CN114628576A - Magnetic tunnel junction stack structure, memory and neural network computing device - Google Patents

Abstract

The present invention provides a magnetic tunnel junction stack structure, comprising: a spin-orbit moment providing layer, a first free layer, a coupling layer, a second free layer, a potential barrier layer and a reference layer sequentially stacked from bottom to top; One of the first free layer and the second free layer is an in-plane magnetization mode, and the other is a perpendicular magnetization mode; the magnetization mode of the reference layer is the same as that of the second free layer. The magnetization modes of the first free layer and the second free layer are set to different magnetization modes, and the combination of the two can be adapted to various applications.

Description

Magnetic tunnel junction stack structure, memory and neural network computing device

technical field

The invention relates to the technical field of computer storage, in particular to a magnetic tunnel junction stack structure, a memory, a neural network computing device, and a spin oscillator.

Background technique

A magnetic tunnel junction (MTJ) includes a free layer, a barrier layer, and a reference layer. Generally used in non-volatile memory devices, the magnetization direction of the reference layer is fixed, and the magnetization direction of the free layer is variable. When the free layer and the reference layer are parallel, the magnetic tunnel junction is in a low resistance state; when the free layer and the reference layer are antiparallel, the magnetic tunnel junction is in a high resistance state. The change of the magnetization direction of the free layer is generally achieved by the spin-orbit moment providing layer. The spin-orbit moment providing layer is generally made of heavy metal (HM). When the current flows through the heavy metal, the free layer is assisted by an external magnetic field or a magnetic bias layer is set to achieve freedom. The magnetic moment of the layer is flipped.

In the process of realizing the present invention, the inventor found that there are at least the following technical problems in the prior art: the current magnetic memory based on spin-orbit moment generally requires an external magnetic field, and the turnover efficiency is low, and the magnetization of the free layer of the magnetic tunnel junction is only Two states, the application is relatively single.

SUMMARY OF THE INVENTION

The magnetic tunnel junction stack structure, memory, neural network computing device, and spin oscillator provided by the present invention; the magnetization modes of the first free layer and the second free layer are set to different magnetization modes, and the combination of the two can be used. Adapt to a variety of applications.

In a first aspect, the present invention provides a magnetic tunnel junction stack structure, comprising: a spin-orbit moment providing layer, a first free layer, a coupling layer, a second free layer, a potential barrier layer and a reference layer that are sequentially stacked from bottom to top ;in,

One of the first free layer and the second free layer is in-plane magnetization, and the other is perpendicular magnetization;

The magnetization of the reference layer is the same as the magnetization of the second free layer.

Optionally, the coupling layer includes:

a first covering area, covering the upper surface of the first free layer;

The second covering area covers the area on the upper surface of the spin-orbit moment providing layer except the covering area of the first free layer.

Optionally, the spin Hall angle of the coupling layer is opposite to the spin Hall angle of the self-selected orbital moment providing layer.

Optionally, the material of one of the coupling layer and the spin-orbit moment providing layer includes one or more of Pt, Pd, Ir or Au, and the material of the other includes Ta, W or Mo. one or more.

Optionally, the material of the first free layer, the second free layer and the reference layer includes one or more of Co, Fe, Ni, B, Pd or Pt; the material of the barrier layer includes MgO, One or more of MgAl ₂ O ₄ or Al ₂ O ₃ .

In a second aspect, the present invention provides a memory, comprising:

A magnetic tunnel junction stack structure as described above; wherein, the first free layer is in an in-plane magnetization manner, the second free layer and the reference layer are in a perpendicular magnetization manner; The saturation magnetization and the saturation magnetization of the second free layer satisfy the following relationship: |Ms1-Ms2|/Ms2≥20%; wherein, Ms1 is the saturation magnetization of the first free layer, and Ms2 is the saturation of the second free layer magnetization;

A current source is electrically connected to the spin-orbit moment providing layer, the current source is used to provide various write currents, and the direction of the current is in-plane and perpendicular to the magnetization direction of the first free layer.

In a third aspect, the present invention also provides a multi-resistance memory, comprising:

As any one of the above-mentioned magnetic tunnel junction stack structure;

A current source is electrically connected to the spin-orbit torque providing layer, and the current source is used to provide various write currents.

Optionally, the first free layer is in a perpendicular magnetization manner, and the second free layer and the reference layer are in an in-plane magnetization manner.

In a fourth aspect, the present invention also provides a neural network computing device, comprising:

Any one of the above-mentioned magnetic tunnel junction stack structures; used for storing corresponding weight values according to a variety of currents;

A current source is electrically connected to the spin-orbit torque providing layer, and the current source is used to provide various write currents.

In a fifth aspect, the present invention also provides a spin oscillator, comprising:

As any one of the above-mentioned magnetic tunnel junction stack structure;

a current source electrically connected to the spin-orbit torque providing layer, the current source for supplying a current to the spin-orbit torque providing layer, the current being greater than three times the flipping current of the first free layer.

The magnetic tunnel junction stack structure provided by the present invention has two free layers, and the first free layer and the second free layer can have magnetization components in both in-plane and vertical directions through the coupling of the first free layer and the second free layer. , each free layer has magnetization components in two directions, and the magnetization components of the two free layers are flipped by different current-driven forms. The structure can not only realize efficient flipping without external magnetic field, but also realize multiple states, thereby enabling the magnetic tunnel junction to have wider applications.

Description of drawings

1 is a schematic structural diagram of a magnetic tunnel junction stack structure according to an embodiment of the present invention;

2 is a schematic diagram of two kinds of magnetic moment changes of the magnetic tunnel junction stack structure according to an embodiment of the present invention;

FIG. 3 is a schematic diagram of a magnetic moment oscillation variation of a magnetic tunnel junction stack structure according to an embodiment of the present invention;

4 is a schematic structural diagram of a magnetic tunnel junction stack structure according to another embodiment of the present invention;

5 is a schematic structural diagram of a magnetic tunnel junction stack structure according to another embodiment of the present invention;

6 is a schematic diagram of various magnetic moment changes of the magnetic tunnel junction stack structure according to another embodiment of the present invention;

FIG. 7 is a schematic diagram of various resistance changes of the magnetic tunnel junction stack structure according to another embodiment of the present invention.

Detailed ways

In order to make the purposes, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments It is only a part of the embodiments of the present invention, but not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

An embodiment of the present invention provides a magnetic tunnel junction stack structure, as shown in FIG. 1 , including: a spin-orbit moment providing layer 100 , a first free layer 200 , a coupling layer 300 , and a second free layer that are sequentially stacked from bottom to top 400, the barrier layer 500 and the reference layer 600; wherein, one of the first free layer 200 and the second free layer 400 is in-plane magnetization, and the other is perpendicular magnetization; The magnetization manner is the same as that of the second free layer 400 . Wherein, in this embodiment, the magnetization direction of the reference layer 600 is fixed, and the magnetization directions of the first free layer 200 and the second free layer 400 are variable. The reference layer 600 and the second free layer 400 are both perpendicularly magnetized or both are in-plane magnetization, and the magnetization directions of the first free layer 200 and the second free layer 400 are different. If the second free layer 400 is in-plane magnetization, the first free layer 200 is perpendicularly magnetized; if the second free layer 400 is perpendicularly magnetized, the first free layer 200 is in-plane magnetization. The spin-orbit torque providing layer 100 supplies current to pass through, and the in-plane magnetization direction of the first free layer 200 or the second free layer 400 is perpendicular to the current direction. When the current passes through the spin-orbit moment providing layer 100 , the magnetic moment of the first free layer 200 is deflected, and the magnetic moment of the second free layer 400 is deflected by the coupling effect. Under different saturation magnetization and different current conditions, the first free layer 200 and the second free layer 400 can be simultaneously flipped or multi-resistance state storage can be realized. As an optional implementation manner, the materials of the first free layer 200 , the second free layer 400 and the reference layer 600 include one or more of Co, Fe, Ni, B, Pd or Pt. As an optional implementation manner, the material of the barrier layer 500 includes one or more of MgO, MgAl ₂ O ₄ , and Al ₂ O ₃ . As a preferred embodiment, the material of one of the coupling layer 300 and the spin-orbit moment providing layer 100 includes one or more of Pt, Pd, Ir or Au, and the material of the other includes Ta One or more of , W or Mo. Among the above-mentioned materials, Pt, Pd, Ir and Au are materials with positive spin Hall angles, and Ta, W and Mo are materials with negative spin Hall angles.

The magnetic tunnel junction stack structure provided by the embodiment of the present invention has two free layers, and the first free layer and the second free layer can have magnetization components in both in-plane and vertical directions through the cooperation of the magnetization mode through the coupling action. , that is, each free layer has magnetization components in two directions, and the magnetization components of the two free layers are flipped through different current-driven forms, and can have multiple states, thereby enabling the magnetic tunnel junction to have a wider range of applications. . The structure can not only realize efficient flipping without external magnetic field, but also realize multiple states, thereby enabling the magnetic tunnel junction to have wider applications. In the above-mentioned embodiments, the memory cells of the magnetic tunnel junction stack structure are plated on the substrate by using traditional molecular beam epitaxy, atomic layer deposition or magnetron sputtering, etc., and then perform photolithography, etching, etc. The shape of the magnetic tunnel junction is ellipse, diamond, rectangle or polygon. For each of the above implementations, the antiferromagnetic coupling effect can be achieved by adjusting the thickness of the coupling layer 300 .

As an optional implementation manner, as shown in FIG. 4 , the coupling layer 300 includes:

a first covering area, covering the upper surface of the first free layer 200;

The second coverage area covers the upper surface of the spin-orbit moment providing layer 100 except for the coverage area of the first free layer 200 .

The coupling layer 300 covers the first free layer 200 and the spin-orbit moment providing layer 100, which is beneficial to improve the turnover efficiency of the first free layer 200, and the antiferromagnetic coupling effect of the coupling layer 300 is preferentially used, and the spin Hall itself is preferably used. Effects stack up.

As an optional implementation manner, in the above-mentioned implementation manner, the spin Hall angle of the coupling layer 300 is opposite to the spin Hall angle of the self-selected orbital moment providing layer. In this embodiment, the coupling layer 300 and the spin-orbit moment providing layer 100 jointly promote the magnetic moment inversion of the first free layer 200 , which is equivalent to increasing the spin Hall angle and improving the inversion efficiency.

An embodiment of the present invention further provides a memory, including: any one of the above-mentioned magnetic tunnel junction stack structures; wherein, the first free layer is in an in-plane magnetization manner, the second free layer and the reference layer is a perpendicular magnetization method; the saturation magnetization of the first free layer and the saturation magnetization of the second free layer satisfy the following relationship: |Ms1-Ms2|/Ms2≥20%; wherein, Ms1 is the first free layer saturation magnetization, Ms2 is the saturation magnetization of the second free layer;

A current source is electrically connected to the spin-orbit moment providing layer, the current source is used to provide various write currents, and the direction of the current is in-plane and perpendicular to the magnetization direction of the first free layer.

The memory provided in this embodiment does not require an external magnetic field, the current drives the magnetic moment of the first free layer 200 to flip, and drives the second free layer 400 to flip through the coupling action, so that two resistance states, high and low, can be realized. As shown in FIG. 2 , FIG. 2 shows the changes of the magnetic moments of the first free layer 200 and the second free layer 400 which are simulated and displayed according to the present embodiment. The free relaxation states of the first free layer 200 and the second free layer 400 in no current state are initial states. For the in-plane magnetization component, when the current drives the in-plane magnetization component of the first free layer 200 from positive to negative, due to the antiferromagnetic effect, the in-plane magnetization component of the second free layer 400 changes from negative to positive. Within a reasonable range, the in-plane antiferromagnetic effect is established regardless of the saturation magnetization of the first free layer 200 and the saturation magnetization of the second free layer 400 . For the perpendicular magnetization component, the larger the saturation magnetization of the first free layer 200 is, the less the antiferromagnetic effect has on it, that is, the smaller the perpendicular magnetization component of the first free layer 200, the smaller the During the inversion process, the precession starts from the initial state. When the current is large enough, the angle of precession is greater than the angle between the initial direction of the magnetic moment and the film interface, that is, the vertical magnetization component of the first free layer 200 changes from negative to positive, so , the antiferromagnetic effect has a certain probability that the perpendicular magnetization component of the second free layer 400 changes from positive to negative to achieve flipping. It can be seen from FIG. 2 that the magnetic moments of the first free layer 200 and the second free layer 400 both have positive and negative values, and the change in the resistance of the magnetic tunnel junction is mainly caused by the magnetic layer (the second one) directly connected to the barrier layer 500 . The included angle between the magnetization direction of the free layer 400) and the magnetization direction of the reference layer 600 is determined. Therefore, the resistance of the magnetic tunnel junction corresponds to two resistance states.

When the saturation magnetization of the first free layer 200 and the saturation magnetization of the second free layer 400 satisfy the following relationship: |Ms1-Ms2|/Ms2<20%, the influence of the antiferromagnetic effect on the first free layer 200 is obvious. Make the perpendicular magnetization component of the first free layer 200 larger, the first free layer 200 starts to precess from the initial state during the flipping process, and the maximum precession angle is smaller than the angle between the initial direction of the magnetic moment and the film interface, that is, the first A free layer 200 cannot reverse the perpendicular magnetization direction, and thus cannot make the perpendicular magnetization component of the second free layer 400 reverse through coupling.

An embodiment of the present invention also provides a multi-resistance memory, including:

As any one of the above-mentioned magnetic tunnel junction stack structure;

A current source is electrically connected to the spin-orbit moment providing layer, and the current source is used to provide various write currents; the memory exhibits various resistance states, enabling multi-resistance state storage, thereby improving storage density . The magnetic tunnel junction stack structure provided by the embodiment of the present invention has two free layers, and the first free layer and the second free layer can have magnetization components in both in-plane and vertical directions through the cooperation of the magnetization mode through the coupling action. , that is, each free layer has magnetization components in two directions, and the magnetization components of the two free layers are flipped through different current-driven forms, and can have multiple states, thereby enabling the magnetic tunnel junction to have a wider range of applications. . The structure can not only realize efficient flipping without external magnetic field, but also realize multiple states, thereby enabling the magnetic tunnel junction to have wider applications.

As an optional implementation manner, as shown in FIG. 5 , the first free layer is in a perpendicular magnetization manner, and the second free layer and the reference layer are in an in-plane magnetization manner. As shown in FIG. 6 , FIG. 6 shows the changes of the magnetic moments of the first free layer 200 and the second free layer 400 which are simulated and displayed according to the present embodiment. The principle is similar, for the perpendicular magnetization components of the first free layer 200 and the second free layer 400, due to the perpendicular magnetization of the first free layer 200, the perpendicular magnetization component of the first free layer 200 itself is very large, and the precession starts from the initial state, and the largest precession The angles are smaller than the angle between the initial direction of the magnetic moment and the film interface. Therefore, the perpendicular magnetization component of the first free layer 200 is not reversed, and the perpendicular magnetization component of the second free layer 400 cannot be reversed through coupling. For the in-plane magnetization components of the first free layer 200 and the second free layer 400, the in-plane magnetization components of the first free layer 200 can be reversed, and at the same time, based on the antiferromagnetic coupling effect of the coupling layer, the second free layer can also be driven. The in-plane magnetization component of layer 400 flips. To sum up, the magnetic moment of the first free layer 200 basically does not change, and the magnitude of the current will cause the deflection angle of the second free layer 400 to be different, achieving a balance among magnetic anisotropy, spin-orbit moment and coupling. The reference layer 600 is magnetized in-plane and the magnetization direction is fixed. The resistance of the magnetic tunnel junction is mainly determined by the angle between the magnetization direction of the second free layer 400 and the magnetization direction of the reference layer 600 . The in-plane magnetization components of the magnetic moments of the second free layer 400 are different. As shown in FIG. 7 , a schematic diagram of the resistance change of the magnetic tunnel junction, under different write currents, the magnetic tunnel junction will have different resistance values, thereby having a multi-resistance storage mode.

Embodiments of the present invention also provide a neural network computing device, comprising:

Any one of the above-mentioned magnetic tunnel junction stack structures; used for storing corresponding weight values according to a variety of currents;

A current source is electrically connected to the spin-orbit torque providing layer, and the current source is used to provide various write currents.

In the above-mentioned neural network computing device, since each storage unit of each magnetic tunnel junction stack structure has a plurality of resistance states, the resistance states can be corresponding to the weight values. Convert the weight value to binary for storage, and one storage unit can complete the storage of a weight. When using the weight, reading a storage unit can get the weight, which saves the binary conversion process, thereby improving the neural network. Computational efficiency. In this embodiment, the magnetic tunnel junction can exhibit multiple resistance states through multiple directions of the magnetic moments of the first free layer 200 or the second free layer 400 , so that the storage of multiple storage states can be realized.

An embodiment of the present invention also provides a spin oscillator, including:

As any one of the above-mentioned magnetic tunnel junction stack structure;

a current source electrically connected to the spin-orbit torque providing layer, the current source for supplying a current to the spin-orbit torque providing layer, the current being greater than three times the flipping current of the first free layer. As shown in FIG. 3 , the simulation according to the present embodiment shows that when a sufficiently large current is continuously applied (for example, when the magnetization reversal current is more than 3 times), the magnetic properties of the first free layer 200 and the second free layer 400 As can be seen from the figure, the magnetic moments of the first free layer 200 and the second free layer 400 both produce oscillation phenomenon, wherein the magnetic moment of the second free layer 400 has a large oscillation amplitude and a strong signal, and is easier to receive. Therefore, this structure can be applied to microwave oscillators.

The above are only specific embodiments of the present invention, but the protection scope of the present invention is not limited thereto. Any person skilled in the art who is familiar with the technical scope disclosed by the present invention can easily think of changes or substitutions. All should be included within the protection scope of the present invention. Therefore, the protection scope of the present invention should be subject to the protection scope of the claims.

Claims (10)

1. A magnetic tunnel junction stack structure, comprising: a spin-orbit moment providing layer, a first free layer, a coupling layer, a second free layer, a barrier layer and a reference layer stacked in sequence from bottom to top; in, One of the first free layer and the second free layer is in-plane magnetization, and the other is perpendicular magnetization; The magnetization of the reference layer is the same as the magnetization of the second free layer. 2. The magnetic tunnel junction stack structure according to claim 1, wherein the coupling layer comprises: a first covering area, covering the upper surface of the first free layer; The second covering area covers the area on the upper surface of the spin-orbit moment providing layer except the covering area of the first free layer. 3 . The magnetic tunnel junction stack structure according to claim 2 , wherein the spin Hall angle of the coupling layer is opposite to the spin Hall angle of the self-selected orbital moment providing layer. 4 . 4. The magnetic tunnel junction stack structure according to claim 2, wherein a material of one of the coupling layer and the spin-orbit moment providing layer comprises one of Pt, Pd, Ir or Au or Several, another material includes one or more of Ta, W or Mo. 5 . The magnetic tunnel junction stack structure according to claim 1 , wherein the materials of the first free layer, the second free layer and the reference layer comprise one of Co, Fe, Ni, B, Pd or Pt. 6 . one or more; the material of the barrier layer includes one or more of MgO, MgAl ₂ O ₄ or Al ₂ O ₃ . 6. A memory, characterized in that, comprising: The magnetic tunnel junction stack structure according to any one of claims 1-5; wherein, the first free layer is in an in-plane magnetization mode, and the second free layer and the reference layer are in a perpendicular magnetization mode; The saturation magnetization of the first free layer and the saturation magnetization of the second free layer satisfy the following relationship: |Ms1-Ms2|/Ms2≥20%; wherein, Ms1 is the saturation magnetization of the first free layer, and Ms2 is the saturation magnetization of the second free layer; A current source is electrically connected to the spin-orbit moment providing layer, the current source is used to provide various write currents, and the direction of the current is in-plane and perpendicular to the magnetization direction of the first free layer. 7. A multi-resistance memory, comprising: The magnetic tunnel junction stack structure according to any one of claims 1-5; A current source is electrically connected to the spin-orbit torque providing layer, and the current source is used to provide various write currents. 8 . The reservoir according to claim 7 , wherein the first free layer is in a perpendicular magnetization mode, and the second free layer and the reference layer are in an in-plane magnetization mode. 9 . 9. A neural network computing device, comprising: a current source, electrically connected to the spin-orbit torque providing layer, the current source is used to provide various write currents; The magnetic tunnel junction stack structure according to any one of claims 1-5; used for storing corresponding weight values according to the multiple currents. 10. A spin oscillator, characterized in that, comprising: The magnetic tunnel junction stack structure according to any one of claims 1-5; a current source, electrically connected to the spin-orbit torque providing layer, the current source for providing a current to the spin-orbit torque providing layer, the current being greater than three times the flipping current of the first free layer.

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