Development of CMOS-based Capacitive Micromachined Ultrasonic Transducers Operated in Collapse-mode
Date Issued
2014
Date
2014
Author(s)
Chung, Wei-Cheng
Abstract
In this work, experimental results of Capacitive Micromachined Ultrasonic Transducers (CMUTs) operated in collapse-mode is presented. The device is implemented with the TSMC 0.35μm CMOS-MEMS process. Through the surface profile measured by a confocal microscope, the collapsed voltage is measured at approximately 50 ~ 60V. With a bias voltage over the collapse voltage, the receiving sensitivity of CMUTs is increased 4 times larger and the center frequency is shifted from 2.7MHz to 7.9MHz. Driven by a commercial pulser, the received echo signal using our device in traditional mode is 2.625Vpp and the fractional bandwidth is 132%. Affected by the deep-collapse operation, the largest received echo signal reaches 3.427Vpp and the fractional bandwidth reduced to approximately 40 ~ 45%. The CMUT center frequency shifts from 3.12MHz to 9.12MHz. We also present an improved wet etch process to significantly increase the yield to almost 100%. Depositing thicker sealing membrane material ensures the robustness of CMUTs. Our developed CMUTs operated in DC bias of 90V in a water tank for over half an hour was demonstrated.
Subjects
互補式金屬氧化物半導體
微機電超音波換能器
崩潰模態
Type
thesis
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