(Invited) Bonding Strength of Cu-Cu Hybrid Bonding for 3D Integration Process

Abstract

Cu-Cu hybrid bonding is a significant technology for fabricating 3D stacked semiconductor devices. In hybrid bonding, the calculation of bonding strength is complex due to the various materials present in the bonding interface. This interface not only includes Cu/Cu and dielectric/dielectric interfaces, but also the Cu/dielectric interface because of the misalignment of Cu pads. In this study, we developed an integrated model regarding total bonding strength, considering the different interfaces. Additionally, considering the thermal expansion of Cu pads, we demonstrated the dependence of bonding strength on misalignment using simulations. At the dielectric/dielectric bonding interface, a phenomenon was observed, in which the H 2 O contained in the dielectric enhanced the bonding strength. We proposed a model for the increase of the bonding strength by filling the bonding interface gap with thermally expanded dielectrics. These results provide understanding regarding a part of the mechanism involved in bonding strength in Cu-Cu hybrid bonding.