第二讲 工艺综述

MEMS和微系统设计 课程内容 MEMS概述及MEMS设计的概述工艺简要回顾系统设计 工艺设计及版图设计主要的机械 电子元件及其设计基础多域耦合设计 以机电耦合为例子器件性能的估计简单的其他域的元件及其简要设计要点设计实例 第二讲主要内容 4 1 制造过程中涉及的关键工艺光刻 成膜 腐蚀 掺杂2 成套工艺体硅 表面 LIGA3 其他先进制造技术软光刻 纳米制造技术 制造过程简要回顾 制造工艺部分讲授 ThickerfilmsdeeperetchesfewerstepsMultipleprocessingcyclesRemovalofunderlyingmaterialstoreleasemechanicalstructuresDepositonofmaterial Patterntransfer Removalofmaterial probetesting secticning individualDIE Assemblyintopackage packageseal finaltest 洁净室的等级 ft feet 30 48cm fpm 0 005m s 1F 0 556oC 光刻过程 SurfacePreparationCoating spinCasting Pre Bake SoftBake AlignmentExposureDevelopmentPost Bake HardBake ProcessingUsingthePhotoresistasaMaskingFilmStrippingPostProcessingCleaning Ashing 对准原理 光刻机的种类 AligenmentandExposureHardware 1 CONTACTALIGENERPROXIMITYALIGNERPROJECTIONALIGNER 2operatingmodes contactforexpose SeparateforalignExamples Kaspar17 OrielKariSussMJB3 Lesswearonmask butpoorerimagethanfromacontactaligner Examples Kaspar Cobilt Examples Perkin ElmerMicralign ProjectionsystemsuseimagingopticsInbetweenthemaskandthewafer 投射式光刻原理 无掩模光刻 幻灯片与投影仪 光刻机的发展及其极限 Raleigh极限对于MASK的featuresize同样具有重要意义 1 负胶2 剥离的好处 图形转移的精度3 台阶覆盖性 成膜工艺 grown filmsTypically converted fromoriginalsubstratematerialExample SiO2formedbyoxidationofSisubstrate deposited filmsCrystalline polycrystalline amorphousElectro depositionNotstandardICprocessLiquidphasedepositonNotstandardICprocessVaporphasedepositionPVD physicalvapordepositionCVD chemicalvapordeposition 1 指标 厚度 2 质量3 速度4 一致性5 温度6 工艺兼容性7 成本 ThemalOxidationofSilicon FormationoftheoxideofsilicononthesiliconsurfaceisknownasoxidationThermalOxidationischaracterizedbyhightemperatures 900 1200DegreeC Twomainprocesses DryOxidationSi s O2 SiO21atm 1000CWetOxidationSi s 2H2O SiO2 2H2Dryoxidationproducesabetter moredense oxideascomparedtowetoxidation Oxidationthickness wetoxidation dryoxidation 640Torrparticalpressureistypical vaporpressureoverliquidwater 95 膜的质量和速度的量级 Thin FilmDepositon Spin onFilmsPolyimide PI photoresist PR Spin onglass SOG PhysicalVaporDeposition PVD EvaporationSputteringChemicalVaporDeposition CVD OxidationLPCVDPECVD 淀积过程中压力的其他影响 淀积工艺控制方式 利用温度 压力对于气体流量 反应速度的影响 KinetictheoryofgasesforagasatSTP N 2 7 1019molecules cm3 N pressure oneatmosphere 1 0132 105pascal 760Torr mmHg 1Pascal 1 132Torr 10 5atmsfractionofmoleculestravelingdistancedwithoutcollidingis isthemeanfreepath atroomtemp 0 7cm P inpasscals 5 3 10 3cm P inTorr atroomtempandoneatatmosphere 0 07 Velocitydistributionforidealgas velocitydistributionisMaxwellian we lluse 900miles houratrmtemprateofsurfacebombardment flux J 3 4 1022 cm2 sec P MT PinTorr Misgram molecularmassmonolayerformationtime moleculesperunitarea bombardrate Impactofpressureondepositionconditions Pressureinfluences Meanfreepath 1 P contaminationrate 1 P roughvacuumhighvacauumveryhighvacuum CVD基本原理 Heatentiresystem ThermallydrivenreactionsRequiresleak tight sealedsystemAvoldunwantedcontamination escapeofhazardousmaterials thereactants Atmospheric highdepositionratesLowpressure LPCVD lowerrates gooduniformity CVD能干什么 SiliconOxideDryoxidation Si O2 SiO2Wetoxidation Si 2H2O SiO2 2H2SiH4 O2 SiO2 2H2SiH4 N2O SiO2 by productsSiCl2H2 N2O SiO2 by productsSi OC2H5 4 SiO2 by productsSiliconNitride3SiH4 4NH3 Si3N4 12H2SiCl2H2 NH3 Si3N4 by productsSiH4 4N2O Si3N4 by productsSiH4 N2 Si3N4 by products Polysilicon SiH4 Si 2H2SiliconCarbidePolycrystallineDiamondParylene polymerizedp xylyene Refractorymetals 2WF6 3SiH4 2W 3SiF4 6H2II VIcompounds e g CdSe ThermalevaporationMainheatingmechanisms resistivolyheat boat containingtung mp3410 tantalum mp2996 molybdenum mp2617 verycommon heater materialsreactionwithboatpotentialproblem electronboamevaporatorsourcematerial directly heatedbyelectronbombardment cangenerateX ray candamagesubstratel deviceslboam 100mA Vacc KVinductivelyheatmaterial directmetal essentiallyeddycurrentlosses SputteringPlasmageneratehighdensity energeticincidentparticles magneticfieldusedtoconfineplasma electricfield bias toaccelerat deplasma metalsrateupto 1 m minute rfplasma dielectricsTypicallyinert noble gasusedtoformincidentions ionenergies fewhundreseV ejectedatoms tenseV o o1Torr 5mm betterstepcoveragethanevaporation SummaryofSiO2characteristics DifferentprofilesofDopants Diffusionvs IonImplantationfurnacevaccum950 1280oCRoomTemperatureGasofdopantionsHighvelocitydopantions 腐蚀 选择性 湿法腐蚀 溶液 化学方法 SiliconEtchingIsotropic 1 HF HNO3 CH3COOH H2O 2 HF 3 HF NH4FAnisotropic 1 KOH 2 EDP EthylenediaminePyrocatechol 3 CsOH 4 NaOH 5 N2H4 H2O Hydrazine MaskingMaterials 1 Photoresist AcideOnly 2 Si3N4 3 SiO2 晶向 晶面 晶族的概念湿法腐蚀的要素 化学反应 多余物的处理等 AnisotropicEtchingofSilicon 2 SiliconNitrideandSiliconDioxideEtching Si3N4Etching1 HFetchesabout600 min10 HFetchesabout5000 minBHFetches5 10 minH3PO4etches100 minat180 SiO2EtchingBHFetches1000 2500 minHFetchesveryquicklyEtchratesforbothSiO2andSi3N4varygeneratlydependingonfilmquality MetalEtching CopperandNickel 1 30 FeCl3 2 5 Piranha 30 H2O2 70 H2SO4 3 KI I2 H2O Nottransparent Chromium usuallyrequiresdepassivation 1 AquaRegia 75 HCL 25 HNO3 2 HCL GlycerinGold Au 1 AquaRegia 2 Iodine 3 AlkaliCyanidew HydrogenPeroxideSilver Aq 1 Iodine 2 HNO3 不同类型的干法腐蚀 等离子体物理方法气体化学反应RIEDRIE PlasmaEtchingSteps Typicalkineticenergy KE ofanelectroninplasmais2 8eVKE 1 2mV2 2 3kT m particlemass V particlemeanvelocity k Boltzmannconstant T temperature K 2eVelectronhasT 15 000KV 6 107cm s 1 342 16176mph XenonDifluoride XeF2 EtchingIsotropicetchingofSiHighselectivityforAl SiO2 Si3N4 PR PSG2XeF2 Si 2Xe SiF4Typicaletchratesof1to3 m minHeatisgeneratesduringexothermicreactionXeF2reactswithwater orvapor toformHF Interhalogen BrF3 ClF3 EtchingNearlyisotropicprofileGasesreactwithSitoformSiF4Surfaceroughness 40to150nmMasks SiO2 SiN4 PR Al Cu Au andNi RIESystem ReactiveIonEtching RIE AsymmetricalparallelplatesystemPlasma sheathandboundarylayerCombinationofphysicalandchemicaletchingAnisotropicetching DisadvantagesofRIEConflictbetweenetchingrateandanisotropicprofile Etchingrate Reactivespeciesconcentration Gaspressure Collision Anisotropic Conflictbetweendamageofhighetchingrateandanisotropicprofile KE Etchingrate damage ClassificationisprimarilybasedonhowpowerissuppliedtocreateplasmaDCdischarge electrodes 500mTorr inefficient nolongerinuseintheICindustry Radiofrequency RF capacitivelycoupled 13 56MHzistheprimaryfrequencyallowedbyFCC 300mTorr verypopularinICindustryMicrowavedischarge 2 45GHzistheallowedfrequency lowtohighpressure VerypopularindiamonddepositionElectronCyclotronResonance ECR discharge Microwavedischargewithamagneticfield CommononlyinJapanInductivedischarge simple highplasmadensitycomparedtocapacitivedischarges CommonintheU S inICindustry ECRSystemsICPSystem DRIE ElectronCyclotronResonmance ECR HigherplasmadensityatlowerpressureControlthedensityofthereactiveionsandtheirkineticenergyseparatelyDownstreamofplasmafurtherlimitstheexposuretoreducedamage InductiveCoupledPlasma ICP SimplesystemAlmostsameprocessresultasthatfromtheECRsystemTwoRFpowergeneratorstocontrolionenergyandiondensityseparately DeepReactionIonEtching HighdensityICPplasmaHignaspectratiostructuresCost 500KVendors STS Alcatel PlasmaTherm WaferSize125mmFeaturewidth100 mEtchdepth200 mEtchTime20minMaskResistSietchrate10 m minMaskselectivity 250 1Uniformity 5 Profile89DegreesUndercut 1 depthProcessregimeRoomtemp EtchChemistriesOrganicFilms Oxygenplasmaisrequired By products CO CO2 H2O Masks Si SiO2 Al orTi Additionoffluorinecontaininggasessignificantlyincreasesetchratebutdecreasesselectivity duetoHFformation OxideandNitrideFilms Flourineplasmaisrequired eg CF4 Mask PR AdditionofO2IncreaseetchrateAdjustsPR oxideandPR nitrideselectivitySilion Fluorineplasma CF4orSF6 Chlorineplasma Cl2 第二讲主要内容 3 1 制造过程中涉及的关键工艺光刻 成膜 腐蚀 掺杂2 成套工艺体硅 表面 LIGA3 其他先进制造技术软光刻 纳米制造技术 表面工艺 FabricationStepsSacrificialLayerDepositionandEtching AlsoSpacerorSacrificialLayer DepositionofStructureMaterialSelectiveEtchingofSpacerLayer 黏附应力 体硅工艺 画出一个简单的体硅工艺流程图 LIGA LIthographieLithographyGalvanoformungEle