介观材料力学.综述

材料的介观力学性能评价及尺度效应参考书目：(1)L.B.FreundandS.Suresh,ThinFilmMaterials:Stress,DefectFormation,andSurfaceEvolutionCambridgeUniversityPress,Cambridge,2003(2)W.D.Nix,Metall.Trans.A20(1989)2217.2Size10-3～10-610-6～10-810-810-3连续介质理论分子动力学介观什么是介观？3材料介观力学性能评价的意义微米尺寸材料的广泛应用MEMSCuOSGSiNTaNIntel90nminterconnect集成电路互连导线4块体材料强度随晶粒尺寸的变化材料介观力学性能？？微米尺寸下材料安全选择与性能预测的需要材料介观力学性能评价的意义5强度材料力学性能指标延性韧性承载能力可发生变形的能力抵抗断裂的能力强度延性韧性疲劳！！6提纲1.金属薄膜的准静态力学性能2.金属薄膜的疲劳性能3.微小柱状单晶试样的力学性能7弹性模量：弹性变形的抗力1.宏观材料的力学性能评价强度：承载能力塑性：变形能力韧性：变形功能量概念硬度：材料软硬程度万能材料实验机常用试样形貌8块材压入测试简介1.金属薄膜的静态力学性能——纳米压入仪测量布氏硬度压痕布氏：稳定/压痕大洛氏硬度压痕洛氏：压痕小/不稳定维氏：兼有布氏和洛氏的优点9加载卸载薄膜基体1.金属薄膜的静态力学性能——纳米压入仪测量10H——硬度A——压头接触面积Ef——薄膜弹性模量压头接触面积函数1.金属薄膜的静态力学性能——纳米压入仪测量11不足：基体影响压头周围材料堆积或塌陷尺寸效应问题残余应力影响1.金属薄膜的静态力学性能——纳米压入仪测量121.金属薄膜的静态力学性能——悬臂梁法属于薄膜弯曲实验方法131.金属薄膜的静态力学性能——悬臂梁法MEMS中的微悬壁梁聚焦离子束（FIB）加工MEMS用微米尺寸悬臂梁试样141.金属薄膜的静态力学性能——悬臂梁法屈服应力-悬臂梁厚度关系曲线151.金属薄膜的静态力学性能——悬臂梁法可能原因：残余应力基体影响压头滑动161.金属薄膜的静态力学性能——微桥法171.金属薄膜的静态力学性能——单轴拉伸获得材料应力-应变最直接的方法自由膜微加工柔性基板粘揭溶去中间介质层溶去基板边缘损伤、卷曲装样困难试样规整制备复杂简单易行数据可靠181.金属薄膜的静态力学性能——单轴拉伸膜基系统拉伸曲线柔性基板310Cu聚酰亚胺19微小力实验机：P=+250N+1N；l=+50mm+5m薄膜夹头0123010203040purepolymerFilm/polymersystemStrain(%)TensileloadF(N)0.00.51.01.52.0050010001500t=60nm100nm275nm470nm700nmStrain(%)Stress(MPa)1.金属薄膜的静态力学性能——单轴拉伸201.金属薄膜的静态力学性能——单轴拉伸t：薄膜厚度尺寸效应柔性基板21Cu薄膜/聚酰亚胺—晶粒尺寸vs薄膜厚度磁控溅射薄膜沉积设备t=60nmt=340nmt=700nm02004006008000306090t(nm)d(nm)10152025300153045d(nm)Frequency(%)t=60nm020040060001020d(nm)Frequency(%)t=700nm221.金属薄膜的静态力学性能——单轴拉伸钝钝钝钝钝钝钝ssss钝钝钝钝ssss表面、界面处位错受约束231.金属薄膜的静态力学性能——延性自由膜：一旦颈缩，快速断裂Stiffsubstrate硬基底附着膜：基底脆断软基底附着膜：可使薄膜延性完全表现延性评价方法？241.金属薄膜的静态力学性能——微裂纹统计及实时电阻法裂纹萌生临界应变：C薄膜表面微裂纹百分数统计实时电阻法测试05101520253035050100150200C(R-R0)/R0(%)Strain(%)0102030405001020304050CStrain(%)Cracksdensity(%/m2)25实时电阻法测定临界应变0510152001020304050Strain(%)60nm100nm275nm470nm705nm(R-R0)/R0%020040060080005101520600800100012001400sy(MPa)Criticalstrain(%)t(nm)CriticalstrainYieldstrength不同薄膜厚度临界应变-屈服强度关系Cu薄膜延性尺寸效应26微裂纹统计法测定临界应变应变薄膜厚度20%30%40%60nm275nm700nm10um薄膜越薄，应变越大，贯穿型大裂纹越多27不同薄膜厚度微裂纹统计法测定临界应变0204002040Cracksdensity(%m-2)t=60nm100nm275nm340nm705nmStrain(%)c0200400600800051015Criticalstrain(%)t(nm)ElectricalresistivitymethodMicrocrackanalyzingmethod两种方法结果对比微裂纹测定与实时电阻测定结果相近金属薄膜延性评价方法28Flexiblesubstrate(Polymer)Rigidsubstrate(Silicon)Goodunderstandingofthefatiguepropertiesareveryimportant!2.金属薄膜的疲劳性能——附着膜29Polymersubstrate(Stretchable)Tension-tensionfatigue(Microforcetester)Keypoint:Subtractingoravoidingtheinfluenceofdeformedsubstrate3%elasticdeformationP=250N+1mNpolyimide2.金属薄膜的疲劳性能——柔性基板30Previousmethodsonfatiguelifetime(Nf)measurementShortcomings:complicatedandstructurallyinstableatdefinitionpointStrainrangechange(Kraftetal.2001)Extrusiondensitycounting(Volkertetal.2008)NfLoad-controlledSaturatedEx-situmeasurement2.金属薄膜的疲劳性能——柔性基板31100101102103104015304560Nf(R-R0)/R0(%)N(Cycles)SuggestionofamuchmoresimplemethodFatiguelifetimeformicrocracknucleation(VerifiedbySEM)RelativechangeinERCuIn-situmeasurement2.金属薄膜的疲劳性能——柔性基板32ThinCuandAlfilms:△ε–NfCurvesFollowingthewell-knownCoffin-Mansonrelationship1021031041050.40.50.60.70.80.91123Cufilms1.35m3.75m(%)Nf(Cycles)100nm175nm700nm1021031041050.40.50.60.70.80.9112Alfilms(%)Nf(Cycles)800nm340nm80nmAlfilms(80nm-800nm)Cufilms(100nm-3.75μm)2.金属薄膜的疲劳性能——柔性基板33ThinCufilms:thicknessdependentNfThethinneristhefilm,thelongeristheNfFatiguelifetimeYieldstrength&ductility2.金属薄膜的疲劳性能——柔性基板34Comparingwithothers’resultsShorterthanothers’experimentalresults1031041051060.50.60.70.80.9112Cufilms200nm100nmWangetal.(2008)(%)Nf(Cycles)Presentresults175nm100nm1021031041051060.11Kraftetal.(2002)3.1m1.5m1.1mWangetal.(2008)3mPresentresults1.35m3.75m(%)Nf(Cycles)CufilmsNano-thickCufilmMicro-thickCufilms2.金属薄膜的疲劳性能——柔性基板35In-situtestinginaSEMchamberThermalfatigueTimevariantresistanceandTBasedontheresistance-temperaturerelationship,ᇫT(ᇫε)canbedeterminedMonig,etal.,Rev.Sci.Ins.75(2004)4997Electricalopen:Nfᇫε=ᇫαxᇫTMismatchinTEC2.金属薄膜的疲劳性能——刚性基板362.金属导线的力学性能评价——试样制备1）光刻2）显影3）溅射掩膜基体光刻胶Cu膜4）二次显影微米级线宽37“工”字型试样2.金属导线的力学性能评价——试样形貌10mm10mm100um1mm5mm3mm38PreviousworkontheThermalfatigueofCuthinfilmsNfvsᇫTandᇫεDamagemorphologyParketal.,ThinSolidFilms504(2006)321Volkertetal.,ThinSolidFilms515(2007)3253300nm-thickCu1.5μmGS200nm-thickCu0.5μmGSInallthepreviousreports,theCufilmshaveathickness200nmandanaveragegrainsize500nm,withinthisregiondislocationisoperativeSo,howaboutthethermalfatigueofmorethinnerandmorefinerCufilms?2.金属薄膜的疲劳性能——刚性基板39Thickness:about60nmGrainsize:about55nmResistanceandtemperatureMeasurement60nm-ultrathinCufilms/lines(5,10,15μmwide)Asinglelayerofgrainalongthethickness051015202530556065707580406080100120140Resistance[]Time[ms]Temperature[oC]j=3.2~26.5MA/cm22.金属薄膜的疲劳性能——刚性基板40Currentdensitydependent△TandNf510152025300306090120T(K)Currentdensity(MA/cm2)5m10m15m510152025050010001500200025003000Timetofailure(min)Currentdensity(MA/cm2)5m10m15mjvs△TjvsNf△ε∝△T~j~NfSizeeffect:thewideristheline,thelongerisNf2.金属薄膜的疲劳性能——刚性基板41Two-stagefatiguelifetimecurves1041051061070.010.110100T(K)15m10m5