Chemomechanical polishing of silicon carbide

In an effort to improve silicon carbide (SIG) substrates surfaces prior to epitaxial growth, two chemomechanical polishing (CMP) techniques were investigated and the results were compared with a mechanical polishing procedure involving various grades of diamond paste. This work focused on silicon-terminated (0001) SiC surfaces. The two CMP techniques utilized (i) chromium oxide(lll) abrasives and (ii) colloidal silica polishing slurry. The best surfaces were obtained after colloidal silica polishing under conditions that combined elevated temperatures (similar to 55 degrees C) with a high slurry alkalinity (pH > 10) and a high solute content. Cross-sectional transmission electron microscopy showed no observable subsurface damage, and atomic force microscopy showed a significant reduction in roughness compared to commercial diamond-polished wafers. Growth experiments following colloidal silica polishing yielded a much improved film surface morphology.