集成电路专业英语 课件 11 Fabrication

11FabricationIntroduction:TheScaleofModernICsModernICscanintegrateover2billiontransistorsandcapacitorsonasinglechip(e.g.,2GbDRAM).Asinglesiliconwafercancontaintenstotensofthousandsofindividualdies.Corechallenge:preciselymodifyingsiliconpropertiesatthenanometerscaleusingrepeatableprocessesinultra-cleanenvironments.TheFoundation:TheCleanroomAsinglemicroscopicparticlecandestroynanoscalecircuitfeatures.Cleanroomsprovidestrictcontrolofairpurity,temperaturestability,andhumidity.ClassificationisdefinedbyISO14644-1particle-countstandards.CleanroomStandards(ISO14644-1)ISO1–3:Ultra-advancedR&DandEUVlithography(<1,000particles≥0.5µm).ISO4–5:AdvancedandcriticalICprocessingsteps.ISO6–8:Lesscriticalandback-endICmanufacturingareas.TheSixEssentialICFabricationStepsOxidationPhotolithographyIonImplantationEtchingChemicalVaporDeposition(CVD)MetallizationStep1:Oxidation–CreatingthePerfectInsulatorSiliconnaturallyformshigh-qualitysilicondioxide(SiO₂).Reaction:Si+O₂→SiO₂.Oxidegrowthiscontrolledusinghigh-temperaturefurnacesorRTP.Dryvs.WetOxidationDryoxidationusesO₂,growsslowly,andproduceshigh-qualitythinoxides.WetoxidationusesH₂Ovapor,growsfaster,andformsthickeroxides.Gateoxidesusedryoxidation;fieldoxidesusewetoxidation.Step2:Photolithography–TheArtofPatterningTransfersgeometricpatternsfrommasksontothewafer.Photoresistcoating,alignment&exposure,anddevelopment.Enablesnanoscalepatterndefinition.PhotoresistTypes:Positivevs.NegativePositiveresist:exposedregionsbecomesoluble;dominantinadvancedfabs.Negativeresist:exposedregionsbecomeinsoluble.Positiveresistsprovidehigherresolutionforcriticallayers.Step3:IonImplantation–DopingwithPrecisionIntroducesdopantstoformn-typeorp-typesiliconregions.Ionsareacceleratedandimplantedthroughpatternedphotoresist.Post-implantannealingrepairsdamageandactivatesdopants.Step4:Etching–SelectiveMaterialRemovalRemovesmaterialaccordingtophotoresist-definedpatterns.Patternetchtransferspatterns;blanketetchremovesfulllayers.Criticalforgates,contacts,andinterconnects.WetEtchingvs.Dry(Plasma)EtchingWetetchingisisotropicandusedfornon-criticalprocesses.Dryplasmaetchingisanisotropicwithverticalsidewalls.Dryetchingdominatesforfeaturessmallerthan3µm.Step5:ChemicalVaporDeposition(CVD)Depositsthinfilmsviachemicalreactionsonheatedwafers.Byproductsareremovedwhilesolidfilmsremain.IncludesLPCVD,PECVD,andMOCVDprocesses.CommonCVDFilmsinICFabricationDielectrics:SiO₂,Si₃N₄,SiOₓNᵧ,low-kmaterials.Conductors:polysilicon,tungsten,titaniumnitride.Filmsserveasinsulators,conductors,andbarrierlayers.Step6:Metallization–CreatingtheWiringFormsinterconnectionsbetweenbillionsoftransistors.Requireslowresistivityandhighelectromigrationresistance.Goodadhesionandsmoothsurfacesareessential.MetallizationMaterials&DepositionAluminum:traditional,easytoetch.Copper:modernstandardwithlowerresistivity.Depositionviasputtering(PVD),CVD,orelectroplating.Summary:TheLayeredConstructionICf