Patent ID: 8859180

Claim:
A process for producing a copolymer for semiconductor lithography, having at least (A) a repeating unit having a structure which has an alkali-soluble group protected by an acid-labile, dissolution-suppressing group, (B) a repeating roup unit having a lactone structure and (C) a repeating unit having an alcoholic hydroxyl group, which process being characterized by dissolving at least one monomer of a monomer giving the repeating unit (A) in an organic solvent to produce a first solution, dissolving at least one monomer of a monomer giving the repeating unit (B) in the organic solvent to produce a second solution, dissolving at least one monomer of a monomer giving the repeating unit (C) in the organic solvent to produce a third solution, contacting each of the resulting solutions with water followed by giving rise to phase separation, and, thereafter, copolymerizing the monomers, and the copolymer being characterized by having an acid value of 0.01 mmol/g or less as determined by dissolving the copolymer in a solvent and subjecting the solution to neutralization titration with a solution of an alkali metal hydroxide using Bromothymol Blue as an indicator, wherein the acid-labile, dissolution-suppressing group of the repeating unit (A) is selected from a structure represented by the following formula (L2) {in the formula (L2), o is a bonding site of the acid-labile, dissolution-suppressing group, R 16 and R 17 are each independently a hydrogen atom or a hydrocarbon group having 1 to 4 carbon atoms, R 18 is a hydrocarbon group having 1 to 12 carbon atoms, and R 16 may bond with R 17 or R 18 to form a ring}.