High-performance uniform stepper-based InP double-heterojunction bipolar transistor (DHBT) on a 3-inch InP substrate

Abstract

In this paper, InP Double-Heterojunction Bipolar Transistors (DHBTs) on a 3-inch InP substrate is demonstrated through stepper-based photolithography. The performance of the fabricated InP DHBTs such as DC characteristics, high-frequency characteristics, and uniformity of the 3-inch wafer is investigated to verify the stepper-based fabrication process. To improve the high-frequency characteristics, the self-aligned base-emitter contact is realized by using the high height-to-width ratio and vertical sidewall emitter profile of the Au electroplating process. The fabricated DHBTs with WE = 0.6 μm and LE = 15 μm exhibits current gain (β) = 50 at VCE = 1.0 V and an open-base common-emitter breakdown voltage (BVCEO) of 5.7 V at JC = 0.01 mA/µm2 and 7.5 V at JC = 0.1 mA/µm2, respectively. Moreover, the fabricated DHBTs with WE = 0.6 μm and LE = 15 μm show excellent fT of 244 GHz and fmax of 221 GHz at JC = 4.4 mA/μm2 and VCE = 1.6 V. In order to evaluate the uniformity of the fabricated DHBTs, we measure current gain (β) and high-frequency characteristics with WE = 0.6 μm and LE = 15 μm and the average values and standard deviation of the β, fT, and fmax are β = 49.3 ± 1.9, fT = 241.4 ± 3.8 GHz, and fmax = 221.5 ± 4.0 GHz, respectively. Thanks to the optimized stepper-based fabrication process, the fabricated InP DHBTs exhibit well-balanced high-frequency characteristics and excellent uniformity.