Design of Pre-Charged CMUTs with a Metal Floating Gate

Capacitive micromachined ultrasonic transducers (CMUTs) require a DC bias voltage for efficient operation. Precharged CMUTs can eliminate the requirement of DC bias voltage, thus ease the design of frontend circuitry for transmit/receive operation. We used a metal floating gate structure to trap cha...

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Bibliographic Details
Main Authors: Annayev, Muhammetgeldi, Adelegan, Oluwafemi J., Yamaner, F. Yalcin, Oralkan, Omer
Format: Conference Proceeding
Language:English
Subjects:
capacitive micromachined ultrasonic transducer
CMUT
Electric potential
energy harvesting
Fabrication
Metals
Pre-charged
Silicon nitride
Ultrasonic imaging
Ultrasonic transducers
Voltage
zero-bias
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Description
Summary:Capacitive micromachined ultrasonic transducers (CMUTs) require a DC bias voltage for efficient operation. Precharged CMUTs can eliminate the requirement of DC bias voltage, thus ease the design of frontend circuitry for transmit/receive operation. We used a metal floating gate structure to trap charges instead of an oxide-nitride interface or a silicon floating island. Because the potential barrier height for metal-oxide interface is much higher than oxide-nitride and oxide-silicon barrier heights, it is possible to retain trapped charge without leakage. Also we do not expect any charge leakage on the metal-nitride side because of the vacuum gap. We used an anodic bonding based process and formed the floating metal under the silicon plate where the metal is sandwiched between silicon dioxide and silicon nitride layers. Initial results show that the proposed structure can store electrical charges to allow operation without a DC bias. The CMUTs fabricated using the described approach will be primarily used as an ultrasound-powered implantable biomedical device.
ISSN:1948-5727
DOI:10.1109/IUS52206.2021.9593593