Observation of Pair Structures of Threading Dislocation and Surface Defect in 4H-SiC Wafer by Mirror Projection Electron Microscopy

Two types of shallow surface defects associated with treading dislocation were found out by using mirror projection electron microscope. One was single groove with a dimension of about 4 nm in depth, 2 μm in width and 15 μm in length, named “as nanogroove”. The other was a shallow groove at 1.3nm in depth being between pair of hillocks at 2-3 nm in height and 1.5 μm in distance, named as “nanohillock pair”. Dislocations combined with the defects were found out by micro-KOH etching method with low-energy scanning electron microscopy. The dislocations were identified by g-b analysis using scanning transmission electron microscopy as threading edge dislocations converted from basal plane dislocation at bulk-epi layer interface or within epi layer.