Composite Ohmic Contacts to SiC
Composite ohmic contacts designed for SiC devices operating in air at 350°C have been studied. Ohmic contacts to n- and p-4H-SiC were protected against inter-diffusion and oxidation by Ta-Si-N layers obtained by sputter deposition from a TaSi2 target in a mixture of Ar and N2. Platinum was sputter-deposited at 250°C to promote adhesion between the Ta-Si- N barrier layer and a thick Au cap layer. Platinum also acts as a barrier to the diffusion of Au. The electrical and mechanical characteristics of the composite contacts were stable after hundreds of hours of annealing in air at 350°C. We report the effects of thermal aging on the specific contact resistance and the semiconductor sheet resistance, and the results of wire bond pull and shear tests following aging for Ta-Si-N / Pt / Au stacks deposited on both SiO2 dielectric layers and the ohmic contact layers.
Robert P. Devaty, David J. Larkin and Stephen E. Saddow
A.V. Adedeji et al., "Composite Ohmic Contacts to SiC", Materials Science Forum, Vols. 527-529, pp. 879-882, 2006