Design and lithographic performances of 193-specific photoacid generators

Abstract

The improvement of the transparency of photoacid generators (PAGs) has an researchers' attention for 193-resist application. In this study, sulfonium salt was chosen as a target PAG. Triphenyl sulfonium salt (TPS) showing strong absorption at 193 nm was selected as a standard PAG. Starting from the ordinary compound, designing several 193-specific PAGs was attempted. Molecular orbital (MO) calculation was used for the estimation of transparency of PAGs. The calculated absorption results fit in with observed absorption spectra of synthesized PAGs in poly(methyl methacrylate) matrix. Furthermore, MO calculation illustrated that polycyclic aromatic systems based on (pi) -system extension concept should be preferable in terms of transparency at 193 nm. A new PAG was synthesized based on the (pi) -extended concept. The resist comprising the new PAG was evaluated in order to verify the effect of transparency improvement. The resist provide good lithographic performances, vertical wall angle without deterioration of photospeed, The MO calculations have materialized a 193-specific PAG for further improvement of resist performances.