A High-Performance Piezoelectric Micromachined Ultrasonic Transducer Hexagonal Array Utilizing Sacrificial Layer Technology

Ultrasonic technology, a non-invasive detection method, has been extensively applied in fields such as ultrasonic ranging and intelligent medical imaging. Piezoelectric micromachined ultrasonic transducers (PMUT), as MEMS device capable of emitting and detecting ultrasound, have increasingly demonstrated their value due to miniaturization, low power consumption, and cost-effectiveness. In this study, we successfully fabricated a batch of PMUTs with varying resonant frequencies on the surface of a (100) silicon wafer using the surface sacrificial layer process. These PMUTs feature low-pressure cavities. The maximum displacement sensitivity and quality factor of the PMUT unit are 56.4 nm/V and 615.8, respectively. Due to the compact arrangement of hexagonal PMUT cells, the filling factor is increased by 9%. These characteristics contribute to enhanced array sound pressure emission capability. Testing the emission sound pressure of PMUT in a water environment, the maximum emission sound pressure at 1 mm is 8.7 kPa/V, and the 3dB bandwidth is expanded to 36%.