WO2024057751A1

WO2024057751A1 - Radioactive-ray-sensitive resin composition and pattern formation method

Info

Publication number: WO2024057751A1
Application number: PCT/JP2023/028119
Authority: WO
Inventors: 克聡錦織; 和也桐山; 拓弘谷口; 奈津子木下
Original assignee: Jsr株式会社
Priority date: 2022-09-13
Filing date: 2023-08-01
Publication date: 2024-03-21
Also published as: TW202411204A

Abstract

Provided are: a radioactive-ray-sensitive resin composition that can exhibit sufficient levels of sensitivity and CDU performance when a next-generation technology is applied to the composition; and a pattern formation method. The radioactive-ray-sensitive resin composition comprises an onium salt compound containing a structure represented by formula (1), a resin containing a structure unit (I) having a phenolic hydroxyl group or a group capable of providing a phenolic hydroxyl group by the action of an acid, and a solvent. (In formula (1), Rf1 and Rf2 each independently represent a hydrogen atom, a monovalent hydrocarbon group having 1 to 20 carbon atoms, a fluorine atom, or a monovalent fluorinated hydrocarbon group having 1 to 20 carbon atoms; R1, R2 and R3 each independently represent a hydrogen atom, or a monovalent organic group having 1 to 20 carbon atoms; n1 and n2 each independently represent an integer of 0 to 4; X1 and X2 each independently represent an oxygen atom or a sulfur atom: L represents a substituted or unsubstituted bivalent hydrocarbon group having 1 to 10 carbon atoms; R4 and R5 each independently represent a hydrogen atom or a monovalent organic group having 1 to 40 carbon atoms; at least one of R4 and R5 represents a monovalent aromatic-ring-containing organic group containing a 5- to 40-membered aromatic ring; and Z+ represents a monovalent radioactive-ray-sensitive onium cation.)

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 using resist compositions is used to form fine circuits in semiconductor devices. As a typical procedure, for example, an acid is generated by exposing a film of a resist composition to radiation through a mask pattern, and a reaction using the acid as a catalyst causes the resin to become alkaline or non-alkaline in the exposed and unexposed areas. A resist pattern is formed on a substrate by creating a difference in solubility in an organic solvent developer.

The above photolithography technology promotes pattern refinement by using short wavelength radiation such as ArF excimer laser or by combining this radiation with liquid immersion exposure method (liquid immersion lithography). As next-generation technology, efforts are being made to utilize even shorter wavelength radiation such as electron beams, X-rays, and EUV (extreme ultraviolet), and resist materials containing styrene-based resins that have increased absorption efficiency of such radiation are also being considered. It's coming. (Patent Document 1).

JP 2019-52294 Publication

The above-mentioned next-generation technology also requires resist performance equivalent to or higher than conventional resists in terms of sensitivity and critical dimension uniformity (CDU) performance, which indicates the variation in hole pattern size.

An object of the present invention is to provide a radiation-sensitive resin composition and a method for forming a resist pattern that can exhibit sensitivity and CDU performance at a sufficient level when next-generation technology is applied.

As a result of intensive studies to solve this problem, the present inventors discovered that the above object could be achieved by adopting the following configuration, and completed the present invention.

That is, in one embodiment, the present invention provides
An onium salt compound having a structure represented by the following formula (1):
a resin including a structural unit (I) having a phenolic hydroxyl group or a group that provides a phenolic hydroxyl group under the action of an acid;
The present invention relates to a radiation-sensitive resin composition comprising:

(In the above formula (1),
R ^f1 and R ^f2 each independently represent a hydrogen atom, a monovalent hydrocarbon group having 1 to 20 carbon atoms, a fluorine atom, or a monovalent fluorinated hydrocarbon group having 1 to 20 carbon atoms.
R ¹ , R ² and R ³ each independently represent a hydrogen atom or a monovalent organic group having 1 to 20 carbon atoms.
Each of _n1 and _n2 is independently an integer of 0 to 4. When _n1 and _n2 are integers of 2 or more, a plurality of R ^f1 , R ^f2 , R ¹ and R ² are the same or different from each other.
^X1 and ^X2 each independently represent an oxygen atom or a sulfur atom.
L is a substituted or unsubstituted divalent hydrocarbon group having 1 to 10 carbon atoms.
^R4 and ^R5 are each independently a hydrogen atom or a monovalent organic group having 1 to 40 carbon atoms, provided that at least one of ^R4 and ^R5 is a monovalent aromatic ring-containing organic group containing an aromatic ring having 5 to 40 ring members.
Z ⁺ is a monovalent radiation-sensitive onium cation.

Since the radiation-sensitive resin composition contains the above-mentioned onium salt compound, it can exhibit sensitivity and CDU performance at a sufficient level. Although the reason for this is not certain, it is inferred as follows. By introducing a cyclic acetal-like structure and an ester bond into the skeleton of the onium salt compound, as well as introducing an aromatic ring at the end, hydrophilicity and hydrophobicity are appropriately balanced, and the radiation-sensitive resin composition is Solubility, affinity with resin, etc. can be improved. As a result, it is presumed that the homogeneous presence of the onium salt compound increases and that excellent sensitivity and CDU performance can be exhibited.

Note that the "number of ring members" refers to the number of atoms that make up the ring. For example, the norbornene ring has 7 ring members, the biphenyl ring has 12 ring members, the naphthalene ring has 10 ring members, the fluorene ring has 13 ring members, and the furan ring has 5 ring members. be. "Fused ring structure" refers to a structure in which adjacent rings share one edge (two adjacent atoms).

In other embodiments, the present invention provides:
a step of directly or indirectly applying the radiation-sensitive resin composition on a substrate to form a resist film;
a step of exposing the resist film;
The present invention relates to a pattern forming method including the step of developing the exposed resist film with a developer.

Since the resist pattern forming method uses the radiation-sensitive resin composition described above that has excellent sensitivity and CDU performance, a high-quality resist pattern can be efficiently formed by lithography that applies next-generation exposure technology. .

Hereinafter, embodiments of the present invention will be described in detail, but the present invention is not limited to these embodiments. Combinations of preferred aspects are also preferred.

《Radiation-sensitive resin composition》
The radiation-sensitive resin composition (hereinafter also simply referred to as "composition") according to the present embodiment includes an onium salt compound, a resin, and a solvent. The above composition may contain other optional components as long as they do not impair the effects of the present invention.

<Onium salt compound>
The onium salt compound is used as a radiation-sensitive acid generator and includes a structure represented by the above formula (1). The composition may contain one or more onium salt compounds.

Examples of the monovalent hydrocarbon group having 1 to 20 carbon atoms represented by R ^f1 and R ^f2 include a monovalent chain hydrocarbon group having 1 to 20 carbon atoms, and a monovalent hydrocarbon group having 3 to 20 carbon atoms. Examples include alicyclic hydrocarbon groups and monovalent aromatic hydrocarbon groups having 6 to 20 carbon atoms.

The monovalent chain hydrocarbon group having 1 to 20 carbon atoms is a straight chain or branched saturated hydrocarbon group having 1 to 20 carbon atoms, or a straight chain or branched unsaturated hydrocarbon group having 1 to 20 carbon atoms. Examples include groups.

The alicyclic hydrocarbon group having 3 to 20 carbon atoms includes a monocyclic or polycyclic saturated hydrocarbon group, or a monocyclic or polycyclic unsaturated hydrocarbon group. As the monocyclic saturated hydrocarbon group, a cyclopentyl group, a cyclohexyl group, a cycloheptyl group, and a cyclooctyl group are preferable. The polycyclic cycloalkyl group is preferably a bridged alicyclic hydrocarbon group such as a norbornyl group, an adamantyl group, a tricyclodecyl group, or a tetracyclododecyl group. Note that a bridged alicyclic hydrocarbon group is a polycyclic alicyclic group in which two carbon atoms that are not adjacent to each other among the carbon atoms constituting the alicyclic ring are bonded by a linking group containing one or more carbon atoms. A cyclic hydrocarbon group.

The monovalent aromatic hydrocarbon group having 6 to 20 carbon atoms is, for example,
Aryl groups such as phenyl, tolyl, xylyl, naphthyl and anthryl; aralkyl groups such as benzyl, phenethyl and naphthylmethyl; and the like.

Examples of the monovalent fluorinated hydrocarbon group having 1 to 20 carbon atoms represented by R ^f1 and R ^f2 include a monovalent fluorinated chain hydrocarbon group having 1 to 20 carbon atoms, and a monovalent fluorinated hydrocarbon group having 3 to 20 carbon atoms. Examples include monovalent fluorinated alicyclic hydrocarbon groups.

Examples of the monovalent fluorinated chain hydrocarbon group having 1 to 20 carbon atoms include trifluoromethyl group, 2,2,2-trifluoroethyl group, pentafluoroethyl group, 2,2,3,3, 3-pentafluoropropyl group, 1,1,1,3,3,3-hexafluoropropyl group, heptafluoro n-propyl group, heptafluoro i-propyl group, nonafluoro n-butyl group, nonafluoro i-butyl group, Nonafluoro t-butyl group, 2,2,3,3,4,4,5,5-octafluoro n-pentyl group, tridecafluoro n-hexyl group, 5,5,5-trifluoro-1,1- Fluorinated alkyl groups such as diethylpentyl groups;
Fluorinated alkenyl groups such as trifluoroethenyl group and pentafluoropropenyl group;
Examples include fluorinated alkynyl groups such as fluoroethynyl group and trifluoropropynyl group.

Examples of the monovalent fluorinated alicyclic hydrocarbon group having 3 to 20 carbon atoms include fluorocyclopentyl group, difluorocyclopentyl group, nonafluorocyclopentyl group, fluorocyclohexyl group, difluorocyclohexyl group, undecafluorocyclohexylmethyl group, Fluorinated cycloalkyl groups such as fluoronorbornyl group, fluoroadamantyl group, fluorobornyl group, fluoroisobornyl group, fluorotricyclodecyl group, fluorotetracyclodecyl group;
Examples include fluorinated cycloalkenyl groups such as a fluorocyclopentenyl group and a nonafluorocyclohexenyl group.

The fluorinated hydrocarbon group is preferably the monovalent fluorinated chain hydrocarbon group having 1 to 20 carbon atoms, more preferably the monovalent fluorinated chain hydrocarbon group having 1 to 10 carbon atoms. As the monovalent fluorinated chain hydrocarbon group having 1 to 10 carbon atoms, groups having 1 to 10 carbon atoms among the above monovalent fluorinated chain hydrocarbon groups having 1 to 20 carbon atoms are preferably used. Can be adopted.

The monovalent organic group having 1 to 20 carbon atoms represented by R ¹ , R ² and R ³ is not particularly limited, and may have a chain structure, a cyclic structure, or a combination thereof. Examples of the chain structure include chain hydrocarbon groups, which may be saturated or unsaturated, linear or branched. Examples of the above-mentioned cyclic structure include cyclic hydrocarbon groups, regardless of whether they are alicyclic, aromatic, or heterocyclic. Two or more ring structures may form a fused ring structure, a bridged ring structure, or a spiro ring structure. Among these, monovalent organic groups include substituted or unsubstituted monovalent chain hydrocarbon groups having 1 to 20 carbon atoms, substituted or unsubstituted monovalent alicyclic hydrocarbon groups having 3 to 20 carbon atoms; , a substituted or unsubstituted monovalent aromatic hydrocarbon group having 6 to 20 carbon atoms, or a combination thereof. In addition, groups having a chain structure or groups having a cyclic structure in which some or all of the hydrogen atoms contained in the group are substituted with a substituent, CO, CS, O , S, SO ₂ or NR', or a group containing a combination of two or more of these. R' is a hydrogen atom or a monovalent hydrocarbon group having 1 to 10 carbon atoms.

Examples of substituents that replace part or all of the hydrogen atoms of the above organic group include halogen atoms such as fluorine, chlorine, bromine, and iodine; hydroxy group; carboxy group; cyano group; nitro group; alkyl group, an alkoxy group, an alkoxycarbonyl group, an alkoxycarbonyloxy group, an acyl group, an acyloxy group, or a group in which the hydrogen atom of these groups is substituted with a halogen atom; oxo group (=O), and the like.

The above monovalent chain hydrocarbon group having 1 to 20 carbon atoms, the above monovalent alicyclic hydrocarbon group having 3 to 20 carbon atoms, and the above monovalent aromatic hydrocarbon group having 6 to 20 carbon atoms are , a monovalent chain hydrocarbon group having 1 to 20 carbon atoms as exemplified by R ^f1 and R ^f2 in the above formula (1), a monovalent alicyclic hydrocarbon group having 3 to 20 carbon atoms, and a monovalent alicyclic hydrocarbon group having 6 to 20 carbon atoms. Twenty monovalent aromatic hydrocarbon groups are listed, respectively. Among these, the alicyclic hydrocarbon group is preferably a monovalent monocyclic alicyclic group having 3 to 10 carbon atoms or a monovalent polycyclic alicyclic group having 6 to 14 carbon atoms.

Examples of the above-mentioned heterocyclic cyclic hydrocarbon group include a group obtained by removing one hydrogen atom from an aromatic heterocyclic structure and a group obtained by removing one hydrogen atom from an aliphatic heterocyclic structure. A 5-membered aromatic structure that has aromaticity by introducing a heteroatom is also included in the heterocyclic structure. Examples of the heteroatom include an oxygen atom, a nitrogen atom, a sulfur atom, and the like.

Examples of the aromatic heterocyclic structure include oxygen atom-containing aromatic heterocyclic structures such as furan, pyran, benzofuran, and benzopyran;
Nitrogen-containing aromatic heterocyclic structures such as pyrrole, imidazole, pyridine, pyrimidine, pyrazine, indole, quinoline, isoquinoline, acridine, phenazine, and carbazole;
Sulfur atom-containing aromatic heterocyclic structures such as thiophene;
Examples include aromatic heterocyclic structures containing multiple heteroatoms such as thiazole, benzothiazole, thiazine, and oxazine.

Examples of the aliphatic heterocyclic structures include oxygen atom-containing aliphatic heterocyclic structures such as oxirane, tetrahydrofuran, tetrahydropyran, dioxolane, and dioxane;
Nitrogen-containing aliphatic heterocyclic structures such as aziridine, pyrrolidine, piperidine, piperazine;
Sulfur atom-containing aliphatic heterocyclic structures such as thietane, thiolane, and thiane;
Examples include aliphatic heterocyclic structures containing multiple heteroatoms such as morpholine, 1,2-oxathiolane, and 1,3-oxathiolane.

Examples of the cyclic structure include structures including a lactone structure, a cyclic carbonate structure, a sultone structure, and a cyclic acetal. Examples of such structures include structures represented by the following formulas (H-1) to (H-10).

In the above formula, m is an integer from 1 to 3.

Preferably, R ¹ and R ² are hydrogen atoms. Preferably, R ³ is also a hydrogen atom.

Each of n ₁ and n ₂ is preferably an integer of 0 to 3, more preferably an integer of 0 to 2, and even more preferably 0 or 1. It is particularly preferred that n ₁ is 0 and n ₂ is 1.

It is preferable that both X ¹ and X ² are oxygen atoms.

The divalent hydrocarbon group having 1 to 10 carbon atoms represented by L corresponds to the monovalent hydrocarbon group having 1 to 10 carbon atoms among the monovalent hydrocarbon groups having 1 to 20 carbon atoms exemplified as R ^f1 and R ^f2 . A group obtained by removing one hydrogen atom from the group can be suitably employed. Among these, L is preferably a divalent chain hydrocarbon group having 1 to 5 carbon atoms, more preferably a methanediyl group or an ethanediyl group, and even more preferably a methanediyl group.

When L has a substituent, a substituent that can be carried by a monovalent organic group having 1 to 20 carbon atoms in R ¹ , R ² and R ³ can be suitably employed.

The monovalent organic groups having 1 to 40 carbon atoms represented by R ⁴ and R ⁵ include the monovalent organic groups having 1 to 20 carbon atoms exemplified as R ¹ , R ² and R ³ . Groups extended up to 40 can be suitably employed.

As the monovalent aromatic ring-containing organic group containing an aromatic ring having 5 to 40 ring members represented by R ⁴ and R ⁵ , the monovalent organic group having 1 to 40 carbon atoms is an aromatic ring having 5 to 40 ring members. There are no particular limitations as long as the structure includes a ring. The number of aromatic rings in the aromatic ring-containing organic group is not particularly limited, and may be an integer of 1, 2, 3, or 4 or more. As the aromatic ring having 5 to 40 ring members, the structure corresponding to the monovalent aromatic hydrocarbon group having 6 to 20 carbon atoms and the aromatic heterocyclic structure in R ¹ , R ² and R ³ has 5 to 40 carbon atoms. A structure expanded to 40 can be suitably employed. Among these, the aromatic ring having 5 to 40 ring members is preferably an aromatic hydrocarbon having 6 to 20 carbon atoms, more preferably a benzene ring or a naphthalene ring, and even more preferably a benzene ring.

One of R ⁴ and R ⁵ is a hydrogen atom or a monovalent chain hydrocarbon group having 1 to 20 carbon atoms, and the other is a monovalent aromatic group containing an aromatic hydrocarbon having 6 to 20 carbon atoms. A ring-containing organic group is preferred. The monovalent linear hydrocarbon group having 1 to 20 carbon atoms is preferably a monovalent linear hydrocarbon group having 1 to 10 carbon atoms, more preferably a methyl group, an ethyl group, or a propyl group. , methyl group is more preferred.

It is preferable that some or all of the hydrogen atoms on the aromatic ring contained in the aromatic ring-containing organic group are substituted with a halogen atom or a halogenated hydrocarbon group. Among these, the halogen atom is preferably a fluorine atom or an iodine atom, more preferably an iodine atom. Further, the halogenated hydrocarbon group is preferably a fluorinated hydrocarbon group, more preferably a fluorinated aliphatic hydrocarbon group, and even more preferably a trifluoromethyl group. This increases the radiation absorption efficiency of the onium salt compound, making it possible to improve the sensitivity of the composition.

When R ⁴ and R ⁵ have a substituent other than a halogen atom and a halogenated hydrocarbon group, the substituent may be a monovalent organic group having 1 to 20 carbon atoms in R ¹ , R ² and R ³ Substituents can be suitably employed.

Specific examples of the anion moiety of the onium salt compound include, but are not limited to, structures of the following formulas (1-1-1) to (1-1-16).

In the above formula (1), examples of the monovalent radiation-sensitive onium cation represented by Z ⁺ include S, I, O, N, P, Cl, Br, F, As, Se, Sn, and Sb. , Te, Bi, and other radiolytic onium cations. Examples of radiolytic onium cations include sulfonium cations, tetrahydrothiophenium cations, iodonium cations, phosphonium cations, diazonium cations, and pyridinium cations. Among these, sulfonium cations or iodonium cations are preferred. The sulfonium cation or iodonium cation is preferably represented by the following formulas (X-1) to (X-6).

In the above formula (X-1), R ^a1 , R ^a2 and R ^a3 are each independently a substituted or unsubstituted linear or branched alkyl group having 1 to 12 carbon atoms, an alkoxy group or an alkoxycarbonyl group. Oxy group, substituted or unsubstituted monocyclic or polycyclic cycloalkyl group having 3 to 12 carbon atoms, substituted or unsubstituted aromatic hydrocarbon group having 6 to 12 carbon atoms, hydroxy group, halogen atom, -OSO ₂ -R ^P , -SO ₂ -R ^Q or ^-SRT , or a ring structure formed by combining two or more of these groups with each other. The ring structure may contain a heteroatom such as O or S between the carbon-carbon bonds forming the skeleton. R ^P , R ^Q and R ^T are each independently a substituted or unsubstituted linear or branched alkyl group having 1 to 12 carbon atoms, or a substituted or unsubstituted alicyclic group having 5 to 25 carbon atoms; It is a hydrocarbon group or a substituted or unsubstituted aromatic hydrocarbon group having 6 to 12 carbon atoms. k1, k2 and k3 are each independently an integer of 0 to 5. When R ^a1 to R ^a3 and R ^P , R ^Q and R ^T are plural, each of the plural R ^a1 to R ^a3 and R ^P , R ^Q and R ^T may be the same or different.

In the above formula (X-2), R ^b1 is a substituted or unsubstituted linear or branched alkyl group or alkoxy group having 1 to 20 carbon atoms, or a substituted or unsubstituted acyl group having 2 to 8 carbon atoms. , or a substituted or unsubstituted aromatic hydrocarbon group having 6 to 8 carbon atoms, a halogen atom, or a hydroxy group. _nk is 0 or 1. When n _k is 0, k4 is an integer from 0 to 4; when n _k is 1, k4 is an integer from 0 to 7. When there is a plurality of R ^b1s , the plurality of R ^b1s may be the same or different, and the plurality of R ^b1s may represent a ring structure formed by being combined with each other. R ^b2 is a substituted or unsubstituted linear or branched alkyl group having 1 to 7 carbon atoms, or a substituted or unsubstituted aromatic hydrocarbon group having 6 or 7 carbon atoms. L ^C is a single bond or a divalent linking group. k5 is an integer from 0 to 4. When there is a plurality of R ^b2s , the plurality of R ^b2s may be the same or different, and the plurality of R ^b2s may represent a ring structure formed by being combined with each other. q is an integer from 0 to 3. In the formula, the ring structure containing S ⁺ may contain a heteroatom such as O or S between the carbon-carbon bonds forming the skeleton.

In the above formula (X-3), R ^c1 , R ^c2 and R ^c3 are each independently a substituted or unsubstituted linear or branched alkyl group having 1 to 12 carbon atoms.

In the above formula (X-4), R ^g1 is a substituted or unsubstituted linear or branched alkyl group or alkoxy group having 1 to 20 carbon atoms, or a substituted or unsubstituted acyl group having 2 to 8 carbon atoms. , a substituted or unsubstituted aromatic hydrocarbon group having 6 to 8 carbon atoms, a halogen atom, or a hydroxy group. n _k2 is 0 or 1. When n _k2 is 0, k10 is an integer from 0 to 4, and when n _k2 is 1, k10 is an integer from 0 to 7. When there is a plurality of R ^g1s , the plurality of R ^g1s may be the same or different, and the plurality of R ^g1s may represent a ring structure formed by being combined with each other. R ^g2 and R ^g3 are each independently a substituted or unsubstituted linear or branched alkyl group having 1 to 12 carbon atoms, an alkoxy group or an alkoxycarbonyloxy group, or a substituted or unsubstituted linear or branched alkyl group having 3 carbon atoms; ~12 monocyclic or polycyclic cycloalkyl groups, substituted or unsubstituted aromatic hydrocarbon groups having 6 to 12 carbon atoms, hydroxy groups, halogen atoms, or these groups are combined with each other. Represents a ring structure. k11 and k12 are each independently an integer of 0 to 4. When there is a plurality of R ^g2 and R ^g3 , each of the plural R ^g2 and R ^g3 may be the same or different.

In the above formula (X-5), R ^d1 and R ^d2 each independently represent a substituted or unsubstituted linear or branched alkyl group having 1 to 12 carbon atoms, an alkoxy group, or an alkoxycarbonyl group, a substituted or an unsubstituted aromatic hydrocarbon group having 6 to 12 carbon atoms, a halogen atom, a halogenated alkyl group having 1 to 4 carbon atoms, a nitro group, or two or more of these groups are combined with each other. Represents a ring structure composed of k6 and k7 are each independently an integer of 0 to 5. When there are a plurality of R ^d1 and R ^d2 , each of the plurality of R ^d1 and R ^d2 may be the same or different.

In the above formula (X-6), R ^e1 and R ^e2 are each independently a halogen atom, a substituted or unsubstituted linear or branched alkyl group having 1 to 12 carbon atoms, or a substituted or unsubstituted is an aromatic hydrocarbon group having 6 to 12 carbon atoms. k8 and k9 are each independently an integer of 0 to 4.

Specific examples of radiation-sensitive onium cations include, but are not limited to, structures of the following formula.

Examples of onium salt compounds include structures in which the above anion moiety and the above radiation-sensitive onium cation are arbitrarily combined. Specific examples of onium salt compounds include, but are not limited to, onium salt compounds represented by the following formulas (1-1) to (1-20) (hereinafter, the following formulas (1-1) to (1-20)). The onium salt compounds represented by are also referred to as "onium salt compounds (1-1) to (1-20)").

The lower limit of the content of the onium salt compound (in the case of a combination of multiple types, the total thereof) is preferably 5 parts by mass, more preferably 10 parts by mass, and even more preferably 20 parts by mass, based on 100 parts by mass of the resin described below. Particularly preferred is 30 parts by mass. The upper limit of the content is preferably 70 parts by mass, more preferably 60 parts by mass or less, even more preferably 55 parts by mass or less, and particularly preferably 50 parts by mass. The content of the onium salt compound is appropriately selected depending on the type of resin used, exposure conditions, required sensitivity, and the like. This makes it possible to exhibit excellent sensitivity and CDU performance during resist pattern formation.

(Method of synthesizing onium salt compounds)
The onium salt compound can be synthesized according to the following scheme. For the sake of simplicity, the above formula (1) is exemplified by the case where _n1 is 0, _n2 is 1, ^R1 and ^R2 are both hydrogen atoms, L is a methanediyl group, and ^X1 and ^X2 are both oxygen atoms. As shown in the scheme below, the target compound (1a) can be synthesized by condensing a ketone and a diol onium salt under an acid catalyst to form a cyclic acetal. Other structures can also be synthesized by appropriately changing the structure of the starting material.

(In the scheme, R ³ , R ⁴ , R ⁵ and Z ⁺ have the same meanings as in formula (1) above.)

<Resin>
The resin is an aggregate of polymers containing a structural unit (I) having a phenolic hydroxyl group or a group that provides a phenolic hydroxyl group by the action of an acid (hereinafter, this resin is also referred to as a "base resin"). In addition to the structural unit (I), the base resin may include a structural unit (II) having an acid-dissociable group, a structural unit (III) having a lactone structure, and the like. Each structural unit will be explained below.

(Structural unit (I))
Structural unit (I) is a structural unit having a phenolic hydroxyl group or a structural unit that provides a phenolic hydroxyl group by the action of an acid. When the resin contains the structural unit (I), the sensitivity etc. of the radiation-sensitive resin composition can be further improved. 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 or EUV. The structural unit (I) 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 a plurality of R ^101s exist, the plurality of R ^101s are the same or different from each other.
R ¹⁰² is a cyano group, a nitro group, an alkyl group, a fluorinated alkyl group, an alkoxycarbonyloxy group, an acyl group, or an acyloxy group. When a plurality of R ^102s exist, the plurality of R ^102s are the same or different from each other.
n ₃ is an integer from 0 to 2, m ₃ is an integer from 1 to 8, and m ₄ is an integer from 0 to 8. However, 1≦m ₃ +m ₄ ≦2n ₃ +5 is satisfied. )

The above R ^α is preferably a hydrogen atom or a methyl group from the viewpoint of copolymerizability of the monomer providing the structural unit (I).

As L ^CA , a single bond or -COO- ^* is preferable.

Examples of the protecting group deprotected by the action of an acid represented by R ¹⁰¹ include groups represented by the following formulas (AL-1) to (AL-3).

In the above formulas (AL-1) and (AL-2), R ^M1 and R ^M2 are monovalent hydrocarbon groups containing heteroatoms such as oxygen atom, sulfur atom, nitrogen atom, and fluorine atom. Good too. The monovalent hydrocarbon group may be linear, branched, or cyclic, preferably an alkyl group having 1 to 40 carbon atoms, and more preferably an alkyl group having 1 to 20 carbon atoms. In formula (AL-1), a is an integer of 0 to 10, preferably an integer of 1 to 5. In the above formulas (AL-1) to (AL-3), * is a bond with an oxygen atom.

In the above formula (AL-2), R ^M3 and R ^M4 each independently represent a hydrogen atom or a monovalent hydrocarbon group, and include a hetero atom such as an oxygen atom, a sulfur atom, a nitrogen atom, or a fluorine atom. It's okay to stay. The monovalent hydrocarbon group may be linear, branched, or cyclic, and is preferably an alkyl group having 1 to 20 carbon atoms. Further, any two of R ^M2 , R ^M3 and R ^M4 may be bonded to each other to form a ring having 3 to 20 carbon atoms together with the carbon atom to which they are bonded or the carbon atom and oxygen atom. As the above-mentioned ring, a ring having 4 to 16 carbon atoms is preferable, and an alicyclic ring is particularly preferable.

In the above formula (AL-3), R ^M5 , R ^M6 and R ^M7 each independently represent a monovalent hydrocarbon group, and contain a hetero atom such as an oxygen atom, a sulfur atom, a nitrogen atom, or a fluorine atom. You can stay there. The monovalent hydrocarbon group may be linear, branched, or cyclic, and is preferably an alkyl group having 1 to 20 carbon atoms. Further, any two of R ^M5 , R ^M6 and R ^M7 may be bonded to each other to form a ring having 3 to 20 carbon atoms together with the carbon atoms to which they are bonded. As the above-mentioned ring, a ring having 4 to 16 carbon atoms is preferable, and an alicyclic ring is particularly preferable.

Among these, the group represented by the above formula (AL-3) is preferable as the protecting group that is deprotected by the action of an acid.

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

The above _n3 is more preferably 0 or 1, and even more preferably 0.

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.

The above structural unit (I) is a structural unit represented by the following formulas (2-1) to (2-11) (hereinafter also referred to as "structural unit (1-1) to structural unit (1-11)"). ) etc. is preferable.

In the above formulas (2-1) to (2-11), R ^α is the same as in the above formula (2).

The lower limit of the content ratio of the structural unit (I) (total if there are multiple types of structural units (I)) is preferably 10 mol%, more preferably 20 mol%, based on the total structural units constituting the resin. Preferably, 30 mol% is more preferable, and 35 mol% is particularly preferable. The upper limit of the content ratio is preferably 90 mol%, more preferably 80 mol%, even more preferably 70 mol%, and particularly preferably 65 mol%. By setting the content of the structural unit (I) within the above range, the radiation-sensitive resin composition can further improve sensitivity and CDU performance.

When polymerizing a monomer having a phenolic hydroxyl group such as hydroxystyrene, the phenolic hydroxyl group is polymerized with a protective group such as an alkali-dissociable group, and then deprotected by hydrolysis. It is preferable to obtain structural unit (I). When a monomer having a phenolic hydroxyl group is polymerized, the phenolic hydroxyl group may be directly polymerized without being protected.

(Structural unit (II))
Structural unit (II) is a structural unit (excluding the structure corresponding to structural unit (I)) having an acid-dissociable group. As used herein, the term "acid-dissociable group" refers to a group that substitutes the hydrogen atom of an alkali-soluble group such as a carboxy group, phenolic hydroxyl group, sulfo group, or sulfonamide group, and is dissociated by the action of an acid. Refers to the base. Therefore, the acid-dissociable group is bonded to the oxygen atom that was bonded to the hydrogen atom in these functional groups.

The structural unit (II) is not particularly limited as long as it has an acid-dissociable group, and includes, for example, a structural unit having a tertiary alkyl ester moiety, and a structure in which the hydrogen atom of a phenolic hydroxyl group is substituted with a tertiary alkyl group. Examples include a structural unit having an acetal bond, a structural unit having an acetal bond, and the like. Among these, a structural unit represented by the following formula (3) (hereinafter also referred to as "structural unit (2-1)") is preferred from the viewpoint of improving the pattern forming properties of the radiation-sensitive resin composition.

In the above formula (3), R ⁷ is a hydrogen atom, a fluorine atom, a methyl group, or a trifluoromethyl group. R ⁸ is a hydrogen atom or 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 formed by combining these with each other and the carbon atoms to which they are bonded. L ¹ represents a single bond or a divalent linking group.

From the viewpoint of copolymerizability of the monomer providing the structural unit (2-1), R ⁷ is preferably a hydrogen atom or a methyl group, and more preferably a methyl group.

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. group, a monovalent aromatic hydrocarbon group having 6 to 20 carbon atoms, and the like.

The chain hydrocarbon groups having 1 to 10 carbon atoms represented by R ⁸ to R ¹⁰ above are monovalent chain hydrocarbon groups having 1 to 20 carbon atoms as shown in R ^f1 and R ^f2 of the above formula (1). Of the hydrogen groups, groups corresponding to carbon numbers to 10 can be suitably employed.

The alicyclic hydrocarbon group having 3 to 20 carbon atoms represented by R ⁸ to R ¹⁰ above is an alicyclic hydrocarbon group having 3 to 20 carbon atoms as shown in R ^f1 and R ^f2 of the above formula (1). groups can be suitably employed.

The monovalent aromatic hydrocarbon group having 6 to 20 carbon atoms represented by R ⁸ above is the monovalent aromatic hydrocarbon group having 6 to 20 carbon atoms shown in R ^f1 and R ^f2 of the above formula (1). groups can be suitably employed.

The above R ⁸ is a linear or branched saturated hydrocarbon group having 1 to 10 carbon atoms, an alicyclic hydrocarbon group having 3 to 20 carbon atoms, or a monovalent aromatic hydrocarbon group having 6 to 10 carbon atoms. preferable.

The divalent alicyclic group having 3 to 20 carbon atoms formed by combining R ⁹ and R ¹⁰ together with the carbon atom to which they are bonded is a monocyclic or polycyclic alicyclic hydrocarbon having the above number of carbon atoms. It is not particularly limited as long as it is a group obtained by removing two hydrogen atoms from the same carbon atoms constituting the carbon ring. Either a monocyclic hydrocarbon group or a polycyclic hydrocarbon group may be used, and the polycyclic hydrocarbon group may be a bridged alicyclic hydrocarbon group or a fused alicyclic hydrocarbon group, and a saturated hydrocarbon group may be used. Either a hydrogen group or an unsaturated hydrocarbon group may be used.

Among the monocyclic alicyclic hydrocarbon groups, the saturated hydrocarbon group is preferably a cyclopentanediyl group, cyclohexanediyl group, cycloheptanediyl group, cyclooctanediyl group, etc., and the unsaturated hydrocarbon group is preferably a cyclopentenediyl group. , cyclohexenediyl group, cycloheptendiyl group, cyclooctenediyl group, cyclodecenediyl group, etc. are preferable. The polycyclic alicyclic hydrocarbon group is preferably a bridged alicyclic saturated hydrocarbon group, such as a bicyclo[2.2.1]heptane-2,2-diyl group (norbornane-2,2-diyl group). ), bicyclo[2.2.2]octane-2,2-diyl group, tricyclo[3.3.1.1 ^3,7 ]decane-2,2-diyl group (adamantane-2,2-diyl group) etc. are preferred.

Examples of the divalent linking group represented by L ¹ above include alkanediyl group, cycloalkanediyl group, alkenediyl group, ^* -R ^LA O-, ^* -R ^LB COO-, etc. (* represents oxygen (Represents a bond with an atom.) However, in the case of groups other than ^* -R ^LB COO-, the carbon atom bonded to the oxygen atom of -COO- in the above formula (3) is a tertiary carbon and does not have a hydrogen atom.

Some or all of the hydrogen atoms on the carbon atoms in R ⁸ to R ¹⁰ and L ¹ are halogen atoms such as fluorine atoms and chlorine atoms, halogenated alkyl groups such as trifluoromethyl group, and alkoxy groups such as methoxy group. , a cyano group, etc. may be substituted.

The above alkanediyl group is preferably an alkanediyl group having 1 to 8 carbon atoms.

Examples of the above-mentioned cycloalkanediyl group include monocyclic cycloalkanediyl groups such as cyclopentanediyl group and cyclohexanediyl group; polycyclic cycloalkanediyl groups such as norbornanediyl group and adamantanediyl group. The above-mentioned cycloalkanediyl group is preferably a cycloalkanediyl group having 5 to 12 carbon atoms.

Examples of the alkenediyl group include ethenediyl group, propenediyl group, butenediyl group, and the like. The alkenediyl group mentioned above is preferably an alkenediyl group having 2 to 6 carbon atoms.

Examples of R ^LA in ^* -R ^LA O- include the above alkanediyl group, the above cycloalkanediyl group, the above alkenediyl group, and the like. Examples of R ^LB in the above ^* -R ^LB COO- include the above alkanediyl group, the above cycloalkanediyl group, the above alkenediyl group, and arenediyl group. Examples of the arenediyl group include a phenylene group, tolylene group, and naphthylene group. The arenediyl group is preferably an arenediyl group having 6 to 15 carbon atoms.

Among these, R ⁸ is an alkyl group having 1 to 4 carbon atoms or an aryl group having 6 to 10 carbon atoms, and R ⁹ and R ¹⁰ are combined with each other to form an alicyclic structure constituted by the carbon atoms to which they are bonded. is preferably a polycyclic or monocyclic cycloalkane structure. L ¹ is preferably a single bond or ^* -R ^LA O-. R ^LA is preferably an alkanediyl group.

As the structural unit (2-1), for example, structural units represented by the following formulas (3-1) to (3-6) (hereinafter, "structural units (2-1-1) to (2-1- (also referred to as ``6)'').

In the above formulas (3-1) to (3-6), R ⁷ to R ¹⁰ and R ^LA have the same meanings as in the above formula (3). R ^LM and R ^LN are each independently a monovalent hydrocarbon group having 1 to 10 carbon atoms. i and j are each independently an integer of 1 to 4. n _A is 0 or 1.

Examples of R ^LM and R ^LN include groups corresponding to 1 to 10 carbon atoms among the monovalent hydrocarbon groups having 1 to 20 carbon atoms represented by R ⁸ in the above formula (3). As R ^LM and R ^LN , a methyl group, an ethyl group, or an isopropyl group is preferable.

i and j are preferably 1, 2 or 4. R ⁸ to R ¹⁰ are preferably a methyl group, ethyl group, isopropyl group or phenyl group.

As the structural unit (2-1), among these, structural unit (2-1-1), structural unit (2-1-2), structural unit (2-1-4), and structural unit (2- 1-5) is preferred. The structural unit (2-1-1) preferably has a cyclopentane structure. In the structural unit (2-1-5), n _A is preferably 0.

The base resin may contain one type of structural unit (II) or a combination of two or more types.

Furthermore, the resin may contain structural units represented by the following formulas (1f) to (2f) as structural units (II) other than the above.

In the above formulas (1f) to (2f), R ^αf is each independently a hydrogen atom, a fluorine atom, a methyl group or a trifluoromethyl group. R ^βf is each independently a hydrogen atom or a chain alkyl group having 1 to 5 carbon atoms. h ₁ is an integer from 1 to 4.

The above R ^βf is preferably a hydrogen atom, a methyl group or an ethyl group. _h1 is preferably 1 or 2.

The lower limit of the content of the structural unit (II) (total if there are multiple types of structural units (II)) is preferably 10 mol%, and 20 mol% based on the total structural units constituting the base resin. It is more preferably 30 mol%, even more preferably 35 mol%. The upper limit of the content ratio is preferably 90 mol%, more preferably 80 mol%, even more preferably 70 mol%, and particularly preferably 65 mol%. By setting the content ratio of structural unit (II) within the above range, the pattern forming properties of the radiation-sensitive resin composition can be further improved.

(Structural unit (III))
The 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 including the structural unit (III), the base resin can adjust the solubility in the developer, and as a result, the radiation-sensitive resin composition can improve lithography performance such as resolution. can. Further, it is possible to improve the adhesion between the resist pattern formed from the base resin and the substrate.

Examples of the structural unit (III) include structural units represented by the following formulas (T-1) to (T-10).

In the above formula, R ^L1 is a hydrogen atom, a fluorine atom, a methyl group or a trifluoromethyl group. R ^L2 to R ^L5 are each independently 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 formed together with the carbon atoms to which they are bonded. L ² 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 from 1 to 3.

As a divalent alicyclic group having 3 to 8 carbon atoms formed by combining the above R ^L4 and R ^L5 together with the carbon atom to which they are bonded, R ⁹ and R ¹⁰ in the above formula (3) are Among the divalent alicyclic groups having 3 to 20 carbon atoms formed together with the carbon atoms to which they are bonded, examples include groups having 3 to 8 carbon atoms. One or more hydrogen atoms on this alicyclic group may be substituted with a hydroxy group.

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. Examples include 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-.

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

When the resin has the structural unit (III), the lower limit of the content is preferably 5 mol%, more preferably 10 mol%, and even more preferably 15 mol%, based on all the structural units constituting the base resin. 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 (III) within the above range, the radiation-sensitive resin composition can further improve lithography performance such as resolution and the adhesion of the formed resist pattern to the substrate.

(Other structural units)
The resin may have other structural units other than the above-mentioned structural units (I) to (III) as appropriate. Other structural units include, for example, structural units having a fluorine atom, alcoholic hydroxyl group, carboxy group, cyano group, nitro group, sulfonamide group, etc. (hereinafter also referred to as "structural unit (IV)". Structural unit (I ) to excluding the structure corresponding to structural unit (III)). Among these, structural units having a fluorine atom, structural units having an alcoholic hydroxyl group, and structural units having a carboxyl group are preferable, and structural units having a fluorine atom and structural units having an alcoholic hydroxyl group are more preferable. Furthermore, the resin may have a structural unit (VII) containing an onium salt structure as a radiation-sensitive acid generating structure or a structural unit (VIII) containing an onium salt structure as an acid diffusion control structure.

Examples of the structural unit (IV) include structural units represented by the following formula.

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

When the resin has a structural unit (IV), the lower limit of the content of the structural unit (IV) with respect to all structural units constituting the resin is preferably 5 mol%, more preferably 10 mol%, and even more preferably 15 mol%. preferable. 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 solubility of the resin in the developer can be made more appropriate.

(Structural unit (VII))
The structural unit (VII) has a first organic acid anion and a first onium cation, which form an onium salt structure (1). The onium salt structure (1) functions as a radiation-sensitive acid-generating structure and generates acid upon exposure. The acid generated by exposure has the function of dissociating acid-dissociable groups of the base resin to generate carboxyl groups and the like.

As used herein, "dissociation" of an acid-dissociable group refers to dissociation upon post-exposure baking at 110°C for 60 seconds.

The content form of the first organic acid anion and the first onium cation in the structural unit (VII) of the base resin is not particularly limited, and the base resin may have the above-mentioned first organic acid anion as a side chain portion. It may have a monoonium cation as a side chain moiety. Having it as a side chain portion means that the corresponding first organic acid anion or first onium cation is bonded (covalently bonded) to the main chain as a side chain structure of the base resin. From the viewpoint of controlling the acid diffusion length, it is preferable that the base resin has the above-mentioned first organic acid anion as a side chain portion.

The first organic acid anion preferably has at least one selected from the group consisting of sulfonic acid anions, carboxylic acid anions, and sulfonimide anions as the acid anion moiety. Examples of the acid generated by exposure include sulfonic acid, carboxylic acid, and sulfonimide, corresponding to the acid anion moiety described above.

Although the structure of the first organic acid anion other than the acid anion moiety is not particularly limited, it preferably has an iodo group in terms of sensitivity and CDU performance. Although the manner in which the iodo group is contained is not particularly limited, it is preferably contained in the form of an iodo group-containing aromatic ring structure. The iodo group-containing aromatic ring structure is a structure in which some or all of the hydrogen atoms of the aromatic ring are substituted with iodo groups.

The aromatic ring in the iodo group-containing aromatic ring structure is preferably a benzene ring.

Although the number of iodo groups in the above iodo group-containing aromatic ring structure is not particularly limited, it is preferably 1 to 4, more preferably 1, 2, or 3, and 2 or 3. It is even more preferable that there be.

The first organic acid anion preferably contains -O-, -CO-, a cyclic structure, or a combination thereof, in addition to or in place of the iodo group-containing aromatic ring structure. The combination also includes a structure (heterocyclic structure) in which -O- or -CO- is incorporated as a ring-forming part in a cyclic structure.

The cyclic structure may be monocyclic, polycyclic, or a combination thereof. Further, the cyclic structure may be an alicyclic structure, an aromatic ring structure, a heterocyclic structure, or a combination thereof. In the case of a combination, a structure in which ring structures are connected in a chain structure may be used.

As the cyclic structure, the cyclic structures shown in R ¹ , R ² and R ³ of the above formula (1) can be suitably employed.

As the chain structure, a structure corresponding to a monovalent chain hydrocarbon group having 1 to 20 carbon atoms as shown in R ^f1 and R ^f2 of the above formula (1) can be suitably employed.

In the radiation-sensitive acid generating structure, the acid anion portion is preferably a sulfonic acid anion, and a fluorine atom or a fluorinated hydrocarbon group is preferably bonded to the carbon atom adjacent to the sulfur atom of the sulfonic acid anion. Thereby, the radiation-sensitive acid generating structure can efficiently exhibit the above-mentioned functions.

The first onium cation is preferably a sulfonium cation or an iodonium cation, and more preferably a sulfonium cation.

The first onium cation in the structural unit (VII) is preferably a fluorine-containing onium cation containing a fluorine atom. The fluorine-containing onium cation preferably has a fluorine-substituted aromatic ring structure. Thereby, sensitivity can be improved by increasing radiation absorption efficiency.

The first onium cation may have an iodo group. The first onium cation may include the iodo group-containing aromatic ring structure as an iodo group-containing mode.

When the structural unit (VII) has a combination of the above structures, the above functions can be efficiently exhibited.

The structural unit (VII) is a structural unit represented by the following formula (a1) (hereinafter also referred to as "structural unit (VII-1)") or a structural unit represented by the following formula (a2) (hereinafter referred to as " (also referred to as "structural unit (VII-2)") is preferable.

In the formula, R ^V is a hydrogen atom or a methyl group. V ¹ is a single bond or an ester group. V ² is a linear, branched or cyclic alkylene group having 1 to 12 carbon atoms, a cycloalkylene group having 3 to 12 carbon atoms, an arylene group having 6 to 10 carbon atoms, or a combination thereof; A part of the methylene group constituting the group, the cycloalkylene group, or the arylene group may be substituted with an ether group, an ester group, or a lactone ring-containing group. ^V3 is a single bond, an ether group, an ester group, a linear or branched alkylene group having 1 to 12 carbon atoms, or a cyclic cycloalkylene group having 3 to 12 carbon atoms, and constitutes the alkylene group. A part of the methylene group may be substituted with an ether group or an ester group. Some or all of the hydrogen atoms of V ² and V ³ may be substituted with a hetero atom or a monovalent hydrocarbon group having 1 to 20 carbon atoms that may contain a hetero atom. Rf ¹ to Rf ⁴ are each independently a hydrogen atom, a fluorine atom, or a trifluoromethyl group, and at least one is a fluorine atom or a fluorinated hydrocarbon group. R ⁴³ to R ⁴⁷ are each independently a monovalent hydrocarbon group having 1 to 20 carbon atoms which may contain a hetero atom, and R ⁴³ and R ⁴⁴ are bonded to each other to form a sulfur bond. A ring may be formed together with the atoms. Preferably, at least one of R ⁴³ to R ⁴⁵ and at least one of R ⁴⁶ to R ⁴⁷ each contain a fluorine-substituted aromatic ring structure.

The monovalent hydrocarbon group having 1 to 20 carbon atoms in V ² and V ³ and R ⁴³ to R ⁴⁷ is an alkyl group having 1 to 12 carbon atoms, a cycloalkyl group having 3 to 12 carbon atoms, or a cycloalkyl group having 6 carbon atoms. ~20 aryl groups are preferable, and some or all of the hydrogen atoms of these groups may be substituted with a heteroatom-containing group, and some of the methylene groups constituting these groups are ether groups, ester groups, etc. , a carbonyl group, a carbonate group, or a sulfonic acid ester group.

Structural units (VII-1) to (VII-2) are preferably represented by the following formulas (a1-1) and (a2-1), respectively.

In the formula, R ^V , R ⁴³ to R ⁴⁷ , Rf ¹ to Rf ⁴ and V ¹ have the same meanings as in the above formula (a1) or (a2). R ⁴⁸ is a linear, branched or cyclic alkyl group having 1 to 4 carbon atoms, a halogen atom other than iodine, a hydroxy group, a linear, branched or cyclic alkoxy group having 1 to 4 carbon atoms, or It is a linear, branched or cyclic alkoxycarbonyl group having 2 to 5 carbon atoms. m is an integer from 0 to 4. n is an integer from 0 to 3.

Examples of the first organic acid anion of the monomer that provides the structural unit (VII) (including the structural unit (VII-1) and the structural unit (VII-2)) include those shown below. Not limited. Note that, among the first organic acid anions shown below that include an aromatic ring structure, all have an iodine-substituted aromatic ring structure, but the structural unit (VII) does not necessarily have an iodine-substituted aromatic ring structure. As the first organic acid anion that does not have an iodine-substituted aromatic ring structure, a structure in which the iodine atom in the following formula is substituted with a hydrogen atom or other substituent can be suitably employed. In the following formula, R ^V has the same meaning as above.

In the above formula, R ^V has the same meaning as in the above formula (a1).

As the first onium cation of the structural unit (VII-1), a monovalent radiation-sensitive onium cation represented by Z ⁺ in the above formula (1) can be suitably employed.

When the base resin contains a structural unit (VII), the lower limit of the content ratio of the structural unit (VII) (or the total content ratio if it contains multiple types) is based on the total structural units constituting the radiation-sensitive acid-generating resin. It is preferably 1 mol%, more preferably 3 mol%, and even more preferably 5 mol%. Moreover, the upper limit of the content ratio is preferably 20 mol%, more preferably 15 mol% or less, and even more preferably 10 mol% or less. By setting the content ratio of the structural unit (VII) within the above range, the function as an acid generating structure can be fully exhibited.

The monomer giving the structural unit (VII-1) to the structural unit (VII-2) can be synthesized, for example, in the same manner as the sulfonium salt having a polymerizable anion described in Japanese Patent No. 5201363. .

(Structural unit (VIII))
The structural unit (VIII) has a second organic acid anion and a second onium cation, and these form an onium salt structure (2). The onium salt structure (2) functions as an acid diffusion control structure, and does not substantially dissociate the acid-dissociable groups of the base resin under the pattern forming conditions using the radiation-sensitive resin composition, and does not dissociate the acid-dissociable groups in the unexposed areas. Examples include a function of suppressing diffusion of acid generated from the radiation-sensitive acid generating structure or the onium salt compound by salt exchange. The acid generated from the acid diffusion control structure can be said to be a relatively weaker acid (higher pKa) than the acid generated from the radiation-sensitive acid generating structure or the onium salt compound. Whether the onium salt structure functions as a radiation-sensitive acid generating structure or an acid diffusion control structure depends on the energy required to dissociate the acid dissociable group of the base resin and the acidity of the onium salt structure or generated acid. It is decided.

The content form of the second organic acid anion and the second onium cation in the structural unit (VIII) of the base resin is not particularly limited, and the base resin may have the second organic acid anion as a side chain portion, It may have a 2-onium cation as a side chain moiety. Having it as a side chain portion means that the corresponding second organic acid anion or second onium cation is bonded (covalently bonded) to the main chain as a side chain structure of the base resin. From the viewpoint of acid scavenging properties, the base resin preferably has the second organic acid anion as a side chain portion.

The second organic acid anion preferably has a carboxylic acid anion as the acid anion moiety. The acid generated by exposure is a carboxylic acid corresponding to the acid anion moiety.

The structural unit (VIII) is preferably a structural unit represented by the following formula (g-1) (hereinafter also referred to as "structural unit (VIII-1)").

In formula (g-1), R ^A is a hydrogen atom or a methyl group.

In formula (g-1), P ¹ is a single bond, ester bond, ether bond, phenylene group or naphthylene group.

In formula (g-1), P ² is a single bond, a saturated hydrocarbylene group having 1 to 12 carbon atoms, or a phenylene group, and the saturated hydrocarbylene group is an ether bond, an ester bond, an amide bond, a lactone bond, It may contain a ring or a sultone ring. The hydrocarbylene group represented by P ² may be linear, branched, or cyclic.

In formula (g-1), P ³ is a single bond, an ester bond or an ether bond.

In formula (g-1), ^R or a linear, branched or cyclic alkoxycarbonyl group having 2 to 5 carbon atoms.

In formula (g-1), R ⁴³ to R ⁴⁵ have the same meanings as in formula (a1) above.

In formula (g-1), x1 is an integer from 0 to 3. When x1 is 2 or more, a plurality of R ^Xs are the same or different.

Examples of the second organic acid anion of the monomer providing the structural unit (VIII) include, but are not limited to, those shown below. In addition, among the second organic acid anions shown below, all have a hydroxy group, but the structural unit (VIII) does not necessarily have a hydroxy group. As the second organic acid anion having no hydroxy group, a structure in which the hydroxy group in the following formula is substituted with a hydrogen atom or other substituent can be suitably employed. In the following formula, ^RA is the same as above.

As the second onium cation of the structural unit (VIII), a sulfonium cation among the monovalent radiation-sensitive onium cations represented by Z ⁺ in the above formula (1) can be suitably employed.

When the base resin contains a structural unit (VIII), the lower limit of the content ratio of the structural unit (VIII) (or the total content ratio if it contains multiple types) is 1 mol% with respect to all the structural units constituting the base resin. is preferable, 2 mol% is more preferable, and 3 mol% is even more preferable. Further, the upper limit of the content ratio is preferably 25 mol%, more preferably 20 mol%, and even more preferably 15 mol%. By setting the content ratio of the structural unit (VIII) within the above range, the function as an acid diffusion control structure can be fully exhibited.

The lower limit of the resin content is preferably 50% by mass, more preferably 55% by mass, and even more preferably 60% by mass based on the total solid content of the radiation-sensitive resin composition. The upper limit of the content is preferably 90% by mass, more preferably 80% by mass, and even more preferably 75% by mass. Here, the term "solid content" refers to all components contained in the radiation-sensitive resin composition, excluding the solvent.

(Resin synthesis method)
The resin serving as the base resin can be synthesized, for example, by carrying out a polymerization reaction of monomers providing each structural unit in a suitable solvent using a radical polymerization initiator or the like.

Regarding the molecular weight of the base resin, the lower limit of the polystyrene equivalent weight average molecular weight (Mw) determined by gel permeation chromatography (GPC) is preferably 2,000, preferably 3,000, more preferably 4,000, and 5 ,000 is more preferred. The upper limit of Mw is preferably 12,000, more preferably 10,000, even more preferably 8,000, and particularly preferably 7,000. If the Mw of the base resin is less than the above lower limit, the heat resistance of the resulting resist film may decrease. If the Mw of the base resin exceeds the above upper limit, the CDU performance of the resist film may deteriorate.

The ratio (Mw/Mn) of Mw to the polystyrene equivalent number average molecular weight (Mn) determined 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 Mw and Mn of the resin in this specification are values measured using gel permeation chromatography (GPC) under the following conditions.
GPC columns: 2 G2000HXL, 1 G3000HXL, 1 G4000HXL (all manufactured by Tosoh)
Column temperature: 40℃
Elution solvent: Tetrahydrofuran Flow rate: 1.0 mL/min Sample concentration: 1.0 mass%
Sample injection volume: 100μL
Detector: Differential refractometer Standard material: Monodisperse polystyrene

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

The high fluorine content resin may, for example, have the structural unit (I) and structural unit (II) in the above base resin as needed, and also have a structural unit represented by the following formula (6) (hereinafter referred to as "structural unit"). (V)") is preferable.

In the above formula (6), 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.

From the viewpoint of copolymerizability of the monomer providing the structural unit G, the above R ¹³ is preferably a hydrogen atom or a methyl group, and more preferably a methyl group.

From the viewpoint of copolymerizability of the monomer providing the structural unit G, the above G ^L is preferably a single bond or -COO-, and -COO- is more preferable.

As the monovalent fluorinated chain hydrocarbon group having 1 to 20 carbon atoms represented by R ¹⁴ above, some or all of the hydrogen atoms possessed by the linear or branched alkyl group having 1 to 20 carbon atoms are fluorine. Examples include those substituted by atoms.

The monovalent fluorinated alicyclic hydrocarbon group having 3 to 20 carbon atoms represented by R ¹⁴ above is a part of the hydrogen atom possessed by a monocyclic or polycyclic hydrocarbon group having 3 to 20 carbon atoms, or Examples include those in which all fluorine atoms are substituted.

The above R ¹⁴ is preferably a fluorinated chain hydrocarbon group, more preferably a fluorinated alkyl group, such as a 2,2,2-trifluoroethyl group or a 1,1,1,3,3,3-hexafluoropropyl group. and 5,5,5-trifluoro-1,1-diethylpentyl group are more preferred.

When the high fluorine content resin has a structural unit (V), the lower limit of the content of the structural unit (V) is preferably 10 mol%, and 15% by mole based on the total structural units constituting the high fluorine content resin. More preferably mol %, even more preferably 20 mol %, particularly preferably 25 mol %. The upper limit of the content ratio is preferably 60 mol%, more preferably 50 mol%, and even more preferably 40 mol%. By setting the content ratio of the structural unit (V) within the above range, it is possible to adjust the mass content of fluorine atoms in the high fluorine content resin more appropriately and further promote uneven distribution on the surface layer of the resist film. .

The high fluorine content resin may have a fluorine atom-containing structural unit (hereinafter also referred to as structural unit (VI)) represented by the following formula (f-1) in addition to the structural unit (V). . By having the structural unit (VI), the high fluorine content resin improves solubility in an alkaline developer and can suppress the occurrence of development defects.

Structural unit (VI) may have (x) an alkali-soluble group, or (y) a group that dissociates under the action of an alkali to increase its solubility in an alkaline developer (hereinafter also referred to simply as an "alkali-dissociable group"). ). Common to both (x) and (y), in the above formula (f-1), R ^C is a hydrogen atom, a fluorine atom, a methyl group or a trifluoromethyl group. R ^D is a single bond, a (s+1)-valent hydrocarbon group having 1 to 20 carbon atoms, and an oxygen atom, a sulfur atom, -NR ^dd -, a ^carbonyl group, -COO- or This is a structure in which -CONH- is bonded, or a structure in which some of the hydrogen atoms of this hydrocarbon group are replaced by an organic group having a heteroatom. R ^dd is a hydrogen atom or a monovalent hydrocarbon group having 1 to 10 carbon atoms. s is an integer from 1 to 3.

When the structural unit (VI) has (x) an alkali-soluble group, R ^F is a hydrogen atom, and A ¹ is an oxygen atom, -COO-* or -SO ₂ O-*. * indicates a site that binds to ^RF . W ¹ is a single bond, a hydrocarbon group having 1 to 20 carbon atoms, or a divalent fluorinated hydrocarbon group. When A ¹ is an oxygen atom, W ¹ is a fluorinated hydrocarbon group having a fluorine atom or a fluoroalkyl group on the carbon atom to which A ¹ is bonded. R ^E is a single bond or a divalent organic group having 1 to 20 carbon atoms. When s is 2 or 3, the plurality of R ^E , W ¹ , A ¹ and R ^F may be the same or different. When the structural unit (VI) has (x) an alkali-soluble group, the affinity for an alkaline developer can be increased and development defects can be suppressed. (x) As the structural unit (VI) having an alkali-soluble group, when A ¹ is an oxygen atom and W ¹ is a 1,1,1,3,3,3-hexafluoro-2,2-methanediyl group is particularly preferred.

When the structural unit (VI) has (y) an alkali-dissociable group, R ^F is a monovalent organic group having 1 to 30 carbon atoms, A ¹ is an oxygen atom, -NR ^aa -, -COO-* or -SO ₂ O-*. R ^aa is a hydrogen atom or a monovalent hydrocarbon group having 1 to 10 carbon atoms. * indicates a site that binds to ^RF . W ¹ is a single bond or a divalent fluorinated hydrocarbon group having 1 to 20 carbon atoms. R ^E is a single bond or a divalent organic group having 1 to 20 carbon atoms. When A ¹ is -COO-* or -SO ₂ O-*, W ¹ or R ^F has a fluorine atom on the carbon atom bonded to A ¹ or on the carbon atom adjacent thereto. When A ¹ is an oxygen atom, W ¹ and R ^E are single bonds, R ^D is a structure in which a carbonyl group is bonded to the R ^E side end of a hydrocarbon group having 1 to 20 carbon atoms, and R ^F is an organic group containing a fluorine atom. When s is 2 or 3, the plurality of R ^E , W ¹ , A ¹ and R ^F may be the same or different. Since the structural unit (VI) has (y) an alkali dissociable group, the surface of the resist film changes from hydrophobic to hydrophilic in the alkaline development step. As a result, the affinity for the developer can be significantly increased, and development defects can be suppressed more efficiently. (y) The structural unit H having an alkali-dissociable group is particularly preferably one in which A ¹ is -COO-* and R ^F or W ¹ or both have a fluorine atom.

As R ^C , a hydrogen atom and a methyl group are preferable, and a methyl group is more preferable, from the viewpoint of copolymerizability of the monomer providing the structural unit (VI).

When R ^E is a divalent organic group, a group having a lactone structure is preferable, a group having a polycyclic lactone structure is more preferable, and a group having a norbornane lactone structure is more preferable.

When the high fluorine content resin has a structural unit (VI), the lower limit of the content of the structural unit (VI) is preferably 30 mol%, and 40% by mole based on the total structural units constituting the high fluorine content resin. More preferably mol %, even more preferably 50 mol %, particularly preferably 55 mol %. The upper limit of the content ratio is preferably 90 mol%, more preferably 80 mol%, and even more preferably 70 mol%. By setting the content of the structural unit (VI) within the above range, the water repellency of the resist film during immersion exposure can be further improved.

The lower limit of Mw of the high fluorine content resin is preferably 2,000, more preferably 4,000, even more preferably 5,000, and particularly preferably 6,000. The upper limit of Mw is preferably 20,000, more preferably 15,000, even more preferably 10,000, and particularly preferably 8,000.

The lower limit of Mw/Mn of the high fluorine content resin is usually 1, more preferably 1.1. The upper limit of Mw/Mn is usually 5, preferably 3, more preferably 2, and even more preferably 1.7.

The lower limit of the content of the high fluorine content resin is preferably 0.1 part by mass, more preferably 0.5 part by mass, even more preferably 1 part by mass, and 1.5 parts by mass, based on 100 parts by mass of the base resin. Parts by weight are particularly preferred. The upper limit of the content is preferably 15 parts by mass, more preferably 10 parts by mass, even more preferably 8 parts by mass, and particularly preferably 5 parts by mass.

By setting the content of the high fluorine content resin within the above range, the high fluorine content resin can be more effectively unevenly distributed on the surface layer of the resist film, and as a result, the surface of the resist film during immersion exposure In addition to improving the water repellency of the resist film, it becomes possible to modify the surface of the resist film and control the composition distribution when immersion exposure is not used. The radiation-sensitive resin composition may contain one or more types of high fluorine content resin.

(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.

<Acid diffusion control agent>
The radiation-sensitive resin composition may contain an acid diffusion control agent, if necessary. The acid diffusion control agent has the effect of controlling the diffusion phenomenon of acid generated from the radiation-sensitive acid generator in the resist film upon exposure, and suppressing undesirable chemical reactions in non-exposed areas. Moreover, the storage stability of the resulting radiation-sensitive resin composition is improved. Furthermore, the resolution of the resist pattern is further improved, and changes in line width of the resist pattern due to fluctuations in standing time from exposure to development can be suppressed, resulting in a radiation-sensitive resin composition with excellent process stability. It will be done.

Examples of acid diffusion control agents include compounds having one nitrogen atom in the same molecule, compounds having two nitrogen atoms in the same molecule, compounds having three nitrogen atoms in the same molecule, amide group-containing compounds, and urea. compounds, nitrogen-containing heterocyclic compounds, and the like.

Further, as an acid diffusion control agent, an onium salt compound (hereinafter also referred to as a "radiation-sensitive weak acid generator" for convenience) that generates an acid with a higher pKa than the acid generated from the radiation-sensitive acid generator when irradiated with radiation. ) can also be suitably used. The acid generated by the radiation-sensitive weak acid generator is a weak acid that does not induce dissociation of the acid-dissociable groups in the resin under conditions that dissociate the acid-dissociable groups. In this specification, "dissociation" of an acid-dissociable group refers to dissociation upon post-exposure baking at 110° C. for 60 seconds.

Examples of the radiation-sensitive weak acid generator include a sulfonium salt compound represented by the following formula (8-1), an iodonium salt compound represented by the following formula (8-2), and the like.

In the above formulas (8-1) and (8-2), J ⁺ is a sulfonium cation and U ⁺ is an iodonium cation. Examples of the sulfonium cation represented by J ⁺ include the sulfonium cations represented by the above formulas (X-1) to (X-4), and examples of the iodonium cation represented by U ⁺ include the sulfonium cations represented by the above formula (X- Examples include iodonium cations represented by 5) to (X-6). E ^- and Q ^- are each independently anions represented by OH ^- , R ^α -COO ^- , and R ^α -SO ₃ ^- . R ^α is an alkyl group, a cycloalkyl group, an aryl group, an aralkyl group, or a combination thereof. The hydrogen atom of the alkyl group or cycloalkyl group represented by R ^α or the hydrogen atom of the aromatic ring of the aryl group or aralkyl group may be substituted with a halogen atom, a hydroxy group, a nitro group, or a halogen atom; It may be substituted with an alkyl group having 1 to 12 carbon atoms, or an alkoxy group having 1 to 12 carbon atoms, substituted or unsubstituted with an atom, a hydroxy group, a nitro group, or a halogen atom. Further, such alkyl groups and alkoxy groups may have ester bonds or ether bonds between their carbon-carbon bonds.

Examples of the radiation-sensitive weak acid generator include compounds represented by the following formula.

The lower limit of the content of the acid diffusion control agent is preferably 10 mol%, more preferably 20 mol%, and even more preferably 30 mol%, based on the total number of moles of the radiation-sensitive acid generator or structural unit (VII). preferable. The upper limit of the content is preferably 70 mol%, more preferably 60 mol%, and even more preferably 50 mol%. By setting the content of the acid diffusion control agent within the above range, the lithography performance of the radiation-sensitive resin composition can be further improved. The radiation-sensitive resin composition may contain one or more acid diffusion control agents.

<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 resin, the radiation-sensitive acid generator, and optionally contained additives.

Examples of the solvent include alcohol solvents, ether solvents, ketone solvents, amide solvents, ester solvents, hydrocarbon solvents, and the like.

Examples of alcohol-based 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, etc. Monoalcoholic solvent of numbers 1 to 18;
Polymers having 2 to 18 carbon atoms such as ethylene glycol, 1,2-propylene glycol, 2-methyl-2,4-pentanediol, 2,5-hexanediol, diethylene glycol, dipropylene glycol, triethylene glycol, and tripropylene glycol. Alcohol-based solvent;
Examples include polyhydric alcohol partially ether-based solvents in which a portion of the hydroxyl groups of the above-mentioned polyhydric alcohol-based solvents are etherified.
In this embodiment, methyl lactate, ethyl lactate, propyl lactate, butyl lactate, methyl 2-hydroxyisobutyrate, i-propyl 2-hydroxyisobutyrate, i-butyl 2-hydroxyisobutyrate, 2-hydroxyisobutyrate- Alcoholic ester solvents such as n-butyl are also included in the alcoholic solvents.

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 (methyl phenyl ether);
Examples include polyhydric alcohol ether solvents in which the hydroxyl groups of the above polyhydric alcohol solvents are etherified.

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

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

Examples of ester solvents include:
Monocarboxylic acid ester solvent such as n-butyl acetate;
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;
Polyhydric carboxylic acid diester solvents such as propylene glycol diacetate, methoxytriglycol acetate, diethyl oxalate, ethyl acetoacetate, and diethyl phthalate can be mentioned.

Examples of hydrocarbon solvents include aliphatic hydrocarbon solvents such as n-hexane, cyclohexane, and methylcyclohexane;
Examples include aromatic hydrocarbon solvents such as benzene, toluene, di-iso-propylbenzene, and n-amylnaphthalene.

Among these, ester solvents and ketone solvents are preferred, polyhydric alcohol partial ether acetate solvents and polyhydric alcohol partial ether solvents are more preferred, and propylene glycol monomethyl ether acetate and propylene glycol monomethyl ether are even more preferred. The radiation-sensitive resin composition may contain one or more solvents.

<Other optional ingredients>
The above-mentioned radiation-sensitive resin composition may contain other optional components in addition to the above-mentioned components. Examples of the above-mentioned other optional components include a crosslinking agent, a 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 can be prepared, for example, by mixing a resin, a radiation-sensitive acid generator, optionally a high fluorine content resin, and a solvent in a predetermined ratio. After mixing, the radiation-sensitive resin composition is preferably filtered using a filter having a pore size of about 0.05 μm to 0.30 μm, for example. The solid content concentration of the radiation-sensitive resin composition is usually 0.1% by mass to 30% by mass, preferably 0.5% by mass to 20% by mass, and more preferably 1% by mass to 10% by mass.

《Resist pattern formation method》
The resist pattern forming method in the present invention includes:
Step (1) of forming a resist film using the radiation-sensitive resin composition (hereinafter also referred to as "resist film forming step");
Step (2) of exposing the resist film (hereinafter also referred to as "exposure step"), and
The method includes a step (3) of developing the exposed resist film (hereinafter also referred to as "developing step").

According to the above resist pattern forming method, since the above radiation sensitive resin composition having excellent sensitivity and CDU performance in the exposure process is used, a high quality resist pattern can be formed. Each step will be explained below.

[Resist film formation process]
In this step (step (1) above), a resist film is formed using the radiation-sensitive resin composition. Examples of the substrate on which this 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 Japanese Patent Publication No. 6-12452, Japanese Patent Application Laid-Open No. 59-93448, etc. may be formed on the substrate. Examples of the coating method include spin coating, casting coating, and roll coating. After coating, pre-baking (PB) (also referred to as soft-baking (SB)) may be performed, if necessary, 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 seconds to 600 seconds, preferably 10 seconds 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 performing immersion exposure, an immersion liquid and a resist film are applied onto the resist film formed above, regardless of the presence or absence of a water-repellent polymer additive such as the high fluorine content resin in the radiation-sensitive resin composition. In order to avoid direct contact with the immersion liquid, an immersion protective film insoluble in the immersion liquid may be provided. The protective film for liquid immersion includes a solvent-removable protective film that is removed with a solvent before the development process (for example, see Japanese Patent Application Laid-open No. 2006-227632), a developer-removable protective film that is removed at the same time as development in the development process ( For example, any of WO2005-069076 and WO2006-035790 may be used. However, from the viewpoint of throughput, it is preferable to use a developer-removable protective film for immersion.

[Exposure process]
In this step (step (2) above), the resist film formed in the resist film forming step (step (1) above) is applied to the resist film through a photomask (in some cases, through an immersion medium such as water). , irradiate and expose with radiation. The radiation used for exposure includes electromagnetic waves such as visible light, ultraviolet rays, far ultraviolet rays, EUV (extreme ultraviolet), X-rays, and gamma rays; electron beams, alpha rays, etc., depending on the line width of the target pattern. Examples include charged particle beams. Among these, far ultraviolet rays, electron beams, and EUV are preferable, and ArF excimer laser light (wavelength 193 nm), KrF excimer laser light (wavelength 248 nm), electron beam, and EUV are more preferable, and wavelength 50 nm is positioned as a next-generation exposure technology. The following electron beam and EUV are more preferable.

When exposure is performed by immersion exposure, examples of the immersion liquid used include water, fluorine-based inert liquid, and the like. The immersion liquid is preferably a liquid that is transparent to the exposure wavelength and has as small a temperature coefficient of refractive index as possible to minimize distortion of the optical image projected onto the film. In the case of excimer laser light (wavelength: 193 nm), water is preferably used from the viewpoint of ease of acquisition and handling, in addition to the above-mentioned viewpoints. When water is used, additives that reduce the surface tension of water and increase surfactant power may be added in small proportions. This additive is preferably one that does not dissolve the resist film on the wafer and has a negligible effect on the optical coating on the lower surface of the lens. The water used is preferably distilled water.

After the above exposure, a post-exposure bake (PEB) is performed, and in the exposed portion of the resist film, the acid dissociation property of the resin, etc. due to the acid generated from the radiation-sensitive acid generator or the radiation-sensitive acid-generating structure due to the exposure. It is preferable to promote dissociation of the group. This PEB causes a difference in solubility in the 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 seconds to 600 seconds, preferably 10 seconds to 300 seconds.

[Development process]
In this step (step (3) above), the resist film exposed in the exposure step (step (2)) 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.

In the case of alkaline development, the developer used for the above development includes, 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 Examples include an alkaline aqueous solution in which at least one alkaline compound such as , 1,5-diazabicyclo-[4.3.0]-5-nonene is dissolved. Among these, a TMAH aqueous solution is preferred, and a 2.38% by mass TMAH aqueous solution is more preferred.

In the case of organic solvent development, examples include organic solvents such as hydrocarbon solvents, ether solvents, ester solvents, ketone solvents, and alcohol solvents, or solvents containing organic solvents. Examples of the organic solvent include one or more of the solvents listed as the solvent for the radiation-sensitive resin composition described above. Among these, ester solvents and ketone solvents are preferred. As the ester solvent, an acetate ester solvent is preferred, and n-butyl acetate and amyl acetate are more preferred. As the ketone solvent, chain ketones are preferred, and 2-heptanone is more preferred. The content of the organic solvent in the developer is preferably 80% by mass or more, more preferably 90% by mass or more, even 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, silicone oil, and the like.

Development methods include, for example, a method in which the substrate is immersed in a tank filled with a developer for a certain period of time (dip method), a method in which the developer is raised on the surface of the substrate by surface tension and then developed by standing still for a certain period of time (paddle 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 onto a rotating substrate (dynamic dispensing method). ), etc.

Hereinafter, the present invention will be specifically explained based on Examples, but the present invention is not limited to these Examples. The methods for measuring various physical property values are shown below.

[Weight average molecular weight (Mw) and number average molecular weight (Mn)]
Mw and Mn of the resin were measured under the conditions described above. Further, the degree of dispersion (Mw/Mn) was calculated from the measurement results of Mw and Mn.

<Synthesis of [Z] onium salt compound>
[Synthesis Example 1: Synthesis of onium salt compound (Z-1)]
An onium salt compound (Z-1) was synthesized according to the reaction scheme below.

Compound (P-1) (20 mmol), 4-iodoacetophenone (30 mmol), and p-toluenesulfonic acid monohydrate (4 mmol) were added to a container containing toluene (100 mL). The mixture was heated under reflux for 3 hours while removing water using a Dean-Stark apparatus. The temperature was returned to room temperature, and ethyl acetate was added. The organic layer was washed twice with aqueous sodium bicarbonate solution. The organic layer was dried with sodium sulfate and filtered. The solvent was distilled off to obtain an onium salt compound (Z-1).

[Synthesis Examples 2 to 12: Synthesis of onium salt compounds (Z-2) to (Z-15)]
By appropriately selecting the precursor and selecting the same formulation as in Synthesis Example 1, onium salt compounds (Z-2) to (Z-15) represented by the following formulas (Z-2) to (Z-15) can be prepared. ) was synthesized.

<[A] Synthesis of resin>
The monomers used in the synthesis of each resin and high fluorine content resin in each Example and Comparative Example are shown below. In the following synthesis examples, unless otherwise specified, "parts by mass" means the value when the total mass of the monomers used is 100 parts by mass, and "mol%" means the total mass of the monomers used. It means the value when the number of moles is 100 mol%.

[Resin synthesis example 1: Synthesis of resin (A-1)]
Compounds (M-2) and (M-8) were dissolved in propylene glycol monomethyl ether (200 parts by mass) so that the molar ratio was 55/45. A monomer solution was prepared by adding 2,2'-azobis(methyl isobutyrate) (10 mol % based on the total monomers) as an initiator. On the other hand, propylene glycol monomethyl ether (100 parts by mass based on the total amount of monomers) was added to an empty reaction vessel, and the mixture was heated to 85° C. with stirring. Next, the monomer solution prepared above was added dropwise over 3 hours, and then heated at 85° C. for an additional 3 hours. After the polymerization reaction was completed, the polymerization solution was cooled to room temperature. The polymer solution was dropped into n-hexane (1,000 parts by mass) to coagulate and purify the polymer. Propylene glycol monomethyl ether (150 parts by mass), methanol (150 parts by mass), triethylamine (1.5 molar equivalent to the amount of compound (M-2) used) and water (compound (M-2) were added to the recovered polymer. ) was added in an amount of 1.5 molar equivalents based on the amount used. The hydrolysis reaction was carried out for 8 hours while refluxing at the boiling point. After the reaction was completed, the solvent and triethylamine were distilled off under reduced pressure. The obtained resin was dissolved in acetone (150 parts by mass). This was dropped into water (2,000 parts by mass) to solidify, and the white powder produced was filtered out. It was dried at 50° C. for 17 hours to obtain a white powdery resin (A-1) in good yield.

[Resin synthesis examples 2 to 16: Synthesis of resins (A-2) to (A-16)]
Resins (A-2) to (A-16) were synthesized by appropriately selecting monomers and performing the same operations as in Resin Synthesis Example 1. In the table, "-" indicates that the corresponding component was not used.

[Synthesis example] Synthesis of resins (A-17) to (A-18) Each monomer was combined and subjected to a copolymerization reaction in a tetrahydrofuran (THF) solvent, then isolated and dried, as shown below. Base resins (A-17) to (A-18) having the compositions were obtained. The composition of the obtained base resin was confirmed by ¹ H-NMR, and the Mw and dispersity (Mw/Mn) were confirmed by the above-mentioned GPC conditions.

Table 1 shows the amount of each structural unit used and the Mw and Mw/Mn values of the obtained resin.

[Resin synthesis example 19: Synthesis of high fluorine content resin (F-1)]
Compounds (M-9) and (M-15) were dissolved in 2-butanone (100 parts by mass based on the total amount of monomers) at a molar ratio of 40/60. Azobisisobutyronitrile (5 mol% based on all monomers) was added thereto as an initiator to prepare a monomer solution. Meanwhile, 2-butanone (50 parts by mass) was placed in an empty container, and the container was purged with nitrogen for 30 minutes. The inside of this container was heated to 80° C., and the above monomer solution was added dropwise over 3 hours while stirring. After the completion of the dropwise addition, the polymerization solution was further heated at 80°C for 3 hours, and then cooled to 30°C or lower. After the polymerization solution was transferred to a separatory funnel, hexane (150 parts by mass) was added to uniformly dilute the polymerization solution. Furthermore, methanol (600 parts by mass) and water (30 parts by mass) were added and mixed. After standing still for 30 minutes, the lower layer was collected and the solvent was replaced with propylene glycol monomethyl ether acetate. In this way, a 10% solution of the high fluorine content resin (F-1) in propylene glycol monomethyl ether acetate was obtained. The high fluorine content resin (F-1) had Mw=7,200 and Mw/Mn=1.7.

<Preparation of radiation-sensitive resin composition>
The [B] acid generator, [D] acid diffusion control agent, and [E] solvent used in the preparation of the radiation-sensitive resin compositions of the following Examples and Comparative Examples are shown below.

[B] Acid generator [B] The above onium salt compounds (Z-1) to (Z-15) and compounds represented by the following formulas (C-1) to (C-3) were used as the acid generator. .

[D] Acid diffusion control agent [D] Compounds represented by the following formulas (D-1) to (D-8) were used as acid diffusion control agents.

[E] Solvent E-1: Propylene glycol monomethyl ether acetate E-2: Propylene glycol monomethyl ether

[Example 1]
[A] 100 parts by mass of resin (A-1), [F] 3 parts by mass of high fluorine content resin (F-1) in solid content, [B] 40 parts by mass of (Z-1) as an acid generator. , [D] 40 mol% of (D-1) as an acid diffusion control agent based on (Z-1), [E] 1,500 parts by mass of (E-1) as a solvent and (E-2) 6,200 parts by mass was blended. This was filtered through a filter with a pore size of 0.2 μm to prepare a radiation-sensitive resin composition (R-1).

[Examples 2 to 41 and Comparative Examples 1 to 3]
Radiation sensitive resin compositions (R-2) to (R-41) and (CR-1 ) to (CR-3) were prepared.

<Formation of resist pattern>
Using a spin coater (CLEAN TRACK ACT12, manufactured by Tokyo Electron), each radiation-sensitive film prepared above was coated on the surface of a 12-inch silicon wafer on which a 20 nm thick lower layer film (AL412 (manufactured by Brewer Science)) was formed. A resin composition was applied. After performing SB (soft baking) at 100° C. for 60 seconds, cooling was performed at 23° C. for 30 seconds to form a resist film with a thickness of 40 nm. Next, this resist film was irradiated with EUV light using an EUV exposure machine (model "NXE3300", manufactured by ASML, NA=0.33, illumination conditions: Conventional s=0.89). The resist film was subjected to PEB (post-exposure baking) at 100° C. for 60 seconds. Next, development was performed at 23° C. for 30 seconds using a 2.38 wt % TMAH aqueous solution to form a positive contact hole pattern of 50 nm pitch and 25 nm.

<Evaluation>
For each resist pattern formed above, the sensitivity and CDU performance of each radiation-sensitive resin composition were evaluated by measuring according to the following method. Note that a scanning electron microscope (“CG-5000” manufactured by Hitachi High Technologies) was used to measure the length of the resist pattern. The evaluation results are shown in Table 3 below.

[sensitivity]
In forming the resist pattern, the exposure amount for forming a 25 nm contact hole pattern was defined as the optimum exposure amount, and this optimum exposure amount was defined as the sensitivity (mJ/cm ² ). The smaller the value, the better the sensitivity. Sensitivity is "A" (very good) if it is less than 52 mJ/ ^cm2 , "B" (good) if it is 52 mJ/ ^cm2 ^or more and less than 55 mJ/cm2, and "C" if it exceeds 55 mJ/ ^cm2 . It was judged as (defective).

[CDU performance]
The 25 nm contact hole pattern was observed from above using the above scanning electron microscope, and a total of 800 lengths were measured at arbitrary points. The dimensional variation (3σ) was determined, and this was defined as the CDU performance (nm). The smaller the value of CDU, the smaller the variation in hole diameter over a long period, and the better. CDU performance is "A" (very good) if it is less than 3.8 nm, "B" (good) if it is 3.8 nm or more and less than 4.0 nm, and "C" (poor) if it is 4.0 nm or more. It was determined that

According to the radiation-sensitive resin composition and pattern forming method of the present invention, sensitivity and CDU can be improved compared to conventional methods. Therefore, these can be suitably used for forming fine resist patterns in the lithography process of various electronic devices such as semiconductor devices and liquid crystal devices.

Claims

An onium salt compound containing a structure represented by the following formula (1),
A resin containing a structural unit (I) having a phenolic hydroxyl group or a group that provides a phenolic hydroxyl group by the action of an acid;
A radiation-sensitive resin composition comprising a solvent and.

(In the above formula (1),
R f1 and R f2 are each independently a hydrogen atom, a monovalent hydrocarbon group having 1 to 20 carbon atoms, a fluorine atom, or a monovalent fluorinated hydrocarbon group having 1 to 20 carbon atoms.
R 1 , R 2 and R 3 are each independently a hydrogen atom or a monovalent organic group having 1 to 20 carbon atoms.
n 1 and n 2 are each independently an integer of 0 to 4. When n 1 and n 2 are integers of 2 or more, the plurality of R f1 , R f2 , R 1 and R 2 are the same or different from each other.
X 1 and X 2 are each independently an oxygen atom or a sulfur atom.
L is a substituted or unsubstituted divalent hydrocarbon group having 1 to 10 carbon atoms.
R 4 and R 5 are each independently a hydrogen atom or a monovalent organic group having 1 to 40 carbon atoms. However, at least one of R 4 and R 5 is a monovalent aromatic ring-containing organic group containing an aromatic ring having 5 to 40 ring members.
Z + is a monovalent radiation-sensitive onium cation. )
The radiation-sensitive resin composition according to claim 1, wherein some or all of the hydrogen atoms on the aromatic ring contained in the aromatic ring-containing organic group are substituted with a halogen atom or a halogenated hydrocarbon group.
The radiation-sensitive resin composition according to claim 2, wherein the halogen atom is an iodine atom.
The radiation-sensitive resin composition according to claim 1, wherein X 1 and X 2 are oxygen atoms.
The radiation-sensitive resin composition according to claim 1, wherein the radiation-sensitive onium cation contains a fluorine atom.
The radiation-sensitive resin composition according to claim 1, wherein n 1 is 0, n 2 is 1, and R 1 and R 2 are hydrogen atoms.
The radiation-sensitive resin composition according to claim 1, wherein the content of the onium salt compound is 5 parts by mass or more and 70 parts by mass or less based on 100 parts by mass of the resin.
The radiation-sensitive resin composition according to claim 1, wherein the resin further contains a structural unit (II) having an acid-dissociable group.
The radiation-sensitive resin composition according to claim 1, further comprising an acid diffusion control agent.
An onium salt compound containing a structure represented by the following formula (1).

(In the above formula (1),
R f1 and R f2 are each independently a hydrogen atom, a monovalent hydrocarbon group having 1 to 20 carbon atoms, a fluorine atom, or a monovalent fluorinated hydrocarbon group having 1 to 20 carbon atoms.
R 1 , R 2 and R 3 are each independently a hydrogen atom or a monovalent organic group having 1 to 20 carbon atoms.
n 1 and n 2 are each independently an integer of 0 to 4. When n 1 and n 2 are integers of 2 or more, the plurality of R f1 , R f2 , R 1 and R 2 are the same or different from each other.
X 1 and X 2 are each independently an oxygen atom or a sulfur atom.
L is a substituted or unsubstituted divalent hydrocarbon group having 1 to 10 carbon atoms.
R 4 and R 5 are each independently a hydrogen atom or a monovalent organic group having 1 to 40 carbon atoms. However, at least one of R 4 and R 5 is a monovalent aromatic ring-containing organic group containing an aromatic ring having 5 to 40 ring members.
Z + is a monovalent radiation-sensitive onium cation. )
A step of directly or indirectly applying the radiation-sensitive resin composition according to any one of claims 1 to 9 on a substrate to form a resist film;
a step of exposing the resist film;
A pattern forming method comprising: developing the exposed resist film with a developer.