US Patent 10007178 Positive resist composition and patterning process

A positive resist composition is provided comprising a polymer having an acid labile group and an acid generator bound to its backbone, in admixture with an onium salt having a specific cation structure capable of generating sulfonic acid having a molecular weight of at least 540. The composition is effective for suppressing acid diffusion, has high resolution, and forms a pattern of satisfactory profile and minimal edge roughness after exposure and development.