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

Abstract

The present invention provides an onium salt capable of generating an acid with moderate acid strength and low diffusion, a chemically amplified positive-type resist composition containing the same, and a method for forming a resist pattern using the resist composition. [Solution] An onium salt represented by the following formula (A). TIFF2026090779000330.tif29102

Description

[Technical Field]

[0001] The present invention relates to an onium salt, a chemically amplified positive-type resist composition, and a resist pattern formation method. [Background technology]

[0002] In recent years, with the increasing integration of integrated circuits, there has been a demand for the formation of finer patterns, and chemically amplified resist compositions using acids as catalysts are primarily used for processing patterns of 0.2 μm or less. High-energy beams such as ultraviolet light, far ultraviolet light, and electron beams (EB) are used as exposure sources in this process, and EB lithography, in particular, which is used as an ultrafine processing technology, has become indispensable as a method for processing photomask blanks when creating photomasks for semiconductor manufacturing. As for the resist compositions used in such photolithography, there are positive types that form patterns by dissolving the exposed areas and negative types that form patterns by leaving the exposed areas intact, and the one that is easier to use is selected depending on the desired form of the resist pattern.

[0003] Generally, EB (electroluminescent) lithography does not use a mask. In the case of positive-type lithography, the area other than the region where the resist film is to be preserved is sequentially irradiated with a micro-area EB. In the case of negative-type lithography, the area where the resist film is to be preserved is sequentially irradiated. This process involves sweeping across the entire area of ​​the processed surface, which takes longer than batch exposure using a photomask. To maintain throughput, the resist film must be highly sensitive. Also, because the lithography time is long, differences tend to occur between the areas lithographed early and those lithographed later. Therefore, the temporal stability of the exposed area in a vacuum is an important performance requirement. Furthermore, in the processing of photomask blanks, which is a particularly important application, some photomask substrates have surface materials such as chromium oxide and other chromium compound films that can easily affect the pattern shape of the chemically amplified resist film. To maintain high resolution and the shape after etching, it is important to maintain a rectangular pattern profile of the resist film regardless of the substrate type.

[0004] The control of the sensitivity and pattern profile of the resist film mentioned above has been improved through various means, including the selection and combination of materials used in the resist composition and process conditions. One such improvement addresses the issue of acid diffusion, which has a significant impact on the resolution of chemically amplified resist films. In photomask processing, it is required that the shape of the resulting resist pattern does not change depending on the time until post-exposure heating (PEB). A major cause of this time-dependent change is the diffusion of acid generated by exposure. This acid diffusion problem has been extensively studied not only in photomask processing but also in general resist compositions, as it significantly affects sensitivity and resolution.

[0005] Patent documents 1 and 2 describe examples of reducing roughness by increasing the bulk of the acid generated from an acid generator to suppress acid diffusion. However, such acid generators are still insufficient in suppressing acid diffusion, so there has been a need for the development of acid generators with even lower diffusion.

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

[0007] Incidentally, polymers containing a large amount of aromatic skeletons with acidic side chains, such as polyhydroxystyrene, have been usefully used as resist compositions for KrF lithography. However, because they exhibit significant absorption of light around 200 nm, they have not been used as materials for resist compositions for ArF lithography. Nevertheless, they are important materials for resist compositions for EB lithography and extreme ultraviolet (EUV) lithography, which are promising techniques for forming patterns smaller than the processing limit of ArF lithography, due to their high etching resistance.

[0008] For positive-type EB lithography resist compositions and EUV lithography resist compositions, the base polymers mainly used are those that, when irradiated with high-energy rays, use the acid generated from a photoacid generator as a catalyst to deprotect the acid-unstable groups (acid-degradable protecting groups) that mask the acidic functional groups of the phenol side chains of the base polymer, thereby making them solubilizable in an alkaline developer. In addition, tertiary alkyl groups, tert-butoxycarbonyl groups, and acetal groups have been mainly used as the acid-unstable groups. While using protecting groups such as acetal groups, which require relatively low activation energy for deprotection, has the advantage of obtaining highly sensitive resist films, if the diffusion of the generated acid is not sufficiently suppressed, the deprotection reaction can occur even in unexposed areas of the resist film, leading to problems such as degradation of the LER and a decrease in the in-plane uniformity of pattern line width (CDU).

[0009] Furthermore, when using a sulfonium salt that generates a low pKa and strong acid, such as the fluorinated alkanesulfonic acid described in Patent Document 4, and a resin having repeating units with acetal groups, there was a problem in that a large LER pattern was formed. In other words, for the deprotection of acetal groups, which require a relatively low activation energy for deprotection, the acid strength of the fluorinated alkanesulfonic acid is too high, so even if acid diffusion is suppressed, the deprotection reaction proceeds due to trace amounts of acid diffused into the unexposed areas.

[0010] Furthermore, Patent Documents 5 and 6 propose photoacid generators that produce non-fluorinated aromatic sulfonic acid having multiple bulky alkyl substituents, and Patent Document 7 proposes a photoacid generator with a triarylbenzenesulfonic acid anion structure. Patent Document 8 proposes a photoacid generator that produces non-fluorinated aromatic sulfonic acid with an iodine-containing aromatic ring introduced. Although the molecular weight of the generated acid is increased by multiple alkyl substituents, aromatic rings, and iodine atoms, thereby reducing acid diffusion, the suppression of acid diffusion is still insufficient when the purpose is to form fine patterns, and there is still room for further improvement. [Prior art documents] [Patent Documents]

[0011] [Patent Document 1] Japanese Patent Publication No. 2009-053518 [Patent Document 2] Japanese Patent Publication No. 2010-100604 [Patent Document 3] Japanese Patent Publication No. 2011-22564 [Patent Document 4] Patent No. 5083528 [Patent Document 5] Patent No. 6248882 [Patent Document 6] Patent No. 7067271 [Patent Document 7] Patent No. 7032549 [Patent Document 8] Japanese Patent Publication No. 2023-177038 [Overview of the project] [Problems that the invention aims to solve]

[0012] In recent years, there has been a demand for resist compositions that excel not only in line-and-space (LS), isoline (IL), and isospace (IS) patterns, but also in hole pattern shape. While the acid generator described in Patent Document 5, which generates a bulky acid and suppresses acid diffusion, produced patterns with good resolution and roughness, it had the problem of corner rounding occurring in hole patterns.

[0013] The present invention has been made in view of the above circumstances, and aims to provide an onium salt that has appropriate acid strength and can generate an acid with low diffusion, a chemically amplified positive resist composition containing the same, and a method for forming a resist pattern using the resist composition. [Means for solving the problem]

[0014] As a result of diligent research to achieve the above objective, the present inventors have found that when an aromatic sulfonic acid type onium salt, which generates aromatic sulfonic acid, is introduced into a resist composition as a photoacid generator, in which the rotational degrees of freedom are suppressed by the bonding of an aromatic ring to which a sulfo group is bonded and another aromatic ring structure containing a bulky substituent via a sulfonamide bond, the acid generated therefrom has an appropriate acidity and excessive diffusion of the acid is suppressed, resulting in a pattern with good resolution and a small LER, and furthermore, a pattern with good rectangular shape due to appropriate dissolution inhibition, the present inventors have come to terms with this finding and have made the present invention.

[0015] In other words, the present invention provides the following onium salt, chemically amplified positive resist composition, and resist pattern formation method. 1. An onium salt represented by the following formula (A). [ka] (In the formula, n1 is 0 or 1. When n1 is 0, n2 is 1, 2, 3, 4 or 5, and when n1 is 1, n2 is 1, 2, 3, 4, 5, 6 or 7. n3 is 0 or 1. n4 is 0, 1, 2, 3 or 4. n5 is 0, 1, 2, 3 or 4. However, when n3 is 0, 0 ≦ n4 + n5 ≦ 4, and when n3 is 1, 0 ≦ n4 + n5 ≦ 6.) R , , F , 2 , + , 2 , , + , , F , , 2 , , , , F , , 1 is each independently a branched or cyclic hydrocarbyl group having 3 to 20 carbon atoms which may contain an iodine atom or a hetero atom, and at least one R 1 is bonded to a carbon atom adjacent to the carbon atom to which S is bonded. When n2 is 2 or more, each R 1 may be the same as or different from each other, and a plurality of R 1 may combine with each other to form a ring together with the carbon atoms to which they are bonded.) R 2 is a hydrocarbyl group having 1 to 20 carbon atoms which may contain a halogen atom other than a fluorine atom or a hetero atom other than a fluorine atom. When n4 is 2, 3 or 4, each R 2 may be the same as or different from each other, and a plurality of R 2 may combine with each other to form a ring together with the carbon atoms to which they are bonded.)​​​​​​​​​​​​​​​​​​​​​​​​​​​​3. The onium salt of 2 that is represented by the following formula (A2). [ka] (In the formula, n3, n4, n5, R 1 , R 2 , R F and Z + (This is the same as above.) 4.Z + However, the onium salt is one of 1 to 3, which is a sulfonium cation represented by the following formula (Z-1) or an iodonium cation represented by the following formula (Z-2). [ka] (In the formula, R ct1 ~R ct5 Each of these is independently a hydrocarbyl group having 1 to 30 carbon atoms, which may contain a halogen atom or a heteroatom. Also, R ct1 and R ct2 However, they may bond with each other to form a ring with the sulfur atom to which they are bonded. 5.Z + However, it is an onium salt of any of the sulfonium cations 1 to 3 represented by the following formula (Z-3). [ka] (In the formula, m1 is 0 or 1. m2 is 0 or 1. m3 is 0 or 1. m4 is 0, 1, 2, 3 or 4. m5 is 0, 1, 2, 3 or 4. m6 is 0, 1, 2, 3, 4, 5 or 6. m7 is 0, 1, 2, 3, 4, 5 or 6. m8 is 0, 1 or 2. m9 is 0, 1 or 2. m10 is 0, 1 or 2. m11 is 0 or 1. m12 is 0, 1, 2, 3 or 4. m13 is 0, 1 or 2. m14 is 0, It is either 1 or 2. However, when m1 is 0, 0 ≤ m6 + m9 ≤ 4, and when m1 is 1, 0 ≤ m6 + m9 ≤ 6. When m2 is 0, 0 ≤ m7 + m10 ≤ 4, and when m2 is 1, 0 ≤ m7 + m10 ≤ 6. When m3 is 0, 1 ≤ m4 + m5 + m8 + m14 ≤ 4, and when m3 is 1, 1 ≤ m4 + m5 + m8 + m14 ≤ 6. When m11 is 0, 0 ≤ m12 + m13 ≤ 4, and when m11 is 1, 0 ≤ m12 + m13 ≤ 6. Also, m4 + m12 ≥ 1. R F1 ~R F3 Each of these is independently a fluorine atom, a fluorinated saturated hydrocarbyl group having 1 to 6 carbon atoms, a fluorinated saturated hydrocarbyloxy group having 1 to 6 carbon atoms, or a fluorinated saturated hydrocarbylthio group having 1 to 6 carbon atoms. When m5 is 2, 3, or 4, each R F1 They may be the same or different from each other. When m6 is 2, 3, 4, 5 or 6, each R F2 They may be the same or different from each other. When m7 is 2, 3, 4, 5 or 6, each R F3 They may be the same as or different from each other. R ct6 ~R ct9 This is a C1-C20 hydrocarbyl group which may contain halogen atoms other than iodine and fluorine atoms, a nitro group, a cyano group, a heteroatom, a C1-C20 hydrocarbyloxy group which may contain a heteroatom, or a C1-C20 hydrocarbylthio group which may contain a heteroatom. When m8 is 2, two R ct6 The two Rs may be identical or different from each other. ct6These may bond with each other to form a ring with the carbon atom to which they are bonded. When m9 is 2, two R ct7 The two Rs may be identical or different from each other. ct7 These may bond with each other to form a ring with the carbon atom to which they are bonded. When m10 is 2, two R ct8 The two Rs may be identical or different from each other. ct8 These may bond with each other to form a ring with the carbon atoms to which they are bonded. When m13 is 2, two R ct9 The two Rs may be identical or different from each other. ct9 These atoms may bond with each other to form a ring with the carbon atoms to which they are bonded. Also, S in sulfonium cations + Aromatic rings that are directly bonded to each other are bonded to each other, forming S + They may form a ring together. L A and L B These are, independently, a single bond, an ether bond, an ester bond, an amide bond, a sulfonic acid ester bond, a sulfonamide bond, a carbonate bond, or a carbamate bond. X L This is a hydrocarbylene group having 1 to 40 carbon atoms, which may contain single bonds or heteroatoms. A photoacid generator consisting of one of the onium salts from 6.1 to 5. A chemically amplified positive-type resist composition containing a photoacid generator as described in 7.6. 8. A chemically amplified positive-type resist composition of 7 further comprising a base polymer containing a polymer that decomposes under the action of an acid, thereby increasing its solubility in an alkaline developer. 9. A chemically amplified positive resist composition of type 8, wherein the polymer contains repeating units represented by the following formula (B1). [ka] (In the formula, a1 is 0 or 1. a2 is 0, 1 or 2. a3 is an integer satisfying 0 ≤ a3 ≤ 5 + 2(a2) - a4. a4 is 1, 2 or 3.) R AThese are a hydrogen atom, a fluorine atom, a methyl group, or a trifluoromethyl group. R 11 This is a halogen atom, a nitro group, a carboxyl group, a saturated hydrocarbyl group having 1 to 6 carbon atoms that may be substituted with a halogen atom, a saturated hydrocarbyloxy group having 1 to 6 carbon atoms that may be substituted with a halogen atom, or a saturated hydrocarbylcarbonyloxy group having 2 to 8 carbon atoms that may be substituted with a halogen atom. When a3 is 2 or more, each R 11 They may be the same as or different from each other. A 1 (This is a single bond or a saturated hydrocarbylene group having 1 to 10 carbon atoms, and some of the -CH2- groups of the saturated hydrocarbylene group may be substituted with -O- groups.) 10. A chemically amplified positive resist composition of 8 or 9, wherein the polymer contains repeating units represented by the following formula (B2-1). [ka] (In the formula, b1 is 0 or 1. b2 is 0, 1 or 2. b3 is an integer satisfying 0 ≤ b3 ≤ 5 + 2(b2) - b4. b4 is 1, 2 or 3. b5 is 0 or 1.) R A These are a hydrogen atom, a fluorine atom, a methyl group, or a trifluoromethyl group. R 21 This is a halogen atom, a saturated hydrocarbyl group having 1 to 6 carbon atoms that may be substituted with a halogen atom, a saturated hydrocarbyloxy group having 1 to 6 carbon atoms that may be substituted with a halogen atom, or a saturated hydrocarbylcarbonyloxy group having 2 to 8 carbon atoms that may be substituted with a halogen atom. When b3 is 2 or more, each R 21 They may be the same as or different from each other. A 2 This is a single bond or a saturated hydrocarbylene group having 1 to 10 carbon atoms, and some of the -CH2- groups of the saturated hydrocarbylene group may be substituted with -O- groups. X is an acid-unstable group when b4 is 1, and when b4 is 2 or 3, it is independently a hydrogen atom or an acid-unstable group, but at least one of them is an acid-unstable group. 11. Any of the 8 to 10 chemically amplified positive resist compositions wherein the polymer contains repeating units represented by the following formula (B2-2). [ka] (In the formula, c1 is 0, 1, or 2. c2 is 0, 1, or 2. c3 is 0, 1, 2, 3, 4, or 5. c4 is 0, 1, or 2.) R A These are a hydrogen atom, a fluorine atom, a methyl group, or a trifluoromethyl group. R 22 and R 23 Each of these is independently a hydrocarbyl group having 1 to 10 carbon atoms, which may contain heteroatoms, and R 22 and R 23 However, they may bond with each other to form a ring with the carbon atoms to which they are bonded. R 24 Each of these is independently a fluorine atom, a fluorinated alkyl group having 1 to 5 carbon atoms, or a fluorinated alkoxy group having 1 to 5 carbon atoms. When c2 is 2, each R 24 They may be the same as or different from each other. R 25 Each of these is independently a hydrocarbyl group having 1 to 10 carbon atoms, which may contain heteroatoms. When c3 is 2, 3, 4, or 5, each R 25 They may be the same as or different from each other. A 3 This refers to a single bond, a phenylene group, a naphthylene group, or *-C(=O)-OA 31 - is A 31 This is an aliphatic hydrocarbylene group having 1 to 20 carbon atoms, which may contain a hydroxyl group, an ether bond, an ester bond, or a lactone ring, or a phenylene group or a naphthylene group. 12. A chemically amplified positive resist composition according to any of 8 to 11, wherein the polymer comprises at least one selected from repeating units represented by the following formula (B3), repeating units represented by the following formula (B4), and repeating units represented by the following formula (B5). [ka] (In the formula, d is 0, 1, 2, 3, 4, 5, or 6; e is 0, 1, 2, 3, or 4; f1 is 0 or 1; f2 is 0, 1, or 2; f3 is 0, 1, 2, 3, 4, or 5.) R A These are a hydrogen atom, a fluorine atom, a methyl group, or a trifluoromethyl group. R 31 and R 32 Each of these is independently a hydroxyl group, a halogen atom, a saturated hydrocarbyl group having 1 to 6 carbon atoms that may be substituted with a halogen atom, a saturated hydrocarbyloxy group having 1 to 6 carbon atoms that may be substituted with a halogen atom, or a saturated hydrocarbylcarbonyloxy group having 2 to 8 carbon atoms that may be substituted with a halogen atom. When d is 2, 3, 4, 5, or 6, each R 31 They may be the same or different from each other. When e is 2, 3 or 4, each R 32 They may be the same as or different from each other. R 33 is a saturated hydrocarbyl group having 1 to 20 carbon atoms, a saturated hydrocarbyloxy group having 1 to 20 carbon atoms, a saturated hydrocarbylcarbonyloxy group having 2 to 20 carbon atoms, a saturated hydrocarbyloxyhydrocarbyl group having 2 to 20 carbon atoms, a saturated hydrocarbylthiohydrocarbyl group having 2 to 20 carbon atoms, a halogen atom, a nitro group, or a cyano group, and when f2 is 1 or 2, it may also be a hydroxyl group. When f3 is 2, 3, 4, or 5, each R 33 They may be the same as or different from each other. A 4 (This is a single bond or a saturated hydrocarbylene group having 1 to 10 carbon atoms, and some of the -CH2- groups of the saturated hydrocarbylene group may be substituted with -O- groups.) 13. Any of the 8 to 12 chemically amplified positive resist compositions wherein the polymer comprises at least one selected from repeating units represented by the following formula (B6), repeating units represented by the following formula (B7), repeating units represented by the following formula (B8), repeating units represented by the following formula (B9), and repeating units represented by the following formula (B10). [ka] (In the formula, g1 and g2 are independently 0, 1, 2, or 3. h1 is 0 or 1. h2 is 0, 1, 2, 3, or 4. h3 is 0, 1, 2, 3, or 4. However, when h1 is 0, 0 ≤ h2 + h3 ≤ 4, and when h1 is 1, 0 ≤ h2 + h3 ≤ 6.) R A These are, independently, a hydrogen atom, a fluorine atom, a methyl group, or a trifluoromethyl group. Z 1 This is a phenylene group which may have a single bond or a substituent. Z 2 This is a single bond, **-C(=O)-OZ 21 -,**-C(=O)-NH-Z 21 - or **-OZ 21 - is Z 21 This is a divalent group obtained by combining an aliphatic hydrocarbylene group, a phenylene group, or a combination thereof, having 1 to 6 carbon atoms, and may contain a halogen atom, a carbonyl group, an ester bond, an ether bond, or a hydroxyl group. Z 3 These are single bonds, ether bonds, ester bonds, amide bonds, sulfonic acid ester bonds, sulfonamide bonds, carbonate bonds, or carbamate bonds. Z 4 This is a single bond, or a divalent group obtained by combining an aliphatic hydrocarbylene group, a phenylene group, or a combination thereof, and may contain a halogen atom, a carbonyl group, an ester bond, an ether bond, or a hydroxyl group. Z 5 Each of these independently comprises a single bond, a phenylene group which may have substituents, a naphthylene group which may have substituents, or a *-C(=O)-OZ51 - is Z 51 is an aliphatic hydrocarbylene group having 1 to 10 carbon atoms, a phenylene group or a naphthylene group, and the aliphatic hydrocarbylene group may contain a halogen atom, a hydroxy group, an ether bond, an ester bond or a lactone ring. Z 6 is a single bond, an ether bond, an ester bond, an amide bond, a sulfonic acid ester bond, a sulfonamide bond, a carbonate bond or a carbamate bond. Z 7 are each independently a single bond, ***-Z 71 -C(=O)-O-, ***-C(=O)-NH-Z 71 - or ***-O-Z 71 - is. Z 71 is a hydrocarbylene group having 1 to 20 carbon atoms which may contain a hetero atom. Z 8 are each independently a single bond, ****-Z 81 -C(=O)-O-, ****-C(=O)-NH-Z 81 - or ****-O-Z 81 - is. Z 81 is a hydrocarbylene group having 1 to 20 carbon atoms which may contain a hetero atom. Z 9 is a single bond, a methylene group, an ethylene group, a phenylene group, a fluorinated phenylene group, a phenylene group substituted with a trifluoromethyl group, *-C(=O)-O-Z 91 -, *-C(=O)-N(H)-Z 91 - or *-O-Z 91 - is. Z 91 is an aliphatic hydrocarbylene group having 1 to 6 carbon atoms, a phenylene group, a fluorinated phenylene group or a phenylene group substituted with a trifluoromethyl group, and may contain a carbonyl group, an ester bond, an ether bond or a hydroxy group. * represents a bond to a carbon atom of the main chain. ** represents a bond to Z 1 represents a bond to. *** represents a bond to Z 6 represents a bond to. **** represents a bond to Z 7 represents a bond to. L1 These are single bonds, ether bonds, ester bonds, carbonyl groups, sulfonic acid ester bonds, sulfonamide bonds, carbonate bonds, or carbamate bonds. Rf 1 and Rf 2 Each of these is independently either a fluorine atom or a fluorinated saturated hydrocarbyl group having 1 to 6 carbon atoms. Rf 3 and Rf 4 Each of these is independently a hydrogen atom, a fluorine atom, or a fluorinated saturated hydrocarbyl group having 1 to 6 carbon atoms. Rf 5 and Rf 6 Each of these is independently a hydrogen atom, a fluorine atom, or a fluorinated saturated hydrocarbyl group having 1 to 6 carbon atoms. However, all Rf 5 and Rf 6 They cannot simultaneously become hydrogen atoms. Rf 7 This is a fluorine atom, a fluorinated alkyl group having 1 to 6 carbon atoms, a fluorinated alkoxy group having 1 to 6 carbon atoms, or a fluorinated alkylthio group having 1 to 6 carbon atoms. When h2 is 2, 3, or 4, each Rf 7 They may be the same as or different from each other. R 41 and R 42 Each of these is independently a hydrocarbyl group having 1 to 20 carbon atoms, which may contain heteroatoms. Also, R 41 and R 42 However, they may bond with each other to form a ring with the sulfur atom to which they are bonded. R 43 This is a C1-C20 hydrocarbyl group which may contain halogen atoms other than fluorine atoms, or heteroatoms. When h3 is 2, 3, or 4, each R 43 They may be the same or different from each other, and there may be multiple R 43 These atoms may bond with each other to form a ring with the carbon atoms to which they are bonded. M - It is a non-nucleophilic counterion. A + (This is an onium cation.) 14. A chemically amplified positive resist composition according to any of 8 to 13, wherein the content of repeating units having an aromatic ring skeleton among all repeating units of the polymer contained in the base polymer is 60 mol% or more. 15. Furthermore, any of the chemically amplified positive resist compositions 7 to 14 containing an organic solvent. 16. Furthermore, a chemically amplified positive resist composition comprising any of 7 to 3, including a quencher. 17. Any of the 7 to 16 chemically amplified positive resist compositions comprising a fluorine atom-containing polymer further comprising at least one selected from repeating units represented by the following formula (E1), repeating units represented by the following formula (E2), repeating units represented by the following formula (E3), and repeating units represented by the following formula (E4), and further comprising at least one selected from repeating units represented by the following formula (E5) and repeating units represented by the following formula (E6). [ka] (In the formula, j1 is 1, 2, or 3. j2 is an integer satisfying 0 ≤ j2 ≤ 5 + 2(j3) - j1. j3 is 0 or 1. k is 1, 2, or 3.) R B These are, independently, a hydrogen atom, a fluorine atom, a methyl group, or a trifluoromethyl group. R C Each of these is independently either a hydrogen atom or a methyl group. R 201 , R 202 , R 204 and R 205 Each of these is independently either a hydrogen atom or a saturated hydrocarbyl group having 1 to 10 carbon atoms. R 203 , R 206 , R 207 and R 208 Each of these is independently a hydrogen atom, a C1-C15 hydrocarbyl group, a C1-C15 fluorinated hydrocarbyl group, or an acid-unstable group, and R 203 , R 206 , R 207 and R 208When the group is a hydrocarbyl group or a fluorinated hydrocarbyl group, an ether bond or a carbonyl group may be interposed between the carbon-carbon bonds. R 209 This is a linear or branched hydrocarbyl group having 1 to 5 carbon atoms, which may have a hydrogen atom or a group containing a heteroatom between the carbon-carbon bonds. When j1 is 2 or 3, each R 209 They may be the same as or different from each other. R 210 This is a linear or branched hydrocarbyl group having 1 to 5 carbon atoms, which may have a heteroatom interposed between the carbon-carbon bonds. When j2 is 2 or more, each R 210 They may be the same as or different from each other. R 211 This is a saturated hydrocarbyl group having 1 to 20 carbon atoms in which at least one hydrogen atom is substituted with a fluorine atom, and a portion of the -CH2- of the saturated hydrocarbyl group may be substituted with an ester bond or an ether bond. X 1 This is a (k+1) valent hydrocarbon group having 1 to 20 carbon atoms or a (k+1) valent fluorinated hydrocarbon group having 1 to 20 carbon atoms. X 2 The bond is a single bond, *-C(=O)-O-, or *-C(=O)-NH-. The asterisk (*) is a bond to a carbon atom in the main chain. X 3 This is a single bond, -O-, *-C(=O)-OX 31 -X 32 - or *-C(=O)-NH-X 31 -X 32 - is X 31 This is a single bond or a saturated hydrocarbylene group having 1 to 10 carbon atoms. 32 A is a single bond, ester bond, ether bond, or sulfonamide bond. * indicates a bond to a carbon atom in the main chain. 18. Furthermore, any of the chemically amplified positive resist compositions of 7 to 17, which include a photoacid generator other than the photoacid generator of 6. A method for forming a resist pattern, comprising the steps of: forming a resist film on a substrate using any of the chemically amplified positive-type resist compositions described in 19.7 to 18; irradiating the resist film with a pattern using high-energy rays; and developing the resist film irradiated with the pattern using an alkaline developer. 20. A resist pattern formation method 19 wherein the high-energy beam is an extreme ultraviolet beam or electron beam with a wavelength of 3 to 15 nm. 21. A method for forming a resist pattern 19 or 20 on the outermost surface of the substrate, wherein the outermost surface is made of a chromium-containing material. 22. A method for forming a resist pattern on any of the substrates 19 to 21, wherein the substrate is a photomask blank. [Effects of the Invention]

[0016] The chemically amplified positive resist composition containing the onium salt of the present invention as a photoacid generator exhibits extremely high resolution and can produce patterns with low LER in microfabrication techniques, particularly EB lithography and EUV lithography. Furthermore, it is suitable as a chemically amplified positive resist material because it can produce patterns with good rectangular shape due to its appropriate dissolution inhibition properties. [Modes for carrying out the invention]

[0017] The present invention will be described in detail below. In the following description, depending on the structure represented by the chemical formula, an asymmetric carbon may be present, and enantiomers or diastereomers may exist. In such cases, one formula will represent all of these isomers. These isomers may be used individually or as a mixture of two or more.

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

[0019] In formula (A), n1 is 0 or 1. When n1 is 0, it is a benzene ring, and when n1 is 1, it is a naphthalene ring, but from the viewpoint of solvent solubility, it is preferable that n1 is a benzene ring with n1 being 0. When n1 is 0, n2 is 1, 2, 3, 4, or 5, and when n1 is 1, it is 1, 2, 3, 4, 5, 6, or 7. From the viewpoint of raw material procurement, it is preferable that n2 is 1, 2, 3, or 4, and more preferably 2 or 3. n3 is 0 or 1. When n3 is 0, it is a benzene ring, and when n3 is 1, it is a naphthalene ring, but from the viewpoint of solvent solubility, it is preferable that n3 is a benzene ring with n3 being 0. n4 is 0, 1, 2, 3, or 4. n5 is 0, 1, 2, 3, or 4. However, when n3 is 0, 0 ≤ n4 + n5 ≤ 4, and when n3 is 1, 0 ≤ n4 + n5 ≤ 6.

[0020] In formula (A), R 1 Each is independently a branched or cyclic hydrocarbyl group having 3 to 20 carbon atoms, which may contain an iodine atom or a heteroatom, and at least one R 1 The sulfur atom is bonded to a carbon atom adjacent to the carbon atom to which S is bonded. Specific examples of the hydrocarbyl group include branched alkyl groups such as isopropyl, sec-butyl, tert-butyl, tert-pentyl, and 2-ethylhexyl; cyclopentyl, cyclohexyl, cyclopentylmethyl, cyclopentylethyl, cyclopentylbutyl, cyclohexylmethyl, cyclohexylethyl, cyclohexylbutyl, norbornyl, oxanorbornyl, and tricyclo[5.2.1.0 2,6Examples include, but are not limited to, cyclic saturated hydrocarbyl groups having 3 to 20 carbon atoms, such as decyl groups and adamantyl groups; aryl groups such as phenyl groups, naphthyl groups, and anthracenyl groups; and groups obtained by combining these. Furthermore, some or all of the hydrogen atoms of the hydrocarbyl group may be substituted with groups containing heteroatoms such as oxygen atoms, sulfur atoms, nitrogen atoms, and halogen atoms, and some of the -CH2- of the hydrocarbyl group may be substituted with groups containing heteroatoms such as oxygen atoms, sulfur atoms, and nitrogen atoms, and as a result, it may contain hydroxyl groups, cyano groups, halogen atoms, carbonyl groups, ether bonds, ester bonds, sulfonic acid ester bonds, carbonate bonds, lactone rings, sultone rings, carboxylic acid anhydrides (-C(=O)-OC(=O)-), haloalkyl groups, etc. Examples of halogen atoms include fluorine atoms, chlorine atoms, bromine atoms, and iodine atoms, but fluorine atoms or iodine atoms are preferred. 1 Preferred C3-C20 branched alkyl groups such as isopropyl group, sec-butyl group, tert-butyl group, tert-pentyl group, and 2-ethylhexyl group; C3-C20 aliphatic cyclic hydrocarbyl groups such as cyclopentyl group, cyclohexyl group, norbornyl group, oxanorbornyl group, and adamantyl group; or C6-C20 aryl groups such as phenyl group and naphthyl group, which may have substituents. Preferred substituents that the aryl group may have include fluorine, chlorine, bromine, iodine, C1-C10 hydrocarbyl groups which may contain heteroatoms, C1-C10 hydrocarbyloxy groups which may contain heteroatoms, and C1-C10 hydrocarbyloxycarbonyl groups which may contain heteroatoms. When n2 is 2 or more, each R 1 They may be the same as or different from each other.

[0021] Also, when n2 is 2 or greater, multiple R 1 However, they may bond with each other to form a ring with the carbon atoms to which they are bonded. A 5- to 8-membered ring is preferred.

[0022] R in equation (A) 1Examples of structures in which the aromatic ring is bonded include, but are not limited to, those shown below. In the following formulas, the dashed line represents S + This is a combination of the two. [ka]

[0023] [ka]

[0024] [ka]

[0025] [ka]

[0026] [ka]

[0027] [ka]

[0028] [ka]

[0029] [ka]

[0030] [ka]

[0031] In equation (A), at least one R 1It is bonded to the carbon atom adjacent to the carbon atom to which S is bonded. This allows the other aromatic ring to which the sulfo group is bonded and R to bond. 1 The spatial proximity of these two elements creates steric hindrance, which suppresses the rotation of the sulfonamide bond, thus greatly inhibiting acid diffusion.

[0032] In formula (A), R 2 This is a C1-C20 hydrocarbyl group which may contain halogen atoms other than fluorine atoms, or heteroatoms other than fluorine atoms. Examples of halogen atoms other than fluorine atoms include chlorine atoms, bromine atoms, iodine atoms, etc. The hydrocarbyl group may be saturated or unsaturated, and may be linear, branched, or cyclic. Specific examples include C1-C20 alkyl groups such as methyl group, ethyl group, n-propyl group, isopropyl group, n-butyl group, isobutyl group, sec-butyl group, tert-butyl group, n-pentyl group, tert-pentyl group, n-hexyl group, n-octyl group, 2-ethylhexyl group, n-nonyl group, n-decyl group; cyclopentyl group, cyclohexyl group, cyclopentylmethyl group, cyclopentylethyl group, cyclopentylbutyl group, cyclohexylmethyl group, cyclohexylethyl group, cyclohexylbutyl group, norbornyl group, tricyclo[5.2.1.0 2,6 Examples include cyclic saturated hydrocarbyl groups having 3 to 20 carbon atoms, such as decyl groups, adamantyl groups, and adamantylmethyl groups; and aryl groups having 6 to 20 carbon atoms, such as phenyl groups, naphthyl groups, and anthracenyl groups. Furthermore, some or all of the hydrogen atoms of the hydrocarbyl group may be substituted with groups containing heteroatoms such as oxygen atoms, sulfur atoms, nitrogen atoms, and halogen atoms, and some of the -CH2- of the hydrocarbyl group may be substituted with groups containing heteroatoms such as oxygen atoms, sulfur atoms, and nitrogen atoms, and as a result, it may contain hydroxyl groups, cyano groups, chlorine atoms, bromine atoms, iodine atoms, carbonyl groups, ether bonds, ester bonds, sulfonic acid ester bonds, carbonate bonds, lactone rings, sultone rings, carboxylic acid anhydrides (-C(=O)-OC(=O)-), haloalkyl groups, etc. When n4 is 2, 3, or 4, each R 2These may be the same or different from each other. Also, when n4 is 2, 3 or 4, multiple R 2 These elements may bond to each other to form a ring with the carbon atoms to which they are bonded. A 5- to 8-membered ring is preferred.

[0033] In formula (A), R F R is a fluorine atom, a fluorinated alkyl group having 1 to 6 carbon atoms, a fluorinated alkoxy group having 1 to 6 carbon atoms, or a fluorinated alkylthio group having 1 to 6 carbon atoms. F Preferably, the substituents are a fluorine atom, a trifluoromethyl group, a difluoromethyl group, a trifluoromethoxy group, a difluoromethoxy group, a trifluoromethylthio group, or a difluoromethylthio group, and more preferably a fluorine atom, a trifluoromethyl group, or a trifluoromethoxy group. The inclusion of a fluorine atom or these substituents having a fluorine atom improves the acid strength of the generated acid due to the electron-withdrawing effect, thus allowing the deprotection reaction of acid-unstable groups such as tertiary esters and tertiary ethers to proceed smoothly. When n5 is 2, 3, or 4, each R F They may be the same as or different from each other.

[0034] The onium salt represented by formula (A) is preferably the one represented by formula (A1) below. [ka] (In the formula, n2, n3, n4, n5, R 1 , R 2 , R F and Z + (This is the same as above.)

[0035] The onium salt represented by formula (A1) is preferably the one represented by the following formula (A2). [ka] (In the formula, n3, n4, n5, R 1 , R 2 , R F and Z + (This is the same as above.)

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

Chemical formula

[0037]

Chemical formula

[0038]

Chemical formula

[0039]

Chemical formula

[0040]

Chemical formula

[0041] I

Chemical formula

[0042] [[ID=s2]]

Chemical formula

[0043]

Chemical formula

[0044] I

Chemical formula

[0045]

Chemical formula

[0046]

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[0047]

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[0048]

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[0049]

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[0050]

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[0051]

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[0052]

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[0053]

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[0054]

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[0055]

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[0056]

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[0057]

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[0058]

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[0059]

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[0060]

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[0061]

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[0062]

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[0063]

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[0064]

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[0065]

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[0066]

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[0067]

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[0068]

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[0069]

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[0070]

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[0071]

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[0072]

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[0073]

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[0074]

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[0075]

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[0076]

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[0077]

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[0078]

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[0079]

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[0080]

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[0081]

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[0082]

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[0083]

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[0084]

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[0085]

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[0086]

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[0087]

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[0088] [ka]

[0089] [ka]

[0090] [ka]

[0091] [ka]

[0092] [ka]

[0093] [ka]

[0094] [ka]

[0095] In formula (A), Z + This is an onium cation. The onium cation is preferably a sulfonium cation represented by the following formula (Z-1) or an iodonium cation represented by the following formula (Z-2). [ka]

[0096] In equations (Z-1) and (Z-2), R ct1 ~R ct5 Each of these is independently a hydrocarbyl group having 1 to 30 carbon atoms, which may contain a halogen atom or a heteroatom.

[0097] Rct1 ~R ct5 Specific examples of halogen atoms represented by include fluorine, chlorine, bromine, and iodine atoms.

[0098] R ct1 ~R ct5 The hydrocarbyl group represented by can be saturated or unsaturated, and can be linear, branched, or cyclic. Specific examples include C1-C30 alkyl groups such as methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, and tert-butyl groups; C3-C30 cyclic saturated hydrocarbyl groups such as cyclopropyl, cyclopentyl, cyclohexyl, cyclopropylmethyl, 4-methylcyclohexyl, cyclohexylmethyl, norbornyl, and adamantyl groups; C2-C30 alkenyl groups such as vinyl, 1-propenyl, 2-propenyl, butenyl, and hexenyl groups; C3-C30 cyclic unsaturated hydrocarbyl groups such as cyclohexenyl; C6-C30 aryl groups such as phenyl, naphthyl, and thienyl groups; C7-C30 aralkyl groups such as benzyl, 1-phenylethyl, and 2-phenylethyl groups; and groups obtained by combining these, but aryl groups are preferred. Furthermore, some or all of the hydrogen atoms of the hydrocarbyl group may be substituted with a group containing a heteroatom such as an oxygen atom, sulfur atom, nitrogen atom, or halogen atom, and some of the -CH2- of the hydrocarbyl group may be substituted with a group containing a heteroatom such as an oxygen atom, sulfur atom, or nitrogen atom, and as a result, it may contain a hydroxyl group, a fluorine atom, a chlorine atom, a bromine atom, an iodine atom, a cyano group, a nitro group, a carbonyl group, an ether bond, an ester bond, a sulfonic acid ester bond, a carbonate bond, a lactone ring, a sultone ring, a carboxylic acid anhydride (-C(=O)-OC(=O)-), a haloalkyl group, etc.

[0099] Also, R ct1 and R ct2 However, they may bond with each other to form a ring with the sulfur atom to which they are bonded. In this case, specific examples of the structure of the ring include those represented by the following formula. [ka] (In the formula, the dashed line represents R ct3 (This is a combination of the two.)

[0100] Specific examples of sulfonium cations represented by formula (Z-1) include those described in paragraphs

[0102] to

[0125] of Japanese Patent Publication No. 2024-003744 and those described in paragraphs

[0070] to

[0085] of Japanese Patent Publication No. 2023-169812, but are not limited to these.

[0101] Specific examples of iodonium cations represented by formula (Z-2) include, but are not limited to, those described in paragraph

[0181] of Japanese Patent Application Publication No. 2024-000259.

[0102] Z + As the onium cation represented by the following formula (Z-3), a sulfonium cation represented by the following formula is also preferred. [ka]

[0103] In formula (Z-3), m1 is either 0 or 1. When m1 is 0, it is a benzene ring, and when m1 is 1, it is a naphthalene ring, but from the viewpoint of solvent solubility, it is preferable that m1 is a benzene ring with a value of 0. m2 is either 0 or 1. When m2 is 0, it is a benzene ring, and when m2 is 1, it is a naphthalene ring, but from the viewpoint of solvent solubility, it is preferable that m1 is a benzene ring with a value of 0. m3 is either 0 or 1. When m3 is 0, it is a benzene ring, and when m3 is 1, it is a naphthalene ring, but from the viewpoint of solvent solubility, it is preferable that m3 is a benzene ring with a value of 0.

[0104] In formula (Z-3), m4 is 0, 1, 2, 3, or 4. The more iodine atoms in the cation structure there are, the higher the absorption, especially for EUV. However, this also leads to poor solvent solubility and concerns about precipitation in the resist composition. Therefore, m4 is preferably 0, 1, 2, or 3, and more preferably 0, 1, or 2.

[0105] In formula (Z-3), m5 is 0, 1, 2, 3, or 4. From the viewpoint of raw material procurement, m5 is preferably 0, 1, 2, or 3, and more preferably 0, 1, or 2. m6 is 0, 1, 2, 3, 4, 5, or 6. From the viewpoint of raw material procurement, m6 is preferably 0, 1, 2, or 3, and more preferably 0, 1, or 2. m7 is 0, 1, 2, 3, 4, 5, or 6. From the viewpoint of raw material procurement, m7 is preferably 0, 1, 2, or 3, and more preferably 0, 1, or 2.

[0106] In formula (Z-3), m8 is 0, 1, or 2. From the viewpoint of raw material procurement, it is preferable that m8 is 0 or 1. m9 is 0, 1, or 2. From the viewpoint of raw material procurement, it is preferable that m9 is 0 or 1. m10 is 0, 1, or 2. From the viewpoint of raw material procurement, it is preferable that m10 is 0 or 1.

[0107] In formula (Z-3), m11 is either 0 or 1. When m11 is 0, it is a benzene ring, and when m11 is 1, it is a naphthalene ring, but from the viewpoint of solvent solubility, a benzene ring with m11 being 0 is preferred.

[0108] In formula (Z-3), m12 is 0, 1, 2, 3, or 4. The more iodine atoms in the cation structure there are, the higher the absorption, especially for EUV. However, this also leads to poor solvent solubility and concerns about precipitation in the resist composition. Therefore, m12 is preferably 0, 1, 2, or 3, and more preferably 0, 1, or 2.

[0109] In formula (Z-3), m13 is 0, 1, or 2. From the viewpoint of raw material procurement, it is preferable that m13 is 0 or 1. m14 is 0, 1, or 2. From the viewpoint of synthesis, it is preferable that m14 is 0 or 1.

[0110] However, when m1 is 0, 0 ≤ m6 + m9 ≤ 4, and when m1 is 1, 0 ≤ m6 + m9 ≤ 6. When m2 is 0, 0 ≤ m7 + m10 ≤ 4, and when m2 is 1, 0 ≤ m7 + m10 ≤ 6. When m3 is 0, 1 ≤ m4 + m5 + m8 + m14 ≤ 4, and when m3 is 1, 1 ≤ m4 + m5 + m8 + m14 ≤ 6. When m11 is 0, 0 ≤ m12 + m13 ≤ 4, and when m11 is 1, 0 ≤ m12 + m13 ≤ 6. Also, m4 + m12 ≥ 1.

[0111] In formula (Z-3), R F1 ~R F3 Each of these is independently a fluorine atom, a fluorinated saturated hydrocarbyl group having 1 to 6 carbon atoms, a fluorinated saturated hydrocarbyloxy group having 1 to 6 carbon atoms, or a fluorinated saturated hydrocarbylthio group having 1 to 6 carbon atoms. Among these, trifluoromethyl, trifluoromethoxy, and trifluorothiomethoxy groups are preferred. When m5 is 2, 3, or 4, each R F1 They may be the same or different from each other. When m6 is 2, 3, 4, 5 or 6, each R F2 They may be the same or different from each other. When m7 is 2, 3, 4, 5 or 6, each R F3 They may be the same as or different from each other.

[0112] In formula (Z-3), R ct6 ~R ct9 This is a C1-C20 hydrocarbyl group which may contain halogen atoms other than iodine and fluorine atoms, a nitro group, a cyano group, a heteroatom, a C1-C20 hydrocarbyloxy group which may contain a heteroatom, or a C1-C20 hydrocarbylthio group which may contain a heteroatom. The hydrocarbyl portion of the hydrocarbyl group, hydrocarbyloxy group, and hydrocarbylthio group may be saturated or unsaturated, and may be linear, branched, or cyclic. For example, in the explanation of formula (A), R 2Examples of hydrocarbyl groups represented by the above are similar to those exemplified. Furthermore, some or all of the hydrogen atoms in the hydrocarbyl portion of the hydrocarbyl group, hydrocarbyloxy group and hydrocarbylthio group may be substituted with a group containing heteroatoms such as oxygen, sulfur, nitrogen, and halogen atoms, and some of the -CH2- of the hydrocarbyl group may be substituted with a group containing heteroatoms such as oxygen, sulfur, and nitrogen atoms, and as a result, the group may contain hydroxyl groups, cyano groups, fluorine atoms, chlorine atoms, bromine atoms, iodine atoms, carbonyl groups, ether bonds, ester bonds, sulfonic acid ester bonds, carbonate bonds, lactone rings, sultone rings, carboxylic acid anhydrides (-C(=O)-OC(=O)-), haloalkyl groups, etc.

[0113] Also, when m8 is 2, the two R ct6 The two Rs may be identical or different from each other. ct6 These may bond with each other to form a ring with the carbon atom to which they are bonded. When m9 is 2, two R ct7 The two Rs may be identical or different from each other. ct7 These may bond with each other to form a ring with the carbon atom to which they are bonded. When m10 is 2, two R ct8 The two Rs may be identical or different from each other. ct8 These may bond with each other to form a ring with the carbon atoms to which they are bonded. When m13 is 2, two R ct9 The two Rs may be identical or different from each other. ct9These elements may bond with each other to form a ring with the carbon atoms to which they are bonded. Specific examples of the ring formed in this case include cyclopropane rings, cyclobutane rings, cyclopentane rings, cyclohexane rings, norbornane rings, adamantane rings, etc. Furthermore, some or all of the hydrogen atoms in the ring may be substituted with groups containing heteroatoms such as oxygen atoms, sulfur atoms, nitrogen atoms, halogen atoms, etc., and some of the -CH2- in the ring may be substituted with groups containing heteroatoms such as oxygen atoms, sulfur atoms, nitrogen atoms, etc. As a result, the ring may contain hydroxyl groups, fluorine atoms, chlorine atoms, bromine atoms, iodine atoms, cyano groups, carbonyl groups, ether bonds, ester bonds, sulfonic acid ester bonds, carbonate bonds, lactone rings, sultone rings, carboxylic acid anhydrides (-C(=O)-OC(=O)-), haloalkyl groups, etc.

[0114] Furthermore, S in the sulfonium cation represented by formula (Z-3) + Aromatic rings that are directly bonded to each other are bonded to each other, forming S + They may form a ring together. Specific examples of the ring structure include those represented by the following formula. [ka]

[0115] In formula (Z-3), L A and L B These are, independently, a single bond, an ether bond, an ester bond, an amide bond, a sulfonic acid ester bond, a sulfonamide bond, a carbonate bond, or a carbamate bond. Of these, L A The bond is preferably a single bond, an ether bond, an ester bond, or a sulfonic acid ester bond, and more preferably an ester bond or a sulfonic acid ester bond. B The bond is preferably a single bond, an ether bond, or an ester bond, and more preferably a single bond.

[0116] In formula (Z-3), X LThis is a 1-40 carbon atom hydrocarbylene group which may contain single bonds or heteroatoms. The hydrocarbylene group may be linear, branched, or cyclic, and specific examples include an alkanediyl group and a cyclic saturated hydrocarbylene group. Specific examples of the heteroatom include an oxygen atom, a nitrogen atom, and a sulfur atom.

[0117] X L Specific examples of C1-C40 hydrocarbylene groups that may contain heteroatoms represented by the formulas shown below are, but are not limited to, those listed below. In the formulas below, * represents L A and L B This represents a combination of two things. [ka]

[0118] [ka]

[0119] [ka]

[0120] [ka]

[0121] Of these, X L -0~X L -22 and X L -47~X L -58 is preferable.

[0122] The sulfonium cation represented by formula (Z-3) is preferably the one represented by formula (Z-3-1) below. [ka] (In the formula, m4~m10, m12~m14, R F1 ~RF3 , R ct6 ~R ct9 , L A , L B and X L (This is the same as above.)

[0123] The cation represented by formula (Z-3-1) is preferably the one represented by formula (Z-3-2) below. [ka] (In the formula, m4~m10, R F1 ~R F3 and R ct6 ~R ct8 (This is the same as above.)

[0124] Specific examples of sulfonium cations represented by formula (Z-3) are listed below, but are not limited to these. In the following formula, Me represents a methyl group. [ka]

[0125] [ka]

[0126] [ka]

[0127] [ka]

[0128] [ka]

[0129] [ka]

[0130]

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[0131]

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[0132]

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[0133]

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[0134]

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[0135]

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[0137]

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[0138]

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[0139]

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[0140]

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[0150]

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[0151] [ka]

[0152] Specific examples of the onium salt of the present invention include any combination of the anion and cation described above.

[0153] The onium salt of the present invention can be synthesized by known methods. As an example, a method for producing the onium salt represented by the following formula (PAG-1-ex) will be described. [ka] (In the formula, n1~n5, R 1 , R 2 , R F and Z + (This is the same as above.)

[0154] The reaction shown in the scheme above is a sulfonamidate reaction between starting material SM-1 and amino aromatic sulfonate SM-2 to obtain the onium aromatic sulfonic acid salt PAG-1-ex. The reaction can be carried out according to conventional methods. Suitable solvents for the reaction include ethers such as tetrahydrofuran (THF), diethyl ether, diisopropyl ether, di-n-butyl ether, and 1,4-dioxane; hydrocarbons such as n-hexane, n-heptane, benzene, toluene, and xylene; aprotic polar solvents such as acetonitrile, dimethyl sulfoxide (DMSO), and N,N-dimethylformamide (DMF); and chlorinated organic solvents such as methylene chloride, chloroform, and carbon tetrachloride. These solvents can be appropriately selected depending on the reaction conditions, and may be used individually or in combination of two or more. In these solvents, starting material SM-1, amino aromatic sulfonate SM-2, and a base are added sequentially or simultaneously, and the reaction is carried out by cooling or heating as necessary. Examples of bases that can be used in the reaction include ammonia; amines such as triethylamine, pyridine, lutidine, colidine, and N,N-dimethylaniline; hydroxides such as sodium hydroxide, potassium hydroxide, and tetramethylammonium hydroxide; and carbonates such as potassium carbonate and sodium bicarbonate. These bases may be used individually or in combination of two or more. It is desirable to confirm the progress of the reaction by silica gel thin-layer chromatography (TLC) for yield. The onium salt PAG-1-ex can be obtained from the resulting reaction solution by conventional aqueous work-up. If necessary, it can be purified by conventional methods such as chromatography and recrystallization.

[0155] The onium salt represented by formula (A) is an onium salt of an aromatic sulfonic acid, and therefore can generate an acid of appropriate intensity by irradiation with high-energy rays. 1 It has one or more groups selected from branched alkyl groups, alicyclic groups, and aryl groups, and various functional groups can be introduced to the aryl group. Therefore, R 1If the group is an aryl group, it is preferable that the aryl group has a functional group. 1 When the group is an aryl group and has a hydrocarbyloxycarbonyl group as a functional group, acid diffusion can be reduced by having multiple heteroatoms due to ester bonds. Also, R 1 When the aryl group has a functional group containing a halogen atom, particularly a fluorine atom, the solvent solubility of the onium salt itself is increased, improving uniform dispersion, and the acidity of the generated sulfonic acid can be strengthened. This promotes the deprotection reaction of the protecting group of the base polymer, and an improvement in resolution can be expected. Furthermore, R 1 When the group is an aryl group and has branched alkyl or alicyclic groups, the exclusion volume of the anion increases, resulting in a bulky structure, which can improve LER (low-diffusion acid) by generating a low-diffusion acid. In addition, the multiple aromatic rings in the anion improve compatibility with the aromatic rings of the base polymer through interaction (π-π stacking interaction), which is expected to suppress excessive acid diffusion. The nitrogen atom derived from the sulfonamide bond has reduced basicity due to the electron-withdrawing effect of the adjacent sulfon bond and does not have the effect of trapping protons of the generated acid. However, since the sulfonamide bond has multiple heteroatoms, excessive acid diffusion can be suppressed by forming hydrogen bonds between lone pairs of electrons and protons. Furthermore, since the NH bond of the sulfonamide bond is weakly acidic, its affinity with the alkaline developer is improved when developed with an alkaline developer, which can suppress development residue in the exposed areas. These effects allow for the uniform generation of acid within the resist film with controlled acid intensity and diffusion, resulting in fine patterns with good resolution and low LER. In positive-type resist compositions using alkaline developers, the unexposed areas exhibit appropriate dissolution inhibition, while the exposed areas suppress development defects, resulting in patterns with good rectangularity.

[0156] The onium salt of the present invention can be suitably used as a photoacid generator.

[0157] [Chemically amplified positive-type resist composition] [(A) Photoacid Generator] The chemically amplified positive resist composition of the present invention contains, as component (A), a photoacid generator consisting of an onium salt represented by formula (A) as an essential component.

[0158] In the chemically amplified positive resist composition of the present invention, the content of (A) photoacid generator is preferably 0.1 to 40 parts by mass, and more preferably 1 to 20 parts by mass, relative to 80 parts by mass of (B) base polymer, as described later. When the content of (A) photoacid generator is within the above range, the amount of acid necessary for deprotection of acid-unstable groups is generated, and storage stability is also good. (A) photoacid generator may be used alone or in combination of two or more types.

[0159] [(B) Base polymer] The resist composition of the present invention includes a base polymer as component (B) which is decomposed by the action of an acid and whose solubility in an alkaline developer increases.

[0160] The polymer is preferably a polymer containing a repeating unit represented by the following formula (B1) (hereinafter also referred to as repeating unit B1). [ka]

[0161] In formula (B1), a1 is 0 or 1. a2 is 0, 1 or 2, where 0 is a benzene skeleton, 1 is a naphthalene skeleton, and 2 is anthracene skeleton. a3 is an integer satisfying 0 ≤ a3 ≤ 5 + 2(a2) - a4. a4 is 1, 2 or 3. When a2 is 0, preferably a3 is 0, 1, 2 or 3 and a4 is 1, 2 or 3. When a2 is 1 or 2, preferably a3 is 0, 1, 2, 3 or 4 and a4 is 1, 2 or 3.

[0162] In formula (B1), R A These are a hydrogen atom, a fluorine atom, a methyl group, or a trifluoromethyl group.

[0163] In formula (B1), R11 This is a halogen atom, a nitro group, a carboxyl group, a saturated hydrocarbyl group having 1 to 6 carbon atoms that may be substituted with a halogen atom, a saturated hydrocarbyloxy group having 1 to 6 carbon atoms that may be substituted with a halogen atom, or a saturated hydrocarbylcarbonyloxy group having 2 to 8 carbon atoms that may be substituted with a halogen atom. The saturated hydrocarbyl group, and the saturated hydrocarbyl portion of the saturated hydrocarbyloxy group and saturated hydrocarbylcarbonyloxy group, may be linear, branched, or cyclic. Specific examples include alkyl groups such as methyl, ethyl, n-propyl, isopropyl, butyl, pentyl, hexyl, and their structural isomers; cycloalkyl groups such as cyclopropyl, cyclobutyl, cyclopentyl, and cyclohexyl; and groups obtained by combining these. If the number of carbon atoms is below the upper limit, solubility in alkaline developer is good. When a3 is 2 or more, each R 11 They may be the same as or different from each other.

[0164] In formula (B1), A 1This is a single bond or a saturated hydrocarbylene group having 1 to 10 carbon atoms, and some of the -CH2- in the saturated hydrocarbylene group may be substituted with -O-. The saturated hydrocarbylene group may be linear, branched, or cyclic, and specific examples include alkanediyl groups having 1 to 10 carbon atoms such as methylene 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, and structural isomers thereof; cyclic saturated hydrocarbylene groups having 3 to 10 carbon atoms such as cyclopropanediyl group, cyclobutanediyl group, cyclopentanediyl group, and cyclohexanediyl group; and groups obtained by combining these. If the saturated hydrocarbylene group contains an ether bond, when a1 in formula (B1) is 1, it may be placed at any position other than between the α-carbon and β-carbon atoms relative to the esterifying oxygen atom. Furthermore, when a1 is 0, the atom bonded to the main chain becomes an etheric oxygen atom, and the second ether bond may be inserted at any position other than between the α-carbon and β-carbon atoms relative to the etheric oxygen atom. It is preferable that the saturated hydrocarbylene group has 10 or fewer carbon atoms, as this allows for sufficient solubility in alkaline developing solutions.

[0165] a1 is 0 and A 1 When it is a single bond, that is, the aromatic ring is directly bonded to the main chain of the polymer (i.e., a linker (-C(=O)-OA) 1 If (-) is not present, preferred examples of repeating unit B1 include units derived from 3-hydroxystyrene, 4-hydroxystyrene, 5-hydroxy-2-vinylnaphthalene, 6-hydroxy-2-vinylnaphthalene, etc. Specifically, these include, but are not limited to, the following. Note that in the following formula, R A This is the same as described above. [ka]

[0166] [ka]

[0167] [ka]

[0168] a1 is 1 (i.e., -C(=O)-OA as the linker) 1 When R has -, preferred examples of repeating unit B1 are, but are not limited to, those shown below. Note that in the following formula, A This is the same as described above. [ka]

[0169] [ka]

[0170] [ka]

[0171] [ka]

[0172] [ka]

[0173] The content of repeating unit B1 is preferably 15 to 90 mol%, and more preferably 15 to 80 mol%, of the total repeating units constituting the polymer. However, if the polymer described later includes at least one of the repeating units represented by formula (B3) and formula (B4) that provide high etching resistance, and that unit has a phenolic hydroxyl group as a substituent, it is preferable to include the ratio of that unit as well within the above range. Repeating unit B1 may be used alone or in combination of two or more types.

[0174] The polymer preferably contains repeating units having acidic functional groups protected by acid-unstable groups, i.e., repeating units protected by acid-unstable groups that become alkali-soluble by the action of acid (hereinafter also referred to as repeating unit B2), in order to provide the positive-type resist composition with the property that the exposed area dissolves in an alkaline developer.

[0175] The most preferred repeating unit B2 is the one represented by the following formula (B2-1) (hereinafter also referred to as repeating unit B2-1). [ka]

[0176] In formula (B2-1), b1 is 0 or 1. b2 is 0, 1 or 2, where 0 is a benzene skeleton, 1 is naphthalene, and 2 is anthracene. b3 is an integer satisfying 0 ≤ b3 ≤ 5 + 2(b2) - b4. b4 is 1, 2 or 3. b5 is 0 or 1. When b2 is 0, preferably b3 is 0, 1, 2 or 3 and b4 is 1, 2 or 3. When b2 is 1 or 2, preferably b3 is 0, 1, 2, 3 or 4 and b4 is 1, 2 or 3.

[0177] In formula (B2-1), R A These are a hydrogen atom, a fluorine atom, a methyl group, or a trifluoromethyl group.

[0178] In formula (B2-1), R 21This is a halogen atom, a saturated hydrocarbyl group having 1 to 6 carbon atoms that may be substituted with a halogen atom, a saturated hydrocarbyloxy group having 1 to 6 carbon atoms that may be substituted with a halogen atom, or a saturated hydrocarbylcarbonyloxy group having 2 to 8 carbon atoms that may be substituted with a halogen atom. The saturated hydrocarbyl group, and the saturated hydrocarbyl portion of the saturated hydrocarbylcarbonyloxy group and saturated hydrocarbyloxy group may be linear, branched, or cyclic. Specific examples include alkyl groups such as methyl, ethyl, n-propyl, isopropyl, butyl, pentyl, hexyl, and their structural isomers; cycloalkyl groups such as cyclopropyl, cyclobutyl, cyclopentyl, and cyclohexyl; and groups obtained by combining these. If the number of carbon atoms is below the upper limit, the solubility in alkaline developer is good. When b3 is 2 or more, each R 21 They may be the same as or different from each other.

[0179] In formula (B2-1), A 2The saturated hydrocarbylene group is a single bond or a saturated hydrocarbylene group having 1 to 10 carbon atoms, and some of the -CH2- atoms of the saturated hydrocarbylene group may be substituted with -O- atoms. The saturated hydrocarbylene group may be linear, branched, or cyclic, and specific examples include alkanediyl groups having 1 to 10 carbon atoms such as methylene groups, ethane-1,2-diyl groups, propane-1,3-diyl groups, butane-1,4-diyl groups, pentane-1,5-diyl groups, hexane-1,6-diyl groups, and structural isomers thereof; cyclic saturated hydrocarbylene groups having 3 to 10 carbon atoms such as cyclopropanediyl groups, cyclobutanediyl groups, cyclopentanediyl groups, and cyclohexanediyl groups; and groups obtained by combining these. If the saturated hydrocarbylene group contains an ether bond, when b1 in formula (B2-1) is 1, the ether bond may be located at any position other than between the α-carbon and β-carbon atoms relative to the esterifying oxygen atom. When b1 is 0, the atom bonded to the main chain becomes an etheric oxygen atom, and the second ether bond may be located at any position other than between the α-carbon and β-carbon atoms relative to the etheric oxygen atom. It is preferable that the saturated hydrocarbylene group has 10 or fewer carbon atoms, as this allows for sufficient solubility in alkaline developing solutions.

[0180] In formula (B2-1), when b4 is 1, X is an acid-unstable group. When b4 is 2 or 3, X is independently either a hydrogen atom or an acid-unstable group, but at least one is an acid-unstable group. That is, the repeating unit B2-1 is a configuration in which at least one phenolic hydroxyl group attached to an aromatic ring is protected by an acid-unstable group, or a carboxyl group attached to an aromatic ring is protected by an acid-unstable group. The acid-unstable group can be any that is removed by acid to yield an acidic group, as has been used in many known chemically amplified positive resist compositions, and is not particularly limited.

[0181] Examples of the acid-unstable group include tertiary saturated hydrocarbyl groups. The tertiary saturated hydrocarbyl group is preferably one having 4 to 18 carbon atoms, in order to obtain the resulting polymerization monomer by distillation.

[0182] The saturated hydrocarbyl group bonded to the tertiary carbon atom of the tertiary saturated hydrocarbyl group is preferably one having 1 to 15 carbon atoms. The saturated hydrocarbyl group having 1 to 15 carbon atoms may be linear, branched, or cyclic, and may contain oxygen atom-containing functional groups such as ether bonds or carbonyl groups between its carbon-carbon bonds. Furthermore, saturated hydrocarbyl groups bonded to tertiary carbon atoms may bond to each other, forming a ring together with the tertiary carbon atom to which they are bonded.

[0183] The alkyl substituents include methyl, ethyl, propyl, adamantyl, norbornyl, tetrahydrofuran-2-yl, 7-oxanorbornan-2-yl, cyclopentyl, 2-tetrahydrofuryl, and tricyclo[5.2.1.0 2,6 ]decyl group, 8-ethyl-8-tricyclo[5.2.1.0 2,6 ]decyl group, 3-methyl-3-tetracyclo[4.4.0.1 2,5 .1 7,10 ]dodecyl group, tetracyclo[4.4.0.1 2,5 .1 7,10 Examples include a dodecyl group and a 3-oxo-1-cyclohexyl group.

[0184] The tertiary saturated hydrocarbyl groups include tert-butyl group, tert-pentyl group, 1-ethyl-1-methylpropyl group, 1,1-diethylpropyl group, 1,1,2-trimethylpropyl group, 1-adamantyl-1-methylethyl group, 1-methyl-1-(2-norbornyl)ethyl group, 1-methyl-1-(tetrahydrofuran-2-yl)ethyl group, 1-methyl-1-(7-oxanorbornan-2-yl)ethyl group, 1-methylcyclopentyl group, 1-ethylcyclopentyl group, 1-Propylcyclopentyl group, 1-Cyclopentylcyclopentyl group, 1-Cyclohexylcyclopentyl group, 1-(2-tetrahydrofuryl)cyclopentyl group, 1-(7-oxanorbornan-2-yl)cyclopentyl group, 1-Methylcyclohexyl group, 1-Ethylcyclohexyl group, 1-Cyclopentylcyclohexyl group, 1-Cyclohexylcyclohexyl group, 2-Methyl-2-norbonyl group, 2-Ethyl-2-norbonyl 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 Examples include, but are not limited to, the dodecyl group, 2-methyl-2-adamantyl group, 2-ethyl-2-adamantyl group, 1-methyl-3-oxo-1-cyclohexyl group, 1-methyl-1-(tetrahydrofuran-2-yl)ethyl group, 5-hydroxy-2-methyl-2-adamantyl group, and 5-hydroxy-2-ethyl-2-adamantyl group.

[0185] Furthermore, the group represented by the following formula (B2-1-1) can be cited as the acid-unstable group. The group represented by formula (B2-1-1) is commonly used as an acid-unstable group and is a useful choice as an acid-unstable group that stably gives patterns where the interface between the pattern and the substrate is relatively rectangular. When X is the group represented by formula (B2-1-1), an acetal structure is formed. [ka] (In the equation, dashed lines represent connections.)

[0186] In formula (B2-1-1), R L1 This is a hydrogen atom or a saturated hydrocarbyl group having 1 to 10 carbon atoms. The saturated hydrocarbyl group may be linear, branched, or cyclic.

[0187] R L1 The group is appropriately selected according to the design of the sensitivity of the decomposition group to acid. For example, if the design is to decompose with a strong acid while ensuring relatively high stability, a group in which the carbon atom bonded to the hydrogen atom or acetal carbon is a tertiary carbon atom is preferred. L1 Examples include, but are not limited to, tert-butyl, tert-pentyl, and 1-adamantyl groups. Linear alkyl groups are preferred when designing for high sensitivity to pH changes using relatively high reactivity. The combination with acid generators and quenchers incorporated into the resist composition also matters, but R L2 If a relatively large alkyl group is selected at the terminal and the change in solubility due to decomposition is designed to be significant, then R L1 Preferably, the carbon atom bonded to the acetal carbon is a secondary carbon atom. L1 Examples include, but are not limited to, isopropyl groups, sec-butyl groups, cyclopentyl groups, and cyclohexyl groups.

[0188] In formula (B2-1-1), R L2This is a hydrocarbyl group having 1 to 30 carbon atoms. The hydrocarbyl group may be saturated or unsaturated, linear, branched, or cyclic, and some of the -CH2- atoms of the hydrocarbyl group may be substituted with heteroatoms such as oxygen or sulfur atoms, resulting in the inclusion of ether bonds, sulfide bonds, etc. Specific examples of the hydrocarbyl group include saturated hydrocarbyl groups having 1 to 30 carbon atoms and aryl groups having 6 to 30 carbon atoms. In particular, to obtain higher resolution in fine pattern formation, R L2 It is preferably a hydrocarbyl group having 1 to 6 carbon atoms. L2 When the group is a hydrocarbyl group with 1 to 6 carbon atoms, the alcohol produced after the deprotection reaction with acid is water-soluble. Therefore, it dissolves in the developer when forming a positive pattern with an alkaline developer, thus suppressing residual defects in the exposed areas.

[0189] Preferred examples of the base represented by formula (B2-1-1) are, but are not limited to, those listed below. Note that in the following formula, R L1 This is the same as above, and the dashed lines represent connections. [ka]

[0190] [ka]

[0191] [ka]

[0192] Other acid-unstable groups can also be used in which the hydrogen atom of a phenolic hydroxyl group is substituted with -CH2COO- (tertiary saturated hydrocarbyl group). In this case, the same tertiary saturated hydrocarbyl group used for protecting the phenolic hydroxyl group as described above can be used.

[0193] Furthermore, as a repeating unit B2, a repeating unit represented by the following formula (B2-2) (hereinafter also referred to as repeating unit B2-2) can be mentioned. Repeating unit B2-2 is a useful option as an acid-unstable group-containing unit that provides good performance against line width fluctuations during development loading because it increases the dissolution rate of the exposed area. [ka]

[0194] In equation (B2-2), c1 is 0, 1, or 2. c2 is 0, 1, or 2. c3 is 0, 1, 2, 3, 4, or 5. c4 is 0, 1, or 2.

[0195] In formula (B2-2), R A These are a hydrogen atom, a fluorine atom, a methyl group, or a trifluoromethyl group.

[0196] In formula (B2-2), R 22 and R 23 Each of these is independently a hydrocarbyl group having 1 to 10 carbon atoms, which may contain heteroatoms, and R 22 and R 23 However, they may bond with each other to form a ring with the carbon atoms to which they are bonded.

[0197] In formula (B2-2), R 24 Each of these is independently a fluorine atom, a fluorinated alkyl group having 1 to 5 carbon atoms, or a fluorinated alkoxy group having 1 to 5 carbon atoms. When c2 is 2, each R 24 They may be the same as or different from each other.

[0198] In formula (B2-2), R 25 Each of these is independently a hydrocarbyl group having 1 to 10 carbon atoms, which may contain heteroatoms. When c3 is 2, 3, 4, or 5, each R 25 They may be the same as or different from each other.

[0199] In formula (B2-2), A 3This refers to a single bond, a phenylene group, a naphthylene group, or *-C(=O)-OA 31 - is A 31 This is an aliphatic hydrocarbylene group having 1 to 20 carbon atoms, which may contain a hydroxyl group, an ether bond, an ester bond, or a lactone ring, or a phenylene group or naphthylene group. * indicates a bond with a carbon atom of the main chain.

[0200] Preferred examples of repeating unit B2-2 are, but are not limited to, those shown below. Note that in the following formula, R A This is the same as described above. [ka]

[0201] [ka]

[0202] The content of repeating unit B2 is preferably 5 to 95 mol%, and more preferably 20 to 80 mol%, of the total repeating units constituting the polymer. Repeating unit B2 may be used alone or in combination of two or more types.

[0203] The polymer may contain at least one selected from the following repeating units: a repeating unit represented by formula (B3) (hereinafter also referred to as repeating unit B3), a repeating unit represented by formula (B4) (hereinafter also referred to as repeating unit B4), and a repeating unit represented by formula (B5) (hereinafter also referred to as repeating unit B5). [ka]

[0204] In equations (B3) and (B4), d is 0, 1, 2, 3, 4, 5, or 6. e is 0, 1, 2, 3, or 4.

[0205] In formulas (B3) and (B4), R 31 and R32 Each of these is independently a hydroxyl group, a halogen atom, a saturated hydrocarbyl group having 1 to 6 carbon atoms that may be substituted with a halogen atom, a saturated hydrocarbyloxy group having 1 to 6 carbon atoms that may be substituted with a halogen atom, or a saturated hydrocarbylcarbonyloxy group having 2 to 8 carbon atoms that 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, 3, 4, 5, or 6, each R 31 They may be the same or different from each other. When e is 2, 3 or 4, each R 32 They may be the same as or different from each other.

[0206] In formula (B5), f1 is 0 or 1. f2 is 0, 1 or 2. When f2 is 0, it is a benzene skeleton; when it is 1, it is a naphthalene skeleton; and when it is 2, it is an anthracene skeleton. f3 is 0, 1, 2, 3, 4 or 5. When f2 is 0, f3 is preferably 0, 1, 2 or 3, and when f2 is 1 or 2, f3 is preferably 0, 1, 2, 3 or 4.

[0207] In formula (B5), R A These are a hydrogen atom, a fluorine atom, a methyl group, or a trifluoromethyl group.

[0208] In formula (B5), R 33 This is a saturated hydrocarbyl group having 1 to 20 carbon atoms, a saturated hydrocarbyloxy group having 1 to 20 carbon atoms, a saturated hydrocarbylcarbonyloxy group having 2 to 20 carbon atoms, a saturated hydrocarbyloxyhydrocarbyl group having 2 to 20 carbon atoms, a saturated hydrocarbylthiohydrocarbyl group having 2 to 20 carbon atoms, a halogen atom, a nitro group, or a cyano group, and when f2 is 1 or 2, it may also be a hydroxyl group. The saturated hydrocarbyl group, saturated hydrocarbyloxy group, saturated hydrocarbylcarbonyloxy group, saturated hydrocarbyloxyhydrocarbyl group, and saturated hydrocarbylthiohydrocarbyl group may be linear, branched, or cyclic. When f3 is 2, 3, 4, or 5, each R 33They may be the same as or different from each other.

[0209] In formula (B5), A 4 A is a single bond or a saturated hydrocarbylene group having 1 to 10 carbon atoms, and some of the -CH2- in the saturated hydrocarbylene group may be substituted with -O-. The saturated hydrocarbylene group may be linear, branched, or cyclic, and a specific example thereof is A in formula (B1). 1 Examples similar to those given in the explanation can be cited.

[0210] When at least one of the repeating units B3 to B5 is used as a constituent unit of the polymer, in addition to the etching resistance of the aromatic ring, the addition of a ring structure to the main chain enhances etching resistance and EB irradiation resistance during pattern inspection.

[0211] To obtain the effect of improving etching resistance, the content of repeating units B3 to B5 is preferably 5 mol% or more of the total repeating units constituting the polymer. Furthermore, the content of repeating units B3 to B5 is preferably 25 mol% or less, and more preferably 20 mol% or less of the total repeating units constituting the polymer. If the amount introduced when there is no functional group or when the functional group is not a hydroxyl group is 25 mol% or less, it is preferable because there is no risk of development defects occurring. Repeating units B3 to B5 may be used individually or in combination of two or more types.

[0212] The polymer preferably contains at least one repeating unit selected from repeating units B1, B2, and B3 to B5, as this is advantageous in achieving both high etching resistance and resolution. In this case, it is preferable that these repeating units make up 60 mol% or more of the total repeating units of the polymer, more preferably 70 mol% or more, even more preferably 80 mol% or more, and even more preferably 90 mol% or more.

[0213] The polymer may contain at least one selected from the following repeating units: a repeating unit represented by formula (B6) (hereinafter also referred to as repeating unit B6), a repeating unit represented by formula (B7) (hereinafter also referred to as repeating unit B7), a repeating unit represented by formula (B8) (hereinafter also referred to as repeating unit B8), a repeating unit represented by formula (B9) (hereinafter also referred to as repeating unit B9), and a repeating unit represented by formula (B10) (hereinafter also referred to as repeating unit B10). [ka]

[0214] In formulas (B6) to (B10), R A These are, independently, a hydrogen atom, a fluorine atom, a methyl group, or a trifluoromethyl group. 1 This is a phenylene group which may have a single bond or a substituent. 2 This is a single bond, **-C(=O)-OZ 21 -,**-C(=O)-NH-Z 21 - or **-OZ 21 - is Z 21 This is a divalent group obtained by combining an aliphatic hydrocarbylene group, a phenylene group, or a combination thereof, having 1 to 6 carbon atoms, and may contain a halogen atom, a carbonyl group, an ester bond, an ether bond, or a hydroxyl group. 3 These are single bonds, ether bonds, ester bonds, amide bonds, sulfonic acid ester bonds, sulfonamide bonds, carbonate bonds, or carbamate bonds. 4 This is a single bond, or a divalent group obtained by combining an aliphatic hydrocarbylene group, a phenylene group, or a combination thereof, and may contain a halogen atom, a carbonyl group, an ester bond, an ether bond, or a hydroxyl group. 5 Each of these independently comprises a single bond, a phenylene group which may have substituents, a naphthylene group which may have substituents, or a *-C(=O)-OZ 51 - is Z 51This is an aliphatic hydrocarbylene group, a phenylene group, or a naphthylene group having 1 to 10 carbon atoms, and the aliphatic hydrocarbylene group may contain a halogen atom, a hydroxyl group, an ether bond, an ester bond, or a lactone ring. 6 These are single bonds, ether bonds, ester bonds, amide bonds, sulfonic acid ester bonds, sulfonamide bonds, carbonate bonds, or carbamate bonds. 7 Each of these is independently a single bond, ***-Z 71 -C(=O)-O-, ***-C(=O)-NH-Z 71 -or ***-OZ 71 -It is. It is. Z 71 This is a hydrocarbylene group having 1 to 20 carbon atoms, which may contain heteroatoms. 8 These are, independently, single bonds, ****-Z 81 -C(=O)-O-,****-C(=O)-NH-Z 81 -or ****-OZ 81 - is Z 81 This is a hydrocarbylene group having 1 to 20 carbon atoms, which may contain heteroatoms. 9 This includes single bonds, methylene groups, ethylene groups, phenylene groups, fluorinated phenylene groups, trifluoromethyl groups, and *-C(=O)-OZ. 91 -, *-C(=O)-N(H)-Z 91 -or *-OZ 91 - is Z 91 This is a phenylene group substituted with an aliphatic hydrocarbylene group, phenylene group, fluorinated phenylene group, or trifluoromethyl group having 1 to 6 carbon atoms, and may contain a carbonyl group, ester bond, ether bond, or hydroxyl group. * represents a bond with a carbon atom of the main chain. ** represents Z 1 This represents a combination with Z. *** represents Z 6 This represents a combination with Z. **** is Z 7 This represents a combination of two things.

[0215] Z 21 , Z 51 and Z 91The aliphatic hydrocarbylene group represented by can be linear, branched, or cyclic, and 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- Examples include alkanediyl groups such as 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, and hexane-1,6-diyl group; cycloalkanediyl groups such as cyclopropanediyl group, cyclobutanediyl group, cyclopentanediyl group, and cyclohexanediyl group; and groups obtained by combining these.

[0216] Z 71 and Z 81 The hydrocarbylene group, which may contain a heteroatom represented by , may be saturated or unsaturated, and may be linear, branched, or cyclic. Specific examples are listed below, but are not limited to these. [ka] (In the equation, dashed lines represent connections.)

[0217] In formula (B6), R 41 and R 42Each of these is independently a hydrocarbyl group having 1 to 20 carbon atoms, which may contain heteroatoms. The hydrocarbyl group may be saturated or unsaturated, and may be linear, branched, or cyclic. Specific examples include C1-C20 alkyl groups such as methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, and tert-butyl groups; C3-C20 cyclic saturated hydrocarbyl groups such as cyclopropyl, cyclopentyl, cyclohexyl, cyclopropylmethyl, 4-methylcyclohexyl, cyclohexylmethyl, norbornyl, and adamantyl groups; C2-C20 alkenyl groups such as vinyl, 1-propenyl, 2-propenyl, butenyl, and hexenyl groups; C3-C20 cyclic unsaturated hydrocarbyl groups such as cyclohexenyl; C6-C20 aryl groups such as phenyl, naphthyl, and thienyl groups; C7-C20 aralkyl groups such as benzyl, 1-phenylethyl, and 2-phenylethyl groups; and groups obtained by combining these, but aryl groups are preferred. Furthermore, some or all of the hydrogen atoms of the hydrocarbyl group may be substituted with a group containing a heteroatom such as an oxygen atom, sulfur atom, nitrogen atom, or halogen atom, and some of the -CH2- of the hydrocarbyl group may be substituted with a group containing a heteroatom such as an oxygen atom, sulfur atom, or nitrogen atom, and as a result, it may contain a hydroxyl 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 sulfonic acid ester bond, a carbonate bond, a lactone ring, a sultone ring, a carboxylic acid anhydride (-C(=O)-OC(=O)-), a haloalkyl group, etc.

[0218] Also, R 41 and R 42 However, they may bond with each other to form a ring with the sulfur atom to which they are bonded. Specific examples of such a ring include those represented by the following formula. [ka] (In the formula, the dashed line represents Z 4 (This is a combination of the two.)

[0219] Specific examples of cations of repeating unit B6 are listed below, but are not limited to these. Note that in the following formula, R A This is the same as described above. [ka]

[0220] [ka]

[0221] [ka]

[0222] [ka]

[0223] [ka]

[0224] [ka]

[0225] [ka]

[0226] [ka]

[0227] [ka]

[0228] [ka]

[0229] In formula (B6), M - The first is a non-nucleophilic counterion. Preferred non-nucleophilic counterions include halide ions, sulfonate anions, imidate anions, and methidate anions. Specific examples of halide ions include chloride ions and bromide ions. Specific examples of sulfonate anions (sulfonate ions) include fluoroalkyl sulfonate ions such as triflate ions, 1,1,1-trifluoroethanesulfonate ions, and nonafluorobutanesulfonate ions; aryl sulfonate ions such as tosylate ions, benzenesulfonate ions, 4-fluorobenzenesulfonate ions, and 1,2,3,4,5-pentafluorobenzenesulfonate ions; and alkyl sulfonate ions such as mesylate ions and butanesulfonate ions. Specific examples of imidate anions (imide ions) include bis(trifluoromethylsulfonyl)imide ions, bis(perfluoroethylsulfonyl)imide ions, and bis(perfluorobutylsulfonyl)imide ions. Specific examples of the methidate anion (methide ion) mentioned above include tris(trifluoromethylsulfonyl)methide ion and tris(perfluoroethylsulfonyl)methide ion.

[0230] Other examples of the aforementioned non-nucleophilic counterions include anions represented by any of the following formulas (B6-1) to (B6-4). [ka]

[0231] In formula (B6-1), R fa R is a hydrocarbyl group having 1 to 40 carbon atoms, which may contain a fluorine atom or a heteroatom. The hydrocarbyl group may be saturated or unsaturated, and may be linear, branched, or cyclic. A specific example is R in formula (B6-1-1) described later. fa1Examples of hydrocarbyl groups represented by the symbol shown are similar to those exemplified.

[0232] The anion represented by formula (B6-1) is preferably the one represented by the following formula (B6-1-1). [ka]

[0233] In formula (B6-1-1), Q 1 and Q 2 Each of these is independently a hydrogen atom, a fluorine atom, or a fluorinated saturated hydrocarbyl group having 1 to 6 carbon atoms, but to improve solvent solubility, it is preferable that at least one of them is a trifluoromethyl group. m is 0, 1, 2, 3, or 4, but it is particularly preferable that it is 1. R fa1 This is a hydrocarbyl group having 1 to 35 carbon atoms, which may contain heteroatoms. The heteroatoms are preferably oxygen atoms, nitrogen atoms, sulfur atoms, halogen atoms, etc., with oxygen atoms being more preferred. From the viewpoint of obtaining high resolution in fine pattern formation, the hydrocarbyl group having 6 to 30 carbon atoms is particularly preferred.

[0234] In formula (B6-1-1), R fa1The C1-C35 hydrocarbyl group represented by can be saturated or unsaturated, and can be linear, branched, or cyclic. Specific examples include C1-C35 alkyl groups such as methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, pentyl, neopentyl, hexyl, heptyl, 2-ethylhexyl, nonyl, undecyl, tridecyl, pentadecyl, heptadecyl, and eicosyl; cyclopentyl, cyclohexyl, 1-adamantyl, 2-adamantyl, 1-adamantylmethyl, norbornyl, norbornyl Examples include cyclic saturated hydrocarbyl groups with 3 to 35 carbon atoms, such as nylmethyl, tricyclodecyl, tetracyclododecyl, tetracyclododecylmethyl, and dicyclohexylmethyl; unsaturated aliphatic hydrocarbyl groups with 2 to 35 carbon atoms, such as 2-propenyl and 3-cyclohexenyl; aryl groups with 6 to 35 carbon atoms, such as phenyl, 1-naphthyl, 2-naphthyl, and 9-fluorenyl; aralkyl groups with 7 to 35 carbon atoms, such as benzyl and diphenylmethyl; and groups obtained by combining these.

[0235] Furthermore, some or all of the hydrogen atoms of the hydrocarbyl group may be substituted with a group containing a heteroatom such as an oxygen atom, sulfur atom, nitrogen atom, or halogen atom, and some of the -CH2- of the hydrocarbyl group may be substituted with a group containing a heteroatom such as an oxygen atom, sulfur atom, or nitrogen atom, and as a result, it may contain a hydroxyl group, a fluorine atom, a chlorine atom, a bromine atom, an iodine atom, a cyano group, a nitro group, a carbonyl group, an ether bond, an ester bond, a sulfonic acid ester bond, a carbonate bond, a lactone ring, a sultone ring, a carboxylic acid anhydride (-C(=O)-OC(=O)-), a haloalkyl group, etc. Specific examples of hydrocarbyl groups containing heteroatoms include tetrahydrofuryl group, methoxymethyl group, ethoxymethyl group, methylthiomethyl group, acetamidomethyl group, trifluoroethyl group, (2-methoxyethoxy)methyl group, acetoxymethyl group, 2-carboxy-1-cyclohexyl group, 2-oxopropyl group, 4-oxo-1-adamantyl group, and 3-oxocyclohexyl group.

[0236] In formula (B6-1-1), L a1 The bond can be a single bond, an ether bond, an ester bond, a sulfonic acid ester bond, a carbonate bond, or a carbamate bond, but from a synthetic viewpoint, an ether bond or an ester bond is preferred, and an ester bond is even more preferred.

[0237] Specific examples of anions represented by formula (B6-1) are listed below, but are not limited to these. Note that in the formula below, Q 1 This is the same as above, and Ac is an acetyl group. [ka]

[0238] [ka]

[0239] [ka]

[0240] [ka]

[0241] [ka]

[0242] [ka]

[0243] [ka]

[0244] [ka]

[0245] [ka]

[0246] [ka]

[0247] [ka]

[0248] [ka]

[0249] In formula (B6-2), R fb1 and R fb2 Each of these is a hydrocarbyl group having 1 to 40 carbon atoms, which may independently contain a fluorine atom or a heteroatom. The hydrocarbyl group may be saturated or unsaturated, and may be linear, branched, or cyclic. A specific example is R in formula (B6-1-1). fa1 Examples of hydrocarbyl groups represented by R include those similar to those exemplified. fb1 and R fb2 Preferably, R is a fluorine atom or a linear fluorinated alkyl group having 1 to 4 carbon atoms. fb1 and R fb2 However, they bond to each other, and the groups to which they bond (-CF2-SO2-N - It may form a ring with -SO2-CF2-), in which case R fb1 and R fb2 The groups obtained by the bonding of these groups are preferably fluorinated ethylene groups or fluorinated propylene groups.

[0250] In formula (B6-3), R fc1 , R fc2 and R fc3Each of these is a hydrocarbyl group having 1 to 40 carbon atoms, which may independently contain a fluorine atom or a heteroatom. The hydrocarbyl group may be saturated or unsaturated, and may be linear, branched, or cyclic. A specific example is R in formula (B6-1-1). fa1 Examples of hydrocarbyl groups represented by R include those similar to those exemplified. fc1 , R fc2 and R fc3 Preferably, R is a fluorine atom or a linear fluorinated alkyl group having 1 to 4 carbon atoms. fc1 and R fc2 However, they bond to each other and the group to which they bond (-CF2-SO2-C - It may form a ring with -SO2-CF2-), in which case R fc1 and R fc2 The groups obtained by the bonding of these groups are preferably fluorinated ethylene groups or fluorinated propylene groups.

[0251] In formula (B6-4), R fd R is a hydrocarbyl group having 1 to 40 carbon atoms, which may contain heteroatoms. The hydrocarbyl group may be saturated or unsaturated, and may be linear, branched, or cyclic. A specific example is R in formula (B6-1-1). fa1 Examples of hydrocarbyl groups represented by the same formula as those exemplified above include those shown.

[0252] Specific examples of anions represented by formula (B6-4) are listed below, but are not limited to these. [ka]

[0253] [ka]

[0254] Further examples of the aforementioned non-nucleophilic counterions include anions having an aromatic ring substituted with an iodine or bromine atom. A specific example of such anion is represented by the following formula (B6-5). [ka]

[0255] In equation (B6-5), x is 1, 2, or 3. y is 1, 2, 3, 4, or 5. z is 0, 1, 2, or 3, where 1 ≤ y + z ≤ 5. y is preferably 1, 2, or 3, more preferably 2 or 3. z is preferably 0, 1, or 2.

[0256] In formula (B6-5), X BI is an iodine atom or a bromine atom. When x and / or y are 2 or more, each X BI They may be the same as or different from each other.

[0257] In formula (B6-5), L 11 This is a saturated hydrocarbylene group having 1 to 6 carbon atoms, which may contain a single bond, an ether bond, or an ester bond, or an ether bond or an ester bond. The saturated hydrocarbylene group may be linear, branched, or cyclic.

[0258] In formula (B6-5), L 12 When x is 1, it is a single bond or a divalent linking group having 1 to 20 carbon atoms, and when x is 2 or 3, it is a (x+1) valent linking group having 1 to 20 carbon atoms, and the linking group may contain an oxygen atom, a sulfur atom, or a nitrogen atom.

[0259] In formula (B6-5), R feThis may include a hydroxyl group, a carboxyl group, a fluorine atom, a chlorine atom, a bromine atom, or an amino group, or a fluorine atom, a chlorine atom, a bromine atom, a hydroxyl group, an amino group, or an ether bond, and may contain a C1-C20 hydrocarbyl group, a C1-C20 hydrocarbyloxy group, a C2-C20 hydrocarbylcarbonyl group, a C2-C20 hydrocarbyloxycarbonyl group, a C2-C20 hydrocarbylcarbonyloxy group, or a C1-C20 hydrocarbylsulfonyloxy group, or -N(R feA )(R feB ), -N(R feC )-C(=O)-R feD Or -N(R feC )-C(=O)-OR feD That is. R feA and R feB Each of these is independently a hydrogen atom or a saturated hydrocarbyl group having 1 to 6 carbon atoms. feC R is a hydrogen atom or a saturated hydrocarbyl group having 1 to 6 carbon atoms, and may also contain a halogen atom, a hydroxyl group, a saturated hydrocarbyloxy group having 1 to 6 carbon atoms, a saturated hydrocarbylcarbonyl group having 2 to 6 carbon atoms, or a saturated hydrocarbylcarbonyloxy group having 2 to 6 carbon atoms. feD This is an aliphatic hydrocarbyl group having 1 to 16 carbon atoms, an aryl group having 6 to 12 carbon atoms, or an aralkyl group having 7 to 15 carbon atoms, and may contain a halogen atom, a hydroxyl group, a saturated hydrocarbyloxy group having 1 to 6 carbon atoms, a saturated hydrocarbylcarbonyl group having 2 to 6 carbon atoms, or a saturated hydrocarbylcarbonyloxy group having 2 to 6 carbon atoms. The aliphatic hydrocarbyl group may be saturated or unsaturated, and may be linear, branched, or cyclic. The hydrocarbyl group, hydrocarbyloxy group, hydrocarbylcarbonyl group, hydrocarbyloxycarbonyl group, hydrocarbylcarbonyloxy group, and hydrocarbylsulfonyloxy group may be linear, branched, or cyclic. When x and / or z is 2 or more, each R fe They may be the same as or different from each other.

[0260] Of these, R feExamples include hydroxyl groups, -N(R feC )-C(=O)-R feD , -N(R feC )-C(=O)-OR feD Fluorine atoms, chlorine atoms, bromine atoms, methyl groups, methoxy groups, etc. are preferred.

[0261] In formula (B6-5), Rf 11 ~Rf 14 Each of these is independently a hydrogen atom, a fluorine atom, or a trifluoromethyl group, but at least one of these is either a fluorine atom or a trifluoromethyl group. Also, Rf 11 and Rf 12 These may combine to form a carbonyl group. In particular, Rf 13 and Rf 14 It is preferable that both are fluorine atoms.

[0262] Specific examples of anions represented by formula (B6-5) are listed below, but are not limited to these. Note that in the following formula, X BI This is the same as described above. [ka]

[0263] [ka]

[0264] [ka]

[0265] [ka]

[0266] [ka]

[0267]

change

[0268]

change

[0269]

change

[0270]

change

[0271]

change

[0272]

change

[0273]

change

[0274]

change

[0275]

change

[0276]

change

[0277]

change

[0278]

change

[0279]

change

[0280]

change

[0281]

change

[0282]

change

[0283]

change

[0284]

change

[0285]

change

[0286] As the non-nucleophilic counterions, the following can also be used: a fluorobenzenesulfonic acid anion bonded to an aromatic group containing an iodine atom, as described in Japanese Patent No. 6648726; an anion having a mechanism for decomposition by acid, as described in International Publication No. 2021 / 200056 and Japanese Patent Application Publication No. 2021-70692; an anion having a cyclic ether group, as described in Japanese Patent Application Publication No. 2018-180525 and Japanese Patent Application Publication No. 2021-35935; and an anion described in Japanese Patent Application Publication No. 2018-92159.

[0287] As the non-nucleophilic counterions, anions of bulky benzenesulfonic acid derivatives that do not contain fluorine atoms, as described in Japanese Patent Publication No. 2006-276759, Japanese Patent Publication No. 2015-117200, Japanese Patent Publication No. 2016-65016, and Japanese Patent Publication No. 2019-202974, as well as benzenesulfonic acid anions or alkylsulfonic acid anions that do not contain fluorine atoms bonded to an aromatic group containing an iodine atom, as described in Japanese Patent No. 6645464.

[0288] As the non-nucleophilic counterion, other options include the bissulfonic acid anion described in Japanese Patent Publication No. 2015-206932, the sulfonamide or sulfonimide anion described in International Publication No. 2020 / 158366, which has a sulfonic acid on one end and a different sulfonamide or sulfonimide on the other, and the sulfonate anion described in Japanese Patent Publication No. 2015-24989.

[0289] In formulas (B7) and (B8), g1 and g2 are independently 0, 1, 2, or 3, but 1 is preferred.

[0290] In equation (B9), h1 is either 0 or 1. h2 is either 0, 1, 2, 3, or 4. h3 is either 0, 1, 2, 3, or 4. However, when h1 is 0, 0 ≤ h2 + h3 ≤ 4, and when h1 is 1, 0 ≤ h2 + h3 ≤ 6.

[0291] In formulas (B7), (B8) and (B9), L 1These are single bonds, ether bonds, ester bonds, carbonyl groups, sulfonic acid ester bonds, sulfonamide bonds, carbonate bonds, or carbamate bonds. Of these, ether bonds, ester bonds, and carbonyl groups are preferred from a synthetic viewpoint, and ester bonds and carbonyl groups are more preferred.

[0292] In formula (B7), Rf 1 and Rf 2 Each of these is independently a fluorine atom or a fluorinated saturated hydrocarbyl group having 1 to 6 carbon atoms. Of these, Rf 1 and Rf 2 To increase the acid strength of the generated acid, it is preferable that all atoms be fluorine atoms. Rf 3 and Rf 4 These are, independently, a hydrogen atom, a fluorine atom, or a fluorinated saturated hydrocarbyl group having 1 to 6 carbon atoms. Of these, Rf is used to improve solvent solubility. 3 and Rf 4 At least one of them is preferably a trifluoromethyl group.

[0293] In formula (B8), Rf 5 and Rf 6 Each of these is independently a hydrogen atom, a fluorine atom, or a fluorinated saturated hydrocarbyl group having 1 to 6 carbon atoms. However, all Rf 5 and Rf 6 These cannot simultaneously become hydrogen atoms. Of these, Rf 5 and Rf 6 At least one of them is preferably a trifluoromethyl group.

[0294] In formula (B9), Rf 7 Rf is a fluorine atom, a fluorinated alkyl group having 1 to 6 carbon atoms, a fluorinated alkoxy group having 1 to 6 carbon atoms, or a fluorinated alkylthio group having 1 to 6 carbon atoms. 7Preferably, the Rf is a fluorine atom, a trifluoromethyl group, a difluoromethyl group, a trifluoromethoxy group, a difluoromethoxy group, a trifluoromethylthio group, or a difluoromethylthio group, and more preferably a fluorine atom, a trifluoromethyl group, or a trifluoromethoxy group. When h2 is 2, 3, or 4, each Rf 7 They may be the same as or different from each other.

[0295] In formula (B9), R 43 This is a C1-C20 hydrocarbyl group which may contain halogen atoms other than fluorine atoms, or heteroatoms. The hydrocarbyl group may be saturated or unsaturated, and may be linear, branched, or cyclic. For example, in the explanation of formula (A), R 2 Examples of hydrocarbyl groups represented by the formula are similar to those exemplified, but are not limited to these. Also, when h3 is 2, 3, or 4, each R 43 They may be the same as or different from each other.

[0296] Also, when h3 is 2, 3, or 4, multiple R 43 These elements may bond with each other to form a ring with the carbon atoms to which they are bonded. Specific examples of the ring formed in this case include cyclopropane rings, cyclobutane rings, cyclopentane rings, cyclohexane rings, norbornane rings, adamantane rings, etc. Furthermore, some or all of the hydrogen atoms in the ring may be substituted with groups containing heteroatoms such as oxygen atoms, sulfur atoms, nitrogen atoms, halogen atoms, etc., and some of the -CH2- in the ring may be substituted with groups containing heteroatoms such as oxygen atoms, sulfur atoms, nitrogen atoms, etc. As a result, the ring may contain hydroxyl groups, fluorine atoms, chlorine atoms, bromine atoms, iodine atoms, cyano groups, carbonyl groups, ether bonds, ester bonds, sulfonic acid ester bonds, carbonate bonds, lactone rings, sultone rings, carboxylic acid anhydrides (-C(=O)-OC(=O)-), haloalkyl groups, etc.

[0297] Specific examples of anions with repeating unit B7 are shown below, but are not limited to these. Note that in the following formula, R A The same as above, and Me is a methyl group. [ka]

[0298] [ka]

[0299] [ka]

[0300] [ka]

[0301] [ka]

[0302] [ka]

[0303] [ka]

[0304] [ka]

[0305] [ka]

[0306] [ka]

[0307] [ka]

[0308] [ka]

[0309] [ka]

[0310] Specific examples of anions with repeating unit B8 are shown below, but are not limited to these. Note that in the following formula, R A This is the same as described above. [ka]

[0311] [ka]

[0312] [ka]

[0313] [ka]

[0314] [ka]

[0315] [ka]

[0316] [ka]

[0317] [ka]

[0318] [ka]

[0319] [ka]

[0320] [ka]

[0321] Specific examples of anions with repeating unit B9 are shown below, but are not limited to these. Note that in the following formula, R A This is the same as described above. [ka]

[0322] [ka]

[0323] [ka]

[0324] [ka]

[0325] [ka]

[0326]

change

[0327]

change

[0328]

change

[0329]

change

[0330]

change

[0331]

change

[0332]

change

[0333]

change

[0334]

change

[0335]

change

[0336]

change

[0337] [ka]

[0338] Specific examples of anions with repeating unit B10 are shown below, but are not limited to these. Note that in the following formula, R A This is the same as described above. [ka]

[0339] In formulas (B7) to (B10), A + This is an onium cation. The onium cation is preferably a sulfonium cation or an iodonium cation. Specific examples of the sulfonium cation include, but are not limited to, those exemplified as specific examples of sulfonium cations represented by formula (Z-1) or formula (Z-3). Specific examples of the iodonium cation include, but are not limited to, those exemplified as specific examples of iodonium cations represented by formula (Z-2).

[0340] The specific structures of repeating units B6 to B10 include any combination of the anions and cations mentioned above.

[0341] Repeating units B6 to B10 are units that generate acid when irradiated with high-energy rays. It is believed that the inclusion of these units in the polymer moderately suppresses acid diffusion, resulting in a pattern with reduced LER. Furthermore, the inclusion of these units in the polymer suppresses the phenomenon of acid volatilizing from the exposed areas and reattaching to the unexposed areas during baking in a vacuum, which is thought to be effective in reducing LER and minimizing shape degradation due to unwanted film loss in the unexposed areas.

[0342] Of the repeating units B6 to B10, repeating units B7 to B10 are preferred for processing photomask blanks because their acid strength is optimal for suppressing acid diffusion and designing acid-unstable groups of polymers, and repeating units B8, B9, and B10 are even more preferred.

[0343] Repeating units B6 to B10 are preferably introduced in an amount of 0.1 to 30 mol%, and more preferably in an amount of 0.5 to 20 mol%, of the total repeating units of the polymer. Repeating units B6 to B10 may be used individually or in combination of two or more types.

[0344] The content of repeating units having an aromatic ring skeleton in the total repeating units of the polymer is preferably 65 mol% or more, more preferably 75 mol% or more, and even more preferably 85 mol% or more. If repeating units B6 to B10 are not included, it is preferable that all units have an aromatic ring skeleton.

[0345] The polymer may contain commonly used (meth)acrylic acid ester units protected by acid-unstable groups, or (meth)acrylic acid ester units having adhesive groups such as lactone structures or hydroxyl groups other than phenolic hydroxyl groups. While these repeating units allow for fine-tuning of the properties of the resist film, they are not required to be included.

[0346] Examples of (meth)acrylic acid ester units having the aforementioned adhesive group include the repeating unit represented by the following formula (B11) (hereinafter also referred to as repeating unit B11), the repeating unit represented by the following formula (B12) (hereinafter also referred to as repeating unit B12), and the repeating unit represented by the following formula (B13) (hereinafter also referred to as repeating unit B13). These units do not exhibit acidity and can be used auxiliaryly as units that provide adhesion to the substrate or as units that adjust solubility. [ka]

[0347] In formulas (B11) to (B13), R A These are, independently, a hydrogen atom, a fluorine atom, a methyl group, or a trifluoromethyl group. 51 R is either an -O- or a methylene group. 52 R is a hydrogen atom or a hydroxyl group. 53 i is a saturated hydrocarbyl group having 1 to 4 carbon atoms. i is 0, 1, 2, or 3.

[0348] When repeating units B11 to B13 are included, their content is preferably 0 to 20 mol%, and more preferably 0 to 10 mol%, of the total repeating units of the polymer. Repeating units B14 to B16 may be used individually or in combination of two or more.

[0349] The aforementioned polymer can be synthesized by copolymerizing each monomer, which is optionally protected with a protecting group, using known methods, and then performing a deprotection reaction as necessary. The copolymerization reaction is not particularly limited, but radical polymerization and anionic polymerization are preferred. For these methods, refer to Japanese Patent Application Publication No. 2004-115630.

[0350] The polymer preferably has a weight-average molecular weight (Mw) of 1,000 to 50,000, and more preferably 2,000 to 20,000. If Mw is 1,000 or more, there is no risk of phenomena such as the pattern heads becoming rounded, reducing resolution, and LER degradation, as is conventionally known. On the other hand, if Mw is 50,000 or less, there is no risk of LER degradation, especially when forming patterns with a pattern line width of 100 nm or less. In this invention, Mw is a polystyrene-converted measurement value obtained by gel permeation chromatography (GPC) using THF or DMF as a solvent.

[0351] The polymer preferably has a narrow dispersion with a molecular weight distribution (Mw / Mn) of preferably 1.0 to 2.0, more preferably 1.0 to 1.9, and even more preferably 1.0 to 1.8. When the dispersion is narrow in this way, after development, no foreign matter will be generated on the pattern, and the shape of the pattern will not deteriorate.

[0352] Furthermore, regarding the base polymer design, the dissolution rate in alkaline developer is preferably 10 nm / min or less, more preferably 7 nm / min or less, and even more preferably 5 nm / min or less. In advanced generations, when the coated film on the substrate is in the thin film region (100 nm or less), the effect of pattern film reduction on alkaline development becomes significant, and if the alkali dissolution rate of the polymer is greater than 10 nm / min, the pattern collapses, making it impossible to form fine patterns. This is particularly noticeable in the fabrication of photomasks, where defect-free conditions are required, as the development process tends to be more intense. In this invention, the dissolution rate of the base polymer in alkaline developer is calculated from the amount of film reduction when a polymer solution (polymer concentration: 16.7% by mass, solvent: propylene glycol monomethyl ether acetate (PGMEA)) is spin-coated onto an 8-inch silicon wafer, baked at 100°C for 90 seconds to form a film with a thickness of 1000 nm, and then developed with a 2.38% by mass aqueous solution of tetramethylammonium hydroxide (TMAH) at 23°C for 100 seconds.

[0353] The base polymer of component (B) may include other polymers other than the polymer mentioned above. Other polymers that are conventionally known as base polymers for resist compositions can be used. The content of other polymers is not particularly limited, as long as it does not impair the effects of the present invention.

[0354] [(C) Organic Solvents] The resist composition of the present invention may contain an organic solvent as component (C). The organic solvent is not particularly limited as long as it is capable of dissolving each component. Examples of such organic solvents include ketones such as cyclohexanone, cyclopentanone, methyl-2-n-pentyl ketone, and 2-heptanone, as described in paragraphs

[0144] to

[0145] of Japanese Patent Application Publication No. 2008-111103; alcohols such as 3-methoxybutanol, 3-methyl-3-methoxybutanol, 1-methoxy-2-propanol, 1-ethoxy-2-propanol, and diacetone alcohol; and propylene glycol monomethyl ether (PGME), ethylene glycol monomethyl ether, and propylene glycol monoethyl ether. Examples include ethers such as ethylene glycol monoethyl ether, propylene glycol dimethyl ether, and diethylene glycol dimethyl ether; esters such as PGMEA, propylene glycol monoethyl ether acetate, ethyl lactate (EL), ethyl pyruvate, butyl acetate, methyl 3-methoxypropionate, ethyl 3-ethoxypropionate, tert-butyl acetate, tert-butyl propionate, and propylene glycol monotert-butyl ether acetate; lactones such as γ-butyrolactone; and mixed solvents thereof. When using acid-unstable acetal groups, high-boiling point alcoholic solvents, specifically diethylene glycol, propylene glycol, glycerin, 1,4-butanediol, and 1,3-butanediol, can be added to accelerate the deprotection reaction of the acetal.

[0355] Among these organic solvents, 1-ethoxy-2-propanol, PGMEA, PGME, cyclohexanone, EL, γ-butyrolactone, and mixtures thereof are preferred.

[0356] If the chemically amplified positive resist composition of the present invention contains (C) an organic solvent, its content is preferably 200 to 10,000 parts by mass, and more preferably 400 to 5,000 parts by mass, per 80 parts by mass of (B) the base polymer. The (C) organic solvent may be used alone or as a mixture of two or more types.

[0357] [(D) Quencher] The chemically amplified positive resist composition of the present invention may optionally contain a quencher as component (D). In this invention, a quencher refers to a compound that traps the acid generated from the acid generator. This suppresses the diffusion rate of the acid generated from the acid generator when it diffuses into the resist film, and even when a substrate with a chromium-containing material on its outermost surface is used as the substrate, the influence of the acid generated in the resist film on the chromium-containing material can be suppressed.

[0358] Examples of the quencher include conventional basic compounds. Examples of conventional basic compounds include primary, secondary, and tertiary aliphatic amines, hybrid 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, carbamates, and the like. In particular, primary, secondary, and tertiary amine compounds described in paragraphs

[0146] to

[0164] of Japanese Patent Publication No. 2008-111103 are preferred, especially amine compounds having a hydroxyl group, ether bond, ester bond, lactone ring, cyano group, or sulfonic acid ester bond, or compounds having a carbamate group described in Japanese Patent Publication No. 3790649. Preferred examples include tris[2-(methoxymethoxy)ethyl]amine, tris[2-(methoxymethoxy)ethyl]amine-N-oxide, dibutylaminobenzoic acid, morpholine derivatives, and imidazole derivatives. By adding such basic compounds, it is possible to further suppress the diffusion rate of the acid in the resist film or correct its shape, for example.

[0359] Furthermore, examples of the quencher include onium salts such as sulfonium salts, iodonium salts, and ammonium salts of carboxylic acids whose α-position is not fluorinated, as described in Japanese Patent Publication No. 2008-158339. Sulfonic acids, imido acids, or methidic acids with α-position fluorinated are necessary for deprotecting acid-unstable groups, but salt exchange with onium salts whose α-position is not fluorinated releases carboxylic acids whose α-position is not fluorinated. Carboxylic acids whose α-position is not fluorinated hardly undergo deprotection reactions and therefore function as quenchers.

[0360] Examples of onium salts of carboxylic acids whose α-position is not fluorinated include those represented by the following formula (D1). [ka]

[0361] In formula (D1), R 101 This refers to a hydrocarbyl group having 1 to 40 carbon atoms, which may contain hydrogen atoms or heteroatoms, but excludes those in which the hydrogen atom bonded to the carbon atom at the α position of the carboxyl group is substituted with a fluorine atom or a fluoroalkyl group.

[0362] R 101 The hydrocarbyl group represented by may be saturated or unsaturated, and may be linear, branched, or cyclic. Specific examples 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 with 3 to 40 carbon atoms, such as decyl 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 cyclic 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-methylphenyl group) Examples include aryl groups having 6 to 40 carbon atoms, such as ethylphenyl group, 4-n-butylphenyl group, di- or trialkylphenyl group (2,4-dimethylphenyl group, 2,4,6-triisopropylphenyl group, etc.), alkylnaphthyl group (methylnaphthyl group, ethylnaphthyl group, etc.), and dialkylnaphthyl group (dimethylnaphthyl group, diethylnaphthyl group, etc.); and aralkyl groups having 7 to 40 carbon atoms, such as benzyl group, 1-phenylethyl group, and 2-phenylethyl group.

[0363] Furthermore, some or all of the hydrogen atoms of the hydrocarbyl group may be substituted with a group containing a heteroatom such as an oxygen atom, sulfur atom, nitrogen atom, or halogen atom, and some of the -CH2- of the hydrocarbyl group may be substituted with a group containing a heteroatom such as an oxygen atom, sulfur atom, or nitrogen atom, and as a result, it may contain a hydroxyl group, a cyano group, a carbonyl group, an ether bond, a thioether bond, an ester bond, a sulfonic acid ester bond, a carbonate bond, a lactone ring, a sultone ring, a carboxylic acid anhydride (-C(=O)-OC(=O)-), a haloalkyl group, etc. Examples of hydrocarbyl groups containing heteroatoms include heteroaryl groups such as thienyl groups; alkoxyphenyl groups such as 4-hydroxyphenyl, 4-methoxyphenyl, 3-methoxyphenyl, 2-methoxyphenyl, 4-ethoxyphenyl, 4-tert-butoxyphenyl, and 3-tert-butoxyphenyl groups; alkoxynaphthyl groups such as methoxynaphthyl, ethoxynaphthyl, n-propoxynaphthyl, and n-butoxynaphthyl groups; dialkoxynaphthyl groups such as dimethoxynaphthyl and diethoxynaphthyl groups; and aryloxoalkyl groups such as 2-aryl-2-oxoethyl groups such as 2-phenyl-2-oxoethyl, 2-(1-naphthyl)-2-oxoethyl, and 2-(2-naphthyl)-2-oxoethyl groups.

[0364] In formula (D1), Mq A + This 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 are the same as those exemplified as specific examples of the sulfonium cation represented by formula (Z-1) and the sulfonium cation represented by formula (Z-3). Specific examples of the iodonium cation are the same as those exemplified as specific examples of the iodonium cation represented by formula (Z-2).

[0365] The anions of the onium salt represented by formula (D1) include, but are not limited to, those listed below. [ka]

[0366] [ka]

[0367] [ka]

[0368] As the quencher, a sulfonium salt of an iodized benzene ring-containing carboxylic acid represented by the following formula (D2) can also be suitably used. [ka]

[0369] In equation (D2), s is 1, 2, 3, 4, or 5. t is 0, 1, 2, or 3, where 1 ≤ s + t ≤ 5. u is 1, 2, or 3.

[0370] In formula (D2), R 111 This includes hydroxyl groups, fluorine atoms, chlorine atoms, bromine atoms, amino groups, nitro groups, cyano groups, saturated hydrocarbyl groups with 1 to 6 carbon atoms, saturated hydrocarbyloxy groups with 1 to 6 carbon atoms, saturated hydrocarbylcarbonyloxy groups with 2 to 6 carbon atoms, saturated hydrocarbylsulfonyloxy groups with 1 to 4 carbon atoms, and -N(R 111A )-C(=O)-R 111B or -N(R 111A )-C(=O)-OR 111B The saturated hydrocarbyl group, saturated hydrocarbyloxy group, saturated hydrocarbylcarbonyloxy group, or saturated hydrocarbylsulfonyloxy group may have some or all of its hydrogen atoms substituted with halogen atoms. 111A R is a hydrogen atom or a saturated hydrocarbyl group having 1 to 6 carbon atoms.111B is a saturated hydrocarbyl group having 1 to 6 carbon atoms or an unsaturated aliphatic hydrocarbyl group having 2 to 8 carbon atoms. When t and / or u are 2 or more, each R 111 They may be the same or different from one another.

[0371] In formula (D2), L 21 This is a single bond or a (u+1) valent linking group having 1 to 20 carbon atoms, and may contain at least one selected from an ether bond, a carbonyl group, an ester bond, an amide bond, a sultone ring, a lactam ring, a carbonate bond, a halogen atom, a hydroxyl group, and a carboxyl group. The saturated hydrocarbyl group, saturated hydrocarbyloxy group, saturated hydrocarbylcarbonyloxy group, and saturated hydrocarbylsulfonyloxy group may be linear, branched, or cyclic.

[0372] In formula (D2), R 112 , R 113 and R 114 Each of these is a C1-C20 hydrocarbyl group which may independently contain a halogen atom or a heteroatom. The hydrocarbyl group may be saturated or unsaturated, and may be linear, branched, or cyclic. Specific examples include C1-C20 alkyl groups, C2-C20 alkenyl groups, C6-C20 aryl groups, C7-C20 aralkyl groups, etc. Furthermore, some or all of the hydrogen atoms of the hydrocarbyl group may be substituted with a hydroxyl group, carboxyl group, halogen atom, oxo group, cyano group, nitro group, sultone ring, sulfo group, or sulfonium salt-containing group, and some of the -CH2- of the hydrocarbyl group may be substituted with an ether bond, ester bond, carbonyl group, amide bond, carbonate bond, or sulfonic acid ester bond. 112 and R 113 However, they may bond with each other to form a ring with the sulfur atom to which they are bonded.

[0373] A specific example of the compound represented by formula (D2) is the one described in Japanese Patent Publication No. 2017-219836. The compound represented by formula (D2) exhibits high absorption, high sensitization effect, and high acid diffusion control effect.

[0374] As the quencher, a nitrogen atom-containing carboxylate compound represented by the following formula (D3) can also be used. [ka]

[0375] In equation (D3), R 121 ~R 124 These are, independently, hydrogen atoms and -L 22 -CO2 - or a hydrocarbyl group having 1 to 20 carbon atoms, which may contain heteroatoms. 121 and R 122 And, R 122 and R 123 or R 123 and R 124 These may bond with each other to form a ring with the carbon atom to which they are bonded. 22 R is a hydroxylene group having 1 to 20 carbon atoms, which may contain single bonds or heteroatoms. 125 This is a hydrocarbyl group having 1 to 20 carbon atoms, which may contain a hydrogen atom or a heteroatom.

[0376] In equation (D3), ring R r This is a ring having 2 to 6 carbon atoms, including carbon and nitrogen atoms in the formula, and some or all of the hydrogen atoms bonded to the carbon atoms of the ring are a hydrocarbyl group having 1 to 20 carbon atoms, or -L 22 -CO2 -The ring may be substituted with a sulfur atom, an oxygen atom, or a nitrogen atom. The ring may be an alicyclic ring or an aromatic ring, and is preferably a 5-membered or 6-membered ring. Specific examples include pyridine rings, pyrrole rings, pyrrolidine rings, piperidine rings, pyrazole rings, imidazoline rings, pyridazine rings, pyrimidine rings, pyrazine rings, imidazoline rings, oxazole rings, thiazole rings, morpholine rings, thiazine rings, triazole rings, and the like.

[0377] The onium carboxylate salt represented by formula (D3) contains at least one -L 22 -CO2 - It has a group. That is, R 121 ~R 124 At least one of them is -L 22 -CO2 - is and / or ring R r At least one hydrogen atom bonded to the carbon atom is -L 22 -CO2 - It has been replaced with this.

[0378] In equation (D3), MQ B + This is a sulfonium cation, an iodonium cation, or an ammonium cation, but a sulfonium cation is preferred. Specific examples of the sulfonium cation include those similar to those exemplified as specific examples of the sulfonium cation represented by formula (Z-1) and formula (Z-3).

[0379] The anions of the compound represented by formula (D3) include, but are not limited to, those listed below. [ka]

[0380] [ka]

[0381] [ka]

[0382] [ka]

[0383] [ka]

[0384] [ka]

[0385] Furthermore, a weak acidic betaine-type compound can also be used as the quencher. Specific examples are listed below, but are not limited to these. [ka]

[0386] As an example of the aforementioned quencher, a polymer-type quencher described in Japanese Patent Publication No. 2008-239918 can be cited. This enhances the rectangularity of the resist pattern by oriented on the surface of the resist film. The polymer-type quencher also has the effect of preventing film thinning of the pattern and rounding of the pattern top when a protective film for immersion lithography is applied.

[0387] If the chemically amplified positive resist composition of the present invention contains (D) a quencher, its content is preferably 0 to 50 parts by mass, and more preferably 0.1 to 40 parts by mass, relative to 80 parts by mass of the base polymer. The quencher may be used alone or in combination of two or more types.

[0388] [(E) Fluorine atom-containing polymer] The chemically amplified positive resist composition of the present invention may contain a fluorine atom-containing polymer as component (E) for the purpose of increasing contrast, suppressing chemical flare of acids during high-energy ray irradiation, shielding from acid mixing from the antistatic film during the process of coating the resist film with an antistatic film material, and suppressing unexpected and unwanted pattern degradation. This polymer may further contain at least one selected from the following repeating units: repeating unit (E1) (hereinafter also referred to as repeating unit E1), repeating unit (E2) (hereinafter also referred to as repeating unit E2), repeating unit (E3) (hereinafter also referred to as repeating unit E3), and repeating unit (E4) (hereinafter also referred to as repeating unit E4), and may also contain at least one selected from the following repeating units: repeating unit (E5) (hereinafter also referred to as repeating unit E5) and repeating unit (E6) (hereinafter also referred to as repeating unit E6). Since the fluorine atom-containing polymer also functions as a surfactant, it can prevent the re-adhesion of insoluble substances to the substrate that may occur during the development process, thus also exhibiting an effect against development defects. [ka]

[0389] In equations (E1) to (E6), j1 is 1, 2, or 3. j2 is an integer satisfying 0 ≤ j2 ≤ 5 + 2(j3) - j1. j3 is 0 or 1. k is 1, 2, or 3. R B These are, independently, a hydrogen atom, a fluorine atom, a methyl group, or a trifluoromethyl group. C Each of these is independently either a hydrogen atom or a methyl group. 201 , R 202 , R 204 and R 205 Each of these is independently a hydrogen atom or a saturated hydrocarbyl group having 1 to 10 carbon atoms. 203 , R 206 , R 207 and R 208 Each of these is independently a hydrogen atom, a C1-C15 hydrocarbyl group, a C1-C15 fluorinated hydrocarbyl group, or an acid-unstable group, and R203 , R 206 , R 207 and R 208 When is a hydrocarbyl group or a fluorinated hydrocarbyl group, an ether bond or a carbonyl group may be interposed between the carbon-carbon bonds. 209 This is a linear or branched hydrocarbyl group having 1 to 5 carbon atoms, which may have a hydrogen atom or a group containing a heteroatom between the carbon-carbon bonds. When j1 is 2 or 3, each R 209 These may be identical or different from each other. 210 This is a linear or branched hydrocarbyl group having 1 to 5 carbon atoms, which may have a heteroatom interposed between the carbon-carbon bonds. When j2 is 2 or more, each R 210 These may be identical or different from each other. 211 This is a saturated hydrocarbyl group having 1 to 20 carbon atoms in which at least one hydrogen atom is substituted with a fluorine atom, and a portion of the -CH2- of the saturated hydrocarbyl group may be substituted with an ester bond or an ether bond. 1 This is a (k+1) valent hydrocarbon group having 1 to 20 carbon atoms or a (k+1) valent fluorinated hydrocarbon group having 1 to 20 carbon atoms. 2 The bond is a single bond, *-C(=O)-O- or *-C(=O)-NH-. * represents a bond with a carbon atom in the main chain. 3 This is a single bond, -O-, *-C(=O)-OX 31 -X 32 - or *-C(=O)-NH-X 31 -X 32 - is X 31 This is a single bond or a saturated hydrocarbylene group having 1 to 10 carbon atoms. 32 A is a single bond, ester bond, ether bond, or sulfonamide bond. * indicates a bond with a carbon atom of the main chain.

[0390] In equations (E1) and (E2), R 201 , R 202 , R 204 and R 205The saturated hydrocarbyl group having 1 to 10 carbon atoms, represented by , 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, isobutyl, sec-butyl, tert-butyl, n-pentyl, n-hexyl, n-heptyl, n-octyl, n-nonyl, and n-decyl groups; and cyclic saturated hydrocarbyl groups having 3 to 10 carbon atoms such as cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl, adamantyl, and norbornyl groups. Of these, saturated hydrocarbyl groups having 1 to 6 carbon atoms are preferred.

[0391] In formulas (E1) to (E4), R 203 , R 206 , R 207 and R 208 The C1-C15 hydrocarbyl group represented by can be linear, branched, or cyclic. Specific examples include C1-C15 alkyl groups, C2-C15 alkenyl groups, and C2-C15 alkynyl groups, but C1-C15 alkyl groups are preferred. Examples of alkyl groups include, in addition to those mentioned above, methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, n-pentyl, n-hexyl, n-heptyl, n-octyl, n-nonyl, n-decyl, n-undecyl, n-dodecyl, n-tridecyl, n-tetradecyl, and n-pentadecyl groups. Fluorinated hydrocarbyl groups include groups in which some or all of the hydrogen atoms bonded to the carbon atoms of the hydrocarbyl group mentioned above are substituted with fluorine atoms.

[0392] In formula (E4), X 1 Examples of (k+1) valent hydrocarbon groups having 1 to 20 carbon atoms, represented by , include alkyl groups having 1 to 20 carbon atoms or cyclic saturated hydrocarbyl groups having 3 to 20 carbon atoms from which k hydrogen atoms have been removed. Also, X 1Examples of (k+1) valent fluorinated hydrocarbon groups having 1 to 20 carbon atoms, as represented by the formula, include groups in which at least one hydrogen atom of the aforementioned (k+1) valent hydrocarbon group is substituted with a fluorine atom.

[0393] Specific examples of repeating units E1 to E4 are shown below, but are not limited to these. Note that in the following formula, R B This is the same as described above. [ka]

[0394] [ka]

[0395] [ka]

[0396] In formula (E5), R 109 and R 110 Examples of C1-C5 hydrocarbyl groups represented by include alkyl groups, alkenyl groups, and alkynyl groups, but alkyl groups are preferred. Examples of alkyl groups include methyl groups, ethyl groups, n-propyl groups, isopropyl groups, n-butyl groups, isobutyl groups, sec-butyl groups, and n-pentyl groups. In addition, a group containing a heteroatom such as an oxygen atom, a sulfur atom, or a nitrogen atom may be interposed between the carbon-carbon bonds of the hydrocarbyl group.

[0397] In formula (E5), -OR 109 It is preferable that R is a hydrophilic group. In this case, R 109 Preferred elements include hydrogen atoms, C1-C5 alkyl groups with oxygen atoms interposed between carbon-carbon bonds, etc.

[0398] In formula (E5), X 2 It is preferable that *-C(=O)-O- or *-C(=O)-NH-. Furthermore, R CIt is preferable that it is a methyl group. 2 The presence of a carbonyl group improves the acid trapping ability derived from the antistatic film. Also, R C When the group is a methyl group, a more rigid polymer with a higher glass transition temperature (Tg) is formed, thus suppressing acid diffusion. This results in good temporal stability of the resist film, and the resolution and pattern shape do not deteriorate.

[0399] The repeating unit E5 can be, but is not limited to, the following. Note that in the following formula, R C This is the same as described above. [ka]

[0400] [ka]

[0401] In formula (E6), X 3 The saturated hydrocarbylene group having 1 to 10 carbon atoms, represented by , 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, and 1,1-dimethylethane-1,2-diyl group.

[0402] In formula (E6), R 211 A saturated hydrocarbyl group having 1 to 20 carbon atoms, represented by , in which at least one hydrogen atom is substituted with a fluorine atom, may be linear, branched, or cyclic. Specific examples include alkyl groups having 1 to 20 carbon atoms or cyclic saturated hydrocarbyl groups having 3 to 20 carbon atoms in which at least one hydrogen atom is substituted with a fluorine atom.

[0403] Examples of repeating units E6 include, but are not limited to, those listed below. Note that in the following formula, R C This is the same as described above. [ka]

[0404] [ka]

[0405] [ka]

[0406] [ka]

[0407] The content of repeating units E1 to E4 is preferably 15 to 95 mol%, and more preferably 20 to 85 mol%, of the total repeating units of the fluorine atom-containing polymer. The content of repeating units E5 and / or E6 is preferably 5 to 85 mol%, and more preferably 15 to 80 mol%, of the total repeating units of the fluorine atom-containing polymer. Repeating units E1 to E6 may be used individually or in combination of two or more types.

[0408] (E) The fluorine atom-containing polymer may contain other repeating units besides those described above. Examples of such repeating units include those described in paragraphs

[0046] to

[0078] of Japanese Patent Application Publication No. 2014-177407. (E) If the fluorine atom-containing polymer contains other repeating units, the content thereof is preferably 50 mol% or less of the total repeating units of the fluorine atom-containing polymer.

[0409] (E) Fluorine atom-containing polymers can be synthesized by known methods, which involve copolymerizing each monomer, optionally protected with a protecting group, and then performing a deprotection reaction as necessary. The copolymerization reaction is not particularly limited, but radical polymerization and anionic polymerization are preferred. For these methods, refer to Japanese Patent Application Publication No. 2004-115630.

[0410] (E) The Mw of the fluorine atom-containing polymer is preferably 2000 to 50000, and more preferably 3000 to 20000. If the Mw is 2000 or higher, the acid does not diffuse, the resolution does not deteriorate, and the stability over time is not impaired. If the Mw is 50000 or lower, the solubility in the solvent is sufficient, and coating defects do not occur. Furthermore, the Mw / Mn of the (E) fluorine atom-containing polymer is preferably 1.0 to 2.2, and more preferably 1.0 to 1.7.

[0411] When the chemically amplified positive resist composition of the present invention contains (E) a fluorine atom-containing polymer, its content is preferably 0.01 to 30 parts by mass, and more preferably 0.1 to 20 parts by mass, per 80 parts by mass of (B) the base polymer. (E) The fluorine atom-containing polymer may be used alone or in combination of two or more types.

[0412] [(F) Other photoacid generators] The chemically amplified positive resist composition of the present invention may contain, as component (F), a photoacid generator other than the onium salt represented by formula (A) (hereinafter also referred to as "other photoacid generator"). The other photoacid generator is not particularly limited as long as it is a compound that generates acid upon irradiation with high-energy rays. Suitable photoacid generators include sulfonium salts, iodonium salts, sulfonyldiazomethane, N-sulfonyloxiimide, oxime-O-sulfonate type photoacid generators, and the like.

[0413] Specific examples of the aforementioned other photoacid generators include nonafluorobutanesulfonate, partially fluorinated sulfonates described in paragraphs

[0247] to

[0251] of Japanese Patent Publication No. 2012-189977, partially fluorinated sulfonates described in paragraphs

[0261] to

[0265] of Japanese Patent Publication No. 2013-101271, those described in paragraphs

[0122] to

[0142] of Japanese Patent Publication No. 2008-111103, and those described in paragraphs

[0080] to

[0081] of Japanese Patent Publication No. 2010-215608. Among these specific examples, arene sulfonate type or alkane sulfonate type photoacid generators are preferred because they generate an acid of appropriate strength for deprotecting the acid-unstable group of repeating unit B2.

[0414] As the photoacid generator, a salt compound containing an anion having the structure shown below is preferred. [ka]

[0415] [ka]

[0416] [ka]

[0417] [ka]

[0418] [ka]

[0419] [ka]

[0420] [ka]

[0421] [ka]

[0422] [ka]

[0423] [ka]

[0424] [ka]

[0425] Furthermore, as the photoacid generator, salt compounds containing an anion represented by the following formula (F1) are also preferred. [ka]

[0426] In equation (F1), p is 1, 2, or 3. q is 1, 2, 3, 4, or 5. r is 0, 1, 2, or 3. s1 is 0 or 1.

[0427] In formula (F1), L 31 These are single bonds, ether bonds, ester bonds, sulfonic acid ester bonds, carbonate bonds, or carbamate bonds.

[0428] In formula (F1), L 32 These are ether bonds, ester bonds, sulfonic acid ester bonds, carbonate bonds, or carbamate bonds.

[0429] In formula (F1), L CWhen p is 1, it is a single bond or a hydroxylene group having 1 to 20 carbon atoms, and when p is 2 or 3, it is a (p+1) valent hydrocarbon group having 1 to 20 carbon atoms. The hydroxylene group and the (p+1) valent hydrocarbon group may contain at least one selected from an ether bond, a carbonyl group, an ester bond, an amide bond, a sultone ring, a lactam ring, a carbonate bond, a halogen atom, a hydroxyl group, and a carboxyl group.

[0430] L C The hydroxylene group, represented by , having 1 to 20 carbon atoms, can be saturated or unsaturated, and can be linear, branched, or cyclic. Specific examples include methanediyl group, ethane-1,1-diyl group, ethane-1,2-diyl group, propane-1,3-diyl group, butane-1,4-diyl group, pentane-1,5-diyl group, hexane-1,6-diyl group, heptane-1,7-diyl group, octane-1,8-diyl group, nonane-1,9-diyl group, decane-1,10-diyl group, undecane-1,11-diyl group, dodecane-1,12-diyl group, etc. Examples include alkanediyl groups with 1 to 20 carbon atoms; cyclic saturated hydrocarbylene groups with 3 to 20 carbon atoms such as cyclopentanediyl, cyclohexanediyl, norbornanediyl, and adamantanediyl; unsaturated aliphatic hydrocarbylene groups with 2 to 20 carbon atoms such as vinylene and propene-1,3-diyl; arylene groups with 6 to 20 carbon atoms such as phenylene and naphthylene; and groups obtained by combining these. Also, L C The (p+1) valent hydrocarbon group having 1 to 20 carbon atoms, represented by , may be saturated or unsaturated, and may be linear, branched, or cyclic. Specific examples include groups obtained by removing one or two hydrogen atoms from the aforementioned specific examples of the 1 to 20 carbon atom hydrocarbylene group.

[0431] In formula (F1), Rf 21 and Rf 22 Each of these is independently a hydrogen atom, a fluorine atom, or a trifluoromethyl group, but at least one is either a fluorine atom or a trifluoromethyl group.

[0432] In formula (F1), R301 This includes a hydroxyl group, a carboxyl group, a saturated hydrocarbyl group having 1 to 6 carbon atoms, a saturated hydrocarbyloxy group having 1 to 6 carbon atoms, a saturated hydrocarbylcarbonyloxy group having 2 to 6 carbon atoms, a fluorine atom, a chlorine atom, a bromine atom, and -N(R 301A )(R 301B ), -N(R 301C )-C(=O)-R 301D or -N(R 301C )-C(=O)-OR 301D That is. R 301A and R 301B Each of these is independently a hydrogen atom or a saturated hydrocarbyl group having 1 to 6 carbon atoms. 301C R is a hydrogen atom or a saturated hydrocarbyl group having 1 to 6 carbon atoms. 301D This is a saturated hydrocarbyl group having 1 to 6 carbon atoms or an unsaturated aliphatic hydrocarbyl group having 2 to 8 carbon atoms.

[0433] R 301 , R 301A and R 301B The saturated hydrocarbyl group having 1 to 6 carbon atoms, represented by R, may be linear, branched, or cyclic. Specific examples include alkyl groups having 1 to 6 carbon atoms such as methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, n-pentyl, and n-hexyl groups; and cyclic saturated hydrocarbyl groups having 3 to 6 carbon atoms such as cyclopropyl, cyclobutyl, cyclopentyl, and cyclohexyl groups. 301 The saturated hydrocarbyl portion of the saturated hydrocarbyloxy group having 1 to 6 carbon atoms, as represented by R, is the same as the specific examples of saturated hydrocarbyl groups mentioned above. 301 Examples of the saturated hydrocarbyl portion of the saturated hydrocarbyl carbonyloxy group having 2 to 6 carbon atoms, as described above, include those having 1 to 5 carbon atoms.

[0434] R 301BThe carbon-2-carbon unsaturated aliphatic hydrocarbyl groups represented by can be linear, branched, or cyclic. Specific examples include carbon-2-carbon alkenyl groups such as vinyl, propenyl, butenyl, and hexenyl groups; carbon-2-carbon alkynyl groups such as ethynyl, propynyl, and butynyl groups; and carbon-3-carbon cyclic unsaturated aliphatic hydrocarbyl groups such as cyclohexenyl and norbornenyl groups.

[0435] In formula (F1), R 302 This is a saturated hydrocarbylene group having 1 to 20 carbon atoms or an arylene group having 6 to 20 carbon atoms, wherein some or all of the hydrogen atoms of the saturated hydrocarbylene group may be substituted with halogen atoms other than fluorine atoms, and some or all of the hydrogen atoms of the arylene group may be substituted with substituents selected from a saturated hydrocarbyl group having 1 to 20 carbon atoms, a saturated hydrocarbyloxy group having 1 to 20 carbon atoms, an aryl group having 6 to 14 carbon atoms, a halogen atom, and a hydroxyl group.

[0436] R 302 The saturated hydrocarbylene groups having 1 to 20 carbon atoms, represented by , may be linear, branched, or cyclic. Specific examples include alkane diyl groups having 1 to 20 carbon atoms, such as methanediyl, ethane-1,1-diyl, ethane-1,2-diyl, propane-1,3-diyl, butane-1,4-diyl, pentane-1,5-diyl, hexane-1,6-diyl, heptane-1,7-diyl, octane-1,8-diyl, nonane-1,9-diyl, decane-1,10-diyl, undecane-1,11-diyl, and dodecane-1,12-diyl; and cyclic saturated hydrocarbylene groups having 3 to 20 carbon atoms, such as cyclopentanediyl, cyclohexanediyl, norbornanediyl, and adamantanediyl.

[0437] R 302Specific examples of arylene groups with 6 to 20 carbon atoms, represented by , include phenylene groups, naphthylene groups, phenanthrendiyl groups, and anthracenediyl groups. The hydrocarbyl portion of the saturated hydrocarbyl group having 1 to 20 carbon atoms and the hydrocarbyloxy group having 1 to 20 carbon atoms, which are substituents on the arylene group, may be linear, branched, or cyclic. Specific examples include alkyl groups having 1 to 20 carbon atoms such as methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, n-pentyl, n-hexyl, n-octyl, n-nonyl, n-decyl, undecyl, dodecyl, tridecyl, tetradecyl, pentadecyl, heptadecyl, octadecyl, nonadecyl, and eicosyl groups; and cyclic saturated hydrocarbyl groups having 3 to 20 carbon atoms such as cyclopropyl, cyclopentyl, cyclohexyl, cyclopropylmethyl, 4-methylcyclohexyl, cyclohexylmethyl, norbornyl, and adamantyl groups. Specific examples of arylene groups having 6 to 14 carbon atoms that are substituents on the aforementioned arylene group include phenylene group, naphthylene group, phenanthrendiyl group, anthracenediyl group, and the like.

[0438] The anion represented by formula (F1) is preferably the anion represented by the following formula (F2). [ka]

[0439] In formula (F2), p, q, r, L 31 , L C and R 301 The same as above. s2 is 1, 2, 3, or 4. R 302A These are saturated hydrocarbyl groups having 1 to 14 carbon atoms, saturated hydrocarbyloxy groups having 1 to 14 carbon atoms, aryl groups having 6 to 14 carbon atoms, halogen atoms, or hydroxyl groups. Note that when s2 is 2, 3, or 4, each R 302A They may be the same as or different from each other.

[0440] Specific examples of anions represented by formula (F1) are listed below, but are not limited to these. [ka]

[0441] [ka]

[0442] [ka]

[0443] [ka]

[0444] [ka]

[0445] [ka]

[0446] [ka]

[0447] [ka]

[0448] [ka]

[0449] [ka]

[0450]

change

[0451]

change

[0452]

change

[0453]

change

[0454]

change

[0455]

change

[0456]

change

[0457]

change

[0458]

change

[0459]

change

[0460]

change

[0461] [ka]

[0462] [ka]

[0463] [ka]

[0464] [ka]

[0465] [ka]

[0466] [ka]

[0467] [ka]

[0468] (F) In other photoacid generators, a sulfonium cation or an iodonium cation is preferred as the cation paired with the anion described above. Specific examples of the sulfonium cation include, but are not limited to, those exemplified as specific examples of the sulfonium cation represented by formula (Z-1) or the sulfonium cation represented by formula (Z-3). Specific examples of the iodonium cation include, but are not limited to, those exemplified as specific examples of the iodonium cation represented by formula (Z-2).

[0469] The acid generated by the aforementioned other photoacid generators is preferably of a pKa of -2.0 or higher, and more preferably of -1.0 or higher. Furthermore, the upper limit of the pKa is preferably 2.0. The pKa values ​​were calculated using the pKa DB in the ACD / Chemsketch ver:9.04 software from Advanced Chemistry Development, Inc.

[0470] If the chemically amplified positive resist composition of the present invention contains (F) other photoacid generators, the content thereof is preferably 1 to 10 parts by mass, and more preferably 1 to 5 parts by mass, per 80 parts by mass of the base polymer. By including other photoacid generators, the amount of acid generated in the exposed areas and the dissolution inhibition of the unexposed areas can be appropriately adjusted. (F) Other photoacid generators may be used alone or in combination of two or more types.

[0471] [(G) Surfactants] The chemically amplified positive resist composition of the present invention may contain a commonly used surfactant as component (G) to improve its applicability to substrates. Numerous surfactants are known, as described in International Publication No. 2006 / 121096, Japanese Patent Publication No. 2008-102383, Japanese Patent Publication No. 2008-304590, Japanese Patent Publication No. 2004-115630, and Japanese Patent Publication No. 2005-8766, and can be selected by reference thereto.

[0472] If the chemically amplified positive resist composition of the present invention contains (G) a surfactant, its content is preferably 2 parts by mass or less, more preferably 1 part by mass or less, and preferably 0.01 parts by mass or more, per 80 parts by mass of the (B) base polymer. The (G) surfactant may be used alone or in combination of two or more types.

[0473] [Method for forming a resist pattern] The resist pattern formation method of the present invention includes the steps of forming a resist film on a substrate using the chemically amplified positive-type resist composition described above, irradiating the resist film with a pattern using high-energy rays (i.e., exposing the resist film with high-energy rays), and developing the resist film irradiated with the pattern using an alkaline developer to obtain a resist pattern.

[0474] As the substrate, for example, substrates for integrated circuit manufacturing (Si, SiO, SiO2, SiN, SiON, TiN, WSi, BPSG, SOG, organic anti-reflective coatings, etc.) or substrates for mask circuit manufacturing (Cr, CrO, CrON, MoSi2, Si, SiO, SiO2, etc.) can be used. The chemically amplified positive resist composition is applied to the substrate by a method such as spin coating to a film thickness of 0.03 to 2 μm, and this is 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.

[0475] Next, the resist film is exposed using high-energy rays to irradiate a pattern. Examples of such high-energy rays include ultraviolet rays, far-ultraviolet rays, excimer laser light (KrF, ArF, etc.), EB, EUV, X-rays, gamma rays, and synchrotron radiation.

[0476] When using ultraviolet light, far ultraviolet light, excimer laser light, EUV, X-rays, gamma rays, or synchrotron radiation as the high-energy rays, a mask is used to form the desired pattern, and the exposure amount is preferably 1 to 300 mJ / cm². 2 More preferably 10-200 mJ / cm² 2 Irradiate in such a manner. When using EB as the high-energy beam, the exposure dose is preferably 1 to 300 μC / cm². 2 More preferably 10-200 μC / cm 2 The image is drawn directly in this manner. Furthermore, the chemically amplified positive resist composition of the present invention is particularly useful for EUV or EB lithography.

[0477] In addition to conventional exposure methods, immersion methods, which involve inserting a liquid between the mask and the resist film, can also be used in some cases. In such cases, a water-insoluble protective film can be used.

[0478] Next, post-exposure baking (PEB) is performed on a hot plate, preferably at 60-150°C for 1-20 minutes, more preferably at 80-140°C for 1-10 minutes.

[0479] Subsequently, the substrate is developed using a developer solution, preferably an alkaline aqueous solution such as a 0.1-5% by mass, more preferably 2-3% by mass TMAH aqueous solution, for 0.1-3 minutes, preferably 0.5-2 minutes, by a conventional method such as the dip method, puddle method, or spray method, thereby forming the desired pattern on the substrate.

[0480] The chemically amplified positive resist composition of the present invention is particularly useful when used under conditions requiring high etching resistance, minimal change in pattern line width even when the time from exposure to PEB is extended, and a low LER (Low Emission Rate). Furthermore, the resist composition of the present invention is particularly useful for application to substrates with surfaces that are prone to pattern peeling or collapse due to difficulty in achieving good adhesion of the resist pattern. Examples of such substrates include substrates in which a chromium compound containing metallic chromium or one or more light elements selected from oxygen, nitrogen, and carbon is deposited by sputtering. The chemically amplified positive resist composition of the present invention is particularly useful for pattern formation using a photomask blank as the substrate. [Examples]

[0481] 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 apparatus used is as follows. • MALDI TOF-MS: S3000 manufactured by JEOL Ltd.

[0482] [1] Synthesis of onium salts [Example 1-1] Synthesis of onium salt PAG-1 [ka]

[0483] (1) Synthesis of intermediate In-1 Under a nitrogen atmosphere, the starting materials SM-1 (14.5g) and N,N-dimethylformamide (0.2g) were dissolved in methylene chloride (100g) in a reaction vessel, and the temperature in the reaction vessel was raised to 40°C. Then, oxalyl chloride (9.5g) was added dropwise. After the dropwise addition, the reaction vessel was aged for 2 hours while maintaining the temperature at 40°C. After aging, the reaction mixture was cooled, and water (50g) was added to stop the reaction. Methylene chloride (50g) was added to extract the target product, followed by a normal aqueous work-up, and after removing the solvent by distillation, hexane was added and recrystallization was performed to obtain 13.7g of intermediate In-1 as white crystals (yield 95%).

[0484] (2) Synthesis of onium salt PAG-1 Under a nitrogen atmosphere, intermediate In-1 (5.8g) and starting material SM-2 (5.0g) were suspended in methylene chloride (70g) in a reaction vessel. Triethylamine (1.4g) was added dropwise, and the mixture was aged at room temperature for 10 hours. After aging, water (30g) was added to stop the reaction. Methylene chloride (30g) was added to extract the target product, followed by a normal aqueous work-up. After removing the solvent by distillation, the mixture was purified by silica gel chromatography to obtain 8.6g of onium salt PAG-1 as white crystals (yield 83%).

[0485] The TOF-MS results for PAG-1 are shown below. MALDI TOF-MS: POSITIVE M + 277(C 18 H 13 OS + equivalent) NEGATIVE M - 764(C 40 H 30 NO 11 S2 - equivalent)

[0486] [Examples 1-2 to 1-10] Synthesis of onium salts PAG-2 to PAG-10 Using corresponding raw materials and known organic synthesis reactions, onium salts PAG-2 to PAG-10, represented by the following formulas, were synthesized. [ka]

[0487] [ka]

[0488] [2] Synthesis of base polymers [Synthesis Example] Synthesis of base polymers (P-1 to P-6) Each monomer was combined according to a known formulation and copolymerized in a solvent. The reaction solution was added to hexane, and the precipitated solid was washed with hexane, then isolated and dried to obtain base polymers (P-1 to P-6) with the following compositions. The compositions of the obtained base polymers are: 1 H-NMR, 13 Mw and Mw / Mn were confirmed by C-NMR using GPC (solvent: THF, standard: polystyrene). [ka]

[0489] [3] Preparation of chemically amplified positive resist compositions [Examples 2-1 to 2-50, Comparative Examples 1-1 to 1-42] Chemically amplified positive resist compositions were prepared by dissolving each component in an organic solvent in the compositions shown in Tables 1 to 3 below, and filtering the resulting solutions through a 5 nm nylon filter and a 1 nm UPE filter. The organic solvent was a mixed solvent consisting of 940 parts by mass of PGMEA, 1870 parts by mass of EL, and 1870 parts by mass of PGME.

[0490] [Table 1]

[0491] [Table 2]

[0492] [Table 3]

[0493] In Tables 1-3, the comparative photoacid generators PAG-A to PAG-E, the blending photoacid generator PAG-Z, the quenchers SQ-1 to SQ-4, and the fluorine atom-containing polymers FP-1 to FP-5 are as follows.

[0494] [ka]

[0495] [ka]

[0496] [ka]

[0497] [ka]

[0498] [4] EB lithography evaluation [Examples 3-1 to 3-50, Comparative Examples 2-1 to 2-42] Each chemically amplified positive resist composition (R-1 to R-50, CR-1 to CR-42) was spin-coated onto a 152 mm square reflective mask blank for EUV exposure, with a chromium compound on its outermost surface, using ACT-M (manufactured by Tokyo Electron Limited). The blanks were 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 obtained resist film was measured using an optical measuring instrument, NanoSpec (manufactured by Nanometrics). Measurements were taken at 81 locations within the plane of the blank substrate, excluding the outer edge portion up to 10 mm inward from the outer edge, and the average thickness and thickness range were calculated.

[0499] Next, exposure was performed using an electron beam lithography system (EBM-5000plus, manufactured by Newflare Technology Co., Ltd., accelerating voltage 50kV), followed by PEB at 110°C for 600 seconds, and development with a 2.38 mass% TMAH aqueous solution to obtain a positive type pattern.

[0500] The obtained resist patterns were evaluated as follows: The fabricated patterned mask blanks were observed using an overhead SEM (scanning electron microscope), and the optimal exposure (μC / cm²) was determined to resolve 200 nm 1:1 line and space (LS) lines at a 1:1 ratio. 2 The resolution (critical resolution) was defined as the minimum dimension at the exposure dose that resolves 200 nm LS at a 1:1 ratio, and the LER of 200 nm LS was measured by SEM. For the critical resolution of isolated space (IS), the critical resolution was defined as the minimum dimension at the exposure dose that resolves 200 nm 9:1 line and space (LS) at a 9:1 ratio. The results are shown in Tables 4 to 6.

[0501] [Table 4]

[0502] [Table 5]

[0503] [Table 6]

[0504] The chemically amplified positive resist compositions (R-1 to R-50) of the present invention all exhibited good resolution, LER, and pattern rectangularity. On the other hand, the comparative resist compositions (CR-1 to CR-42) showed degradation in resolution and LER due to insufficient optimization of acid diffusion.

[0505] [4] Residue defect evaluation [Examples 5-1 to 5-50, Comparative Examples 4-1 to 4-42] A substrate coated with resist compositions (R-1 to R-50, CR-1 to CR-42) on a reflective mask blank for EUV exposure masks was fully printed using an electron beam exposure system (EBM-5000plus, manufactured by Newflare Technology Co., Ltd., accelerating voltage 50kV) at the optimal exposure level for each resist composition. The substrate was then subjected to PEB at 110°C for 600 seconds, developed with a 2.38% by mass TMAH aqueous solution, and the development residue was evaluated using a mask defect inspection system (Lasertec M9650). The total number of defects after development is shown in Tables 7-9.

[0506] [Table 7]

[0507] [Table 8]

[0508] [Table 9]

[0509] [Table 10]

[0510] The chemically amplified positive-type resist compositions (R-1 to R-50) of the present invention all showed a lower total number of defects after development compared to the comparative resist compositions (CR-1 to CR-42).

[0511] The resist pattern formation method using the chemically amplified positive resist composition of the present invention is useful for semiconductor device manufacturing, particularly for photolithography in the processing of transmissive and reflective photomask blanks.

Claims

1. An onium salt represented by the following formula (A). 【Chemistry 1】 (In the formula, n1 is 0 or 1. n2 is 1, 2, 3, 4 or 5 when n1 is 0, and 1, 2, 3, 4, 5, 6 or 7 when n1 is 1. n3 is 0 or 1. n4 is 0, 1, 2, 3 or 4. n5 is 0, 1, 2, 3 or 4, provided that when n3 is 0, 0 ≤ n4 + n5 ≤ 4, and when n3 is 1, 0 ≤ n4 + n5 ≤ 6.) R 1 Each is independently a branched or cyclic hydrocarbyl group having 3 to 20 carbon atoms, which may contain an iodine atom or a heteroatom, and at least one R 1 S is bonded to a carbon atom adjacent to the carbon atom to which it is bonded. When n2 is 2 or more, each R 1 They may be the same or different from each other, and there may be multiple R 1 These atoms may bond with each other to form a ring with the carbon atoms to which they are bonded. R 2 This is a C1-C20 hydrocarbyl group which may contain halogen atoms other than fluorine atoms, or heteroatoms other than fluorine atoms. When n4 is 2, 3, or 4, each R 2 They may be the same or different from each other, and there may be multiple R 2 These atoms may bond with each other to form a ring with the carbon atoms to which they are bonded. R F This is a fluorine atom, a fluorinated alkyl group having 1 to 6 carbon atoms, a fluorinated alkoxy group having 1 to 6 carbon atoms, or a fluorinated alkylthio group having 1 to 6 carbon atoms. When n5 is 2, 3 or 4, each R F may be the same as or different from each other. Z + This is an onium cation.

2. The onium salt according to claim 1, which is represented by the following formula (A1). 【Chemistry 2】 (In the formula, n2, n3, n4, n5, R 1 , R 2 , R F and Z + (This is the same as above.)

3. The onium salt according to claim 2, which is represented by the following formula (A2). 【Transformation 3】 (In the formula, n3, n4, n5, R 1 , R 2 , R F and Z + (This is the same as above.)

4. Z + The onium salt according to claim 1, wherein the sulfonium cation is represented by the following formula (Z-1) or the iodonium cation is represented by the following formula (Z-2). 【Chemistry 4】 (In the formula, R ct1 ~R ct5 Each of these is independently a hydrocarbyl group having 1 to 30 carbon atoms, which may contain a halogen atom or a heteroatom. Also, R ct1 and R ct2 However, they may bond with each other to form a ring with the sulfur atom to which they are bonded.

5. Z + The onium salt according to claim 1, wherein the sulfonium cation is represented by the following formula (Z-3). 【Transformation 5】 (In the formula, m1 is 0 or 1. m2 is 0 or 1. m3 is 0 or 1. m4 is 0, 1, 2, 3 or 4. m5 is 0, 1, 2, 3 or 4. m6 is 0, 1, 2, 3, 4, 5 or 6. m7 is 0, 1, 2, 3, 4, 5 or 6. m8 is 0, 1 or 2. m9 is 0, 1 or 2. m10 is 0, 1 or 2. m11 is 0 or 1. m12 is 0, 1, 2, 3 or 4. m13 is 0, 1 or 2. m14 is 0, It is either 1 or 2. However, when m1 is 0, 0 ≤ m6 + m9 ≤ 4, and when m1 is 1, 0 ≤ m6 + m9 ≤ 6. When m2 is 0, 0 ≤ m7 + m10 ≤ 4, and when m2 is 1, 0 ≤ m7 + m10 ≤ 6. When m3 is 0, 1 ≤ m4 + m5 + m8 + m14 ≤ 4, and when m3 is 1, 1 ≤ m4 + m5 + m8 + m14 ≤ 6. When m11 is 0, 0 ≤ m12 + m13 ≤ 4, and when m11 is 1, 0 ≤ m12 + m13 ≤ 6. Also, m4 + m12 ≥ 1. R F1 ~R F3 Each of these is independently a fluorine atom, a fluorinated saturated hydrocarbyl group having 1 to 6 carbon atoms, a fluorinated saturated hydrocarbyloxy group having 1 to 6 carbon atoms, or a fluorinated saturated hydrocarbylthio group having 1 to 6 carbon atoms. When m5 is 2, 3, or 4, each R F1 They may be the same as or different from each other. When m6 is 2, 3, 4, 5 or 6, each R F2 They may be the same as or different from each other. When m7 is 2, 3, 4, 5 or 6, each R F3 They may be the same as or different from each other. R ct6 ~R ct9 This is a C1-C20 hydrocarbyl group which may contain halogen atoms other than iodine and fluorine atoms, a nitro group, a cyano group, a heteroatom, a C1-C20 hydrocarbyloxy group which may contain a heteroatom, or a C1-C20 hydrocarbylthio group which may contain a heteroatom. When m8 is 2, two R ct6 The two Rs may be the same or different from each other. ct6 These may bond with each other to form a ring with the carbon atoms to which they are bonded. When m9 is 2, two R ct7 The two Rs may be the same or different from each other. ct7 These may bond with each other to form a ring with the carbon atoms to which they are bonded. When m10 is 2, two R ct8 The two Rs may be the same or different from each other. ct8 These may bond with each other to form a ring with the carbon atoms to which they are bonded. When m13 is 2, two R ct9 The two Rs may be the same or different from each other. ct9 These atoms may bond with each other to form a ring with the carbon atoms to which they are bonded. Furthermore, S in sulfonium cations + Aromatic rings that are directly bonded to each other are bonded to each other and form S + They may form a ring together. L A and L B These are, independently, a single bond, an ether bond, an ester bond, an amide bond, a sulfonic acid ester bond, a sulfonamide bond, a carbonate bond, or a carbamate bond. X L This is a hydrocarbylene group having 1 to 40 carbon atoms, which may contain single bonds or heteroatoms.

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

7. A chemically amplified positive-type resist composition comprising the photoacid generator described in claim 6.

8. Furthermore, the chemically amplified positive-type resist composition according to claim 7, further comprising a base polymer containing a polymer that decomposes under the action of an acid, thereby increasing its solubility in an alkaline developer.

9. The chemically amplified positive resist composition according to claim 8, wherein the polymer contains repeating units represented by the following formula (B1). 【Transformation 6】 (In the formula, a1 is 0 or 1. a2 is 0, 1 or 2. a3 is an integer that satisfies 0 ≤ a3 ≤ 5 + 2(a2) - a4. a4 is 1, 2 or 3.) R A These are a hydrogen atom, a fluorine atom, a methyl group, or a trifluoromethyl group. R 11 This is a halogen atom, a nitro group, a carboxyl group, a saturated hydrocarbyl group having 1 to 6 carbon atoms that may be substituted with a halogen atom, a saturated hydrocarbyloxy group having 1 to 6 carbon atoms that may be substituted with a halogen atom, or a saturated hydrocarbylcarbonyloxy group having 2 to 8 carbon atoms that may be substituted with a halogen atom. When a3 is 2 or more, each R 11 They may be the same as or different from each other. A 1 This is a single bond or a saturated hydrocarbylene group having 1 to 10 carbon atoms, and the saturated hydrocarbylene group is -CH 2 (Some of the hyphens may be replaced with -O-.)

10. The chemically amplified positive resist composition according to claim 8, wherein the polymer contains repeating units represented by the following formula (B2-1). 【Transformation 7】 (In the formula, b1 is 0 or 1. b2 is 0, 1 or 2. b3 is an integer satisfying 0 ≤ b3 ≤ 5 + 2(b2) - b4. b4 is 1, 2 or 3. b5 is 0 or 1.) R A These are a hydrogen atom, a fluorine atom, a methyl group, or a trifluoromethyl group. R 21 This is a halogen atom, a saturated hydrocarbyl group having 1 to 6 carbon atoms that may be substituted with a halogen atom, a saturated hydrocarbyloxy group having 1 to 6 carbon atoms that may be substituted with a halogen atom, or a saturated hydrocarbylcarbonyloxy group having 2 to 8 carbon atoms that may be substituted with a halogen atom. When b3 is 2 or more, each R 21 They may be the same as or different from each other. A 2 This is a single bond or a saturated hydrocarbylene group having 1 to 10 carbon atoms, and the saturated hydrocarbylene group is -CH 2 Some of the hyphens may be replaced with -O-. X is an acid-unstable group when b4 is 1, and when b4 is 2 or 3, it is independently a hydrogen atom or an acid-unstable group, but at least one of them is an acid-unstable group.

11. The chemically amplified positive resist composition according to claim 8, wherein the polymer contains repeating units represented by the following formula (B2-2). 【Transformation 8】 (In the formula, c1 is 0, 1, or 2. c2 is 0, 1, or 2. c3 is 0, 1, 2, 3, 4, or 5. c4 is 0, 1, or 2.) R A These are a hydrogen atom, a fluorine atom, a methyl group, or a trifluoromethyl group. R 22 and R 23 Each of these is independently a hydrocarbyl group having 1 to 10 carbon atoms, which may contain heteroatoms, and R 22 and R 23 However, they may bond with each other to form a ring with the carbon atoms to which they are bonded. R 24 Each of these is independently a fluorine atom, a fluorinated alkyl group having 1 to 5 carbon atoms, or a fluorinated alkoxy group having 1 to 5 carbon atoms. When c2 is 2, each R 24 They may be the same as or different from each other. R 25 Each of these is independently a hydrocarbyl group having 1 to 10 carbon atoms, which may contain heteroatoms. When c3 is 2, 3, 4, or 5, each R 25 They may be the same as or different from each other. A 3 This refers to a single bond, a phenylene group, a naphthylene group, or *-C(=O)-O-A 31 - is true. A 31 This is an aliphatic hydrocarbylene group having 1 to 20 carbon atoms, which may contain a hydroxyl group, an ether bond, an ester bond, or a lactone ring, or a phenylene group or a naphthylene group.

12. The chemically amplified positive resist composition according to claim 8, wherein the polymer comprises at least one selected from repeating units represented by the following formula (B3), repeating units represented by the following formula (B4), and repeating units represented by the following formula (B5). 【Chemistry 9】 (In the formula, d is 0, 1, 2, 3, 4, 5, or 6; e is 0, 1, 2, 3, or 4; f1 is 0 or 1; f2 is 0, 1, or 2; f3 is 0, 1, 2, 3, 4, or 5.) R A These are a hydrogen atom, a fluorine atom, a methyl group, or a trifluoromethyl group. R 31 and R 32 Each of these is independently a hydroxyl group, a halogen atom, a saturated hydrocarbyl group having 1 to 6 carbon atoms that may be substituted with a halogen atom, a saturated hydrocarbyloxy group having 1 to 6 carbon atoms that may be substituted with a halogen atom, or a saturated hydrocarbylcarbonyloxy group having 2 to 8 carbon atoms that may be substituted with a halogen atom. When d is 2, 3, 4, 5, or 6, each R 31 They may be the same as or different from each other. When e is 2, 3, or 4, each R 32 They may be the same as or different from each other. R 33 This is a saturated hydrocarbyl group having 1 to 20 carbon atoms, a saturated hydrocarbyloxy group having 1 to 20 carbon atoms, a saturated hydrocarbylcarbonyloxy group having 2 to 20 carbon atoms, a saturated hydrocarbyloxyhydrocarbyl group having 2 to 20 carbon atoms, a saturated hydrocarbylthiohydrocarbyl group having 2 to 20 carbon atoms, a halogen atom, a nitro group, or a cyano group, and when f2 is 1 or 2, it may also be a hydroxyl group. When f3 is 2, 3, 4, or 5, each R 33 They may be the same as or different from each other. A 4 This is a single bond or a saturated hydrocarbylene group having 1 to 10 carbon atoms, and the saturated hydrocarbylene group is -CH 2 (Some of the hyphens may be replaced with -O-.)

13. The chemically amplified positive resist composition according to claim 8, wherein the polymer comprises at least one selected from repeating units represented by the following formula (B6), repeating units represented by the following formula (B7), repeating units represented by the following formula (B8), repeating units represented by the following formula (B9), and repeating units represented by the following formula (B10). 【Chemistry 10】 (In the formula, g1 and g2 are independently 0, 1, 2, or 3. h1 is 0 or 1. h2 is 0, 1, 2, 3, or 4. h3 is 0, 1, 2, 3, or 4. However, when h1 is 0, 0 ≤ h2 + h3 ≤ 4, and when h1 is 1, 0 ≤ h2 + h3 ≤ 6.) R A These are, independently, a hydrogen atom, a fluorine atom, a methyl group, or a trifluoromethyl group. Z 1 This is a phenylene group which may have a single bond or a substituent. Z 2 This is a single bond, **-C(=O)-O-Z 21 -, **-C(=O)-NH-Z 21 - or **- O - Z 21 - is Z 21 This is a divalent group obtained by combining an aliphatic hydrocarbylene group, a phenylene group, or a combination thereof, having 1 to 6 carbon atoms, and may contain a halogen atom, a carbonyl group, an ester bond, an ether bond, or a hydroxyl group. Z 3 These are single bonds, ether bonds, ester bonds, amide bonds, sulfonic acid ester bonds, sulfonamide bonds, carbonate bonds, or carbamate bonds. Z 4 This is a single bond, or a divalent group obtained by combining an aliphatic hydrocarbylene group, a phenylene group, or a combination thereof, and may contain a halogen atom, a carbonyl group, an ester bond, an ether bond, or a hydroxyl group. Z 5 Each of these independently comprises a single bond, a phenylene group which may have substituents, a naphthylene group which may have substituents, or *-C(=O)-O-Z 51 - is Z 51 This is an aliphatic hydrocarbylene group, a phenylene group, or a naphthylene group having 1 to 10 carbon atoms, and the aliphatic hydrocarbylene group may contain a halogen atom, a hydroxyl group, an ether bond, an ester bond, or a lactone ring. Z 6 These are single bonds, ether bonds, ester bonds, amide bonds, sulfonic acid ester bonds, sulfonamide bonds, carbonate bonds, or carbamate bonds. Z 7 is, independently of each other, a single bond, ***-Z 71 -C(=O)-O-, ***-C(=O)-NH-Z 71 - or ***-O-Z 71 -. Z 71 is a hydrocarbylene group having 1 to 20 carbon atoms which may contain a heteroatom. Z 8 is, independently of each other, a single bond, ****-Z 81 -C(=O)-O-, ****-C(=O)-NH-Z 81 - or ****-O-Z 81 -. Z 81 is a hydrocarbylene group having 1 to 20 carbon atoms which may contain a heteroatom. Z 9 This includes single bonds, methylene groups, ethylene groups, phenylene groups, fluorinated phenylene groups, trifluoromethyl groups, and *-C(=O)-O-Z. 91 -, *-C(=O)-N(H)-Z 91 - or * - O - Z 91 - is Z 91 This is a phenylene group substituted with an aliphatic hydrocarbylene group having 1 to 6 carbon atoms, a phenylene group, a fluorinated phenylene group, or a trifluoromethyl group, and may contain a carbonyl group, an ester bond, an ether bond, or a hydroxyl group. * represents a bond with a carbon atom in the main chain. ** represents Z 1 This represents a combination with Z. *** represents Z 6 This represents a combination with Z. **** is Z 7 This represents a combination of two things. L 1 These are single bonds, ether bonds, ester bonds, carbonyl groups, sulfonic acid ester bonds, sulfonamide bonds, carbonate bonds, or carbamate bonds. Rf 1 and Rf 2 Each of these is independently either a fluorine atom or a fluorinated saturated hydrocarbyl group having 1 to 6 carbon atoms. Rf 3 and Rf 4 Each of these is independently a hydrogen atom, a fluorine atom, or a fluorinated saturated hydrocarbyl group having 1 to 6 carbon atoms. Rf 5 and Rf 6 Each of these is independently a hydrogen atom, a fluorine atom, or a fluorinated saturated hydrocarbyl group having 1 to 6 carbon atoms. However, all Rf 5 and Rf 6 They cannot simultaneously become hydrogen atoms. Rf 7 This is a fluorine atom, a fluorinated alkyl group having 1 to 6 carbon atoms, a fluorinated alkoxy group having 1 to 6 carbon atoms, or a fluorinated alkylthio group having 1 to 6 carbon atoms. When h2 is 2, 3, or 4, each Rf 7 They may be the same as or different from each other. R 41 and R 42 Each of these is independently a hydrocarbyl group having 1 to 20 carbon atoms, which may contain heteroatoms. Also, R 41 and R 42 However, they may bond with each other to form a ring with the sulfur atom to which they are bonded. R 43 This is a C1-C20 hydrocarbyl group which may contain halogen atoms other than fluorine atoms, or heteroatoms. When h3 is 2, 3, or 4, each R 43 They may be the same or different from each other, and there may be multiple R 43 These atoms may bond with each other to form a ring with the carbon atoms to which they are bonded. M - It is a non-nucleophilic counterion. A + This is an onium cation.

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

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

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

17. The chemically amplified positive resist composition according to claim 7, further comprising a fluorine atom-containing polymer that includes at least one selected from the repeating units represented by the following formula (E1), the repeating units represented by the following formula (E2), the repeating units represented by the following formula (E3), and the repeating units represented by the following formula (E4), and which may further include at least one selected from the repeating units represented by the following formula (E5) and the repeating units represented by the following formula (E6). 【Chemistry 11】 (In the formula, j1 is 1, 2, or 3. j2 is an integer satisfying 0 ≤ j2 ≤ 5 + 2(j3) - j1. j3 is 0 or 1. k is 1, 2, or 3.) R B These are, independently, a hydrogen atom, a fluorine atom, a methyl group, or a trifluoromethyl group. R C Each of these is independently either a hydrogen atom or a methyl group. R 201 , R 202 , R 204 and R 205 Each of these is independently either a hydrogen atom or a saturated hydrocarbyl group having 1 to 10 carbon atoms. R 203 , R 206 , R 207 and R 208 Each of these is independently a hydrogen atom, a C1-C15 hydrocarbyl group, a C1-C15 fluorinated hydrocarbyl group, or an acid-unstable group, R 203 , R 206 , R 207 and R 208 When the group is a hydrocarbyl group or a fluorinated hydrocarbyl group, an ether bond or a carbonyl group may be interposed between the carbon-carbon bonds. R 209 This is a linear or branched hydrocarbyl group having 1 to 5 carbon atoms, which may have a hydrogen atom or a group containing a heteroatom between the carbon-carbon bonds. When j1 is 2 or 3, each R 209 They may be the same as or different from each other. R 210 This is a linear or branched hydrocarbyl group having 1 to 5 carbon atoms, which may have a heteroatom interposed between the carbon-carbon bonds. When j2 is 2 or more, each R 210 They may be the same as or different from each other. R 211 This is a saturated hydrocarbyl group having 1 to 20 carbon atoms in which at least one hydrogen atom is substituted with a fluorine atom, and the saturated hydrocarbyl group is -CH 2 - may be partially substituted with an ester bond or an ether bond. X 1 This is a (k+1) valent hydrocarbon group having 1 to 20 carbon atoms or a (k+1) valent fluorinated hydrocarbon group having 1 to 20 carbon atoms. X 2 The bond is a single bond, *-C(=O)-O-, or *-C(=O)-NH-. The asterisk (*) is a bond to a carbon atom in the main chain. X 3 This is a single bond, -O-, *-C(=O)-O-X 31 -X 32 - or * - C (= O) - NH - X 31 -X 32 - is true. X 31 This is a single bond or a saturated hydrocarbylene group having 1 to 10 carbon atoms. 32 A is a single bond, ester bond, ether bond, or sulfonamide bond. * indicates a bond to a carbon atom in the main chain.

18. Furthermore, the chemically amplified positive resist composition according to claim 7, comprising a photoacid generator other than the photoacid generator described in claim 6.

19. A method for forming a resist pattern, comprising the steps of: forming a resist film on a substrate using the chemically amplified positive-type resist composition described in claim 7; irradiating the resist film with a pattern using high-energy rays; and developing the resist film irradiated with the pattern using an alkaline developer.

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

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

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

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