Synergistic effect of composite complex agent on BTA removal in post CMP cleaning of copper interconnection

Benzotriazole (BTA) is a common corrosion inhibitor for chemical mechanical polishing (CMP) of multilayer copper wiring of integrated circuit. It is also the main object to be removed in post CMP cleaning. In this study, a new type of alkaline cleaning solution based on composite complex agent was proposed to remove BTA effectively. The optimal cleaning concentration ratio and pH value of the new complex complexing agent were explored through electrochemical measurement and contact angle measurement. When the components of cleaning solution were 250 ppm diethylenetriaminepentaacetic acid (DTPA), 1000 ppm FA/OII chelating agent and 100 ppm polyethyleneimine (PEI) (pH = 10.5), the contact angle of copper surface contaminated by BTA can be reduced from 58.1° contaminated by BTA to 25.1°. Density Functional Theory (DFT) proved that DTPA could reduce the adsorption energy of BTA on copper surface. The result of atomic force microscopy (AFM) and scanning electron microscopy (SEM) on copper surface showed that composite complexing agent does not cause corrosion and a lower surface roughness was obtained after cleaning. X-ray photoelectron spectroscopy (XPS) results verified that the cleaning solution could complex copper ions, break the Cu-N bond and promote the decomposition of the Cu-BTA adsorbed chemically on Cu2O, so as to remove BTA effectively. •Adsorption energy of BTA and DTPA on copper surface was calculated by periodic DFT computations.•FA/OII can be used as pH regulator and complexing agent for BTA removal.•The pH value of the cleaning solution is stable at 10.5 for optimal removal of BTA.•Effect and mechanism of composite complex agent were studied by electrochemical, contact angle, AFM, SEM and XPS.•Composite complex agent can complex copper ions, form copper amine complex and cleave Cu-N bond between Cu-BTA.