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

A resist composition comprising

• an acid generator comprising a salt represented by formula (I):
• wherein, in formula (I),
• Q1 and Q2 each independently represent a fluorine atom or a perfluoroalkyl group having 1 to 6 carbon atoms,
• R1 and R2 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 R1 and R2 may be the same or different form each other,
• X1 represents *—CO—O—, *—O—CO—, *—O—CO—O— or *—O—, wherein * represents a bonding site to C(R1) (R2) or C(Q1) (Q2),
• L1 represents a single bond or a divalent saturated hydrocarbon group having 1 to 28 carbon atoms, and —CH2— included in the saturated hydrocarbon group may be replaced by —O—, —S—, —SO2— or —CO—,
• R3 represents a cyclic hydrocarbon group having 3 to 18 carbon atoms which may have a substituent, and —CH2— included in the cyclic hydrocarbon group may be replaced by —O—, —S—, —SO2— or —CO—,
• R4 represents a cyclic hydrocarbon group having 3 to 18 carbon atoms which has a substituent and —CH2— included in the cyclic hydrocarbon group may be replaced by —S—, —SO2— 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),
• Rb4 to Rb6 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;
• Rb4 and Rb5 may be bonded to each other to form a ring together with a sulfur atom to which Rb4 and Rb5 are bonded, and —CH2— included in the ring may be replaced by —O—, —S—or —CO—,
• Rb7 and Rb8 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 Rb7 may be the same or different, and when n2 is 2 or more, a plurality of Rb8 may be the same or different;
• Rb9 and Rb10 each independently represent a chain hydrocarbon group having 1 to 36 carbon atoms or an alicyclic hydrocarbon group having 3 to 36 carbon atoms, Rb9 and Rb10 may be bonded to each other to form a ring together with sulfur atoms to which Rb9 and Rb10 are bonded, and —CH2— included in the ring may be replaced by —O—, —S— or —CO—;
• Rb11 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;
• Rb12 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;
• Rb11 and Rb12 may be bonded to each other to form a ring, including —CH—CO— to which Rb11 and Rb12 are bonded, and —CH2— included in the ring may be replaced by —O—, —S— or —CO—,
• Rb13 to Rb18 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;
• Lb31 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 Rb13 are the same or different, when p2 is 2 or more, a plurality of Rb14 are the same or different, when q2 is 2 or more, a plurality of Rb15 are the same or different, when r2 is 2 or more, a plurality of Rb16 are the same or different, when s2 is 2 or more, a plurality of Rb17 are the same or different, and when t2 is 2 or more, a plurality of Rb18 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.