New areas of medical study and clinical applications are being developed with the use of high frequency (10-100 MHz) ultrasound imaging. Ultrasound images made with these frequencies have resolutions which approach 20 microns. Initial clinical applications of high frequency ultrasound include imaging the eye, the vasculature, the skin, and cartilage. The advantage that two-dimensional imaging arrays offer over linear arrays is that they enable dynamic control of the ultrasound beam in two directions. This capability reduces the size of image slices, reduces phase aberrations, and provides volumetric scanning capability. High-frequency, two-dimensional ultrasonic transducer 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, which only compounds the fabrication difficulties. We propose an innovative, scaleable approach to manufacturing low-cost, high-frequency, two-dimensional, multi-layer ultrasonic transducer arrays with low impedance and high sensitivity. The approach uses reactive Physical Vapor Deposition to deposit high-quality, dense, perovskite lead zirconate titanate (PZT) films as the piezoelectric material and a combination of photolithography, sputtering, and masking to provide the interlayer electrodes and element interconnections.
Creare will demonstrate an innovative approach for manufacturing high-frequency, highly sensitive, two- dimensional ultrasonic imaging arrays which will be of benefit in all areas of biomedical imaging. The commercial potential of this project is evidenced by the support of a major biomedical ultrasound company.
