Superconformal Cobalt Electrodeposition with a Hydrogen Evolution Reaction Suppressing Additive

In this study, superconformal cobalt filling of submicron trenches by electrodeposition is investigated in the presence of 2-mercaptobenzimidazole (MBI), which suppresses both cobalt deposition and the hydrogen evolution reaction (HER). The mechanism through which this single additive enables superconformal cobalt filling is investigated. The formation and breakdown of the suppression layer are characterized by linear sweep voltammetry and chronoamperometry. The convection-driven local concentration of MBI exerts different suppressing effects on cobalt reduction and the HER, leading to a change in the deposition rate and the current efficiency of cobalt. These phenomena induce a deposition rate differential between the top and bottom of the submicron trench, enabling bottom-up cobalt filling with a V-shape profile.