Kung Po-Yu, Huang Wei-Lun, Kao Chin-Li, Lin Yung-Sheng, Hung Yun-Ching, Kao C R
Department of Materials Science and Engineering, National Taiwan University, Taipei 10617, Taiwan.
Product Characterization, Corporate R&D, Advanced Semiconductor Engineering (ASE) Group, Kaohsiung City 811, Taiwan.
Materials (Basel). 2022 Nov 4;15(21):7783. doi: 10.3390/ma15217783.
Cu-to-Cu direct bonding plays an important role in three-dimensional integrated circuits (3D IC). However, the bonding process always requires high temperature, high pressure, and a high degree of consistency in height. In this study, Sn is passivated over electroplated copper. Because Sn is a soft material and has a low melting point, a successful bond can be achieved under low temperature and low pressure (1 MPa) without any planarization process. In this experiment, Sn thickness, bonding temperature, and bonding pressure are variables. Three values of thicknesses of Sn, i.e., 1 μm, 800 nm, and 600 nm were used to calculate the minimum value of Sn thickness required to compensate for the height difference. Additionally, the bonding process was conducted at two temperatures, 220 °C and 250 °C, and their optimized parameters with required pressure were found. Moreover, the optimized parameters after the Cu planarization were also investigated, and it was observed that the bonding can succeed under severe conditions as well. Finally, transmission electron microscopy (TEM) was used to observe the adhesion property between different metals and intermetallic compounds (IMCs).
铜到铜直接键合在三维集成电路（3D IC）中起着重要作用。然而，键合过程总是需要高温、高压以及高度一致的高度。在本研究中，锡被沉积在电镀铜上。由于锡是一种软材料且熔点低，在低温低压（1兆帕）下无需任何平面化工艺就能实现成功键合。在本实验中，锡的厚度、键合温度和键合压力是变量。使用三种锡厚度值，即1微米、800纳米和600纳米来计算补偿高度差所需的锡厚度最小值。此外，键合过程在220℃和250℃两个温度下进行，并找到了它们的优化参数以及所需压力。此外，还研究了铜平面化后的优化参数，并且观察到在苛刻条件下键合也能成功。最后，使用透射电子显微镜（TEM）来观察不同金属与金属间化合物（IMC）之间的粘附性能。
