Micromachined temperature compensated pressure sensor implemented using a multi-sensor integration platform
Abstract/Contents
- Abstract
- Micromachined pressure sensors are widely used in our everyday lives; they are used in automobiles for tire pressure monitor, in medical devices for blood pressure track, and in indoor navigation for altitude measurement. While the requirements for a pressure sensor vary depending upon the specific application, a common requirement is accurate sensing over a wide operating temperature range. This dissertation begins by introducing our capacitive pressure sensor design and demonstrating how it outperforms a commercially available piezoresistive pressure sensor with respect to temperature insensitivity. The capacitive pressure sensors were designed to use a central subset of the entire circular diaphragm as the electrode to improve fractional capacitance change. The capacitive pressure sensors show an order of magnitude smaller temperature coefficient of sensitivity (TCS) compared to the piezoresistive reference pressure sensor. To further reduce temperature dependence, a resonant thermometer with resolution of 1 m°C was cofabricated with the capacitive pressure sensor, enabling the tracking of temperature fluctuations on the die to correct the associated pressure error. Experimental results indicate that the temperature-induced errors are successfully suppressed, and the sensors have remaining errors within ±0.15 kPa over the tested temperature range. In the second part of the dissertation, the design and performance of our resonant pressure sensors are discussed. The development of the resonant sensors was motivated by the emerging demand of altimeters which require high resolution in pressure sensing (a one-meter elevation change corresponds to a ten-Pascal pressure change, i.e., 10 Pa/meter). As the design is coupled to the die strain, the accuracy of the resonant pressure sensors is strongly influenced by errors induced by both temperature and package stress. We addressed this limitation with a multiple sensor solution whereby temperature and strain sensors were cofabricated to reduce the pressure sensor's temperature and package stress dependence, thus improving accuracy. The devices show sensitivity to pressure ranging between 50 and 150 ppm/kPa with a minimum detectable signal of approximately 7 Pa in a one-kHz bandwidth. After temperature is compensated for, the sensors have remaining offset errors within ±0.3 kPa. Throughout this work, a multiple sensor integration platform was used to fabricate the sensors. Key innovations include time insensitive vapor etching of silicon dioxide with hydrofluoric acid to release structures as well as the fabrication of structures that can be driven and sensed in both in-plane (x, y) and out-of-plane (z) directions on either bulk silicon or SOI wafer substrates. Such a multi-sensor integration platform is suitable for a variety of MEMS devices, such as accelerometers, gyroscopes, switches, and resonators.
Description
| Type of resource | text |
|---|---|
| Form | electronic; electronic resource; remote |
| Extent | 1 online resource. |
| Publication date | 2013 |
| Issuance | monographic |
| Language | English |
Creators/Contributors
| Associated with | Chiang, Chia-Fang |
|---|---|
| Associated with | Stanford University, Department of Mechanical Engineering. |
| Primary advisor | Kenny, Thomas Williams |
| Thesis advisor | Kenny, Thomas Williams |
| Thesis advisor | Howe, Roger Thomas |
| Thesis advisor | O'Brien, Gary (Gary J.) |
| Advisor | Howe, Roger Thomas |
| Advisor | O'Brien, Gary (Gary J.) |
Subjects
| Genre | Theses |
|---|
Bibliographic information
| Statement of responsibility | Chia-Fang Chiang. |
|---|---|
| Note | Submitted to the Department of Mechanical Engineering. |
| Thesis | Thesis (Ph.D.)--Stanford University, 2013. |
| Location | electronic resource |
Access conditions
- Copyright
- © 2013 by Chia-Fang Chiang
- License
- This work is licensed under a Creative Commons Attribution Non Commercial 3.0 Unported license (CC BY-NC).
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