Towards improved reliability of RF-MEMS: mechanical aspects and experimental testing of a micro-switch design with embed
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TECHNICAL PAPER
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 J. Iannacci1 Received: 24 March 2020 / Accepted: 13 May 2020 Springer-Verlag GmbH Germany, part of Springer Nature 2020
Abstract 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 thermoselectro-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).
1 Introduction Employment of MEMS (microelectromechanical systems) technology for the manufacturing of Radio Frequency (RF) passive components of various complexity (i.e. RFMEMS), is more and more attractive in recent years, with particular focus on commercial applications. The reasons are to be sought in the remarkable performance RF-MEMS technology enables if compared to standard implementations of similar devices (De Los Santos 2002). For instance, variable capacitors (varactors) with large tuning range and high Q-factor are presented in literature (Hyung et al. 2008; Cazzorla et al. 2015), as well as inductors (Zine-El-Abidine et al. 2003; Hikmat and Mohamed Ali 2017), switches (Goldsmith et al. 1998; Sedaghat-Pisheh
& J. Iannacci [email protected] 1
Center for Materials and Microsystems (CMM), Fondazione Bruno Kessler (FBK), Via Sommarive, 18, 38123 Trento, Italy
and Rebeiz 2009; Daneshmand and Mansour 2007; Iannacci 2018a) and complete networks, like phase shifters (Topalli et al. 2008; Bakri-Kassem et al. 2011), reconfigurable impedance matching networks (Lu et al. 2003; Larcher et al. 2009; Singh et al. 2019) and multi-state step attenuators (Khaira et al. 2018; Iannacci et al. 2016, 2009a). Availability of lumped passiv
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