SOT-MRAM storage unit and preparation method thereof

Abstract

The invention provides an SOT-MRAM memory cell and a preparation method thereof, and the SOT-MRAM memory cell comprises a magnetic tunnel junction which comprises a free layer, a barrier layer and a reference layer which are sequentially stacked from bottom to top, the free layer has vertical magnetization with a variable direction, and the reference layer has vertical magnetization with a fixed direction; the spin-orbit coupling layer is positioned below the magnetic tunnel junction, is in contact with the free layer and is used for generating a spin-orbit moment so as to enable the free layer to be magnetized and overturned; the first ferromagnetic layer and the second ferromagnetic layer are located above the spin-orbit coupling layer and located on the two sides of the magnetic tunnel junction, the first ferromagnetic layer and the second ferromagnetic layer both have in-plane horizontal magnetization, and the magnetization direction is parallel to the direction of write current passing through the spin-orbit moment coupling layer so as to generate a horizontal magnetic field for the magnetic tunnel junction. According to the method, deterministic magnetization overturning of the free layer can be realized by utilizing the spin-orbit moment under the condition of no external magnetic field.

Description

Technical Field

[0001] The present invention relates to the technical field of MRAM memories, and particularly to a SOT-MRAM storage cell and a preparation method thereof. Background Art

[0002] With the rapid development of spintronics, the spin-orbit coupling effect (SOC) has attracted more and more extensive attention, mainly including the spin Hall effect and the interfacial Edelstein effect and their inverse effects, which can realize the mutual conversion of voltage-controllable current and spin current. The spin-orbit torque (SOT) is based on the SOC effect and uses the spin current induced by the charge current to generate a spin transfer torque, so as to achieve the purpose of regulating magnetic storage cells. Due to the separation of its read and write paths, it has excellent performances such as low energy consumption, fast writing speed, strong magnetic moment flipping, high efficiency, and high stability, showing great prospects in the field of magnetic storage devices and other fields.

[0003] The spin-orbit torque type magnetic random access memory (SOT-MRAM) uses the SOT generated by the spin current as the information writing method, which not only maintains the excellent characteristics of MRAM such as high speed and low power consumption, but also realizes the separation of the read and write paths, which is more conducive to improving the anti-breakdown and long-life performances of the device.

[0004] At present, for the SOT-MRAM that uses a magnetic tunnel junction with excellent performance and perpendicular magnetic anisotropy as the basic storage cell, a single spin-orbit torque cannot achieve deterministic directional magnetization flipping. Generally, with the help of an externally applied magnetic field in a specific direction, the deterministic magnetic moment flipping of the perpendicular free layer in the magnetic tunnel junction and information writing can be achieved. However, the introduction of the externally applied magnetic field increases the circuit complexity and reliability risk, which is not conducive to the integration of the device. Therefore, how to make the spin-orbit torque complete deterministic magnetization flipping under the condition of no externally applied magnetic field and realize integrated applications compatible with the existing CMOS process is still an urgent technical problem in this field. Summary of the Invention

[0005] To solve the above problems, the present invention provides a SOT-MRAM storage cell, which can use the spin-orbit torque to achieve deterministic magnetization flipping of the free layer under the condition of no externally applied magnetic field.

[0006] On the one hand, the present invention provides a SOT-MRAM storage cell, including: A magnetic tunnel junction, including a free layer, a barrier layer, and a reference layer stacked in sequence from bottom to top, wherein the free layer has a vertically variable magnetization direction, and the reference layer has a vertically fixed magnetization direction; A spin - orbit coupling layer, located below the magnetic tunnel junction and in contact with the free layer, is configured to generate a spin - orbit torque to flip the magnetization of the free layer. A first ferromagnetic layer and a second ferromagnetic layer, located above the spin - orbit coupling layer and on both sides of the magnetic tunnel junction. Both the first ferromagnetic layer and the second ferromagnetic layer have in - plane horizontal magnetization, and the magnetization directions are parallel to the direction of the write current passing through the spin - orbit torque coupling layer, so as to generate a horizontal magnetic field for the magnetic tunnel junction.

[0007] Optionally, the materials of the first ferromagnetic layer and the second ferromagnetic layer are one of Fe, FeCo, and FeN.

[0008] Optionally, the material of the spin - orbit torque coupling layer is a heavy metal, a doped heavy metal, a heavy - metal alloy, or a topological insulator.

[0009] Optionally, further comprising: A first antiferromagnetic layer, located above the first ferromagnetic layer, configured to pin the magnetization direction of the first ferromagnetic layer; A second antiferromagnetic layer, located above the second ferromagnetic layer, configured to pin the magnetization direction of the second ferromagnetic layer.

[0010] Optionally, the materials of the first antiferromagnetic layer and the second antiferromagnetic layer are IrMn or PtMn.

[0011] Optionally, further comprising: A first protective layer, located above the first antiferromagnetic layer; A second protective layer, located above the second antiferromagnetic layer.

[0012] Optionally, the materials of the first protective layer and the second protective layer are Ta or Ru.

[0013] Optionally, further comprising: an insulating dielectric layer, surrounding the sidewalls and the top of the magnetic tunnel junction and covering the surface of the spin - orbit coupling layer.

[0014] On the other hand, the present invention provides a method for manufacturing an SOT - MRAM memory cell, comprising: Providing a substrate; Depositing and forming a spin - orbit coupling layer on the substrate; Forming a magnetic tunnel junction on the spin - orbit torque coupling layer. The magnetic tunnel junction includes a free layer, a barrier layer, and a reference layer stacked in sequence from bottom to top. The free layer has vertically variable magnetization, and the reference layer has vertically fixed magnetization; An insulating dielectric layer, a ferromagnetic layer, an antiferromagnetic layer, and a protective layer are sequentially conformally deposited on the surface of the spin-orbit torque coupling layer and the surface of the magnetic tunnel junction; Lithography and etching are respectively performed on both sides of the magnetic tunnel junction to form a stacked structure including a ferromagnetic layer / antiferromagnetic layer / protective layer from bottom to top on both sides of the magnetic tunnel junction; Magnetic field annealing is performed under vacuum conditions such that the magnetization directions of the ferromagnetic layers on both sides of the magnetic tunnel junction are in the horizontal direction and parallel to the direction of the write current passing through the spin-orbit torque coupling layer.

[0015] Optionally, the material of the ferromagnetic layer is one of Fe, FeCo, and FeN; The material of the antiferromagnetic layer is IrMn or PtMn; The material of the protective layer is Ta or Ru.

[0016] In the SOT-MRAM storage cell provided by the present invention, ferromagnetic layers are respectively arranged on both sides of the magnetic tunnel junction, and the magnetization directions of the ferromagnetic layers on both sides are parallel to the direction of the write current flowing through the spin-orbit coupling layer. Thus, a horizontal magnetic field parallel to the write current direction is generated by the ferromagnetic layers on both sides on the magnetic tunnel junction, and the positive and negative directions of the write current can realize the up-and-down directional flipping of the magnetic moment of the free layer. Description of the Drawings

[0017] Figure 1 It is a schematic structural diagram of an SOT-MRAM storage cell provided by an embodiment of the present invention; Figures 2 to 5 It is a schematic cross-sectional structural diagram of each step of the method for manufacturing an SOT-MRAM storage cell provided by an embodiment of the present invention. Detailed Embodiments

[0018] 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 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 shall 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 confusing the concepts of the present disclosure.

[0019] 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 for the purpose of clear expression, some details are enlarged 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 additionally design regions / layers with different shapes, sizes, and relative positions according to actual needs.

[0020] 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.

[0021] Figure 1 A three-dimensional view of a SOT-MRAM memory cell provided by an embodiment of the present invention is shown. As Figure 1 shown, the SOT-MRAM memory cell includes a magnetic tunnel junction 101, a spin-orbit coupling layer 102, and a first ferromagnetic layer 1041 and a second ferromagnetic layer 1042 located on both sides of the magnetic tunnel junction 101. Specifically, the magnetic tunnel junction 101 includes a basic sandwich structure, that is, a free layer, a barrier layer, and a reference layer (not shown in the figure) stacked in sequence from bottom to top, where the free layer has a vertically variable magnetization direction and the reference layer has a vertically fixed magnetization direction. The spin-orbit coupling layer 102 is located below the magnetic tunnel junction 101 and is in contact with the free layer of the magnetic tunnel junction 101. The spin-orbit coupling layer 102 is used to generate a spin-orbit torque by using the spin Hall effect to flip the magnetization of the free layer. The first ferromagnetic layer 1041 and the second ferromagnetic layer 1042 are located above the spin-orbit torque coupling layer 102 and are respectively located on both sides of the magnetic tunnel junction 101. Both ferromagnetic layers have in-plane horizontal magnetization, and the magnetization directions are parallel to the direction of the write current passing through in the spin-orbit torque coupling layer 102 during data writing to generate a horizontal magnetic field for the magnetic tunnel junction 101.

[0022] Optionally, referring to Figure 1 , as an implementation manner, the SOT-MRAM memory cell may further include a first antiferromagnetic layer 1051 and a second antiferromagnetic layer 1052. The first antiferromagnetic layer 1051 is located above the first ferromagnetic layer 1041 and is used to pin the magnetization direction of the first ferromagnetic layer 1041. The second antiferromagnetic layer 1052 is located above the second ferromagnetic layer 1042 and is used to pin the magnetization direction of the second ferromagnetic layer 1042.

[0023] Further, a first protective layer 1061 may be disposed above the first antiferromagnetic layer 1051 to prevent oxidation of the first antiferromagnetic layer 1051. Similarly, a second protective layer 1062 may be disposed above the second antiferromagnetic layer 1052 to prevent oxidation of the second antiferromagnetic layer 1052.

[0024] In the above embodiment, ferromagnetic materials such as Fe, FeCo, and FeCoB are used for the free layer and the reference layer of the magnetic tunnel junction 101. The barrier layer is commonly MgO. The material of the spin-orbit torque coupling layer 102 is a heavy metal, a doped heavy metal, a heavy metal alloy, or a topological insulator. The materials of the first ferromagnetic layer 1041 and the second ferromagnetic layer 1042 are one of Fe, FeCo, and FeN. The materials of the first antiferromagnetic layer 1051 and the second antiferromagnetic layer 1052 are IrMn or PtMn. The materials of the first protective layer 1061 and the second protective layer 1062 are Ta or Ru.

[0025] In addition, considering the device manufacturing process, there will be an insulating dielectric layer (not shown in the figure) surrounding the sidewalls and the top of the magnetic tunnel junction 101 and covering the surface of the spin-orbit coupling layer 102.

[0026] In the SOT-MRAM storage cell provided by the present invention, ferromagnetic layers are respectively disposed on both sides of the magnetic tunnel junction, and the magnetization directions of the ferromagnetic layers on both sides are fixedly parallel to the direction of the write current flowing through the spin-orbit coupling layer. Therefore, a horizontal magnetic field parallel to the write current direction is generated by the ferromagnetic layers on both sides on the magnetic tunnel junction, and the positive and negative directions of the write current can realize the up-and-down directional flipping of the magnetic moment of the free layer.

[0027] For the SOT-MRAM storage cell provided in the above embodiment, the present invention also provides a manufacturing method of the SOT-MRAM storage cell. Figures 2 to 5 The structural cross-sectional views of each step in the manufacturing process are shown.

[0028] As Figure 2 shown, a substrate 201 is provided, and a spin-orbit coupling layer 202 is deposited on the substrate 201. Ta, Pt, etc. can be grown by thin film growth processes such as PVD to obtain the spin-orbit coupling layer. Then, thin films of each layer of the magnetic tunnel junction are grown on the spin-orbit torque coupling layer 202, and the thin films of each layer of the magnetic tunnel junction are processed into a magnetic tunnel junction 203 by photolithography and etching. The magnetic tunnel junction 203 is generally cylindrical, and the magnetic tunnel junction 203 at least includes a free layer, a barrier layer, and a reference layer stacked in sequence from bottom to top. The free layer has a vertically variable magnetization, and the reference layer has a vertically fixed magnetization.

[0029] As Figure 3As shown, an insulating dielectric layer 204 is conformally formed on the exposed surface of the spin-orbit torque coupling layer 202 and the surface of the magnetic tunnel junction 203. The insulating dielectric layer 204 can be SiN and is used to protect the magnetic tunnel junction 203.

[0030] Next, referring to Figure 4 , a ferromagnetic layer 205 with high magnetization intensity, an antiferromagnetic layer 206, and a protective layer 207 are sequentially deposited on the insulating dielectric layer 204. The ferromagnetic layer 205 can be one of Fe, FeCo, and FeN, the material of the antiferromagnetic layer 206 can be IrMn or PtMn, and the material of the protective layer 207 can be Ta or Ru, etc.

[0031] Then, as Figure 5 shown, photolithography and etching are respectively performed on both sides of the magnetic tunnel junction 203 to form a stacked structure including a ferromagnetic layer / antiferromagnetic layer / protective layer in sequence from bottom to top on both sides of the magnetic tunnel junction 203. In Figure 5 , the ferromagnetic layer 2051 / antiferromagnetic layer 2061 / protective layer 2071 form a stacked structure, and the ferromagnetic layer 2052 / antiferromagnetic layer 2062 / protective layer 2072 form a stacked structure. It can be understood that these two stacked structures can be obtained through appropriate exposure patterns.

[0032] Finally, magnetic field annealing is performed under vacuum conditions such that the magnetization directions of the ferromagnetic layers 2051 and 2052 are in the horizontal direction and parallel to the writing current direction passing through in the spin-orbit torque coupling layer during data writing, forming an external horizontal magnetic field for the magnetic tunnel junction. Specifically, under magnetic field annealing, the ferromagnetic layer 2051 is pinned to a horizontal direction by the antiferromagnetic layer 2061, the ferromagnetic layer 2052 is pinned to a horizontal direction by the antiferromagnetic layer 2062, and the ferromagnetic layers 2051 and 2052 jointly form a horizontal magnetic field for the magnetic tunnel junction, thereby causing the spin-orbit torque generated when positive and negative currents are written in the spin-orbit coupling layer to be able to directionally flip the free layer magnetic moment.

[0033] In addition, SiO2 insulating dielectric can be redeposited to protect the formed device structure.

[0034] In the above description, technical details such as the patterning and etching of each layer are not described in detail. However, those skilled in the art should understand that various technical means can be used to form layers, regions, etc. with the required shapes. In addition, 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. In addition, although the above embodiments are described separately, this does not mean that the measures in each embodiment cannot be advantageously combined.

[0035] As described above, it is only the specific implementation manner 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 those skilled in the art within the technical scope disclosed by the present invention should be covered 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

1. A SOT-MRAM memory cell, characterized in that, Comprising: A magnetic tunnel junction including a free layer, a barrier layer, and a reference layer stacked in sequence from bottom to top, wherein the free layer has vertically variable magnetization and the reference layer has vertically fixed magnetization; A spin-orbit coupling layer located below the magnetic tunnel junction and in contact with the free layer, the spin-orbit coupling layer being configured to generate a spin-orbit torque to flip the magnetization of the free layer; An insulating dielectric layer surrounding the peripheral sidewalls and the top of the magnetic tunnel junction and covering the surface of the spin-orbit coupling layer; A first ferromagnetic layer and a second ferromagnetic layer located above the insulating dielectric layer and on both sides of the magnetic tunnel junction, both the first ferromagnetic layer and the second ferromagnetic layer having in-plane horizontal magnetization with the magnetization direction parallel to the direction of the write current passing through the spin-orbit torque coupling layer to generate a horizontal magnetic field for the magnetic tunnel junction.

2. The SOT-MRAM memory cell according to claim 1, wherein The materials of the first ferromagnetic layer and the second ferromagnetic layer are one of Fe, FeCo, and FeN.

3. The SOT-MRAM memory cell according to claim 1, wherein The material of the spin-orbit torque coupling layer is a heavy metal, a doped heavy metal, a heavy metal alloy, or a topological insulator.

4. The SOT-MRAM memory cell according to claim 1, wherein Further comprising: A first antiferromagnetic layer located above the first ferromagnetic layer for pinning the magnetization direction of the first ferromagnetic layer; A second antiferromagnetic layer located above the second ferromagnetic layer for pinning the magnetization direction of the second ferromagnetic layer; The materials of the first antiferromagnetic layer and the second antiferromagnetic layer are IrMn or PtMn.

5. The SOT-MRAM memory cell according to claim 4, wherein Further comprising: A first protective layer located above the first antiferromagnetic layer; A second protective layer located above the second antiferromagnetic layer; The materials of the first protective layer and the second protective layer are Ta or Ru.

6. The SOT-MRAM memory cell according to claim 5, wherein Further comprising: SiO2 insulating dielectric covering the surfaces of the first protective layer, the second protective layer, and the exposed insulating dielectric layer.

7. The SOT-MRAM memory cell according to claim 1, wherein The sides and the top surface of the first ferromagnetic layer and the second ferromagnetic layer are covered by the SiO2 insulating dielectric.

8. The SOT-MRAM memory cell according to claim 7, wherein The first ferromagnetic layer and the second ferromagnetic layer are separated from the magnetic tunnel junction by the insulating dielectric layer and the SiO2 insulating dielectric.

9. The SOT-MRAM memory cell according to claim 7, wherein There is an interface between the insulating dielectric layer and the SiO2 insulating dielectric.

10. The SOT-MRAM memory cell according to any one of claims 1 to 9, characterized in that, The material of the insulating dielectric layer is SiN.

11. The SOT-MRAM memory cell according to any one of claims 1 to 9, characterized in that, The insulating dielectric layer is conformal with the peripheral sidewalls and the top of the magnetic tunnel junction and the surface of the spin-orbit coupling layer.

12. The SOT-MRAM memory cell according to claim 11, wherein The insulating dielectric layer is in a rectangular wave shape and is located on the same side surface of the spin-orbit coupling layer.

13. A method for fabricating a SOT-MRAM memory cell, characterized in that, Comprising: Providing a substrate; Depositing and forming a spin-orbit coupling layer on the substrate; Forming a magnetic tunnel junction on the spin-orbit torque coupling layer, the magnetic tunnel junction including a free layer, a barrier layer, and a reference layer stacked in sequence from bottom to top, wherein the free layer has vertically variable magnetization and the reference layer has vertically fixed magnetization; Conformally depositing and forming an insulating dielectric layer, a ferromagnetic layer, an antiferromagnetic layer, and a protective layer in sequence on the surface of the spin-orbit torque coupling layer and the surface of the magnetic tunnel junction; Performing photolithography and etching on both sides of the magnetic tunnel junction respectively to form a stacked structure including a ferromagnetic layer / antiferromagnetic layer / protective layer in sequence from bottom to top on both sides of the magnetic tunnel junction; Magnetic annealing is carried out under vacuum conditions, such that the magnetization directions of the ferromagnetic layers on both sides of the magnetic tunnel junction are in the horizontal direction and parallel to the direction of the write current passing through the spin-orbit torque coupling layer.

14. The method according to claim 13, wherein The material of the ferromagnetic layer is one of Fe, FeCo, and FeN; The material of the antiferromagnetic layer is IrMn or PtMn; The material of the protective layer is Ta or Ru.

Images