Patents by Inventor Katsuomi Shiozawa

Katsuomi Shiozawa 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: 8163576
    Abstract: A semiconductor device and a manufacturing method thereof are provided which enable reduction and enhanced stability of contact resistance between the back surface of a nitride substrate and an electrode formed thereover. A nitride semiconductor device includes an n-type Ga—N substrate (1) over which a semiconductor element is formed, and an n-electrode (10) as a metal electrode formed over the back surface of the GaN substrate (1). A connection layer (20) is formed between the GaN substrate (1) and the n-electrode (10), and the connection layer (2) is composed of a material that is other than nitride semiconductors and that contains silicon.
    Type: Grant
    Filed: December 18, 2009
    Date of Patent: April 24, 2012
    Assignee: Mitsubishi Electric Corporation
    Inventors: Katsuomi Shiozawa, Kyozo Kanamoto, Kazushige Kawasaki, Hitoshi Sakuma, Yuji Abe
  • Patent number: 7964424
    Abstract: A method for manufacturing a nitride semiconductor light-emitting element comprises: forming a semiconductor laminated structure wherein an n-type nitride semiconductor epitaxial layer, an active layer, and a p-type nitride semiconductor epitaxial layer are laminated on a substrate; forming a p-type electrode having a first electrode layer containing Pd and a second electrode layer containing Ta on the p-type nitride semiconductor epitaxial layer; heat treating at a temperature between 400° C. and 600° C. in ambient containing oxygen after forming the p-type electrode; and forming a pad electrode containing Au on the p-type electrode after the heat treating.
    Type: Grant
    Filed: November 5, 2008
    Date of Patent: June 21, 2011
    Assignee: Mitsubishi Electric Corporation
    Inventors: Kyozo Kanamoto, Katsuomi Shiozawa, Kazushige Kawasaki, Shinji Abe, Hitoshi Sakuma
  • Patent number: 7939943
    Abstract: A nitride semiconductor device with a p electrode having no resistance between itself and other electrodes, and a method of manufacturing the same are provided. A p electrode is formed of a first Pd film, a Ta film, and a second Pd film, which is an antioxidant film for preventing oxidation of the Ta film, and on a p-type contact layer of a nitride semiconductor. On the second Pd film, a pad electrode is formed. The second Pd film as an antioxidant film is formed on the entire upper surface of the Ta film which forms the p electrode, to prevent oxidation of the Ta film. This inhibits the resistance between the p electrode and the pad electrode, thereby preventing a failure in contact between the p electrode and the pad electrode and providing the low-resistance p electrode.
    Type: Grant
    Filed: November 11, 2008
    Date of Patent: May 10, 2011
    Assignee: Mitsubishi Electric Corporation
    Inventors: Katsuomi Shiozawa, Kyozo Kanamoto, Toshiyuki Oishi, Hiroshi Kurokawa, Kenichi Ohtsuka, Yoichiro Tarui, Yasunori Tokuda
  • Patent number: 7842962
    Abstract: A P-type electrode material is provided on a top surface of a P-type contact layer. The P-type electrode material is formed with an AuGa film, an Au film, a Pt film, and an Au film. The AuGa film is provided on the P-type contact layer. The Au film is provided on the AuGa film. The Pt film is provided on the Au film. The Au film is provided on the Pt film. With this, a nitride semiconductor device having a P-type electrode which can decrease a contact resistance between a P-type contact layer and the P-type electrode is obtained.
    Type: Grant
    Filed: November 16, 2005
    Date of Patent: November 30, 2010
    Assignee: Mitsubishi Denki Kabushiki Kaisha
    Inventors: Katsuomi Shiozawa, Toshiyuki Oishi, Kazushige Kawasaki, Yuji Abe
  • Patent number: 7795738
    Abstract: A nitride semiconductor device with a p electrode having no resistance between itself and other electrodes, and a method of manufacturing the same are provided. A p electrode is formed of a first Pd film, a Ta film, and a second Pd film, and on a p-type contact layer of a nitride semiconductor. On the second Pd film, a pad electrode is formed. The second Pd film is formed on the entire upper surface of the Ta film which forms part of the p electrode, and serves as an antioxidant film that prevents oxidation of the Ta film. Preventing oxidation of the Ta film, the second Pd film can reduce the resistance that may exist between the p electrode and the pad electrode, thereby preventing a failure in contact between the p electrode and the pad electrode and providing the p electrode with low resistance.
    Type: Grant
    Filed: December 4, 2008
    Date of Patent: September 14, 2010
    Assignee: Mitsubishi Electric Corporation
    Inventors: Katsuomi Shiozawa, Kyozo Kanamoto, Hiroshi Kurokawa, Yasunori Tokuda, Kyosuke Kuramoto, Hitoshi Sakuma
  • Patent number: 7791097
    Abstract: A nitride semiconductor device includes an n-type GaN substrate with a semiconductor device formed thereon and an n-type electrode which is a metal electrode formed on the rear surface of the GaN substrate. A surface modified layer and a reaction layer are interposed between the GaN substrate and n-type electrode. The surface modified layer serves as a carrier supplying layer, and is formed by causing the rear surface of the GaN substrate to react with a Si-containing plasma to be modified. The reaction layer is generated by partially removing a deposited material deposited on the surface modified layer by cleaning to generate a deposited layer and then causing Ti contained in a first metal layer and the deposited layer to partially react by heat treatment.
    Type: Grant
    Filed: July 2, 2007
    Date of Patent: September 7, 2010
    Assignee: Mitsubishi Electric Corporation
    Inventors: Kyozo Kanamoto, Katsuomi Shiozawa, Kazushige Kawasaki, Hitoshi Sakuma, Junichi Horie, Toshihiko Shiga, Toshiyuki Oishi
  • Publication number: 20100129991
    Abstract: A semiconductor device and a manufacturing method thereof are provided which enable reduction and enhanced stability of contact resistance between the back surface of a nitride substrate and an electrode formed thereover. A nitride semiconductor device includes an n-type Ga—N substrate (1) over which a semiconductor element is formed, and an n-electrode (10) as a metal electrode formed over the back surface of the GaN substrate (1). A connection layer (20) is formed between the GaN substrate (1) and the n-electrode (10), and the connection layer (2) is composed of a material that is other than nitride semiconductors and that contains silicon.
    Type: Application
    Filed: December 18, 2009
    Publication date: May 27, 2010
    Applicant: MITSUBISHI ELECTRIC CORPORATION
    Inventors: Katsuomi SHIOZAWA, Kyozo Kanamoto, Kazushige Kawasaki, Hitoshi Sakuma, Yuji Abe
  • Patent number: 7714439
    Abstract: A nitride semiconductor device according to the present invention includes a P-type contact layer and a P-type electrode provided on the P-type contact layer. The P-type electrode includes a AuGa film provided on the P-type contact layer, a Au film provided on the AuGa film, a Pt film 4 provided on the Au film, and a Au film provided on the Pt film. The ratio of the thickness of the AuGa film to the total thickness of the AuGa film and the Au film is not less than 12% but not more than 46%.
    Type: Grant
    Filed: August 24, 2007
    Date of Patent: May 11, 2010
    Assignee: Mitsubishi Electric Corporation
    Inventors: Katsuomi Shiozawa, Hitoshi Sakuma, Kazushige Kawasaki, Toshihiko Shiga, Toshiyuki Oishi
  • Patent number: 7683398
    Abstract: A semiconductor device and a manufacturing method thereof are provided which enable reduction and enhanced stability of contact resistance between the back surface of a nitride substrate and an electrode formed thereover. A nitride semiconductor device includes an n-type GaN substrate (1) over which a semiconductor element is formed, and an n-electrode (10) as a metal electrode formed over the back surface of the GaN substrate (1). A connection layer (20) is formed between the GaN substrate (1) and the n-electrode (10), and the connection layer (20) is composed of a material that is other than nitride semiconductors and that contains silicon.
    Type: Grant
    Filed: March 2, 2007
    Date of Patent: March 23, 2010
    Assignee: Mitsubishi Electric Corporation
    Inventors: Katsuomi Shiozawa, Kyozo Kanamoto, Kazushige Kawasaki, Hitoshi Sakuma, Yuji Abe
  • Patent number: 7678597
    Abstract: A method of manufacturing a semiconductor device provides a semiconductor device with a gallium-nitride-based semiconductor structure that allows long-term stable operation without degradation in device performance. After formation of an insulation film on a surface other than on a ridge surface, an oxygen-containing gas such as O2, O3, NO, N2O, or NO2 is supplied to oxidize a p-type GaN contact layer from the surface and to thereby form an oxide film on the surface of the p-type GaN contact layer. Then, a p-type electrode that establishes contact with the p-type GaN contact layer is formed by evaporation or sputtering on the oxide film and on the insulation film. Heat treatment is subsequently performed at temperatures between 400 and 700° C. in an atmosphere containing a nitrogen-containing gas such as N2 or NH3 or an inert gas such as Ar or He.
    Type: Grant
    Filed: November 26, 2008
    Date of Patent: March 16, 2010
    Assignee: Mitsubishi Electric Corporation
    Inventors: Kenichi Ohtsuka, Yoichiro Tarui, Yosuke Suzuki, Katsuomi Shiozawa, Kyozo Kanamoto, Toshiyuki Oishi, Yasunori Tokuda, Tatsuo Omori
  • Publication number: 20090245311
    Abstract: Provided are a process for producing a nitride semiconductor laser that is a process applied to materials wherein a diffusion of an impurity is not easily attained, such as nitride semiconductor material, and substituted for any process including the step of local diffusion of an impurity, which has been hitherto carried out for GaAlAs based or AlGaInP based semiconductors, and that is a process which is effective, high in precision, and suitable for mass production; and a nitride semiconductor laser produced by this process. The nitride-semiconductor-producing process of the present invention includes the steps of: preparing a substrate having an MQW active layer made of a nitride semiconductor containing In; irradiating a vicinity of a light-emitting end face of the multiquantum well active layer, or a planned region of the light-emitting end face selectively with a laser beam; and performing heating treatment after the laser-irradiating step.
    Type: Application
    Filed: March 4, 2009
    Publication date: October 1, 2009
    Applicant: MITSUBISHI ELECTRIC CORPORATION
    Inventors: Kyozo KANAMOTO, Katsuomi Shiozawa
  • Patent number: 7582908
    Abstract: A nitride semiconductor device and its manufacturing method are provided which are capable of achieving low-resistance ohmic properties and high adhesion. A nitride semiconductor device has an n-type GaN substrate over which a semiconductor element is formed and an n-electrode as a metal electrode formed over the back surface of the GaN substrate. A surface denatured layer functioning as a carrier supply layer is provided between the GaN substrate and the n-electrode. The surface denatured layer is formed by denaturing the back surface of the GaN substrate by causing it to react with a material that contains silicon.
    Type: Grant
    Filed: March 26, 2007
    Date of Patent: September 1, 2009
    Assignee: Mitsubishi Electric Corporation
    Inventors: Kyozo Kanamoto, Katsuomi Shiozawa, Kazushige Kawasaki, Hitoshi Sakuma, Yoshiyuki Suehiro
  • Publication number: 20090170304
    Abstract: A method of manufacturing a semiconductor device is provided, which can reduce the contact resistance of an ohmic electrode to a p-type nitride semiconductor layer and can achieve long-term stable operation. In forming, in an electrode forming step, a p-type ohmic electrode of a metal film by successive lamination of a Pd film which is a first p-type ohmic electrode and a Ta film which is a second p-type ohmic electrode on a p-type GaN contact layer, the metal film is formed to include an oxygen atom. In the presence of an oxygen atom in the metal film, then in a heat-treatment step, the p-type ohmic electrode of the metal film is heat-treated in an atmosphere that contains no oxygen atom-containing gas.
    Type: Application
    Filed: December 18, 2008
    Publication date: July 2, 2009
    Applicant: MITSUBISHI ELECTRIC CORPORATION
    Inventors: Yoichiro Tarui, Kenichi Ohtsuka, Yosuke Suzuki, Katsuomi Shiozawa, Kyozo Kanamoto, Toshiyuki Oishi, Yasunori Tokuda, Tatsuo Omori
  • Publication number: 20090160054
    Abstract: A nitride semiconductor device is provided which reduces the contact resistance at the interface between a P-type electrode and a nitride semiconductor layer. A nitride semiconductor device includes a P-type nitride semiconductor layer and a P-type electrode formed on the P-type nitride semiconductor layer. The P-type electrode is formed by successive laminations of a metal layer of a metal having a work function of 5.1 eV or more, a Pd layer of palladium, and a Ta layer of tantalum on the P-type nitride semiconductor layer.
    Type: Application
    Filed: November 13, 2008
    Publication date: June 25, 2009
    Applicant: MITSUBISHI ELECTRIC CORPORATION
    Inventors: Katsuomi Shiozawa, Kyozo Kanamoto, Toshiyuki Oishi, Yoichiro Tarui, Yasunori Tokuda
  • Publication number: 20090146308
    Abstract: A nitride semiconductor device with a p electrode having no resistance between itself and other electrodes, and a method of manufacturing the same are provided. A p electrode is formed of a first Pd film, a Ta film, and a second Pd film, and on a p-type contact layer of a nitride semiconductor. On the second Pd film, a pad electrode is formed. The second Pd film is formed on the entire upper surface of the Ta film which forms part of the p electrode, and serves as an antioxidant film that prevents oxidation of the Ta film. Preventing oxidation of the Ta film, the second Pd film can reduce the resistance that may exist between the p electrode and the pad electrode, thereby preventing a failure in contact between the p electrode and the pad electrode and providing the p electrode with low resistance.
    Type: Application
    Filed: December 4, 2008
    Publication date: June 11, 2009
    Applicant: MITSUBISHI ELECTRIC CORPORATION
    Inventors: Katsuomi Shiozawa, Kyozo Kanamoto, Hiroshi Kurokawa, Yasunori Tokuda, Kyosuke Kuramoto, Hitoshi Sakuma
  • Publication number: 20090142871
    Abstract: A method of manufacturing a semiconductor device provides a semiconductor device with a gallium-nitride-based semiconductor structure that allows long-term stable operation without degradation in device performance. After formation of an insulation film on a surface other than on a ridge surface, an oxygen-containing gas such as O2, O3, NO, N2O, or NO2 is supplied to oxidize a p-type GaN contact layer from the surface and to thereby form an oxide film on the surface of the p-type GaN contact layer. Then, a p-type electrode that establishes contact with the p-type GaN contact layer is formed by evaporation or sputtering on the oxide film and on the insulation film. Heat treatment is subsequently performed at temperatures between 400 and 700° C. in an atmosphere containing a nitrogen-containing gas such as N2 or NH3 or an inert gas such as Ar or He.
    Type: Application
    Filed: November 26, 2008
    Publication date: June 4, 2009
    Applicant: MITSUBISHI ELECTRIC CORPORATION
    Inventors: Kenichi Ohtsuka, Yoichiro Tarui, Yosuke Suzuki, Katsuomi Shiozawa, Kyozo Kanamoto, Toshiyuki Oishi, Yasunori Tokuda, Tatsuo Omori
  • Publication number: 20090140389
    Abstract: A nitride semiconductor device with a p electrode having no resistance between itself and other electrodes, and a method of manufacturing the same are provided. A p electrode is formed of a first Pd film, a Ta film, and a second Pd film, which is an antioxidant film for preventing oxidation of the Ta film, and on a p-type contact layer of a nitride semiconductor. On the second Pd film, a pad electrode is formed. The second Pd film as an antioxidant film is formed on the entire upper surface of the Ta film which forms the p electrode, to prevent oxidation of the Ta film. This inhibits the resistance between the p electrode and the pad electrode, thereby preventing a failure in contact between the p electrode and the pad electrode and providing the low-resistance p electrode.
    Type: Application
    Filed: November 11, 2008
    Publication date: June 4, 2009
    Applicant: MITSUBISHI ELECTRIC CORPORATION
    Inventors: Katsuomi Shiozawa, Kyozo Kanamoto, Toshiyuki Oishi, Hiroshi Kurokawa, Kenichi Ohtsuka, Yoichiro Tarui, Yasunori Tokuda
  • Publication number: 20090130790
    Abstract: A method for manufacturing a nitride semiconductor light-emitting element comprises: forming a semiconductor laminated structure wherein an n-type nitride semiconductor epitaxial layer, an active layer, and a p-type nitride semiconductor epitaxial layer are laminated on a substrate; forming a p-type electrode having a first electrode layer containing Pd and a second electrode layer containing Ta on the p-type nitride semiconductor epitaxial layer; heat treating at a temperature between 400° C. and 600° C. in an ambient containing oxygen after forming the p-type electrode; and forming a pad electrode containing Au on the p-type electrode after the heat treating.
    Type: Application
    Filed: November 5, 2008
    Publication date: May 21, 2009
    Applicant: MITSUBISHI ELECTRIC CORPORATION
    Inventors: Kyozo Kanamoto, Katsuomi Shiozawa, Kazushige Kawasaki, Shinji Abe, Hitoshi Sakuma
  • Publication number: 20090127661
    Abstract: Semiconductor devices, in particular nitride semiconductor devices for use in the manufacture of laser diodes, prevent peeling-off of the electrode, and at the same time reduces the complexity of processes and a reduction in yield. A nitride semiconductor device according to the invention includes a P-type nitride semiconductor layer with a ridge on its surface, an SiO2 film covering at least the side face of the ridge, an adherence layer formed on a surface of the SiO2 film and composed mainly of silicon, and a P-type electrode formed on the upper surface of the ridge and on a surface of the adherence layer.
    Type: Application
    Filed: November 17, 2008
    Publication date: May 21, 2009
    Applicant: MITSUBISHI ELECTRIC CORPORATION
    Inventors: Katsuomi Shiozawa, Kyozo Kanamoto, Toshiyuki Oishi, Hiroshi Kurokawa, Kazushige Kawasaki, Shinji Abe, Hitoshi Sakuma
  • Publication number: 20080311694
    Abstract: An SiO2 film is formed on a semiconductor layer stack, the SiO2 film having a thickness da and an etch rate Ra in buffered (BHF). A waveguide ridge with the SiO2 film thereon is formed using a resist pattern 76. An SiN film is formed on top and both sides of the waveguide ridge, while leaving the resist pattern in place, the SiN film having a thickness db and an etch rate Rb in BHF, where 1<(db/Rb)/(da/Ra). Then the resist pattern and the overlying portion of the SiN film are removed by lift-off to form an opening in the SiN film. Wet etching for a predetermined period of time with BHF removes the SiO2 film from the waveguide ridge, while leaving the SiN film in place.
    Type: Application
    Filed: November 29, 2007
    Publication date: December 18, 2008
    Applicant: MITSUBISHI ELECTRIC CORPORATION
    Inventors: Kazushige Kawasaki, Takafumi Oka, Katsuomi Shiozawa