TEM studies of the defects introduced by ion implantation in SiC

We have undertaken a systematic study of the defects formed by ion implantation in SiC for a large variety of experimental conditions. B, N, Al and Ne ions were implanted into 6H-SiC at room temperature RT and at 650 degrees C. Multiple energy implants were carried out in order to obtain "flat" dopant profiles. The samples were annealed from 1100 degrees C to 1750 degrees C for various duration times. Transmission Electron Microscopy (TEM) analysis was carried out on cross-sectional samples using weak beam dark field imaging conditions. All these defects are of interstitial type (clusters or loops). A statistical analysis of digital images was performed to extract the depth-distributions of the defects. The depth-distributions were compared with Monte-Carlo simulations of the ion implantation process. It is shown that when implanted at RT, the defect distributions follow the "damage" profiles i.e., defects appear in regions where atomic displacements occur in the target. In contrast, the defects found after implantation at 650 degrees C always mirror the "range" profile before and after annealing. We show that there is a concentration threshold under which no defect appear. These results are discussed in terms of point defect annihilation, clustering and dopant activation in SiC. (C) 1999 Elsevier Science B.V. All rights reserved.