Modeling and simulation of MEMS test structures using finite element method for stress mapping in thin film coatings

Thermal stress, which is due to the mismatch of coefficients of thermal expansion in multilayered structures, is often responsible for failure of thin film devices. MEMS test structures are quick and inexpensive approach for mechanical characterization of thin films during the fabrication process. The research presented here describes a test structure for in situ stress measurements based on rotational beam technique via finite element method analysis. A model was developed to induce tensile and compressive stresses on blanket thin film coatings. Evolution of the tensile/compressive stress induces certain displacement of the thin film as a function of applied temperature. The rotation of the indicator beam due to deflection/displacement of the blanket thin film is further investigated. The optimized layout of the test structure is proposed considering the stress profile and torsion of the indicator beam.