the acid generated from a photoacid generator in the chemically amplified positive resist composition, thereby preventing the acid from diffusing into unexposed areas and forming a desired pattern.

[0039] The acid diffusion control mechanism of the onium salt compound is thought to be as follows. The acid generated by the photoacid generator in the resist composition must be strongly acidic in order to deprotect the acid labile groups in the base polymer. For example, in EB lithography, sulfonic acids in which the α-position of the sulfo group is fluorinated or unfluorinated are generally used. When the photoacid generator and the onium salt compound coexist in the resist composition, the acid generated from the photoacid generator is trapped by the onium salt compound, and the onium salt compound becomes a phenolic compound. It is also possible that the onium salt compound itself undergoes photodecomposition. In this case, the generated phenolic compound is a weak acid, which does not deprotect the acid labile groups in the base polymer, and therefore it is presumed that the onium salt compound functions strongly as an acid diffusion controller.

[0040] Acid diffusion controllers, also known as onium salt-type quenchers, generally tend to produce smaller LERs in resist patterns than acid diffusion controllers that use amine compounds. This is thought to be due to the indefinite repetition of salt exchange between a strong acid and the onium salt compound. In other words, the location where strong acid is generated at the end of exposure is different from the location where the strong acid-generating onium salt was initially present. Repeated cycles of photoinduced acid generation and salt exchange average out the acid generation points, and this smoothing effect is thought to reduce the LER of the resist pattern after development.

[0041] Since the onium salt compound represented by formula (A1) does not have absorption in the short wavelength region of 300 to 400 nm, it is possible to inspect for microdefects in a resist film obtained from the chemically amplified positive resist composition of the present invention using an inspection device that uses short wavelength inspection light. Here, the wavelength of the inspection light used in the inspection device for checking for microdefects in the resist film can be, but is not limited to, 355 nm.

[0042] In order to prevent photosensitivity due to the inspection light, the extinction coefficient (k value) of the resist film obtained from the chemically amplified positive resist composition of the present invention is preferably 0.01 or less, more preferably 0.005 or less, and even more preferably 0.003 or less.

[0043] R in formula (A1) 1 ~R 5 It is preferable that at least one of R contains a fluorine atom, a chlorine atom, a bromine atom, or an iodine atom. 1 ~R 5 At least one of the groups is preferably a halogen atom, a halogenated alkyl group having 1 to 6 carbon atoms, or a halogenated alkyloxy group having 1 to 6 carbon atoms. This improves the solubility in the organic solvent used as the solvent for the resist composition, and even when a large amount of formula (A1) is added relative to the acid generator for the purpose of improving LER, aggregation does not occur and the occurrence of defects can be prevented.

[0044] In addition, when an antistatic film is formed on a resist film, R 1 ~R 5 It is preferable that at least one of R contains a fluorine atom, a chlorine atom, a bromine atom, or an iodine atom. 1 ~R 5At least one of the R in formula (A1) is preferably a halogen atom, a halogenated alkyl group having 1 to 6 carbon atoms, or a halogenated alkyloxy group having 1 to 6 carbon atoms. This allows the onium salt compound represented by formula (A1) to be dispersed in the resist film without aggregation, thereby effectively trapping weak acids contained in the antistatic film. Furthermore, when R in formula (A1) 1 ~R 5 When at least one of the groups contains a fluorine atom, the onium salt compound represented by formula (A1) is localized near the interface between the resist film and the antistatic film, and the weak acid contained in the antistatic film can be trapped very efficiently. As a result, the deterioration of the resolution of the resist caused by the antistatic film can be suppressed, and good resolution can be obtained even when the antistatic film is used.

[0045] In the chemically amplified positive resist composition of the present invention, the content of the onium salt compound represented by formula (A1) is preferably 0.1 to 100 parts by mass, and more preferably 1 to 80 parts by mass, relative to 80 parts by mass of the (B) base polymer described below. When the content of the onium salt compound represented by formula (A1) is within this range, it functions satisfactorily as an acid diffusion controller, and there is no risk of performance degradation such as reduced sensitivity or defects due to insufficient solubility. The onium salt compounds represented by formula (A1) may be used alone, or two or more may be used in combination.

[0046] Furthermore, as a ratio of the content of the photoacid generator described below, the content ratio of the photoacid generator to the onium salt compound represented by formula (A1) (photoacid generator / onium salt compound represented by formula (A1)) is preferably less than 4, and more preferably less than 3. When the content ratio is within the above range, acid diffusion can be sufficiently suppressed, and excellent resolution and CDU can be obtained.

[0047] Furthermore, it is preferred that the amount of the photoacid generator (described below) added is 5 parts by mass or more relative to 80 parts by mass of the polymer, and that the total amount of the onium salt compound represented by Formula (A1) and the photoacid generator added is 10 parts by mass or more relative to 80 parts by mass of the polymer. If the amount added satisfies these conditions and the ratio of photoacid generator / onium salt compound represented by Formula (A1) is less than 4 as described above, it is possible to obtain sufficient acid generation points in exposed areas and further suppress acid diffusion, thereby achieving excellent resolution and CDU.

[0048] [(B) Base polymer] The base polymer of the component (B) includes a polymer containing a repeating unit represented by the following formula (B1) (hereinafter also referred to as repeating unit B1). [ka]

[0049] In formula (B1), R A is a hydrogen atom, a fluorine atom, a methyl group, or a trifluoromethyl group.

[0050] 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.

[0051] In formula (B1), R 21is a halogen atom, a saturated hydrocarbylcarbonyloxy group having 2 to 8 carbon atoms which may be substituted with a halogen atom, a saturated hydrocarbyl group having 1 to 6 carbon atoms which may be substituted with a halogen atom, or a saturated hydrocarbyloxy group having 1 to 6 carbon atoms which may be substituted with a halogen atom. The saturated hydrocarbyl group and the saturated hydrocarbyl moiety of the saturated hydrocarbylcarbonyloxy group and saturated hydrocarbyloxy group may be linear, branched, or cyclic. Specific examples include alkyl groups such as methyl, ethyl, n-propyl, isopropyl, butyl, pentyl, 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 21 may be the same as or different from each other.

[0052] In formula (B1), A 1is a single bond or a saturated hydrocarbylene group having 1 to 10 carbon atoms, and one or more -CH2- constituting 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, the ether bond may be located anywhere except between the carbon atoms at the α-position and the β-position relative to the ester oxygen. When a1 is 0, the atom bonding to the main chain is an ether oxygen, 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 ether oxygen. 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.

[0053] a1 is 0 and A 1 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 1 -) is absent), preferred examples of the repeating unit B1 include units derived from 3-hydroxystyrene, 4-hydroxystyrene, 5-hydroxy-2-vinylnaphthalene, 6-hydroxy-2-vinylnaphthalene, etc. As the repeating unit B1, a repeating unit represented by the following formula (B1-1) is preferred from the viewpoint of achieving a particularly excellent CDU. By including a repeating unit represented by formula (B1-1), the solubility of the exposed area in an alkaline developer is improved, dimensional errors caused by minute differences in the contact impact of the developer are alleviated, and an excellent CDU can be achieved. [ka] (In the formula, RA and a4 are the same as above.)

[0054] 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.)

[0055] 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 this unit has a phenolic hydroxy group as a substituent, the proportion of the repeating unit B1 is also preferably within the above range. The repeating unit B1 may be used alone or in combination of two or more types.

[0056] 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 unit having an acidic functional group protected by an acid labile group (a 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, and the polymer exhibits better solubility in an alkaline developer.

[0057] Such a repeating unit includes one represented by the following formula (B2) (hereinafter also referred to as repeating unit B2). [ka]

[0058] In formula (B2), 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.

[0059] In formula (B2), R 22 is a halogen atom, a saturated hydrocarbylcarbonyloxy group having 2 to 8 carbon atoms which may be substituted with a halogen atom, a saturated hydrocarbyl group having 1 to 6 carbon atoms which may be substituted with a halogen atom, or a saturated hydrocarbyloxy group having 1 to 6 carbon atoms which may be substituted with a halogen atom. The saturated hydrocarbyl group and the saturated hydrocarbyl moiety of the saturated hydrocarbylcarbonyloxy group and saturated hydrocarbyloxy group may be linear, branched, or cyclic. Specific examples include alkyl groups such as methyl, ethyl, n-propyl, isopropyl, butyl, pentyl, 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 22 may be the same as or different from each other.

[0060] In formula (B2), A 2is a single bond or a saturated hydrocarbylene group having 1 to 10 carbon atoms, and one or more -CH2- constituting 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) is 1, the bond may be located anywhere except between the carbon atoms α and β to the ester oxygen. When b1 is 0, the atom bonding to the main chain is an ether oxygen, 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 ether oxygen. 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.

[0061] In formula (B2), 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 greater, provided that at least one of the groups is an acid labile group. That is, in the repeating unit B2, 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 groups that have been used in many known chemically amplified resist compositions and that are cleaved by an acid to give an acidic group can be used.

[0062] Selecting a tertiary saturated 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 saturated 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 saturated 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 be bonded to each other to form a ring.

[0063] 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.

[0064] Further, examples of tertiary saturated hydrocarbyl groups having these as substituents include tert-butyl group, tert-pentyl group, 1-ethyl-1-methylpropyl group, 1,1-diethylpropyl group, 1,1,2-trimethylpropyl group, 1-adamantyl-1-methylethyl group, 1-methyl-1-(2-norbornyl)ethyl group, 1-methyl-1-(tetrahydrofuran-2-yl)ethyl group, 1-methyl-1-(7-oxanorbornan-2-yl)ethyl group, 1-methylcyclopentyl group, 1-ethylcyclopentyl group, 1 -propylcyclopentyl group, 1-isopropylcyclopentyl group, 1-cyclopentylcyclopentyl group, 1-cyclohexylcyclopentyl group, 1-(2-tetrahydrofuryl)cyclopentyl group, 1-(7-oxanorbornan-2-yl)cyclopentyl group, 1-methylcyclohexyl group, 1-ethylcyclohexyl group, 1-cyclopentylcyclohexyl group, 1-cyclohexylcyclohexyl group, 2-methyl-2-norbornyl group, 2-ethyl-2-norbornyl group, 8-methyl-8-tricyclo[5.2.1.0] 2,6 ]decyl group, 8-ethyl-8-tricyclo[5.2.1.0 2,6 ]decyl group, 3-methyl-3-tetracyclo[4.4.0.1 2,5 .1 7,10 ]dodecyl group, 3-ethyl-3-tetracyclo[4.4.0.1 2,5 .1 7,10 ]dodecyl group, 2-methyl-2-adamantyl group, 2-ethyl-2-adamantyl group, 1-methyl-3-oxo-1-cyclohexyl group, 1-methyl-1-(tetrahydrofuran-2-yl)ethyl group, 5-hydroxy-2-methyl-2-adamantyl group, and 5-hydroxy-2-ethyl-2-adamantyl group, but are not limited to these.

[0065] Further, examples of the acid labile group include groups represented by the following formula (B2-1). The group represented by formula (B2-1) is often used as an acid labile group and is a suitable option as an acid labile group that stably gives a pattern in which the interface between the pattern and the substrate is relatively rectangular. When X is a group represented by formula (B2-1), an acetal structure is formed. [ka]

[0066] In formula (B2-1), R L1 is a hydrogen atom or a saturated hydrocarbyl group having 1 to 10 carbon atoms. L2 is a saturated hydrocarbyl group having a carbon number of 1 to 30. The saturated hydrocarbyl group may be linear, branched, or cyclic.

[0067] R L1 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 L2 When a relatively large alkyl group is selected at the end of the polymer, and the polymer is designed to have a large change in solubility due to decomposition, R L1 Preferably, the carbon bonded to the acetal carbon is a secondary carbon atom. L1 Examples of the alkyl group include an isopropyl group, a sec-butyl group, a cyclopentyl group, and a cyclohexyl group.

[0068] Among the acetal groups, R L2 is preferably a polycyclic alkyl group having 7 to 30 carbon atoms. L2 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. L2is 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.

[0069] Preferred examples of the group represented by formula (B2-1) include, but are not limited to, the following: L1 is the same as above. [ka]

[0070] 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.

[0071] The content of the repeating unit B2 is preferably 5 to 45 mol % of all the repeating units constituting the polymer. The repeating unit B2 may be used alone or in combination of two or more.

[0072] 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]

[0073] In the formulae (B3) and (B4), c and d each independently represent an integer of 0 to 4.

[0074] In formulas (B3) and (B4), R23 and R 24 are each independently a hydroxy group, a halogen atom, a saturated hydrocarbylcarbonyloxy group having 2 to 8 carbon atoms which may be substituted with a halogen atom, a saturated hydrocarbyl group having 1 to 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 c is 2 or more, each R 23 may be the same or different. When d is 2 or more, each R 24 may be the same as or different from each other.

[0075] In formula (B5), e1 is 0 or 1. e2 is an integer of 0 to 5. e3 is an integer of 0 to 2, and when e3 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. When e3 is 0, e2 is preferably an integer of 0 to 3, and when e3 is 1 or 2, e2 is preferably an integer of 0 to 4.

[0076] In formula (B5), R A is the same as above. R 25 is an acetyl group, 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 e2 is 2 or more, each R 25 may be the same as or different from each other.

[0077] R 25 Preferred 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 preferred.

[0078] 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.

[0079] Among the above-mentioned preferred substituents, examples of substituents that are particularly easy to prepare as a monomer and that are suitably used include a chlorine atom, a bromine atom, an iodine atom, a methyl group, an ethyl group, and a methoxy group.

[0080] In formula (B5), A 3is a single bond or a saturated hydrocarbylene group having 1 to 10 carbon atoms, and one or more -CH2- constituting 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 e1 in formula (B5) is 1, the ether bond may be located anywhere except between the carbon atoms at the α-position and the β-position relative to the ester oxygen. When e1 is 0, the atom bonding to the main chain is an ether oxygen, 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 ether oxygen. 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.

[0081] e1 is 0 and A 3 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 3 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.

[0082] Also, when e1 is 1 (i.e., -C(=O)-OA as a linker 3 In the case where R A is the same as above. [ka]

[0083] [ka]

[0084] 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.

[0085] 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.

[0086] The polymer preferably contains at least one selected from the group consisting of repeating units B1, B2, and B3 to B5, as structural units, in order to achieve 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.

[0087] The polymer may further contain at least one 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]

[0088] 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; -OZ 11 -, -C(=O)-OZ 11 - or -C(=O)-NH-Z 11 - and Z 11 Z 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 -Z 21 -C(=O)-O-, and Z 21 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, -OZ31 -, -C(=O)-OZ 31 - or -C(=O)-NH-Z 31 - and Z 31 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 is a single bond or a hydrocarbylene group having 1 to 30 carbon atoms which may contain a hetero atom. f1 and f2 are each independently 0 or 1, but Z 4 When is a single bond, f1 and f2 are 0.

[0089] In formulas (B7) and (B11), Z 2 Ga-Z 21 -C(=O)-O-, Z 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.)

[0090] 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.

[0091] 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.

[0092] 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]

[0093] [ka]

[0094] 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 1 ~R 10 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.

[0095] 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 R 34 , R36 and R 37 , or R 39 and R 40 However, they 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.)

[0096] In the formulae (B7) to (B9), specific structures of the sulfonium cation include, but are not limited to, those shown below. [ka]

[0097] [ka]

[0098] In the formulae (B11) to (B13), specific structures of the iodonium cation include, but are not limited to, those shown below. [ka]

[0099] [ka]

[0100] 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.

[0101] The base polymer (B) may be a mixture of a polymer containing the repeating unit B1 and at least one selected from the repeating units B6 to B13, and a polymer containing the repeating unit B1 but not the repeating units B6 to B13. In this case, the content of the polymer containing the repeating unit B1 but not the repeating units 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 the repeating units B6 to B13.

[0102] The content of repeating units having an aromatic ring skeleton among all repeating units of the polymer contained in the base polymer is preferably 65 mol % or more, more preferably 85 mol % or more, and even more preferably all units are repeating units having an aromatic ring skeleton, which improves the polymerization uniformity of the polymer and the in-plane uniformity of the resist film, thereby enabling the production of an excellent CDU.

[0103] As described in Patent Document 8, examples of the base polymer that contain a lactone functional group are known, but polymers that contain lactone functional groups result in reduced liposolubility and therefore reduced resistance to alkaline developers, which can cause deterioration of the pattern shape and lead to a decrease in CDU. Therefore, it is preferable that the polymer in the chemically amplified positive resist composition of the present invention does not contain a lactone functional group.

[0104] 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.

[0105] 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 LER and CDU deterioration, 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) as a solvent.

[0106] 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.

[0107] [(C) Photoacid generator] The chemically amplified positive resist composition of the present invention may contain a photoacid generator (hereinafter also referred to as an additive-type photoacid generator) as component (C). The additive-type photoacid generator is not particularly limited as long as it is a compound that generates an acid upon exposure to high-energy rays. Suitable photoacid generators include sulfonium salts, iodonium salts, sulfonyldiazomethane, N-sulfonyloxyimide, and oxime-O-sulfonate-type acid generators.

[0108] Specific examples of the photoacid generator include nonafluorobutanesulfonate, the partially fluorinated sulfonates described in paragraphs

[0247] to

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

[0261] to

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

[0122] to

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

[0080] to

[0081] of JP 2010-215608 A. Among these, arylsulfonate-type or alkane sulfonate-type photoacid generators are preferred because they generate an acid of suitable strength for deprotecting the acid labile group in the repeating unit represented by formula (B2).

[0109] Such a photoacid generator is preferably a compound having a sulfonate anion of the structure shown below: Examples of the counter cation include those mentioned above as specific examples of the sulfonium cation in formulae (B7) to (B9) and those mentioned above as specific examples of the iodonium cation in formulae (B11) to (B13). [ka]

[0110] [ka]

[0111] [ka]

[0112] [ka]

[0113] [ka]

[0114] [ka]

[0115] [ka]

[0116] [ka]

[0117] In the chemically amplified positive resist composition of the present invention, the content of the (C) additive-type photoacid generator is preferably 5 to 30 parts by mass, more preferably 5 to 20 parts by mass, relative to 80 parts by mass of the (B) base polymer. When the base polymer contains repeating units B6 to B13 (i.e., when a polymer-bound acid generator is used), the addition of the additive-type photoacid generator may be omitted. The (C) additive-type photoacid generator may be used alone, or two or more types may be used in combination.

[0118] [(D) Fluorine-containing polymer] The chemically amplified positive resist composition of the present invention may contain, as component (D), a fluorine-containing polymer containing at least one repeating unit selected from the group consisting of a repeating unit represented by formula (D1) below (hereinafter also referred to as repeating unit D1) and repeating units represented by formulas (D2), (D3), (D4), and (D5) below (hereinafter also referred to as repeating units D2, D3, D4, and D5, respectively) for the purposes of achieving high contrast, shielding against acid chemical flare upon high-energy radiation exposure, and preventing acid mixing from the antistatic coating during the process of applying an antistatic coating material to the resist film, thereby suppressing unexpected and unnecessary pattern degradation. The fluorine-containing polymer also has a surfactant function, which prevents insoluble matter from reattaching to the substrate during the development process, thereby effectively reducing development defects. [ka]

[0119] In formulas (D1) to (D5), R C are each independently a hydrogen atom or a methyl group. D are each independently a hydrogen atom, a fluorine atom, a methyl group, or a trifluoromethyl group. 51 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. 52 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. 53 , R 54 , R 56 and R 57 are each independently a hydrogen atom or a saturated hydrocarbyl group having 1 to 10 carbon atoms. 55 , R 58 , R 59 and R 60 are each independently a hydrogen atom, a hydrocarbyl group having 1 to 15 carbon atoms, a fluorinated hydrocarbyl group, or an acid labile group, and R 55 , R 58 , R 59 and R 60When k is a hydrocarbyl group or a fluorinated hydrocarbyl group, an ether bond or a carbonyl group may be present between the carbon-carbon bond. k1 is an integer of 1 to 3. k2 is an integer that satisfies 0≦k2≦5+2k3−k1. k3 is 0 or 1. m is an integer of 1 to 3. X 1 is a single bond, —C(═O)—O—, or —C(═O)—NH—. X 2 is a (m+1)-valent hydrocarbon group having 1 to 20 carbon atoms or a (m+1)-valent fluorinated hydrocarbon group having 1 to 20 carbon atoms.

[0120] R 51 and R 52 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 these groups.

[0121] In formula (D1), -OR 51 is preferably a hydrophilic group. In this case, R 51 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.

[0122] Examples of the repeating unit D1 include, but are not limited to, those shown below. C is the same as above. [ka]

[0123] [ka]

[0124] In the repeating unit D1, X 1is preferably -C(=O)-O- or -C(=O)-NH-. C is preferably a methyl group. 1 The presence of a carbonyl group in R improves the acid trapping ability of the antistatic film. C When the methyl group is used, the polymer becomes more rigid with a higher glass transition temperature (Tg), which suppresses acid diffusion, resulting in good stability of the resist film over time and preventing degradation of resolution and pattern shape.

[0125] In formulas (D2) and (D3), R 53 , R 54 , R 56 and R 57 Examples of saturated hydrocarbyl groups having 1 to 10 carbon atoms represented by the formula (I) include alkyl groups such as methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, n-pentyl, n-hexyl, n-heptyl, n-octyl, n-nonyl, and n-decyl; and cyclic saturated hydrocarbyl groups such as cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl, adamantyl, and norbornyl. Of these, saturated hydrocarbyl groups having 1 to 6 carbon atoms are preferred.

[0126] In formulas (D2) to (D5), R 55 , R 58 , R 59 and R 60 Examples of the hydrocarbyl group having 1 to 15 carbon atoms represented by the formula (I) include an alkyl group, an alkenyl group, an alkynyl group, etc., with an alkyl group being preferred. In addition to the alkyl groups mentioned above, examples of the alkyl group include an n-undecyl group, an n-dodecyl group, a tridecyl group, a tetradecyl group, a pentadecyl group, etc. Furthermore, 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.

[0127] X 2The (m+1)-valent hydrocarbon group having 1 to 20 carbon atoms and the (m+1)-valent fluorinated hydrocarbon group having 1 to 20 carbon atoms represented by the following formula (I) include groups in which m hydrogen atoms have been further removed from the aforementioned hydrocarbyl group or fluorinated hydrocarbyl group, etc.

[0128] Specific examples of the repeating units D2 to D5 include, but are not limited to, the following: D is the same as above. [ka]

[0129] [ka]

[0130] [ka]

[0131] The content of repeating unit D1 is preferably 5 to 85 mol %, more preferably 15 to 80 mol %, of all repeating units in (D) fluorine-containing polymer. The content of repeating units D2 to D5 is preferably 15 to 95 mol %, more preferably 20 to 85 mol %, of all repeating units in (D) fluorine-containing polymer. Repeating units D1 to D5 may be used alone or in combination of two or more.

[0132] The (D) fluorine-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 (D) fluorine-containing polymer contains other repeating units, the content of such other repeating units is preferably 50 mol % or less of all repeating units.

[0133] The (D) fluorine-containing 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, reference can be made to JP-A-2004-115630.

[0134] The Mw of the (D) fluorine-containing polymer is preferably 2,000 to 50,000, more preferably 3,000 to 20,000. If the Mw is less than 2,000, 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 (D) fluorine-containing polymer preferably has an Mw / Mn ratio of 1.0 to 2.2, more preferably 1.0 to 1.7.

[0135] In the chemically amplified positive resist composition of the present invention, the content of the fluorine-containing polymer (D) is preferably from 0.01 to 30 parts by mass, and more preferably from 0.1 to 20 parts by mass, relative to 80 parts by mass of the base polymer (B). The fluorine-containing polymer (D) may be used alone, or two or more types may be used in combination.

[0136] [(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 the respective components. 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, ethylene glycol monomethyl ether, propylene glycol monoethyl ether, and ethylene glycol monomethyl ether. Examples of suitable solvents include ethers such as propylene glycol monoethyl ether, propylene glycol dimethyl ether, and diethylene glycol dimethyl ether; esters such as propylene glycol monomethyl ether acetate, propylene glycol monoethyl ether acetate, ethyl lactate, ethyl pyruvate, butyl acetate, methyl 3-methoxypropionate, ethyl 3-ethoxypropionate, tert-butyl acetate, tert-butyl propionate, and propylene glycol 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.

[0137] Among these organic solvents, 1-ethoxy-2-propanol, propylene glycol monomethyl ether acetate, propylene glycol monomethyl ether, cyclohexanone, ethyl lactate, γ-butyrolactone, and mixed solvents thereof are preferred.

[0138] 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.

[0139] [(F) Basic compounds] The chemically amplified positive resist composition of the present invention may also contain (F) a basic compound as an acid diffusion controller other than the component (A) for the purpose of correcting pattern shape, etc. By adding a basic compound, acid diffusion can be effectively controlled, and even when a substrate whose outermost surface is made of a material containing chromium is used, the effect of acid generated within the resist film on the chromium-containing material can be suppressed.

[0140] 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.

[0141] 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.

[0142] [(G) Surfactant] The chemically amplified positive resist composition of the present invention may contain a commonly used surfactant in order to improve its coatability onto a substrate. When using a surfactant, many known surfactants are available, as described in JP-A-2004-115630, and these can be used as a reference for selection. 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.

[0143] [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.

[0144] The substrate may be, for example, a substrate for manufacturing integrated circuits (Si, SiO, SiO2, SiN, SiON, TiN, WSi, BPSG, SOG, organic anti-reflective coating, etc.), or a substrate for manufacturing mask circuits (Cr, CrO, CrON, MoSi2, Si, SiO, SiO2, SiON, SiN, SiONC, CoTa, NiTa, TaBN, SnO2, etc.). The resist composition described above is applied to the substrate by a method such as spin coating to a film thickness of 0.03 to 2 μm, and this is pre-baked on a hot plate preferably at 60 to 150°C for 1 to 20 minutes, more preferably at 80 to 140°C for 1 to 10 minutes, to form a resist film.

[0145] 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.

[0146] 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 , more preferably 10 to 400 μC / cm 2 Irradiate so that

[0147] 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.

[0148] 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.

[0149] 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.

[0150] The chemically amplified positive resist composition of the present invention is useful because it exhibits particularly good resolution and is capable of forming patterns with excellent LER and CDU. Furthermore, the chemically amplified positive resist composition of the present invention is particularly useful for forming patterns on substrates having a surface made of a material that is prone to pattern peeling or pattern collapse, since it is easy to obtain good adhesion of the resist pattern. Examples of such substrates include substrates having a sputtering film formed on the outermost surface thereof by a sputtering film of metallic chromium or a chromium compound containing one or more light elements selected from oxygen atoms, nitrogen atoms, and carbon atoms; substrates having a sputtering film formed on the outermost surface thereof by a sputtering film of metallic tantalum or a tantalum compound containing one or more light elements selected from oxygen atoms, nitrogen atoms, and carbon atoms; and SiO x The chemically amplified positive resist composition of the present invention is particularly useful for pattern formation using a photomask blank as the substrate.

[0151] In the resist pattern forming method 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 resist pattern shape, such as a material containing at least one element selected from chromium, silicon, tantalum, molybdenum, cobalt, nickel, tungsten, and tin, 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 with high resolution and excellent LER and CDU by exposure.

[0152] The chemically amplified positive resist composition of the present invention is capable of suppressing the occurrence of defects, and therefore makes it possible to produce a patterned substrate with a reduced number of defects even when forming a very small pattern.

[0153] Furthermore, when a pattern is formed using the chemically amplified positive resist composition of the present invention, defect inspection can be carried out using a short wavelength of 400 nm or less, making it possible to detect minute defects. [Example]

[0154] 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 measurement value obtained by GPC. The following apparatuses were used. · 1 H-NMR: JEOL Ltd., ECA-500

[0155] [1] Synthesis of acid diffusion controller [Synthesis Example 1-1] Synthesis of triphenylsulfonium 3,5-bis(trifluoromethyl)phenolate (QA) [ka]

[0156] 200 g of pure water was added to 50 g of the raw material 3,5-bis(trifluoromethyl)phenol, and 34.8 g of a 25% by mass aqueous solution of sodium hydroxide was added to this and stirred for 30 minutes. After stirring, 400 g of methylene chloride and 648.5 g of a 10% by mass aqueous solution of triphenylsulfonium chloride, a salt compound, were added, and the organic layer was separated. The organic layer was further washed with water and concentrated under reduced pressure. Methyl isobutyl ketone was added to the concentrated residue, and the mixture was concentrated under reduced pressure again. Hexane was added to the resulting residue, and recrystallization was carried out. The resulting crystals were collected and then dried under vacuum to obtain the target product, triphenylsulfonium 3,5-bis(trifluoromethyl)phenolate (QA) (yield: 100.8 g, 94%). The nuclear magnetic resonance spectrum of compound QA ( 1 H-NMR / DMSO-d6) is shown in Figure 1.

[0157] [Synthesis Examples 1-2 and 1-3] Synthesis of Compounds QB and QC The following compounds QB and QC were synthesized in the same manner as in Synthesis Example 1-1, except that the raw materials and salt compounds were changed. [ka]

[0158] [2] Polymer synthesis [Synthesis Example 2-1] Synthesis of Polymer A1 A 3-L flask was charged with 407.5 g of acetoxystyrene, 42.5 g of acenaphthylene, and 1,275 g of toluene as a solvent. The reaction vessel was cooled to -70°C under a nitrogen atmosphere, and degassed under reduced pressure and nitrogen flow were repeated three times. After warming to room temperature, 34.7 g of 2,2'-azobis(2,4-dimethylvaleronitrile) (V-65, Fujifilm Wako Pure Chemical Industries, Ltd.) was added as a polymerization initiator. The temperature was raised to 55°C and the reaction was allowed to proceed for 40 hours. A mixed solvent of 970 g of methanol and 180 g of water was added dropwise to the reaction solution while stirring. After the addition was complete, the mixture was allowed to stand for 30 minutes, allowing it to separate into two layers. The lower layer (polymer layer) was concentrated under reduced pressure, and this polymer layer was redissolved in a mixed solvent of 0.45 L of methanol and 0.54 L of THF. 160 g of triethylamine and 30 g of water were added thereto, and a deprotection reaction was carried out at 60°C for 40 hours. This deprotection reaction solution was concentrated under reduced pressure, and 548 g of methanol and 112 g of acetone were added to the concentrated solution to form a solution. 990 g of hexane was added dropwise to the solution while stirring. After the dropwise addition was completed, the solution was allowed to stand for 30 minutes, allowing it to separate into two layers. 300 g of THF was added to the lower layer (polymer layer), and 1030 g of hexane was added dropwise to the solution while stirring. After 30 minutes, the lower layer (polymer layer) was concentrated under reduced pressure. The resulting polymer solution was neutralized with 82 g of acetic acid, concentrated, dissolved in 0.3 L of acetone, and then added to 10 L of water to precipitate, followed by filtration and drying, yielding 280 g of a white polymer. 1 Measurements by 1 H-NMR and GPC revealed that the polymer had a copolymer composition ratio of hydroxystyrene:acenaphthylene=89.3:10.7, Mw of 5000, and Mw / Mn of 1.63. 100 g of the obtained polymer was reacted with 50 g of (2-methyl-1-propenyl) methyl ether under acidic conditions, followed by neutralization, separation, and crystallization to obtain Polymer A1 in a yield of 125 g.

[0159] [Synthesis Example 2-2] Synthesis of Polymers A-2 to A-7 and Polymer P-1 Polymers A-2 to A-7 and polymer P-1 were synthesized in the same manner as in Synthesis Example 2-1, except that the raw material compounds used were changed.

[0160] The structures of polymers A-1 to A-6 are shown below. [ka]

[0161] The structure of comparative polymer A-7 is shown below. [ka]

[0162] The structure of polymer P-1 is shown below. [ka]

[0163] [3] Preparation of positive resist composition [Examples 1-1 to 1-35, Comparative Examples 1-1 to 1-12] Chemically amplified positive resist compositions (R-1 to R-35, CR-1 to CR-12) were prepared by dissolving each component in an organic solvent according to the compositions shown in Tables 1 to 3 below, and filtering each of the resulting solutions through a 0.02 μm UPE filter.

[0164] In Tables 1 to 3, the organic solvents are PGMEA (propylene glycol monomethyl ether acetate), EL (ethyl lactate), and PGME (propylene glycol monomethyl ether).

[0165] In Tables 1 to 3, the structures of the acid diffusion controllers QD and QE, photoacid generators PAG-A to PAG-C, and fluorine-containing polymers C-1 and C-2 for comparative examples are as follows: QD, QE: [ka]

[0166] PAG-A~PAG-C: [ka]

[0167] C-1, C-2: [ka]

[0168] [Table 1]

[0169] [Table 2]

[0170] [Table 3]

[0171] [4] Defect evaluation [Examples 2-1 to 2-35, Comparative Examples 2-1 to 2-9] Each chemically amplified positive resist composition (R-1 to R-35, CR-1 to CR-9) was prepared and stirred for 8 hours using a stirrer, after which it was visually inspected to ensure that the resist composition had dissolved in the solvent.

[0172] The prepared resist compositions (R-1 to R-35, CR-1 to CR-9) were each subjected to ACT-M (Tokyo Electron Ltd.) Using The resist was spin-coated onto a mask blank whose outermost surface was a Cr film and pre-baked on a hot plate at 110°C for 600 seconds to produce an 80 nm thick resist film. The entire surface was then patterned using an electron beam exposure system (EBM-5000plus, manufactured by NuFlare Technology, Inc., accelerating voltage 50 kV), subjected to PEB at 110°C for 600 seconds, and developed in a 2.38% by weight TMAH aqueous solution. The development residue was evaluated using a mask defect inspection system (M9650, manufactured by Lasertec Corporation). The results are shown in Tables 4 and 5.

[0173] [Table 4]

[0174] [Table 5]

[0175] The chemically amplified positive resist compositions (R-1 to R-35) of the present invention, which contain an onium salt compound represented by formula (A1), all exhibited excellent defect suppression properties compared to the comparative resist compositions (CR-1 to CR-9). reduction Furthermore, among the onium salt compounds represented by formula (A1), for QA and QB, which have halogen atoms, no increase in the number of defects was observed even when the amount added was increased up to 35 parts by mass, but for QC to QE, as the amount added increased, aggregates were formed, and an increase in the number of defects and insolubilization were observed.

[0176] [5] EB lithography evaluation [Examples 3-1 to 3-34, Comparative Examples 3-1 to 3-10] Each chemically amplified positive resist composition was spin-coated onto a 152 mm square mask blank with a Cr film as the outermost surface using ACT-M (Tokyo Electron Limited), and pre-baked on a hot plate at 110°C for 600 seconds to produce a resist film with a thickness of 80 nm. The resist film was then exposed using an electron beam exposure system (EBM-5000plus, NuFlare Technology Inc., accelerating voltage 50 kV), subjected to PEB at 110°C for 600 seconds, and developed with a 2.38% by mass aqueous solution of TMAH to obtain a positive pattern.

[0177] 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 required to resolve a 200 nm LS at a 1:1 ratio was defined as the resolution (limiting resolution). Using an SEM, 80 edges were detected for each of the 32 edges of the 200 nm LS pattern, and the LER (nm) was calculated by multiplying the standard deviation (σ) by 3σ. Furthermore, dimensions were measured at 144 locations within the blank substrate for the 200 nm LS pattern obtained by irradiation at the optimal exposure dose, and the CDU was calculated as 3σ, which is the standard deviation (σ). The smaller this value, the better the CDU of the LS pattern. The results are shown in Tables 6 and 7.

[0178] [Table 6]

[0179] [Table 7]

[0180] Compared to the comparative resist compositions, all of the chemically amplified positive resist compositions of the present invention, which contain an onium salt compound represented by formula (A1), exhibited good resolution and also showed good values ​​for LER and CDU.

[0181] Among the onium salt compounds represented by formula (A1), when compounds containing at least one fluorine atom, chlorine atom, bromine atom, or iodine atom, such as QA and QB, are used, the compounds have high solubility in organic solvents and do not aggregate even when added in large amounts. As shown in Examples 3-7 and 3-24, extremely good LER and CDU were achieved.

[0182] The resist composition (CR-10) containing the A-7 polymer having a lactone skeleton had reduced developer resistance due to reduced lipophilicity, resulting in deteriorated pattern shape. As shown in Comparative Example 3-8, the resist composition had inferior resolution, LER, and CDU compared to the chemically amplified positive resist composition of the present invention.

[0183] A resist composition (CR-11) in which the content ratio of the photoacid generator to the onium salt compound represented by formula (A1) was 4 or more was unable to sufficiently suppress acid diffusion, and as shown in Comparative Example 3-9, the resulting resist composition exhibited inferior resolution, LER, and CDU compared to the chemically amplified positive resist composition of the present invention.

[0184] In the resist composition (CR-12) in which the total amount of the photoacid generator and the onium salt compound represented by formula (A1) added was less than 10 parts by mass, it was not possible to obtain sufficient acid generation points in the exposed areas, and it was not possible to sufficiently suppress acid diffusion. As a result, as shown in Comparative Example 3-10, the resolution, LER, and CDU were inferior to the chemically amplified positive resist composition of the present invention.

[0185] [6] Extinction coefficient (k value) measurement [Examples 4-1 to 4-9, Comparative Examples 4-1 to 4-3] Each chemically amplified positive resist composition shown in Table 8 was spin-coated onto a silicon wafer to a film thickness of 100 nm to prepare evaluation substrates. The prepared substrates were irradiated with light at wavelengths of 400 nm, 355 nm, 330 nm, and 300 nm using a VUV-VASE (manufactured by JA Woollam), and the extinction coefficients (k values) were measured. To prevent photosensitivity of the resist film due to irradiation with the inspection light, the k value is preferably 0.01 or less, and more preferably 0.003 or less. The results are shown in Table 8.

[0186] [Table 8]

[0187] The onium salt compound represented by formula (A1) exhibited a good k value of 0.01 or less at all wavelengths, and an extremely good k value of 0.003 or less at wavelengths of 400 nm, 355 nm, and 330 nm. On the other hand, the comparative example exhibited a k value of more than 0.01 at all wavelengths, which was enough to sensitize the resist film.

[0188] [7] EB lithography evaluation when applying antistatic film [Examples 5-1 to 5-9, Comparative Examples 5-1 to 5-5] Each chemically amplified positive resist composition shown in Table 9 was spin-coated onto a 152 mm square mask blank with a Cr film as the outermost surface using ACT-M (Tokyo Electron Limited), and then pre-baked on a hot plate at 110°C for 600 seconds to produce a resist film with a thickness of 80 nm. A conductive polymer composition was then spin-coated onto the resist film, and pre-baked on a hot plate at 70°C for 600 seconds to produce an antistatic film with a thickness of 15 nm. The resist film was then exposed using an electron beam exposure system (EBM-5000plus, NuFlare Technology, Inc., accelerating voltage 50 kV), subjected to PEB at 110°C for 600 seconds, and developed with a 2.38% by mass TMAH aqueous solution to produce a positive pattern.

[0189] 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 The minimum dimension at the exposure dose that resolves a 200 nm LS at 1:1 was taken as the resolution (limiting resolution). The results are shown in Table 9.

[0190] [Table 9]

[0191] Chemically amplified positive resist compositions of the present invention containing the halogen-containing onium salt compounds QA or QB represented by formula (A1) demonstrated excellent resolution, even when coated with an antistatic film. On the other hand, resist compositions containing QC or QD exhibited good resolution, while resist compositions containing QE exhibited poor resolution. This is believed to be the result of an undesired reaction in which weak acids present in the antistatic film slightly deprotected the protecting groups in the base polymer in unexposed areas. Compounds QA to QD are highly basic and have a structure that easily traps acids, making the aforementioned undesired reaction unlikely to occur. Furthermore, compound QA contains fluorine atoms, allowing it to localize near the interface with the antistatic film coated on top of the resist film, effectively trapping weak acids in the antistatic film and achieving excellent resolution. Compound QB also contains iodine atoms, preventing aggregation in the resist film and providing highly uniform dispersibility, effectively trapping weak acids in the antistatic film and achieving excellent resolution.

[0192] As is clear from the above explanation, by using the chemically amplified positive resist composition of the present invention, it is possible to form a pattern with extremely high resolution, good LER and CDU, and few defects. Furthermore, because the composition is not photosensitive to short-wavelength light, even smaller defects can be detected by defect inspection using a short-wavelength light source. The method for forming a resist pattern using the chemically amplified positive resist composition of the present invention is useful for semiconductor device manufacturing, particularly photolithography in processing photomask blanks.

Claims

1. A chemically amplified positive resist composition comprising: (A) an onium salt compound 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 (however, the base polymer does not include a polymer that contains a repeating unit having a lactone ring); and (C) a photoacid generator, the content of repeating units having an aromatic ring skeleton is 65 mol% or more of all repeating units of the polymer contained in the base polymer, the content ratio of the photoacid generator to the onium salt compound represented by formula (A1) is less than 4, the content of the photoacid generator is 5 parts by mass or more relative to 80 parts by mass of the polymer, and the total content of the onium salt compound represented by formula (A1) and the photoacid generator is 10 parts by mass or more relative to 80 parts by mass of the polymer, A chemically amplified positive resist composition that provides a resist film having an extinction coefficient (k value) of 0.01 or less for inspection light having a wavelength of 300 to 400 nm. 【Chemical 1】 [In the formula, R 1 ~R 5 each independently represents a hydrogen atom, a halogen atom, a nitro group, a cyano group, an aldehyde group, a hydrocarbyl group having 1 to 18 carbon atoms which may contain a heteroatom, —C(O)OR 6 , -C(O)R 7 , -OR 8 , -S(O) 2 R 9 or -S(O) 2 N(R 10 ) 2 It is. 6 and R 7 R are each independently a hydrocarbyl group having 1 to 19 carbon atoms which may contain a heteroatom. 8 and R 9 R are each independently a hydrocarbyl group having 1 to 20 carbon atoms which may contain a heteroatom. 10 are each independently a hydrogen atom or a hydrocarbyl group having 1 to 20 carbon atoms which may contain a heteroatom. Q + is a sulfonium cation represented by the following formula (A2) or an iodonium cation represented by the following formula (A3). 【Chemistry 2】 (In the formula, R 11 ~R 15 each independently represents a hydrocarbyl group having 1 to 20 carbon atoms which may contain a heteroatom. 11 and R 12 may be bonded to each other to form a ring together with the sulfur atom to which they are attached. 【Chemistry 3】 (In the formula, R A is a hydrogen atom, a fluorine atom, a methyl group, or a trifluoromethyl group. 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 21 is a halogen atom, a saturated hydrocarbylcarbonyloxy group having 2 to 8 carbon atoms which may be substituted with a halogen atom, a saturated hydrocarbyl group having 1 to 6 carbon atoms which may be substituted with a halogen atom, or a saturated hydrocarbyloxy group having 1 to 6 carbon atoms which may be substituted with a halogen atom. A 1 is a single bond or a saturated hydrocarbylene group having 1 to 10 carbon atoms, and —CH 2 - may be replaced by -O-.

2. R 1 ~R 5 2. The chemically amplified positive resist composition according to claim 1, wherein at least one of the following is a group containing a fluorine atom, a chlorine atom, a bromine atom or an iodine atom.

3. 2. The chemically amplified positive resist composition according to claim 1, wherein the repeating unit represented by formula (B1) is represented by the following formula (B1-1): 【Chemistry 4】 (In the formula, R A and a4 are the same as above.)

4. 2. The chemically amplified positive resist composition according to claim 1, wherein the polymer further comprises a repeating unit represented by the following formula (B2): 【Chemistry 5】 (In the formula, R A is the same as above. 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 22 is a halogen atom, a saturated hydrocarbylcarbonyloxy group having 2 to 8 carbon atoms which may be substituted with a halogen atom, a saturated hydrocarbyl group having 1 to 6 carbon atoms which may be substituted with a halogen atom, or a saturated hydrocarbyloxy group having 1 to 6 carbon atoms which may be substituted with a halogen atom. A 2 is a single bond or a saturated hydrocarbylene group having 1 to 10 carbon atoms, and —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.

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): 【Chemistry 6】 (In the formula, R A is the same as above. c and d each independently represent an integer of 0 to 4. e1 is 0 or 1. e2 is an integer of 0 to 5. e3 is an integer of 0 to 2. R 23 and R 24 are each independently a hydroxy group, a halogen atom, a saturated hydrocarbylcarbonyloxy group having 2 to 8 carbon atoms which may be substituted with a halogen atom, a saturated hydrocarbyl group having 1 to 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 25 is an acetyl group, 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 3 is a single bond or a saturated hydrocarbylene group having 1 to 10 carbon atoms, and —CH 2 - may be replaced by -O-.

6. 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 repeating units represented by the following formulas (B6) to (B13): 【Chemistry 7】 (In the formula, R B are each independently a hydrogen atom or a methyl group. Z 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-Z 11 -, -C(=O)-O-Z 11 - or -C(=O)-NH-Z 11 - and Z 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. Z 2 is a single bond or -Z 21 -C(=O)-O-, and Z 21 is a hydrocarbylene group having 1 to 20 carbon atoms which may contain a heteroatom. Z 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-Z 31 -, -C(=O)-O-Z 31 - or -C(=O)-NH-Z 31 - and Z 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. Z 4 is a single bond or a hydrocarbylene group having 1 to 30 carbon atoms which may contain a heteroatom. f1 and f2 are each independently 0 or 1, but Z 4 is a single bond, f1 and f2 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.)

7. 2. The chemically amplified positive resist composition according to claim 1, further comprising (D) a polymer containing at least one repeating unit selected from the group consisting of a repeating unit represented by the following formula (D1) and repeating units represented by the following formulas (D2) to (D5): 【Chemistry 8】 (In the formula, R C are each independently a hydrogen atom or a methyl group. R D are each independently a hydrogen atom, a fluorine atom, a methyl group, or a trifluoromethyl group. R 51 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 52 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 53 , R 54 , R 56 and R 37 are each independently a hydrogen atom or a saturated hydrocarbyl group having 1 to 10 carbon atoms. R 55 , R 58 , R 59 and R 60 are each independently a hydrogen atom, a hydrocarbyl group having 1 to 15 carbon atoms, a fluorinated hydrocarbyl group, or an acid labile group; R 55 , R 58 , R 59 and R 60 When the group is a hydrocarbyl group or a fluorinated hydrocarbyl group, an ether bond or a carbonyl group may be present between the carbon-carbon bonds. k1 is an integer of 1 to 3. k2 is an integer that satisfies 0≦k2≦5+2k3−k1. k3 is 0 or 1. m is an integer of 1 to 3. X 1 is a single bond, —C(═O)—O—, or —C(═O)—NH—. X 2 is a (m+1)-valent hydrocarbon group having 1 to 20 carbon atoms or a (m+1)-valent fluorinated hydrocarbon group having 1 to 20 carbon atoms.

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 photomask blank.

13. A photomask blank comprising a resist film obtained from the chemically amplified positive resist composition according to any one of claims 1 to 8.

14. The photomask blank according to claim 13, further comprising an antistatic film.

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