Time-Domain Modeling and Characterization of Capacitive MEMS Switches

For the first time, a metal-insulator-semiconductor (MIS) device that consists of silicon (Si) nanocrystals embedded in a silicon oxide film is proposed to investigate how the charge accumulation and relaxation can be manipulated by the nanocrystals for high reliable capacitive RF MEMS switch. A tri-layer structure, used as the insulator in our MIS device, comprises a thicker (about 100 nm) rapid thermal oxidation (RTO) silicon dioxide (SiO2) layer, a Si+SiO2 middle layer (about 100 nm) deposited by RF sputtering technique, and a RF-sputtered silicon dioxide capping layer. The electrical properties of the device have been characterized using capacitance versus voltage (C-V) measurements. The experiment results show a significant change of charge trapping and detrapping mechanisms in the composite insulator due to the presence of the Si nanocrystals in the middle layer. This result offers a possibility that the trapping or detrapping mechanisms in the dielectric can be manipulated by embedding nanocrystals in terms of materials (Ge, Si or other), density, size of nanocrystals and their distribution. It is anticipated that the charge trapping and their relaxation time in the dielectric of capacitive MEMS switch can be reduced.

This paper presents a new characterization method to measure the RF power handling of capacitive RF MEMS switches. Historically, the RF power handling was characterized by analyzing the pull-in and release voltage shift under several RF power settings. However, this technique is problematic especially because of possible charging under high DC voltages. We present a new measurement setup that includes capacitance measurement in parallel with the RF signal. This technique enables characterization of the RF MEMS switches in a non-destructive manner including a direct measure of the capacitance variation under RF power. This method is better aligned with the device requirements where the RF Power handling will be specified relative to a resulting capacitance change (analogous to a P1dB) and not a voltage pull-in related to the DC operation. In this paper, we will show the measurement setup, the theory and early measurements of a capacitive RF MEMS tuner in the open state in a series configuration. The results have shown small but significant differences between DC and RF measurement approaches up to 6.5W of input power.

We report a study over a wide range of high-K dielectric materials (Al <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">x</inf> O <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">y</inf> , HfO <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">x</inf> , TiO <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">x</inf> …) deposited by different techniques (Evaporation, ALD, PEALD…) for high power RF applications. Main results show that ALD technique is matching the McPherson trend based on thermochemical prediction. Furthermore ALD materials are promising to meet high power requirements for capacitive RF MEMS switches. As a result, Thermal ALD HfO <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</inf> was integrated in high power capacitive RF MEMS switches in order to improve their RF performances, power handling and reliability.

This paper presents the design, fabrication and testing of capacitive RF MEMS switches for microwave/mm- wave applications on high-resistivity silicon substrate or glass. The feasibility study and demonstrator fabrication of a new concept of reflector network using MEMS switch based phase-shifters concept for space antennas is presented. These switches can be accurately modeled using 3-D static solvers. The loss in the up-state position is equivalent to the CPW line loss and is 0.1-0.3 dB at 10-40 GHz. It is seen that the capacitance, inductance and series resistance can be accurately extracted from DC-40 GHz S-parameter measurements. The reflector array antennas utilization for phase control avoids the use of very expensive directive antennas and covers a very large frequencies range. We will deal with the configuration, the composition and arrangement of MEMS switches, used to control the phase shift of the electromagnetic wave reflected by each elementary cell.

The paper presents a design and mathematical analysis of capacitive RF MEMS switch for achieving high isolation, low insertion loss and low pull in voltage. The proposed design includes central electrode for RF path and ground plane around it. Structure is simulated on silicon substrate with gold as the conducting material. Silicon dioxide is used as the dielectric layer to ensure better isolation of the switch along with reliability. High isolation of -35dB and insertion loss of less than -0.1dB is achieved for the frequency range upto 30 GHz. The structure has very low pull in voltage which gives it advantages in terms of low power consumption with other MEMS switches. RF design is implemented on CST microwave studio. Era of new wireless standards like 5G requires high linearity & wider bandwidth operation. RF MEMS switches have many wireless communication application including cellular base station, mobile handset and tunable filters etc.

RF MEMS switches provide a low-cost, high performance solution for many RF/microwave applications these switches will be important building blocks for designing phase shifters, switched filters reflector array antennas for military and commercial markets. In this paper, progress in characterizing of THALES capacitive MEMS devices under high RF power is presented. The design, fabrication and testing of capacitive RF MEMS switches for microwave/mm- wave applications on high-resistivity silicon substrate is presented. The switches tested demonstrated power handling capabilities of 1W (30 dBm) for continuous RF power. The reliability of these switches was tested at various power levels indicating that under continuous RF power. In addition a description of the power failures and their associated operating conditions is presented. The PC-based test stations to cycle switches and measure lifetime under DC and RF loads have been developed. Best-case lifetimes of 10¹⁰ cycles have been achieved in several switches from different lots under 30 dbm RF power.

RF MEMS capacitive switches can be used for band switching and adaptive antenna matching in cell phone Front End Modules. They are extremely linear and, if made in standard silicon technology, can be integrated into other applications in the phone. Many efforts have been put in the intrinsic reliability of the RF MEMS capacitive switches. The main failure mechanism is stiction due to dielectric charging. The progress made in RF MEMS processing has shifted the focus towards the package. It is generally accepted that a hermetic package is needed to keep the effect of charging within specification. Since packages are very small (typically 300nl), new hermeticity tests are needed because the leak rate tests are not sensitive enough for these small packages. In this paper we demonstrate the reliability of a capacitive RF MEMS switch package. The product is assembled using a AuSn bonding process in which a Silicon cap wafer is assembled on top of the MEMS die. The package is filled with pure N2 to the desired pressure. Hermeticity is determined by measuring the pressure dependence of the mechanical resonance of the MEMS top electrode. First we will describe the method we have used to determine the pressure inside the cavity and how to apply that to hermeticity testing. Second, we describe how the requirements for the leak rate of the package can be determined. Finally we show with the use of temperature, humidity and high pressure N2 testing that our package fulfills these requirements. Although the method may not be new, the combination of extensive reliability testing and understanding the RF MEMS device using FEM simulations has not been reported before.

Silicon MEMS as electrostatically levitated rotational gyroscopes and 2D optical scanners, and wafer level packaged devices as integrated capacitive pressure sensors and MEMS switches are described. MEMS which use non-silicon materials as LTCC with electrical feedthrough, SiC and LiNbO3 for probe cards for wafer-level burn-in test, molds for glass press molding and SAW wireless passive sensors respectively are also described.

A built-in self-test (BIST) scheme which partitions the fixed (instead of movable) capacitance plates of a capacitive MEMS device is proposed. The BIST technique divides the fixed capacitance plate(s) at each side of the movable microstructure into three portions: one for electrostatic activation and the other two equal portions for capacitance sensing. Due to such partitioning, the BIST technique can be applied to surface-, bulk-micromachined MEMS devices and other technologies. Further, sensitivity and symmetry BIST methods based on this partitioning are also introduced. The combination of both BIST modes covers a larger defect set, thus a robust testing for the device can be expected. The BIST technique is verified by three typical capacitive MEMS devices. Simulation results show that the proposed technique is an effective BIST solution for various capacitive MEMS devices.

Microelectromechanical Systems (MEMS) for radio frequency (RF) applications or RF MEMS provides an opportunity to revolutionize the wireless communication. This paper describes the Performance of low loss Fixed-Fixed RF MEMS capacitive switch at higher frequencies. Many researchers focus on RF MEMS capacitive switch, which presents good performance at microwave frequencies. Modelling of RF MEMS devices is essential for design optimization and device reliability. One of the most important RF MEMS components is MEMS switch. A novel approach of designing the RF MEMS switch is presented here to obtain the better performance of the switch at higher frequency ranges from 0.1 to 40 GHz .The RF MEMS capacitive Fixed-Fixed switch exhibit lower losses, better reliability, and good performance at higher frequencies.

This paper aimed to design and analysis of non-uniform meander capacitive shunt RF MEMS switch. The less pull in voltage is obtained in flexure type membrane by proposed RF MEMS Switch. The selection of materials for the beam and dielectric layer is expressed in this paper and also shown the performance depends on materials utilized for the design. The high isolation of -31.15dB actuating at the pull-in voltage of 7.69V with a spring constant of 3.28N/m produced the switch and is obtained by the optimization process. Capacitive contact switches have capability of power handling. The actuated switch state provides an excellent isolation. It shorts the ground by RF signal. MEMS technology is the integration of electrical and mechanical components on single platform i.e. substrate [10]. From the literature, various researchers have proposed different RF MEMS Switch, but still there few challenges on optimization of the Switch for best performance. The electromechanical analysis such as Upstate, Downstate capacitances and stress analysis have been carried out. The performance of the switch is analyzed by taking appropriate materials selected by Ashby’s approach. These optimized dimensions are feasible to fabricate. The substrate height, material for the substrate and coplanar waveguides are used for the impendence matching. For obtaining the less pull in voltage overlapping area is to be increased.

This paper presents a unique model of shunt capacitive Microelectromechanical switch which works at RF frequency (12-18 GHz) with low insertion loss and high isolation. Low actuation voltage, removal of stiction and making a switch to work at Ku band frequency are main goals of this design. The ribs that are used in this model are made very stiff to avoid stiction problem. Hafnium Dioxide (HfO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> ) has been used as dielectric material with high dielectric constant (k~25) leading to high isolation. The designed switch is optimized to work at a very low actuation voltage (~11.32 Volt) with high isolation, -20 dB and low insertion loss, -0.095 dB.

Capacitive structures are sensitive to the electrostatic force created by the RF signal going through them. In the case of MEMS tunable capacitors, the consequences on performances and capacitance values are to be quantified. Two systems are studied: one-gap with RF signal and actuation voltage on same electrodes, and two-gaps with RF signal separated from actuation. Computational results show great influence of power on pull-in, even for low power levels, for both MEMS capacitor structures.

In today’s world one of the major concerns for the electronics engineers and scientists is how to reduce the power consumption of the electronics devices. To overcome this problem we come across different technologies. Radio Frequency (RF) Microelectromechanical (MEMS) switches are one of the leading technologies for past two decades. But the main concern with RF MEMS switches is its high actuation voltage and high switching time. This paper generally concentrates on the simulation of RF MEMS contact switch having Y-shaped cantilever beam to obtain low actuation voltage with less switching time. The simulation and results are obtained by the Intellisuite 8.7v software. The actuation voltage depends on the air gap, Young’s modulus, thickness of the beam etc. The “pull-in” voltage is found to be 1.2 V and the switching time is about 52.3 µs.

The characterization of RF MEMS capacitive switch is presented to understand dielectric charging, failure mode, and hold-down lifetime. The characterization included the understanding of beam stiction failure with respect to the voltage at minimum capacitance, VCmin, from low voltage bipolar capacitance-voltage sweep, and the acceleration effect of temperature described by Arrhenius model. The simplified 3 points VCmin method is suggested for dielectric charging detection with low cost and short test time for defective part screening and application in automated test equipment. The hold-down lifetime improved with taller standoff bumps by increasing release voltage and minimizing dielectric charging on the actuator electrode.