半导体材料生长55-66

1SemiconductormaterialsLecturer:AiminLiu&WeifengLiu刘爱民刘维峰23DryEtchingDryetchingmethodsGlowdischargemethodsDryphysicaletching(Sputteretching)PlasmaassistedetchingDrychemicaletching(Plasmaetching)Reactiveionetching(RIE)IonbeammethodsIonmillingReactiveionbeametchingChemicalassistedionmillingCommonmaterialstodryetchSi,SiO2,Si3N4,Al,W,Ti,TiN,TiSi2,PhotoresistDifficultmaterialstodryetchFe,Ni,Co,Cu,Al2O3,LiNbO3,etc.4RF-poweredplasmaetchsystemRF-poweredplasmaetchsystem5Barrelplasmasystem6789EtchantsandetchproductsSolidEtchgasEtchproductSi,SiO2,Si3N4PSG,andBPSGCF4,SF6,andNF3SiF4SiCl2andCCl2F2SiCl2andSiCl4AlBCl3,CCl4,Cl2Al2Cl6andAlCl3OrganicsolidsPhotoresists,etc.O2O2+CF4CO,CO2,H2OCO,CO2,HFRefractorymetals(W,Ta,Ti,Mo,etc.)CF4WF6…..GaAs,InPCl2andCCl2F2GaCl3,AsCl5,….10PlasmaassistedetchingPlasmaassistedetchingsequenceTakeamoleculargasCF4EstablishaglowdischargeCF4+eCF3+F+eRadicalsreactwithsolidfilmstoformvolatileproductSi+4FSiF4Pumpawayvolatileproduct(SiF4)11MaskFilm++Ionicspecies++++PhysicalEtching•Notveryselectivesinceallmaterialssputterataboutthesamerate.•Physicalsputteringcancausedamagetosurface,withextentandamountofdamageadirectfunctionofionenergy(notiondensity).IonEnhancedEtching•Thechemicalandphysicalcomponentsofplasmaetchingdonotalwaysactindependently-bothintermsofnetetchrateandinresultingetchprofile.•FigureshowsetchrateofsiliconasXeF2gas(notplasma)andAr+ionsareintroducedtothesiliconsurface.Onlywhenbotharepresentdoesappreciableetchingoccur.•Etchprofilescanbeveryanisotopic,andselectivitycanbegood.NoplasmasputteringSILICONVLSITECHNOLOGYFundamentals,PracticeandModelingByPlummer,Deal&Griffin©2000byPrenticeHallUpperSaddleRiverNJ1213Chemicalvs.chemical/physicaletchingPurelychemicaletching(usingonlyreactiveneutralspecies)IsotropicetchingChemical+physicaletching(usingreactiveneutralspeciesandionicspecies)Anisotropicetching14•Manydifferentmechanismsproposedforthissynergisticetchingbetweenphysicalandchemicalcomponents.Twomechanismsareshownabove.•Ionbombardmentcanenhanceetchprocess(suchasbydamagingthesurfacetoincreasereaction,orbyremovingetchbyproducts),orcanremoveinhibitorthatisanindirectbyproductofetchprocess(suchaspolymerformationfromcarboningasorfromphotoresist).•Whatevertheexactmechanism(multiplemechanismsmayoccuratthesametime):•needbothcomponentsforetchingtooccur.•getanisotropicetchingandlittleundercuttingbecauseofdirectedionflux.•getselectivityduetochemicalcomponentandchemicalreactions.Therearemanyapplicationsinetchingtoday.Ion-EnhancedEtchingChemicalcomponentselectivityPhysicalcomponentanisotropyvolatilityofbyproductsRolesofions:Adsorption,Reaction,Formationofbyproducts,removalSILICONVLSITECHNOLOGYFundamentals,PracticeandModelingByPlummer,Deal&Griffin©2000byPrenticeHallUpperSaddleRiverNJ15Effectoftheinhibitorw/oinhibitor=Isotropicw/inhibitor=Anisotropic16PlasmaassistedetchingDrychemicaletching(Plasmaetching)RFenergyisappliedtoaseparateelectrodewiththesubstratesgrounded.Materialisremovedfromthesubstratebychemicalmeans.PurelychemicaletchingGlowdischargeisusedtoproducechemicallyreactivespecies(atoms,radicals,orions)Reactive-ionEtching(RIE)IfRFenergyisappliedtothesubstratesinalowpressurehalogen-richenvironment,materialcanberemovedbybothchemicalmeansandionbombardmentofthesubstratesurface.Greatercontroloverlinewidthsandedgeprofilesispossiblewithoxides,nitrides,polysiliconandaluminum.Acombinationofphysical/chemicaletchingAccomplishedbyreplacingtheneutralgasinar.f.sputteringsystembyoneormorechemicalspeciesGlowdischargeisusedtoproducechemicallyreactivespecies(atoms,radicals,orions)andchemicallyinertionsHighlyanisotropicetching17溅射离子刻蚀原理及斜面刻蚀分析1.刻面效应2.再沉积效应3.阴影效应18192021超声喷雾热分解装置示意图222324（a）UndopedZnOfilmsurfaceandcrosssection100nm100nm(b)N-IncodopedZnOfilmsurfaceandcrosssection100nm100nm2567123456扩散系统示意框图1.氢气入口；2.氢气出口；3.石墨舟；4.加入炉管；5.抽气口；6.分子泵；7.机械泵。26源晶片盖石墨扩散舟结构图Structureofgraphitecrucible27A铂片GaSbSchematicdiagramofAnodicOxidationequipmentGaSb做阳极，铂片做阴极，电解液是酒石酸与乙烯乙二醇混合后的一种水溶液28其他简单工艺设备高温退火炉快速退火炉闭管蒸发方法电化学镀膜介质阻挡29工艺实例（一）30工艺实例（二）313233陷光结构类型制作金字塔绒面制作多孔硅玻璃基片织构压花法溶胶凝胶法其他材料介质膜3435363738图1.腐蚀后的ZnO薄膜表面图2.腐蚀后的ZnO薄膜断面绒度的影响折射率的影响棱锥倾角的影响39工艺实例（三）4041第6结课（II-VI材料特性）以ZnO半导体材料为例的两种应用424344SemiconductormaterialsclassificationElementalsemiconductor--Si,GeCompoundsemiconductorIV-IV---SiCIII-V----AlP,AlAs,GaAs,GaSb,InP,InAs,II-VI---ZnO,ZnS,ZnSeAlloysBinary---Si1-xGexTenary---AlGaAs,AlInAs,Quaternary---AlGaAsSb45DalianUniversityofTechnologyZnO材料结构及基本特性Zn原子和O原子各自组成一个六方密堆积结构的子格子，沿c轴平移0.385c，套构形成纤锌矿结构Zn极化面和O极化面化学键处于离子键和共价键的中间状态ZnO的禁带宽度为3.37eV，激子束缚能高达60meV，ZnO晶格常数a=3.2496Å，c=5.2065Å，c/a=1.60246DalianUniversityofTechnology压电特性透明导电特性气敏和湿敏特性紫外光发射特性（1）室温下的Eg=3.37eV（2）激子束缚能60meV远大于室温热离化能26meVZnO光电材料特性及发光器件研究进展1996年在第23届国际半导体物理年会报道了ZnO会在室温下获得高效的与激子相关的受激发射，并迅速成为半导体光电领域研究的新热点1998年，Z.K.Tang报道的ZnO激子发射温度可高达到550oC，使得全球范围内对ZnO的研究不断升温2005年M.KAWASAKI在Nat.Mater.报道了ZnOp-i-n同质结发光管，在室温下实现紫外电致发光，成为ZnO发光管研究过程中的一个重大突破47试验设计依据DalianUniversityofTechnology研究得最多的n-type掺杂剂是Al，Ga和In。采用Al掺杂制得的ZnO:Al薄膜电阻率一般