1、纳米结构的图形转移技术纳米结构的图形转移技术纳米结构的图形转移技术纳米结构的图形转移技术物理方法化学方法图形转移技术光学光刻技术非光刻图形制备技术纳米结构的自组装技术传统方法Here comes your footer 2传统的光学光刻技术 光刻是制造半导体器件和集成电路微图形结构的关键工艺技术，思路起源于印制技术中的照相制版，属于平面工艺。光学平面印制工艺分为两步：掩膜的制备和图形的转移。Here comes your footer 3传统光刻技术遇到的困境：最小特征线宽（Minimum Feature Size，MFS）决定不仅与曝光光源波长以及光学系统有关，而且还与曝光材料等工艺细节有关
2、：MFS=k1/NA式中：k1是为工艺因子；为曝光波长；NA 为投 影光刻物镜的数值孔径。1）降低工艺因子(k1)：OAI（离轴照明）、PSM（移相掩模）及OPC（光学邻近效应校正）等2）缩短曝光波长()：436nm(g线)365nm(i线)248nm(KrF)193nm(ArF)157nm NGL(下一代光刻术)3）提高物镜的数值孔径(NA)：非浸没式：0.280.420.480.600.680.750.780.82 0.85(极限)浸没式：1.3(2003)1.44(04-06)1.64(2007)Here comes your footer 4新一代光刻技术和纳米制造 曝光波长限制了光学
3、光刻技术向更小尺寸器件的应用，进入0.1m以下的光刻必须采用新一代光刻技术，如X射线光刻(XRL)、极紫外光刻(EUVL)、电子束光刻(EBL)和离子束光刻(IBL)等。但是由于短波长光源的获得，以及新的透镜材料、更高数字孔径光学系统的加工，还有大部分材料都强烈的吸收深紫外而被破坏，而且，光刻设备所花费的巨大成本，均成为了光刻技术的瓶颈。Here comes your footer 5电子束光刻（Electron Beam Lithography）1在显微镜的基础上发展起来的。其研究始于20世纪60年代，由德意志联邦共和国杜平根大学的 G.Mollenstedt和R.Speidel提出2用电磁
4、场将电子束聚焦成微细束辐照在电子抗蚀剂上，由于电子束可以方便地有电磁场偏转扫描，所以可以将复杂的电路图形直接写到硅片上而无需掩模版.3优点：高分辨、长焦深、无需掩模(即电子束直写)、可以在计算机控制下直写任意图形；缺点：曝光速度慢；生产效率比较低；难以实现高精度的对准和套刻4电子束光刻中使用的曝光机一般有两种类型：直写式与投影式。直写式就是直接将会聚的电子束斑打在表面涂有光刻胶的衬底上，不需要光学光刻工艺中最昂贵和制备费时的掩模；投影式则是通过高精度的透镜系统将电子束通过掩模图形平行地缩小投影到表面涂有光刻胶的衬底上。Here comes your footer 6几种电子束曝光系统的性能He
5、re comes your footer 7极紫外光刻和X射线光刻 采用波长在0.110nm的X射线或者波长在1070nm的软X射线（即紫外光）进行光刻，缩小特征线宽的极限；传统的透镜对极紫外光不是透明的，也不能聚焦X射线，而其能量辐射会很快地破坏掩模和透镜用的材料；最显著的特点是采用Mo/Si多层材料构成布拉格反射器，而非传统光学光刻中的球面透镜，用做掩模的材料是可以吸收极紫外线的TaN,Cr,W等；XRL的优点：高分辨力；大焦深和大像场等；分辨力可达40nm，它可用于UL-SI、纳米加工和 MEMS等。XRL的缺点：采用大型的、昂贵的同步加速器，巨额耗资，对量产IC工艺难以接受；高集成的1
6、倍掩模版难制作；与光学光刻机相比，生产效率极低。制作所需的设备将是非常昂贵Here comes your footer 8离子束光刻技术 离子束光刻(IPL)的研究始于20世纪70年代，它是将离子源(气体或液态金属)发出的离子通过多极静电离子透镜，将掩模图像缩小后聚焦于涂有抗蚀剂的片子上，进行曝光和步进重复操作。IPL的优点：离子束曝光基本上不存在邻近效应，故有比电子束光刻更高的分辨力；在同样能量下，感光胶对离子的灵敏度要比电子高数百倍。IPL的缺点：液态金属离子源发射的离子具有较大的能量分散，而聚焦离子束系统所采用的静电透镜具有较大的色差系数，色差会影响离子束聚焦；由于离子的质量大，在感光胶
7、中的曝光深度有限，故限制了离子束曝光的应用范围。Here comes your footer 9原子光刻技术 原子光刻技术(AL)是贝尔实验室G.Timp等人最早提出的，它是利用激光梯度场对原子的作用力来改变原子束流在传播过程中的密度分布，使原子按一定规律沉积在基板上，在基板上形成纳米级的条纹、点阵或所需要 的特定图案。AI 的优点：原子呈 中性，不像电子和离子那样容易受到电荷的影响，因而具有极高的分辨力；原子的德布罗意波长非常短，其衍射极限比常规光刻所用的紫外光 的衍射极限小很多。AL的缺点：部分原子在聚焦时偏 离理想聚焦点，形成原子透镜的像差；原子与梯度场的作用时间等也影响成像质量Here
8、 comes your footer 10摩尔定律：1965年Gordon Moore提出了芯片集成度每两年翻一番(后来改为每18个月翻一番)。自那时以来，IC集成度的增长一直遵循这一定律。从光学光刻的发展来看：分辨率(R)每三年缩小0.7倍，曝光波长()每六年上一新台阶，数值孔径(NA)每年增加0.03，工艺因子(K1)每年减少0.03，并相应提高了套刻精度、像场尺寸、片径和生产率。光学光刻的进展示意图Here comes your footer 11非光刻图形技术（1）纳米压印技术和软刻印技术 代替物理的光和电子源，利用一块橡胶聚合物作为工具，采用日常所见的印刷、模锻、模铸和压印等力学过程
9、来制造纳米结构，称之为软刻印技术（Soft Lighography）和纳米压印技术(Nano-Imprint Lithography，NIL)。（2）扫描探针技术 彻底抱起自上而下的手段，采用自底而上的人工组装方法，也就是从移动原子或者分子的开始组装并构建纳米功能结构，最成功的是STM微分析技术发展而来的扫描探针技术。Here comes your footer 12软刻印技术 软刻印术主要有两钟：微接触印刷法、毛细管微模制法。微接触印刷法是由 Whitesides等人于1993年提出的。它的主要思想是使用具有纳米图案的弹性印章将自组织单分子膜印到基片上。用毛细管微模制法制作纳米图形结构，也要
10、像微接触印刷法那样，先制作浅浮雕式母板并且由母板制作PDMS印章，但在这里不称其为印章而称为铸模更合适。微接触印刷法的工艺流程图毛细管微模法的工艺流程图Here comes your footer 13纳米压印技术 纳米压印技术是软刻印技术的发展，采用绘有纳米图案的刚性压模将基片上的聚合物薄膜压出纳米级花纹，通过热的或者化学的方法固化在聚合物上保留模板图形，再对压印件进行常规的刻蚀、剥离等加工，最终制成纳米结构和器件。它可以大批量重复性地在大面积上制备纳米图形结构，并且所制成的高分辨率图案具有相当好的均匀性和重复性。该技术还有制作成本低、简单易行、效率高等优点。纳米压印技术主要包括热压印技术和
11、紫外压印技术。Here comes your footer 14热压印工艺紫外压印工艺热塑性聚合物：PMMA等Tg以上透明印章：石英玻璃印章（硬模）或PMMA印章（软模）聚合反应而固化成型保持足够的模压时间，施加足够的模压压力，使聚合物填充满模腔。等固化完全时再脱模，脱模要小心，防止用力过度而使模具损伤Here comes your footer 15 紫外压印一个新的发展，是提出了步进-闪光压印，它可以达到10nm的分辨率。紫外压印的工艺过程是：先将低粘度的单体溶液滴在要压印的衬底上，用很低的压力将模板压到园片上，使液态分散开并填充模板中的空腔。紫外光透过模板背面辐照单体，固化成型后，移去模
12、板。最后刻蚀残留层和进行图案转移，得到高深宽比的结构。采用小模板的方式,提高了在基板上大面积压印转移的能力，降低了掩模板制造成本，也降低了采用大掩模板（光刻胶厚度不均匀）带来的误差。另外，紫外压印相对于热压印来说，不需要高温、高压的条件，可以廉价的在纳米尺度得到高分辨率的图形。生产中常采用步进-闪光纳米压印技术Here comes your footer 16Here comes your footer 17（a）SiO2压模被用12次后的SEM 照片（b）用（a）压模压成的聚合物图案的SEM照片Here comes your footer 18三种压印技术的比较Here comes your
13、 footer 19扫描探针技术 前面提到几种图形转移技术都是从一个宏观的大尺度图形开始，在刻出纳米结构之前按比例缩小图形的横向尺度。但是没有哪一种自上而下的方法能够简单而低成本的制造各种材料的纳米结构。于是一些科学家开始研究自底向上的方法，也就是从原子或者分子开始组装并构建纳米结构。这些方法可以制备最小的纳米结构，而且不是很昂贵。人工组装技术自组装技术扫描探针技术Here comes your footer 20扫描探针技术 扫描探针显微镜不仅仅可以让科学家观察原子世界，它们也可以利用针尖和表面原子、分子的相互作用力来操纵单个原子、单个分子或者用来制备表面纳米结构，即谈针尖可以沿着表面移动纳
14、米粒子并使其重新排列，说制作的纳米图形特征线宽可以达到单个原子的宽度。操作模式主要包括横向操作和纵向操作。Here comes your footer 21 移动过程中第一个垂直的STM操作是由Eigler完成的，他在液氦温度线移动35个Xe原子在单晶Ni（110）表面过程了最小的IBM公司商标 下图是48个Fe原子在Cu（111）表面构成的一个量子围栏，围栏说构成的量子阱诱导表面电子的量子限域效应，从而在图中可以观察到电子波的驻波现象。Here comes your footer 22 1993年Eigler等在Cu(111)表面上成功地移动了101个吸附的铁原子，写成中文的“原子”两个字，
15、这是首次用原子写成的汉字，也是最小的汉字。Here comes your footer 23 中国科学院北京真空物理实验室的研究人员于1993年底至1994年初，以超真空扫描隧道显微镜（STM）为手段，在Si重构表面上开展了原子操纵的研究，取得了世界水平的成果。他们在室温下，用STM的针尖，并通过针尖与样品之间的相互作用，把硅晶体表面的原子拨出，从而在表面上形成一定规则的图形，如“中国”等字样，这些沟槽的线宽平均为2 nm，是当时在室温时，人们在Si表面“写”出的最小汉字。凹陷的地方是原子被拨出后显示的深黑色沟槽，凸起的亮点是散落的原子形成的，显白色。Here comes your foote
16、r 24Nano-imprint lithography:Templates,imprinting and wafer pattern transferW.J.Dauksher*,N.V.Le,E.S.Ainley,K.J.Nordquist,K.A.Gehoski,S.R.Young,J.H.Baker,D.Convey,P.S.MangatMotorola Labs,Embedded Systems Research,2100 E.Elliot Road,MD:EL-317,Tempe,AZ 85284,USAMicroelectronic Engineering 83(2006)9299
17、32Here comes your footer 25background knowledgeAdvancement in resolutionShorter wavelengthHigh priceProhibitive for many companyNano-imprint lithographyLow pressure，Room temperatureIts resolution is only limited by the resolution of the template fabrication process.Defect-free template fabrication a
18、nd a high throughput imprint tool meeting overlay requirements.Here comes your footer 26a low viscosity photocurable monomerUltraviolet light photopolymerizes the monomerHere comes your footer 27Nano-imprint templatesEarly imprint template fabricationMore recently,two methods have been employed to f
19、abricate templatesusing a 6in.*6in.*0.25in.conventional photomask plate and leveraged established Cr-based processes to define features in the glass substrateThe first method uses a much thinner(15 nm)layer of Cr as a hardmask，which acts as a sufficient hardmask because of the high etch selectivity
20、of glass to Cr in a fluorine-based process.The second fabrication scheme attempts to address issues related to SEM and defect inspection by incorporating a layer of conducting and transparent indium tin oxide(ITO)on the glass substrate.Here comes your footer 28Nano-imprint templatesThe current focus
21、:the needs for 32 nm node lithography、high resolutionThe standard template manufacturing process uses a thin resist layer of ZEP-520A and a chrome thickness of 15 nm as the etch mask to define the quartz images using a Leica VB6To achieve smaller dimensions,the thickness of both the resist and the c
22、hrome layers needed to be reduced.For the post fabrication,we have targeted an aspect ratio of 1:2.5 which minimized the liquid develop surface tension issue that often causes features to fall over.As for the contacts,the new resist thickness of 100 nm provided the resolution necessary to create the
23、 smaller structures.Here comes your footer 29High resolution posts and contacts.A template on which 1:1 posts of 40 nm and 1:7.5 contacts of 30 nm have been createdHere comes your footer 30InspectionInspection of the templates using electron beams for applications requiring sub-50 nm lithography wil
24、l be needed.Hence,the template will require a scheme to dissipate charge during the inspection processThe ITO layer：do an excellent job controlling the charging.E-beam inspection images of an ITO template:140 nm features with programmed defects have been successfully inspected(at 50 nm pixel inspect
25、ion).Here comes your footer 31repairationWe have recently focused on exploring repairing clear and opaque defects on nano-imprint templates using focused ion beam(FIB)and e-beam technologiesRepairs were performed on templates after chrome patterning and after relief etching of the quartzSEM images o
26、f the imprinted templates revealed high spots in the cured monomer wherethe repairs have been made.These high spots appear to be caused by excess milling,or lack of depth control.Here comes your footer 32Nano-imprint toolImprio 100 tool(Molecular Imprints Inc.):designed as a step-and-repeat patterni
27、ng tool and can accommodate wafer sizes up to 200 mm in diameterclass 0.1 mini-environment:In order to minimize defect issues during the imprint process,the tool is equipped with a class 0.1 mini-environment.a multiple jet dispense head:for the dispensing of the etch barrier which led to reducing th
28、e imprint time.Etch barrier thickness comparison between single and multi-jet dispense systems.Here comes your footer 33Pattern transfera multi-layer scheme:pattern the underlying filmsBecause of the presence of a residual layer of the etch barrier(EB)over the transfer layer,it is essential to minim
29、ize the thickness of the etch barrier for subsequent pattern transfer of sub-45 nm features into wafer-level films such as oxides.Our focus has been on developing a very robust wafer-level pattern transfer process with an optimized imprinting process using a multi-jet dispense system which results i
30、n a very thin layer of the residual layer.Here comes your footer 34Fabrication of complex nanoscale structures on various substratesKang-Soo Han,Sung-Hoon Hong,and Heon LeeaDepartment of Materials Science and Engineering,Korea University,APPLIED PHYSICS LETTERS 91,123118 2007Here comes your footer 3
31、5Significance Three dimensional 3D nanostructures on various substrates,including Si wafer,glass plate,and polyethylene terephtalate PET polymer film,can be used for micro-and nanoelectro-mechanical system devices,photonic bandgap structures,optoelectronic devices,bionanodevices and tissue engineeri
32、ngAdvanced reverse nanoimprint lithographys yield-limiting step:the detachment of the mold.High pressure and temperatureHere comes your footer 36Creative point:by using PVA material as a mold and an UV glue,the UV light based reverse nanoimprinting process is done with low pressure.PVA:polyvinyl alc
33、ohol UV glue:3%of UV initiator(IGAcure184),7%of ethylene glycol dimethacrylate,which is commonly used as a cross-linking agent,and 90%of ethanolHere comes your footer 37Reasons:UV glue:appropriate bond strength and low viscosity.After bonding,no residual layer needs to be remained.The quartz mold wa
34、s easily detached because the bonding strength of the nanostructured layer to the quartz mold was still weaker than that of the PVA moldHere comes your footer 38Experimental programFIG.Fabrication procedure of the PVA mold.2000rmp;20s;2-3 times at RTSi-based template was used as the master mold:usin
35、g conventional deep ultraviolet photolithography and reactive ion etching.Silane-based hydrophobic self-assembled monolayer(SAM)antistiction treatment:obtain defect-free releaseHere comes your footer 39FIG.Overall fabrication process of multistacked dual-side patterned films using UV-curable reverse
36、 nanoimprint lithography.immersed in water at room temperature for 2 h to remove the PVA moldHere comes your footer 40The surface patterns were formed from the PVA mold;The patterns on the interface side were originated from the quartz mold;The nanostructured layer was bonded to the Si wafer and gla
37、ss plate using the UV-curable glue;no residual layer comprising the UV-curable glue was observed.Here comes your footer 41Here comes your footer 42summary a nanostructured layer containing patterns as small as 250 nm on both sides was transferred to various substrates such as Si wafers,a glass plate
38、,and flexible PET films by combining a water soluble PVA mold with an UV-curable glue.By repeating the reverse nanoimprinting processes,the nanostructured layer was stacked on the previous layer,suggesting that 3D micro-and nanostructurescan be fabricated on various substrates.Here comes your footer 43Here comes your footer 44
