Effect of Chelating Agent on Reducing Galvanic Corrosion between Cobalt and Copper in Alkaline Slurry

Cobalt has been as the copper-interconnects barrier in the ultra-large scale integrated circuit, but serious galvanic corrosion happens between cobalt and copper during the process of barrier polishing. The effects of chelating agent on reducing galvanic corrosion between cobalt and copper were investigated in this work. The result of potentiodynamic polarization measurements, static etching corrosion experiments and polishing experiments indicated that the chelating agent could inhibit the corrosion of Co by increasing the pH of the slurries with the hydroxyl itself contained and prevent the dissolution of the mixture oxides passive film on cobalt surface. While the passive film on copper surface dissolved when the chelating agent was added and the concentration was increased to the 5 ml/L. Cobalt had higher erosion potential than copper and the galvanic corrosion could be prevented effectively when the difference of open circuit potential of them decreased to 20 mV.