Starting Point of Step-Bunching Defects on 4H-SiC Si-Face Substrates

On 4H-SiC Si-face substrates after H2etching, the defect with “line” feature parallel to a step as “bunched-step line” was observed. Using X-ray topography and KOH etching, we confirmed that the bunched-step line originated from basal plane dislocation (BPD). Use of the substrate with the lowest BPD density will be effective to reduce bunched-step line that would affect oxide layer reliability on an epitaxial layer. However, more detail investigation needs to classify the BPD that would become a starting point of bunched-step line.