Electrochemical etching of silicon carbide

Both n- and p-type SiC of different doping levels were electrochemically et ched by HF. The etch rate (up to 1.5 mu m/min) and the surface morphology o f p-type 6H-SiC were sensitive to the applied voltage and the HF concentrat ion. The electrochemical valence of 6.3 +/- 0.5 elementary charge per SiC m olecule was determined. At p-n junctions (p-type layer on a n-type 6H-SiC s ubstrate) a selective etching of the p-type epilayer could be achieved. For a planar 6H-4H polytype junction (n-type, both polytypes with equal doping concentrations) the 4H region was selectively etched under UV illumination . Thus polytype junctions could be marked by electrochemical etching. With HCl instead of HF no etching of SiC occurs, but a SiO2 layer (thickness up to 8 mu m) is formed by anodic oxidation.