Design of low actuation voltage RF MEMS cantilever switch

This paper presents the design, fabrication and testing of capacitive copper RF MEMS switches with various hinge geometries, fabricated on high-resistivity silicon substrates. The switches were fabricated using a simple low-cost four-mask process and 0.6-1.0 /spl mu/m thick membranes were made out of sputtered copper. The capacitive airgap in between the membrane and the signal line is 1.5-2.0 /spl mu/m. The lowest actuation voltage measured on the fabricated switches is 9 V. The measured insertion loss of a fabricated switch and its associated transmission time was 0.9 dB (mainly contributed by the transmission line itself) and the isolation was measured to be 25 dB at 40 GHz.

Design and Simulation of RF MEMS Switch for X-band Applications

Design, fabrication and characterization of miniature RF MEMS switched capacitor based phase shifter

Research into operational aspects of mini (<5kg) unmanned aerial vehicles (UAV) and structural health monitoring systems (SHM) is being conducted at the Defence Science and Technology Organisation and La Trobe University. A fundamental area of interest is investigating the problems associated with robustness of the control and health monitoring sensors for such systems. While many technologies for UAV and SHM systems can be, and have been, adapted from those currently available in large manned aircraft; cost, weight, and size constraints have prevented mini UAVs from including many of the robust mechanisms common to larger aircraft. Moreover, the ubiquitous nature of the sensing requirements for SHM systems has limited their uptake, due mainly to the same issues of cost, weight and size. This paper details the design of a reconfigurable multivariable MEMS (Micro Electro Mechanical System) array to address these issues. This array is composed of multiple instances of identical sensors, which can be dynamically reconfigured to achieve the desired measurand(s) with tradeoffs against accuracy. The available measurands include such items as; accelerations, rotational rates, magnetic fields (X, Y and Z directions), temperature and pressure. The paper presents the design of a reconfigurable multivariable MEMS sensor array together with simulation results.

This paper reports a novel method to evaluate and improve the reliability of mechanical stops during design and validation phases of MEMS (Micro ElectroMechanical System) in shock environments. Firstly, inplane stop contact behavior is modeled through both steady-state and dynamic mechanical FEM (Finite-Element Modeling) to validate physics package and to extract nonlinear stiffness and stress distribution as functions of contact force applied on a cylinder-to-plane Hertz contact type. Then, the transient response of a MEMS including stops behavior is modeled with a lumped impact element approach which allows to compute contact force as a function of applied half-sine shock parameters. Finally, several shock tests have been performed on numerous devices embedding previously modeled stops to evaluate experimental survival rate. Fitting experimental data to numerical results combined with Weibull theory exhibits a good compliance which allows to estimate silicon Weibull parameters respectively at 0.7 GPa, 1.1 GPa and 4 for threshold stress, average stress and Weibull modulus.

Although Micro-Electro-Mechanical Systems (MEMS) are forming the basis for a rapidly growing industry and fields of research, many MEMS designers still rely on back-of-the-envelope calculations due to a lack of efficient computer-aided design (CAD) tools that can assist with the initial stages of design exploration. This paper introduces case-based reasoning (CBR) techniques to the design of MEMS, as part of a larger MEMS synthesis framework currently under development at UC Berkeley. Having the ability to draw upon past design knowledge is advantageous to the MEMS designer, allowing reuse and modification of previous successful designs to help deal with the complexities of a new design problem. CBR utilizes past successful MEMS designs and sub-assemblies as building blocks stored in an indexed library. Reasoning tools find cases in the library with solved problems similar to the current design problem in order to propose promising conceptual designs. This paper discusses case representation and case library design as well as the results of case retrieval studies, focusing on MEMS resonant structures. The paper recommends strategies for integrating the MEMS case library with evolutionary computation when parameter optimization over the retrieved conceptual designs is not sufficient or there are gaps of knowledge in the case library.

Low Actuation Wideband RF MEMS Shunt Capacitive Switch

We present a framework to support design refinement during the virtual prototyping of microelectromechanical systems (MEMS). By instantiating MEMS components and connecting them to each other via ports, the designer can both configure complex systems and simulate them. We examine design refinement in the context of ease of use and representation of the virtual prototype. We propose the use of a common, formal grammar representation for the design entities in the virtual prototype—MEMS components, behavioral models and CAD models. We show that the formal grammar approach leads to easy creation of virtual prototypes. In this paper, we focus on ports—the fundamental building blocks of a virtual prototype. Ports mediate all interactions within and between aspects of the virtual prototype. For even moderately complex designs, there can be many interactions present. The representation and organization of all possible ports is important in the context of design refinement. We provide a set-theoretic formalism that defines the algebra of ports. We present a formal grammar for ports that represents a port as a set of attributes, and provide a design refinement mechanism that involves adding or modifying attributes in the port. We illustrate our framework with a MEMS example. We demonstrate that the MEMS designer can evaluate multiple design alternatives quickly and accurately with our framework.

Non-conventional or advanced machining techniques are becoming the enabling fabrication techniques for many emerging fields including Micro Electro Mechanical Systems (MEMS) or Microsystems Technology (MST). The processes used for MEMS fabrication include standard semiconductor fabrication processes and emerging micromachining techniques. Among the challenges emerging from the manufacturing of MEMS devices, post-processing seems to be one of the most sensitive issues. The non-traditional common post-processing techniques are bulk micromachining and surface micromachining. It has been a challenge for MEMS designers to develop a micromachining technique that is compatible with IC (Integrated Circuits) processes and also capable of making MEMS structures through both bulk and surface micromachining with acceptable surface roughness requirements. The selected micromachining process should not affect the integrity of the free standing structure due to the reduced selectivity and aggressive etch of the adjacent electronic circuitry. Moreover, the integrity of the released structure, the dynamic properties as well as the electrostatic characteristics, are strongly dependent on the achieved roughness of the surfaces produced by the etching process. Hence, this paper presents the surface roughness characterisation of gas phase micromachining with XeF2 that is suitable for fabricating integrated MEMS with both micromechanical and microelectronics components. This paper also presents some fabricated microsystems using this process.

In this paper, we report monolithic integration of MEMS (micro electro mechanical systems) actuators and high-voltage driver circuits into a silicon chip. Driver circuits of up to 40 V were prepared on an 8-/spl mu/m-thick SOI (silicon-on-insulator) wafer by the DMOS (double-diffused metal oxide semiconductor) processes, after which MEMS electrostatic actuators were integrated into an identical SOI layer by post-processing using DRIE (deep reactive ion etching). This technique opens up a new way of high-voltage ASIC (application specific integrated circuit) for MEMS designer. As a prototype application model, we have developed microlens optical scanners and other elementary MEMS electrostatic actuators with multi-channel driver circuits.

Fostered by the development of new technologies, microelectromechanical systems (MEMS) are massively present on board of vehicles, within information equipment as well as in medical and healthcare equipment. A smart approach to the design of MEMS devices is in terms of the simultaneous optimization of multiple objective functions subject to a set of constraints. This leads to the family of solutions minimizing the degree of conflict among the objectives (Pareto front). Accordingly, in this paper, a procedure of optimal shape design of MEMS based on evolutionary computing is proposed and validated on three case studies.

RF-MEMS switches may be divided into capacitive and metal-to-metal types in terms of type of connection. In capacitive switches in the OFF-state the beam does not attach to the transmission line due to the presence of a thin dielectric layer and it gets released easily. Capacitive switches are better compared with the metal-to-metal types due to their ability to transmit signals of higher frequency and power. In this paper, a novel RF MEMS shunt capacitive switch with a unique spring design is proposed. The proposed design benefits from high isolation, low loss, low actuation voltage, small size and weight compared to similar switches and is designed for application in the Ka-band. Step structure is used in the mechanical design of the switch to reduce the air gap between the bridge and the transmission line that has resulted in reduction of actuation voltage to 2.2 V. The proposed switch has been placed upon a coplanar waveguide (CPW) line with an impedance of 50 Ohms. $${\text{SiO}}_{2}$$ with a thickness of 1000 A has been used as dielectric to increase isolation and down-state capacitance. The unique design of the spring results in the reduction of stress to a minimum at all points of the switch especially the springs at the time of applying the actuation voltage. This advantage would reduce switch failures as time passes and results in increased life of the switch. Up-state capacitance is 93.3 fF and down-state capacitance is 2.64 pF. Therefore, a capacitive ratio of 28 is obtained. The dynamic behavior of the switch is studied by using the COMSOL Multiphysics software package and the RF characteristics have been obtained by using the HFSS software and show good RF performance. The results show that in the up-state, the designed switch including S11 is less than − 11.5 dB and S21 is more than − 0.85 dB at 1–40 GHz. In the down-state, the switch has excellent isolation in the Ka-band. Maximum isolation is − 71 dB that occurs at the resonance frequency of 30.5 GHz.

The design and development of novel microelectromechanical systems’ (MEMS) coplanar waveguide (CPW) transmission lines, using microshield and groove, are presented in the paper to operate between 5–60 GHz. The quasi-static capacitances of CPW are calculated using the conformal mapping technique to express the propagation properties, i.e., the characteristic impedance and effective permittivity. Simulation results have shown a considerable loss reduction to levels that compare favorably with the conventional CPW. These transmission lines can be widely used in the development of phase shifters, filters, and antennas, because of their advantages in loss reduction and improvement in the performance.

We report recent advances made in building an integrated MEMS (Micro Electro Mechanical Systems) CAD, modelling system using the framework of SESES. It provides flexible coupling of electrical, thermal and mechanical deformation phenomena in a uniform and consistent environment. The system is tailored to the specific requirements of MEMS design. SESES achieves excellent computational accuracy and efficiency on engineering workstations using an automatic mesh adaptation algorithm in 2 and 3 dimensions and a super-fast linear solver. Near-optimal data structures enable meshes of ca. 100 000 finite elements to be solved on a workstation.

In recent decades, with the advancement of microtechnology, various sensors and actuators have been developed based on MEMS (micro electromechanical systems) technology. Their low power usage, miniature size, and high precision are significant advantages of these electronic devices, so their utilization has been expanded in industrial applications. The energy collection method of piezoelectric energy harvesters was briefly discussed in this work. The methods involved in improving the power of piezoelectric energy harvesters are structural modification, various cross-sections of bluff bodies, and single and multi-layer cantilever beam arrangements are discussed in detail. Finally, a new dimensional piezoelectric energy harvester has been developed to harness the electrical energy from FIV (flow induced vibrations). In addition to this, we focused on the structural modified cantilever piezoelectric energy harvesters with rectangular and trapezoidal sections to harvest the power using COMSOL software. The results demonstrate that a harvester having a trapezoidal section provides more stress and displacement in comparison with rectangular sections. A Finite Element Model (FEM) is implemented to generate the harvester voltage from the piezoelectric patch when subjected to the disturbances. In addition, the dimensions of the beam, layer, and pressure of fluid can be estimated using a FEM model to obtain the voltage from the harvester.