Extraction of emitter and base series resistances of bipolar transistors from a single DC measurement

A new procedure for extracting the emitter and base series resistances of bipolar junction transistors is presented. The parameters are extracted from a single measurement in the forward active region on one transistor test structure with two separate base contacts, making it a simple and attractive tool for bipolar transistor characterization. The procedure comprises two methods for extracting the emitter resistance and two for extracting the base resistance. The choice of method is governed by the amount of current crowding or conductivity modulation present in the intrinsic base region. The new extraction procedure was successfully applied to transistors fabricated in an in-house double polysilicon bipolar transistor process and a commercial 0.8-mu m single polysilicon BiCMOS process. We found that the simulated and measured Gummel characteristics are in excellent agreement and the extracted series resistances agree well with those obtained by means of HF measurements. By adding external resistors to the emitter and base and then extracting the series resistances, me verified that the two base contact test structure offers a simple means of separating the influence of emitter and base series resistances on the transistor characteristics.