Defect mapping in 4H-SiC wafers

A new non destructive method has been applied for revealing micropipes in SiC wafers. Two 4H-polytype commercial wafers have been studied. The comparison made with the commonly used KOH etching shows some discrepancy in the absolute values, which can be attributed to the specificity of the two techniques. However the distribution course is identical. More micropipes are found close to the periphery of the wafers. In addition, the dislocation density and their distribution over the wafers are obtained and they are analysed in conjunction with microhardness measurements. It appears that these dislocations cannot be directly related to the micropipes.