Suppression of both sidewall injection and hot-carrier effects using laterally graded emitter in bipolar transistors

As scaling down the feature size of a bipolar transistor, the spacer between the emitter contact and the base contact becomes so much smaller that the diffused extrinsic base may encroach on the heavily-doped emitter. Two major serious problems concerned are the degradations due to the sidewall injection at forward bias and the hot carrier stress at reverse bias. A novel structure, so called Laterally Graded Emitter (LGE), has been recently proposed to solve these problems in BiCMOS applications. But it still has some limitations to apply such structure to the advanced bipolar transistors. The authors present a study on the utility of LGE structure for scaled bipolar transistors by two-dimensional numerical simulator PISCES-II B