A Base-Emitter Self-Aligned Multi-Finger Si1−xGex/SiPower Heterojunction Bipolar Transistor

Abstract

With a crystal orientation dependent on the etch rate of Si inKOH-based solution, a base-emitter self-aligned large-area multi-fingerconfiguration power SiGe heterojunction bipolar transistor (HBT) device(with an emitter area of about 880 μm2) is fabricated with2 μm double-mesa technology. The maximum dc current gain is 226.1. Thecollector–emitter junction breakdown voltage BVCEO is 10 Vand the collector-base junction breakdown voltage BVCBO is16 V with collector doping concentration of 1×1017 cm−3and thickness of 400 nm. The device exhibited a maximum oscillationfrequency fmax of 35.5 GHz and a cut-off frequency fT of24.9 GHz at a dc bias point of IC = 70 mA andthe voltage between collector and emitter is VCE = 3 V. Loadpull measurements in class-A operation of the SiGe HBT are performed at1.9 GHz with input power ranging from 0 dBm to 21 dBm. A maximum outputpower of 29.9 dBm (about 977 mW) is obtained at an input power of 18.5 dBmwith a gain of 11.47 dB. Compared to a non-self-aligned SiGe HBT withthe same heterostructure and process, fmax andfT are improved by about 83.9% and 38.3%, respectively.