SIPOS-passivation for high voltage power devices with planar junction termination

Power diodes have been fabricated with a planar junction termination suitable for breakdown voltages up to 6.2 kV. The devices were passivated with a double layer of SIPOS (semi-insulating polycrystalline silicon) and silicon nitride, directly deposited on the silicon surface. The influence of the SIPOS layer on the current distribution in the device while in the blocking state was investigated by numerical simulation and experimentally. It was found that SIPOS acts simply as a resistive layer and that the portion of the reverse current which flows through the passivation layer is given by the balance of the resistances of the space charge region and the SIPOS layer. Therefore, if the resistance of the SIPOS layer is adjusted carefully (by its oxygen content and its lateral and vertical dimensions), high voltage diodes can be passivated with a semi-insulating material, and an excellent blocking behavior can be achieved.<
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