Determination of elastic constants of thin films for improved CAD modeling of SAW filters and resonators

Surface acoustic waves (SAWs) propagating in anisotropic and piezoelectric substrates are investigated. The mass- and stress-loading effect, caused by two different isotropic and metallic films with finite thickness, is taken into account by analyzing the multilayered structure. The mass density and the elastic stiffness constants of the metallic layers are determined by fitting calculated to measured velocity dispersion curves. High-precision group delay time measurements are made. The thicknesses of the metallic films are measured with a transmission electron microscope (TEM). A least square fit yields are unknown elastic constants and the densities of the aluminum and the aluminum oxide layer. These improved values of material constants are further used in efficient CAD tools for high performance SAW filter modeling and synthesis