Increase in Ce3+ Concentration of Ceria Nanoparticles for High Removal Rate of SiO2 in Chemical Mechanical Planarization

Abstract

Ceria nanoparticles (NPs) are used as abrasives for silicon dioxide (SiO2) chemical mechanical planarization (CMP) due to the strong chemical bonds between the Ce3+ ions of ceria NPs and the hydrated silicate species on the surface of SiO2 films. However, the limited concentration of Ce3+ ions in ceria NPs remains a major challenge for this application. Herein, we report a simple strategy to synthesize ceria NPs with high concentrations of Ce3+ ions for enhanced adsorption reactions with silicate anions. Three types of ceria NPs approximately 70 nm in size were synthesized via the aggregation of different sized primary NPs. As the particle size of the primary NPs decreased from 70 nm to 5 nm, the Ce3+ concentration of the ceria NPs increased from 15.6 to 24.0%. The adsorption isotherm fits the Freundlich model and the constants of adsorption capacity (KF) and adsorption intensity (1/n) indicate that the adsorption affinity for silicate anions increased with increasing Ce3+ concentration. The increase in Ce3+ concentration led to an increase in the chemical adsorption between ceria NPs and silicate anions, resulting in a high removal rate of SiO2 during CMP.