Electrochemical investigations for copper electrodeposition of through-silicon via

This study uses electrochemical techniques with a rotating disk electrode (RDE) to investigate the effects of Cu²⁺ concentration and additives on electrodeposition of through-silicon vias (TSV). The plating bath with both PEG and SPS has an obvious suppression effect on Cu-RDE with a thin boundary layer from −350 to −634 mV (vs. Hg/Hg₂SO₄) and a wide potential range for the via-filling operation. The impedance and potentiodynamic scans show the adsorption of small molecule SPS is more stable than PEG, and the effect of PEG or SPS depends on the thickness of boundary layer obviously only in Tafel region. This study obtained high filling powers in both deep and shallow vias using the plating bath of 50 g/L Cu²⁺, and TSV filling in wafer-segment scale, with 20 μm via diameter and 100 μm via depth, verifies the performance predicted by the electrochemical techniques.