Salt, acid generator, resist composition and method for producing resist pattern

1 . A salt represented by formula (I):

wherein, in formula (I),

Q 1 and Q 2 each independently represent a hydrogen atom, a fluorine atom, an alkyl group having 1 to 6 carbon atoms, or a perfluoroalkyl group having 1 to 6 carbon atoms,

R 1 and R 2 each independently represent a hydrogen atom, a fluorine atom, an alkyl group having 1 to 6 carbon atoms, or a perfluoroalkyl group having 1 to 6 carbon atoms,

z represents an integer of 0 to 6, and when z is 2 or more, a plurality of R 1 and R 2 may be the same or different from each other,

X 1 represents *—CO—O—, *—O—CO—, *—O—CO—O— or *—O—, and * represents a bonding site to C(R 1 )(R 2 ) or C(Q 1 )(Q 2 ),

L 1 and L 2 each independently represent a single bond or an aliphatic hydrocarbon group having 1 to 12 carbon atoms, and —CH 2 — included in the aliphatic hydrocarbon group may be replaced by —O— or —CO—,

A 1 represents a ring represented by the following, —CH 2 — included in the ring may be replaced by —CO—, a hydrogen atom included in the ring may be substituted with an alkyl group having 1 to 6 carbon atoms or a hydroxy group, and one of two * represents a bonding site to L 1 and the other one represents a bonding site to L 2 ,

Ar 1 represents an aromatic hydrocarbon group having 6 to 10 carbon atoms, or a heterocyclic aromatic hydrocarbon group having 4 to 9 carbon atoms,

R 3 represents *—O—R 10 , *—O—CO—R 10 , *—O—CO—O—R 10 or *—O-L 10 -CO—O—R 10 , and * represents a bonding site to Ar 1 ,

L 10 represents an alkanediyl group having 1 to 6 carbon atoms,

R 10 represents an acid-labile group,

R 4 represents a halogen atom, a haloalkyl group having 1 to 12 carbon atoms, or a hydrocarbon group having 1 to 18 carbon atoms, the hydrocarbon group may have a substituent, and —CH 2 — included in the haloalkyl group and the hydrocarbon group may be replaced by —O—, —CO—, —S— or —SO 2 —,

m4 represents an integer of 0 to 8, and when m4 is 2 or more, a plurality of R 4 may be the same or different from each other, and

Z + represents an organic cation.

2 . The salt according to claim 1 , wherein Ar 1 is a group derived from a benzene ring, a naphthalene ring, a furan ring or a thiophene ring.

3 . The salt according to claim 1 , wherein X 1 is *—CO—O— or *—O—CO—.

4 . The salt according to claim 1 , wherein L 1 and L 2 are each independently a single bond or an alkanediyl group having 1 to 8 carbon atoms and —CH 2 — included in the alkanediyl group may be replaced by —O— or —CO—.

5 . The salt according to claim 1 , wherein m4 is an integer of 1 or more, and at least one of R 4 is an iodine atom.

6 . The salt according to claim 1 , wherein the acid-labile group as for R 10 is a group represented by formula (Ia) or a group represented by formula (2a):

wherein, in formula (Ia), R aa1 , R aa2 and R aa3 each independently represent an alkyl group having 1 to 8 carbon atoms, an alkenyl group having 2 to 8 carbon atoms, an alicyclic hydrocarbon group having 3 to 20 carbon atoms, an aromatic hydrocarbon group having 6 to 18 carbon atoms, or groups obtained by combining these groups, or R aa1 and R aa2 may be bonded to each other to form an alicyclic hydrocarbon group having 3 to 20 carbon atoms together with carbon atoms to which R aa1 and R aa2 are bonded, and

* represents a bonding site:

wherein, in formula (2a), R aa1′ and R aa2′ each independently represent a hydrogen atom or a hydrocarbon group having 1 to 12 carbon atoms, R aa3′ represents a hydrocarbon group having 1 to 20 carbon atoms, or R aa2′ and R aa3′ may be bonded to each other to form a heterocyclic group having 3 to 20 carbon atoms together with —C—X a — to which R aa2′ and R aa3′ are bonded, and —CH 2 — included in the hydrocarbon group and the heterocyclic group may be replaced by —O— or —S—,

X a represents an oxygen atom or a sulfur atom, and

* represents a bonding site.

7 . An acid generator comprising the salt according to claim 1 .

8 . A resist composition comprising the acid generator according to claim 7 .

9 . The resist composition according to claim 8 , further comprising a resin including a structural unit having an acid-labile group, wherein

the structural unit having an acid-labile group includes at least one selected from the group consisting of a structural unit represented by formula (a1-0), a structural unit represented by formula (a1-1) and a structural unit represented by formula (a1-2):

wherein, 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—, k1 represents an integer of 1 to 7, and * represents a bonding site to —CO—,

R a01 , R a4 and R a5 each independently represent a hydrogen atom, a halogen atom, or an alkyl group having 1 to 6 carbon atoms which may have a halogen atom,

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, an aromatic hydrocarbon group having 6 to 18 carbon atoms, or groups obtained by combining these groups,

R a6 and R a7 each independently represent an alkyl group having 1 to 8 carbon atoms, an alkenyl group having 2 to 8 carbon atoms, an alicyclic hydrocarbon group having 3 to 18 carbon atoms, an aromatic hydrocarbon group having 6 to 18 carbon atoms, or groups formed by combining these groups,

m1′ represents an integer of 0 to 14,

n1 represents an integer of 0 to 10, and

n1′ represents an integer of 0 to 3.

10 . The resist composition according to claim 8 , further comprising a resin including a structural unit having an acid-labile group, wherein

the resin including a structural unit having an acid-labile group further incudes a structural unit represented by formula (a2-A):

wherein, 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 hydroxy group, an alkyl group having 1 to 6 carbon atoms, an alkoxy group having 1 to 6 carbon atoms, an alkoxyalkyl group having 2 to 12 carbon atoms, an alkoxyalkoxy group having 2 to 12 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 —, and * represents a bonding site to carbon atoms to which —R a50 is bonded,

A a52 represents an alkanediyl group having 1 to 8 carbon atoms,

X a51 and X a52 each independently represent —O—, —CO—O— or —O—CO—,

nb represents 0 or 1, and

mb represents an integer of 0 to 4, and when mb is an integer of 2 or more, a plurality of R a51 may be the same or different from each other.

11 . The resist composition according to claim 8 , further comprising a resin including a structural unit having an acid-labile group, wherein

the resin including a structural unit having an acid-labile group further includes 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), a structural unit represented by formula (a3-3) and a structural unit represented by formula (a3-4):

wherein, in formula (a3-1), formula (a3-2), formula (a3-3) and formula (a3-4),

L a4 , L a5 and L a6 each independently represent —O— or a group represented by *—O—(CH 2 ) k3 —CO—O— (k3 represents an integer of 1 to 7),

L a7 represents —O—, *—O-L a8 -O—, *—O-L a8 -CO—O—, *—O-L a8 -CO—O-L a9 -CO—O— or *—O-L a8 -O—CO-L a9 -O—,

L a8 and L a9 each independently represent an alkanediyl group having 1 to 6 carbon atoms,

* represents a bonding site to a carbonyl group,

R a18 , R a19 , R a20 and R a24 each independently represent a hydrogen atom, a halogen atom, or an alkyl group having 1 to 6 carbon atoms which may have 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, and

when p1, q1, r1 and/or w1 are 2 or more, a plurality of R a21 , R a22 , R a23 and/or R a25 s may be the same or different from each other.

12 . The resist composition according to claim 8 , further comprising a salt generating an acid having an acidity lower than that of an acid generated from the acid generator.

13 . A method for producing a resist pattern, which comprises:

(1) a step of applying the resist composition according to claim 8 on a substrate,

(2) a step of drying the applied composition to form a composition layer,

(3) a step of exposing the composition layer,

(4) a step of heating the exposed composition layer, and

(5) a step of developing the heated composition layer.