In BEOL interconnects, following the deposition of a Ta-based diffusion barrier, a continuous and conductive copper seed layer is required to enable subsequent electrochemical deposition (ECD) of bulk copper P1.At the MET5 level of a 40nm BSI CMOS Image Sensor process, this Cu seed layer serves as the critical catalytic and conductive surface for the dual-damascene structure A1.Without this highly conductive layer, the electroplating current cannot be uniformly distributed across the wafer, prev