Conoscopy as a Failure Analysis Method for Single Crystals

Conoscopy is widely used to evaluate single crystals used as substrates on which epitaxial layers are grown in the LED industry, where the quality of the single crystal affects the reliability of the final product, the LED chip, and the package. However, the application of this method is currently restricted to characterizing birefringence. We performed conoscopy measurements on single crystals with failure modes (e.g., birefringence, lineages, dislocations, polycrystallinity, and amorphousness) and examined whether it was possible to inspect such failures using conoscopy. Sapphire (α-Al2O3) and silicon carbide (6H–SiC) single crystals containing failures were investigated. X-ray diffraction and transmission electron microscopy analyses were also performed; their results were compared with the conoscopy results. Conoscopy was shown to inspect birefringence as well as other failure modes. Comparison of the conoscopic patterns obtained via simulation and experiment shows that quantitative evaluation of the failure level is possible. These results show that conoscopy can be used to quickly and easily investigate various failure mechanisms in single crystals.