Capacitive Micromachined Ultrasonic Transducers (CMUTs) for Underwater Imaging Applications
Abstract
:1. Introduction
2. Structural Design
Parameters | Value |
---|---|
Membrane radius/μm | 90 |
Membrane thickness/μm | 2.8 |
Electrode radius/μm | 45 |
Electrode thickness/μm | 1 |
Number of cells | 900 |
Electrode insulation layer thickness/μm | 0.15 |
Insulation layer thickness/μm | 0.15 |
Cavity height/μm | 0.65 |
3. Fabrication Process
Parameter | SOI Wafer | Silicon Wafer | |
---|---|---|---|
Size (inches) | 6 | 6 | |
Conductive type | Device layer | P | P |
Handle wafer | N | ||
Resistivity (ohm∙cm) | Device layer | 0.01–0.08 | 0.01–0.02 |
Handle wafer | 0.01–0.02 | ||
Orientation | (100) | (100) | |
Thickness (μm) | Device layer | 2.8 ± 0.1 | 400 ± 10 |
Box layer | 0.8 ± 0.08 | ||
Handle wafer | 430 ±15 |
- Step 1
- Standard RCA cleaning is performed on both the silicon wafer and the SOI wafer to remove organic matter, dust and oxide layers.
- Step 2
- The silicon wafer is then oxidized to form a 0.8- oxide layer, which will be part-etched to form cavities, as shown in Figure 2a.
- Step 3
- Gluing and exposure processes are performed on the front area of the silicon wafer; a 0.65- oxide layer is etched to form the cavities and a 0.15- oxide layer is left behind to prevent membrane contact with the substrate, as shown in Figure 2b.
- Step 4
- Step 5
- The handle layer of the SOI wafer, the buried oxide (box) layer of the SOI wafer and the oxide layer are etched to produce the basic transducer structure, as shown in Figure 2d.
- Step 6
- A silicon dioxide layer is deposited on the vibration membrane to prevent the formation of an ohmic contact between the top electrodes and the vibration membrane, as shown in Figure 2e.
- Step 7
- A metal layer is sputtered on the vibration membrane by the evaporation method, and the top electrodes and pads are formed by the peeling method, as shown in Figure 2f.
4. Experimental Results
4.1. C-V Characteristics
4.2. Underwater Experiments
4.2.1. Output Pressure and Bandwidth Testing
Distance/cm | Measurement Pressure/Pa | Theoretical Pressure/Pa | Derivation Pressure/Pa | |
---|---|---|---|---|
1 | 10.00 | 786.7700 | 807.3977 | 20.6277 |
2 | 15.00 | 769.6664 | 733.4918 | −36.1746 |
3 | 20.00 | 701.2516 | 666.3509 | −34.9007 |
4 | 25.00 | 598.6294 | 605.3558 | 6.7264 |
5 | 30.00 | 513.1109 | 549.9440 | 36.8331 |
6 | 35.00 | 444.6961 | 499.6043 | 54.9082 |
7 | 40.00 | 461.7998 | 453.8725 | −7.9273 |
8 | 45.00 | 427.5924 | 412.3269 | −15.2655 |
9 | 50.00 | 393.3850 | 374.5841 | −18.8009 |
10 | 55.00 | 324.9702 | 340.2962 | 15.3260 |
11 | 60.00 | 307.8665 | 309.14684 | 1.28034 |
12 | 65.00 | 290.7628 | 280.8488 | −9.9140 |
13 | 70.00 | 273.6591 | 255.1410 | −18.5181 |
4.2.2. Distance Testing
Real Distance/cm | Measurement Distance/cm | Deviation/cm | |
---|---|---|---|
1 | 5 | 5.65 | 0.65 |
2 | 10 | 11.46 | 1.46 |
3 | 15 | 15.22 | 0.22 |
4 | 20 | 21.72 | 1.72 |
5 | 25 | 26.45 | 1.45 |
6 | 30 | 31.67 | 1.67 |
7 | 35 | 36.37 | 1.37 |
8 | 40 | 41.25 | 1.25 |
9 | 45 | 46.30 | 1.3 |
10 | 50 | 51.31 | 1.31 |
11 | 55 | 55.85 | 0.85 |
12 | 60 | 61.23 | 1.23 |
13 | 65 | 65.83 | 0.83 |
14 | 70 | 70.67 | 0.67 |
4.2.3. Underwater Imaging
5. Conclusions
Acknowledgments
Author Contributions
Conflicts of Interest
References
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Song, J.; Xue, C.; He, C.; Zhang, R.; Mu, L.; Cui, J.; Miao, J.; Liu, Y.; Zhang, W. Capacitive Micromachined Ultrasonic Transducers (CMUTs) for Underwater Imaging Applications. Sensors 2015, 15, 23205-23217. https://doi.org/10.3390/s150923205
Song J, Xue C, He C, Zhang R, Mu L, Cui J, Miao J, Liu Y, Zhang W. Capacitive Micromachined Ultrasonic Transducers (CMUTs) for Underwater Imaging Applications. Sensors. 2015; 15(9):23205-23217. https://doi.org/10.3390/s150923205
Chicago/Turabian StyleSong, Jinlong, Chenyang Xue, Changde He, Rui Zhang, Linfeng Mu, Juan Cui, Jing Miao, Yuan Liu, and Wendong Zhang. 2015. "Capacitive Micromachined Ultrasonic Transducers (CMUTs) for Underwater Imaging Applications" Sensors 15, no. 9: 23205-23217. https://doi.org/10.3390/s150923205
APA StyleSong, J., Xue, C., He, C., Zhang, R., Mu, L., Cui, J., Miao, J., Liu, Y., & Zhang, W. (2015). Capacitive Micromachined Ultrasonic Transducers (CMUTs) for Underwater Imaging Applications. Sensors, 15(9), 23205-23217. https://doi.org/10.3390/s150923205