Magnetic tunnel junction device

Abstract

The present invention provides a magnetic tunnel junction device, a memory, and an integrated circuit. The magnetic tunnel junction device includes: a heavy metal layer, a free layer stacked above the heavy metal layer, a barrier layer, and a reference layer; a perpendicular enhancement layer disposed between the heavy metal layer and the free layer and adjacent to the heavy metal layer, the material of the perpendicular enhancement layer having a high perpendicular magnetic anisotropy; and a first coupling layer disposed between the perpendicular enhancement layer and the free layer. In the magnetic tunnel junction device of the present invention, the free layer still has high thermal stability at a small size.

Description

Technical Field

[0001] The present invention relates to the technical field of magnetic memories, and in particular to a magnetic tunnel junction device. Background Art

[0002] The SOT-MRAM that realizes the free layer magnetic moment flip based on the Spin Orbit Torque (SOT) is considered to be the main writing method for the next-generation MRAM due to its low power consumption and high writing speed. The magnetic tunnel junction (MTJ), as the core storage structure of the SOT-MRAM, includes a free layer, a barrier layer, and a reference layer, where different magnetization states of the free layer are used to store different data information. The data information stored in the MTJ is non-volatile, and the storage time of the data depends on the thermal stability coefficient of the free layer. To obtain a higher storage density, the required MTJ size of the magnetic memory also needs to be smaller. However, as the MTJ size decreases, especially below 10 nm, it is difficult to obtain a free layer structure with a high thermal stability coefficient using the existing material systems. Therefore, it is necessary to propose an MTJ structure that can make the free layer have a high thermal stability coefficient when the MTJ size decreases. Summary of the Invention

[0003] To solve the above problems, the present invention provides a magnetic tunnel junction device, in which the free layer still has high thermal stability at a smaller size.

[0004] In a first aspect, the present invention provides a magnetic tunnel junction device, including:

[0005] A heavy metal layer, the material of the heavy metal layer having a spin orbit torque effect;

[0006] A free layer, disposed on one side of the heavy metal layer and having magnetic anisotropy perpendicular to the surface of the heavy metal layer;

[0007] A barrier layer, disposed on the surface of the free layer away from the heavy metal layer;

[0008] A reference layer, disposed on the surface of the barrier layer away from the free layer and having magnetic anisotropy perpendicular to the surface of the heavy metal layer;

[0009] A perpendicular strengthening layer, disposed between the heavy metal layer and the free layer and adjacent to the heavy metal layer, the material of the perpendicular strengthening layer having high perpendicular magnetic anisotropy; and

[0010] A first coupling layer, disposed between the perpendicular strengthening layer and the free layer.

[0011] Optionally, the material of the perpendicular strengthening layer is any one of FePt, Nd5Fe 14 B, and SmCo5.

[0012] Optionally, the material of the first coupling layer includes any one of Ta, Ir, Mo, and Ru.

[0013] Optionally, the material of the heavy metal layer includes any one of Ta, Pt, Pd, and W.

[0014] Optionally, it further includes:

[0015] A synthetic antiferromagnetic layer disposed on the side of the reference layer away from the barrier layer;

[0016] A second coupling layer disposed between the synthetic antiferromagnetic layer and the reference layer.

[0017] Optionally, it further includes:

[0018] A bias layer disposed on the side of the heavy metal layer opposite to the side where the free layer is disposed, and the bias layer has a magnetization direction in the horizontal direction;

[0019] A protective layer disposed on the surface of the bias layer close to the heavy metal layer;

[0020] An insulating layer disposed on the surface of the protective layer close to the heavy metal layer, and the insulating layer surrounds the periphery of the bias layer and the protective layer.

[0021] In a second aspect, the present invention provides a magnetic tunnel junction device, including:

[0022] A heavy metal layer, the material of the heavy metal layer having a spin-orbit torque effect;

[0023] A free layer disposed on one side of the heavy metal layer and having magnetic anisotropy perpendicular to the surface of the heavy metal layer;

[0024] A barrier layer disposed on the surface of the free layer away from the heavy metal layer;

[0025] A reference layer disposed on the surface of the barrier layer away from the free layer and having magnetic anisotropy perpendicular to the surface of the heavy metal layer; and

[0026] A perpendicular enhancement layer disposed on the side of the heavy metal layer opposite to the side where the free layer is disposed, and the perpendicular enhancement layer generates antiferromagnetic coupling with the free layer through the heavy metal layer.

[0027] Optionally, the material of the perpendicular enhancement layer is any one of FePt, Nd5Fe 14 B, and SmCo5.

[0028] Optionally, the material of the heavy metal layer includes any one of Ta, Pt, Pd, and W.

[0029] Optionally, it further includes:

[0030] A synthetic antiferromagnetic layer disposed on a side of the reference layer away from the barrier layer;

[0031] A coupling layer disposed between the synthetic antiferromagnetic layer and the reference layer.

[0032] Optionally, it further includes:

[0033] A bias layer disposed on a side of the perpendicular enhancement layer away from the heavy metal layer, the bias layer having a magnetization direction in the horizontal direction;

[0034] A protection layer disposed between the bias layer and the perpendicular enhancement layer;

[0035] An insulating layer disposed between the protection layer and the perpendicular enhancement layer, and the insulating layer surrounds the periphery of the bias layer and the protection layer.

[0036] In a third aspect, the present invention provides a memory, the memory including the magnetic tunnel junction device provided in the first aspect or the second aspect.

[0037] In a fourth aspect, the present invention provides an integrated circuit including the memory provided in the third aspect.

[0038] In the magnetic tunnel junction device provided by the present invention, a perpendicular enhancement layer is added to the MTJ stack structure. The perpendicular enhancement layer is a ferromagnetic material with high magnetic anisotropy, forms ferromagnetic or antiferromagnetic coupling with the free layer, enhances the perpendicular magnetic anisotropy of the free layer, so that the free layer still has high thermal stability under a small size. Description of the Drawings

[0039] Figure 1 It is a schematic diagram of the stack structure of the magnetic tunnel junction device provided by an embodiment of the present invention;

[0040] Figure 2 It is a schematic diagram of the stack structure of the magnetic tunnel junction device provided by an embodiment of the present invention. Detailed Embodiments

[0041] To make the objectives, 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. However, it should be understood that these descriptions are merely exemplary and are not intended to limit the scope of the present disclosure. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts fall within the scope of protection of the present invention. In addition, in the following description, the descriptions of well-known structures and technologies are omitted to avoid unnecessarily obscuring the concepts of the present disclosure.

[0042] Various schematic structural diagrams according to embodiments of the present disclosure are shown in the accompanying drawings. These figures are not drawn to scale, where certain details are enlarged for the purpose of clear expression and some details may be omitted. The shapes of various regions and layers shown in the figures, as well as their relative sizes and positional relationships, are merely exemplary. In practice, there may be deviations due to manufacturing tolerances or technical limitations, and those skilled in the art can design regions / layers with different shapes, sizes, and relative positions according to actual needs.

[0043] In the context of the present disclosure, when a layer / element is referred to as being "on" another layer / element, the layer / element can be directly on the other layer / element, or there can be an intermediate layer / element between them. Additionally, if a layer / element is "on" another layer / element in one orientation, then when the orientation is reversed, the layer / element can be "under" the other layer / element.

[0044] Figure 1 A schematic diagram of the stacked structure of a magnetic tunnel junction device provided by an embodiment of the present invention is shown. As Figure 1 shown, an embodiment of the present invention provides a magnetic tunnel junction device, which includes: a heavy metal layer 103. The material of the heavy metal layer 103 has a spin-orbit torque effect. After a current is passed through the heavy metal layer 103, effects such as the spin Hall effect and the Rashba effect are generated. The material of the heavy metal layer 103 generally includes any one of Ta, Pt, Pd, and W. A free layer 106, a barrier layer 107, and a reference layer 108 are sequentially stacked above the heavy metal layer 103. The free layer 106 has magnetic anisotropy perpendicular to the surface of the heavy metal layer 103, and the magnetization direction of the free layer 106 can be flipped in a direction perpendicular to the surface of the heavy metal layer 103. The barrier layer 107 is generally an oxide layer, such as magnesium oxide, aluminum oxide, etc. The reference layer 108 has magnetic anisotropy perpendicular to the surface of the heavy metal layer 103, and the reference layer 108 has a fixed magnetization direction.

[0045] In an embodiment of the present invention, a perpendicular strengthening layer 104 and a first coupling layer 105 are provided between the heavy metal layer 103 and the free layer 106. The perpendicular strengthening layer 104 is adjacent to the heavy metal layer 103, and there is spin-orbit coupling between the perpendicular strengthening layer 104 and the heavy metal layer 103. The first coupling layer 105 is disposed between the free layer 106 and the perpendicular strengthening layer 104. The material of the perpendicular strengthening layer 104 is required to have very high perpendicular magnetic anisotropy. For example, any one of FePt, Nd5Fe 14 B, and SmCo5 can still have high magnetic anisotropy and thermal stability below 10 nm. The first coupling layer 105 can use a ferromagnetic material or an antiferromagnetic material. For example, any one of Ta, Ir, Mo, and Ru can be used to achieve ferromagnetic coupling or antiferromagnetic coupling at the upper and lower interfaces (i.e., between the perpendicular strengthening layer 104 and the free layer 106).

[0046] When the first coupling layer 105 uses a ferromagnetic material, the magnetization directions of the perpendicular strengthening layer 104 and the free layer 106 are the same in the stable state. This coupling state requires a relatively large coupling coefficient of the first coupling layer 105. When the SOT flips the perpendicular strengthening layer, the free layer can flip synchronously.

[0047] When the first coupling layer 105 uses an antiferromagnetic material, the magnetization directions of the perpendicular strengthening layer 104 and the free layer 106 are opposite in the stable state. Since the stray fields of the perpendicular strengthening layer and the free layer cancel each other out, this coupling state requires a relatively small coupling coefficient of the first coupling layer 105. When the SOT flips the perpendicular strengthening layer, the free layer can flip with a delay.

[0048] By adopting the composite structure of the perpendicular strengthening layer 104 / the first coupling layer 105 / the free layer 106 in the embodiment of the present invention, the perpendicular strengthening layer pins the free layer, which can enhance the perpendicular magnetic anisotropy of the free layer and effectively improve the thermal stability of the free layer, especially practical in MTJs below 10 nm. In addition, the free layer 106 does not have to be limited to high perpendicular magnetic anisotropy in material selection and can be other systems with higher TMR but lower perpendicular anisotropy.

[0049] Furthermore, in order to stabilize the magnetization direction of the reference layer 108, a synthetic antiferromagnetic (SAF) layer 110 can be provided above the reference layer 108. A second coupling layer 109 is provided between the synthetic antiferromagnetic (SAF) layer 110 and the reference layer 108. The second coupling layer 109 is generally an antiferromagnetic material, such as iridium (Ir) and ruthenium (Ru), to achieve antiferromagnetic coupling between the reference layer 108 and the synthetic antiferromagnetic layer 110. The reference layer 108 and the synthetic antiferromagnetic layer 110 have opposite magnetization directions. A capping layer 111 can also be provided on the synthetic antiferromagnetic (SAF) layer 110 to play a protective role and prevent the device from being oxidized.

[0050] Furthermore, in order for the free layer 106 to achieve deterministic switching, a bias layer 100 is provided below the heavy metal layer 103. The bias layer 100 has a magnetization direction in the horizontal direction. A protective layer 101 is provided on the surface of the bias layer 100 close to the heavy metal layer 103, and an insulating layer 102 is provided between the protective layer 101 and the heavy metal layer 103 to play an isolation role. The material of the bias layer 100 is NiFe or CoFe, and the material of the insulating layer 102 is SiO2. The insulating layer 102 surrounds the periphery of the bias layer 100 and the protective layer 101. The stray field generated by the bias layer 100 is equivalent to an external magnetic field, which assists the free layer 106 to achieve deterministic switching.

[0051] Figure 2 FIG. shows a schematic diagram of a stacked structure of a magnetic tunnel junction device according to another embodiment of the present invention. As Figure 2 shown, an embodiment of the present invention provides a magnetic tunnel junction device, which includes: a heavy metal layer 205. The material of the heavy metal layer 205 has a spin-orbit torque effect (generating, for example, a spin Hall effect and a Rashba effect after passing an electric current). The material of the heavy metal layer 205 generally includes any one of Ta, Pt, Pd, and W. A free layer 206, a barrier layer 207, and a reference layer 208 are sequentially stacked above the heavy metal layer 205. The free layer 206 has magnetic anisotropy perpendicular to the surface of the heavy metal layer 205, and the magnetization direction of the free layer 206 can be flipped in a direction perpendicular to the surface of the heavy metal layer 205. The barrier layer 207 is generally an oxide layer, such as magnesium oxide, aluminum oxide, etc. The reference layer 208 has magnetic anisotropy perpendicular to the surface of the heavy metal layer 205, and the reference layer 208 has a fixed magnetization direction.

[0052] In the embodiment of the present invention, a perpendicular strengthening layer 204 is provided on the other side of the heavy metal layer 205 opposite to the side where the free layer 206 is provided, and the perpendicular strengthening layer 204 is adjacent to the heavy metal layer 205. The material of the perpendicular strengthening layer 204 is required to have very high perpendicular magnetic anisotropy. For example, any one of FePt, Nd5Fe 14 B, and SmCo5 can be used, and it can still have high magnetic anisotropy and thermal stability below 10 nm. The heavy metal layer 205 here serves as a coupling layer between the perpendicular strengthening layer 204 and the free layer 206, and is an antiferromagnetic coupling. In the stable state, the magnetization directions of the free layer 206 and the perpendicular strengthening layer 204 are opposite. Since the stray fields of the perpendicular strengthening layer and the free layer cancel each other out, this coupling state requires a smaller coupling coefficient of the coupling layer. When the SOT flips the perpendicular strengthening layer, the free layer can be delayed in flipping.

[0053] In the embodiments of the present invention, by adopting a composite structure of a perpendicular strengthening layer 204 / a heavy metal layer 205 / a free layer 206, the perpendicular strengthening layer pins the free layer, which can enhance the perpendicular magnetic anisotropy of the free layer and effectively improve the thermal stability of the free layer. It is particularly practical in MTJs below 10 nm. In addition, the material selection of the free layer 206 does not have to be limited to high perpendicular magnetic anisotropy, and it can be other systems with higher TMR but lower perpendicular anisotropy.

[0054] Furthermore, in order to stabilize the magnetization direction of the reference layer 208, a synthetic antiferromagnet (SAF) layer 210 can be provided above the reference layer 208, and a coupling layer 209 is provided between the synthetic antiferromagnet (SAF) layer 210 and the reference layer 208. The coupling layer 209 is generally an antiferromagnetic material, such as iridium (Ir) and ruthenium (Ru), to achieve antiferromagnetic coupling between the reference layer 208 and the synthetic antiferromagnet layer 210. The reference layer 208 and the synthetic antiferromagnet layer 210 have opposite magnetization directions. A capping layer 211 can also be provided on the synthetic antiferromagnet (SAF) layer 210 to play a protective role and prevent the device from oxidizing.

[0055] Furthermore, in order for the free layer 206 to achieve deterministic flipping, a bias layer 201 is provided below the perpendicular strengthening layer 204, and the bias layer 201 has a magnetization direction in the horizontal direction. A protective layer 202 is provided between the bias layer 201 and the perpendicular strengthening layer 204, and an insulating layer 203 is provided between the protective layer 202 and the perpendicular strengthening layer 204 to play an isolation role. The material of the bias layer 201 is NiFe or CoFe, and the material of the insulating layer 203 is SiO2. The insulating layer 203 surrounds the bias layer 201 and the protective layer 202 on all sides. The stray field generated by the bias layer 201 is equivalent to an external magnetic field to assist the free layer 206 to achieve deterministic flipping.

[0056] The following describes a memory including the above magnetic tunnel junction device according to an embodiment of the present invention. The memory may include word lines, bit lines, source lines, transistors, and a magnetic tunnel junction device having the structure of the foregoing embodiment. The magnetic tunnel junction device is connected to the word lines and bit lines through transistors respectively, and the magnetic tunnel junction device is also directly connected to the source line to implement the functions of writing data and reading data in the memory. Correspondingly, the free layer of the magnetic tunnel junction device in the memory has high thermal stability at a small size.

[0057] In addition, the memory of this embodiment can be applied to the field of integrated circuits. For this reason, another embodiment of the present invention provides an integrated circuit, which includes at least one memory in the above embodiment.

[0058] In the above description, no detailed explanations are made for technical details such as the composition of each layer. However, those skilled in the art should understand that various technical means can be used to form layers, regions, etc. of the required shapes. Additionally, in order to form the same structure, those skilled in the art can also design methods that are not exactly the same as the methods described above. Moreover, although the embodiments are described separately above, this does not mean that the measures in each embodiment cannot be used advantageously in combination.

[0059] As described above, the above are only specific embodiments of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed by the present invention should be covered by 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

1. A magnetic tunnel junction device, characterized in that, Comprising: A heavy metal layer, the material of the heavy metal layer having a spin-orbit torque effect; A free layer, disposed on one side of the heavy metal layer and having magnetic anisotropy perpendicular to the surface of the heavy metal layer; A barrier layer, disposed on the surface of the free layer away from the heavy metal layer; A reference layer, disposed on the surface of the barrier layer away from the free layer and having magnetic anisotropy perpendicular to the surface of the heavy metal layer; A perpendicular enhancement layer, disposed between the heavy metal layer and the free layer and adjacent to the heavy metal layer, the material of the perpendicular enhancement layer having high perpendicular magnetic anisotropy; And A first coupling layer, disposed between the perpendicular enhancement layer and the free layer, the first coupling layer being used to achieve ferromagnetic coupling or antiferromagnetic coupling between the perpendicular enhancement layer and the free layer; There is spin-orbit coupling between the perpendicular enhancement layer and the heavy metal layer; If the perpendicular enhancement layer and the free layer are ferromagnetically coupled, when the spin-orbit torque flips the magnetization direction of the perpendicular enhancement layer, the magnetization direction of the free layer flips synchronously; If the perpendicular enhancement layer and the free layer are antiferromagnetically coupled, when the spin-orbit torque flips the magnetization direction of the perpendicular enhancement layer, the magnetization direction of the free layer flips with a delay.

2. The magnetic tunnel junction device according to claim 1, wherein The material of the vertical strengthening layer is any one of FePt, Nd5Fe 14 B, and SmCo5.

3. The magnetic tunnel junction device according to claim 1, wherein The material of the first coupling layer includes any one of Ta, Ir, Mo, and Ru.

4. The magnetic tunnel junction device according to claim 1, wherein The material of the heavy metal layer includes any one of Ta, Pt, Pd, and W.

5. The magnetic tunnel junction device according to claim 1, characterized in that, Further comprising: A synthetic antiferromagnetic layer, disposed on the side of the reference layer away from the barrier layer; A second coupling layer, disposed between the synthetic antiferromagnetic layer and the reference layer.

6. The magnetic tunnel junction device according to claim 1, wherein Further comprising: A bias layer, disposed on the other side of the heavy metal layer opposite to the side where the free layer is disposed, the bias layer having a magnetization direction in the horizontal direction; A protective layer, disposed on the surface of the bias layer close to the heavy metal layer; An insulating layer, disposed on the surface of the protective layer close to the heavy metal layer, and the insulating layer surrounds the periphery of the bias layer and the protective layer.

7. A magnetic tunnel junction device, characterized in that, Comprising: A heavy metal layer, the material of the heavy metal layer having a spin-orbit torque effect; A free layer, disposed on one side of the heavy metal layer and having magnetic anisotropy perpendicular to the surface of the heavy metal layer; A barrier layer, disposed on the surface of the free layer away from the heavy metal layer; A reference layer, disposed on the surface of the barrier layer away from the free layer and having magnetic anisotropy perpendicular to the surface of the heavy metal layer; And A perpendicular enhancement layer, disposed on the other side of the heavy metal layer opposite to the side where the free layer is disposed, the perpendicular enhancement layer generating antiferromagnetic coupling with the free layer through the heavy metal layer; There is spin-orbit coupling between the perpendicular enhancement layer and the heavy metal layer; When the spin-orbit torque flips the magnetization direction of the perpendicular enhancement layer, the magnetization direction of the free layer flips with a delay.

8. The magnetic tunnel junction device according to claim 7, characterized in that The material of the vertical reinforcement layer is any one of FePt, Nd5Fe 14 B, and SmCo5.

9. The magnetic tunnel junction device according to claim 7, characterized in that, The material of the heavy metal layer includes any one of Ta, Pt, Pd, and W.

10. The magnetic tunnel junction device according to claim 7, characterized in that, Further comprising: A synthetic antiferromagnetic layer, disposed on the side of the reference layer away from the barrier layer; A coupling layer, disposed between the synthetic antiferromagnetic layer and the reference layer.

11. The magnetic tunnel junction device according to claim 7, characterized in that, Further comprising: A bias layer is disposed on a side of the perpendicular reinforcement layer away from the heavy metal layer, and the bias layer has a magnetization direction in a horizontal direction; A protective layer is disposed between the bias layer and the perpendicular reinforcement layer; An insulating layer is disposed between the protective layer and the perpendicular reinforcement layer, and the insulating layer surrounds the periphery of the bias layer and the protective layer.

12. A memory, characterized in that, Comprising: The magnetic tunnel junction device according to any one of claims 1 to 11.

13. An integrated circuit, characterized in that, The integrated circuit includes at least one memory according to claim 12.

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