Simultaneous extraction of the base and thermal resistances of bipolar transistors

A method for the simultaneous extraction of the base resistance R_b and thermal resistance R_th of bipolar transistors is described. The technique can be applied to single devices without the requirement of special structures. The measurements are based on the collector-base voltage dependence of the base-emitter voltage under constant emitter current steering and accounts for the influence of Early effect and self-heating. Results are obtained for advanced HBTs with several emitter widths enabling the extraction of R_th and the intrinsic and extrinsic contribution of R_b. A detailed comparison is made with other extraction techniques and reveals an excellent agreement.