Patents by Inventor Robert T. Leonard

Robert T. Leonard 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: 11519098
    Abstract: Silicon carbide (SiC) wafers, SiC boules, and related methods are disclosed that provide improved dislocation distributions. SiC boules are provided that demonstrate reduced dislocation densities and improved dislocation uniformity across longer boule lengths. Corresponding SiC wafers include reduced total dislocation density (TDD) values and improved TDD radial uniformity. Growth conditions for SiC crystalline materials include providing source materials in oversaturated quantities where amounts of the source materials present during growth are significantly higher than what would typically be required. Such SiC crystalline materials and related methods are suitable for providing large diameter SiC boules and corresponding SiC wafers with improved crystalline quality.
    Type: Grant
    Filed: January 29, 2020
    Date of Patent: December 6, 2022
    Assignee: Wolfspeed, Inc.
    Inventors: Yuri Khlebnikov, Robert T. Leonard, Elif Balkas, Steven Griffiths, Valeri Tsvetkov, Michael Paisley
  • Publication number: 20210230769
    Abstract: Silicon carbide (SiC) wafers, SiC boules, and related methods are disclosed that provide improved dislocation distributions. SiC boules are provided that demonstrate reduced dislocation densities and improved dislocation uniformity across longer boule lengths. Corresponding SiC wafers include reduced total dislocation density (TDD) values and improved TDD radial uniformity. Growth conditions for SiC crystalline materials include providing source materials in oversaturated quantities where amounts of the source materials present during growth are significantly higher than what would typically be required. Such SiC crystalline materials and related methods are suitable for providing large diameter SiC boules and corresponding SiC wafers with improved crystalline quality.
    Type: Application
    Filed: January 29, 2020
    Publication date: July 29, 2021
    Inventors: Yuri Khlebnikov, Robert T. Leonard, Elif Balkas, Steven Griffiths, Valeri Tsvetkov, Michael Paisley
  • Patent number: 9099377
    Abstract: Micropipe-free, single crystal, silicon carbide (SiC) and related methods of manufacture are disclosed. The SiC is grown by placing a source material and seed material on a seed holder in a reaction crucible of the sublimation system, wherein constituent components of the sublimation system including the source material, reaction crucible, and seed holder are substantially free from unintentional impurities. By controlling growth temperature, growth pressure, SiC sublimation flux and composition, and a temperature gradient between the source material and the seed material or the SiC crystal growing on the seed material during the PVT process, micropipe-inducing process instabilities are eliminated and micropipe-free SiC crystal is grown on the seed material.
    Type: Grant
    Filed: September 13, 2007
    Date of Patent: August 4, 2015
    Assignee: Cree, Inc.
    Inventors: Cem Basceri, Yuri Khlebnikov, Igor Khlebnikov, Cengiz Balkas, Murat N. Silan, Hudson McD. Hobgood, Calvin H. Carter, Jr., Vijay Balakrishna, Robert T. Leonard, Adrian R. Powell, Valeri T. Tsvetkov, Jason R. Jenny
  • Patent number: 8980445
    Abstract: A semiconductor crystal and associated growth method are disclosed. The crystal includes a seed portion and a growth portion on the seed portion. The seed portion and the growth portion form a substantially right cylindrical single crystal of silicon carbide. A seed face defines an interface between the growth portion and the seed portion, with the seed face being substantially parallel to the bases of the right cylindrical crystal and being off-axis with respect to a basal plane of the single crystal. The growth portion replicates the polytype of the seed portion and the growth portion has a diameter of at least about 100 mm.
    Type: Grant
    Filed: July 6, 2006
    Date of Patent: March 17, 2015
    Assignee: Cree, Inc.
    Inventors: Robert T. Leonard, Mark Brady, Adrian Powell
  • Patent number: 8785946
    Abstract: A high quality single crystal wafer of SiC is disclosed having a diameter of at least about 3 inches and a 1 c screw dislocation density from about 500 cm?2 to about 2000 cm?2.
    Type: Grant
    Filed: February 26, 2013
    Date of Patent: July 22, 2014
    Assignee: Cree, Inc.
    Inventors: Adrian Powell, Mark Brady, Stephan G. Mueller, Valeri F. Tsvetkov, Robert T. Leonard
  • Patent number: 8624267
    Abstract: A high quality single crystal wafer of SiC is disclosed having a diameter of at least about 3 inches and a 1 c screw dislocation density from about 500 cm?2 to about 2000 cm?2.
    Type: Grant
    Filed: February 26, 2013
    Date of Patent: January 7, 2014
    Assignee: Cree, Inc.
    Inventors: Adrian Powell, Mark Brady, Stephan G. Mueller, Valeri F. Tsvetkov, Robert T. Leonard
  • Patent number: 8410488
    Abstract: Micropipe-free, single crystal, silicon carbide (SiC) and related methods of manufacture are disclosed. The SiC is grown by placing a source material and seed material on a seed holder in a reaction crucible of the sublimation system, wherein constituent components of the sublimation system including the source material, reaction crucible, and seed holder are substantially free from unintentional impurities. By controlling growth temperature, growth pressure, SiC sublimation flux and composition, and a temperature gradient between the source material and the seed material or the SiC crystal growing on the seed material during the PVT process, micropipe-inducing process instabilities are eliminated and micropipe-free SiC crystal is grown on the seed material.
    Type: Grant
    Filed: September 13, 2007
    Date of Patent: April 2, 2013
    Assignee: Cree, Inc.
    Inventors: Cem Basceri, Yuri Khlebnikov, Igor Khlebnikov, Cengiz Balkas, Murat N. Silan, Hudson McD. Hobgood, Calvin H. Carter, Jr., Vijay Balakrishna, Robert T. Leonard, Adrian R. Powell, Valeri T. Tsvetkov, Jason R. Jenny
  • Patent number: 8384090
    Abstract: A high quality single crystal wafer of SiC is disclosed having a diameter of at least about 3 inches and a 1c screw dislocation density of less than about 2000 cm?2.
    Type: Grant
    Filed: November 15, 2007
    Date of Patent: February 26, 2013
    Assignee: Cree, Inc.
    Inventors: Adrian Powell, Mark Brady, Stephan G. Mueller, Valeri F. Tsvetkov, Robert T. Leonard
  • Patent number: 7563321
    Abstract: The invention is an improvement in the method of producing a high quality bulk single crystal of silicon carbide in a seeded sublimation system. In a first embodiment, the improvement comprises reducing the number of macrosteps in a growing crystal by incorporating a high concentration of nitrogen atoms in the initial one (1) millimeter of crystal growth.
    Type: Grant
    Filed: December 8, 2004
    Date of Patent: July 21, 2009
    Assignee: Cree, Inc.
    Inventors: Adrian Powell, Valeri F. Tsvetkov, Mark Brady, Robert T. Leonard
  • Publication number: 20080169476
    Abstract: A high quality single crystal wafer of SiC is disclosed having a diameter of at least about 3 inches and a 1c screw dislocation density of less than about 2000 cm 2.
    Type: Application
    Filed: November 15, 2007
    Publication date: July 17, 2008
    Applicant: CREE, INC.
    Inventors: Adrian Powell, Mark Brady, Stephan G. Mueller, Valeri F. Tsvetkov, Robert T. Leonard
  • Publication number: 20080008641
    Abstract: A semiconductor crystal and associated growth method are disclosed. The crystal includes a seed portion and a growth portion on the seed portion. The seed portion and the growth portion form a substantially right cylindrical single crystal of silicon carbide. A seed face defines an interface between the growth portion and the seed portion, with the seed face being substantially parallel to the bases of the right cylindrical crystal and being off-axis with respect to a basal plane of the single crystal. The growth portion replicates the polytype of the seed portion and the growth portion has a diameter of at least about 100 mm.
    Type: Application
    Filed: July 6, 2006
    Publication date: January 10, 2008
    Inventors: Robert T. Leonard, Mark Brady, Adrian Powell
  • Patent number: 7314520
    Abstract: A high quality single crystal wafer of SiC is disclosed having a diameter of at least about 3 inches and a 1 c screw dislocation density of less than about 2000 cm?2.
    Type: Grant
    Filed: October 4, 2004
    Date of Patent: January 1, 2008
    Assignee: Cree, Inc.
    Inventors: Adrian Powell, Mark Brady, Stephen G. Mueller, Valeri F. Tsvetkov, Robert T. Leonard