Patents by Inventor Takashi Aigo
Takashi Aigo 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: 11114295Abstract: 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: GrantFiled: June 15, 2020Date of Patent: September 7, 2021Assignee: SHOWA DENKO K.K.Inventors: Takashi Aigo, Wataru Ito, Tatsuo Fujimoto
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Publication number: 20200312656Abstract: 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: June 15, 2020Publication date: October 1, 2020Applicant: SHOWA DENKO K.K.Inventors: Takashi Aigo, Wataru Ito, Tatsuo Fujimoto
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Patent number: 10727047Abstract: 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: GrantFiled: February 16, 2016Date of Patent: July 28, 2020Assignee: SHOWA DENKO K.K.Inventors: Takashi Aigo, Wataru Ito, Tatsuo Fujimoto
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Patent number: 10626520Abstract: 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: GrantFiled: July 29, 2016Date of Patent: April 21, 2020Assignee: SHOWA DENKO K.K.Inventors: Takashi Aigo, Wataru Ito, Tatsuo Fujimoto
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Patent number: 10450672Abstract: 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: GrantFiled: July 16, 2015Date of Patent: October 22, 2019Assignee: SHOWA DENKO K.K.Inventors: Takashi Aigo, Wataru Ito, Tatsuo Fujimoto
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Patent number: 10435813Abstract: 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: GrantFiled: February 12, 2016Date of Patent: October 8, 2019Assignee: SHOWA DENKO K.K.Inventors: Wataru Ito, Takashi Aigo, Tatsuo Fujimoto
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Publication number: 20180266012Abstract: 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: ApplicationFiled: February 12, 2016Publication date: September 20, 2018Applicant: SHOWA DENKO K.K.Inventors: Wataru ITO, Takashi AIGO, Tatsuo FUJIMOTO
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Publication number: 20180216251Abstract: 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: ApplicationFiled: July 29, 2016Publication date: August 2, 2018Applicant: NIPPON STEEL & SUMITOMO METAL CORPORATIONInventors: Takashi AIGO, Wataru ITO, Tatsuo FUJIMOTO
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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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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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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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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: 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: 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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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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Publication number: 20130320357Abstract: Provided are an epitaxial silicon carbide single crystal substrate having a high-quality silicon carbide single crystal thin film with less stacking faults on a silicon carbide single crystal substrate and a production method therefor. The epitaxial silicon carbide single crystal substrate is produced by growing a silicon carbide epitaxial layer on a silicon carbide single crystal substrate having an off-angle of 4° or less so that the number of stacking faults emitting light at wavelengths ranging from 400 to 600 nm by photoluminescence on the substrate is less than 10/cm2 in total. Additionally, the method for producing the epitaxial silicon carbide single crystal substrate forms the epitaxial layer by using chlorosilane as a silicon-based material gas and hydrocarbon gas as a carbon-based gas, at a growth temperature of 1600° C. to 1700° C., at a C/Si ratio of 0.5 to 1.0, and at a growth rate of 1 to 3 ?m/hr.Type: ApplicationFiled: April 20, 2012Publication date: December 5, 2013Applicant: NIPPON STEEL & SUMITOMO METAL CORPORATIONInventors: Takashi Aigo, Hiroshi Tsuge, Masakazu Katsuno, Tatsuo Fujimoto, Hirokatsu Yashiro, Wataru Ito
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Publication number: 20130217213Abstract: 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: ApplicationFiled: November 15, 2011Publication date: August 22, 2013Applicant: NIPPON STEEL & SUMITOMO METAL CORPORATIONInventors: Takashi Aigo, Hiroshi Tsuge, Masakazu Katsuno, Tatsuo Fujimoto, Hirokatsu Yashiro
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Publication number: 20130049014Abstract: 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: ApplicationFiled: May 10, 2011Publication date: February 28, 2013Applicant: NIPPON STEEL CORPORATIONInventors: Takashi Aigo, Hiroshi Tsuge, Taizo Hoshino, Tatsuo Fujimoto, Masakazu Katsuno, Masashi Nakabayashi, Hirokatsu Yashiro