Piezoelectric micromachined ultrasonic transducers (PMUTs) offer the potential for miniaturization while preserving the resonant operation in the kHz to the lower MHz range. This feature enables their integration into medical implantable devices, fingerprint sensors, or ultrasonic-based communication where bulk-based transducers may be impractical due to their dimensions. Regardless of the final application, the reliability and lifetime performance of PMUTs also determine the overall service life of the device. This contribution features a comprehensive study of the lifetime performance of in-house fabricated PMUTs by considering several aspects such as delamination, leakage current, decrease in remnant polarization, and the piezoelectric material lead zirconate titanate (PZT) itself. This material is characterized by X-ray diffraction (XRD) measurements, while a TSDC (Thermally stimulated depolarization current) experiment confirmed the presence of oxygen vacancies. These oxygen vacancies appear to have negatively impacted the service life. The deflection of each PMUT remained nearly stable for more than 2 10 excitation cycles in an almost continuous operation at their respective resonance frequencies and a peak-to-peak voltage of 5 V (50 kV/cm). A final comparison with the ferroelectric hysteresis loop and the deflection indicates that a significant decrease in the remnant polarization and maximum polarization is also reflected in the out-of-plane displacement of the PMUTs.
Helmerich et al. (2026) studied this question.