Patents by Inventor Ritsuko Kawasaki
Ritsuko Kawasaki 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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Publication number: 20040224449Abstract: To provide a laser apparatus and a laser annealing method with which a crystalline semiconductor film with a larger crystal grain size is obtained and which are low in their running cost. A solid state laser easy to maintenance and high in durability is used as a laser, and laser light emitted therefrom is linearized to increase the throughput and to reduce the production cost as a whole. Further, both the front side and the back side of an amorphous semiconductor film is irradiated with such laser light to obtain the crystalline semiconductor film with a larger crystal grain size.Type: ApplicationFiled: June 21, 2004Publication date: November 11, 2004Applicant: Semiconductor Energy Laboratory Co., Ltd.Inventors: Shunpei Yamazaki, Hisashi Ohtani, Koichiro Tanaka, Kenji Kasahara, Ritsuko Kawasaki
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Patent number: 6809382Abstract: To improve the operation characteristic and reliability of a semiconductor device by optimizing the structure of bottom gate type or inverted stagger type TFTs arranged in circuits of the semiconductor device in accordance with the function of the respective circuits. At least LDD regions that overlap with a gate electrode are formed in an N channel type TFT of a driving circuit, and LDD regions that do not overlap with the gate electrode are formed in an N channel type TFT of a pixel matrix circuit. The concentration of the two kinds of LDD regions is differently set from each other, to thereby obtain the optimal circuit operation.Type: GrantFiled: August 4, 2003Date of Patent: October 26, 2004Assignee: Semiconductor Energy Laboratory Co., Ltd.Inventors: Ritsuko Kawasaki, Hidehito Kitakado, Kenji Kasahara, Shunpei Yamazaki
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Publication number: 20040203219Abstract: For crystallizing an amorphous semiconductor film by means of irradiation of laser beams, a top surface and a back surface of the amorphous semiconductor film are irradiated with the laser beams. In this case, an effective energy intensity Io of the laser beams to be applied onto the top surface and an effective energy intensity Io′ of the laser beams to be applied onto the back surface satisfy the relationship of 0<Io′/Io<1 or 1<Io′/Io. Thus, a laser annealing method capable of providing a crystalline semiconductor film with large grain diameters can be provided.Type: ApplicationFiled: May 3, 2004Publication date: October 14, 2004Applicant: Semiconductor Energy Laboratory Co., Ltd.Inventors: Kenji Kasahara, Ritsuko Kawasaki, Hisashi Ohtani, Koichiro Tanaka
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Patent number: 6780687Abstract: Protrusions called ridges are formed on the surface of a crystalline semiconductor film formed by a laser crystallization method or the like. A heat absorbing layer are formed below a semiconductor film. When the semiconductor film is crystallized by laser, a temperature difference is produced between a semiconductor film 1010 positioned above a heat absorbing layer 1011 and a semiconductor film 1013 of the other region to produce a difference in thermal expansion at the boundary of the outside end 1015 of the heat absorbing layer. This difference produces a strain to form a surface wave. The surface wave starting at the outer periphery of the heat absorbing layer is formed in the vicinity of the heat absorbing layer. When the semiconductor layer is solidified after it is melted, the protrusions of the surface wave remain as protrusions after the semiconductor film is solidified.Type: GrantFiled: January 25, 2001Date of Patent: August 24, 2004Assignee: Semiconductor Energy Laboratory Co., Ltd.Inventors: Setsuo Nakajima, Ritsuko Kawasaki
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Publication number: 20040161913Abstract: A crystalline semiconductor film having crystal grains of large grain size or crystal grains in which the position and the size are controlled is formed to manufacture a TFT, whereby a semiconductor device that enables a high-speed operation is realized. First, a reflecting member is provided on a rear surface side of a substrate on which a semiconductor film is formed (semiconductor film substrate). When a front surface side of the semiconductor film substrate is irradiated with a laser beam that penetrates the semiconductor film substrate, the laser beam is reflected by the reflecting member to irradiate the semiconductor film from the rear surface side. With this method, an effective energy density is raised in the semiconductor film, and an output time is made long. Thus, the cooling rate of the semiconductor film is made gentle and crystal grains of large grain size are formed.Type: ApplicationFiled: November 19, 2001Publication date: August 19, 2004Inventors: Ritsuko Kawasaki, Setsuo Nakajima
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Publication number: 20040147065Abstract: The present invention provides a semiconductor device in which a bottom-gate TFT or an inverted stagger TFT arranged in each circuit is suitably constructed in conformity with the functionality of the respective circuits, thereby attaining an improvement in the operating efficiency and reliability of the semiconductor device. In the structure, LDD regions in a pixel TFT are arranged so as not to overlap with a channel protection insulating film and to overlap with a gate electrode by at least a portion thereof. LDD regions in an N-channel TFT of a drive circuit is arranged so as not to overlap with a channel protection insulating film and to overlap with a gate electrode by at least a portion thereof. LDD regions in a P-channel TFT of the drive circuit is arranged so as to overlap with a channel protection insulating film and to overlap with the gate electrode.Type: ApplicationFiled: January 14, 2004Publication date: July 29, 2004Applicant: Semiconductor Energy Laboratory Co., Ltd.Inventors: Hidehito Kitakado, Ritsuko Kawasaki, Kenji Kasahara
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Publication number: 20040140470Abstract: A crystalline semiconductor film in which the position and size of a crystal grain is controlled is fabricated, and the crystalline semiconductor film is used for a channel formation region of a TFT, so that a high performance TFT is realized. An island-like semiconductor layer is made to have a temperature distribution, and a region where temperature change is gentle is provided to control the nucleus generation speed and nucleus generation density, so that the crystal grain is enlarged. In a region where an island-like semiconductor layer 1003 overlaps with a base film 1002, a thick portion is formed in the base film 1002. The volume of this portion increases and heat capacity becomes large, so that a cycle of temperature change by irradiation of a pulse laser beam to the island-like semiconductor layer becomes gentle (as compared with other thin portion).Type: ApplicationFiled: July 24, 2003Publication date: July 22, 2004Applicant: Semiconductor Energy Laboratory Co., Ltd.Inventors: Ritsuko Kawasaki, Kenji Kasahara, Hisashi Ohtani
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Publication number: 20040124419Abstract: Protrusions called ridges are formed on the surface of a crystalline semiconductor film formed by a laser crystallization method or the like. A heat absorbing layer are formed below a semiconductor film. When the semiconductor film is crystallized by laser, a temperature difference is produced between a semiconductor film 1010 positioned above a heat absorbing layer 1011 and a semiconductor film 1013 of the other region to produce a difference in thermal expansion at the boundary of the outside end 1015 of the heat absorbing layer. This difference produces a strain to form a surface wave. The surface wave starting at the outer periphery of the heat absorbing layer is formed in the vicinity of the heat absorbing layer. When the semiconductor layer is solidified after it is melted, the protrusions of the surface wave remain as protrusions after the semiconductor film is solidified.Type: ApplicationFiled: December 18, 2003Publication date: July 1, 2004Applicant: Semiconductor Energy Laboratory Co., Ltd., a Japan corporationInventors: Setsuo Nakajima, Ritsuko Kawasaki
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Patent number: 6753212Abstract: To provide a laser apparatus and a laser annealing method with which a crystalline semiconductor film with a larger crystal grain size is obtained and which are low in their running cost. A solid state laser easy to maintenance and high in durability is used as a laser, and laser light emitted therefrom is linearized to increase the throughput and to reduce the production cost as a whole. Further, both the front side and the back side of an amorphous semiconductor film is irradiated with such laser light to obtain the crystalline semiconductor film with a larger crystal grain size.Type: GrantFiled: August 21, 2001Date of Patent: June 22, 2004Assignee: Semiconductor Energy Laboratory Co., Ltd.Inventors: Shunpei Yamazaki, Hisashi Ohtani, Koichiro Tanaka, Kenji Kasahara, Ritsuko Kawasaki
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Patent number: 6746901Abstract: To realize TFT enabling high-speed operation by fabricating a crystalline semiconductor film in which positions and sizes of crystal grains are controlled and using the crystalline semiconductor film in a channel forming region of TFT, a film thickness is stepped by providing a stepped difference in at least one layer of a matrix insulating film among a plurality of matrix insulating films having refractive indices different from each other. By irradiating laser beam from a rear face side of a substrate (or both sides of a surface side and the rear face side of the substrate), there is formed an effective intensity distribution of laser beam with regard to a semiconductor film and there is produced a temperature gradient in correspondence with a shape of the stepped difference and a distribution of the film thickness of the matrix insulating film in the semiconductor film.Type: GrantFiled: May 3, 2001Date of Patent: June 8, 2004Assignee: Semiconductor Energy Laboratory Co., Ltd.Inventors: Kenji Kasahara, Ritsuko Kawasaki, Hisashi Ohtani
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Patent number: 6744008Abstract: For crystallizing an amorphous semiconductor film by means of irradiation of laser beams, a top surface and a back surface of the amorphous semiconductor film are irradiated with the laser beams. In this case, an effective energy intensity Io of the laser beams to be applied onto the top surface and an effective energy intensity Io′ of the laser beams to be applied onto the back surface satisfy the relationship of 0<Io′/Io<1 or 1<Io′/Io. Thus, a laser annealing method capable of providing a crystalline semiconductor film with large grain diameters can be provided.Type: GrantFiled: August 17, 2000Date of Patent: June 1, 2004Assignee: Semiconductor Energy Laboratory Co., Ltd.Inventors: Kenji Kasahara, Ritsuko Kawasaki, Hisashi Ohtani, Koichiro Tanaka
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Publication number: 20040092061Abstract: The invention relates to a method for manufacturing a semiconductor device, and it is an object of the invention to form a semiconductor area formed in island-like patterns as a single crystal or an area which can be regarded as a single crystal, and to simultaneously achieve a laminated structure by which various characteristics of TFTs can be stabilized, wherein an insulation film is formed on a glass substrate, and island like semiconductor layer is formed thereon. A laser beam passed through a cylindrical lens is made into a linear laser beam and irradiated onto the island-like semiconductor layer by an optical system.Type: ApplicationFiled: August 27, 2003Publication date: May 13, 2004Applicant: Semiconductor Energy Laboratory Co., Ltd.Inventors: Ritsuko Kawasaki, Kenji Kasahara, Shunpei Yamazaki
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Patent number: 6730550Abstract: To provide a laser apparatus and a laser annealing method with which a crystalline semiconductor film with a larger crystal grain size is obtained and which are low in their running cost. A solid state laser easy to maintenance and high in durability is used as a laser, and laser light emitted therefrom is linearized to increase the throughput and to reduce the production cost as a whole. Further, both the front side and the back side of an amorphous semiconductor film is irradiated with such laser light to obtain the crystalline semiconductor film with a larger crystal grain size.Type: GrantFiled: August 10, 2000Date of Patent: May 4, 2004Assignee: Semiconductor Energy Laboratory Co., Ltd.Inventors: Shunpei Yamazaki, Hisashi Ohtani, Koichiro Tanaka, Kenji Kasahara, Ritsuko Kawasaki
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Publication number: 20040079952Abstract: In a semiconductor device including a laminate of a first insulating layer, a crystalline semiconductor layer, and a second insulating layer, characteristics of the device are improved by determining its structure in view of stress balance. In the semiconductor device including an active layer of the crystalline semiconductor layer having tensile stress on a substrate, tensile stress is given to the first insulating layer formed to be in close contact with a surface of the semiconductor layer at a substrate side, and compressive stress is given to the second insulating layer formed to be in close contact with a surface of the semiconductor layer at a side opposite to the substrate side.Type: ApplicationFiled: October 14, 2003Publication date: April 29, 2004Applicant: Semiconductor Energy LaboratoryInventors: Shunpei Yamazaki, Taketomi Asami, Toru Takayama, Ritsuko Kawasaki, Hiroki Adachi, Naoya Sakamoto, Masahiko Hayakawa, Hiroshi Shibata, Yasuyuki Arai
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Publication number: 20040063258Abstract: To realize TFT enabling high-speed operation by fabricating a crystalline semiconductor film in which positions and sizes of crystal grains are controlled and using the crystalline semiconductor film in a channel forming region of TFT, a film thickness is stepped by providing a stepped difference in at least one layer of a matrix insulating film among a plurality of matrix insulating films having refractive indices different from each other. By irradiating laser beam from a rear face side of a substrate (or both sides of a surface side and the rear face side of the substrate), there is formed an effective intensity distribution of laser beam with regard to a semiconductor film and there is produced a temperature gradient in correspondence with a shape of the stepped difference and a distribution of the film thickness of the matrix insulating film in the semiconductor film.Type: ApplicationFiled: October 6, 2003Publication date: April 1, 2004Applicant: Semiconductor Energy Laboratory Co., Ltd.Inventors: Kenji Kasahara, Ritsuko Kawasaki, Hisashi Ohtani
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Patent number: 6709902Abstract: The present invention provides a semiconductor device in which a bottom-gate TFT or an inverted stagger TFT arranged in each circuit is suitably constructed in conformity with the functionality of the respective circuits, thereby attaining an improvement in the operating efficiency and reliability of the semiconductor device. In the structure, LDD regions in a pixel TFT are arranged so as not to overlap with a channel protection insulating film and to overlap with a gate electrode by at least a portion thereof. LDD regions in an N-channel TFT of a drive circuit is arranged so as not to overlap with a channel protection insulating film and to overlap with a gate electrode by at least a portion thereof. LDD regions in a P-channel TFT of the drive circuit is arranged so as to overlap with a channel protection insulating film and to overlap with the gate electrode.Type: GrantFiled: January 4, 2002Date of Patent: March 23, 2004Assignee: Semiconductor Energy Laboratory Co., Ltd.Inventors: Hidehito Kitakado, Ritsuko Kawasaki, Kenji Kasahara
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Publication number: 20040026740Abstract: To improve the operation characteristic and reliability of a semiconductor device by optimizing the structure of bottom gate type or inverted stagger type TFTs arranged in circuits of the semiconductor device in accordance with the function of the respective circuits. At least LDD regions that overlap with a gate electrode are formed in an N channel type TFT of a driving circuit, and LDD regions that do not overlap with the gate electrode are formed in an N channel type TFT of a pixel matrix circuit. The concentration of the two kinds of LDD regions is differently set from each other, to thereby obtain the optimal circuit operation.Type: ApplicationFiled: August 4, 2003Publication date: February 12, 2004Applicant: Semiconductor Energy Laboratory Co., Ltd.Inventors: Ritsuko Kawasaki, Hidehito Kitakado, Kenji Kasahara, Shunpei Yamazaki
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Patent number: 6677221Abstract: In a semiconductor device employing a glass substrate, the object of the present invention is to provide a high performance semiconductor device with a large screen at low cost, which prevents the semiconductor device from being contaminated by impurities from the glass substrate. In a semiconductor device comprising a blocking film provided in contact with a glass substrate and TFTs provided on the blocking film, the blocking film is characterized by being made of a tantalum oxide film.Type: GrantFiled: June 10, 2002Date of Patent: January 13, 2004Assignees: Semiconductor Energy Laboratory Co., Ltd., Sharp Kabushiki KaishaInventors: Ritsuko Kawasaki, Hiroki Adachi, Kazuhide Tomiyasu, Hiroyuki Ogawa
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Patent number: 6653657Abstract: To provide a TFT that can operate at a high speed by forming a crystalline semiconductor film while controlling the position and the size of a crystal grain in the film to use the crystalline semiconductor film for a channel forming region of the TFT. Instead of a metal or a highly heat conductive insulating film, only a conventional insulating film is used as a base film to introduce a temperature gradient. A level difference of the base insulating film is provided in a desired location to generate the temperature distribution in the semiconductor film in accordance with the arrangement of the level difference. The starting point and the direction of lateral growth are controlled utilizing the temperature distribution.Type: GrantFiled: December 11, 2000Date of Patent: November 25, 2003Assignee: Semoconductor Energy Laboratory Co., Ltd.Inventors: Ritsuko Kawasaki, Kenji Kasahara, Hisashi Ohtani
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Patent number: 6645826Abstract: In a semiconductor device including a laminate of a first insulating layer, a crystalline semiconductor layer, and a second insulating layer, characteristics of the device are improved by determining its structure in view of stress balance. In the semiconductor device including an active layer of the crystalline semiconductor layer having tensile stress on a substrate, tensile stress is given to the first insulating layer formed to be in close contact with a surface of the semiconductor layer at a substrate side, and compressive stress is given to the second insulating layer formed to be in close contact with a surface of the semiconductor layer at a side opposite to the substrate side.Type: GrantFiled: March 7, 2002Date of Patent: November 11, 2003Assignee: Semiconductor Energy Laboratory Co., Ltd.Inventors: Shunpei Yamazaki, Taketomi Asami, Toru Takayama, Ritsuko Kawasaki, Hiroki Adachi, Naoya Sakamoto, Masahiko Hayakawa, Hiroshi Shibata, Yasuyuki Arai