RELATIONSHIP BETWEEN REMAINING SOLVENT AND ACID DIFFUSION IN CHEMICALLY AMPLIFIED DEEP-ULTRAVIOLET RESISTS

For clarification of the diffusion path of photogenerated acid in the resist film, the prebake temperature dependence and tert-butoxycarbony l (t-BOC) blocking level dependence on acid diffusion were investigate d for chemically amplified deep ultraviolet (DUV) positive resists. Th e resists consisted of a t-BOC protected polystyrene base resin and a 2,4-dimethylbenzenesulfonic acid derivative as a photoacid generator ( PAG). The concentration of remaining solvent in the resist film decrea sed as the prebake temperature or t-BOC blocking level increased. The acid diffusion coefficient was almost independent of exposure dose; ho wever, it decreased with increasing prebake temperature or blocking le vel. Therefore, it was considered that the concentration of remaining solvent in the resist film corresponds to one of the acid diffusion pa ths. Moreover, hydrophilic OH sites, whose concentration was the recip rocal of the blocking level, were also considered to correspond to a d iffusion path in the polymer matrix, based on the fact that the acid d iffusion length increased gradually with decreasing t-BOC blocking lev el, even when the solvent concentration remained constant. Based on th e experimental analysis results, the existence of two diffusion paths, as well as of explicit relationships among the remaining solvent, t-B OC blocking level and acid diffusion length was confirmed.