Corrosion and Passivation of Copper
Copper corrosion has challenged the integrated circuit manufacturing process since its first use in dual Damascene structures in the 1990’s. Copper oxides that form on the surface of metallic copper; Cu2O and CuO, must be removed to achieve good conductivity between the metal layers. Galvanic and electrogalvanic corrosion must be minimized. During processing, corrosion can occur for various reasons, electrogalvanic, by exposure to oxidizing solutions, or simply by exposure to air. Post-etch and post-chemical-mechanical planarization cleaning formulations have been developed to address these challenges, plus clean the post-etch residue from the features or remove the slurry on the wafer. Various corrosion inhibitors are used in cleaning formulations, including azole compounds, diols, and carboxylic acids. These compounds are soluble in aqueous solutions and inhibit corrosion by forming passive films. Once the corrosion is prevented, the compounds must be easily removed from the copper surface and leave little or no post-clean organic residue.
Keywords: copper corrosion, copper passivator, copper corrosion inhibitor, benzotriazole, triazole, diol, triol, carboxylic acid, dual damascene, post-CMP clean, post-etch via clean
11.1 Introduction and Overview
Copper corrosion and the protection or passivation of copper (Cu) surfaces during cleaning has been a ...