Weak trigger current thyristor with noise tripping immunity - has gate layer raised to several sites of cathode at which they are insulated from overlying metallisation

摘要

The thyristor has portions (22) of the trigger layer (13) which project up into the cathode layer (21). An isolating layer (30) is interposed between the projections and the cathode metallisation (16). An isolating layer (31) also covers parts of the device outside the cathode metallisation and has an opening to allow contact between the trigger metallisation (17) and the trigger layer. The projections may be circular or band shaped. The device has a high sensitivity to trigger current and at the same time a high immunity to interference tripping. Mfr. is based on a type N silicon substrate. Layers of silica are deposited on the lower or anode face (15) and on the upper face to form the trigger layer and the projections into the cathode region. The layers are diffused simultaneously with arsenic and gallium. The layer of silica at the upper face is masked, except where it is wished to make the trigger metallisation, and etched.