Micromachined diaphragm transducers for miniaturised ultrasound arrays

Miniaturised ultrasound transducer arrays with integrated electronics will in future enable significant advances in high resolution medical imaging and in acoustic tweezing for bioscience research. However, their development has been limited by challenges in scaling down conventional piezoelectric ultrasound transducer fabrication and interconnection techniques. Piezoelectric thin film transducers on silicon substrates can overcome these challenges by reducing dimensional constraints in fabrication and facilitating integration with electronics, including allowing low drive voltages in transmission. We present the design, fabrication and testing of diaphragm transducers to evaluate the feasibility of integrated piezoelectric micromachined ultrasonic transducers (PMUTs). Transducers have been designed, then fabricated with 80 μm and 130 μm diameter diaphragms, the latter in arrays with ~500 diaphragms. Receive measurements demonstrate functionality of both devices, with pulse-echo bandwidths of approximately 90% for the 80 μm diaphragms, demonstrating initial feasibility for ultrasound imaging.