Design and Fabrication of RF MEMS Switch by the CMOS Process

This work investigates the fabrication of a RF (ratio frequency) MEMS (micro elector mechanical system) switch using the standard 0.35 μm 2P4M (double polysilicon four metal) CMOS (complementary metal oxide semiconductor) process and the post-process. The switch is a capacitive type, which is actuated by an electrostatic force. The structure of the switch consists of a CPW (coplanar waveguides) transmission lines and a suspended membrane. The CPW lines and the membrane are the metal layers of the CMOS process. The main advantage of the RF switch is only needed a simple post-process, which is compatible with the CMOS process. The post-process uses an etchant, silox vapox Ⅲ, to etch oxide layer to release the suspended membrane and springs. Experiment results show that the pull-in voltage of the switch is about 17 V. The insertion loss and return loss in the range of 10 to 40 GHz are -2.5 dB and -13 dB, respectively.