Wafer-Level Epitaxial Silicon Packaging for Out-of-Plane RF MEMS Resonators With Integrated Actuation Electrodes

This paper presents an integrated solution for wafer-level packaging and electrostatic actuation of out-of-plane radio frequency microelectromechanical system resonators. By integrating the electrodes into the epitaxial-grown silicon layer, both the encapsulation and the out-of-plane actuation can be built in one process step, which results in an ultracompact and robust packaging. First, designs and fabrication processes of the out-of-plane electrode are described. The mechanical and electrical properties of the electrode are discussed, modeled, and characterized. A 200 kHz torsional mode beam resonator and an 11.2 MHz transverse-mode differential square plate resonator are fabricated using this packaging method and their performances are presented and discussed.