Investigation of Thermal Design Issues of a Bimaterial MEMS

As the application of micro-electromechanical systems (MEMS) in today’s sensors and actuators have become common, there are still many open questions in terms of analytical analysis, which is related to their operation in multiple physical domains. Beside the numerical analysis it is essential to have a precise view of their behaviour which is required to derive system level models in the later phases of the design process to perform design of experiment (DoE) analysis as well. In this paper the out of plane displacement of bimaterial microbeams is investigated which are the parts of a larger MEMS, designed to use for Kelvin probe measurements. The analytical formula for maximal displacement is derived from the well-known expression using the different coefficients of thermal expansions (CTEs) when a beam composed of two materials is heated. The derived formula is compared to numerical simulation, where an empirical scaling factor is introduced to compensate the inaccuracies. The material and geometry dependence of this scale factor were also investigated and presented in this article.