Combined fluid flow simulation with electrochemical measurement for mechanism investigation of high-rate Cu pattern electroplating

Abstract

BackgroundCu pattern electroplating plays an essential role in the interconnection and microstructure fabrication of high-power device packaging. However, improving efficiency while ensuring the preparation quality is an urgent breakthrough direction. MethodsA new electrolyte formula suitable for the high-rate Cu pattern electroplating was put forward, including 300 mg/L polyethylene glycol (PEG, molecular weight=8000) and 6 mg/L thiazolinyl polydipropyl sulfonate (SH110). The mechanism of high-rate Cu pattern electroplating was investigated by the combination of fluid flow simulation and the electrochemical measurements including galvanostatic measurements (GMs) and cyclic voltametric (CV) tests. The Cu pattern was electroplated in the Haring-Cell with air bubble as the forced convection method. Significant findingsThe simulation results indicate that the flow rate on the ring-shaped cathodic pattern surface gradually increases with the Cu growing up, which also increase from the pattern surface to the bulk electrolyte. The GMs results suggest that the cathodic polarization of the convection-dependent additives raises with the current density, which is strengthened by strong convection with current density lower than 6 ASD but have the opposite effect with current density larger than 8 ASD. The CV tests indicating that the aggregation of weak convection and strong polarization promote the antagonistic effect between thiolate of SH110 and PEG, the nucleation and the electroplating rate. Nevertheless, the synergistic effect of thiazoline of SH110 and PEG are enhanced with strong convection and weak polarization. The adsorption model during the Cu pattern electroplating process is established and verified by electroplating experiment with the optimum current density of 8 ASD. The Cu pattern is mirror bright with the high electroplating rate of over 90 μm/h.