Copolymer, photoresist composition, and process for forming resist pattern with high aspect ratio

摘要

A novel copolymer includes a repeating unit (A) represented by, for example, Formula (I) below, and a repeating unit (B) derived from an unsaturated carboxylic anhydride. The novel copolymer is suitable for the preparation of a photoresist composition that has satisfactory transparency, high sensitivity and definition and exhibits satisfactory DOF properties in the field of photolithography using a deep UV light source. By the use of the photoresist composition, a process forms a resist pattern with a high aspect ratio.