The use of EM simulation in on-wafer microwave device de-embedding

This paper describes the use of EM simulation as a convenient method to provide an equivalent circuit model of the external parasitic pad structure of microwave devices. The extraction of accurate device models from measured data is an essential prerequisite of microwave circuit design. The first stage of the modelling process is to de-embed the intrinsic device response from the parasitic network associated with the on-wafer measurement environment. The normal approach is by means of open and short test structures to characterise the embedding network. In addition to requiring that special test structures be fabricated, this method has uncertainty associated with imperfect short and open terminating impedances and is sensitive to noise on the measurement data. In this work, it is shown how EM simulation of the embedding network can be used to deembed microwave HBT data. This approach is shown to give good agreement with the measured test piece approach thereby validating the simulation method.