New insulated-gate thyristor structure with MOSFET coupled base regions

Abstract

A new insulated-gate thyristor (IGTH) structure in which the base of n-p-n transistor is coupled to the base of p-n-p transistor through a MOSFET is described for the first time, In the new structure, called base coupled insulated gate thyristor (BC-IGTH), the parasitic lateral p-n-p carrier injection inherent in previously reported thyristor structures such as the MCT, BRT, and IGTH is absent. The absence of parasitic lateral p-n-p carrier injection results in low on state voltage drop and high controllable current capability for this structure. The turn-on process in the new structure is fundamentally different from other MOS-gated thyristor structures in that in the new structure, the higher gain n-p-n transistor is turned-on first, which then provides the base drive for the lower gain p-n-p transistor. Multicellular 800 V devices of the new thyristor structure were fabricated using a double-diffused DMOS process, and were found to give on-state drop of 1.1 V at 200 A/cm/sup 2/, and controllable currents in excess of 100 A/cm/sup 2/ were obtained by forming MOS-gate controlled emitter-to-base resistive shorts.