Atomistic Modeling of Interfacial Cracking in Copper-To-Copper Direct Bonding

Copper-to-copper (Cu-Cu) direct bonding is a crucial technology for high-density 3D integration in advanced semiconductor packaging, offering superior reliability over conventional solder-based approaches. However, void formation at the bonding interface remains a significant challenge, potentially compromising mechanical integrity. This study employs large-scale molecular dynamics (MD) simulations to investigate the atomic-scale mechanisms of void evolution in Cu-Cu direct bonding under cyclic mechanical loading. Using polycrystalline Cu models with varying void distributions, grain size distributions, and interfacial bonding ratios, we examine how cyclic tensile loading influences void shrinkage and coalescence. Our results reveal that dislocation activity and grain growth near the bonding interface drive void elimination, with non-uniform void distributions promoting faster void coalescence, while evenly spaced voids shrink more gradually. Samples with a higher bonding ratio exhibit faster void reduction, though extended cyclic loading enhances void closure across all cases. These findings suggest that cyclic mechanical stress can be leveraged to improve bonding quality, offering insights into optimizing Cu−Cu bonding for high-density 3D integration systems.

Recommended citation: S. Yang, J. Lu. "Atomistic Modeling of Interfacial Cracking in Copper-To-Copper Direct Bonding. " IEEE Electronic Components and Technology Conference (ECTC). 2025: 1206-1210. https://doi.org/10.1109/ECTC51687.2025.00207