Over 450-GHz (f_{mathit {t}}) and (f_{mathrm {max}}) InP/InGaAs DHBTs With a Passivation Ledge Fabricated by Utilizing SiN/SiO₂ Sidewall Spacers

摘要

This paper describes InP/InGaAs double heterojunction bipolar transistor (HBT) technology that uses SiN/SiO₂ sidewall spacers. This technology enables the formation of ledge passivation and narrow base metals by i-line lithography. With this process, HBTs with various emitter sizes and emitter-base (EB) spacings can be fabricated on the same wafer. The impact of the emitter size and EB spacing on the current gain and high-frequency characteristics is investigated. The reduction of the current gain is <5% even though the emitter width decreases from 0.5 to (0.25~mu ) m. A high current gain of over 40 is maintained even for a 0.25- (mu ) m emitter HBT. The HBTs with emitter widths ranging from 0.25 to (0.5~mu ) m also provide peak f (_{t}) of over 430 GHz. On the other hand, peak f (_{max }) greatly increases from 330 to 464 GHz with decreasing emitter width from 0.5 to 0.25 (mu ) m. These results indicate that the 0.25- (mu ) m emitter HBT with the ledge passivaiton exhibits balanced high-frequency performance (f (_{t } = 452) GHz and f (_{max } = 464) GHz), while maintaining a current gain of over 40.