Design and simulation of a low-actuation-voltage MEMS switch

This paper presents a low-actuation-voltage micro-electro-mechanical system (MEMS) capacitive shunt switch which has a very large bandwidth (4 GHz to 24 GHz). In this work, the isolation of MEMS switch is improved by adding two short high impedance transmission lines at the beginning and end of a coplanar waveguide (CPW). Simulating the switch demonstrates that a return loss (S11) is less than -26 dB for the entire frequency band, and perfect matching at 20 GHz in upstate position. A ramp dual pulse driver is also designed for reducing the capacitive charge injection for considering the reliability of the switch. The simulation results show that the shifting of voltage due to the capacitive charge is reduced by more than 35% of the initial value. Finally, the dynamic behavior of the MEMS switch is simulated by modal analysis and using CoventorWare to calculate the natural frequencies of the switch and its mode shapes. The switching ON and OFF time are 4.48 and 2.43 μs, respectively, with an actuation voltage of less than 15 V

Design for reliability applied to RF-MEMS devices and circuits issued from different TRL environments

Ces travaux de thèse visent à aborder la fiabilité des composants RF-MEMS (commutateurs en particulier) pendant la phase de conception en utilisant différents approches de procédés de fabrication. Ça veut dire que l'intérêt est focalisé en comment éliminer ou diminuer pendant la conception les effets des mécanismes de défaillance plus importants au lieu d'étudier la physique des mécanismes. La détection des différents mécanismes de défaillance est analysée en utilisant les performances RF du dispositif et le développement d'un circuit équivalent. Cette nouvelle approche permet à l'utilisateur final savoir comment les performances vont évoluer pendant le cycle de vie. La classification des procédés de fabrication a été faite en utilisant le Technology Readiness Level du procédé qui évalue le niveau de maturité de la technologie. L'analyse de différentes approches de R&D est décrite en mettant l'accent sur les différences entre les niveaux dans la classification TRL. Cette thèse montre quelle est la stratégie optimale pour aborder la fiabilité en démarrant avec un procédé très flexible (LAAS-CNRS comme exemple de baisse TRL), en continuant avec une approche composant (CEA-Leti comme moyenne TRL) et en finissant avec un procédé standard co-intégré CMOS-MEMS (IHP comme haute TRL) dont les modifications sont impossibles.This thesis is intended to deal with reliability of RF-MEMS devices (switches, in particular) from a designer point of view using different fabrication process approaches. This means that the focus will be on how to eliminate or alleviate at the design stage the effects of the most relevant failure mechanisms in each case rather than studying the underlying physics of failure. The detection of the different failure mechanisms are investigated using the RF performance of the device and the developed equivalent circuits. This novel approach allows the end-user to infer the evolution of the device performance versus time going one step further in the Design for Reliability in RF-MEMS. The division of the fabrication process has been done using the Technology Readiness Level of the process. It assesses the maturity of the technology prior to incorporating it into a system or subsystem. An analysis of the different R&D approaches will be presented by highlighting the differences between the different levels in the TRL classification. This thesis pretend to show how reliability can be improved regarding the approach of the fabrication process starting from a very flexible one (LAAS-CNRS as example of low-TRL) passing through a component approach (CEA-Leti as example of medium-TRL) and finishing with a standard co-integrated CMOS-MEMS process (IHP example of high TRL)

RF-MEMS switches for reconfigurable antennas

This thesis was submitted for the degree of Doctor of Philosophy and awarded by Brunel University.Reconfigurable antennas are attractive for many military and commercial applications where it is required to have a single antenna that can be dynamically reconfigured to transmit or receive on multiple frequency bands and patterns. RF-MEMS is a promising technology that has the potential to revolutionize RF and microwave system implementation for next generation telecommunication applications. Despite the efforts of top industrial and academic labs, commercialization of RFMEMS switches has lagged expectations. These problems are connected with switch design (high actuation voltage, low restoring force, low power handling), packaging (contamination layers) and actuation control (high impact force, wear, fatique). This Thesis focuses on the design and control of a novel ohmic RF-MEMS switch specified for reconfigurable antennas applications. This new switch design focuses on the failure mechanisms restriction, the simplicity in fabrication, the power handling and consumption, as well as controllability. Finally, significant attention has been paid in the switch’s electromagnetic characteristics. Efficient switch control implies increased reliability. Towards this target three novel control modes are presented. 1) Optimization of a tailored pulse under Taguchi’s statistical method, which produces promising results but is also sensitive to fabrication tolerances. 2) Quantification of resistive damping control mode, which produces better results only during the pull-down phase of the switch while it is possible to be implemented successfully in very stiff devices. 3) The “Hybrid” control mode, which includes both aforementioned techniques, offering outstanding switching control, as well as immunity to fabrication tolerances, allowing an ensemble of switches rendering an antenna reconfigurable, to be used. Another issue that has been addressed throughout this work is the design and optimization of a reconfigurable, in pattern and frequency, three element Yagi-Uda antenna. The optimization of the antenna’s dimensions has been accomplished through the implementation of a novel technique based on Taguchi’s method, capable of systematically searching wider areas, named as “Grid-Taguchi” method

Realization of micromachined-electromechanical devices for wireless communication applications

As the communication technology evolves day by day, the demands for low cost, low power, multifunctional and higher-speed data communication circuits are increasing enormously. All these essential requirements enforce significant challenges on the current technology and illustrate the need for new designs and advanced architectures. The challenges of reconfigurability, spectrum efficiency, security, miniaturization and cost minimization can only be met by ensuring that the transceiver/receiver is comprised of low-energy, low-cost, adaptive and high performance RF devices. With the potential to enable wide operational bandwidths, eliminate off-chip passive components, make interconnect losses negligible, and produce almost ideal switches and resonators in the context of a planar fabrication process compatible with existing IC processes, micromachining and Micro-Electro-Mechanical Systems (MEMS) has emerged to overcome the aforementioned problems of communication circuits. Up to date RF MEMS technology prove that on-chip switches with zero standby power consumption, low switching power and low actuation voltage; high quality inductors, capacitors and varactors; highly stable (quartz-like) oscillators and high performance filters operating in the tens of MHz to several GHz frequency range can be realized. The availability of such RF and microwave components will provide designers with the elements they have long hoped for to create novel and simple, but powerful, reconfigurable systems. In this thesis, realization of RF MEMS components such as capacitive switches, parallel plate variable capacitors, micromachined inductors and resonators for wireless communication applications are presented. The design and fabrication of each component are given in detail. The performance improvement of some blocks by integrating RF MEMS devices is demonstrated. Also the fabrication process problems limiting the performance parameters of RF MEMS components are addressed

Development of a low actuation voltage electrostatic RF MEMS switch

The research focused on the design, fabrication and measurement of a low actuation voltage micro electro mechanical high frequency switch. The fabricated micro switch offers outstanding radio frequency parameters for a very large frequency band, with actuation voltage and switching time less than 20 volts and 3 micro seconds, respectively

Multi-Port RF MEMS Switches and Switch Matrices

Microwave and millimeter wave switch matrices are essential components in telecommunication systems. These matrices enhance satellite capacity by providing full and flexible interconnectivity between the received and transmitted signals and facilitate optimum utilization of system bandwidth. Waveguide and semiconductor technology are two prominent candidates for the realizing such types of switch matrices. Waveguide switches are dominant in high frequency applications of 100 ? 200 GHz and in high power satellite communication. However, their heavy and bulky profile reinforces the need for a replacement. In some applications, semiconductor switches are an alternative to mechanical waveguide switches and utilize PIN diodes to create the ON and OFF states. Although, these switches are small in size, they exhibit poor RF performance and low power handling. RF MEMS technology is a good candidate to replace the conventional switches and to realize an entire switch matrix. This technology has a great potential to offer superior RF performance with miniaturized dimensions. Because of the advantages of MEMS technology numerous research studies have been devoted to develop RF MEMS switches. However, they are mostly concentrated on Single-Pole Single-Throw (SPST) configurations and very limited work has been performed on MEMS multi-port switches and switch matrices. Here, this research has been dedicated on developing multi-port RF MEMS switches and amenable interconnect networks for switch matrix applications. To explore the topic, three tasks are considered: planar (2D) multi-port RF MEMS switches, 3D multi-port RF MEMS switches, and RF MEMS switch matrix integration. One key objective of this thesis is to investigate novel configurations for planar multi-port (SPNT), C-type, and R-type switches. Such switches represent the basic building blocks of switch matrices operating at microwave frequencies. An in house monolithic fabrication process dedicated to electrostatic multi-port RF MEMS switches is developed and fine tuned. The measurement results exhibit an excellent RF performance verifying the concept. Also, thermally actuated multi-port switches for satellite applications are designed and analyzed. The switch performance at room condition as well as at a very low temperature of 77K degrees (to resemble the harsh environment of satellite applications) is measured and discussed in detail. For the first time, a new category of 3D RF MEMS switches is introduced to the MEMS community. These switches are not only extremely useful for high power applications but also have a great potential for high frequencies and millimetre-waves. The concept is based on the integration of vertically actuated MEMS actuators inside 3D transmission lines such as waveguides and coaxial lines. An SPST and C-type switches based on the integration of rotary thermal and electrostatic actuators are designed and realized. The concept is verified for the frequencies up to 30GHz with measured results. A high power test analysis and measurement data indicates no major change in performance as high as 13W. The monolithic integration of the RF MEMS switch matrix involves the design and optimization of a unique interconnect network which is amenable to the MEMS fabrication process. While the switches and interconnect lines are fabricated on the front side, taking advantage of the back side patterning provides a high isolation for cross over junctions. Two different techniques are adopted to optimize the interconnect network. They are based on vertical three-via interconnects and electromagnetically coupled junctions. The data illustrates that for a return loss of less than -20dB up to 30GHz, an isolation of better than 40dB is obtained. This technique not only eliminates the need for expensive multilayer manufacturing process such as Low Temperature Co-fired Ceramics (LTCC) but also provides a unique approach to fabricate the entire switch matrix monolithically

RF-MEMS switches for reconfigurable antennas

Reconfigurable antennas are attractive for many military and commercial applications where it is required to have a single antenna that can be dynamically reconfigured to transmit or receive on multiple frequency bands and patterns. RF-MEMS is a promising technology that has the potential to revolutionize RF and microwave system implementation for next generation telecommunication applications. Despite the efforts of top industrial and academic labs, commercialization of RFMEMS switches has lagged expectations. These problems are connected with switch design (high actuation voltage, low restoring force, low power handling), packaging (contamination layers) and actuation control (high impact force, wear, fatique). This Thesis focuses on the design and control of a novel ohmic RF-MEMS switch specified for reconfigurable antennas applications. This new switch design focuses on the failure mechanisms restriction, the simplicity in fabrication, the power handling and consumption, as well as controllability. Finally, significant attention has been paid in the switch’s electromagnetic characteristics. Efficient switch control implies increased reliability. Towards this target three novel control modes are presented. 1) Optimization of a tailored pulse under Taguchi’s statistical method, which produces promising results but is also sensitive to fabrication tolerances. 2) Quantification of resistive damping control mode, which produces better results only during the pull-down phase of the switch while it is possible to be implemented successfully in very stiff devices. 3) The “Hybrid” control mode, which includes both aforementioned techniques, offering outstanding switching control, as well as immunity to fabrication tolerances, allowing an ensemble of switches rendering an antenna reconfigurable, to be used. Another issue that has been addressed throughout this work is the design and optimization of a reconfigurable, in pattern and frequency, three element Yagi-Uda antenna. The optimization of the antenna’s dimensions has been accomplished through the implementation of a novel technique based on Taguchi’s method, capable of systematically searching wider areas, named as “Grid-Taguchi” method.EThOS - Electronic Theses Online ServiceGBUnited Kingdo

Microelectromechanical Systems and Devices

The advances of microelectromechanical systems (MEMS) and devices have been instrumental in the demonstration of new devices and applications, and even in the creation of new fields of research and development: bioMEMS, actuators, microfluidic devices, RF and optical MEMS. Experience indicates a need for MEMS book covering these materials as well as the most important process steps in bulk micro-machining and modeling. We are very pleased to present this book that contains 18 chapters, written by the experts in the field of MEMS. These chapters are groups into four broad sections of BioMEMS Devices, MEMS characterization and micromachining, RF and Optical MEMS, and MEMS based Actuators. The book starts with the emerging field of bioMEMS, including MEMS coil for retinal prostheses, DNA extraction by micro/bio-fluidics devices and acoustic biosensors. MEMS characterization, micromachining, macromodels, RF and Optical MEMS switches are discussed in next sections. The book concludes with the emphasis on MEMS based actuators

Advanced Applications of Nanoelectromechanical Systems

Nanoelectromechanical systems (NEMS) have advanced the technologies in a wide spectrum of fields, including nonlinear dynamics, sensors for force detection, mass spectrometry, inertial imaging, calorimetry, and charge sensing. Due to their low power consumption, fast response time, large dynamic range, high quality factor, and low mass, NEMS have achieved unprecedented measurement sensitivity. For optimized system functionalization and design, precise characterization of material properties at the nanoscale is essential. In this thesis, we will discuss three applications of NEMS: mechanical switches, using anharmonic nonlinearity to measure device and material properties, and mass spectrometry and inertial imaging. The first application of NEMS we discuss is NEMS switches, switches with physical moving parts. Conventional electronics, based largely on silicon transistors, is reaching a physical limit in both size and power consumption. Mechanical switches provide a promising solution to surpass this limit by forcing a jump between the on and off states. Graphene, which is a single sheet of carbon atoms arranged in a hexagonal structure, has high mechanical strength and strong planar bonding, making it an ideal candidate for nanoelectromechanical switches. In addition, graphene is conductive, which decreases resistive heating at the contact area, therefore reducing bonding issues and subsequently reducing degradation. We demonstrate using exfoliated graphene to fabricate suspended graphene NEMS switches with successful switching. The second application of NEMS we discuss in this thesis is the use of mechanical nonlinearity to measure device and material properties. While the nonlinear dynamics of NEMS have been used previously to investigate the longitudinal speed of sound of materials at nano- and micro-scales, we correct a previously attempted method that employs the anharmonicity of NEMS arising from deflection-dependent stress to interrogate the transport of RF acoustic phonons at nanometer scales. In contrast to existing approaches, this decouples intrinsic material properties, such as longitudinal speed of sound, from properties associated with linear dynamics, such as tension, of the structure. We demonstrate this approach through measurements of the longitudinal speed of sound in several NEMS devices composed of single crystal silicon along different crystal orientations. Good agreement with literature values is reported. The third application of NEMS we discuss is mass spectrometry and inertial imaging. Currently, only doubly clamped beams and cantilevers have been experimentally demonstrated for mass spectrometry. We extend the one-dimension model for mass spectrometry to a novel method for inertial imaging. We further extend the theory of mass spectrometry and inertial imaging to two dimensions by using a plate geometry. We show that the mode shape is critical in performing NEMS mass spectrometry and inertial imaging, and that the mode shapes in plates deviate from the ideal scenario with isotropic stress. We experiment with various non-ideal conditions to match non-ideal mode shape observed.</p