Experimental Validation of Mixed Electromechanical and Electromagnetic Modeling of RF-MEMS Devices Within a Standard IC Simulation Environment

The validity and applicability of a high-level simulation approach of radio-frequency microelectromechanical-system (RF-MEMS) devices, based on a library of analytical compact models of elementary MEMS components, are investigated through an extensive comparison between simulation results and measurements of some representative devices (variable capacitors and series ohmic switches). The in-house developed simulation tool is implemented in a standard IC simulation environment supporting behavioral description capabilities. The devices are built in a silicon substrate technology with suspended gold membranes. We analyze the mechanical, electrical, and RF response of the devices. The RF behavior is modeled by extracting a lumped element network from measured S-parameters (scattering-parameters) to account for parasitic effects and by wrapping this network around the intrinsic MEMS device simulated with the compact models. We show that an accuracy within 5% is obtained in all considered physical domains and conditions, provided that some effective parameters (including the residual air gap in the actuated state and the RF parasitic elements) are properly extracted from measurements and accounted for in the simulations. The main factors limiting the model's predictive capability are due to process nonidealities, such as plate bending due to residual stress gradient, oxide charging, surface roughness, and suspended membrane thickness variations, rather than for instance in-plane geometric process variations.