High-quality high-throughput silicon laser milling using a 1 kW sub-picosecond laser

Abstract

We report on high-quality high-throughput laser milling of silicon with a sub-ps laser delivering more than 1 kW of average laser power on the workpiece. In order to avoid heat accumulation effects, the processing strategy for high-quality laser milling was adapted to the available average power by using five-pulse bursts, a large beam diameter of 372 µm to limit the peak fluence per pulse to approximately 0.7<i>J</i>/<i>c</i><i>m</i>², and a high feed rate of 24 m/s. As a result, smooth surfaces with a low roughness of <i>S</i>_a≤0.6µ<i>m</i> were achieved up to the investigated milling depth of 313 µm while maintaining a high material removal rate of 230<i>m</i><i>m</i>³/min.