Influence of Flow Pattern on the Thickness Variation of Electrodeposited Copper

In this study, the effects of flow patterns and organic additives on the uniformity of electrodeposited Cu were investigated. The experiments were performed using nozzle-based, paddle-based, or mixed convection systems in additive-free or additive-containing electrolyte with varying nozzle flow rates (0. 2, 5, and 10 L/min), and paddle stirring speeds (0, 5, and 10 cm/s). With nozzle spray convection, localized Cu growth was observed due to the uneven flow pattern, and this non-uniformity was alleviated by the presence of additives (SPS, PEG, and JGB). The electrochemical analysis and simulation results confirmed that the reduction in thickness deviation could be attributed to the convection-dependent adsorption of additives followed by the alleviation of the potential difference within the electrode. With paddle-based convection, the localized Cu growth due to uneven flow pattern was not observed, but a deviation in Cu brightness between the center and the edge was observed. Under the mixed convection, the overall uniformity was greatly improved compared to the nozzle- or paddle-based convections. It was also confirmed that the thickness deviation depended on both the nozzle injection rate and the paddle rotating speed. The results of this study demonstrate the necessity of optimizing flow conditions to improve the uniformity of the deposited film. The results could provide useful data for the design of flow in an electroplating cell in industrial processes.