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SynopsisThe major photoproduct from irradiation of triphenylsulfonium salts is a Bronsted acid. This photochemical process has been used in several polymer film applications where the acid is used for crosslinking of films or other acid catalyzed reactions. Despite the widespread application of these materials, very little is known about the efficiency of acid generation in polymer films or the extent of the catalytic chain. This paper describes the use of a merocyanine dye technique to analyze for acid production in polymer films. The amount of acid produced on irradiation can be determined by this method and the extent of the catalytic chain can then be determined.

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Triarylsulfonium salts have been widely used as acid photogenerators in chemically amplified photoresists. A technique was developed for measuring the amount of acid which is generated on irradiation of polymer films contaming suffonium salts and the results of these measurements were used to obtain an understanding of the importance of acid chemistry on the lithographic performance of acid-catalyzed resists. The results from both electron beam and ultraviolet irradiations suggest that polarity effects are very important factors in detennining the efficiency of acid generation. The effect of sulfonium salt loading percentage on acid generating efficiency was also studied. Thennal analysis of polymer films containing sulfonium salts has shown greater plasticization effects for sulfomum 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.

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