Modeling of Polyimide MIM Capacitors for Applications in Planar Monolithic Microwave Integrated Circuits

Polymide Metal-Insulator-Metal (MIM) overlay capacitors for use in Monolithic Microwave Integrated Circuits (MMICs) based on High Electron Mobility Transistors (HEMTs) on Gallium Arsenide substrates are presented. Modeling of the capacitors was performed using a 2-dimensional electromagnetic CAD simulator to obtain Scattering (S-) parameters for different capacitor dimensions for operating frequencies from 0.05 to 8 GHz. The behaviour of the capacitor as a function of operating frequencies is studied by means of Smith chart. The capacitor is finally represented by a proposed equivalent circuit model to describe its overall behavior for planar MMIC simulations.