Innovative Fabrication of 2D Ultrasonic Imaging Arrays

Current ultrasound images in mine warfare, biomedical imaging and non-destructive testing are limited by the use of linear transducer arrays which result in thick image "slices", errors from phase aberrations and primitive volumetric scanning capability. Two-dimensional arrays will overcome these limitations. Two-dimensional arrays have not been manufactured because of difficulty in fabricating the small structures and low transducer element sensitivity. The low sensitivity can be overcome by employing multi-layer structures. We propose an innovative, scaleable approach to manufacture low-cost, two-dimensional, multi-layer transducer arrays with low impedance and high sensitivity. Our approach uses plasma-enhanced, reactive Physical Vapor Deposition (PVD) to deposit high- quality, perovskite lead-zirconate lead-titanate (PZT) films as the piezoelectric material and photolithogrpahy with PVD and an innovative, manufacturing scheme to provide the interlayer electrodes and element interconnections. In Phase I, we will demonstrate the feasibility of the approach by fabricating a two-dimensional, multi-layered array and measuring its impedance characteristics and acoustic performance. In Phase II, we will build fully populated two-dimensional, multi-layered imaging arrays and test them for element sensitivity, interelement isolation, electrical impedance and beamforming performance and use them to form three-dimensional images.