Behavior of Bonding Strength on Wafer-to-Wafer Cu-Cu Hybrid Bonding

In this study, we investigated the relationship between misalignment and bonding strength before and after annealing in the Cu-Cu hybrid bonding process. Before the annealing process, the bonding strength tended to decrease linearly as the misalignment increased. However, we found that this correlation changed after the annealing, seemingly due to thermal expansion of Cu. To reveal this phenomenon, the thermal stress simulation was conducted. The simulated results showed thermal expansion of Cu affects the bonding strength of Cu.