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

1. A resist composition comprising

an acid generator comprising a salt represented by formula (I):

wherein, in formula (I),

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

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

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

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

L 1 represents a single bond or a divalent saturated hydrocarbon group having 1 to 28 carbon atoms, and —CH 2 — included in the saturated hydrocarbon group may be replaced by —O—, —S—, —SO 2 — or —CO—,

R 3 represents a cyclic hydrocarbon group having 3 to 18 carbon atoms which may have a substituent, and —CH 2 — included in the cyclic hydrocarbon group may be replaced by —O—, —S—, —SO 2 — or —CO—,

R 4 represents a cyclic hydrocarbon group having 3 to 18 carbon atoms which has a substituent and —CH 2 — included in the cyclic hydrocarbon group may be replaced by —S—, —SO 2 — or —CO—, and

Z + represents an organic cation represented by any one of formula (b2-1) to formula (b2-4):

wherein, in formula (b2-1) to formula (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 included 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 included 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 included 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 a sulfur atom to which R b4 and R b5 are bonded, and —CH 2 — included 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, a plurality of R b7 may be the same or different, and when n2 is 2 or more, a plurality of R b8 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 sulfur atoms to which R b9 and R b10 are bonded, and —CH 2 — included 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 a 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 included in the chain hydrocarbon may be substituted with an aromatic hydrocarbon group having 6 to 18 carbon atoms, and a hydrogen atom included 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 —CH—CO— to which R b11 and R b12 are bonded, and —CH 2 — included 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; and

when o2 is 2 or more, a plurality of R b13 are the same or different, when p2 is 2 or more, a plurality of R b14 are the same or different, when q2 is 2 or more, a plurality of R b15 are the same or different, when r2 is 2 or more, a plurality of R b16 are the same or different, when s2 is 2 or more, a plurality of R b17 are the same or different, and when t2 is 2 or more, a plurality of R b18 are the same or different;

a resin having an acid-labile group and

an inner salt generating an acid having an acidity lower than that of an acid generated from the acid generator.

2. The resist composition according to claim 1 , wherein X 1 represents *—CO—O—, *—O—CO— or *—O—CO—O—, wherein * represents a bonding site to C(R 1 ) (R 2 ) or C(Q 1 ) (Q 2 ).

3. The resist composition according to claim 1 , wherein L 1 is: (i) a single bond, (ii) an alkanediyl group, wherein —CH 2 — included in the alkanediyl group may be replaced by —O— or —CO—, or (iii) a group obtained by combining an alkanediyl group and an alicyclic saturated hydrocarbon group, wherein —CH 2 — included in the alkanediyl group may be replaced by —O— or —CO—, and —CH 2 — included in the alicyclic saturated hydrocarbon group may be replaced by —O—, —S—, —SO 2 — or —CO—.

4. The resist composition according to claim 1 , wherein the resin having an acid-labile group comprises at least one selected from the group consisting of a structural unit represented by formula (a1-1) and a structural unit represented by formula (a1-2):

wherein, 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—,

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 group obtained 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.

5. The resist composition according to claim 1 , further comprising a resin including a structural unit having a fluorine atom.

6. The resist composition according to claim 1 , wherein zi represents 0.

7. The resist composition according to claim 1 , wherein at least one of R 1 and R 2 represent a fluorine atom.

8. The resist composition according to claim 1 , wherein the resin having an acid-labile group comprises 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 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 bond to carbon atoms 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, 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.

9. The resist composition according to claim 1 , wherein the acid generator does not comprise a salt having a cation other than an organic cation represented by any one of formula (b2-1) to formula (b2-4).

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

(1) a step of applying the resist composition according to claim 1 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.