Two-stage-driven cantilever-based RF MEMS micro-switch

Our newly-designed micro-switches feature the mitigation of this tip-first-touching and a low driving voltage while keeping the device miniaturization. Our micro-switches consist of two kinds of beams suspending a movable electrode. On applying a voltage, the outer beams first start to deflect down because the gap between two driving electrodes is designed small. Following the contact of the two driving electrodes, the movable electrode is strongly pulled onto the transmission line, resulting in the deflection of the inner beam. This movement can be driven by a low voltage because of decreasing the gap above the transmission line. More interestingly, the tip-first-touching of the movable electrode onto the transmission line can be mitigated, because small deflection of the inner beam leads to making the tilting angle of the movable electrode small. The micro-switches are fabricated by silicon deep dry etching of an SOI wafer and electrostatic bonding onto a glass substrate. Surface roughness measurement by the alpha-step showed that the two kinds of beams had the step height accordingly to the design. It is expected that the driving voltage can be decreased by as large as 78% by using the two-stage driving. The fabricated devices are now under careful characterization. Our newly-designed micro-switches can be driven by a low voltage with a longer lifetime. They maintain the excellent RF characteristics of low insertion loss and high isolation. Therefore, these micro-switches will be expected to be widely used for a wireless communication with a cellular phone and a mobile terminal, which rapidly expands the amount of the data traffic, near the future.