A tunneling magnetoresistance and a manufacturing method thereof

Abstract

The present invention provides a tunneling magnetoresistance and a manufacturing method thereof. The tunneling magnetoresistance includes: a first pinned layer; a free layer disposed opposite to the first pinned layer; a tunneling barrier layer located between the first pinned layer and the free layer; and a second pinned layer located on a side of the free layer facing away from the tunneling barrier layer. The second pinned layer can provide a weak exchange bias field for the free layer. After the external environmental temperature or the external magnetic field is removed, the exchange bias field can pin the direction of the free layer in the initial state, thereby avoiding the problem that the initial state of the vortex magnetization of the tunneling magnetoresistance is unstable and is easily affected by changes in the external environment, resulting in the drift of the magnetization curve. It has the effect of stabilizing the free layer and increasing the temperature stability of the free layer.

Description

Technical Field

[0001] The present invention relates to the technical field of magnetic sensors, and particularly relates to a tunneling magnetoresistance and a manufacturing method thereof. Background Art

[0002] Magnetic sensing technology is widely used in fields such as new energy, intelligent transportation, industrial control, intelligent household appliances, and intelligent networks. Currently, the widely promoted technology is TMR (Tunneling Magneto Resistance), that is, tunneling magnetoresistance.

[0003] The common problem of currently used tunneling magnetoresistance with vortex magnetization effect is that the initial state of vortex magnetization is unstable and is easily affected by changes in the external environment, resulting in the drift of the magnetization curve. The thermal stability and magnetic stability of the vortex magnetization curve are relatively poor. Under the condition of an external magnetic field or a change in the external temperature, the magnetic curve is prone to drift and cannot return to the initial state well, resulting in device performance failure or unstable operation. Summary of the Invention

[0004] Therefore, the technical problem to be solved by the present invention is to overcome the problem that the initial state of vortex magnetization of the tunneling magnetoresistance in the prior art is unstable and is easily affected by changes in the external environment, resulting in the drift of the magnetization curve, so as to provide a tunneling magnetoresistance and a manufacturing method thereof.

[0005] The present invention provides a tunneling magnetoresistance, including: a first pinning layer; a free layer disposed opposite to the first pinning layer; a tunneling barrier layer located between the first pinning layer and the free layer; and a second pinning layer located on a side of the free layer away from the tunneling barrier layer.

[0006] Optionally, the pinning field direction of the second pinning layer is perpendicular to the surface of the second pinning layer opposite to the tunneling barrier layer.

[0007] Optionally, the material of the second pinning layer includes IrMn or PtMn.

[0008] Optionally, the thickness of the second pinning layer is 6 nm to 12 nm.

[0009] Optionally, the free layer is a composite structure, and the free layer includes a stacked first free sub-layer and second free sub-layer, and the first free sub-layer is located between the second free sub-layer and the tunneling barrier layer.

[0010] Optionally, the free layer further includes: a spacer layer located between the first free sub-layer and the second free sub-layer.

[0011] Optionally, the material of the spacer layer includes Ta.

[0012] Optionally, the thickness of the spacer layer is 0.1 nm to 0.5 nm.

[0013] Optionally, the material of the first free layer includes CoFeB; the material of the second free layer includes NiFe.

[0014] Optionally, the thickness of the first free layer is 1 nm to 3.5 nm; the thickness of the second free layer is 30 nm to 60 nm.

[0015] Optionally, the first pinning layer includes: a first sub-pinning film, a second sub-pinning film, a third sub-pinning film, and a fourth sub-pinning film. The first sub-pinning film, the second sub-pinning film, the third sub-pinning film, and the fourth sub-pinning film are stacked in sequence in the direction from the free layer to the tunneling barrier layer; the material of the first sub-pinning film includes CoFeB; the material of the second sub-pinning film includes Ru; the material of the third sub-pinning film includes CoFe; the material of the fourth sub-pinning film includes IrMn or PtMn.

[0016] Optionally, the thickness of the first sub-pinning film is 2 nm to 3 nm; the thickness of the second sub-pinning film is 0.7 nm to 0.9 nm; the thickness of the third sub-pinning film is 1.8 nm to 2.2 nm; the thickness of the fourth sub-pinning film is 7 nm to 20 nm.

[0017] The present invention also provides a method for manufacturing a tunneling magnetoresistance for forming the tunneling magnetoresistance of the present invention, including the following steps: forming a first pinning layer; forming a tunneling barrier layer on the first pinning layer; forming a free layer on a side of the tunneling barrier layer facing away from the first pinning layer; and forming a second pinning layer on a side of the free layer facing away from the tunneling barrier layer.

[0018] Optionally, the method for forming the free layer includes: forming a first free layer on a side of the tunneling barrier layer facing away from the first pinning layer; and forming a second free layer on a side of the first free layer facing away from the tunneling barrier layer.

[0019] Optionally, the method for forming the free layer further includes: forming a spacer layer between the step of forming the first free layer and the step of forming the second free layer.

[0020] The technical solution of the present invention has the following beneficial effects:

[0021] 1. The tunneling magnetoresistance provided by the present invention includes: a first pinned layer; a free layer disposed opposite to the first pinned layer; a tunneling barrier layer located between the first pinned layer and the free layer; and a second pinned layer located on the side of the free layer facing away from the tunneling barrier layer. The second pinned layer can provide a weak exchange bias field for the free layer. After the external environmental temperature or the external magnetic field is removed, the exchange bias field can pin the direction of the free layer in the initial state, thus avoiding the problem that the initial state of the vortex magnetization of the tunneling magnetoresistance is unstable and is easily affected by changes in the external environment, resulting in the drift of the magnetization curve. It has the function of stabilizing the free layer and increasing the temperature stability of the free layer.

[0022] 2. Further, the pinning field direction of the second pinned layer is perpendicular to the surface of the second pinned layer opposite to the tunneling barrier layer. The second pinned layer can provide a weak exchange bias field perpendicular to the surface of the second pinned layer opposite to the tunneling barrier layer. The combined magnetic moment formed by the exchange bias field and the applied magnetic field during the operation of the tunneling magnetoresistance has a certain angle with the exchange bias field, making the magnetocrystalline anisotropy field of the free layer in the magnetization direction greater than the demagnetizing field. Therefore, the magnetic vortex effect remains in a stable state.

[0023] 3. Further, the free layer is a composite structure, and the free layer includes a stacked first free sub-layer and second free sub-layer. Using a double-layer free layer can increase the magnitude of the magnetocrystalline anisotropy field of the free layer in the magnetization direction and adjust the stability of the free layer.

[0024] 4. Further, the thickness of the second free sub-layer is 30 nm to 60 nm. Using a relatively thick second free sub-layer makes it impossible for the second pinned layer to completely pin the second free sub-layer, so that the magnetic moment direction of the free layer can change with the change of the external magnetic field direction. After the external magnetic field is removed, the magnetic moment direction of the free layer can return to the direction of the initial state.

[0025] 5. Further, a spacer layer is located between the first free sub-layer and the second free sub-layer. The spacer layer can prevent the mutual diffusion between the first free sub-layer and the second free sub-layer and can increase the temperature stability of the free layer.

[0026] 6. Further, the first pinned layer includes: a first sub-pinned film, a second sub-pinned film, a third sub-pinned film, and a fourth sub-pinned film. The first sub-pinned film, the second sub-pinned film, the third sub-pinned film, and the fourth sub-pinned film are stacked in sequence in the direction from the free layer to the tunneling barrier layer. The combination of the first sub-pinned film, the second sub-pinned film, and the third sub-pinned film is a ferromagnetic layer, and the fourth sub-pinned film is an antiferromagnetic layer. The magnetic moment direction of the ferromagnetic layer is fixed by the coupling of the antiferromagnetic layer and does not change with the change of the external magnetic field direction. The ferromagnetic layer and the antiferromagnetic layer form a first pinned layer with a fixed magnetic moment direction.

[0027] 7. The manufacturing method of the tunneling magnetoresistance provided by the present invention forms a second pinning layer on one side of the free layer facing away from the tunneling barrier layer. The second pinning layer can provide a weak exchange bias field for the free layer. After the external environmental temperature or the external magnetic field is removed, the exchange bias field can pin the direction of the free layer in the initial state, thus avoiding the problems that the initial state of the vortex magnetization of the tunneling magnetoresistance is unstable and is easily affected by changes in the external environment, resulting in the drift of the magnetization curve, and has the effects of stabilizing the free layer and increasing the temperature stability of the free layer. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] In order to more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the following will briefly introduce the drawings required for the description of the specific embodiments or the prior art. Obviously, the drawings in the following description are some embodiments of the present invention. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0029] Figures 1 to 10 Schematic structural diagram of the formation process of the tunneling magnetoresistance provided by an embodiment of the present invention;

[0030] Figure 11 Schematic diagram of the magnetization curve of the tunneling magnetoresistance provided by an embodiment of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0031] The following will clearly and completely describe the technical solutions of the present invention in conjunction with the drawings. Obviously, the described embodiments are some embodiments of the present invention, rather than all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts fall within the protection scope of the present invention.

[0032] In the description of the present invention, it should be noted that the orientation or positional relationship indicated by the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", etc. is based on the orientation or positional relationship shown in the drawings, and is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation to the present invention. In addition, the terms "first", "second", "third" are only used for descriptive purposes and cannot be understood as indicating or implying relative importance.

[0033] In the description of the present invention, it should be noted that unless otherwise clearly specified and defined, the terms "installation", "connection", and "coupling" should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be directly connected or indirectly connected through an intermediate medium, and it can also be the communication inside two components. It can be a wireless connection or a wired connection. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0034] In addition, the technical features involved in different embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0035] The present invention provides a method for manufacturing a tunneling magnetoresistance, including the following steps: forming a first pinning layer; forming a tunneling barrier layer on the first pinning layer; forming a free layer on a side of the tunneling barrier layer facing away from the first pinning layer; and forming a second pinning layer on a side of the free layer facing away from the tunneling barrier layer.

[0036] Figures 1 to 10 It is a schematic structural diagram of the formation process of the tunneling magnetoresistance provided by an embodiment of the present invention.

[0037] Please refer to Figure 1 , and provide a substrate 1.

[0038] The substrate 1 can be a silicon substrate or a glass substrate.

[0039] Please refer to Figure 2 , and form an isolation layer 2 on the surface of one side of the substrate 1.

[0040] The material of the isolation layer 2 includes Al2O3 or SiO2, and the thickness of the isolation layer 2 is 50 nm to 200 nm. For example, it can be 50 nm, 100 nm, 150 nm, or 200 nm.

[0041] Please refer to Figure 3 , and form a seed layer 3 on the surface of the isolation layer 2 on the side facing away from the substrate 1.

[0042] Specifically, the seed layer 3 is a composite seed layer formed by at least a combination of a first sub-seed layer and a second sub-seed layer. The first sub-seed layer is on the surface of the isolation layer 2 on the side facing away from the substrate 1, and the second sub-seed layer is on the surface of the first sub-seed layer on the side facing away from the isolation layer 2. That is, the first sub-seed layer is between the isolation layer 2 and the second sub-seed layer.

[0043] The material of the first sub-seed layer is Ta, and the thickness of the first sub-seed layer is 5 nm to 20 nm. For example, it can be 5 nm, 10 nm, 15 nm, or 20 nm.

[0044] The material of the second sub-seed layer is Ru, and the thickness of the second sub-seed layer is 5 nm to 20 nm. For example, it can be 5 nm, 10 nm, 15 nm or 20 nm.

[0045] Using the composite seed layer makes the surface roughness of the grown first pinning layer 4 smaller, which is more conducive to the growth of the first pinning layer 4 thin film.

[0046] Please refer to Figure 4 , and a first pinning layer 4 is formed on the surface of the seed layer 3 on the side facing away from the isolation layer 2.

[0047] In this embodiment, the step of forming the first pinning layer 4 includes: forming a fourth sub-pinning film 404 on the surface of the seed layer 3 on the side facing away from the isolation layer 2; forming a third sub-pinning film 403 on the surface of the fourth sub-pinning film 404 on the side facing away from the seed layer 3; forming a second sub-pinning film 402 on the surface of the third sub-pinning film 403 on the side facing away from the fourth sub-pinning film 404; forming a first sub-pinning film 401 on the surface of the second sub-pinning film 402 on the side facing away from the third sub-pinning film 403.

[0048] In one embodiment, the material of the fourth sub-pinning film 404 includes IrMn or PtMn, and the thickness of the fourth sub-pinning film 404 is 7 nm to 20 nm. For example, it can be 7 nm, 10 nm, 15 nm or 20 nm.

[0049] In one embodiment, the material of the third sub-pinning film 403 includes CoFe, and the thickness of the third sub-pinning film 403 is 1.8 nm to 2.2 nm. For example, it can be 1.8 nm, 2 nm or 2.2 nm.

[0050] In one embodiment, the material of the second sub-pinning film 402 includes Ru, and the thickness of the second sub-pinning film 402 is 0.7 nm to 0.9 nm. For example, it can be 0.7 nm, 0.8 nm or 0.9 nm.

[0051] In one embodiment, the material of the first sub-pinning film 401 includes CoFeB, and the thickness of the first sub-pinning film 401 is 2 nm to 3 nm. For example, it can be 2 nm, 2.5 nm or 3 nm.

[0052] In one embodiment, the first sub-pinning film 401, the second sub-pinning film 402, and the third sub-pinning film 403 are combined into a ferromagnetic layer, and the fourth sub-pinning film 404 is an antiferromagnetic layer.

[0053] In this embodiment, the magnetic moment direction of the first pinning layer 4 is parallel to the opposite surface of the seed layer 3 and the isolation layer 2, or perpendicular to the opposite surface of the seed layer 3 and the isolation layer 2.

[0054] Please refer toFigure 5 , a tunneling barrier layer 5 is formed on one side of the first pinning layer 4 facing away from the seed layer 3.

[0055] The material of the tunneling barrier layer 5 includes MgO.

[0056] The thickness of the tunneling barrier layer 5 is 0.5 nm to 1.5 nm. For example, it can be 0.5 nm, 1 nm, 1.2 nm or 1.5 nm.

[0057] Please refer to Figure 6 , a first free sub-layer 601 is formed on the surface of the tunneling barrier layer 5 on the side facing away from the first pinning layer 4.

[0058] The material of the first free sub-layer 601 includes CoFeB, and the thickness of the first free sub-layer 601 is 1 nm to 3.5 nm. For example, it can be 1 nm, 2 nm, 3 nm or 3.5 nm.

[0059] Please refer to Figure 7 , a spacer layer 603 is formed on the surface of the first free sub-layer 601 on the side facing away from the tunneling barrier layer 5.

[0060] The material of the spacer layer 603 includes Ta, and the thickness of the spacer layer 603 is 0.1 nm to 0.5 nm. For example, it can be 0.1 nm, 0.2 nm, 0.4 nm or 0.5 nm.

[0061] Please refer to Figure 8 , a second free sub-layer 602 is formed on the surface of the spacer layer 603 on the side facing away from the first free sub-layer 601.

[0062] The material of the second free sub-layer 602 includes NiFe, and the thickness of the second free sub-layer 602 is 30 nm to 60 nm. For example, it can be 30 nm, 40 nm, 50 nm or 60 nm.

[0063] In this embodiment, a relatively thick second free sub-layer 602 is adopted, so that the second pinning layer 7 cannot completely pin the second free sub-layer 602, and the magnetic moment direction of the free layer 6 can change with the change of the external magnetic field direction. After the external magnetic field is removed, the magnetic moment direction of the free layer 6 can be restored to the direction of the initial state. If the thickness of the second free sub-layer 602 is too thin, the second free sub-layer 602 will be strongly pinned by the second pinning layer 7, and the magnetic moment direction of the second free sub-layer 602 cannot change with the change of the external magnetic field direction. If the thickness of the second free sub-layer 602 is too thick, the first free sub-layer 601 will not be pinned by the second pinning layer 7, and the free layer 6 cannot be well stabilized.

[0064] In this embodiment, the free layer 6 is a composite structure, and the free layer 6 includes a stacked first free sub-layer 601, a second free sub-layer 602 and a spacer layer 603.

[0065] Adopting a double-layer free layer can increase the magnitude of the magnetocrystalline anisotropy field of the free layer 6 in the magnetization direction and adjust the stability of the free layer 6.

[0066] The spacer layer 603 can prevent mutual diffusion between the first free sub-layer 601 and the second free sub-layer 602, and can increase the temperature stability of the free layer 6. If the thickness of the spacer layer 603 is too small, it is difficult to prevent mutual diffusion between the first free sub-layer 601 and the second free sub-layer 602. If the thickness of the spacer layer 603 is too large, it is difficult for the pinning field of the second free sub-layer 602 to penetrate the spacer layer 603 to pin the first free sub-layer 601, and the free layer 6 cannot become an integral composite structure.

[0067] Please refer to Figure 9 , and a second pinning layer 7 is formed on the surface of the second free sub-layer 602 on the side facing away from the spacer layer 603.

[0068] The second pinning layer 7 provides a weak exchange bias field for the free layer 6. Specifically, during the annealing magnetization process, an external magnetic field is applied along the direction perpendicular to the surface of the first pinning layer and the tunneling barrier layer facing each other. After the annealing magnetization is completed, the second pinning layer can provide a weak exchange bias field perpendicular to the surface of the second pinning layer and the tunneling barrier layer facing each other for the free layer.

[0069] The combined magnetic moment formed by the exchange bias field and the external magnetic field during the operation of the tunneling magnetoresistance has a certain angle θ with the exchange bias field. From the system energy density E T = (-K u + 1 / 2μ0M s 2 )COS 2 θ, K u is the crystal axis anisotropy coefficient, μ0 is the vacuum permeability, and M s is the saturation magnetization. It can be known that when θ has a certain angle, the magnetocrystalline anisotropy field of the free layer in the magnetization direction is greater than the demagnetizing field. Therefore, the magnetic vortex effect remains in a stable state.

[0070] The material of the second pinning layer 7 includes IrMn or PtMn.

[0071] The thickness of the second pinning layer 7 is 6 nm to 12 nm. For example, it can be 6 nm, 8 nm, 10 nm or 12 nm; within the thickness range of 6 nm to 12 nm, the exchange bias field decreases as the thickness of the second pinning layer 7 increases. If the thickness of the second pinning layer 7 is too large, it will result in too small an exchange bias field. If the thickness of the second pinning layer 7 is too small, it will also result in too small an exchange bias field or no exchange bias field. Therefore, the thickness of the second pinning layer 7 is reasonably selected according to the magnitude of the required exchange bias field.

[0072] In this embodiment, the second pinning layer 7 can provide a relatively weak exchange bias field for the first free sub-layer 601 and the second free sub-layer 602. After the external environmental temperature or the external magnetic field is removed, the exchange bias field can pin the directions of the first free sub-layer 601 and the second free sub-layer 602 in the initial state.

[0073] Please refer to Figure 10 , and a covering layer 8 is formed on the surface of the second pinning layer 7 on the side facing away from the spacer layer 603.

[0074] The material of the covering layer 8 includes Ta or Ru, and the thickness of the covering layer 8 is 5 nm to 10 nm. For example, it can be 5 nm, 6 nm, 8 nm or 10 nm.

[0075] The manufacturing method of the tunneling magnetoresistance provided by the present invention forms a second pinning layer on the side of the free layer facing away from the tunneling barrier layer. The second pinning layer can provide a relatively weak exchange bias field perpendicular to the surface of the second pinning layer and the tunneling barrier layer facing each other. After the external environmental temperature or the external magnetic field is removed, the exchange bias field can pin the free layer in the initial state direction, thereby avoiding the problem that the initial state of the vortex magnetization of the tunneling magnetoresistance is unstable and easily affected by changes in the external environment, resulting in the drift of the magnetization curve, and having the effect of stabilizing the free layer and increasing the temperature stability of the free layer.

[0076] This embodiment further provides a tunneling magnetoresistance. Please refer to Figure 10 , including: a first pinning layer 4; a free layer 6 disposed opposite to the first pinning layer 4; a tunneling barrier layer 5 located between the first pinning layer 4 and the free layer 6; and a second pinning layer 7 located on the side of the free layer 6 facing away from the tunneling barrier layer 5.

[0077] The tunneling magnetoresistance further includes a substrate 1, and the substrate 1 is located on the side of the first pinning layer 4 facing away from the tunneling barrier layer 5.

[0078] The substrate 1 can be a silicon substrate or a glass substrate.

[0079] In this embodiment, the tunneling magnetoresistance further includes an isolation layer 2 and a seed layer 3 located between the substrate 1 and the first pinning layer 4. The isolation layer 2 and the seed layer 3 are stacked in sequence in the direction from the substrate 1 to the first pinning layer 4. That is, the isolation layer 2 is located between the substrate 1 and the seed layer 3, and the seed layer 3 is located between the isolation layer 2 and the first pinning layer 4.

[0080] The material of the isolation layer 2 includes Al2O3 or SiO2, and the thickness of the isolation layer 2 is 50 nm to 200 nm. For example, it can be 50 nm, 100 nm, 150 nm or 200 nm.

[0081] The seed layer 3 is a composite seed layer formed by at least a combination of a first sub-seed layer and a second sub-seed layer. The first sub-seed layer is located on the surface of the isolation layer 2 facing away from the substrate 1, and the second sub-seed layer is located on the surface of the first sub-seed layer facing away from the isolation layer 2. That is, the first sub-seed layer is located between the isolation layer 2 and the second sub-seed layer.

[0082] The material of the first sub-seed layer is Ta, and the thickness of the first sub-seed layer is 5 nm to 20 nm. For example, it can be 5 nm, 10 nm, 15 nm or 20 nm.

[0083] The material of the second sub-seed layer is Ru, and the thickness of the second sub-seed layer is 5 nm to 20 nm. For example, it can be 5 nm, 10 nm, 15 nm or 20 nm.

[0084] Using the composite seed layer makes the surface roughness of the grown first pinning layer 4 smaller, which is more conducive to the growth of the first pinning layer 4 thin film.

[0085] The first pinning layer 4 includes: a first sub-pinning film 401, a second sub-pinning film 402, a third sub-pinning film 403 and a fourth sub-pinning film 404. The first sub-pinning film 401, the second sub-pinning film 402, the third sub-pinning film 403 and the fourth sub-pinning film 404 are stacked in sequence in the direction from the free layer 6 to the tunneling barrier layer 5.

[0086] In one embodiment, the material of the fourth sub-pinning film 404 includes IrMn or PtMn, and the thickness of the fourth sub-pinning film 404 is 7 nm to 20 nm. For example, it can be 7 nm, 10 nm, 15 nm or 20 nm.

[0087] In one embodiment, the material of the third sub-pinning film 403 includes CoFe, and the thickness of the third sub-pinning film 403 is 1.8 nm to 2.2 nm. For example, it can be 1.8 nm, 2 nm or 2.2 nm.

[0088] In one embodiment, the material of the second sub-pinning film 402 includes Ru, and the thickness of the second sub-pinning film 402 is 0.7 nm to 0.9 nm. For example, it can be 0.7 nm, 0.8 nm or 0.9 nm.

[0089] In one embodiment, the material of the first sub-pinning film 401 includes CoFeB, and the thickness of the first sub-pinning film 401 is 2 nm to 3 nm. For example, it can be 2 nm, 2.5 nm or 3 nm.

[0090] In one embodiment, the first sub-pinning film 401, the second sub-pinning film 402 and the third sub-pinning film 403 are combined into a ferromagnetic layer, and the fourth sub-pinning film 404 is an antiferromagnetic layer.

[0091] In this embodiment, the magnetic moment direction of the first pinning layer 4 is parallel to the opposite surfaces of the seed layer 3 and the isolation layer 2, or perpendicular to the opposite surfaces of the seed layer 3 and the isolation layer 2.

[0092] The material of the tunneling barrier layer 5 includes MgO.

[0093] The thickness of the tunneling barrier layer 5 is 0.5 nm to 1.5 nm. For example, it can be 0.5 nm, 1 nm, 1.2 nm or 1.5 nm.

[0094] In this embodiment, the free layer 6 is a composite structure, and the free layer 6 includes a stacked first free sub-layer 601, a second free sub-layer 602 and a spacer layer 603.

[0095] The first free sub-layer 601 is located on the surface of the tunneling barrier layer 5 on the side opposite to the first pinning layer 4.

[0096] The material of the first free sub-layer 601 includes CoFeB, and the thickness of the first free sub-layer 601 is 1 nm to 3.5 nm. For example, it can be 1 nm, 2 nm, 3 nm or 3.5 nm.

[0097] The second free sub-layer 602 is located between the second pinning layer 7 and the spacer layer 603.

[0098] The material of the second free sub-layer 602 includes NiFe, and the thickness of the second free sub-layer 602 is 30 nm to 60 nm. For example, it can be 30 nm, 40 nm, 50 nm or 60 nm.

[0099] In this embodiment, a relatively thick second free sub-layer 602 is adopted so that the second pinning layer 7 cannot completely pin the second free sub-layer 602, enabling the magnetic moment direction of the free layer 6 to change with the change of the external magnetic field direction. After the external magnetic field is removed, the magnetic moment direction of the free layer 6 can be restored to the direction of the initial state. If the thickness of the second free sub-layer 602 is too thin, the second free sub-layer 602 will be strongly pinned by the second pinning layer 7, and the magnetic moment direction of the second free sub-layer 602 cannot change with the change of the external magnetic field direction. If the thickness of the second free sub-layer 602 is too thick, the first free sub-layer 601 will not be pinned by the second pinning layer 7, and the free layer 6 cannot be well stabilized.

[0100] The spacer layer 603 is located between the first free sub-layer 601 and the second free sub-layer 602.

[0101] The material of the spacer layer 603 includes Ta, and the thickness of the spacer layer 603 is 0.1 nm to 0.5 nm. For example, it can be 0.1 nm, 0.2 nm, 0.4 nm or 0.5 nm.

[0102] Adopting a double - layer free layer can increase the magnitude of the magnetocrystalline anisotropy field of the free layer 6 in the magnetization direction and adjust the stability of the free layer 6.

[0103] The spacer layer 603 can prevent the mutual diffusion between the first free sub - layer 601 and the second free sub - layer 602 and can increase the temperature stability of the free layer 6. If the thickness of the spacer layer 603 is too small, it is difficult to prevent the mutual diffusion between the first free sub - layer 601 and the second free sub - layer 602. If the thickness of the spacer layer 603 is too large, it is difficult for the pinning field of the second free sub - layer 602 to penetrate the spacer layer 603 to pin the first free sub - layer 601, and the free layer 6 cannot form an integral composite structure.

[0104] The second pinning layer 7 provides a weak exchange bias field for the free layer 6.

[0105] Specifically, the magnetic moment direction of the second pinning layer is perpendicular to the surface of the second pinning layer opposite to the tunneling barrier layer. The second pinning layer can provide a weak exchange bias field perpendicular to the surface of the second pinning layer opposite to the tunneling barrier layer for the free layer.

[0106] The combined magnetic moment formed by the exchange bias field and the externally applied magnetic field during the operation of tunneling magnetoresistance has a certain angle θ with the exchange bias field. From the system energy density E T =(-K u +1 / 2μ0M s 2 )COS 2 θ, K u is the crystal axis anisotropy coefficient, μ0 is the vacuum permeability, M s is the saturation magnetization intensity. It can be known that when θ has a certain angle, the magnetocrystalline anisotropy field of the free layer in the magnetization direction is greater than the demagnetizing field. Therefore, the magnetic vortex effect remains in a stable state. The material of the second pinning layer 7 includes IrMn or PtMn.

[0107] The thickness of the second pinning layer 7 is 6nm - 12nm. For example, it can be 6nm, 8nm, 10nm or 12nm. Within the thickness range of 6nm - 12nm, the exchange bias field decreases with the increase of the thickness of the second pinning layer 7. If the thickness of the second pinning layer 7 is too large, it will lead to too small an exchange bias field. If the thickness of the second pinning layer 7 is too small, it will also lead to too small an exchange bias field or no exchange bias field. Therefore, the thickness of the second pinning layer 7 is reasonably selected according to the magnitude of the required exchange bias field.

[0108] In this embodiment, the second pinning layer 7 can provide a weak exchange bias field for the first free sub - layer 601 and the second free sub - layer 602. After the external environmental temperature or the external magnetic field is removed, the exchange bias field can pin the directions of the first free sub - layer 601 and the second free sub - layer 602 in the initial state.

[0109] A covering layer 8 is provided on the surface of the second pinning layer 7 on the side facing away from the free layer 6.

[0110] The material of the covering layer 8 includes Ta or Ru, and the thickness of the covering layer 8 is 5 nm to 10 nm. For example, it can be 5 nm, 6 nm, 8 nm or 10 nm.

[0111] Another embodiment of the present invention further provides a tunneling magnetoresistance, including: a first pinning layer; a free layer disposed opposite to the first pinning layer; a tunneling barrier layer located between the first pinning layer and the free layer; and a second pinning layer located on the side of the free layer facing away from the tunneling barrier layer.

[0112] In this embodiment, the free layer is a single-layer free layer, the material of the free layer includes NiFe, and the thickness of the free layer is 30 nm to 60 nm. For example, it can be 30 nm, 40 nm, 50 nm or 60 nm.

[0113] Other structures the same as those in the above embodiment will not be elaborated here one by one.

[0114] Another embodiment of the present invention further provides a method for manufacturing a tunneling magnetoresistance, including the following steps: forming a first pinning layer; forming a tunneling barrier layer on the first pinning layer; forming a free layer on the side of the tunneling barrier layer facing away from the first pinning layer; and forming a second pinning layer on the side of the free layer facing away from the tunneling barrier layer.

[0115] In this embodiment, after forming the tunneling barrier layer, a free layer is formed on the surface of the tunneling barrier layer on the side facing away from the first pinning layer. The free layer is a single-layer free layer, the material of the free layer includes NiFe, and the thickness of the free layer is 30 nm to 60 nm. For example, it can be 30 nm, 40 nm, 50 nm or 60 nm.

[0116] Other steps the same as those in the above embodiment will not be elaborated here one by one.

[0117] Please refer to Figure 11 , Figure 11 in which the horizontal axis is the magnetic field strength, Figure 11 the vertical axis in Figure 11 is the TMR ratio,

[0118] The tunneling magnetoresistance provided by the present invention is provided with a second pinning layer on the side of the free layer facing away from the tunneling barrier layer compared with the prior art. The second pinning layer can provide a relatively weak exchange bias field perpendicular to the surface of the second pinning layer and the tunneling barrier layer for the free layer. After the external environmental temperature or the external magnetic field is removed, the exchange bias field can pin the direction of the free layer in the initial state, thereby avoiding the problem that the initial state of the vortex magnetization of the tunneling magnetoresistance is unstable and is easily affected by changes in the external environment, resulting in the drift of the magnetization curve, and has the effect of stabilizing the free layer and increasing the temperature stability of the free layer.

[0119] Obviously, the above embodiments are merely examples given for clear illustration and are not limitations on the implementation manners. For those of ordinary skill in the art, other different forms of changes or variations can be made based on the above description. It is not necessary and impossible to list all the implementation manners here. And the obvious changes or variations derived therefrom still fall within the protection scope of the present invention.

Claims

1. A tunnel magnetoresistance, characterized in that include: a first pinning layer; a free layer disposed opposite the first pinned layer, the free layer being a composite structure, the free layer comprising a first free sublayer and a second free sublayer stacked together, the free layer further comprising: a spacer layer located between the first free sublayer and the second free sublayer, the first free sublayer comprising CoFeB, the spacer layer comprising Ta, and the second free sublayer having a thickness of 30 nm to 60 nm; a tunneling barrier layer located between the first pinned layer and the free layer, wherein the first free sub-layer is located between the second free sub-layer and the tunneling barrier layer; A second pinned layer is located on a side of the free layer facing away from the tunneling barrier layer, and the thickness of the second pinned layer is 6 nm to 12 nm.

2. The tunnel magnetoresistance according to claim 1, wherein A pinning field direction of the second pinned layer is perpendicular to an opposite surface of the second pinned layer and the tunnel barrier layer.

3. The tunnel magnetoresistance according to claim 1, wherein The material of the second pinning layer includes IrMn or PtMn.

4. The tunnel magnetoresistance according to claim 1, wherein The thickness of the spacer layer is 0.1 nm to 0.5 nm.

5. The tunnel magnetoresistance according to claim 1, wherein The material of the second free sub-layer includes NiFe.

6. The tunnel magnetoresistance according to claim 1, wherein The thickness of the first free sub-layer is 1 nm to 3.5 nm.

7. The tunnel magnetoresistance according to claim 1, wherein The first pinning layer includes: a first sub-pinning film, a second sub-pinning film, a third sub-pinning film and a fourth sub-pinning film, wherein the first sub-pinning film, the second sub-pinning film, the third sub-pinning film and the fourth sub-pinning film are sequentially stacked in a direction from the free layer to the tunnel barrier layer; The material of the first sub-pinning film includes CoFeB; The material of the second sub-pinning film includes Ru; The material of the third sub-pinning film includes CoFe; The material of the fourth sub-pinning film includes IrMn or PtMn.

8. The tunnel magnetoresistance according to claim 7, characterized in that The thickness of the first sub-pinning film is 2 nm to 3 nm; the thickness of the second sub-pinning film is 0.7 nm to 0.9 nm; the thickness of the third sub-pinning film is 1.8 nm to 2.2 nm; and the thickness of the fourth sub-pinning film is 7 nm to 20 nm.

9. A method for manufacturing a tunnel magnetoresistance, for forming the tunnel magnetoresistance according to any one of claims 1 to 8, characterized in that: The steps include: forming a first pinning layer; forming a tunnel barrier layer on the first pinned layer; Forming a free layer on a side of the tunneling barrier layer facing away from the first pinned layer, wherein the free layer is a composite structure, and a method for forming the free layer includes: forming a first free sub-layer on a side of the tunneling barrier layer facing away from the first pinned layer; The material of the first free sub-layer includes CoFeB, a spacer layer is formed on the side of the first free sub-layer facing away from the tunnel barrier layer, and the material of the spacer layer includes Ta; a second free sub-layer is formed on the side of the spacer layer facing away from the first free sub-layer, and the thickness of the second free sub-layer is 30nm to 60nm; A second pinning layer is formed on a side of the free layer facing away from the tunneling barrier layer, and the thickness of the second pinning layer is 6 nm to 12 nm.

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