원래 이름 기록: SHIN-ETSU CHEMICAL CO., LTD.

The sulfonium salt monomer is for a chemically amplified resist composition processed by photolithography using, in particular, high-energy radiation such as KrF excimer laser, ArF excimer laser, an electron beam (EB) or EUV, has excellent solvent solubility and a high sensitivity and contrast, and is excellent in lithographic performance such as exposure tolerance (EL), LWR, CDU and depth of focus (DOF), and excellent in resistance to pattern collapse and etch resistance even in fine pattern formation, a polymer comprising repeat units derived from the sulfonium salt monomer. The sulfonium salt monomer has the formula (a).

A composition for forming an organic film, containing: resin and/or compound (A) for forming organic film; polymer (B) not containing halogen atom and containing repeating unit represented by following formula (1) and repeating unit represented by following formula (1′); and solvent (C), where Rand Rindependently represent saturated or unsaturated organic group having 1-20 carbon atoms and optionally having substituent, and “y” and “z” independently satisfy 0<y<1 and 0<z<1, wherein y+z=1. This can provide composition for forming organic film making it possible to form film excellent in coating property wherein coating defects, as pinholes on substrate (wafer), film-formability (in-plane uniformity), and filling property, composition not containing fluorine atom and containing particular polymer. Furthermore, the invention can provide method for forming organic film using composition for forming organic film, patterning process using composition for forming organic film, and polymer.