A digital test structure for simultaneous bird's beak length and misalignment measurement in polysilicon emitter bipolar technologies

A test structure for geometrical measurements on bipolar processes is presented. Both bird's beak length and misalignment between active areas and active area openings in a polysilicon emitter bipolar technology can be obtained from a unique measurement using it. Although it is a digital structure, the accuracy can be improved by means of a fitting on the contact resistance values. Another structure for obtaining misalignment, based on the voltage-dividing potentiometer principle, is included in order to compare results.