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).
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Patent number: 9957639Abstract: 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: GrantFiled: February 27, 2015Date of Patent: May 1, 2018Assignee: NIPPON STEEL & SUMITOMO METAL CORPORATIONInventors: Takashi Aigo, Wataru Ito, Tatsuo Fujimoto
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Patent number: 9915011Abstract: 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: GrantFiled: December 1, 2009Date of Patent: March 13, 2018Assignee: NIPPON STEEL & SUMITOMO METAL CORPORATIONInventors: Tatsuo Fujimoto, Noboru Ohtani, Masakazu Katsuno, Masashi Nakabayashi, Hirokatsu Yashiro
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Publication number: 20180066380Abstract: 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: ApplicationFiled: February 18, 2016Publication date: March 8, 2018Applicant: NIPPON STEEL & SUMITOMO METAL CORPORATIONInventors: Komomo TANI, Takayuki YANO, Tatsuo FUJIMOTO, Hiroshi TSUGE, Kazuhito KAMEI, Kazuhiko KUSUNOKI, Kazuaki SEKI
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Publication number: 20170365463Abstract: 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: ApplicationFiled: February 16, 2016Publication date: December 21, 2017Applicant: NIPPON STEEL & SUMITOMO METAL CORPORATIONInventors: Takashi AIGO, Wataru ITO, Tatsuo FUJIMOTO
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Publication number: 20170342593Abstract: 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: ApplicationFiled: December 4, 2015Publication date: November 30, 2017Applicant: NIPPON STEEL & SUMITOMO METAL CORPORATIONInventors: Shinya SATO, Tatsuo FUJIMOTO, Masakazu KATSUNO, Hiroshi TSUGE, Masashi NAKABAYASHI
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Patent number: 9777403Abstract: 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: GrantFiled: October 14, 2009Date of Patent: October 3, 2017Assignee: NIPPON STEEL & SUMITOMO METAL CORPORATIONInventors: Masashi Nakabayashi, Tatsuo Fujimoto, Masakazu Katsuno, Hiroshi Tsuge
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Patent number: 9691607Abstract: 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: GrantFiled: April 7, 2011Date of Patent: June 27, 2017Assignee: NIPPON STEEL & SUMITOMO METAL CORPORATIONInventors: Takashi Aigo, Hiroshi Tsuge, Taizo Hoshino, Tatsuo Fujimoto, Masakazu Katsuno, Masashi Nakabayashi, Hirokatsu Yashiro
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Publication number: 20170159208Abstract: 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: ApplicationFiled: July 16, 2015Publication date: June 8, 2017Applicant: NIPPON STEEL & SUMITOMO METAL CORPORATIONInventors: Takashi AIGO, Wataru ITO, Tatsuo FUJIMOTO
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Publication number: 20160251775Abstract: 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: ApplicationFiled: February 27, 2015Publication date: September 1, 2016Applicant: NIPPON STEEL & SUMITOMO METAL CORPORATIONInventors: Takashi AIGO, Wataru ITO, Tatsuo FUJIMOTO
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Patent number: 9234297Abstract: Provided are a method for manufacturing a SiC single crystal having high crystal quality and, in particular, extremely low screw dislocation density and a SiC single crystal ingot obtained by the method. In particular, provided is a silicon carbide single crystal substrate that is a substrate cut from a bulk silicon carbide single crystal grown by the Physical Vapior Transport (PVT) method, in which the screw dislocation density is smaller in the peripheral region than in the center region, so that screw dislocations are partially reduced. The method is a method for manufacturing a SiC single crystal by the PVT method using a seed crystal and the ingot is a SiC single crystal ingot obtained by the method. Particularly, the silicon carbide single crystal substrate is a silicon carbide single crystal substrate in which when, by representing the diameter of the substrate as R, a center circle region having a diameter of 0.Type: GrantFiled: August 29, 2012Date of Patent: January 12, 2016Assignee: NIPPON STEEL & SUMITOMO METAL CORPORATIONInventors: Shinya Sato, Tatsuo Fujimoto, Hiroshi Tsuge, Masakazu Katsuno
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Publication number: 20150361585Abstract: Provided is a method for manufacturing an SiC single-crystal substrate making it possible to obtain an epitaxial SiC wafer provided with a high-quality SiC single-crystal thin film devoid of surface defects, etc. Also provided is said SiC single-crystal substrate. A method for manufacturing an SiC single-crystal substrate for an epitaxial SiC wafer having a high-quality SiC single-crystal thin film devoid of surface defects, etc., wherein the surface of the SiC single-crystal substrate is polished using chemical-mechanical polishing (CMP) at a speed of no more than 100 nm/h to remove the surface in a thickness of 100 nm or greater, and produce no more than 1 approximately circular pit per cm2, the pit having a diameter of 0.5-1.5 ?m and a depth of 50-500 nm.Type: ApplicationFiled: May 26, 2014Publication date: December 17, 2015Applicant: NIPPON STEEL & SUMITOMO METAL CORPORATIONInventors: Takashi AIGO, Wataru ITO, Tatsuo FUJIMOTO
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Publication number: 20150267319Abstract: 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: ApplicationFiled: November 15, 2013Publication date: September 24, 2015Applicant: NIPPON STEEL & SUMITOMO METAL CORPORATIONInventors: Shinya Sato, Tatsuo Fujimoto, Hiroshi Tsuge, Masakazu Katsuno
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Patent number: 9068277Abstract: The invention provides an apparatus for manufacturing good quality single-crystal silicon carbide stably without formation of cracks and the like, which apparatus comprises: at least a crucible for accommodating silicon carbide feedstock powder and seed crystal; heat insulation material installed around the crucible; and a heating device for heating the crucible, wherein the outer profile of the crucible includes at least one region of narrower diameter than a vertically adjacent region, insulation material is also installed in the space left by the diameter difference, and thickness of the insulation material at the narrower diameter region is greater than that of the insulation material at the vertically adjacent region. The apparatus for manufacturing single-crystal silicon carbide enables precise control of the temperature gradient inside the crucible, thereby enabling manufacture of good quality single-crystal silicon carbide.Type: GrantFiled: April 1, 2009Date of Patent: June 30, 2015Assignee: NIPPON STEEL & SUMITOMO METAL CORPORATIONInventors: Masashi Nakabayashi, Tatsuo Fujimoto, Hiroshi Tsuge, Masakazu Katsuno, Noboru Ohtani
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Publication number: 20150075422Abstract: The present invention provides an epitaxial SiC monocrystalline substrate having a high quality epitaxial film suppressed in occurrence of step bunching in epitaxial growth using a substrate with an off angle of 6° or less and a method of production of the same, that is, an epitaxial silicon carbide monocrystalline substrate comprised of a silicon carbide monocrystalline substrate with an off angle of 6° or less on which a silicon carbide monocrystalline thin film is formed, the epitaxial silicon carbide monocrystalline substrate characterized in that the silicon carbide monocrystalline thin film has a surface with a surface roughness (Ra value) of 0.5 nm or less and a method of production of the same.Type: ApplicationFiled: November 19, 2014Publication date: March 19, 2015Inventors: Takashi Aigo, Hiroshi Tsuge, Taizo Hoshino, Tatsuo Fujimoto, Masakasu Katsuno, Masashi Nakabayashi, Hirokatsu Yashiro
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Patent number: 8936680Abstract: The present invention, which provides a crucible for producing single-crystal silicon carbide, and a production apparatus and a production method for single-crystal silicon carbide, which are capable of stably growing a single-crystal silicon carbide ingot good in crystallinity at high yield, is a crucible for producing single-crystal silicon carbide having a crucible vessel for holding silicon carbide raw material and a crucible cover for attaching a seed crystal and is adapted to sublimate a silicon carbide raw material in the crucible vessel to supply silicon carbide sublimation gas onto a seed crystal attached to the crucible cover and grow single-crystal silicon carbide on the seed crystal, which crucible for producing single-crystal silicon carbide is provided in the crucible vessel and the crucible cover with threaded portions to be screwed together and is provided with a sublimation gas discharge groove or grooves capable of regulating flow rate by relative rotation of the threaded portions; and is aType: GrantFiled: February 25, 2010Date of Patent: January 20, 2015Assignee: Nippon Steel & Sumitomo Metal CorporationInventors: Masakazu Katsuno, Tatsuo Fujimoto, Hiroshi Tsuge, Masashi Nakabayashi
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Patent number: 8927396Abstract: An object of the present invention is to provide a production process of an epitaxial silicon carbide single crystal substrate having a high-quality silicon carbide single crystal thin film reduced in the surface defect and the like on a silicon carbide single crystal substrate with a small off-angle. According to the present invention, in the production process of an epitaxial silicon carbide single crystal substrate having a high-quality silicon carbide single crystal thin film reduced in the surface defect and the like on a silicon carbide single crystal substrate with an off-angle of 4° or less, pretreatment etching to a depth of 0.1 to 1 ?m is performed at a temperature of 1,550 to 1,650° C. by flowing a gas containing silicon and chlorine together with a hydrogen gas such that the silicon atom concentration becomes from 0.0001 to 0.01% based on hydrogen atoms in the hydrogen gas, and thereafter, an epitaxial layer is formed.Type: GrantFiled: November 15, 2011Date of Patent: January 6, 2015Assignee: Nippon Steel & Sumitomo Metal CorporationInventors: Takashi Aigo, Hiroshi Tsuge, Masakazu Katsuno, Tatsuo Fujimoto, Hirokatsu Yashiro
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Publication number: 20140363607Abstract: Provided are a method for manufacturing a SiC single crystal having high crystal quality and, in particular, extremely low screw dislocation density and a SiC single crystal ingot obtained by the method. In particular, provided is a silicon carbide single crystal substrate that is a substrate cut from a bulk silicon carbide single crystal grown by the Physical Vapior Transport (PVT) method, in which the screw dislocation density is smaller in the peripheral region than in the center region, so that screw dislocations are partially reduced. The method is a method for manufacturing a SiC single crystal by the PVT method using a seed crystal and the ingot is a SiC single crystal ingot obtained by the method. Particularly, the silicon carbide single crystal substrate is a silicon carbide single crystal substrate in which when, by representing the diameter of the substrate as R, a center circle region having a diameter of 0.Type: ApplicationFiled: August 29, 2012Publication date: December 11, 2014Applicant: NIPPON STEEL & SUMITOMO METAL CORPORATIONInventors: Shinya Sato, Tatsuo Fujimoto, Hiroshi Tsuge, Masakazu Katsuno
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Patent number: 8901570Abstract: Provided is an epitaxial silicon carbide single-crystal substrate in which a silicon carbide epitaxial film having excellent in-plane uniformity of doping density is disposed on a silicon carbide single-crystal substrate having an off angle that is between 1° to 6°. The epitaxial film is grown by repeating a dope layer that is 0.5 ?m or less and a non-dope layer that is 0.1 ?m or less. The dope layer is formed with the ratio of the number of carbon atoms to the number of silicon atoms (C/Si ratio) in a material gas being 1.5 to 2.0, and the non-dope layer is formed with the C/Si ratio being 0.5 or more but less than 1.5. The resulting epitaxial silicon carbide single-crystal substrate comprises a high-quality silicon carbide epitaxial film, which has excellent in-plane uniformity of doping density, on a silicon carbide single-crystal substrate having a small off angle.Type: GrantFiled: May 10, 2011Date of Patent: December 2, 2014Assignee: Nippon Steel & Sumitomo Metal CorporationInventors: Takashi Aigo, Hiroshi Tsuge, Taizo Hoshino, Tatsuo Fujimoto, Masakazu Katsuno, Masashi Nakabayashi, Hirokatsu Yashiro
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Patent number: 8795624Abstract: Provided is a monocrystalline silicon carbide ingot containing a dopant element, wherein a maximum concentration of the dopant element is less than 5×1017 atoms/cm3 and the maximum concentration is 50 times or less than that of a minimum concentration of the dopant element. Also provided is a monocrystalline silicon carbide wafer made by cutting and polishing the monocrystalline silicon carbide ingot, wherein a electric resistivity at room temperature of the wafer is 5×103 ?cm or more. Further provided is a method for manufacturing the monocrystalline silicon carbide including growing the monocrystalline silicon carbide on a seed crystal from a sublimation material by a sublimation method. The sublimation material includes a solid material containing a dopant element, and the specific surface of the solid material containing the dopant element is 0.5 m2/g or less.Type: GrantFiled: October 5, 2005Date of Patent: August 5, 2014Assignee: Nippon Steel & Sumitomo Metal CorporationInventors: Masashi Nakabayashi, Tatsuo Fujimoto, Mitsuru Sawamura, Noboru Ohtani
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Patent number: 8673254Abstract: Provided is a monocrystalline silicon carbide ingot containing a dopant element, wherein a maximum concentration of the dopant element is less than 5×1017 atoms/cm3 and the maximum concentration is 50 times or less than that of a minimum concentration of the dopant element. Also provided is a monocrystalline silicon carbide wafer made by cutting and polishing the monocrystalline silicon carbide ingot, wherein a electric resistivity at room temperature of the wafer is 5×103 ?cm or more. Further provided is a method for manufacturing the monocrystalline silicon carbide including growing the monocrystalline silicon carbide on a seed crystal from a sublimation material by a sublimation method. The sublimation material includes a solid material containing a dopant element, and the specific surface of the solid material containing the dopant element is 0.5 m2/g or less.Type: GrantFiled: March 4, 2011Date of Patent: March 18, 2014Assignee: Nippon Steel & Sumitomo Metal CorporationInventors: Masashi Nakabayashi, Tatsuo Fujimoto, Mitsuru Sawamura, Noboru Ohtani