Built-in-self-test techniques for MEMS

As predicted by technology roadmaps, embedded micro-electro-mechanical-systems (MEMS) is yet another step in the continuous search for higher levels of integration and miniaturization. MEMS are analog components and the test paradigm is similar to the case of analog and mixed-signal circuits. However, given the fact that they work with signals other than electrical, the test of these embedded parts poses new challenges. In this paper, we will review some recent works in this field and we will present a complete approach to MEMS built-in-self-test (BIST) based on pseudorandom testing.     

Self-tuning fault diagnosis of MEMS

Multiple-model adaptive estimation techniques have been previously successfully applied to fault diagnosis of microsystems. Their diagnosis performance highly depends on the accuracy of modeling techniques used in representing faults. This paper presents the application of a self-tuning forgetting factor technique in the modeling of faults in MEMS and its effects on diagnosis performance compared with the application of Kalman filters and fixed gain estimation techniques. The self-tuning-based modeling used in the diagnosis algorithm was experimentally implemented. It demonstrated superior results compared to Kalman filter and fixed gain estimation techniques by accelerating the diagnosis process.     

硅基梳齿式MEMS器件及封装的失效调查

对典型硅基梳齿式MEMS器件进行失效调查和分析,验证其主要失效模式,分析其失效机理.利用电子扫描显微镜(SEM),X射线透视系统、扫描声学显微镜(SAM),X射线能谱成份分析(EDX)、金相切片分析、封装气体分析及电性能测试等分析技术,发现在工艺制造中的机械失效是造成此类器件失效的主要原因.另外,此类器件的封装失效主要表现为气密性失效和装配工艺失效.     

Generation of Electrically Induced Stimuli for MEMS Self-Test

A major task for the implementation of Built-In-Self-Test (BIST) strategies for MEMS is the generation of the test stimuli. These devices can work in different energy domains and are thus designed to sense signals which are generally not electrical. In this work, we describe, for different types of MEMS, how the required non-electrical test stimuli can be induced on-chip by means of electrical signals. This provides the basis for adding BIST strategies for MEMS parts embedded in the coming generation of integrated systems. The on-chip test signal generation is illustrated for the case of MEMS transducers which exploit such physical principles as time-varying electrostatic capacitance, piezo-resistivity effect and Seebeck effect. These principles are used in devices such as accelerometers, infrared imagers, pressure sensors or tactile sensors. For implementation, we have used two major MEMS technologies including CMOS-compatible bulk micromachining and surface micromachining. We illustrate the ability to generate on-chip test stimuli and to implement a self-test strategy for the case of a complete application. This corresponds to an infrared imager that can be used in multiple applications such as overheating detection, night vision, and earth tracking for satellite positioning. The imager consists of an array of thermal pixels that sense an infrared radiation. Each pixel is implemented as a suspended membrane that contains several thermopiles along the different support arms. The on-chip test signal generation proposed requires only slight modifications and allows a production test of the imager with a standard test equipment, without the need of special infrared sources and the associated optical equipment. The test function can also be activated off-line in the field for validation and maintenance purposes.     

基于MEMS加速度传感器的轴承故障检测

提出了一种通过利用低成本的MEMS加速度传感器进行振动分析,实现检测电动机深沟球轴承多重故障的简易方法。首先分析了轴承多故障特征频率,然后通过快速傅里叶变换算法对轴承出现故障的电动机振动频率进行了分析,从振动频谱中提取故障频率来诊断轴承多重故障的存在。同时,基频分量周围的边带频率分量表明由于故障轴承存在空气间隙。在空载、单相以及失衡电压条件下通过实验对提出的方法进行了研究,结果显示提取出的故障频率与理论值两者十分接近,表明提出的方法能够有效检测并识别出感应电动机的多故障特征。     

串联MEMS开关的瞬态电磁场分析

提出了一种串联MEMS开关的电磁耦合模型 ,并且应用该模型 ,对采用表面硅工艺和体硅工艺制作的MEMS开关 ,采用全波分析方法 ,进行了瞬态电磁场分析。由于开关尺寸为微米量级 ,而驱动电压高达 4 0～ 6 0V ,这样的瞬态高压有可能对开关上的信号产生影响。理论仿真结果显示 ,开关驱动路对信号路有很强的耦合场存在。实验结果同样显示 ,耦合到信号路的信号可以输入信号产生最大值为 6 0 %的失真     

MEMS可靠性技术

MEMS的可靠性是其能否成功应用的一个关键。本文对MEMS可靠性测试的要求与可靠性测试系统ShiMMeR进行了分析,通过对MEMS的可靠性实验与失效模型的综述,对MEMS的可靠性设计进行了探讨。     

THERMODEL: A Tool for Thermal Model Generation, and Application for MEMS

This paper presents a tool and a method for the generation of reduced order thermal models, in order to assure modeling the effect of the package on the thermal behavior of the packaged device. The method is generic, and can be based either on the simulated or on the measured thermal transient response of the real packages. It is based on the generation of the time constant density spectrum of the thermal response function, from which we automatically generate a reduced order thermal model in the form of an RC ladder network model. Beyond presenting the generic methodology experimental results are also presented, based both on the simulation and measurement of MEMS elements and packages.     

用于MEMS微电容检测的全差分放大器

设计了一种用于MEMS电容传感器的低噪声低失调全差分运算放大器.微传感器传感电容一般很小,传感电容的变化更小.低噪声低失调放大器大大提高了整个传感器检测电路精度.该放大器采用连续时间共模反馈方法稳定共模输出、低阻结点斩波和动态匹配方法以期达到有稳定输出的低噪声低失调全差分放大器,给出基于HJTC 0.18 μtm CMOS 1P6M工艺的仿真结果,经过精心设计,各项指标达到或超过应用要求.     

一种用于微拉伸系统的MEMS弹簧设计与制作

针对微拉伸测试系统支撑梁因塑性变形带来的误差,采用UV-LIGA技术制备出S型支撑弹簧来代替刚性梁,这样即可测量大变形薄膜的力学性能.实验结果表明,用UV-LIGA工艺制备的Ni金属S形弹簧具有良好的均匀性,在较大的变形范围内有很好的线弹性.     

基于阳极键合干法刻蚀技术的MEMS隧道加速度计的加工及测试

提出了一种基于北京大学硅玻璃键合深刻蚀释放工艺的扩展工艺,用来加工微型隧道加速度计.采用HP4145B半导体分析仪在大气环境下对所加工的器件进行了开环测试,验证了隧道电流的存在以及隧道间隙与隧道电流之间的指数关系.实验结果外推出的隧道势垒的范围为1.182～2.177eV.大部分器件的开启电压在14～16V之间.在-1,0和+1g三种状态下对开启电压分别进行了测试,得到加速度计的灵敏度约为87mV/g.     

Electromagnetic modelling of conductor-backed CPW based RF MEMS capacitive shunt switch

This article will detail the creation of an electromagnetic model of an RF MEMS capacitive shunt switch using the conductor-backed CPW configuration. Full-wave S-parameter analysis has been carried out to extract the S-parameter of the switches for different variants. The modelling also covers the effect of the tapering of the RF signal line as well as the permittivity variation on the switch parameters. Further, the ground metallisation effect because of the CB-CPW configuration on the switch parameters has been modelled and compared with the standard topology. A scalable lumped circuit model for the proposed topology has been generated which can be easily incorporated in the circuit simulator. The topology demonstrated can achieve frequency downscaling without increasing the size and complexity of the circuit. Comparison of modelled and full wave simulated results shows good agreement.     

Pseudorandom BIST for test and characterization of linear and nonlinear MEMS

In this paper we study the use of the pseudorandom (PR) technique for test and characterization of linear and nonlinear devices, in particular for micro electro mechanical systems (MEMS). The PR test technique leads to a digital built-in-self-test (BIST) technique that is accurate in the presence of parametric variations, noise tolerant, and has high-quality test metrics. We will describe the use of the PR test technique for testing linear and nonlinear MEMS, where impulse response samples of the device under test are considered to verify its functionality. Next, we illustrate and evaluate the application of this technique for linear and nonlinear MEMS characterization.     

Review of high level fault modeling approaches for mixed-signal systems

In the modern analogue design, Transistor Level Fault Simulation (TLFS) plays the important part since every fault in the whole circuit has to be simulated at that level. Unfortunately, it is a very CPU intensive task even though it maintains the high accuracy. Therefore, High Level Fault Modeling (HLFM) and High Level Fault Simulation (HLFS) are required in order to alleviate the efforts of simulation. In this paper, different HLFM approaches are reviewed at the device level during last two decades. We clarify their domains of application and evaluate their strengths and current limitations. We also analyze causes of faults and introduce various test approaches.     

基于MEMS共面波导腔的带阻滤波器的设计

应用计算机辅助设计了一种基于共面波导结构的MEMS带阻滤波器.研究了微尺度电磁学、力学、温度等效应.利用ANSOF的HFSS软件模拟分析了滤波器的损耗参数,并应用ANSYS软件分析复合结构的热应力分布,得出了阻带中心频率在18GHz的MEMS带阻滤波器件,提供了一些有意义的理论分析及应用.     

Design and simulation of High Q MEMS LC-tank for oscillators

This research focuses on the design of a high-performance MEMS LC-tank using a high Q MEMS inductor and capacitor. A two different gap varactor has been used to avoid pull-in voltage at 2.4 GHz. The layout has been done by CoventorWare software. The DC voltage is 2.5 v, which is applied to the plates and results of 2.04 pF could be gained. The Q factor of the varactor is computed at about 557.27, which is good enough to make a low-phase noise VCO. A hollow spiral inductor with a silicon base substrate for compatibility with CMOS technology has been designed. The Greenhouse equation has been used to obtain the dimensions of the inductor. A suspended inductor has been implemented to avoid substrate coupling. The simulation has been done by CoventorWare. The Q factor of the inductor has been calculated using Yue's model. The resultant values of inductance and the Q factor at 2.4 GHz, are 2.89 nH and 27, respectively, which are in good agreement with the results of theoretical computation. The results were verified with the well-documented literature.     

新型双向电容式MEMS加速度计特性分析

文章研究了一新型的栅形条电容MEMS加速度计,通过新型结构设计降低了传感器的机械噪声和电子噪声。用软件ANSOFT-Maxwell对栅形条电容的宽度、厚度及叠加宽度对检测电容的影响进行了分析。用深度离子刻蚀工艺和硅-玻璃键合工艺制作了传感器,初步测试结果表明其在X和Y方向的灵敏度分别为0.53pF/g 、0.49pF/g。制作的栅形条谐振子在大气下的品质因子达到514,说明栅形条结构可大大降低机械噪声。     

Characteristics of a novel biaxial capacitive MEMS accelerometer

A novel MEMS accelerometer with grid strip capacitors is developed.The mechanical and electrical noise can be reduced greatly for the novel structure design.ANSOFT-Maxwell software was used to analyze the fringing electric field of the grid strip structure and its effects on the designed accelerometer.The effects of the width,thickness and overlapping width of the grid strip on the sensing capacitance are analyzed by using the ANSOFT-Maxwell software.The results show that the parameters have little effect on the characteristics of the presented accelerometer.The designed accelerometer was fabricated based on deep RIE and silicon-glass bonding processes.The preliminary tested sensitivities are 0.53 pF/g and 0.49 pF/g in the x and y axis directions,respectively.A resonator with grid strip structure was also fabricated whose tested quality factor is 514 in air,which proves that the grid strip structure can reduce mechanical noise.     

MEMS结构在BOE中释放时气泡的产生与预防

微电子机械系统(MEMS)器件加工中,采用表面Si工艺和体Si工艺的混合工艺或MEMS SOI工艺,用SiO2的湿法腐蚀液缓冲氢氟酸(BOE)释放MEMS Si结构时将会出现一个新问题,阐述了该新问题的工作机理并给出可行的解决方法.以100 mm(4英寸)p型双面抛光Si片(100)替代MEMS器件Si结构,详细阐述了经过不同方法处理的Si片表面在不同温度下的BOE溶液以及加有表面活性剂的BOE溶液中是否产生气泡,并通过测量BOE溶液与Si片表面的接触角大小来衡量表面活性剂的效果.文章指出BOE溶液的温度、Si片表面的粗糙度以及表面活性剂的类型对气泡的产生具有很大的影响,同时指出阴性表面活性剂为抑制气泡产生的最佳表面活性剂.