Gaseous etching of 6H-SiC at relatively low temperatures

A comparison was made of on- and off-axis 6H-SiC substrate surfaces etched in H-2, atomic hydrogen, C2H4/H-2, and HCl/H-2 at the relatively low-temperature range of 1400-1500 degrees C. Well-defined terraces with three-bilayer height steps were obtained on the on-axis 6H-SiC substrates etched as low as 1450 degrees 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 degrees 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. (C) 2000 Published by Elsevier Science B.V. All rights reserved.