The effect of thermal annealing of Au contacts on 6H-SiC and 4H-SiC

The annealing effects of gold contacts on SiC single crystal substrates have been investigated using SPM and XPS/AES. Ultra-thin Au films with thicknesses of 30 Angstrom and 150 Angstrom, respectively, were fabricated onto both 4H- and 6H-SiC substrates via rf sputtering. The Au/SiC systems were then undergone a series of annealing with temperatures ranging from 200 degrees C to 400 degrees C. This study reveals that the sputtering system can generally produce a thin film of uniformly distributed nano-meter sized granular particles. The size of the particles increases with both the thickness of the ultra-thin film and annealing temperature. The thicker Au film revealed pin-hole damages after 300 degrees C annealing and severe cracking and spalling after 400 degrees C. However, the thinner Au film only demonstrated the increase of particle sizes. The atomic ratio of gold to silicon in the surface region decreases with the increase of annealing temperature, which indicates the diffusion of gold into silicon carbide. No significant changes of the Schottky barrier heights have been found for Au contacts onto both 6H- and 4H-SiC in the annealing temperature range. After the 400 degrees C annealing, a noticeable SiO2/SiOx peak was unveiled in the XPS spectra.