低功耗电阻型MEMS半导体气体传感器研究进展北大核心

电阻型MEMS半导体气体传感器在环境空气质量监测和有毒有害气体检测等领域得到了广泛应用，但是受限于功耗较高的原因，这类传感器难以广泛应用于便携式气体检测系统。文章综述了近年来低功耗电阻型MEMS半导体气体传感器的研究进展，分别从气敏材料、传感器结构和传感器模组的集成电路等方面探讨如何实现低功耗的电阻型MEMS半导体气体传感器的制备，并展望低功耗的电阻型MEMS半导体气体传感器未来的发展方向。     

一种新颖的MEMS表面工艺牺牲层厚度的电测量方法

牺牲层厚度是MEMS表面工艺中的一个重要参数，对它的测量和控制有着重要的意义。目前大多采用光机械的方法来测量，但是测试方法复杂、测试时间长。本文介绍了一种新颖的MEMS表面工艺牺牲层厚度测试技术，实现了牺牲层厚度的电测量。测试方法简单快捷，并且很便于测试系统集成。     

微型电场传感器在工频电场测量中的应用研究

该文基于高性能的MEMS电场敏感芯片研制出一种新型的工频电场测量系统。针对芯片调制被测电场后其输出信号的特征,采用正交相关检测原理提出一种可抑制背景干扰噪声的工频电场解调算法,设计出小型化、空间分辨力高的工频电场测量探头,并在基础上提出MEMS工频电场测量系统的系统级设计方案,成功实现了MEMS电场敏感芯片输出信号的无线采集、滤波、以及电场信号的高精度解调。高压输电线路下工频电场测量结果表明,MEMS工频电场测量系统与传统电场测量仪的测量结果具有良好的一致性。     

Microelectromechanical systems

The evolution and maturity of microelectromechanical systems (MEMS) in the coming years will be driven less by captive fabrication facilities and process development and more by innovative, aggressive electromechanical systems design. MEMS is poised to take full advantage of advances in information technology and couple them to advances in other disciplines to drive a fundamentally new approach to electromechanical system design and fabrication. By merging sensing and actuation with computation, MEMS will not only invest existing systems with enhanced capabilities and reliability but also will make possible radically new devices and systems designs that will exploit the miniaturization, multiplicity, and microelectronics of MEMS. For the first time, approaches akin to VLSI electronics can be taken to usher in an equally exciting and productive era of VLSI electromechanics     

半导体激光器的光学反馈干涉及传感应用

分析和讨论了激光反馈干涉现象 ,根据半导体激光器的反馈干涉理论 ,研究了反馈干涉模型及其信号的调制和解调方法 ,介绍了典型的传感应用。理论和实验表明 ,激光反馈干涉的理论不同于传统干涉 ,信号处理方法也有其特点。半导体激光器的光学反馈干涉系统具有结构简单、光路易准直、无需附加器件的特点 ,因而能够发展成小型、在线测量和过程控制的传感器 ,测量距离、位移和速度 ,在微机械、光学工程等领域具有应用前景。     

A BioMEMS review: MEMS technology for physiologically integrated devices

MEMS devices are manufactured using similar microfabrication techniques as those used to create integrated circuits. They often, however, have moving components that allow physical or analytical functions to be performed by the device. Although MEMS can be aseptically fabricated and hermetically sealed, biocompatibility of the component materials is a key issue for MEMS used in vivo. Interest in MEMS for biological applications (BioMEMS) is growing rapidly, with opportunities in areas such as biosensors, pacemakers, immunoisolation capsules, and drug delivery. The key to many of these applications lies in the leveraging of features unique to MEMS (for example, analyte sensitivity, electrical responsiveness, temporal control, and feature sizes similar to cells and organelles) for maximum impact. In this paper, we focus on how the biological integration of MEMS and other implantable devices can be improved through the application of microfabrication technology and concepts. Innovative approaches for improved physical and chemical integration of systems with the body are reviewed. An untapped potential for MEMS may lie in the area of nervous and endocrine system actuation, whereby the ability of MEMS to deliver potent drugs or hormones, combined with their precise temporal control, may provide new treatments for disorders of these systems.     

Design and implementation of capacitive proximity sensor usingmicroelectromechanical systems technology

This paper presents an innovative proximity sensor using microelectromechanical systems (MEMS) technology. The proximity sensor works on the principle of fringe capacitance. The target object does not need to be part of the measuring system and could be either a conductor or nonconductor. Modeling of the proximity sensor is performed and closed-form analytical solution is obtained for a ring-shaped sensing pattern. The proximity sensors could be batch fabricated using MEMS technology, and the fabrication process is relatively simple. Measurement of the prototype sensors revealed promising results. The size of the proximity sensor could vary from a few hundred micrometers to the size of the substrate. The flexibility on sensor size, sensing patterns, and sensing pattern geometrical parameters makes the sensor very versatile and capable of precision measurement of proximity in the range from micrometers to centimeters. The small size of the sensor makes it possible to surface mount the sensor in many space-constrained places. This advantage is vital in many areas, such as MEMS, microrobotics, precision engineering, machine automation, inspection tools, and many other applications. The ability of the proximity sensor in measuring relative permittivity of materials also finds the sensor useful applications in biomedical and tissue engineering. In addition, this micro proximity sensor is an ideal building block for many other types of sensors, such as force, tactile, and flow sensors     

Microfluidics meets MEMS

The use of planar fluidic devices for performing small-volume chemistry was first proposed by analytical chemists, who coined the term "miniaturized total chemical analysis systems" (/spl mu/TAS) for this concept. More recently, the /spl mu/TAS field has begun to encompass other areas of chemistry and biology. To reflect this expanded scope, the broader terms "microfluidics" and "lab-on-a-chip" are now often used in addition to /spl mu/TAS. Most microfluidics researchers rely on micromachining technologies at least to some extent to produce microflow systems based on interconnected micrometer-dimensioned channels. As members of the microelectromechanical systems (MEMS) community know, however, one can do more with these techniques. It is possible to impart higher levels of functionality by making features in different materials and at different levels within a microfluidic device. Increasingly, researchers have considered how to integrate electrical or electrochemical function into chips for purposes as diverse as heating, temperature sensing, electrochemical detection, and pumping. MEMS processes applied to new materials have also resulted in new approaches for fabrication of microchannels. This review paper explores these and other developments that have emerged from the increasing interaction between the MEMS and microfluidics worlds.     

Pulse drive and capacitance measurement circuit for MEMS electrostatic actuators

In this paper we present an electronic circuit for position or capacitance estimation of MEMS electrostatic actuators based on a switched capacitor technique. The circuit uses a capacitive divider configuration composed by a fixed capacitor and the variable capacitance of the electrostatic actuator for generating an output signal that is a function of the input voltage and capacitive ratio. The proposed circuit can be used to simultaneously actuate and sense position of an electrostatic MEMS actuator without extra sensing elements. This approach is compatible with the requirements of most analog feedback systems and the circuit topology of pulsed digital oscillators.     

基于法布里-珀罗低相干干涉的绝对距离测量系统

提出了一种基于光纤法布里-珀罗低相干干涉的 绝对距离测量系统,不仅能对绝对距离进行测 量,而且还能对温度、压力、应力等量进行绝对测量。系统利用闪耀光栅将来自法布里-珀 罗干涉仪的低相 干干涉信号进行散射,使不同波长的干涉信号由线阵CCD 不同的像元探测。利用CCD探测到 的干涉信号 相邻波谷的波数差得到法布里-珀罗干涉仪的腔长,从而实现绝对距离测量。与其它低相干 干涉测量系统相 比,此系统无需扫描干涉仪的光程,一次成像即实现测量。测量系统简单,测量速度快,对 静态物理量和 动态物理量都能进行测量。系统的光纤结构使得它还能进行远程测量。实验结果表明系统对 绝对距离测量的分辨率可达3.317 nm,10次重 复测量的标准差为10.7 nm。     

A Monolithic Phased Array Using 3-bit Distributed RF MEMS Phase Shifters

This paper presents a novel electronically scanning phased-array antenna with 128 switches monolithically implemented using RF microelectromechanical systems (MEMS) technology. The structure, which is designed at 15 GHz, consists of four linearly placed microstrip patch antennas, 3-bit distributed RF MEMS low-loss phase shifters, and a corporate feed network. MEMS switches and high-Q metal-air-metal capacitors are employed as loading elements in the phase shifter. The system is fabricated monolithically using an in-house surface micromachining process on a glass substrate and occupies an area of 6 cm times 5 cm. The measurement results show that the phase shifter can provide nearly 20deg/50deg/95deg phase shifts and their combinations at the expense of 1.5-dB average insertion loss at 15 GHz for eight combinations. It is also shown by measurements that the main beam can be steered to required directions by suitable settings of the RF MEMS phase shifters.     

柔性MEMS流速传感器的制造及其电路设计

针对流速传感器大多存在测量量程小、柔性小而无法适应较大量程和复杂曲面的测量问题,提出了一种宽量程柔性MEMS流速传感器,结合热损失和热温差的工作原理实现对流速的测量.选取聚酰亚胺(PI)作为柔性衬底材料和铂(Pt)薄膜为热敏材料,采用金属牺牲层MEMS工艺制造了带空腔的柔性流速传感器芯片,尺寸为9 mm×7 mm×30μm.设计了采用双惠斯通电桥的恒温差测控电路.测量结果表明:制造的柔性MEMS流速传感器的TCR为0.2418％/℃,实验实现了0～36 m/s的输入风速测量,在低速、高速段内的灵敏度分别为2和0.295 mV/(m/s).同时,测量电路还展现出良好的温度补偿效应.所提出的柔性MEMS流速传感器具有宽量程、测试精度高、灵敏度高和易于实施温度补偿的优点,有望用于航空航天、国防等领域.     

A highly simple failure detection method for electrostatic microactuators: application to automatic testing and accelerated lifetime estimation

Reliability and testability are two important factors for the development of batch fabrication of microelectromechanical systems (MEMS) or mixed MEMS/IC applications. In that frame, an easy-to-implement electrical method of detection of failures is presented in this paper, valid for every kind of electrostatic microactuators showing pull-in behavior, with great expectation value in the case of arrayed MEMS. The method relies on the detection of a pull-in current peak at very low frequency. An experimental setup is described and results are shown obtained with prototypes of electrostatic microactuators with parallel capacitances created by deep reactive ion etching on silicon-on-insulator wafers. This method is really suitable for automation and application to on-line testing during mass production and reliability studies. The functional schematic of a test circuitry is proposed for implementation in an industrial tester or for built-in self-test purposes. Then, in order to illustrate the benefits of this method for reliability studies, it is used in conjunction with high voltage testing for accelerated lifetime measurements. A time gain factor of 20 is achieved with above-mentioned test structures.     

Measurement of river surface currents with coherent microwave systems

River surface currents have been measured using coherent microwave systems from a bridge, a cableway, several riverbanks, a helicopter, and an airplane. In most cases, the microwave measurements have been compared with conventional measurements of near-surface currents and found to be accurate to within about 10 cm/s. In all cases, the basis for the microwave measurement of surface current is the Doppler shift induced in the signal backscattered from the rough water surface. In this paper, we outline the principles of the measurements and the various implementations that have been used to make microwave measurements of surface currents. Continuous-wave (CW) microwave systems have been used from a bridge to make long-term measurements of surface currents; these are compared with current-meter measurements and with time series of stage. A compact CW system has been developed and used on a cableway to measure surface currents at various distances across a river; these measurements have been compared with acoustic ones. Pulsed Doppler radars have been used to measure river surface currents from a riverbank, a helicopter, and an airplane. In the first two cases, comparisons with both current-meter and acoustic measurements have been made. We suggest that the CW system would be preferable to the pulsed Doppler radar to make such measurements from helicopters in the future. Finally, we consider the implications of our experiments for the measurement of surface currents from aircraft or satellites using interferometric synthetic aperture radars (INSARs). We find that a combination along-track, cross-track INSAR is necessary but that significant limitations are inherent in the technique.     

FPGA-Based Decentralized Control of Arrayed MEMS for Microrobotic Application

In this paper, the authors have developed and implemented a decentralized decision-making strategy using field-programmable gate array (FPGA) technology as a prototype for an integrated controller of a microelectromechanical systems (MEMS) array for air-flow planar micromanipulation. The MEMS array was proposed to be integrated in a hybrid multichip module containing the FPGA-based controller. Algorithms and architectures, used for the decentralized control implementation and the hardware resource optimization, are described. A charge-coupled device camera was used to make each MEMS like an autonomous system when the distributed MEMS chip was tested. Finally, under air-flow condition, the FPGA-based decentralized control system successfully performed an object manipulation.     

MEMS空间光调制器的研究现状与发展趋势

空间光调制器是自适应光学系统中用来实时校正波前畸变的关键器件,其发展水平能够反映整个自适应光学系统的水平。基于微电子机械系统(MEMS)技术的空间光调制器具有体积小、能耗低、驱动器单元密度高以及与集成电路工艺兼容性好等优点,而成为空间光调制器领域研究的热点。详细介绍了MEMS空间光调制器的研究现状和存在的主要问题,并分析了MEMS空间光调制器的未来发展趋势。     

Metallic Glass as a Mechanical Material for Microscanners

Microelectromechanical system (MEMS) actuators essentially have movable silicon structures where the mechanical motion can be activated electronically. The microscanner is one of the most successfully commercialized MEMS devices which are widely used for collecting optical information, manipulating light, and displaying images. While silicon is abundant, it is also brittle and stiff and when microprocessed, defects are not uncommon. These defects result in weakness under torsional stress and this has been the key factor limiting the scanning performance of the microscanner. Here a metallic glass (MG)‐based microscanner is reported with MG as the material for the moving torsion bars. The low elastic modulus, high fracture toughness, and high strength of MG offers, for the first time, an ultralarge rotating angle of 146° with power consumption lowered to the microwatt range, and a smaller driving force and better actuation performance, than conventional single crystal silicon and polycrystalline silicon. The high spatial resolution and large scanning field of the MG‐based microscanner are demonstrated in the tomographic imaging of a human finger. This development of an MG‐based MEMS possibly opens a new field of low‐powered MEMS devices with extreme actuation and enhanced sensing.     

A Behavioral Model of MEMS Convective Accelerometers for the Evaluation of Design and Calibration Strategies at System Level

This paper presents a behavioral model that can be used to improve the manufacturability of systems based on MEMS convective sensors. This model permits to handle faults related to process scattering, taking into account not only the electrical and lateral geometrical parameters but also the influence of the cavity depth. Moreover correlations between conductive and convective phenomena are included. The model is validated with respect to FEM simulations and a very good agreement is obtained between the behavioral model and FEM results. The proposed model can then be used in system-level simulations, for instance to evaluate the impact of process scattering on the performances of the sensing part and/or to investigate different design and calibration strategies with respect to the system robustness.     

Study of intermodulation in RF MEMS variable capacitors

This paper provides a rigorous study of the causes and physical origins of intermodulation distortion (IMD) in RF microelectromechanical systems (MEMS) capacitors, its analytical dependence on the MEMS device design parameters, and its effects in RF systems. It is shown that not only third-order products exist, but also fifth order and higher. The high-order terms are mainly originated by the nonlinear membrane displacement versus applied voltage and, in the case considered in this study, with an additional contribution from the nonlinear dependence of the reflection coefficient phase on the displacement. It is also shown that the displacement nonlinear behavior also contributes to the total mean position of the membrane. In order to study these effects in depth, an analytical frequency-dependent IMD model for RF MEMS based on a mobile membrane is proposed and particularized to the case of a MEMS varactor-a device for which IMD can be significant. The model is validated, up to the fifth order, theoretically (using harmonic balance) and empirically (the IMD of a MEMS varactor is measured). To this end, a two-tone IMD reflection measurement system for MEMS is proposed.     

Micromachined microsensors for manufacturing

The rapid development of microelectromechanical systems (MEMS) technologies in recent years has provided a high degree of spatial miniaturization and integration of electromechanical components, which enable integrated sensing and control in manufacturing. This article provides an overview of the state of the art of micromachined microsensors for the measurement of mechanical signals in the manufacturing industry for automobiles, manufacturing, medical equipment, environment, robotics, food, and other consumer products. Measurements of pressure, acceleration, and acoustic emission (AE) are the three physical quantities that are most encountered in industrial and manufacturing applications. Discussed are the major design parameters of such microsensors, such as dynamic range, sensitivity, resolution, and accuracy and provide a real-world application. Also discussed are the issues related to the spatial integration of signal processing, power supply, and wireless communication with the sensing elements, which are of direct relevance to the overall performance of the microsensors.