Comparison of 20- to 1000-Hz pulsed laser and continuous laser ablation of single-crystal germanium wafers

Abstract

To compare the processing efficiency and quality of 20- to 1000-Hz pulsed laser and continuous laser ablating single-crystal germanium wafers, experiments and numerical simulations were performed. The experiments were conducted by varying the duty cycle and repetition frequency of a pulsed laser to ablate single-crystal germanium with the same total laser energy and irradiation time of 100 ms, and comparing the temperature-rise profile during ablation and the damage morphology after ablation. The temperature-rise curves during the ablation and the damage morphologies after the ablation were compared. Numerical simulations were performed to compute the dislocation field of single-crystal germanium ablated by laser with different parameters to compare the size of the heat-affected zone (HAZ) formed on the sample surface after the laser ablation with different parameters. The results show that the sample surface has the largest ablated pore size and the smallest HAZ after ablation at a laser repetition frequency of 20 Hz and a duty cycle of 5%; the smallest pore size and the largest HAZ after ablation at a laser repetition frequency of 1000 Hz and a duty cycle of 50%, and the continuous laser results are in the middle.