US Patent 7378218 Polymer, resist composition and patterning process

A fluorinated polymer comprising recurring units of formulae (1a) to (1d) and having a Mw of 1,000-500,000 is provided. R1 is an acid labile group, R2 is a single bond or methylene, a1, a2, a3, and a4 are numbers from more than 0 to less than 1, and 0<a1+a2+a3+a4≦1, b is 1 or 2, and c is 0 or 1. A resist composition comprising the polymer, when processed by the lithography involving ArF exposure, has many advantages including resolution, line edge roughness, etch resistance