High-purity silicasol and preparation method thereof

Abstract

The invention discloses high-purity silica sol and a preparation method thereof; general low-purity silica sol which is prepared by soluble glass or silicon powder is treated by high-purity siloxane (all metal impurity is less than 1ppm) under alkaline condition; the chemical composition on the surface of the silicon dioxide in the silica sol is changed so as to form a core-shell structure of silicon dioxide grain; wherein, the core is normal low-purity silicon dioxide grain and the shell is high-purity silicon dioxide; the content of all metal impurities in the shell is less than 1ppm; compared with the STOBER-method silica sol, the silica sol has low production cost and has excellent stability under the alkaline condition, the neutral and acidic condition. Furthermore, the silica sol has higher stability and higher purity compared with the normal silica sol which is prepared by soluble glass or silicon powder.

Description

technical field [0001] The invention relates to a high-purity silica sol and a preparation method thereof. Background technique [0002] The polishing of semiconductor materials and the performance improvement of some special coatings require high-purity and high-stability silica sol. Ordinary silica sol is mainly prepared from water glass through ion exchange and other processes, and can also be prepared from silica powder through hydrolysis in alkaline aqueous solution. The silica sol prepared by these methods contains more or less metal impurities such as alkali metal ions such as sodium and potassium, and high-valent ions such as iron and aluminum. These metal impurities will have a negative impact on some applications such as semiconductor polishing, so for these applications the less impurity metal ions the better. Most silica sols contain 20%-50% silicon dioxide and the rest is water. Part of the metal impurities in silica sol exists in water in the form of ions, a...

AI Technical Summary

Problems solved by technology

However, the biggest disadvantage of the silica sol in this method is that the price