Development of shunt type ohmic RF MEMS switches actuated by piezoelectric cantilever

Abstract This paper presents the design, fabrication, and characterization of shunt type ohmic RF MEMS switches actuated by piezoelectricity. Since the proposed RF MEMS switches are actuated by piezoelectricity, they can be operated at an extremely low operation voltage of 5 V with a negligible power consumption of less than 0.1 μW. The proposed switches are primarily composed of piezoelectric cantilever actuators, a contact electrode and coplanar wave transmission lines suspended over the substrate. Unlike existing series type switches, the RF signal line of the shunt type ohmic switches is directly connected from the RF input port to the RF output port without any discontinuity, and their contact electrode is interconnected to all grounds. In this work, we consider three different types of RF MEMS switches in order to find the best geometry. The RF MEMS switch with one piezoelectric cantilever (Type-A) shows very poor isolation characteristic although it has better insertion loss than the others. The other two RF switches, which employ four piezoelectric cantilevers (Type-B and Type-C), differ in terms of the configuration of the cantilevers and the centered contact electrode. One has a centered contact electrode of square shape (Type-B), while the contact electrode of the other switch has a diamond shape (Type-C). They show relatively good isolation characteristics even at a very high frequency of 20 GHz, since the use of four piezoelectric cantilevers can generate a sufficiently large contacting force between the contact electrode and the RF signal line. The two fabricated RF MEMS switches have isolations of −23.0 and −24.0 dB, respectively, at an operation voltage of 5 V and a frequency of 20 GHz. The power-handling capability of the proposed RF MEMS switches increases to 1.4 W when an Iridium thin film coating is applied on the gold contact electrode.