A parallel-plate MEMS variable capacitor with vertical thin-film comb actuators

A novel parallel-plate MEMS variable capacitor with a thin-film vertical comb actuator is proposed. The actuator can vertically displace both plates of the capacitor. Making use of the fringing field, this actuator exhibits linear displacement behavior, caused by the induced electrostatic force between the actuator's electrodes. The proposed capacitor has a low parasitic capacitance and linear capacitance response versus bias voltages due to the plates that are mechanically connected to the actuator which is electrically isolated from the capacitor's parallel-plates. The tuning range is measured and found to be 7:1 at 1 GHz. The fabricated MEMS variable capacitor exhibits a self-resonance frequency of 9 GHz at zero DC bias voltage.