In-situ surface preparation of nominally on-axis 4H-SiC substrates

A study of the in-situ surface preparation has been performed for both Si- and C-face 4H-SiC nominally on-axis samples. The surface was studied after etching under C-rich, Si-rich and under pure hydrogen ambient conditions at the same temperature, pressure and time interval using a hot-wall chemical vapor deposition reactor. The surfaces of all the samples were analyzed using optical microscopy with Normarski diffractional interference contrast and atomic force microscopy with tapping mode before and after in-situ etching. Polishing related damages were found to be removed under all etching conditions, also the surface step structure was uncovered and a few defect-selective etch pits were observed. For the Si-face sample, the best surface morphology was obtained after Si-rich etching conditions with more uniform and small macro-step height which resulted in the lowest surface roughness. For the C-face sample the surface morphology was comparable under all etching conditions and not much difference was found except for the etching rate. Si droplets were not observed under any etching conditions.