Copolymer for positive type lithography, polymerization initiator used in production of said copolymer, and composition for semiconductor lithography

摘要

A copolymer for positive type lithography, having at least a recurring unit (A) having a structure wherein an alkali-soluble group is protected by an acid-dissociating, dissolution-suppressing group, represented by the following formula (A) [in the formula (A), R₁₀ is a hydrogen atom or a hydrocarbon group which may be substituted by fluorine atom; R₁₁ is a crosslinked, alicyclic hydrocarbon group; n is an integer of 0 or 1; and R₁₂ is an acid-dissociating, dissolution-suppressing group], and a terminal structure (B) having a structure wherein an alkali-soluble group is protected by an acid-dissociating, dissolution-suppressing group, represented by the following formula (B) [in the formula (B), R₂₁ is a hydrocarbon group which may contain nitrogen atom; R₂₂ is an acid-dissociating, dissolution-suppressing group; and p is a site of bonding with copolymer main chain]. The copolymer is used in chemically amplified positive type lithography and is superior in lithography properties (e.g. dissolution contrast).