Patents Assigned to Alpha & Omega Semiconductor, Ltd.
  • Patent number: 7504676
    Abstract: This invention discloses an improved semiconductor power device includes a plurality of power transistor cells wherein each cell further includes a planar gate padded by a gate oxide layer disposed on top of a drift layer constituting an upper layer of a semiconductor substrate wherein the planar gate further constituting a split gate including a gap opened in a gate layer whereby the a total surface area of the gate is reduced. The transistor cell further includes a JFET (junction field effect transistor) diffusion region disposed in the drift layer below the gap of the gate layer wherein the JFET diffusion region having a higher dopant concentration than the drift region for reducing a channel resistance of the semiconductor power device.
    Type: Grant
    Filed: May 31, 2006
    Date of Patent: March 17, 2009
    Assignee: Alpha & Omega Semiconductor, Ltd.
    Inventors: Anup Bhalla, Francois Hebert, Daniel S. Ng
  • Publication number: 20090057869
    Abstract: A circuit package assembly is disclosed. The assembly includes a conductive substrate; a high-side n-channel metal oxide semiconductor field effect transistor (NMOSFET) having a source on a side facing a surface of the conductive substrate and in electrical contact therewith and a low-side standard n-channel metal oxide semiconductor field effect transistor (NMOSFET) having a drain on a side facing the conductive substrate and in electrical contact therewith. Co-packaging of high-side and low-side NMOSFETs in this manner may reduce package size and parasitic inductance and capacitance compared to conventional packaging.
    Type: Application
    Filed: August 31, 2007
    Publication date: March 5, 2009
    Applicant: ALPHA & OMEGA SEMICONDUCTOR, LTD.
    Inventors: Francois Hebert, Xiaotian Zhang, Kai Liu, Ming Sun, Anup Bhalla
  • Patent number: 7495877
    Abstract: A switching device includes a high-side MOSFET chip having a first high-side source connected to a low-side drain of a low-side MOSFET chip. The switching device further includes a transient reverse current diversion circuit connected to a drain of the low side MOSFET chip for diverting a reverse transient current therethrough whereby a reverse transient current in turning off the low side MOSFET chip is diverted from passing through a body diode of the low side MOSFET chip reducing a transient ringing oscillation. The reverse transient current diversion circuit includes a diode for conducting the reverse transient current from the drain. The reverse transient current diversion circuit further includes a capacitor connected between the diode and a source of the low side MOSFET chip.
    Type: Grant
    Filed: March 26, 2006
    Date of Patent: February 24, 2009
    Assignee: Alpha & Omega Semiconductor, Ltd.
    Inventor: Sanjay Havanur
  • Patent number: 7492005
    Abstract: This invention discloses an improved trenched metal oxide semiconductor field effect transistor (MOSFET) device that includes a trenched gate surrounded by a source region encompassed in a body region above a drain region disposed on a bottom surface of a substrate. The MOSFET cell further includes a shielded gate trench (SGT) structure below and insulated from the trenched gate. The SGT structure is formed substantially as a round hole having a lateral expansion extended beyond the trench gate and covered by a dielectric liner layer filled with a trenched gate material. The round hole is formed by an isotropic etch at the bottom of the trenched gate and is insulated from the trenched gate by an oxide insulation layer. The round hole has a lateral expansion beyond the trench walls and the lateral expansion serves as a vertical alignment landmark for controlling the depth of the trenched gate.
    Type: Grant
    Filed: December 28, 2005
    Date of Patent: February 17, 2009
    Assignee: Alpha & Omega Semiconductor, Ltd.
    Inventors: Hong Chang, Sung-Shan Tai, Tiesheng Li, Yu Wang
  • Patent number: 7489535
    Abstract: This invention discloses a circuit trimming system that includes a one-time programmable memory (OTP). The OTP further includes a forward biased trim device connected between a voltage supply Vcc and a ground voltage wherein the Vcc having a reduced voltage substantially lower than a trimming voltage for a reversed biased device at ten volts or higher. The OTP further includes a drive circuit provided to select the OTP at a low current operating condition and for turning on a high trim current through the forward biased trim device for trimming and programming the OTP. The trimming system further includes a sense circuit connected across the forward biased trim device is for sensing a current and voltage of the forward biased trim device.
    Type: Grant
    Filed: October 28, 2006
    Date of Patent: February 10, 2009
    Assignee: Alpha & Omega Semiconductor Ltd.
    Inventor: Shekar Mallikararjunaswamy
  • Publication number: 20080304306
    Abstract: A high voltage and high power boost converter is disclosed. The boost converter includes a boost converter IC and a discrete Schottky diode, both of which are co-packaged on a standard single common die pad.
    Type: Application
    Filed: June 11, 2007
    Publication date: December 11, 2008
    Applicant: ALPHA & OMEGA SEMICONDUCTOR, LTD.
    Inventors: Allen Chang, Wai-Keung Peter Cheng
  • Publication number: 20080304305
    Abstract: A boost converter for high power and high output voltage applications includes a low voltage controller integrated circuit and a high voltage, vertical, discrete field effect transistor, both of which are packed in a single package.
    Type: Application
    Filed: June 11, 2007
    Publication date: December 11, 2008
    Applicant: ALPHA & OMEGA SEMICONDUCTOR, LTD.
    Inventors: Allen Chang, Wai-Keung Peter Cheng
  • Publication number: 20080272371
    Abstract: A method for determining the depth etch, a method of forming a shielded gate trench (SGT) structure and a semiconductor device wafer are disclosed. A material layer is formed over part of a substrate having a trench. The material fills the trench. A resist mask is placed over a test portion of the material layer thereby defining a test structure that lies underneath the resist mask. The resist mask does not cover the trench. The material is isotropically etched and a signal related to a resistance change of the test structure is measured. A lateral undercut DL of the test structure is determined from the signal and an etch depth DT is determined from DL. The wafer may comprise one or more test structures forming a bridge circuit; one or more metal contacts that electrically connect the test structures through contact holes: and resist layer including over the test structures.
    Type: Application
    Filed: March 23, 2007
    Publication date: November 6, 2008
    Applicant: ALPHA & OMEGA SEMICONDUCTOR, LTD.
    Inventors: Tiesheng Li, Yu Wang, Yingying Lou, Anup Bhalla
  • Patent number: 7443225
    Abstract: A semiconductor power device includes a circuit to provide a gate signal wherein the gate signal has a negative temperature coefficient of gate driving voltage for decreasing a gate driving voltage with an increase temperature whereby the semiconductor power device has a net Ids temperature coefficient that is less than or equal to zero. In an exemplary embodiment, the gate voltage driver includes a diode that has a negative forward voltage temperature coefficient connected between a gate and a source of the semiconductor power device. In another embodiment, the gate voltage is integrated with the semiconductor power device manufactured as part of an integrated circuit with the semiconductor power device.
    Type: Grant
    Filed: June 30, 2006
    Date of Patent: October 28, 2008
    Assignee: Alpha & Omega Semiconductor, Ltd.
    Inventors: Sik K Lui, Anup Bhalla, Sanjay Havanur
  • Patent number: 7436022
    Abstract: This invention discloses a semiconductor power device that includes an active cell area having a plurality of power transistor cells and a junction barrier Schottky (JBS) area. The semiconductor power device includes the JBS area that further includes a plurality of Schottky diodes each having a PN junction disposed on an epitaxial layer near a top surface of a semiconductor substrate wherein the PN junction further includes a counter dopant region disposed in the epitaxial layer for reducing a sudden reversal of dopant profile near the PN junction for preventing an early breakdown in the PN junction.
    Type: Grant
    Filed: April 29, 2006
    Date of Patent: October 14, 2008
    Assignee: Alpha & Omega Semiconductors, Ltd.
    Inventors: Anup Bhalla, Daniel Ng, Sik K Lui
  • Publication number: 20080233748
    Abstract: A method for determining the depth etch, a method of forming a shielded gate trench (SGT) structure and a semiconductor device wafer are disclosed. A material layer is formed over part of a substrate having a trench. The material fills the trench. A resist mask is placed over a test portion of the layer of material. The resist mask does not cover the trench. The layer of material is isotropically etched. An etch depth may be determined from a characteristic of etching of the material underneath the mask. Such a method may be used for forming SGT structures. The wafer may comprise a layer of material disposed on at least a portion of a surface of semiconductor wafer; a resist mask comprising an angle-shaped test portion disposed over a portion of the layer of material; and a ruler marking on the surface of the substrate proximate the test portion.
    Type: Application
    Filed: March 23, 2007
    Publication date: September 25, 2008
    Applicant: ALPHA & OMEGA SEMICONDUCTOR, LTD.
    Inventors: Yingying Lou, Tiesheng Li, Yu Wang, Anup Bhalla
  • Patent number: 7400118
    Abstract: A high efficiency single-inductor dual-control loop power converter (SIDL) is proposed for converting unregulated DC input into regulated DC output to a power load. The SIDL includes: an energy storage loop having: a power inductor, a power capacitor and a power diode. A PWM switching power regulating loop for converting the unregulated DC input into the regulated DC output. a power-efficiency maximizing loop in parallel connection with the power diode. The power-efficiency maximizing loop includes: a power shunt transistor in parallel connection with the power diode and a real-time control loop adjusting, in response to a freewheeling current through the power diode, conductance of the power shunt transistor in a manner that a higher freewheeling current results in a higher conductance of the power shunt transistor.
    Type: Grant
    Filed: June 1, 2007
    Date of Patent: July 15, 2008
    Assignee: Alpha & Omega Semiconductor, Ltd.
    Inventors: Zhiye Zhang, Yu-Cheng Chang
  • Patent number: 7378884
    Abstract: This invention discloses a new MOSFET device. The MOSFET device has an improved operation characteristic achieved by connecting a shunt FET of low impedance to the MOSFET device. The shunt FET is to shunt a transient current therethrough. The shunt FET is employed for preventing an inadvertent turning on of the MOSFET device. The inadvertent turning on of the MOSFET may occur when a large voltage transient occurs at the drain of the MOSFET device. By connecting the gate of the shunt FET to the drain of the MOSFET device, a low impedance path is provided at the right point of time during the circuit operation to shunt the current without requiring any external circuitry.
    Type: Grant
    Filed: May 21, 2007
    Date of Patent: May 27, 2008
    Assignee: Alpha & Omega Semiconductor, Ltd.
    Inventors: Anup Bhalla, Sik K. Lui
  • Patent number: 7355433
    Abstract: This invention discloses a circuit for performing an unclamped inductive test on a metal oxide semiconductor field effect transistor (MOSFET) device driven by a gate driver. The circuit includes a current sense circuit for measuring an unclamped inductive testing (UIS) current that increases with an increase of a pulse width inputted from the gate driver to the MOSFET device wherein the current sensing circuit is provided to turn off the gate driver when a predefined UIS current is reached. The test circuit further includes a MOSFET failure detection circuit connected to a drain terminal of the MOSFET device for measuring a drain voltage change for detecting the MOSFET failure during the UIS test. The test circuit further includes a first switch for switching ON/OFF a power supply to the MOSFET device to and a second switch connected between a drain and source terminal of the MOSFET.
    Type: Grant
    Filed: December 14, 2005
    Date of Patent: April 8, 2008
    Assignee: Alpha & Omega Semiconductor, Ltd
    Inventors: Sik K Lui, Anup Bhalla
  • Patent number: 7256446
    Abstract: This invention discloses a one-time programmable (OTP) memory cell. The OTP memory cell includes a dielectric layer disposed between two conductive polysilicon segments wherein the dielectric layer is ready to change from a non-conductive state to a conductive state through an induced voltage breakdown. In a preferred embodiment, one of the conductive polysilicon segments further includes an etch undercut configuration for conveniently inducing the voltage breakdown in the dielectric layer. In a preferred embodiment, the dielectric layer is further formed as sidewalls covering the edges and corners of a first polysilicon segments to conveniently induce a voltage breakdown in the dielectric layer by the edge and corner electrical field effects.
    Type: Grant
    Filed: May 5, 2005
    Date of Patent: August 14, 2007
    Assignee: Alpha and Omega Semiconductor, Ltd.
    Inventors: Yongzhong Hu, Sung-Shan Tai
  • Patent number: 7221195
    Abstract: This invention discloses a new MOSFET device. The MOSFET device has an improved operation characteristic achieved by connecting a shunt FET of low impedance to the MOSFET device. The shunt FET is to shunt a transient current therethrough. The shunt FET is employed for preventing an inadvertent turning on of the MOSFET device. The inadvertent turning on of the MOSFET may occur when a large voltage transient occurs at the drain of the MOSFET device. By connecting the gate of the shunt FET to the drain of the MOSFET device, a low impedance path is provided at the right point of time during the circuit operation to shunt the current without requiring any external circuitry.
    Type: Grant
    Filed: March 18, 2005
    Date of Patent: May 22, 2007
    Assignee: Alpha & Omega Semiconductor, Ltd.
    Inventors: Anup Bhalla, Sik K. Lui
  • Patent number: 7208818
    Abstract: A semiconductor package including a relatively thick lead frame having a plurality of leads and a first lead frame pad, the first lead frame pad including a die coupled thereto, bonding wires connecting the die to the plurality of leads, the bonding wires being aluminum, and a resin body encapsulating the die, bonding wires and at least a portion of the lead frame.
    Type: Grant
    Filed: July 20, 2004
    Date of Patent: April 24, 2007
    Assignee: Alpha and Omega Semiconductor Ltd.
    Inventors: Leeshawn Luo, Anup Bhalla, Sik K. Lui, Yueh-Se Ho, Mike F. Chang, Xiao Tian Zhang
  • Patent number: 7183616
    Abstract: This invention discloses a method for configuring a power MOSFET package by packaging several paralleled and separated MOSFET chips in the assembly. The method further includes a step of connecting the gate pad on each of these MOSFET chips with a low-resistance gate bus. The package resistance and inductance are significantly reduced and switching speed and heat dissipation are substantially improved.
    Type: Grant
    Filed: July 30, 2002
    Date of Patent: February 27, 2007
    Assignee: Alpha & Omega Semiconductor, Ltd.
    Inventors: Anup Bhalla, Sik K Lui, Leeshawn Luo, Yueh-Se Ho
  • Patent number: 7122882
    Abstract: A semiconductor integrated circuit package having a common source current sensing circuit includes a main die having an integrated circuit, the main die including a source bonding pad and a gate bonding pad disposed on an upper surface, a leadframe having a leadframe pad disposed under the main die, and a monitoring die including a source bonding pad and a gate bonding pad disposed on an upper surface, the monitoring die being coupled to the main die in such manner that the main die source bonding pad is coupled to the monitoring die source bonding pad and the main die gate bonding pad is coupled to the monitoring die gate bonding pad and such that the main die and monitoring die upper surfaces are adjacent to one another.
    Type: Grant
    Filed: November 2, 2004
    Date of Patent: October 17, 2006
    Assignee: Alpha and Omega Semiconductor Ltd.
    Inventors: Sik K. Lui, Anup Bhalla
  • Patent number: 7049668
    Abstract: A trench MOSFET (Metal Oxide Semiconductor Field Effect Transistor) structure includes crisscrossing trenches formed in a semiconductor substrate. The trenches include inner surfaces filled with conductive material which is electrically separated from the substrate by insulating material. The conductive material is in contact with an overlying first metal layer through a plurality of first contact openings formed in a first insulating layer which is sandwiched between the first metal layer and the trenches. The conductive material in the trenches and the first metal layer constitute the gate of the MOSFET structure. There is also a second metal layer in contact with a source layer formed in the substrate through a plurality of second contact openings formed in a second insulating layer which is sandwiched between the first metal layer and the second metal layer. The second metal layer and the source layer constitute the source of the MOSFET structure.
    Type: Grant
    Filed: August 25, 1998
    Date of Patent: May 23, 2006
    Assignee: Alpha and Omega Semiconductor, Ltd.
    Inventor: Fwu-Iuan Hshieh