Silicon-Micromachined Piezoelectric Bimorph Acoustic Transducer
| Category: Engineering and Physical Sciences |
Reference Number: 00265 |
Description
The idea of using a bimorph structure for a micromachined piezoelectric acoustic transducer on parylene diaphragm has been invented and tested. Both the sensitivity and signal-to-noise ratio of the bimorph, parylene-diaphragm microphone have been demonstrated to be much higher than those of a conventional uni-morph piezoelectric microphone made on a silicon nitride diaphragm. Among various parylene materials, we find parylene-D to be the best choice for supporting the bimorph diaphragm because it can withstand high processing temperature and also is mechanically flexible.
The micromachined piezoelectric bimorph microphone consists of two transverse-expander piezoelectric thin films secured together face to face in such a manner that mechanical bending of the element under acoustic pressure will cause it to develop a corresponding voltage between two outer electrodes. Since parylene-D has high thermal stability, it allows us to sputter-deposit (at 250 ºC) another ZnO layer on the backside of the wafer to form a face-to-face piezoelectric bimorph structure.
Applications
- Microphone, acoustic pressure sensor, microspeaker, acoustic transducers
- MEMS piezoelectric sensors and actuators (numerous arbitrarily shaped structures on silicon substrate)
- High performance and low cost parts in Audio system, communication system, multimedia system, hearing aid system
- High sensitive and biomedical compatible acoustic and ultrasonic transducers
Main Advantages
General advantages as a micromachined piezoelectric microphone
- Size miniaturization with extremely small weight
- Little power consumption and no polarization voltage needed
- Potentially low cost due to the batch processing and possibility of integrating microphones and circuits on a single chip
Unique advantages of piezoelectric bimorph structure (Compared with a conventional uni-morph microphone)
- Easier control of the neutral plane position than a uni-morph structure and effective conversion of mechanical strain into electrical voltage and vice versa
- Simple structure containing only piezoelectric film, electrodes and very flexible parylene (does not introduce any significant stiffness in the diaphragm, nor residual stress);
- With larger sensitivity and signal/noise ratio and higher fundamental resonant frequency, it has inherently higher figure of merit than a uni-morph device.
- Conformal deposition allowing various diaphragm shapes
Inventor(s)
Dr. Eun Sok Kim & Dr. Meng-Nian Niu
Department of Electrical Engineering, University of Hawaii
Contact Information
For licensing information, please contact Andrea Yuen at
ayuen@hawaii.edu
For all other inquiries, please write to:
Office of Technology Transfer & Economic Development
University of Hawai’i
2800 Woodlawn Drive, Suite 280
Honolulu, HI 96822