Two-Step Chemical Mechanical Polishing of 4H-SiC (0001) Wafer

Chemical mechanical polishing (CMP), as a widely used global smoothing technique, requires a high polishing rate and a low surface roughness. However, it is difficult to meet these requirements with single-step polishing. To obtain a perfect 4H-SiC wafer surface, we studied a two-step CMP 4H-SiC wafer using a-Al2O3-based slurry and nano-SiO2-based slurry. Before the two-step process was determined, the effect of concentration of KMnO4 and pH on the polishing rate of 4H-SiC was first studied with Al2O3 as the abrasive, and the maximum polishing rate of 1400 nm h−1 was determined under the condition of pH of 2.00 and KMnO4 concentration of 6.5 wt% in the step. Furthermore, the effect of H2O2 concentration on the polishing rate of 4H-SiC was investigated using SiO2 as the abrasive and V2O5 as the catalyst. It was determined that under the condition of V2O5 concentration of 4 wt% and H2O2 concentration of 10 wt%, the maximum polishing rate of the second step polishing was 150 nm h−1, and a perfect surface was obtained, with a surface roughness of 0.066 nm. In addition, the in situ friction coefficients have used to characterize the two-step process. At the end, the CMP mechanisms of the above two slurry have been deduced and preliminarily demonstrated.