WO2024080128A1

WO2024080128A1 - Actinic ray-sensitive or radiation-sensitive resin composition, resist film, pattern-forming method, and electronic device production method

Info

Publication number: WO2024080128A1
Application number: PCT/JP2023/034808
Authority: WO
Inventors: 朝日 ▲高▼木; 直紘丹呉; 和博丸茂
Original assignee: 富士フイルム株式会社
Priority date: 2022-10-12
Filing date: 2023-09-26
Publication date: 2024-04-18

Abstract

The present invention addresses the problem of providing an actinic ray-sensitive or radiation-sensitive resin composition from which a resist pattern having a small LWR can be formed. An actinic ray-sensitive or radiation-sensitive resin composition according to the present invention comprises: a resin of which the polarity increases due to the action of an acid; a photoacid generator that includes an anion and a cation and generates an acid when irradiated with an actinic ray or radiation; a first acid diffusion control agent including a first anion and a first cation; and a second acid diffusion control agent including a second anion and a second cation. The first anion has a predetermined alicyclic structure that includes multiple rings and is optionally substituted. The ClogP value of the first anion is at most -1.50. The volume of the second anion is greater than that of the first anion. The volume of the second anion is at least 250 Å3.

Description

Actinic ray- or radiation-sensitive resin composition, resist film, pattern forming method, and method for manufacturing electronic device

The present invention relates to an actinic ray- or radiation-sensitive resin composition, a resist film, a pattern forming method, and a method for manufacturing an electronic device.

Since the development of resists for KrF excimer lasers (248 nm), pattern formation methods using chemical amplification have been used to compensate for the loss of sensitivity due to light absorption. Examples of pattern formation methods using chemical amplification include the following methods.
An actinic ray-sensitive or radiation-sensitive resin film (hereinafter also referred to as a "resist film") formed using an actinic ray-sensitive or radiation-sensitive resin composition (hereinafter also referred to as a "resist composition") containing a photoacid generator is exposed to light to generate an acid from the photoacid generator. The acid is used as a catalyst to change the solubility of the resin contained in the resist composition in a developer (e.g., an alkaline aqueous solution or an organic solvent). Thereafter, the exposed or unexposed portion of the resist film is removed using the developer to obtain a desired pattern.

As resist compositions for use in such methods, various configurations have been proposed.
For example, Patent Document 1 discloses a composition containing a quencher having a specific structure.

JP 2020-046662 A

The inventors have studied the resist composition described in Patent Document 1 and found that there is room for improvement in the LWR (Line Width Roughness) of the resulting resist pattern.

Therefore, an object of the present invention is to provide an actinic ray-sensitive or radiation-sensitive resin composition which is capable of forming a resist pattern with small LWR.
Another object of the present invention is to provide a resist film formed using the actinic ray-sensitive or radiation-sensitive resin composition, as well as a pattern forming method and a device manufacturing method using the actinic ray-sensitive or radiation-sensitive resin composition.

　As a result of extensive research into solving the above problems, the inventors have discovered that the problems can be solved by the following configuration.

[1] A resin whose polarity increases under the action of an acid;
a photoacid generator which comprises an anion and a cation and generates an acid when exposed to actinic rays or radiation;
a first acid diffusion controller comprising a first anion and a first cation;
a second acid diffusion control agent comprising a second anion and a second cation;
an acid dissociation constant A of an acidic compound obtained by replacing the cation in the photoacid generator with a proton is smaller than both an acid dissociation constant B of an acidic compound obtained by replacing the first cation in the first acid diffusion controller with a proton and an acid dissociation constant C of an acidic compound obtained by replacing the second cation in the second acid diffusion controller with a proton;
the first anion has a polycyclic alicyclic structure which may have a substituent, a methylene group constituting the polycyclic alicyclic structure may be substituted with -O-, -CO-, -S-, or -SO ₂ -, an ethylene group constituting the polycyclic alicyclic structure may be substituted with a vinylene group, and when the polycyclic alicyclic structure has a plurality of substituents, two of the substituents may be bonded to each other to form a ring;
the first anion has a ClogP value of −1.50 or less;
the volume of the second anion is greater than the volume of the first anion;
The actinic ray-sensitive or radiation-sensitive resin composition, wherein the second anion has a volume of 250 ^Å3 or more.
[2] The actinic ray-sensitive or radiation-sensitive resin composition according to [1], wherein the first anion has an adamantane structure which may have a substituent, a methylene group constituting the adamantane structure may be substituted with -O-, -CO-, -S-, or -SO ₂ -, an ethylene group constituting the adamantane structure may be substituted with a vinylene group, and when the adamantane structure has a plurality of substituents, two of the substituents may be bonded to each other to form a ring.
[3] The actinic ray-sensitive or radiation-sensitive resin composition according to [1] or [2], wherein the first anion has a volume of ²⁰⁰ Å3 or less.
[4] The actinic ray-sensitive or radiation-sensitive resin composition according to any one of [1] to [3], wherein the first cation has a ClogP value of 5.00 or more.
[5] The actinic ray-sensitive or radiation-sensitive resin composition according to any one of [1] to [4], wherein the content of the first acid diffusion controller is 15 mass% or less based on the total solid content in the actinic ray-sensitive or radiation-sensitive resin composition.
[6] The actinic ray-sensitive or radiation-sensitive resin composition according to any one of [1] to [5], wherein at least one of the first acid diffusion controller and the second acid diffusion controller contains at least one atom selected from the group consisting of a fluorine atom and an iodine atom.
[7] A resist film formed using the actinic ray-sensitive or radiation-sensitive resin composition according to any one of [1] to [6].
[8] A step 1 of forming a resist film on a substrate using the actinic ray-sensitive or radiation-sensitive resin composition according to any one of [1] to [6];
A step 2 of exposing the resist film;
and step 3 of developing the exposed resist film with a developer to obtain a resist pattern.
[9] A method for producing an electronic device, comprising the pattern forming method according to [8].

According to the present invention, there is provided an actinic ray-sensitive or radiation-sensitive resin composition capable of forming a resist pattern with small LWR.
The present invention can also provide a resist film formed using the above-mentioned actinic ray-sensitive or radiation-sensitive resin composition, as well as a pattern forming method and a device manufacturing method using the above-mentioned actinic ray-sensitive or radiation-sensitive resin composition.

The present invention will be described in detail below.
The following description of the configuration may be based on a representative embodiment of the present invention, but the present invention is not limited to such an embodiment.

In this specification, a numerical range expressed using "~" means a range that includes the numerical values written before and after "~" as the lower and upper limits.

In the present specification, the notation of groups (atomic groups) that does not indicate whether they are substituted or unsubstituted includes not only groups that have no substituents but also groups that have a substituent, unless it is contrary to the spirit of the present invention. For example, an "alkyl group" includes not only an alkyl group that has no substituents (unsubstituted alkyl group) but also an alkyl group that has a substituent (substituted alkyl group).
As the substituent, unless otherwise specified, a monovalent substituent is preferred.
As used herein, an "organic group" refers to a group containing at least one carbon atom.
In this specification, the bonding direction of the divalent linking group is not limited unless otherwise specified. For example, when Y is -COO- in a compound represented by the formula "X-Y-Z", Y may be -CO-O- or -O-CO-. That is, the compound may be "X-CO-O-Z" or "X-O-CO-Z".
In this specification, (meth)acrylate refers to acrylate and methacrylate, and (meth)acrylic refers to acrylic and methacrylic.

In this specification, "actinic rays" or "radiation" refers to, for example, the emission line spectrum of a mercury lamp, far ultraviolet light represented by an excimer laser, extreme ultraviolet light (EUV light: extreme ultraviolet), X-rays, and electron beams (EB).
In this specification, "light" means actinic rays or radiation.
In this specification, unless otherwise specified, the term "exposure" includes not only exposure to the emission line spectrum of a mercury lamp, far ultraviolet light represented by an excimer laser, extreme ultraviolet light (EUV: extreme ultraviolet), X-rays, and the like, but also drawing with particle beams such as electron beams and ion beams.

In this specification, "ppm" means "parts-per-million (10 ^-6 ),""ppb" means "parts-per-billion (10 ^-9 )," and "ppt" means "parts-per-trillion (10 ^-12 )."
In this specification, 1 Å is equal to 1×10 ⁻¹⁰ m.

In this specification, weight average molecular weight (Mw), number average molecular weight (Mn), and polydispersity index (also referred to as "PDI") (Mw/Mn) are defined as polystyrene equivalent values measured using a Gel Permeation Chromatography (GPC) device (Tosoh Corporation HLC-8120GPC) (solvent: tetrahydrofuran, flow rate (sample injection amount): 10 μL, column: Tosoh Corporation TSK gel Multipore HXL-M, column temperature: 40°C, flow rate: 1.0 mL/min, detector: differential refractive index detector).

In this specification, the acid dissociation constant (pKa) refers to the pKa in an aqueous solution. When the pKa in an aqueous solution cannot be calculated, the "pKa in a dimethyl sulfoxide (DMSO) solution" is used.
The pKa can be calculated, for example, by calculation based on the database of Hammett's substituent constants and known literature values, and by using molecular orbital calculation method.Specific methods of molecular orbital calculation method include a method of calculating by calculating H ⁺ dissociation free energy in aqueous solution based on thermodynamic cycle.The calculation method of H ⁺ dissociation free energy can be calculated, for example, by DFT (density functional theory), but there are various other methods reported in literature, etc., and it is not limited thereto.
In this specification, pKa is a value calculated using the following software package 1 based on a database of Hammett's substituent constants and known literature values.
Software package 1: Advanced Chemistry Development (ACD/Labs) Software V8.14 for Solaris (1994-2007 ACD/Labs)
In addition, when the pKa cannot be calculated by the above method, a value obtained by a molecular orbital calculation method is used. As a specific method using the molecular orbital calculation method, a value obtained using Gaussian 16 based on DFT is used.

In this specification, the ClogP value is the value obtained by calculating the common logarithm logP of the partition coefficient P between 1-octanol and water. Any known method and software can be used to calculate the ClogP value, but unless otherwise specified, in this invention, the structure is drawn using ChemDraw Professional (version 20.1.1.125) manufactured by PerkinElmer, and the value calculated using the above software is used.

"Solids" refers to the components that form the resist film, and does not include solvents. In addition, if a component forms a resist film, it is considered to be a solid even if it is in liquid form.

In this specification, when the term "acid diffusion control agent" is used, it refers to a concept that includes a first acid diffusion control agent and a second acid diffusion control agent.

[Actinic ray- or radiation-sensitive resin composition (resist composition)]
The resist composition of the present invention will be described in detail below.
The resist composition of the present invention comprises: a resin whose polarity increases under the action of an acid; a photoacid generator comprising an anion and a cation and generating an acid upon exposure to actinic rays or radiation; a first acid diffusion controller comprising a first anion and a first cation; and a second acid diffusion controller comprising a second anion and a second cation;
the acid dissociation constant A of the acidic compound obtained by replacing the cation in the photoacid generator with a proton is smaller than both of the acid dissociation constant B of the acidic compound obtained by replacing the first cation in the first acid diffusion controller with a proton and the acid dissociation constant C of the acidic compound obtained by replacing the second cation in the second acid diffusion controller with a proton;
the first anion has a polycyclic alicyclic structure which may have a substituent, a methylene group constituting the polycyclic alicyclic structure may be substituted with -O-, -CO-, -S-, or -SO ₂ -, an ethylene group constituting the polycyclic alicyclic structure may be substituted with a vinylene group, and when the polycyclic alicyclic structure has a plurality of substituents, two of the substituents may be bonded to each other to form a ring;
The first anion has a ClogP value of −1.50 or less, the second anion has a volume greater than the volume of the first anion, and the second anion has a volume of 250 Å ³ or more.

Although the reason why the resist composition having the above-mentioned structure can solve the problems of the present invention is not necessarily clear, the present inventors speculate as follows.
The mechanism by which the effects are obtained is not limited by the following speculation. In other words, even if the effects are obtained by a mechanism other than the following, it is included in the scope of the present invention.
In pattern formation, it is known that an acid generated from a photoacid generator by exposure reacts unintentionally with a resin in an unexposed area, which is one of the causes of an increase in LWR. The resist composition of the present invention can effectively suppress the reaction between the acid and the resin in the unexposed area by containing the above-mentioned two specific acid diffusion control agents. Specifically, a first acid diffusion control agent having a small volume and a highly hydrophilic first anion moves to the boundary between the hydrophilic exposed area and the hydrophobic unexposed area to suppress acid diffusion, and a second acid diffusion control agent having a large volume and a second anion that is difficult to move suppresses acid diffusion in the unexposed area outside the boundary. This makes it possible to suppress the reaction between the acid and the resin in the entire unexposed area, and as a result, the LWR of the obtained pattern can be reduced.

[Specific resin]
The resist composition of the present invention contains a resin whose polarity increases under the action of an acid (hereinafter, also referred to as a "specific resin").
The specific resin preferably has a group that decomposes under the action of an acid to increase its polarity (hereinafter, also referred to as an "acid-decomposable group"), and more preferably contains a repeating unit having an acid-decomposable group.
When the specific resin has an acid-decomposable group, typically, in the pattern formation method of the present invention, when an alkaline developer is used as the developer, a positive pattern is preferably formed, and when an organic developer is used as the developer, a negative pattern is preferably formed.
Examples of the repeating unit having an acid-decomposable group include a repeating unit having an acid-decomposable group and a repeating unit having an acid-decomposable group containing an unsaturated bond.

<Repeating Unit Having Acid-Decomposable Group>
The specific resin preferably contains a repeating unit having an acid-decomposable group.
The acid-decomposable group refers to a group that is decomposed by the action of an acid to generate a polar group. The acid-decomposable group preferably has a structure in which a polar group is protected by a group that is eliminated by the action of an acid (a leaving group).
In other words, the specific resin preferably has a repeating unit having a group that decomposes under the action of an acid to generate a polar group, and the resin having this repeating unit has increased polarity under the action of an acid, thereby increasing its solubility in an alkaline developer and decreasing its solubility in an organic solvent.

The polar group is preferably an alkali-soluble group, and examples thereof include acidic groups such as a carboxy group, a phenolic hydroxyl group, a fluorinated alcohol group, a sulfonic acid group, a phosphate group, a sulfonamide group, a sulfonylimide group, an (alkylsulfonyl)(alkylcarbonyl)methylene group, an (alkylsulfonyl)(alkylcarbonyl)imide group, a bis(alkylcarbonyl)methylene group, a bis(alkylcarbonyl)imide group, a bis(alkylsulfonyl)methylene group, a bis(alkylsulfonyl)imide group, a tris(alkylcarbonyl)methylene group, and a tris(alkylsulfonyl)methylene group, as well as an alcoholic hydroxyl group.
Among these, the polar group is preferably a carboxy group, a phenolic hydroxyl group, a fluorinated alcohol group (preferably a hexafluoroisopropanol group), or a sulfonic acid group, and more preferably a carboxy group or a phenolic hydroxyl group.

Examples of the leaving group which is eliminated by the action of an acid include groups represented by the formulae (Y1) to (Y4).
Formula (Y1): -C(Rx ₁ )(Rx ₂ )(Rx ₃ )
Formula (Y2): -C(=O)OC( _Rx1 )( _Rx2 )( _Rx3 )
Formula (Y3): -C(R ₃₆ )(R ₃₇ )(OR ₃₈ )
Formula (Y4): -C(Rn)(H)(Ar)

In formula (Y1) and formula (Y2), Rx ₁ to Rx ₃ each independently represent an alkyl group (linear or branched), a cycloalkyl group (monocyclic or polycyclic), an alkenyl group (linear or branched), or an aryl group (monocyclic or polycyclic). When all of Rx ₁ to Rx ₃ are alkyl groups (linear or branched), it is preferable that at least two of Rx ₁ to Rx ₃ are methyl groups.
In particular, Rx ₁ to Rx ₃ each preferably independently represent an alkyl group or a cycloalkyl group, and more preferably represent a linear alkyl group.
The alkyl group is preferably an alkyl group having 1 to 5 carbon atoms, and examples thereof include a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, an isobutyl group, and a t-butyl group.
Examples of the cycloalkyl group include monocyclic cycloalkyl groups such as a cyclopentyl group and a cyclohexyl group, and polycyclic cycloalkyl groups such as a norbornyl group, a tricyclodecanyl group, a tetracyclodecanyl group, a tetracyclododecanyl group, and an adamantyl group.
The aryl group is preferably an aryl group having 6 to 10 carbon atoms, and examples thereof include a phenyl group, a naphthyl group, and an anthryl group.
The alkenyl group is preferably a vinyl group.
Two of Rx ₁ to Rx ₃ may be bonded to form a monocycle or polycycle.
The ring formed by combining two of Rx ₁ to Rx ₃ is preferably a cycloalkyl group, more preferably a monocyclic cycloalkyl group such as a cyclopentyl group or a cyclohexyl group, or a polycyclic cycloalkyl group such as a norbornyl group, a tricyclodecanyl group, a tetracyclodecanyl group, a tetracyclododecanyl group, or an adamantyl group, and more preferably a monocyclic cycloalkyl group having 5 to 6 carbon atoms, or a polycyclic cycloalkyl group having 6 to 12 carbon atoms.
In the cycloalkyl group formed by combining two of _Rx1 to _Rx3 , one of the methylene groups constituting the ring may be substituted with a heteroatom such as an oxygen atom or a sulfur atom, a group containing a heteroatom such as a -CO- group, a _-SO2- group, or a _-SO3- group, or a vinylidene group. Also, one or more of the ethylene groups constituting the cycloalkane ring may be substituted with a vinylene group.
In the group represented by formula (Y1) or formula (Y2), _Rx1 is preferably a methyl group or an ethyl group, and _Rx2 and _Rx3 are bonded to form the above-mentioned cycloalkyl group.
When the resist composition is, for example, a resist composition for EUV exposure, it is also preferable that the groups represented by Rx ₁ to Rx ₃ and the rings formed by bonding two of Rx ₁ to Rx ₃ further have a fluorine atom or an iodine atom as a substituent.

In formula (Y3), R ₃₆ to R ₃₈ each independently represent a hydrogen atom or a monovalent organic group, and R ₃₇ and R ₃₈ may be bonded to each other to form a ring.
Examples of the monovalent organic group include an alkyl group, a cycloalkyl group, an aryl group, an aralkyl group, and an alkenyl group.
The preferred embodiments of the alkyl group, cycloalkyl group, aryl group and aralkyl group are the same as those of the groups represented by Rx ₁ to Rx ₃ above.
It is also preferable that R ₃₆ is a hydrogen atom.
In the above alkyl, cycloalkyl, aryl and aralkyl groups, one or more methylene groups may be substituted with a heteroatom such as an oxygen atom or a sulfur atom, or a group containing a heteroatom such as a -CO- group, -SO ₂ - group or -SO ₃ - group.
R ₃₈ may be bonded to another substituent in the main chain of the repeating unit to form a ring. The group formed by bonding R ₃₈ to another substituent in the main chain of the repeating unit is preferably an alkylene group such as a methylene group.
When the resist composition is, for example, a resist composition for EUV exposure, it is also preferable that the groups represented by R ₃₆ to R ₃₈ and the ring formed by bonding R ₃₇ and R ₃₈ further have a fluorine atom or an iodine atom as a substituent.

In formula (Y4), Ar represents an aromatic ring group. Rn represents an alkyl group, a cycloalkyl group, or an aryl group. Rn and Ar may be bonded to each other to form a non-aromatic ring. Ar is preferably an aryl group.
The preferred embodiments of the alkyl group, cycloalkyl group, and aryl group are the same as those of the groups represented by Rx ₁ to Rx ₃ above.
When the resist composition is, for example, a resist composition for EUV exposure, it is preferable that the group represented by Ar and the group represented by Rn each have a fluorine atom or iodine atom as a substituent.

In terms of excellent acid decomposition properties of the repeating unit, when a non-aromatic ring is directly bonded to the polar group (or a residue thereof) in the leaving group protecting the polar group, it is also preferable that the ring atom in the non-aromatic ring adjacent to the ring atom directly bonded to the polar group (or a residue thereof) does not have a halogen atom such as a fluorine atom as a substituent.

The group that is eliminated by the action of an acid may be a 2-cyclopentenyl group having a substituent (such as an alkyl group), such as a 3-methyl-2-cyclopentenyl group, or a cyclohexyl group having a substituent (such as an alkyl group), such as a 1,1,4,4-tetramethylcyclohexyl group.

The repeating unit having an acid-decomposable group is preferably a repeating unit represented by formula (A).

_L1 represents a divalent linking group, _R1 represents a hydrogen atom, a fluorine atom, an iodine atom, an alkyl group or an aryl group, and _R2 represents a leaving group which is eliminated by the action of an acid.

_L1 represents a divalent linking group.
Examples of the divalent linking group include -CO-, -O-, -S-, -SO-, -SO ₂ -, divalent hydrocarbon groups (e.g., alkylene groups, cycloalkylene groups, alkenylene groups, arylene groups, etc.), and linking groups in which a plurality of these are linked together.
The divalent hydrocarbon group may have a fluorine atom or an iodine atom as a substituent.
Among these, _L1 is preferably -CO-, -Rt-, -COO-Rt-, -COO-Rt-CO- or -Rt-CO-, and more preferably -CO- or -COO-Rt-CO-. Rt is a divalent hydrocarbon group, preferably an alkylene group or an arylene group, and more preferably an alkylene group.
The alkylene group may be linear or branched. The number of carbon atoms in the alkylene group is not particularly limited, but is preferably 1 to 10, and more preferably 1 to 3.
The total number of fluorine atoms and iodine atoms that the alkylene group may have is not particularly limited, but is preferably 2 or more, more preferably 2 to 10, and even more preferably 3 to 6.
The arylene group is preferably a phenylene group.

_R1 represents a hydrogen atom, a fluorine atom, an iodine atom, an alkyl group, or an aryl group. The alkyl group and the aryl group may have a fluorine atom or an iodine atom as a substituent.
The alkyl group may be either linear or branched. The number of carbon atoms in the alkyl group is not particularly limited, but is preferably 1 to 10, and more preferably 1 to 3.
The total number of fluorine atoms and iodine atoms which the alkyl group may have is not particularly limited, but is preferably 1 or more, more preferably 1 to 5, and even more preferably 1 to 3.
The alkyl group may contain a heteroatom such as an oxygen atom.

_R2 represents a leaving group which is eliminated by the action of an acid. The leaving group may have a fluorine atom or an iodine atom as a substituent.
Examples of the leaving group include the leaving groups represented by the above formulae (Y1) to (Y4).

The repeating unit having an acid-decomposable group is preferably a repeating unit represented by formula (AI).

In formula (AI), _Xa1 represents a hydrogen atom or an alkyl group which may have a substituent. T represents a single bond or a divalent linking group. _Rx1 to _Rx3 each independently represent an alkyl group (linear or branched), a cycloalkyl group (monocyclic or polycyclic), an alkenyl group (linear or branched), or an aryl group (monocyclic or polycyclic).
Two of Rx ₁ to Rx ₃ may be bonded to form a monocyclic or polycyclic ring (eg, a monocyclic or polycyclic cycloalkyl group).

_Xa1 represents a hydrogen atom or an alkyl group which may have a substituent.
Examples of the alkyl group which may have a substituent include a methyl group or a group represented by -CH ₂ -R _11. R ₁₁ represents a halogen atom, a hydroxyl group, or a monovalent organic group. Examples of the monovalent organic group include an alkyl group having 5 or less carbon atoms which may have a halogen atom, an acyl group having 5 or less carbon atoms which may have a halogen atom, and an alkoxy group having 5 or less carbon atoms which may have a halogen atom. An alkyl group having 1 to 3 carbon atoms is preferred, and a methyl group is more preferred.
_Xa1 is preferably a hydrogen atom, a methyl group, a trifluoromethyl group, or a hydroxymethyl group.

T represents a single bond or a divalent linking group.
Examples of the divalent linking group include an alkylene group, an aromatic ring group, -COO-Rt-, and -O-Rt-, where Rt represents an alkylene group or a cycloalkylene group.
T is preferably a single bond or --COO--Rt--.
Rt is preferably an alkylene group having 1 to 5 carbon atoms, and more preferably a methylene group, an ethylene group, or a propylene group.

Rx ₁ to Rx ₃ each independently represent an alkyl group (straight-chain or branched), a cycloalkyl group (monocyclic or polycyclic), an alkenyl group (straight-chain or branched), or an aryl group (monocyclic or polycyclic).
Two of Rx ₁ to Rx ₃ may be bonded to form a monocyclic or polycyclic ring (eg, a monocyclic or polycyclic cycloalkyl group).
Preferred embodiments of the alkyl group, cycloalkyl group, alkenyl group and aryl group represented by Rx ₁ to Rx ₃ are the same as the groups represented by Rx ₁ to Rx ₃ in formulae (Y1) and (Y2).
The cycloalkyl group formed by combining two of _Rx1 to _Rx3 is preferably a monocyclic cycloalkyl group such as a cyclopentyl group or a cyclohexyl group, or a polycyclic cycloalkyl group such as a norbornyl group, a tricyclodecanyl group, a tetracyclododecanyl group, or an adamantyl group. Of these, a monocyclic cycloalkyl group having 5 to 6 carbon atoms or a polycyclic cycloalkyl group having 6 to 12 carbon atoms is preferable.
In the cycloalkyl group formed by combining two of _Rx1 to _Rx3 , for example, one of the methylene groups constituting the ring may be substituted with a heteroatom such as an oxygen atom or a sulfur atom, a group containing a heteroatom such as a -CO- group, a _-SO2- group, or a _-SO3- group, or a vinylidene group. Furthermore, in these cycloalkyl groups, one or more of the ethylene groups constituting the cycloalkane ring may be substituted with a vinylene group.
In the repeating unit represented by formula (AI), for example, _Rx1 is preferably a methyl group or an ethyl group, and _Rx2 and _Rx3 are bonded to form the above-mentioned cycloalkyl group.
The groups represented by _Rx1 to _Rx3 may have a substituent. Examples of the substituent include an alkyl group having 1 to 4 carbon atoms, a halogen atom, a hydroxyl group, an alkoxy group having 1 to 4 carbon atoms, a carboxy group, and an alkoxycarbonyl group having 2 to 6 carbon atoms.

The repeating unit represented by formula (AI) is preferably an acid-decomposable tertiary alkyl (meth)acrylate repeating unit (a repeating unit in which _Xa1 represents a hydrogen atom or a methyl group and T represents a single bond or -COO-Rt-).

Examples of repeating units having an acid-decomposable group include the repeating units described in paragraphs [0053] to [0057] of WO 2020/158467.

The specific resin may have, as the repeating unit having an acid-decomposable group, a repeating unit having an acid-decomposable group containing an unsaturated bond.
As the repeating unit having an acid-decomposable group containing an unsaturated bond, a repeating unit represented by formula (B) is preferred.

In formula (B), Xb represents a hydrogen atom, a halogen atom, or an alkyl group which may have a substituent. L represents a single bond or a divalent linking group which may have a substituent. Ry ₁ to Ry ₃ each independently represent a linear or branched alkyl group, a monocyclic or polycyclic cycloalkyl group, an alkenyl group, an alkynyl group, or a monocyclic or polycyclic aryl group. However, at least one of Ry ₁ to Ry ₃ represents an alkenyl group, an alkynyl group, a monocyclic or polycyclic cycloalkenyl group, or a monocyclic or polycyclic aryl group.
Two of Ry ₁ to Ry ₃ may be bonded to form a monocyclic or polycyclic ring (such as a monocyclic or polycyclic cycloalkyl group or cycloalkenyl group).

Xb represents a hydrogen atom, a halogen atom, or an alkyl group which may have a substituent.
The preferred embodiments of Xb are the same as those of _Xa1 in formula (AI).

L represents a single bond or a divalent linking group which may have a substituent.
Examples of the divalent linking group include a -Rt- group, a -CO- group, a -COO-Rt- group, a -COO-Rt-CO- group, a -Rt-CO- group, and a -O-Rt- group.
Rt represents an alkylene group, a cycloalkylene group, or an aromatic ring group, and is preferably an aromatic ring group. Rt may have a substituent, and examples of the substituent include a halogen atom, a hydroxyl group, and an alkoxy group.
L is preferably a -Rt- group, a -CO- group, a -COO-Rt-CO- group, or a -Rt-CO- group.

Ry ₁ to Ry ₃ each independently represent an alkyl group (linear or branched), a cycloalkyl group (monocyclic or polycyclic), an alkenyl group, an alkynyl group, a cycloalkenyl group (monocyclic or polycyclic), or an aryl group (monocyclic or polycyclic), provided that at least one of Ry ₁ to Ry ₃ represents an alkenyl group, an alkynyl group, a cycloalkenyl group (monocyclic or polycyclic), or an aryl group (monocyclic or polycyclic).
Two of Ry ₁ to Ry ₃ may be bonded to form a monocyclic or polycyclic ring (such as a monocyclic or polycyclic cycloalkyl group or cycloalkenyl group).
Preferred embodiments of the alkyl group, cycloalkyl group, alkenyl group and aryl group represented by Ry ₁ to Ry ₃ above are the same as the groups represented by Rx ₁ to Rx ₃ in formula (Y-1).
The alkynyl group represented by Ry ₁ to Ry ₃ is preferably an ethynyl group.
As the cycloalkenyl group represented by Ry ₁ to Ry ₃ , a structure containing a double bond in a part of a monocyclic cycloalkyl group such as a cyclopentyl group or a cyclohexyl group is preferable.
In the cycloalkyl group or cycloalkenyl group formed by combining two of _Ry1 to _Ry3 , for example, one of the methylene groups constituting the ring may be replaced with a heteroatom such as an oxygen atom or a sulfur atom, a group containing a heteroatom such as a -CO- group, an _-SO2- group or an _-SO3- group, a vinylidene group, or a combination thereof. Furthermore, in these cycloalkyl groups or cycloalkenyl groups, one or more of the ethylene groups constituting the cycloalkane ring or cycloalkene ring may be replaced with a vinylene group.
In the repeating unit represented by formula (B), for example, _Ry1 is a methyl group, an ethyl group, a vinyl group, an allyl group, or an aryl group, and _Ry2 and _Ry3 are bonded to form the above-mentioned cycloalkyl group or cycloalkenyl group.

When the groups represented by Ry ₁ to Ry ₃ have a substituent, the substituent is preferably an alkyl group having 1 to 4 carbon atoms, a halogen atom, a hydroxyl group, an alkoxy group having 1 to 4 carbon atoms, a carboxy group, or an alkoxycarbonyl group having 2 to 6 carbon atoms.

The repeating unit represented by formula (B) is preferably an acid-decomposable (meth)acrylic acid tertiary ester repeating unit (a repeating unit in which Xb represents a hydrogen atom or a methyl group and L represents a -CO- group), an acid-decomposable hydroxystyrene tertiary alkyl ether repeating unit (a repeating unit in which Xb represents a hydrogen atom or a methyl group and L represents a phenyl group), or an acid-decomposable styrene carboxylic acid tertiary ester repeating unit (a repeating unit in which Xb represents a hydrogen atom or a methyl group and L represents a -Ar-CO- group (Ar is an aromatic group)).

When the specific resin contains a repeating unit having an acid-decomposable group containing an unsaturated bond, the content is preferably 15 to 80 mol %, more preferably 20 to 70 mol %, and even more preferably 30 to 60 mol %, based on the total repeating units in the specific resin.

The content of the repeating units having an acid-decomposable group is preferably 15 mol% or more, more preferably 20 mol% or more, and even more preferably 30 mol% or more, based on the total repeating units in the specific resin. The upper limit is preferably 90 mol% or less, more preferably 80 mol% or less, even more preferably 70 mol% or less, and particularly preferably 60 mol% or less, based on the total repeating units in the specific resin.

The specific resin may contain at least one type of repeating unit selected from the group consisting of Group A below, and/or at least one type of repeating unit selected from the group consisting of Group B below.
Group A: A group consisting of the following repeating units (20) to (25).
(20) A repeating unit having an acid group, as described below (21) A repeating unit having neither an acid decomposable group nor an acid group, and having a fluorine atom, a bromine atom or an iodine atom, as described below (22) A repeating unit having a lactone group, a sultone group or a carbonate group, as described below (23) A repeating unit having a photoacid generating group, as described below (24) A repeating unit represented by formula (V-1) or the following formula (V-2), as described below (25) Group B of repeating units for reducing mobility of the main chain: a group consisting of the following repeating units (30) to (32).
(30) A repeating unit having at least one group selected from a lactone group, a sultone group, a carbonate group, a hydroxyl group, a cyano group, and an alkali-soluble group, as described below. (31) A repeating unit having an alicyclic hydrocarbon structure and not exhibiting acid decomposability, as described below. (32) A repeating unit represented by formula (III), as described below, which has neither a hydroxyl group nor a cyano group.

The specific resin preferably has an acid group, and preferably contains a repeating unit having an acid group. When the specific resin has an acid group, the interaction between the specific resin and the acid generated from the photoacid generator is superior. As a result, the diffusion of the acid is further suppressed, and the cross-sectional shape of the formed pattern can become more rectangular.

When the resist composition is used for EUV exposure, the specific resin preferably has at least one type of repeating unit selected from Group A above.
When the resist composition is used for EUV exposure, the specific resin also preferably contains a fluorine atom or an iodine atom.
When the resist composition is used for ArF exposure, the specific resin preferably has one type of repeating unit selected from Group B above.
When the resist composition is used for ArF exposure, it is also preferable that the specific resin contains neither fluorine atoms nor silicon atoms.
When the resist composition is used for ArF exposure, it is also preferable that the specific resin does not contain an aromatic group.

<Repeating Unit Having an Acid Group>
The specific resin may have a repeating unit having an acid group.
The acid dissociation constant of the acid group is preferably 13 or less, more preferably 10 or less, and the lower limit is preferably 3 or more, more preferably 5 or more.
The content of the acid group in the specific resin is not particularly limited, but is often 0.2 to 6.0 mmol/g. Among them, 0.8 to 6.0 mmol/g is preferable, 1.2 to 5.0 mmol/g is more preferable, and 1.6 to 4.0 mmol/g is even more preferable. When the content of the acid group is within the above range, development proceeds well, and the formed pattern shape and resolution are more excellent.
The acid group is preferably, for example, a carboxy group, a phenolic hydroxyl group, a fluorinated alcohol group (preferably a hexafluoroisopropanol group), a sulfonic acid group, a sulfonamide group, or an isopropanol group.
In the hexafluoroisopropanol group, one or more (preferably one or two) fluorine atoms may be substituted with a group other than a fluorine atom (such as an alkoxycarbonyl group).
The repeating unit having an acid group preferably has a structure different from that of a repeating unit having an acid-decomposable group and a repeating unit having a lactone group, a sultone group, or a carbonate group, which will be described later.
The repeating unit having an acid group may have a fluorine atom or an iodine atom.

The repeating unit having an acid group is preferably a repeating unit represented by the following formula (1):

In formula (1), A represents a hydrogen atom, an alkyl group, a cycloalkyl group, a halogen atom, or a cyano group.
R represents a halogen atom, an alkyl group, a cycloalkyl group, an aryl group, an alkenyl group, an aralkyl group, an alkoxy group, an alkylcarbonyloxy group, an alkylsulfonyloxy group, an alkyloxycarbonyl group, or an aryloxycarbonyl group. When there are multiple R, R may be the same or different, and may form a ring together. R is preferably a hydrogen atom.
a represents an integer of 1 to 3. b represents an integer of 0 to (5-a).

Examples of repeating units having an acid group include the repeating units described in paragraphs [0081] to [0086] of WO 2020/158467.

The content of repeating units having an acid group is preferably 10 mol% or more, and more preferably 15 mol% or more, based on the total repeating units in the specific resin. The upper limit is preferably 70 mol% or less, more preferably 65 mol% or less, and even more preferably 60 mol% or less, based on the total repeating units in the specific resin.

<Repeating Unit Having Neither an Acid-Decomposable Group nor an Acid Group and Having a Fluorine Atom, a Bromine Atom, or an Iodine Atom>
The specific resin may have a repeating unit (hereinafter also referred to as "unit X") that has neither an acid decomposable group nor an acid group and has a fluorine atom, a bromine atom or an iodine atom, which is different from the above-mentioned <repeating unit having an acid decomposable group> and <repeating unit having an acid group>. It is preferable that the unit X is different from other types of repeating units belonging to group A, such as the <repeating unit having a lactone group, a sultone group or a carbonate group> and the <repeating unit having a photoacid generating group> described below.

The repeating unit X is preferably a repeating unit represented by formula (C).

_L5 represents a single bond or -COO-. _R9 represents a hydrogen atom or an alkyl group which may have a fluorine atom or an iodine atom. _R10 represents a hydrogen atom, an alkyl group which may have a fluorine atom or an iodine atom, a cycloalkyl group which may have a fluorine atom or an iodine atom, an aryl group which may have a fluorine atom or an iodine atom, or a group which combines these.

Examples of the unit X include the repeating units described in paragraph [0093] of WO 2020/158467.

The content of unit X is preferably 0 mol% or more, more preferably 5 mol% or more, and even more preferably 10 mol% or more, based on all repeating units in the specific resin. The upper limit is preferably 50 mol% or less, more preferably 45 mol% or less, and even more preferably 40 mol% or less, based on all repeating units in the specific resin.

<Repeating Unit Having a Lactone Group, a Sultone Group, or a Carbonate Group>
The specific resin may have a repeating unit (hereinafter also referred to as "unit Y") having at least one type selected from the group consisting of a lactone group, a sultone group, and a carbonate group.
It is also preferred that the unit Y does not have a hydroxyl group or an acid group such as a hexafluoropropanol group.

The lactone group or sultone group may have a lactone structure or sultone structure. The lactone structure or sultone structure is preferably a 5- to 7-membered lactone structure or a 5- to 7-membered sultone structure. Among them, a 5- to 7-membered lactone structure having another ring structure condensed thereto in the form of a bicyclo structure or a spiro structure, or a 5- to 7-membered sultone structure having another ring structure condensed thereto in the form of a bicyclo structure or a spiro structure, is more preferred.
The specific resin preferably has a repeating unit having a lactone group or sultone group obtained by removing one or more hydrogen atoms from a ring member atom of a lactone structure represented by any one of the following formulae (LC1-1) to (LC1-21), or a sultone structure represented by any one of the following formulae (SL1-1) to (SL1-3), and the lactone group or sultone group may be directly bonded to the main chain. For example, the ring member atom of the lactone group or sultone group may constitute the main chain of the specific resin.

The lactone structure or sultone structure may have a substituent (Rb ₂ ). Preferred substituents (Rb ₂ ) include an alkyl group having 1 to 8 carbon atoms, a cycloalkyl group having 4 to 7 carbon atoms, an alkoxy group having 1 to 8 carbon atoms, an alkoxycarbonyl group having 1 to 8 carbon atoms, a carboxy group, a halogen atom, a cyano group, and an acid-decomposable group. n2 represents an integer of 0 to 4. When n2 is 2 or more, the multiple Rb _2s may be different from each other, or the multiple Rb _2s may be bonded to each other to form a ring.

An example of a repeating unit having a group containing a lactone structure represented by any one of formulas (LC1-1) to (LC1-21) or a sultone structure represented by any one of formulas (SL1-1) to (SL1-3) is a repeating unit represented by the following formula (AI).

In formula (AI), Rb ₀ represents a hydrogen atom, a halogen atom, or an alkyl group having 1 to 4 carbon atoms. Preferred substituents that the alkyl group of Rb ₀ may have include a hydroxyl group and a halogen atom. Examples of the halogen atom include a fluorine atom, a chlorine atom, a bromine atom, and an iodine atom.
_Rb0 is preferably a hydrogen atom or a methyl group.
Ab represents a single bond, an alkylene group, a divalent linking group having a monocyclic or polycyclic alicyclic hydrocarbon structure, an ether group, an ester group, a carbonyl group, a carboxy group, or a divalent linking group combining these. Ab is preferably a single bond or a linking group represented by -Ab ₁ -CO ₂ -. Ab ₁ is a linear or branched alkylene group, or a monocyclic or polycyclic cycloalkylene group, and is preferably a methylene group, an ethylene group, a cyclohexylene group, an adamantylene group, or a norbornylene group.
V represents a group obtained by removing one hydrogen atom from a ring member atom of a lactone structure represented by any of formulas (LC1-1) to (LC1-21), or a group obtained by removing one hydrogen atom from a ring member atom of a sultone structure represented by any of formulas (SL1-1) to (SL1-3).

When optical isomers exist in the repeating unit having a lactone group or a sultone group, any optical isomer may be used. In addition, one optical isomer may be used alone, or multiple optical isomers may be used in combination. When one optical isomer is mainly used, the optical purity (ee) is preferably 90 or more, and more preferably 95 or more.

The carbonate group is preferably a cyclic carbonate ester group.

The repeating unit having a cyclic carbonate group is preferably a repeating unit represented by the following formula (A-1).

In formula (A-1), R _A ¹ represents a hydrogen atom, a halogen atom, or a monovalent organic group (preferably a methyl group). n represents an integer of 0 or more. R _A ² represents a substituent. When n is 2 or more, a plurality of R _A ² may be the same or different. A represents a single bond or a divalent linking group. As the divalent linking group, an alkylene group, a divalent linking group having a monocyclic or polycyclic alicyclic hydrocarbon structure, an ether group, an ester group, a carbonyl group, a carboxy group, or a divalent linking group formed by combining these is preferable. Z represents an atomic group forming a monocyclic or polycyclic ring together with the group represented by -O-CO-O- in the formula.

Examples of the unit Y are shown below: In the formula, Rx represents a hydrogen atom, _-CH3 , _-CH2OH or _CF3 .

The content of the unit Y is preferably 1 mol% or more, and more preferably 10 mol% or more, based on all repeating units in the specific resin. The upper limit is preferably 85 mol% or less, more preferably 80 mol% or less, even more preferably 70 mol% or less, and particularly preferably 60 mol% or less, based on all repeating units in the specific resin.

<Repeating Unit Having Photoacid Generating Group>
The specific resin may contain, as a repeating unit other than the above, a repeating unit having a group that generates an acid upon irradiation with actinic rays or radiation (hereinafter, also referred to as a "photoacid generating group").
An example of the repeating unit having a photoacid generating group is a repeating unit represented by formula (4).

R ⁴¹ represents a hydrogen atom or a methyl group. L ⁴¹ represents a single bond or a divalent linking group. L ⁴² represents a divalent linking group. R ⁴⁰ represents a structural moiety that is decomposed by irradiation with actinic rays or radiation to generate an acid in a side chain.
Examples of the repeating unit having a photoacid generating group are shown below.

Examples of repeating units having a photoacid generating group include the repeating units described in paragraphs [0094] to [0105] of JP2014-041327A and the repeating unit described in paragraph [0094] of WO2018/193954.

The content of the repeating unit having a photoacid generating group is preferably 1 mol% or more, and more preferably 5 mol% or more, based on the total repeating units in the specific resin. The upper limit is preferably 40 mol% or less, more preferably 35 mol% or less, and even more preferably 30 mol% or less, based on the total repeating units in the specific resin.

<Repeating unit represented by formula (V-1) or the following formula (V-2)>
The specific resin may have a repeating unit represented by the following formula (V-1) or the following formula (V-2).
The repeating units represented by the following formulae (V-1) and (V-2) are preferably repeating units different from the repeating units described above.

In the formula, _R6 and _R7 each independently represent a hydrogen atom, a hydroxyl group, an alkyl group, an alkoxy group, an acyloxy group, a cyano group, a nitro group, an amino group, a halogen atom, an ester group (-OCOR or -COOR: R is an alkyl group or a fluorinated alkyl group having 1 to 6 carbon atoms), or a carboxy group. As the alkyl group, a linear, branched or cyclic alkyl group having 1 to 10 carbon atoms is preferable.
n3 represents an integer of 0 to 6.
n4 represents an integer of 0 to 4.
_X4 is a methylene group, an oxygen atom, or a sulfur atom.
Examples of the repeating unit represented by formula (V-1) or (V-2) include the repeating units described in paragraph [0100] of WO 2018/193954.

<Repeating units for reducing main chain mobility>
The specific resin preferably has a high glass transition temperature (Tg) in order to suppress excessive diffusion of the generated acid or pattern collapse during development. The Tg is preferably higher than 90° C., more preferably higher than 100° C., even more preferably higher than 110° C., and particularly preferably 125° C. or higher. The upper limit is preferably 400° C. or lower, more preferably 350° C. or lower, in order to provide an excellent dissolution rate in the developer.
In this specification, the Tg of a polymer such as a specific resin is calculated by the following method. First, the Tg of a homopolymer consisting of only each repeating unit contained in the polymer is calculated by the Bicerano method. Next, the mass ratio (%) of each repeating unit to the total repeating units in the polymer is calculated. Next, the Tg at each mass ratio is calculated using the Fox formula (described in Materials Letters 62 (2008) 3152, etc.), and these are summed up to obtain the Tg (°C) of the polymer.
The Bicerano method is described in Prediction of Polymer Properties, Marcel Dekker Inc., New York (1993). The calculation of Tg by the Bicerano method can be performed using polymer property estimation software MDL Polymer (MDL Information Systems, Inc.).

In order to increase the Tg of the specific resin (preferably to make the Tg exceed 90° C.), it is preferable to reduce the mobility of the main chain of the specific resin. Methods for reducing the mobility of the main chain of the specific resin include the following methods (a) to (e).
(a) introduction of a bulky substituent into the main chain; (b) introduction of a plurality of substituents into the main chain; (c) introduction of a substituent inducing an interaction between specific resins into the vicinity of the main chain; (d) formation of a main chain with a cyclic structure; (e) linking of a cyclic structure to the main chain. Note that the specific resin preferably has a repeating unit showing a homopolymer Tg of 130° C. or higher.

One example of a specific means for achieving the above is the method of introducing the repeating units described in paragraphs [0107] to [0133] of WO 2018/193954.

<Repeating Unit Having at Least One Group Selected from Lactone Group, Sultone Group, Carbonate Group, Hydroxyl Group, Cyano Group, and Alkali-Soluble Group>
The specific resin may have a repeating unit having at least one type of group selected from a lactone group, a sultone group, a carbonate group, a hydroxyl group, a cyano group, and an alkali-soluble group.
Examples of the repeating unit having a lactone group, a sultone group, or a carbonate group contained in the specific resin include the repeating units described above in <Repeat units having a lactone group, a sultone group, or a carbonate group>. The preferred content is also as described above in <Repeat units having a lactone group, a sultone group, or a carbonate group>.

The specific resin may have a repeating unit having a hydroxyl group or a cyano group, in order to further improve the adhesion to the substrate and the affinity for the developer.
The repeating unit having a hydroxyl group or a cyano group is preferably a repeating unit having an alicyclic hydrocarbon structure substituted with a hydroxyl group or a cyano group.
The repeating unit having a hydroxyl group or a cyano group preferably does not have an acid-decomposable group. Examples of the repeating unit having a hydroxyl group or a cyano group include those described in paragraphs [0081] to [0084] of JP2014-098921A.

The specific resin may have a repeating unit having an alkali-soluble group.
Examples of the alkali-soluble group include a carboxy group, a sulfonamide group, a sulfonylimide group, a bissulfonylimide group, and an aliphatic alcohol group (e.g., a hexafluoroisopropanol group) in which the α-position is substituted with an electron-withdrawing group, and the carboxy group is preferred. The specific resin contains a repeating unit having an alkali-soluble group, thereby increasing the resolution in contact hole applications. Examples of the repeating unit having an alkali-soluble group include those described in paragraphs [0085] and [0086] of JP2014-098921A.

<Repeating Unit Having an Alicyclic Hydrocarbon Structure and Not Showing Acid Decomposability>
The specific resin may have an alicyclic hydrocarbon structure and a repeating unit that does not exhibit acid decomposability. This can reduce elution of low molecular weight components from the resist film into the immersion liquid during immersion exposure. Examples of repeating units that have an alicyclic hydrocarbon structure and do not exhibit acid decomposability include repeating units derived from 1-adamantyl (meth)acrylate, diamantyl (meth)acrylate, tricyclodecanyl (meth)acrylate, or cyclohexyl (meth)acrylate.

<Repeating unit represented by formula (III) having neither a hydroxyl group nor a cyano group>
The specific resin may have a repeating unit represented by formula (III) that has neither a hydroxyl group nor a cyano group.

In formula (III), _R5 represents a hydrocarbon group having at least one cyclic structure and having neither a hydroxyl group nor a cyano group.
Ra represents a hydrogen atom, an alkyl group or a -CH ₂ -O-Ra ₂ group, where Ra ₂ represents a hydrogen atom, an alkyl group or an acyl group.
Examples of the repeating unit represented by formula (III) that does not have either a hydroxyl group or a cyano group include the repeating units described in paragraphs [0087] to [0094] of JP2014-098921A.

<Other repeating units>
The specific resin may have repeating units other than the repeating units described above.
For example, the specific resin may have a repeating unit selected from the group consisting of a repeating unit having an oxathiane ring group, a repeating unit having an oxazolone ring group, a repeating unit having a dioxane ring group, and a repeating unit having a hydantoin ring group.

In addition to the repeating structural units described above, the specific resin may have various repeating structural units for the purpose of adjusting dry etching resistance, suitability for standard developing solutions, substrate adhesion, resist profile, resolution, heat resistance, sensitivity, etc.

The specific resin can be synthesized according to a conventional method (for example, radical polymerization).
The weight average molecular weight of the specific resin, as calculated as polystyrene by the GPC method, is preferably 30,000 or less, more preferably 1,000 to 30,000, even more preferably 3,000 to 30,000, and particularly preferably 5,000 to 15,000.
The polydispersity index (PDI) of the specific resin is preferably from 1 to 5, more preferably from 1 to 3, even more preferably from 1.2 to 3.0, and particularly preferably from 1.2 to 2.0. The smaller the polydispersity index, the better the resolution and resist shape, and furthermore, the smoother the sidewalls of the resist pattern are, and the better the roughness is.

The content of the specific resin is preferably from 40.0 to 99.9 mass %, and more preferably from 60.0 to 90.0 mass %, based on the total solid content of the resist composition.
The specific resin may be used alone or in combination of two or more kinds.

[Photoacid generator]
The resist composition contains a photoacid generator which is composed of anions and cations and generates an acid upon exposure to actinic rays or radiation.
The photoacid generator is a compound in which the acid dissociation constant A (pKa(A)) of the acidic compound obtained by replacing the cation with a proton is smaller than both the acid dissociation constant B (pKa(B)) of the acidic compound obtained by replacing a first cation of a first acid diffusion controller described below with a proton, and the acid dissociation constant C (pKa(C)) of the acidic compound obtained by replacing a second cation of a second acid diffusion controller described below with a proton. In other words, the acid dissociation constant A is smaller than the acid dissociation constant B, and the acid dissociation constant A is smaller than the acid dissociation constant C.
The photoacid generator may be in the form of a low molecular weight compound, or may be incorporated into a part of a polymer (e.g., the above-mentioned specific resin).Furthermore, the form of a low molecular weight compound and the form of being incorporated into a part of a polymer may be used in combination.
When the photoacid generator is in the form of a low molecular weight compound, the molecular weight of the photoacid generator is preferably 3000 or less, more preferably 2000 or less, and even more preferably 1000 or less. There is no particular lower limit, but a molecular weight of 100 or more is preferable.
The photoacid generator is preferably in the form of a low molecular weight compound.

Examples of photoacid generators include compounds (onium salts) represented by "M ⁺ X ^- ", and are preferably compounds that generate an organic acid upon exposure to light.
Examples of the organic acid include sulfonic acids (aliphatic sulfonic acids, aromatic sulfonic acids, camphorsulfonic acids, etc.), carboxylic acids (aliphatic carboxylic acids, aromatic carboxylic acids, aralkyl carboxylic acids, etc.), carbonylsulfonylimide acids, bis(alkylsulfonyl)imide acids, and tris(alkylsulfonyl)methide acids.

In the compound represented by "M ⁺ X ^- ", M ⁺ represents a cation.
The cation is preferably an organic cation.
The organic cation is not particularly limited, and the valence of the organic cation may be monovalent or divalent or higher.
Among them, the organic cation is preferably a cation represented by formula (ZaI) (hereinafter also referred to as "cation (ZaI)") or a cation represented by formula (ZaII) (hereinafter also referred to as "cation (ZaII)").

In the above formula (ZaI), R ²⁰¹ , R ²⁰² and R ²⁰³ each independently represent an organic group.
The number of carbon atoms in the organic group is preferably 1 to 30, and more preferably 1 to 20. Two of R ²⁰¹ to R ²⁰³ may be bonded to form a ring structure, and the ring may contain an oxygen atom, a sulfur atom, an ester group, an amide group, or a carbonyl group. Examples of the group formed by bonding two of R ²⁰¹ to R ²⁰³ include an alkylene group (e.g., a butylene group and a pentylene group) and -CH ₂ -CH ₂ -O-CH ₂ -CH ₂ -.

Suitable embodiments of the organic cation in formula (ZaI) include cation (ZaI-1), cation (ZaI-2), cation (ZaI-3b), and cation (ZaI-4b), which will be described later.

First, the cation (ZaI-1) will be described.
The cation (ZaI-1) is an arylsulfonium cation in which at least one of R ²⁰¹ to R ²⁰³ in the above formula (ZaI) is an aryl group.
In the arylsulfonium cation, all of R ₂₀₁ to R ₂₀₃ may be aryl groups, or some of R ₂₀₁ to R ₂₀₃ may be aryl groups, with the remainder being alkyl groups or cycloalkyl groups.
One of R ₂₀₁ to R ₂₀₃ may be an aryl group, and the remaining two of R ²⁰¹ to R ²⁰³ may be bonded to form a ring structure, which may contain an oxygen atom, a sulfur atom, an ester group, an amide group, or a carbonyl group in the ring. Examples of the group formed by bonding two of R ²⁰¹ to R ²⁰³ include alkylene groups in which one or more methylene groups may be substituted with oxygen atoms, sulfur atoms, ester groups, amide groups, and/or carbonyl groups (e.g., butylene group, pentylene group, and -CH ₂ -CH ₂ -O-CH ₂ -CH ₂ -).
Arylsulfonium cations include triarylsulfonium cations, diarylalkylsulfonium cations, aryldialkylsulfonium cations, diarylcycloalkylsulfonium cations, and aryldicycloalkylsulfonium cations.

The aryl group contained in the arylsulfonium cation is preferably a phenyl group or a naphthyl group, more preferably a phenyl group.The aryl group may be an aryl group having a heterocyclic structure with an oxygen atom, a nitrogen atom, or a sulfur atom.The heterocyclic structure may include a pyrrole residue, a furan residue, a thiophene residue, an indole residue, a benzofuran residue, and a benzothiophene residue.When the arylsulfonium cation has two or more aryl groups, the two or more aryl groups may be the same or different.
Examples of the alkyl group or cycloalkyl group that the arylsulfonium cation may have include a linear alkyl group having 1 to 15 carbon atoms, a branched alkyl group having 3 to 15 carbon atoms, and a cycloalkyl group having 3 to 15 carbon atoms, and a methyl group, an ethyl group, a propyl group, an n-butyl group, a sec-butyl group, a t-butyl group, a cyclopropyl group, a cyclobutyl group, or a cyclohexyl group is preferable.

Examples of the substituent that the aryl group, alkyl group, and cycloalkyl group of R ²⁰¹ to R ²⁰³ may have include an alkyl group (e.g., having 1 to 15 carbon atoms), a cycloalkyl group (e.g., having 3 to 15 carbon atoms), an aryl group (e.g., having 6 to 14 carbon atoms), an alkoxy group (e.g., having 1 to 15 carbon atoms), a cycloalkylalkoxy group (e.g., having 1 to 15 carbon atoms), a halogen atom (e.g., fluorine and iodine), a hydroxyl group, a carboxy group, an ester group, a sulfinyl group, a sulfonyl group, an alkylthio group, and a phenylthio group.
The above-mentioned substituent may further have a substituent, and it is also preferable that the above-mentioned alkyl group has a halogen atom as a substituent to form a halogenated alkyl group such as a trifluoromethyl group.
The above-mentioned substituent may be an acid-decomposable group. The definition and preferred embodiments of the acid-decomposable group are as described above.

Next, the cation (ZaI-2) will be described.
Cation (ZaI-2) is a cation in which R ²⁰¹ to R ²⁰³ in formula (ZaI) each independently represent an organic group not having an aromatic ring. The aromatic ring also includes an aromatic ring containing a heteroatom.
The organic group not having an aromatic ring preferably has 1 to 30 carbon atoms, and more preferably has 1 to 20 carbon atoms.
R ²⁰¹ to R ²⁰³ are each independently preferably an alkyl group, a cycloalkyl group, an allyl group, or a vinyl group, more preferably a linear or branched 2-oxoalkyl group, a 2-oxocycloalkyl group, or an alkoxycarbonylmethyl group, and still more preferably a linear or branched 2-oxoalkyl group.

Examples of the alkyl group and cycloalkyl group of R ²⁰¹ to R ²⁰³ include linear alkyl groups having 1 to 10 carbon atoms and branched alkyl groups having 3 to 10 carbon atoms (e.g., methyl, ethyl, propyl, butyl, and pentyl groups), as well as cycloalkyl groups having 3 to 10 carbon atoms (e.g., cyclopentyl, cyclohexyl, and norbornyl groups).
R ²⁰¹ to R ²⁰³ may be further substituted with a halogen atom, an alkoxy group (eg, having 1 to 5 carbon atoms), a hydroxyl group, a cyano group, or a nitro group.
It is also preferred that the substituents of R ²⁰¹ to R ²⁰³ each independently form an acid-decomposable group through any combination of the substituents.

Next, the cation (ZaI-3b) will be described.
The cation (ZaI-3b) is a cation represented by the following formula (ZaI-3b).

In formula (ZaI-3b), R _1c to R _5c each independently represent a hydrogen atom, an alkyl group, a cycloalkyl group, an aryl group, an alkoxy group, an aryloxy group, an alkoxycarbonyl group, an alkylcarbonyloxy group, a cycloalkylcarbonyloxy group, a halogen atom, a hydroxyl group, a nitro group, an alkylthio group, or an arylthio group.
R _6c and R _7c each independently represent a hydrogen atom, an alkyl group (eg, a t-butyl group), a cycloalkyl group, a halogen atom, a cyano group, or an aryl group.
R _x and R _y each independently represent an alkyl group, a cycloalkyl group, a 2-oxoalkyl group, a 2-oxocycloalkyl group, an alkoxycarbonylalkyl group, an allyl group, or a vinyl group.
The substituents of R _1c to R _7c and R _x and R _y may be acid-decomposable groups.

Any two or more of R _1c to R _5c , and R _x and R _y may be bonded to each other to form a ring, and each of these rings may independently have an oxygen atom, a sulfur atom, an ester group, an amide group, or a carbon-carbon double bond. R _5c and R _6c , and R _5c and R _x may be bonded to each other to form a ring, and each of these rings may independently have a carbon-carbon double bond. R _6c and R _7c may be bonded to each other to form a ring.
In addition, the formed ring having an oxygen atom or the like means, for example, that two bondable groups (e.g., _Rx and _Ry ) are bonded to each other to form an alkylene group, and a methylene group in such an alkylene group is substituted with an oxygen atom or the like.
Examples of the ring include an aromatic or non-aromatic hydrocarbon ring, an aromatic or non-aromatic heterocyclic ring, and a polycyclic condensed ring formed by combining two or more of these rings. The ring is preferably a 3- to 10-membered ring, more preferably a 4- to 8-membered ring, and even more preferably a 5- or 6-membered ring.

Examples of the group formed by combining any two or more of R _1c to R _5c , R _6c and R _7c , and R _x and R _y include a butylene group, a pentylene group, and -CH ₂ -CH ₂ -O-CH _{2 -CH 2} _- .
The groups formed by combining _R5c and _R6c , and _R5c and _Rx are preferably a single bond or an alkylene group. Examples of the alkylene group include a methylene group and an ethylene group.

Next, the cation (ZaI-4b) will be described.
The cation (ZaI-4b) is a cation represented by the following formula (ZaI-4b).

In formula (ZaI-4b), l represents an integer of 0 to 2; r represents an integer of 0 to 8.
R ₁₃ represents a hydrogen atom, a halogen atom (e.g., a fluorine atom or an iodine atom), a hydroxyl group, an alkyl group, a halogenated alkyl group, an alkoxy group, a carboxy group, an alkoxycarbonyl group, or a group containing a cycloalkyl group (which may be a cycloalkyl group itself or a group containing a cycloalkyl group as a part). These groups may have a substituent.
R ₁₄ represents a hydroxyl group, a halogen atom (e.g., a fluorine atom and an iodine atom, etc.), an alkyl group, a halogenated alkyl group, an alkoxy group, an alkoxycarbonyl group, an alkylcarbonyl group, an alkylsulfonyl group, a cycloalkylsulfonyl group, or a group containing a cycloalkyl group (which may be a cycloalkyl group itself or a group containing a cycloalkyl group as a part). These groups may have a substituent. When there are multiple R _14s , the multiple R _14s may be the same or different.
Each R ₁₅ independently represents an alkyl group, a cycloalkyl group, or a naphthyl group. Two R ₁₅ may be bonded to each other to form a ring. When two R ₁₅ are bonded to each other to form a ring, the ring structure may contain a heteroatom such as an oxygen atom or a nitrogen atom.
In one embodiment, it is preferred that two R ₁₅ are alkylene groups and are bonded to each other to form a ring structure.
The alkyl group, the cycloalkyl group, the naphthyl group, and the ring formed by bonding two R ₁₅ together may have a substituent.

In formula (ZaI-4b), the alkyl groups of R ₁₃ , R ₁₄ and R ₁₅ may be either linear or branched. The number of carbon atoms in the alkyl group is preferably 1 to 10. The alkyl group is preferably a methyl group, an ethyl group, an n-butyl group or a t-butyl group.
The groups represented by R ₁₃ to R ₁₅ may be acid-decomposable groups.

Next, formula (ZaII) will be described.
In formula (ZaII), R ²⁰⁴ and R ²⁰⁵ each independently represent an aryl group, an alkyl group or a cycloalkyl group.
The aryl group of R ²⁰⁴ and R ²⁰⁵ is preferably a phenyl group or a naphthyl group, more preferably a phenyl group. The aryl group of R ²⁰⁴ and R ²⁰⁵ may be an aryl group having a heterocycle with an oxygen atom, a nitrogen atom, or a sulfur atom. Examples of the skeleton of the aryl group having a heterocycle include pyrrole, furan, thiophene, indole, benzofuran, and benzothiophene.
The alkyl group and cycloalkyl group of R ²⁰⁴ and R ²⁰⁵ are preferably a linear alkyl group having 1 to 10 carbon atoms or a branched alkyl group having 3 to 10 carbon atoms (e.g., a methyl group, an ethyl group, a propyl group, a butyl group, or a pentyl group), or a cycloalkyl group having 3 to 10 carbon atoms (e.g., a cyclopentyl group, a cyclohexyl group, or a norbornyl group).

The aryl group, alkyl group, and cycloalkyl group of R ²⁰⁴ and R ²⁰⁵ may each independently have a substituent. Examples of the substituent that the aryl group, alkyl group, and cycloalkyl group of R ²⁰⁴ and R ²⁰⁵ may have include an alkyl group (e.g., having 1 to 15 carbon atoms), a cycloalkyl group (e.g., having 3 to 15 carbon atoms), an aryl group (e.g., having 6 to 15 carbon atoms), an alkoxy group (e.g., having 1 to 15 carbon atoms), a halogen atom, a hydroxyl group, and a phenylthio group. The substituent of R ²⁰⁴ and R ²⁰⁵ may be an acid-decomposable group.

Specific examples of organic cations are shown below, but the present invention is not limited to these.

In "M ⁺ X ^- ", X ^- is an organic anion having an acid dissociation constant A (pKa(A)) of an acidic compound A bonded to a proton that is smaller than the acid dissociation constant of an acidic compound obtained by replacing a cation of an acid diffusion controller described later with a proton.
The acid dissociation constant A is not particularly limited as long as it satisfies the above requirements, but is preferably −10.00 to 4.00, more preferably −8.00 to 2.00, and even more preferably −8.00 to 0.00.

The anion is preferably an organic anion.
The organic anion is not particularly limited, and examples thereof include monovalent or divalent or higher organic anions.
As the organic anion, anions having a significantly low ability to cause a nucleophilic reaction are preferred, and non-nucleophilic anions are more preferred.

Examples of non-nucleophilic anions include sulfonate anions (aliphatic sulfonate anions, aromatic sulfonate anions, camphorsulfonate anions, etc.), carboxylate anions (aliphatic carboxylate anions, aromatic carboxylate anions, aralkyl carboxylate anions, etc.), sulfonylimide anions, bis(alkylsulfonyl)imide anions, and tris(alkylsulfonyl)methide anions.

The aliphatic moiety in the aliphatic sulfonate anion and the aliphatic carboxylate anion may be any of a linear or branched alkyl group and a cycloalkyl group, and is preferably a linear or branched alkyl group having 1 to 30 carbon atoms, or a cycloalkyl group having 3 to 30 carbon atoms.
The alkyl group may be, for example, a fluoroalkyl group (which may have a substituent other than a fluorine atom, or may be a perfluoroalkyl group).

The aryl group in the aromatic sulfonate anion and aromatic carboxylate anion is preferably an aryl group having 6 to 14 carbon atoms, such as a phenyl group, a tolyl group, and a naphthyl group.

The alkyl group, cycloalkyl group, and aryl group listed above may have a substituent. The substituent is not particularly limited, but examples include a nitro group, a halogen atom such as a fluorine atom or a chlorine atom, a carboxy group, a hydroxyl group, an amino group, a cyano group, an alkoxy group (preferably having 1 to 15 carbon atoms), an alkyl group (preferably having 1 to 10 carbon atoms), a cycloalkyl group (preferably having 3 to 15 carbon atoms), an aryl group (preferably having 6 to 14 carbon atoms), an alkoxycarbonyl group (preferably having 2 to 7 carbon atoms), an acyl group (preferably having 2 to 12 carbon atoms), an alkoxycarbonyloxy group (preferably having 2 to 7 carbon atoms), an alkylthio group (preferably having 1 to 15 carbon atoms), an alkylsulfonyl group (preferably having 1 to 15 carbon atoms), an alkyliminosulfonyl group (preferably having 1 to 15 carbon atoms), and an aryloxysulfonyl group (preferably having 6 to 20 carbon atoms).

The aralkyl group in the aralkyl carboxylate anion is preferably an aralkyl group having 7 to 14 carbon atoms.
Examples of the aralkyl group having 7 to 14 carbon atoms include a benzyl group, a phenethyl group, a naphthylmethyl group, a naphthylethyl group, and a naphthylbutyl group.

An example of a sulfonylimide anion is the saccharin anion.

The alkyl group in the bis(alkylsulfonyl)imide anion and the tris(alkylsulfonyl)methide anion is preferably an alkyl group having 1 to 5 carbon atoms. Substituents for these alkyl groups include a halogen atom, an alkyl group substituted with a halogen atom, an alkoxy group, an alkylthio group, an alkyloxysulfonyl group, an aryloxysulfonyl group, and a cycloalkylaryloxysulfonyl group, and a fluorine atom or an alkyl group substituted with a fluorine atom is preferred.
In addition, the alkyl groups in the bis(alkylsulfonyl)imide anion may be bonded to each other to form a ring structure, which increases the acid strength.

Other non-nucleophilic anions include, for example, phosphorus fluorides (eg, PF ₆ ⁻ ), boron fluorides (eg, BF ₄ ⁻ ), and antimony fluorides (eg, SbF ₆ ⁻ ).

Preferred non-nucleophilic anions are aliphatic sulfonate anions in which at least the α-position of the sulfonic acid is substituted with a fluorine atom, aromatic sulfonate anions substituted with a fluorine atom or a group having a fluorine atom, bis(alkylsulfonyl)imide anions in which an alkyl group is substituted with a fluorine atom, or tris(alkylsulfonyl)methide anions in which an alkyl group is substituted with a fluorine atom. Among these, perfluoroaliphatic sulfonate anions (preferably having 4 to 8 carbon atoms) or benzenesulfonate anions having fluorine atoms are more preferable, and nonafluorobutanesulfonate anions, perfluorooctanesulfonate anions, pentafluorobenzenesulfonate anions, or 3,5-bis(trifluoromethyl)benzenesulfonate anions are even more preferable.

As a non-nucleophilic anion, an anion represented by the following formula (AN2) is preferred.

In formula (AN2), o represents an integer from 1 to 3. p represents an integer from 0 to 10. q represents an integer from 0 to 10.

Each Xf independently represents a hydrogen atom, a fluorine atom, an alkyl group substituted with at least one fluorine atom, or an organic group having no fluorine atom. The number of carbon atoms in the alkyl group is preferably 1 to 10, more preferably 1 to 4. The alkyl group substituted with at least one fluorine atom is preferably a perfluoroalkyl group.
A plurality of Xf's may be the same or different.
Xf is preferably a fluorine atom or a perfluoroalkyl group having 1 to 4 carbon atoms, and more preferably a fluorine atom or CF _3. Of these, it is preferable that both Xf are fluorine atoms.

^R4 and ^R5 each independently represent a hydrogen atom, a fluorine atom, an alkyl group, or an alkyl group substituted with at least one fluorine atom. When a plurality of ^R4s and ^R5s are present, ^R4s and ^R5s may be the same or different.
The alkyl group preferably has a carbon number of 1 to 4. The alkyl group may have a substituent.
^R4 and ^R5 are preferably a hydrogen atom.

L represents a divalent linking group.
When a plurality of L's are present, each L may be the same or different.
Examples of the divalent linking group include -CO-, -O-, -S-, -SO-, -SO ₂ -, -CONH-, and hydrocarbon groups having 1 to 17 carbon atoms (e.g., alkylene groups, cycloalkylene groups, or alkenylene groups), as well as groups combining two or more of these.
The hydrocarbon group may have a substituent. Examples of the substituent include a halogen atom, a hydroxyl group, a carboxy group, an alkyl group having 1 to 7 carbon atoms, an alkoxy group having 1 to 5 carbon atoms, an acyl group having 1 to 5 carbon atoms, an alkyloxycarbonyl group having 1 to 5 carbon atoms, and an aryl group having 6 to 8 carbon atoms. In addition, one or more of the methylene groups constituting the cycloalkylene group may be substituted with -O-, -S-, or -CO-.
Among these, the divalent linking group is preferably --O--, --CO--, an alkylene group, or a cycloalkylene group.

(L) _q is preferably, for example, a group represented by formula (AN2-1).
* ^a- ( _Rt1 ) _x - _Q1 -(( _Rt2 ) _y - _Q2 ) _z- * ^b formula (AN2-1)
In formula (AN2-1), * ^a represents the bonding position to C(R ⁴ )(R ⁵ ) in formula (AN2), and * ^b represents the bonding position to W in formula (AN2).
x, y, and z each independently represent an integer of 0 to 10, preferably 0 to 3, and more preferably 1 or 2.
_Rt1 and _Rt2 each independently represent a divalent hydrocarbon group.
Examples of the hydrocarbon group include an alkylene group (preferably having 1 to 7 carbon atoms), a cycloalkylene group (preferably having 3 to 17 carbon atoms), and an alkenylene group (preferably having 2 to 8 carbon atoms). The hydrocarbon group may have a substituent, and a methylene group constituting the cycloalkylene group may be substituted with -O-, -CO-, -S-, or -SO ₂ -. The cycloalkylene group may be either monocyclic or polycyclic.
Q ₁ represents —COO—, —CO—, —O—, —O—CO—O—, —S—, —CONH—, —SO— or —SO ₂ —, and is preferably —COO—, —CO— or —O—.
_Q2 represents a single bond when y is 0, and represents a single bond or a divalent linking group mentioned for _Q1 when y is an integer of 1 or more. _Q2 is preferably a single bond, -COO-, -CO- or -O-.
When a plurality of Rt ₁ , Rt ₂ and Q ₂ are present, the plurality of Rt ₁ , Rt ₂ and Q ₂ may be the same or different.

W represents an organic group containing a cyclic structure, and is preferably a cyclic organic group.
Examples of the cyclic organic group include an alicyclic group, an aryl group, and a heterocyclic group.
The alicyclic group may be either a monocyclic or polycyclic group. Examples of the monocyclic alicyclic group include monocyclic cycloalkyl groups such as a cyclopentyl group, a cyclohexyl group, and a cyclooctyl group. Examples of the polycyclic alicyclic group include polycyclic cycloalkyl groups such as a norbornyl group, a tricyclodecanyl group, a tetracyclodecanyl group, a tetracyclododecanyl group, a decahydronaphthyl group, and an adamantyl group.
Among these, alicyclic groups having a bulky structure having 7 or more carbon atoms, such as a norbornyl group, a tricyclodecanyl group, a tetracyclodecanyl group, a tetracyclododecanyl group, and an adamantyl group, are preferred.
The aryl group may be either a monocyclic or polycyclic group, and examples of the aryl group include a phenyl group, a naphthyl group, a phenanthryl group, and an anthryl group.
The heterocyclic group may be either a single ring or a polycyclic ring. In particular, when the heterocyclic group is a polycyclic ring, the diffusion of the acid can be more suppressed. The heterocyclic group may have aromaticity or may not have aromaticity. Examples of the heterocyclic ring having aromaticity include a furan ring, a thiophene ring, a benzofuran ring, a benzothiophene ring, a dibenzofuran ring, a dibenzothiophene ring, and a pyridine ring. Examples of the heterocyclic ring having no aromaticity include a tetrahydropyran ring, a lactone ring, a sultone ring, and a decahydroisoquinoline ring.

The cyclic organic group may have a substituent. Examples of the substituent include an alkyl group (which may be either linear or branched, and preferably has 1 to 12 carbon atoms), a cycloalkyl group (which may be either monocyclic, polycyclic, or spirocyclic, and preferably has 3 to 20 carbon atoms), an aryl group (which preferably has 6 to 14 carbon atoms), a hydroxyl group, an alkoxy group, an ester group, an amide group, a urethane group, a ureido group, a thioether group, a sulfonamide group, and a sulfonate ester group. The carbon that constitutes the cyclic organic group (the carbon that contributes to the ring formation) may be a carbonyl carbon.

The anion represented by formula (AN2) is preferably SO ₃ ^- -CF ₂ -CH ₂ -OCO-(L) _q' -W, SO ₃ ^- -CF ₂ -CHF-CH ₂ -OCO-(L) _q' -W, SO ₃ ^- -CF ₂ -COO-(L) _q' -W, SO ₃ ^- -CF ₂ -CF ₂ -CH ₂ -CH ₂ -(L) _q -W, or SO ₃ ^- -CF ₂ -CH(CF ₃ )-OCO-(L) _q' -W. Here, L, q and W are the same as those in formula (AN2). q' represents an integer of 0 to 10.

Furthermore, examples of non-nucleophilic anions include anions represented by the following formulas (d1-1) to (d1-4).

In formula (d1-1), R ⁵¹ represents a hydrocarbon group (for example, an aryl group such as a phenyl group) which may have a substituent (for example, a hydroxyl group).

In formula (d1-2), Z ^2c represents a hydrocarbon group having 1 to 30 carbon atoms which may have a substituent (with the proviso that the carbon atom adjacent to S is not substituted with a fluorine atom).
The hydrocarbon group in Z ^2c may be either linear or branched, and may have a cyclic structure. In addition, the carbon atom in the hydrocarbon group (preferably, when the hydrocarbon group has a cyclic structure, the carbon atom that is a ring atom) may be a carbonyl carbon. Examples of the hydrocarbon group include a group having a norbornyl group that may have a substituent. The carbon atom forming the norbornyl group may be a carbonyl carbon.
It is preferable that "Z ^2c -SO ₃ ^- " in formula (d1-2) is different from the anion represented by formula (AN2) above. For example, Z ^2c is preferably other than an aryl group. For example, in Z ^2c , the atoms at the α-position and the β-position relative to -SO ₃ ^- are preferably atoms other than a carbon atom having a fluorine atom as a substituent. For example, it is preferable that the atom at the α-position and/or the atom at the β-position relative to -SO ₃ ^- in Z ^2c is a ring member atom in a cyclic group.

In formula (d1-3), R ⁵² represents an organic group (preferably a hydrocarbon group having a fluorine atom), Y ³ represents a linear, branched, or cyclic alkylene group, arylene group, or carbonyl group, and Rf represents a hydrocarbon group.

In formula (d1-4), R ⁵³ and R ⁵⁴ each independently represent an organic group (preferably a hydrocarbon group having a fluorine atom), and R ⁵³ and R ⁵⁴ may be bonded to each other to form a ring.

The organic anion may be used alone or in combination of two or more types.

The content of the photoacid generator is preferably from 5 to 30 mass %, more preferably from 5 to 25 mass %, and even more preferably from 10 to 20 mass %, relative to the total solids content of the resist composition, from the viewpoint that the cross-sectional shape of the formed pattern becomes more rectangular.
The photoacid generator may be used alone or in combination of two or more kinds.

[Acid Diffusion Controller]
The resist composition of the present invention contains at least two types of acid diffusion controllers: a first acid diffusion controller and a second acid diffusion controller.
The acid diffusion controller is a compound consisting of an anion and a cation, and has an acid dissociation constant (pKa(Q)) greater than the pKa(A) of acidic compound A obtained by replacing the cation of the photoacid generator with a proton. In other words, the acid diffusion controller is an onium salt that generates an acid that is weaker than the acid generated by the photoacid generator.
When such an acid diffusion controller collides with the acid generated from the photoacid generator, the acid generated from the photoacid generator is exchanged with the cation of the acid diffusion controller, and a weak acid with a lower catalytic activity is released. Due to this reaction, the acid diffusion controller apparently traps the acid generated from the photoacid generator, etc., and acts as a quencher that suppresses the reaction of the acid in the unexposed area with the resin.

The anion contained in the acid diffusion controller has a pKa (Q) greater than the above-mentioned pKa (A).
The anion is preferably an organic anion.
The organic anion is not particularly limited, and examples thereof include monovalent or divalent or higher organic anions.
As the organic anion, anions having a significantly low ability to cause a nucleophilic reaction are preferred, and non-nucleophilic anions are more preferred.

Examples of non-nucleophilic anions include sulfonate anions, carboxylate anions, sulfonylimide anions, bis(alkylsulfonyl)imide anions, and tris(alkylsulfonyl)methide anions. In terms of the ability to appropriately adjust the relationship between pKa(A) and pKa(Q), carboxylate anions, sulfonylimide anions, bis(alkylsulfonyl)imide anions, and tris(alkylsulfonyl)methide anions are preferred, with carboxylate anions being more preferred.

The cation contained in the acid diffusion controller is preferably an organic cation.
Examples of the organic cation include a sulfonium cation, an ammonium cation, and an iodonium cation. As the organic cation, for example, an organic cation that can be contained in the photoacid generator can be used.
Of these, cation (ZaI) is preferred, cation (ZaI-1) or cation (ZaI-3b) is more preferred, and cation (ZaI-1) is even more preferred.

The acid diffusion controller is preferably a compound having a fluorine atom or an iodine atom in the molecule, in that the effect of the present invention is more excellent. In other words, it is preferable that at least one compound selected from the first acid diffusion controller and the second acid diffusion controller has a fluorine atom or an iodine atom in the molecule.

The first acid diffusion control agent and the second acid diffusion control agent are described in detail below.

<First Acid Diffusion Controller>
The first acid diffusion controller is an acid diffusion controller comprising a first anion and a first cation.

(First anion)
The first anion is an organic anion having a polycyclic alicyclic structure and an anionic group.

The polycyclic alicyclic structure is a structure formed by condensing at least two or more alicyclic rings.
The upper limit of the number of rings contained in the polycyclic alicyclic structure is not particularly limited, but is preferably, for example, 8 or less, and more preferably 5 or less. The lower limit is not particularly limited, but may be 2 or more, and is preferably 3 or more.
The polycyclic alicyclic structure preferably has a bridged structure. Examples of the polycyclic alicyclic structure having a bridged structure include an adamantane structure and a norbornane structure.
The polycyclic alicyclic structure preferably has 5 to 36 ring atoms, more preferably 6 to 20 ring atoms, and even more preferably 7 to 15 ring atoms.
Examples of polycyclic alicyclic structures are shown below.

Among the polycyclic alicyclic structures, an adamantane structure (structure represented by formula (a1)), a norbornane structure (structure represented by formula (a2)), a structure represented by formula (a3), or a structure represented by formula (a4) is preferred, an adamantane structure or a norbornane structure is more preferred, and an adamantane structure is even more preferred.

One or more methylene groups constituting the polycyclic alicyclic structure may be substituted with —O—, —S—, —SO ₂ —, or —CO—, and an ethylene group constituting the polycyclic alicyclic structure may be substituted with a vinylene group.
For example, the polycyclic alicyclic structure may be an adamantanone structure (structure represented by formula (a1-1) below) in which one methylene group constituting the adamantane structure is replaced with —CO—, or a norbornane structure (structure represented by formula (a2-3) below) in which one ethylene group constituting the norbornane structure is replaced with a vinylene group.
As long as the same groups are not consecutive, two or more adjacent methylene groups may be replaced with -O-, -S-, -SO ₂ -, or -CO-, respectively. For example, two adjacent methylene groups may be replaced with -O- and -CO-, respectively, to form a lactone ring.
Examples of polycyclic alicyclic structures in which at least one methylene group constituting the polycyclic alicyclic structure is replaced with -O-, -S-, -SO ₂ -, or -CO-, or at least one ethylene group constituting the polycyclic alicyclic structure is replaced with a vinylene group, are shown below.

Among these, the polycyclic alicyclic structure is preferably an adamantane structure, an adamantanone structure, a norbornane structure, a norbornene structure, a structure represented by formula (a3-1), or a structure represented by formula (a15-1), and more preferably an adamantane structure or an adamantanone structure.
The number of polycyclic alicyclic structures in the first anion is not particularly limited, but is preferably 1 to 2, and more preferably 1.

The polycyclic alicyclic structure may have a substituent.
Examples of the substituent that the polycyclic alicyclic structure may have include a hydroxyl group, a halogen atom, an alkyl group (preferably having 1 to 6 carbon atoms), a cycloalkyl group (preferably having 4 to 8 carbon atoms), an alkoxy group (preferably having 1 to 6 carbon atoms), an alkyloxycarbonyl group (preferably having 2 to 12 carbon atoms), an alkylthio group (preferably having 1 to 6 carbon atoms), an aryl group (preferably having 6 to 12 carbon atoms), an aralkyl group (preferably having 7 to 13 carbon atoms), an acyl group (preferably having 2 to 5 carbon atoms), and an acyloxy group (preferably having 2 to 5 carbon atoms).
The alkoxy group, the alkyloxycarbonyl group, the alkylthio group, the acyl group, and the acyloxy group include an alkyl group or a cycloalkyl group, and the alkyl group may be either linear or branched.
The above-mentioned substituents may further have a substituent if possible. For example, the above-mentioned alkyl group or cycloalkyl group may have a halogen atom.
As the substituent that the polycyclic alicyclic structure may have, a hydroxyl group, a halogen atom, or an alkyl group having 1 to 6 carbon atoms which may have a halogen atom is preferable, and a hydroxyl group, a fluorine atom, an iodine atom, or an alkyl group having 1 to 3 carbon atoms which may have a fluorine atom or an iodine atom is more preferable.
When the polycyclic alicyclic structure has a substituent, the number of the substituents is not particularly limited, but is preferably 1 to 5, and more preferably 1 to 4.
When the polycyclic alicyclic structure has a plurality of substituents, two of the substituents may be bonded to each other to form a ring. Examples of the ring formed by bonding two substituents to each other include cycloalkanes, cyclic acetals, and cyclic thioacetals.
When two substituents are bonded to each other to form a ring, the two substituents may be bonded to the same carbon atom in the alicyclic structure, or may be bonded to different carbon atoms.

Examples of the anionic group include groups represented by -CO ₂ ^- , -SO ₃ ^- , -SO ₂ -N ^- and -SO ₂ -N ^- -SO ₂ -, with the group represented by -CO ₂ ^- being preferred.
The anionic group and the polycyclic alicyclic structure may be bonded directly or via a linking group, but are preferably bonded directly.

In terms of enabling appropriate adjustment of hydrophilicity, it is also preferable that the first anion does not have a hydrophobic substituent (for example, an alkyl group or a fluorine atom).
In terms of enabling appropriate adjustment of hydrophilicity, it is also preferable for the first anion to have at least one site selected from a hydroxyl group, a carbonyl group, an ether bond, a thioether bond, and an ester bond, and it is more preferable for the first anion to have at least one site selected from a hydroxyl group, a carbonyl group, an ether bond, and an ester bond.

The first anion is preferably an anion represented by the following formula (QA1):

In formula (QA1), W ₁ represents a polycyclic alicyclic structure which may have a substituent. The definition and preferred embodiments of the polycyclic alicyclic structure are as described above.
Examples of the substituent that the polycyclic alicyclic structure may have include a hydroxyl group, a halogen atom, an alkyl group (preferably having 1 to 6 carbon atoms), a cycloalkyl group (preferably having 4 to 8 carbon atoms), an alkoxy group (preferably having 1 to 6 carbon atoms), an alkyloxycarbonyl group (preferably having 2 to 12 carbon atoms), an alkylthio group (preferably having 1 to 6 carbon atoms), an aryl group (preferably having 6 to 12 carbon atoms), an aralkyl group (preferably having 7 to 13 carbon atoms), an acyl group (preferably having 2 to 5 carbon atoms), and an acyloxy group (preferably having 2 to 5 carbon atoms).
The alkoxy group, the alkyloxycarbonyl group, the alkylthio group, the acyl group, and the acyloxy group include an alkyl group or a cycloalkyl group, and the alkyl group may be either linear or branched.
The above-mentioned substituents may further have a substituent if possible. For example, the above-mentioned alkyl group or cycloalkyl group may have a halogen atom.
As the substituent that the polycyclic alicyclic structure may have, a hydroxyl group, a halogen atom, or an alkyl group having 1 to 6 carbon atoms which may have a halogen atom is preferable, a hydroxyl group, a fluorine atom, an iodine atom, or an alkyl group having 1 to 3 carbon atoms which may have a fluorine atom or an iodine atom is more preferable, and a hydroxyl group is still more preferable.
When the polycyclic alicyclic structure has a substituent, the number of the substituents is not particularly limited, but is preferably 1 to 5, and more preferably 1 to 3.
When the polycyclic alicyclic structure has a plurality of substituents, two of the substituents may be bonded to each other to form a ring. Examples of the ring formed by bonding two substituents to each other include cycloalkanes, cyclic acetals, and cyclic thioacetals.
When two substituents are bonded to each other to form a ring, the two substituents may be bonded to the same carbon atom in the alicyclic structure, or may be bonded to different carbon atoms.
The ring formed by bonding the two substituents together may further have a substituent. Examples of the substituent include the substituent that the polycyclic alicyclic structure may have, and a hydroxyl group is preferred.

L _Q1 represents a single bond or a divalent linking group.
Examples of the divalent linking group include divalent hydrocarbon groups, -O-, -CO-, -S-, -SO ₂ -, and combinations of these, provided that the group adjacent to X _Q ^- is a divalent hydrocarbon group.
Examples of the divalent hydrocarbon group include an alkylene group, a cycloalkylene group, an alkenylene group, and an arylene group.
The alkylene group may be either linear or branched, and preferably has 1 to 12 carbon atoms, more preferably 1 to 6 carbon atoms, and even more preferably 1 to 4 carbon atoms.
The cycloalkylene group may be either a monocyclic or polycyclic ring, and is preferably a monocyclic ring. The number of carbon atoms in the cycloalkylene group is preferably 3 to 12, more preferably 4 to 8, and even more preferably 4 to 6. A methylene group constituting the cycloalkylene group may be replaced by -O-, -CO-, -S-, or -SO ₂ -.
The alkenylene group may be either linear or branched, and preferably has 2 to 12 carbon atoms, more preferably 2 to 6 carbon atoms.
The arylene group preferably has 6 to 12 carbon atoms, and more preferably 6 to 10 carbon atoms.
The divalent hydrocarbon group may have a substituent. Examples of the substituent include the groups exemplified as the substituent that the polycyclic alicyclic structure may have, and a hydroxyl group or a halogen atom is preferable, and a fluorine atom or an iodine atom is more preferable.
Among them, the divalent linking group is preferably * ^W -O-CO-alkylene group-* ^X which may have a halogen atom, * ^W -CO-O-alkylene group-* ^X which may have a halogen atom, * ^W -O-CO-cycloalkylene group-* ^X , * ^W -CO-O-cycloalkylene group-* ^X , * ^W -O-alkylene group-* ^X which may have a halogen atom, ^W -CO-alkylene group-* ^X which may have a halogen atom, or * ^W -O-cycloalkylene group-* ^X . * ^W represents the bonding position with _W1 , and * ^X represents the bonding position ^with _XQ- .
L _Q1 is preferably a single bond, * ^W -O-CO-alkylene group-* ^X , * ^W -CO-O-alkylene group-* ^X or * ^W -O-alkylene group-* ^X .

X _Q ^- represents an anionic group. Examples of the anionic group include -CO ₂ ^- and -SO ₃ ^- , with -CO ₂ ^- being preferred.

Examples of the structure of the first anion represented by formula (QA1), as well as the ClogP value and volume V (unit: Å ³ ) of each anion are shown below. The method for measuring the volume V will be described later.

The anion represented by formula (QA1) may be an anion represented by formula (QA1-1).

In formula (QA1-1), L _Q1 and X _Q ^- have the same meanings and preferred embodiments as L _Q1 and X _Q ^- in formula (QA1).

_W2 is a polycyclic alicyclic structure which may have a substituent. The definition and preferred embodiments of the polycyclic alicyclic structure are as described above.
Examples of the substituent that the polycyclic alicyclic structure represented by _W2 may have include a hydroxyl group, a halogen atom, an alkyl group (preferably having 1 to 6 carbon atoms), a cycloalkyl group (preferably having 4 to 8 carbon atoms), an alkoxy group (preferably having 1 to 6 carbon atoms), an alkyloxycarbonyl group (preferably having 2 to 12 carbon atoms), an alkylthio group (preferably having 1 to 6 carbon atoms), an aryl group (preferably having 6 to 12 carbon atoms), an aralkyl group (preferably having 7 to 13 carbon atoms), an acyl group (preferably having 2 to 5 carbon atoms), and an acyloxy group (preferably having 2 to 5 carbon atoms).
The alkoxy group, the alkyloxycarbonyl group, the alkylthio group, the acyl group, and the acyloxy group include an alkyl group or a cycloalkyl group, and the alkyl group may be either linear or branched.
The above-mentioned substituents may further have a substituent if possible. For example, the above-mentioned alkyl group or cycloalkyl group may have a halogen atom.
As the substituent that the polycyclic alicyclic structure may have, a hydroxyl group, a halogen atom, or an alkyl group having 1 to 3 carbon atoms that may have a halogen atom is preferable, and a hydroxyl group, a fluorine atom, or an iodine atom is more preferable.

_Y1 and _Y2 each independently represent a methylene group or a heteroatom, preferably a methylene group, a sulfur atom, or an oxygen atom, more preferably an oxygen atom. In particular, _Y1 and _Y2 are preferably the same atom, more preferably _Y1 and _Y2 are an oxygen atom.

R _Q1 is a divalent linking group.
Examples of the divalent linking group include a divalent hydrocarbon group, --O--, --CO--, --S--, --SO ₂ --, and combinations of these.
Examples of the divalent hydrocarbon group include an alkylene group, a cycloalkylene group, an alkenylene group, and an arylene group.
The alkylene group may be either linear or branched, and preferably has 1 to 12 carbon atoms, more preferably 1 to 6 carbon atoms, and even more preferably 1 to 4 carbon atoms.
The cycloalkylene group may be either a monocyclic or polycyclic ring, and is preferably a monocyclic ring. The number of carbon atoms in the cycloalkylene group is preferably 3 to 12, and more preferably 4 to 8. A methylene group constituting the cycloalkylene group may be replaced by -O-, -CO-, -S-, or -SO ₂ -.
The alkenylene group may be either linear or branched, and preferably has 2 to 12 carbon atoms, more preferably 2 to 6 carbon atoms.
The arylene group may be either a monocyclic or polycyclic group, and is preferably a monocyclic group. The arylene group preferably has 6 to 12 carbon atoms, and more preferably has 6 to 10 carbon atoms.
The divalent hydrocarbon group may have a substituent. Examples of the substituent include the groups exemplified as the substituent that the polycyclic alicyclic structure may have, and are preferably a hydroxyl group, a halogen atom, an alkoxy group having 1 to 6 carbon atoms, or an alkyl group having 1 to 6 carbon atoms which may have a halogen atom, more preferably a hydroxyl group, a fluorine atom, an iodine atom, an alkyl group having 1 to 3 carbon atoms which may have a fluorine atom or an iodine atom, or an alkoxy group having 1 to 3 carbon atoms, and still more preferably a hydroxyl group.
When the divalent hydrocarbon group has a substituent, the number of the substituents is not particularly limited, but is preferably 1 to 8, more preferably 1 to 6, and even more preferably 1 to 4.
The divalent linking group is preferably an alkylene group which may have a halogen atom or a hydroxyl group, or a cycloalkylene group which may have a halogen atom or a hydroxyl group, and more preferably an alkylene group.

Examples of the structure of the first anion represented by formula (QA1-1), as well as the ClogP value and volume V (unit: Å ³ ) of each anion are shown below.

The first anion may be an anion represented by formula (QA2).

In formula (QA2), W ₂ , Y ₁ , Y ₂ , L _Q1 and X _Q- have the same meanings and preferred ^embodiments as W ₂ , Y ₁ , Y ₂ , L _Q1 and _{X Q-} ⁱⁿ formula (QA1-1).
R _Q2 is a trivalent linking group.
The trivalent linking group includes a trivalent hydrocarbon group.
The methylene group constituting the trivalent hydrocarbon group may be substituted with -O-, -S-, -CO-, or -SO ₂ -.
The trivalent hydrocarbon group may have a substituent. Examples of the substituent include the groups exemplified as the substituent that the polycyclic alicyclic structure may have, and are preferably a hydroxyl group, a halogen atom, or an alkyl group having 1 to 6 carbon atoms which may have a halogen atom, more preferably a hydroxyl group, a fluorine atom, an iodine atom, or an alkyl group having 1 to 3 carbon atoms which may have a fluorine atom or an iodine atom, and still more preferably a hydroxyl group.
The trivalent hydrocarbon group is preferably a branched aliphatic hydrocarbon group having 2 to 6 carbon atoms or a monocyclic alicyclic group having 3 to 8 carbon atoms, and more preferably a branched aliphatic hydrocarbon group having 2 to 6 carbon atoms.

Examples of the structure of the first anion represented by formula (QA2), as well as the ClogP value and volume V (unit: Å ³ ) of each anion are shown below.

The first anion is preferably an anion represented by formula (QA1), in that the effects of the present invention are more excellent, and more preferably an anion represented by formula (QA1) that does not contain any ring other than the polycyclic alicyclic structure represented by _W1 .

The pKa(B) of the acidic compound B formed by combining the first anion and a proton is not particularly limited as long as it is larger than the above-mentioned pKa(A), but the difference between pKa(B) and pKa(A) (pKa(B)-pKa(A)) is preferably 0.50 or more, more preferably 1.00 or more, and even more preferably 2.00 or more. There is no particular upper limit, and it is preferably 10.00 or less, and more preferably 8.00 or less.
The pKa(B) is preferably from −3.00 to 8.00, more preferably from −1.00 to 7.00, and even more preferably from 0.00 to 5.00.

The ClogP value of the first anion is −1.50 or less, and is preferably −2.00 or less, and more preferably −2.50 or less, in terms of providing better effects of the present invention. There is no particular lower limit, but is preferably −5.00 or more, more preferably −4.00 or more, and even more preferably −3.00 or more, in terms of providing better effects of the present invention.
If the ClogP value of the first anion exceeds −1.50, the ability to quench the acid at the boundary between the exposed and unexposed areas decreases, which is undesirable since it deteriorates the effect of the present invention.

The volume of the first anion is not particularly limited as long as it is smaller than the volume of the second anion described below, but in terms of better effects of the present invention, it is preferably ³⁰⁰ Å3 or less, more preferably 250 ^Å3 or less, even more preferably ²⁰⁰ Å3 or less, and particularly preferably 190 ^Å3 or less. There is no particular lower limit, but it is preferably 100 ^Å3 or more, and more preferably 150 ^Å3 or more.
The volume of the anion can be calculated by the following method.
The anion structure is optimized by the PM3 (Parameterized Model number 3) method using MOPAC7 included in Winmostar (QM) (V10.7.5 for 64-bit Windows, software manufactured by X-Ability). The Van der Waals volume of the obtained optimized structure is calculated by the method described in Non-Patent Document 1 using Winmostar (software manufactured by X-Ability).
Non-Patent Document 1: Improvement of molecular surface area and volume calculation program, Teruo Nagao, pp. 111-120, No. 27, 1993, Journal of Hakodate National College of Technology

(First Cation)
The first cation is not particularly limited, and for example, any organic cation that can be contained in the photoacid generator can be used. Among them, a sulfonium cation or an iodonium cation is preferable, and a sulfonium cation is more preferable.
As the first cation, the above-mentioned cation (ZaI) is preferable, and the above-mentioned cation (ZaI-1) is more preferable, in terms of obtaining a better effect of the present invention.
Among these, the first cation is preferably a triarylsulfonium cation, and more preferably a triphenylsulfonium cation.
In terms of being able to appropriately control the hydrophilicity of the cation, the first cation preferably has an electron-donating group as a substituent, and preferably has an alkyl group which may have a halogen atom or an alkoxy group as a substituent.
In terms of obtaining better effects of the present invention, it is also preferable that the first cation has an iodine atom or a fluorine atom.

In order to obtain a more excellent effect of the present invention, the ClogP value of the first cation is preferably 3.00 or more, and more preferably 5.00 or more. There is no particular upper limit, but it is preferably 20.00 or less, and more preferably 15.00 or less.

In order to obtain a more excellent effect of the present invention, the content of the first acid diffusion controller is preferably 30.0% by mass or less, more preferably 20.0% by mass or less, and even more preferably 15.0% by mass or less, based on the total solid content of the resist composition excluding the solvent. Although there is no particular lower limit, it is preferably 0.1% by mass or more, more preferably 1.0% by mass or more, and even more preferably 3.0% by mass or more.
In order to obtain a more excellent effect of the present invention, the mass ratio of the content of the first acid diffusion controller to the content of the photoacid generator is preferably 0.1 to 3.0, more preferably 0.2 to 2.0, and even more preferably 0.3 to 1.0.

<Second Acid Diffusion Controller>
The second acid diffusion controller is an acid diffusion controller comprising a second anion and a second cation.

(Second Anion)
The second anion is preferably an organic anion having an anionic group.
Examples of the anionic group include groups represented by -CO ₂ ^- , -SO ₃ ^- , -SO ₂ -N ^- and -SO ₂ -N ^- -SO ₂ -, with the group represented by -CO ₂ ^- being preferred.

In terms of obtaining superior effects of the present invention, the second anion preferably has a ring structure.
Examples of the ring structure include a monocyclic or polycyclic aromatic ring structure and a monocyclic or polycyclic alicyclic structure, with a polycyclic aromatic ring structure or a polycyclic alicyclic structure being preferred, and a polycyclic alicyclic structure being more preferred.
Examples of the aromatic ring structure include a benzene ring structure, a naphthalene structure, and an anthracene structure.
The monocyclic alicyclic structure includes a monocyclic cycloalkyl ring having 3 to 8 carbon atoms.
The polycyclic alicyclic structure may be the polycyclic alicyclic structure possessed by the first anion, and preferred embodiments are also the same.
The number of ring structures in the second anion is not particularly limited, but is preferably 1 or more, and more preferably 2 or more. The upper limit is not particularly limited, but is preferably 5 or less, and more preferably 4 or less.
When the second anion has two or more ring structures, the combination is not particularly limited, but it preferably has one or more polycyclic alicyclic structures, and more preferably has a polycyclic alicyclic structure and a monocyclic alicyclic structure.

An example of the second anion is an anion represented by formula (QA3).

In formula (QA3), _W3 represents an alicyclic structure which may have a substituent.
The alicyclic structure may be either a polycyclic or monocyclic structure, with a polycyclic alicyclic structure being preferred.
The monocyclic alicyclic structure is, for example, a cycloalkane. The cycloalkane preferably has 3 to 8 carbon atoms, and more preferably has 5 to 6 carbon atoms.
The definition and preferred embodiments of the polycyclic alicyclic structure are as described above.
Examples of the substituent that the alicyclic structure may have include a hydroxyl group, a halogen atom, an alkyl group (preferably having 1 to 6 carbon atoms), a cycloalkyl group (preferably having 4 to 8 carbon atoms), an alkoxy group (preferably having 1 to 6 carbon atoms), an alkyloxycarbonyl group (preferably having 2 to 12 carbon atoms), an alkylthio group (preferably having 1 to 6 carbon atoms), an aryl group (preferably having 6 to 12 carbon atoms), an aralkyl group (preferably having 7 to 13 carbon atoms), an acyl group (preferably having 2 to 5 carbon atoms), and an acyloxy group (preferably having 2 to 5 carbon atoms).
The alkoxy group, the alkyloxycarbonyl group, the alkylthio group, the acyl group, and the acyloxy group include an alkyl group or a cycloalkyl group, and the alkyl group may be either linear or branched.
The above-mentioned substituents may further have a substituent if possible. For example, the above-mentioned alkyl group or cycloalkyl group may have a halogen atom.
The substituent that the alicyclic structure may have is preferably a hydroxyl group, an alkyl group having 1 to 6 carbon atoms which may have a halogen atom, or an alkyloxycarbonyl group having 2 to 12 carbon atoms which may have a halogen atom, and more preferably a hydroxyl group, an alkyl group having 1 to 3 carbon atoms which may have a halogen atom, or an alkyloxycarbonyl group having 3 to 8 carbon atoms.
When the polycyclic alicyclic structure has a plurality of substituents, two of the substituents may be bonded to each other to form a ring. Examples of the ring formed by bonding two substituents to each other include cycloalkanes, cyclic acetals, and cyclic thioacetals.
When two substituents are bonded to each other to form a ring, the two substituents may be bonded to the same carbon atom in the alicyclic structure, or may be bonded to different carbon atoms.
The ring formed by bonding the two substituents together may further have a substituent. Examples of the substituent include the substituent that the polycyclic alicyclic structure may have, and a hydroxyl group is preferred.

L _Q3 represents a single bond or a divalent substituent.
Examples of the divalent linking group include divalent hydrocarbon groups, -O-, -CO-, -S-, -SO ₂ -, and combinations of these, provided that the group adjacent to X _Q ^- is a divalent hydrocarbon group.
Examples of the divalent hydrocarbon group include an alkylene group, a cycloalkylene group, an alkenylene group, and an arylene group.
The alkylene group may be either linear or branched, and preferably has 1 to 12 carbon atoms, more preferably 1 to 6 carbon atoms, and even more preferably 1 to 4 carbon atoms.
The cycloalkylene group may be either a monocyclic or polycyclic ring, and is preferably a monocyclic ring. The number of carbon atoms in the cycloalkylene group is preferably 3 to 12, more preferably 4 to 8, and even more preferably 4 to 6. A methylene group constituting the cycloalkylene group may be replaced by -O-, -CO-, -S-, or -SO ₂ -.
The alkenylene group may be either linear or branched, and preferably has 2 to 12 carbon atoms, more preferably 2 to 6 carbon atoms.
The arylene group preferably has 6 to 12 carbon atoms, and more preferably 6 to 10 carbon atoms.
The divalent hydrocarbon group may have a substituent. Examples of the substituent include the groups exemplified as the substituent that the polycyclic alicyclic structure may have, and a hydroxyl group or a halogen atom is preferable, and a fluorine atom or an iodine atom is more preferable.
L _Q3 is preferably a single bond, * ^W3 -O-CO-alkylene group-* ^X which may have a halogen atom, * ^W3 -CO-O-alkylene group-* ^X which may have a halogen atom, * ^W3 -CO-O-cycloalkylene group-* ^X or * ^W3 -O-CO-cycloalkylene group-* ^X . * ^W3 represents the bonding position to _W3 , and * ^X represents the bonding position ^to _XQ- .

X _Q ^- represents an anionic group.
X _Q ^- has the same meaning as X _Q ^- in formula (Q1), and the preferred embodiments are also the same.

Examples of the structure of the second anion represented by formula (Q3), as well as the ClogP value and volume V (unit: Å ³ ) of each anion are shown below.

The anion represented by formula (QA3) is also preferably an anion represented by formula (QA3-1).

In formula (QA3-1), W ₂ , Y ₁ , Y ₂ , X _Q ⁻ and R _Q1 have the same meanings and preferred embodiments as W ₂ , Y ₁ , Y ₂ , X _Q ⁻ and R _Q1 in formula (QA1-1).
Among these, R _Q1 is preferably an alkylene group which may have a halogen atom.
In formula (QA3-1), L 3 _Q3 has the same meaning as L _{3 Q3} in formula (QA3), and the preferred embodiments are also the same.
Examples of the structure of the second anion represented by formula (QA3-1), as well as the ClogP value and volume V (unit: Å ³ ) of each anion are shown below.

The second anion is preferably an anion represented by formula (QA4).

In formula (QA4), W ₂ , Y ₁ , Y ₂ , L _Q1 and X _Q- have the same meanings as W ₂ , Y ₁ , Y ₂ , L _Q1 and X ^Q- in formula (QA1-1), and _the preferred embodiments are also ^the same.
R _Q4 is a trivalent linking group.
The trivalent linking group includes a trivalent hydrocarbon group.
The methylene group constituting the trivalent hydrocarbon group may be substituted with -O-, -S-, -CO-, or -SO ₂ -.
The trivalent hydrocarbon group may have a substituent. Examples of the substituent include the groups exemplified as the substituent that the polycyclic alicyclic structure may have, and are preferably a hydroxyl group, a halogen atom, or an alkyl group having 1 to 6 carbon atoms which may have a halogen atom, more preferably a hydroxyl group, a fluorine atom, an iodine atom, or an alkyl group having 1 to 3 carbon atoms which may have a fluorine atom or an iodine atom, and still more preferably a hydroxyl group.
The trivalent hydrocarbon group is preferably a branched aliphatic hydrocarbon group having 3 to 8 carbon atoms or a trivalent monocyclic alicyclic group having 3 to 8 carbon atoms, more preferably a trivalent monocyclic alicyclic group having 3 to 8 carbon atoms.

Examples of the structure of the second anion represented by formula (QA4), as well as the ClogP value and volume V (unit: Å ³ ) of each anion are shown below.

As the second anion, an anion represented by formula (QA3) or an anion represented by formula (QA4) is preferable, an anion represented by formula (QA3) is more preferable, and an anion represented by formula (QA3-1) is even more preferable.

The pKa(C) of the acidic compound C formed by combining the second anion and a proton is not particularly limited as long as it is larger than the above-mentioned pKa(A), but the difference between pKa(C) and pKa(A) (pKa(C)-pKa(A)) is preferably 0.50 or more, more preferably 1.00 or more, and even more preferably 2.00 or more. There is no particular upper limit, and it is preferably 10.00 or less, and more preferably 8.00 or less.
The pKa(C) is preferably from −3.00 to 8.00, more preferably from −1.00 to 7.00, and even more preferably from 0.00 to 5.00.

The volume of the second anion is larger than that of the first anion and is 250 Å ³ or more.
In terms of obtaining superior effects of the present invention, the volume of the second anion is preferably 260 ^Å3 or more. There is no particular upper limit, but the volume is preferably ⁵⁰⁰ Å3 or less, and more preferably 400 ^Å3 or less.
If the volume of the second anion is less than 250 ^Å3 , the ability to quench the acid in the unexposed area decreases, which is undesirable since it deteriorates the effect of the present invention.
The volume of the second anion can be calculated by the method described above.

In order to obtain a more excellent effect of the present invention, the ClogP value of the second anion is preferably -5.00 to 3.00, more preferably -3.00 to 0.00, even more preferably -2.00 to -0.50, and particularly preferably -1.50 to -1.00.

(Second Cation)
The first cation is not particularly limited, and for example, an organic cation that can be contained in the photoacid generator can be used.
The preferred embodiments of the second cation are the same as those of the first cation.
The first cation and the second cation can be the same or different.

The ClogP value of the second cation is preferably 3.00 or more, and more preferably 5.00 or more. There is no particular upper limit, but it is preferably 20.00 or less, and more preferably 15.00 or less.

In terms of obtaining superior effects of the present invention, the content of the second acid diffusion controller is preferably from 0.1 to 30.0 mass %, more preferably from 1.0 to 20.0 mass %, and even more preferably from 3.0 to 10.0 mass %, based on the total solid content excluding the solvent of the resist composition.
In order to obtain a more excellent effect of the present invention, the mass ratio of the content of the second acid diffusion controller to the content of the photoacid generator is preferably from 0.1 to 3.0, more preferably from 0.2 to 2.0, and even more preferably from 0.3 to 1.0.
In order to obtain a more excellent effect of the present invention, the mass ratio of the content of the second acid diffusion controller to the content of the first acid diffusion controller is preferably 0.1 to 3.0, more preferably 0.2 to 2.0, and even more preferably 0.3 to 1.0.

The resist composition may contain an acid diffusion controller other than those mentioned above.
Examples of acid diffusion control agents other than those mentioned above include basic compounds, low molecular weight compounds having a nitrogen atom and a group that is eliminated by the action of an acid, and compounds whose acid diffusion control ability is reduced or lost by irradiation with actinic rays or radiation.
For example, the compounds described in paragraphs [0132] to [0164] of International Publication No. 2020/066824, as well as the known compounds disclosed in paragraphs [0627] to [0664] of U.S. Patent Application Publication No. 2016/0070167A1, paragraphs [0095] to [0187] of U.S. Patent Application Publication No. 2015/0004544A1, paragraphs [0403] to [0423] of U.S. Patent Application Publication No. 2016/0237190A1, and paragraphs [0259] to [0328] of U.S. Patent Application Publication No. 2016/0274458A1 can be used.

[Hydrophobic resin]
The resist composition may contain a hydrophobic resin that is different from the specific resin.
The hydrophobic resin is preferably designed to be unevenly distributed on the surface of the resist film, but unlike a surfactant, it does not necessarily have to have a hydrophilic group in the molecule, and does not necessarily have to contribute to uniform mixing of polar and non-polar substances.
The effects of adding a hydrophobic resin include control of the static and dynamic contact angle of water on the resist film surface, and suppression of outgassing.

From the viewpoint of uneven distribution on the membrane surface layer, the hydrophobic resin preferably has one or more of a fluorine atom, a silicon atom, and a _CH3 partial structure contained in the side chain portion of the resin, and more preferably has two or more of them.
The hydrophobic resin preferably has a hydrocarbon group having at least 5 carbon atoms. Such a group may be present in the main chain of the resin, or may be substituted on a side chain.
Examples of hydrophobic resins include the compounds described in paragraphs [0275] to [0279] of WO 2020/004306.

The hydrophobic resin may be used alone or in combination of two or more kinds.
When the resist composition contains a hydrophobic resin, the content of the hydrophobic resin is preferably from 0.01 to 20.0 mass %, and more preferably from 0.1 to 15.0 mass %, based on the total solid content of the resist composition.

[Surfactant]
The resist composition may contain a surfactant.
When a surfactant is contained, a pattern having superior adhesion and fewer development defects can be formed.
The surfactant is preferably a fluorine-based and/or silicon-based surfactant, and from the standpoint of environmental regulations, a silicon-based surfactant is more preferred.
Examples of the fluorine-based and/or silicon-based surfactant include the surfactants described in paragraphs [0218] and [0219] of WO 2018/193954.

The surfactant may be used alone or in combination of two or more kinds.
When the resist composition contains a surfactant, the content of the surfactant is preferably from 0.0001 to 2.0 mass %, more preferably from 0.0005 to 1.0 mass %, and even more preferably from 0.1 to 1.0 mass %, relative to the total solid content of the resist composition.

〔solvent〕
The resist composition preferably contains a solvent.
The solvent preferably contains (M1) propylene glycol monoalkyl ether carboxylate, and (M2) at least one selected from the group consisting of propylene glycol monoalkyl ether, lactate ester, acetate ester, alkoxypropionate ester, chain ketone, cyclic ketone, lactone, and alkylene carbonate.

The combination of the above-mentioned solvent and the specific resin is preferable in terms of improving the coatability of the resist composition and reducing the number of development defects of the pattern. The above-mentioned solvent has a good balance of the solubility, boiling point, and viscosity of the above-mentioned resin, so that it can suppress unevenness in the thickness of the resist film and the occurrence of precipitates during spin coating.
Details of the components (M1) and (M2) are described in paragraphs [0218] to [0226] of WO 2020/004306, the contents of which are incorporated herein by reference.

The solvent may further contain a component other than the component (M1) and the component (M2).
When the solvent further contains a component other than the component (M1) and the component (M2), the content of the component other than the component (M1) and the component (M2) is preferably 5 to 30 mass % based on the total amount of the solvent.

In order to further improve the coatability of the resist composition, the content of the solvent in the resist composition is preferably 70 to 99.5% by mass, and more preferably 80 to 99% by mass.

[Other additives]
The resist composition may contain additives other than those mentioned above.
Other additives include dissolution-inhibiting compounds (compounds with a molecular weight of 3000 or less that are decomposed by the action of acid and have reduced solubility in organic developers), dyes, plasticizers, photosensitizers, light absorbers, and compounds that promote solubility in developers (for example, phenol compounds with a molecular weight of 1000 or less, and alicyclic or aliphatic compounds containing a carbonyl group).

The resist composition may contain water, but it is preferable that the water content is small.
The content of water is often 1 to 30,000 ppm by mass relative to the total mass of the resist composition, and is preferably 10,000 ppm by mass or less, more preferably 5,000 ppm by mass or less, and even more preferably 1,000 ppm by mass or less. There is no particular lower limit, and 0 ppm by mass is preferable.

The resist composition may contain residual monomers, but the content thereof is preferably small. Examples of the residual monomers include monomers used in the synthesis of the specific resin.
The content of the residual monomer is often 1 to 30,000 ppm by mass relative to the total mass of the resist composition, and is preferably 10,000 ppm by mass or less, more preferably 5,000 ppm by mass or less, and even more preferably 1,000 ppm by mass or less. There is no particular lower limit, and 0 ppm by mass is preferable.

The resist composition of the present specification is suitably used as a resist composition for EUV exposure.
EUV light has a wavelength of 13.5 nm, which is shorter than ArF light (wavelength 193 nm) and the like, and therefore the number of incident photons is smaller when exposed at the same sensitivity. Therefore, the effect of "photon shot noise," which is the stochastic variation in the number of photons, is large, leading to deterioration of LER and bridge defects. One method of reducing photon shot noise is to increase the exposure dose to increase the number of incident photons, but this is a trade-off with the demand for higher sensitivity.

[Pattern formation method]
The pattern forming method of the present invention includes the following steps.
Step 1: A step of forming a resist film on a substrate using a resist composition. Step 2: A step of exposing the resist film. Step 3: A step of developing the exposed resist film using a developer to form a resist pattern. Each step may be performed only once or multiple times.
Each step will be described in detail below.

[Step 1: Resist film formation step]
Step 1 is a step of forming a resist film on a substrate using a resist composition.
The resist composition is as defined above.

An example of a method for forming a resist film on a substrate using a resist composition is a method in which the resist composition is applied onto a substrate.
It is preferable to filter the resist composition before coating as necessary. The pore size of the filter is preferably 0.1 μm or less, more preferably 0.05 μm or less, and even more preferably 0.03 μm or less. The filter is preferably made of polytetrafluoroethylene, polyethylene, or nylon.

The substrate is not particularly limited, and may be a substrate generally used in the manufacturing process of semiconductors such as ICs, or circuit boards such as liquid crystal or thermal heads, and in other lithography processes for photofabrication, etc. Specific examples include inorganic substrates such as silicon, SiO ₂ , and SiN.
In addition, an undercoat film (for example, an inorganic film, an organic film, or an anti-reflective film) may be formed under the resist film.

The resist composition can be applied onto a substrate, for example, using a spinner or coater. The preferred application method is spin coating using a spinner. The rotation speed when spin coating using a spinner is preferably 1000 to 3000 rpm.

After coating the resist composition, a drying treatment may be carried out to form a resist film. As a drying method, for example, a method of drying by heating may be mentioned. Heating may be carried out by a means provided in a normal exposure machine and/or a developing machine, and may be carried out using a hot plate or the like.
The heating temperature is preferably 80 to 150° C., more preferably 80 to 140° C., and even more preferably 80 to 130° C. The heating time is preferably 30 to 1000 seconds, more preferably 60 to 800 seconds, and even more preferably 60 to 600 seconds.

The thickness of the resist film is not particularly limited, but is preferably 10 to 120 nm, since it allows for the formation of fine patterns with higher accuracy. In particular, when EUV exposure is performed, the thickness of the resist film is more preferably 10 to 65 nm, and even more preferably 15 to 50 nm. Furthermore, when ArF immersion exposure is performed, the thickness of the resist film is more preferably 10 to 120 nm, and even more preferably 15 to 90 nm.

A top coat may be formed on the resist film using a top coat composition.
The top coat composition is preferably a composition that does not mix with the resist film and can be applied uniformly onto the resist film.
The thickness of the top coat is preferably from 10 to 200 nm, more preferably from 20 to 100 nm, and even more preferably from 40 to 80 nm.
The composition and method of forming the top coat are not particularly limited, and a known top coat can be formed using a known method. For example, the top coat can be formed based on the description in paragraphs [0072] to [0082] of JP2014-059543A.
For example, it is preferable to form a top coat containing a basic compound described in JP 2013-061648 A on a resist film. It is also preferable that the top coat contains a compound containing at least one group or bond selected from the group consisting of an ether bond, a thioether bond, a hydroxyl group, a thiol group, a carbonyl group, and an ester group.

[Step 2: Exposure Step]
Step 2 is a step of exposing the resist film to light.
The exposure method may be a method in which the formed resist film is irradiated with actinic rays or radiation through a predetermined mask.
Examples of the actinic ray or radiation include infrared light, visible light, ultraviolet light, far ultraviolet light, extreme ultraviolet light, X-rays, and electron beams, preferably having a wavelength of 250 nm or less, more preferably having a wavelength of 220 nm or less, and particularly preferably having a wavelength of 1 to 200 nm, specifically, KrF excimer laser (248 nm), ArF excimer laser (193 nm), F2 excimer laser (157 nm), EUV (13.5 nm), X-rays, and electron beams.

After exposure, it is preferable to perform post-exposure baking (PEB) before development. The post-exposure baking promotes the reaction of the exposed area, resulting in better sensitivity and pattern shape. Heating can be performed by a means provided in a normal exposure machine and/or development machine, and may be performed using a hot plate or the like.
The heating temperature is preferably from 80 to 150°C, more preferably from 80 to 140°C, and even more preferably from 80 to 130°C.
The heating time is preferably from 10 to 1,000 seconds, more preferably from 10 to 180 seconds, and even more preferably from 30 to 120 seconds.

[Step 3: Development Step]
Step 3 is a step of developing the exposed resist film with a developer to obtain a resist pattern.
The developer may be an alkaline developer or a developer containing an organic solvent (hereinafter, also referred to as an "organic developer").

Examples of the developing method include a method of immersing a substrate in a tank filled with a developing solution for a certain period of time (dip method), a method of piling up the developing solution on the substrate surface by surface tension and leaving it still for a certain period of time to develop (paddle method), a method of spraying the developing solution on the substrate surface (spray method), and a method of continuously discharging the developing solution while scanning a developing solution discharge nozzle at a constant speed onto a substrate rotating at a constant speed (dynamic dispense method).
After the step of developing, a step of stopping the development may be carried out while replacing the developer with another solvent.
The developing time is not particularly limited as long as the resin in the unexposed area is sufficiently dissolved, and is preferably from 10 to 300 seconds, more preferably from 20 to 120 seconds.
The temperature of the developer is preferably from 0 to 50°C, and more preferably from 15 to 35°C.

The alkaline developer is preferably an aqueous alkaline solution containing an alkali. Examples of the type of the aqueous alkaline solution include an alkaline solution containing a quaternary ammonium salt such as tetramethylammonium hydroxide, an inorganic alkali, a primary amine, a secondary amine, a tertiary amine, an alcohol amine, or a cyclic amine. Among them, the alkaline developer is preferably an aqueous solution of a quaternary ammonium salt such as tetramethylammonium hydroxide (TMAH).
The alkaline developer may contain an appropriate amount of alcohol. The alkaline developer usually has a basic compound concentration of 0.1 to 20% by mass. The alkaline developer usually has a pH of 10.0 to 15.0.

The organic developer preferably contains at least one selected from the group consisting of ketone solvents, ester solvents, alcohol solvents, amide solvents, ether solvents, and hydrocarbon solvents. As the ketone solvents and ester solvents, the organic solvents described in paragraphs [0179] to [0180] of JP 2022-125078 A can be used, and as the alcohol solvents, amide solvents, ether solvents, and hydrocarbon solvents, the solvents disclosed in paragraphs <0715> to <0718> of US Patent Application Publication No. 2016/0070167 A1 can be used.

The organic solvent contained in the organic developer may be a mixture of two or more organic solvents, or may be mixed with water.
The water content of the entire organic developer is preferably less than 50% by mass, more preferably less than 20% by mass, even more preferably less than 10% by mass, and particularly preferably substantially free of water.
The content of the organic solvent in the organic developer is preferably from 50 to 100% by mass, more preferably from 80 to 100% by mass, still more preferably from 90 to 100% by mass, and particularly preferably from 95 to 100% by mass, based on the total mass of the developer.
The developer may contain a surfactant, if necessary.

[Other steps]
The above pattern forming method preferably includes, after step 3, a rinsing step of cleaning the pattern with a rinsing liquid.

The rinsing liquid is not particularly limited as long as it does not dissolve the pattern.
The rinsing liquid used in the rinsing step after the development step using an alkaline developer is, for example, pure water.
As a rinse liquid used in a rinse step following a development step using an organic developer, a solution containing a general organic solvent that does not dissolve the pattern can be used. The organic solvent contained in the rinse liquid is preferably at least one organic solvent selected from the group consisting of hydrocarbon solvents, ketone solvents, ester solvents, alcohol solvents, amide solvents, and ether solvents.
A suitable amount of a surfactant may be added to the rinse solution.

The above cleaning method is not particularly limited, and examples include a method in which the rinse solution is continuously discharged onto a substrate rotating at a constant speed (spin coating method), a method in which the substrate is immersed in a tank filled with the rinse solution for a certain period of time (dip method), and a method in which the rinse solution is sprayed onto the substrate surface (spray method).

The pattern forming method may include a heating step (Post Bake) after the rinsing step. This step removes the developer and rinsing solution remaining between and inside the patterns. This step also anneals the resist pattern, improving the surface roughness of the pattern.
The heating step after the rinsing step is preferably carried out at 40 to 250° C. (preferably 90 to 200° C.) for 10 seconds to 3 minutes (preferably 30 seconds to 120 seconds).

The formed pattern may be used as a mask to perform an etching process on the substrate, which is the object to be etched. In other words, the pattern formed in step 3 may be used as a mask to process the substrate (or the base film and the substrate) to form a pattern on the substrate.
Although the method for processing the substrate (or the undercoat film and the substrate) is not particularly limited, a method is preferred in which the substrate (or the undercoat film and the substrate) is dry-etched using the pattern formed in step 3 as a mask to form a pattern on the substrate. The dry etching is preferably oxygen plasma etching.

The resist composition and various materials used in the pattern formation method of the present invention (e.g., solvent, developer, rinse solution, anti-reflective film forming composition, top coat forming composition, etc.) preferably do not contain impurities such as metals. The content of impurities contained in these materials is preferably 1 mass ppm or less, more preferably 10 mass ppb or less, even more preferably 100 mass ppt or less, particularly preferably 10 mass ppt or less, and most preferably 1 mass ppt or less. There is no particular lower limit, and 0 mass ppt is preferable. Here, examples of metal impurities include Na, K, Ca, Fe, Cu, Mg, Al, Li, Cr, Ni, Sn, Ag, As, Au, Ba, Cd, Co, Pb, Ti, V, W, and Zn.

An example of a method for removing impurities such as metals from various materials is filtration using a filter. For filtration using a filter, the method described in paragraph [0321] of WO 2020/004306 can be used.

Methods for reducing metal and other impurities contained in various materials include, for example, selecting raw materials with low metal content as the raw materials that make up the various materials, filtering the raw materials that make up the various materials, and performing distillation under conditions that minimize contamination as much as possible, such as lining the inside of the equipment with Teflon (registered trademark).

In addition to filtration, impurities may be removed using an adsorbent, or a combination of filtration and an adsorbent may be used. As the adsorbent, known adsorbents may be used, for example, inorganic adsorbents such as silica gel and zeolite, and organic adsorbents such as activated carbon. In order to reduce impurities such as metals contained in the various materials, it is necessary to prevent the incorporation of metal impurities in the manufacturing process. Whether metal impurities have been sufficiently removed from the manufacturing equipment can be confirmed by measuring the content of metal components contained in the cleaning solution used to clean the manufacturing equipment. The content of metal components contained in the cleaning solution after use is preferably 100 parts per trillion (ppt) by mass or less, more preferably 10 ppt by mass or less, and even more preferably 1 ppt by mass or less. There is no particular lower limit, and 0 ppt by mass or more is preferable.

A conductive compound may be added to an organic processing liquid such as a developer and a rinse liquid in order to prevent breakdown of chemical piping and various parts (such as filters, O-rings, and tubes) due to static charging and subsequent static discharge. The conductive compound is not particularly limited, but an example thereof is methanol. The amount added is not particularly limited, but from the viewpoint of maintaining favorable development characteristics or rinsing characteristics, it is preferably 10% by mass or less, and more preferably 5% by mass or less. The lower limit is not particularly limited, but 0.01% by mass or more is preferable.
The chemical liquid piping may be made of, for example, stainless steel (SUS), or various piping coated with antistatic polyethylene, polypropylene, or fluororesin (polytetrafluoroethylene, perfluoroalkoxy resin, etc.). Similarly, the filter and O-ring may be made of antistatic polyethylene, polypropylene, or fluororesin (polytetrafluoroethylene, perfluoroalkoxy resin, etc.).

[Device Manufacturing Method]
The present invention also relates to a method for manufacturing an electronic device, which includes the above-mentioned pattern formation method, and an electronic device manufactured by this manufacturing method.
The electronic device of the present invention is suitably mounted in electric and electronic equipment (such as home appliances, OA (Office Automation), media-related equipment, optical equipment, and communication equipment).

The present invention will be described in further detail below with reference to examples.
The materials, amounts, ratios, processing contents, processing procedures, etc. shown in the following examples can be changed as appropriate without departing from the spirit of the present invention. Therefore, the scope of the present invention should not be interpreted as being limited by the following examples.

[Preparation of resist composition]
The components contained in the resist compositions used in the examples and comparative examples are shown below.

〔resin〕
The structures of the monomers that give the repeating units contained in the resins (P-1) to (P-10) are shown below.

Table 1 shows the compositions of the resins (P-1) to (P-10) of the respective examples and comparative examples.
In Table 1, the weight average molecular weight (Mw) and polydispersity index ("PDI" (Mw/Mn)) are polystyrene equivalent values measured by GPC (carrier: tetrahydrofuran (THF)). The "content [mol %]" column in Table 1 indicates the content (mol %) of each repeating unit relative to the total repeating units in the resin.

[Photoacid generator and acid diffusion controller]
The structures of the cations (C-1) to (C-8) contained in the photoacid generators and acid diffusion controllers of the respective Examples and Comparative Examples are shown below.

Below are the anions (PA-1) to (PA-2) contained in the photoacid generators of each Example and Comparative Example, and the pKa of the acidic compounds formed when each anion is bonded to a proton.

Below are shown the first anions (A1-1) to (A1-5) contained in the first acid diffusion controller of each Example, the anions (CA1-1) to (CA1-2) contained in the first acid diffusion controller of each Comparative Example, and the pKa of the acidic compound formed when each anion is bonded to a proton.

Below are shown the second anions (A2-1) to (A2-6) contained in the second acid diffusion controller of each Example, the anions (CA2-1) to (CA2-2) contained in the second acid diffusion controller of each Comparative Example, and the pKa of the acidic compound formed when each anion is bonded to a proton.

The photoacid generator, first acid diffusion controller, and second acid diffusion controller in each of the examples and comparative examples are compounds consisting of the cations and anions shown in Table 1. For example, the first acid diffusion controller used in Example 1 is a compound consisting of a cation (C-1) (first cation) and an anion (A1-1) (first anion), and is represented by the following structure.

〔solvent〕
As a solvent for the resist composition, a mixed solvent having the following composition was used.
Propylene glycol monomethyl ether acetate 79% by mass
Propylene glycol monomethyl ether 20% by mass
γ-butyrolactone 1% by mass

[Hydrophobic resin]
The structures of the monomers that give the respective repeating units contained in the hydrophobic resins (D-1) to (D-8) are shown below.

Table 2 shows the composition of each of the hydrophobic resins (D-1) to (D-8).
In Table 2, the weight average molecular weight (Mw) and polydispersity index ("PDI" (Mw/Mn)) are polystyrene equivalent values measured by GPC (carrier: tetrahydrofuran (THF)). The "content [mol %]" column in Table 2 indicates the content (mol %) of each repeating unit relative to the total repeating units in the resin.

[Surfactant]
The surfactants (E-1) to (E-3) used as additives in the resist composition are shown below.
E-1: Megafac F176 (manufactured by DIC, fluorosurfactant)
E-2: Megafac R08 (manufactured by DIC, fluorine and silicon surfactant)
E-3: PF656 (manufactured by OMNOVA, fluorosurfactant)

A mixed liquid was prepared by mixing the components and the solvent in the ratio shown in Table 3. The solvent was added so that the solid concentration was 2.5 mass %.
The resulting mixture was filtered in this order through a UPE (ultra high molecular weight polyethylene) filter having a pore size of 0.1 μm, a Nylon filter having a pore size of 0.02 μm, and a UPE filter having a pore size of 0.01 μm, to obtain resist compositions of each of the Examples and Comparative Examples.

[Formation of Resist Pattern by Organic Solvent Development (Formation of Pattern 1)]
A base film-forming composition AL412 (manufactured by Brewer Science) was applied onto a silicon wafer and baked at 205° C. for 60 seconds to form a base film having a thickness of 5 nm. Next, the resist composition of each of the examples and comparative examples was applied onto the obtained base film and baked at 90° C. for 60 seconds to form a resist film having a thickness of 35 nm.
The wafer coated with the resist film was subjected to pattern exposure using an EUV exposure apparatus (Micro Exposure Tool, NA (numerical aperture) 0.3, Quadruple, outer sigma 0.68, inner sigma 0.36) manufactured by Exitech Corp. As the exposure mask, a line and space pattern with a line width of 20 nm and a space width of 20 nm was used.
The exposed resist film was baked at 90° C. for 60 seconds, and then developed for 30 seconds using butyl acetate as a developer, followed by spin drying to obtain a negative-type line-and-space pattern with a line width of 20 nm and a space width of 20 nm.

[Formation of Resist Pattern by Alkaline Aqueous Solution Development (Formation of Pattern 2)]
A base film-forming composition AL412 (manufactured by Brewer Science) was applied onto a silicon wafer and baked at 205° C. for 60 seconds to form a base film having a thickness of 5 nm. Next, the resist composition of each of the Examples and Comparative Examples was applied onto the obtained base film and baked at 90° C. for 60 seconds to form a resist film having a thickness of 30 nm.
The wafer coated with the resist film was subjected to pattern exposure using an EUV exposure device (Micro Exposure Tool, NA (numerical aperture) 0.3, Quadruple, outer sigma 0.68, inner sigma 0.36) manufactured by Exitech Corp. An exposure mask having a line and space pattern with a line width of 20 nm and a space width of 20 nm was used.
The exposed resist film was baked at 90° C. for 60 seconds, and then developed for 30 seconds using a tetramethylammonium hydroxide aqueous solution (concentration: 2.38% by mass) as a developer. After rinsing with pure water for 30 seconds, the resist film was spin-dried to obtain a positive-type line-and-space pattern with a line width of 20 nm and a space width of 20 nm.

[LWR evaluation]
The line and space pattern resolved at the optimum exposure dose was observed from above the pattern using a critical dimension scanning electron microscope (SEM (S-9380II, Hitachi, Ltd.)). The line width of the line and space pattern was measured at any point, and 3σ (nm) was calculated when σ was the standard deviation of all the measured values obtained. From the obtained 3σ value, the LWR was evaluated according to the following evaluation criteria.

5: 3σ is 3.0 nm or less 4: 3σ is more than 3.0 nm and less than 3.5 nm 3: 3σ is more than 3.5 nm and less than 4.0 nm 2: 3σ is more than 4.0 nm and less than 4.5 nm 1: 3σ is more than 4.5 nm

[result]
The components of each resist composition and the LWR evaluation results of pattern 1 are shown in Tables 3 and 4.
In Tables 3 and 4, the content [wt %] indicates the content (wt %) of each component relative to the total solid content of the resist composition.
In Tables 3 and 4, pKa(A) means the above-mentioned acid dissociation constant A, pKa(B) means the above-mentioned acid dissociation constant B, and pKa(C) means the above-mentioned acid dissociation constant C.
In Tables 3 and 4, the ClogP values were calculated using ChemDraw Professional (version 20.1.1.125, manufactured by PerkinElmer) according to the method described above.
In Tables 3 and 4, the volumes are values calculated using Winmostar (QM) (version 20.1.1.125, manufactured by X-Ability) using the method described above.
Table 4 is a continuation of Table 3. For example, the resist composition of Example 1 contains the first anion A1-1 shown in Table 3 and the resin P-1 shown in Table 4.

It was confirmed from the results in Tables 3 and 4 that the resist composition of the present invention was capable of forming a resist pattern with small LWR.
From a comparison between Examples 1 to 3 and 5, it was confirmed that the effect of the present invention is more excellent when the volume of the first anion is 200 Å ³ or less.
From a comparison between Examples 1 and 6 to 9, it was confirmed that the effects of the present invention are more excellent when the ClogP value of the first cation is 5.00 or more.
From a comparison between Examples 1 and 10 to 13, it was confirmed that the effects of the present invention were more excellent when the content of the first acid diffusion controller was 15 mass % or less based on the total solid content of the resist composition.
From a comparison of Examples 1, 4, and 13 to 17, it was confirmed that the effects of the present invention are more excellent when at least one selected from the first acid diffusion controller and the second acid diffusion controller has a fluorine atom.
From the comparison of Examples 1 to 3, 5, and 15, it was confirmed that the effects of the present invention are more excellent when the polycyclic alicyclic structure of the first anion is an adamantane structure or an adamantanone structure.
For pattern 2 formed by the above-mentioned aqueous alkaline solution development, the same results as for pattern 1 were obtained.

Claims

A resin whose polarity increases under the action of an acid;
a photoacid generator which comprises an anion and a cation and generates an acid when exposed to actinic rays or radiation;
a first acid diffusion controller comprising a first anion and a first cation;
a second acid diffusion control agent comprising a second anion and a second cation;
an acid dissociation constant A of an acidic compound obtained by replacing the cation in the photoacid generator with a proton is smaller than both an acid dissociation constant B of an acidic compound obtained by replacing the first cation in the first acid diffusion controller with a proton and an acid dissociation constant C of an acidic compound obtained by replacing the second cation in the second acid diffusion controller with a proton,
the first anion has a polycyclic alicyclic structure which may have a substituent, a methylene group constituting the polycyclic alicyclic structure may be substituted with -O-, -CO-, -S-, or -SO 2 -, an ethylene group constituting the polycyclic alicyclic structure may be substituted with a vinylene group, and when the polycyclic alicyclic structure has a plurality of substituents, two of the substituents may be bonded to each other to form a ring;
the first anion has a ClogP value of −1.50 or less;
the volume of the second anion is greater than the volume of the first anion;
the second anion has a volume of 250 Å3 or more.
2. The actinic ray-sensitive or radiation-sensitive resin composition according to claim 1, wherein the first anion has an adamantane structure which may have a substituent, a methylene group constituting the adamantane structure may be substituted with -O-, -CO-, -S-, or -SO 2 -, an ethylene group constituting the adamantane structure may be substituted with a vinylene group, and when the adamantane structure has a plurality of substituents, two of the substituents may be bonded to each other to form a ring.
2. The actinic ray-sensitive or radiation-sensitive resin composition according to claim 1, wherein the first anion has a volume of 200 Å3 or less.
The actinic ray-sensitive or radiation-sensitive resin composition according to claim 1, wherein the ClogP value of the first cation is 5.00 or more.
The actinic ray-sensitive or radiation-sensitive resin composition according to claim 1, wherein the content of the first acid diffusion control agent is 15 mass% or less based on the total solid content in the actinic ray-sensitive or radiation-sensitive resin composition.
The actinic ray-sensitive or radiation-sensitive resin composition according to claim 1, wherein at least one of the first acid diffusion control agent and the second acid diffusion control agent contains at least one selected from the group consisting of fluorine atoms and iodine atoms.
A resist film formed using the actinic ray-sensitive or radiation-sensitive resin composition according to any one of claims 1 to 6.
A step 1 of forming a resist film on a substrate using the actinic ray-sensitive or radiation-sensitive resin composition according to any one of claims 1 to 6;
a step 2 of exposing the resist film;
and step 3 of developing the exposed resist film with a developer to obtain a resist pattern.
A method for manufacturing an electronic device, comprising the pattern formation method according to claim 8.