All-electrically-controlled magnetic tunnel junction device

Abstract

The invention relates to an all-electrically-controlled magnetic tunnel junction device, and belongs to the technical field of magnetic tunnel junctions. Comprising an SOT electrode, a free layer, a barrier layer, a fixed layer and an SAF which are sequentially arranged from top to bottom, and a functional layer used for generating a stray field is arranged below the SAF; and the functional layer adopts an antiferromagnetic and ferromagnetic double-film layer with in-plane magnetic anisotropy or a ferromagnetic layer with vertical magnetic anisotropy. The stray field is generated through the functional layer, and after in-plane current is applied to the SOT layer, the SOT layer is assisted to write in the free layer without an external magnetic field, so that device integration, device size reduction and miniaturization are facilitated, and high-speed, high-density and low-power-consumption data storage is realized.

Description

Technical Field

[0001] This invention relates to the field of magnetic tunnel junction technology, and more particularly to a magnetic tunnel junction device that is entirely electrically controlled. Background Technology

[0002] Spin-orbit Torque-Magnetic Random Access Memory (SOT-MRAM) has advantages such as non-volatility, high-speed and low-power data writing (<1 ns, <~0.1 pJ / bit) and high device durability, and is a key technology that is expected to break through the power consumption bottleneck of integrated circuits in the post-Moore era.

[0003] The core structure of a spin orbital magnetic memory, such as Figure 1 As shown in (a), the structure mainly includes a magnetic tunnel junction (MTJ) for storing data and an SOT layer 1 for providing a spin-orbit torque (SOT) for writing data. The core structure of the MTJ consists of a fixed layer 4 (Ferromagnets: FM) made of ferromagnetic metal, a barrier layer 3 made of oxide, and a free layer 2 made of ferromagnetic metal. The magnetic moment direction of the free layer 2 can be changed by external excitation, switching between two directions of the easy magnetization axis, while the magnetic moment direction of the fixed layer 4 is not easily changed by external excitation, thus remaining fixed in one direction. When the magnetic moment directions of the free layer 2 and the fixed layer 4 are parallel, the MTJ exhibits low resistance; when the magnetic moment directions of the free layer 2 and the fixed layer 4 are antiparallel, the MTJ exhibits high resistance. Thus, the high and low resistance states of the MTJ can be used to store data "1" and "0" respectively.

[0004] The structure of MTJ can be divided into top-stitched and bottom-stitched structures based on the positional relationship between SOT layer 1 and fixing layer 4. Traditional SOT-MTJs mostly adopt the top-stitched structure, such as... Figure 1 As shown in (a), the film layers are stacked from bottom to top as SOT layer 1, free layer 2, barrier layer 3, and fixed layer 4, wherein the magnetic moment direction of fixed layer 4 is pinned by the adjacent SAF5 (Synthetic Antiferromagnet). This structure has several bottlenecks: First, it is difficult to guarantee the quality of SAF in multilayer films grown by magnetron sputtering, and element diffusion can occur during annealing, leading to pinning failure; second, it is difficult to ensure that the etching endpoint of each MTJ is precisely consistent at the nanoscale, and this inconsistency will negatively affect the device writing performance.

[0005] Another type of SOT device with a bottom-pinned structure, such as Figure 1As shown in (b), the film stacking from bottom to top consists of SAF5, a fixed layer 4, a barrier layer 3, a free layer 2, and an SOT layer 1. Its advantages are: firstly, the bottom pinning structure maintains stable pinning strength even as device dimensions are miniaturized, supporting higher-density integration; secondly, it avoids etching stop issues, which helps improve device consistency.

[0006] In a spin-orbit magnetic memory (MTJ), the free layer 2 can be either perpendicular magnetic anisotropy (PMA) or in-plane magnetic anisotropy (IMA). For example... Figure 2 As shown, when the free layer 2 has a PMA, the magnetic moment of the free layer 2 switches in the vertical direction, that is, the ±z direction. This type of SOT device is defined as a type z device. In this case, the thermal stability of the free layer 2 is provided by the PMA, and the MTJ can be fabricated into a cylindrical shape. The top view of the corresponding SOT device is shown below. Figure 2 As shown in (d).

[0007] When free layer 2 has an IMA, the magnetic moment of free layer 2 is in the in-plane direction, that is... Figure 2 (b) in the ±y direction or Figure 2 (c) Switching between ±x directions; at this time, in order to ensure sufficient thermal stability of the free layer 2, the MTJ is usually fabricated into an elliptical cylinder, and the top view of the corresponding SOT device is as follows. Figure 2 (e) and Figure 2 As shown in (f), the easy magnetization axis of the free layer 2 magnetic moment is the major axis of an ellipse. Based on whether the easy magnetization axis is located in the x-axis direction or the y-axis direction, this type of SOT device is defined as type x. Figure 2 (f) and typey ( Figure 2 (e) Device (default SOT current along ±x direction).

[0008] When the polarization direction of the spin current is perpendicular to the direction of the free layer 2 magnetic moment, i.e., in a type Z or type X device, there is a problem when using SOT to flip the direction of the free layer 2 magnetic moment: an external magnetic field is needed to break the symmetry of SOT and achieve a deterministic flip of the magnetic moment. This requirement seriously hinders the integration and practical application of SOT devices. Summary of the Invention

[0009] To address or partially address the problems existing in related technologies, this invention proposes a fully electrically controlled magnetic tunnel junction device, aiming to solve the problem of requiring an external magnetic field to be applied to SOT flip-MTJ. This eliminates the need for an external magnetic field, facilitates device integration, reduces device size, and achieves miniaturization, thereby enabling high-speed, high-density, and low-power data storage.

[0010] The aforementioned electrically controlled magnetic tunnel junction device includes, from top to bottom, an SOT electrode, a free layer, a barrier layer, a fixed layer, and a SAF, with a functional layer for generating stray fields disposed below the SAF. The functional layer adopts an antiferromagnetic + ferromagnetic double film layer with in-plane magnetic anisotropy or a ferromagnetic layer with perpendicular magnetic anisotropy.

[0011] In some designs, the SOT electrode has a thickness of 1-20 nm and is made of a strongly spin-orbit coupled material.

[0012] In some embodiments, the SOT electrode is made of W, Pt, Ta, Ir, FePt, CoFe, or Co. Alternatively, [Pt / Hf] can be used. n Or [Pt / Au] n Multilayer membrane material, where n is the number of repetitions of the basic membrane structure (n≥1). or Pt x Au 1-x Or AuxTa 1-x Alloy materials; Or Bi x Se 1-x Bi x Te 1-x Bi x Sb 1-x W x Te 1-x Mo x Te 1-x Topological material, where x is the elemental ratio, with a value ranging from 0 to 1.

[0013] In some embodiments, the free layer or fixed layer is a CoFeB alloy, wherein the percentage of Co:Fe:B in the alloy is 20:60:20, 40:40:20, or 60:20:20.

[0014] In some schemes, the SAF is a synthetically produced antiferromagnetic multilayer film used as a pinning and fixing layer; for vertically anisotropic systems, [Co / Pt] is used. m / Co / Ru / [Co / Pt] n The subscripts m and n represent the number of repetitions of [Co / Pt]. For in-plane anisotropic systems, CoFe(B) / Ru / CoFe(B) / antiferromagnetic is used, where the antiferromagnetic layer is IrMn, FeMn, PtMn, or IrMn3.

[0015] In some schemes, the barrier layer is made of magnesium oxide and / or aluminum oxide.

[0016] In some schemes, the ferromagnetic film with in-plane magnetic anisotropy and antiferromagnetic double film is made of Co, CoFe or NiFe; The antiferromagnetic film with in-plane magnetic anisotropy and antiferromagnetic double film layer is made of IrMn, FeMn, PtMn, GdFeCo or IrMn3; The ferromagnetic film is located on top or the antiferromagnetic film is located on top, and the thickness of the antiferromagnetic film is 4~30nm.

[0017] In some schemes, the ferromagnetic layer with perpendicular magnetic anisotropy is made of Co / Pt multilayer film, CoPt alloy or FePt alloy, and the thickness of the ferromagnetic layer is 1~20nm.

[0018] The technical solution provided by this invention may include the following beneficial effects: This application generates stray fields through the functional layer. After applying an in-plane current to the SOT layer, the SOT layer is assisted in writing to the free layer without the need for an external magnetic field. This facilitates device integration, reduces device size, and achieves miniaturization, thereby enabling high-speed, high-density, and low-power data storage.

[0019] It should be understood that the above general description and the following detailed description are exemplary and explanatory only, and are not intended to limit the invention. Attached Figure Description

[0020] The above and other objects, features and advantages of the present invention will become more apparent from the more detailed description of exemplary embodiments of the invention in conjunction with the accompanying drawings, wherein the same reference numerals generally represent the same components in the exemplary embodiments of the invention.

[0021] Figure 1 This is a schematic diagram of an existing spin-orbit moment magnetic storage device; Figure 2 A schematic diagram of the magnetic field direction of an existing spin-orbit moment magnetic storage device; Figure 3 This is another schematic diagram of the magnetic field direction of an existing spin-orbit moment magnetostore; Figure 4 This is a schematic diagram of the structure of the typez device shown in Embodiment 1; Figure 5 This is a schematic diagram of the structure of the typex device shown in Embodiment 2; Figure 6 These are schematic diagrams of the magnetic tunnel junction devices shown in Embodiments 3 and 4.

[0022] Figure label: 1. SOT layer; 2. Free layer; 3. Barrier layer; 4. Fixed layer; 5. SAF; 6. Functional layer; 61. Ferromagnetic film; 62. Antiferromagnetic film; 63. Ferromagnetic layer. Detailed Implementation

[0023] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments, but the scope of protection of the present invention is not limited to the content described.

[0024] Analysis of the design mechanism of this invention: like Figure 3 As shown, this invention employs a bottom-pinned device structure. The film layers, stacked from bottom to top, mainly include a functional layer 6, SAF5 (for in-plane films, an additional antiferromagnetic layer is needed to pin the SAF), a fixing layer 4, a barrier layer 3, a free layer 5, and an SOT layer 1. Unlike traditional bottom-pinned SOT-MRAM films, this invention adds a functional layer 6 at the bottom of SAF5 to generate a stray field, enabling magnetic field-free writing of the SOT-MTJ. Specifically: For type Z devices, such as Figure 3 As shown in (a), the core film of this functional layer is an antiferromagnetic + ferromagnetic double film with in-plane magnetic anisotropy. The magnetic moment direction of the antiferromagnetic + ferromagnetic double film is pinned by the exchange bias field (EBF) generated by the AFM + FM interface. This functional layer can provide stray fields in the in-plane direction, enabling magnetic field-free data writing of p-MTJ.

[0025] For Type X devices, such as Figure 3 As shown in (b), the functional layer is a ferromagnetic layer 63 with strong vertical magnetic anisotropy, thereby providing a stray field in the vertical direction to realize data writing of i-MTJ without external magnetic field.

[0026] Example 1: This application provides a typez device, such as Figure 4 As shown, from bottom to top, it mainly includes functional layer 6, SAF5, fixed layer 4, barrier layer 3, free layer 2, and SOT layer 1.

[0027] The core structure of the MTJ consists of a free layer 2 made of ferromagnetic metal, a barrier layer 3 made of oxide, and a fixed layer 4 made of ferromagnetic metal. The free layer 2 exhibits perpendicular magnetic anisotropy, and the fixed layer 4 is fixed in the vertical direction via exchange coupling through SAF. The functional layer 6 is an antiferromagnetic (AFM) + ferromagnetic (FM) double film with in-plane magnetic anisotropy. Through annealing with an in-plane magnetic field, an exchange bias is formed between the FM layer and the AFM layer, thereby pinning the magnetic moment of the FM layer in-plane (after pinning, the direction of the magnetic moment of the FM layer is as follows). Figure 4As shown, its direction is ±x (but its direction can be any other direction besides ±y), providing a stray field for the flipping of free layer 2. After applying an in-plane current to the SOT layer, the stray field of functional layer 6 assists the SOT in writing to the free layer.

[0028] The free layer 2 is a CoFeB alloy, and a common element ratio can be Co. 20 Fe 60 B 20 Co 40 Fe 40 B 20 or Co 60 Fe 20 B 20 The numbers here represent percentages of elements, but are not limited to the element ratios described here.

[0029] The barrier layer 3 is a metal oxide, including magnesium oxide and aluminum oxide.

[0030] The fixing layer 4 is a CoFeB alloy, and the commonly used element ratio can be Co. 20 Fe 60 B 20 Co 40 Fe 40 B 20 or Co 60 Fe 20 B 20 The numbers here represent percentages of elements, but are not limited to the element ratios described here.

[0031] The SAF5 multilayer film can be made of [Co / Pt]. m / Co / Ru / [Co / Pt] n , where n is the number of times the basic membrane structure is repeated (n≥1), and specific implementation schemes include but are not limited to this.

[0032] In the functional layer 6 (FM+AFM bilayer film), the antiferromagnetic film 62 (AFM layer) uses an antiferromagnetic material, including but not limited to: IrMn, FeMn, PtMn, GdFeCo, etc., and the element ratios of each material are not limited to those listed. For example, the antiferromagnetic IrMn can be IrMn or IrMn3, etc., and the AFM thickness is 4~30nm. The ferromagnetic film 61 (FM layer) uses a ferromagnetic material, including but not limited to Co, CoFe, NiFe, etc., and the FM layer thickness is 1~20nm. The top and bottom positions of the FM layer and AFM layer in the FM+AFM bilayer film can be interchanged.

[0033] The SOT layer 1 is the write electrode, with a thickness of 1~20nm, and utilizes a strong spin-orbit coupling material, including but not limited to: heavy metal materials such as W, Pt, Ta, and Ir; ferromagnetic materials such as FePt, CoFe, and Co; and [Pt / Hf]. n [Pt / Au] n Multilayer membrane materials, where n is the number of repetitions of the basic membrane structure (n≥1), Pt x Au 1-x Au x Ta 1-x alloy materials, Bi x Se 1-x Bi x Te 1-x Bi x Sb 1-x W x Te 1-x Mo x Te 1-x Isotopological materials, where x is the elemental ratio, with a value ranging from 0 to 1.

[0034] The typez device is cylindrical in shape.

[0035] Example 2: This application provides a Type-X device, such as Figure 5 As shown, from bottom to top, the core structure mainly includes a functional layer 6, SAF5, a fixed layer 4, a barrier layer 3, a free layer 2, and a SOT layer 1. The MTJ core structure comprises a free layer 2 made of ferromagnetic metal, a barrier layer 3 made of oxide, and a fixed layer 4 made of ferromagnetic metal. The free layer 2 exhibits in-plane magnetic anisotropy, and the fixed layer 4 is fixed in the in-plane direction via exchange coupling with SAF5. The functional layer 6 is a ferromagnetic layer 63 (FM layer) with strong perpendicular magnetic anisotropy, providing a stray field for the flipping of the free layer 2. After an in-plane current is applied to the SOT layer 1, the stray field of the ferromagnetic layer 63 (FM layer) assists the SOT layer 1 in writing to the free layer.

[0036] The free layer 2 is a CoFeB alloy, and the commonly used element ratio can be Co. 20 Fe 60 B 20 Co 40 Fe 40 B 20 or Co 60 Fe 20 B 20 The numbers here represent percentages of elements, but are not limited to the element ratios described here.

[0037] The barrier layer is a metal oxide, including magnesium oxide and aluminum oxide.

[0038] The fixing layer 4 is a CoFeB alloy, and the commonly used element ratio can be Co. 20 Fe 60 B 20 Co 40 Fe 40 B 20 or Co 60 Fe 20 B 20 The numbers here represent percentages of elements, but are not limited to the element ratios described here.

[0039] The SAF5 multilayer film can be of the CoFe(B) / Ru / CoFe(B) / antiferromagnetic type, wherein the antiferromagnetic layer can be IrMn, FeMn, PtMn, or IrMn3.

[0040] The ferromagnetic layer 63 is made of a ferromagnetic material with strong perpendicular magnetic anisotropy, including but not limited to Co / Pt multilayer films, CoPt alloys, FePt alloys, etc., and the thickness of the ferromagnetic layer 63 (FM layer) is 1~20nm. The ferromagnetic layer 63 (FM layer) can also be further pinned in the vertical direction by adding antiferromagnetic materials to adjacent film layers.

[0041] The SOT layer 1 is the write electrode, with a thickness of 1-20 nm, and utilizes a strong spin-orbit coupling material, including but not limited to: heavy metal materials such as W, Pt, Ta, and Ir; ferromagnetic materials such as FePt, CoFe, and Co; and [Pt / Hf]. n [Pt / Au] n Multilayer membrane materials, where n is the number of repetitions of the basic membrane structure (n≥1), Pt x Au 1-x Au x Ta 1-x alloy materials, Bi x Se 1-x Bi x Te 1-x Bi x Sb 1-x W x Te 1-x Mo x Te 1-x Isotopological materials, where x is the elemental ratio, with a value ranging from 0 to 1.

[0042] Type-X devices are cylindrical, elliptical, or cuboid in shape.

[0043] Example 3: This application provides a vertical magnetic anisotropic spin orbital moment device, such as... Figure 6 As shown in (a), the core structure consists of a Pt electrode providing SOT and a Co electrode.20 Fe 60 B 20 / MgO / Co 20 Fe 60 B 20 It consists of p-MTJ, SAF and FM+AFM bilayer membranes. Figure 6 (c) is a top view of the device, with the magnetic moment direction in the figure representing the magnetic moment direction of the Co layer. A 4nm Co ferromagnetic layer magnetized along the x-direction is obtained by annealing with an in-plane magnetic field of +x, and pinned to it using a 10nm antiferromagnetic IrMn layer. The easy magnetization direction of the free layer magnetic moment is in the ±z direction, and the magnetic tunnel junction is cylindrical in shape. By passing a current through the Pt layer to generate a SOT, the stray field generated in the Co layer acts on the free layer, which is equivalent to an external magnetic field, enabling the writing of the p-MTJ (type z device) without an external magnetic field.

[0044] Example 4: This application provides a vertical magnetic anisotropic spin orbital moment device, such as... Figure 6 As shown in (b), the core structure consists of a Pt electrode providing SOT and a Co electrode. 20 Fe 60 B 20 / MgO / Co 20 Fe 60 B 20 It consists of i-MTJ, SAF pinned by 5nm IrMn and vertically magnetized [Co (0.3nm) / Pt (0.8nm)]6. Figure 6 (d) is a top view of the device, where the magnetic moment direction is the direction of the magnetic moment of the Co / Pt multilayer film. The easy magnetization direction of the free layer magnetic moment is the ±x direction, and the magnetic tunnel junction is cylindrical. By passing a current through the Pt layer to generate SOT, the stray field generated in the Co / Pt multilayer film acts on the free layer, which is equivalent to an external magnetic field, realizing the writing of i-MTJ (typex device) without an external magnetic field.

[0045] The various embodiments of the present invention have been described above. These descriptions are exemplary and not exhaustive, nor are they limited to the disclosed embodiments. Many modifications and variations will be apparent to those skilled in the art without departing from the scope and spirit of the described embodiments. The terminology used herein is chosen to best explain the principles, practical application, or improvement of the technology in the market, or to enable others skilled in the art to understand the embodiments disclosed herein.

Claims

1. A magnetic tunnel junction device controlled entirely by electricity, comprising, from top to bottom, an SOT electrode, a free layer, a barrier layer, a fixed layer, and a SAF, characterized in that: A functional layer for generating stray fields is provided below the SAF; The functional layer adopts an antiferromagnetic + ferromagnetic double film layer with in-plane magnetic anisotropy or a ferromagnetic layer with perpendicular magnetic anisotropy.

2. The electrically controlled magnetic tunnel junction device according to claim 1, characterized in that: The SOT electrode has a thickness of 1-20 nm and is made of a strong spin-orbit coupling material.

3. The electrically controlled magnetic tunnel junction device according to claim 2, characterized in that: The SOT electrode is made of W, Pt, Ta, Ir, FePt, CoFe or Co; Alternatively, [Pt / Hf] can be used. n Or [Pt / Au] n Multilayer membrane material, where n is the number of repetitions of the basic membrane structure (n≥1). or Pt x Au 1-x Or AuxTa 1-x Alloy materials; Or Bi x Se 1-x Bi x Te 1-x Bi x Sb 1-x W x Te 1-x Mo x Te 1-x Topological material, where x is the elemental ratio, with a value ranging from 0 to 1.

4. The electrically controlled magnetic tunnel junction device according to claim 1, characterized in that: The free layer or fixed layer is made of CoFeB alloy, wherein the percentage of Co:Fe:B in the alloy is 20:60:20, 40:40:20 or 60:20:

20.

5. The electrically controlled magnetic tunnel junction device according to claim 1, characterized in that: The SAF is a synthetically produced antiferromagnetic multilayer film used for anchoring and fixing layers; for vertically anisotropic systems, the SAF uses [Co / Pt]. m / Co / Ru / [Co / Pt] n The subscripts m and n represent the number of repetitions of [Co / Pt]. For in-plane anisotropic systems, the SAF adopts CoFe(B) / Ru / CoFe(B) / antiferromagnetic, wherein the antiferromagnetic layer is IrMn, FeMn, PtMn or IrMn3.

6. The electrically controlled magnetic tunnel junction device according to claim 1, characterized in that: The barrier layer is made of magnesium oxide or aluminum oxide.

7. The electrically controlled magnetic tunnel junction device according to claim 1, characterized in that: The ferromagnetic film with an antiferromagnetic + ferromagnetic double layer having in-plane magnetic anisotropy is made of Co, CoFe or NiFe; The antiferromagnetic film with in-plane magnetic anisotropy and antiferromagnetic double film layer is made of IrMn, FeMn, PtMn or IrMn3; The ferromagnetic film is located on top or the antiferromagnetic film is located on top, and the thickness of the antiferromagnetic film is 4~30nm.

8. The electrically controlled magnetic tunnel junction device according to claim 1, characterized in that: The ferromagnetic layer with perpendicular magnetic anisotropy is made of Co / Pt multilayer film, CoPt alloy or FePt alloy, and the thickness of the ferromagnetic layer is 1~20nm.

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