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:
Mar. 17, 1992
Filed:
Apr. 30, 1991
Tsutomu Amai, Tokyo, JP;
Masanobu Ogino, Yokosuka, JP;
Kabushiki Kaisha Toshiba, Kawasaki, JP;
Abstract
The ratio between variations in the oxygen concentration before and after a silicon wafer is subjected to two types of heat treatments in which the temperatures and processing times are different is defined. The silicon wafer is subjected to a first heat treatment, and the interstitial oxygen concentrations before and after the first heat treatment are respectively set to [Oi].sub.1ini and [Oi].sub.1af. The silicon wafer is successively subjected to second and third heat treatments, and the interstitial oxygen concentrations before and after the second and third heat treatments are respectively set to [Oi].sub.2ini and [Oi].sub.2af. At this time, the interstitial oxygen concentrations [Oi].sub.1ini, [Oi].sub.1af, [Oi].sub.2ini and [Oi].sub.2af are so set as to satisfy the condition that ([Oi].sub.2ini -[Oi].sub.2af)/[Oi].sub.1ini -[Oi].sub.1af).gtoreq.20.