*Power Device Works 10 TECHNICAL REPORTS Technologies for Seventh Generation High Performance, High Ruggedness Power Chips Authors: Kenji Suzuki * and Fumihito Masuoka*

For the evolution of power electronics, it is essential to enhance the performance of Insulate Gate Bipolar Transistors (IGBTs) and diodes, both mounted on the power modules. Since the late 1980s, Mitsubishi Electric has been developing low-loss structures for IGBTs such as by fine pattern processing and the CSTBTTM(1-2). Diode performance has also been improved by thin wafer processing and cathode profile optimization. This paper presents the high performance and ruggedness (i.e., wide Safe Operating Area (SOA)) seventh generation IGBT and diode, which have been developed by employing an ultra-thin wafer process and newly optimized profiles in the backside doping layer. 1. Seventh generation IGBT The first to third generation IGBTs were of the planar type structure, and their performance was improved by applying the conventional finer cell-pitch patterning technology. The fourth and later generations adopted a trench-type structure instead; and the fifth and later generations adopted the Mitsubishi Electric’s proprietary CSTBTTM structure, where a Carrier-Stored (CS) layer is formed beneath the Channel Dope layer. Since the CS layer can enhance the electron injection efficiency to hold high enough holes on the emitter side during on-state, i.e. carrier storing effect, it is possible to reduce the on-state forward voltage drop Von. The sixth generation IGBT employed the narrower trench-gate pitch to enhance the carrier storing effect and the performance was further improved. In addition, the high energy ion implantation was used to form the CS layer, and the variance in the threshold voltage was successfully reduced. The performance of the IGBT is described by the Figure Of Merit (FOM) defined by: offsatC