Kirkendall voids are detrimental to the Cu-Sn bonding interface, causing the failure of the high-density package. Herein, the perpendicularly aligned nanotwinned Cu (p-ntCu) and the horizontally aligned nanotwinned Cu (h-ntCu) are prepared by controlling the electrodeposition procedure. The p-ntCu shows advantages both in fast-bonding process and in void suppression through the in-situ microstructure evolution. Compared with h-ntCu, the abundant perpendicularly aligned twin boundaries in p-ntCu provide fast interdiffusion paths to build a bonding interface. In the bonding process, p-ntCu grows to ultra-large-grained Cu with an average grain size of 6.68 μm. The reduced density of normal grain boundaries in p-ntCu lowers the Cu diffusion rate and contributes to more balanced interdiffusion at the bonding interface, which is confirmed by molecular dynamics simulation and kinetic calculations of intermetallic compound (IMC) growth. In addition, the low impurity content in p-ntCu further reduces the diffusion flux imbalance and limits the nucleation of Kirkendall vacancies. Consequently, the p-ntCu/Sn interface keeps void-free during 150 °C long-term thermal aging due to the synergistic effect of reduced grain-boundary diffusion and lower impurity content, which will be beneficial for achieving high-reliability Cu-Sn bonding.

中文翻译：

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通过纳米孪晶铜的微观结构演变提高 Cu-Sn 键合的可靠性


Kirkendall 空隙对 Cu-Sn 键合界面有害，导致高密度封装失效。在此，通过控制电沉积程序制备了垂直排列的纳米孪晶 Cu （p-ntCu） 和水平排列的纳米孪晶 Cu （h-ntCu）。p-ntCu 在快速键合工艺和通过原位微观结构演变抑制空隙方面都显示出优势。与 h-ntCu 相比，p-ntCu 中丰富的垂直排列孪晶界为构建键合界面提供了快速的相互扩散路径。在键合过程中，p-ntCu 生长成平均晶粒尺寸为 6.68 μm 的超大晶粒 Cu。p-ntCu 中正常晶界密度的降低降低了 Cu 扩散速率，并有助于在键合界面处实现更平衡的相互扩散，这可以通过分子动力学模拟和金属间化合物 （IMC） 生长的动力学计算得到证实。此外，p-ntCu 中的低杂质含量进一步降低了扩散通量不平衡并限制了 Kirkendall 空位的成核。因此，由于晶界扩散减少和杂质含量降低的协同作用，p-ntCu/Sn 界面在 150 °C 长期热老化期间保持无空洞，这将有利于实现高可靠性的 Cu-Sn 键合。