Patents by Inventor Allan T. Mitchell

Allan T. Mitchell 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: 4905062
    Abstract: A sealed gate FAMOS transistor (28) disposes a thermal oxide layer (40) about the floating gate (34) in order to isolate the floating gate (34) from the planar isolating regions (44) between floating gates (34). Trench isolating regions (54) are provided between control gates (50) to enhance programmability of the sealed gate FAMOS transistor (28).
    Type: Grant
    Filed: February 17, 1989
    Date of Patent: February 27, 1990
    Assignee: Texas Instruments Incorporated
    Inventors: Agerico L. Esquivel, Allan T. Mitchell
  • Patent number: 4878996
    Abstract: The disclosure relates to a method for reducing filament formation over the BN+ oxide in semiconductor devices wherein a sidewall oxide is formed on the side walls of the first polysilicon layer prior to subsequent formation of the intermediate insulating layer, formation of a second polysilicon layer and subsequent anisotropic etch to provide for removal of all polysilicon over the field oxide.
    Type: Grant
    Filed: January 23, 1989
    Date of Patent: November 7, 1989
    Assignee: Texas Instruments Incorporated
    Inventors: Allan T. Mitchell, Howard L. Tigelaar, Shaym G. Garg, Kalipatnam V. Rao
  • Patent number: 4853895
    Abstract: An electrically erasable, programmable read only memory (EEPROM) having an erase window directly overlying both a control gate layer (24) and a column line (12) is disclosed. Column lines (12) are implanted into a semiconductor substrate (16) and covered with a first insulating layer (18). A floating gate layer (20) overlies the first insulating layer (18) and is covered with a second insulating layer (22). The control gate layer (24) overlies the second insulating layer (22) and is covered by a third insulating layer (26). A passage (28) extends through the third insulating layer (26), control gate layer (24) and second insulating layer (22) and contains a sidewall insulator (30) on walls thereof. A tunnel oxide (32) resides within the passage (28) and is contacted by a programming electrode layer (34) which additionally overlies the third insulating layer (26) and fills the passage (28).
    Type: Grant
    Filed: November 30, 1987
    Date of Patent: August 1, 1989
    Assignee: Texas Instruments Incorporated
    Inventors: Allan T. Mitchell, Bert R. Riemenschneider
  • Patent number: 4839705
    Abstract: An X-cell EEPROM array includes a plurality of common source regions (50) that each border on four gate regions (46), both formed at a face of a semiconductor substrate (10). Each gate region (46) further adjoins a common drain region (52). Each drain region (52) is a common drain for two EEPROM select and memory transistors. A common erase region (54) is implanted into the semiconductor layer (10) in a position remote from the source regions (50) and the drain regions (52). Four floating gate electrodes (40) extend over tunnel windows (22) that are formed on the semiconductor layer (10) in positions adjacent a single erase region (54). An integral contact (64) is made through multilevel oxide (56, 58) from a metal erase line (70) to each erase region (54).
    Type: Grant
    Filed: December 16, 1987
    Date of Patent: June 13, 1989
    Assignee: Texas Instruments Incorporated
    Inventors: Howard L. Tigelaar, Allan T. Mitchell, Bert R. Riemenschneider, James L. Paterson
  • Patent number: 4833514
    Abstract: The invention provides an EPROM having a high quality dielectric to separate the floating gate from low quality dielectric layers used in the prior art by the method outlined as follows. First, the polycrystalline silicon floating gates are formed and partially patterned on the surface of a substrate. A thin thermally grown oxide layer is then formed over the entire array. The source/drain regions are then implanted through the thin silicon dioxide layer into the substrate. Next a thick silicon dioxide layer is deposited by chemical vapor deposition on the surface of the array. The surface of the array is then coated with photoresist which, because of its nature, provides a planarized surface on the top layer of photoresist. The photoresist and the silicon dioxide layer are then etched using an etching process which provides an etching ratio of 1:1 between photoresist and silicon dioxide. The photoresist is completely etched away thus leaving the planarized silicon dioxide surface.
    Type: Grant
    Filed: November 18, 1987
    Date of Patent: May 23, 1989
    Assignee: Texas Instruments Incorporated
    Inventors: Agerico L. Esquivel, Allan T. Mitchell
  • Patent number: 4829019
    Abstract: A method of forming semiconductor devices wherein a gap is formed beneath the field oxide between the channel stop implant and source/drain regions in the moat or active element region to prevent or minimize encroachment of channel stop impurity toward the source/drain regions to form spurious pn junctions and/or reduce the active element region.
    Type: Grant
    Filed: May 12, 1987
    Date of Patent: May 9, 1989
    Assignee: Texas Instruments Incorporated
    Inventors: Allan T. Mitchell, Howard L. Tigelaar, Bert R. Riemenschneider
  • Patent number: 4806201
    Abstract: The disclosure relates to a method for reducing filament formation over the BN+ oxide in semiconductor devices wherein a sidewall oxide is formed on the side walls of the first polysilicon layer prior to subsequent formation of the intermediate insulating layer, formation of a second polysilicon layer and subsequent anisotropic etch to provide for removal of all polysilicon over the field oxide.
    Type: Grant
    Filed: March 21, 1988
    Date of Patent: February 21, 1989
    Assignee: Texas Instruments Incorporated
    Inventors: Allan T. Mitchell, Howard L. Tigelaar, Shaym G. Garg, Kalipatnam V. Rao
  • Patent number: 4799992
    Abstract: A process for the fabrication of integrated circuits, wherein the interlevel dielectric material is partially etched back prior to reflow. This provides a pre-reflow profile which prevents filament problems in subsequently-patterned conductor levels, and which also avoids cracking of the interlevel dielectric during reflow.
    Type: Grant
    Filed: October 31, 1985
    Date of Patent: January 24, 1989
    Assignee: Texas Instruments Incorporated
    Inventors: Kalipatnam V. Rao, Allan T. Mitchell, James L. Paterson
  • Patent number: 4749443
    Abstract: The disclosure relates to a method for reducing filament formation over the BN+ oxide in semiconductor devices wherein a sidewall oxide is formed on the side walls of the first polysilicon layer prior to subsequent formation of the intermediate insulating layer, formation of a second polysilicon layer and subsequent anisotropic etch to provide for removal of all polysilicon over the field oxide.
    Type: Grant
    Filed: December 4, 1986
    Date of Patent: June 7, 1988
    Assignee: Texas Instruments Incorporated
    Inventors: Allan T. Mitchell, Howard L. Tigelaar
  • Patent number: 4713142
    Abstract: Using a method according to one embodiment of the present invention, an EPROM array may be fabricated providing a dense EPROM array.First the polycrystalline silicon floating gates are formed and partially patterned on the surface of a substrate. A thin thermally grown oxide layer is then formed over the entire array. The source/drain regions are then implanted through the thin silicon dioxide layer into the substrate. Next a thick silicon dioxide layer is deposited by chemical vapor deposition on the surface of the array. The surface of the array is then coated with photoresist which, because of its nature, provides a planarized surface on the top layer of photoresist. The photoresist and the silicon dioxide layer are then etched using an etching process which provides an etching ratio of 1 to 1 between photoresist and silicon dioxide. The photoresist is completely etched away thus leaving the planarized silicon dioxide surface.
    Type: Grant
    Filed: April 4, 1986
    Date of Patent: December 15, 1987
    Assignee: Texas Instruments Incorporated
    Inventors: Allan T. Mitchell, James L. Paterson
  • Patent number: 4597060
    Abstract: Using a method according to one embodiment of the present invention, an EPROM array may be fabricated providing a dense EPROM array.First the polycrystalline silicon floating gates are formed and partially patterned on the surface of a substrate. A thin thermally grown oxide layer is then formed over the entire array. The source/drain regions are then implanted through the thin silicon dioxide layer into the substrate. Next a thick silicon dioxide layer is deposited by chemical vapor deposition on the surface of the array. The surface of the array is then coated with photoresist which, because of its nature, provides a planarized surface on the top layer of photoresist. The photoresist and the silicon dioxide layer are then etched using an etching process which provides an etching ratio of 1 to 1 between photoresist and silicon dioxide. The photoresist is completely etched away thus leaving the planarized silicon dioxide surface.
    Type: Grant
    Filed: May 1, 1985
    Date of Patent: June 24, 1986
    Assignee: Texas Instruments Incorporated
    Inventors: Allan T. Mitchell, James L. Paterson