Onium salt compound, polymer compound comprising the salt compound, chemically amplified resist composition comprising the polymer compound, and method for patterning using the composition

A polymer compound comprising a repeating unit represented by the following formula (5), a repeating unit represented by the following formula (6), and a repeating unit represented by the following formula (7):

• wherein R1 represents a hydrogen atom, a trifluoromethyl group, an alkyl group having 1 to 5 carbon atoms, or an alkoxy group having 1 to 5 carbon atoms;
• and A represents a group represented by the following formula (2) or formula (3):
• wherein R2, R3, R4, R5 and R6 each independently represent a substituted or unsubstituted alkyl group having 1 to 20 carbon atoms, a substituted or unsubstituted allyl group having 3 to 10 carbon atoms, a substituted or unsubstituted perfluoroalkyl group having 1 to 10 carbon atoms, a substituted or unsubstituted benzyl group, or a substituted or unsubstituted aryl group having 6 to 30 carbon atoms;
• and two or more of R2, R3 and R4 may be linked to each other to form a saturated or unsaturated carbon ring or a saturated or unsaturated heterocyclic ring;
• wherein R7 represents a hydrogen atom, an alkyl group having 1 to 30 carbon atoms, or an alkyl group having 1 to 30 carbon atoms which is substituted with a group selected from an ether group, an ester group, a carbonyl group, an acetal group, an epoxy group, a nitrile group and an aldehyde group;
• and R8 represents a hydrogen atom, a methyl group, or a trifluoromethyl group;
• wherein X represents one selected from olefin, vinyl, styrene, and derivatives thereof.