Quantification and minimization of energy loss mechanisms in microelectromechanical resonators
Abstract/Contents
- Abstract
- This work focuses on quantifying and minimizing energy loss in encapsulated capacitive microelectromechanical (MEM) resonators. This is important to reduce phase and frequency noise in the output signal of these resonators. Improving upon these metrics creates accelerometers, gyroscopes, and timing references that have more resolution and higher stability. Energy loss of a MEM resonator is measured by its quality factor, which is the ratio of the energy stored in the resonator to the energy lost per cycle of motion. The common energy loss mechanisms that affect the quality factor of MEM resonators are thermoelastic dissipation (TED), gas damping, Akhiezer damping, and anchor damping. This work quantities energy loss of these loss mechanisms using the different temperature dependence of each mechanism. Insight from quantifying these energy loss mechanisms in different resonator designs is used to design a resonator with a quality factor that is limited by the material loss limit of silicon, which is the highest possible quality factor that a capacitive resonator can achieve, resulting in an fxQ product of 2.2x10^13 Hz. Of all of the energy loss mechanisms, anchor damping is the least understood for resonant frequencies below 100 MHz. Anchor damping occurs because mechanical energy leaks out of the resonator at the attachment point, or anchor, to the substrate. This work experimentally explores how factors including outer packaging, substrate thickness, anchor placement, and anchor design affect anchor loss. Anchor damping in a bulk mode resonator was reduced by almost an order of magnitude by removing the silver paste adhering the die to the chip carrier. Thinning the substrate enhances the quality factor by a factor of 1.5x. The placement of anchors at two nodes on the edge of a ring resonator is has a 2x greater quality factor than that of a ring resonator with a center anchor. A more compliant anchor reduces anchor damping by an order of magnitude in bulk mode resonators. These results initiate an understanding of the mechanism by which anchor loss occurs in MEM resonators below 100 MHz. Lastly, this thesis presents a variant of the Epi-Seal encapsulation fabrication process where small and large transduction gaps can be fabricated for resonators without etch-holes. The traditional Epi-Seal process uses epitaxial silicon to seal devices at the wafer level in an oxide-free, particle-free, low pressure environment, creating resonators with long term stability. This new variant is important because it increases the design space for capacitive MEM resonators to include large etch-hole free masses and large and small transduction gaps with all the advantages of the original process.
Description
| Type of resource | text |
|---|---|
| Form | electronic resource; remote; computer; online resource |
| Extent | 1 online resource. |
| Place | California |
| Place | [Stanford, California] |
| Publisher | [Stanford University] |
| Copyright date | 2021; ©2021 |
| Publication date | 2021; 2021 |
| Issuance | monographic |
| Language | English |
Creators/Contributors
| Author | Vukasin, Gabrielle Davis |
|---|---|
| Degree supervisor | Kenny, Thomas William |
| Thesis advisor | Kenny, Thomas William |
| Thesis advisor | Howe, Roger Thomas |
| Thesis advisor | Senesky, Debbie |
| Degree committee member | Howe, Roger Thomas |
| Degree committee member | Senesky, Debbie |
| Associated with | Stanford University, Department of Mechanical Engineering |
Subjects
| Genre | Theses |
|---|---|
| Genre | Text |
Bibliographic information
| Statement of responsibility | Gabrielle Davis Vukasin. |
|---|---|
| Note | Submitted to the Department of Mechanical Engineering. |
| Thesis | Thesis Ph.D. Stanford University 2021. |
| Location | https://purl.stanford.edu/gr989qf9868 |
Access conditions
- Copyright
- © 2021 by Gabrielle Davis Vukasin
- License
- This work is licensed under a Creative Commons Attribution Non Commercial 3.0 Unported license (CC BY-NC).
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