Temperature dependence of the electromechanical characteristics of superconducting RF-MEMS switches

Micro-electro-mechanical-system (MEMS) switches are very interesting for high frequency applications. These switches are electrostatically actuated micromechanical meanders-suspended bridges. In the field of millimeter wave radio astronomy, cryogenic circuits are frequently made of superconducting niobium and elements combining these circuits with MEMS devices of compatible technologies are of high potential for new applications. The initial profile of the bridge has been numerically simulated. This suggested the influence of possible residual stress in Nb thin films on the behavior of MEMS. A study of the capacitance variation as a function of the applied voltage has been performed for this type of MEMS at room and low temperatures down to 150 K. It is associated with a mechanical study of the vibrating modes of the structure and with X-rays characterization of the Nb film. An identification of specific sets of geometric parameters to reach good performance and temperature stability was done.