介观材料力学综述课件

1、材料的介观力学性能评价及尺度效应参考书目：L. B. Freund and S. Suresh, Thin Film Materials: Stress, Defect Formation,and Surface Evolution Cambridge University Press, Cambridge,2003(2) W. D. Nix, Metall. Trans. A 20 (1989) 2217.Size10-3 10-6 10-6 10-8 10-3 连续介质理论分子动力学介观什么是介观？2材料介观力学性能评价的意义微米尺寸材料的广泛应用MEMSCuOSGSiNTaNIntel

2、90 nm interconnect集成电路互连导线3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4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！5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6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7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

3、洛氏：压痕小/不稳定维氏：兼有布氏和洛氏的优点8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9H 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10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111. 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121. 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131. 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141. 金属薄膜的静态力学性能 悬臂梁法可能

4、原因：残余应力基体影响压头滑动151. 金属薄膜的静态力学性能 微桥法161. 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171. 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18微小力实验机：P = + 250 N + 1 N； l = + 50 mm + 5 m薄膜夹头1. 金属薄膜的静态力学性能单轴拉伸191. 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20Cu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

5、= 60 nmt = 340 nmt = 700 nm211. 金属薄膜的静态力学性能单轴拉伸表面、界面处位错受约束221. 金属薄膜的静态力学性能 延性自由膜：一旦颈缩，快速断裂Stiff substrate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 ？231. 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24实时电阻法测定临界应变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25微裂纹统计法测定临界应变应变薄膜厚度20%30%40%60 nm275 nm700 nm10um薄膜越薄，应变越大，贯穿型

6、大裂纹越多26不同薄膜厚度微裂纹统计法测定临界应变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27Flexible substrate(Polymer)Rigid substrate(Silicon)Good understanding of the fatigue properties are very important !2. 金属薄膜的疲劳性能附着膜28Polymer substrate (Stretchable)Tension-tension fatigue (Microforce tester)Key point: Subtracting or avoidi

7、ng the influence of deformed substrate 3 % elastic deformationP = 250 N + 1 mNpolyimide 2. 金属薄膜的疲劳性能柔性基板29Previous methods on fatigue lifetime (Nf) measurementShortcomings: complicated and structurally instable at definition pointStrain range change (Kraft et al. 2001)Extrusion density counting (Vol

8、kert et al. 2008)NfLoad-controlledSaturatedEx-situ measurement2. 金属薄膜的疲劳性能柔性基板30Suggestion of a much more simple methodFatigue lifetime for microcrack nucleation (Verified by SEM)Relative change in ERCuIn-situ measurement2. 金属薄膜的疲劳性能柔性基板31Thin Cu and Al films: Nf CurvesFollowing the well-known Coffi

9、n-Manson relationshipAl films (80nm-800nm)Cu films (100nm-3.75 m)2. 金属薄膜的疲劳性能柔性基板32Thin Cu films: thickness dependent NfThe thinner is the film, the longer is the NfFatigue lifetimeYield strength & ductility2. 金属薄膜的疲劳性能柔性基板33Comparing with others resultsShorter than others experimental resultsNano-t

10、hick Cu filmMicro-thick Cu films2. 金属薄膜的疲劳性能柔性基板34In-situ testing in a SEM chamberThermal fatigueTime variant resistance and TBased on the resistance-temperature relationship, T () can be determinedMonig, et al., Rev. Sci. Ins. 75 (2004) 4997Electrical open: Nf = x TMismatch in TEC2. 金属薄膜的疲劳性能刚性基板35

11、2. 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36“工”字型试样2. 金属导线的力学性能评价试样形貌10mm10mm100um1mm5mm3mm37Previous work on the Thermal fatigue of Cu thin filmsNf vs T and Damage morphology Park et al., Thin Solid Films 504 (2006) 321Volkert et al., Thin Solid Films 515 (2007) 3253300 nm-thick Cu1.5 m GS

12、200 nm-thick Cu0.5 m GSIn all the previous reports, the Cu films have a thickness 200 nm and an average grain size 500 nm, within this region dislocation is operativeSo, how about the thermal fatigue of more thinner and more finer Cu films ?2. 金属薄膜的疲劳性能刚性基板38Thickness: about 60 nmGrain size: about 5

13、5 nmResistance and temperature Measurement60 nm-ultrathin Cu films/lines ( 5,10,15 m wide)A single layer of grain along the thicknessj = 3.2 26.5 MA/cm22. 金属薄膜的疲劳性能刚性基板39Current density dependent T and Nfj vs T j vs NfT j NfSize effect: the wider is the line, the longer is Nf 2. 金属薄膜的疲劳性能刚性基板40Two-s

14、tage fatigue lifetime curves Low cycle region ( j 10 MA/cm2)Thermally controlled damage Mechanically controlled damage 2. 金属薄膜的疲劳性能刚性基板41Damage mechanismLow cycle region:Burst to electrical openHigh cycle region:Formation of damage bands2. 金属薄膜的疲劳性能刚性基板42Damage bands in high cycle regionGrain extrus

15、ionTEM imageExtrusion of grain arraysDifferent from all the previous reports !2. 金属薄膜的疲劳性能刚性基板43AFM analysesTwo dimension AFM imageThree dimension AFM image2. 金属薄膜的疲劳性能刚性基板44Damage band forming mechanismCompressive-compressive fatigueTEM2. 金属薄膜的疲劳性能刚性基板45微小试样的力学性能评价试样制备FIB单晶46降低梯度塑性的影响微小试样的力学性能评价试样形貌及特征纳米压头试样47微小试样的力学性能评价压缩性能N