Magnetic random access memory unit and memory

Abstract

The invention provides a magnetic random storage unit, which comprises an antiferromagnetic layer used for providing an in-plane exchange bias field in a fixed direction for a free layer; the free layer is located on the surface of one side of the antiferromagnetic layer, the free layer has vertical magnetization with variable directions, and the free layer has asymmetric voltage control vertical magnetic anisotropy and DM interaction; the insulating layer is located on the surface of the side, away from the antiferromagnetic layer, of the free layer; the reference layer is located on the surface of the side, away from the free layer, of the insulating layer, the reference layer comprises two spaced parts, and the two parts have vertical magnetization with the fixed direction; a first power-on port and a second power-on port are respectively led out from the two parts of the reference layer and are used for applying voltage when write operation is carried out on the magnetic random storage unit. According to the magnetic random storage unit, the write-in error rate can be reduced.

Description

Technical Field

[0001] The present invention relates to the field of memory technology, and in particular to a magnetic random access memory unit and a memory. Background Art

[0002] Spintronic devices are a new type of electronic device that uses electron spin as a state variable. Due to the low switching energy of the spin state, spintronic devices consume much less energy than traditional electronic devices, and have the characteristics of small size, high speed, and non-volatility of data, which can achieve more efficient information storage and processing. Spintronic devices are mainly regulated by magnetic moments generated by electric current, such as spin transfer torque (STT) and spin orbit torque (SOT). However, these effects require large write currents, which restricts the improvement of power consumption and density of spintronic devices, especially magnetic storage.

[0003] One current solution is to control the magnetic moment based on voltage-controlled magnetic anisotropy (VCMA). This method of using electric fields to drive the spin state can solve the problems of high power consumption, large size and slow response in STT-MRAM, and is considered to be one of the main writing methods for the next generation of magnetic memory. However, voltage-controlled magnetic anisotropy cannot accurately control the direction of the magnetic moment, and there are problems such as cumbersome write operations and high write error rates.

[0004] In summary, the magnetic random access memory cells based on voltage-controlled magnetic anisotropy still need further research and improvement. Summary of the invention

[0005] In view of this, the present invention provides a magnetic random access memory unit, which can reduce the write error rate.

[0006] In a first aspect, the present invention provides a magnetic random access memory cell, comprising:

[0007] Antiferromagnetic layer;

[0008] A free layer is located on one side of the antiferromagnetic layer, the antiferromagnetic layer is used to provide a fixed-direction in-plane exchange bias field to the free layer, the free layer has a direction-variable perpendicular magnetization, and the free layer has an asymmetric voltage-controlled perpendicular magnetic anisotropy and DM interaction;

[0009] An insulating layer, located on a surface of the free layer away from the antiferromagnetic layer;

[0010] A reference layer is located on a surface of the insulating layer away from the free layer, the reference layer includes two spaced-apart parts, and the two parts of the reference layer have a perpendicular magnetization with a fixed direction;

[0011] A first power-on port and a second power-on port are respectively led out from two parts of the reference layer, and are used to apply a voltage when performing a write operation on the magnetic random access memory cell.

[0012] Optionally, the voltage states of the two parts of the reference layer determine the resistance state information of the magnetic random access memory cell, and when a high level voltage is applied to the first power-on port and a low level voltage is applied to the second power-on port, the magnetic random access memory cell is in a first resistance state;

[0013] When a low-level voltage is applied to the first power-on port and a high-level voltage is applied to the second power-on port, the magnetic random access memory unit is in a second resistance state.

[0014] Optionally, the cross-sectional shape of the free layer is an axisymmetric figure, and the width gradually decreases from the middle to both ends.

[0015] Optionally, the insulating layer includes two spaced-apart parts, the two parts of the insulating layer are symmetrically arranged at two ends of the free layer surface close to the edge, the edge of the insulating layer is aligned with the edge of the free layer, when the free layer domain wall is of the Nye type, the direction of the exchange bias field is perpendicular to the symmetry axis of the two parts of the insulating layer, when the free layer domain wall is of the Bloch type, the direction of the exchange bias field is parallel to the symmetry axis of the two parts of the insulating layer;

[0016] Two portions of the reference layer overlap two portions of the insulating layer.

[0017] Optionally, the insulating layer and the free layer have the same cross-sectional shape;

[0018] The two parts of the reference layer are symmetrically arranged at both ends of the insulating layer surface near the edge, and the edge of the reference layer is aligned with the edge of the insulating layer. When the free layer domain wall is of the Née type, the direction of the exchange bias field is perpendicular to the symmetry axis of the two parts of the reference layer. When the free layer domain wall is of the Bloch type, the direction of the exchange bias field is parallel to the symmetry axis of the two parts of the reference layer.

[0019] Optionally, the material of the antiferromagnetic layer is selected from one of IrMn, PtMn, FeMn and NiO, and provides an in-plane exchange bias field greater than 100 Oe.

[0020] Optionally, the material of the free layer is selected from one of Co, Fe, FeB, Ir / Fe, Ir / CoFe, Fe / Cr, CoFe and CoFeB.

[0021] Optionally, a width of the domain wall formed inside the free layer is smaller than a width in the middle of a cross section of the free layer.

[0022] Optionally, it also includes:

[0023] A coupling layer, located on a surface of the reference layer away from the insulating layer;

[0024] A pinning layer, located on a surface of the coupling layer away from the reference layer, wherein the pinning layer has a perpendicular magnetization opposite to the magnetization direction of the reference layer;

[0025] The stack of the coupling layer and the pinning layer includes two parts that are symmetrically arranged and overlap with two parts of the reference layer.

[0026] In a second aspect, the present invention provides a memory including the above-mentioned magnetic random access memory unit.

[0027] The magnetic random storage unit provided by the present invention has an antiferromagnetic layer that provides an exchange bias field for the free layer, the free layer has asymmetric voltage-controlled perpendicular magnetic anisotropy and DM interaction, and the reference layer is divided into two parts. The magnetic moment writing of the free layer can be directly controlled by only changing the voltage direction of the two parts of the reference layer. The magnetic moment of the free layer will undergo a bipolar reversal, the writing operation is simple, and the writing error rate is low. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 A schematic diagram of a cross-sectional structure of a magnetic random access memory unit according to an embodiment of the present invention;

[0029] Figure 2 A schematic diagram of a three-dimensional structure of a magnetic random access memory unit according to an embodiment of the present invention;

[0030] Figure 3 Schematic diagram of the VCMA effect curve of the asymmetric free layer;

[0031] Figure 4 Schematic diagram of magnetization direction of the free layer when different write voltages are applied;

[0032] Figure 5 A schematic diagram of a cross-sectional structure of a magnetic random access memory unit according to an embodiment of the present invention;

[0033] Figure 6 A schematic diagram of a three-dimensional structure of a magnetic random access memory unit according to an embodiment of the present invention;

[0034] Figure 7 FIG. 4 is a schematic cross-sectional structure diagram of a magnetic random access memory unit according to an embodiment of the present invention. DETAILED DESCRIPTION

[0035] 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.

[0036] 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.

[0037] In the present application, the terms "upper", "lower", "left", "right", "front", "back", "top", "bottom", "inner", "outer", "middle", "vertical", "horizontal", "lateral", "longitudinal" and the like indicate positions or positional relationships based on the positions or positional relationships shown in the drawings. These terms are mainly used to better describe the present application and its embodiments, and are not used to limit the indicated devices, elements or components to have a specific orientation, or to be constructed and operated in a specific orientation.

[0038] In addition, some of the above terms may be used to express other meanings in addition to indicating orientation or positional relationship. For example, the term "on" may also be used to express a certain dependency or connection relationship in some cases. For those of ordinary skill in the art, the specific meanings of these terms in this application can be understood according to specific circumstances.

[0039] 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.

[0040] An embodiment of the present invention provides a magnetic random access memory cell, referring to Figure 1 and Figure 2 The magnetic random access memory cell comprises: an antiferromagnetic layer 101, a free layer 102, an insulating layer 103 and a reference layer 104,

[0041] The free layer 102 is located on one side of the antiferromagnetic layer 101. The antiferromagnetic layer 101 is used to provide a fixed-direction in-plane exchange bias field to the free layer 102. The free layer 102 has a direction-variable perpendicular magnetization, and the free layer 102 has an asymmetric voltage-controlled perpendicular magnetic anisotropy and DM interaction.

[0042] The insulating layer 103 is located on a surface of the free layer 102 away from the antiferromagnetic layer 101;

[0043] The reference layer 104 is located on a surface of the insulating layer 103 away from the free layer 102. The reference layer 104 includes two spaced-apart parts. The two parts of the reference layer 104 have a perpendicular magnetization with a fixed direction.

[0044] A first power-on port A and a second power-on port B are respectively led out from two parts of the reference layer 104 for applying voltage when performing a write operation on the magnetic random access memory cell.

[0045] Furthermore, in this embodiment, the material of the antiferromagnetic layer 101 is selected from one of IrMn, PtMn, FeMn and NiO, and provides an in-plane exchange bias field greater than 100 Oe.

[0046] In this embodiment, the cross-sectional shape of the free layer 102 is an axisymmetric shape, and the width gradually decreases from the middle to both ends. For example, the cross-sectional shape of the free layer 102 can be an ellipse or a circle. Figure 2 The schematic diagram of the three-dimensional structure of a magnetic random access memory cell according to an embodiment is shown in FIG. The cross-sectional shape of the free layer 102 is designed to be elliptical. The material of the free layer 102 can be one of Co, Fe, FeB, Ir / Fe stack, Ir / CoFe stack, Fe / Cr stack, CoFe and CoFeB.

[0047] In this embodiment, the insulating layer 103 includes two spaced-apart parts, the two parts of the insulating layer 103 are symmetrically arranged at two ends of the surface of the free layer 102 close to the edge, and the edge of the insulating layer 103 is aligned with the edge of the free layer 102 .

[0048] When the free layer domain wall is of the Née type, the direction of the exchange bias field is perpendicular to the symmetry axis of the two parts of the insulating layer. When the free layer domain wall is of the Bloch type, the direction of the exchange bias field is parallel to the symmetry axis of the two parts of the insulating layer.

[0049] The cross-sectional shape of the two parts of the insulating layer 103 is a closed figure composed of a circular arc and a straight line. The insulating layer 103 is an oxide layer, and the commonly used material is magnesium oxide (MgO) or aluminum oxide (AlO x ).

[0050] Correspondingly, two portions of the reference layer 104 overlap with two portions of the insulating layer 103 , that is, the reference layer 104 and the insulating layer 103 have the same cross-sectional shape.

[0051] In the magnetic random access memory cell of the embodiment of the present invention, during the write operation, factors affecting the MTJ resistance include: the magnetization direction of the reference layer, the direction of the exchange bias field, the direction of the DM interaction (abbreviated as DMI), and the application method of the port voltage.

[0052] The magnetization direction of the reference layer, the direction of the exchange bias field, and the direction of the DMI are determined by the characteristics of the device itself, and the application method of the port voltage is controllable. The voltage state of the two parts of the reference layer 104 determines the resistance state information of the magnetic random memory cell. When a high-level voltage is applied to the first power-on port and a low-level voltage is applied to the second power-on port, the magnetic random memory cell is in the first resistance state; when a low-level voltage is applied to the first power-on port and a high-level voltage is applied to the second power-on port, the magnetic random memory cell is in the second resistance state.

[0053] Specifically, the free layer includes an asymmetric voltage-controlled perpendicular magnetic anisotropy (VCMA) effect and a DM interaction (DMI). Figure 3 is a schematic diagram of an asymmetric VCMA effect curve, such as Figure 3 As shown in the figure, when a positive voltage is applied, the perpendicular anisotropy of the free layer will decrease, and when a negative voltage is applied, the perpendicular anisotropy of the free layer will increase, and the VCMA coefficient under positive voltage is greater than the VCMA coefficient under negative voltage. The DMI coefficient of the free layer should be greater than 0.1mJ / m 2 The two reference layers have the same magnetization direction, and can be regarded as two magnetic tunnel junctions (MTJs) together with the insulating layer and the free layer. The two power ports set on the top are equivalent to connecting two MTJs in series and placed in opposite directions. The resistance values ​​of the two MTJs are consistent. The resistance between the two ports is the sum of the resistance values ​​of the two MTJs, and its size is determined by the magnetization state of the free layer.

[0054] When no voltage is applied to the two powered ports, each magnetic layer is perpendicular anisotropic. When an external voltage is applied, the area of ​​the free layer close to the higher potential changes to the in-plane direction, and the direction of the in-plane magnetic moment is determined by the direction of the exchange bias field provided by the antiferromagnetic layer; the area with a lower potential maintains a perpendicular direction, and the direction is determined by the chirality of the domain wall formed by the DMI. When the voltage is removed, the free layer changes to the magnetization direction of the perpendicular magnetization area, achieving bipolar magnetization reversal.

[0055] The switching mechanism of the free layer is described in detail below.

[0056] In this embodiment, the mechanism of bipolar magnetization reversal comes from the combined effect of DMI and exchange bias field. Exchange bias, VCMA, and DMI are all interface effects that act on the magnetic moment of the free layer. When DMI is positive, the magnetic moment inside the free layer tends to rotate counterclockwise along the domain wall direction. Figure 4 As shown, the exchange bias field of the antiferromagnetic layer is in the +x direction. When a high level is applied to the first energized port A and a low level is applied to the second energized port B, the VCMA voltage on the left is positive, and the PMA decreases. Due to the asymmetric VCMA effect, the decrease is large. The VCMA voltage on the right is negative, and the PMA increases. Due to the asymmetric VCMA effect, the increase is small. Therefore, the overall PMA coefficient of the free layer decreases, and the vertical magnetization state is no longer maintained, and a domain wall will be formed inside the free layer. Different free layer materials form different types of domain walls. Since the PMA coefficient on the left is small, it will become an in-plane state, and due to the influence of the exchange bias field, its direction is in the +x direction. The PMA coefficient on the right is large, and the vertical magnetization direction will be maintained. However, due to the influence of DMI, it is easier to maintain the +z direction than the left. After the voltage is removed, the free layer will switch to the +z direction as a whole. The width of the domain wall formed inside the free layer should be smaller than the middle width of the free layer cross section. The width of the domain wall belongs to the material property, and the width of the domain wall usually does not exceed 30nm.

[0057] Similarly, when a low level is applied to the first powered port A and a high level is applied to the second powered port B, the VCMA voltage on the left is negative, the PMA increases but the amplitude is small, and the VCMA voltage on the right is positive, the PMA decreases but the amplitude is large. At this time, the right side is in the +x direction, and the left side will become the -z direction. After the voltage is removed, the free layer switches to the -z direction as a whole.

[0058] In the magnetic random access memory cell of the embodiment of the present invention, the antiferromagnetic layer provides an exchange bias field for the free layer, the free layer has asymmetric voltage-controlled perpendicular magnetic anisotropy and DM interaction, and the reference layer is divided into two parts. The magnetic moment writing of the free layer can be directly controlled by only changing the voltage direction of the two parts of the reference layer. The magnetic moment of the free layer will undergo a bipolar reversal, the writing operation is simple, and the writing error rate is low.

[0059] In one embodiment, reference Figure 5 and Figure 6 , the magnetic random access memory cell comprises:

[0060] Antiferromagnetic layer 201;

[0061] The free layer 202 is located on one side of the antiferromagnetic layer 201. The antiferromagnetic layer 201 is used to provide a fixed-direction in-plane exchange bias field to the free layer 202. The free layer 202 has a direction-variable perpendicular magnetization, and the free layer 202 has an asymmetric voltage-controlled perpendicular magnetic anisotropy and DM interaction.

[0062] The insulating layer 203 is located on a surface of the free layer 202 away from the antiferromagnetic layer 201;

[0063] The reference layer 204 is located on a surface of the insulating layer 203 away from the free layer 202 . The reference layer 204 includes two spaced-apart parts. The two parts of the reference layer 204 have perpendicular magnetization with fixed directions.

[0064] Different from the above-mentioned embodiment, the insulating layer 203 in this embodiment is no longer divided into two parts, and the insulating layer 203 and the free layer 202 have the same cross-sectional shape, which is an axisymmetric figure, and the width gradually decreases from the middle to the two ends. For example, the cross-sectional shape of the insulating layer 203 and the free layer 202 can be elliptical or circular. This structure is easier to implement in terms of process, and it is not easy to short-circuit between the free layer and the reference layer.

[0065] Correspondingly, the two parts of the reference layer 204 are symmetrically arranged at both ends of the surface of the insulating layer 203 near the edge, and the edge of the reference layer 204 is aligned with the edge of the insulating layer 203. When the domain wall of the free layer is of the Néel type, the direction of the exchange bias field is perpendicular to the symmetry axis of the two parts of the reference layer 204, and when the domain wall of the free layer is of the Bloch type, the direction of the exchange bias field is parallel to the symmetry axis of the two parts of the reference layer 204.

[0066] The cross-sectional shape of the two parts of the reference layer 204 is a closed figure composed of a circular arc and a straight line.

[0067] The working principle and technical effects of the magnetic random access memory unit provided by the embodiment of the present invention can be referred to the description of the aforementioned embodiment.

[0068] Further, in Figure 1 The storage unit structure shown is expanded on the basis of Figure 7 As shown, the magnetic random access memory cell also includes:

[0069] The coupling layer 105 is located on a surface of the reference layer 104 that is away from the insulating layer 103;

[0070] A pinning layer 106 is located on a surface of the coupling layer 105 that is away from the reference layer 104 , and the pinning layer 106 has a perpendicular magnetization that is opposite to the magnetization direction of the reference layer 104 ;

[0071] The stack of the coupling layer 105 and the pinning layer 106 includes two parts that are symmetrically arranged and overlap with two parts of the reference layer 104 .

[0072] Further references Figure 7 It can be understood that, in the embodiment of the present invention, in order to apply a voltage, power ports A and B can be drawn out from above the two parts of the pinning layer 106 to apply a voltage.

[0073] Of course, the above-mentioned stacking of coupling layer and pinning layer is also applicable to Figure 5 The memory cell structure shown in Figure 1. The stacking of the coupling layer and the pinning layer can enhance the thermal stability of the reference layer.

[0074] The working principle and technical effects of the magnetic random access memory unit provided by the embodiment of the present invention can be referred to the description of the aforementioned embodiment.

[0075] On the other hand, an embodiment of the present invention further provides a memory, comprising the magnetic random access memory unit of the above embodiment.

[0076] 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 magnetic random access memory cell, characterized in that: include: Antiferromagnetic layer; A free layer is located on one side of the antiferromagnetic layer, the antiferromagnetic layer is used to provide a fixed-direction in-plane exchange bias field to the free layer, the free layer has a direction-variable perpendicular magnetization, and the free layer has an asymmetric voltage-controlled perpendicular magnetic anisotropy and DM interaction; An insulating layer, located on a surface of the free layer away from the antiferromagnetic layer; A reference layer is located on a surface of the insulating layer away from the free layer, the reference layer includes two spaced-apart parts, and the two parts of the reference layer have a perpendicular magnetization with a fixed direction; A first power-on port and a second power-on port are respectively led out from two parts of the reference layer, and are used to apply a voltage when performing a write operation on the magnetic random access memory cell.

2. The magnetic random access memory cell according to claim 1, characterized in that: The voltage states of the two parts of the reference layer determine the resistance state information of the magnetic random access memory cell. When a high level voltage is applied to the first power-on port and a low level voltage is applied to the second power-on port, the magnetic random access memory cell is in a first resistance state. When a low-level voltage is applied to the first power-on port and a high-level voltage is applied to the second power-on port, the magnetic random access memory unit is in a second resistance state.

3. The magnetic random access memory cell according to claim 1, characterized in that: The cross-sectional shape of the free layer is an axisymmetric figure, and the width gradually decreases from the middle to both ends.

4. The magnetic random access memory cell according to claim 1, characterized in that: The insulating layer comprises two spaced-apart parts, the two parts of the insulating layer are symmetrically arranged at two ends of the free layer surface near the edge, the edge of the insulating layer is aligned with the edge of the free layer, when the domain wall of the free layer is of the Nye type, the direction of the exchange bias field is perpendicular to the symmetry axis of the two parts of the insulating layer, when the domain wall of the free layer is of the Bloch type, the direction of the exchange bias field is parallel to the symmetry axis of the two parts of the insulating layer; Two portions of the reference layer overlap two portions of the insulating layer.

5. The magnetic random access memory cell according to claim 1, characterized in that: The insulating layer and the free layer have the same cross-sectional shape; The two parts of the reference layer are symmetrically arranged at both ends of the insulating layer surface near the edge, and the edge of the reference layer is aligned with the edge of the insulating layer. When the free layer domain wall is of the Née type, the direction of the exchange bias field is perpendicular to the symmetry axis of the two parts of the reference layer. When the free layer domain wall is of the Bloch type, the direction of the exchange bias field is parallel to the symmetry axis of the two parts of the reference layer.

6. The magnetic random access memory cell according to claim 1, characterized in that: The material of the antiferromagnetic layer is selected from one of IrMn, PtMn, FeMn and NiO, and provides an in-plane exchange bias field greater than 100 Oe.

7. The magnetic random access memory cell according to claim 1, characterized in that: The material of the free layer is selected from one of Co, Fe, FeB, Ir / Fe, Ir / CoFe, Fe / Cr, CoFe and CoFeB.

8. The magnetic random access memory cell according to claim 1, characterized in that: The width of the domain wall formed inside the free layer is smaller than the middle width of the cross section of the free layer.

9. The magnetic random access memory cell according to claim 1, characterized in that: Also includes: A coupling layer, located on a surface of the reference layer away from the insulating layer; A pinning layer, located on a surface of the coupling layer away from the reference layer, wherein the pinning layer has a perpendicular magnetization opposite to the magnetization direction of the reference layer; The stack of the coupling layer and the pinning layer includes two parts that are symmetrically arranged and overlap with two parts of the reference layer.

10. A memory, characterized in that: The invention comprises a magnetic random access memory cell as claimed in any one of claims 1 to 9.

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