Mapping of micropipes and downfalls on 4H-SiC epilayers by Candela optical surface analyzer

We use Candela CS20 optical surface analyzer to detect micropipe and downfall defects of 4H-SiC epilayers grown on 3-inch 4H-SiC substrates. Although both micropipes and downfalls appear as growth pits with different sizes in the topographic image, the micropipes are found to have a signature of bright elongated streaks in the scattered light image. Using this unique feature, the micropipes are distinguished from the downfalls. The resulting defect maps show that the downfalls are averagely distributed on the wafer, whereas the micropipes are clustered at the wafer edge. This micropipe distribution is also confirmed by the cross-polarized scanning method. We demonstrate that Candela CS20 optical surface analyzer is a promising defect inspection tool which can not only map the morphological defects but also help to analyze the origins of different defects.