In-situ electrochemical probing of passivation and repassivation at copper–azole interfaces during chemical mechanical planarization

Corrosion inhibitors in Cu chemical mechanical planarization (CMP) must suppress dissolution at rest and rapidly restore protection after abrasive disruption. We compared the monocyclic azoles 1,2,4-triazole (TAZ) and 3-amino-1,2,4-triazole (ATA) with the fused-ring azoles benzotriazole (BTA) and 5-methyl-1H-benzotriazole (MBTA) in an acidic H 2 O 2 -based slurry. TAZ and ATA reduced the material removal rate from 579.6 to 342.0 and 315.5 nm min −1 , whereas BTA and MBTA lowered it to 14.2 and 20.2 nm min −1 . BTA and MBTA also reduced the static etch rate from 92.9 to 7.3 and 6.4 nm min −1 . Polarization measurements showed that MBTA decreased the apparent corrosion current density from 136 to 0.18 µA cm −2 . Impedance and X-ray photoelectron spectroscopy indicated greater interfacial resistance and lower Cu(II) shake-up satellite contributions for the fused-ring inhibitors. Distribution-of-relaxation-times analysis showed long-time features for TAZ and ATA, interpreted cautiously near the measurement boundary. During in situ electrochemical polishing at each slurry’s pre-polishing open-circuit potential, BTA and MBTA maintained lower average currents and repeatedly recovered toward low-current states after transient excursions. Density functional theory predicted stronger BTA adsorption than ATA on metallic and oxidized Cu surfaces. Under the tested conditions, BTA and MBTA provide stronger static inhibition and lower net current during polishing, consistent with interfacial re-coverage but without resolving repassivation kinetics.