Investigation of galvanic corrosion between TaN_x barriers and copper seed by electrochemical impedance spectroscopy

In this article, electrochemical impedance spectroscopy is used to characterize the mechanism of galvanic corrosion between copper (Cu) seeds and tantalum nitride (Ta Nx) barriers deposited with different N2 flow rates. By way of software simulating with EIS data, an equivalent circuit is built up to explain the corrosion behavior of the Ta Nx films' relation to the Cu seeds in an acidic chemical-mechanical-polishing slurry. The equivalent circuit can respond to changes in resistance and capacitance elements of the Cu-Ta Nx electrochemical system. It is found that the charge-transfer resistance of the Ta Nx galvanic corrosion increases with the N2 flow rate, whereas the resistance of a tantalum-oxide layer is opposite because increasing the N content of the Ta Nx films inhibits corrosion and oxidation of the Ta metals. The result is consistent with our previous investigation that the galvanic corrosion of the Ta Nx films to the Cu seeds is retarded by the N element [C. C. Hung, Y. S. Wang, W. H. Lee, S. C. Chang, and Y. L. Wang, Electrochem. Solid-State Lett., 10, H127 (2007)].