| CPC C09G 1/02 (2013.01) [H01L 21/30625 (2013.01)] | 13 Claims |
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1. A method of manufacturing a polishing composition containing a colloidal silica dispersion comprising silica particles,
the method comprising preparing the colloidal silica dispersion so as to provide colloidal silica particles having a shape coefficient SF1 of 1.20 to 1.80 and an Rsp of 0.15 to 0.7,
measuring the Rsp using pulse NMR,
subjecting the colloidal silica dispersion to a thermal history at a temperature of 110° C. or higher and lower than 150° C., in particle growth of activated silicate under alkaline conditions in the presence of potassium ions,
obtaining a blank aqueous solution by removing the silica particles from the colloidal silica dispersion to measure Rb, which is an inverse of a relaxation time of said blank solution, wherein
Rsp is calculated based on equation (1):
Rsp=(Rav−Rb)/(Rb) (1)
wherein Rsp is an index that indicates water affinity; Rav is an inverse of a relaxation time of the colloidal silica dispersion; and
the shape coefficient SF1 is calculated based on equation (2):
SF1=(area of a circle whose diameter is a maximum diameter of the particle)/(projected area) (2),
wherein the method of preparing the colloidal silica dispersion comprises:
a step (I) of obtaining activated silicate; a step (II) of heating and regulating the size of the activated silicate; and an optional step (III) of adjusting the concentration of the resulting silica sol, wherein
step (I) is divided into a step (a) of obtaining activated silicate; an optional step (a1) of increasing the purity of the activated silicate; and an optional step (a2) of collecting the activated silicate with an increased purity, in which step (a) is a step of contacting a hydrogen-type strongly acidic cation exchange resin having a pH of 3 to 7 with an aqueous solution of an alkali metal silicate in which an aqueous alkali metal silicate containing 300 to 10,000 ppm of a metal oxide other than silica, based on the silica content, is dissolved at a concentration of 1 to 6% by weight, as the SiO2 content derived from the silicate, to thereby produce an aqueous solution of activated silicate having a SiO2 concentration of 1 to 6% by mass, and collecting the resulting solution,
step (II) includes the following steps (b) and (c):
step (b): adding an aqueous solution of potassium hydroxide to the aqueous solution of the activated silicate collected in the step (a) to produce a stabilized aqueous solution of the activated silicate having a SiO2 concentration of 1 to 6% by mass, and having a pH of 7 to 9; and
step (c): supplying, with sufficient stirring, an aqueous solution of an alkali metal silicate obtained by adding an aqueous solution of potassium hydroxide to the aqueous solution of the activated silicate collected in the step (b) or an aqueous solution of an alkali metal silicate having a pH of 10 to 12.5 and a SiO2 concentration of 0.1 to 8% by weight obtained by concentrating or diluting the aqueous solution obtained above, and an aqueous solution of activated silicate obtained as in the step (b), while maintaining the temperature of the resulting mixture at 110° C. to lower than 150° C., in a period of 1 to 30 hours, until the pH of the mixture reaches 9 to 12, and
step (III) is a step of concentrating the silica sol to a concentration of 10 to 50% by mass, wherein impurities may be removed from the silica sol before or after being concentrated.
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