US Patent 9250523 Resist composition and patterning process

A polymer capable of increasing alkali solubility under the action of acid, as a base resin is blended with a copolymer comprising recurring units derived from acenaphthylene, indene, benzofuran or benzothiophene and fluorine-containing recurring units, as a polymeric additive to formulate a resist composition. The photoresist film formed using the resist composition is effective for minimizing outgassing therefrom during the EUV lithography. The resist film has a hydrophilic surface and is effective for suppressing formation of blob defects after development.