| 摘要 |
<p>PROBLEM TO BE SOLVED: To obtain both a high-purity colloidal silica usable for polishing processing of an electronic material such as a silicon wafer, a compound semiconductor wafer, a semiconductor device wafer, a magnetic disk substrate or a rock crystal substrate, containing a trace amount of metal impurities and producible at a low cost, and to provide a method for producing the colloidal silica. SOLUTION: The colloidal silica has <=50 ppm alkali metal content bases on silica and <=100 ppb or <=1,000 ppb each content of Cu or Zn based on the silica. The colloidal silica is obtained by bringing an aqueous solution of an alkali silicate into contact with a cation exchange resin, preparing an aqueous solution of active silicic acid, then bringing the resultant aqueous solution of the active silicic acid into contact with a chelating resin, removing the metal impurities, as necessary, further adding a chelating agent or an oxidizing agent, or the like subsequently using an organic alkali, growing colloidal particles and concentrating the silica by ultrafiltration.</p> |
