WO2009128486A1 - 磁気メモリ素子の記録方法 - Google Patents
磁気メモリ素子の記録方法 Download PDFInfo
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- WO2009128486A1 WO2009128486A1 PCT/JP2009/057622 JP2009057622W WO2009128486A1 WO 2009128486 A1 WO2009128486 A1 WO 2009128486A1 JP 2009057622 W JP2009057622 W JP 2009057622W WO 2009128486 A1 WO2009128486 A1 WO 2009128486A1
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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
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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
- G11C11/165—Auxiliary circuits
- G11C11/1675—Writing or programming circuits or methods
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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
- G11C11/165—Auxiliary circuits
- G11C11/1693—Timing circuits or methods
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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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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
- Y10S—TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y10S977/00—Nanotechnology
- Y10S977/902—Specified use of nanostructure
- Y10S977/932—Specified use of nanostructure for electronic or optoelectronic application
- Y10S977/933—Spintronics or quantum computing
- Y10S977/935—Spin dependent tunnel, SDT, junction, e.g. tunneling magnetoresistance, TMR
Definitions
- the present invention includes a storage layer that can change the magnetization direction and holds information as the magnetization direction of the magnetic material, and a magnetization reference layer that is provided to the storage layer via an insulating layer and serves as a reference for the magnetization direction.
- the present invention relates to a recording method of a magnetic memory element in which information is recorded by a current flowing between a storage layer and a magnetization reference layer through an insulating layer.
- DRAMs Dynamic RAMs
- RAMs random access memories
- Magnetic magnetic memory element As a non-volatile memory, a flash memory or the like has been put into practical use, but in recent years, a magnetic memory using a magnetoresistive effect has attracted attention as a high-speed, large-capacity, low power consumption non-volatile memory, and development has been promoted. Yes.
- a magnetic random access memory Magnetic magnetic memory element
- TMR tunnel magnetoresistance
- RAM MRAM
- FIG. 9A is an explanatory diagram showing the basic structure of the MTJ element and the reading operation of the stored information.
- the MTJ element 100 has a structure in which a tunnel insulating layer 104, which is a nonmagnetic thin insulating layer, is sandwiched between two ferromagnetic layers of a storage layer 105 and a magnetization reference layer 103.
- MTJ magnetic tunnel junction
- the memory layer 105 is made of a ferromagnetic conductor having uniaxial magnetic anisotropy, can change the magnetization direction by an external action, and can hold the magnetization direction as information. For example, whether the magnetization direction is “parallel” or “antiparallel” with respect to the magnetization direction of the magnetization reference layer 103 is stored as information of “0” and “1”, respectively.
- the TMR effect that changes is used.
- This resistance value takes a minimum value when the magnetization direction of the storage layer 105 and the magnetization direction of the magnetization reference layer 103 are parallel, and takes a maximum value when the magnetization direction is antiparallel.
- FIG. 9B is a partial perspective view showing an example of the structure of an MRAM memory cell including the MTJ element 100.
- word lines as row wirings and bit lines as column wirings are arranged in a matrix
- MTJ elements 100 are arranged at the positions of their intersections, and memory cells corresponding to 1 bit are formed. Yes.
- a write bit line 122 and a read bit line 123 are provided above the memory cell with an interlayer insulating film interposed therebetween, and the MTJ element 100 is disposed below and in contact with the read bit line 123.
- a write word line 121 is disposed under the lead electrode layer 106 of the MTJ element 100 with an insulating layer interposed therebetween.
- a MOS (Metal Oxide Semiconductor) type field effect transistor is provided in the lower portion of the memory cell as a selection transistor 110 for selecting the memory cell in a read operation on a semiconductor substrate 111 such as a silicon substrate.
- the gate electrode 115 of the transistor 110 is formed in a band shape connecting cells, and also serves as a read word line.
- the source region 114 is connected to the extraction electrode layer 106 of the MTJ element 100 via the read connection plug 107, and the drain region 116 is connected to the sense line 124 that is a read row wiring.
- writing (recording) of information to the MTJ element 100 of a desired memory cell is performed by using a write word line 121 in a row including the memory cell, a write bit line 122 in a column, and the like.
- a write current is supplied to each of the two, and a combined magnetic field of these currents is generated at the intersection of the two write wirings.
- the storage layer 105 of the MTJ element 100 of the desired memory cell is “parallel” or “anti-parallel” with respect to a predetermined magnetization direction, that is, the magnetization direction of the magnetization reference layer 103. Magnetized in the direction, information is written (recorded).
- a selection signal is applied to the gate electrode 115 which is a read word line in a row including a desired memory cell, and all the selection transistors 110 in the row are turned on (conducting). ) State.
- a read voltage is applied between the read bit line 123 and the sense line 124 in a column including a desired memory cell.
- only a desired memory cell is selected, and the difference in the magnetization direction of the storage layer 105 of the MTJ element 100 is detected as the difference in the magnitude of the tunnel current flowing through the MTJ element 100 using the TMR effect.
- the tunnel current is taken out from the sense line 124 to a peripheral circuit (not shown) and measured.
- the TMR type MRAM is a nonvolatile memory that reads information by utilizing the magnetoresistive effect based on the spin-dependent conduction phenomenon peculiar to nanomagnets, and is rewritten by reversal of the magnetization direction, so that it is practically infinite. It is reported that the number of times of rewriting is possible and the access time is high (see, for example, R. Scheuerlein et al., ISSCC Digest of Technical Papers, pp.128-129, Feb.2000).
- Magnetic memory element that uses magnetization reversal by spin injection for writing as an element for writing (recording) information to a storage layer of the magnetic memory element based on different principles.
- Spin injection is a current consisting of a group of electrons whose spin direction is biased in one direction by passing a current through a ferromagnetic conductive layer (magnetization reference layer) with a fixed magnetization direction (spin-polarized current). ) And injecting this current into a magnetic conductive layer (memory layer) whose magnetization direction can be changed.
- the magnetization direction of the storage layer is changed by the interaction between the spin-polarized electrons and the electrons of the magnetic material constituting the storage layer.
- a force is applied to match the magnetization direction. Therefore, the magnetization direction of the storage layer can be reversed by passing a spin-polarized current having a current density equal to or higher than a certain threshold (see, for example, Patent Document 1 and Non-Patent Document 1 described later).
- FIG. 10 shows an MRAM (hereinafter, referred to as a spin injection MTJ element) whose magnetization direction is reversed by spin injection, which is shown in Patent Document 2 described later, and uses magnetization reversal by spin injection.
- 1 is a partial perspective view showing an example of a structure of “spin torque MRAM”.
- spin torque MRAM word lines 215 that are row wirings and bit lines 218 that are column wirings are arranged in a matrix, and one spin injection MTJ element 220 is arranged at the position of each intersection thereof.
- a memory cell corresponding to is formed.
- FIG. 10 shows four memory cells.
- a selection transistor 210 described later is formed in each memory cell, and the word line 215 also serves as the gate electrode of the selection transistor 210.
- the drain region 216 is formed in common to the left and right selection transistors in the figure, and a row wiring 219 is connected to the drain region 216.
- FIG. 11 is a partial cross-sectional view showing the structure of the memory cell of the spin torque MRAM.
- each layer of the base layer 201, the antiferromagnetic layer 202, the magnetization fixed layer 203a, the intermediate layer 203b, the magnetization reference layer 203c, the tunnel insulating layer 204, the storage layer 205, and the protective layer 206 in order from the lower layer. are stacked to form the spin injection MTJ element 220.
- the layer structure of the spin injection MTJ element 220 is basically the same as that of the normal MTJ element 100.
- the magnetization fixed layer 203a, the intermediate layer 203b, and the magnetization reference layer 203c are stacked on the antiferromagnetic layer 20202, and constitute a fixed magnetization layer as a whole.
- the magnetization direction of the magnetization fixed layer 203 a made of a ferromagnetic conductor is fixed by the antiferromagnetic layer 20202.
- the magnetization reference layer 203c made of a ferromagnetic conductor forms antiferromagnetic coupling with the magnetization fixed layer 203a via the intermediate layer 203b which is a nonmagnetic layer.
- the magnetization direction of the magnetization reference layer 203c is fixed in a direction opposite to the magnetization direction of the magnetization fixed layer 203a. In the example shown in FIG. 11, the magnetization direction of the magnetization fixed layer 203a is fixed to the left, and the magnetization direction of the magnetization reference layer 203c is fixed to the right.
- the fixed magnetic layer has the above-described laminated ferrimagnetic structure
- the sensitivity of the fixed magnetic layer to the external magnetic field can be reduced. Therefore, the magnetization variation of the fixed magnetic layer due to the external magnetic field is suppressed, and the stability of the MTJ element is improved. be able to. Further, since the magnetic fluxes leaking from the magnetization fixed layer 203a and the magnetization reference layer 203c cancel each other, the magnetic flux leaking from the fixed magnetization layer can be minimized by adjusting these film thicknesses.
- the memory layer 5 is made of a ferromagnetic conductor having uniaxial magnetic anisotropy, can change the magnetization direction by an external action, and can hold the magnetization direction as information. For example, whether the magnetization direction is “parallel” or “antiparallel” with respect to the magnetization direction of the magnetization reference layer 203c is stored as information of “0” and “1”, respectively.
- a tunnel insulating layer 204 which is a nonmagnetic thin insulating layer, is provided between the magnetization reference layer 203c and the storage layer 205.
- the magnetic reference junction 203c, the tunnel insulation layer 204, and the storage layer 205 form a magnetic tunnel junction. (MTJ) is formed.
- a gate insulating film 212, a source electrode 213, a source are formed as a selection transistor 210 for selecting the memory cell in a well region 211a of the semiconductor substrate 211 such as a silicon substrate.
- a MOS field effect transistor including a region 214, a gate electrode 215, a drain region 216, and a drain electrode 217 is provided.
- the gate electrode 215 of the selection transistor 210 is formed in a band shape connecting cells, and also serves as a word line as a first row wiring.
- the drain electrode 217 is connected to the row wiring 219 which is the second row wiring, and the source electrode 213 is connected to the base layer 201 of the spin injection MTJ element 220 via the connection plug 207.
- the protective layer 206 of the spin injection MTJ element 220 is connected to a bit line 218 which is a column wiring provided above the memory cell.
- a selection signal is applied to the word line 215 in the row including the desired memory cell, and all the selection transistors 210 in that row are turned on (conduction). ) State.
- a write voltage is applied between the bit line 218 and the row wiring 219 in a column including a desired memory cell.
- a desired memory cell is selected, a spin-polarized current flows through the storage layer 205 of the spin injection MTJ element 220, the storage layer 205 is magnetized in a predetermined magnetization direction, and information is recorded.
- the magnetization direction of the magnetization reference layer 203c of the spin injection MTJ element 220 is in an “antiparallel” state with respect to the magnetization direction of the storage layer 205, and the magnetization direction of the storage layer 205 is magnetized by writing this.
- a write current having a current density equal to or higher than the threshold value is allowed to flow from the storage layer 205 to the magnetization reference layer 203c.
- a spin-polarized electron flow having an electron density equal to or higher than the threshold value flows from the magnetization reference layer 203c to the storage layer 205, and magnetization reversal occurs.
- the write current having a current density equal to or higher than the threshold is In the opposite direction, that is, flowing from the magnetization reference layer 203c to the storage layer 205, as a matter of fact, an electron flow having an electron density equal to or higher than a threshold value flows from the storage layer 205 to the magnetization reference layer 203c.
- reading of information from the spin injection MTJ element 220 is performed using the TMR effect, as with the MTJ element 100.
- Both the writing and reading of the spin injection MTJ element 220 utilize the interaction between electrons in the storage layer 205 and the spin-polarized current flowing through this layer, and reading is performed by the current density of the spin-polarized current. Is performed in a small region, and writing is performed in a region where the current density of the spin-polarized current exceeds a threshold value.
- the spin-injection MTJ element 220 As the volume of the storage layer decreases, magnetization can be reversed with a smaller current in proportion to the volume. (See Non-Patent Document 1).
- information is written into the memory cell selected by the selection transistor 210, there is no possibility of erroneously writing to another adjacent cell, unlike writing by a current magnetic field.
- most of wiring can be shared for writing and reading, the structure is simplified.
- the influence of the shape of the magnetic material is small compared to the magnetic field writing, it is easy to increase the yield during manufacturing. In these respects, the spin torque MRAM is suitable for miniaturization, high density, and large capacity as compared with the MRAM that performs writing with a current magnetic field.
- the current that can be passed through the spin injection MTJ element 220 during writing is limited by the current that can be passed through the selection transistor 210 (transistor saturation current).
- transistor saturation current In general, as the gate width or gate length of a transistor becomes smaller, the saturation current of the transistor also becomes smaller. Therefore, in order to secure a write current to the spin injection MTJ element 220, downsizing of the selection transistor 210 is limited. Therefore, in order to make the selection transistor 210 as small as possible and to maximize the density and capacity of the spin torque MRAM, it is essential to reduce the write current threshold as much as possible.
- the threshold of current required for magnetization reversal by spin injection is phenomenologically proportional to the spin damping constant ⁇ of the storage layer 205, the square of the saturation magnetization Ms, and the volume V, and inversely proportional to the spin injection efficiency ⁇ . It is shown. Therefore, by appropriately selecting these, the threshold value of the current required for magnetization reversal can be lowered.
- the spin-injection MTJ element 220 in order for the spin-injection MTJ element 220 to be a reliable memory element, the memory retention characteristics (thermal stability of magnetization) of the storage layer 205 are ensured, and the magnetization direction does not change due to thermal motion. is required.
- the thermal stability is proportional to the saturation magnetization amount Ms and the volume V of the storage layer 205.
- the saturation magnetization amount Ms and the volume V of the storage layer 205 are related to both the current threshold required for magnetization reversal and the thermal stability, and these factors are reduced to lower the current threshold required for magnetization reversal. In addition, there is a trade-off relationship that thermal stability is also lowered.
- the average of the inversion thresholds is considered in consideration of the inversion threshold variation of the spin injection MTJ element and the inversion threshold variation caused by the transistor and the wiring. It is set to apply a write pulse that is considerably larger than the value. Therefore, when the above phenomenon appears, it becomes impossible to ensure a write error rate of 10 ⁇ 25 or less in actual writing to the spin torque MRAM memory chip.
- the MRAM and the spin torque RAM hold information as the magnetization direction of the magnetic material constituting the storage layer, the magnetization direction of the storage layer changes when exposed to a strong external magnetic field, and the information is lost. .
- the resistance to an external magnetic field is remarkably reduced, so that a magnetic shield for reducing the external magnetic field acting on the magnetic memory element is essential.
- the above-described commercially available MRAM (MR2A16) Is also equipped.
- a certain amount of thickness and volume are necessary, and an increase in the volume and weight of the memory IC or an increase in price is inevitable.
- the present invention has been made in view of such circumstances, and its purpose is to change the magnetization direction and to insulate the storage layer from the storage layer that holds information as the magnetization direction of the magnetic material.
- a method for recording a magnetic memory element wherein the recording layer includes a magnetization reference layer that is provided via a layer and serves as a reference for a magnetization direction, and information is recorded by a current flowing between the storage layer and the magnetization reference layer through an insulating layer.
- the present invention comprises a storage layer made of a ferromagnetic conductor and capable of changing the magnetization direction and holding information as the magnetization direction of the magnetic material; provided to the storage layer via an insulating layer, and ferromagnetic And a reference magnetization layer that has a fixed magnetization direction and serves as a reference for the magnetization direction, and records information by current flowing between the storage layer and the reference magnetization layer through the insulating layer.
- the recording method for a magnetic memory element when recording one piece of information, one or more main pulses and one or more sub-pulses are applied in the same direction, and after the one or more main pulses, 1 Two or more sub-pulses are applied, and the sub-pulse applied after the main pulse is a pulse having a pulse width shorter than that of the main pulse or a pulse having a pulse height lower than that of the main pulse. Is there The at least one condition is satisfied pulses, characterized in that those related to the recording method for a magnetic memory device.
- the pulse may be voltage control, current control, or power control.
- the one or more main pulses are followed by the one or more main pulses.
- the sub-pulse applied after the main pulse is a pulse having a shorter pulse width than the main pulse or a pulse having a pulse height lower than that of the main pulse.
- the writing error caused by the injection of excessive writing power is not corrected, and the result is as it is, so the writing error rate is high. In addition, the resistance to an external magnetic field during writing is low.
- the present invention since one or more sub-pulses are applied after the one or more main pulses, there is a possibility that a write error caused by the main pulses can be corrected by writing with the sub-pulses. Is expensive.
- at least one of the sub-pulse applied after the main pulse is a pulse having a pulse width shorter than that of the main pulse or a pulse having a pulse height lower than that of the main pulse.
- the pulse Since the pulse satisfies the condition, excessive energy is hardly accumulated in the writing by the sub-pulse, and the high recording voltage error is not easily generated. Due to the above effects, in the recording method of the magnetic memory element of the present invention, the write error rate is reduced and the resistance to an external magnetic field at the time of writing is improved.
- 4 is a graph showing an example of a write pulse train in the magnetic memory element recording method.
- 4 is a graph showing an example of a write pulse train in the magnetic memory element recording method. It is a graph which shows the example of the write pulse train in the recording method of the magnetic memory element based on Embodiment 2 of this invention.
- 4 is a graph showing an example of a write pulse train in the magnetic memory element recording method. It is a graph which shows the relationship between a write error rate and a pulse interval in the recording method of the magnetic memory element of Example 1 of this invention.
- FIG. 2 is an explanatory diagram (a) showing a basic structure of an MTJ element, a read operation of stored information, and a partial perspective view (b) showing an example of a structure of a memory cell of an MRAM comprising an MTJ element. It is a fragmentary perspective view which shows the structure of the spin torque MRAM shown by patent document 2.
- FIG. 2 is a partial cross-sectional view showing the structure of a memory cell of a spin torque MRAM composed of a spin injection MTJ element.
- FIG. 6 is a graph showing a relationship between a write pulse voltage and a write error rate. It is a figure which shows the structure of the write pulse generation circuit which produces
- a set of three consecutive pulses in a pulse train composed of the one or more main pulses and the one or more sub-pulses applied thereafter Therefore, it is preferable to provide at least one set in which at least one of the pulse width and the pulse height gradually decreases.
- the subsequent pulses And a pulse satisfying at least one of a pulse width of 2 ns or more and 10 ns or less, or a pulse height of 0.7 times or more and 0.95 times or less of the previous pulse, and It is preferable to provide a time interval of 5 ns or more between the end of the previous pulse and the tip of the subsequent pulse.
- the subsequent pulses Satisfying at least one of the following conditions: the pulse width is 3 ns or less, or the pulse height is 0.95 times or less of the previous pulse, and the end of the previous pulse and the tip of the subsequent pulse The time interval between and should be less than 5 ns.
- Embodiment 1 In the first embodiment, an example of a recording method of a spin injection MTJ element according to claims 1 to 3 will be mainly described.
- FIG. 15 and FIG. 16 show the structure of the memory cell of the spin torque MRAM used in this embodiment and the configuration of the spin injection MTJ element.
- FIG. 15 shows a structure of an MRAM (hereinafter referred to as a spin torque MRAM) that includes an MTJ element whose magnetization direction is reversed by spin injection (hereinafter referred to as a spin injection MTJ element) and uses magnetization reversal by spin injection. It is a fragmentary perspective view which shows an example.
- a spin torque MRAM word lines 15 as row wirings and bit lines 18 as column wirings are arranged in a matrix, and one spin injection MTJ element 20 is arranged at the position of each intersection thereof. A memory cell corresponding to is formed.
- FIG. 15 shows four memory cells.
- a selection transistor 10 described later is formed in each memory cell, and the word line 15 also serves as a gate electrode of the selection transistor 10.
- the drain region 16 is formed in common to the left and right selection transistors in the figure, and a row wiring 19 is connected to the drain region 16.
- FIG. 16 is a partial cross-sectional view showing the structure of the memory cell of the spin torque MRAM.
- each layer of the underlayer 1, the antiferromagnetic layer 2, the magnetization fixed layer 3a, the intermediate layer 3b, the magnetization reference layer 3c, the tunnel insulating layer 4, the storage layer 5, and the protective layer 6 in order from the lower layer. are stacked to form the spin injection MTJ element 20.
- the magnetization fixed layer 3a, the intermediate layer 3b, and the magnetization reference layer 3c are stacked on the antiferromagnetic layer 2, and constitute a fixed magnetization layer as a whole.
- the magnetization direction of the magnetization fixed layer 3 a made of a ferromagnetic conductor is fixed by the antiferromagnetic layer 2.
- the magnetization reference layer 3c made of a ferromagnetic conductor forms antiferromagnetic coupling with the magnetization fixed layer 3a via the intermediate layer 3b which is a nonmagnetic layer.
- the magnetization direction of the magnetization reference layer 3c is fixed in a direction opposite to the magnetization direction of the magnetization fixed layer 3a. In the example shown in FIG. 16, the magnetization direction of the magnetization fixed layer 3a is fixed to the left, and the magnetization direction of the magnetization reference layer 3c is fixed to the right.
- the fixed magnetic layer has the above-described laminated ferrimagnetic structure
- the sensitivity of the fixed magnetic layer to the external magnetic field can be reduced. Therefore, the magnetization variation of the fixed magnetic layer due to the external magnetic field is suppressed, and the stability of the MTJ element is improved. be able to. Further, since the magnetic flux leaking from the magnetization fixed layer 3a and the magnetization reference layer 3c cancel each other, the magnetic flux leaking from the fixed magnetization layer can be minimized by adjusting these film thicknesses.
- the memory layer 5 is made of a ferromagnetic conductor having uniaxial magnetic anisotropy, can change the magnetization direction by an external action, and can hold the magnetization direction as information. For example, whether the magnetization direction is “parallel” or “anti-parallel” to the magnetization direction of the magnetization reference layer 3c is stored as information of “0” and “1”, respectively.
- a gate insulating film 12 a source electrode 13, a source as a selection transistor 10 for selecting the memory cell in a well region 11 a isolated from a semiconductor substrate 11 such as a silicon substrate.
- a MOS field effect transistor including a region 14, a gate electrode 15, a drain region 16, and a drain electrode 17 is provided.
- the gate electrode 15 of the selection transistor 10 is formed in a band shape connecting cells, and also serves as a word line as a first row wiring. Further, the drain electrode 17 is connected to a row wiring 19 which is a second row wiring, and the source electrode 13 is connected to the base layer 1 of the spin injection MTJ element 20 via the connection plug 7. On the other hand, the protective layer 6 of the spin injection MTJ element 20 is connected to a bit line 18 that is a column wiring provided above the memory cell.
- a selection signal is applied to the word line 15 in the row including the desired memory cell, and all the selection transistors 10 in that row are turned on (conduction). ) State.
- a write voltage is applied between the bit line 18 and the row wiring 19 in the column including the desired memory cell.
- a desired memory cell is selected, a spin-polarized current flows through the storage layer 5 of the spin injection MTJ element 20, the storage layer 5 is magnetized in a predetermined magnetization direction, and information is recorded.
- the magnetization direction of the magnetization reference layer 3c of the spin injection MTJ element 20 is initially in an “antiparallel” state with respect to the magnetization direction of the storage layer 5, and the magnetization direction of the storage layer 5 is magnetized by writing this.
- a write current having a current density equal to or higher than the threshold is passed from the storage layer 5 to the magnetization reference layer 3c.
- a spin-polarized electron flow having an electron density equal to or higher than the threshold value flows from the magnetization reference layer 3c to the storage layer 5, and magnetization reversal occurs.
- the write current having a current density equal to or higher than the threshold is In the opposite direction, that is, flowing from the magnetization reference layer 3c to the storage layer 5, as a matter of fact, an electron flow having an electron density equal to or higher than a threshold value flows from the storage layer 5 to the magnetization reference layer 3c.
- reading of information from the spin injection MTJ element 20 is performed using the TMR effect.
- Both the writing and reading of the spin injection MTJ element 20 utilize the interaction between the electrons in the storage layer 5 and the spin-polarized current flowing through this layer, and the reading is the current density of the spin-polarized current. Is performed in a small region, and writing is performed in a region where the current density of the spin-polarized current exceeds a threshold value.
- the magnetization reference layer 3c may have a fixed magnetization direction in combination with an antiferromagnetic material such as PtMn or IrMn so that the magnetization is not reversed or destabilized during the recording operation, or has a coercive force such as CoPt.
- an antiferromagnetic material such as PtMn or IrMn so that the magnetization is not reversed or destabilized during the recording operation, or has a coercive force such as CoPt.
- a large material may be used, it may be processed into a larger area than the storage layer 5, or may be magnetized in a specific direction by an external magnetic field.
- the magnetization reference layer 3c may be a single ferromagnetic layer or may be magnetically coupled antiparallel to the magnetization fixed layer 3a via an intermediate layer 3b made of a nonmagnetic metal such as Ru as shown in FIG. You may make it do.
- the magnetization of the magnetization reference layer 3c may be in-plane magnetization or perpendicular magnetization. Further, the magnetization reference layer 3c may be disposed below the storage layer 5, may be disposed above, or may be disposed above and below.
- the tunnel insulating layer 4 is preferably made of a ceramic material such as oxide or nitride.
- a magnesium oxide MgO layer as the tunnel insulating layer 4 and to provide a CoFeB layer at least on the tunnel insulating layer 4 side of the magnetization reference layer 3c and the storage layer 5 because the magnetoresistance change rate can be increased.
- FIG. 1 is a graph showing an example of a write pulse train in the magnetic memory element recording method according to the first embodiment.
- a sub-pulse having the same pulse height as the main pulse and a shorter pulse width than the main pulse is applied.
- the main pulse and the sub pulse may be voltage control, current control, or power control.
- FIG. 1 (1) shows a case where one sub pulse is applied after one main pulse.
- the main pulse is a pulse having a pulse height and a pulse width sufficient to record information, as in the case of writing with a conventional single pulse.
- the variation in the inversion threshold of the spin injection MTJ element, the variation in the inversion threshold due to the transistor and the wiring, etc. Considering this, a write pulse that is considerably larger than the average value of the inversion threshold is applied. As a result, the higher the write pulse, the higher the recording voltage error that increases the write error rate.
- the writing error caused by the writing with the main pulse is not corrected, and the result is as it is, so the writing error rate is high.
- the resistance to an external magnetic field during writing is low.
- the present embodiment since a sub pulse having a pulse height exceeding the inversion threshold is applied after the main pulse, there is a possibility that a write error caused by the main pulse can be corrected by writing with the sub pulse. high.
- the pulse width of the sub-pulse is shorter than the pulse width of the main pulse, excessive energy is not easily accumulated by writing with the sub-pulse, and the above-described high recording voltage error is unlikely to appear. Due to the above effects, in the magnetic memory element recording method according to the present embodiment, the write error rate is reduced and the resistance to an external magnetic field during writing is improved.
- a time interval of 3 ns or more, more preferably 5 ns or more, between the end of the main pulse and the tip of the sub-pulse is preferable to provide a time interval of 3 ns or more, more preferably 5 ns or more, between the end of the main pulse and the tip of the sub-pulse. This is to ensure a sufficient time for dissipating excess energy accumulated by writing with the main pulse.
- FIG. 1 (2) two sub-pulses are applied after one main pulse, and the pulse widths of the main pulse, sub-pulse 1 and sub-pulse 2 gradually decrease corresponding to claim 2.
- An example configured as a set of three consecutive pulses is shown. In this case, the correction is repeated twice by the writing by the sub pulse 1 and the writing by the sub pulse 2, and the pulse width becomes shorter as the pulse is applied later, and the high recording voltage error due to excessive energy accumulation is less likely to appear. Therefore, there is a higher possibility that the write error rate is improved.
- FIG. 2 is a graph showing an example of a write pulse train based on the first embodiment, and shows examples of various main pulses.
- FIG. 2A and FIG. 2B are examples in which a short pause period of about 1 ns is provided in the main pulse to pause the writing power injection. As shown in FIG. 2 (a), there is no effect even if a pause period is provided in the middle part of the main pulse. However, if a pause period is provided near the end of the main pulse as shown in FIG. As a result, the write power injected into the memory is effectively gradually reduced to make the above high recording voltage error less likely to appear (see Japanese Patent Application No. 2008-107768).
- FIG. 2 (c) and FIG. 2 (d) are examples in which two main pulses are applied.
- FIG. 2C shows a case where the main pulse 1 and the main pulse 2 having the same pulse height and pulse width are applied
- FIG. 2D shows the main pulse 1 and the main pulse having different pulse heights and pulse widths. The case where the pulse 2 is applied is shown. In any case, writing by the preceding main pulse 1 is invalidated by writing by the following main pulse 2, so that there is no particular effect of applying a plurality of main pulses.
- FIG. 3 is a graph showing an example of a write pulse train based on the first embodiment, and shows examples of various sub-pulses.
- FIG. 3A shows an example in which two, generally a plurality of sub-pulses are applied after the main pulse, and correction is repeated twice by writing by sub-pulses, generally a plurality of times, so that the write error rate is improved. Is more likely.
- FIGS. 3B and 3C are examples in which a sub-pulse preceding the last main pulse is provided, and there is no particular effect of applying such a sub-pulse.
- Embodiment 2 In the second embodiment, another example of the recording method of the spin injection MTJ element according to claims 1 and 2 will be mainly described.
- FIGS. 4 and 5 are graphs showing examples of write pulse trains in the magnetic memory element recording method according to the second embodiment.
- the second embodiment when recording one piece of information, after the main pulse, a sub-pulse having the same pulse width as the main pulse and a pulse height lower than that of the main pulse is applied. Even if the main pulse and the sub pulse are voltage control or current control, May be power control
- FIG. 4 shows a case where one sub-pulse is applied after one main pulse
- FIGS. 4A and 4B are explanatory diagrams for explaining the effect.
- the main pulse is a pulse having a pulse height and a pulse width sufficient to record information, as in the case of writing with a conventional single pulse.
- a write pulse that is considerably larger than the average value of the inversion threshold is applied.
- the pulse height of the sub-pulse may be smaller than the inversion threshold.
- writing is not performed even if a sub-pulse is applied, sub-pulse 2 is invalid, and the writing result by the main pulse is maintained as it is.
- the pulse height of the main pulse is not so high as compared with the inversion threshold, and the high recording rate in which the write error rate increases due to excessive energy injection in writing by the main pulse. Voltage error elephants rarely appear. That is, good writing with a small writing error rate is performed by the main pulse, and no correction is required.
- both the magnetic memory element having an average inversion threshold and the magnetic memory element having a high inversion threshold have a low write error rate and good writing. It can be performed.
- FIG. 5 shows that two sub-pulses are applied after one main pulse, and corresponding to claim 2, the main pulse, sub-pulse 1 and sub-pulse 2 are continuously reduced in pulse height.
- An example configured as a set of three pulses is shown.
- the magnetic memory element having an average inversion threshold is corrected by writing with the sub-pulse 1 and is the same as the case shown in FIG. effective.
- the secondary pulse 2 is invalid.
- FIG. 5B in the magnetic memory element having a high inversion threshold, as in the case shown in FIG. 4B, the pulse height of the main pulse is not significantly higher than the inversion threshold. Good writing is performed by the main pulse, and no correction is required.
- FIG. 5 shows that two sub-pulses are applied after one main pulse, and corresponding to claim 2, the main pulse, sub-pulse 1 and sub-pulse 2 are continuously reduced in pulse height.
- An example configured as a set of three pulses is shown.
- the magnetic memory element having an average inversion threshold is corrected by writing with the
- the correction is repeated twice by the writing by the subpulse 1 and the writing by the subpulse 2, and the correction is applied later. Since the high recording voltage error due to the excessive energy injection is less likely to appear as the pulse, the possibility that the write error rate is improved becomes higher.
- the recording method based on Embodiments 1 and 2 of the present invention was applied to a spin torque MRAM composed of spin injection MTJ elements, and the effects of the present invention were verified.
- Examples 1 and 2 are experiments that provide the basis for claims 3 to 5, and
- Example 4 is an experiment that provides the basis for claim 2.
- erasing, recording, and reproduction were repeated while applying a magnetic field in the major axis direction of the element, and the writing error rate was measured. The direction in which the magnetic field was applied was opposite to the magnetization direction to be recorded.
- Example 1 In Example 1, the write pulse train shown in FIG. 1A was applied corresponding to the recording method of the magnetic memory element based on the first embodiment.
- the spin torque MRAM used is composed of the spin injection MTJ element 20 composed of the following layers.
- Underlayer 1 Ta film with a film thickness of 5 nm
- Antiferromagnetic layer 2 Antiferromagnetic layer 2: PtMn film having a film thickness of 30 nm
- Magnetization fixed layer 3a CoFe film having a thickness of 2 nm
- Intermediate layer 3b Ru film having a thickness of 0.7 nm
- Magnetization reference layer 3c CoFeB film having a thickness of 2 nm
- Tunnel insulating layer 4 a magnesium oxide MgO film having a thickness of 0.8 nm
- Memory layer 5 CoFeB film having a thickness of 3 nm
- Protective layer 6 Ta film with a thickness of 5 nm
- the planar shape of the spin injection MTJ element 20 is an ellipse having a major axis length of 150 to 250 nm and a minor axis length of 70 to 85 nm, and the coercive force of the memory layer 5 is 140 Oe.
- a subpulse having a pulse voltage of 0.8V and a pulse width W was applied following a main pulse having a pulse voltage of 0.8V and a pulse width of 30ns.
- the pulse width W of the sub-pulse and the pulse interval D between the end of the main pulse and the tip of the sub-pulse were variously changed, and the relationship between these and the write error rate was examined.
- FIG. 6 is a graph showing the relationship between the write error rate and the pulse interval D when a sub-pulse having a pulse width W of 1 to 30 ns is applied. It can be seen from FIG. 6 that there are two different tendencies. That is, when a pulse with a pulse width W of 1 ns is used as the sub-pulse, the error rate improvement effect is remarkable when the pulse interval D is 1 ns, and there is almost no improvement effect when the pulse interval D exceeds 5 ns.
- the error rate improvement effect according to the present invention is remarkable when the pulse interval D is 3 ns or more, preferably 5 ns or more.
- the pulse width W of the sub-pulse is 30 ns, which is the same as the pulse width of the main pulse, no improvement is observed.
- Example 2 the write pulse train shown in FIG. 4 was applied corresponding to the recording method of the magnetic memory element based on the second embodiment.
- the spin torque MRAM used has the same layer configuration as the spin injection MTJ element 20 used in Example 1, and is composed of the spin injection MTJ element 20 in which the coercive force of the storage layer 5 is 125 Oe.
- a sub-pulse of a pulse voltage V and a pulse width of 30 ns was applied following a main pulse of a pulse voltage of 0.9 V and a pulse width of 30 ns.
- the pulse voltage V of the sub pulse and the pulse interval D between the end of the main pulse and the tip of the sub pulse were variously changed, and the relationship between them and the write error rate was examined.
- FIG. 7 is a graph showing the results of examining the relationship between the write error rate and the ratio of the pulse voltage of the main pulse and the sub-pulse while changing the pulse interval D in the range of 1 to 10 ns. Although not as clear as in FIG. 6, there are two different trends in FIG.
- the improvement effect appears only when the ratio of the pulse voltage of the main pulse to the subpulse is 0.7 or more and 1.0 or less.
- the improvement effect is remarkable when it is 8 or more and 0.95 or less.
- the existence of a lower limit in the pulse voltage of an effective sub pulse indicates that writing by the sub pulse is being performed.
- the improvement effect that appears when the ratio of the pulse voltage of the main pulse to the subpulse is 0.8 or more and 0.95 or less is the same as the above.
- the improvement effect that appears when the pulse voltage ratio is 0.3 or more and 0.95 or less and the pulse voltage of the sub-pulse is less than the inversion threshold is the effect of another invention. it is conceivable that.
- Example 3 the resistance to the external magnetic field of the recording method of the magnetic memory element according to the first embodiment was examined.
- the spin torque MRAM used has the same layer configuration as the spin injection MTJ element 20 used in Example 1, and is composed of the spin injection MTJ element 20 in which the coercive force of the storage layer 5 is 212 Oe.
- the write error rate when the write pulse voltage was changed in the range of 0.5 to 0.7 V was examined.
- the polarity of the voltage was positive.
- FIG. 8 is a graph showing the positions where the write error rates are 0.1, 0.01, and 0.001, respectively, connected to the external magnetic field and the write pulse voltage by contour lines.
- FIG. 8B shows the result in the case of the comparative example recorded with a single pulse having a pulse width of 100 ns.
- the contour line has a curve that rises to the right as expected in the region where the external magnetic field is relatively small, but it is not expected in the region where the external magnetic field is large, and the write error rate is not improved even if the pulse voltage is increased. appear.
- the above-described high recording voltage error occurs in which the write error rate increases rather as the pulse voltage increases.
- FIG. 8A shows a case in which a sub-pulse having a pulse width of 3 ns is applied after a pulse interval of 10 ns is provided after the main pulse having a pulse width of 100 ns.
- the contour line becomes an upward curve to a region where the external magnetic field is large. If the external magnetic field is constant, the write error rate decreases as the pulse voltage increases.
- the write error rate when the write pulse voltage is increased can be improved, the write operation range can be expanded, and the magnetic field is increased when a large external magnetic field acts. Resistance is improved.
- the recording method of the magnetic memory element based on the first embodiment it is possible to perform a recording operation with few errors in a wide operating environment subjected to the action of the external magnetic field, and shield the external magnetic field in the large-capacity spin torque MRAM.
- the thickness and size of the magnetic shield to be reduced can be reduced, and the spin torque MRAM can be reduced in size, weight, and cost.
- Example 4 the write error rate was examined when a pulse train in which a main pulse having a pulse width of 10 ns was combined with subpulses having various pulse widths and pulse intervals was used as the write pulse train.
- the pulse height of the main pulse and the sub-pulse is the same, and the pulse width of the sub-pulse applied later is the same as the pulse width of the sub-pulse applied before, It was shorter than that.
- the spin torque MRAM used has the same layer configuration as the spin injection MTJ element 20 used in Example 1, and is composed of the spin injection MTJ element 20 in which the coercive force of the storage layer 5 is 130 Oe. While applying an external magnetic field of 50 Oe to the spin injection MTJ element 20, a main pulse and a sub pulse with a pulse voltage of 1.1 V were applied.
- Table 1 shows the pulse widths and pulse intervals of the main pulse and the sub-pulse in time series, and finally shows the write error rate when the write pulse train is used.
- Comparative Example 1 In Comparative Example 1, a single pulse was applied, and the write error rate in this case was 8.0 ⁇ 10 ⁇ 2 .
- Comparative Example 2 is a case where the sub pulse is applied prior to the main pulse.
- the write error rate in this case is 8.1 ⁇ 10 ⁇ 2, which is the same as that in Comparative Example 1 within the error range, and indicates that the sub pulse preceding the main pulse is invalid.
- Pulse train 1 and pulse train 2 are cases where one sub-pulse is applied 10 ns after the main pulse.
- the pulse width of the sub-pulse is 3 ns better than 2 ns. This may be because the pulse width is a little too short at 2 ns for sufficient writing by the sub-pulse.
- the pulse trains 3 to 5 two or three sub-pulses are applied after the main pulse, and the write error rate is improved compared to the pulse train 2 having one sub-pulse.
- the pulse configuration after the main pulse is the same as the pulse train 2, and the write error rate is almost the same.
- the pulse train 7 and the pulse train 8 are cases where a sub-pulse having a short pulse width of 1 ns is applied 1 ns after the main pulse, and the write error rate is improved as compared with the first comparative example. Also in this case, the write error rate was improved in the pulse train 8 in which two short sub-pulses having a pulse width of 1 ns were continued than in the pulse train 7 having one sub-pulse.
- the results of the pulse train 7 and the pulse train 8 may overlap the effects of the present invention and the effects of another invention.
- FIG. 13 is a diagram showing a configuration of a write pulse generation circuit that generates a write pulse composed of a main pulse and a sub pulse of the above embodiment from one rectangular pulse.
- the write pulse generation circuit 30 is configured using a plurality of buffers 32, 33, and 34 and a plurality of logic circuits 35 and 36.
- a rectangular pulse signal is input to the input terminal 31 of the write pulse generation circuit 30.
- a rectangular pulse signal input to the input terminal 31 is input to one input terminal of an OR logic circuit 36, a non-inverting input terminal of an AND logic circuit 35, and buffers 32 and 33 connected in series. .
- the buffers 32 and 33 connected in series are for generating the width of the sub-pulse, and an arbitrary sub-pulse width td1 can be selected by selecting the delay time of the buffers 32 and 33.
- the outputs of the buffers 32 and 33 are input to the non-inverting input terminal of the AND logic circuit 35.
- the output of the AND logic circuit 35 is input to the other input terminal of the OR logic circuit 36 through the buffer 34.
- the buffer 34 generates a time td2 between the main pulse and the sub-pulse, and an arbitrary time td2 can be set by selecting a delay time of the buffer 34.
- a write pulse composed of a main pulse and a sub pulse is obtained by the logic circuit 36 of OR logic, and is output from the output terminal 37 of the write pulse generation circuit 30.
- FIG. 14 is a diagram showing a configuration of a write pulse generation circuit 40 that generates a write pulse using a waveform memory and a D / A conversion circuit.
- the waveform memory 41 stores waveform data of write pulses composed of main pulses and sub-pulses.
- the waveform data of the write pulse is composed of time-series data of a plurality of words, with N bits that can select an output level from 2N stages as one word.
- the waveform memory 41 is provided with N ports for reading, and these N ports are connected to N input terminals of the D / A conversion circuit 42, respectively.
- the D / A conversion circuit 42 inputs the waveform data of the write pulse from the waveform memory 41 for each N-bit data (one word), converts it into an analog signal, and outputs it as a write pulse.
- the D / A conversion circuit 42 can be configured with, for example, a ladder resistor circuit.
- the present invention has been described based on the embodiment, but the present invention is not limited to these examples, and it is needless to say that the present invention can be appropriately changed without departing from the gist of the invention.
- the spin injection magnetization reversal type MTJ that improves the transient characteristics at the time of writing, reduces the number of write failures, reduces the threshold of the write current density, and enables high integration, high speed, and low power consumption.
- the element can be realized, and it can contribute to the practical use of a small-sized, lightweight, and low-cost nonvolatile memory.
Abstract
Description
実施の形態1では、主として、請求項1~3に関わるスピン注入MTJ素子の記録方法の例について説明する。
実施の形態2では、主として、請求項1および2に関わるスピン注入MTJ素子の記録方法の別の例について説明する。
電力制御であってもよい
実施例1では、実施の形態1に基づく磁気メモリ素子の記録方法に対応して、図1(1)に示した書き込みパルス列を印加した。用いたスピントルクMRAMは、下記の層で構成されるスピン注入MTJ素子20からなるものである。
反強磁性層2反強磁性層2 :膜厚30nmのPtMn膜、
磁化固定層3a :膜厚2nmのCoFe膜、
中間層3b :膜厚0.7nmのRu膜、
磁化基準層3c :膜厚2nmのCoFeB膜、
トンネル絶縁層4:膜厚0.8nmの酸化マグネシウムMgO膜、
記憶層5 :膜厚3nmのCoFeB膜、
保護層6 :膜厚5nmのTa膜
実施例2では、実施の形態2に基づく磁気メモリ素子の記録方法に対応して、図4に示した書き込みパルス列を印加した。用いたスピントルクMRAMは、実施例1で用いたスピン注入MTJ素子20と同じ層構成を有し、記憶層5の保磁力が125Oeであるスピン注入MTJ素子20からなるものである。このスピン注入MTJ素子20に50Oeの外部磁場を印加しながら、パルス電圧0.9V、パルス幅30nsの主パルスに続いて、パルス電圧V、パルス幅30nsの副パルスを印加した。この際、副パルスのパルス電圧Vと、主パルスの終端と副パルスの先端との間のパルス間隔Dとを種々に変え、それらと書き込みエラー率との関係を調べた。
実施例3では、実施の形態1に基づく磁気メモリ素子の記録方法の、外部磁場に対する耐性を調べた。用いたスピントルクMRAMは、実施例1で用いたスピン注入MTJ素子20と同じ層構成を有し、記憶層5の保磁力が212Oeであるスピン注入MTJ素子20からなるものである。このスピン注入MTJ素子20に0~200Oeの外部磁場を印加しながら、書き込みパルス電圧を0.5~0.7Vの範囲で変化させた場合の書き込みエラー率を調べた。電圧の極性は正とした。
実施例4では、書き込みパルス列として、パルス幅10nsの主パルスに種々のパルス幅およびパルス間隔の副パルスを組み合わせたパルス列を用いた場合の、書き込みエラー率を調べた。この際、実施の形態1に対応して、主パルスと副パルスのパルス高さは同じとし、後に印加される副パルスのパルス幅は、前に印加される副パルスのパルス幅と同じか、それよりも短くした。用いたスピントルクMRAMは、実施例1で用いたスピン注入MTJ素子20と同じ層構成を有し、記憶層5の保磁力が130Oeであるスピン注入MTJ素子20からなるものである。このスピン注入MTJ素子20に50Oeの外部磁場を作用させながら、パルス電圧が1.1Vの主パルスおよび副パルスを印加した。
図13は1つの矩形のパルスから上記の実施形態の主パルスと副パルスとからなる書き込みパルスを生成する書き込みパルス発生回路の構成を示す図である。
この書き込みパルス発生回路30は、複数のバッファ32,33,34と複数の論理回路35,36を用いて構成される。書き込みパルス発生回路30の入力端31には矩形のパルス信号が入力される。入力端31に入力された矩形のパルス信号は、OR論理の論理回路36の一方の入力端、AND論理の論理回路35の非反転入力端、直列に接続されたバッファ32,33に入力される。ここで、直列に接続されたバッファ32,33は副パルスの幅を生成するためのもので、バッファ32,33の遅延時間の選定により任意の副パルスの幅td1を選定することができる。バッファ32,33の出力はAND論理の論理回路35の非反転入力端に入力される。AND論理の論理回路35の出力はバッファ34を通じてOR論理の論理回路36の他方の入力端に入力される。ここで、バッファ34は主パルスと副パルスとの間の時間td2を生成するもので、バッファ34の遅延時間の選定により任意の時間td2を設定することができる。そして、OR論理の論理回路36によって主パルスと副パルスで構成される書き込みパルスが得られ、書き込みパルス発生回路30の出力端37より出力される。
Claims (6)
- 強磁性導体からなり、磁化方向の変化が可能で、情報を磁性体の磁化方向として保持する記憶層と;前記記憶層に対して絶縁層を介して設けられ、強磁性導体からなり、磁化方向が固定され、磁化方向の基準となる基準磁化層と;を少なくとも有し、前記絶縁層を通じて前記記憶層と前記基準磁化層との間に流れる電流によって情報の記録が行われる磁気メモリ素子に対する記録方法において、
1つの情報を記録するに際し、1つ以上の主パルスと1つ以上の副パルスとを同じ向きに印加し、
前記の1つ以上の主パルスの後に、1つ以上の前記副パルスを印加し、
前記主パルスの後に印加する副パルスを、前記主パルスに比べてパルス幅が短いパルスであるか、又は前記主パルスに比べてパルス高さが低いパルスであるかの、少なくとも一方の条件を満たすパルスとする
磁気メモリ素子の記録方法。 - 前記の1つ以上の主パルスと、その後に印加される前記の1つ以上の前記副パルスとからなるパルス列中に、連続する3つのパルスの組みであって、パルス幅及びパルス高さの少なくとも一方が漸次減少していく組みを少なくとも一組設ける、請求項1に記載した磁気メモリ素子の記録方法。
- 前記の1つ以上の主パルスの終端と、その後に印加される前記の1つ以上の前記副パルスの先端との間に、3ns以上の時間間隔を設ける、請求項1に記載した磁気メモリ素子の記録方法。
(なお、パルスの終端および先端は、それぞれ、パルスの立ち下がり及び立ち上がりにおける高さがパルス高さの最大値の半分になる位置とする。以下、同様。) - 前記の1つ以上の主パルスと、その後に印加される前記の1つ以上の前記副パルスとからなるパルス列中の、任意に選ばれた連続する2つのパルスの組みにおいて、後のパルスを、パルス幅が2ns以上、10ns以下であるか、又はパルス高さが前のパルスの0.7倍以上、0.95倍以下であるかの、少なくとも一方の条件を満たすパルスとし、且つ、前のパルスの終端と後のパルスの先端との間に5ns以上の時間間隔を設ける、請求項1又は2に記載した磁気メモリ素子の記録方法。
- 前記の1つ以上の主パルスと、その後に印加される前記の1つ以上の前記副パルスとからなるパルス列中の、任意に選ばれた連続する2つのパルスの組みにおいて、後のパルスを、パルス幅が3ns以下であるか、又はパルス高さが前のパルスの0.8倍以下であるかの、少なくとも一方の条件を満たし、且つ、前のパルスの終端と後のパルスの先端との時間間隔を5ns未満とする、請求項1又は2に記載した磁気メモリ素子の記録方法。
- 前記の1つ以上の主パルスと、その後に印加される前記の1つ以上の前記副パルスとからなるパルス列中の、任意に選ばれた連続する2つのパルスの組みにおいて、後のパルスを、パルス幅が3ns以下であるか、又はパルス高さが前のパルスの0.95倍以下であるかの、少なくとも一方の条件を満たし、且つ、前のパルスの終端と後のパルスの先端との時間間隔を5ns未満とする、請求項1又は2に記載した磁気メモリ素子の記録方法。
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JP2012014787A (ja) * | 2010-06-30 | 2012-01-19 | Sony Corp | 記憶装置 |
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KR20100132969A (ko) | 2010-12-20 |
TWI451410B (zh) | 2014-09-01 |
TW201003651A (en) | 2010-01-16 |
CN102007543A (zh) | 2011-04-06 |
JPWO2009128486A1 (ja) | 2011-08-04 |
JP5234106B2 (ja) | 2013-07-10 |
US8169818B2 (en) | 2012-05-01 |
CN102007543B (zh) | 2013-11-27 |
US20110032744A1 (en) | 2011-02-10 |
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