Design and fabrication of a tuning fork shaped voltage controlled resonator with additional tuning electrodes for low-voltage applications

Abstract

In this work a silicon voltage-controlled microelectromechanical tuning-fork resonator with electrostatic actuation and separate frequency tuning electrodes is presented. The released device is fabricated using a silicon-on-insulator (SOI) wafer by a 2-step process involving only Focused Ion Beam (FIB) masking and Cryogenic Deep Reactive Ion etching (DRIE). This process is ideal for rapid prototyping, as the time to turn a design into the final device is only a few hours. The design of the resonator is optimized to accommodate the restrictions of the fabrication process, to maximize the frequency tunability and to minimize the biasing voltage. Separating tuning and driving electrodes enables the resonance frequency adjustment by over 10000 ppm (fcentral > 1.5 MHz, quality factor Q ≈ 2000) with a tuning voltage of 12 volts.