Chemically amplified resist composition and patterning process

A chemically amplified resist composition comprising:

• (A) a polymer adapted to increase its solubility in an aqueous alkaline under the action of an acid, the polymer comprising repeat units having the formula (A1), and repeat units having the formula (B1), and lacking repeat units adapted to generate an acid upon exposure;
• and
• (B) a photoacid generator having the formula (PAG-a) or (PAG-b) which generates an acid under the action of KrF excimer laser, ArF excimer laser, electron beams or extreme ultraviolet radiation:
• wherein a1 is 0 or 1, a2 is an integer of 0 to 3,
• RA is hydrogen, fluorine, methyl, or trifluoromethyl,
• X1 is a single bond, a phenylene group, a naphthylene group or *—C(═O)—O—X11—, X11 is a C1-C10 saturated hydrocarbylene group which may contain a hydroxy moiety, ether bond, ester bond, sulfide bond, sulfonamide bond, lactone ring or sultone ring, or a phenylene or naphthylene group, the asterisk (*) designates a point of attachment to the carbon atom in the backbone,
• Ra1 and Ra2 are each independently hydrogen, or a C1-C20 hydrocarbyl group which may contain a heteroatom, excluding that Ra1 and Ra2 are hydrogen at the same time, Ra1 and Ra2 may bond together to form a ring with the carbon atom to which they are attached,
• Ra3 is a C1-C20 hydrocarbyl group which may contain a halogen atom or a heteroatom, and a plurality of Ra3 moieties may bond together to form a ring with the carbon atom to which they are attached when a2≥2;
• wherein b1 is an integer of 1 to 4, b2 is an integer of 0 to 3, the sum of b1+b2 is from 1 to 5,
• RA is hydrogen, fluorine, methyl or trifluoromethyl,
• X2 is a single bond or *—C(═O)—O—, the asterisk (*) designates a point of attachment to the carbon atom in the backbone,
• Rb1 is a halogen atom, a cyano group, a C1-C20 hydrocarbyl group which may contain a heteroatom, a C1-C20 hydrocarbyloxy group which may contain a heteroatom, a C2-C20 hydrocarbylcarbonyl group which may contain a heteroatom, a C2-C20 hydrocarbylcarbonyloxy group which may contain a heteroatom, or a C2-C20 hydrocarbyloxycarbonyl group which may contain a heteroatom, and a plurality of Rb1 moieties may bond together to form a ring with the carbon atom to which they are attached when b2≥2;
• wherein R0 is hydrogen or a C1-C50 hydrocarbyl group, some or all of the hydrogen atoms of the hydrocarbyl group may be substituted by halogen atoms, and some constituent —CH2— of the hydrocarbyl group may be substituted by —O— or —C(═O)—,
• Xa+ is an organic cation;
• wherein R1 and R2 are each independently a C1-C20 hydrocarbyl group which may contain a heteroatom, R1 and R2 may bond together to form a ring with the sulfur atom to which they are attached,
• R3 is a C1-C20 hydrocarbylene group which may contain a heteroatom,
• LA is a divalent linking group, and
• LB is a single bond, or a C1-C20 hydrocarbylene group which may contain a heteroatom.