Interfacial Reactions in Nickel/titanium Ohmic Contacts to N-type Silicon Carbide

The complex sequence of reactions and resulting material phases that occur during formation of ohmic contacts using a trilayer titanium/nickel/titanium structure on n-SiC have been studied. The Ti∕Ni∕Ti contacts on SiC were rectifying in the as-deposited state, but became ohmic upon annealing at 1000°C for 2min in a N2 ambient, resulting in a specific contact resistance (ρC) as low as 1×10−4Ωcm2. X-ray diffraction, Auger electron spectroscopy data and transmission electron microscopy analysis showed that Ni2Si, TiC and graphitic-bound C formed as a result of the annealing. The top Ti layer remained intact as predominantly titanium oxide with minor amounts of TiC. The Ni layer was converted to a double Ni2Si layer containing graphitic C nonuniformly distributed. The bottom Ti layer was converted to a TiC layer separating the two Ni2Si layers, and graphitic C was concentrated in a discontinuous layer near the Ni2Si∕SiC interface. The reasons for the formation of this complicated microstructure were discussed.