Fabrication of high-speed InGaP/GaAs HBT's by using a wet-etched SABM technique

Abstract

We have fabricated high-speed InGaP/GaAs HBT's by using a wet-etched self-aligned base metal (SABM) technique to reduce the base resistance (R-B). A citric-acid-based etchant was newly developed for the SABM process, which proved to be very controllable and repeatable. The newly developed wet-etched self-aligned SABM process can be applied for emitter widths below 2 pm and the fabricated device with a 2x20 mum(2) emitter had a f(T) of 75 GHz and a f(max) of 150 GHz. This performance is one of the best-reported results among HBT's with similar structures. This result indicates that the SABM process using the citric acid is well suited for high-speed InGaP/GaAs HBT manufacturing. In this paper, we present the newly developed emitter etching process for SABM and show the fabricated device performances.