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Abstract: This paper presents a simple and robust process for fabrication of functional electrostatic RF-MEMS switching devices with lifetimes easily exceeding 108 cycles by unipolar actuation at 100Hz. The device implements a switchable air gap capacitor and is therefore not limited in lifetime by dielectric charging as opposed to contact-type capacitive switches implementing high-k dielectrics. Even though these switched air gap capacitors have a rather low capacitance ratio of around 5–6, they can still form adequate switching devices and RF-circuits by making use of properly designed transmission lines and when combined with high-Q inductors. Examples described include tunable notch band filters designed for the 2GHz and 20GHz range and a tunable stop band filter. The novelty of the proposed process is that it combines a sacrificial layer consisting of a single layer with a single dry etching step for the dimples which define the height of the air gap in the down-state. This air gap is switched by electrostatic actuation of a thick (7μm) electroplated nickel bridge structure. The device is realized in a 4 lithographic steps process with low complexity and high robustness. [Copyright &y& Elsevier]

Abstract: This work focuses on electrostatically actuated micro-electro-mechanical systems (MEMS) capacitive switches, intended for adaptive output stage of power amplifiers. These devices are particularly attractive because theoretically they are capable of very high quality factor values due to the air gap between plates and the low resistivity of lines and bridge. On the other hand, substrate parasitic effects, overlooked up to date, can seriously impair device performance. In this paper, we introduce a lumped element equivalent circuit taking into account substrate effects. Model validation is based on measurements carried out in the 50MHz–40GHz range. [Copyright &y& Elsevier]