Rapid Determination of the Electrodeposition Potential for Cu Superfilling Using a Nanocones Array Structured Electrode

Abstract

Organic additives are indispensable for successful Cu superfilling in advanced interconnect metallization but their effects during filling are too complex to monitor. Hence time-consuming real wafer plating is usually performed to optimize operating conditions. Based on our previous study showing a peak in the current-potential curve only with both bis-(3-sulfopropyl) disulfide (SPS) and polyethylene glycol (PEG), a simple method to rapidly determine a suitable potential range for feature filling was developed using a nanocones array (NCA) structured electrode. Flat and NCA electrodes were employed to mimic the via top and entire via, respectively. The difference in current between the two electrodes was linked to the current contribution of the via bottom. Results showed that the current contribution of the via top or bottom depended on applied potential and solution composition. Without additives or with SPS alone, the current of the via bottom was always smaller than that of the via top, indicating poor superfilling. In the presence of PEG with or without SPS, we identified a potential range where the current of the via bottom was larger than that of the via top. Plating in through silicon vias demonstrated the method we propose is applicable to real wafer plating.