Conceptual Study of Sub-600 V IGBTs

Abstract

Very low voltage, 60 to 600V IGBTs were compared to power MOSFETs with conventional and superjunction drift layers of identical voltage classes using mixed-mode numerical device simulation. This study was done in the light of forthcoming 4 0 0 V c l a s s I G B T s f o r u s e i n E V / H E V v e h i c l e s : t h e 6 0 0 V borderline, which previously separated the bulk of power MOSFET from IGBT applications, has become fragile recently. We find that the 400 V class must not represent a lower limit for IGBTs based on silicon: in fact, LV IGBTs could offer lower losses down to the 60 to 100 V level. Most importantly, low voltage IGBTs may outperform power MOSFETs not only with respect to onstate voltage drop but also regarding switching offering up to 30% lower turn-off losses. The paper presents physics based arguments focusing on the device transconductance to augment these projections. LV IGBTs or hybrid devices (monolithic integration o f M O S F E T p l u s I G B T ) c o u l d b e c o m e l o w e r c o s t , h i g h performance alternatives to SJ power MOSFETs thanks to short development cycles common in mature silicon technologies. Index Terms-Insulated Gate Bipolar Transistor (IGBT), power MOSFET, superjunction power MOSFET, technology trade-off, emitter efficiency.