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-temper ature range of 1400-1500 degrees C. Well-defined terraces with three-bilaye r 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 cleanl iness of the reactor. The effects of adding HCl depended on its concentrati on and temperature; i.e. at low temperature and high HCl concentration, the surface had a hillock pattern, while well-defined steps formed at the reve rse conditions. The etch rate with atomic hydrogen was high even at a low t emperature (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 resu lted in a worse surface after etching. Off-axis substrates were smoother, w hile 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.