Patents by Inventor Xizeng Shi

Xizeng Shi 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).

  • Publication number: 20070171702
    Abstract: An MRAM array has a plurality of MRAM devices that are arranged in rows and columns with segmented word lines. A magnetic biasing field is coupled to each of the MRAM devices. The MRAM devices are programmed by providing a bidirectional bit line current to a selected bit line of the plurality of bit lines and a word line current pulse to one word line segment of one row of word line segments by discharging coupled word line segments. The field biasing device may be permanent magnetic layers or write biasing lines in proximity to the fixed magnetic layer of each of the MRAM and has a magnetic orientation equivalent to the magnetic orientation of a word line segment magnetic field generated by the word line current pulse.
    Type: Application
    Filed: January 25, 2006
    Publication date: July 26, 2007
    Inventors: Xizeng Shi, Po-Kang Wang, Hsu Yang
  • Publication number: 20070140033
    Abstract: A configurable MRAM device is achieved. The device comprises a memory array of magnetic memory cells. A first part of the array comprises the memory cells that can be accessed for reading and writing during normal operation. A second part of the array comprises the memory cells that can be read only during a power up initialization. The second part of the array is used to store configuration data for altering the physical operation of the memory array. Programmable current sources and timing delays use the stored configuration data to optimize device performance. A redundant section of memory cells is activated by the configuration data.
    Type: Application
    Filed: December 20, 2005
    Publication date: June 21, 2007
    Inventors: Hsu Yang, Po-Kang Wang, Xizeng Shi
  • Publication number: 20070115717
    Abstract: An MRAM reference cell sub-array provides a mid-point reference current to sense amplifiers. The MRAM reference cell sub-array has MRAM cells arranged in rows and columns. Bit lines are associated with each column of the sub-array. A coupling connects the bit lines of pairs of the columns together at a location proximally to the sense amplifiers. The MRAM cells of a first of the pair of columns are programmed to a first magneto-resistive state and the MRAM cells of a second of the pair of columns are programmed to a second magneto-resistive state. When one row of data MRAM cells is selected for reading, a row of paired MRAM reference cells are placed in parallel to generate the mid-point reference current for sensing. The MRAM reference sub-array may be programmed electrically or aided by a magnetic field. A method for verifying programming of the MRAM reference sub-array is discussed.
    Type: Application
    Filed: November 21, 2005
    Publication date: May 24, 2007
    Inventors: Hsu Yang, Po-Kang Wang, Xizeng Shi
  • Patent number: 7211874
    Abstract: An MTJ MRAM cell element, whose free layer has a shape induced magnetic anisotropy, is formed between orthogonal word and bit lines. The bit line is a composite line which includes a high conductivity current carrying layer and a soft adjacent magnetic layer (SAL). During operation, the soft magnetic layer concentrates the magnetic field of the current and, due to its proximity to the free layer, it magnetically couples with the free layer to produce two magnetization states of greater and lesser stability. During switching, the layer is first placed in the less stable state by a word line current, so that a small bit line current can switch its magnetization direction. After switching, the state reverts to its more stable form as a result of magnetostatic interaction with the SAL, which prevents it from being accidentally rewritten when it is not actually selected and also provides stability against thermal agitation.
    Type: Grant
    Filed: April 6, 2004
    Date of Patent: May 1, 2007
    Assignees: Headway Technologies, Inc., Applied Spintronics, Inc.
    Inventors: Yimin Guo, Po-Kang Wang, Xizeng Shi, Tai Min
  • Patent number: 7184302
    Abstract: In an MRAM array based on MTJs, the size of segmented word line select transistors and their associated connections become a significant overhead, especially when the operating point is chosen deep along the hard axis of the asteroid curve. This problem has been overcome by placing the big segmented word line select transistors under the MTJ array and reducing the overall MRAM cell array down to a level comparable to a simple Cross Point MRAM array.
    Type: Grant
    Filed: March 30, 2005
    Date of Patent: February 27, 2007
    Assignees: Headway Technologies, Inc., Applied Spintadnics, Inc.
    Inventors: Hsu Kai Yang, Po-Kang Wang, Xizeng Shi
  • Patent number: 7180769
    Abstract: The word line segment select transistor of a segmented word line array is placed on the word line current source side. This eliminates many undesirable effects currently associated with segmented word line MRAM arrays.
    Type: Grant
    Filed: April 12, 2005
    Date of Patent: February 20, 2007
    Assignees: Headway Technologies, Inc., Applied Spintronics, Inc.
    Inventors: Po-Kang Wang, Yin Rong, Hsu Kai Yang, Xizeng Shi
  • Patent number: 7123506
    Abstract: A method and system for programming a magnetic memory is disclosed. The method and system further include turning on a word line current and turning on a bit line current. The word line current is for generating at least one hard axis field. The bit line current is for generating at least one easy axis field. In one aspect, the method and system further include turning off the word line current and the bit line current such that a state of the at least one magnetic memory cell is repeatably obtained. In another aspect, the word line current is turned off after the bit line current is turned off.
    Type: Grant
    Filed: June 3, 2004
    Date of Patent: October 17, 2006
    Assignees: Applied Spintronics Technology, Inc., Headway Technologies, Inc.
    Inventors: Xizeng Shi, Son Le, Po-Kang Wang, Tai Min
  • Publication number: 20060227597
    Abstract: The word line segment select transistor of a segmented word line array is placed on the word line current source side. This eliminates many undesirable effects currently associated with segmented word line MRAM arrays.
    Type: Application
    Filed: April 12, 2005
    Publication date: October 12, 2006
    Inventors: Po-Kang Wang, Yin Rong, Hsu Kai Yang, Xizeng Shi
  • Publication number: 20060221673
    Abstract: In an MRAM array based on MTJs, the size of segmented word line select transistors and their associated connections become a significant overhead, especially when the operating point is chosen deep along the hard axis of the asteroid curve. This problem has been overcome by placing the big segmented word line select transistors under the MTJ array and reducing the overall MRAM cell array down to a level comparable to a simple Cross Point MRAM array.
    Type: Application
    Filed: March 30, 2005
    Publication date: October 5, 2006
    Inventors: Hsu Yang, Po-Kang Wang, Xizeng Shi
  • Publication number: 20060211155
    Abstract: An MTJ MRAM cell is formed between ultra-thin orthogonal word and bit lines of high conductivity material whose thickness is less than 100 nm. Lines of this thickness produce switching magnetic fields at the cell free layer that are enhanced by a factor of approximately two for a given current. Because the lines require thinner depositions, there is no necessity of removing material by CMP during patterning and polishing. Therefore, there is a uniform spacing between the lines and the cell free layer.
    Type: Application
    Filed: May 22, 2006
    Publication date: September 21, 2006
    Inventors: Tai Min, Pokang Wang, Xizeng Shi, Yimin Guo
  • Patent number: 7067330
    Abstract: An MTJ MRAM cell is formed between ultra-thin orthogonal word and bit lines of high conductivity material whose thickness is less than 100 nm. Lines of this thickness produce switching magnetic fields at the cell free layer that are enhanced by a factor of approximately two for a given current. The fabrication of a cell with such thin lines is actually simplified as a result of the thinner depositions because the fabrication process eliminates the necessity of removing material by CMP during patterning and polishing, thereby producing uniform spacing between the lines and the cell free layer.
    Type: Grant
    Filed: July 16, 2004
    Date of Patent: June 27, 2006
    Assignees: Headway Technologies, Inc., Applied Spintronics, Inc.
    Inventors: Tai Min, Pokang Wang, Xizeng Shi, Yimin Guo
  • Patent number: 7067866
    Abstract: A method and system for providing magnetic memory cells in a magnetic memory is disclosed. The method and system include providing each magnetic memory element, providing a first write line and a second write line for each magnetic memory element. The magnetic memory element has a top portion and a bottom portion. The first write line is below the magnetic memory element and is electrically connected with the bottom portion of the magnetic memory element. The second write line is above the magnetic memory element. The second write line is electrically isolated from the magnetic memory element and oriented at an angle to the first write line. The magnetic memory cell allows for a simplified fabrication process, a reduced cell size, and an improved programming efficiency.
    Type: Grant
    Filed: June 26, 2003
    Date of Patent: June 27, 2006
    Assignee: Applied Spintronics Technology, Inc.
    Inventor: Xizeng Shi
  • Patent number: 7027324
    Abstract: A method and system for providing a magnetic memory including magnetic memory cells associated with a word line segment is disclosed. The magnetic memory cell includes a magnetic storage device and an isolation device. The isolation device is coupled to the magnetic tunneling junction and with a combined word line for reading and writing to the magnetic memory cell. The magnetic storage device and the isolation device are configured such that no direct current path to ground exists during the writing to the magnetic memory cell. In one aspect, in a write mode, the combined word line associated with the word line segment and the word line segment are activated. In the read mode, at least a portion of the memory cells associated with the word line segment are selected using the combined word line.
    Type: Grant
    Filed: June 9, 2004
    Date of Patent: April 11, 2006
    Assignees: Headway Technologies, Inc., Applied Spintronics Technology, Inc.
    Inventors: Hsu Kai (Karl) Yang, Xizeng Shi, Po-Kang Wang, Bruce Yee Yang
  • Patent number: 7009266
    Abstract: A method and system for providing a magnetic element and a magnetic memory using the magnetic element are disclosed. The magnetic memory includes a plurality of magnetic elements. The method and system include providing a plurality of layers and a passivation layer for each of the plurality of magnetic elements. A portion of the layers in the magnetic element includes at least one magnetic layer. The plurality of layers also has a top and a plurality of sides. The passivation layer covers at least a portion of the plurality of sides.
    Type: Grant
    Filed: February 17, 2004
    Date of Patent: March 7, 2006
    Assignees: Applied Spintronics Technology, Inc., Headway Technologies, Inc.
    Inventors: Xizeng Shi, Po-Kang Wang, Yimin Guo, Tai Min
  • Patent number: 7007372
    Abstract: An inductive write element is disclosed for use in a magnetic data recording system. The write element provides increased data rate and data density capabilities through improved magnetic flux flow through the element. The write element includes a magnetic yoke constructed of first and second magnetic poles. The first pole includes a pedestal constructed of a high magnetic moment (high Bsat) material, which is preferably FeRhN nanocrystalline films with lamination layers of CoZrCr. The second pole includes a thin inner layer of high Bsat material (also preferably FeRhN nanocrystalline films with lamination layers of CoZrCr), the remainder being constructed of a magnetic material capable of being electroplated, such as a Ni—Fe alloy. An electrically conductive coil passes through the yoke between the first and second poles to induce a magnetic flux in the yoke when an electrical current is caused to flow through the coil.
    Type: Grant
    Filed: September 5, 2003
    Date of Patent: March 7, 2006
    Assignee: Western Digital (Fremont), Inc.
    Inventors: Yingjian Chen, Hua-Ching Tong, Lei Wang, Xizeng Shi
  • Publication number: 20060013038
    Abstract: Magnetic Random Access Memory (MRAM) can be programmed and read as fast as Static Random Access Memory (SRAM) and has the non-volatile characteristics of electrically eraseable programmable read only memory (EEPROM), FLASH EEPROM or one-time-programmable (OTP) EPROM. Due to the randomness of manufacturing process, the magnetic tunnel junctions (MTJ) in MRAM cells will require different row and column current combinations to program and not to disturb the other cells. Based on adaptive current sources for programming, this disclosure teaches methods, designs, test algorithms and manufacturing flows for generating EEPROM, FLASH EEPROM or OTP EPROM like memories from MRAM.
    Type: Application
    Filed: July 13, 2004
    Publication date: January 19, 2006
    Inventors: Hsu Kaiyang, Xizeng Shi, Po-Kang Wang, Bruce Yang
  • Publication number: 20060014346
    Abstract: An MTJ MRAM cell is formed between or below an intersection of ultra-thin orthogonal word and bit lines of high conductivity material whose thickness is less than 100 nm. Lines of this thickness produce switching magnetic fields at the cell free layer that are enhanced by a factor of approximately two for a given current. The fabrication of a cell with such thin lines is actually simplified as a result of the thinner depositions because the fabrication process eliminates the necessity of removing material by CMP during patterning and polishing, thereby producing uniform spacing between the lines and the cell free layer.
    Type: Application
    Filed: December 1, 2004
    Publication date: January 19, 2006
    Inventors: Tai Min, Pokang Wang, Xizeng Shi, Yimin Guo
  • Publication number: 20060014306
    Abstract: An MTJ MRAM cell is formed between ultra-thin orthogonal word and bit lines of high conductivity material whose thickness is less than 100 nm. Lines of this thickness produce switching magnetic fields at the cell free layer that are enhanced by a factor of approximately two for a given current. The fabrication of a cell with such thin lines is actually simplified as a result of the thinner depositions because the fabrication process eliminates the necessity of removing material by CMP during patterning and polishing, thereby producing uniform spacing between the lines and the cell free layer.
    Type: Application
    Filed: July 16, 2004
    Publication date: January 19, 2006
    Inventors: Tai Min, Pokang Wang, Xizeng Shi, Yimin Guo
  • Publication number: 20050280960
    Abstract: An MTJ element is formed between orthogonal word and bit lines. The bit line is a composite line which includes a high conductivity layer and a soft magnetic layer under the high conductivity layer. During operation, the soft magnetic layer concentrates the magnetic field of the current and, due to its proximity to the free layer, it magnetically couples with the free layer in the MTJ. This coupling provides thermal stability to the free layer magnetization and ease of switching and the coupling may be further enhanced by inducing a shape or crystalline anisotropy into the free layer during formation.
    Type: Application
    Filed: August 25, 2005
    Publication date: December 22, 2005
    Inventors: Yimin Guo, Tai Min, Pokang Wang, Xizeng Shi
  • Patent number: 6977838
    Abstract: A method and system for providing a magnetic memory are disclosed. The method and system include providing a plurality of magnetic memory cells and at least one programmable current source. Each of the plurality of magnetic memory cells includes a first magnetic element. The programmable current source(s) are for programming a portion of the plurality of magnetic memory cells. Each of the programmable current source(s) includes a controller and a current source coupled to the controller. The controller is for determining a current provided by the current source and includes at least a second magnetic element. The second magnetic element(s) are substantially the same as the first magnetic element. The controller determines the current provided by the current source based on the at least the second magnetic element.
    Type: Grant
    Filed: February 17, 2004
    Date of Patent: December 20, 2005
    Assignees: Applied Spintronics Technology, Inc., Headway Technologies
    Inventors: David Tsang, Xizeng Shi, Po-Kang Wang, Hsu Kai (Karl) Yang, David Hu