Determination of the Contribution of the Ground-Shield Losses to the Microwave Performance of On-Chip Coplanar Waveguides

In this article, we characterize and model two parasitic effects that become apparent in the performance of coplanar waveguide interconnects in CMOS. One is the transverse resistance introduced by a patterned ground shield in coplanar waveguide interconnects, which significantly contributes to the shunt losses. The other one is the parasitic coupling between the input and output ports through the ground shield. The latter effect is particularly accentuated in relatively short lines and complicates the determination of the propagation constant using line-line algorithms at several tens of gigahertz. We demonstrate that using the proposed methodology, excellent model-experiment correlation can be achieved in the modeling of these types of interconnects up to at least 60 GHz.