Capacitive RF switches manufactured by the CMOS–MEMS technique

Abstract

This work investigates the fabrication and characterization of a capacitive radio frequency (RF) switch using the complementary metal oxide semiconductor (CMOS)–microelectromechanical system (MEMS) technique. The micromechanical RF switch had a high isolation and a low driving voltage. The structure of the micromechanical RF switch contains a coplanar waveguide (CPW), a suspended membrane, eight springs and four suspended inductors in series. The suspended inductors are used to enhance the characteristic of the RF switch. The finite element method software, CoventorWare, is employed to simulate the mechanical behaviors of the RF switch. After completion of the CMOS process, the RF switch requires a post-process to release the suspended structures. The post-process utilizes a dry etching and a wet etching to etch the sacrificial layer, and to obtain the suspended structures of the RF switch. Experimental results reveal that the RF switch has an insertion loss of 0.85dB at 35GHz and an isolation of 25dB at 35GHz. The driving voltage of the switch is about 11V.