The Cu seed deposition step seamlessly follows the Ta-based liner deposition and provides a critical conductive nucleation foundation for the subsequent electrochemical deposition (ECD) of the bulk Metal 6 Cu P1. Because this specific step resides in the Direct Bond Interconnect (DBI) module, the resulting metal structure will eventually serve as the ultimate wafer-to-wafer hybrid bonding interface (Engineering Practice). Consequently, the seed layer must ensure exceptionally dense and uniform E