A new collector structure for thin wafer NPT-IGBT with low dose p- Si injection layer and high dose p+ Ge contact layer

We have proposed a new collector structure for thin wafer IGBTs to improve contact resistances without sacrificing turnoff losses. The proposed structure has a low dose p- Si injection layer and a high dose p+ Ge contact. We also demonstrate, for the first time, the performance of 1.2 kV 200 A class thin wafer NPT IGBTs using this new collector structure. As a result, from simulations and measurements, we found that the high dose p+ Ge layer acts to suppress the hole-injection and also provides low contact resistances without consequently sacrificing turnoff losses.