JPWO2011027404A1 - Magnetic memory - Google Patents

Abstract

A magnetic memory having a small recording current density, excellent thermal stability, and suitable for miniaturization is provided. A magnetic memory including a plurality of selection transistors and tunnel magnetoresistive elements, wherein the tunnel magnetoresistive element is formed on a first base layer 302 having a periodic texture in one direction and on the first base layer 302. A second underlayer 303 oriented in a rock salt structure, and a hard magnetic layer 21 formed on the second underlayer 303 and mainly composed of a Co-based alloy oriented in the hcp (1010) direction; A laminated ferri-recording layer 2 having a nonmagnetic layer 22 formed on the hard magnetic layer 21 and a soft magnetic layer 23 formed on the nonmagnetic layer 22, and comprising a Co-based alloy as a main component. The hard magnetic layer 21 and the soft magnetic layer 23 are antiferromagnetically coupled.

Description

  The present invention relates to a magnetic memory using spin torque magnetization reversal that reverses the direction of magnetic poles of a magnet using spin torque.

  In recent years, magnetic random access memory (MRAM) that has the potential to replace conventional dynamic random access memory (DRAM) has attracted attention. In the conventional MRAM, as described in Patent Document 1, for example, one magnetization of a tunnel magnetoresistive effect (TMR) element having a multilayer structure of a magnetic film / a nonmagnetic insulating film / a magnetic film is obtained from the TMR element. A system is employed in which recording is performed by reversing using a combined magnetic field generated by currents flowing in two metal wirings provided vertically in directions perpendicular to each other.

  However, even in the MRAM, if the size of the TMR element is reduced to increase the capacity, the magnitude of the magnetic field required for magnetization reversal increases, and it is necessary to pass a large amount of current through the metal wiring. It has been pointed out that it will lead to the destruction.

  Spin torque magnetization reversal has been proposed as a method of reversing magnetization without using a magnetic field, and its application to magnetic memory is being studied. The spin torque magnetization reversal technique is disclosed in Non-Patent Documents 1 to 4 and Patent Document 2, for example.

  Non-Patent Document 1 theoretically indicates that magnetization reversal is possible only by passing a current of a certain level or more through a giant magnetoresistive effect (GMR) film or tunnel magnetoresistive effect (TMR) film used in a magnetic reproducing head. Is shown in In Non-Patent Document 2, a pillar having a diameter of 130 nm including a Co / Cu / Co multilayer film (GMR film) is formed between two Cu electrodes, a current is passed through the pillar, and Co is generated from the spin of the flowing current. There has been reported an example of a recording method in which the magnetization of the Co layer is reversed by using the spin torque applied to the magnetization of the layer.

  In Non-Patent Document 3, spin torque magnetization reversal was demonstrated using a nanopillar using a TMR film. In particular, it is disclosed that spin torque magnetization reversal using a TMR film can provide an output equivalent to or higher than that of a conventional MRAM. Non-Patent Document 4 discloses a threshold current density that is not necessary for rewriting spin torque magnetization reversal.

  The above spin torque magnetization reversal will be described with reference to FIGS. 1 (a) and 1 (b). In FIG. 1A and FIG. 1B, a bit line 1 includes a first ferromagnetic layer (recording layer) 2, an intermediate layer (barrier layer) 3, and a magnetization direction fixed. A magnetoresistive element composed of two ferromagnetic layers (fixed layers) 4 and a transistor 6 whose conduction is controlled by a gate electrode 5 are connected, and the other terminal of the transistor is connected to a source line 7.

  As shown in FIG. 1A, when the magnetization of the fixed layer 4 and the recording layer 2 is changed from the antiparallel (high resistance) state to the parallel (low resistance) state, the current 8 is changed from the bit line 1 to the source line 7. Shed. At this time, the electrons 9 flow from the source line 7 to the bit line 1.

  On the other hand, when the magnetizations of the fixed layer 4 and the recording layer 2 are changed from the parallel (low resistance) state to the antiparallel (high resistance) state as shown in FIG. What is necessary is just to flow in the direction of line 1. At this time, the electrons 9 flow from the bit line 1 to the source line 7.

  Magnetization reversal is possible with the above configuration, but when the cross-sectional area of the recording layer is reduced to increase the recording density, the magnetization is reversed due to thermal fluctuation, that is, the recording is lost and the retention is not maintained. Became a problem.

  Therefore, for example, as described in Patent Document 2, the recording layer 2 is composed of two ferromagnetic layers 210 and 230 sandwiching the nonmagnetic layer 220, and the magnetization directions are opposite to each other. There has been proposed a structure called a laminated ferri structure that is arranged in such a manner as to be stabilized with respect to an intruding magnetic field from the outside (see FIG. 2).

US Pat. No. 5,734,605 JP 2005-294376 A

Journal of Magnetics and Magnetic Materials, 159, L1-6 (1996) Physical Review Letters, Vol. 84, no. 14, pp. 2149-2152 (2000) Applied Physics Letters, Vol. 84, no. 16, pp. 3118-3120 (2004) Physical Review B, Vol. 62, no. 1, pp. 570-578 (2000)

  Magnetic memories are required to have a large capacity, and there is a high demand for higher density. However, these conventional MRAMs have the following problems in response to this requirement.

  In a magnetic memory using spin torque magnetization reversal, it is extremely important to reduce the rewrite current and ensure the thermal stability to ensure the non-volatility. It is known that the rewriting current for spin torque magnetization reversal is determined by the current density, and the threshold current density Jc0 is given by Equation 1.

Jc0∝ (α · Ms · t / g) (Hk + Meff / 2μ0) (1)
Where α is the Gilbert damping constant, Ms is the saturation magnetization of the recording layer 2, t is the thickness of the recording layer, g is the spin torque efficiency, Hk is the anisotropic magnetic field of the recording layer, and Meff is perpendicular to the film surface. Effective magnetization of the recording layer minus the effect of the demagnetizing field acting in the direction, μ 0 is the vacuum permeability.

  On the other hand, the energy barrier that characterizes the thermal stability, that is, the energy required for magnetization reversal between two stable magnetization directions is given by Equation 2.

E to 1/2 × (Ms · Hk · S · t) (2)
Here, S is a cross-sectional area of the TMR pillar.

  As can be seen from Equations 1 and 2, both Jc0 and E are quantities proportional to Ms · t. Therefore, if Ms · t is increased in order to ensure thermal stability, Jc0 also increases and the power consumption required for writing increases. On the other hand, if Ms · t is decreased in order to reduce the threshold current, E is also decreased and the thermal stability is impaired. That is, Jc0 and E are in a trade-off relationship.

On the other hand, in the MRAM using the laminated ferri-recording layer described in Patent Document 2, since the magnetization directions of the recording layers are opposite to each other, the net magnetization having a vector action that is effective for spin torque magnetization reversal. There is an advantage that the value of Ms · t is reduced and Jc0 can be reduced. On the other hand, for the thermal stability, Ms · t in (Equation 2) is the sum of the total magnetizations of the two magnetic layers, so that the magnetic layer becomes thermally stable as the volume of the magnetic layer increases. That is, the laminated ferri-recording layer has a structure having both low Jc0 and high E. Hk which determines E of the laminated ferri-recording layer is Hk = Hku + r · Hsp (3)
Can be written. Here, Hku is an induced crystal magnetic anisotropy magnetic field, Hsp is a shape magnetic anisotropy magnetic field caused by the difference between the short side and long side length of the element cross section, and r is the upper and lower sides of the laminated ferri-recording layer. This is a coefficient representing the effect of the magnetostatic coupling magnetic fields of the two magnetic films shielding the shape magnetic anisotropic magnetic field.

  In general, the shape magnetic anisotropy field increases as the major axis / minor axis (aspect ratio) of the cross section of the element increases, but in the case of a magnetic memory using spin torque magnetization reversal, the magnetization of the recording layer is increased if the aspect ratio is too large. It is known that the inversion process becomes non-uniform, leading to an increase in recording current density and a decrease in thermal stability.

  To keep E constant regardless of memory miniaturization, it is necessary to increase Hk. Therefore, if the aspect ratio is increased to increase Hsp, the recording current density increases and the thermal stability decreases. End up. Accordingly, Hku must be increased to keep E corresponding to memory miniaturization. However, in the conventional magnetic memory, a soft magnetic material having a small coercive force Hc or Hku is used as the material of the recording layer, and thus it is impossible to increase Hku. Also, a hard magnetic material having a large Hku cannot be used as a recording layer as it is because the crystal axes of the crystal grains are scattered and the directions of magnetization are not uniform.

  An object of the present invention is to provide a magnetic memory having a small recording current density, excellent thermal stability, and suitable for miniaturization.

  As one form for achieving the above object, a magnetic memory including a selection transistor and a plurality of tunnel magnetoresistive effect elements connected to one end of the select transistor, wherein the tunnel magnetoresistive effect element is unidirectional. A first underlayer having a periodic texture; a second underlayer formed on the first underlayer and oriented in a rock salt structure; and formed on the second underlayer, hcp A laminate having a hard magnetic layer mainly composed of a Co-based alloy oriented in the (1010) direction, a nonmagnetic layer formed on the hard magnetic layer, and a soft magnetic layer formed on the nonmagnetic layer The Co base comprising the ferri recording layer, a barrier layer formed on the laminated ferri recording layer, and a ferromagnetic pinned layer formed on the barrier layer, and constituting the laminated ferri recording layer Hard magnets mainly composed of alloys A magnetic memory, characterized in that it is antiferromagnetically coupled to the said the layer soft magnetic layer.

  In the magnetic memory, the magnetization of the fixed layer is fixed by an exchange coupling force from an antiferromagnetic layer provided in contact with the fixed layer.

  In the magnetic memory, the pinned layer includes first and second ferromagnetic layers sandwiching a nonmagnetic intermediate layer, and the first and second ferromagnetic layers are antiferromagnetic with each other. The magnetic memory is characterized by being exchange-coupled to.

  In the magnetic memory, the Co-based alloy is an alloy made of a material containing at least Co, Pt, and Cr.

  In the magnetic memory, the Co-based alloy may include at least one of SiO2, TiO, TiO2, ZrO2, Cr2O3, CoO, and Ta2O5 as an additive.

  In the magnetic memory, the fixed layer is mainly composed of CoFeB, the barrier layer is composed of MgO, and the soft magnetic layer constituting the laminated ferri recording layer is composed mainly of CoFeB. .

  In the magnetic memory, the aspect ratio of the laminated ferri-recording layer in the in-plane direction of the recording layer is approximately 1.

  In the magnetic memory, the selection transistor is a field effect transistor.

  In the magnetic memory, a source line connected to the other end of the selection transistor not connected to the tunnel magnetoresistive element, a first write driver circuit connected to the source line, and the selection transistor A bit line connected to the other end of the tunnel magnetoresistive element not connected to the amplifier, an amplifier for amplifying a read signal and a second write driver circuit connected to the bit line, and a resistance of the selection transistor And a third write driver to which the word line is connected.

  A magnetic memory having a small recording current density, excellent thermal stability, and suitable for miniaturization can be provided.

It is a principal part schematic diagram of the magnetic memory for demonstrating the principle of spin torque magnetization reversal (magnetization reversal from an antiparallel state to a parallel state). It is a principal part schematic diagram of a magnetic memory in order to explain the principle (magnetization reversal from a parallel state to an antiparallel state) of spin torque magnetization reversal. It is a principal part schematic diagram of the other conventional magnetic memory. It is a principal part schematic sectional drawing of the magnetic memory which concerns on a 1st Example. It is a figure which shows the relationship between Ra and TMR ratio. It is a figure which shows an example of the magnetic field-magnetization hysteresis in a 1st Example. It is the schematic of the hard-magnetic layer for demonstrating the orientation effect (when there exists a texture) by a texture. It is the schematic of the hard-magnetic layer for demonstrating the orientation effect (when there is no texture) by a texture. It is a figure which shows an example of the magnetic field-magnetization hysteresis of a laminated ferri structure. It is a figure showing an example of the memory array circuit which concerns on a 2nd Example.

  Hereinafter, an example explains.

  First, the principle for obtaining a TMR element that achieves both high thermal stability and small Jc0 will be described.

  FIG. 3 is a cross-sectional view of a TMR film using a laminated ferrimagnetic recording layer having a hard magnetic layer of this example. In FIG. 3, 301 is a lower electrode, 302 is a textured underlayer, 303 is a rock salt underlayer for controlling the orientation of the hard magnetic film, 2 is a laminated ferri-recording layer, and 21 is a hard magnetic layer. Layer, 22 is a metal intermediate layer, 23 is a soft magnetic layer, 3 is a barrier layer, 4 is a laminated ferrimagnetic fixed layer, 41 is a soft magnetic layer, 42 is a metal intermediate layer (nonmagnetic layer), and 43 is a soft magnetic layer , 304 are antiferromagnetic layers for fixing the magnetization direction of the laminated ferrimagnetic pinned layer, and 305 is a cap layer. A magnetic memory can be configured by connecting a selection transistor to the TMR element. The function of each layer is described below.

  The texture underlayer 302 creates a difference in strain between two directions, a direction parallel to the texture and a direction perpendicular to the texture, and controls the in-plane orientation of the hard magnetic layer 21. The underlayer 303 has a specific crystal structure and controls crystal orientation in a direction perpendicular to the film surface of the hard magnetic layer 21 epitaxially grown thereon.

  The hard magnetic layer 21 has a large magnetocrystalline anisotropy magnetic field and contributes to the improvement of thermal stability. The hard magnetic layer 21 and the soft magnetic layer 23 are antiferromagnetically coupled via the metal intermediate layer (nonmagnetic layer) 22. The soft magnetic layer 23 is made of a material having a high spin polarizability, and has a function of reducing a threshold current density of spin torque magnetization reversal.

  That is, the soft magnetic layer 23 contributes to lower threshold current density and the hard magnetic layer 21 contributes to higher thermal stability. The laminated ferri-fixed layer 4 functions as a spin-polarized electron filter as in the conventional TMR element.

  Specific examples showing specific materials will be described in detail below. In this embodiment, a case where a Co-based alloy is used as the hard ferromagnetic layer 21 is shown. As the Co-based alloy, an alloy made of a material containing at least Co, Pt, and Cr, and other elements such as Mo, W, Ta, Ti, V, and B can be contained as a metal. In addition to these metals, oxidation of silicon dioxide (SiO2), titanium monoxide (TiO), titanium dioxide (TiO2), zirconia (ZrO2), chromium oxide (Cr2O3), CoO, tantalum pentoxide (Ta2O5), etc. A thing can also be contained.

  For example, Ru is used as the material of the soft magnetic layer 23 and CoxFeyBz as the material of the nonmagnetic layer 22. Particularly, a CoFe alloy having z of about 20% can obtain a high TMR ratio when MgO is used as the material of the barrier layer 3.

  As the material of the fixed layer, CoxFeyBz is used as the soft magnetic layer 41, Ru is used as the nonmagnetic layer 42, CoFe is used as the soft magnetic layer 43, and any of IrMn, PtMn, PdMn, FeMn, and IrCrMn is used as the antiferromagnetic layer 304. In order to direct the easy axis of magnetization of the Co-based alloy into the film plane, it is necessary to use an appropriate base.

  Furthermore, in order to direct the direction of the easy magnetization axis in one direction, it is necessary to control the distortion of the hard magnetic film 21 using a texture. Based on the study of various materials, we use a three-layer film of Ta / Ru / Ta with good flatness as the lower electrode 301, use Al as the base layer 302 to be textured thereon, and a hard magnetic layer thereon. As the underlayer 303 for controlling the crystal structure of No. 21, a two-layer film formed from the bottom in the order of NiAl alloy and Cr was used.

  This two-layer film has a rock salt structure and is particularly strongly oriented in the (112) direction. Typical film thicknesses are Ta (5 nm) / Ru (10 nm) / Ta (5 nm) for the lower electrode 301, Al (10 nm) for the underlayer 302, NiAl (10 nm) / Cr (10 nm) for the underlayer 303, and hard The magnetic layer 21 is CoCrPtB (6 nm), the nonmagnetic layer 22 is Ru (0.8 nm), the soft magnetic layer 23 is Co20Fe60B20 (2.5 nm), the barrier layer 3 is MgO (1 nm), and the soft magnetic layer 41 is Co20Fe60B20 (3 nm). ), The nonmagnetic layer 42 is Ru (0.8 nm), the soft magnetic layer 43 is CoFe (2.5 nm), and the antiferromagnetic layer 304 is IrMn (8 nm).

  Hereinafter, the case of this film thickness will be described in detail, but generally the film thickness is not limited to this. However, regarding the film thickness t1 of the hard magnetic layer 21 and the film thickness t2 of the soft magnetic layer 23, the following cautions are necessary. That is, when the saturation magnetization of the hard magnetic layer 21 is Ms1 and the saturation magnetization of the soft magnetic layer 23 is Ms2, | Ms1 · t1−Ms2 · t2 | <0.5 T · nm is desirable. This is to reduce the threshold current density Jc0 by reducing the effective amount of magnetization of the laminated ferri recording layer.

  First, the details of the texture will be described. The size of the texture irregularities can be evaluated by the average roughness Ra. Ra is an amount obtained by averaging the size of the unevenness measured by line scanning with an atomic force microscope by the length of the scanned line. In this example, Ra before applying the texture was about 0.08 nm. In order to add a texture to this, light ion beam etching is performed by making the beam incident obliquely from above the TMR element.

  FIG. 4 shows the relationship between the value of average roughness Ra and the characteristics of TMR. It can be seen that the TMR ratio decreases rapidly as Ra increases. The TMR ratio is represented by {(RH−RL) / RL} × 100 (%), where RL is a low resistance and RH is a high resistance. If Ra is 0.15 nm or more, a defect penetrating the barrier layer 3 is formed, and the characteristics of the TMR element are greatly deteriorated. As a result of detailed investigations of the element fabrication process by the inventors, it was found that an increase in magnetic anisotropy and maintenance of a large TMR ratio can be achieved by setting Ra = 0.15 nm or less.

  Next, characteristics of the NiAl / Cr alloy constituting the underlayer 303 will be described. First, a NiAl (10 nm) / Cr (10 nm) thin film was grown by sputtering on a flat Al film having no texture. The sputtering temperature is room temperature. At this time, when the crystal structure perpendicular to the Al film surface was evaluated by X-rays of θ-2θ type, a strong (112) orientation of the rock salt structure was detected.

  After CoCrPtB, which becomes a hard magnetic layer, was grown by sputtering and then evaluated again by θ-2θ type X-ray, it was found that CoCrPtB was strongly oriented in the (10-10) direction. It was. Therefore, when an X-ray pole figure was taken in order to investigate the orientation in the CoCrPtB film surface, no particularly strong orientation was observed.

  When the microstructure of the CoCrPtB film was further examined by cross-sectional TEM observation, the CoCrPtB film had a granular structure composed of crystal grains, and Cr was segregated between adjacent crystal grains.

  Therefore, NiAl (10 nm) / Cr (10 nm) / CoCrPtB (6 nm) was formed on the Al film subjected to the texture processing by the ion beam treatment as described above. First, it was confirmed again that CoCrPtB was strongly oriented in the (10-10) direction when evaluated with ordinary θ-2θ type X-rays. Next, when the pole figure on the X-ray was evaluated, it was confirmed that the (0001) direction of CoCrPtB was oriented in a direction parallel to the texture.

  Since the easy axis of CoCrPtB is in the (0001) direction, it is expected from this fact that the easy axis is induced only in the direction parallel to the texture. FIG. 5 is a magnetic field-magnetization hysteresis curve when an external magnetic field is applied in a direction parallel to the texture. Thus, in the case of the CoCrPtB film of this example, it was found that the direction parallel to the texture is the easy axis of magnetization, the coercive force is about 3000 Oe, and the anisotropic magnetic field is about 6000 Oe.

  As described above, FIGS. 6 (a) and 6 (b) are diagrams illustrating the orientation of the case where the texture is introduced and the case where the texture is not introduced. When the texture is introduced, the crystal axis and the easy axis of magnetization are aligned in a direction parallel to the texture as shown in FIG. This induces uniaxial magnetic anisotropy. On the other hand, when no texture is introduced, the crystal axis and the easy axis of magnetization are randomly distributed in the plane as shown in FIG. 6B, so that no uniaxial magnetic anisotropy is induced.

  Next, when a Ru / Co20Fe60B20 film was formed on the CoCrPtB film grown on the textured Al / NiAl / Cr film and the magnetic characteristics were evaluated, a two-stage hysteresis curve as shown in FIG. 7 was observed. This two-stage hysteresis curve is caused by the exchange coupling magnetic field (Hex to 850 Oe) felt by CoFeB. The CoCrPtB film and the Co20Fe60B20 film are antiferromagnetically coupled via the Ru film. confirmed.

  As described above, it was confirmed that (1) the CoCrPtB film is aligned in the uniaxial direction in the plane, and (2) the CoCrPtB film and the Co20Fe60B20 film are antiferromagnetically coupled to function as a laminated ferri layer. Next, in order to confirm the actual spin torque magnetization reversal characteristics, an exchange-biased TMR element (see FIG. 3) in which the direction of the fixed layer is fixed by the exchange coupling magnetic field of the antiferromagnetic film is manufactured. Evaluated. After film formation, the TMR film was processed into a 50 × 50 nm square by electron beam drawing and ion beam etching, and finally heat-treated at a temperature of 300 ° C. in a magnetic field to obtain a measuring element.

  Next, the electrical characteristics of the fabricated device were measured. The plus in the current direction is the direction in which current flows from the fixed layer 4 to the recording layer 2. At this time, the magnetization direction of the ferromagnetic film 21 that opposes the fixed layer 4 via the insulating layer 3 is the same as that of the fixed layer 4. The magnetization is reversed from the parallel direction to the antiparallel direction with respect to the magnetization direction. Conversely, when a current is passed in the negative direction, the magnetization direction of the ferromagnetic film 21 opposed through the fixed layer 4 and the insulating layer 3 is magnetized from the antiparallel direction to the parallel direction with respect to the magnetization direction of the fixed layer 4. Invert.

  The value of Jc0 is an arithmetic average of Jc0 in the spin torque magnetization reversal of both the magnetization reversal from the parallel direction to the antiparallel direction and the magnetization reversal from the antiparallel direction to the parallel direction. The TMR ratio was almost 100% for all elements, and the sheet resistance RA was about 10 ΩμmΛ2 (square micron).

  Next, an experiment of spin torque magnetization reversal was performed. In the experiment, the current density required for the magnetization reversal was measured by changing the width of the current pulse used for the magnetization reversal, and the threshold current density Jc0 and the thermal stability index Δ = E / kBT were calculated. As a result, Jc0 was 1.5 MA / cmΛ2 (square centimeter) and Δ = 350, and Δ, which was 10 or less in the past, could be greatly improved (30 times or more). As a result, the area of the tunnel magnetoresistive effect element can be reduced to about 1/30 of the conventional one.

  First, Jc0 is small because a laminated ferrimagnetic structure is used. The saturation magnetization Ms of Co20Fe60B20 used in this example is about 1.0T, the saturation magnetization Ms of CoCrPtB is 0.4T, and both Ms · t (t indicates the thickness of the magnetic layer) is 0. 1 T · nm. Since the effective amount of magnetization is small in this way, a small Jc0 can be obtained.

  On the other hand, the reason why a large Δ is obtained is that the magnetocrystalline anisotropy magnetic field Hku of CoCrPtB is as extremely large as 6000 Oe. This is a result that could not be achieved with a conventional magnetic memory using a soft magnetic film, and the in-plane uniaxial orientation of the CoCrPtB film was realized using a NiAl / Cr underlayer and a texture formed by ion beam etching. It depends on what was done.

  A conventional tunnel magnetoresistive effect element using a soft magnetic film uses magnetic anisotropy due to a shape magnetic anisotropy magnetic field Hsp, so that the element has a so-called aspect ratio (aspect ratio) such as a rectangle or an ellipse. It was necessary to make it larger. However, in the present embodiment, a large Hk and Δ value can be realized even with a square (aspect ratio: 1) element, which has a great effect on miniaturization of the magnetic memory size. Further, the value of Δ is a value at which Δ = 87.5 even if the element size is 25 × 25 nm, and is a value that can sufficiently cope with further miniaturization of the element. When the aspect ratio is approximately 1, it indicates a range of 0.9 to 1.1.

  In this embodiment, the rock salt structure underlayer is formed on the textured underlayer, but conversely, the textured underlayer may be formed on the rock salt structure underlayer. In addition, CoCrPtB was used, but when at least one oxide such as SiO2, TiO, TiO2, ZrO2, Cr2O3, CoO, Ta2O5 was added to this, grain boundary separation occurred due to segregation of the oxide to the grain boundary. The structure can be promoted to form a granular structure more clearly.

  The granular structure is a structure in which nanoscale metal fine particles are densely dispersed in an insulator matrix, and electric conduction is caused by an electron tunnel effect between the fine particles. In this case, the spin torque magnetization reversal can be further smoothed. However, if the grain boundary separation structure is promoted too much and the crystal grains are isolated, each crystal grain becomes a magnetization reversal volume unit. As a result, Δ decreases. It is desirable that the oxide be added in an amount smaller than that in normal magnetic recording medium production, for example, several percent or less with respect to CoCrPtB.

  As described above, according to this embodiment, a magnetic memory having a small recording current density, excellent thermal stability, and suitable for miniaturization can be provided.

  Next, a second embodiment will be described with reference to FIG. The matters described in the first embodiment and not described in the present embodiment are the same as those in the first embodiment.

  FIG. 8 shows an example of a memory circuit. In FIG. 8, reference numeral 1 denotes a bit line, reference numeral 81 denotes the TMR element described in the first embodiment, reference numeral 7 denotes a source line, reference numeral 6 denotes a cell selection transistor, reference numeral 82 denotes a word line, and reference numeral 87 denotes one memory cell. Reference numerals 101-1, 101-2, and 101-2 'denote write drivers, reference numerals 102-1 and 102-2 denote resistance control drivers, and reference numeral 103 denotes a sense amplifier. Reference numerals 83 and 85 are resistance change elements (transistors in this example) for controlling the magnitude of the current flowing through the bit line, and reference numerals 84 and 86 are resistance control elements for controlling the conduction state of the resistance change elements 83 and 85. This is a word line. A field effect transistor was used as the selection transistor 6.

  In the case of writing in this configuration, for example, when writing to the memory cell 87, first, the write enable signal is sent to the write driver connected to the bit line 1 through which a current is desired to be boosted, and then the resistance control driver A predetermined current is passed through the bit line 1 by controlling the voltage. Depending on the direction of the current, either the write driver connected to the resistance change element 83 or the write driver connected to the resistance change element 85 is dropped to the ground, and the current direction is controlled by adjusting the potential difference.

  Next, after a predetermined time has elapsed, a write enable signal is sent to the write driver connected to the word line, the write driver is boosted, and the selection transistor 6 is turned on. As a result, a current flows through the TMR element, and spin torque magnetization reversal is performed. After the selection transistor 6 is turned on for a predetermined time, the signal to the write driver is disconnected and the selection transistor 6 is turned off.

  At the time of reading, only the bit line 1 connected to the memory cell to be read is boosted to the read voltage V, only the source line connected to the selection transistor 6 is selected by the other write driver, the transistor 6 is turned on and the current is turned on. The voltage difference applied to both ends of the resistance of the TMR element is amplified by the sense amplifier, and reading is performed.

  In this case, the current direction at the time of reading is always from the source line 7 to the bit line 1. This reduces erroneous writing due to the read current and allows a larger read current to flow, thereby enabling high-speed reading. Since this structure is the simplest arrangement of 1 transistor + 1 memory cell, the area occupied by the unit cell can be made highly integrated as 2F × 4F = 8F∧2.

  As described above, according to this embodiment, a magnetic memory having a small recording current density, excellent thermal stability, and suitable for miniaturization can be provided. In addition, a magnetic memory circuit can be provided.

DESCRIPTION OF SYMBOLS 1 ... Bit line, 2 ... Recording layer, 3 ... Barrier layer, 4 ... Fixed layer, 5 ... Gate electrode, 6 ... Selection transistor, 7 ... Source line, 8 ... Current direction, 9 ... Direction where electron moves, 21 ... Hard magnetic layer, 22 ... nonmagnetic layer, 23 ... soft magnetic layer, 41 ... soft magnetic layer, 42 ... nonmagnetic layer, 43 ... soft magnetic layer, 81 ... TMR element, 82 ... word line, 83, 85 ... resistance control Element, 84, 86 ... Resistance control element control word line, 87 ... Memory cell, 101-1, 101-2, 101-2 '... Write driver, 102-1, 102-2 ... Resistance control driver, 103 ... Sense Amplifiers 210, 230 ... ferromagnetic layer, 220 ... nonmagnetic layer, 301 ... lower electrode layer, 302 ... texture underlayer, 303 ... underlayer, 304 ... antiferromagnetic layer, 305 ... cap layer.

Claims (10)

A magnetic memory including a selection transistor and a plurality of tunneling magneto-resistance effect elements connected to one end of the selection transistor,
The tunnel magnetoresistive element is
A first underlayer having a periodic texture in one direction;
A second underlayer formed on the first underlayer and oriented in a rock salt structure;
A hard magnetic layer mainly formed of a Co-based alloy oriented in the hcp (1010) direction; a nonmagnetic layer formed on the hard magnetic layer; A laminated ferri-recording layer having a soft magnetic layer formed on the magnetic layer;
A barrier layer formed on the laminated ferri-recording layer;
A ferromagnetic pinned layer formed on the barrier layer,
A magnetic memory, wherein the hard magnetic layer mainly comprising the Co-based alloy constituting the laminated ferri recording layer and the soft magnetic layer are antiferromagnetically coupled. The magnetic memory according to claim 1.
The magnetic memory according to claim 1, wherein the magnetization of the fixed layer is fixed by an exchange coupling force from an antiferromagnetic layer provided in contact with the fixed layer. The magnetic memory according to claim 1 or 2,
The pinned layer includes first and second ferromagnetic layers sandwiching a nonmagnetic intermediate layer, and the first and second ferromagnetic layers are antiferromagnetically exchange-coupled to each other. Features magnetic memory. The magnetic memory according to any one of claims 1 to 3,
The magnetic memory according to claim 1, wherein the Co-based alloy is an alloy made of a material containing at least Co, Pt, and Cr. The magnetic memory according to claim 4.
The Co-based alloy includes at least one of SiO2, TiO, TiO2, ZrO2, Cr2O3, CoO, and Ta2O5 as an additive. The magnetic memory according to any one of claims 1 to 5,
The magnetic memory characterized in that the fixed layer is mainly composed of CoFeB, the barrier layer is composed of MgO, and the soft magnetic layer constituting the laminated ferri-recording layer is mainly composed of CoFeB. The magnetic memory according to any one of claims 1 to 6,
2. A magnetic memory according to claim 1, wherein an aspect ratio of the laminated ferri recording layer in the in-plane direction of the recording layer is approximately 1. The magnetic memory according to any one of claims 1 to 7,
The magnetic memory according to claim 1, wherein the selection transistor is a field effect transistor. The magnetic memory according to any one of claims 1 to 8,
A source line to which the other end of the selection transistor not connected to the tunnel magnetoresistive element is connected;
A first write driver circuit connected to the source line;
A bit line to which the other end of the tunnel magnetoresistive element not connected to the selection transistor is connected;
An amplifier for amplifying a read signal and a second write driver circuit connected to the bit line;
A word line for controlling the resistance of the selection transistor;
And a third write driver to which the word line is connected. The magnetic memory according to any one of claims 1 to 9,
The first underlayer is formed on the second underlayer,
The magnetic memory, wherein the hard magnetic layer is formed on the first underlayer.

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