Experimental 75mm-diameter 4H- and 6H-type wafers were examined by using synchrotron white-beam X-ray topography, X-ray peak position mapping and KOH etching. The topographic images of the wafer revealed dark lines of orientation contrast which were associated with the presence of low-angle boundaries that had a radial distribution around the high-contrast central regions of the wafers. The misorientations which were associated with the boundaries were measured by means of high-resolution diffraction mapping and were found to be of the order of 500arcsec. They were either of pure tilt-type, with the rotation axis in the basal plane, or were of mixed tilt-and-twist type. The KOH etching results provided further evidence for the types of dislocation which were associated with these boundaries. That is, etching of the wafers confirmed that basal-plane dislocation made up the tilt boundaries, and that threading dislocations added a twist component. On the basis of the orientations and distributions of the defect arrays, it was postulated that radial buckling or basal-plane dislocation polygonization could produce the boundaries.

X-Ray Characterization of 3-Inch Diameter 4H and 6H-SiC Experimental Wafers. T.A.Kuhr, W.M.Vetter, M.Dudley, M.Skowronski: Materials Science Forum, 2000, 338-342, 473-6