Papers by Keyword: Optical Surface Analyzer

Abstract: We developed a production technology for epitaxial growth with a smooth surface morphology for 4º off Si-face 4H-SiC epitaxial layers on 100 mm-diameter substrates. High-contrast topography images by optical surface analyzer revealed that a step bunching free surface was obtained throughout the whole area of the wafer surface. However, short-length steps still remained locally on the epitaxial surfaces. Using photoluminescence imaging, it was clarified that the short-length steps were morphological in nature and did not contain stacking faults. The short-length steps were generated by step-flow growth pinning caused by the shallow pits of threading screw dislocations revealed by molten KOH etching.

Abstract: Availability of high-quality, large diameter SiC wafers in quantity has bolstered the commercial application of and interest in both SiC- and nitride-based device technologies. Successful development of SiC devices requires low defect densities, which have been achieved only through significant advances in substrate and epitaxial layer quality. Cree has established viable materials technologies to attain these qualities on production wafers and further developments are imminent. Zero micropipe (ZMP) 100 mm 4HN-SiC substrates are commercially available and 1c dislocations densities were reduced to values as low as 175 cm-2. On these low defect substrates we have achieved repeatable production of thick epitaxial layers with defect densities of less than 1 cm-2 and as low as 0.2 cm-2. These accomplishments rely on precise monitoring of both material and manufacturing induced defects. Selective etch techniques and an optical surface analyzer is used to inspect these defects on our wafers. Results were verified by optical microscopy and x-ray topography.