Patents by Inventor Takafumi Yao

Takafumi Yao 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: 8878345
    Abstract: A structural body includes a sapphire underlying substrate; and a semiconductor layer of a group III nitride semiconductor disposed on the underlying substrate. An upper surface of the underlying substrate is a crystal surface tilted at an angle of 0.5° or larger and 4° or smaller with respect to a normal line of an a-plane which is orthogonal to an m-plane and belongs to a {11-20} plane group, from the m-plane which belongs to a {1-100} plane group.
    Type: Grant
    Filed: February 8, 2011
    Date of Patent: November 4, 2014
    Assignee: AETech Corporation
    Inventors: Takafumi Yao, Hyun-Jae Lee, Katsushi Fujii
  • Publication number: 20130062739
    Abstract: A structural body includes a sapphire underlying substrate; and a semiconductor layer of a group III nitride semiconductor disposed on the underlying substrate. An upper surface of the underlying substrate is a crystal surface tilted at an angle of 0.5° or larger and 4° or smaller with respect to a normal line of an a-plane which is orthogonal to an m-plane and belongs to a {11-20} plane group, from the m-plane which belongs to a {1-100} plane group.
    Type: Application
    Filed: February 8, 2011
    Publication date: March 14, 2013
    Applicant: Takafumi YAO
    Inventors: Takafumi Yao, Hyun-Jae Lee, Katsushi Fujii
  • Patent number: 8216869
    Abstract: A manufacturing method of a group III nitride semiconductor includes the steps of: depositing a metal layer on an AlN template substrate or an AlN single crystal substrate formed by depositing an AlN single crystal layer with a thickness of not less than 0.1 ?m nor more than 10 ?m on a substrate made of either one of sapphire, SiC, and Si; forming a metal nitride layer having a plurality of substantially triangular-pyramid-shaped or triangular-trapezoid-shaped microcrystals by performing a heating nitridation process on the metal layer under a mixed gas atmosphere of ammonia; and depositing a group III nitride semiconductor layer on the metal nitride layer.
    Type: Grant
    Filed: August 27, 2008
    Date of Patent: July 10, 2012
    Assignee: Dowa Electronics Material Co., Ltd.
    Inventors: Takafumi Yao, Meoung-Whan Cho, Ryuichi Toba
  • Patent number: 8124504
    Abstract: A GaN-based thin film (thick film) is grown using a metal buffer layer grown on a substrate. (a) A metal buffer layer (210) made of, for example, Cr or Cu is vapor-deposited on a sapphire substrate (120). (b) A substrate obtained by vapor-depositing the metal buffer layer (210) on the sapphire substrate (120) is nitrided in an ammonia gas ambient, thereby forming a metal nitride layer (212). (c) A GaN buffer layer (222) is grown on the nitrided metal buffer layers (210, 212). (d) Finally, a GaN single-crystal layer (220) is grown. This GaN single-crystal layer (220) can be grown to have various thicknesses depending on the objects. A freestanding substrate can be fabricated by selective chemical etching of the substrate fabricated by the above steps. It is also possible to use the substrate fabricated by the above steps as a GaN template substrate for fabricating a GaN-based light emitting diode or laser diode.
    Type: Grant
    Filed: January 21, 2010
    Date of Patent: February 28, 2012
    Assignees: Tohoku Techno Arch Co., Ltd., Furukawa Co., Ltd., Mitsubishi Chemical Corporation, Wavesquare Inc., Dowa Holdings Co., Ltd., Epivalley Co. Ltd.
    Inventors: Takafumi Yao, Meoung-Whan Cho
  • Patent number: 8119499
    Abstract: A semiconductor substrate fabrication method according to the first aspect of this invention is characterized by including a preparation step of preparing an underlying substrate, a stacking step of stacking, on the underlying substrate, at least two multilayered films each including a peeling layer and a semiconductor layer, and a separation step of separating the semiconductor layer.
    Type: Grant
    Filed: August 24, 2006
    Date of Patent: February 21, 2012
    Assignees: Tohoku Techno Arch Co., Ltd., Furukawa Co., Ltd., Mitsubishi Chemical Corporation, Dowa Holdings Co., Ltd., Epivalley Co., Ltd., Wavesquare Inc.
    Inventors: Takafumi Yao, Meoung-Whan Cho
  • Patent number: 7906409
    Abstract: A device manufacturing method includes a buffer layer forming step of forming a buffer layer on an underlying substrate, a mask pattern forming step of forming, on the buffer layer, a mask pattern which partially covers the buffer layer, a growth step of growing a group III nitride crystal from regions exposed by the mask pattern on the surface of the buffer layer, thereby forming a structure in which a plurality of crystal members are arranged with gaps therebetween so as to partially cover the buffer layer and the mask pattern, a channel forming step of forming a channel, to supply a second etchant for the buffer layer to the buffer layer, by selectively etching the mask pattern using a first etchant for the mask pattern, and a separation step of separating the plurality of crystal members from the underlying substrate and separating the plurality of crystal members from each other by supplying the second etchant to the buffer layer through the gaps and the channel and selectively etching the buffer layer.
    Type: Grant
    Filed: March 17, 2009
    Date of Patent: March 15, 2011
    Assignee: Canon Kabushiki Kaisha
    Inventors: Takafumi Yao, Meoung-Whan Cho
  • Patent number: 7829435
    Abstract: A GaN-based thin film (thick film) is grown using a metal buffer layer grown on a substrate. (a) A metal buffer layer (210) made of, for example, Cr or Cu is vapor-deposited on a sapphire substrate (120). (b) A substrate obtained by vapor-depositing the metal buffer layer (210) on the sapphire substrate (120) is nitrided in an ammonia gas ambient, thereby forming a metal nitride layer (212). (c) A GaN buffer layer (222) is grown on the nitrided metal buffer layers (210, 212). (d) Finally, a GaN single-crystal layer (220) is grown. This GaN single-crystal layer (220) can be grown to have various thicknesses depending on the objects. A freestanding substrate can be fabricated by selective chemical etching of the substrate fabricated by the above steps. It is also possible to use the substrate fabricated by the above steps as a GaN template substrate for fabricating a GaN-based light emitting diode or laser diode.
    Type: Grant
    Filed: August 21, 2009
    Date of Patent: November 9, 2010
    Assignees: Tohoku Techno Arch Co., Ltd., Furukawa Co., Ltd., Mitsubishi Chemical Corporation, Dowa Holdings Co., Ltd., Epivalley Co., Ltd., Wavesquare Inc.
    Inventors: Takafumi Yao, Meoung-Whan Cho
  • Patent number: 7829207
    Abstract: A manufacture method that can manufacture ZnO based compound semiconductor crystal of good quality. A ZnO substrate is prepared to have a principal surface made of a plurality of terraces of (0001) planes arranged stepwise along an m-axis direction, the envelop of the principal surface being inclined relative to the (0001) plane by about 2 degrees or less. ZnO based compound semiconductor crystal is grown on the principal surface.
    Type: Grant
    Filed: September 27, 2008
    Date of Patent: November 9, 2010
    Assignees: Stanley Electric Co., Ltd., Tokyo Denpa Co., Ltd., Tohoku University
    Inventors: Hiroyuki Kato, Michihiro Sano, Katsumi Maeda, Hiroshi Yoneyama, Takafumi Yao, Meoung Whan Cho
  • Publication number: 20100120234
    Abstract: A GaN-based thin film (thick film) is grown using a metal buffer layer grown on a substrate. (a) A metal buffer layer (210) made of, for example, Cr or Cu is vapor-deposited on a sapphire substrate (120). (b) A substrate obtained by vapor-depositing the metal buffer layer (210) on the sapphire substrate (120) is nitrided in an ammonia gas ambient, thereby forming a metal nitride layer (212). (c) A GaN buffer layer (222) is grown on the nitrided metal buffer layers (210, 212). (d) Finally, a GaN single-crystal layer (220) is grown. This GaN single-crystal layer (220) can be grown to have various thicknesses depending on the objects. A freestanding substrate can be fabricated by selective chemical etching of the substrate fabricated by the above steps. It is also possible to use the substrate fabricated by the above steps as a GaN template substrate for fabricating a GaN-based light emitting diode or laser diode.
    Type: Application
    Filed: January 21, 2010
    Publication date: May 13, 2010
    Inventors: Takafumi Yao, Meoung-Whan Cho
  • Publication number: 20100009516
    Abstract: A GaN-based thin film (thick film) is grown using a metal buffer layer grown on a substrate. (a) A metal buffer layer (210) made of, for example, Cr or Cu is vapor-deposited on a sapphire substrate (120). (b) A substrate obtained by vapor-depositing the metal buffer layer (210) on the sapphire substrate (120) is nitrided in an ammonia gas ambient, thereby forming a metal nitride layer (212). (c) A GaN buffer layer (222) is grown on the nitrided metal buffer layers (210, 212). (d) Finally, a GaN single-crystal layer (220) is grown. This GaN single-crystal layer (220) can be grown to have various thicknesses depending on the objects. A freestanding substrate can be fabricated by selective chemical etching of the substrate fabricated by the above steps. It is also possible to use the substrate fabricated by the above steps as a GaN template substrate for fabricating a GaN-based light emitting diode or laser diode.
    Type: Application
    Filed: August 21, 2009
    Publication date: January 14, 2010
    Inventors: Takafumi Yao, Meoung-Whan Cho
  • Publication number: 20090239356
    Abstract: A device manufacturing method includes a buffer layer forming step of forming a buffer layer on an underlying substrate, a mask pattern forming step of forming, on the buffer layer, a mask pattern which partially covers the buffer layer, a growth step of growing a group III nitride crystal from regions exposed by the mask pattern on the surface of the buffer layer, thereby forming a structure in which a plurality of crystal members are arranged with gaps therebetween so as to partially cover the buffer layer and the mask pattern, a channel forming step of forming a channel, to supply a second etchant for the buffer layer to the buffer layer, by selectively etching the mask pattern using a first etchant for the mask pattern, and a separation step of separating the plurality of crystal members from the underlying substrate and separating the plurality of crystal members from each other by supplying the second etchant to the buffer layer through the gaps and the channel and selectively etching the buffer layer.
    Type: Application
    Filed: March 17, 2009
    Publication date: September 24, 2009
    Inventors: Takafumi Yao, Meoung-Whan Cho
  • Publication number: 20090057835
    Abstract: A manufacturing method of a group III nitride semiconductor includes the steps of: depositing a metal layer on an AlN template substrate or an AlN single crystal substrate formed by depositing an AlN single crystal layer with a thickness of not less than 0.1 ?m nor more than 10 ?m on a substrate made of either one of sapphire, SiC, and Si; forming a metal nitride layer having a plurality of substantially triangular-pyramid-shaped or triangular-trapezoid-shaped microcrystals by performing a heating nitridation process on the metal layer under a mixed gas atmosphere of ammonia; and depositing a group III nitride semiconductor layer on the metal nitride layer.
    Type: Application
    Filed: August 27, 2008
    Publication date: March 5, 2009
    Applicants: Tohoku Techno Arch Co., Ltd., Dowa Electronics Materials Co., Ltd.
    Inventors: Takafumi Yao, Meoung-Whan Cho, Ryuichi Toba
  • Publication number: 20090045398
    Abstract: A manufacture method that can manufacture ZnO based compound semiconductor crystal of good quality. A ZnO substrate is prepared to have a principal surface made of a plurality of terraces of (0001) planes arranged stepwise along an m-axis direction, the envelop of the principal surface being inclined relative to the (0001) plane by about 2 degrees or less. ZnO based compound semiconductor crystal is grown on the principal surface.
    Type: Application
    Filed: September 27, 2008
    Publication date: February 19, 2009
    Inventors: Hiroyuki Kato, Michihiro Sano, Katsumi Maeda, Hiroshi Yoneyama, Takafumi Yao, Meoung Whan Cho
  • Patent number: 7482618
    Abstract: A method for manufacturing a semiconductor device includes the steps of: (a) preparing a non-polar single crystal substrate; (b) epitaxially growing an MgO layer on the non-polar single crystal substrate to a thickness of 3 nm or thicker to have rocksalt structure at a substrate temperature of 500° C. to 800° C.; (c) growing on the MgO layer a low temperature growth layer made of ZnO group material at a substrate temperature of 500° C. or lower; (d) annealing the low temperature growth layer above the substrate at a temperature of 700° C. or higher; and (e) epitaxially growing a high temperature growth layer of ZnO group material on the annealed low temperature growth layer at a temperature of 600° C. or higher.
    Type: Grant
    Filed: January 6, 2005
    Date of Patent: January 27, 2009
    Assignees: Stanley Electric Co., Ltd.
    Inventors: Hiroyuki Kato, Kazuhiro Miyamoto, Michihiro Sano, Takafumi Yao
  • Patent number: 7479188
    Abstract: A process for producing an inexpensive large high-quality GaN substrate which comprises forming a MgO buffer layer on a high-quality substrate, generating a ZnO layer on the MgO buffer layer while performing polarity control, growing a GaN layer on the ZnO layer while performing polarity control, and melting the ZnO layer, thereby producing a GaN substrate.
    Type: Grant
    Filed: March 19, 2004
    Date of Patent: January 20, 2009
    Assignee: Tohoku Techno Arch Co., Ltd.
    Inventors: Takafumi Yao, Takuma Suzuki, Hang-ju Ko, Agus Setiawan
  • Publication number: 20080299746
    Abstract: A semiconductor substrate fabrication method according to the first aspect of this invention is characterized by including a preparation step of preparing an underlying substrate, a stacking step of stacking, on the underlying substrate, at least two multilayered films each including a peeling layer and a semiconductor layer, and a separation step of separating the semiconductor layer.
    Type: Application
    Filed: August 24, 2006
    Publication date: December 4, 2008
    Inventors: Takafumi Yao, Meoung-Whan Cho
  • Publication number: 20080261378
    Abstract: A GaN-based thin film (thick film) is grown using a metal buffer layer grown on a substrate. (a) A metal buffer layer (210) made of, for example, Cr or Cu is vapor-deposited on a sapphire substrate (120). (b) A substrate obtained by vapor-depositing the metal buffer layer (210) on the sapphire substrate (120) is nitrided in an ammonia gas ambient, thereby forming a metal nitride layer (212). (c) A GaN buffer layer (222) is grown on the nitrided metal buffer layers (210, 212). (d) Finally, a GaN single-crystal layer (220) is grown. This GaN single-crystal layer (220) can be grown to have various thicknesses depending on the objects. A freestanding substrate can be fabricated by selective chemical etching of the substrate fabricated by the above steps. It is also possible to use the substrate fabricated by the above steps as a GaN template substrate for fabricating a GaN-based light emitting diode or laser diode.
    Type: Application
    Filed: March 31, 2006
    Publication date: October 23, 2008
    Applicant: TOHOKU TECHNO ARCH CO., LTD.
    Inventors: Takafumi Yao, Meoung-Whan Cho
  • Patent number: 7438762
    Abstract: A manufacture method that can manufacture ZnO based compound semiconductor crystal of good quality. A ZnO substrate is prepared to have a principal surface made of a plurality of terraces of (0001) planes arranged stepwise along an m-axis direction, the envelop of the principal surface being inclined relative to the (0001) plane by about 2 degrees or less. ZnO based compound semiconductor crystal is grown on the principal surface.
    Type: Grant
    Filed: August 24, 2006
    Date of Patent: October 21, 2008
    Assignee: Stanley Electric Co., Ltd., Tokyo Denpa Co., Ltd., and Tohoku University
    Inventors: Hiroyuki Kato, Michihiro Sano, Katsumi Maeda, Hiroshi Yoneyama, Takafumi Yao, Meoung Whan Cho
  • Publication number: 20070152233
    Abstract: A manufacture method that can manufacture ZnO based compound semiconductor crystal of good quality. A ZnO substrate is prepared to have a principal surface made of a plurality of terraces of (0001) planes arranged stepwise along an m-axis direction, the envelop of the principal surface being inclined relative to the (0001) plane by about 2 degrees or less. ZnO based compound semiconductor crystal is grown on the principal surface.
    Type: Application
    Filed: August 24, 2006
    Publication date: July 5, 2007
    Inventors: Hiroyuki Kato, Michihiro Sano, Katsumi Maeda, Hiroshi Yoneyama, Takafumi Yao, Meoung Cho
  • Publication number: 20060252164
    Abstract: A process for producing an inexpensive large high-quality GaN substrate which comprises forming a MgO buffer layer on a high-quality substrate, generating a ZnO layer on the MgO buffer layer while performing polarity control, growing a GaN layer on the ZnO layer while performing polarity control, and melting the ZnO layer, thereby producing a GaN substrate.
    Type: Application
    Filed: March 19, 2004
    Publication date: November 9, 2006
    Inventors: Takafumi Yao, Takuma Suzuki, Hang-ju Ko, Agus Setiawan