Radiation-sensitive composition and resist pattern formation method

Abstract

This radiation-sensitive composition comprises: a polymer (A) which contains a structural unit having an acid-dissociable group; and a first onium salt represented by formula (1), and satisfies at least one among a first requirement and a second requirement, wherein at least one selected from the group consisting of a structural unit derived from a radiation-sensitive onium salt in the polymer (A) contained in said composition, the first onium salt, and a second onium salt contains an iodonium cation. X1 is a carboxy group or –COO-. c among a X1s in the formula are –COO-. R2 is a substituent different from a carboxy group and –COO-. First requirement: The polymer (A) further contains a structural unit derived from a radiation-sensitive onium salt. Second requirement: The second onium salt, which is a non-polymer and is a radiation-sensitive onium salt different from the first onium salt, is further contained.

Description

Radiation-sensitive composition and method for forming resist pattern

[0001] [CROSS-REFERENCE TO RELATED APPLICATIONS] This application claims priority to Japanese Patent Application No. 2024-84380, filed May 23, 2024, the entire contents of which are incorporated herein by reference. The present disclosure relates to a radiation-sensitive composition and a method for forming a resist pattern.

[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 those from 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 the generated 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] As the structures of various electronic devices become finer, there is a demand for even finer resist patterns in lithography processes. Furthermore, in response to the demand for even finer resist patterns, various efforts have been made to improve the resolution and resist pattern shape of radiation-sensitive compositions used in lithographic microfabrication (see, for example, Patent Document 1). Patent Document 1 discloses that a resist pattern can be formed with good CDU (critical dimension uniformity) by incorporating into a resist composition a salt composed of a sulfonate anion having a partial structure in which a halogen atom or a haloalkyl group is bonded to a benzene ring, and a cation.

[0004] JP 2023-36004 A

[0005] In recent years, efforts to further miniaturize resist patterns have been progressing rapidly, and attempts have been made to form patterns with line widths of 40 nm or less. Radiation-sensitive compositions used to form resist patterns are required to exhibit good CDU performance and high sensitivity even when forming such fine resist patterns.

[0006] It is believed that by incorporating an onium salt component comprising an iodonium cation and an organic anion into a resist composition, the radiation absorption efficiency (particularly EUV) can be increased, thereby improving the sensitivity of the resist composition. However, while onium salt components having an iodonium cation are highly sensitive, they also have poor storage stability, making them difficult to use as components of resist compositions.

[0007] The present disclosure has been made in consideration of the above-mentioned problems, and a main object of the present disclosure is to provide a radiation-sensitive composition and a method of forming a resist pattern that ensure storage stability, have high sensitivity to radiation, and exhibit good CDU performance.

[0008] The present inventors have found that the above-mentioned problems can be solved by using a specific onium salt. Specifically, the present disclosure provides the following radiation-sensitive composition and method for forming a resist pattern.

[0009] In one aspect, the present disclosure provides a polymer (A) containing a structural unit having an acid-dissociable group and a polymer having the following formula (1): (In formula (1), R １ is an (a+b)-valent organic group. １ is a carboxy group or —COO － However, a number of X in the formula １ Of these, c are -COO － It is. ２ represents a carboxy group and —COO － a is an integer of 2 or more; b is an integer of 0 or more; c is an integer of 1 or more, and satisfies c≦a. M ｄ＋ is a d-valent radiation-sensitive cation. d is 1 or 2. e is an integer of 1 or more, and satisfies d×e=c. When b is 2 or more, b R ２and a first onium salt represented by the following formula (1):

[0010] In another aspect, the present disclosure provides 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, exposing the resist film to light, and developing the exposed resist film.

[0011] According to the present disclosure, it is possible to obtain a radiation-sensitive composition that is highly sensitive to radiation, can form a resist pattern with excellent CDU performance, and has guaranteed storage stability.

[0012] Matters related to the implementation of the present disclosure will be described in detail below. In this specification, a numerical range described using "to" means that the numerical values ​​before and after "to" are included as the lower limit and upper limit.

[0013] 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 solely 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 solely of an alicyclic hydrocarbon structure and may also 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 solely of an aromatic ring structure and may contain a chain structure or an alicyclic hydrocarbon structure as part of it. The term "organic group" refers to an atomic group obtained by removing any hydrogen atom from a carbon-containing compound (i.e., an organic compound). An "aromatic ring" is a cyclic structure contained in an aromatic compound, and the ring structure may be composed of only carbon (for example, aromatic hydrocarbons and their derivatives), or may contain elements other than carbon, like an aromatic heterocycle. An "aliphatic ring" is a cyclic structure not contained in an aromatic compound, and the ring structure may be composed of only carbon (for example, an aliphatic hydrocarbon ring and its derivatives), or may contain elements other than carbon, like an aliphatic heterocycle.

[0014] The "main chain" of a polymer refers to the "backbone" portion of the polymer, which is the longest chain of atoms. It is acceptable for this "backbone" portion to contain a ring structure. For example, "having a specific structure in the main chain" means that the specific structure constitutes a part of the main chain of the polymer. A "side chain" refers to a portion branched from the "backbone" of the polymer. A "structural unit" refers to a unit that primarily constitutes the main chain structure, and at least two or more units are included in the main chain structure. A structural unit is typically a monomer unit. The term "structural unit" also includes a unit obtained by reacting a monomer unit having a reactive group with a compound having a functional group capable of reacting with the reactive group, and a unit obtained by polymerizing a monomer protected with a protecting group such as an alkali-dissociable group and then deprotecting the monomer by hydrolysis. "(Meth)acrylate" is a term that encompasses both "acrylate" and "methacrylate."

[0015] 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 categorized as "substituted monovalent hydrocarbon groups," and fluoroalkanediyl groups are categorized as "substituted divalent hydrocarbon groups." The same applies to other groups to which "substituted or unsubstituted" is attached.

[0016] <Radiation-Sensitive Composition> The radiation-sensitive composition of the present disclosure (hereinafter also referred to as "the composition") contains a polymer (A) including a structural unit having an acid-dissociable group, and a first onium salt represented by the following formula (1): (In formula (1), R １ is an (a+b)-valent organic group. １ is a carboxy group or —COO － However, a number of X in the formula １ Of these, c are -COO － It is. ２ represents a carboxy group and —COO－ a is an integer of 2 or more; b is an integer of 0 or more; c is an integer of 1 or more, and satisfies c≦a. M ｄ＋ is a d-valent radiation-sensitive cation. d is 1 or 2. e is an integer of 1 or more, and satisfies d×e=c. When b is 2 or more, b R ２ are the same or different.)

[0017] The composition contains an iodonium cation. The iodonium cation may be contained in the first onium salt or in the polymer (A). The composition may further contain a non-polymeric onium salt (hereinafter also referred to as a "second onium salt") different from the first onium salt, and the second onium salt may contain an iodonium cation. Hereinafter, the non-polymeric radiation-sensitive onium salts (first onium salt, second onium salt) and the polymer containing a structural unit derived from the radiation-sensitive onium salt are collectively referred to as the "onium salt component."

[0018] Polymer (A) The polymer (A) contained in the present composition is not particularly limited as long as it contains a structural unit having an acid-dissociable group. The acid-dissociable group is a group that substitutes a hydrogen atom of an acid group such as a carboxy group or a hydroxy group, and is a group that is eliminated by the action of an acid. The structural unit having an acid-dissociable group is usually introduced into the polymer (A) for the purpose of adjusting the sensitivity of the polymer (A) and its solubility in a developer. The polymer (A) preferably constitutes a base resin in the present composition. Hereinafter, the structural unit having an acid-dissociable group contained in the polymer (A) will also be referred to as a "first structural unit."

[0019] The polymer (A) may further include a structural unit different from the first structural unit. For example, the polymer (A) may further include a structural unit derived from a radiation-sensitive onium salt. Hereinafter, the structural unit derived from a radiation-sensitive onium salt contained in the polymer (A) will also be referred to as a "second structural unit."

[0020] The second structural unit is typically a structural unit derived from a monomer comprising a radiation-sensitive onium cation and an organic anion. The radiation-sensitive onium cation decomposes to liberate an organic anion, and the organic anion thus liberated combines with hydrogen atoms extracted from components contained in the composition (e.g., a radiation-sensitive acid generator, a first onium salt, a solvent, etc.), thereby generating an acid derived from the organic anion. Herein, the term "radiation" encompasses electron beams and electromagnetic waves. Examples of electron beams include visible light, ultraviolet light, far ultraviolet light, and extreme ultraviolet (EUV). Examples of electromagnetic waves include X-rays and gamma rays. Examples of organic anions include sulfonate anions and carboxylate anions. The second structural unit is an optional component, and the polymer (A) may not necessarily contain the second structural unit.

[0021] First Onium Salt The first onium salt is an onium salt represented by the above formula (1), which generates an acid upon irradiation with radiation. By incorporating the first onium salt together with an iodonium cation into the radiation-sensitive composition, it is possible to improve the sensitivity and CDU performance while ensuring the storage stability of the radiation-sensitive composition. The reason why such an effect is obtained is not clear, but one hypothesis is that the "-COO" group contained in the first onium salt － It is believed that the interaction between the iodonium cation and the carboxyl group weakens the basicity of the organic anion constituting the first onium salt, thereby suppressing the decomposition of the iodonium cation. However, this assumption does not limit the present invention in any way.

[0022] In the above formula (1), R １ The (a+b)-valent organic group represented by the formula (R) may be a group having a chain structure or may have a cyclic structure. １ The (a+b)-valent organic group represented by the formula (I) is an aromatic ring, an aliphatic ring, a chain hydrocarbon, or a chain hydrocarbon having -O-, -S-, -CO-, -NH-, -SO-, -SO between the carbon-carbon bonds. ２ - or a divalent linking group W consisting of a combination thereof １Examples of the divalent linking group W include a group obtained by removing (a+b) hydrogen atoms from a chain compound containing the following: １ Examples thereof include —CO—O— and —CO—NH ２ - etc.

[0023] Specific examples of aromatic rings include aromatic hydrocarbons such as a benzene ring, a naphthalene ring, an anthracene ring, and a phenanthrene ring; aromatic hydrocarbon derivatives such as a naphthoquinone ring and an anthraquinone ring; and aromatic heterocycles such as an oxygen-containing heterocycle, a nitrogen-containing heterocycle, and a sulfur-containing heterocycle. Examples of oxygen-containing heterocycles include a furan ring, a pyran ring, a benzopyran ring, and a coumarin ring. Examples of nitrogen-containing heterocycles include a pyrrole ring, an imidazole ring, a pyrazole ring, a triazole ring, a pyridine ring, a pyrimidine ring, a pyridazine ring, a pyrazine ring, an indole ring, and a benzimidazole ring. Examples of sulfur-containing heterocycles include a thiophene ring. Among these, in terms of being able to further increase sensitivity, a heterocycle having -O-, -S-, -CO-, -NH-, -SO-, -SO between the carbon-carbon bond of the aromatic hydrocarbon or the aromatic hydrocarbon is preferred. ２ - or a divalent linking group W consisting of a combination thereof １ A ring containing the following is preferred, and a benzene ring, a naphthalene ring, an anthracene ring, a phenanthrene ring, a naphthoquinone ring or an anthraquinone ring is more preferred.

[0024] Specific examples of the aliphatic ring include an aliphatic hydrocarbon ring and an aliphatic heterocycle.Specific examples of the aliphatic hydrocarbon ring include monocyclic saturated alicyclic hydrocarbons such as a cyclopropane ring, a cyclobutane ring, a cyclopentane ring, and a cyclohexane ring; monocyclic unsaturated alicyclic hydrocarbons such as a cyclobutene ring, a cyclopentene ring, a cyclohexene ring, and a cycloheptene ring; polycyclic saturated alicyclic hydrocarbons such as a norbornane ring, an adamantane ring, and a tricyclodecane ring; polycyclic unsaturated alicyclic hydrocarbons such as a norbornene ring, a tricyclodecene ring, and an indane ring; and the like.

[0025] Specific examples of the aliphatic heterocycle include cyclic ethers, lactones, cyclic acetals, cyclic carbonates, and sultones. These aliphatic heterocycles may have either a monocyclic structure or a polycyclic structure. The polycyclic structure may be any of a bridged structure, a fused ring structure, and a spiro ring structure, or may be a combination of two or more of a bridged structure, a fused ring structure, and a spiro ring structure. When the aliphatic heterocycle has a fused ring structure or a spiro ring structure, R １ The two or more rings constituting the formula (I) may be solely aliphatic heterocyclic rings, or may be a combination of an aliphatic heterocyclic ring and an alicyclic hydrocarbon ring.

[0026] Examples of the chain hydrocarbon include saturated chain hydrocarbons having 1 to 20 carbon atoms and unsaturated chain hydrocarbons having 2 to 20 carbon atoms. Specific examples of these include saturated chain hydrocarbons such as methane, ethane, propane, butane, pentane, hexane, and heptane. Examples of unsaturated chain hydrocarbons include alkenes such as ethene, propene, and butene; and alkynes such as ethyne, propyne, and butyne.

[0027] R １ is an aromatic hydrocarbon, a chain hydrocarbon, or an aromatic hydrocarbon or a chain hydrocarbon having —O—, —S—, —CO—, —NH—, —SO—, —SO between its carbon-carbon bond, in that it can improve sensitivity and CDU performance. ２ - or a divalent linking group W consisting of a combination thereof １ A group in which (a+b) hydrogen atoms have been removed from a heteroatom-containing compound containing the following is preferred, and a group in which (a+b) hydrogen atoms have been removed from an aromatic hydrocarbon or a chain hydrocarbon is more preferred.

[0028] a number of X in the above formula (1) １ are each independently a carboxy group or —COO － However, a number of X in the above formula (1) １ Of these, c (c≧1) are -COO － a is preferably 2 to 6, more preferably 2 to 4, and even more preferably 2 or 3.

[0029] R ２ represents a carboxy group and —COO －The substituent may be any substituent different from the above. Specific examples of the substituent include a halogeno group (such as a fluoro group, a chloro group, a bromo group, or an iodo group), a substituted or unsubstituted alkyl group, a substituted or unsubstituted alkoxy group, a substituted or unsubstituted cycloalkyl group, a substituted or unsubstituted cycloalkyloxy group, a substituted or unsubstituted aryloxy group, a substituted or unsubstituted aralkyloxy group, an ester group (-COOR, where R is a monovalent hydrocarbon group having 1 to 20 carbon atoms), an amide group (-NH-CO-R' or -CO-NH-R', where R' is a hydrogen atom or a monovalent hydrocarbon group having 1 to 20 carbon atoms), an alkylsulfonyl group, a cycloalkylsulfonyl group, a hydroxy group, a cyano group, and a nitro group. When one or more hydrogen atoms of an alkyl group, alkoxy group, cycloalkyl group, cycloalkyloxy group, aryloxy group, or aralkyloxy group are substituted, examples of the substituent include a halogeno group, a hydroxy group, a cyano group, and a nitro group.

[0030] b is preferably 0 to 10, more preferably 0 to 4, and even more preferably 0 to 2.

[0031] In the above formula (1), R １ Two or more Xs for １ The bonding position of R is not particularly limited. １ is a benzene ring and a is 2, two X １ One of the R in the formula (1) may be in the ortho position, meta position, or para position relative to the other. １ is "-COO － " is bonded to a first carbon atom and a carboxy group is bonded to a second carbon atom, and the first carbon atom and the second carbon atom are preferably adjacent to each other. For example, １ is a benzene ring, a is 2, and c is 1, then "-COO － " is preferably in the ortho position relative to the carboxy group bonded to the benzene ring. １ is a naphthalene ring, a is 2, and c is 1, "-COO －" is preferably in the ortho position relative to the carboxy group bonded to the naphthalene ring. When the first carbon atom and the second carbon atom are adjacent to each other, "-COO － It is believed that the iodonium cation is further stabilized by the combination of " and the carboxy group, thereby improving the storage stability of the composition.

[0032] M ｄ＋ The d-valent radiation-sensitive cation represented by the formula (I) is preferably a sulfonium cation or an iodonium cation, and more preferably a triarylsulfonium cation or a diaryliodonium cation, in that it can further increase the sensitivity of the present composition. ｄ＋ is preferably an iodonium cation, more preferably a diaryliodonium cation.

[0033] Specific examples of the first onium salt include onium salts represented by the following formulae: However, the first onium salt is not limited to these specific examples. (In the formula, M ＋ is a radiation-sensitive cation.

[0034] Second Onium Salt The second onium salt is a component that is optionally blended into the composition. The second onium salt is a substance that generates an acid upon irradiation with radiation, and typically has a radiation-sensitive onium cation and an organic anion that is the conjugate base of the acid. The organic anion is usually an anion obtained by removing a proton from the acid group of an organic acid. However, the organic anion of the second onium salt is different from the organic anion that constitutes the onium salt represented by formula (1) above.

[0035] The second onium salt may be a so-called radiation-sensitive acid generator or an acid diffusion controller. The present composition may contain both an acid generator and an acid diffusion controller as the second onium salt. Here, the acid generator is generally a substance that, upon exposure, generates in the present composition a strong acid capable of cleaving an acid-dissociable group possessed by a component in the radiation-sensitive composition from that component. The acid diffusion controller is generally a substance that can inhibit the diffusion of an acid derived from the acid generator generated upon exposure in the resist film, thereby inhibiting a chemical reaction caused by the acid in unexposed regions. The acid diffusion controller typically generates in the present composition a weak acid that, upon exposure, does not induce cleavage of an acid-dissociable group possessed by a component in the radiation-sensitive composition.

[0036] The second onium salt is classified as an acid generator or an acid diffusion controller depending on the strength of its acidity relative to the first onium salt in the composition. The degree of acidity can be evaluated by the acid dissociation constant (pKa). For example, the acid dissociation constant of the acid generated by the acid diffusion controller is usually −3 or higher, preferably −1≦pKa≦7, and more preferably 0≦pKa≦5. In a preferred embodiment of the composition, the second onium salt is a substance that generates an acid with a stronger acidity than the acid generated by the first onium salt. That is, in a preferred embodiment of the composition, the first onium salt is an acid diffusion controller, and the second onium salt is an acid generator. The molecular weight of the second onium salt is preferably 1,000 or less, more preferably 800 or less, and even more preferably 600 or less.

[0037] Iodonium Cation In the present composition, at least one onium salt component selected from the group consisting of the second structural unit in the polymer (A), the first onium salt, and the second onium salt contains an iodonium cation. In one embodiment of the present composition, the radiation-sensitive onium salt that provides the second structural unit in the polymer (A) and the non-polymeric radiation-sensitive onium salt are each onium salts composed of a radiation-sensitive onium cation and an organic anion that is the conjugate base of an acid, and at least a portion of these onium salts have an iodonium cation as the radiation-sensitive onium cation.

[0038] In the present composition, the component having an iodonium cation may be only one of the second structural unit in the polymer (A), the first onium salt, and the second onium salt, or may be two or more of them. Thus, only the polymer (A) may have an iodonium cation, only the first onium salt may have an iodonium cation, or only the second onium salt may have an iodonium cation. Alternatively, two or more of the polymer (A), the first onium salt, and the second onium salt may have an iodonium cation.

[0039] That is, the present composition preferably satisfies one or more of the following first and second requirements, and at least one selected from the group consisting of the second structural unit, the first onium salt, and the second onium salt contained in the present composition preferably contains an iodonium cation. First requirement: The polymer (A) further contains a second structural unit. Second requirement: The composition further contains a second onium salt that is a non-polymer and is a radiation-sensitive onium salt different from the first onium salt.

[0040] Specific embodiments in which the present composition contains an iodonium cation include the following embodiments 1 to 3, and embodiments in which two or more of these are combined. Embodiment 1: The first onium salt has an iodonium cation (i.e., M ｄ＋ is an iodonium cation). Aspect 2: The second requirement is satisfied, and the second onium salt has an iodonium cation. Aspect 3: The first requirement is satisfied, and the second structural unit in the polymer (A) contains an iodonium cation. In terms of facilitating adjustment of the sensitivity and lithography properties of the composition, it is preferred that at least a portion of the non-polymeric radiation-sensitive onium salts contained in the composition have an iodonium cation.

[0041] From the viewpoint of increasing the sensitivity of the present composition, the iodonium cation is preferably a diaryliodonium cation. Specific preferred examples of the iodonium cation include cations represented by the following formula (2): (In formula (2), Ar １ and Ar ２are each independently a group in which one hydrogen atom has been removed from a ring portion of a substituted or unsubstituted aromatic ring.

[0042] In the above formula (2), Ar １ or Ar ２ The aromatic ring may be an aromatic hydrocarbon ring or an aromatic heterocycle. Examples of the aromatic hydrocarbon ring include a benzene ring, a naphthalene ring, an anthracene ring, and a phenanthrene ring. Examples of the aromatic heterocycle include an oxygen-containing heterocycle such as a furan ring; a sulfur-containing heterocycle such as a thiophene ring; and a nitrogen-containing heterocycle such as a pyridine ring. Among these, an aromatic hydrocarbon ring or a sulfur-containing aromatic heterocycle is preferred, a benzene ring or a naphthalene ring is more preferred, and a benzene ring is even more preferred.

[0043] Ar １ or Ar ２ The aromatic ring of may have a substituent. Examples of the substituent include R ２ Examples of the substituent represented by the formula (I) include the groups exemplified above and a carboxy group.

[0044] In order to further enhance the sensitivity of the present composition, the aromatic ring (i.e., I) of the diaryliodonium cation is preferably ＋ Preferably, at least one of an iodo group, a fluoro group, and a fluoroalkyl group is bonded to the aromatic ring bonded to the aromatic ring. The fluoroalkyl group is preferably a trifluoromethyl group.

[0045] Specific examples of iodonium cations include cations represented by the following formula: However, the iodo cations in the present disclosure are not limited to the cations represented by the following formula.

[0046] Specific embodiments of the radiation-sensitive composition that satisfy one or more of Requirement 1 and Requirement 2 and in which at least one structural unit derived from a radiation-sensitive onium salt in the polymer (A), selected from the group consisting of a first onium salt and a second onium salt, contains an iodonium cation include, for example, the following embodiments [1] to [6] and embodiments that combine two or more of these embodiments. Embodiment [1]: The composition contains a polymer (A), a first onium salt, and a second onium salt, wherein the first onium salt is an acid diffusion controller, the second onium salt is an acid generator, and the second onium salt that is the acid generator has an iodonium cation. Embodiment [2]: The composition contains a polymer (A), a first onium salt, and a second onium salt, wherein the first onium salt is an acid diffusion controller, the second onium salt is an acid generator, and the first onium salt that is the acid diffusion controller has an iodonium cation. Aspect [3]: The composition contains a polymer (A), a first onium salt, and a second onium salt, wherein the first onium salt is an acid diffusion controller, the second onium salt is an acid generator, and both the first onium salt that is an acid diffusion controller and the second onium salt that is an acid generator have iodonium cations. Aspect [4]: ​​The composition contains a polymer (A) and a first onium salt, wherein the polymer (A) contains a second structural unit and functions as an acid generator, the first onium salt is an acid diffusion controller, and the second structural unit contains an iodonium cation. Aspect [5]: The composition contains a polymer (A) and a first onium salt, wherein the polymer (A) contains a second structural unit and functions as an acid generator, the first onium salt is an acid diffusion controller, and the first onium salt contains an iodonium cation. Aspect [6]: The composition contains a polymer (A) and a first onium salt, wherein the polymer (A) contains a second structural unit and functions as an acid generator, the first onium salt is an acid diffusion controller, and the second structural unit and the first onium salt contain an iodonium cation.

[0047] The radiation-sensitive compositions of the above-described embodiments [1] to [6] may further contain other solid components (such as an acid generator, an acid diffusion controller, or a high-fluorine-containing polymer) in addition to the components contained in each embodiment. For example, embodiment [1] may further contain a high-fluorine-containing polymer, and embodiment [4] may further contain a second onium salt as an acid generator. In this specification, the term "solid components" refers to components other than the solvent contained in the composition.

[0048] Next, the polymer (A), the second onium salt, and the optional components contained in the composition will be described in detail. Unless otherwise specified, each component contained in the composition may be used alone or in combination of two or more.

[0049] <Polymer (A)> (First structural unit) The first structural unit is not particularly limited as long as it has an acid-dissociable group. Examples of the first structural unit include a structural unit represented by the following formula (1-1) (hereinafter also referred to as "structural unit (1a)"), a structural unit represented by the following formula (1-2) (hereinafter also referred to as "structural unit (1b)"), and a structural unit represented by the following formula (1-3) (hereinafter also referred to as "structural unit (1c)"). In this specification, a structural unit having an acid-dissociable group and a hydroxyl group bonded to an aromatic ring is classified as a first structural unit. (In formula (1-1), R ３０ is a hydrogen atom, a fluorine atom, a methyl group, or a trifluoromethyl group. ２ R is a divalent chain organic group or an alicyclic hydrocarbon group. ３１ is a hydrogen atom or a substituted or unsubstituted monovalent hydrocarbon group having 1 to 20 carbon atoms. ３２ and R ３３ are each independently a substituted or unsubstituted monovalent hydrocarbon group having 1 to 20 carbon atoms, a monovalent aromatic heterocyclic group, or R ３２ and R ３３ are aligned with each other and R ３２ and R ３３ represents an alicyclic hydrocarbon structure having 3 to 20 carbon atoms, which is formed together with the carbon atom to which R is bonded. ３１ When is a hydrogen atom, R３２ and R ３３ or both of which are, independently of each other, a substituted or unsubstituted monovalent alicyclic unsaturated hydrocarbon group, a substituted or unsubstituted monovalent aromatic hydrocarbon group, or a monovalent aromatic heterocyclic group, or R ３２ and R ３３ are aligned with each other and R ３２ and R ３３ represents an alicyclic unsaturated hydrocarbon structure having 3 to 20 carbon atoms, which is formed together with the carbon atom to which it is bonded. g1 is 0 or 1. In formula (1-2), R ３０ is a hydrogen atom, a fluorine atom, a methyl group, or a trifluoromethyl group. ３ represents a single bond, -O-, -CO-, * ２ -COO- or * ２ -CONH-. ２ " represents a bond to the main chain. ３４ , R ３５ and R ３６ 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. ２８ is a monovalent substituent. g2 is an integer of 0 to 4. In formula (1-3), R ３０ is a hydrogen atom, a fluorine atom, a methyl group, or a trifluoromethyl group. ４ represents a single bond, -O-, -CO-, * ３ -COO- or * ３ -CONH-. ３ " represents a bond to the main chain. ３７ 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. ３８ and R ３９ 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 ３８ and R ３９ are aligned with each other and R ３８ and R ３９represents an alicyclic hydrocarbon structure having 3 to 20 carbon atoms formed together with the carbon atom to which R is bonded. ２９ is a monovalent substituent. g3 is an integer of 0 to 4.

[0050] In the above formula (1-1), R ３０ In view of the copolymerizability of the monomer that gives the structural unit (1a), R is preferably a hydrogen atom or a methyl group, and more preferably a methyl group. ３０ is preferably a hydrogen atom from the viewpoint of copolymerizability of the monomer that gives the structural unit (1b). ３０ is preferably a hydrogen atom or a methyl group.

[0051] R in the above formulas (1-1) to (1-3) ３１ ~R ３３ , R ３４ ~R ３６ or R ３７ ~R ３９ 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.

[0052] The monovalent chain hydrocarbon group having 1 to 20 carbon atoms may be saturated or unsaturated, and may be linear or branched. 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. Among these, R ３１ ~R ３３ The monovalent chain hydrocarbon group having 1 to 20 carbon atoms represented by the formula (I) is preferably an alkyl group or an alkenyl group, more preferably an alkyl group having 1 to 4 carbon atoms or an alkenyl group having 2 to 4 carbon atoms.

[0053] Examples of monovalent alicyclic hydrocarbon groups having 3 to 20 carbon atoms include monovalent monocyclic alicyclic saturated hydrocarbon groups such as cyclopentyl, cyclohexyl, methylcyclopentyl, ethylcyclopentyl, methylcyclohexyl, and ethylcyclohexyl groups; monovalent monocyclic unsaturated hydrocarbon groups such as cyclopentenyl, cyclohexenyl, methylcyclopentenyl, and methylcyclohexenyl groups; monovalent polycyclic saturated alicyclic hydrocarbon groups such as norbornyl, adamantyl, and tricyclodecyl groups; and monovalent polycyclic unsaturated alicyclic hydrocarbon groups such as norbornenyl, tricyclodecenyl, and indanyl groups. Furthermore, when the monovalent alicyclic hydrocarbon group having 3 to 20 carbon atoms has a polycyclic structure, the polycyclic structure may be any one of a fused ring structure, a bridged structure, and a spiro ring structure, or a combination of two or more of these. The monovalent alicyclic hydrocarbon group having 3 to 20 carbon atoms may further have a chain structure in addition to the alicyclic structure shown above.

[0054] Examples of the monovalent aromatic hydrocarbon group having 6 to 20 carbon atoms include aryl groups such as phenyl, tolyl, xylyl, mesityl, naphthyl, methylnaphthyl, anthryl, methylanthryl, and indenyl; and aralkyl groups such as benzyl, phenethyl, naphthylmethyl, and anthrylmethyl. The monovalent aromatic hydrocarbon group having 6 to 20 carbon atoms may further have a chain structure or an alicyclic structure in addition to the aromatic ring structure described above. Examples of the monovalent aromatic heterocyclic group include a furyl group and a thienyl group.

[0055] R ３４ ~R ３６ or R ３７ ~R ３９ Examples of the monovalent oxyhydrocarbon group having 1 to 20 carbon atoms represented by the formula (I) include the above-mentioned R ３１ ~R ３３ , R ３４ ~R ３６ and R ３７ ~R ３９ 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 ３４ ~R ３６ or R ３７ ~R３９ Of these, the monovalent oxyhydrocarbon group represented by the formula (I) is preferably an alkoxy group, a cycloalkoxy group, or a cycloalkylalkoxy group.

[0056] R ３２ and R ３３ are aligned with each other and R ３２ and R ３３ an alicyclic hydrocarbon structure having 3 to 20 carbon atoms formed together with the carbon atom to which R is bonded, or ３８ and R ３９ are aligned with each other and R ３８ and R ３９ 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 aliphatic hydrocarbon structures such as a cyclopropane structure, cyclobutane structure, cyclopentane structure, cyclohexane structure, cycloheptane structure, and cyclooctane structure; monocyclic unsaturated aliphatic hydrocarbon structures such as a cyclopentene structure and cyclohexene structure; and polycyclic aliphatic hydrocarbon structures such as a norbornane structure, adamantane structure, tricyclodecane structure, and tetracyclododecane structure.

[0057] R ３１ ~R ３３ , R ３４ ~R ３６ or R ３７ ~R ３９ When the group represented by the formula (I) has a substituent, examples of the substituent include a halogeno group, a hydroxyl group, and an alkoxy group having 1 to 3 carbon atoms.

[0058] L in the above formula (1-1) ２ The divalent chain organic group represented by the formula (I) includes a linear or branched saturated hydrocarbon group having 1 to 20 carbon atoms, a methylene group contained in the chain or branched saturated hydrocarbon group being a heteroatom-containing group (for example, -O-, -S-, -CO-, -COO-, -NH-, -NHCO-, -SO ２ -), and a divalent group having 2 to 20 carbon atoms. ２ Specific and preferred examples of the divalent alicyclic hydrocarbon group represented by the formula (1-1) include R ３１ ~R ３３Examples of the monovalent alicyclic hydrocarbon group include groups in which one hydrogen atom has been removed from the groups exemplified as the monovalent alicyclic hydrocarbon group represented by the formula: ２ is preferably a chain organic group. ３ Or L in formula (1-3) ４ is preferably a single bond, —COO— or —CONH—.

[0059] R in the above formula (1-2) ２８ , R in the above formula (1-3) ２９ Specific examples of R in the above formula (1) include ２ Examples of the substituent represented by the formula (I) include the same groups as those exemplified above and a carboxy group. g2 and g3 each preferably represent an integer of 0 to 2.

[0060] Of the first structural units, specific examples of the structural unit (1a) include structural units represented by the following formula:

[0061] Specific examples of the structural unit (1b) include structural units represented by the following formulas:

[0062] Specific examples of the structural unit (1c) include structural units represented by the following formulas:

[0063] In the formula, R ３０ is a hydrogen atom, a fluorine atom, a methyl group, or a trifluoromethyl group, but the first structural unit is not limited to the above specific examples.

[0064] In the polymer (A), the content of the first structural unit is preferably 10 mol% or more, more preferably 15 mol% or more, and even more preferably 20 mol% or more, based on the total amount of structural units contained in 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, based on the total amount of structural units contained in the polymer (A). By setting the content of the first structural unit within the above range, the difference in dissolution rate in a developer between an exposed portion and an unexposed portion can be appropriately increased while maintaining good sensitivity of the composition, thereby improving the CDU performance of the composition.

[0065] (Second structural unit) The second structural unit is a structural unit derived from a radiation-sensitive onium salt. When the organic anion in the second structural unit is a sulfonate anion, the second structural unit is thought to function primarily as a radiation-sensitive acid generator by generating a strong acid that induces dissociation of an acid-dissociable group under normal conditions. On the other hand, when the organic anion in the second structural unit is a carboxylate anion, the second structural unit is thought to function primarily as an acid diffusion controller by generating a weak acid that does not induce dissociation of an acid-dissociable group under normal conditions. Here, "normal conditions" refers to conditions in which post-exposure baking (PEB) is performed at 110°C for 60 seconds.

[0066] The second structural unit is typically a structural unit derived from a monomer having a radiation-sensitive onium cation, an organic anion, and a group participating in polymerization. ３ － Ya-COO － ) 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 organic anion may form a counter ion. In order to further improve the CDU performance of the present composition, it is preferable that the second structural unit be bonded to the main chain of the polymer via a linking group, and that the organic anion be a sulfonate anion (—SO ３ － ) is more preferably bonded to the main chain of the polymer via a linking group.

[0067] The radiation-sensitive cation in the second structural unit is preferably a sulfonium cation or an iodonium cation, more preferably a triarylsulfonium cation or a diaryliodonium cation, from the viewpoint of enhancing the sensitivity of the present composition. From the viewpoint of further enhancing the sensitivity of the present composition, the aromatic ring (i.e., S ＋ or I ＋Preferably, at least one of an iodo group, a fluoro group, and a fluoroalkyl group is bonded to the aromatic ring bonded to the aromatic ring. The fluoroalkyl group is preferably a trifluoromethyl group.

[0068] When the present composition does not contain a non-polymeric radiation-sensitive onium salt having an iodonium cation, the polymer (A) contains the second structural unit, and the second structural unit contains an iodonium cation. In other words, in this case, the present composition satisfies the first requirement, and the structural unit derived from the radiation-sensitive onium salt in the polymer (A) contains an iodonium cation.

[0069] Specific examples of the second structural unit include structural units represented by the following formulas: However, the second structural unit is not limited to these specific examples. (In the formula, R ４０ is a hydrogen atom, a fluorine atom, a methyl group, or a trifluoromethyl group. ＋ is a sulfonium cation or an iodonium cation. － is a sulfonate anion.)

[0070] When the polymer (A) contains the second structural unit, the content of the second structural unit in the polymer (A) is preferably 1 mol% or more, more preferably 2 mol% or more, and even more preferably 5 mol% or more, based on the total amount of structural units contained in the polymer (A). Furthermore, the content of the second structural unit in the polymer (A) is preferably 25 mol% or less, more preferably 20 mol% or less, based on the total amount of structural units contained in the polymer (A). By setting the content of the second structural unit within the above range, the sensitivity and CDU performance of the composition can be suitably improved.

[0071] Examples of the structural unit (other structural unit) that the polymer (A) may contain include the following third structural unit, fourth structural unit, fifth structural unit, and the like.

[0072] (Third structural unit) The polymer (A) may further contain a structural unit having an aromatic ring and a hydroxyl group bonded to the aromatic ring (referred to as the "third structural unit"). The polymer (A) having a hydroxyl group bonded to the aromatic ring is advantageous in that it can further improve the CDU performance of the composition, is highly effective in suppressing dissolution of unexposed areas into a developer, and can sufficiently reduce development defects. Furthermore, the polymer (A) containing the third 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. The third structural unit differs from the first structural unit in that it does not have an acid-dissociable group, and differs from the second structural unit in that it does not have an onium salt structure.

[0073] A preferred example of the third structural unit is a structural unit represented by the following formula (3). (In formula (3), R ５０ is a hydrogen atom, a fluoro group, a methyl group, or a trifluoromethyl group. １ represents a single bond, —COO—, or —CONH—. １ is a group obtained by removing (n1+n2+1) hydrogen atoms from an aromatic ring. ４ is a substituent different from a hydroxyl group. n1 is an integer of 1 or more. n2 is an integer of 0 or more. When n2 is 2 or more, a plurality of R ４ are the same or different.)

[0074] In the above formula (3), R ５０ is preferably a hydrogen atom or a methyl group from the viewpoint of copolymerizability of the monomer that provides the third structural unit.

[0075] A １ is a group obtained by removing (n1+n2+1) hydrogen atoms from the ring portion of an aromatic ring. The aromatic ring is preferably an aromatic hydrocarbon ring, such as a benzene ring, a naphthalene ring, an anthracene ring, or a phenanthrene ring. From the viewpoint of ease of synthesis of a monomer that provides a third structural unit and sensitivity, A １ The aromatic ring contained in is preferably a benzene ring or a naphthalene ring, more preferably a benzene ring.

[0076] The position of the hydroxyl group bonded to the aromatic ring is not particularly limited. For example, when the third structural unit has a hydroxyl group bonded to a benzene ring, the bonding position of the hydroxyl group on the benzene ring in the third structural unit may be any of the ortho-position, meta-position, and para-position relative to other groups.

[0077] R ４ R may be any group other than a hydroxyl group. ４ Specific examples of R in the above formula (1) include ２ Examples of the substituent represented by the formula (I) include groups other than a hydroxyl group. n1 is preferably 1 to 3, and more preferably 1 or 2. n2 is preferably 0 to 5, more preferably 0 to 2, and even more preferably 0 or 1.

[0078] Specific examples of the third structural unit include structural units represented by the following formulae: However, the third structural unit is not limited to these specific examples. (In the formula, R ５０ is a hydrogen atom, a fluoro group, a methyl group, or a trifluoromethyl group.

[0079] In the polymer (A), the content of the third structural unit is preferably 10 mol% or more, more preferably 15 mol% or more, and even more preferably 20 mol% or more, based on the total amount of structural units contained in the polymer (A). Furthermore, the content of the third structural unit is preferably 70 mol% or less, more preferably 65 mol% or less, and even more preferably 60 mol% or less, based on the total amount of structural units contained in the polymer (A). By setting the content of the third structural unit within the above range, the CDU performance of the present composition can be made even better.

[0080] (Fourth Structural Unit) The fourth structural unit is a structural unit (excluding the first to third structural units) having a lactone structure, a cyclic carbonate structure, a sultone structure, or a ring structure formed by combining two or more of these.

[0081] Specific examples of the fourth structural unit include structural units represented by the following formulas: However, the fourth structural unit is not limited to these specific examples. (In the formula, R Ｌ１ is a hydrogen atom, a fluorine atom, a methyl group, or a trifluoromethyl group.

[0082] When the polymer (A) contains the fourth structural unit, the content of the fourth structural unit is preferably 1 mol% or more, more preferably 2 mol% or more, based on the total amount of the structural units contained in the polymer (A). The content of the fourth structural unit in the polymer (A) is preferably 30 mol% or less, more preferably 20 mol% or less, and even more preferably 15 mol% or less, based on the total amount of the structural units contained in the polymer (A).

[0083] (Fifth structural unit) The fifth structural unit may further include a structural unit having an alcoholic hydroxyl group (excluding the first to fourth structural units). By introducing the fifth structural unit into the polymer (A), the effect of suppressing development defects can be enhanced when a resist pattern is formed using the present composition. Here, in this specification, an "alcoholic hydroxyl group" refers to a group having a structure in which a hydroxy group is directly bonded to an aliphatic hydrocarbon group. The aliphatic hydrocarbon group may be a chain hydrocarbon group or an alicyclic hydrocarbon group.

[0084] The fifth structural unit is preferably a structural unit derived from an unsaturated monomer having an alcoholic hydroxyl group. The structure of the unsaturated monomer that provides the fifth structural unit is not particularly limited. Specific examples of the fifth structural unit include structural units represented by the following formulas. However, the fifth structural unit is not limited to these specific examples. (In the formula, R Ａ is a hydrogen atom, a fluorine atom, a methyl group, or a trifluoromethyl group.

[0085] When the polymer (A) contains the fifth structural unit, from the viewpoint of enhancing the effect of suppressing development defects in the resist pattern, the content of the fifth structural unit is preferably 1 mol% or more, more preferably 3 mol% or more, based on the total amount of structural units contained in the polymer (A), and the content of the fifth structural unit is preferably 30 mol% or less, more preferably 20 mol% or less, based on the total amount of structural units contained in the polymer (A).

[0086] In addition to the above, other structural units contained in the polymer (A) include, for example, 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); structural units containing a non-acid-dissociable hydrocarbon group (specifically, a structural unit derived from styrene or a halogenated styrene, a structural unit derived from vinylnaphthalene, a structural unit derived from n-pentyl(meth)acrylate); and structural units derived from (meth)acrylic acid. Examples of structural units derived from styrene or a halogenated styrene include a styrene unit and a bromostyrene unit. The content ratio of these structural units can be appropriately set depending on the respective structural units, as long as the effects of the present invention are not impaired.

[0087] The weight average molecular weight (Mw) of the polymer (A) 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. The Mw of the polymer (A) 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. By setting the Mw of the polymer (A) within the above range, the coatability of the composition can be improved and development defects can be sufficiently suppressed, which is advantageous.

[0088] The ratio of Mw to the polystyrene-equivalent number average molecular weight (Mn) of the polymer (A) measured by GPC (Mw / Mn, hereinafter also referred to as "dispersity") is preferably 5.0 or less, more preferably 3.0 or less, and even more preferably 2.0 or less. The Mw / Mn of the polymer (A) is usually 1.0 or more.

[0089] The polymer (A) is preferably blended into the composition as at least a part of the base resin, and the content of the polymer (A) in the composition 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.

[0090] The polymer (A) can be synthesized, for example, by polymerizing monomers that provide each structural unit in an appropriate solvent using 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)), peroxide radical initiators (e.g., benzoyl peroxide), and the like. Examples of the solvent 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, more preferably 50 to 120°C. The reaction time is preferably 1 to 48 hours, more preferably 2 to 24 hours.

[0091] <Second Onium Salt> The present composition preferably contains a second onium salt from the viewpoint of ensuring high sensitivity and excellent CDU performance. That is, the present composition preferably satisfies the second requirement. When the present composition satisfies the second requirement, the first onium salt may have an iodonium cation, or the second onium salt may have an iodonium cation. Furthermore, both the first onium salt and the second onium salt may have an iodonium cation. In terms of further enhancing the effects of increasing the sensitivity and improving the CDU performance of the present composition, it is preferred that both the first onium salt and the second onium salt have an iodonium cation.

[0092] The second onium salt may be an acid generator or an acid diffusion controller. In a preferred embodiment of the present composition, the present composition contains a first onium salt and a second onium salt, wherein the first onium salt is an acid diffusion controller and the second onium salt is an acid generator.

[0093] Examples of the radiation-sensitive cation constituting the second onium salt include an iodonium cation and a sulfonium cation. Specific examples of the iodonium cation are as described above. From the viewpoint of the sensitivity of the composition, the sulfonium cation is preferably an arylsulfonium cation, and more preferably a triarylsulfonium cation. Specific examples of the sulfonium cation include cations represented by the following formula:

[0094] Examples of organic anions constituting the second onium salt include sulfonate anions, carboxylate anions, imide anions, and methide anions. Of these, sulfonate anions are preferred because they can increase the sensitivity of the composition. Specific examples of sulfonate anions include anions represented by the following formulas:

[0095]

[0096]

[0097] Specific examples of the second onium salt include appropriate combinations of the radiation-sensitive cations exemplified as specific examples of the iodonium cation and sulfonium cation with the anions exemplified as specific examples of the organic anions constituting the second onium salt. Furthermore, the second onium salt contained in the present composition may further contain an onium salt capable of functioning as an acid diffusion controller (for example, an onium salt composed of a carboxylate ion and a radiation-sensitive cation), or may contain two or more onium salts capable of functioning as acid generators.

[0098] In order to enhance the effect of improving storage stability while providing excellent sensitivity and CDU performance of the composition, the content of the first onium salt in the composition is preferably 5 parts by mole or more, more preferably 10 parts by mole or more, and even more preferably 15 parts by mole or more, relative to the total amount (100 parts by mole) of the second onium salt contained in the composition and the monomer that provides the second structural unit in the polymer (A). Furthermore, the content of the first onium salt is preferably 200 parts by mole or less, more preferably 100 parts by mole or less, and even more preferably 80 parts by mole or less, relative to the total amount (100 parts by mole) of the second onium salt contained in the composition and the monomer that provides the second structural unit in the polymer (A).

[0099] When a second onium salt is blended into the present composition, the content of the second onium salt is preferably 1 part by mass or more, and more preferably 5 parts by mass or more, per 100 parts by mass of polymer (A), from the viewpoint of fully obtaining the effect of improving sensitivity and CDU performance by blending the second onium salt. Furthermore, from the viewpoint of suppressing the occurrence of development defects due to the blending of the second onium salt, the content of the second onium salt is preferably 60 parts by mass or less, and more preferably 40 parts by mass or less, per 100 parts by mass of polymer (A).

[0100] <Other Components> The present composition may further contain components (hereinafter also referred to as "other components") other than the polymer (A), the first onium salt, and the second onium salt. Examples of other components include the following components.

[0101] High-Fluorine Content Polymer The high-fluorine content polymer (hereinafter also referred to as "polymer (F)") is a polymer having a higher mass content of fluorine atoms than polymer (A). Polymer (F) may be contained in the present composition as a water-repellent additive. Furthermore, polymer (F) may be blended into the present composition as a surface modifier that adjusts the hydrophilicity / hydrophobicity of the surface of the resist film, or as a modifier that further improves lithography performance.

[0102] 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 even more 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.

[0103] Examples of the fluorine atom-containing structural unit (hereinafter also referred to as "structural unit (f)") contained in polymer (F) include the structural unit (fa) and structural unit (fb) shown below. Polymer (F) may contain either the structural unit (fa) or the structural unit (fb) as the structural unit (f), or may contain both the structural unit (fa) and the structural unit (fb).

[0104] (Structural Unit (fa)) The structural unit (fa) is a structural unit represented by the following formula (9-1): By adjusting the content of the structural unit (fa) in the polymer (F), the fluorine atom content of the polymer (F) can be adjusted. (In formula (9-1), R Ｃ is a hydrogen atom, a fluoro group, a methyl group, or a trifluoromethyl group. G is a single bond, an oxygen atom, a sulfur atom, —COO—, or —SO ２ -O-NH-, -CONH- or -O-CO-NH-. Ｅ is a monovalent fluorinated chain hydrocarbon group having 1 to 20 carbon atoms or a monovalent fluorinated alicyclic hydrocarbon group having 3 to 20 carbon atoms.

[0105] In the above formula (9-1), R C From the viewpoint of copolymerizability of the monomer that provides the structural unit (fa), G is preferably a hydrogen atom or a methyl group, and more preferably a methyl group. From the viewpoint of copolymerizability of the monomer that provides the structural unit (fa), G is preferably a single bond or —COO—, and more preferably —COO—.

[0106] R ＥExamples of the monovalent fluorinated chain hydrocarbon group having 1 to 20 carbon atoms represented by the formula (R) include a linear or branched alkyl group having 1 to 20 carbon atoms in which some or all of the hydrogen atoms have been substituted with fluorine atoms. E Examples of the monovalent fluorinated alicyclic hydrocarbon group having 3 to 20 carbon atoms represented by the formula (I) include monocyclic or polycyclic alicyclic hydrocarbon groups having 3 to 20 carbon atoms in which some or all of the hydrogen atoms have been substituted with fluorine atoms. Ｅ is preferably a monovalent fluorinated chain hydrocarbon group, more preferably a monovalent fluorinated alkyl group, and even more preferably a 2,2,2-trifluoroethyl group, a 1,1,1,3,3,3-hexafluoropropyl group or a 5,5,5-trifluoro-1,1-diethylpentyl group.

[0107] When the polymer (F) has the structural unit (fa), the content of the structural unit (fa) is preferably 30 mol% or more, more preferably 40 mol% or more, and even more preferably 50 mol% or more, based on all structural units constituting the polymer (F). The content of the structural unit (fa) is preferably 95 mol% or less, more preferably 90 mol% or less, and even more preferably 85 mol% or less, based on all structural units constituting the polymer (F). By setting the content of the structural unit (fa) within the above range, the mass content of fluorine atoms in the polymer (F) can be more appropriately adjusted, further promoting uneven distribution of fluorine atoms in the surface layer of the resist film. This can further improve the water repellency of the resist film during immersion exposure.

[0108] (Structural Unit (fb)) The structural unit (fb) is a structural unit represented by the following formula (9-2): By including the structural unit (fb), the polymer (F) has improved solubility in an alkaline developer, which can further suppress the occurrence of development defects. (In formula (9-2), R Ｆ is a hydrogen atom, a fluoro group, a methyl group, or a trifluoromethyl group. ５９ is a hydrocarbon group having 1 to 20 carbon atoms and a valence of (s+1), or R ６０is a group in which an oxygen atom, a sulfur atom, —NR′—, a carbonyl group, —CO—O—, or —CO—NH— is bonded to the terminal of the R ６０ is a single bond or a divalent organic group having 1 to 20 carbon atoms. １２ represents a single bond, a divalent hydrocarbon group having 1 to 20 carbon atoms, or a divalent fluorinated chain hydrocarbon group having 1 to 20 carbon atoms. １１ represents an oxygen atom, —NR″—, —CO—O—*, or —SO ２ -O-*. R" is a hydrogen atom or a monovalent hydrocarbon group having 1 to 10 carbon atoms. "*" is R ６１ The binding site that binds to R ６１ is a hydrogen atom or a monovalent organic group having 1 to 30 carbon atoms. s is an integer of 1 to 3. However, when s is 2 or 3, multiple R ６０ , X １２ , A １１ and R ６１ are the same or different.)

[0109] The structural unit (fb) is divided into a structural unit having an alkali-soluble group and a structural unit having a group that dissociates under the action of an alkali to increase the solubility in an alkali developer (hereinafter, also simply referred to as an “alkali-dissociable group”).

[0110] When the structural unit (fb) has an alkali-soluble group, R ６１ is a hydrogen atom, and A １１ represents an oxygen atom, —COO—*, or —SO ２ O-*. "*" is R ６１ indicates the binding site to X １２ represents a single bond, a divalent hydrocarbon group having 1 to 20 carbon atoms, or a divalent fluorinated hydrocarbon group having 1 to 20 carbon atoms. １１ is an oxygen atom, X １２ Is A １１ is a fluorinated hydrocarbon group having a fluorine atom or a fluoroalkyl group on the carbon atom to which R is bonded. ６０ is a single bond or a divalent organic group having 1 to 20 carbon atoms. When s is 2 or 3, multiple R ６０ , X １２ , A １１ and R ６１When the structural unit (fb) has an alkali-soluble group, it is possible to increase the affinity for an alkali developer and suppress development defects.

[0111] When the structural unit (fb) has an alkali-dissociable group, R ６１ is a monovalent organic group having 1 to 30 carbon atoms, and A １１ is an oxygen atom, —NR″—, —COO—*, or —SO ２ O-*. "*" is R ６１ indicates the binding site to X １２ is a single bond or a divalent fluorinated hydrocarbon group having 1 to 20 carbon atoms. ６０ is a single bond or a divalent organic group having 1 to 20 carbon atoms. １１ -COO-* or -SO ２ If O-*, then X １２ or R ６１ Is A １１ A has a fluorine atom on the carbon atom bonded to or adjacent to the carbon atom. １１ is an oxygen atom, X １２ or R ６０ is a single bond, and R ５９ is a hydrocarbon group having 1 to 20 carbon atoms. ６０ A carbonyl group is bonded to the end of the R ６１ is an organic group having a fluorine atom. When s is 2 or 3, a plurality of R ６０ , X １２ , A １１ and R ６１ are the same or different from each other. When the structural unit (fb) has an alkali dissociable group, the surface of the resist film changes from hydrophobic to hydrophilic in the alkali development step. This can increase the affinity to the developer and more efficiently suppress development defects. Examples of the structural unit (fb) having an alkali dissociable group include A １１ is -COO-*, and R ６１ or X １２ It is particularly preferred that both of them have a fluorine atom.

[0112] When polymer (F) has structural unit (fb), the content of structural unit (fb) is preferably 40 mol% or more, more preferably 50 mol% or more, and even more preferably 60 mol% or more, based on all structural units constituting polymer (F). Furthermore, the content of structural unit (fb) is preferably 95 mol% or less, more preferably 90 mol% or less, and even more preferably 85 mol% or less, based on all structural units constituting polymer (F). By setting the content of structural unit (fb) within the above range, the water repellency of the resist film during immersion exposure can be further improved.

[0113] In addition to the structural unit (fa) and the structural unit (fb), the polymer (F) may also include a structural unit having an acid-dissociable group or a structural unit having an alicyclic hydrocarbon structure represented by the following formula (10) (hereinafter also referred to as "structural unit (g)"). (In the above formula (10), R Ｇ１ is a hydrogen atom, a fluorine atom, a methyl group, or a trifluoromethyl group. Ｇ２ is a monovalent alicyclic hydrocarbon group having 3 to 20 carbon atoms.

[0114] In the above formula (10), R Ｇ２ The monovalent alicyclic hydrocarbon group having 3 to 20 carbon atoms represented by the formula (1-1) is ３１ ~R ３３ Examples of the monovalent alicyclic hydrocarbon group include the same groups as those exemplified as the monovalent alicyclic hydrocarbon group represented by the following formula:

[0115] When polymer (F) contains a structural unit represented by formula (10), the content of the structural unit is preferably 10 mol% or more, more preferably 20 mol% or more, and even more preferably 30 mol% or more, based on all structural units constituting polymer (F). The content of the structural unit represented by formula (10) is preferably 70 mol% or less, more preferably 60 mol% or less, and even more preferably 50 mol% or less, based on all structural units constituting polymer (F).

[0116] The Mw of the polymer (F) measured by GPC is preferably 1,000 or more, more preferably 3,000 or more, and even more preferably 4,000 or more. The Mw of the polymer (F) is preferably 50,000 or less, more preferably 30,000 or less, and even more preferably 20,000 or less. The dispersity (Mw / Mn) of the polymer (F) measured by GPC, which is expressed as the ratio of Mn to Mw, is preferably 1.0 or more and 5.0 or less, and more preferably 1.0 or more and 3.0 or less.

[0117] When the composition contains polymer (F), the content of 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 polymer (A). The content of polymer (F) is preferably 10 parts by mass or less, more preferably 5 parts by mass or less, relative to 100 parts by mass of polymer (A).

[0118] The solvent is preferably one that can dissolve or disperse the components to be blended in the composition, and an organic solvent is preferably used. Specific examples of the solvent include alcohols, ethers, ketones, amides, esters, and hydrocarbons.

[0119] 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.

[0120] 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.

[0121] 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.

[0122] Of these, the solvent 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.

[0123] Other Optional Components The present composition may further contain, as other components, components other than the polymer (F) and the solvent (hereinafter also referred to as "other optional components"). Examples of the other optional components include surfactants, alicyclic skeleton-containing compounds (e.g., 1-adamantanecarboxylic acid, 2-adamantanone, t-butyl deoxycholate, etc.), sensitizers, and uneven distribution promoters.

[0124] <Method for producing radiation-sensitive composition> The present composition can be produced by mixing the polymer (A), the first onium salt, and optionally other components such as a solvent in desired proportions, and filtering the resulting mixture, preferably using a filter (for example, a filter with a pore size of approximately 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, good coatability can be achieved, and a good resist pattern shape can be obtained, which is advantageous.

[0125] 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.

[0126] <<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 a "coating step"), a step of exposing the resist film obtained by the coating step (hereinafter also referred to as an "exposure step"), and a step of developing the resist film exposed by the exposure step (hereinafter also referred to as a "developing step"). Examples of patterns formed by the method of forming a resist pattern according to the present disclosure include a line-and-space pattern and a hole pattern. Because 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 that has good sensitivity, good CDU, and good resolution. Each step will be described below.

[0127] [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 (also referred to as SB or pre-bake (PB)) 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.

[0128] [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.

[0129] 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, an acid diffusion controller, or a polymer (A) containing a second structural unit). 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.

[0130] [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.

[0131] 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.

[0132] 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).

[0133] The present invention will be described in detail below based on examples, but the present invention is not limited to these examples. In the following examples, "parts" and "%" are by mass unless otherwise specified.

[0134] The method for measuring the molecular weight of the polymer is as follows. [Weight-average molecular weight (Mw) and number-average molecular weight (Mn)] Using Tosoh GPC columns (2 G2000HXL, 1 G3000HXL, 1 G4000HXL), the weight-average molecular weight (Mw) and number-average molecular weight (Mn) were measured by gel permeation chromatography (GPC) using monodisperse polystyrene as the standard under the following analytical conditions: flow rate: 1.0 mL / min, elution solvent: tetrahydrofuran, sample concentration: 1.0 mass%, sample injection volume: 100 μL, column temperature: 40 ° C., detector: differential refractometer. The dispersity (Mw / Mn) was calculated from the measurement results of Mw and Mn.

[0135] <[A] Polymer Synthesis> The monomers used in the synthesis of the polymers in each of the Examples and Comparative Examples are shown below.

[0136] Synthesis Example 1 Synthesis of Polymer (A-1) Compound (M-1) and compound (M-4) were dissolved in 1-methoxy-2-propanol (200 parts by mass relative to the total amount of monomers) so that the molar ratio was 40 / 60. Next, azobisisobutyronitrile was added as an initiator in an amount of 6 mol % relative to the total amount of monomers to prepare a monomer solution. Meanwhile, 1-methoxy-2-propanol (100 parts by mass relative to the total amount of monomers) was added to an empty reaction vessel and heated to 85°C with stirring. Next, the monomer solution prepared above was added dropwise over 3 hours, and then heated at 85°C for an additional 3 hours. After completion of the polymerization reaction, the polymerization solution was cooled to room temperature.

[0137] The cooled polymerization solution was poured into hexane (500 parts by mass relative to the polymerization solution), and the precipitated white powder was filtered off. The filtered white powder was washed twice with hexane (100 parts by mass relative to the polymerization solution) and then dissolved in 1-methoxy-2-propanol (300 parts by mass). Next, methanol (500 parts by mass), triethylamine (50 parts by mass), and ultrapure water (10 parts by mass) were added, and a hydrolysis reaction was carried out at 70°C for 6 hours with stirring.

[0138] After the reaction was completed, the remaining solvent was distilled off, and the resulting solid was dissolved in acetone (100 parts by mass). This solution was added dropwise to 500 parts by mass of water to coagulate the resin, and the resulting solid was filtered off. The resulting mixture was dried at 50°C for 12 hours to obtain a white powdery polymer (A-1).

[0139] Synthesis Examples 2 to 11 Polymers (A-2) to (A-11) were synthesized in the same manner as in Synthesis Example 1, except that the types and ratios of monomers were changed as shown in Table 1.

[0140] Synthesis Example 12 4-hydroxystyrene (hereinafter referred to as "HS"), compound (M-4), and compound (M-3) were dissolved in 1-methoxy-2-propanol (200 parts by mass relative to the total amount of monomers) so that the molar ratio was 30 / 60 / 10. Next, azobisisobutyronitrile was added as an initiator in an amount of 6 mol% relative to the total amount of monomers to prepare a monomer solution. Meanwhile, 1-methoxy-2-propanol (100 parts by mass relative to the total amount of monomers) was added to an empty reaction vessel and heated to 85°C with stirring. Next, the monomer solution prepared above was added dropwise over 3 hours, and then the mixture was heated at 85°C for an additional 3 hours. After completion of the polymerization reaction, the polymerization solution was cooled to room temperature.

[0141] The cooled polymerization solution was poured into hexane (500 parts by mass relative to the polymerization solution), and the precipitated white powder was filtered off. The filtered white powder was washed twice with hexane (100 parts by mass relative to the polymerization solution), and then dried at 50°C for 12 hours to obtain a white powdery polymer (A-11).

[0142] Synthesis Examples 13 to 15 Polymers (A-13) to (A-15) were synthesized in the same manner as in Synthesis Example 12, except that the types and ratios of the monomers were changed as shown in Table 1.

[0143]

[0144] <Preparation of Radiation-Sensitive Composition> The radiation-sensitive acid generators, acid diffusion controllers, and solvents used in the preparation of the radiation-sensitive compositions are shown below. [B] Radiation-Sensitive Acid Generator Compounds represented by the following formulae (B-1) to (B-9) were used as radiation-sensitive acid generators.

[0145] [C] Acid Diffusion Controller Compounds represented by the following formulae (C-1) to (C-17) were used as acid diffusion controllers.

[0146] [D] Solvent D-1: Propylene glycol monomethyl ether acetate D-2: Methyl 2-hydroxyisobutyrate D-3: Propylene glycol 1-monomethyl ether D-4: Diacetone alcohol

[0147] Example 1 100 parts by mass of polymer (A-1), 20 parts by mass of radiation-sensitive acid generator (B-1), 20 mol % of acid diffusion controller (C-1) based on the radiation-sensitive acid generator (B-1), 2,000 parts by mass of solvent (D-1), and 4,800 parts by mass of solvent (D-2) were blended and mixed, and the mixture was then filtered through a filter having a pore size of 0.20 μm to prepare radiation-sensitive composition (R-1).

[0148] [Examples 2 to 39 and Comparative Examples 1 to 3] Radiation-sensitive compositions (R-2) to (R-39) and (CR-1) to (CR-3) were prepared in the same manner as in Example 1, except that the types and amounts of each component shown in Table 2 below were used.

[0149]

[0150] <Formation of Resist Pattern> Using each of the radiation-sensitive compositions (R-2) to (R-39) and (CR-1) to (CR-3), a resist pattern was formed by the following procedure. - Formation of Resist Pattern by EUV Exposure Each radiation-sensitive composition was applied to the surface of a 12-inch silicon wafer on which a 20 nm-thick underlayer film (AL412 (manufactured by Brewer Science)) had been formed, using a spin coater (CLEAN TRACK ACT12, manufactured by Tokyo Electron Ltd.). After soft baking (SB) at 100°C for 60 seconds, the wafer was cooled at 23°C for 30 seconds to form a 40 nm-thick resist film. Next, this resist film was irradiated with EUV light using an EUV exposure machine (model "NXE3300", manufactured by ASML, NA = 0.33, illumination conditions: Conventional s = 0.89). The exposed resist film was subjected to PEB (post-exposure bake) at 100°C for 60 seconds. It was then developed using a 2.38 wt% aqueous TMAH solution at 23°C for 30 seconds to form a positive-tone 50 nm pitch, 25 nm contact hole pattern. Formation of a resist pattern by KrF exposure: The radiation-sensitive composition prepared above was applied to the surface of a 12-inch silicon wafer on which a 20 nm thick underlayer film (DUV42 (Nissan Chemical Industries)) had been formed using a spin coater (CLEAN TRACK ACT12, Tokyo Electron Limited). After SB at 130°C for 60 seconds, the wafer was cooled at 23°C for 30 seconds to form a 70 nm thick resist film. Next, this resist film was irradiated with KrF light using a KrF exposure machine (model "S210D", manufactured by Nikon Corporation, NA = 0.55, illumination conditions: Annular s = 0.8, mask 150 nm LS). After exposure, the resist film was subjected to PEB at 110°C for 60 seconds. Next, it was developed using a 2.38 mass% TMAH aqueous solution at 23°C for 30 seconds to form a positive 150 nm line and space pattern.

[0151] <Evaluation> The sensitivity and CDU performance of each radiation-sensitive resin composition were evaluated by measuring each resist pattern according to the methods below. A scanning electron microscope (Hitachi High-Technologies Corporation's "CG-5000") was used to measure the resist patterns. The evaluation results are shown in Table 3. The storage stability of each radiation-sensitive composition was also evaluated according to the methods below.

[0152] [Sensitivity] In forming the resist pattern, the exposure dose for forming a 25 nm contact hole pattern was defined as the optimum exposure dose, and this optimum exposure dose was used as the sensitivity (mJ / cm ２ The smaller the value, the better the sensitivity. ２ "S" (very good) for less than 56 mJ / cm ２ More than 58mJ / cm ２ "A" (good) if less than 58 mJ / cm ２ More than 61mJ / cm ２ "B" (fairly good) in the following cases: 61 mJ / cm ２ When the test result exceeded this, it was judged as "C" (poor).

[0153] [CDU Performance] Using the above-mentioned scanning electron microscope, a 25 nm contact hole pattern was observed from above, and a total of 800 lengths were measured at random points. The dimensional variation (3σ) was calculated and defined as CDU (nm). The smaller the CDU value, the smaller the variation in hole diameter over a long period, indicating better performance. CDU was rated as "S" (very good) when it was less than 3.4 nm, "A" (good) when it was 3.4 nm or more but less than 3.6 nm, "B" (fairly good) when it was 3.6 nm or more but less than 3.8 nm, and "C" (poor) when it was 3.8 nm or more.

[0154] [Storage Stability] After preparing the radiation-sensitive composition, it was stored at -15°C for 2 weeks or at 35°C for 2 weeks. Thereafter, the optimal exposure dose for forming a 150 nm line and space pattern was determined in the resist pattern formation by KrF exposure described above. Based on the optimal exposure dose of the radiation-sensitive composition stored at -15°C for 2 weeks as a reference, the radiation-sensitive composition stored at 35°C for 2 weeks was rated as "C" (poor) if it increased sensitivity by 1.0% or more or decreased sensitivity by 1.0% or more. The radiation-sensitive composition was rated as "B" (fairly good) if it increased sensitivity by less than 1.0% but 0.7% or more or decreased sensitivity by less than 1.0% but 0.7% or more. All other cases were rated as "A" (good).

[0155]

[0156] As is clear from the results in Table 3, the radiation-sensitive compositions of Examples 1 to 39 all had good sensitivity and CDU performance while ensuring storage stability, compared to the radiation-sensitive compositions of Comparative Examples 1 to 3.

[0157] The radiation-sensitive composition and method for forming a resist pattern according to the present disclosure can improve sensitivity and CDU performance while ensuring storage stability, and therefore can be suitably used for forming fine resist patterns in lithography processes for various electronic devices such as semiconductor devices and liquid crystal devices.

Claims

1. A polymer (A) containing a structural unit having an acid-dissociable group, and a polymer represented by the following formula (1): (In formula (1), R １ is an (a+b)-valent organic group. １ is a carboxy group or —COO － However, a number of X in the formula １ Of these, c are -COO － It is. ２ represents a carboxy group and —COO － a is an integer of 2 or more; b is an integer of 0 or more; c is an integer of 1 or more, and satisfies c≦a. M ｄ＋ is a d-valent radiation-sensitive cation. d is 1 or 2. e is an integer of 1 or more, and satisfies d×e=c. When b is 2 or more, b R ２ and a first onium salt represented by the following formula (1):

2. R in the above formula (1) １ is "-COO － 2. The radiation-sensitive composition according to claim 1, wherein the radiation-sensitive composition has a first carbon atom to which "" is bonded and a second carbon atom to which a carboxy group is bonded, and the first carbon atom and the second carbon atom are adjacent to each other.

3. R ​​in the above formula (1) １ represents an aromatic ring, an aliphatic ring, a chain hydrocarbon, or a chain hydrocarbon having —O—, —S—, —CO—, —NH—, —SO—, —SO between its carbon-carbon bonds. ２ 2. The radiation-sensitive composition according to claim 1, wherein the divalent linking group is a group obtained by removing (a+b) hydrogen atoms from a chain compound containing a divalent linking group consisting of a, b, c, d ...

4. M in the above formula (1) ｄ＋ The radiation-sensitive composition according to claim 1 , wherein is an iodonium cation.

5. The radiation-sensitive composition according to claim 1, which satisfies the second requirement, and wherein the second onium salt generates an acid stronger in acidity than the acid generated by the first onium salt.

6. The radiation-sensitive composition according to claim 1, which satisfies the second requirement and wherein the second onium salt has an iodonium cation.

7. The radiation-sensitive composition according to claim 6, wherein the first onium salt and the second onium salt have an iodonium cation.

8. The radiation-sensitive composition according to claim 1, which satisfies the first requirement and in which the structural unit derived from the radiation-sensitive onium salt in said polymer (A) contains an iodonium cation.

9. The radiation-sensitive composition according to claim 1, wherein the iodonium cation is represented by the following formula (2): (In formula (2), Ar １ and Ar ２ are each independently a group in which one hydrogen atom has been removed from a ring portion of a substituted or unsubstituted aromatic ring.

10. The radiation-sensitive composition according to claim 1, wherein the polymer (A) contains a structural unit having an aromatic ring and a hydroxyl group bonded to the aromatic ring.

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. The method for forming a resist pattern according to claim 11, wherein the resist film is exposed using extreme ultraviolet light.

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