Solid State MEMS Resonators in Silicon

Abstract

Two of the greatest challenges in MEMS are those of packaging and integration with CMOS technology. Development of solid state RF MEMS resonators in silicon, resonators that do not require any release etch step, eliminates the necessity for complex encapsulation methods and costly packaging. Such solid state solution could also enable direct integration into front-end-of-line (FEOL) processing in CMOS, making these devices an attractive choice for on-chip signal generation and signal processing. This thesis discusses the physics, design considerations, and process developments to build such solid state MEMS resonators in silicon, showing a series of incremental stages of the prototyping of such devices. The major challenge of building solid state MEMS resonators lies in maintaining comparable device performance relative to released ones, especially quality factor Q. Energy localization structures, such as acoustic Bragg reflectors (ABRs) are implemented for such solid state resonators to maintain high Q and suppress spurious modes. Towards the goal of high aspectratio structures that have the capability of direct CMOS integration, deep trench (DT) capacitor based MEMS resonators are studied and demonstrated. This concept enables high Q, low loss multi-GHz resonators in a simple, robust manufacturing process.