Patents by Inventor Jijun Sun
Jijun Sun 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).
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Patent number: 8686484Abstract: A spin-torque magnetoresistive memory element has a high magnetoresistance and low current density. A free magnetic layer is positioned between first and second spin polarizers. A first tunnel barrier is positioned between the first spin polarizer and the free magnetic layer and a second tunnel barrier is positioned between the second spin polarizer and the free magnetic layer. The magnetoresistance ratio of the second tunnel barrier has a value greater than double the magnetoresistance ratio of the first tunnel barrier.Type: GrantFiled: June 10, 2011Date of Patent: April 1, 2014Assignee: EverSpin Technologies, Inc.Inventors: Renu Whig, Jon Slaughter, Nicholas Rizzo, Jijun Sun, Frederick Mancoff, Dimitri Houssameddine
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Patent number: 8647891Abstract: A sensor and fabrication process are provided for forming reference layers with substantially orthogonal magnetization directions having zero offset with a small compensation angle. An exemplary embodiment includes a sensor layer stack of a magnetoresistive thin-film based magnetic field sensor, the sensor layer stack comprising a pinning layer; a pinned layer including a layer of amorphous material over the pinning layer, and a first layer of crystalline material over the layer of amorphous material; a nonmagnetic coupling layer over the pinned layer; a fixed layer over the nonmagnetic coupling layer; a tunnel barrier over the fixed layer; and a sense layer over the nonmagnetic intermediate layer. Another embodiment includes a sensor layer stack where a pinned layer including two crystalline layers separated by a amorphous layer.Type: GrantFiled: June 4, 2013Date of Patent: February 11, 2014Assignee: Everspin Technologies, Inc.Inventors: Jijun Sun, Phillip Mather, Srinivas Pietambaram, Jon Slaughter, Renu Whig, Nicholas Rizzo
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Publication number: 20130264666Abstract: A sensor and fabrication process are provided for forming reference layers with substantially orthogonal magnetization directions having zero offset with a small compensation angle. An exemplary embodiment includes a sensor layer stack of a magnetoresistive thin-film based magnetic field sensor, the sensor layer stack comprising a pinning layer; a pinned layer including a layer of amorphous material over the pinning layer, and a first layer of crystalline material over the layer of amorphous material; a nonmagnetic coupling layer over the pinned layer; a fixed layer over the nonmagnetic coupling layer; a tunnel barrier over the fixed layer; and a sense layer over the nonmagnetic intermediate layer. Another embodiment includes a sensor layer stack where a pinned layer including two crystalline layers separated by a amorphous layer.Type: ApplicationFiled: June 4, 2013Publication date: October 10, 2013Inventors: Jijun Sun, Phillip Mather, Srinivas Pietambaram, Jon Slaughter, Renu Whig, Nicholas Rizzo
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Patent number: 8508221Abstract: A sensor and fabrication process are provided for forming reference layers with substantially orthogonal magnetization directions having zero offset with a small compensation angle. An exemplary embodiment includes a sensor layer stack of a magnetoresistive thin-film based magnetic field sensor, the sensor layer stack comprising a pinning layer; a pinned layer including a layer of amorphous material over the pinning layer, and a first layer of crystalline material over the layer of amorphous material; a nonmagnetic coupling layer over the pinned layer; a fixed layer over the nonmagnetic coupling layer; a tunnel barrier over the fixed layer; and a sense layer over the nonmagnetic intermediate layer. Another embodiment includes a sensor layer stack where a pinned layer including two crystalline layers separated by a amorphous layer.Type: GrantFiled: August 30, 2010Date of Patent: August 13, 2013Assignee: Everspin Technologies, Inc.Inventors: Jijun Sun, Phillip Mather, Srinivas Pietambaram, Jon Slaughter, Renu Whig, Nicholas Rizzo
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Publication number: 20120313191Abstract: A spin-torque magnetoresistive memory element has a high magnetoresistance and low current density. A free magnetic, layer is positioned between first and second spin polarizers. A first tunnel barrier is positioned between the first spin polarizer and the free magnetic layer and a second tunnel barrier is positioned between the second spin polarizer and the free magnetic layer. The magnetoresistance ratio of the second tunnel barrier has a value greater than double the magnetoresistance ratio of the first tunnel barrier.Type: ApplicationFiled: June 10, 2011Publication date: December 13, 2012Applicant: EVERSPIN TECHNOLOGIES, INC.Inventors: Renu WHIG, Jon SLAUGHTER, Nicholas RIZZO, Jijun SUN, Frederick MANCOFF, Dimitri HOUSSAMEDDINE
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Patent number: 8216703Abstract: A magnetic tunnel junction (MTJ) (10) employing a dielectric tunneling barrier (16), useful in magnetoresistive random access memories (MRAMs) and other devices, has a synthetic antiferromagnet (SAF) structure (14, 16), comprising two ferromagnetic (FM) layers (26, 41; 51, 58; 61, 68) separated by a coupling layer (38, 56, 66). Improved magnetoresistance (MR) ratio is obtained by providing a further layer (44, 46, 46?, 47, 52, 62), e.g. containing Ta, preferably spaced apart from the coupling layer (38, 56, 66) by a FM layer (41, 30-2, 54). The further layer (44, 46, 46?, 47, 52, 62) may be a Ta dusting layer (44) covered by a FM layer (30-2), or a Ta containing FM alloyed layer (46), or a stack (46?) of interleaved FM and N-FM layers, or other combination (47, 62). Furthering these benefits, another FM layer, e.g., CoFe, NiFe, (30, 30-1, 51, 61) is desirably provided between the further layer (44, 46, 46?, 47, 52, 62) and the tunneling barrier (16).Type: GrantFiled: February 21, 2008Date of Patent: July 10, 2012Assignee: Everspin Technologies, Inc.Inventors: Jijun Sun, Jon M. Slaughter
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Publication number: 20120049843Abstract: A sensor and fabrication process are provided for forming reference layers with substantially orthogonal magnetization directions having zero offset with a small compensation angle. An exemplary embodiment includes a sensor layer stack of a magnetoresistive thin-film based magnetic field sensor, the sensor layer stack comprising a pinning layer; a pinned layer including a layer of amorphous material over the pinning layer, and a first layer of crystalline material over the layer of amorphous material; a nonmagnetic coupling layer over the pinned layer; a fixed layer over the nonmagnetic coupling layer; a tunnel barrier over the fixed layer; and a sense layer over the nonmagnetic intermediate layer. Another embodiment includes a sensor layer stack where a pinned layer including two crystalline layers separated by a amorphous layer.Type: ApplicationFiled: August 30, 2010Publication date: March 1, 2012Applicant: EVERSPIN TECHNOLOGIES, INC.Inventors: Jijun SUN, Phillip MATHER, Srinivas PIETAMBARAM, Jon SLAUGHTER, Renu WHIG, Nicholas RIZZO
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Publication number: 20120015099Abstract: A method for depositing uniform and smooth ferromagnetic thin films with high deposition-induced microstructural anisotropy includes a magnetic material deposited in two or more static oblique deposition steps from opposed directions to form a free layer having a high kink Hk, a high energy barrier to thermal reversal, a low critical current in spin-torque switching embodiments, and improved resistance to diffusion of material from adjacent layers in the device. Nonmagnetic layers deposited by the static oblique deposition technique may be used as seed layers for a ferromagnetic free layer or to generate other types of anisotropy determined by the deposition-induced microstructural anisotropy. Additional magnetic or non-magnetic layers may be deposited by conventional methods adjacent to oblique layer to provide magnetic coupling control, reduction of surface roughness, and barriers to diffusion from additional adjacent layers in the device.Type: ApplicationFiled: July 15, 2010Publication date: January 19, 2012Applicant: EVERSPIN TECHNOLOGIES, INC.Inventors: Jijun SUN, Jon SLAUGHTER, Nicholas RIZZO
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Methods and apparatus for a synthetic anti-ferromagnet structure with reduced temperature dependence
Patent number: 7684161Abstract: A synthetic antiferromagnet (SAF) structure includes a first ferromagnetic layer, a first insertion layer, a coupling layer, a second insertion layer, and a second ferromagnetic layer. The insertion layers comprise materials selected such that SAF exhibits reduced temperature dependence of antiferromagnetic coupling strength. The insertion layers may include CoFe or CoFeX alloys. The thickness of the insertion layers is selected such that they do not increase the uniaxial anisotropy or deteriorate any other properties.Type: GrantFiled: April 18, 2006Date of Patent: March 23, 2010Assignee: Everspin Technologies, Inc.Inventors: Srinivas V. Pietambaram, Renu W. Dave, Jon M. Slaughter, JiJun Sun -
Patent number: 7635654Abstract: Methods and apparatus are provided for magnetic tunnel junction (MTJ) devices and arrays, comprising metal-insulator-metal (M-I-M) structures with opposed first and second ferro-magnetic electrodes with alterable relative magnetization direction. The insulator is formed by depositing an oxidizable material (e.g., Al) on the first electrode, naturally oxidizing it, e.g., at about 0.03 to 10 milli-Torr for up to a few thousand seconds at temperatures below about 35° C., then further rapidly (e.g., plasma) oxidizing at a rate much larger than that of the initial natural oxidation. The second electrode of the M-I-M structure is formed on this oxide. More uniform tunneling properties result. A second oxidizable material layer is optionally provided after the initial natural oxidation and before the rapid oxidation step during which it is substantially entirely converted to insulating oxide. A second natural oxidation cycle may be optionally provided before the second layer is rapidly oxidized.Type: GrantFiled: January 27, 2006Date of Patent: December 22, 2009Assignee: Everspin Technologies, Inc.Inventors: JiJun Sun, John T. Martin, Jon M. Slaughter
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Publication number: 20090213503Abstract: A magnetic tunnel junction (MTJ) (10) employing a dielectric tunneling barrier (16), useful in magnetoresistive random access memories (MRAMs) and other devices, has a synthetic antiferromagnet (SAF) structure (14, 16), comprising two ferromagnetic (FM) layers (26, 41; 51, 58; 61, 68) separated by a coupling layer (38, 56, 66). Improved magnetoresistance (MR) ratio is obtained by providing a further layer (44, 46, 46?, 47, 52, 62), e.g. containing Ta, preferably spaced apart from the coupling layer (38, 56, 66) by a FM layer (41, 30-2, 54). The further layer (44, 46, 46?, 47, 52, 62) may be a Ta dusting layer (44) covered by a FM layer (30-2), or a Ta containing FM alloyed layer (46), or a stack (46?) of interleaved FM and N-FM layers, or other combination (47, 62). Furthering these benefits, another FM layer, e.g., CoFe, NiFe, (30, 30-1, 51, 61) is desirably provided between the further layer (44, 46, 46?, 47, 52, 62) and the tunneling barrier (16).Type: ApplicationFiled: February 21, 2008Publication date: August 27, 2009Applicant: FREESCALE SEMICONDUCTOR, INC.Inventors: Jijun Sun, Jon M. Slaughter
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Patent number: 7572645Abstract: Methods and apparatus are provided for magnetic tunnel junctions (MTJs) (10, 50) employing synthetic antiferromagnet (SAF) free layers (14, 14?). The MTJ (10, 50) comprises a pinned ferromagnetic (FM) layer (32, 18), the SAF (14) and a tunneling barrier (16) therebetween. The SAF (14) has a first higher spin polarization FM layer (30) proximate the tunneling barrier (16) and a second FM layer (26) desirably separated from the first FM layer (30) by a coupling layer (28), with magnetostriction adapted to compensate the magnetostriction of the first FM layer (30). Such compensation reduces the net magnetostriction of the SAF (14) to near zero even with high spin polarization proximate the tunneling barrier (16). Higher magnetoresistance ratios (MRs) are obtained without adverse affect on other MTJ (10, 50) properties. NiFe combinations are desirable for the first (30) and second (26) free FM layers, with more Fe in the first (30) free layer and less Fe in the second (26) free layer.Type: GrantFiled: November 15, 2006Date of Patent: August 11, 2009Assignee: Everspin Technologies, Inc.Inventors: Jijun Sun, Renu W. Dave, Jason A. Janesky, Jon M. Slaughter
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Publication number: 20090121266Abstract: Exchange-coupled magnetic multilayer structures for use with toggle MRAM devices and the like include a tunnel barrier layer (108) and a synthetic antiferromagnet (SAF) structure (300) formed on the tunnel barrier layer (108), wherein the SAF (300) includes a plurality (e.g., four or more) of ferromagnetic layers (302, 306, 310, 314) antiferromagnetically or ferromagnetically coupled by a plurality of respective coupling layers (304, 308, 312). The microcrystalline texture of one or more of the ferromagnetic layers is reduced to substantially zero as measured from X-Ray Diffraction by exposure of various layers to oxygen, by forming a detexturing layer, by adding oxygen during the ferromagnetic or coupling layer fabrication, and/or by using amorphous materials.Type: ApplicationFiled: November 13, 2007Publication date: May 14, 2009Applicant: FREESCALE SEMICONDUCTOR, INC.Inventors: Srinivas V. Pietambaram, Jason A. Janesky, Jon M. Slaughter, Jijun Sun
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Publication number: 20090059444Abstract: A two-axis, single-chip external magnetic field sensor incorporates tunneling magneto-resistance (TMR) technology. In one embodiment, an integrated device includes at least two sensor elements having pinned layers with orientation situated at a known angle (e.g., 90 degrees) with respect to each other. In the presence of a magnetic field, the information from the multiple sensor elements can be processed (e.g., using a conventional bridge configuration) to determine the orientation of the integrated sensor with respect to the external field. In order to achieve an integrated sensor with multiple pinned layer orientations, a novel processing method utilizes antiferromagnetic pinning layers different materials with different blocking temperatures (e.g., PtMn and IrMn).Type: ApplicationFiled: August 30, 2007Publication date: March 5, 2009Applicant: FREESCALE SEMICONDUCTOR, INC.Inventors: Phillip Glenn Mather, Jijun Sun, Young Sir Chung
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Publication number: 20090046397Abstract: A synthetic antiferromagnet (SAF) structure includes a bottom ferromagnetic layer, a coupling layer formed over the bottom ferromagnetic layer, and a top ferromagnetic layer formed over the coupling layer. One of the top and bottom ferromagnetic layers comprises an amorphous alloy characterized by (Co100-aFea)100-zBz, where a is less than approximately 10 atomic percent, and z is greater than approximately 20 atomic percent. In general, a magnetic device includes at least one magnetic layer comprising an amorphous CoFeB alloy characterized by (Co100-aFea)100-zBz, where a is less than approximately 10 atomic percent, and z is greater than approximately 20 atomic percent.Type: ApplicationFiled: August 15, 2007Publication date: February 19, 2009Applicant: FREESCALE SEMICONDUCTOR, INC.Inventors: Jijun Sun, Renu W. Dave, Jon M. Slaughter
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Publication number: 20080205130Abstract: A magnetic tunnel junction (MTJ) structure for use with toggle MRAM devices and the like includes a tunnel barrier layer and a synthetic antiferromagnet (SAF) structure formed on the tunnel barrier layer, wherein the SAF includes a plurality (e.g., three or more) ferromagnetic layers antiferromagnetically or ferromagnetically coupled by a plurality of respective coupling layers. The bottom ferromagnetic layer adjacent the tunnel barrier layer has a high spin polarization and a high intrinsic anisotropy field (Hki) while one or more of the remaining ferromagnetic layers has a low intrinsic anisotropy field Hki.Type: ApplicationFiled: February 28, 2007Publication date: August 28, 2008Applicant: FREESCALE SEMICONDUCTOR, INC.Inventors: Jijun Sun, Nicholas D. Rizzo, Jon M. Slaughter
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Publication number: 20080113220Abstract: Methods and apparatus are provided for magnetic tunnel junctions (MTJs) (10, 50) employing synthetic antiferromagnet (SAF) free layers (14, 14?). The MTJ (10, 50) comprises a pinned ferromagnetic (FM) layer (32, 18), the SAF (14) and a tunneling barrier (16) therebetween. The SAF (14) has a first higher spin polarization FM layer (30) proximate the tunneling barrier (16) and a second FM layer (26) desirably separated from the first FM layer (30) by a coupling layer (28), with magnetostriction adapted to compensate the magnetostriction of the first FM layer (30). Such compensation reduces the net magnetostriction of the SAF (14) to near zero even with high spin polarization proximate the tunneling barrier (16). Higher magnetoresistance ratios (MRs) are obtained without adverse affect on other MTJ (10, 50) properties. NiFe combinations are desirable for the first (30) and second (26) free FM layers, with more Fe in the first (30) free layer and less Fe in the second (26) free layer.Type: ApplicationFiled: November 15, 2006Publication date: May 15, 2008Inventors: Jijun Sun, Renu W. Dave, Jason A. Janesky, Jon M. Slaughter
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Patent number: 7329935Abstract: Low power magnetoresistive random access memory elements and methods for fabricating the same are provided. In one embodiment, a magnetoresistive random access device has an array of memory elements. Each element comprises a fixed magnetic portion, a tunnel barrier portion, and a free SAF structure. The array has a finite magnetic field programming window Hwin represented by the equation Hwin?(Hsat??sat)?(Hsw+?sw), where Hsw is a mean switching field for the array, Hsat is a mean saturation field for the array, and Hsw for each memory element is represented by the equation HSW??{square root over (HkHSAT)}, where Hk represents a total anisotropy and HSAT represents an anti-ferromagnetic coupling saturation field for the free SAF structure of each memory element. N is an integer greater than or equal to 1. Hk, HSAT, and N for each memory element are selected such that the array requires current to operate that is below a predetermined current value.Type: GrantFiled: October 16, 2006Date of Patent: February 12, 2008Assignee: Freescale Semiconductor, Inc.Inventors: Nicholas D. Rizzo, Renu W. Dave, Bradley N. Engel, Jason A. Janesky, JiJun Sun
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Methods and apparatus for a synthetic anti-ferromagnet structure with reduced temperature dependence
Publication number: 20070243639Abstract: A synthetic antiferromagnet (SAF) structure includes a first ferromagnetic layer, a first insertion layer, a coupling layer, a second insertion layer, and a second ferromagnetic layer. The insertion layers comprise materials selected such that SAF exhibits reduced temperature dependence of antiferromagnetic coupling strength. The insertion layers may include CoFe or CoFeX alloys. The thickness of the insertion layers is selected such that they do not increase the uniaxial anisotropy or deteriorate any other properties.Type: ApplicationFiled: April 18, 2006Publication date: October 18, 2007Inventors: Srinivas Pietambaram, Renu Dave, Jon Slaughter, JiJun Sun -
Publication number: 20070178608Abstract: Methods and apparatus are provided for magnetic tunnel junction (MTJ) devices and arrays, comprising metal-insulator-metal (M-I-M) structures with opposed first and second ferro-magnetic electrodes with alterable relative magnetization direction. The insulator is formed by depositing an oxidizable material (e.g., Al) on the first electrode, naturally oxidizing it, e.g., at about 0.03 to 10 milli-Torr for up to a few thousand seconds at temperatures below about 35° C., then further rapidly (e.g., plasma) oxidizing at a rate much larger than that of the initial natural oxidation. The second electrode of the M-I-M structure is formed on this oxide. More uniform tunneling properties result. A second oxidizable material layer is optionally provided after the initial natural oxidation and before the rapid oxidation step during which it is substantially entirely converted to insulating oxide. A second natural oxidation cycle may be optionally provided before the second layer is rapidly oxidized.Type: ApplicationFiled: January 27, 2006Publication date: August 2, 2007Inventors: JiJun Sun, John Martin, Jon Slaughter