Design and fabrication strategy for an efficient lead zirconate titanate based piezoelectric micromachined ultrasound transducer

This paper presents the design and fabrication strategy of a lead zirconate titanate (PZT)-based piezoelectric micromachined ultrasound transducers (pMUT) with the objective of maximizing its performance. Choosing the most suitable thickness of the PZT layer, the radius of the top electrode, and the effect of the residual stress on the resonance frequency of a pMUT are investigated by finite element method (FEM) simulation and analytical equations. Three different architectures of pMUTs are presented: (i) a pMUT with a top center electrode, (ii) a pMUT with a top center and ring electrode, (iii) a pMUT with a patterned PZT layer. All three pMUT architectures were fabricated and their displacement response, resonance frequency, and Q-factor are compared. The fabricated pMUT in all three architectures has a radius of 205 mu m, a Si membrane thickness of 6 mu m, and a PZT thickness of 1 mu m. The experimental results were compared to FEM simulation. The proposed architectures have a displacement response of 6.6 mu m V-1, 7.5 mu m V-1, and 8.6 mu m V-1, respectively, for their optimum design parameters.