Removal mechanism on 4H–SiC single crystal by picosecond laser ablation-assisted chemical mechanical polishing (CMP)

Abstract

The properties of the single-crystal 4H–SiC are complex and difficult to understand. Consequently, determining the effect of the surface and subsurface structures and composition changes of picosecond laser ablation (PLA) on the material removal mechanism during the CMP stage is challenging. In this study, we used PLA of 4H–SiC surfaces to investigate the mechanism underlying the effect of PLA-assisted CMP, which is considerably larger than the laser ablation threshold, on the removal of 4H–SiC to improve the material removal rate and surface quality of CMP. The TEM and contact angle detection results indicated that the reduction in the fracture strength and increase in the surface energy of high-power PLA contributed to the removal form and chemical action of CMP. Subsequent experimental results showed that the contact angle and hardness of the PLA-treated surfaces in the hydrophilic range were reduced by 45% and 48.6%, respectively. The material removal rate (MRR) of PLA-CMP (alumina slurry) at 45 min was 3.67 μm/h that was a 70% improved CMP removal relative to no picosecond laser ablation (NPLA). The mechanism of PLA-assisted CMP removal was revealed to be related to the plastic cutting of the abrasive and high pressure and temperature, leading to the softening-removal-softening cycle of the material. This study provides a new perspective on the ultraprecise and high-efficiency fabrication of high-quality single-crystal 4H–SiC.