(347c) Studies On Chemical Mechanical Planarization of Ta for Semiconductor Processing

The chemical mechanical planarization (CMP) of barrier metal tantalum with and without the additive guanidine hydrochloride (GHCL) is characterized. Silica based slurries at various pH values were used for the CMP experiments. Results show that GHCL enhances the removal rate over a wide range of pH. Potentiodynamic polarization studies of Ta in solutions with and with GHCL were carried out. In situ open circuit potential (OCP) measurements of Ta disc under static and rotating conditions were also performed. Ex situ and in situ electrochemical characterization of Ta in the slurry shows that the dissolution of Ta is not enhanced by the GHCL. Instead, the protective oxide film formed on the tantalum surface was weakened by the GHCL leading to easier mechanical removal and thus enhanced overall removal rate.