Non-uniformly magnetized memory cells

Abstract

The present invention provides a non-uniformly magnetized storage unit. The storage unit includes a spin Hall effect layer and two parallel magnetic tunnel junctions located on the same side surface of the spin Hall effect layer. Each magnetic tunnel junction includes: a free layer, a barrier layer, and a reference layer stacked sequentially in a direction away from the spin Hall effect layer. The two reference layers have fixed magnetization directions. The two magnetic tunnel junctions have different shapes, or the two magnetic tunnel junctions have the same shape but are arranged differently on the spin Hall effect layer, so that the slopes of the easy magnetization axes of the two magnetic tunnel junctions are opposite in sign, so that when the spin Hall effect layer is energized, the two free layers exhibit opposite magnetization directions. When energized, the free layers in the two magnetic tunnel junctions do not require an external magnetic field. By passing currents in different directions, the two magnetic tunnel junctions are always in complementary resistance states, and differential storage is achieved by reading signals, thereby saving the area of ​​the storage unit and reducing costs.

Description

Technical Field

[0001] The present invention relates to the technical field of memory, and in particular to a non-uniformly magnetized memory unit. Background Art

[0002] Spin-orbit torque magnetic RAM (SOT-MRAM) is one of the more promising memory devices in the future due to its high write speed and low power consumption.

[0003] The SOT-MRAM device cell consists of a magnetic tunnel junction (MTJ) and a spin Hall effect layer (SHE). The MTJ includes a free layer, a barrier layer, and a reference layer. The reference layer has a fixed magnetization direction, while the free layer has a variable magnetization direction. When the free layer and the reference layer are parallel, the MTJ exhibits a low-resistance state; when the free layer and the reference layer are antiparallel, the MTJ exhibits a high-resistance state. When current flows through the SHE, the magnetic moment of the free layer is reversed, either with the aid of an external magnetic field or by setting a magnetic bias layer.

[0004] In order to improve data reliability and increase data reading speed, a differential storage unit with a 2T2R structure is often used. However, the storage unit of the traditional differential storage unit has problems such as large area and high cost. Summary of the Invention

[0005] The main purpose of the present invention is to provide a non-uniform magnetization storage unit to solve the problems of large storage unit area and high cost of differential storage units in the prior art.

[0006] To achieve the above objectives, according to one aspect of the present invention, a non-uniformly magnetized storage cell is provided, comprising a spin Hall effect layer and two parallel magnetic tunnel junctions located on the same side surface of the spin Hall effect layer. Each magnetic tunnel junction comprises: a free layer, a barrier layer, and a reference layer stacked sequentially in a direction away from the spin Hall effect layer. The two reference layers have fixed magnetization directions. The two magnetic tunnel junctions have different shapes, or the two magnetic tunnel junctions have the same shape but are arranged in different manners on the spin Hall effect layer, so that the slopes of the easy magnetization axes of the two magnetic tunnel junctions are opposite in sign, thereby causing the two free layers to exhibit opposite magnetization directions when power is applied to the spin Hall effect layer.

[0007] Furthermore, both the free layer and the reference layer are in-plane magnetized.

[0008] Furthermore, the cross-sections of the two magnetic tunnel junctions in a direction parallel to the spin Hall effect layer are respectively a first cross-section and a second cross-section, the first cross-section and the second cross-section are each an axially symmetric figure having at most two symmetry axes, and the slopes of the easy magnetization axes of the first cross-section and the second cross-section are opposite in sign.

[0009] Furthermore, both the first cross section and the second cross section are elliptical, and preferably the ratio of the major axis to the minor axis in the ellipse is greater than 1.5, and the slope of the major axis in the ellipse is k0, 0<|k0|<3.

[0010] Furthermore, the cross-sections of the two magnetic tunnel junctions in a direction parallel to the spin Hall effect layer are both right-angled trapezoids, the slopes of the hypotenuses of the right-angled trapezoids in the two magnetic tunnel junctions are opposite in sign, and the slope of the hypotenuse is k1, 0<|k1|<3.

[0011] Furthermore, the cross-sections of the two magnetic tunnel junctions in a direction parallel to the spin Hall effect layer are both hypotenuse trapezoids, and the hypotenuse with the smaller absolute value of the slope in the hypotenuse trapezoid is defined as the first hypotenuse. The slopes of the first hypotenuses of the hypotenuse trapezoids in the two magnetic tunnel junctions are opposite in sign, and the slope of the first hypotenuse is k2, 0<|k2|<3.

[0012] Furthermore, the cross-sections of the two magnetic tunnel junctions in a direction parallel to the spin Hall effect layer are both parallelograms, the parallelograms in the two magnetic tunnel junctions located on the same plane are axially symmetric, and preferably, the slope of at least two sides of the parallelogram is k3, 0<|k3|<3.

[0013] Furthermore, the storage unit also includes a differential storage unit, which includes: a transistor connected to one end of the spin Hall effect layer; and a sensitive amplifier, wherein one end of the two magnetic tunnel junctions away from the spin Hall effect layer is respectively connected to the sensitive amplifier.

[0014] Furthermore, the material of the spin Hall effect layer includes a topological insulating material and / or a heavy metal material, preferably the topological insulating material is selected from any one or more of BixSe(1-x), SbxTe(1-x), BixTe(1-x), and the heavy metal material is selected from any one or more of Ta, Pt, Pd and W.

[0015] Furthermore, the materials of the free layer and the reference layer are independently selected from any one or more of Co, CoFe, CoFeB, Co / Mo / CoFeB and CoFe / Mo / CoFeB, and the material of the barrier layer preferably includes MgO and / or MgAl2O4.

[0016] The technical solution of the present invention provides a non-uniformly magnetized storage unit, comprising a spin Hall effect layer and two magnetic tunnel junctions located on the same side surface of the spin Hall effect layer. The magnetic tunnel junctions include a free layer, a barrier layer, and a reference layer stacked sequentially in a direction away from the spin Hall effect layer. The reference layer has a fixed magnetization direction. The two magnetic tunnel junctions have different shapes, or the two magnetic tunnel junctions have different arrangements on the spin Hall effect layer, so that when the spin Hall effect layer is energized, the free layers exhibit opposite magnetization directions. Due to the difference in arrangement or shape, the slopes of the easy magnetization axes of the free layers in the two magnetic tunnel junctions are opposite, resulting in opposite magnetization directions when energized. Therefore, without the need for an external magnetic field, the two magnetic tunnel junctions are always in complementary resistance states by passing currents in different directions, and differential storage is achieved by reading signals. This not only reduces the read error rate but also saves the area of ​​the storage unit and reduces the cost. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] The accompanying drawings, which constitute part of the present invention, are intended to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are intended to explain the present invention and do not constitute an undue limitation of the present invention. In the accompanying drawings:

[0018] Figure 1 A schematic side view of a non-uniformly magnetized storage unit provided in an embodiment of the present application is shown;

[0019] Figure 2 Shown Figure 1 A schematic top view of a non-uniformly magnetized memory cell as shown in FIG.

[0020] Figures 3 to 8 Schematic diagrams of top views of two parallel magnetic tunnel junctions located on the same side surface of the spin Hall effect layer in a non-uniformly magnetized memory cell are shown, wherein both the free layer and the reference layer are magnetized in-plane;

[0021] Figure 9 A schematic structural diagram of a non-uniformly magnetized memory cell further comprising a sense amplifier is shown.

[0022] The above drawings include the following reference numerals:

[0023] 10. Spin Hall effect layer; 20. Magnetic tunnel junction; 210. Free layer; 220. Barrier layer; 230. Reference layer; 30. Sensitive amplifier. DETAILED DESCRIPTION

[0024] It should be noted that, in the absence of conflict, the embodiments and features of the embodiments of the present invention can be combined with each other. The present invention will be described in detail below with reference to the accompanying drawings and in combination with the embodiments.

[0025] In order to enable those skilled in the art to better understand the solutions of the present invention, the technical solutions 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 embodiments described 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 should fall within the scope of protection of the present invention.

[0026] It should be noted that the terms "first," "second," and the like in the specification and claims of the present invention and the accompanying drawings are used to distinguish similar objects and are not necessarily used to describe a particular order or precedence. It should be understood that the terms used in this manner are interchangeable where appropriate for the embodiments of the present invention described herein. In addition, the terms "including," "having," and any variations thereof are intended to cover non-exclusive inclusions. For example, a process, method, system, product, or apparatus comprising a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units that are not explicitly listed or that are inherent to these processes, methods, products, or apparatuses.

[0027] As described in the background art, in order to improve data reliability and increase data reading speed, a differential storage unit with a 2T2R structure is often used in the prior art. However, the storage unit of the traditional differential storage unit has problems such as large area and high cost.

[0028] The inventors of this application have studied the above problems and proposed a non-uniform magnetization storage unit, such as Figure 1 and Figure 2 As shown, the device includes a spin Hall effect layer 10 and two parallel magnetic tunnel junctions 20 located on the same side surface of the spin Hall effect layer 10. Each magnetic tunnel junction 20 includes: a free layer 210, a barrier layer 220, and a reference layer 230 stacked in sequence in a direction away from the spin Hall effect layer 10. The two reference layers 230 have fixed magnetization directions. The two magnetic tunnel junctions 20 have different shapes, or the two magnetic tunnel junctions 20 have the same shape but are arranged in different ways on the spin Hall effect layer 10, so that the slopes of the easy magnetization axes of the two magnetic tunnel junctions 20 are opposite in sign, so that the two free layers 210 exhibit opposite magnetization directions after the spin Hall effect layer 10 is energized.

[0029] The free layers 210 in the two magnetic tunnel junctions 20 have different easy magnetization axis directions due to differences in arrangement or shape, and exhibit opposite magnetization directions after power is applied. Therefore, no external magnetic field is required. By passing currents in different directions, the two magnetic tunnel junctions 20 are always in complementary resistance states, and differential storage is achieved by reading signals, which not only reduces the read error rate but also saves the area of ​​the storage unit and reduces costs.

[0030] In the non-uniform magnetization memory cell of the present invention, the free layer 210 and the reference layer 230 may both be in-plane magnetized.

[0031] When the free layer 210 and the reference layer 230 are both in-plane magnetized, in order to enable the two free layers 210 to exhibit opposite magnetization directions, in a preferred embodiment, the cross-sections of the two magnetic tunnel junctions 20 in a direction parallel to the spin Hall effect layer 10 are respectively a first cross-section and a second cross-section, and the first cross-section and the second cross-section are each an axially symmetric figure having at most two symmetry axes, and the slopes of the easy magnetization axes of the first cross-section and the second cross-section are opposite in sign.

[0032] When the first cross section and the second cross section are each an axisymmetric figure, in an optional first embodiment, the first cross section and the second cross section are both elliptical, and the major axes of the two ellipses are the easy magnetization axes ( Figure 2 The two oblique dotted lines in the figure are opposite in sign and negative in slope. Figure 2 Preferably, the ratio of the major axis to the minor axis in the ellipse is greater than 1.5, and the slope of the major axis in the ellipse is k0, 0<|k0|<3.

[0033] When the first cross-section and the second cross-section are each axially symmetrical, in an optional second embodiment, both the first cross-section and the second cross-section are rhombus-shaped. In this case, the long diagonals of the two rhombuses are oriented along the easy magnetization axis, and the slopes of the long diagonals of the two rhombuses are opposite in sign. Preferably, the slope of at least two sides of the rhombus is k3, where 0<|k3|<3.

[0034] When the first cross section and the second cross section are each an axisymmetric figure, in an optional third embodiment, the first cross section and the second cross section are both rectangular, in which case the long sides of the two rectangles are in the direction of the easy magnetization axis, and the slopes of the long sides of the two rectangles are opposite in sign. Preferably, the slope of at least two sides of the rectangle is k3, 0<|k3|<3

[0035] When the free layer 210 and the reference layer 230 are both magnetized in-plane, the two magnetic tunnel junctions 20 of the present invention are not limited to the above embodiment. In another optional embodiment, the first cross section and the second cross section may both be right-angled trapezoids, and the slopes of the hypotenuses of the right-angled trapezoids in the two magnetic tunnel junctions 20 are opposite in sign and negative, and the hypotenuse slope is k1, 0<|k1|<3, such as Figure 3 and Figure 4 shown.

[0036] In another optional embodiment, the first cross section and the second cross section may both be hypotenuse trapezoids, and the hypotenuse with the smaller absolute value of the slope in the hypotenuse trapezoid is defined as the first hypotenuse. The slopes of the first hypotenuses of the hypotenuse trapezoids in the two magnetic tunnel junctions 20 are opposite in sign, and the hypotenuse slope is k2, 0<|k2|<3, such as Figure 5 and Figure 6 As shown.

[0037] In another optional embodiment, the first cross section and the second cross section may both be non-axisymmetric parallelograms. In the two magnetic tunnel junctions 20, the parallelograms are located on the same plane, and the slope of at least one side of one parallelogram is opposite to that of at least one side of the other parallelogram. Preferably, the slope of at least two sides of the parallelogram is k3, 0<|k3|<3, such as Figure 7 shown.

[0038] When both the free layer 210 and the reference layer 230 are magnetized in-plane, the first cross section and the second cross section may have different shapes. In an optional embodiment, one is an ellipse and the other is a parallelogram. The slopes of the easy magnetization axes of the two units are opposite in sign, such as Figure 8 shown.

[0039] In the non-uniform magnetization memory cell of the present invention, the material of the spin Hall effect layer 10 may include a topological insulating material and / or a heavy metal material. Those skilled in the art can reasonably select the material of the spin Hall effect layer 10 based on the existing technology. Preferably, the topological insulating material is selected from any one or more of BixSe(1-x), SbxTe(1-x), and BixTe(1-x). Preferably, the heavy metal material is selected from any one or more of Ta, Pt, Pd, and W.

[0040] In the non-uniform magnetization memory cell of the present invention, preferably, the materials of the free layer 210 and the reference layer 230 are independently selected from one or more of Co, CoFe, CoFeB, Co / Mo / CoFeB, and CoFe / Mo / CoFeB. Preferably, the material of the barrier layer 220 includes MgO and / or MgAl2O4. However, this is not limited to the aforementioned preferred materials. Those skilled in the art may also appropriately select the materials for the free layer 210, reference layer 230, and barrier layer 220 based on existing technologies.

[0041] The non-uniform magnetization storage unit of the present invention may also include a differential storage unit. Preferably, the differential storage unit includes a transistor and a sense amplifier 30. The transistor is connected to one end of the spin Hall effect layer 10. The ends of the two magnetic tunnel junctions 20 away from the spin Hall effect layer 10 are respectively connected to the sense amplifier 30. Figure 9 shown.

[0042] When a write operation is performed on the non-uniformly magnetized memory cell, the word line WL is energized to enable the transistor, the write bit line WBL is energized, and the source line SL is grounded. When a read operation is performed on the non-uniformly magnetized memory cell, the word line WL is energized to enable the transistor, the source line SL is energized, and the sense amplifier 30 reads data through the read bit lines RBL1 and RBL2. Figure 9 shown.

[0043] by Figure 9 Taking the non-uniformly magnetized storage cell shown in the figure as an example, the method of achieving differential storage of the read signal is explained: in the initial state, the in-plane magnetization directions of the free layers 210 in the two magnetic tunnel junctions 20 are consistent. Regardless of whether a positive current or a negative current is passed through the spin Hall effect layer 10 first, the magnetization directions of the two free layers 210 are always opposite. At the same time, the magnetization direction of the reference layer 230 is consistent and fixed, so that the resistance of the two magnetic tunnel junctions 20 is respectively in a high and low resistance state, presenting a complementary state. After the current passes through the magnetic tunnel junction 20, the current size is compared through the sense amplifier 30 to achieve differential storage.

[0044] From the above description, it can be seen that the above embodiments of the present invention achieve the following technical effects:

[0045] 1. The non-uniform magnetization storage unit of the present invention utilizes the arrangement or shape difference of the free layer in the magnetic tunnel junction, without the need for external magnetic field magnetization reversal or additional magnetic bias layer, to achieve differential data storage;

[0046] 2. The above-mentioned non-uniformly magnetized storage cell directly sets two magnetic tunnel junctions on the same side of the spin Hall effect layer to realize a differential structure. Compared with the traditional 2T2R structure differential storage cell, it reduces the use of selection transistors, source lines, word lines, bit lines, etc., simplifies the array structure, improves integration, and reduces costs.

[0047] The foregoing description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Those skilled in the art will readily appreciate that various modifications and variations of the present invention are possible. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present invention are intended to be within the scope of protection of the present invention.

Claims

1. A non-uniform magnetization storage unit, characterized in that: A spin Hall effect layer and two parallel magnetic tunnel junctions located on the same side surface of the spin Hall effect layer, each of the magnetic tunnel junctions comprising: A free layer, a barrier layer, and a reference layer are sequentially stacked in a direction away from the spin Hall effect layer, the two reference layers having fixed magnetization directions, the two magnetic tunnel junctions having different shapes, or the two magnetic tunnel junctions having the same shape but having different arrangements on the spin Hall effect layer, so that the slopes of the easy magnetization axes of the two magnetic tunnel junctions are opposite in sign, thereby causing the two free layers to exhibit opposite magnetization directions when power is applied to the spin Hall effect layer; The free layer and the reference layer are both magnetized in-plane; The cross-sections of the two magnetic tunnel junctions in a direction parallel to the spin Hall effect layer are respectively a first cross-section and a second cross-section, the first cross-section and the second cross-section are each an axially symmetric figure having at most two axes of symmetry, and the slopes of the easy magnetization axes of the first cross-section and the second cross-section are opposite in sign.

2. The non-uniform magnetization memory cell according to claim 1, wherein: The first cross section and the second cross section are both elliptical, and preferably, the ratio of the major axis to the minor axis in the ellipse is greater than 1.5, and the slope of the major axis in the ellipse is k0, 0<|k0|<3.

3. The non-uniform magnetization memory cell according to claim 1, wherein: The cross-sections of the two magnetic tunnel junctions in a direction parallel to the spin Hall effect layer are both right-angled trapezoids, the slopes of the hypotenuses of the right-angled trapezoids in the two magnetic tunnel junctions are opposite in sign, and the slope of the hypotenuse is k1, 0<|k1|<3.

4. The non-uniform magnetization memory cell according to claim 1, wherein: The cross-sections of the two magnetic tunnel junctions in a direction parallel to the spin Hall effect layer are both hypotenuse trapezoids, and the hypotenuse with the smaller absolute value of the slope in the hypotenuse trapezoid is defined as the first hypotenuse. The slopes of the first hypotenuses of the hypotenuse trapezoids in the two magnetic tunnel junctions are opposite in sign, and the slope of the first hypotenuse is k2, 0<|k2|<3.

5. The non-uniform magnetization memory cell according to claim 1, wherein: The cross-sections of the two magnetic tunnel junctions in a direction parallel to the spin Hall effect layer are both parallelograms, and the parallelograms located on the same plane in the two magnetic tunnel junctions are axially symmetrical. Preferably, the slope of at least two sides of the parallelogram is k3, 0<|k3|<3.

6. The non-uniform magnetization memory cell according to any one of claims 1 to 5, characterized in that: The storage unit further includes a differential storage unit, and the differential storage unit includes: a transistor connected to one end of the spin Hall effect layer; A sensitive amplifier is provided, wherein one end of the two magnetic tunnel junctions away from the spin Hall effect layer is connected to the sensitive amplifier respectively.

7. The non-uniform magnetization memory cell according to any one of claims 1 to 5, characterized in that: The material of the spin Hall effect layer includes a topological insulating material and / or a heavy metal material. Preferably, the topological insulating material is selected from any one or more of BixSe(1-x), SbxTe(1-x), and BixTe(1-x). Preferably, the heavy metal material is selected from any one or more of Ta, Pt, Pd, and W.

8. The non-uniform magnetization memory cell according to any one of claims 1 to 5, characterized in that: The materials of the free layer and the reference layer are independently selected from any one or more of Co, CoFe, CoFeB, Co / Mo / CoFeB and CoFe / Mo / CoFeB. Preferably, the material of the barrier layer includes MgO and / or MgAl2O4.

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