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

A PVDF-on-Silicon 8-element ultrasound transducer array (1 mm x 1 mm and element spacing of 1 mm) 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 mum 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 backing/water interface. The fabricated array elements are tested in a water tank and their pulse-echo response are recorded. The central frequency of each element is 25 MHz with a 100% measured 6-dB bandwidth (60% 3-dB bandwidth).