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4H silicon carbide (4H-SiC) substrate wafers without surface / subsurface damages and low surface roughness are ideal substrates for the development of power electronics and radio frequency (RF) microwave devices, which hold great promise in applications of new energy, rail transportation, smart grid and 5G communication. The processing of 4H-SiC substrate wafers includes slicing, grinding, lapping, polishing and cleaning. However, the surface damages ( SDs) and subsurface damages (SSDs) introduced during the processing of 4H-SiC substrates affects the properties of 4H-SiC substrates and epitaxial layers, and thus the performance and reliability of devices based on 4H-SiC. This paper focuses on the formation and removal mechanisms of SDs / SSDs during the processing of 4H-SiC substrate wafers. Based on the detection method of SDs / SSDs, the morphologies and characterization approaches of SDs / SSDs are reviewed. Finally, three commonly used technologies for the removal SDs / SSDs, along with their technical advantages, development challenges and trends, are briefly discussed. [ABSTRACT FROM AUTHOR]

As one of the most important steps in machine processing of 4H-silicon carbide (4H-SiC) wafers, lapping exerts an important impact on the quality of 4H-SiC substrate wafers. In this paper, the effects of diamond abrasive morphology and dispersion medium on the material removal rate and surface parameters of 4H-SiC wafers were investigated. Based on the contact between diamond abrasive and 4H-SiC wafer surface during lapping process, a simple wafer material removal rate model was derived. It is found that the abrasive morphology significantly affects the material removal rate of 4H-SiC substrate wafers, the higher the material removal rate, the smaller the total thickness variation (TTV) is obtained for 4H-SiC substrate wafers. Due to the anisotropy of C-face and Si-face of 4H-SiC, the material removal rate of C-face is higher than that of Siface. In terms of effect of the dispersion medium, the Zeta potential absolute value of the water-based slurry is high, and the abrasive is evenly dispersed. It is beneficial to control the disc temperature during the lapping process due to the large thermal conductivity of water. The Zeta potential absolute value of the glycol-based slurry is small, and the abrasive is prone to agglomeration. As the abrasive cutting depth deepens in lapping process, the material removal rate of 4H-SiC wafer increases, and the maximum value of scratch depth also aggravates accordingly. [ABSTRACT FROM AUTHOR]