Microbridge testing of thin films

Abstract

In the present work, we describe a novel microbridge testing method for thin films. The single-layer, bilayer and trilayer thin film microbridge samples were prepared with the microelectromechanical fabrication technique such that they were easy to handle. The microbridge test was conducted with a load- and displacement-sensing nanoindenter system equipped with a microwedge probe. In the mechanics analysis, we considered residual stress in each layer, modeled the substrate deformation with three coupled springs and derived the load–deflection formula in a closed form. For brittle thin films, the microbridge testing method allows us to evaluate simultaneously the Young's modulus, the residual stress and the bending fracture strength. In addition, the microbridge test can characterize the yield strength for ductile thin films.