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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]

Owing to the superior properties of the wide bandgap, high carrier mobility, high thermal conductivity and high stability, 4H silicon carbide (4H-SiC) holds great promise for applications in electrical vehicles, 5G communications, and new-energy systems. Although the industrialization of 150 mm 4H-SiC substrates and epitaxial layers has been successfully achieved, the existence of a high density of dislocations is one of the most severe bottlenecks for advancing the performance and reliability of 4H-SiC based high-power and high-frequency electronics. In this topical review, the classification and basic properties of dislocations in 4H-SiC are introduced. The generation, evolution, and annihilation of dislocations during the single-crystal growth of 4H-SiC boules, the processing of 4H-SiC wafers, as well as the homoepitaxy of 4H-SiC layers are systematically reviewed. The characterization and discrimination of dislocations in 4H-SiC are presented. The effect of dislocations on the electronic and optical properties of 4H-SiC wafers and epitaxial layers, as well as the role of dislocations on the performance and reliability of 4H-SiC based power devices are finally presented. This topical review provides insight into the fundamentals and evolution of dislocations in 4H-SiC, and is expected to provide inspiration for further control of dislocations in 4H-SiC. [ABSTRACT FROM AUTHOR]

Basal plane dislocations (BPDs) are one of the most harmful dislocations in 4H silicon carbide (4H-SiC). Understanding the nucleation of BPDs is the basis of reducing the density of BPDs in 4H-SiC. In this work, we investigate the nucleation mechanism of BPDs, as well as the effect of doping on the nucleation of BPDs in 4H-SiC using nanoindentation. It is found that the shear stress plays a dominant role in the nucleation of BPDs in undoped 4H-SiC. This indicates that the shear component of the thermal stress during the growth of 4H-SiC single crystals and that of the mechanical stress during the processing of 4H-SiC wafers both give rise to the nucleation of BPDs. Nitrogen (N) doping is found to facilitate the nucleation of BPDs and decrease the shear stress required for the nucleation of BPDs. In contrast, vanadium (V) doping hinders the nucleation of BPDs, which promotes the polymorph transition from 4H-SiC to 3C-SiC. [ABSTRACT FROM AUTHOR]

Basal plane dislocations (BPDs) are one of the most harmful dislocations in 4H silicon carbide (4H-SiC). Understanding the nucleation of BPDs is the basis of reducing the density of BPDs in 4H-SiC. In this work, we investigate the nucleation mechanism of BPDs, as well as the effect of doping on the nucleation of BPDs in 4H-SiC using nanoindentation. It is found that the shear stress plays a dominant role in the nucleation of BPDs in undoped 4H-SiC. This indicates that the shear component of the thermal stress during the growth of 4H-SiC single crystals and that of the mechanical stress during the processing of 4H-SiC wafers both give rise to the nucleation of BPDs. Nitrogen (N) doping is found to facilitate the nucleation of BPDs and decrease the shear stress required for the nucleation of BPDs. In contrast, vanadium (V) doping hinders the nucleation of BPDs, which promotes the polymorph transition from 4H-SiC to 3C-SiC. [ABSTRACT FROM AUTHOR]