Investigating Substrate Network Effects on Si/SiGe HBT Performance Up to 500 GHz

Abstract

This article explores the impact of the substrate network on the high-frequency performance characteristics of silicon/silicon–germanium (Si/SiGe) heterojunction bipolar transistors (HBTs). The influence of the substrate network becomes particularly significant at frequencies above 100 GHz, necessitating advanced measurement and de-embedding techniques. In this study, we employ the advanced 16-term error calibration method to accurately extract the maximum oscillation frequency ( ${f}_{\text {MAX}}\text {)}$ up to 500 GHz. This approach allows us to observe second-order effects, such as the impact of substrate network, for the first time. Our findings reveal that the substrate network has significant implications for the optimization of high-frequency Si/SiGe HBTs, especially on ${f}_{\text {MAX}}$ . The study provides insights into substrate-related parasitic effects and proposes strategies to mitigate these effects.