第四章_化学气相沉积优秀PPT.ppt
第四章_化学气相沉积第一页，本课件共有88页要点：要点：化学气相淀积的基本原理化学气相淀积的基本原理过程、反应、速度过程、反应、速度CVD特点特点CVD装置装置低压低压CVD等离子体化学气相淀积等离子体化学气相淀积PECVD金属有机物化学气相沉淀（金属有机物化学气相沉淀（MOCVD）第二页，本课件共有88页4.1简介Hardestmat.-Damagedthehardnesssensor2.5mmhigh,grownin1daysingle-crystal diamond grown by CVDC.S.Yan et al.,Physica Status Solidi(a)201,R25(2004).第三页，本课件共有88页化学气相淀积，简称化学气相淀积，简称CVD(ChemicalVaporDeposition)是把含有构成薄膜元是把含有构成薄膜元素的一种或者几种化合物或单质气体供素的一种或者几种化合物或单质气体供给基片，借助气相作用或在基片上的化给基片，借助气相作用或在基片上的化学反应生成所需薄膜。学反应生成所需薄膜。gasinletgasdecompositiongasreactionsubstrateadsorptiongasexhaust定义定义第四页，本课件共有88页1)气体分解方式气体分解方式 gas decomposition (1)thermal deposition (2)plasma deposition (3)photon(laser,UV)deposition2)CVD种类种类according to temp.,pressure,CVDchemicalvapordepositionAPCVDatmosphericpressure.LPCVDlow-pressure.VLPCVDverylowpressurePECVDplasma-enhanced.LECVDlaser-enhanced.MOCVDmetal-organic.ECRCVDelectron-cyclotronresonance.VPEvapor-phaseepitaxy第五页，本课件共有88页3)优势优势advantageslow cost dielectric(poly-silicon,Si3N4,SiO2)and metal thin filmhigh deposition ratehigh or low pressurecontrol thickness,defect and resistivityhigh film qualityLTCVD for semiconductors,ex.,Si3N4,SiO2 and epilayerlow radioactive damageBut high deposition temperature and environment damage第六页，本课件共有88页4)沉积参数parametersforthinfilmstructure(1)temperatureofsubstrateandchamber(2)growthrate(3)gaspressureTheseparametersaffectonsurfacespeedoftheinvolvedatoms.第七页，本课件共有88页OverviewnotallcomponentsarefoundinallCVDsystems:SourcegasReactsonsubstratetodepositfilm第八页，本课件共有88页4.2化学反应类型化学反应类型1.热分解热分解Pyrolysis-thermaldecompositionAB(g)-A(s)+B(g)ex:SidepositionfromSilaneat650oCSiH4(g)-Si(s)+2H2(g)usetodeposit:Al,Ti,Pb,Mo,Fe,Ni,B,Zr,C,Si,Ge,SiO2,Al2O3,MnO2,BN,Si3N4,GaN,Si1-xGex,.第九页，本课件共有88页2.还原还原ReductionoftenusingH2(metal,substrate)AX(g)+H2(g)A(s)+HX(g)-oftenlowertemperaturethanpyrolysis-reversible=canuseforcleaningtooex:Wdepositionat300oCWF6(g)+3H2(g)W(s)+6HF(g)-usetodeposit:Al,Ti,Sn,Ta,Nb,Cr,Mo,Fe,B,Si,Ge,TaB,TiB2,SiO2,BP,Nb3Ge,Si1-xGex,.第十页，本课件共有88页3.氧化氧化/氮化反应氮化反应Oxidation/NitritionoftenusingO2/N2AX(g)+O2(g)-AO(s)+OX(g)ex:SiO2depositionfromsilaneandoxygenat450oC(lowertempthanthermaloxidation)SiH4(g)+O2(g)-SiO2(s)+2H2(g)usetodeposit:Al2O3,TiO2,Ta2O5,SnO2,ZnO,.第十一页，本课件共有88页4.置换反应置换反应ExchangeoftenusingamoniaorwatervaporAX(g)+NH3(g)-AN(s)+HX(g)AX(g)+H2O(g)-AO(s)+HX(g)ex:depositwearresistantfilm(BN)at1100oCBF3(g)+NH3(g)-BN(s)+3HF(g)usetodeposit:TiN,TaN,AlN,SiC,Al2O3,In2O3,SnO2,SiO2,.第十二页，本课件共有88页5.歧化反应歧化反应Disproportionationcompoundsinvolvingelementswithmultiplevalencestates（多种价态）2AB(g)A(s)+AB2(g)ex:usetodeposit:Al,C,Ge,Si,III-Vcompounds,.第十三页，本课件共有88页6.可逆输运可逆输运ReversibleTransferex:usetodeposit:GaInAs,AlGaAs,InP,FeSi2,.第十四页，本课件共有88页Howdoesreactiongo?Dependsonparameters:TemperaturePressurereactants(purity,concentration)Thermodynamicsanddynamics第十五页，本课件共有88页第十六页，本课件共有88页第十七页，本课件共有88页4.3Reactionlaw1.CVD热力学热力学判断反应、方向、平衡判断反应、方向、平衡ignoresrateinformationDGristhecriteria.DGr0(Textbookp111)第十八页，本课件共有88页notstrictlycorrectinflowingsystem(nonequilibrium)EllinghamplotscanbeusefulMoCl5,ReCl3andAsCl3areallreducedbyHtometalsandHClNi,Fe,andCochloridesreduceatintermediatetemperaturesSiCl4reducesathightemperaturemanyothermetalchloridesaretoostableCrCl2isclose-butnotquiteFig.4.2第十九页，本课件共有88页第二十页，本课件共有88页第二十一页，本课件共有88页4.4CVD过程动力学气气体体输输入入气气体体对对流流气气相相扩扩散散表表面面吸吸附附表表面面反反应应表表面面脱脱附附薄薄膜膜成成核核生生长长第二十二页，本课件共有88页1.CVDFilmGrowthStepsoncereactionisidentified,considertheprocessindetail:源source:productionofappropriategas气相传输transportofgastosubstrate沉积depositionoffilm:吸附吸附adsorptionofgasonsubstrate反应反应reactiononsubstratephasetransformationrecrystallization,graingrowth废气排除废气排除transportofwasteproductsawayfromsubstrate第二十三页，本课件共有88页A.CVDSources源类型typesofsourcesgasses(easiest)volatileliquidssublimablesolidscombinationmaterialsshouldbe稳定稳定stableatroomtemperature挥发性挥发性sufficientlyvolatilehighenoughpartialpressuretogetgoodgrowthratesreactiontemperaturestagnantlayer(滞流层、边界层滞流层、边界层)diffusegasthroughstagnantlayertosurface第二十七页，本课件共有88页masstransportdependsonfundamentalparametersexperimentalparameters反应物浓度反应物浓度reactantconcentrationpressure扩散扩散diffusivitygasvelocity边界层厚度边界层厚度boundarylayerthicknesstemperaturedistributionreactorgeometrygasproperties(viscosity.)第二十八页，本课件共有88页B.气相扩散模型气相扩散模型(Grove,1967)AB(g)-A(s)+B(g)F1=fluxtosurfaceF2=fluxconsumedinfilmCG=concentrationofABingasCS=concentrationofABatsurface第二十九页，本课件共有88页F1=hG(CG-CS)=D/*(nG-nS)wherehG=gasdiffusionrateconstant,orDF2=kSCSwhereks=surfacerateconstantinsteadystate:F1=F2=FgrowthrateoffilmisproportionaltoFTT3/23/2/p第三十页，本课件共有88页C.Tworate-limitingcasesa传质限制机制传质限制机制masstransferlimitedsmallhGgrowthcontrolledbytransfertosubstratehGisnotverytemperaturedependentcommonlimitathighertemperatureslowerpressure,higherT Quicker diffusion Quicker diffusion第三十一页，本课件共有88页b表面反应限制表面反应限制surfacereactionlimitedkS=C*exp(-Er/RT)smallkSgrowthcontrolledbyprocessesonsurfaceadsorption,decompositionsurfacemigration,chemicalreactiondesorptionofproductskS=C*exp(-Er/RT)ishighlytemperaturedependent(increaseswithT)commonlimitatlowertemperaturesoftenpreferred第三十二页，本课件共有88页第三十三页，本课件共有88页4.5CVD装置1.电阻加热电阻加热2.高频感应加热高频感应加热3.红外加热红外加热4.激光加热激光加热视不同反应温度，视不同反应温度，选择不同的加热方式选择不同的加热方式要领是对基片局部加热要领是对基片局部加热1.加热方式加热方式第三十四页，本课件共有88页2.反应室结构反应室结构卧式开管卧式开管CVD装置装置a、开口体系、开口体系特点：具有高的生产能力，但沿气流方向存特点：具有高的生产能力，但沿气流方向存在气体浓度、膜厚分布不均匀性问题。在气体浓度、膜厚分布不均匀性问题。反应气体不断提供，反应副产物不断被抽走，反应气体不断提供，反应副产物不断被抽走，常压、稍高于一个大压（有利于废气排除），低压常压、稍高于一个大压（有利于废气排除），低压第三十五页，本课件共有88页立式CVD装置特点：特点：膜厚均匀性好，膜厚均匀性好，但不易获得高但不易获得高的生产力。的生产力。第三十六页，本课件共有88页转筒转筒CVD装置装置特点：特点：膜厚均匀性好，膜厚均匀性好，高的生产力。高的生产力。第三十七页，本课件共有88页热壁热壁CVD与冷壁与冷壁CVD反应原料可以是气体，液体，固体，后二者需要加热；反应原料可以是气体，液体，固体，后二者需要加热；低温下会反应的原料，需隔离；低温下会反应的原料，需隔离；反应产物是挥发性的固体，需对反应器壁加热。反应产物是挥发性的固体，需对反应器壁加热。(a)不加热非活性(b)不加热活性(c)加热平衡(d)加热活性冷壁冷壁CVD热壁热壁CVD第三十八页，本课件共有88页b、闭口体系在一个封闭的管子中进行化学气相沉积。管抽真空，将反应物和基板放入，密封。两端产生温度差，发生化学输运反应。特点：污染少，不要真空装置；缺点：生长速度慢，封闭管只能用一次，控制不易。第三十九页，本课件共有88页4.6CVD类型第四十页，本课件共有88页气压气压1mtorr-1torr(ratherthan1atm)低总压、高分压低总压、高分压=higherDofgastosubstrate通常是表面速率限制机制通常是表面速率限制机制surfacereactionlimitingAdvantages中等反应速率中等反应速率均匀性好均匀性好uniformity台阶覆盖度好台阶覆盖度好coverageoversteps缺陷浓度低缺陷浓度低,污染少污染少高产率高产率1.LowPressureCVD(低压低压CVD)第四十一页，本课件共有88页LPCVDMeanfreepath:=kT/(2Pd2)第四十二页，本课件共有88页J1/p1/p第四十三页，本课件共有88页第四十四页，本课件共有88页第四十五页，本课件共有88页第四十六页，本课件共有88页2.PlasmaEnhancedCVD(等离子体辅助等离子体辅助CVD)低压低压CVD中利用辉光放电等离子体的影响生长薄膜。中利用辉光放电等离子体的影响生长薄膜。压强：压强：5500Pa第四十七页，本课件共有88页PECVD deposition films（1）3SiH4+4NH3 Si3N4+12H2 （2）SiH4+2N2O SiO2+2N2+2H2 （3）SiH4 Si+2H2 （4）(1-x)SiH4+xPH3 Si1-xPx+H2 CPaArN350250,67,2PlasmaCPaArN350250,67,2PlasmaCAr625500,PlasmaCAr700600,Plasma第四十八页，本课件共有88页Usingelectronenergy(plasma)astheactivationmethodtoenabledepositionatalowtemperatureandatareasonablerateDisadvantagesRequirementofavacuumsystem,andamoresophisticatedreactorforplasmaMoreexpensivethanthethermallyactivatedCVDsystemDifficultyindepositinghighpurityfilmsSubstratedamagingbystrongionbombardmentAdvantagesRelativelylowtemperaturesonlargeareasHighergrowthratethanthermalCVDHigheradhesionGoodstepcoverageAschematicdiagramofPECVDsystemTab.5-2,pp131第四十九页，本课件共有88页plasmainvicinityofsubstrate:Plasmabreaksupgasmoleculeshigherreactivitycanuselowertemperaturescanuselowerpressureselectronsinplasma:ionizegastokeepplasmagoingactivategasbydissociationtoenhanceCVDtypicallyabout1%ofgasisactivated降低反应温度，降低反应温度，达达600以下，以下，典型温度典型温度300-350,避免一般避免一般CVD高温的引起高温的引起:1.基板变形和组基板变形和组织结构变化；织结构变化；2.基板材料与基板材料与膜层互扩散。膜层互扩散。第五十页，本课件共有88页等离子体的作用等离子体的作用电子、离子密度达电子、离子密度达1091012个个/cm3(maybe more),平均电子能达平均电子能达110ev主要用于介质膜沉积（主要用于介质膜沉积（example:低厚度、高低厚度、高、低漏电、高、低漏电、高绝缘的介质薄膜）绝缘的介质薄膜）(1)产生化学活性的基团和离子，降低反应温度；产生化学活性的基团和离子，降低反应温度；(2)加速反应物在表面的扩散作用，提高成膜速度；加速反应物在表面的扩散作用，提高成膜速度；(3)溅射清洗作用，增强薄膜附着力；溅射清洗作用，增强薄膜附着力；(4)增强碰撞散射作用，使形成的薄膜厚度均匀。增强碰撞散射作用，使形成的薄膜厚度均匀。第五十一页，本课件共有88页PPECVDPSputtering（stillwithlowpressure）ionssuffermorecollisionsingasphase=lessenergywhenreachcathode=minimalsputteringeffectsionenergydependsongaspressureandcathodevoltagecanuseRFplasmadischarges(especiallyforinsulatingfilms)第五十二页，本课件共有88页processparameterssubstratetemperaturecontrolbyexternalheaterverylittleheatingfromPECVDprocessgasflowhigherflowratescanincreasedepositionrateanduniformitybutwastesgaspressurechangestheenergyofionsreachingelectrodescanchangedepositionrateincreasespressuremayleadtochemicalreactionsinthegaseffectsalsodependongasconcentration第五十三页，本课件共有88页power影响电子数目和电子的能量影响电子数目和电子的能量太高引起气相反应太高引起气相反应沉积速率随能量上升沉积速率随能量上升frequency决定等离子体性质决定等离子体性质改变离子轰击特性改变离子轰击特性可用双频系统进行调节可用双频系统进行调节第五十四页，本课件共有88页CVD等离子体的激励方式：等离子体的激励方式：直流、射频、微波、电子回旋共振直流、射频、微波、电子回旋共振直流、射频二极放电的缺点：直流、射频二极放电的缺点：1.有电极，存在阴极溅射的污染有电极，存在阴极溅射的污染2.高功率，等离子体密度较大时，高功率，等离子体密度较大时，出现弧光放电。出现弧光放电。3.直流二极还只能用于薄膜和电直流二极还只能用于薄膜和电极都是导体的情况。极都是导体的情况。（1）高频感应）高频感应PECVD(电感电感)克服上述缺点，但等离子体的克服上述缺点，但等离子体的均匀性较差。均匀性较差。第五十五页，本课件共有88页RFsource电荷积累（oninsulatingsurfaces）-极性反转（beforechargesaturates）lowfrequencies(1MHz)reversesdirectionbeforeionsreachsubstrateanodeandcathodemaybesymmetric(identicalprocessesateachelectrode)ormaybeasymmetric(allowinggreateruseofionbombardmentatoneelectrode)第五十六页，本课件共有88页（2）微波）微波CVD微波能量的馈入：波导微波能量的馈入：波导微波天线（图示为微波天线（图示为1/4波长谐振腔）波长谐振腔）微波波长：微波波长：2.45GHz，或，或915MHz。特点：特点：能在很宽的气压范围能在很宽的气压范围内产生等离子体。内产生等离子体。102103Pa，甚至甚至104Pa。第五十七页，本课件共有88页(3)电子回旋共振等离子体（电子回旋共振等离子体（ECR,HighDensityPECVD）磁场与微波电场相垂直，磁场与微波电场相垂直，电子在电磁场作用下作回旋共振运动，共振频率为：电子在电磁场作用下作回旋共振运动，共振频率为：微波频率：微波频率：2.45GHz，磁感应强度：磁感应强度：875Gs第五十八页，本课件共有88页特点：特点：1.工作真空度高，工作真空度高，10-110-3Pa，以便吸收微波能量，以便吸收微波能量2.电离率几乎为电离率几乎为100，是一种离子束辅助沉积机制，是一种离子束辅助沉积机制 a)台阶覆盖性好；台阶覆盖性好；b)沉积离子能量为数沉积离子能量为数ev，具有溅射镀膜的特点。，具有溅射镀膜的特点。第五十九页，本课件共有88页3.MetalorganicCVD(MOCVD)UsesmatalorganicasprecursorsourceMetalorganic:compoundscontainingmetalatomsbondedtoorganicradicalsDepositawiderangeofmaterialsintheformofamorphous,epitaxialandpolycrystallinefilmsLowerdepositiontemperatureMetalorganicprecursorshavelowerdecompositiontemperaturesthanhalides,hydridesorhalohydridesAdvantagesDisadvantagesExpensiveprecursorsNotwidelyavailableforspecificcoatingMostmetalorganicsarevolatileliquidsthusaccuratepressurecontrolneededLowthermalstabilityofprecursorsduetotheirpolymerizationorhydrolysisLossofvolatilityandformationofresidueduetoageing第六十页，本课件共有88页CompareofepitaxialmethodsGrowthmethodtimefeatureslimitLPE1963GrowthformsupersaturatedsolutionontosubstrateLimitedsubstrateareasandpoorcontroloverthegrowthofverythinlayersVPE1958UsemetalhalideastransportagentstogrowNoAlcontainedcompound,thicklayerMBE19581967DepositepilayeratultrahighvacuumHardtogrowmaterialswithhighvaporpressureMOCVD1968UsemetalorganiccompoundsasthesourcesSomeofthesourceslikeAsH3areverytoxic.第六十一页，本课件共有88页SomeaboutthenameofMOCVDInthereference,MOCVDalsohavesomeothernames.Differentpeoplepreferdifferentname.Allthenamesrefertothesamegrowthmethod.MOCVD(Metalorganicchemicalvapordeposition)OMCVD(OrganometallicCVD)MOVPE(MOvaporphaseepitaxy)OMVPEAP-MOCVD(AtmosphereMOCVD)LP-MOCVD(LowpressureMOCVD)ex:(CH3)3Ga.tri-methylGalliumadvantage:volatileatrelativelylowtemperatures第六十二页，本课件共有88页TheMOVDgrowthsystem第六十三页，本课件共有88页第六十四页，本课件共有88页VacuumandExhaustsystemGashandlesystemComputerControlReactorMOCVDGrowthSystem第六十五页，本课件共有88页GashandlingsystemThefunctionofgashandlingsystemismixingandmeteringofthegasthatwillenterthereactor.Timingandcompositionofthegasenteringthereactorwilldeterminetheepilayerstructure.Leak-tightofthegaspanelisessential,becausetheoxygencontaminationwilldegradethegrowingfilmsproperties.Fast switchofvalvesystemisveryimportantforthinfilmandabruptinterfacestructuregrowth,Accurate controlofflowrate,pressureandtemperaturecanensurethestableandrepeat.第六十六页，本课件共有88页ExhaustsystemPumpandpressurecontrollerForlowpressuregrowth,weusemechanicpumpandpressurecontrollertocontrolthegrowthpressure.Thepumpshouldbedesignedtohandlelargegasload.wastegastreatmentsystemThetreatmentofexhaustgasisamatterofsafetyconcern.TheMOCVDsystemforGaAsandInPusetoxicmaterialslikeAsH3andPH3.TheexhaustgasesstillcontainsomenotreactedAsH3andPH3,Normally,thetoxicgasneedtoberemovedbyusingchemicalscrubber.ForGaNsystem,itisnotaproblem.第六十七页，本课件共有88页VaporpressureofmostcommonMOcompoundsCompoundPat298K(torr)ABMeltpoint(oC)(Al(CH3)3)2TMAl14.2278010.4815Al(C2H5)3TEAl0.041362510.78-52.5Ga(CH3)3TMGa23818258.50-15.8Ga(C2H5)3TEGa4.7925309.19-82.5In(CH3)3TMIn1.7528309.7488In(C2H5)3TEIn0.3128158.94-32Zn(C2H5)2DEZn8.5321908.28-28Mg(C5H5)2Cp2Mg0.05355610.56175Logp(torr)=B-A/T第六十八页，本课件共有88页CalculatethemoleflowrateofMOsourcesNormally,weusetheformulatocalculatemol/min.F(mol/min)=pMO/pBubbler*flowrate(ml/min)/22400(mol/ml)Weneedtocalculatethemoleflowratebeforewedeterminethegrowthcondition.Ifwewanttogrowalloys,wecanusethemoleflowratetoestimatethealloyscomposition.Forexample,ifwegrowAlGaN,wecanestimatetheAlconcentrationusethefollowingformulaifweassumetheefficiencyofAlandGasourcesisthesame.xAl=FAl/(FAl+FGa)第六十九页，本课件共有88页ThebasicreactiondescribeGaNgrowthcansimplywriteasGa(CH3)3+NH3GaN+3CH4Thegrowthprocedureasfollows:1.MOsourcesandhydridesinjecttothereactor.2.Thesourcesaremixedinsidethereactorandtransfertothedepositionarea3.Atthedepositionarea,hightemperatureresultinthedecompositionofsourcesandothergas-phasereaction,formingthefilmprecursorswhichareusefulforfilmgrowthandby-products.Gasphaseandsurfacereaction第七十页，本课件共有88页4.Thefilmprecursorstransporttothegrowthsurface5.Thefilmprecursorsabsorbonthegrowthsurface6.Thefilmprecursorsdiffusetothegrowthsite7.Atthesurface,filmatomsincorporateintothegrowingfilmthroughsurfacereaction8.Theby-productsofthesurfacereactionsabsorbfromsurface9.Theby-productstransporttothemaingasflowregionawayfromthedepositionareatowardsthereactorexit第七十一页，本课件共有88页reaction第七十二页，本课件共有88页TwoStepMOCVDGrowthprocedureHightemperaturetreatmentBufferlayerEpilayerGrowthTMGaNH3Temperature1150oC550oC1050oCGa(CH3)3+NH3 GaN+CH4MOCVDgrowGaNandrelatedmaterials第七十三页，本课件共有88页4.Photo-assistedchemicalvapordeposition(PACVD)Usinglightasheatingsource(arclamp,CO2lasers,Nd-YAGlasers,excimerlasers,argonionlasers)AdvantagesLowerdepositiontemperatureEnhanceddepositionrateLocalizedepositionorselectedareadepositionAvoidsfilmdamagebylowexcitationenergies(5eV)AschematicdiagramofPACVDsystem第七十四页，本课件共有88页第七十五页，本课件共有88页ECR第七十六页，本课件共有88页第七十七页，本课件共有88页5.Atomic layer deposition(ALD)FirstALDreactorwasasimplevacuumapparatusfordepositionofZnSfromtheelements第七十八页，本课件共有88页第七十九页，本课件共有88页第八十页，本课件共有88页第八十一页，本课件共有88页第八十二页，本课件共有88页第八十三页，本课件共有88页第八十四页，本课件共有88页第八十五页，本课件共有88页第八十六页，本课件共有88页WhenCVD,WhenPVD第八十七页，本课件共有88页思考题Chapter5:1.化学气相沉积原理，特点及分类。2.化学气相反应类型有哪些？3.CVD沉积中，为何有表面限制和传质限制两种机制？4.低压化学气相沉积有何特点，为什么？5.PECVD的原理，优点，等离子体产生方法有哪些？6.MOCVD的原理，特点。7.ALD与常规CVD相比，有什么特点？第八十八页，本课件共有88页
