Dynamics and squeeze film gas damping of a capacitive RF MEMS switch

We report on measurements of the time-dependent capacitance of an RF MEMS shunt switch. A high time-resolution detection set-up is used to determine switching time and motion of the device. From the equation of motion the damping force is extracted. The measured damping force is found to be approximately proportional to the speed over the gap to the third power (F-D proportional to v/z(3)), in good agreement with squeeze film damping theory. Significant influence of slip-flow effects on the motion is observed. Measurements at low pressure show underdamped harmonic oscillations in the opening motion and contact bounce effects in the closing motion. Effects of dielectric charging on the C-V curves are discussed. Experimental results are compared with electromechanical and damping simulations.