A micromachined, single-crystal silicon, tunable resonator

Abstract

We present a fully integrated, single-crystal silicon (SCS), micromachined tunable resonator with a natural resonant frequency of nominally 1 MHz and a room temperature quality factor approaching 10,000 in vacuum. The microelectromechanical systems (MEMS) process used to create the SCS tunable resonators is fully compatible with VLSI technology. These resonators can be electrostatically excited and turned simultaneously or independently in both the x and y dimensions (in-plane), and can be further enhanced with a third dimension excitation (out-of-plane, z) and with reference marks (tips) for position detection in sensor applications. The dimensions of our microbeam tunable resonators are sub-micrometer in width and a few micrometers in height, with variable lengths ranging from 10 mu m to a few hundred mu m to achieve the desired natural (un-tuned) resonant frequencies. The prototype first generation tunable resonator has a measured out-of-plane (z) natural resonant frequency of 0.96 MHz and a quality factor of 4370. This resonator has a linear tuning range (with respect to the transverse (z) tuning force) of 60 kHz with a maximum required dc tuning voltage of 35 V. We describe the structure, the fabrication process, the frequency tuning, and the non-linear frequency response of the tunable resonators.