Gaseous etching of 6H–SiC at relatively low temperatures

Abstract

A comparison was made of on- and off-axis 6H–SiC substrate surfaces etched in H 2, atomic hydrogen, C 2H 4/H 2, and HCl/H 2 at the relatively low-temperature range of 1400–1500°C. Well-defined terraces with three-bilayer height steps were obtained on the on-axis 6H–SiC substrates etched as low as 1450°C, with reproducibility dependent on the history or cleanliness of the reactor. The effects of adding HCl depended on its concentration and temperature; i.e. at low temperature and high HCl concentration, the surface had a hillock pattern, while well-defined steps formed at the reverse conditions. The etch rate with atomic hydrogen was high even at a low temperature (1200°C), and it produced a surface pattern with hillock depressions. The surface after etching depended on the original substrate surface condition; polishing damage caused by high applied load always resulted in a worse surface after etching. Off-axis substrates were smoother, while the original off-cut step pattern was not changed after etching in H 2.