The Effect of Sn Orientation on Intermetallic Compound Growth in Idealized Sn-Cu-Ag Interconnects
The Effect of Sn Orientation on Intermetallic Compound Growth in Idealized Sn-Cu-Ag Interconnects
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DOI：
10.1007/s11664-012-2306-0
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发表时间：
2013-04-01
影响因子：
2.1
通讯作者：
Morris, J. W., Jr.
中科院分区：
文献类型：
--
作者：
Kinney, Chris;Linares, Xioranny;Morris, J. W., Jr.
本文研究了Cu中电迁移过程中晶体取向对界面金属间化合物层生长的影响||SN||铜焊点。样品是薄的，平面的Sn-Ag-Cu（SAC）焊料层之间的铜条受到单轴电流。采用电子背散射衍射（EBSD）对试验前后的显微组织进行了表征。EBSD数据的最有用的表示通过Sn c轴和电流方向之间的角度来识别Sn晶粒取向。测试样品包括c轴几乎平行于电流的单晶接头（“绿色”样品）和c轴垂直于电流的单晶接头（“红色”样品）。在电流密度为10（4）A/cm（2）（稳态温度为150 A摄氏度）时，“绿色”样品中的金属间化合物层以可观察到的速率生长，但“红色”样品中没有。1.15 × 10（4）A/cm（2）的电流密度（温度160 A ℃）导致两个样品中可测量的金属间化合物生长。生长前沿几乎是平面的，并且生长速率恒定（在初始孵育期之后）;“绿色”样品中的生长速率是“红色”样品中的生长速率的约10倍。接头内Cu浓度恒定，表明金属间化合物的生长主要由电迁移通量决定。测量的生长速率和文献值的Cu在Sn中的扩散被用来提取值的有效电荷，z（*），这决定了Cu的电迁移。对于垂直于c轴的电流，z（*）的计算值明显大于沿着c轴的电流。
The work reported here explores the influence of crystal orientation on the growth of the interfacial intermetallic layer during electromigration in Cu||Sn||Cu solder joints. The samples were thin, planar Sn-Ag-Cu (SAC) solder layers between Cu bars subject to a uniaxial current. Electron backscatter diffraction (EBSD) was used to characterize the microstructure before and after testing. The most useful representation of the EBSD data identifies the Sn grain orientation by the angle between the Sn c-axis and the current direction. The tested samples included single-crystal joints with c-axis nearly parallel to the current ("green" samples) and with c-axis perpendicular to the current ("red" samples). At current density of 10(4) A/cm(2) (steady-state temperature of 150A degrees C), an intermetallic layer grew at an observable rate in the "green" samples, but not in the "red" ones. A current density of 1.15 x 10(4) A/cm(2) (temperature 160A degrees C) led to measurable intermetallic growth in both samples. The growth fronts were nearly planar and the growth rates constant (after an initial incubation period); the growth rates in the "green" samples were about 10x those in the "red" samples. The Cu concentrations were constant within the joints, showing that the intermetallic growth is dominated by the electromigration flux. The measured growth rates and literature values for the diffusion of Cu in Sn were used to extract values for the effective charge, z (*), that governs the electromigration of Cu. The calculated value of z (*) is significantly larger for current perpendicular to the c-axis than along it.