Evaluation of wafer bonded CMUTs with rectangular membranes featuring high fill factor
| Autor: | Butrus T. Khuri-Yakub, Xuefeng Zhuang, S.H. Wong, K. Butts-Pauly, Mario Kupnik, Der-Song Lin |
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| Rok vydání: | 2008 |
| Předmět: |
Materials science
Acoustics and Ultrasonics Modal analysis Transducers Electric Capacitance Sensitivity and Specificity Article Capacitive micromachined ultrasonic transducers Optics Electrical and Electronic Engineering Center frequency Instrumentation Electrical impedance Ultrasonography Guided wave testing business.industry Membranes Artificial Equipment Design Micro-Electrical-Mechanical Systems Image Enhancement Equipment Failure Analysis Computer-Aided Design Continuous wave Ultrasonic sensor business Acoustic impedance |
| Zdroj: | IEEE Transactions on Ultrasonics, Ferroelectrics and Frequency Control. 55:2053-2065 |
| ISSN: | 0885-3010 |
| Popis: | Increasing fill factor is one design approach used to increase average output displacement, output pressure, and sensitivity of capacitive micromachined ultrasonic transducers (CMUTs). For rectangular cells, the cell-to-cell spacing and the aspect ratio determine the fill factor. In this paper, we explore the effects of these parameters on performance, in particular the nonuniformity of collapse voltage between neighboring cells and presence of higher order modes in air or immersed operation. We used a white light interferometer to measure nonuniformity in deflection between neighboring cells. We found that reducing the cell-to-cell spacing could cause bending of the center support post, which amplifies nonuniformities in collapse voltage to 18.4% between neighboring cells. Using a 2-D finite element model (FEM), we found that for our designs, increasing the support post width to 1.67 times the membrane thickness alleviated the post bending problem. Using impedance and interferometer measurements to observe the effects of aspect ratio on higher order modes, we found that the (1,3) modal frequency approached the (1,1) modal frequency as the aspect ratio of the rectangles increased. In air operation, under continuous wave (CW) excitation at the center frequency, the rectangular cells behaved in the (1,1) mode. In immersion, because of dispersive guided modes, these cells operated in a higher order mode when excited with a CW signal at the center frequency. This contributed to a loss of output pressure; for this reason our rectangular design was unsuitable for CW operation in immersion. |
| Databáze: | OpenAIRE |
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