Understanding material limits for encapsulated combo sensor design and fabrication
Abstract/Contents
- Abstract
- Due to growing demand in the consumer space, there has been a push to create combo sensors and to reduce overall chip size. The 'epi-seal' process, developed by Robert Bosch GmBH and Stanford University, enables wafer-scale packaging of devices in an environment that has shown no long-term aging effects, using a thin-film encapsulation that results in the smallest reported package size. In order for this process to become truly viable for co-fabrication of sensors with different design constraints, we made several process modifications to produce sensors with high-sensitivity but low cross-sensitivity between different environmental factors. To prove this concept, we co-fabricate X/Y and Z-axis accelerometers, a pressure sensor, and resonant thermometer, where cross-sensitivity is improved by more than 700x; remaining cross-sensitivities can then be compensated based on real-time measurements from other sensors. In order for sensors to scale down and sustain sensitivity performance, I examine two material limits that can be prohibitive to sensor miniaturization: stiction and fatigue. Stiction studies with as-fabricated epi-seal devices reveal adhesion forces between contacting surfaces that are asperity-dominated and on average 35 μN. In order to overcome this force, I investigate several dynamic anti-stiction methods that lead to effective stiction forces being reduced by over 60%. Fatigue studies using high-displacement resonators fabricated in the epi-seal process were performed to observe any potential aging effects in single-crystal silicon. In contrast to literature, long-term (> 10^10 cycles) fatigue experiments with these devices showed no signs of fatigue damage up to 7.5 GPa. A cross-comparison with these literature results reveals that fatigue can indeed be prevented, only with atomically smooth side-walled devices that are fabricated in a packaging technology that prevents stress corrosion.
Description
| Type of resource | text |
|---|---|
| Form | electronic; electronic resource; remote |
| Extent | 1 online resource. |
| Publication date | 2016 |
| Issuance | monographic |
| Language | English |
Creators/Contributors
| Associated with | Hong, Vu Anh |
|---|---|
| Associated with | Stanford University, Department of Mechanical Engineering. |
| Primary advisor | Kenny, Thomas William |
| Thesis advisor | Kenny, Thomas William |
| Thesis advisor | Howe, Roger Thomas |
| Thesis advisor | Nelson, Drew |
| Advisor | Howe, Roger Thomas |
| Advisor | Nelson, Drew |
Subjects
| Genre | Theses |
|---|
Bibliographic information
| Statement of responsibility | Vu Anh Hong. |
|---|---|
| Note | Submitted to the Department of Mechanical Engineering. |
| Thesis | Thesis (Ph.D.)--Stanford University, 2016. |
| Location | electronic resource |
Access conditions
- Copyright
- © 2016 by Vu Anh Hong
- License
- This work is licensed under a Creative Commons Attribution Non Commercial 3.0 Unported license (CC BY-NC).
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