Effects of dishing and annealing temperature on wafer to wafer hybrid bonding

Wafer-to-wafer hybrid bonding technology is one of the most advanced interconnection techniques in terms of performance and integration density. However, the dishing effects introduced by the chemical mechanical polishing process prior to hybrid bonding can significantly impact the quality of the bonding. In this study, molecular dynamics (MD) was employed to investigate the influence of dishing effects and annealing temperature on the quality of wafer-to-wafer hybrid bonding. The simulation of Cu-Cu diffusion bonding process took into consideration the dishing value, annealing temperature, and annealing time. Extending the bonding time could improve the bonding quality. Increasing the bonding temperature could also enhance the degree of interface bonding. However, when the dishing values were 10 Å and 20 Å, even with prolonged bonding time and elevated bonding temperature, it was not possible to ensure a void-free bonding process. The dishing value was the most critical factor determining the presence of voids in the bonded interface. Under a constant annealing temperature, if voids existed at the bonding interface, the volume of interface voids followed a power-law relationship with both the initial dishing values and the annealing time.