Patents by Inventor Yoichiro Tarui
Yoichiro Tarui 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).
-
Publication number: 20110244643Abstract: A manufacturing method of a silicon carbide semiconductor device in which an electric field applied to a gate oxide film can be relaxed and thereby reliability can be ensured, and by the method manufacturing costs can be reduced. Well regions, channel regions, and gate electrodes are formed so that, given that extending lengths, with respect to the inner sides of source regions, of each of the well regions, the channel regions, and the gate electrodes are Lwell, Lch, and Lg, respectively, a relationship of Lch<Lg<Lwell is satisfied; and the channel regions are further formed by diffusing by activation annealing boron as a third impurity, having been implanted by activation annealing into the source regions, into a silicon carbide layer.Type: ApplicationFiled: June 20, 2011Publication date: October 6, 2011Applicant: MITSUBISHI ELECTRIC CORPORATIONInventor: Yoichiro TARUI
-
Patent number: 8026160Abstract: In a semiconductor device using a SiC substrate, a Junction Termination Edge (JTE) layer is hardly affected by fixed charge so that a stable dielectric strength is obtained. A semiconductor device according to a first aspect of the present invention includes a SiC epi-layer having n type conductivity, an impurity region in a surface of the SiC epi-layer and having p type conductivity, and JTE layers adjacent to the impurity region, having p type conductivity, and having a lower impurity concentration than the impurity region. The JTE layers are spaced by a distance from an upper surface of the SiC epi-layer, and SiC regions having n type conductivity are present on the JTE layers.Type: GrantFiled: May 9, 2006Date of Patent: September 27, 2011Assignee: Mitsubishi Electric CorporationInventors: Yoichiro Tarui, Ken-ichi Ohtsuka, Masayuki Imaizumi
-
Publication number: 20110223694Abstract: A wafer WF is mounted in a substrate holder, and the substrate holder is placed in a film forming furnace. The film forming furnace is evacuated by a vacuum pump through a gas discharge part to remove remaining oxygen as completely as possible. Then, a temperature in the film forming furnace is heated to a range of 800° C. to 950° C. under reduced pressure while an inert gas such as Ar or helium (He) is being introduced through a gas introduction part. When the temperature reaches this temperature range, an inflow of the inert gas is stopped. Vaporized ethanol is introduced as a source gas into the film forming furnace through the gas introduction part, thus forming a graphite film on an entire surface of the wafer WF.Type: ApplicationFiled: December 7, 2010Publication date: September 15, 2011Applicant: MITSUBISHI ELECTRIC CORPORATIONInventors: Yukio UDA, Koichi SEKIYA, Kazuo KOBAYASHI, Yoichiro TARUI
-
Publication number: 20110195563Abstract: A method of manufacturing a silicon carbide semiconductor device according to the present invention includes the steps of (a) forming an implantation mask made up of a plurality of unit masks on a silicon carbide semiconductor layer, and (b) implanting predetermined ion in the silicon carbide semiconductor layer at a predetermined implantation energy by using the implantation mask. In the step (a), the implantation mask is formed such that a length from any point in the unit mask to an end of the unit mask can be equal to or less than a scattering length obtained when the predetermined ion is implanted in silicon carbide at the predetermined implantation energy and the implantation mask can have a plurality of regions different from each other in terms of a size and an arrangement interval of the unit masks.Type: ApplicationFiled: October 6, 2010Publication date: August 11, 2011Applicant: MITSUBISHI ELECTRIC CORPORATIONInventors: Koji Okuno, Yoichiro Tarui
-
Publication number: 20110193100Abstract: A method of manufacturing an SiC semiconductor device according to the present invention includes the steps of (a) by using a single mask, etching regions of an SiC semiconductor layer which serve as an impurities implantation region and a mark region, to form recesses, (b) by using the same mask as in the step (a), performing ion-implantation in the recesses of the regions which serve as the impurities implantation region and the mark region, at least from an oblique direction relative to a surface of the SiC semiconductor layer and (c) positioning another mask based on the recess of the region which serves as the impurities implantation region or the mark region, and performing well implantation in a region containing the impurities implantation region.Type: ApplicationFiled: October 25, 2010Publication date: August 11, 2011Applicant: MITSUBISHI ELECTRIC CORPORATIONInventors: Noriaki TSUCHIYA, Yoichiro Tarui
-
Publication number: 20110147766Abstract: A method of manufacturing a silicon carbide semiconductor device is provided that includes a step of forming in a surface of a silicon carbide wafer of first conductivity type a first region of second conductivity type having a predetermined space thereinside by ion-implanting aluminum as a first impurity and boron as a second impurity; a step of forming a JTE region in the surface of the silicon carbide wafer from the first region by diffusing the boron ion-implanted in the first region toward its neighboring zones by an activation annealing treatment; a step of forming a first electrode on the surface of the silicon carbide wafer at the space inside the first region and at an inner part of the first region; and a step of forming a second electrode on the opposite surface of the silicon carbide wafer. Thereby, a JTE region can be formed that has a wide range of impurity concentration and a desired breakdown voltage without increasing the number of steps of the manufacturing process.Type: ApplicationFiled: February 28, 2011Publication date: June 23, 2011Applicant: MITSUBISHI ELECTRIC CORPORATIONInventor: Yoichiro TARUI
-
Patent number: 7939943Abstract: 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: GrantFiled: November 11, 2008Date of Patent: May 10, 2011Assignee: Mitsubishi Electric CorporationInventors: Katsuomi Shiozawa, Kyozo Kanamoto, Toshiyuki Oishi, Hiroshi Kurokawa, Kenichi Ohtsuka, Yoichiro Tarui, Yasunori Tokuda
-
Publication number: 20110095301Abstract: There was a problem that it was difficult to manufacture silicon carbide semiconductor devices with suppressed variations in characteristics without increasing the number of process steps. A silicon carbide semiconductor device according to the present invention includes an N type SiC substrate and an N type SiC epitaxial layer as a silicon carbide semiconductor substrate of a first conductivity type, a plurality of recesses intermittently formed in a surface of the N type SiC epitaxial layer, P type regions as second-conductivity-type semiconductor layers formed in the N type SiC epitaxial layer in the bottoms of the plurality of recesses, and a Schottky electrode selectively formed over the surface of the N type SiC epitaxial layer, wherein the plurality of recesses all have an equal depth.Type: ApplicationFiled: June 22, 2010Publication date: April 28, 2011Applicant: MITSUBISHI ELECTRIC CORPORATIONInventor: Yoichiro TARUI
-
Patent number: 7919403Abstract: A method of manufacturing a silicon carbide semiconductor device is provided that includes a step of forming in a surface of a silicon carbide wafer of first conductivity type a first region of second conductivity type having a predetermined space thereinside by ion-implanting aluminum as a first impurity and boron as a second impurity; a step of forming a JTE region in the surface of the silicon carbide wafer from the first region by diffusing the boron ion-implanted in the first region toward its neighboring zones by an activation annealing treatment; a step of forming a first electrode on the surface of the silicon carbide wafer at the space inside the first region and at an inner part of the first region; and a step of forming a second electrode on the opposite surface of the silicon carbide wafer. Thereby, a JTE region can be formed that has a wide range of impurity concentration and a desired breakdown voltage without increasing the number of steps of the manufacturing process.Type: GrantFiled: November 30, 2009Date of Patent: April 5, 2011Assignee: Mitsubishi Electric CorporationInventor: Yoichiro Tarui
-
Publication number: 20100314629Abstract: In order to obtain a silicon carbide semiconductor device that ensures both stability of withstand voltage and reliability in high-temperature operations in its termination end-portion provided for electric-field relaxation in the perimeter of a cell portion driven as a semiconductor element, the termination end-portion is provided with an inorganic protection film having high heat resistance that is formed on an exposed surface of a well region as a first region formed on a side of the cell portion, and an organic protection film having a high electrical insulation capability with a little influence by electric charges that is formed on a surface of an electric-field relaxation region formed in contact relation to an outer lateral surface of the well region and apart from the cell portion, and on an exposed surface of the silicon carbide layer.Type: ApplicationFiled: February 12, 2008Publication date: December 16, 2010Applicant: MITSUBISHI ELECTRIC CORPORATIONInventors: Yoichiro Tarui, Kenichi Ohtsuka, Naruhisa Miura, Yoshinori Matsuno, Masayuki Imaizumi
-
Publication number: 20100289110Abstract: A semiconductor device using one or more guard rings includes a p-type guard ring region surrounding a pn junction region, an insulating film covering the p-type guard ring region, one or more conductive films electrically connected with the p-type guard ring region through one or more contact holes made in the insulating film, and a semi-insulating film covering the insulating film and the conductive films. Thus, a desired breakdown voltage characteristic can be ensured even if a foreign matter or the like adheres to a surface of the conductive films.Type: ApplicationFiled: December 31, 2009Publication date: November 18, 2010Applicant: MITSUBISHI ELECTRIC CORPORATIONInventors: Yoichiro TARUI, Atsushi Narazaki, Ryoichi Fujii
-
Publication number: 20100291762Abstract: A method of manufacturing a silicon carbide semiconductor device is provided that includes a step of forming in a surface of a silicon carbide wafer of first conductivity type a first region of second conductivity type having a predetermined space thereinside by ion-implanting aluminum as a first impurity and boron as a second impurity; a step of forming a JTE region in the surface of the silicon carbide wafer from the first region by diffusing the boron ion-implanted in the first region toward its neighboring zones by an activation annealing treatment; a step of forming a first electrode on the surface of the silicon carbide wafer at the space inside the first region and at an inner part of the first region; and a step of forming a second electrode on the opposite surface of the silicon carbide wafer. Thereby, a JTE region can be formed that has a wide range of impurity concentration and a desired breakdown voltage without increasing the number of steps of the manufacturing process.Type: ApplicationFiled: November 30, 2009Publication date: November 18, 2010Applicant: MITSUBISHI ELECTRIC CORPORATIONInventor: Yoichiro TARUI
-
Publication number: 20100258815Abstract: An objective is to provide a manufacturing method of a silicon carbide semiconductor device in which an electric field applied to a gate oxide film can be relaxed and thereby reliability can be ensured, and by the manufacturing method increase of the manufacturing cost can also be prevented as much as possible. Well regions, channel regions, and gate electrodes are formed so that, given that extending lengths, with respect to the inner sides of source regions, of each of the well regions, the channel regions, and the gate electrodes are Lwell, Lch, and Lg, respectively, a relationship of Lch<Lg<Lwell is satisfied; and the channel regions are further formed by diffusing by activation annealing boron as a third impurity, having been implanted by activation annealing into the source regions, into a silicon carbide layer.Type: ApplicationFiled: November 19, 2009Publication date: October 14, 2010Applicant: MITSUBISHI ELECTRIC CORPORATIONInventor: Yoichiro TARUI
-
Patent number: 7678597Abstract: 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: GrantFiled: November 26, 2008Date of Patent: March 16, 2010Assignee: Mitsubishi Electric CorporationInventors: Kenichi Ohtsuka, Yoichiro Tarui, Yosuke Suzuki, Katsuomi Shiozawa, Kyozo Kanamoto, Toshiyuki Oishi, Yasunori Tokuda, Tatsuo Omori
-
Publication number: 20090261348Abstract: In a semiconductor device using a SiC substrate, a Junction Termination Edge (JTE) layer is hardly affected by fixed charge so that a stable dielectric strength is obtained. A semiconductor device according to a first aspect of the present invention includes a SiC epi-layer having n type conductivity, an impurity region in a surface of the SiC epi-layer and having p type conductivity, and JTE layers adjacent to the impurity region, having p type conductivity, and having a lower impurity concentration than the impurity region. The JTE layers are spaced by a distance from an upper surface of the SiC epi-layer, and SiC regions having n type conductivity are present on the JTE layers.Type: ApplicationFiled: May 9, 2006Publication date: October 22, 2009Applicant: MITSUBISHI ELECTRIC CORPORATIONInventors: Yoichiro Tarui, Ken-ichi Ohtsuka, Masayuki Imaizumi
-
Publication number: 20090250705Abstract: A p base ohmic contact of a silicon carbide semiconductor device consists of a p++ layer formed by high-concentration ion implantation and a metal electrode. Since the high-concentration ion implantation performed at the room temperature significantly degrades the crystal of the p++ layer to cause a process failure, a method for implantation at high temperatures is used. In terms of switching loss and the like of devices, it is desirable that the resistivity of the p base ohmic contact should be lower. In well-known techniques, nothing is mentioned on a detailed relation among the ion implantation temperature, the ohmic contact resistivity and the process failure. Then, in the ion implantation step, the temperature of a silicon carbide wafer is maintained in a range from 175° C. to 300° C., more preferably in a range from 175° C. to 200° C. The resistivity of the p base ohmic contact using a p++ region formed by ion implantation at a temperature in a range from 175° C. to 300° C.Type: ApplicationFiled: November 7, 2008Publication date: October 8, 2009Applicant: MITSUBISHI ELECTRIC CORPORATIONInventors: Tomokatsu WATANABE, Sunao Aya, Naruhisa Miura, Keiko Sakai, Shohei Yoshida, Toshikazu Tanioka, Yukiyasu Nakao, Yoichiro Tarui, Masayuki Imaizumi
-
Patent number: 7564072Abstract: A semiconductor device includes an anode electrode in Schottky contact with an n-type drift layer formed in an SiC substrate and a JTE region formed outside the anode electrode. The JTE region is made up of a first p-type zone formed in an upper portion of the drift layer under an edge of the anode electrode and a second p-type zone formed outside the first p-type zone having a lower surface impurity concentration than the first p-type zone. The second p-type zone is provided 15 ?m or more outwardly away from the edge of the anode electrode. The surface impurity concentration of the first p-type zone ranges from 1.8×1013 to 4×1013 cm?2, and that of the second p-type zone ranges from 1×1013 to 2.5×1013 cm?2.Type: GrantFiled: June 2, 2005Date of Patent: July 21, 2009Assignee: Mitsubishi Denki Kabushiki KaishaInventors: Kenichi Ohtsuka, Yoichiro Tarui, Yoshinori Matsuno, Kenichi Kuroda, Hiroshi Sugimoto
-
Publication number: 20090170304Abstract: 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: ApplicationFiled: December 18, 2008Publication date: July 2, 2009Applicant: MITSUBISHI ELECTRIC CORPORATIONInventors: Yoichiro Tarui, Kenichi Ohtsuka, Yosuke Suzuki, Katsuomi Shiozawa, Kyozo Kanamoto, Toshiyuki Oishi, Yasunori Tokuda, Tatsuo Omori
-
Publication number: 20090160054Abstract: 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: ApplicationFiled: November 13, 2008Publication date: June 25, 2009Applicant: MITSUBISHI ELECTRIC CORPORATIONInventors: Katsuomi Shiozawa, Kyozo Kanamoto, Toshiyuki Oishi, Yoichiro Tarui, Yasunori Tokuda
-
Publication number: 20090142871Abstract: 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: ApplicationFiled: November 26, 2008Publication date: June 4, 2009Applicant: MITSUBISHI ELECTRIC CORPORATIONInventors: Kenichi Ohtsuka, Yoichiro Tarui, Yosuke Suzuki, Katsuomi Shiozawa, Kyozo Kanamoto, Toshiyuki Oishi, Yasunori Tokuda, Tatsuo Omori