Effect of Piezoelectric Layer on Resonant Frequency of Silicon MEMS Membranes

A quantitative criterion for assessing the influence of piezoelectric layer thickness on the resonant frequency of a multilayer membrane in devices such as MEMS ultrasonic sensors is proposed. It is shown that this criterion enables comparison of membrane designs with different geometries, determination of permissible piezoelectric layer thicknesses, and optimization of the ratio of silicon and piezoelectric layer thicknesses. Practical relationships for selecting silicon and piezoelectric layer thicknesses are presented, using a typical Si/SiO2/Mo/ZnO/Mo structure as an example. The results are applicable to the design of membrane structures with the required dynamic characteristics.