Study on the film forming mechanism, corrosion inhibition effect and synergistic action of two different inhibitors on copper surface chemical mechanical polishing for GLSI

Abstract

As the most basic interconnection metallic material, copper (Cu) has been widely used in giant-large scale integrated circuits (GLSI). Corrosion inhibitors always play a crucial role in the Cu chemical mechanical polishing (CMP) process. The passivation of hydrogen peroxide (H2O2) alone is too weak to adequately protect against chemical corrosion on the surface of Cu film, thus, it is necessary to add corrosion inhibitors to the slurry. As a representative corrosion inhibitor, 1, 2, 4-triazole was compared with a novel corrosion inhibitor known as TT-LYK (ethanol, 2, 2′-[[(methyl-1H-benzotriazol-1-yl) methyl] imino] bis-), and their mixed inhibitor was studied in this paper. Different analytical methods such as the potentiodynamic polarization test, physical appearance phenomenon analysis, contact angle measurement and dynamic polishing experiment were used to compare their inhibition properties, and the fitting of different adsorption isotherms and static erosion tests were used to clarify the adsorption types and passivation processes respectively. The results indicated that both TT-LYK and 1, 2, 4-triazole achieved the goal of inhibiting Cu surface corrosion, but the inhibition effect of TT-LYK was slightly weaker at the same mass fraction. The corrosion protection of the two inhibitors is mainly attributable to the presence of organic inhibitor molecules on the surface of Cu by chemisorption and physisorption simultaneously. The passivation processes of both can be divided into two steps. First, the direct growth of the Cu-inhibitor passivation film occurs, followed by the redeposition of the Cu-inhibitor complex. From the results of electrochemical experiments, it can be concluded that the structure of the thin passivation film growing on the Cu surface varies with the inhibitor, and the composition of the passivation film was investigated by XPS and Raman spectrum analysis. At the same time, the surface roughness after polishing was found to decrease with the increase in inhibition effect of the inhibitors. According to the inhibition characteristics of these two inhibitors, a mixed corrosion inhibitor (TT-LYK and 1, 2, 4-triazole) was proposed in this study. Under the synergistic inhibition action, better inhibition effect and surface quality for Cu CMP were obtained. This outcome may be ascribed to the variation in the structure and density of the passivation film.