Focused light birefringence for three-dimensional observation of dislocations in silicon carbide wafers

We report a novel method known as focused light birefringence for the three-dimensional observation of dislocations in silicon carbide (SiC) wafers. Dislocations in SiC wafers can adversely affect device performance and production yield, which necessitates their characterization. The existing methods for observing dislocations have some limitations such as sample destruction and the need for sophisticated x-ray facilities. The proposed method utilizes birefringence observations with focused light, which enables the detection of three-dimensional dislocations in SiC substrates and epilayers using a continuous-wave laser and objective lens. The results of experiments showed the successful observation of contrasts representing stress fields around dislocations in freestanding SiC epilayers. In addition, the method allowed the detection of dislocations with conversion structures from basal-plane to threading-edge dislocations, as well as those with threading from the epilayer into the substrate in a 10 μm thick epilayer sample. Compared to other methods, the focused light birefringence method offers advantages such as non-destructiveness and applicability to both SiC substrates and epilayers. The proposed method is effective for the three-dimensional observation of dislocations in SiC wafers and makes it possible to better understand the effect of such dislocations on device performance.