Two Movable-Plate Nitride-Loaded MEMS Variable Capacitor

A microelectromechanical systems (MEMS) variable capacitor having two movable plates loaded with a nitride layer is proposed. A trench in the silicon substrate underneath the capacitor is used to decrease the parasitic capacitance. The use of an insulation dielectric layer on the bottom plate of the MEMS capacitor increases the capacitor's tuning range and eliminates stiction. Experimental and theoretical results are presented for two capacitors having different capacitance values. The measured tuning range is found to be 280% at 1 GHz. The achievable tuning range far exceeds that of the traditional parallel-plate MEMS variable capacitors. The proposed MEMS variable capacitor is built using the MetalMUMP's process.