Output Pressure and Pulse-Echo Characteristics of CMUTs as Function of Plate Dimensions

Søren Elmin Diederichsen, Jesper Mark Fly Hansen, Mathias Engholm, Jørgen Arendt Jensen, Erik Vilain Thomsen

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Abstract

This paper presents an experimental study of the acoustic performance of Capacitive Micromachined Ultrasonic Transducers (CMUTs) as function of plate dimensions. The objective is to increase the output pressure without decreasingthe pulse-echo signal. The CMUTs are fabricated with a LOCOS process, followed by direct wafer fusion bonding to a Silicon-On-Insulator (SOI) wafer. In this way, the plate thickness is determined by the SOI wafer device layer thickness, resulting in CMUTs with plate thicknesses of 2, 9.3 and 15 μm. The corresponding radii and gap heights resulting in an immersion frequency of 5MHz and a pull-in voltage of 200V are obtained using finite element analysis. Hydrophone and plane reflector measurements are used to assess the acoustic performance. Increasing the plate thickness from 2μm to 15μm decreases the pulse-echo bandwidth from >100% to 30%. A maximum in both peak-to-peak output pressure and pulse-echo signal is obtained for the 9.3μm plate, which still has a moderate pulseecho bandwidth of 60%. The 9.3μm plate results in a 1.9 times higher peak-to-peak output pressure and a 3.6 times higherpulse-echo signal compared to the 2μm plate. By adjusting the plate dimensions of a CMUT it is possible to optimize its acoustic performance for medical imaging applications, including visualization of deeper structures in the body, as well as nonlinear imaging such as tissue harmonic imaging.
Original languageEnglish
Title of host publication2017 IEEE International Ultrasonics Symposium (IUS)
Number of pages4
PublisherIEEE
Publication date2017
ISBN (Electronic)978-1-5386-3383-0
DOIs
Publication statusPublished - 2017
Event2017 IEEE International Ultrasonics Symposium (IUS) - Omni Shoreham Hotel, Washington, United States
Duration: 6 Sep 20179 Sep 2017
http://ewh.ieee.org/conf/ius/2017/

Conference

Conference2017 IEEE International Ultrasonics Symposium (IUS)
LocationOmni Shoreham Hotel
Country/TerritoryUnited States
CityWashington
Period06/09/201709/09/2017
Internet address

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