Thermal and electrical properties of Au/B4C, Ni/B4C, and Ta/Si contacts to silicon carbide

The role of silicon and boron carbide interface layers on thermal stability and electrical properties of tantalum, gold, and nickel contacts to 6H- and 4H-n-silicon carbide are presented in this report. Thin Ta/Si, Au/B4C, and Ni/B4C layers were deposited on SiC using electron-beam evaporation or sputter-deposition techniques. The structures were annealed either in ultra-high vacuum or in N-H ambient, at temperatures ranging from about 400 to 1150 °C. The samples were characterized using atomic force microscopy for surface topography, auger electron spectrometry for depth profiling, and glancing angle X-ray diffraction for microstructure and phase identification analyses. Transmission line model structures for current-voltage measurements and contact resistance evaluation were prepared using photolithography and lift-off techniques. Our results indicate that Ta in the Ta/SiC system decomposes SiC at about 800 °C, forming tantalum carbide with the accumulation of silicon at the TaC/SiC interface. In the Ta/Si/SiC system decomposition of SiC also occurs about the same temperature resulting in the structure TaC/Si/SiC. The Au/B4C/SiC system appears to be the most thermally stable with the lowest specific contact resistance of about 1×10−6 Ω cm2 for samples heat-treated above 1050 °C for 30 min.