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

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 C-o, 25 C-o, and 45 C-o) 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 SiO2 films during polishing. The changes in all the parameters of slurries stored at 15 degrees C and 45 degrees C for three weeks, except for DO concentration, were reversible and returned to their values at 25 degrees C when the slurries were brought back to 25 degrees C. DO concentration increased by similar to 14% and decreased by similar to 18% in the slurries stored for three weeks at 15 degrees C and 45 degrees C, respectively, compared to that of ceria slurry stored at 25 degrees C. They did not return to the original values even after keeping them at 25 degrees 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 Ce3+ species into less reactive Ce4+-superoxo or a Ce3+-peroxo species, resulting in lower SiO2 removal rates.