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

1. A salt represented by formula (I):

wherein, in formula (I),

R 1 represents —O—R 10 ,

R 2 and R 3 each independently represent a hydroxy group or —O—R 10 ,

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

R 4 , R 5 , R 6 , R 7 , R 8 and R 9 each independently represent a halogen atom, an alkyl fluoride 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 hydrocarbon group may be replaced by —O—, —CO—, —S— or —SO 2 —,

R 10 represents an acid-labile group represented by formula (2a):

wherein, in formula (2a),

R aa1 ′ represents a hydrogen atom or a hydrocarbon group having 1 to 12 carbon atoms, R aa2 ′ represents 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 ′ are 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 bond;

X 1 , X 2 and X 3 each independently represent an oxygen atom or a sulfur atom,

m1 represents an integer of 1 to 5, and when m1 is 2 or more, a plurality of groups in parentheses may be the same or different from each other,

m2 represents an integer of 0 to 5, and when m2 is 2 or more, a plurality of groups in parentheses may be the same or different from each other,

m3 represents an integer of 0 to 5, and when m3 is 2 or more, a plurality of groups in parentheses may be the same or different from each other, and when m2 or m3 is 1 or more, and R 1 , R 2 and R 3 each independently represent —O—R 10 , a plurality of R 10 , may be the same or different from each other,

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

m5 represents an integer of 0 to 4, and when m5 is 2 or more, a plurality of R 5 may be the same or different from each other,

m6 represents an integer of 0 to 4, and when m6 is 2 or more, a plurality of R 6 may be the same or different from each other,

m7 represents an integer of 0 to 4, and when m7 is 2 or more, a plurality of R 7 may be the same or different from each other,

m8 represents an integer of 0 to 5, and when m8 is 2 or more, a plurality of R 8 may be the same or different from each other,

m9 represents an integer of 0 to 5, and when m9 is 2 or more, a plurality of R 9 may be the same or different from each other,

in which 1≤m1+m7≤5, 0≤m2+m8≤5, 0≤m3+m9≤5, and

AI − represents a sulfonic acid anion.

2. The salt according to claim 1 , wherein X 1 , X 2 and X 3 are an oxygen atom.

3. The salt according to claim 1 , wherein either m8 or m9 is an integer of 1 or more, and

R 8 and R 9 each independently represent a fluorine atom, an iodine atom or a trifluoromethyl group.

4. The salt according to claim 1 , wherein the sulfonic acid anion is an anion represented by formula (I-A):

wherein, in formula (I-A),

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

L1 represents a saturated hydrocarbon group having 1 to 24 carbon atoms, —CH 2 — included in the saturated hydrocarbon group may be replaced by —O— or —CO—, and a hydrogen atom included in the saturated hydrocarbon group may be substituted with a fluorine atom or a hydroxy group, and

Y 1 represents a methyl group which may have a substituent or an alicyclic hydrocarbon group having 3 to 24 carbon atoms which may have a substituent, and —CH 2 — included in the alicyclic hydrocarbon group may be replaced by —O—, —SO 2 — or —CO—.

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

6. A resist composition comprising the acid generator according to claim 5 and a resin having an acid-labile group.

7. The resist composition according to claim 6 , wherein the resin having an acid-labile group is 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, a halogen atom, or an alkyl group having 1 to 6 carbon atoms which may have a halogen atom,

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 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.

8. The resist composition according to claim 6 , wherein the resin having an acid-labile group includes 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 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 6 , further comprising a salt generating an acid having an acidity lower than that of an acid generated from the acid generator.

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

(1) a step of applying the resist composition according to claim 6 on a substrate,

(2) a step of drying the applied resist 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.

11. The salt according to claim 3 , wherein

a bonding site of one R 8 is p-position,

a bonding site of one R 9 is p-position.

12. The salt according to claim 4 , wherein

Y 1 represents an alicyclic hydrocarbon group having 3 to 24 carbon atoms which may have a substituent, and —CH 2 — included in the alicyclic hydrocarbon group may be replaced by —O—, —SO 2 — or —CO—.

13. The salt according to claim 1 , wherein

m1 is 1 or 2,

m2 is 1, and

m3 is 0 or 1.

14. The salt according to claim 1 , wherein

R aa2 ′ represents a hydrocarbon group having 1 to 12 carbon atoms,

R aa3 ′ represents a hydrocarbon group having 1 to 20 carbon atoms, and

—CH 2 — included in the hydrocarbon group may be replaced by —O— or —S—.

15. The salt according to claim 1 , wherein R aa2 ′ and R aa3 ′ are bonded to each other to form a heterocyclic group together with carbon atoms and X a to which R aa2 ′ and R aa3 ′ are bonded,

the heterocyclic group includes at least one of the following groups, and

* represents a bond;

16. The salt according to claim 1 , wherein R 10 represents any one of the following groups: