In-depth understanding of the corrosion mechanisms of Co and Cu in chemical mechanical polishing (CMP): Insights from electrochemistry and triboelectrochemistry

Cu and Co serve as interconnect metals in back-end-of-line (BEOL) integrated circuit fabrication. Chemical mechanical polishing (CMP) achieves planarization through chemical oxidation and dissolution by slurry components, which inevitably causes excessive corrosion and surface defects. Consequently, a critical aspect of metal CMP slurry engineering involves suppressing surface defects from both electrochemical and triboelectrochemical effects. Selecting effective corrosion inhibitors is crucial for optimizing both material removal rate and surface quality. In this work, typical azole inhibitor 1, 2, 4-triazaole (TAZ) was systematically evaluated for both the Cu and Co polishing slurries. Corrosion kinetics and thermodynamic parameters were determined by analyzing temperature-dependent corrosion current density variations. Electrochemical results demonstrate that TAZ significantly elevates apparent corrosion activation energies from 13.84 to 20.98 kJ·mol⁻¹ for Co and 13.51–44.78 kJ·mol⁻¹ for Cu, while achieving superior inhibition efficiency for Cu ( η = 80.97 % at 2 mM) compared to Co ( η = 30.68 % at 10 mM). KPFM and DFT calculations confirm substantially increased work function on Cu surfaces even at low TAZ concentrations. Moreover, triboelectrochemical measurements reveal divergent friction-driven mechanisms where mechanical action enhances cathodic processes on Co, shown by positive OCP shifts, but promoting anodic dissolution on Cu through negative OCP shifts. TAZ effectively mitigates tribocorrosion by forming lubricating adsorption layers that reduce coefficients of friction by over 40 % and suppress material loss. These insights provide a fundamental basis for the rational screening and selection of inhibitors optimized for dynamic CMP conditions.