Thermally stable low resistivity ohmic contacts for high power and high temperature SiC device applications

Ti/Al/p-SiC and Ni/n-SiC ohmic contacts with improved electrical and thermal properties in respect to their application in high power and high temperature SiC devices are reported in this work. Contact resistivity as a function of annealing was investigated over the temperature range of 700/spl deg/C -950/spl deg/C. The lowest resistivity of 1.42/spl times/10/sup -5/ /spl Omega/.cm/sup 2/ for the Ti/Al contact was obtained after annealing at 900/spl deg/C while for the Ni contact the lowest resistivity of 4.9/spl times/10/sup -6/ /spl Omega/ cm/sup 2/ was achieved at 950/spl deg/C. The contact stability during prolonged ageing and at high operating temperatures and current density was studied as a criterion for their reliability. It was found that both contacts were thermally stable during ageing in an inert ambient (N/sub 2/) at high temperature of 600/spl deg/C for 100 hours as well as at operating temperatures up to 450/spl deg/C in air and at current density of 10/sup 3/ A/cm/sup 2/ passed through the contacts during the heating. The improved electrical and thermal properties of the Ti/Al/p-SiC and Ni/n-SiC ohmic contacts were demonstrated in the power p-n SiC diode developed.