Radiation-sensitive composition, resist pattern formation method, and polymer

Abstract

This radiation-sensitive composition comprises a polymer which contains, in the same molecule, a first structural unit having an acid-dissociable group, a second structural unit having a radiation-sensitive onium cation and a sulfonic acid anion, and a third structural unit having a radiation-sensitive onium cation and a carboxylic acid anion, and in which the content ratio of the first structural unit is at least 55 mol% with respect to all the structural units.

Description

Radiation-sensitive composition, method for forming resist pattern, and polymer

[0001] [Cross-Reference to Related Applications] This application claims priority to Japanese Patent Application No. 2023-131998, filed on August 14, 2023, the entire contents of which are incorporated herein by reference. The present disclosure relates to a radiation-sensitive composition, a method for forming a resist pattern, and a polymer.

[0002] In lithography techniques used in the manufacturing processes of various electronic devices such as semiconductor devices and liquid crystal devices, a radiation-sensitive composition is irradiated with far ultraviolet rays (such as an ArF excimer laser), extreme ultraviolet rays (EUV), electron beams, or the like to generate an acid in the exposed area, and a chemical reaction involving this acid causes a difference in the dissolution rate in a developer between the exposed area and the unexposed area, thereby forming a resist pattern on a substrate.

[0003] For example, Patent Document 1 discloses a resist composition containing a resin having a repeating unit with an internal salt structure. Patent Document 1 discloses that by introducing a repeating unit with an internal salt structure into a resin, the solubility is improved and the resin is allowed to exhibit the function of capturing acid in unexposed areas.

[0004] International Publication No. 2017 / 104355

[0005] In particular, in recent years, the use of components that are poorly soluble in a developer as components of resist compositions has been increasing, with the aim of increasing the sensitivity of the resist composition. When a resist composition containing such a component that is poorly soluble in a developer is used, the region of the resist film that is to be dissolved in the developer may not be sufficiently dissolved in the developer during the development process, resulting in residual resist film in that region. Furthermore, residue that is not dissolved in the developer may adhere to the pattern surface, causing defects in the resulting resist pattern. As resist patterns become increasingly finer, such defects increasingly affect the performance of semiconductor devices. Therefore, when forming a resist pattern, it is increasingly important to suppress development residues while reducing defects.

[0006] The present disclosure has been made in consideration of the above-mentioned problems, and an object of the present disclosure is to provide a radiation-sensitive composition that can suppress development residues and form a resist pattern in which the occurrence of defects is suppressed, and a method of forming a resist pattern that uses the radiation-sensitive composition.

[0007] According to one aspect of the present disclosure, there is provided a radiation-sensitive composition containing a polymer that includes, in the same molecule, a first structural unit having an acid-dissociable group, a second structural unit having a radiation-sensitive onium cation and a sulfonate anion, and a third structural unit having a radiation-sensitive onium cation and a carboxylate anion, wherein the content of the first structural unit is 55 mol % or more based on all structural units.

[0008] According to another aspect of the present disclosure, there is provided a method for forming a resist pattern, the method including the steps of forming a resist film on a substrate using the radiation-sensitive composition described above, exposing the resist film to light, and developing the exposed resist film.

[0009] According to another aspect of the present disclosure, there is provided a polymer comprising, in the same molecule, a first structural unit having an acid-dissociable group, a second structural unit having a radiation-sensitive onium cation and a sulfonate anion, and a third structural unit having a radiation-sensitive onium cation and a carboxylate anion, wherein the content of the first structural unit is 55 mol % or more based on all structural units.

[0010] The radiation-sensitive composition of the present disclosure can provide a radiation-sensitive composition that can form a resist pattern with minimal development residues and suppressed defect generation. Furthermore, the method of forming a resist pattern of the present disclosure uses the radiation-sensitive composition of the present disclosure, making it possible to form a resist pattern with minimal development residues and suppressed defect generation.

[0011] Matters related to the embodiments will be described in detail below. In this specification, a numerical range described using "to" means that the numerical values ​​described before and after "to" are included as the lower and upper limits. A "structural unit" refers to a unit that mainly constitutes the main chain structure, and at least two or more units are included in the main chain structure.

[0012] The expression "substituted or unsubstituted p-valent hydrocarbon group (where p is an integer of 1 or more)" encompasses p-valent hydrocarbon groups (i.e., unsubstituted p-valent hydrocarbon groups) and groups in which p hydrogen atoms have been removed from the hydrocarbon structural portion of a substituted hydrocarbon group. Examples of substituted or unsubstituted p-valent hydrocarbon groups include alkyl groups and fluoroalkyl groups where p=1, and alkanediyl groups and fluoroalkanediyl groups where p=2. Of these, fluoroalkyl groups are "substituted monovalent hydrocarbon groups," and fluoroalkanediyl groups are "substituted divalent hydrocarbon groups." The same applies to other groups to which "substituted or unsubstituted" is attached.

[0013] <Radiation-Sensitive Composition> The radiation-sensitive composition of the present disclosure (hereinafter also referred to as "the composition") contains a polymer (hereinafter also referred to as "polymer [A]") that contains, in the same molecule, a first structural unit having an acid-dissociable group, a second structural unit having a radiation-sensitive onium cation and a sulfonate anion, and a third structural unit having a radiation-sensitive onium cation and a carboxylate anion, wherein the content of the first structural unit is 55 mol% or more of all structural units. Furthermore, the composition may further contain, as an optional component, one or more compounds different from the polymer [A]. Unless otherwise specified, each component may be used alone, or two or more may be used in combination.

[0014] Here, in this specification, the term "hydrocarbon group" includes chain hydrocarbon groups, alicyclic hydrocarbon groups, and aromatic hydrocarbon groups. The term "chain hydrocarbon group" refers to a linear hydrocarbon group or a branched hydrocarbon group that does not contain a cyclic structure and is composed only of a chain structure. However, the chain hydrocarbon group may be saturated or unsaturated. The term "alicyclic hydrocarbon group" refers to a hydrocarbon group that contains only an alicyclic hydrocarbon structure as a ring structure and does not contain an aromatic ring structure. However, the alicyclic hydrocarbon group does not necessarily have to be composed only of an alicyclic hydrocarbon structure and also includes groups that have a chain structure as part of it. The term "aromatic hydrocarbon group" refers to a hydrocarbon group that contains an aromatic ring structure as a ring structure. However, the aromatic hydrocarbon group does not necessarily have to be composed only of an aromatic ring structure and may contain a chain structure or an alicyclic hydrocarbon structure as part of it. The term "aromatic ring group" refers to an n-valent group obtained by removing n hydrogen atoms (where n is an integer of 1 or more) from the ring portion of a substituted or unsubstituted aromatic ring. The term "alicyclic group" refers to an n-valent group formed by removing n (n is an integer of 1 or more) hydrogen atoms from the ring portion of a substituted or unsubstituted aliphatic ring. The term "aromatic heterocyclic group" refers to an n-valent group formed by removing n (n is an integer of 1 or more) hydrogen atoms from the ring portion of a substituted or unsubstituted aromatic heterocycle. The term "organic group" refers to an atomic group formed by removing any hydrogen atom from a compound containing carbon (i.e., an organic compound). The term "aromatic ring" includes aromatic hydrocarbon rings and aromatic heterocycles.

[0015] <Regarding the Polymer [A]> The polymer [A] includes a structural unit having an acid-dissociable group (hereinafter also referred to as the "first structural unit"). The acid-dissociable group is a group that substitutes a hydrogen atom of an acid group such as a carboxy group or a hydroxyl group, and is a group that dissociates under the action of an acid. When the polymer [A] includes the first structural unit, the acid-dissociable group in the first structural unit is dissociated by the acid generated by exposure of the composition to light to form an acid group, thereby changing the solubility of the polymer [A] in a developer. This allows the composition to be endowed with lithography performance such as good line width roughness (LWR) performance and critical dimension uniformity (CDU) performance.

[0016] The polymer (A) also contains, in the same molecule as the first structural unit, a structural unit having a radiation-sensitive onium cation and a sulfonate anion (hereinafter also referred to as the “second structural unit”), and a structural unit having a radiation-sensitive onium cation and a carboxylate anion (hereinafter also referred to as the “third structural unit”).

[0017] The content of the first structural unit in the polymer [A] is 55 mol% or more relative to all structural units constituting the polymer [A]. If the content of the first structural unit in the polymer [A] is less than 55 mol%, the resist film in the developer-dissolvable region cannot be sufficiently dissolved in the developer, and the resist film tends to remain undissolved in holes or spaces, or residue that does not dissolve in the developer tends to adhere to the pattern surface. In order to minimize development residue, the content of the first structural unit in the polymer [A] is preferably 60 mol% or more, more preferably 65 mol% or more, and even more preferably 70 mol% or more relative to all structural units constituting the polymer [A]. Furthermore, the content of the first structural unit is preferably 90 mol% or less, more preferably 85 mol% or less, and even more preferably 80 mol% or less relative to all structural units constituting the polymer [A]. By setting the content of the first structural unit within the above range, the generation of development residue can be suppressed while maintaining good sensitivity of the composition.

[0018] The polymer [A] may further contain a structural unit having an aromatic ring and a hydroxyl group bonded to the aromatic ring (hereinafter also referred to as a "fourth structural unit"). The polymer [A] having the fourth structural unit is advantageous in that it can further improve the limiting resolution of the composition, and is highly effective in suppressing dissolution of unexposed areas into a developer, thereby sufficiently reducing development defects. In particular, polymers having the fourth structural unit can be preferably used in pattern formation using exposure to radiation with a wavelength of 50 nm or less, such as electron beams or EUV. In this specification, a structural unit having an acid-dissociable group together with a hydroxyl group bonded to an aromatic ring is classified as a first structural unit.

[0019] The polymer (A) may further include a structural unit (hereinafter also referred to as a "fifth structural unit") that is different from the first structural unit, the second structural unit, the third structural unit, and the fourth structural unit. Examples of the fifth structural unit include a structural unit having a lactone structure, a cyclic carbonate structure, a sultone structure, or a ring structure that combines two or more of these (hereinafter also referred to as a "structural unit (U5-1)"); a structural unit having an alcoholic hydroxyl group (hereinafter also referred to as a "structural unit (U5-2)"); and the like.

[0020] In the present composition, the polymer [A] preferably has an iodine group ("*-I", where "*" represents a bond) in order to improve sensitivity. When an iodine group is introduced into the polymer, it is possible to improve sensitivity, but it is thought that the solubility in a developer may decrease. In this regard, the polymer [A] can achieve both solubility in a developer and improved sensitivity.

[0021] When the polymer [A] contains an iodine group, from the viewpoint of fully achieving the effects of improving the sensitivity of the present composition and the effects of improving lithography performance, the polymer [A] preferably contains a structural unit having an iodine group (hereinafter also referred to as an "iodine group-containing structural unit"), and more preferably contains structural units having two or more iodine groups in the same structural unit. When the polymer [A] contains an iodine group-containing structural unit, any structural unit constituting the polymer [A] may contain an iodine group, or two or more structural units may contain an iodine group. For example, an embodiment in which at least one structural unit selected from the group consisting of the first structural unit, the second structural unit, and the third structural unit in the polymer [A] contains an iodine group may be mentioned. Furthermore, when the polymer [A] contains a fourth structural unit, the fourth structural unit may contain an iodine group. Furthermore, the first structural unit, the second structural unit, the third structural unit, and the fourth structural unit may contain an iodine group.

[0022] When the polymer [A] includes a fifth structural unit, the fifth structural unit in the polymer [A] may have an iodo group. When the fifth structural unit has an iodo group, any one of the fifth structural units in the polymer [A] may have an iodo group. For example, there may be mentioned an embodiment in which at least one structural unit selected from the group consisting of the structural unit (U5-1) and the structural unit (U5-2) has an iodo group.

[0023] In terms of the high effect of improving the lithography performance of the present composition, it is preferable that at least one structural unit selected from the group consisting of the first structural unit, the second structural unit, the third structural unit, and the fourth structural unit of the polymer (A) has an iodine group.

[0024] The bonding position of the iodo group in the iodo group-containing structural unit is not particularly limited. In order to enhance the sensitivity improvement effect of the present composition, the iodo group-containing structural unit preferably has an aromatic ring and has a structure in which the iodo group is bonded to the aromatic ring. The number of iodo groups bonded to the aromatic ring in the iodo group-containing structural unit is, for example, 1 to 5. In order to further enhance the sensitivity of the present composition, the iodo group-containing structural unit preferably has two or more iodo groups bonded to the aromatic ring. When the iodo group-containing structural unit has two or more iodo groups, the two or more iodo groups may be bonded to the same aromatic ring or different aromatic rings in the iodo group-containing structural unit. The aromatic ring to which the iodo group is bonded is preferably a benzene ring or a naphthalene ring, and more preferably a benzene ring.

[0025] When the iodo group-containing structural unit is a structural unit having an onium salt structure, it is sufficient that one or both of the cation moiety and the organic anion moiety constituting the onium salt structure have an iodo group. That is, in the iodo group-containing structural unit having an onium salt structure, the cation moiety constituting the onium salt structure may have an iodo group, the organic anion moiety may have an iodo group, or both the cation moiety and the organic anion moiety may have an iodo group.

[0026] It is preferable that the iodo group-containing structural unit contains a structural unit having an acid-dissociable group, in order to improve the sensitivity and development contrast of the present composition.In order to improve the sensitivity and development contrast, in the structural unit having an acid-dissociable group and an iodo group, it is preferable that the iodo group is bonded to an aromatic ring, and it is more preferable that the acid-dissociable group has an aromatic ring and the iodo group is bonded to the aromatic ring.

[0027] Specific embodiments of the polymer [A] having an iodo group include the following [1] to [5] and combinations of two or more of these. [1] An embodiment in which at least a portion of the first structural units in the polymer [A] have an iodo group. [2] An embodiment in which at least a portion of the second structural units in the polymer [A] have an iodo group. [3] An embodiment in which at least a portion of the third structural units in the polymer [A] have an iodo group. [4] An embodiment in which the polymer [A] contains a fourth structural unit, and at least a portion of the fourth structural units in the polymer [A] have an iodo group. [5] An embodiment in which the polymer [A] contains a fifth structural unit, and at least a portion of the fifth structural units in the polymer [A] have an iodo group.

[0028] From the viewpoint of improving the sensitivity of the present composition, the polymer [A] having an iodine group preferably contains structural units having an iodine group in an amount of 2 mol% or more, more preferably 5 mol% or more, and even more preferably 10 mol% or more, based on all structural units constituting the polymer [A]. Furthermore, from the viewpoint of ensuring the solubility of the present composition in a developer, the content of structural units having an iodine group is preferably 90 mol% or less, more preferably 75 mol% or less, and even more preferably 65 mol% or less, based on all structural units constituting the polymer [A].

[0029] Next, the polymer (A) and any optional components contained in the composition will be described in detail.

[0030] <Polymer [A]> First Structural Unit Examples of the first structural unit include a structural unit represented by the following formula (i-1) (hereinafter also referred to as "structural unit (I-1)"), a structural unit represented by the following formula (i-2) (hereinafter also referred to as "structural unit (I-2)"), and a structural unit represented by the following formula (i-3) (hereinafter also referred to as "structural unit (I-3)"). (In formula (i-1), R １２ is a hydrogen atom, a fluorine atom, a methyl group, or a trifluoromethyl group. ３ is a single bond or * １ -COO(CH ２ ) ｇ３ - is. ｇ３ is an integer between 1 and 10. １ " represents a bond to the main chain. １３ is a hydrogen atom or a substituted or unsubstituted monovalent hydrocarbon group having 1 to 20 carbon atoms. １４ and R １５ are each independently a substituted or unsubstituted monovalent hydrocarbon group having 1 to 20 carbon atoms, a monovalent aromatic heterocyclic group, or R １４ and R １５ are aligned with each other and R １４ and R １５ represents an alicyclic hydrocarbon structure having 3 to 20 carbon atoms, which is formed together with the carbon atom to which R is bonded. １３ When is a hydrogen atom, R １４ and R １５ or both of R are, independently of each other, a substituted or unsubstituted monovalent unsaturated hydrocarbon group, a substituted or unsubstituted aromatic heterocyclic group, or １４ and R １５ are aligned with each other and R １４ and R １５ represents an alicyclic unsaturated hydrocarbon structure having 3 to 20 carbon atoms, which is formed together with the carbon atom to which R is bonded. １６ is a hydrogen atom, a fluorine atom, a methyl group, or a trifluoromethyl group. ４ represents a single bond, -O-, -CO-, * ２ -COO- or * ２ -CONH-. ２ " represents a bond to the main chain.１７ , R １８ and R １９ are each independently a hydrogen atom, a substituted or unsubstituted monovalent hydrocarbon group having 1 to 20 carbon atoms, or a substituted or unsubstituted monovalent oxyhydrocarbon group having 1 to 20 carbon atoms. ３５ is a monovalent substituent. g1 is an integer of 0 to 4. In formula (i-3), R ３１ is a hydrogen atom, a fluorine atom, a methyl group, or a trifluoromethyl group. ５ represents a single bond, -O-, -CO-, * ３ -COO- or * ３ -CONH-. ３ " represents a bond to the main chain. ３２ R is a hydrogen atom, a substituted or unsubstituted monovalent hydrocarbon group having 1 to 20 carbon atoms, or a substituted or unsubstituted monovalent oxyhydrocarbon group having 1 to 20 carbon atoms. ３３ and R ３４ are each independently a hydrogen atom, a substituted or unsubstituted monovalent hydrocarbon group having 1 to 20 carbon atoms, or a substituted or unsubstituted monovalent oxyhydrocarbon group having 1 to 20 carbon atoms, or R ３３ and R ３４ are aligned with each other and R ３３ and R ３４ represents an alicyclic hydrocarbon structure having 3 to 20 carbon atoms formed together with the carbon atom to which R is bonded. ３６ is a monovalent substituent. g2 is an integer of 0 to 4.

[0031] In the above formula (i-1), R １２ In view of the copolymerizability of the monomer that gives the structural unit (I-1), R is preferably a hydrogen atom or a methyl group, and more preferably a methyl group. １６ is preferably a hydrogen atom from the viewpoint of copolymerizability of the monomer that gives the structural unit (I-2). ３１ is preferably a hydrogen atom or a methyl group. ４ Or L in formula (i-3) ５ is preferably a single bond, —COO— or —CONH—.

[0032] R １３ ~R１５ , R １７ ~R １９ or R ３２ ~R ３４ Examples of the monovalent hydrocarbon group having 1 to 20 carbon atoms represented by the formula (I) include a monovalent chain hydrocarbon group having 1 to 20 carbon atoms, a monovalent alicyclic hydrocarbon group having 3 to 20 carbon atoms, and a monovalent aromatic hydrocarbon group having 6 to 20 carbon atoms.

[0033] Examples of the monovalent chain hydrocarbon group having 1 to 20 carbon atoms include alkyl groups such as methyl, ethyl, n-propyl, i-propyl, n-butyl, and t-butyl; alkenyl groups such as ethenyl, propenyl, and butenyl; and alkynyl groups such as ethynyl, propynyl, and butynyl. １３ ~R １５ , R １７ ~R １９ or R ３２ ~R ３４ The monovalent chain hydrocarbon group having 1 to 20 carbon atoms represented by the formula (I) is preferably an alkyl group, more preferably an alkyl group having 1 to 4 carbon atoms.

[0034] Examples of the monovalent alicyclic hydrocarbon group having 3 to 20 carbon atoms include monovalent monocyclic alicyclic saturated hydrocarbon groups such as a cyclopentyl group, a cyclohexyl group, a methylcyclopentyl group, an ethylcyclopentyl group, a methylcyclohexyl group, and an ethylcyclohexyl group; monovalent monocyclic unsaturated hydrocarbon groups such as a cyclopentenyl group, a cyclohexenyl group, a methylcyclopentenyl group, and a methylcyclohexenyl group; monovalent polycyclic saturated alicyclic hydrocarbon groups such as a norbornyl group, an adamantyl group, and a tricyclodecyl group; and monovalent polycyclic unsaturated alicyclic hydrocarbon groups such as a norbornenyl group, a tricyclodecenyl group, and an indanyl group.

[0035] Examples of the monovalent aromatic hydrocarbon group having 6 to 20 carbon atoms include aryl groups such as a phenyl group, a tolyl group, a xylyl group, a mesityl group, a naphthyl group, a methylnaphthyl group, an anthryl group, a methylanthryl group, and an indenyl group; and aralkyl groups such as a benzyl group, a phenethyl group, a naphthylmethyl group, and an anthrylmethyl group.

[0036] R １４or R １５ Examples of the monovalent unsaturated hydrocarbon group represented by the formula (I) include the above-mentioned monocyclic or polycyclic alicyclic unsaturated hydrocarbon group and aromatic hydrocarbon group. Examples of the monovalent aromatic heterocyclic group include a furyl group and a thienyl group.

[0037] R １４ and R １５ are aligned with each other and R １４ and R １５ an alicyclic hydrocarbon structure having 3 to 20 carbon atoms formed together with the carbon atom to which R is bonded, and ３３ and R ３４ are aligned with each other and R ３３ and R ３４ Examples of the alicyclic hydrocarbon structure having 3 to 20 carbon atoms constituted together with the carbon atom to which it is bonded include monocyclic saturated alicyclic hydrocarbon structures such as a cyclopropane structure, cyclobutane structure, cyclopentane structure, cyclohexane structure, cycloheptane structure, and cyclooctane structure; monocyclic unsaturated alicyclic hydrocarbon structures such as cyclopentene and cyclohexene; and polycyclic alicyclic hydrocarbon structures such as a norbornane structure, adamantane structure, tricyclodecane structure, and tetracyclododecane structure.

[0038] R １７ ~R １９ or R ３２ ~R ３４ Examples of the monovalent oxyhydrocarbon group having 1 to 20 carbon atoms represented by the formula (I) include the above-mentioned R １３ ~R １５ , R １７ ~R １９ and R ３２ ~R ３４ Examples of the monovalent hydrocarbon group having 1 to 20 carbon atoms include groups containing an oxygen atom at the bond-side terminal of the groups exemplified by R １７ ~R １９ or R ３２ ~R ３４ Of these, the monovalent oxyhydrocarbon group represented by the formula (I) is preferably an alkoxy group, a cycloalkoxy group, or a cycloalkylalkoxy group.

[0039] R １３ ~R １５ , R １７ ~R １９or R ３２ ~R ３４ When the group represented by R has a substituent, examples of the substituent include a halogen atom (a fluorine atom, a chlorine atom, a bromine atom, an iodine atom, etc.), a hydroxyl group, an alkoxy group having 1 to 3 carbon atoms, etc. １４ and R １５ are aligned with each other and R １４ and R １５ forms an alicyclic hydrocarbon structure having 3 to 20 carbon atoms together with the carbon atom to which it is bonded, or ３３ and R ３４ are aligned with each other and R ３３ and R ３４ When these groups together with the carbon atom to which they are bonded form an alicyclic hydrocarbon structure having 3 to 20 carbon atoms, the above-exemplified substituents or alkyl groups may be bonded to the alicyclic hydrocarbon structure.

[0040] R ３５ or R ３６ Examples of the monovalent substituent represented by the formula (I) include an alkyl group having 1 to 3 carbon atoms, an alkoxy group having 1 to 3 carbon atoms, a halogen atom (for example, a fluorine atom, a chlorine atom, a bromine atom, or an iodine atom), and a hydroxyl group. ３６ The monovalent substituent represented by the following formula is preferably a hydroxyl group. g1 is preferably 0 to 2, and more preferably 0 or 1. g2 is preferably 0 to 2, and more preferably 1 or 2.

[0041] Specific examples of the structural unit (I-1) include structural units represented by the following formulas: (In the formula, R １２ is a hydrogen atom, a fluorine atom, a methyl group, or a trifluoromethyl group.

[0042] Specific examples of the structural unit (I-2) include structural units represented by the following formulas: (In the formula, R １６ is a hydrogen atom, a fluorine atom, a methyl group, or a trifluoromethyl group.

[0043] Specific examples of the structural unit (I-3) include structural units represented by the following formula: (In the formula, R３１ is a hydrogen atom, a fluorine atom, a methyl group, or a trifluoromethyl group.

[0044] Second structural unit The second structural unit has an onium salt structure formed by a radiation-sensitive onium cation and a sulfonate anion, and generates an acid upon exposure. More specifically, the second structural unit is thought to be formed by the radiation-sensitive onium cation being decomposed by the action of radiation to liberate a sulfonate anion, which then bonds with hydrogen abstracted from components contained in the composition (e.g., a radiation-sensitive acid generator, an acid diffusion controller, a solvent, etc.) to generate an acid (specifically, a sulfonic acid or a sulfonic acid group) derived from the sulfonate anion. Note that ammonium cations are not included in the radiation-sensitive onium cations (the same applies to the third structural unit).

[0045] The sulfonic acid or sulfonic acid group generated by the action of radiation can eliminate the acid-dissociable group contained in the composition to generate an acid group. This makes it possible to change the solubility of the composition in a developer. In particular, a polymer containing a second structural unit is advantageous in that it can improve lithography performance (specifically, CDU and LWR) while suppressing a decrease in resolution due to acid diffusion. In this specification, the term "radiation" includes electron beams (visible light, ultraviolet light, far ultraviolet light, extreme ultraviolet light (EUV), etc.) and electromagnetic waves (X-rays, gamma rays, etc.).

[0046] The second structural unit is typically a structural unit derived from a monomer having a radiation-sensitive onium cation, a sulfonate anion, and a group participating in polymerization. ３ －) may be bonded to the main chain of the polymer via a linking group, and the radiation-sensitive onium cation may form a counter ion. Alternatively, the radiation-sensitive onium cation may be bonded to the main chain of the polymer via a linking group, and the sulfonate anion may form a counter ion. When the radiation-sensitive onium cation is bonded to the main chain of the polymer via a linking group, from the viewpoints of the sensitivity of the composition and ease of synthesis of the monomer, it is preferable that the radiation-sensitive onium cation is a sulfonium cation.

[0047] Specific examples of the second structural unit include structural units represented by the following formula (1) or (3). (In formula (1), R １ is a hydrogen atom, a fluorine atom, a methyl group, or a trifluoromethyl group. １ represents —O—, —COO— or a divalent aromatic ring group. １ Is, L １ is a divalent organic group when L is —O— or —COO—; １ is a divalent aromatic ring group, Y is a single bond or a divalent organic group. ａ＋ is a radiation-sensitive onium cation having a valence of a, and a is 1 or 2. In formula (3), R １ is a hydrogen atom, a fluorine atom, a methyl group, or a trifluoromethyl group. １１ R is a single bond, —O—, —COO— or a divalent aromatic ring group. ２３ is an alkanediyl group having 1 to 6 carbon atoms, an alkenediyl group having 2 to 6 carbon atoms, or an arylene group having 6 to 12 carbon atoms, or a divalent group R containing —O— or —COO— between the carbon-carbon bonds in the alkanediyl group having 1 to 6 carbon atoms, the alkenediyl group having 2 to 6 carbon atoms, or the arylene group having 6 to 12 carbon atoms ａ or an alkanediyl group having 1 to 6 carbon atoms, an alkenediyl group having 2 to 6 carbon atoms, an arylene group having 6 to 12 carbon atoms, or the above-mentioned divalent group R ａ is a group in which one or more hydrogen atoms of R have been substituted. ２１ and R ２２are each independently a substituted or unsubstituted alkyl group having 1 to 12 carbon atoms, a substituted or unsubstituted alkenyl group having 2 to 12 carbon atoms, or a substituted or unsubstituted aryl group having 6 to 20 carbon atoms. － is a sulfonate anion.)

[0048] In the above formula (1) and formula (3), R １ is preferably a hydrogen atom or a methyl group from the viewpoint of copolymerizability of the monomer that provides the second structural unit. １ , L １１ When L is a divalent aromatic ring group, examples of the divalent aromatic ring group include groups in which two hydrogen atoms have been removed from a benzene ring or a naphthalene ring. １ , L １１ and R ２１ ~R ２３ When each group has a substituent, examples of the substituent include a fluorine atom, a chlorine atom, a bromine atom, an iodine atom, an alkoxy group, a cycloalkyloxy group, an ester group, an alkylsulfonyl group, a cycloalkylsulfonyl group, a hydroxyl group, a carboxy group, a cyano group, a nitro group, an acetyl group, a fluoroacetyl group, an alkoxycarbonyl group, an alkoxycarbonyloxy group, and an oxo group.

[0049] In the above formula (1), A １ When is a divalent organic group, the divalent organic group may be a group having a chain structure (hereinafter also referred to as a "chain organic group") or a group having a cyclic structure.

[0050] A １ When the divalent organic group represented by the formula (I) is a chain organic group, examples of the chain organic group include a linear or branched saturated hydrocarbon group having 1 to 40 carbon atoms, a linear or branched unsaturated hydrocarbon group having 1 to 40 carbon atoms, a monovalent group having 2 to 40 carbon atoms and having a (thio)ether group or an ester group between the carbon-carbon bonds of the linear or branched hydrocarbon group, and a monovalent group having 1 to 40 carbon atoms in which any hydrogen atom in the monovalent group or linear or branched hydrocarbon group has been substituted.

[0051] A １When the divalent organic group represented by the formula (I) is a group having a cyclic structure, A １ Examples of the cyclic structure that A has include an alicyclic hydrocarbon structure having 3 to 20 carbon atoms, an aliphatic heterocyclic structure having 3 to 20 carbon atoms, and an aromatic ring structure having 6 to 20 carbon atoms. These cyclic structures may have a substituent. １ is a group having a cyclic structure, A １ may have a chain structure in addition to a cyclic structure.

[0052] Examples of the alicyclic hydrocarbon structure having 3 to 20 carbon atoms include a monocyclic aliphatic hydrocarbon structure having 3 to 20 carbon atoms and a polycyclic aliphatic hydrocarbon structure having 6 to 20 carbon atoms. The monocyclic aliphatic hydrocarbon structure having 3 to 20 carbon atoms and the polycyclic aliphatic hydrocarbon structure having 6 to 20 carbon atoms may be either saturated or unsaturated. Furthermore, the polycyclic aliphatic hydrocarbon structure may be any of a bridged structure, a fused ring structure, and a spiro ring structure.

[0053] Examples of the ring contained in the monocyclic aliphatic hydrocarbon structure include cyclopentane, cyclohexane, cycloheptane, cyclooctane, cyclopentene, cyclohexene, cycloheptene, cyclooctene, cyclodecene, etc. The polycyclic aliphatic hydrocarbon structure is preferably a bridged alicyclic saturated hydrocarbon structure or a condensed alicyclic saturated hydrocarbon structure, examples of which include a norbornane structure, a bicyclo[2.2.2]octane structure, an adamantane structure, and a steroid structure.

[0054] Examples of the aliphatic heterocyclic structure having 3 to 20 carbon atoms include a cyclic ether structure, a lactone structure, a cyclic acetal structure, a cyclic carbonate structure, and a sultone structure. The aliphatic heterocyclic structure may be either a monocyclic structure or a polycyclic structure. The polycyclic structure may be either a bridged structure, a fused ring structure, or a spiro ring structure. １ The aliphatic heterocyclic structure having 3 to 20 carbon atoms represented by the formula (I) may be a combination of two or more of a bridged structure, a fused ring structure, and a spiro ring structure. １ When the aliphatic heterocyclic structure having 3 to 20 carbon atoms represented by the formula (I) has a spiro ring structure, the two or more rings constituting the spiro ring structure may be only aliphatic heterocyclic rings, or may be a combination of an aliphatic heterocyclic ring and an alicyclic hydrocarbon ring.

[0055] Examples of the ring contained in the aromatic ring structure having 6 to 20 carbon atoms include a benzene ring, a naphthalene ring, an anthracene ring, an indene ring, and a fluorene ring. １ preferably has a cyclic structure.

[0056] The radiation-sensitive cation (Y ａ＋ The radiation-sensitive cation (Y) preferably has a triarylsulfonium cation structure or a diaryliodonium cation structure. ａ＋ ) has a triarylsulfonium cation structure or a diaryliodonium cation structure, and the aromatic ring (i.e., S ＋ or I ＋ Preferably, an iodo group, a fluoro group, or a fluoroalkyl group is bonded to the aromatic ring bonded to the aromatic ring. The fluoroalkyl group is preferably a trifluoromethyl group.

[0057] When a in the above formula (1) is 1, Y ａ＋ Specific examples of the cation represented by the formula (4A), the formula (4B), or the formula (4C) are preferred. (In formula (4A), R １ａ , R ２ａ and R ３ａ are each independently an iodo group, a fluoro group, or a fluoroalkyl group. ４ａ and R ５ａ are each independently a monovalent substituent, or R ４ａ and R ５ａ are combined together to represent a single bond or a divalent group connecting the rings to which they are attached. ６ａ is a monovalent substituent. a1, a2, and a3 each independently represent an integer of 0 to 5. a4, a5, and a6 each independently represent an integer of 0 to 3. r is 0 or 1, provided that a1 + a4 ≦ 5, a2 + a5 ≦ 5, and a3 + a6 ≦ 2 × r + 5 are satisfied. In formula (4B), R ７ａand R ８ａ are each independently an iodo group, a fluoro group, or a fluoroalkyl group. ９ａ and R １０ａ are each independently a monovalent substituent. a7 and a8 are each independently an integer of 0 to 5. a9 and a10 are each independently an integer of 0 to 3, provided that a7 + a9 ≦ 5 and a8 + a10 ≦ 5 are satisfied. In formula (4C), R １１ａ is an iodo group, a fluoro group, or a fluoroalkyl group. １２ａ is a monovalent substituent. a11 is an integer of 0 to 5. a12 is an integer of 0 to 3. t2 is 0 or 1. However, a11 + a12 ≦ 2 × t2 + 5 is satisfied. R １３ａ is a monovalent organic group having 1 to 20 carbon atoms, a hydroxyl group, a nitro group, or a halogen atom. a13 is an integer of 0 to 6. t1 is an integer of 0 to 3. R １４ａ is a single bond or a divalent organic group having 1 to 20 carbon atoms.

[0058] R １ａ , R ２ａ , R ３ａ , R ７ａ , R ８ａ and R １１ａ is preferably an iodo group, a fluoro group, a trifluoromethyl group, a 2,2,2-trifluoroethyl group, or a perfluoroethyl group, and more preferably an iodo group, a fluoro group, or a trifluoromethyl group. Furthermore, it is preferable that a1, a2, and a3 satisfy "a1 + a2 + a3 ≧ 1", a7 and a8 satisfy "a7 + a8 ≧ 1", and a11 and a12 satisfy "a11 + a12 ≧ 1". Having a structure in which an iodo group, a fluoro group, or a trifluoromethyl group is directly bonded to an aromatic ring can further improve the sensitivity of the composition, and a radiation-sensitive composition with excellent lithography performance can be obtained.

[0059] In the above formulas (4A) to (4C), R ４ａ , R ５ａ , R ６ａ , R ９ａ , R １０ａ and R １２ａExamples of the monovalent substituent represented by the formula (I) include a chloro group, a bromo group, a substituted or unsubstituted alkyl group (excluding a fluoroalkyl group), a substituted or unsubstituted alkoxy group, a substituted or unsubstituted cycloalkyl group, a substituted or unsubstituted cycloalkyloxy group, an ester group, an alkylsulfonyl group, a cycloalkylsulfonyl group, a hydroxyl group, a carboxy group, a cyano group, and a nitro group.

[0060] When a in the above formula (1) is 1, the radiation-sensitive cation (Y ａ＋ Specific examples of the radiation-sensitive cation (Y) include cations represented by the following formulae: ａ＋ ) are not limited to these.

[0061] In the above formula (3), the sulfonate anion (J － ) preferably has a structure in which an iodine group is bonded to an aromatic ring, in that this can further increase the sensitivity of the present composition.

[0062] In order to further improve the CDU performance of the present composition, the second structural unit is preferably a structural unit represented by the above formula (1). Specific examples of the second structural unit represented by the above formula (1) include a structural unit represented by the following formula (1a): (In formula (1a), R １ is a hydrogen atom, a fluorine atom, a methyl group, or a trifluoromethyl group. １ R is a single bond, —O—, —COO— or a divalent aromatic ring group. ２６ is a divalent organic group having 1 to 40 carbon atoms. ２４ and R ２５ are each independently a hydrogen atom, a fluorine atom, an alkyl group having 1 to 10 carbon atoms, or a fluoroalkyl group having 1 to 10 carbon atoms. ６ is a single bond or —COO—. ａ＋ is a cation with a valence of a. a is 1 or 2.

[0063] In the above formula (1a), R １ , L１ , Y ａ＋ The explanation of formula (1) above applies to R and a. ２４ ~R ２６ When each group has a substituent, the substituent may be L １ , L １１ and R ２１ ~R ２３ When each group has a substituent, examples of the substituent include the groups exemplified above. ２６ Examples of the divalent organic group having 1 to 40 carbon atoms represented by the formula (1) are A １ is a divalent organic group.

[0064] Further specific examples of the second structural unit include structural units represented by the following formulas. (In the formula, R ２０ is a hydrogen atom, a fluorine atom, a methyl group, or a trifluoromethyl group. ａ＋ is a radiation-sensitive onium cation with a valence of a, where a is 1 or 2. － is a sulfonate anion.)

[0065] The content of the second structural unit in the polymer [A] is preferably 3 mol% or more, more preferably 7 mol% or more, based on the total structural units constituting the polymer [A]. The content of the second structural unit is preferably 30 mol% or less, more preferably 20 mol% or less, and even more preferably 13 mol% or less, based on the total structural units constituting the polymer [A]. By setting the content of the second structural unit within the above range, the CDU performance of the composition can be further improved.

[0066] Third Structural Unit The third structural unit has an onium salt structure formed by a radiation-sensitive onium cation and a carboxylate anion, and generates an acid upon exposure. More specifically, the third structural unit liberates a carboxylate anion when the radiation-sensitive onium cation decomposes under the action of radiation, and the liberated carboxylate anion bonds with a hydrogen atom extracted from a component contained in the composition to generate an acid derived from the carboxylate anion (i.e., a carboxylic acid or a carboxylic acid group). This third structural unit generates an acid with a lower acidity than the acid generated by the second structural unit upon exposure. Specifically, the second structural unit generates a strong acid that induces dissociation of an acid-dissociable group under normal conditions, while the third structural unit generates a weak acid that does not induce dissociation of an acid-dissociable group under normal conditions. Note that "normal conditions" here refers to conditions in which post-exposure baking (PEB) is performed at 110°C for 60 seconds.

[0067] The third structural unit is introduced into the polymer as a component that suppresses chemical reactions caused by acid in unexposed areas. By introducing such a third structural unit into the polymer, the CDU of the composition can be further improved. Furthermore, changes in the line width of the resist pattern due to variations in the exposure time until development can be suppressed, thereby providing a radiation-sensitive composition with excellent process stability.

[0068] The third structural unit is typically a structural unit derived from a monomer having a radiation-sensitive onium cation, a carboxylate anion, and a group participating in polymerization. － ) may be bonded to the main chain of the polymer directly or via a linking group, and the radiation-sensitive onium cation may form a counter ion. Alternatively, the radiation-sensitive onium cation may be bonded to the main chain of the polymer directly or via a linking group, and the carboxylate anion may form a counter ion. When the radiation-sensitive onium cation is bonded to the main chain of the polymer directly or via a linking group, from the viewpoints of the sensitivity and CDU of the composition and the ease of synthesis of the monomer, it is preferable that the radiation-sensitive onium cation is a sulfonium cation. Note that the third structural unit is different from the second structural unit.

[0069] Specific examples of the third structural unit include structural units represented by the following formula (2) or (4). (In formula (2), R ２ is a hydrogen atom, a fluorine atom, a methyl group, or a trifluoromethyl group. ２ represents a single bond, —O—, —COO—, or a divalent aromatic ring group. ２ Is, L ２ is a divalent organic group when L is —O— or —COO—; ２ is a single bond or a divalent organic group when M is a divalent aromatic ring group. ｂ＋ is a b-valent radiation-sensitive onium cation, and b is 1 or 2. In formula (4), R ２ is a hydrogen atom, a fluorine atom, a methyl group, or a trifluoromethyl group. ２ R is a single bond, —O—, —COO— or a divalent aromatic ring group. ２９ is an alkanediyl group having 1 to 6 carbon atoms, an alkenediyl group having 2 to 6 carbon atoms, or an arylene group having 6 to 12 carbon atoms, or a divalent group R containing —O— or —COO— between the carbon-carbon bonds in the alkanediyl group having 1 to 6 carbon atoms, the alkenediyl group having 2 to 6 carbon atoms, or the arylene group having 6 to 12 carbon atoms ｂ or an alkanediyl group having 1 to 6 carbon atoms, an alkenediyl group having 2 to 6 carbon atoms, an arylene group having 6 to 12 carbon atoms, or the above-mentioned divalent group R ｂ is a group in which one or more hydrogen atoms of R have been substituted. ２７ and R ２８ are each independently a substituted or unsubstituted alkyl group having 1 to 12 carbon atoms, a substituted or unsubstituted alkenyl group having 2 to 12 carbon atoms, or a substituted or unsubstituted aryl group having 6 to 20 carbon atoms. － is a carboxylate anion.)

[0070] In the above formulas (2) and (4), R ２ is preferably a hydrogen atom or a methyl group from the viewpoint of copolymerizability of the monomer that provides the third structural unit. ２When L is a divalent aromatic ring group, examples of the divalent aromatic ring group include groups in which two hydrogen atoms have been removed from a benzene ring or a naphthalene ring. ２ and R ２７ ~R ２９ When each group has a substituent, the substituent may be L １ , L １１ and R ２１ ~R ２３ When each group has a substituent, the same groups as the substituents can be mentioned.

[0071] In the above formula (2), A ２ is a divalent organic group, A ２ The divalent organic group represented by the formula (1) is A １ The divalent organic groups exemplified as the radiation-sensitive onium cation (M ｂ＋ ) is the radiation-sensitive onium cation (Y ａ＋ ) are exemplified as the radiation-sensitive onium cations.

[0072] In the above formula (4), the carboxylate anion (E － ) preferably has a structure in which an iodine group is bonded to an aromatic ring, in that this can further increase the sensitivity of the present composition.

[0073] In order to further improve the CDU performance of the present composition, the third structural unit is preferably a structural unit represented by the above formula (2). Specific examples of the third structural unit include structural units represented by the following formulas: (In the formula, R ３０ is a hydrogen atom, a fluorine atom, a methyl group, or a trifluoromethyl group. ｂ＋ is a b-valent radiation-sensitive onium cation, and b is 1 or 2. － is a carboxylate anion.)

[0074] The content of the third structural unit in the polymer [A] is preferably 3 mol% or more, more preferably 7 mol% or more, based on all structural units constituting the polymer [A]. The content of the third structural unit is preferably 40 mol% or less, more preferably 25 mol% or less, and even more preferably 15 mol% or less, based on all structural units constituting the polymer [A]. By setting the content of the third structural unit within the above range, the CDU performance of the composition can be further improved.

[0075] In terms of further improving the CDU performance of the present composition, it is preferable that in the polymer [A], the second structural unit is a structural unit represented by the above formula (1) and the third structural unit is a structural unit represented by the above formula (2).

[0076] Fourth Structural Unit The fourth structural unit is a structural unit (excluding the first structural unit, the second structural unit, and the third structural unit) having an aromatic ring and a hydroxyl group bonded to the aromatic ring. Examples of the aromatic ring to which the hydroxyl group is bonded include a benzene ring, a naphthalene ring, an anthracene ring, and a phenanthrene ring. Of these, a benzene ring or a naphthalene ring is preferred, and a benzene ring is more preferred. The number of hydroxyl groups bonded to the aromatic ring is not particularly limited. The number of hydroxyl groups bonded to the aromatic ring is preferably 1 to 3, and more preferably 1 or 2. The position of the hydroxyl group bonded to the aromatic ring is also not particularly limited. For example, when the polymer [A] has a hydroxyl group bonded to a benzene ring, the position of the hydroxyl group on the benzene ring may be any of the ortho, meta, and para positions relative to other groups.

[0077] The aromatic ring to which the hydroxyl group is bonded may further have a substituent different from the hydroxyl group bonded thereto, such as an alkyl group having 1 to 5 carbon atoms, an alkoxy group having 1 to 5 carbon atoms, or a halogen atom (e.g., a fluorine atom, a chlorine atom, a bromine atom, or an iodine atom).

[0078] Specific examples of the fourth structural unit include a structural unit represented by the following formula (iii). (In formula (iii), R １１ is a hydrogen atom, a fluoro group, a methyl group, or a trifluoromethyl group.７ represents a single bond, -O-, -CO-, * ６ -COO- or * ６ -CONH-. ６ " represents a bond to the main chain. ４ is a monovalent group having a hydroxyl group bonded to an aromatic ring.

[0079] In the above formula (iii), R １１ is preferably a hydrogen atom or a methyl group from the viewpoint of copolymerizability of the monomer that provides the fourth structural unit. ７ is a single bond or * ６ —COO— is preferred, and a single bond is more preferred in that it can further increase the sensitivity of the present composition. ４ is preferably a group in which one hydrogen atom has been removed from the ring portion of an aromatic ring to which a hydroxyl group is bonded (i.e., a monovalent aromatic ring group substituted with a hydroxyl group). ４ The aromatic ring in the ring may further have a substituent other than a hydroxyl group, specific examples of which are as described above.

[0080] Specific examples of the fourth structural unit include structural units represented by the following formulas. (In the formula, R １１ is a hydrogen atom, a fluoro group, a methyl group, or a trifluoromethyl group.

[0081] When the polymer [A] contains a fourth structural unit, the content of the fourth structural unit is preferably 5 mol% or more, more preferably 10 mol% or more, even more preferably 15 mol% or more, and even more preferably 20 mol% or more, based on the total structural units constituting the polymer [A]. Furthermore, the content of the fourth structural unit is preferably 80 mol% or less, more preferably 75 mol% or less, and even more preferably 70 mol% or less, based on the total structural units constituting the polymer [A]. By setting the content of the fourth structural unit within the above range, the lithography performance and development defect suppression properties of the composition can be further improved, which is preferable.

[0082] The present composition may contain, in addition to the polymer [A], a polymer containing a fourth structural unit. From the viewpoint of obtaining a radiation-sensitive composition that is excellent in lithography performance (such as LWR performance and CDU performance) and development defect suppression, the present composition preferably contains, as the polymer [A], a polymer having the first structural unit, the second structural unit, the third structural unit, and the fourth structural unit in the same molecule.

[0083] Fifth Structural Unit (Structural Unit (U5-1)) The structural unit (U5-1) is a structural unit having a lactone structure, a cyclic carbonate structure, a sultone structure, or a ring structure formed by combining two or more of these (excluding the first, second, third, and fourth structural units).

[0084] Specific examples of the structural unit (U5-1) include structural units represented by the following formulas: (In the formula, R Ｌ１ is a hydrogen atom, a fluorine atom, a methyl group, or a trifluoromethyl group.

[0085] When the polymer [A] contains the structural unit (U5-1), the content of the structural unit (U5-1) is preferably 1 mol % or more, more preferably 3 mol % or more, based on all structural units constituting the polymer [A]. The content of the structural unit (U5-1) is preferably 30 mol % or less, more preferably 20 mol % or less, and even more preferably 15 mol % or less, based on all structural units constituting the polymer [A].

[0086] (Structural Unit (U5-2)) The structural unit (U5-2) may further have a structural unit having an alcoholic hydroxyl group (excluding those corresponding to the first structural unit, second structural unit, third structural unit, fourth structural unit and structural unit (U5-1)). Here, in this specification, an "alcoholic hydroxyl group" refers to a group having a structure in which a hydroxyl group is directly bonded to an aliphatic hydrocarbon group. The aliphatic hydrocarbon group may be a chain hydrocarbon group or an alicyclic hydrocarbon group.

[0087] The structural unit (U5-2) is preferably a structural unit derived from an unsaturated monomer having an alcoholic hydroxyl group. The structure of the unsaturated monomer that gives the structural unit (U5-2) is not particularly limited. Specific examples of the structural unit (U5-2) include structural units represented by the following formula: (In the formula, R Ａ is a hydrogen atom, a fluorine atom, a methyl group, or a trifluoromethyl group.

[0088] When the polymer [A] contains the structural unit (U5-2), the content of the structural unit (U5-2) is preferably 1 mol % or more, more preferably 3 mol % or more, based on all structural units constituting the polymer [A]. The content of the structural unit (U5-2) is preferably 30 mol % or less, more preferably 20 mol % or less, based on all structural units constituting the polymer [A].

[0089] Examples of the fifth structural unit include, in addition to the structural unit (U5-1) and the structural unit (U5-2), structural units containing a cyano group, a nitro group, or a sulfonamide group (specifically, a structural unit derived from 2-cyanomethyladamantan-2-yl(meth)acrylate, etc.), structural units containing a non-acid-dissociable hydrocarbon group (specifically, a structural unit derived from substituted or unsubstituted styrene (e.g., a styrene unit, an iodostyrene unit, etc.), a structural unit derived from vinylnaphthalene, a structural unit derived from n-pentyl(meth)acrylate, etc.), a structural unit having a fluorine atom that is different from the structural unit (U5-1) and the structural unit (U5-2); a structural unit derived from (meth)acrylic acid; and the like. The content ratio of these structural units can be appropriately set depending on each structural unit, as long as it does not impair the effects of the present disclosure.

[0090] In the present composition, the content of the polymer [A] is preferably 50% by mass or more, more preferably 70% by mass or more, and even more preferably 85% by mass or more, based on the total amount of solids contained in the composition. Furthermore, the content of the polymer [A] is preferably 99% by mass or less, more preferably 98% by mass or less, and even more preferably 95% by mass or less, based on the total amount of solids contained in the composition. The polymer [A] preferably constitutes the base resin of the present composition. In this specification, the term "base resin" refers to a polymer component that accounts for 50% by mass or more of the total amount of solids contained in the composition. The polymer [A] constituting the base resin may be one type or two or more types. When the present composition contains two or more types of polymer [A], the total content of these two or more polymers is preferably 50% by mass or more, based on the total amount of solids contained in the composition.

[0091] The weight average molecular weight (Mw) of the polymer [A], as measured by gel permeation chromatography (GPC) in terms of polystyrene, is preferably 1,000 or more, more preferably 2,000 or more, even more preferably 3,000 or more, and even more preferably 4,000 or more. Furthermore, Mw is preferably 50,000 or less, more preferably 30,000 or less, even more preferably 20,000 or less, and even more preferably 15,000 or less. Setting the Mw of the polymer [A] within the above range is advantageous in that the coatability of the composition can be improved and development defects can be sufficiently suppressed.

[0092] The ratio (Mw / Mn) of Mw to Mn (polystyrene equivalent number average molecular weight) of the polymer (A) measured by GPC is preferably 5.0 or less, more preferably 3.0 or less, and even more preferably 2.0 or less. Mw / Mn is usually 1.0 or more, and preferably 1.1 or more.

[0093] The polymer (A) can be synthesized by polymerizing monomers that provide each structural unit in an appropriate solvent using, for example, a known radical polymerization initiator. Examples of the radical polymerization initiator include azo radical initiators (e.g., azobisisobutyronitrile (AIBN), 2,2'-azobis(4-methoxy-2,4-dimethylvaleronitrile), etc.) and peroxide radical initiators (e.g., benzoyl peroxide).

[0094] Examples of solvents used in the polymerization include linear alkanes, cycloalkanes, aromatic hydrocarbons, halogenated hydrocarbons, saturated carboxylic acid esters, ketones, ethers, and alcohols. The reaction temperature in the polymerization is preferably 40 to 150° C., and more preferably 50 to 120° C. The reaction time is preferably 1 to 48 hours, and more preferably 2 to 24 hours.

[0095] Optional components contained in the composition include [B] a radiation-sensitive acid generator, [D] a solvent, and [F] a high-fluorine-containing polymer.

[0096] <[B] Radiation-sensitive Acid Generator> The radiation-sensitive acid generator [B] is a compound that generates an acid upon exposure to light. The radiation-sensitive acid generator [B] preferably has an onium salt structure composed of a radiation-sensitive cation and an organic anion. The radiation-sensitive acid generator [B] may be a non-polymer composed of a radiation-sensitive cation and an organic anion, or may be a polymer containing a structural unit having an onium salt structure. When the radiation-sensitive acid generator [B] is a non-polymer, the molecular weight of the radiation-sensitive acid generator [B] is preferably 1,000 or less, more preferably 800 or less, and even more preferably 600 or less. The radiation-sensitive acid generator [B] is a compound different from the polymer [A].

[0097] The radiation-sensitive acid generator (B) may be a radiation-sensitive acid generator or an acid diffusion controller. The present composition may contain either a radiation-sensitive acid generator or an acid diffusion controller as the radiation-sensitive acid generator (B), or may contain both a radiation-sensitive acid generator and an acid diffusion controller. Here, the "radiation-sensitive acid generator" is a compound that generates a strong acid that induces dissociation of an acid-dissociable group under the above-described normal conditions upon exposure.

[0098] The "acid diffusion controller" is a component that can suppress the diffusion of acid generated in the resist film upon exposure of the composition, thereby suppressing chemical reactions caused by the acid in unexposed areas. By incorporating an acid diffusion controller into the composition, the lithography performance (LWR performance and CDU performance) of the composition can be further improved. Furthermore, changes in the line width of the resist pattern due to variations in the delay time between exposure and development can be suppressed, resulting in a radiation-sensitive composition with excellent process stability.

[0099] As the acid diffusion controller, a compound having an onium salt structure that generates an acid with a lower acidity than the acid generated by the radiation-sensitive acid generator (hereinafter also referred to as a "photodegradable base") is preferably used. The degree of acidity can be evaluated by the acid dissociation constant (pKa). The acid dissociation constant of the acid generated by the acid diffusion controller is usually -3 or more, preferably -1≦pKa≦7, and more preferably 0≦pKa≦5. The acid generated by the acid diffusion controller is typically a weak acid that does not induce dissociation of an acid-dissociable group under the above-mentioned normal conditions.

[0100] The composition may contain a radiation-sensitive acid generator (B) together with the polymer (A), and may generate an acid group by elimination of an acid-dissociable group due to an acid generated upon irradiation with radiation, thereby changing the solubility of the polymer (A) in a developer. Furthermore, from the viewpoint of further improving the sensitivity of the composition, the composition may contain an acid diffusion controller as the radiation-sensitive acid generator (B) together with the polymer (A).

[0101] Non-Polymer When a non-polymer is used as the radiation-sensitive acid generator [B], a compound that generates a sulfonic acid, a carboxylic acid, or a sulfonamide in the composition upon exposure to light is preferably used as the radiation-sensitive acid generator [B]. Among these, a compound that generates a sulfonic acid or a carboxylic acid in the composition is more preferably used. Specifically, the radiation-sensitive acid generator [B] preferably contains at least one selected from the group consisting of an onium salt represented by the following formula (5) and an onium salt represented by the following formula (6): (In formula (5) and formula (6), Y １１ and Y １２ is a monovalent organic group having 1 to 40 carbon atoms. ＋ is a monovalent radiation-sensitive cation.

[0102] In order to enhance the sensitivity of the composition, Y １１ or Y １２ The monovalent organic group represented by the formula (I) preferably has an aromatic ring structure, and more preferably has a structure in which an iodo group is bonded to an aromatic ring.

[0103] As the compound represented by the formula (5), Y in the formula (5) １１ , X ＋ Alternatively, the use of a compound in which both of them have an iodine group is preferable in that the sensitivity of the present composition can be increased. １２ , X ＋ Alternatively, the use of a compound in which both of them have an iodine group is preferable in that the sensitivity of the present composition can be increased.

[0104] When the organic anion has an iodo group, the radiation-sensitive acid generator [B] can preferably be at least one selected from the group consisting of onium salts represented by the following formula (5A) and onium salts represented by the following formula (6A). Among these, the onium salt represented by the following formula (5A) can be preferably used as the radiation-sensitive acid generator, and the onium salt represented by the following formula (6A) can be preferably used as the photodegradable base. (In formula (5A), W １is a monovalent aromatic ring group having 5 to 40 carbon atoms and containing an iodo group. １２ is a single bond or an (n1+1)-valent organic group, where n1 is an integer of 1 or more. ｆ１ Is, L １２ is a single bond, it is a (n1+1)-valent fluorinated hydrocarbon group, and L １２ is a (n1+1)-valent organic group, it is a divalent fluorinated hydrocarbon group. ＋ is a monovalent radiation-sensitive cation. (In formula (6A), W ２ is a monovalent aromatic ring group having 5 to 40 carbon atoms and an iodo group. n2 is an integer of 1 or more. ｃ１ represents a single bond or a divalent organic group when n2 is 1, and represents an (n2+1)-valent organic group when n2 is 2 or more. ＋ is a monovalent radiation-sensitive cation.

[0105] In the above formula (5A) and formula (6A), W １ Or W ２ The monovalent aromatic ring group represented by the formula (I) is preferably a group in which one hydrogen atom has been removed from the ring portion of a substituted aromatic ring. Examples of the aromatic ring include a benzene ring, a naphthalene ring, an anthracene ring, an indene ring, and a fluorene ring. Among these, a benzene ring or a naphthalene ring is preferred, and a benzene ring is more preferred. The substituent substituting the hydrogen atom of the aromatic ring includes an iodine group. In addition, W １ Or W ２ The aromatic ring in the ring may further have, in addition to the iodo group, a substituent other than the iodo group, such as a fluoro group, a bromo group, a chloro group, or a hydroxyl group.

[0106] R ｆ１ The divalent fluorinated hydrocarbon group represented by the formula (I) is preferably a linear or branched fluorinated saturated hydrocarbon group. The fluorinated saturated hydrocarbon group preferably has a structure in which any hydrogen atom in a linear alkanediyl group (preferably having 1 to 5 carbon atoms, more preferably having 1 to 3 carbon atoms) is substituted with a fluoroalkyl group (preferably a trifluoromethyl group) or a fluoro group.

[0107] The sensitivity of the present composition can be improved. ｆ１The divalent fluorinated hydrocarbon group represented by the formula ３ － It is preferable that R is a group in which a fluoroalkyl group (preferably a trifluoromethyl group) or a fluoro group is bonded to the carbon atom to which R ｆ１ is a (n1+1)-valent fluorinated hydrocarbon group, examples of the fluorinated hydrocarbon group include groups in which (n1-1) hydrogen atoms have been removed from the divalent fluorinated hydrocarbon group. n1 is preferably 1 to 5, more preferably 1 to 3, and even more preferably 1 or 2.

[0108] L １２ The divalent linking group represented by the formula: ２ -, -CONH-, or any methylene group in the alkanediyl group having 2 to 10 carbon atoms is -O-, -CO-, -COO-, -O-CO-O-, -S-, or -SO ２ A divalent group substituted with - or -CONH- is preferred.

[0109] R ｃ１ The divalent organic group represented by the formula (I) is a substituted or unsubstituted alkanediyl group having 1 to 20 carbon atoms, and any methylene group in the alkanediyl group is -O-, -CO-, -COO-, -OCO-, -O-CO-O-, -S-, -SO ２ Examples of the substituent include a divalent group substituted with -, -CONH-, or -NHCO-. Examples of the substituent include a fluorine atom and a hydroxyl group. ｃ１ The number of carbon atoms in the divalent organic group represented by R is preferably 1 to 10. ｃ１ is an (n2+1)-valent organic group, examples of the organic group include groups in which (n2-1) hydrogen atoms have been removed from the above-mentioned divalent organic groups. n2 is preferably 1 to 5, more preferably 1 to 3, and even more preferably 1 or 2.

[0110] Cation The cation contained in the radiation-sensitive acid generator [B] preferably has a sulfonium cation structure or an iodonium cation structure, from the viewpoint of increasing the sensitivity of the composition and forming a resist film with excellent lithography performance. The cation contained in the radiation-sensitive acid generator [B] preferably has an aromatic ring bonded to the sulfonium cation or iodonium cation, and at least one group selected from the group consisting of a fluoroalkyl group, a fluoro group (excluding fluoro groups in fluoroalkyl groups), and an iodo group bonded to the aromatic ring.

[0111] From the viewpoint of sensitivity, the cation contained in the radiation-sensitive acid generator (B) preferably has a triarylsulfonium cation structure or a diaryliodonium cation structure, specifically, a cation represented by the above formula (4A) or (4B).

[0112] Specific examples of onium salts used as radiation-sensitive acid generators include compounds represented by the following structural formulas: However, the radiation-sensitive acid generator is not limited to the following compounds.

[0113] Specific examples of onium salts used as photodegradable bases include compounds represented by the following structural formulas: However, the photodegradable base is not limited to the following compounds.

[0114] When the composition contains a radiation-sensitive acid generator (B), the content of the radiation-sensitive acid generator (B) in the composition is preferably 0.1 parts by mass or more, more preferably 0.5 parts by mass or more, and even more preferably 1 part by mass or more, relative to 100 parts by mass of the polymer (A) contained in the composition. Furthermore, the content of the radiation-sensitive acid generator (B) is preferably 20 parts by mass or less, more preferably 15 parts by mass or less, and even more preferably 10 parts by mass or less, relative to 100 parts by mass of the polymer (A). By ensuring that the content of the radiation-sensitive acid generator (B) falls within the above range, the occurrence of development defects can be sufficiently suppressed, while the effects of increasing the sensitivity of the composition and improving lithography performance can be sufficiently obtained.

[0115]

[0033] With regard to the content of the radiation-sensitive acid generator (B) in more detail, when the composition contains a radiation-sensitive acid generator as the radiation-sensitive acid generator (B), the content of the radiation-sensitive acid generator is preferably 0.5 parts by mass or more, more preferably 1 part by mass or more, and even more preferably 2 parts by mass or more, relative to 100 parts by mass of the polymer (A) contained in the composition. Furthermore, the content of the radiation-sensitive acid generator is preferably 15 parts by mass or less, more preferably 10 parts by mass or less, and even more preferably 5 parts by mass or less, relative to 100 parts by mass of the polymer (A). By setting the content of the radiation-sensitive acid generator within the above range, the sensitivity and lithography performance of the composition can be further improved.

[0116] When the composition contains a photodegradable base as the radiation-sensitive acid generator (B), the content of the photodegradable base in the composition is preferably 1 part by mass or more, more preferably 2 parts by mass or more, relative to 100 parts by mass of the polymer (A) contained in the composition, and preferably 20 parts by mass or less, more preferably 15 parts by mass or less, and even more preferably 10 parts by mass or less, relative to 100 parts by mass of the polymer (A).

[0117] <Solvent [D]> The solvent [D] is not particularly limited as long as it can dissolve or disperse the components blended in the composition. Organic solvents are preferably used as the solvent [D]. Specific examples of the solvent [D] include alcohols, ethers, ketones, amides, esters, hydrocarbons, etc.

[0118] Examples of alcohols include aliphatic monoalcohols having 1 to 18 carbon atoms, such as 4-methyl-2-pentanol and n-hexanol; alicyclic monoalcohols having 3 to 18 carbon atoms, such as cyclohexanol; polyhydric alcohols having 2 to 18 carbon atoms, such as 1,2-propylene glycol; and partial ethers of polyhydric alcohols having 3 to 19 carbon atoms, such as propylene glycol monomethyl ether. Examples of ethers include dialkyl ethers, such as diethyl ether, dipropyl ether, dibutyl ether, dipentyl ether, diisoamyl ether, dihexyl ether, and diheptyl ether; cyclic ethers, such as tetrahydrofuran and tetrahydropyran; and aromatic ring-containing ethers, such as diphenyl ether and anisole.

[0119] Examples of ketones include chain ketones such as acetone, methyl ethyl ketone, methyl n-propyl ketone, methyl n-butyl ketone, diethyl ketone, methyl isobutyl ketone, 2-heptanone, ethyl n-butyl ketone, methyl n-hexyl ketone, di-isobutyl ketone, and trimethylnonanone; cyclic ketones such as cyclopentanone, cyclohexanone, cycloheptanone, cyclooctanone, and methylcyclohexanone; 2,4-pentanedione, acetonylacetone, acetophenone, and diacetone alcohol. Examples of amides include cyclic amides such as N,N'-dimethylimidazolidinone and N-methylpyrrolidone; and chain amides such as N-methylformamide, N,N-dimethylformamide, N,N-diethylformamide, acetamide, N-methylacetamide, N,N-dimethylacetamide, and N-methylpropionamide.

[0120] Examples of esters include monocarboxylic acid esters such as n-butyl acetate, ethyl lactate, and methyl 2-hydroxyisobutyrate; polyhydric alcohol carboxylates such as propylene glycol diacetate; polyhydric alcohol partial ether carboxylates such as propylene glycol monomethyl ether acetate; polycarboxylic acid diesters such as diethyl oxalate; carbonates such as dimethyl carbonate and diethyl carbonate; and cyclic esters such as γ-butyrolactone. Examples of hydrocarbons include aliphatic hydrocarbons having 5 to 12 carbon atoms such as n-pentane and n-hexane; and aromatic hydrocarbons having 6 to 16 carbon atoms such as toluene and xylene.

[0121] The solvent [D] preferably contains at least one selected from the group consisting of esters and ketones, and more preferably contains at least one selected from the group consisting of polyhydric alcohol partial ether carboxylates and cyclic ketones. One or more kinds of solvent [D] can be used.

[0122] <[F] High-Fluorine-Content Polymer> The [F] high-fluorine-content polymer (hereinafter also referred to as “[F] polymer”) is a polymer having a higher mass content of fluorine atoms than the [A] polymer. The [F] polymer is contained in the present composition as, for example, a water-repellent additive or an additive for improving lithography performance, etc.

[0123] The fluorine atom content of the polymer [F] is not particularly limited as long as it is larger than that of the polymer [A]. The fluorine atom content of the polymer [F] is preferably 1% by mass or more, more preferably 4% by mass or more, and particularly preferably 7% by mass or more. The fluorine atom content of the polymer [F] is preferably 60% by mass or less, more preferably 40% by mass or less. The fluorine atom content (% by mass) of the polymer is １３ The polymer structure can be determined by C-NMR spectrum measurement or the like, and the amount can be calculated from the structure.

[0124] When the composition contains the polymer [F], the content of the polymer [F] in the composition is preferably 0.05 parts by mass or more, more preferably 0.1 parts by mass or more, and even more preferably 0.5 parts by mass or more, relative to 100 parts by mass of the polymer [A]. The content of the polymer [F] is preferably 15 parts by mass or less, more preferably 10 parts by mass or less, and even more preferably 5 parts by mass or less, relative to 100 parts by mass of the polymer [A]. The composition may contain only one type of polymer [F], or two or more types.

[0125] <Other Optional Components> The present composition may further contain a component (hereinafter also referred to as "other optional components") different from the above-described polymer [A], radiation-sensitive acid generator [B], solvent [D], and high-fluorine-content polymer [F]. Examples of the other optional components include nitrogen-containing compounds (e.g., alkylamines, aromatic amines, polyamines, nitrogen-containing heterocyclic compounds (e.g., N-(undecan-1-ylcarbonyloxyethyl)morpholine), nitrogen-containing compounds having an acid-dissociable group (e.g., N-(t-butoxycarbonyl)di-n-octylamine, N-t-butoxycarbonyl-4-hydroxypiperidine), surfactants, alicyclic skeleton-containing compounds (e.g., 1-adamantanecarboxylic acid, 2-adamantanone, t-butyl deoxycholate), sensitizers, and localization promoters.

[0126] <Method for producing radiation-sensitive composition> The present composition can be produced, for example, by mixing the polymer [A] and, if necessary, components such as the solvent [D] in desired proportions, and filtering the resulting mixture, preferably using a filter (for example, a filter with a pore size of about 0.2 μm). The solids concentration of the present composition is preferably 0.1% by mass or more, more preferably 0.5% by mass or more, and even more preferably 1% by mass or more. The solids concentration of the present composition is preferably 50% by mass or less, more preferably 20% by mass or less, and even more preferably 5% by mass or less. By setting the solids concentration of the present composition within the above range, it is possible to improve the coatability and form a good resist pattern shape, which is advantageous.

[0127] The composition thus obtained can be used as a positive pattern-forming composition for forming a pattern using an alkaline developer, or as a negative pattern-forming composition for forming a pattern using a developer containing an organic solvent.

[0128] <<Method of Forming Resist Pattern>> The method of forming a resist pattern according to the present disclosure includes a step of applying the present composition to one surface of a substrate (hereinafter also referred to as the "coating step"), a step of exposing the resist film obtained by the coating step (hereinafter also referred to as the "exposure step"), and a step of developing the resist film exposed by the exposure step (hereinafter also referred to as the "developing step"). Examples of patterns formed by the method of forming a resist pattern according to the present disclosure include line and space patterns and hole patterns. Since the method of forming a resist pattern according to the present disclosure uses the present composition to form a resist film, it is possible to form a resist pattern with good sensitivity, good lithography performance, and few development defects. Each step will be described below.

[0129] [Coating Step] In the coating step, the present composition is applied to one side of a substrate to form a resist film on the substrate. Conventional substrates can be used as the substrate on which the resist film is formed, including, for example, silicon wafers, silicon dioxide wafers, and aluminum-coated wafers. Alternatively, an organic or inorganic anti-reflective coating, such as that disclosed in JP-A-59-93448, may be formed on the substrate. Examples of methods for applying the present composition include spin coating, casting coating, and roll coating. After coating, a soft bake (SB, also referred to as pre-baking) may be performed to volatilize the solvent in the coating. The SB temperature is preferably 60°C or higher, more preferably 80°C or higher. The SB temperature is preferably 140°C or lower, more preferably 120°C or lower. The SB time is preferably 5 seconds or longer, more preferably 10 seconds or longer. The SB time is preferably 600 seconds or shorter, more preferably 300 seconds or shorter. The average thickness of the resist film formed is preferably 10 to 1,000 nm, and more preferably 20 to 500 nm.

[0130] [Exposure Step] In the exposure step, the resist film obtained in the coating step is exposed. This exposure is carried out by irradiating the resist film with radiation through a photomask, and optionally through an immersion medium such as water. Examples of radiation include electromagnetic waves such as visible light, ultraviolet light, far ultraviolet light, extreme ultraviolet light (EUV), X-rays, and gamma rays; charged particle beams such as electron beams and alpha rays, depending on the line width of the desired pattern. Among these, the radiation irradiated onto the resist film formed using the present composition is preferably far ultraviolet light, EUV, or electron beams, more preferably ArF excimer laser light (wavelength 193 nm), KrF excimer laser light (wavelength 248 nm), EUV, or electron beams, even more preferably ArF excimer laser light, EUV, or electron beams, even more preferably EUV or electron beams, and particularly preferably EUV.

[0131] After the exposure, post-exposure baking (PEB) is preferably performed to promote dissociation of acid-dissociable groups in the exposed portions of the resist film by acid generated from a compound that generates acid upon exposure (such as a radiation-sensitive acid generator). This PEB can increase the difference in solubility in a developer between the exposed and unexposed portions. The PEB temperature is preferably 50°C or higher, more preferably 80°C or higher. The PEB temperature is preferably 180°C or lower, more preferably 130°C or lower. The PEB time is preferably 5 seconds or longer, more preferably 10 seconds or longer. The PEB time is preferably 600 seconds or shorter, more preferably 300 seconds or shorter.

[0132] [Development Step] In the development step, the exposed resist film is developed. This allows a desired resist pattern to be formed. After development, the resist film is generally washed with a rinse liquid such as water or alcohol, and then dried. The development method in the development step may be alkali development or organic solvent development.

[0133] In the case of alkaline development, examples of the developer used for development include an alkaline aqueous solution containing at least one alkaline compound dissolved therein, such as sodium hydroxide, potassium hydroxide, sodium carbonate, sodium silicate, sodium metasilicate, aqueous ammonia, ethylamine, n-propylamine, diethylamine, di-n-propylamine, triethylamine, methyldiethylamine, ethyldimethylamine, triethanolamine, tetramethylammonium hydroxide (TMAH), pyrrole, piperidine, choline, 1,8-diazabicyclo-[5.4.0]-7-undecene, and 1,5-diazabicyclo-[4.3.0]-5-nonene. Among these, an aqueous TMAH solution is preferred, and a 2.38% by mass TMAH solution is more preferred. In the case of organic solvent development, examples of the developer include one or more organic solvents such as hydrocarbons, ethers, esters, ketones, and alcohols, and solvents containing the above organic solvents.

[0134] Examples of the developing method include a method of immersing a substrate in a tank filled with a developer for a certain period of time (dip method), a method of developing by piling up the developer on the surface of the substrate by surface tension and leaving it to stand for a certain period of time (puddle method), a method of spraying the developer onto the surface of the substrate (spray method), and a method of continuously discharging the developer while scanning a developer discharging nozzle at a constant speed onto a substrate that is rotating at a constant speed (dynamic dispense method).

[0135] 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. In the following examples, "parts" and "%" are by mass unless otherwise specified. Measurement methods for various physical properties are shown below.

[0136] [Weight-average molecular weight (Mw), number-average molecular weight (Mn), and dispersity (Mw / Mn) of polymer] The weight-average molecular weight (Mw) and number-average molecular weight (Mn) of the polymer were measured by gel permeation chromatography (GPC) using GPC columns manufactured by Tosoh Corporation (two "SuperAW2500", one "SuperAW3000", and one "SuperAW4000") under the following conditions. The dispersity (Mw / Mn) was calculated from the measurement results of Mw and Mn. Eluent: N,N-dimethylformamide (manufactured by Wako Pure Chemical Industries, Ltd.) Additive: 0.2 mass% lithium bromide Flow rate: 1.0 mL / min Sample concentration: 1.0 mass% Sample injection amount: 100 μL Column temperature: 40°C Detector: differential refractometer Standard material: monodisperse polystyrene

[0137] [Synthesis Example] Synthesis of base resins (A-1) to (A-20) and (CA-1), (CA-2) The monomers shown below were combined and copolymerized in N,N-dimethylformamide (DMF) solvent to obtain base resins (A-1) to (A-20) and (CA-1), (CA-2) having the compositions shown in Table 1. Unless otherwise specified, in the following synthesis examples, "mol %" refers to a value when the total number of moles of the monomers used is taken as 100 mol %. The composition of the obtained base resins is １ The polymers were confirmed by H-NMR, and the Mw and dispersity (Mw / Mn) were confirmed by the above-mentioned GPC (eluent: DMF, standard substance: polystyrene). The Mw and Mw / Mn of each polymer obtained are shown in Table 1.

[0138] (In the formula, X ＋ is the counter ion shown in Table 1.)

[0139]

[0140]

[0141]

[0142] In Table 1, the notation in the "Second structural unit" column indicates the counter ion (X) of the onium salt shown in the "Type" column as the monomer that gives the second structural unit. ＋) indicates that the onium salt, which is the cation described in the "Counter ion" column, was used. Similarly, the notation in the "Third structural unit" column indicates that the counter ion (X) of the onium salt described in the "Type" column was used as the monomer that provides the third structural unit. ＋ ) indicates that an onium salt, which is the cation described in the "Counter ion" column, was used. In Synthesis Examples 12, 15, and 18, two types of monomers were used as the monomer that provides the second structural unit. Regarding the notations in Table 1, for example, in Synthesis Example 12, this indicates that a monomer that provides the second structural unit was used so that the proportion of structural units derived from mg-1 (counter ion is cat 2) in the base resin (A-12) was 5 mol % and the proportion of structural units derived from mg-2 (counter ion is cat 3) was 5 mol % (total amount of second structural units: 10 mol %). Regarding the first structural unit, fourth structural unit, and other structural units, in examples in which two types of monomers were used, the amount of each monomer and the total amount are also shown in the table.

[0143] [Examples and Comparative Examples] Radiation-sensitive compositions were prepared by dissolving each component according to the composition shown in Table 2 in a solvent containing 100 ppm of FC-4430 (manufactured by 3M) as a surfactant, and filtering the resulting solution through a 0.2 μm nylon filter. In the following examples and comparative examples, unless otherwise specified, "parts by mass" refers to a value when the polymer is taken as 100 parts by mass.

[0144] In Table 2, the components other than the base resin are as follows.

[0145] (Radiation-sensitive acid generator PAG1 and acid diffusion controller Q-1)

[0146] (Organic solvent) PGMEA: Propylene glycol monomethyl ether acetate PGME: Propylene glycol monomethyl ether EL: Ethyl lactate GBL: γ-butyrolactone DAA: Diacetone alcohol HBM: Methyl 2-hydroxyisobutyrate

[0147] (High fluorine content polymer) F-1: Mw = 8,900, Mw / Mn = 2.0

[0148]

[0149] <Formation of Contact Hole (CH) Pattern> Each of the radiation-sensitive compositions prepared above was applied to the surface of a 12-inch silicon wafer on which an underlayer film (Brewer Science's "AL412") with an average thickness of 20 nm had been formed, using a spin coater (Tokyo Electron's "CLEAN TRACK ACT12"). Prebaking was performed at 130°C for 60 seconds, followed by cooling at 23°C for 30 seconds to form a resist film with an average thickness of 50 nm. Next, this resist film was irradiated with EUV light using an EUV exposure machine (ASML's "NXE3400", NA = 0.33, σ 0.9 / 0.6, quadrupole illumination conditions). After irradiation, the resist film was subjected to post-exposure baking (PEB) at 130°C for 60 seconds. Next, the resist was developed using a 2.38% by mass aqueous solution of TMAH at 23° C. for 30 seconds to form a positive contact hole pattern (diameter 25 nm, pitch 50 nm).

[0150] <Evaluation> Each CH pattern formed above was evaluated for CDU, defects, development residues, and limiting resolution according to the following methods. A scanning electron microscope (Hitachi High-Technologies' "CG-4100") was used to measure the pattern length. The evaluation results are shown in Table 2.

[0151] [CDU] The CH pattern was observed from above using the scanning electron microscope, and the diameters of a total of 800 CH patterns were measured at random locations. The 3 sigma value was calculated from the distribution of the measured values, and this was designated as CDU (nm). The smaller the CDU value, the smaller the hole diameter variation over a long period (i.e., the diameter variation between different holes), and the better. Using the CDU of Comparative Example 1 as the standard, an improvement of more than 6% was designated "A," an improvement of more than 2% to 6% was designated "B," an improvement of more than 0% to 2% was designated "C," and no improvement was designated "D." The CDU of Comparative Example 1 was designated "-."

[0152] [Defects] The above CH pattern was observed using a KLA-Tencor "KLA2905." The number of defects in the unexposed areas per 12-inch silicon wafer was measured and evaluated according to the following evaluation criteria: A: The number of defects was 200 or less; B: The number of defects was more than 200 and not more than 500; C: The number of defects was more than 500 and not more than 1,000; D: The number of defects was more than 1,000.

[0153] [Development Residue] A wafer having a resist film formed thereon was produced by performing the same operations as in the CH pattern formation method described above up to the operation of forming a resist film with an average thickness of 50 nm. Next, without performing pattern exposure using an EUV exposure machine, the wafer was post-baked for 60 seconds on a hot plate at 130°C. Next, development was performed for 30 seconds in a 2.38 mass% TMAH aqueous solution to produce a wafer for development residue evaluation. This wafer for development residue evaluation was observed with a defect inspection device (Applied Materials' "COMPLUS"), and the number of defects due to development residue (residue defects) was counted using a defect review SEM (Hitachi High-Technologies' "RS-5500"). Depending on the number of residue defects counted, evaluation was performed according to the following evaluation criteria. A: The number of residual defects is 5 or less. B: The number of residual defects is 6 to 10. C: The number of residual defects is 11 to 20. D: The number of residual defects is 21 to 50. E: The number of residual defects is 51 or more.

[0154] [Limiting Resolution] In forming the CH pattern, the exposure dose was gradually reduced from the optimum exposure dose to form the CH pattern. The obtained CH pattern was observed using the scanning electron microscope, and the minimum dimension at which the pattern resolved was defined as the limiting resolution (nm). The limiting resolution was evaluated according to the following evaluation criteria. The smaller the limiting resolution value, the better the finer the pattern that can be formed. A: Limiting resolution diameter is less than 21 nm B: Limiting resolution diameter is 21 nm or more and less than 22 nm C: Limiting resolution diameter is 22 nm or more and less than 23 nm D: Limiting resolution diameter is 23 nm or more and less than 24 nm E: Limiting resolution diameter is 24 nm or more

[0155]

[0156] As is clear from the results shown in Table 2, in which the resist films and resist patterns formed after EUV exposure were evaluated, the radiation-sensitive compositions of Examples 1 to 20 all exhibited better suppression of development residues than Comparative Example 1 or better suppression of defects than Comparative Example 2. In addition to suppression of development residues, the radiation-sensitive compositions of Examples 9, 10, and 14 to 16 also exhibited better CDU than Comparative Example 1. In addition to suppression of development residues, the radiation-sensitive compositions of Examples 11 and 12 also exhibited better suppression of defects than Comparative Example 1. In addition to suppression of development residues, the radiation-sensitive compositions of Examples 9 to 16 and 18 also exhibited better limiting resolution than Comparative Example 1. In addition to suppression of defects, the radiation-sensitive compositions of Examples 1 to 7, 9, 10, and 12 to 20 also exhibited better CDU than Comparative Example 2. In addition to suppression of defects, the radiation-sensitive composition of Example 20 exhibited better suppression of development residues than Comparative Example 2. In addition to suppression of defects, the radiation-sensitive compositions of Examples 9 to 16 and 18 also exhibited better limiting resolution than Comparative Example 2.

[0157]

[0023] The above results demonstrate that the radiation-sensitive composition and method for forming a resist pattern according to the present disclosure effectively suppress development residues and defects, and can form resist patterns that are also excellent in CDU and limiting resolution. Therefore, these compositions can be suitably used in the fabrication processes of semiconductor devices, which are expected to become even more miniaturized in the future.

Claims

1. A radiation-sensitive composition comprising a polymer containing, in the same molecule, a first structural unit having an acid dissociable group, a second structural unit having a radiation-sensitive onium cation and a sulfonate anion, and a third structural unit having a radiation-sensitive onium cation and a carboxylate anion, wherein the content of the first structural unit is 55 mol % or more of all structural units.

2. The radiation-sensitive composition according to claim 1, wherein the polymer has an iodine group.

3. The radiation-sensitive composition according to claim 2, wherein at least a portion of the first structural units in the polymer have an iodine group.

4. The radiation-sensitive composition according to claim 2, wherein at least a portion of the second structural units in the polymer have an iodine group.

5. The radiation-sensitive composition according to claim 2, wherein at least a portion of the third structural units in the polymer have an iodine group.

6. The radiation-sensitive composition according to claim 1, wherein the polymer further comprises a fourth structural unit having an aromatic ring and a hydroxyl group bonded to the aromatic ring.

7. The radiation-sensitive composition according to claim 6, wherein at least a portion of the fourth structural units has an iodine group.

8. The radiation-sensitive composition according to claim 1, wherein the second structural unit is represented by the following formula (1): (In formula (1), R １ is a hydrogen atom, a fluorine atom, a methyl group or a trifluoromethyl group. １ is -O-, -COO- or a divalent aromatic ring group. １ L １ is a divalent organic group when L is -O- or -COO-; １ is a divalent aromatic ring group, Y is a single bond or a divalent organic group. ａ＋ is a radiation-sensitive onium cation having a valence of a. a is 1 or 2.

9. The radiation-sensitive composition according to claim 1, wherein the third structural unit is represented by the following formula (2): (In formula (2), R ２ is a hydrogen atom, a fluorine atom, a methyl group or a trifluoromethyl group. ２ represents a single bond, -O-, -COO- or a divalent aromatic ring group. ２ L ２ is a divalent organic group when L is -O- or -COO-; ２ is a single bond or a divalent aromatic ring group, M is a single bond or a divalent organic group. ｂ＋ is a b-valent radiation-sensitive onium cation. b is 1 or 2.

10. The radiation-sensitive composition according to claim 1, wherein the second structural unit is represented by the following formula (1), and the third structural unit is represented by the following formula (2). (In formula (1), R １ is a hydrogen atom, a fluorine atom, a methyl group or a trifluoromethyl group. １ is -O-, -COO- or a divalent aromatic ring group. １ L １ is a divalent organic group when L is -O- or -COO-; １ is a divalent aromatic ring group, Y is a single bond or a divalent organic group. ａ＋ is a radiation-sensitive onium cation having a valence of a. a is 1 or 2. (In formula (2), R ２ is a hydrogen atom, a fluorine atom, a methyl group or a trifluoromethyl group. ２ represents a single bond, -O-, -COO- or a divalent aromatic ring group. ２ L ２ is a divalent organic group when L is -O- or -COO-; ２ is a single bond or a divalent aromatic ring group, M is a single bond or a divalent organic group. ｂ＋ is a b-valent radiation-sensitive onium cation. b is 1 or 2.

11. A method for forming a resist pattern, comprising: forming a resist film on a substrate using the radiation-sensitive composition according to any one of claims 1 to 10; exposing the resist film; and developing the exposed resist film.

12. A polymer comprising, in the same molecule, a first structural unit having an acid dissociable group, a second structural unit having a radiation-sensitive onium cation and a sulfonate anion, and a third structural unit having a radiation-sensitive onium cation and a carboxylate anion, wherein the content of the first structural unit is 55 mol % or more of all structural units.

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