Magnetic tunnel junction film

Abstract

The invention provides a magnetic tunnel junction thin film, and the thin film comprises a magnetic tunnel junction lamination layer which comprises a reference layer, a barrier layer and a free layer, the first magnetic enhancement layer is arranged on the surface, away from the barrier layer, of the free layer, and the first magnetic enhancement layer is made of metal halide. According to the magnetic tunnel junction thin film provided by the invention, the vertical magnetic anisotropy of the magnetic tunnel junction can be enhanced on the premise that the tunnel magnetoresistance effect and the spin transfer torque effect are not influenced.

Description

Technical Field

[0001] The present invention relates to the field of magnetic storage technology, and in particular to a magnetic tunnel junction film. Background Art

[0002] Magnetic tunnel junction (MTJ) is the core unit of magnetic random access memory (MRAM). Its typical structure is a sandwich structure, namely, reference layer, barrier layer and free layer. The reference layer is generally pinned by antiferromagnetism, so that the direction of the magnetic moment of the reference layer remains unchanged; the barrier layer is used as a non-magnetic spacer to provide spin filtering effect; the direction of the magnetic moment of the free layer can be changed by magnetic field or current. The relative directions of the magnetic moments of the reference layer and the free layer correspond to the parallel state (low resistance state) and the antiparallel state (high resistance state), respectively.

[0003] Based on the application of microcontroller units and wearable system-on-chip, embedded MRAM that meets reflow soldering is required. In this case, high energy barrier is a basic requirement. High energy barrier requires the device to have strong magnetic anisotropy, that is, perpendicular magnetic anisotropy field enhancement; at the same time, lower write voltage and write current density are required to support multiple writes to meet the requirements of firmware and software upgrades. In the prior art, while enhancing the perpendicular magnetic anisotropy of the magnetic tunnel junction, it is easy to cause the tunnel magnetoresistance effect and spin transfer torque effect that affect the magnetic tunnel junction. Summary of the invention

[0004] The magnetic tunnel junction film provided by the present invention can enhance the perpendicular magnetic anisotropy of the magnetic tunnel junction without affecting the tunnel magnetoresistance effect and the spin transfer torque effect.

[0005] The present invention provides a magnetic tunnel junction film, the magnetic tunnel junction film comprising:

[0006] A magnetic tunnel junction stack, comprising a reference layer, a barrier layer and a free layer arranged in sequence;

[0007] A first magnetic enhancement layer is provided on a surface of the free layer away from the barrier layer, and the first magnetic enhancement layer is made of metal halide.

[0008] Optionally, the highest atomic number of the metal element in the metal halide is not higher than 88, and the highest atomic number of the halogen element is not higher than 85.

[0009] Optionally, the thickness of the first magnetic enhancement layer is 0.2 nm-1 nm; the first magnetic enhancement layer includes a single layer or a multilayer film formed by one or a combination of two or more of LiF, NaCl and NaF.

[0010] Optionally, the free layer includes:

[0011] A first free layer is arranged on a surface of the barrier layer away from the reference layer;

[0012] A transition layer is arranged on a surface of the first free layer away from the barrier layer, wherein the transition layer comprises one or a combination of two or more of Mo, W, Pt, Ta, Ru, Ir, Mg and MgO;

[0013] The second free layer is arranged on a surface of the transition layer away from the first free layer.

[0014] Optionally, a tunnel magnetoresistance ratio of the first free layer is higher than a tunnel magnetoresistance ratio of the second free layer.

[0015] Optionally, the magnetic tunnel junction film further includes:

[0016] The second magnetic enhancement layer is arranged on a surface of the first magnetic enhancement layer away from the free layer, and the second magnetic enhancement layer is made of a metal or metal oxide with high temperature annealing resistance and anti-diffusion properties.

[0017] Optionally, the second magnetic enhancement layer includes a single layer or a multilayer film formed by one or a combination of two or more of Ir, Mo, Mg and MgO.

[0018] Optionally, the reference layer, the barrier layer and the free layer of the magnetic tunnel junction stack are arranged in sequence from bottom to top.

[0019] Optionally, the magnetic tunnel junction film further includes:

[0020] A ferromagnetic layer is provided on a surface of the first magnetic enhancement layer away from the free layer. The ferromagnetic layer, the first magnetic enhancement layer and the free layer form a composite free layer.

[0021] Optionally, the reference layer, the barrier layer and the free layer of the magnetic tunnel junction stack are arranged in sequence from top to bottom.

[0022] The magnetic tunnel junction film provided by the present invention arranges the first magnetic enhancement layer on the surface of the free layer away from the barrier layer. On the one hand, it can utilize the interface between the free layer and the first magnetic enhancement layer to generate extremely strong magnetic anisotropy. On the other hand, since the magnetic enhancement layer is arranged on the surface of the free layer away from the barrier layer, it will not interfere with the barrier layer, and will not reduce the spin transfer torque effect and the tunnel magnetoresistance effect, thereby ensuring the writing efficiency and reading efficiency of the magnetic tunnel junction. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 A schematic diagram of a magnetic tunnel junction thin film according to an embodiment of the present invention;

[0024] Figure 2A schematic diagram of a magnetic tunnel junction film having a composite free layer according to another embodiment of the present invention;

[0025] Figure 3 A schematic diagram of a magnetic tunnel junction film having a second magnetic enhancement layer according to another embodiment of the present invention;

[0026] Figure 4 It is a schematic diagram of a magnetic tunnel junction film having a top pinning structure according to another embodiment of the present invention. DETAILED DESCRIPTION

[0027] In order to make the purpose, technical solution and advantages of the embodiments of the present invention clearer, the technical solution in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0028] The embodiment of the present invention provides a magnetic tunnel junction film, such as Figure 1 As shown, the magnetic tunnel junction film includes:

[0029] A magnetic tunnel junction stack includes a reference layer, a barrier layer and a free layer arranged in sequence; in some embodiments, no additional film is added to the magnetic tunnel junction stack, which can ensure that the tunnel magnetoresistance effect and the spin transfer torque effect of the magnetic tunnel junction stack are not affected, and will not affect the writing and reading efficiency of the magnetic tunnel junction stack.

[0030] The first magnetic enhancement layer is arranged on the surface of the free layer away from the barrier layer, and the first magnetic enhancement layer is made of metal halide. In some embodiments, the first magnetic enhancement layer is arranged on the surface of the free layer, and a very strong magnetic anisotropy can be formed by utilizing the interface between the first magnetic enhancement layer and the free layer.

[0031] The magnetic tunnel junction film provided by the embodiment of the present invention arranges the first magnetic enhancement layer on the surface of the free layer away from the barrier layer. On the one hand, it can utilize the interface between the free layer and the first magnetic enhancement layer to generate extremely strong magnetic anisotropy. On the other hand, since the magnetic enhancement layer is arranged on the surface of the free layer away from the barrier layer, it will not interfere with the barrier layer, and will not reduce the spin transfer torque effect and the tunnel magnetoresistance effect, thereby ensuring the writing efficiency and reading efficiency of the magnetic tunnel junction.

[0032] As an optional implementation, the highest atomic number of the metal element in the metal halide is not higher than 88, and the highest atomic number of the halogen element is not higher than 85.

[0033] In some embodiments, the first magnetic enhancement layer is made of a material with a low atomic number, and the spin-orbit coupling effect is very weak, which can maintain or even further reduce the damping coefficient of the free layer, thereby reducing the critical switching current.

[0034] As an optional implementation, the thickness of the first magnetic enhancement layer is 0.2 nm-1 nm; the first magnetic enhancement layer includes a single layer or a multilayer film formed by one or a combination of two or more of LiF, NaCl and NaF.

[0035] In some embodiments, LiF, NaCl and NaF are typical metal halides formed by low atomic number materials. When forming the first magnetic enhancement layer, a single-layer film can be formed by using one or a combination of two or more of LiF, NaCl and NaF, or a multi-layer film can be formed, and each layer of the film can be formed by using one or a combination of two or more of LiF, NaCl and NaF.

[0036] As an optional implementation, Figure 2 As shown, the free layer includes:

[0037] A first free layer is arranged on a surface of the barrier layer away from the reference layer;

[0038] A transition layer is arranged on a surface of the first free layer away from the barrier layer, wherein the transition layer comprises one or a combination of two or more of Mo, W, Pt, Ta, Ru, Ir, Mg and MgO;

[0039] The second free layer is arranged on a surface of the transition layer away from the first free layer.

[0040] In some embodiments, the free layer is preferably a composite free layer, such as a composite free layer formed by a first free layer, a transition layer and a second free layer, wherein the transition layer includes one or a combination of more than two of Mo, W, Pt, Ta, Ru, Ir, Mg and MgO; the transition layer can be a single-layer film or a multi-layer film. When a multi-layer film is used, each layer of the film can include one or a combination of more than two of Mo, W, Pt, Ta, Ru, Ir, Mg and MgO.

[0041] As an optional implementation manner, the tunnel magnetoresistance ratio of the first free layer is higher than the tunnel magnetoresistance ratio of the second free layer.

[0042] In some embodiments, the first free layer uses a magnetic material with a high tunnel magnetoresistance ratio and lattice matching with the barrier layer, such as CoFeB, CoFe, etc.; the second free layer uses a magnetic material matching with the first magnetic enhancement layer, such as Fe, or Fe-rich CoFeB, etc.

[0043] As an optional implementation, Figure 3 As shown, the magnetic tunnel junction film also includes:

[0044] The second magnetic enhancement layer is arranged on a surface of the first magnetic enhancement layer away from the free layer, and the second magnetic enhancement layer is made of a metal or metal oxide with high temperature annealing resistance and anti-diffusion properties.

[0045] In some embodiments, the second magnetic enhancement layer is made of metal or metal oxide with high temperature annealing resistance and diffusion resistance properties, which can effectively improve the high temperature annealing resistance of the entire magnetic tunnel junction film and also play a role in diffusion resistance during the preparation process.

[0046] As an optional embodiment, the second magnetic enhancement layer includes a single layer or a multilayer film formed by one or a combination of two or more of Ir, Mo, Mg and MgO.

[0047] In some embodiments, the second magnetic enhancement layer may be a single-layer film or a multi-layer film. When a single-layer film is used, the single-layer film includes one or a combination of two or more of Ir, Mo, Mg and MgO. When a multi-layer film is used, each thin film may include one or a combination of two or more of Ir, Mo, Mg and MgO.

[0048] In the aforementioned embodiment, the structure of the magnetic tunnel junction film with a second magnetic enhancement layer is illustrated by taking the case where the free layer has a first free layer, a transition layer and a second free layer as an example, but this does not limit the present invention. In the case where a single layer of ferromagnetic material is used to form the free layer, a second magnetic enhancement layer can also be formed on the surface of the first magnetic enhancement layer and the free layer.

[0049] As an optional implementation manner, the reference layer, the barrier layer and the free layer of the magnetic tunnel junction stack are arranged in sequence from bottom to top.

[0050] In some embodiments, when the reference layer, barrier layer and free layer of the magnetic tunnel junction stack are arranged from bottom to top, the preparation process should adopt the method of preparing the reference layer, barrier layer and free layer in sequence from bottom to top, and then continue to prepare the first magnetic enhancement layer. When the magnetic tunnel junction film has a second magnetic enhancement layer, the second magnetic enhancement layer is prepared on the first magnetic enhancement layer.

[0051] As an optional implementation, Figure 4 As shown, the magnetic tunnel junction film also includes:

[0052] A ferromagnetic layer is provided on a surface of the first magnetic enhancement layer away from the free layer. The ferromagnetic layer, the first magnetic enhancement layer and the free layer form a composite free layer.

[0053] In some embodiments, the ferromagnetic layer and the free layer can form a composite free layer, that is, the first magnetic enhancement layer is disposed in the composite free layer. This preparation method eliminates the need to prepare a transition layer in the composite free layer, which is beneficial for simplifying the process when using a composite free layer.

[0054] As an optional implementation, continue as Figure 4 As shown, the reference layer, barrier layer and free layer of the magnetic tunnel junction stack are arranged in sequence from top to bottom.

[0055] In some embodiments, when the reference layer, barrier layer and free layer of the magnetic tunnel junction are arranged in sequence from top to bottom, it is necessary to first prepare a ferromagnetic layer during the preparation process, then prepare a first magnetic enhancement layer on the ferromagnetic layer, and then prepare a free layer, a barrier layer and a reference layer in sequence on the first magnetic enhancement layer, thereby forming a top pinned structure.

[0056] The above is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily thought of by a person skilled in the art within the technical scope disclosed by the present invention should be included in the protection scope of the present invention. Therefore, the protection scope of the present invention should be based on the protection scope of the claims.

Claims

1. A magnetic tunnel junction thin film, It is characterized in that The magnetic tunnel junction film comprises: A magnetic tunnel junction stack, comprising a reference layer, a barrier layer and a free layer arranged in sequence; A first magnetic enhancement layer is provided on a surface of the free layer away from the barrier layer, and the first magnetic enhancement layer is made of metal halide.

2. The magnetic tunnel junction thin film according to claim 1, It is characterized in that The highest atomic number of the metal element in the metal halide is not higher than 88, and the highest atomic number of the halogen element is not higher than 85.

3. The magnetic tunnel junction thin film according to claim 1, It is characterized in that The thickness of the first magnetic enhancement layer is 0.2 nm-1 nm; the first magnetic enhancement layer includes a single layer or a multilayer film formed by one or a combination of two or more of LiF, NaCl and NaF.

4. The magnetic tunnel junction thin film according to claim 1, It is characterized in that The free layer comprises: A first free layer is arranged on a surface of the barrier layer away from the reference layer; A transition layer is arranged on a surface of the first free layer away from the barrier layer, wherein the transition layer comprises one or a combination of two or more of Mo, W, Pt, Ta, Ru, Ir, Mg and MgO; The second free layer is arranged on a surface of the transition layer away from the first free layer.

5. The magnetic tunnel junction thin film according to claim 4, It is characterized in that The tunnel magnetoresistance ratio of the first free layer is higher than the tunnel magnetoresistance ratio of the second free layer.

6. The magnetic tunnel junction thin film according to claim 1, It is characterized in that The magnetic tunnel junction film further comprises: The second magnetic enhancement layer is arranged on a surface of the first magnetic enhancement layer away from the free layer, and the second magnetic enhancement layer is made of a metal or metal oxide with high temperature annealing resistance and diffusion resistance.

7. The magnetic tunnel junction thin film according to claim 6, It is characterized in that The second magnetic enhancement layer includes a single layer or a multilayer film formed by one or a combination of two or more of Ir, Mo, Mg and MgO.

8. The magnetic tunnel junction thin film according to any one of claims 2 to 7, It is characterized in that The reference layer, the barrier layer and the free layer of the magnetic tunnel junction stack are arranged in sequence from bottom to top.

9. The magnetic tunnel junction thin film according to claim 1, It is characterized in that The magnetic tunnel junction film further comprises: A ferromagnetic layer is provided on a surface of the first magnetic enhancement layer away from the free layer. The ferromagnetic layer, the first magnetic enhancement layer and the free layer form a composite free layer.

10. The magnetic tunnel junction thin film according to claim 9, It is characterized in that The reference layer, the barrier layer and the free layer of the magnetic tunnel junction stack are arranged in sequence from top to bottom.

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