A novel 3D low voltage electrostatic RF MEMS switch with two movable electrodes

This paper will report on the design and fabrication of a novel 3D electrostatic RF MEMS switch, which uses two movable electrodes. The concept of two movable electrodes represents a unique feature of this device and is introduced to the RF MEMS community for the first time. Since the operating principle of the switch is based on electrostatic actuation, this unique feature results in a lower operating voltage. Combining the special bulk and surface micromachining techniques has enabled the realization of this new 3D RF MEMS switch. There are two main configuration for the device structure: 1) in the first device structure all parts are made up of bulk-micromachined free-structures. 2) In the second device structure the lower part is made up of a movable bulk-micromachined cantilever and the upper section is made up of surface micromachined movable thin film structures. By applying a DC voltage between movable plates, they come in touch and provide a pass for the RF signal (on-state of the switch) and as the DC voltage is removed, electrodes will be separated and disconnect the RF signal (off-state). The substrate can be used as a third electrode to separate beams in case of stiction. The monolithic nature of this switch technology makes it possible to develop various switch configurations like SPNT, C-type, and R-type switches, and switch matrices monolithically. This switch can be used as the basic building blocks for microwave switch matrices, multiplexers / demultiplexers, and phase shifters operating at microwave frequencies. The aim is to use the new features of this switch to achieve an acceptable low switching voltage, a better RF performance and particularly reliable switching operation. In this paper design considerations, HFSS simulation and the preliminary fabrication results of the switch are demonstrated.