Investigation of Laser Irradiated Areas with Electron Backscatter Diffraction

In this work, two silicon nitride (SiNx) layers with two different refraction indices, deposited on polished or damage-etched 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 near-surface crystallographic orientation and crystallinity.In this work an indirect ablation was observed for SiNx (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-photon-absorption coefficient of SiNx (n = 2.1) was estimated to be 2.105 cm/TW.