In this work we compare non-contact charge-voltage imaging and UV-photoluminescence (UV-PL) imaging of yield killer defects in epitaxial 4H-SiC wafers.  Two significant findings are based on macro- and micro-scale imaging, respectively.  1- Whole wafer images demonstrate that only a fraction of the UV-PL defects in triangular, downfall and carrot categories are electrically active. 2- Micro-scale images reveal similarities and differences between PL and electrical defect images.  Presented for the first time, micrometer resolution leakage patterns within triangular defects are consistent with the microstructure modeling in reference 1. The results imply that the depletion layer leakage within killer defects corresponds to exposed 3C-SiC polytypes. This leakage may be a consequence of the lower 2.2eV energy gap of 3C-SiC compared to 3.3eV in 4H-SiC.

Abstract