Bottom-up Filling of Damascene Trenches with Gold in a Sulfite Electrolyte

Superconformal Au deposition is demonstrated in a Na(3)Au(SO(3))(2 +) Na(2)SO(3) electrolyte using Bi species to catalyze the reduction of Au(SO(3))(2)(3−). Micromolar additions of Bi(3+) to the sulfite-based electrolyte accelerate the reduction of Au(SO(3))(2)(3−) as shown by hysteretic voltammetry and rising chronoamperometric transients. Superconformal feature filling is observed over a defined range of Bi(3+) concentration, potential and hydrodynamics. Over a more limited parameter range, approximately −0.9 V to −0.95 V, void-free, bottom-up filling of Damascene trenches is achieved. Furthermore, in the presence of significant convection the bottom-up filling is accompanied by passivation of the free surface. Bottom-up feature filling is characterized by a counterintuitive dependence of the free surface reactivity on the available flux of the Bi(3+) accelerator species suggestive of an unusual coupling between hydrodynamic transport, shear and interfacial chemistry.