The patent badge is an abbreviated version of the USPTO patent document. The patent badge does contain a link to the full patent document.
The patent badge is an abbreviated version of the USPTO patent document. The patent badge covers the following: Patent number, Date patent was issued, Date patent was filed, Title of the patent, Applicant, Inventor, Assignee, Attorney firm, Primary examiner, Assistant examiner, CPCs, and Abstract. The patent badge does contain a link to the full patent document (in Adobe Acrobat format, aka pdf). To download or print any patent click here.
Patent No.:
Date of Patent:
Nov. 20, 2001
Filed:
Mar. 02, 1998
Applicant:
Inventors:
Isao Uchiyama, Fukushima-ken, JP;
Hiroyuki Takamatsu, Shirakawa, JP;
Toshio Ajito, Fukushima-ken, JP;
Assignee:
Shin-Etsu Handotai Co., Ltd., Tokyo, JP;
Primary Examiner:
Assistant Examiner:
Int. Cl.
CPC ...
H01L 2/13063 ;
U.S. Cl.
CPC ...
H01L 2/13063 ;
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.