Papers by Author: Thomas Kerr

Abstract: Several morphological defects in 4H SiC epitaxial wafers, including Comets and Triangles, may significantly impact on the yield and reliability of SiC devices. The formation of these epilayer defects is closely related to the substrate quality. This paper focuses on the study of the substrate quality and its relationship with defects in the epilayers. The crystalline quality of 4H n+ substrates has been characterized by x-ray diffraction, and the distribution of dislocations has been determined using etching in molten KOH. The relationship between Comet and Triangle epilayer defects and the dislocations has been established. A 10-fold reduction in the overall dislocation density in the 4H SiC substrates was achieved through technological improvements. The improvement was validated by the reduction in the number of the epilayer defects.

Abstract: SiC substrates produced at II-VI, Inc. have been characterized using x-ray rocking curve mapping (topography). The rocking curves have been measured in the
-scan mode for the (0006) Bragg reflection of 6H and the (0004) reflection of 4H SiC substrates. The maps contain information extracted from the rocking curves, such as the peak angle (
) and the rocking curve broadening (FWHM). In the case when lattice distortion is present due to the elastic or plastic deformation, the peak angle (
) changes gradually upon scanning, with the d
/dx gradient proportional to the lattice curvature in the plane of diffraction. Multi-peak reflections and/or sharp change in the value of
indicate the presence of misoriented grains. X-ray rocking curve mapping of SiC substrates yields excellent measures of crystalline quality that contain important information on the lattice strain and sub-grain misorientation.