Patents by Inventor Tomohiko Ohta
Tomohiko Ohta 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: 20060174819Abstract: The present invention is a method for producing a single crystal of which a whole plane in a radial direction is a defect-free region with pulling the single crystal from a raw material melt in a chamber by Czochralski method, wherein a pulling condition is changed in a direction of the crystal growth axis during pulling the single crystal so that a margin of a pulling rate is always a predetermined value or more that the single crystal of which the whole plane in a radial direction is a defect-free region can be pulled. Thereby, there can be provided a method for producing a single crystal in which when a single crystal is produced by CZ method, the single crystal of which a whole plane in a radial direction is a defect-free region entirely in a direction of the crystal growth axis can be produced with stability.Type: ApplicationFiled: May 27, 2004Publication date: August 10, 2006Applicant: SHIN-ETSU HANDOTAI CO., LTD.Inventors: Nobuaki Mitamura, Tomohiko Ohta, Izumi Fusegawa, Masahiro Sakurada, Atsushi Ozaki
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Patent number: 7078203Abstract: The present invention provides isolated polynucleotide sequences encoding the proteins ROC1 and ROC2, the isolated proteins themselves, expression vectors containing at least a fragment of the ROC1 and ROC2 polynucleotide sequences, and host cells comprising the same. Methods of producing the ROC1 and ROC2 proteins are also disclosed, and methods of detecting the polynucleotides in samples are included in this invention, as are antibodies to the ROC1 and ROC2 proteins and antisense molecules complementary to polynucleotides encoding the same. The present invention further includes methods for screening bioactive agents that are capable of binding to a ROC protein, methods of screening bioactive agents capable of interfering with the binding of ROC proteins, and methods of screening bioactive agents capable of modulating the activity of a ROC protein. Such screening methods are capable of identifying compounds that have pharmacological.Type: GrantFiled: March 31, 2000Date of Patent: July 18, 2006Assignee: The University of North Carolina at Chapel HillInventors: Yue Xiong, Tomohiko Ohta
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Publication number: 20050252441Abstract: In a method for producing a silicon single crystal by Czochralski method, the single crystal is grown with controlling a growth rate between a growth rate at a boundary where a defect region detected by Cu deposition remaining after disappearance of OSF ring disappears when gradually decreasing a growth rate of silicon single crystal during pulling and a growth rate at a boundary where a high oxygen precipitation Nv region having a density of BMDs of 1×107 numbers/cm3 or more and/or a wafer lifetime of 30 ?sec or less after oxygen precipitation treatment disappears when gradually decreasing the growth rate further. Thereby, there is provided a silicon single crystal which does not belong to any of V region rich in vacancy, OSF region and I region rich in interstitial silicon, and has excellent electrical characteristics and gettering capability, so that yield of devices can be surely improved, and also an epitaxial wafer.Type: ApplicationFiled: May 7, 2003Publication date: November 17, 2005Inventors: Masahiro Sakurada, Nobuaki Mitamura, Izumi Fusegawa, Tomohiko Ohta
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Publication number: 20050160966Abstract: The present invention is a method of manufacturing a silicon single crystal by Czochralski method without performing Dash Necking method, wherein a temperature variation at a surface of a silicon melt is kept at ±5° C. or less at least for a period from a point of bringing the tip end of a seed crystal into contact with the silicon melt to a point of shifting to pull the single crystal.Type: ApplicationFiled: April 23, 2003Publication date: July 28, 2005Applicant: SHIN-ETSU HANDOTAI CO., LTDInventors: Izumi Fusegawa, Sadayuki Okuni, Nobuaki Mitamura, Tomohiko Ohta, Nobuo Katuoka
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Patent number: 6913646Abstract: There can be provided a silicon single crystal wafer grown according to Czochralski method wherein the whole plane of the wafer is occupied by N region on the outside of OSF generated in a shape of a ring by thermal oxidation treatment and there exists no defect region detected by Cu deposition. Thereby, there can be produced a silicon single crystal wafer according to CZ method, which does not belong to any of V region rich in vacancies, OSF region and I region rich in interstitial silicons, and can surely improve electric characteristics such as oxide dielectric breakdown voltage characteristics or the like under stable manufacture conditions.Type: GrantFiled: December 26, 2001Date of Patent: July 5, 2005Assignee: Shin-Etsu Handotai Co., Ltd.Inventors: Masahiro Sakurada, Takeshi Kobayashi, Tatsuo Mori, Izumi Fusegawa, Tomohiko Ohta
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Patent number: 6893499Abstract: According to the present invention, there is disclosed a silicon single crystal wafer grown according to the CZ method which is a wafer having a diameter of 200 mm or more produced from a single crystal grown at a growth rate of 0.5 mm/min or more without doping except for a dopant for controlling resistance, wherein neither an octahedral void defect due to vacancies nor a dislocation cluster due to interstitial silicons exists as a grown-in defect, and a method for producing it.Type: GrantFiled: June 28, 2001Date of Patent: May 17, 2005Assignee: Shin-Etsu Handotai Co., Ltd.Inventors: Izumi Fusegawa, Koji Kitagawa, Ryoji Hoshi, Masahiro Sakurada, Tomohiko Ohta
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Publication number: 20050081779Abstract: The present invention provides a heater for manufacturing a crystal by the Czochralski method comprising at least terminal portions supplied with current and a heat generating portion by resistance heating, and being arranged so as to surround a crucible containing a raw material melt, wherein the heater has a uniform heat generation distribution to the raw material melt after deformation while in use during crystal manufacture. It is thus possible to prevent hindrance of monocrystallization and unstable crystal quality caused by ununiform temperature in the raw material melt due to deformation of the shape of the heater's heat generating portion while in use during crystal manufacture.Type: ApplicationFiled: September 8, 2003Publication date: April 21, 2005Inventors: Susumu Sonokawa, Ryoji Hoshi, Wataru Sato, Tomohiko Ohta
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Publication number: 20050064632Abstract: In a method for producing an SOI wafer comprising steps of implanting hydrogen ions etc. from a surface of a bond wafer 21 to form an ion-implanted layer 24 inside the wafer, bonding the ion-implanted surface of the bond wafer and a surface of a base wafer 22 via an oxide film 23 or directly, and forming an SOI wafer by delaminating a part of the bond wafer at the ion-implanted layer by heat treatment, wherein a silicon wafer consisting of silicon single crystal grown by Chochralski method, which is occupied by N region outside OSF generated in a ring shape and has no defect region detected by Cu deposition method, is used as the bond wafer. Thereby, even in the case of forming an extremely thin SOI layer 27 such that, for example, its thickness is 200 nm or less, there is provided an SOI wafer which has an excellent electric property without causing micro pits by cleaning with hydrofluoric acid etc., and in addition, can be produced without increasing the number of process.Type: ApplicationFiled: October 24, 2003Publication date: March 24, 2005Inventors: Masahiro Sakurada, Nobuaki Mitamura, Izumi Fusegawa, Tomohiko Ohta
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Patent number: 6764548Abstract: The present invention provides an apparatus and a method for producing a silicon semiconductor single crystal which can stabilize and homogenize an amount of precipitated oxygen in the direction of the crystal growth axis when growing a silicon semiconductor single crystal. The apparatus for producing a silicon semiconductor single crystal by the Czochralski method comprises a main growth furnace having a crucible retaining silicon melt disposed therein for growing a silicon semiconductor single crystal, and an upper growth furnace for housing therein and cooling the silicon semiconductor single crystal pulled from the silicon melt, wherein the upper growth furnace communicated to a ceiling section of the main growth furnace is provided with an upper insulating member for surrounding a pulled silicon semiconductor single crystal.Type: GrantFiled: August 20, 2002Date of Patent: July 20, 2004Assignee: Shin-Etsu Handotai Co., Ltd.Inventors: Ryoji Hoshi, Takahiro Yanagimachi, Izumi Fusegawa, Tomohiko Ohta, Yuuichi Miyahara, Tetsuya Igarashi
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Patent number: 6632411Abstract: The present invention provides a silicon wafer sliced from a silicon single crystal ingot grown by the Czochralski method under such conditions that V-rich region should become dominant, wherein count number of particles having a size of 0.1 &mgr;m or more is 1 count/cm2 or less when particles are counted by using a particle counter and a method for producing a silicon single crystal. Thus, there is provided a production technique that can improve productivity and reduce cost for high quality silicon wafers of excellent device characteristics by further reducing density and size of defects such as COP.Type: GrantFiled: November 23, 2001Date of Patent: October 14, 2003Assignee: Shin-Etsu Handotai Co., Ltd.Inventors: Ryoji Hoshi, Izumi Fusegawa, Tomohiko Ohta, Shigemaru Maeda
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Patent number: 6632280Abstract: An apparatus for growing a single crystal (20) comprising at least a main chamber (1) enclosing a crucible (5, 6) for accommodating a raw material melt (4) and a heater (7) for heating the raw material melt and a pulling chamber (2) continuously provided above the main chamber, into which a grown single crystal is pulled and stored, wherein the apparatus further comprises a cooling cylinder (11) that extends at least from a ceiling of the main chamber toward a raw material melt surface so as to surround a single crystal under pulling (3) and is forcibly cooled with a cooling medium, and an auxiliary cooling member (13) extending below the cooling cylinder and having a cylindrical shape or a shape tapered toward the downward direction. There is provided an apparatus for growing a single crystal that can exert cooling effect on a grown single crystal to the maximum extent so as to accelerate the crystal growth rate and safely produce a single crystal without leakage of cooling medium due to breakage etc.Type: GrantFiled: September 21, 2001Date of Patent: October 14, 2003Assignee: Shin-Etsu Handotai Co., Ltd.Inventors: Ryoji Hoshi, Koji Kitagawa, Izumi Fusegawa, Tomohiko Ohta
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Patent number: 6605152Abstract: The present invention provides a catch pan for melt leakage provided under a crucible at a bottom portion of a chamber in a single crystal pulling apparatus based on the CZ method, wherein the catch pan for melt leakage comprises at least a bottom portion and a barrel portion, and the bottom portion and the barrel portion are connected by screw-fitting or by using a tap bolt. There is provided a catch pan for melt leakage provided in a single crystal pulling apparatus, which can, even if a melt flows out of the crucible by a certain possible cause in a CZ method single crystal pulling apparatus, prevent the melt flowed out from reaching lower mechanisms including metal parts, piping and so forth, and thereby prevent bad influences on operators and peripheral equipments.Type: GrantFiled: October 31, 2001Date of Patent: August 12, 2003Assignee: Shin-Etsu Handotai Co., Ltd.Inventors: Koji Mizuishi, Tomohiko Ohta
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Patent number: 6592662Abstract: In a method manufacturing a silicon single crystal 8 according to an MCZ method, a flow rate of an inert gas flowing in a growth furnace 1 during growth of the silicon single crystal 8 and/or a pressure in the growth furnace 1 is altered according to a pulling amount of the silicon single crystal 8 to adjust an interstitial oxygen concentration therein. By altering a flow rate of an inert gas flowing in the growth furnace or a pressure therein, an amount of oxygen evaporating as an oxide from a surface of a silicon melt 10 in the vicinity of a crystal growth interface can be easily adjusted, and thereby, an oxygen amount included in the silicon melt 10 can be controlled with ease.Type: GrantFiled: October 24, 2001Date of Patent: July 15, 2003Assignee: Shin-Etsu Handotai Co., Ltd.Inventors: Izumi Fusegawa, Ryoji Hoshi, Kouichi Inokoshi, Tomohiko Ohta
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Publication number: 20030116082Abstract: There can be provided a silicon single crystal wafer grown according to Czochralski method wherein the whole plane of the wafer is occupied by N region on the outside of OSF generated in a shape of a ring by thermal oxidation treatment and there exists no defect region detected by Cu deposition. Thereby, there can be produced a silicon single crystal wafer according to CZ method, which does not belong to any of V region rich in vacancies, OSF region and I region rich in interstitial silicons, and can surely improve electric characteristics such as oxide dielectric breakdown voltage characteristics or the like under stable manufacture conditions.Type: ApplicationFiled: August 27, 2002Publication date: June 26, 2003Inventors: Masahiro Sakurada, Takeshi Kobayashi, Tatsuo Mori, Izumi Fusegawa, Tomohiko Ohta
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Publication number: 20030106484Abstract: According to the present invention, there is disclosed a silicon single crystal wafer grown according to the CZ method which is a wafer having a diameter of 200 mm or more produced from a single crystal grown at a growth rate of 0.5 mm/min or more without doping except for a dopant for controlling resistance, wherein neither an octahedral void defect due to vacancies nor a dislocation cluster due to interstitial silicons exists as a grown-in defect, and a method for producing it.Type: ApplicationFiled: December 26, 2002Publication date: June 12, 2003Inventors: Izumi Fusegawa, Koji Kitagawa, Ryoji Hoshi, Masahiro Sakurada, Tomohiko Ohta
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Patent number: 6565822Abstract: An epitaxial silicon wafer, which has no projections having a size of 100 nm or more and a height of 5 nm or more on an epitaxial layer, and a method for producing an epitaxial silicon wafer, wherein a single crystal ingot containing no I-region is grown when a silicon single crystal is grown by the CZ method, and an epitaxial layer is deposited on a silicon wafer sliced from the single crystal ingot and containing no I-region for the entire surface. An epitaxial wafer of high quality with no projection-like surface distortion observed as particles on an epi-layer surface is provided by forming a wafer having no I-region for the entire surface from a single crystal and depositing an epitaxial layer thereon, and a single crystal having no I-region for entire plane is produced with good yield and high productivity, thereby improving productivity of epi-wafers and realizing cost reduction.Type: GrantFiled: September 21, 2000Date of Patent: May 20, 2003Assignee: Shin-Etsu Handotai Co., Ltd.Inventors: Ryoji Hoshi, Susumu Sonokawa, Masahiro Sakurada, Tomohiko Ohta, Izumi Fusegawa
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Publication number: 20030089300Abstract: The present invention provides an apparatus and a method for producing a silicon semiconductor single crystal which can stabilize and homogenize an amount of precipitated oxygen in the direction of the crystal growth axis when growing a silicon semiconductor single crystal. The apparatus for producing a silicon semiconductor single crystal by the Czochralski method comprises a main growth furnace having a crucible retaining silicon melt disposed therein for growing a silicon semiconductor single crystal, and an upper growth furnace for housing therein and cooling the silicon semiconductor single crystal pulled from the silicon melt, wherein the upper growth furnace communicated to a ceiling section of the main growth furnace is provided with an upper insulating member for surrounding a pulled silicon semiconductor single crystal.Type: ApplicationFiled: August 20, 2002Publication date: May 15, 2003Inventors: Ryoji Hoshi, Takahiro Yanagimachi, Izumi Fusegawa, Tomohiko Ohta, Yuuichi Miyahara, Tetsuya Igarashi
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Publication number: 20030070605Abstract: An apparatus for growing a single crystal (20) comprising at least a main chamber (1) enclosing a crucible (5, 6) for accommodating a raw material melt (4) and a heater (7) for heating the raw material melt and a pulling chamber (2) continuously provided above the main chamber, into which a grown single crystal is pulled and stored, wherein the apparatus further comprises a cooling cylinder (11) that extends at least from a ceiling of the main chamber toward a raw material melt surface so as to surround a single crystal under pulling (3) and is forcibly cooled with a cooling medium, and an auxiliary cooling member (13) extending below the cooling cylinder and having a cylindrical shape or a shape tapered toward the downward direction. There is provided an apparatus for growing a single crystal that can exert cooling effect on a grown single crystal to the maximum extent so as to accelerate the crystal growth rate and safely produce a single crystal without leakage of cooling medium due to breakage etc.Type: ApplicationFiled: September 21, 2001Publication date: April 17, 2003Inventors: Ryoji Hoshi, Koji Kitagawa, Izumi Fusegawa, Tomohiko Ohta
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Patent number: 6482260Abstract: There is disclosed a method for producing a silicon single crystal in accordance with the Czochralski method wherein a crystal is pulled with controlling a temperature in a furnace so that &Dgr;G may be 0 or a negative value, where &Dgr;G is a difference between the temperature gradient Gc (°C./mm) at the center of a crystal and the temperature gradient Ge (°C./mm) at the circumferential portion of the crystal, namely &Dgr;G=(Ge−Gc), wherein G is a temperature gradient in the vicinity of a solid-liquid interface of a crystal from the melting point of silicon to 1400° C.Type: GrantFiled: November 30, 2000Date of Patent: November 19, 2002Assignee: Shin-Etsu Handotai Co., Ltd.Inventors: Masahiro Sakurada, Hideki Yamanaka, Tomohiko Ohta
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Publication number: 20020157600Abstract: In a method manufacturing a silicon single crystal 8 according to an MCZ method, a flow rate of an inert gas flowing in a growth furnace 1 during growth of the silicon single crystal 8 and/or a pressure in the growth furnace 1 is altered according to a pulling amount of the silicon single crystal 8 to adjust an interstitial oxygen concentration therein. By altering a flow rate of an inert gas flowing in the growth furnace or a pressure therein, an amount of oxygen evaporating as an oxide from a surface of a silicon melt 10 in the vicinity of a crystal growth interface can be easily adjusted, and thereby, an oxygen amount included in the silicon melt 10 can be controlled with ease.Type: ApplicationFiled: October 24, 2001Publication date: October 31, 2002Inventors: Izumi Fusegawa, Ryoji Hoshi, Kouichi Inokoshi, Tomohiko Ohta