Microelectromechanical Systems Products Research Articles

An Artificial-Intelligence-Driven Predictive Model for Surface Defect Detections in Medical MEMS.

With the advancement of miniaturization in electronics and the ubiquity of micro-electro-mechanical systems (MEMS) in different applications including computing, sensing and medical apparatus, the importance of increasing production yields and ensuring the quality standard of products has become an important focus in manufacturing. Hence, the need for high-accuracy and automatic defect detection in the early phases of MEMS production has been recognized. This not only eliminates human interaction in the defect detection process, but also saves raw material and labor required. This research developed an automated defects recognition (ADR) system using a unique plenoptic camera capable of detecting surface defects of MEMS wafers using a machine-learning approach. The developed algorithm could be applied at any stage of the production process detecting defects at both entire MEMS wafer and single component scale. The developed system showed an F1 score of 0.81 U on average for true positive defect detection, with a processing time of 18 s for each image based on 6 validation sample images including 371 labels.

Automated data monitoring of MEMS cleanroom parametric requirements

<p>Cleanroom parameters such as temperature, relative humidity and particle count are vital in maintaining cleanliness. People and machines working inside the cleanroom are main contributors for the sudden changes of the separameters. Measurements and monitoring of these parameters are therefore necessary to reduce rejects and downtime in the production of micro-electro-mechanical systems (MEMS). This paper presents a method of developmentof an automated data monitoring of MEMS cleanroom parametric requirements. The prototype developed uses DHT11 sensor and Sharp dust sensor for measuring the temperature, humidity and particle count respectively which are displayed in an LCD display. These parameters are recorded through a data logger for analysis and control. Additionally, agraphical user interface was also developed using visual studio for the working personnel and for supervisory monitoring and control. As a result, the possible quality compromise in the production of MEMS is detected when the monitored parameters are beyond the range.</p>

Ni–P electroless on nonconductive substrates as metal deposition process for MEMS fabrication

During past decades Micro Electro Mechanical Systems (MEMS) have been developed and presented in the market. It is important to find new processes and methods to facilitate MEMS production regarding to growing demand of MEMS devices in IoT, smart and intelligent systems, consumer electronics and medical applications. In this paper, Ni–P layer deposition on insulator substrates is presented. The layer is deposited based on chemical reactions in electroless process. There is a similar method, electroplating, for metal deposition but the substrate must be conductor to transfer electrons and provide essential conditions for electroplating. Electroplating process is not applicable for insulator substrates, while the proposed electroless process can be useful. Different steps, materials, conditions and experimental results for Ni–P electroless are presented. A fabrication process for DC contact RF MEMS switch based on Ni–P electroless is introduced, too. As one advantage of this process, Ni and Ni–P are ferromagnetic material and any suspended structure can be actuated by magnetic fields. It will be beneficial when applying other actuation mechanisms like electrostatic, thermal or piezoelectric are difficult or impossible to be applied.

3D Printed MEMS Technology-Recent Developments and Applications.

Microelectromechanical systems (MEMS) are of high interest for recent electronic applications. Their applications range from medicine to measurement technology, from microfluidics to the Internet of Things (IoT). In many cases, MEMS elements serve as sensors or actuators, e.g., in recent mobile phones, but also in future autonomously driving cars. Most MEMS elements are based on silicon, which is not deformed plastically under a load, as opposed to metals. While highly sophisticated solutions were already found for diverse MEMS sensors, actuators, and other elements, MEMS fabrication is less standardized than pure microelectronics, which sometimes blocks new ideas. One of the possibilities to overcome this problem may be the 3D printing approach. While most 3D printing technologies do not offer sufficient resolution for MEMS production, and many of the common 3D printing materials cannot be used for this application, there are still niches in which the 3D printing of MEMS enables producing new structures and thus creating elements for new applications, or the faster and less expensive production of common systems. Here, we give an overview of the most recent developments and applications in 3D printing of MEMS.

Validating the Critical Point of Spontaneous Parametric Downconversion for Over 600 Scanning MEMS Micromirrors on Wafer Level

Sensors and actuators based on resonant micro-electro-mechanical systems (MEMS), such as scanning micro mirrors, are well-established in automotive and consumer products. As the areas of application broaden, the requirements for the MEMS are increasing. Devices outside of the performance specifications have to be rejected which is costly due to the high processing times of MEMS technologies. In particular, nonlinear system behavior is often found to cause unexpected device failure or performance issues. Thus, accurate simulation or rather system models which account for nonlinear sensor dynamics can not only increase process yield, but more importantly, lead to a comprehensive understanding of the underlying physics and to improved MEMS design. We have studied [1] the possibility of a rather drastic device failure induced by nonlinearities on the example of a resonant scanning MEMS micro mirror. On the level of a few selected chips, we have carefully measured the complex nonlinear system behavior and modeled it by a nonlinear mode-coupling phenomenon known as spontaneous parametric down-conversion (SPDC). The most intriguing feature of SPDC is the sudden change from a rather linear to a nonlinear system behavior at the critical oscillation amplitude. However, the threshold only lies within the range of the mirror's operational amplitude, if certain frequency resonance conditions regarding the mechanical modes are met. Thus, the critical amplitude strongly depends on the frequency spectrum of the MEMS design which in turn is largely influenced by fabrication imperfections. We validate the dependence of the critical amplitude on the resonance condition by measuring it for over 600 micro mirrors on wafer-level. Our work does not only validate the theory of SPDC with measurements on such a large scale, but also demonstrates modeling strategies which are essential for MEMS product design.

Empirical High Cycle Fatigue Assessment Model of MEMS Devices

Abstract Many microelectromechanical systems (MEMS) devices generate large deflections and stresses under some severe loads, and this cumulative stress often causes structural fatigue when applying high cyclic loads. It affects the reliability and quality of the product and can easily damage structures in harsh environments. For example, accelerometers and gyroscopes in motion sensors always combine a movable mass component with a bending or torsion spring, which can severely deform their structure at some large accelerations or angular accelerations. After this high cycle of deformation, the spring structure will be damaged and cause device failure, we call this failure mode high cycle fatigue (HCF). This is very common for MEMS products, but it is difficult for designers to predict it at design stage. To prevent early fatigue problems and reduce product development time, we developed a simulation process and empirical prediction model to help designers predict HCF and improve fatigue strength of moving structures used in MEMS devices. In this study, a bending and a torsion beam are used as test vehicles. A combination of dynamic and electromechanical coupling simulations was developed and applied to analyze the effects of frequency under HCF testing. The test structures were fabricated using silicon-on-insulator (SOI) MEMS technique and these test structures were used to validate empirical life prediction equation developed in this research. The frequency effect of HCF was also to be included in the developed prediction model. Based on the test results, the accuracy of the empirical prediction equation is improved by including frequency effect.

MEMS at Bosch – Si plasma etch success story, history, applications, and products

MEMS (micro electro mechanical systems) are tiny mechanical structures in the micrometer range combined with an ASIC (application specific integrated circuit). MEMS at Bosch look back on more than 25 years of development and production and started based on KOH wet‐etching with restrictions in geometry due to the crystal‐oriented etch behavior of KOH. Based on several years of experience in plasma processing and the availability of new prototype plasma sources, the “Bosch Process,” a three‐dimensional plasma etch process for silicon was invented. This is the key enabler for today's huge variety of MEMS products in our every day life.

Nondestructive surface profiling of hidden MEMS using an infrared low-coherence interferometric microscope

There are a wide range of applications for micro-electro-mechanical systems (MEMS). The automotive and consumer market is the strongest driver for the growing MEMS industry. A 100 % test of MEMS is particularly necessary since these are often used for safety-related purposes such as the ESP (Electronic Stability Program) system. The production of MEMS is a fully automated process that generates 90 % of the costs during the packaging and dicing steps. Nowadays, an electrical test is carried out on each individual MEMS component before these steps. However, after encapsulation, MEMS are opaque to visible light and other defects cannot be detected. Therefore, we apply an infrared low-coherence interferometer for the topography measurement of those hidden structures. A lock-in algorithm-based method is shown to calculate the object height and to reduce ghost steps due to the -unambiguity. Finally, measurements of different MEMS-based sensors are presented.

Uncertainty Quantification of Microstructure-Governed Properties of Polysilicon MEMS.

In this paper, we investigate the stochastic effects of the microstructure of polysilicon films on the overall response of microelectromechanical systems (MEMS). A device for on-chip testing has been purposely designed so as to maximize, in compliance with the production process, its sensitivity to fluctuations of the microstructural properties; as a side effect, its sensitivity to geometrical imperfections linked to the etching process has also been enhanced. A reduced-order, coupled electromechanical model of the device is developed and an identification procedure, based on a genetic algorithm, is finally adopted to tune the parameters ruling microstructural and geometrical uncertainties. Besides an initial geometrical imperfection that can be considered specimen-dependent due to its scattering, the proposed procedure has allowed identifying an average value of the effective polysilicon Young’s modulus amounting to 140 GPa, and of the over-etch depth with respect to the target geometry layout amounting to m. The procedure has been therefore shown to be able to assess how the studied stochastic effects are linked to the scattering of the measured input–output transfer function of the device under standard working conditions. With a continuous trend in miniaturization induced by the mass production of MEMS, this study can provide information on how to handle the foreseen growth of such scattering.

A SysML Based Conceptual Framework for System Level Design in Micromechanical Electrical System

The design of a microelectromechanical systems (MEMS) is a hard task due to the complexity of the systems. Model driven engineering approaches, like modelbased systems engineering (MBSE) and SysML provide a way for the systematic design of MEMS. However, the conceptual design of MEMS is an iterative and multidisciplinary issue, which makes a long time for design space exploration. In this study, a SysML based method is proposed to implement the system design and simulation models of MEMS product. The design process reaches from requirements specification to the detailed modeling and simulation of the system. This proposed method was illustrated by designing a high-resistivity silicon based patch antenna which is used as RF front in a Beidou receiver. The results showed that the SysML based information from the different diagrams of Beidou receiver and the multidisciplinary design phases can be connected and used during the development of new MEMS product, resulting in shortened development cycles.

Glass Imprint Templates by Spark Assisted Chemical Engraving for Microfabrication by Hot Embossing

As the field of microelectromechanical systems (MEMS) matures, new demands are being placed on the microfabrication of complex architectures in robust materials, such as hard plastics. Iterative design optimization in a timely manner—rapid prototyping—places challenges on template fabrication, for methods such as injection moulding and hot embossing. In this paper, we demonstrate the possibility of using spark assisted chemical engraving (SACE) to produce micro patterned glass templates. The direct, write-based approach enabled the facile fabrication of smooth microfeatures with variations in all three-dimensions, which could be replicated by hot embossing different thermoplastics. As a proof of principle, we demonstrated the technique for a high glass transition temperature polycarbonate. Good fidelity over more than 10 cycles provides evidence that the approach is viable for rapid prototyping and has the potential to satisfy commercial-grade production at medium-level output volumes. Glass imprint templates showed no degradation after use, but care must be taken due to brittleness. The technique has the potential to advance microfabrication needs in academia and could be used by MEMS product developers.

Test Method for Contactless On-Wafer MEMS Characterization and Production Monitoring

Microelectromechanical systems (MEMS) are widely utilized in various devices ranging from consumer electronics and medical devices to modern industrial equipment. Their fabrication with the help of semiconductor technology leads to very low cost devices. However, the fabrication test systems need to be extended to cover the mechanical domain of MEMS devices. Therefore, this paper presents a new concept that is able to evaluate the stiffness of silicon membranes in MEMS microphones. Due to the use of electromagnetic waves in the millimeter-wave spectrum, an optical line of sight is not necessary. The test setup can be parallelized to improve the throughput, and it can gain important feedback information to tune operating parameters of the production process.

Application of microelectromechanical sensors in the integrated navigation system of ground transport and agricultural technological vehicle

The questions of assessment of achievable performance values of the integrated inertial-satellite navigation system complexed with odometer sensor and used for ground transport and agricultural technological vehicle are considered. Construction of relatively cheap modern navigation systems for ground transport and agricultural technological vehicles is provided by integrating diverse navigation systems, which include inertial-satellite systems that combine into a single hardware system the inertial and satellite modules. Achievable accuracy of gaining the navigation parameters is achieved by using special algorithms for processing of measurement information in combination with complexion of the system with an external source of additional information, where odometer sensor belongs. The most promising sensors are sensors, built using the technology of production of microelectromechanical systems - MEMS / MEMC (Micro-Electro Mechanical Systems). The navigation systems based on MEMS sensors have several advantages. The main advantages are small weight and size characteristics (volume less 1sm3, and weighs less than 1 gram), low power consumption, high reliability, resistance to vibro-impact loads (up to 2000g), easy integration of sensors and electronic modules of the navigation system, low cost. The main disadvantage is the need for the synthesis of complex algorithms of processing of measuring information to obtain the desired accuracy of the estimate of navigation parameters. The navigation system, where as MEMS sensors were used gyroscopes ADXRS-150 in conjunction with accelerometers ADXL-210 manufactured by Analog Devices, was considered. The main design and technological characteristics of sensors were shown, the selection criteria for sensors were formulated, technical and economic effect assessment of the use of MEMS in the navigation system is provided. The practical importance has the estimation of achievable accuracy characteristics of system under actual operating conditions. The paper presents the results of field tests of the navigation system based on MEMS sensors and designed for forklift carrying out transportation in the sea port. The results of experimental studies confirmed the effectiveness of the MEMS application as a sensing element of inertial-satellite navigation system of ground transport and agricultural technological vehicle that creates the foundation for the new high-tech developments.

Low-Temperature Aluminum-Aluminum Wafer Bonding

Aluminum-aluminum thermo-compression wafer bonding is becoming increasingly important in the production of microelectromechanical systems (MEMS) devices. As the chemically highly stable aluminum oxide layer acts as a diffusion barrier between the two aluminum metallization layers, up to now the process has required bonding temperatures of 300°C or more. By using the EVG®580 ComBond® system, in which a surface treatment and subsequent wafer bonding are both performed in a high vacuum cluster, for the first time successful Al-Al wafer bonding was possible at a temperature of 100°C. The bonded interfaces of blank Al wafers and Al wafers with patterned frames were characterized using C-mode scanning acoustic microscopy (C-SAM) and transmission electron microscopy (TEM) as well as dicing yield and pull tests representative for the bonding strength. The investigations revealed areas of oxide-free, atomic contact at the Al-Al bonded interface.

Photomechanical Ablation of 304L Stainless Steel, Aluminum Oxide (Al<sub>2</sub>O<sub>3</sub>) Thin Film, and Pure Silicon

Recently, a number of studies have focused on micro-manufacturing processes, which find use in a variety of applications, including the production of microelectromechanical systems (MEMS). The process of ablation in materials is mainly governed by the laser source and scanning speed. The rate of material ablation is influenced by chemical and physical properties. In this work, the energy from a CO2 laser was used to ablate three different materials, namely, stainless steel 304L, a thin film of amorphous aluminum oxide (Al2O3), and pure silicon, due to their wide use in MEMS technology. The laser parameters used were an average power of 18 W and a spot size of 200 μm. The maximum depth during the photomechanical ablation process was 72 μm in the case of 304L steel and 77 μm in the case of the Al2O3 thin film for a scan rate of 24 mm/min. However, at the same scan rate, silicon did not exhibit any penetration. As expected, while increasing scanning speed the ablation depth decreases due to reduced interaction time between laser and material. The theoretical ytterbium fiber laser shown in this study can thus be employed in the manufacturing of a wide variety of materials used in the production of MEMS as well as those used in clean energy technologies.

Integrating MEMS and ICs

The majority of microelectromechanical system (MEMS) devices must be combined with integrated circuits (ICs) for operation in larger electronic systems. While MEMS transducers sense or control physical, optical or chemical quantities, ICs typically provide functionalities related to the signals of these transducers, such as analog-to-digital conversion, amplification, filtering and information processing as well as communication between the MEMS transducer and the outside world. Thus, the vast majority of commercial MEMS products, such as accelerometers, gyroscopes and micro-mirror arrays, are integrated and packaged together with ICs. There are a variety of possible methods of integrating and packaging MEMS and IC components, and the technology of choice strongly depends on the device, the field of application and the commercial requirements. In this review paper, traditional as well as innovative and emerging approaches to MEMS and IC integration are reviewed. These include approaches based on the hybrid integration of multiple chips (multi-chip solutions) as well as system-on-chip solutions based on wafer-level monolithic integration and heterogeneous integration techniques. These are important technological building blocks for the ‘More-Than-Moore’ paradigm described in the International Technology Roadmap for Semiconductors. In this paper, the various approaches are categorized in a coherent manner, their merits are discussed, and suitable application areas and implementations are critically investigated. The implications of the different MEMS and IC integration approaches for packaging, testing and final system costs are reviewed. Combining micrometer-sized movable components and electronic devices adds functionality to integrated circuits. Microelectromechanical systems (MEMS) are flexible transducers that can measure acceleration or the presence of chemicals, to give just two examples. Andreas C. Fischer and colleagues from the KTH Royal Institute of Technology in Sweden review both traditional and emerging approaches forplacing MEMS on the same platform as the electronics needed to process the electrical signals they produce, thus producing smaller and cheaper components. Such approaches include creating the MEMS and electronics on separate substrates and then combining them, or developing fabrication processes that are able to define both types of device on the same substrate. The researchers conclude that the most cost-effective solution depends on the specific application.

Integration of PVDF (Polyvinylidene Fluoride) in MEMS Production

The combination of materials with new processing setups often leads to new opportunities in well-known technologies. Polyvinylidene fluoride (PVDF) is widely used because of its chemical resistance and thermal properties. Usually, it is shaped by spray casting to produce plumber components. PVDF is also known for its piezoelectric behavior, which can be measured in PVDF films, like it was shown by Kawai [1] and others long ago. Nevertheless, piezoelectric materials are used in the production of micro-electro-mechanical systems (MEMS), PVDF is not. Therefore, the main idea is to evaluate the possibilities and afterwards develop a way to integrate PVDF into MEMS product for example as membranes with piezoelectric behavior. It has been observed, that PVDF films which were exposed to an electrical field during drying show a higher piezoelectric behavior than those which were not or have been polarized by an electric field after drying the film.

Recent developments in MEMS sensors: a review of applications, markets and technologies

Purpose – The purpose of this paper is to provide an introduction to micro-electromechanical systems (MEMS) sensors and their commercialisation and to consider a number of recent applications, markets and product developments. Design/methodology/approach – Following an introduction and a brief historical background to MEMS sensors and their commercialisation, the paper describes a selection of recent applications, with an emphasis on high volume uses. Various market figures are included to place these applications in a commercial context. Sensors for both physical variables and gases are considered. Findings – The paper shows that MEMS sensor applications continue to grow in the automotive, consumer electronics and other industries, which consume many millions of sensors annually. New product developments reflect the requirement for smaller and lower-cost sensors with enhanced performance and greater functionality. Markets for physical sensors dominate but MEMS technology is making progressive inroads in the gas sensing field. Originality/value – This article provides a timely review of a selection of recent MEMS sensor applications, markets and product developments.

Process Parameter Effects on Dimensional Accuracy of Micro-Injection Moulded Part

Micro-injection moulding is becoming increasingly important among the available processes for production of micro-electromechanical systems (MEMS) and microsystem technologies (MSTs), and higher number of polymer products is being manufactured by this process. Due to the sensitive nature of applications of this process, such as medical and aerospace applications, achieving high quality parts with high dimensional accuracy is crucial. In this work, a design of experiment (DoE) approach is used. The aim is to study the effects of three process parameters which are commonly used for research in this domain, on the dimensional accuracy of microchannels with different sizes; they are injection velocity, injection pressure, and melt temperature. The study focuses on two polymers, polyoxymethylene (POM) and liquid crystal polymer (LCP). Experimental results showed that higher melt temperature and injection pressure resulted in higher dimensional accuracy. Nevertheless, high settings for the three parameters resulted in higher percentage of flash in most cases. In conclusion, the most influential factors were shown to be melt temperature and injection pressure.

Design and modelling of silicon MEMS accelerometer

In developing micro electro mechanical systems (MEMS), finite element analysis (FEA) is usually relied upon to study these micro-structures in determining stress, deformation, resonance, temperature distribution, electromagnetic interference, and electrical properties. With this kind of approach, the performance of the devices can be easily expanded, as well as reducing the time and cost of MEMS production. This paper focuses on the modelling of silicon MEMS accelerometer in an attempt to design a surface micro-machined accelerometer that satisfies certain pre-determined specifications.