A high performance 0.18μm BiCMOS technology employing high carbon content in the base layer of the SiGe HBT to achieve low variability of hFE

We present a 0.18μm BiCMOS technology in which the hFE variability of silicon-germanium heterojunction bipolar transistors (SiGe HBTs) is greatly minimized by means of increased neutral base recombination adding high carbon content in the base layer. In this work, we propose, for the first time, to use a high concentration of carbon in the base of SiGe HBTs as a practical way to increase the base current in a predictable and controlled way. Consequently, variability of hFE is greatly decreased and a significant improvement of device matching can be achieved. Furthermore, to guarantee a sufficiently high value of hFE we propose a silicon-germanium cap architecture to increase the collector current. HBTs fabricated using this technology exhibit a peak fT of 90GHz and a peak fMAX of 140GHz with an fTxBVceo of 255GHzV. Together with state of the art 0.18μm CMOS platform and high quality passives this technology is a viable candidate for the design of high frequency analog circuits.