Method of purifying alkaline solution and method of etching semiconductor wafers

Abstract

A method of purifying an alkaline solution is capable of extremely efficiently nonionizing metallic impurity ions in an alkaline solution at a low cost. A method of etching semiconductor wafers in turn is capable of etching semiconductor wafers using the purified alkaline solution without deteriorating the quality of the semiconductor wafers. A reducing agent having an oxidation potential lower than a reversible electrode potential of metallic ions existing in the alkaline solution is dissolved in the alkaline solution to thereby nonionize the metallic ions existing in the alkaline solution.

Dependencies are inferred from the claim text.