"This work presents a novel approach to modeling and control of an RF- MEMS switch. The model presented in this work is comprehensive and generic in nature such that it takes into account the effect of squeeze film damping, impact force and electrostatic force effects on the dynamic behavior of the switch during pull-in and release of its membrane. This model makes it adaptable to any similar switch regardless of the form and/or dimensions. Simulation results of the switch dynamics is validated against experimental data for an identical switch. Model response to electrostatic voltage shows very good agreement with experiments. The proposed model is then used to construct a feedback controller capable of improving response parameters of the membrane during operation. Due to micro-dimensions of the switch, real time displacement measurement of the membrane is not readily available. Therefore, the proposed controller utilizes measurement of switch capacitors current as a platform for real time estimates of the membrane position. Membrane Current measurement was not available for control purposes due to the lack of the fabricated RF MEMS switch. Consequently, approximate model for current-displacement relationship is constructed from numerical solution of the nonlinear model data and system identification techniques using Simulink."--Abstract.

Micro-Electro-Mechanical (MEM) devices like switches, varactors and oscillators have shown great potential for use in communication devices, sensors and actuators. Electrostatically actuated switches in particular have been shown to have superior performance characteristics over traditional semiconductor switches. However, their widespread insertion in integrated electronics is critically dependent on a thorough understanding of two broad issues - manufacturing process variations and failure mechanisms. Variations during fabrication lead to uncertain material and/or geometric parameters causing a significant impact on device performance. Such uncertainties need to be accounted for during the robust design of these switches. In terms of failure mechanisms limiting the lifetime of MEMS switches, dielectric charging is considered to be the most critical. It can cause the switch to either remain stuck after removal of the actuation voltage or to fail to contact under application of voltage. There is a need for accurate and computationally efficient, multi-physics CAD tools for incorporating the effect of dielectric charging. In this work, we have attempted to address some of the aforementioned challenges. We have come up with new algorithms for improving the effciency of coupled electro-mechanical simulations done in existing commercially available software like ANSYS. The gains in efficiency are accomplished through eliminating the need for repeated mesh update or re-meshing during finite element electrostatic modeling. This is achieved through the development of a `map' between the deformed and un-deformed geometries. Thus only one finite element discretization on the original undeformed geometry is needed for performing electrostatic analysis on all subsequent deformed geometries. We have generalized this concept of `mapping' to perform stochastic electrostatic analysis in the presence of geometric uncertainties. The different random realizations of geometry are considered as deformed geometries. The electrostatic problem on each of these random samples is then obtained using the `mapping' and the finite element simulation on the mean geometry. Statistics such as the mean and standard deviation of the desired system response such as capacitance and vertical force are efficiently computed. This approach has been shown to be orders of magnitude faster than standard Monte Carlo approaches. Next, we have developed a methodology for the model order reduction of MEMS devices under random input conditions to facilitate fast time and frequency domain analyses. In this approach, the system matrices are represented in terms of polynomial expansions of input random variables. The coefficients of these polynomials are obtained by deterministic model order reduction for specific values of the input random variables. These values are chosen `smartly' using a Smolyak algorithm. The stochastic reduced order model is cast in the form of an augmented, deterministic system. The proposed method provides significant efficiency over standard Monte Carlo. Finally, we have developed a physics based, one dimensional macroscopic model for the quantitative description of the process of dielectric charging. The fidelity of the model relies upon the utilization of experimentally-obtained data to assign values to model parameters that capture the non-linear behavior of the dielectric charging process. The proposed model can be easily cast in the form of a simple SPICE circuit. Its compact, physics-based form enables its seamless insertion in non-linear, SPICE-like, circuit simulators and makes it compatible with system-level MEMS computer-aided analysis and design tools. The model enables the efficient simulation of dielectric charging under different, complex control voltage waveforms. In addition, it provides the means for expedient simulation of the impact of dielectric charging on switch performance degradation. It is used to demonstrate failure of a switch in Architect. We conclude with a description of how this one dimensional model can be combined in a detailed two dimensional coupled electro-mechanical framework.

This paper presents a study of the behaviour of electrically actuated RF-MEMS switches with ohmic contact. We will discuss about the relationship between the actuation voltage, displacement and the corresponding contact force experienced by the switch. We will demonstrate the linear behaviour of the switch when factors such as width or length of the switch arm are varied. Experimental results for DC actuation are also presented.

Small, low power devices for manipulation of high frequency (above 10 GHz) signals are an enabling technology for improved communications and remote sensing equipment. MEMS devices for switching of microwave or millimetre wave signals show promise for applications in areas such as agile radio systems, reconfigurable tuning and matching networks, and phased arrays. The mechanical operating principle of MEMS switches allows these devices to achieve electrical performance (including linearity, isolation, and insertion loss) competitive with or in some cases exceeding that possible with semiconductor technology, in combination with small size and low power consumption. In applications where fast (microsecond) switching times are not required, at frequencies sufficiently high that semiconductor switches are challenging to design or lossy, MEMS technology has excellent potential. The technology of MEMS switches using electrostatic actuation and metal-to-metal or metal-to-dielectric contact has been extensively developed. Unfortunately, practical difficulties such as high actuation voltage, poor reliability, or poor power handling have proven hard to resolve, and the wider adoption of these devices has been delayed. It is therefore worthwhile to develop novel device designs that may be able to comprehensively avoid these issues. The aim of this project was to investigate and validate a concept for a piezoelectric contact-less MEMS switch. The device uses a variable capacitance principle, avoiding the need for contact during switching. Piezoelectric actuation allows high power handling to be achieved with a reasonable (predicted sub 25 V) actuation voltage. A comprehensive model for the mechanical and electrical behaviour of the device was developed. In order to inform the design of a high performance device, the effects of the structure, materials, and applied RF power were considered. Predictions from this model were compared with the results of finite element analysis. Static test structures were designed to validate the electrical performance model and fabricated on glass wafers. S-parameter measurements made on these validation structures were compared with the expected results from the model. Finally, a fabrication process was developed to produce a device in silicon. Additional electrical measurements were carried out on a prototype version of this silicon structure (fabricated without piezoelectric material) to further study the performance of this contact-less RF MEMS switch design.

This handbook volume aims to provide a comprehensive, self-contained, and authoritative reference in MEMS. It covers the theoretical and practical aspects including but not limited to sensors, actuators, RF MEMS, micro fluids and bio MEMS systems. It is particularly recommended to undergraduates, postgraduates, researchers, scientists, and field experts. This comprehensive summary will provide a solid knowledge background and inspire innovations in this highly interdisciplinary field. The handbook series consists of 5 volumes: Micro/nano fabrication technology, MEMS, Nanomaterial, Nanomedicine and Applications of micro-/nanotechnologies in IT. Experienced researchers and experts are invited to contribute in each of these areas.The series is published under Springer Major Reference works, which allows continuous online update and publication. These features allow newcomers and other readers to keep in touch with the most up-to-date information in micro-/nanotechnologies.It presents an overview of the knowledge base, as well as selected topics and provides comprehensive and authoritative information on the field for researchers, engineers, scientists and graduate students who are involved in different aspects of micro-/nanotechnologies.This publication will provide inspiration for innovative research and application ideas for continued growth of the field.