Core-shell based MTJ, magnetic storage device and method

Abstract

The present invention relates to a core-shell-based magnetic storage junction (MTJ), magnetic memory device, and method. The MTJ comprises: a heavy metal ring layer and a fixed layer, a spacer layer, and a free layer stacked in sequence; the heavy metal ring layer is sleeved on the outer wall of the free layer; both the fixed layer and the free layer are made of ferromagnetic material; the spacer layer is made of non-magnetic metal material or oxide-based insulating material; the tops of the free layer and the heavy metal ring layer serve as current input terminals, and the bottom of the fixed layer serves as a current output terminal. The MTJ device is a dual-port device. Based on the structure of the heavy metal ring layer sleeved on the periphery of the free layer, it can improve the switching efficiency of the MTJ device and facilitate further miniaturization of the MTJ device, thereby achieving device miniaturization.

Description

Technical Field

[0001] The present invention relates to the technical field of magnetic storage devices, and in particular to a core-shell structure-based MTJ, a magnetic storage device and a storage method. Background Art

[0002] With the scaling of semiconductor devices and the continuous reduction in device process dimensions, Moore's Law has slowed. The increased static power consumption caused by transistor leakage current has become a bottleneck for further improvement in traditional CMOS devices. Emerging non-volatile memory technologies, driven by the rapid development of spintronics and magnetism, are poised to address the severe static power consumption issues faced by these devices. Among them, magnetic random access memory (MRAM), based on magnetic tunnel junctions (MTJs), has emerged as the most promising non-volatile memory device due to its high read and write speeds, low static power consumption, unlimited write cycles, and compatibility with CMOS manufacturing technologies and processes. Currently, the most common write mechanism for MRAM is based on the spin transfer torque effect, hence the name STT-MRAM. However, the write current, power consumption, and voltage required for this type of memory are excessive, potentially leading to device breakdown. Recently, a new write method based on the spin-orbit torque effect has been proposed, hence the name SOT-MRAM. This approach adds a layer of heavy metal or antiferromagnetic thin film material with strong spin-orbit coupling beneath the ferromagnetic layer of the magnetic tunnel junction. When current flows through this layer, a spin-orbit torque is generated due to the spin Hall effect or the Raschbach effect. This acts on the adjacent ferromagnetic layer, causing its magnetic moment to flip, thereby enabling the writing of data to the magnetic tunnel junction. Compared to STT-MRAM, this type of device offers faster write speeds and lower write power consumption. Moreover, the write current does not flow through the magnetic tunnel junction structure, effectively reducing the risk of device breakdown. However, this device is a three-terminal device, which reduces integration density. Furthermore, the SOT itself cannot independently flip the PMA MTJ, requiring an external magnetic field or specialized structures. Another novel writing method involves the synergistic action of the STT and SOT to flip the PMA MTJ. This method overcomes the drawback of using SOT alone, which requires an external magnetic field or specialized structures. However, the required write current cannot be reduced with device size, hindering device miniaturization, and its flipping efficiency still needs to be improved. Therefore, there is an urgent need for an MTJ device, a magnetic storage device, and a storage method that have high switching efficiency and are easy to miniaturize. Summary of the Invention

[0003] The purpose of the present invention is to provide a core-shell-based MTJ, a magnetic storage device and a method. The MTJ device includes a fixed layer, a spacer layer and a free layer stacked in sequence. By arranging a heavy metal ring layer on the periphery of the free layer, and using the top of the free layer and the heavy metal ring layer as current input terminals, the switching efficiency of the magnetic tunnel junction and the thermal stability coefficient of the device are improved, thereby enabling the device size to be further miniaturized, which is conducive to device miniaturization.

[0004] To achieve the above object, the present invention provides the following solutions:

[0005] The present invention provides a core-shell based MTJ, comprising: a heavy metal ring layer and a fixed layer, a spacer layer and a free layer stacked in sequence;

[0006] The heavy metal ring layer is sleeved on the outer wall of the free layer;

[0007] The fixed layer and the free layer are both made of ferromagnetic materials;

[0008] The spacer layer is made of non-magnetic metal material or oxide insulating material;

[0009] The tops of the free layer and the heavy metal ring layer are current input terminals, and the bottom of the fixed layer is a current output terminal;

[0010] The heavy metal ring layer is used to generate a spin-polarized current under the action of the spin Hall effect when injecting current into the top of the free layer, and diffuse the spin-polarized current into the free layer;

[0011] The free layer is used to pass the spin-polarized current into the spacer layer and the fixed layer, and to flip the magnetic moment of the free layer based on the spin-orbit torque and the spin transfer torque generated at the interface between the free layer and the spacer layer.

[0012] Optionally, there is a preset distance between the heavy metal ring layer and the spacer layer.

[0013] Optionally, the coercive force of the fixed layer is greater than the coercive force of the free layer.

[0014] Optionally, the resistance of the heavy metal ring layer is smaller than the resistance of the free layer.

[0015] Optionally, the top of the heavy metal ring layer and the top of the free layer are in the same horizontal plane.

[0016] Optionally, the ferromagnetic material is CoFeB, CoNiCo, CoFe or NiFe; the non-magnetic metal material is Cu or Au; the oxide insulating material is MgO or Al2O3; and the material used for the heavy metal ring layer is Pt, Ta or W.

[0017] Optionally, when the magnetic moment directions of the free layer and the fixed layer are parallel, the MTJ device is in a low resistance state; when the magnetic moment directions of the free layer and the fixed layer are antiparallel, the MTJ device is in a high resistance state.

[0018] The present invention also provides a magnetic storage device, comprising at least one storage unit; each of the storage units is the MTJ.

[0019] The present invention also provides a storage method based on the MTJ, the method comprising:

[0020] Obtaining a resistance state of the MTJ device; the resistance state includes a high resistance state and a low resistance state; when the logic data of the high resistance state is 1, the logic data of the low resistance state is 0; when the logic data of the high resistance state is 0, the logic data of the low resistance state is 1;

[0021] When the resistance state is the high resistance state, a positive polarity current is passed through the top of the MTJ device;

[0022] Based on the spin-orbit torque effect and the spin transfer torque effect, the magnetic moment of the free layer is reversed, and the resistance state of the MTJ device is changed to the low-resistance state, thereby realizing the storage of low-resistance logic data;

[0023] When the resistance state is the low resistance state, a negative polarity current is passed to the top of the MTJ device;

[0024] Based on the spin-orbit torque effect and the spin transfer torque effect, the magnetic moment of the free layer is reversed, and the resistance state of the MTJ device changes to the high-resistance state, thereby realizing the storage of high-resistance logic data.

[0025] According to the specific embodiments provided by the present invention, the present invention discloses the following technical effects:

[0026] The present invention relates to a core-shell MTJ magnetic storage device and method. The MTJ comprises: a heavy metal ring layer and a fixed layer, a spacer layer, and a free layer stacked in sequence; the heavy metal ring layer is sleeved on the outer wall of the free layer; both the fixed layer and the free layer are made of ferromagnetic material; the spacer layer is made of a non-magnetic metal material or an oxide-based insulating material; the tops of the free layer and the heavy metal ring layer serve as current input terminals, and the bottom of the fixed layer serves as a current output terminal. The MTJ device is a dual-port device. Based on the structure of the heavy metal ring layer sleeved on the periphery of the free layer, it can improve the switching efficiency of the MTJ device and facilitate further miniaturization of the MTJ device, thereby achieving device miniaturization. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0028] Figure 1 A structural diagram of a core-shell MTJ device provided in Example 1 of the present invention;

[0029] Figure 2 Schematic diagram of the principle of forming a spin-polarized flow in a heavy metal ring layer provided in Example 1 of the present invention;

[0030] Figure 3 Schematic diagram of the parallel state and antiparallel state of the MTJ device provided in Example 1 of the present invention;

[0031] Figure 4 This is a schematic diagram of the flipping principle between the parallel state and the antiparallel state of the MTJ device provided in Example 1 of the present invention.

[0032] Reference numerals:

[0033] 1-heavy metal ring layer; 2-free layer; 3-spacer layer; 4-fixed layer. DETAILED DESCRIPTION

[0034] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. 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 are within the scope of protection of the present invention.

[0035] In the existing technology, a new writing method using the synergistic effect of STT and SOT to complete the flipping of PMA MTJ still has the problem that when using it, special attention needs to be paid to the order of the two currents SOT and STT and the ratio of the currents, which is not easy to operate. In addition, the magnitude of the write current is proportional to the energy barrier and cannot be reduced as the device size decreases.

[0036] The present invention aims to provide a core-shell-based MTJ, magnetic memory device, and method. The MTJ device comprises a fixed layer, a spacer layer, and a free layer stacked in sequence. By providing a heavy metal ring layer around the periphery of the free layer, with the tops of the free layer and the heavy metal ring layer serving as current input terminals, the magnetic tunnel junction switching efficiency and the device's thermal stability coefficient are improved, thereby further miniaturizing the device size and facilitating device miniaturization. Furthermore, the device's write current can be further reduced as the device size is reduced, thereby reducing the device's power consumption. Furthermore, the device's switching current and switching voltage can be further reduced, preventing breakdown.

[0037] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the present invention is further described in detail below with reference to the accompanying drawings and specific embodiments.

[0038] Example 1

[0039] like Figure 1 As shown, this embodiment provides a core-shell based MTJ, characterized in that it includes: a heavy metal ring layer 1 and a fixed layer 4, a spacer layer 3 and a free layer 2 stacked in sequence; wherein the fixed layer 4, the spacer layer 3 and the free layer 2 are a three-layer thin film structure. Figure 1 (a) is the cross-sectional view of the MTJ device; Figure 1 (b) is a plan view of the MTJ device, where FL / NM / RL represent the free layer, spacer layer, and fixed layer from top to bottom.

[0040] The heavy metal ring layer 1 is sleeved on the outer wall of the free layer 2. The MTJ device uses a portion of the free layer 2 in the three-layer thin film structure as the core and the heavy metal ring layer 1 (eg, Pt) outside the free layer 2 as the shell.

[0041] The heavy metal ring layer 1 and the spacer layer 3 are insulated and cannot be in contact with each other. Therefore, a preset distance is required between the heavy metal ring layer 1 and the spacer layer 3 .

[0042] In order to facilitate the flow of current into the top of the MTJ, the top of the heavy metal ring layer 1 and the top of the free layer 2 are required to be in the same horizontal plane. Being in the same horizontal plane here does not have any limiting effect, and the relative position relationship between the top of the heavy metal ring layer 1 and the top of the free layer 2 can also be adjusted according to actual needs.

[0043] Both the pinned layer 4 and the free layer 2 are made of ferromagnetic materials. Although both the free layer 2 and the pinned layer 4 are made of ferromagnetic materials, their properties are not identical. They have different coercive forces. The pinned layer 4 has a larger coercive force, making its magnetic moment direction difficult to change, while the free layer 2 has a smaller coercive force, making its magnetic moment direction easily changeable. The ferromagnetic material is CoFeB, CoNiCo, CoFe, or NiFe.

[0044] The spacer layer 3 is made of non-magnetic metal material or oxide-based insulating material; the non-magnetic metal material is Cu or Au; the oxide-based insulating material is MgO or Al2O3.

[0045] It should be noted that the materials involved in the structure of this device may be, but are not limited to, any materials with similar functional properties.

[0046] The material used for the heavy metal ring layer is Pt (platinum), Ta (tantalum) or W (tungsten).

[0047] It should be noted that the material of the heavy metal ring layer can be replaced by an antiferromagnetic thin film material with a Raschbach effect, or a topological insulator material with a spin Hall effect; the antiferromagnetic thin film material is, for example, a PtMn compound, an IrMn compound, etc.; the topological insulator material is, for example, a BiSb alloy, etc.

[0048] The materials used for the heavy metal ring layer 1, free layer 2, spacer layer 3 and fixed layer 4 are only for the purpose of clearly illustrating some of the materials listed in this solution. The above specific materials do not have any limiting effect on this solution, and any materials that meet the requirements can be used according to actual needs.

[0049] In addition, for the materials used in the various layer structures described in this embodiment, the ratio and content of each element in the compound can be adjusted arbitrarily according to actual needs.

[0050] In order to allow more current flowing into the top of the device to flow into the heavy metal ring layer 1 , the resistance of the heavy metal ring layer 1 may be required to be much smaller than the resistance of the free layer 2 .

[0051] The MTJ device in this embodiment is a dual-port device, wherein the tops of the free layer 2 and the heavy metal ring layer 1 are current input terminals, and the bottom of the fixed layer 4 is a current output terminal;

[0052] The heavy metal ring layer 1 is used to generate a spin-polarized current under the action of the spin Hall effect when injecting current into the top of the free layer 2, and diffuse the spin-polarized current into the free layer 2;

[0053] The free layer 2 is used to pass the spin-polarized current into the spacer layer 3 and the fixed layer 4, and flip the magnetic moment of the free layer 2 based on the spin-orbit torque and the spin transfer torque generated at the interface between the free layer 2 and the spacer layer 3.

[0054] The principle of the MTJ device in this embodiment is as follows:

[0055] When current is applied to the top of the MTJ device, it flows through the heavy metal ring layer 1 and the free layer 2 at the top of the three-layer thin-film structure. Because the resistance of the heavy metal ring layer 1 is much lower than that of the free layer 2, the current initially flows primarily through the heavy metal ring layer 1, generating the SOT effect. Driven by the spin Hall effect (SHE), the heavy metal ring layer 1 generates a spin-polarized current perpendicular to the direction of the current flow. This spin-polarized current diffuses and enters the adjacent free layer 2. The current in the heavy metal ring layer 1 and the current in the free layer 2 then flow together into the spacer layer 3 and the pinned layer 4. Driven by the spin transfer torque effect, a spin transfer torque (STT) is generated at the interface between the free layer 2 and the spacer layer 3. This SOT and STT effect generates a spin-orbit torque (SOT) and a spin transfer torque (STT) in the device, which act together on the magnetic moment of the free layer 2, causing it to flip. Ultimately, MTJ devices will use current as the input parameter and the resistance state of the magnetic tunnel junction as the output parameter to realize the storage function of logical data in a single device.

[0056] Since the STT effect is an interface effect, even though the current only flows through the free layer 2 at the end of the free layer 2, the full STT effect can still be produced. Therefore, this design can simultaneously produce the STT effect and the SOT effect using a single current.

[0057] Spin Hall Effect (SHE):

[0058] like Figure 2 As shown, in the heavy metal ring layer 1, for electrons with different spin orientations, the scattering forces generated by spin-orbit coupling are in opposite directions, so that the two electrons with different spin orientations gather on both sides of the heavy metal ring layer 1, thereby forming a pure spin current.

[0059] Principle of spin-orbit torque (SOT) effect:

[0060] When current flows through heavy metal ring layer 1, a spin-polarized current perpendicular to the current direction is generated in this layer due to the spin Hall effect (SHE). This spin-polarized current diffuses into the adjacent ferromagnetic layer, the free layer 2, and exerts a torque on the magnetic moment in the ferromagnetic layer, thereby flipping the magnetic moment of the free layer 2. This torque is called the spin-orbit torque.

[0061] The resistance state of the magnetic tunnel junction is determined by the directions of the magnetic moments of the free layer 2 and the fixed layer 4. Figure 3 As shown in (a), when the magnetic moment directions of the free layer 2 and the fixed layer 4 are parallel, the MTJ device is in a low resistance state; Figure 3 As shown in (b), when the magnetic moments of the free layer 2 and the pinned layer 4 are antiparallel, the MTJ device is in a high resistance state. The resistance state of the magnetic tunnel junction can be used to represent and store logical information.

[0062] Principle of Spin Transfer Torque (STT) Effect:

[0063] like Figure 4 (a) shows the process of the MTJ device flipping from a parallel state to an antiparallel state. When an electron flow is injected from the free layer 2 (i.e., a negative polarity current is injected from the top of the free layer 2), due to the spin scattering effect, electrons with the same magnetic moment direction as the fixed layer 4 can pass smoothly, while electrons with the opposite magnetic moment direction will be reflected back to the free layer 2. At this time, only electrons with the opposite magnetic moment direction to the fixed layer 4 remain in the free layer 2. These electrons will exert a torque on the magnetic moment of the free layer 2, which is called the spin transfer torque, thereby causing the magnetic moment of the free layer 2 to flip.

[0064] like Figure 4 (b) shows the process of the MTJ device flipping from the antiparallel state to the parallel state. When an electron flow is injected from the fixed layer 4 (i.e., a positive polarity current is injected from the top of the free layer 2), the magnetic moment of the electrons will be polarized by the magnetic moment of the fixed layer 4. Subsequently, these electrons tunnel through the spacer layer 3 and reach the free layer 2, thereby generating a torque on the magnetic moment of the free layer 2. This torque is called the spin transfer torque, which causes the magnetic moment of the free layer 2 to flip.

[0065] In this embodiment, the externally coated heavy metal ring layer 1 maximizes the spin-orbit torque effect, reusing the current flowing through the heavy metal ring layer 1. This produces both a spin-transfer torque effect and a spin-orbit torque effect, significantly improving the switching efficiency of the MTJ device under current drive. This can further reduce the switching current and switching voltage of the device, preventing breakdown; improve the device's thermal stability, enabling further device size reduction and improving device stability; and further reduce the device's write current as the device size decreases, thereby reducing device power consumption.

[0066] Example 2

[0067] This embodiment provides a magnetic memory device, including at least one memory unit; each of the memory units is the MTJ described in Embodiment 1.

[0068] Example 3

[0069] This embodiment provides a storage method of the MTJ described in Embodiment 1, the method comprising:

[0070] Obtaining a resistance state of the MTJ device; the resistance state includes a high resistance state and a low resistance state; when the logic data of the high resistance state is 1, the logic data of the low resistance state is 0; when the logic data of the high resistance state is 0, the logic data of the low resistance state is 1;

[0071] When the resistance state is the high resistance state, a positive polarity current is passed through the top of the MTJ device;

[0072] Based on the spin-orbit torque effect and the spin transfer torque effect, the magnetic moment of the free layer 2 is reversed, and the resistance state of the MTJ device is changed to the low-resistance state, thereby realizing the storage of low-resistance logic data;

[0073] When the resistance state is the low resistance state, a negative polarity current is passed to the top of the MTJ device;

[0074] Based on the spin-orbit torque effect and the spin transfer torque effect, the magnetic moment of the free layer 2 is reversed, and the resistance state of the MTJ device changes to the high-resistance state, thereby realizing the storage of high-resistance logic data.

[0075] The various embodiments in this specification are described in a progressive manner, and each embodiment focuses on the differences from other embodiments. The same or similar parts between the various embodiments can be referenced to each other.

[0076] This document uses specific examples to illustrate the principles and implementation methods of the present invention. The above examples are only intended to help understand the method and core concept of the present invention. At the same time, those skilled in the art will find that the specific implementation methods and application scopes may vary based on the concept of the present invention. In summary, the contents of this specification should not be construed as limiting the present invention.

Claims

1. A core-shell based MTJ, characterized in that: The MTJ device comprises: a heavy metal ring layer and a fixed layer, a spacer layer and a free layer stacked in sequence; The heavy metal ring layer is sleeved on the outer wall of the free layer; The fixed layer and the free layer are both made of ferromagnetic materials; The spacer layer is made of non-magnetic metal material or oxide insulating material; The tops of the free layer and the heavy metal ring layer are current input terminals, and the bottom of the fixed layer is a current output terminal; The heavy metal ring layer is used to generate a spin-polarized current under the action of the spin Hall effect when injecting current into the top of the free layer, and diffuse the spin-polarized current into the free layer; The free layer is configured to pass the spin-polarized current into the spacer layer and the fixed layer, and flip the magnetic moment of the free layer based on the spin-orbit torque and the spin transfer torque generated at the interface between the free layer and the spacer layer; The resistance of the heavy metal ring layer is smaller than that of the free layer, and the current mainly flows through the heavy metal ring layer, generating a spin-orbit torque effect; The current in the heavy metal ring layer and the current in the free layer will flow into the spacer layer and the fixed layer together. Under the action of the spin transfer torque effect, a spin transfer torque will be generated at the interface between the free layer and the spacer layer; under the action of the spin-orbit torque effect and the spin transfer torque effect, spin-orbit torque and spin transfer torque will be generated, and will act together on the magnetic moment of the free layer, causing it to flip.

2. The MTJ according to claim 1, wherein: There is a preset distance between the heavy metal ring layer and the spacer layer.

3. The MTJ according to claim 1, wherein: The coercive force of the pinned layer is greater than the coercive force of the free layer.

4. The MTJ according to claim 1, wherein: The top of the heavy metal ring layer and the top of the free layer are in the same horizontal plane.

5. The MTJ according to claim 1, wherein: The ferromagnetic material is CoFeB, CoNiCo, CoFe or NiFe; the non-magnetic metal material is Cu or Au; the oxide insulating material is MgO or Al2O3; and the material used for the heavy metal ring layer is Pt, Ta or W.

6. The MTJ according to claim 1, wherein: When the magnetic moments of the free layer and the pinned layer are parallel, the MTJ device is in a low resistance state; when the magnetic moments of the free layer and the pinned layer are antiparallel, the MTJ device is in a high resistance state.

7. A magnetic memory device, characterized in that: The device comprises at least one memory cell; each of the memory cells is the MTJ according to any one of claims 1 to 6.

8. A storage method based on the MTJ according to any one of claims 1 to 6, characterized in that: The method comprises: Obtaining a resistance state of the MTJ device; the resistance state includes a high resistance state and a low resistance state; when the logic data of the high resistance state is 1, the logic data of the low resistance state is 0; when the logic data of the high resistance state is 0, the logic data of the low resistance state is 1; When the resistance state is the high resistance state, a positive polarity current is passed through the top of the MTJ device; Based on the spin-orbit torque effect and the spin transfer torque effect, the magnetic moment of the free layer is reversed, and the resistance state of the MTJ device is changed to the low-resistance state, thereby realizing the storage of low-resistance logic data; When the resistance state is the low resistance state, a negative polarity current is passed to the top of the MTJ device; Based on the spin-orbit torque effect and the spin transfer torque effect, the magnetic moment of the free layer is reversed, and the resistance state of the MTJ device changes to the high-resistance state, thereby realizing the storage of high-resistance logic data.

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