Mechanism of Cobalt Bottom-Up Filling for Advanced Node Interconnect Metallization

A mechanism of cobalt bottom-up trench fill for advanced node interconnect metallization was studied. The mechanism in question employs a single additive which suppresses cobalt plating and directly impacts the plating rate. Hydrogen, generated simultaneously during plating by electrolysis, reacts with the suppressor via hydrogen reduction, and the product of this reaction is a deactivated form of the suppressor. The local plating rate is governed by the relative concentrations of the activated/deactivated forms. Cyclic voltammetry (CV) shows that the suppressor deactivation is impacted by electrochemical potential, suppressor concentration, rotation rate, and pH, all of which may be controlled to generate bottom up fill in interconnects. Such impacts were confirmed on the plating of patterned coupons. This hydrogen reduction-induced deactivation mechanism provides a theoretical explanation for bottom-up plating in a single additive bath, and the factors that may impact the bottom-up filling.