Ni/Ti ohmic and Schottky contacts on 4H-SiC formed with a single thermal treatment

Abstract

The behaviour of Ni/Ti bilayer contacts on 4H-SiC with different thermal anneals is reported, as well as their impact on the electrical characteristics of both Schottky and PN diodes processed on the same wafer. A 350 °C rapid thermal annealing (RTA) provides the optimal forward performances of Schottky contacts with the lowest forward voltage drop (1.1 V at 100 A/cm 2). The ohmic contact improves by increasing the RTA temperature, as inferred from the contact resistivity ( ρ C) decrease detected from rectangular TLM test structures. For higher RTA temperatures (700–900 °C), the contact shows good ohmic characteristics on PN diodes and not severely degraded rectifying properties on Schottky diodes. Concerning reverse measurements, a significant improvement in the breakdown voltage of Schottky diodes has been observed with a 900 °C contact annealing, due to the high Schottky barrier formed with this high temperature treatment.