薄膜力学7-断裂1_精品文档.pdf

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EM397:

ThinFilmMechanicsVII.IntroductiontoFractureinThinFilmsNanshuLuTheUniversityofTexasatAustinFall2013Tension-inducedcrackingFilmsubjectedtoahightensilestressCracksnucleateatthesurfacedefectsMultiplecrackscannucleateandpropagatesimultaneouslySubstrateFilmdebondingChannelcracksCrosssection:

Topview:

CourtesyofJunHeofIntelCorp.Fractureoflow-kdielectricsSiliconOSGTsuietal.,J.Mater.Res.20,2266-2273（2005）.PassivationfilmsonmetalinterconnectsSiNfilmonAlafterthermalcyclesHuang,Suo,Ma,J.Mech.Phys.Solids50,1079（2002）CourtesyofJ.B.HanofAgilentTechnologies,Singapore.Topview:

Edgeview:

HardfilmsonsoftsubstratesGSDTFTislanda-SionpolymersubstrateGleskova,Wagner,Suo,Appl.Phys.Lett.,75,3011（1999）Cracks500nmAlfilmonKeptonsubstrate（CourtesyofZ.SuoofHarvardUniv.）Mudcracks10m10mSlickhornGulch,SanJuanRiverCanyon,Utah（http:

/）1mSiNonSi（CourtesyofQ.Ma,IntelCorp.）Crackingofanisotropicfilms（c）（c）A1mxerogelsilicafilmonSisubstrate（Chowetal.,J.Appl.Phys.87,7788-7792,2000）.（a）A0.5mAlGaNfilmon0.7mGaNheterostructureonsapphire（Hearneetal.,Appl.Phys.Lett.76,1534-1536,2000）（b）A22mGaNfilmonsapphire（EtzkornandClarke,J.Appl.Phys.89,1025-1034,2001）Debondingdebonding10m10mDebondingfromedges,drivenbytensileresidualstressesinthefilm.Compression-inducedbuckle-delaminationBuckling-delaminationwithcompressivemismatchstrainFilmSubstrateBlisteringTiW/low-K/Sistack,fromVolinsky,MRSSymp.Proc.749,2003.a-Sionglass,fromThouless,J.Am.Ceram.Soc.76,2936-38,1993.a-SionSi,fromCookandSuo,MRSBulletin,27,45-51,2002.DLConglass,fromMoonetal.,ActaMat.50,1219-1227（2002）.http:

/www.eng.usf.edu/volinsky/ThermalbarriercoatingMumm,Evans,andSpitsberg,ActaMater49,2329（2001）Wrinkle-inducedcrackingSiGefilmonglass,fromYin,etal.,J.Appl.Phys.94,6875（2003）.liquidliquidMetalextrusionininterconnectsElectromirgationinducesahighcompressivestressintheAllines,whichcausescrackingofsurroundingdielectricsandextrusionofaluminumintothecracks.（Suo,ReliabilityofMetalInterconnects.ComprehensiveStructuralIntegrity,Vol.8,Chap.8.08,Elsevier,2003.）CrackpropagationinmultilevelinterconnectsFracturemechanismsinthinfilmstructuresUndertension:

ChannelingortunnelingDebondingSubstratespallingUndercompression:

Buckle-delaminationWrinkle-inducedcrackingExtrusionRoleofFractureMechanicsFractureanalysisforreliabilitycontrolCrackornot?

When?

Where?

How?

Whatcanonedotoavoidorreducecracking?

Material/processcharacterizationFracturetoughnessofthinfilmsInterfacetoughness（adhesion）FundamentaloffracturemechanicsEnergyreleaserateStressintensityfactorFracturetoughnessMixedmodefractureInterfacefractureLawn,FractureofBrittleSolids.CambridgeUniversityPress,1993.HutchinsonandSuo,Mixedmodecrackinginlayeredmaterials.AdvancesinAppliedMechanics29,63-191（1992）.Suo,ReliabilityofMetalInterconnects.ComprehensiveStructuralIntegrity,Vol.8,Chap.8.08,Elsevier,2003.StressconcentrationyyxInglissolution:

2a2bbaay21）0,（AssumeabreakingstrengthB.Then,thecriticalremotestressis121baBcAtthetipofasharpcrack,b0,whichimpliesanyremotetensilestresswillcausefracture!

?

Griffith:

EnergyApproachReferencestate:

VEU220Introduceacrack:

strainenergypartlyreleased,butsurfaceenergyincreasestaEU222taEgatatUG222220GaForacracktogrow:

aEc2FracturedrivingforceandresistanceDrivingforce:

releaseofelasticstrainenergy-energyreleaserateAUGFractureresistance:

creationofnewsurfaces2Assumesmallscaleyieldingnearthecracktip;fractureresistancethusincludesenergydissipationduetoplasticdeformation:

pw2Fracturecriterion:

GForglass:

1J/m2;forsteel:

1000J/m2.Cracktipfields:

stressintensityfactorsModeI:

ModeII:

ModeIII:

23sin2sin12cos2rKIIxy23sin2sin12cos2rKIyy2cos2rKIIIyzSolutionsfromelasticity:

Stressintensityfactors:

KI,KII,KIII.SmallscaleyieldingrpK-annulusYrarp0Elasticitypredictssquarerootsingularityatthecracktip.Plasticyieldoccursnearthecracktip.arpSmallscaleyieldingassumes:

K-fieldisonlycorrectwithinanannulus,whichconnectthecracktipprocesswiththeremoteloading.221ypKrFracturetoughnessCrackgrowthwhenthestressintensityfactorreachesacriticalvalue,calledfracturetoughness.cKKFromtheenergyapproach:

GIrwinsrelation:

2EKG2EKcstrainplane1stressplane2EEE