Structural pattern formation in titanium nickel contacts on silicon carbide following high-temperature annealing
The composition and microstructure of compound contacts to 4H-SiC containing both titanium and nickel were investigated. Samples were prepared by metal evaporation on commercial 4H-SiC wafers followed by rapid thermal annealing (RTA). Contact structures with three different metal deposition sequences were investigated: (A) SiC/Ti(4 nm)/Ni(150 nm); (B) SiC/Ti(100 nm)/Ni(50 nm) and (C) SiC/Ti(4 nm)/Ni(50 nm)/Ti(100 nm). RTA was performed in a vacuum at 800, 925 and 1040 °C for a period of 800 s. X-ray diffraction, Auger electron spectroscopy and transmission electron microscopy were used for the characterization. A distinct spatial separation of nickel silicide and titanium carbide layers was observed in all samples. It was discovered that the final distribution of solid-state reaction products in B- and C-samples was independent of the order of the deposition of the initial metal films. In both samples, a two-phase TiC+C layer was found to be adjacent to the SiC substrate. Factors controlling phase formation and segregation are discussed. A two-stage reaction model is proposed to explain the reaction zone structure formed in the Ni-Ti-SiC system after high-temperature treatment.