High-back-resistance planar semiconductor component with lacquer coating

摘要

A planar high-back-resistance diode, or a semiconductor component containing at least one such diode is proposed. In addition to the usual terminal electrodes, the diode also contains narrow metal strips which are applied to the oxide on top of the high-resistance zone of the p-n junction. The metal strips have to be positioned in such a way that they do not affect the spread of the space-charge zone when a reverse voltage is applied. For this reason, they should be situated if possible outside the space-charge zone on the high-resistance part of the p-n junction. Coating planar high-back-resistance diodes with lacquer for the purpose of passivation has hitherto presented substantial difficulties. The charges impressed on the silicon dioxide/lacquer boundary surface by the lacquer migrate under the influence of temperature and electrical surface fields. This ion migration results in polarisation at the surface of the lacquer-coated p-n junction, as a result of which the breakdown characteristic is impaired or destruction even takes place. The proposed metal-ring system acts as a barrier to this ion migration. Diodes having such rings exhibit virtually no change in their blocking properties after a hot reverse test (150 DEG C, 400 V, 20 hours). As a result failures can be completely avoided.