微纳米分子系统研究领域的最新进展——IEEE NEMS 2011国际会议综述

2011年2月20日至23日,第6届IEEE国际纳米/微米工程及分子系统大会（IEEE-NEMS 2011）在台湾高雄市召开,来自世界各地的300多位专家、学者齐聚一堂,分享其在微纳米科技领域的最新研究成果。本文选取微流体技术与芯片实验室、生物医学MEMS器件、纳米新材料奇妙特性及其应用、新型传感器执行器及其系统等4个角度,详细介绍了微纳米科技领域的研究现状,并对其发展趋势进行了分析。     

自组装技术在MEMS中的应用

起源于生物化学领域的自组装技术正被广泛地应用到了化学、材料、生物、电子、机械等不同的学科中。在MEMS和NEMS中,自组装作为一种新型的“自下而上”的微(纳)结构制备和装配技术而得到积极的关注,并显示出良好的应用前景。在阐述自组装技术发展的基础上,介绍了该技术在MEMS中的典型应用,讨论一些待解决的关键问题,最后展望了自组装技术的发展趋势。     

Advances in pulsed-laser-deposited AIN thin films for high-temperature capping, device passivation, and piezoelectric-based RF MEMS/NEMS resonator applications

In this paper we report recent advances in pulsed-laser-deposited AIN thin films for high-temperature capping of SiC, passivation of SiC-based devices, and fabrication of a piezoelectric MEMS/NEMS resonator on Pt-metallized SiO₂/Si. The AlN films grown using the reactive laser ablation technique were found to be highly stoichiometric, dense with an optical band gap of 6.2 eV, and with a surface smoothness of less than 1 nm. A low-temperature buffer-layer approach was used to reduce the lattice and thermal mismatch strains. The dependence of the quality of AlN thin films and its characteristics as a function of processing parameters are discussed. Due to high crystallinity, near-perfect stoichiometry, and high packing density, pulsed-laser-deposited AlN thin films show a tendency to withstand high temperatures up to 1600°C, and which enables it to be used as an anneal capping layer for SiC wafers for removing ion-implantation damage and dopant activation. The laser-deposited AlN thin films show conformal coverage on SiC-based devices and exhibit an electrical break-down strength of 1.66 MV/cm up to 350°C when used as an insulator in Ni/AlN/SiC metal-insulator-semiconductor (MIS) devices. Pulsed laser deposition (PLD) AlN films grown on Pt/SiO₂/Si (100) substrates for radio-frequency microelectrical and mechanical systems and nanoelectrical and mechanical systems (MEMS and NEMS) demonstrated resonators having high Q values ranging from 8,000 to 17,000 in the frequency range of 2.5–0.45 MHz. AlN thin films were characterized by x-ray diffraction, Rutherford backscattering spectrometry (in normal and oxygen resonance mode), atomic force microscopy, ultraviolet (UV)-visible spectroscopy, and scanning electron microscopy. Applications exploiting characteristics of high bandgap, high bond strength, excellent piezoelectric characteristics, extremely high chemical inertness, high electrical resistivity, high breakdown strength, and high thermal stability of the pulsed-laser-deposited thin films have been discussed in the context of emerging developments of SiC power devices, for high-temperature electronics, and for radio frequency (RF) MEMS.     

从MEMS到NEMS进程中的技术思考

回顾和概括了MEMS机电器件进入μm/nm尺度后解决的几个关键性问题。结合微机电器件发展的典型事例进行分析,对我国科学工作者在其中的贡献给予肯定。分析目前机电器件走向nm尺度的一些相关概念理解和需要着重研究的纳米效应问题。对机电器件从微到纳的发展趋势进行了展望。     

纳机电系统阻尼及噪声研究进展

在微机电系统(MEMS)领域,自1989年Tang等人首次提出横向多晶硅谐振器结构以来,有关谐振器振动过程中阻尼问题的研究一直就是影响和推进谐振器发展的一个主要方面。近几年,随着器件尺寸的进一步缩小,器件尺寸进入亚微米级甚至是纳米级领域,阻尼及噪声问题更是成为影响器件工作特性的一个重要因素。本文就近几年微机电系统和纳机电系统中,相关MEMS谐振器以及微悬臂梁的阻尼和噪声问题的研究,作了一些介绍和分析。     

MEMS器件VHDL-AMS宏模型

随着MEMS集成度的提高,迫切需要有相应的CAD工具进行系统级的设计与模拟,由于MEMS器件的工作原理包含了多种能量的耦合,宏模型的建立成了系统级设计的“瓶颈”。模拟硬件描述语言(如VHDL-AMS)提供了一种有效的方法,即建立起表示MEMS器件动态特性的常微分方程和代数方程(DAE),然后对其描述,形成相应的库单元,利用现有电路分析软件进行系统级模拟。本文介绍了MEMS器件VHDL描述的过程,并给出了横向谐振器描述的例子。     

Ultrathin TiN Membranes as a Technology Platform for CMOS‐Integrated MEMS and BioMEMS Devices

A standard complementary metal‐oxide‐semiconductor (CMOS) process is successfully modified to encompass the preparation of suspended TiN membranes of only 50 nm thickness from one of the metal layer stacks of the back‐end flow. The layers’ elastomechanical constants are determined with high precision by laser Doppler vibrometry. Residual stress gradients are compensated and a state of moderate tensile strain is introduced into the membranes. Test systems of TiN beams and bridges operating in a capacitive coupling scheme are optimized for the low voltage range attainable with CMOS devices. TiN actuators are particularly suited for applications in biotechnology like sensing of pressure or viscosity in microfluidic devices due to their high corrosion resistance in liquid electrolyte surroundings. The established inclusion of the process in a CMOS pilot line enables the production of cheap and monolithically integrated microelectromechanical systems (MEMS) and bio‐microelectromechanical systems (BioMEMS) devices.     

MEMS加工技术及其工艺设备

微电子机械和纳米技术的研究覆盖了亚微米到纳米尺寸的特征范围,它主要依靠光刻和图形转换设备和工艺获得,但又不仅限于半导体加工范畴。光学光刻设备、感应耦合等离子体刻蚀,金属的溅射涂覆,金属的等离子体增强CVD、介质隔离、掺杂注入、粒子柬微写设备和X射线源可以看作MEMS和纳米技术的机械加工手段,其各有独具的优势限制。现正被用于定制的MEMS器件到真空微电子器件和新颖的纳米工具的研究与开发应用。抗蚀剂喷涂技术为复杂形貌的MEMS器件光刻提供了高均匀性作图的厚胶基础。对于MEMS技术进入产业化的主要技术瓶颈-MEMS封装技术研究与开发已成为当今世界各国关注的热点。同时,对于MEMS器件的测试技术的研究,目前在国际上也引起了高度的重视。     

MEMS器件在冲击下的可靠性

MEMS器件在制造、运输和使用过程中不可避免地受到不同程度的冲击作用,分析和认识MEMS器件在冲击下的响应和失效模式,对提高器件的耐冲击和可靠性具有一定的指导意义。本文综述了MEMS器件的冲击测试和理论分析方法,对MEMS器件的可靠性设计具有一定参考价值。     

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.     

Investigation of RF sputtered PSG films for MEMS and semiconductor devices

In this work, we report the preparation of phospho-silicate-glass (PSG) films using RF magnetron sputtering process and its application as a sacrificial layer in surface micromachining technology. For this purpose, a 76 mm diameter target of phosphorus-doped silicon dioxide was prepared by conventional solid-state reaction route using P₂O₅ and SiO₂ powders. The PSG films were deposited in a RF (13.56 MHz) magnetron sputtering system at 200-300 W RF power, 10-20 mTorr pressure and 45 mm target-to-substrate spacing without external substrate heating. To confirm the presence of phosphorus in the deposited films, hot-probe test and sheet resistance measurements were performed on silicon wafers following deposition of PSG film and a drive-in step. As a final confirmatory test, a p-n diode was fabricated in a p-type Si wafer using the deposited film as a source of phosphorus diffusion. The phosphorus concentration in the target and the deposited film were analyzed using energy dispersive X-rays (EDAX) tool. The etch rate of the PSG film in buffered HF was measured to be about 30 times higher as compared to that of thermally grown SiO₂ films. The application of RF sputtered PSG film as sacrificial layer in surface micromachining technology has been explored. To demonstrate the compatibility with MEMS process, micro-cantilevers and micro-bridges of silicon nitride were fabricated using RF sputtered PSG as a sacrificial layer in surface micromachining. It is envisaged that the lower deposition temperature in RF sputtering (<150 °C) compared to CVD process for PSG film preparation is advantageous, particularly for making MEMS on temperature sensitive substrates.     

MEMS器件WLP封装温度特性的有限元模拟分析与实验

圆片级封装(WLP)技术是一种常用于微电子机械系统(MEMS)器件封装的有效方法。对于具有可动结构的MEMS器件来说,WLP的温度特性会对其性能和可靠性产生重要影响。通过对具有不同面阵列凸点分布形式的WLP封装结构进行有限元模拟,分析了封装过程中芯片有源面在温度载荷影响下的应力分布和变形情况,并通过实验对有限元模拟结果进行了修正。结果表明:对于具有3×3,6×6,9×9面阵列凸点分布形式的WLP封装结构来说,其芯片有源面变形的实际测试结果与修正后的模拟结果非常吻合,误差量分别为5.4%,4.1%和0.3%。     

A novel fabrication process of MEMS devices on polyimide flexible substrates

Micro-electro-mechanic-system (MEMS) devices on flexible substrate are important for non-planar and non-rigid surface applications. In this paper, a novel and cost-effective fabrication process for an 8 × 8 MEMS temperature sensor array with a lateral dimension of 2.5 mm × 5.5 mm on a polyimide flexible substrate is developed. A 40 μm thick polyimide substrate is formed on a rigid silicon wafer using as a mechanical carrier throughout the fabrication by four successive spin coating liquid polyimide. The arrayed temperature sensing elements made of 1200 Å sputtered platinum thin film on polyimide substrate show excellent linearity with a temperature coefficient of resistance of 0.0028/°C. The purposed sensor obtains a high sensitivity of 0.781 Ω/°C at 8 mA at constant drive current. Because of the low heat capacity and excellent thermal isolation, the temperature sensing element shows excellent high sensitivity and a fast thermal response. The finished devices are flexible enough to be folded and twisted achieving any desired shape and form. Employing spin-coated liquid polyimide substrate instead of solid polyimide sheet minimizes the thermal cycling as well as improves the production yield. This fabrication technique first introduces the spin-coated PDMS (Polydimethylsiloxane) interlayer between the silicon carrier and the polyimide substrate and makes the polyimide-based devices separate much easier and greatly simplifies the fabrication process with a high production yield. A non-successive two-stage cure procedure for the polyimide precursor is developed to meet low-temperature requirement of the PDMS interlayer. The fabrication procedure developed in this research is compatible with conventional MEMS technology through an optimized integration process. The novel flexible MEMS technology can benefit the development of other new flexible polyimide-based devices.     

MEMS技术研究及应用

首先阐述了微电子机械系统 (MEMS)技术的基本概念、特点及概况 ;其次 ,介绍了MEMS技术的分类及在各领域的应用产品 ;最后 ,重点介绍了RFMEMS技术 ,包括某些RFMEMS器件的典型结构及性能指标     

MEMS/microelectronics self-assembly based on analogy of Langmuir-Blodgett approach

A self-assembly method is introduced for the assembly of micro-parts onto Si substrates based on analogy of the Langmuir−Blodgett technique. To perform the assembly, Si substrates are prepared with solder-coated binding sites. The micro-parts are suspended in the butyl acetate-water mixture, and after gentle agitation, the micro-parts form a uniform and well-ordered 2-D aggregate at the butyl acetate-water interface. The micro-parts are attached onto the substrate by passing the substrate vertically through the aggregate of micro-parts. Due to the mechanism of the Langmuir−Blodgett technique, the micro-parts are attached onto the substrate. The butyl acetate-water mixture is then heated to 100 °C, molten solder and air bubbles in the boiling water make it possible for the micro-parts to self-align on the substrate. This methodology could give a self-assembly yield of up to 90%, providing a practicable method for micro-assembly.     

能同时测量纳米器件机械和电气特性的测试系统

研究纳米级材料的电气特性通常要综合使用探测和显微技术对感兴趣的点进行确定性测量。但是,必须考虑的一个额外因素是施加的探针压力对测试结果的影响,因为很多材料具有压力相关性,压力会引起材料的电气特征发生巨大的变化。现在,一种新的测量技术能够将纳米材料的电气和机械特性表示为施加探针压力的函数,为人们揭示之前无法看到的纳米现象。     

移动互联网络时代MEMS技术的创新发展

微电子机械系统(MEMS)技术是半导体微电子学的创新,利用Si基集成电路的平面工艺从两维加工向三维加工发展,开创了MEMS新的领域。综述并分析了与信息产业以及移动网络相关的MEMS主流产品(加速度计、陀螺仪、微麦克风、数字微镜器件(DMD)、喷墨头和RF MEMS)的技术发展现状和趋势,同时预测了MEMS新兴产品(光滤波器、微小电子鼻、微扬声器、微超声器、微能量采集器和纳机电系统(NEMS))的科研现状和面临的技术挑战。从当前世界MEMS技术发展的特点(系统集成、与CMOS工艺结合走向标准加工、纳米制造与微米、纳米融合和多应用领域扩展)出发,结合国内MEMS技术发展的现状,提出我国MEMS技术发展的建议。     

芯片冷却技术中的微/纳米材料与结构的研究进展

分析和讨论了芯片冷却技术中应用到的微/纳米材料和结构方面的进展,并对其应用前景作了一定展望。这些内容对于发展新的芯片冷却技术及相关高热流密度器件的冷却应用具有重要的参考价值。     

射频微电子机械系统的发展与展望

介绍了射频微电子机械系统 ( RF MEMS)的最新进展、研究内容及应用前景。该系统装置包括开关、继电器、电容器、电感器、滤波器及微波和毫米波元件。     

On the reliability of electrostatic NEMS/MEMS devices: Review of present knowledge on the dielectric charging and stiction failure mechanisms and novel characterization methodologies

This paper reviews the state of the art knowledge related to critical failure mechanisms in electrostatic micro- and nano-electromechanical systems (MEMS and NEMS) which are the dielectric charging and stiction. It describes also the recent employed nanoscale characterization techniques for these phenomena based on Kelvin probe force microscopy (KPFM) and force–distance curve measurements. The influence of relative humidity and dielectric deposition conditions on the charging/discharging processes is discussed. Moreover, different stiction mechanisms induced by electrostatic force and/or meniscus formation are analyzed. Finally, novel characterization methods are presented and used to correlate between the results from MEMS devices and metal–insulator–metal (MIM) capacitors. These methods are employed in view of application in electrostatic capacitive MEMS switches and could be easily extended to explore other NEMS/MEMS devices. The study provides an accurate understanding of the charging and stiction related failure mechanisms, presents guidelines for a proper packaging environment, and reveals precise explanations for the literature reported device level measurements of electrostatic MEMS devices.