Electrostatic – Tuning of hermetically encapsulated composite resonator

Abstract

MEMS resonators have promising future as frequency references with high levels of stability. In this paper, we present electrostatic-tuning of frequency for temperature compensation in Si-SiO2 composite resonators. This tuning technique uses the spring-softening effect for compensation. It is implemented by adjusting the DC bias voltage applied to the resonant structure. Electrostatic-tuning of silicon MEMS resonators has proven difficult because of the very large temperature induced frequency variation that must be overcome (2000 ppm). Si-SiO2 composite resonators have at least 10x less frequency variation over temperature, and lend themselves to electrostatic-tuning for compensation. This paper presents our first results for a tuning-based compensation approach over a full (70ºC-wide) commercial temperature range.