Chemically amplified positive resist composition and method for forming resist pattern

Abstract

To provide a chemically amplified positive resist composition that can form a resist film enabling formation of a pattern with a very high resolution, reduced LER, superior rectangularity, and minimized influence of development loading, and a resist pattern forming process using the chemically amplified positive resist composition.SOLUTION: A chemically amplified positive resist composition comprises a base polymer, which comprises a polymer comprising units containing phenolic hydroxy groups, represented by a formula (A1), and repeat units containing carboxy groups protected with acid labile groups, represented by a specific formula, and which turns alkali soluble under action of acid. An aromatic ring-containing repeat units account for at least 65 mol% of the overall repeat units of the polymer in the base polymer.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, the increasing integration density of integrated circuits has led to a demand for finer pattern formation, and chemically amplified resist compositions using acids as catalysts are primarily used for processing patterns of 0.2 μm or less. High-energy radiation, such as ultraviolet, far ultraviolet, extreme ultraviolet (EUV), and electron beam (EB), is used as the exposure source for this process. EB lithography, which is particularly used as an ultrafine processing technology, has also become essential as a method for processing photomask blanks when producing photomasks for semiconductor manufacturing.

[0003] In EB lithography, EB writing is typically performed without a mask. In positive-tone lithography, EBs are sequentially irradiated onto the resist film in areas other than the desired area, while in negative-tone lithography, EBs are sequentially irradiated onto the desired area. Because the EBs sweep across the entire finely divided area of ​​the processing surface, this process takes longer than one-shot exposure using a photomask. To maintain throughput, highly sensitive resist films are required. In particular, photomask blank processing, which is an important application, can involve surface materials, such as chromium oxide and other chromium compound films deposited on photomask substrates, that can easily affect the pattern shape of chemically amplified resist films. Maintaining a rectangular resist pattern profile, regardless of substrate type, is also an important performance requirement for maintaining high resolution and post-etching shape. Low line-edge roughness (LER) is also a key performance requirement. In recent years, in order to achieve miniaturization, the multi-beam mask writing (MBMW) drawing process is sometimes used to process mask blanks. In this case, a low-sensitivity resist (high dose region) that is advantageous for roughness is used, and optimization of the resist composition in this high dose region has also come into the spotlight.

[0004] Various improvements have been made to control sensitivity and pattern profile by varying the selection and combination of materials used in resist compositions, process conditions, etc. One such improvement is the suppression of acid diffusion, which has a significant impact on the resolution of resist films. In photomask processing, it is required that the shape of the resulting resist pattern does not change depending on the time between exposure and heating. The main cause of time-dependent changes in resist pattern shape is the diffusion of acid generated by exposure. This issue of acid diffusion has been extensively studied, not only in photomask processing but also in general resist compositions, as it has a significant impact on sensitivity and resolution.

[0005] Patent Documents 1 and 2 describe examples in which acid diffusion is suppressed and LER is reduced by increasing the bulkiness of the acid generated from an acid generator. However, these acid generators still do not sufficiently suppress acid diffusion, and therefore, there has been a demand for the development of an acid generator with even smaller acid diffusion.

[0006] Furthermore, Patent Document 3 describes an example in which acid diffusion is controlled by introducing a repeating unit having a sulfonium structure that generates sulfonic acid upon exposure into a polymer used in a resist composition. This method of suppressing acid diffusion by introducing a repeating unit that generates acid upon exposure into a base polymer is effective as a method for obtaining a pattern with small LER. However, base polymers containing such repeating units that generate acid upon exposure can sometimes have problems with solubility in organic solvents, depending on the structure and introduction rate of the unit.

[0007] Polymers containing a large amount of aromatic skeletons with acidic side chains, such as polyhydroxystyrene, are useful as base polymers for resist compositions for KrF lithography, but have not been used as base polymers for resist compositions for ArF lithography due to their high absorption of light with wavelengths around 200 nm. However, they are important materials for resist compositions for EB lithography and EUV lithography, which are effective techniques for forming patterns smaller than the processing limit of ArF excimer laser light, because they provide high etching resistance.

[0008] The base polymers used in positive-tone resist compositions for EB lithography and EUV lithography are primarily made soluble in alkaline developers by using the acid generated by irradiating a photoacid generator with high-energy radiation as a catalyst to deprotect the acid-labile groups masking the acidic functional groups on the phenol side chains of the base polymer. Furthermore, tertiary alkyl groups, tert-butoxycarbonyl groups, acetal groups, and the like have typically been used as the acid-labile groups. While using acid-labile groups such as acetal groups, which require relatively low activation energy for deprotection, offers the advantage of producing highly sensitive resist films, insufficient suppression of the diffusion of the generated acid can lead to deprotection reactions in unexposed areas of the resist film, resulting in problems such as degradation of resolution and LER.

[0009] On the other hand, during the development process of photomask manufacturing, a phenomenon known as developer loading occurs, which results in differences in the finished pattern dimensions between dense and sparsely patterned regions on the photomask. In other words, developer loading results in uneven distribution of the finished pattern dimensions depending on the surrounding pattern distribution. Factors contributing to this include differences in the elimination reaction during acid generation due to differences in EB energy and differences in the dissolution rate in alkaline developer between sparsely and densely patterned regions. Patent Document 4 proposes a method for correcting developer loading by adjusting the incident dose within an EB lithography system and irradiating EBs to write patterns on a photomask. However, conventional correction methods do not fully take into account the developer loading phenomenon. As a result, conventional correction methods have poor developer loading correction accuracy. To address this issue, methods for writing resist films and improving post-patterning development methods, as described in Patent Documents 5 and 6, have been developed. However, these methods are insufficient for uniformly distributing sparsely and densely patterned fine patterns in advanced generations, and improvements to resist compositions are desired. [Prior art documents] [Patent documents]

[0010] [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] Japanese Patent Application Laid-Open No. 2007-150243 [Patent Document 5] Patent No. 5443548 [Patent Document 6] Patent No. 6281244 Summary of the Invention [Problem to be solved by the invention]

[0011] The present invention has been made in order to solve the above-mentioned problems, and an object of the present invention is to provide a chemically amplified positive resist composition that is capable of forming a resist film that has extremely high resolution, small LER, excellent rectangularity, and is capable of forming a pattern in which the effects of development loading are suppressed, and a method of forming a resist pattern that uses the chemically amplified positive resist composition. [Means for solving the problem]

[0012] As a result of extensive investigations into achieving the above-mentioned object, the present inventors discovered that by incorporating into a resist composition, as a base polymer, a polymer containing a phenolic hydroxy group-containing unit and a repeating unit in which a carboxy group is protected with an acid labile group that is a tertiary hydrocarbyl group in which a phenyl group is bonded to a tertiary carbon atom, it is possible to obtain patterns that exhibit good resolution, pattern shape, and LER, and in which the effects of development loading are suppressed, which led to the completion of the present invention.

[0013] 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 base polymer protected by an acid labile group and which becomes alkali-soluble upon the action of an acid, the base polymer comprises a polymer containing a phenolic hydroxy group-containing unit represented by the following formula (A1) and a repeating unit represented by the following formula (A2) in which a carboxy group is protected with an acid labile group, A chemically amplified positive resist composition in which, of all repeating units of the polymer contained in the base polymer, repeating units having an aromatic ring skeleton account for 65 mol % or more. [ka] (In the formula, a1 is an integer that satisfies 0≦a1≦5+2a3−a2. a2 is an integer of 1 to 3. a3 is an integer of 0 to 2. R A is a hydrogen atom, a fluorine atom, a methyl group, or a trifluoromethyl group. X 1 is a single bond, *-C(=O)-O-, or *-C(=O)-NH-. * is a bond to a carbon atom in the main chain. A 1 is a single bond or a saturated hydrocarbylene group having 1 to 10 carbon atoms, and some of the -CH2- constituting the saturated hydrocarbylene group may be substituted with -O-. R 1 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. [ka] (In the formula, R A is a hydrogen atom, a fluorine atom, a methyl group, or a trifluoromethyl group. X 2 is a single bond, *-C(=O)-OX 21X is a phenylene group or a naphthylene group, and the phenylene group or naphthylene group may be substituted with an alkoxy group having 1 to 10 carbon atoms which may contain a fluorine atom or a halogen atom. 21 teeth , charcoal It is an aliphatic hydrocarbylene group, phenylene group, or naphthylene group having a prime number of 1 to 20, and the aliphatic hydrocarbylene group may contain at least one selected from an alkoxy group having 1 to 10 carbon atoms, which may contain a fluorine atom, a hydroxy group, an ether bond, an ester bond, and a lactone ring. * represents a bond to a carbon atom in the main chain. R B and R C are each independently a hydrocarbyl group having 1 to 10 carbon atoms which may contain a heteroatom, and R B and R C may be bonded to each other to form a ring together with the carbon atoms to which they are attached. R 2 are each independently a halogen atom, a cyano group, an acyl group having 1 to 5 carbon atoms, an alkoxy group having 1 to 5 carbon atoms, a fluorinated alkyl group having 1 to 5 carbon atoms, or a fluorinated alkoxy group having 1 to 5 carbon atoms. R 3 are each independently a hydrocarbyl group having 1 to 10 carbon atoms which may contain a heteroatom. b1 is 1 or 2, b2 is an integer of 0 to 2, b3 is an integer of 0 to 5, and b4 is an integer of 0 to 2. 2. The chemically amplified positive resist composition of 1, wherein the phenolic hydroxy group-containing unit is a repeating unit represented by the following formula (A1-1): [ka] (In the formula, R A and a2 are the same as above.) 3. The chemically amplified positive resist composition of 1 or 2, wherein the repeating unit in which the carboxy group is protected with an acid labile group is a repeating unit represented by the following formula (A2-1): [ka] (In the formula, RA , R B , R C , X 2 , R 2 , R 3 , b1, b2 and b3 are the same as above.) 4.R 2 The resist composition of any one of 1 to 3, wherein is a fluorine atom, a trifluoromethyl group, or a trifluoromethoxy group. 5. The chemically amplified positive resist composition of any one of 1 to 4, wherein the base polymer comprises a polymer comprising a phenolic hydroxy group-containing unit represented by formula (A1), a repeating unit represented by formula (A2) in which a carboxy group is protected with an acid labile group, and a unit represented by formula (A3) below in which a phenolic hydroxy group is protected with an acid labile group, or a polymer comprising a phenolic hydroxy group-containing unit represented by formula (A1) and a repeating unit represented by formula (A2) in which a carboxy group is protected with an acid labile group, and a polymer comprising a phenolic hydroxy group-containing unit represented by formula (A1) and a unit represented by formula (A3) below in which a phenolic hydroxy group is protected with an acid labile group. [ka] (In the formula, R A is the same as above. c1 is an integer that satisfies 0≦c1≦5+2c3−c2. c2 is an integer from 1 to 3. c3 is an integer from 0 to 2. X 3 is a single bond, *-C(=O)-O-, or *-C(=O)-NH-. * is a bond to a carbon atom in the main chain. A 3 is a single bond or a saturated hydrocarbylene group having 1 to 10 carbon atoms, and some of the -CH2- constituting the saturated hydrocarbylene group may be substituted with -O-. R 4 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. R 5 is an acid labile group when c2 is 1, and is a hydrogen atom or an acid labile group when c2 is 2 or more, but at least one is an acid labile group. 6. The chemically amplified positive resist composition of any one of 1 to 5, wherein the unit in which the phenolic hydroxy group is protected with an acid labile group is a repeating unit represented by the following formula (A3-1): [ka] (In the formula, R A is the same as above. R 6 is an acid labile group having an aromatic hydrocarbon group having 6 to 20 carbon atoms and / or an alicyclic hydrocarbon group having 5 to 20 carbon atoms. 7. The chemically amplified positive resist composition of any one of 1 to 6, wherein the polymer contained in the base polymer further contains a repeating unit represented by any one of the following formulas (B1) to (B3). [ka] (In the formula, R A is the same as above. d and e each independently represent an integer of 0 to 4. f represents an integer of 0 to 5. g represents an integer of 0 to 2. X 4 is a single bond, *-C(=O)-O-, or *-C(=O)-NH-. * is a bond to a carbon atom in the main chain. A 4 is a single bond or a saturated hydrocarbylene group having 1 to 10 carbon atoms, and some of the -CH2- constituting the saturated hydrocarbylene group may be substituted with -O-. R 11 and R 12 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, or a saturated hydrocarbyloxy group having 1 to 8 carbon atoms which may be substituted with a halogen atom. R 13represents 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 or a cyano group, and when g is 1 or 2, it may also be a hydroxy group. 8. The chemically amplified positive resist composition of any one of 1 to 7, wherein the polymer contained in the base polymer further contains a repeating unit represented by any one of the following formulas (C1) to (C8). [ka] (In the formula, R A is the same as above. Y 1 represents a single bond, an aliphatic hydrocarbylene group having 1 to 6 carbon atoms, a phenylene group, a naphthylene group, or a group having 7 to 18 carbon atoms obtained by combining these, or *-OY 11 -, *-C(=O)-OY 11 - or *-C(=O)-NH-Y 11 - and Y 11 represents an aliphatic hydrocarbylene group having 1 to 6 carbon atoms, a phenylene group, a naphthylene group, or a group having 7 to 18 carbon atoms obtained by combining these, and may contain a carbonyl group, an ester bond, an ether bond, or a hydroxy group. Y 2 is a single bond or **-Y 21 -C(=O)-O-, and Y 21 is a hydrocarbylene group having 1 to 20 carbon atoms which may contain a heteroatom. Y 3 represents a single bond, a methylene group, an ethylene group, a phenylene group, a fluorinated phenylene group, a phenylene group substituted with a trifluoromethyl group, *-OY 31 -, *-C(=O)-OY 31 - or *-C(=O)-NH-Y 31 -It is. Y 31represents 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. * indicates a bond to a carbon atom in the main chain, and ** indicates a bond to an oxygen atom in the formula. Y 4 is a single bond or a hydrocarbylene group having 1 to 30 carbon atoms which may contain a heteroatom. 1 and k 2 are each independently 0 or 1, but Y 4 When is a single bond, k 1 and k 2 is 0. R 21 ~R 38 are each independently a halogen atom or a hydrocarbyl group having 1 to 20 carbon atoms which may contain a heteroatom. 21 and R 22 may be bonded to each other to form a ring together with the sulfur atom to which they are attached, and R 23 and R 24 , R 26 and R 27 , or R 29 and R 30 may be bonded to each other to form a ring together with the sulfur atom to which they are attached. R HF is a hydrogen atom or a trifluoromethyl group. Xa - is a non-nucleophilic counterion. 9. The chemically amplified positive resist composition according to any one of 1 to 8, further comprising a fluorine atom-containing polymer that contains at least one repeating unit selected from the group consisting of a repeating unit represented by the following formula (D1), a repeating unit represented by the following formula (D2), a repeating unit represented by the following formula (D3), and a repeating unit represented by the following formula (D4), and that may further contain at least one repeating unit selected from the group consisting of a repeating unit represented by the following formula (D5) and a repeating unit represented by the following formula (D6). [ka] (In the formula, R B are each independently a hydrogen atom, a fluorine atom, a methyl group, or a trifluoromethyl group. R C are each independently a hydrogen atom or a methyl group. R 101 , R 102 , R 104 and R 105 are each independently a hydrogen atom or a saturated hydrocarbyl group having 1 to 10 carbon atoms. R 103 , R 106 , R 107 and R 108 are each independently a hydrogen atom, a hydrocarbyl group having 1 to 15 carbon atoms, a fluorinated hydrocarbyl group having 1 to 15 carbon atoms, or an acid labile group, and R 103 , R 106 , R 107 and R 108 When is a hydrocarbyl group or a fluorinated hydrocarbyl group, an ether bond or a carbonyl group may be present between the carbon-carbon bonds. R 109 is a hydrogen atom or a linear or branched hydrocarbyl group having 1 to 5 carbon atoms which may have a group containing a heteroatom interposed between its carbon-carbon bond. R 110 teeth, a hydrogen atom, or It is a linear or branched hydrocarbyl group having 1 to 5 carbon atoms, which may have a group containing a hetero atom interposed between its carbon-carbon bond. R 111 is a saturated hydrocarbyl group having 1 to 20 carbon atoms in which at least one hydrogen atom has been substituted with a fluorine atom, and some of the -CH2- groups constituting the saturated hydrocarbyl group may be substituted with an ester bond or an ether bond. x is an integer of 1 to 3. y is an integer that satisfies 0≦y≦5+2z−x. z is 0 or 1. m is an integer of 1 to 3. Z 1 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. Z 2is a single bond, *-C(=O)-O-, or *-C(=O)-NH-. * is a bond to a carbon atom in the main chain. Z 3 is a single bond, -O-, *-C(=O)-OZ 31 -Z 32 -or*-C(=O)-NH-Z 31 -Z 32 -It is. Z 31 is a single bond or a saturated hydrocarbylene group having 1 to 10 carbon atoms. 32 is a single bond, an ester bond, an ether bond, or a sulfonamide bond. * is a bond to a carbon atom in the main chain. 10. The chemically amplified positive resist composition according to any one of 1 to 9, further comprising an organic solvent. 11. The chemically amplified positive resist composition according to any one of 1 to 10, further comprising a photoacid generator. 12. The chemically amplified positive resist composition of 11, wherein the acid strength (pKa) of the anion of the photoacid generator is −2.0 or higher. 13. The chemically amplified positive resist composition of any one of 1 to 12, wherein the dissolution rate of the overexposed portion of a resist film obtained from the chemically amplified positive resist composition is 50 nm / sec or higher. 14. 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 13; irradiating the resist film with a pattern using high-energy rays; and developing the resist film irradiated with the pattern using an alkaline developer. 15. The method for forming a resist pattern according to 14, wherein the high-energy radiation is extreme ultraviolet radiation or an electron beam. 16. The method for forming a resist pattern according to 14 or 15, 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. 17. The method for forming a resist pattern according to any one of 14 to 16, wherein the substrate is a transmission or reflection mask blank. 18. A transmission or reflection mask blank coated with any one of the chemically amplified positive resist compositions set forth in any one of 1 to 13. [Effects of the Invention]

[0014] The chemically amplified positive resist composition of the present invention is capable of forming a pattern with high resolution, small LER, and excellent rectangularity with a good shape after exposure, as well as a pattern with reduced effects from development loading, and is therefore suitable as a resist composition for forming a resist film that is sensitive to high-energy rays such as ultraviolet light, far ultraviolet light, EB, EUV, X-rays, gamma rays, and synchrotron radiation, which are used in the processing of semiconductors, photomask blanks, etc. Furthermore, a pattern formation method that uses the chemically amplified positive resist composition of the present invention is capable of forming a pattern that has high resolution and etching resistance, and that has reduced LER and a pattern with reduced effects from development loading, and therefore is suitable for use in microfabrication techniques, in particular EUV lithography and EB lithography. DETAILED DESCRIPTION OF THE INVENTION

[0015] The present invention will be described in detail below. In the following description, some structures represented by chemical formulas may have asymmetric carbon atoms, and enantiomers or diastereomers may exist. In such cases, a single formula will be used to represent all isomers. These isomers may be used singly or as a mixture.

[0016] [Chemically amplified positive resist composition] The chemically amplified positive resist composition of the present invention contains a base polymer that is protected by an acid labile group and becomes alkali-soluble upon the action of an acid.

[0017] The base polymer contains a phenolic hydroxy group-containing unit (hereinafter also referred to as repeating unit A1) and a repeating unit in which the carboxy group is protected with an acid labile group (hereinafter also referred to as repeating unit A2).

[0018] The repeating unit A1 is represented by the following formula (A1). [ka]

[0019] In formula (A1), a1 is an integer that satisfies 0≦a1≦5+2a3−a2, a2 ​​is an integer of 1 to 3, and a3 is an integer of 0 to 2.

[0020] In formula (A1), R A is a hydrogen atom, a fluorine atom, a methyl group, or a trifluoromethyl group.

[0021] In formula (A1), X 1 is a single bond, *-C(=O)-O-, or *-C(=O)-NH-. * is a bond to a carbon atom in the main chain.

[0022] In formula (A1), A 1 is a single bond or a saturated hydrocarbylene group having 1 to 10 carbon atoms, and a portion of the -CH2- constituting the saturated hydrocarbylene group may be substituted with -O-. The saturated hydrocarbylene group may be linear, branched, or cyclic, and specific examples thereof include alkanediyl groups having 1 to 10 carbon atoms, such as methylene, ethane-1,2-diyl, propane-1,3-diyl, butane-1,4-diyl, pentane-1,5-diyl, and hexane-1,6-diyl, and structural isomers thereof; cyclic saturated hydrocarbylene groups having 3 to 10 carbon atoms, such as cyclopropanediyl, cyclobutanediyl, cyclopentanediyl, and cyclohexanediyl; and groups obtained by combining these groups.

[0023] In formula (A1), R 1is 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 a1 is 2 or more, each R 1 may be the same as or different from each other.

[0024] X 1 and A 1 When both are single bonds, preferred examples of the repeating unit A1 include units derived from 3-hydroxystyrene, 4-hydroxystyrene, 5-hydroxy-2-vinylnaphthalene, 6-hydroxy-2-vinylnaphthalene, etc. Among these, more preferred are repeating units represented by the following formula (A1-1): [ka] (In the formula, R A and a2 are the same as above.)

[0025] X 1 When R is other than a single bond, preferred examples of the repeating unit A1 include, but are not limited to, those shown below. A is the same as above. [ka]

[0026] [ka]

[0027] The repeating unit A1 is preferably introduced in a range of 10 to 95 mol %, more preferably 30 to 85 mol %, of all repeating units of the polymer contained in the base polymer. However, when at least one of the repeating units represented by formula (B1) and the repeating unit represented by formula (B2), which will be described later and which impart high etching resistance to the polymer, is contained, and when this unit has a phenolic hydroxy group as a substituent, it is preferable that the ratio thereof also be added to fall within the above range. The repeating unit A1 may be used alone or in combination of two or more types.

[0028] The repeating unit A2 is represented by the following formula (A2). [ka]

[0029] In formula (A2), R A is the same as above. X 2 is a single bond, *-C(=O)-OX 21 X is a phenylene group or a naphthylene group, and the phenylene group or naphthylene group may be substituted with an alkoxy group having 1 to 10 carbon atoms which may contain a fluorine atom or a halogen atom. 21 represents an aliphatic hydrocarbylene group having 1 to 20 carbon atoms, a phenylene group, or a naphthylene group, and the aliphatic hydrocarbylene group may contain at least one selected from an alkoxy group having 1 to 10 carbon atoms, which may contain a fluorine atom, a hydroxy group, an ether bond, an ester bond, and a lactone ring. * represents a bond to a carbon atom in the main chain.

[0030] The aliphatic hydrocarbylene group may be saturated or unsaturated, and may be linear, branched, or cyclic. Specific examples include methanediyl group, ethane-1,1-diyl group, ethane-1,2-diyl group, propane-1,1-diyl group, propane-1,2-diyl group, propane-1,3-diyl group, propane-2,2-diyl group, butane-1,1-diyl group, butane-1,2-diyl group, butane-1,3-diyl group, butane-2,3-diyl group, butane-1,4-diyl group, 1,1-dimethylethane-1,2-diyl group, pentane-1,5-diyl group, 2-methylbutane-1,2-diyl group, hexamethylethane-1,5 ... alkanediyl groups such as cyclohexanediyl, cyclopropanediyl, cyclobutane-1,1-diyl, cyclobutanediyl, cyclopentanediyl, and cyclohexanediyl; divalent polycyclic saturated hydrocarbylene groups such as adamantanediyl and norbornanediyl; and divalent groups obtained by combining these groups.

[0031] X in formula (A2) 2 Examples of structures in which R is changed include, but are not limited to, those shown below. A is the same as above, and the dashed line represents R in formula (A2). B and R C is the bond to the carbon atom to which it is bonded. [ka]

[0032] [ka]

[0033] [ka]

[0034] [ka]

[0035] In formula (A2), R B and R C are each independently a hydrocarbyl group having 1 to 10 carbon atoms which may contain a heteroatom. The hydrocarbyl group may be saturated or unsaturated, and may be linear, branched, or cyclic. Specific examples include alkyl groups having 1 to 10 carbon atoms, such as methyl, ethyl, n-propyl, isopropyl, n-butyl, sec-butyl, tert-butyl, cyclopentyl, cyclohexyl, 2-ethylhexyl, and n-octyl; and cyclic saturated hydrocarbyl groups having 3 to 10 carbon atoms, such as cyclopentyl, cyclohexyl, norbornyl, tricyclodecanyl, and adamantyl.

[0036] Also, R B and R C and may be bonded to each other to form a ring together with the carbon atoms to which they are bonded. Examples of the ring include a cyclopropane ring, a cyclobutane ring, a cyclopentane ring, and a cyclohexane ring. Of these, a cyclopentane ring and a cyclohexane ring are preferred.

[0037] In formula (A2), R 2 are each independently a halogen atom, a cyano group, an acyl group having 1 to 5 carbon atoms, an alkoxy group having 1 to 5 carbon atoms, a fluorinated alkyl group having 1 to 5 carbon atoms, or a fluorinated alkoxy group having 1 to 5 carbon atoms. Among these, a fluorine atom, a fluorinated alkyl group having 1 to 5 carbon atoms, or a fluorinated alkoxy group having 1 to 5 carbon atoms is preferred, and a fluorine atom, a trifluoromethyl group, or a trifluoromethoxy group is more preferred.

[0038] In formula (A2), R 3 are each independently a hydrocarbyl group having 1 to 10 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 B and R CExamples of the hydrocarbyl group represented by the formula (I) include the same as those exemplified above.

[0039] In formula (A2), b1 is an integer of 1 or 2, with 1 being preferred.

[0040] In the formula (A2), b2 is an integer of 0 to 2.

[0041] In formula (A2), b3 is an integer of 0 to 5, and is preferably 0 or 1.

[0042] In formula (A2), b4 is an integer of 0 to 2. When b4 is 0, it represents a benzene ring, when b4 is 1 it represents a naphthalene ring, and when b4 is 2 it represents an anthracene ring, but from the viewpoint of solvent solubility, it is preferable that b4 is 0 and is a benzene ring.

[0043] The repeating unit A2 is preferably one represented by the following formula (A2-1). [ka] (In the formula, R A , R B , R C , X 2 , R 2 , R 3 , b1, b2 and b3 are the same as above.)

[0044] Examples of the repeating unit A2 include, but are not limited to, those shown below. A is the same as above. [ka]

[0045] [ka]

[0046] [ka]

[0047]

change

[0048]

change

[0049]

change

[0050]

change

[0051]

change

[0052]

change

[0053]

change

[0054]

change

[0055]

change

[0056]

change

[0057]

change

[0058]

change

[0059]

change

[0060]

change

[0061]

change

[0062]

change

[0063]

change

[0064]

change

[0065]

change

[0066]

change

[0067]

change

[0068] [ka]

[0069] [ka]

[0070] [ka]

[0071] [ka]

[0072] The base polymer may be a polymer containing a repeating unit A1, a repeating unit A2, and a unit represented by the following formula (A3) in which a phenolic hydroxy group is protected with an acid labile group (hereinafter also referred to as repeating unit A3), or may be a polymer containing a repeating unit A1 and a repeating unit A2, and a polymer containing a repeating unit A1 and a repeating unit A3. [ka]

[0073] In formula (A3), R A is the same as above. c1 is an integer that satisfies 0≦c1≦5+2c3−c2. c2 is an integer from 1 to 3. c3 is an integer from 0 to 2.

[0074] In formula (A3), X 3 is a single bond, *-C(=O)-O-, or *-C(=O)-NH-. * is a bond to a carbon atom in the main chain.

[0075] In formula (A3), A 3is a single bond or a saturated hydrocarbylene group having 1 to 10 carbon atoms, and a portion of the -CH2- constituting the saturated hydrocarbylene group may be substituted with -O-. The saturated hydrocarbylene group may be linear, branched, or cyclic. Specific examples thereof include A in formula (A1): 1 Examples of the above-mentioned examples are the same as those given in the explanation of the above.

[0076] In formula (A3), R 4 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, and specific examples thereof include R 1 When the number of carbon atoms is equal to or less than the upper limit, the solubility in an alkaline developer is good. When c1 is 2 or more, each R 4 may be the same as or different from each other.

[0077] In formula (A3), R 5 is an acid labile group when c2 is 1, and is a hydrogen atom or an acid labile group when c2 is 2 or more, provided that at least one is an acid labile group.

[0078] Examples of the repeating unit A3 include, but are not limited to, those shown below. A and R 5 is the same as above. [ka]

[0079] R 5The acid labile group represented by the formula (I) is not particularly limited, and any group that can be used as long as it is one that has been used in many known chemically amplified resist compositions and that is cleaved by an acid to give an acidic group can be used. Examples of the acid labile group include those described in paragraphs

[0030] to

[0082] of JP 2014-219657 A.

[0080] The acid labile group is preferably one represented by the following formulas (AL-1) to (AL-19). [ka] (In the formula, the dashed lines represent bonds.)

[0081] In formulas (AL-1) to (AL-19), R L1 are each independently a saturated hydrocarbyl group or an aryl group having 6 to 20 carbon atoms. L2 and R L4 are each independently a hydrogen atom or a saturated hydrocarbyl group having 1 to 20 carbon atoms. L3 is an aryl group having 6 to 20 carbon atoms. The saturated hydrocarbyl group may be linear, branched, or cyclic. The aryl group is preferably a phenyl group. R F is a fluorine atom or a trifluoromethyl group. n is an integer of 1 to 5. Particularly preferred structures are (AL-1), (AL-2) and (AL-19), which can improve resolution by suppressing swelling during alkaline development.

[0082] Selecting a tertiary hydrocarbyl group as the acid labile group is preferable because it provides a pattern with a small LER even when the resist film is formed to a thickness of, for example, 10 to 100 nm and a fine pattern with a line width of 45 nm or less is formed. The tertiary hydrocarbyl group preferably has 4 to 18 carbon atoms so that the resulting polymerization monomer can be obtained by distillation. Furthermore, the group bonded to the tertiary carbon atom of the tertiary hydrocarbyl group may be a saturated hydrocarbyl group having 1 to 20 carbon atoms, which may contain an ether bond or an oxygen-containing functional group such as a carbonyl group, and the groups bonded to the tertiary carbon atom may bond to each other to form a ring.

[0083] 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.

[0084] Examples of the tertiary hydrocarbyl group include a tert-butyl group, a tert-pentyl group, a 1-ethyl-1-methylpropyl group, a 1,1-diethylpropyl group, a 1,1,2-trimethylpropyl group, a 1-adamantyl-1-methylethyl group, a 1-methyl-1-(2-norbornyl)ethyl group, a 1-methyl-1-(tetrahydrofuran-2-yl)ethyl group, a 1-methyl-1-(7-oxanorbornan-2-yl)ethyl group, a 1-methylcyclopentyl group, a 1-ethylcyclopentyl group, a 1-propylcyclopentyl group, a 1-iso ... Propylcyclopentyl group, 1-cyclopentylcyclopentyl group, 1-cyclohexylcyclopentyl group, 1-(2-tetrahydrofuryl)cyclopentyl group, 1-(7-oxanorbornan-2-yl)cyclopentyl group, 1-methylcyclohexyl group, 1-ethylcyclohexyl group, 1-isopropylcyclohexyl group, 1-cyclopentylcyclohexyl group, 1-cyclohexylcyclohexyl group, 2-methyl-2-norbornyl group, 2-ethyl-2-norbornyl group, 8-methyl-8-tricyclo[5.2.1.0] 2,6 ]decyl group, 8-ethyl-8-tricyclo[5.2.1.0 2,6 ]decyl group, 3-methyl-3-tetracyclo[4.4.0.1 2,5 .1 7,10 ]dodecyl group, 3-ethyl-3-tetracyclo[4.4.0.1 2,5 .1 7,10 ]dodecyl group, 3-isopropyl-3-tetracyclo[4.4.0.1 2,5 .1 7,10 ]dodecyl group, 2-methyl-2-adamantyl group, 2-ethyl-2-adamantyl group, 2-isopropyl-2-adamantyl group, 1-methyl-3-oxo-1-cyclohexyl group, 1-methyl-1-(tetrahydrofuran-2-yl)ethyl group, 5-hydroxy-2-methyl-2-adamantyl group, 5-hydroxy-2-ethyl-2-adamantyl group, 2-(4-fluorophenyl)-2-propyl group, and the like.

[0085] Furthermore, an acetal group represented by the following formula (AL-20) is often used as an acid labile group, and is a useful option as an acid labile group that stably gives a pattern in which the interface between the pattern and the substrate is relatively rectangular. [ka]

[0086] In formula (AL-20), R L5 is a hydrogen atom or a saturated hydrocarbyl group having 1 to 10 carbon atoms. L6 is a saturated hydrocarbyl group having 1 to 30 carbon atoms.

[0087] R L5 is selected appropriately depending on the design of the sensitivity of the decomposable group to acid. For example, if the design is to ensure relatively high stability while being decomposed by strong acid, a hydrogen atom is selected, and if the design is to use relatively high reactivity to increase sensitivity to pH changes, a linear alkyl group is selected. Depending on the combination with the acid generator and basic compound to be compounded in the resist composition, R L6 When a relatively large alkyl group is substituted at the end of the polymer, and the polymer is designed to have a large change in solubility due to decomposition, R L5 Preferably, the carbon bonded to the acetal carbon is a secondary carbon atom. L5 Examples of the alkyl group include an isopropyl group, a sec-butyl group, a cyclopentyl group, and a cyclohexyl group.

[0088] Among the acetal groups, R L6 is preferably a polycyclic alkyl group having 7 to 30 carbon atoms. L6 When R is a polycyclic alkyl group, it is preferable that a bond is formed between the secondary carbon atom constituting the polycyclic ring structure and the acetal oxygen. When R is bonded on the secondary carbon atom of the ring structure, the polymer becomes a stable compound compared to when R is bonded on the tertiary carbon atom, and the storage stability of the resist composition is improved, and there is no deterioration in resolution. In addition, when R is bonded on the secondary carbon atom of the ring structure, the polymer becomes a stable compound compared to when R is bonded on the tertiary carbon atom.L6 is bonded to a primary carbon atom via a linear alkyl group having one or more carbon atoms, the polymer has a good glass transition temperature (Tg), and the developed resist pattern does not suffer from shape defects due to baking.

[0089] Preferred examples of the group represented by formula (AL-20) include, but are not limited to, the following: L5 is the same as above. [ka]

[0090] The repeating unit A2 is preferably introduced in an amount of 2 to 40 mol % of all repeating units of the polymer contained in the base polymer, and the repeating unit A3 is preferably introduced in an amount of 2 to 40 mol % of all repeating units of the polymer contained in the base polymer. The repeating units A2 and A3 together are preferably introduced in an amount of 8 to 60 mol %, more preferably 10 to 40 mol %, of all repeating units of the polymer contained in the base polymer.

[0091] The base polymer is designed as follows: ,centre By designing a mixture of two types of groups, an enolic hydroxy group and a carboxy group, protected with an acid labile group, the dissolution rate of the exposed area is improved by the carboxylate group while maintaining the pattern rigidity of the phenolic group, so the dissolution contrast between the exposed and unexposed areas is optimized while maintaining good resolution of the exposed area. In particular, since the carboxy group protected with an acid labile group has a phenolic hydroxy group, it is possible to increase the number of acid labile group units. , mostAn appropriate dissolution contrast is achieved. As a result, high resolution is exhibited while suppressing the effects of development loading, and a pattern with small dimensional difference can be obtained regardless of the pattern density. When producing a photomask, the development conditions are stronger than when processing a wafer substrate, so it is necessary to form a pattern with good resolution and small dimensional difference while suppressing the effects of development loading. Therefore, the chemically amplified positive resist composition of the present invention is particularly ideal for processing photomask substrates.

[0092] The acid labile group also has the effect of suppressing the influence of backscattering during writing, and therefore exhibits rectangular performance without the pattern shape becoming inversely tapered in a sensitivity range of 50 μC or more, preferably 100 μC or more.

[0093] It is preferable that the polymer contained in the base polymer further contains at least one repeating unit selected from the group consisting of a repeating unit represented by the following formula (B1) (hereinafter also referred to as repeating unit B1), a repeating unit represented by the following formula (B2) (hereinafter also referred to as repeating unit B2), and a repeating unit represented by the following formula (B3) (hereinafter also referred to as repeating unit B3). [ka]

[0094] In the formulae (B1) and (B2), d and e each independently represent an integer of 0 to 4.

[0095] In formulas (B1) and (B2), R 11 and R 12 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, or a saturated hydrocarbyloxy group having 1 to 8 carbon atoms which may be substituted with a halogen atom. The saturated hydrocarbyl group, saturated hydrocarbyloxy group, and saturated hydrocarbylcarbonyloxy group may be linear, branched, or cyclic. When d is 2 or more, each R11 may be the same or different. When e is 2 or more, each R 12 may be the same as or different from each other.

[0096] In formula (B3), R A is the same as above. f is an integer of 0 to 5. g is an integer of 0 to 2.

[0097] In formula (B3), R 13 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, or a cyano group, and when g is 1 or 2, it may be a hydroxy group. The saturated hydrocarbyl group, saturated hydrocarbyloxy group, saturated hydrocarbylcarbonyloxy group, saturated hydrocarbyloxyhydrocarbyl group, and saturated hydrocarbylthiohydrocarbyl group may be linear, branched, or cyclic. When f is 2 or more, each R 13 may be the same as or different from each other.

[0098] In formula (B3), X 4 is a single bond, *-C(=O)-O-, or *-C(=O)-NH-. * is a bond to a carbon atom in the main chain.

[0099] In formula (B3), A 4 is a single bond or a saturated hydrocarbylene group having 1 to 10 carbon atoms, and a portion of the -CH2- constituting the saturated hydrocarbylene group may be substituted with -O-. The saturated hydrocarbylene group may be linear, branched, or cyclic. Specific examples thereof include A in formula (A1): 1 Examples of the above-mentioned examples are the same as those given in the explanation of the above.

[0100] When repeating units B1 to B3 are used, in addition to the etching resistance of the aromatic ring, the addition of a ring structure to the main chain has the effect of improving resistance to EB irradiation during etching and pattern inspection.

[0101] To obtain the effect of improving etching resistance, repeating units B1 to B3 are preferably incorporated in an amount of 5 mol % or more of all repeating units of the polymer contained in the base polymer. Furthermore, repeating units B1 to B3 are preferably incorporated in an amount of 30 mol % or less, more preferably 25 mol % or less, of all repeating units constituting the base polymer. When no functional group is present or the functional group is other than a hydroxy group, it is preferable that the amount incorporated is 30 mol % or less, since this does not cause development defects. Repeating units B1 to B3 may be used singly or in combination of two or more.

[0102] Of all the repeating units of the polymer contained in the base polymer, the content of at least one selected from the repeating unit A1 and the repeating units B1 to B3 is preferably 50 mol % or more, more preferably 55 mol % or more, and even more preferably 60 mol % or more.

[0103] The polymer contained in the base polymer may further contain at least one repeating unit selected from the repeating units represented by any of the following formulas (C1) to (C8). [ka]

[0104] In formulas (C1) to (C8), R A is the same as above. Y 1 represents a single bond, an aliphatic hydrocarbylene group having 1 to 6 carbon atoms, a phenylene group, a naphthylene group, or a group having 7 to 18 carbon atoms obtained by combining these, or *-OY 11 -, *-C(=O)-OY 11 - or *-C(=O)-NH-Y 11 - and Y 11Y is an aliphatic hydrocarbylene group having 1 to 6 carbon atoms, a phenylene group, a naphthylene group, or a group having 7 to 18 carbon atoms obtained by combining these, and may contain a carbonyl group, an ester bond, an ether bond, or a hydroxy group. 2 is a single bond or **-Y 21 -C(=O)-O-, and Y 21 Y is a hydrocarbylene group having 1 to 20 carbon atoms which may contain a heteroatom. 3 represents a single bond, a methylene group, an ethylene group, a phenylene group, a fluorinated phenylene group, a phenylene group substituted with a trifluoromethyl group, *-OY 31 -, *-C(=O)-OY 31 - or *-C(=O)-NH-Y 31 -It is. Y 31 represents an aliphatic hydrocarbylene group having 1 to 6 carbon atoms, a phenylene group, a fluorinated phenylene group, a phenylene group substituted with a trifluoromethyl group, or a group having 7 to 20 carbon atoms obtained by combining these, and may contain a carbonyl group, an ester bond, an ether bond, or a hydroxy group. * represents a bond to a carbon atom in the main chain, and ** represents a bond to an oxygen atom in the formula. Y 4 is a single bond or a hydrocarbylene group having 1 to 30 carbon atoms which may contain a heteroatom. 1 and k 2 are each independently 0 or 1, but Y 4 When is a single bond, k 1 and k 2 is 0.

[0105] The repeating unit represented by formula (C4) or (C8) is a repeating unit that generates an acid in which the β-position of the sulfonyl group is difluoromethylated when irradiated with high-energy radiation such as ultraviolet light, far ultraviolet light, EB, EUV, X-rays, gamma rays, or synchrotron radiation. The acid has an acid strength suitable for deprotection of a polymer containing the repeating unit A2. Furthermore, by using a polymer containing a repeating unit represented by formula (C4) or (C8) as the base polymer of a resist composition, it is possible to appropriately control the migration and diffusion of the generated acid.

[0106] Photoacid generators that generate arenesulfonic acid upon irradiation with high-energy radiation are also commonly used to deprotect polymers containing units protected with an acetal group, a tertiary alkyl group, or a tert-butoxycarbonyl group. However, even when an arenesulfonic acid-generating unit is introduced as a repeating unit of a base polymer to achieve the effects of the present invention, the base polymer often does not dissolve in a solvent due to its low solvent solubility. On the other hand, the polymers of the present invention containing repeating units represented by formula (C4) or (C8) have sufficient liposolubility, making them easy to produce and handle, and also facilitating the preparation of resist compositions.

[0107] In formulas (C2) and (C6), Y 2 Ga-Y 21 -C(=O)-O-, Y 21 Examples of the hydrocarbylene group represented by the formula (I) which may contain a heteroatom include, but are not limited to, those shown below. [ka] (In the formula, the dashed lines represent bonds.)

[0108] In formulas (C2) and (C6), R HF is a hydrogen atom or a trifluoromethyl group. In the repeating units C2 and C6, R HF Specific examples of when R is a hydrogen atom include those described in JP-A-2010-116550. HF Specific examples of repeating units C3 and C7 in which is a trifluoromethyl group include those described in JP-A-2010-77404. Examples of repeating units C3 and C7 in which is a trifluoromethyl group include those described in JP-A-2012-246265 and JP-A-2012-246426.

[0109] In formulas (C1) and (C5), 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.

[0110] Y 4 The hydrocarbylene group having 1 to 30 carbon atoms and optionally containing a hetero atom, represented by the following formula, may be saturated or unsaturated, and may be linear, branched, or cyclic. Specific examples thereof include alkanediyl groups such as methanediyl group, ethane-1,2-diyl group, propane-1,3-diyl group, butane-1,4-diyl group, pentane-1,5-diyl group, hexane-1,6-diyl group, heptane-1,7-diyl group, octane-1,8-diyl group, nonane-1,9-diyl group, decane-1,10-diyl group, undecane-1,11-diyl group, dodecane-1,12-diyl group, tridecane-1,13-diyl group, tetradecane-1,14-diyl group, pentadecane-1,15-diyl group, hexadecane-1,16-diyl group, and heptadecane-1,17-diyl group; cyclopentanediyl group, cyclohexane Examples of the alkylene groups include cyclic saturated hydrocarbylene groups such as diyl group, norbornanediyl group, and adamantanediyl group; arylene groups such as phenylene group, methylphenylene group, ethylphenylene group, n-propylphenylene group, isopropylphenylene group, n-butylphenylene group, isobutylphenylene group, sec-butylphenylene group, tert-butylphenylene group, naphthylene group, methylnaphthylene group, ethylnaphthylene group, n-propylnaphthylene group, isopropylnaphthylene group, n-butylnaphthylene group, isobutylnaphthylene group, sec-butylnaphthylene group, and tert-butylnaphthylene group; and groups obtained by combining these groups.

[0111] In addition, some or all of the hydrogen atoms of the hydrocarbylene group may be substituted with a group containing a heteroatom such as an oxygen atom, a sulfur atom, a nitrogen atom or a halogen atom, and some of the -CH- constituting the hydrocarbylene group may be substituted with a group containing a heteroatom such as an oxygen atom, a sulfur atom or a nitrogen atom, thereby forming a hydroxy group, a cyano group, a fluorine atom, a chlorine atom, a bromine atom, an iodine atom, a carbonyl group, an ether bond, an ester bond, a sulfonate ester bond, a carbonate bond, a lactone ring, a sultone ring, a carboxylic acid anhydride (-C(=O)-OC(=O)-), a haloalkyl group, or the like.

[0112] Preferred examples of the anions of the monomers that provide the repeating units C4 and C8 include, but are not limited to, those shown below. [ka]

[0113] [ka]

[0114] In formulas (C1) to (C8), R 21 ~R 38 are each independently a halogen atom or a hydrocarbyl group having 1 to 20 carbon atoms which may contain a heteroatom.

[0115] Examples of the halogen atom include a fluorine atom, a chlorine atom, a bromine atom, and an iodine atom.

[0116] The hydrocarbyl group having 1 to 20 carbon atoms may be saturated or unsaturated, and may be linear, branched, or cyclic. Specific examples thereof include alkyl groups having 1 to 20 carbon atoms, such as methyl, ethyl, n-propyl, isopropyl, n-butyl, 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 having 3 to 20 carbon atoms, such as a ]decanyl group, an adamantyl group, or an adamantylmethyl group; and aryl groups having 6 to 20 carbon atoms, such as a phenyl group, a naphthyl group, or an anthracenyl group. Some or all of the hydrogen atoms in 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, or a group containing a heteroatom, such as an oxygen atom, a sulfur atom, or a nitrogen atom, may be present between the carbon-carbon bonds of the hydrocarbyl group, and as a result, the hydrocarbyl group may contain a hydroxy group, a fluorine atom, a chlorine atom, a bromine atom, an iodine atom, a cyano group, a carbonyl group, an ether bond, an ester bond, a sulfonate ester bond, a carbonate bond, a lactone ring, a sultone ring, a carboxylic anhydride (-C(=O)-OC(=O)-), a haloalkyl group, or the like.

[0117] Also, R 23 and R 24 , R 26 and R 27 , or R 29 and R 30 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.)

[0118] In the formulas (C2) to (C4), specific structures of the sulfonium cation include, but are not limited to, those shown below. [ka]

[0119] [ka]

[0120] [ka]

[0121] [ka]

[0122] [ka]

[0123] [ka]

[0124] [ka]

[0125] [ka]

[0126] [ka]

[0127] [ka]

[0128]

change

[0129]

change

[0130]

change

[0131]

change

[0132]

change

[0133]

change

[0134]

change

[0135]

change

[0136]

change

[0137]

change

[0138]

change

[0139] [ka]

[0140] In the formulae (C5) to (C8), specific structures of the iodonium cation include, but are not limited to, those shown below. [ka]

[0141] [ka]

[0142] Of the repeating units C1 to C8, the repeating unit C4 is preferred for processing the photomask blank because it has the optimum acid strength in designing the acid labile groups of the polymer.

[0143] The repeating units C1 to C8 are units that generate acid upon irradiation with high-energy rays. It is believed that the inclusion of these units in the polymer appropriately suppresses acid diffusion, resulting in a pattern with reduced LER. Furthermore, the inclusion of these units in the polymer suppresses the phenomenon in which acid volatilizes from the exposed areas and reattaches to the unexposed areas during baking in a vacuum, which is believed to be effective in reducing LER and reducing shape deterioration due to unwanted film loss in the unexposed areas.

[0144] The repeating units C1 to C8 are preferably introduced in an amount of 0.1 to 30 mol %, more preferably 0.5 to 20 mol %, of the total repeating units of the polymer contained in the base polymer. The repeating units C1 to C8 may be used singly or in combination of two or more.

[0145] Of all the repeating units of the polymer contained in the base polymer, the content of repeating units having an aromatic ring skeleton is preferably 65 mol% or more, more preferably 75 mol% or more, and even more preferably 85 mol% or more. When the repeating units C1 to C8 are not contained, it is preferable that all units have an aromatic ring skeleton.

[0146] Of all the repeating units of the polymer contained in the base polymer, the content of at least one selected from repeating units A1, A2, A3, and B1 to B3 is preferably 80 mol % or more, more preferably 90 mol % or more.

[0147] The polymer may contain commonly used (meth)acrylate units protected with an acid labile group, or (meth)acrylate units having an adhesive group such as a lactone structure or a hydroxy group other than a phenolic hydroxy group. These repeating units allow for fine adjustment of the properties of the resist film, but they do not necessarily have to be included.

[0148] Examples of the (meth)acrylic acid ester unit having the adhesive group include a repeating unit represented by the following formula (B4) (hereinafter also referred to as repeating unit B4), a repeating unit represented by the following formula (B5) (hereinafter also referred to as repeating unit B5), and a repeating unit represented by the following formula (B6) (hereinafter also referred to as repeating unit B6). These units are not acidic and can be used auxiliary units that impart adhesion to substrates or adjust solubility. [ka]

[0149] In formulas (B4) to (B6), R A is the same as above. R 41 is —O— or a methylene group. 42 is a hydrogen atom or a hydroxy group. 43 is a saturated hydrocarbyl group having 1 to 4 carbon atoms. h is an integer of 0 to 3.

[0150] When repeating units B4 to B6 are contained, the content thereof is preferably 0 to 20 mol %, more preferably 0 to 10 mol %, of all repeating units of the polymer contained in the base polymer. The repeating units B4 to B6 may be used alone or in combination of two or more.

[0151] 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.

[0152] The polymer preferably has a weight-average molecular weight (Mw) of 1,000 to 50,000, more preferably 2,000 to 20,000. When Mw is 1,000 or more, there is no risk of the conventionally known phenomenon of pattern heads becoming rounded, reducing resolution and deteriorating LER. On the other hand, when Mw is 50,000 or less, there is no risk of LER degradation, particularly when forming a pattern with a line width of 100 nm or less. In the present invention, Mw is a value measured in terms of polystyrene by gel permeation chromatography (GPC) using tetrahydrofuran (THF) or dimethylformamide (DMF) as a solvent.

[0153] The polymer preferably has a narrow molecular weight distribution (Mw / Mn) of 1.0 to 2.0, preferably 1.0 to 1.9, and more preferably 1.0 to 1.8. When the polymer has such a narrow distribution, foreign matter is not generated on the pattern after development, and the pattern shape is not deteriorated.

[0154] Furthermore, the base polymer is designed to have a dissolution rate in an alkaline developer of preferably 10 nm / min or less, more preferably 7 nm / min or less, and even more preferably 5 nm / min or less. In advanced-generation photomasks, when the coating film on the substrate is thin (100 nm or less), the pattern is significantly affected by pattern film loss during alkaline development. If the polymer's alkaline dissolution rate exceeds 10 nm / min, the pattern collapses, making it impossible to form fine patterns. This is particularly true in the production of photomasks, which require a defect-free design, since the development process tends to be intense. In this invention, the dissolution rate of the base polymer in an alkaline developer was calculated from the film loss observed when an 8-inch silicon wafer was spin-coated with a polymer solution (polymer concentration: 16.7 wt %, solvent: propylene glycol monomethyl ether acetate (PGMEA)), baked at 100°C for 90 seconds to form a 1000 nm-thick film, and then developed at 23°C for 100 seconds with a 2.38 wt % aqueous solution of tetramethylammonium hydroxide (TMAH).

[0155] [Fluorine atom-containing polymer] The chemically amplified positive resist composition of the present invention, for the purposes of achieving high contrast, shielding against acid chemical flare during high-energy radiation exposure and against acid mixing from the antistatic coating during the process of applying an antistatic coating material to the resist film, and suppressing unexpected and unnecessary pattern degradation, may contain a fluorine atom-containing polymer containing at least one repeating unit selected from the group consisting of repeating units represented by formula (D1), (D2), (D3), and (D4) (hereinafter also referred to as repeating units D1, D2, D3, and D4, respectively), and optionally further containing at least one repeating unit selected from the group consisting of repeating units represented by formula (D5) and (D6) (hereinafter also referred to as repeating units D5 and D6, respectively). The fluorine atom-containing polymer also functions as a surfactant, preventing redeposition of insoluble matter onto the substrate during the development process and thereby exhibiting an effect against development defects. [ka]

[0156] In formulas (D1) to (D6), R B are each independently a hydrogen atom, a fluorine atom, a methyl group, or a trifluoromethyl group. C are each independently a hydrogen atom or a methyl group. 101 , R 102 , R 104 and R 105 are each independently a hydrogen atom or a saturated hydrocarbyl group having 1 to 10 carbon atoms. 103 , R 106 , R 107 and R 108 are each independently a hydrogen atom, a hydrocarbyl group having 1 to 15 carbon atoms, a fluorinated hydrocarbyl group having 1 to 15 carbon atoms, or an acid labile group, and R 103 , R 106 , R 107 and R 108 When R is a hydrocarbyl group or a fluorinated hydrocarbyl group, an ether bond or a carbonyl group may be present between the carbon-carbon bond. 109 R is a hydrogen atom or a linear or branched hydrocarbyl group having 1 to 5 carbon atoms which may have a heteroatom-containing group interposed between its carbon-carbon bond. 110 teeth, a hydrogen atom, or R is a linear or branched hydrocarbyl group having 1 to 5 carbon atoms, which may have a heteroatom-containing group interposed between its carbon-carbon bond. 111 is a saturated hydrocarbyl group having 1 to 20 carbon atoms in which at least one hydrogen atom has been substituted with a fluorine atom, and some of the -CH2- groups constituting the saturated hydrocarbyl group may be substituted with an ester bond or an ether bond. x is an integer of 1 to 3. y is an integer satisfying the relationship 0≦y≦5+2z-x. z is 0 or 1. m is an integer of 1 to 3. Z 1 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. 2is a single bond, *-C(=O)-O-, or *-C(=O)-NH-. * is a bond to a carbon atom in the main chain. Z 3 is a single bond, -O-, *-C(=O)-OZ 31 -Z 32 -or*-C(=O)-NH-Z 31 -Z 32 -It is. Z 31 is a single bond or a saturated hydrocarbylene group having 1 to 10 carbon atoms. 32 is a single bond, an ester bond, an ether bond, or a sulfonamide bond. * is a bond to a carbon atom of the main chain.

[0157] In formulas (D1) and (D2), R 101 , R 102 , R 104 and R 105 Examples of saturated hydrocarbyl groups having 1 to 10 carbon atoms represented by the formula (I) include alkyl groups having 1 to 10 carbon atoms, such as methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, n-pentyl, n-hexyl, n-heptyl, n-octyl, n-nonyl, and n-decyl; and cyclic saturated hydrocarbyl groups having 3 to 10 carbon atoms, such as cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl, adamantyl, and norbornyl. Of these, saturated hydrocarbyl groups having 1 to 6 carbon atoms are preferred.

[0158] In formulas (D1) to (D4), R 103 , R 106 , R 107 and R 108Examples of the hydrocarbyl group having 1 to 15 carbon atoms represented by the formula (I) include an alkyl group having 1 to 15 carbon atoms, an alkenyl group having 2 to 15 carbon atoms, and an alkynyl group having 2 to 15 carbon atoms, with an alkyl group having 1 to 15 carbon atoms being preferred. In addition to the alkyl groups mentioned above, examples of the alkyl group include a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, an isobutyl group, a sec-butyl group, an n-pentyl group, an n-hexyl group, an n-heptyl group, an n-octyl group, an n-nonyl group, an n-decyl group, an n-undecyl group, an n-dodecyl group, an n-tridecyl group, an n-tetradecyl group, and an n-pentadecyl group. Examples of the fluorinated hydrocarbyl group include groups in which some or all of the hydrogen atoms bonded to the carbon atoms of the hydrocarbyl group mentioned above have been substituted with fluorine atoms.

[0159] In formula (D4), Z 1 Examples of the (m+1)-valent hydrocarbon group having 1 to 20 carbon atoms and represented by the formula (I) include a group in which m hydrogen atoms have been further removed from an alkyl group having 1 to 20 carbon atoms or a cyclic saturated hydrocarbyl group having 3 to 20 carbon atoms. 1 Examples of the (m+1)-valent fluorinated hydrocarbon group having 1 to 20 carbon atoms and represented by the formula (I) include groups in which at least one hydrogen atom of the aforementioned (m+1)-valent hydrocarbon group has been substituted with a fluorine atom.

[0160] Specific examples of the repeating units D1 to D4 include, but are not limited to, the following: B is the same as above. [ka]

[0161] [ka]

[0162] [ka]

[0163] In formula (D5), R 109 and R 110 Examples of the hydrocarbyl group having 1 to 5 carbon atoms represented by the formula (I) include an alkyl group, an alkenyl group, and an alkynyl group, with an alkyl group being preferred. Examples of the alkyl group include a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, an isobutyl group, a sec-butyl group, and an n-pentyl group. In addition, a group containing a heteroatom such as an oxygen atom, a sulfur atom, or a nitrogen atom may be present between the carbon-carbon bonds of these groups.

[0164] In formula (D5), -OR 110 In this case, R is preferably a hydrophilic group. 110 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.

[0165] In formula (D5), Z 2 is preferably *-C(=O)-O- or *-C(=O)-NH-. C is preferably a methyl group. 2 The presence of a carbonyl group in R improves the acid trapping ability of the antistatic film. C When the methyl group is used, the polymer becomes more rigid with a higher glass transition temperature (Tg), which suppresses acid diffusion, resulting in good stability of the resist film over time and preventing degradation of resolution and pattern shape.

[0166] Examples of the repeating unit D5 include, but are not limited to, those shown below. C is the same as above. [ka]

[0167] [ka]

[0168] In formula (D6), Z3 The saturated hydrocarbylene group having 1 to 10 carbon atoms represented by the formula (I) may be linear, branched, or cyclic, and specific examples thereof include a methanediyl group, an ethane-1,1-diyl group, an ethane-1,2-diyl group, a propane-1,1-diyl group, a propane-1,2-diyl group, a propane-1,3-diyl group, a propane-2,2-diyl group, a butane-1,1-diyl group, a butane-1,2-diyl group, a butane-1,3-diyl group, a butane-2,3-diyl group, a butane-1,4-diyl group, and a 1,1-dimethylethane-1,2-diyl group.

[0169] In formula (D6), R 111 The saturated hydrocarbyl group having 1 to 20 carbon atoms, represented by the formula (I) above, in which at least one hydrogen atom has been substituted with a fluorine atom, may be linear, branched, or cyclic, and specific examples thereof include an alkyl group having 1 to 20 carbon atoms or a cyclic saturated hydrocarbyl group having 3 to 20 carbon atoms in which at least one hydrogen atom has been substituted with a fluorine atom.

[0170] Examples of the repeating unit D6 include, but are not limited to, those shown below. C is the same as above. [ka]

[0171] [ka]

[0172] [ka]

[0173] [ka]

[0174] The content of repeating units D1 to D4 is preferably 15 to 95 mol %, more preferably 20 to 85 mol %, of all repeating units in the fluorine atom-containing polymer. The content of repeating units D5 and / or D6 is preferably 5 to 85 mol %, more preferably 15 to 80 mol %, of all repeating units in the fluorine atom-containing polymer. The repeating units D1 to D6 may be used alone or in combination of two or more.

[0175] The fluorine atom-containing polymer may contain repeating units other than the repeating units described above. Examples of such repeating units include those described in paragraphs

[0046] to

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

[0176] The fluorine atom-containing polymer can be synthesized by copolymerizing each monomer, optionally protected with a protecting group, according to a known method, followed by a deprotection reaction as needed. The copolymerization reaction is not particularly limited, but is preferably radical polymerization or anionic polymerization. For these methods, reference can be made to JP 2004-115630 A.

[0177] The Mw of the fluorine atom-containing polymer is preferably 2000 to 50000, more preferably 3000 to 20000. If the Mw is less than 2000, the diffusion of the acid is promoted, which may result in a deterioration in resolution and a loss of stability over time. If the Mw is too large, the solubility in the solvent decreases, which may cause coating defects. Furthermore, the fluorine atom-containing polymer preferably has an Mw / Mn ratio of 1.0 to 2.2, more preferably 1.0 to 1.7.

[0178] When the chemically amplified positive resist composition of the present invention contains the fluorine atom-containing polymer, the content thereof is preferably 0.01 to 30 parts by mass, more preferably 0.1 to 20 parts by mass, and even more preferably 0.5 to 10 parts by mass, relative to 80 parts by mass of the base polymer.

[0179] [Organic solvents] The chemically amplified positive resist composition of the present invention may contain an organic solvent. The organic solvent is not particularly limited as long as it can dissolve each component. Examples of such organic solvents include ketones such as cyclohexanone and methyl-2-n-pentyl ketone; alcohols such as 3-methoxybutanol, 3-methyl-3-methoxybutanol, 1-methoxy-2-propanol, 1-ethoxy-2-propanol, and diacetone alcohol; propylene glycol monomethyl ether (PGME), ethylene glycol monomethyl ether, propylene glycol monoethyl ether, and ethylene glycol monomethyl ether; and propylene glycol monoethyl ether (PGME). Examples of suitable solvents include ethers such as propylene glycol monoethyl ether, propylene glycol dimethyl ether, and diethylene glycol dimethyl ether; esters such as PGMEA, propylene glycol monoethyl ether acetate, ethyl lactate (EL), ethyl pyruvate, butyl acetate, methyl 3-methoxypropionate, ethyl 3-ethoxypropionate, tert-butyl acetate, tert-butyl propionate, and propylene glycol monotert-butyl ether acetate; lactones such as γ-butyrolactone; and mixed solvents thereof. When an acetal-based acid labile group is used, a high-boiling alcohol solvent, specifically, diethylene glycol, propylene glycol, glycerin, 1,4-butanediol, 1,3-butanediol, or the like, can be added to accelerate the deprotection reaction of the acetal.

[0180] Among these organic solvents, 1-ethoxy-2-propanol, PGMEA, PGME, cyclohexanone, EL, γ-butyrolactone, and mixed solvents thereof are preferred.

[0181] When the chemically amplified positive resist composition of the present invention contains the organic solvent, the content thereof is preferably 200 to 10,000 parts by mass, and more preferably 400 to 5,000 parts by mass, relative to 80 parts by mass of the base polymer. The organic solvent may be used alone, or two or more types may be mixed and used.

[0182] [Photoacid generator] The chemically amplified positive resist composition of the present invention may contain a photoacid generator. The 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.

[0183] 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 the specific examples, arylsulfonate-type or alkane sulfonate-type photoacid generators are preferred because they generate an acid of suitable strength for deprotecting the acid labile group in the repeating unit represented by formula (A2) or (A3).

[0184] As such a photoacid generator, a compound having an anion of the structure shown below is preferred. [ka]

[0185] [ka]

[0186] [ka]

[0187] [ka]

[0188] [ka]

[0189] [ka]

[0190] [ka]

[0191] The cation paired with the anion is preferably a sulfonium cation represented by the following formula (E) or an iodonium cation represented by the following formula (F). [ka]

[0192] In formulas (E) and (F), R 201 ~R 205 are each independently a halogen atom or a hydrocarbyl group having 1 to 20 carbon atoms which may contain a heteroatom.

[0193] Examples of the halogen atom include a fluorine atom, a chlorine atom, a bromine atom, and an iodine atom.

[0194] The hydrocarbyl group having 1 to 20 carbon atoms may be saturated or unsaturated, and may be linear, branched, or cyclic. Specific examples thereof include alkyl groups having 1 to 20 carbon atoms, such as methyl, ethyl, n-propyl, isopropyl, n-butyl, 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 having 3 to 20 carbon atoms, such as a ]decanyl group, an adamantyl group, or an adamantylmethyl group; and aryl groups having 6 to 20 carbon atoms, such as a phenyl group, a naphthyl group, or an anthracenyl group. Some or all of the hydrogen atoms in 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, or a group containing a heteroatom, such as an oxygen atom, a sulfur atom, or a nitrogen atom, may be present between the carbon-carbon bonds of the hydrocarbyl group, and as a result, the hydrocarbyl group may contain a hydroxy group, a fluorine atom, a chlorine atom, a bromine atom, an iodine atom, a cyano group, a carbonyl group, an ether bond, an ester bond, a sulfonate ester bond, a carbonate bond, a lactone ring, a sultone ring, a carboxylic anhydride (-C(=O)-OC(=O)-), a haloalkyl group, or the like.

[0195] Also, R 201 and R 202 may be bonded to each other to form a ring together with the sulfur atom to which they are bonded. In this case, the ring formed is the same as that of R 23 and R 24 , R 26 and R 27 , or R 29 and R 30 The rings which can be formed by bonding together with the sulfur atom to which they are bonded are the same as those exemplified above.

[0196] Specific examples of the sulfonium cation represented by formula (E) include the same as those exemplified as specific examples of the sulfonium cation in formulae (C2) to (C4). Specific examples of the iodonium cation represented by formula (F) include the same as those exemplified as specific examples of the iodonium cation in formulae (C5) to (C8).

[0197] The acid generated by the photoacid generator preferably has a pKa of -2.0 or higher, more preferably -1.0 or higher. The upper limit of the pKa is preferably 2.0. The pKa value was calculated using the pKa DB in the software ACD / Chemsketch ver. 9.04 manufactured by Advanced Chemistry Development, Inc.

[0198] When the chemically amplified positive resist composition of the present invention contains a photoacid generator, the content thereof is preferably 1 to 30 parts by mass, and more preferably 2 to 20 parts by mass, relative to 80 parts by mass of the base polymer. The photoacid generators may be used alone or in combination of two or more.

[0199] [Quencher] The chemically amplified positive resist composition of the present invention preferably contains a quencher (acid diffusion inhibitor). Examples of the quencher include conventional basic compounds. Examples of conventional basic compounds include primary, secondary, and tertiary aliphatic amines, mixed amines, aromatic amines, heterocyclic amines, nitrogen-containing compounds having a carboxyl group, nitrogen-containing compounds having a sulfonyl group, nitrogen-containing compounds having a hydroxyl group, nitrogen-containing compounds having a hydroxyphenyl group, alcoholic nitrogen-containing compounds, amides, imides, and carbamates. In particular, the primary, secondary, and tertiary amine compounds described in paragraphs

[0146] to

[0164] of JP 2008-111103 A are preferred, including amine compounds having a hydroxyl group, an ether bond, an ester bond, a lactone ring, a cyano group, or a sulfonate ester bond, and compounds having a carbamate group described in Japanese Patent Publication No. 3790649 A. Preferred examples include tris[2-(methoxymethoxy)ethyl]amine, tris[2-(methoxymethoxy)ethyl]amine-N-oxide, dibutylaminobenzoic acid, morpholine derivatives, imidazole derivatives, etc. Addition of such basic compounds can, for example, further suppress the diffusion rate of acid in the resist film or correct the shape.

[0200] Further, examples of the quencher include onium salts such as sulfonium salts, iodonium salts, and ammonium salts of carboxylic acids not fluorinated at the α-position, as described in JP-A-2008-158339. Sulfonic acids, imide acids, or methide acids fluorinated at the α-position are necessary for deprotecting acid labile groups, and salt exchange with onium salts not fluorinated at the α-position releases carboxylic acids not fluorinated at the α-position. Carboxylic acids not fluorinated at the α-position hardly undergo deprotection reactions, and therefore function as quenchers.

[0201] Examples of onium salts of carboxylic acids that are not fluorinated at the α-position include those represented by the following formula (G1). [ka]

[0202] In formula (G1), R 301 represents a hydrocarbyl group having 1 to 40 carbon atoms which may contain a hydrogen atom or a heteroatom, but excludes those in which the hydrogen atom bonded to the carbon atom at the α-position of the sulfo group is substituted with a fluorine atom or a fluoroalkyl group.

[0203] The hydrocarbyl group may be saturated or unsaturated, and may be linear, branched, or cyclic. Specific examples thereof include alkyl groups having 1 to 40 carbon atoms, such as methyl, ethyl, n-propyl, isopropyl, n-butyl, sec-butyl, tert-butyl, n-pentyl, tert-pentyl, n-hexyl, n-octyl, 2-ethylhexyl, n-nonyl, and n-decyl; cyclopentyl, cyclohexyl, cyclopentylmethyl, cyclopentylethyl, cyclopentylbutyl, cyclohexylmethyl, cyclohexylethyl, cyclohexylbutyl, norbornyl, and tricyclo[5.2.1.0]. 2,6 ]Cyclic saturated hydrocarbyl groups having 3 to 40 carbon atoms such as decanyl group, adamantyl group, and adamantylmethyl group; C2 to 40 alkenyl groups such as vinyl group, allyl group, propenyl group, butenyl group, and hexenyl group; C3 to 40 unsaturated aliphatic hydrocarbyl groups such as cyclohexenyl group; phenyl group, naphthyl group, alkylphenyl group (2-methylphenyl group, 3-methylphenyl group, 4-methylphenyl group, 4-ethylphenyl group, 4-tert-butyl ... Examples of the alkyl groups include aryl groups having 6 to 40 carbon atoms, such as aryl groups (e.g., t-butylphenyl group, 4-n-butylphenyl group), dialkylphenyl groups (e.g., 2,4-dimethylphenyl group, 2,4,6-triisopropylphenyl group), alkylnaphthyl groups (e.g., methylnaphthyl group, ethylnaphthyl group), and dialkylnaphthyl groups (e.g., dimethylnaphthyl group, diethylnaphthyl group); and aralkyl groups having 7 to 40 carbon atoms, such as benzyl group, 1-phenylethyl group, and 2-phenylethyl group.

[0204] Furthermore, some of the hydrogen atoms of the hydrocarbyl group may be substituted with heteroatom-containing groups such as oxygen atoms, sulfur atoms, nitrogen atoms, and halogen atoms, and some of the -CH- of the hydrocarbyl group may be substituted with heteroatom-containing groups such as oxygen atoms, sulfur atoms, and nitrogen atoms, and as a result, the hydrocarbyl group may contain a hydroxy group, a cyano group, a carbonyl group, an ether bond, a thioether bond, an ester bond, a sulfonate ester bond, a carbonate bond, a lactone ring, a sultone ring, a carboxylic anhydride (-C(=O)-OC(=O)-), a haloalkyl group, or the like. Examples of the hydrocarbyl group containing a heteroatom include heteroaryl groups such as a thienyl group; alkoxyphenyl groups such as a 4-hydroxyphenyl group, a 4-methoxyphenyl group, a 3-methoxyphenyl group, a 2-methoxyphenyl group, a 4-ethoxyphenyl group, a 4-tert-butoxyphenyl group, and a 3-tert-butoxyphenyl group; alkoxynaphthyl groups such as a methoxynaphthyl group, an ethoxynaphthyl group, an n-propoxynaphthyl group, and an n-butoxynaphthyl group; dialkoxynaphthyl groups such as a dimethoxynaphthyl group and a diethoxynaphthyl group; and aryloxoalkyl groups such as a 2-aryl-2-oxoethyl group, a 2-(1-naphthyl)-2-oxoethyl group, and a 2-(2-naphthyl)-2-oxoethyl group.

[0205] In formula (G1), Mq + is an onium cation. The onium cation is preferably a sulfonium cation, an iodonium cation, or an ammonium cation, and more preferably a sulfonium cation or an iodonium cation. Specific examples of the sulfonium cation include the same as those exemplified as specific examples of the sulfonium cation in formulas (C2) to (C4). Specific examples of the iodonium cation include the same as those exemplified as specific examples of the iodonium cation in formulas (C5) to (C8).

[0206] Examples of the anion of the salt represented by formula (G1) include, but are not limited to, those shown below. [ka]

[0207] [ka]

[0208] [ka]

[0209] As the quencher, a sulfonium salt of an iodinated benzene ring-containing carboxylic acid represented by the following formula (G2) can also be suitably used. [ka]

[0210] In formula (G2), R 401 represents a hydroxy group, a fluorine atom, a chlorine atom, a bromine atom, an amino group, a nitro group, a cyano group, or a saturated hydrocarbyl group having 1 to 6 carbon atoms, a saturated hydrocarbyloxy group having 1 to 6 carbon atoms, a saturated hydrocarbylcarbonyloxy group having 2 to 6 carbon atoms, or a saturated hydrocarbylsulfonyloxy group having 1 to 4 carbon atoms, in which some or all of the hydrogen atoms may be substituted with halogen atoms, or -N(R 401A )-C(=O)-R 401B or -N(R 401A )-C(=O)-OR 401B R 401A is a hydrogen atom or a saturated hydrocarbyl group having 1 to 6 carbon atoms. 401B is a saturated hydrocarbyl group having 1 to 6 carbon atoms or an unsaturated aliphatic hydrocarbyl group having 2 to 8 carbon atoms.

[0211] In formula (G2), p is an integer of 1 to 5. q is an integer of 0 to 3. r is an integer of 1 to 3. L 1is a single bond or a (r+1)-valent linking group having 1 to 20 carbon atoms, and may contain at least one selected from an ether bond, a carbonyl group, an ester bond, an amide bond, a sultone ring, a lactam ring, a carbonate bond, a halogen atom, a hydroxy group, and a carboxy group. The saturated hydrocarbyl group, saturated hydrocarbyloxy group, saturated hydrocarbylcarbonyloxy group, and saturated hydrocarbylsulfonyloxy group may be linear, branched, or cyclic. When q and / or r is 2 or more, each R 401 may be the same or different from each other.

[0212] In formula (G2), R 402 , R 403 and R 404 are each independently a hydrocarbyl group having 1 to 20 carbon atoms which may contain a halogen atom or a heteroatom. The hydrocarbyl group may be saturated or unsaturated and may be linear, branched, or cyclic. Specific examples thereof include an alkyl group having 1 to 20 carbon atoms, an alkenyl group having 2 to 20 carbon atoms, an aryl group having 6 to 20 carbon atoms, and an aralkyl group having 7 to 20 carbon atoms. Some or all of the hydrogen atoms in the hydrocarbyl group may be substituted with a hydroxy group, a carboxy group, a halogen atom, an oxo group, a cyano group, a nitro group, a sultone ring, a sulfo group, or a sulfonium salt-containing group. Some of the -CH2- groups in the hydrocarbyl group may be substituted with an ether bond, an ester bond, a carbonyl group, an amide bond, a carbonate bond, or a sulfonate ester bond. Furthermore, R 402 and R 403 may be bonded to each other to form a ring together with the sulfur atom to which they are attached.

[0213] Specific examples of the compound represented by formula (G2) include those described in JP 2017-219836 A. The compound represented by formula (G2) has high absorption, a high sensitizing effect, and a high acid diffusion control effect.

[0214] As the quencher, a nitrogen atom-containing carboxylate compound represented by the following formula (G3) can also be used. [ka]

[0215] In formula (G3), R 501 ~R 504 are each independently a hydrogen atom, -L 2 -CO2 - or a hydrocarbyl group having 1 to 20 carbon atoms which may contain a hetero atom. 501 and R 502 and R 502 and R 503 and, or R 503 and R 504 and may be bonded to each other to form a ring together with the carbon atoms to which they are attached. 2 R is a single bond or a hydrocarbylene group having 1 to 20 carbon atoms which may contain a heteroatom. 505 is a hydrocarbyl group having 1 to 20 carbon atoms which may contain a hydrogen atom or a heteroatom.

[0216] In formula (G3), ring R is a ring containing carbon atoms and nitrogen atoms and having 2 to 6 carbon atoms, and some or all of the hydrogen atoms bonded to the carbon atoms of the ring are hydrocarbyl groups having 1 to 20 carbon atoms, or -L 2 -CO2 - and some of the carbon atoms of the ring may be substituted with sulfur atoms, oxygen atoms, or nitrogen atoms. The ring may be an alicyclic ring or an aromatic ring, and is preferably a 5- or 6-membered ring, specific examples of which include a pyridine ring, a pyrrole ring, a pyrrolidine ring, a piperidine ring, a pyrazole ring, an imidazoline ring, a pyridazine ring, a pyrimidine ring, a pyrazine ring, an imidazoline ring, an oxazole ring, a thiazole ring, a morpholine ring, a thiazine ring, and a triazole ring.

[0217] The onium carboxylic acid salt represented by formula (G3) has at least one -L 2 -CO2 - group, i.e., R 501 ~R 504 At least one of the 2 -CO2 -and / or at least one of the hydrogen atoms bonded to the carbon atom of the ring R is -L 2 -CO2 - is replaced by

[0218] In formula (G3), Q + is a sulfonium cation, an iodonium cation, or an ammonium cation, and is preferably a sulfonium cation. Examples of the sulfonium cation include the same as those exemplified as the sulfonium cation represented by formula (E).

[0219] Examples of the anion of the compound represented by formula (G3) include, but are not limited to, those shown below. [ka]

[0220] [ka]

[0221] [ka]

[0222] [ka]

[0223] [ka]

[0224] [ka]

[0225] Furthermore, a weak acid betaine type compound can also be used as the quencher. Specific examples thereof include, but are not limited to, the following: [ka]

[0226] Further examples of the quencher include the polymer-type quencher described in JP 2008-239918 A. This quencher enhances the rectangularity of the resist pattern by orienting on the surface of the resist film. The polymer-type quencher also has the effect of preventing pattern film loss and pattern top rounding when a protective film for immersion lithography is applied.

[0227] When the chemically amplified positive resist composition of the present invention contains a quencher, the content thereof is preferably from 0 to 50 parts by mass, and more preferably from 0.1 to 40 parts by mass, relative to 80 parts by mass of the base polymer. The quenchers may be used alone or in combination of two or more.

[0228] When the chemically amplified positive resist composition of the present invention contains both a photoacid generator and a quencher, the ratio of the photoacid generator to the quencher, in mass ratio, is preferably less than 6, more preferably less than 5, and even more preferably less than 4. When the ratio of the photoacid generator to the quencher contained in the chemically amplified positive resist composition is within the above range, acid diffusion can be sufficiently suppressed, and excellent resolution and dimensional uniformity can be obtained.

[0229] [Surfactants] The chemically amplified positive resist composition of the present invention may contain a commonly used surfactant to improve its coatability onto a substrate. When using a surfactant, many surfactants are known, as described in JP-A-2004-115630, and a surfactant can be selected by reference to these. The content of the surfactant is preferably 0 to 5 parts by mass relative to 80 parts by mass of the base polymer. When the chemically amplified positive resist composition of the present invention contains a fluorine atom-containing polymer, the fluorine atom-containing polymer also functions as a surfactant, and therefore the surfactant need not be included.

[0230] The chemically amplified positive resist composition of the present invention is designed so that the dissolution rate of the overexposed portions of the resulting resist film in an alkaline developer is preferably 50 nm / sec or higher, more preferably 100 nm / sec or higher, and even more preferably 200 nm / sec or higher, from the viewpoint of improving development loading. A dissolution rate of 50 nm / sec or higher allows the resist film to dissolve uniformly in an alkaline developer, even if there are differences in the pattern layout of sparse and dense patterns, thereby reducing linewidth fluctuations. The dissolution rate of the overexposed portions in the present invention was calculated from the film loss amount when the chemically amplified positive resist composition of the present invention was spin-coated onto an 8-inch silicon wafer and baked at 110°C for 60 seconds to form a resist film with a thickness of 90 nm, exposed to KrF excimer laser light with an energy amount sufficient to complete the deprotection reaction of the polymer, baked at 110°C for 60 seconds, and then developed at 23°C with a 2.38 wt% TMAH aqueous solution using a resist development analyzer.

[0231] Furthermore, the dissolution rate of the unexposed portions of a resist film obtained from the chemically amplified positive resist composition of the present invention in an alkaline developer is preferably 10 nm / min or less, more preferably 8 nm / min or less, and even more preferably 6 nm / min or less. When the resist film is in the thin-film region (100 nm or less), the effect of pattern film loss in the alkaline developer becomes significant. If the dissolution rate of the unexposed portions exceeds 10 nm / min, the pattern collapses, making it impossible to form a fine pattern. This is particularly noticeable in the production of photomasks, which require a defect-free environment, because the development process tends to be intense. The dissolution rate of the unexposed portions was calculated from the film loss amount when a 6-inch silicon wafer was spin-coated with the chemically amplified positive resist composition of the present invention, baked at 110°C for 240 seconds to form an 80 nm-thick resist film, and then developed at 23°C for 80 seconds in a 2.38 wt% TMAH aqueous solution.

[0232] [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.

[0233] The substrate may be, for example, a substrate used for manufacturing integrated circuits (Si, SiO, SiO2, SiN, SiON, TiN, WSi, BPSG, SOG, organic anti-reflective coating, etc.), or a substrate used for manufacturing transmission or reflection mask circuits (Cr, CrO, CrON, MoSi2, Si, SiO, SiO2, SiON, SiONC, CoTa, NiTa, TaBN, SnO2, etc.). The chemically amplified positive resist composition is applied to the substrate by a method such as spin coating to a film thickness of 0.03 to 2 μm, and the composition is then pre-baked on a hot plate preferably at 60 to 150°C for 1 to 20 minutes, more preferably at 80 to 140°C for 1 to 10 minutes, to form a resist film.

[0234] 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.

[0235] When ultraviolet rays, far ultraviolet rays, excimer laser light, EUV, X-rays, gamma rays, or synchrotron radiation is used as the high-energy rays, a mask for forming a desired pattern is used, and the exposure dose is preferably 1 to 500 mJ / cm. 2 , more preferably 10 to 400 mJ / cm 2 When EB is used, the exposure dose is preferably 1 to 500 μC / cm 2 directly to form the desired pattern. 2 , more preferably 10 to 400 μC / cm 2 Irradiate so that

[0236] 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.

[0237] Next, PEB is performed on a hot plate, preferably at 60 to 150° C. for 1 to 20 minutes, more preferably at 80 to 140° C. for 1 to 10 minutes.

[0238] 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 %, TMAH, etc., by a conventional method such as dipping, puddling, or spraying for preferably 0.1 to 3 minutes, more preferably 0.5 to 2 minutes, to form a desired pattern on the substrate.

[0239] The chemically amplified positive resist composition of the present invention is useful because it can form a pattern with particularly good resolution and small LER. Furthermore, the chemically amplified positive resist composition of the present invention is particularly useful for pattern formation on substrates having a surface made of a material that is prone to pattern peeling or pattern collapse, since it is difficult to obtain good resist pattern adhesion. Examples of such substrates include substrates having a sputtering film formed on the outermost surface by sputtering a film of metallic chromium or a chromium compound containing one or more light elements selected from oxygen, nitrogen, and carbon, SiO , SiO x , a tantalum compound, a molybdenum compound, a cobalt compound, a nickel compound, a tungsten compound, or a tin compound in the outermost layer. The chemically amplified positive resist composition of the present invention is particularly useful for pattern formation using a photomask blank as the substrate. In this case, the photomask blank may be either a transmissive or reflective type.

[0240] As a transmission mask blank, a photomask blank having a light-shielding film made of a chromium-based material may be a photomask blank for a binary mask or a photomask blank for a phase shift mask. In the case of a photomask blank for a binary mask, the light-shielding film may have an antireflection layer and a light-shielding layer made of a chromium-based material, or the entire antireflection film on the surface layer side or only the layer further above the antireflection film on the surface layer side may be made of a chromium-based material, with the remaining portion being made of a silicon-based compound material that may contain, for example, a transition metal. In addition, in the case of a photomask blank for a phase shift mask, the target photomask blank may be a photomask blank for a phase shift mask having a chromium-based light-shielding film on a phase shift film.

[0241] The above-mentioned photomask blank having a chromium-based material in the outermost layer is very well known, as is disclosed in JP-A Nos. 2008-26500 and 2007-302873, or as examples of prior art therein. Therefore, detailed description will be omitted. However, for example, when a light-shielding film having an antireflection layer and a light-shielding layer is formed using a chromium-based material, the following film configuration can be used.

[0242] When a light-shielding film having an anti-reflection layer and a light-shielding layer is formed using a chromium-based material, the layer structure may be such that the anti-reflection layer and the light-shielding layer are laminated in this order from the surface side, or the anti-reflection layer, the light-shielding layer, and the anti-reflection layer are laminated in this order. The anti-reflection layer and the light-shielding layer may each be multi-layered, and the composition between layers with different compositions may change discontinuously or continuously. The chromium-based material used includes metallic chromium and metallic chromium containing light elements such as oxygen, nitrogen, and carbon. Specifically, metallic chromium, chromium oxide, chromium nitride, chromium carbide, chromium oxide nitride, chromium carbide oxide, chromium nitride carbonitride, chromium oxynitride, etc. may be used.

[0243] A reflective mask blank includes a substrate, a multilayer reflective film formed on one main surface (front surface) of the substrate, specifically a multilayer reflective film that reflects exposure light such as EUV light, and an absorber film formed on the multilayer reflective film, specifically an absorber film that absorbs exposure light such as EUV light and reduces reflectance. From the reflective mask blank (EUV reflective mask blank), a reflective mask (EUV reflective mask) is manufactured having an absorber pattern (absorber film pattern) formed by patterning the absorber film. The wavelength of EUV light used in EUV lithography is 13 to 14 nm, and is typically light with a wavelength of about 13.5 nm.

[0244] Although the multilayer reflective film is preferably provided in contact with one main surface of the substrate, a base film may be provided between the substrate and the multilayer reflective film as long as the effects of the present invention are not lost. The absorber film may be formed in contact with the multilayer reflective film, but a protective film (protective film for the multilayer reflective film) may be provided between the multilayer reflective film and the absorber film, preferably in contact with the multilayer reflective film, and more preferably in contact with both the multilayer reflective film and the absorber film. The protective film is used to protect the multilayer reflective film during processing such as cleaning and repair. Furthermore, the protective film preferably has the function of protecting the multilayer reflective film when the absorber film is patterned by etching and preventing oxidation of the multilayer reflective film. Meanwhile, a conductive film used for electrostatically chucking the reflective mask to an exposure device may be provided under the other main surface (back surface) of the substrate, which is the surface opposite to the one main surface, preferably in contact with the other main surface. Here, one main surface of the substrate is the front surface and the upper side, and the other main surface is the back surface and the lower side, but the front and back and top and bottom of both are defined for convenience, and the one main surface and the other main surface are either of the two main surfaces (film formation surfaces) of the substrate, and the front and back and top and bottom are interchangeable. More specifically, it can be formed by a method such as that described in JP 2021-139970 A or exemplified as prior art therein.

[0245] According to the method for forming a resist pattern of the present invention, even when a substrate (e.g., a transmission or reflection type mask blank) is used whose outermost surface is made of a material that is likely to affect the shape of the resist pattern, such as a material containing chromium, silicon, or tantalum, it is possible to obtain a high-resolution pattern with small dimensional difference that is independent of pattern density and in which the effects of development loading are suppressed. [Example]

[0246] The present invention will be specifically described below with reference to Synthesis Examples, Examples, and Comparative Examples, but the present invention is not limited to the following Examples. The copolymer composition ratios are molar ratios, and Mw is the weight average molecular weight in terms of polystyrene measured by GPC.

[0247] [1] Polymer synthesis [Synthesis Example 1-1] Synthesis of Polymer P-1 Under a nitrogen atmosphere, a 300 mL dropping cylinder was charged with 50.6 g of 3-acetoxystyrene, 29.4 g of 2-(3-hydroxyphenyl)propan-2-yl methacrylate, 8.6 g of dimethyl-2,2'-azobis-(2-methylpropionate) (Fujifilm Wako Pure Chemical Industries, Ltd., product name V601), and 124 g of methyl ethyl ketone as a solvent to prepare a solution. Furthermore, 62 g of methyl ethyl ketone was added to a separate 500 mL polymerization flask under a nitrogen atmosphere, and the solution was added dropwise over 4 hours while heated to 80°C. After the addition was complete, stirring was continued for 18 hours while maintaining the polymerization temperature at 80°C, and then the mixture was cooled to room temperature. The resulting polymerization solution was added dropwise to 1300 g of hexane, and the precipitated copolymer was filtered off. The filtered copolymer was washed twice with 500 g of hexane. The resulting copolymer was dissolved in a mixed solvent of 144 g of tetrahydrofuran and 48 g of methanol in a 1 L flask under a nitrogen atmosphere, and 22.3 g of ethanolamine was added and stirred at 60°C for 3 hours. The reaction solution was concentrated under reduced pressure, and the resulting concentrate was dissolved in a mixed solvent of 240 g of ethyl acetate and 60 g of water. The resulting solution was transferred to a separatory funnel, and 11.1 g of acetic acid was added and separated. The lower layer was distilled off, and 60 g of water and 14.8 g of pyridine were added to the resulting organic layer and separated. The lower layer was distilled off, and 60 g of water was added to the resulting organic layer, followed by washing and separation (a total of five times). The organic layer after separation was concentrated and then dissolved in 130 g of acetone. The resulting acetone solution was added dropwise to 1200 g of water, and the resulting crystallized precipitate was filtered and washed with water. After suction filtration for 2 hours, the filtered product was again dissolved in 130 g of acetone. The resulting acetone solution was added dropwise to 1200 g of water, and the resulting crystallized precipitate was filtered, washed with water, and dried to obtain 50.1 g of the target polymer P-1, which was a white polymer. 13 C-NMR, 1 Measurement by H-NMR and GPC gave the following analytical results. [ka]

[0248] [Synthesis Examples 1-2 to 1-39, Comparative Synthesis Example 1-1] Synthesis of Polymers P-2 to P-39 and Comparative Polymer cP-1 Polymers P-2 to P-39 and comparative polymer cP-1 shown in Tables 1 and 2 were synthesized in the same manner as in Synthesis Example 1-1, except that the type and compounding ratio of each monomer was changed. In Tables 1 and 2, the introduced ratio indicates the molar ratio.

[0249] [Table 1]

[0250] [Table 2]

[0251] The structure of the repeating unit introduced into the polymer is shown below. [ka]

[0252] [ka]

[0253] [ka]

[0254] [ka]

[0255] [ka]

[0256] [ka]

[0257] The dissolution rates of the polymers in alkaline developers were calculated by spin-coating a polymer solution (polymer concentration: 16.7% by mass, solvent: PGMEA) onto an 8-inch silicon wafer and baking it at 100°C for 90 seconds to form a film with a thickness of 1000 nm, then developing it with a 2.38% by mass aqueous TMAH solution at 23°C for 100 seconds and measuring the amount of film loss. As a result, the dissolution rates of polymers P-1 to P-39 were 10 nm / min or less, and the dissolution rate of comparative polymer cP-1 was 20 nm / min.

[0258] [Synthesis Examples 2-1 to 2-6, Comparative Synthesis Examples 1-2 to 1-4] Synthesis of Polymers AP-1 to AP-6 and Comparative Polymers cP-2 to cP-4 Polymers AP-1 to AP-6 and comparative polymers cP-2 to cP-4 shown below were synthesized in the same manner as in Synthesis Example 1-1, except that the raw material compounds used were changed. [ka]

[0259] [ka]

[0260] [ka]

[0261] The dissolution rates of polymers AP-1 to AP-6 and comparative polymers cP-2 to cP-4 in an alkaline developer were 10 nm / min or less.

[0262] [2] Preparation of chemically amplified positive resist composition [Examples 1-1 to 1-58, Comparative Examples 1-1 to 1-5] Chemically amplified positive resist compositions were prepared by dissolving each component in an organic solvent according to the formulations shown in Tables 3 to 6 below, and filtering the resulting solution through a 0.02 μm UPE filter. The organic solvent was a mixed solvent of 650 parts by mass of PGMEA, 1810 parts by mass of EL, and 1810 parts by mass of PGME.

[0263] [Table 3]

[0264] [Table 4]

[0265] [Table 5]

[0266] [Table 6]

[0267] In Tables 3 to 6, the structures of quenchers Q-1 to Q-3, photoacid generators PAG-A to PAG-C, and fluorine atom-containing polymers D-1 to D-5 are as follows: [ka]

[0268] [ka]

[0269] [ka]

[0270] [3] EB lithography evaluation [Examples 2-1 to 2-58, Comparative Examples 2-1 to 2-5] Each chemically amplified positive resist composition (R-1 to R-58, CR-1 to CR-5) was spin-coated onto a 152 mm square photomask blank with a chrome 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. The thickness of the resulting resist film was measured using an optical measuring device, Nanospec (Nanometrics). Measurements were taken at 81 locations on the surface of the blank substrate, excluding the outer edge extending 10 mm inward from the outer periphery, and the average thickness and thickness range were calculated.

[0271] Furthermore, the film was exposed using an electron beam exposure device (EBM-5000plus manufactured by NuFlare Technology, Inc., acceleration voltage 50 kV), subjected to PEB at 110°C for 600 seconds, and developed with a 2.38 mass % TMAH aqueous solution to obtain a positive pattern.

[0272] The obtained resist patterns were evaluated as follows: The prepared patterned mask blanks were observed with a top-down SEM (scanning electron microscope), and the exposure dose required to resolve 200 nm 1:1 line and space (LS) at 1:1 was determined as the optimal exposure dose (μC / cm 2 ), and the minimum dimension at the exposure dose that resolves a 200 nm LS at a 1:1 ratio is taken as the resolution (limiting resolution), and the LER of the 200 nm LS was measured using an SEM. For development loading evaluation, the exposure dose (μC / cm) that resolves a designed 200 nm 1:1 LS at a 1:1 ratio within the substrate surface was used. 2 The space dimensions of a 200nm LS pattern formed by the 200nm LS method and a 200nm LS pattern with dummy patterns of densities of 15%, 25%, 33%, 45%, 50%, 55%, 66%, 75%, 85%, and 95% arranged around the pattern were measured using an SEM, and the differences in the dense and sparse pattern dimensions were compared. The pattern shape was visually judged to be rectangular or not.

[0273] The dissolution rate of the overexposed area was measured by spin-coating the resist solution onto an 8-inch silicon wafer, baking it at 110°C for 60 seconds to form a resist film with a thickness of 90 nm, and then measuring the exposure dose (mJ / cm) required to resolve a 200 nm 1:1 line and space (LS) at 1:1. 2 The resist was exposed to KrF excimer laser light at 110°C, baked for 60 seconds at 110°C, and then developed at 23°C with a 2.38% by mass TMAH aqueous solution using a resist development analyzer (RDA-800 manufactured by Litho Tech Japan Co., Ltd.), and the resist properties were calculated. The results are shown in Tables 7 to 9.

[0274] [Table 7]

[0275] [Table 8]

[0276] [Table 9]

[0277] [4] Etching resistance evaluation [Example 3-1, Comparative Example 3-1] Each chemically amplified positive resist composition (R-11, CR-4) was spin-coated onto a 152 mm square photomask blank with a chrome outermost surface using ACT-M (Tokyo Electron Limited). The resulting resist was pre-baked on a hot plate at 110°C for 600 seconds to produce a 120 nm thick resist film. The thickness of the resulting resist film was measured using an optical measuring device, Nanospec (Nanometrics). Measurements were performed at 81 locations on the blank substrate, excluding the outer edge extending 10 mm inward, and the average film thickness and film thickness range were calculated. The resulting coated substrate was dry-etched using a dry etching system (UNAXIS G4) under the following conditions, and the film loss rate (Å / sec) was calculated from the remaining film after etching. The results are shown in Table 10.

[0278] RF1(RIE): Pulse 700V RF2(ICP):CW 400W Pressure: 6mTorr Cl2: 185sccm O2: 55sccm He: 9.25 sccm Etching time: 75 seconds

[0279] [Table 10]

[0280] All of the chemically amplified positive resist compositions (R-1 to R-58) of the present invention exhibited good resolution, LER, and pattern rectangularity, and suppressed development loading. Furthermore, when comparing R-20 and R-56 to R-58, good resolution performance was achieved in the range of 50 μC or higher. On the other hand, among the comparative resist compositions (CR-1 to CR-5), CR-1 had an excessively low dissolution rate in the overexposed areas, resulting in insufficient suppression of development loading. CR-2 had a high dissolution rate in the unexposed areas of the polymer, resulting in a rounded head and degraded resolution. CR-3, CR-4, and CR-5 had insufficient base polymer design, resulting in insufficient performance in terms of resolution, LER, and pattern rectangularity. This is thought to be due to the successful optimization of the dissolution contrast and exposed area dissolution rate by the specially structured acrylate base polymer design, which allowed for the achievement of high resolution, LER, pattern rectangularity, and suppression of development loading. Furthermore, dry etching evaluation using R-11 showed that it had better etching resistance than CR-4, suggesting that a base polymer containing 65 mol% or more of an aromatic ring skeleton is effective for mask processing.

[0281] The method of forming a resist pattern using the chemically amplified positive resist composition of the present invention is useful for the production of semiconductor devices, particularly for photolithography in the processing of transmission and reflection photomask blanks.

Claims

1. A chemically amplified positive resist composition comprising a base polymer protected by an acid labile group and which becomes alkali-soluble upon the action of an acid, the base polymer comprises a polymer containing a phenolic hydroxy group-containing unit represented by the following formula (A1) and a repeating unit represented by the following formula (A2) in which a carboxy group is protected with an acid labile group, Among all repeating units of the polymer contained in the base polymer, repeating units having an aromatic ring skeleton account for 65 mol% or more, A chemically amplified positive resist composition, wherein the resist film obtained from the chemically amplified positive resist composition has a dissolution rate of 50 nm / sec or more in overexposed areas. 【Chemical 1】 (In the formula, a1 is an integer that satisfies 0≦a1≦5+2a3−a2. a2 is an integer of 1 to 3. a3 is an integer of 0 to 2. R A is a hydrogen atom, a fluorine atom, a methyl group, or a trifluoromethyl group. X 1 is a single bond, *-C(=O)-O-, or *-C(=O)-NH-. * is a bond to a carbon atom in the main chain. A 1 is a single bond or a saturated hydrocarbylene group having 1 to 10 carbon atoms, and —CH 2 A part of - may be substituted with -O-. R 1 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. 【Chemistry 2】 (In the formula, R A is a hydrogen atom, a fluorine atom, a methyl group, or a trifluoromethyl group. X 2 is a single bond, *-C(=O)-O-X 21 -, a phenylene group, or a naphthylene group, and the phenylene group or naphthylene group may be substituted with a halogen atom or an alkoxy group having 1 to 10 carbon atoms which may contain a fluorine atom. 21 represents an alkoxy group having 1 to 10 carbon atoms which may contain a fluorine atom, a hydroxy group, an ether bond, an ester bond or an aliphatic hydrocarbylene group having 1 to 20 carbon atoms which may contain a lactone ring, a phenylene group or a naphthylene group, and the aliphatic hydrocarbylene group may contain at least one selected from an alkoxy group having 1 to 10 carbon atoms which may contain a fluorine atom, a hydroxy group, an ether bond, an ester bond or a lactone ring. * represents a bond to a carbon atom in the main chain. R B and R C are each independently a hydrocarbyl group having 1 to 10 carbon atoms which may contain a heteroatom, and R B and R C may be bonded to each other to form a ring together with the carbon atoms to which they are attached. R 2 are each independently a halogen atom, a cyano group, an acyl group having 1 to 5 carbon atoms, an alkoxy group having 1 to 5 carbon atoms, a fluorinated alkyl group having 1 to 5 carbon atoms, or a fluorinated alkoxy group having 1 to 5 carbon atoms. R 3 are each independently a hydrocarbyl group having 1 to 10 carbon atoms which may contain a heteroatom. b1 is 1 or 2, b2 is an integer from 0 to 2, b3 is an integer from 0 to 5, and b4 is an integer from 0 to 2.

2. 2. The chemically amplified positive resist composition according to claim 1, wherein the phenolic hydroxy group-containing unit is a repeating unit represented by the following formula (A1-1): 【Chemistry 3】 (In the formula, R A and a2 are the same as above.)

3. 2. The chemically amplified positive resist composition according to claim 1, wherein the repeating unit in which the carboxy group is protected with an acid labile group is a repeating unit represented by the following formula (A2-1): 【Chemistry 4】 (In the formula, R A , R B , R C , X 2 , R 2 , R 3 , b1, b2 and b3 are the same as above.)

4. R 2 2. The resist composition according to claim 1, wherein is a fluorine atom, a trifluoromethyl group, or a trifluoromethoxy group.

5. 2. The chemically amplified positive resist composition according to claim 1, wherein the base polymer comprises a polymer containing a phenolic hydroxy group-containing unit represented by formula (A1), a repeating unit represented by formula (A2) in which a carboxy group is protected with an acid labile group, and a unit represented by formula (A3) in which a phenolic hydroxy group is protected with an acid labile group; or a polymer containing a phenolic hydroxy group-containing unit represented by formula (A1) and a repeating unit represented by formula (A2) in which a carboxy group is protected with an acid labile group, and a polymer containing a phenolic hydroxy group-containing unit represented by formula (A1) and a unit represented by formula (A3) in which a phenolic hydroxy group is protected with an acid labile group. 【Chemistry 5】 (In the formula, R A is the same as above. c1 is an integer that satisfies 0≦c1≦5+2c3−c2. c2 is an integer from 1 to 3. c3 is an integer from 0 to 2. X 3 is a single bond, *-C(=O)-O-, or *-C(=O)-NH-. * is a bond to a carbon atom in the main chain. A 3 is a single bond or a saturated hydrocarbylene group having 1 to 10 carbon atoms, and —CH 2 A part of - may be substituted with -O-. R 4 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. R 5 is an acid labile group when c2 is 1, and is a hydrogen atom or an acid labile group when c2 is 2 or more, provided that at least one is an acid labile group.

6. 6. The chemically amplified positive resist composition according to claim 5, wherein the unit in which the phenolic hydroxy group is protected with an acid labile group is a repeating unit represented by the following formula (A3-1): 【Chemistry 6】 (In the formula, R A is the same as above. 6 is an acid labile group having an aromatic hydrocarbon group having 6 to 20 carbon atoms and / or an alicyclic hydrocarbon group having 5 to 20 carbon atoms.

7. 7. The chemically amplified positive resist composition according to claim 1, wherein the polymer contained in the base polymer further contains a repeating unit represented by any one of the following formulas (B1) to (B3): 【Chemistry 7】 (In the formula, R A is the same as above. d and e each independently represent an integer of 0 to 4. f represents an integer of 0 to 5. g represents an integer of 0 to 2. X 4 is a single bond, *-C(=O)-O-, or *-C(=O)-NH-. * is a bond to a carbon atom in the main chain. A 4 is a single bond or a saturated hydrocarbylene group having 1 to 10 carbon atoms, and —CH 2 A part of - may be substituted with -O-. R 11 and R 12 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, or a saturated hydrocarbyloxy group having 1 to 8 carbon atoms which may be substituted with a halogen atom. R 13 represents 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, or a cyano group, and may also represent a hydroxy group when g is 1 or 2.

8. 7. The chemically amplified positive resist composition according to claim 1, wherein the polymer contained in the base polymer further contains a repeating unit represented by any one of the following formulas (C1) to (C8): 【Chemistry 8】 (In the formula, R A is the same as above. Y 1 represents a single bond, an aliphatic hydrocarbylene group having 1 to 6 carbon atoms, a phenylene group, a naphthylene group, or a group having 7 to 18 carbon atoms obtained by combining these, or *-O-Y 11 -, *-C(=O)-O-Y 11 - or *-C(=O)-NH-Y 11 - and Y 11 represents an aliphatic hydrocarbylene group having 1 to 6 carbon atoms, a phenylene group, a naphthylene group, or a group having 7 to 18 carbon atoms obtained by combining these, and may contain a carbonyl group, an ester bond, an ether bond, or a hydroxy group. Y 2 is a single bond or **-Y 21 -C(=O)-O-, and Y 21 is a hydrocarbylene group having 1 to 20 carbon atoms which may contain a heteroatom. Y 3 represents a single bond, a methylene group, an ethylene group, a phenylene group, a fluorinated phenylene group, a phenylene group substituted with a trifluoromethyl group, *-O-Y 31 -, *-C(=O)-O-Y 31 - or *-C(=O)-NH-Y 31 - is. Y 31 represents an aliphatic hydrocarbylene group having 1 to 6 carbon atoms, a phenylene group, a fluorinated phenylene group, a phenylene group substituted with a trifluoromethyl group, or a group having 7 to 20 carbon atoms obtained by combining these, and may contain a carbonyl group, an ester bond, an ether bond, or a hydroxy group. * indicates a bond to a carbon atom in the main chain, and ** indicates a bond to an oxygen atom in the formula. Y 4 is a single bond or a hydrocarbylene group having 1 to 30 carbon atoms which may contain a heteroatom. 1 and k 2 are each independently 0 or 1, 4 When is a single bond, k 1 and k 2 is 0. R 21 ~R 38 are each independently a halogen atom or a hydrocarbyl group having 1 to 20 carbon atoms which may contain a heteroatom. 21 and R 22 may be bonded to each other to form a ring together with the sulfur atom to which they are attached, and R 23 and R 24 , R 26 and R 27 , or R 29 and R 30 may be bonded to each other to form a ring together with the sulfur atom to which they are attached. R HF is a hydrogen atom or a trifluoromethyl group. Xa - is a non-nucleophilic counterion.)

9. The chemically amplified positive resist composition according to any one of claims 1 to 6, further comprising a fluorine atom-containing polymer that contains at least one repeating unit selected from the group consisting of a repeating unit represented by the following formula (D1), a repeating unit represented by the following formula (D2), a repeating unit represented by the following formula (D3), and a repeating unit represented by the following formula (D4), and that may further contain at least one repeating unit selected from the group consisting of a repeating unit represented by the following formula (D5) and a repeating unit represented by the following formula (D6): 【Chemistry 9】 (In the formula, R B are each independently a hydrogen atom, a fluorine atom, a methyl group, or a trifluoromethyl group. R C are each independently a hydrogen atom or a methyl group. R 101 , R 102 , R 104 and R 105 are each independently a hydrogen atom or a saturated hydrocarbyl group having 1 to 10 carbon atoms. R 103 , R 106 , R 107 and R 108 are each independently a hydrogen atom, a hydrocarbyl group having 1 to 15 carbon atoms, a fluorinated hydrocarbyl group having 1 to 15 carbon atoms, or an acid labile group; R 103 , R 106 , R 107 and R 108 When is a hydrocarbyl group or a fluorinated hydrocarbyl group, an ether bond or a carbonyl group may be present between the carbon-carbon bond. R 109 is a hydrogen atom or a linear or branched hydrocarbyl group having 1 to 5 carbon atoms which may have a group containing a heteroatom interposed between its carbon-carbon bonds. R 110 is a linear or branched hydrocarbyl group having 1 to 5 carbon atoms which may have a heteroatom-containing group interposed between its carbon-carbon bonds. R 111 is a saturated hydrocarbyl group having 1 to 20 carbon atoms in which at least one hydrogen atom is substituted with a fluorine atom, and —CH 2 A portion of the - may be substituted with an ester bond or an ether bond. x is an integer of 1 to 3. y is an integer that satisfies 0≦y≦5+2z−x. z is 0 or 1. m is an integer of 1 to 3. Z 1 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. Z 2 is a single bond, *-C(=O)-O-, or *-C(=O)-NH-. * is a bond to a carbon atom in the main chain. Z 3 is a single bond, -O-, *-C(=O)-O-Z 31 -Z 32 - or *-C(=O)-NH-Z 31 -Z 32 - is. Z 31 is a single bond or a saturated hydrocarbylene group having 1 to 10 carbon atoms. 32 is a single bond, an ester bond, an ether bond, or a sulfonamide bond. * is a bond to a carbon atom in the main chain.)

10. 7. The chemically amplified positive resist composition according to claim 1, further comprising an organic solvent.

11. 7. The chemically amplified positive resist composition according to claim 1, further comprising a photoacid generator.

12. 12. The chemically amplified positive resist composition according to claim 11, wherein the acid strength (pKa) of the anion of said photoacid generator is −2.0 or more.

13. 7. 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 any one of claims 1 to 6; 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.

14. 14. The method for forming a resist pattern according to claim 13, wherein the high-energy radiation is extreme ultraviolet radiation or an electron beam.

15. 14. The method for forming a resist pattern according to claim 13, wherein the outermost surface of the substrate is made of a material containing at least one element selected from the group consisting of chromium, silicon, tantalum, molybdenum, cobalt, nickel, tungsten, and tin.

16. 14. The method for forming a resist pattern according to claim 13, wherein the substrate is a transmission or reflection mask blank.

17. A transmission or reflection mask blank coated with the chemically amplified positive resist composition according to any one of claims 1 to 6.

Images