Etch-Hole Free, Large Gap Wafer Scale Encapsulation Process for Microelectromechanical Resonators

Abstract

We present a fabrication process for wafer-level encapsulated MEMS devices that allows for large masses without etch-holes with small and large transduction gaps. This combination of features allows for large masses with combdrive transduction with reduced thermoelastic dissipation. The omission of wafer bonding in this process reduces the footprint of an encapsulated device and creates a hermetically sealed cavity free of particles and organics. We present the performance of a bulk mode resonator (Q = 1.7M) and a flexural mode resonator (Q = 11k, 68k) that utilizes the small and large transduction gap capability. These devices exemplify the ability of this fabrication process to create single die containing high-Q silicon-based timing references and inertial sensors.