Effects of substituents in triphenylsulfonium cation on its radiation-induced decomposition and dissolution kinetics of chemically amplified resists

The suppression of stochastic effects is the most important issue in the development of resist materials. To suppress the stochastic effects in chemically amplified resists, a high acid generator concentration is required, which, however, likely affects the dissolution kinetics of resist films. In this study, the effects of substituents in the phenyl group of triphenylsulfonium triflate (TPS-TF) on the decomposition and dissolution kinetics of poly(4-hydroxystyrene) (PHS) films dispersed with monosubstituted TPS-TF were investigated using electron pulse radiolysis, γ-radiolysis, electron radiolysis, and quartz crystal microbalance. The phenyl group of TPS-TF was substituted with fluorine, iodine, or methyl groups at the fourth position. The electronegativity of the substituents had little effect on the reaction rate of the methanol-solvated electrons. The dipole moment of the TPS cation affected the C-S bond cleavage. The monosubstitution of the phenyl group of the TPS cation significantly affected the dissolution rate of the PHS films.