The Metal 5 (M5) copper deposition step is critical for forming the fifth routing layer in the back-end-of-line (BEOL) dual-damascene structure A2.Following the deposition of a Ta-based barrier and a copper seed layer, this step completely fills the high-aspect-ratio V5 vias and M5 trenches with bulk copper before the subsequent chemical mechanical planarization (CMP) step P3.Copper is utilized as the interconnect material because its low electrical resistance and high allowable current density