Fabrication of low pull-in voltage RF MEMS switches on glass substrate in recessed CPW configuration for V-band application

A new technique for the fabrication of radio frequency (RF) microelectromechanical systems (MEMS) shunt switches in recessed coplaner waveguide (CPW) configuration on glass substrates is presented. Membranes with low spring constant are used for reducing the pull-in voltage. A layer of silicon dioxide is deposited on glass wafer and is used to form the recess, which partially defines the gap between the membrane and signal line. Positive photoresist S1813 is used as a sacrificial layer and gold as the membrane material. The membranes are released with the help of Pirhana solution and finally rinsed in low surface tension liquid to avoid stiction during release. Switches with 500 µm long two-meander membranes show very high isolation of greater than 40 dB at their resonant frequency of 61 GHz and pull-in voltage less than 15 V, while switches with 700 µm long six-strip membranes show isolation greater than 30 dB at the frequency of 65 GHz and pull-in voltage less than 10 V. Both types of switches show insertion loss less than 0.65 dB up to 65 GHz.

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