WO2011052475A1 - 磁気メモリ素子、磁気メモリ、及びその初期化方法 - Google Patents
磁気メモリ素子、磁気メモリ、及びその初期化方法 Download PDFInfo
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- WO2011052475A1 WO2011052475A1 PCT/JP2010/068590 JP2010068590W WO2011052475A1 WO 2011052475 A1 WO2011052475 A1 WO 2011052475A1 JP 2010068590 W JP2010068590 W JP 2010068590W WO 2011052475 A1 WO2011052475 A1 WO 2011052475A1
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- 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
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- 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
- G11C11/161—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 details concerning the memory cell structure, e.g. the layers of the ferromagnetic memory cell
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- 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
- G11C11/56—Digital stores characterised by the use of particular electric or magnetic storage elements; Storage elements therefor using storage elements with more than two stable states represented by steps, e.g. of voltage, current, phase, frequency
- G11C11/5607—Digital stores characterised by the use of particular electric or magnetic storage elements; Storage elements therefor using storage elements with more than two stable states represented by steps, e.g. of voltage, current, phase, frequency using magnetic storage elements
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- G—PHYSICS
- G11—INFORMATION STORAGE
- G11C—STATIC STORES
- G11C19/00—Digital stores in which the information is moved stepwise, e.g. shift registers
- G11C19/02—Digital stores in which the information is moved stepwise, e.g. shift registers using magnetic elements
- G11C19/08—Digital stores in which the information is moved stepwise, e.g. shift registers using magnetic elements using thin films in plane structure
- G11C19/0808—Digital stores in which the information is moved stepwise, e.g. shift registers using magnetic elements using thin films in plane structure using magnetic domain propagation
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- 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
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- G—PHYSICS
- G11—INFORMATION STORAGE
- G11C—STATIC STORES
- G11C13/00—Digital stores characterised by the use of storage elements not covered by groups G11C11/00, G11C23/00, or G11C25/00
- G11C13/0002—Digital stores characterised by the use of storage elements not covered by groups G11C11/00, G11C23/00, or G11C25/00 using resistive RAM [RRAM] elements
- G11C13/0021—Auxiliary circuits
- G11C13/0069—Writing or programming circuits or methods
- G11C2013/0083—Write to perform initialising, forming process, electro forming or conditioning
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- 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
Definitions
- the present invention relates to a magnetic memory element, a magnetic memory, and an initialization method thereof.
- the present invention relates to a magnetic memory element, a magnetic memory, and an initialization method thereof, which are made of a material having perpendicular magnetic anisotropy, particularly utilizing domain wall motion.
- Magnetic memory especially Magnetic Random Access Memory (MRAM)
- MRAM Magnetic Random Access Memory
- N Non-Patent Document 1
- the most common method of writing information to the MRAM is to arrange a wiring for writing around the magnetic memory element, and to change the magnetization direction of the magnetic memory element by a magnetic field generated by passing a current through the wiring. It is a method of switching. Since this method uses magnetization reversal by a magnetic field, writing in 1 nanosecond or less is possible in principle, which is preferable for realizing a high-speed MRAM.
- the magnetic field for switching the magnetization of the magnetic material that has ensured thermal stability and disturbance magnetic field resistance is generally about several tens of Oe (Yersted), and in order to generate such a magnetic field, about several mA. A current is required.
- the chip area is inevitably increased, and the power consumption required for writing increases, so that it is inferior in competitiveness compared to other random access memories.
- the write current further increases, which is not preferable in terms of scaling.
- the first is a spin injection magnetization reversal method.
- This is a laminated film composed of a first magnetic layer (magnetization free layer) having reversible magnetization and a second magnetic layer (reference layer) electrically connected to and fixed in magnetization.
- Spin-polarized conduction electrons and local electrons in the first magnetic layer (magnetization free layer) when a current is passed between the second magnetic layer (reference layer) and the first magnetic layer (magnetization free layer) Is used to reverse the magnetization of the first magnetic layer (magnetization free layer).
- the magnetoresistive effect developed between the first magnetic layer (magnetization free layer) and the second magnetic layer (reference layer) is used.
- the MRAM using the spin transfer magnetization reversal method is a two-terminal element. Since spin injection magnetization reversal occurs at a certain current density or higher, the current required for writing is reduced as the element size is reduced. That is, it can be said that the spin injection magnetization reversal method is excellent in scaling.
- an insulating layer is provided between the first magnetic layer (magnetization free layer) and the second magnetic layer (reference layer), and a relatively large current flows through the insulating layer during writing. Rewriting resistance and reliability are problems.
- the current path for writing and the current path for reading are the same, there is a concern about erroneous writing during reading. Thus, although spin transfer magnetization reversal is excellent in scaling, there are some barriers to practical use.
- the magnetization reversal method using the current-induced domain wall motion phenomenon which is the second method, can solve the above-mentioned problems of spin injection magnetization reversal.
- An MRAM using a current-induced domain wall motion phenomenon is disclosed in, for example, Japanese Patent Application Laid-Open No. 2005-191032.
- an MRAM using a current-induced domain wall motion phenomenon is fixed so that the magnetizations at both ends of the first magnetic layer (magnetization free layer) having reversible magnetization are substantially antiparallel to each other. Yes.
- a domain wall is introduced into the first magnetic layer.
- Non-Patent Document 2 A.
- Non-Patent Document 2 requires about 1 ⁇ 10 18 [A / cm 2 ] as the current density necessary for current-induced domain wall motion.
- the write current becomes 1 mA when the width of the layer (magnetization free layer) in which the domain wall motion occurs is 100 nm and the film thickness is 10 nm. This cannot satisfy the above-mentioned conditions concerning the write current.
- Non-Patent Document 3 (S. Fukami et al., “Micromagnetic analysis of current 7 and Jenpine.
- the write current can be sufficiently reduced by using a material having perpendicular magnetic anisotropy as a ferromagnetic layer (magnetization free layer) in which current-induced domain wall motion occurs.
- a material having perpendicular magnetic anisotropy as a ferromagnetic layer (magnetization free layer) in which current-induced domain wall motion occurs.
- Japanese Patent Application Laid-Open No. 2004-153248 discloses a magnetoresistive effect element, a manufacturing method thereof, a magnetic head, and a magnetic reproducing apparatus.
- the magnetoresistive effect element includes a magnetoresistive effect film, a pair of electrodes, and a phase separation layer.
- the magnetoresistive film includes a first ferromagnetic layer whose magnetization direction is substantially fixed in one direction, a second ferromagnetic layer whose magnetization direction changes according to an external magnetic field, and the first and second layers And an intermediate layer formed between the ferromagnetic layers.
- the pair of electrodes are electrically connected to the magnetoresistive film that allows a sense current to flow in a direction substantially perpendicular to the film surface of the magnetoresistive film.
- the phase separation layer has first and second phases in which an alloy made of several elements is separated in a solid phase, and one of the first and second phases is oxygen, nitrogen, fluorine, and It is formed between the pair of electrodes containing at least one element selected from the group consisting of carbon at a high concentration.
- Japanese Patent Laid-Open No. 2005-209251 discloses a method for initializing a magnetic memory.
- a storage layer that retains information according to the magnetization state of a magnetic material includes a magnetic storage element including a plurality of magnetic layers, and a first wiring and a second wiring that intersect each other.
- the current pulse of the first wiring and the second wiring By stopping the application of the current pulses of the wirings at approximately the same time, the magnetization states of the storage layers of the magnetic storage elements are made uniform.
- Japanese Patent Application Laid-Open No. 2008-147488 discloses a magnetoresistive element and MRAM.
- the magnetoresistive element includes at least two first magnetization fixed layers whose magnetization directions are fixed, a magnetization free layer that is formed on a first plane and has a variable magnetization direction, and a nonmagnetic layer.
- a second magnetization fixed layer connected to the magnetization free layer and having a magnetization direction fixed, and the two first magnetization fixed layers are opposed to the second magnetization fixed layer with the magnetization free layer interposed therebetween.
- a write current is passed from one end of the magnetization free layer to the other end in the first plane.
- the layer in which domain wall motion occurs (magnetization free layer) ) Must have two regions (magnetization fixed regions) in which magnetization is fixed antiparallel, and a region in which domain wall movement occurs (domain wall movement region).
- the magnetization fixed region needs to have a first magnetization fixed region whose magnetization is fixed in the first direction and a second magnetization fixed region whose magnetization is fixed in the second direction. Therefore, in manufacturing the MRAM, a process (initialization) for fixing the magnetizations of the first magnetization fixed region and the second magnetization fixed region in the antiparallel direction is necessary.
- the magnitude of the magnetic field that can be initialized is limited to a certain finite range (initialization margin).
- initialization margin it is difficult to obtain a large initialization margin by simply changing the magnetic characteristics of the first magnetization fixed region and the second magnetization fixed region.
- the initialization margin is as large as possible, and it is preferable that a configuration enabling initialization can be manufactured as easily as possible.
- An object of the present invention is to provide a large initialization margin in an MRAM that uses current-induced domain wall motion in a method of writing information and a layer in which domain wall motion occurs is made of a material having perpendicular magnetic anisotropy. It is to provide a structure and an initialization method.
- the magnetic memory element of the present invention includes a perpendicular first magnetization free layer, a nonmagnetic layer, a reference layer, a first magnetization fixed layer group, and a first blocking layer.
- the first magnetization free layer is made of a ferromagnetic material having perpendicular magnetic anisotropy, and is connected to the first magnetization fixed region, the second magnetization fixed region, the first magnetization fixed region, and the second magnetization fixed region.
- the nonmagnetic layer is provided in the vicinity of the first magnetization free layer.
- the reference layer is made of a ferromagnetic material and is provided on the nonmagnetic layer.
- the first magnetization fixed layer group is provided in the vicinity of the first magnetization fixed region.
- the first blocking layer is provided between the first magnetization fixed layer group and the first magnetization fixed region, or sandwiched between the first magnetization fixed layer group.
- a magnetic memory according to the present invention includes the plurality of magnetic memory elements arranged in a matrix and a control circuit that controls writing and reading of data to and from each of the plurality of magnetic memory elements.
- the method for initializing a magnetic memory element of the present invention includes applying a first magnetic field to the magnetic memory element in a direction substantially perpendicular to the upper plane of the first magnetization free layer, and applying a first magnetic field to the magnetic memory element. Applying a second magnetic field having a smaller absolute value than the first magnetic field in a direction opposite to the first magnetic field.
- the magnetic memory element includes a perpendicular first magnetization free layer, a nonmagnetic layer, a reference layer, a first magnetization fixed layer group, and a first blocking layer.
- the first magnetization free layer is made of a ferromagnetic material having perpendicular magnetic anisotropy, and is connected to the first magnetization fixed region, the second magnetization fixed region, the first magnetization fixed region, and the second magnetization fixed region.
- the nonmagnetic layer is provided in the vicinity of the first magnetization free layer.
- the reference layer is made of a ferromagnetic material and is provided on the nonmagnetic layer.
- the first magnetization fixed layer group is provided in the vicinity of the first magnetization fixed region.
- the first blocking layer is provided between the first magnetization fixed layer group and the first magnetization fixed region, or sandwiched between the first magnetization fixed layer group.
- the method for initializing a magnetic memory includes the step of executing the above-described method for initializing a magnetic memory element on a plurality of magnetic memory elements.
- the magnetic memory includes a plurality of magnetic memory elements arranged in a matrix.
- Each of the plurality of magnetic memory elements includes a perpendicular first magnetization free layer, a nonmagnetic layer, a reference layer, a first magnetization fixed layer group, and a first blocking layer.
- the first magnetization free layer is made of a ferromagnetic material having perpendicular magnetic anisotropy, and is connected to the first magnetization fixed region, the second magnetization fixed region, the first magnetization fixed region, and the second magnetization fixed region.
- the nonmagnetic layer is provided in the vicinity of the first magnetization free layer.
- the reference layer is made of a ferromagnetic material and is provided on the nonmagnetic layer.
- the first magnetization fixed layer group is provided in the vicinity of the first magnetization fixed region.
- the first blocking layer is provided between the first magnetization fixed layer group and the first magnetization fixed region, or sandwiched between the first magnetization fixed layer group.
- a structure in which a large initialization margin is obtained in an MRAM that uses current-induced domain wall motion in an information writing method and a layer in which domain wall motion occurs is made of a material having perpendicular magnetic anisotropy, and an initial Can be provided.
- FIG. 1A schematically shows a typical structure of a main part of a magnetic memory element according to an embodiment of the present invention.
- FIG. 1B schematically shows a typical structure of a main part of the magnetic memory element according to the embodiment of the present invention.
- FIG. 1C schematically shows a typical structure of a main part of the magnetic memory element according to the embodiment of the present invention.
- FIG. 2A schematically shows an example of magnetization states in the memory states of “0” and “1” of the magnetic memory element according to the embodiment of the present invention.
- FIG. 2B schematically shows an example of magnetization states in the memory states of “0” and “1” of the magnetic memory element according to the embodiment of the present invention.
- FIG. 1A schematically shows a typical structure of a main part of a magnetic memory element according to an embodiment of the present invention.
- FIG. 1B schematically shows a typical structure of a main part of the magnetic memory element according to the embodiment of the present invention.
- FIG. 2A schematically shows an example of
- FIG. 3A schematically shows a method of writing information to the magnetic memory element according to the embodiment of the present invention.
- FIG. 3B schematically shows a method of writing information to the magnetic memory element according to the embodiment of the present invention.
- FIG. 4A schematically shows a method of reading information from the magnetic memory element according to the embodiment of the present invention.
- FIG. 4B schematically shows a method of reading information from the magnetic memory element according to the exemplary embodiment of the present invention.
- FIG. 5 shows a configuration example of a circuit for one bit of the magnetic memory cell according to the embodiment of the present invention.
- FIG. 6 is a block diagram showing an example of the configuration of the magnetic memory according to the embodiment of the present invention.
- FIG. 7A schematically shows a part of the simplest configuration of the magnetic memory element.
- FIG. 7B schematically shows a method for initializing the magnetization state in the simplest configuration of the magnetic memory element.
- FIG. 7C schematically shows a method for initializing the magnetization state in the simplest configuration of the magnetic memory element.
- FIG. 7D schematically shows a method of initializing the magnetization state in the simplest configuration of the magnetic memory element.
- FIG. 7E schematically shows a method for initializing the magnetization state in the simplest configuration of the magnetic memory element.
- FIG. 7F schematically shows a combined magnetization curve of a system composed of the first magnetization free layer and the magnetization fixed layer group in the simplest configuration of the magnetic memory element.
- FIG. 8A schematically shows a part of the structure of the magnetic memory element according to the exemplary embodiment of the present invention.
- FIG. 8A schematically shows a part of the structure of the magnetic memory element according to the exemplary embodiment of the present invention.
- FIG. 8B schematically shows a method for initializing the magnetization state in the magnetic memory element according to the embodiment of the present invention.
- FIG. 8C schematically shows a method of initializing the magnetization state in the magnetic memory element according to the embodiment of the present invention.
- FIG. 8D schematically shows a method of initializing the magnetization state in the magnetic memory element according to the embodiment of the present invention.
- FIG. 8E schematically shows a method for initializing the magnetization state in the magnetic memory element according to the exemplary embodiment of the present invention.
- FIG. 8F schematically shows a method of initializing the magnetization state in the magnetic memory element according to the embodiment of the present invention.
- FIG. 8G schematically shows a method of initializing the magnetization state in the magnetic memory element according to the embodiment of the present invention.
- FIG. 8H schematically shows a method for initializing the magnetization state in the magnetic memory element according to the embodiment of the present invention.
- FIG. 8I schematically shows a combined magnetization curve of a system including the first magnetization free layer and the magnetization fixed layer group in the magnetic memory element according to the embodiment of the present invention.
- FIG. 8J schematically shows a combined magnetization curve of a system composed of the first magnetization free layer and the magnetization fixed layer group in the magnetic memory element according to the embodiment of the present invention.
- FIG. 9 shows a magnetization curve in an element to which the embodiment of the present invention is applied.
- FIG. 10A schematically shows the structure of the first modification example of the magnetic memory element according to the exemplary embodiment of the present invention.
- FIG. 10A schematically shows the structure of the first modification example of the magnetic memory element according to the exemplary embodiment of the present invention.
- FIG. 10B schematically shows the structure of the first modification example of the magnetic memory element according to the exemplary embodiment of the present invention.
- FIG. 11A schematically shows a structure of a second modification of the magnetic memory element according to the exemplary embodiment of the present invention.
- FIG. 11B schematically shows the structure of the second modification example of the magnetic memory element according to the exemplary embodiment of the present invention.
- FIG. 11C schematically shows the structure of the second modification example of the magnetic memory element according to the exemplary embodiment of the present invention.
- FIG. 12A schematically shows a structure of a third modification of the magnetic memory element according to the exemplary embodiment of the present invention.
- FIG. 12B schematically shows the structure of the third modification example of the magnetic memory element according to the exemplary embodiment of the present invention.
- FIG. 13A schematically shows a part of the structure of the third modified example of the magnetic memory element according to the exemplary embodiment of the present invention.
- FIG. 13B schematically shows a method of initializing the magnetization state in the third modification of the magnetic memory element according to the embodiment of the present invention.
- FIG. 13C schematically shows a method of initializing the magnetization state in the third modification of the magnetic memory element according to the embodiment of the present invention.
- FIG. 13D schematically shows a method of initializing the magnetization state in the third modification of the magnetic memory element according to the embodiment of the present invention.
- FIG. 13E schematically shows a magnetization state initialization method in the third modification example of the magnetic memory element according to the embodiment of the present invention.
- FIG. 13F schematically shows a method for initializing the magnetization state in the third modification of the magnetic memory element according to the embodiment of the present invention.
- FIG. 13G schematically shows a combined magnetization curve of a system including the first magnetization free layer and the magnetization fixed layer group in the third modification of the magnetic memory element according to the embodiment of the present invention.
- FIG. 13H schematically shows a combined magnetization curve of a system including the first magnetization free layer and the magnetization fixed layer group in the third modification example of the magnetic memory element according to the embodiment of the present invention.
- FIG. 14 schematically shows the structure of a fourth modification of the magnetic memory element according to the embodiment of the present invention.
- FIG. 15A schematically shows a part of the structure of the fourth modification example of the magnetic memory element according to the exemplary embodiment of the present invention.
- FIG. 15B schematically shows a method of initializing the magnetization state in the fourth modification example of the magnetic memory element according to the embodiment of the present invention.
- FIG. 15C schematically shows a magnetization state initialization method in the fourth modification example of the magnetic memory element according to the embodiment of the present invention.
- FIG. 15D schematically shows a method for initializing the magnetization state in the fourth modification example of the magnetic memory element according to the embodiment of the present invention.
- FIG. 15E schematically shows a method of initializing the magnetization state in the fourth modification example of the magnetic memory element according to the embodiment of the present invention.
- FIG. 15A schematically shows a part of the structure of the fourth modification example of the magnetic memory element according to the exemplary embodiment of the present invention.
- FIG. 15B schematically shows a method of initializing the magnetization state in the fourth modification example of the magnetic memory element according to the embodiment of
- FIG. 15F schematically shows a magnetization state initialization method in the fourth modification example of the magnetic memory element according to the embodiment of the present invention.
- FIG. 15G schematically shows a magnetization state initialization method in the fourth modification example of the magnetic memory element according to the embodiment of the present invention.
- FIG. 15H schematically shows a method for initializing the magnetization state in the fourth modified example of the magnetic memory element according to the embodiment of the present invention.
- FIG. 15I schematically shows a method of initializing the magnetization state in the fourth modification example of the magnetic memory element according to the embodiment of the present invention.
- FIG. 15J schematically shows a magnetization state initialization method in the fourth modification example of the magnetic memory element according to the embodiment of the present invention.
- FIG. 15G schematically shows a magnetization state initialization method in the fourth modification example of the magnetic memory element according to the embodiment of the present invention.
- FIG. 15H schematically shows a method for initializing the magnetization state in the fourth modified example of the magnetic memory element according to the embodiment of the present
- FIG. 15K schematically shows a combined magnetization curve of a system including the first magnetization free layer and the magnetization fixed layer group in the fourth modification example of the magnetic memory element according to the embodiment of the present invention.
- FIG. 15L schematically shows a combined magnetization curve of a system including the first magnetization free layer and the magnetization fixed layer group in the fourth modification example of the magnetic memory element according to the embodiment of the present invention.
- FIG. 16A schematically shows the structure of the fifth modification example of the magnetic memory element according to the embodiment of the present invention.
- FIG. 16B schematically shows the structure of the fifth modification example of the magnetic memory element according to the exemplary embodiment of the present invention.
- FIG. 17A schematically shows a writing method of the fifth modification example of the magnetic memory element according to the exemplary embodiment of the present invention.
- FIG. 17B schematically shows a writing method of the fifth modification example of the magnetic memory element according to the exemplary embodiment of the present invention.
- FIG. 18A schematically shows a structure of a sixth modification example of the magnetic memory element according to the exemplary embodiment of the present invention.
- FIG. 18B schematically shows the structure of the sixth modification example of the magnetic memory element according to the embodiment of the present invention.
- FIG. 18C schematically shows the structure of the sixth modification example of the magnetic memory element according to the exemplary embodiment of the present invention.
- FIG. 18D schematically shows the structure of the sixth modification example of the magnetic memory element according to the exemplary embodiment of the present invention.
- FIG. 19A schematically shows a writing method of the sixth modification example of the magnetic memory element according to the exemplary embodiment of the present invention.
- FIG. 19A schematically shows a writing method of the sixth modification example of the magnetic memory element according to the exemplary embodiment of the present invention.
- FIG. 19B schematically shows a writing method of the sixth modification example of the magnetic memory element according to the exemplary embodiment of the present invention.
- FIG. 20A schematically shows another structure of the sixth modification example of the magnetic memory element according to the exemplary embodiment of the present invention.
- FIG. 20B schematically shows another structure of the sixth modification example of the magnetic memory element according to the exemplary embodiment of the present invention.
- FIG. 20C schematically shows another structure of the sixth modification example of the magnetic memory element according to the exemplary embodiment of the present invention.
- FIG. 21A schematically shows another writing method of the sixth modification example of the magnetic memory element according to the exemplary embodiment of the present invention.
- FIG. 21B schematically shows another writing method of the sixth modification example of the magnetic memory element according to the exemplary embodiment of the present invention.
- FIG. 21A schematically shows another writing method of the sixth modification example of the magnetic memory element according to the exemplary embodiment of the present invention.
- FIG. 21B schematically shows another writing method of the sixth modification example of the magnetic memory element according to the exemplary
- FIG. 22A schematically shows a structure of a seventh modification example of the magnetic memory element according to the exemplary embodiment of the present invention.
- FIG. 22B schematically shows the structure of the seventh modification example of the magnetic memory element according to the exemplary embodiment of the present invention.
- FIG. 23A schematically shows another structure of the seventh modification example of the magnetic memory element according to the exemplary embodiment of the present invention.
- FIG. 23B schematically shows another structure of the seventh modification example of the magnetic memory element according to the exemplary embodiment of the present invention.
- FIG. 24A schematically shows the structure of the eighth modification example of the magnetic memory element according to the exemplary embodiment of the present invention.
- FIG. 24B schematically shows the structure of the eighth modification example of the magnetic memory element according to the exemplary embodiment of the present invention.
- FIG. 24A schematically shows the structure of the eighth modification example of the magnetic memory element according to the exemplary embodiment of the present invention.
- FIG. 24B schematically shows the structure of the eighth modification example of the magnetic memory element according to the exemplary embodiment of the present
- FIG. 25A schematically shows another structure of the eighth modification example of the magnetic memory element according to the exemplary embodiment of the present invention.
- FIG. 25B schematically shows another structure of the eighth modification example of the magnetic memory element according to the exemplary embodiment of the present invention.
- FIG. 26 schematically shows still another structure of the eighth modification example of the magnetic memory element according to the embodiment of the present invention.
- the magnetic memory according to the present embodiment has a plurality of magnetic memory cells arranged in an array, and each magnetic memory cell has a magnetic memory element.
- FIG. 1A to 1C schematically show typical structures of main parts of a magnetic memory element according to an embodiment of the present invention.
- 1A is a perspective view
- FIG. 1B is an xz sectional view
- FIG. 1C is an xy plan view.
- the z axis indicates the substrate vertical direction
- the xy axis is parallel to the substrate plane.
- the magnetic memory element 70 includes a first magnetization free layer 10, a nonmagnetic layer 30, a reference layer 40, a magnetization fixed layer group 60, and a blocking layer 65.
- FIG. 1C is a plan view schematically showing the structure of the first magnetization free layer 10.
- the first magnetization free layer 10 is made of a ferromagnetic material having perpendicular magnetic anisotropy.
- the first magnetization free layer 10 is composed of three regions: a first magnetization fixed region 11a, a second magnetization fixed region 11b, and a magnetization free region 12.
- the first magnetization fixed region 11a and the second magnetization fixed region 11b have magnetization substantially fixed in one direction.
- the magnetizations of the first magnetization fixed region 11a and the second magnetization fixed region 11b are fixed in antiparallel directions.
- the first magnetization fixed region 11a and the second magnetization fixed region 11b are depicted as being fixed in the + z direction and the ⁇ z direction, respectively.
- the magnetization of the magnetization free region 12 can be reversed. In this case, it can face either the + z direction or the ⁇ z direction.
- the boundary between the first magnetization fixed region 11a and the magnetization free region 12 and the second according to the magnetization direction of the magnetization free region 12 and the second A domain wall is formed at one of the boundaries between the magnetization fixed region 11 b and the magnetization free region 12.
- FIG. 1C when the magnetization of the magnetization free region 12 is in the + z direction, a domain wall is formed at the boundary between the second magnetization fixed region 11b and the magnetization free region 12, and when the magnetization of the magnetization free region 12 is in the ⁇ z direction, A domain wall is formed at the boundary between the one magnetization fixed region 11 a and the magnetization free region 12.
- the first magnetization fixed region 11a is adjacent to one end of the magnetization free region 12, and the second magnetization fixed region 11b is adjacent to another end of the magnetization free region 12. To do.
- the first magnetization fixed region 11a is adjacent to the ⁇ x direction end of the magnetization free region 12, and the second magnetization fixed region 11b is adjacent to the + x direction end of the magnetization free region 12. ing.
- the first magnetization free layer 10, the nonmagnetic layer 30, and the reference layer 40 are stacked in this order.
- the reference layer 40 is made of a ferromagnetic material.
- the nonmagnetic layer 30 is made of a nonmagnetic material, and preferably made of an insulator.
- the magnetic tunnel junction Magnetic Tunnel Junction; MTJ
- MTJ Magnetic Tunnel Junction
- the nonmagnetic layer 30 and the reference layer 40 connected to the first magnetization free layer 10 via the nonmagnetic layer 30 are connected to the magnetization free region 12 of the first magnetization free layer 10.
- the shapes of the nonmagnetic layer 30 and the reference layer 40 are arbitrary.
- the reference layer 40 is preferably made of a ferromagnetic material having perpendicular magnetic anisotropy and has a magnetization substantially fixed in one direction.
- the magnetization of the reference layer 40 is fixed in the + z direction.
- the reference layer 40 may have the following laminated structure.
- the reference layer 40 may have a structure in which three layers of a ferromagnetic material, a nonmagnetic material, and a ferromagnetic material are laminated in this order.
- the non-magnetic material sandwiched between the two ferromagnetic materials preferably has a function of magnetically coupling the upper and lower ferromagnetic materials in an antiparallel direction (laminated ferri-coupled).
- Ru is exemplified as the nonmagnetic material having such a function.
- an antiferromagnetic material may be adjacent to the reference layer 40. This is because the magnetization direction of the interface can be fixed in one direction by adjoining antiferromagnetic materials and performing heat treatment in a magnetic field.
- a typical antiferromagnetic material is exemplified by Pt—Mn.
- the magnetization fixed layer group 60 contains at least one of a ferromagnetic material and an antiferromagnetic material.
- the magnetization fixed layer group 60 has a function of directing the magnetizations of the first magnetization fixed region 11a and the second magnetization fixed region 11b of the first magnetization free layer 10 in the antiparallel direction and fixing the magnetization in one direction.
- the magnetization fixed layer group 60 may be composed of two regions, a first magnetization fixed layer group 60a and a second magnetization fixed layer group 60b.
- the first magnetization fixed layer group 60a is magnetically coupled to the first magnetization fixed region 11a
- the second magnetization fixed layer group 60b is magnetically coupled to the second magnetization fixed region 11b. It has been.
- the magnetic coupling mentioned here includes strong coupling due to exchange coupling and includes weak coupling due to magnetostatic coupling.
- the first magnetization fixed layer group 60a and the second magnetization fixed layer group 60b are made of a ferromagnetic material, and the first magnetization fixed layer group 60a, the first magnetization fixed region 11a, and the The two magnetization fixed layer group 60b and the second magnetization fixed region 11b are depicted as being ferromagnetically coupled.
- a blocking layer 65 is provided adjacent to the magnetization fixed layer group 60.
- the first blocking layer 65a is provided between the first magnetization fixed layer group 60a and the first magnetization fixed region 11a of the first magnetization free layer 10 is shown.
- the blocking layer 65 is provided so as to be sandwiched between the magnetization fixed layer group 60 and the first magnetization free layer 10 or in the magnetization fixed layer group 60.
- the first magnetization fixed region 11a and the second magnetization fixed region 11b are connected to different external wirings, and the reference layer 40 is connected to another external wiring. That is, the magnetic memory element 70 is a three-terminal element.
- the magnetization fixed layer group 60 is provided on a path where the first magnetization free layer 10 is connected to an external wiring. There may be. That is, in the example of FIG. 1, the first magnetization fixed layer group 60a and the second magnetization fixed layer group 60b may be connected to different external wirings.
- FIG. 2A and 2B schematically show examples of magnetization states in the memory states of “0” and “1” of the magnetic memory element according to the embodiment of the present invention.
- 2A shows the state of magnetization in the “0” state
- FIG. 2B shows the state of magnetization in the “1” state.
- the magnetization of the first magnetization fixed region 11a is fixed in the + z direction
- the magnetization of the second magnetization fixed region 11b is fixed in the ⁇ z direction.
- the magnetization of the magnetization free region 12 has a + z direction component.
- a domain wall DW is formed at the boundary between the magnetization free region 12 and the second magnetization fixed region 11b.
- the magnetization of the magnetization free region 12 has a ⁇ z direction component.
- a domain wall DW is formed at the boundary between the magnetization free region 12 and the first magnetization fixed region 11a.
- the magnetization arrangement of the MTJ formed from the first magnetization free layer 10, the nonmagnetic layer 30, and the reference layer 40 is They are parallel and antiparallel respectively. Therefore, when a current is passed through the MTJ, a low resistance and a high resistance are realized. It should be noted that the correspondence between the magnetization state and the memory state (“0”, “1”) defined in FIGS. 2A and 2B is arbitrary and is not limited to this.
- FIGS. 3A and 3B schematically show a method of writing information to the magnetic memory element according to the embodiment of the present invention.
- layers other than the first magnetization free layer 10 are omitted for simplicity.
- a write current is introduced in the direction (+ x direction) indicated by the arrow Iwrite in FIG. 3A.
- conduction electrons flow from the second magnetization fixed region 11 b to the first magnetization fixed region 11 a via the magnetization free region 12 in the first magnetization free layer 10.
- a spin transfer torque acts on the domain wall DW formed at the boundary between the second magnetization fixed region 11 b and the magnetization free region 12.
- STT spin transfer torque
- the domain wall DW moves in the negative direction of the x axis. That is, current-induced domain wall movement occurs.
- the conduction electrons decrease in the negative direction of the x axis from the boundary between the magnetization free region 12 and the first magnetization fixed region 11a (because it also flows into the first magnetization fixed layer group 60a). Therefore, the domain wall DW stops at the boundary between the magnetization free region 12 and the first magnetization fixed region 11a. This state corresponds to the “1” state defined in FIG. 2B. In this way, “1” writing can be performed.
- a write current is introduced in the direction indicated by the arrow Iwrite in FIG. 3B.
- conduction electrons flow from the first magnetization fixed region 11 a to the first magnetization fixed region 11 a via the magnetization free region 12 in the first magnetization free layer 10.
- the spin transfer torque acts on the domain wall DW formed at the boundary between the second magnetization fixed region 11b and the magnetization free region 12.
- the domain wall DW moves in the positive direction of the x axis. That is, current-induced domain wall movement occurs.
- the conduction electrons decrease in the positive direction of the x axis from the boundary between the magnetization free region 12 and the second magnetization fixed region 11b (because it also flows into the second magnetization fixed layer group 60b). Therefore, the domain wall DW stops at the boundary between the magnetization free region 12 and the second magnetization fixed region 11b.
- This state corresponds to the “0” state defined in FIG. 2A. In this way, “0” writing can be performed. Note that the state does not change when “0” writing in the “0” state and “1” writing in the “1” state are performed. That is, overwriting is possible.
- FIG. 4A and 4B schematically show a method of reading information from the magnetic memory element according to the embodiment of the present invention.
- a method of reading information from the magnetic memory element 70 having the configuration shown in FIG. 1 will be described.
- information is read mainly using a tunneling magnetoresistive effect (TMR effect).
- TMR effect tunneling magnetoresistive effect
- MTJ magnetic tunnel junction
- the direction of this Iread is arbitrary.
- FIG. 4A when Iread is introduced in the “0” state defined in FIG. 2A, the magnetization is in a parallel state in the MTJ, so that low resistance is realized. Also, as shown in FIG. 4B, when Iread is introduced in the “1” state defined in FIG. 2B, the magnetization is antiparallel in the MTJ, so that high resistance is realized. In this way, information stored in the magnetic memory element 70 can be detected as a difference in resistance value.
- FIG. 5 shows a configuration example of a circuit for one bit of the magnetic memory cell according to the embodiment of the present invention.
- the magnetic memory element 70 is a three-terminal element, and is connected to the word line WL, the ground line GL, and the bit line pair BLa, BLb.
- the terminal connected to the reference layer 40 is connected to the ground line GL for reading.
- a terminal connected to the first magnetization fixed region 11a (via the first magnetization fixed layer group 60a) is connected to one of the source / drain of the transistor TRa, and the other of the source / drain is connected to the bit line BLa. Yes.
- a terminal connected to the second magnetization fixed region 11b (via the second magnetization fixed layer group 60b) is connected to one of the source / drain of the transistor TRb, and the other of the source / drain is connected to the bit line BLb. Yes.
- the gates of the transistors TRa and TRb are connected to a common word line WL.
- the word line WL is set to the high level, and the transistors TRa and TRb are turned on.
- one of the bit line pair BLa and BLb is set to a high level, and the other is set to a low level (ground level).
- a write current flows between the bit line BLa and the bit line BLb via the transistors TRa and TRb and the first magnetization free layer 10.
- the word line WL is set to a high level, and the transistors TRa and TRb are turned on. Further, the bit line BLa is set to an open state. On the other hand, the bit line BLb is set to a high level. As a result, a read current flows from the bit line BLb through the transistor TRb and the MTJ of the magnetic memory element 70 to the ground line GL. This enables reading using the magnetoresistive effect.
- FIG. 6 is a block diagram showing an example of the configuration of the magnetic memory according to the embodiment of the present invention.
- the magnetic memory 90 includes a memory cell array 110, an X driver 120, a Y driver 130, and a controller 140.
- the memory cell array 110 has a plurality of magnetic memory cells 80 arranged in an array.
- Each of the magnetic memory cells 80 has the magnetic memory element 70 described above.
- each magnetic memory cell 80 is connected to the word line WL, the ground line GL, and the bit line pair BLa, BLb.
- the X driver 120 is connected to a plurality of word lines WL, and drives a selected word line connected to the accessed magnetic memory cell 80 among the plurality of word lines WL.
- the Y driver 130 is connected to a plurality of bit line pairs BLa and BLb, and sets each bit line to a state corresponding to data writing or data reading.
- the controller 140 controls each of the X driver 120 and the Y driver 130 in accordance with data writing or data reading.
- the X driver 120, the Y driver 130, and the controller 140 can be regarded as a control circuit that controls writing and reading of data.
- the magnetic memory 90 is exemplified by MRAM.
- the first magnetization free layer 10 is preferably made of a ferromagnetic material having perpendicular magnetic anisotropy.
- alloy materials such as Fe alloy, Gd—Co alloy, Co—Cr—Pt alloy, Co—Re—Pt alloy, Co—Ru—Pt alloy, Co—W alloy, Co / Pt multilayer film, Co / Pd Alternating laminated films such as laminated films, Co / Ni laminated films, Co / Cu laminated films, Co / Ag laminated films, Co / Au laminated films, Fe / Pt laminated films, Fe / Pd laminated films, Fe / Pd laminated films, Fe / Au laminated films, etc.
- Non-Patent Document 4 T. Koyama et al., “Control”. of Domain Wall Position by Electric Current in Structured Co / Ni Wire with Permanent Magnetic Anisotropy ”, Applied Physics 101, Physics 101. 10 suitable materials.
- the nonmagnetic layer 30 is preferably made of an insulating material. Specifically, Mg—O, Al—O, Al—N, Ti—O and the like are exemplified.
- the reference layer 40 is made of a ferromagnetic material having perpendicular magnetic anisotropy, for example. At this time, materials that can be used for the reference layer 40 are omitted because they overlap with those exemplified as materials that can be used for the first magnetization free layer 10. However, since the reference layer 40 is required to have stable and fixed magnetization, it is preferable that the reference layer 40 be a magnetic material as hard as possible. In this respect, an Fe—Pt alloy, an Fe—Pd alloy, a Co—Pt alloy, a Co / Pt laminated film, a Co / Pd laminated film, and the like are preferable. In addition, the magnetization direction needs to be fixed in one direction, and the leakage magnetic field to the outside is preferably small.
- the reference layer 40 has a laminated structure such as ferromagnetic material / Ru / ferromagnetic material.
- the reference layer 40 may be composed of a ferromagnetic material having in-plane magnetic anisotropy. In this case, any magnetic material can be used. A typical example is Co—Fe.
- the embodiment in which a material having in-plane magnetic anisotropy is used for the reference layer 40 will be described later as a sixth modification.
- the magnetization fixed layer group 60 contains a ferromagnetic material or an antiferromagnetic material.
- the magnetization fixed layer group 60 includes a first magnetization fixed layer group 60 a and a second magnetization fixed layer group 60 b, and the first magnetization fixed layer group 60 a and the second magnetization fixed layer group 60 b include
- the material may be made of a ferromagnetic material having perpendicular magnetic anisotropy.
- the material that can be specifically used is omitted because it overlaps with the material exemplified in the first magnetization free layer 10.
- Examples of materials that can be used when the magnetization fixed layer group 60 is made of an antiferromagnetic material include Pt—Mn, Ir—Mn, Fe—Mn, and Ni—O.
- the blocking layer 65 may be designed so as to weaken the strong exchange coupling in the first magnetization free layer 10 and the magnetization fixed layer group 60, or the magnetization fixed layer group 60, and the material used is not limited. The inventor was able to obtain desired characteristics by using Pt as the material of the blocking layer 65.
- the blocking layer 65 can be made of a ferromagnetic material. Specifically, NiFeB, CoZrB, etc. are illustrated. Since these materials can also function as an underlayer of the magnetization free layer 10, it is particularly effective in the configuration shown in FIG. 14 (described later).
- the first magnetization free layer 10 is composed of a first magnetization fixed region 11a, a second magnetization fixed region 11b, and a magnetization free region 12, and the first magnetization fixed region 11a and the second magnetization fixed region 11b are They have magnetizations fixed in antiparallel directions. Therefore, in the manufacturing process of the magnetic memory element 70 in the present embodiment, a process for directing the magnetizations of the first magnetization fixed region 11a and the second magnetization fixed region 11b in the antiparallel direction is required. Hereinafter, this process is referred to as initialization.
- FIG. 7A to 7F schematically show a method for initializing the magnetization state in the simplest configuration of a magnetic memory element that writes information using domain wall motion.
- FIG. 7A is a cross-sectional view schematically showing the “simplest configuration”.
- 7A to 7E for the sake of simplicity, only the first magnetization free layer 10 and the magnetization fixed layer group 60 are illustrated, and other configurations are omitted.
- the first magnetization free layer 10 includes a first magnetization fixed region 11a, a second magnetization fixed region 11b, and a magnetization free region 12, and the first magnetization fixed region 11a is the first magnetization fixed region 11a.
- the magnetization pinned layer group 60a and the second magnetization pinned region 11b are depicted as being ferromagnetically coupled to the second magnetization pinned layer group 60b, respectively.
- the switching magnetic fields of the first magnetization fixed layer group 60 a and the second magnetization fixed layer group 60 b are sufficiently larger than those of the first magnetization free layer 10.
- the switching magnetic field of the first magnetization fixed layer group 60a is smaller than the switching magnetic field of the second magnetization fixed layer group 60b.
- FIG. 7A schematically show the magnetization structure in each step.
- FIG. 7F schematically shows a combined magnetization curve of a system including the first magnetization free layer 10 and the magnetization fixed layer group 60.
- a sufficiently large magnetic field is first applied in one direction. Now, let this magnetic field be the + z direction. At this time, the magnetization of all portions is directed in the + z direction. The state at this time is shown in FIG. 7B. Next, a magnetic field is applied in a direction opposite to the direction in which it was first applied. In this case, this direction is the ⁇ z direction. At this time, as shown in FIG. 7C, the magnetization of the magnetization free region 12 having the smallest switching magnetic field is first reversed in the ⁇ z direction. At this time, domain walls are formed both at the boundary between the first magnetization fixed region 11 a and the magnetization free region 12 and at the boundary between the second magnetization fixed region 11 b and the magnetization free region 12.
- FIG. 7D A state after initialization in which a single domain wall is introduced into the first magnetization free layer 10 is realized. If the magnetic field in the ⁇ z direction is further increased here, the domain wall movement occurs in the portion composed of the second magnetization fixed region 11b and the second magnetization fixed layer group 60b, and this region is also reversed in the ⁇ z direction. The state at this time is shown in FIG. 7E. In this case, there is no domain wall.
- FIG. 7F The transition of the magnetization structure from FIG. 7B to FIG. 7E is schematically shown in FIG. 7F.
- the horizontal axis indicates the z-direction magnetic field (H) applied from the outside
- the vertical axis indicates the combined magnetization (M) of the system including the first magnetization free layer 10 and the magnetization fixed layer group 60.
- the portion (1) in the figure indicates that the magnetization free region 12 has undergone magnetization reversal, as shown in FIG. 7C.
- the part (2) indicates that the magnetization of the first magnetization fixed region 11a and the first magnetization fixed layer group 60a is further reversed as shown in FIG. 7D.
- the portion (3) indicates that the magnetization inversion of the second magnetization fixed region 11b and the second magnetization fixed layer group 60b is further reversed as shown in FIG. 7E.
- the initialization margin in this system is from the magnetic field in which the domain wall movement occurs in the portion consisting of the first magnetization fixed region 11a and the first magnetization fixed layer group 60a, and in the portion consisting of the second magnetization fixed region 11b and the second magnetization fixed layer group 60b.
- the range is up to the magnetic field where the domain wall motion occurs. The range is shown as D (between (2) and (3)) in FIG. 7F.
- the initialization method as shown in FIGS. 7B to 7F has the following problems.
- the second magnetization fixed region 11b and the second magnetization fixed layer group are generated from the magnetic field in which the domain wall movement occurs in the portion including the first magnetization fixed region 11a and the first magnetization fixed layer group 60a.
- the range up to the magnetic field where the domain wall motion occurs in the portion consisting of 60b is the initialization margin.
- this initialization margin is as large as possible.
- FIGS. 8A to 8J schematically show a method for initializing the magnetization state in the magnetic memory element according to the embodiment of the present invention.
- FIG. 8A schematically shows a part of the structure of the magnetic memory element 70 according to the embodiment of the present invention.
- FIG. 8A to FIG. 8H only the first magnetization free layer 10, the magnetization fixed layer group 60, and the blocking layer 65 are illustrated for simplicity, and other portions are omitted.
- the second magnetization fixed layer group 60b is ferromagnetically strongly coupled to the second magnetization fixed region 11b, while the first magnetization fixed layer group 60a is ferromagnetic to the first magnetization fixed region 11a.
- the coupling is weakened by the insertion of the blocking layer 65 between them.
- FIGS. 8B to 8J schematically show the magnetization structure in each step.
- FIGS. 8I and 8J schematically show a combined magnetization curve of a system composed of the first magnetization free layer 10 and the magnetization fixed layer group 60.
- a sufficiently large magnetic field is first applied in one direction.
- this magnetic field be the + z direction. That is, the direction is substantially perpendicular to the upper plane (or lower plane) of the first magnetization free layer 10 and is the upward direction.
- substantially vertical means substantially vertical including a measurement error and a setting error, and may be slightly deviated from the vertical due to restrictions on the setting of the apparatus, a measurement error, and the like.
- the magnetization of all portions is directed in the + z direction.
- the state at this time is shown in FIG. 8B.
- a magnetic field is applied in a direction opposite to the direction in which it was first applied.
- this direction is the ⁇ z direction.
- the magnetization of the magnetization free region 12 having the smallest switching magnetic field is first reversed in the ⁇ z direction.
- domain walls are formed both at the boundary between the first magnetization fixed region 11 a and the magnetization free region 12 and at the boundary between the second magnetization fixed region 11 b and the magnetization free region 12.
- the magnetic field in the -z direction is further increased.
- the domain wall motion occurs only in the first magnetization fixed region 11a, which is the next region where the reversal magnetic field is small, and this region is also reversed in the -z direction.
- FIG. 8D The state at this time is shown in FIG. 8D.
- a domain wall is formed only at the boundary between the magnetization free region 12 and the second magnetization fixed region 11b.
- the first magnetization fixed layer group 60a does not reverse because the magnetic coupling with the first magnetization fixed region 11a is weak.
- the magnetic field in the -z direction is further increased.
- the region composed of the second magnetization fixed region 11b and the second magnetization fixed layer group 60b that is likely to be reversed next is reversed.
- the state at this time is shown in FIG. 8E. If the magnetic field in the ⁇ z direction is further increased, the magnetization of the first magnetization fixed layer group 60a is finally reversed, and all the magnetizations are directed in the ⁇ z direction.
- the state at this time is shown in FIG. 8F. In this case, there is no domain wall.
- FIG. 8I schematically shows the transition of the magnetization structure from FIG. 8B to FIG. 8F described above as a magnetization curve.
- the horizontal axis indicates the magnetic field (H) applied from the outside in the z direction
- the vertical axis indicates the combined magnetization (M) of the system including the first magnetization free layer 10 and the magnetization fixed layer group 60.
- the portion (1) in the figure indicates that the magnetization free region 12 has undergone magnetization reversal, as shown in FIG. 8C.
- the portion (2) indicates that the magnetization of the first magnetization fixed region 11a is further reversed as shown in FIG. 8D.
- the part (3) indicates that the magnetization inversion of the second magnetization fixed region 11b and the second magnetization fixed layer group 60b is further reversed as shown in FIG. 8E.
- the part (4) indicates that the magnetization of the first magnetization fixed layer group 60a is further reversed as shown in FIG. 8F.
- Each state shown in FIGS. 8B to 8F corresponds to a part indicated by B to F in the magnetization curve of FIG. 8I.
- FIG. 8I represents a full loop of the magnetization curve of the magnetic memory element 70.
- a minor loop of the magnetization curve is used. Specific steps are described below. Now, after the state shown in FIG. 8E is formed, the application of the magnetic field in the ⁇ z direction is stopped, and the magnetic field in the + z direction is applied. At this time, since the first magnetization fixed region 11a is weakly and ferromagnetically coupled to the first magnetization fixed layer group 60a, this region is first reversed in the + z direction. The state at this time is shown in FIG. 8G. At this time, a domain wall is formed at the boundary between the first magnetization fixed region 11 a and the magnetization free region 12.
- the initialization margin in this method is that the magnetic field from when the first magnetization fixed region 11a and the magnetization free region 12 are inverted to when the second magnetization fixed region 11b and the second magnetization fixed layer group 60b are inverted is initialized. It becomes a margin.
- FIG. 8J schematically shows the transition of the magnetization structure in the initialization method using the minor loop described above as a magnetization curve.
- the horizontal axis indicates the z-direction magnetic field (H) applied from the outside
- the vertical axis indicates the combined magnetization (M) of the system composed of the first magnetization free layer 10 and the magnetization fixed layer group 60.
- the portions (1) to (3) in the figure are the same as those in FIG. 8I.
- the portion (2) ′ indicates that the magnetization of the first magnetization fixed region 11a is reversed as shown in FIG. 8G.
- the portion (1) ′ indicates that the magnetization free region 12 is further reversed in magnetization as shown in FIG. 8H.
- Each state shown in FIGS. 8G to 8H corresponds to a portion indicated by G and H in the magnetization curve of FIG. 8J.
- the first effect is that a perpendicular domain wall motion MRAM with a large initialization margin can be manufactured.
- the first magnetization free layer 10 which is a layer in which the domain wall moves is composed of the first magnetization fixed region 11a, the second magnetization fixed region 11b, and the magnetization free region 12, and A so-called initialization process is required in which the magnetizations of the magnetization fixed region 11a and the second magnetization fixed region 11b are directed in antiparallel directions.
- this initialization is performed using an external magnetic field.
- the initialization margin which is an allowable range of the external magnetic field used at this time, is sufficiently large.
- the perpendicular domain wall motion MRAM in order to orient the magnetizations of the first magnetization fixed region 11a and the second magnetization fixed region 11b of the first magnetization free layer 10 in antiparallel, the first magnetization fixed region 11a and the second magnetization fixed region 11b. It can be considered that the first magnetization fixed layer group 60a and the second magnetization fixed layer group 60b are adjacent to the fixed region 11b, respectively. In order to realize initialization in such a configuration, a method of making the magnetic characteristics of the first magnetization fixed layer group 60a and the second magnetization fixed layer group 60b different can be considered.
- the present embodiment is characterized in that the magnetic characteristics of the first magnetization fixed layer group 60a and the second magnetization fixed layer group 60b are not different from each other, but the magnitude of the magnetic coupling is controlled by using the blocking layer 65. To do.
- Such a configuration can be manufactured relatively easily. That is, it can be said that a perpendicular domain wall motion MRAM with a large initialization margin can be easily manufactured.
- FIG. 9 shows a magnetization curve in an element to which the embodiment of the present invention is applied.
- FIG. 9 is an average magnetization curve of about 100 million elements.
- the horizontal axis is the magnetic field, and the vertical axis is the magnetization.
- a Co / Ni laminated film is used for the first magnetization free layer 10
- a Co / Pt laminated film is used for the first magnetization fixed layer group 60a and the second magnetization fixed layer group 60b
- Pt is used for the blocking layer 65. It was.
- a major loop and a minor loop are shown.
- the major loop and minor loop shown in FIG. 9 are almost the same as those in FIGS. 8I and 8J, respectively.
- the initialization margin is about 1500 Oe. This value can be said to be a sufficiently large value for manufacturing a megabit MRAM.
- (First modification) 10A and 10B schematically show a structure of a first modification of the magnetic memory element according to the exemplary embodiment of the present invention.
- the first modification relates to the position of the blocking layer 65.
- the first blocking layer 65 a as the blocking layer 65 is sandwiched between the first magnetization fixed layer group 60 a and the first magnetization fixed region 11 a in the first magnetization free layer 10.
- the position of the blocking layer 65 is arbitrary. 10A and 10B show a modification thereof. In FIG. 10, for the sake of simplicity, only the first magnetization free layer 10, the magnetization fixed layer group 60, and the blocking layer 65 are illustrated, and the other portions are omitted.
- FIG. 10A shows an example of the first modification.
- the first magnetization fixed layer group 60 includes a 1-1 magnetization fixed layer group 60a-1 and a 1-2 magnetization fixed layer group 60a-2.
- the first blocking layer 65a is provided so as to be sandwiched between the 1-1 magnetization fixed layer group 65a-1 and the 1-2 magnetization fixed layer group 65a-2.
- the first blocking layer 65a is provided between the 1-1 magnetization fixed layer group 60a-1 and the 1-2 magnetization fixed layer group 60a-2, so that the 1-1 magnetization fixed layer group 60a is provided.
- -1 and the first-second magnetization fixed layer group 60a-2 are weakly coupled to each other, so that the memory state of the magnetic memory element 70 is initialized by the initialization method described with reference to FIGS. 8A to 8J.
- FIG. 10B shows another example of the first modification.
- the first magnetization fixed layer group 60 includes a 1-1 magnetization fixed layer group 60a-1 and a 1-2 magnetization fixed layer group 60a-2.
- the first blocking layer 65a includes a 1-1 blocking layer 65a-1 and a 1-2 blocking layer 65a-2.
- the 1-1 blocking layer 65a-1 is provided so as to be sandwiched between the 1-1 magnetization fixed layer group 60a-1 and the 1-2 magnetization fixed layer group 60a-2.
- the first-second blocking layer 65 a-2 is provided between the first-first magnetization fixed layer group 60 a-1 and the first magnetization fixed layer group 11 a in the first magnetization free layer 10.
- the 1-1 magnetization fixed layer group 60a-1 and the 1-2 magnetization fixed layer group 60a-2, and the 1-1 magnetization fixed layer group 60a-1 and the first magnetization fixed region 11a are magnetic.
- the memory state of the magnetic memory element 70 can be initialized by the initialization method described with reference to FIGS. 8A to 8J.
- the blocking layer 65 is provided so as to be sandwiched between the magnetization fixed layer group 60 and the first magnetization free layer 10 or between the magnetization fixed layer group 60. It is only necessary that the position and number are arbitrary.
- (Second modification) 11A to 11C schematically show the structure of a second modification of the magnetic memory element according to the embodiment of the present invention.
- the second modification relates to the position of the magnetization fixed layer group 60.
- the magnetization fixed layer group 60 is provided in the negative z-axis direction, that is, on the substrate side with respect to the first magnetization free layer 10.
- the position of the magnetization fixed layer group 60 is arbitrary.
- 11A, 11B, and 11C show modifications thereof.
- FIGS. 11A to 11C only the first magnetization free layer 10, the magnetization fixed layer group 60, and the blocking layer 65 are illustrated for simplicity, and other portions are omitted.
- FIG. 11A shows an example of the second modification.
- the magnetization fixed layer group 60 is provided in the positive direction of the z-axis with respect to the first magnetization free layer 10, that is, on the side opposite to the substrate.
- the first blocking layer 65a is provided between the first magnetization fixed region 11a and the first magnetization fixed layer group 60a in the first magnetization free layer 10.
- the second magnetization fixed layer group 60 b is provided adjacent to the second magnetization fixed layer group 11 b in the first magnetization free layer 10.
- the memory state of the magnetic memory element 70 can be initialized by exactly the same initialization method as described with reference to FIGS. 8A to 8J.
- FIG. 11B shows another example of the second modified example.
- the magnetization fixed layer group 60 is provided above and below the first magnetization free layer 10.
- a first blocking layer 65a is provided between the first-first magnetization fixed layer group 60a-1 and the first magnetization fixed region 11a in the first magnetization free layer 10.
- the first-second magnetization fixed layer group 60 a-2, the second-first magnetization fixed layer group 60 b-1, and the second-second magnetization fixed layer group 60 b-2 are each a first magnetization fixed region in the first magnetization free layer 10.
- 11a, the second magnetization fixed region 11b, and the second magnetization fixed region 11b are provided adjacent to each other.
- the memory state of the magnetic memory element 70 can be initialized by exactly the same initialization method as described with reference to FIGS. 8A to 8J.
- FIG. 11C shows another example of the second modification.
- the magnetization fixed layer group 60 is provided with respect to the first magnetization free layer 10 in the positive z-axis direction, that is, on the opposite side of the substrate.
- the first-second magnetization fixed layer group 60a-2 is provided adjacent to the first magnetization fixed region 11a in the first magnetization free layer 10, and the first blocking layer 65a and the first-first magnetization fixed layer 11 are provided thereon.
- the layer group 60a-1 is provided in this order. That is, the first blocking layer 65a is provided so as to be sandwiched between the 1-1 magnetization fixed layer group 60a-1 and the 1-2 magnetization fixed layer group 60a-2. Even in such a structure, the memory state of the magnetic memory element 70 can be initialized by the same initialization method as that described with reference to FIGS. 8A to 8J.
- the magnetization fixed layer group 60 magnetically affects the first magnetization fixed region 11 a and the second magnetization fixed region 11 b in the first magnetization free layer 10.
- the position is arbitrary.
- (Third Modification) 12A and 12B schematically show the structure of a third modification of the magnetic memory element 70 according to the embodiment of the present invention.
- the third modification relates to the number of magnetization fixed layer groups 60.
- the first magnetization fixed layer group 60 is provided in the vicinity of the first magnetization fixed region 11a in the first magnetization free layer 10, and the second magnetization
- the second magnetization fixed layer group 60b is provided in the vicinity of the fixed region 11b, and two magnetization fixed layer groups are provided in total.
- the number of the magnetization fixed layer groups 60 is arbitrary.
- 12A and 12B show a modification thereof. In FIG. 12A and FIG. 12B, only the first magnetization free layer 10, the magnetization fixed layer group 60, and the blocking layer 65 are illustrated for simplicity, and other portions are omitted.
- FIG. 12A shows an example of the third modification.
- the magnetization fixed layer group 60 is composed of one of the first magnetization fixed layer groups 60a.
- the first magnetization fixed layer group 60a is connected to the first magnetization fixed region 11a in the first magnetization free layer 10 through the first blocking layer 65a, and is weakly magnetically coupled.
- FIG. 12B shows another example of the third modification.
- the magnetization fixed layer group 60 includes a 1-1 magnetization fixed layer group 60a-1, a 1-2 magnetization fixed layer group 60a-2, and a 2-1 magnetization fixed layer group 60b-. 1 consists of a total of three.
- the first-first magnetization fixed layer group 60a-1 is connected to the first magnetization fixed region 11a in the first magnetization free layer 10 through the first blocking layer 65a, and is weakly magnetically coupled.
- the first-second magnetization fixed layer group 60a-2 is provided adjacent to the first magnetization fixed region 11a in the first magnetization free layer 10
- the second-first magnetization fixed layer group 60b-1 is the first magnetization free layer. 10 adjacent to the second magnetization fixed region 11b.
- FIGS. 13A to 13H schematically show an initialization method in a system in which the magnetization fixed layer group 60 shown in FIG. 12A is composed of one.
- FIG. 13A schematically shows a part of the structure of the magnetic memory element 70 shown in FIG. 12A.
- the first magnetization fixed layer group 60a is ferromagnetically coupled to the first magnetization fixed region 11a, but the coupling is weakened by the insertion of the blocking layer 65 therebetween.
- FIGS. 13G and 13H schematically show the combined magnetization curve of the system composed of the first magnetization free layer 10 and the magnetization fixed layer group 60.
- a sufficiently large magnetic field is first applied in one direction. Now, let this magnetic field be the + z direction. At this time, the magnetization of all portions is directed in the + z direction. The state at this time is shown in FIG. 13B. Next, a magnetic field is applied in a direction opposite to the direction in which it was first applied. In this case, this direction is the ⁇ z direction. At this time, as shown in FIG. 13C, the magnetizations of the magnetization free region 12 having the smallest switching magnetic field and the second magnetization fixed region 11b are first reversed in the ⁇ z direction. At this time, a domain wall is formed at the boundary between the first magnetization fixed region 11 a and the magnetization free region 12.
- FIG. 13D the first magnetization fixed layer group 60a does not reverse because the magnetic coupling with the first magnetization fixed region 11a is weak.
- FIG. 13E the magnetization of the first magnetization fixed layer group 60a is finally reversed, and all the magnetizations are directed in the ⁇ z direction.
- FIG. 13E The state at this time is shown in FIG. 13E.
- FIG. 13G schematically shows the transition of the magnetization structure from FIG. 13B to FIG. 13D described above as a magnetization curve.
- the horizontal axis indicates the z-direction magnetic field (H) applied from the outside
- the vertical axis indicates the combined magnetization (M) of the system including the first magnetization free layer 10 and the magnetization fixed layer group 60.
- the portion (1) in the figure indicates that the magnetization free region 12 and the second magnetization fixed region 11b are reversed in magnetization as shown in FIG. 13C.
- the portion (2) indicates that the magnetization of the first magnetization fixed region 11a is further reversed as shown in FIG. 13D.
- the portion (3) indicates that the magnetization of the first magnetization fixed layer group 60a is further reversed as shown in FIG. 13E.
- Each state shown in FIGS. 13B to 13E corresponds to a part indicated by BE in the magnetization curve of FIG. 13G.
- FIG. 13G represents a full loop of the magnetization curve of the magnetic memory element 70.
- a minor loop of the magnetization curve is used. Specific steps in the system shown in FIG. 13A are described below. After the state shown in FIG. 13D is formed, the magnetic field in the ⁇ z direction is reduced. At this time, since the first magnetization fixed region 11a is weakly and ferromagnetically coupled to the first magnetization fixed layer group 60a, this region is first reversed in the + z direction. The state at this time is shown in FIG. 13F. At this time, a domain wall is formed at the boundary between the first magnetization fixed region 11 a and the magnetization free region 12. In the example shown in FIGS.
- the memory state of the magnetic memory element 70 is initialized in this way.
- the initialization margin in this method is a magnetic field from when the first magnetization fixed region 11a is inverted until the magnetization free region 12 and the second magnetization fixed region 11b are inverted.
- FIG. 13H schematically shows the transition of the magnetization structure in the initialization method using the minor loop described above as a magnetization curve.
- the horizontal axis indicates the z-direction magnetic field (H) applied from the outside
- the vertical axis indicates the combined magnetization (M) of the system including the first magnetization free layer 10 and the magnetization fixed layer group 60.
- the parts (1) to (2) in the figure are the same as those in FIG. 13G.
- the portion (2) ′ indicates that the magnetization of the first magnetization fixed region 11a is reversed as shown in FIG. 13F.
- the state shown in FIG. 13F corresponds to the portion indicated by F in the magnetization curve of FIG. 13H.
- the magnetization fixed layer group 60 magnetically affects at least one of the first magnetization fixed region 11 a and the second magnetization fixed region 11 b in the first magnetization free layer 10. And the number is arbitrary.
- FIG. 14 schematically shows the structure of a fourth modification of the magnetic memory element 70 according to the embodiment of the present invention.
- the fourth modification relates to the number of blocking layers 65.
- FIG. 14 shows a modification thereof. In FIG. 14, only the first magnetization free layer 10, the magnetization fixed layer group 60, and the blocking layer 65 are illustrated for simplicity, and the other portions are omitted.
- FIG. 14 shows an example of the third modification.
- two blocking layers 65, a first blocking layer 65 a and a second blocking layer 65 b are provided.
- the first blocking layer 65a is provided adjacent to the first magnetization fixed layer group 11a
- the second blocking layer 65b is provided adjacent to the second magnetization fixed layer group 11b
- a first magnetization fixed layer group 60a and a second magnetization fixed layer group 60b are provided adjacent to the first blocking layer 65a and the second blocking layer 65b, respectively, on the side opposite to the first magnetization free layer 10.
- the first magnetization fixed layer group 60a is connected to the first magnetization fixed region 11a in the first magnetization free layer 10 via the first blocking layer 65a, and is weakly magnetically coupled to the second magnetization fixed layer.
- the layer group 60b is connected to the second magnetization fixed region 11b in the first magnetization free layer 10 through the second blocking layer 65b, and is weakly magnetically coupled.
- FIG. 15A to 15L schematically show an initialization method in the configuration having two blocking layers 65 shown in FIG.
- FIG. 15A schematically shows a part of the structure of the magnetic memory element 70 shown in FIG.
- the first magnetization fixed layer group 60a is ferromagnetically coupled to the first magnetization fixed region 11a, but the coupling is weakened by inserting the first blocking layer 65a therebetween.
- the second magnetization fixed layer group 60b is ferromagnetically coupled to the second magnetization fixed region 11b, but the coupling is weakened by inserting the second blocking layer 65b therebetween.
- An initialization method in such a system will be described with reference to FIGS. 15B to 15L.
- 15B to 15J schematically show the magnetization structure in each step.
- 15K and 15L schematically show a combined magnetization curve of a system including the first magnetization free layer 10 and the magnetization fixed layer group 60.
- FIG. 15K and 15L schematically show a combined magnetization curve of a system including the first magnet
- FIGS. 15B to 15L a sufficiently large magnetic field is first applied in one direction. Now, let this magnetic field be the + z direction. At this time, the magnetization of all portions is directed in the + z direction. The state at this time is shown in FIG. 15B. Next, a magnetic field is applied in a direction opposite to the direction in which it was first applied. In this case, this direction is the ⁇ z direction. At this time, as shown in FIG. 15C, the magnetization of the magnetization free region 12 having the smallest switching magnetic field is first reversed in the ⁇ z direction. At this time, domain walls are formed at the boundary between the first magnetization fixed region 11 a and the magnetization free region 12 and at the boundary between the second magnetization fixed region 11 b and the magnetization free region 12.
- FIGS. 15D and 15E show the state of magnetization at each step when domain wall movement occurs in the order of the first magnetization fixed region 11a and the second magnetization fixed region 11b.
- the first magnetization fixed layer group 60a and the second magnetization fixed layer group 60b have weak magnetic coupling between the first magnetization fixed region 11a and the second magnetization fixed region 11b.
- FIG. 13K schematically shows the transition of the magnetization structure from FIG. 15B to FIG. 15G described above as a magnetization curve.
- the horizontal axis indicates the magnetic field (H) applied from the outside in the z direction
- the vertical axis indicates the combined magnetization (M) of the system including the first magnetization free layer 10 and the magnetization fixed layer group 60.
- the portion (1) in the figure indicates that the magnetization free region 12 has undergone magnetization reversal as shown in FIG. 15C.
- the part (2) indicates that the magnetization of the first magnetization fixed region 11a is further reversed as shown in FIG. 15D.
- the portion (3) indicates that the magnetization of the second magnetization fixed region 11b is further reversed as shown in FIG. 15E.
- the portion (4) indicates that the magnetization of the first magnetization fixed layer group 60a is further reversed as shown in FIG. 15F.
- the portion (5) indicates that the magnetization of the second magnetization fixed layer group 60b is further reversed as shown in FIG. 15G.
- Each state shown in FIGS. 15B to 15G corresponds to a part indicated by BG in the magnetization curve of FIG. 15K.
- FIG. 15K represents a full loop of the magnetization curve of the magnetic memory element 70.
- a minor loop of the magnetization curve is used. Specific steps in the system shown in FIG. 15A are described below. After the state shown in FIG. 15F is formed, a magnetic field is applied in the + z direction. At this time, since the second magnetization fixed region 11a is weakly and ferromagnetically coupled to the first magnetization fixed layer group 60a, this region is first reversed in the + z direction. The state at this time is shown in FIG. 15H. At this time, a domain wall is formed at the boundary between the magnetization free region 12 and the second magnetization fixed region 11b.
- the initialization margin in this method is the range from the magnetic field in which the second magnetization fixed region 11b and the magnetization free region 12 are inverted to the magnetic field in which the first magnetization fixed region 11a is inverted.
- FIG. 15L schematically shows the transition of the magnetization structure in the initialization method using the minor loop described above as a magnetization curve.
- the horizontal axis indicates the z-direction magnetic field (H) applied from the outside
- the vertical axis indicates the combined magnetization (M) of the system including the first magnetization free layer 10 and the magnetization fixed layer group 60.
- the parts (1) to (4) in the figure are the same as those in FIG. 15K.
- the portion (3) ′ indicates that the magnetization of the second magnetization fixed region 11b is reversed as shown in FIG. 15H.
- the portion (1) ′ indicates that the magnetization free region 12 is further reversed as shown in FIG. 15I.
- the portion (2) ′ indicates that the magnetization of the first magnetization fixed region 11a is further reversed as shown in FIG. 15J.
- Each state shown in FIGS. 15H to 15J corresponds to a portion indicated by G and H in the magnetization curve of FIG. 15L.
- the magnetic characteristics of the first magnetization fixed layer group 60a and the second magnetization fixed layer group 60b need to be different from each other. .
- Such a difference in magnetic characteristics can be realized by a difference in configuration such as material and structure (eg, film thickness, shape, crystal structure, use of laminated film and combination of films).
- (Fifth modification) 16A and 16B schematically show the structure of a fifth modification of the magnetic memory element 70 according to the embodiment of the present invention.
- the fifth modification relates to the shape of the first magnetization free layer 10.
- the first magnetization free layer 10 serves as an information storage layer, and so far, the shape of the first magnetization free layer 10 is rectangular in the xy plane (in the plane parallel to the substrate surface). Further, the first magnetization fixed region 11 a is connected to one end of the magnetization free region 12, and the second magnetization fixed region 11 b is connected to the other end of the magnetization free region 12.
- the shape of the first magnetization free layer 10 is arbitrary, and the arrangement of the first magnetization fixed region 11a, the second magnetization fixed region 11b, and the magnetization free region 12 is also arbitrary.
- FIG. 16A shows an example.
- the first magnetization fixed region 11 a and the second magnetization fixed region 11 b of the first magnetization free layer 10 may be formed so that the width thereof is wider than that of the magnetization free region 12.
- FIG. 16A shows an example in which the second magnetization fixed region 11b is formed so as to be wider than other regions.
- the first magnetization fixed region 11a and the second magnetization fixed region 11b are formed so that the width thereof is wider than that of the magnetization free region 12, thereby further stabilizing the write operation.
- the domain wall extends from the boundary between the first magnetization fixed region 11 a and the magnetization free region 12 to the second magnetization fixed region 11 b and the magnetization free region. Move to the border with 12 and stop. Here, it is preferable that the domain wall accurately stops at this boundary. However, as shown in FIG. 16A, if the width of the second magnetization fixed region 11b is wide, the current density is sufficiently lowered. The domain wall comes to stop more reliably.
- FIG. 16B shows another example.
- the first magnetization free layer 10 may be formed in a Y shape as shown in FIG. 16B.
- the first magnetization free layer 10 is provided with a magnetization free region 12 provided extending in the x direction, a first magnetization fixed region 11a provided connected to one end ( ⁇ x side) thereof, Similarly, it is formed by a second magnetization fixed region 11b provided connected to one end. That is, the first magnetization free layer 10 forms a three-way path.
- the magnetizations of the first magnetization fixed region 11a and the second magnetization fixed region 11b are fixed at least partially in the vertical direction and in antiparallel directions.
- the magnetization of the magnetization free region 12 is either vertical or vertical.
- FIG. 17A schematically shows a method of writing “1” from the state “0”
- FIG. 17B schematically shows a method of writing “0” from the state of “1”.
- the first magnetization fixed region 11a and the second magnetization fixed region 11b have magnetization fixed in the upward direction and the downward direction, respectively, and the state where the magnetization free region 12 is magnetized in the downward direction is “0”.
- the state, the state magnetized upward, is defined as “1” state.
- the “0” state as shown in FIG.
- a domain wall is formed at the boundary between the first magnetization fixed region 11 a and the magnetization free region 12.
- a current is supplied in the direction of the dotted line in FIG. It moves to the opposite side to the end connected to and transitions to the “1” state as shown in FIG. 17B.
- a domain wall is formed at the boundary between the second magnetization fixed region 11 b and the magnetization free region 12.
- a current is supplied in the direction of the dotted line in FIG. It moves to the opposite side to the end connected to and transitions to the “0” state as shown in FIG. 17A. In this way, information can be rewritten.
- the domain wall is extracted at the end of the magnetization free region 12, and writing is performed.
- a more stable writing operation can be realized.
- a nonmagnetic layer 30 and a reference layer 40 are provided to read information from the first magnetization free layer 10 which is an information storage layer.
- the first magnetization free layer 10 which is an information storage layer.
- the sixth modification relates to another reading mode.
- a second magnetization free layer 20 is newly provided.
- a contact layer 50 is preferably provided.
- the second magnetization free layer 20, the nonmagnetic layer 30, and the reference layer 40 are provided adjacent to each other in this order, thereby forming a magnetic tunnel junction (MTJ).
- MTJ magnetic tunnel junction
- the center of gravity of the second magnetization free layer 20 is provided so as to be shifted in the xy plane with respect to the center of gravity of the magnetization free region 12 of the first magnetization free layer 10.
- the direction of this shift is defined as the first direction.
- the second magnetization free layer 20 and the reference layer 40 are made of a ferromagnetic material having magnetic anisotropy in the in-plane direction.
- the direction of magnetic anisotropy of the second magnetization free layer 20 is arbitrary in the in-plane direction.
- the magnetization of the reference layer 40 is substantially fixed in one direction. This direction is preferably parallel to the first direction.
- 18A to 18D show an example in which the first direction is the y direction, that is, the direction perpendicular to the longitudinal direction of the first magnetization free layer 10.
- 20A to 20C show examples in which the first direction is the x direction, that is, the direction parallel to the longitudinal direction of the first magnetization free layer 10.
- the information stored in the magnetization direction in the perpendicular direction of the magnetization free region 12 is stored in the MTJ having in-plane magnetization composed of the second magnetization free layer 20, the nonmagnetic layer 30, and the reference layer 40. Can be read.
- the principle will be described with reference to FIGS. 19A and 19B and FIGS. 21A and 21B.
- 19A and 19B schematically show the magnetization states in the respective data states in the structure as shown in FIGS. 18A to 18D
- FIGS. 21A and 21B are shown in FIGS. 20A to 20C.
- the state of magnetization in each data state in the structure as shown is schematically shown.
- FIG. 19A the state of magnetization of each layer in the “0” state is indicated by arrows.
- FIG. 19B the state of magnetization in the “1” state is indicated by an arrow.
- the magnetizations of the first magnetization fixed region 11a, the second magnetization fixed region 11b, and the reference layer 40 are depicted as being fixed in the positive z-axis direction, the negative direction, and the negative y-axis direction, respectively.
- the magnetization of the first magnetization fixed region 11a, the second magnetization fixed region 11b, and the reference layer 40 is arbitrary. Since this optionality is obvious, it is omitted.
- the magnetization of the second magnetization free layer 20 is caused by the leakage magnetic flux generated by the magnetization of the magnetization free region 12 in the downward direction.
- Ax is negative direction. This is because the second magnetization free layer 20 is disposed below the magnetization free region 12 (in the negative z-axis direction), and the center of gravity of the second magnetization free layer 20 is in the negative y-axis direction with respect to the magnetization free region 12. This is because they are provided in a shifted manner. As a result, the magnetizations of the second magnetization free layer 20 and the reference layer 40 become parallel, and this MTJ is in a low resistance state.
- the magnetization of the second magnetization free layer 20 is caused by the leakage magnetic flux generated by the upward magnetization of the magnetization free region 12. Direct in the positive direction.
- the magnetizations of the second magnetization free layer 20 and the reference layer 40 become antiparallel, and this MTJ enters a high resistance state.
- the information stored as the magnetization in the perpendicular direction of the magnetization free region 12 is transmitted to the magnetization of the second magnetization free layer 20 having the in-plane magnetization, and can be read out by the MTJ composed of the in-plane magnetization.
- FIG. 21A shows the magnetization state of each layer in the “0” state by arrows
- FIG. 21B shows the magnetization state in the “1” state by arrows.
- the magnetizations of the first magnetization fixed region 11a, the second magnetization fixed region 11b, and the reference layer 40 are depicted as being fixed in the positive direction of the z axis, the negative direction, and the positive direction of the x axis, respectively. There is arbitraryness between. Since this optionality is obvious, it is omitted.
- the magnetization of the second magnetization free layer 20 is caused by the leakage magnetic flux generated by the upward magnetization of the magnetization free region 12 x Direct in the positive direction.
- the second magnetization free layer 20 is disposed above the magnetization free region 12 (z-axis positive direction), and the center of gravity of the second magnetization free layer 20 is in the x-axis positive direction with respect to the magnetization free region 12. This is because they are shifted.
- the magnetizations of the second magnetization free layer 20 and the reference layer 40 become parallel, and this MTJ enters a low resistance state.
- the magnetization of the second magnetization free layer 20 is caused by the leakage magnetic flux generated by the magnetization of the magnetization free region 12 in the downward direction. Axis negative direction.
- the magnetizations of the second magnetization free layer 20 and the reference layer 40 become antiparallel, and this MTJ enters a high resistance state.
- the information stored as the magnetization in the perpendicular direction of the magnetization free region 12 is transmitted to the magnetization of the second magnetization free layer 20 having the in-plane magnetization, and can be read out by the MTJ composed of the in-plane magnetization.
- MR ratio magnetoresistive effect ratio
- the second magnetization free layer 20 and the reference layer 40 are made of a material having in-plane magnetic anisotropy. Specifically, Co—Fe—B and the like are exemplified.
- the nonmagnetic layer 30 is preferably composed of a nonmagnetic material. Specifically, Mg—O and the like are exemplified.
- FIG. 23A and FIG. 23B schematically show the structure of a seventh modification of the magnetic memory element 70 according to the embodiment of the present invention.
- the seventh modification relates to the positional relationship between the nonmagnetic layer 30 and the reference layer 40 for reading, the blocking layer 65 for initialization, and the magnetization fixed layer group 60.
- the magnetization fixed layer group 60 is depicted as being provided on opposite sides of the first magnetization free layer 10, but in this embodiment, these positional relationships are arbitrary. 22A and 22B and FIGS. 23A and 23B show modifications thereof.
- 22A and 22B show an example of the seventh modification.
- the nonmagnetic layer 30 and the reference layer 40 for reading, the blocking layer 65 for initialization, and the magnetization fixed layer group 60 are all provided on the same side with respect to the first magnetization free layer 10.
- 22A is a perspective view
- FIG. 22B is a cross-sectional view
- an example of the direction of magnetization is indicated by an arrow.
- the nonmagnetic layer 30 is provided adjacent to the upper surface of the first magnetization free layer 10
- the reference layer 40 is adjacent to the upper surface of the nonmagnetic layer 30. Is provided.
- the first blocking layer 65a is provided adjacent to the upper surface of the first magnetization fixed region 11a, and the first magnetization fixed layer group 60a is provided adjacent to the upper surface of the first blocking layer 65a.
- the second magnetization fixed layer group 60b is provided adjacent to the upper surface of the second magnetization fixed region 11b.
- FIG. 23A and FIG. 23B show another example of the seventh modified example.
- the nonmagnetic layer 30 and the reference layer 40 for reading, and the blocking layer 65 and the magnetization fixed layer group 60 for initialization are all provided on the same side with respect to the first magnetization free layer 10.
- FIG. 23A is a perspective view
- FIG. 23B is a cross-sectional view
- an example of the direction of magnetization is indicated by an arrow.
- the first blocking layer 65a is provided adjacent to the upper surface of the first magnetization fixed region 11a
- the first magnetization fixed layer group 60a is the upper surface of the first blocking layer 65a. It is provided adjacent to.
- the second magnetization fixed layer group 60b is provided adjacent to the upper surface of the second magnetization fixed region 11b. Further, the contact layer 50 is provided adjacent to the upper surface of the second magnetization fixed layer group 60b, and the second magnetization free layer 20, the nonmagnetic layer 30, and the reference layer 40 are provided adjacent to the contact layer 50 in this order. Yes.
- the positional relationship among the nonmagnetic layer 30 and the reference layer 40 for reading, the blocking layer 65 for initialization, and the magnetization fixed layer group 60 is arbitrary, and is relative to the first magnetization free layer 10. They may be provided on the same side or on different sides.
- FIG. 25A, FIG. 25B, and FIG. 26 schematically show the structure of an eighth modification of the magnetic memory element 70 according to the embodiment of the present invention.
- the eighth modification relates to a domain wall pinning site in the first magnetization free layer 10.
- the magnetic memory element 70 information is stored as the position of the domain wall. Therefore, the stability of the stored information depends on the pin potential depth of the domain wall pinning site. In the embodiments described so far, examples have been shown in which the domain wall pinning sites are not actively formed. However, in the embodiment of the present invention, the domain walls are pinned on the first magnetization free layer 10. Sites may be actively formed. FIG. 24A and FIG. 24B, FIG. 25A, FIG. 25B, and FIG.
- FIGS. 24A and 24B, FIGS. 25A and 25B show an example of the eighth modification example, in which a step is formed in the cross section of the first magnetization free layer 10 as a pinning site of the domain wall.
- 24A and 25A are perspective views
- FIGS. 24B and 25B are cross-sectional views, respectively.
- the position of this step becomes a pinning site of the domain wall, and the stability of stored information is improved. Can be increased.
- a step adjustment layer 55 may be provided to form such a step.
- FIG. 26 shows another example of the eighth modification example in which the planar shape of the first magnetization free layer 10 is modulated as a domain wall pinning site.
- a notch N is provided as this modulation.
- the position of the notch N becomes a pinning site of the domain wall, and the stability of the stored information can be further improved.
- Non-volatile semiconductor memory devices used for mobile phones, mobile personal computers and PDAs, and microcomputers with built-in non-volatile memory used for automobiles, etc. as examples of utilization of the present embodiment (including modifications) shown above Is mentioned.
- the current writing domain wall motion is used in the information writing method, and the layer in which the domain wall motion occurs is made of a material having perpendicular magnetic anisotropy.
- the layer in which domain wall motion occurs is made of a material having perpendicular magnetic anisotropy, and has a large initialization margin, it is easier to manufacture.
- a configuration can be provided.
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Abstract
Description
まず、本発明の実施の形態に係る磁気メモリ素子の構成について説明する。図1A~図1Cは、本発明の実施の形態に係る磁気メモリ素子の主要な部分の代表的な構造を模式的に示している。図1Aはその斜視図を、図1Bはx-z断面図を、図1Cはx-y平面図をそれぞれ示している。なお、図に示されているx-y-z座標系において、z軸は基板垂直方向を示し、x-y軸は基板平面に平行であるものとする。
次に、本発明の実施の形態に係る磁気メモリ素子のメモリ状態について説明する。
図2A及び図2Bは、本発明の実施の形態に係る磁気メモリ素子の“0”、“1”それぞれのメモリ状態における磁化の状態の例を模式的に示している。図2Aは“0”状態における磁化の状態を、図2Bは“1”状態における磁化の状態をそれぞれ示している。なおここでは第1磁化固定領域11aの磁化は+z方向に固定され、第2磁化固定領域11bの磁化は-z方向に固定されているものとしている。
次に、本発明の実施の形態に係る磁気メモリ素子への情報の書き込み方法について説明する。
図3A及び図3Bは、本発明の実施の形態に係る磁気メモリ素子への情報の書き込み方法を模式的に示している。なお、図3A及び図3Bでは、簡単のために第1磁化自由層10以外の層は省略されている。いま、図2Aで定義された“0”状態において図3Aに矢印Iwriteで示された方向(+x方向)に書き込み電流を導入する。このとき伝導電子は第1磁化自由層10において第2磁化固定領域11bから磁化自由領域12を経由して第1磁化固定領域11aへと流れる。このとき第2磁化固定領域11bと磁化自由領域12の境界に形成された磁壁DWにはスピントランスファートルク(Spin Transfer Torque;STT)が働く。その結果、磁壁DWはx軸の負方向に移動する。すなわち電流誘起磁壁移動が起こる。ここで、伝導電子は磁化自由領域12と第1磁化固定領域11aとの境界よりもx軸の負の方向では減少する(第1磁化固定層群60aへも流れ込むため)。そのため、磁壁DWは磁化自由領域12と第1磁化固定領域11aとの境界で停止する。この状態は図2Bで定義された“1”状態に相当する。このようにして“1”書き込みを行うことができる。
次に、本発明の実施の形態に係る磁気メモリ素子からの情報の読み出し方法について説明する。
図4A及び図4Bは、本発明の実施の形態に係る磁気メモリ素子からの情報の読み出し方法を模式的に示している。ここでは、図1に示された構成を有する磁気メモリ素子70からの情報の読み出し方法を示す。本実施の形態においては、主にトンネル磁気抵抗効果(Tunneling Magnetoresistive effect;TMR effect)を利用して情報の読み出しを行う。そのために第1磁化自由層10(磁化自由領域12)、非磁性層30、リファレンス層40から構成される磁気トンネル接合(MTJ)を貫通する方向に電流Ireadを導入する。なお、このIreadの方向には任意性がある。
次に、本発明の実施の形態に係る磁気メモリ素子70を有する磁気メモリセル80に書き込み電流及び読み出し電流を導入するための回路構成について説明する。
図5は、本発明の実施の形態に係る磁気メモリセルの1ビット分の回路の構成例を示している。図5に示される例では、磁気メモリ素子70は3端子の素子であり、ワード線WL、グラウンド線GL、及びビット線対BLa、BLbに接続されている。例えば、リファレンス層40につながる端子は、読み出しのためのグラウンド線GLに接続されている。(第1磁化固定層群60aを経由して)第1磁化固定領域11aにつながる端子は、トランジスタTRaのソース/ドレインの一方に接続され、ソース/ドレインの他方は、ビット線BLaに接続されている。(第2磁化固定層群60bを経由して)第2磁化固定領域11bにつながる端子は、トランジスタTRbのソース/ドレインの一方に接続され、ソース/ドレインの他方は、ビット線BLbに接続されている。トランジスタTRa、TRbのゲートは、共通のワード線WLに接続されている。
次に、第1磁化自由層10、非磁性層30、リファレンス層40、磁化固定層群60、及び遮断層65に用いることのできる材料について説明する。
次に、本発明の実施の形態に係る磁気メモリ素子70のメモリ状態の初期化方法について図を参照して説明する。本実施の形態においては、第1磁化自由層10は第1磁化固定領域11a、第2磁化固定領域11b、磁化自由領域12から構成され、第1磁化固定領域11a、第2磁化固定領域11bは互いに反平行方向に固定された磁化を有する。従って、本実施の形態における磁気メモリ素子70の製造工程においては、第1磁化固定領域11a、第2磁化固定領域11bの磁化を反平行方向に向けるプロセスが必要となる。以下、このプロセスを初期化と言うことにする。
次に、本実施の形態で得られる効果について説明する。
第1の効果として、初期化マージンの大きな垂直磁化磁壁移動MRAMを製造できることが挙げられる。上述のように垂直磁化磁壁移動MRAMにおいては、磁壁が移動する層である第1磁化自由層10は第1磁化固定領域11aと第2磁化固定領域11bと磁化自由領域12から構成され、第1磁化固定領域11aと第2磁化固定領域11bの磁化を反平行方向に向ける、いわゆる初期化というプロセスが必要であった。一般的にはこの初期化は外部磁場を用いて行うことが考えられるが、このとき用いる外部磁場の大きさとして許される範囲である初期化マージンは十分大きいことが好ましい。本実施の形態を用いることによって、この大きな初期化マージンを得ることができる。
図9は、本発明の実施の形態を適用した素子における磁化曲線が示されている。なお、図9は約1億個の素子の平均的な磁化曲線である。横軸は磁界、縦軸は磁化である。ここでは第1磁化自由層10にはCo/Ni積層膜を、第1磁化固定層群60a、第2磁化固定層群60bにはCo/Pt積層膜を、そして遮断層65にはPtを用いた。図9においては、メジャーループ、及びマイナーループが示されている。図9に示されたメジャーループ、マイナーループはそれぞれ図8I、図8Jとほぼ同一である。また、この場合の初期化マージンは約1500Oeとなっている。この値は、メガビット級のMRAMを製造する上で十分大きな値ということができる。
以上で説明された磁気メモリ素子70は、以下に説明される変形例を用いて実施してもよい。
図10A及び図10Bは、本発明の実施の形態に係る磁気メモリ素子の第1の変形例の構造を模式的に示している。第1の変形例は遮断層65の位置に関する。
図11A~図11Cは、本発明の実施の形態に係る磁気メモリ素子の第2の変形例の構造を模式的に示している。第2の変形例は磁化固定層群60の位置に関する。
図12A及び図12Bは、本発明の実施の形態に係る磁気メモリ素子70の第3の変形例の構造を模式的に示している。第3の変形例は磁化固定層群60の数の関する。
図14は、本発明の実施の形態に係る磁気メモリ素子70の第4の変形例の構造を模式的に示している。第4の変形例は遮断層65の数に関する。
図16A及び図16Bは、本発明の実施の形態に係る磁気メモリ素子70の第5の変形例の構造を模式的に示している。第5の変形例は第1磁化自由層10の形状に関する。
図18A~図18D、図19A~図19B、図20A~図20C、図21A~図21Bは、本発明の実施の形態に係る磁気メモリ素子70の第6の変形例の構造を模式的に示している。第6の変形例は読み出し方法に関する。
図22A及び図22B、図23A及び図23Bは、本発明の実施の形態に係る磁気メモリ素子70の第7の変形例の構造を模式的に示している。第7の変形例は、読み出しのための非磁性層30及びリファレンス層40と、初期化のための遮断層65及び磁化固定層群60の位置関係に関する。
図24A及び図24B、図25A及び図25B、図26は、本発明の実施の形態に係る磁気メモリ素子70の第8の変形例の構造を模式的に示している。第8の変形例は第1磁化自由層10における磁壁のピニングサイトに関する。
Claims (12)
- 垂直磁気異方性を有する強磁性体から構成され、第1磁化固定領域と第2磁化固定領域と前記第1磁化固定領域及び前記第2磁化固定領域に接続する磁化自由領域とを備える第1磁化自由層と、
前記第1磁化自由層の近傍に設けられた非磁性層と、
強磁性体から構成され、前記非磁性層上に設けられたリファレンス層と、
前記第1磁化固定領域の近傍に設けられた第1磁化固定層群と、
前記第1磁化固定層群と前記第1磁化固定領域との間、又は前記第1磁化固定層群内に挟まれて設けられた第1遮断層と
を具備する
磁気メモリ素子。 - 請求項1に記載の磁気メモリ素子であって、
前記第2磁化固定領域の近傍に設けられた第2磁化固定層群を更に具備する
磁気メモリ素子。 - 請求項2に記載の磁気メモリ素子であって、
前記第2磁化固定層群は、前記第2磁化固定領域に隣接して設けられる
磁気メモリ素子。 - 請求項2記載の磁気メモリ素子であって、
前記第2磁化固定層群と前記第2磁化固定領域、または前記第2磁化固定層群内に挟まれて設けられた前記第2遮断層を更に具備し、
前記第1磁化固定層群と前記第2磁化固定層群とは異なる構成を有する
磁気メモリ素子。 - 請求項2乃至4のいずれか一項に記載の磁気メモリ素子であって、
前記第1磁化固定層群及び前記第2磁化固定層群は、前記第1磁化自由層に対して同じ側に設けられ、
前記非磁性層及び前記リファレンス層は、前記第1磁化自由層に対して前記第1磁化固定層群及び前記第2磁化固定層群と反対の側に設けられる
磁気メモリ素子。 - 請求項1乃至5のいずれか一項に記載の磁気メモリ素子であって、
前記非磁性層は、前記磁化自由領域に隣接して設けられ、
前記リファレンス層は、前記非磁性層に隣接して前記磁化自由領域とは反対側に設けられ、
前記リファレンス層は垂直磁気異方性を有する強磁性体により構成される
磁気メモリ素子。 - 請求項1乃至5のいずれか一項に記載の磁気メモリ素子であって、
基板平行平面内において前記磁化自由領域に対して第1方向にずれて設けられた第2磁化自由層を更に具備し、
前記第2磁化自由層及び前記リファレンス層は面内磁気異方性を有する強磁性体により構成され、
前記リファレンス層は前記第1の方向に略平行方向に固定された磁化を有する
磁気メモリ素子。 - 行列上に配置された、請求項1乃至7のいずれか一項に記載の複数の磁気メモリ素子と、
前記複数の磁気メモリ素子の各々へのデータの書き込み及び読み出しを制御する制御回路と
を具備する
磁気メモリ。 - 磁気メモリ素子の初期化方法であって、
ここで、前記磁気メモリ素子は、
垂直磁気異方性を有する強磁性体から構成され、第1磁化固定領域と第2磁化固定領域と前記第1磁化固定領域及び前記第2磁化固定領域に接続する磁化自由領域とを備える第1磁化自由層と、
前記第1磁化自由層の近傍に設けられた非磁性層と、
強磁性体から構成され、前記非磁性層上に設けられたリファレンス層と、
前記第1磁化固定領域の近傍に設けられた第1磁化固定層群と、
前記第1磁化固定層群と前記第1磁化固定領域との間、又は前記第1磁化固定層群内に挟まれて設けられた第1遮断層と
を具備し、
前記磁気メモリ素子の初期化方法は、
前記磁気メモリ素子に、前記第1磁化自由層の上側平面に対して略垂直な向きに第1の磁界を印加するステップと、
前記磁気メモリ素子に、前記第1の磁界とは逆の向きに前記第1の磁界よりも絶対値の小さな第2の磁界を印加するステップと
を具備する
磁気メモリ素子の初期化方法。 - 請求項9記載の磁気メモリ素子の初期化方法であって、
前記第2の磁界の大きさが、前記第1磁化固定層群の少なくとも一部分が反転しない大きさに設定される
磁気メモリ素子の初期化方法。 - 請求項9又は10に記載の磁気メモリ素子の初期化方法であって、
前記第2の磁界を印加するステップの後、前記磁気メモリ素子に、前記第1の磁界と同じ向きに前記第1の磁界よりも絶対値の小さな第3の磁界を印加するステップを更に具備する
磁気メモリ素子の初期化方法。 - 磁気メモリの初期化方法であって、
ここで、前記磁気メモリは、行列上に配置された複数の磁気メモリ素子を具備し、
前記複数の磁気メモリ素子の各々は、
垂直磁気異方性を有する強磁性体から構成され、第1磁化固定領域と第2磁化固定領域と前記第1磁化固定領域及び前記第2磁化固定領域に接続する磁化自由領域とを備える第1磁化自由層と、
前記第1磁化自由層の近傍に設けられた非磁性層と、
強磁性体から構成され、前記非磁性層上に設けられたリファレンス層と、
前記第1磁化固定領域の近傍に設けられた第1磁化固定層群と、
前記第1磁化固定層群と前記第1磁化固定領域との間、又は前記第1磁化固定層群内に挟まれて設けられた第1遮断層と
を備え、
前記磁気メモリの初期化方法は、
前記複数の磁気メモリ素子に、請求項9乃至11のいずれか一項に記載の磁気メモリ素子の初期化方法を実行するステップを具備する
磁気メモリの初期化方法。
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