US Patent 11635690 Positive resist composition and patterning process

A positive resist composition comprising a base polymer comprising recurring units (a) having the structure of an ammonium salt of fluorosulfonic acid having an iodized or brominated aromatic ring, 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 exhibits a high sensitivity, high resolution, low edge roughness and dimensional uniformity, and forms a pattern of good profile after exposure and development.