Effect of Redistributed Layer Metal Thermal Expansion on the Hybrid Bonding Surface Roughness

Hybrid bonding is a promising technology to achieve 3D integrated chips with fine-pitch vertical interconects and high reliability. Many studies focus on the surface roughness during the bonding process, because the surface roughness is a key factor that will influence the bonding interface quality. However, there is no research pay attention to the surface roughness variation owing to the thermal expansion mismatch between redistributed layer (RDL) metal and dieleric mateiral during the bonding process. This paper first analysis this mechanism based on the finite element method. And conclude that fine pitch of RDL metal, thick dieletric layer and small coefficient of thermal expansion (CTE) of RDL metal are beneficial to the surface roughness variation and bonding quality.