Impact of Ge implantation on the electrical characteristics of TiSi/sub 2/ p/sup +//n shallow junctions with an a-Si (or a poly-Si) buffer layer

A new technology for forming a titanium-silicide shallow junction by combining germanium implantation with an amorphous-silicon (or a poly-silicon) buffer layer has been proposed for MOSFETs. The use of a buffer layer between Ti and Si can avoid the consumption of bulk-silicon and the recession of TiSi/sub 2/ film into the source/drain junctions during the silicidation process. In this study, the important role of germanium-implantation on the formation of TiSi/sub 2/ contacted p/sup +//n junctions was examined. After subsequent implantation of Ge/sup +/ and B/sup +/ into the TiSi/sub 2/ film, samples were annealed at different temperatures to form p/sup +//n junctions and C54-TiSi/sub 2/. Since the penetration of titanium atoms was suppressed due to the germanium-implantation, the periphery leakage and the generation leakage were improved and TiSi/sub 2//Si interfaces were even smooth. Therefore, p/sup +//n junctions with a very low leakage current (0.192 nA/cm/sup 2/ at -5 V) and an excellent forward ideality factor (n/spl ap/1.002) can be obtained. From the secondary ion mass spectrometry (SIMS) analysis, the junction depth is 400.