A New Generation of High Frequency SiGe HBTs

摘要

The addition of a small amount of C in the B-doped base layer of a npn SiGe heterojunction bipolar transistor (HBT) paved the way for exposing the high frequency (HF) performance potential of such devices more than 10 years ago.1 Significantly, the suppression of thermal diffusion and point-defect assisted enhanced diffusion, due to the presence of C, helps to sustain steep base profiles through the fabrication process. As a consequence, the base transit time, the crucial delay time in previous HF bipolar transistor generations, could be reduced without degradation of the base sheet resistance, by realizing a highly-concentrated, narrow base doping in combination with a carefully tailored SiGe profile.