P2H-3 Guided Lamb Waves in AlN Free Strips

An electro-acoustic micro-device based on the propagation of guided acoustic Lamb-waves in aluminum nitride (AlN) free strip is described. The AlN thin film was deposited by sputtering technique, optimized to achieve an high degree of orientation (rocking curve FWHM ~ 3.5deg) of the c-axis perpendicular to the plate surface. The AlN beam was micro- machined using anisotropic reactive ion etching (RIE) technique, followed by an isotropic RIE process to remove the silicon underlayer. Simulation results obtained for the dispersion phase velocity curves and the electromechanical coupling coefficient (K^-2), are reported. Finally, delay-lines were implemented on the structure and tested for the propagation of the first symmetrical Lamb mode (SO) at the frequency of 1.23 GHz. Measurements are in good accordance with theoretical predictions and show how the structure is suitable for arrays integration of electro- acoustic devices on a single chip for applications to sensing devices and signal processing systems.