Evaluation of the standard addition method to determine rate constants for acid generation in chemically amplified photoresist at 157 nm

Abstract

The rate constants for acid generation (C parameter) in chemically amplified photoresist are determined for four photoacid generators (norbornene dicarboximidyl triflate, triphenyl sulfonium triflate, bis-4-t-butylphenyl iodonium perfluorooctane sulfonate, and bis-4-t-butylphenyl iodonium triflate) under exposure to 157nm radiation using a standard addition technique. The technique utilizes an in film neutralization of photogenerated acid by base quencher to determine the increase in exposure energy necessary to produce an equivalent fee acid concentration at each loading of base. We present a general model to interpret the data that also accounts for the strong absorption of radiation by the resist film. An average absorption coefficient of 13.2micrometers <SUP>-1</SUP> (base e) has been measured at 157nm for these resist films. Results from 157nm irradiation are compared to deep ultraviolet and ionizing radiation, indicating that resist photochemistry at 157nm includes processes important to both energy regimes.