Modeling of Coplanar Structures on Lossy Si-Substrates by Conformal Mapping

Layers beneath metallization layers have a strong influence on the properties of passive elements like transmission lines, inductors etc. For an accurate modeling of active and passive elements a deembedding procedure for the parasitic elements is required. The influence of low resistive silicon substrate on the properties of coplanar structures (CPS) like pads is investigated in this paper from 50 MHz up to 40 GHz. A model of lumped elements is derived regarding the resistivity of the substrate. Measurements are in good agreement with analytic computations applying a conformal mapping technique and with simulations using Agilent ADS-Momentum.