High-frequency analysis of SOI lateral bipolar transistor (LBT) structure for RF analog applications

The Lateral Bipolar Transistor (LBT) on SOI substrate for RF analog applications with extrinsic base on the top of the collector n-region is analyzed. The extrinsic base affects f/sub T/ and f/sub max/ in several ways. First, it increases C/sub BC/ making it dependent on lithography resolution. Second, depending on collector-base voltage, a collector-base depletion region decreases the effective collector cross-section area thus causing the Kirk effect to occur at lower collector currents. Third, the electrons injected from emitter flow partly through the extrinsic base-collector depletion region increasing the effective transit time. With respect to those effects, the technological parameters are varied and the impact on f/sub T/ and f/sub max/ are analyzed. It is shown that the increase of f/sub T/ can be achieved without sacrificing f/sub max/ considerably only by changing device geometry, still using the same doping profile of the intrinsic transistor region.