Comparative study of methods for counting of dislocations in 4H-SiC

Three experimental techniques to determine the density of the three relevant dislocation types (basal plane, threading edge and threading screw) in SiC were investigated: etching by molten KOH with and without the addition of Na<inf>2</inf>O<inf>2</inf> and X-ray topography. The applicability to implement these techniques for a reliable full-wafer scale analysis is tested experimentally. The limitations are found to be mainly determined by the feature sizes. Based on simple considerations, the range of acceptable sizes of the dislocation-related features is estimated. Etching with Na<inf>2</inf>O<inf>2</inf> allows to distinguish between all three types of dislocations, but a reliable detection is difficult to set up due to a too large spread of etch pit size. Without the addition of Na<inf>2</inf>O<inf>2</inf>, TSD and TED cannot be distinguished, but etch pit sizes become more homogeneous, enabling robust etch pit detection over a wider range of dislocation densities. X-ray topography gives reliable results for TSDs and BPDs whereas the measurement of TEDs is limited.