SOT-MRAM memory cell and SOT-MRAM memory

Abstract

The invention provides an SOT-MRAM memory cell and an SOT-MRAM memory, the SOT-MRAM memory cell comprises a spin-orbit moment effect layer, a magnetic tunnel junction above the spin-orbit moment effect layer, and a spin current enhancement layer / growth auxiliary layer located below the spin-orbit moment effect layer, the spin current enhancement layer is opposite to the magnetic tunnel junction, the growth auxiliary layer is located below the spin current enhancement layer, and the spin current enhancement layer is located below the magnetic tunnel junction. The growth auxiliary layer is used for assisting the growth of the spin current enhancement layer, and the electrochemical potential of the growth auxiliary layer is higher than that of the spin current enhancement layer, so that an interface electric field is formed at the interface of the growth auxiliary layer and the spin current enhancement layer; wherein the spin orbit moment effect layer is used for generating a first spin current transmitted to the direction of the free layer of the magnetic tunnel junction and a second spin current transmitted to the direction of the spin current enhancement layer; when the second spin current is transmitted to the interface with the interface electric field, the polarization direction of the second spin current is additionally deflected, and the second spin current and the first spin current jointly apply spin orbit moment to the magnetic moment of the free layer of the magnetic tunnel junction.

Description

Technical Field

[0001] The present invention relates to the technical field of magnetic memory, and in particular to a SOT-MRAM storage unit and a SOT-MRAM memory. Background Art

[0002] Spin-orbit torque magnetic random access memory (SOT-MRAM) has higher charge-spin conversion efficiency than spin-transfer torque magnetic random access memory (STT-MRAM), and has the characteristics of high speed, low power consumption, and high reliability, and has strong application potential. The SOT-MRAM storage cell includes a SOT effect layer that provides spin-orbit torque (SOT) and a magnetic tunnel junction (MTJ).

[0003] For SOT-MRAM storage cells, how to achieve efficient SOT flipping is a common goal in the industry. Generally speaking, SOT efficiency is closely related to the SOT effect layer. Selecting strong spin orbit coupling (SOC) and high spin Hall angle (SHA) materials can improve the spin charge conversion efficiency; selecting low resistivity materials can reduce the shunting effect of the magnetic storage layer (free layer, FL). However, it is difficult to take both high SHA and low resistivity into account, and other means are needed to improve SOT efficiency. Summary of the invention

[0004] In view of this, the present invention provides a SOT-MRAM storage unit and a SOT-MRAM memory, which can improve the SOT efficiency.

[0005] In a first aspect, the present invention provides a SOT-MRAM storage cell, comprising:

[0006] Spin-orbit moment effect layer;

[0007] A magnetic tunnel junction, located on the spin-orbit moment effect layer;

[0008] a spin current enhancement layer, located below the spin-orbit moment effect layer and opposite to the magnetic tunnel junction; and

[0009] A growth auxiliary layer, located below the spin current enhancement layer, for assisting the growth of the spin current enhancement layer, and the growth auxiliary layer has a higher electrochemical potential than the spin current enhancement layer, so that an interface electric field is formed at the interface between the growth auxiliary layer and the spin current enhancement layer;

[0010] Wherein, the spin-orbit moment effect layer is used to generate a first spin current transmitted toward the free layer of the magnetic tunnel junction and a second spin current transmitted toward the spin current enhancement layer;

[0011] When the second spin current is transmitted to the interface where the interface electric field exists, the polarization direction of the second spin current is deflected, and together with the first spin current, the second spin current exerts a spin-orbit moment on the magnetic moment of the free layer of the magnetic tunnel junction.

[0012] Optionally, the spin current enhancement layer is an oxide material having a tunneling effect, selected from MgO, AlO x , any one of MgAlO and HfO2;

[0013] The growth auxiliary layer is Fe-rich CoFeB.

[0014] Optionally, the spin current enhancement layer is a material with high electrical conductivity, selected from any one of graphene, vanadium diselenide (VSe2), and niobium diselenide (NbSe2);

[0015] Corresponding to graphene, the growth auxiliary layer is SiC;

[0016] Corresponding to vanadium diselenide or niobium diselenide, the growth auxiliary layer is fluorophlogopite.

[0017] Optionally, a characteristic size of the spin current enhanced layer is larger than a characteristic size of the magnetic tunnel junction.

[0018] Optionally, the thickness of the spin current enhanced layer is smaller than the spin diffusion length of the second spin current in the spin current enhanced layer.

[0019] Optionally, the growth auxiliary layer has in-plane magnetic anisotropy.

[0020] Optionally, it also includes:

[0021] Two bottom electrodes, disposed at two ends below the spin-orbit moment effect layer, for passing current through the spin-orbit moment effect layer;

[0022] The insulating layer is filled in the gaps between the two bottom electrodes and the growth auxiliary layer and the spin current enhancement layer.

[0023] Optionally, the insulating layer is SiO2, SiN or SiON.

[0024] Optionally, the spin-orbit torque effect layer is a heavy metal layer.

[0025] In a second aspect, the present invention provides a SOT-MRAM memory, comprising the above-mentioned SOT-MRAM storage unit.

[0026] The SOT-MRAM storage unit and the SOT-MRAM memory provided by the present invention, by adding a spin current enhancement layer and a growth auxiliary layer matching the spin current enhancement layer below the SOT effect layer, additionally utilize the second spin current transmitted in the direction of the spin current enhancement layer, thereby achieving an improvement in SOT efficiency while also taking into account zero field reversal, which is beneficial to process integration. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 A schematic diagram of the structure of a SOT-MRAM storage unit according to an embodiment of the present invention;

[0028] Figure 2 A schematic diagram of a spin current enhancement layer / growth auxiliary layer material combination according to an embodiment of the present invention;

[0029] Figure 3 A schematic diagram of a spin current enhancement layer / growth auxiliary layer material combination according to an embodiment of the present invention;

[0030] Figure 4 A schematic diagram of a spin current enhancement layer / growth auxiliary layer material combination according to an embodiment of the present invention;

[0031] Figure 5 FIG. 4 is a schematic diagram of the flipping principle of a SOT-MRAM storage unit according to an embodiment of the present invention. DETAILED DESCRIPTION

[0032] In order to make the purpose, technical solution and advantages of the embodiments of the present invention clearer, the technical solution in the embodiments of the present invention will be clearly and completely described below in conjunction with the 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 creative work are within the scope of protection of the present invention.

[0033] It should be noted that the terms "first", "second", etc. in the specification and claims of the present application and the above-mentioned drawings are used to distinguish similar objects, and are not necessarily used to describe a specific order or sequential order. It should be understood that the data used in this way can be interchanged where appropriate, so that the embodiments of the present application described here. In addition, the terms "including" and "having" and any of their variations are intended to cover non-exclusive inclusions, for example, a process, method, system, product or device comprising a series of steps or units is not necessarily limited to those steps or units clearly listed, but may include other steps or units that are not clearly listed or inherent to these processes, methods, products or devices.

[0034] Some embodiments of the present invention are described in detail below in conjunction with the accompanying drawings. In the absence of conflict, the following embodiments and features in the embodiments can be combined with each other.

[0035] An embodiment of the present invention provides a SOT-MRAM storage unit, such as Figure 1 As shown, the SOT-MRAM memory cell includes:

[0036] Spin orbit torque effect layer 103;

[0037] A magnetic tunnel junction 104 is located on the spin-orbit torque effect layer 103;

[0038] The spin current enhancement layer 102 is located below the spin-orbit moment effect layer 103 and opposite to the magnetic tunnel junction 104; and

[0039] A growth auxiliary layer 101 is located below the spin current enhancement layer 102 and is used to assist the growth of the spin current enhancement layer 102. The growth auxiliary layer 101 has a higher electrochemical potential than the spin current enhancement layer 102 so that an interface electric field is formed at the interface between the growth auxiliary layer 101 and the spin current enhancement layer 102.

[0040] Among them, the spin-orbit moment effect layer 103 is used to generate a first spin current transmitted toward the free layer of the magnetic tunnel junction and a second spin current transmitted toward the spin current enhancement layer 102; when the second spin current is transmitted to the interface where the interface electric field exists, the polarization direction of the second spin current is deflected, and together with the first spin current, the second spin current exerts a spin-orbit moment on the magnetic moment of the free layer of the magnetic tunnel junction.

[0041] refer to Figure 1 In the coordinate system shown in , part of the spin electrons of the second spin current will be reflected at the interface of the SOT effect layer / spin current enhancement layer during the transmission in the -z direction, but the polarization direction remains unchanged. When the second spin current is transmitted to the interface where the interface electric field exists, the polarization direction of the second spin current is additionally deflected by the interface electric field, and the polarization component in the z direction is introduced, and the spin-orbit moment is applied to the magnetic moment of the free layer of the magnetic tunnel junction together with the first spin current, so as to improve the SOT efficiency. At the same time, it is well known that the vertical SOT-MTJ commonly used in the industry needs to apply an x-direction magnetic field to it or introduce spin polarization in the z direction to break its system symmetry when realizing the flipping of a certain direction. In the present application, the deflection of the polarization direction of the second spin current just introduces the spin polarization in the z direction, so the zero-field flip of the SOT can be achieved.

[0042] Specifically, in this embodiment, the stacked structure of the magnetic tunnel junction 104 is not specifically limited. Figure 1The magnetic tunnel junction shown is used as an example, and includes a free layer, a barrier layer, a reference layer, and a top pinning layer above the reference layer for pinning the magnetization direction of the reference layer. The free layer of the magnetic tunnel junction 104 is close to the spin-orbit torque effect layer 103 .

[0043] In the embodiment of the present invention, the spin-orbit torque effect layer 103 may be a heavy metal layer.

[0044] The properties of the spin current enhancement layer 102 require that spin electrons can be transmitted therein. Therefore, the spin current enhancement layer 102 can be divided into two categories: one is an oxide material with low conductivity but tunneling effect, for example, the spin current enhancement layer can be MgO, AlO x , MgAlO and HfO2.

[0045] The other type is materials with relatively high conductivity. For example, the spin current enhancement layer can be graphene, vanadium diselenide (VSe2), niobium diselenide (NbSe2) and other high conductivity materials. High conductivity materials, i.e. materials with very low resistivity, can be selected from materials with resistivity in the range of 5E-3μΩ*cm to 5E+3μΩ*cm.

[0046] The growth auxiliary layer 101 is used to assist the growth of the spin current enhancement layer 102, which is equivalent to a seed layer. This requires that the lattice structure of the growth auxiliary layer 101 must match the lattice structure of the spin current enhancement layer 102. At the same time, it is considered that the electrochemical potential of the growth auxiliary layer 101 is higher than that of the spin current enhancement layer 102.

[0047] Figures 2 to 4 Several optional material combinations of the spin current enhancement layer and the growth auxiliary layer are given, but not limited thereto. For example, if the spin current enhancement layer 102 is MgO, the growth auxiliary layer 101 can be Fe-rich CoFeB. CoFeB can reduce the crystallization temperature of MgO to obtain excellent MgO crystals. If the spin current enhancement layer 102 is graphene, the corresponding growth auxiliary layer 101 can be SiC. If the spin current enhancement layer 102 is vanadium diselenide or niobium diselenide, the growth auxiliary layer 101 can be fluorophlogopite.

[0048] The working principle of the SOT-MRAM storage unit of the embodiment of the present invention to realize information writing is as follows:

[0049] The basic principle of conventional SOT-MRAM memory cell flipping is the spin Hall effect (SHE). A charge flow Jc (x direction) is introduced into the SOT effect layer, and the spin currents Js polarized in the ±y directions are transmitted along the ±z directions respectively. The spin current transmitted toward the free layer (i.e., along the +z direction) will exert a spin-orbit moment (SOT) on the magnetic moment of the free layer, assisting its flipping.

[0050] On the basis of the above principle, the SOT-MRAM storage unit of the embodiment of the present invention adds a spin current enhancement layer and a growth auxiliary layer matching the spin current enhancement layer below the SOT effect layer. The spin current enhancement layer and the growth auxiliary layer have different dielectric properties. The growth auxiliary layer has a higher electrochemical potential than the spin current enhancement layer. Due to the difference in electrochemical potential, an interface electric field is formed at the interface between the two. Figure 5 As shown in the figure, after the spin current generated from the SOT effect layer and transmitted to the spin current enhancement layer (i.e., along the -z direction) enters the interface of the spin current enhancement layer / growth auxiliary layer, its spin polarization direction will produce additional deflection and be reflected back under the action of the interface electric field. On the one hand, it supplements the spin current in the +z direction and improves the SOT efficiency. On the other hand, since the deflected polarization direction will introduce a component along the z direction during the deflection process, it assists the free layer flipping, and thus the deterministic flipping of the free layer can be achieved without an external magnetic field.

[0051] From the above, it can be seen that the SOT-MRAM storage unit of the embodiment of the present invention, without changing the material system of the SOT effect layer, additionally utilizes the second spin current in the -z direction through the spin current enhancement layer and the growth auxiliary layer, thereby achieving an improvement in SOT efficiency while also taking into account zero-field reversal, which is beneficial to process integration.

[0052] Further, refer to Figure 1 The spin current enhancement layer 102 is opposite to the magnetic tunnel junction 104 in the vertical direction, and the characteristic size of the spin current enhancement layer 102 is larger than the characteristic size of the magnetic tunnel junction 104 .

[0053] In addition, the thickness of the spin current enhancement layer 102 cannot be too thick, and its thickness is smaller than the spin diffusion length of the second spin current in the spin current enhancement layer. The resistance of the spin current enhancement layer 102 is higher than the resistance of the spin-orbit moment effect layer 103 .

[0054] Furthermore, the growth auxiliary layer 101 has in-plane magnetic anisotropy, so that an in-plane magnetic field in the x direction can be provided through the growth auxiliary layer to assist in completing the zero field switching.

[0055] Further, refer to Figure 1 , the SOT-MRAM memory cell also includes:

[0056] Two bottom electrodes, denoted as a first bottom electrode and a second bottom electrode, are disposed at two ends below the spin-orbit moment effect layer 103, and are used to pass current through the spin-orbit moment effect layer;

[0057] The insulating layer is filled in the gap between the two bottom electrodes and the growth auxiliary layer 101 and the spin current enhancement layer 102. The optional materials of the insulating layer include SiO2, SiN or SiON.

[0058] It can be understood that the two bottom electrodes and the insulating layer can be seen as a substrate structure, and before forming a memory cell, the two bottom electrodes and the insulating layer need to be formed first.

[0059] Another embodiment of the present invention further provides a SOT-MRAM memory, comprising the SOT-MRAM storage unit of the above embodiment.

[0060] The above is only a specific embodiment 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 a person skilled in the art within the technical scope disclosed by the present invention should be included in the protection scope of the present invention. Therefore, the protection scope of the present invention should be based on the protection scope of the claims.

Claims

1. A SOT-MRAM storage cell, characterized in that: include: Spin-orbit moment effect layer; A magnetic tunnel junction, located on the spin-orbit moment effect layer; a spin current enhancement layer, located below the spin-orbit moment effect layer and opposite to the magnetic tunnel junction; and A growth auxiliary layer, located below the spin current enhancement layer, for assisting the growth of the spin current enhancement layer, and the growth auxiliary layer has a higher electrochemical potential than the spin current enhancement layer, so that an interface electric field is formed at the interface between the growth auxiliary layer and the spin current enhancement layer; Wherein, the spin-orbit moment effect layer is used to generate a first spin current transmitted toward the free layer of the magnetic tunnel junction and a second spin current transmitted toward the spin current enhancement layer; When the second spin current is transmitted to the interface where the interface electric field exists, the polarization direction of the second spin current is deflected, and together with the first spin current, the second spin current exerts a spin-orbit moment on the magnetic moment of the free layer of the magnetic tunnel junction.

2. The SOT-MRAM memory cell according to claim 1, characterized in that: The spin current enhancement layer is an oxide material with tunneling effect, selected from MgO, AlO x , any one of MgAlO and HfO2; The growth auxiliary layer is Fe-rich CoFeB.

3. The SOT-MRAM memory cell according to claim 1, characterized in that: The spin current enhancement layer is a material with high conductivity, selected from any one of graphene, vanadium diselenide (VSe2), and niobium diselenide (NbSe2); Corresponding to graphene, the growth auxiliary layer is SiC; Corresponding to vanadium diselenide or niobium diselenide, the growth auxiliary layer is fluorophlogopite.

4. The SOT-MRAM memory cell according to claim 1, characterized in that: The characteristic size of the spin current enhancement layer is greater than the characteristic size of the magnetic tunnel junction.

5. The SOT-MRAM memory cell according to claim 1, characterized in that: The thickness of the spin current enhancement layer is smaller than the spin diffusion length of the second spin current in the spin current enhancement layer.

6. The SOT-MRAM memory cell according to claim 1, characterized in that: The growth assisting layer has in-plane magnetic anisotropy.

7. The SOT-MRAM memory cell according to claim 1, characterized in that: Also includes: Two bottom electrodes, disposed at two ends below the spin-orbit moment effect layer, for passing current through the spin-orbit moment effect layer; The insulating layer is filled in the gaps between the two bottom electrodes and the growth auxiliary layer and the spin current enhancement layer.

8. The SOT-MRAM memory cell according to claim 7, characterized in that: The insulating layer is SiO2, SiN or SiON.

9. The SOT-MRAM memory cell according to claim 1, characterized in that: The spin-orbit torque effect layer is a heavy metal layer.

10. A SOT-MRAM memory, characterized in that: The SOT-MRAM memory cell comprises the SOT-MRAM memory cell as claimed in any one of claims 1 to 9.

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