Optical quantitative determination of doping levels and their distribution in SiC

We report the development of an absorption measurement-based characterization tool for the quantitative determination of doping levels and their lateral distribution in silicon carbide wafers. Calibration plots for the technologically important silicon carbide polytypes 4H–SiC (n-/p-type), 6H–SiC (n-/p-type) and 15R–SiC (n-type) are presented. A review of the underlying physical effects of the measurement procedure as well as a description of the experimental setup is given. The applicability of the characterization tool as a production friendly non-contact wafer quality test is demonstrated by showing several mappings of the lateral doping level distribution. The accuracy of the described measurement procedure is typically 15–20% and is of the same order as its electrical Hall measurement counterpart.