Electrostatic fringing-field actuator (EFFA): Application towards a low-complexity RF-MEMS technology

This paper presents a novel electrostatic actuator using fringing fields as actuation mechanism, ie electrostatic fringing-field actuator or EFFA. The novel device is produced on an insulating substrate in a simple 2-mask process involving only one sacrificial layer and one metallisation. As a proof of concept, we produced and characterized EFFA-based tuneable RF devices and circuits in various technological implementations of remarkable simplicity. This simplicity allows a vast flexibility for the processing and as a result strongly eases the integration of the EFFA ´s into existing technologies. We report a non-deembedded measured capacitance ratio of 1:3 and a lifetime of more than 10 cycles with 40 V bipolar actuation at 100 Hz in N₂ atmosphere. Both the capacitance ratio and the C-V profile were tuned by modifying the technology, e.g. coating the substrate before processing the EFFA ´s, and the design, e.g. switching from clamped-free to clamped-clamped devices. Finally, note that the fringing-field actuation principle we demonstrated by means of RF-MEMS components can be used also as an electrostatic sensing mechanism.