The effect of NaOH on the morphology of dislocation-related pits in SiC during etching in molten eutectic KOH-NaOH

Abstract

Silicon carbide (SiC), a third-generation semiconductor material, has become a prominent research focus in the new energy automobile industry owing to its excellent physical and chemical properties. Ensuring the reliability of SiC power devices necessitates accurate characterization of dislocation defects. This study aims to optimize the molten KOH etching method by adjusting the additive composition to improve the characterization of dislocation defects in SiC substrates and enhance the clarity and stability of etch-pit contours. Optical microscopy (OM) and laser scanning confocal microscopy (LSC) were systematically employed to investigate the effects of the different additives on the etching rate and pit morphology. The specific effects on the etching process were examined by varying the NaOH concentration in the molten eutectic KOH-NaOH solution. The study found that reducing the etching rate helps maintain clear etch pit contours, and that the etching temperature has a more significant effect on the etching rate than the etching duration. Ultimately, a molten eutectic KOH-NaOH etchant with a NaOH concentration of 20 wt% was successfully developed. This etchant ensures a high etching efficiency while maintaining well-defined etch pit contours and accommodates a broader range of etching temperatures and durations. Compared to the conventional method of adding strong oxidizers, the developed 20 wt% NaOH molten eutectic KOH-NaOH etchant offers enhanced safety, cost-effectiveness, and efficiency. This provides a more stable and reliable method for characterizing dislocation defects in SiC, contributing to the advancement of SiC power devices in the new-energy automobile industry.