Observation of Basal Plane Dislocation in 4H-SiC Wafer by Mirror Projection Electron Microscopy and Low-Energy SEM

Abstract

Basal plane dislocation (BPD) with dislocation lines in shallow areas near the surface in 4H-SiC epitaxial wafer was observed by mirror projection electron microscopy (MPJ) and low-energy scanning electron microscopy (LE-SEM). A contrast of dislocation line of BPD appeared in a MPJ observation as gradually weakened dark line toward the upper stream of offcut of wafer, and the contrast almost agreed with the LE-SEM image taken at the same BPD by not a morphology-sensitive imaging method but a potential-sensitive imaging method. Thus an origin of the contrast corresponding to BPD in MPJ is considered to surface potential change due to charging on dislocation line. MPJ observation can gives a BPD image with same quality as a potential-sensitive image by LE-SEM, in extremely short time and damage-and contamination-free condition at no electron irradiation on wafer.