Reliability Of Microelectromechanical Systems Research Articles

Characterizing MEMS Switch Reliability for Cryogenic Applications such as Quantum Computing

Micro Electromechanical Systems (MEMS) switches offer many advantages over conventional larger switches. One potential application we are exploring is the use of commercial radio frequency (RF) MEMS switches for quantum computing applications. However, it is well-documented that cryogenic temperatures can cause mechanical reliability issues for MEMS. Furthermore, commercial RF MEMS switches are designed for room temperature operation, thus their reliability at cryogenic temperatures is unknown. Commercial MEMS switches are also packaged inside sealed housings, which prevent the use of optical methods for characterization and inspection. We are therefore developing test methods to evaluate the reliability of commercial RF MEMS switches at cryogenic temperatures. We describe our test methods and preliminary reliability test data from room temperature down to 55 K.

Characterization of Sand and Dust Pollution Degradation Based on Sensitive Structure of Microelectromechanical System Flow Sensor.

The effect of sand and dust pollution on the sensitive structures of flow sensors in microelectromechanical systems (MEMS) is a hot issue in current MEMS reliability research. However, previous studies on sand and dust contamination have only searched for sensor accuracy degradation due to heat conduction in sand and dust cover and have yet to search for other failure-inducing factors. This paper aims to discover the other inducing factors for the accuracy failure of MEMS flow sensors under sand and dust pollution by using a combined model simulation and sample test method. The accuracy of a flow sensor is mainly reflected by the size of its thermistor, so in this study, the output value of the thermistor value was chosen as an electrical characterization parameter to verify the change in the sensor's accuracy side by side. The results show that after excluding the influence of heat conduction, when sand particles fall on the device, the mutual friction between the sand particles will produce an electrostatic current; through the principle of electrostatic dissipation into the thermistor, the principle of measurement leads to the resistance value becoming smaller, and when the sand dust is stationary for some time, the resistance value returns to the expected level. This finding provides theoretical guidance for finding failure-inducing factors in MEMS failure modes.

FRACTAL PULL-IN MOTION OF ELECTROSTATIC MEMS RESONATORS BY THE VARIATIONAL ITERATION METHOD

The dynamic pull-in instability of a microstructure is a vast research field and its analysis is of great significance for ensuring the effective operation and reliability of micro-electromechanical systems (MEMS). A fractal modification for the traditional MEMS system is suggested to be closer to the real state as a practical application in the air with impurities or humidity. In this paper, we establish a fractal model for a class of electrostatically driven microstructure resonant sensors and find the phenomenon of pull-in instability caused by DC bias voltage and AC excitation voltage. The variational iteration method has been extended to obtain approximate analytical solutions and the pull-in threshold value for the fractal MEMS system. The result obtained from this method shows good agreement with the numerical solution. The simple and efficient operability is demonstrated through theoretical analysis and results comparisons.

Mechanical Property Measurement of Micro/Nanoscale Materials for MEMS: A Review

By virtue of a great progress of semiconductor fabrication technologies, micro electro‐mechanical systems (MEMS) have been developed for a wide variety of industries. For reliability of MEMS, micromaterials in MEMS need to be examined experimentally, and the obtained results need to be reflected in the design of MEMS. In addition, with the benefit of such the MEMS technology, nowadays mechanical characteristics of nanomaterials have been evaluated precisely. Nanoscale mechanical testing provides an opportunity to find new unique physical phenomena, such as plastic deformation in Si at intermediate temperatures. In this review paper, mechanical testing technologies developed for investigating micro and nanoscale materials are reviewed. Then, mechanical characteristics of Si and other materials evaluated using the micro and nano mechanical testing technologies are introduced. © 2022 Institute of Electrical Engineers of Japan. Published by Wiley Periodicals LLC.

Research on A Novel Reliable MEMS Bistable Solid State Switch

As a result of the unpredictable nature of extreme environments (including temperature, humidity, impact, and other factors), micro-electro-mechanical systems (MEMS) solid-state fuze control modules have an urgent requirement for a MEMS solid-state switch (MEMS-S3). In particular, this switch must remain stable without any energy input after a state transition (i.e., it must be bistable). In this paper, a MEMS bistable solid-state switch (MEMS-bS3) is designed that is based on the concept of producing a micro-explosion. The reliable state switching of the MEMS-bS3 is studied via heat conduction theory and verified via both simulations and experimental methods. The experimental results show that these switches can produce micro-explosions driven by 33 V/47 μF pulse energy. However, the metal film bridge (MFB) structures used in this switch with smaller dimensions (80×20 μm2, 90×30 μm2, and 100×40 μm2) could not enable the switch to realize a reliable state transition, and the state transition rate was less than 40%. When the MFB dimensions reached 120×60 μm2 or 130×70 μm2, the state transition rate exceeded 80%, and the response time was on the μs-scale.

Design, development and testing of digital MEMS pressure sensor array for full-scale vibroacoustic measurements

This manuscript addresses design, development, and application of micro-electro-mechanical systems (MEMS) based digital pressure sensor array for vibroacoustic measurements. These vibroacoustic measurements were conducted on a A320 type single aisle aircraft demonstrator subjected to broadband as well as tonal excitations. Cabin noise levels were measured with both condenser microphones as well as digital MEMS pressure sensor array. The measured cabin noise shows strong qualitative as well as quantitative agreement between both type of measurement devises for full scale cabin noise measurements inside an aircraft demonstrator. The observed strong agreement is valid for both single wall (fuselage with thermal insulation) and double wall (fuselage with thermal insulation and trim panel) cabin noise measurements. Such strong agreement within 1.0 dB tolerance is significantly motivating for further development of reliable but low-cost MEMS based measurement devises and corresponding efficient data post-processing algorithms for full scale vibroacoustic measurements in general. Additionally, it is also demonstrated that the large number of MEMS based digital pressure sensors can be used in areas where the physical space constraints are high. This demonstration shows strong potential to derive additional vibroacoustic indicator for the development and the testing of future noise control solutions in a non-traditional way.

Noise as Diagnostic Tool for Quality and Reliability of MEMS.

This perspective explores future research approaches on the use of noise characteristics of microelectromechanical systems (MEMS) devices as a diagnostic tool to assess their quality and reliability. Such a technique has been applied to electronic devices. In comparison to these, however, MEMS have much more diverse materials, structures, and transduction mechanisms. Correspondingly, we must deal with various types of noise sources and a means to separate their contributions. In this paper, we first provide an overview of reliability and noise in MEMS and then suggest a framework to link noise data of specific devices to their quality or reliability. After this, we analyze 13 classes of MEMS and recommend four that are most amenable to this approach. Finally, we propose a noise measurement system to separate the contribution of electrical and mechanical noise sources. Through this perspective, our hope is for current and future designers of MEMS to see the potential benefits of noise in their devices.

Reliable, Compact, and Tunable MEMS Bandpass Filter Using Arrays of Series and Shunt Bridges for 28-GHz 5G Applications

This work presents radio frequency (RF) microelectromechanical system (MEMS)-based compact, high power, and reliable tunable bandpass filter for millimeter-wave RF front end. The design is fabricated on 635- $\mu \text{m}$ alumina substrate using surface micromachining process. All functional building blocks of the filter are fabricated and tested independently to ensure the optimum filter performances. Total area of the filter is only 2.3 mm2 including bias lines and pads. The proposed filter can be tuned to any frequency between 27 and 29 GHz and it demonstrates insertion loss of 1.92 dB and matching of 23.4 dB at 28 GHz with fractional bandwidth (FBW) of 6.7%. Filter also gives bandwidth tuning of 4.4 GHz with acceptable loss. Filter works satisfactorily up to 1 billion cycles with 1 W of power. Device reliability tested within a low-cost package. To the best of our knowledge, this is the first reported tunable MEMS bandpass filter in the literature which has undergone and presented with extensive reliability results.

A survey of Mechanical failure and design for Reliability of MEMS

In this paper, several experimental mechanical investigation techniques are presented to evaluate the reliability of micro-electro-mechanical systems (MEMS). Microsystems in recent years have spread in many everyday devices. We find micro-scale sensors and actuators in automotive, biomedical and aerospace applications where are demanded very strict performance requirements. Electromechanical non-linear coupling is often a crucial problem both in design and also for the reliability of the system. Mechanism of failure and failure modes has to be taken into account in order to evaluate the reliability of the final system. Focusing on device failure, it emerges that mechanical damage is the most significant source. In this paper a survey of recent advance in mechanical testing of MEMS is presented including: mechanical fatigue, mechanical strength and plasticity, surface and contact failure and creep. Different design of testing specimens is discussed to identify the material properties and failure modes behavior in order to obtain design rules and strategies.

Predicting strength distributions of MEMS structures using flaw size and spatial density

The populations of flaws in individual layers of microelectromechanical systems (MEMS) structures are determined and verified using a combination of specialized specimen geometry, recent probabilistic analysis, and topographic mapping. Strength distributions of notched and tensile bar specimens are analyzed assuming a single flaw population set by fabrication and common to both specimen geometries. Both the average spatial density of flaws and the flaw size distribution are determined and used to generate quantitative visualizations of specimens. Scanning probe-based topographic measurements are used to verify the flaw spacings determined from strength tests and support the idea that grain boundary grooves on sidewalls control MEMS failure. The findings here suggest that strength controlling features in MEMS devices increase in separation, i.e., become less spatially dense, and decrease in size, i.e., become less potent flaws, as processing proceeds up through the layer stack. The method demonstrated for flaw population determination is directly applicable to strength prediction for MEMS reliability and design.

Ultrahigh superelastic damping at the nano-scale: A robust phenomenon to improve smart MEMS devices

Micro and nano pillars of Copper-based shape memory alloys (SMAs) with feature sizes between about 2 μm and 250 nm are known to exhibit ultra-high mechanical damping due to the nucleation and motion of stress-induced martensite interfaces during superelastic straining. While this behavior could be extremely useful to protect micro electro-mechanical systems (MEMS) against vibrations in aggressive environments, a fundamental question must yet be answered in order to envisage further applications, namely, whether this damping is reproducible and stable over long times and many cycles, or whether the damping is a signal of accumulating damage that could compromise long-term usage. In the present paper this crucial question is answered; we show that micropillar arrays of Cu-Al-Ni SMAs exhibit a completely recoverable and reproducible superelastic response, with an ultra-high damping loss factor η > 0.1, or even higher for sub-micrometer pillars, η > 0.2, even after thousands of cycles (>5000) and after long times spanning more than four years. Furthermore, the first high-frequency tests on such nanoscale SMAs show that their superelastic response is very fast and relevant to ultra-high damping even at frequencies as high as 1000 Hz. This paves the way for the design of micro/nano dampers, based on SMAs, to improve the reliability of MEMS in noisy environments.

A reliable MEMS switch using electrostatic levitation

In this study, a microelectromechanical system (MEMS) beam is experimentally released from pull-in using electrostatic levitation. A MEMS cantilever with a parallel plate electrode configuration is pulled-in by applying a voltage above the pull-in threshold. An electrode is fixed to the substrate on each side of the beam to allow electrostatic levitation. Large voltage pulses upwards of 100 V are applied to the side electrodes to release the pulled-in beam. A large voltage is needed to overcome the strong parallel plate electrostatic force and stiction forces, which hold the beam in its pulled-in position. A relationship between bias voltage and release voltage is experimentally extracted. This method of releasing pulled-in beams is shown to be reliable and repeatable without damaging the cantilever or electrodes. The proposed approach is of great interest for any MEMS component that suffers from the pull-in instability, which is usually irreversible and permanently destroys the device, as electrostatic levitation allows pulled-in structures to be released and reused. It has a promising application in MEMS switches by creating a normally closed switch as opposed to current MEMS switches, which are normally open.

An Analytical Temperature-Dependent Design Model for Contour-Mode MEMS Resonators and Oscillators Verified by Measurements.

The importance of micro-electromechanical systems (MEMS) for radio-frequency (RF) applications is rapidly growing. In RF mobile-communication systems, MEMS-based circuits enable a compact implementation, low power consumption and high RF performance, e.g., bulk-acoustic wave filters with low insertion loss and low noise or fast and reliable MEMS switches. However, the cross-hierarchical modelling of micro-electronic and micro-electromechanical constituents together in one multi-physical design process is still not as established as the design of integrated micro-electronic circuits, such as operational amplifiers. To close the gap between micro-electronics and micro-electromechanics, this paper presents an analytical approach towards the linear top-down design of MEMS resonators, based on their electrical specification, by the solution of the mechanical wave equation. In view of the central importance of thermal effects for the performance and stability of MEMS-based RF circuits, the temperature dependence was included in the model; the aim was to study the variations of the RF parameters of the resonators and to enable a temperature dependent MEMS oscillator simulation. The variations of the resonator parameters with respect to the ambient temperature were then verified by RF measurements in a vacuum chamber at temperatures between −35 C and 85 C. The systematic body of data revealed temperature coefficients of the resonant frequency between −26 ppm/K and −20 ppm/K, which are in good agreement with other data from the literature. Based on the MEMS resonator model derived, a MEMS oscillator was designed, simulated, and measured in a vacuum chamber yielding a measured temperature coefficient of the oscillation frequency of −26.3 ppm/K. The difference of the temperature coefficients of frequency of oscillator and resonator turned out to be mainly influenced by the limited Q-factor of the MEMS device. In both studies, the analytical model and the measurement showed very good agreement in terms of temperature dependence and the prediction of fabrication results of the resonators designed. This analytical modelling approach serves therefore as an important step towards the design and simulation of micro-electronics and micro-electromechanics in one uniform design process. Furthermore, temperature dependences of MEMS oscillators can now be studied by simulations instead of time-consuming and complex measurements.

Interview

Zongda Hu from the Chinese Academy of Sciences, China, talks to Electronics Letters about his paper ‘Highly sensitive resonant pressure sensor based on mode-localization effect’, page 882. Zongda Hu My field of research is concerned with Micro-Electro-Mechanical System (MEMS) including pressure sensor, accelerometer, gyroscope, and so on. As we all know, MEMS sensors have different advantages with low-power consumption, small volume, and low price in contrast with traditional sensors. I started working in this field whilst pursuing my master's degree in 2012. My tutor, Professor Yu, who has already worked in this field for almost 30 years guides me in this novel area. I appreciate it so much. The most interesting issue is developing a perfect sensor with high sensitivity, high resolution, and long-term stability. The exploration of petroleum and gas resources is the particular application which interests me as the harsh underground environment requires more reliable MEMS sensors. The exploration of petroleum needs pressure sensors to detect the pressure value in the drilling well. By measuring the gradient, the pressure values at different depths in the well can be accurately grasped. The distribution of petroleum is surveyed by measurement. We are aiming to obtain a more sensitive pressure sensor with high signal-to-noise ratio and large dynamic in contrast with traditional sensors which have insufficient precision. We proposed a novel resonant pressure sensor with two mechanically-coupled resonators. We use the amplitude ratios as the readout for the mode-localized sensors, which is different from the traditional resonant sensors using frequency readouts. The measured result shows that the relative sensitivity is two orders higher than traditional resonant sensors. Mode-localization effects which we used in our resonant pressure sensor, can enhance sensitivity greatly in any resonant sensors. This is expected to lead to high resolution, which will minimize the noise impact of the interface circuit. The amplitude-related metrics, such as amplitude ratios, are generally elected as the readout for the mode-localized sensors which is different from the traditional resonant sensors using frequency readouts. However, linear sensing across the veering point is still under investigation due to the inherent loci veering phenomenon. We have to choose a linear sensing range of the amplitude ratios in order to adapt a linear interface circuit system. The mode-localization effect developed in the present research is likely to have a broad technological impact. The present resonant sensor is not famous for its precision, but for its long-term stability. The sensitivity enhanced by mode-localization effect is a key to break the shackles on resonant sensors. The higher the sensitivity of the sensor is, the smaller the effect of circuit noise should be. We can obtain ultra-resolution resonant sensor through this method. In the long term, mode-localization detection method is expected to grow rapidly. Methods based on mode-localization effect have exploded in popularity and real world applications using this method are one of the most recent major breakthrough in some areas, including geological exploration, aerospace, and military industry. As we all know, the temperature in the Earth's crust can reach higher than 200 degrees Celsius. Thermal stress and thermal expansion in normal resonators will cause great measurement deviations. We are planning to focus on designing a micro-mechanical resonator structure that can release thermal stress extremely effectively. Besides, we also take aluminium nitride material into consideration for its good temperature characteristic. Such resonator systems will have sufficient robustness in such a high temperature environment. The current developed trend of MEMS technology is expected to the foreseeable future. This will open up new applications in fields such as the pressure sensor in our cell phone, the accelerometer in the airbags of our cars, and gyroscopes in drone. However, production of MEMS sensors according to design specifications is extremely difficult because the limitations in manufacturing conditions will result in inconsistencies with predictable design. In addition, integrating sensors and circuits is still a big challenge for industrialisation. But I believe that MEMS technology will be the cornerstone for the development of all walks of life in the future.

Analysis of the bending stiffness and adhesion effect in RF-MEMS structures

Microelectromechanical system (MEMS) is a special branch with a wide range of applications in sensing, switching and actuating devices. Designing the reliable MEMS for thin free-standing structures like as bridges and cantilevers requires understanding of the tribomechanical properties of the materials and structures.The effect of geometrical dimensions (cross-section dimensions and length) on mechanical and tribological behavior of free-standing MEMS structures made of electroplated gold was analyzed in this paper. Special attention was given to the dependences between stiffness and cantilever length and the dependences between bending stress and variable travel range of actuated load. The force position was moved from the beams free-end toward to the anchor. The tests were performed at room temperature (22°C) and relative humidity RH of 40% with a noise- and vibration-isolated and environment-controlled XE-70 AFM from Park Systems using the contact mode. Each measurement was repeated many times in order to improve the accuracy of the experimental results. The stiffness of a microcantilever varies if the position of the acting force is changed. The experimental results obtained were in good correlation with those obtained analytically.

A Highly Reliable MEMS Relay With Two-Step Spring System and Heat Sink Insulator for High-Power Switching Applications

This paper reports a highly reliable electrostatic microelectromechanical systems (MEMS) relay for high-power switching applications. The main proposal to elevate reliability is to reduce thermal damage in the contact area. Since a contact resistance is the key parameter determining the amount of Joule-heating and the corresponding thermal damage, we devised a unique spring structure to maximize the contact force (resulting in a low contact resistance) using a reasonable actuation voltage named a two-step spring system. Another important feature was applied to alleviate Joule-heating, which is to use an insulator having high thermal conductivity to dissipate the generated heat efficiently, named a heat sink insulator. The fabricated MEMS relay exhibited 2 mΩ in contact resistance, which is the lowest level reported so far with an actuation voltage of 45 V. Reliability was remarkably enhanced over ten times by the heat sink insulator. Consequently, by applying these two approaches simultaneously, the fabricated MEMS relay was successfully operated up to the 5.3 ×10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">6</sup> cycles at 1 V/200 mA in ambient air and hot switching condition, which is the highest reliability reported at that power level.

A Highly Reliable Two-Axis MEMS Relay Demonstrating a Novel Contact Refresh Method

This paper reports on a two-axis actuated microelectromechanical systems (MEMS) relay to realize a unique contact-refresh concept. In comparison with all other conventional MEMS relays utilizing only several designated contact spots during their whole lifetime, the proposed concept can change the real contact spots (asperities) by altering the lateral position of contact asperities, thus providing highly reliable contact endurance. In addition, it can enhance lifetime of the switches that fail by contact resistance increase, and potentially even for switches that fail by contact stiction if the contact position is changed before a critical number of switching cycles is reached; however, the device inevitably has a relatively large device area and additional control circuitry in this stage of development. The fabricated relays showed vertical actuation voltages under 40 V, a switching delay of 190 $\mu \text{s}$ , and a maximum lateral displacement of 10 $\mu \text{m}$ . Owing to the suggested contact-refresh scheme, the total contact endurance in one switching device was dramatically increased, and the sum of dozens of lifetimes measured at the selected lateral positions reached $6 \times 10^{7}$ cycles at 100 mA in hot switching conditions (Au-to-Au contact), which is nearly 50 times higher than the average value of the measured lifetimes in a designated contact spot. [2014-0225]

High Reliability of MEMS Packaged Capacitive Pressure Sensor Employing 3C-SiC for High Temperature

Abstract This study develops the prototype of a micro-electro-mechanical systems (MEMS) packaged capacitive pressure sensor employing 3C-SiC diaphragm for high temperature devices. The 3C-SiC diaphragm is designed with the thicknesses of 1.0 μm and the width and length of 2.0 mm x 2.0 mm. The fabricated sensor is combined with a reliable stainless steel o-ring packaging concept as a simple assembly approach to reduce the manufacturing cost. There is an o-ring seal at the sensor devices an advantageous for high reliability, small size, lightweight, smart interface features and easy maintenance services. The stability and performance of the prototype devices has been tested for three test group and measured by using LCR meter. The prototypes of MEMS capacitive pressure sensor are characterized under static pressure of 5.0 MPa and temperatures up to 500 °C in a stainless steel chamber with direct capacitance measurement. At room temperature (27 °C), the sensitivity of the sensor is 0.0096 pF/MPa in the range of pressure (1.0–5.0 MPa), with nonlinearity of 0.49%. At 300 °C, the sensitivity is 0.0127 pF/MPa, and the nonlinearity of 0.46%. The sensitivity increased by 0.0031 pF/MPa; corresponding temperature coefficient of sensitivity is 0.058%/°C. At 500 °C, the maximum temperature coefficient of output change is 0.073%/°C being measured at 5.0 MPa. The main impact of this work is the ability of the sensor to operate up to 500 °C, compare to the previous work using similar 3C-SiC diaphragm that can operates only 300 °C. The results also show that MEMS packaged capacitive pressure sensor employing 3C-SiC is performed high reliability for high temperature up to 500 °C. In addition, a reliable stainless steel o-ring packaging concept of MEMS packaged capacitive pressure sensor.

A novel optimal configuration form redundant MEMS inertial sensors based on the orthogonal rotation method.

In order to improve the accuracy and reliability of micro-electro mechanical systems (MEMS) navigation systems, an orthogonal rotation method-based nine-gyro redundant MEMS configuration is presented. By analyzing the accuracy and reliability characteristics of an inertial navigation system (INS), criteria for redundant configuration design are introduced. Then the orthogonal rotation configuration is formed through a two-rotation of a set of orthogonal inertial sensors around a space vector. A feasible installation method is given for the real engineering realization of this proposed configuration. The performances of the novel configuration and another six configurations are comprehensively compared and analyzed. Simulation and experimentation are also conducted, and the results show that the orthogonal rotation configuration has the best reliability, accuracy and fault detection and isolation (FDI) performance when the number of gyros is nine.

Accelerated life tests for prognostic and health management of MEMS devices

Microelectromechanical systems (MEMS) offer numerous applications thanks to their miniaturization, low power consumption and tight integration with control and sense electronics. They are used in automotive, biomedical, aerospace and communication technologies to achieve different functions in sensing, actuating and controlling. However, these microsystems are subject to degradations and failure mechanisms which occur during their operation and impact their performances and consequently the performances of the systems in which they are used. These failures are due to different influence factors such as temperature, humidity, etc. The reliability of MEMS is then considered as a major obstacle for their development. In this context, it is necessary to continuously monitor them to assess their health status, detect abrupt faults, diagnose the causes of the faults, anticipate incipient degradations which may lead to complete failures and take appropriate decisions to avoid abnormal situations or negative outcomes. These tasks can be performed within Prognostics and Health Management (PHM) framework. This paper presents a hybrid PHM method based on physical and data-driven models and applied to a microgripper. The MEMS is first modeled in a form of differential equations. In parallel, accelerated life tests are performed to derive its degradation model from the acquired data. The nominal behavior and the degradation models are then combined and used to monitor the microgripper, assess its health state and estimate its Remaining Useful Life (RUL).