Excimer laser ablation removal of thin chromium films from glass substrates

The excimer laser has been widely used for the removal of thin metal films. In this work, excimer laser ablation was applied to remove chromium films from glass substrates. To understand the removal mechanism and to seek the optimal processing conditions for pattern generation, a one-dimensional heat flow model was formulated which incorporated melting and vaporization. Morphological investigations were carried out experimentally on samples having different chromium film thicknesses that were irradiated with a KrF excimer laser. The thresholds for film damage, complete removal and glass damage were determined experimentally and compared with the calculated results. The measured single-shot ablation rate is about twice as high as the numerical predictions based on a heat conduction theory. The removal mechanism of the chromium film is found to be divided into two steps of pure vaporization and melt expulsion by vapor recoil pressure. Optimal processing conditions were determined to enhance the accuracy and quality of film removal for pattern generation. Finally, the slit disk of a rotary encoder was manufactured using the optimal processing conditions established.