Piezoelectric micromachined ultrasonic transducers: Modeling and simulation of structural parameters on transmitting performance

The purpose of the present study is to numerically analyze and optimize structural parameters effecting on the transmitting performance of piezoelectric micromachined ultrasonic transducers (PMUTs) with a vibration layer. Using the finite elements method (FEM), a planar and two curved (dome-shaped and concave) structures of PMUTs based on aluminum nitride (AlN) were modeled separately. By applied a sine excitation working on a frequency band ranged from 20 kHz to 25 MHz, resultant transmitting performances with various structural parameters of each PMUT model were estimated numerically in water. The obtained results clearly show that there is a relative higher transmitting performance both of the dome-shaped and concave structures comparing with that of the planar one. Importantly, the transmitting performance would be optimized with a diameter of 64 μm for the top electrode of the planar element, which is consistent with previous theoretic works, and a radius of 200 μm would be suggested for the curvature of the curved structures so as to launch a larger acoustic pressure. In conclusion, both the physical parameters and geometric structures of a PMUT-based ultrasound sensor combining its work frequency could be optimized efficiently with a numerical method.