Transient capacitance measurement of MEM capacitor

Abstract

Previously, steady-state measurement methods have been used to characterize micro-electro-mechanical (MEM) capacitor performance during reliability testing and the testing has concentrated on detecting failure of the device. This paper shows that the dynamic performance of the MEM capacitor changes during continuous actuation. Therefore, continuous measurement of MEM capacitor during actuation is important for the reliability testing. This paper presents high frequency measurements of MEM capacitor capacitance as a function of time due to change in the control voltage. Behavior of the MEM capacitor is also modeled and the simulated results are compared with the measurement data. The transient capacitance measurements show that the increased actuation voltage decreases the time it takes for the MEM capacitor to change from minimum capacitance value to maximum capacitance value (switch ON), as predicted by the modeling. However, measurements also show that the time it takes to change from maximum capacitance to minimum capacitance (switch OFF) remains the same regardless of the control voltage and may even increase as trapped charge is accumulated into the dielectric layer. Using the MEM capacitor model, an accurate estimation of the charge trapped in the dielectric layer can be obtained from the measured transient capacitance. The paper also presents a method for performing the transient capacitance measurements and the measurement set-up.