Active Planarization Method from Rough Surface of 4º-off 4H-SiC (0001) Controlled by Step Bunching and Debunching Mechanism Using Dynamic AGE-ing<sup>®</sup>

In this study, we developed two planarization mechanisms, macroscopic and microscopic, controlled by adjusting the C/Si ratio during Dynamic AGE-ing ® (DA) sublimation etching. Using these mechanisms, we planarized rough 4H-SiC wafers without the use of chemical mechanical polishing (CMP). Macro planarization forms macro step bunching (MSB) using high C/Si ratio DA etching, straightens the steps using step tension, and removes scratch marks caused by mechanical processing. Microscopic planarization involves debunching these MSBs using low C/Si ratio DA etching. It was observed that debunching progressed more quickly on wafers before CMP finishing due to the higher density of MSBs with ramified structures, which serve as starting points for debunching. The rate at which the MSB is shortened by step debunching increases with rising temperature, reaching about 20 μm/min at 1800 °C. By utilizing these mechanisms, we achieved high-quality planarization (initial Ra = 0.6 nm) to Ra = 0.18 nm for φ6-inch 4H-SiC wafers that had not undergone CMP. Furthermore, by performing DA sublimation growth on this planarized wafer, we achieved an in-grown stacking fault (IGSF) density of 0.09 cm⁻² and a basal plane dislocation (BPD) to threading edge dislocation (TED) conversion ratio of 99.95 %.