Revisiting the Roles of Chelator, Inhibitor, Oxidant, and Abrasive in High-Rate Copper CMP

This study examined the effects of oxalic acid (chelator), glycine, hydrogen peroxide (oxidant), sodium dioctyl sulfosuccinate (surfactant), and silica nanoparticles (abrasive) on copper removal in chemical mechanical polishing (CMP). A key focus was determining whether glycine acts as a chelator or inhibitor in acidic slurries. Response surface methodology evaluated the five slurry components at three concentration levels each. A quadratic model for copper removal rate was developed from 30 runs and validated with five additional formulations. Material removal rates were studied along with dissolution measurements and Tafel polarization for corrosion behavior. Atomic force microscopy assessed post-polishing planarization. The highest polishing rate was ≈ 2300 nm min −1 , with dissolution contributing less than 5% of total removal in most slurries and not exceeding 13% in any formulation. Glycine inhibited dissolution in acidic slurries at pH 3, differing from previous reports that emphasized its complexing role. Corrosion potentials ranged from 190 to 450 mV (vs SCE), with higher values indicating greater passivation, particularly in slurries with high glycine and low oxalic acid. Dioctyl sulfosuccinate suppressed corrosion current, improving surface quality and uniformity without significantly reducing removal rates. Polished copper surfaces achieved peak-to-valley height of ≈8 nm and RMS roughness as low as 0.8 nm.