Effect of Oxidizers on Chemical Mechanical Planarization of Ruthenium with Colloidal Silica Based Slurry

Abstract

We investigated effect of oxidizers on chemical mechanical planarization (CMP) of ruthenium (Ru). Several commonly used oxidizers with different standard reduction potentials were used in the Ru CMP test, and their corrosion behaviors and states of surface oxidation were analyzed. We found that Ru only had a high polishing rate with slurries containing sodium periodate and sodium hypochlorite. We also observed that Ru film underwent severe pitting corrosion with these slurries, and formed a porous RuO3/RuO2 oxide layer. Ru film was unable to achieve high corrosion current density as well as form a porous RuO3/RuO2 oxide layer except for these two oxidizers. Both the corrosion and oxidation (formation of RuO3/RuO2 layer) processes influenced the Ru polishing rate, but the oxidation process was assumed to play a more decisive role in the Ru CMP. The mechanism for the types of oxidizers in Ru corrosion and oxidation processes is discussed and explained through a diagram of the equilibrium electronic band of Ru metal electrodes and oxidizers in an aqueous solution.