Stabilization of the 3C-SiC/SOI system by an intermediate silicon nitride layer

The material system 3C-SiC on SOI (silicon on insulator) offers outstanding possibilities for high temperature applications. In order to fully benefit from these possibilities, the quality of especially the SOI substrate must be maintained throughout all process steps of device fabrication. This wor k demonstrates the stabilizing effect of a 6 nm thin silicon nitride layer at the interface silicon overlayer/buried oxide layer (SOL/BOX) of a UNIBON D-SOI substrate. This layer was formed by implantation of nitrogen into a S OI substrate and subsequent annealing for 2 h at 1100 degrees C. The improv ed stability of the SOI system during SiC deposition is explained by the fo llowing fact: the wetting angle of silicon at the melting point is decrease d from 87 degrees (Si on SiO2) to 25 degrees (Si on Si3N4). The improved we tting behavior decreases the tendency of silicon to redistribute and to for m cavities. A 2.6 mu m thick layer of cubic SiC was deposited at 1200 degre es C on a UNIBOND SOI substrate. This sample was only partly implanted with nitrogen. At the non-implanted part, a significant redistribution of the S OL occurred and cavities were extended from the SOL deep into the BOX. Wher eas at the N-implanted part, the BOX was completely protected by the silico n nitride layer and only small cavities were extended into the SOL (thickne sses of SOL and BOX were about 150 and 400 nm. respectively). The crystal q uality of the SiC layer was almost the same in both cases. Furthermore, the results indicate that an optimization of the whole process will even lead to better results. (C) 1999 Elsevier Science S.A. All rights reserved.