An integrated microelectromechanical microwave switch based on piezoelectric actuation

Abstract

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 µm 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 SiO 2 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 µm for a 1400 µm 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.

Manufacture of Radio Frequency Micromachined Switches with Annealing

“…The reason is that the springs of the RF switch in this work is designed as S-shape, resulting in reducing the stiffness of springs and the actuation voltage. Kügeler et al [ 7 ] developed a RF micromachined switch with piezoelectrically actuated elements. The isolation of the RF switch was 20 dB at 15 GHz, and its actuation voltage was 10 V. The piezoelectric material is not compatible with the commercial CMOS process, so it is difficult to integrate with circuitry on-a-chip.…”

“…The actuation voltage of the RF switch was 25 V. The RF switch had an insertion loss of 0.29 dB at 24 GHz and an isolation of 30.1 dB at 24 GHz. Kügeler et al [ 7 ] proposed a silicon based micromachined switch with piezo-electrically actuated elements. The switch consisted of two piezoelectric activated beams with a coplanar waveguide (CPW).…”

“…The switch had an isolation of 42 dB at 24.5 GHz and an insertion loss of 0.25 dB at 25.6 GHz. The actuation voltage of the switch was 17 V. In this work, we uses the commercial CMOS process to manufacture a micromechanical RF switch, and its fabrication is easier than Czaplewski et al [ 5 ], Park et al [ 6 ], Kügeler et al [ 7 ], Chang et al [ 8 ], and Zheng et al [ 9 ].…”

Pi-shaped MEMS architecture for lowering actuation voltage of RF switching

“…There exist several methods to improve the parameters of RF MEMS switches with primary emphasize on lowering the actuation voltage. Piezoelectric actuation is an attractive method used by several researchers including Kugeler et al [5]. An extremely low actuation voltage (2.5 V) has been obtained.…”

A ZnO thin-film driven microcantilever for nanoscale actuation and sensing

“…As sensors, they operate in the opposite mode using the piezoelectric effect. Typical piezoelectric cantilever actuators include ultrasonic motors [1], atomic force microscopy (AFM) probes [2], microelectromechanical system (MEMS) switches [3,4], bandpass filters [5], and scanning MEMS mirrors [6,7], whereas piezoelectric cantilever sensors can be accelerometers, force sensors, or pressure sensors [8][9][10].…”