Two routes to polycrystalline CoSi2 thin films by co-sputtering Co and Si

Two processes for the fabrication of polycrystalline CoSi₂ thin films based on the codeposition of Co and Si by sputtering were studied and compared. The first process involved “annealing after deposition”, where Co and Si are codeposited at ambient temperature and then crystallized by annealing. This process yielded randomly oriented plate-like CoSi₂ grains with a grain size that is governed by the nanostructure of the as-deposited film. Polycrystalline CoSi₂ thin films were obtained at a process temperature of 170 °C, which was much lower than the annealing temperature of 500 °C needed for Co/Si bilayers. The second process involved “heating during deposition”, where Co and Si are codeposited on heated substrates. This process yielded CoSi₂ grains with a columnar structure, and the grain size and degree of (1 1 1) orientation are temperature dependent. The sheet resistance of the resulting films was determined by the preparation temperature regardless of the deposition process used, i.e. “annealing after deposition” or “heating during deposition”. Temperatures of 500 °C and higher were needed to achieve CoSi₂ resistivity of 40 μΩ cm or lower for both processes.