JP7467148B2 - Resin, resist composition, and method for producing resist pattern - Google Patents

Description

The present invention relates to a resin, a resist composition, and a method for producing a resist pattern using the resist composition.

Patent Document 1 describes a resist composition containing a resin having a structural unit derived from the following compound.

特許文献３には、下記構造単位を有する樹脂を含有するレジスト組成物が記載されている。
Patent Document 2 describes a resist composition containing a resin having a structural unit derived from the following compound.

Patent Document 3 describes a resist composition containing a resin having the following structural unit.

JP 2010-237334 A JP 2010-250072 A JP 2002-214788 A

The present invention provides a resin that forms a resist pattern with better CD uniformity (CDU) than a resist pattern formed with a resist composition containing the above resin.

［式（Ｉ）中、
Ｒ^１は、水素原子又はメチル基を表す。
Ｘ^１は、式（Ｘ^１－１）～式（Ｘ^１－７）のいずれかで表される基を表す。

（式（Ｘ^１－１）～式（Ｘ^１－７）中、
＊、＊＊は結合部位であり、＊＊はＬ^１との結合部位を表す。）
Ｌ^１は、単結合又は置換基を有していてもよい炭素数１～４８の炭化水素基を表し、該炭化水素基に含まれる－ＣＨ₂－は、－Ｏ－、－Ｓ－、－ＣＯ－又は－ＳＯ_２－に置き換わっていてもよい。
Ｒ^２、Ｒ^３、Ｒ^４及びＲ^５は、それぞれ独立に、水素原子又は炭素数１～６の飽和炭化水素基を表す（但し、Ｒ^２、Ｒ^３、Ｒ^４及びＲ^５の少なくとも１つは炭素数１～６の飽和炭化水素基を表す。）か、Ｒ^２又はＲ^４及びＲ^３又はＲ^５は、互いに結合してそれらが結合する炭素原子とともに炭素数１～４のアルキル基を有してもよい炭素数３～５の脂環式炭化水素基を形成している。］

［式（ＩＩＩ）中、
Ｒ^６は、水素原子又はメチル基を表す。
Ａ^１は、単結合又は^＊－ＣＯ－Ｏ－を表し、＊は－Ｒ^６が結合する炭素原子との結合部位を表す。
Ｒ^７は、ハロゲン原子、ヒドロキシ基、炭素数１～４のハロアルキル基又は炭素数１～１２のアルキル基を表し、該アルキル基に含まれる－ＣＨ₂－は、－Ｏ－又は－ＣＯ－で置き換わっていてもよい。
ｍｉは、１～３のいずれかの整数を表す。
ｎｉは、０～４のいずれかの整数を表し、ｎｉが２以上のとき、複数のＲ^７は互いに同一であっても異なってもよい。但し、ｍｉ＋ｎｉ≦５である。］
［２］Ｌ^１が、単結合、炭素数１～６のアルカンジイル基（該アルカンジイル基に含まれる－ＣＨ₂－は、－Ｏ－又は－ＣＯ－に置き換わっていてもよい。）又は炭素数３～１８の２価の脂環式炭化水素基と炭素数１～６のアルカンジイル基とから形成される２価の炭化水素基（該炭化水素基に含まれる－ＣＨ₂－は、－Ｏ－又は－ＣＯ－に置き換わっていてもよい。）である［１］記載の樹脂。
［３］Ｒ^２又はＲ^４及びＲ^３又はＲ^５は、互いに結合してそれらが結合する炭素原子とともに炭素数１～４のアルキル基を有してもよい炭素数３～５の脂環式炭化水素基を形成している［１］又は［２］記載の樹脂。
［４］Ｘ^１が、式（Ｘ^１－１）、式（Ｘ^１－３）又は式（Ｘ^１－４）のいずれかで表される基である［１］～［３］のいずれかに記載の樹脂。
［５］Ａ^１が単結合である［１］～［４］のいずれかに記載の樹脂。
［６］さらに、式（ａ１－１）で表される構造単位及び式（ａ１－２）で表される構造単位からなる群より選ばれる少なくとも１種の構造単位を含む［１］～［５］のいずれかに記載の樹脂。

［式（ａ１－１）及び式（ａ１－２）中、
Ｌ^ａ１及びＬ^ａ２は、それぞれ独立に、－Ｏ－又は＊－Ｏ－（ＣＨ_２）_ｋ１－ＣＯ－Ｏ－を表し、ｋ１は１～７のいずれかの整数を表し、＊は－ＣＯ－との結合部位を表す。
Ｒ^ａ４及びＲ^ａ５は、それぞれ独立に、水素原子又はメチル基を表す。
Ｒ^ａ６及びＲ^ａ７は、それぞれ独立に、炭素数１～８のアルキル基、炭素数３～１８の脂環式炭化水素基又はこれらを組合せた基を表す。
ｍ１は、０～１４のいずれかの整数を表す。
ｎ１は、０～１０のいずれかの整数を表す。
ｎ１’は、０～３のいずれかの整数を表す。］
［７］さらに、式（ａ２－Ａ）で表される構造単位を含む［１］～［６］のいずれかに記載の樹脂。

［式（ａ２－Ａ）中、
Ｒ^a50は、水素原子、ハロゲン原子又はハロゲン原子を有していてもよい炭素数１～６のアルキル基を表す。
Ｒ^a51は、ハロゲン原子、ヒドロキシ基、炭素数１～６のアルキル基、炭素数１～６のアルコキシ基、炭素数２～４のアルキルカルボニル基、炭素数２～４のアルキルカルボニルオキシ基、アクリロイルオキシ基又はメタクリロイルオキシ基を表す。
Ａ^a50は、単結合又は^＊－Ｘ^a51－（Ａ^a52－Ｘ^a52）_nｂ－を表し、＊は－Ｒ^a50が結合する炭素原子との結合部位を表す。
Ａ^a52は、炭素数１～６のアルカンジイル基を表す。
Ｘ^a51及びＸ^a52は、それぞれ独立に、－Ｏ－、－ＣＯ－Ｏ－又は－Ｏ－ＣＯ－を表す。
ｎｂは、０又は１を表す。
ｍｂは０～４のいずれかの整数を表す。ｍｂが２以上のいずれかの整数である場合、複数のＲ^a51は互いに同一であっても異なってもよい。］
［８］［１］～［７］のいずれかに記載の樹脂と、酸発生剤とを含有するレジスト組成物。
［９］酸発生剤が、式（Ｂ１）で表される塩を含む［８］記載のレジスト組成物。

［式（Ｂ１）中、
Ｑ^ｂ１及びＱ^ｂ２は、それぞれ独立に、フッ素原子又は炭素数１～６のペルフルオロアルキル基を表す。
Ｌ^ｂ１は、炭素数１～２４の２価の飽和炭化水素基を表し、該２価の飽和炭化水素基に含まれる－ＣＨ_２－は、－Ｏ－又は－ＣＯ－に置き換わっていてもよく、該２価の飽和炭化水素基に含まれる水素原子は、フッ素原子又はヒドロキシ基で置換されていてもよい。
Ｙは、置換基を有していてもよいメチル基又は置換基を有していてもよい炭素数３～１８の脂環式炭化水素基を表し、該脂環式炭化水素基に含まれる－ＣＨ_２－は、－Ｏ－、－Ｓ（Ｏ）_２－又は－ＣＯ－に置き換わっていてもよい。
Ｚ^＋は、有機カチオンを表す。］
［１０］酸発生剤から発生する酸よりも酸性度の弱い酸を発生する塩をさらに含有する［８］又は［９］記載のレジスト組成物。
［１１］（１）［８］～［１０］のいずれかに記載のレジスト組成物を基板上に塗布する工程、
（２）塗布後の組成物を乾燥させて組成物層を形成する工程、
（３）組成物層に露光する工程、
（４）露光後の組成物層を加熱する工程、及び
（５）加熱後の組成物層を現像する工程、を含むレジストパターンの製造方法。 The present invention includes the following inventions.
[1] A resin containing a structural unit represented by formula (I) and a structural unit represented by formula (III).

[In formula (I),
^R1 represents a hydrogen atom or a methyl group.
X ¹ represents a group represented by any one of formulas (X ¹ -1) to (X ¹ -7).

(In formulas (X ¹ -1) to (X ¹ -7),
* and ** are binding sites, and ** represents the binding site to ^L1 .)
L ¹ represents a single bond or a hydrocarbon group having 1 to 48 carbon atoms which may have a substituent, and --CH ₂ -- contained in the hydrocarbon group may be replaced by --O--, --S--, --CO-- or --SO ₂ --.
R ² , R ³ , R ⁴ and R ⁵ each independently represent a hydrogen atom or a saturated hydrocarbon group having 1 to 6 carbon atoms (provided that at least one of R ² , R ³ , R ⁴ and R ⁵ represents a saturated hydrocarbon group having 1 to 6 carbon atoms), or R ² or R ⁴ and R ³ or R ⁵ are bonded to each other to form, together with the carbon atom to which they are bonded, an alicyclic hydrocarbon group having 3 to 5 carbon atoms which may have an alkyl group having 1 to 4 carbon atoms.]

[In the formula (III),
^R6 represents a hydrogen atom or a methyl group.
A ¹ represents a single bond or ^* -CO-O-, and * represents the bonding site with the carbon atom to which -R ⁶ is bonded.
^R7 represents a halogen atom, a hydroxy group, a haloalkyl group having 1 to 4 carbon atoms or an alkyl group having 1 to 12 carbon atoms, and --CH ₂ -- contained in the alkyl group may be replaced by --O-- or --CO--.
mi represents an integer of 1 to 3.
ni represents an integer of 0 to 4, and when ni is 2 or more, the multiple R ^7s may be the same or different from each other, provided that mi+ni≦5.
[2] The resin according to [1], wherein L ¹ is a single bond, an alkanediyl group having 1 to 6 carbon atoms (-CH ₂ - contained in the alkanediyl group may be replaced with -O- or -CO-), or a divalent hydrocarbon group formed from a divalent alicyclic hydrocarbon group having 3 to 18 carbon atoms and an alkanediyl group having 1 to 6 carbon atoms (-CH ₂ - contained in the hydrocarbon group may be replaced with -O- or -CO-).
[3] The resin according to [1] or [2], wherein ^R2 or ^R4 and ^R3 or ^R5 are bonded to each other to form, together with the carbon atom to which they are bonded, an alicyclic hydrocarbon group having 3 to 5 carbon atoms which may have an alkyl group having 1 to 4 carbon atoms.
[4] The resin according to any one of [1] to [3], wherein X ¹ is a group represented by any one of formula (X ¹ -1), formula (X ¹ -3) and formula (X ¹ -4).
[5] The resin according to any one of [1] to [4], wherein A ¹ is a single bond.
[6] The resin according to any one of [1] to [5], further comprising at least one structural unit selected from the group consisting of a structural unit represented by formula (a1-1) and a structural unit represented by formula (a1-2):

[In formula (a1-1) and formula (a1-2),
L ^a1 and L ^a2 each independently represent --O-- or *-O--(CH ₂ ) _k1 --CO--O--, where k1 represents an integer of 1 to 7, and * represents a bonding site with --CO--.
R ^a4 and R ^a5 each independently represent a hydrogen atom or a methyl group.
R ^a6 and R ^a7 each independently represent an alkyl group having 1 to 8 carbon atoms, an alicyclic hydrocarbon group having 3 to 18 carbon atoms, or a combination thereof.
m1 represents an integer of 0 to 14.
n1 represents an integer of 0 to 10.
n1′ represents an integer of 0 to 3.
[7] The resin according to any one of [1] to [6], further comprising a structural unit represented by formula (a2-A):

[In formula (a2-A),
R ^a50 represents a hydrogen atom, a halogen atom or an alkyl group having 1 to 6 carbon atoms which may have a halogen atom.
R ^a51 represents a halogen atom, a hydroxyl group, an alkyl group having 1 to 6 carbon atoms, an alkoxy group having 1 to 6 carbon atoms, an alkylcarbonyl group having 2 to 4 carbon atoms, an alkylcarbonyloxy group having 2 to 4 carbon atoms, an acryloyloxy group or a methacryloyloxy group.
A ^a50 represents a single bond or ^* -X ^a51 -(A ^a52 -X ^a52 ) _nb -, where * represents the bonding site with the carbon atom to which -R ^a50 is bonded.
A ^a52 represents an alkanediyl group having 1 to 6 carbon atoms.
X ^a51 and X ^a52 each independently represent —O—, —CO—O— or —O—CO—.
nb represents 0 or 1.
mb represents an integer of 0 to 4. When mb is an integer of 2 or more, multiple R ^a51 may be the same or different.
[8] A resist composition comprising the resin according to any one of [1] to [7] and an acid generator.
[9] The resist composition according to [8], wherein the acid generator contains a salt represented by formula (B1):

[In formula (B1),
Q ^b1 and Q ^b2 each independently represent a fluorine atom or a perfluoroalkyl group having 1 to 6 carbon atoms.
L ^b1 represents a divalent saturated hydrocarbon group having 1 to 24 carbon atoms, in which -CH ₂ - may be replaced by -O- or -CO-, and in which a hydrogen atom may be replaced by a fluorine atom or a hydroxyl group.
Y represents an optionally substituted methyl group or an optionally substituted alicyclic hydrocarbon group having 3 to 18 carbon atoms, and one -CH ₂ - contained in the alicyclic hydrocarbon group may be replaced by -O-, -S(O) ₂ - or -CO-.
Z ⁺ represents an organic cation.
[10] The resist composition according to [8] or [9], further comprising a salt capable of generating an acid having a weaker acidity than the acid generated from the acid generator.
[11] (1) A step of applying the resist composition according to any one of [8] to [10] onto a substrate;
(2) A step of drying the applied composition to form a composition layer;
(3) exposing the composition layer to light;
(4) a step of heating the composition layer after exposure; and (5) a step of developing the composition layer after heating.

By using a resist composition containing the resin of the present invention, it is possible to produce resist patterns with good CD uniformity (CDU).

In this specification, unless otherwise specified, "(meth)acrylate" means "at least one selected from the group consisting of acrylate and methacrylate". The terms "(meth)acrylic acid" and "(meth)acryloyl" have the same meaning. When a structural unit having "CH ₂ ═C(CH ₃ )-CO-" or "CH ₂ ═CH-CO-" is exemplified, a structural unit having both groups is also exemplified. In addition, in this specification, "derived from" or "derived from" refers to a polymerizable C═C bond contained in the molecule becoming a -C-C- group upon polymerization. In the groups described in this specification, those that can have both a linear structure and a branched structure may be either of them. "Combined group" means a group in which two or more of the exemplified groups are bonded, and the valence of the groups may be appropriately changed depending on the bond form. When stereoisomers exist, all stereoisomers are included.
In this specification, the term "solids content of a resist composition" refers to the sum of the components excluding the solvent (E), which will be described later, from the total amount of the resist composition.

〔resin〕
The resin of the present invention is a resin (hereinafter, sometimes referred to as “resin (A)”) that contains a structural unit represented by formula (I) (hereinafter, sometimes referred to as structural unit (I)) and a structural unit represented by formula (III) (hereinafter, sometimes referred to as structural unit (III)).

<Structural Unit (I)>
In formula (I), R ¹ is preferably a methyl group.
Examples of the divalent hydrocarbon group having 1 to 48 carbon atoms for ^L1 include a divalent chain hydrocarbon group such as an alkanediyl group, a divalent monocyclic or polycyclic alicyclic saturated hydrocarbon group, and a divalent aromatic hydrocarbon group, and may be a divalent hydrocarbon group formed by combining two or more of these groups.

Examples of the alkanediyl group include linear alkanediyl groups such as a methylene group, an ethylene group, a propane-1,3-diyl group, a butane-1,4-diyl group, a pentane-1,5-diyl group, a hexane-1,6-diyl group, a heptane-1,7-diyl group, an octane-1,8-diyl group, a nonane-1,9-diyl group, a decane-1,10-diyl group, an undecane-1,11-diyl group, and a dodecane-1,12-diyl group;
Examples of branched alkanediyl groups include ethane-1,1-diyl group, propane-1,1-diyl group, propane-1,2-diyl group, propane-2,2-diyl group, pentane-2,4-diyl group, 2-methylpropane-1,3-diyl group, 2-methylpropane-1,2-diyl group, pentane-1,4-diyl group, and 2-methylbutane-1,4-diyl group.
Examples of the monocyclic divalent alicyclic saturated hydrocarbon group include monocyclic cycloalkanediyl groups such as a cyclobutane-1,3-diyl group, a cyclopentane-1,3-diyl group, a cyclohexane-1,4-diyl group, and a cyclooctane-1,5-diyl group.
Examples of the polycyclic divalent alicyclic saturated hydrocarbon group include polycyclic cycloalkanediyl groups such as norbornane-1,4-diyl group, norbornane-2,5-diyl group, adamantane-1,5-diyl group, and adamantane-2,6-diyl group.
Examples of the divalent aromatic hydrocarbon group include aryl groups such as a phenylene group, a naphthylene group, an anthrylene group, a biphenylene group, and a phenanthrylene group.
Examples of divalent hydrocarbon groups which are a combination of two or more types include -alicyclic saturated hydrocarbon group-alkanediyl group-, -alkanediyl group-alicyclic saturated hydrocarbon group-, -alkanediyl group-alicyclic saturated hydrocarbon group-alkanediyl group-, -alkanediyl group-aromatic hydrocarbon group-, -aromatic hydrocarbon group-alkanediyl group-, -alkanediyl group-aromatic hydrocarbon group-alkanediyl group-, -alicyclic saturated hydrocarbon group-aromatic hydrocarbon group-, -aromatic hydrocarbon group-alicyclic saturated hydrocarbon group-, and the like.

Examples of the substituent on the hydrocarbon group of ^L1 include a hydroxy group, a cyano group, a carboxyl group, an alkoxy group having 1 to 12 carbon atoms, an acyl group having 2 to 13 carbon atoms, an acyloxy group having 2 to 13 carbon atoms, and a combination of two or more of these groups.
Examples of the alkoxy group having 1 to 12 carbon atoms include a methoxy group, an ethoxy group, a propoxy group, a butoxy group, a pentyloxy group, and a hexyloxy group.
Examples of the acyl group having 2 to 13 carbon atoms include an acetyl group, a propionyl group, and a butyryl group.
Examples of the acyloxy group having 2 to 13 carbon atoms include an acetyloxy group, a propionyloxy group, and a butyryloxy group.
The divalent hydrocarbon group having 1 to 48 carbon atoms represented by L ¹ may have one or more substituents.

The --CH ₂ -- contained in the divalent hydrocarbon group having 1 to 48 carbon atoms of L ¹ may be replaced by --O--, --S--, --CO-- or --SO ₂ --.
When the divalent hydrocarbon group having 1 to 48 carbon atoms represented by ^L1 has a substituent, or when --CH ₂ -- contained in the hydrocarbon group is replaced by --O--, --S--, --CO-- or --SO ₂ --, the number of carbon atoms before replacement is regarded as the number of carbon atoms of the hydrocarbon group.

The divalent hydrocarbon group having 1 to 48 carbon atoms represented by ^L1 includes an alkanediyl group having 1 to 12 carbon atoms (-CH ₂ - contained in the alkanediyl group may be replaced by -O- or -CO-), a divalent alicyclic hydrocarbon group having 3 to 18 carbon atoms (-CH ₂ - contained in the alicyclic hydrocarbon group may be replaced by -O- or -CO-), a divalent hydrocarbon group formed from a divalent alicyclic hydrocarbon group having 3 to 18 carbon atoms and an alkanediyl group having 1 to 12 carbon atoms (-CH ₂ - contained in the hydrocarbon group may be replaced by -O- or -CO-), a divalent aromatic hydrocarbon group having 6 to 18 carbon atoms, a divalent hydrocarbon group formed from a divalent aromatic hydrocarbon group having 6 to 18 carbon atoms and an alkanediyl group having 1 to 12 carbon atoms (-CH ₂ - contained in the hydrocarbon group may be replaced by -O- or -CO-). is preferably an alkanediyl group having 1 to 6 carbon atoms (-CH ₂ - contained in the alkanediyl group may be replaced by -O- or -CO-), a divalent alicyclic hydrocarbon group having 3 to 18 carbon atoms (-CH ₂ - contained in the alicyclic hydrocarbon group may be replaced by -O- or -CO-) or a divalent hydrocarbon group formed from a divalent alicyclic hydrocarbon group having 3 to 18 carbon atoms and an alkanediyl group having 1 to 6 carbon atoms (-CH ₂ - contained in the hydrocarbon group may be replaced by -O- or -CO-), more preferably an alkanediyl group having 1 to 6 carbon atoms (-CH ₂ - contained in the alkanediyl group may be replaced by -O- or -CO-). It is more preferably a divalent hydrocarbon group formed from a divalent alicyclic hydrocarbon group having 3 to 18 carbon atoms and an alkanediyl group having 1 to 6 carbon atoms (-CH ₂ - contained in the hydrocarbon group may be replaced by -O- or -CO-), and even more preferably an alkanediyl group having 1 to 4 carbon atoms (-CH ₂ - contained in the alkanediyl group may be replaced by -O- or -CO-), a group represented by *-A ¹¹ -X ^1A -A ¹² - or a group represented by *-X ^1A -A ¹³ -.

X ^1A represents a divalent alicyclic hydrocarbon group having 3 to 18 carbon atoms, and is preferably a cyclohexanediyl group or an adamantanediyl group.
A ¹¹ , A ¹² and A ¹³ each independently represent an alkanediyl group having 1 to 6 carbon atoms (-CH ₂ - contained in the alkanediyl group may be replaced by -O- or -CO-). A ¹¹ is preferably a methylene group. A ¹² and A ¹³ are preferably **-CO-O-, **-O-CO-O- or **-O-.
* represents the binding site to ^X1 . ** represents the binding site to ^X1A .
L ¹ is preferably a single bond, an alkanediyl group having 1 to 6 carbon atoms (-CH ₂ - contained in the alkanediyl group may be replaced with -O- or -CO-), a divalent alicyclic hydrocarbon group having 3 to 18 carbon atoms (-CH ₂ - contained in the alicyclic hydrocarbon group may be replaced with -O- or -CO-), or a divalent hydrocarbon group formed from a divalent alicyclic hydrocarbon group having 3 to 18 carbon atoms and an alkanediyl group having 1 to 6 carbon atoms (-CH ₂ - contained in the hydrocarbon group may be replaced with -O- or -CO-), and is preferably a single bond, an alkanediyl group having 1 to 6 carbon atoms (-CH ₂ - contained in the alkanediyl group may be replaced with -O- or -CO-). - may be replaced by -O- or -CO-) or a divalent hydrocarbon group formed from a divalent alicyclic hydrocarbon group having 3 to 18 carbon atoms and an alkanediyl group having 1 to 6 carbon atoms (-CH ₂ - contained in the hydrocarbon group may be replaced by -O- or -CO-), and a single bond, an alkanediyl group having 1 to 4 carbon atoms (-CH ₂ - contained in the alkanediyl group may be replaced by -O- or -CO-), a group represented by *-A ¹¹ -X ^1A -A ¹² -, or a group represented by *-X ^1A -A ¹³ - is even more preferred, and a single bond, *-CH ₂ It is still more preferable that it is --CO--O--, *-adamantanediyl group -CO--O-- or *-adamantanediyl group -O--CO--O--, and it is still more preferable that it is a single bond, *-adamantanediyl group -CO--O-- or *-adamantanediyl group -O--CO--O--.

Examples of the saturated hydrocarbon group having 1 to 6 carbon atoms represented by R ² , R ³ , R ⁴ , and R ⁵ include chain saturated hydrocarbon groups such as alkyl groups, such as a methyl group, ethyl group, propyl group, isopropyl group, butyl group, isobutyl group, tert-butyl group, pentyl group, and hexyl group, and alicyclic saturated hydrocarbon groups such as cycloalkyl groups, such as a cyclopropyl group, cyclobutyl group, cyclopentyl group, and cyclohexyl group.
R ² , R ³ , R ⁴ and R ⁵ are preferably a hydrogen atom or an alkyl group having 1 to 4 carbon atoms (provided that at least one of R ² , R ³ , R ⁴ and R ⁵ is an alkyl group having 1 to 4 carbon atoms), or a group in which R ² or R ⁴ and R ³ or R ⁵ are bonded together to form an alicyclic hydrocarbon group having 3 to 5 carbon atoms which may have an alkyl group having 1 to 4 carbon atoms together with the carbon atoms to which they are bonded, and among these, a hydrogen atom or a methyl group (provided that at least one of R ² , R ³ , R ⁴ and R ⁵ is a methyl group), or a group in which R ² or R ⁴ and R ³ or R ⁵ are bonded together to form an alicyclic hydrocarbon group having 3 to 5 carbon atoms which may have a methyl group together with the carbon atoms to which they are bonded,
It is more preferable that ^R2 or ^R4 and ^R3 or ^R5 are bonded to each other to form, together with the carbon atom to which they are bonded, an alicyclic hydrocarbon group having 3 to 5 carbon atoms which may have an alkyl group having 1 to 4 carbon atoms, and among these, it is preferable that ^R2 or ^R4 and ^R3 or ^R5 are bonded to each other to form, together with the carbon atom to which they are bonded, an alicyclic hydrocarbon group having 3 to 5 carbon atoms which may have a methyl group,
It is more preferable that ^R2 or ^R4 and ^R3 or ^R5 are bonded to each other to form, together with the carbon atom to which they are bonded, a cyclopropyl group or a cyclobutyl group having at least one alkyl group having 1 to 4 carbon atoms, and among these, it is preferable that ^R2 or ^R4 and ^R3 or ^R5 are bonded to each other to form, together with the carbon atom to which they are bonded, a cyclopropyl group or a cyclobutyl group having at least one methyl group.
When ^R2 or ^R4 and ^R3 or ^R5 are bonded to each other to form, together with the carbon atom to which they are bonded, an alicyclic hydrocarbon group having 3 to 5 carbon atoms which may have an alkyl group having 1 to 4 carbon atoms, the alicyclic hydrocarbon group is preferably a cyclopropyl group or a cyclobutyl group, more preferably a cyclopropyl group.
Furthermore, when the alicyclic hydrocarbon group having 3 to 5 carbon atoms has an alkyl group having 1 to 4 carbon atoms, the number of alkyl groups having 1 to 4 carbon atoms bonded to the alicyclic hydrocarbon group having 3 to 5 carbon atoms may be 1 or more, and preferably 2 or more. Furthermore, the alkyl group is preferably an alkyl group having 1 to 3 carbon atoms, more preferably a methyl group or an ethyl group, and even more preferably a methyl group.

Examples of the structural unit (I) include the structural units shown below.

Specific examples of the structural unit (I) include structural units in which a methyl group corresponding to R ¹ in the structural units represented by formulae (I-1) to (I-28) is replaced with a hydrogen atom. Among these, structural units represented by formulae (I-1), (I-2), and (I-12) to (I-20) are preferred, and structural units represented by formulae (I-1), (I-2), (I-12), (I-14), (I-15), and (I-19) to (I-22) are more preferred.

The content of structural unit (I) is generally 1 to 90 mol%, preferably 3 to 80 mol%, more preferably 5 to 75 mol%, even more preferably 7 to 75 mol%, still more preferably 7 to 70 mol%, and even more preferably 7 to 65 mol%, based on the total structural units in resin (A).

（式中、全ての符号は、それぞれ前記と同じ意味を表す。Ｘ^1Aは、単結合、１，４－フェニレン基又は－ＣＯ－Ｏ－Ａｒ¹－＊を表し、Ａｒ¹は１，４－フェニレン基を表す。＊はカルボニル基の炭素原子との結合位を表す。） <Method for producing a compound from which a structural unit represented by formula (I) is derived>
In the compound from which the structural unit represented by formula (I) is derived, a compound in which X ¹ is a group represented by any one of formulas (X ¹ -1), (X ¹ -3) or (X ¹ -4) (hereinafter, sometimes referred to as compound (I1)) can be obtained by reacting a compound represented by formula (I1-a) with carbonyldiimidazole in a solvent, and then further reacting the resulting mixture with a compound represented by formula (I-b).

(In the formula, all symbols have the same meaning as above. ^{X 1A} represents a single bond, a 1,4-phenylene group, or --CO--O--Ar ¹ -*, Ar ¹ represents a 1,4-phenylene group, and * represents the bonding position with the carbon atom of the carbonyl group.)

Solvents include tetrahydrofuran, chloroform, and acetonitrile.
The reaction temperature is usually 0° C. to 80° C., and the reaction time is usually 0.5 hours to 24 hours.
Examples of the compound represented by formula (I1-a) include compounds represented by the following formula, and are readily available on the market.

Examples of the compound represented by formula (Ib) include compounds represented by the following formula, and are readily available on the market.

（式中、全ての符号は、それぞれ前記と同じ意味を表す。Ｘ^1Bは、－Ａｒ¹－＊又は－ＣＯ－Ｏ－Ａｒ¹－＊を表す。＊は酸素原子との結合位を表す。） In the compound from which the structural unit represented by formula (I) is derived, a compound in which X ¹ is a group represented by formula (X ¹ -2) or formula (X ¹ -5) (a compound represented by formula (I2)) can be obtained by reacting a compound represented by formula (I2-a) with a compound represented by formula (I-b) in a solvent in the presence of a base.

(In the formula, all symbols have the same meaning as above. ^{X 1B} represents --Ar ¹ -* or --CO--O--Ar ¹ -*. * represents the bonding position with the oxygen atom.)

Solvents include tetrahydrofuran, chloroform, and acetonitrile.
The base includes potassium hydroxide and the like.
The reaction temperature is usually 0° C. to 80° C., and the reaction time is usually 0.5 hours to 24 hours.
Examples of the compound represented by formula (I2-a) include compounds represented by the following formula, which are readily available on the market.

（式中、全ての符号は、それぞれ前記と同じ意味を表す。Ｘ^1Cは、－Ａｒ¹－又は－ＣＯ－Ｏ－Ａｒ¹－＊を表す。＊は酸素原子との結合位を表す。） In the compound from which the structural unit represented by formula (I) is derived, a compound in which X ¹ is a group represented by formula (X ¹ -6) or formula (X ¹ -7) (a compound represented by formula (I3)) can be obtained by reacting a compound represented by formula (I3-a) with carbonyldiimidazole in a solvent, and then further reacting the resulting mixture with a compound represented by formula (I-b).

(In the formula, all symbols have the same meaning as above. ^{X 1C} represents --Ar ¹ -- or --CO--O--Ar ¹ -*. * represents the bonding position with the oxygen atom.)

Solvents include tetrahydrofuran, chloroform, and acetonitrile.
The reaction temperature is usually 0° C. to 80° C., and the reaction time is usually 0.5 hours to 24 hours.

<Structural unit (III)>
In formula (III), R ⁵ is preferably a hydrogen atom.
Examples of the halogen atom for ^R6 include a fluorine atom, a chlorine atom, a bromine atom, and an iodine atom.
The haloalkyl group having 1 to 4 carbon atoms in ^R6 represents an alkyl group having 1 to 4 carbon atoms and a halogen atom, and examples thereof include a chloromethyl group, a bromomethyl group, a fluoromethyl group, a difluoromethyl group, a trifluoromethyl group, and a perfluorobutyl group.
Examples of the alkyl group having 1 to 12 carbon atoms for ^R6 include alkyl groups such as a methyl group, an ethyl group, a propyl group, an isopropyl group, a butyl group, an isobutyl group, a tert-butyl group, a pentyl group, a hexyl group, an octyl group, and a nonyl group. The number of carbon atoms in the alkyl group is preferably 1 to 9, and more preferably 1 to 4.
When --CH ₂ -- contained in the alkyl group represented by R ⁶ is replaced by --O-- or --CO--, the number of carbon atoms before replacement is regarded as the total number of carbon atoms in the alkyl group. In addition, R ² may have a hydroxy group (a group in which -CH ₂ - in a methyl group is replaced with -O-), a carboxyl group (a group in which -CH ₂ -CH ₂ - in an ethyl group is replaced with -O-CO-), an alkoxy group having 1 to 11 carbon atoms (a group in which -CH ₂ - in an alkyl group having 2 to 12 carbon atoms is replaced with -O-), an alkoxycarbonyl group having 2 to 11 carbon atoms (a group in which -CH ₂ -CH ₂ - in an alkyl group having 3 to 12 carbon atoms is replaced with -O-CO-), an alkylcarbonyl group having 2 to 12 carbon atoms (a group in which -CH ₂ - in an alkyl group having 2 to 12 carbon atoms is replaced with -CO-), or an alkylcarbonyloxy group having 2 to 11 carbon atoms (a group in which -CH ₂ -CH ₂ - in an alkyl group having 3 to 12 carbon atoms is replaced with -CO-O-).
Examples of the alkoxy group having 1 to 11 carbon atoms include a methoxy group, an ethoxy group, a propoxy group, a butoxy group, a pentyloxy group, a hexyloxy group, an octyloxy group, a 2-ethylhexyloxy group, a nonyloxy group, a decyloxy group, and an undecyloxy group.
Examples of the alkoxycarbonyl group having 2 to 11 carbon atoms include a methoxycarbonyl group, an ethoxycarbonyl group, and a butoxycarbonyl group. Examples of the alkylcarbonyl group having 2 to 12 carbon atoms include an acetyl group, a propionyl group, and a butyryl group. Examples of the alkylcarbonyloxy group having 2 to 11 carbon atoms include an acetyloxy group, a propionyloxy group, and a butyryloxy group.
Among them, ^R6 is preferably a halogen atom, a haloalkyl group having 1 to 4 carbon atoms, or an alkyl group having 1 to 12 carbon atoms (wherein the --CH ₂ -- contained in the alkyl group may be replaced by --O-- or --CO--), and more preferably a fluorine atom, a haloalkyl group having 1 to 3 carbon atoms, or an alkyl group having 1 to 6 carbon atoms (wherein the --CH ₂ -- contained in the alkyl group may be replaced by --O-- or --CO--).
mi is preferably 1 or 2.
ni is preferably an integer of 0 to 2, and more preferably 0.

Examples of the structural unit (III) include the structural units shown below.

Specific examples of the structural unit (III) include structural units represented by formulae (III-1) to (III-8) in which the hydrogen atom corresponding to ^R5 is replaced with a methyl group, and structural units represented by formulae (III-9) to (III-16) in which the methyl group corresponding to ^R5 is replaced with a hydrogen atom. Among these, the structural units represented by formulae (III-1) to (III-8) are preferred, the structural units represented by formulae (III-1) to (III-4) are more preferred, and the structural unit represented by formula (III-1) is even more preferred.

The content of structural unit (III) in resin (A) is preferably 3 to 80 mol %, more preferably 5 to 70 mol %, even more preferably 5 to 60 mol %, and even more preferably 5 to 50 mol %, based on all structural units.

The resin (A) of the present invention may be a polymer containing one or more structural units other than the structural unit (I) and the structural unit (III). Examples of structural units other than the structural unit (I) and the structural unit (III) include a structural unit having an acid labile group other than the structural unit (I) (hereinafter sometimes referred to as "structural unit (a1)"), a structural unit having a halogen atom that is a structural unit other than a structural unit having an acid labile group (hereinafter sometimes referred to as "structural unit (a4)"), a structural unit not having an acid labile group other than the structural unit (III) (hereinafter sometimes referred to as "structural unit (s)"), and a structural unit having a non-leaving hydrocarbon group (hereinafter sometimes referred to as "structural unit (a5)"). Here, the acid labile group means a group that has a leaving group and that is released by contact with an acid to form a hydrophilic group (e.g., a hydroxyl group or a carboxyl group). In particular, resin (A) preferably contains a structural unit having an acid labile group in addition to structural unit (I) and structural unit (III), and more preferably contains at least one structural unit selected from the group consisting of structural units represented by formula (a1-1) and structural units represented by formula (a1-2).

［式（１）中、Ｒ^a1、Ｒ^a２及びＲ^a3は、それぞれ独立に、炭素数１～８のアルキル基、炭素数３～２０の脂環式炭化水素基又はこれらを組み合わせた基を表すか、Ｒ^a1及びＲ^a2は互いに結合してそれらが結合する炭素原子とともに炭素数３～２０の脂環式炭化水素基を形成する。
ｍａ及びｎａは、それぞれ独立して、０又は１を表し、ｍａ及びｎａの少なくとも一方は１を表す。
＊は結合部位を表す。］

［式（２）中、Ｒ^ａ１’及びＲ^ａ２’は、それぞれ独立に、水素原子又は炭素数１～１２の炭化水素基を表し、Ｒ^ａ３’は、炭素数１～２０の炭化水素基を表すか、Ｒ^ａ２’及びＲ^ａ３’は互いに結合してそれらが結合する炭素原子及びＸとともに炭素数３～２０の複素環基を形成し、該炭化水素基及び該複素環基に含まれる－ＣＨ_２－は、－Ｏ－又は－Ｓ－で置き換わってもよい。
Ｘは、酸素原子又は硫黄原子を表す。
ｎａ’は、０又は１を表す。
＊は結合部位を表す。］ <Structural Unit (a1)>
The structural unit (a1) is derived from a monomer having an acid labile group (hereinafter, may be referred to as "monomer (a1)").
The acid labile group contained in the resin (A) is preferably a group represented by formula (1) (hereinafter also referred to as group (1)) and/or a group represented by formula (2) (hereinafter also referred to as group (2)).

[In formula (1), R ^a1 , R ^a2 , and R ^a3 each independently represent an alkyl group having 1 to 8 carbon atoms, an alicyclic hydrocarbon group having 3 to 20 carbon atoms, or a combination thereof, or R ^a1 and R ^a2 are bonded to each other to form an alicyclic hydrocarbon group having 3 to 20 carbon atoms together with the carbon atom to which they are bonded.
ma and na each independently represent 0 or 1, and at least one of ma and na represents 1.
* indicates a binding site.]

[In formula (2), R ^a1' and R ^a2' each independently represent a hydrogen atom or a hydrocarbon group having 1 to 12 carbon atoms; R ^a3' represents a hydrocarbon group having 1 to 20 carbon atoms; or R ^a2' and R ^a3' are bonded to each other to form a heterocyclic group having 3 to 20 carbon atoms together with the carbon atom to which they are bonded and X, and -CH ₂ - contained in the hydrocarbon group and the heterocyclic group may be replaced by -O- or -S-.
X represents an oxygen atom or a sulfur atom.
na′ represents 0 or 1.
* indicates a binding site.]

アルキル基と脂環式炭化水素基とを組み合わせた基としては、例えば、メチルシクロヘキシル基、ジメチルシクロへキシル基、メチルノルボルニル基、シクロヘキシルメチル基、アダマンチルメチル基、アダマンチルジメチル基、ノルボルニルエチル基等が挙げられる。
好ましくは、ｍａは０であり、ｎａは１である。
Ｒ^a1及びＲ^a2が互いに結合して脂環式炭化水素基を形成する場合の－Ｃ（Ｒ^a1）（Ｒ^a2）（Ｒ^a3）としては、下記の基が挙げられる。脂環式炭化水素基は、好ましくは炭素数３～１２である。＊は－Ｏ－との結合部位を表す。

Examples of the alkyl group for R ^a1 , R ^a2 and R ^a3 include a methyl group, an ethyl group, a propyl group, a butyl group, a pentyl group, a hexyl group, a heptyl group and an octyl group.
The alicyclic hydrocarbon group in R ^a1 , R ^a2 and R ^a3 may be either monocyclic or polycyclic. Examples of the monocyclic alicyclic hydrocarbon group include cycloalkyl groups such as a cyclopentyl group, a cyclohexyl group, a cycloheptyl group and a cyclooctyl group. Examples of the polycyclic alicyclic hydrocarbon group include a decahydronaphthyl group, an adamantyl group, a norbornyl group and the following groups (* represents a bonding site). The number of carbon atoms in the alicyclic hydrocarbon group in ^{R a1} , R ^a2 and R ^a3 is preferably 3 to 16.

Examples of the group combining an alkyl group with an alicyclic hydrocarbon group include a methylcyclohexyl group, a dimethylcyclohexyl group, a methylnorbornyl group, a cyclohexylmethyl group, an adamantylmethyl group, an adamantyldimethyl group, and a norbornylethyl group.
Preferably, ma is 0 and na is 1.
When R ^a1 and R ^a2 are bonded to each other to form an alicyclic hydrocarbon group, examples of -C(R ^a1 )(R ^a2 )(R ^a3 ) include the following groups. The alicyclic hydrocarbon group preferably has 3 to 12 carbon atoms. * represents the bonding site with -O-.

Ｒ^ａ１’及びＲ^ａ２’のうち、少なくとも１つは水素原子であることが好ましい。
ｎａ’は、好ましくは０である。 Examples of the hydrocarbon group for R ^a1′ , R ^a2′ and R ^a3′ include an alkyl group, an alicyclic hydrocarbon group, an aromatic hydrocarbon group and a group formed by combining these groups.
Examples of the alkyl group and alicyclic hydrocarbon group include the same groups as those exemplified for R ^a1 , R ^a2 and R ^a3 .
Examples of the aromatic hydrocarbon group include aryl groups such as a phenyl group, a naphthyl group, an anthryl group, a biphenyl group, and a phenanthryl group.
Examples of the combined group include a combination of the above-mentioned alkyl group and alicyclic hydrocarbon group (for example, a cycloalkylalkyl group), aralkyl groups such as a benzyl group, aromatic hydrocarbon groups having an alkyl group (p-methylphenyl group, p-tert-butylphenyl group, tolyl group, xylyl group, cumenyl group, mesityl group, 2,6-diethylphenyl group, 2-methyl-6-ethylphenyl group, etc.), aromatic hydrocarbon groups having an alicyclic hydrocarbon group (p-cyclohexylphenyl group, p-adamantylphenyl group, etc.), and aryl-cyclohexyl groups such as a phenylcyclohexyl group.
When R ^a2' and R ^a3' are bonded to each other to form a heterocyclic group together with the carbon atom to which they are bonded and X, examples of -C(R ^a1' )(R ^a2' )-X-R ^a3' include the following groups: * represents a bond.

At least one of R ^a1' and R ^a2' is preferably a hydrogen atom.
na′ is preferably 0.

Examples of the group (1) include the following groups.
A group in which R ^a1 , R ^a2 and R ^a3 in formula (1) are alkyl groups, ma = 0 and na = 1. As the group, a tert-butoxycarbonyl group is preferable.
A group in which R ^a1 and R ^a2 together with the carbon atom to which they are bonded form an adamantyl group, R ^a3 is an alkyl group, ma=0, and na=1 in the formula (1).
A group represented by formula (1), in which R ^a1 and R ^a2 each independently represent an alkyl group, R ^a3 represents an adamantyl group, ma=0, and na=1.
Specific examples of the group (1) include the following groups: * represents a binding site.

Specific examples of the group (2) include the following groups: * represents a bonding site.

The monomer (a1) is preferably a monomer having an acid labile group and an ethylenically unsaturated bond, more preferably a (meth)acrylic monomer having an acid labile group.
Of the (meth)acrylic monomers having an acid labile group, preferred are those having an alicyclic hydrocarbon group having 5 to 20 carbon atoms. When a resin (A) having a structural unit derived from a monomer (a1) having a bulky structure such as an alicyclic hydrocarbon group is used in a resist composition, the resolution of the resist pattern can be improved.

［式（ａ１－０）、式（ａ１－１）及び式（ａ１－２）中、
Ｌ^a01、Ｌ^ａ１及びＬ^ａ２は、それぞれ独立に、－Ｏ－又は＊－Ｏ－（ＣＨ_２）_ｋ１－ＣＯ－Ｏ－を表し、ｋ１は１～７のいずれかの整数を表し、＊は－ＣＯ－との結合部位を表す。
Ｒ^a01、Ｒ^ａ４及びＲ^ａ５は、それぞれ独立に、水素原子又はメチル基を表す。
Ｒ^a02、Ｒ^a03及びＲ^a04は、それぞれ独立に、炭素数１～８のアルキル基、炭素数３～１８の脂環式炭化水素基又はこれらを組み合わせた基を表す。
Ｒ^ａ６及びＲ^ａ７は、それぞれ独立に、炭素数１～８のアルキル基、炭素数３～１８の脂環式炭化水素基又はこれらを組合せることにより形成される基を表す。
ｍ１は０～１４のいずれかの整数を表す。
ｎ１は０～１０のいずれかの整数を表す。
ｎ１’は０～３のいずれかの整数を表す。］ The structural unit derived from a (meth)acrylic monomer having group (1) is preferably a structural unit represented by formula (a1-0) (hereinafter, may be referred to as structural unit (a1-0)), a structural unit represented by formula (a1-1) (hereinafter, may be referred to as structural unit (a1-1)), or a structural unit represented by formula (a1-2) (hereinafter, may be referred to as structural unit (a1-2)). More preferably, it is at least one structural unit selected from the group consisting of the structural unit (a1-1) and the structural unit (a1-2). These may be used alone or in combination of two or more.

[In formula (a1-0), formula (a1-1) and formula (a1-2),
L ^a01 , L ^a1 and L ^a2 each independently represent --O-- or *-O--(CH ₂ ) _k1 --CO--O--, where k1 represents an integer of 1 to 7, and * represents a bonding site with --CO--.
R ^a01 , R ^a4 and R ^a5 each independently represent a hydrogen atom or a methyl group.
R ^a02 , R ^a03 and R ^a04 each independently represent an alkyl group having 1 to 8 carbon atoms, an alicyclic hydrocarbon group having 3 to 18 carbon atoms or a combination thereof.
R ^a6 and R ^a7 each independently represent an alkyl group having 1 to 8 carbon atoms, an alicyclic hydrocarbon group having 3 to 18 carbon atoms, or a group formed by combining these.
m1 represents an integer of 0 to 14.
n1 represents an integer of 0 to 10.
n1' represents an integer of 0 to 3.

R ^a01 , R ^a4 and R ^a5 are preferably methyl groups.
L ^a01 , L ^a1 and L ^a2 are preferably an oxygen atom or *-O-(CH ₂ ) _k01 -CO-O- (wherein k01 is preferably an integer of 1 to 4, more preferably 1), and more preferably an oxygen atom.
Examples of the alkyl group, alicyclic hydrocarbon group and combination of these groups in R ^a02 , R ^a03 , R ^a04 , R ^a6 and R ^a7 include the same groups as those exemplified for R ^a1 , R ^a2 and R ^a3 in formula (1).
The alkyl group in R ^a02 , R ^a03 , and R ^a04 is preferably an alkyl group having 1 to 6 carbon atoms, more preferably a methyl group or an ethyl group, and even more preferably a methyl group.
The alkyl group for R ^a6 and R ^a7 is preferably an alkyl group having 1 to 6 carbon atoms, more preferably a methyl group, an ethyl group or an isopropyl group, and even more preferably an ethyl group or an isopropyl group.
The alicyclic hydrocarbon group of R ^a02 , R ^a03 , R ^a04 , R ^a6 and R ^a7 preferably has 5 to 12 carbon atoms, and more preferably 5 to 10 carbon atoms.
In the group in which an alkyl group and an alicyclic hydrocarbon group are combined, the total number of carbon atoms in the combination of the alkyl group and the alicyclic hydrocarbon group is preferably 18 or less.
R ^a02 and R ^a03 each independently represent preferably an alkyl group having 1 to 6 carbon atoms, more preferably a methyl group or an ethyl group.
R ^a04 is preferably an alkyl group having 1 to 6 carbon atoms or an alicyclic hydrocarbon group having 5 to 12 carbon atoms, and more preferably a methyl group, an ethyl group, a cyclohexyl group or an adamantyl group.
R ^a6 and R ^a7 each independently represent preferably an alkyl group having 1 to 6 carbon atoms, more preferably a methyl group, an ethyl group or an isopropyl group, and even more preferably an ethyl group or an isopropyl group.
m1 is preferably an integer of 0 to 3, and more preferably 0 or 1.
n1 is preferably an integer of 0 to 3, and more preferably 0 or 1.
n1' is preferably 0 or 1.

Examples of the structural unit (a1-0) include structural units represented by any one of formulas (a1-0-1) to (a1-0-12) and structural units in which a methyl group corresponding to R ^a01 in the structural unit (a1-0) is replaced with a hydrogen atom, and structural units represented by any one of formulas (a1-0-1) to (a1-0-10) are preferred.

Examples of the structural unit (a1-1) include structural units derived from monomers described in JP 2010-204646 A. Among these, structural units represented by any one of formulas (a1-1-1) to (a1-1-4) and structural units in which the methyl group corresponding to R ^a4 in the structural unit (a1-1) is replaced with a hydrogen atom are preferred, and structural units represented by any one of formulas (a1-1-1) to (a1-1-4) are more preferred.

Examples of the structural unit (a1-2) include structural units represented by any one of formulas (a1-2-1) to (a1-2-6) and structural units in which a methyl group corresponding to R ^a5 in the structural unit (a1-2) is replaced with a hydrogen atom, and structural units represented by any one of formulas (a1-2-2), (a1-2-5) and (a1-2-6) are preferred.

When the resin (A) contains the structural unit (a1-0), the content thereof is usually 5 to 60 mol %, preferably 5 to 50 mol %, and more preferably 10 to 40 mol %, based on all structural units in the resin (A).
When the resin (A) contains the structural unit (a1-1) and/or the structural unit (a1-2), the total content thereof is usually 3 to 80 mol %, preferably 5 to 70 mol %, more preferably 7 to 60 mol %, even more preferably 7 to 50 mol %, and still more preferably 10 to 45 mol %, based on all structural units in the resin (A).

［式（ａ１－４）中、
Ｒ^a32は、水素原子、ハロゲン原子、又は、ハロゲン原子を有してもよい炭素数１～６のアルキル基を表す。
Ｒ^a33は、ハロゲン原子、ヒドロキシ基、炭素数１～６のアルキル基、炭素数１～６のアルコキシ基、炭素数２～４のアルキルカルボニル基、炭素数２～４のアルキルカルボニルオキシ基、アクリロイルオキシ基又はメタクリロイルオキシ基を表す。
ｌａは０～４のいずれかの整数を表す。ｌａが２以上である場合、複数のＲ^a33は互いに同一であっても異なってもよい。
Ｒ^a34及びＲ^a35はそれぞれ独立に、水素原子又は炭素数１～１２の炭化水素基を表し、Ｒ^a36は、炭素数１～２０の炭化水素基を表すか、Ｒ^a35及びＲ^a36は互いに結合してそれらが結合する－Ｃ－Ｏ－とともに炭素数２～２０の２価の炭化水素基を形成し、該炭化水素基及び該２価の炭化水素基に含まれる－ＣＨ₂－は、－Ｏ－又は－Ｓ－で置き換わってもよい。］ An example of the structural unit (a1) having a group (2) is a structural unit represented by formula (a1-4) (hereinafter, sometimes referred to as "structural unit (a1-4)").

[In formula (a1-4),
R ^a32 represents a hydrogen atom, a halogen atom, or an alkyl group having 1 to 6 carbon atoms which may have a halogen atom.
R ^a33 represents a halogen atom, a hydroxy group, an alkyl group having 1 to 6 carbon atoms, an alkoxy group having 1 to 6 carbon atoms, an alkylcarbonyl group having 2 to 4 carbon atoms, an alkylcarbonyloxy group having 2 to 4 carbon atoms, an acryloyloxy group or a methacryloyloxy group.
la represents an integer of 0 to 4. When la is 2 or more, multiple R ^a33 may be the same or different.
R ^a34 and R ^a35 each independently represent a hydrogen atom or a hydrocarbon group having 1 to 12 carbon atoms, R ^a36 represents a hydrocarbon group having 1 to 20 carbon atoms, or R ^a35 and R ^a36 are bonded to each other to form a divalent hydrocarbon group having 2 to 20 carbon atoms together with the -C-O- to which they are bonded, and the -CH ₂ - contained in the hydrocarbon group and the divalent hydrocarbon group may be replaced by -O- or -S-.]

芳香族炭化水素基としては、フェニル基、ナフチル基、アントリル基、ビフェニル基、フェナントリル基等のアリール基等が挙げられる。
組み合わせた基としては、上述したアルキル基と脂環式炭化水素基とを組み合わせた基（例えばシクロアルキルアルキル基）、ベンジル基等のアラルキル基、アルキル基を有する芳香族炭化水素基（ｐ－メチルフェニル基、ｐ－ｔｅｒｔ－ブチルフェニル基、トリル基、キシリル基、クメニル基、メシチル基、２，６－ジエチルフェニル基、２－メチル－６－エチルフェニル基等）、脂環式炭化水素基を有する芳香族炭化水素基（ｐ－シクロヘキシルフェニル基、ｐ－アダマンチルフェニル基等）、フェニルシクロヘキシル基等のアリール－シクロアルキル基等が挙げられる。特に、Ｒ^a36としては、炭素数１～１８のアルキル基、炭素数３～１８の脂環式炭化水素基、炭素数６～１８の芳香族炭化水素基又はこれらを組み合わせることにより形成される基が挙げられる。 Examples of the alkyl group in R ^a32 and R ^a33 include a methyl group, an ethyl group, a propyl group, an isopropyl group, a butyl group, a pentyl group, a hexyl group, etc. The alkyl group is preferably an alkyl group having 1 to 4 carbon atoms, more preferably a methyl group or an ethyl group, and even more preferably a methyl group.
Examples of the halogen atom in R ^a32 and R ^a33 include a fluorine atom, a chlorine atom, and a bromine atom.
Examples of the alkyl group having 1 to 6 carbon atoms which may have a halogen atom include a trifluoromethyl group, a difluoromethyl group, a methyl group, a perfluoroethyl group, a 2,2,2-trifluoroethyl group, a 1,1,2,2-tetrafluoroethyl group, an ethyl group, a perfluoropropyl group, a 2,2,3,3,3-pentafluoropropyl group, a propyl group, a perfluorobutyl group, a 1,1,2,2,3,3,4,4-octafluorobutyl group, a butyl group, a perfluoropentyl group, a 2,2,3,3,4,4,5,5,5-nonafluoropentyl group, a pentyl group, a hexyl group, and a perfluorohexyl group.
Examples of the alkoxy group include a methoxy group, an ethoxy group, a propoxy group, a butoxy group, a pentyloxy group, and a hexyloxy group. Among these, an alkoxy group having 1 to 4 carbon atoms is preferred, a methoxy group or an ethoxy group is more preferred, and a methoxy group is even more preferred.
Alkylcarbonyl groups include acetyl, propionyl and butyryl groups.
Examples of the alkylcarbonyloxy group include an acetyloxy group, a propionyloxy group, and a butyryloxy group.
Examples of the hydrocarbon group for R ^a34 , R ^a35 and R ^a36 include an alkyl group, an alicyclic hydrocarbon group, an aromatic hydrocarbon group and a combination thereof.
Examples of the alkyl group include a methyl group, an ethyl group, a propyl group, a butyl group, a pentyl group, a hexyl group, a heptyl group, and an octyl group.
The alicyclic hydrocarbon group may be either monocyclic or polycyclic. Examples of the monocyclic alicyclic hydrocarbon group include cycloalkyl groups such as cyclopentyl, cyclohexyl, cycloheptyl, and cyclooctyl. Examples of the polycyclic alicyclic hydrocarbon group include decahydronaphthyl, adamantyl, and norbornyl groups, as well as the following groups (* indicates a bonding site):

Examples of the aromatic hydrocarbon group include aryl groups such as a phenyl group, a naphthyl group, an anthryl group, a biphenyl group, and a phenanthryl group.
Examples of the combined group include a group combining the above-mentioned alkyl group and alicyclic hydrocarbon group (for example, a cycloalkylalkyl group), an aralkyl group such as a benzyl group, an aromatic hydrocarbon group having an alkyl group (p-methylphenyl group, p-tert-butylphenyl group, tolyl group, xylyl group, cumenyl group, mesityl group, 2,6-diethylphenyl group, 2-methyl-6-ethylphenyl group, etc.), an aromatic hydrocarbon group having an alicyclic hydrocarbon group (p-cyclohexylphenyl group, p-adamantylphenyl group, etc.), an aryl-cycloalkyl group such as a phenylcyclohexyl group, etc. In particular, R ^a36 may be an alkyl group having 1 to 18 carbon atoms, an alicyclic hydrocarbon group having 3 to 18 carbon atoms, an aromatic hydrocarbon group having 6 to 18 carbon atoms, or a group formed by combining these.

In formula (a1-4), R ^a32 is preferably a hydrogen atom.
R ^a33 is preferably an alkoxy group having 1 to 4 carbon atoms, more preferably a methoxy group or an ethoxy group, and even more preferably a methoxy group.
As la, 0 or 1 is preferable, and 0 is more preferable.
R ^a34 is preferably a hydrogen atom.
R ^a35 is preferably an alkyl group or an alicyclic hydrocarbon group having 1 to 12 carbon atoms, and more preferably a methyl group or an ethyl group.
The hydrocarbon group of R ^a36 is preferably an alkyl group having 1 to 18 carbon atoms, an alicyclic hydrocarbon group having 3 to 18 carbon atoms, an aromatic hydrocarbon group having 6 to 18 carbon atoms, or a group formed by combining these, and more preferably an alkyl group having 1 to 18 carbon atoms, an alicyclic hydrocarbon group having 3 to 18 carbon atoms, or an aralkyl group having 7 to 18 carbon atoms. The alkyl group and alicyclic hydrocarbon group in R ^a36 are preferably unsubstituted. The aromatic hydrocarbon group in R ^a36 is preferably an aromatic ring having an aryloxy group having 6 to 10 carbon atoms.
The --OC(R ^a34 )(R ^a35 )--O--R ^a36 in the structural unit (a1-4) is eliminated upon contact with an acid (eg, p-toluenesulfonic acid) to form a hydroxy group.

Examples of the structural unit (a1-4) include structural units derived from monomers described in JP 2010-204646 A. Preferred examples include structural units represented by formulas (a1-4-1) to (a1-4-12) and structural units in which the hydrogen atom corresponding to R ^a32 in the structural unit (a1-4) is replaced with a methyl group, and more preferred examples include structural units represented by formulas (a1-4-1) to (a1-4-5) and (a1-4-10).

When resin (A) has structural unit (a1-4), its content is preferably 5 to 60 mol %, more preferably 5 to 50 mol %, and even more preferably 10 to 40 mol %, based on the total of all structural units in resin (A).

式（ａ１－５）中、
Ｒ^a8は、ハロゲン原子を有してもよい炭素数１～６のアルキル基、水素原子又はハロゲン原子を表す。
Ｚ^a1は、単結合又は＊－（ＣＨ₂）_h3－ＣＯ－Ｌ⁵⁴－を表し、ｈ３は１～４のいずれかの整数を表し、＊は、Ｌ⁵¹との結合部位を表す。
Ｌ⁵¹、Ｌ⁵²、Ｌ⁵³及びＬ⁵⁴は、それぞれ独立に、－Ｏ－又は－Ｓ－を表す。
ｓ１は、１～３のいずれかの整数を表す。
ｓ１’は、０～３のいずれかの整数を表す。 Examples of the structural unit derived from a (meth)acrylic monomer having the group (2) include a structural unit represented by formula (a1-5) (hereinafter, may be referred to as "structural unit (a1-5)").

In formula (a1-5),
R ^a8 represents an alkyl group having 1 to 6 carbon atoms which may have a halogen atom, a hydrogen atom or a halogen atom.
Z ^a1 represents a single bond or *-(CH ₂ ) _h3 -CO-L ⁵⁴ -, h3 represents an integer of 1 to 4, and * represents the bonding site to L ⁵¹ .
L ⁵¹ , L ⁵² , L ⁵³ and L ⁵⁴ each independently represent --O-- or --S--.
s1 represents an integer of 1 to 3.
s1′ represents an integer of 0 to 3.

Examples of the halogen atom include a fluorine atom and a chlorine atom, with a fluorine atom being preferred.
Examples of the alkyl group having 1 to 6 carbon atoms which may have a halogen atom include a methyl group, an ethyl group, a propyl group, a butyl group, a pentyl group, a hexyl group, a heptyl group, an octyl group, a fluoromethyl group, and a trifluoromethyl group.
In formula (a1-5), R ^a8 is preferably a hydrogen atom, a methyl group or a trifluoromethyl group.
L ⁵¹ is preferably an oxygen atom.
It is preferable that one of L ⁵² and L ⁵³ is —O— and the other is —S—.
It is preferable that s1 is 1.
s1' is preferably an integer of 0 to 2.
Z ^a1 is preferably a single bond or *--CH ₂ --CO--O--.

Examples of the structural unit (a1-5) include structural units derived from monomers described in JP-A-2010-61117. Among them, the structural units represented by formulas (a1-5-1) to (a1-5-4) are preferred, and the structural unit represented by formula (a1-5-1) or (a1-5-2) is more preferred.

When resin (A) has structural unit (a1-5), its content is preferably 1 to 50 mol %, more preferably 3 to 45 mol %, even more preferably 5 to 40 mol %, and even more preferably 5 to 30 mol %, based on the total structural units of resin (A).

［式（ａ１－０Ｘ）中、
Ｒ^ｘ１は、水素原子又はメチル基を表す。
Ｒ^ｘ２及びＲ^ｘ３は、互いに独立に、炭素数１～６の飽和炭化水素基を表す。
Ａｒ^ｘ１は、炭素数６～３６の芳香族炭化水素基を表す。］ Examples of the structural unit (a1) include a structural unit represented by the formula (a1-0X) (hereinafter, sometimes referred to as a structural unit (a1-0X)).

[In formula (a1-0X),
R ^x1 represents a hydrogen atom or a methyl group.
R ^x2 and R ^x3 each independently represent a saturated hydrocarbon group having 1 to 6 carbon atoms.
Ar ^x1 represents an aromatic hydrocarbon group having 6 to 36 carbon atoms.

The saturated hydrocarbon group for R ^x2 and R ^x3 includes an alkyl group, an alicyclic hydrocarbon group, and a group formed by combining these.
Examples of the alkyl group include a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, a sec-butyl group, a tert-butyl group, a pentyl group, and a hexyl group.
The alicyclic hydrocarbon group may be either monocyclic or polycyclic, and examples of the monocyclic alicyclic hydrocarbon group include a cyclopropyl group, a cyclobutyl group, a cyclopentyl group, and a cyclohexyl group.
Examples of the aromatic hydrocarbon group for Ar ^x1 include aryl groups having 6 to 36 carbon atoms, such as a phenyl group, a naphthyl group, and anthryl group.
The aromatic hydrocarbon group preferably has 6 to 24 carbon atoms, more preferably has 6 to 18 carbon atoms, and is further preferably a phenyl group.
Ar ^x1 is preferably an aromatic hydrocarbon group having 6 to 18 carbon atoms, more preferably a phenyl group or naphthyl group, and even more preferably a phenyl group.
R ^x1 , R ^x2 and R ^x3 are each preferably independently a methyl group or an ethyl group, and more preferably a methyl group.

Examples of the structural unit (a1-0X) include the structural units shown below and structural units in which the methyl group corresponding to R ^x1 in the structural unit (a1-0X) is replaced with a hydrogen atom. The structural unit (a1-0X) is preferably the structural unit (a1-0X-1) to the structural unit (a1-0X-3).

When the resin (A) has the structural unit (a1-0X), the content thereof is preferably 5 to 60 mol %, more preferably 5 to 50 mol %, and even more preferably 10 to 40 mol %, based on all monomers in the resin (A).
The resin (A) may contain two or more types of the structural unit (a1-0X).

Further, examples of the structural unit (a1) include the following structural units.

When resin (A) contains the above structural units, the content thereof is preferably 5 to 60 mol %, more preferably 5 to 50 mol %, and even more preferably 10 to 40 mol %, based on the total structural units of resin (A).

<Structural unit (s)>
As the monomer from which the structural unit (s) is derived, a monomer having no acid labile group known in the resist field can be used.
The structural unit (s) preferably has a hydroxy group or a lactone ring. By using a resin having a structural unit having a hydroxy group and no acid labile group (hereinafter sometimes referred to as "structural unit (a2)") and/or a structural unit having a lactone ring and no acid labile group (hereinafter sometimes referred to as "structural unit (a3)") in the resist composition of the present invention, the resolution of the resist pattern and adhesion to the substrate can be improved.

<Structural unit (a2)>
The hydroxy group contained in the structural unit (a2) may be an alcoholic hydroxy group or a phenolic hydroxy group.
When a resist pattern is produced from the resist composition of the present invention, in the case where a high energy ray such as a KrF excimer laser (248 nm), an electron beam, or EUV (extreme ultraviolet light) is used as an exposure light source, the structural unit (a2) having a phenolic hydroxyl group is preferred, and it is preferable to use the structural unit (a2-A) described below. In addition, in the case where an ArF excimer laser (193 nm) or the like is used, the structural unit (a2) having an alcoholic hydroxyl group is preferred, and it is more preferable to use the structural unit (a2-1) described below. The structural unit (a2) may contain one type alone, or may contain two or more types.

［式（ａ２－Ａ）中、
Ｒ^a50は、水素原子、ハロゲン原子又はハロゲン原子を有してもよい炭素数１～６のアルキル基を表す。
Ｒ^a51は、ハロゲン原子、ヒドロキシ基、炭素数１～６のアルキル基、炭素数１～６のアルコキシ基、炭素数２～４のアルキルカルボニル基、炭素数２～４のアルキルカルボニルオキシ基、アクリロイルオキシ基又はメタクリロイルオキシ基を表す。
Ａ^a50は、単結合又は＊－Ｘ^a51－（Ａ^a52－Ｘ^a52）_nｂ－を表し、＊は－Ｒ^a50が結合する炭素原子との結合部位を表す。
Ａ^a52は、それぞれ独立に、炭素数１～６のアルカンジイル基を表す。
Ｘ^a51及びＸ^a52は、それぞれ独立に、－Ｏ－、－ＣＯ－Ｏ－又は－Ｏ－ＣＯ－を表す。
ｎｂは、０又は１を表す。
ｍｂは０～４のいずれかの整数を表す。ｍｂが２以上のいずれかの整数である場合、複数のＲ^a51は互いに同一であっても異なってもよい。］ In the structural unit (a2), an example of a structural unit having a phenolic hydroxy group is a structural unit represented by formula (a2-A) (hereinafter, may be referred to as "structural unit (a2-A)").

[In formula (a2-A),
R ^a50 represents a hydrogen atom, a halogen atom or an alkyl group having 1 to 6 carbon atoms which may have a halogen atom.
R ^a51 represents a halogen atom, a hydroxyl group, an alkyl group having 1 to 6 carbon atoms, an alkoxy group having 1 to 6 carbon atoms, an alkylcarbonyl group having 2 to 4 carbon atoms, an alkylcarbonyloxy group having 2 to 4 carbon atoms, an acryloyloxy group or a methacryloyloxy group.
A ^a50 represents a single bond or *-X ^a51 -(A ^a52 -X ^a52 ) _nb -, where * represents the bonding site with the carbon atom to which -R ^a50 is bonded.
Each A ^a52 independently represents an alkanediyl group having 1 to 6 carbon atoms.
X ^a51 and X ^a52 each independently represent —O—, —CO—O— or —O—CO—.
nb represents 0 or 1.
mb represents an integer of 0 to 4. When mb is an integer of 2 or more, multiple R ^a51 may be the same or different.

Examples of the halogen atom in R ^a50 include a fluorine atom, a chlorine atom, and a bromine atom.
Examples of the alkyl group having 1 to 6 carbon atoms which may have a halogen atom for ^R include a trifluoromethyl group, a difluoromethyl group, a methyl group, a perfluoroethyl group, a 2,2,2-trifluoroethyl group, a 1,1,2,2-tetrafluoroethyl group, an ethyl group, a perfluoropropyl group, a 2,2,3,3,3-pentafluoropropyl group, a propyl group, a perfluorobutyl group, a 1,1,2,2,3,3,4,4-octafluorobutyl group, a butyl group, a perfluoropentyl group, a 2,2,3,3,4,4,5,5,5-nonafluoropentyl group, a pentyl group, a hexyl group, and a perfluorohexyl group.
R ^a50 is preferably a hydrogen atom or an alkyl group having 1 to 4 carbon atoms, more preferably a hydrogen atom, a methyl group or an ethyl group, and even more preferably a hydrogen atom or a methyl group.
Examples of the alkyl group for R ^a51 include a methyl group, an ethyl group, a propyl group, an isopropyl group, a butyl group, a sec-butyl group, a tert-butyl group, a pentyl group, and a hexyl group.
Examples of the alkoxy group for R ^a51 include a methoxy group, an ethoxy group, a propoxy group, an isopropoxy group, a butoxy group, a sec-butoxy group, and a tert-butoxy group. An alkoxy group having 1 to 4 carbon atoms is preferable, a methoxy group or an ethoxy group is more preferable, and a methoxy group is even more preferable.
Examples of the alkylcarbonyl group for R ^a51 include an acetyl group, a propionyl group, and a butyryl group.
The alkylcarbonyloxy group for R ^a51 includes an acetyloxy group, a propionyloxy group, and a butyryloxy group.
R ^a51 is preferably a methyl group.

Examples of *-X ^a51 -(A ^a52 -X ^a52 ) _nb - include *-O-, *-CO-O-, *-O-CO-, *-CO-O-A ^a52 -CO-O-, *-O-CO-A ^a52 -O-, *-O-A ^a52 -CO-O-, *-CO-O-A ^a52 -O-CO-, and *-O-CO-A ^a52 -O-CO-. Of these, *-CO-O-, *-CO-O-A ^a52 -CO-O- or *-O-A ^a52 -CO-O- are preferred.

Examples of the alkanediyl group include a methylene group, an ethylene group, a propane-1,3-diyl group, a propane-1,2-diyl group, a butane-1,4-diyl group, a pentane-1,5-diyl group, a hexane-1,6-diyl group, a butane-1,3-diyl group, a 2-methylpropane-1,3-diyl group, a 2-methylpropane-1,2-diyl group, a pentane-1,4-diyl group, and a 2-methylbutane-1,4-diyl group.
A ^a52 is preferably a methylene group or an ethylene group.

A ^a50 is preferably a single bond, *-CO-O- or *-CO-O-A ^a52 -CO-O-, more preferably a single bond, *-CO-O- or *-CO-O-CH ₂ -CO-O-, further preferably a single bond or *-CO-O-.

mb is preferably 0, 1 or 2, more preferably 0 or 1, and particularly preferably 0.
The hydroxy group is preferably bonded to the ortho- or para-position of the benzene ring, and more preferably to the para-position.

Examples of the structural unit (a2-A) include structural units derived from monomers described in JP-A-2010-204634 and JP-A-2012-12577.
Examples of the structural unit (a2-A) include structural units represented by formulae (a2-2-1) to (a2-2-6) and structural units in which a methyl group corresponding to R ^a50 in the structural unit (a2-A) is replaced with a hydrogen atom in the structural units represented by formulae (a2-2-1) to (a2-2-6). The structural unit (a2-A) is preferably a structural unit represented by formula (a2-2-1), a structural unit represented by formula (a2-2-3), or a structural unit represented by formula (a2-2-6), and a structural unit in which a methyl group corresponding to R ^a50 in the structural unit (a2-A) is replaced with a hydrogen atom in the structural unit represented by formula (a2-2-1), the structural unit represented by formula (a2-2-3), or the structural unit represented by formula (a2-2-6).

When the structural unit (a2-A) is contained in the resin (A), the content of the structural unit (a2-A) is preferably 5 to 80 mol %, more preferably 10 to 70 mol %, even more preferably 10 to 60 mol %, and still more preferably 10 to 50 mol %, based on all structural units.
The structural unit (a2-A) can be incorporated into the resin (A) by, for example, polymerizing the structural unit (a1-4) and then treating with an acid such as p-toluenesulfonic acid. Alternatively, the structural unit (a2-A) can be incorporated into the resin (A) by polymerizing the structural unit (a1-4) and then treating with an alkali such as tetramethylammonium hydroxide.

式（ａ２－１）中、
Ｌ^a3は、－Ｏ－又は＊－Ｏ－（ＣＨ₂）_k2－ＣＯ－Ｏ－を表し、
ｋ２は１～７のいずれかの整数を表す。＊は－ＣＯ－との結合部位を表す。
Ｒ^a14は、水素原子又はメチル基を表す。
Ｒ^a15及びＲ^a16は、それぞれ独立に、水素原子、メチル基又はヒドロキシ基を表す。
ｏ１は、０～１０のいずれかの整数を表す。 An example of the structural unit (a2) having an alcoholic hydroxy group is a structural unit represented by formula (a2-1) (hereinafter sometimes referred to as "structural unit (a2-1)").

In formula (a2-1),
L ^a3 represents —O— or *—O—(CH ₂ ) _k2 —CO—O—;
k2 represents an integer of 1 to 7. * represents a bonding site with —CO—.
R ^a14 represents a hydrogen atom or a methyl group.
R ^a15 and R ^a16 each independently represent a hydrogen atom, a methyl group or a hydroxyl group.
o1 represents an integer of 0 to 10.

In formula (a2-1), L ^a3 is preferably --O--, --O--(CH ₂ ) _f1 --CO--O-- (wherein f1 represents an integer of 1 to 4), and more preferably --O--.
R ^a14 is preferably a methyl group.
R ^a15 is preferably a hydrogen atom.
R ^a16 is preferably a hydrogen atom or a hydroxy group.
o1 is preferably an integer of 0 to 3, and more preferably 0 or 1.

Examples of the structural unit (a2-1) include structural units derived from monomers described in JP 2010-204646 A. A structural unit represented by any one of formulas (a2-1-1) to (a2-1-6) is preferred, a structural unit represented by any one of formulas (a2-1-1) to (a2-1-4) is more preferred, and a structural unit represented by formula (a2-1-1) or formula (a2-1-3) is even more preferred.

When resin (A) contains structural unit (a2-1), its content is usually 1 to 45 mol %, preferably 1 to 40 mol %, more preferably 1 to 35 mol %, even more preferably 1 to 20 mol %, and even more preferably 1 to 10 mol %, based on the total structural units of resin (A).

<Structural unit (a3)>
The lactone ring of the structural unit (a3) may be a monocyclic ring such as a β-propiolactone ring, a γ-butyrolactone ring, or a δ-valerolactone ring, or may be a condensed ring of a monocyclic lactone ring with another ring. Preferred examples include a γ-butyrolactone ring, an adamantanelactone ring, or a bridged ring containing a γ-butyrolactone ring structure (for example, a structural unit represented by the following formula (a3-2)).

［式（ａ３－１）、式（ａ３－２）、式（ａ３－３）及び式（ａ３－４）中、
Ｌ^ａ４、Ｌ^ａ５及びＬ^ａ６は、それぞれ独立に、－Ｏ－又は＊－Ｏ－（ＣＨ_２）_ｋ３－ＣＯ－Ｏ－（ｋ３は１～７のいずれかの整数を表す。）で表される基を表す。
Ｌ^ａ７は、－Ｏ－、＊－Ｏ－Ｌ^ａ８－Ｏ－、＊－Ｏ－Ｌ^ａ８－ＣＯ－Ｏ－、＊－Ｏ－Ｌ^ａ８－ＣＯ－Ｏ－Ｌ^ａ９－ＣＯ－Ｏ－又は＊－Ｏ－Ｌ^ａ８－Ｏ－ＣＯ－Ｌ^ａ９－Ｏ－を表す。
Ｌ^ａ８及びＬ^ａ９は、それぞれ独立に、炭素数１～６のアルカンジイル基を表す。
＊はカルボニル基との結合部位を表す。
Ｒ^ａ１８、Ｒ^ａ１９及びＲ^ａ２０は、それぞれ独立に、水素原子又はメチル基を表す。
Ｒ^ａ２４は、ハロゲン原子を有してもよい炭素数１～６のアルキル基、水素原子又はハロゲン原子を表す。
Ｘ^ａ３は、－ＣＨ_２－又は酸素原子を表す。
Ｒ^ａ２１は炭素数１～４の脂肪族炭化水素基を表す。
Ｒ^ａ２２、Ｒ^ａ２３及びＲ^ａ２５は、それぞれ独立に、カルボキシ基、シアノ基又は炭素数１～４の脂肪族炭化水素基を表す。
ｐ１は０～５のいずれかの整数を表す。
ｑ１は、０～３のいずれかの整数を表す。
ｒ１は、０～３のいずれかの整数を表す。
ｗ１は、０～８のいずれかの整数を表す。
ｐ１、ｑ１、ｒ１及び／又はｗ１が２以上のとき、複数のＲ^ａ２１、Ｒ^ａ２２、Ｒ^ａ２３及び／又はＲ^ａ２５は互いに同一であってもよく、異なっていてもよい。］ The structural unit (a3) is preferably a structural unit represented by formula (a3-1), formula (a3-2), formula (a3-3) or formula (a3-4). One of these may be contained alone, or two or more of them may be contained.

[In formula (a3-1), formula (a3-2), formula (a3-3) and formula (a3-4),
L ^a4 , L ^a5 and L ^a6 each independently represent a group represented by —O— or *-O-(CH ₂ ) _k3 —CO—O- (k3 represents an integer of any one of 1 to 7).
L ^a7 represents -O-, *-OL ^a8 -O-, *-OL ^a8 -CO-O-, *-OL ^a8 -CO-OL ^a9 -CO-O- or *-OL ^a8 -O-CO-L ^a9 -O-.
L ^a8 and L ^a9 each independently represent an alkanediyl group having 1 to 6 carbon atoms.
* indicates the bonding site with the carbonyl group.
R ^a18 , R ^a19 and R ^a20 each independently represent a hydrogen atom or a methyl group.
R ^a24 represents an alkyl group having 1 to 6 carbon atoms which may have a halogen atom, a hydrogen atom or a halogen atom.
X ^a3 represents —CH ₂ — or an oxygen atom.
R ^a21 represents an aliphatic hydrocarbon group having 1 to 4 carbon atoms.
R ^a22 , R ^a23 and R ^a25 each independently represent a carboxy group, a cyano group or an aliphatic hydrocarbon group having 1 to 4 carbon atoms.
p1 represents an integer of 0 to 5.
q1 represents an integer of 0 to 3.
r1 represents an integer of 0 to 3.
w1 represents an integer of 0 to 8.
When p1, q1, r1 and/or w1 is 2 or more, a plurality of R ^a21 , R ^a22 , R ^a23 and/or R ^a25 may be the same as or different from each other.

Examples of the aliphatic hydrocarbon group for R ^a21 , R ^a22 , R ^a23 and R ^a25 include alkyl groups such as a methyl group, an ethyl group, a propyl group, an isopropyl group, a butyl group, a sec-butyl group and a tert-butyl group.
The halogen atom for R ^a24 includes a fluorine atom, a chlorine atom, a bromine atom and an iodine atom.
Examples of the alkyl group for R ^a24 include a methyl group, an ethyl group, a propyl group, an isopropyl group, a butyl group, a sec-butyl group, a tert-butyl group, a pentyl group, and a hexyl group, and are preferably alkyl groups having 1 to 4 carbon atoms, and more preferably a methyl group or an ethyl group.
Examples of the alkyl group having a halogen atom for R ^a24 include a trifluoromethyl group, a perfluoroethyl group, a perfluoropropyl group, a perfluoroisopropyl group, a perfluorobutyl group, a perfluorosec-butyl group, a perfluorotert-butyl group, a perfluoropentyl group, a perfluorohexyl group, a trichloromethyl group, a tribromomethyl group, and a triiodomethyl group.
Examples of the alkanediyl group in L ^a8 and L ^a9 include a methylene group, an ethylene group, a propane-1,3-diyl group, a propane-1,2-diyl group, a butane-1,4-diyl group, a pentane-1,5-diyl group, a hexane-1,6-diyl group, a butane-1,3-diyl group, a 2-methylpropane-1,3-diyl group, a 2-methylpropane-1,2-diyl group, a pentane-1,4-diyl group, and a 2-methylbutane-1,4-diyl group.

In formulae (a3-1) to (a3-3), L ^a4 to L ^a6 each independently represent preferably —O— or *-O-(CH ₂ ) _k3 -CO-O-, where k3 is an integer from 1 to 4, more preferably —O— and *-O-CH ₂ -CO-O-, and still more preferably an oxygen atom.
R ^a18 to R ^a21 are preferably methyl groups.
R ^a22 and R ^a23 each independently represent preferably a carboxy group, a cyano group, or a methyl group.
p1, q1 and r1 each independently represent preferably any integer of 0 to 2, and more preferably 0 or 1.

（式中、Ｒ^ａ２４、Ｌ^ａ７は、上記と同じ意味を表す。） In formula (a3-4), R ^a24 is preferably a hydrogen atom or an alkyl group having 1 to 4 carbon atoms, more preferably a hydrogen atom, a methyl group or an ethyl group, and even more preferably a hydrogen atom or a methyl group.
R ^a25 is preferably a carboxy group, a cyano group or a methyl group.
L ^a7 is preferably —O— or *-OL ^a8 —CO—O—, and more preferably —O—, —O—CH ₂ —CO—O— or —O—C ₂ H ₄ —CO—O—.
w1 is preferably an integer of 0 to 2, and more preferably 0 or 1.
In particular, the formula (a3-4) is preferably the formula (a3-4)'.

(In the formula, R ^a24 and L ^a7 have the same meanings as above.)

Examples of the structural unit (a3) include structural units derived from monomers described in JP-A-2010-204646, JP-A-2000-122294, and JP-A-2012-41274. As the structural unit (a3), structural units represented by any one of formulas (a3-1-1), (a3-1-2), (a3-2-1), (a3-2-2), (a3-3-1), (a3-3-2), and (a3-4-1) to (a3-4-12), and structural units in which methyl groups corresponding to R ^a18 , R ^a19 , R ^a20 , and R ^a24 in formulas (a3-1) to (a3-4) are replaced with hydrogen atoms are preferred.

When the resin (A) contains the structural unit (a3), the total content thereof is usually 5 to 70 mol %, preferably 10 to 65 mol %, and more preferably 10 to 60 mol %, based on all structural units in the resin (A).
Furthermore, the content of the structural unit (a3-1), the structural unit (a3-2), the structural unit (a3-3) or the structural unit (a3-4) is preferably 5 to 60 mol %, more preferably 5 to 50 mol %, and even more preferably 10 to 50 mol %, based on the total structural units of the resin (A).

［式（ａ４）中、
Ｒ⁴¹は、水素原子又はメチル基を表す。
Ｒ⁴²は、炭素数１～２４のフッ素原子を有する飽和炭化水素基を表し、該飽和炭化水素基に含まれる－ＣＨ₂－は、－Ｏ－又は－ＣＯに置き換わっていてもよい。］
Ｒ⁴²で表される飽和炭化水素基は、鎖式炭化水素基及び単環又は多環の脂環式炭化水素基、並びに、これらを組み合わせることにより形成される基等が挙げられる。 <Structural unit (a4)>
Examples of the structural unit (a4) include the following structural units.

[In formula (a4),
^R41 represents a hydrogen atom or a methyl group.
R ⁴² represents a saturated hydrocarbon group having 1 to 24 carbon atoms and containing a fluorine atom, and --CH ₂ -- contained in the saturated hydrocarbon group may be replaced by --O-- or --CO.]
Examples of the saturated hydrocarbon group represented by R ⁴² include chain hydrocarbon groups, monocyclic or polycyclic alicyclic hydrocarbon groups, and groups formed by combining these groups.

組み合わせにより形成される基としては、１以上のアルキル基又は１以上のアルカンジイル基と、１以上の脂環式炭化水素基とを組み合わせることにより形成される基が挙げられ、－アルカンジイル基－脂環式炭化水素基、－脂環式炭化水素基－アルキル基、－アルカンジイル基－脂環式炭化水素基－アルキル基等が挙げられる。 Examples of the chain hydrocarbon group include methyl, ethyl, propyl, butyl, pentyl, hexyl, heptyl, octyl, decyl, dodecyl, pentadecyl, hexadecyl, heptadecyl, and octadecyl groups. Examples of the monocyclic or polycyclic alicyclic hydrocarbon group include cycloalkyl groups such as cyclopentyl, cyclohexyl, cycloheptyl, and cyclooctyl groups; decahydronaphthyl, adamantyl, and norbornyl groups; and polycyclic alicyclic hydrocarbon groups such as the following groups (* indicates a bonding site):

Examples of groups formed by combination include groups formed by combining one or more alkyl groups or one or more alkanediyl groups with one or more alicyclic hydrocarbon groups, such as -alkanediyl group-alicyclic hydrocarbon group, -alicyclic hydrocarbon group-alkyl group, and -alkanediyl group-alicyclic hydrocarbon group-alkyl group.

［式（ａ４－０）中、
Ｒ⁵は、水素原子又はメチル基を表す。
Ｌ^4ａは、単結合又は炭素数１～４の２価の脂肪族飽和炭化水素基を表す。
Ｌ^3ａは、炭素数１～８のペルフルオロアルカンジイル基又は炭素数３～１２のペルフルオロシクロアルカンジイル基を表す。
Ｒ⁶は、水素原子又はフッ素原子を表す。］ The structural unit (a4) includes at least one structural unit selected from the group consisting of formulae (a4-0), (a4-1), (a4-2), (a4-3) and (a4-4).

[In formula (a4-0),
^R5 represents a hydrogen atom or a methyl group.
L ^4a represents a single bond or a divalent aliphatic saturated hydrocarbon group having 1 to 4 carbon atoms.
^L3a represents a perfluoroalkanediyl group having 1 to 8 carbon atoms or a perfluorocycloalkanediyl group having 3 to 12 carbon atoms.
^R6 represents a hydrogen atom or a fluorine atom.

Examples of the divalent aliphatic saturated hydrocarbon group for ^L4a include linear alkanediyl groups such as a methylene group, an ethylene group, a propane-1,3-diyl group, and a butane-1,4-diyl group, and branched alkanediyl groups such as an ethane-1,1-diyl group, a propane-1,2-diyl group, a butane-1,3-diyl group, a 2-methylpropane-1,3-diyl group, and a 2-methylpropane-1,2-diyl group.
Examples of the perfluoroalkanediyl group in ^L3a include a difluoromethylene group, a perfluoroethylene group, a perfluoropropane-1,1-diyl group, a perfluoropropane-1,3-diyl group, a perfluoropropane-1,2-diyl group, a perfluoropropane-2,2-diyl group, a perfluorobutane-1,4-diyl group, a perfluorobutane-2,2-diyl group, a perfluorobutane-1,2-diyl group, a perfluoropentane-1,5-diyl group, a perfluoropentane-2,2-diyl group, a perfluoropentane- Examples of the perfluorohexane-3,3-diyl group include perfluorohexane-1,6-diyl group, perfluorohexane-2,2-diyl group, perfluorohexane-3,3-diyl group, perfluoroheptane-1,7-diyl group, perfluoroheptane-2,2-diyl group, perfluoroheptane-3,4-diyl group, perfluoroheptane-4,4-diyl group, perfluorooctane-1,8-diyl group, perfluorooctane-2,2-diyl group, perfluorooctane-3,3-diyl group, and perfluorooctane-4,4-diyl group.
Examples of the perfluorocycloalkanediyl group in ^L3a include a perfluorocyclohexanediyl group, a perfluorocyclopentanediyl group, a perfluorocycloheptanediyl group, and a perfluoroadamantanediyl group.

L ^4a is preferably a single bond, a methylene group or an ethylene group, more preferably a single bond or a methylene group.
L ^3a is preferably a perfluoroalkanediyl group having 1 to 6 carbon atoms, and more preferably a perfluoroalkanediyl group having 1 to 3 carbon atoms.

Examples of the structural unit (a4-0) include the structural units shown below and structural units in which the methyl group corresponding to R ⁵ in the structural unit (a4-0) shown below is replaced with a hydrogen atom.

［式（ａ４－１）中、
Ｒ^a41は、水素原子又はメチル基を表す。
Ｒ^a42は、置換基を有していてもよい炭素数１～２０の飽和炭化水素基を表し、該飽和炭化水素基に含まれる－ＣＨ_２－は、－Ｏ－又は－ＣＯ－に置き換わっていてもよい。
Ａ^a41は、置換基を有していてもよい炭素数１～６のアルカンジイル基又は式（ａ－ｇ１）で表される基を表す。ただし、Ａ^ａ４１及びＲ^ａ４２のうち少なくとも１つは、置換基としてハロゲン原子（好ましくはフッ素原子）を有する。

〔式（ａ－ｇ１）中、
ｓは０又は１を表す。
Ａ^a42及びＡ^a44は、それぞれ独立に、置換基を有していてもよい炭素数１～５の２価の飽和炭化水素基を表す。
Ａ^a43は、単結合又は置換基を有していてもよい炭素数１～５の２価の脂肪族炭化水素基を表す。
Ｘ^a41及びＸ^a42は、それぞれ独立に、－Ｏ－、－ＣＯ－、－ＣＯ－Ｏ－又は－Ｏ－ＣＯ－を表す。
ただし、Ａ^a42、Ａ^a43、Ａ^a44、Ｘ^a41及びＸ^a42の炭素数の合計は７以下である。〕
＊は結合部位であり、右側の＊が－Ｏ－ＣＯ－Ｒ^a42との結合部位である。］

[In formula (a4-1),
R ^a41 represents a hydrogen atom or a methyl group.
R ^a42 represents a saturated hydrocarbon group having 1 to 20 carbon atoms which may have a substituent, and --CH ₂ -- contained in the saturated hydrocarbon group may be replaced by --O-- or --CO--.
A ^a41 represents an alkanediyl group having 1 to 6 carbon atoms which may have a substituent, or a group represented by formula (a-g1), provided that at least one of A ^a41 and R ^a42 has a halogen atom (preferably a fluorine atom) as a substituent.

[In formula (a-g1),
s represents 0 or 1.
A ^a42 and A ^a44 each independently represent a divalent saturated hydrocarbon group having 1 to 5 carbon atoms which may have a substituent.
A ^a43 represents a single bond or a divalent aliphatic hydrocarbon group having 1 to 5 carbon atoms which may have a substituent.
X ^a41 and X ^a42 each independently represent --O--, --CO--, --CO--O-- or --O--CO--.
However, the total number of carbon atoms of A ^a42 , A ^a43 , A ^a44 , X ^a41 and X ^a42 is 7 or less.
* indicates a binding site, and the * on the right side is the binding site with -O-CO-R ^a42 .]

組み合わせにより形成される基としては、１以上のアルキル基又は１以上のアルカンジイル基と、１以上の脂環式飽和炭化水素基とを組み合わせることにより形成される基が挙げられ、－アルカンジイル基－脂環式飽和炭化水素基、－脂環式飽和炭化水素基－アルキル基、－アルカンジイル基－脂環式飽和炭化水素基－アルキル基等が挙げられる。 Examples of the saturated hydrocarbon group for R ^a42 include chain saturated hydrocarbon groups, monocyclic or polycyclic alicyclic saturated hydrocarbon groups, and groups formed by combining these.
Examples of the chain saturated hydrocarbon group include a methyl group, an ethyl group, a propyl group, a butyl group, a pentyl group, a hexyl group, a heptyl group, an octyl group, a decyl group, a dodecyl group, a pentadecyl group, a hexadecyl group, a heptadecyl group, and an octadecyl group.
Examples of the monocyclic or polycyclic alicyclic saturated hydrocarbon group include cycloalkyl groups such as a cyclopentyl group, a cyclohexyl group, a cycloheptyl group, and a cyclooctyl group; and polycyclic alicyclic saturated hydrocarbon groups such as a decahydronaphthyl group, an adamantyl group, a norbornyl group, and the following groups (* represents a bonding site):

Examples of groups formed by combination include groups formed by combining one or more alkyl groups or one or more alkanediyl groups with one or more alicyclic saturated hydrocarbon groups, such as -alkanediyl group-alicyclic saturated hydrocarbon group, -alicyclic saturated hydrocarbon group-alkyl group, and -alkanediyl group-alicyclic saturated hydrocarbon group-alkyl group.

［式（ａ－ｇ３）中、
Ｘ^a43は、酸素原子、カルボニル基、＊－Ｏ－ＣＯ－又は＊－ＣＯ－Ｏ－を表す。
Ａ^a45は、ハロゲン原子を有していてもよい炭素数１～１７の脂肪族炭化水素基を表す。
＊はＲ^a42との結合部位を表す。］
ただし、Ｒ^a42－Ｘ^a43－Ａ^a45において、Ｒ^a42がハロゲン原子を有しない場合は、Ａ^a45は、少なくとも１つのハロゲン原子を有する炭素数１～１７の脂肪族炭化水素基を表す。 Examples of the substituent that R ^a42 may have include at least one selected from a halogen atom and a group represented by formula (a-g3). Examples of the halogen atom include a fluorine atom, a chlorine atom, a bromine atom, and an iodine atom, and a fluorine atom is preferable.

[In formula (a-g3),
X ^a43 represents an oxygen atom, a carbonyl group, *-O-CO- or *-CO-O-.
A ^a45 represents an aliphatic hydrocarbon group having 1 to 17 carbon atoms which may have a halogen atom.
* indicates the binding site with ^Ra42 .]
However, in R ^a42 -X ^a43 -A ^a45 , when R ^a42 does not have a halogen atom, A ^a45 represents an aliphatic hydrocarbon group having 1 to 17 carbon atoms and at least one halogen atom.

組み合わせにより形成される基としては、１以上のアルキル基又は１以上のアルカンジイル基と、１以上の脂環式炭化水素基とを組み合わせることにより形成される基が挙げられ、－アルカンジイル基－脂環式炭化水素基、－脂環式炭化水素基－アルキル基、－アルカンジイル基－脂環式炭化水素基－アルキル基等が挙げられる。 Examples of the aliphatic hydrocarbon group in A ^a45 include alkyl groups such as a methyl group, an ethyl group, a propyl group, a butyl group, a pentyl group, a hexyl group, a heptyl group, an octyl group, a decyl group, a dodecyl group, a pentadecyl group, a hexadecyl group, a heptadecyl group, and an octadecyl group;
Examples of the alicyclic hydrocarbon groups include monocyclic alicyclic hydrocarbon groups such as a cyclopentyl group, a cyclohexyl group, a cycloheptyl group, and a cyclooctyl group; and polycyclic alicyclic hydrocarbon groups such as a decahydronaphthyl group, an adamantyl group, a norbornyl group, and the following groups (* represents a bonding site):

Examples of groups formed by combination include groups formed by combining one or more alkyl groups or one or more alkanediyl groups with one or more alicyclic hydrocarbon groups, such as -alkanediyl group-alicyclic hydrocarbon group, -alicyclic hydrocarbon group-alkyl group, and -alkanediyl group-alicyclic hydrocarbon group-alkyl group.

R ^a42 is preferably an aliphatic hydrocarbon group which may have a halogen atom, and more preferably an aliphatic hydrocarbon group having an alkyl group having a halogen atom and/or a group represented by formula (a-g3).
When R ^a42 is an aliphatic hydrocarbon group having a halogen atom, it is preferably an aliphatic hydrocarbon group having a fluorine atom, more preferably a perfluoroalkyl group or a perfluorocycloalkyl group, still more preferably a perfluoroalkyl group having 1 to 6 carbon atoms, and particularly preferably a perfluoroalkyl group having 1 to 3 carbon atoms. Examples of perfluoroalkyl groups include a perfluoromethyl group, a perfluoroethyl group, a perfluoropropyl group, a perfluorobutyl group, a perfluoropentyl group, a perfluorohexyl group, a perfluoroheptyl group, and a perfluorooctyl group. Examples of perfluorocycloalkyl groups include a perfluorocyclohexyl group.
When R ^a42 is an aliphatic hydrocarbon group having a group represented by formula (a-g3), the total number of carbon atoms in R ^a42 , including the number of carbon atoms in the group represented by formula (a-g3), is preferably 15 or less, and more preferably 12 or less. When R a42 has a group represented by formula (a-g3) as a substituent, the number thereof is preferably 1.

［式（ａ－ｇ２）中、
Ａ^a46は、ハロゲン原子を有していてもよい炭素数１～１７の２価の脂肪族炭化水素基を表す。
Ｘ^a44は、＊－Ｏ－ＣＯ－又は＊－ＣＯ－Ｏ－を表す（＊はＡ^a46との結合部位を表す）。
Ａ^a47は、ハロゲン原子を有していてもよい炭素数１～１７の脂肪族炭化水素基を表す。
ただし、Ａ^a46、Ａ^a47及びＸ^a44の炭素数の合計は１８以下であり、Ａ^a46及びＡ^a47のうち、少なくとも一方は、少なくとも１つのハロゲン原子を有する。
＊はカルボニル基との結合部位を表す。］ When R ^a42 is an aliphatic hydrocarbon having a group represented by formula (a-g3), R ^a42 is more preferably a group represented by formula (a-g2).

[In formula (a-g2),
A ^a46 represents a divalent aliphatic hydrocarbon group having 1 to 17 carbon atoms which may have a halogen atom.
X ^a44 represents *--O--CO-- or *--CO--O-- (* represents the bonding site with A ^a46 ).
A ^a47 represents an aliphatic hydrocarbon group having 1 to 17 carbon atoms which may have a halogen atom.
However, the total number of carbon atoms of A ^a46 , A ^a47 and X ^a44 is 18 or less, and at least one of A ^a46 and A ^a47 has at least one halogen atom.
* indicates the bonding site with the carbonyl group.

The aliphatic hydrocarbon group of A ^a46 preferably has 1 to 6 carbon atoms, and more preferably has 1 to 3 carbon atoms.
The aliphatic hydrocarbon group of A ^a47 preferably has 4 to 15 carbon atoms, more preferably 5 to 12 carbon atoms, and A ^a47 is even more preferably a cyclohexyl group or an adamantyl group.

A preferred structure of the group represented by formula (a-g2) is the following structure (* indicates the bonding site with the carbonyl group).

Examples of the alkanediyl group in A ^a41 include linear alkanediyl groups such as a methylene group, an ethylene group, a propane-1,3-diyl group, a butane-1,4-diyl group, a pentane-1,5-diyl group, and a hexane-1,6-diyl group; and branched alkanediyl groups such as a propane-1,2-diyl group, a butane-1,3-diyl group, a 2-methylpropane-1,2-diyl group, a 1-methylbutane-1,4-diyl group, and a 2-methylbutane-1,4-diyl group.
Examples of the substituent in the alkanediyl group of A ^a41 include a hydroxy group and an alkoxy group having 1 to 6 carbon atoms.
A ^a41 is preferably an alkanediyl group having 1 to 4 carbon atoms, more preferably an alkanediyl group having 2 to 4 carbon atoms, and even more preferably an ethylene group.

Examples of the divalent saturated hydrocarbon group represented by A ^a42 , A ^a43 and A ^a44 in the group represented by formula (a-g1) include a linear or branched alkanediyl group, a monocyclic divalent alicyclic hydrocarbon group, and a group formed by combining an alkanediyl group and a divalent alicyclic hydrocarbon group, etc. Specific examples include a methylene group, an ethylene group, a propane-1,3-diyl group, a propane-1,2-diyl group, a butane-1,4-diyl group, a 1-methylpropane-1,3-diyl group, a 2-methylpropane-1,3-diyl group, a 2-methylpropane-1,2-diyl group, etc.
Examples of the substituent of the divalent saturated hydrocarbon group represented by A ^a42 , A ^a43 and A ^a44 include a hydroxy group and an alkoxy group having 1 to 6 carbon atoms.
It is preferred that s is 0.

In the group represented by formula (a-g1), examples of the group in which X ^a42 is -O-, -CO-, -CO-O- or -O-CO- include the following groups. In the following examples, * and ** each represent a bonding site, and ** is the bonding site with -O-CO-R ^a42 .

Examples of the structural unit represented by formula (a4-1) include the structural units shown below and structural units in which a methyl group corresponding to R ^a41 in the structural unit represented by formula (a4-1) in the following structural units is replaced with a hydrogen atom.

［式（ａ４－２）中、
Ｒ^f5は、水素原子又はメチル基を表す。
Ｌ⁴⁴は、炭素数１～６のアルカンジイル基を表し、該アルカンジイル基に含まれる－ＣＨ₂－は、－Ｏ－又は－ＣＯ－に置き換わっていてもよい。
Ｒ^f6は、炭素数１～２０のフッ素原子を有する飽和炭化水素基を表す。
ただし、Ｌ⁴⁴及びＲ^f6の合計炭素数の上限は２１である。］ The structural unit represented by formula (a4-1) is preferably a structural unit represented by formula (a4-2).

[In formula (a4-2),
R ^f5 represents a hydrogen atom or a methyl group.
L ⁴⁴ represents an alkanediyl group having 1 to 6 carbon atoms, and --CH ₂ -- contained in the alkanediyl group may be replaced by --O-- or --CO--.
R ^f6 represents a saturated hydrocarbon group having 1 to 20 carbon atoms and containing a fluorine atom.
However, the upper limit of the total number of carbon atoms of L ⁴⁴ and R ^f6 is 21.

Examples of the alkanediyl group having 1 to 6 carbon atoms for L ⁴⁴ include the same groups as those exemplified as the alkanediyl group for A ^a41 .
Examples of the saturated hydrocarbon group of R ^f6 include the same groups as those exemplified for R ^a42 .
As the alkanediyl group having 1 to 6 carbon atoms in L ⁴⁴ , an alkanediyl group having 2 to 4 carbon atoms is preferable, and an ethylene group is more preferable.

Examples of the structural unit represented by formula (a4-2) include structural units represented by formulas (a4-1-1) to (a4-1-11). The structural unit represented by formula (a4-2) also includes a structural unit in which a methyl group corresponding to ^Rf5 in the structural unit (a4-2) is replaced with a hydrogen atom.

［式（ａ４－３）中、
Ｒ^f7は、水素原子又はメチル基を表す。
Ｌ⁵は、炭素数１～６のアルカンジイル基を表す。
Ａ^f13は、フッ素原子を有していてもよい炭素数１～１８の２価の飽和炭化水素基を表す。
Ｘ^f12は、＊－Ｏ－ＣＯ－又は＊－ＣＯ－Ｏ－を表す（＊はＡ^f13との結合部位を表す。）。
Ａ^f14は、フッ素原子を有していてもよい炭素数１～１７の飽和炭化水素基を表す。
但し、Ａ^f13及びＡ^f14の少なくとも１つは、フッ素原子を有し、Ｌ⁵、Ａ^f13及びＡ^f14の合計炭素数の上限は２０である。］ Examples of the structural unit (a4) include a structural unit represented by formula (a4-3).

[In formula (a4-3),
R ^f7 represents a hydrogen atom or a methyl group.
^L5 represents an alkanediyl group having 1 to 6 carbon atoms.
A ^f13 represents a divalent saturated hydrocarbon group having 1 to 18 carbon atoms which may have a fluorine atom.
X ^f12 represents *--O--CO-- or *--CO--O-- (* represents the bonding site to A ^f13 ).
A ^f14 represents a saturated hydrocarbon group having 1 to 17 carbon atoms which may have a fluorine atom.
However, at least one of A ^f13 and A ^f14 has a fluorine atom, and the upper limit of the total number of carbon atoms of L ⁵ , A ^f13 and A ^f14 is 20.]

Examples of the alkanediyl group in ^L5 include the same groups as those exemplified as the alkanediyl group in ^Aa41 .
The divalent saturated hydrocarbon group optionally having a fluorine atom for A ^f13 is preferably a divalent aliphatic saturated hydrocarbon group optionally having a fluorine atom and a divalent alicyclic saturated hydrocarbon group optionally having a fluorine atom, and more preferably a perfluoroalkanediyl group.
Examples of the divalent aliphatic hydrocarbon group which may have a fluorine atom include alkanediyl groups such as a methylene group, an ethylene group, a propanediyl group, a butanediyl group, and a pentanediyl group; and perfluoroalkanediyl groups such as a difluoromethylene group, a perfluoroethylene group, a perfluoropropanediyl group, a perfluorobutanediyl group, and a perfluoropentanediyl group.
The divalent alicyclic hydrocarbon group which may have a fluorine atom may be either monocyclic or polycyclic. Examples of the monocyclic group include a cyclohexanediyl group and a perfluorocyclohexanediyl group. Examples of the polycyclic group include an adamantanediyl group, a norbornanediyl group, and a perfluoroadamantanediyl group.
Examples of the saturated hydrocarbon group and the saturated hydrocarbon group which may have a fluorine atom of A ^f14 include the same groups as those exemplified for R ^a42 . Among them, a trifluoromethyl group, a difluoromethyl group, a methyl group, a perfluoroethyl group, a 2,2,2-trifluoroethyl group, a 1,1,2,2-tetrafluoroethyl group, an ethyl group, a perfluoropropyl group, a 2,2,3,3,3-pentafluoropropyl group, a propyl group, a perfluorobutyl group, a 1,1,2,2,3,3,4,4-octafluorobutyl group, a butyl group, a perfluoropentyl group, a 2,2,3,3,4,4,5,5,5-nonafluoropentyl group, a pentyl group, Preferred are fluorinated alkyl groups such as a hexyl group, a perfluorohexyl group, a heptyl group, a perfluoroheptyl group, an octyl group, and a perfluorooctyl group, a cyclopropylmethyl group, a cyclopropyl group, a cyclobutylmethyl group, a cyclopentyl group, a cyclohexyl group, a perfluorocyclohexyl group, an adamantyl group, an adamantylmethyl group, an adamantyldimethyl group, a norbornyl group, a norbornylmethyl group, a perfluoroadamantyl group, and a perfluoroadamantylmethyl group.

In formula (a4-3), L ⁵ is preferably an ethylene group.
The divalent saturated hydrocarbon group for A ^f13 is preferably a group containing a divalent chain hydrocarbon group having 1 to 6 carbon atoms and a divalent alicyclic hydrocarbon group having 3 to 12 carbon atoms, more preferably a divalent chain hydrocarbon group having 2 to 3 carbon atoms.
The saturated hydrocarbon group of A ^f14 is preferably a group containing a chain hydrocarbon group having 3 to 12 carbon atoms and an alicyclic hydrocarbon group having 3 to 12 carbon atoms, and more preferably a group containing a chain hydrocarbon group having 3 to 10 carbon atoms and an alicyclic hydrocarbon group having 3 to 10 carbon atoms. Among these, A ^f14 is preferably a group containing an alicyclic hydrocarbon group having 3 to 12 carbon atoms, and more preferably a cyclopropylmethyl group, a cyclopentyl group, a cyclohexyl group, a norbornyl group, or an adamantyl group.

Examples of the structural unit represented by formula (a4-3) include structural units represented by formulas (a4-1'-1) to (a4-1'-11). The structural unit represented by formula (a4-3) also includes a structural unit in which the methyl group corresponding to ^Rf7 in the structural unit (a4-3) is replaced with a hydrogen atom.

［式（ａ４－４）中、
Ｒ^f21は、水素原子又はメチル基を表す。
Ａ^f21は、－（ＣＨ₂）_j1－、－（ＣＨ₂）_j2－Ｏ－（ＣＨ₂）_j3－又は－（ＣＨ₂）_j4－ＣＯ－Ｏ－（ＣＨ₂）_j5－を表す。
ｊ１～ｊ５は、それぞれ独立に、１～６のいずれかの整数を表す。
Ｒ^f22は、フッ素原子を有する炭素数１～１０の飽和炭化水素基を表す。］ The structural unit (a4) also includes a structural unit represented by formula (a4-4).

[In formula (a4-4),
R ^f21 represents a hydrogen atom or a methyl group.
A ^f21 represents --(CH ₂ ) _j1 --, --(CH ₂ ) _j2 --O--(CH ₂ ) _j3 -- or --(CH ₂ ) _j4 --CO--O--(CH ₂ ) _j5 --.
j1 to j5 each independently represent an integer of 1 to 6.
R ^f22 represents a saturated hydrocarbon group having 1 to 10 carbon atoms and containing a fluorine atom.]

Examples of the saturated hydrocarbon group of R ^f22 include the same as the saturated hydrocarbon group represented by R ^a42 . R ^f22 is preferably an alkyl group having 1 to 10 carbon atoms and containing a fluorine atom, or an alicyclic hydrocarbon group having 1 to 10 carbon atoms and containing a fluorine atom, more preferably an alkyl group having 1 to 10 carbon atoms and containing a fluorine atom, and even more preferably an alkyl group having 1 to 6 carbon atoms and containing a fluorine atom.

In formula (a4-4), A ^f21 is preferably --(CH ₂ ) _j1 --, more preferably an ethylene group or a methylene group, and even more preferably a methylene group.

Examples of the structural unit represented by formula (a4-4) include the following structural units and structural units represented by the following formula in which a methyl group corresponding to R ^f21 in the structural unit (a4-4) is replaced with a hydrogen atom:

When resin (A) has structural unit (a4), its content is preferably 1 to 20 mol %, more preferably 2 to 15 mol %, and even more preferably 3 to 10 mol %, based on the total structural units of resin (A).

［式（ａ５－１）中、
Ｒ⁵¹は、水素原子又はメチル基を表す。
Ｒ⁵²は、炭素数３～１８の脂環式炭化水素基を表し、該脂環式炭化水素基に含まれる水素原子は炭素数１～８の脂肪族炭化水素基で置換されていてもよい。
Ｌ⁵⁵は、単結合又は炭素数１～１８の２価の飽和炭化水素基を表し、該飽和炭化水素基に含まれる－ＣＨ_２－は、－Ｏ－又は－ＣＯ－に置き換わっていてもよい。］ <Structural unit (a5)>
The non-leaving hydrocarbon group contained in the structural unit (a5) may be a group having a linear, branched or cyclic hydrocarbon group. Among these, the structural unit (a5) is preferably a group having an alicyclic hydrocarbon group.
An example of the structural unit (a5) is a structural unit represented by formula (a5-1).

[In formula (a5-1),
^R51 represents a hydrogen atom or a methyl group.
R ⁵² represents an alicyclic hydrocarbon group having 3 to 18 carbon atoms, and a hydrogen atom contained in the alicyclic hydrocarbon group may be substituted with an aliphatic hydrocarbon group having 1 to 8 carbon atoms.
L ⁵⁵ represents a single bond or a divalent saturated hydrocarbon group having 1 to 18 carbon atoms, and --CH ₂ -- contained in the saturated hydrocarbon group may be replaced by --O-- or --CO--.]

The alicyclic hydrocarbon group in ^R52 may be either monocyclic or polycyclic. Examples of the monocyclic alicyclic hydrocarbon group include a cyclopropyl group, a cyclobutyl group, a cyclopentyl group, and a cyclohexyl group. Examples of the polycyclic alicyclic hydrocarbon group include an adamantyl group, a norbornyl group, and the like.
Examples of the aliphatic hydrocarbon group having 1 to 8 carbon atoms include alkyl groups such as a methyl group, an ethyl group, a propyl group, an isopropyl group, a butyl group, a sec-butyl group, a tert-butyl group, a pentyl group, a hexyl group, an octyl group, and a 2-ethylhexyl group.
An example of the alicyclic hydrocarbon group having a substituent is a 3-methyladamantyl group.
R ⁵² is preferably an unsubstituted alicyclic hydrocarbon group having 3 to 18 carbon atoms, and more preferably an adamantyl group, a norbornyl group or a cyclohexyl group.
The divalent saturated hydrocarbon group for L ⁵⁵ includes a divalent chain saturated hydrocarbon group and a divalent alicyclic saturated hydrocarbon group, and is preferably a divalent chain saturated hydrocarbon group.
Examples of the divalent chain saturated hydrocarbon group include alkanediyl groups such as a methylene group, an ethylene group, a propanediyl group, a butanediyl group, and a pentanediyl group.
The divalent alicyclic saturated hydrocarbon group may be either monocyclic or polycyclic. Examples of the monocyclic alicyclic saturated hydrocarbon group include cycloalkanediyl groups such as cyclopentanediyl and cyclohexanediyl. Examples of the polycyclic divalent alicyclic saturated hydrocarbon group include adamantanediyl and norbornanediyl.

式（Ｌ１－１）中、
Ｘ^x1は、＊－Ｏ－ＣＯ－又は＊－ＣＯ－Ｏ－を表す（＊はＬ^ｘ１との結合部位を表す。）。
Ｌ^x1は、炭素数１～１６の２価の脂肪族飽和炭化水素基を表す。
Ｌ^x2は、単結合又は炭素数１～１５の２価の脂肪族飽和炭化水素基を表す。
ただし、Ｌ^x1及びＬ^x2の合計炭素数は、１６以下である。
式（Ｌ１－２）中、
Ｌ^x3は、炭素数１～１７の２価の脂肪族飽和炭化水素基を表す。
Ｌ^x4は、単結合又は炭素数１～１６の２価の脂肪族飽和炭化水素基を表す。
ただし、Ｌ^x3及びＬ^x4の合計炭素数は、１７以下である。
式（Ｌ１－３）中、
Ｌ^x5は、炭素数１～１５の２価の脂肪族飽和炭化水素基を表す。
Ｌ^x6及びＬ^x7は、それぞれ独立に、単結合又は炭素数１～１４の２価の脂肪族飽和炭化水素基を表す。
ただし、Ｌ^x5、Ｌ^x6及びＬ^x7の合計炭素数は、１５以下である。
式（Ｌ１－４）中、
Ｌ^x8及びＬ^x9は、単結合又は炭素数１～１２の２価の脂肪族飽和炭化水素基を表す。
Ｗ^x1は、炭素数３～１５の２価の脂環式飽和炭化水素基を表す。
ただし、Ｌ^x8、Ｌ^x9及びＷ^x1の合計炭素数は、１５以下である。 Examples of the divalent saturated hydrocarbon group represented by L ⁵⁵ in which --CH ₂ -- is replaced by --O-- or --CO-- include groups represented by formulae (L1-1) to (L1-4). In the following formulae, * and ** each represent a bonding site, and * represents a bonding site with an oxygen atom.

In formula (L1-1),
X ^x1 represents *--O--CO-- or *--CO--O-- (* represents the bonding site with L ^x1 ).
L ^x1 represents a divalent aliphatic saturated hydrocarbon group having 1 to 16 carbon atoms.
L ^x2 represents a single bond or a divalent aliphatic saturated hydrocarbon group having 1 to 15 carbon atoms.
However, the total number of carbon atoms of L ^x1 and L ^x2 is 16 or less.
In formula (L1-2),
L ^x3 represents a divalent aliphatic saturated hydrocarbon group having 1 to 17 carbon atoms.
L ^x4 represents a single bond or a divalent aliphatic saturated hydrocarbon group having 1 to 16 carbon atoms.
However, the total number of carbon atoms of L ^x3 and L ^x4 is 17 or less.
In formula (L1-3),
L ^x5 represents a divalent aliphatic saturated hydrocarbon group having 1 to 15 carbon atoms.
L ^x6 and L ^x7 each independently represent a single bond or a divalent aliphatic saturated hydrocarbon group having 1 to 14 carbon atoms.
However, the total number of carbon atoms of L ^x5 , L ^x6 and L ^x7 is 15 or less.
In formula (L1-4),
L ^x8 and L ^x9 each represent a single bond or a divalent aliphatic saturated hydrocarbon group having 1 to 12 carbon atoms.
W ^x1 represents a divalent alicyclic saturated hydrocarbon group having 3 to 15 carbon atoms.
However, the total number of carbon atoms of L ^x8 , L ^x9 and W ^x1 is 15 or less.

L ^x1 is preferably a divalent aliphatic saturated hydrocarbon group having 1 to 8 carbon atoms, more preferably a methylene group or an ethylene group.
L ^x2 is preferably a single bond or a divalent aliphatic saturated hydrocarbon group having 1 to 8 carbon atoms, more preferably a single bond.
L ^x3 is preferably a divalent aliphatic saturated hydrocarbon group having 1 to 8 carbon atoms.
L ^x4 is preferably a single bond or a divalent aliphatic saturated hydrocarbon group having 1 to 8 carbon atoms.
L ^x5 is preferably a divalent aliphatic saturated hydrocarbon group having 1 to 8 carbon atoms, more preferably a methylene group or an ethylene group.
L ^x6 is preferably a single bond or a divalent aliphatic saturated hydrocarbon group having 1 to 8 carbon atoms, more preferably a methylene group or an ethylene group.
L ^x7 is preferably a single bond or a divalent aliphatic saturated hydrocarbon group having 1 to 8 carbon atoms.
L ^x8 is preferably a single bond or a divalent aliphatic saturated hydrocarbon group having 1 to 8 carbon atoms, more preferably a single bond or a methylene group.
L ^x9 is preferably a single bond or a divalent aliphatic saturated hydrocarbon group having 1 to 8 carbon atoms, more preferably a single bond or a methylene group.
W ^x1 is preferably a divalent alicyclic saturated hydrocarbon group having 3 to 10 carbon atoms, more preferably a cyclohexanediyl group or an adamantanediyl group.

Examples of the group represented by formula (L1-1) include the divalent groups shown below.

Examples of the group represented by formula (L1-2) include the divalent groups shown below.

Examples of the group represented by formula (L1-3) include the divalent groups shown below.

Examples of the group represented by formula (L1-4) include the divalent groups shown below.

L ⁵⁵ is preferably a single bond or a group represented by the formula (L1-1).

樹脂（Ａ）が、構造単位（ａ５）を有する場合、その含有率は、樹脂（Ａ）の全構造単位に対して、１～３０モル％が好ましく、２～２０モル％がより好ましく、３～１５モル％がさらに好ましい。 Examples of the structural unit (a5-1) include the structural units shown below and structural units in which a methyl group corresponding to R ⁵¹ in the structural unit (a5-1) shown below has been replaced with a hydrogen atom.

When the resin (A) has the structural unit (a5), the content thereof is preferably from 1 to 30 mol %, more preferably from 2 to 20 mol %, and even more preferably from 3 to 15 mol %, based on all structural units in the resin (A).

<Structural Unit (II)>
Resin (A) may further contain a structural unit that decomposes upon exposure to generate an acid (hereinafter, sometimes referred to as "structural unit (II)"). Specific examples of the structural unit (II) include the structural units described in JP-A-2016-79235, and are preferably a structural unit having a sulfonate group or carboxylate group and an organic cation in a side chain, or a structural unit having a sulfonio group and an organic anion in a side chain.

［式（ＩＩ－２－Ａ’）中、
Ｘ^ＩＩＩ３は、炭素数１～１８の２価の飽和炭化水素基を表し、該飽和炭化水素基に含まれる－ＣＨ_２－は、－Ｏ－、－Ｓ－又は－ＣＯ－に置き換わっていてもよく、該飽和炭化水素基に含まれる水素原子は、ハロゲン原子、ハロゲン原子を有していてもよい炭素数１～６のアルキル基又はヒドロキシ基で置き換わっていてもよい。
Ａ^ｘ１は、炭素数１～８のアルカンジイル基を表し、該アルカンジイル基に含まれる水素原子は、フッ素原子又は炭素数１～６のペルフルオロアルキル基で置換されていてもよい。
ＲＡ^－は、スルホナート基又はカルボキシレート基を表す。
Ｒ^ＩＩＩ３は、水素原子、ハロゲン原子又はハロゲン原子を有していてもよい炭素数１～６のアルキル基を表す。
ＺＡ^＋は、有機カチオンを表す。］ The structural unit having a sulfonate group or a carboxylate group in the side chain is preferably a structural unit represented by formula (II-2-A').

[In formula (II-2-A′),
^XIII3 represents a divalent saturated hydrocarbon group having 1 to 18 carbon atoms, in which -CH ₂ - contained in the saturated hydrocarbon group may be replaced by -O-, -S- or -CO-, and a hydrogen atom contained in the saturated hydrocarbon group may be replaced by a halogen atom, an alkyl group having 1 to 6 carbon atoms which may have a halogen atom, or a hydroxy group.
A ^x1 represents an alkanediyl group having 1 to 8 carbon atoms, and a hydrogen atom contained in the alkanediyl group may be substituted by a fluorine atom or a perfluoroalkyl group having 1 to 6 carbon atoms.
^RA- represents a sulfonate group or a carboxylate group.
R ^III3 represents a hydrogen atom, a halogen atom or an alkyl group having 1 to 6 carbon atoms which may have a halogen atom.
ZA ⁺ represents an organic cation.

Examples of the halogen atom represented by R ^III3 include a fluorine atom, a chlorine atom, a bromine atom, and an iodine atom.
Examples of the alkyl group having 1 to 6 carbon atoms which may have a halogen atom and which is represented by R ^III3 include the same as the alkyl group having 1 to 6 carbon atoms which may have a halogen atom and which is represented by R ^a8 .
Examples of the alkanediyl group having 1 to 8 carbon atoms represented by A ^x1 include a methylene group, an ethylene group, a propane-1,3-diyl group, a butane-1,4-diyl group, a pentane-1,5-diyl group, a hexane-1,6-diyl group, an ethane-1,1-diyl group, a propane-1,1-diyl group, a propane-1,2-diyl group, a propane-2,2-diyl group, a pentane-2,4-diyl group, a 2-methylpropane-1,3-diyl group, a 2-methylpropane-1,2-diyl group, a pentane-1,4-diyl group, and a 2-methylbutane-1,4-diyl group.
Examples of the perfluoroalkyl group having 1 to 6 carbon atoms which may be substituted in A ^x1 include a trifluoromethyl group, a perfluoroethyl group, a perfluoropropyl group, a perfluoroisopropyl group, a perfluorobutyl group, a perfluorosec-butyl group, a perfluorotert-butyl group, a perfluoropentyl group, and a perfluorohexyl group.
Examples of the divalent saturated hydrocarbon group having 1 to 18 carbon atoms represented by ^XIII3 include linear or branched alkanediyl groups, and monocyclic or polycyclic divalent alicyclic saturated hydrocarbon groups, and combinations of these may also be used.
Specific examples of the alkyl group include linear alkanediyl groups such as methylene, ethylene, propane-1,3-diyl, propane-1,2-diyl, butane-1,4-diyl, pentane-1,5-diyl, hexane-1,6-diyl, heptane-1,7-diyl, octane-1,8-diyl, nonane-1,9-diyl, decane-1,10-diyl, undecane-1,11-diyl, and dodecane-1,12-diyl; butane-1,3-diyl, 2-methylpropane-1,3-diyl, and 2-methylpropane-1,3-diyl. Examples of the divalent alkyl group include branched alkanediyl groups such as pan-1,2-diyl group, pentane-1,4-diyl group, and 2-methylbutane-1,4-diyl group; cycloalkanediyl groups such as cyclobutane-1,3-diyl group, cyclopentane-1,3-diyl group, cyclohexane-1,4-diyl group, and cyclooctane-1,5-diyl group; and divalent polycyclic alicyclic saturated hydrocarbon groups such as norbornane-1,4-diyl group, norbornane-2,5-diyl group, adamantane-1,5-diyl group, and adamantane-2,6-diyl group.
Examples of saturated hydrocarbon groups in which -CH ₂ - is replaced by -O-, -S- or -CO- include divalent groups represented by formulae (X1) to (X53), where the number of carbon atoms before -CH ₂ - in the saturated hydrocarbon group is replaced by -O-, -S- or -CO- is 17 or less. In the following formulae, * and ** represent bonding sites, and * represents the bonding site with A ^x1 .

^X3 represents a divalent saturated hydrocarbon group having 1 to 16 carbon atoms.
^X4 represents a divalent saturated hydrocarbon group having 1 to 15 carbon atoms.
^X5 represents a divalent saturated hydrocarbon group having 1 to 13 carbon atoms.
^X6 represents a divalent saturated hydrocarbon group having 1 to 14 carbon atoms.
^X7 represents a trivalent saturated hydrocarbon group having 1 to 14 carbon atoms.
^X8 represents a divalent saturated hydrocarbon group having 1 to 13 carbon atoms.

Examples of ZA ⁺ in formula (II-2-A') include the same cations as Z ⁺ in the salt represented by formula (B1).

［式（ＩＩ－２－Ａ）中、Ｒ^ＩＩＩ３、Ｘ^ＩＩＩ３及びＺＡ^＋は、上記と同じ意味を表す。
ｚ２Ａは、０～６のいずれかの整数を表す。
Ｒ^ＩＩＩ２及びＲ^ＩＩＩ４は、それぞれ独立して、水素原子、フッ素原子又は炭素数１～６のペルフルオロアルキル基を表し、ｚ２Ａが２以上のとき、複数のＲ^ＩＩＩ２及びＲ^ＩＩＩ４は互いに同一であってもよいし、異なっていてもよい。
Ｑ^ａ及びＱ^ｂは、それぞれ独立して、フッ素原子又は炭素数１～６のペルフルオロアルキル基を表す。］
Ｒ^ＩＩＩ２、Ｒ^ＩＩＩ４、Ｑ^ａ及びＱ^ｂで表される炭素数１～６のペルフルオロアルキル基としては、後述のＱ^ｂ１で表される炭素数１～６のペルフルオロアルキル基と同じものが挙げられる。 The structural unit represented by formula (II-2-A') is preferably a structural unit represented by formula (II-2-A).

In formula (II-2-A), R ^III3 , X ^III3 and ZA ⁺ are as defined above.
z2A represents an integer of 0 to 6.
R ^III2 and R ^III4 each independently represent a hydrogen atom, a fluorine atom, or a perfluoroalkyl group having 1 to 6 carbon atoms, and when z2A is 2 or greater, a plurality of R ^III2's and R ^III4 's may be the same or different.
Q ^a and Q ^b each independently represent a fluorine atom or a perfluoroalkyl group having 1 to 6 carbon atoms.
Examples of the perfluoroalkyl group having 1 to 6 carbon atoms represented by R ^III2 , R ^III4 , Q ^a and Q ^b include the same perfluoroalkyl groups having 1 to 6 carbon atoms represented by Q ^b1 described below.

［式（ＩＩ－２－Ａ－１）中、
Ｒ^ＩＩＩ２、Ｒ^ＩＩＩ３、Ｒ^ＩＩＩ４、Ｑ^a、Ｑ^b及びＺＡ^＋は、上記と同じ意味を表す。
Ｒ^ＩＩＩ５は、炭素数１～１２の飽和炭化水素基を表す。
ｚ２Ａ１は、０～６のいずれかの整数を表す。
Ｘ^Ｉ2は、炭素数１～１１の２価の飽和炭化水素基を表し、該飽和炭化水素基に含まれる－ＣＨ_２－は、－Ｏ－、－Ｓ－又は－ＣＯ－に置き換わっていてもよく、該飽和炭化水素基に含まれる水素原子は、ハロゲン原子又はヒドロキシ基で置換されていてもよい。］
Ｒ^ＩＩＩ５で表される炭素数１～１２の飽和炭化水素基としては、メチル基、エチル基、プロピル基、イソプロピル基、ブチル基、ｓｅｃ－ブチル基、ｔｅｒｔ－ブチル基、ペンチル基、ヘキシル基、ヘプチル基、オクチル基、ノニル基、デシル基、ウンデシル基及びドデシル基等の直鎖又は分岐のアルキル基が挙げられる。
Ｘ^Ｉ２で表される２価の飽和炭化水素基としては、Ｘ^ＩＩＩ３で表される２価の飽和炭化水素基と同様のものが挙げられる。 The structural unit represented by formula (II-2-A) is preferably a structural unit represented by formula (II-2-A-1).

[In formula (II-2-A-1),
R ^III2 , R ^III3 , R ^III4 , Q ^a , Q ^b and ZA ⁺ have the same meanings as above.
R ^III5 represents a saturated hydrocarbon group having 1 to 12 carbon atoms.
z2A1 represents an integer of 0 to 6.
X ^I2 represents a divalent saturated hydrocarbon group having 1 to 11 carbon atoms, -CH ₂ - contained in the saturated hydrocarbon group may be replaced by -O-, -S- or -CO-, and a hydrogen atom contained in the saturated hydrocarbon group may be replaced by a halogen atom or a hydroxyl group.]
Examples of the saturated hydrocarbon group having 1 to 12 carbon atoms represented by R ^III5 include linear or branched alkyl groups such as a methyl group, an ethyl group, a propyl group, an isopropyl group, a butyl group, a sec-butyl group, a tert-butyl group, a pentyl group, a hexyl group, a heptyl group, an octyl group, a nonyl group, a decyl group, an undecyl group, and a dodecyl group.
Examples of the divalent saturated hydrocarbon group represented by X ^I2 include the same as the divalent saturated hydrocarbon group represented by X ^III3 .

［式（ＩＩ－２－Ａ－２）中、Ｒ^ＩＩＩ３、Ｒ^ＩＩＩ５及びＺＡ^＋は、上記と同じ意味を表す。
ｍ及びｎは、互いに独立に、１又は２を表す。］ As the structural unit represented by formula (II-2-A-1), a structural unit represented by formula (II-2-A-2) is more preferable.

In formula (II-2-A-2), R ^III3 , R ^III5 and ZA ⁺ are as defined above.
m and n each independently represent 1 or 2.

Examples of the structural unit represented by formula (II-2-A') include the following structural units, structural units in which the group corresponding to the methyl group of R ^III3 is replaced with a hydrogen atom, a halogen atom (e.g., a fluorine atom) or an alkyl group having 1 to 6 carbon atoms which may have a halogen atom (e.g., a trifluoromethyl group), and structural units described in WO 2012/050015. ZA ⁺ represents an organic cation.

［式（ＩＩ－１－１）中、
Ａ^ＩＩ１は、単結合又は２価の連結基を表す。
Ｒ^ＩＩ１は、炭素数６～１８の２価の芳香族炭化水素基を表す。
Ｒ^ＩＩ２及びＲ^ＩＩ３は、それぞれ独立して、炭素数１～１８の炭化水素基を表し、Ｒ^ＩＩ２及びＲ^ＩＩ３は互いに結合してそれらが結合する硫黄原子とともに環を形成していてもよい。
Ｒ^II4は、水素原子、ハロゲン原子又はハロゲン原子を有してもよい炭素数１～６のアルキル基を表す。
Ａ^－は、有機アニオンを表す。］
Ｒ^ＩＩ１で表される炭素数６～１８の２価の芳香族炭化水素基としては、フェニレン基及びナフチレン基等が挙げられる。
Ｒ^ＩＩ２及びＲ^ＩＩ３で表される炭化水素基としては、アルキル基、脂環式炭化水素基、芳香族炭化水素基及びこれらを組み合わせることにより形成される基等が挙げられる。
Ｒ^ＩＩ４で表されるハロゲン原子としては、フッ素原子、塩素原子、臭素原子及びヨウ素原子等が挙げられる。
Ｒ^ＩＩ４で表されるハロゲン原子を有していてもよい炭素数１～６のアルキル基としては、Ｒ^ａ８で表されるハロゲン原子を有していてもよい炭素数１～６のアルキル基と同じものが挙げられる。
Ａ^ＩＩ１で表される２価の連結基としては、例えば、炭素数１～１８の２価の飽和炭化水素基が挙げられ、該２価の飽和炭化水素基に含まれる－ＣＨ_２－は、－Ｏ－、－Ｓ－又は－ＣＯ－で置き換わっていてもよい。具体的には、Ｘ^ＩＩＩ３で表される炭素数１～１８の２価の飽和炭化水素基と同じものが挙げられる。 The structural unit having a sulfonio group and an organic anion in the side chain is preferably a structural unit represented by formula (II-1-1).

[In formula (II-1-1),
A ^II1 represents a single bond or a divalent linking group.
R ^II1 represents a divalent aromatic hydrocarbon group having 6 to 18 carbon atoms.
R ^II2 and R ^II3 each independently represent a hydrocarbon group having 1 to 18 carbon atoms, and R ^II2 and R ^II3 may be bonded to each other to form a ring together with the sulfur atom to which they are bonded.
R ^II4 represents a hydrogen atom, a halogen atom or an alkyl group having 1 to 6 carbon atoms which may have a halogen atom.
A ⁻ represents an organic anion.
Examples of the divalent aromatic hydrocarbon group having 6 to 18 carbon atoms represented by R ^II1 include a phenylene group and a naphthylene group.
Examples of the hydrocarbon group represented by R ^II2 and R ^II3 include an alkyl group, an alicyclic hydrocarbon group, an aromatic hydrocarbon group, and a group formed by combining these groups.
Examples of the halogen atom represented by ^RII4 include a fluorine atom, a chlorine atom, a bromine atom, and an iodine atom.
Examples of the alkyl group having 1 to 6 carbon atoms which may have a halogen atom and which is represented by R ^II4 include the same as the alkyl group having 1 to 6 carbon atoms which may have a halogen atom and which is represented by R ^a8 .
Examples of the divalent linking group represented by A ^II1 include a divalent saturated hydrocarbon group having 1 to 18 carbon atoms, in which -CH ₂ - may be replaced by -O-, -S- or -CO-. Specific examples include the same as the divalent saturated hydrocarbon group having 1 to 18 carbon atoms represented by X ^III3 .

Examples of the structural unit containing a cation in formula (II-1-1) include structural units represented by the following formulas and structural units in which the group corresponding to the methyl group in R ^II4 is replaced with a hydrogen atom, a fluorine atom, trifluoromethyl, or the like.

Examples of the organic anion represented by ^A- include a sulfonate anion, a sulfonylimide anion, a sulfonylmethide anion, a carboxylate anion, etc. The organic anion represented by ^A- is preferably a sulfonate anion, and the sulfonate anion is more preferably an anion contained in the salt represented by the above formula (B1).

Examples of the sulfonylimide anion represented by A ¹ - include the following.

Examples of sulfonylmethide anions include the following:

Examples of carboxylate anions include the following:

Examples of the structural unit represented by formula (II-1-1) include structural units represented below.

樹脂（Ａ）中に、構造単位（ＩＩ）を含有する場合の構造単位（ＩＩ）の含有率は、樹脂（Ａ）の全構造単位に対して、好ましくは１～２０モル％であり、より好ましくは２～１５モル％であり、さらに好ましくは３～１０モル％である。

When the resin (A) contains the structural unit (II), the content of the structural unit (II) is preferably 1 to 20 mol %, more preferably 2 to 15 mol %, and even more preferably 3 to 10 mol %, based on the total structural units of the resin (A).

Resin (A) may have structural units other than the above-mentioned structural units, and examples of such structural units include structural units well known in the art.

Resin (A) is preferably a resin consisting of structural units (I) and (III), a resin consisting of structural units (I), (III), (a1-1) and (a1-2), a resin consisting of structural units (I), (III) and (a1-1), a resin consisting of structural units (I), (III) and (a1-2), a resin consisting of structural units (I), (III), (a1-1), (a1-2) and (a1-3), a resin consisting of structural units (I), (III), (a1-1), (a1-2) and (a1-3) resins consisting of structural units (I), (III), (a1-1) and (s); resins consisting of structural units (I), (III), (a1-2) and (s); resins consisting of structural units (I), (III) and (s); resins consisting of structural units (I), (III), (a1-1), (a1-2), (s) and (a4) and/or (a5); or a resin consisting of only the structural unit (I), the structural unit (III), the structural unit (a1-1), the structural unit (a1-2) and the structural unit (a4). More preferably, the resin consists of the structural unit (I) and the structural unit (III), the resin consists of the structural unit (I), the structural unit (a2-A), the structural unit (a1-1) and the structural unit (a1-2), the resin consists of the structural unit (I), the structural unit (III) and the structural unit (a1-1), the resin consists of the structural unit (I) and the structural unit (I) Resins consisting of structural units (I), (III), (a1-1), (a1-2), and (s); resins consisting of structural units (I), (III), (a1-1), and (s); resins consisting of structural units (I), (III), (a1-2), and (s); resins consisting of structural units (I), (III), (a1-2), and (s); resins consisting of structural units (I), (III), and (s).

The structural unit (s) is preferably at least one selected from the group consisting of the structural unit (a2) and the structural unit (a3). The structural unit (a2) is preferably a structural unit represented by formula (a2-A) or a structural unit (a2-1). The structural unit (a3) is preferably at least one selected from the group consisting of a structural unit represented by formula (a3-1), a structural unit represented by formula (a3-2), and a structural unit represented by formula (a3-4).

Each structural unit constituting the resin (A) may be used alone or in combination of two or more kinds, and can be produced by a known polymerization method (e.g., radical polymerization method) using a monomer that derives these structural units. The content of each structural unit in the resin (A) can be adjusted by the amount of the monomer used in the polymerization.
The weight average molecular weight of the resin (A) is preferably 2,000 or more (more preferably 2,500 or more, and even more preferably 3,000 or more) and 50,000 or less (more preferably 30,000 or less, and even more preferably 15,000 or less).
In this specification, the weight average molecular weight is a value determined by gel permeation chromatography. Gel permeation chromatography can be measured under the analytical conditions described in the Examples.

[Resist Composition]
The resist composition of the present invention contains a resin (A) and an acid generator (hereinafter sometimes referred to as “acid generator (B)”).
The acid generator may be any acid generator known in the resist field.
The resist composition of the present invention may further contain a resin other than the resin (A).
The resist composition of the present invention preferably contains a quencher such as a salt that generates an acid having a weaker acidity than the acid generated from the acid generator (hereinafter may be referred to as "quencher (C)"), and preferably contains a solvent (hereinafter may be referred to as "solvent (E)").

<Resins other than resin (A)>
The resist composition of the present invention may use a resin other than resin (A). The resin other than resin (A) may be a resin that does not contain at least one of structural unit (I) and structural unit (III). Examples of such a resin include a resin obtained by removing structural unit (I) from resin (A) (hereinafter referred to as "resin (AY)"), a resin obtained by removing structural unit (III) from resin (A) (hereinafter referred to as "resin (AZ)"), and a resin consisting of only structural unit (a4) and structural unit (a5) (hereinafter referred to as "resin (X)").

As the resin (X), a resin containing the structural unit (a4) is particularly preferred.
In the resin (X), the content of the structural unit (a4) is preferably 30 mol % or more, more preferably 40 mol % or more, and even more preferably 45 mol % or more, based on the total amount of all structural units in the resin (X).
Examples of structural units that the resin (X) may further have include the structural unit (a2), the structural unit (a3), and structural units derived from other known monomers. Among these, the resin (X) is preferably a resin consisting only of the structural unit (a4) and/or the structural unit (a5).

Each structural unit constituting the resin (X) may be used alone or in combination of two or more, and can be produced by a known polymerization method (e.g., radical polymerization method) using a monomer that derives these structural units. The content of each structural unit in the resin (X) can be adjusted by the amount of the monomer used in the polymerization.
The weight average molecular weight of resin (AY), resin (AZ) and resin (X) is preferably 6,000 or more (more preferably 7,000 or more) and 80,000 or less (more preferably 60,000 or less), independently of each other. The method for measuring the weight average molecular weight of resin (AY), resin (AZ) and resin (X) is the same as that for resin (A).
When the resist composition of the present invention contains resin (AY) and/or resin (AZ), the total content thereof is usually 1 to 2,500 parts by mass (more preferably 10 to 1,000 parts by mass) per 100 parts by mass of resin (A).
Furthermore, when the resist composition contains resin (X), the content thereof is preferably 1 to 60 parts by mass, more preferably 1 to 50 parts by mass, even more preferably 1 to 40 parts by mass, particularly preferably 1 to 30 parts by mass, and particularly preferably 1 to 8 parts by mass, relative to 100 parts by mass of resin (A).

[0113] In the resist composition of the present invention, the resin (A) may be used in combination with a resin other than the resin (A). In this case, it is preferable to use a resin containing a structural unit having an acid labile group and/or a resin containing a structural unit having a fluorine atom in combination, and it is more preferable to use the resin (AY), resin (AZ) and/or resin (X) in combination.
The content of resin (A) in the resist composition is preferably 80% by mass or more and 99% by mass or less, more preferably 90% by mass or more and 99% by mass or less, based on the solid content of the resist composition. When a resin other than resin (A) is contained, the total content of resin (A) and the resin other than resin (A) is preferably 80% by mass or more and 99% by mass or less, more preferably 90% by mass or more and 99% by mass or less, based on the solid content of the resist composition. The solid content of the resist composition and the resin content therein can be measured by a known analytical means such as liquid chromatography or gas chromatography.

<Acid Generator (B)>
The acid generator (B) may be either nonionic or ionic. Examples of nonionic acid generators include sulfonate esters (e.g., 2-nitrobenzyl ester, aromatic sulfonate, oxime sulfonate, N-sulfonyloxyimide, sulfonyloxyketone, diazonaphthoquinone 4-sulfonate), sulfones (e.g., disulfone, ketosulfone, sulfonyldiazomethane), and the like. Examples of ionic acid generators include onium salts containing onium cations (e.g., diazonium salts, phosphonium salts, sulfonium salts, iodonium salts). Examples of the anions of the onium salts include sulfonate anion, sulfonylimide anion, sulfonylmethide anion, and the like.

As the acid generator (B), compounds that generate acid when exposed to radiation, such as those described in JP-A-63-26653, JP-A-55-164824, JP-A-62-69263, JP-A-63-146038, JP-A-63-163452, JP-A-62-153853, JP-A-63-146029, U.S. Pat. No. 3,779,778, U.S. Pat. No. 3,849,137, German Patent No. 3914407, and European Patent No. 126,712, can be used. Compounds produced by known methods may also be used. Two or more types of acid generators (B) may be used in combination.

［式（Ｂ１）中、
Ｑ^ｂ１及びＱ^ｂ２は、それぞれ独立に、フッ素原子又は炭素数１～６のペルフルオロアルキル基を表す。
Ｌ^ｂ１は、炭素数１～２４の２価の飽和炭化水素基を表し、該２価の飽和炭化水素基に含まれる－ＣＨ_２－は、－Ｏ－又は－ＣＯ－に置き換わっていてもよく、該２価の飽和炭化水素基に含まれる水素原子は、フッ素原子又はヒドロキシ基で置換されていてもよい。
Ｙは、置換基を有していてもよいメチル基又は置換基を有していてもよい炭素数３～１８の脂環式炭化水素基を表し、該脂環式炭化水素基に含まれる－ＣＨ_２－は、－Ｏ－、－Ｓ（Ｏ）_２－又は－ＣＯ－に置き換わっていてもよい。
Ｚ^＋は、有機カチオンを表す。］ The acid generator (B) is preferably a fluorine-containing acid generator, and more preferably a salt represented by formula (B1) (hereinafter, sometimes referred to as "acid generator (B1)").

[In formula (B1),
Q ^b1 and Q ^b2 each independently represent a fluorine atom or a perfluoroalkyl group having 1 to 6 carbon atoms.
L ^b1 represents a divalent saturated hydrocarbon group having 1 to 24 carbon atoms, in which -CH ₂ - may be replaced by -O- or -CO-, and in which a hydrogen atom may be replaced by a fluorine atom or a hydroxyl group.
Y represents an optionally substituted methyl group or an optionally substituted alicyclic hydrocarbon group having 3 to 18 carbon atoms, and one -CH ₂ - contained in the alicyclic hydrocarbon group may be replaced by -O-, -S(O) ₂ - or -CO-.
Z ⁺ represents an organic cation.

Examples of the perfluoroalkyl group represented by Q ^b1 and Q ^b2 include a trifluoromethyl group, a perfluoroethyl group, a perfluoropropyl group, a perfluoroisopropyl group, a perfluorobutyl group, a perfluorosec-butyl group, a perfluorotert-butyl group, a perfluoropentyl group, and a perfluorohexyl group.
It is preferable that Q ^b1 and Q ^b2 each independently represent a fluorine atom or a trifluoromethyl group, and it is more preferable that both represent a fluorine atom.

Examples of the divalent saturated hydrocarbon group for L ^b1 include a linear alkanediyl group, a branched alkanediyl group, and a monocyclic or polycyclic divalent alicyclic saturated hydrocarbon group, and may be a group formed by combining two or more of these groups.
Specific examples of such straight-chain alkanediyl groups include methylene, ethylene, propane-1,3-diyl, butane-1,4-diyl, pentane-1,5-diyl, hexane-1,6-diyl, heptane-1,7-diyl, octane-1,8-diyl, nonane-1,9-diyl, decane-1,10-diyl, undecane-1,11-diyl, dodecane-1,12-diyl, tridecane-1,13-diyl, tetradecane-1,14-diyl, pentadecane-1,15-diyl, hexadecane-1,16-diyl, and heptadecane-1,17-diyl groups;
branched alkanediyl groups such as ethane-1,1-diyl group, propane-1,1-diyl group, propane-1,2-diyl group, propane-2,2-diyl group, pentane-2,4-diyl group, 2-methylpropane-1,3-diyl group, 2-methylpropane-1,2-diyl group, pentane-1,4-diyl group, and 2-methylbutane-1,4-diyl group;
monocyclic divalent alicyclic saturated hydrocarbon groups such as cycloalkanediyl groups, such as cyclobutane-1,3-diyl group, cyclopentane-1,3-diyl group, cyclohexane-1,4-diyl group, and cyclooctane-1,5-diyl group;
Examples of the polycyclic divalent alicyclic saturated hydrocarbon groups include norbornane-1,4-diyl group, norbornane-2,5-diyl group, adamantane-1,5-diyl group, and adamantane-2,6-diyl group.

［式（ｂ１－１）中、
Ｌ^ｂ２は、単結合又は炭素数１～２２の２価の飽和炭化水素基を表し、該飽和炭化水素基に含まれる水素原子は、フッ素原子に置換されていてもよい。
Ｌ^ｂ３は、単結合又は炭素数１～２２の２価の飽和炭化水素基を表し、該飽和炭化水素基に含まれる水素原子は、フッ素原子又はヒドロキシ基に置換されていてもよく、該飽和炭化水素基に含まれる－ＣＨ_２－は、－Ｏ－又は－ＣＯ－に置き換わっていてもよい。
ただし、Ｌ^ｂ２とＬ^ｂ３との炭素数合計は、２２以下である。
式（ｂ１－２）中、
Ｌ^ｂ４は、単結合又は炭素数１～２２の２価の飽和炭化水素基を表し、該飽和炭化水素基に含まれる水素原子は、フッ素原子に置換されていてもよい。
Ｌ^ｂ５は、単結合又は炭素数１～２２の２価の飽和炭化水素基を表し、該飽和炭化水素基に含まれる水素原子は、フッ素原子又はヒドロキシ基に置換されていてもよく、該飽和炭化水素基に含まれる－ＣＨ_２－は、－Ｏ－又は－ＣＯ－に置き換わっていてもよい。
ただし、Ｌ^ｂ４とＬ^ｂ５との炭素数合計は、２２以下である。
式（ｂ１－３）中、
Ｌ^ｂ６は、単結合又は炭素数１～２３の２価の飽和炭化水素基を表し、該飽和炭化水素基に含まれる水素原子は、フッ素原子又はヒドロキシ基に置換されていてもよい。
Ｌ^ｂ７は、単結合又は炭素数１～２３の２価の飽和炭化水素基を表し、該飽和炭化水素基に含まれる水素原子は、フッ素原子又はヒドロキシ基に置換されていてもよく、該飽和炭化水素基に含まれる－ＣＨ_２－は、－Ｏ－又は－ＣＯ－に置き換わっていてもよい。
ただし、Ｌ^ｂ６とＬ^ｂ７との炭素数合計は、２３以下である。］ Examples of the divalent saturated hydrocarbon group represented by L ^b1 in which -CH ₂ - is replaced by -O- or -CO- include groups represented by any of formulas (b1-1) to (b1-3). In the groups represented by formulas (b1-1) to (b1-3) and specific examples thereof represented by formulas (b1-4) to (b1-11), * and ** represent bonding sites, and * represents the bonding site to -Y.

[In formula (b1-1),
L ^b2 represents a single bond or a divalent saturated hydrocarbon group having 1 to 22 carbon atoms, and a hydrogen atom contained in the saturated hydrocarbon group may be substituted with a fluorine atom.
L ^b3 represents a single bond or a divalent saturated hydrocarbon group having 1 to 22 carbon atoms, a hydrogen atom contained in the saturated hydrocarbon group may be substituted with a fluorine atom or a hydroxy group, and -CH ₂ - contained in the saturated hydrocarbon group may be substituted with -O- or -CO-.
However, the total number of carbon atoms in L ^b2 and L ^b3 is 22 or less.
In formula (b1-2),
L ^b4 represents a single bond or a divalent saturated hydrocarbon group having 1 to 22 carbon atoms, and a hydrogen atom contained in the saturated hydrocarbon group may be substituted with a fluorine atom.
L ^b5 represents a single bond or a divalent saturated hydrocarbon group having 1 to 22 carbon atoms, a hydrogen atom contained in the saturated hydrocarbon group may be substituted with a fluorine atom or a hydroxy group, and -CH ₂ - contained in the saturated hydrocarbon group may be substituted with -O- or -CO-.
However, the total number of carbon atoms in L ^b4 and L ^b5 is 22 or less.
In formula (b1-3),
L ^b6 represents a single bond or a divalent saturated hydrocarbon group having 1 to 23 carbon atoms, and a hydrogen atom contained in the saturated hydrocarbon group may be substituted with a fluorine atom or a hydroxy group.
L ^b7 represents a single bond or a divalent saturated hydrocarbon group having 1 to 23 carbon atoms, a hydrogen atom contained in the saturated hydrocarbon group may be substituted with a fluorine atom or a hydroxy group, and -CH ₂ - contained in the saturated hydrocarbon group may be substituted with -O- or -CO-.
However, the total number of carbon atoms in L ^b6 and L ^b7 is 23 or less.

In the groups represented by formulae (b1-1) to (b1-3), when --CH ₂ -- contained in the saturated hydrocarbon group is replaced with --O-- or --CO--, the number of carbon atoms before replacement is regarded as the number of carbon atoms of the saturated hydrocarbon group.
Examples of the divalent saturated hydrocarbon group include the same divalent saturated hydrocarbon groups as those represented by L ^b1 .

L ^b2 is preferably a single bond.
L ^b3 is preferably a divalent saturated hydrocarbon group having 1 to 4 carbon atoms.
L ^b4 is preferably a divalent saturated hydrocarbon group having 1 to 8 carbon atoms, and a hydrogen atom contained in the divalent saturated hydrocarbon group may be substituted with a fluorine atom.
L ^b5 is preferably a single bond or a divalent saturated hydrocarbon group having 1 to 8 carbon atoms.
L ^b6 is preferably a single bond or a divalent saturated hydrocarbon group having 1 to 4 carbon atoms, and a hydrogen atom contained in the saturated hydrocarbon group may be substituted with a fluorine atom.
L ^b7 is preferably a single bond or a divalent saturated hydrocarbon group having 1 to 18 carbon atoms, in which a hydrogen atom contained in the saturated hydrocarbon group may be substituted with a fluorine atom or a hydroxy group, and -CH ₂ - contained in the divalent saturated hydrocarbon group may be substituted with -O- or -CO-.

［式（ｂ１－４）中、
Ｌ^ｂ８は、単結合又は炭素数１～２２の２価の飽和炭化水素基を表し、該飽和炭化水素基に含まれる水素原子は、フッ素原子又はヒドロキシ基に置換されていてもよい。
式（ｂ１－５）中、
Ｌ^ｂ９は、炭素数１～２０の２価の飽和炭化水素基を表し、該２価の飽和炭化水素基に含まれる－ＣＨ_２－は－Ｏ－又は－ＣＯ－に置き換わっていてもよい。
Ｌ^ｂ１０は、単結合又は炭素数１～１９の２価の飽和炭化水素基を表し、該２価の飽和炭化水素基に含まれる水素原子は、フッ素原子又はヒドロキシ基に置換されていてもよい。
ただし、Ｌ^ｂ９及びＬ^ｂ１０の合計炭素数は２０以下である。
式（ｂ１－６）中、
Ｌ^ｂ１１は、炭素数１～２１の２価の飽和炭化水素基を表す。
Ｌ^ｂ１２は、単結合又は炭素数１～２０の２価の飽和炭化水素基を表し、該２価の飽和炭化水素基に含まれる水素原子は、フッ素原子又はヒドロキシ基に置換されていてもよい。
ただし、Ｌ^ｂ１１及びＬ^ｂ１２の合計炭素数は２１以下である。
式（ｂ１－７）中、
Ｌ^ｂ１３は、炭素数１～１９の２価の飽和炭化水素基を表す。
Ｌ^ｂ１４は、単結合又は炭素数１～１８の２価の飽和炭化水素基を表し、該２価の飽和炭化水素基に含まれる－ＣＨ_２－は－Ｏ－又は－ＣＯ－に置き換わっていてもよい。
Ｌ^ｂ１５は、単結合又は炭素数１～１８の２価の飽和炭化水素基を表し、該２価の飽和炭化水素基に含まれる水素原子は、フッ素原子又はヒドロキシ基に置換されていてもよい。
ただし、Ｌ^ｂ１３～Ｌ^ｂ１５の合計炭素数は１９以下である。
式（ｂ１－８）中、
Ｌ^ｂ１６は、炭素数１～１８の２価の飽和炭化水素基を表し、該２価の飽和炭化水素基に含まれる－ＣＨ_２－は－Ｏ－又は－ＣＯ－に置き換わっていてもよい。
Ｌ^ｂ１７は、炭素数１～１８の２価の飽和炭化水素基を表す。
Ｌ^ｂ１８は、単結合又は炭素数１～１７の２価の飽和炭化水素基を表し、該２価の飽和炭化水素基に含まれる水素原子は、フッ素原子又はヒドロキシ基に置換されていてもよい。
ただし、Ｌ^ｂ１６～Ｌ^ｂ１８の合計炭素数は１９以下である。］
Ｌ^ｂ８は、好ましくは炭素数１～４の２価の飽和炭化水素基である。
Ｌ^ｂ９は、好ましくは炭素数１～８の２価の飽和炭化水素基である。
Ｌ^ｂ１０は、好ましくは単結合又は炭素数１～１９の２価の飽和炭化水素基であり、より好ましくは単結合又は炭素数１～８の２価の飽和炭化水素基である。
Ｌ^ｂ１１は、好ましくは炭素数１～８の２価の飽和炭化水素基である。
Ｌ^ｂ１２は、好ましくは単結合又は炭素数１～８の２価の飽和炭化水素基である。
Ｌ^ｂ１３は、好ましくは炭素数１～１２の２価の飽和炭化水素基である。
Ｌ^ｂ１４は、好ましくは単結合又は炭素数１～６の２価の飽和炭化水素基である。
Ｌ^ｂ１５は、好ましくは単結合又は炭素数１～１８の２価の飽和炭化水素基であり、より好ましくは単結合又は炭素数１～８の２価の飽和炭化水素基である。
Ｌ^ｂ１６は、好ましくは炭素数１～１２の２価の飽和炭化水素基である。
Ｌ^ｂ１７は、好ましくは炭素数１～６の２価の飽和炭化水素基である。
Ｌ^ｂ１８は、好ましくは単結合又は炭素数１～１７の２価の飽和炭化水素基であり、より好ましくは単結合又は炭素数１～４の２価の飽和炭化水素基である。 The divalent saturated hydrocarbon group represented by L ^b1 in which one --CH ₂ -- is replaced by --O-- or --CO-- is preferably a group represented by formula (b1-1) or formula (b1-3).
Examples of the group represented by formula (b1-1) include groups represented by formulas (b1-4) to (b1-8).

[In formula (b1-4),
L ^b8 represents a single bond or a divalent saturated hydrocarbon group having 1 to 22 carbon atoms, and a hydrogen atom contained in the saturated hydrocarbon group may be substituted with a fluorine atom or a hydroxy group.
In formula (b1-5),
L ^b9 represents a divalent saturated hydrocarbon group having 1 to 20 carbon atoms, and --CH ₂ -- contained in the divalent saturated hydrocarbon group may be replaced by --O-- or --CO--.
L ^b10 represents a single bond or a divalent saturated hydrocarbon group having 1 to 19 carbon atoms, and a hydrogen atom contained in the divalent saturated hydrocarbon group may be substituted with a fluorine atom or a hydroxyl group.
However, the total number of carbon atoms in L ^b9 and L ^b10 is 20 or less.
In formula (b1-6),
L ^b11 represents a divalent saturated hydrocarbon group having 1 to 21 carbon atoms.
L ^b12 represents a single bond or a divalent saturated hydrocarbon group having 1 to 20 carbon atoms, and a hydrogen atom contained in the divalent saturated hydrocarbon group may be substituted with a fluorine atom or a hydroxy group.
However, the total number of carbon atoms in L ^b11 and L ^b12 is 21 or less.
In formula (b1-7),
L ^b13 represents a divalent saturated hydrocarbon group having 1 to 19 carbon atoms.
L ^b14 represents a single bond or a divalent saturated hydrocarbon group having 1 to 18 carbon atoms, and --CH ₂ -- contained in the divalent saturated hydrocarbon group may be replaced by --O-- or --CO--.
L ^b15 represents a single bond or a divalent saturated hydrocarbon group having 1 to 18 carbon atoms, and a hydrogen atom contained in the divalent saturated hydrocarbon group may be substituted with a fluorine atom or a hydroxy group.
However, the total number of carbon atoms of L ^b13 to L ^b15 is 19 or less.
In formula (b1-8),
L ^b16 represents a divalent saturated hydrocarbon group having 1 to 18 carbon atoms, and --CH ₂ -- contained in the divalent saturated hydrocarbon group may be replaced by --O-- or --CO--.
L ^b17 represents a divalent saturated hydrocarbon group having 1 to 18 carbon atoms.
L ^b18 represents a single bond or a divalent saturated hydrocarbon group having 1 to 17 carbon atoms, and a hydrogen atom contained in the divalent saturated hydrocarbon group may be substituted with a fluorine atom or a hydroxy group.
However, the total number of carbon atoms of L ^b16 to L ^b18 is 19 or less.]
L ^b8 is preferably a divalent saturated hydrocarbon group having 1 to 4 carbon atoms.
L ^b9 is preferably a divalent saturated hydrocarbon group having 1 to 8 carbon atoms.
L ^b10 is preferably a single bond or a divalent saturated hydrocarbon group having 1 to 19 carbon atoms, and more preferably a single bond or a divalent saturated hydrocarbon group having 1 to 8 carbon atoms.
L ^b11 is preferably a divalent saturated hydrocarbon group having 1 to 8 carbon atoms.
L ^b12 is preferably a single bond or a divalent saturated hydrocarbon group having 1 to 8 carbon atoms.
L ^b13 is preferably a divalent saturated hydrocarbon group having 1 to 12 carbon atoms.
L ^b14 is preferably a single bond or a divalent saturated hydrocarbon group having 1 to 6 carbon atoms.
L ^b15 is preferably a single bond or a divalent saturated hydrocarbon group having 1 to 18 carbon atoms, and more preferably a single bond or a divalent saturated hydrocarbon group having 1 to 8 carbon atoms.
L ^b16 is preferably a divalent saturated hydrocarbon group having 1 to 12 carbon atoms.
L ^b17 is preferably a divalent saturated hydrocarbon group having 1 to 6 carbon atoms.
L ^b18 is preferably a single bond or a divalent saturated hydrocarbon group having 1 to 17 carbon atoms, and more preferably a single bond or a divalent saturated hydrocarbon group having 1 to 4 carbon atoms.

［式（ｂ１－９）中、
Ｌ^b19は、単結合又は炭素数１～２３の２価の飽和炭化水素基を表し、該飽和炭化水素基に含まれる水素原子は、フッ素原子に置換されていてもよい。
Ｌ^b20は、単結合又は炭素数１～２３の２価の飽和炭化水素基を表し、該飽和炭化水素基に含まれる水素原子は、フッ素原子、ヒドロキシ基又はアルキルカルボニルオキシ基に置換されていてもよい。該アルキルカルボニルオキシ基に含まれる－ＣＨ₂－は、－Ｏ－又は－ＣＯ－に置き換わっていてもよく、該アルキルカルボニルオキシ基に含まれる水素原子は、ヒドロキシ基に置換されていてもよい。
ただし、Ｌ^b19及びＬ^b20の合計炭素数は２３以下である。
式（ｂ１－１０）中、
Ｌ^b21は、単結合又は炭素数１～２１の２価の飽和炭化水素基を表し、該飽和炭化水素基に含まれる水素原子は、フッ素原子に置換されていてもよい。
Ｌ^b22は、単結合又は炭素数１～２１の２価の飽和炭化水素基を表す。
Ｌ^b23は、単結合又は炭素数１～２１の２価の飽和炭化水素基を表し、該飽和炭化水素基に含まれる水素原子は、フッ素原子、ヒドロキシ基又はアルキルカルボニルオキシ基に置換されていてもよい。該アルキルカルボニルオキシ基に含まれる－ＣＨ₂－は、－Ｏ－又は－ＣＯ－に置き換わっていてもよく、該アルキルカルボニルオキシ基に含まれる水素原子は、ヒドロキシ基に置換されていてもよい。
ただし、Ｌ^b21、Ｌ^b22及びＬ^b23の合計炭素数は２１以下である。］
式（ｂ１－１１）中、
Ｌ^b24は、単結合又は炭素数１～２０の２価の飽和炭化水素基を表し、該飽和炭化水素基に含まれる水素原子は、フッ素原子に置換されていてもよい。
Ｌ^b25は、炭素数１～２１の２価の飽和炭化水素基を表す。
Ｌ^b26は、単結合又は炭素数１～２０の２価の飽和炭化水素基を表し、該飽和炭化水素基に含まれる水素原子は、フッ素原子、ヒドロキシ基又はアルキルカルボニルオキシ基に置換されていてもよい。該アルキルカルボニルオキシ基に含まれる－ＣＨ₂－は、－Ｏ－又は－ＣＯ－に置き換わっていてもよく、該アルキルカルボニルオキシ基に含まれる水素原子は、ヒドロキシ基に置換されていてもよい。
ただし、Ｌ^b24、Ｌ^b25及びＬ^b26の合計炭素数は２１以下である。 Examples of the group represented by formula (b1-3) include groups represented by formulas (b1-9) to (b1-11).

[In formula (b1-9),
L ^b19 represents a single bond or a divalent saturated hydrocarbon group having 1 to 23 carbon atoms, and a hydrogen atom contained in the saturated hydrocarbon group may be substituted with a fluorine atom.
L ^b20 represents a single bond or a divalent saturated hydrocarbon group having 1 to 23 carbon atoms, a hydrogen atom contained in the saturated hydrocarbon group may be substituted with a fluorine atom, a hydroxyl group or an alkylcarbonyloxy group, -CH ₂ - contained in the alkylcarbonyloxy group may be replaced with -O- or -CO-, and a hydrogen atom contained in the alkylcarbonyloxy group may be substituted with a hydroxyl group.
However, the total number of carbon atoms of L ^b19 and L ^b20 is 23 or less.
In formula (b1-10),
L ^b21 represents a single bond or a divalent saturated hydrocarbon group having 1 to 21 carbon atoms, and a hydrogen atom contained in the saturated hydrocarbon group may be substituted with a fluorine atom.
L ^b22 represents a single bond or a divalent saturated hydrocarbon group having 1 to 21 carbon atoms.
L ^b23 represents a single bond or a divalent saturated hydrocarbon group having 1 to 21 carbon atoms, and a hydrogen atom contained in the saturated hydrocarbon group may be substituted with a fluorine atom, a hydroxyl group or an alkylcarbonyloxy group. -CH ₂ - contained in the alkylcarbonyloxy group may be replaced with -O- or -CO-, and a hydrogen atom contained in the alkylcarbonyloxy group may be substituted with a hydroxyl group.
However, the total number of carbon atoms of L ^b21 , L ^b22 and L ^b23 is 21 or less.]
In formula (b1-11),
L ^b24 represents a single bond or a divalent saturated hydrocarbon group having 1 to 20 carbon atoms, and a hydrogen atom contained in the saturated hydrocarbon group may be substituted with a fluorine atom.
L ^b25 represents a divalent saturated hydrocarbon group having 1 to 21 carbon atoms.
L ^b26 represents a single bond or a divalent saturated hydrocarbon group having 1 to 20 carbon atoms, and a hydrogen atom contained in the saturated hydrocarbon group may be substituted with a fluorine atom, a hydroxyl group or an alkylcarbonyloxy group. -CH ₂ - contained in the alkylcarbonyloxy group may be replaced with -O- or -CO-, and a hydrogen atom contained in the alkylcarbonyloxy group may be substituted with a hydroxyl group.
However, the total number of carbon atoms of L ^b24 , L ^b25 and L ^b26 is 21 or less.

In addition, in the groups represented by formulae (b1-9) to (b1-11), when a hydrogen atom contained in the saturated hydrocarbon group is substituted with an alkylcarbonyloxy group, the number of carbon atoms before substitution is regarded as the number of carbon atoms of the saturated hydrocarbon group.
Examples of the alkylcarbonyloxy group include an acetyloxy group, a propionyloxy group, a butyryloxy group, a cyclohexylcarbonyloxy group, and an adamantylcarbonyloxy group.

Examples of the group represented by formula (b1-4) include the following.

Examples of the group represented by formula (b1-5) include the following.

Examples of the group represented by formula (b1-6) include the following.

Examples of the group represented by formula (b1-7) include the following.

Examples of the group represented by formula (b1-8) include the following.

Examples of the group represented by formula (b1-2) include the following.

Examples of the group represented by formula (b1-9) include the following.

Examples of the group represented by formula (b1-10) include the following.

Examples of the group represented by formula (b1-11) include the following.

Ｙで表される脂環式炭化水素基としては、好ましくは式（Ｙ１）～式（Ｙ２０）、式（Ｙ２６）、式（Ｙ２７）、式（Ｙ３０）、式（Ｙ３１）、式（Ｙ３９）～式（Ｙ４１）のいずれかで表される基であり、より好ましくは式（Ｙ１１）、式（Ｙ１５）、式（Ｙ１６）、式（Ｙ２０）、式（Ｙ２６）、式（Ｙ２７）、式（Ｙ３０）、式（Ｙ３１）、式（Ｙ３９）又は式（Ｙ４０）で表される基であり、さらに好ましくは式（Ｙ１１）、式（Ｙ１５）、式（Ｙ２０）、式（Ｙ２６）、式（Ｙ２７）、式（Ｙ３０）、式（Ｙ３１）、式（Ｙ３９）又は式（Ｙ４０）で表される基である。
Ｙで表される脂環式炭化水素基が式（Ｙ２８）～式（Ｙ３５）、式（Ｙ３９）～式（Ｙ４０）等の酸素原子を含むスピロ環である場合には、２つの酸素原子間のアルカンジイル基は、１以上のフッ素原子を有することが好ましい。また、ケタール構造に含まれるアルカンジイル基のうち、酸素原子に隣接するメチレン基には、フッ素原子が置換されていないのが好ましい。 Examples of the alicyclic hydrocarbon group represented by Y include groups represented by formulae (Y1) to (Y11) and (Y36) to (Y38).
When a -CH ₂ - contained in the alicyclic hydrocarbon group represented by Y is replaced by -O-, -S(O) ₂ - or -CO-, the number may be 1 or may be 2 or more. Examples of such groups include groups represented by formulae (Y12) to (Y35) and formulae (Y39) to (Y41).

The alicyclic hydrocarbon group represented by Y is preferably a group represented by any one of the formulae (Y1) to (Y20), (Y26), (Y27), (Y30), (Y31), (Y39) to (Y41), more preferably a group represented by the formula (Y11), (Y15), (Y16), (Y20), (Y26), (Y27), (Y30), (Y31), (Y39) or (Y40), and even more preferably a group represented by the formula (Y11), (Y15), (Y20), (Y26), (Y27), (Y30), (Y31), (Y39) or (Y40).
When the alicyclic hydrocarbon group represented by Y is a spiro ring containing an oxygen atom, such as those of formulae (Y28) to (Y35) and (Y39) to (Y40), the alkanediyl group between the two oxygen atoms preferably has one or more fluorine atoms. Furthermore, among the alkanediyl groups contained in the ketal structure, it is preferable that the methylene group adjacent to the oxygen atom is not substituted with a fluorine atom.

Examples of the substituent on the methyl group represented by Y include a halogen atom, a hydroxy group, an alicyclic hydrocarbon group having 3 to 16 carbon atoms, an aromatic hydrocarbon group having 6 to 18 carbon atoms, a glycidyloxy group, a -(CH ₂ ) _ja -CO-O-R ^b1 group or a -(CH ₂ ) _ja -O-CO-R ^b1 group (wherein R ^b1 represents an alkyl group having 1 to 16 carbon atoms, an alicyclic hydrocarbon group having 3 to 16 carbon atoms, an aromatic hydrocarbon group having 6 to 18 carbon atoms, or a combination thereof; ja represents an integer of 0 to 4; -CH ₂ - contained in the alkyl group and the alicyclic hydrocarbon group may be replaced by -O-, -S(O) ₂ - or -CO-; and a hydrogen atom contained in the alkyl group, the alicyclic hydrocarbon group and the aromatic hydrocarbon group may be replaced by a hydroxy group or a fluorine atom).
Substituents of the alicyclic hydrocarbon group represented by Y include a halogen atom, a hydroxy group, an alkyl group having 1 to 12 carbon atoms which may be substituted with a hydroxy group, an alicyclic hydrocarbon group having 3 to 16 carbon atoms, an alkoxy group having 1 to 12 carbon atoms, an aromatic hydrocarbon group having 6 to 18 carbon atoms, an aralkyl group having 7 to 21 carbon atoms, an alkylcarbonyl group having 2 to 4 carbon atoms, a glycidyloxy group, a -(CH ₂ ) _ja -CO-O-R ^b1 group, or a -(CH ₂ ) _ja -O-CO-R ^b1 group (wherein R ^b1 represents an alkyl group having 1 to 16 carbon atoms, an alicyclic hydrocarbon group having 3 to 16 carbon atoms, an aromatic hydrocarbon group having 6 to 18 carbon atoms, or a combination thereof. ja represents an integer of 0 to 4. The -CH ₂ - contained in the alkyl group and the alicyclic hydrocarbon group is preferably -O-, -S(O) ₂ - or -CO-, and a hydrogen atom contained in the alkyl group, the alicyclic hydrocarbon group and the aromatic hydrocarbon group may be replaced by a hydroxy group or a fluorine atom.

Examples of the halogen atom include a fluorine atom, a chlorine atom, a bromine atom, and an iodine atom.
Examples of the alicyclic hydrocarbon group include a cyclopentyl group, a cyclohexyl group, a methylcyclohexyl group, a dimethylcyclohexyl group, a cycloheptyl group, a cyclooctyl group, a norbornyl group, an adamantyl group, etc. The alicyclic hydrocarbon group may have a chain hydrocarbon group, such as a methylcyclohexyl group, a dimethylcyclohexyl group, etc.
Examples of the aromatic hydrocarbon group include aryl groups such as a phenyl group, a naphthyl group, an anthryl group, a biphenyl group, and a phenanthryl group. The aromatic hydrocarbon group may have a chain hydrocarbon group or an alicyclic hydrocarbon group. Examples of the aromatic hydrocarbon group having a chain hydrocarbon group include a tolyl group, a xylyl group, a cumenyl group, a mesityl group, a p-methylphenyl group, a p-ethylphenyl group, a p-tert-butylphenyl group, a 2,6-diethylphenyl group, and a 2-methyl-6-ethylphenyl group. Examples of the aromatic hydrocarbon group having an alicyclic hydrocarbon group include a p-adamantylphenyl group and a p-cyclohexylphenyl group.
Examples of the alkyl group include a methyl group, an ethyl group, a propyl group, an isopropyl group, a butyl group, a sec-butyl group, a tert-butyl group, a pentyl group, a hexyl group, a heptyl group, a 2-ethylhexyl group, an octyl group, a nonyl group, a decyl group, an undecyl group, and a dodecyl group.
Examples of the alkyl group substituted with a hydroxy group include hydroxyalkyl groups such as a hydroxymethyl group and a hydroxyethyl group.
Examples of the alkoxy group include a methoxy group, an ethoxy group, a propoxy group, a butoxy group, a pentyloxy group, a hexyloxy group, a heptyloxy group, an octyloxy group, a decyloxy group, and a dodecyloxy group.
Examples of the aralkyl group include a benzyl group, a phenethyl group, a phenylpropyl group, a naphthylmethyl group, and a naphthylethyl group.
Examples of the alkylcarbonyl group include an acetyl group, a propionyl group, and a butyryl group.

Examples of Y include the following.

Y is preferably an alicyclic hydrocarbon group having 3 to 18 carbon atoms which may have a substituent, more preferably an adamantyl group which may have a substituent, in which -CH ₂ - constituting the alicyclic hydrocarbon group or the adamantyl group may be replaced by -CO-, -S(O) ₂ - or -CO-, and further preferably an adamantyl group, a hydroxyadamantyl group, an oxoadamantyl group or a group represented by the following:

As the anion in the salt represented by formula (B1), anions represented by formulas (B1-A-1) to (B1-A-55) are preferred [hereinafter, they may be referred to as "anion (B1-A-1)" depending on the formula number. ], and anions represented by any of formulas (B1-A-1) to (B1-A-4), (B1-A-9), (B1-A-10), (B1-A-24) to (B1-A-33), (B1-A-36) to (B1-A-40), and (B1-A-47) to (B1-A-55) are more preferred.

ここでＲ^ｉ２～Ｒ^ｉ７は、互いに独立に、例えば、炭素数１～４のアルキル基、好ましくはメチル基又はエチル基である。Ｒ^ｉ８は、例えば、炭素数１～１２の鎖式炭化水素基、好ましくは炭素数１～４のアルキル基、炭素数５～１２の脂環式炭化水素基又はこれらを組合せることにより形成される基、より好ましくはメチル基、エチル基、シクロヘキシル基又はアダマンチル基である。Ｌ^Ａ４１は、単結合又は炭素数１～４のアルカンジイル基である。Ｑ^ｂ１及びＱ^ｂ２は、上記と同じ意味を表す。
式（Ｂ１）で表される塩におけるアニオンとしては、具体的には、特開２０１０－２０４６４６号公報に記載されたアニオンが挙げられる。

Here, R ⁱ² to R ⁱ⁷ are each independently, for example, an alkyl group having 1 to 4 carbon atoms, preferably a methyl group or an ethyl group. ^{R i8} is, for example, a chain hydrocarbon group having 1 to 12 carbon atoms, preferably an alkyl group having 1 to 4 carbon atoms, an alicyclic hydrocarbon group having 5 to 12 carbon atoms, or a group formed by combining these, more preferably a methyl group, an ethyl group, a cyclohexyl group, or an adamantyl group. L ^A41 is a single bond or an alkanediyl group having 1 to 4 carbon atoms. Q ^b1 and Q ^b2 have the same meaning as above.
Specific examples of the anion in the salt represented by formula (B1) include the anions described in JP-A-2010-204646.

Preferable anions in the salt represented by formula (B1) include the anions represented by formulas (B1a-1) to (B1a-34).

Among these, anions represented by any of formulas (B1a-1) to (B1a-3), (B1a-7) to (B1a-16), (B1a-18), (B1a-19), and (B1a-22) to (B1a-34) are preferred.

Examples of the organic cation of Z ⁺ include an organic onium cation, an organic sulfonium cation, an organic iodonium cation, an organic ammonium cation, a benzothiazolium cation, and an organic phosphonium cation. Among these, an organic sulfonium cation and an organic iodonium cation are preferred, and an arylsulfonium cation is more preferred. Specific examples include cations represented by any one of formulas (b2-1) to (b2-4) (hereinafter, these may be referred to as "cation (b2-1)" depending on the formula number).

式（ｂ２－１）～式（ｂ２－４）において、
Ｒ^b4～Ｒ^b6は、それぞれ独立に、炭素数１～３０の鎖式炭化水素基、炭素数３～３６の脂環式炭化水素基又は炭素数６～３６の芳香族炭化水素基を表し、該鎖式炭化水素基に含まれる水素原子は、ヒドロキシ基、炭素数１～１２のアルコキシ基、炭素数３～１２の脂環式炭化水素基又は炭素数６～１８の芳香族炭化水素基で置換されていてもよく、該脂環式炭化水素基に含まれる水素原子は、ハロゲン原子、炭素数１～１８の脂肪族炭化水素基、炭素数２～４のアルキルカルボニル基又はグリシジルオキシ基で置換されていてもよく、該芳香族炭化水素基に含まれる水素原子は、ハロゲン原子、ヒドロキシ基又は炭素数１～１２のアルコキシ基で置換されていてもよい。
Ｒ^b4とＲ^b5とは、互いに結合してそれらが結合する硫黄原子と一緒になって環を形成してもよく、該環に含まれる－ＣＨ₂－は、－Ｏ－、－Ｓ－又は－ＣＯ－に置き換わってもよい。
Ｒ^b7及びＲ^b8は、それぞれ独立に、ヒドロキシ基、炭素数１～１２の脂肪族炭化水素基又は炭素数１～１２のアルコキシ基を表す。
ｍ２及びｎ２は、それぞれ独立に０～５のいずれかの整数を表す。
ｍ２が２以上のとき、複数のＲ^b7は同一でも異なってもよく、ｎ２が２以上のとき、複数のＲ^b8は同一でも異なってもよい。
Ｒ^b9及びＲ^b10は、それぞれ独立に、炭素数１～３６の鎖式炭化水素基又は炭素数３～３６の脂環式炭化水素基を表す。
Ｒ^b9とＲ^b10とは、互いに結合してそれらが結合する硫黄原子と一緒になって環を形成してもよく、該環に含まれる－ＣＨ₂－は、－Ｏ－、－Ｓ－又は－ＣＯ－に置き換わってもよい。
Ｒ^b11は、水素原子、炭素数１～３６の鎖式炭化水素基、炭素数３～３６の脂環式炭化水素基又は炭素数６～１８の芳香族炭化水素基を表す。
Ｒ^b12は、炭素数１～１２の鎖式炭化水素基、炭素数３～１８の脂環式炭化水素基又は炭素数６～１８の芳香族炭化水素基を表し、該鎖式炭化水素に含まれる水素原子は、炭素数６～１８の芳香族炭化水素基で置換されていてもよく、該芳香族炭化水素基に含まれる水素原子は、炭素数１～１２のアルコキシ基又は炭素数１～１２のアルキルカルボニルオキシ基で置換されていてもよい。
Ｒ^b11とＲ^b12とは、互いに結合してそれらが結合する－ＣＨ－ＣＯ－を含めて環を形成していてもよく、該環に含まれる－ＣＨ₂－は、－Ｏ－、－Ｓ－又は－ＣＯ－に置き換わってもよい。
Ｒ^b13～Ｒ^b18は、それぞれ独立に、ヒドロキシ基、炭素数１～１２の脂肪族炭化水素基又は炭素数１～１２のアルコキシ基を表す。
Ｌ^b31は、硫黄原子又は酸素原子を表す。
ｏ２、ｐ２、ｓ２、及びｔ２は、それぞれ独立に、０～５のいずれかの整数を表す。
ｑ２及びｒ２は、それぞれ独立に、０～４のいずれかの整数を表す。
ｕ２は０又は１を表す。
ｏ２が２以上のとき、複数のＲ^b13は同一又は相異なり、ｐ２が２以上のとき、複数のＲ^b14は同一又は相異なり、ｑ２が２以上のとき、複数のＲ^b15は同一又は相異なり、ｒ２が２以上のとき、複数のＲ^b16は同一又は相異なり、ｓ２が２以上のとき、複数のＲ^b17は同一又は相異なり、ｔ２が２以上のとき、複数のＲ^b18は同一又は相異なる。
脂肪族炭化水素基とは、鎖式炭化水素基及び脂環式炭化水素基を表す。
鎖式炭化水素基としては、メチル基、エチル基、プロピル基、イソプロピル基、ブチル基、ｓｅｃ－ブチル基、ｔｅｒｔ－ブチル基、ペンチル基、ヘキシル基、オクチル基及び２－エチルヘキシル基のアルキル基が挙げられる。
特に、Ｒ^b9～Ｒ^b12の鎖式炭化水素基は、好ましくは炭素数１～１２である。
脂環式炭化水素基としては、単環式又は多環式のいずれでもよく、単環式の脂環式炭化水素基としては、シクロプロピル基、シクロブチル基、シクロペンチル基、シクロへキシル基、シクロヘプチル基、シクロオクチル基、シクロデシル基等のシクロアルキル基が挙げられる。多環式の脂環式炭化水素基としては、デカヒドロナフチル基、アダマンチル基、ノルボルニル基及び下記の基等が挙げられる。

特に、Ｒ^b9～Ｒ^b12の脂環式炭化水素基は、好ましくは炭素数３～１８、より好ましくは炭素数４～１２である。
水素原子が脂肪族炭化水素基で置換された脂環式炭化水素基としては、メチルシクロヘキシル基、ジメチルシクロへキシル基、２－メチルアダマンタン－２－イル基、２－エチルアダマンタン－２－イル基、２－イソプロピルアダマンタン－２－イル基、メチルノルボルニル基、イソボルニル基等が挙げられる。水素原子が脂肪族炭化水素基で置換された脂環式炭化水素基においては、脂環式炭化水素基と脂肪族炭化水素基との合計炭素数が好ましくは２０以下である。
芳香族炭化水素基としては、フェニル基、ビフェニル基、ナフチル基、フェナントリル基等のアリール基が挙げられる。芳香族炭化水素基は、鎖式炭化水素基又は脂環式炭化水素基を有していてもよく、鎖式炭化水素基を有する芳香族炭化水素基としては、トリル基、キシリル基、クメニル基、メシチル基、ｐ－エチルフェニル基、ｐ－ｔｅｒｔ－ブチルフェニル基、２，６－ジエチルフェニル基、２－メチル－６－エチルフェニル基等が挙げられ、脂環式炭化水素基を有する芳香族炭化水素基としては、ｐ－シクロへキシルフェニル基、ｐ－アダマンチルフェニル基等等が挙げられる。なお、芳香族炭化水素基が、鎖式炭化水素基又は脂環式炭化水素基を有する場合は、炭素数１～１８の鎖式炭化水素基及び炭素数３～１８の脂環式炭化水素基が好ましい。
水素原子がアルコキシ基で置換された芳香族炭化水素基としては、ｐ－メトキシフェニル基等が挙げられる。
水素原子が芳香族炭化水素基で置換された鎖式炭化水素基としては、ベンジル基、フェネチル基、フェニルプロピル基、トリチル基、ナフチルメチル基、ナフチルエチル基等のアラルキル基が挙げられる。
アルコキシ基としては、メトキシ基、エトキシ基、プロポキシ基、ブトキシ基、ペンチルオキシ基、ヘキシルオキシ基、ヘプチルオキシ基、オクチルオキシ基、デシルオキシ基及びドデシルオキシ基等が挙げられる。
アルキルカルボニル基としては、アセチル基、プロピオニル基及びブチリル基等が挙げられる。
ハロゲン原子としては、フッ素原子、塩素原子、臭素原子及びヨウ素原子等が挙げられる。
アルキルカルボニルオキシ基としては、メチルカルボニルオキシ基、エチルカルボニルオキシ基、プロピルカルボニルオキシ基、イソプロピルカルボニルオキシ基、ブチルカルボニルオキシ基、ｓｅｃ－ブチルカルボニルオキシ基、ｔｅｒｔ－ブチルカルボニルオキシ基、ペンチルカルボニルオキシ基、ヘキシルカルボニルオキシ基、オクチルカルボニルオキシ基及び２－エチルヘキシルカルボニルオキシ基等が挙げられる。
Ｒ^b4とＲ^b5とが互いに結合してそれらが結合する硫黄原子と一緒になって形成する環は、単環式、多環式、芳香族性、非芳香族性、飽和及び不飽和のいずれの環であってもよい。この環は、炭素数３～１８の環が挙げられ、好ましくは炭素数４～１８の環である。また、硫黄原子を含む環は、３員環～１２員環が挙げられ、好ましくは３員環～７員環であり、例えば下記の環が挙げられる。＊は結合部位を表す。

Ｒ^b9とＲ^b10とが一緒になって形成する環は、単環式、多環式、芳香族性、非芳香族性、飽和及び不飽和のいずれの環であってもよい。この環は、３員環～１２員環が挙げられ、好ましくは３員環～７員環である。例えば、チオラン－１－イウム環（テトラヒドロチオフェニウム環）、チアン－１－イウム環、１，４－オキサチアン－４－イウム環等が挙げられる。
Ｒ^b11とＲ^b12とが一緒になって形成する環は、単環式、多環式、芳香族性、非芳香族性、飽和及び不飽和のいずれの環であってもよい。この環は、３員環～１２員環が挙げられ、好ましくは３員環～７員環である。オキソシクロヘプタン環、オキソシクロヘキサン環、オキソノルボルナン環、オキソアダマンタン環等が挙げられる。

In formulas (b2-1) to (b2-4),
R ^b4 to R ^b6 each independently represent a chain hydrocarbon group having 1 to 30 carbon atoms, an alicyclic hydrocarbon group having 3 to 36 carbon atoms, or an aromatic hydrocarbon group having 6 to 36 carbon atoms, a hydrogen atom contained in the chain hydrocarbon group may be substituted with a hydroxy group, an alkoxy group having 1 to 12 carbon atoms, an alicyclic hydrocarbon group having 3 to 12 carbon atoms, or an aromatic hydrocarbon group having 6 to 18 carbon atoms, a hydrogen atom contained in the alicyclic hydrocarbon group may be substituted with a halogen atom, an aliphatic hydrocarbon group having 1 to 18 carbon atoms, an alkylcarbonyl group having 2 to 4 carbon atoms, or a glycidyloxy group, and a hydrogen atom contained in the aromatic hydrocarbon group may be substituted with a halogen atom, a hydroxy group, or an alkoxy group having 1 to 12 carbon atoms.
R ^b4 and R ^b5 may be bonded to each other to form a ring together with the sulfur atom to which they are bonded, and --CH ₂ -- contained in the ring may be replaced by --O--, --S-- or --CO--.
R ^b7 and R ^b8 each independently represent a hydroxy group, an aliphatic hydrocarbon group having 1 to 12 carbon atoms, or an alkoxy group having 1 to 12 carbon atoms.
m2 and n2 each independently represent an integer of 0 to 5.
When m2 is 2 or more, multiple R ^b7s may be the same or different, and when n2 is 2 or more, multiple R ^b8s may be the same or different.
R ^b9 and R ^b10 each independently represent a chain hydrocarbon group having 1 to 36 carbon atoms or an alicyclic hydrocarbon group having 3 to 36 carbon atoms.
R ^b9 and R ^b10 may be bonded to each other to form a ring together with the sulfur atom to which they are bonded, and --CH ₂ -- contained in the ring may be replaced by --O--, --S-- or --CO--.
R ^b11 represents a hydrogen atom, a chain hydrocarbon group having 1 to 36 carbon atoms, an alicyclic hydrocarbon group having 3 to 36 carbon atoms, or an aromatic hydrocarbon group having 6 to 18 carbon atoms.
R ^b12 represents an open chain hydrocarbon group having 1 to 12 carbon atoms, an alicyclic hydrocarbon group having 3 to 18 carbon atoms, or an aromatic hydrocarbon group having 6 to 18 carbon atoms, a hydrogen atom contained in the open chain hydrocarbon may be substituted with an aromatic hydrocarbon group having 6 to 18 carbon atoms, and a hydrogen atom contained in the aromatic hydrocarbon group may be substituted with an alkoxy group having 1 to 12 carbon atoms or an alkylcarbonyloxy group having 1 to 12 carbon atoms.
R ^b11 and R ^b12 may be bonded to each other to form a ring including the --CH--CO-- to which they are bonded, and --CH ₂ -- contained in the ring may be replaced by --O--, --S-- or --CO--.
R ^b13 to R ^b18 each independently represent a hydroxy group, an aliphatic hydrocarbon group having 1 to 12 carbon atoms, or an alkoxy group having 1 to 12 carbon atoms.
L ^b31 represents a sulfur atom or an oxygen atom.
o2, p2, s2, and t2 each independently represent an integer of 0 to 5.
q2 and r2 each independently represent an integer of 0 to 4.
u2 represents 0 or 1.
When o2 is 2 or more, multiple R ^b13 are the same or different; when p2 is 2 or more, multiple R ^b14 are the same or different; when q2 is 2 or more, multiple R ^b15 are the same or different; when r2 is 2 or more, multiple R ^b16 are the same or different; when s2 is 2 or more, multiple R ^b17 are the same or different; and when t2 is 2 or more, multiple R ^b18 are the same or different.
The aliphatic hydrocarbon group refers to a chain hydrocarbon group and an alicyclic hydrocarbon group.
Examples of the chain hydrocarbon group include alkyl groups such as methyl, ethyl, propyl, isopropyl, butyl, sec-butyl, tert-butyl, pentyl, hexyl, octyl and 2-ethylhexyl groups.
In particular, the chain hydrocarbon groups of R ^b9 to R ^b12 preferably have 1 to 12 carbon atoms.
The alicyclic hydrocarbon group may be either monocyclic or polycyclic, and examples of the monocyclic alicyclic hydrocarbon group include cycloalkyl groups such as cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl, cycloheptyl, cyclooctyl, and cyclodecyl. Examples of the polycyclic alicyclic hydrocarbon group include decahydronaphthyl, adamantyl, and norbornyl groups, as well as the following groups:

In particular, the alicyclic hydrocarbon groups of R ^b9 to R ^b12 preferably have 3 to 18 carbon atoms, and more preferably have 4 to 12 carbon atoms.
Examples of the alicyclic hydrocarbon group in which a hydrogen atom is substituted with an aliphatic hydrocarbon group include a methylcyclohexyl group, a dimethylcyclohexyl group, a 2-methyladamantan-2-yl group, a 2-ethyladamantan-2-yl group, a 2-isopropyladamantan-2-yl group, a methylnorbornyl group, an isobornyl group, etc. In the alicyclic hydrocarbon group in which a hydrogen atom is substituted with an aliphatic hydrocarbon group, the total number of carbon atoms in the alicyclic hydrocarbon group and the aliphatic hydrocarbon group is preferably 20 or less.
Examples of the aromatic hydrocarbon group include aryl groups such as a phenyl group, a biphenyl group, a naphthyl group, and a phenanthryl group. The aromatic hydrocarbon group may have a chain hydrocarbon group or an alicyclic hydrocarbon group. Examples of the aromatic hydrocarbon group having a chain hydrocarbon group include a tolyl group, a xylyl group, a cumenyl group, a mesityl group, a p-ethylphenyl group, a p-tert-butylphenyl group, a 2,6-diethylphenyl group, and a 2-methyl-6-ethylphenyl group. Examples of the aromatic hydrocarbon group having an alicyclic hydrocarbon group include a p-cyclohexylphenyl group and a p-adamantylphenyl group. When the aromatic hydrocarbon group has a chain hydrocarbon group or an alicyclic hydrocarbon group, a chain hydrocarbon group having 1 to 18 carbon atoms and an alicyclic hydrocarbon group having 3 to 18 carbon atoms are preferred.
An example of the aromatic hydrocarbon group in which a hydrogen atom is substituted with an alkoxy group is a p-methoxyphenyl group.
Examples of the chain hydrocarbon group in which a hydrogen atom has been substituted with an aromatic hydrocarbon group include aralkyl groups such as a benzyl group, a phenethyl group, a phenylpropyl group, a trityl group, a naphthylmethyl group, and a naphthylethyl group.
Examples of the alkoxy group include a methoxy group, an ethoxy group, a propoxy group, a butoxy group, a pentyloxy group, a hexyloxy group, a heptyloxy group, an octyloxy group, a decyloxy group, and a dodecyloxy group.
Examples of the alkylcarbonyl group include an acetyl group, a propionyl group, and a butyryl group.
Examples of the halogen atom include a fluorine atom, a chlorine atom, a bromine atom, and an iodine atom.
Examples of the alkylcarbonyloxy group include a methylcarbonyloxy group, an ethylcarbonyloxy group, a propylcarbonyloxy group, an isopropylcarbonyloxy group, a butylcarbonyloxy group, a sec-butylcarbonyloxy group, a tert-butylcarbonyloxy group, a pentylcarbonyloxy group, a hexylcarbonyloxy group, an octylcarbonyloxy group, and a 2-ethylhexylcarbonyloxy group.
The ring formed by R ^b4 and R ^b5 bonding to each other together with the sulfur atom to which they are bonded may be any of monocyclic, polycyclic, aromatic, non-aromatic, saturated and unsaturated rings. Examples of this ring include rings having 3 to 18 carbon atoms, and preferably rings having 4 to 18 carbon atoms. Examples of the ring containing a sulfur atom include 3- to 12-membered rings, and preferably 3- to 7-membered rings, and examples of such rings include the following rings. * represents a bonding site.

The ring formed by R ^b9 and R ^b10 together may be any of monocyclic, polycyclic, aromatic, non-aromatic, saturated and unsaturated rings. This ring may be a 3- to 12-membered ring, preferably a 3- to 7-membered ring. Examples of the ring include a thiolane-1-ium ring (tetrahydrothiophenium ring), a thian-1-ium ring, and a 1,4-oxathiane-4-ium ring.
The ring formed by R ^b11 and R ^b12 together may be any of monocyclic, polycyclic, aromatic, non-aromatic, saturated and unsaturated rings. This ring may be a 3- to 12-membered ring, preferably a 3- to 7-membered ring. Examples of the ring include an oxocycloheptane ring, an oxocyclohexane ring, an oxonorbornane ring, and an oxoadamantane ring.

Among the cations (b2-1) to (b2-4), the cation (b2-1) is preferred.
Examples of the cation (b2-1) include the following cations.

Examples of the cation (b2-2) include the following cations.

Examples of the cation (b2-3) include the following cations.

Examples of the cation (b2-4) include the following cations.

The acid generator (B) is a combination of the above-mentioned anion and the above-mentioned organic cation, which can be combined in any desired manner. The acid generator (B) is preferably a combination of an anion represented by any of formulas (B1a-1) to (B1a-3), (B1a-7) to (B1a-16), (B1a-18), (B1a-19), and (B1a-22) to (B1a-34) and a cation (b2-1) or a cation (b2-3).

The acid generator (B) is preferably any of the compounds represented by formulas (B1-1) to (B1-48). Among these, those containing an arylsulfonium cation are preferred, and those represented by formulas (B1-1) to (B1-3), (B1-5) to (B1-7), (B1-11) to (B1-14), (B1-20) to (B1-26), (B1-29), and (B1-31) to (B1-48) are particularly preferred.

In the resist composition of the present invention, the content of the acid generator is preferably 1 part by mass or more and 45 parts by mass or less, more preferably 3 parts by mass or more and 40 parts by mass or less, per 100 parts by mass of resin (A).

<Solvent (E)>
The content of the solvent (E) in the resist composition is usually from 90% by mass to 99.9% by mass, preferably from 92% by mass to 99% by mass, and more preferably from 94% by mass to 99% by mass. The content of the solvent (E) can be measured by a known analytical method such as liquid chromatography or gas chromatography.
Examples of the solvent (E) include glycol ether esters such as ethyl cellosolve acetate, methyl cellosolve acetate, and propylene glycol monomethyl ether acetate; glycol ethers such as propylene glycol monomethyl ether; esters such as ethyl lactate, butyl acetate, amyl acetate, and ethyl pyruvate; ketones such as acetone, methyl isobutyl ketone, 2-heptanone, and cyclohexanone; cyclic esters such as γ-butyrolactone; etc. One type of solvent (E) may be used alone, or two or more types may be used.

<Quencher (C)>
Examples of the quencher (C) include a basic nitrogen-containing organic compound and a salt that generates an acid having a weaker acidity than the acid generated from the acid generator (B). The content of the quencher (C) is preferably about 0.01 to 15 mass %, and more preferably about 0.01 to 10 mass %, based on the solid content of the resist composition.
The basic nitrogen-containing organic compound includes amines and ammonium salts. The amines include aliphatic amines and aromatic amines. The aliphatic amines include primary amines, secondary amines, and tertiary amines.
Examples of amines include 1-naphthylamine, 2-naphthylamine, aniline, diisopropylaniline, 2-, 3- or 4-methylaniline, 4-nitroaniline, N-methylaniline, N,N-dimethylaniline, diphenylamine, hexylamine, heptylamine, octylamine, nonylamine, decylamine, dibutylamine, dipentylamine, dihexylamine, diheptylamine, dioctylamine, dinonylamine, didecylamine, triethylamine, trimethylamine, tripropylamine, tributaryamine, ethylamine, tripentylamine, trihexylamine, triheptylamine, trioctylamine, trinonylamine, tridecylamine, methyldibutylamine, methyldipentylamine, methyldihexylamine, methyldicyclohexylamine, methyldiheptylamine, methyldioctylamine, methyldinonylamine, methyldidecylamine, ethyldibutylamine, ethyldipentylamine, ethyldihexylamine, ethyldiheptylamine, ethyldioctylamine, ethyldinonylamine, ethyldi Decylamine, dicyclohexylmethylamine, tris[2-(2-methoxyethoxy)ethyl]amine, triisopropanolamine, ethylenediamine, tetramethylenediamine, hexamethylenediamine, 4,4'-diamino-1,2-diphenylethane, 4,4'-diamino-3,3'-dimethyldiphenylmethane, 4,4'-diamino-3,3'-diethyldiphenylmethane, 2,2'-methylenebisaniline, imidazole, 4-methylimidazole, pyridine, 4-methylpyridine, 1,2-di(2-pyridinyl)amine ... Examples of the di(4-pyridyl)ethane include 1,2-di(4-pyridyl)ethane, 1,2-di(2-pyridyl)ethene, 1,2-di(4-pyridyl)ethene, 1,3-di(4-pyridyl)propane, 1,2-di(4-pyridyloxy)ethane, di(2-pyridyl)ketone, 4,4'-dipyridyl sulfide, 4,4'-dipyridyl disulfide, 2,2'-dipyridylamine, 2,2'-dipicolylamine, and bipyridine. Preferred is diisopropylaniline, and more preferred is 2,6-diisopropylaniline.
Examples of the ammonium salt include tetramethylammonium hydroxide, tetraisopropylammonium hydroxide, tetrabutylammonium hydroxide, tetrahexylammonium hydroxide, tetraoctylammonium hydroxide, phenyltrimethylammonium hydroxide, 3-(trifluoromethyl)phenyltrimethylammonium hydroxide, tetra-n-butylammonium salicylate, and choline.

The acidity of a salt that generates an acid weaker than the acid generated from the acid generator (B) is indicated by the acid dissociation constant (pKa). A salt that generates an acid weaker than the acid generated from the acid generator (B) is a salt whose acid dissociation constant of the acid generated from the salt is usually -3<pKa, preferably -1<pKa<7, and more preferably 0<pKa<5.
Examples of the salt that generates an acid having a weaker acidity than the acid generated from the acid generator (B) include the salt represented by the following formula, the salt represented by formula (D) described in JP-A-2015-147926 (hereinafter sometimes referred to as "weak acid inner salt (D)"), and the salts described in JP-A-2012-229206, JP-A-2012-6908, JP-A-2012-72109, JP-A-2011-39502, and JP-A-2011-191745. A salt that generates a carboxylic acid having a weaker acidity than the acid generated from the acid generator (B) (salt having a carboxylate anion) is preferred, and a weak acid inner salt (D) is more preferred.

Examples of the weak acid inner salt (D) include the following salts.

<Other Ingredients>
The resist composition of the present invention may contain components other than the above-mentioned components (hereinafter, sometimes referred to as "other components (F)") as necessary. There are no particular limitations on the other components (F), and additives known in the resist field, such as sensitizers, dissolution inhibitors, surfactants, stabilizers, dyes, etc., can be used.

Preparation of Resist Composition
The resist composition of the present invention can be prepared by mixing the resin (A) of the present invention, the acid generator (B), and a salt that generates an acid weaker in acidity than the acid generated from the acid generator, as well as the resin (AX), the resin (X), the quencher (C), the solvent (E), and other components (F) as necessary. The order of mixing is arbitrary and is not particularly limited. The temperature during mixing can be selected from 10 to 40° C., depending on the type of resin, the solubility of the resin in the solvent (E), and the like. The mixing time can be selected from 0.5 to 24 hours, depending on the mixing temperature. The mixing means is not particularly limited, and stirring and mixing can be used.
After mixing the components, it is preferable to filter the mixture using a filter having a pore size of about 0.003 to 0.2 μm.

<Method for Producing Resist Pattern>
The method for producing a resist pattern of the present invention comprises the steps of:
(1) applying the resist composition of the present invention onto a substrate;
(2) A step of drying the applied composition to form a composition layer;
(3) exposing the composition layer to light;
(4) a step of heating the composition layer after exposure, and (5) a step of developing the composition layer after heating.
The resist composition can be applied onto a substrate using a commonly used device such as a spin coater. Examples of the substrate include inorganic substrates such as silicon wafers. Before applying the resist composition, the substrate may be cleaned, and an anti-reflective film or the like may be formed on the substrate.
The composition after coating is dried to remove the solvent and form a composition layer. Drying is carried out, for example, by evaporating the solvent using a heating device such as a hot plate (so-called pre-baking), or by using a vacuum device. The heating temperature is preferably 50 to 200°C, and the heating time is preferably 10 to 180 seconds. The pressure during drying under reduced pressure is preferably about 1 to 1.0 x ¹⁰⁵ Pa.
The obtained composition layer is usually exposed using an exposure machine. The exposure machine may be an immersion exposure machine. As the exposure light source, various types can be used, such as those that emit ultraviolet laser light such as KrF excimer laser (wavelength 248 nm), ArF excimer laser (wavelength 193 nm), and _F2 excimer laser (wavelength 157 nm), those that convert the wavelength of laser light from a solid laser light source (YAG or semiconductor laser, etc.) to emit harmonic laser light in the far ultraviolet or vacuum ultraviolet range, and those that irradiate electron beams or extreme ultraviolet light (EUV). In this specification, irradiation with these radiations may be collectively referred to as "exposure". During exposure, exposure is usually performed through a mask corresponding to the desired pattern. When the exposure light source is an electron beam, exposure may be performed by direct drawing without using a mask.
The composition layer after exposure is subjected to a heat treatment (so-called post-exposure bake) in order to promote the deprotection reaction of the acid labile groups. The heating temperature is usually about 50 to 200°C, preferably about 70 to 150°C.
The heated composition layer is usually developed using a developing device and a developer. Examples of the developing method include a dip method, a paddle method, a spray method, and a dynamic dispense method. The developing temperature is preferably, for example, 5 to 60° C., and the developing time is preferably, for example, 5 to 300 seconds. By selecting the type of developer as follows, a positive resist pattern or a negative resist pattern can be produced.
When a positive resist pattern is produced from the resist composition of the present invention, an alkaline developer is used as the developer. The alkaline developer may be any of various alkaline aqueous solutions used in this field. Examples include aqueous solutions of tetramethylammonium hydroxide and (2-hydroxyethyl)trimethylammonium hydroxide (commonly known as choline). The alkaline developer may contain a surfactant.
After development, the resist pattern is preferably washed with ultrapure water, and then water remaining on the substrate and the pattern is removed.
When producing a negative resist pattern from the resist composition of the present invention, a developer containing an organic solvent (hereinafter sometimes referred to as an "organic developer") is used as the developer.
Examples of the organic solvent contained in the organic developer include ketone solvents such as 2-hexanone and 2-heptanone; glycol ether ester solvents such as propylene glycol monomethyl ether acetate; ester solvents such as butyl acetate; glycol ether solvents such as propylene glycol monomethyl ether; amide solvents such as N,N-dimethylacetamide; and aromatic hydrocarbon solvents such as anisole.
The content of the organic solvent in the organic developer is preferably from 90% by mass to 100% by mass, more preferably from 95% by mass to 100% by mass, and further preferably consists essentially of the organic solvent.
Among them, the organic developer is preferably a developer containing butyl acetate and/or 2-heptanone. The total content of butyl acetate and 2-heptanone in the organic developer is preferably 50% by mass or more and 100% by mass or less, more preferably 90% by mass or more and 100% by mass or less, and even more preferably substantially only butyl acetate and/or 2-heptanone.
The organic developer may contain a surfactant and may contain a small amount of water.
During development, the development may be stopped by replacing the organic developer with a different type of solvent.
The resist pattern after development is preferably washed with a rinse solution. There are no particular limitations on the rinse solution as long as it does not dissolve the resist pattern, and a solution containing a general organic solvent can be used, preferably an alcohol solvent or an ester solvent.
After cleaning, it is preferable to remove any rinsing liquid remaining on the substrate and the pattern.

<Application>
The resist composition of the present invention is suitable as a resist composition for KrF excimer laser exposure, a resist composition for ArF excimer laser exposure, a resist composition for electron beam (EB) exposure, or a resist composition for EUV exposure, and is more suitable as a resist composition for electron beam (EB) exposure or a resist composition for EUV exposure, and is useful for semiconductor microfabrication.

The present invention will be described in more detail with reference to examples. In the examples, "%" and "parts" expressing the content or amount used are based on mass unless otherwise specified.
The weight average molecular weight is a value determined by gel permeation chromatography under the following conditions.
Apparatus: HLC-8120GPC model (manufactured by Tosoh Corporation)
Column: TSKgel Multipore H _XL -M x 3 + guard column (Tosoh Corporation)
Eluent: tetrahydrofuran Flow rate: 1.0 mL/min
Detector: RI detector Column temperature: 40°C
Injection volume: 100 μl
Molecular weight standard: Standard polystyrene (Tosoh Corporation)
The structure of the compound was confirmed by measuring the molecular ion peak using mass spectrometry (LC: Agilent 1100 model, MASS: Agilent LC/MSD model). In the following examples, the value of this molecular ion peak is indicated by "MASS".

式（Ｉ－１－ａ）で表される化合物０．６５部及びアセトニトリル２０部を混合し、２３℃で３０分間攪拌した後、式（Ｉ－１－ｂ）で表される化合物１．３４部を添加し、５０℃に昇温後、５０℃で２時間撹拌した。得られた混合物に、式（Ｉ－１－ｃ）で表される化合物１．０７部を添加し、５０℃で２時間撹拌した。得られた混合物を２３℃まで冷却した後、クロロホルム５０部及びイオン交換水２０部を加えて２３℃で３０分間攪拌した後、分液して有機層を取り出した。得られた有機層に、イオン交換水２０部を添加し、２３℃で３０分間攪拌した後、分液して有機層を取り出した。この水洗操作を５回繰り返した。得られた有機層を濃縮し、濃縮混合物をカラム（シリカゲル６０Ｎ（球状、中性）１００－２１０μｍ；関東化学（株）製、展開溶媒：ｎ－ヘプタン／酢酸エチル＝１／１）を用いて分取することにより、式（Ｉ－１）で表される化合物１．２７部を得た。
ＭＡＳＳ：２１１．１［Ｍ＋Ｈ］^＋ Synthesis Example 1: Synthesis of compound represented by formula (I-1)

0.65 parts of the compound represented by formula (I-1-a) and 20 parts of acetonitrile were mixed and stirred at 23 ° C. for 30 minutes, after which 1.34 parts of the compound represented by formula (I-1-b) were added, and the mixture was heated to 50 ° C. and stirred at 50 ° C. for 2 hours. 1.07 parts of the compound represented by formula (I-1-c) were added to the resulting mixture and stirred at 50 ° C. for 2 hours. The resulting mixture was cooled to 23 ° C., and then 50 parts of chloroform and 20 parts of ion-exchanged water were added and stirred at 23 ° C. for 30 minutes, and then the organic layer was separated and taken out. 20 parts of ion-exchanged water was added to the resulting organic layer and stirred at 23 ° C. for 30 minutes, and then the organic layer was separated and taken out. This water washing operation was repeated five times. The obtained organic layer was concentrated, and the concentrated mixture was separated using a column (silica gel 60N (spherical, neutral) 100-210 μm; manufactured by Kanto Chemical Co., Ltd., developing solvent: n-heptane/ethyl acetate=1/1) to obtain 1.27 parts of the compound represented by formula (I-1).
MASS: 211.1 [M+H] ⁺

式（Ｉ－１４ａ－ａ）で表される化合物１．１１部及びアセトニトリル２０部を混合し、２３℃で３０分間攪拌した後、式（Ｉ－１－ｂ）で表される化合物１．３４部を添加し、５０℃に昇温後、５０℃で２時間撹拌した。得られた混合物に、式（Ｉ－１－ｃ）で表される化合物１．０７部を添加し、５０℃で２時間撹拌した。得られた混合物を２３℃まで冷却した後、クロロホルム５０部及びイオン交換水２０部を加えて２３℃で３０分間攪拌した後、分液して有機層を取り出した。得られた有機層に、イオン交換水２０部を添加し、２３℃で３０分間攪拌した後、分液して有機層を取り出した。この水洗操作を５回繰り返した。得られた有機層を濃縮し、濃縮混合物をカラム（シリカゲル６０Ｎ（球状、中性）１００－２１０μｍ；関東化学（株）製、展開溶媒：ｎ－ヘプタン／酢酸エチル＝１／１）を用いて分取することにより、式（Ｉ－１４ａ）で表される化合物１．９２部を得た。
ＭＡＳＳ：２７３．１［Ｍ＋Ｈ］^＋ Synthesis Example 2: Synthesis of compound represented by formula (I-14a)

1.11 parts of the compound represented by formula (I-14a-a) and 20 parts of acetonitrile were mixed and stirred at 23 ° C. for 30 minutes, after which 1.34 parts of the compound represented by formula (I-1-b) were added, and the mixture was heated to 50 ° C. and stirred at 50 ° C. for 2 hours. 1.07 parts of the compound represented by formula (I-1-c) were added to the resulting mixture and stirred at 50 ° C. for 2 hours. The resulting mixture was cooled to 23 ° C., and then 50 parts of chloroform and 20 parts of ion-exchanged water were added and stirred at 23 ° C. for 30 minutes, and then the organic layer was separated and taken out. 20 parts of ion-exchanged water was added to the resulting organic layer and stirred at 23 ° C. for 30 minutes, and then the organic layer was separated and taken out. This water washing operation was repeated five times. The obtained organic layer was concentrated, and the concentrated mixture was separated using a column (silica gel 60N (spherical, neutral) 100-210 μm; manufactured by Kanto Chemical Co., Ltd., developing solvent: n-heptane/ethyl acetate=1/1) to obtain 1.92 parts of the compound represented by formula (I-14a).
MASS: 273.1 [M+H] ⁺

式（Ｉ－１５－ａ）で表される化合物１．５５部及びアセトニトリル２０部を混合し、２３℃で３０分間攪拌した後、式（Ｉ－１－ｂ）で表される化合物１．３４部を添加し、５０℃に昇温後、５０℃で２時間撹拌した。得られた混合物に、式（Ｉ－１－ｃ）で表される化合物１．０７部を添加し、５０℃で２時間撹拌した。得られた混合物を２３℃まで冷却した後、クロロホルム５０部及びイオン交換水２０部を加えて２３℃で３０分間攪拌した後、分液して有機層を取り出した。得られた有機層に、イオン交換水２０部を添加し、２３℃で３０分間攪拌した後、分液して有機層を取り出した。この水洗操作を５回繰り返した。得られた有機層を濃縮し、濃縮混合物をカラム（シリカゲル６０Ｎ（球状、中性）１００－２１０μｍ；関東化学（株）製、展開溶媒：ｎ－ヘプタン／酢酸エチル＝１／１）を用いて分取することにより、式（Ｉ－１５）で表される化合物２．１９部を得た。
ＭＡＳＳ：３３１．１［Ｍ＋Ｈ］^＋ Synthesis Example 3: Synthesis of compound represented by formula (I-15)

1.55 parts of the compound represented by formula (I-15-a) and 20 parts of acetonitrile were mixed and stirred at 23 ° C. for 30 minutes, after which 1.34 parts of the compound represented by formula (I-1-b) were added, and the mixture was heated to 50 ° C. and stirred at 50 ° C. for 2 hours. 1.07 parts of the compound represented by formula (I-1-c) were added to the resulting mixture and stirred at 50 ° C. for 2 hours. The resulting mixture was cooled to 23 ° C., and then 50 parts of chloroform and 20 parts of ion-exchanged water were added and stirred at 23 ° C. for 30 minutes, and then the organic layer was separated and taken out. 20 parts of ion-exchanged water was added to the resulting organic layer and stirred at 23 ° C. for 30 minutes, and then the organic layer was separated and taken out. This water washing operation was repeated five times. The obtained organic layer was concentrated, and the concentrated mixture was separated using a column (silica gel 60N (spherical, neutral) 100-210 μm; manufactured by Kanto Chemical Co., Ltd., developing solvent: n-heptane/ethyl acetate=1/1) to obtain 2.19 parts of the compound represented by formula (I-15).
MASS: 331.1 [M+H] ⁺

Synthesis Example 4: Synthesis of compound represented by formula (I-2)
0.65 parts of the compound represented by formula (I-1-a) and 20 parts of acetonitrile were mixed and stirred at 23 ° C. for 30 minutes, after which 1.34 parts of the compound represented by formula (I-1-b) were added, and the mixture was heated to 50 ° C. and stirred at 50 ° C. for 2 hours. 1.18 parts of the compound represented by formula (I-2-c) were added to the resulting mixture and stirred at 50 ° C. for 2 hours. The resulting mixture was cooled to 23 ° C., and then 50 parts of chloroform and 20 parts of ion-exchanged water were added and stirred at 23 ° C. for 30 minutes, and then the organic layer was separated and taken out. 20 parts of ion-exchanged water was added to the resulting organic layer and stirred at 23 ° C. for 30 minutes, and then the organic layer was separated and taken out. This water washing operation was repeated five times. The obtained organic layer was concentrated, and the concentrated mixture was separated using a column (silica gel 60N (spherical, neutral) 100-210 μm; manufactured by Kanto Chemical Co., Ltd., developing solvent: n-heptane/ethyl acetate=1/1) to obtain 1.19 parts of the compound represented by formula (I-2).
MASS: 225.1 [M+H] ⁺

式（Ｉ－２２－ａ）で表される化合物１．９９部及びアセトニトリル２０部を混合し、２３℃で３０分間攪拌した後、式（Ｉ－１－ｂ）で表される化合物１．３４部を添加し、５０℃に昇温後、５０℃で２時間撹拌した。得られた混合物に、式（Ｉ－１－ｃ）で表される化合物１．０７部を添加し、５０℃で２時間撹拌した。得られた混合物を２３℃まで冷却した後、クロロホルム５０部及びイオン交換水２０部を加えて２３℃で３０分間攪拌した後、分液して有機層を取り出した。得られた有機層に、イオン交換水２０部を添加し、２３℃で３０分間攪拌した後、分液して有機層を取り出した。この水洗操作を５回繰り返した。得られた有機層を濃縮し、濃縮混合物をカラム（シリカゲル６０Ｎ（球状、中性）１００－２１０μｍ；関東化学（株）製、展開溶媒：ｎ－ヘプタン／酢酸エチル＝１／１）を用いて分取することにより、式（Ｉ－２２）で表される化合物２．３８部を得た。
ＭＡＳＳ：３８９．２［Ｍ＋Ｈ］^＋ Synthesis Example 5: Synthesis of compound represented by formula (I-22)

1.99 parts of the compound represented by formula (I-22-a) and 20 parts of acetonitrile were mixed and stirred at 23 ° C. for 30 minutes, after which 1.34 parts of the compound represented by formula (I-1-b) were added, and the mixture was heated to 50 ° C. and stirred at 50 ° C. for 2 hours. 1.07 parts of the compound represented by formula (I-1-c) were added to the resulting mixture and stirred at 50 ° C. for 2 hours. The resulting mixture was cooled to 23 ° C., and then 50 parts of chloroform and 20 parts of ion-exchanged water were added and stirred at 23 ° C. for 30 minutes, and then the organic layer was separated and taken out. 20 parts of ion-exchanged water was added to the resulting organic layer and stirred at 23 ° C. for 30 minutes, and then the organic layer was separated and taken out. This water washing operation was repeated five times. The obtained organic layer was concentrated, and the concentrated mixture was separated using a column (silica gel 60N (spherical, neutral) 100-210 μm; manufactured by Kanto Chemical Co., Ltd., developing solvent: n-heptane/ethyl acetate=1/1) to obtain 2.38 parts of the compound represented by formula (I-22).
MASS: 389.2 [M+H] ⁺

式（Ｉ－１９－ａ）で表される化合物１．７８部及びアセトニトリル２０部を混合し、２３℃で３０分間攪拌した後、式（Ｉ－１－ｂ）で表される化合物１．３４部を添加し、５０℃に昇温後、５０℃で２時間撹拌した。得られた混合物に、式（Ｉ－１－ｃ）で表される化合物１．０７部を添加し、５０℃で２時間撹拌した。得られた混合物を２３℃まで冷却した後、クロロホルム５０部及びイオン交換水２０部を加えて２３℃で３０分間攪拌した後、分液して有機層を取り出した。得られた有機層に、イオン交換水２０部を添加し、２３℃で３０分間攪拌した後、分液して有機層を取り出した。この水洗操作を５回繰り返した。得られた有機層を濃縮し、濃縮混合物をカラム（シリカゲル６０Ｎ（球状、中性）１００－２１０μｍ；関東化学（株）製、展開溶媒：ｎ－ヘプタン／酢酸エチル＝１／１）を用いて分取することにより、式（Ｉ－１９）で表される化合物２．０２部を得た。
ＭＡＳＳ：４０５．２［Ｍ＋Ｈ］^＋ Synthesis Example 6: Synthesis of compound represented by formula (I-19)

1.78 parts of the compound represented by formula (I-19-a) and 20 parts of acetonitrile were mixed and stirred at 23 ° C. for 30 minutes, after which 1.34 parts of the compound represented by formula (I-1-b) were added, and the mixture was heated to 50 ° C. and stirred at 50 ° C. for 2 hours. 1.07 parts of the compound represented by formula (I-1-c) were added to the resulting mixture and stirred at 50 ° C. for 2 hours. The resulting mixture was cooled to 23 ° C., and then 50 parts of chloroform and 20 parts of ion-exchanged water were added and stirred at 23 ° C. for 30 minutes, and then the organic layer was separated and taken out. 20 parts of ion-exchanged water was added to the resulting organic layer and stirred at 23 ° C. for 30 minutes, and then the organic layer was separated and taken out. This water washing operation was repeated five times. The obtained organic layer was concentrated, and the concentrated mixture was separated using a column (silica gel 60N (spherical, neutral) 100-210 μm; manufactured by Kanto Chemical Co., Ltd., developing solvent: n-heptane/ethyl acetate=1/1) to obtain 2.02 parts of the compound represented by formula (I-19).
MASS: 405.2 [M+H] ⁺

以下、これらのモノマーを式番号に応じて「モノマー（ａ１－１－３）」等という。 Synthesis of Resin The compounds (monomers) used in the synthesis of the resin are shown below.

Hereinafter, these monomers will be referred to as "monomer (a1-1-3)" etc. according to their formula numbers.

Example 1 [Synthesis of Resin A1]
As monomers, acetoxystyrene, monomer (a1-1-3), monomer (I-1) and monomer (III-1) were used, and the molar ratio [acetoxystyrene:monomer (a1-1-3):monomer (I-1):monomer (III-1)] was mixed to a ratio of 32:26:30:12, and further, 1.5 times by mass of methyl isobutyl ketone was mixed with this monomer mixture relative to the total mass of all monomers. Azobisisobutyronitrile and azobis(2,4-dimethylvaleronitrile) were added as initiators to the obtained mixture at 2.1 mol% and 6.3 mol% relative to the total monomer amount, respectively, and polymerization was carried out by heating at 73 ° C. for about 5 hours. Thereafter, a 25% aqueous solution of tetramethylammonium hydroxide was added to the polymerization reaction liquid, and the mixture was stirred for 12 hours, and then separated. The obtained organic layer was poured into a large amount of n-heptane to precipitate a resin, which was then filtered and collected to obtain Resin A1 (copolymer) having a weight average molecular weight of about 5.3 × 10 ³ in a yield of 64%. This Resin A1 has the following structural units.

Example 2 [Synthesis of Resin A2]
As monomers, acetoxystyrene, monomer (a1-1-3), monomer (I-14a) and monomer (III-1) were used, and the molar ratio [acetoxystyrene:monomer (a1-1-3):monomer (I-14a):monomer (III-1)] was mixed to a ratio of 32:26:30:12, and further, 1.5 times by mass of methyl isobutyl ketone was mixed with this monomer mixture relative to the total mass of all monomers. Azobisisobutyronitrile and azobis(2,4-dimethylvaleronitrile) were added as initiators to the obtained mixture at 2.1 mol% and 6.3 mol% relative to the total monomer amount, respectively, and polymerization was carried out by heating at 73 ° C. for about 5 hours. Thereafter, a 25% aqueous solution of tetramethylammonium hydroxide was added to the polymerization reaction liquid, and the mixture was stirred for 12 hours, and then separated. The obtained organic layer was poured into a large amount of n-heptane to precipitate a resin, which was then filtered and recovered to obtain Resin A2 (copolymer) with a weight average molecular weight of about 5.2 × 10 ³ in a yield of 60%. This Resin A2 has the following structural units.

Example 3 [Synthesis of Resin A3]
As monomers, acetoxystyrene, monomer (a1-1-3), monomer (I-15) and monomer (III-1) were used, and the molar ratio [acetoxystyrene:monomer (a1-1-3):monomer (I-15):monomer (III-1)] was mixed to a ratio of 32:26:30:12, and further, 1.5 times by mass of methyl isobutyl ketone was mixed with this monomer mixture relative to the total mass of all monomers. Azobisisobutyronitrile and azobis(2,4-dimethylvaleronitrile) were added as initiators to the obtained mixture at 2.1 mol% and 6.3 mol% relative to the total monomer amount, respectively, and polymerization was carried out by heating at 73 ° C. for about 5 hours. Thereafter, a 25% aqueous solution of tetramethylammonium hydroxide was added to the polymerization reaction liquid, and the mixture was stirred for 12 hours, and then separated. The obtained organic layer was poured into a large amount of n-heptane to precipitate a resin, which was then filtered and collected to obtain Resin A3 (copolymer) having a weight average molecular weight of about 5.0 × 10 ³ in a yield of 70%. This Resin A3 has the following structural units.

Example 4 [Synthesis of Resin A4]
As monomers, acetoxystyrene, monomer (a1-2-6), monomer (I-1) and monomer (III-1) were used, and the molar ratio [acetoxystyrene:monomer (a1-2-6):monomer (I-1):monomer (III-1)] was mixed to a ratio of 32:26:30:12, and further, 1.5 times by mass of methyl isobutyl ketone was mixed with this monomer mixture relative to the total mass of all monomers. Azobisisobutyronitrile and azobis(2,4-dimethylvaleronitrile) were added as initiators to the obtained mixture at 2.1 mol% and 6.3 mol% relative to the total monomer amount, respectively, and polymerization was carried out by heating at 73 ° C. for about 5 hours. Thereafter, a 25% aqueous solution of tetramethylammonium hydroxide was added to the polymerization reaction liquid, and the mixture was stirred for 12 hours, and then separated. The obtained organic layer was poured into a large amount of n-heptane to precipitate a resin, which was then filtered and recovered to obtain Resin A4 (copolymer) with a weight average molecular weight of about 5.2 × 10 ³ in a yield of 81%. This Resin A4 has the following structural units.

Example 5 [Synthesis of Resin A5]
As monomers, acetoxystyrene, monomer (I-1) and monomer (III-1) were used, and the molar ratio [acetoxystyrene:monomer (I-1):monomer (III-1)] was mixed to a ratio of 32:56:12. Furthermore, 1.5 times by mass of methyl isobutyl ketone was mixed with this monomer mixture relative to the total mass of all monomers. Azobisisobutyronitrile and azobis(2,4-dimethylvaleronitrile) were added as initiators to the obtained mixture at 2.1 mol% and 6.3 mol% relative to the total monomer amount, respectively, and polymerization was carried out by heating at 73 ° C. for about 5 hours. Thereafter, a 25% aqueous solution of tetramethylammonium hydroxide was added to the polymerization reaction liquid, and the mixture was stirred for 12 hours and then separated. The obtained organic layer was poured into a large amount of n-heptane to precipitate the resin, which was then filtered and collected to obtain a resin A5 (copolymer) having a weight average molecular weight of about 5.1 × 10 ³ in a yield of 65%. This resin A5 has the following structural units.

Example 6 [Synthesis of Resin A6]
Monomer (I-1) and monomer (III-1) were used as monomers, and the molar ratio [monomer (I-1):monomer (III-1)] was mixed to a ratio of 62:38. Furthermore, 1.5 times the mass of methyl isobutyl ketone was mixed with this monomer mixture relative to the total mass of all monomers. Azobisisobutyronitrile and azobis(2,4-dimethylvaleronitrile) were added as initiators to the obtained mixture at 2.1 mol% and 6.3 mol% relative to the total monomer amount, respectively, and polymerization was carried out by heating at 73 ° C. for about 5 hours. Thereafter, a 25% aqueous solution of tetramethylammonium hydroxide was added to the polymerization reaction liquid, and the mixture was stirred for 12 hours and then separated. The obtained organic layer was poured into a large amount of n-heptane to precipitate the resin, which was then filtered and collected to obtain a resin A6 (copolymer) having a weight average molecular weight of about 5.4 × 10 ³ in a yield of 55%. This resin A6 has the following structural units.

Example 7 [Synthesis of Resin A7]
As monomers, acetoxystyrene, monomer (a1-1-3), monomer (a1-2-6), monomer (I-1) and monomer (III-1) were used, and the molar ratio [acetoxystyrene:monomer (a1-1-3):monomer (a1-2-6):monomer (I-1):monomer (III-1)] was mixed to a ratio of 32:10:16:30:12, and further, 1.5 times by mass of methyl isobutyl ketone was mixed with respect to the total mass of all monomers to this monomer mixture. Azobisisobutyronitrile and azobis(2,4-dimethylvaleronitrile) were added as initiators to the obtained mixture at 2.1 mol% and 6.3 mol% with respect to the total monomer amount, respectively, and polymerization was carried out by heating this at 73 ° C. for about 5 hours. Thereafter, a 25% aqueous solution of tetramethylammonium hydroxide was added to the polymerization reaction liquid, and the mixture was stirred for 12 hours, and then separated. The obtained organic layer was poured into a large amount of n-heptane to precipitate a resin, which was then filtered and recovered to obtain Resin A7 (copolymer) with a weight average molecular weight of about 5.5 × 10 ³ in a yield of 72%. This Resin A7 has the following structural units.

Example 8 [Synthesis of Resin A8]
As monomers, acetoxystyrene, monomer (a1-1-3), monomer (a1-2-6), monomer (I-2) and monomer (III-1) were used, and the molar ratio [acetoxystyrene:monomer (a1-1-3):monomer (a1-2-6):monomer (I-2):monomer (III-1)] was mixed to a ratio of 32:10:16:30:12, and further, 1.5 times by mass of methyl isobutyl ketone was mixed with respect to the total mass of all monomers to this monomer mixture. Azobisisobutyronitrile and azobis(2,4-dimethylvaleronitrile) were added as initiators to the obtained mixture at 2.1 mol% and 6.3 mol% with respect to the total monomer amount, respectively, and polymerization was carried out by heating at 73 ° C. for about 5 hours. Thereafter, a 25% aqueous solution of tetramethylammonium hydroxide was added to the polymerization reaction liquid, and the mixture was stirred for 12 hours, and then separated. The obtained organic layer was poured into a large amount of n-heptane to precipitate a resin, which was then filtered and recovered to obtain Resin A8 (copolymer) having a weight average molecular weight of about 5.3 × 10 ³ in a yield of 69%. This Resin A8 has the following structural units.

Example 9 [Synthesis of Resin A9]
As monomers, acetoxystyrene, monomer (a1-1-3), monomer (a1-2-6), monomer (I-19) and monomer (III-1) were used, and the molar ratio [acetoxystyrene:monomer (a1-1-3):monomer (a1-2-6):monomer (I-19):monomer (III-1)] was mixed to a ratio of 32:10:16:30:12, and further, 1.5 times the mass of methyl isobutyl ketone was mixed with this monomer mixture relative to the total mass of all monomers. Azobisisobutyronitrile and azobis(2,4-dimethylvaleronitrile) were added as initiators to the obtained mixture at 2.1 mol% and 6.3 mol% relative to the total monomer amount, respectively, and polymerization was carried out by heating at 73 ° C. for about 5 hours. Thereafter, a 25% aqueous solution of tetramethylammonium hydroxide was added to the polymerization reaction liquid, and the mixture was stirred for 12 hours, and then separated. The obtained organic layer was poured into a large amount of n-heptane to precipitate a resin, which was then filtered and recovered to obtain Resin A9 (copolymer) with a weight average molecular weight of about 5.2 × 10 ³ in a yield of 62%. This Resin A9 has the following structural units.

Example 10 [Synthesis of Resin A10]
As monomers, acetoxystyrene, monomer (a1-1-3), monomer (a1-2-6), monomer (I-22) and monomer (III-1) were used, and the molar ratio [acetoxystyrene:monomer (a1-1-3):monomer (a1-2-6):monomer (I-22):monomer (III-1)] was mixed to a ratio of 32:10:16:30:12, and further, 1.5 times by mass of methyl isobutyl ketone was mixed with respect to the total mass of all monomers to this monomer mixture. Azobisisobutyronitrile and azobis(2,4-dimethylvaleronitrile) were added as initiators to the obtained mixture at 2.1 mol% and 6.3 mol% with respect to the total monomer amount, respectively, and polymerization was carried out by heating this at 73 ° C. for about 5 hours. Thereafter, a 25% aqueous solution of tetramethylammonium hydroxide was added to the polymerization reaction liquid, and the mixture was stirred for 12 hours, and then separated. The obtained organic layer was poured into a large amount of n-heptane to precipitate a resin, which was then filtered and recovered to obtain Resin A10 (copolymer) having a weight average molecular weight of about 5.48 × 10 ³ in a yield of 64%. This Resin A10 has the following structural units.

Synthesis Example 7 [Synthesis of Resin AX1]
As monomers, acetoxystyrene and monomer (IX-1) were used, and the molar ratio [acetoxystyrene:monomer (IX-1)] was mixed to a ratio of 38:62. Furthermore, 1.5 times the mass of methyl isobutyl ketone was mixed with this monomer mixture relative to the total mass of all monomers. Azobisisobutyronitrile and azobis(2,4-dimethylvaleronitrile) were added as initiators to the obtained mixture at 2.1 mol% and 6.3 mol% relative to the total monomer amount, respectively, and polymerization was carried out by heating at 73 ° C. for about 5 hours. Thereafter, a 25% aqueous solution of tetramethylammonium hydroxide was added to the polymerization reaction liquid, and the mixture was stirred for 12 hours and then separated. The obtained organic layer was poured into a large amount of n-heptane to precipitate the resin, which was then filtered and collected to obtain resin AX1 (copolymer) having a weight average molecular weight of about 5.2 × 10 ³ in a yield of 64%. This resin AX1 has the following structural units.

Synthesis Example 8 [Synthesis of Resin AX2]
As monomers, acetoxystyrene and monomer (IX-2) were used, and the molar ratio [acetoxystyrene:monomer (IX-2)] was mixed to a ratio of 38:62. Furthermore, 1.5 times the mass of methyl isobutyl ketone was mixed with this monomer mixture relative to the total mass of all monomers. Azobisisobutyronitrile and azobis(2,4-dimethylvaleronitrile) were added as initiators to the obtained mixture at 2.1 mol% and 6.3 mol% relative to the total monomer amount, respectively, and polymerization was carried out by heating at 73 ° C. for about 5 hours. Thereafter, a 25% aqueous solution of tetramethylammonium hydroxide was added to the polymerization reaction liquid, and the mixture was stirred for 12 hours and then separated. The obtained organic layer was poured into a large amount of n-heptane to precipitate the resin, which was then filtered and collected to obtain resin AX2 (copolymer) having a weight average molecular weight of about 5.3 × 10 ³ in a yield of 60%. This resin AX2 has the following structural units.

Synthesis example for September [Synthesis of resin AX3]
Monomer (a1-1-3) and monomer (III-1) were used as monomers, and the molar ratio [monomer (a1-1-3):monomer (III-1)] was mixed to a ratio of 62:38, and further, 1.5 times the mass of methyl isobutyl ketone was mixed with this monomer mixture relative to the total mass of all monomers. Azobisisobutyronitrile and azobis(2,4-dimethylvaleronitrile) were added as initiators to the obtained mixture in an amount of 2.1 mol% and 6.3 mol% relative to the total monomer amount, respectively, and polymerization was carried out by heating at 73 ° C. for about 5 hours. Thereafter, the polymerization solution was poured into a large amount of n-heptane to precipitate the resin, and the resin was filtered and collected to obtain resin AX3 having a weight average molecular weight of about 5.4 × 10 ³ in a yield of 61%. This resin AX3 has the following structural units.

Synthesis Example 10 [Synthesis of Resin AX4]
Monomer (a1-2-5) and monomer (III-1) were used as monomers, and the molar ratio [monomer (a1-2-5):monomer (III-1)] was mixed to a ratio of 62:38, and further, 1.5 times the mass of methyl isobutyl ketone was mixed with this monomer mixture relative to the total mass of all monomers. Azobisisobutyronitrile and azobis(2,4-dimethylvaleronitrile) were added as initiators to the obtained mixture in an amount of 2.1 mol% and 6.3 mol% relative to the total monomer amount, respectively, and polymerization was carried out by heating at 73 ° C. for about 5 hours. Thereafter, the polymerization solution was poured into a large amount of n-heptane to precipitate the resin, and the resin was filtered and collected to obtain resin AX4 having a weight average molecular weight of about 5.7 × 10 ³ in a yield of 83%. This resin AX4 has the following structural units.

<Preparation of Resist Composition>
The components shown in Table 1 were mixed and dissolved to obtain a mixture, which was then filtered through a fluororesin filter having a pore size of 0.2 μm to prepare a resist composition.

＜クエンチャー（Ｃ）＞
（酸発生剤から発生する酸よりも酸性度の弱い酸を発生する塩）
Ｄ１：特開２０１１－３９５０２号公報記載の方法で合成

＜溶剤＞
プロピレングリコールモノメチルエーテルアセテート ４００部
プロピレングリコールモノメチルエーテル １５０部
γ－ブチロラクトン ５部 <Resin>
A1 to A10, AX1 to AX4: Resin A1 to Resin A10, Resin AX1 to Resin AX4
<Acid Generator (B)>
B1-25: Salt represented by formula (B1-25); synthesized by the method described in JP 2011-126869 A

<Quencher (C)>
(Salts that generate acids with weaker acidity than the acid generated by the acid generator)
D1: Synthesized by the method described in JP-A-2011-39502

<Solvent>
Propylene glycol monomethyl ether acetate 400 parts Propylene glycol monomethyl ether 150 parts γ-butyrolactone 5 parts

(Electron Beam Exposure Evaluation of Resist Composition)
A 6-inch silicon wafer was treated with hexamethyldisilazane at 90° C. for 60 seconds on a direct hot plate. A resist composition was spin-coated onto this silicon wafer so that the film thickness of the composition layer was 0.04 μm. The wafer was then pre-baked on a direct hot plate at the temperature shown in the “PB” column of Table 1 for 60 seconds to form a composition layer. A contact hole pattern (hole pitch 40 nm/hole diameter 17 nm) was directly written on the composition layer formed on the wafer using an electron beam lithography machine (ELS-F125 125 keV, manufactured by Elionix Co., Ltd.) by changing the exposure dose stepwise.
After exposure, post-exposure baking was performed on a hot plate at the temperature shown in the "PEB" column of Table 1 for 60 seconds, and then paddle development was performed for 60 seconds using a 2.38 mass % aqueous tetramethylammonium hydroxide solution to obtain a resist pattern.
In the resist pattern obtained after development, the exposure amount at which a hole diameter of 17 nm was formed was defined as effective sensitivity.

<CD Uniformity (CDU) Evaluation>
In the effective sensitivity, the hole diameter of a pattern formed with a hole diameter of 17 nm was measured 24 times for each hole, and the average value was taken as the average hole diameter of one hole. The standard deviation was calculated using the population of 400 average hole diameters of patterns formed with a hole diameter of 17 nm on the same wafer.
The results are shown in Table 2. The values in the table indicate standard deviations (nm).
Compared to Comparative Compositions 1-4, Compositions 1-10 had smaller standard deviations and better CD uniformity (CDU) ratings.

The resin of the present invention and the resist composition containing it can produce resist patterns with good CD uniformity (CDU), making them suitable for semiconductor microfabrication and extremely useful industrially.

Claims (10)

A resin comprising a structural unit represented by formula (I) and a structural unit represented by formula (III).
[In formula (I),
^R1 represents a hydrogen atom or a methyl group.
X ¹ represents a group represented by any one of formulas (X ¹ -1) to (X ¹ -7).
(In formulas (X ¹ -1) to (X ¹ -7),
* and ** are binding sites, and ** represents the binding site to ^L1 .)
L ¹ represents a single bond or a hydrocarbon group having 1 to 48 carbon atoms which may have a substituent, and --CH ₂ -- contained in the hydrocarbon group may be replaced by --O--, --S--, --CO-- or --SO ₂ -- .
R2 or ^R4 and ^R3 or ^R5 are bonded to each other to form, together with the carbon atoms ^to which they are bonded, an alicyclic hydrocarbon group having 3 to 5 carbon atoms which may have an alkyl group having 1 to 4 carbon atoms.]
[In the formula (III),
^R6 represents a hydrogen atom or a methyl group.
A ¹ represents a single bond or *-CO-O-, and * represents the bonding site with the carbon atom to which -R ⁶ is bonded.
^R7 represents a halogen atom, a hydroxy group, a haloalkyl group having 1 to 4 carbon atoms or an alkyl group having 1 to 12 carbon atoms, and --CH ₂ -- contained in the alkyl group may be replaced by --O-- or --CO--.
mi represents an integer of 1 to 3.
ni represents an integer of 0 to 4, and when ni is 2 or more, the multiple R ^7s may be the same or different from each other, provided that mi+ni≦5. The resin according to claim 1, wherein L ¹ is a single bond, an alkanediyl group having 1 to 6 carbon atoms (-CH ₂ - contained in the alkanediyl group may be replaced with -O- or -CO-), or a divalent hydrocarbon group formed from a divalent alicyclic hydrocarbon group having 3 to 18 carbon atoms and an alkanediyl group having 1 to 6 carbon atoms (-CH ₂ - contained in the hydrocarbon group may be replaced with -O- or -CO-). 3. The resin according to claim 1, wherein X ¹ is a group represented by any one of formula (X ¹ -1), formula (X ¹ -3) and formula (X ¹ -4). The resin according to any one of claims 1 to 3 , wherein A ¹ is a single bond. The resin according to any one of claims 1 to 4 , further comprising at least one structural unit selected from the group consisting of a structural unit represented by formula (a1-1) and a structural unit represented by formula (a1-2):
[In formula (a1-1) and formula (a1-2),
L ^a1 and L ^a2 each independently represent --O-- or *-O--(CH ₂ ) _k1 --CO--O--, where k1 represents an integer of 1 to 7, and * represents a bonding site with --CO--.
R ^a4 and R ^a5 each independently represent a hydrogen atom or a methyl group.
R ^a6 and R ^a7 each independently represent an alkyl group having 1 to 8 carbon atoms, an alicyclic hydrocarbon group having 3 to 18 carbon atoms, or a combination thereof.
m1 represents an integer of 0 to 14.
n1 represents an integer of 0 to 10.
n1′ represents an integer of 0 to 3. The resin according to any one of claims 1 to 5 , further comprising a structural unit represented by formula (a2-A):
[In formula (a2-A),
R ^a50 represents a hydrogen atom, a halogen atom or an alkyl group having 1 to 6 carbon atoms which may have a halogen atom.
R ^a51 represents a halogen atom, a hydroxyl group, an alkyl group having 1 to 6 carbon atoms, an alkoxy group having 1 to 6 carbon atoms, an alkylcarbonyl group having 2 to 4 carbon atoms, an alkylcarbonyloxy group having 2 to 4 carbon atoms, an acryloyloxy group or a methacryloyloxy group.
A ^a50 represents a single bond or *-X ^a51 -(A ^a52 -X ^a52 ) _nb -, where * represents the bonding site with the carbon atom to which -R ^a50 is bonded.
A ^a52 represents an alkanediyl group having 1 to 6 carbon atoms.
X ^a51 and X ^a52 each independently represent —O—, —CO—O— or —O—CO—.
nb represents 0 or 1.
mb represents an integer of 0 to 4. When mb is an integer of 2 or more, multiple R ^a51 may be the same or different. A resist composition comprising the resin according to any one of claims 1 to 6 and an acid generator. 8. The resist composition according to claim 7 , wherein the acid generator comprises a salt represented by formula (B1).
[In formula (B1),
Q ^b1 and Q ^b2 each independently represent a fluorine atom or a perfluoroalkyl group having 1 to 6 carbon atoms.
L ^b1 represents a divalent saturated hydrocarbon group having 1 to 24 carbon atoms, in which -CH ₂ - may be replaced by -O- or -CO-, and in which a hydrogen atom may be replaced by a fluorine atom or a hydroxyl group.
Y represents an optionally substituted methyl group or an optionally substituted alicyclic hydrocarbon group having 3 to 18 carbon atoms, and one -CH ₂ - contained in the alicyclic hydrocarbon group may be replaced by -O-, -S(O) ₂ - or -CO-.
Z ⁺ represents an organic cation. 9. The resist composition according to claim 7, further comprising a salt capable of generating an acid having a weaker acidity than the acid generated from the acid generator. (1) A step of applying the resist composition according to any one of claims 7 to 9 onto a substrate;
(2) A step of drying the applied composition to form a composition layer;
(3) exposing the composition layer to light;
(4) a step of heating the composition layer after exposure; and (5) a step of developing the composition layer after heating.
A method for producing a resist pattern comprising the steps of: