Temperature-compensated silicon MEMS resonators with high quality factors and low motional impedances
- Microelectromechanical systems (MEMS) have become ubiquitous today, existing alongside electronics in many products and fabricated using standard semiconductor fabrication techniques. The focus of this work is on furthering the performance of silicon resonators for frequency / time references, based on the epi-seal encapsulation process that has been demonstrated to be crucial for the stability of MEMS. Temperature-compensation via heavy doping is investigated and the temperature dependence of the elastic constants of silicon is extracted for several doping types and concentrations. The values are shown to be able to predict the frequency-temperature dependence of various resonators operating in the linear regime. Also addressed is the relatively large motional impedance of capacitive resonators (typically ~100 kΩ) in the epi-seal process. The motional impedance can be significantly decreased by having narrower capacitive gaps, and two methods compatible with the epi-seal process are demonstrated: the first by adding a selective epitaxial deposition step to the epi-seal process, and the other by designing movable electrodes that can pull-in closer to the resonator. Furthermore, high quality factor Lamé mode resonators are demonstrated here with f × Q products of 2 × 1013 Hz, in conjunction with first-order temperature compensation and low second-order temperature dependences. Lastly, charge-biasing is presented as a viable alternative to voltage-biasing for lower power consumption: charges introduced on the resonator body within the epi-seal cavity via mechanical switches show no signs of leakage even after a year. All these features can co-exist simultaneously on the same resonator with the demonstrated epi-seal stability, providing a pathway for further enhancing the performance of MEMS resonators.
|Type of resource
|electronic; electronic resource; remote
|1 online resource.
|Ng, Eldwin Jiaqiang
|Stanford University, Department of Mechanical Engineering.
|Howe, Roger Thomas
|Howe, Roger Thomas
|Statement of responsibility
|Eldwin Jiaqiang Ng.
|Submitted to the Department of Mechanical Engineering.
|Thesis (Ph.D.)--Stanford University, 2015.
- © 2015 by Eldwin Jiaqiang Ng
- This work is licensed under a Creative Commons Attribution Non Commercial 3.0 Unported license (CC BY-NC).
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