Polyethyleneimine polymer as an effective corrosion inhibitor for advanced node tungsten post-CMP cleaning

Abstract

The effectiveness of polyethyleneimine (PEI) as a corrosion inhibitor during tungsten (W) post-chemical mechanical planarization (post-CMP) cleaning processes for advanced devices was investigated in this study using bare W wafers. The corrosion inhibition performance of PEI, evaluated under neutral conditions, showed over 70 % efficiency at an optimal concentration of 1 mM and achieved exceptional inhibition exceeding 90 % in a tetramethylammonium hydroxide (TMAH)-containing solution. Electrochemical impedance spectroscopy (EIS), adsorption isotherm studies, contact angle analysis, density functional theory (DFT) analysis, and X-ray photoelectron spectroscopy (XPS) were employed to elucidate the inhibition mechanism of PEI on the W surface. The proposed mechanism highlights the adsorption-initiation by the electrostatic attraction between the positively charged amino group in PEI and the negatively charged W surface. In addition to this, the larger molecular size of the PEI molecule enhances the Van der Waals force of attraction with the W surface. A slight increase in the contact angle with the PEI was observed, which indicates the adsorption of the inhibitor molecule on the W surface. The adsorption isotherm and XPS analyses suggest possible chemical interactions of PEI with the W surface. Further, the interaction between PEI and W was also confirmed with the DFT analysis.