Simple and Robust Air Gap-Based MEMS Switch Technology for RF-Applications

This paper presents a simple and robust process for fabrication of functional electrostatic RF-MEMS switching devices with lifetimes easily exceeding 10⁸ cycles with unipolar actuation at 100 Hz. 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. It is shown how these switched capacitors, even though having a capacitance ratio of only 2.8, can still form adequate switching devices and RF-circuits by proper design and combining of these devices with high-Q inductors and transmission lines. 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 air gap in the down-state. This airgap is switched by electrostatic actuation of a thick electroplated nickel bridge-structure. The device is realized in a 4-lithographic steps process with low complexity and high robustness.