Radiation-sensitive composition and method for forming resist pattern

Abstract

This radiation-sensitive composition contains: a polymer (F) comprising a structural unit having a fluorine atom and an alkali dissociable group; and a compound represented by formula (1). In formula (1), R11, R12, and R13 are each independently a C1-20 monovalent aliphatic hydrocarbon group.

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. 2024-50039, filed on March 26, 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 an ArF excimer laser), extreme ultraviolet rays (EUV), electron beams, or the like to generate an acid in the exposed area, and a chemical reaction involving this acid causes a difference in the dissolution rate in a developer between the exposed area and the unexposed area, thereby forming a resist pattern on a substrate.

[0003] With the miniaturization of various electronic device structures, there is a demand for further miniaturization of resist patterns in lithography processes. Furthermore, in response to the demand for further miniaturization of 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 a radiation-sensitive resin composition containing: a first polymer having a structural unit containing a phenolic hydroxy group and a structural unit containing an acid-dissociable group; a second polymer having at least one of a fluorine atom and a silicon atom and a structural unit containing an alkali-dissociable group; a specific first compound that generates an acid that dissociates the acid-dissociable group in the first polymer upon irradiation with radiation; and a specific second compound that generates an acid that does not substantially dissociate the acid-dissociable group in the first polymer upon irradiation with radiation.

[0004] International Publication No. 2018 / 230334

[0005] In recent years, attempts have been made to form fine patterns, for example, with line widths of 40 nm or less. Furthermore, as resist patterns become finer, further improvements in various performances are desired. As one such improvement, suppressing the occurrence of defects during resist pattern formation has become increasingly important as resist patterns become finer.

[0006] If the properties (sensitivity, etc.) of a radiation-sensitive composition change over time, these changes may affect the shape of the resist pattern, the occurrence of defects, etc. In particular, in recent years, with the further miniaturization of resist patterns and the increasing sensitivity of radiation-sensitive compositions, there has been a demand for stabilization of the properties of radiation-sensitive compositions used in resist pattern formation.

[0007] The present disclosure has been made in consideration of the above-mentioned problems, and a primary object of the present disclosure is to provide a radiation-sensitive composition that can suppress the occurrence of defects during resist pattern formation and has excellent storage stability, and a method of forming a resist pattern using the radiation-sensitive composition.

[0008] According to one aspect of the present disclosure, there is provided a radiation-sensitive composition containing a polymer (F) including a structural unit having a fluorine atom and an alkali-dissociable group, and a compound represented by the following formula (1): (In formula (1), R １１ , R １２ and R １３ are each independently a monovalent aliphatic hydrocarbon group having 1 to 20 carbon atoms.

[0009] According to another aspect of the present disclosure, there is provided a method for forming a resist pattern, the method including the steps of forming a resist film on a substrate using the radiation-sensitive composition described above, exposing the resist film to light, and developing the exposed resist film.

[0010] According to the present disclosure, it is possible to obtain a radiation-sensitive composition that can suppress the occurrence of defects during resist pattern formation and that has excellent storage stability. Furthermore, according to the method of forming a resist pattern of the present disclosure, the occurrence of defects can be suppressed by using the radiation-sensitive composition of the present disclosure.

[0011] Matters relating to the embodiments 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 and upper limits.

[0012] 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 contain 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). The term "aromatic ring" refers to an aromatic hydrocarbon ring and an aromatic heterocycle.

[0013] 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 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 of which are contained in the main chain structure. A structural unit is typically a monomer unit. However, a "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-labile group and then deprotecting the monomer by hydrolysis. "(Meth)acrylate" is a term that encompasses both "acrylate" and "methacrylate."

[0014] The expression "substituted or unsubstituted p-valent hydrocarbon group (where p is an integer of 1 or more)" encompasses p-valent hydrocarbon groups (i.e., unsubstituted p-valent hydrocarbon groups) and groups in which p hydrogen atoms have been removed from the hydrocarbon structural portion of a substituted hydrocarbon group. Examples of substituted or unsubstituted p-valent hydrocarbon groups include alkyl groups and fluoroalkyl groups where p=1, and alkanediyl groups and fluoroalkanediyl groups where p=2. Of these, fluoroalkyl groups are "substituted monovalent hydrocarbon groups," and fluoroalkanediyl groups are "substituted divalent hydrocarbon groups." The same applies to other groups to which "substituted or unsubstituted" is attached.

[0015] <Radiation-Sensitive Composition> The radiation-sensitive composition of the present disclosure (hereinafter also referred to as "the composition") contains a polymer (F) including a structural unit having a fluorine atom and an alkali-dissociable group, and a compound represented by the following formula (1) (hereinafter also referred to as "compound (S)"): (In formula (1), R １１ , R １２ and R １３ are each independently a monovalent aliphatic hydrocarbon group having 1 to 20 carbon atoms.

[0016] The present composition containing polymer (F) and compound (S) can suppress the occurrence of development defects during resist pattern formation and provide a radiation-sensitive composition with excellent storage stability. While the reason for this effect is unclear, the following may be an example: By incorporating polymer (F) into the radiation-sensitive composition, during resist pattern formation, the alkali-dissociable groups dissociate upon contact with the developer, increasing the polarity of polymer (F), thereby enhancing the hydrophilicity of the resist film surface, thereby enhancing the ability to suppress the occurrence of defects (hereinafter also referred to as "defect suppression"). On the other hand, the alkali-dissociable groups in polymer (F) exhibit increased reactivity when an electron-withdrawing group such as a fluorine atom is located in the vicinity of the alkali-dissociable group, making them more susceptible to reaction with, for example, the solvent component in the composition. For this reason, the properties of radiation-sensitive compositions containing polymer (F) are likely to change over time, and these changes in properties are likely to affect the shape of the resist pattern, the occurrence of defects, and the like. In this regard, compound (S) has a relatively low nucleophilicity, and therefore has a low probability of reacting with polymer (F), and also exhibits high solubility in polymer components including polymer (F) and radiation-sensitive acid generators. This allows each component contained in the radiation-sensitive composition to be maintained in a stable state, and as a result, it is believed that the composition containing polymer (F) and compound (S) can achieve both defect suppression and storage stability. However, the above reasons are merely speculation and do not limit the present invention in any way.

[0017] The components contained in the present composition and the components that may be optionally blended are specifically described below. Note that, unless otherwise specified, each component contained in the present composition may be used alone or in combination of two or more.

[0018] <Polymer (F)> The polymer (F) contains a structural unit having a fluorine atom and an alkali-dissociable group (hereinafter also referred to as "structural unit (i)"). Herein, the "alkali-dissociable group" refers to a group that substitutes a hydrogen atom of an acid group such as a carboxy group or a hydroxy group, and that is eliminated in a 2.38 mass% aqueous solution of tetramethylammonium hydroxide (TMAH) at 23°C for 1 minute.

[0019] The polymer (F) preferably has a mass content of fluorine atoms (hereinafter also referred to as "fluorine atom content") of 1 mass% or more, more preferably 4 mass% or more, and even more preferably 7 mass% or more. The fluorine atom content of the polymer (F) is preferably 60 mass% or less, more preferably 40 mass% or less. The fluorine atom content (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 determined structure.

[0020] The number of fluorine atoms contained in one structural unit (i) may be at least 1. From the viewpoint of sufficiently suppressing the occurrence of defects during resist pattern formation, the number of fluorine atoms contained in the structural unit (i) is preferably 2 to 10. Furthermore, from the viewpoint of achieving a high level of both defect suppression and storage stability of the present composition, the number of fluorine atoms contained in the structural unit (i) is more preferably 2 to 6, and even more preferably 2 to 4.

[0021] The polymer (F) may be composed of only the structural unit (i). Alternatively, the polymer (F) may further contain, in addition to the structural unit (i), a structural unit different from the structural unit (i). Examples of the structural unit different from the structural unit (i) include one or more of a structural unit having an acid-dissociable group (referred to as "structural unit (ii)"); and a structural unit having a monovalent fluorinated aliphatic hydrocarbon group (referred to as "structural unit (iii)"). Each structural unit will be described in detail below.

[0022] (Structural Unit (i)) The structural unit (i) is not particularly limited as long as it has an alkali-dissociable group. A preferred specific example of the structural unit (i) is a structural unit represented by the following formula (2): (In formula (2), R Ｆ is a hydrogen atom, a fluoro group, a methyl group, a trifluoromethyl group, or a methoxymethyl group. １ is a single bond, —O—, —CO—, —COO—, —NH—, or —CONH—. ２１ is a hydrocarbon group having 1 to 20 carbon atoms and a valence of (s+1), or R ２２At the end of the side, there is an oxygen atom, a sulfur atom, and -NR ２４ R is a group to which -, a carbonyl group, a sulfonyl group, -CO-O- or -CO-NH- is bonded, or a (s+1)-valent group having a heterocyclic structure and 3 to 20 carbon atoms. ２４ is a hydrogen atom or a monovalent organic group. ２２ represents a single bond or a divalent fluorinated chain hydrocarbon group having 1 to 20 carbon atoms. １ represents an oxygen atom, —CO—O—*, or —SO ２ -O-*. "*" is R ２３ Represents a bond with R. ２３ is a monovalent organic group having 1 to 30 carbon atoms. １ is -CO-O-* or -SO ２ -O-*, then R ２２ and R ２３ At least one of １ or a group in which a fluorine atom is bonded to a carbon atom bonded to the carbon atom bonded to R ２３ But, X １ and a fluorine atom or a trifluoromethyl group bonded to the aromatic ring. ２３ In this case, X １ The bonding position of the fluorine atom or trifluoromethyl group to the aromatic ring bonded to X １ The bond position of X is 2 or 3. １ is an oxygen atom, R ２２ is a single bond, and R ２１ is an (s+1)-valent hydrocarbon group having 1 to 20 carbon atoms, and R ２３ is X １ A carbonyl group is bonded to the end of the R-side group, and a fluorine atom is bonded to the carbon atom adjacent to the carbonyl group. s is an integer of 1 to 3. However, when s is 2 or 3, multiple R ２２ are the same or different, and multiple X １ are the same or different, and multiple R ２３ are the same or different.)

[0023] In the above formula (2), R ＦA is a hydrogen atom, a fluoro group, a methyl group, a trifluoromethyl group, or a methoxymethyl group. Among these, a hydrogen atom or a methyl group is preferred from the viewpoint of copolymerizability of the monomer that provides the structural unit (i). １ is preferably a single bond or —COO—, more preferably —COO—, from the viewpoint of copolymerizability of the monomer that provides the structural unit (i).

[0024] R ２１ Examples of the (s+1)-valent hydrocarbon group having 1 to 20 carbon atoms represented by the formula (I) include an (s+1)-valent chain hydrocarbon group having 1 to 20 carbon atoms, an (s+1)-valent alicyclic hydrocarbon group having 3 to 20 carbon atoms, and an (s+1)-valent aromatic hydrocarbon group having 6 to 20 carbon atoms.

[0025] Examples of the (s+1)-valent chain hydrocarbon group having 1 to 20 carbon atoms include groups obtained by removing s hydrogen atoms (where s is an integer from 1 to 3) from a monovalent chain hydrocarbon group having 1 to 20 carbon atoms. Specific examples of the monovalent chain hydrocarbon group 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. R ２１ Of these, the (s+1)-valent chain hydrocarbon group having 1 to 20 carbon atoms represented by the following formula is preferably a saturated chain hydrocarbon group, more preferably a saturated chain hydrocarbon group having 1 to 4 carbon atoms.

[0026] Examples of the (s+1)-valent alicyclic hydrocarbon group having 3 to 20 carbon atoms include groups obtained by removing s hydrogen atoms from a monovalent alicyclic hydrocarbon group having 3 to 20 carbon atoms. Specific examples of the monovalent alicyclic hydrocarbon group include monovalent monocyclic alicyclic saturated hydrocarbon groups such as a cyclopentyl group, a cyclohexyl group, a methylcyclopentyl group, an ethylcyclopentyl group, a methylcyclohexyl group, and an ethylcyclohexyl group; monovalent monocyclic unsaturated hydrocarbon groups such as a cyclopentenyl group, a cyclohexenyl group, a methylcyclopentenyl group, and a methylcyclohexenyl group; monovalent polycyclic saturated alicyclic hydrocarbon groups such as a norbornyl group, an adamantyl group, and a tricyclodecyl group; and monovalent polycyclic unsaturated alicyclic hydrocarbon groups such as a norbornenyl group, a tricyclodecenyl group, and an indanyl group.

[0027] Examples of the (s+1)-valent aromatic hydrocarbon group having 6 to 20 carbon atoms include groups obtained by removing s hydrogen atoms from a monovalent aromatic hydrocarbon group having 6 to 20 carbon atoms. Specific 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.

[0028] R ２１ In the (s+1)-valent group having a heterocyclic structure of 3 to 20 carbon atoms and represented by the formula (I), examples of the heterocyclic structure include an aliphatic heterocyclic structure having 3 to 20 carbon atoms and an aromatic heterocyclic structure having 4 to 20 carbon atoms. Specific examples of these aliphatic heterocyclic structures having 3 to 20 carbon atoms include a cyclic ether structure, a lactone structure, a cyclic carbonate structure, a sultone structure, and a thioxane structure. The aliphatic heterocyclic structure may be either a monocyclic structure or a polycyclic structure, and may also be any of a bridged structure, a fused ring structure, and a spiro ring structure. In addition, R ２１ The aliphatic heterocyclic structure having 3 to 20 carbon atoms represented by the formula (I) may be a combination of two or more of a bridged structure, a fused ring structure, and a spiro ring structure. Examples of the aromatic heterocyclic structure having 4 to 20 carbon atoms include a furan ring structure, a benzofuran ring structure, a thiophene structure, a benzothiophene ring structure, a pyridine ring structure, a quinoline ring structure, and an isoquinoline ring structure. ２１ is a (s+1)-valent group having a heterocyclic structure and 3 to 20 carbon atoms, R ２１ is preferably a group having an aliphatic heterocyclic structure having 3 to 20 carbon atoms.

[0029] R ２４ Examples of the monovalent organic group represented by R include a monovalent chain hydrocarbon group having 1 to 10 carbon atoms, a monovalent alicyclic hydrocarbon group having 3 to 10 carbon atoms, and a monovalent aromatic hydrocarbon group having 6 to 12 carbon atoms. ２４ is preferably a hydrogen atom, an alkyl group having 1 to 6 carbon atoms, or a phenyl group, more preferably a hydrogen atom or an alkyl group having 1 to 3 carbon atoms.

[0030] R２２ When R is a divalent fluorinated chain hydrocarbon group having 1 to 20 carbon atoms, examples of the fluorinated chain hydrocarbon group include a group in which one or more hydrogen atoms in a divalent chain hydrocarbon group having 1 to 20 carbon atoms have been substituted with a fluorine atom. The divalent chain hydrocarbon group having 1 to 20 carbon atoms may be linear or branched, and may be saturated or unsaturated. Specific examples of these groups include R ２１ Examples of the groups include those obtained by removing one hydrogen atom from the monovalent chain hydrocarbon groups having 1 to 20 carbon atoms shown in the description of R. ２２ Of these, the divalent fluorinated chain hydrocarbon group having 1 to 20 carbon atoms represented by the formula (I) is preferably a linear or branched fluoroalkanediyl group, and more preferably a linear or branched fluoroalkanediyl group having 1 to 4 carbon atoms.

[0031] R ２３ Examples of the monovalent organic group having 1 to 30 carbon atoms and represented by the formula (I) include a monovalent chain hydrocarbon group having 1 to 30 carbon atoms, a monovalent fluorinated chain hydrocarbon group having 1 to 30 carbon atoms, a monovalent alicyclic hydrocarbon group having 3 to 30 carbon atoms, a monovalent fluorinated alicyclic hydrocarbon group having 3 to 30 carbon atoms, a monovalent aromatic hydrocarbon group having 6 to 30 carbon atoms, a monovalent fluorinated aromatic hydrocarbon group having 6 to 30 carbon atoms, and a group in which any methylene group in a monovalent hydrocarbon group or monovalent fluorinated hydrocarbon group having 1 to 30 carbon atoms has been replaced with a heteroatom-containing group such as -O-, -CO-, -COO-, -NH-, or -CONH-. ２３ may be a group having a chain structure or a group having a cyclic structure.

[0032] However, in the above formula (2), X １ is -CO-O-* or -SO ２ -O-* satisfies the following condition (I), and X １ When R is an oxygen atom, the following condition (II) is satisfied. ２２ and R ２３ At least one of １ or a group in which a fluorine atom is bonded to the carbon atom bonded to R ２３ But, X １and a fluorine atom or a trifluoromethyl group bonded to the aromatic ring. ２３ But, X １ and a fluorine atom or a trifluoromethyl group bonded to the aromatic ring, １ The bonding position of the fluorine atom or trifluoromethyl group to the aromatic ring bonded to X １ Condition (II): R ２２ is a single bond, and R ２１ is a hydrocarbon group having 1 to 20 carbon atoms, and R ２３ is X １ It is a group in which a carbonyl group is bonded to the end of the alkyl group and a fluorine atom is bonded to the carbon atom adjacent to the carbonyl group.

[0033] In condition (I), R ２２ and R ２３ At least one of １ (This carbon atom is called "carbon atom Y １ ") or carbon atom Y １ The carbon atom adjacent to (this carbon atom is referred to as "carbon atom Y ２ When a fluorine atom is bonded to the carbon atom Y １ or carbon atom Y ２ The number of fluorine atoms bonded to the carbon atom Y is not particularly limited, and may be one or more. １ and carbon atom Y ２ is preferably a carbon atom constituting a hydrocarbon group having one or more carbon atoms, and more preferably a carbon atom constituting a saturated chain hydrocarbon group having one or more carbon atoms. ２２ and R ２３ are each independently a saturated chain hydrocarbon group or a fluorinated saturated chain hydrocarbon group, which can improve the defect suppression property, and R ２２ and R ２３ At least one of them preferably has a fluorine atom.

[0034] If condition (I) is satisfied, R ２３ But, X １and a group having a fluorine atom or a trifluoromethyl group bonded to the aromatic ring. In this case, X in the aromatic ring １ When the bonding position of R is the 1st position, the fluorine atom or trifluoromethyl group is bonded to the 2nd or 3rd position of the aromatic ring. ２３ Specific examples include an o-fluorophenyl group, an o-trifluoromethylphenyl group, an m-fluorophenyl group, and an m-trifluoromethylphenyl group.

[0035] In condition (II), R ２３ But, X １ A carbonyl group is bonded to the end of the carbon atom Y, and the carbon atom adjacent to the carbonyl group (this carbon atom is referred to as "carbon atom Y") ３ When a fluorine atom is bonded to the carbon atom Y ３ The number of fluorine atoms bonded to the carbon atom Y is not particularly limited, and may be one or more. ３ is preferably a carbon atom constituting a hydrocarbon group having 1 or more carbon atoms, and more preferably a carbon atom constituting a saturated chain hydrocarbon group having 1 or more carbon atoms. s is an integer of 1 to 3, and preferably 1 or 2.

[0036] The structural unit (i) preferably generates a carboxyl group or a hydroxyl group upon elimination of the alkali-dissociable group. Specific preferred examples of the structural unit (i) include a structural unit represented by the following formula (2A) and a structural unit represented by the following formula (2B). (In formula (2A) and formula (2B), R ｆ１ , R ｆ２ and R ｆ３ are each independently a single bond, a methylene group, a monofluoromethylene group, or a perfluoromethylene group, provided that R ｆ１ and R ｆ２ At least one of R has a fluorine atom. ２２ａ R is a single bond or a divalent fluorinated chain hydrocarbon group having 1 to 12 carbon atoms. ２１ａ is a hydrocarbon group having 1 to 20 carbon atoms and a valence of (s+1). ２３ａ and R ２３ｂis a hydrogen atom, a fluorine atom, or a monovalent organic group having 1 to 20 carbon atoms. Ｆ , A １ , R ２１ and s is R in the above formula (1). Ｆ , A １ , R ２１ and s are synonymous.)

[0037] In order to achieve a higher level of both storage stability and defect suppression properties of the present composition, the structural unit (i) preferably satisfies the above condition (I), and is more preferably a structural unit represented by the above formula (2A). ２２ａ is an alkanediyl group or a fluoroalkanediyl group, and R ２３ａ is preferably a hydrogen atom, an alkyl group, or a fluoroalkyl group. ２３ａ is more preferably an alkyl group or a fluoroalkyl group. The number of fluorine atoms in the above formula (2A) and formula (2B) is preferably 2 to 10, more preferably 2 to 6, and even more preferably 2 to 4.

[0038] Specific examples of the structural unit (i) include structural units represented by the following formulae: However, the structural unit (i) is not limited to these specific examples.

[0039] (In the formula, R Ｆ is a hydrogen atom, a fluoro group, a methyl group, a trifluoromethyl group, or a methoxymethyl group.

[0040] In the polymer (F), the content of the structural unit (i) is preferably 40 mol% or more, more preferably 50 mol% or more, and even more preferably 60 mol% or more, based on the total amount of structural units contained in the polymer (F). Furthermore, the content of the structural unit (i) is preferably 90 mol% or less, more preferably 85 mol% or less, based on the total amount of structural units contained in the polymer (F). By setting the content of the structural unit (i) within the above range, the occurrence of defects during resist pattern formation can be sufficiently suppressed.

[0041] (Structural Unit (ii)) The structural unit (ii) is a structural unit having an acid-dissociable group. The structural unit (ii) may be introduced into the polymer (F), for example, to increase the difference in solubility of the polymer (F) between exposed and unexposed areas. Here, in this specification, the term "acid-dissociable group" refers to a group that substitutes a hydrogen atom of an acid group such as a carboxy group or a hydroxyl group, and is eliminated by the action of an acid.

[0042] The structural unit (ii) is not particularly limited as long as it has an acid-dissociable group. Examples of the structural unit (ii) include a structural unit represented by the following formula (4-1) (hereinafter also referred to as "structural unit (iia)"), a structural unit represented by the following formula (4-2) (hereinafter also referred to as "structural unit (iib)"), and a structural unit represented by the following formula (4-3) (hereinafter also referred to as "structural unit (iic)"). (In formula (4-1), 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, R ３２ 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 ３３represents 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 (4-2), 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 -OC(R ３４ ) (R ３５ ) (R ３６ g2 is an integer of 0 to 4. In formula (4-3), 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 ３９ represents an alicyclic hydrocarbon structure having 3 to 20 carbon atoms formed together with the carbon atom to which R is bonded. ２９ is -COO-C(R ３７ ) (R ３８ ) (R ３９ g3 is an integer of 0 to 4.

[0043] In the above formula (4-1), R ３０ In view of the copolymerizability of the monomer that gives the structural unit (iia), 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 (iib). ３０ is preferably a hydrogen atom or a methyl group. ３ and L in formula (4-3) ４ are each preferably a single bond, —COO— or —CONH—.

[0044] L in the above formula (4-1) 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 (2) include R ２２ Examples 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.

[0045] R in the above formulas (4-1) to (4-3) 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 (2) 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. Specific examples of these groups include R ２２ Examples include the same monovalent hydrocarbon groups as those exemplified in the description of the above.

[0046] R ３２ and R ３３are 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, and ３５ and R ３６ are aligned with each other and R ３５ and R ３６ Examples of the alicyclic hydrocarbon structure having 3 to 20 carbon atoms constituted together with the carbon atom to which it is bonded include monocyclic saturated alicyclic hydrocarbon structures such as a cyclopropane structure, cyclobutane structure, cyclopentane structure, cyclohexane structure, cycloheptane structure, and cyclooctane structure; monocyclic unsaturated alicyclic hydrocarbon structures such as cyclopentene and cyclohexene; and polycyclic alicyclic hydrocarbon structures such as a norbornane structure, adamantane structure, tricyclodecane structure, and tetracyclododecane structure.

[0047] 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 ３６ ~R ３６ and a group containing an oxygen atom at the bond-side terminal of a monovalent hydrocarbon group having 1 to 20 carbon atoms. ３１ ~R ３３ or R ３６ ~R ３９ Of these, the monovalent oxyhydrocarbon group represented by the formula (I) is preferably an alkoxy group, a cycloalkoxy group, or a cycloalkylalkoxy group.

[0048] R ３１ ~R ３３ , R ３４ ~R ３６ or R ３７ ~R ３９ When the group represented by R has a substituent, examples of the substituent include a halogen atom, a hydroxyl group, and an alkoxy group having 1 to 3 carbon atoms. ３２ and R ３３ are aligned with each other and R ３２ and R ３３forms an alicyclic hydrocarbon structure having 3 to 20 carbon atoms together with the carbon atom to which it is bonded, or ３８ and R ３９ are aligned with each other and R ３８ and R ３９ When the ring structure is an alicyclic hydrocarbon structure having 3 to 20 carbon atoms together with the carbon atom to which it is bonded, the above-exemplified substituents and alkyl groups may be bonded to the ring.

[0049] R ２８ or R ２９ Examples of the monovalent substituent represented by the formula (I) include an alkyl group having 1 to 3 carbon atoms, an alkoxy group having 1 to 3 carbon atoms, a hydroxyl group, a halogen atom (for example, a fluorine atom, a chlorine atom, a bromine atom, an iodine atom), etc. g2 and g3 are each preferably 0 to 2.

[0050] Specific examples of the structural unit (ii) as the structural unit (iia) include structural units represented by the following formula: In addition, the structural unit (ii) is not limited to the specific examples shown below. ３０ is a hydrogen atom, a fluorine atom, a methyl group or a trifluoromethyl group.

[0051] Specific examples of the structural unit (iib) include structural units represented by the following formulas:

[0052] Specific examples of the structural unit (iic) include structural units represented by the following formulas:

[0053] When the polymer (F) contains the structural unit (ii), the content of the structural unit (ii) is preferably 5 mol% or more, more preferably 10 mol% or more, and even more preferably 15 mol% or more, based on the total amount of structural units contained in the polymer (F). The content of the structural unit (ii) is preferably 50 mol% or less, more preferably 40 mol% or less, based on the total amount of structural units contained in the polymer (F). By setting the content of the structural unit (ii) within the above range, the defect suppression properties of the composition can be further improved.

[0054] (Structural Unit (iii)) The structural unit (iii) is a structural unit having a monovalent fluorinated aliphatic hydrocarbon group. By introducing the structural unit (iii) into the polymer (F), the fluorine atom content in the polymer (F) can be easily adjusted.

[0055] Specific examples of the structural unit (iii) include a structural unit represented by the following formula (5). (In formula (5), R Ｃ is a hydrogen atom, a fluoro group, a methyl group, a trifluoromethyl group, or a methoxymethyl 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.

[0056] In the above formula (5), R C From the viewpoint of copolymerizability of the monomer that provides the structural unit (iii), 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 (iii), G is preferably a single bond or —COO—, and more preferably —COO—.

[0057] R Ｅ Examples 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.

[0058] Specific examples of the structural unit (iii) include structural units represented by the following formula: However, the structural unit (iii) is not limited to the specific examples shown below.

[0059] When polymer (F) has structural unit (iii), the content of structural unit (iii) is preferably 30 mol % or less, more preferably 20 mol % or less, based on the total amount of structural units contained in polymer (F). By setting the content of structural unit (iii) within the above range, it is possible to more appropriately adjust the fluorine atom content of polymer (F) and further promote uneven distribution of fluorine atoms in the surface layer of the resist film while ensuring defect suppression.

[0060] In addition to the above, examples of structural units that the polymer (F) may have include a structural unit having an aromatic ring and a hydroxyl group bonded to the aromatic ring; a structural unit containing a non-acid-dissociable hydrocarbon group (specifically, a structural unit derived from styrene or fluorinated styrene, a structural unit derived from vinylnaphthalene, a structural unit derived from cyclopentyl(meth)acrylate, a structural unit derived from cyclohexyl(meth)acrylate, etc.); and a structural unit having a fluorine atom and a hydroxyl group (specifically, 3-hydroxy-3,3-di(trifluoromethyl)-propyl(meth)acrylate, etc.). The content ratio of these structural units can be appropriately set depending on each structural unit, as long as the effects of the present invention are not impaired.

[0061] The Mw of polymer (F) measured by gel permeation chromatography (GPC) is preferably 1,000 or more, more preferably 3,000 or more, and even more preferably 4,000 or more. The Mw of polymer (F) is preferably 50,000 or less, more preferably 30,000 or less, and even more preferably 20,000 or less. The molecular weight distribution (Mw / Mn) of polymer (F) measured by GPC, which is expressed as the ratio of Mn to Mw, is preferably 1 or more and 5 or less, and more preferably 1 or more and 3 or less.

[0062] In the present composition, the content of polymer (F) is preferably 0.1 mass% or more, more preferably 0.5 mass% or more, and even more preferably 1 mass% or more, based on the total amount of solids contained in the composition. Furthermore, the content of polymer (F) is preferably 15 mass% or less, more preferably 10 mass% or less, based on the total amount of solids contained in the composition. In this specification, "solids" refers to components other than the solvent contained in the composition.

[0063] The polymer (F) 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-based radical initiators (e.g., azobisisobutyronitrile (AIBN), 2,2'-azobis(4-methoxy-2,4-dimethylvaleronitrile)), peroxide-based 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.

[0064] <Compound (S)> Compound (S) is represented by the following formula (1): Compound (S) is preferably blended in the present composition as a solvent. (In formula (1), R １１ , R １２ and R １３ are each independently a monovalent aliphatic hydrocarbon group having 1 to 20 carbon atoms.

[0065] In the above formula (1), R １１ , R １２ or R １３ Examples of the monovalent aliphatic hydrocarbon group having 1 to 20 carbon atoms represented by the formula (2) include a monovalent chain hydrocarbon group having 1 to 20 carbon atoms and a monovalent alicyclic hydrocarbon group having 3 to 20 carbon atoms. Specific examples of these include R ２１ Examples of the groups include the same groups as those shown in the description of the group represented by the formula:

[0066] From the viewpoint of the reactivity of the polymer components such as polymer (F) contained in the present composition with alkali and the availability of compound (S), R １１ , R １２ or R １３ is preferably a monovalent chain hydrocarbon group having 1 to 20 carbon atoms, more preferably an alkyl group having 1 to 10 carbon atoms, and even more preferably an alkyl group having 1 to 6 carbon atoms. １１ and R１２ is preferably an alkyl group having 1 to 3 carbon atoms, more preferably a methyl group or an ethyl group. １３ is preferably an alkyl group having 1 to 4 carbon atoms, more preferably an alkyl group having 1 to 3 carbon atoms.

[0067] Specific examples of compound (S) include methyl 2-hydroxyisobutyrate, ethyl 2-hydroxyisobutyrate, isopropyl 2-hydroxyisobutyrate, tert-butyl 2-hydroxyisobutyrate, methyl 2-hydroxy-2-methylbutyrate, ethyl 2-hydroxy-2-methylbutyrate, and isopropyl 2-hydroxy-2-methylbutyrate.

[0068] The content of compound (S) in the composition is preferably 10% by mass or more relative to the total amount of solvent contained in the composition. By setting the content of compound (S) within the above range, the storage stability of the composition can be made more excellent. In order to further enhance the effect of improving the storage stability of the composition, the content of compound (S) is more preferably 15% by mass or more, even more preferably 20% by mass or more, even more preferably 25% by mass or more, and particularly preferably 30% by mass or more relative to the total amount of solvent contained in the composition.

[0069] <Other Components> The present composition may further contain, in addition to the polymer (F) and the compound (S), a component other than the polymer (F) and the compound (S) (hereinafter also referred to as "other components"). Examples of the other components include a polymer containing a structural unit having an aromatic ring and a hydroxyl group bonded to the aromatic ring (hereinafter also referred to as "polymer (A)"), a solvent other than the compound (S) (hereinafter also referred to as "other solvent"), a radiation-sensitive acid generator, etc.

[0070] <Polymer (A)> Polymer (A) contains a structural unit having an aromatic ring and a hydroxyl group bonded to the aromatic ring (this will be referred to as a "first structural unit"). Polymer (A) is a polymer different from polymer (F). In one preferred embodiment of the present composition, polymer (A) is a base resin, and polymer (F) is a polymer having a higher fluorine atom content than polymer (A) (also referred to as a "high-fluorine-content polymer"). When a resist film is formed using a radiation-sensitive composition containing polymer (A) and polymer (F), polymer (F) tends to be more easily distributed unevenly in the surface layer of the resist film than polymer (A).

[0071] Here, in this specification, the term "base resin" refers to the main component of the polymer components contained in the radiation-sensitive composition. Specifically, in one embodiment of the present composition containing polymer (A) as the base resin and polymer (F) as an additive, the content of polymer (A) is greater than that of polymer (F). In this case, the content of polymer (A) is greater than 50% by mass, preferably 70% by mass or more, and more preferably 85% by mass or more, based on the total amount of polymer (A) and polymer (F) contained in the present composition. When polymer (F) is incorporated into the radiation-sensitive composition as an additive, polymer (F) is incorporated into the present composition as, for example, a water-repellent additive, a surface modifier that adjusts the hydrophilicity / hydrophobicity of the surface of a resist film, or a modifier that further improves lithography performance.

[0072] The polymer (A) contains a structural unit (first structural unit) having an aromatic ring and a hydroxyl group bonded to the aromatic ring, and is a polymer different from the polymer (F). However, "the polymer (A) is a polymer different from the polymer (F)" does not mean that the polymer (F) does not contain a structural unit having an aromatic ring and a hydroxyl group bonded to the aromatic ring. In other words, the polymer (F) may further contain, in addition to the structural unit (i), a structural unit having an aromatic ring and a hydroxyl group bonded to the aromatic ring. When the polymer (F) contains a structural unit having an aromatic ring and a hydroxyl group bonded to the aromatic ring, the content of the structural unit is, for example, 30 mol% or less, or may be 20 mol% or less, based on the total amount of structural units contained in the polymer (F).

[0073] The polymer (A) may contain, together with the first structural unit, one or more of the following: a structural unit having an acid-dissociable group (this will be referred to as the "second structural unit"); a structural unit having an onium salt structure formed from a radiation-sensitive onium cation and an organic anion (this will be referred to as the "third structural unit"); a structural unit having a lactone structure, a cyclic carbonate structure, a sultone structure, or a ring structure combining two or more of these (this will be referred to as the "fourth structural unit"); and a structural unit having an alcoholic hydroxyl group (this will be referred to as the "fifth structural unit"). Each structural unit will be described in detail below.

[0074] (First structural unit) The polymer (A) having a hydroxyl group bonded to an aromatic ring is advantageous in that it can further improve the LWR (line width roughness) performance and CDU (critical dimension uniformity) performance of the composition, and it is highly effective in suppressing dissolution of unexposed areas into a developer, thereby further reducing development defects. Furthermore, the polymer (A) having a hydroxyl group bonded to an aromatic ring is particularly suitable for pattern formation using exposure to radiation with a wavelength of 50 nm or less, such as electron beams or EUV. The first structural unit differs from the second structural unit in that it does not have an acid-dissociable group, and from the third structural unit in that it does not have an onium salt structure. In other words, in this specification, a structural unit having both an acid-dissociable group and a hydroxyl group bonded to an aromatic ring is classified as the second structural unit, and a structural unit having both a hydroxyl group bonded to an aromatic ring and an onium salt structure is classified as the third structural unit.

[0075] A specific example of the first 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—. ２ is an aromatic ring group. 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.)

[0076] 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 first structural unit.

[0077] A ２ 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 the first structural unit and sensitivity, A ２ The aromatic ring contained in the first structural unit is preferably a benzene ring or a naphthalene ring, more preferably a benzene ring. The position of the hydroxyl group bonded to the aromatic ring is not particularly limited. For example, when the first structural unit has a hydroxyl group bonded to a benzene ring, the bonding position of the hydroxyl group on the benzene ring in the first structural unit may be any of the ortho-position, meta-position, and para-position relative to other groups.

[0078] R ４ R may be any group other than a hydroxyl group. ４ Specific examples of n1 include a fluorine atom, a chlorine atom, a bromine atom, an iodine atom, a substituted or unsubstituted alkyl group, a substituted or unsubstituted alkoxy group, a substituted or unsubstituted cycloalkyl group, a substituted or unsubstituted cycloalkyloxy group, an ester group (—COOR), an alkylsulfonyl group, a cycloalkylsulfonyl group, a carboxy group, a cyano group, and a nitro group. n1 is preferably 1 to 3, and preferably 1 or 2. n2 is preferably 0 to 5, more preferably 0 to 2, and even more preferably 0 or 1.

[0079] Specific examples of the first structural unit include structural units represented by the following formulae: However, the first 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.

[0080] In the polymer (A), the content of the first structural unit is preferably 10 mol% or more, more preferably 20 mol% or more, and even more preferably 25 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 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 first structural unit within the above range, the CDU performance of the present composition can be made even better.

[0081] (Second structural unit) The second structural unit is a structural unit having an acid-dissociable group, and is usually introduced into the polymer (A) in order to adjust the solubility in a developer and the sensitivity of the polymer (A). In this specification, a structural unit having an acid-dissociable group and a hydroxyl group bonded to an aromatic ring is classified as the second structural unit.

[0082] In this specification, the structural unit having an acid-dissociable group in polymer (F) is referred to as the “structural unit (ii),” and the structural unit having an acid-dissociable group in polymer (A) is referred to as the “second structural unit.” The structural unit (ii) contained in polymer (F) and the second structural unit contained in polymer (A) in the present composition may be the same or different.

[0083] The second structural unit is not particularly limited as long as it has an acid-dissociable group. Examples of the second structural unit include a structural unit represented by the above formula (4-1), a structural unit represented by the above formula (4-2), and a structural unit represented by the above formula (4-3).

[0084] In the polymer (A), the content of the second structural unit is preferably 5 mol% or more, more preferably 10 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 second structural unit is preferably 65 mol% or less, more preferably 60 mol% or less, and even more preferably 55 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 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 LWR performance and CDU performance of the composition.

[0085] Third Structural Unit The polymer (A) may further contain a structural unit (referred to as the "third structural unit") having an onium salt structure formed by a radiation-sensitive onium cation and an organic anion. It is believed that the third structural unit liberates an organic anion when the radiation-sensitive onium cation decomposes under the action of radiation, and the liberated organic anion bonds with hydrogen abstracted from components contained in the composition (e.g., a radiation-sensitive acid generator, an acid diffusion controller, a solvent, etc.), thereby generating an acid derived from the organic anion. Examples of the organic anion include a sulfonate anion and a carboxylate anion. In this specification, the term "radiation" includes electron beams (visible light, ultraviolet light, far ultraviolet light, extreme ultraviolet light (EUV), etc.) and electromagnetic waves (X-rays, gamma rays, etc.).

[0086] When the organic anion in the third structural unit is a sulfonate anion, the third structural unit is thought to function primarily as a radiation-sensitive acid generator by generating a strong acid that induces dissociation of the acid-dissociable group under normal conditions. On the other hand, when the organic anion in the third structural unit is a carboxylate anion, the third structural unit is thought to function primarily as an acid diffusion controller by generating a weak acid that does not induce dissociation of the 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.

[0087] The third 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 LWR performance and CDU performance of the present composition, it is preferable that the third structural unit be bonded to the main chain of the polymer via a linking group, and that the organic anion be a sulfonate anion (—SO３ － ) is more preferably bonded to the main chain of the polymer via a linking group.

[0088] The radiation-sensitive cation in the third 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) possessed by the triarylsulfonium cation or diaryliodonium cation is preferably a ＋ 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.

[0089] It is preferable that at least a portion of the third structural units contained in the polymer (A) have an iodo group in the structural unit, since this can further increase the sensitivity while maintaining good LWR performance and CDU performance of the present composition. When the third structural unit has an iodo group, the iodo group is preferably bonded to an aromatic ring. Furthermore, when the third structural unit has an iodo group, the radiation-sensitive onium cation may have an iodo group, the organic anion may have an iodo group, or both the radiation-sensitive onium cation and the organic anion may have an iodo group.

[0090] Specific examples of the third structural unit include structural units represented by the following formulas: However, the specific examples of the third structural unit are not limited to these. (In the formula, R ４０ is a hydrogen atom, a fluorine atom, a methyl group, or a trifluoromethyl group. ＋ is a radiation-sensitive onium cation. － is a sulfonate anion or a carboxylate anion.

[0091] When the polymer (A) contains a third structural unit, the content of the third 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). The content of the third 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 third structural unit within the above range, the LWR performance and CDU performance of the composition can be sufficiently improved.

[0092] Fourth Structural Unit The polymer (A) is a structural unit having a lactone structure, a cyclic carbonate structure, a sultone structure, or a ring structure formed by combining two or more of these (excluding those corresponding to the first to third structural units; this will be referred to as the "fourth structural unit").

[0093] Specific examples of the fourth structural unit include structural units represented by the following formulas: However, the specific examples of the fourth structural unit are not limited to these. (In the formula, R Ｌ１ is a hydrogen atom, a fluorine atom, a methyl group, or a trifluoromethyl group.

[0094] When the polymer (A) contains the fourth structural unit, the content of the fourth structural unit is preferably 2 mol% or more, more preferably 5 mol% or more, based on the total amount of structural units contained in the polymer (A). The content of the fifth structural unit in the polymer (A) is preferably 35 mol% or less, more preferably 25 mol% or less, based on the total amount of structural units contained in the polymer (A).

[0095] Fifth structural unit The fifth structural unit is a structural unit having an alcoholic hydroxyl group (excluding those corresponding to the first to fourth structural units). By introducing the fifth structural unit into polymer (A), the effect of suppressing development defects can be enhanced when a resist pattern is formed using this 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.

[0096] 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, specific examples of the fifth structural unit are not limited to these. (In the formula, R Ａ is a hydrogen atom, a fluorine atom, a methyl group, or a trifluoromethyl group.

[0097] 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).

[0098] In addition to the above, examples of structural units contained in the polymer (A) include 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 (e.g., a styrene unit, a bromostyrene unit), a structural unit derived from vinylnaphthalene, a structural unit derived from n-pentyl(meth)acrylate); and structural units derived from (meth)acrylic acid. The content ratio of these structural units can be appropriately set depending on each structural unit, as long as the effects of the present invention are not impaired.

[0099] From the viewpoint of obtaining a radiation-sensitive composition having excellent sensitivity, the polymer (A) preferably has an iodine group. When the polymer (A) has an iodine group, only one of the first to fifth structural units described above may have an iodine group, or two or more of them may have an iodine group. Furthermore, for example, when the first structural unit has an iodine group, some of the first structural units may have an iodine group, or all of the first structural units may have an iodine group.

[0100] The weight average molecular weight (Mw) of the polymer (A) measured by 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.

[0101] 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. Mw / Mn is usually 1.0 or more.

[0102] In the present composition, the content of polymer (A) is preferably 50% by mass or more, more preferably 70% by mass or more, and even more preferably 85% by mass or more, based on the total amount of solids contained in the present composition. As with polymer (F), polymer (A) can be synthesized by polymerizing monomers that provide each structural unit in an appropriate solvent using a known radical polymerization initiator or the like.

[0103] When the composition contains polymer (A) and polymer (F), the content of polymer (F) in the composition is preferably 0.1 parts by mass or more, more preferably 0.5 parts by mass or more, and even more preferably 1 part by mass or more, per 100 parts by mass of polymer (A). The content of polymer (F) is preferably 15 parts by mass or less, more preferably 10 parts by mass or less, and even more preferably 7 parts by mass or less, per 100 parts by mass of polymer (F).

[0104] (Other Solvents) The present composition may contain other solvents together with the compound (S). The other solvents are preferably solvents capable of dissolving or dispersing the components blended in the present composition. Specific examples of other solvents include various organic solvents, such as alcohols, ethers, ketones, amides, esters, hydrocarbons, etc. From the viewpoint of ensuring good film thickness uniformity, at least one selected from the group consisting of alcohols, ethers, ketones, and esters is preferred.

[0105] 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, propylene glycol monoethyl ether, propylene glycol mono-n-propyl ether, and propylene glycol mono-n-butyl ether.

[0106] 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.

[0107] 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; and 2,4-pentanedione, acetonylacetone, acetophenone, and diacetone alcohol.

[0108] Examples of the 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.

[0109] Examples of esters include monocarboxylic acid esters such as n-butyl acetate and ethyl lactate; 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.

[0110] 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.

[0111] When the composition contains other solvents, the content of the other solvents is preferably 90% by mass or less, based on the total amount of solvents contained in the composition, from the viewpoint of improving the storage stability of the composition, more preferably 85% by mass or less, even more preferably 80% by mass or less, still more preferably 75% by mass or less, and particularly preferably 70% by mass or less, based on the total amount of solvents contained in the composition.

[0112] As the other solvent, a compound having a hydroxyl group (hereinafter also referred to as a "hydroxyl group-containing compound") can be preferably used. Of the above, the hydroxyl group-containing compound is preferably at least one selected from the group consisting of alcohols and ketones, and more preferably at least one selected from the group consisting of polyhydric alcohol partial ethers having 3 to 19 carbon atoms and diacetone alcohol. When the composition contains other solvents, the content of the hydroxyl group-containing compound in the composition is preferably 25% by mass or more, more preferably 35% by mass or more, and even more preferably 50% by mass or more, based on the total amount of the other solvents.

[0113] (Radiation-sensitive acid generator) A radiation-sensitive acid generator is a substance that generates an acid upon irradiation with radiation. The radiation-sensitive acid generator may be an ionic radiation-sensitive acid generator or a non-ionic radiation-sensitive acid generator. The radiation-sensitive acid generator is preferably an ionic radiation-sensitive acid generator, and an onium salt having a radiation-sensitive onium cation and an organic anion that is a conjugate base of an acid is preferably used. The organic anion is usually an anion obtained by removing a proton from an acid group of an organic acid.

[0114] The radiation-sensitive acid generator 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 radiation-sensitive acid generator. The acid generator is a substance that generates a strong acid in the present composition upon exposure, capable of cleaving an acid-dissociable group from a component in the radiation-sensitive composition. The acid diffusion controller is 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 radiation-sensitive acid generator is classified as an acid generator or an acid diffusion controller depending on the strength of its acid relative to the components in the present composition (specifically, the polymer (A) when it contains a third structural unit, or other radiation-sensitive acid generators when it contains two or more radiation-sensitive acid generators). The 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 more, preferably −1≦pKa≦7, and more preferably 0≦pKa≦5.

[0115] The radiation-sensitive acid generator may be any component different from the polymer (F) and the polymer (A), and may be a low-molecular-weight compound (also referred to as a non-polymer) without a molecular weight distribution, or may be a polymer. A low-molecular-weight compound (non-polymer) is preferred as the radiation-sensitive acid generator, since it allows for easy adjustment of the sensitivity of the composition and provides greater freedom in selecting the radiation-sensitive acid generator to be incorporated into the composition. The molecular weight of the radiation-sensitive acid generator is preferably 1,000 or less, more preferably 800 or less, and even more preferably 600 or less.

[0116] Acid Generator The type of acid generator to be incorporated into the composition is not particularly limited, and any known radiation-sensitive acid generator used in resist pattern formation can be used as appropriate. The acid generator is preferably a compound that generates, under the above-mentioned normal conditions, an acid in the composition that is more acidic (preferably a strong acid such as a sulfonic acid, imidic acid, or methide acid) than the acid generated by the acid diffusion controller (more specifically, the photodegradable base), thereby inducing dissociation of the acid-dissociable group.

[0117] When an onium salt is used as the acid generator, from the viewpoint of increasing the sensitivity of the present composition and forming a resist film with superior lithography performance, the acid generator preferably has a sulfonium cation or an iodonium cation, and more preferably has an arylsulfonium cation or an aryliodonium cation. Specific examples of the radiation-sensitive onium cation include cations represented by the following formulas:

[0118]

[0119] The organic anion contained in the acid generator is not particularly limited, but is preferably a sulfonate anion, an imide anion, or a methide anion, in that it can increase the sensitivity of the composition. Specific examples of sulfonate anions include anions represented by the following formula:

[0120]

[0121]

[0122] When an acid generator is incorporated into the composition, the content of the acid generator is preferably 0.5 parts by mass or more, more preferably 1 part by mass or more, and even more preferably 2 parts by mass or more, relative to 100 parts by mass of polymer (A), from the viewpoint of fully obtaining the effect of improving sensitivity due to the incorporation of the acid generator. Furthermore, from the viewpoint of suppressing the occurrence of development defects due to the acid generator, the content of the acid generator is preferably 30 parts by mass or less, more preferably 25 parts by mass or less, and even more preferably 20 parts by mass or less, relative to 100 parts by mass of polymer (A).

[0123] When an acid generator is incorporated into the present composition, an onium salt having an iodine atom is preferably used as the acid generator, since this can further enhance the CDU performance of the present composition. In the acid generator having an iodine atom, the number of iodine atoms in one molecule is preferably two or more, from the viewpoint of sufficiently improving the CDU performance of the radiation-sensitive composition. In the acid generator, it is preferable that the organic anion has one or more iodine atoms, since this can improve the sensitivity and CDU performance of the present composition in a well-balanced manner. Furthermore, it is preferable that the radiation-sensitive onium cation has one or more iodine atoms, since this can further enhance the CDU performance of the present composition. Note that when the radiation-sensitive onium cation has one or more iodine atoms, the radiation-sensitive onium cation may be an iodonium cation or a sulfonium cation having an iodo group.

[0124] Acid Diffusion Controller: From the viewpoint of improving the lithography properties of the present composition, the present composition preferably contains, as an acid diffusion controller, an onium salt having a radiation-sensitive onium cation and an organic anion that is a conjugate base of the acid (hereinafter also referred to as a "photodegradable base"). The photodegradable base is preferably an onium salt that generates a carboxylic acid, a sulfonic acid, or a sulfonamide upon exposure. Furthermore, in terms of being able to form a resist film with higher lithography performance, an onium salt having a sulfonium cation or an iodonium cation is preferably used as the photodegradable base.

[0125] Specific examples of the radiation-sensitive onium cation contained in the photodecomposable base include the same onium cations as those exemplified as the radiation-sensitive onium cation that may be contained in the acid generator.

[0126] Examples of the organic anion contained in the photodegradable base include anions represented by the following formula:

[0127] When an acid diffusion controller is blended in the composition, the content of the acid diffusion controller is preferably 1 part by mass or more, more preferably 2 parts by mass or more, per 100 parts by mass of polymer (A) from the viewpoint of sufficiently improving the sensitivity, CDU performance, and film thickness uniformity. Furthermore, from the viewpoint of suppressing the occurrence of development defects caused by the acid diffusion controller, the content of the acid diffusion controller is preferably 30 parts by mass or less, more preferably 20 parts by mass or less, per 100 parts by mass of polymer (A).

[0128] When an acid diffusion controller is incorporated into the composition, the content of the acid diffusion controller in the composition is preferably 2 mol% or more, more preferably 5 mol% or more, and even more preferably 10 mol% or more, based on the total amount of the acid generator contained in the composition and the monomer that provides the third structural unit in the polymer (A). Furthermore, the content of the acid diffusion controller is preferably 90 mol% or less, more preferably 80 mol% or less, and even more preferably 70 mol% or less, based on the total amount of the acid generator contained in the composition and the monomer that provides the third structural unit. By setting the content of the acid diffusion controller within the above range, the CDU performance of the composition can be further improved.

[0129] When an acid diffusion controller is incorporated into the present composition, an onium salt having an iodine atom is preferably used as the acid diffusion controller, since this can further enhance the CDU performance of the present composition. The number of iodine atoms in one molecule of the acid diffusion controller is preferably one or more, more preferably two or more, from the viewpoint of sufficiently improving the CDU performance of the radiation-sensitive composition. When the organic anion in the acid diffusion controller has one or more iodine atoms, this is preferred because it can improve the sensitivity, CDU performance, and film thickness uniformity of the present composition in a well-balanced manner. Furthermore, when the organic anion has an aromatic ring and two or more hydroxyl groups bonded to the aromatic ring, this is preferred because it can provide the present composition with excellent sensitivity and CDU performance.

[0130] (Other Optional Components) The present composition may further contain components other than the above-described polymer (F), compound (S), polymer (A), radiation-sensitive acid generator, and other solvents (hereinafter also referred to as "other optional components"). Examples of 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. The content of the other optional components can be appropriately set depending on each compound, as long as the effects of the present invention are not impaired.

[0131] <Method for producing radiation-sensitive composition> The composition can be produced, for example, by mixing the polymer (F), the compound (S), and other components blended as needed in desired proportions, and filtering the resulting mixture, preferably using a filter (e.g., a filter with a pore size of about 0.2 μm). The solids concentration of the 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 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 composition within the above range, good coatability can be achieved, and a good resist pattern shape can be obtained, which is advantageous.

[0132] 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.

[0133] <<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 and CDU performance and few development defects. Each step will be described below.

[0134] [Coating Step] In the coating step, the 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 composition include spin coating, casting coating, and roll coating. After coating, a soft bake (hereinafter also referred to as "SB") 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. Soft baking is also called pre-baking.

[0135] [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.

[0136] After the exposure, post-exposure baking (PEB) is preferably performed to promote dissociation of acid-dissociable groups in the exposed portions of the resist film by acid generated from a compound that generates acid upon exposure (such as a radiation-sensitive acid generator). This PEB can increase the difference in solubility in a developer between the exposed and unexposed portions. The PEB temperature is preferably 50°C or higher, more preferably 80°C or higher. The PEB temperature is preferably 180°C or lower, more preferably 130°C or lower. The PEB time is preferably 5 seconds or longer, more preferably 10 seconds or longer. The PEB time is preferably 600 seconds or shorter, more preferably 300 seconds or shorter.

[0137] [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.

[0138] 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.

[0139] 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).

[0140] The present invention will be specifically described below with reference to synthesis examples, examples, and comparative examples, but the present invention is not limited to the following examples. In the following examples, "parts" and "%" are by mass unless otherwise specified.

[0141] The methods for measuring the physical properties of the polymer are shown below. [Weight-average molecular weight (Mw) and number-average molecular weight (Mn)] The Mw and Mn of the polymer were measured by gel permeation chromatography (GPC) using GPC columns manufactured by Tosoh Corporation (two "G2000HXL", one "G3000HXL", and one "G4000HXL") under the following conditions: Eluent: tetrahydrofuran (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) Flow rate: 1.0 mL / min Sample concentration: 1.0 mass% Sample injection amount: 100 μL Column temperature: 40° C. Detector: differential refractometer Standard material: monodisperse polystyrene

[0142] <[P] Polymer Synthesis> [Synthesis Examples A1 to A36] Synthesis of Base Polymers (A-1) to (A-36) Each monomer was combined and copolymerized in tetrahydrofuran (THF) solvent. The resulting mixture was crystallized in methanol and repeatedly washed with hexane. After isolation and drying, base polymers (A-1) to (A-36) with the compositions shown in Table 1 were obtained. The resulting base polymers had the following compositions: １ The Mw and dispersity (Mw / Mn) were confirmed under the above-mentioned GPC conditions. The types and proportions of each monomer are shown in Table 1.

[0143]

[0144]

[0145] <[F] Polymer Synthesis> [Synthesis Example F1] (Synthesis of High Fluorine Content Polymer (F-1)) Monomer (E-1) and monomer (M-6) were dissolved in 2-butanone so that the molar ratio of the final polymer obtained would be 70 / 30, and AIBN (azobisisobutyronitrile) was added as an initiator to prepare a monomer solution. 2-Butanone was placed in a reaction vessel, and the vessel was purged with nitrogen for 30 minutes. The temperature inside the reaction vessel was raised to 80°C, and the monomer solution was added dropwise with stirring to carry out a polymerization reaction for 6 hours. Thereafter, the polymerization solution was cooled to 30°C or below. After replacing the solvent with acetonitrile, an operation of adding hexane, stirring, and recovering the acetonitrile layer was repeated three times. The solvent was replaced with propylene glycol monomethyl ether acetate to obtain a solution of high fluorine content polymer (F-1). The composition of the obtained high fluorine content polymer was １３ The molecular weight and the dispersity (Mw / Mn) were confirmed by C-NMR, and the Mw and the dispersity (Mw / Mn) were confirmed under the GPC conditions described above. The Mw and the dispersity (Mw / Mn) are shown in Table 2 together with the types and proportions of the monomers.

[0146] [Synthesis Examples F2 to F27] Synthesis of high fluorine content polymers (F-2) to (F-25), (Fc-1), and (Fc-2) High fluorine content polymers (F-2) to (F-25), (Fc-1), and (Fc-2) were obtained in the same manner as in Synthesis Example F1, except that the monomers used in Synthesis Example F1 were changed. The types and proportions of the monomers constituting each of the obtained polymers, as well as the Mw and dispersity (Mw / Mn), are shown in Table 2.

[0147]

[0148]

[0149] <Preparation of Radiation-Sensitive Composition> [B] Radiation-sensitive acid generator, [D] acid diffusion controller, and [S] solvent used in preparing the radiation-sensitive compositions of Examples 1 to 85 and Comparative Examples 1 to 3 are shown below.

[0150] [B] Radiation-sensitive Acid Generator Compounds represented by the following formulae (B-1) to (B-12) were used as radiation-sensitive acid generators.

[0151] [D] Acid Diffusion Controller Compounds represented by the following formulae (D-1) to (D-8) were used as acid diffusion controllers.

[0152] [S] Solvent The following solvents (S-1) to (S-6) were used as solvents: (S-1): PGMEA (propylene glycol monomethyl ether acetate) (S-2): HBM (methyl 2-hydroxyisobutyrate) (S-3): PGME (propylene glycol monomethyl ether) (S-4): DAA (diacetone alcohol) (S-5): HBE (ethyl 2-hydroxyisobutyrate) (S-6): HBP (isopropyl 2-hydroxyisobutyrate)

[0153] Example 1 A mixture of 100 parts by mass of (A-1) as a polymer [A], 45 parts by mass of (B-7) as a radiation-sensitive acid generator [B], 35 mol% of (D-1) as an acid diffusion controller relative to (B-7), 5 parts by mass of (F-1) as a high-fluorine content polymer [F], 2,000 parts by mass of (S-1), 4,000 parts by mass of (S-2), and 4,000 parts by mass of (S-3) as solvents [S], was filtered through a membrane filter with a pore size of 0.2 μm to prepare a radiation-sensitive composition (R-1).

[0154] Examples 2 to 85 and Comparative Examples 1 to 3 Radiation-sensitive compositions (R-2) to (R-85) 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 were changed as shown in Tables 3, 4, and 5. In Tables 3, 4, and 5, the content of the acid diffusion controller [D] represents the proportion (mol %) to the total amount of the radiation-sensitive acid generator [B] and the monomer that provides the third structural unit in the polymer [A].

[0155]

[0156]

[0157]

[0158] <Formation of Resist Pattern for Evaluating Defect Suppression> Each of the radiation-sensitive compositions prepared above was applied to the surface of a 12-inch silicon wafer on which a 20-nm-thick underlayer film (AL412 (Brewer Science)) had been formed, using a spin coater (CLEAN TRACK ACT12, 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 45-nm-thick resist film. Next, this resist film was irradiated with EUV light using an EUV exposure machine (model "NXE3400," ASML, NA = 0.33, illumination conditions: Conventional s = 0.89). The resist film after EUV exposure was subjected to PEB (post-exposure bake) at 110°C for 60 seconds. Next, development was carried out using a 2.38 wt % aqueous solution of TMAH at 23° C. for 30 seconds to form a positive-type 48 nm pitch, 24 nm contact hole pattern.

[0159] [Evaluation of Defect Suppression] The number of defects in the contact hole patterns formed as described above was measured using a defect inspection device (KLA-Tencor's "KLA2925"). The observed defects were classified into defects determined to be derived from the resist film and foreign matter derived from the external environment. The number of development defects determined to be derived from the resist film was evaluated as "A" (good) when the number of defects determined to be derived from the resist film was 50 or less, "B" (fairly good) when the number was more than 50 but not more than 100, and "C" (poor) when the number was more than 100. The evaluation results are shown in Tables 6 and 7.

[0160] <Formation of Resist Pattern for Storage Stability Evaluation> (KrF Exposure, Alkali Development) 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, Ltd.)) had been formed using a spin coater (CLEAN TRACK ACT12, Tokyo Electron Co., Ltd.). After SB at 100°C for 60 seconds, the wafer was cooled at 23°C for 30 seconds to form a 45-nm-thick resist film. Next, the resist film was irradiated with KrF light using a KrF exposure machine (model "S210D," Nikon Corporation, NA = 0.55, illumination conditions: Annular s = 0.8, mask 150 nm LS). The resist film was subjected to PEB at 90°C for 60 seconds. The wafer was then developed at 23°C for 30 seconds using a 2.38 wt% TMAH aqueous solution to form a positive 150-nm line-and-space pattern.

[0161] [Evaluation of Storage Stability] After preparing the radiation-sensitive compositions, a portion was stored at -15°C for 3 weeks, and the remainder was stored at 35°C for 3 weeks. Thereafter, the optimal exposure dose for forming a 150 nm line and space pattern was determined in the resist pattern formation by the above-described KrF exposure. Based on the optimal exposure dose of the radiation-sensitive composition stored at -15°C for 3 weeks, if the optimal exposure dose of the radiation-sensitive composition stored at 35°C for 3 weeks increased the sensitivity by 1.2% or more or decreased the sensitivity by 1.2% or more, the composition was rated as "C." If the optimal exposure dose increased the sensitivity by less than 1.2% but 0.6% or more or decreased the sensitivity by less than 1.2% but 0.6% or more, the composition was rated as "B." Otherwise, the composition was rated as "A." The evaluation results are shown in Tables 6 and 7.

[0162]

[0163]

[0164] As shown in Tables 6 and 7, the defect inhibition ability and storage stability of all of the radiation-sensitive compositions of Examples 1 to 85 were rated A or B. In contrast, the radiation-sensitive composition containing the polymer (F) but not the compound (S) (Comparative Example 1) was rated C for storage stability. Furthermore, the defect inhibition ability of the radiation-sensitive compositions containing the compound (S) but not the polymer (F) (Comparative Examples 2 and 3) was rated C. From these results, it can be said that the radiation-sensitive compositions of Examples 1 to 85 exhibited well-balanced improvements in defect inhibition ability and storage stability.

[0165] As described above, the radiation-sensitive composition and method for forming a resist pattern according to the present disclosure can achieve an improved balance between defect suppression and storage stability. Therefore, the radiation-sensitive composition and method for forming a resist pattern according to the present disclosure can be suitably used in processes for fabricating semiconductor devices, which are expected to become even more miniaturized in the future.

Claims

1. A radiation-sensitive composition comprising: a polymer (F) containing a structural unit having a fluorine atom and an alkali-dissociable group; and a compound represented by the following formula (1): (In formula (1), R １１ , R １２ and R １３ are each independently a monovalent aliphatic hydrocarbon group having 1 to 20 carbon atoms.

2. The radiation-sensitive composition according to claim 1, further comprising a polymer (A) containing a structural unit having an aromatic ring and a hydroxyl group bonded to the aromatic ring.

3. The radiation-sensitive composition according to claim 2, wherein the polymer (A) further contains a structural unit having an acid-dissociable group.

4. The radiation-sensitive composition according to claim 1, wherein the structural unit having a fluorine atom and an alkali-dissociable group is represented by the following formula (2): (In formula (2), R Ｆ is a hydrogen atom, a fluoro group, a methyl group, a trifluoromethyl group, or a methoxymethyl group. １ is a single bond, —O—, —CO—, —COO—, —NH—, or —CONH—. ２１ is a hydrocarbon group having 1 to 20 carbon atoms and a valence of (s+1), or R ２２ At the end of the side, there is an oxygen atom, a sulfur atom, and -NR ２４ R is a group to which -, a carbonyl group, a sulfonyl group, -CO-O- or -CO-NH- is bonded, or a (s+1)-valent group having a heterocyclic structure and 3 to 20 carbon atoms. ２４ is a hydrogen atom or a monovalent organic group. ２２ represents a single bond or a divalent fluorinated chain hydrocarbon group having 1 to 20 carbon atoms. １ represents an oxygen atom, —CO—O—*, or —SO ２ -O-*. "*" is R ２３ Represents a bond with R. ２３ is a monovalent organic group having 1 to 30 carbon atoms. １ is -CO-O-* or -SO ２ -O-*, then R ２２ and R ２３ At least one of １ or a group in which a fluorine atom is bonded to a carbon atom bonded to the carbon atom bonded to R ２３ But, X １ and a fluorine atom or a trifluoromethyl group bonded to the aromatic ring. ２３ In this case, X １ The bonding position of the fluorine atom or trifluoromethyl group to the aromatic ring bonded to X １ The bond position of X is 2 or 3. １ is an oxygen atom, R ２２ is a single bond, and R ２１ is an (s+1)-valent hydrocarbon group having 1 to 20 carbon atoms, and R ２３ is X １ A carbonyl group is bonded to the end of the R-side group, and a fluorine atom is bonded to the carbon atom adjacent to the carbonyl group. s is an integer of 1 to 3. However, when s is 2 or 3, multiple R ２２ are the same or different, and multiple X １ are the same or different, and multiple R ２３ are the same or different.) 5. The radiation-sensitive composition according to claim 1, further comprising a radiation-sensitive acid generator comprising a radiation-sensitive cation and an organic anion.

6. The radiation-sensitive composition according to claim 1, which contains the compound represented by formula (1) as a solvent, and the content of the compound represented by formula (1) is 10 mass % or more based on the total amount of the solvent.

7. The radiation-sensitive composition according to claim 1, which contains, as solvents, the compound represented by formula (1) and another solvent different from the compound represented by formula (1).

8. The radiation-sensitive composition according to claim 7, wherein the other solvent is at least one selected from the group consisting of alcohols, ethers, ketones and esters.

9. 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 8; exposing the resist film; and developing the exposed resist film.

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