飞秒激光双光子聚合加工微纳结构

针对微/纳机电系统（MEMS/NEMS）零部件加工制造难题,研究具有亚衍射极限空间分辨率的飞秒激光双光子聚合加工方法,搭建钛蓝宝石飞秒激光微纳加工系统,对液态聚合物材料进行飞秒激光双光子聚合加工工艺试验研究。结果表明:随着激光功率的降低,单个固化点的尺寸减小,加工分辨率提高;扫描步距减小,所加工工件的表面粗糙度数值减小,但加工效率降低。基于CAD软件设计出微米墙和纳米线构成的三维微纳结构,利用飞秒激光双光子聚合加工得到该三维微纳结构实物,通过优化工艺参数加工出直径小于100 nm的纳米线,从而证明飞秒激光双光子聚合加工方法为微/纳器件的制造提供了一种有效方法。     

Tensile tests of micro anchors anodically bonded between Pyrex glass and aluminum thin film coated on silicon wafer

Micro anchor is a kind of typical structures in micro/nano electromechanical systems (MEMS/NEMS), and it can be made by anodic bonding process, with thin films of metal or alloy as an intermediate layer. At the relative low temperature and voltage, specimens with actually sized micro anchor structures were anodically bonded using Pyrex 7740 glass and patterned crystalline silicon chips coated with aluminum thin film with a thickness comprised between 50 nm and 230 nm. To evaluate the bonding quality, tensile pulling tests have been finished with newly designed flexible fixtures for these specimens. The experimental results exhibit that the bonding tensile strength increases with the bonding temperature and voltage, but it decreases with the increase of the thickness of Al intermediate layer. This kind of thickness effect of the intermediate layer was not mentioned in the literature on anodic bonding.     

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。     

Nanotribology and nanomechanics of MEMS/NEMS and BioMEMS/BioNEMS materials and devices

The micro/nanoelectromechanical systems (MEMS/NEMS) need to be designed to perform expected functions typically in millisecond to picosecond range. Expected life of the devices for high speed contacts can vary from few hundred thousand to many billions of cycles, e.g., over a hundred billion cycles for digital micromirror devices (DMDs), which puts serious requirements on materials. For BioMEMS/BioNEMS, adhesion between biological molecular layers and the substrate, and friction and wear of biological layers may be important. There is a need for development of a fundamental understanding of adhesion, friction/stiction, wear, and the role of surface contamination, and environment. Most mechanical properties are known to be scale dependent. Therefore, the properties of nanoscale structures need to be measured. MEMS/NEMS materials need to exhibit good mechanical and tribological properties on the micro/nanoscale. There is a need to develop lubricants and identify lubrication methods that are suitable for MEMS/NEMS. Methods need to be developed to enhance adhesion between biomolecules and the device substrate. Component-level studies are required to provide a better understanding of the tribological phenomena occurring in MEMS/NEMS. The emergence of micro/nanotribology and atomic force microscopy-based techniques has provided researchers a viable approach to address these problems. This paper presents a review of micro/nanoscale adhesion, friction, and wear studies of materials and lubrication studies for MEMS/NEMS and BioMEMS/BioNEMS, and component-level studies of stiction phenomena in MEMS/NEMS devices.     

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。     

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。     

MMI微压印模板的设计与研究

微纳米压印技术作为代替传统光刻的一种新兴技术,有着重要的应用潜力。近年来在直接加工微器件如微流体、微生物器件,特别是在微平面光学器件方面得到了较快的发展。采用微压印法直接加工聚合物微平面光学器件是一个具有实用价值和研究价值的课题。该文首先讨论并选取了聚甲基丙稀酸甲酯(PMMA),研究了聚合物多模干涉(MMI)耦合器器件的微压印模板的设计和加工,讨论了压印模板材料的影响。根据典型基于MMI聚合物分光器件模板的设计实例,由聚合物的光学性能和分光要求,设计出模板的几何尺寸,通过微细加工工艺加工出模板,并给出了初步的热压印实验结果。     

Correlation between chemistry of polymer building blocks and microelectronics reliability

Among various materials, polymers are widely used in microelectronics as different product constituents, such as encapsulants, conductive or non-conductive adhesives, underfills, molding compounds, insulators, dielectrics, and coatings. The behavior of these polymer constituents determines the performance, such as functionality and reliability, of the final products. Therefore, the successful development of microelectronics depends on, to some extent, the optimal design and processing of polymer materials. Due to the development trends of microelectronics, characterized mainly by ongoing miniaturization down to the nano scale, technology and functionality integration, eco-designing, shorter-time-to-market, development and application of polymers become one of the bottlenecks for microelectronic industry. Aiming at optimizing the product/process development, we have been spending a lot of effort to understand and design polymer behavior in microelectronics, such as material pre-selection, processing, characterization and modeling. Although these efforts are necessary, the ultimate benefits can only be realized if the relationship between chemistry and the behavior can be understood and predicted. This paper presents some results of our effort to establish the links between chemical details of the polymers and microelectronics reliability.     

基于聚焦离子束注入的微纳加工技术研究

提出了聚焦离子束注入（focused ion beam implantation,FIBI）和聚焦离子束XeF2气体辅助刻蚀（gas assisted etching,GAE）相结合的微纳加工技术。通过扫描电镜观察FIBI横截面研究了聚焦离子束加工参数与离子注入深度的关系。当镓离子剂量大于1.4×1017ion/cm2时,聚焦离子束注入层中观察到均匀分布、直径10～15nm的纳米颗粒层。以此作为XeF2气体反应的掩膜,利用聚焦离子束XeF2气体辅助刻蚀（FIB-GAE）技术实现了多种微纳米级结构和器件加工,如纳米光栅、纳米电极和微正弦结构等。结果表明该方法灵活高效,很有发展前途。     

石墨烯微纳结构加工技术的研究进展

简单介绍了石墨烯独特的光电子性质,说明实现其在光电子器件中应用的有效方法是进行微纳加工。接下来对主要的石墨烯微纳加工技术——掩膜光刻、转移压印以及激光直写和干涉进行详细阐述,通过实例对每种加工技术的关键步骤和特点进行说明,并分析比较了不同加工技术的优缺点。然后对近期出现的转移压印辅助光刻和飞秒直写辅助转移压印技术的加工流程进行详细介绍,阐述将两种加工技术相结合应用于石墨烯微纳结构加工的优势。最后,简单展望了石墨烯微纳加工未来的发展趋势,指出需进一步研究的问题,对如何更好地实现石墨烯微纳结构的加工提出一些建议。     

Rapid,One‐Step,Digital Selective Growth of ZnO Nanowires on 3D Structures Using Laser Induced Hydrothermal Growth

For functional nanowire based electronics fabrication, conventionally, combination of complex multiple steps, such as (1) chemical vapor deposition (CVD) growth of nanowire, (2) harvesting of nanowire, (3) manipulation and placement of individual nanowires, and (4) integration of nanowire to circuit are necessary. Each step is very time consuming, expensive, and environmentally unfriendly, and only a very low yield is achieved through the multiple steps. As an alternative to conventional complex multistep approach, original findings are presented on the first demonstration of rapid, one step, digital selective growth of nanowires directly on 3D micro/nanostructures by developing a novel approach; laser induced hydrothermal growth (LIHG) without any complex integration of series of multiple process steps such as using any conventional photolithography process or CVD. The LIHG process can grow nanowires by scanning a focused laser beam as a local heat source in a fully digital manner to grow nanowires on arbitrary patterns and even on the non‐flat, 3D micro/nano structures in a safer liquid environment, as opposed to a gas environment. The LIHG process can greatly reduce the processing lead time and simplify the nanowire‐based nanofabrication process by removing multiple steps for growth, harvest, manipulation/placement, and integration of the nanowires. LIHG process can grow nanowire directly on 3D micro/nano structures, which will be extremely challenging even for the conventional nanowire integration processes. LIHG does not need a vacuum environment to grow nanowires but can be performed in a solution environment which is safer and cheaper. LIHG can also be used for flexible substrates such as temperature‐sensitive polymers due to the low processing temperature. Most of all, the LIHG process is a digital process that does not require conventional vacuum deposition or a photolithography mask.     

Compact meta-material transmission line balun based on meander lines structure and MEMS technology

This paper presents a novel compact meta-structure microstrip balun, which is characterized by left-handed properties. In the novel structure, two coupled meander lines are used to generate series capacitor and series inductor. Compared with conventional composite right/left-handed transmission-line structures, the new structure has smaller size and is easily fabricated by MEMS (Micro Electromechanical Systems) technology. Using such a meta-structure, a wide band microstrip balun is designed and fabricated. Good performance in phase error in wide pass band has been achieved.     

Packaging for microelectromechanical and nanoelectromechanical systems

Packaging is a core technology for the advancement of microelectromechanical systems (MEMS) and nanoelectromechanical systems (NEMS). We discuss MEMS packaging challenges in the context of functional interfaces, reliability, modeling and integration. These challenges are application-dependent; therefore, two case studies on accelerometers and BioMEMS are presented for an in-depth illustration. Presently, most NEMS are in the exploratory stage and hence a unique path to identify the relevant packaging issues for these devices has not been determined. We do, however, expect the self-assembly of nano-devices to play a key role in NEMS packaging. We demonstrate this point in two case studies, one on a silicon nanowire biosensor, and the other on self-assembly in molecular biology. MEMS/NEMS have the potential to have a tremendous impact on various sectors such as automotive, aerospace, heavy duty applications, and health care. Packaging engineers have an opportunity to make this impact a reality by developing low-cost, high-performance and high-reliability packaging solutions.     

纳米压印技术

传统光学光刻技术的高成本促使科学家去开发新的非光学方法,以取代集成电路工厂目前所用的工艺.另外,微机电系统(MEMS)的成功启发科学家借用MEMS中的相关技术,将其使用到纳米科技中去,这是得到纳米结构的一种有效途经.纳米压印在过去的几年里受到了高度重视,因为它成功地证明了它有成本低、分辨率高的潜力.纳米压印技术主要包括热压印、紫外压印(含步进-闪光压印)和微接触印刷等.本文详细讨论纳米压印材料的制备及常用的三种工艺的工艺步骤和它们各自的优缺点.并对这三种工艺进行了比较.最后列举了一些典型应用,如微镜、金属氧化物半导体场效应管、光栅等.     

Polymer MEMS actuators for underwater micromanipulation

Conventional MEMS actuators are not suitable for underwater applications such as cell grasping due to two main reasons: 1) their required actuation voltage are typically higher than 2 V, which would cause electrolysis in water and 2) they have small displacement/deflection due to their inherent driving principles. In this paper, three-different types of novel polymer-based MEMS underwater actuators developed in our laboratory are discussed: 1) ionic conducting polymer films (ICPF) actuator, which actuates by stress gradient induced by ionic movement due to electric field; 2) parylene thermal actuator, which actuates due to the induced stress gradient across a structure made of different layers of materials with different thermal expansion coefficients; and 3) polyaniline (PANI) actuator, which actuates due to its volumetric change caused by a reversible electrochemical oxidation-reduction (redox) reaction. All these polymer micro actuators can be actuated underwater with large deflections and require less power input than conventional MEMS actuators. The experimental results from characterizing these prototype actuators are presented in this paper.     

基于光学聚焦方法的热驱动微执行器位移测量

随着微机电系统（MEMS）设计日趋成熟,度量问题越来越成为微系统技术中的热点。使用改进的拉普拉斯求和方法（SML）和深度估计法来测量热度驱动微夹持器末端的弯曲程度。实验中,使用了10幅在42℃时微夹持器的水下工作图像来验证这种光学聚焦方法,结果证明使用光学聚焦方法可以测量出作为驱动器反馈输入的末端弯曲大小,实现对驱动器运动的精确控制。     

Laser Micro/Nano-Structuring Pushes Forward Smart Sensing: Opportunities and Challenges

Post-pandemic era poses an imperative demand on progressive sensing devices whose performance largely relies on the morphologies and structures of sensing materials. Despite substantial efforts and advances that have been made in sensing materials with different micro/nanoscale dimensionalities, it is still challenging to couple micro/nano platforms with sensing materials together for the precise and scalable production of high-performance sensors toward practical application scenarios. Owing to noncontact, precise, and high-efficiency features, laser micro/nanofabrication offers a promising solution to achieve high-quality micro/nano sensors with novel functionalities in a relatively short time. Herein, this review begins with a glance over the development of micro/nano-structured sensors and briefly discusses the importance of laser micro/nanostructuring technology for micro/nano-engineering of the sensors. Next, representative processing methods are elaborated in detail from a laser-pulse-type point of view, with potential applications toward chemical, physical, and biological targets based on different sensing mechanisms summarized. Finally, the perspectives on the opportunities and challenges of laser micro/nanostructuring strategies and materials for micro/nanosensors are presented.     

用于聚合物基微流体MEMS的等离子体活性晶圆键合技术

Lab-on-chip或μ-TAS(micro-totalanalysissystems)结合流体处理、检测及数据分析,是一种便携式的低成本高效器件。在微流体应用中,聚合物具有比硅或玻璃器件更明显的优势,它包括:宽泛的材料选择性,成本低、效率高,使用任意性,生物兼容性,抗化学品和工艺灵活性。为了实现采用这类材料制备小型集成化系统,我们发展了新的制备与封装技术。这项工作着眼于运用等离子体活化低温直接键合技术实现纳/微结构聚合物在低温条件下进行封装。由纳米压印光刻制作的纳/微结构的聚合物器件,可能是异质(聚合物与玻璃或硅)或同质(聚合物与聚合物)键合。为了改进键合材料的物理和化学熔合,键合工序通常在接近聚合物的玻璃化转变温度的高温下进行。但遗憾的是,高温损伤了微细图形,特别是对于高深宽比结构。在EVG810LT 等离子体反应室里,我们采用软射频频率等离子体表面处理,来进行聚合物的等离子体活化,它能在不改变聚合物体特性的前提下清洗和活化聚合物顶层。最终结果是,在EVG501晶圆键合机上,两个活化的表面在低温下通过施加一个适中的、均匀的接触压力而连接在一起,保证了空腔密封并防止了小结构的破坏和变形。键合工艺条件为:真空条件为从大气到200~1000Pa、接触压力为2～5kN、温度从室温到80℃。RR     

UV nanoimprint lithography with rigid polymer molds

Transparent polymers are considered as alternative low-cost mold materials in UV nanoimprint lithography (UV-NIL). Here, we demonstrate a nanoimprint process with molds made of rigid polymers novel for this application. These polymer molds are found to show high performance in the patterning with UV-NIL. Sub-50 nm structures were fabricated with this process.     

Deformation analysis in microstructures and micro-devices

The mechanical behaviors of microstructures and micro-devices have drawn the attention from researchers on materials and mechanics in recent years. To understand the rule of these behaviors, the deformation measurement techniques with micro/nanometer sensitivity and spatial resolution are required. In this paper, a micro-marker identification method is developed to measure microstructure deformation. The micro-markers were directly produced on the top surface of microstructures by taking advantage of ion milling of focused ion beam (FIB) system. Based on the analysis of marker images captured by electronic microscope with specific correlation software, the deformation information in microstructures can be easily obtained. The principle of the technique is introduced in detail in the paper. An example experiment was executed to measure the displacement and strain distribution in a MEMS device. Obtained results show that the technique can be well applied to the deformation measurement of the micro/nano-electro-mechanical-systems (MEMS/NEMS).