2-Mercaptopyridine as a new leveler for bottom-up filling of micro-vias in copper electroplating

In order to achieve a perfect bottom-up electroplated Cu filling with a minimal surface thickness, 2-mercaptopyridine (2-MP) was investigated as a new leveler for replacing Janus Green B (JGB) for bottom-up copper filling. Electrochemical impedence results indicate that 2-MP has a stronger suppression for Cu deposition than JGB. With the addition of 2-MP, the filling capability of the electroplating solution is improved significantly with the Cu thickness on surface decreasing from ∼16 μm to ∼10 μm. The interaction mechanisms of 2-MP, bis(3-sulfopropyl) disulfide (SPS), Cl− and tri-block copolymer of PEG and PPG with ethylene oxide terminal blocks (EPE) in the plating solution are studied by galvanostatic measurements (GMs). The acceleration effect of SPS and the inhibition effect of 2-MP on copper deposition occur in the presence of EPE, and the convection-dependent adsorption (CDA) behavior of additives usually occurs with the injection of four additives at optional concentrations. Further, it was found that when 1.0 ppm 2-MP, 1.0 ppm SPS and 200 ppm EPE were injected into the basic electrolyte, the potential difference (Δh) value of the electrolyte became positive, and the bottom-up electroplated copper filling was obtained in the electrolyte in absence of Cl−. The interaction mechanisms of three additives for bottom-up filling have been investigated by GMs.