Patents by Inventor Ryoichi Matsumoto

Ryoichi Matsumoto 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).

  • Patent number: 5106432
    Abstract: A wafer alignment mark consists of patterns, such as a chevron and two stripes, formed in the surface of a semiconductor wafer. Each pattern is defined by a pair of parallel grooves, separation between all pairs of grooves being the same. Each groove provides one sharp edge which can be reliably detected by an automatic alignment system.A wafer fabrication process uses peripheral etching to form grooves in a wafer substrate around the periphery of windows opened for dopant diffusion and alignment mark formation, and forms Si.sub.3 N.sub.4 tapers in the grooves. Although ultimately removed, the grooves create a pattern with nearly vertical sidewalls in the substrate which, when transferred to an epitaxial layer, forms wafer alignment marks with sharp edges.
    Type: Grant
    Filed: May 15, 1990
    Date of Patent: April 21, 1992
    Assignee: Oki Electric Industry Co., Ltd.
    Inventors: Ryoichi Matsumoto, Toshikazu Kuroda, Takao Kato