Investigations on beam membrane and dielectric materials using Ashby’s methodology and their impact on the performance of a MEMS capacitive switch

The micro-electro-mechanical-system switch performance significantly depends on materials used for the design of different components. The two most important elements of the MEMS switch are the beam membrane and dielectric layer. Thus, the selection of a material for these two components should be done with utmost care. In this paper, Ashby’s material selection methodology is employed for choosing the best material for the beam membrane and dielectric layer by investigating a database of materials. The material indices for beam membrane selection are Young’s modulus, Poisson’s ratio, thermal coefficient, electrical resistivity, thermal conductivity, and fracture strength. To obtain the best dielectric material, hold down voltage, dielectric charging, thermal conductivity and stability are considered as material indices to get optimized performance in the switch. To validate the results of material selection using Ashby’s method, the top five selected materials for beam membrane and dielectric are applied on a MEMS switch and impacts of these materials on the electromechanical and RF performance have been presented. The results conclude that the Au and Al₂O₃ are preferred choice for beam membrane and dielectric material to offer good performance for the frequencies in the range of 50–100 GHz.