Phase and structure transformations in the titanium interlayer during the nickel silicidation on Si(1 0 0) substrate

Recently, promising results for epitaxial cobalt and nickel silicide formation have been obtained using a thin titanium interlayer and as a mechanism for such an interlayer promoting effect the removal of a native oxide from a silicon substrate due to the gettering effect of titanium was suggested. However, detailed information about transformations in the Ti layer during its growth and annealing process still lacks. In this paper, phase and structure transformations in the Ti interlayer during growth and consequent silicidation annealing are studied on the system Ni/Ti/Si(1 0 0). The Ni (4 nm)/Ti (1.4 nm) bilayers were deposited onto unheated (1 0 0) Si substrate with a native oxide layer by rf sputtering inside the AES – microscope and analyzed by in situ Auger electron spectroscopy, X-ray photoelectron spectroscopy and ex situ transmission electron microscopy. During the Ti interlayer deposition process a following sequence of the growth mechanism and phases were revealed. Initially, small 3D TiO2 islands are formed due to reduction of a native silicon oxide followed by the formation of the TiO and TiOx phase between TiO2 islands as well as on their top. During the silicidation annealing at 300 °C the continuous Ti-related interlayer, composed mainly (∼85%) of Ti oxides (TiO and TiO2) transforms into less compact island-like TiO2 layer what promotes Ni diffusion into silicon resulting in the nickel silicide, NiSi2 formation.