A new approach for direct observation of base width modulation in vertical bipolar transistors

A new DC measurement technique that allows direct observation of the forward and reverse Early effects is described. The technique employs a special test structure and is used to accurately determine the Early voltage parameters in the Gummel-Poon model. The improvements provided by this method over existing parameter extraction techniques are realized by using a direct measurement of the normalized base charge as a function of the emitter and collector junction biases. The new technique described here allows the Early voltage parameters to be extracted as a function of applied bias in a straightforward manner and is suitable for high volume measurements for statistical characterization and for process monitoring in an industrial setting.