Storage Temperature Effects on the Slurry Health Parameters and SiO₂ Removal Rates during Chemical Mechanical Polishing

Abstract

Temperature is one of the parameters that needs to be continuously monitored and controlled during handling, storage, and transportation to achieve repeatable and consistent CMP performances. Here, we investigated the effect of three different storage temperatures (15 o C, 25 o C, and 45 o C) on several slurry health parameters (particle size, zeta potential, pH, total dissolved solids, conductivity, and dissolved oxygen (DO) concentration) of a ceria-based slurry and also on removal rates of SiO 2 films during polishing. The changes in all the parameters of slurries stored at 15 °C and 45 °C for three weeks, except for DO concentration, were reversible and returned to their values at 25 °C when the slurries were brought back to 25 °C. DO concentration increased by ∼14% and decreased by ∼18% in the slurries stored for three weeks at 15 °C and 45 °C, respectively, compared to that of ceria slurry stored at 25 °C. They did not return to the original values even after keeping them at 25 °C for 6 h. The increase in storage temperature causes an increase in the adsorption of dissolved oxygen onto the ceria surface, which can transform Ce 3+ species into less reactive Ce 4+ -superoxo or a Ce 3+ -peroxo species, resulting in lower SiO 2 removal rates.