Patents by Inventor Vishnu Khemka

Vishnu Khemka 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: 10103257
    Abstract: A plurality of trench stripes are disposed in parallel in an epitaxial layer on a drain and extends from a top region to a bottom region of a first surface of the semiconductor. A first polysilicon layer is in each of the trench stripes. The first polysilicon layer extends between the drain and the first surface proximal to the top region and the bottom region, and between the drain and a level below the first surface in a middle region between the top region and the bottom region. A second polysilicon layer is over the first polysilicon layer in the middle region, wherein the first poly silicon layer forms a shield, and the second polysilicon layer forms a gate. A source is in a silicon mesa stripe surrounding the first trench stripe.
    Type: Grant
    Filed: November 10, 2017
    Date of Patent: October 16, 2018
    Assignee: NXP USA, Inc.
    Inventors: Ganming Qin, Vishnu Khemka, Ljubo Radic, Bernhard Grote, Tanuj Saxena, Moaniss Zitouni
  • Patent number: 9397233
    Abstract: A semiconductor process and apparatus provide a high voltage deep trench capacitor structure (10) that is integrated in an integrated circuit, alone or in alignment with a fringe capacitor (5). The deep trench capacitor structure is constructed from a first capacitor plate (4) that is formed from a doped n-type SOI semiconductor layer (e.g., 4a-c). The second capacitor plate (3) is formed from a doped p-type polysilicon layer (3a) that is tied to the underlying substrate (1).
    Type: Grant
    Filed: June 2, 2010
    Date of Patent: July 19, 2016
    Assignee: North Star Innovations Inc.
    Inventors: Ronghua Zhu, Vishnu Khemka, Amitava Bose, Todd C. Roggenbauer
  • Patent number: 9196680
    Abstract: A laterally diffused metal oxide semiconductor field effect transistor (LDMOSFET) includes: a source contact region, a gate contact region, a drain contact region, and an n-type buried layer. The LDMOSFET also includes a p-type body region formed in an n-type epitaxial layer, the p-type body region directly contacting the source contact region and extending past an end of the source contact region toward the drain contact region. The LDMOSFET also includes a p-type reduced surface field (PRSF) region formed in the n-type epitaxial layer, the PRSF region disposed between the p-type body region and the n-type buried layer. The LDMOSFET also includes an n-type drift region formed in the n-type epitaxial layer, the n-type drift region directly contacting the drain contact region. The LDMOSFET also includes an n-type diffusion region in the n-type epitaxial layer, the n-type diffusion region electrically connecting the n-type buried layer with the n-type drift region.
    Type: Grant
    Filed: June 24, 2014
    Date of Patent: November 24, 2015
    Assignee: MAXIM INTEGRATED PRODUCTS, INC.
    Inventors: Vishnu Khemka, Ronghua Zhu, Tahir Arif Khan, Vijay Parthasarathy
  • Patent number: 9196681
    Abstract: A laterally diffused metal oxide semiconductor field effect transistor (LDMOSFET) includes a p-type body region formed in an n-type epitaxial layer, the p-type body region directly contacting a source contact region and extending past an end of the source contact region toward a drain contact region. The LDMOSFET also includes a p-type reduced surface field (PRSF) region formed in the n-type epitaxial layer, the PRSF region disposed between the p-type body region and the n-type buried layer. The LDMOSFET also includes an n-type drain drift region formed in the n-type epitaxial layer, the n-type drain drift region directly contacting the drain contact region. The LDMOSFET also includes an n-type drift region formed in the n-type epitaxial layer, the n-type drift region directly contacting the n-type drain drift region.
    Type: Grant
    Filed: June 24, 2014
    Date of Patent: November 24, 2015
    Assignee: MAXIM INTEGRATED PRODUCTS, INC.
    Inventors: Vishnu Khemka, Ronghua Zhu, Tahir Arif Khan, Vijay Parthasarathy
  • Patent number: 8987818
    Abstract: A split gate power transistor includes a laterally configured power MOSFET including a doped silicon substrate, a gate oxide layer formed on a surface of the substrate, and a split polysilicon layer formed over the gate oxide layer. The polysilicon layer is cut into two electrically isolated portions, a first portion forming a polysilicon gate positioned over a channel region of the substrate, and a second portion forming a polysilicon field plate formed over a portion of a transition region of the substrate. The two polysilicon portions are separated by a gap. A lightly doped region is implanted in the substrate below the gap, thereby forming a bridge having the same doping type as the substrate body. The field plate also extends over a field oxide filled trench formed in the substrate. The field plate is electrically coupled to a source of the split gate power transistor.
    Type: Grant
    Filed: December 6, 2011
    Date of Patent: March 24, 2015
    Assignee: Maxim Integrated Products, Inc.
    Inventors: Joel Montgomery McGregor, Vishnu Khemka
  • Patent number: 8969958
    Abstract: A split gate power transistor includes a doped substrate, a gate oxide layer on the substrate, and a split polysilicon layer over the gate oxide layer, which forms a polysilicon gate positioned over a channel region and a first portion of a transition region and a polysilicon field plate positioned over a second portion of the transition region and a shallow trench isolation region. The two polysilicon portions are separated by a gap. The field plate is electrically coupled to a source of the split gate power transistor. One or more body extension regions, each having the same doping type as the body substrate, extend at least underneath the edge of the field plate adjacent to the gap. The body extension regions force the portion of the transition region underneath the field plate into deep-depletion, thereby preventing the formation of a hole inversion layer in this region.
    Type: Grant
    Filed: April 30, 2012
    Date of Patent: March 3, 2015
    Assignee: Maxim Integrated Products, Inc.
    Inventors: Vishnu Khemka, Ronghua Zhu, Tahir Arif Khan, Bernhard Heinrich Grote
  • Patent number: 8963241
    Abstract: A split gate power transistor includes a doped substrate, a gate oxide layer on the substrate, and a split polysilicon layer over the gate oxide layer, which forms a polysilicon gate and a polysilicon field plate. The two polysilicon portions are separated by a gap. The field plate is electrically coupled to a source of the split gate power transistor. One or more polysilicon extension tabs extend from the field plate to at least above the edge of the first doped region. The polysilicon gate is cut to form a cut-out region for the end of each polysilicon extension tab extending toward the body substrate. The one or more polysilicon extension tabs force the portion of the transition region underneath the field plate into deep-depletion, thereby preventing the formation of a hole inversion layer in this region.
    Type: Grant
    Filed: April 30, 2012
    Date of Patent: February 24, 2015
    Assignee: Maxim Integrated Products, Inc.
    Inventors: Vishnu Khemka, Ronghua Zhu, Tahir Arif Khan, Bernhard Heinrich Grote
  • Patent number: 8946851
    Abstract: A split gate power transistor includes a laterally configured power MOSFET including a doped silicon substrate having a first doped region and a second doped region of an opposite type as the first doped region, a gate oxide layer formed on a surface of the substrate, and a split polysilicon layer formed over the gate oxide layer. The polysilicon layer is cut into two electrically isolated portions, a first portion forming a polysilicon gate positioned over a channel region and a transition region of the substrate, and a second portion forming a polysilicon field plate formed entirely over a field oxide filled trench formed in the second doped region. The two polysilicon portions are separated by a gap. A lightly doped region is implanted in the substrate below the gap and adjacent to the trench, thereby forming a fill region having the same doping type as the first doped region.
    Type: Grant
    Filed: April 13, 2012
    Date of Patent: February 3, 2015
    Assignee: Maxim Integrated Products, Inc.
    Inventors: Joel Montgomery McGregor, Vishnu Khemka
  • Publication number: 20100230736
    Abstract: A semiconductor process and apparatus provide a high voltage deep trench capacitor structure (10) that is integrated in an integrated circuit, alone or in alignment with a fringe capacitor (5). The deep trench capacitor structure is constructed from a first capacitor plate (4) that is formed from a doped n-type SOI semiconductor layer (e.g., 4a-c). The second capacitor plate (3) is formed from a doped p-type polysilicon layer (3a) that is tied to the underlying substrate (1).
    Type: Application
    Filed: June 2, 2010
    Publication date: September 16, 2010
    Inventors: Ronghua Zhu, Vishnu Khemka, Amitava Bose, Todd C. Roggenbauer
  • Patent number: 7732274
    Abstract: A semiconductor process and apparatus provide a high voltage deep trench capacitor structure (10) that is integrated in an integrated circuit, alone or in alignment with a fringe capacitor (5). The deep trench capacitor structure is constructed from a first capacitor plate (4) that is formed from a doped n-type SOI semiconductor layer (e.g., 4a-c). The second capacitor plate (3) is formed from a doped p-type polysilicon layer (3a) that is tied to the underlying substrate (1).
    Type: Grant
    Filed: May 23, 2007
    Date of Patent: June 8, 2010
    Assignee: Freescale Semiconductor, Inc.
    Inventors: Ronghua Zhu, Vishnu Khemka, Amitava Bose, Todd C. Roggenbauer
  • Patent number: 7608908
    Abstract: Higher voltage device isolation structures (40, 60, 70, 80, 90, 90?) are provided for semiconductor integrated circuits having strongly doped buried layers (24, 24?). One or more dielectric lined deep isolation trenches (27, 27?, 27?, 27??) separates adjacent device regions (411, 412; 611, 612; 711, 712; 811, 812; 911, 912). Electrical breakdown (BVdss) between the device regions (411, 412; 611, 612; 711, 712; 811, 812; 911, 912) and the oppositely doped substrate (22, 22?) is found to occur preferentially where the buried layer (24, 24?) intersects the dielectric sidewalls (273, 274; 273?, 274?; 273?, 274?) of the trench (27, 27?, 27?, 27??). The breakdown voltage (BVdss) is increased by providing a more lightly doped region (42, 42?, 62, 72, 82) of the same conductivity type as the buried layer (24, 24?), underlying the buried layer (24, 24?) at the trench sidewalls (273, 274; 273?, 274?; 273?, 274?).
    Type: Grant
    Filed: May 22, 2008
    Date of Patent: October 27, 2009
    Assignee: Freescale Semiconductor, Inc.
    Inventors: Vishnu Khemka, Amitava Bose, Michael C. Butner, Bernhard H. Grote, Tahir A. Khan, Shifeng Shen, Ronghua Zhu
  • Publication number: 20080293211
    Abstract: A semiconductor process and apparatus provide a high voltage deep trench capacitor structure (10) that is integrated in an integrated circuit, alone or in alignment with a fringe capacitor (5). The deep trench capacitor structure is constructed from a first capacitor plate (4) that is formed from a doped n-type SOI semiconductor layer (e.g., 4a-c). The second capacitor plate (3) is formed from a doped p-type polysilicon layer (3a) that is tied to the underlying substrate (1).
    Type: Application
    Filed: May 23, 2007
    Publication date: November 27, 2008
    Inventors: Ronghua Zhu, Vishnu Khemka, Amitava Bose, Todd C. Roggenbauer
  • Patent number: 7309638
    Abstract: A semiconductor component comprises a first semiconductor region (110, 310), a second semiconductor region (120, 320) above the first semiconductor region, a third semiconductor region (130, 330) above the second semiconductor region, a fourth semiconductor region (140, 340) above the third semiconductor region, a fifth semiconductor region (150, 350) above the second semiconductor region and at least partially contiguous with the fourth semiconductor region, a sixth semiconductor region (160, 360) above and electrically shorted to the fifth semiconductor region, and an electrically insulating layer (180, 380) above the fourth semiconductor region and the fifth semiconductor region. A junction (145, 345) between the fourth semiconductor region and the fifth semiconductor region forms a zener diode junction, which is located only underneath the electrically insulating layer. In one embodiment, a seventh semiconductor region (170) circumscribes the third, fourth, fifth, and sixth semiconductor regions.
    Type: Grant
    Filed: July 14, 2005
    Date of Patent: December 18, 2007
    Assignee: Freescale Semiconductor, Inc.
    Inventors: Vishnu Khemka, Vijay Parthasarathy, Ronghua Zhu, Amitava Bose, Todd C. Roggenbauer
  • Patent number: 7276419
    Abstract: A semiconductor device may include first, second, and third semiconductor layers. The first and third layers may have a first dopant type, and the second layer may have a second dopant type. A first region within the third semiconductor layer may have the second dopant type. A second region between the first region and the second semiconductor layer may have the first dopant type. A third region above the second region may have the first dopant type. A fourth semiconductor region adjacent to the third region may have a first concentration of the second dopant type. A source contact region may have a second concentration of the second dopant type adjacent to the third semiconductor region and adjacent to the fourth semiconductor region. The second concentration may be higher than the first concentration.
    Type: Grant
    Filed: October 31, 2005
    Date of Patent: October 2, 2007
    Assignee: Freescale Semiconductor, Inc.
    Inventors: Vishnu Khemka, John M. Pigott, Ronghua Zhu, Amitava Bose, Randall C. Gray, Jeffrey J. Braun
  • Publication number: 20070224738
    Abstract: A microelectronic assembly and a method for constructing a microelectronic assembly are provided. The microelectronic assembly may include a semiconductor substrate with an isolation trench (62) formed therein. The isolation trench (62) may have first and second opposing inner walls (74, 76) and a floor (78). First and second conductive plates (106) may be formed over the first and second opposing inner walls (74, 76) of the isolation trench (62) respectively such that there is a gap (90) between the first and second conductive plates (106). First and second semiconductor devices (114) may be formed in the semiconductor substrate on opposing sides of the isolation trench (62). The method may include forming a trench (62) in a semiconductor substrate, forming first and second conductive plates (106) within the trench, and forming first and second semiconductor devices (114) in the semiconductor substrate on opposing sides of the trench (62).
    Type: Application
    Filed: March 27, 2006
    Publication date: September 27, 2007
    Inventors: Vishnu Khemka, Amitava Bose, Todd Roggenbauer, Ronghua Zhu
  • Publication number: 20070221967
    Abstract: A semiconductor device may include a semiconductor substrate having a first dopant type. A first semiconductor region within the semiconductor substrate may have a plurality of first and second portions (44, 54). The first portions (44) may have a first thickness, and the second portions (54) may have a second thickness. The first semiconductor region may have a second dopant type. A plurality of second semiconductor regions (42) within the semiconductor substrate may each be positioned at least one of directly below and directly above a respective one of the first portions (44) of the first semiconductor region and laterally between a respective pair of the second portions (54) of the first semiconductor region. A third semiconductor region (56) within the semiconductor substrate may have the first dopant type. A gate electrode (64) may be over at least a portion of the first semiconductor region and at least a portion of the third semiconductor region (56).
    Type: Application
    Filed: March 27, 2006
    Publication date: September 27, 2007
    Inventors: Vishnu Khemka, Amitava Bose, Todd Roggenbauer, Ronghua Zhu
  • Publication number: 20070200184
    Abstract: A power metal-oxide-semiconductor field effect transistor (MOSFET) (100) incorporates a stepped drift region including a shallow trench insulator (STI) (112) partially overlapped by the gate (114) and which extends a portion of the distance to a drain region (122). A silicide block extends from and partially overlaps STI (112) and drain region (122). The STI (112) has a width that is approximately 50% to 75% of the drift region.
    Type: Application
    Filed: February 24, 2006
    Publication date: August 30, 2007
    Inventors: Ronghua Zhu, Amitava Bose, Vishnu Khemka, Todd Roggenbauer
  • Publication number: 20070200136
    Abstract: The present disclosure relates to isolated Zener diodes (100) that are substantially free of substrate current injection when forward biased. In particular, the Zener diodes (100) include an “isolation tub” structure that includes surrounding walls (150, 195) and a base (130) formed of semiconductor regions. In addition, the diodes (100) include silicide block (260) extending between anode (210) and cathode (220) regions. The reduction or elimination of substrate current injection overcomes a significant shortcoming of conventional Zener diodes that generally all suffer from substrate current injection when they are forward biased. Due to this substrate current injection, the current from each of a conventional diode's two terminals is not the same.
    Type: Application
    Filed: February 28, 2006
    Publication date: August 30, 2007
    Inventors: Ronghua Zhu, Vishnu Khemka, Amitava Bose, Todd Roggenbauer
  • Publication number: 20070096225
    Abstract: A semiconductor device may include first, second, and third semiconductor layers. The first and third layers may have a first dopant type, and the second layer may have a second dopant type. A first region within the third semiconductor layer may have the second dopant type. A second region between the first region and the second semiconductor layer may have the first dopant type. A third region above the second region may have the first dopant type. A fourth semiconductor region adjacent to the third region may have a first concentration of the second dopant type. A source contact region may have a second concentration of the second dopant type adjacent to the third semiconductor region and adjacent to the fourth semiconductor region. The second concentration may be higher than the first concentration.
    Type: Application
    Filed: October 31, 2005
    Publication date: May 3, 2007
    Inventors: Vishnu Khemka, John Pigott, Ronghua Zhu, Amitava Bose, Randall Gray, Jeffrey Braun
  • Publication number: 20070045767
    Abstract: Structure and method are provided for semiconductor devices. The devices include trenches filled with highly doped polycrystalline semiconductor, extending from the surface into the body of the device for, among other things: (i) reducing substrate current injection, (ii) reducing ON-resistance and/or (iii) reducing thermal impedance to the substrate. For isolated LDMOS devices, the resistance between the lateral isolation wall (tied to the source) and the buried layer is reduced, thereby reducing substrate injection current. When placed in the drain of a lateral device or in the collector of a vertical device, the poly-filled trench effectively enlarges the drain or collector region, thereby lowering the ON-resistance. For devices formed on an oxide isolation layer, the poly-filled trench desirably penetrates this isolation layer thereby improving thermal conduction from the active regions to the substrate. The poly filled trenches are conveniently formed by etch and refill.
    Type: Application
    Filed: August 25, 2005
    Publication date: March 1, 2007
    Inventors: Ronghua Zhu, Vishnu Khemka, Amitava Bose