Patents by Inventor Thomas W. Sigmon

Thomas W. Sigmon 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: 6933530
    Abstract: A process for direct integration of a thin-film silicon p-n junction diode with a magnetic tunnel junction for use in advanced magnetic random access memory (MRAM) cells for high performance, non-volatile memory arrays. The process is based on pulsed laser processing for the fabrication of vertical polycrystalline silicon electronic device structures, in particular p-n junction diodes, on films of metals deposited onto low temperature-substrates such as ceramics, dielectrics, glass, or polymers. The process preserves underlayers and structures onto which the devices are typically deposited, such as silicon integrated circuits. The process involves the low temperature deposition of at least one layer of silicon, either in an amorphous or a polycrystalline phase on a metal layer. Dopants may be introduced in the silicon film during or after deposition.
    Type: Grant
    Filed: September 17, 2004
    Date of Patent: August 23, 2005
    Assignee: The Regents of the University of California
    Inventors: Daniel Toet, Thomas W. Sigmon
  • Patent number: 6828180
    Abstract: A process for direct integration of a thin-film silicon p-n junction diode with a magnetic tunnel junction for use in advanced magnetic random access memory (MRAM) cells for high performance, non-volatile memory arrays. The process is based on pulsed laser processing for the fabrication of vertical polycrystalline silicon electronic device structures, in particular p-n junction diodes, on films of metals deposited onto low temperature-substrates such as ceramics, dielectrics, glass, or polymers. The process preserves underlayers and structures onto which the devices are typically deposited, such as silicon integrated circuits. The process involves the low temperature deposition of at least one layer of silicon, either in an amorphous or a polycrystalline phase on a metal layer. Dopants may be introduced in the silicon film during or after deposition.
    Type: Grant
    Filed: September 27, 2002
    Date of Patent: December 7, 2004
    Assignee: The Regents of the University of California
    Inventors: Daniel Toet, Thomas W. Sigmon
  • Patent number: 6680485
    Abstract: A process for formation of thin film transistors (TFTs) on plastic substrates replaces standard thin film transistor fabrication techniques, and uses sufficiently lower processing temperatures so that inexpensive plastic substrates may be used in place of standard glass, quartz, and silicon wafer-based substrates. The silicon based thin film transistor produced by the process includes a low temperature substrate incapable of withstanding sustained processing temperatures greater than about 250° C., an insulating layer on the substrate, a layer of silicon on the insulating layer having sections of doped silicon, undoped silicon, and poly-silicon, a gate dielectric layer on the layer of silicon, a layer of gate metal on the dielectric layer, a layer of oxide on sections of the layer of silicon and the layer of gate metal, and metal contacts on sections of the layer of silicon and layer of gate metal defining source, gate, and drain contacts, and interconnects.
    Type: Grant
    Filed: February 17, 1998
    Date of Patent: January 20, 2004
    Assignee: The Regents of the University of California
    Inventors: Paul G. Carey, Patrick M. Smith, Thomas W. Sigmon, Randy C. Aceves
  • Patent number: 6541316
    Abstract: A process for direct integration of a thin-film silicon p-n junction diode with a magnetic tunnel junction for use in advanced magnetic random access memory (MRAM) cells for high performance, non-volatile memory arrays. The process is based on pulsed laser processing for the fabrication of vertical polycrystalline silicon electronic device structures, in particular p-n junction diodes, on films of metals deposited onto low temperature-substrates such as ceramics, dielectrics, glass, or polymers. The process preserves underlayers and structures onto which the devices are typically deposited, such as silicon integrated circuits. The process involves the low temperature deposition of at least one layer of silicon, either in an amorphous or a polycrystalline phase on a metal layer. Dopants may be introduced in the silicon film during or after deposition.
    Type: Grant
    Filed: December 22, 2000
    Date of Patent: April 1, 2003
    Assignee: The Regents of the University of California
    Inventors: Daniel Toet, Thomas W. Sigmon
  • Publication number: 20030036238
    Abstract: A process for direct integration of a thin-film silicon p-n junction diode with a magnetic tunnel junction for use in advanced magnetic random access memory (MRAM) cells for high performance, non-volatile memory arrays. The process is based on pulsed laser processing for the fabrication of vertical polycrystalline silicon electronic device structures, in particular p-n junction diodes, on films of metals deposited onto low temperature-substrates such as ceramics, dielectrics, glass, or polymers. The process preserves underlayers and structures onto which the devices are typically deposited, such as silicon integrated circuits. The process involves the low temperature deposition of at least one layer of silicon, either in an amorphous or a polycrystalline phase on a metal layer. Dopants may be introduced in the silicon film during or after deposition.
    Type: Application
    Filed: September 27, 2002
    Publication date: February 20, 2003
    Applicant: The Regents of the University of California
    Inventors: Daniel Toet, Thomas W. Sigmon
  • Publication number: 20020081786
    Abstract: A process for direct integration of a thin-film silicon p-n junction diode with a magnetic tunnel junction for use in advanced magnetic random access memory (MRAM) cells for high performance, non-volatile memory arrays. The process is based on pulsed laser processing for the fabrication of vertical polycrystalline silicon electronic device structures, in particular p-n junction diodes, on films of metals deposited onto low temperature-substrates such as ceramics, dielectrics, glass, or polymers. The process preserves underlayers and structures onto which the devices are typically deposited, such as silicon integrated circuits. The process involves the low temperature deposition of at least one layer of silicon, either in an amorphous or a polycrystalline phase on a metal layer. Dopants may be introduced in the silicon film during or after deposition.
    Type: Application
    Filed: December 22, 2000
    Publication date: June 27, 2002
    Applicant: The Regents of the University of California
    Inventors: Daniel Toet, Thomas W. Sigmon
  • Patent number: 5817550
    Abstract: A process for formation of thin film transistors (TFTs) on plastic substrates replaces standard thin film transistor fabrication techniques, and uses sufficiently lower processing temperatures so that inexpensive plastic substrates may be used in place of standard glass, quartz, and silicon wafer-based substrates. The process relies on techniques for depositing semiconductors, dielectrics, and metals at low temperatures; crystallizing and doping semiconductor layers in the TFT with a pulsed energy source; and creating top-gate self-aligned as well as back-gate TFT structures. The process enables the fabrication of amorphous and polycrystalline channel silicon TFTs at temperatures sufficiently low to prevent damage to plastic substrates. The process has use in large area low cost electronics, such as flat panel displays and portable electronics.
    Type: Grant
    Filed: March 5, 1996
    Date of Patent: October 6, 1998
    Assignee: Regents of the University of California
    Inventors: Paul G. Carey, Patrick M. Smith, Thomas W. Sigmon, Randy C. Aceves
  • Patent number: 5565377
    Abstract: A process for forming retrograde and oscillatory profiles in crystalline and polycrystalline silicon. The process consisting of introducing an n- or p-type dopant into the silicon, or using prior doped silicon, then exposing the silicon to multiple pulses of a high-intensity laser or other appropriate energy source that melts the silicon for short time duration. Depending on the number of laser pulses directed at the silicon, retrograde profiles with peak/surface dopant concentrations which vary from 1-1e4 are produced. The laser treatment can be performed in air or in vacuum, with the silicon at room temperature or heated to a selected temperature.
    Type: Grant
    Filed: October 27, 1994
    Date of Patent: October 15, 1996
    Assignee: Regents of the University of California
    Inventors: Kurt H. Weiner, Thomas W. Sigmon
  • Patent number: 5456763
    Abstract: A process for producing multi-terminal devices such as solar cells wherein a pulsed high energy source is used to melt and crystallize amorphous silicon deposited on a substrate which is intolerant to high processing temperatures, whereby to amorphous silicon is converted into a microcrystalline/polycrystalline phase. Dopant and hydrogenization can be added during the fabrication process which provides for fabrication of extremely planar, ultra shallow contacts which results in reduction of non-current collecting contact volume. The use of the pulsed energy beams results in the ability to fabricate high efficiency microcrystalline/polycrystalline solar cells on the so-called low-temperature, inexpensive plastic substrates which are intolerant to high processing temperatures.
    Type: Grant
    Filed: March 29, 1994
    Date of Patent: October 10, 1995
    Assignee: The Regents of the University of California
    Inventors: James L. Kaschmitter, Thomas W. Sigmon
  • Patent number: 5425860
    Abstract: A method for producing beta silicon carbide thin films by co-depositing thin films of amorphous silicon and carbon onto a substrate, whereafter the films are irradiated by exposure to a pulsed energy source (e.g. excimer laser) to cause formation of the beta-SiC compound. Doped beta-SiC may be produced by introducing dopant gases during irradiation. Single layers up to a thickness of 0.5-1 micron have been produced, with thicker layers being produced by multiple processing steps. Since the electron transport properties of beta silicon carbide over a wide temperature range of 27.degree.-730.degree. C. is better than these properties of alpha silicon carbide, they have wide application, such as in high temperature semiconductors, including hetero-junction bipolar transistors and power devices, as well as in high bandgap solar arrays, ultra-hard coatings, light emitting diodes, sensors, etc.
    Type: Grant
    Filed: April 7, 1993
    Date of Patent: June 20, 1995
    Assignee: The Regents of the University of California
    Inventors: Joel B. Truher, James L. Kaschmitter, Jesse B. Thompson, Thomas W. Sigmon
  • Patent number: 5346850
    Abstract: A method or process of crystallizing and doping amorphous silicon (a-Si) on a low-temperature plastic substrate using a short pulsed high energy source in a selected environment, without heat propagation and build-up in the substrate. The pulsed energy processing of the a-Si in a selected environment, such as BF3 and PF5, will form a doped micro-crystalline or poly-crystalline silicon (pc-Si) region or junction point with improved mobilities, lifetimes and drift and diffusion lengths and with reduced resistivity. The advantage of this method or process is that it provides for high energy materials processing on low cost, low temperature, transparent plastic substrates. Using pulsed laser processing a high (>900.degree. C.), localized processing temperature can be achieved in thin films, with little accompanying temperature rise in the substrate, since substrate temperatures do not exceed 180.degree. C. for more than a few microseconds.
    Type: Grant
    Filed: October 29, 1992
    Date of Patent: September 13, 1994
    Assignee: Regents of the University of California
    Inventors: James L. Kaschmitter, Joel B. Truher, Kurt H. Weiner, Thomas W. Sigmon
  • Patent number: 5316969
    Abstract: Shallow regions are formed in a semiconductor body by irradiating the surface region with a pulsed laser beam in an atmosphere including the dopant. The pulsed laser beam has sufficient intensity to drive in dopant atoms from the atmosphere but insufficient intensity to melt the semiconductor material. A silicide layer can be placed over the surface of the semiconductor material prior to irradiation with the dopant being driven from the atmosphere through the silicide into the surface region of the semiconductor body. Alternatively, the silicide layer can include dopant atoms prior to irradiating the surface region.
    Type: Grant
    Filed: December 21, 1992
    Date of Patent: May 31, 1994
    Assignee: Board of Trustees of the Leland Stanford Junior University
    Inventors: Emi Ishida, Thomas W. Sigmon, William T. Lynch
  • Patent number: 4177084
    Abstract: A method is provided for producing a low-defect layer of silicon on a sapphire substrate. A silicon-on-sapphire (SOS) wafer is formed by initially epitaxially depositing silicon on the sapphire substrate to form a monocrystalline layer which is substantially free of lattice defects near its surface, but which exhibits a high defect density near the sapphire substrate. The wafer is subsequently subjected to an ion implantation to form an amorphous region in the silicon near the silicon-sapphire interface. The implanted ions are preferably "channeled" through the silicon layer to insure that the amorphous region will be localized in the imperfect region near the substrate, leaving the upper region of the silicon layer undamaged. During a subsequent high temperature anneal cycle, monocrystalline silicon is regrown from the residual upper regions of the silicon down to the silicon-sapphire interface, producing a silicon layer having a greatly reduced defect density throughout the layer.
    Type: Grant
    Filed: June 9, 1978
    Date of Patent: December 4, 1979
    Assignee: Hewlett-Packard Company
    Inventors: Silvanus S. Lau, James W. Mayer, Thomas W. Sigmon