Micromachined DC contact capacitive switch on low-resistivity silicon substrate

Abstract

A DC contact capacitive shunt switch on low-resistivity Si substrate is designed and demonstrated. There are two main differences between this design and the conventional capacitive shunt switch. First, the dielectric layer is fabricated on the ground planes of the coplanar waveguide (CPW) transmission line. The contact between the metal bridge and the center conductor becomes DC contact when the metal bridge is driven down. As a result, the down-state capacitance degradation problem can be solved and the down-state capacitance as high as 30pF can be achieved. Second, the switch is fabricated on a low-resistivity silicon substrate. This is the first time where a RF MEMS switch can be fabricated on a low-resistivity silicon substrate without any wafer transfer technology; thus, it can greatly simplify the fabrication process and reduce cost. Measurement results show that the insertion loss is lower than 0.4dB until 26.5GHz and the isolation is 15dB at 1GHz, 26dB at 10GHz and 27dB at 26.5GHz. The down-state resistance and the inductance are 1.3Ω and 2 pH, respectively.