Nitroxide‐mediated polymerization of adamantyl‐functional methacrylates for 193 nm photoresists

Abstract

Three different methacrylic monomers (γ‐butyrolactone methacrylate (GBLMA), 3‐hydroxyl‐1‐adamantyl methacrylate (HAMA), and 2‐methyl‐2‐adamantyl methacrylate (MAMA)), that are most often terpolymerized for 193 nm photoresists, were studied individually by nitroxide mediated polymerization (NMP) with succinimidyl ester terminated BlocBuilder (NHS‐BlocBuilder) using a small fraction ∼ 0.05 mol/mol (5 mol%) in the initial mixture of 2,3,4,5,6 pentafluorostyrene (PFS) controlling co‐monomer. The copolymerizations were done in 0.35 g/g (35 wt%) dioxane solution and were studied as functions of temperature (75 versus 90 °C) and added free SG1 nitroxide (none versus SG1:NHS‐BlocBuilder molar ratio ≈ 0.15) with the objective of minimizing the dispersity (). MAMA/PFS copolymerizations were not strongly influenced by temperature or addition of free nitroxide, with relatively linear number average molecular weight versus conversion plots and = 1.28–1.55. Further, MAMA/PFS polymerization kinetics was notably slower compared to GBLMA or HAMA copolymerizations with PFS. For GBLMA/PFS and HAMA/PFS copolymerizations, was reduced at the lower temperature of 75 °C but added SG1 did not play a strong role. For GBLMA/PFS, was reduced from 1.70–1.71 at 90 °C to 1.42–1.50 at 75 °C and for HAMA/PFS, was reduced from 1.36–1.47 at 90 °C to 1.22–1.31 at 75 °C.