Microelectromechanical Systems Shunt Research Articles

New Analytical Capacitance Modeling of the Perforated Switch Considering the Fringing Effect

Movable suspended microstructures are common features of sensors and devices in the field of micro electro mechanical systems (MEMS). This paper addresses the study of approach to model the capacitance for the crab-type meander-based RF MEMS shunt switch with etching holes on the beam. The presented paper evaluates the parallel-plate capacitance and fringing-field capacitance caused by the etching holes on the beam and introduces empirical formulae. From the literature study, an accurate empirical formula is presented. The capacitance involves a parallel plate and a fringing field. The parallel-plate capacitance term is proposed by the authors of this work; the fringing-field capacitance term is adopted from previous work. The proposed accurate empirical capacitance formulae are derived by curve fitting the simulated values through the commercially available FEM solver. The two existing benchmark models of fringing-field capacitance are used to modify the perforated MEMS switch to obtain the proposed formula. With the existing models and presented formula, the capacitances are computed for a wide range of dimensions; the simulated results of the presented formula are validated with the calculated results. The deviation of the presented formula has an error estimation of ±0.1%. The variation of the capacitance with different deictic thicknesses and errors is estimated and analyzed for the presented formula. The Mejis model is found to be satisfactory for a lower air gap and a 1-μm-thick beam. The Yang's model is sufficient for a higher air gap and a large number of etching holes. The proposed formulae are good for the ligament efficiency μ ≤ 0.5, with thickness >1 μm, and the deviation of error estimation is within ±5%.

Design of Novel Capacitive RF MEMS Shunt Switch with Aluminum Nitride (AlN) Dielectric

In this paper, design of novel capacitive RF microelectromechanical systems (MEMS) shunt switch with butterfly structured beam is presented to reduce the actuation voltage. With aluminum nitride (AlN) dielectric layer the RF characteristics of designed switch renders the excellent performance over 5GHz to 60GHz frequency. The reported capacitance ratio of switch maximum 125 at 3 um air gap. The realized switch exhibit low actuation voltages, in the range of 3-10 volts, an insertion loss of 0.5dB, and return loss of greater than 17dB over operating frequency range 5-60GHz, and an isolation loss greater than 20dB over operating frequency range 10-60 GHZ. The characterization of proposed switch actuation voltage has been compared with straight and meander type supported beams and at a different air gap. Improved isolation loss of aluminium dielectric layered based switch has been compared with silicon dioxide (SiO2) and silicon nitride (Si3N4) dielectric layers. The electromechanical analysis and electromagnetic analysis simulations ware carried out by 3D MEMS commercial software package, Intellisuite and full wave electromagnetic simulator, Ansoft HFSS respectively for designed switches.

RF MEMS Shunt Capacitive Switches Using AlN Compared to $\hbox{Si}_{3}\hbox{N}_{4}$ Dielectric

RF microelectromechanical systems (MEMS) capacitive switches for two different dielectrics, aluminum nitride (AlN) and silicon nitride <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">$(\hbox{Si}_{3}\hbox{N}_{4})$</tex></formula> , are presented. The switches have been characterized and compared in terms of DC and RF performance (5–40 GHz). Switches based on AlN have higher down-state capacitance for similar dielectric thicknesses and provide better isolation and smaller insertion losses compared to <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">$\hbox{Si}_{3}\hbox{N}_{4}$ </tex></formula> switches. Experiments were carried out on RF MEMS switches with stiffening bars to prevent membrane deformation due to residual stress and with different spring and meander-type anchor designs. For a <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">$\sim$</tex></formula> 300-nm dielectric thickness, an air gap of 2.3 <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">$\mu\hbox{m}$</tex></formula> and identical spring-type designs, the AlN switches systematically show an improvement in the isolation by more than <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">$-$</tex> </formula> 12 dB ( <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">$-$</tex></formula> 35.8 dB versus <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex Notation="TeX">$-$</tex></formula> 23.7 dB) and a better insertion loss ( <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">$-$</tex></formula> 0.68 dB versus <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">$-$</tex></formula> 0.90 dB) at 40 GHz compared to <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">$\hbox{Si}_{3}\hbox{N}_{4}$</tex></formula> . DC measurements show small leakage current densities for both dielectrics ( <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">$&lt;10^{-8}\ \hbox{A/cm}^{2}$</tex> </formula> at 1 MV/cm). However, the resulting leakage current for AlN devices is ten times higher than for <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">$\hbox{Si}_{3}\hbox{N}_{4}$</tex></formula> when applying a larger electric field. The fabricated switches were also stressed by applying different voltages in air and vacuum, and dielectric charging effects were investigated. AlN switches eliminate the residual or injected charge faster than the <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">$\hbox{Si}_{3}\hbox{N}_{4}$</tex></formula> devices do. <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">$\hfill$</tex></formula> [2011-0359]

Analytic Modeling Of RF MEMS Shunt Connected Capacitive Switches

—This paper deals with a general analytic approach for the design of RF microelectromechanical system (MEMS) switches. The chosen configuration for these microwave devices is composed of twocoplanar transmission line sections separated by a metal membrane providing a shunt connected variable impedance. Using a bias voltage it is possible to actuate the switch. The adopted methodology for the development of the circuital model is based on the image impedance parameter representation of a two-port network. Synthesis equations are presented, and design considerations are discussed. The proposed approach is validated by means of electromagnetic simulations.

Simulation and Design on Structure for Experimental Verification of Dielectric Charging of Millimeter-Wave MEMS Switches

Lifetimes of RF MEMS (Micro-electro-mechanical systems) capacitive switches are hindered by dielectric charging effects. A novel test structure for experimental verification of millimeter-wave MEMS switch dielectric accumulation charge is presented. The structure, which is designed using EM simulation software CST Microwave Studio and HFSS, consists of Coplanar Waveguide (CPW), a 2-way power divider and two symmetric capacitive MEMS switches. The input signal is equally divided into two output signals in the 2-way power divider due to symmetry, and the isolation between two output ports the power divider of is less than -48dB at 35GHz. The designed millimeter-wave capacitive MEMS shunt switch has 0.076dB insertion and -55dB isolation at 35GHz. The two symmetric capacitive MEMS switches in this structure can provide a strong comparability for different switch dielectric accumulation charge situations.

A low-voltage and low-power RF MEMS series and shunt switches actuated by combination of electromagnetic and electrostatic forces

This paper reports new RF microelectromechanical systems (MEMS) switches actuated by the combination of electromagnetic and electrostatic forces for low-voltage and low-power operation. The proposed RF MEMS switches have utilized the proper combination of two actuation mechanisms: taking advantage of the large actuation force from electromagnetic actuation for initial movement and the low-power feature from electrostatic actuation for holding the actuator position. Both series- and shunt-type switches have been implemented using the proposed actuation mechanism. From the fabricated switches, feasibility of operation has been successfully demonstrated. The fabricated switches can be operated within several hundred microseconds. In the series-type switch, the isolation has been measured as -34dB and insertion loss as -0.37dB at 20 GHz. In the shunt type switch, the isolation is -20.7dB and insertion loss is -0.85dB at 19.5 GHz. The proposed RF MEMS switches are mechanically robust and the combination of electromagnetic and electrostatic actuations makes it possible to achieve excellent switching characteristics at low power and low voltage below 5 V.

V-band 2-b and 4-b low-loss and low-voltage distributed MEMS digital phase shifter using metal-air-metal capacitors

Low-loss digital distributed phase shifters have been developed using micromachined capacitive shunt switches for V-band applications. Instead or conventional metal-insulator-metal capacitors, high-Q metal-air-metal capacitors were used in series with the microelectromechanical system (MEMS) shunt capacitive switches to minimize the dielectric loss. The operation voltage for the phase shifters was also reduced by applying the bias directly to the MEMS shunt switches through choke spiral inductors. Fabricated 2-b (270/spl deg/) and 4-b (337.5/spl deg/) distributed phase shifters showed low average insertion losses of 2.2 dB at 60 GHz and 2.8 dB at 65 GHz, respectively. The average phase errors for 2-b and 4-b phase shifters were 6.5% and 1.3%, respectively. The return losses are better than 10 dB over a wide frequency range from 40 to 70 GHz. Most of the circuits operated at 15-35-V bias voltages. These phase shifters present promising solution to low-loss integrated phase shifting devices at the V-band and above.

High-isolation CPW MEMS shunt switches. 2. Design

For pt.1 see ibid., vol.48, no.6, p.1045-1052 (2000). In this paper, the second of two parts, the equivalent RLC model of the shunt switch is used in the design of tuned two- and four-bridge "cross" switches from 10 to 40 GHz. The cross switch attained an insertion loss of less than 0.3-0.6 dB, a return loss below -20 dB from 22 to 38 GHz in the up state, and a down-state isolation of 45-50 dB with only 1.5 pF of down-state capacitance (C/sub d/). Also, an X-band microelectromechanical system (MEMS) switch with an insertion loss of less than 0.2 dB and an isolation of 35 dB is presented. This is done by inductively tuning the LC series resonance of the shunt switch. The MEMS bridge height is 1.5-2.5 /spl mu/m, resulting in a pull-down voltage of 15-25 V. Application areas are in low-loss high-isolation communication and radar.