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, 1990
Filed:
Apr. 13, 1989
Shoji Nakanishi, Tokyo, JP;
Seiko Instruments Inc., , JP;
Abstract
A method of concurrently forming thick and thin field silicon oxide films for use as element separation on the silicon substrate. An under-layer silicon oxide film is formed over the silicon substrate. A silicon nitride film is chemically-vapor-deposited over the under-layer silicon oxide film. The silicon nitride film is selectively etched to expose the under-layer silicon oxide film to thereby form openings. The silicon substrate is annealed within a heated atmosphere of ammonia gas to convert a surface portion of the exposed under-layer silicon oxide film into a thermally nitrified silicon oxide film within the openings. The thermally nitrified silicon oxide film is selectively removed from some of the openings and maintained in the other openings. The silicon substrate is thermally oxidized through the openings to concurrently form relatively thick field oxide film within said some of the openings and relatively thin field oxide film within the other openings.