Passivation of high voltage power devices by thermal oxidation

High voltage power devices were passivated by thermal oxidation in a dry-wet process at 800 to 900 C. The leakage currents after passivation are less than 0.6/microA. The passivation process was tested p-n-p structures with negative and positive bevel angles and break-down voltages up to 5 kV and on complete thyristor structures. Complete passivation was obtained by an Al203- layer sputtered on top of the thermal SiO2-film. Metal contacts were prepared by evaporation of nickel. Bias and high-temperature stress tests show good stability of the passivated devices.