A new V.MOS/Bipolar Darlington transistor for power applications

This paper deals with the design, processing, and electrical characteristics of a new monolithic power device comprising a V.MOS Field-Effect-Transistor as the driver component, and a bipolar low Emitter Concentration Transistor as the power output component. The study of the device has been made on the base of a 3,9 × 3,9 mm2chip. The device design is such that there is a complete compatibility between processing of the multiepitaxial bipolar power transistor and of the V.MOS transistor. The influence of the main parameters of the structure was studied, including : - Channel width of the V.MOS - Gate oxide thickness - Characteristics of the epitaxial layers A diffusion processing insuring a high gain for the bipolar transistor and a low threshold voltage of the V.MOS F.E.T. has been developed. The electrical measurements exhibit nice characteristics for medium voltage applications: - low threshold voltage : Vth< 2,5 V - high forward transconductance : gm> 5 A/V - low saturation voltage drop : Vsat< 1.8 V (for Ic = 10 A, VG= 10 V) - medium breakdow-voltage : BV> 90 V.