Capacitive RF MEMS Switches Fabricated in Standard 0.35-μm CMOS Technology

The objective of this paper is to investigate the integration of capacitive type RF microelectromechanical systems (MEMS) switches in a standard CMOS technology. A maskless monolithic integration process dedicated to electrostatically actuated capacitive type RF MEMS switches is developed and optimized. The fabricated switches consist of composite metal-dielectric warped membranes. The warped-plate structure is used to increase the capacitance ratio of the switch. The switches are fabricated using the interconnect metal and dielectric layers available in a standard 0.35-mu m CMOS process. Measurement results for the first switch show an insertion loss less than 0.98 dB, a return loss below 13 dB up to 20 GHz in the up-state, and a down-state isolation of 12.4-17.9 dB from 10 to 20 GHz. The capacitance ratio is enhanced up to 91: 1 using the warped-plate structure. A second cascaded switch consisting of two shunt capacitive switches and a slow-wave high-impedance transmission line section is designed and fabricated for high-isolation applications. The measured insertion loss for this switch is less than 1.41 dB up to 20 GHz, the return loss is below 19 dB, and the isolation is 19-40 dB across the frequency band from 10 to 20 GHz. The proposed RF MEMS switches can be used in millimeter-wave CMOS RF front-ends where multi-band functionality and reconfigurability is required.