Huang Jian-Yuan, Tran Dinh-Phuc, Lee Kang-Ping, Lin Yi-Quan, Kuo Emile, Chen Tsung-Chuan, Chen Yao-Tsung, Chung Stream, Chen Chih
Institute of Pioneer Semiconductor Innovation, National Yang Ming Chiao Tung University, Hsinchu 300093, Taiwan.
Department of Materials Science and Engineering, National Yang Ming Chiao Tung University, Hsinchu 300093, Taiwan.
Materials (Basel). 2025 Aug 8;18(16):3725. doi: 10.3390/ma18163725.
This study investigates the use of nanocrystalline Cu (NC-Cu) to suppress interfacial voids in low-temperature Cu-Cu bonding for 3D IC packaging. We quantitatively compared the void characteristics of electrodeposited NC-Cu (grain size ~89.3 nm) and (111)-oriented nanotwinned Cu (NT-Cu, ~621.8 nm) bonded at 200 °C. Plan-view STEM-HAADF analysis revealed that NC-Cu achieved a much lower void area ratio (1.8%) than NT-Cu (4.0%), attributed to its high grain boundary density, which enhances atomic diffusion and grain boundary migration. At 250 °C, typical Ostwald ripening was observed, with fewer but larger voids. However, a rise in total void area fraction suggests a competing mechanism-possibly new void nucleation at grain boundaries triggered by residual defects from the electroplating process. These results highlight the superior void-mitigating capability of NC-Cu under low thermal budgets.
本研究探讨了使用纳米晶铜（NC-Cu）来抑制用于3D IC封装的低温铜-铜键合中的界面空洞。我们定量比较了在200°C下键合的电沉积NC-Cu（晶粒尺寸约89.3 nm）和（111）取向的纳米孪晶铜（NT-Cu，约621.8 nm）的空洞特性。平面STEM-HAADF分析表明，NC-Cu的空洞面积比（1.8%）远低于NT-Cu（4.0%），这归因于其高晶界密度，该密度增强了原子扩散和晶界迁移。在250°C时，观察到典型的奥斯特瓦尔德熟化现象，空洞数量减少但尺寸增大。然而，总空洞面积分数的增加表明存在一种竞争机制——可能是由电镀过程中的残余缺陷引发的晶界处新的空洞形核。这些结果突出了NC-Cu在低热预算下优异的空洞缓解能力。
