Reverse-blocking IGBTs with V-groove isolation layer for three-level power converters

Multilevel power converters are among the most effective approaches to reduce power loss and to improve efficiency in power conversion systems. Reverse-blocking IGBTs (RB-IGBTs) have been improved and extended to higher breakdown voltage to be used as bidirectional switches in multilevel converter applications. In this work, a hybrid isolation process by combining thermal diffusion and V-Groove etching is developed to form 1200-1700-V RB-IGBTs. The details on 1700-V RB-IGBTs are presented in this paper. Compared with that of full diffusion, the thermal budget of the frontside surface deep boron diffusion has been reduced to less than one-third. Sufficient reverse-blocking capability and switching robustness have been successfully demonstrated. At the same switching loss level, on-state voltage of a 50 A-rated planar gate RB-IGBT is reduced to approximately 1.9 V compared with that of serially connected trenchgate field-stop IGBT (FS-IGBT) and free-wheeling diode (FWD). Experimental benchmarking on 1200-A module demonstrated that the energy loss in three-level inverter was reduced to 18% by using RB-IGBTs instead of IGBT and FWD pairs at typical switching frequencies for high-power, medium-voltage applications.