WO2008072421A1 - 磁気抵抗効果素子及びmram - Google Patents
磁気抵抗効果素子及びmram Download PDFInfo
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- WO2008072421A1 WO2008072421A1 PCT/JP2007/070571 JP2007070571W WO2008072421A1 WO 2008072421 A1 WO2008072421 A1 WO 2008072421A1 JP 2007070571 W JP2007070571 W JP 2007070571W WO 2008072421 A1 WO2008072421 A1 WO 2008072421A1
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- magnetization
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Classifications
-
- G—PHYSICS
- G11—INFORMATION STORAGE
- G11C—STATIC STORES
- G11C11/00—Digital stores characterised by the use of particular electric or magnetic storage elements; Storage elements therefor
- G11C11/02—Digital stores characterised by the use of particular electric or magnetic storage elements; Storage elements therefor using magnetic elements
- G11C11/16—Digital stores characterised by the use of particular electric or magnetic storage elements; Storage elements therefor using magnetic elements using elements in which the storage effect is based on magnetic spin effect
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B82—NANOTECHNOLOGY
- B82Y—SPECIFIC USES OR APPLICATIONS OF NANOSTRUCTURES; MEASUREMENT OR ANALYSIS OF NANOSTRUCTURES; MANUFACTURE OR TREATMENT OF NANOSTRUCTURES
- B82Y10/00—Nanotechnology for information processing, storage or transmission, e.g. quantum computing or single electron logic
-
- G—PHYSICS
- G11—INFORMATION STORAGE
- G11C—STATIC STORES
- G11C11/00—Digital stores characterised by the use of particular electric or magnetic storage elements; Storage elements therefor
- G11C11/02—Digital stores characterised by the use of particular electric or magnetic storage elements; Storage elements therefor using magnetic elements
- G11C11/16—Digital stores characterised by the use of particular electric or magnetic storage elements; Storage elements therefor using magnetic elements using elements in which the storage effect is based on magnetic spin effect
- G11C11/165—Auxiliary circuits
- G11C11/1653—Address circuits or decoders
- G11C11/1655—Bit-line or column circuits
-
- G—PHYSICS
- G11—INFORMATION STORAGE
- G11C—STATIC STORES
- G11C11/00—Digital stores characterised by the use of particular electric or magnetic storage elements; Storage elements therefor
- G11C11/02—Digital stores characterised by the use of particular electric or magnetic storage elements; Storage elements therefor using magnetic elements
- G11C11/16—Digital stores characterised by the use of particular electric or magnetic storage elements; Storage elements therefor using magnetic elements using elements in which the storage effect is based on magnetic spin effect
- G11C11/165—Auxiliary circuits
- G11C11/1659—Cell access
-
- G—PHYSICS
- G11—INFORMATION STORAGE
- G11C—STATIC STORES
- G11C11/00—Digital stores characterised by the use of particular electric or magnetic storage elements; Storage elements therefor
- G11C11/02—Digital stores characterised by the use of particular electric or magnetic storage elements; Storage elements therefor using magnetic elements
- G11C11/16—Digital stores characterised by the use of particular electric or magnetic storage elements; Storage elements therefor using magnetic elements using elements in which the storage effect is based on magnetic spin effect
- G11C11/165—Auxiliary circuits
- G11C11/1675—Writing or programming circuits or methods
-
- H—ELECTRICITY
- H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
- H10B—ELECTRONIC MEMORY DEVICES
- H10B61/00—Magnetic memory devices, e.g. magnetoresistive RAM [MRAM] devices
- H10B61/20—Magnetic memory devices, e.g. magnetoresistive RAM [MRAM] devices comprising components having three or more electrodes, e.g. transistors
- H10B61/22—Magnetic memory devices, e.g. magnetoresistive RAM [MRAM] devices comprising components having three or more electrodes, e.g. transistors of the field-effect transistor [FET] type
-
- H—ELECTRICITY
- H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
- H10N—ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
- H10N50/00—Galvanomagnetic devices
- H10N50/10—Magnetoresistive devices
-
- G—PHYSICS
- G11—INFORMATION STORAGE
- G11C—STATIC STORES
- G11C2213/00—Indexing scheme relating to G11C13/00 for features not covered by this group
- G11C2213/70—Resistive array aspects
- G11C2213/74—Array wherein each memory cell has more than one access device
Definitions
- the present invention relates to a magnetoresistance effect element and a magnetic random access memory (MRAM) that uses the magnetoresistance effect element as a memory cell.
- MRAM magnetic random access memory
- the present invention relates to an MRAM based on a domain wall displacement method, and a magnetoresistance effect element used in the MRAM.
- MRAM is a promising nonvolatile memory in terms of high integration and high speed operation.
- a “magnetoresistive element” exhibiting a magnetoresistance effect such as a TMR (Tunnel Magneto Resistance) effect is used as a memory cell.
- a magnetic tunnel junction (MTJ: Magnetic Tunnel Junction) sandwiched between ferromagnetic layers of a tunnel barrier layer is formed.
- the two ferromagnetic layers consist of a magnetization fixed layer (pinned layer) in which the magnetization direction is fixed and a magnetization free layer (free layer) in which the magnetization direction is reversible. Be done.
- the resistance value (R + AR) of the MTJ in the case of antiparallel "of the magnetizations of the magnetization fixed layer and the magnetization free layer is the resistance value in the case of their forces being" parallel "by the magnetoresistance effect.
- R is known to be larger.
- the memory cell of the MRAM stores data in a non-volatile manner by utilizing the change in its resistance value. Data is read out by passing a read current through the MTJ and measuring the resistance of MTJ. On the other hand, writing of data is performed by reversing the direction of magnetization of the magnetization free layer.
- a "current magnetic field method” is known.
- the write current is applied to the write wiring disposed in the vicinity of the magnetoresistive element. The flow is made to flow. Then, a write magnetic field generated by the write current is applied to the magnetization free layer, whereby the magnetization direction of the magnetization free layer is changed. At this time, the magnetic field generated by the write current of 1 mA is about several Oe to several tens Oe.
- the reversal magnetic field necessary for the magnetization reversal of the magnetization free layer be designed to be several tens of Oe or so. Therefore, it is very difficult to realize data writing with a write current of 1 mA or less.
- current magnetic field type MRAM is more disadvantageous than other RAMs.
- the switching magnetic field required for the magnetization switching of the magnetization free layer becomes larger in inverse proportion to the size of the magnetoresistance effect element. That is, there is a problem that the write current increases as the memory cell is miniaturized.
- Japanese Patent Application Laid-Open No. 2005-150303 describes a technique aimed at improving the thermal disturbance resistance and reducing the reversal magnetic field in the current magnetic field type MRAM.
- the magnetoresistive effect element according to the art has a ferromagnetic tunnel junction including a three-layer structure of a first ferromagnetic layer / tunneling barrier layer / second ferromagnetic layer.
- the first ferromagnetic layer has a coercivity greater than that of the second ferromagnetic layer.
- the magnetization of the end portion of the second ferromagnetic layer is fixed in a direction having a component orthogonal to the magnetization easy axis direction of the second ferromagnetic layer.
- spin injection method using spin transfer (spin transfer) has been proposed as a data writing method to replace the current magnetic field method.
- spin transfer spin transfer
- spin injection method spin-polarized current is injected into the magnetization free layer, and the spin and conductor of the conduction electron responsible for the current.
- the direct interaction between the magnetic moment and the magnetic moment inverts the magnetization, which is more likely to occur as the current density increases, so that the write current can be reduced as the memory cell size is reduced.
- the magnetization of the magnetization free layer is reversed due to the spin transfer effect.
- the magnetization direction of the magnetization free layer can be defined by the direction of the write current passing through the MTJ. Furthermore, with the miniaturization of memory cells, it is also possible to reduce the write current.
- the write current larger than the read current passes through the MTJ, the following problem is considered to occur.
- an insulating film is used as a tunnel barrier layer of the MTJ, and the upper limit value of the write current is determined from the limit of the withstand voltage of the insulating film. This is not preferable from the point of view of writing.
- the resistance value of the tunnel barrier layer is lowered to increase the upper limit value, the read signal becomes small. This is not preferable from the viewpoint of reading. That is, the writing must be performed within the margin of the withstand voltage of the insulating film satisfying the read restriction and above the current at which magnetization reversal occurs, which is disadvantageous.
- the magnetization free layer includes a junction overlapping the tunnel barrier layer, a neck adjacent to both ends of the junction, and a pair of magnetization fixed portions formed adjacent to the neck. Fixed magnetizations in opposite directions are given to the pair of magnetization fixed parts. As a result, the magnetization free layer has a domain wall in the above junction.
- the write current flows in a planar manner.
- the pair of magnetization fixed portions serve as a source of different spin-polarized electrons.
- the direction of the write current is controlled according to the write data, and depending on the direction, spin-polarized electrons are supplied to the junction from any of the magnetization fixed portions.
- the magnetization of the magnetization free layer is reversed by the Sfar effect.
- This magnetization reversal means the change of the position of the domain wall described above. That is, the domain wall moves between the pair of constricted portions in accordance with the direction of the write current.
- the horizontal spin injection method as described in Japanese Patent Laid-Open No. 2005-191032 can also be referred to as the “domain wall displacement method”.
- the magnetization free layer has a pair of magnetization fixed portions on both sides of the junction whose magnetization direction is variable.
- the pair of magnetization fixed parts are introduction sources of different spin polarized electrons, and fixed magnetizations in opposite directions are given to each other.
- the junctions and the pair of magnetization fixed portions are arranged in a straight line. Therefore, when the spin-polarized electrons are excessively introduced at the time of data writing, the domain wall may intrude into one of the magnetization fixed portions. That means that the magnetization direction of one magnetization fixed portion is disturbed. In the worst case, the magnetization direction of one magnetization fixed portion is completely reversed, and the domain wall disappears.
- the magnetization of the magnetization fixed portion may become unstable.
- One object of the present invention is to provide a novel magnetoresistance effect element and MR based on a domain wall displacement method.
- Another object of the present invention is to provide a technology capable of holding the magnetization of the magnetization fixed region in the magnetization free layer more stably when the write current is supplied to the magnetization free layer. It is.
- a magnetoresistance effect element based on a domain wall displacement system.
- the magnetoresistive element comprises a magnetization free layer and a magnetization fixed layer connected to the magnetization free layer via the nonmagnetic layer.
- the magnetization free layer includes a magnetization switching region, a first magnetization fixed region, and a second magnetization fixed region.
- the magnetization inversion region overlaps the magnetization fixed layer, and also has reversible magnetization.
- the first magnetization fixed region is connected to one end in the magnetization easy axis direction of the magnetization switching region, and has a first fixed magnetization.
- the second magnetization fixed region is connected to the other end of the magnetization inversion region in the easy magnetization axis direction, and has a second fixed magnetization.
- the first magnetization fixed region and the magnetization switching region form one three-fork, and the second magnetization fixed region and the magnetization switching region form another three-fork.
- an MRAM based on a domain wall displacement system comprises a plurality of magnetic memory cells arranged in an array. Each of the plurality of magnetic memory cells supplies the magnetoresistive effect element and the write current to the magnetization free layer.
- the magnetoresistive effect element and the MRAM according to the present invention when a write current is supplied to the magnetization free layer, it is possible to stably hold the magnetization of the magnetization fixed region in the magnetization free layer. It becomes. As a result, the upper limit of the magnitude of the write current is increased, and the write margin is expanded.
- FIG. 1 is a side view schematically showing the structure of a magnetoresistive element according to a first embodiment of the present invention.
- FIG. 2A is a plan view showing the structure of the magnetization free layer of the magnetoresistance effect element according to the first example.
- FIG. 2B is a plan view showing the structure of the magnetization free layer of the magnetoresistance effect element according to the first example.
- FIG. 3 is a diagram for explaining data writing to the magnetoresistive element according to the first embodiment.
- FIG. 4A is a plan view showing a modification of the magnetization free layer according to the first embodiment.
- FIG. 4B is a plan view showing another modification of the magnetization free layer according to the first embodiment.
- FIG. 4C is a plan view showing still another modification of the magnetization free layer according to the first embodiment.
- FIG. 4D is a plan view showing still another modification of the magnetization free layer according to the first embodiment.
- FIG. 5A is a plan view showing an example of the shape of the magnetization switching region included in the magnetization free layer.
- FIG. 5B is a plan view showing another example of the shape of the magnetization switching region included in the magnetization free layer.
- FIG. 5C is a plan view showing still another example of the shape of the magnetization switching region included in the magnetization free layer.
- FIG. 6 is a plan view showing the structure of the magnetization free layer of the magnetoresistance effect element according to the second example of the present invention.
- FIG. 7 is a diagram for explaining data writing to the magnetoresistive element according to the second embodiment.
- FIG. 8 is a side view schematically showing the structure of a magnetoresistance effect element according to a third example of the present invention.
- FIG. 9 is a plan view showing an arrangement example of magnetoresistive effect element groups according to a fourth example of the present invention.
- FIG. 10 is a side view schematically showing a structure of a magnetoresistance effect element according to a fifth example of the present invention.
- FIG. 11A is a side view showing a modified example of the magnetoresistance effect element according to the fifth example.
- FIG. 11B is a side view showing another modification of the magnetoresistance effect element according to the fifth example.
- FIG. 12 is a side view schematically showing a structure of a magnetoresistance effect element according to a sixth example of the present invention.
- FIG. 13A is a side view showing a modification of the magnetoresistance effect element according to the sixth example. It is.
- FIG. 13B is a side view showing another modification of the magnetoresistance effect element according to the sixth example.
- FIG. 14 is a circuit diagram showing an example of a magnetic memory cell according to an embodiment of the present invention.
- FIG. 15 is a circuit diagram schematically showing a configuration of an MRAM according to an embodiment of the present invention.
- FIG. 1 is a side view schematically showing the structure of the magnetoresistance effect element according to the first embodiment.
- the magnetoresistive element has a laminated structure in which a magnetization free layer 1, a tunnel barrier layer 2 and a magnetization fixed layer 3 are sequentially laminated.
- the stacking direction is defined as “Z direction”. That is, the direction perpendicular to the main surface of each layer is the Z direction.
- Each layer is formed on an XY plane perpendicular to the Z direction.
- the magnetization free layer (free layer) 1 includes a ferromagnetic layer. Also, as will be described in detail later, the magnetization free layer 1 has a region in which the direction of magnetization can be reversed.
- the tunnel barrier layer 2 is a nonmagnetic layer.
- the tunnel barrier layer 2 is formed of an insulating film.
- the tunnel barrier layer 2 is sandwiched between the magnetization free layer 1 and the magnetization fixed layer 3.
- the tunnel barrier layer 2 may have a force S having the same width as the magnetization free layer 1 and the same width as the magnetization fixed layer 3.
- the width of the tunnel barrier layer 2 may be changed halfway from the same width as the magnetization fixed layer 3 to the same width as the magnetization free layer 1.
- the magnetization fixed layer (pin layer) 3 includes a ferromagnetic layer in contact with the tunnel barrier layer 2, and the direction of the magnetization is fixed in one in-plane direction by an antiferromagnetic layer or the like (not shown). It is done.
- the magnetization direction of the magnetization fixed layer 3 in contact with the tunnel barrier layer 2 is fixed in the + X direction.
- the magnetization fixed layer 3 may have a laminated structure in which a plurality of ferromagnetic layers are magnetically coupled via the nonmagnetic layer. In that case, for example, adjacent The ferromagnetic layers are antiferromagnetically coupled via the nonmagnetic layer. Thereby, the leakage magnetic field from the magnetization fixed layer 3 is reduced, and the fixed magnetization also becomes stronger.
- the magnetization free layer 1 and the magnetization fixed layer 3 are connected via the tunnel barrier layer 2.
- An MT J is formed by the magnetization free layer 1, the tunnel barrier layer 2, and the magnetization fixed layer 3.
- an electrode layer and a cap layer are provided in the magnetoresistance effect element.
- FIG. 2A is a plan view showing in detail the structure of the magnetization free layer 1 according to the present embodiment.
- the magnetization free layer 1 according to the present embodiment includes a first magnetization fixed region 11, a second magnetization fixed region 12, and a magnetization switching region 13.
- the first magnetization fixed region 11, the second magnetization fixed region 12, and the magnetization switching region 13 are formed on the same XY plane.
- the magnetization switching region 13 is a region in contact with the tunnel barrier layer 2 and overlaps the magnetization fixed layer 3 (shown by a broken line in FIG. 2A). That is, an MTJ is formed by the magnetization switching region 13 of the magnetization free layer 1, the tunnel barrier layer 2, and the magnetization fixed layer 3.
- the longitudinal direction of the magnetization switching region 13, that is, the easy magnetization axis coincides with the X direction.
- the magnetization direction of the magnetization switching region 13 can be reversed, and the force S can be + X direction or ⁇ X direction. In other words, the magnetization direction of the magnetization switching region 13 can be “anti-parallel” that is “parallel” to the magnetization direction of the magnetization fixed layer 3.
- the first magnetization fixed region 11 is one end of the magnetization switching region 13 in the X direction (direction of easy magnetization axis)
- the second magnetization fixed region 12 is connected to the other end (second end) 13 b in the X direction of the magnetization inversion region 13.
- the side of the second magnetization fixed region 12 is in contact with the second end 13 b of the magnetization switching region 13. That is, another triple junction is formed by the second magnetization fixed region 12 and the magnetization switching region 13.
- the first magnetization fixed region 11 is formed along the S 1 axis that intersects the X axis. At this time, a wide angle and a narrow angle are formed at the intersection of the X-axis and the S-axis in the above-mentioned three-way junction.
- the portion of the first magnetization fixed region 11 extending to the wide angle side is hereinafter referred to as “first wide angle portion l la”, and the portion extending to the narrow angle side is hereinafter referred to as “first narrow angle portion l lb” Referenced.
- the first wide angle portion 11 a forms an angle of 90 degrees or more with respect to the magnetization easy axis of the magnetization switching region 13.
- the first narrow corner portion l ib forms an angle of 90 degrees or less with respect to the magnetization easy axis of the magnetization switching region 13.
- the second magnetization fixed region 12 is formed along the T axis intersecting the X axis. At this time, a wide angle and a narrow angle are formed by the intersection of the X axis and the ⁇ axis in the above-mentioned trifurcated road.
- the portion of the second magnetization fixed region 12 extending to the wide angle side is hereinafter referred to as "second wide angle portion 12a", and the portion extending to the narrow angle side is hereinafter referred to as "second narrow angle portion 12b".
- the second wide angle portion 12 a forms an angle of 90 degrees or more with respect to the magnetization easy axis of the magnetization switching region 13.
- the second narrow corner portion 12 b forms an angle of 90 degrees or less with respect to the magnetization easy axis of the magnetization switching region 13.
- the magnetizations of the first magnetization fixed region 11 and the second magnetization fixed region 12 are fixed along the longitudinal direction by magnetic anisotropy.
- the magnetization (first fixed magnetization) of the first magnetization fixed region 11 is fixed in the direction from the first wide-angle portion 11a toward the first narrow corner lib.
- the magnetization (second fixed magnetization) of the region 12 is fixed in the direction from the second wide-angle portion 12a to the second narrow angle portion 12b.
- the magnetization of the first magnetization fixed region 11 is fixed in the direction from the first narrow angle portion l ib to the first wide angle portion 11a
- the magnetization of the second magnetization fixed region 12 is the second narrow. It may be fixed in the direction from the corner 12b to the second wide angle part 12a.
- the X component of the fixed magnetization is reversed between the first magnetization fixed region 11 and the second magnetization fixed region 12.
- a pigging layer not shown may be used.
- the first piging layer is provided in the vicinity of the first magnetization fixed region 11 or adjacent to the first magnetization fixed region 11.
- the first pinned layer is formed of a ferromagnetic or antiferromagnetic material and is magnetically coupled to the first magnetization fixed region 11.
- it is provided in the vicinity of the second pigeon layer force S, the second magnetization fixed region 12 or adjacent to the second magnetization fixed region 12.
- the second pinned layer is formed of a ferromagnetic material or an antiferromagnetic material and is magnetically coupled to the second magnetization fixed region 12.
- Magnetic coupling includes exchange coupling and magnetostatic coupling.
- FIG. 3 shows two possible magnetization states of the magnetization free layer 1 according to the present embodiment.
- the magnetization direction of the magnetization switching region 13 is the X direction, that is, the direction is antiparallel to the magnetization direction (+ X direction) of the magnetization fixed layer 3
- the resistance value of the MTJ is relatively large.
- This antiparallel state is associated with, for example, data “1”.
- the magnetization direction of the magnetization switching region 13 is in the + X direction, that is, when the direction is parallel to the magnetization direction (+ X direction) of the magnetization fixed layer 3
- the resistance value of the MTJ is compared Small.
- This parallel state is associated with, for example, data "0".
- the magnetization (-X direction) of the magnetization switching region 13 is continuously connected from the second wide-angle portion 12a of the second magnetization fixed region 12.
- the magnetization of the first magnetization fixed region 11 is Since the three-way junction has a component in the + X direction, the domain wall DW is present at the first end 13a of the magnetization switching region 13.
- the magnetization switching region is The 13 magnetizations (in the + X direction) are continuously connected from the first wide-angle portion 11a of the first magnetization fixed region 11.
- the magnetization of the second magnetization fixed region 12 has a component in the X direction in the three-way junction.
- the domain wall DW is present at the second end 13b of the magnetization switching region 13.
- the X component of the fixed magnetization is reversed between the first magnetization fixed region 11 and the second magnetization fixed region 12 Therefore, the domain wall DW is introduced into the magnetization free layer 1.
- data “1” and “0” can be distinguished. These two states are equivalent in energy.
- Data is read out by detecting the resistance value of the MTJ. Specifically, a read current is caused to flow between the magnetization fixed layer 3 and the magnetization free layer 1 so as to penetrate the MTJ. The resistance value of the MTJ is detected based on the read current, and data "!" or "0" is sensed.
- Data writing is performed by the “horizontal spin injection method”. That is, the write current does not penetrate the MTJ but flows in a planar manner in the magnetization free layer 1.
- the write current flows from the wide-angle portion of one magnetization fixed region, through the magnetization switching region 13 and to the wide-angle portion of the other magnetization fixed region.
- the first wide-angle portion 11a of the first magnetization fixed region 11 serves as a spin supply source for supplying electrons having a magnetic moment in the + X direction (+ X direction spin polarized electrons) to the magnetization switching region 13. Play a role.
- the second wide-angle portion 12a of the second magnetization fixed region 12 has a magnetic moment in the -X direction. It serves as a spin source that supplies electrons (one spin-polarized electron in the X direction) to the magnetization switching region 13.
- Data writing can also be described in terms of domain wall motion.
- the domain wall DW moves from the first end 13a in the + X direction, and reaches the second end 13b.
- the domain wall DW moves from the first end 13a in the + X direction, and reaches the second end 13b.
- the domain wall DW moves from the second end 13 b in the X direction to reach the first end 13 a.
- the data writing is realized by the “domain wall displacement method”.
- the above-mentioned writing is possible even when the angle formed by the magnetization reversal region 13 between the wide angle part l la, 12 a or the narrow angle part l lb, 12 b and the magnetization switching region 13 is 90 degrees.
- the angle between the wide-angle portion l la, 12 a and the magnetization switching region 13 increases within the range of 90 to 180 degrees, the spin component contributing to the domain wall movement increases. As a result, the write efficiency is improved, and the write current can be further reduced. In that sense, it is preferable that the angle between the wide angle part l la, 12a and the magnetization inversion area 13 be larger than 90 degrees as shown in the drawing.
- a three-way junction is formed by each of the magnetization fixed regions 11 and 12 and the magnetization switching region 13.
- the magnetization free layer 1 has narrow corners 1 lb and 12 b in which the write current does not flow.
- the effects ij of these narrow corners l lb and 12 b are as follows.
- the wide-angle portion 11a of the first magnetization fixed region 11 is magnetically affected by the narrow angle portion l ib where the write current does not flow.
- the magnetization of the wide-angle portion 11a is continuously connected to the magnetization of the narrow corner l ib and stabilized by the magnetization of the narrow corner l ib. Therefore, at the time of data writing, the domain wall DW intrudes into the wide-angle portion 11 a and stops near the end of the magnetization switching region 13.
- the narrow angle portion l ib prevents the domain wall movement at the wide angle portion 11a. The same applies to the narrow corner 12b.
- the magnetization free layer 1 includes the first magnetization fixed region 11, the second magnetization fixed region 12, and the magnetization switching region 13.
- the first magnetization fixed region 11 and the magnetization switching region 13 form a three-way junction, and the first magnetization fixed region 11 includes the wide angle portion 11 a and the narrow corner portion l ib.
- the second magnetization fixed region 12 and the magnetization switching region 13 also form a three-fork path, and the second magnetization fixed region 12 includes a wide angle portion 12a and a narrow angle portion 12b.
- the width, length, and angle of each region can be designed arbitrarily. As in the example shown in FIG.
- the X component of fixed magnetization in the three-way junction is reversed at the first wide-angle portion 11a and the second wide-angle portion 12a. Therefore, it is possible to realize data writing by the method shown in FIG.
- the first magnetization fixed region 11 and the second magnetization fixed region 12 are mirror symmetric with the magnetization inversion region 13 interposed therebetween. This is preferable in that the injection efficiency of spin-polarized electrons is balanced between the data “!!” “write” and the data “0” write, and variations in the write efficiency can be suppressed.
- the magnetization switching region 13 has a first region B1 located closer to the first end 13a than the central portion, and a second region B2 located closer to the second end 13b than the central portion. And contains.
- the cross-sectional areas of the first region B1 and the second region B2 are different from the cross-sectional area of the central portion. From the viewpoint of energy, the smaller the area of the domain wall DW, the more stable the domain wall DW.
- the domain wall DW tends to stop in front of the first area B1 or the second area B2.
- the central portion is thicker than the first region B1 and the second region B2.
- the domain wall DW is prevented from stopping near the central portion.
- the magnetization free layer 1 and the magnetization fixed layer 3 for example, Fe (iron), Co (cobalt), Ni (nickel), or an alloy containing any of these as a main component can be used.
- Fe Ni, Fe-Co-Ni and Fe-Co are desirable.
- nonmagnetic elements to these magnetic substances properties such as magnetic properties, crystallinity, mechanical properties, and chemical properties may be adjusted. .
- the nonmagnetic elements to be added include Ag (silver), Cu (copper), Au (gold), B (boron), C (carbon), N (nitrogen), O (oxygen), Mg (magnesium), A1.
- the magnetization free layer 1 is a layer in which the domain wall moves, and preferably has a crystal structure that can realize smooth domain wall movement. Lattice defects, grain boundaries, etc. become piungsites that prevent smooth domain wall movement. Therefore, it is desirable that the magnetization free layer 1 have a structure such as an amorphous structure or a single crystal structure that does not contain much pin Jung site.
- amorphous structure P, Si, B, C, etc. are added to the magnetic material, film formation is performed in a nitrogen atmosphere, film formation rate is controlled, or film formation is performed by cooling the substrate. And so on.
- the magnetization fixed layer 3 in order to prevent magnetization reversal, it is desirable to use a material having a large coercivity.
- a magnetic material that can obtain a high MR ratio.
- Fe, Co, Ni, or an alloy made of them may be selected as the material of the magnetization fixed layer 3.
- the magnetic properties can be adjusted by adding 4d, 5d transition metal elements, rare earth elements and the like to such magnetic materials.
- tunnel barrier layer 2 As a material of tunnel barrier layer 2, Al 2 O 3 (aluminum oxide), SiO 2 (silicon oxide),
- An insulator such as MgO (magnesium oxide) or A1N (aluminum nitride) can be used.
- nonmagnetic metals such as Cu, Cr, Al, Zn (zinc) can also be used as the material of the tunnel barrier layer 2.
- the write current does not penetrate MTJ. Since it is not necessary to pass a write current to the tunnel barrier layer 2 for each write, deterioration of the tunnel barrier layer 2 is suppressed.
- the read characteristics depend on the properties of the MTJ including the tunnel barrier layer 2, while the write properties depend only on the properties of the magnetization free layer 1. Therefore, it becomes possible to design the read characteristic and the write characteristic almost independently. In other words, it becomes possible to design the write characteristic which is not greatly restricted by the read characteristic. That is, the design freedom of the write characteristics is improved. This also contributes to the expansion of the write margin.
- the magnetization free layer 1 has narrow corners 1 lb and 12 b.
- the narrow corners l lb and 12 b play a role of stabilizing the magnetization of the wide angle portions l la and 12 a, and prevent the domain wall DW from invading the wide angle portions l la and 12 a. That is, when the write current is supplied to the magnetization free layer 1, the magnetization of the magnetization fixed regions 11 and 12 can be stably held. This means that the upper limit of the magnitude of the write current is increased, and the write margin is expanded.
- FIG. 6 is a plan view showing the structure of the magnetization free layer 1 according to the second embodiment.
- the S axis in which the first magnetization fixed region 11 is formed and the T axis in which the second magnetization fixed region 12 is formed are substantially parallel.
- the first magnetization fixed region 11 and the second magnetization fixed region 12 are rotationally symmetric about the magnetization switching region 13.
- the wide angle portion 11 a of the first magnetization fixed region 11 faces the narrow angle portion 12 b of the second magnetization fixed region 12, and the narrow angle portion l ib of the first magnetization fixed region 11 is the wide angle portion of the second magnetization fixed region 12. It is facing 12a.
- the fixed direction of the magnetization (first fixed magnetization) of the first magnetization fixed region 11 and the fixed direction of the magnetization (second fixed magnetization) of the second magnetization fixed region 12 are the same as in the first embodiment. is there. That is, the first fixed magnetization is fixed in the direction from the first wide-angle portion 11a to the first narrow corner portion l ib, and the second fixed magnetization is fixed. Is fixed in the direction from the second wide angle part 12a to the second narrow angle part 12b (see FIG. 6). Alternatively, the first fixed magnetization is fixed in the direction from the first narrow angle portion l ib to the first wide angle portion 11a, and the second fixed magnetization is in the direction from the second narrow angle portion 12b to the second wide angle portion 12a.
- the X component of the fixed magnetization in the three-way junction is reversed at the first wide-angle portion 1 la and the second wide-angle portion 12a.
- the direction of the first fixed magnetization and the direction of the second fixed magnetization are antiparallel.
- FIG. 7 shows two possible magnetization states of the magnetization free layer 1 according to this example.
- Data writing is performed in the same manner as in the first embodiment. That is, the write current flows from one wide-angle portion to the other wide-angle portion in the magnetization free layer 1.
- the storage data S'T ' is rewritten to "0”
- electrons flow from the first wide angle portion 11a to the second wide angle portion 12a.
- the domain wall DW moves from the first end 13a in the + X direction to reach the second end 13b.
- the domain wall DW moves from the second end 13 b to ⁇ X Move to reach the first end 13a.
- the same effect as that of the first embodiment can be obtained.
- a shape of the magnetization free layer 1 a modification similar to the modification shown in FIG. 4A to FIG. 4D can be considered.
- various modifications shown in FIGS. 5A to 5C may be applied as the magnetization switching region 13.
- FIG. 8 is a side view schematically showing the structure of the magnetoresistance effect element according to the third example.
- the magnetization free layer 1 is provided with a plurality of magnetically coupled ferromagnetic layers.
- the magnetization free layer 1 has a stacked structure in which a first magnetization free layer la, a nonmagnetic layer 20, and a second magnetization free layer lb are sequentially stacked. Of these, the second magnetization free layer lb is in contact with the tunnel insulating layer 2.
- the first magnetization free layer la and the second magnetization free layer lb are connected via the nonmagnetic layer 20, and are ferromagnetically or antiferromagnetically coupled to each other.
- Magnetization Free Layer At least one force of la and lb has the magnetization fixed regions 11 and 12 and the magnetization switching region 13 shown in the above-described embodiment.
- both of the magnetization free layers la and lb may have the magnetization fixed regions 11 and 12 and the magnetization switching region 13.
- the write current may be applied to both of the magnetization free layers la and lb, or may be applied to only one of them. When the write current is supplied to only one magnetization free layer, when the magnetization of the magnetization switching region 13 is reversed, the magnetization of the magnetization switching region 13 of the other magnetization free layer is simultaneously reversed.
- the first magnetization free layer la has the magnetization fixed regions 11 and 12 and the magnetization inversion region 13, and the second magnetization free layer lb is only the magnetization inversion region 13. have.
- the write current is caused to flow only to the first magnetization free layer la.
- the magnetization of the magnetization switching region 13 of the first magnetization free layer la is reversed, the magnetization of the magnetization switching region 13 of the second magnetization free layer lb is simultaneously reversed.
- the write characteristics depend only on the first magnetization free layer la.
- the second magnetization free layer lb forms an MTJ together with the tunnel barrier layer 2 and the magnetization fixed layer 3 and contributes to the read characteristics.
- the write characteristics can be optimized by forming the first magnetization free layer la with a material suitable for domain wall movement.
- the second magnetization free layer lb of a material having a large MR ratio, the read-out characteristics can be improved.
- the nonmagnetic layer 20 has the same width as the first magnetization free layer la, but may have the same width as the second magnetization free layer lb. Alternatively, the width of the nonmagnetic layer 20 may change halfway from the same width as the second magnetization free layer lb to the same width as the first magnetization free layer la.
- the nonmagnetic layer 20 can play a role of protecting the first magnetization free layer la, in which the domain wall moves, from damage due to oxidation or etching in the manufacturing process. From that point of view, it is preferable that the nonmagnetic layer 20 be formed so as to completely cover the surface of the first magnetization free layer la, as shown in FIG.
- FIG. 9 is a plan view showing an example of the arrangement of a plurality of magnetoresistance effect elements.
- a plurality of magnetoresistance effect elements are arranged in an array.
- the magnetization fixed regions of the magnetization free layer 1 are magnetically coupled to each other between adjacent magnetoresistive elements. There is. This makes it possible to further stabilize the fixed magnetization of the magnetization fixed regions 11 and 12.
- FIG. 10 is a side view schematically showing the structure of the magnetoresistance effect element according to the fifth example.
- the magnetization free layer 1 is not planar but has a three-dimensional shape, and the magnetization fixed regions 11 and 12 and the magnetization switching region 13 are not formed on the same plane.
- the magnetization reversal region 13 is formed on the XY plane, and the magnetization fixed regions 11 and 12 are formed on a plane close to the YZ plane.
- the XZ-plane shape of the magnetization free layer 1 shown in FIG. 10 various modifications can be considered as the XZ-plane shape, as in the embodiments described above.
- the magnetization free layer 1 according to this example can have the same XZ plane shape as the XY plane shape of the magnetization free layer 1 shown in FIGS. 2A, 2B, 4A to 4D, and 6.
- various modifications shown in FIGS. 5A to 5C may be applied as the magnetization switching region 13.
- the fixing direction of the magnetization (first fixed magnetization) of the first magnetization fixed region 11 and the fixing direction of the magnetization (second fixed magnetization) of the second magnetization fixed region 12 have already been described.
- the first fixed magnetization is fixed in the direction from the first wide-angle portion 11a to the first narrow corner portion l ib
- the second fixed magnetization is in the direction from the second wide-angle portion 12a to the second narrow corner portion 12b. It is fixed.
- the first fixed magnetization is fixed in the direction from the first narrow corner portion l ib to the first wide angle portion 11a
- the second fixed magnetization is the second narrow angle.
- the X component of the fixed magnetization in the three-way junction is reversed at the first wide-angle portion 11a and the second wide-angle portion 12a.
- the first fixed magnetization and the second fixed magnetization include the Z component.
- FIGS. 11A and 11B show modified examples of the magnetoresistance effect element according to this example.
- an antiferromagnetic layer 30 is provided outside the magnetization fixed regions 11 and 12.
- an antiferromagnetic layer 30 is provided inside the magnetization fixed regions 11 and 12. These antiferromagnetic layers 30 are magnetized so as to fix the direction of magnetization of the magnetization fixed regions 11 and 12. It is magnetically coupled to each of the fixed regions 11 and 12. Such a configuration makes it possible to easily fix the magnetization directions of the magnetization fixed regions 11 and 12.
- the same effect as that of the first embodiment can be obtained. Furthermore, since the magnetization fixed regions 11 and 12 are arranged in the perpendicular direction, the area of the magnetoresistive element can be reduced.
- FIG. 12 is a side view schematically showing the structure of the magnetoresistance effect element according to the sixth example.
- the assist wiring 40 is provided in the vicinity of the magnetoresistance effect element.
- a predetermined current flows through the assist wiring, whereby an assist magnetic field is generated.
- the assist magnetic field is applied to the magnetization free layer 1 to assist the movement of the domain wall. That is, at the time of data writing, a current is caused to flow through the assist wiring such that an assist magnetic field directed to assist domain wall movement in the magnetization free layer 1 is generated.
- the assist wiring 40 extending in the Y direction is disposed below the magnetization reversal region 13 of the magnetoresistive effect element.
- a current in the + Y direction flows in the assist wiring 40.
- the assist magnetic field force S in the + X direction is applied to the magnetization switching region 13 of the magnetization free layer 1.
- the assist magnetic field facilitates magnetization of the magnetization switching region 13 in the + X direction, that is, the assist magnetic field assists the domain wall movement in the + X direction.
- a current in the Y direction flows through the assist wiring 40.
- the positions and the number of assist interconnections 40 are not limited to those shown in FIG.
- the assist magnetic field force generated by the assist wiring 40 and the magnetization reversal region 13 are applied simultaneously with the supply of the write current to the magnetization free layer 1. Since the domain wall movement is assisted by the assist magnetic field, the amount of the write current to be supplied to the magnetization free layer 1 can be reduced. That is, the value of the minimum write current required for domain wall movement is further reduced. This means that the write margin is further broadened.
- the assist wiring 40 shown in FIG. 12 is preferably a wiring for supplying a write current to the magnetization free layer 1. That is, it is preferable that a wire for supplying the write current to the magnetization free layer 1 be used in combination as the assist wire 40.
- the assist wire 40 is connected to the wide angle portion 11 a or 12 a of the magnetization free layer 1.
- the write current is supplied to or withdrawn from the wide-angle portion 11a or 12a through the assist wire 40.
- an assist magnetic field generated by the write current is applied to the magnetization switching region 13.
- FIGS. 13A and 13B show a modified example of the assist wiring 40.
- FIG. The assist wiring 40 shown in FIGS. 13A and 13B has a yoke structure. That is, a part of the surface of the assist wiring 40 which is not opposed to the magnetization switching region 13 is covered with the magnetic force substance 41.
- the bottom surface of the assist wiring 40 is covered with the magnetic body 41
- the side surface and the bottom surface of the assist wiring 40 are covered with the magnetic body 41.
- Such a yoke structure increases the assist magnetic field, and the write current can be further reduced.
- FIG. 14 is a circuit diagram showing an example of a magnetic memory cell using the magnetoresistive effect element described above.
- selection transistors 50a, 50b 1S for supplying a write current are connected to the magnetization free layer 1.
- one of the source / drain of the selection transistor 50a is connected to the first wide-angle portion 11a of the first magnetization fixed region 11, and the other is connected to the first bit line 51a.
- one of the source / drain of the select transistor 50b is connected to the second wide-angle portion 12a of the second magnetization fixed region 12, and the other is connected to the second bit line 51b.
- the gates of the select transistors 50 a and 50 b are connected to the word line 52.
- the magnetization fixed layer 3 is connected to the ground wire 53.
- the word line 52 is turned on, the ground line 53 is turned off, and a predetermined potential difference is applied between the bit lines 51a and 51b.
- the write current is, for example, "first bit line 51a-selection transistor 50a-first wide angle portion 11a of first magnetization fixed region 11-magnetization inversion region 13-second wide angle portion 12a of second magnetization fixed region 12". —Select transistor 50b-second bit Flow along the line 51b ". Reverse current paths are also possible. Thereby, the data writing shown in the above-described embodiment is realized.
- the word line 52 is turned on, the ground line 53 is turned on, and the bit lines 51a and 5 lb are set to the same potential.
- the read current flows in the path of "bit line 51a, 51b-selected transistor 50a, 50b-magnetization free layer 1-tunnel barrier layer 2-magnetization fixed layer 3-ground line 53".
- the stored data can be sensed based on the read current.
- FIG. 15 shows an example of the configuration of an MRAM 100 in which a plurality of magnetic memory cells 110 are arranged in an array.
- Each magnetic memory cell 110 has the configuration shown in FIG.
- the word line 52 is connected to the X selector 120, and the X selector 120 selects the word line 52 connected to the magnetic memory cell 110 to be accessed.
- the bit lines 51 a and 51 b are connected to the Y selector 130 and the Y side current termination circuit 140.
- the Y selector 130 selects the bit line 51a (or 51b) connected to the magnetic memory cell 110 to be accessed.
- Write current is supplied to or withdrawn from the magnetic memory cell 110 to be accessed through the selected bit line.
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JP2002056665A (ja) * | 2000-06-20 | 2002-02-22 | Hewlett Packard Co <Hp> | 磁気的に安定な磁気抵抗メモリ素子 |
JP2005150303A (ja) * | 2003-11-13 | 2005-06-09 | Toshiba Corp | 磁気抵抗効果素子および磁気メモリ |
JP2005191032A (ja) * | 2003-12-24 | 2005-07-14 | Toshiba Corp | 磁気記憶装置及び磁気情報の書込み方法 |
WO2006090656A1 (ja) * | 2005-02-23 | 2006-08-31 | Osaka University | パルス電流による磁壁移動に基づいた磁気抵抗効果素子および高速磁気記録装置 |
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JP5472821B2 (ja) * | 2008-12-19 | 2014-04-16 | 日本電気株式会社 | 磁気抵抗素子の初期化方法、及び磁気抵抗素子 |
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US20100008131A1 (en) | 2010-01-14 |
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US7936627B2 (en) | 2011-05-03 |
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