Annealing effects of Al/n-type 6H SiC rectifying contacts

The annealing effects of Al/n-type 6H SiC rectifying contacts have been studied on different surface polarities of Si- and C-faces by V-I, C-V, and AES measurements. Good rectification characteristics with low reverse leakage current were obtained by annealing above 660°C for 3 min in argon. By annealing at 900°C, the electrodes without deep interface levels were fabricated on both Si- and C-faces, and the built-in voltages Obtained were 1.7 V. The preliminary reliabilities of the electrodes were examined at 300 K in dry air for 1000 h, which showed promising results. At annealing temperatures lower than 900°C, Si-faced samples showed smaller degradation of capacitance characteristics than C-faced samples. From the AES measurements at the Al-SiC interfaces, as the effects of heat treatment at 900°C, the isolation of adsorbed oxygen from the intermixed region of Al, Si, and C was clearly observed. The results also suggested the formation of Al4C3. These two mechanisms are considered to contribute to forming stable contacts. Larger amounts of oxygen adsorption were also observed on C-faced samples. This oxygen was considered as the key factor for the electrical degradation that occurred on the C-faced samples.