Control of Overfill Bumps in Damascene Cu Electrodeposition

Abstract

Electroanalytical measurements and feature filling experiments have been conducted to study the effect of levelers, such as dodecyltrimethylammonium chloride (DTAC) and branched polyethyleneimine (PEI), on Cu electrodeposition in the presence of various combinations of superfilling additives. Surface saturation of either leveler yields substantial inhibition of Cu deposition reaction that is similar in magnitude to that provided by PEG-Cl. Addition of the levelers to the PEG-Cl-SPS superfilling electrolyte leads to quenching of the characteristic voltammetric hysteresis. This behavior is attributed to ion-pairing between the cationic functional group of the leveler and the anionic sulfonate tail group of the accelerator SPS. This deactivation process stems from either leveler adsorption from the electrolyte and/or lateral interactions during area reduction in accordance with the curvature enhanced adsorbate coverage mechanism. The combined processes may be optimized to enable the bottom-up filling dynamic to be sustained while overfill bump formation is effectively attenuated.