Patents by Inventor Tatsuo Fujimoto

Tatsuo Fujimoto 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: 20200312656
    Abstract: An epitaxial silicon carbide single crystal wafer having a small depth of shallow pits and having a high quality silicon carbide single crystal thin film and a method for producing the same are provided. The epitaxial silicon carbide single crystal wafer according to the present invention is produced by forming a buffer layer made of a silicon carbide epitaxial film having a thickness of 1 ?m or more and 10 ?m or less by adjusting the ratio of the number of carbon to that of silicon (C/Si ratio) contained in a silicon-based and carbon-based material gas to 0.5 or more and 1.0 or less, and then by forming a drift layer made of a silicon carbide epitaxial film at a growth rate of 15 ?m or more and 100 ?m or less per hour. According to the present invention, the depth of the shallow pits observed on the surface of the drift layer can be set at 30 nm or less.
    Type: Application
    Filed: June 15, 2020
    Publication date: October 1, 2020
    Applicant: SHOWA DENKO K.K.
    Inventors: Takashi Aigo, Wataru Ito, Tatsuo Fujimoto
  • Patent number: 10727047
    Abstract: An epitaxial silicon carbide single crystal wafer and a method for producing the same, wherein the epitaxial silicon carbide single crystal wafer is produced by forming a buffer layer made of a silicon carbide epitaxial film having a thickness of 1 ?m or more and 10 ?m or less by adjusting the ratio of the number of carbon to that of silicon (C/Si ratio) contained in a silicon-based and carbon-based material gas to 0.5 or more and 1.0 or less, and then by forming a drift layer made of a silicon carbide epitaxial film at a growth rate of 15 ?m or more and 100 ?m or less per hour, thereby bringing a depth of shallow pits observed on the surface of the drift layer to 30 nm or less.
    Type: Grant
    Filed: February 16, 2016
    Date of Patent: July 28, 2020
    Assignee: SHOWA DENKO K.K.
    Inventors: Takashi Aigo, Wataru Ito, Tatsuo Fujimoto
  • Patent number: 10711369
    Abstract: The present invention provides a method for producing an SiC single crystal, enabling obtaining an SiC single crystal substrate in which a screw dislocation-reduced region is ensured in a wide range, and an SiC single crystal substrate. The SiC single crystal substrate is produced using a seed crystal having an off angle in the off orientation from a {0001} plane by a production method wherein in advance of a growth main step of performing crystal growth to form a facet {0001} plane in the crystal peripheral part on the crystal end face having grown thereon the bulk silicon carbide single crystal and obtain more than 50% of the thickness of the obtained SiC single crystal, a growth sub-step of growing the crystal at a higher nitrogen concentration than in the growth main step and at a growth atmosphere pressure of 3.9 to 39.9 kPa and a seed crystal temperature of 2,100° C. to less than 2,300° C. is included.
    Type: Grant
    Filed: December 4, 2015
    Date of Patent: July 14, 2020
    Assignee: SHOWA DENKO K.K.
    Inventors: Shinya Sato, Tatsuo Fujimoto, Masakazu Katsuno, Hiroshi Tsuge, Masashi Nakabayashi
  • Patent number: 10626520
    Abstract: A method for producing an epitaxial silicon carbide single crystal wafer comprised of a silicon carbide single crystal substrate having a small off angle on which a high quality silicon carbide single crystal film with little basal plane dislocations is provided, that is, a method for producing an epitaxial silicon carbide single crystal wafer epitaxially growing silicon carbide on a silicon carbide single crystal substrate using a thermal CVD method, comprising supplying an etching gas inside the epitaxial growth reactor to etch the surface of the silicon carbide single crystal substrate so that the arithmetic average roughness Ra value becomes 0.5 nm to 3.0 nm, then starting epitaxial growth to convert 95% or more of the basal plane dislocations at the surface of the silicon carbide single crystal substrate to threading edge dislocations.
    Type: Grant
    Filed: July 29, 2016
    Date of Patent: April 21, 2020
    Assignee: SHOWA DENKO K.K.
    Inventors: Takashi Aigo, Wataru Ito, Tatsuo Fujimoto
  • Publication number: 20190383704
    Abstract: To provide a controller for an internal combustion engine which can determine presence or absence of misfire with good accuracy, even when the rotational variation occurs due to factors other than misfire. A controller for an internal combustion engine calculates, as a reference detection period, the detection period detected within a reference angle interval including a top dead center; calculates a period deviation which is a deviation between the reference detection period and the each detection period; calculates a former period deviation integration value by integrating the period deviation in a former angle interval before the top dead center; calculates a later period deviation integration value by integrating the period deviation in a later angle interval after the top dead center; and determines presence or absence of misfire in the combustion stroke based on the former period deviation integration value and the later period deviation integration value.
    Type: Application
    Filed: April 26, 2019
    Publication date: December 19, 2019
    Applicant: Mitsubishi Electric Corporation
    Inventors: Tatsuo FUJIMOTO, Nobuyoshi TOMOMATSU, Kenichiro YONEZAWA, Kenichi YAMAGATA, Takuma KUSAGAKI
  • Patent number: 10450672
    Abstract: The object is to produce with good reproducibility an epitaxial silicon carbide wafer having a high quality silicon carbide single crystal thin film with little step bunching. To achieve this object, for etching the silicon carbide single crystal substrate in the epitaxial growth furnace, hydrogen carrier gas and silicon-based material gas are used. After the etching treatment is finished as well, the epitaxial growth conditions are changed in the state in the state supplying these gases. When the conditions stabilize, a carbon-based material gas is introduced for epitaxial growth.
    Type: Grant
    Filed: July 16, 2015
    Date of Patent: October 22, 2019
    Assignee: SHOWA DENKO K.K.
    Inventors: Takashi Aigo, Wataru Ito, Tatsuo Fujimoto
  • Patent number: 10435813
    Abstract: The present invention provides a method of epitaxial growth of an SiC thin film by the thermal CVD process wherein it is possible to improve the in-plane uniformity of the doping density and possible to grow an SiC thin film by a uniform thickness. This method is an epitaxial growth method for silicon carbide characterized by comprising adjusting a ratio of the hydrocarbon gas and silicon feedstock gas so as to become, by C/Si ratio, 0.5 to 1.5 in range, making the hydrocarbon gas contact a hydrocarbon decomposition catalyst heated to 1000° C. to 1200° C. so as to make at least part of the hydrocarbon gas break down into carbon and hydrogen, and supplying carbon contained in the hydrocarbon gas and silicon contained in the silicon feedstock gas to the silicon carbide single crystal substrate.
    Type: Grant
    Filed: February 12, 2016
    Date of Patent: October 8, 2019
    Assignee: SHOWA DENKO K.K.
    Inventors: Wataru Ito, Takashi Aigo, Tatsuo Fujimoto
  • Publication number: 20190024257
    Abstract: Provided are: a silicon carbide single crystal substrate which is cut out from a silicon carbide bulk single crystal grown by the Physical Vapor Transport method; and a process for producing the same. The number of screw dislocations in one of the semicircle areas of the substrate is smaller than that in the other thereof, namely, the number of screw dislocations in a given area of the substrate is reduced. The semicircle areas of the substrate correspond respectively to the halves of the substrate.
    Type: Application
    Filed: September 24, 2018
    Publication date: January 24, 2019
    Applicant: SHOWA DENKO K.K.
    Inventors: Shinya SATO, Tatsuo FUJIMOTO, Hiroshi TSUGE, Masakazu KATSUNO
  • Patent number: 10119200
    Abstract: Provided are: a silicon carbide single crystal substrate which is cut out from a silicon carbide bulk single crystal grown by the Physical Vapor Transport method; and a process for producing the same. The number of screw dislocations in one of the semicircle areas of the substrate is smaller than that in the other thereof, namely, the number of screw dislocations in a given area of the substrate is reduced. The semicircle areas of the substrate correspond respectively to the halves of the substrate.
    Type: Grant
    Filed: November 15, 2013
    Date of Patent: November 6, 2018
    Assignee: SHOWA DENKO K.K.
    Inventors: Shinya Sato, Tatsuo Fujimoto, Hiroshi Tsuge, Masakazu Katsuno
  • Publication number: 20180266012
    Abstract: The present invention provides a method of epitaxial growth of an SiC thin film by the thermal CVD process wherein it is possible to improve the in-plane uniformity of the doping density and possible to grow an SiC thin film by a uniform thickness. This method is an epitaxial growth method for silicon carbide characterized by comprising adjusting a ratio of the hydrocarbon gas and silicon feedstock gas so as to become, by C/Si ratio, 0.5 to 1.5 in range, making the hydrocarbon gas contact a hydrocarbon decomposition catalyst heated to 1000° C. to 1200° C. so as to make at least part of the hydrocarbon gas break down into carbon and hydrogen, and supplying carbon contained in the hydrocarbon gas and silicon contained in the silicon feedstock gas to the silicon carbide single crystal substrate.
    Type: Application
    Filed: February 12, 2016
    Publication date: September 20, 2018
    Applicant: SHOWA DENKO K.K.
    Inventors: Wataru ITO, Takashi AIGO, Tatsuo FUJIMOTO
  • Patent number: 10066316
    Abstract: The present invention provides a method of raising the rate of reduction of the dislocation density accompanying growth of an SiC single crystal to counter the increase in the threading screw dislocations formed near the interface of the seed crystal and grown SiC single crystal and thereby produce an SiC single-crystal ingot with a small threading screw dislocation density from the initial stage of growth.
    Type: Grant
    Filed: February 18, 2016
    Date of Patent: September 4, 2018
    Assignee: SHOWA DENKO K.K.
    Inventors: Komomo Tani, Takayuki Yano, Tatsuo Fujimoto, Hiroshi Tsuge, Kazuhito Kamei, Kazuhiko Kusunoki, Kazuaki Seki
  • Publication number: 20180216251
    Abstract: A method for producing an epitaxial silicon carbide single crystal wafer comprised of a silicon carbide single crystal substrate having a small off angle on which a high quality silicon carbide single crystal film with little basal plane dislocations is provided, that is, a method for producing an epitaxial silicon carbide single crystal wafer epitaxially growing silicon carbide on a silicon carbide single crystal substrate using a thermal CVD method, comprising supplying an etching gas inside the epitaxial growth reactor to etch the surface of the silicon carbide single crystal substrate so that the arithmetic average roughness Ra value becomes 0.5 nm to 3.0 nm, then starting epitaxial growth to convert 95% or more of the basal plane dislocations at the surface of the silicon carbide single crystal substrate to threading edge dislocations.
    Type: Application
    Filed: July 29, 2016
    Publication date: August 2, 2018
    Applicant: NIPPON STEEL & SUMITOMO METAL CORPORATION
    Inventors: Takashi AIGO, Wataru ITO, Tatsuo FUJIMOTO
  • Patent number: 9957639
    Abstract: The present invention provides a method for producing an epitaxial silicon carbide wafer comprising epitaxially growing SiC on an SiC substrate to produce an epitaxial SiC wafer during which further reducing stacking faults and comet defects than the conventional technologies to obtain an epitaxial SiC wafer having a high quality epitaxial film. The method for producing the epitaxial silicon carbide wafer is characterized in that a pre-growth atmosphere gas flowing into the growth furnace before the start of epitaxial growth contains hydrogen gas and has a balance of an inert gas and unavoidable impurities, and the hydrogen gas is contained in 0.1 to 10.0 vol % with respect to the inert gas.
    Type: Grant
    Filed: February 27, 2015
    Date of Patent: May 1, 2018
    Assignee: NIPPON STEEL & SUMITOMO METAL CORPORATION
    Inventors: Takashi Aigo, Wataru Ito, Tatsuo Fujimoto
  • Patent number: 9915011
    Abstract: The invention provides a low resistivity silicon carbide single crystal wafer for fabricating semiconductor devices having excellent characteristics. The low resistivity silicon carbide single crystal wafer has a specific volume resistance of 0.001 ?cm to 0.012 ?cm and 90% or greater of the entire wafer surface area is covered by an SiC single crystal surface of a roughness (Ra) of 1.0 nm or less.
    Type: Grant
    Filed: December 1, 2009
    Date of Patent: March 13, 2018
    Assignee: NIPPON STEEL & SUMITOMO METAL CORPORATION
    Inventors: Tatsuo Fujimoto, Noboru Ohtani, Masakazu Katsuno, Masashi Nakabayashi, Hirokatsu Yashiro
  • Publication number: 20180066380
    Abstract: The present invention provides a method of raising the rate of reduction of the dislocation density accompanying growth of an SiC single crystal to counter the increase in the threading screw dislocations formed near the interface of the seed crystal and grown SiC single crystal and thereby produce an SiC single-crystal ingot with a small threading screw dislocation density from the initial stage of growth.
    Type: Application
    Filed: February 18, 2016
    Publication date: March 8, 2018
    Applicant: NIPPON STEEL & SUMITOMO METAL CORPORATION
    Inventors: Komomo TANI, Takayuki YANO, Tatsuo FUJIMOTO, Hiroshi TSUGE, Kazuhito KAMEI, Kazuhiko KUSUNOKI, Kazuaki SEKI
  • Publication number: 20170365463
    Abstract: An epitaxial silicon carbide single crystal wafer having a small depth of shallow pits and having a high quality silicon carbide single crystal thin film and a method for producing the same are provided. The epitaxial silicon carbide single crystal wafer according to the present invention is produced by forming a buffer layer made of a silicon carbide epitaxial film having a thickness of 1 ?m or more and 10 ?m or less by adjusting the ratio of the number of carbon to that of silicon (C/Si ratio) contained in a silicon-based and carbon-based material gas to 0.5 or more and 1.0 or less, and then by forming a drift layer made of a silicon carbide epitaxial film at a growth rate of 15 ?m or more and 100 ?m or less per hour. According to the present invention, the depth of the shallow pits observed on the surface of the drift layer can be set at 30 nm or less.
    Type: Application
    Filed: February 16, 2016
    Publication date: December 21, 2017
    Applicant: NIPPON STEEL & SUMITOMO METAL CORPORATION
    Inventors: Takashi AIGO, Wataru ITO, Tatsuo FUJIMOTO
  • Publication number: 20170342593
    Abstract: The present invention provides a method for producing an SiC single crystal, enabling obtaining an SiC single crystal substrate in which a screw dislocation-reduced region is ensured in a wide range, and an SiC single crystal substrate. The SiC single crystal substrate is produced using a seed crystal having an off angle in the off orientation from a {0001} plane by a production method wherein in advance of a growth main step of performing crystal growth to form a facet {0001} plane in the crystal peripheral part on the crystal end face having grown thereon the bulk silicon carbide single crystal and obtain more than 50% of the thickness of the obtained SiC single crystal, a growth sub-step of growing the crystal at a higher nitrogen concentration than in the growth main step and at a growth atmosphere pressure of 3.9 to 39.9 kPa and a seed crystal temperature of 2,100° C. to less than 2,300° C. is included.
    Type: Application
    Filed: December 4, 2015
    Publication date: November 30, 2017
    Applicant: NIPPON STEEL & SUMITOMO METAL CORPORATION
    Inventors: Shinya SATO, Tatsuo FUJIMOTO, Masakazu KATSUNO, Hiroshi TSUGE, Masashi NAKABAYASHI
  • Patent number: 9777403
    Abstract: A single-crystal silicon carbide and a single-crystal silicon carbide wafer of good-quality are disclosed that are low in dislocations, micropipes and other crystal defects and enable high yield and high performance when applied to a device, wherein the ratio of doping element concentrations on opposite sides in the direction of crystal growth of the interface between the seed crystal and the grown crystal is 5 or less and the doping element concentration of the grown crystal in the vicinity of the seed crystal is 2×1019 cm?3 to 6×1020 cm?3.
    Type: Grant
    Filed: October 14, 2009
    Date of Patent: October 3, 2017
    Assignee: NIPPON STEEL & SUMITOMO METAL CORPORATION
    Inventors: Masashi Nakabayashi, Tatsuo Fujimoto, Masakazu Katsuno, Hiroshi Tsuge
  • Patent number: 9691607
    Abstract: Disclosed is a process for producing an epitaxial single-crystal silicon carbide substrate by epitaxially growing a silicon carbide film on a single-crystal silicon carbide substrate by chemical vapor deposition. The step of crystal growth in the process comprises a main crystal growth step, which mainly occupies the period of epitaxial growth, and a secondary crystal growth step, in which the growth temperature is switched between a set growth temperature (T0) and a set growth temperature (T2) which are respectively lower and higher than a growth temperature (T1) used in the main crystal growth step. The basal plane dislocations of the single-crystal silicon carbide substrate are inhibited from being transferred to the epitaxial film. Thus, a high-quality epitaxial film is formed.
    Type: Grant
    Filed: April 7, 2011
    Date of Patent: June 27, 2017
    Assignee: NIPPON STEEL & SUMITOMO METAL CORPORATION
    Inventors: Takashi Aigo, Hiroshi Tsuge, Taizo Hoshino, Tatsuo Fujimoto, Masakazu Katsuno, Masashi Nakabayashi, Hirokatsu Yashiro
  • Publication number: 20170159208
    Abstract: The object is to produce with good reproducibility an epitaxial silicon carbide wafer having a high quality silicon carbide single crystal thin film with little step bunching. To achieve this object, for etching the silicon carbide single crystal substrate in the epitaxial growth furnace, hydrogen carrier gas and silicon-based material gas are used. After the etching treatment is finished as well, the epitaxial growth conditions are changed in the state in the state supplying these gases. When the conditions stabilize, a carbon-based material gas is introduced for epitaxial growth.
    Type: Application
    Filed: July 16, 2015
    Publication date: June 8, 2017
    Applicant: NIPPON STEEL & SUMITOMO METAL CORPORATION
    Inventors: Takashi AIGO, Wataru ITO, Tatsuo FUJIMOTO