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RF MEMS switches have demonstrated excellent performance. However, before such switches can be fully implemented, they must demonstrate high reliability and robust power-handling capability. Numerical simulation is a vital part of design to meet these goals. This paper demonstrates a fully integrated electrothermal model of an RF MEMS switch which...
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... INTEGRATED ELECTROTHERMAL MODELING Fig. 1 shows a simplified view of a RF MEMS switch which consists of a current-carrying beam. To short the switch to ground, electrostatic force is applied to pull the beam down to contact a portion of the lower electrode. This type of switch can be implemented, for example, in a microstrip line, with the beam acting as a portion of the line ...
Context 2
... this work, the beam is modeled in the up state shown in Fig. 1. With RF current flowing through the beam, the average heat generated is equivalent to the electrical power loss, given by (1) where is the average power loss per unit volume, is the current density within the beam, and is the electrical resis- tivity. Hence, to calculate the heat generated in the beam, we must first evaluate the ...
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We propose an extended finite element-boundary integral method (EFE-BI) to model the electromagnetic (EM) behavior of RF-MEMS switches over a wide frequency range from UHF to terahertz. Our new method integrates EM with finite element heat transfer analysis to extract heat dissipation on the micrometer-scale switch beam due to the non-uniform radio...
We propose an extended finite element-boundary integral method (EFE-BI) to model the electromagnetic (EM) behavior of RF-MEMS switches over a wide frequency range from UHF to terahertz. Our new method integrates EM with finite element heat transfer analysis to extract heat dissipation on the micrometer-scale switch beam due to the non-uniform radio...
Citations
... The key benefits of RF microelectromechanical switches, as opposed to alternative solid-state devices, are low power requirement, good electrical efficiency, and best linearity. In general, by altering the micro-beam and electrostatic air gap thickness, a switch configuration with a low pull-in voltage is obtained [8][9][10]. As a micro-beam material, the gold thin film is an outstanding alternative. ...
This communication describes the capacitive analysis and design aspects of Radio Frequency (RF) MEMS switch over 1-80 GHz frequency range. Especially capacitive RF MEMS switches are compatible for higher-order frequency applications like 5G taken into consideration. A new verity of MEMS structure is used in the RF MEMS switch design, which helped reduce the pull-in voltage. CPW transmission line is used for the switch design. Two separate bottom electrodes are used to reduce the required actuation voltage. Si3N4 dielectric material and its relative permittivity are 7.8 used. Complete design and simulation are done using FEM tools. The isolation loss is -30 dB, and the insertion loss is -1.22 dB.
... The switching time is the mechanical parameter, in electrostatic switch this will depends on the actuation voltage (V P ), supply voltage (V s ) and the natural resonant frequency (x 0 ). It can be expressed as (Jensen et al. 2003;Saias et al. 2003) ...
In this communication, we have designed, simulated, performance improved, fabricated and characterized a shunt capacitive RF MEMS switch with perforated serpentine membrane (Au). Fabrication is done using surface micromachining with four masks. AlN dielectric material of 50 nm thickness is offering
high isolation of − 58.5 dB at 31.5 GHz, and incorporation of perforation to the membrane the switch insertion loss is very low i.e., − 0.4 dB. The perforated serpentine membrane with non-uniform meanders of 500 nm thickness using Au material is helped to reduce the actuation voltage, the fabricated switch is requiring 4.5 V actuation voltage. DC sputtering PVD is used to deposit metal (Au) and dielectric (AlN) thin Films. S1813 photoresist is used as a sacrificial layer and the membrane structure is released using piranha, IPA and critical point drying (Pressure 1260 Psi, Temperature 31 °C).
... The perforated membrane eases the releasing process, and the perforated holes dimension is below 10 m x10 m then it won't be impact on the capacitance of the switch. The perforated area won't be more than 60% of overall area [51][52]. The switch designed in this paper is a capacitive based, so the switching depend on the capacitance when the membrane is in up state and down state,i.e., ...
In this paper, we have designed, simulated, fabricated and characterized a clamped-clamped micro mechanical structure based shunt capacitive RF MEMS switch. The clamped-clamped micromechanical structure is micromachined using gold metal thickness of 500 nm. AlN is used as dielectric material, and it is deposited using DC sputtering PVD process. In MEMS Technology, particularly in devices fabrication, releasing the membrane is a difficult task, here we have presented a novel wet process to release the membrane. Primarily the S1813 sacrificial layer is etched by using piranha solution and cleaned with IPA solution. Critical point drying is done after fabrication to reduce the stiction effect on the switch. Overall, the switch requires the pull-in voltage of 5.5 V for 1.8 μm displacement. In the process of optimization, primarily the switch is designed and simulated using finite element method tools. The reliability of the capacitive RF MEMS switches depends on the stiction problem caused by dielectric charging, the proposed capacitive switch dielectric charging behavior is characterized using CV curve method.
... As pointed out in [27], these models do not account for the multiscale nature of actual surface roughness. In [28] and [29], the electrothermomechanical deformation of a MEMS device is studied for a simple smooth geometry. In [14], [17], [22], [27], and [30]- [32], fractal geometry has been used to represent surface roughness in the contact analyses of MEMS devices and to relate contact parameters, such as the real area of contact, contact pressure, and contact resistance for simple linear elastic and elastic-plastic material models. ...
Three-dimensional fractal representations of surface roughness are incorporated into a finite-element framework to obtain the electrothermomechanical behavior of ohmic contacts in radio frequency (RF) microelectromechanical systems (MEMS) switches. Fractal surfaces are generated from the Weierstrass-Mandelbrot function and are representatives of atomic force microscope surface roughness measurements of contact surfaces in fabricated RF MEMS switches with metal contacts. A specialized finite-element scheme is developed, which couples the thermomechanical asperity creep deformations with the electromechanical contact characteristics to obtain predictions of contact parameters and their evolution as a function of time and loading. A dislocation-density-based crystal plasticity framework is also used to investigate microstructure evolution at microcontacts and its effects on contact parameters. Using this approach, simulations are made to investigate how surface roughness, initial residual strains, and operating temperature can affect asperity contact behavior. Based on these predictions, tribological design guidelines can be obtained to increase the lifetime of low-contact-resistance RF MEMS switches by limiting stiction and electrical resistance increase.
... The reliability of these switches are reported to sustain up to 0.1-40 billion cycles, while only handling power with maximum capacity of 0.5 W [4-7]. The major failure modes of RF MEMS switches are shown to occur due to membrane stiction, buckling, and creep [5]. ...
... Overall, the residual stresses generated in RF MEMS switches ultimately affect the general state of stress, and therefore, failure mechanisms of the MEMS device. While loaded with high frequency alternating current, the RF MEMS switch undergoes an electron crowding phenomena, otherwise known as the skin effect [5]. Due to selfinductance, the electrons flowing through the switch will be crowded on the edges of the conductor, creating a localized area of high temperature near the edges of the RF switch. ...
... For the frequencies considered in this study (ω ≥ 0.1 GHz), the time constant for the thermal response is much longer than the period of variation of the input power. Therefore, the temperature distribution throughout the switch membrane is calculated using the steady state heat equation given by [5]: ...
In this paper, the reliability of capacitive shunt RF MEMS switches have been investigated using three dimensional (3D) coupled multiphysics finite element (FE) analysis. The coupled field analysis involved three consecutive multiphysics interactions. The first interaction is characterized as a two-way sequential electromagnetic (EM)-thermal field coupling. The second interaction represented a one-way sequential thermal-structural field coupling. The third interaction portrayed a two-way sequential structural-electrostatic field coupling. An automated substructuring algorithm was utilized to reduce the computational cost of the complicated coupled multiphysics FE analysis. The results of the substructured FE model with coupled field analysis is shown to be in good agreement with the outcome of previously published experimental and numerical studies. The current numerical results indicate that the pull-in voltage and the buckling temperature of the RF switch are functions of the microfabrication residual stress state, the switch operational frequency and the surrounding packaging temperature. Furthermore, the current results point out that by introducing proper mechanical approaches such as corrugated switches and through-holes in the switch membrane, it is possible to achieve reliable pull-in voltages, at various operating temperatures. The performed analysis also shows that by controlling the mean and gradient residual stresses, generated during microfabrication, in conjunction with the proposed mechanical approaches, the power handling capability of RF MEMS switches can be increased, at a wide range of operational frequencies. These design features of RF MEMS switches are of particular importance in applications where a high RF power (frequencies above 10 GHz) and large temperature variations are expected, such as in satellites and airplane condition monitoring.
... Considering the dependence of the contact resistance on the size of the contact area, the mechanical force, and the quality of the contact [1], [23], the trenches can reduce the ohmic contact resistance by increasing the contact area and, thus, minimize heat dissipated in the surrounding area. Enhanced RF power handling can therefore be expected, which lowers the temperature at the contact area [24]- [26] and reduces the failure due to electromigration and microscopic bonding. Moreover, the use of a trench effectively creates a self-aligned structure. ...
This paper introduces a new concept in 3-D RF microelectromechanical systems switches intended for power applications. The novel switch architecture employs electrothermal hydraulic microactuators to provide mechanical actuation and 3-D out-of-plane silicon cantilevers that have both spring action and latching mechanisms. This facilitates an off-state gap separation distance of 200 mum between ohmic contacts, without the need for any hold power. Having a simple assembly, many of the inherent problems associated with the more traditional suspension-bridge and cantilever-type-beam architectures can be overcome. A single-pole single-throw switch has been investigated, and its measured on-state insertion and return losses are less than 0.3 dB up to 10 GHz and greater than 15 dB up to 12 GHz, respectively, while the off-state isolation is better than 30 dB up to 12 GHz. The switch works well in both hot- and cold-switching modes, with 4.6 W of RF power at 10 GHz and without any signs of degradation to the ohmic contacts.
... Usually, these dependences are not taken into account in full wave EM (Electromagnetic) simulation. There are some works dealing with multidomain modelling of RF-MEMS switches2345 where in-house simulation tools or a combination of commercial simulation tools are used for taking into account the dependence of the electrical performance on the mechanical or thermal properties. Furthermore, although RF-MEMS switches are 3D structures, they can also be seen as 2.5D structures because of their very high aspect ratio. ...
In this paper proposes different strategies for the electrical modelling of capacitive and resistive RF-MEMS switches which take into account the dependence of the electrical performance on the mechanical properties and technological processes. The EM modelling of MEMS switches is addressed with 2.5D and 3D full wave EM softwares. More specifically, ADS-Momentumtrade (2.5D) and EMDStrade (3D) from Agilent Technologies are used. Capacitive RF-MEMS switches were fabricated with the LAAS-CNRS 6-mask RF-MEMS process in Toulouse, France, and resistive RF-MEMS switches were fabricated with the FBK-irst 8-mask RF-MEMS process in Trento, Italy. It is shown that, by applying the proposed strategies, 2.5D and 3D simulations are in good agreement with characterization results.
... Self-actuation occurs when the root mean square (RMS) of the RF voltage across electrode and beam, V RM S , exceeds the pull-in voltage, V p . Electromigration occurs when the RMS of the RF current density through the golden beam, J RM S , exceeds 0.5 MA/cm 2 [58] and rips loose atoms out of the conductor lattice. ...
The dissertation discusses RF MEMS technology for millimeter-wave radar sensors. RF MEMS, which stands for radio frequency micro-electromechanical system, and radar sensor fundamentals are briefly introduced. Of particular interest are: Firstly, a self-aligned fabrication process for capacitive fixed-fixed beam RF MEMS components is disclosed. It enables scaling of the critical dimensions and reduces the number of processing steps by 40% as compared with a conventional RF MEMS fabrication process. Scaling of the critical dimensions of RF MEMS components offers the potential of submicrosecond T/R switching times. RF MEMS varactors with beam lengths of 30 μm are demonstrated using the self-aligned fabrication process, and the performance of a 4 by 4 RF MEMS varactor bank is discussed as well. At 20 GHz, the measured capacitance values range between 180.5 fF and 199.2 fF. The measured capacitance ratio is 1.15, when a driving voltage of 35 V is applied, and the measured loaded Q factor ranges between 14.5 and 10.8. The measured cold-switched power handling is 200 mW. The simulated switching time is 354.6 ns. Secondly, an analog RF MEMS slotline TTD phase shifter is disclosed, for use in conjunction with ultra wideband (UWB) tapered slot antennas, such as the Vivaldi aerial and the double exponentially tapered slot antenna. It is designed for transistor to transistor logic (TTL) bias voltage levels and exhibits a measured phase shift of 28.2°/dB (7.8 ps/dB) and 59.2°/cm at 10 GHz, maintaining a 75 Ω; differential impedance match (S<sub>11<sub>dd</sub></sub> ≤ -15.8 dB). The input third-order intercept point (IIP3) is 5 dBm at 10 GHz for a Δf of 50 kHz, measured in a 100 Ω differential transmission line system. Ph.D. Electrical Engineering University of Michigan http://deepblue.lib.umich.edu/bitstream/2027.42/61348/1/vcaeken.pdf
... The steady state temperature distribution on a MEMS bridge is solved using the generalized heat conduction equation with constant thermal conductivity given by where T is the temperature of the MEMS bridge (degree Celsius), g is the rate of heat generated ), and k is the thermal conductivity of the bridge[20]. In the capacitive switch the microwave power induces current in the suspended bridge, which results in Ohmic heating. ...
A stable, multiple energy domain and multi scale simulation tool for Microsystems is developed. A structured design methodology is adopted for design and optimization of RF MEMS shunt switch and MEMS inductor. The CAD tool developed is a device specific and incorporates physical parameters such as surface roughness. The tool analyzes the impact of surface roughness and also does thermal analysis. These are useful for understanding reliability and failure mechanisms of RF MEMS components.
... Coupled EM-thermal analysis and measurement techniques have been reported in the past [3], [4] and applied for the RF characterization of MEMS switches [5]. Excellent prediction capabilities are demonstrated with coupled finite element method (FEM) [6]- [9] and finite difference [5], [10] based electro-thermal analysis. However, these techniques are formulated for the device level simulations and owing to the numerical solution of the partial differential kernel, they impose some memory restrictions and require longer running time. ...
Circuit simulations driven modeling approach with embedded multi-physics of capacitive radio frequency microelectromechanical systems switches is presented in this paper. Finite element method simulations in electromagnetic, electromagnetic-thermal and thermal-stress domains are sequentially performed to model and capture the behavioral phenomenology inherent to the selected device. Computed effects are then utilized to modify the original electromagnetic model, giving rise to the updated solutions with included electromagnetic-thermal-stress- electromagnetic physics. To enable circuit level design with the multi- physics models of capacitive microelectromechanical switches, an artificial neural network technique is utilized. Compared to the finite element method simulations, the developed neural network models are about 1500 times faster while maintaining smaller than 0.5% relative difference. Finally, these models are integrated in a circuit simulator, where the sensitivity study and optimization are performed to further demonstrate the advantages of the proposed modeling approach.
