Compared to aluminum nitride (AlN) with simple stoichiometry, lead zirconate titanate thin films (PZT) are the other promising candidate in advanced micro-electro-mechanical system (MEMS) devices due to their excellent piezoelectric and dielectric properties. The fabrication of PZT thin films with a large area is challenging but in urgent demand. Therefore, it is necessary to establish the relationships between synthesis parameters and specific properties. Compared to sol-gel and pulsed laser deposition techniques, this review highlights a magnetron sputtering technique owing to its high feasibility and controllability. In this review, we survey the microstructural characteristics of PZT thin films, as well as synthesis parameters (such as substrate, deposition temperature, gas atmosphere, and annealing temperature, etc.) and functional proper-ties (such as dielectric, piezoelectric, and ferroelectric, etc). The dependence of these influential factors is particularly emphasized in this review, which could provide experimental guidance for researchers to acquire PZT thin films with expected properties by a magnetron sputtering technique.

Piezoelectric micromachined ultrasonic transducers (PMUT) are promising elements to fabricate a two-dimensional (2D) array with a pitch small enough (approximately half wavelength) to form and receive arbitrary acoustic beams for medical imaging. However, PMUT arrays have so far failed to combine the wide, high-frequency bandwidth needed to achieve a high axial resolution. In this paper, a polydimethylsiloxane (PDMS) backing structure is introduced into the PMUTs to improve the device bandwidth while keeping a sub-wavelength (λ) pitch. We implement this backing on a 16 × 8 array with 75 µm pitch (3λ/4) with a 15 MHz working frequency. Adding the backing nearly doubles the bandwidth to 92% (−6 dB) and has little influence on the impulse response sensitivity. By widening the transducer bandwidth, this backing may enable using PMUT ultrasonic arrays for high-resolution 3D imaging.

Lead zirconate titanate (PZT) films have shown great potential in piezoelectric micro-electronic-mechanical system (piezo-MEMS) owing to their strong piezoelectric response. However, the fabrication of PZT films on wafer-level suffers with achieving excellent uniformity and properties. Here, we successfully prepared perovskite PZT films with similar epitaxial multilayered structure and crystallographic orientation on 3-inch silicon wafers, by introducing a rapid thermal annealing (RTA) process. Compared to films without RTA treatment, these films exhibit (001) crystallographic orientation at certain composition that expecting morphotropic phase boundary. Furthermore, dielectric, ferroelectric and piezoelectric properties on different positions only fluctuate within 5%. The relatively dielectric constant, loss, remnant polarization and transverse piezoelectric coefficient are 850, 0.1, 38 μC/cm² and −10 C/m², respectively. Both uniformity and properties have reached the requirement for the design and fabrication of piezo-MEMS devices. This broadens the design and fabrication criteria for piezo-MEMS, particularly for piezoelectric micromachined ultrasonic transducers.