US Patent 11586110 Positive resist composition and patterning process

A positive resist composition comprising a base polymer comprising recurring units (a) of an ammonium salt of a carboxylic acid having an iodized or brominated hydrocarbyl group and recurring units (b1) having an acid labile group-substituted carboxyl group and/or recurring units (b2) having an acid labile group-substituted phenolic hydroxyl group has a high sensitivity and resolution and forms a pattern of good profile with reduced edge roughness and improved dimensional uniformity.