JP2012153680A - Salt, acid generator, resist composition and method for producing resist pattern - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a salt, an acid generator, and a resist composition, which provide a resist pattern having excellent resolution.SOLUTION: The salt is represented by formula (I) [in formula, R-Rand Xeach represent predetermined groups, also Rand R, Rand R, Rand R, Rand R, Rand R, Rand R, Rand R, or Rand Rmay optionally form a ring, provided that one of R-Rrepresents a bond with X, a broken line represents a single bond or a double bond, n1 represents 1 or 2, n2 represents 0 or 1, and Zrepresents an organic counter ion].

Description

  The present invention relates to a salt for an acid generator used for microfabrication of a semiconductor, an acid generator, a resist composition, and a method for producing a resist pattern.

Patent Document 1 describes a resist composition containing a salt represented by the following formula as a salt for an acid generator.

JP 2008-74843 A

With further advancement of microfabrication technology, for example, resist compositions used for semiconductor manufacturing are required to have good resolution.

［式（Ｉ）中、
Ｒ^１及びＲ^２は、互いに独立に、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。
Ｘ^１は、２価の炭素数１〜１７の飽和炭化水素基を表し、前記２価の飽和炭化水素基に含まれる水素原子は、フッ素原子で置換されていてもよく、前記２価の飽和炭化水素基に含まれるメチレン基は、酸素原子又はカルボニル基で置き換わっていてもよい。
Ｒ^３は、下記式（ｂ）で表される基である。

（式（ｂ）中、
Ｒ^４、Ｒ^５、Ｒ^６、Ｒ^７、Ｒ^８、Ｒ^９、Ｒ^１０、Ｒ^１１、Ｒ^１２及びＲ^１３は、互いに独立に、水素原子、水酸基、アルコキシ基、炭素数１〜１８の脂肪族炭化水素基を表すか、Ｒ^４とＲ^５、Ｒ^５とＲ^６、Ｒ^６とＲ^７、Ｒ^６とＲ^１３、Ｒ^７とＲ^８、Ｒ^８とＲ^１１、Ｒ^１１とＲ^１２又はＲ^１２とＲ^１３が一緒になって、環を形成してもよく、該環に含まれるメチレン基は、酸素原子又はカルボニル基で置き換わっていてもよい。但し、Ｒ^４、Ｒ^５、Ｒ^６、Ｒ^７、Ｒ^８、Ｒ^９、Ｒ^１０、Ｒ^１１、Ｒ^１２及びＲ^１３のいずれか１つはＸ^１との結合手を表す。
---は、単結合又は二重結合を表す。
ｎ１は、１又は２を表す。
ｎ２は、０又は１を表す。ｎ１＋ｎ２は２である。）
Ｚ^１＋は、有機対イオンを表す。］ The present invention includes the following inventions.
[1] A salt represented by the formula (I).

[In the formula (I),
R ¹ and R ² each independently represent a fluorine atom or a C 1-6 perfluoroalkyl group.
X ¹ represents a divalent saturated hydrocarbon group having 1 to 17 carbon atoms, a hydrogen atom contained in the divalent saturated hydrocarbon group may be substituted with a fluorine atom, and the divalent saturated The methylene group contained in the hydrocarbon group may be replaced with an oxygen atom or a carbonyl group.
R ³ is a group represented by the following formula (b).

(In the formula (b),
R ⁴ , R ⁵ , R ⁶ , R ⁷ , R ⁸ , R ⁹ , R ¹⁰ , R ¹¹ , R ¹² and R ¹³ are each independently a hydrogen atom, a hydroxyl group, an alkoxy group, a C 1-18 fat. Represents a group hydrocarbon group, R ⁴ and R ⁵ , R ⁵ and R ⁶ , R ⁶ and R ⁷ , R ⁶ and R ¹³ , R ⁷ and R ⁸ , R ⁸ and R ¹¹ , R ¹¹ and R ¹² or R ¹² and R ¹³ may be combined to form a ring, and the methylene group contained in the ring may be replaced with an oxygen atom or a carbonyl group. However, any one of R ⁴ , R ⁵ , R ⁶ , R ⁷ , R ⁸ , R ⁹ , R ¹⁰ , R ¹¹ , R ¹² and R ¹³ represents a bond to X ¹ .
--- represents a single bond or a double bond.
n1 represents 1 or 2.
n2 represents 0 or 1. n1 + n2 is 2. )
Z ¹⁺ represents an organic counter ion. ]

[式（ｃ）中、
Ｒ^１４、Ｒ^１５、Ｒ^１６及びＲ^１７は、互いに独立に、水素原子、水酸基、アルコキシ基、炭素数１〜１８の脂肪族炭化水素基を表す。但し、Ｒ^１４、Ｒ^１５、Ｒ^１６及びＲ^１７のいずれか１つはＸ^１との結合手を表す。] [2] The salt according to [1], wherein the group represented by the formula (b) is a group represented by the formula (c).

[In the formula (c),
R ¹⁴ , R ¹⁵ , R ¹⁶ and R ¹⁷ each independently represent a hydrogen atom, a hydroxyl group, an alkoxy group, or an aliphatic hydrocarbon group having 1 to 18 carbon atoms. However, any one of R ¹⁴ , R ¹⁵ , R ¹⁶ and R ¹⁷ represents a bond with X ¹ . ]

[式（ｄ）中、＊は、Ｘ^１との結合手を表す。]
〔４〕Ｚ^１＋が、トリアリールスルホニウムカチオンである〔１〕〜〔３〕のいずれかに記載の塩。
〔５〕上記〔１〕〜〔４〕のいずれか記載の塩を含有する酸発生剤。
〔６〕上記〔１〕記載の酸発生剤と樹脂と溶剤とを含有するレジスト組成物。
〔７〕樹脂が、酸に不安定な基を有し、かつアルカリ水溶液に不溶又は難溶であり、酸と作用してアルカリ水溶液で溶解しえる樹脂である〔６〕記載のレジスト組成物。
〔８〕さらに、塩基性化合物を含有する〔６〕又は〔７〕記載のレジスト組成物。 [3] The salt according to [2], wherein the formula (c) is a group represented by the following formula (d).

Wherein (d), * represents a bond to ^{X 1.} ]
[4] The salt according to any one of [1] to [3], wherein Z ¹⁺ is a triarylsulfonium cation.
[5] An acid generator containing the salt according to any one of [1] to [4].
[6] A resist composition comprising the acid generator according to the above [1], a resin, and a solvent.
[7] The resist composition according to [6], wherein the resin is a resin having an acid labile group and insoluble or hardly soluble in an alkaline aqueous solution and capable of dissolving in an alkaline aqueous solution by acting with an acid.
[8] The resist composition according to [6] or [7], further containing a basic compound.

[9] (1) A step of applying the resist composition according to any one of [6] to [8] on a substrate,
(2) a step of removing the solvent from the composition after coating to form a composition layer;
(3) a step of exposing the composition layer using an exposure machine;
(4) A step of heating the composition layer after exposure,
(5) a step of developing the composition layer after heating;
A method for producing a resist pattern including:

  According to the salt of the present invention, a resist pattern having excellent resolution can be formed by using a resist composition containing this salt.

  In the present specification, unless otherwise specified, in the description of the structural formula of the compound, the following examples of substituents are applied to any structural formula having the same substituent while appropriately selecting the number of carbon atoms. . Those which can be linear, branched or cyclic include any of them, and they may be mixed. When stereoisomers exist, all stereoisomers are included.

The hydrocarbon group includes an aliphatic hydrocarbon group and an aromatic hydrocarbon group.
The aliphatic hydrocarbon group includes both a chain and a cyclic group, and includes a combination of a chain and a cyclic aliphatic hydrocarbon group unless otherwise defined. Moreover, although these aliphatic hydrocarbon groups may contain the carbon-carbon double bond in the part, a saturated group is preferable.
Of the chain aliphatic hydrocarbon groups, the monovalent one typically includes an alkyl group.
Examples of the alkyl group include a methyl group (C ₁ ), an ethyl group (C ₂ ), a propyl group (C ₃ ), a butyl group (C ₄ ), a pentyl group (C ₅ ), a hexyl group (C ₆ ), a heptyl group ( C ₇ ), octyl group (C ₈ ), decyl group (C ₁₀ ), dodecyl group (C ₁₂ ), hexadecyl group (C ₁₄ ), pentadecyl group (C ₁₅ ), hexyldecyl group (C ₁₆ ), heptadecyl group ( C ₁₇ ) and octadecyl group (C ₁₈ ).
Examples of the divalent group of chain aliphatic hydrocarbon groups include alkanediyl groups in which one hydrogen atom has been removed from an alkyl group.
Examples of alkanediyl groups include methylene group, ethylene group, propane-1,3-diyl group, propane-1,2-diyl group, butane-1,4-diyl group, pentane-1,5-diyl group, hexane- 1,6-diyl group, heptane-1,7-diyl group, octane-1,8-diyl group, nonane-1,9-diyl group, decane-1,10-diyl group, undecane-1,11-diyl Group, dodecane-1,12-diyl group, tridecane-1,13-diyl group, tetradecane-1,14-diyl group, pentadecane-1,15-diyl group, hexadecane-1,16-diyl group, heptadecane-1 , 17-diyl group, methylidene group, ethylidene group, propylidene group, 2-propylidene group, 1-methyl-1,3-propylene group, 2-methyl-1,3-propylene group, 2-methyl group Le-1,2-propylene group, 1-methyl-1,4-butylene, and 2-methyl-1,4-butylene group.

  The cyclic aliphatic hydrocarbon group (hereinafter sometimes referred to as “alicyclic hydrocarbon group”) typically means a cycloalkyl group, and includes any of the monocyclic and polycyclic groups shown below. Is also included.

As a monovalent alicyclic hydrocarbon group, a monocyclic aliphatic hydrocarbon group represents 1 hydrogen atom of a cycloalkane represented by the following formulas (KA-1) to (KA-7). It is a group that has been removed.

The polycyclic aliphatic hydrocarbon group is a group in which one hydrogen atom of a cycloalkane represented by the following formulas (KA-8) to (KA-20) is removed.

Examples of the divalent alicyclic hydrocarbon group include groups in which two hydrogen atoms have been removed from the alicyclic hydrocarbon of the formula (KA-1) to the formula (KA-20).
Of the monocyclic and polycyclic aliphatic hydrocarbon groups, a particularly saturated group is sometimes referred to as a “saturated cyclic hydrocarbon group”.

The aliphatic hydrocarbon group may have a substituent. As such a substituent, a halogen atom, a hydroxy group, an alkoxy group, an alkylthio group, an acyl group, an acyloxy group, an aryl group, an aralkyl group, and an aryloxy group may be mentioned unless otherwise limited.
Here, as a halogen atom, a fluorine atom, a chlorine atom, a bromine atom, and an iodine atom are mentioned.
Examples of alkoxy groups include methoxy group (C ₁ ), ethoxy group (C ₂ ), propoxy group (C ₃ ), butoxy group (C ₄ ), pentyloxy group (C ₅ ), hexyloxy group (C ₆ ), heptyl Examples thereof include an oxy group (C ₇ ), an octyloxy group (C ₈ ), a decyloxy group (C ₁₀ ), and a dodecyloxy group (C ₁₂ ).
Examples of the alkylthio group include those in which an oxygen atom of an alkoxy group is replaced by a sulfur atom, such as a methylthio group, an ethylthio group, a propylthio group, a butylthio group, a pentylthio group, a hexylthio group, a heptylthio group, an octylthio group, a decylthio group, and the like. Examples include dodecylthio group.
As the acyl group, acetyl group (C ₂ ), propionyl group (C ₃ ), butyryl group (C ₄ ), valeryl group (C ₅ ), hexylcarbonyl group (C ₆ ), heptylcarbonyl group (C ₇ ), octyl An alkyl group such as a carbonyl group (C ₈ ), a decylcarbonyl group (C ₁₀ ) and a dodecylcarbonyl group (C ₁₂ ) and a carbonyl group, and an aryl group such as a benzoyl group (C ₇ ) and a carbonyl group Combined are included.
Examples of the acyloxy group include an acetyloxy group, a propionyloxy group, a butyryloxy group, and an isobutyryloxy group.
Examples of the aralkyl group include benzyl group (C ₇ ), phenethyl group (C ₈ ), phenylpropyl group (C ₉ ), naphthylmethyl group (C ₁₁ ), and naphthylethyl group (C ₁₂ ).
The aryloxy group includes phenyloxy group (C ₆ ), naphthyloxy group (C ₁₀ ), antonyloxy group (C ₁₄ ), biphenyloxy group (C ₁₂ ), phenanthryloxy group (C ₁₄ ) and full A combination of an aryl group such as an oleenyloxy group (C ₁₃ ) and an oxygen atom is exemplified.

A typical example of the aromatic hydrocarbon group is an aryl group.
Examples of the aryl group include a phenyl group (C ₆ ), a naphthyl group (C ₁₀ ), an antonyl group (C ₁₄ ), a biphenyl group (C ₁₂ ), a phenanthryl group (C ₁₄ ), and a fluorenyl group (C ₁₃ ). .
The aromatic hydrocarbon group may have a substituent. Unless such a substituent is particularly limited, a halogen atom, a hydroxy group, an alkoxy group, an acyl group, an acyloxy group, an alkyl group, and an aryloxy group are exemplified.

  The saturated hydrocarbon group means a saturated group among the above-described aliphatic hydrocarbon groups, that is, a saturated group among the above-described chain and cyclic aliphatic hydrocarbon groups. Further, the saturated hydrocarbon group may have the same substituent as the aliphatic hydrocarbon group.

Further, "(meth) acrylic monomer" means at least one monomer having a structure of "CH ₂ = CH-CO-" or _{"CH 2 = C (CH 3)} -CO- ". Similarly, “(meth) acrylate” and “(meth) acrylic acid” mean “at least one of acrylate and methacrylate” and “at least one of acrylic acid and methacrylic acid”, respectively.

［式（Ｉ）中、
Ｒ^１及びＲ^２は、互いに独立に、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。
Ｘ^１は、２価の炭素数１〜１７の飽和炭化水素基を表し、前記２価の飽和炭化水素基に含まれる水素原子は、フッ素原子で置換されていてもよく、前記２価の飽和炭化水素基に含まれるメチレン基は、酸素原子又はカルボニル基で置き換わっていてもよい。
Ｒ^３は、下記式（ｂ）で表される基である。

（式（ｂ）中、
Ｒ^４、Ｒ^５、Ｒ^６、Ｒ^７、Ｒ^８、Ｒ^９、Ｒ^１０、Ｒ^１１、Ｒ^１２及びＲ^１３は、互いに独立に、水素原子、水酸基、アルコキシ基、炭素数１〜１８の脂肪族炭化水素基を表すか、Ｒ^４とＲ^５、Ｒ^５とＲ^６、Ｒ^６とＲ^７、Ｒ^６とＲ^１３、Ｒ^７とＲ^８、Ｒ^８とＲ^１１、Ｒ^１１とＲ^１２又はＲ^１２とＲ^１３が一緒になって、環を形成してもよく、該環に含まれるメチレン基は、酸素原子又はカルボニル基で置き換わっていてもよい。但し、Ｒ^４、Ｒ^５、Ｒ^６、Ｒ^７、Ｒ^８、Ｒ^９、Ｒ^１０、Ｒ^１１、Ｒ^１２及びＲ^１３のいずれか１つはＸ^１との結合手を表す。
---は、単結合又は二重結合を表す。
ｎ１は、１又は２を表す。
ｎ２は、０又は１を表す。ｎ１＋ｎ２は２である。）
Ｚ^１＋は、有機対イオンを表す。］ <Salt represented by formula (I)>
The salt of the present invention is represented by the formula (I).

[In the formula (I),
R ¹ and R ² each independently represent a fluorine atom or a C 1-6 perfluoroalkyl group.
X ¹ represents a divalent saturated hydrocarbon group having 1 to 17 carbon atoms, a hydrogen atom contained in the divalent saturated hydrocarbon group may be substituted with a fluorine atom, and the divalent saturated The methylene group contained in the hydrocarbon group may be replaced with an oxygen atom or a carbonyl group.
R ³ is a group represented by the following formula (b).

(In the formula (b),
R ⁴ , R ⁵ , R ⁶ , R ⁷ , R ⁸ , R ⁹ , R ¹⁰ , R ¹¹ , R ¹² and R ¹³ are each independently a hydrogen atom, a hydroxyl group, an alkoxy group, a C 1-18 fat. Represents a group hydrocarbon group, R ⁴ and R ⁵ , R ⁵ and R ⁶ , R ⁶ and R ⁷ , R ⁶ and R ¹³ , R ⁷ and R ⁸ , R ⁸ and R ¹¹ , R ¹¹ and R ¹² or R ¹² and R ¹³ may be combined to form a ring, and the methylene group contained in the ring may be replaced with an oxygen atom or a carbonyl group. However, any one of R ⁴ , R ⁵ , R ⁶ , R ⁷ , R ⁸ , R ⁹ , R ¹⁰ , R ¹¹ , R ¹² and R ¹³ represents a bond to X ¹ .
--- represents a single bond or a double bond.
n1 represents 1 or 2.
n2 represents 0 or 1. n1 + n2 is 2. )
Z ¹⁺ represents an organic counter ion. ]

  Examples of the perfluoroalkyl group include a perfluoromethyl group, a perfluoroethyl group, a perfluoropropyl group, a perfluoroisopropyl group, a perfluorobutyl group, a perfluoro sec-butyl group, a perfluoro tert-butyl group, a perfluoropentyl group, and a perfluorohexyl group. It is done.

In the formula (I), R ¹ and R ² are independently of each other preferably a perfluoromethyl group or a fluorine atom, more preferably a fluorine atom.
In X ¹ , the methylene group is replaced by an oxygen atom or a carbonyl group, preferably formula (X1-A) to formula (X1-F), more preferably formula (X1-A) or formula (X1-B) And more preferably a group represented by the formula (X1-A). Note that the groups represented by the formulas (X1-A) to (X1-F) are bonded to C (R ¹ ) (R ² ) on the left side and bonded to an oxygen atom on the right side.

［式中、Ｘ^１１は、炭素数１〜１５の飽和炭化水素基を表す。
Ｘ^１２は、炭素数１〜１４の飽和炭化水素基を表す。
Ｘ^１３〜Ｘ^１７は、互いに独立に、炭素数１〜１３の飽和炭化水素基を表す。］

^{Wherein, X 11} represents a saturated hydrocarbon group having 1 to 15 carbon atoms.
X ¹² represents a saturated hydrocarbon group having 1 to 14 carbon atoms.
X ^{13 to} X ¹⁷ each independently represent a saturated hydrocarbon group having 1 to 13 carbon atoms. ]

X ^{11 to} X ¹⁷ are preferably —CH ₂ —, — (CH ₂ ) ₂ —, — (CH ₂ ) ₄ —, — (CH ₂ ) ₈ —, and — (CH ₂ ) ₁₂ —.

Examples of the divalent group represented by the formula (X1-B) include the following.

Examples of the divalent group represented by the formula (X1-C) include the following.

Examples of the divalent group represented by the formula (X1-D) include the following.

Examples of the divalent group represented by the formula (X1-E) include the following.

Examples of the divalent group represented by the formula (X1-F) include the following.

（式（ｂ）中、
Ｒ^４、Ｒ^５、Ｒ^６、Ｒ^７、Ｒ^８、Ｒ^９、Ｒ^１０、Ｒ^１１、Ｒ^１２及びＲ^１３は、互いに独立に、水素原子、水酸基、アルコキシ基、炭素数１〜１８の脂肪族炭化水素基を表すか、Ｒ^４とＲ^５、Ｒ^５とＲ^６、Ｒ^６とＲ^７、Ｒ^６とＲ^１３、Ｒ^７とＲ^８、Ｒ^８とＲ^１１、Ｒ^１１とＲ^１２又はＲ^１２とＲ^１３が一緒になって、環を形成してもよく、該環に含まれるメチレン基は、酸素原子又はカルボニル基で置き換わっていてもよい。但し、Ｒ^４、Ｒ^５、Ｒ^６、Ｒ^７、Ｒ^８、Ｒ^９、Ｒ^１０、Ｒ^１１、Ｒ^１２及びＲ^１３のいずれか１つはＸ^１との結合手を表す。
---（破線と下線との組み合わせ）は、単結合又は二重結合を表す。
ｎ１は、１又は２を表す。
ｎ２は、０又は１を表す。ｎ１＋ｎ２は２である。）
ｎ１が２であるとき、２つのＲ^７は、互いに同一でも異なってもよい。 R ³ is a group represented by the following formula (b).

(In the formula (b),
R ⁴ , R ⁵ , R ⁶ , R ⁷ , R ⁸ , R ⁹ , R ¹⁰ , R ¹¹ , R ¹² and R ¹³ are each independently a hydrogen atom, a hydroxyl group, an alkoxy group, a C 1-18 fat. Represents a group hydrocarbon group, R ⁴ and R ⁵ , R ⁵ and R ⁶ , R ⁶ and R ⁷ , R ⁶ and R ¹³ , R ⁷ and R ⁸ , R ⁸ and R ¹¹ , R ¹¹ and R ¹² or R ¹² and R ¹³ may be combined to form a ring, and the methylene group contained in the ring may be replaced with an oxygen atom or a carbonyl group. However, any one of R ⁴ , R ⁵ , R ⁶ , R ⁷ , R ⁸ , R ⁹ , R ¹⁰ , R ¹¹ , R ¹² and R ¹³ represents a bond to X ¹ .
--- (A combination of a broken line and an underline) represents a single bond or a double bond.
n1 represents 1 or 2.
n2 represents 0 or 1. n1 + n2 is 2. )
When n1 is 2, two R ⁷ may be the same or different from each other.

In the formula (b), R ⁴ and R ⁵ , R ⁵ and R ⁶ , R ⁶ and R ⁷ , R ⁶ and R ¹³ , R ⁷ and R ⁸ , R ⁸ and R ¹¹ , R ¹¹ and R ¹² or R Examples of the ring formed by combining ¹² and R ¹³ include alicyclic hydrocarbons, aromatic hydrocarbons, and heterocycles, with alicyclic hydrocarbons and aromatic hydrocarbons being preferred. However, when n1 is 2, two R ⁷ may be combined to form a ring.
Examples of the ring, in particular, a methylene group contained in an alicyclic hydrocarbon or aromatic hydrocarbon replaced with an oxygen atom or a carbonyl group include an oxanorbornane ring.

（式中、Ｒ^９及びＲ^１０は、上記と同義である。
Ｒ^１４、Ｒ^１５、Ｒ^１６及びＲ^１７は、互いに独立に、水素原子、水酸基、アルコキシ基、炭素数１〜１８の脂肪族炭化水素基を表す。但し、Ｒ^９、Ｒ^１０、Ｒ^１４〜Ｒ^１９のいずれか１つはＸ^１との結合手を表す。] Examples of the group represented by the formula (b) include the following groups.

(In the formula, R ⁹ and R ¹⁰ are as defined above.
R ¹⁴ , R ¹⁵ , R ¹⁶ and R ¹⁷ each independently represent a hydrogen atom, a hydroxyl group, an alkoxy group, or an aliphatic hydrocarbon group having 1 to 18 carbon atoms. ^However, any one of ^{R 9, R 10, R 14} ~R 19 represents a bond to ^{X 1.} ]

[式（ｃ）中、
Ｒ^１４、Ｒ^１５、Ｒ^１６及びＲ^１７は、互いに独立に、水素原子、水酸基、アルコキシ基、炭素数１〜１８の脂肪族炭化水素基を表す。但し、Ｒ^１４、Ｒ^１５、Ｒ^１６及びＲ^１７のいずれか１つはＸ^１との結合手を表す。] Among these, R ³ is more preferably the following formula (c) in which R ⁹ and R ¹⁰ are hydrogen atoms in the above formula (c ′).

[In the formula (c),
R ¹⁴ , R ¹⁵ , R ¹⁶ and R ¹⁷ each independently represent a hydrogen atom, a hydroxyl group, an alkoxy group, or an aliphatic hydrocarbon group having 1 to 18 carbon atoms. However, any one of R ¹⁴ , R ¹⁵ , R ¹⁶ and R ¹⁷ represents a bond with X ¹ . ]

（式中、＊はＸ^１との結合手を表す。）
なかでも、式（ｄ）で表される基が好ましい。 Examples of the group represented by the formula (b) include the following.

(In the formula, * represents a bond to ^{X 1.)}
Of these, a group represented by the formula (d) is preferable.

Examples of the salt represented by the formula (I) include the following salts.

Examples of Z ¹⁺ include onium cations such as sulfonium cations, iodonium cations, ammonium cations, benzothiazolium cations, and phosphonium cations. Among these, a sulfonium cation and an iodonium cation are preferable, and an arylsulfonium cation is more preferable.

Z ¹⁺ is preferably represented by any one of formulas (b2-1) to (b2-4).

In these formulas (b2-1) to (b2-4),
R ^{b4 to} R ^b6 each independently represent an aliphatic hydrocarbon group having 1 to 30 carbon atoms, a saturated cyclic hydrocarbon group having 3 to 18 carbon atoms, or an aromatic hydrocarbon group having 6 to 18 carbon atoms. The aliphatic hydrocarbon group may be substituted with a hydroxy group, an alkoxy group having 1 to 12 carbon atoms or an aromatic hydrocarbon group having 6 to 18 carbon atoms, and the saturated cyclic hydrocarbon group includes a halogen atom, It may be substituted with an acyl group having 2 to 4 carbon atoms or a glycidyloxy group, and the aromatic hydrocarbon group is a halogen atom, a hydroxy group, an aliphatic hydrocarbon group having 1 to 18 carbon atoms, or 3 to 3 carbon atoms. It may be substituted with an 18 saturated cyclic hydrocarbon group or an alkoxy group having 1 to 12 carbon atoms.

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 represent the integer of 0-5 independently of each other.

R ^b9 and R ^b10 each independently represent an aliphatic hydrocarbon group having 1 to 18 carbon atoms or a saturated cyclic hydrocarbon group having 3 to 18 carbon atoms.
R ^b11 represents a hydrogen atom, an aliphatic hydrocarbon group having 1 to 18 carbon atoms, a saturated cyclic hydrocarbon group having 3 to 18 carbon atoms, or an aromatic hydrocarbon group having 6 to 18 carbon atoms.
The aliphatic hydrocarbon group of R ^{b9 to} R ^b11 preferably has 1 to 12 carbon atoms, and the saturated cyclic hydrocarbon group preferably has 3 to 18 carbon atoms, more preferably 4 to 12 carbon atoms.
R ^b12 represents an aliphatic hydrocarbon group having 1 to 12 carbon atoms, a saturated cyclic hydrocarbon group having 3 to 18 carbon atoms, or an aromatic hydrocarbon group having 6 to 18 carbon atoms. The aromatic hydrocarbon group is an aliphatic hydrocarbon group having 1 to 12 carbon atoms, an alkoxy group having 1 to 12 carbon atoms, a saturated cyclic hydrocarbon group having 3 to 18 carbon atoms, or an alkylcarbonyloxy having 1 to 12 carbon atoms. It may be substituted with a group.
R ^b9 and R ^b10 , and R ^b11 and R ^b12 may be bonded together independently to form a 3- to 12-membered ring (preferably a 3- to 7-membered ring). The methylene group of these rings may be replaced with an oxygen atom, a sulfur atom or a carbonyl group.

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 ^b11 represents -S- or -O-.
o2, p2, s2, and t2 each independently represent an integer of 0 to 5.
q2 and r2 each independently represents an integer of 0 to 4.
u2 represents 0 or 1.
When any of o2 to t2 is 2, any of the plurality of R ^{b13 to} R ^b18 may be the same as or different from each other.

  Examples of the alkylcarbonyloxy group include a methylcarbonyloxy group, an ethylcarbonyloxy group, an n-propylcarbonyloxy group, an isopropylcarbonyloxy group, an n-butylcarbonyloxy group, a sec-butylcarbonyloxy group, a tert-butylcarbonyloxy group, Examples thereof include a pentylcarbonyloxy group, a hexylcarbonyloxy group, an octylcarbonyloxy group, and a 2-ethylhexylcarbonyloxy group.

Preferred aliphatic hydrocarbon groups are methyl, ethyl, n-propyl, isopropyl, n-butyl, sec-butyl, tert-butyl, pentyl, hexyl, octyl and 2-ethylhexyl. It is.
Preferred saturated cyclic hydrocarbon groups are cyclopropyl group, cyclobutyl group, cyclopentyl group, cyclohexyl group, cycloheptyl group, cyclodecyl group, 2-alkyl-2-adamantyl group, 1- (1-adamantyl) -1-alkyl group, And an isobornyl group.
Preferred aromatic hydrocarbon groups are phenyl group, 4-methylphenyl group, 4-ethylphenyl group, 4-tert-butylphenyl group, 4-cyclohexylphenyl group, 4-methoxyphenyl group, biphenylyl group, naphthyl group. It is.
Examples of the aliphatic hydrocarbon group (aralkyl group) whose substituent is an aromatic hydrocarbon group include a benzyl group.
Examples of the ring formed by R ^b9 and R ^b10 include a thiolane-1-ium ring (tetrahydrothiophenium ring), a thian-1-ium ring, and a 1,4-oxathian-4-ium ring.
^Examples of the ring formed by R ^b11 and R ^b12 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 preferable, the cation represented by the formula (b2-1-1) is more preferable, and the triphenylsulfonium cation (formula (b2) In (1-1), v2 = w2 = x2 = 0) is more preferable.

式（ｂ２−１−１）中、
Ｒ^b19〜Ｒ^b21は、互いに独立に、ハロゲン原子（より好ましくはフッ素原子）、ヒドロキシ基、炭素数１〜１８の脂肪族炭化水素基、炭素数３〜１８の飽和環状炭化水素基又は炭素数１〜１２のアルコキシ基を表す。
脂肪族炭化水素基は、好ましくは炭素数１〜１２であり、飽和環状炭化水素基は、好ましくは炭素数４〜１８である。
前記脂肪族炭化水素基は、ヒドロキシ基、炭素数１〜１２のアルコキシ基又は炭素数６〜１８の芳香族炭化水素基で置換されていてもよい。
前記飽和環状炭化水素基は、ハロゲン原子、炭素数２〜４のアシル基又はグリシジルオキシ基で置換されていてもよい。
ｖ２〜ｘ２は、互いに独立に、０〜５の整数（好ましくは０又は１）を表す。ｖ２〜ｘ２のいずれかが２以上のとき、それぞれ、複数のＲ^b19〜Ｒ^b21のいずれかは、互いに同一でも異なってもよい。
なかでも、Ｒ^b19〜Ｒ^b21は、互いに独立に、好ましくは、ハロゲン原子（より好ましくはフッ素原子）、ヒドロキシ基、炭素数１〜１２のアルキル基又は炭素数１〜１２のアルコキシ基である。

In formula (b2-1-1),
R ^{b19 to} R ^b21 are each independently a halogen atom (more preferably a fluorine atom), a hydroxy group, an aliphatic hydrocarbon group having 1 to 18 carbon atoms, a saturated cyclic hydrocarbon group having 3 to 18 carbon atoms, or a carbon number. 1 to 12 alkoxy groups are represented.
The aliphatic hydrocarbon group preferably has 1 to 12 carbon atoms, and the saturated cyclic hydrocarbon group preferably has 4 to 18 carbon atoms.
The aliphatic hydrocarbon group may be substituted with a hydroxy group, an alkoxy group having 1 to 12 carbon atoms, or an aromatic hydrocarbon group having 6 to 18 carbon atoms.
The saturated cyclic hydrocarbon group may be substituted with a halogen atom, an acyl group having 2 to 4 carbon atoms, or a glycidyloxy group.
v2 to x2 each independently represent an integer of 0 to 5 (preferably 0 or 1). When any one of v2 to x2 is 2 or more, any one of the plurality of R ^{b19 to} R ^b21 may be the same as or different from each other.
Among these, R ^{b19 to} R ^b21 are preferably each independently a halogen atom (more preferably a fluorine atom), a hydroxy group, an alkyl group having 1 to 12 carbon atoms, or an alkoxy group having 1 to 12 carbon atoms.

  Specific examples of the cation include those described in JP2010-204646A.

  The salt represented by the formula (I) is a combination of the above-mentioned anions and cations. Although the above-mentioned anion and cation can be combined arbitrarily, the salt represented below is preferable.

（式中、Ｒ^１、Ｒ^２、Ｒ^３及びＺ^１＋は、それぞれ上記と同義である。） Among the salts represented by the formula (I), a method for producing the salt represented by the formula (b1) is shown below.

(Wherein R ¹ , R ² , R ³ and Z ¹⁺ are as defined above.)

First, the salt represented by the formula (b1-c) is obtained by reacting the salt represented by the formula (b1-a) with the compound represented by the formula (b1-b).
The salt represented by the formula (b1-a) can be synthesized, for example, by the method described in JP2008-13551A.

式（ｂ１−ｄ）で表される化合物としては、以下で表される化合物等が挙げられる。

The salt represented by the formula (b1) can be obtained by reacting the obtained salt represented by the formula (b1-c) with the compound represented by the formula (b1-d) in a solvent. it can.
Examples of the solvent here include acetonitrile.

Examples of the compound represented by the formula (b1-d) include compounds represented by the following.

<Acid generator>
The acid generator of the present invention (hereinafter sometimes referred to as “acid generator (B)”) contains a salt (I). The salt (I) may be used alone or in combination of two or more.
Therefore, the acid generator (B) of the present invention may further contain a known salt other than the salt (I). Known salts other than the salt (I) include, for example, a salt composed of an organic cation contained in the salt (I) and a known anion (anion other than the sulfonate anion contained in the salt (I)) and the salt (I). And a salt composed of a sulfonate anion and a known cation (cation other than the organic cation contained in the salt (I)).

  As a salt used together with salt (I), what is represented by a formula (B1-1)-a formula (B1-17) is mentioned, for example. Among them, those containing a triphenylsulfonium cation are preferable. Formula (B1-1), Formula (B1-2), Formula (B1-6), Formula (B1-11), Formula (B1-12), Formula (B1- The salts represented by 13) and formula (B1-14) are more preferred.

  The content of the salt (I) is preferably 10 parts by mass or more (more preferably 30 parts by mass or more), preferably 100 parts by mass or less (more preferably 90 parts by mass or less) with respect to 100 parts by mass of the total amount of the acid generator. More preferably, it is 70 parts by mass or less.

<Resist composition>
The resist composition of the present invention contains an acid generator containing a salt represented by the formula (I) and a resin. As described above, the acid generator may contain a salt other than the salt represented by the formula (I) as the acid generator.
When the acid generator (B) is used in the resist composition, the total content of the salt (I) and the acid generator (B) is preferably 1 mass relative to 100 parts by mass of the resin (A) described later. Part or more (more preferably 3 parts by mass or more), preferably 40 parts by mass or less (more preferably 35 parts by mass or less, further preferably 30 parts by mass or less, particularly preferably 25 parts by mass or less).

<Resin (hereinafter sometimes referred to as “resin (A)”)>
The resin (A) is a resin having an acid labile group and insoluble or hardly soluble in an alkaline aqueous solution, and can be dissolved in an alkaline aqueous solution by the action of an acid. The resin (A) can be produced by polymerizing a monomer having an acid labile group (hereinafter sometimes referred to as “monomer having an acid labile group (a1)”). The resin becomes alkali-soluble by the action of acid. “Can be dissolved in an alkaline aqueous solution by the action of an acid” means “insoluble or hardly soluble in an alkaline aqueous solution before contact with an acid but becomes soluble in an alkaline aqueous solution after contact with an acid”. To do. As the monomer (a1) having an acid labile group, one type may be used alone, or two or more types may be used in combination.

<Monomer (a1) having an acid labile group>
The term “acid-labile group” means a group that cleaves a leaving group upon contact with an acid to form a hydrophilic group (for example, a hydroxy group or a carboxy group). Examples of the acid labile group include a group represented by the formula (1) and a group represented by the formula (2).

［式（１）中、Ｒ^a1〜Ｒ^a3は、互いに独立に、炭素数１〜８のアルキル基又は炭素数３〜２０の脂環式炭化水素基を表すか、Ｒ^a1及びＲ^a2は互いに結合して炭素数２〜２０の２価の炭化水素基を形成する。＊は結合手を表す。］

［式（２）中、Ｒ^a1'及びＲ^a2'は、互いに独立に、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^a3'が互いに結合して炭素数２〜２０の２価の炭化水素基を形成し、前記炭化水素基及び２価の基に含まれるメチレン基は、酸素原子又は硫黄原子で置き換わっていてもよい。

In Expression (1), R ^a1 ~R ^a3 are each independently either an alicyclic hydrocarbon group of the alkyl group or 3 to 20 carbon atoms having 1 to 8 carbon atoms, R ^a1 and R ^a2 are each Bonding to form a divalent hydrocarbon group having 2 to 20 carbon atoms. * Represents a bond. ]

[In Formula (2), R ^{a1 ′} and R ^{a2 ′} each independently represent a hydrogen atom or a hydrocarbon group having 1 to 12 carbon atoms, and R ^{a3 ′} represents a hydrocarbon group having 1 to 20 carbon atoms. R ^{a2 ′} and ^{a3 ′} are bonded to each other to form a divalent hydrocarbon group having 2 to 20 carbon atoms, and the methylene group contained in the hydrocarbon group and the divalent group is an oxygen atom or sulfur. It may be replaced with an atom.

In the formula (1), the alicyclic hydrocarbon group preferably has 1 to 16 carbon atoms.
In the case where R ^a1 and R ^a2 are bonded to each other to form a divalent hydrocarbon group, examples of the —C (R ^a1 ) (R ^a2 ) (R ^a3 ) group include the following groups. The carbon number of the divalent hydrocarbon group is preferably 3 to 12 carbon atoms.

Examples of the acid labile group represented by the formula (1) include a 1,1-dialkylalkoxycarbonyl group (in the formula (1), R ^{a1 to} R ^a3 are alkyl groups, preferably tert- Butoxycarbonyl group), 2-alkyl-2-adamantyloxycarbonyl group (in the formula (1), R ^a1 , R ^a2 and a carbon atom form an adamantyl group, and R ^a3 is an alkyl group) and 1- ( 1-adamantyl) -1-alkylalkoxycarbonyl group (in the formula (1), R ^a1 and R ^a2 are alkyl groups, and R ^a3 is an adamantyl group).

In the formula (2), preferably, at least one of R ^{a1 ′} and R ^{a2 ′} is a hydrogen atom.
Specific examples of the group represented by the formula (2) include the following groups.

  The monomer (a1) having an acid labile group is preferably a monomer having an acid labile group and a carbon-carbon double bond, more preferably a (meth) acryl having an acid labile group. Monomer.

  Of the (meth) acrylic monomers having an acid labile group, those having an alicyclic hydrocarbon group having 5 to 20 carbon atoms are preferred. If a resin obtained by polymerizing the monomer (a1) having a bulky structure such as an alicyclic hydrocarbon group is used, the resolution of the resist can be improved.

  As the (meth) acrylic monomer having an acid labile group and an alicyclic hydrocarbon group, a monomer represented by the formula (a1-1) or a monomer represented by the formula (a1-2) is preferably used. Can be mentioned. These may be used alone or in combination of two or more.

［式（ａ１−１）及び式（ａ１−２）中、
Ｌ^a1及びＬ^a2は、互いに独立に、−Ｏ−又は^＊−Ｏ−（ＣＨ₂）_k1−ＣＯ−Ｏ−を表し、ｋ１は１〜７の整数を表し、＊は−ＣＯ−との結合手を表す。
Ｒ^a4及びＲ^a5は、互いに独立に、水素原子又はメチル基を表す。
Ｒ^a6及びＲ^a7は、互いに独立に、炭素数１〜８のアルキル基又は炭素数３〜１０の脂環式炭化水素基を表す。
ｍ１は０〜１４の整数を表す。
ｎ１は０〜１０の整数を表す。
ｎ２は０又は１の整数を表す。］

[In Formula (a1-1) and Formula (a1-2),
L ^a1 and L ^a2 each independently represent —O— or ^* —O— (CH ₂ ) _k1 —CO—O—, k1 represents an integer of 1 to 7, and * represents a bond to —CO—. Represents a hand.
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 or an alicyclic hydrocarbon group having 3 to 10 carbon atoms.
m1 represents the integer of 0-14.
n1 represents an integer of 0 to 10.
n2 represents an integer of 0 or 1. ]

L ^a1 and L ^a2 are preferably —O— or ^* —O— (CH ₂ ) _k1 —CO—O—, more preferably —O—. k1 is preferably an integer of 1 to 4, more preferably 1.
R ^a4 and R ^a5 are preferably methyl groups.
The alkyl group for R ^a6 and R ^a7 preferably has 6 or less carbon atoms. The alicyclic hydrocarbon group preferably has 8 or less carbon atoms, more preferably 6 or less.
m1 is preferably an integer of 0 to 3, more preferably 0 or 1.
n1 is preferably an integer of 0 to 3, more preferably 0 or 1.

Examples of the monomer represented by the formula (a1-1) include monomers described in JP 2010-204646 A. Monomers represented by the following formulas (a1-1-1) to (a1-1-6) are preferred, and monomers represented by the following formulas (a1-1-1) to (a1-1-3) are more preferred. .

Examples of the monomer represented by the formula (a1-2) include 1-ethyl-1-cyclopentyl (meth) acrylate, 1-ethyl-1-cyclohexyl (meth) acrylate, 1-ethyl-1-cycloheptyl (meta ) Acrylate, 1-methyl-1-cyclopentyl (meth) acrylate, 1-isopropyl-1-cyclopentyl (meth) acrylate, and the like. Monomers represented by the following formulas (a1-2-1) to (a1-2-6) are preferred, and monomers represented by the following formulas (a1-2-3) to (a1-2-4) are more preferred. A monomer represented by the following formula (a1-2-3) is more preferable.

  The content of the structural unit derived from the monomer represented by the formula (a1-1) or the monomer represented by the formula (a1-2) in the resin is usually 10 to 95 mol% in all the units of the resin, Preferably it is 15-90 mol%, More preferably, it is 20-85 mol%.

<Monomer having acid-stable group>
The resin (A) is preferably a co-polymerization of a monomer (a1) having an acid labile group and a monomer having no acid labile group (hereinafter sometimes referred to as “acid stable monomer”). It is a coalescence. An acid stable monomer may be used individually by 1 type, and may use 2 or more types together.
When the resin (A) is a copolymer of a monomer (a1) having an acid labile group and an acid stable monomer, the structural units derived from the monomer (a1) having an acid labile group are all Preferably it is 10-80 mol% with respect to 100 mol% of structural units, More preferably, it is 20-60 mol%. Further, the content of the structural unit derived from the monomer having an adamantyl group (particularly the monomer (a1-1) having an acid labile group) is preferably relative to the monomer (a1) having an acid labile group. 15 mol% or more. When the ratio of the monomer having an adamantyl group is increased, the dry etching resistance of the resist is improved.

  As an acid stable monomer, Preferably, the monomer which has a hydroxyl group or a lactone ring is mentioned. Derived from an acid stable monomer having a hydroxy group (hereinafter referred to as “acid stable monomer having a hydroxy group (a2)”) or an acid stable monomer having a lactone ring (hereinafter referred to as “acid stable monomer having a lactone ring (a3)”) If a resin having a structural unit to be used is used, the resolution of the resist and the adhesion to the substrate can be improved.

<Acid-stable monomer having a hydroxy group (a2)>
When the resist composition is used for KrF excimer laser exposure (248 nm), high energy beam exposure such as electron beam or EUV light, the acid-stable monomer (a2) having a hydroxy group is preferably a phenolic hydroxyl group which is a hydroxystyrene. An acid stable monomer (a2-0) having When using short-wavelength ArF excimer laser exposure (193 nm) or the like, the acid-stable monomer (a2) having a hydroxy group is preferably an acid-stable monomer having a hydroxyadamantyl group represented by the formula (a2-1). use. The acid-stable monomer (a2) having a hydroxy group may be used alone or in combination of two or more.

  Examples of the monomer (a2-0) having a phenolic hydroxyl group include styrene monomers such as p- or m-hydroxystyrene represented by the formula (a2-0).

［式（ａ２−０）中、
Ｒ^a30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^a31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のアシル基、炭素数２〜４のアシルオキシ基、アクリロイル基又はメタクリロイル基を表す。
ｍａは０〜４の整数を表す。ｍａが２以上の整数である場合、複数のＲ^a31は同一であっても異なってもよい。］

[In the formula (a2-0),
R ^a30 represents a hydrogen atom, a halogen atom or an alkyl group having 1 to 6 carbon atoms which may have a halogen atom.
R ^a31 is 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 acyl group having 2 to 4 carbon atoms, an acyloxy group having 2 to 4 carbon atoms, an acryloyl group, or methacryloyl. Represents a group.
ma represents an integer of 0 to 4. When ma is an integer of 2 or more, the plurality of R ^a31 may be the same or different. ]

The alkyl group for R ^a30 is preferably an alkyl group having 1 to 4 carbon atoms, more preferably an alkyl group having 1 or 2 carbon atoms, and particularly preferably a methyl group.
The alkoxy group is preferably an alkoxy group having 1 to 4 carbon atoms, more preferably an alkoxy group having 1 or 2 carbon atoms, and particularly preferably a methoxy group.
ma is preferably 0 to 2, more preferably 0 or 1, and particularly preferably 0.

When obtaining a copolymer resin having a structural unit derived from a monomer having such a phenolic hydroxyl group, the corresponding (meth) acrylic acid ester monomer, acetoxystyrene, and styrene are radically polymerized and then deacetylated with an acid. Can be obtained.
As a monomer which has a phenolic hydroxyl group, the monomer described in Unexamined-Japanese-Patent No. 2010-204634 is mentioned, for example. Monomers represented by the following formulas (a2-0-1) and (a2-0-2) are preferred. When manufacturing resin (A), what protected the phenolic hydroxyl group in these with the suitable protective group can also be used.

  The content of the structural unit derived from the monomer represented by the formula (a2-0) in the resin is usually from 5 to 90 mol%, preferably from 10 to 85 mol%, more preferably, in all units of the resin. Is 15 to 80 mol%.

  Examples of the acid stable monomer having a hydroxyadamantyl group include a monomer represented by the formula (a2-1).

式（ａ２−１）中、
Ｌ^a3は、−Ｏ−又は^＊−Ｏ−（ＣＨ₂）_k2−ＣＯ−Ｏ−を表し、
ｋ２は１〜７の整数を表す。＊は−ＣＯ−との結合手を表す。
Ｒ^a14は、水素原子又はメチル基を表す。
Ｒ^a15及びＲ^a16は、互いに独立に、水素原子、メチル基又はヒドロキシ基を表す。
ｏ１は、０〜１０の整数を表す。

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 bond 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 hydroxy group.
o1 represents an integer of 0 to 10.

In the formula (a2-1), L ^a3 is preferably, -O -, - O- (CH 2) f1 -CO-O- and is (wherein f1 is an integer from 1 to 4), more preferably Is —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, more preferably 0 or 1.

As an acid stable monomer (a2-1) which has a hydroxyadamantyl group, the monomer described in Unexamined-Japanese-Patent No. 2010-204646 is mentioned, for example. Monomers represented by the following formulas (a2-1-1) to (a2-1-6) are preferred, and monomers represented by the following formulas (a2-1-1) to (a2-1-4) are more preferred. A monomer represented by the following formula (a2-1-1) or (a2-1-3) is more preferable.

  The content of the structural unit derived from the monomer represented by the formula (a2-1) in the resin is usually 3 to 40 mol%, preferably 5 to 35 mol%, more preferably, in all units of the resin. Is 5 to 30 mol%.

<Acid-stable monomer having a lactone ring (a3)>
The lactone ring possessed by the acid stable monomer (a3) may be, for example, a monocycle such as a β-propiolactone ring, γ-butyrolactone ring, or δ-valerolactone ring, and a monocyclic lactone ring and other rings The condensed ring may be used. Among these lactone rings, a γ-butyrolactone ring or a condensed ring of γ-butyrolactone ring and another ring is preferable.

  The acid-stable monomer (a3) having a lactone ring is preferably represented by the formula (a3-1), the formula (a3-2) or the formula (a3-3). These 1 type may be used independently and may use 2 or more types together.

式（ａ３−１）〜式（ａ３−３）中、
Ｌ^a4〜Ｌ^a6は、互いに独立に、−Ｏ−又は^＊−Ｏ−（ＣＨ₂）_k3−ＣＯ−Ｏ−を表す。
ｋ３は１〜７の整数を表す。＊は−ＣＯ−との結合手を表す。
Ｒ^a18〜Ｒ^a20は、互いに独立に、水素原子又はメチル基を表す。
Ｒ^a21は、炭素数１〜４のアルキル基を表す。
ｐ１は０〜５の整数を表す。
Ｒ^a22及びＲ^a23は、互いに独立に、カルボキシ基、シアノ基又は炭素数１〜４のアルキル基を表す。
ｑ１及びｒ１は、互いに独立に、０〜３の整数を表す。ｐ１、ｑ１又はｒ１が２以上のとき、それぞれ、複数のＲ^a21、Ｒ^a22又はＲ^a23は、互いに同一でも異なってもよい。

In formula (a3-1) to formula (a3-3),
L ^{a4 to} L ^a6 each independently represent —O— or ^* —O— (CH ₂ ) _k3 —CO—O—.
k3 represents an integer of 1 to 7. * Represents a bond with -CO-.
R ^{a18 to} R ^a20 each independently represent a hydrogen atom or a methyl group.
R ^a21 represents an alkyl group having 1 to 4 carbon atoms.
p1 represents an integer of 0 to 5.
R ^a22 and R ^a23 each independently represent a carboxy group, a cyano group, or an alkyl group having 1 to 4 carbon atoms.
q1 and r1 each independently represent an integer of 0 to 3. When p1, q1 or r1 is 2 or more, a plurality of R ^a21 , R ^a22 or R ^a23 may be the same as or different from each other.

In the formula (a3-1) to the formula (a3-3), examples of L ^{a4 to} L ^a6 include those described for L ^a3 .
L ^{a4 to} L ^a6 are preferably each independently —O— or ^* —O— (CH ₂ ) _k3 —CO—O—, more preferably —O—. k3 is preferably an integer of 1 to 4, more preferably 1.
R ^{a18 to} R ^a21 are preferably methyl groups.
R ^a22 and R ^a23 are independently of each other preferably a carboxy group, a cyano group or a methyl group.
p1 to r1 are independently from each other, preferably 0 to 2, more preferably 0 or 1.

Examples of the acid-stable monomer (a3) having a lactone ring include monomers described in JP 2010-204646 A. In the following formulas (a3-1-1) to (a3-1-4), (a3-2-1) to (a3-2-4), (a3-3-1) to (a3-3-4) Monomers represented by the following formulas (a3-1-1) to (a3-1-2) and (a3-2-3) to (a3-2-4) are more preferred, A monomer represented by formula (a3-1-1) or (a3-2-3) is more preferable.

  The content of the structural unit derived from the acid-stable monomer (a3) having a lactone ring in the resin is usually 5 to 50 mol%, preferably 10 to 45 mol%, more preferably, in all units of the resin. 15 to 40 mol%.

<Other monomer (a4)>
The resin may have a structural unit derived from another known monomer (a4) other than the above-mentioned monomers.

  Preferably, the resin (A) polymerizes at least the monomer (a1) having an acid labile group, the acid stable monomer (a2) having a hydroxy group, and / or the acid stable monomer (a3) having a lactone ring. Copolymer. In the copolymer, the monomer (a1) having an acid labile group is more preferably at least one of a monomer (a1-1) having an adamantyl group and a monomer (a1-2) having a cyclohexyl group. (More preferably, the monomer (a1-1) having an adamantyl group), and the acid-stable monomer (a2) having a hydroxy group is preferably an acid-stable monomer (a2-1) having a hydroxyadamantyl group, More preferably, the acid-stable monomer (a3) having a γ-butyrolactone ring is an acid-stable monomer (a3-1) and an acid-stable monomer (a3-2) having a condensed ring of a γ-butyrolactone ring and a norbornane ring. At least one. Resin (A) can be manufactured by a well-known polymerization method (for example, radical polymerization method).

The weight average molecular weight of the resin (A) is preferably 2,500 or more (more preferably 3,000 or more) and 50,000 or less (more preferably 30,000 or less). In addition, the weight average molecular weight here is calculated | required as a conversion value of a standard polystyrene reference | standard by gel permeation chromatography analysis, and the detailed analysis conditions of this analysis are explained in full detail in the Example of this application.
The content of the resin (A) is preferably 80% by mass or more in the solid content of the composition. The “solid content in the composition” means the total of resist composition components excluding the solvent (E) described later. The solid content in the composition and the content of the resin (A) relative thereto can be measured, for example, by a known analysis means such as liquid chromatography or gas chromatography.

<Basic compound (hereinafter sometimes referred to as “basic compound (C)”)>
The resist composition of the present invention preferably contains a basic compound (C). The basic compound (C) acts as a quencher.
The basic compound (C) is preferably a basic nitrogen-containing organic compound, and examples thereof include amines and ammonium salts. Examples of amines include aliphatic amines and aromatic amines. Aliphatic amines include primary amines, secondary amines and tertiary amines. The basic compound (C) is preferably a compound represented by the formula (C1) to a compound represented by the formula (C8), more preferably a compound represented by the formula (C1-1). It is done.

［式（Ｃ１）中、Ｒ^c1、Ｒ^c2及びＲ^c3は、互いに独立に、水素原子、炭素数１〜６のアルキル基、炭素数５〜１０の脂環式炭化水素基又は炭素数６〜１０の芳香族炭化水素基を表し、該アルキル基及び該脂環式炭化水素基に含まれる水素原子は、ヒドロキシ基、アミノ基又は炭素数１〜６のアルコ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、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５〜１０の脂環式炭化水素又は炭素数６〜１０の芳香族炭化水素基で置換されていてもよい。］

[In formula (C1), R ^c1 , R ^c2 and R ^c3 are each independently a hydrogen atom, an alkyl group having 1 to 6 carbon atoms, an alicyclic hydrocarbon group having 5 to 10 carbon atoms, or 6 to 6 carbon atoms. 10 represents an aromatic hydrocarbon group, and the hydrogen atom contained in the alkyl group and the alicyclic hydrocarbon group may be substituted with a hydroxy group, an amino group or an alkoxy group having 1 to 6 carbon atoms, The hydrogen atom contained in the aromatic hydrocarbon group is an alkyl group having 1 to 6 carbon atoms, an alkoxy group having 1 to 6 carbon atoms, an alicyclic hydrocarbon having 5 to 10 carbon atoms, or an aromatic group having 6 to 10 carbon atoms. It may be substituted with a group hydrocarbon group. ]

［式（Ｃ１−１）中、Ｒ^c2及びＲ^c3は、上記と同じ意味を表す。
Ｒ^c4は、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５〜１０の脂環式炭化水素又は炭素数６〜１０の芳香族炭化水素基を表す。
ｍ３は０〜３の整数を表し、ｍ３が２以上のとき、複数のＲ^c4は、互いに同一でも異なってもよい。］

[In Formula (C1-1), R ^c2 and R ^c3 represent the same meaning as described above.
R ^c4 represents an alkyl group having 1 to 6 carbon atoms, an alkoxy group having 1 to 6 carbon atoms, an alicyclic hydrocarbon having 5 to 10 carbon atoms, or an aromatic hydrocarbon group having 6 to 10 carbon atoms.
m3 represents an integer of 0 to 3, and when m3 is 2 or more, a plurality of R ^{c4 s} may be the same as or different from each other. ]

［式（Ｃ２）、式（Ｃ３）及び式（Ｃ４）中、
Ｒ^c5、Ｒ^c6、Ｒ^c7及びＲ^c8は、互いに独立に、Ｒ^c1と同じ意味を表す。
Ｒ^c9は、炭素数１〜６のアルキル基、炭素数３〜６の脂環式炭化水素基又は炭素数２〜６のアルカノイル基を表す。
ｎ３は０〜８の整数を表し、ｎ３が２以上のとき、複数のＲ^c9は、互いに同一でも異なってもよい。］
アルカノイル基としては、アセチル基、２−メチルアセチル基、２，２−ジメチルアセチル基、プロピオニル基、ブチリル基、イソブチリル基、ペンタノイル基、２，２−ジメチルプロピオニル基等が挙げられる。

[In Formula (C2), Formula (C3) and Formula (C4),
R ^c5 , R ^c6 , R ^c7 and R ^c8 represent the same meaning as R ^c1 independently of each other.
R ^c9 represents an alkyl group having 1 to 6 carbon atoms, an alicyclic hydrocarbon group having 3 to 6 carbon atoms, or an alkanoyl group having 2 to 6 carbon atoms.
n3 represents an integer of 0 to 8, and when n3 is 2 or more, the plurality of R ^c9 may be the same as or different from each other. ]
Examples of the alkanoyl group include acetyl group, 2-methylacetyl group, 2,2-dimethylacetyl group, propionyl group, butyryl group, isobutyryl group, pentanoyl group, and 2,2-dimethylpropionyl group.

［式（Ｃ５）及び式（Ｃ６）中、
Ｒ^c10、Ｒ^c11、Ｒ^c12、Ｒ^c13及びＲ^c16は、互いに独立に、Ｒ^c1と同じ意味を表す。
Ｒ^c14、Ｒ^c15及びＲ^c17は、互いに独立に、Ｒ^c4と同じ意味を表す。
ｏ３及びｐ３は、互いに独立に、０〜３の整数を表し、ｏ３又はｐ３が２以上であるとき、それぞれ、複数のＲ^c14及びＲ^c15は互いに同一でも異なってもよい。
Ｌ^c1は、炭素数１〜６のアルカンジイル基、−ＣＯ−、−Ｃ（＝ＮＨ）−、−Ｓ−又はこれらを組合せた２価の基を表す。］

[In Formula (C5) and Formula (C6),
R ^c10 , R ^c11 , R ^c12 , R ^c13 and R ^c16 independently represent the same meaning as R ^c1 .
R ^c14 , R ^c15 and R ^c17 represent the same meaning as R ^c4 independently of each other.
o3 and p3 each independently represent an integer of 0 to 3, and when o3 or p3 is 2 or more, the plurality of R ^c14 and R ^c15 may be the same as or different from each other.
L ^c1 represents an alkanediyl group having 1 to 6 carbon atoms, —CO—, —C (═NH) —, —S—, or a divalent group obtained by combining these. ]

［式（Ｃ７）及び式（Ｃ８）中、
Ｒ^c18、Ｒ^c19及びＲ^c20は、互いに独立に、Ｒ^c4と同じ意味を表す。
ｑ３、ｒ３及びｓ３は、互いに独立に、０〜３の整数を表し、ｑ３、ｒ３及びｓ３が２以上であるとき、それぞれ、複数のＲ^c18、Ｒ^c19及びＲ^c20は互いに同一でも異なってもよい。
Ｌ^c2は、単結合又は炭素数１〜６のアルカンジイル基、−ＣＯ−、−Ｃ（＝ＮＨ）−、−Ｓ−又はこれらを組合せた２価の基を表す。］

[In Formula (C7) and Formula (C8),
R ^c18, R ^c19 and R ^{c 20,} independently of each other, represent the same meaning as R ^c4.
q3, r3 and s3, independently of each other, represent an integer of 0 to 3, q3, when r3 and s3 is 2 or more, respectively, or different from the plurality of R ^c18, R ^c19 and R ^{c 20} identical to one another Good.
L ^c2 represents a single bond or an alkanediyl group having 1 to 6 carbon atoms, —CO—, —C (═NH) —, —S—, or a divalent group obtained by combining these. ]

  Examples of the compound represented by the formula (C1) 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, tributylamine, tri Pentylamine, trihexylamine, triheptylamine, trioctylamine, trinonylamine, tridecylamine, methyldibutylamine, methyldipentylamine, methyl Hexylamine, methyldicyclohexylamine, methyldiheptylamine, methyldioctylamine, methyldinonylamine, methyldidecylamine, ethyldibutylamine, ethyldipentylamine, ethyldihexylamine, ethyldiheptylamine, ethyldioctylamine, ethyldinonyl Amine, ethyldidecylamine, dicyclohexylmethylamine, tris [2- (2-methoxyethoxy) ethyl] amine, triisopropanolamine ethylenediamine, tetramethylenediamine, hexamethylenediamine, 4,4′-diamino-1,2-diphenyl Examples include ethane, 4,4′-diamino-3,3′-dimethyldiphenylmethane, 4,4′-diamino-3,3′-diethyldiphenylmethane, and preferably diisopropyl Ruanirin. Particularly preferred include 2,6-diisopropylaniline.

Examples of the compound represented by the formula (C2) include piperazine.
Examples of the compound represented by the formula (C3) include morpholine.
Examples of the compound represented by the formula (C4) include piperidine and hindered amine compounds having a piperidine skeleton described in JP-A No. 11-52575.
Examples of the compound represented by the formula (C5) include 2,2′-methylenebisaniline.
Examples of the compound represented by the formula (C6) include imidazole and 4-methylimidazole.
Examples of the compound represented by the formula (C7) include pyridine and 4-methylpyridine.
Examples of the compound represented by the formula (C8) include 1,2-di (2-pyridyl) ethane, 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′-dipiconylamine, bipyridine and the like.

  As ammonium salts, tetramethylammonium hydroxide, tetraisopropylammonium hydroxide, tetrabutylammonium hydroxide, tetrahexylammonium hydroxide, tetraoctylammonium hydroxide, phenyltrimethylammonium hydroxide, 3- (trifluoromethyl) phenyltrimethyl Ammonium hydroxide, tetra-n-butylammonium salicylate, choline and the like can be mentioned.

  The content of the basic compound (C) is preferably about 0.01 to 5% by mass, more preferably about 0.01 to 3% by mass, and particularly preferably based on the solid content of the resist composition. It is about 0.01-1 mass%.

<Solvent (sometimes referred to as "solvent (E)")
The resist composition of the present invention may contain a solvent (E). The content of the solvent (E) is, for example, 90% by mass or more in the resist composition, preferably 92% by mass or more, more preferably 94% by mass or more, for example 99.9% by mass or less, preferably 99% by mass or less. It is.
The content rate of a solvent (E) can be measured by well-known analysis means, such as a liquid chromatography or a gas chromatography, for example.

  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; ethyl lactate, butyl acetate, amyl acetate and And esters such as ethyl pyruvate; ketones such as acetone, methyl isobutyl ketone, 2-heptanone and cyclohexanone; cyclic esters such as γ-butyrolactone; A solvent (E) may be used individually by 1 type, and may use 2 or more types together.

<Other components (hereinafter sometimes referred to as “other components (F)”)>
The resist composition of this invention may contain the other component (F) as needed. The component (F) is not particularly limited, and additives known in the resist field, for example, sensitizers, dissolution inhibitors, surfactants, stabilizers, dyes and the like can be used.

<Preparation of resist composition>
The resist composition is prepared by mixing resin (A), acid generator (B) and solvent (E) or resin (A), acid generator (B), basic compound (C) and solvent (E). Can be prepared. The mixing order is arbitrary and is not particularly limited. The temperature at the time of mixing can select an appropriate temperature range from the range of 10-40 degreeC according to the kind etc. of resin, the solubility with respect to solvent (E), such as resin. An appropriate 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 resin (A), the acid generator (B), the solvent (E), and the basic compound (C) or the component (F) used as necessary at a preferable content, the pore diameter is about 0.2 μm. It is preferable to perform filtration or the like using this filter.

<Method for producing resist pattern>
The method for producing a resist pattern of the present invention comprises:
(1) The process of apply | coating the resist composition of this invention on a board | substrate,
(2) a step of removing the solvent from the composition after coating to form a composition layer;
(3) a step of exposing the composition layer using an exposure machine;
(4) A step of heating the composition layer after exposure,
(5) The process which develops the composition layer after a heating using a image development apparatus is included.

  Application of the resist composition onto the substrate can be performed by a commonly used apparatus such as a spin coater.

The composition after application is dried to remove the solvent. The removal of the solvent can be performed, for example, by evaporating the solvent using a heating device such as a hot plate or using a decompression device. The solvent is removed and a composition layer can be formed. As for the temperature in this case, about 50-200 degreeC is illustrated, for example. The pressure is exemplified by about 1 to 1.0 × 10 ⁵ Pa.

The obtained composition layer is exposed using an exposure machine. The exposure machine may be an immersion exposure machine. At this time, exposure is usually performed through a mask corresponding to a required pattern. The exposure light source emits ultraviolet laser light such as KrF excimer laser (wavelength 248 nm), ArF excimer laser (wavelength 193 nm), F ₂ laser (wavelength 157 nm), solid-state laser light source (YAG or semiconductor laser, etc.) Various types of laser beam can be used, such as those that convert the wavelength of the laser beam from) to radiate a harmonic laser beam in the far ultraviolet region or the vacuum ultraviolet region.

The composition layer after the exposure is subjected to heat treatment for promoting the deprotection group reaction. As heating temperature, it is about 50-200 degreeC normally, Preferably it is about 70-150 degreeC.
The heated composition layer is usually developed using an alkali developer using a developing device.
The alkaline developer used here may be various alkaline aqueous solutions used in this field. Examples thereof include an aqueous solution of tetramethylammonium hydroxide and (2-hydroxyethyl) trimethylammonium hydroxide (commonly called choline).
After development, it is preferable to rinse with ultrapure water to remove water 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 EB, or a resist composition for EUV exposure machines.

Hereinafter, the present invention will be described in detail by way of examples.
In Examples and Comparative Examples, “%” and “part” representing content and use amount are based on mass unless otherwise specified.
The weight average molecular weight is a value obtained by gel permeation chromatography (HLC-8120GPC, manufactured by Tosoh Corporation, three columns are “TSKgel Multipore HXL-M”, and the solvent is tetrahydrofuran) using polystyrene as a standard product.
Column: TSKgel Multipore H _XL -M x 3 + guardcolumn (manufactured by 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 (manufactured by Tosoh Corporation)

  The structure of the compound was confirmed by measuring the molecular peak using mass spectrometry (LC is model 1100 manufactured by Agilent, and MASS is LC / MSD manufactured by Agilent). In the following examples, the value of this molecular peak is indicated by “MASS”.

Example 1: Synthesis of a salt represented by the formula (I1)

The salt represented by the formula (I1-a) was synthesized by the method described in JP 2008-127367 A.
5.00 parts of a salt represented by the formula (I1-a) and 25 parts of chloroform are charged, stirred at 30 ° C. for 30 minutes, and 1.83 parts of a compound represented by the formula (I1-b) are charged at 60 ° C. Was stirred for 1 hour to obtain a solution containing the compound represented by the formula (I1-c).

5.00 parts of the compound represented by the formula (I1-e), 1.33 parts of the catalyst K ₂ CO ₃ and 12 parts of DMF were charged, stirred at 40 ° C. for 20 minutes, and the compound represented by the formula (I1-d) 2.00 parts was added and stirred at 60 ° C. for 2 hours. After washing with water, MgSO ₃ was added to the obtained organic layer, stirred for 30 minutes, and filtered. The filtrate was concentrated and the supernatant was removed. Propylene glycol monoether acetate was added to the resulting concentrate and stirred. The supernatant was removed to obtain a compound represented by the formula (I1-f).

  To the obtained solution containing the compound represented by the formula (I1-c), 1.51 parts of the compound represented by the formula (I1-f) was charged and stirred at 23 ° C. for 3 hours. To the resulting reaction mass, 10 parts of ion-exchanged water was added, and stirring and liquid separation were performed. Water washing was performed 5 times. The obtained organic layer was charged with 1.00 parts of activated carbon, stirred at 23 ° C. for 30 minutes, and filtered. The filtrate was concentrated, and 20 parts of tert-butyl methyl ether was added to the resulting concentrate and stirred, and the supernatant was removed. The resulting residue was dissolved in acetonitrile and concentrated. Thereafter, 20 parts of tert-butyl methyl ether was added to the resulting concentrate and stirred, and the supernatant was removed. The obtained residue was dissolved in chloroform and concentrated to obtain 0.84 parts of the salt represented by the formula (I1).

MS (ESI (+) Spectrum): M ⁺ 263.1
MS (ESI (-) Spectrum): M ^- 463.0

Synthesis Example 1 (Synthesis of Resin A1)
10.54 parts of 2-methyl-2-adamantyl methacrylate, 14.60 parts of p-acetoxystyrene and 3.55 parts of 3-hydroxy-1-adamantyl methacrylate were mixed, and 1,4-dioxane 47 was added to this mixture. 0.09 part was added to make a solution. This solution was heated to about 87 ° C., 2.96 parts of azobisisobutyronitrile was added, and the mixture was kept at the same temperature for 6 hours. After cooling, the reaction solution was poured into a mixed solution of 285.67 parts of methanol and 122.43 parts of ion-exchanged water to precipitate a polymer, and the precipitated polymer was filtered.
The total amount of the polymer obtained and 2.93 parts of 4-dimethylaminopyridine were added to methanol of the same mass as the polymer and heated to reflux for 15 hours. The reaction mixture was cooled, neutralized by adding 2.16 parts of glacial acetic acid, and poured into a large amount of water to precipitate. The precipitated polymer was filtered off. The obtained polymer was dissolved in acetone, poured into a large amount of water, and the polymer was precipitated and purified by repeating the operation three times, and the weight average molecular weight was about 3.7 × 10 ³ . 28.15 parts of resin were obtained. This is designated as resin A1.

Synthesis Example 2 (Synthesis of Resin A2)
14.06 parts of 2-methyl-2-adamantyl methacrylate, 27.26 parts of p-ethoxyethylstyrene and 4.73 parts of 3-hydroxy-1-adamantyl methacrylate were mixed, and 1,4-dioxane was added to this mixture. 62.78 parts was added to make a solution. This solution was heated to about 87 ° C., 2.96 parts of azobisisobutyronitrile was added, and the mixture was kept at the same temperature for 6 hours. After cooling, the reaction solution was poured into a mixed solution of 389.89 parts of methanol and 163.24 parts of ion-exchanged water to precipitate a polymer, and the precipitated polymer was filtered.
The total amount of the obtained polymer and 4.10 parts of 4-dimethylaminopyridine were added to methanol of the same mass as the polymer and heated to reflux for 15 hours. The reaction mixture was cooled, neutralized by adding 2.16 parts of glacial acetic acid, and poured into a large amount of water to precipitate. The precipitated polymer was filtered off. The obtained polymer is dissolved in acetone, poured into a large amount of water, precipitated, filtered, and purified by repeating the operation three times, and dried to give a weight average molecular weight of 4.8 × 10 ³ 32.15 parts of coalescence were obtained. This is called Resin A2.

Examples 1-4 and Reference Example 1
The components shown in Table 1 below were mixed and dissolved, and further filtered through a fluororesin filter having a pore size of 0.2 μm to prepare a resist composition.
<Resin>
Resin A1 and Resin A2 obtained in Synthesis Examples 1 and 2
<Acid generator>
Acid generator I1: salt represented by formula (I-1) Acid generator B1

<Basic compound>
Basic Compound C1: 2,6-Diisopropylaniline Basic Compound C2: Tetra-n-butylammonium salicylate <Solvent (E)>
D1:
Propylene glycol monomethyl ether acetate 400.0 parts Propylene glycol monomethyl ether 150.0 parts γ-butyrolactone 5.0 parts

(Evaluation as a resist composition for electron beams)
The silicon wafer was processed at 90 ° C. for 60 seconds using hexamethyldisilazane on a direct hot plate. Thereafter, the resist composition shown in Table 1 was spin-coated so that the film thickness after drying was 0.04 μm. After applying the resist composition, it was pre-baked (PB) at a temperature shown in Table 1 for 60 seconds on a direct hot plate. Each wafer obtained was exposed to a line-and-space pattern using an electron beam drawing machine ["HL-800D 50 keV" manufactured by Hitachi, Ltd., with the exposure amount being changed stepwise.
After the exposure, post-exposure baking (PEB) was performed on the hot plate at the temperature shown in Table 1 for 60 seconds, and paddle development was further performed with a 2.38 wt% tetramethylammonium hydroxide aqueous solution for 60 seconds.
In each resist film, an exposure amount at which a 50 nm-wide line and space pattern is 1: 1 was defined as an effective sensitivity.

Resolution evaluation: In the effective sensitivity, the resist pattern is observed with a scanning electron microscope, the resolution of 50 nm is ○, the resolution is not 50 nm, or the top is round, The case where there was skirting or pattern collapse was observed was marked with x.
These results are shown in Table 2.

  According to the salt of the present invention, a pattern having excellent resolution can be obtained using a resist composition containing this salt.

Claims (9)

A salt represented by the formula (I).

[In the formula (I),
R ¹ and R ² each independently represent a fluorine atom or a C 1-6 perfluoroalkyl group.
X ¹ represents a divalent saturated hydrocarbon group having 1 to 17 carbon atoms, a hydrogen atom contained in the divalent saturated hydrocarbon group may be substituted with a fluorine atom, and the divalent saturated The methylene group contained in the hydrocarbon group may be replaced with an oxygen atom or a carbonyl group.
R ³ is a group represented by the following formula (b).

(In the formula (b),
R ⁴ , R ⁵ , R ⁶ , R ⁷ , R ⁸ , R ⁹ , R ¹⁰ , R ¹¹ , R ¹² and R ¹³ are each independently a hydrogen atom, a hydroxyl group, an alkoxy group, a C 1-18 fat. Represents a group hydrocarbon group, R ⁴ and R ⁵ , R ⁵ and R ⁶ , R ⁶ and R ⁷ , R ⁶ and R ¹³ , R ⁷ and R ⁸ , R ⁸ and R ¹¹ , R ¹¹ and R ¹² or R ¹² and R ¹³ may be combined to form a ring, and the methylene group contained in the ring may be replaced with an oxygen atom or a carbonyl group. However, any one of R ⁴ , R ⁵ , R ⁶ , R ⁷ , R ⁸ , R ⁹ , R ¹⁰ , R ¹¹ , R ¹² and R ¹³ represents a bond to X ¹ .
--- represents a single bond or a double bond.
n1 represents 1 or 2.
n2 represents 0 or 1. n1 + n2 is 2. )
Z ¹⁺ represents an organic counter ion. ] The salt according to claim 1, wherein the group represented by the formula (b) is a group represented by the formula (c).

[In the formula (c),
R ¹⁴ , R ¹⁵ , R ¹⁶ and R ¹⁷ each independently represent a hydrogen atom, a hydroxyl group, an alkoxy group, or an aliphatic hydrocarbon group having 1 to 18 carbon atoms. However, any one of R ¹⁴ , R ¹⁵ , R ¹⁶ and R ¹⁷ represents a bond with X ¹ . ] The salt according to claim 2, wherein the formula (c) is a group represented by the following formula (d).

Wherein (d), * represents a bond to ^{X 1.} ] The salt according to any one of claims 1 to 3, wherein Z ¹⁺ is a triarylsulfonium cation.   The acid generator containing the salt in any one of Claims 1-4.   A resist composition comprising the acid generator according to claim 5, a resin and a solvent.   The resist composition according to claim 6, wherein the resin is a resin having an acid labile group, insoluble or hardly soluble in an aqueous alkali solution, and capable of acting on an acid and dissolving in the aqueous alkali solution.   Furthermore, the resist composition of Claim 6 or 7 containing a basic compound. (1) The process of apply | coating the resist composition in any one of Claims 6-8 on a board | substrate,
(2) a step of removing the solvent from the composition after coating to form a composition layer;
(3) a step of exposing the composition layer using an exposure machine;
(4) A step of heating the composition layer after exposure,
(5) a step of developing the composition layer after heating;
A method for producing a resist pattern including: