Measurement method for accurate extraction of the base-to-emitter intrinsic and peripheral capacitances of bipolar transistors

A simple measurement method to determine the intrinsic and peripheral emitter junction capacitances is described. The method is based on measurements of BJT's with different emitter geometries and is demonstrated on transistors of an advanced BiCMOS technology. The method can be applied directly to standard deep-submicrometer devices. No special test devices are required. By determining peripheral capacitance for different processes, the method enables the examination of process schemes designed to suppress the effect of the peripheral emitter on the transistor action. The method also provides a useful approach to monitor the scaling behavior of the intrinsic and peripheral capacitances. Results indicate the peripheral capacitance starts dominating the total capacitance as the emitter is scaled into the submicrometer range. For devices with quarter micron emitter widths, the peripheral capacitance is found to be 3 to 4 times higher than the intrinsic capacitance, and puts a fundamental limitation on device design.<
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