Effect of EDTA-based alkaline cleaning solution on TAZ removal in post CMP cleaning of copper interconnection

Abstract

1,2,4-triazole (TAZ) has been proved to be an alternative to Benzotriazole (BTA) as an corrosion inhibitor in chemical mechanical polishing (CMP) of multilayer copper interconnection for integrated circuit. It has also become the main object to be removed in post CMP cleaning. In this paper, a new type of alkaline cleaning solution based on EDTA was proposed to remove TAZ on copper surface. The optimal concentration ratio and pH value of the alkaline cleaning solution were explored using electrochemical measurement, X-ray photoelectron spectroscopy (XPS) and atomic force microscopy (AFM) and scanning electron microscopy (SEM). When the components of the cleaning solution were 25mg/L ethylenediaminetetraacetic acid (EDTA) and 600mg/L dodecylbenzene sulfonic acid (LABSA) (pH = 10.6), the Cu-1,2,4-trazole compounds formed by TAZ contamination on the copper surface can be effectively removed. Density Functional Theory (DFT) was used to confirm that EDTA could break the bond of Cu-1,2,4-triazole through the strong interaction between O16、H2、H36 and copper surface. No corrosion was observed on the cleaned copper surface and surface roughness was lower, which indicated that the cleaning solution was suitable for the removal of TAZ on copper surface.