Fumed silica to colloidal silica conversion process

摘要

A method of manufacturing a colloidal silica dispersion, by dissolving a fumed silica in an aqueous solvent having an alkali metal hydroxide to produce an alkaline silicate solution; removing the alkali metal via ion exchange to produce a silicic acid solution; adjusting the temperature, concentration and pH of the silicic acid solution to values sufficient to initiate nucleation and particle growth at elevated temperatures; and cooling the silicic acid solution at a rate sufficient to produce the colloidal silica dispersion. The colloidal silica particles in the colloidal silica dispersion have a mean particle size about 2 nm to about 100 nm. Also provided is a method of chemical mechanical polishing a surface of a substrate by contacting the substrate and a composition having a plurality of colloidal silica particles according to the present invention and a medium for suspending the particles. The contacting is carried out at a temperature and for a period of time sufficient to planarize the substrate.