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CMUTS in permanent contact operation for high output pressure

Ho, Min-Chieh and Hoffmann, Maik and Unger, Alexander and Kwan Kyu, Park and Kupnik, Mario and Kuhri-Yakup, Butrus T. (2015):
CMUTS in permanent contact operation for high output pressure.
In: ASME 2015, InterPACKICNMM, San Francsico, CA, USA, July 6-9, 2015, [Conference or Workshop Item]

Abstract

We present the operation of capacitive micromachined ultrasonic transducers (CMUTs) in permanent contact mode as an efficient transducer. The gap height of our transducers is chosen to be lightly smaller than the static deflection of the plate due to the pressure difference between the ambient and the vacuum cavity. Thus, the plates are in contact with the bottom of the cavities even with no dc bias applied. The devices were fabricated based on the thick box process. High-temperature assisted direct wafer bonding technique was used to fabricate devices with such large cell size (radii ~ 2000 μm) featuring low frequencies ~100 - 150 kHz. Extensive acoustic characterization was performed to demonstrate the behavior of such CMUTs in terms of displacement profile, output pressure and acoustic pitch-catch response. A maximum sound pressure of ~145 dB (SPL) at the transducer surface is measured at 240 V dc and 10 V ac with 100 cycles of burst signal. This is a great improvement from conventional CMUTs (with deeper gap height, operating at 55 kHz), which requires 350 V dc and 200 V ac in order to achieve an output pressure of 129 dB (SPL) at the transducer surface. The results presented in this paper demonstrate that operating CMUTs in permanent contact mode indeed enhances the device output pressure, and provides a good candidate for efficient ultrasonic transducers.

Item Type: Conference or Workshop Item
Erschienen: 2015
Creators: Ho, Min-Chieh and Hoffmann, Maik and Unger, Alexander and Kwan Kyu, Park and Kupnik, Mario and Kuhri-Yakup, Butrus T.
Title: CMUTS in permanent contact operation for high output pressure
Language: English
Abstract:

We present the operation of capacitive micromachined ultrasonic transducers (CMUTs) in permanent contact mode as an efficient transducer. The gap height of our transducers is chosen to be lightly smaller than the static deflection of the plate due to the pressure difference between the ambient and the vacuum cavity. Thus, the plates are in contact with the bottom of the cavities even with no dc bias applied. The devices were fabricated based on the thick box process. High-temperature assisted direct wafer bonding technique was used to fabricate devices with such large cell size (radii ~ 2000 μm) featuring low frequencies ~100 - 150 kHz. Extensive acoustic characterization was performed to demonstrate the behavior of such CMUTs in terms of displacement profile, output pressure and acoustic pitch-catch response. A maximum sound pressure of ~145 dB (SPL) at the transducer surface is measured at 240 V dc and 10 V ac with 100 cycles of burst signal. This is a great improvement from conventional CMUTs (with deeper gap height, operating at 55 kHz), which requires 350 V dc and 200 V ac in order to achieve an output pressure of 129 dB (SPL) at the transducer surface. The results presented in this paper demonstrate that operating CMUTs in permanent contact mode indeed enhances the device output pressure, and provides a good candidate for efficient ultrasonic transducers.

Divisions: 18 Department of Electrical Engineering and Information Technology
18 Department of Electrical Engineering and Information Technology > Institute for Electromechanical Design
18 Department of Electrical Engineering and Information Technology > Institute for Electromechanical Design > Measurement and Sensor Technology
Event Title: ASME 2015, InterPACKICNMM
Event Location: San Francsico, CA, USA
Event Dates: July 6-9, 2015
Date Deposited: 10 Feb 2016 10:50
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