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