In this study, an effective seeding technology, plasma immersion ion implantation of palladium (PIII Pd), was proposed to achieve defect-free gap filling for copper electroplating (Cu-ECP). It was found that a threshold dosage (∼5.2×10 18 m −2 ) of PIII Pd was required to drive Cu-ECP and the dependence of Pd dosage on the implantation time was quasi-linear. The thickness of electroplated copper films increased as the Pd dosage increased. Too high a Pd dosage caused a rough copper film with high resistivity (>10 μΩ cm) while too low a Pd dosage resulted in an insufficient nucleation site for Cu-ECP, leading to poor film adhesion. In addition, a higher substrate bias of PIII was suggested to enhance the gap-filling capability of Cu-ECP and the Cu(111) formation of electroplated copper films.