Electrodeposition of Cu in the PEI-PEG-Cl-SPS Additive System

The impact of branched polyethyleneimine (PEI) on Cu electrodeposition from an acidified cupric sulfate electtrolyte containing a combination of superfilling additives, specifically polyethylene glycol, bis(3-sulfopropyl)disulfide, and chloride , is examined. Electroanalytical measurements reveal that adsorption of cationic PEI leads to inhibition of the metal deposition reaction to an extent similar to that provided by adsorption. However, unlike the suppressor, PEI is shown to deactivate adsorbed SPS accelerator. As a result, addition of PEI quenches the hysteretic voltammetric response that is a signature of competitive adsorption in the additive system. Trench-filling experiments in a electrolyte demonstrate that the deactivating interaction between PEI adsorption and adsorbed SPS can be optimized to prevent overfill bump formation without substantial detrimental impact on bottom-up, void-free feature filling.