Increasing process margin in SiGe heterojunction bipolar technology by adding carbon

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