Phase Formation and Morphology of Nickel Silicide Thin Films Synthesized by Catalyzed Chemical Vapor Reaction of Nickel with Silane

The synthesis of nickel silicide thin films via a vapor–solid reaction has been studied by exposing thin (10 nm) Ni films to silane (SiH 4 ). The crystalline phases, the Ni/Si stoichiometric ratios, as well as the surface and interface properties of the resulting silicide films were investigated as a function of the growth parameters such as the SiH 4 partial pressure, the reaction temperature, and the exposure time. At low temperature (300 °C), SiH 4 exposure led to the self-limiting deposition of Si on Ni by catalytic decomposition of SiH 4 but not to silicate formation. Between 350 and 400 °C, phase pure orthorhombic NiSi films were obtained that were formed directly without any apparent intermediate Ni-rich silicide phases. A transformation to NiSi 2 occurred at 450 °C and above, and at 500 °C phase pure NiSi 2 was obtained. Here, the transient formation of NiSi was observed that transformed into NiSi 2 for prolonged SiH 4 exposure. The results indicate that the Si solubility governs the phase formation sequence whereas kinetics are determined by Ni diffusion and the reaction rate. Resistivity values of 21 and 36 μΩ cm were found for the NiSi and NiSi 2 thin films, respectively, corresponding to the values reported for films obtained by solid-state reactions.