Review of the properties of gold material for MEMS membrane applications

Materials selection for radio frequency (RF) microelectromechanical (MEM) switches application is important for overall design and fabrication of devices. The processing techniques and microstructures of the materials in these devices differ from the techniques used in bulk structures. Although the properties and morphology of a bulk material may be well characterised, thin film materials have properties substantially different. MEM switches for RF and cryogenic applications has been developed where the switch is integrated in a coplanar waveguide on a LaAlO₃ substrate as structure with a gold membrane bridge suspended above an area of the centre superconductor (YBa₂Cu₃O₇) covered with a BaTiO₃ dielectric. The gold (Au) membrane is actuated by the electrostatic attractive force acting between transmission line and the membrane when a dc control voltage is applied. The value of the actuation force greatly depends on the geometry and mechanical properties of the bridge material. A summary and review of the state-of-the-art in MEM switches using Au membrane elements is presented and its application for cryogenic temperature is discussed.