The thermal stability study and improvement of 4H-SiC ohmic contact

The thermal stability of the standard Ni/SiC and a TiW/Ni/SiC Ohmic contacts was investigated and compared after being aged at 400 degrees C in the N-2 atmosphere. The Ohmic contact was characterized using a combination of I-V measurements, the optical microscopic imaging, X-ray diffraction (XRD), and Auger electron spectroscopy (AES) techniques. It is shown that the standard Ni/SiC Ohmic contact failed after being aged at 400 degrees C for 20 h in the N-2 atmosphere, while the TiW/Ni/SiC Ohmic contact could stand after 100 h. The TiW/Ni/SiC Ohmic contact was found kept a smooth surface morphology during the rapid thermal annealing and aging process, while the standard Ni/SiC Ohmic metal surface was found rougher. Both the Ohmic contact deteriorations after high temperature aging could be attributed to the formation of graphite which is confirmed by the XRD results. The XRD and AES results reveal that the better thermal stability of the TiW/Ni/SiC could be explained by the formation of CW3 and TiC, which deter the C atom diffusion to form graphite. (C) 2014 AIP Publishing LLC.