A new procedure for extraction of series resistances for bipolar transistors from DC measurements

A new procedure for direct extraction of the base and emitter resistances is presented. The parameters are extracted from a single measurement on a transistor test structure with two separated base contacts. The proposed extraction procedure was successfully applied to transistors fabricated in a double polysilicon bipolar transistor process and a commercial 0.8 μm single polysilicon BiCMOS process. The extracted values show good agreement with those obtained by means of high frequency measurements. Furthermore, the method was verified by simulations and extraction from modelled data using a distributed resistor-diode transistor model. Both emitter current crowding effects and conductivity modulation in the base are considered in the model. The comparison between measured and modelled transistor characteristics using the extracted values as input in the Gummel-Poon model also validates the DC extraction method. The method was found to be valid as long as conductivity modulation in the base is dominant over emitter current crowding effects as a cause for the decrease in the base resistance