Picosecond laser modification enhances machinability of SiC slices through surface structure evolution

Abstract

The excellent physical and chemical stability of single-crystal 4H-SiC slices renders them challenging to process. Laser modification processing is an effective approach to enhance the machinability of single-crystal 4H-SiC slices. The control variable method was conducted to investigate the evolution of SiC cutting sheets surface quality and structural characteristics under picosecond laser modification. Picosecond laser-modified SiC cut sheets were characterized using both pre-analytical and experimental methods: The optimal process parameters under these experimental conditions were determined to be 7.96 J/cm² for energy density, 180 mm/s for scanning speed, and 18 μm for scanning spacing. Laser modification significantly improves the mechanical properties and machinability of SiC slices. These substances were deposited on the surface in the form of SiO₂ smoke particles and crystalline Si (c-Si). Obvious residual tensile stresses were observed on the surface, along with subsurface defects caused by heat transfer during the laser modification process. Additionally, upon conclusion of the laser modification, rapid cooling promotes the recrystallization of SiC vapours on the subsurface, isolated from the atmosphere and deposited there. This work will provide a theoretical basis and practical guidance for the efficient processing of single crystal SiC cutting sheets in laser synergistic CMP.