A high-force and high isolation metal-contact RF MEMS switch

Abstract

A simple structure, high-force and high isolation metal contact RF MEMS switch was fabricated based on micro electroplating technology, and the mechanical and RF performance of the switch were measured. After release and annealing, the switch’s cantilever beam showed a tip-up of less than 1 µm over the beam length of 485 µm, indicating a good stress control and thermal stability of the electroplated gold. The pull-in voltage and the switching characteristics at different temperatures, ranging from 25 to 90 °C, were investigated. A fast, stable and temperature independent switching process was observed as the actuation voltage was 10% larger than the pull-in voltage. Based on the classical cantilever beam model, both the electrostatic actuation force and the return force of the switch were larger than 1000 μN, and the extracted effective spring constant of the free-standing beam was 718 N/m. Cold RF tests were carried out at various temperatures by a network analyzer, and we found that temperature showed very less influence on the insertion and isolation of the switch in the present case. At 25 °C, the insertion loss was −0.13 dB at 10 GHz, and was lower than −0.3 dB over the 0.05−20 GHz frequency range. The isolation was −36 dB at 10 GHz, and was higher than −27 dB over the entire scanning frequency range. The high isolation performance is consistent with a lumped-element equivalent circuit analysis of the switch.