Formation of ion beam mixed silicides on Si (100) at elevated substrate temperatures

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Abstract
High-resolution transmission electron microscopy and Rutherford backscattering spectroscopy have been used to study the structure and composition of intermixed regions between thin films of Ni deposited on single crystals of (100) silicon. A comparison has been made between thin films of silicide which have been either thermally grown or ion-beam reacted at different substrate temperatures. It is shown that not only can high temperature, silicide phases be produced at lower temperatures by ion-beam mixing, but also the structure of the Si/silicide interface and the morphology of the silicide depend on whether the mixing was induced thermally or by ion irradiation. It was found that depending on the temperature of the substrate, Ni3Si2, NiSi, NiSi2, were observed to form. Ion mixing at 500 °C led to the formation of a unique morphological structure. At this temperature, two distinct silicide layers formed (NiSi and NiSi2) with the silicon-rich phase at the surface away from the Si/silicide interface. Premixing by ion irradiation before thermal treatment of the samples was found to influence the detailed microstructure of the reacted region. The premixing produced less oxidation of nickel during thermal treatment compared to that observed on samples which were reacted solely by thermal processing; it also resulted in a more uniform, planar interface.