Patents by Inventor Nobuhiko Koto

Nobuhiko Koto has filed for patents to protect the following inventions. This listing includes patent applications that are pending as well as patents that have already been granted by the United States Patent and Trademark Office (USPTO).

  • Process for purifying nitrogen trifluoride gas
    Patent number: 4980144
    Abstract: This invention relates to a process for obtaining a high purity nitrogen trifluoride gas which is used as a dry etching agent for semiconductors or a cleaning gas for CVD apparatus, etc., particularly to a process for removing oxygen difluoride. This is a process for purifying a nitrogen trifluoride gas by, after removing hydrogen fluoride from a nitrogen trifluoride crude gas, contacting with at least one aqueous solution containing one selected from the group consisting of sodium thiosulfate, hydrogen iodide and sodium sulfide.
    Type: Grant
    Filed: May 24, 1989
    Date of Patent: December 25, 1990
    Assignee: Mitsui Toatsu Chemicals, Inc.
    Inventors: Nobuhiko Koto, Toshihiko Nishitsuji, Naruyuki Iwanaga, Isao Harada