4――东京工大细野秀雄

HideoHOSONOFrontierResearchCenter&MaterialsandStructuresLaboratory(MSL)TokyoInstituteofTechnology,Yokohama,JAPANTAOS-TFTstodriveFPDSFeaturesandCurrentStatusFPDInternationalinchina@Beijing(Dec10)1.Largemobility(10-20ｃｍ2/Vs)2.EasyfabricationbysputteringatLT3.Homogenous(nograinboudary)4.OpticallytransparentOutline‡HistoryofOxideTFT‡UniqueCharacteristicsofTAOSHowuniqueandwhycf.a-Si:H‡Featuresofa-InGaZnOx-TFTmobility,controllability,stabilization,tailstate,negativebias-lightillumination(NBL)instability‡FPDapplication‡Futureissues19501960197019801990200020101968ZnOFET(gm=10mhos)1996Epi-SnO2:Sb(μeff~1cm2/Vs)2004/11TAOS–TFT(TIT)2003poly-ZnOTFTrush2005/12FlexibleB/WE-Paper(Toppan)2005LCDpanel(Casio)2006AMOLEDpanel(ETRI)2006/12ColorE-PaperAMOLEDpanel(LG)2007/8AMOLEDpanel(Samsung)FlexibleOLED(LG)1961CdSTFT~1964poly-SnO2FETpoly-In2O3FET(gm=0.3mhos)1951pnJFET1960SiMOSFET1979a-Si:HTFTCommercialization1975a-Si:H19835“B/WLCD198510”ColorLCD1995TAOS(TIT)2008/1AMLCDpanel(Samsung)HighTcOxideElectronicsAmorphousTCOOxideTFTrevival1948W.ShockleyOxideTFTsandFPDs1950.1960.1970.1980.1990.2000Photoconductivityina-Se(Xerography)Glassysemicond.(V2O5basedoxide)ChalcogenideglassDVD)Switchingandmemoryeffectina-chal.filma-Si:H‘Giant-Microelectronics’Flexibleelectronics(novela-sc)HistoryofamorphoussemiconductoranddeviceapplicationJNCS(1996),Nature(2004)Materialdesignconcept(electronpathway)Materialdesignconcept(electronpathway)crystalamorphousionicoxidesemicon.M:(n-1)d10ns0(n≥5)covalentsemicon.DesigningTAOSwithalargee-HallmobilityIn-Zn-O(IZO):30cm2(Vs)-1)μHall(Nex1018cm-3)In-Ga-Zn-O(IGZO):15cm2(Vs)-1)StructureATAOSMaterial:In2O3-Ga2O3-ZnO(IGZO)[e-mail].(2006)5s04s04s0ElectronTransportPropertiesofa-IGZOAPL(2004)EFEmobility@Ne2x1018cm-3MobilityincreaseswithNecf.c-SiTAOSisafirsta-semiconductorinwhichEfexceedsthemobilitygapSiCarriersareNOTgeneratedCarriersareNOTgeneratedPStreetModel(PRL1982)P+Si-ArrowedForbiddenEFcannotexceedthemobilitygapbydopingCarrierdopingina-Si:HSpear&LeComber,SSC(1975)(VBM)(CBM)impossibleR.A.Street(Ed.),TechnologyandApplicationsofAmorphousSilicon,Springer-Verlag,Berlin,2000TailStateDensityfromDevicesimulation1016a-IGZO/a-SiO2(annealed):S=0.12V/dec(Dit=2.5x1011cm-2)a-Si:H/a-SiNx:H(typical):S=0.4V/dec1021Eca-Si:H10181016Dit=0.9×1011cm-2/eVEca-IGZOAssumption:Constantmobility&two-stepsubgapDOSs(depletion)(enhancementtype)APL(2007)a-IGZOTFTonGlassFieldEffectMobilityμ=14cm2(Vs)-1Cf.a=Si:Hμ=~1cm2(Vs)-1DepositedbyDCsputteringNature(2004),JJAP(2006),J.SID(2006)a-Si:H–TFT:tailstateandTFToperationSuccessofreductionoftailstatesina-SiDepositedbyglowdischargemethod1973SuccessinPNcontrolbysubstitutionaldoping1975SuccessinTFToperation1979a-Si:HglowdischargedP.G.LeComber,W.E.Spear,A.GhaithSolidStateCommun.J.Non-Cryst.Sol.Electron.Lett.sputteredevaporatedIn-Zn-Ga-O(IGZO)ControllabilityandStabilityofNControllabilityandStabilityofNControllabilityandStabilityofNeeeI-VNevs.PO2In3+formanextendedconductionbandbypercolationofIn5sorbitals.PolyhedralviewPolyhedralviewIn5s-In5sconnectionsIn5s-In5sconnectionsIn3+formanextendedconductionbandbottombypercolationofIn5sorbitals.ConductionBandBottomina-IGZOPhys.Rev.B(2006)combinedEXAFSmeasurementswithVASPsimulationLUMOIn5s3D-connectedlStableamorphousstructurelExcellentcontrollabilityofcarrierdensitylHighelectronmobilityIn3+aselectronpathwayformer(4d)10(5s)0Zn2+asamorphousstructurestabilizertetrahedralcoordinationGa3+ascarriergenerationsuppresserhighionicfieldstrengthZ/rWhya-IGZOforTFT-Channellayer?stablestoichiometriccompoundexcellentsputtertargetHighQualityas-depositedLowQualityas-deposited300◦Cannealeda-In-GZOonSiO2/SiTFTPerformance:AnnealingeffectsUnannealedDryannealedWetannealedSubgapDOSEcDefectmodel()⎟⎟⎠⎞⎜⎜⎝⎛⎟⎟⎠⎞⎜⎜⎝⎛−−⋅+⎟⎟⎠⎞⎜⎜⎝⎛−⋅=2expexpgagatataWEEcNWEEcNEgSubgapDOS(ATLAS)WetannealingiseffectivetoreducesubgapDOS.μexp:~6.0~9.5~12(cm2/Vs)μcalc:~6.5~9.0~11(cm2/Vs)NTA:~2.5~2.8~3.0(x1017cm-3)WTA:~0.15~0.115~0.065(eV)TotalDOS:~1017cm-3(a)(b)(a)(b)図１１．a-IGZO－TFTの光照射下での特性。照射フォトン数は1013cm-2s-1.20)toλ460nmInsensitiveLightSensitivitySID’08Cf.Banggap~390nmHardX-rayPhotoEmissionSpectroscopy:Bulk&S-electronSensitiveLargephotoelectronescapedepth(5-10nm)HighIonizationCrosssectionofselectrontop,d,felectronsExcitation:hν=7935.2eVDetector:GammadataScientaCo.,R4000-10KVResolution:~[e-mail].,APL(2003).OriginofphotoresponsetosubgaplightAngledependentHX-PESspectradepthprofileofSubgapDOSFilmsurfaceWet-annealedUnannealedSubgapdefect(Peakenergy~2.7eV,width~1.5eV)d2nm:1020cm-3VBM(CBM)Subgapstatefora-IGZO・Exponentialtailanddeepstates・TailstateDOS(~1017cm-3)・Localizedstate(beforeannealing)・DeepstateDOS(~1016cm-3)・HighdensityVB-DOS(1020cm-3)SmallS-Value(0.1V/dec.)DifficultyofinversionoperationLowvalencestateAsianMater.(2010)ByHardX-rayPEInstabilitybyL-NBS(AnnealedTFTswitht=40nm)NBS(dark)Illumination(nobias)Illumined-NBS(E=2.7eV,460nm)ΔVth~0VΔVth~-1VΔVth10VLargeVthshiftundersubgaplightilluminationPh~1014cm-2s-1Ph~1014cm-2s-1NegativeVthshiftbylightilluminatedNBSPosi