MEMS 開発における解析支援技術

Summary form only given. MEMS (micro electro mechanical systems) and NEMS (nano electro mechanical systems ) have been developed based on silicon micromachining for practical applications. Sophisticated MEMS device used as a two-axis rotating gyroscope for navigation control system was developed. A silicon ring rotor is electrostatically levitated and rotated at 12,000rpm. The 4mm diameter ring rotor and 5m radial gap between rotor and electrode were fabricated using deep RIE (reactive ion etching) and the rotor is sandwiched between two glasses which have control electrodes. The levitation is actively controlled by force balancing in all directions using a capacitive displacement sensing and an electrostatic actuation. The rotation is based on the principle of a variable capacitance motor. The function as the high performance gyroscope and accelerometer were successfully demonstrated. Small size relays for high frequency operation are required for LSI tester. MEMS relay which uses a thermal bimetal actuator for making contact to multi-springs was developed. The springs have electrical connections to the backside using electrical feedthrough in a glass, which results in high frequency response up to 20 GHz. Excellent reliability more than 10/sup 7/ cycles was achieved owing to the hermetic scaling performed by wafer level packaging using anodic bonding of glass and silicon. Multiprobe data storage has been developed. High density electrical feedthrough in a glass was used for the interconnection to its control IC. Electrical rewritable recording on a conductive polymer film and a ferroelectric recording were performed. Electron field emitter array for the purpose of multi-column electron beam lithography was developed using carbon nano tube emitter and electrostatic lens for focusing. It was evident that hydrogen covered carbon nano tube reduces the work function for field emission and the emission noise. Highly sensitive sensors using micro-nano structures such as thin cantilevers have been developed. Bow-tie antenna for near field optical microscope and magnetic resonant force microscope will be presented.

본 논문에서는 MEMS(Micro Electro Mechanical System) 가속도센서를 위한 CMOS readout 회로를 설계하였다. 설계된 CMOS readout 회로는 MEMS 가속도 센서, 커패시턴스-전압 변환기(CVC), 그리고 2차 스위치드 커패시터 <TEX>${\Sigma}{\Delta}$</TEX> 변조기로 구성된다. 이들 회로에는 저주파 잡음과 오프셋을 감소시키기 위한 correlated-double-sampling(CDS)와 chopper-stabilization(CHS) 기법이 적용되었다. 설계 결과 CVC는 150mV/g의 민감도와 0.15%의 비선형성을 갖는다. 설계된 <TEX>${\Sigma}{\Delta}$</TEX> 변조기는 입력전압 진폭이 100mV가 증가할 때, 출력의 듀티 싸이클은 10%씩 증가하며, 0.45%의 비선형성을 갖는다. 전체 회로의 민감도는 150mV/g이며, 전력소모는 5.6mW이다. 제안된 회로는 CMOS 0.35um 공정을 이용하여 설계하였고, 공급 전압은 3.3V이며, 동작 주파수는 2MHz이다. 설계된 칩의 크기는 PAD를 포함하여 <TEX>$0.96mm{\times}0.85mm$</TEX>이다. This paper presents a CMOS readout circuit for MEMS(Micro Electro Mechanical System) acceleration sensors. It consists of a MEMS accelerometer, a capacitance to voltage converter(CVC) and a second-order switched-capacitor <TEX>${\Sigma}{\Delta}$</TEX> modulator. Correlated-double-sampling(CDS) and chopper-stabilization(CHS) techniques are used in the CVC and <TEX>${\Sigma}{\Delta}$</TEX> modulator to reduce the low-frequency noise and DC offset. The sensitivity of the designed CVC is 150mV/g and its non-linearity is 0.15%. The duty cycle of the designed <TEX>${\Sigma}{\Delta}$</TEX> modulator output increases about 10% when the input voltage amplitude increases by 100mV, and the modulator's non-linearity is 0.45%. The total sensitivity is 150mV/g and the power consumption is 5.6mW. The proposed circuit is designed in a 0.35um CMOS process with a supply voltage of 3.3V and a operating frequency of 2MHz. The size of the designed chip including PADs is <TEX>$0.96mm{\times}0.85mm$</TEX>.

A major challenge in Micro Electro Mechanical System (MEMS) education, is dealing with the multi-disciplinary nature of the field, which may include solid mechanics, fluid mechanics, electronics etc. Instead of teaching these subjects independently, we link this multi-disciplinary knowledge domain by the second-order system equation. In addition, the related CAD software is introduced during the explanation of the second order system equation. This teaching method makes the student understand MEMS more quickly and systemically, and if needed, they can seek the related knowledge and study further on their own.

Micro electro mechanical systems (MEMS) have experienced an explosive growth over the past few years driven mainly by its physical properties and its promising technological applications in many different fields, particularly in space and Radio Frequency (RF) systems. MEMS technology exhibits greater advantages over the existing semiconductor switches. In this paper, electro-thermal performances of a two hot arms actuator MEMS switch have been investigated. The switch is designed using CST Microwave Studio. Some mathematical equations have been developed to see the temperature distribution of the hot arms as voltage applied on it. Based on this thermal distribution, the linear thermal expansion of the hot arms and the air gap used in this switch is expressed mathematically. The developed equations have been solved and analyzed using the MATLAB software. This analysis shows that this MEMS switch has a wider range of linear operation and has extremely higher breakdown voltage.

Diversity of application fields and properties of new materials generate new failure mechanisms in Micro electro Mechanical Systems (MEMS). Now if we take into account the lessons from the past in microelectronics, we note that failure analysis played a major rule not only in development time reduction but also in qualification and reliability evaluation Most of the researches which have been done in MEMS reliability are about new material properties and fabrication technologies. Only a few fault detection methods have been introduced for fault detection in MEMS. Some of these methods can be used only for special MEMS. Additionally most of them need a precise model of system. In this paper a new intelligent method is proposed for fault detection in MEMS. In addition some parts of proposed neural network are changed in order to implement it as a BIST mechanism.

MEMS (Micro Electro Mechanical Systems) technology is becoming a crucial enabling technology for optical and RF telecommunication applications due to the performance, cost and integration advantages. All-optical switches and silicon optical benches for optical network systems and RF MEMS components such as RF MEMS switches, tunable capacitors, high Q inductors, and thin film bulk acoustic resonators for miniaturized single chip RF transceivers are discussed. Despite all the promising aspects, practical problems to be addressed for successful commercialization are not trivial. By reviewing optical and RF MEMS research activities and some of the implementation examples, key success factors of MEMS components for the commercialization are discussed.

Non-conventional or advanced machining techniques are becoming the enabling fabrication techniques for many emerging fields including Micro Electro Mechanical Systems (MEMS) or Microsystems Technology (MST). The processes used for MEMS fabrication include standard semiconductor fabrication processes and emerging micromachining techniques. Among the challenges emerging from the manufacturing of MEMS devices, post-processing seems to be one of the most sensitive issues. The non-traditional common post-processing techniques are bulk micromachining and surface micromachining. It has been a challenge for MEMS designers to develop a micromachining technique that is compatible with IC (Integrated Circuits) processes and also capable of making MEMS structures through both bulk and surface micromachining with acceptable surface roughness requirements. The selected micromachining process should not affect the integrity of the free standing structure due to the reduced selectivity and aggressive etch of the adjacent electronic circuitry. Moreover, the integrity of the released structure, the dynamic properties as well as the electrostatic characteristics, are strongly dependent on the achieved roughness of the surfaces produced by the etching process. Hence, this paper presents the surface roughness characterisation of gas phase micromachining with XeF2 that is suitable for fabricating integrated MEMS with both micromechanical and microelectronics components. This paper also presents some fabricated microsystems using this process.

In this paper, we report monolithic integration of MEMS (micro electro mechanical systems) actuators and high-voltage driver circuits into a silicon chip. Driver circuits of up to 40 V were prepared on an 8-/spl mu/m-thick SOI (silicon-on-insulator) wafer by the DMOS (double-diffused metal oxide semiconductor) processes, after which MEMS electrostatic actuators were integrated into an identical SOI layer by post-processing using DRIE (deep reactive ion etching). This technique opens up a new way of high-voltage ASIC (application specific integrated circuit) for MEMS designer. As a prototype application model, we have developed microlens optical scanners and other elementary MEMS electrostatic actuators with multi-channel driver circuits.

Inertial Measurement Units (IMUs) using MEMS (Micro Electro Mechanical Systems) sensors, to detect rotation and acceleration, are extremely sensitive to vibration and shock. Because these IMUs are used in aircraft, missiles, and even in gun launched projectiles, the vibration and shock levels can be extremely high. We have been successful in designing isolation systems that protect the MEMS sensors from these harsh environments. These isolation systems attenuate the shock and vibration in frequency ranges that would otherwise degrade IMU performance and even damage the sensors. In designing an isolation system, for an IMU with MEMS devices, the designer must first acquire a good definition of the shock and vibration environment to which the IMU will be exposed. Then the designer must determine the frequencies and levels to which the MEMS devices are sensitive. Finally the designer must have knowledge of IMU properties such as resonant frequencies, mass properties, clock frequencies, etc. By knowing all of this information, and how it affects IMU performance, the designer can determine the proper parameters for the isolation system. A well designed isolation system using these parameters will be capable of protecting the MEMS devices while maintaining IMU performance through out all specified environments.

This paper presents pedagogical issues and experience in teaching the introduction to MEMS (Micro Electro-Mechanical System) course to a group of engineering students, primarily Mechanical Engineering students. The paper draws upon the author’s experience in teaching the MEMS course. Since MEMS is highly inter-disciplinary, the presentation of various relevant topics in MEMS, which may or may not be familiar to a mechanical engineering student, is of critical importance. These topics vary from physics, electrochemistry, materials, and electronic engineering, to various areas in mechanical engineering. An integrated approach for the presentation of subjects, especially in design and fabrication, was found to be very helpful. Moreover, the paradigm shift from the macro world, that most students are familiar and comfortable with, to the micro world is significant and needs to be emphasized. The author found the concept of scaling law, when shifting to the micro world, to be essential in the presentation of MEMS to engineering students in order for them to comprehend the size factor in MEMS. In addition, understanding and appreciation of the strengths and limitations of MEMS are also critical in learning MEMS. Finally, a good textbook will facilitate the learning process of such vast subject. A bibliography of useful textbooks and reference books used by the author will be listed at the end of this paper.

In this paper, we discuss how finite element analysis (FEA) can be used to simulate certain micro electro mechanical systems (MEMS). The mechanical behavior of many MEMS devices is a direct result of non-mechanical physical phenomena, such as electrostatics, electromagnetics or heat transfer. This coupling of mechanical behavior with other physical effects, combined with considerations associated with their small dimensions, poses significant challenges to the analysis of MEMS. These challenges can be met by FEA software capable of performing multiphysics analysis with no limitations on the dimensions of the objects in a model. With such software at their disposal, engineers can use the results of their simulations to design MEMS devices.

With recent development in wireless communication and Micro Electro Mechanical Systems (MEMS) technology, it becomes easier to monitor rotating machinery conditions by mounting compact wireless MEMS accelerometers directly on the rotor. This has the potential to provide more accurate dynamic characteristics of the rotating machine and hence achieving high monitoring performance. In this paper, a tiny MEMS accelerometer together with a battery powered microcontroller is mounted on the flywheel to acquire the on-rotor accelerations of a two-stage reciprocating compressor. The measured acceleration data is streamed to a host computer wirelessly via Bluetooth Low Energy (BLE) module. The true tangential acceleration is reconstructed by combining two orthogonal outputs of the sensor, which contain gravitational accelerations. To evaluate the performance of the wireless sensor, three different fault conditions including intercooler leakage, second stage discharge valve leakage and asymmetric stator winding of the motor driver are simulated individually on the compressor test rig. To confirm the wireless sensor performance, an incremental optical encoder was installed on the compressor flywheel to acquire the Instantaneous Angular Speed (IAS) signal for comparison with signals from the wireless sensor. The experimental results show that the running status of the compressor can be remotely monitored, allowing different leakages and motor faults to be diagnosed based on the tangential acceleration reconstructed from a wireless on-rotor 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.

The dramatic progress in integrated circuit technology has led to a huge increase of achievable digital computing power not accompanied by a parallel evolution in the capability to interface the real world that is “analog ” and not digital. This capability is fundamental in manyproducts and represents the driving force in [heir evolufion. Technologies like Bipolar-CMOS-DMOS (BCD), available since many years to realize Power ICs, appear to be more suitable than the pure CMOS to play the role of building analog interfaces. An emerging frontier of analog interfaces is represented by Micro Electro Mechanical Systems (MEMS) where the manufacturing technology developed in many years of microelectronics is being applied to micro-machined silicon. creating new solutions hat combine electrical, mechanical, fluidic and optical elements. In this paper an overview of BCD technology trends and of new applications of MEMS devices will be examined.

RF MEMS (radio frequency micro electro mechanical systems) technology holds great promise for wireless communication and sensor systems. Excellent MEMS switching devices have recently been developed, but because of packaging problems, no commercial integrated product exists. The objective of the ongoing work at CFD Research Corporation (CFDRC) and Morgan Research Corporation (MORGAN) is to develop novel packaging concepts, design tools, and demonstrated RF MEMS packaged devices for high frequency applications.