纳米材料和纳米结构第09讲-纳米图案化技术

纳米结构和纳米材料ArtificialPatterningofNanostructures

纳米结构的人工图案化技术

第九讲

1IntroductionEnormousAchievementObtainedbyMicroelectronics(微电子取得了巨大的成就)••••Richfunctionalityinapplications〔应用功能广泛〕Lowenergyconsumptioninoperations〔运行过程能耗低〕Lowcostinfabrications〔制作本钱低廉〕Extendedintonon-electricareassuchasmicro-actuators,-sensorsand〔深入微制动器、感应器和微DNA探测等非电子领域〕

micro-DNAprobesFabrication:frommicrometertonanometerscale制造：从微米到纳米尺寸•••Horizontaldevicefeaturesize:0.18μmto35nm〔水平技术参数：0.18微米到35纳米〕Verticaldevicefeaturesize:lessthan1.5nm〔垂直技术参数：小于1.5纳米〕Artificiallypatternednanostructureswithreproducibility,suchasquantum〔人工纳米结构图案的可重复性，如量子点、光子点阵〕 dots,photoniclatticesetc.Promisingtechniques:electronbeamlithography(EBL),X-raylithography(XRL),extremeultravioletlithography(EUVL)〔有前景的技术：电子发射平版印刷术、X射线平版印刷术、远紫外线平版印刷术〕 Lithography-平版印刷术〔光刻〕Similartotraditionalopticallithography,nanolithographyalsoconsistsofthreeparts:〔与传统光学印刷术相同的是：纳米光刻也包括3局部〕•Atool〔一种工具〕•Aproperresist〔一种适宜的反蚀药剂〕•Apatterntransferprocess〔一个图案转换过程〕Aspecificnanostructurepatterniscarriedbyanilluminatingsourceandbeamedontoaresistlayersensitivetotheparticularsource,andthepatternintheresististhentransferredontoanunderlyingsubstrate〔具体的纳米图案先通过一种照明材料显现出来，然后发射到对照明源反响敏感的防腐层，最终在反蚀剂的图案转移到衬底〕Differencesbetweennanolithographyandopticallithography〔纳米刻录和光学刻录的区别〕:•Exposingsources〔显现材料〕•Masks〔面具〕•resists〔反蚀剂〕2Nanolithography〔纳米平版印刷术〕•8nmlinesinAuPdusinga0.5nme-beam(1976)〔用0.5纳米的电子束在AuPd刻录的8纳米图案〕 2-1ElectronBeamLithography(EBL)〔电子书刻蚀〕EBL:amethodthatallowstheoriginaldigitalimagetobetransferreddirectlytotheinterestedsubstratewithouttheuseofmask〔EBL技术：是一种可以不用面具直接将初始图案转移到衬底的方法〕Progresshistory: •50nmlinesintometalfilmusingaresistwitha10nme-beam(1964)〔在某种反蚀剂用10纳米电子束金属薄膜刻录的50纳米图案〕•FabricationofAharonov-Bohminterferencedevicebye-beam(1984)〔阿哈罗诺夫－玻姆电子干预仪的制造〕•1-2nmlinesinmetalhalide(1985)〔在金属卤化物刻蚀的1-2纳米图案〕•Fabricationofresearchandprototypenanoelectronicdevices,makingmasks forotheradvancedlithographies〔研究标准纳米电子仪的制造，专门用于其他先进刻蚀技术面具的生产〕 EBL-电子束直写技术InEBLnanofabrication,workingconditionsatwhichelectronscatteringcausesminimalresistexposureshouldbeespeciallynote〔在EBL刻蚀纳米产品的制造中会引起最小反蚀剂的曝光的电子分散的工作环境应该非常注意〕dTwomodes:veryhigh/lowenergyelectrons〔俩种模式：高能量和低能量电子模式〕•Inhighenergycase,thebeambroadeningintheresistthroughelasticscatteringisminimalandthebeampenetratesdeeplyintothesubstrate〔在高能量模式，电子束有小局部通过弹性散射会大范围扩散到反蚀剂中并深度渗入衬底〕•Inlowenergycase,electronsareunabletoscatteroverlargedistancesintheresistandthereforebemoreeffective〔在低能量模式：电子不能在反蚀剂中大范围扩散，因此更有效率〕Keyfactorsine-beamnanolithography〔电子束刻蚀的关键因素〕•SpeedandPrecision〔速度和精确度〕•YieldandProcessContro〔产量和过程控制〕l•Fundamentallimitsofe-beam/resistinteractions〔电子束和反蚀剂反响的严格限制〕2-1-1EBLMachineThreeessentialpartsofanEBLequipment:anelectrongun,avacuumsystem,andacontrolsystem〔电子刻蚀仪的3个重要组成：电子枪，真空系统、控制系统〕Electrongun:generates,accelerates,focuses,andprojectsabeamofelectronsontoasubstrate〔电子枪：产生器，加速器，聚集器和把电子束发射到衬底的工程〕Vacuumsystem:createsavacuumenvironmentintheelectronguncolumnandtheworkingchamber〔真空系统：在电子枪栏和工作室创造真空环境〕Controlsystem:providesthemanipulationcapabilityfortheelectronbeamgeneration,propagation,andtiming,aswellascontroloverthesubstratetranslation〔控制系统：对电子束产生量、增值量和时间的控制以及转移到衬底过程的控制〕TwowaystogenerateactualpatternsbyEBLmachine:〔电子刻蚀仪产生实际图案的俩种方式〕•Rasterscanning:byscanningtheexposingbeaminonedirectionatafixedratewhilethesubstratemovingunderthebeambyacontrolledstage〔光栅扫描：通过在电子束下衬底在控制平台下移动时扫描某个方向显现的一定速率的电子束〕•Vectorscanning:bydeflectingtheexposurebeamonlytothoseregionsofthesubstratethatrequireexposure〔矢量扫描：通过衬底某个区域需要显现的电子束的偏转〕2-1-2E-beamResists〔电子束反蚀剂〕Electronbeamexposurealtersthenatureoftheresistthroughbreakingthechemicalbonds,withtheresultthatasubsequentimmersionofthesampleinachemicalsolutionremovestheexposedparts(positiveresist),ortheunexposedparts(negativeresist),oftheresistfilmUsuallypolymericsolutionsappliedtothesubstratesurfacebyspincoatinganddriedbybakingtoformauniformthinlayerwhosethicknessshouldnotexceedtheminimumfeaturesizerequiredPMMA(聚甲基丙烯酸甲酯)isastandardhigh-resolutionpolymericresistused,withabestresolutionof10nmlinesInorganicresistwithfarsuperiorresolutiontoPMMA:metalhalide,metaloxide,andsemiconductoroxideswhichundergoaradiolysisreactionunderelectronirradiation(1-5nm)电子束反蚀剂电子曝光通过打断化学键的方式决定了反蚀剂的性质，随后在化学试剂中对样品的渗入消除试剂的反响局部或剩余局部；通常将聚合物粘在衬底外表，并将其烘烤至不超过要求的最小参数大小；PMMA是一种标准的高溶解度聚合物反蚀剂，最适合大小10纳米；比PMMA溶解度大得多的无机试剂有：金属卤化物，金属氧化物，以及半导体氧化物——因为他们能够承受1-5纳米的电子辐射反响AnecessaryprocesstotransfertheEBL-madepatternfromtheresistontotheunderlyingsubstrateTwobasicpatterntransfermethods•Additiveprocess:addinganewmaterialtothesurfaceofthe substrate,wheretheresisthasbeenremovedthroughthepatterningprocess;includingLift-offprocessandPlatingprocess•Subtractiveprocess:removingsomematerialsfromsubstrateselectivelyonlyintheareaswheretheresisthasbeenremoved2-1-3PatternTransferProcess图案转移过程将EBL制作的图案从反蚀剂转移到下面衬底的必要过程；俩种根本的转移方式：1、添加方式：在通过图案形成过程已经出去反蚀剂的衬底外表加一种新材料；包括剥离法和电镀法；2、抽离方式：去掉衬底已除去反蚀剂区域局部的材料TheLift-offprocessflowAnundercutprofileinPMMAresistTheElectroplatingProcessflowSubtractivePatternTransferProcessAdvantagesofX-rayenergysourceandXRL•Greatpenetratingpower•Scatteringfreeproperty•Withveryhighresolutionwhileeliminatingdepthoffocus,reflection,andscatteringproblems•Withprecisefeaturesizeandbetteredgecontrol•Beindependentofpatterngeometry,substratetopography,andsubstratereflectivityDifferencesbetweenXRLandotherlithography•Sources(synchrotronradiationandlaserplasma)•Masks•resists2-2X-rayLithography(XRL)X射线刻蚀X射线能量来源和X射线刻蚀的优点：1、强大的穿透能；2、自由散射性能；3、在消除聚焦，反射，散射问题深度的同时有很高的分辨率4、准确的大小参数和边缘控制;5、与图案形状、衬底形状和衬底反射率无关X射线刻蚀与其他刻蚀的区别：1源〔同步加速辐射和激光等离子体〕；2、面具；3、反蚀剂TypicalschematicdiagramsofXRLsystem(1)UtilizingapointX-raysourceTypicalschematicdiagramsofXRLsystem(2)ASynchrotron-basedXRLsystemMaskFabrication:themostdifficultchallengeofXRLMesa-台面；pyrex-硼硅酸玻璃；attenuation-衰减AgoldadditiveprocessforX-raymaskfabricationResistrequirement〔反蚀剂要求〕•Highsensitivitytoionizingradiation〔对离子辐射强烈敏感〕•Goodetchresistancei