LASER-INDUCED DECOMPOSITION AND ABLATION DYNAMICS STUDIED BY NANOSECOND INTERFEROMETRY .1. A TRIAZENOPOLYMER FILM

The dynamic behavior of a photoetching process of a photosensitive tri azenopolymer film during and after XeF excimer laser irradiation was s tudied by nanosecond interferometry, accompanied with time-resolved tr ansmission and reflectance measurements, A new optical setup for nanos econd interferometry, which was free from the disturbance of ejected p roducts, was developed and applied. At a fluence of 250 mJ/cm(2) a sli ght swelling of the film and darkening of the irradiated surface was i nitially observed, and then the etching process of the film was brough t out around the peak time of the excitation laser pulse. The etching developed during the excitation laser pulse and stopped almost at the end of the excimer laser pulse. On the other hand, at a fluence of 60 mJ/cm(2), the etching started from nearly the end of the excimer laser pulse and persisted for 50 ns. The fluence dependent etching behavior was interpreted in terms of coupled photochemical and thermal decompo sition processes of the triazenopolymer.