Radio frequency (RF) microelectromechanical systems (MEMS) switches

This dissertation presents a procedure to optimize the design of Radio Frequency (RF) Microelectromechanical Systems (MEMS) switches. While electromechanical modeling for MEMS switches now exists, switches are being designed without enough consideration of the electromagnetic interactions within the system. Using the procedure developed in this dissertation will result in better RF performance since it provides S-parameter modeling based on Maxwell equations by using appropriate boundaries, excitations and analysis methods. The results from this modeling can be studied and switches can then be optimized for specific applications. Modeling is performed on ten switch designs and variations and S-parameter results are analyzed. Modeling is then done for a coplanar waveguide design provided by Morgan, A Stanley Company; results are analyzed, and minor design modifications are suggested.; This work addresses many issues involved in the design of RF MEMS switches. Switch geometries, materials and fabrication processes are considered. Switches may be made from cantilever beams or fixed-fixed beams. The switches may be actuated by electrostatic, piezoelectric or electromagnetic forces. The effort presented in this dissertation concentrates on switches actuated by electrostatic forces. Finite element modeling is used to verify the designs. The MultiUser MEMS Process (MUMPS) was used to fabricate initial polysilicon switches and this micromachining process is described. However, the models should be applicable to switches made from other materials and with other fabrication processes. Device testing is reported. However, the initial designs were not optimized, so testing of these fabricated switches was truncated and modeling of optimized switches was prioritized. Physical effects, such as temperature, fringing fields, and mounting geometries, are considered. The procedure for performing electromagnetic modeling is developed and design optimization was performed using this procedure. Two specific types of switches, series and shunt, are modeled. The application will determine the desired characteristics of the switch. Different materials, polysilicon and gold for the switches, and silicon and quartz for the substrate, are considered. The decision on all these options will depend on the specific application. The modeling procedure will help designers to select desired switch designs.