CN110676288A - Magnetic tunnel junction structure and magnetic random access memory - Google Patents
Magnetic tunnel junction structure and magnetic random access memory Download PDFInfo
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- H—ELECTRICITY
- H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
- H10N—ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
- H10N50/00—Galvanomagnetic devices
- H10N50/10—Magnetoresistive devices
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- H—ELECTRICITY
- H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
- H10B—ELECTRONIC MEMORY DEVICES
- H10B61/00—Magnetic memory devices, e.g. magnetoresistive RAM [MRAM] devices
- H10B61/20—Magnetic memory devices, e.g. magnetoresistive RAM [MRAM] devices comprising components having three or more electrodes, e.g. transistors
- H10B61/22—Magnetic memory devices, e.g. magnetoresistive RAM [MRAM] devices comprising components having three or more electrodes, e.g. transistors of the field-effect transistor [FET] type
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Abstract
The application provides a magnetic tunnel junction structure and a magnetic random access memory, the magnetic tunnel junction structure comprises a free layer, a partition layer and a high-spin-excitation-rate spin-excitation layer with vertical anisotropy are arranged on the free layer, spin electrons are gathered around the free layer, and the spin transfer torque for turning the magnetization vector of the free layer is increased. Due to the introduction of the spin-excited layer, the spin transfer torque of the magnetic tunnel junction in the writing process is effectively improved, and the critical current (I) of the MTJ device is greatly facilitatedC0) The writing speed of the MRAM circuit is improved, the writing power consumption is reduced, the durability is improved, and the method is very suitable for the application environment with quick and ultra-low power consumption.
Description
Technical Field
The present invention relates to the field of memory technologies, and in particular, to a magnetic tunnel junction structure and a magnetic random access memory.
Background
Magnetic Random Access Memory (MRAM) in a Magnetic Tunnel Junction (MTJ) having Perpendicular Anisotropy (PMA), as a free layer for storing information, has two magnetization directions in a vertical direction, that is: upward and downward, respectively corresponding to "0" and "1" or "1" and "0" in binary, in practical application, the magnetization direction of the free layer will remain unchanged when reading information or leaving empty; during writing, if a signal different from the existing state is input, the magnetization direction of the free layer will be flipped by one hundred and eighty degrees in the vertical direction. The ability of the magnetization direction of the free layer of the magnetic random access Memory to be kept unchanged is called data retention ability or thermal stability, and the requirement is different in different application situations, for a typical Non-volatile Memory (NVM), the requirement of data retention ability is to retain data for ten years at 125 ℃, and the data retention ability or thermal stability is reduced when external magnetic field flipping, thermal disturbance, current disturbance or multiple read-write operations are performed.
In order to increase the storage density of MRAM, the Critical Dimension (CD) of the magnetic tunnel junction is becoming smaller in recent years. When the size is further reduced, it is found that the thermal stability factor (Δ) of the magnetic tunnel junction is drastically deteriorated. In order to increase the thermal stability factor (Δ) of the ultra-small MRAM device, the effective perpendicular anisotropy energy density may be increased by reducing the thickness of the free layer, adding or changing the free layer into a material with a low saturation magnetic susceptibility, and so on, thereby maintaining a higher thermal stability factor (Δ), but the critical write current density may be correspondingly increased greatly, which may result in a decrease in the endurance of the memory cell, and at the same time, the Tunneling Magnetoresistance (TMR) of the magnetic Tunnel junction may be decreased, thereby increasing the error rate of the memory read operation.
Disclosure of Invention
In order to solve the above technical problems, it is an object of the present invention to provide a magnetic tunnel junction structure and a magnetic random access memory having an additional spin-excited structure above a free layer, and a spin transfer torque required for switching a magnetization vector of the free layer in combination with a spin-excited layer and a reference layer, which have an excitation and accumulation effect.
The purpose of the application and the technical problem to be solved are realized by adopting the following technical scheme.
According to the magnetic tunnel junction structure provided by the application, the magnetic tunnel junction structure is arranged in a magnetic random access memory unit, and the magnetic tunnel junction structure at least comprises a free layer, a barrier layer and a reference layer from top to bottom; the free layer is disposed above the substrate and includes: the isolation layer is arranged on the free layer and comprises a buffer layer and a spin diffusion layer from bottom to top, the buffer layer is formed by a metal oxide layer, and the spin diffusion layer is made of metal with high spin diffusion length; a spin-excited layer disposed on the spin diffusion layer and formed of a magnetic material having a high spin excitation rate of perpendicular anisotropy; the buffer layer provides an additional perpendicular anisotropy interface anisotropy source for the free layer and guides the formation of crystal lattices of the spin diffusion layer, the spin diffusion layer guides the crystal lattice growth required by the spin excitation layer, and the directions of the magnetization vectors of the spin excitation layer and the reference layer are fixed and are not changed and are perpendicular to the plane of the material and are antiparallel to each other.
The technical problem solved by the application can be further realized by adopting the following technical measures.
In an embodiment of the present application, the buffer layer has a thickness of 0.5 nm to 1.4 nm; the buffer layer is made of MgO or ZrO2、ZnO、Al2O3、GaO、Fe3O4、Fe2O3、CoO、NiO、Y2O3、SrO、Sc2O3、 TiO2、HfO2、V2O5、Nb2O5、Ta2O5、CrO3、MoO3、WO3、RuO2、OsO2、TcO、ReO、RhO、 IrO、SnO、SbO、MgZnO、Mg3B2O6、MgAl2O4、SrTiO3Or a combination thereof, preferably MgO.
In one embodiment of the present application, the spin diffusion layer has a thickness of 0.2 nm to 5.0 nm; the spin diffusion layer is made of Cu, Ag, Au, Al, Ge, Ti, Zn, Ga, In, Ti, V, Cr, Zr, Nb, Mo, Tc, Ru, Si or a combination thereof, and is preferably made of a single-layer material Ag, Au, Al or a double-layer material Cu/Ag, Cu/Au, Cu/Al from bottom to top.
In an embodiment of the present application, the thickness of the spin-excited layer is 0.4 nm to 4.0 nm; the material for forming the spin-excited layer isCo、[Co/Pt]n、[Co/Pd]n、[Co/Ni]n、[Co/AgPt]n、[Co/AgPd]n、[Co/AgNi]n、 [Co/AuPt]n、[Co/AuPd]n、[Co/AuNi]n、[Co/AlPt]n、[Co/AlPd]n、[Co/AlNi]n、[Co/Ag/Pt]n、 [Co/Ag/Pd]n、[Co/Ag/Ni]n、[Co/Au/Pt]n、[Co/Au/Pd]n、[Co/Au/Ni]n、[Co/Al/Pt]n、[Co/Al/Pd]n、 [Co/Al/Ni]n、Fe、[Fe/Pt]n、[Fe/Pd]n、[Fe/Ni]n、[Fe/AgPt]n、[Fe/AgPd]n、[Fe/AgNi]n、[Fe/AuPt]n、 [Fe/AuPd]n、[Fe/AuNi]n、[Fe/AlPt]n、[Fe/AlPd]n、[Fe/AlNi]n、[Fe/Ag/Pt]n、[Fe/Ag/Pd]n、 [Fe/Ag/Ni]n、[FeAu/Pt]n、[Fe/Au/Pd]n、[Fe/Au/Ni]n、[Fe/Al/Pt]n、[Fe/Al/Pd]n、[Fe/Al/Ni]n、 [CoFe/Pt]n、[Fe/Co]n、[Co/Fe]n、[CoFe/Pd]n、[CoFe/Ni]nA single or multilayer structure of CoFe, CoFeNi, or FeNi, or a combination thereof, wherein n is greater than or equal to 1; or the spin-activated layer is made of an alloy having magnetocrystalline anisotropy, and is formed of CoPt, FePt, CoFePt, CoPd, FePd, CoFePd, CoAgPt, FeAgPt, CoFeAgPt, CoAgPd, FeAgPd, CoFeAgPd, CoAuPt, FeAuPt, CoFeAuPt, CoAuPd, FeAuPd, CoFeAuPd, CoAlPt, FeAlPt, CoFeAlPt, CoAlPd, FeAlPd, CoAlPd, CoFeAlPd, Co3Pt、D022-Mn3Ga、D022-Mn3Ge、L10-FePt、 L10-CoPt、L10-FePd、L10-CoPd or a combination thereof.
In an embodiment of the present application, the spin-excited layer is an antiferromagnetic layer, the antiferromagnetic layer has a structure of ferromagnetic material layer/(Ru, Rh or Ir)/ferromagnetic material layer, the ferromagnetic material layer has a single-layer or multi-layer structure or a combination thereof and/or the magnetocrystalline anisotropic alloy, and the magnetization vector of the ferromagnetic material layer adjacent to the spin diffusion layer and the magnetization vector of the reference layer are both fixed and invariant and perpendicular to the material plane and are antiparallel to each other.
In an embodiment of the present application, the magnetic tunnel junction includes a capping layer, a spin-on layer, a blocking layer, the free layer, the barrier layer, the reference layer, a lattice blocking layer, a first antiferromagnetic layer and a seed layer from top to bottom, the first antiferromagnetic layer is formed of a ferromagnetic material, wherein the first antiferromagnetic layer is ferromagnetically coupled with the reference layer; the magnetization vectors of the spin-excited layer and the reference layer are antiparallel.
In an embodiment of the application, an antiferromagnetic coupling layer and a second antiferromagnetic layer are further included between the spin excitation layer and the cover layer from bottom to top, the antiferromagnetic coupling layer is formed of a transition metal material capable of forming antiferromagnetic coupling, the second antiferromagnetic layer is formed of a ferromagnetic material, and the second antiferromagnetic layer and the spin excitation layer form antiferromagnetic coupling through the antiferromagnetic coupling layer.
It is another objective of the present invention to provide a magnetic random access memory, wherein the storage unit comprises any one of the foregoing magnetic tunnel junction structures, a top electrode disposed above the magnetic tunnel junction structure, and a bottom electrode disposed below the magnetic tunnel junction structure.
It is yet another object of the present invention to provide a data writing method of a magnetic random access memory cell including a magnetic tunnel junction structure including a spin-on layer, an isolation layer, a free layer, a barrier layer, and a reference layer; the data writing method comprises the following steps: judging the resistance state of the magnetic tunnel junction; selectively passing electron current from the reference layer or the spin-excited layer into the magnetic tunnel junction when writing in dissimilar data logic according to the resistance state; when the electron current enters a level, the electron current is spin-excited, screening the spin electrons that can reach the free layer by the magnetization vector of the entering level, and gathering the spin electrons around the free layer by the surrounding layer of the free layer; the writing of the dissimilar data logic is accomplished by exciting and focusing the spin electrons to flip the magnetization vector of the free layer.
In an embodiment of the present application, the magnetic tunnel junction is a logic 1 in a high resistance state when the magnetization vectors of the reference layer and the free layer are antiparallel; to write a logic 0, passing the electron current from the reference layer into the magnetic tunnel junction; when the electron current passes through the reference layer, the electron current is excited by spin, spin electrons which can reach the free layer are screened through the magnetization vector of the reference layer, and most or all spin vectors of the spin electrons are in the same direction with the magnetization vector of the reference layer; the spin vector of the spin electrons passing through the free layer and the magnetization vector of the spin-excited layer are in opposite directions and will be reflected at the interface of the spacer layer and/or the spin-excited layer to be concentrated around the free layer; and the magnetization vector direction of the free layer is reversed through the same spin vector direction of the spin electrons excited by the reference layer and the spin electrons reflected by the spacing layer and/or the spin excitation layer interface, so that the writing of logic 0 is realized.
In an embodiment of the present application, the magnetic tunnel junction is a logic 0 in a high resistance state when the magnetization vectors of the reference layer and the free layer are parallel; for writing a logic 1, passing the electron current from the spin-activated layer into the magnetic tunnel junction; when the electron current passes through the spin-excited layer, the electron current is spin-excited, spin electrons which can reach the free layer are screened through the magnetization vector of the spin-excited layer, and most or all spin vectors of the spin electrons are consistent with the magnetization vector of the spin-excited layer; the spin vector of the spin electron passing through the free layer is in the opposite direction to the magnetization vector of the reference layer, and will be reflected at the interface of the barrier layer and/or the reference layer to be focused around the free layer; and the magnetization vector direction of the free layer is reversed through the same spin vector direction of the spin electrons excited by the spin excitation layer and the spin electrons reflected by the barrier layer and/or the reference layer interface, so that the writing of logic 1 is realized.
In an embodiment of the present application, an annealing operation is performed at a temperature of not less than 350 ℃ for at least 30 minutes after the bottom electrode, seed layer, antiferromagnetic layer, lattice partition layer, reference layer, barrier layer, free layer, partition layer, spin-on layer, capping layer, and top electrode are deposited.
The magnetic tunnel junction unit structure effectively improves the spin transfer torque of the magnetic tunnel junction in the writing process through the introduced spin excitation layer, is very favorable for reducing the critical current (IC0) of an MTJ (magnetic tunnel junction) device, improves the writing speed of an MRAM (magnetic random access memory) circuit, reduces the writing power consumption, improves the durability, and is very suitable for the application environment of rapid ultra-low power consumption.
Drawings
FIG. 1 is a diagram illustrating an exemplary MRAM cell structure;
FIG. 2 is a schematic diagram of a magnetic tunnel junction structure according to an embodiment of the present application;
FIGS. 3a and 3b are schematic diagrams illustrating a data writing process of a magnetic tunnel junction according to an embodiment of the present application;
FIG. 4 is a schematic diagram of a MRAM cell according to an embodiment of the present application;
FIG. 5 is a schematic diagram of a magnetic tunnel junction structure according to an embodiment of the present application;
fig. 6 is a schematic structural diagram of a magnetic tunnel junction according to an embodiment of the present application.
Detailed Description
Refer to the drawings wherein like reference numbers refer to like elements throughout. The following description is based on illustrated embodiments of the application and should not be taken as limiting the application with respect to other embodiments that are not detailed herein.
The following description of the various embodiments refers to the accompanying drawings, which illustrate specific embodiments that can be used to practice the present application. In the present application, directional terms such as "up", "down", "front", "back", "left", "right", "inner", "outer", "side", and the like are merely referring to the directions of the attached drawings. Accordingly, the directional terminology is used for purposes of illustration and understanding, and is in no way limiting.
The terms "first," "second," "third," and the like in the description and in the claims of the present application and in the above-described drawings, if any, are used for distinguishing between similar elements and not necessarily for describing a particular sequential or chronological order. It should be understood that the objects so described are interchangeable under appropriate circumstances. Furthermore, the terms "include" and "have," as well as variations of other related examples, are intended to cover non-exclusive inclusions.
The terminology used in the description of the present application is for the purpose of describing particular embodiments only and is not intended to be limiting of the concepts of the present application. Unless the context clearly dictates otherwise, expressions used in the singular form encompass expressions in the plural form. In the present specification, it will be understood that terms such as "including," "having," and "containing" are intended to specify the presence of the features, integers, steps, acts, or combinations thereof disclosed in the specification, and are not intended to preclude the presence or addition of one or more other features, integers, steps, acts, or combinations thereof. Like reference symbols in the various drawings indicate like elements.
The drawings and description are to be regarded as illustrative in nature, and not as restrictive. In the drawings, elements having similar structures are denoted by the same reference numerals. In addition, the size and thickness of each component shown in the drawings are arbitrarily illustrated for understanding and ease of description, but the present application is not limited thereto.
In the drawings, the range of configurations of devices, systems, components, circuits is exaggerated for clarity, understanding, and ease of description. It will be understood that when an element is referred to as being "on" another element, it can be directly on the other element or intervening elements may also be present.
In addition, in the description, unless explicitly described to the contrary, the word "comprise" will be understood to mean that the recited components are included, but not to exclude any other components. Further, in the specification, "on.
To further illustrate the technical means and effects of the present invention adopted to achieve the predetermined objects, the following detailed description is given to a magnetic tunnel junction structure and a magnetic random access memory according to the present invention with reference to the accompanying drawings and specific embodiments.
FIG. 1 is a diagram of an exemplary MRAM cell structure. The magnetic memory cell structure includes at least a Bottom Electrode (BE) 10, a Magnetic Tunnel Junction (MTJ)20, and a top Electrode (topeletrode) 30 forming a multi-layer structure.
In some embodiments, the bottom electrode 10 is titanium (Ti), titanium nitride (TiN), tantalum (Ta), tantalum nitride (TaN), ruthenium (Ru), tungsten (W), tungsten nitride (WN), or combinations thereof; the top electrode 30 is made of titanium (Ti), titanium nitride (TiN), tantalum (Ta), tantalum nitride (TaN), tungsten (W), tungsten nitride (WN), or a combination thereof. The magnetic memory cell structure is typically implemented by Physical Vapor Deposition (PVD), and is typically planarized after the bottom electrode 10 is deposited to achieve surface flatness for the magnetic tunnel junction 20.
In some embodiments, the magnetic tunnel junction 20 comprises, from top to bottom, a Capping Layer (CL) 290, a Free Layer (FL) 260, a Barrier Layer (Tunnel Barrier, TBL)250, a Reference Layer (RL) 240, a lattice Breaking Layer (CBL) 230, an antiferromagnetic Anti-ferromagnetic Layer (SyAF) 220, and a Seed Layer (Seed Layer; SL) 210.
As shown in fig. 1, in some embodiments, the free layer 260 is composed of a single or multi-layer structure of CoFeB, FeCo/CoFeB, or CoFeB/(Ta, W, Mo, or Hf)/CoFeB. Wherein, the data retention capacity (DataRetention) can be calculated by the following formula:
wherein tau is the time when the magnetization vector is unchanged under the condition of thermal disturbance, tau0For the trial time (typically 1ns), E is the energy barrier of the free layer, kBBoltzmann constant, T is the operating temperature.
The thermal stability factor (Δ) can then be expressed as the following equation:
wherein, KeffIs the effective isotropic energy density of the free layer, V is the volume of the free layer, KVConstant of bulk anisotropy MsSaturation susceptibility of the free layer, demagnetization constant in the direction perpendicular to Nz, t thickness of the free layer, KiIs the interfacial anisotropy constant, DMTJThe critical dimension of the MRAM (generally referred to as the diameter of the free layer 260), AsFor stiffness integral exchange constant, DnThe size of the inverted nucleus (generally referred to as the diameter of the inverted nucleus) during free layer inversion. Experiments show that when the thickness of the free layer is thicker, the free layer shows in-plane anisotropy, and when the thickness of the free layer is thinner, the free layer shows vertical anisotropy, KVGenerally, the contribution of demagnetization energy to the vertical anisotropy is negative, so that the vertical anisotropy is completely derived from the interfacial effect Ki。
In addition, as the volume of the free layer 260 is reduced, the smaller the spin-polarized current that needs to be injected for a write or switching operation. Critical current I for write operationc0The relationship between the compound and the thermal stability is strongly related, and can be expressed as the following formula:
wherein alpha is a damping constant,
η is the spin polarizability, which is the approximate planck constant. While increasing thermal stability, it becomes exceptionally important to reduce the critical current.
However, in order to increase the density of the magnetic random access memory, the critical dimension (critical dimension) of the magnetic tunnel junction 200 is made smaller and smaller. When the size is further reduced, it is found that the Thermal Stability (Thermal Stability Factor) of the magnetic tunnel junction 200 is drastically deteriorated. For ultra-small sized MRAM magnetic memory cells, to improve thermal stability, the thickness of the free layer 260 may typically be reduced, the saturation susceptibility of the free layer 260 may be reduced, or the interfacial anisotropy may be increased. If the thickness of the free layer 260 is reduced, the Tunneling Magnetoresistance Ratio (TMR) is reduced, which increases the error rate in the read operation; under the condition of constant thickness, the addition or change of the free layer 260 into a material with low saturation magnetic susceptibility in the free layer 260 also reduces the tunneling magnetic resistivity, thereby reducing the spin polarization rate, which is not beneficial to the read/write operation of the device.
FIG. 2 is a schematic diagram of a magnetic memory cell according to an embodiment of the present disclosure. The prior art also refers to fig. 1 to facilitate understanding. As shown in fig. 2, in an embodiment of the present application, a magnetic tunnel junction structure is disposed in a magnetic random access memory cell, and the magnetic tunnel junction structure includes at least a Free Layer (FL) 260, a barrier Layer (TBL) 250, and a Reference Layer (RL) 240. The reference layer 240 is located below the barrier layer 250, and has invariance of magnetization vectors; the barrier layer 250 material is preferably MgO; the free layer 260 is located over the barrier layer 250 and has a variability of magnetization vectors. The disposing over the free layer 260 further includes: a barrier Layer (Spacer)270 disposed on the free Layer 260, wherein the barrier Layer 270 includes a Buffer Layer (Buffer Layer)271 and a spin diffusion Layer (spin diffusion Layer)272 from bottom to top, the Buffer Layer 271 is formed of a metal oxide Layer, and the spin diffusion Layer 272 is made of a metal having a high spin diffusion length; a Spin Polarization Layer (SPL) 280 disposed on the Spin diffusion Layer 272 and formed of a magnetic material having a high Spin excitation rate with a perpendicular anisotropy; the buffer layer 271 provides an additional source of perpendicular anisotropy interface anisotropy for the free layer 260, and guides the lattice formation of the spin diffusion layer 272, the spin diffusion layer 272 guides the lattice growth required for the spin-excited layer 280, and the spin-excited layer 280 has invariance of the magnetization vector, which is always antiparallel to the magnetization vector of the reference layer 260.
In an embodiment of the present application, the thickness of the buffer layer 271 is 0.5 nm to 1.4 nm; the buffer layer 271 is formed of MgO or ZrO2、ZnO、Al2O3、GaO、Fe3O4、Fe2O3、CoO、NiO、Y2O3、SrO、 Sc2O3、TiO2、HfO2、V2O5、Nb2O5、Ta2O5、CrO3、MoO3、WO3、RuO2、OsO2、TcO、ReO、 RhO、IrO、SnO、SbO、MgZnO、Mg3B2O6、MgAl2O4、SrTiO3Or a combination thereof, preferably MgO.
The buffer layer 271 has a multifunctional role: (1) an additional source of perpendicular anisotropy interfacial anisotropy is provided for the free layer 260, thereby increasing the thermal stability of the free layer 260; (2) metal oxides have a long spin diffusion length, and spin polarized electrons (spinpoled electrons) are consumed negligibly during their conduction; (3) the buffer layer 271 provides a good substrate for subsequent lattice growth of the spin diffusion layer 272. Further, a heating/cooling process may be performed after the deposition of the buffer layer 271 to enhance the crystallization property thereof. The spin diffusion length is a characteristic length value of a certain material, wherein spin electrons accumulate in a length range and decay exponentially.
In one embodiment of the present application, the spin diffusion layer 272 is generally made of a metal having a long spin diffusion length, and the spin diffusion layer 272 has a thickness of 0.2 nm to 5.0 nm; the spin diffusion layer 272 is formed of Cu, Ag, Au, Al, Ge, Ti, Zn, Ga, In, Ti, V, Cr, Zr, Nb, Mo, Tc, Ru, Si, or a combination thereof, and preferably is a single-layer material of Ag, Au, Al, or a bottom-up double-layer material of Cu/Ag, Cu/Au, Cu/Al.
The spin diffusion layer 272 functions as: (1) as a seed layer for the subsequent spin-excited layer 280, the required lattice growth of the spin-excited layer 280 is promoted, ensuring good vertical anisotropy; (2) the high resistance effect of the magnetic tunnel junction of the buffer layer 270 with the oxide inserted between the free layer 260 and the spin-activated layer 280 is eliminated, and the connection resistance is reduced. Further, the spin diffusion layer 272 may be surface plasma treated after it is deposited to facilitate subsequent growth of the spin-excited layer 280.
The overall effect of the partition layer 270 is: (1) a "de-ferromagnetism" (de-coupling) of the free layer 260 and the spin-activated layer 280 is achieved; (2) the junction Resistance area product (RA) of the Magnetic Tunnel Junction (MTJ) cannot be increased, and the reading performance of the MTJ unit structure cannot be affected; (3) the buffer layer 271 and the spin diffusion layer 272 each have a long spin diffusion length, and the spin scattering rate at the interface between the buffer layer 271 and the spin diffusion layer 272 is low, so that spin electrons are not substantially attenuated when they pass through the blocking layer 270. In some embodiments, for MgO/Ag, the spin diffusion length is up to 300 nm.
In an embodiment of the present application, the spin-excited layer 280 has a thickness of 0.4 nm to 4.0 nm, and is made of a magnetic material with a high spin-excitation rate and a perpendicular anisotropy; the spin-activated layer 280 is formed of Co, [ Co/Pt ]]n、[Co/Pd]n、[Co/Ni]n、[Co/AgPt]n、[Co/AgPd]n、[Co/AgNi]n、[Co/AuPt]n、[Co/AuPd]n、 [Co/AuNi]n、[Co/AlPt]n、[Co/AlPd]n、[Co/AlNi]n、[Co/Ag/Pt]n、[Co/Ag/Pd]n、[Co/Ag/Ni]n、 [Co/Au/Pt]n、[Co/Au/Pd]n、[Co/Au/Ni]n、[Co/Al/Pt]n、[Co/Al/Pd]n、[Co/Al/Ni]n、Fe、[Fe/Pt]n、 [Fe/Pd]n、[Fe/Ni]n、[Fe/Co]n、[Co/Fe]n、[Fe/AgPt]n、[Fe/AgPd]n、[Fe/AgNi]n、[Fe/AuPt]n、 [Fe/AuPd]n、[Fe/AuNi]n、[Fe/AlPt]n、[Fe/AlPd]n、[Fe/AlNi]n、[Fe/Ag/Pt]n、[Fe/Ag/Pd]n、[Fe/Ag/Ni]n、[Fe/Au/Pt]n、[Fe/Au/Pd]n、[Fe/Au/Ni]n、[Fe/Al/Pt]n、[Fe/Al/Pd]n、[Fe/Al/Ni]n、 [Fe/Co]n、[Co/Fe]n、[CoFe/Pt]n、[CoFe/Pd]n、[CoFe/Ni]nA single or multilayer structure of CoFe, CoFeNi, or FeNi, or a combination thereof, wherein n is greater than or equal to 1; or the spin-activated layer is made of an alloy having magnetocrystalline anisotropy, and is formed of CoPt, FePt, CoFePt, CoPd, FePd, CoFePd, CoAgPt, FeAgPt, CoFeAgPt, CoAgPd, FeAgPd, CoFeAgPd, CoAuPt, FeAuPt, CoFeAuPt, CoAuPd, FeAuPd, CoFeAuPd, CoAlPt, FeAlPt, CoFeAlPt, CoAlPd, FeAlPd, CoAlPd, CoFeAlPd, Co3Pt、D022-Mn3Ga、D022-Mn3Ge、L10-FePt、 L10-CoPt、L10-FePd、L10-CoPd or a combination thereof.
In an embodiment of the present application, the spin-excited layer 280 is formed of an antiferromagnetic layer, the structure of the antiferromagnetic layer is a ferromagnetic material layer/(Ru, Rh or Ir)/ferromagnetic material layer, the ferromagnetic material layer is the single-layer or multi-layer structure or the combination thereof and/or the magnetocrystalline anisotropic alloy, the magnetization vector of the ferromagnetic material layer adjacent to the spin diffusion layer 272 and the magnetization vector of the reference layer 240 are both fixed and perpendicular to the material plane, and are antiparallel to each other.
In some embodiments, the Perpendicular Anisotropy (PMA) material is typically a Magnetic material containing Co or Fe, with a planar orientation (111) of the FCC structure having a lattice length of about 0.354 nm. In general, in materials with higher perpendicular anisotropy, a nonmagnetic substrate or interlayer of Co or Fe requires a face centered cubic FCC structure also with a planar crystal orientation (111) with a lattice length greater than that of Co or Fe (-0.354 nm) and with a higher degree of lattice mismatch. The metal elements (and their FCC lattice lengths) meeting the above conditions are: ag (0.408 nm), Au (0.407 nm), Al (0.405 nm), Pt (0.392 nm), Pd (0.389 nm), Ir (0.384 nm), etc. Although Cu has a long spin diffusion length, its lattice length is about 0.361 nm, and the lattice mismatch with Co or Fe lattice length (-0.354 nm) is low, so it is not suitable for direct substrate or interlayer, and can be used as indirect substrate. The spin diffusion length of metal materials such as Pt, Pd and Ir is extremely short, and the spin diffusion length is basically spin absorption loss material (spin sinker), so the spin absorption loss material is not suitable for being used as a spin diffusion layer material or a substrate material and can be used as an interlayer material. The preferred spin diffusion layer material is Ag, Au, Al or Cu/Ag, Cu/Au, Cu/Al.
Fig. 3a and 3b are schematic diagrams illustrating a data writing process of a magnetic tunnel junction according to an embodiment of the present application. Please also refer to fig. 2 to facilitate understanding. The present application discloses a data writing method of a magnetic random access memory cell, the magnetic random access memory cell comprises a magnetic tunnel junction, the magnetic tunnel junction structure comprises a spin-on layer 280, an isolation layer 270, a free layer 260, a barrier layer 250 and a reference layer 240; the data writing method comprises the following steps: judging the resistance state of the magnetic tunnel junction; selectively passing electron current from the reference layer or the spin-excited layer into the magnetic tunnel junction when writing in dissimilar data logic according to the resistance state; when the electron current enters a level, the electron current is spin-excited, screening the spin electrons that can reach the free layer by the magnetization vector of the entering level, and gathering the spin electrons around the free layer by the surrounding layer of the free layer; the writing of the dissimilar data logic is accomplished by exciting and focusing the spin electrons to flip the magnetization vector of the free layer.
In one embodiment of the present application, as shown in FIG. 3a, when the magnetization vectors of the reference layer 240 and the free layer 260 are antiparallel, then a "high" resistance is present, i.e.: a logical "1"; to achieve the writing of a logic "0", the electron current is passed from one end of the reference layer 240 into the Magnetic Tunnel Junction (MTJ), and when the electrons pass through the reference layer 240, the electrons are spin-excited, and can reach the spin electrons in the free layer 260, and most of the electrons are spin electrons with spin vectors consistent with the magnetization vector of the reference layer 240; the spintrons 11, which pass through the free layer 260 and have a spin vector opposite to the magnetization vector of the spin-activated layer 280, will be reflected at the interface of the spacer layer 270 and the spin-activated layer 280 and thus focused around the free layer 260. Thus, the spin electrons excited by the reference layer 240 and the spin electrons reflected at the spacer layer 270/spin-excited layer 280 interface have the same spin vector direction, and the magnetic moment of the free layer 260 starts to flip under their common spin transfer torque, thereby enabling writing of a logic "0". Due to the introduction of the spin-excited layer 280, an additional spin-electron current is generated at the interface of the spacer layer 270/spin-excited layer 280, thereby increasing the total amount of spin transfer torque, which is equivalent to a large increase in spin polarizability (η), effectively reducing the critical write current.
In one embodiment of the present application, as shown in FIG. 3b, when the magnetization vectors of the reference layer 240 and the free layer 260 are parallel, this assumes a "low" resistance state, i.e.: a logical "0"; to achieve the writing of a logical "1", the electron current is passed from one end of the spin-excited layer 280 into the Magnetic Tunnel Junction (MTJ), and when the electrons pass through the spin-excited layer 280, the electrons are spin-excited, and only spin electrons having a spin vector substantially identical to the magnetization vector of the spin-excited layer 280 can reach the free layer 260; the spintrons 12 that pass through the free layer 260 and have a spin vector opposite that of the reference layer 240 will be reflected at the interface of the barrier layer 250 and the reference layer 240 due to their opposite magnetization vector to the reference layer 240 and again collect near the free layer 260. Since the spin electrons reflected at the reference layer 249/barrier layer 250 interface and the spin electrons excited by the spin-excited layer 280 have the same spin vector direction, the magnetic moment of the free layer 260 starts to flip under the effect of their common spin transfer torque, and thus, writing of logic "1" is achieved. Due to the introduction of the spin-excited layer 280, an additional flow of spin electrons is generated in the spin-excited layer 280, thereby increasing the spin transfer torque.
FIG. 4 is a diagram illustrating a MRAM cell structure according to an embodiment of the present disclosure. In an embodiment of the present application, the Magnetic random access memory cell is a one Transistor one Magnetic tunneling junction (1T 1MTJ) structure. The transistor 8 may be an NMOS or a PMOS, one end of the transistor 8 is connected to a Source Line (SL) 7, the other end is connected to a Magnetic Tunnel Junction (MTJ), the transistor 8 is controlled to be turned on and off by a Word Line (Word Line, WL)6, and the other end of the Magnetic Tunnel Junction (MTJ) is connected to a Bit Line (Bit Line)9 for data reading/writing. In some embodiments, the transistor 8 and the Magnetic Tunnel Junction (MTJ) may also be connected in other ways, such as: 2T1MTJ or 2T2MTJ, etc., to optimize the read and write performance of the MRAM circuit.
Fig. 5 is a schematic structural diagram of a magnetic tunnel junction according to an embodiment of the present application. In an embodiment of the present application, the magnetic tunnel junction 200 comprises, from top to bottom, a capping layer 290, a spin-activated layer 280, a blocking layer 270, the free layer 260, the barrier layer 250, the reference layer 240, a lattice blocking layer 230, a first antiferromagnetic layer 220a and a seed layer 210, the first antiferromagnetic layer 220a being formed of a ferromagnetic material, wherein the first antiferromagnetic layer 220a is ferromagnetically coupled to the reference layer 240; the magnetization vectors of the spin-activated layer 280 and the reference layer 240 are antiparallel.
In one embodiment of the present application, the seed layer 210 is generally composed of Ta, Ti, TiN, TaN, W, WN, Ru, Pt, Ni, Cr, CrCo, CoFeB or a combination thereof. Furthermore, it may be a multilayer structure of Ta/Ru, CoFeB/Ta/Pt, CoFeB/Ta/Ru, CoFeB/Ta/Ru/Pt, Ta/Pt or Ta/Pt/Ru, etc. The seed layer 210 is used to optimize the crystal structure of the subsequent first antiferromagnetic layer 220 a.
In one embodiment of the present application, the first antiferromagnetic layer 220a has [ Co/Pt ]]nCo/Ru、[Co/Pt]nCo/Ir、[Co/Pt]nCo/Ru/Co、[Co/Pt]nCo/Ir/Co、[Co/Pt]nCo/Ru/Co[Pt/Co]mOr [ Co/Pt ]]nCo/Ir/Co[Pt/Co]mA superlattice structure, wherein n>m.gtoreq.1, the first antiferromagnetic layer 220a has a strong perpendicular anisotropy (PMA).
The reference layer 240 has a magnetic polarization invariant under ferromagnetic coupling of the first antiferromagnetic layer 220a, and its composition material is typically Co, Fe, Ni, CoFe, CoFeB or their combination. Since the first antiferromagnetic layer 220a has a Face Centered Cubic (FCC) crystal structure and the reference layer 240 has a Body Centered Cubic (BCC) crystal structure, the lattices are not matched, and in order to realize the transition and ferromagnetic coupling from the first antiferromagnetic layer 220a to the reference layer 240, a lattice-blocking layer 230, which is typically composed of Ta, W, Mo, Hf, Fe, Co (Ta, W, Mo or Hf), Fe (Ta, W, Mo or Hf), FeCo (Ta, W, Mo or Hf), FeCoB (Ta, W, Mo or Hf), or the like, is typically added between two layers of materials.
The total thickness of the barrier layer 250 is 0.6 nm to 1.5 nm. The material is MgO, and the method can be realized by directly sputtering and depositing the MgO target material, or by firstly sputtering and depositing Mg on the Mg target material and then changing the Mg into the MgO through an oxidation process.
The free layer 260 has a structure of CoFeB, Fe/CoFeB, Fe/FeB, FeCo/CoFeB, CoFeB/(W, Mo, V, Nb, Cr, Hf, Ti, Zr, Ta, Sc, Y, Zn, Ru, Os, Ru, Rh, Ir, Pd, Pt)/CoFeB, Fe/CoFeB/(W, Mo, V, Nb, Cr, Hf, Ti, Zr, Ta, Sc, Y, Zn, Ru, Os, Ru, Rh, Ir, Pd, Pt)/CoFeB or CoFe/CoFeB/(W, Mo, V, Nb, Cr, Hf, Ti, Zr, Ta, Sc, Y, Zn, Ru, Os, Ru, Rh, Ir, Pd, Pt)/CoFeB. Further, optionally, a plasma process may be used to perform surface plasma treatment after the free layer deposition for surface modification or selective removal.
The capping layer 290 is made of a multi-layer material of W, Zn, Al, Cu, Ca, Ti, V, Cr, Mo, Mg, Nb, Ru, Hf, V, Cr, Pt, or a combination thereof, and has a total thickness of 0.5 nm to 10.0 nm.
Fig. 6 is a schematic view of a magnetic tunnel junction structure according to an embodiment of the present application, please refer to fig. 5 for understanding. In an embodiment of the present application, an antiferromagnetic coupling layer 220c and a second antiferromagnetic layer 220b are further included between the spin excitation layer and the capping layer from bottom to top, the antiferromagnetic coupling layer 220c is formed of a transition metal material capable of forming antiferromagnetic coupling, the second antiferromagnetic layer 220b is formed of a ferromagnetic material, and the second antiferromagnetic layer 220b and the spin excitation layer 280 form antiferromagnetic coupling through the antiferromagnetic coupling layer 220 c.
In some embodiments, the first antiferromagnetic layer 220a has [ Co/Pt ]]nCo、Co/[Co/Pt]nCo， [Co/Pd]nCo、Co/[Co/Pd]nCo, a superlattice structure, where n ≧ 1, the first antiferromagnetic layer 220a has strong perpendicular anisotropy (PMA).
In some embodiments, the material of the antiferromagnetic coupling layer 220c is selected from Ru or Ir, and further the first RKKY peak (0.3 nm-0.6 nm) of Ru may be selected, the second RKKY peak (0.7 nm-0.9 nm) of Ru may be selected, or even the first RKKY peak (0.3 nm-0.6 nm) of Ir may be selected.
In some embodiments, the second antiferromagnetic layer 220b has a superlattice structure of Co/[ Pt/Co ] n, Co/[ Pt/Co ] nPt, Co/[ Pd/Co ] n, Co/[ Pd/Co ] nPd, where n ≧ 1, and the second antiferromagnetic layer 220b has a strong perpendicular anisotropy (PMA).
Referring to fig. 2 to 6, in an embodiment of the present application, a memory cell of a magnetic random access memory includes any one of the above-described magnetic tunnel junction 200 structures, a top electrode 300 disposed above the magnetic tunnel junction 200 structure, and a bottom electrode 100 disposed below the magnetic tunnel junction 200 structure.
In an embodiment of the present application, an annealing operation is performed at a temperature greater than 350 ℃ for at least 30 minutes after the bottom electrode, seed layer, antiferromagnetic layer, lattice partition layer, reference layer, barrier layer, free layer, capping layer, and top electrode are deposited.
The magnetic tunnel junction unit structure effectively improves the spin transfer torque of the magnetic tunnel junction in the writing process through the introduced spin excitation layer, is very favorable for reducing the critical current (IC0) of an MTJ (magnetic tunnel junction) device, improves the writing speed of an MRAM (magnetic random access memory) circuit, reduces the writing power consumption, improves the durability, and is very suitable for the application environment of rapid ultra-low power consumption.
The terms "in one embodiment of the present application" and "in various embodiments" are used repeatedly. This phrase generally does not refer to the same embodiment; it may also refer to the same embodiment. The terms "comprising," "having," and "including" are synonymous, unless the context dictates otherwise.
Although the present application has been described with reference to specific embodiments, it should be understood that various changes, substitutions and alterations can be made herein without departing from the spirit and scope of the application, and all changes, substitutions and alterations that fall within the spirit and scope of the application are to be understood as being covered by the following claims.
Claims (11)
1. The utility model provides a magnetic tunnel junction structure sets up in magnetic random access memory unit, the magnetic tunnel junction from top to bottom structure includes free layer, barrier layer and reference layer at least, its characterized in that, the free layer top sets up and includes:
the isolation layer is arranged on the free layer and comprises a buffer layer and a spin diffusion layer from bottom to top, the buffer layer is formed by a metal oxide layer, and the spin diffusion layer is made of metal with high spin diffusion length;
a spin-excited layer disposed on the spin diffusion layer and formed of a magnetic material having a high spin excitation rate of perpendicular anisotropy;
wherein the buffer layer provides an additional source of perpendicular anisotropy interface anisotropy for the free layer and directs lattice formation of the spin diffusion layer, the spin diffusion layer directs lattice growth required for the spin-activated layer, and the magnetization vector of the spin-activated layer is antiparallel to the magnetization vector of the reference layer.
2. The magnetic tunnel junction structure of claim 1 wherein the buffer layer has a thickness of 0.5 nm to 1.4 nm; the buffer layer is made of MgO or ZrO2、ZnO、Al2O3、GaO、Fe3O4、Fe2O3、CoO、NiO、Y2O3、SrO、Sc2O3、TiO2、HfO2、V2O5、Nb2O5、Ta2O5、CrO3、MoO3、WO3、RuO2、OsO2、TcO、ReO、RhO、IrO、SnO、SbO、MgZnO、Mg3B2O6、MgAl2O4、SrTiO3Or a combination thereof, preferably MgO.
3. The magnetic tunnel junction structure of claim 1 wherein the spin diffusion layer has a thickness of 0.2 nm to 5.0 nm; the spin diffusion layer is formed from Cu, Ag, Au, Al, Ge, Ti, Zn, Ga, In, Ti, V, Cr, Zr, Nb, Mo, Tc, Ru, Si or a combination thereof, preferably Ag, Au, Al or Cu/Ag, Cu/Au, Cu/Al.
4. The mtj structure of claim 1, wherein the thickness of the spin-activated layer is between 0.4 nm and 4.0 nm; the material for forming the spin-excited layer is Co, [ Co/Pt ]]n、[Co/Pd]n、[Co/Ni]n、[Co/AgPt]n、
[Co/AgPd]n、[Co/AgNi]n、[Co/AuPt]n、[Co/AuPd]n、[Co/AuNi]n、[Co/AlPt]n、[Co/AlPd]n、[Co/AlNi]n、[Co/Ag/Pt]n、[Co/Ag/Pd]n、[Co/Ag/Ni]n、[Co/Au/Pt]n、[Co/Au/Pd]n、[Co/Au/Ni]n、[Co/Al/Pt]n、[Co/Al/Pd]n、[Co/Al/Ni]n、Fe、[Fe/Pt]n、[Fe/Pd]n、[Fe/Ni]n、[Fe/AgPt]n、
[Fe/AgPd]n、[Fe/AgNi]n、[Fe/AuPt]n、[Fe/AuPd]n、[Fe/AuNi]n、[Fe/AlPt]n、[Fe/AlPd]n、[Fe/AlNi]n、[Fe/Ag/Pt]n、[Fe/Ag/Pd]n、[Fe/Ag/Ni]n、[Fe/Au/Pt]n、[Fe/Au/Pd]n、[Fe/Au/Ni]n、[Fe/Al/Pt]n、[Fe/Al/Pd]n、[Fe/Al/Ni]n、[Fe/Co]n、[Co/Fe]n、[CoFe/Pt]n、[CoFe/Pd]n、
[CoFe/Ni]nA single or multilayer structure of CoFe, CoFeNi, or FeNi, or a combination thereof, wherein n is greater than or equal to 1; or the spin-activated layer is made of an alloy having magnetocrystalline anisotropy, and is formed of CoPt, FePt, CoFePt, CoPd, FePd, CoFePd, CoAgPt, FeAgPt, CoFeAgPt, CoAgPd, FeAgPd, CoFeAgPd, CoAuPt, FeAuPt, CoFeAuPt, CoAuPd, FeAuPd, CoFeAuPd, CoAlPt, FeAlPt, CoFeAlPt, CoAlPd, FeAlPd, CoAlPd, CoFeAlPd, Co3Pt、D022-Mn3Ga、D022-Mn3Ge、L10-FePt、L10-CoPt、L10-FePd、L10-CoPd or a combination thereof.
5. The magnetic tunnel junction structure according to claim 4, wherein the spin-excited layer is an antiferromagnetic layer having a structure of a ferromagnetic material layer/(Ru, Rh or Ir)/ferromagnetic material layer, the ferromagnetic material layer is the single-layer or multi-layer structure or a combination thereof and/or the magnetocrystalline anisotropy alloy or a combination thereof, and a magnetization vector of the ferromagnetic material layer adjacent to the spin diffusion layer of the spin-excited layer is antiparallel to a magnetization vector direction of the reference layer.
6. The magnetic tunnel junction structure of claim 1 wherein the magnetic tunnel junction comprises, in a top-down configuration, a capping layer, a spin-on layer, a spacer layer, the free layer, the barrier layer, the reference layer, a lattice spacer layer, a first antiferromagnetic layer formed of a ferromagnetic material, and a seed layer, wherein the first antiferromagnetic layer is ferromagnetically coupled to the reference layer; the magnetization vectors of the spin-excited layer and the reference layer are antiparallel.
7. The magnetic tunnel junction structure of claim 6 further comprising an antiferromagnetic coupling layer and a second antiferromagnetic layer from bottom to top between the spin excitation layer and the capping layer, wherein the antiferromagnetic coupling layer is formed of a transition metal material capable of forming antiferromagnetic coupling, and the second antiferromagnetic layer is formed of a ferromagnetic material, and wherein the second antiferromagnetic layer and the spin excitation layer are antiferromagnetically coupled through the antiferromagnetic coupling layer.
8. A magnetic random access memory comprising the magnetic tunnel junction structure of any of claims 1-7, a top electrode disposed above the magnetic tunnel junction structure, and a bottom electrode disposed below the magnetic tunnel junction structure.
9. A data writing method of a magnetic random access memory cell, the magnetic random access memory cell comprising a magnetic tunnel junction, the magnetic tunnel junction structure comprising a spin-activated layer, an isolation layer, a free layer, a barrier layer, and a reference layer, the data writing method comprising the steps of:
judging the resistance state of the magnetic tunnel junction;
selectively passing electron current from the reference layer or the spin-excited layer into the magnetic tunnel junction when writing in dissimilar data logic according to the resistance state;
when the electron current enters a level, the electron current is spin-excited, screening the spin electrons that can reach the free layer by the magnetization vector of the entering level, and gathering the spin electrons around the free layer by the surrounding layer of the free layer;
the writing of the dissimilar data logic is accomplished by exciting and focusing the spin electrons to flip the magnetization vector of the free layer.
10. The magnetic tunnel junction structure of claim 9 wherein when the magnetization vectors of the reference layer and the free layer are antiparallel, the magnetic tunnel junction is a logic 1 in the high resistance state; to write a logic 0, passing the electron current from the reference layer into the magnetic tunnel junction; when the electron current passes through the reference layer, the electron current is excited by spin, spin electrons which can reach the free layer are screened through the magnetization vector of the reference layer, and most or all spin vectors of the spin electrons are in the same direction with the magnetization vector of the reference layer; the spin vector of the spin electrons passing through the free layer and the magnetization vector of the spin-excited layer are in opposite directions and will be reflected at the interface of the spacer layer and/or the spin-excited layer to be concentrated around the free layer; and the magnetization vector direction of the free layer is reversed through the same spin vector direction of the spin electrons excited by the reference layer and the spin electrons reflected by the spacing layer and/or the spin excitation layer interface, so that the writing of logic 0 is realized.
11. The magnetic tunnel junction structure of claim 9 wherein the magnetic tunnel junction is a logic 0 in a high resistance state when the magnetization vectors of the reference layer and the free layer are parallel; for writing a logic 1, passing the electron current from the spin-activated layer into the magnetic tunnel junction; when the electron current passes through the spin-excited layer, the electron current is spin-excited, spin electrons which can reach the free layer are screened through the magnetization vector of the spin-excited layer, and most or all spin vectors of the spin electrons are consistent with the magnetization vector of the spin-excited layer; the spin vector of the spin electron passing through the free layer is in the opposite direction to the magnetization vector of the reference layer, and will be reflected at the interface of the barrier layer and/or the reference layer to be focused around the free layer; and the magnetization vector direction of the free layer is reversed through the spin vector direction of the spin electrons excited by the spin excitation layer and the spin electrons reflected by the barrier layer and/or the reference layer interface, so that the writing of logic 1 is realized.
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| Publication number | Priority date | Publication date | Assignee | Title |
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| CN113140670A (en) * | 2020-01-16 | 2021-07-20 | 上海磁宇信息科技有限公司 | Magnetic tunnel junction vertical antiferromagnetic layer and random access memory |
| CN113346006A (en) * | 2020-03-02 | 2021-09-03 | 上海磁宇信息科技有限公司 | Magnetic tunnel junction structure and magnetic random access memory thereof |
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| CN114497357A (en) * | 2020-11-11 | 2022-05-13 | 浙江驰拓科技有限公司 | Magnetic Tunnel Junction Devices |
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| CN113140670A (en) * | 2020-01-16 | 2021-07-20 | 上海磁宇信息科技有限公司 | Magnetic tunnel junction vertical antiferromagnetic layer and random access memory |
| CN111261772A (en) * | 2020-02-10 | 2020-06-09 | 北京航空航天大学 | Magnetic tunnel junction, method for forming the same, and magnetic memory |
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