Patents by Inventor Tomohiko Ohta

Tomohiko Ohta 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).

  • Publication number: 20020157602
    Abstract: The present invention provides a catch pan for melt leakage provided under a crucible at a bottom portion of a chamber in a single crystal pulling apparatus based on the CZ method, wherein the catch pan for melt leakage comprises at least a bottom portion and a barrel portion, and the bottom portion and the barrel portion are connected by screw-fitting or by using a tap bolt. There is provided a catch pan for melt leakage provided in a single crystal pulling apparatus, which can, even if a melt flows out of the crucible by a certain possible cause in a CZ method single crystal pulling apparatus, prevent the melt flowed out from reaching lower mechanisms including metal parts, piping and so forth, and thereby prevent bad influences on operators and peripheral equipments.
    Type: Application
    Filed: October 31, 2001
    Publication date: October 31, 2002
    Applicant: SHIN-ETSU HANDOTAI CO.
    Inventors: Koji Mizuishi, TOMOHIKO OHTA
  • Publication number: 20020157598
    Abstract: The present invention provides a silicon wafer sliced from a silicon single crystal ingot grown by the Czochralski method under such conditions that V-rich region should become dominant, wherein count number of particles having a size of 0.1 &mgr;m or more is 1 count/cm2 or less when particles are counted by using a particle counter and a method for producing a silicon single crystal. Thus, there is provided a production technique that can improve productivity and reduce cost for high quality silicon wafers of excellent device characteristics by further reducing density and size of defects such as COP.
    Type: Application
    Filed: November 23, 2001
    Publication date: October 31, 2002
    Inventors: Ryoji Hoshi, Izumi Fusegawa, Tomohiko Ohta, Shigemaru Maeda
  • Patent number: 6423285
    Abstract: In a method for producing a silicon single crystal by growing a single crystal ingot while a magnetic field perpendicular to a crystal growth axis is applied to a silicon melt contained in a quartz crucible during pulling of the single crystal from the melt contained in the quartz crucible, the crystal growth is performed so that one of a low temperature region and a high temperature region generated at a surface of the silicon melt contained in the crucible should always cover a solid-liquid interface of the crystal growth, or a ratio of vertical magnetic field component to horizontal magnetic field component for magnetic field strength at the crystal center of the surface of the silicon melt contained in the quartz crucible is controlled to be 0.3 or more and 0.5 or less.
    Type: Grant
    Filed: November 7, 2000
    Date of Patent: July 23, 2002
    Assignee: Shin-Etsu Handotai Co., Ltd.
    Inventors: Kirio Itoi, Eiichi Iino, Tohru Ishizuka, Tomohiko Ohta, Izumi Fusegawa
  • Publication number: 20010000093
    Abstract: There is disclosed a method for producing a silicon single crystal in accordance with the Czochralski method wherein a crystal is pulled with controlling a temperature in a furnace so that &Dgr;G may be 0 or a negative value, where &Dgr;G is a difference between the temperature gradient Gc (° C./mm) at the center of a crystal and the temperature gradient Ge (° C./mm) at the circumferential portion of the crystal, namely &Dgr;G=(Ge−Gc), wherein G is a temperature gradient in the vicinity of a solid-liquid interface of a crystal from the melting point of silicon to 1400° C.
    Type: Application
    Filed: November 30, 2000
    Publication date: April 5, 2001
    Applicant: Shin-Etsu Handotai Co., Ltd.,
    Inventors: Masahiro Sakurada, Hideki Yamanaka, Tomohiko Ohta
  • Patent number: 6190452
    Abstract: There is disclosed a method for producing a silicon single crystal in accordance with the Czochralski method wherein a crystal is pulled with controlling a temperature in a furnace so that &Dgr;G may be 0 or a negative value, where &Dgr;G is a difference between the temperature gradient Gc (° C./mm) at the center of a crystal and the temperature gradient Ge (° C./mm) at the circumferential portion of the crystal, namely &Dgr;G=(Ge−Gc), wherein G is a temperature gradient in the vicinity of a solid-liquid interface of a crystal from the melting point of silicon to 1400° C.
    Type: Grant
    Filed: June 8, 1999
    Date of Patent: February 20, 2001
    Assignee: Shin-Etsu Handotai Co., Ltd.
    Inventors: Masahiro Sakurada, Hideki Yamanaka, Tomohiko Ohta
  • Patent number: 6156119
    Abstract: In a method for producing a silicon single crystal of high quality, the silicon single crystal is grown based on a magnetic field applied Czochralski method. The single crystal is grown at a high growth rate satisfying the equation Vave.gtoreq.120/r, where Vave denotes an average crystal growth rate, and r denotes a radius of the single crystal, and a rotation number R of the single crystal in growing satisfies the equation R.ltoreq.1250/r. Oxygen concentration in-plane distribution is 10% or less, and a deformation ratio of a constant diameter portion in the silicon single crystal in a direction perpendicular to a crystal growth axis direction is 5% or less. The silicon single crystal has a high uniformity of oxygen concentration in-plane distribution without deformation of crystal, even if the crystal is grown at a growth rate exceeding the upper limits found in conventional techniques.
    Type: Grant
    Filed: March 17, 1999
    Date of Patent: December 5, 2000
    Assignee: Shin-etsu Handotai Co., Ltd.
    Inventors: Ryoji Hoshi, Kouichi Inokoshi, Tomohiko Ohta
  • Patent number: 6153009
    Abstract: In a Czochralski method for producing a silicon single crystal by growing the crystal, the pulling rate of the single crystal is gradually increased during formation of a tail part after formation of a predetermined or constant diameter part of the single crystal. The length t of the tail part is defined to be a or more, where a represents a distance from the tip end of the tail part to a position of an extraordinary oxygen precipitation area when the tail part is formed after the predetermined or constant diameter part is grown. Productivity and yield of the silicon single crystal are improved by preventing rapid change in temperature while the single crystal is separated from the melt in the tailing process, to suppress generation of an area where the amount of precipitated oxygen is extraordinarily large and an OSF ring due to rapid increase in temperature when the tail part is formed, in the predetermined or constant diameter part near the tail part.
    Type: Grant
    Filed: March 16, 1999
    Date of Patent: November 28, 2000
    Assignee: Shin-Etsu Handotai Co., Ltd.
    Inventors: Toshiharu Uesugi, Toshio Hisaichi, Izumi Fusegawa, Tomohiko Ohta, Tetsuya Igarashi, Tetsuhiro Oda
  • Patent number: 6117231
    Abstract: A silicon wafer sliced from a silicon single crystal having a low oxygen concentration is used as an epitaxial substrate to provide semiconductor silicon single crystal wafers exhibiting good electrical characteristics at a low cost. A semiconductor silicon single crystal having a resistivity in a range of 0.005 to 0.02 .OMEGA..multidot.cm and an oxygen concentration of 12.times.10.sup.17 atoms/cm.sup.3 (ASTM'79) or less is manufactured by a Czochralski (CZ) method. The resulting silicon single crystal is shaped into a silicon single crystal substrate on which a silicon single crystal is epitaxially grown.
    Type: Grant
    Filed: April 13, 1999
    Date of Patent: September 12, 2000
    Assignee: Shin-Etsu Handotai Co., Ltd.
    Inventors: Izumi Fusegawa, Toshirou Hayashi, Ryoji Hoshi, Tomohiko Ohta
  • Patent number: 6071337
    Abstract: A method and apparatus for producing crystals by the Czochralski method whereby the thermal history during crystal growth according to the CZ method can be controlled with ease and accuracy. The apparatus comprises a crucible for receiving a raw material, a heater for heating and melting the raw material, and a heat insulating cylinder disposed so as to surround the crucible and the heater, wherein a portion of the heat insulating cylinder that is located above an upper end of the heater is so configured that its inner diameter is larger than the outer diameter of the heater at its lower end, and that its inner diameter at its upper end is equal to or less than the inner diameter of the heater while its outer diameter is equal to or greater than the outer diameter of the heater. This apparatus is used to produce crystals and to control the temperature distribution inside the crystal producing apparatus or the thermal history of crystals.
    Type: Grant
    Filed: August 14, 1998
    Date of Patent: June 6, 2000
    Assignee: Shin-Etsu Handotai Co., Ltd
    Inventors: Masahiro Sakurada, Yuichi Miyahara, Tomohiko Ohta
  • Patent number: 5972106
    Abstract: A device and method for producing single crystals by the Czohralski method can control the temperature distribution and thermal history of single crystals to improve the production efficiency and quality of single crystals. The device includes a cylinder coaxially surrounding a single crystal pulling rod, having an upper end airtightly connected to the ceiling of a pulling chamber and a lower end close to the surface of a melt in a crucible. A heat insulating element is attached to the lower end of the cylinder, and is surrounded by a surface of the crystal, the inside wall of the crucible and the surface of the melt. The heat insulating element is sized to occupy 30-95% by volume of the space above the melt, and the space has a height corresponding to the radius of the crystal.
    Type: Grant
    Filed: February 10, 1997
    Date of Patent: October 26, 1999
    Assignee: Shin-Etsu Handotai Co., LTD.
    Inventors: Tomohiko Ohta, Susumu Sonokawa, Satoshi Soeta, Yoshihiro Kodama
  • Patent number: 5948163
    Abstract: A crystal manufacturing apparatus includes a crucible for containing a material, a heater for heating and melting the material, and a heat insulating cylinder arranged so as to surround the crucible and the heater. The crystal manufacturing apparatus is operated in accordance with the Czochralski method. The heat insulating cylinder is arranged to be vertically movable. When two or more crystals are pulled within a single batch, the vertical position of the heat insulating cylinder is changed between the manufacture of the crystals, so that the thermal histories of the crystals are made different from one another. Moreover, when a crystal is pulled in accordance with the Czochralski method, the heat insulating cylinder is moved vertically while the crystal is being pulled.
    Type: Grant
    Filed: February 10, 1997
    Date of Patent: September 7, 1999
    Assignee: Shin-Etsu Handotai Co., Ltd.
    Inventors: Masahiro Sakurada, Tomohiko Ohta
  • Patent number: 5882398
    Abstract: A single crystal of silicon is manufactured in accordance with the Czochralski method. A magnetic field is applied to a quartz crucible filled with silicon melt. Subsequently, a single crystal of silicon is pulled in a state in which no magnetic field is applied to the crucible, so as to obtain a single crystal of silicon. Therefore, the inner surface of a quartz crucible becomes very unlikely to deteriorate, and when the inner surface deteriorates, the deteriorated inner surface is restored. Accordingly, it is possible to manufacture a single crystal of silicon having a large diameter without generating a dislocation in the crystal. Moreover, even when a single crystal of silicon having a large diameter is manufactured, a larger number of single crystals of silicon can be manufactured from a single quartz crucible, and the pulling apparatus can be operated over a longer period of time using a single quartz crucible, thereby making it possible to manufacture a longer single crystal.
    Type: Grant
    Filed: January 23, 1997
    Date of Patent: March 16, 1999
    Assignee: Shin-Etsu Handotai Co., Ltd.
    Inventors: Susumu Sonokawa, Toshiro Hayashi, Atsushi Iwasaki, Tomohiko Ohta
  • Patent number: 5851283
    Abstract: A single crystal production apparatus based on an HMCZ method for production a large-diametered single crystal having a uniform microscopic oxygen concentration distribution in its crystal growth direction to thereby provide a wafer having a high in-plane uniformity of oxygen concentration distribution. In the single crystal production apparatus based on the HMCZ method, when B denotes a vertical position of the bottom surface of a melt within a crucible and L denotes the depth of the melt at the time of starting crystal pulling operation, a vertical position of the coil central axis Cc of superconducting electromagnets 12 and 15 is controlled to be a proper value included in a range from a position below the position B by {(1/3).times.L} to a position above the position B by {(1/3).times.L} to pull the single crystal.
    Type: Grant
    Filed: December 20, 1996
    Date of Patent: December 22, 1998
    Assignee: Shin-Etsu Handotai Co. Ltd.
    Inventors: Ryouji Hoshi, Masashi Sonokawa, Izumi Fusegawa, Tomohiko Ohta
  • Patent number: 5766346
    Abstract: An apparatus for producing a silicon single crystal by the MCZ method is disclosed in which electrodes and magnets are arranged so as to make such a condition that a line of magnetic force passing through the central axis of the crucible and a horizontal electric current which results from the supply of a direct current to the heater forms a counterclockwise angle of more than 0.degree. and less than 180.degree. on the basis of the condition where the direction of the line of magnetic force coincides with the direction of the horizontal electric current.
    Type: Grant
    Filed: December 5, 1996
    Date of Patent: June 16, 1998
    Assignee: Shin-Etsu Handotai Co., Ltd.
    Inventors: Toshirou Hayashi, Ryouji Hoshi, Izumi Fusegawa, Tomohiko Ohta
  • Patent number: 5725661
    Abstract: An equipment for producing silicon single crystals based on an MCZ method, which enables an operator to be protected from dangerous exposure to magnetic field without involving increase in the size of the silicon single crystal production equipment. In the silicon single crystal production equipment based on the MCZ method, a growth furnace control apparatus for control of a pulling apparatus is located away from the pulling apparatus by a predetermined distance so that the intensity of magnetic field immediately close to the growth furnace control apparatus can become 300 gausses or less. A monitoring camera for observing the growing condition of the silicon single crystal is mounted to a window 5a of a growth furnace to be operatively connected to a monitor of the growth furnace control apparatus and to cause the growth furnace control apparatus to control the pulling apparatus on a remote control basis.
    Type: Grant
    Filed: July 1, 1996
    Date of Patent: March 10, 1998
    Assignee: Shin-Etsu Handotai Co., Ltd.
    Inventors: Izumi Fusegawa, Toshiro Hayashi, Tomohiko Ohta, Masayuki Arai
  • Patent number: 5704973
    Abstract: Proposed is an improvement in the method and single crystal growing chamber for the preparation of a single crystal rod of silicon by the Czochralski method, according to which the distance between the surface of the melt of silicon contained in a crucible and the lower surface of the top wall of the crystal growing chamber is equal to or larger than the diameter of the crucible and the heat-insulating cylinder surrounding the crucible containing the melt of silicon and the heater has such a height as to reach the lower surface of the top wall of the chamber so as to keep the single crystal rod under growing is kept at a temperature not lower than 700.degree. C. until reaching the lower surface of the top wall of the chamber thereby decreasing the density of the crystal defects of BMD type in the seed end of the single crystal rod as grown so that the uniformity in the distribution of BMD density is increased throughout the single crystal rod.
    Type: Grant
    Filed: June 18, 1996
    Date of Patent: January 6, 1998
    Assignee: Shin-Etsu Handotai Co., Ltd.
    Inventors: Masahiro Sakurada, Wataru Sato, Tomohiko Ohta