In the manufacture of metal interconnects for semiconductor devices, trenches and vias in dielectric layers on the Si wafer are filled by copper electrodeposition. The acceleration of deposition at the bottom of trenches and vias is a key to the bottom-up filling of these high aspect ratio cavities. We report the detection of this acceleration effect by rotating ring disk electrode experiments. The Cu (I)-complex, which forms on the disk electrode, was captured as a current (I-ring) on the ring electrode. I-ring increased in periodic reverse pulse current mode, as compared to direct or pulse current. The periodic reverse pulse current produced the most bottom-up filling based on microscopic observations of via cross sections. I-ring increased with the additions of Cl-, which also produced greater bottom-up filling. I-ring increased with additions of SPS, which were also found to improve bottom-up filling.