Multimode frequency analysis for the dynamic characterization of microstructures

A dynamic characterization of SiO 2 -Au composite cantilever beams and Si 3 N 4 -Au composite microbridges, has been performed to determine the effective residual stress in thin film-based microstructures. For the cantilever beams, the first three resonant frequencies were measured and compared to the theoretical ones obtained with a simple analytical model taking into account the effect of the gold layer on the shift of the resonant frequencies. A very good agreement is obtained between theoretical and experimental values showing the validity of the approach. Concerning the composite microbridges, the Rayleigh-Ritz method has been applied to obtain the relationship between the resonant frequencies and the effective residual stress. Using this method, the effective residual stress within the Si 3 N 4 -Au composite microbridges has been determined, (sigma) eff equals 610 +/- 40 MPa.