Study on electro-mechanical transduction employing piezoelectricity on the gate of a field-effect transistor and its application to hydrophones
- Title
- Study on electro-mechanical transduction employing piezoelectricity on the gate of a field-effect transistor and its application to hydrophones
- Authors
- 성민
- Date Issued
- 2016
- Publisher
- 포항공과대학교
- Abstract
- In contrast to the induced charge or voltage in conventional piezoelectric sensors, changes in the bound surface charge density and the corresponding changes in the electric field from a piezoelectric body do not depend on the size of the piezoelectric material. In this thesis, we describe a new transduction mechanism, the piezoelectric gate on a field-effect transistor (PiGoFET), focusing on the applications in micro-hydrophones. In the PiGoFET transduction mechanism, a piezoelectric body is combined directly on the gate of a field-effect transistor (FET) to decouple the sensitivity from the dimensions of the piezoelectric body, enabling the miniaturization of hydrophones. We describe a theoretical model of the PiGoFET, which shows that high sensitivity can be achieved with a small hydrophone due to the dimensionless characteristics of the PiGoFET transduction mechanism. The operating principle of the PiGoFET was analyzed using the theoretical model, which was experimentally verified in macro-scale device to within 2 dB. Using the verified theoretical framework for the PiGoFET, a micro-machined PiGoFET (micro-PiGoFET) hydrophone was designed and fabricated via hybrid bonding integration in a CMOS-compatible manner. The hybrid bonding integration employs separate wafers for the piezoelectric MEMS and CMOS processes, which are combined via eutectic wafer bonding to complete the micro-PiGoFET device. The resulting micro-PiGoFET hydrophone was characterized as an underwater acoustic receiver for frequencies in the range 50−1000 Hz. The internal pre-stress and polarization of PZT in the micro-PiGoFET were exploited to improve the sensitivity and signal-to-noise ratio (SNR). The measured sensitivity −156 ± 1 dB (Ref. V/μPa) of the micro-PiGoFET hydrophone was comparable to that of commercial reference hydrophone (B&K 8103) coupled with a charge amplifier (B&K 2692), provided that the noise floor of those sensors are similar. These results demonstrate the potential for high-performance miniaturized hydrophone systems for wide-band and low-frequency applications, as well as system-on-chip functionality.
- URI
- http://postech.dcollection.net/jsp/common/DcLoOrgPer.jsp?sItemId=000002232874
https://oasis.postech.ac.kr/handle/2014.oak/92640
- Article Type
- Thesis
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