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Microfabrication of electrode patterns for high-frequency ultrasound transducer arrays

Microfabrication of electrode patterns for high-frequency ultrasound transducer arrays

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Authors

  • Anne L. Bernassau
  • Luis Garcia-Gancedo
  • David Hutson
  • Christine E. M. Demore
  • Jim J. McAneny
  • Tim W. Button
  • Sandy Cochran

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Info

Original languageEnglish
Pages1820-1829
Number of pages10
JournalIEEE Transactions on Ultrasonics, Ferroelectrics and Frequency Control
Journal publication dateAug 2012
Volume59
Issue8
DOIs
StatePublished

Abstract

High-frequency ultrasound is needed for medical imaging with high spatial resolution. A key issue in the development of ultrasound imaging arrays to operate at high frequencies (>= 30 MHz) is the need for photolithographic patterning of array electrodes. To achieve this directly on 1-3 piezocomposite, the material requires not only planar, parallel, and smooth surfaces, but also an epoxy composite filler that is resistant to chemicals, heat, and vacuum. This paper reports, first, on the surface finishing of 1-3 piezocomposite materials by lapping and polishing. Excellent surface flatness has been obtained, with an average surface roughness of materials as low as 3 nm and step heights between ceramic/polymer of similar to 80 nm. Subsequently, high-frequency array elements were patterned directly on top of these surfaces using a photolithography process. A 30-MHz linear array electrode pattern with 50-mu m element pitch has been patterned on the lapped and polished surface of a high-frequency 1-3 piezocomposite. Excellent electrode edge definition and electrical contact to the composite were obtained. The composite has been lapped to a final thickness of similar to 55 mu m. Good adhesion of electrodes on the piezocomposite has been achieved and electrical impedance measurements have demonstrated their basic functionality. The array was then packaged, and acoustic pulse-echo measurements were performed. These results demonstrate that direct patterning of electrodes by photolithography on 1-3 piezocomposite is feasible for fabrication of high-frequency ultrasound arrays. Furthermore, this method is more conducive to mass production than other reported array fabrication techniques.

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