Surface Modification and High-Resolution Nondistractive Analysis toward Dislocation-free SiC Growth

点击翻译按钮获取中文摘要

Surface modification and high-resolution nondestructive analysis toward dislocation-free silicon carbide (SiC) growth were carried out. Crystal defects in grown layers were observed nondestructively by an electron beam induced current (EBIC) method. It is difficult to detect crystal defects in commercially available SiC wafers due to the high defect density over 10000cm^-2. To obtain a high resolution EBIC mapping image, an accelerating voltage of the electron beam and the metal of collection Schottky electrode of an EBIC signal were examined. The clear mapping EBIC image with a high resolution of 0.5μm was realized at the accelerating voltage of 10kV and the nickel electrode. In addition, behaviors of crystal defects in SiC were discussed based on the change of EBIC signals. Some basal-plane dislocations extended to the [11-20] direction were resolved to the threading dislocations at the interface between the epilayer and wafer substrate. It is considered that the dislocations in SiC can be converted by the surface modification (treatment) helium the epitaxial growth. SiC surfaces were modified by a thermal etching method in a mixed gas of chlorine and oxygen. A typical etching rate of a 4H-type SiC (0001) Si face was 0.5μm/h at 950℃ Many pits appeared after the modification, and they were corresponding to the crystal defects. A shape of the etch pits was a distorted hexagon, and the kind of crystal defects such as screw, edge and basal-plane dislocations could be classified easily by the size of etch pits. Basal-plane dislocations in the epilayer were reduced by the use of surface modified SiC substrate.