The Effects of Carbon Doping on the Single-Event Transient Response of SiGe HBTs

The impact of carbon doping on the single-event transient (SET) response of SiGe heterojunction bipolar transistors (HBTs) was evaluated using pulsed-laser charge generation via two-photon absorption (TPA). Special device structures with different amounts of carbon were fabricated by GlobalFoundries and characterized. Despite the fact that carbon is known to introduce bulk traps in the SiGe film, experimental results show no measurable difference in the SET response of SiGe HBTs fabricated with different amounts of carbon. Technology computer-aided design (TCAD) simulations showed that the amount of carbon required to observe changes in the SET response would significantly impair the electrical performance of the device. Thus, within practical limits, carbon has no impact on the SET response of SiGe HBTs.

I. Introduction

The performance of most commercially available, high-frequency silicon-germanium (SiGe) heterojunction bipolar transistors (HBTs) strongly depends on the vertical scaling of the doping profile [1]. The base width, , is a critical parameter when optimizing the maximum transit () and oscillation () frequencies. As technology scaling progresses, values necessarily decrease, enabling higher operational frequencies for SiGe HBTs [2]. However, these narrower base widths pose added challenges to the manufacturing processes, as the required tolerances and thermal processing constraints become more stringent.