Patents by Inventor Andrew J. Walker

Andrew J. Walker 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: 7023739
    Abstract: An exemplary NAND string memory array provides for capacitive boosting of a half-selected memory cell channel to reduce program disturb effects of the half selected cell. To reduce the effect of leakage current degradation of the boosted level, multiple programming pulses of a shorter duration are employed to limit the time period during which such leakage currents may degrade the voltage within the unselected NAND strings. In addition, multiple series select devices at one or both ends of each NAND string further ensure reduced leakage through such select devices, for both unselected and selected NAND strings. In certain exemplary embodiments, a memory array includes series-connected NAND strings of memory cell transistors having a charge storage dielectric, and includes more than one plane of memory cells formed above a substrate.
    Type: Grant
    Filed: December 5, 2003
    Date of Patent: April 4, 2006
    Assignee: Matrix Semiconductor, Inc.
    Inventors: En-Hsing Chen, Andrew J. Walker, Roy E. Scheuerlein, Sucheta Nallamothu, Alper Ilkbahar, Luca G. Fasoli
  • Patent number: 7012299
    Abstract: The traditional nitride-only charge storage layer of a SONOS device is replaced by a multifilm charge storage layer comprising more than one dielectric material. Examples of such a multifilm charge storage layer are alternating layers of silicon nitride and silicon dioxide, or alternating layers of silicon nitride and aluminum oxide. The use of more than one material introduces additional barriers to migration of charge carriers within the charge storage layer, and improves both endurance and retention of a SONOS-type memory cell comprising such a charge storage layer.
    Type: Grant
    Filed: September 23, 2003
    Date of Patent: March 14, 2006
    Assignee: Matrix Semiconductors, Inc.
    Inventors: Maitreyee Mahajani, Andrew J. Walker, En-Hsing Chen
  • Patent number: 7005350
    Abstract: A three-dimensional flash memory array incorporates thin film transistors having a charge storage dielectric arranged in series-connected NAND strings to achieve a 4F2 memory cell layout. The memory array may be programmed and erased using only tunneling currents, and no leakage paths are formed through non-selected memory cells. Each NAND string includes two block select devices for respectively coupling one end of the NAND string to a global bit line, and the other end to a shared bias node. Pairs of NAND strings within a block share the same global bit line. The memory cells are preferably depletion mode SONOS devices, as are the block select devices. The memory cells may be programmed to a near depletion threshold voltage, and the block select devices are maintained in a programmed state having a near depletion mode threshold voltage. NAND strings on more than one layer may be connected to global bit lines on a single layer.
    Type: Grant
    Filed: December 31, 2002
    Date of Patent: February 28, 2006
    Assignee: Matrix Semiconductor, Inc.
    Inventors: Andrew J. Walker, En-Hsing Chen, Sucheta Nallamothu, Roy E. Scheuerlein, Alper Ilkbahar, Luca Fasoli, Igor Koutnetsov, Christopher Petti
  • Patent number: 6992349
    Abstract: There is provided a monolithic three dimensional array of charge storage devices which includes a plurality of device levels, wherein at least one surface between two successive device levels is planarized by chemical mechanical polishing.
    Type: Grant
    Filed: May 20, 2004
    Date of Patent: January 31, 2006
    Assignee: Matrix Semiconductor, Inc.
    Inventors: Thomas H. Lee, Andrew J. Walker, Christopher J. Petti, Igor G. Kouznetzov
  • Patent number: 6960794
    Abstract: A thin film transistor with a channel less than 100 angstroms thick, preferably less than 80 angstroms thick, preferably less than 60 angstroms thick. The very thin channel reduces variability of threshold voltage from one TFT to the next. This is particularly advantageous for TFT memory arrays. It is possible that an extremely thin channel restricts the size of grains, forcing many small grains to be formed.
    Type: Grant
    Filed: December 31, 2002
    Date of Patent: November 1, 2005
    Assignee: Matrix Semiconductor, Inc.
    Inventors: Andrew J. Walker, S. Brad Herner, Maitreyee Mahajani, En-Hsing Chen, Roy E. Scheuerlein, Sucheta Nallamothu, Mark Clark
  • Patent number: 6940109
    Abstract: A semiconductor device comprises two transistors where a gate electrode of one transistor and source or drain of another transistor are located in the same rail. A monolithic three dimensional array contains a plurality of such devices. The transistors in different levels of the array preferably have a different orientation.
    Type: Grant
    Filed: February 18, 2004
    Date of Patent: September 6, 2005
    Assignee: Matrix Semiconductor, Inc.
    Inventors: Kedar Patel, Alper Ilkbahar, Roy Scheuerlein, Andrew J. Walker
  • Patent number: 6897514
    Abstract: There is provided a floating gate transistor, such as an EEPROM transistor, and method of making the transistor using two masking steps. The method of making a transistor includes patterning a floating gate layer using a first photoresist mask to form a floating gate rail and doping an active area using the floating gate rail as a mask to form source and drain regions in the active area. The method also includes patterning a control gate layer, a control gate dielectric layer, the floating gate rail, a tunnel dielectric layer and the active area using a second photoresist mask to form a control gate, a control gate dielectric, a floating gate, a tunnel dielectric and a channel island region.
    Type: Grant
    Filed: February 5, 2002
    Date of Patent: May 24, 2005
    Assignee: Matrix Semiconductor, Inc.
    Inventors: Igor G. Kouznetsov, Andrew J. Walker
  • Patent number: 6888750
    Abstract: A nonvolatile memory array is provided. The array includes an array of nonvolatile memory devices, at least one driver circuit, and a substrate. The at least one driver circuit is not located in a bulk monocrystalline silicon substrate. The at least one driver circuit may be located in a silicon on insulator substrate or in a compound semiconductor substrate.
    Type: Grant
    Filed: August 13, 2001
    Date of Patent: May 3, 2005
    Assignee: Matrix Semiconductor, Inc.
    Inventors: Andrew J. Walker, Mark G. Johnson, N. Johan Knall, Igor G. Kouznetsov, Christopher J. Petti
  • Patent number: 6881994
    Abstract: There is provided a monolithic three dimensional array of charge storage devices which includes a plurality of device levels, wherein at least one surface between two successive device levels is planarized by chemical mechanical polishing.
    Type: Grant
    Filed: August 13, 2001
    Date of Patent: April 19, 2005
    Assignee: Matrix Semiconductor, Inc.
    Inventors: Thomas H. Lee, Vivek Subramanian, James M. Cleeves, Andrew J. Walker, Christopher J. Petti, Igor G. Kouznetzov, Mark G. Johnson, Paul Michael Farmwald, Brad Herner
  • Patent number: 6858899
    Abstract: A thin film transistor includes an insulating substrate, an active layer located over the substrate, a gate electrode located over the substrate; and a charge storage region located between the active layer and the gate electrode. The charge storage region includes a tunneling dielectric located adjacent to the active layer, a blocking dielectric located adjacent to the gate electrode and a charge storage dielectric located between the tunneling dielectric and the blocking dielectric. At least one of the tunneling dielectric, the charge storage dielectric and the blocking dielectric comprises a layer having a dielectric constant greater than 3.9, such as a metal oxide layer.
    Type: Grant
    Filed: October 15, 2002
    Date of Patent: February 22, 2005
    Assignee: Matrix Semiconductor, Inc.
    Inventors: Maitreyee Mahajani, Andrew J. Walker
  • Patent number: 6849905
    Abstract: An array of transistors includes a plurality of transistors, a plurality of word lines extending in a first direction and a plurality of bit lines extending in a second direction. Each transistor includes a source, a drain, a channel and a localized charge storage dielectric. A first transistor of the plurality of transistors and a second transistor of the plurality of transistors share a common source/drain. A first localized charge storage dielectric of the first transistor does not overlap the common source/drain and a second localized charge storage dielectric of the second transistor overlaps the common source/drain.
    Type: Grant
    Filed: December 23, 2002
    Date of Patent: February 1, 2005
    Assignee: Matrix Semiconductor, Inc.
    Inventors: Alper Ilkbahar, Roy Scheuerlein, Andrew J. Walker, Luca Fasoli
  • Patent number: 6841813
    Abstract: There is provided a monolithic three dimensional TFT mask ROM array. The array includes a plurality of device levels. Each of the plurality of device levels contains a first set of enabled TFTs and a second set of partially or totally disabled TFTs.
    Type: Grant
    Filed: October 26, 2001
    Date of Patent: January 11, 2005
    Assignee: Matrix Semiconductor, Inc.
    Inventors: Andrew J. Walker, Christopher Petti
  • Patent number: 6815781
    Abstract: A semiconductor device, such as an inverted staggered thin film transistor, includes a gate electrode, a gate insulating layer located above the gate electrode, an active layer located above the gate insulating layer and an insulating fill layer located above the active layer. A first opening and a second opening are located in the insulating fill layer, a first source or drain electrode is located in the first opening and a second source or drain electrode is located in the second opening. At least one of the first and the second source or drain electrodes comprise a polysilicon layer and a metal silicide layer.
    Type: Grant
    Filed: October 15, 2002
    Date of Patent: November 9, 2004
    Assignee: Matrix Semiconductor, Inc.
    Inventors: Michael A. Vyvoda, S. Brad Herner, Christopher J. Petti, Andrew J. Walker
  • Publication number: 20040214379
    Abstract: There is provided a monolithic three dimensional array of charge storage devices which includes a plurality of device levels, wherein at least one surface between two successive device levels is planarized by chemical mechanical polishing.
    Type: Application
    Filed: May 20, 2004
    Publication date: October 28, 2004
    Applicant: Matrix Semiconductor, Inc.
    Inventors: Thomas H. Lee, Andrew J. Walker, Christopher J. Petti, Igor G. Kouznetzov
  • Publication number: 20040207001
    Abstract: There is provided a floating gate transistor, such as an EEPROM transistor, and method of making the transistor using two masking steps. The method of making a transistor includes patterning a floating gate layer using a first photoresist mask to form a floating gate rail and doping an active area using the floating gate rail as a mask to form source and drain regions in the active area. The method also includes patterning a control gate layer, a control gate dielectric layer, the floating gate rail, a tunnel dielectric layer and the active area using a second photoresist mask to form a control gate, a control gate dielectric, a floating gate, a tunnel dielectric and a channel island region.
    Type: Application
    Filed: May 20, 2004
    Publication date: October 21, 2004
    Applicant: MATRIX SEMICONDUCTOR, INC.
    Inventors: Igor G. Kouznetsov, Andrew J. Walker
  • Publication number: 20040206996
    Abstract: There is provided a monolithic three dimensional array of charge storage devices which includes a plurality of device levels, wherein at least one surface between two successive device levels is planarized by chemical mechanical polishing.
    Type: Application
    Filed: May 10, 2004
    Publication date: October 21, 2004
    Applicant: Matrix Semiconductor, Inc.
    Inventors: Thomas H. Lee, Vivek Subramanian, James M. Cleeves, Andrew J. Walker, Christopher J. Petti, Igor G. Kouznetzov, Mark G. Johnson, Paul Michael Farmwald, Brad Herner
  • Publication number: 20040159860
    Abstract: A semiconductor device comprises two transistors where a gate electrode of one transistor and source or drain of another transistor are located in the same rail. A monolithic three dimensional array contains a plurality of such devices. The transistors in different levels of the array preferably have a different orientation.
    Type: Application
    Filed: February 18, 2004
    Publication date: August 19, 2004
    Applicant: Matrix Semiconductor, Inc.
    Inventors: Kedar Patel, Alper Ilkbahar, Roy Scheuerlein, Andrew J. Walker
  • Publication number: 20040145024
    Abstract: An exemplary NAND string memory array provides for capacitive boosting of a half-selected memory cell channel to reduce program disturb effects of the half selected cell. To reduce the effect of leakage current degradation of the boosted level, multiple programming pulses of a shorter duration are employed to limit the time period during which such leakage currents may degrade the voltage within the unselected NAND strings. In addition, multiple series select devices at one or both ends of each NAND string further ensure reduced leakage through such select devices, for both unselected and selected NAND strings. In certain exemplary embodiments, a memory array includes series-connected NAND strings of memory cell transistors having a charge storage dielectric, and includes more than one plane of memory cells formed above a substrate.
    Type: Application
    Filed: December 5, 2003
    Publication date: July 29, 2004
    Inventors: En-Hsing Chen, Andrew J. Walker, Roy E. Scheuerlein, Sucheta Nallamothu, Alper Ilkbahar, Luca G. Fasoli
  • Publication number: 20040124415
    Abstract: A thin film transistor with a channel less than 100 angstroms thick, preferably less than 80 angstroms thick, preferably less than 60 angstroms thick. The very thin channel reduces variability of threshold voltage from one TFT to the next. This is particularly advantageous for TFT memory arrays. It is possible that an extremely thin channel restricts the size of grains, forcing many small grains to be formed.
    Type: Application
    Filed: December 31, 2002
    Publication date: July 1, 2004
    Inventors: Andrew J. Walker, S. Brad Herner, Maitreyee Mahajani, En-Hsing Chen, Roy E. Scheuerlein, Sucheta Nallamothu, Mark Clark
  • Publication number: 20040124466
    Abstract: A three-dimensional flash memory array incorporates thin film transistors having a charge storage dielectric arranged in series-connected NAND strings to achieve a 4F2 memory cell layout. The memory array may be programmed and erased using only tunneling currents, and no leakage paths are formed through non-selected memory cells. Each NAND string includes two block select devices for respectively coupling one end of the NAND string to a global bit line, and the other end to a shared bias node. Pairs of NAND strings within a block share the same global bit line. The memory cells are preferably depletion mode SONOS devices, as are the block select devices. The memory cells may be programmed to a near depletion threshold voltage, and the block select devices are maintained in a programmed state having a near depletion mode threshold voltage. NAND strings on more than one layer may be connected to global bit lines on a single layer.
    Type: Application
    Filed: December 31, 2002
    Publication date: July 1, 2004
    Inventors: Andrew J. Walker, En-Hsing Chen, Sucheta Nallamothu, Roy E. Scheuerlein, Alper Ilkbahar, Luca Fasoli, Igor Kouznetsov, Christopher Petti