Design and Fabrication of a MEMS Flexural Plate Wave Device Based on LTO/ZnO/LTO/Si3N4 Multilayered Composite Membrane

Abstract

The MEMS A0mode Lamb wave (flexural plate wave) ultrasonic devices have been shown to be extremely useful for sensor and actuator applications. The design and fabrication process of a MEMS flexural plate wave device based on the LTO/ZnO/LTO/Si3N4multilayered composite membrane are presented. The flexural plate wave was respectively launched and received by both Al interdigital transducers. In order to reduce the stress of the thin membrane induced mainly by the in-plane compressive stress of ZnO film, two fabrication process of DC and RF magnetron sputtering were used to deposit the ZnO films, respectively. The FPW device based on LTO(0.2μm)/ZnO(1μm)/ LTO(2μm)/Si3N4(0.5μm) thin membrane was fabricated. The center frequency of the MEMS flexural plate wave device is measured at 3.69MHz, which agrees with the theoretical predictions.