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

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-μm Au) and shows <;50-mV/°C variation in the pull-down voltage at 25 °C-125 °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_ο = 105 - 115 kHz and Q_m ≈ 8, respectively, with a measured switching time of about 3-3.8 μs. The applications areas are in low-loss RF MEMS, phase shifters, and reconfigurable networks.