Microbridge tests: I. On asymmetrical trilayer films

In this paper, we extended the microbridge testing method to characterize mechanical properties of asymmetrical trilayer thin films by taking the initial deflection into account. Theoretically, we analyzed the deformation of a trilayer microbridge with the deformable boundary condition, which is represented by a set of spring compliances, and derived a load-deflection formula in closed form. Using dimensional analysis and finite element calculation, we had the spring compliances as functions of the film thickness and the thickness-averaged Young's modulus. Experimentally, we fabricated asymmetrical trilayer microbridge samples of SiO₂/Si ₃N₄/SiO₂ on 4 inch p-type (1 0 0) silicon wafers, measured the profile of the initial deflection and conducted the microbridge tests with a load and displacement sensing nanoindenter system equipped with a microwedge indenter. The experimental results verified the proposed microbridge testing method. The newly developed microbridge testing method can be applied to characterize mechanical properties of multilayer films.