Patents by Inventor Chiho Kokubo

Chiho Kokubo 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: 7176490
    Abstract: It is a problem to provide a semiconductor device production system using a laser crystallization method capable of preventing grain boundaries from forming in a TFT channel region and further preventing conspicuous lowering in TFT mobility due to grain boundaries, on-current decrease or off-current increase. An insulation film is formed on a substrate, and a semiconductor film is formed on the insulation film. Due to this, preferentially formed is a region in the semiconductor film to be concentratedly applied by stress during crystallization with laser light. Specifically, a stripe-formed or rectangular concavo-convex is formed on the semiconductor film. Continuous-oscillation laser light is irradiated along the striped concavo-convex or along a direction of a longer or shorter axis of rectangle.
    Type: Grant
    Filed: March 24, 2005
    Date of Patent: February 13, 2007
    Assignee: Semiconductor Energy Laboratory Co., Ltd.
    Inventors: Atsuo Isobe, Koji Dairiki, Hiroshi Shibata, Chiho Kokubo, Tatsuya Arao, Masahiko Hayakawa, Hidekazu Miyairi, Akihisa Shimomura, Koichiro Tanaka, Shunpei Yamazaki, Mai Akiba
  • Publication number: 20070015323
    Abstract: An objective is to provide a method of manufacturing a semiconductor device, and a semiconductor device manufactured by using the manufacturing method, in which a laser crystallization method is used that is capable of preventing the formation of grain boundaries in TFT channel formation regions, and is capable of preventing conspicuous drops in TFT mobility, reduction in the ON current, and increases in the OFF current, all due to grain boundaries. Depressions and projections with stripe shape or rectangular shape are formed. Continuous wave laser light is then irradiated to a semiconductor film formed on an insulating film along the depressions and projections with stripe shape of the insulating film, or along a longitudinal axis direction or a transverse axis direction of the rectangular shape. Note that although it is most preferable to use continuous wave laser light at this point, pulse wave laser light may also be used.
    Type: Application
    Filed: August 31, 2006
    Publication date: January 18, 2007
    Applicant: Semiconductor Energy Laboratory Co., Ltd.
    Inventors: Atsuo Isobe, Shunpei Yamazaki, Chiho Kokubo, Koichiro Tanaka, Akihisa Shimomura, Tatsuya Arao, Hidekazu Miyairi, Mai Akiba
  • Publication number: 20070001228
    Abstract: In a conventional method of crystallization using a laser beam, variance (or dispersion) in a TFT characteristic becomes large, which causes various functions of a semiconductor device comprising TFTs as components of its electronic circuit to be restrained. A first shape of semiconductor region having on its one side a plurality of sharp convex top-end portions is formed first and a continuous wave laser beam is used for radiation from the above region so as to crystallize the first shape of semiconductor region. A continuous wave laser beam condensed in one or plural lines is used for the laser beam. The first shape of semiconductor region is etched to form a second shape of semiconductor region in which a channel forming region and a source and drain region are formed. The second shape of semiconductor region is disposed so that a channel forming range would be formed on respective crystal regions extending from the plurality of convex end portions.
    Type: Application
    Filed: September 7, 2006
    Publication date: January 4, 2007
    Applicant: Semiconductor Energy Laboratory Co., Ltd.
    Inventors: Chiho Kokubo, Aiko Shiga, Shunpei Yamazaki, Hidekazu Miyairi, Koji Dairiki, Koichiro Tanaka
  • Publication number: 20070004104
    Abstract: A method for manufacturing a semiconductor device having steps of forming an amorphous semiconductor on a substrate having an insulating surface; patterning the amorphous semiconductor to form plural first island-like semiconductors; irradiating a linearly condensed laser beam on the plural first island-like semiconductors while relatively scanning the substrate, thus crystallizing the plural first island-like semiconductors; patterning the plural first island-like semiconductors that have been crystallized to form plural second island-like semiconductors; forming plural transistors using the plural second island-like semiconductors; and forming a unit circuit using a predetermined number of the transistors, where the second island-like semiconductors used for the predetermined number of the transistors are formed from the first island-like semiconductors that are different from each other.
    Type: Application
    Filed: September 5, 2006
    Publication date: January 4, 2007
    Applicant: Semiconductor Energy Laboratory Co., Ltd.
    Inventors: Munehiro Azami, Chiho Kokubo, Aiko Shiga, Atsuo Isobe, Hiroshi Shibata, Shunpei Yamazaki
  • Patent number: 7148092
    Abstract: To provide a semiconductor device composed of a semiconductor element or a group of semiconductor elements, in which a crystalline semiconductor film having as few grain boundaries as possible in a channel formation region is formed on an insulating surface, which can operate at high speed, which have high current drive performance, and which are less fluctuated between elements.
    Type: Grant
    Filed: January 28, 2003
    Date of Patent: December 12, 2006
    Assignee: Semiconductor Energy Laboratory Co., Ltd.
    Inventors: Atsuo Isobe, Shunpei Yamazaki, Chiho Kokubo, Koichiro Tanaka, Akihisa Shimomura, Tatsuya Arao, Hidekazu Miyairi
  • Patent number: 7148507
    Abstract: A semiconductor device production system using a laser crystallization method is provided which can avoid forming grain boundaries in a channel formation region of a TFT, thereby preventing grain boundaries from lowering the mobility of the TFT greatly, from lowering ON current, and from increasing OFF current. Rectangular or stripe pattern depression and projection portions are formed on an insulating film. A semiconductor film is formed on the insulating film. The semiconductor film is irradiated with continuous wave laser light by running the laser light along the stripe pattern depression and projection portions of the insulating film or along the major or minor axis direction of the rectangle. Although continuous wave laser light is most preferred among laser light, it is also possible to use pulse oscillation laser light in irradiating the semiconductor film.
    Type: Grant
    Filed: December 17, 2004
    Date of Patent: December 12, 2006
    Assignee: Semiconductor Energy Laboratory Co., Ltd.
    Inventors: Atsuo Isobe, Shunpei Yamazaki, Koji Dairiki, Hiroshi Shibata, Chiho Kokubo, Tatsuya Arao, Masahiko Hayakawa, Hidekazu Miyairi, Akihisa Shimomura, Koichiro Tanaka, Mai Akiba
  • Patent number: 7135389
    Abstract: A laser irradiation method using a laser crystallization method which can heighten an efficiency of substrate processing as compared to a conventional one and also heighten mobility of a semiconductor film is provided. It is an irradiation method of a laser beam in which, pattern information of a sub-island formed on a substrate is stored, and a beam spot of a laser beam is condensed so as to become linear, and by use of the stored pattern information, a scanning path of the beam spot is determined so as to include the sub-island, and by moving the beam spot along the scanning path, the laser beam is irradiated to the sub-island, characterized in that on the occasion of scanning the beam spot, when the beam spot has reached to the sub-island, the beam spot and the sub-island are contacted at a plurality of points.
    Type: Grant
    Filed: December 13, 2002
    Date of Patent: November 14, 2006
    Assignee: Semiconductor Energy Laboratory Co., Ltd.
    Inventors: Shunpei Yamazaki, Chiho Kokubo, Aiko Shiga, Koichiro Tanaka, Hidekazu Miyairi, Koji Dairiki
  • Publication number: 20060246638
    Abstract: The orientation ratio of a crystalline semiconductor film obtained by crystallizing an amorphous semiconductor film through heat treatment and irradiation of intense light such as laser light, ultraviolet rays, or infrared rays is enhanced, and a semiconductor device whose active region is formed from the crystalline semiconductor film and a method of manufacturing the semiconductor device are provided. In a semiconductor film containing silicon and germanium as its ingredient and having a crystal structure, the {101} plane reaches 30% or more of all the lattice planes detected by Electron backscatter diffraction.
    Type: Application
    Filed: April 25, 2006
    Publication date: November 2, 2006
    Applicant: SEMICONDUCTOR ENERGY LABORATORY CO., LTD.
    Inventors: Taketomi Asami, Mitsuhiro Ichijo, Satoshi Toriumi, Takashi Ohtsuki, Toru Mitsuki, Kenji Kasahara, Tamae Takano, Chiho Kokubo, Shunpei Yamazaki, Takeshi Shichi
  • Patent number: 7129121
    Abstract: A method for manufacturing a semiconductor device having steps of forming an amorphous semiconductor on a substrate having an insulating surface; patterning the amorphous semiconductor to form plural first island-like semiconductors; irradiating a linearly condensed laser beam on the plural first island-like semiconductors while relatively scanning the substrate, thus crystallizing the plural first island-like semiconductors; patterning the plural first island-like semiconductors that have been crystallized to form plural second island-like semiconductors; forming plural transistors using the plural second island-like semiconductors; and forming a unit circuit using a predetermined number of the transistors, where the second island-like semiconductors used for the predetermined number of the transistors are formed from the first island-like semiconductors that are different from each other.
    Type: Grant
    Filed: June 23, 2005
    Date of Patent: October 31, 2006
    Assignee: Semiconductor Energy Laboratory Co., Ltd.
    Inventors: Munehiro Azami, Chiho Kokubo, Aiko Shiga, Atsuo Isobe, Hiroshi Shibata, Shunpei Yamazaki
  • Patent number: 7115903
    Abstract: An insulating film having depressions and projections are formed on a substrate. A semiconductor film is formed on the insulating film. Thus, for crystallization by using laser light, a part where stress concentrates is selectively formed in the semiconductor film. More specifically, stripe or rectangular depressions and projections are provided in the semiconductor film. Then, continuous-wave laser light is irradiated along the stripe depressions and projections formed in the semiconductor film or in a direction of a major axis or minor axis of the rectangle.
    Type: Grant
    Filed: December 27, 2002
    Date of Patent: October 3, 2006
    Assignee: Semiconductor Energy Laboratory Co., Ltd.
    Inventors: Atsuo Isobe, Koji Dairiki, Hiroshi Shibata, Chiho Kokubo, Tatsuya Arao, Masahiko Hayakawa, Hidekazu Miyairi, Akihisa Shimomura, Koichiro Tanaka, Shunpei Yamazaki, Mai Akiba
  • Patent number: 7109069
    Abstract: In a conventional method of crystallization using a laser beam, variance (or dispersion) in a TFT characteristic becomes large, which causes various functions of a semiconductor device comprising TFTs as components of its electronic circuit to be restrained. A first shape of semiconductor region having on its one side a plurality of sharp convex top-end portions is formed first and a continuous wave laser beam is used for radiation from the above region so as to crystallize the first shape of semiconductor region. A continuous wave laser beam condensed in one or plural lines is used for the laser beam. The first shape of semiconductor region is etched to form a second shape of semiconductor region in which a channel forming region and a source and drain region are formed. The second shape of semiconductor region is disposed so that a channel forming range would be formed on respective crystal regions extending from the plurality of convex end portions.
    Type: Grant
    Filed: December 18, 2002
    Date of Patent: September 19, 2006
    Assignee: Semiconductor Energy Laboratory Co., Ltd.
    Inventors: Chiho Kokubo, Aiko Shiga, Shunpei Yamazaki, Hidekazu Miyairi, Koji Dairiki, Koichiro Tanaka
  • Patent number: 7105392
    Abstract: An objective is to provide a method of manufacturing a semiconductor device, and a semiconductor device manufactured by using the manufacturing method, in which a laser crystallization method is used that is capable of preventing the formation of grain boundaries in TFT channel formation regions, and is capable of preventing conspicuous drops in TFT mobility, reduction in the ON current, and increases in the OFF current, all due to grain boundaries. Depressions and projections with stripe shape or rectangular shape are formed. Continuous wave laser light is then irradiated to a semiconductor film formed on an insulating film along the depressions and projections with stripe shape of the insulating film, or along a longitudinal axis direction or a transverse axis direction of the rectangular shape. Note that although it is most preferable to use continuous wave laser light at this point, pulse wave laser light may also be used.
    Type: Grant
    Filed: January 28, 2003
    Date of Patent: September 12, 2006
    Assignee: Semiconductor Energy Laboratory Co., Ltd.
    Inventors: Atsuo Isobe, Shunpei Yamazaki, Chiho Kokubo, Koichiro Tanaka, Akihisa Shimomura, Tatsuya Arao, Hidekazu Miyairi, Mai Akiba
  • Patent number: 7098084
    Abstract: In a crystallization process of an amorphous semiconductor film, a first polycrystalline semiconductor film, in which amorphous regions are dotted within the continuous crystal region, is obtained by performing heat treatment after introducing a metallic element which promotes crystallization on the amorphous semiconductor film. At this point, the amorphous regions are kept within a predetermined range. A laser beam having a wave length region, which can give more energy to the amorphous region than to the crystal region, is irradiated to the first polycrystalline semiconductor film, it is possible to crystallize the amorphous region without destroying the crystal region. If a TFT is manufactured based on a second polycrystalline semiconductor film, which is obtained through the above-mentioned crystallization processes, the TFT with high electric characteristics and less fluctuation can be obtained.
    Type: Grant
    Filed: March 7, 2001
    Date of Patent: August 29, 2006
    Assignee: Semiconductor Energy Laboratory Co., Ltd.
    Inventors: Koichiro Tanaka, Hideto Ohnuma, Chiho Kokubo
  • Patent number: 7034337
    Abstract: The orientation ratio of a crystalline semiconductor film obtained by crystallizing an amorphous semiconductor film through heat treatment and irradiation of intense light such as laser light, ultraviolet rays, or infrared rays is enhanced, and a semiconductor device whose active region is formed from the crystalline semiconductor film and a method of manufacturing the semiconductor device are provided. In a semiconductor film containing silicon and germanium as its ingredient and having a crystal structure, the {101} plane reaches 30% or more of all the lattice planes detected by Electron backscatter diffraction.
    Type: Grant
    Filed: March 4, 2004
    Date of Patent: April 25, 2006
    Assignee: Semiconductor Energy Laboratory Co., Ltd.
    Inventors: Taketomi Asami, Mitsuhiro Ichijo, Satoshi Toriumi, Takashi Ohtsuki, Toru Mitsuki, Kenji Kasahara, Tamae Takano, Chiho Kokubo, Shunpei Yamazaki, Takeshi Shichi
  • Patent number: 6974732
    Abstract: To effectively crystallize an amorphous semiconductor film comprising silicon by utilizing nickel element and remove nickel element contributed to the crystallization, a mask 103 is provided on an amorphous silicon film 102, oxide film patterns 107 and 108 including nickel are formed, phosphorus is doped in a region 109, thereafter, heating is performed, nickel element is diffused via paths 110 and 111 and nickel element diffuses in the amorphous silicon film and gettered by phosphorus at the region 109 by which crystallization of diffusion of nickel and gettering of nickel can be carried out simultaneously.
    Type: Grant
    Filed: September 8, 2003
    Date of Patent: December 13, 2005
    Assignee: Semiconductor Energy Laboratory Co., Ltd.
    Inventors: Hisashi Ohtani, Tamae Takano, Chiho Kokubo
  • Publication number: 20050269569
    Abstract: There is disclosed a semiconductor device and a method of fabricating the semiconductor device in which a heat treatment time required for crystal growth is shortened and a process is simplified. Two catalytic element introduction regions are arranged at both sides of one active layer and crystallization is made. A boundary portion where crystal growth from one catalytic element introduction region meets crystal growth from the other catalytic element introduction region is formed in a region which becomes a source region or drain region.
    Type: Application
    Filed: June 14, 2005
    Publication date: December 8, 2005
    Applicant: Semiconductor Energy Laboratory Co., Ltd.
    Inventors: Chiho Kokubo, Hirokazu Yamagata, Shunpei Yamazaki
  • Publication number: 20050245007
    Abstract: A method for manufacturing a semiconductor device having steps of forming an amorphous semiconductor on a substrate having an insulating surface; patterning the amorphous semiconductor to form plural first island-like semiconductors; irradiating a linearly condensed laser beam on the plural first island-like semiconductors while relatively scanning the substrate, thus crystallizing the plural first island-like semiconductors; patterning the plural first island-like semiconductors that have been crystallized to form plural second island-like semiconductors; forming plural transistors using the plural second island-like semiconductors; and forming a unit circuit using a predetermined number of the transistors, where the second island-like semiconductors used for the predetermined number of the transistors are formed from the first island-like semiconductors that are different from each other.
    Type: Application
    Filed: June 23, 2005
    Publication date: November 3, 2005
    Applicant: Semiconductor Energy Laboratory Co., Ltd.
    Inventors: Munehiro Azami, Chiho Kokubo, Aiko Shiga, Atsuo Isobe, Hiroshi Shibata, Shunpei Yamazaki
  • Publication number: 20050233557
    Abstract: In a crystallization process of an amorphous semiconductor film, a first polycrystalline semiconductor film, in which amorphous regions are dotted within the continuous crystal region, is obtained by performing heat treatment after introducing a metallic element which promotes crystallization on the amorphous semiconductor film. At this point, the amorphous regions are kept within a predetermined range. A laser beam having a wave length region, which can give more energy to the amorphous region than to the crystal region, is irradiated to the first polycrystalline semiconductor film, it is possible to crystallize the amorphous region without destroying the crystal region. If a TFT is manufactured based on a second polycrystalline semiconductor film, which is obtained through the above-mentioned crystallization processes, the TFT with high electric characteristics and less fluctuation can be obtained.
    Type: Application
    Filed: June 8, 2005
    Publication date: October 20, 2005
    Inventors: Koichiro Tanaka, Hideto Ohnuma, Chiho Kokubo
  • Patent number: 6956235
    Abstract: The orientation of a crystalline semiconductor film obtained by crystallizing an amorphous semiconductor film is improved and a TFT formed from this crystalline semiconductor film is provided. In a semiconductor device whose TFT is formed from a semiconductor layer mainly containing silicon, the semiconductor layer has a channel formation region and an impurity region doped with an impurity of one type of conductivity.
    Type: Grant
    Filed: April 29, 2004
    Date of Patent: October 18, 2005
    Assignee: Semiconductor Energy Laboratory Co., Ltd.
    Inventors: Shunpei Yamazaki, Toru Mitsuki, Kenji Kasahara, Taketomi Asami, Tamae Takano, Takeshi Shichi, Chiho Kokubo
  • Publication number: 20050221545
    Abstract: When a semiconductor film is irradiated with laser light, the semiconductor film is instantaneously melted and expand locally. In order to reduce internal stress generated by this expansion, strain is locally generated in the semiconductor film. Accordingly, a variation is caused among portions with strain and portions without strain, and a variation is caused also by a difference in extent of strain. According to the present invention, after laser light irradiation, an oxide film (referred to as a chemical oxide) is formed by using a solution containing ozone (typically, ozone water) to form an oxide film of 1 to 10 nm in total, and further, a heat treatment for reducing strain of a semiconductor film (a heat treatment of heating the semiconductor film instantaneously to approximately 400 to 1000° C.) is performed.
    Type: Application
    Filed: March 25, 2005
    Publication date: October 6, 2005
    Applicant: Semiconductor Energy Laboratory Co., Ltd.
    Inventors: Chiho Kokubo, Shunpei Yamazaki, Tamae Takano, Hiroaki Irie