Magnetoresistive random access memory (MRAM) typically employs an array of magnetic storage elements, or cells, which are each located at, or near, an intersection, or crossing, of a corresponding word line with a corresponding bit line. Those skilled in the art know that spin transfer can be used as an alternative to, or in addition to, an external magnetic field in programming current perpendicular to plane (CPP) configurations MRAM cells, which may be either of the magnetic tunnel junction (MTJ) type or of the spin valve (SV) type. When a spin-polarized write current passes through a data storage layer of the cell, which is a free ferromagnetic layer, a portion of the spin angular momentum of the electrons incident on the data storage layer is transferred to the data storage layer. A spin transfer effect, that is caused by conduction electrons traveling from a pinned ferromagnetic layer of the cell to the data storage layer, switches the magnetization orientation of the data storage layer from a direction that is opposite to that of the magnetization orientation of the pinned layer, to a direction that coincides with that of the magnetization orientation of the pinned layer, for example, to program, or write, a logical “0” to the cell; and, a spin transfer effect that is caused by conduction electrons traveling in the opposite direction, switches the magnetization orientation of the data storage layer back to the direction that is opposite to that of the magnetization orientation of the pinned layer, for example, to write a logical “1” to the cell.
In some MRAM arrays, data storage layers may be susceptible to an inadvertent switching, for example, caused by thermally induced lattice vibration. This thermal instability of the storage layers may be due to a reduction in the size and/or magnetization thereof. Furthermore, a significant amount of Joule heating may be generated by a write current, and those cells, which are adjacent to one being written, particularly in ultra high density MRAM arrays, may be inadvertently switched due to the heating. Thus, there is a need for MRAM cell configurations that provide for enhanced thermal stability.
Various embodiments of the present disclosure are generally directed to an apparatus and method for storing data. In accordance with some embodiments, an apparatus comprises a free ferromagnetic data storage layer having a first thickness, a free ferromagnetic stabilization layer having a second thickness greater than the first thickness, and a multi-layered coupling layer disposed between and adapted to ferromagnetically couple the data storage layer and the stabilization layer.
The following drawings are illustrative of particular embodiments of the disclosure and therefore do not limit the scope. The drawings are not to scale (unless so stated) and are intended for use in conjunction with the explanations in the following detailed description. Embodiments of the disclosure will hereinafter be described in conjunction with the appended drawings, wherein like numerals denote like elements.
The following detailed description is exemplary in nature and is not intended to limit the scope, applicability, or configuration in any way. Rather, the following description provides practical illustrations for implementing exemplary embodiments.
According to embodiments of the present disclosure, second spacer layer 131 is conductive and provides either ferromagnetic coupling or antiferromagnetic coupling between data storage layer 111 and stabilization layer 113, wherein a strength of the coupling is greater than a coercivity of the stabilization layer 113; when a magnetization orientation of data storage layer 111 is switched, or re-programmed, the magnetization orientation of stabilization layer 113 will follow, as will be further described in conjunction with
The antiferromagnetic coupling between layers 111 and 113, which is illustrated by
In the foregoing detailed description, embodiments of the disclosure have been described. These implementations, as well as others, are within the scope of the appended claims.
This application is a continuation of application Ser. No. 12/248,257 filed on Oct. 9, 2008, now issued as U.S. Pat. No. 7,880,209.
Number | Name | Date | Kind |
---|---|---|---|
5920446 | Gill | Jul 1999 | A |
6252796 | Lenssen et al. | Jun 2001 | B1 |
6381106 | Pinarbasi | Apr 2002 | B1 |
6469926 | Chen | Oct 2002 | B1 |
6531723 | Engel et al. | Mar 2003 | B1 |
6532164 | Redon et al. | Mar 2003 | B2 |
6603677 | Redon et al. | Aug 2003 | B2 |
6633498 | Engel et al. | Oct 2003 | B1 |
6700753 | Singleton et al. | Mar 2004 | B2 |
6711052 | Subramanian et al. | Mar 2004 | B2 |
6714444 | Huai et al. | Mar 2004 | B2 |
6744086 | Daughton et al. | Jun 2004 | B2 |
6759263 | Ying et al. | Jul 2004 | B2 |
6760266 | Garni et al. | Jul 2004 | B2 |
6765819 | Bhattacharyya et al. | Jul 2004 | B1 |
6801415 | Slaughter et al. | Oct 2004 | B2 |
6818961 | Rizzo et al. | Nov 2004 | B1 |
6829161 | Huai et al. | Dec 2004 | B2 |
6831312 | Slaughter et al. | Dec 2004 | B2 |
6835423 | Chen et al. | Dec 2004 | B2 |
6838740 | Huai et al. | Jan 2005 | B2 |
6842368 | Hayakawa | Jan 2005 | B2 |
6847547 | Albert et al. | Jan 2005 | B2 |
6850433 | Sharma et al. | Feb 2005 | B2 |
6865109 | Covington | Mar 2005 | B2 |
6888703 | Dieny et al. | May 2005 | B2 |
6888742 | Nguyen et al. | May 2005 | B1 |
6920063 | Huai et al. | Jul 2005 | B2 |
6943040 | Min et al. | Sep 2005 | B2 |
6958927 | Nguyen et al. | Oct 2005 | B1 |
6967366 | Janesky et al. | Nov 2005 | B2 |
6979586 | Guo et al. | Dec 2005 | B2 |
6985385 | Nguyen et al. | Jan 2006 | B2 |
6992359 | Nguyen et al. | Jan 2006 | B2 |
6998150 | Li et al. | Feb 2006 | B2 |
7009877 | Huai et al. | Mar 2006 | B1 |
7019949 | Freitag et al. | Mar 2006 | B2 |
7057921 | Valet | Jun 2006 | B2 |
7067330 | Min et al. | Jun 2006 | B2 |
7088609 | Valet | Aug 2006 | B2 |
7098495 | Sun et al. | Aug 2006 | B2 |
7099186 | Braun | Aug 2006 | B1 |
7102916 | Trouilloud et al. | Sep 2006 | B2 |
7105372 | Min et al. | Sep 2006 | B2 |
7110287 | Huai et al. | Sep 2006 | B2 |
7129098 | Rizzo et al. | Oct 2006 | B2 |
7169623 | Ditizio | Jan 2007 | B2 |
7184300 | Savtchenko et al. | Feb 2007 | B2 |
7189583 | Drewes | Mar 2007 | B2 |
7190611 | Nguyen et al. | Mar 2007 | B2 |
7196882 | Deak | Mar 2007 | B2 |
7233039 | Huai et al. | Jun 2007 | B2 |
7242045 | Nguyen et al. | Jul 2007 | B2 |
7285836 | Ju et al. | Oct 2007 | B2 |
7379280 | Fukumoto et al. | May 2008 | B2 |
7466524 | Freitag et al. | Dec 2008 | B2 |
7477491 | Li et al. | Jan 2009 | B2 |
7479394 | Horng et al. | Jan 2009 | B2 |
7489541 | Pakala et al. | Feb 2009 | B2 |
7495867 | Sbiaa et al. | Feb 2009 | B2 |
7572645 | Sun et al. | Aug 2009 | B2 |
7880209 | Xi et al. | Feb 2011 | B2 |
7985994 | Zheng et al. | Jul 2011 | B2 |
8179716 | Xi et al. | May 2012 | B2 |
8203871 | Lou et al. | Jun 2012 | B2 |
8289756 | Zheng et al. | Oct 2012 | B2 |
8294227 | Zheng et al. | Oct 2012 | B2 |
8362534 | Zheng et al. | Jan 2013 | B2 |
20040012994 | Slaughter et al. | Jan 2004 | A1 |
20040017639 | Deak | Jan 2004 | A1 |
20040170055 | Albert et al. | Sep 2004 | A1 |
20040179311 | Li et al. | Sep 2004 | A1 |
20040197579 | Chen et al. | Oct 2004 | A1 |
20060061919 | Li et al. | Mar 2006 | A1 |
20060093862 | Parkin | May 2006 | A1 |
20070008661 | Min et al. | Jan 2007 | A1 |
20070035890 | Sbiaa | Feb 2007 | A1 |
20070195468 | Freitag et al. | Aug 2007 | A1 |
20080113220 | Sun et al. | May 2008 | A1 |
20080191251 | Ranjan et al. | Aug 2008 | A1 |
20080205130 | Sun et al. | Aug 2008 | A1 |
20100090300 | Xi et al. | Apr 2010 | A1 |
20100176471 | Zhu et al. | Jul 2010 | A1 |
20110121418 | Xi et al. | May 2011 | A1 |
Entry |
---|
Emley, N.C., et al., “Reduction of spin transfer by synthetic antiferromagnets,” Applied Physics Letters, May 24, 2004, pp. 4257-4259, vol. 84, No. 21, US. |
Hayakawa, J., et al., “Current-Induced Magnetization Switching in MgO Barrier Based Magnetic Tunnel Junction with CoFeB/Ru/CoFeB Synthetic Ferrimagnetic Free Layer,” Japanese Journal of Applied Physics, 2006, pp. L1057-L1060, vol. 45, No. 40, The Japan Society of Applied Physics, Japan. |
Miura, K., et al., “A novel SPRAM (SPin-transfer torque RAM) with a synthetic ferrimagnetic free layer for higher immunity to read disturbance and reducing write-current dispersion,” Symposium on VLSI Technology Digest of Technical Papers, 2007, pp. 234-235, Japan. |
Sun, J.Z., “Spin angular momentum transfer in current-perpendicular nanomagnetic junctions,” IBM J. Res. & Ev., Jan. 1, 2006, pp. 81-100, vol. 50, No. 1. |
Yen, C-T, et al., “Reduction in critical current density for spin torque transfer switching with composite free layer,” Applied Physics Letters 93, 2008, pp. 1-3, American Institute of Physics. |
Number | Date | Country | |
---|---|---|---|
20110121418 A1 | May 2011 | US |
Number | Date | Country | |
---|---|---|---|
Parent | 12248257 | Oct 2008 | US |
Child | 13015320 | US |