DIFFUSE REFLECTIVITY MEASUREMENTS OF POLYIMIDE DURING ARGON FLUORIDE EXCIMER-LASER ABLATION

The diffuse reflectivity of polyimide during Pulsed 193-nm excimer las er irradiation has been compared to the specular reflectivity of the m aterial over the fluence range 0.6-190 mJ/cm2. Diffuse reflectivity is observed to decrease with increasing fluence by a factor of approxima tely 3 over the intensity range, and remains a roughly constant fracti on (0.3-0.4) of total target reflectivity. These results indicate that appreciable scattering of reflected laser radiation out of the specul ar direction does not occur under ablation conditions, and therefore c annot account for the specularly reflected pulse truncation observed p reviously.