Effects of nitrilotriacetic acid and corrosion inhibitor on cobalt barrier chemical–mechanical polishing: Experimental and density functional theory analysis

Abstract

Nitrilotriacetic acid (NTA) was used as a complexing agent for Co barrier chemical–mechanical polishing (CMP), and 2,2'-{[(methyl-1H-benzotriazol-1-yl)methyl]imino}bisethanol (TT-LYK) as a corrosion inhibitor. The mechanism of both the complexing agent and inhibitor—individually and combined—on the Co surface was comprehensively studied. Static etch rate (SER) experiments showed that NTA is an effective complexing agent for Co. After adding NTA, Co SER increases from ∼0 to ∼15 Å/min, and a complexing mechanism is proposed. Scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS) were used to analyze the surface state and species composition. The active site of TT-LYK was analyzed by density functional theory and the adsorption mechanism of TT-LYK on the Co (0001) plane. The calculations showed that TT-LYK molecules were vertically adsorbed through atoms N9 and N10 as well as O17–H··Co hydrogen bonds, and parallel adsorbed through benzene and triazole rings. CMP, atomic force microscopy (AFM), potentiodynamics, and electrochemical impedance spectroscopy (EIS) were used to study the mechanism of NTA and TT-LYK under polishing conditions. TT-LYK inhibits chemical corrosion of the concave surface, and NTA promotes removal of the oxide film on the convex surface. In combination, NTA and TT-LYK impart a high-quality Co surface.