Long-term stability of Ni–silicide ohmic contact to n-type 4H–SiC

The thermal stability of Ni2Si/n-SiC ohmic contacts with Au overlayer without or with Ta–Si–N diffusion barrier was investigated after long anneals at 400 °C in air. Current–voltage characteristics, sheet resistance measurements, Rutherford backscattering spectrometry, X-ray diffraction and scanning electron microscopy were used to characterize the contacts before and after aging. It is shown that aging of Au/Ni2Si/n-SiC contact at 400 °C for 50 h resulted in electrical failure, as well as complete contact degradation for 150 h due to interdiffusion/reaction processes in the contact. The Au/Ta35Si15N50/Ni2Si/n-SiC contact is thermally stable after 150 h of aging at 400 °C and has great potential for use in SiC-based devices for high-temperature operation.