Metal emitter SiGe:C HBTs

SiGe:C heterojunction bipolar transistors (HBTs) offer high cut-off frequencies, f/sub T/, but low open base breakdown voltages, BV/sub CEO/, due to the relatively high current gain, h/sub FE/. In this paper, we show that the integration of a metal emitter, made by complete silicidation of a mono-emitter, increases the base current, I/sub B/ without reducing the collector current, I/sub C/. Hence, the BV/sub CEO/ is increased without affecting the f/sub T/. Furthermore, this metal emitter reduces the emitter series resistance, R/sub E/, and increases the f/sub T/ compared with a mono-emitter. SiGe:C HBTs with f/sub T/=230GHz and BV/sub CEO/=1.8V have been realised using a metal emitter in a self-aligned integration scheme.