Capacitive micromachined ultrasonic transducers with substrate-embedded springs
Abstract/Contents
- Abstract
- After the first capacitive micromachined ultrasonic transducer (CMUT) was invented in 1994, it became one of the candidate technologies to advance the state-of-the-art of medical ultrasound imaging. Benefiting from its fabrication technique based on the semiconductor industry, CMUT technology has broadened the medical and therapeutic applications such as real-time volumetric ultrasound imaging, catheter-based forward-looking intravascular ultrasound (IVUS), photoacoustic imaging, high-intensity focused ultrasound (HIFU) and so on. In spite of many advantages, however, CMUT technology has been criticized with its relatively low transmit sensitivity (~10 kPa/V) or low average volume displacement efficiency (0.1 nm/V) as well as large drive and bias voltage requirements (in a range of a few hundreds of volts). In order to resolve these issues and open up new potential of clinical applications, this dissertation describes the design, fabrication, and system implementation of CMUTs with substrate-embedded springs, so-called post-CMUT (PCMUT). Since PCMUT structure resembles an ideal piston transducer, the improvements in performance mainly stem from the higher average displacement of the top plate for a given gap height. The overview of the first generation PCMUT is introduced and two main issues in simulation and fabrication aspects of the first generation PCMUT is discussed. To further improve the PCMUT device, a 3D finite element analysis (FEA) model of the PCMUT is demonstrated to predict the performance of the first generation PCMUT. In addition, the design guideline of the second generation PCMUT is proposed for achieving the maximum fractional bandwidth (100 %) as well as with the highest transmit sensitivity (~28 kPa/V). The second generation PCMUT is fabricated by using three combination MEMS processes: usage of two silicon-on-insulator (SOI) wafers, wafer bonding process, and wafer polishing process. The second generation PCMUT achieves high transmit sensitivity (~21 kPa/V) or large average volume displacement efficiency (1.1 nm/V) with a low bias voltage (55 V). Compared to a commercial piezoelectric transducer, the second generation PCMUT improves 2.75 times of the maximum output pressure and 5.25 times of the average volume displacement efficiency with respect to the same voltage. After fabrication and performance characterization of the second generation PCMUT, this dissertation demonstrates the feasibility of PCMUT to use it in medical imaging system by integrating PCMUT with a custom-built integrated circuit (IC). Photoacoustic imaging is also presented for one of its application examples.
Description
| Type of resource | text |
|---|---|
| Form | electronic; electronic resource; remote |
| Extent | 1 online resource. |
| Publication date | 2015 |
| Issuance | monographic |
| Language | English |
Creators/Contributors
| Associated with | Lee, Byung Chul |
|---|---|
| Associated with | Stanford University, Department of Electrical Engineering. |
| Primary advisor | Khuri-Yakub, Butrus T, 1948- |
| Thesis advisor | Khuri-Yakub, Butrus T, 1948- |
| Thesis advisor | Howe, Roger Thomas |
| Thesis advisor | Solgaard, Olav |
| Advisor | Howe, Roger Thomas |
| Advisor | Solgaard, Olav |
Subjects
| Genre | Theses |
|---|
Bibliographic information
| Statement of responsibility | Byung Chul Lee. |
|---|---|
| Note | Submitted to the Department of Electrical Engineering. |
| Thesis | Thesis (Ph.D.)--Stanford University, 2015. |
| Location | electronic resource |
Access conditions
- Copyright
- © 2015 by Byung Chul Lee
- License
- This work is licensed under a Creative Commons Attribution Non Commercial 3.0 Unported license (CC BY-NC).
Also listed in
Loading usage metrics...