Polymer effects on the photochemistry of triarylsulfonium salts

Abstract

Triarylsulfonium salts are used for both curing and microelectronic imaging of polymer films. The major products from the photodecomposition of sulfonium salts are a Broensted acid along with a mixture of diarylsulfides. The amount of acid which is produced on irradiation of polymer films containing triarylsulfonium salts is dependent on the structures of both the polymer and sulfonium salt. The results from both electron beam and ultraviolet experiments suggest that polarity effects are very important factors in determining how much acid is produced. The effect of sulfonium salt loading percentage was also studied. Thermal analysis of polymer films has shown greater plasticization effects for sulfonium salts in polar polymer films indicating that the interaction between sulfonium salts and polymers is better for polar polymers. ESR experiments have determined the nature of the radicals which are produced following irradiation and these results suggest a mechanistic understanding of the polymer structural effects. In the case of acid-sensitive polymers, it has been possible to determine the extent of acid-catalyzed chemistry which, in turn, provides a means of estimating the acid diffusion range in this polymer film.