Resin, resist composition and method for producing resist pattern

1. A resin comprising a structural unit represented by formula (I), a structural unit represented by formula (a2-A), and at least one structural unit selected from the group consisting of a structural unit represented by formula (a1-1) and a structural unit represented by formula (a1-2):

wherein, in formula (I),

R 1 represents a hydrogen atom or a methyl group,

L 1 and L 2 each independently represent —O— or —S—,

s1 represents an integer of 1 to 3, and

s2 represents an integer of 0 to 3: and

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 bonding site 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;

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 bonding site 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.

2. A resist composition comprising the resin according to claim 1 and an acid generator.

3. The resist composition according to claim 2 , wherein the acid generator comprises a salt represented by formula (B1):

wherein, in formula (B1),

Q b1 and Q b2 each independently represent a fluorine atom or a perfluoroalkyl group having 1 to 6 carbon atoms,

L b1 represents a divalent saturated hydrocarbon group having 1 to 24 carbon atoms, —CH 2 — included in the divalent saturated hydrocarbon group may be replaced by —O— or —CO—, and a hydrogen atom included in the divalent saturated hydrocarbon group may be substituted with a fluorine atom or a hydroxy group,

Y represents a methyl group which may have a substituent or an alicyclic hydrocarbon group having 3 to 18 carbon atoms which may have a substituent, and —CH 2 — included in the alicyclic hydrocarbon group may be replaced by —O—, —S(O) 2 — or —CO—, and

Z + represents an organic cation.

4. The resist composition according to claim 2 , further comprising a salt generating an acid having an acidity lower than that of an acid generated from the acid generator.

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

(1) a step of applying the resist composition according to claim 2 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.