Towards improved reliability of RF-MEMS: mechanical aspects and experimental testing of a micro-switch design with embedded active self-recovery mechanism to counteract stiction

摘要

In this work, the operation of an active self-recovery mechanism embedded within microelectromechanical systems (MEMS) switches for Radio Frequency (RF) passives (i.e. RF-MEMS) is reported and discussed. The mechanism is able to counteract stiction induced by charge accumulation and micro-welding formation. It is based on the thermoelectric effect, allowing restoring the MEMS switch back to normal operation after failure. The goal is achieved by means of two factors, namely, the entrapped charges dispersion speed-up within the insulating layer between the electrodes, and the application of shear forces on the welding joints, both induced by the heat. Preliminary experimental results, collected by a few fabricated RF-MEMS switch samples, confirm the viability of the proposed approach. Moreover, the coupled thermos-electro-mechanical multi-physical behaviour of the discussed RF-MEMS switch is also analysed by means of Finite Element Method simulations. In particular, the results of experiments carried out with a dynamic 3D profiling setup show that when driving a current through a micro-heater embedded under the MEMS intentionally brought to stiction due to charge accumulation, the release of the switching membrane and the restoration of its operability is speeded-up. In addition, the reported characterisation includes also the pull-in/pull-out characteristic and the RF measurement of the S-parameters (scattering parameters).