Spin-orbit magnetic storage unit

Abstract

This invention provides a spin-orbit moment magnetic storage cell, comprising: a heavy metal layer, a magnetic tunnel junction located on one side of the heavy metal layer, and a shunt electrode located on the other side of the heavy metal layer. The material of the heavy metal layer exhibits a spin-orbit moment effect, and the heavy metal layer has a non-centrosymmetric structure along a first direction or a second direction, wherein the first direction is the direction of current flowing from one end to the opposite end in the heavy metal layer, and the second direction is the opposite direction of the first direction; both the free layer and the reference layer of the magnetic tunnel junction have magnetic anisotropy perpendicular to the surface of the heavy metal layer; the shunt electrode and the magnetic tunnel junction have an overlapping region facing each other. The spin-orbit moment magnetic storage cell of this invention can achieve deterministic flipping of the free layer of the magnetic tunnel junction.

Description

Technical Field

[0001] This invention relates to the field of magnetic memory technology, and in particular to a spin-orbit moment magnetic memory cell. Background Technology

[0002] Spin Orbit Torque (SOT) based magnetic memory (SOT-MRAM) has higher write speed and lower power consumption compared to spin-transfer torque magnetic memory (STT-MRAM), and has good application prospects. It is considered to be the main writing method for next-generation MRAM.

[0003] The core of a SOT-MRAM memory cell is the magnetic tunnel junction, which works by utilizing the spin Hall effect (SHE) and the Rashba effect to flip the free-layer magnetic moment, thereby changing the resistance of the magnetic tunnel junction and enabling data storage. However, for perpendicularly magnetized magnetic tunnel junctions, using only the spin orbital moment is insufficient to accurately flip the free-layer magnetic moment. A common solution is to introduce an external magnetic field, but this is complex to implement. Therefore, it is necessary to propose a magnetic cell structure that can achieve deterministic flipping of the free layer without an external magnetic field. Summary of the Invention

[0004] To address the aforementioned problems, this invention provides a spin-orbit moment magnetic storage cell in which the free layer can deterministically flip without the assistance of an external magnetic field.

[0005] In a first aspect, the present invention provides a spin-orbit magnetic storage cell, comprising:

[0006] A heavy metal layer, wherein the material of the heavy metal layer has a spin orbital moment effect, and the heavy metal layer has a non-centrosymmetric structure along a first direction or a second direction, wherein the first direction is the direction of the current flowing from one end to the opposite end in the heavy metal layer, and the second direction is the opposite direction of the first direction;

[0007] A magnetic tunnel junction located on one side of the heavy metal layer includes at least a free layer, a barrier layer, and a reference layer, wherein the free layer is adjacent to the heavy metal layer, and both the free layer and the reference layer have magnetic anisotropy perpendicular to the surface of the heavy metal layer;

[0008] A shunt electrode is located on the other side of the heavy metal layer, and the shunt electrode and the magnetic tunnel junction have an overlapping area facing each other.

[0009] Optionally, the shunt electrode has an angle θ with the first direction or the second direction, where 45°≤θ≤90°.

[0010] Optionally, the cross-section of the heavy metal layer is a non-centrally symmetric cross-section composed of trapezoids and rectangles.

[0011] Optionally, the magnetic tunnel junction has a circular cross-sectional shape, the shunt electrode has a rectangular cross-sectional shape, and the width of the shunt electrode is smaller than the diameter of the magnetic tunnel junction.

[0012] Optionally, the material of the shunt electrode is any one of TaN, Cu, Ti / TiN combination, Ta / TaN combination, and Al.

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

[0014] Optionally, the free layer is a ferromagnetic material, using any one of Co, CoFe, and CoFeB.

[0015] Optionally, the barrier layer is a magnesium oxide thin film.

[0016] Optionally, the reference layer is a ferromagnetic material, using any one of Co, CoFe, and CoFeB.

[0017] In a second aspect, the present invention provides a magnetic memory comprising a memory array composed of spin-orbit magnetic memory cells provided in the first aspect.

[0018] Thirdly, the present invention provides an integrated circuit including the magnetic memory provided by the second aspect.

[0019] The spin-orbit moment magnetic storage cell provided by this invention allows the current to flow out from the shunt electrode after a current is applied to the heavy metal layer from one side, bypassing the other side of the heavy metal layer. Because the heavy metal layer has a non-centrosymmetric structure, a non-uniform spin current is induced. Under this asymmetric spin current, the spin Hall effect and Rashba effect exhibit different properties with respect to different initial magnetization directions, inducing asymmetry with respect to the initial magnetization direction. Furthermore, the fact that current flows into the heavy metal layer from only one side also induces current asymmetry. Based on these two asymmetries of current and magnetization, deterministic flipping of the free layer can be achieved. Attached Figure Description

[0020] Figure 1 This is a schematic diagram of the structure of a spin-orbit magnetic storage cell provided in an embodiment of the present invention;

[0021] Figure 2 This is a top view of the structure of a spin-orbit magnetic storage cell provided in an embodiment of the present invention;

[0022] Figure 3 This is a top view of the structure of a spin-orbit magnetic storage cell provided in an embodiment of the present invention;

[0023] Figure 4 This is a top view of the structure of a spin-orbit magnetic storage cell provided in an embodiment of the present invention;

[0024] Figure 5 This is a top view of the structure of a spin-orbit magnetic storage cell provided in an embodiment of the present invention;

[0025] Figure 6 Based on Figure 1 The diagram shows the current path through which current j1 is passed to the left side of the spin-orbit moment magnetic storage cell.

[0026] Figure 7 Based on Figure 1 The diagram shows the current path of current j2 flowing through the right side of the spin orbital magnetic storage cell. Detailed Implementation

[0027] 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.

[0028] 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.

[0029] 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.

[0030] Figure 1 This diagram illustrates a structural schematic of a spin-orbit magnetic storage cell according to an embodiment of the present invention, wherein... Figure 1 (a) is a top view. Figure 1 (b) is a side view. For example... Figure 1 As shown, this embodiment of the invention provides a spin-orbit moment magnetic storage cell, comprising: a heavy metal layer 101, wherein the material forming the heavy metal layer 101 exhibits a spin-orbit moment effect (including the spin Hall effect and the Rashba effect). For example, the heavy metal layer 101 can be any one of Ta, Pt, Pd, and W. By adjusting the material of the heavy metal layer, the ratio between the magnetic moment generated by the Rashba effect and the magnetic moment generated by the spin Hall effect can be controlled to be greater than 0.5. For example, when Ta is used as the heavy metal layer, the Rashba effect is larger. Furthermore, the heavy metal layer 101 has a non-centrosymmetric structure along a first direction or a second direction, i.e., the cross-section of the heavy metal layer 101 is a non-centrosymmetric section, wherein the first direction is the direction of current flowing from one end to the opposite end in the heavy metal layer, and the second direction is the opposite direction of the first direction. Figure 1 In (a), the direction of current flow from left to right can be defined as the first direction, and the direction of current flow from right to left as the second direction. Figure 1 (a) It can be seen that the cross-section of the heavy metal layer 101 is trapezoidal. Of course, the heavy metal layer 101 can also have other cross-sectional shapes, which will be described in detail in subsequent embodiments.

[0031] A magnetic tunnel junction 102 is disposed on one side of the heavy metal layer 101 (above the heavy metal layer 101 in this embodiment). The magnetic tunnel junction 102 includes at least a free layer 1021, a barrier layer 1022, and a reference layer 1023. The free layer 1021 is disposed adjacent to the heavy metal layer 101. Both the free layer 1021 and the reference layer 1023 have magnetic anisotropy perpendicular to the surface of the heavy metal layer 101. In terms of material selection, the combination of the materials of the free layer 1021 and the heavy metal layer 101 should have a strong Rashba effect, such as a Co / Ta combination, a CoFe / Ta combination, or a CoFeB / Ta combination. The barrier layer 1022 is a magnesium oxide thin film, and the reference layer 1023 is a ferromagnetic material, using any one of Co, CoFe, and CoFeB.

[0032] A shunt electrode 103 is disposed on the other side of the heavy metal layer 101 (below the heavy metal layer 101 in this embodiment), and the shunt electrode 103 and the magnetic tunnel junction 102 have an overlapping area facing each other. Specifically, the shunt electrode 103 can be configured to have an angle θ with the first direction or the second direction, where 45°≤θ≤90°, and in this embodiment, θ=90°. The port of the shunt electrode 103 is located at the bottom of the magnetic tunnel junction 102, and its function is to ensure that when current is passed through one end of the heavy metal layer 101, the current flows out through the shunt electrode 103 and does not flow through the other end of the heavy metal layer. In order to ensure that the current flows to the shunt electrode, the low resistance characteristic of the shunt electrode needs to be guaranteed. The shunt electrode can generally be any one of TaN, Cu, Ti / TiN combination, Ta / TaN combination, and Al. The heavy metal layer and the shunt electrode are used to pass current to excite the magnetic moment reversal of the free layer.

[0033] The magnetic tunnel junction 102 has a circular cross-sectional shape, the shunt electrode 103 has a rectangular cross-sectional shape, and the width of the shunt electrode 103 is smaller than the diameter of the magnetic tunnel junction 102.

[0034] Figures 2 to 5 Several embodiments of the spin-orbit magnetic storage cell of the present invention are listed.

[0035] Figure 2 The spin-orbit magnetic storage cell shown has a trapezoidal cross-sectional shape for the heavy metal layer 201, a circular cross-sectional shape for the magnetic tunnel junction 202, and a rectangular cross-sectional shape for the shunt electrode 203. The width of the shunt electrode 203 is smaller than the diameter of the magnetic tunnel junction 202, and there is an overlapping area between them. The shunt electrode 203 is moderately tilted, with an angle θ < 90° between it and either the first or second direction.

[0036] Figure 3 The spin-orbit magnetic storage cell shown has an isosceles trapezoidal cross-sectional shape for the heavy metal layer 301, a circular cross-sectional shape for the magnetic tunnel junction 302 (which is not located on the axis of symmetry of the heavy metal layer 301), and a rectangular cross-sectional shape for the shunt electrode 303. The width of the shunt electrode 303 is smaller than the diameter of the magnetic tunnel junction 302, and there is an overlapping area between the two. The shunt electrode 303 is perpendicular to either the first or second direction.

[0037] Figure 4 The spin-orbit magnetic storage cell shown has a heavy metal layer 401 with a cross-sectional shape composed of rectangles of varying widths, forming an overall asymmetrical structure. The magnetic tunnel junction 402 has a circular cross-sectional shape, while the shunt electrode 403 has a rectangular cross-sectional shape. The width of the shunt electrode 403 is smaller than the diameter of the magnetic tunnel junction 402, and there is an overlapping area between them. The shunt electrode 403 is perpendicular to either the first or second direction.

[0038] Figure 5 The spin-orbit magnetic storage cell shown has a heavy metal layer 501 with a cross-sectional shape composed of rectangles of varying widths, forming an overall asymmetrical structure. The magnetic tunnel junction 502 has a circular cross-sectional shape, while the shunt electrode 503 has a rectangular cross-sectional shape. The width of the shunt electrode 503 is smaller than the diameter of the magnetic tunnel junction 502, and the two have an overlapping area. The shunt electrode 503 is tilted, maintaining an acute angle with either the first or second direction.

[0039] Using the spin-orbit moment magnetic storage unit provided in the above embodiments, to Figure 1 The spin-orbit moment magnetic storage cell shown is the object of analysis, and the reference is... Figure 6 When a current j1 is applied to the left side of the heavy metal layer, j1 flows downwards from the shunt electrode, bypassing the right side of the heavy metal layer. (Reference) Figure 7 When a current j2 is applied to the right side of the heavy metal layer, j2 flows downwards from the shunt electrode, bypassing the left side of the heavy metal layer. The current in the heavy metal layer can be drawn outwards through the shunt electrode. Due to the non-centrosymmetric structure of the heavy metal layer, the current flowing through it forms a non-uniform current, inducing a non-uniform spin current. Under this asymmetric spin current, the spin Hall effect and Rashba effect have different properties for different initial magnetization directions, inducing asymmetry with respect to the initial magnetization direction. Furthermore, the fact that current flows into the heavy metal layer from only one side also induces current asymmetry. Based on these two asymmetries of current and magnetization, the following flipping process can be achieved: j1 will flip the free layer magnetization to negative, and j2 will flip the free layer magnetization to positive. Thus, the free layer can be deterministically flipped without the assistance of an external magnetic field. Additionally, the spin-orbit moment magnetic storage cell of this embodiment has no special requirements for the MTJ structure and has minimal impact on MTJ performance. The structural asymmetry of the heavy metal layer is in-plane, making it easier to process compared to out-of-plane asymmetry.

[0040] It should be noted that the direction of j1 does not affect the writing result; that is, if current j1 flows in from the shunt electrode and out from the left side of the heavy metal layer, the effect is the same. Similarly, the direction of j2 does not affect the writing result; that is, if current j2 flows in from the shunt electrode and out from the right side of the heavy metal layer, the effect is the same. In practical applications, the values ​​of j1 and j2 may not be the same. The values ​​of j1 and j2 can be made the same by fine-tuning the position of the shunt electrode.

[0041] On the other hand, another embodiment of the present invention provides a magnetic memory comprising a storage array composed of spin-orbit moment magnetic storage cells of the above embodiments.

[0042] The magnetic memory of this embodiment can be applied to the field of integrated circuits. Therefore, another embodiment of the present invention provides an integrated circuit that includes at least one magnetic memory as described in the above embodiment.

[0043] 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.

[0044] 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 spin-orbit magnetic storage cell, characterized in that, include: A heavy metal layer, wherein the material of the heavy metal layer has a spin orbital moment effect, and the heavy metal layer has a non-centrosymmetric structure along a first direction or a second direction, wherein the first direction is the direction of the current flowing from one end to the opposite end in the heavy metal layer, and the second direction is the opposite direction of the first direction; A magnetic tunnel junction located on one side of the heavy metal layer includes at least a free layer, a barrier layer, and a reference layer, wherein the free layer is adjacent to the heavy metal layer, and both the free layer and the reference layer have magnetic anisotropy perpendicular to the surface of the heavy metal layer; A shunt electrode is located on the other side of the heavy metal layer, and the shunt electrode and the magnetic tunnel junction have an overlapping area facing each other; The shunt electrode is used to draw the current outward when a current is passed through one end of the heavy metal layer, so that the current does not pass through the other end of the heavy metal layer, thereby inducing current asymmetry. Furthermore, due to the non-centrosymmetric structure of the heavy metal layer, a non-uniform spin current is induced, which further induces asymmetry about the initial magnetization direction.

2. The spin-orbit magnetic storage unit according to claim 1, characterized in that, The cross-section of the heavy metal layer is a non-centrally symmetrical cross-section composed of trapezoids and rectangles.

3. The spin-orbit magnetic storage unit according to claim 1, characterized in that, The magnetic tunnel junction has a circular cross-sectional shape, the shunt electrode has a rectangular cross-sectional shape, and the width of the shunt electrode is smaller than the diameter of the magnetic tunnel junction.

4. The spin-orbit magnetic storage unit according to claim 3, characterized in that, The shunt electrode has an angle with the first direction or the second direction. , .

5. The spin-orbit magnetic storage unit according to claim 1, characterized in that, The material of the shunt electrode is any one of TaN, Cu, Ti / TiN combination, Ta / TaN combination, and Al.

6. The spin-orbit magnetic storage unit according to claim 1, characterized in that, The material of the heavy metal layer is any one of Ta, Pt, Pd and W.

7. The spin-orbit magnetic storage unit according to claim 1, characterized in that, The free layer is a ferromagnetic material, using any one of Co, CoFe, and CoFeB.

8. The spin-orbit magnetic storage unit according to claim 1, characterized in that, The barrier layer is a magnesium oxide thin film.

9. The spin-orbit magnetic storage unit according to claim 1, characterized in that, The reference layer is a ferromagnetic material, using any one of Co, CoFe, and CoFeB.

10. A magnetic storage device, characterized in that, The magnetic memory includes a storage array composed of spin-orbit magnetic storage units as described in any one of claims 1-9.

11. An integrated circuit, characterized in that, The integrated circuit includes at least one magnetic memory as described in claim 10.

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