Geometric and material nonlinearity during the deformation of micron-scale thin-film bilayers subject to thermal loading

Creep analysis of bimaterial microcantilever beam for sensing device using artificial neural network (ANN)

“…A finite element model has been built based on the experiment carried out by Yanhang Zhang and Martin L. Dunn [1]. This model is analyzed based on the experimental data for the linear and geometric nonlinear behavior of bimaterial microcantilever subjected to thermal loading due to the combined creep and stress relaxation.…”

“…It has an overall size of 280 μm (l) × 50 μm (w) × 2 μm (which thickness of 0.5 μm in gold and 1.5 μm in polysilicon), similar to the model and conditions used for the experimental study [1]. The cantilevers were held at the modest temperature of 120 o C. The polysilicon will deform elastically at this temperature, and will not affect the creep and/or stress relaxation of the gold layer.…”

“…The cantilevers were held at the modest temperature of 120 o C. The polysilicon will deform elastically at this temperature, and will not affect the creep and/or stress relaxation of the gold layer. The stress relaxation process is modeled by taking a simple power law in the gold, From the experimental work, the relaxation data is found to be as n = 5 [1] but the actual value of A depends on the film thickness with some unknown relationship. Inelasticity in the Au film is observed to be stress relaxation.…”

“…Results obtained from ANSYS® 8.1 finite element (FE) simulations, which show good agreement with experimental work [1], is used to train the neural network. Parametric studies are carried out to analyze the effects of creep on the microcantilever beam in term of curvature and stress developed with time.…”

Temperature effects on the mechanical reliability of MEMS structures: experimental study on creep and thermal fatigue

“…Some works in the literature were focused on the study of creep in MEMS that appears when static loads are associated to medium and high temperatures: Modlinski et al [2] characterized the bridge of a capacitive switch made by an Al alloy, Larsen et al [3] presented the design for a test structure devoted to investigation on creep for electroplated nickel, Zhang and Dunn [4] studied creep on thin gold-polysilicon bilayer films subjected to thermal loading. It was observed that long-term deformation of metal parts of microdevices may play a key role in the lifetime of a device, making creep a very important issue in the reliability of MEMS.…”