Effects of substrate surface preparation on chemical vapor deposition growth of 4H-SiC epitaxial layers

The effects of chemical mechanical polish (CMP) and pre-growth oxidation and etching of vicinal 4H-SiC substrates on the quality of epitaxial films have been investigated. Samples with and without a collodial silica CMP and oxidation/etch treatment were studied with optical microscopy, cross section transmission electron microscopy (TEM) and atomic force microscopy (AFM) before and after chemical vapor deposition. Evidence of polishing damage was evident prior to growth in all samples without CMP treatment. Oxidation and etching appeared to generate defects by preferential etching of bulk defects such as dislocations and low angle grain boundaries. Evidence of the polishing damage remained after chemical vapor deposition (CVD) growth on the samples without CMP and the defect density was worse for the oxidized samples compared to the unoxidized ones. The unoxidized CMP wafer had the lowest defect density and rms roughness of the samples studied.