Dissolution Rates of Polymers and Copolymers Based on Methyl, Ethyl, and Butyl Methacrylate

摘要

The rate of dissolution (DR) of thin (1 micrometer) films of various methacrylate polymers was measured using lasers interferometry. The polymers were all of high (Mn greater than 600,000) molecular weight and included homopolymers of methyl methacrylate, MMA, ethyl methacrylate, EMA, and n-butyl methacrylate, BMA, as well as copolymers of MMA with EMA and with BMA. Glass transition temperatures estimated by DSC ranged from 36 C (PBMA) to 115 C (PMMA). Films were applied to silicon wafers by conventional spinning and baking. The DRs in methyl isobutyl ketone at 30 C ranged from 0.042 micrometer (PMMA) to c. 150 micrometer/min (PBMA). Activation energy, Ea, in the limited span of 20 to 40 decreased as Tg decreased. In agreement with other workers, Ea for PMMA was 25 kcal/mol. However, the Ea dropped almost to half that value for PEMA and for BMA-rich copolymers. Keywords: Dissolution rate, Lithography, Resist, Interferometry.