Pulse-Echo Ultrasound Imaging Using an AlN Piezoelectric Micromachined Ultrasonic Transducer Array With Transmit Beam-Forming

This work demonstrates short-range and high-resolution ultrasonic imaging using 8 MHz aluminum nitride (AlN) piezoelectric micromachined ultrasonic transducer (PMUT) arrays, which are compatible with complementary metal-oxide semiconductor circuitry and wafer-level mass manufacture. Because AlN has a low dielectric constant, the PMUTs have low capacitance and a custom 1.8 V interface application-specified integrated circuit with on-chip charge-pump (1.8 to 32 V) is capable of providing sufficient output current to drive the PMUT array. Transmit beam-forming is used to produce a 90 μm focused acoustic beam-width. A pressure map measured with a needle hydrophone agrees with finite element method-simulations. Finally, 1-D and 2-D pulse-echo imaging was conducted using metal targets.