Electromechanical characterization of low actuation voltage RF MEMS capacitive switches based on DC CV measurements

This paper reports on the enhancements introduced into the ITC-irst RF MEMS multi-user fabrication process, which have been assessed by means of the electromechanical characterization of a set of test structures consisting of low actuation voltage capacitive switches. A simple quasistatic CV measurement has been used to extract the switch capacitance in both the on and off states (C"o"n and C"o"f"f) and the voltage needed for the actuation of the different designs. The devices under test use folded serpentine springs and large area actuation electrodes to decrease the pull-in voltage. The spring constant of the suspensions is used to control the actuation voltage of the different designs with a slight increase of the overall size and without affecting the switching performance at higher frequencies. The introduction of a floating metal layer into the flow of the fabrication process has allowed a great increase in the off state capacitances, getting C"o"f"f/C"o"n ratios up to 10 times greater than the ones obtained for the same structures without this feature.