A 200-A/2000-V MOS-GTO with improved cell design

A large-area MOS-controlled thyristor (MOS-GTO) has been realized by introducing a new wafer-scale repair technique. The large-area device has a diameter of 3 cm. It has been contacted with an IC-compatible pressure contact and has been fabricated on a lowly doped n-type substrate suitable for very-high-voltage applications comparable to conventional GTOs. The snubbered and unsnubbered turn-off currents were 400 and 200 A, respectively. The currents could be switched up to a final anode-to-cathode voltage of >1500 V. The unique turn-off capabilities have been achieved by an improved design of the MOS-controlled emitter cell. The main feature of the new cell design is an integrated emitter series resistor, which avoids current filamentation during turn-off. In addition an n⁺ buried layer underneath the source of the MOS-controlled emitter cell has been used to reduce the parasitic action of the MOS part of the emitter cell during the on-state