DC EXTRACTION OF THE BASE AND EMITTER RESISTANCES IN POLYSILICON-EMITTER NPN BJTS

Five DC techniques of extracting the base and emitter resistances of p olysilicon-emitter npn bipolar junction transistors (BJTs) are present ed and compared. The five techniques include three previously publishe d techniques and two new techniques, constant base current and I-B-I-E plane fitting. Application of the five methods to a 0.8 x 16 mu m(2) npn BJT shows that all but the method of impact ionization yield compa rable R-e and R-bb values at high currents. The impact ionization meth od, which extracts R-e and R-bb in the impact ionization region and at low base currents, yields markedly different R, and R-bb values, indi cating that the values of the parasitic resistances depend on the curr ent range over which the extraction is performed. Thus the choice of w hich method is best to use depends on the current range over which R-e and R-bb are to be measured, and the validity of the assumptions used in the method when applied to the device.