JP2005150482A - Magnetoresistance effect element and magnetic memory device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a magnetoresistance effect element, an inverting current and inverting current density of which are reduced by enhancing the efficiency of spin injection magnetization reversal, while maintaining a high rate of a change in magnetic reluctance independently of the reduction in the in-plane size and the film thickness of a storage cell, and to provide a magnetic memory device. <P>SOLUTION: The magnetoresistance effect element comprises a spin injection magnetization reversal element 10 including a magnetization free layer (storage layer) 1, and a first spin filter layer 2 and a second spin filter layer 12 located at both sides of the magnetization free layer while being magnetically separated by nonmagnetic spacer layers 3, 13 respectively. The magnetization directions of the spin filter layers are reversely fixed, and the magnetic memory device comprises an MRAM the memory cell part of which is configured with the magnetoresistance effect element. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a magnetoresistive effect element configured such that information is written to a magnetization free layer by spin injection magnetization reversal by current, and stored information is read by current, and a magnetic memory device using the magnetoresistive effect element Is.

  As a nonvolatile memory, an MRAM (Random Access Memory) with high speed, high integration, and low power consumption is known. The MRAM has a structure shown in FIG. 13, for example, and a TMR (Tunneling Magneto Resistive) element 100 serving as a memory element of a memory cell includes a memory layer 101 and a magnetization fixed layer 102 whose magnetization rotates relatively easily, A tunnel barrier layer 103 made of an insulator is sandwiched between the storage layer 101 and the magnetization fixed layer 102 so that the magnetic coupling between the storage layer 101 and the magnetization fixed layer 102 is cut and a tunnel current flows. Play the role of Note that the top coat layer on the storage layer 101 and the underlying conductive layer under the magnetization fixed layer 102 are not shown.

  For example, a source region 106 and a drain region 107 are formed in a p-type well region 105 formed in the p-type silicon semiconductor substrate 104, and a gate insulating film 108 and a gate electrode formed between these regions. An insulated gate field effect transistor 110 for n-type readout is configured together with 109. A write word line 111, a TMR element 100, and a bit line 112 are disposed on the transistor 110 (however, an interlayer insulating film is not shown). A sense line 114 is connected to the source region 106 via a source electrode 113. The field effect transistor 110 functions as a switching element for reading, and a read bypass wiring 115 drawn from between the word line 111 and the TMR element 100 is connected to the drain region 107 via the drain electrode 116. .

  In writing information, current is passed through the bit lines 112 and the word lines 111 wired in a matrix, and the magnetic spin of the cell (memory layer 101) is inverted by the synthetic magnetic field at the intersection, and the direction is shown in FIG. Thus, information is recorded as “1” and “0” information. In addition, reading is performed using the TMR effect (a phenomenon in which the resistance value changes depending on the direction of the magnetic spin) applying the magnetoresistive effect, and the state in which the magnetic spin is antiparallel and the resistance is high. In the low state, information “1” and “0” are detected by the read current.

  However, such writing in the MRAM is performed by the current magnetic field generated from the bit line 112 and the word line 111 (both current lines) orthogonal to each other. Therefore, when the memory cell is reduced in order to increase the storage capacity, the reversal magnetic field rapidly increases. There is a problem that the required current increases rapidly. In addition, when the size of the memory cell is about 200 nmφ or less, which is necessary to make the capacity exceed gigabit (Gbit), the upper limit of the allowable current density of the wiring is exceeded, and there is a problem that writing becomes difficult.

  In contrast, spin injection magnetization reversal, which is reversed by supplying a polarized spin current (spin injection), has a feature that the current required for magnetization reversal decreases as the memory cell size decreases. Is preferred.

  FIG. 15 shows an example 120 of a spin transfer magnetization reversal element (a magnetoresistive effect element capable of spin transfer magnetization reversal) having a conventional structure shown in Non-Patent Documents 1 and 2 described later. This main film structure is composed of a storage layer (magnetization free layer) 121 made of a magnetic film, a nonmagnetic spacer layer 123, and a spin filter layer (magnetization pinned layer) 122 made of a magnetic film. Further, after being laminated in the order shown in the figure on the base film made of the antiferromagnetic layer 124, electrodes (not shown) are provided on the memory layer 121 and the antiferromagnetic layer 124 (this is not shown). The stacking order of the multilayer film may be reversed upside down). In this multilayer film, a magnetization fixed layer (also referred to as a magnetic film as a reference layer) constituting the magnetoresistive film also serves as a spin filter layer 122 for obtaining a polarized spin current. That is, the magnetoresistive effect film is configured such that a resistance change is caused by a difference in relative angle between the magnetization directions of the storage layer 121 and the spin filter layer (magnetization pinned layer) 122 (when the parallel arrangement is used, the resistance is small and the antiparallel arrangement is used). In the case of resistance is large).

Here, the saturation magnetization (M _S : magnetic moment per unit volume) × film thickness (t) of the spin filter layer 122 is set to be larger than that of the storage layer (magnetization free layer) 121. Alternatively, it may be said that the number of magnetic moments per unit area of the spin filter layer 122 is set to be larger than that of the storage layer 121. Alternatively, the film thickness of the spin filter layer 122 may be larger than the spin diffusion length of the magnetic film, and the film thickness of the storage layer 121 may be smaller than the spin diffusion length of the magnetic film. If the spin filter layer 122 and the storage layer 121 are made of the same magnetic material, the film thickness of the spin filter layer 122> the film thickness of the storage layer 121.

The memory layer 121 is a memory cell that is processed so that the in-plane size is ˜200 nmφ or less, and is substantially made into a single magnetic domain. The memory cell has a shape having an aspect ratio (aspect ratio), for example, an ellipse (see FIG. 17B) in order to have shape magnetic anisotropy. Although the processing region of the memory cell is shown to include up to the spin filter layer 122 in FIG. 15, the processing is stopped on the upper surface of the spin filter layer 122, and from the spin filter layer 122 as shown in FIG. The leakage magnetic field may be prevented from reaching the storage layer 121. The memory cell is embedded in a surrounding nonmagnetic insulating film (SiO ₂ , Al ₂ O _3, etc.) 125, and an electrode 142 is formed thereon.

  FIG. 17 shows a structural example (1 transistor-1 memory cell: 1T1J) in which the spin transfer magnetization switching element 120 is incorporated in the MRAM. For example, in the p-type well region 135 formed in the p-type silicon semiconductor substrate, FIG. The source region 136 and the drain region 137 are formed, and together with the gate insulating film 138 and the gate electrode 139 formed between these regions, an n-type insulated gate field effect transistor 130 for writing and reading is configured. . On this transistor 130, the spin transfer magnetization switching element 120 is connected to the bit line 142 via a cap layer 140 (not shown) (however, the interlayer insulating film 141 is shown in a simplified manner). A sense line is connected to the source region 136 through a plug 143a and a source electrode 143. The drain region 137 of the field effect transistor 130 is connected to the element 120 via the drain electrode 146 and the plug 146a. In this MRAM, a write word line and a read bypass wiring which are necessary for the memory cell of FIG. 13 using a TMR element are unnecessary for writing and reading described later.

  In FIG. 15, an arrow drawn in the magnetic film indicates the magnetization direction. The magnetization of the storage layer (magnetization free layer) 121 can be freely reversed to the right or left in the figure. The magnetization of the spin filter layer 122 is fixed in one direction, and functions as a spin filter for forming a polarized spin current that flows perpendicular to the film surface. The magnetization of the spin filter layer 122 is fixed by exchange coupling with the antiferromagnetic layer (AF layer) 124 in FIG. Instead of using such an AF layer, a so-called coercive force difference type using the difference in coercivity between the memory layer 121 and the spin filter layer 122 may be used (the same applies hereinafter).

As a constituent material of the nonmagnetic spacer layer 123, Cu, Al ₂ O ₃ or the like is used. The former is a GMR film (giant magnetoresistive film), and the latter is a TMR film (tunnel magnetoresistive film). The thickness of the spacer layer 123 is appropriately determined in consideration of the spacer material, the magnetic interlayer interaction between the magnetic films, the resistance value of the element, and the like. When the spacer layer 123 has a structure as a CPP-GMR film (a direct current giant magnetoresistive film) using a metal film, a magnetic interlayer interaction between the memory layer 121 and the spin filter layer 122 does not occur. And a thickness of ˜5 nm or more. If it is too thick, scattering of conduction electrons increases, so it is desirable that the thickness be about several tens of nm or less. When the spacer layer 123 has a structure as a TMR film using Al ₂ O ₃ , the product RA of the resistance and the film area of the TMR film is set to be several Ωμm ² or less in order to prevent dielectric breakdown due to the applied voltage. , Al ₂ O ₃ film thickness must be set (approximately 0.5 to 0.7 nm).

Kojiro Rooftop: 50th Joint Conference on Applied Physics, (2003), 27p-N-1; 1st Technical Meeting on Nanomagnetics, Japan Society of Applied Magnetics, (2003.4.25); AIST Workshop “Spintronics New tides, ”(2003.6.3-4), 21; K. Yagami, A. Tulapurkar and Y. Suzuki: PASPS-9, (2003.6.11-12), D7, 228-231. Kojiro Rooftop and Yoshishige Suzuki: “Materia” Vol. 42, No. 9 (2003) P640-647 “Current Status and Issues of Spin-Injection Magnetization Reversal”

However, at present, the spin injection magnetization reversal requires a current of several mA and a current density of 10 ⁷ A / cm ² , and the dielectric breakdown of the memory element using the TMR film, the element selection FET (field effect) Problems such as breakdown of transistors) occur. In addition, adjusting related factors in order to lower the reversal current or current density has the problem of reducing the resistance to thermal fluctuations and increasing the magnetization reversal time. Further, the value of the reversal current I _C ⁺ that changes the magnetization arrangement from parallel to anti-parallel and the reversal current I _C ⁻ that changes from anti-parallel to parallel are different (| I _C ⁺ |> | I _C ⁻ |). However, this will be described later in detail.

  In order to reduce the reversal current, for example, if the area of the memory cell is reduced, the reversal current is reduced proportionally, but the current density is not reduced. In this method, even if the inversion current decreases, the element resistance increases as the memory cell area decreases, so the voltage applied to the element does not decrease. Therefore, the breakdown of the element or the breakdown of the FET Cannot be avoided.

  Further, if the thickness of the memory cell is reduced, both the reversal current and the current density are reduced, but a practical lower limit thickness (2 nm) in consideration of the interface reaction between the upper and lower films adjacent to the memory layer (magnetization free layer). However, it is difficult to significantly reduce the film thickness further.

Decrease in plane size or thickness of the above-described memory cells, it becomes possible to reduce the volume V of the memory cell, thus reducing the magnetic anisotropic energy K _u V of the memory cell, as a result, the thermal fluctuation resistance (K _U V / k _B T) is lowered, which is not desirable. Since the reversal current is substantially proportional to the memory cell volume, the reversal current can be reduced by an order of magnitude if the volume is reduced by an order of magnitude. However, the thermal fluctuation resistance is also reduced by an order of magnitude, making it difficult to maintain K _U V / k _B T _300K > 60, which is required as a magnetic memory (K _U : magnetic anisotropy per unit volume). Energy, k _B : Boltzmann constant, T: temperature, generally 300 K).

The reduction of the saturation magnetization M _S of the memory layer is effective in reducing the reversal current and the reversal current density because the reversal current I _C and the reversal current density J _C are approximately proportional to the square of M _S. Fluctuation resistance decreases.

  Reducing the demagnetizing field in the film thickness direction of the memory layer is effective in reducing the reversal current and reversal current density, but increases the magnetization reversal time.

  Improving the polarizability of the memory layer does not affect the thermal fluctuation resistance and inversion time, and can reduce the inversion current and the inversion current density, but using an ideal polarizability 1.0 material (half metal) However, the reversal current and reversal current density are only reduced to about half.

On the other hand, magnetization is reversed at a current density of 10 ⁶ A / cm ² by using a magnetic field generated by a current flowing perpendicularly to the film surface by making the cell size into the order of several μm to form multiple magnetic domains. However, since the reversal current is as large as several tens mA and the cell size is large, there is a problem that the capacity of the memory cannot be increased.

By making the resistance of the TMR film extremely small, it is possible to perform spin injection magnetization reversal without causing dielectric breakdown. However, since the magnetoresistance change rate is reduced, the S / N ratio is lowered, and the magnetic memory It is difficult to use. For example, by reducing the product RA of the resistance and the area of the memory cell to several Ωμm ² , the voltage required for the magnetization reversal becomes about 0.5 V, and the dielectric breakdown voltage of the TMR film at this time is 0.7 to 0. It can be 8 V or less. However, at this time, the TMR ratio required for securing the S / N ratio as a magnetic memory is 40% or more, and the actual TMR ratio is about several percent, so that it is difficult to use at present. .

As described above, it is desired to reduce I _C and J _C while maintaining a high rate of change in magnetic resistance without reducing thermal fluctuation resistance and without increasing the inversion time, but it has not yet been realized. Absent.

  Next, an approximate description of spin injection magnetization reversal will be given. A current necessary for writing is passed in a direction perpendicular to the film surface (that is, the stacking direction of the multilayer film). In FIG. 15, the direction in which electrons flow from the storage layer (magnetization free layer) 121 to the spin filter layer 122 is defined as + current (+ I), and the opposite is defined as −current (−I). In the figure, electrons are represented by ●, and the arrow above ● represents the direction of spin.

  In the case of −I, the down spin (spin parallel to the magnetization direction of the spin filter layer 122) is reflected by the spin filter layer 122, but the up spin (spin parallel to the magnetization direction of the spin filter layer 122) has no resistance. Passes through the spin filter layer 122 and enters the storage layer 121. The upspin (s electrons) that enters the memory layer 121 interacts with the magnetic moment (d electrons) of the memory layer 121 (sd-interaction), gives a torque for reversal to the magnetic moment of the memory layer 121, and stores the memory. The magnetization of the layer 121 is aligned parallel to that of the spin filter layer 122.

  On the other hand, in the case of + I, the storage layer 121 is sufficiently thin (the thickness of the storage layer 121 is equal to or less than the spin diffusion length of the storage layer magnetic film), so that both upspin and downspin can pass through, but upspin passes through the spin filter layer 122. While passing without resistance, the down spin is reflected by the surface of the spin filter layer 122 and returns to the storage layer 121 while maintaining the spin angular momentum (without changing the spin direction). The reflected down spin passes through the memory layer 121 again by the action of the electric field, and is reflected again at the interface with the spin filter layer 122. That is, the down spin causes multiple reflection, and apparently, the down spin (s electrons) flowing into the storage layer 121 is larger than the up spin (s electrons). As a result, the sd-interaction has the effect of downspin, and the magnetization of the storage layer 121 is directed to the left in the drawing, that is, opposite to the magnetization of the spin filter layer 122, thereby realizing an antiparallel arrangement.

  As can be seen from the above principle, in the realization of the inversion from the antiparallel arrangement to the parallel arrangement as shown in FIG. 16A, only the upspin in the current acts on the magnetic moment (d electrons) of the memory layer 121. On the other hand, in the realization of the inversion from the parallel arrangement to the antiparallel arrangement as shown in FIG. 16B, the action of the up spin electrons is added together with the down spin electrons in the current. In the latter case, the reverse current required to change the parallel moment from the antiparallel arrangement to the parallel arrangement is applied to give the torque that the up spin electrons reverse the magnetic moment reversed by the down spin electrons. It becomes larger than the reversal current for That is, the asymmetry of the reversal current occurs.

Here, the critical current equation of magnetization reversal described in the literature “Materia” Vol. 42 No. 9 (2003) P640-647 “Present state and problems of spin injection magnetization reversal” is shown. Assuming that the magnetic moment of the memory layer magnetic film converges to θ = 0 or π (that is, relaxes), an extended LLG (Landau-Lifschitz-Gilbert) equation with a spin torque term is solved analytically, I _C ^{P → AP} (the critical current value at which the magnetization arrangement equilibrium is from the parallel state to the antiparallel state) and I _C ^{AP → P} (the critical current value at which the magnetization arrangement equilibrium is from the antiparallel state to the parallel state) ) Are respectively expressed by the following equations (1) and (2).

［ここで、ｅは電子の電荷、αは制動係数、γはジャイロ磁気定数（＞０）、θは記憶層磁性膜の磁化方向とスピンフィルター層（磁化固定層）磁性膜の磁化方向との成す角、Ｈ_extは外部印加磁界、Ｈ_aniは記憶層の異方性磁界であって、一軸異方性を持つ単磁区の記憶層においてはＨ_Cに等しい。Ｍ_Sは記憶層の飽和磁化、μ_Bはボーア磁子、Ａ及びｄはそれぞれ記憶層の面積と厚さである。２πＭ_Sは、膜厚方向の反磁界に相当する（４πＭ_Sの１／２）。ｇ(θ)（＞０）はスピン注入磁化反転効率を表し、ｇ(０)はθ＝０、即ち、磁化平行配列から反平行配列への反転のとき、ｇ(π)はθ＝π、即ち、磁化反平行配列から平行配列への反転のときのスピン注入磁化反転効率である。］

[Where e is the charge of the electron, α is the damping coefficient, γ is the gyromagnetic constant (> 0), θ is the magnetization direction of the magnetic film of the storage layer and the magnetization direction of the magnetic film of the spin filter layer (magnetization fixed layer). The angle formed, H _ext is an externally applied magnetic field, and H _ani is the anisotropic magnetic field of the memory layer, and is equal to H _C in a single magnetic domain memory layer having uniaxial anisotropy. M _S is the saturation magnetization of the storage layer, μ _B is the Bohr magneton, and A and d are the area and thickness of the storage layer, respectively. 2πM _S corresponds to a demagnetizing field in the film thickness direction (1/2 of 4πM _S ). g (θ) (> 0) represents spin injection magnetization reversal efficiency, and g (0) is θ = 0, that is, g (π) is θ = π, when reversal from magnetization parallel arrangement to antiparallel arrangement is performed. That is, it is the spin injection magnetization reversal efficiency when reversing from the magnetization antiparallel arrangement to the parallel arrangement. ]

In these equations (1) and (2), g (θ) is a geometric scalar function related to the spin-dependent transmittance and the spin-flip scattering that can occur in the multilayer system. It is expressed as the following equation (3).

In this equation (3), g (0) <g (π) regardless of the value of P. Therefore, regardless of the magnetic field term in [] of the molecule in the above equations (1) and (2), It can be seen that | I _C ^{P → AP} |> | I _C ^{AP → P} | (H _ext = 0).

  The object of the present invention is to improve the efficiency of magnetization reversal while maintaining a high rate of change in magnetic resistance without reducing the in-plane size and film thickness of the memory cell, and to reduce the reversal current and reversal current density. A resistive effect element and a magnetic memory device are provided.

  That is, the present invention provides a magnetization free layer (storage layer), and a first magnetic layer and a second magnetic layer (spin filter layer or magnetization pinned layer) that are magnetically separated and arranged on both sides of the magnetization free layer, respectively. And a magnetoresistive effect element in which the magnetization directions of these magnetic layers are fixed to be opposite to each other, and a magnetoresistive memory device in which the magnetoresistive effect element constitutes a memory cell portion.

According to the present invention, the first and second magnetic layers whose magnetization directions are opposite to each other are magnetically insulated and arranged on both sides of the magnetization free layer (storage layer), specifically on the upper and lower sides thereof. The efficiency of magnetization reversal by injecting a polarized spin current into the memory layer, particularly the reversal efficiency (g (0) described above) for making the parallel arrangement → antiparallel arrangement significantly improved. As a result, the magnetization reversal current and Both reversal current densities can be reduced by an order of magnitude or more from the conventional structure. Depending on the size of the memory cell, the material of the nonmagnetic spacer, and the material of the magnetic film, the magnetization reversal current is 1 mA or less and the reversal current density is ~ 5 × 10 ⁶ A / cm in a memory cell having a size of ~ 200 nmφ or less. Can be ² or less.

As described above, since the reversal current in the memory cell can be reduced to 1 mA or less, it is not necessary to make the RA of the memory cell extremely small as several Ωμm ² as in the prior art, and spin injection is also performed in the memory cell of several tens of Ωμm ² RA. Magnetization reversal becomes possible. For this reason, it is easier to manufacture than conventional magnetoresistive elements that enable spin injection magnetization reversal due to low resistance (several Ωμm ² ), high manufacturing yield, high reliability, and conventional magnetoresistive effect. The breakdown voltage is higher than that of the element, and the magnetoresistance ratio (magnetoresistivity change rate) is further increased.

Therefore, according to the present invention, without decreasing the M _S and volume of the storage cell, since reducing the switching current by improving the efficiency of spin injection magnetization reversal, there is no reduction in thermal stability, also, the inversion time There is no increase. Thus, after reducing the inversion current and the inversion current density, it is possible to realize the thermal fluctuation resistance (K _U V / k _B T _300K )> 60 and the inversion time (τ) <˜5 nsec.

Thermal fluctuation resistance can be improved by increasing the coercive force H _C (or anisotropic magnetic field), which mainly depends on the shape of the memory cell, but the reversal current also increases. According to the present invention, since the effect of reducing the reversal current sufficiently exceeding the increase in reversal current due to the increase in H _C can be obtained, it becomes possible to make H _C larger by one digit or more than the conventional structure. Along with this, effects such as reduction of the magnetization reversal time τ, reduction of the influence of the disturbance magnetic field on the write state, and reduction of fluctuation of the reversal current due to the external magnetic field can be obtained.

Further, according to the present invention, since the influence of _HC variation on the reversal current value is small, the demand for memory cell shape control is relaxed, which is advantageous in mass production.

Spin injection magnetization reversal can change the magnetization direction of the storage layer by changing the direction of current flow. However, according to the present invention, the current spin polarization can be made the same in both current directions. Therefore, there is no difference in the magnitude of I _C ^± , and the problem of asymmetry of the reversal current is eliminated.

  According to the present invention, since the spin-polarized current (electrons) is reflected multiple times while passing through the storage layer, the effective polarizability of the storage layer magnetic film is improved and the magnetoresistance ratio is improved. That is, the effective polarizability can be improved without changing the material of the memory layer.

Furthermore, according to the present invention, spin injection magnetization reversal in the magnetoresistive effect element can be performed by a minute current, and therefore, writing in the MRAM can be efficiently performed by spin injection magnetization reversal. For this reason, it is possible to miniaturize the element (memory cell size is 0.2 μmφ or less), to increase the capacity of the MRAM beyond Gbit, and to scale the capacity corresponding to the design rule to be reduced. Can be increased. Further, the element area corresponding to 1 bit can be reduced to 6F ² (F is equivalent to the wiring width according to the design rule) which is the theoretical minimum area.

  Furthermore, since the spin injection magnetization can be reversed, the structure is simplified. That is, a current magnetic field generating word line is not required, a bypass line connecting the element and the drain of the FET is not required, and a clad structure in which a magnetic film is disposed around the current line for current magnetic field convergence is not required. Since writing and reading can be controlled by changing the magnitude of the current flowing through the element, the control circuit is simplified. For example, writing is performed with a current of about 100 μA, and a signal can be read with a current of about 10 μA.

  As described above, a large-capacity nonvolatile magnetic memory (MRAM) with ultra-low power consumption and high-speed response can be realized.

  In the magnetoresistive element and the magnetic memory device of the present invention, the number of magnetic moments per unit area of the first magnetic layer and the second magnetic layer in order to effectively cause the magnetoresistive effect and the spin transfer magnetization reversal. Needs to be larger than that of the magnetization free layer. The thickness of the magnetization free layer is, for example, 1 to 10 nm (preferably 1 to 5 nm), although it depends on the magnetic film material.

  The element structure includes a laminate of the first magnetic layer, a first nonmagnetic layer as a nonmagnetic spacer, the magnetization free layer, a second nonmagnetic layer as a nonmagnetic spacer, and the second magnetic layer. It is good to be constituted by.

  In this case, information is written to the magnetization free layer by spin injection magnetization reversal by a current flowing in the stacking direction of the stacked body, the first magnetic layer and the second magnetic layer function as a spin filter layer, and The stored information may be read by a current flowing in the stacking direction. For example, the first magnetic layer, the first nonmagnetic layer, and the magnetization free layer constitute a first giant magnetoresistive film, and the second magnetic layer, the second nonmagnetic layer, and the magnetization free layer, Constitutes the second giant magnetoresistive film.

  In order to read (output) information using the magnetoresistive effect, it is desirable that the laminated structures on both sides of the magnetization free layer are formed asymmetric with respect to each other.

  In this case, terminals for information writing and information reading may be provided on the respective sides of the first magnetic layer and the second magnetic layer, but the laminated structures on both sides of the magnetization free layer are formed symmetrically. However, information writing terminals and information reading terminals are provided on the respective sides of the first magnetic layer and the second magnetic layer, and information reading terminals are also provided in the magnetization free layer. If desired, a desired output can be obtained.

  The first magnetic layer, the first nonmagnetic layer, and the magnetization free layer constitute a giant magnetoresistive film, and the second magnetic layer, the second nonmagnetic layer, and the magnetization free layer are giant. The magnetoresistive film need not be configured. Alternatively, the first magnetic layer, the first nonmagnetic layer, and the magnetization free layer may or may not constitute a giant magnetoresistive film, and the second magnetic layer and the second nonmagnetic layer And the magnetization free layer constitute a tunnel magnetoresistive film, a sufficient output can be taken out by the tunnel magnetoresistive film.

  A first antiferromagnetic layer and / or a second antiferromagnetic layer for fixing the magnetization direction of each of the magnetic layers by exchange coupling to the first magnetic layer and / or the second magnetic layer, respectively. It should be joined.

  In addition, the first magnetic layer or the second magnetic layer, and the third ferromagnetic layer are stacked via a third nonmagnetic layer, and a stacked ferrimagnetic structure in which antiferromagnetic coupling is performed by RKKY interaction is provided. If formed, the magnetization directions of the first and second magnetic layers can be easily fixed in opposite directions. In this case, an antiferromagnetic layer is joined to the third ferromagnetic layer, and its magnetization is fixed by exchange coupling.

  The present invention is suitable for a magnetic memory device in which the magnetoresistive element described above constitutes a memory cell portion.

  In particular, the present invention is preferably applied to an MRAM (Magnetic Random Access Memory) in which the first magnetic layer side is connected to a bit line and the second magnetic layer side is connected to a switching element such as a field effect transistor.

  Alternatively, the present invention may be applied to a cross-point type memory device in which the first magnetic layer side is connected to a bit line and the second magnetic layer side is connected to a word line.

  Next, preferred embodiments of the present invention will be described in detail with reference to the drawings.

First Embodiment FIGS. 1 to 3 show a first embodiment of the present invention.

<Structure of spin injection magnetization reversal element (spin filter layer 2 / Cu spacer layer 3 / memory layer 1 / Cu spacer layer 13 / spin filter layer 12)>
As shown in FIG. 1, the spin-injection magnetization reversal element 10 having a novel multilayer film structure according to the present embodiment is formed on the top and bottom of a magnetic film as a storage layer (magnetization free layer) 1 having a thickness of 1 to 10 nm. It has a structure in which magnetic films as two spin filter layers 2 and 12 are arranged via magnetic metal films (spacer layers) 3 and 13, respectively. In this case, the point is that the magnetization directions of the two spin filter layers 2 and 12 are fixed in opposite directions.

The material (composition) of the memory layer 1 and the spin filter layers 2 and 12 is not particularly limited, and any magnetic material can be used. The memory layer 1 and the spin filter layers 2 and 12 may be the same magnetic material or different magnetic materials. Here, a Co-based alloy soft magnetic film (for example, Co—Fe ₁₀ ) whose magnetic anisotropy is in the in-plane direction is used. However, the saturation magnetization (M _S : magnetic moment per unit volume) × film thickness (t) of the spin filter layers 2 and 12 must be larger than M _S × t of the storage layer (magnetization free layer) 1. Alternatively, it may be said that the number of magnetic moments per unit area of the spin filter layers 2 and 12 is made larger than that of the storage layer 1. Alternatively, it can be said that the film thickness of the spin filter layers 2 and 12 is made larger than the spin diffusion length of these magnetic films, while the film thickness of the storage layer 1 is made smaller than the spin diffusion length of these magnetic films. If the spin filter layers 2 and 12 and the storage layer 1 are made of the same magnetic material, the spin filter layer thickness> the storage layer thickness.

  The material of the nonmagnetic metal spacer layers 3 and 13 may be any material that exhibits a magnetoresistive effect in combination with a magnetic film material. Here, for example, Cu is used for both of the two spacer layers 3 and 13. The materials of the two spacer layers 3 and 13 do not need to be the same, but at least one of the spacer materials must be a material that exhibits a magnetoresistive effect in combination with the magnetic films on both sides opposed thereto. Don't be. The thickness of the spacer layers 3 and 13 is set to ˜5 nm or more so that the magnetic interlayer interaction between the storage layer 1 and the two spin filter layers 2 and 12 does not occur. If this is too thick, scattering of conduction electrons increases, so it is desirable that the thickness be about 10 nm or less.

The magnetizations of the spin filter layers 2 and 12 are pinned (fixed) by exchange coupling with the antiferromagnetic layers (AF layers) 4 and 14. As these AF materials, for example, one is PtMn and the other is Mn—Ir ₂₅ . Alternatively, PtMn having different thicknesses may be used for the two AF layers 4 and 14. In both cases, by utilizing the fact that the blocking temperatures of the two AF materials are different, the heat treatment temperature in the magnetic field is changed and the treatment is performed twice, so that the direction of the exchange coupling magnetic field with the two spin filter layers 2 and 12 is reversed. Orient.

  The in-plane size of the memory cell is the same as that already described in the conventional example, and has a size of ˜200 nmφ or less, and has a substantially elliptical shape to give shape anisotropy (see FIG. 3).

  In the processing of the memory cell, all the multilayer films shown in FIG. 1 are punched into the same shape. However, since spin filter layers 2 and 12 having opposite magnetizations exist above and below the memory layer 1, these spin films are formed. Since the leakage magnetic field from the filter layer cancels each other in the storage layer 1, the influence on the storage layer 1 is almost eliminated. As shown in FIG. 3, the memory layer 1 alone or the memory layer 1 and the spacer layers 3 and 13 are processed into a memory cell shape, and the upper and lower spin filter layers 2 and 12 are not processed (for example, as a solid film). Needless to say, the leakage magnetic field from the spin filter layer may be cut off. In this case, the periphery of the memory cell is covered with a nonmagnetic insulating film 5, and the spin filter layers 2 and 12, the antiferromagnetic layers 4 and 14, and the cap layer 20 (the antiferromagnetic layer 4 are formed thereon). Necessary when the sample is taken out into the atmosphere after film formation)) and an electrode 142 and a lower electrode 146 are provided.

<Writing information to memory cell>
FIG. 2 shows the operation at the time of writing. When electrons are passed between the terminals 17 and 18 from the top to the bottom of the figure, + current (+ I), and when they flow in the opposite direction, −current (− I).

  In the following description, the magnetization direction of the lower spin filter layer 12 is used as a reference. In the case of -I, as shown in FIG. 2A, the down spin electrons (the magnetization direction of the lower spin filter layer 12 and the spin direction are reversed) with respect to the lower spin filter layer 12 are reflected by the lower filter layer 12 Up-spin electrons (the magnetization direction of the lower spin filter layer 12 and the spin direction are the same) pass through the lower spin filter layer 12 without resistance, and then enter the storage layer 1. Spin torque is applied to the magnetic moment of the storage layer 1 through sd-interaction so as to be parallel to the magnetization direction of the spin filter layer 12. The up-spin electrons that have passed through the storage layer 1 become down-spin electrons for the upper spin filter layer 2 and are reflected at the interface and returned to the storage layer 1 to cause sd-interaction again. The reflected upspin electrons enter the upper spin filter layer 2 again by the action of an electric field and are reflected, and thus multiple reflections of the upspin electrons occur. As a result, the storage layer 1 is aligned in parallel with the magnetization of the lower spin filter layer 12.

In this way, compared to the conventional example described above, the down spin electrons are removed when entering the lower spin filter layer 12, and the up spin electrons of the lower spin filter layer 12 are removed by the upper spin filter layer 2. Since multiple reflection occurs, the spin-inversion magnetization reversal efficiency (corresponding to the above g (π)) from the antiparallel arrangement to the parallel arrangement when the lower spin filter layer 12 is used as a reference is improved, and I _C ⁻ (memory layer The critical current for reversing the magnetization of 1 to be parallel to the magnetization of the lower spin filter layer 12 is reduced.

  On the other hand, in the case of + I, as shown in FIG. 2 (B), unlike the above-described conventional example, first, down spin electrons (in the figure, the spin indicated by a right arrow.) Is reflected by the upper surface of the upper spin filter layer 2, and the up spin electrons pass through the upper spin filter layer 2 without resistance, and then enter the memory layer 1. Then, torque is applied to the magnetic moment of the storage layer 1 through sd-interaction so that the magnetization of the storage layer 1 is parallel to the magnetization direction of the upper spin filter layer 2. The up-spin electrons that have passed through the storage layer 1 become down-spin electrons for the lower spin filter layer 12 and are reflected at the interface and returned to the storage layer 1 to cause sd-interaction again. The reflected up-spin electrons enter the lower spin filter layer 12 again by the action of an electric field and are reflected, and thus multiple reflections of the up-spin electrons occur. As a result, the storage layer 1 is aligned in parallel with the magnetization of the upper spin filter layer 2. Compared to the case of -I, the magnetization direction of the storage layer 1 is reversed.

Thus, compared with the above-described conventional example, the down spin electrons are removed when entering the upper spin filter layer 2, so there is no competition phenomenon between the up spin electrons and the down spin electrons, and the spin injection magnetization reversal efficiency ( (Corresponding to the above g (0)) is improved, and I _C ⁺ (critical current for reversing the magnetization of the storage layer and being antiparallel to the magnetization of the lower spin filter layer 12) is reduced.

As described above, by adopting a double spin filter structure in which the spin filter layers 2 and 12 are provided on the upper and lower sides, the inversion current and the inversion current density are reduced by an order of magnitude or more compared to the conventional example (FIGS. 15 and 16). To do. That is, the reversal current and the reversal current density in the case where Co—Fe ₁₀ having a thickness of 2.5 nm is used as the memory layer 1 and the memory cell size is an elliptical shape having a major axis of 100 to 200 nm and a minor axis of 50 to 100 nm are conventionally obtained. In the structure of the example, they were 3 to 7 mA and 3 to 7 × 10 ⁷ A / cm ² , respectively, but in the form of this example, they were 0.3 to 0.7 mA and 10 ⁶ A / cm ² , respectively. . In addition, the thermal fluctuation resistance is K _U V / k _B T _300K > 100 and the inversion time τ <˜2 nsec, sufficiently satisfying the necessary conditions for the magnetic memory.

<Reading information>
In the above, it should be noted that, in the above multilayer film configuration, if the memory layer 1 is completely symmetrical, the write information is converted into the current I (several 10 μA) as shown in FIGS. In other words, no change in magnetoresistance occurs (no output). That is, the magnetoresistance change caused by the first GMR film (giant magnetoresistive film) 15 generated in the upper spin filter layer 2 / Cu layer 3 / memory layer 1, and the memory layer 1 / Cu layer 13 / lower spin filter layer 12 and the magnetoresistance change caused by the second GMR film 16 canceling each other out.

  However, in reality, since it is not completely symmetrical, an output signal can be obtained although it is weak. More positively, the thickness of the two spacer layers 3 and 13 and the thickness of the two spin filter layers 2 and 12 are slightly shifted, or the film forming conditions are changed to cause a difference in film quality and interface state. By making the spin-dependent scattering above and below the storage layer 1 different, the magnetoresistance change is different between when the magnetization of the storage layer 1 is directed rightward and leftward in the figure, and the CPP-GMR ratio An output of 0.2% to 1% can be obtained. The read current I may flow from the top to the bottom of the figure, but may flow in the opposite direction.

Second Embodiment FIG. 4 shows a second embodiment of the present invention.

<Structure of spin injection magnetization reversal element (spin filter layer 2 / Cu spacer layer 3 / memory layer 1 + terminal 19 / Cu spacer layer 13 / spin filter layer 12)>
The spin transfer magnetization switching element 40 according to the present embodiment is a two-terminal element in which the spin transfer magnetization switching element 10 according to the first embodiment described above has terminals (or electrodes) 17 and 18 arranged above and below the element. Compared to the three-terminal element structure, a third terminal 19 is provided in the memory layer 1.

  In this case, writing is performed between the terminals 17-18. At the time of reading, resistance changes due to differences in the relative angles of the magnetization directions of the storage layer 1 and the upper and lower spin filter layers 2, 12 are individually determined, that is, the terminals 17-19. Or between the terminals 18-19, even if the upper and lower GMR film structures 15 and 16 of the memory layer 1 are provided symmetrically, there is no cancellation of the respective resistance changes, and the first An output higher than that of the embodiment, for example, an output of several percent or more in the CPP-GMR ratio can be obtained.

  Although the device structure is more complicated, in addition to the original resistance change of the CPP-GMR film, the effect of increasing the resistance change by increasing the effective polarizability of the memory layer 1 due to the multiple reflection effect of the polarized spin electrons described above is obtained. It is done. In the present embodiment, the combination of the materials of the spacer layers 3 and 13 may be changed and combined with the following embodiments.

Third Embodiment FIG. 5 shows a third embodiment of the present invention.

<Structure of spin injection magnetization reversal element (spin filter layer 2 / Cu spacer layer 3 / memory layer 1 / Ru spacer layer 53 / spin filter layer 12)>
In the spin transfer magnetization switching element 50 according to the present embodiment, one of the two spacer layers 53 is combined with the magnetic film to be used in the GMR in the spin transfer magnetization switching element 10 according to the first embodiment described above. A metal that hardly causes an effect (if the magnetic film is a Co-based alloy, a metal other than Cu), such as a Ru or Ru / Ta / Ru composite film, is used.

  As described above, the combination of the nonmagnetic metal layer 53 other than the memory layer 1 / Cu / spin filter layer 12 exhibits almost no GMR effect, and the spin filter layer 12 functions only as a spin filter. Refer to the magnetization of the GMR film. It does not function as a layer. Therefore, only the combination of the spin filter layer 2 (magnetization reference layer) / Cu spacer layer 3 / memory layer 1 functions as a GMR film, and the resistance change accompanying the magnetization reversal of the memory layer 1 can be detected. As a result, even if it is a two-terminal element, a resistance change (output) equivalent to that in the second embodiment described above can be obtained.

  What should be noted here is the selection of a metal material other than Cu. The spacer layer 53 needs to be formed of a material that hardly causes an interface reaction with the magnetic films adjacent to the upper and lower sides thereof (i.e., less likely to be solid solution = less likely to be alloyed). For example, Ta is nonmagnetic and does not exhibit a GMR effect, but an interface reaction with a Co-based magnetic film is likely to occur. On the other hand, Ru, which does not easily cause an interface reaction with the Co-based magnetic film, is preferable.

  When a metal other than Cu is brought into contact with the memory layer 1 as a spacer material, the damping factor against the precession of the magnetic moment of the memory layer 1 may increase due to the spin pumping effect, and the spin injection magnetization reversal current is proportional to it. Will increase. The increase of the braking factor depends on the spacer material, and further relates to the thickness thereof, the thickness of the memory layer 1, and the like. Cu has no effect of increasing the braking factor, has a small interface reaction, and has a low resistivity. Therefore, it can be said that Cu is the most easy to use (with few side effects) nonmagnetic metal spacer material. Although Ta does not increase the braking factor, there is a concern about the interface reaction with the magnetic film as described above.

  When Ru is used as a spacer material, it should be appropriately selected in consideration of the balance between an increase in reversal current due to an increase in braking factor and an effect of increasing output. For example, a Ru (thickness to 1 nm) / Ta (thickness several nm) / Ru (thickness to 1 nm) composite film is a combination that has a small interface reaction with a magnetic film and hardly causes an increase in a braking factor. It is effective as

Fourth Embodiment FIG. 6 shows a fourth embodiment of the present invention.

<Structure of spin injection magnetization reversal element (spin filter layer 2 / Cu spacer layer 3 / memory layer 1 / Al ₂ O ₃ spacer layer 63 / spin filter layer 12)>
Unlike the spin transfer magnetization switching element 10 according to the first embodiment described above, the spin transfer magnetization switching element 60 according to the present embodiment uses one of the two nonmagnetic spacer layers as the Al ₂ O ₃ layer 63. .

In this case, the storage layer 1 / Cu spacer layer 3 / spin filter layer 2 functions as the GMR film 15, but the storage layer 1 / Al ₂ O ₃ spacer layer 63 / spin filter layer 12 (magnetization reference layer) is the TMR film 65. Function as. The film thickness of the Al ₂ O ₃ layer 63 is determined in consideration of the element resistance, and is selected from 0.5 to 1.5 nm. According to the double spin filter structure of the present embodiment, the spin injection magnetization reversal current in the TMR film 65 (for example, an area of 0.01 μm ² ) can be 1 mA or less. For this reason, the RA of the TMR film 65 can be set to several tens of Ωμm ² or less so as not to cause dielectric breakdown of the element.

Therefore, the feature of the structure according to the present embodiment is that a high rate of change in resistance can be obtained by having the TMR film structure 65. Combined with the effect that the rate of change in resistance increases due to the increase in effective polarizability of the memory layer 1 due to the multiple reflection effect of polarized spin electrons, even if RA is several tens of Ωμm ² or less, several tens of% The above resistance change rate is obtained. In the case of a general TMR film, the TMR ratio decreases as the resistance decreases (the thickness of the insulating barrier layer such as Al ₂ O ₃ decreases). For example, when RA is several Ωμm ² , the TMR ratio is −10 % Or less. However, according to the double spin filter structure of the present embodiment, the resistance change rate increases due to an increase in the effective polarizability of the memory layer due to the multiple reflection effect of the polarized spin electrons described above. Even with a low-resistance TMR film, it is possible to obtain a resistance change rate of several tens of percent or more.

  On the other hand, since the portion of the spin filter layer 2 / Cu spacer layer 3 / memory layer 1 functions as the CPP-GMR film 15, the rate of change in magnetoresistance due to the TMR film structure 65 is reduced. Since the rate is as small as several percent or less, it hardly affects the resistance change rate of the entire element.

Incidentally, in the portion of the storage layer 1 / the Al ₂ O ₃ layer 63 / spin filter layer 12 described above, another insulating material layer the Al ₂ O ₃ layer 63 is an insulating barrier layer, for example, AlN, even MgO layer such I do not care. Further, in the above-described spin filter layer 2 / Cu spacer layer 3 / memory layer 1, the Cu spacer layer 3 may be the Ru, Ru / Ta / Ru layer described in the third embodiment. . In this case, the GMR effect hardly appears, and the spin filter layer 2 functions only as a spin filter. For this reason, only the resistance change in the TMR structure 65 appears as the resistance change of the element, which is preferable.

Fifth Embodiment FIG. 7 shows a fifth embodiment of the present invention.

<Structure of spin injection magnetization reversal element (antiferromagnetic layer 4 / spin filter layer 2 / Cu spacer layer 3 / memory layer 1 / Al ₂ O ₃ spacer layer 63 / spin filter layer 12 / Ru layer 71 / pinned layer 72 / Antiferromagnetic layer 14)>
The spin transfer magnetization reversal element 70 according to the present embodiment is the same as that of each of the above-described embodiments, for example, the spin transfer magnetization reversal element 60 according to the fourth embodiment. To do.

  That is, the single-layer spin filter layer has a three-layer structure of the spin filter magnetic layer 12 / Ru layer 71 / magnetic layer (pinned layer) 72. The thickness of the Ru layer 71 in the laminated ferrimagnetic structure 75 is set to 0.7 to 0.8 nm so that the magnetizations of the two magnetic layers 12 and 72 are antiferromagnetically coupled by the RKKY interaction. The thicknesses of the two magnetic layers 12 and 72 forming the laminated ferri structure 75 may be the same or may have a slight difference.

Further, the saturation magnetization (M _S : magnetic moment per unit volume) × film thickness (t) of each of the spin filter layers 2 and 12 is made larger than M _S × t of the storage layer (magnetization free layer) 1. Alternatively, it may be said that the number of magnetic moments per unit area of the spin filter layers 2 and 12 is made larger than that of the storage layer 1. Alternatively, it can be said that the film thickness of the spin filter layers 2 and 12 is larger than the spin diffusion length of these magnetic films, and the film thickness of the storage layer 1 is smaller than the spin diffusion length of these magnetic films. If the spin filter layers 2 and 12 and the storage layer 1 are made of the same magnetic material, the spin filter layer thickness> the storage layer thickness.

  A feature of the structure according to this embodiment is that the magnetization directions of the upper and lower two spin filter layers 2 and 12 facing the storage layer 1 via the nonmagnetic spacer layers 3 and 63 can be easily antiparallel. . In this case, the same material can be used for the two upper and lower antiferromagnetic layers (AF layers) 4 and 14. By one heat treatment in a magnetic field, an exchange coupling magnetic field is induced in the spin filter layer 2 and the pinned layer 72 by the AF layers 4 and 14 in the same direction, and the spin filter layer 12 and the pinned layer 72 are laminated. Since the antiferromagnetic coupling is caused by the ferrimagnetic structure 75, the magnetization directions of the spin filter layer 2 and the spin filter layer 12 become antiparallel due to the heat treatment in the magnetic field.

In this embodiment, PtMn is used as the AF layers 4 and 14, and the spin filter layers 2 and 12 and the pinned layer 72 are all made of a Co-based alloy, for example, Co—Fe ₁₀ or Co—Fe ₂₅ . Each of these magnetic films has a thickness of 5 to 100 nm, preferably 5 to 20 nm. The thickness of the memory layer 1 is 1 to 10 nm, preferably 2 to 4 nm. The thickness of the Cu layer 3 is 5 to 50 nm, desirably 5 to 10 nm. The thickness of the Al ₂ O ₃ layer 63 is 0.5 to 1.5 nm. The thicknesses of these layers may be similarly adopted in the above-described embodiments. Further, as in the fourth embodiment described above, a Ru, Ru / Ta / Ru layer or the like may be used instead of the Cu layer 3, and an AlN, MgO layer or the like may be used instead of the Al ₂ O ₃ layer 63.

Sixth Embodiment FIG. 8 shows a sixth embodiment of the present invention.
<Use of single crystal film>
In each of the above-described embodiments, the multilayer film composed of the magnetic layer and the spacer layer is a polycrystalline film or an amorphous film. In this embodiment, each multilayer layer or a part thereof is epitaxially grown. A single crystal film is used.

  For example, in the element according to the first embodiment described above, as shown in FIG. 8A, as the GMR films 15 and 16, the Co layer 1 / Cu layer 3 and 13 / Co layers 2 and 12 are epitaxial films, respectively. The formed spin injection magnetization reversal element 80A is configured. Alternatively, for example, in the fourth embodiment described above, as shown in FIG. 8B, the spin transfer magnetization switching element in which the Fe layer 12 / MgO layer 63 / Fe layer 1 is formed as an epitaxial film as the TMR film 65, respectively. 80B is configured.

Here, as a method of epitaxially growing a single crystal film, an MgO film (up to 5 nm or more) is formed on an MgO single crystal substrate ((001) surface) 81 or by sputtering or the like on an SiO ₂ substrate or the like. It is obtained by forming a film and forming the above various metal films thereon.

For example, when the MgO film is formed on SiO ₂ , it becomes a single crystal film ((001) plane orientation) when the thickness is ˜5 nm or more, and when a film such as Fe is formed thereon, the single crystal film is epitaxially grown. .

  If the structure of the TMR film is all made of a single crystal, the tunnel insulating barrier film can also be a single crystal lower layer film / Fe (spin filter layer) / MgO (tunnel insulating barrier film) / Fe (memory layer). A single crystal film is formed.

Moreover, if the tunnel insulating barrier film is a polycrystalline film or an amorphous film, such as single crystal underlayer film / Fe (spin filter layer) / Al ₂ O ₃ / memory layer magnetic film, a single crystal is formed up to the spin filter layer. Become a film. Also in this case, when the Al ₂ O ₃ film is formed, first, a metal Al film is formed. At this time, a single crystal Al film is formed, and this is oxidized to obtain an Al ₂ O ₃ film. Therefore, an extremely flat Al ₂ O ₃ film can be obtained. Therefore, as compared with the polycrystalline TMR film, not only the single crystal spin filter layer / Al ₂ O ₃ film interface but also the Al ₂ O ₃ film / memory layer (polycrystalline or amorphous) interface can be made extremely flat. This structure is easier to manufacture.

  As described above, the single crystal film used for at least a part of the multilayer film has a flat interface at the atomic level compared to the polycrystalline film, and there is no grain boundary in the film. And a higher spin injection magnetization reversal efficiency can be obtained.

Seventh Embodiment FIGS. 9 and 10 show a seventh embodiment of the present invention.

<Application to MRAM>
FIG. 9A shows an example of an MRAM structure when the present invention is applied to an MRAM, and FIG. 9B is an enlarged view of a main part thereof. This MRAM forms 1 bit by 1 transistor-1 magnetization reversal element (1T1J). For example, the MRAM shown in FIG. 17 except that the spin injection magnetization reversal element 70 shown in FIG. 7 is incorporated in the memory cell portion. The structure is basically the same as that of the MRAM structure, and common portions are denoted by common reference numerals and description thereof is omitted.

  That is, the spin transfer magnetization switching element 70 is formed in the multilayer structure shown in FIG. 7, and its upper part is connected to the bit line 142 via a cap layer 90 of Ta or the like as shown in FIG. 9B. The lower part thereof is connected to the drain electrode 146 through a base conductive layer 91 such as Ta. The storage layer 1 and the upper and lower nonmagnetic spacer layers 3 and 63 are processed so that the in-plane size is about 200 nmφ or less, thereby forming a storage cell having a substantially single magnetic domain.

The memory cell has a shape having an aspect ratio (aspect ratio), for example, an ellipse (see FIG. 3) in order to have shape magnetic anisotropy. The processing region of the memory cell is configured such that the processing is stopped on the upper surface of the second spin filter layer 12 to increase the area of the spin filter layer 12 and prevent the leakage magnetic field from reaching the storage layer 1. The same applies to the upper first spin filter layer 2. The first spin filter has a larger area than the storage cell on the nonmagnetic insulating film (SiO ₂ , Al ₂ O _3, etc.) 95 that embeds the storage cell. A filter layer 2 and further an antiferromagnetic layer 4 are laminated. In the figure, 96a represents an insulating film, and 96b, 96c, and 96d represent interlayer insulating films.

  This spin-injection magnetization reversal element 70 has a simple structure in which a current flows only perpendicularly to the film surface, and writing (magnetization reversal of the storage layer 1) can be performed as shown in FIGS. This is done by changing the direction of the current flowing perpendicular to the film surface. Writing is possible with a large current (about 100 μA), and reading is possible with a small current (about 10 μA).

Although the various embodiments described above can be used for the film structure of the element, the structure of the above-described fifth embodiment is preferable as the resistance change is large and the manufacturing is easy. Here, a Ta underlayer is provided on the electrode 146 provided on the drain of the FET 130, and the PtMn layer 14 (thickness 20 to 40 nm) / Co—Fe layer 72 (thickness 5 to 10 nm) / Ru layer 71 (thickness). 0.7 to 0.8 nm) / Co—Fe layer 12 (thickness 5 to 10 nm) / Al ₂ O ₃ layer 63 (thickness 0.5 to 1.5 nm) / Co—Fe layer 1 (thickness 2) -3 nm) / Cu layer 3 (thickness 5-10 nm) / Co—Fe layer 2 (thickness 5-10 nm) / PtMn layer 4 (thickness 20-40 nm), and a Ta cap layer 90 Is deposited.

The composition of each Co—Fe magnetic layer is 5 to 50 at% Fe, but any magnetic material with M _S > 400 emu / cm ³ (400 kA / m) may be used. When M _S is 400 emu / cm ² (400 kA / m) or less, the memory cell volume is very small, and it becomes difficult to maintain the thermal fluctuation resistance. The size of the memory cell is approximately elliptical with a major axis of 100 to 200 nm and a minor axis of 50 to 100 nm. The orientation of the memory cells on the drain is arbitrary. The coercive force of the memory cell can be as large as several hundred Oe to 1 kOe (several tens of kA / m).

  The MRAM according to this embodiment has a magnetization reversal time of ˜2 nsec or less, and realizes a high-speed response that is characteristic of a magnetic memory. The voltage required for writing is 1 V or less and the necessary current is 1 mA or less, and can be reduced to about 0.2 V and 0.2 mA, respectively, by optimizing the thickness of the storage layer 1 and the storage cell size.

  FIG. 10 shows an MRAM in the case where a magnetoresistive effect element 70 that performs spin-injection magnetization reversal is used in a memory cell, as compared with a conventional example that performs magnetization reversal by a current magnetic field. FIG. 10A schematically shows a cross-sectional view and a plan view of the main part of the MRAM using the magnetization reversal by the current magnetic field shown in FIG. 13, and FIG. 10B shows the present embodiment. The main part sectional drawing and the top view of MRAM using magnetization reversal by injection | pouring of a polarized spin current are shown roughly.

For the reason described above, the MRAM according to the present embodiment can reduce the in-plane size of the memory cell to the order of about 0.1 μmφ, so that the scaling in the semiconductor process is possible and the most advanced design. Rules can be used. A current line for generating a magnetic field (write word line) is not required, and therefore the magnetic flux concentration clad structures 150 and 151 and the bypass line 115 are also unnecessary. As a result, the element area per bit is 6F ² which is the theoretical minimum area from the conventional ²⁰ F ² (F is a design rule). With the miniaturization of design rules, the area of the memory cell portion is reduced to about 0.06 μm ² . This makes it possible to increase the capacity exceeding Gbit. Since the write current is about 100 μA and the read current is 10 μA or less, the memory has an extremely low power consumption, and the response speed is as high as about 1 nsec. A large-capacity, nonvolatile solid-state memory having the advantages of existing memories such as SRAM (Static Random Access Memory) and DRAM (Dynamic Random Access Memory) is realized.

Eighth Embodiment FIG. 11 shows an eighth embodiment of the present invention.

<Application to cross-point element>
FIG. 11 shows a case where the present invention is applied to a cross-point type memory (see US Pat. No. 5,640,343), and the above-described spin-injection magnetization reversal elements 10 to 10 are provided between two orthogonal wirings 142 and 160. Any one of 80 is arranged.

  In this example, as compared with the MRAM as shown in FIG. 9 using a switching transistor, writing and reading are not performed through the transistor, but only by a current between the bit line 142 and the word line 160. The same effect as described in the seventh embodiment can be obtained.

Ninth Embodiment FIG. 12 shows a ninth embodiment of the present invention.

<Shape of memory cell>
As shown in FIG. 12A, the shape of the memory cell is not limited to the approximate ellipse described in each of the above embodiments, but also a rectangle, a ring shape, etc., as shown in FIGS. Any shape having a uniaxial magnetic anisotropy may be used (the arrow in the figure indicates the direction of the easy axis of magnetization).

  However, when the magnetic film of the storage layer has some magnetic anisotropy such as crystal magnetic anisotropy, the shape magnetic anisotropy is not necessarily required. For example, a square or circular memory cell having biaxial magnetocrystalline anisotropy in the plane may be used. For example, a single crystal film in which, for example, the (001) plane is preferentially grown using a magnetic material (Co-based alloy or the like) having an fcc structure may be manufactured. In this case, for example, the two axes of the <± 1,0,0> direction and the <0, ± 1,0> direction become easy magnetization axes, and binary (2-bit) recording is possible. When there are a plurality of magnetic anisotropies in the plane of the memory cell, multilevel recording is possible.

  The embodiment of the present invention described above can be variously modified based on the technical idea of the present invention.

  For example, if it has the basic structure described above with both sides (upper and lower) of the storage layer sandwiched between spin filter layers with opposite magnetization directions, the configuration of the multilayer film can be variously changed, and its constituent materials and physical properties, The shape, size, etc. may be changed as appropriate. Also, the type and structure of the memory incorporating the above-described spin-injection magnetization switching element are not limited to those described above.

  In the above example, the multilayer film that is the main part of the spin transfer magnetization reversal element is formed on an appropriate substrate / underlayer film, and an electrode is disposed on the upper part. The upper and lower layers may be laminated, and are appropriately selected in consideration of ease of production. The base film may be a composite film having an appropriate CMOS (Complementary Metal-Oxide-Semiconductor) configuration including the above-described FET, but may have other base configurations.

  In a magnetoresistive effect element in which magnetically separated magnetic layers are arranged on both sides of a magnetization free layer (storage layer) and the magnetization directions of these magnetic layers are fixed in opposite directions, the film is perpendicular to the film surface. A magnetoresistive effect element in which the effect of magnetization reversal (that is, spin injection magnetization reversal) for reversing the magnetization direction of the magnetization free layer by flowing a current to the magnetic free layer, and a magnetic memory such as MRAM using the magnetization reversal method are provided. Can be provided.

1 is a schematic cross-sectional view of a spin-injection magnetization switching element according to a first embodiment of the present invention. It is a schematic sectional drawing which shows the principle of writing (A), (B) and reading (C), (D). FIG. 3 is an enlarged cross-sectional view of a main part of the spin injection magnetization switching element. It is a schematic sectional drawing of the spin injection magnetization reversal element by the 2nd Embodiment of this invention. It is a schematic sectional drawing of the spin injection magnetization reversal element by the 3rd Embodiment of this invention. It is a schematic sectional drawing of the spin injection magnetization reversal element by the 4th Embodiment of this invention. It is a schematic sectional drawing of the spin injection magnetization reversal element by the 5th Embodiment of this invention. It is a schematic sectional drawing of the spin injection magnetization reversal element by the 6th Embodiment of this invention. It is principal part sectional drawing (A) and its principal part enlarged view (B) of MRAM using the spin-injection magnetization inversion element by the 7th Embodiment of this invention. FIG. 6 is a schematic cross-sectional view and a plan view of an MRAM using spin injection magnetization reversal compared to an MRAM using magnetization reversal by a current magnetic field. It is principal part sectional drawing of the cross point type | mold memory using the spin injection magnetization switching element by the 8th Embodiment of this invention. It is a top view which shows the various shapes of the memory cell using the spin injection magnetization reversal element by the 9th Embodiment of this invention. It is principal part sectional drawing of MRAM using the magnetization reversal by the current magnetic field by a prior art example. It is a schematic sectional drawing which shows the principle of writing and reading similarly. It is a schematic sectional drawing of the spin injection magnetization reversal element by another prior art example. It is a schematic sectional drawing which shows the principle of writing similarly. FIG. 4 is a cross-sectional view (A) of a main part and an enlarged view (B) of a main part of the MRAM using the spin injection magnetization switching element.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1,121 ... Memory layer (magnetization free layer) 2, 12, 122 ... Spin filter layer,
3, 13, 53, 63, 123 ... nonmagnetic spacer layer, 4, 14, 124 ... antiferromagnetic layer,
5, 30, 95, 96, 125, 141 ... insulating film,
10, 40, 50, 60, 70, 80, 120 ... spin-injection magnetization reversal element,
15, 16 ... GMR film, 17, 18, 19 ... terminal, 20, 90, 140 ... cap layer,
65 ... TMR film, 71 ... Ru layer, 72 ... pinned layer, 75 ... laminated ferrimagnetic structure,
91 ... underlying conductive layer, 130 ... field effect transistor for writing and reading,
135 ... well region, 136 ... source region, 137 ... drain region,
138 ... Gate insulating film, 139 ... Gate electrode, 142 ... Electrode (bit line),
143 ... Source electrode, 143a, 146a ... Plug, 146 ... Drain electrode

Claims (15)

  It has a magnetization free layer and a first magnetic layer and a second magnetic layer that are magnetically separated and arranged on both sides of the magnetization free layer, and the magnetization directions of these magnetic layers are fixed opposite to each other. Magnetoresistive effect element.   The magnetoresistive element according to claim 1, wherein the number of magnetic moments per unit area of the first magnetic layer and the second magnetic layer is larger than that of the magnetization free layer.   2. The magnetoresistive element according to claim 1, wherein the magnetoresistive element is configured by a stacked body of the first magnetic layer, the first nonmagnetic layer, the magnetization free layer, the second nonmagnetic layer, and the second magnetic layer. Effect element.   Information is written in the magnetization free layer by spin injection magnetization reversal by a current flowing in the stacking direction of the stacked body, the first magnetic layer and the second magnetic layer function as a spin filter layer, and in the stacking direction. The magnetoresistive effect element according to claim 3, wherein stored information is read out by a flowing current.   The first magnetic layer, the first nonmagnetic layer, and the magnetization free layer constitute a first giant magnetoresistive film, and the second magnetic layer, the second nonmagnetic layer, and the magnetization free layer are the first The magnetoresistive effect element according to claim 4, comprising two giant magnetoresistive effect films.   The magnetoresistive effect element according to claim 5, wherein a laminated structure on both sides of the magnetization free layer is formed asymmetrically with respect to each other.   7. The magnetoresistive element according to claim 6, wherein terminals for writing information and reading information are provided on the first magnetic layer and the second magnetic layer, respectively.   The information writing terminal is provided on each of the first magnetic layer and the second magnetic layer, and the information reading terminal is provided on the magnetization free layer. Magnetoresistive effect element.   The first magnetic layer, the first nonmagnetic layer, and the magnetization free layer constitute a giant magnetoresistive film, and the second magnetic layer, the second nonmagnetic layer, and the magnetization free layer comprise a giant magnetoresistance. The magnetoresistive effect element according to claim 4 which does not constitute an effect film.   The first magnetic layer, the first nonmagnetic layer, and the magnetization free layer may or may not constitute a giant magnetoresistive film, and the second magnetic layer, the second nonmagnetic layer, and the The magnetoresistive element according to claim 4, wherein the magnetization free layer constitutes a tunnel magnetoresistive film.   A first antiferromagnetic layer and / or a second antiferromagnetic layer for fixing the magnetization direction of each magnetic layer by exchange coupling is joined to the first magnetic layer and / or the second magnetic layer, respectively. The magnetoresistive effect element according to claim 1.   The first magnetic layer or the second magnetic layer and the third ferromagnetic layer are stacked via a third nonmagnetic layer, and a stacked ferrimagnetic structure is formed in which antiferromagnetic coupling is achieved by RKKY interaction. The magnetoresistive effect element according to claim 1.   A magnetic memory device in which the magnetoresistive effect element according to claim 1 constitutes a memory cell unit.   14. The magnetic memory device according to claim 13, wherein the magnetic memory device is configured as an MRAM (Magnetic Random Access Memory) in which the first magnetic layer side is connected to a bit line and the second magnetic layer side is connected to a switching element. 14. The magnetic memory device according to claim 13, wherein the magnetic memory device is configured as a cross-point type in which a side of the first magnetic layer is connected to a bit line and a side of the second magnetic layer is connected to a word line.

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