Increasing process margin in SiGe heterojunction bipolar technology by adding carbon

The incorporation of low carbon concentration within the SiGe region of a heterojunction bipolar transistor (HBT) can significantly suppress boron outdiffusion caused by a variety of subsequent processing steps. Thus, it provides greater flexibility in process design and wider latitude in process margin. We demonstrate almost ideal base current characteristics and cutoff, maximum oscillation frequencies of more than 70 GHz, and delays per stage down to 15 ps for ring oscillators with integrated SiGe:C HBT's.