Fluorine-containing sulfonic acid salts, photo-acid generator and resist composition and pattern formation method utilizing same

A resist composition comprising at least a base resin, a photoacid generator and a solvent, wherein the photoacid generator comprises a fluorine-containing sulfonic acid salt of the following general formula (4):

• where X each independently represents a hydrogen atom or a fluorine atom;
• n represents an integer of 1 to 10;
• R1 represents a hydrogen atom, a C1-C20 alkyl group, a C2-C20 alkenyl group or oxoalkyl group, or a C6-C18 aryl group or aralkyl group;
• any of hydrogen atoms on carbons in R1 may be substituted with a substituent;
• R2 represents either RAO or RBRCN;
• RA, RB and RC each independently represents a hydrogen atom, a C1-C20 alkyl group, a C2-C20 alkenyl group, a C1-C20 oxoalkyl group, a C6-C18 aryl group, a C6-C18 aralkyl group, or a C3-C30 lactone group;
• RB and RC may be bonded to each other to form a 3- to 18-membered heterocyclic ring with a nitrogen atom (N) in RBRCN;
• any of hydrogen atoms on carbons in RA, RB and RC may be substituted with a substituent;
• A represents any one of groups of the following formulas:
• and M+ represents a monovalent cation.