Comparative evaluation of poly(pentafluoroaryl methacrylate)s and their non-fluorinated analogues as positive-working electron-beam resists

In order to rationalise the effects of fluorination on the performance of positive-working electron-beam resists based on methacrylate polymers, poly(pentafluorophenyl methacrylate) and poly(pentafluorobenzyl methacrylate) and their non-fluorinated analogues have been synthesized, and their electron-beam sensitivities and oxygen plasma etch rates determined for comparison with the corresponding parameters for alkyl methacrylate and fluoroalkyl methacrylate polymers reported in the literature. The fluoroaryl polymers were found to have enhanced dry-etch resistances, and in the case of poly(pentafluorophenyl methacrylate), to display a higher lithographic sensitivity than its parent non-fluorinated polymer. The plasma resistances and the lithographic sensitivities of the materials are considered, respectively, in terms of the potential for nucleophilic degradation of the ester side-groups, and of the thermochemistry of the available pathways for radiation-induced decomposition.