Picosecond Laser-Assisted Chemical Mechanical Polishing (CMP): Aiming at the Si-Face of Single-Crystal 6H-SiC Wafer

Abstract

Silicon carbide (SiC) presents huge application potential in semiconductor devices. However, attributed to its high hardness and stability, there always appears an urgent problem about how to improve the efficiency of chemical mechanical polishing (CMP) of the SiC Si-face. In this study, an effective picosecond laser-assisted CMP method is proposed, which first preprocesses the Si-face with picosecond laser and then carries out CMP. Scanning electron microscopy (SEM), nano scratch tester (NST), and X-ray photoelectron spectroscopy (XPS) was employed to investigate the surface alteration of SiC Si-face by picosecond laser pretreatment (PLP). The results demonstrate that the ripples and polycrystalline layer produced by PLP improve the surface machinability, and the C–O, Si–C–O, and Si–O bonds oxidized by PLP lead to easier removal by CMP. Hence compared with the no laser pretreated (NLP) samples, the material removal rate (MRR) of PLP samples is much higher in the first 45 min of CMP and the surface roughness (Rq) is lower after CMP. The proposed method has certain scientific significance and industrial production guidance for SiC semiconductor device manufacture.