ION-BEAM SYNTHESIS OF DEEP BURIED NISI2 LAYERS IN SILICON BY 6 MEV NI IMPLANTATION

Type-A/A/A heteroepitaxial layer systems of Si/NiSi2/Si with thicknesses of 2.8-mu-m/0.5-mu-m/bulk have been formed by ion beam synthesis using 6 MeV Ni-58 high-dose implantation into (111)-silicon and furnace annealing. The layer systems are characterized by spreading resistance depth profiling and cross-sectional TEM. The depth distribution of NiSi2 precipitates in the as-implanted state is shown to have a significant impact on layer formation during the anneal. From investigations at different doses it is concluded that both the wafer surface and large precipitates present after implantation or formed in the early stages of the anneal act as competing sinks for diffusing Ni atoms, resulting in a dose dependent redistribution of Ni atoms towards the sample surface and/or within the buried layer. The influence of annealing time and temperature on the structure of the deep buried layers is described.