Characterization of Dislocations in 4H-SiC

Accurate characterization of dislocations is crucial for optimizing the performance of SiC-based power devices. The traditional way to measure dislocation density in SiC industry is KOH etching, a destructive approach that makes the wafer no longer available for epitaxial growth. Another major limitation of this technique is the accuracy of the data since some dislocations can be hardly recognized. For example, the etch pit of threading screw dislocation is similar to that of threading edge dislocation, both of which are usually in hexagonal shape while the primary difference is the size. However, those challenges and limitations in KOH etching do not exist in X-ray topography. In this paper, the non-destructive approach, X-ray topography, is introduced to characterize dislocations in 4H-SiC industry. Threading screw dislocations were measured by both KOH etching and X-ray topography, the result of which indicates that some threading screw dislocations clearly visible in X-ray topograph are not recognizable in KOH etching image. In addition, some 60° prismatic dislocations not recognized in KOH etching image can be observed in X-ray topographs. Moreover, unlike destructive KOH etching, wafers measured by X-ray topography can be further used for annealing, epitaxial growth, ion implantation and etc., which is beneficial to SiC fundamental research.