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Long-term measurement results of pre-charged CMUTs with zero external bias operation

  • We present long-term measurement results (<1.5 years) of CMUTs, which have been pre-charged for zero external bias operation. The fabrication is based on a direct wafer bonding process with a thick-buried-oxide-layer, which allows the realization of only partially connected, donut-shaped bottom electrodes. The only partially connected bottom electrode has a central portion that is completely encapsulated by 3-μm-thick thermally-grown silicon dioxide, and, thus, electrically floating. The devices are pre-charged by applying a dc voltage higher than the pull-in voltage, which injects charges into the electrically floating portion and creates a sufficiently strong intrinsic electric field in the gap. Measurements of resonant frequency at various bias voltages show that the charges have completely remained in the floating portion for the last 19 months. We prove the zero-external-bias operations with the pre-charged CMUTs by measuring the electrical input impedance, the ac signal displacement, and pitch-catch measurements under zeroWe present long-term measurement results (<1.5 years) of CMUTs, which have been pre-charged for zero external bias operation. The fabrication is based on a direct wafer bonding process with a thick-buried-oxide-layer, which allows the realization of only partially connected, donut-shaped bottom electrodes. The only partially connected bottom electrode has a central portion that is completely encapsulated by 3-μm-thick thermally-grown silicon dioxide, and, thus, electrically floating. The devices are pre-charged by applying a dc voltage higher than the pull-in voltage, which injects charges into the electrically floating portion and creates a sufficiently strong intrinsic electric field in the gap. Measurements of resonant frequency at various bias voltages show that the charges have completely remained in the floating portion for the last 19 months. We prove the zero-external-bias operations with the pre-charged CMUTs by measuring the electrical input impedance, the ac signal displacement, and pitch-catch measurements under zero external dc bias voltage. Our results show that pre-charging CMUTs is feasible, and that the devices are capable of long-term, zero external bias voltage operation.show moreshow less

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Metadaten
Author: Min-Chieh Ho, Mario Kupnik, Kwan Kyu Park, Butrus T. Khuri-Yakub
DOI:https://doi.org/10.1109/ULTSYM.2012.0022
ISBN:978-1-4673-4561-3
Title of the source (English):IEEE International Ultrasonics Symposium, Dresden, Germany, 7 - 10 October 2012
Publisher:IEEE
Place of publication:Piscataway, NJ
Document Type:Conference Proceeding
Language:English
Year of publication:2012
First Page:89
Last Page:92
Faculty/Chair:Fakultät 1 MINT - Mathematik, Informatik, Physik, Elektro- und Informationstechnik / FG Elektronische Systeme und Sensorik
Institution name at the time of publication:Fakultät für Maschinenbau, Elektrotechnik und Wirtschaftsingenieurwesen (eBTU) / LS Allgemeine Elektrotechnik und Messtechnik
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