Nitroxide-Mediated Polymerization of Adamantyl-Functional Methacrylates for 193 nm Photoresists

Three different methacrylic monomers (gamma-butyrolactone methacrylate (GBLMA), 3-hydroxyl-1-adamantyl methacrylate (HAMA), and 2-methyl-2adamantyl 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 similar to 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 8C) and added free SG1 nitroxide (none versus SG1: NHS-BlocBuilder molar ratio approximate to 0.15) with the objective of minimizing the dispersity (Mw= Mn). MAMA/ PFS copolymerizations were not strongly influenced by temperature or addition of free nitroxide, with relatively linear number average molecular weight Mn versus conversion plots andM(w)/M-n = 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, Mw= Mn was reduced at the lower temperature of 75 degrees C but added SG1 did not play a strong role. For GBLMA/ PFS, Mw= Mn was reduced from 1.70-1.71 at 90 degrees C to 1.42-1.50 at 75 degrees C and for HAMA/ PFS, Mw= Mn was reduced from 1.36-1.47 at 90 degrees C to 1.22-1.31 at 75 degrees C.