Investigation of laser irradiated areas with electron backscatter diffraction

Abstract

In this work, two silicon nitride (SiNx) layers with two different refraction indices, deposited on polished or damageetched silicon wafers were locally irradiated by laser pulses. The focus was set on the investigation of the ablation mechanisms. Thereby, an ultra-short laser source (pulse duration 10 ps, wavelength 532 nm, Gaussian profile) was used. The irradiated areas were investigated by electron backscatter diffraction (EBSD) in order to analyze the nearsurface crystallographic orientation and crystallinity. In this work an indirect ablation was observed for SiN x (n = 1.9). Further, a change from an indirect ablation to a partial lift-off for SiNx (n = 2.1) was determined to be fluence dependent. At low fluences, the SiNx was completely removed. However, at higher fluences, SiNx was not completely removed, due to direct ablation. The two-photonabsorption coefficient of SiNx (n = 2.1) was estimated to be 2·105 cm/TW.