Effect of pre-treatment and nickel layer thickness on nickel silicide/silicon carbide contact

This investigation deals with the impact of pre-treatment and Ni thickness on the reactions of Ni–silicide/SiC contact fabrication. The specimens have been prepared by sputter depositing 3–100nm Ni layer on 4H–SiC wafer followed by annealing at 800°C in vacuum for 20min. The results by means of XPS show as follows: among the chemical cleaning procedures which have been tested, the recipe NH4OH:H2O2:H2O = 1:1:5, 85°C, 5min; HF 10%, 80°C, 2min; boiling water 10min is the most effective for SiC substrates. However, due to short time exposure in the air before experiment, certain contamination re-occurs. After annealing, the dominant silicide formed is Ni2Si, whereas C on the surface is graphite. Argon ion etching before the Ni deposition helps the formation of multi-layer structure. For the samples without pre-treatment or with chemical cleaning procedure, there is more C agglomerated at the surface and no multi-layer structure formed. Under the action of Ar ion etching, SiC decomposes more quickly and Ni diffuses faster. This effect together with limited C diffusivity in the formed silicide is a probable reason for the formation of the multi-layer structure. The silicides formed at the interface are dependent on the Ni layer thickness and substrate surface condition.