Magnetic tunnel junction device

Abstract

The application provides a magnetic tunnel junction device, comprising: a reference layer, a barrier layer, a free layer and a cap layer which are sequentially stacked, the reference layer has a fixed magnetization which is substantially perpendicular to the plane of the reference layer, the free layer comprises: a first ferromagnetic layer, a second ferromagnetic layer and an antiferromagnetic coupling layer between the first ferromagnetic layer and the second ferromagnetic layer, the first ferromagnetic layer is adjacent to the barrier layer, the first ferromagnetic layer has a magnetization which is perpendicular to the film surface and can be reversed, and the second ferromagnetic layer has a magnetization which is opposite to the magnetization direction of the first ferromagnetic layer. And a spacer layer is arranged between the two ferromagnetic layers of the free layer and the antiferromagnetic coupling layer or between the two ferromagnetic layers, so as to improve the saturation magnetization of the free layer. The magnetic tunnel junction device of the application has high perpendicular anisotropy and low switching current.

Description

Technical Field

[0001] This invention relates to the field of magnetoresistive random access memory technology, and more particularly to a magnetic tunnel junction device. Background Technology

[0002] Magnetoresistive random access memory (MRAM) is a novel type of solid-state non-volatile memory. The core unit of MRAM is a magnetic tunnel junction (MTJ), which consists of a free layer, a reference layer, and a barrier layer sandwiched between them. The magnetization direction of the reference layer is fixed and does not flip during device operation; the magnetization direction of the free layer is collinear (parallel or antiparallel) with that of the reference layer. By utilizing the spin torque of electrons, the magnetization direction of the free layer can be flipped to achieve parallel (lower resistance) or antiparallel (higher resistance) magnetization directions between the reference layer and the free layer, thus enabling the writing of "0" or "1".

[0003] For MTJ devices, in order to improve the data retention time, the vertical anisotropy performance Hk of the free layer can be increased. However, with the increase of Hk, the write current will also increase, resulting in increased power consumption of the device. Summary of the Invention

[0004] To address the above problems, this invention provides a magnetic tunnel junction device that has high vertical anisotropy while having a low flip current.

[0005] In a first aspect, the present invention provides a magnetic tunnel junction device, comprising: a reference layer, a barrier layer, a free layer and a capping layer stacked sequentially, wherein the reference layer has a fixed magnetization substantially perpendicular to the plane of the reference layer, and the free layer comprises: a first ferromagnetic layer, a second ferromagnetic layer and an antiferromagnetic coupling layer located between the first ferromagnetic layer and the second ferromagnetic layer, wherein the first ferromagnetic layer is disposed adjacent to the barrier layer, the first ferromagnetic layer has a magnetization perpendicular to the thin film surface and reversible, and the second ferromagnetic layer has a magnetization opposite to the magnetization direction of the first ferromagnetic layer;

[0006] The free layer also includes:

[0007] A first spacer layer is located between the first ferromagnetic layer and the antiferromagnetic coupling layer;

[0008] The second spacer layer is located between the second ferromagnetic layer and the antiferromagnetic coupling layer.

[0009] Optionally, the materials of the first spacer layer and the second spacer layer are selected from any one of Ta, Mo, W, Hf, Nb, V, Y, Cr, and Ru.

[0010] Optionally, the antiferromagnetic coupling layer is selected from any one of Mo, Ir, Ru and Cr.

[0011] Optionally, the free layer further includes:

[0012] The first antiferromagnetic reinforcement layer is located between the first spacer layer and the antiferromagnetic coupling layer;

[0013] The second antiferromagnetic reinforcement layer is located between the second spacer layer and the antiferromagnetic coupling layer.

[0014] Optionally, the materials of the first antiferromagnetic reinforcement layer and the second antiferromagnetic reinforcement layer are Co, Fe, and their alloys.

[0015] In a second aspect, the present invention provides a magnetic tunnel junction device, comprising: a reference layer, a barrier layer, a free layer and a capping layer stacked sequentially, wherein the reference layer has a fixed magnetization substantially perpendicular to the plane of the reference layer, and the free layer comprises: a first ferromagnetic layer, a second ferromagnetic layer and an antiferromagnetic coupling layer located between the first ferromagnetic layer and the second ferromagnetic layer, wherein the first ferromagnetic layer is disposed adjacent to the barrier layer, the first ferromagnetic layer has a magnetization perpendicular to the thin film surface and is reversible, and the second ferromagnetic layer has a magnetization opposite to the magnetization direction of the first ferromagnetic layer;

[0016] The free layer also includes:

[0017] A first spacer layer is located between the first ferromagnetic layers, such that the first ferromagnetic layer is divided into a first sub-layer near the barrier layer and a second sub-layer near the antiferromagnetic coupling layer.

[0018] A second spacer layer is located between the second ferromagnetic layers, such that the second ferromagnetic layer is divided into a first sub-layer near the antiferromagnetic coupling layer and a second sub-layer near the capping layer.

[0019] Optionally, the materials of the first spacer layer and the second spacer layer are selected from any one of Ta, Mo, W, Hf, Nb, V, Y, Cr, and Ru.

[0020] Optionally, the antiferromagnetic coupling layer is selected from any one of Mo, Ir, Ru and Cr.

[0021] Optionally, the free layer further includes:

[0022] The first antiferromagnetic reinforcement layer is located between the second sub-layer of the first ferromagnetic layer and the antiferromagnetic coupling layer;

[0023] The second antiferromagnetic reinforcement layer is located between the first sublayer of the second ferromagnetic layer and the antiferromagnetic coupling layer.

[0024] Optionally, the materials of the first antiferromagnetic reinforcement layer and the second antiferromagnetic reinforcement layer are Co, Fe, and their alloys.

[0025] Thirdly, the present invention provides a magnetoresistive random access memory, the magnetoresistive random access memory including a magnetic tunnel junction device as provided in the first or second aspect.

[0026] The magnetic tunnel junction device provided by this invention employs a layered structure for the free layer, comprising two ferromagnetic layers and an antiferromagnetic coupling layer located between the two ferromagnetic layers. This results in high vertical anisotropy of the free layer, thereby improving the data retention time of the device. Furthermore, a spacer layer is inserted between the two ferromagnetic layers and the antiferromagnetic coupling layer, or directly between the two ferromagnetic layers, to increase the saturation magnetization of the free layer. This leads to a lower switching current, reduced power consumption, and improved durability of the device. Attached Figure Description

[0027] Figure 1 This is a schematic diagram of the structure of a magnetic tunnel junction device provided in an embodiment of the present invention;

[0028] Figure 2 This is a schematic diagram of the structure of a magnetic tunnel junction device provided in an embodiment of the present invention;

[0029] Figure 3 This is a schematic diagram of the structure of a magnetic tunnel junction device provided in an embodiment of the present invention;

[0030] Figure 4 This is a schematic diagram of the structure of a magnetic tunnel junction device provided in an embodiment of the present invention. Detailed Implementation

[0031] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. However, it should be understood that these descriptions are merely exemplary and not intended to limit the scope of this disclosure. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention. Furthermore, in the following description, descriptions of well-known structures and technologies are omitted to avoid unnecessarily obscuring the concepts of this disclosure.

[0032] The accompanying drawings illustrate various structural schematics according to embodiments of the present disclosure. These drawings are not to scale, and some details have been enlarged for clarity, and some details may have been omitted. The shapes of the various regions and layers shown in the drawings, as well as their relative sizes and positional relationships, are merely exemplary and may deviate from reality due to manufacturing tolerances or technical limitations. Furthermore, those skilled in the art can design regions / layers with different shapes, sizes, and relative positions as needed.

[0033] In the context of this disclosure, when a layer / element is referred to as being "above" another layer / element, the layer / element may be directly above the other layer / element, or there may be an intermediate layer / element between them. Additionally, if a layer / element is "above" another layer / element in one orientation, then when the orientation is reversed, the layer / element may be "below" the other layer / element.

[0034] It is known that for the free layer of a magnetic tunnel junction to flip, the write current needs to exceed the critical flip current I of the magnetic tunnel junction device. c0 Critical reversal current I c0 The larger the magnetization factor, the greater the power consumption of the device. Therefore, it is necessary to appropriately reduce the switching current of the device. The applicant's research has found that, for a given thermal stability factor Δ, in a magnetic tunnel junction device, as the saturation magnetization Ms increases, the switching current I... c This will reduce [the current]. Therefore, this application proposes a magnetic tunnel junction device with high vertical anisotropy and low flip current.

[0035] Figure 1 A cross-sectional structural schematic diagram of a magnetic tunnel junction device 100 provided in an embodiment of the present invention is shown. Figure 1As shown, this embodiment of the invention provides a magnetic tunnel junction device 100, which includes: a reference layer 101, a barrier layer 102, a free layer 103, and a capping layer 104 stacked sequentially from bottom to top. The capping layer 104 is a layer of heavy metal, such as Ta, which can serve a protective function. The reference layer 101 has a fixed magnetization approximately perpendicular to its plane, and the barrier layer 102 can be a layer of magnesium oxide (MgO). Specifically, in this embodiment, the free layer 103 adopts a multi-layer structure, including a first ferromagnetic layer 1031, a first spacer layer 1032, an antiferromagnetic coupling layer 1033, a second spacer layer 1034, and a second ferromagnetic layer 1035. The first ferromagnetic layer 1031 is disposed adjacent to the barrier layer 102, the second ferromagnetic layer 1035 is close to the capping layer 104, and the antiferromagnetic coupling layer 1033 is located between the first ferromagnetic layer 1031 and the second ferromagnetic layer 1035. The first ferromagnetic layer 1031 has a magnetization perpendicular to the film surface and is reversible, while the second ferromagnetic layer 1035 has a magnetization opposite to that of the first ferromagnetic layer 1031. Inserting an antiferromagnetic coupling (AFC) layer 1033 between the first ferromagnetic layer 1031 and the second ferromagnetic layer 1035 allows the magnetic moments of the two ferromagnetic layers to cancel each other out, reducing the demagnetization field and improving the overall magnetic anisotropy (Hk) of the free layer.

[0036] Furthermore, a first spacer layer 1032 is disposed between the first ferromagnetic layer 1031 and the antiferromagnetic coupling layer 1033, and a second spacer layer 1034 is disposed between the second ferromagnetic layer 1035 and the antiferromagnetic coupling layer 1033. By inserting spacers between the antiferromagnetic coupling layer and the two ferromagnetic layers, boron (B) can be absorbed and the structure adjusted, thereby improving the crystal structure of the two ferromagnetic layers. For example, the saturation magnetization Ms of the first ferromagnetic layer 1031 and the second ferromagnetic layer 1035 can be increased.

[0037] In one implementation, the antiferromagnetic coupling layer 1033 can be any of Mo, Ir, Ru, and Cr. Adjusting the thickness of the antiferromagnetic coupling layer 1033 can change the coupling strength between the first ferromagnetic layer 1031 and the second ferromagnetic layer 1035. The materials of the first spacer layer 1032 and the second spacer layer 1034 can be the same or different. Typically, a relatively light heavy metal material that can absorb boron (B) is chosen, such as Ta, Mo, W, Hf, Nb, V, Y, Cr, and Ru.

[0038] Furthermore, such as Figure 2 As shown, in Figure 1Based on the structure, a first antiferromagnetic reinforcement layer 1036 can be inserted between the first spacer layer 1032 and the antiferromagnetic coupling layer 1033, and a second antiferromagnetic reinforcement layer 1037 can be inserted between the second spacer layer 1034 and the antiferromagnetic coupling layer 1033. The first antiferromagnetic reinforcement layer 1036 and the second antiferromagnetic reinforcement layer 1037 are mainly used to improve the coupling effect of the antiferromagnetic coupling layer 1033, and are generally made of Co, Fe and their alloys.

[0039] Figure 3 A cross-sectional structural schematic diagram of a magnetic tunnel junction device 200 provided in an embodiment of the present invention is shown. Figure 3 As shown, this embodiment of the invention provides a magnetic tunnel junction device 200, which includes a reference layer 201, a barrier layer 202, a free layer 203, and a capping layer 204 stacked sequentially from bottom to top. The capping layer 204 is a layer of heavy metal, such as Ta, which can serve a protective function. The reference layer 201 has a fixed magnetization that is approximately perpendicular to the plane of the reference layer 201, and the barrier layer 202 can be a layer of magnesium oxide (MgO). Specifically, in this embodiment, the free layer 203 adopts a multi-layer structure, including a first ferromagnetic layer 2031, a second ferromagnetic layer 2035, and an antiferromagnetic coupling layer 2033 located between the first ferromagnetic layer 2031 and the second ferromagnetic layer 2035. The first ferromagnetic layer 2031 is disposed adjacent to the barrier layer 202, and the second ferromagnetic layer 2035 is close to the capping layer 204. The first ferromagnetic layer 2031 has a magnetization perpendicular to the film surface and is reversible, while the second ferromagnetic layer 2035 has a magnetization opposite to that of the first ferromagnetic layer 2031. Inserting the antiferromagnetic coupling (AFC) layer 2033 between the first ferromagnetic layer 2031 and the second ferromagnetic layer 2035 can cancel out the magnetic moments of the two ferromagnetic layers, reduce the demagnetization field, and improve the overall magnetic anisotropy (Hk) of the free layer.

[0040] Furthermore, a first spacer layer 2032 is disposed between the first ferromagnetic layer 2031 and the first spacer layer 2032, which divides the first ferromagnetic layer 2031 into a first sub-layer 2031a near the barrier layer 202 and a second sub-layer 2031b near the antiferromagnetic coupling layer 2033. The first spacer layer 2032 can be used to absorb boron (B) element and improve the lattice structure of the first ferromagnetic layer, for example, it can increase the saturation magnetization Ms of the first ferromagnetic layer.

[0041] Similarly, a second spacer layer 2034 is disposed between the layers of the second ferromagnetic layer 2035. The second spacer layer 2034 divides the second ferromagnetic layer 2035 into a first sublayer 2035a near the antiferromagnetic coupling layer 2033 and a second sublayer 2035b near the capping layer 204. The second spacer layer 2034 can be used to absorb boron (B) element and improve the lattice structure of the second ferromagnetic layer, for example, it can increase the saturation magnetization Ms of the second ferromagnetic layer.

[0042] In one implementation, the antiferromagnetic coupling layer 2033 can be any of Mo, Ir, Ru, and Cr. Adjusting the thickness of the antiferromagnetic coupling layer 2033 can change the coupling strength between the first ferromagnetic layer 2031 and the second ferromagnetic layer 2035. The materials of the first spacer layer 2032 and the second spacer layer 2034 can be the same or different. Typically, a relatively light heavy metal material that can absorb boron (B) is chosen, such as Ta, Mo, W, Hf, Nb, V, Y, Cr, and Ru.

[0043] Furthermore, such as Figure 4 As shown, in Figure 3 Based on the structure, a first antiferromagnetic reinforcement layer 2036 can be inserted between the second sub-layer 2031b of the first ferromagnetic layer and the antiferromagnetic coupling layer 2033, and a second antiferromagnetic reinforcement layer 2037 can be inserted between the first sub-layer 2035a of the second ferromagnetic layer and the antiferromagnetic coupling layer 2033. The first antiferromagnetic reinforcement layer 2036 and the second antiferromagnetic reinforcement layer 2037 are mainly used to improve the coupling effect of the antiferromagnetic coupling layer 2033, and are generally made of Co, Fe and their alloys.

[0044] The magnetic tunnel junction device provided in this invention employs a layered structure for the free layer, comprising two ferromagnetic layers and an antiferromagnetic coupling layer located between the two ferromagnetic layers. This results in high vertical anisotropy of the free layer, thereby improving the data retention time of the device. Furthermore, a spacer layer is inserted between the two ferromagnetic layers and the antiferromagnetic coupling layer, or directly between the two ferromagnetic layers, to increase the saturation magnetization of the free layer. This leads to a lower switching current, reduced power consumption, and improved durability of the device.

[0045] Furthermore, embodiments of the present invention also provide a magnetoresistive random access memory, which includes the aforementioned magnetic tunnel junction device.

[0046] The above description does not provide detailed technical specifications regarding the structure of each layer. However, those skilled in the art should understand that layers and regions of desired shapes can be formed using various technical means. Furthermore, to form the same structure, those skilled in the art can also design methods that are not entirely identical to those described above. Additionally, although various embodiments have been described above, this does not mean that the measures in the various embodiments cannot be advantageously combined.

[0047] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A magnetic tunnel junction device, characterized in that, include: A reference layer, a barrier layer, a free layer, and a capping layer are stacked sequentially. The reference layer has a fixed magnetization that is approximately perpendicular to the plane of the reference layer. The free layer includes a first ferromagnetic layer, a second ferromagnetic layer, and an antiferromagnetic coupling layer located between the first ferromagnetic layer and the second ferromagnetic layer. The first ferromagnetic layer is disposed adjacent to the barrier layer. The first ferromagnetic layer has a magnetization that is perpendicular to the film surface and can be flipped. The second ferromagnetic layer has a magnetization that is opposite to the magnetization direction of the first ferromagnetic layer. The free layer also includes: A first spacer layer is located between the first ferromagnetic layer and the antiferromagnetic coupling layer and is disposed adjacent to the first ferromagnetic layer and the antiferromagnetic coupling layer. The first spacer layer is used to increase the saturation magnetization of the first ferromagnetic layer. The second spacer layer is located between the second ferromagnetic layer and the antiferromagnetic coupling layer and is disposed adjacent to the second ferromagnetic layer and the antiferromagnetic coupling layer. The second spacer layer is used to increase the saturation magnetization of the second ferromagnetic layer.

2. The magnetic tunnel junction device according to claim 1, characterized in that, The materials of the first spacer layer and the second spacer layer are selected from any one of Ta, Mo, W, Hf, Nb, V, Y, Cr, and Ru.

3. The magnetic tunnel junction device according to claim 1, characterized in that, The antiferromagnetic coupling layer is selected from any one of Mo, Ir, Ru and Cr.

4. A magnetoresistive random access memory, characterized in that, Includes the magnetic tunnel junction device as described in any one of claims 1 to 3.

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