Investigation of Al ₂O ₃ and TiO ₂ as gate insulators for 4H-SiC pulsed power devices

Achieving high quality and high electric breakdown of oxide on 4H-SiC substrates is still a major research challenge. 500Å Al ₂O ₃ and TiO ₂ were deposited on 4H-SiC by high vacuum and low-temperature e-beam evaporation. AFM (Atomic Force Microscopy) results show that a surface mean height of 4-7 Å of Al ₂O ₃ was found on Si substrate and 74 Å of Al ₂O ₃ was found on SiC substrate. MIS capacitors were fabricated using one mask to evaluate the quality of these gate materials. C-V measurements at 10kHz show that Al ₂O ₃ and TiO ₂ have dielectric constants of more than 9 and 20, respectively. The leakage current of an Al ₂O ₃ MIS capacitor is about 10 ^-9 A on a capacitor area of 150μm×150μm at a gate voltage of ±10V. An Al ₂O ₃ MIS capacitor has a lower leakage current than a TiO ₂ MIS capacitor due to its large band gap offsets. Its breakdown electric field strength is more than 8MV/cm. This research indicates that e-beam deposited Al ₂O ₃ may be a promising dielectric material for the pulsed power SiC devices.