Sulfonium salt monomer, polymer, chemically amplified resist composition, and pattern forming method

Abstract

Provided are: a sulfonium salt monomer used in a chemically amplified resist composition that is excellent in solvent solubility, has high sensitivity and high contrast, and is excellent in lithographic performance of LWR, CDU, EL, DOF, or the like in photolithography using a high energy ray; a polymer containing a repeat unit derived from the sulfonium salt monomer; a chemically amplified resist composition containing the polymer; and a pattern forming method using the chemically amplified resist composition. A sulfonium salt monomer having the following formula (A): wherein Z- is an aromatic sulfonic acid anion having a polymerizable group.