Wafer-to-wafer Cu hybrid bonding relies on non-elastic Cu-pad expansion to achieve permanent CuCu pad bonding between the bonded wafers. Understanding the mechanism and being able to predict the amount of Cu expansion and the mechanism of this Cu expansion is the key for defining the chemical-mechanical polishing specifications and process window, as well as lowering the required annealing temperature for achieving proper CuCu bonding. Cu primary creep is investigated as the potential mechanism for Cu expansion through finite element simulations. Pad expansion results for different processing conditions are reported. Comparison with measurements indicates that primary creep is however not the dominant mechanism for Cu expansion in wafer-to-wafer hybrid bonding.

晶圆到晶圆的铜混合键合依赖于非弹性铜焊盘扩展来实现键合晶圆之间的永久铜铜焊盘键合。了解机制并能够预测 Cu 膨胀量和这种 Cu 膨胀机制是定义化学机械抛光规范和工艺窗口以及降低实现适当 Cu Cu 键合所需的退火温度的关键。通过有限元模拟研究了铜初级蠕变作为铜膨胀的潜在机制。报告了不同处理条件下的焊盘扩展结果。与测量结果的比较表明，初级蠕变并不是晶圆间混合键合中铜膨胀的主要机制。