An integrated microelectromechanical microwave switch based on piezoelectric actuation

In the field of microwave applications, microelectromechanical systems (MEMS) are attractive devices in order to force miniaturization by on chip integration. Here, we describe the design, fabrication and testing of a silicon based micromachined switch using piezo-electrically actuated elements. The microwave circuit consists of a coplanar waveguide (CPW) design with two piezoelectric activated beams integrated between the middle line and the ground planes. During operation the beams short the CPW by two overhanging bridge contacts and therefore the transmission characteristics of the microwave circuit change. The CPW is realized by 3 A mu m thick electroplated copper to yield good transmission characteristics, whereas the clamped-clamped beams benefit from a 250 nm thin PZT film between 100 nm thin Pt electrodes on top of a SiO2 layer. By the use of double side clamped beams awkward stress compensation of the piezoelectric stack is omitted. Instead the system relies on some initial mechanical stress. Measurements prove deflections of more than 13 A mu m for a 1400 A mu m long beam with operation voltages below 10 V. This is in good agreement with finite element simulations. The novel RF-MEMS is predicted to reach an isolation (in "on" state) of more than 20 dB up to 15 GHz.