Patents Assigned to Sixpoint Materials, Inc.
  • Patent number: 11767609
    Abstract: GaN wafers and bulk crystal have dislocation density approximately 1/10 of dislocation density of seed used to form the bulk crystal and wafers. Masks are formed selectively on GaN seed dislocations, and new GaN grown on the seed has fewer dislocations and often 1/10 or less of dislocations present in seed.
    Type: Grant
    Filed: May 3, 2021
    Date of Patent: September 26, 2023
    Assignee: SixPoint Materials, Inc.
    Inventor: Tadao Hashimoto
  • Patent number: 11742800
    Abstract: The present invention provides a terahertz oscillator utilizing a GaN Gunn diode. A terahertz wave is generated in the active layer of the Gunn diode fabricated on GaN substrate. A GaN substrate is designed to act as a waveguide of the terahertz wave. Since the waveguide and the Gunn diodes are integrated, the terahertz wave generated in the active layer couples well with the waveguide made of the GaN substrates. The terahertz wave is emitted from the edge of the waveguide efficiently. To ensure high-reliability through reduction of radiation loss and mitigation of electromigration of anode metal, a GaN substrate with low dislocation density is used. The dislocation density of the GaN substrate is less than 1×106 cm?2. Particularly, usage of a GaN substrate made by the ammonothermal method is preferred.
    Type: Grant
    Filed: November 18, 2022
    Date of Patent: August 29, 2023
    Assignee: SixPoint Materials, Inc.
    Inventor: Tadao Hashimoto
  • Patent number: 10355115
    Abstract: The present invention discloses an electronic device formed of a group III nitride. In one embodiment, a substrate is fabricated by the ammonothermal method and a drift layer is fabricated by hydride vapor phase epitaxy. After etching a trench, p-type contact pads are made by pulsed laser deposition followed by n-type contact pads by pulsed laser deposition. The bandgap of the p-type contact pad is designed larger than that of the drift layer. Upon forward bias between p-type contact pads (gate) and n-type contact pads (source), holes and electrons are injected into the drift layer from the p-type contact pads and n-type contact pads. Injected electrons drift to the backside of the substrate (drain).
    Type: Grant
    Filed: October 27, 2017
    Date of Patent: July 16, 2019
    Assignee: SixPoint Materials, Inc.
    Inventors: Tadao Hashimoto, Daisuke Ueda
  • Patent number: 10354863
    Abstract: In one instance, the seed crystal of this invention provides a nitrogen-polar c-plane surface of a GaN layer supported by a metallic plate. The coefficient of thermal expansion of the metallic plate matches that of GaN layer. The GaN layer is bonded to the metallic plate with bonding metal. The bonding metal not only bonds the GaN layer to the metallic plate but also covers the entire surface of the metallic plate to prevent corrosion of the metallic plate and optionally spontaneous nucleation of GaN on the metallic plate during the bulk GaN growth in supercritical ammonia. The bonding metal is compatible with the corrosive environment of ammonothermal growth.
    Type: Grant
    Filed: September 26, 2017
    Date of Patent: July 16, 2019
    Assignee: SixPoint Materials, Inc.
    Inventors: Tadao Hashimoto, Edward Letts, Daryl Key
  • Patent number: 10316431
    Abstract: The present invention provides a method of growing an ingot of group III nitride. Group III nitride crystals such as GaN are grown by the ammonothermal method on both sides of a seed to form an ingot and the ingot is sliced into wafers. The wafer including the first-generation seed is sliced thicker than the other wafers so that the wafer including the first-generation seed does not break. The wafer including the first-generation seed crystal can be used as a seed for the next ammonothermal growth.
    Type: Grant
    Filed: October 20, 2015
    Date of Patent: June 11, 2019
    Assignees: SixPoint Materials, Inc., Seoul Semiconductor Co., Ltd.
    Inventors: Tadao Hashimoto, Edward Letts, Sierra Hoff
  • Patent number: 10287709
    Abstract: In one instance, the seed crystal of this invention provides a nitrogen-polar c-plane surface of a GaN layer supported by a metallic plate. The coefficient of thermal expansion of the metallic plate matches that of GaN layer. The GaN layer is bonded to the metallic plate with bonding metal. The bonding metal not only bonds the GaN layer to the metallic plate but also covers the entire surface of the metallic plate to prevent corrosion of the metallic plate and optionally spontaneous nucleation of GaN on the metallic plate during the bulk GaN growth in supercritical ammonia. The bonding metal is compatible with the corrosive environment of ammonothermal growth.
    Type: Grant
    Filed: September 26, 2017
    Date of Patent: May 14, 2019
    Assignee: SixPoint Materials, Inc.
    Inventors: Tadao Hashimoto, Edward Letts, Daryl Key
  • Patent number: 10242868
    Abstract: In one instance, the seed crystal of this invention provides a nitrogen-polar c-plane surface of a GaN layer supported by a metallic plate. The coefficient of thermal expansion of the metallic plate matches that of GaN layer. The GaN layer is bonded to the metallic plate with bonding metal. The bonding metal not only bonds the GaN layer to the metallic plate but also covers the entire surface of the metallic plate to prevent corrosion of the metallic plate and optionally spontaneous nucleation of GaN on the metallic plate during the bulk GaN growth in supercritical ammonia. The bonding metal is compatible with the corrosive environment of ammonothermal growth.
    Type: Grant
    Filed: September 26, 2017
    Date of Patent: March 26, 2019
    Assignee: SixPoint Materials, Inc.
    Inventors: Tadao Hashimoto, Edward Letts, Daryl Key
  • Patent number: 10161059
    Abstract: In one instance, the invention provides a bulk crystal of group III nitride having a thickness of more than 1 mm without cracking above the sides of a seed crystal. This bulk group III nitride crystal is expressed as Gax1Aly1In1-x1-y1N (0?x1?1, 0?x1+y1?1) and the seed crystal is expressed as Gax2Aly2In1-x2-y2N (0?x2?1, 0?x2+y2?1). The bulk crystal of group III nitride can be grown in supercritical ammonia or a melt of group III metal using at least one seed crystal having basal planes of c-orientation and sidewalls of m-orientation. By exposing only c-planes and m-planes in this instance, cracks originating from the sides of the seed crystal are avoided.
    Type: Grant
    Filed: May 24, 2015
    Date of Patent: December 25, 2018
    Assignees: SixPoint Materials, Inc., Seoul Semiconductor Co., Ltd.
    Inventors: Tadao Hashimoto, Edward Letts
  • Patent number: 10156530
    Abstract: The invention provides, in one instance, a group III nitride wafer sliced from a group III nitride ingot, polished to remove the surface damage layer and tested with x-ray diffraction. The x-ray incident beam is irradiated at an angle less than 15 degree and diffraction peak intensity is evaluated. The group III nitride wafer passing this test has sufficient surface quality for device fabrication. The invention also provides, in one instance, a method of producing group III nitride wafer by slicing a group III nitride ingot, polishing at least one surface of the wafer, and testing the surface quality with x-ray diffraction having an incident beam angle less than 15 degree to the surface. The invention also provides, in an instance, a test method for testing the surface quality of group III nitride wafers using x-ray diffraction having an incident beam angle less than 15 degree to the surface.
    Type: Grant
    Filed: July 22, 2015
    Date of Patent: December 18, 2018
    Assignees: SixPoint Materials, Inc., Seoul Semiconductor Co., Ltd.
    Inventor: Tadao Hashimoto
  • Patent number: 10141435
    Abstract: The present invention discloses an electronic device formed of a group III nitride. In one embodiment, a substrate is fabricated by the ammonothermal method and a drift layer is fabricated by hydride vapor phase epitaxy. After etching a trench, p-type contact pads are made by pulsed laser deposition followed by n-type contact pads by pulsed laser deposition. The bandgap of the p-type contact pad is designed larger than that of the drift layer. Upon forward bias between p-type contact pads (gate) and n-type contact pads (source), holes and electrons are injected into the drift layer from the p-type contact pads and n-type contact pads. Injected electrons drift to the backside of the substrate (drain).
    Type: Grant
    Filed: October 27, 2017
    Date of Patent: November 27, 2018
    Assignee: SixPoint Materials, Inc.
    Inventors: Tadao Hashimoto, Daisuke Ueda
  • Patent number: 10134883
    Abstract: The present invention discloses an electronic device formed of a group III nitride. In one embodiment, a substrate is fabricated by the ammonothermal method and a drift layer is fabricated by hydride vapor phase epitaxy. After etching a trench, p-type contact pads are made by pulsed laser deposition followed by n-type contact pads by pulsed laser deposition. The bandgap of the p-type contact pad is designed larger than that of the drift layer. Upon forward bias between p-type contact pads (gate) and n-type contact pads (source), holes and electrons are injected into the drift layer from the p-type contact pads and n-type contact pads. Injected electrons drift to the backside of the substrate (drain).
    Type: Grant
    Filed: October 27, 2017
    Date of Patent: November 20, 2018
    Assignee: SixPoint Materials, Inc.
    Inventors: Tadao Hashimoto, Daisuke Ueda
  • Patent number: 10134884
    Abstract: The present invention discloses an electronic device formed of a group III nitride. In one embodiment, a substrate is fabricated by the ammonothermal method and a drift layer is fabricated by hydride vapor phase epitaxy. After etching a trench, p-type contact pads are made by pulsed laser deposition followed by n-type contact pads by pulsed laser deposition. The bandgap of the p-type contact pad is designed larger than that of the drift layer. Upon forward bias between p-type contact pads (gate) and n-type contact pads (source), holes and electrons are injected into the drift layer from the p-type contact pads and n-type contact pads. Injected electrons drift to the backside of the substrate (drain).
    Type: Grant
    Filed: October 27, 2017
    Date of Patent: November 20, 2018
    Assignee: SixPoint Materials, Inc.
    Inventors: Tadao Hashimoto, Daisuke Ueda
  • Patent number: 10087548
    Abstract: Present invention discloses a high-pressure vessel of large size formed with a limited size of e.g. Ni—Cr based precipitation hardenable superalloy. Vessel may have multiple zones. For instance, the high-pressure vessel may be divided into at least three regions with flow-restricting devices and the crystallization region is set higher temperature than other regions. This structure helps to reliably seal both ends of the high-pressure vessel, at the same time, may help to greatly reduce unfavorable precipitation of group III nitride at the bottom of the vessel. Invention also discloses novel procedures to grow crystals with improved purity, transparency and structural quality. Alkali metal-containing mineralizers are charged with minimum exposure to oxygen and moisture until the high-pressure vessel is filled with ammonia. Several methods to reduce oxygen contamination during the process steps are presented.
    Type: Grant
    Filed: September 10, 2015
    Date of Patent: October 2, 2018
    Assignee: SixPoint Materials, Inc.
    Inventors: Tadao Hashimoto, Edward Letts, Masanori Ikari
  • Patent number: 10024809
    Abstract: The invention provides, in one instance, a group III nitride wafer sliced from a group III nitride ingot, polished to remove the surface damage layer and tested with x-ray diffraction. The x-ray incident beam is irradiated at an angle less than 15 degree and diffraction peak intensity is evaluated. The group III nitride wafer passing this test has sufficient surface quality for device fabrication. The invention also provides, in one instance, a method of producing group III nitride wafer by slicing a group III nitride ingot, polishing at least one surface of the wafer, and testing the surface quality with x-ray diffraction having an incident beam angle less than 15 degree to the surface. The invention also provides, in an instance, a test method for testing the surface quality of group III nitride wafers using x-ray diffraction having an incident beam angle less than 15 degree to the surface.
    Type: Grant
    Filed: July 22, 2015
    Date of Patent: July 17, 2018
    Assignees: SixPoint Materials, Inc., Seoul Semiconductor Co., Ltd.
    Inventor: Tadao Hashimoto
  • Patent number: 9985102
    Abstract: The present invention discloses methods to create higher quality group III-nitride wafers that then generate improvements in the crystalline properties of ingots produced by ammonothermal growth from an initial defective seed. By obtaining future seeds from carefully chosen regions of an ingot produced on a bowed seed crystal, future ingot crystalline properties can be improved. Specifically the future seeds are optimized if chosen from an area of relieved stress on a cracked ingot or from a carefully chosen N-polar compressed area. When the seeds are sliced out, miscut of 3-10° helps to improve structural quality of successive growth. Additionally a method is proposed to improve crystal quality by using the ammonothermal method to produce a series of ingots, each using a specifically oriented seed from the previous ingot. When employed, these methods enhance the quality of Group III nitride wafers and thus improve the efficiency of any subsequent device.
    Type: Grant
    Filed: February 27, 2014
    Date of Patent: May 29, 2018
    Assignee: SixPoint Materials, Inc.
    Inventors: Edward Letts, Tadao Hashimoto, Masanori Ikari
  • Patent number: 9909230
    Abstract: In one instance, the invention provides a method of growing bulk crystal of group III nitride using a seed crystal selected by (a) measuring x-ray rocking curves of a seed crystal at more than one point, (b) quantifying the peak widths of the measured x-ray rocking curves, and (c) evaluating the distribution of the quantified peak widths. The invention also includes the method of selecting a seed crystal for growing bulk crystal of group III nitride. The bulk crystal of group III nitride can be grown in supercritical ammonia or a melt of group III metal using at least one seed selected by the method above.
    Type: Grant
    Filed: January 22, 2016
    Date of Patent: March 6, 2018
    Assignee: SixPoint Materials, Inc.
    Inventors: Tadao Hashimoto, Edward Letts, Daryl Key
  • Patent number: 9885121
    Abstract: Provided is a high-pressure reactor suitable for a high-pressure process using supercritical ammonia grow bulk crystal of group III nitride having lateral dimension larger than 2 inches or to form various transition metal nitrides. The reactor has nutrient distributed along the reactor's longitudinal axis and seed material positioned at the reactor's inner wall and along the reactor's longitudinal axis. Nutrient diffuses through supercritical ammonia from the reactor's longitudinal axis and deposits on the seed material positioned by the reactor's inner wall. Both the nutrient and seed material are heated by the same heater. Material growth can primarily be due to material diffusion through supercritical ammonia. This configuration and methodology reduce convective movement of supercritical ammonia due to temperature differential, providing a more quiescent environment in which group III nitride or transition metal nitride is formed.
    Type: Grant
    Filed: June 27, 2016
    Date of Patent: February 6, 2018
    Assignee: SixPoint Materials, Inc.
    Inventor: Tadao Hashimoto
  • Patent number: 9834863
    Abstract: Bulk crystal of group III nitride having thickness greater than 1 mm with improved crystal quality, reduced lattice bowing and/or reduced crack density and methods of making. Bulk crystal has a seed crystal, a first crystalline portion grown on the first side of the seed crystal and a second crystalline portion grown on the second side of the seed crystal. Either or both crystalline portions have an electron concentration and/or an oxygen concentration similar to the seed crystal. The bulk crystal can have an additional seed crystal, with common faces (e.g. same polarity, same crystal plane) of seed crystals joined so that a first crystalline part grows on the first face of the first seed crystal and a second crystalline part grows on the first face of the second seed crystal. Each crystalline part's electron concentration and/or oxygen concentration may be similar to its corresponding seed crystal.
    Type: Grant
    Filed: January 16, 2015
    Date of Patent: December 5, 2017
    Assignees: SixPoint Materials, Inc., Seoul Semiconductor Co., Ltd.
    Inventors: Tadao Hashimoto, Edward Letts
  • Patent number: 9822465
    Abstract: In one instance, the invention provides a group III nitride crystal having a first side exposing nitrogen polar c-plane of single crystalline or highly oriented polycrystalline group III nitride and a second side exposing group III polar surface, polycrystalline phase, or amorphous phase of group III nitride. Such structure is useful as a seed crystal for ammonothermal growth of bulk group III nitride crystals. The invention also discloses the method of fabricating such crystal. The invention also discloses the method of fabricating a bulk crystal of group III nitride by ammonothermal method using such crystal.
    Type: Grant
    Filed: December 2, 2015
    Date of Patent: November 21, 2017
    Assignee: SixPoint Materials, Inc.
    Inventor: Tadao Hashimoto
  • Patent number: 9803293
    Abstract: The present invention discloses a production method for group III nitride ingots or pieces such as wafers. To solve the coloration problem in the wafers grown by the ammonothermal method, the present invention composed of the following steps; growth of group III nitride ingots by the ammonothermal method, slicing of the ingots into wafers, annealing of the wafers in a manner that avoids dissociation or decomposition of the wafers. This annealing process is effective to improve transparency of the wafers and/or otherwise remove contaminants from wafers.
    Type: Grant
    Filed: February 25, 2009
    Date of Patent: October 31, 2017
    Assignee: SixPoint Materials, Inc.
    Inventors: Tadao Hashimoto, Edward Letts, Masanori Ikari