Fabrication techniques for emproving the performance of PVDF-on-silicon ultrasonic transducer arrays

A PVDF-on-Silicon 8-element ultrasound transducer array (1mm x 1mm and element spacing of 1mm) is fabricated and characterized. To improve the performance of the transducer, new CMOS-compatible fabrication technologies are introduced. These include: 1) micro-contact printing on non-radiating. areas, and 2) glass microspheres (7-20 mu m in diameter) embedded low melting temperature alloy (LMA) material for backside electrical connection. The first improvement removes the impedance mismatching of adhesive layer (e.g., lower sensitivity between the PVDF and backside contact while the second one improves the pulse-echo signal quality by eliminating reflections at the backingAvater interface. The fabricated arrav elements are tested in a water tank and their pulse-echo response are recorded. The central frequency of each element is 25MHz with a 100% measured 6-dB bandwidth (60% 3-dB bandwidth).