Regina Moser, Matthias Domke, Jan Winter, Heinz P. Huber, Gerd Marowsky
May 17, 2018
Ultrashort laser pulses are widely used for the precise structuring of semiconductors like silicon (Si). We present here, for the first time, a comparative study of experimentally obtained and numerically simulated two-dimensional ablation profiles based on parameters of commercially relevant and widely used near-infrared and diode pumped femtosecond lasers. Single pulse laser ablation was studied at a center wavelength of 1040 nm and pulse duration of 380 fs (FWHM) in an irradiating fluence regime from 1 J/cm 2 to 10 J/cm 2 . Process thresholds for material transport and removal were determined. Three regimes, scaling with the fluence, could be identified: low and middle fluence regimes and a hydrodynamic motion regime. By comparing the simulated and experimental ablation profiles, two conclusions can be drawn: At 2 J/cm 2 , the isothermal profile of 3800 K is in excellent agreement with the observed two-dimensional ablation. Thus exceeding a temperature of 3800 K can be accepted as a simplified ablation condition at that fluence. Furthermore, we observed a distinct deviation of the experimental from the simulated ablation profiles for irradiated fluences above 4 J/cm 2 . This points to hydrodynamic motion as an important contributing mechanism for laser ablation at higher fluences.