A resonance method for the determination of Young's modulus and residual stress of thin microstructures

With the recent progress in microsystems technology there is a growing need for accurate knowledge of material properties in design. Especially on thin films, material properties are strongly affected by layer thickness and deposition parameters. Since traditional methods for the characterization of bulk materials are hardly applicable on thin films novel extraction techniques are required. The following paper deals with a resonant method to determine Young's modulus and residual stress simultaneously. Therefore an array of microbridges with variable length is etched into the layer material. Samples are stimulated electrostatically to small signal oscillations and their resonance frequency is measured by a laser doppler interferometer. Based on the theory of prestressed beams both material parameters can be separated independently by nonlinear function fitting. Accuracy of this approach will be assessed and first results are presented.