多形態(tài)多晶硅薄膜力學(xué)行為及與微結(jié)構(gòu)關(guān)聯(lián)特性研究的中期報(bào)告AbstractThisreportpresentsamid-termprogressreportonthestudyofthemechanicalbehaviorandmicrostructuralpropertiesofpolycrystallinesiliconthinfilmswithmulti-modalmorphologies.Theresearchfocusesonexploringthecorrelationbetweenmicrostructureandmechanicalpropertiesofpolycrystallinesiliconthinfilmswithdifferentmorphologyusingexperimentalandnumericaltechniques.Theexperimentalworkincludesdepositionofpolycrystallinesiliconthinfilmsusingplasma-enhancedchemicalvapordeposition(PECVD)andcharacterizationusingscanningelectronmicroscopy(SEM)andX-raydiffraction(XRD).Thenumericalworkincludesdevelopingafiniteelementmodeltosimulatethemechanicalbehaviorofpolycrystallinesiliconthinfilmsundervariousloadingconditions.IntroductionPolycrystallinesiliconthinfilmshavegainedwideapplicationsinmicroelectronics,photovoltaicsandmicro-electro-mechanicalsystems(MEMS)duetotheirgoodelectricalandopticalproperties.Themechanicalbehaviorofpolycrystallinesiliconthinfilmsplaysanimportantroleinthereliabilityandperformanceofthesedevices.However,themechanicalpropertiesofpolycrystallinesiliconthinfilmsaresensitivetotheirmicrostructure,whichisstronglyinfluencedbydepositionparameterssuchassubstratetemperature,depositionrate,andgasflowrate.Therefore,investigatingthemicrostructure-mechanicalbehaviorrelationshipofpolycrystallinesiliconthinfilmsiscrucialfortheirdesignandfabrication.ExperimentalProcedurePolycrystallinesiliconthinfilmsweredepositedonsiliconsubstratesusingPECVD.Thedepositionconditionswerevariedtoobtaindifferentmorphologies,includingcolumnar,mixed-columnar,andporous.ThemorphologyofthethinfilmswascharacterizedusingSEMandXRD.Thethinfilmsweretestedusinganano-indentationinstrumenttodeterminetheirmechanicalproperties.TheindentationtestswereperformedwithaBerkovichindenterunderarangeofloadingconditions,includingdifferentmaximumloadsandloadingrates.Theload-displacementcurveswererecordedduringtheindentationtests,andthemechanicalpropertiessuchasYoung’smodulusandhardnesswerecalculated.NumericalModelingAfiniteelementmodelwasdevelopedtosimulatetheelastic-plasticbehaviorofpolycrystallinesiliconthinfilmsundervariousloadingconditions.ThemicrostructureofthethinfilmswasrepresentedbyaVoronoitessellationmodel,wherethegrainsizeandorientationwereobtainedfromSEMandXRDmeasurements.Themechanicalpropertiesofthethinfilms,includingelasticmodulus,Poisson’sratio,andyieldstrength,werecalibratedusingnano-indentationexperiments.Thefiniteelementmodelwasusedtoperformindentationsimulationsundervariousloadingconditions.Thesimulationswerecomparedwiththeexperimentalresultstovalidatethemodel.Theeffectsofmicrostructureandloadingconditionsonthemechanicalbehaviorofpolycrystallinesiliconthinfilmswereinvestigatedusingthefiniteelementmodel.ResultsandDiscussionTheSEMimagesofthepolycrystallinesiliconthinfilmsshowedsignificantvariationsinmorphologywithdifferentdepositionconditions.Thecolumnarandmixed-columnarthinfilmshadasimilargrainsizeandorientation,whiletheporousthinfilmshadlargergrainsizesandamorerandomgrainorientation.Thenano-indentationtestsshowedthatthemechanicalpropertiesofthethinfilmsweresensitivetotheirmorphologyandloadingconditions.Thecolumnarandmixed-columnarthinfilmsshowedahigherYoung’smodulusandhardnessthantheporousthinfilms.Theloadingratehadasignificanteffectonthemechanicalpropertiesofthethinfilms,especiallyforthecolumnarandmixed-columnarthinfilms.Thefiniteelementsimulationsshowedgoodagreementwiththeexperimentalresults,indicatingthattheVoronoitessellationmodelcouldeffectivelyrepresentthemicrostructureofpolycrystallinesiliconthinfilms.Thesimulationsalsorevealedthatthegrainsizeandorientationhadasignificanteffectonthemechanicalbehaviorofthethinfilms,especiallyfortheporousthinfilms.Theloadingratealsohadamarkedeffectonthemechanicalbehaviorofthethinfilms.ConclusionThisreportpresentsamid-termprogressreportonthestudyofthemechanicalbehaviorandmicrostructuralpropertiesofpolycrystallinesiliconthinfilmswithmulti-modalmorphologies.Theexperimentalandnumericalresultsdemonstratedthatthemechanicalpropertiesofpolycrystallinesiliconthinfilmsweresensitivetotheirmicrostructureandloadingconditions.TheVoronoitessellationmodelwasaneffectivemethodtosimulatethemicrostructureofpolycrysta