Ti ∕ Ni bilayer Ohmic contact on 4H-SiC

Abstract

Electric contact properties and interface structures of titanium/nickel (Ti∕Ni) bilayer Ohmic contact and the aluminum (Al) overlay on 4H silicon carbide (4H-SiC) were investigated. The Al overlay was used for wiring and bonding pads to pass high currents, and usually deposited after the high temperature annealing of the Ohmic contact. We found that the adhesion between the Ti∕Ni Ohmic contact and the Al overlay was improved compared to that of the Ni Ohmic contact and the Al overlay. Auger electron spectroscopy depth profiles showed that in the case of the Ti∕Ni Ohmic contacts, titanium carbide (TiC) exists at the interface between Ni silicide and the Al overlay. This TiC leads the Al to diffuse into the Ni-silicide layer, and the adhesion between Ni silicide and the Al is improved. Moreover, the authors compared the contact resistance before/after 500°C annealing after the Al deposition, and the authors found that the contact resistance was affected by the interface carbon structures.