Patents by Inventor Toko Yagi

Toko Yagi 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).

  • Method and apparatus for detecting heavy metals in silicon wafer bulk with high sensitivity
    Patent number: 6140131
    Abstract: The present invention is to provide a method and apparatus for detecting heavy metals within the bulk of a silicon wafer with high sensitivity. An electric field is applied to a surface of the silicon wafer in order to aggregate heavy metals existing within the bulk of the silicon wafer to the surface of the wafer or the vicinity thereof, and the heavy metals aggregated to the surface of the wafer or the vicinity of the surface are analyzed. The application of an electric field is performed through corona-discharge treatment of the surface of the wafer, or through application of voltage to the surface of the wafer via a contact or non-contact electrode. Alternatively, an x-ray beam is radiated onto the surface of the silicon wafer in order to aggregate heavy metals existing within the bulk of the silicon wafer to the surface of the wafer or the vicinity thereof, and the heavy metals aggregated to the surface of the wafer or the vicinity thereof are analyzed.
    Type: Grant
    Filed: September 24, 1998
    Date of Patent: October 31, 2000
    Assignee: Shin-Etsu Handotai Co., Ltd.
    Inventors: Ken Sunakawa, Kiichiro Asako, Toko Yagi, Yoshinori Hayamizu