MANUFACTURING METHOD OF HIGH PURITY CAUSTIC SODA AQUEOUS SOLUTION AND ACTIVATION METHOD OF ACTIVE CARBON THEREFOR

摘要

PROBLEM TO BE SOLVED: To provide a method of commercially manufacturing a high purity caustic soda aqueous solution which is reduced in iron and nickel content to the level capable of using as an etching agent of silicon wafer at a low cost.;SOLUTION: In this method of manufacturing a high purity caustic soda aqueous solution for wafer etching, a caustic soda aqueous solution is contacted with an active carbon activated by immersion treatment in nitric acid, and its iron content is reduced to not higher than 200 ppb, and its nickel content to not higher than 20 ppb.;COPYRIGHT: (C)2005,JPO&NCIPI