Integration Of Microelectromechanical Systems Research Articles

Multi-Stimuli Operando Transmission Electron Microscopy for Two-Terminal Oxide-Based Devices.

The integration of microelectromechanical systems (MEMS)-based chips for in situ transmission electron microscopy (TEM) has emerged as a highly promising technique in the study of nanoelectronic devices within their operational parameters. This innovative approach facilitates the comprehensive exploration of electrical properties resulting from the simultaneous exposure of these devices to a diverse range of stimuli. However, the control of each individual stimulus within the confined environment of an electron microscope is challenging. In this study, we present novel findings on the effect of a multi-stimuli application on the electrical performance of TEM lamella devices. To approximate the leakage current measurements of macroscale electronic devices in TEM lamellae, we have developed a postfocused ion beam (FIB) healing technique. This technique combines dedicated MEMS-based chips and in situ TEM gas cells, enabling biasing experiments under environmental conditions. Notably, our observations reveal a reoxidation process that leads to a decrease in leakage current for SrTiO3-based memristors and BaSrTiO3-based tunable capacitor devices following ion and electron bombardment in oxygen-rich environments. These findings represent a significant step toward the realization of multi-stimuli TEM experiments on metal-insulator-metal devices, offering the potential for further exploration and a deeper understanding of their intricate behavior.

(Invited) SAE-MEMS Technology for Electrostatic Vibrational Energy Harvesters

Energy harvesting [1] is expected to be a self-powering technology for small wireless sensor nodes in the next generation Internet-of-Things (IoT). In particular, small vibrational energy harvesters (VEHs) based on micro-electro-mechanical systems (MEMS) technology, which are battery-free and can generate electricity even at night or in the dark, are being investigated worldwide for next-generation power sources for small wireless IoT nodes [2,3]. Electrostatic MEMS VEHs, which use semi-permanent charge-holding dielectrics called "electrets," are useful for power generation using environmental vibrations because they have a higher output power density at lower frequencies than other methods [4]. Further miniaturization, higher performance, and higher productivity will be required to use electret-type MEMS VEHs as power sources for compact wireless IoT nodes and other devices. Although the integration of MEMS VEHs with power management circuits enables miniaturization, higher performance, and improved productivity, the monolithic integration of electret-type MEMS VEHs and electronic circuits is an unexplored area in conventional technology. Conventional electrostatic MEMS VEHs involve corona discharge, electron beam irradiation, X-ray irradiation, or high-temperature treatment as electret charge processing, which imposes restrictions on the design and manufacturing of MEMS structures and the integration of MEMS and electronic circuits. Recently, self-assembled electrets (SAEs), which are electrets that do not require any charging process, have been developed using materials for organic electroluminescent devices [5]. The surface charge density of SAEs is equivalent to those of previously reported electrets for VEHs, and thus SAE is expected to improve the performance of VEH and simplify the manufacturing process. However, there have been no reports of MEMS devices using SAEs.Our proposed method is the first technology to form SAEs inside MEMS structures using only a vacuum evaporation process at room temperature, and we have succeeded in actual vibration power generation [6]. This technology can be integrated into existing semiconductor processes because the electret formation requires only room-temperature deposition, making it possible to monolithically integrate electret-type MEMS VEHs and electronic circuits on the same substrate. In addition, since the SAE surface potential is proportional to the film thickness, the amount of electricity generated can be further increased by increasing the thickness of the SAE film. Therefore, this technology is expected to accelerate the miniaturization, performance, and productivity improvement of MEMS environmental vibration power generation devices. Akinaga, “Recent advances and future prospects in energy harvesting technologies,” Jpn. J. Appl. Phys. 59 (2020) 110201.D. Mitcheson, E. M. Yeatman, G. K. Rao, A. S. Holmes, and T. C. Green, “Energy Harvesting from Human and Machine Motion for Wireless Electronic Devices” Proc. IEEE 96 (2008) 1457–1486.Suzuki, “Recent progress in MEMS electret generator for energy harvesting,” IEEJ Trans. Elec. Electron. Eng. 6 (2011) 101-111.Toshiyoshi, S. Ju, H. Honma, C.-H. Ji, and H. Fujita, “MEMS vibrational energy harvesters,” Sci. Technol. Adv. Mater. 20 (2019) 124-143.Tanaka, N. Matsuura, and H. Ishii, “Self-Assembled Electret for Vibration-Based Power Generator,” Sci. Rep. 10 (2020) 6648.Yamane, H. Kayaguchi, K. Kawashima, H. Ishii, and Y. Tanaka, “MEMS post-processed self-assembled electret for vibratory energy harvesters,” Appl. Phys. Lett. 119 (2021) 254102.

High-temperature adaptive through-silicon via with pyrolyzed carbon via-sealing plates for packaging 3D carbon nanostructure-based devices fabricated using C-MEMS

Through-silicon via (TSV) is a key packaging technology that facilitates the 2.5D/3D integration of microelectromechanical system (MEMS) devices. Among various MEMS technologies, C-MEMS enables micro/nanoscale 3D carbon structure manufacturing using high-temperature (600–1200 °C) pyrolysis. These high-temperature conditions limit the application of conventional TSV technologies to C-MEMS devices. This study presents a novel TSV with carbon via-sealing plates that are adaptable to C-MEMS device packaging. Via holes are drilled before integrating the MEMS device to protect the delicate micro/nanoscale structures. Moreover, the topside via inlet is sealed with a thin conductive pyrolyzed carbon plate to prevent the contamination of the via interior during the C-MEMS process and ensure an electrical connection between the devices and the vias. After integrating the C-MEMS devices, TSV fabrication is completed by coating the via inside with a metal layer from the wafer's bottom side, achieving a conductance per unit area of approximately 327 S/mm2 (via diameter = 33 μm, length = 100 μm). The applicability of the proposed wafer-level TSV technology to C-MEMS devices is then verified through the implementation of a suspended carbon nanowire-based gas sensor integrated with the developed TSV, which exhibits excellent signal transmission. Furthermore, the proposed TSV packaging technology can be applied to various micro/nanofabrication technologies because of its high-temperature/wet-process compatibility and cost-effective fabrication.

Energy efficient integrated MEMS neural network for simultaneous sensing and computing

Biological systems seamlessly combine multiple functions in lightweight and energy-efficient structures. Such capability in synthetic structures would be desirable in numerous engineering applications such as aerospace, robotics and wearable devices. Here we report an integrated silicon-based structure configured to sense, perform different classification algorithms, and produce an action signal within the same physical layer. The algorithms are coded in the mechanical responses of the sensing elements of multiple coupled micro-electro-mechanical systems (MEMS), simultaneously capturing acceleration measurements to produce an actuated signal. This all-in-one structure operates with zero circuitry and low power consumption. As a demonstration, we designed and fabricated a network of three MEMS neurons to successfully perform both simple signal classification and activity recognition problems (standing and sitting) with only 9.92 × 10−17 kWh and 17.79 × 10−19 kWh energy consumption per operation, respectively. Our approach will enable emergent technologies, such as wearable devices, to perform complex computations with power from a single battery charge.

Photoacoustic Imaging Based on Broadened Bandwidth Aluminum Nitride Piezoelectric Micromachined Ultrasound Transducers

This letter reports broadened bandwidth aluminum nitride (AlN) piezoelectric micromachined ultrasound transducers (BB-PMUT) for photoacoustic imaging (PAI). PMUT based on microelectromechanical systems (MEMS) technology has gained significant attention for PA endoscopic imaging inside colorectal and even blood vessels due to its miniature size, high sensitivity, and versatility. Broadened bandwidth, resulting from variable membrane cavity size during the fabrication process, provides benefits to imaging spatial resolution improvement. Moreover, AlN thin film is a nontoxic material, which makes it harmless for biomedical applications with potential of complementary metal-oxide semiconductor (CMOS) MEMS integration. In this letter, a BB-PMUT is designed and fabricated. The vibration modes, impedance, and bandwidth are analyzed. The BB-PMUT provides a wider fractional bandwidth (65%) for signal detection, which significantly increases the resolution compared with traditional single frequency PMUT design. We have conducted experimental validation on an agar sample to present the sensor's performance in improving axial resolution.

Electroplated Al Press Marking for Wafer-Level Bonding

Heterogeneous integration of micro-electro mechanical systems (MEMS) and complementary metal oxide semiconductor (CMOS) integrated circuits (ICs) by 3D stacking or wafer bonding is an emerging approach to advance the functionality of microdevices. Aluminum (Al) has been of interest as one of the wafer bonding materials due to its low cost and compatibility with CMOS processes. However, Al wafer bonding typically requires a high temperature of 450 C or more due to the stable native oxide which presents on the Al surface. In this study, a wafer bonding technique for heterogeneous integration using electroplated Al bonding frame is demonstrated. The bonding mechanism relies on the mechanical deformation of the electroplated Al bonding frame through a localized bonding pressure by the groove structures on the counter wafer, i.e., press marking. The native oxide on the surface was removed and a fresh Al surface at the bonding interface was released through such a large mechanical deformation. The wafer bonding was demonstrated at the bonding temperatures of 250–450 C. The influence of the bonding temperature to the quality of the bonded substrates was investigated. The bonding shear strength of 8–100 MPa was obtained, which is comparable with the other Al bonding techniques requiring high bonding temperature.

MEMS post-processed self-assembled electret for vibratory energy harvesters

Electret-based microelectromechanical system (MEMS) vibratory energy harvesting is a key technology for converting the mechanical energy of environmental vibrations into electricity. Unfortunately, conventional electret charging methods generally rely on high-voltage and high-temperature processes that present limitations to MEMS design and production. Here, we show a MEMS post-processed self-assembled electret (SAE) that enables the integration of electrets with MEMS vibratory devices via evaporation as a post-MEMS process. Owing to the spontaneous orientation of polar molecules, the surface potential of the SAE can build up at room temperature in a microscopic region without charging processes, which enhances the design and fabrication flexibility of electret-based MEMS energy harvesters. We develop a MEMS vibratory device followed by post-processing the SAE and confirm induced electrical currents caused by the electrical field of the SAE at the vibrational input. This SAE-based MEMS technology is a promising design guideline for highly integrated single-chip MEMS vibratory energy harvesters.

A Hybrid Fuzzy Decision Model for Evaluating MEMS and IC Integration Technologies.

Integrated devices incorporating MEMS (microelectromechanical systems) with IC (integrated circuit) components have been becoming increasingly important in the era of IoT (Internet of Things). In this study, a hybrid fuzzy MCDM (multi-criteria decision making) model was proposed to effectively evaluate alternative technologies that incorporate MEMS with IC components. This model, composed of the fuzzy AHP (analytic hierarchy process) and fuzzy VIKOR (VIseKriterijumska Optimizacija I Kompromisno Resenje) methods, solves the decision problem of how best to rank MEMS and IC integration technologies in a fuzzy environment. The six important criteria and the major five alternative technologies associated with our research themes were explored through literature review and expert investigations. The priority weights of criteria were derived using fuzzy AHP. After that, fuzzy VIKOR was deployed to rank alternatives. The empirical results show that development schedule and manufacturing capability are the two most important criteria and 3D (three-dimensional) SiP (system-in-package) and monolithic SoC (system-on-chip) are the top two favored technologies. The proposed fuzzy decision model could serve as a reference for the future strategic evaluation and selection of MEMS and IC integration technologies.

다중 IMU 센서와 연합형 필터 융합 기반의 GPS-free 위치 추정

Localization techniques based on the integration of MEMSs(Micro Electro Mechanical Systems) and GPS(Global Positioning System) have been widely used in various fields, including aerospace, biomedical, automotive, and robotics, among others. However, it is well known that GPS signals are weakened or blocked in tunnels, urban canyons, or indoor environments. A solution is to use multiple IMU(Inertial Measurement Unit) sensors. In this paper, we present a federated fusion algorithm for GPS-free localization using multiple MEMS IMUs. The federated filter uses a master fusion algorithm to combine the outputs of independent sensors so that the current position can be estimated. The proposed structure exploits a quaternion-based extended Kalman filter and a linear Kalman filter for attitude estimations and velocity estimations, respectively. The effectiveness of the proposed algorithm was demonstrated with MATLAB simulation.

A rapid technique to integrate micro-components on released MEMS dies using SU-8

This technical note reports a rapid technique to post-process and assemble micro-components onto dies including released movable microstructures. The method is applied to microelectromechanical systems (MEMS) chips that were fabricated using a commercial process, PolyMUMPs from MEMSCAP. It allows the assembly of a micro-polyhedron over released micromotors and ensures that the micromotors remain fully functional. The micro-polyhedrons are fabricated using laser ablation and are spin coated with a thin layer of SU-8, acting as a bonding layer. Then, they are bonded to chips that are placed on a 3D integration platform with a navigating mask, which protects the released structure during the subsequent assembly steps. The resulting micro-polyhedron-integrated-micromotors were tested and found to rotate similarly to devices without micro-polyhedrons, demonstrating that the developed procedure can be applied for post-release 3D integration of MEMS without significantly affecting the mechanical performance of the devices.

On-Chip Fully Integrated Field Emission Arrays for High-Voltage MEMS Applications

Vacuum-sealed fully integrated diode and triode field emission arrays based on Ti Spindt-type field emitters have been developed in a scalable, CMOS-compatible process directly on Si. Diode characterization in air demonstrates effective vacuum sealing and field emission conduction, with current drivability that scales with array size. Triode characterization in vacuum demonstrates gate-modulated field emission of the output current and highlights new effects observed in a fully integrated geometry with closely spaced electrodes. Demonstrating up to 200-V blocking voltage and similar magnitude punchthrough voltages, the arrays can be utilized as high-voltage devices in CMOS applications or with microelectromechanical systems (MEMS) technologies using post-CMOS MEMS integration techniques. Low-temperature measurements reveal areas of improvement for electrode isolation; combined with the use of improved cathode materials, these devices have the potential to be used in high-power applications.

Tunable Infrared Metamaterial Emitter for Gas Sensing Application.

We present an on-chip tunable infrared (IR) metamaterial emitter for gas sensing applications. The proposed emitter exhibits high electrical-thermal-optical efficiency, which can be realized by the integration of microelectromechanical system (MEMS) microheaters and IR metamaterials. According to the blackbody radiation law, high-efficiency IR radiation can be generated by driving a Direct Current (DC) bias voltage on a microheater. The MEMS microheater has a Peano-shaped microstructure, which exhibits great heating uniformity and high energy conversion efficiency. The implantation of a top metamaterial layer can narrow the bandwidth of the radiation spectrum from the microheater to perform wavelength-selective and narrow-band IR emission. A linear relationship between emission wavelengths and deformation ratios provides an effective approach to meet the requirement at different IR wavelengths by tailoring the suitable metamaterial pattern. The maximum radiated power of the proposed IR emitter is 85.0 µW. Furthermore, a tunable emission is achieved at a wavelength around 2.44 µm with a full-width at half-maximum of 0.38 µm, which is suitable for high-sensitivity gas sensing applications. This work provides a strategy for electro-thermal-optical devices to be used as sensors, emitters, and switches in the IR wavelength range.

Design and simulation of a novel RF-MEMS tunable narrow band LC filter in the UHF band

The design and simulation of a continuously tunable LC filter by integration of microelectromechanical systems (MEMS) is presented in this work. The proposed tunable LC filter consists of a tunable capacitor and four inductors. The novelties of this RF-MEMS circuit include the integration of both mechanical suspensions with electrical inductors and the electrostatic actuator with the electrical capacitor. This filter is designed based on standard MetalMUMPs fabrication process trademark of MEMSCAP. With this filter, the frequency range from 2.5 to 3 GHz is achieved in the UHF band. High-quality performance is determined based on the 3 dB-bandwidth with about 83 MHz. The insertion loss of − 2.8 dB and the return loss of − 17.58 dB up to − 21.43 dB are other bold characteristic points of this design. The power consumption is near-zero thanks to the use of the electrostatic actuator. Therefore this filter can be used in low power and high-performance RF tuning applications. The group delay of this filter is less than 2.5 ns and the quality factor is from 45 to 85.

A Review on Microscopic Visual Servoing for Micromanipulation Systems: Applications in Micromanufacturing, Biological Injection, and Nanosensor Assembly.

Micromanipulation is an interdisciplinary technology that integrates advanced knowledge of microscale/nanoscale science, mechanical engineering, electronic engineering, and control engineering. Over the past two decades, it has been widely applied in the fields of MEMS (microelectromechanical systems), bioengineering, and microdevice integration and manufacturing. Microvision servoing is the basic tool for enabling the automatic and precise micromanipulation of microscale/nanoscale entities. However, there are still many problems surrounding microvision servoing in theory and the application of this technology’s micromanipulation processes. This paper summarizes the research, development status, and practical applications of critical components of microvision servoing for micromanipulation, including geometric calibration, autofocus techniques, depth information, and visual servoing control. Suggestions for guiding future innovation and development in this field are also provided in this review.

In-Plane High-Sensitivity Capacitive Accelerometer in a 3-D CMOS-Compatible Surface Micromachining Process

This paper proposes a novel design for a 3-D, high-sensitivity, single-axis lateral capacitive accelerometer. The accelerometer utilizes the entire area of the sensor for both sensing and the proof mass, which mitigates the tradeoffs often needed in conventional 2-D designs. The accelerometer structure is optimized to target the highest possible performance. Innovative Z-shaped supporting beams are introduced to limit the vertical displacement within the transducer’s submicron gap. The design was fabricated in a novel 3-D complementary metal–oxide–semiconductor-compatible surface micromachining process. This process allows the use of non-conductive materials with attractive mechanical properties to build capacitive microelectromechanical system (MEMS) devices. Polyimide is used as a core structural layer which is combined with other materials such as silicon nitride or silicon carbide to build the final sensors. The photolithography steps are limited to four, and the number of materials used is also limited to four, in order to keep the process feasible. The overall thermal budget is 300 °C, which enables above-IC MEMS integration. While the used materials provide good results, this process is not limited to them, and other materials can be used, if needed. The fabricated accelerometer measures <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$500 \times 500 \,\,\mu \text{m}^{2}$ </tex-math></inline-formula> and achieves 58 fF/g sensitivity in a ±4 g range in an open-loop system, yielding a competitive sensitivity per unit area. [2018-0125]

Development of a microthrust balance and ion beam measurement system: Characterizing a dual-mode thruster for spacecraft

There is a rapid progression toward spacecraft miniaturization due to the prospect of reduced launch costs, the requirement for satellite constellations, and the integration of microelectromechanical systems (MEMS). Satellite propulsion is required for increased mission flexibility and orbital debris mitigation, but down-scaling of such devices has proven non-trivial. Some electrostatic thrusters are both challenging and promising given their increase in performance with small geometry, but the relatively low thrust produced through ion acceleration limits their mission applicability. For this reason, it may be desirable to produce thrusters that are able operate across a wide range of specific impulses, depending on maneuver time, thrust bit requirements, and several other factors that influence propulsion system selection. At RAPPEL, a bimodal thruster that can operate at high specific impulse with electrospray propulsion or high thrust using cold gas expansion has been developed. Inevitably, such a propulsion system comes with complications related to performance characterization. A novel and economical data acquisition system has been established to measure the performance of both modes in high vacuum. For the cold gas mode, a torsional thrust balance was built in-house to measure thrust levels between 1−15mN, and can be easily modified for lower ranges. The natural frequency of the thrust stand was measured to be 5.6Hz. The vacuum system sustained pressures below 5mbar while the cold gas nozzle operated, and 1.3×10−5mbar during electrospray operation. A 3-D printed linear cold gas nozzle was used to validate the thrust stand. Its thrust was close to 9mN at a mass flow rate of 20mg/s of nitrogen, producing a specific impulse of just under 45s. Due to the noise present in thrust stand measurements at the sub-mN force-level produced by electrosprays, the thrust stand was built to also accommodate a complementary ion beam current measurement system. The power processing unit, used to generate square-wave ±2500V signals using optodiodes, was built to operate a bipolar ionic liquid ion source (ILIS). The rise and fall times of the push/pull switch were close to 1ms and 30ms, respectively. The electrical power system used to operate the electrospray and measure its performance is examined in detail, followed by the results from validation of both data acquisition systems.

GNSS/MEMS IMU ultra‐tightly integrated navigation system based on dual‐loop NCO control method and cascaded channel filters

A coherent scheme of federated architecture for the ultra-tight integration of global navigation satellite system (GNSS) and MEMS (micro-electro-mechanical system) inertial measurement unit (IMU) is presented. Inside the receiver baseband, both the controls for code numerically controlled oscillator (NCO) and carrier NCO are designed. They are each composed of two parts, one part is derived from the navigation solutions of outer loop, and the other part is given on the basis of the channel pre-filter outputs from inner loop. Each tacking channel has two filters of cascaded structure, one is the traditional pre-filter which is used to achieve GNSS signal tracking errors, and the second one is an extractor which is constructed to extract navigation solution derivation errors from the designed NCO controls and the signal tracking errors. For the ultra-tight integration navigation filter, the receiver clock residual error model after compensating the receiver clock drift is derived in detail. Finally, semi-physical simulation environment of the proposed ultra-tight integration scheme is built and closed-loop experiment under high dynamics scenario is put forward. The simulation results show that the proposed integration scheme can stably and robustly track the GNSS signals, and can achieve accurate navigation solutions even in harsh cases.

Pole tilt monitoring system using MEMs accelerometer and BeagleBone Black

Electric pole could tilt in the event of heavy storms, soil erosion and object crashing onto poles, causing serious damages if they are not fixed before condition worsen. Therefore, to monitor the health of the electric pole, a system to monitor its tilting angle is needed. In this paper, for the first time, to the best of our knowledge, an integration of Micro Electro-Mechanical Systems (MEMs) accelerometer with BeagleBone Black microcomputer will be used to develop an electric pole tile angle monitoring system. The accuracy of measuring tilt angle using single axis accelerometer versus triple axis accelerometer and the effect of rolling on tilt angle reading using single axis accelerometer versus triple axis accelerometer will be presented. Three-axis accelerometer achieves greater accuracy as the percentage error of tilting and rolling for the three-axis accelerometer are better than the single-axis accelerometer.

MOS Integrated MEMS Structure for Bio-sensing

Biosensors are used to identify analytes such as DNA molecules, proteins or micro-organisms. These devices couple a biological recognition element (the probe) with a physical transducer to generate an observable signal. The work presented here shows a cantilever embedded MOSFET (Metal oxide semiconductor field effect transistor) structure for biosensing. The main features of the structure are piezoelectric actuation/sensing and MOSFET based readout making it suitable for parallel array operation in conjunction with phase coding schemes. The integration of MEMS (Micro electro mechanical systems) structure with CMOS (Complementary MOS) fabrication process also leads to realizability of the system on a chip. The proposed structure has detection capability in sub-picogram range. A CMOS compatible fabrication process flow has also been suggested in this paper along with two different phase coding schemes for noise cancellation.

Interactive Design of MEMS Varactors With High Accuracy and Application in an Ultralow Noise MEMS-Based RF VCO

The monolithic integration of microelectromechanical systems (MEMS) varactors into the backend of line metal stack of a state of the art semiconductor process is an attractive alternative to the field effect transistor or bipolar transistor varactors for continuous frequency tuning of ultralow phase noise voltage-controlled oscillators (VCOs). An efficient design of MEMS varactors according to application-specific demands requires a deep insight into the electromechanical and electromagnetic (EM) device properties and an accurate prediction of the varactor phase noise contribution to the overall phase noise of the MEMS-based VCO. Generally, MEMS varactors are designed using a combination of finite-element method and EM softwares. Due to the large computational and time effort, the required deep insight into the MEMS device is hard to achieve. This paper presents interactive design methodologies to predict the electromechanical, EM, and the phase noise properties of a MEMS varactor with high accuracy. These methodologies are verified by fabricated MEMS varactors and an experimental MEMS-based VCO with continuous frequency tuning.