Photoresist composition

1. A photoresist composition comprising a salt represented by the formula (I):

wherein R 1 and R 2 independently each represent a fluorine atom or a C1-C6 perfluoroalkyl group, X 1 represents a C1-C17 divalent saturated hydrocarbon group in which one or more hydrogen atoms can be replaced by a fluorine atom and in which one or more —CH 2 — can be replaced by —O— or —CO—, s1 represents 1 or 2, and t1 represents 0 or 1, with proviso that the sum of s1 and t1 is 1 or 2, R 3 represents a C6-C18 aromatic hydrocarbon group or a C1-C12 saturated hydrocarbon group in which one or more hydrogen atoms can be replaced by a C1-C6 alkyl group or a nitro group and in which one or more —CH 2 — can be replaced by —O—, u1 represents an integer of 0 to 5, and (Z 1 ) + represents an organic cation,

a salt represented by the formula (II), the formula (III-A) or the formula (III-B):

wherein R 4 in formula (II) is a group represented by the formula (II-A)

wherein R 6 represents a C1-C17 hydrocarbon group in which one or more hydrogen atoms can be replaced by a fluorine atom or —OH and in which one or more —CH 2 — can be replaced by —O— or —CO—, R 7 represents a C1-C6 alkyl group, and R 8 represents a C1-C6 fluorinated alkyl group, and (Z 2 ) + represents an organic cation;

wherein R 4 in formula (III-A) represents a C1-C24 hydrocarbon group in which one or more hydrogen atoms can be replaced by a fluorine atom or —OH and in which one or more —CH 2 — can be replaced by —O— or —CO—, and (Z 2 ) + is the same as defined above;

wherein R 4 in formula (III-B) represents a C1-C24 hydrocarbon group in which one or more hydrogen atoms can be replaced by a fluorine atom or —OH and in which one or more —CH 2 — can be replaced by —O— or —CO—, and (Z 2 ) + is the same as defined above, and R 5 represents a C1-C24 hydrocarbon group in which one or more hydrogen atoms can be replaced by a fluorine atom or —OH and in which one or more —CH 2 — can be replaced by —O— or —CO—, and

a resin being insoluble or poorly soluble in an aqueous alkali solution but becoming soluble in an aqueous alkali solution by the action of an acid.

2. The photoresist composition according to claim 1 , containing a salt represented by the formula (II).

3. The photoresist composition according to claim 1 , wherein X 1 is *—CO—O—CH 2 — in which * represents a binding position to —C(R 1 )(R 2 )—.

4. The photoresist composition according to claim 1 , wherein (Z 1 ) + is a triarylsulfonium cation.

5. The photoresist composition according to claim 1 , wherein (Z 2 ) + is a triarylsulfonium cation.

6. The photoresist composition according to claim 1 or 2 , which further comprises a solvent.

7. The photoresist composition according to claim 1 or 2 , which further comprises a basic compound.

8. A process for producing a photoresist pattern comprising:

(1) a step of applying the photoresist composition according to claim 1 or 2 on a substrate to form a photoresist composition layer,

(2) a step of forming a photoresist film by drying the photoresist composition layer formed,

(3) a step of exposing the photoresist film to radiation,

(4) a step of heating the photoresist film after exposing, and

(5) a step of developing the photoresist film after heating.