WO2022190599A1

WO2022190599A1 - Radiation-sensitive resin composition and pattern formation method

Info

Publication number: WO2022190599A1
Application number: PCT/JP2022/000063
Authority: WO
Inventors: 研丸山
Original assignee: Jsr株式会社
Priority date: 2021-03-09
Filing date: 2022-01-05
Publication date: 2022-09-15
Also published as: TW202246892A; JPWO2022190599A1

Abstract

Provided is a radiation sensitive resin composition that can form a resist film having sufficient levels of sensitivity, CDU performance, and development residue-inhibiting properties when next generation technology is used. Also provided is a pattern formation method. Provided is a radiation sensitive resin composition that contains: a resin comprising a structural unit represented by formula (1); one or at least two onium salts comprising an organic acid anion part and an onium cation part; and a solvent, wherein at least a portion of the onium cation part in the onium salt comprises an aromatic ring structure having a fluorine atom. (In formula (1), R is a hydrogen atom, an alkyl group having 1-5 carbon atoms, or a halogenated alkyl group having 1-5 carbon atoms, Y¹ is a divalent linking group, and X¹ is an acid dissociating group.)

Description

RADIATION-SENSITIVE RESIN COMPOSITION AND PATTERN-FORMING METHOD

The present invention relates to a radiation-sensitive resin composition and a pattern forming method.

Photolithography technology that uses resist compositions is used to form fine circuits in semiconductor devices. As a typical procedure, for example, an acid is generated by exposing the film of the resist composition to radiation through a mask pattern, and the acid is used as a catalyst to react with the resin in the exposed area and the unexposed area. A resist pattern is formed on a substrate by creating a difference in solubility in an organic solvent-based developer.

In the above photolithography technology, short-wave radiation such as ArF excimer laser is used, and this radiation is combined with liquid immersion lithography (liquid immersion lithography) to promote pattern miniaturization. As a next-generation technology, the use of even shorter wavelength radiation such as electron beams, X-rays and EUV (extreme ultraviolet rays) is being attempted, and resist materials containing acid generators with benzene rings that improve the absorption efficiency of such radiation. is also under consideration (Japanese Patent Application Laid-Open No. 2014-2359).

JP 2014-2359 A

Even with the above-mentioned next-generation technology, in addition to sensitivity, critical dimension uniformity (CDU) performance, which is an index of uniformity of line width and hole diameter, and development residue control performance that suppresses the generation of residue during development, are equivalent to conventional technologies. The above resist properties are required.

It is an object of the present invention to provide a radiation-sensitive resin composition and a pattern forming method capable of forming a resist film having sufficient levels of sensitivity, CDU performance, and development residue suppression even when next-generation technology is applied. aim.

As a result of extensive studies aimed at solving this problem, the inventors have found that the above objects can be achieved by adopting the following configuration, and have completed the present invention.

The present invention, in one embodiment,
a resin containing a structural unit represented by the following formula (1) (hereinafter also referred to as “structural unit (I)”);
one or more onium salts containing an organic acid anion portion and an onium cation portion;
containing a solvent and
The present invention relates to a radiation-sensitive resin composition containing an aromatic ring structure in which at least a portion of the onium cation moiety in the onium salt has a fluorine atom.

(In the above formula (1),
R is a hydrogen atom, an alkyl group having 1 to 5 carbon atoms or a halogenated alkyl group having 1 to 5 carbon atoms, Y ¹ is a divalent linking group, and X ¹ is an acid dissociable group. )

According to the radiation-sensitive resin composition, it is possible to construct a resist film that satisfies sensitivity, CDU performance, and development residue suppression. Although the reason for this is not clear, it is presumed as follows. The absorption of radiation such as EUV with a wavelength of 13.5 nm by fluorine atoms is very large, thereby increasing the sensitivity of the radiation-sensitive resin composition. In addition, the aromatic ring structure having a fluorine atom contained in the onium cation moiety enhances the water repellency of the resist film, suppresses intermixing between the resist film and its underlying film, and exhibits development residue suppressing properties. Furthermore, the acid-dissociable group possessed by the structural unit (I) in the resin has a high degree of freedom through a linking group or an ester bond, and thus has a high contact probability with an acid generated by exposure, thus facilitating an acid-dissociation reaction. happens to Therefore, the dissolution contrast between the exposed area and the unexposed area is increased, and excellent pattern formability is exhibited. It is presumed that the above resist performance can be exhibited by these combined actions. The "aromatic ring structure containing fluorine" includes not only a structure in which a fluorine atom is directly bonded to an aromatic ring structure, but also a structure in which a fluorine atom is bonded to an aromatic ring structure via another atom (e.g., an aromatic ring structure (such as a structure in which a fluorine atom is bonded to a substituent that is bonded to ).

In another embodiment of the present invention, the step of directly or indirectly applying the radiation-sensitive resin composition onto a substrate to form a resist film;
exposing the resist film;
and developing the exposed resist film with a developer.

The pattern forming method uses the radiation-sensitive resin composition, which is excellent in sensitivity, CDU performance, and development residue suppressing property, so that a high-quality resist pattern can be efficiently formed.

Although the embodiments of the present invention will be described in detail below, the present invention is not limited to these embodiments.

<<Radiation sensitive resin composition>>
The radiation-sensitive resin composition (hereinafter also simply referred to as "composition") according to this embodiment contains a resin, one or more onium salts, and a solvent. The above composition may contain other optional components as long as they do not impair the effects of the present invention. By containing a predetermined resin and an onium salt, the radiation-sensitive resin composition can impart a high level of sensitivity, CDU performance and development residue suppression to the resulting resist film.

<Resin>
The resin is an aggregate of polymers containing the structural unit (I) (hereinafter, this resin is also referred to as "base resin"). The base resin includes, in addition to the structural unit (I), a structural unit having a phenolic hydroxyl group or a structural unit that gives a phenolic hydroxyl group by the action of an acid (hereinafter both are collectively referred to as "structural unit (II)"), It may contain a structural unit (III) containing a lactone structure or the like. Each structural unit will be described below.

(Structural unit (I))
Structural unit (I) is represented by the following formula (1).

In the above formula (1), the alkyl group having 1 to 5 carbon atoms represented by R is preferably a linear or branched alkyl group, specifically a methyl group, an ethyl group, a propyl group, isopropyl group, n-butyl group, isobutyl group, tert-butyl group, pentyl group, isopentyl group, neopentyl group and the like.

In the above formula (1), the halogenated alkyl group having 1 to 5 carbon atoms represented by R is a group in which some or all of the hydrogen atoms of the alkyl group having 1 to 5 carbon atoms are substituted with halogen atoms. is mentioned. The halogen atom includes a fluorine atom, a chlorine atom, a bromine atom, an iodine atom and the like, and a fluorine atom is particularly preferred.

The divalent linking group of Y ¹ is not particularly limited, but preferable examples include a divalent hydrocarbon group which may have a substituent, a divalent linking group containing a hetero atom, and the like.
A hydrocarbon group "having a substituent" means that some or all of the hydrogen atoms in the hydrocarbon group are substituted with substituents (groups or atoms other than hydrogen atoms).
The hydrocarbon group may be an aliphatic hydrocarbon group or an aromatic hydrocarbon group.
An aliphatic hydrocarbon group means a hydrocarbon group without aromaticity.
The aliphatic hydrocarbon group as the divalent hydrocarbon group for Y ¹ may be saturated or unsaturated, and is usually preferably saturated.
More specific examples of the aliphatic hydrocarbon group include linear or branched aliphatic hydrocarbon groups and aliphatic hydrocarbon groups containing rings in their structures.

The linear or branched aliphatic hydrocarbon group preferably has 1 to 10 carbon atoms, more preferably 1 to 6 carbon atoms, still more preferably 1 to 4 carbon atoms, and most preferably 1 to 3 carbon atoms.
As the straight-chain aliphatic hydrocarbon group, a straight _- chain alkylene group is preferable, and specifically, a methylene group [--CH.sub.2--], an ethylene group [-- ₍ CH.sub.2) _.sub.2-- ], a trimethylene group [ -(CH ₂ ) ₃ -], tetramethylene group [-(CH ₂ ) ₄ -], pentamethylene group [-(CH ₂ ) ₅ -] and the like.
The branched aliphatic hydrocarbon group is preferably a branched alkylene group, and specifically, -CH(CH ₃ )-, -CH(CH ₂ CH ₃ )-, -C(CH ₃ ) _2- , -C(CH ₃ )(CH ₂ CH ₃ )-, -C(CH ₃ )(CH ₂ CH ₂ CH ₃ )-, -C(CH ₂ CH ₃ ) ₂ - and other alkylmethylene groups;- CH(CH ₃ )CH ₂ -, -CH(CH ₃ )CH(CH ₃ )-, -C(CH ₃ ) ₂ CH ₂ -, -CH(CH ₂ CH ₃ )CH ₂ -, -C(CH ₂ Alkylethylene groups such as CH ₃ ) ₂ -CH ₂ -; alkyltrimethylene groups such as -CH(CH ₃ )CH ₂ CH ₂ - and -CH ₂ CH(CH ₃ )CH ₂ -; -CH(CH ₃ ) Examples include alkylalkylene groups such as alkyltetramethylene groups such as CH ₂ CH ₂ CH ₂ — and —CH ₂ CH(CH ₃ )CH ₂ CH ₂ —. As the alkyl group in the alkylalkylene group, a linear alkyl group having 1 to 5 carbon atoms is preferable.
The linear or branched aliphatic hydrocarbon group may or may not have a substituent.

The aliphatic hydrocarbon group containing a ring in the structure includes an alicyclic hydrocarbon group (a group obtained by removing two hydrogen atoms from an aliphatic hydrocarbon ring), and an alicyclic hydrocarbon group that is linear or branched. Examples thereof include a group bonded to the end of a chain aliphatic hydrocarbon group and a group in which an alicyclic hydrocarbon group intervenes in the middle of a linear or branched aliphatic hydrocarbon group. Examples of the straight-chain or branched-chain aliphatic hydrocarbon group include those mentioned above.
The alicyclic hydrocarbon group preferably has 3 to 20 carbon atoms, more preferably 3 to 12 carbon atoms.
The alicyclic hydrocarbon group may be polycyclic or monocyclic. As the monocyclic alicyclic hydrocarbon group, a group obtained by removing two hydrogen atoms from a monocycloalkane is preferable. The monocycloalkane preferably has 3 to 6 carbon atoms, and specific examples include cyclopentane and cyclohexane. The polycyclic alicyclic hydrocarbon group is preferably a group obtained by removing two hydrogen atoms from a polycycloalkane, and the polycycloalkane preferably has 7 to 12 carbon atoms, specifically adamantane. , norbornane, isobornane, tricyclodecane, tetracyclododecane and the like.
The alicyclic hydrocarbon group may or may not have a substituent.

An aromatic hydrocarbon group is a hydrocarbon group having an aromatic ring.
The aromatic hydrocarbon group as the divalent hydrocarbon group for Y ¹ preferably has 3 to 30 carbon atoms, more preferably 5 to 30 carbon atoms, still more preferably 5 to 20 carbon atoms, and 6 to 15 is particularly preferred and 6-10 is most preferred. However, the number of carbon atoms does not include the number of carbon atoms in the substituent.
Specific examples of aromatic rings possessed by aromatic hydrocarbon groups include aromatic hydrocarbon rings such as benzene, biphenyl, fluorene, naphthalene, anthracene, and phenanthrene; Atom-substituted heteroaromatic rings; and the like. The heteroatom in the aromatic heterocycle includes oxygen atom, sulfur atom, nitrogen atom and the like.
Specifically, the aromatic hydrocarbon group includes a group obtained by removing two hydrogen atoms from the aromatic hydrocarbon ring (arylene group); a group obtained by removing one hydrogen atom from the aromatic hydrocarbon ring (aryl group ) in which one of the hydrogen atoms is substituted with an alkylene group (e.g., benzyl group, phenethyl group, 1-naphthylmethyl group, 2-naphthylmethyl group, 1-naphthylethyl group, arylalkyl such as 2-naphthylethyl group a group obtained by removing one hydrogen atom from the aryl group in the group); and the like. The alkylene group (alkyl chain in the arylalkyl group) preferably has 1 to 4 carbon atoms, more preferably 1 to 2 carbon atoms, and particularly preferably 1 carbon atom.
The aromatic hydrocarbon group may or may not have a substituent.

The heteroatom in the "heteroatom-containing divalent linking group" of Y ¹ is an atom other than a carbon atom and a hydrogen atom, such as an oxygen atom, a nitrogen atom, a sulfur atom, a halogen atom and the like.
The bivalent linking group containing a hetero atom includes -O-, -C(=O)-O-, -C(=O)-, -OC(=O)-O-, -C(= O)—NH—, —NH— (H may be substituted with a substituent such as an alkyl group, an acyl group, an aryl group, etc.), —S—, —S(=O) ₂ —, —S( =O) ₂ -O-, -NH-C(=O)-, =N-, general formula -Y ²¹ -O-Y ²² -, -[Y ²¹ -C(=O)-O] _mp -Y 22- or a group represented by -Y ²¹ -O-C(=O)-Y ²² - [wherein Y ²¹ and Y ²² are each independently a divalent carbon group ^optionally having a substituent is a hydrogen group, O is an oxygen atom, and mp is an integer of 0-3. ] and the like.
When Y ¹ is -NH-, its H may be substituted with a substituent such as an alkyl group, an acyl group or an aryl group (aromatic group). Y ²¹ and Y ²² are each independently a divalent hydrocarbon group optionally having a substituent. Examples of the divalent hydrocarbon group include the same as those exemplified above as the “optionally substituted divalent hydrocarbon group” for Y ¹ .
Y ²¹ is preferably a straight-chain aliphatic hydrocarbon group, more preferably a straight-chain alkylene group, more preferably a straight-chain alkylene group having 1 to 5 carbon atoms, particularly a methylene group or an ethylene group. preferable.
Y ²² is preferably a linear or branched aliphatic hydrocarbon group, more preferably a methylene group, an ethylene group or an alkylmethylene group.
The heteroatom-containing divalent linking group is preferably a linear group having an oxygen atom as a heteroatom, such as a group containing an ether bond or an ester bond, and the above formulas -Y ²¹ -O—Y ²² -, A group represented by -[Y ²¹ -C(=O)-O] _mp -Y ²² - or -Y ²¹ -OC(=O)-Y ²² - is more preferred.

Among the above, the divalent linking group for Y ¹ is particularly a linear or branched alkylene group, a divalent alicyclic hydrocarbon group, or a divalent linking group containing a hetero atom. preferable. Among these, a linear or branched alkylene group or a divalent linking group containing a hetero atom is preferable.

In the above formula ( ¹ ), the acid-labile group represented by X1 means that at least the bond between the acid-labile group and an atom adjacent to the acid-labile group is cleaved by the action of an acid. It is a group having acid dissociation properties.

The acid-dissociable group is not particularly limited, and includes a group that forms a cyclic or chain tertiary alkyl ester with a carboxy group in (meth)acrylic acid or the like; an acetal-type acid-dissociable group such as an alkoxyalkyl group; Widely known.
Here, the term "tertiary alkyl ester" refers to an ester formed by substituting a hydrogen atom of a carboxy group with a chain or cyclic alkyl group, and the carbonyloxy group (-C(=O )—O—) is a structure in which a tertiary carbon atom of the chain or cyclic alkyl group is bonded to the terminal oxygen atom. In this tertiary alkyl ester, when an acid acts, the bond between the oxygen atom and the tertiary carbon atom is cleaved to form a carboxy group.
The chain or cyclic alkyl group may have a substituent.
Hereinafter, a group that is acid-dissociable by forming a carboxy group and a tertiary alkyl ester is referred to as a "tertiary alkyl ester-type acid-dissociable group" for convenience.

Examples of the tertiary alkyl ester-type acid-dissociable group include an aliphatic branched-chain acid-dissociable group and an acid-dissociable group containing an aliphatic cyclic group.
Here, "aliphatic branched" means having a branched structure without aromaticity. The structure of the "aliphatic branched acid-dissociable group" is not limited to a group composed of carbon and hydrogen (hydrocarbon group), but is preferably a hydrocarbon group. Also, the "hydrocarbon group" may be either saturated or unsaturated, but is usually preferably saturated.
Examples of aliphatic branched acid-labile groups include groups represented by —C(R ⁷¹ )(R ⁷² )(R ⁷³ ). In the formula, R ⁷¹ to R ⁷³ are each independently a linear alkyl group having 1 to 5 carbon atoms. The group represented by —C(R ⁷¹ )(R ⁷² )(R ⁷³ ) preferably has 4 to 8 carbon atoms, specifically a tert-butyl group and a 2-methyl-2-butyl group. , 2-methyl-2-pentyl group, 3-methyl-3-pentyl group and the like. A tert-butyl group is particularly preferred.

An "aliphatic cyclic group" indicates a monocyclic or polycyclic group having no aromatic character.
The aliphatic cyclic group in the "acid-labile group containing an aliphatic cyclic group" may or may not have a substituent.
The basic ring structure of the aliphatic cyclic group excluding substituents is not limited to a group composed of carbon and hydrogen (hydrocarbon group), but is preferably a hydrocarbon group. Also, the hydrocarbon group may be either saturated or unsaturated, but is usually preferably saturated.
Aliphatic cyclic groups may be monocyclic or polycyclic.
Aliphatic cyclic groups include, for example, groups obtained by removing one or more hydrogen atoms from monocycloalkane; and the like. Also, some of the carbon atoms constituting the ring of these alicyclic hydrocarbon groups may be substituted with ether bonds (--O--).

Examples of the acid dissociable group containing an aliphatic cyclic group include groups represented by the following formulas (1-1) to (1-9) and the following formulas (2-1) to (2-6). mentioned.

[In the formula, R ¹⁴ is an alkyl group and g is an integer of 0 to 8. ]

[In the formula, R ¹⁵ and R ¹⁶ are each independently an alkyl group. ]

In formulas (1-1) to (1-9), the alkyl group for R ¹⁴ may be linear, branched or cyclic, preferably linear or branched.
The linear alkyl group preferably has 1 to 5 carbon atoms, more preferably 1 to 4 carbon atoms, and still more preferably 1 or 2 carbon atoms.
The branched-chain alkyl group preferably has 3 to 10 carbon atoms, more preferably 3 to 5 carbon atoms.
Examples of the cyclic alkyl group include those similar to the aliphatic cyclic groups described above.
g is preferably an integer of 0 to 3, more preferably an integer of 1 to 3, and even more preferably 1 or 2.
In formulas (2-1) to (2-6), examples of alkyl groups for R ¹⁵ to R ¹⁶ include the same alkyl groups for R ¹⁴ above.
In the above formulas (1-1) to (1-9) and (2-1) to (2-6), some of the carbon atoms constituting the ring are substituted with etheric oxygen atoms (--O--) may
Further, in formulas (1-1) to (1-9) and (2-1) to (2-6), hydrogen atoms bonded to carbon atoms constituting the ring may be substituted with substituents.

An "acetal-type acid-dissociable group" generally replaces a hydrogen atom at the end of an OH-containing polar group such as a carboxy group or a hydroxyl group and bonds to an oxygen atom. Then, the acid acts to break the bond between the acetal-type acid-dissociable group and the oxygen atom to which the acetal-type acid-dissociable group is bonded, forming an OH-containing polar group such as a carboxy group or a hydroxyl group. be.

X ¹ in the above formula (1) is preferably represented by the following formula (s1) or (s2) in addition to the above acid dissociable group.

(In the above formula (s1),
Cy is an aliphatic cyclic group formed with a carbon atom.
Ra ⁰¹ to Ra ⁰³ each independently represents a hydrogen atom, a substituted or unsubstituted monovalent chain saturated hydrocarbon group having 1 to 10 carbon atoms, or a substituted or unsubstituted monovalent is an aliphatic cyclic saturated hydrocarbon group, or represents an aliphatic cyclic structure formed by combining two or more of these with each other, provided that the aliphatic cyclic structure forms a crosslinked structure no.
In the above formula (s2),
Cy is synonymous with the above formula (s1).
Ra ⁰⁴ is a substituted or unsubstituted aromatic hydrocarbon group.
In the above formula, both * indicate a bond with an oxygen atom. )

The aliphatic cyclic group represented by Cy may be a monocyclic group or a polycyclic group. A monocyclic aliphatic cyclic group includes a group obtained by removing one or more hydrogen atoms from a monocycloalkane. The monocycloalkane preferably has 3 to 6 carbon atoms, and specific examples include cyclopentane and cyclohexane. Polycyclic aliphatic cyclic groups include groups obtained by removing one or more hydrogen atoms from polycycloalkanes. Among these, a monocyclic aliphatic cyclic group is preferable, and a group obtained by removing one or more hydrogen atoms from cyclopentane or cyclohexane is more preferable.

Some or all of the hydrogen atoms in the above aliphatic cyclic group may be substituted.

In formula (s1), examples of monovalent chain saturated hydrocarbon groups having 1 to 10 carbon atoms in Ra ⁰¹ to Ra ⁰³ include alkyl groups having 1 to 10 carbon atoms.
Examples of monovalent saturated aliphatic hydrocarbon groups having 3 to 20 carbon atoms in Ra ⁰¹ to Ra ⁰³ include monocyclic saturated aliphatic hydrocarbon groups and saturated polycyclic aliphatic hydrocarbon groups.
Among them, Ra ⁰¹ to Ra ⁰³ are particularly preferably hydrogen atoms from the viewpoint of ease of synthesizing the monomeric compound from which the structural unit (I) is derived.

The chain saturated hydrocarbon group or aliphatic cyclic saturated hydrocarbon group represented by Ra ⁰¹ to Ra ⁰³ may or may not have a substituent.

The aliphatic cyclic group having no crosslinked structure represented by Cy in formula (s2) is the same as the aliphatic cyclic group represented by Cy in formula (s1).

In formula (s2), examples of the aromatic hydrocarbon group for Ra ⁰⁴ include groups obtained by removing one or more hydrogen atoms from an aromatic hydrocarbon ring having 5 to 30 carbon atoms. Among them, Ra ⁰⁴ is preferably a group obtained by removing one or more hydrogen atoms from an aromatic hydrocarbon ring having 6 to 15 carbon atoms, and most preferably a group obtained by removing one or more hydrogen atoms from benzene.

Specific examples of the acid-dissociable group represented by the formula (s1) are given below. * indicates a bond.

Specific examples of the acid-dissociable group represented by the formula (s2) are given below. * indicates a bond.

Specific examples of the structural unit represented by formula (1) are shown below. In each formula, R ^α represents a hydrogen atom, a methyl group or a trifluoromethyl group.

Specific examples of the structural unit (I) having an acid-labile group represented by formula (s1) or (s2) are shown below. In the formula below, R ^α represents a hydrogen atom, a methyl group or a trifluoromethyl group.

Among the above examples, the structural unit (I) is represented by the above formulas (a1-3-13) to (a1-3-24), (a1-3-33) to (a1-3-34), formula (a01- 1-01) to (a01-1-08), formulas (s1-1) to (s1-4), and formulas (s2-1) to (s1-6). is preferred.

The content ratio of the structural unit (I) in the resin (total when multiple types of the structural unit (I) are present) is preferably 10 mol% or more, more preferably 20 mol%, based on the total structural units constituting the resin. The above is more preferable, and 30 mol % or more is even more preferable. The content ratio is preferably 70 mol % or less, more preferably 60 mol % or less, and even more preferably 50 mol % or less. By setting the content of the structural unit (I) within the above range, the radiation-sensitive resin composition can further improve the sensitivity and CDU performance.

(Structural unit (II))
Structural unit (II) is a structural unit having a phenolic hydroxyl group or a structural unit giving a phenolic hydroxyl group by the action of an acid. The phenolic hydroxyl group of the structural unit (II) also includes a phenolic hydroxyl group that is deprotected by the action of an acid generated by exposure to light. By including the structural unit (II) in the resin, the solubility in the developer can be adjusted more appropriately, and as a result, the sensitivity and the like of the radiation-sensitive resin composition can be further improved. Further, when KrF excimer laser light, EUV, electron beam, or the like is used as the radiation to be irradiated in the exposure step in the resist pattern forming method, the structural unit (II) improves etching resistance and contributes to the improvement of the developer solubility difference (dissolution contrast) between In particular, it can be suitably applied to pattern formation using exposure to radiation with a wavelength of 50 nm or less, such as electron beams and EUV. Structural unit (II) is preferably represented by the following formula (2).

(in the above formula (2),
R ^α is a hydrogen atom, a fluorine atom, a methyl group or a trifluoromethyl group.
L ^CA is a single bond, -COO- ^* or -O-. * is a bond on the aromatic ring side.
R ¹⁰¹ is a hydrogen atom or a protecting group that is deprotected by the action of an acid. When multiple R ¹⁰¹ are present, the multiple R ¹⁰¹ are the same or different.
R ¹⁰² is a cyano group, nitro group, alkyl group, fluorinated alkyl group, alkoxycarbonyloxy group, acyl group or acyloxy group. When multiple R ¹⁰² are present, the multiple R ¹⁰² are the same or different from each other.
n ₃ is an integer of 0-2, m ₃ is an integer of 1-8, and m ₄ is an integer of 0-8. However, 1≦m ₃ +m ₄ ≦2n ₃ +5 is satisfied. )

From the viewpoint of copolymerizability of the monomer that provides the structural unit (II), R ^α is preferably a hydrogen atom or a methyl group.

^LCA is preferably a single bond or -COO- ^* .

Examples of the protective group represented by R ¹⁰¹ deprotected by the action of an acid include the same acid-labile groups as X ¹ in formula (1) above.

Examples of the alkyl group for R ¹⁰² include linear or branched alkyl groups having 1 to 8 carbon atoms such as methyl group, ethyl group and propyl group. Examples of the fluorinated alkyl group include linear or branched fluorinated alkyl groups having 1 to 8 carbon atoms such as trifluoromethyl group and pentafluoroethyl group. The alkoxycarbonyloxy group includes, for example, a chain or alicyclic alkoxycarbonyloxy group having 2 to 16 carbon atoms such as a methoxycarbonyloxy group, a butoxycarbonyloxy group and an adamantylmethyloxycarbonyloxy group. Acyl groups include, for example, aliphatic or aromatic acyl groups having 2 to 12 carbon atoms such as acetyl group, propionyl group, benzoyl group and acryloyl group. The acyloxy group includes, for example, aliphatic or aromatic acyloxy groups having 2 to 12 carbon atoms such as acetyloxy group, propionyloxy group, benzoyloxy group and acryloyloxy group.

As the above n3 _, 0 or 1 is more preferable, and 0 is even more preferable.

The above m ₃ is preferably an integer of 1 to 3, more preferably 1 or 2.

The above m ₄ is preferably an integer of 0 to 3, more preferably an integer of 0 to 2.

As the structural unit (II), structural units represented by the following formulas (2a-1) to (2a-10) (hereinafter also referred to as “structural units (2a-1) to structural units (2a-10)” .) and the like are preferable.

In formulas (2a-1) to (2a-10) above, R ^α is the same as in formula (2) above.

Among these, the structural units (2a-1) to (2a-4), (2a-6), (2a-8) and (2a-9) are preferred.

The content ratio of the structural unit (II) (total when multiple types of structural units (II) are present) is preferably 5 mol% or more, more preferably 8 mol% or more, based on the total structural units constituting the resin. Preferably, 10 mol % or more is more preferable, and 15 mol % or more is particularly preferable. The content is preferably 50 mol % or less, more preferably 40 mol % or less, even more preferably 35 mol % or less, and particularly preferably 30 mol % or less. By setting the content ratio of the structural unit (II) within the above range, the radiation-sensitive resin composition can further improve the sensitivity and CDU performance.

When polymerizing a monomer having a phenolic hydroxyl group such as hydroxystyrene, the phenolic hydroxyl group is protected by a protective group such as an alkali-dissociable group, and then polymerized, and then hydrolyzed to deprotect. It is preferred to obtain the structural unit (II).

(Structural unit (III))
Structural unit (III) is a structural unit containing at least one selected from the group consisting of a lactone structure, a cyclic carbonate structure and a sultone structure. By further having the structural unit (III), the base resin can adjust the solubility in the developer, and as a result, the radiation-sensitive resin composition improves lithography performance such as resolution. be able to. Moreover, the adhesion between the resist pattern formed from the base resin and the substrate can be improved.

Structural units (III) include, for example, structural units represented by the following formulas (T-1) to (T-10).

In the formula above, R ^L1 is a hydrogen atom, a fluorine atom, a methyl group or a trifluoromethyl group. R ^L2 to R ^L5 each independently represent a hydrogen atom, an alkyl group having 1 to 4 carbon atoms, a cyano group, a trifluoromethyl group, a methoxy group, a methoxycarbonyl group, a hydroxy group, a hydroxymethyl group, or a dimethylamino group; be. R ^L4 and R ^L5 may be a divalent alicyclic group having 3 to 8 carbon atoms combined with each other and composed together with the carbon atoms to which they are attached. L2 is a single bond or a ^divalent linking group. X is an oxygen atom or a methylene group. k is an integer from 0 to 3; m is an integer of 1-3.

The divalent alicyclic group having 3 to 8 carbon atoms in which the above R 1 ^L4 and R 1 ^L5 are combined and formed together with the carbon atoms to which they are bonded is the above-mentioned monocyclic or polycyclic alicyclic carbonized carbon atoms. There is no particular limitation as long as it is a group obtained by removing two hydrogen atoms from the same carbon atoms constituting a hydrogen carbocyclic ring. Either a monocyclic hydrocarbon group or a polycyclic hydrocarbon group may be used, and the polycyclic hydrocarbon group may be either a bridged alicyclic hydrocarbon group or a condensed alicyclic hydrocarbon group. It may be either a hydrogen group or an unsaturated hydrocarbon group. The condensed alicyclic hydrocarbon group is a polycyclic alicyclic hydrocarbon group in which a plurality of alicyclic rings share a side (a bond between two adjacent carbon atoms).

Examples of the divalent linking group represented by L ² include a divalent linear or branched hydrocarbon group having 1 to 10 carbon atoms, and a divalent alicyclic carbonized group having 4 to 12 carbon atoms. A hydrogen group, or a group composed of one or more of these hydrocarbon groups and at least one group selected from -CO-, -O-, -NH- and -S- may be mentioned.

Among these, as the structural unit (III), a structural unit containing a lactone structure is preferable, a structural unit containing a norbornanelactone structure is more preferable, and a structural unit derived from norbornanelactone-yl (meth)acrylate is even more preferable.

The content of the structural unit (III) (total when multiple types of the structural unit (III) are present) is preferably 5 mol% or more, more preferably 10 mol% or more, based on the total structural units constituting the base resin. More preferably, 15 mol % or more is even more preferable. The content ratio is preferably 50 mol % or less, more preferably 40 mol % or less, and even more preferably 35 mol % or less. By setting the content of the structural unit (III) within the above range, the radiation-sensitive resin composition can further improve the lithography performance such as resolution and the adhesion of the formed resist pattern to the substrate. .

(other structural units)
The base resin optionally has other structural units in addition to the structural units (I) to (III). Examples of the other structural units include structural units (IV) containing a polar group (excluding structural units (II) and (III)) and other structural units having an acid-dissociable group. (V) (excluding those corresponding to the structural unit (I)), and the like.

(Structural unit (IV))
By further having the structural unit (IV), the base resin can adjust the solubility in the developer, and as a result, the lithography performance such as the resolution of the radiation-sensitive resin composition can be improved. can be done. Examples of the polar group include a hydroxy group, a carboxyl group, a cyano group, a nitro group, a sulfonamide group and the like. Among these, a hydroxy group and a carboxy group are preferred, and a hydroxy group is more preferred.

Structural units (IV) include, for example, structural units represented by the following formula.

In the above formula, ^RA is a hydrogen atom, a fluorine atom, a methyl group or a trifluoromethyl group.

When the base resin has the structural unit (IV), the lower limit of the content ratio of the structural unit (IV) (the total when there are multiple types of the structural unit (IV)) is , 1 mol % is preferred, 5 mol % is more preferred, and 10 mol % is even more preferred. Moreover, the upper limit of the content ratio is preferably 40 mol %, more preferably 30 mol %, and even more preferably 25 mol %. By setting the content of the structural unit (IV) within the above range, the lithography performance such as the resolution of the radiation-sensitive resin composition can be further improved.

(Structural unit (V))
Structural unit (V) is a structural unit containing an acid-labile group (but different from structural unit (I) and structural unit (II)). The structural unit (V) is not particularly limited as long as it contains an acid-dissociable group. and a structural unit having an acetal bond. From the viewpoint of improving the pattern formability of the radiation-sensitive resin composition, a structural unit represented by the following formula (3) (hereinafter referred to as "structure Unit (V-1)”) is preferred.

In formula (3) above, ^R7 is a hydrogen atom, a fluorine atom, a methyl group or a trifluoromethyl group. R ⁸ is a monovalent hydrocarbon group having 1 to 20 carbon atoms. R ⁹ and R ¹⁰ are each independently a monovalent chain hydrocarbon group having 1 to 10 carbon atoms or a monovalent alicyclic hydrocarbon group having 3 to 20 carbon atoms, or these groups represents a divalent alicyclic group having 3 to 20 carbon atoms which is combined with the carbon atoms to which they are bonded.

R ⁷ is preferably a hydrogen atom or a methyl group, more preferably a methyl group, from the viewpoint of copolymerizability of the monomer that gives the structural unit (V-1).

Examples of the monovalent hydrocarbon group having 1 to 20 carbon atoms represented by R ⁸ include a chain hydrocarbon group having 1 to 10 carbon atoms and a monovalent alicyclic hydrocarbon group having 3 to 20 carbon atoms. groups, monovalent aromatic hydrocarbon groups having 6 to 20 carbon atoms, and the like.

The chain hydrocarbon group having 1 to 10 carbon atoms represented by R ⁸ to R ¹⁰ includes a linear or branched saturated hydrocarbon group having 1 to 10 carbon atoms, or a linear or branched hydrocarbon group having 1 to 10 carbon atoms. A branched chain unsaturated hydrocarbon group is mentioned.

Examples of the alicyclic hydrocarbon group having 3 to 20 carbon atoms represented by R ⁸ to R ¹⁰ include monocyclic or polycyclic saturated hydrocarbon groups and monocyclic or polycyclic unsaturated hydrocarbon groups. be done.

Examples of the monovalent aromatic hydrocarbon group having 6 to 20 carbon atoms represented by R ⁸ include aryl groups such as phenyl group, tolyl group, xylyl group, naphthyl group and anthryl group; benzyl group and phenethyl group; , an aralkyl group such as a naphthylmethyl group, and the like.

R ⁸ above includes a linear or branched saturated hydrocarbon group having 1 to 5 carbon atoms, a linear or branched unsaturated hydrocarbon group having 1 to 5 carbon atoms, and an alicyclic hydrocarbon having 3 to 12 carbon atoms. A monovalent aromatic hydrocarbon group having 6 to 12 carbon atoms is preferred.

The divalent alicyclic group having 3 to 20 carbon atoms in which the groups represented by R ⁹ and R ¹⁰ are combined together and formed together with the carbon atoms to which they are bonded are monocyclic hydrocarbon groups and polycyclic hydrocarbon groups. Any hydrocarbon group may be used.

Among these, R ⁸ is an alkyl group having 1 to 4 carbon atoms, and R ⁹ and R ¹⁰ are combined together and the alicyclic structure composed of the carbon atom to which they are attached is a polycyclic or monocyclic cycloalkane. A structure is preferred.

As the structural unit (V-1), for example, structural units represented by the following formulas (3-1) to (3-6) (hereinafter referred to as "structural units (V-1-1) to (V-1- 6)”) and the like.

In formulas (3-1) to (3-6) above, R ⁷ to R ¹⁰ have the same meanings as in formula (3) above. i and j are each independently an integer of 1 to 4; k and l are 0 or 1;

As i and j, 1 is preferable. ^R8 is preferably a methyl group, an ethyl group or an isopropyl group. R ⁹ and R ¹⁰ are preferably a methyl group or an ethyl group.

The base resin may contain one or a combination of two or more structural units (V).

When the base resin contains the structural unit (V), the lower limit of the content ratio of the structural unit (V) (the total content ratio when multiple types are included) is 3 mol% with respect to the total structural units constituting the base resin. is preferred, 5 mol % is more preferred, and 10 mol % is even more preferred. Moreover, the upper limit of the content ratio is preferably 50 mol %, more preferably 40 mol %, and even more preferably 30 mol %. By setting the content of the structural unit (V) within the above range, the pattern formability of the radiation-sensitive resin composition can be further improved.

(Method for synthesizing resin)
The resin serving as the base resin can be synthesized, for example, by polymerizing monomers that provide each structural unit using a known radical polymerization initiator or the like in an appropriate solvent.

The molecular weight of the base resin is not particularly limited, but the lower limit of the polystyrene equivalent weight average molecular weight (Mw) by gel permeation chromatography (GPC) is preferably 1,000, more preferably 2,000, and further 3,000. Preferably, 4,000 is particularly preferred. Moreover, the upper limit of Mw is preferably 50,000, more preferably 30,000, even more preferably 15,000, and particularly preferably 12,000. When the Mw of the resin is within the above range, the obtained resist film has good heat resistance and developability.

The ratio (Mw/Mn) of Mw to the polystyrene equivalent number average molecular weight (Mn) measured by GPC of the base resin is usually 1 or more and 5 or less, preferably 1 or more and 3 or less, and more preferably 1 or more and 2 or less.

The method for measuring Mw and Mn of the resin in this specification is described in Examples.

The resin content is preferably 70% by mass or more, more preferably 75% by mass or more, and even more preferably 80% by mass or more, relative to the total solid content of the radiation-sensitive resin composition.

<Other resins>
The radiation-sensitive resin composition of the present embodiment may contain, as another resin, a resin having a higher mass content of fluorine atoms than the base resin (hereinafter also referred to as "high fluorine content resin"). good. When the radiation-sensitive resin composition contains a high fluorine content resin, it can be unevenly distributed on the surface layer of the resist film with respect to the base resin, and as a result, the state of the resist film surface and the components in the resist film The distribution can be controlled as desired.

As the high fluorine content resin, for example, the structural unit (I) to the structural unit (V) in the base resin may be used singly or in combination, and a structural unit represented by the following formula (6) (hereinafter referred to as , also referred to as “structural unit (VI)”).

In formula (6) above, R ¹³ is a hydrogen atom, a methyl group or a trifluoromethyl group. G is a single bond, an oxygen atom, a sulfur atom, -COO-, -SO ₂ ONH-, -CONH- or -OCONH-. R ¹⁴ 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.

When the high fluorine content resin has the structural unit (VI), the lower limit of the content of the structural unit (VI) is preferably 50 mol%, preferably 60%, based on the total structural units constituting the high fluorine content resin. mol % is more preferred, 70 mol % is even more preferred, and 80 mol % is particularly preferred. The upper limit of the content ratio is preferably 100 mol %, more preferably 98 mol %, and even more preferably 95 mol %. By setting the content of the structural unit (VI) within the above range, the mass content of fluorine atoms in the high-fluorine content resin can be adjusted more appropriately, and uneven distribution on the surface layer of the resist film can be further promoted. .

In addition to the structural unit (VI), the high fluorine content resin has a structural unit (x) an alkali-soluble group or (y) a group dissociated by the action of an alkali to increase the solubility in an alkaline developer (hereinafter referred to as Also referred to as a structural unit (VII)). By having the structural unit (VII), the high fluorine content resin can improve the solubility in an alkaline developer and suppress the occurrence of development defects.

When the high fluorine content resin has the structural unit (VII), the lower limit of the content of the structural unit (VII) is preferably 10 mol%, 20 mol % is more preferred, 30 mol % is even more preferred, and 35 mol % is particularly preferred. The upper limit of the content ratio is preferably 90 mol %, more preferably 75 mol %, and even more preferably 60 mol %. By setting the content of the structural unit (VII) within the above range, the water repellency of the resist film during immersion exposure can be further improved.

The lower limit of the content of the high fluorine content resin is preferably 0.1 parts by mass, more preferably 0.5 parts by mass, still more preferably 1 part by mass, and 1.5 parts by mass with respect to 100 parts by mass of the base resin. Parts by weight are particularly preferred. The upper limit of the content is preferably 12 parts by mass, more preferably 10 parts by mass, still more preferably 8 parts by mass, and particularly preferably 5 parts by mass.

(Method for synthesizing high fluorine content resin)
The high fluorine content resin can be synthesized by a method similar to the method for synthesizing the base resin described above.

<Onium salt>
The onium salt contains an organic acid anion portion and an onium cation portion, and is a component that generates an acid upon exposure. When at least a part of the onium cation portion in the onium salt contains an aromatic ring structure having a fluorine atom, it is possible to achieve high sensitivity and development residue suppression properties by improving the efficiency of acid generation.

The form of the onium salt contained in the radiation-sensitive resin composition is not particularly limited. It is preferably at least one selected from the group consisting of acid diffusion control agents that contain the above onium cation moiety and generate an acid having a higher pKa than the acid generated from the above radiation-sensitive acid generator upon exposure to radiation. . Each of these functions is described below.

The acid generated by exposure to the onium salt is considered to have two functions in the radiation-sensitive resin composition depending on the strength of the acid. As the first function, the acid generated by exposure dissociates the acid-dissociable group of the structural unit when the resin contains a structural unit having an acid-labile group to generate a carboxyl group or the like. be done. An onium salt having this first function is called a radiation-sensitive acid generator. As a second function, under the pattern forming conditions using the radiation-sensitive resin composition, the acid-dissociable groups of the resin are not substantially dissociated, and are generated from the radiation-sensitive acid generator in the unexposed areas. The function of suppressing the diffusion of the acid that has been added by salt exchange is exemplified. An onium salt having this second function is called an acid diffusion controller. It can be said that the acid generated from the acid diffusion control agent is a relatively weak acid (acid having a high pKa) than the acid generated from the radiation-sensitive acid generator. Whether the onium salt functions as a radiation-sensitive acid generator or an acid diffusion control agent is determined by the energy required for dissociation of the acid dissociable group of the resin, the acidity of the onium salt, and the like. The form in which the radiation-sensitive acid generator is contained in the radiation-sensitive resin composition is preferably a form in which the onium salt structure exists alone as a (low-molecular-weight) compound.

When the radiation-sensitive resin composition contains the radiation-sensitive acid generator, the polarity of the resin in the exposed area increases, and the resin in the exposed area becomes soluble in the developer in the case of alkaline aqueous solution development. On the other hand, in the case of organic solvent development, it becomes sparingly soluble in the developer.

In addition, since the radiation-sensitive resin composition contains the acid diffusion control agent, it is possible to suppress the diffusion of the acid in the unexposed area, thereby forming a resist pattern having excellent pattern developability and CDU performance. can.

In the radiation-sensitive resin composition, at least one of the organic acid anion moiety in the radiation-sensitive acid generator and the organic acid anion moiety in the acid diffusion controller preferably contains an iodine-substituted aromatic ring structure. . Absorption of radiation such as EUV with a wavelength of 13.5 nm by iodine atoms is very large, thereby increasing the sensitivity. In addition, when the organic acid anion portion of the onium salt contains an iodine-substituted aromatic ring structure, the molecular weight of the iodine atom can control acid diffusion and improve the CDU performance. When the organic acid anion portion of the onium salt contains an iodine-substituted aromatic ring structure, the iodine-substituted aromatic ring structure and the fluorine atom-containing aromatic ring structure may be present in the same compound, or may be present in different compounds. good too.

Regardless of the form in which the onium salt is contained, the organic acid anion portion preferably has at least one selected from the group consisting of sulfonate anions, carboxylate anions and sulfonimide anions. Moreover, the onium cation is preferably at least one selected from the group consisting of sulfonium cations and iodonium cations. When the onium salt has a combination of these structures, the above functions can be efficiently exhibited.

Examples of the acid generated by exposure include those that generate sulfonic acid, carboxylic acid, and sulfonimide by exposure corresponding to the above organic acid anions.

For example, as an onium salt that gives a sulfonic acid by exposure,
(1) compounds in which one or more fluorine atoms or fluorinated hydrocarbon groups are attached to carbon atoms adjacent to the sulfonate anion;
(2) A compound in which neither a fluorine atom nor a fluorinated hydrocarbon group is bonded to the carbon atom adjacent to the sulfonate anion.

As the onium salt that gives a carboxylic acid by exposure,
(3) compounds in which one or more fluorine atoms or fluorinated hydrocarbon groups are attached to the carbon atoms adjacent to the carboxylate anion;
(4) A compound in which neither a fluorine atom nor a fluorinated hydrocarbon group is bonded to the carbon atom adjacent to the carboxylate anion.

Among these, those corresponding to (1) above are preferable as the radiation-sensitive acid generator. As the acid diffusion control agent, those corresponding to the above (2), (3) or (4) are preferable, and those corresponding to (2) or (4) are particularly preferable.

<Radiation-sensitive acid generator>
Onium salts as radiation-sensitive acid generators contain an organic acid anion moiety and an onium cation moiety. The radiation-sensitive acid generator is preferably represented by formula (A-1) or formula (A-2) below.

In formulas (A-1) and (A-2), L ¹ is a single bond, an ether bond or an ester bond, or an alkylene group having 1 to 6 carbon atoms which may contain an ether bond or an ester bond. is. The alkylene group may be linear, branched, or cyclic.

R ¹ is a hydroxy group, a carboxy group, a fluorine atom, a chlorine atom, a bromine atom or an amino group, or a fluorine atom, a chlorine atom, a bromine atom, a hydroxy group, an amino group or an alkoxy group having 1 to 10 carbon atoms; An alkyl group having 1 to 20 carbon atoms, an alkoxy group having 1 to 20 carbon atoms, an alkoxycarbonyl group having 2 to 10 carbon atoms, an acyloxy group having 2 to 20 carbon atoms, or an alkyl group having 1 to 20 carbon atoms, which may be contained. a sulfonyloxy group, or -NR ⁸ -C(=O)-R ⁹ or -NR ⁸ -C(=O)-OR ⁹ , where R ⁸ is a hydrogen atom, a halogen atom, a hydroxy group, a carbon an alkoxy group having 1 to 6 carbon atoms, an acyl group having 2 to 6 carbon atoms or an alkyl group having 1 to 6 carbon atoms which may contain an acyloxy group having 2 to ⁶ carbon atoms; 16 alkyl group, alkenyl group having 2 to 16 carbon atoms, or aryl group having 6 to 12 carbon atoms, halogen atom, hydroxy group, alkoxy group having 1 to 6 carbon atoms, acyl group having 2 to 6 carbon atoms, Alternatively, it may contain an acyloxy group having 2 to 6 carbon atoms. The alkyl group, alkoxy group, alkoxycarbonyl group, acyloxy group, acyl group and alkenyl group may be linear, branched or cyclic.

Among these, R ¹ is preferably a hydroxy group, --NR ⁸ --C(=O)--R ⁹ , a fluorine atom, a chlorine atom, a bromine atom, a methyl group, a methoxy group, or the like.

R ² is a single bond or a divalent linking group having 1 to 20 carbon atoms when p is 1, and a trivalent or tetravalent linking group having 1 to 20 carbon atoms when p is 2 or 3. and the linking group may contain an oxygen atom, a sulfur atom or a nitrogen atom.

Rf ¹ to Rf ⁴ are each independently a hydrogen atom, a fluorine atom or a trifluoromethyl group, at least one of which is a fluorine atom or a trifluoromethyl group. Also, Rf ¹ and Rf ² may combine to form a carbonyl group. ^In particular, both Rf3 and ^Rf4 are preferably fluorine atoms.

R ³ , R ⁴ , R ⁵ , R ⁶ and R ⁷ are each independently a C 1-20 monovalent hydrocarbon group optionally containing a heteroatom. R ³ , R ⁴ and R ⁵ contain one or more fluorine atoms, and R ⁶ and R ⁷ contain one or more fluorine atoms. Also, any two of R ³ , R ⁴ and R ⁵ may bond with each other to form a ring together with the sulfur atom to which they bond. The monovalent hydrocarbon group may be linear, branched, or cyclic, and specific examples thereof include an alkyl group having 1 to 12 carbon atoms, an alkenyl group having 2 to 12 carbon atoms, and an alkenyl group having 2 to 12 carbon atoms. , an aryl group having 6 to 20 carbon atoms, an aralkyl group having 7 to 12 carbon atoms, and the like. Also, some or all of the hydrogen atoms in these groups are substituted with hydroxy groups, carboxy groups, halogen atoms, cyano groups, amido groups, nitro groups, mercapto groups, sultone groups, sulfone groups, or sulfonium salt-containing groups. and some of the carbon atoms of these groups may be substituted with ether bonds, ester bonds, carbonyl groups, carbonate groups or sulfonate ester bonds.

　p is an integer that satisfies 1≤p≤3. q and r are integers satisfying 0≦q≦5, 0≦r≦3, and 0≦q+r≦5. q is preferably an integer that satisfies 1≤q≤3, more preferably 2 or 3. r is preferably an integer that satisfies 0≦r≦2.

Examples of the organic acid anion portion of the radiation-sensitive acid generator represented by the above formulas (A-1) and (A-2) include, but are not limited to, those shown below. All of the compounds shown below are organic acid anion moieties having an iodine-substituted aromatic ring structure. A structure substituted with an atom or group other than an iodine atom such as a substituent of can be preferably employed.

The onium cation moiety in the radiation-sensitive acid generator represented by formula (A-1) above is preferably represented by formula (Q-1) below.

In the above formula (Q-1), Ra1 and Ra2 each independently represent a substituent. n1 represents an integer of 0 to 5, and when n1 is 2 or more, a plurality of Ra1 may be the same or different. n2 represents an integer of 0 to 5, and when n2 is 2 or more, a plurality of Ra2 may be the same or different. n3 represents an integer of 0 to 5, and when n3 is 2 or more, a plurality of Ra3 may be the same or different. Ra3 represents a fluorine atom or a group having one or more fluorine atoms. Ra1 and Ra2 may be linked together to form a ring. When n1 is 2 or more, a plurality of Ra1 may be linked together to form a ring. When n2 is 2 or more, a plurality of Ra2 may be linked together to form a ring.

The substituents represented by Ra1 and Ra2 are preferably alkyl groups, cycloalkyl groups, alkoxy groups, cycloalkyloxy groups, alkoxycarbonyl groups, alkylsulfonyl groups, hydroxyl groups, halogen atoms, and halogenated hydrocarbon groups.

The alkyl groups of Ra1 and Ra2 may be straight-chain alkyl groups or branched-chain alkyl groups. The alkyl group preferably has 1 to 10 carbon atoms, and particularly preferably methyl group, ethyl group, n-butyl group and t-butyl group.

Cycloalkyl groups for Ra1 and Ra2 include monocyclic or polycyclic cycloalkyl groups (preferably cycloalkyl groups having 3 to 20 carbon atoms). Among these, cyclopropyl group, cyclopentyl group, cyclohexyl group, cycloheptyl group and cyclooctyl group are particularly preferred.

Examples of the alkyl group portion of the alkoxy groups of Ra1 and Ra2 include those previously listed as the alkyl groups of Ra1 and Ra2. As this alkoxy group, a methoxy group, an ethoxy group, an n-propoxy group and an n-butoxy group are particularly preferred.

Examples of the cycloalkyl group portion of the cycloalkyloxy groups of Ra1 and Ra2 include those previously listed as the cycloalkyl groups of Ra1 and Ra2. A cyclopentyloxy group and a cyclohexyloxy group are particularly preferred as the cycloalkyloxy group.

Examples of the alkoxy group portion of the alkoxycarbonyl groups of Ra1 and Ra2 include those previously listed as the alkoxy groups of Ra1 and Ra2. As this alkoxycarbonyl group, a methoxycarbonyl group, an ethoxycarbonyl group and an n-butoxycarbonyl group are particularly preferred.

Examples of the alkyl group portion of the alkylsulfonyl groups of Ra1 and Ra2 include those previously listed as the alkyl groups of Ra1 and Ra2. Moreover, examples of the cycloalkyl group portion of the cycloalkylsulfonyl groups of Ra1 and Ra2 include those previously listed as the cycloalkyl groups of Ra1 and Ra2. Among these alkylsulfonyl groups and cycloalkylsulfonyl groups, methanesulfonyl group, ethanesulfonyl group, n-propanesulfonyl group, n-butanesulfonyl group, cyclopentanesulfonyl group and cyclohexanesulfonyl group are particularly preferred.

Each group of Ra1 and Ra2 may further have a substituent. Examples of this substituent include a halogen atom such as a fluorine atom (preferably a fluorine atom), a hydroxy group, a carboxyl group, a cyano group, a nitro group, an alkoxy group, a cycloalkyloxy group, an alkoxyalkyl group, and a cycloalkyloxyalkyl group. , alkoxycarbonyl, cycloalkyloxycarbonyl, alkoxycarbonyloxy, and cycloalkyloxycarbonyloxy groups.

The halogen atoms of Ra1 and Ra2 include a fluorine atom, a chlorine atom, a bromine atom and an iodine atom, with a fluorine atom being preferred.

Halogenated alkyl groups are preferred as the halogenated hydrocarbon groups for Ra1 and Ra2. Examples of the alkyl group and halogen atom that constitute the halogenated alkyl group include those mentioned above. Among them, a fluorinated alkyl group is preferred, and _CF3 is more preferred.

As described above, Ra1 and Ra2 may be linked together to form a ring (ie, a heterocyclic ring containing a sulfur atom). In this case, Ra1 and Ra2 preferably form a single bond or a divalent linking group. , —SO—, —SO ₂ —, an alkylene group, a cycloalkylene group, an alkenylene group, or a combination of two or more thereof, preferably having a total carbon number of 20 or less. When n1 is 2 or more, a plurality of Ra1 may be linked together to form a ring, and when n2 is 2 or more, a plurality of Ra2 may be linked together to form a ring. Such an example includes, for example, a mode in which two Ra1s are linked to each other to form a naphthalene ring together with the benzene ring to which they are linked.

Ra3 is a fluorine atom or a group having a fluorine atom. Examples of groups having fluorine atoms include groups in which alkyl groups, cycloalkyl groups, alkoxy groups, cycloalkyloxy groups, alkoxycarbonyl groups and alkylsulfonyl groups as Ra1 and Ra2 are substituted with fluorine atoms. Among them, fluorinated alkyl groups are preferable, and CF ₃ , C ₂ F ₅ , C ₃ F ₇ , C ₄ F ₉ , C ₅ F ₁₁ , C ₆ F ₁₃ , C ₇ F ₁₅ and C ₈ F ₁₇ _, _CH2CF3 _, _CH2CH2CF3 _, _CH2C2F5 _, _CH2CH2C2F5 _, _CH2C3F7 _, _CH2CH2C3F7 _, _CH2C4F _{_} _{_} _{_} _{_} _{_} _{_} _{_} ₉ and CH ₂ CH ₂ C ₄ F ₉ are more preferred, and CF ₃ is particularly preferred.

Ra3 is preferably a fluorine atom or _CF3 , more preferably a fluorine atom.

n1 and n2 are each independently preferably an integer of 0 to 3, preferably an integer of 0 to 2.

n3 is preferably an integer of 1 to 3, more preferably 1 or 2.

(n1+n2+n3) is preferably an integer of 1 to 15, more preferably an integer of 1 to 9, even more preferably an integer of 2 to 6, and particularly preferably an integer of 3 to 6. When (n1+n2+n3) is 1, it is preferred that n3=1 and Ra3 is a fluorine atom or _CF3 . When (n1+n2+n3) is 2, a combination where n1 = n3 = 1 and Ra1 and Ra3 are each independently a fluorine atom or _CF3 , and n3 = 2 and Ra3 is a fluorine atom or _CF3 A combination is preferred. When (n1+n2+n3) is 3, a combination of n1=n2=n3=1 and each of Ra1 to Ra3 is independently a fluorine atom or CF ₃ is preferred.

Specific examples of such an onium cation moiety represented by the above formula (Q-1) include the following. All of the compounds shown below _are sulfonium cation moieties containing an aromatic ring structure having a fluorine atom. is substituted with an atom or group other than a fluorine atom such as a hydrogen atom or another substituent.

When the onium cation moiety in the radiation-sensitive acid generator represented by formula (A-2) contains an aromatic ring structure having a fluorine atom, the onium cation moiety is a diaryliodonium cation having one or more fluorine atoms. Preferably.

Specific examples of such onium cation moieties include the following. All of the compounds shown below _are iodonium cation moieties containing an aromatic ring structure having a fluorine atom. is substituted with an atom or group other than a fluorine atom such as a hydrogen atom or another substituent.

The methods for synthesizing the radiation-sensitive acid generators represented by the above formulas (A-1) and (A-2) can also be performed by known methods, particularly by salt exchange reaction. A known radiation-sensitive acid generator can also be used as long as it does not impair the effects of the present invention.

These radiation-sensitive acid generators may be used alone or in combination of two or more. The lower limit of the content of the radiation-sensitive acid generator is preferably 0.5 parts by mass, more preferably 1 part by mass, still more preferably 2 parts by mass, and particularly preferably 4 parts by mass, relative to 100 parts by mass of the base resin. . The upper limit of the content is preferably 20 parts by mass, more preferably 18 parts by mass, still more preferably 15 parts by mass, and particularly preferably 12 parts by mass. As a result, excellent sensitivity and CDU performance can be exhibited during resist pattern formation.

<Acid diffusion control agent>
The onium salt as the acid diffusion control agent contains an organic acid anion portion and an onium cation portion, and generates an acid having a higher pKa than the acid generated from the radiation-sensitive acid generator upon exposure to radiation. The acid diffusion control agent is preferably represented by the following formula (S-1) or the following formula (S-2).

In formulas (S-1) and (S-2), R ¹ is a hydrogen atom, a hydroxy group, a fluorine atom, a chlorine atom, an amino group, a nitro group or a cyano group, or optionally substituted with a halogen atom; an alkyl group having 1 to 6 carbon atoms, an alkoxy group having 1 to 6 carbon atoms, an acyloxy group having 2 to 6 carbon atoms or an alkylsulfonyloxy group having 1 to 4 carbon atoms, or -NR ^1A -C(=O)-R ^1B or -NR ^1A -C(=O)-OR ^1B . R ^1A is a hydrogen atom or an alkyl group having 1 to 6 carbon atoms, and R ^1B is an alkyl group having 1 to 6 carbon atoms or an alkenyl group having 2 to 8 carbon atoms.

R ³ , R ⁴ , R ⁵ , R ⁶ and R ⁷ are each independently a C 1-20 monovalent hydrocarbon group optionally containing a heteroatom. R ³ , R ⁴ and R ⁵ are preferably monovalent hydrocarbon groups containing one or more fluorine atoms or groups having fluorine atoms, and R ⁶ and R ⁷ are one or more fluorine atoms or fluorine atoms It is preferably a monovalent hydrocarbon group containing a group having Also, any two of R ³ , R ⁴ and R ⁵ may bond with each other to form a ring together with the sulfur atom to which they bond. The monovalent hydrocarbon group may be linear, branched, or cyclic, and specific examples thereof include an alkyl group having 1 to 12 carbon atoms, an alkenyl group having 2 to 12 carbon atoms, and an alkenyl group having 2 to 12 carbon atoms. , an aryl group having 6 to 20 carbon atoms, an aralkyl group having 7 to 12 carbon atoms, and the like. Also, some or all of the hydrogen atoms in these groups may be substituted with substituents.

L ¹ is a single bond or a divalent linking group having 1 to 20 carbon atoms, and is an ether bond, a carbonyl group, an ester bond, an amide bond, a sultone ring, a lactam ring, a carbonate bond, a halogen atom, a hydroxy group or a carboxy may contain groups.

m and n are integers satisfying 0≤m≤5, 0≤n≤3, and 0≤m+n≤5, but integers satisfying 1≤m≤3 and 0≤n≤2 are preferable.

The anions of the acid diffusion control agent represented by the above formula (S-1) or (S-2) include, but are not limited to, those shown below. All of the compounds shown below are organic acid anion moieties having an iodine-substituted aromatic ring structure. A structure substituted with an atom or group other than an iodine atom such as a substituent of can be preferably employed.

The onium cation moiety in the radiation-sensitive acid generator can be suitably employed as the onium cation moiety in the acid diffusion controller represented by formulas (S-1) and (S-2).

The acid diffusion controllers represented by the above formulas (S-1) and (S-2) can also be synthesized by known methods, particularly by salt exchange reaction. Known acid diffusion control agents can also be used as long as they do not impair the effects of the present invention. In addition, the case where the organic acid anion portion and the onium cation portion share the same aromatic ring structure is also included in the acid diffusion control agent of the present embodiment.

These acid diffusion control agents may be used alone or in combination of two or more. The lower limit of the content of the acid diffusion control agent is preferably 0.5 parts by mass, more preferably 1 part by mass, and even more preferably 1.5 parts by mass with respect to 100 parts by mass of the base resin. Moreover, the upper limit of the content is preferably 15 parts by mass, more preferably 12 parts by mass, and even more preferably 8 parts by mass. As a result, excellent sensitivity and CDU performance can be exhibited during resist pattern formation.

(Structure (1) of other organic acid anion moieties)
Radiation-sensitive acid generators (including both radiation-sensitive strong acid generators and acid diffusion controllers) are organic acid anion moieties represented by the above formulas (A-1) and (A-2). Together with or instead of the organic acid anion portion of the radioactive strong acid generator or the organic acid anion portion of the acid diffusion control agent represented by the above formula (S-1) or (S-2), the following formula (bd1) It may contain structures as depicted.

In the above formula (bd1),
R ^x1 to R ^x4 each independently represent a hydrogen atom, a substituted or unsubstituted hydrocarbon group, or a ring structure formed by combining two or more of these.
R ^y1 to R ^y2 each independently represent a hydrogen atom, a substituted or unsubstituted hydrocarbon group, or a ring structure formed by combining with each other.

is a double bond or a single bond.
R ^z1 to R ^z4 each independently represent a hydrogen atom, a substituted or unsubstituted hydrocarbon group, or a ring structure formed by combining two or more of these. However, at least one of R ^x1 to R ^x4 , R ^y1 to R ^y2 and R ^z1 to R ^z4 has an acid anion structure.

The hydrocarbon groups in R ^x1 to R ^x4 , R ^y1 to R ^y2 and R ^z1 to R ^z4 may each be an aliphatic hydrocarbon group, an aromatic hydrocarbon group, a cyclic hydrocarbon group, or a chain It may be a hydrocarbon group having a shape.
For example, the hydrocarbon group which may have a substituent in R ^x1 to R ^x4 , R ^y1 to R ^y2 and R ^z1 to R ^z4 includes a cyclic group which may have a substituent and a substituent. A chain alkyl group which may have a chain, or a chain alkenyl group which may have a substituent may be mentioned.

The cyclic group which may have a substituent is preferably a cyclic hydrocarbon group, and the cyclic hydrocarbon group may be an aromatic hydrocarbon group or an aliphatic hydrocarbon group. may An aliphatic hydrocarbon group means a hydrocarbon group without aromaticity. Also, the aliphatic hydrocarbon group may be saturated or unsaturated, and is usually preferably saturated. In addition, the cyclic hydrocarbon groups in R ^x1 to R ^x4 , R ^y1 to R ^y2 and R ^z1 to R ^z4 may contain heteroatoms such as heterocycles.

The aromatic hydrocarbon groups in R ^x1 to R ^x4 , R ^y1 to R ^y2 and R ^z1 to R ^z4 are hydrocarbon groups having an aromatic ring. The aromatic hydrocarbon group preferably has 3 to 30 carbon atoms, more preferably 5 to 30 carbon atoms, still more preferably 5 to 20 carbon atoms, and particularly preferably 6 to 15 carbon atoms, 6 to 12 carbon atoms are most preferred. However, the number of carbon atoms does not include the number of carbon atoms in the substituent.

Specific examples of aromatic rings possessed by aromatic hydrocarbon groups in R ^x1 to R ^x4 , R ^y1 to R ^y2 and R ^z1 to R ^z4 include benzene, fluorene, naphthalene, anthracene, phenanthrene, biphenyl, or aromatic rings thereof. and aromatic heterocycles in which some of the carbon atoms constituting are substituted with hetero atoms.

Specific examples of aromatic hydrocarbon groups for R ^x1 to R ^x4 , R ^y1 to R ^y2 and R ^z1 to R ^z4 include groups obtained by removing one hydrogen atom from the above aromatic rings.

The cyclic aliphatic hydrocarbon group for R ^x1 to R ^x4 , R ^y1 to R ^y2 and R ^z1 to R ^z4 includes an aliphatic hydrocarbon group containing a ring in its structure. The aliphatic hydrocarbon group containing a ring in this structure includes an alicyclic hydrocarbon group (a group obtained by removing one hydrogen atom from an aliphatic hydrocarbon ring), and an alicyclic hydrocarbon group that is linear or branched. Examples thereof include a group bonded to the end of a chain aliphatic hydrocarbon group and a group in which an alicyclic hydrocarbon group intervenes in the middle of a linear or branched aliphatic hydrocarbon group.

The alicyclic hydrocarbon group preferably has 3 to 20 carbon atoms, more preferably 3 to 12 carbon atoms.

The alicyclic hydrocarbon group may be a polycyclic group or a monocyclic group.

Among them, the cyclic aliphatic hydrocarbon group for R ^x1 to R ^x4 , R ^y1 to R ^y2 and R ^z1 to R ^z4 is preferably a group obtained by removing one or more hydrogen atoms from monocycloalkane or polycycloalkane. .

The linear aliphatic hydrocarbon group, which may be bonded to the alicyclic hydrocarbon group, preferably has 1 to 10 carbon atoms, more preferably 1 to 6 carbon atoms, and 1 to 4 carbon atoms. is more preferred, and those with 1 to 3 carbon atoms are most preferred.

The branched aliphatic hydrocarbon group, which may be bonded to the alicyclic hydrocarbon group, preferably has 2 to 10 carbon atoms, more preferably 3 to 6 carbon atoms, and 3 or 4 carbon atoms. is more preferred, and one having 3 carbon atoms is most preferred.

Examples of substituents in the cyclic groups R ^x1 to R ^x4 , R ^y1 to R ^y2 and R ^z1 to R ^z4 include alkyl groups, alkoxy groups, halogen atoms, halogenated alkyl groups, hydroxyl groups, nitro groups and carbonyl groups. etc.

The chain alkyl groups of R ^x1 to R ^x4 , R ^y1 to R ^y2 and R ^z1 to R ^z4 may be linear or branched.

The linear alkyl group preferably has 1 to 20 carbon atoms, more preferably 1 to 15 carbon atoms, and most preferably 1 to 10 carbon atoms.

The branched-chain alkyl group preferably has 3 to 20 carbon atoms, more preferably 3 to 15 carbon atoms, and most preferably 3 to 10 carbon atoms.

The chain alkenyl groups represented by R ^x1 to R ^x4 , R ^y1 to R ^y2 and R ^z1 to R ^z4 may be linear or branched and preferably have 2 to 10 carbon atoms, It preferably has 2 to 5 carbon atoms, more preferably 2 to 4 carbon atoms, and particularly preferably 3 carbon atoms.

Examples of substituents on the chain alkyl or alkenyl groups of R ^x1 to R ^x4 , R ^y1 to R ^y2 and R ^z1 to R ^z4 include alkoxy groups, halogen atoms (fluorine atom, chlorine atom, bromine atom, iodine atom, atoms, etc.), halogenated alkyl groups, hydroxyl groups, carbonyl groups, nitro groups, amino groups, and cyclic groups for the above R ^x1 to R ^x4 , R ^y1 to R ^y2 and R ^z1 to R ^z4 .

The hydrocarbon groups for R ^x1 to R ^x4 , R ^y1 to R ^y2 and R ^z1 to R ^z4 are, among the above hydrocarbon groups, optionally substituted cyclic groups and substituted A chain alkyl group which may be substituted is preferred.

In formula (bd1), R ^y1 to R ^y2 may be bonded to each other to form a ring structure. This ring structure may be an alicyclic hydrocarbon or an aromatic hydrocarbon. Also, this ring structure may be a polycyclic structure consisting of other ring structures.

The alicyclic hydrocarbon formed by R ^y1 to R ^y2 may be polycyclic or monocyclic. A monocycloalkane is preferred as the monocyclic alicyclic hydrocarbon. Polycycloalkanes are preferred as polycyclic alicyclic hydrocarbons.

The aromatic hydrocarbon ring formed by R ^y1 to R ^y2 is benzene, fluorene, naphthalene, anthracene, phenanthrene, biphenyl, or an aromatic heteroaromatic ring in which some of the carbon atoms constituting these aromatic rings are substituted with heteroatoms. rings and the like.

The ring structure (alicyclic hydrocarbon, aromatic hydrocarbon) formed by R ^y1 to R ^y2 may have a substituent. Examples of substituents here include those similar to the substituents for the aforementioned cyclic groups R ^x1 to R ^x4 , R ^y1 to R ^y2 and R ^z1 to R ^z4 .

The ring structure formed by R ^y1 to R ^y2 is more preferably an aromatic hydrocarbon which may have a substituent, from the viewpoints of short diffusion of acid generated by exposure and controllability of acid diffusion.

In formula (bd1), two or more of R ^z1 to R ^z4 may be mutually bonded to form a ring structure. For example, R ^z1 may form a ring structure with any of R ^z2 to R ^z4 . The ring structure may be an alicyclic hydrocarbon or an aromatic hydrocarbon.

The alicyclic hydrocarbon formed by two or more of R ^z1 to R ^z4 may be polycyclic or monocyclic. A monocycloalkane is preferred as the monocyclic alicyclic hydrocarbon. Polycycloalkanes are preferred as polycyclic alicyclic hydrocarbons.

The aromatic hydrocarbon ring formed by two or more of R ^z1 to R ^z4 is benzene, fluorene, naphthalene, anthracene, phenanthrene, biphenyl, or some of the carbon atoms constituting these aromatic rings are heteroatoms. A substituted aromatic heterocycle and the like can be mentioned.

The ring structure (alicyclic hydrocarbon, aromatic hydrocarbon) formed by R ^z1 to R ^z4 may have a substituent.

In formula (bd1), two or more of R ^x1 to R ^x4 may be mutually bonded to form a ring structure. For example, R ^x1 may form a ring structure with any of R ^x2 to R ^x4 . The ring structure may be an alicyclic hydrocarbon or an aromatic hydrocarbon.

The alicyclic hydrocarbon formed by two or more of R ^x1 to R ^x4 may be polycyclic or monocyclic. A monocycloalkane is preferred as the monocyclic alicyclic hydrocarbon. Polycycloalkanes are preferred as polycyclic alicyclic hydrocarbons.

The aromatic hydrocarbon ring formed by two of R ^x1 to R ^x4 is benzene, fluorene, naphthalene, anthracene, phenanthrene, biphenyl, or some of the carbon atoms constituting these aromatic rings are substituted with heteroatoms. and aromatic heterocycles.

The ring structure (alicyclic hydrocarbon, aromatic hydrocarbon) formed by R ^x1 to R ^x4 may have a substituent.

The ring structure formed by two or more of R ^x1 to R ^x4 is preferably an alicyclic hydrocarbon from the viewpoint of acid diffusion controllability.

In the formula (bd1), at least one of R ^x1 to R ^x4 , R ^y1 to R ^y2 and R ^z1 to R ^z4 has an acid anion structure, and the entire organic acid anion portion becomes an n-valent anion. n is an integer of 1 or more. The organic acid anion moiety represented by the above formula (bd1) is radiation-sensitive to generate an acid acting on the acid-dissociable group in the base resin in the composition by selecting the acid anion structure in the molecule. It functions as a strong acid generator or as an acid diffusion control agent that traps (controls diffusion of acid) the acid generated from the radiation-sensitive strong acid generator upon exposure.

The acid anion structures possessed by R ^x1 to R ^x4 , R ^y1 to R ^y2 and R ^z1 to R ^z4 include a sulfonate anion structure, a carboxylate anion structure, an imide anion structure, a methide anion structure, a carbanion structure, a borate anion structure, Examples include those having a halogen anion structure, a phosphate anion structure, an antimonate anion structure, an arsenate anion structure, and the like. Among these, those having a sulfonate anion structure and those having a carboxylate anion structure are preferred.

In the organic anion moiety represented by the above formula (bd1), each of R ^x1 to R ^x4 , R ^y1 to R ^y2 and R ^z1 to R ^z4 may be the above acid anion structure. When two or more of R ^x1 to R ^x4 are mutually bonded to form a ring structure, a carbon atom forming the ring structure or a hydrogen atom bonded to the carbon atom is substituted with the above acid anion structure. may The same applies to R ^y1 to R ^y2 and R ^z1 to R ^z4 .

Specific examples of the organic anion moiety represented by the above formula (bd1) include, but are not limited to, the following.

(Structure (2) of other organic acid anion moieties)
Examples of the structure of the other organic acid anion moiety include the structure (1) of the other organic acid anion moiety as well as the structure represented by the following formula (b1).

(In the above formula (b1),
R ^b1 is a C 17-50 monovalent hydrocarbon group having a steroid skeleton.
^Yb1 is a divalent linking group or a single bond containing a heteroatom.
V ^b1 is an alkylene group, a fluorinated alkylene group, or a single bond.
R ^fa and R ^fb are each independently a hydrogen atom, a fluorine atom or a fluorinated alkyl group having 1 to 5 carbon atoms.
Z ^b1 is an acid anion structure. )

In the formula ( ^b1 ), Rb1 represents a monovalent hydrocarbon group having 17 to 50 carbon atoms and having a steroid skeleton. The steroid skeleton may have a substituent.
As used herein, the term "steroid skeleton" refers to a ring structure represented by the following chemical formula (St), in which three six-membered rings and one five-membered ring are condensed.

In the above formula (St), the number adjacent to the carbon atom indicates the carbon number. In this specification, when referring to the positions of carbon atoms in the steroid skeleton, the carbon numbers shown in the above formula (St) are used.

The steroid skeleton of the monovalent hydrocarbon group in R ^b1 preferably has at least one hydroxyl group. That is, in the steroid skeleton of R ^b1 , at least one hydrogen atom in the ring structure represented by the formula (St) is preferably substituted with a hydroxyl group.

When the steroid skeleton has hydroxyl groups, the number of hydroxyl groups is not particularly limited, and examples include 1 to 10, 1 to 5, 1 to 3, and the like. The number of hydroxyl groups is preferably 1 to 3, more preferably 2 or 3, still more preferably 3.

The steroid skeleton of R ^b1 may contain a substituent other than a hydroxyl group. For example, an alkyl group, a carboxy group, an oxo group (=O), an alkoxy group, an alkylcarbonyloxy group, a formyloxy group (HC(=O)- O—), a lactone-containing cyclic group, or the like may be attached.

When the steroid skeleton in R ^b1 has an alkyl group as a substituent, the position of the alkyl group is not particularly limited, and examples thereof include the 10th, 13th and 17th positions. The alkyl groups are preferably present at the 10- and 13-positions.

When the steroid skeleton in R ^b1 has a substituent other than an alkyl group and a hydroxyl group, the position of the substituent is not particularly limited, and examples thereof include any of the 3-, 7- and 12-positions. For example, one or two of the 3-, 7- and 12-positions may have the substituent. Also, when the substituent is a lactone-containing cyclic group, it may be at the 17-position.

R ^b1 has 17 to 50 carbon atoms, preferably 17 to 40 carbon atoms, more preferably 17 to 30 carbon atoms, and particularly preferably 17 to 22 carbon atoms.
The number of carbon atoms in ^Rb1 here includes the carbon atoms constituting the steroid skeleton and the carbon atoms in the substituents bonded to the steroid skeleton.

R ^b1 is preferably a group represented by the following formulas (R ^b1 -1) to (R ^b1 -3). When enantiomers and diastereomers exist, the following formula represents those stereoisomers and includes them.

[In formula (R ^b1 -1), R ^S11 , R ^S12 and R ^S13 each independently represent a hydrogen atom, a hydroxyl group, or a heteroatom-containing substituent other than a hydroxyl group. In formula (R ^b1 -2), R ^s21 and R ^s22 are each independently a hydrogen atom, a hydroxyl group, or a heteroatom-containing substituent other than a hydroxyl group. R ^S23 represents an alkyl group which may contain a heteroatom. In formula (R ^b1 -3), R ^S31 , R ^S32 and R ^S33 each independently represent a hydrogen atom, a hydroxyl group, or a heteroatom-containing substituent other than a hydroxyl group. R ^S34 represents a lactone-containing cyclic group. * represents a bond that binds to Y ^b1 in formula (b1). ]

In the above formula (R ^b1 -1), substituents other than a hydroxyl group containing a hetero atom in R ^S11 to R ^S13 include a carboxy group, an oxo group (=O), an alkoxy group, an alkylcarbonyloxy group, and a formyloxy group. (HC(=O)-O-) and the like. In the above formula (R ^b1 -2), the same applies to substituents other than a hydroxyl group containing a heteroatom in R ^S21 and R ^S22 . The same applies to substituents other than a hydroxyl group containing a heteroatom in R ^S31 to R ^S33 in the formula (R ^b1 -3).

In formula (R ^b1 -1), at least one of R ^S11 to R ^S13 is preferably a hydroxyl group, and two or more of R ^S11 to R ^S13 are preferably hydroxyl ^groups ^. are all hydroxyl groups. Among R ^S11 to R ^S13 , those that are not hydroxyl groups are preferably hydrogen atoms.

In formula (R ^b1 -2), at least one of R ^s21 and R ^s22 is preferably a hydroxyl group, and both R ^s21 and R ^s22 are preferably hydroxyl groups. Of R ²¹ and R ²² , those that are not hydroxyl groups are preferably hydrogen atoms.
In formula (R ^b1 -2), R ^S23 represents an alkyl group which may contain a heteroatom. The alkyl group may be linear or branched. As the alkyl group, an alkyl group having 1 to 10 carbon atoms is preferable.

In the formula (R ^b1 -3), at least one of R ^S31 to R ^S13 is preferably a hydroxyl group, two or more of R ^S31 to R ^S33 are preferably hydroxyl groups, and R ^S3 to R More preferably, all of ^S33 are hydroxyl groups. Among R ^S31 to R ^S33 , those that are not hydroxyl groups are preferably hydrogen atoms.

Among them, R ^b1 is more preferably a group represented by formula (R ^b1 -1).

Specific examples of R ^b1 are shown below, but are not limited thereto. In the formula below, * indicates a bond that bonds to Y ^b1 in formula (b1).

Among the above, R ^b1 is preferably represented by formulas (Rb-1-1) to (Rb-1-19), and more preferably represented by formulas (Rb-1-1) to (Rb-1-7).

In formula (b1), R ^fa and R ^fb are each independently a hydrogen atom, a fluorine atom or a fluorinated alkyl group having 1 to 5 carbon atoms.

In formula (b1), ^Yb1 represents a heteroatom-containing divalent linking group or a single bond.
Examples of the heteroatom-containing divalent linking group for ^Yb1 include the same as those exemplified for the heteroatom-containing divalent linking group for Y1 in the above formula ( ¹ ).

^Yb1 is preferably a divalent linking group containing an ester bond or an ether bond.

In formula ( ^b1 ), Vb1 represents an alkylene group, a fluorinated alkylene group, or a single bond.
The alkylene group or fluorinated alkylene group for V ^b1 may be linear or branched, but is preferably linear. The alkylene group or fluorinated alkylene group for V ^b1 preferably has 1 to 4 carbon atoms, more preferably 1 to 3 carbon atoms.

As the acid anion structure represented by Z ^b1 , the acid anion structures of R ^x1 to R ^x4 , R ^y1 to R ^y2 and R ^z1 to R ^z4 in the above formula (bd1) can be preferably employed.

Specific examples of the organic acid anion moiety represented by formula (b1) are listed below, but are not limited to these specific examples. In the formula, k and k' each independently represent an integer of 0 to 5, and k'' represents an integer of 1 to 5. Although all of the examples shown below are organic acid anion moieties having a sulfonate anion, a structure in which the sulfonate anion is replaced with a carboxylate anion can also be preferably employed. When the organic acid anion moiety has a carboxylate anion, fluorine atoms may not be bonded to the carbon atoms at the α- and β-positions of the carboxylate anion.

The organic acid anion moiety represented by the above formula (b1) is preferably represented by the following formula (b1-an1). Although the organic acid anion moiety having a sulfonate anion is shown below, a structure in which the sulfonate anion is replaced with a carboxylate anion can also be preferably employed. When the organic acid anion moiety has a carboxylate anion, fluorine atoms may not be bonded to the carbon atoms at the α- and β-positions of the carboxylate anion.

[In the formula, R ^S11 to R ^S13 are the same as in the general formula (R ^b1 -1). V ^b11 represents a single bond, —CHF— or —CF ₂ —. k represents an integer of 1 to 5; ]

In formula (b1-an1), R ^S11 to R ^S13 are the same as in general formula (R ^b1 -1).

<Solvent>
The radiation-sensitive resin composition according to this embodiment contains a solvent. The solvent is not particularly limited as long as it can dissolve or disperse at least the onium salt, the base resin (at least one of the radiation-sensitive acid-generating resin and the resin), and optional additives.

Examples of solvents include alcohol-based solvents, ether-based solvents, ketone-based solvents, amide-based solvents, ester-based solvents, and hydrocarbon-based solvents.

Examples of alcohol solvents include
Carbon such as iso-propanol, 4-methyl-2-pentanol, 3-methoxybutanol, n-hexanol, 2-ethylhexanol, furfuryl alcohol, cyclohexanol, 3,3,5-trimethylcyclohexanol, diacetone alcohol Monoalcoholic solvents of numbers 1 to 18;
C2-C18 poly(ethylene glycol, 1,2-propylene glycol, 2-methyl-2,4-pentanediol, 2,5-hexanediol, diethylene glycol, dipropylene glycol, triethylene glycol, tripropylene glycol, etc.) a alcohol-based solvent;
A polyhydric alcohol partial ether solvent obtained by etherifying a part of the hydroxy groups of the above polyhydric alcohol solvent may be used.

Examples of ether solvents include
Dialkyl ether solvents such as diethyl ether, dipropyl ether, dibutyl ether;
Cyclic ether solvents such as tetrahydrofuran and tetrahydropyran;
Aromatic ring-containing ether solvents such as diphenyl ether and anisole (methylphenyl ether);
Examples thereof include polyhydric alcohol ether solvents obtained by etherifying the hydroxy groups of the above polyhydric alcohol solvents.

Examples of ketone solvents include linear ketone solvents such as acetone, butanone, and methyl-iso-butyl ketone:
Cyclic ketone solvents such as cyclopentanone, cyclohexanone, and methylcyclohexanone:
2,4-pentanedione, acetonylacetone, acetophenone and the like.

Examples of amide solvents include cyclic amide solvents such as N,N'-dimethylimidazolidinone and N-methylpyrrolidone;
Chain amide solvents such as N-methylformamide, N,N-dimethylformamide, N,N-diethylformamide, acetamide, N-methylacetamide, N,N-dimethylacetamide, N-methylpropionamide, and the like.

Examples of ester solvents include
monocarboxylic acid ester solvents such as n-butyl acetate and ethyl lactate;
Polyhydric alcohol partial ether acetate solvents such as diethylene glycol mono-n-butyl ether acetate, propylene glycol monomethyl ether acetate, dipropylene glycol monomethyl ether acetate;
Lactone solvents such as γ-butyrolactone and valerolactone;
Carbonate solvents such as diethyl carbonate, ethylene carbonate, propylene carbonate;
Polyvalent carboxylic acid diester solvents such as propylene glycol diacetate, methoxytriglycol acetate, diethyl oxalate, ethyl acetoacetate, ethyl lactate and diethyl phthalate can be used.

Examples of hydrocarbon solvents include aliphatic hydrocarbon solvents such as n-hexane, cyclohexane, and methylcyclohexane;
Aromatic hydrocarbon solvents such as benzene, toluene, di-iso-propylbenzene, n-amylnaphthalene, and the like are included.

Among these, alcohol-based solvents, ester-based solvents, and ketone-based solvents are preferable, and monoalcohol-based solvents, polyhydric alcohol partial ether acetate-based solvents, polyvalent carboxylic acid diester-based solvents, cyclic ketone-based solvents, and lactone-based solvents are preferred. More preferred are diacetone alcohol, propylene glycol monomethyl ether acetate, ethyl lactate, cyclohexanone, and γ-butyrolactone. The radiation-sensitive resin composition may contain one or more solvents.

<Other optional ingredients>
The radiation-sensitive resin composition may contain other optional components in addition to the components described above. Examples of the other optional components include a cross-linking agent, an uneven distribution promoter, a surfactant, an alicyclic skeleton-containing compound, a sensitizer, and the like. These other optional components may be used alone or in combination of two or more.

<Method for preparing radiation-sensitive resin composition>
The radiation-sensitive resin composition comprises, for example, an onium salt, a base resin (at least one of a radiation-sensitive acid-generating resin and a resin), a solvent, and, if necessary, other optional components in a predetermined ratio. It can be prepared by mixing. After mixing, the radiation-sensitive resin composition is preferably filtered through, for example, a filter having a pore size of about 0.05 μm to 0.2 μm. The solid content concentration of the radiation-sensitive resin composition is usually 0.1% by mass to 50% by mass, preferably 0.5% by mass to 30% by mass, more preferably 1% by mass to 20% by mass.

<<Pattern formation method>>
The pattern formation method in this embodiment includes:
Step (1) of directly or indirectly coating the radiation-sensitive resin composition on a substrate to form a resist film (hereinafter also referred to as “resist film forming step”);
Step (2) of exposing the resist film (hereinafter also referred to as “exposure step”), and
A step (3) of developing the exposed resist film (hereinafter also referred to as a “development step”) is included.

According to the pattern forming method, a high-quality resist pattern can be formed because the radiation-sensitive resin composition is excellent in sensitivity and CDU performance in the exposure process and excellent in suppressing development residue in the development process. can be done. Each step will be described below.

[Resist film forming step]
In this step (step (1) above), a resist film is formed from the radiation-sensitive resin composition. Examples of the substrate on which the resist film is formed include conventionally known substrates such as silicon wafers, silicon dioxide, and aluminum-coated wafers. Further, for example, an organic or inorganic antireflection film disclosed in JP-B-6-12452, JP-A-59-93448, etc. may be formed on the substrate. Examples of coating methods include spin coating, casting coating, and roll coating. After coating, if necessary, prebaking (PB) may be performed in order to volatilize the solvent in the coating film. The PB temperature is usually 60°C to 140°C, preferably 80°C to 120°C. The PB time is usually 5 to 600 seconds, preferably 10 to 300 seconds. The thickness of the resist film to be formed is preferably 10 nm to 1,000 nm, more preferably 10 nm to 500 nm.

When immersion exposure is performed, regardless of the presence or absence of the water-repellent polymer additive such as the high fluorine content resin in the radiation-sensitive resin composition, the immersion liquid and the resist film are placed on the formed resist film. In order to avoid direct contact with the immersion liquid, an immersion protective film that is insoluble in the immersion liquid may be provided. As the liquid immersion protective film, a solvent peelable protective film that is peeled off with a solvent before the development process (see, for example, JP-A-2006-227632), a developer peelable protective film that is peeled off at the same time as development in the development process ( For example, see WO2005-069076 and WO2006-035790) may be used. However, from the viewpoint of throughput, it is preferable to use a developer-peeling protective film for liquid immersion.

Further, when the exposure step, which is the next step, is performed with radiation having a wavelength of 50 nm or less, a resin having the structural units (I) to (IV) and, if necessary, the structural unit (V) as the base resin in the composition is preferably used.

[Exposure process]
In this step (step (2) above), the resist film formed in the resist film forming step (step (1) above) is coated through a photomask (in some cases, through an immersion medium such as water). , emit radiation and expose. Radiation used for exposure depends on the line width of the desired pattern. A charged particle beam and the like can be mentioned. Among these, far ultraviolet rays, electron beams, and EUV are preferred, and ArF excimer laser light (wavelength 193 nm), KrF excimer laser light (wavelength 248 nm), electron beams, and EUV are more preferred. The following electron beams and EUV are more preferable.

When exposure is performed by immersion exposure, examples of the immersion liquid used include water and fluorine-based inert liquids.

After the exposure, a post-exposure bake (PEB) is performed to accelerate the dissociation of the acid-dissociable groups of the resin or the like by the acid generated from the radiation-sensitive acid generator upon exposure in the exposed portions of the resist film. is preferred. This PEB causes a difference in solubility in a developer between the exposed area and the unexposed area. The PEB temperature is usually 50°C to 180°C, preferably 80°C to 130°C. The PEB time is usually 5 to 600 seconds, preferably 10 to 300 seconds.

[Development process]
In this step (step (3) above), the resist film exposed in the exposure step (step (2) above) is developed. Thereby, a predetermined resist pattern can be formed. After development, it is common to wash with a rinsing liquid such as water or alcohol and dry.

As the developer used for the above development, in the case of alkali development, for example, 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 , 1,5-diazabicyclo-[4.3.0]-5-nonene, and the like. Among these, a TMAH aqueous solution is preferable, and a 2.38% by mass TMAH aqueous solution is more preferable.

In addition, in the case of organic solvent development, organic solvents such as hydrocarbon solvents, ether solvents, ester solvents, ketone solvents, alcohol solvents, or solvents containing organic solvents can be used. Examples of the organic solvent include one or more of the solvents listed above as the solvent for the radiation-sensitive resin composition. Among these, ester solvents and ketone solvents are preferred. As the ester solvent, an acetate solvent is preferable, and n-butyl acetate and amyl acetate are more preferable. As the ketone-based solvent, a chain ketone is preferable, and 2-heptanone is more preferable. The content of the organic solvent in the developer is preferably 80% by mass or more, more preferably 90% by mass or more, still more preferably 95% by mass or more, and particularly preferably 99% by mass or more. Examples of components other than the organic solvent in the developer include water and silicon oil.

Examples of the developing method include a method of immersing the substrate in a tank filled with a developer for a certain period of time (dip method), and a method of developing by standing still for a certain period of time while the developer is heaped up on the surface of the substrate by surface tension (puddle method). method), a method in which the developer is sprayed onto the surface of the substrate (spray method), and a method in which the developer is continuously applied while scanning the developer dispensing nozzle at a constant speed on the substrate rotating at a constant speed (dynamic dispensing method). ) etc. can be mentioned.

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. Methods for measuring various physical properties are shown below.

[Mw and Mn]
Mw and Mn of the polymer are determined by gel permeation chromatography (GPC) using Tosoh GPC columns (2 "G2000HXL", 1 "G3000HXL", 1 "G4000HXL") under the following conditions: It was measured.
Eluent: Tetrahydrofuran (manufactured by Wako Pure Chemical Industries, Ltd.)
Flow rate: 1.0 mL/min Sample concentration: 1.0% by mass
Sample injection volume: 100 μL
Column temperature: 40°C
Detector: Differential refractometer Standard substance: Monodisperse polystyrene

The structures of the sulfonium salt or iodonium salt radiation-sensitive acid generators PAG1 to PAG13 used in the radiation-sensitive resin compositions of the examples are shown below.

[Synthesis example] Synthesis of base polymers (P-1) to (P-9) Each monomer was combined and subjected to a copolymerization reaction in a tetrahydrofuran (THF) solvent, crystallized in methanol, and further washed with hexane repeatedly. After isolation and drying, base polymers (P-1) to (P-9) having the following compositions were obtained. The composition of the resulting base polymer was confirmed by ¹ H-NMR, and the Mw and dispersity (Mw/Mn) were confirmed by the above GPC (solvent: THF, standard: polystyrene).
P-1: Mw=7,700, Mw/Mn=1.7
P-2: Mw=8.000, Mw/Mn=1.7
P-3: Mw=8,200, Mw/Mn=1.7
P-4: Mw=7,600, Mw/Mn=1.7
P-5: Mw=7,500, Mw/Mn=1.7
P-6: Mw=7,900, Mw/Mn=1.7
P-7: Mw=7,600, Mw/Mn=1.7
P-8: Mw=8,000, Mw/Mn=1.8
P-9: Mw=7,100, Mw/Mn=1.6

[Examples, Comparative Examples]
A radiation-sensitive resin composition was prepared by filtering a solution obtained by dissolving each component with the composition shown in Table 1 in a solvent in which 100 ppm of FC-4430 manufactured by 3M was dissolved as a surfactant and filtered through a 0.2 μm size filter. was prepared.

In Table 1, each component is as follows.
Organic solvent: PGMEA (propylene glycol monomethyl ether acetate)
GBL (γ-butyrolactone)
CHN (cyclohexanone)
PGME (propylene glycol monomethyl ether)
DAA (diacetone alcohol)
EL (ethyl lactate)

Acid diffusion control agents (Q-1) to (Q-5)

High fluorine content resin F-1: Mw = 8,900, Mw/Mn = 2.0

[Evaluation of sensitivity by EUV exposure]
On a 12-inch silicon wafer, using a spin coater ("CLEAN TRACK ACT 12" from Tokyo Electron Ltd.), after coating a composition for forming a lower anti-reflection film ("ARC66" from Bulwer Science) , and 205° C. for 60 seconds to form a lower antireflection film having an average thickness of 105 nm. Each of the radiation-sensitive resin compositions shown in Table 1 was applied onto the lower antireflection film using the above spin coater, followed by PB at 130° C. for 60 seconds. Then, by cooling at 23° C. for 30 seconds, a resist film with an average thickness of 55 nm was formed. This resist film was scanned with an EUV scanner ("NXE3300" by ASML (NA 0.33, σ 0.9/0.6, quadruple pole illumination, pitch 46 nm on wafer, +20% bias hole pattern mask)). was exposed using PEB was performed on a hot plate at 120° C. for 60 seconds, and development was performed with a 2.38 mass % tetramethylammonium hydroxide (TMAH) aqueous solution for 30 seconds to form a resist pattern with 23 nm holes and a 46 nm pitch. The exposure dose for forming the resist pattern of 23 nm holes with a pitch of 46 nm was defined as the optimum exposure dose (Eop), and the optimum exposure dose was defined as the sensitivity (mJ/cm ² ).

[Evaluation of CDU]
A resist pattern with a 23 nm hole and a 46 nm pitch was formed in the same manner as above by irradiating with the exposure amount of Eop obtained above. The formed resist pattern was observed from above the pattern using a scanning electron microscope ("CG-5000" manufactured by Hitachi High-Technologies Corporation). The hole diameter was measured at 16 points in the range of 500 nm and the average value was obtained. Also, the average value was measured at a total of 500 arbitrary points. A 3 sigma value was obtained from the distribution of the measured values, and the obtained 3 sigma value was used as an evaluation value (nm) of the CDU performance. The smaller the evaluation value of the CDU performance, the smaller the dispersion of the hole diameter in the long period and the better. Table 1 shows the results.

[Evaluation of Development Residue]
A wafer having a resist film formed thereon was prepared by performing the same operations as above up to the operation of forming a resist film having an average thickness of 55 nm. Next, PEB was performed for 60 seconds on a hot plate at 120° C. without performing pattern exposure using an EUV scanner. Then, it was developed with a 2.38% by mass TMAH aqueous solution for 30 seconds, rinsed with pure water for 30 seconds, and dried. Thus, a wafer for evaluation of development residue was produced. This wafer was observed with a defect inspection apparatus COMPLUS (manufactured by AMAT), and the presence or absence of residual defects was confirmed using a defect review SEM RS5500 (manufactured by Hitachi High-Technologies Corporation) to count the number of residual defects. Evaluation was made using the following indices according to the number of residual defects counted.
A: 5 or less B: 6-10
C: 11-20
D: 21-50
E: 51 or more

As a result of evaluating the resist pattern formed through the above EUV exposure, the radiation-sensitive resin composition of the example was excellent in sensitivity, CDU performance and development residue.

According to the radiation-sensitive resin composition and resist pattern forming method described above, a resist pattern having good sensitivity to exposure light and excellent CDU performance and development residue suppressing property can be formed. Therefore, these materials can be suitably used in processing processes of semiconductor devices, which are expected to further miniaturize in the future.

Claims

a resin containing a structural unit represented by the following formula (1);
one or more onium salts containing an organic acid anion portion and an onium cation portion;
containing a solvent and
A radiation-sensitive resin composition comprising an aromatic ring structure in which at least a portion of the onium cation moiety in the onium salt has a fluorine atom.

(In the above formula (1),
R is a hydrogen atom, an alkyl group having 1 to 5 carbon atoms or a halogenated alkyl group having 1 to 5 carbon atoms, Y 1 is a divalent linking group, and X 1 is an acid dissociable group. )
The onium salt is a radiation-sensitive acid generator containing the organic acid anion portion and the onium cation portion, and the radiation-sensitive acid generator containing the organic acid anion portion and the onium cation portion, and is irradiated with radiation to generate the radiation-sensitive acid generator. is at least one selected from the group consisting of an acid diffusion control agent that generates an acid having a higher pKa than the acid generated from
2. The radiation-sensitive resin composition according to claim 1, wherein at least one of the onium cation moiety in the radiation-sensitive acid generator and the onium cation moiety in the acid diffusion controller contains the aromatic ring structure having the fluorine atom.
3. The radiation-sensitive resin composition according to claim 1, wherein the organic acid anion portion includes a structure represented by the following formula (bd1) or (b1).

(In the above formula (bd1),
R x1 to R x4 each independently represent a hydrogen atom, a substituted or unsubstituted hydrocarbon group, or a ring structure formed by combining two or more of these.
R y1 to R y2 each independently represent a hydrogen atom, a substituted or unsubstituted hydrocarbon group, or a ring structure formed by combining with each other.

is a double bond or a single bond.
R z1 to R z4 each independently represent a hydrogen atom, a substituted or unsubstituted hydrocarbon group, or a ring structure formed by combining two or more of these. However, at least one of R x1 to R x4 , R y1 to R y2 and R z1 to R z4 has an acid anion structure.
In the above formula (b1),
R b1 is a C 17-50 monovalent hydrocarbon group having a steroid skeleton.
Yb1 is a divalent linking group or a single bond containing a heteroatom.
V b1 is an alkylene group, a fluorinated alkylene group, or a single bond.
R fa and R fb are each independently a hydrogen atom, a fluorine atom or a fluorinated alkyl group having 1 to 5 carbon atoms.
Z b1 is an acid anion structure. )
4. The radiation-sensitive resin composition according to any one of claims 1 to 3, wherein X 1 in formula (1) is represented by formula (s1) or (s2) below.

(In the above formula (s1),
Cy is an aliphatic cyclic group formed with a carbon atom.
Ra 01 to Ra 03 each independently represents a hydrogen atom, a substituted or unsubstituted monovalent chain saturated hydrocarbon group having 1 to 10 carbon atoms, or a substituted or unsubstituted monovalent is an aliphatic cyclic saturated hydrocarbon group, or represents an aliphatic cyclic structure formed by combining two or more of these with each other, provided that the aliphatic cyclic structure forms a crosslinked structure no.
In the above formula (s2),
Cy is synonymous with the above formula (s1).
Ra 04 is a substituted or unsubstituted aromatic hydrocarbon group.
In the above formula, both * indicate a bond with an oxygen atom. )
The radiation-sensitive resin composition according to any one of claims 1 to 4, wherein the resin further contains a structural unit having a phenolic hydroxyl group.
The radiation-sensitive resin composition according to any one of claims 1 to 5, wherein the resin further contains a structural unit containing at least one selected from the group consisting of a lactone structure, a cyclic carbonate structure and a sultone structure.
The radiation-sensitive resin composition according to any one of claims 1 to 6, further comprising a high-fluorine content resin having a higher mass content of fluorine atoms than the resin.
A step of directly or indirectly applying the radiation-sensitive resin composition according to any one of claims 1 to 7 onto a substrate to form a resist film;
exposing the resist film;
and developing the exposed resist film with a developer.
The pattern forming method according to claim 8, wherein the exposure is performed using extreme ultraviolet rays or electron beams.