Magnetic storage unit and preparation method thereof

Abstract

The invention provides a magnetic memory cell, comprising: a magnetic tunnel junction stack having a first surface and a second surface opposite to each other; the spin orbit moment layer is provided with a third surface and a fourth surface which are opposite to each other, and the first surface is electrically connected with the third surface; the first electrode is electrically connected with the second surface; the second electrode is electrically connected with the fourth surface, and the first electrode and the second electrode are arranged in a spaced mode in the horizontal direction. According to the magnetic storage unit and the preparation method thereof provided by the invention, the combined action of spin orbit torque and spin transfer torque can be realized by adopting a two-end structure, and meanwhile, the area required by the magnetic storage unit is reduced.

Description

Technical Field

[0001] The present invention relates to the field of magnetic storage technology, and in particular to a magnetic storage unit and a preparation method thereof. Background Art

[0002] The spin-orbit torque-based magnetic tunnel junction (SOT-MTJ) device is one of the core structures of magnetic random access memory (SOT-MRAM) products. SOT-MTJ devices mainly use the spin-polarized current generated by the heavy metal orbital layer to flip the magnetic moment of the free layer to realize data writing. Compared with the spin-transfer torque-based magnetic tunnel junction (STT-MTJ) device, SOT-MTJ devices have the characteristics of fast writing speed, unlimited erase and write cycles, and read-write separation.

[0003] The deterministic writing of SOT-MTJ is one of the main difficulties in industrialization at present. Limited by the writing mechanism of SOT-MTJ devices, for devices with perpendicular magnetic anisotropy (PMA), in the absence of horizontal external magnetic field assistance, the flipping process of the device under the action of current alone is random. The introduction of the external magnetic field not only increases the write power consumption, but also is not conducive to the design of high-density storage units. At the same time, the existing SOT-MRAM is a three-terminal device with separate reading and writing, so two transistors are required to control the read and write operations of the storage unit respectively. The 2T1M (2 transistors and 1 MTJ) structure undoubtedly increases the area of ​​the read and write unit, which will be detrimental to the application of SOT-MRAM in the field of high-density storage. Summary of the Invention

[0004] The magnetic storage unit and the preparation method thereof provided by the present invention can realize the combined effect of spin-orbit torque and spin-transfer torque by adopting a two-end structure, and at the same time, reduce the area required for the magnetic storage unit.

[0005] In a first aspect, the present invention provides a magnetic storage unit comprising:

[0006] a magnetic tunnel junction stack having opposing first and second surfaces;

[0007] a spin-orbit moment layer having a third surface and a fourth surface opposite to each other, wherein the first surface is electrically connected to the third surface;

[0008] a first electrode, the first electrode being electrically connected to the second surface;

[0009] The second electrode is electrically connected to the fourth surface, and the first electrode and the second electrode are spaced apart in a horizontal direction.

[0010] Optionally, edges of the magnetic tunnel junction stack and the spin-track moment layer are aligned.

[0011] Optionally, the first surface is a lower surface of the magnetic tunnel junction stack, and the third surface is an upper surface of the spin-orbit moment layer;

[0012] The magnetic storage unit further comprises:

[0013] A hard mask is provided on the second surface, edges of the hard mask, the magnetic tunnel junction stack, and the spin-orbit moment layer are aligned, and the first electrode is electrically connected to the second surface through the hard mask.

[0014] Optionally, the magnetic tunnel junction stack includes a free layer, a barrier layer and a reference layer arranged in sequence from bottom to top.

[0015] Optionally, the first surface is an upper surface of the magnetic tunnel junction stack, and the third surface is a lower surface of the spin-orbit moment layer;

[0016] The magnetic storage unit further comprises:

[0017] A hard mask is arranged on the fourth surface, the edges of the hard mask, the magnetic tunnel junction stack and the spin-orbit moment layer are aligned, a through hole is provided on the hard mask, and the second electrode passes through the through hole to form an electrical connection with the fourth surface.

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

[0019] Optionally, the edge of the first electrode is aligned with the first edge of the second surface; or, the edge of the first electrode extends beyond the edge of the second surface, so that a portion of the first electrode is electrically connected to the second surface;

[0020] The edge of the second electrode is aligned with the second edge of the fourth surface; or, the edge of the second electrode extends beyond the edge of the fourth surface, so that a portion of the second electrode is electrically connected to the fourth surface;

[0021] The horizontal arrangement direction of the first edge and the second edge is parallel to the long axis direction of the magnetic tunnel junction stack and the spin-orbit moment layer.

[0022] In a second aspect, the present invention provides a method for preparing a magnetic storage unit, comprising:

[0023] preparing a bottom electrode on the substrate;

[0024] forming a magnetic tunnel junction stack and a spin-orbit moment layer on a substrate having a bottom electrode;

[0025] Etching the magnetic tunnel junction stack and the spin-orbit moment layer to form an intermediate unit, so that the bottom electrode is located at a first end along a length direction within a horizontal plane of the intermediate unit;

[0026] A top electrode is formed on the middle unit so that the top electrode is located at a second end along a length direction within a horizontal plane of the middle unit.

[0027] Optionally, forming a magnetic tunnel junction stack and a spin-orbit moment layer on a substrate having a bottom electrode includes:

[0028] forming a spin-orbit moment layer on a substrate having a bottom electrode;

[0029] A free layer, a barrier layer and a reference layer of a magnetic tunnel junction stack are sequentially formed on the spin-orbit moment layer from bottom to top.

[0030] Optionally, etching the magnetic tunnel junction stack and the spin-orbit moment layer to form an intermediate unit includes:

[0031] forming a hard mask on the magnetic tunnel junction stack;

[0032] performing photolithography and etching on the hard mask so that the hard mask has a target pattern;

[0033] The magnetic tunnel junction stack and the spin-orbit moment layer are etched according to the hard mask.

[0034] Optionally, forming a magnetic tunnel junction stack and a spin-orbit moment layer on a substrate having a bottom electrode includes:

[0035] A reference layer, a barrier layer and a free layer of a magnetic tunnel junction stack are sequentially formed from bottom to top on a substrate having a bottom electrode;

[0036] A spin-orbit moment layer is formed on the free layer.

[0037] Optionally, etching the magnetic tunnel junction stack and the spin-orbit moment layer to form an intermediate unit includes:

[0038] forming a hard mask on the spin-orbit moment layer;

[0039] performing photolithography and etching on the hard mask so that the hard mask has a target pattern;

[0040] The spin-orbit moment layer and the magnetic tunnel junction stack are etched according to the hard mask.

[0041] In the technical solution provided by the present invention, the magnetic tunnel junction stack and the spin-orbit moment layer are electrically contacted, and the two electrodes are spaced apart in the horizontal direction. Thus, when a potential difference exists between the two electrodes, current can be generated in the spin-orbit moment layer, forming a spin-orbit moment effect, and current can be generated in the free layer, forming a spin-transfer torque effect. This combines the advantages of both spin-orbit moment and spin-orbit moment, achieving purely electrically controlled deterministic writing of the magnetic storage unit. The technical solution provided by the present invention adopts a purely electrically controlled writing method, does not require an additional magnetic field, and the device structure is a two-terminal device. Therefore, it can save the area required for the external magnetic field and additional transistors, which is conducive to the realization of high-density storage. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] Figure 1 Schematic diagram of the structure of a magnetic storage unit according to an embodiment of the present invention;

[0043] Figure 2 A schematic structural diagram of a magnetic storage unit according to another embodiment of the present invention;

[0044] Figure 3 A schematic structural diagram of a magnetic storage unit according to another embodiment of the present invention;

[0045] Figure 4 A schematic structural diagram of a magnetic storage unit according to another embodiment of the present invention;

[0046] Figures 5a-5i A flow chart of a method for preparing a magnetic storage unit according to another embodiment of the present invention;

[0047] Figures 6a-6i A flow chart of a method for preparing a magnetic storage unit according to another embodiment of the present invention; DETAILED DESCRIPTION

[0048] To make the objectives, technical solutions, and advantages of the embodiments of the present invention more clear, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts shall fall within the scope of protection of the present invention.

[0049] An embodiment of the present invention provides a magnetic storage unit, such as Figure 1-2 Shown, including:

[0050] A magnetic tunnel junction stack 3, wherein the magnetic tunnel junction stack 3 has a first surface and a second surface opposite to each other;

[0051] a spin-orbit moment layer 2, the spin-orbit moment layer 2 having a third surface and a fourth surface opposite to each other, wherein the first surface is electrically connected to the third surface; in some embodiments, the spin-orbit moment layer comprises a spin-orbit moment buffer layer and a spin-orbit moment layer, one surface of the spin-orbit moment buffer layer is in contact with the second electrode, and the other surface of the spin-orbit moment layer is in contact with the free layer of the tunnel junction stack; the spin-orbit moment buffer layer is made of a metal material with a large resistivity, such as tantalum nitride, and the spin-orbit moment layer is made of a heavy metal or topological material with a large spin Hall angle, such as tungsten, tantalum, platinum, or bismuth-selenide alloy;

[0052] a first electrode 5, the first electrode 5 being electrically connected to the second surface;

[0053] The second electrode 1 is electrically connected to the fourth surface, and the first electrode 5 and the second electrode 1 are spaced apart in the horizontal direction. In some embodiments, the first electrode and the second electrode are made of metals such as tungsten, titanium nitride, tantalum, or tantalum nitride.

[0054] In the technical solution provided by the embodiment of the present invention, the magnetic tunnel junction stack 3 and the spin-orbit moment layer 2 are electrically contacted, and the two electrodes are spaced apart in the horizontal direction. Therefore, when there is a potential difference between the two electrodes, a current can be generated in the spin-orbit moment layer 2, forming a spin-orbit moment effect, and a current can be generated in the free layer, forming a spin-transfer torque effect. At the same time, the advantages of the spin-orbit moment and the spin-orbit moment are combined to achieve purely electrically controlled deterministic writing of the magnetic storage unit. The technical solution provided by the embodiment of the present invention adopts a purely electrically controlled writing method, does not require an additional magnetic field, and the device structure is a two-terminal device. Therefore, it can save the area required for the external magnetic field and additional transistors, which is conducive to the realization of high-density storage.

[0055] As an optional implementation, continue as Figure 1-2 As shown, the edges of the magnetic tunnel junction stack 3 and the spin-track moment layer 2 are aligned.

[0056] As an optional implementation, continue as Figure 1 As shown, the first surface is the lower surface of the magnetic tunnel junction stack 3, and the third surface is the upper surface of the spin-orbit moment layer 2;

[0057] The magnetic storage unit further comprises:

[0058] A hard mask 4 is provided on the second surface, edges of the hard mask 4 , the magnetic tunnel junction stack 3 and the spin-orbit moment layer 2 are aligned, and the first electrode 5 is electrically connected to the second surface through the hard mask 4 .

[0059] In some embodiments, when the hard mask contacts the magnetic tunnel junction stack, the hard mask is a metal hard mask, such as tantalum, tantalum nitride, or titanium carbide. The metal hard mask can directly contact the corresponding electrode to form a conductive connection. Therefore, when forming the first electrode, the remaining portion of the metal hard mask can directly contact the first electrode. By aligning the hard mask, magnetic tunnel junction stack, and spin-orbit moment edges, the etching process can be completed in a single step using a self-aligned method, increasing the etching process window of the magnetic tunnel junction and avoiding the problem of magnetic tunnel junction short circuit caused by sidewall metal deposition during the etching process.

[0060] As an optional implementation, continue as Figure 1 As shown, the magnetic tunnel junction stack 3 includes a free layer, a barrier layer and a reference layer arranged in sequence from bottom to top.

[0061] In some embodiments, the magnetic moment direction of the free layer is along the normal direction of the free layer, and the free layer is in contact with the spin-orbit moment layer.

[0062] As an optional implementation, Figure 2 As shown, the first surface is the upper surface of the magnetic tunnel junction stack 3, and the third surface is the lower surface of the spin-orbit moment layer 2;

[0063] The magnetic storage unit further comprises:

[0064] A hard mask is arranged on the fourth surface, the edges of the hard mask, the magnetic tunnel junction stack 3 and the spin-orbit moment layer 2 are aligned, a through hole is provided on the hard mask, and the second electrode 1 passes through the through hole to form an electrical connection with the fourth surface.

[0065] In some embodiments, when the spin-orbit moment layer is on top, the hard mask is typically made of tantalum nitride or silicon nitride. Most of the thickness of this hard mask will be consumed during the etching process, but some thickness may still be retained. When some thickness of the hard mask is retained, it is necessary to prepare a through hole on the hard mask when preparing the second electrode so that the second electrode and the spin-orbit moment layer form a conductive connection.

[0066] As an optional implementation, continue as Figure 2 As shown, the magnetic tunnel junction stack 3 includes a free layer, a barrier layer and a reference layer arranged in sequence from top to bottom.

[0067] In the aforementioned embodiments, the interface between the first electrode and the second electrode is in complete contact with the adjacent film layer. In other embodiments, the interface between the first electrode and the second electrode may also be in partial contact with the adjacent film layer, for example Figure 3-Figure 4 The structure shown.

[0068] As an optional embodiment, the edge of the first electrode is aligned with the first edge of the second surface; or, the edge of the first electrode exceeds the edge of the second surface, so that a portion of the first electrode is electrically connected to the second surface;

[0069] The edge of the second electrode is aligned with the second edge of the fourth surface; or, the edge of the second electrode extends beyond the edge of the fourth surface, so that a portion of the second electrode is electrically connected to the fourth surface;

[0070] The horizontal arrangement direction of the first edge and the second edge is parallel to the long axis direction of the magnetic tunnel junction stack and the spin-orbit moment layer.

[0071] In some embodiments, increasing the horizontal distance between the first electrode and the second electrode as much as possible can fully utilize the length of the spin-orbit moment layer, making the SOT effect of the spin-orbit moment layer more obvious while not affecting the current in the magnetic tunnel junction.

[0072] In a second aspect, the present invention provides a method for preparing a magnetic storage unit, comprising:

[0073] preparing a bottom electrode on the substrate;

[0074] forming a magnetic tunnel junction stack and a spin-orbit moment layer on a substrate having a bottom electrode;

[0075] Etching the magnetic tunnel junction stack and the spin-orbit moment layer to form an intermediate unit, so that the bottom electrode is located at a first end along a length direction within a horizontal plane of the intermediate unit;

[0076] A top electrode is formed on the middle unit so that the top electrode is located at a second end along a length direction within a horizontal plane of the middle unit.

[0077] As an optional embodiment, forming a magnetic tunnel junction stack and a spin-orbit moment layer on a substrate having a bottom electrode includes:

[0078] forming a spin-orbit moment layer on a substrate having a bottom electrode;

[0079] A free layer, a barrier layer and a reference layer of a magnetic tunnel junction stack are sequentially formed on the spin-orbit moment layer from bottom to top.

[0080] As an optional implementation manner, etching the magnetic tunnel junction stack and the spin-orbit moment layer to form the intermediate unit includes:

[0081] forming a hard mask on the magnetic tunnel junction stack;

[0082] performing photolithography and etching on the hard mask so that the hard mask has a target pattern;

[0083] The magnetic tunnel junction stack and the spin-orbit moment layer are etched according to the hard mask.

[0084] As an optional embodiment, forming a magnetic tunnel junction stack and a spin-orbit moment layer on a substrate having a bottom electrode includes:

[0085] A reference layer, a barrier layer and a free layer of a magnetic tunnel junction stack are sequentially formed from bottom to top on a substrate having a bottom electrode;

[0086] A spin-orbit moment layer is formed on the free layer.

[0087] As an optional implementation manner, etching the magnetic tunnel junction stack and the spin-orbit moment layer to form the intermediate unit includes:

[0088] forming a hard mask on the spin-orbit moment layer;

[0089] performing photolithography and etching on the hard mask so that the hard mask has a target pattern;

[0090] The spin-orbit moment layer and the magnetic tunnel junction stack are etched according to the hard mask.

[0091] like Figures 5a-5i As shown, the method for preparing the magnetic storage unit provided by the present invention is exemplarily shown, which is as follows:

[0092] First, a substrate such as Figure 5a As shown, the substrate includes a dielectric 7, a diffusion barrier layer 8 and a bottom metal connection line 6;

[0093] A through hole 9 is formed by etching on the substrate, as shown in FIG. Figure 5b As shown, the conductive material is filled in the through hole 9 to form the bottom electrode 10. Figure 5c As shown;

[0094] On the substrate with the bottom electrode fabricated, a spin-orbit moment layer 2, a magnetic tunnel junction stack 3, and a hard mask layer 4 are sequentially formed. Figure 5d As shown; in this embodiment, the hard mask layer can be a metal hard mask layer, which is used to protect the magnetic tunnel junction during the etching process, and in the process of forming the top electrode, it serves as a conductor to connect the top electrode and the magnetic tunnel junction.

[0095] The hard mask layer 4, the magnetic tunnel junction stack 3 and the spin-orbit moment layer 2 are etched, and the etched pattern is covered with a protective layer 11, as shown in FIG. Figure 5e As shown;

[0096] A dielectric is deposited on the protective layer, such as Figure 5f As shown;

[0097] A through hole 12 is formed by etching the dielectric and protective layer 11. Figure 5g As shown;

[0098] Conductive material is deposited in the through hole 12 to form a top electrode 13, as shown in FIG. Figure 5f As shown;

[0099] A top metal connection line 14 is formed on the top electrode to complete the preparation of the magnetic storage unit. Figure 5g shown.

[0100] like Figures 6a-6i As shown, the method for preparing the magnetic storage unit provided by the present invention is exemplarily shown, which is as follows:

[0101] First, a substrate such as Figure 6a As shown, the substrate includes a dielectric 7, a diffusion barrier layer 8 and a bottom metal connection line 6;

[0102] A through hole 9 is formed by etching on the substrate, as shown in FIG. Figure 6b As shown, the conductive material is filled in the through hole 9 to form the bottom electrode 10. Figure 6c As shown;

[0103] On the substrate with the bottom electrode fabricated, a magnetic tunnel junction stack 3, a spin-orbit moment layer 2, and a hard mask layer 4 are sequentially formed. Figure 6d As shown; in this embodiment, the hard mask layer can be, for example, tantalum nitride or silicon nitride, and most or all of its thickness will be consumed during the etching process. If there is still residual hard mask when forming the top electrode, it is necessary to form a through hole in the hard mask and then make the formed top electrode contact with the spin-orbit moment layer.

[0104] The hard mask layer 4, the spin-orbit moment layer 2 and the magnetic tunnel junction stack 3 are etched, and the protective layer 11 is covered on the etched pattern. Figure 6e As shown;

[0105] A dielectric is deposited on the protective layer, such as Figure 6f As shown;

[0106] A through hole 12 is formed by etching the dielectric and protective layer 11. Figure 6g As shown;

[0107] Conductive material is deposited in the through hole 12 to form a top electrode 13, as shown in FIG. Figure 6f As shown;

[0108] A top metal connection line 14 is formed on the top electrode to complete the preparation of the magnetic storage unit. Figure 6g shown.

[0109] In the aforementioned embodiments, when preparing the top electrode, the through hole can be formed using a single etching method or a two-step etching method combining reactive ion etching and ion beam etching. For example, when the top electrode partially contacts the magnetic tunnel junction stack or the spin-orbit moment layer, reactive ion etching can be used to etch down to the protective layer formed by silicon nitride, and then ion beam etching can be used to etch the protective layer formed by silicon nitride.

[0110] 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 changes or substitutions that can be easily conceived by a person skilled in the art within the technical scope disclosed in the present invention should be included in the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be based on the scope of protection of the claims.

Claims

1. A magnetic storage unit, characterized in that include: a magnetic tunnel junction stack having opposing first and second surfaces; a spin-orbit moment layer having a third surface and a fourth surface opposite to each other, wherein the first surface is electrically connected to the third surface; a first electrode, the first electrode being electrically connected to the second surface; The second electrode is electrically connected to the fourth surface, and the first electrode and the second electrode are spaced apart in a horizontal direction.

2. The magnetic storage unit according to claim 1, wherein Edges of the magnetic tunnel junction stack and the spin-orbit moment layer are aligned.

3. The magnetic storage unit according to claim 1, wherein The first surface is the lower surface of the magnetic tunnel junction stack, and the third surface is the upper surface of the spin-orbit moment layer; The magnetic storage unit further comprises: A hard mask is provided on the second surface, edges of the hard mask, the magnetic tunnel junction stack, and the spin-orbit moment layer are aligned, and the first electrode is electrically connected to the second surface through the hard mask.

4. The magnetic storage unit according to claim 3, wherein: The magnetic tunnel junction stack includes a free layer, a barrier layer and a reference layer arranged in sequence from bottom to top.

5. The magnetic storage unit according to claim 1, wherein The first surface is an upper surface of the magnetic tunnel junction stack, and the third surface is a lower surface of the spin-orbit moment layer; The magnetic storage unit further comprises: A hard mask is arranged on the fourth surface, the edges of the hard mask, the magnetic tunnel junction stack and the spin-orbit moment layer are aligned, a through hole is provided on the hard mask, and the second electrode passes through the through hole to form an electrical connection with the fourth surface.

6. The magnetic storage unit according to claim 5, wherein: The magnetic tunnel junction stack includes a free layer, a barrier layer and a reference layer arranged in sequence from top to bottom.

7. The magnetic storage unit according to claim 1, wherein The edge of the first electrode is aligned with the first edge of the second surface; or, the edge of the first electrode extends beyond the edge of the second surface, so that a portion of the first electrode is electrically connected to the second surface; The edge of the second electrode is aligned with the second edge of the fourth surface; or, the edge of the second electrode extends beyond the edge of the fourth surface, so that a portion of the second electrode is electrically connected to the fourth surface; The horizontal arrangement direction of the first edge and the second edge is parallel to the long axis direction of the magnetic tunnel junction stack and the spin-orbit moment layer.

8. A method for preparing a magnetic storage unit, characterized in that: include: preparing a bottom electrode on the substrate; forming a magnetic tunnel junction stack and a spin-orbit moment layer on a substrate having a bottom electrode; Etching the magnetic tunnel junction stack and the spin-orbit moment layer to form an intermediate unit, so that the bottom electrode is located at a first end along a length direction within a horizontal plane of the intermediate unit; A top electrode is formed on the middle unit so that the top electrode is located at a second end along a length direction within a horizontal plane of the middle unit.

9. The method according to claim 8, characterized in that The step of forming a magnetic tunnel junction stack and a spin-orbit moment layer on a substrate having a bottom electrode comprises: forming a spin-orbit moment layer on a substrate having a bottom electrode; A free layer, a barrier layer and a reference layer of a magnetic tunnel junction stack are sequentially formed on the spin-orbit moment layer from bottom to top.

10. The method according to claim 9, characterized in that The etching of the magnetic tunnel junction stack and the spin-orbit moment layer to form an intermediate unit includes: forming a hard mask on the magnetic tunnel junction stack; performing photolithography and etching on the hard mask so that the hard mask has a target pattern; The magnetic tunnel junction stack and the spin-orbit moment layer are etched according to the hard mask.

11. The method according to claim 8, characterized in that The step of forming a magnetic tunnel junction stack and a spin-orbit moment layer on a substrate having a bottom electrode comprises: A reference layer, a barrier layer and a free layer of a magnetic tunnel junction stack are sequentially formed from bottom to top on a substrate having a bottom electrode; A spin-orbit moment layer is formed on the free layer.

12. The method according to claim 11, characterized in that The etching of the magnetic tunnel junction stack and the spin-orbit moment layer to form an intermediate unit includes: forming a hard mask on the spin-orbit moment layer; performing photolithography and etching on the hard mask so that the hard mask has a target pattern; The spin-orbit moment layer and the magnetic tunnel junction stack are etched according to the hard mask.

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