Efficient and slurryless ultrasonic vibration assisted electrochemical mechanical polishing for 4H-SiC wafers

This paper proposes a slurryless, highly efficient polishing method called ultrasonic vibration assisted electrochemical mechanical polishing (UAECMP) to realize 4H-SiC wafers with subnanometer surface roughness. UAECMP involves using ultrasonic vibration to simultaneously assist anodic oxidation of the SiC surface and mechanical removal of the generated oxide layer. The performance of UAECMP was evaluated by experiments and theoretical analyses. For a 4H-SiC (0001) surface, UAECMP achieved a material removal rate (MRR) of 14.54 mu m/h, which was 4.5 times greater than that of ordinary electrochemical mechanical polishing (ECMP) and 290 times greater than that of mechanical polishing. Ultrasonic vibration increased the anodic oxidation rate by introducing local transient strain to the SiC surface and increasing the temperatures of the polishing area and electrolyte. The effect increased with the amplitude of the ultrasonic vibration. However, increasing the ultrasonic vibration amplitude also increased the surface roughness due to the large fluctuations of polishing marks caused by the grinding stone and SiC surface impact and the increasing residual oxide. Therefore, we propose a high-efficiency and-quality polishing process for SiC wafers that combines UAECMP and ECMP. The proposed polishing process may help simplify the existing manufacturing process for SiC wafers.

Automated summary

This paper proposes a slurryless, highly efficient polishing method called ultrasonic vibration assisted electrochemical mechanical polishing (UAECMP) for achieving subnanometer surface roughness on 4H-SiC wafers. The performance of UAECMP was evaluated and compared to ordinary electrochemical mechanical polishing and mechanical polishing. The results showed that UAECMP achieved a significantly higher material removal rate and that ultrasonic vibration played a crucial role in increasing the anodic oxidation rate. However, increasing the ultrasonic vibration amplitude also led to an increase in surface roughness, suggesting the need for a combined UAECMP and ECMP process.