Patents by Inventor Masakatu Kojima

Masakatu Kojima 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: 5738942
    Abstract: Provided is a process for producing a semiconductor silicon wafer by which an intrinsic gettering effect can be improved and at the same time the top side can be made free from faults. A silicon ingot is produced and sliced to obtain silicon wafers. Then, a polycrystal silicon depositing film is formed on one side of a silicon wafer, which is subjected to a heat treatment in an inert gas, a reducing gas or a mixture thereof to discharge oxygen from the vicinity of the other side. Alternatively, after discharging oxygen from the silicon wafer by a heat treatment, a polycrystal silicon depositing film may be formed on one side of the silicon wafer.
    Type: Grant
    Filed: December 29, 1995
    Date of Patent: April 14, 1998
    Assignee: Kabushiki Kaisha Toshiba
    Inventors: Atsuko Kubota, Masakatu Kojima, Norihiko Tsuchiya, Shuichi Samata, Masanori Numano, Yoshihiro Ueno
  • Patent number: 5534294
    Abstract: Provided is a process for producing a semiconductor silicon wafer by which an intrinsic gettering effect can be improved and at the same time the top side can be made free from faults. A silicon ingot is produced and sliced to obtain silicon wafers. Then, a polycrystal silicon depositing film is formed on one side of a silicon wafer, which is subjected to a heat treatment in an inert gas, a reducing gas or a mixture thereof to discharge oxygen from the vicinity of the other side. Alternatively, after discharging oxygen from the silicon wafer by a heat treatment, a polycrystal silicon depositing film may be formed on one side of the silicon wafer.
    Type: Grant
    Filed: July 22, 1994
    Date of Patent: July 9, 1996
    Assignee: Kabushiki Kaisha Toshiba
    Inventors: Atsuko Kubota, Masakatu Kojima, Norihiko Tsuchiya, Shuichi Samata, Masanori Numano, Yoshihiro Ueno
  • Patent number: 5073229
    Abstract: A crystal pulling method includes the steps of disposing a separation wall concentrically with an in a semiconductor crystal pulling crucible to divide the crucible into an inner chamber and an outer chamber, putting first doped material melt into the inner chamber and second material melt into the outer chamber, and pulling crystal from the first material melt in the inner chamber while the second material melt in the outer chamber is being supplied to the inner chamber via a coupling member which connects the inner and outer chamber with each other but suppresses the outflow of impurity from the inner chamber to the outer chamber. Assume that k is the segregation coefficient of doping impurity in the first material melt, r is half the inner diameter of the inner chamber, and R is half the inner diameter of the outer chamber. The second material melt in the outer chamber is undoped melt, and the condition of (r/R)>.sqroot.
    Type: Grant
    Filed: June 29, 1990
    Date of Patent: December 17, 1991
    Assignee: Kabushiki Kaisha Toshiba
    Inventors: Youji Yamashita, Masakatu Kojima
  • Patent number: 5034200
    Abstract: A crystal pulling apparatus of double structure crucible has a crucible body which is divided into inner and outer chambers by a cylindrical partition wall coaxially disposed in the crucible body. A melt supplying path used to supply melt from the outer chamber of the crucible to the inner chamber in which the crystal is pulled is formed of a small through hole formed in the partition wall or the small through hole and a pipe-like passage formed in communication with small through hole. The radius of the inner chamber of the double structure crucible has a specified relation determined by the segregation coefficient of dopant impurity with respect to the radius of the outer chamber. This is, the radius of the inner chamber is set substantially equal to .sqroot.k times the radius of the outer chamber when the segregation coefficient of the dopant impurity is k.
    Type: Grant
    Filed: December 19, 1989
    Date of Patent: July 23, 1991
    Assignee: Kabushiki Kaisha Toshiba
    Inventors: Youji Yamashita, Masakatu Kojima
  • Patent number: 5021225
    Abstract: In a crystal pulling process using an integral type double crucible, a cylindrical separation wall is mounted in and is coaxial with a crucible, for receiving semiconductor material melt to divide the crucible into inner and outer chambers. A coupling tube fixed at the side wall of the separation wall and having a pipe-like passage with a small hole is provided to make a pass between the inner and outer chambers. While material melt in the outer chamber is being supplied to the inner chamber via the coupling tube, crystal is pulled from the melt received in the inner chamber and having an impurity composition different from that of the melt in the outer chamber.
    Type: Grant
    Filed: February 21, 1989
    Date of Patent: June 4, 1991
    Assignee: Kabushiki Kaisha Toshiba
    Inventors: Youji Yamashita, Masakatu Kojima
  • Patent number: 4894206
    Abstract: The present invention discloses a crystal pulling apparatus having a double-crucible structure, wherein an inner crucible is located in an outer crucible. An end of a pipe-like passage is located in a through hole formed in a side wall of an inner crucible located in an outer crucible, and a melt is supplied from the outer crucible to the inner crucible through the pipe-like passage, during crystal pulling. During melting or neckdown, prior to crystal pulling, diffusion of an impurity between the melts in the outer crucible and the inner crucible, and exchange of the melts between the outer crucible and the inner crucible are prevented by the pipe-like passage.
    Type: Grant
    Filed: September 1, 1987
    Date of Patent: January 16, 1990
    Assignee: Kabushiki Kaisha Toshiba
    Inventors: Youji Yamashita, Masakatu Kojima, Yoshiaki Matsushita, Masanobu Ogino
  • Patent number: 4734267
    Abstract: An apparatus for growing compound semiconductor single crystals includes a collector which removes the excess amount of melt B.sub.2 O.sub.3 from the crucible containing melt GaP and melt B.sub.2 O.sub.3.The collector moves up and down independently with reference to the shaft used in pulling the single crystals from the crucible.
    Type: Grant
    Filed: July 6, 1983
    Date of Patent: March 29, 1988
    Assignee: Tokyo Shibaura Denki Kabushiki Kaisha
    Inventor: Masakatu Kojima
  • Patent number: 4497777
    Abstract: An apparatus for producing monocrystalline silicon uniformly containing oxygen at a high concentration. The invention provides an apparatus that employs an improvement in the Czochralski method for producing monocrystalline silicon. The apparatus includes an annular shaped member which floats on the surface of the silicon melt and prevents the escape of oxygen from the silicon melt. The member rotates around a pull of monocrystalline silicon which is pulled through the aperture of the member. The member preferably is made of quartz which supplies oxygen to the silicon melt and thereby increases the concentration of oxygen in the melt.
    Type: Grant
    Filed: April 22, 1982
    Date of Patent: February 5, 1985
    Assignee: Tokyo Shibaura Denki Kabushiki Kaisha
    Inventor: Masakatu Kojima