RF MEMS Capacitive Switches for Wide Temperature Range Applications Using a Standard Thin-Film Process

摘要

In this paper, the design, fabrication, and measurements of a capacitive RF microelectromechanical systems (RF MEMS) switch with very low sensitivity to thermal stress is presented. The switch is built by thin-film technology (0.8-$mu$m Au) and shows ${<} $ 50-mV/$^{circ}$ C variation in the pull-down voltage at 25 $^{circ}$C–125 $^{circ}$C. The effects of the residual biaxial stress and stress gradients are studied in detail and the final switch design is very tolerant to a wide range of stress. The switch exhibits excellent RF and mechanical performances, and a capacitance ratio of about 51–57 ($C_{u} = 54 - 66$ fF, $C_{d} = 3.1 - 3.4$ pF) is reported. The mechanical resonant frequency and quality factor are $f_{o} = 105-115$ kHz and $Q _{m} approx 8$, respectively, with a measured switching time of about 3–3.8 $mu$ s. The applications areas are in low-loss RF MEMS, phase shifters, and reconfigurable networks.