Development of MEMS-Based Lamb Wave Acoustic Devices

In this paper, lamb wave acoustic (LWA) devices based on ZnO/Si plate of 30-μm thickness have been fabricated. Devices with four different designs having acoustic wavelengths of 20, 40, 60, and 80 μm have been fabricated to study its effect on the acoustic velocity for both the lowest order antisymmetric (A0) and symmetric (S0) modes. The variation in effective phase difference in all the fabricated LWA devices is studied. An optimum device design is identified with appropriate distance between centers of the input and output IDTs to obtain a phase difference of 180° in antisymmetric and symmetric modes. The obtained phase difference of 180° is very critical in fabricating an oscillator for realization of wireless sensor devices. LWA devices offer high sensitivity to mass loading and thus hold tremendous potential for chemical sensing applications.