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 Al
4
C
3
. 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.