CN112928203A - Magnetic tunnel junction structure with multiple covering layers and magnetic random access memory - Google Patents

Abstract

The application provides a magnetic tunnel junction structure of a multilayer covering layer and a magnetic random access memory. According to the method, through the design of a multilayer covering layer structure and the process thereof, the magnetic perpendicular anisotropy of the free layer from the interface effect of the covering layer and the free layer is increased, relatively high tunneling magnetoresistance ratio can be kept on the premise that the area product of junction resistance is reduced, and meanwhile, the situation that deposited metal penetrates through the covering layer and reaches the interface of the free layer/the bottom covering layer in the process of deposition or/and annealing of the covering layer is avoided, so that the thermal stability is kept.

Description

Magnetic tunnel junction structure with multiple covering layers and magnetic random access memory

Technical Field

The present invention relates to the field of memory technologies, and in particular, to a magnetic tunnel junction structure with multiple capping layers 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 remain unchanged is called data retention capability or thermal stability, and is required to be different in different application situations, for a typical Non-volatile Memory (NVM), for example: the data storage capacity is required to be capable of storing data for at least ten years at 125 ℃ or 150 ℃, and the data retention capacity or the thermal stability is reduced when external magnetic field overturning, thermal disturbance, current disturbance or reading and writing are carried out for multiple times.

In order to increase the storage density of MRAM and meet the circuit requirements of CMOS with higher technology node, the Critical Dimension (CD) of the magnetic tunnel junction is smaller and smaller, and correspondingly, the Resistance Area Product (RA) of the magnetic tunnel junction is also smaller and smaller. While the critical size of the magnetic Tunnel junction is reduced, it is required to secure a sufficiently high Tunneling Magnetoresistance Ratio (TMR) to secure a high reading speed. In order to reduce RA, the thickness of the bottom capping layer is usually reduced, but the crystal structure is drastically deteriorated, and the subsequently deposited metal capping layer easily reaches the interface between the free layer and the capping layer through the capping layer during deposition or/and subsequent annealing process, thereby affecting the interface characteristics of the MTJ cell structure and deteriorating the thermal stability.

Disclosure of Invention

In order to solve the above-mentioned problems, an object of the present invention is to provide a magnetic tunnel junction structure of a multi-layer capping layer and a magnetic random access memory.

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 is arranged in a magnetic random access memory unit and is formed through sputtering deposition, and thermal annealing treatment is carried out after deposition. The magnetic tunnel junction structure comprises a Covering Layer (CL), a Free Layer (FL), a Barrier Layer (TB), a Reference Layer (RL), a Crystal Breaking Layer (CBL), an Anti-ferromagnetic Layer (SyAF) and a Seed Layer (SL), wherein the covering Layer comprises: a first capping layer formed of a metal oxide, preferably MgO having a NaCl crystal system cubic lattice structure, for providing an additional perpendicular anisotropic interface to the free layer; a second capping layer disposed over the first capping layer, formed of a ferromagnetic material, the second capping layer having a thickness of no greater than 1.5 atomic layers; a third capping layer disposed above the second capping layer and formed of a high-Z (high atomic number) metal having high electronegativity; a fourth capping layer disposed over the third capping layer and formed of a low-Z (low atomic number) metal having a high electronegativity; and the fifth covering layer is arranged above the fourth covering layer. The second covering layer realizes the transformation from an amorphous state to a crystalline state after thermal annealing treatment, and provides another interface anisotropy source between the first covering layer and the second covering layer; the third capping layer prevents at least one of a material and atoms of the fourth capping layer from diffusing into the first capping layer and the second capping layer during a process.

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 total thickness of the first capping layer is 0.4nm to 2.0nm, and the forming material is MgO, ZnO, Al₂O₃，MgAl₂O₄，Mg₃B₂O₆，SiMg₂O₄，SiZn₂O₄，SiAl₂O₄，MgZnO₄Or a combination thereof.

In an embodiment of the present application, the first cover layer is formed by directly performing sputter deposition on a metal oxide target, or by performing sputter deposition on a metal target first and then changing the deposited metal into a metal oxide through an oxidation process; further, after the first cap layer is formed, optionally, a heating process is performed to perform a heat treatment while maintaining a vacuum state, and then the temperature is cooled to room temperature or an ultra-low temperature to form a NaCl crystal face-centered cubic lattice structure.

In one embodiment of the present application, the metal oxide or metal deposition process is performed by a PVD process with a working pressure of 0.1mTorr to 10.0 mTorr.

In an embodiment of the present application, the oxidation process employs O, O₂Or O₃The working gas pressure adopts normal pressure or ultralow pressure, wherein the ultralow pressure is less than 0.1 mTorr.

In an embodiment of the present application, when a technical scheme of performing metal deposition first and oxidizing to generate a metal oxide is adopted, the metal deposition is performed by depositing once and oxidizing once, or by depositing for multiple times and oxidizing multiple times. Namely, the first covering layer is a double-layer MgO/MgOx structure, x is less than 1, and MgOx is realized by a mode of firstly carrying out sputtering deposition on a Mg metal target material and then oxidizing a sputtering deposited Mg film to form MgOx.

In one embodiment of the present application, high temperatures are used to deposit metal oxides or metals.

In one embodiment of the present application, the heating process uses infrared, microwave or laser as a radiation source, and the temperature thereof is 150 ℃ to 600 ℃.

In an embodiment of the present application, He, N2, Ne, Ar, Kr, or Xe gas is introduced during the heating process.

In one embodiment of the present application, the heat treatment time varies from 10 seconds to 1 hour.

In an embodiment of the present application, during the heating process, a vertical magnetic field is introduced, and the magnetic field strength of the vertical magnetic field is 1.5T to 5.0T; the magnetization direction of the perpendicular magnetic field is perpendicular to the film plane of the first cover layer.

In one embodiment of the present application, the ultra low temperature is 10K to 20K, preferably 10K, 77K, 100K or 20K.

In one embodiment of the present application, He gas is introduced prior to the cooling operation.

In an embodiment of the present application, the second capping layer has a thickness of not more than 0.6nm and is composed of CoFeB, FeB, CoB, CoC, FeC, CoFeC or a combination thereof, and the second capping layer is used to adjust the coercivity and the vertical anisotropy field of the free layer.

In an embodiment of the present application, the third capping layer has a total thickness of 0nm to 0.5nm, and the formation material is Ru, Rh, Pd, Ag, Re, Os, Ir, Pt, Au, or a combination thereof.

In an embodiment of the present application, the total thickness of the fourth capping layer is 0.1nm to 4.0nm, the forming material is Zr, Nb, Ti, V, Cr, Ta, W, Hf, Mo or a combination thereof, and the fourth capping layer is used for absorbing at least one of B and C of the second capping layer.

In an embodiment of the present application, a total thickness of the fifth capping layer is 1.0nm to 10.0nm, and a material of the fifth capping layer is a single-layer or multi-layer metal or alloy formed by at least one of Ru and Ir, for example, a double-layer structure W/Ru from bottom to top, which is used as an etching barrier layer in a subsequent etching process.

In one embodiment of the present application, the sputter deposition pressure is between 1mTorr and 20mTorr, preferably between 1mTorr and 5 mTorr.

In one embodiment of the present application, the sputtering ion source is Ar⁺，Kr⁺Or Xe⁺Preferably Kr⁺Or Xe⁺。

In one embodiment of the present application, the sputter deposition energy is 20eV to 700eV, preferably 20eV to 150 eV.

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.

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, capping layer, and top electrode are deposited.

According to the method, through the multilayer covering layer and the combination of the amorphous deposition and the structural design of barrier material/atomic diffusion, on the premise that the area product of junction resistance is reduced, relatively high tunneling magnetic resistance rate can be kept, the magnetic perpendicular anisotropy of the free layer derived from the interface effect of the covering layer and the free layer is increased, and meanwhile, the situation that deposited metal penetrates through the covering layer and reaches the interface of the free layer/the bottom covering layer in the deposition or/and annealing process of the covering layer is avoided, so that the thermal stability is kept.

Drawings

FIG. 1 is a diagram illustrating an exemplary MRAM cell structure;

FIG. 2 is a diagram illustrating a magnetic memory cell structure of an embodiment of the magnetic random access memory of the present application;

FIG. 3 is a schematic illustration of heating and cooling of a first cover layer according to an embodiment of the present application;

FIG. 4aIs composed ofSchematic diagram of atomic arrangement in the MgO capping layer before the first capping layer of the embodiment of the present application is subjected to heating and cooling treatment;

FIG. 4bIs composed ofThe atomic arrangement diagram in the MgO covering layer after the first covering layer is heated and cooled is shown in the embodiment of the application;

FIG. 5 is a schematic diagram of another capping layer deposited over the first capping layer in an embodiment of the present disclosure;

FIG. 6 is a periodic table of the electronegativity of elements.

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 other similar variations of embodiments, 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 illustrating an exemplary MRAM cell structure. The magnetic memory cell structure includes a multi-layer structure formed by at least a Bottom Electrode (BE) 10, a Magnetic Tunnel Junction (MTJ)20, and a Top Electrode (Top Electrode) 30.

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 (MTJ)20 includes, from top to bottom, a Capping Layer (CL) 27, a Free Layer (FL) 26, a Barrier Layer (Tunnel Barrier, TBL)25, a Reference Layer (RL) 24, a lattice Breaking Layer (CBL) 23, an antiferromagnetic Anti-ferromagnetic Layer (SyAF) 22, and a Seed Layer (Seed Layer; SL) 21.

In some embodiments, as shown in fig. 1, the capping layer 27 generally includes a multilayer film with MgO at the bottom, and the free layer 26 is composed of a single-layer or multilayer structure of CoFeB, CoFeB/CoFeB, or CoFeB/(Ta, W, Mo, or Hf)/CoFeB. In order to increase the density of the magnetic random access memory, the capping layer 27 generally has a structure with a (001) plane crystal orientation of NaCl crystal system, and in this case, the capping layer 27 may provide an additional interface anisotropy to the free layer 26, thereby enhancing the thermal stability of the MTJ cell structure.

In a Magnetic Tunnel Junction (MTJ) with perpendicular anisotropy (PMA), as a free layer for storing information, two magnetization directions are possessed in the perpendicular direction, that is: up and down, corresponding to "0" and "1" in the binary, respectively.

To achieve fast writing of a logic "0" or "1", a typical write requires that the write current density (J) be greater than the critical current density (Jc 0). Wherein the content of the first and second substances,

the time of writing is tpw, then:

the ratio of the portion of the write current (J) exceeding the critical current (Jc0) to the critical current is J, J being J/Jc 0-1.

Wherein alpha is a secondary damping coefficient,

to approximate Planck's constant, Ms is the saturation susceptibility of the free layer, T is the effective thickness of the free layer, HK is the perpendicular effective anisotropy field, kB is the Boltzmann's constant, T is the temperature, η spin susceptibility, γ is the gyromagnetic ratio, Δ is the thermodynamic stability factor of the Magnetic Tunnel Junction (MTJ), τ relax relaxation time, and θ 0 is the free layer magnetization vector initialization angle.

In fast caches, for example: as an alternative to SRAM, MRAM is required to have a read and write speed that matches SRAM. In addition, MTJ, which is a core memory cell of a magnetic memory (MRAM), must also be compatible with CMOS processes and must be able to withstand long term annealing at 350 ℃ or higher; meanwhile, a Magnetic memory cell of MRAM is required to have strong Magnetic Immunity (Magnetic Immunity).

However, in order to increase the storage density of MRAM and meet the circuit requirements of CMOS with higher technology node, the Critical Dimension (CD) of the magnetic tunnel junction is getting smaller, and the Resistance Area Product (RA) of the magnetic tunnel junction is also getting smaller. While the critical dimension of the magnetic Tunnel is reduced, it is required to ensure a Tunneling Magnetoresistance Ratio (TMR) high enough to ensure a high reading speed. In order to reduce RA, the thickness of the capping layer 27 is usually reduced, and when the thickness of MgO is reduced, the crystal structure of the subsequently deposited metal M is rapidly deteriorated, and the subsequently deposited metal M easily passes through MgO during deposition or/and a subsequent annealing process to reach the bottom MgO interface of the free layer and/or the capping layer, and further, the interface characteristics of the MTJ cell structure are affected, so that the thermal stability is deteriorated, and correspondingly, the magnetic field immunity is also greatly reduced.

FIG. 2 is a diagram illustrating a magnetic memory cell structure of an embodiment of the magnetic random access memory of the present application; FIG. 3 is a schematic illustration of heating and cooling of a first cover layer according to an embodiment of the present application; FIG. 4a is a schematic diagram showing the atomic arrangement of the MgO blanket layer before the first blanket layer of the present application is subjected to heating and cooling processes; FIG. 4b is a schematic diagram showing the atomic arrangement of the MgO blanket layer after the first blanket layer of the present embodiment is subjected to heating and cooling treatment; FIG. 5 is a schematic diagram of a second capping layer deposited over the first capping layer in accordance with an embodiment of the present disclosure; FIG. 6 is a periodic table of the electronegativity of elements. 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 20 is disposed in a magnetic random access memory cell, wherein the magnetic tunnel junction structure 20 is formed by sputter deposition and then subjected to a thermal annealing process after the deposition. The magnetic tunnel junction 20 includes a Capping Layer (CL) 27, a Free Layer (FL) 26, a Barrier Layer (TBL) 25, a Reference Layer (RL) 24, a lattice Breaking Layer (CBL) 23, an Anti-ferromagnetic Layer (SyAF) 22, and a Seed Layer (Seed Layer; SL)21, wherein the Capping Layer 27 includes: a first cladding layer 271 formed of a metal oxide, preferably MgO having a NaCl crystal system cubic lattice structure, for providing an additional perpendicular anisotropic interface to the free layer; a second capping layer 272 disposed over the first capping layer 271 and formed of a ferromagnetic material, the second capping layer 272 having a thickness of not more than 1.5 atomic layers; a third cladding layer 273 disposed above the second cladding layer 272 and formed of a high-Z (high atomic number) metal having high electronegativity; a fourth cladding layer 274, disposed over the third cladding layer 273, formed of a low-Z (low atomic number) metal having high electronegativity; a fifth cladding layer 275, disposed over the fourth cladding layer 274, formed of Ru and/or Ir.

In one embodiment of the present application, the first cladding layer 271 has a total thickness of 0.4nm to 1.2nm and is a metal or metal oxide having a cubic lattice (001) structure of NaCl system, such as MgO, ZnO, Al₂O₃,MgAl₂O₄，Mg₃B₂O₆， SiMg₂O₄，SiZn₂O₄，SiAl₂O₄，MgZnO₄Or a combination thereof. The primary function of the first cladding layer 271 is to provide an additional perpendicular anisotropic interface to the free layer 26, thereby enhancing its thermal stability. The method can be realized by directly carrying out sputtering deposition on the metal oxide target material, or by carrying out sputtering deposition on the metal target material firstly and then changing the metal deposited by an oxidation process into the metal oxide. Furthermore, the metal oxide or metal deposition process is realized by adopting a PVD process, the working pressure is 0.1 mTorr-10.0 mTorr, and the crystallization phase of the NaCl crystal system (001) can be enhanced by selecting smaller pressure. Preferably, the metal is Mg and the metal oxide is MgO.

In one embodiment of the present application, the oxidation process may use O, O₂Or O₃The working pressure can adopt normal pressure or ultra-low pressure, such as: less than 0.1 mTorr.

In some implementationsIn the example, when the technical scheme of firstly performing metal deposition and oxidizing to generate metal oxide is adopted, the metal deposition and the oxidation are realized by depositing once and oxidizing once or depositing for multiple times and oxidizing for multiple times. That is, the first capping layer is a double layer of MgO/MgO_xStructure, x<1，MgO_xFirstly, sputtering deposition is carried out on a Mg metal target material, and then, the sputtering deposited Mg film is oxidized to form MgO_xIs realized in the following manner.

In one embodiment of the present application, high temperatures are used to deposit metal oxides or metals.

In one embodiment of the present application, as shown in fig. 3, the first cladding layer 271 is heat treated and cooled to room temperature or ultra-low temperature, so that MgO of the first cladding layer 271 before the deposition of the second cladding layer 272 has a perfect FCC (001) structure.

In one embodiment of the present application, the heating process may use Infrared (IR), Microwave (MW) or Laser (Laser/Beam) as a radiation source, which is at a temperature of 150 ℃ to 600 ℃. Further, a small amount of He, N2, Ne, Ar, Kr or Xe, etc. may be introduced to increase the heat transfer efficiency of the thermal process chamber. The heat treatment time is different from 10 seconds to 1 hour.

In one embodiment of the present application, a vertical magnetic field with a magnetic field strength of 1.5T to 5.0T may be introduced during the heating process. The magnetization direction thereof is perpendicular to the film plane of the first cover layer 271.

In one embodiment of the present application, during the cooling process, cooling to Room Temperature (RT) or ultra-low Temperature condensation (Cryogenic Cool) is adopted, such as: 10K, 77K, 100K, 200K, etc. Further, He or the like is generally introduced before the condensing stage and the sample (wafer) to obtain a higher cooling effect.

In one embodiment of the present application, as shown in fig. 4a and 4b, after the heating and cooling processes, the first cladding layer 271 has a more perfect NaCl crystal system (001) atomic arrangement. The heating process has the advantages that Mg atoms and O atoms can be arranged from new positions, so that the perfect NaCl crystal system (001) plane crystal orientation structure is inclined, the cooling process can reduce the activity of atoms on the upper surface of the first covering layer 271, the atom arrangement is more orderly, and the interface is more perfect.

In one embodiment of the present application, the second capping layer 272 has a thickness of no more than 0.6nm and is made of CoFeB, FeB, CoB, CoC, FeC, CoFeC or a combination thereof. After subsequent annealing of the second cladding layer 272, the second cladding layer 272 achieves a transformation from an amorphous state to a crystalline state. Meanwhile, between the first cladding layer 271 and the second cladding layer 272, the second cladding layer 272 provides another source of interfacial anisotropy, thereby facilitating an increase in coercivity and perpendicular anisotropy field. Furthermore, during the deposition process, since the second cladding layer 272 is amorphous, the damage to the first cladding layer 271 is greatly reduced.

In an embodiment of the present application, the third cover layer 277 has a total thickness of 0nm to 0.5nm and is formed of a high-Z metal having high electronegativity, such as: the forming material is Ru, Rh, Pd, Ag, Re, Os, Ir, Pt, Au or the combination thereof. The third cover layer 277 mainly functions to prevent the material of the fourth cover layer 274 from diffusing into the first cover layer 271 and the second cover layer 272, thereby causing damage to the crystal lattice and interface thereof.

In an embodiment of the present application, the material of the fourth cladding layer 274 is Zr, Nb, Ti, V, Cr, Ta, W, Hf, Mo or a combination thereof. The thickness is z, 0.1z4.0 nm. The fourth capping layer 274 mainly serves to absorb B and/or C, etc. in the second capping layer 272, so that the second capping layer 272 has stronger crystallization property after the MTJ film layer is annealed.

In an embodiment of the present application, the material of the fifth capping layer 275 is Ru, Ir or a combination thereof, and the thickness thereof is 1.0nm to 10.0nm, which mainly functions as an etch stop layer for the subsequent etching.

As shown in fig. 6, which is a periodic table of electronegativity of elements, in order not to damage the first cladding layer 271, that is: the crystal structure of MgO coverage test suggests the use of a Formation entropy (format entropy) element higher than that of O, namely: a high electronegativity element.

In one embodiment of the present application, as shown in FIG. 5, during sputter deposition, the most important thing isThat is, the damage of the sputtering atoms of the second cap layer 272 and the sputtering gas or ions to the first cap layer 271 is reduced. Further, the sputtering deposition pressure is 1mTorr to 20mTorr, preferably, 1mTorr to 5 mTorr; the source of the sputtering ions is Ar⁺Kr + or Xe⁺Preferably, Kr⁺Or Xe⁺(ii) a The sputtering deposition energy is 20eV to 700eV, preferably 20eV to 150 eV. Higher gas pressures, heavier inert gas ion sources and lower sputtering gas capability can effectively avoid damage to the first cladding layer 271. In one embodiment of the present application, high temperatures may be used to deposit MgO or Mg.

In an embodiment of the present application, referring to fig. 5, the layers above the first cover layer 271 may be implemented as the corresponding embodiment of fig. 5 to form the cover layers of each layer.

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 20 structures, a top electrode 30 disposed above the magnetic tunnel junction 20 structure, and a bottom electrode 10 disposed below the magnetic tunnel junction 20 structure.

In an embodiment of the present application, the material of the seed layer 21 of the magnetic tunnel junction 20 is one or a combination of Ti, TiN, Ta, TaN, W, WN, Ru, Pt, Cr, CrCo, Ni, CrNi, CoB, FeB, CoFeB, etc. selected from Ti, TiN, Ta, TaN, W, WN, Ru, Pt, Cr, CrCo, Ni, CoFeB, and CoFeB. In some embodiments, the seed layer 21 may be selected from one of tantalum Ta/ruthenium Ru, tantalum Ta/platinum Pt/ruthenium Ru, and the like.

The antiferromagnetic layer 22, formally known as an antiparallel ferromagnetic super-lattice (Anti-Parallel ferromagnetic super-lattice) layer 22, is also known as a Synthetic antiferromagnetic (Synthetic Anti-ferromagnetic, SyAF) layer. Typically from [ cobalt Co/platinum Pt ]]_nCo/(Ru, Ir, Rh) and Co/Pt]_nCo/(Ru, Ir, Rh)/(Co, Co [ Co/Pt ] Co]_m) [ cobalt Co/palladium Pd ]]_nCo/(Ru, Ir, Rh) and Co/Pt]_nCo/(Ru, Ir, Rh)/(Co,Cobalt Co [ cobalt Co/platinum Pt ]]_m) [ cobalt Co/nickel Ni ]]_nCo/(Ru, Ir, Rh) or [ Co/Ni ]]_nCo/(Ru, Ir, Rh)/(Co, Co [ Ni/Co ]]_m) A superlattice composition, wherein n>m.gtoreq.0, preferably, the monolayer thickness of cobalt (Co) and platinum (Pt) is below 0.5nm, such as: 0.10 nm, 0.15 nm, 0.20 nm, 0.25 nm, 0.30 nm, 0.35 nm, 0.40 nm, 0.45 nm, or 0.50 nm …. In some embodiments, the thickness of each layer structure of the antiferromagnetic layer 22 is the same or different. The antiferromagnetic layer 22 has a strong perpendicular anisotropy (PMA).

In one embodiment of the present application, the reference layer 24 has a magnetic polarization invariance under ferromagnetic coupling of the antiferromagnetic layer 22. The reference layer 24 is made of one or a combination of cobalt Co, iron Fe, nickel Ni, cobalt ferrite CoFe, cobalt boride CoB, iron boride FeB, cobalt iron carbon CoFeC, and cobalt iron boron alloy CoFeB, and the thickness of the reference layer 25 is between 0.5nm and 1.5 nm.

Since the antiferromagnetic layer 22 has a Face Centered Cubic (FCC) crystal structure and the reference layer 24 has a Body Centered Cubic (BCC) crystal structure, the lattices are not matched, in order to realize the transition and ferromagnetic coupling from the antiferromagnetic layer 22 to the reference layer 24, a lattice-blocking layer 23 is typically added between two layers of materials, the material of the lattice-blocking layer 23 is one or a combination of tantalum Ta, tungsten W, molybdenum Mo, hafnium Hf, iron Fe, cobalt Co, including but not limited to cobalt Co (tantalum Ta, tungsten W, molybdenum Mo, or hafnium Hf), iron Fe (tantalum Ta, tungsten W, molybdenum Mo, or hafnium Hf), iron cobalt FeCo (tantalum Ta, tungsten W, molybdenum Mo, or hafnium Hf), or iron cobalt boron FeCoB (tantalum, tungsten W, molybdenum Mo, or hafnium Hf), and the thickness of the lattice-blocking layer 23 is 0.1nm to 0.5 nm.

In some embodiments, barrier layer 25 is formed of a non-magnetic metal oxide having a thickness between 0.6nm and 1.5 nm, including magnesium oxide MgO, magnesium zinc oxide MgZnO, zinc oxide ZnO, aluminum oxide Al₂O₃MgN, Mg boron oxide, Mg₃B₂O₆Or MgAl₂O₄. Preferably, magnesium oxide MgO may be used.

In an embodiment of the present application, the free layer 26 has a variable magnetic polarization, and is made of a single-layer structure selected from CoB, FeB, CoFeB, or a double-layer structure of CoFe/CoFeB, or CoFeB/(W, Mo, V, Nb, Cr, Hf, Ti, Zr, Ta, Sc, Y, Zn, Ru, Os, Rh, Ir, Pd, and/or Pt)/CoFeB, CoFeB/(W, Mo, V, Nb, Cr, Hf, Ti, Zr, Ta, Sc, Y, Zn, Ru, Os, Rh, Ir, Pd, and/or Pt)/CoFeB, or a three-layer structure of Fe/Co/(W, Mo, V/(W, V, W, Mo, and Pt)/CoFeB, A four-layer structure of niobium Nb, chromium Cr, hafnium Hf, titanium Ti, zirconium Zr, tantalum Ta, scandium Sc, yttrium Y, zinc Zn, ruthenium Ru, osmium Os, rhodium Rh, iridium Ir, palladium Pd and/or platinum Pt)/CoFeB, cobalt ferrite/CoFeB/(tungsten W, molybdenum Mo, vanadium V, niobium Nb, chromium Cr, hafnium Hf, titanium Ti, zirconium Zr, tantalum Ta, scandium Sc, yttrium Y, zinc Zn, ruthenium Ru, osmium Os, rhodium Rh, iridium Ir, palladium Pd and/or platinum Pt)/CoFeB; the thickness of the free layer 26 is between 1.2nm and 3.0 nm.

In an embodiment of the present application, after all the film layers are deposited, an annealing process is performed on the magnetic tunnel junction 20 at a temperature of no less than 350 ℃ for no less than 30 minutes to change the reference layer 24 and the free sub-layer 26 from an amorphous phase to a Body Centered Cubic (BCC) crystal structure.

Through the design of the multilayer covering layer structure, relatively high tunneling magnetic resistance rate can be kept on the premise that the area product of junction resistance is reduced, and meanwhile, the situation that deposited metal penetrates through the covering layer and reaches the interface of a free layer/a bottom covering layer in a deposition or/and annealing process of the covering layer is avoided, so that thermal stability is kept.

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 (10)

1. A magnetic tunnel junction structure of a magnetic random access memory is arranged in a magnetic random access memory unit, the magnetic tunnel junction is formed by sputtering deposition and is subjected to thermal annealing treatment after deposition, the magnetic tunnel junction structure comprises a covering layer, a free layer, a barrier layer, a reference layer, a lattice partition layer, an anti-ferromagnetic layer and a seed layer from top to bottom, and the covering layer is characterized by comprising:

a first capping layer disposed above the free layer, formed of a metal oxide having a cubic lattice structure of NaCl crystal system, for providing an additional magnetic perpendicular anisotropy interface to the free layer;

a second capping layer disposed over the first capping layer, formed of a ferromagnetic material, the second capping layer having a thickness of no greater than 1.5 atomic layers;

a third capping layer disposed above the second capping layer and formed of a high-Z metal having a high electronegativity;

a fourth capping layer disposed above the third capping layer and formed of a low-Z metal having a high electronegativity;

a fifth cover layer disposed over the fourth cover layer;

wherein the second capping layer realizes the transformation from an amorphous state to a crystalline state after the thermal annealing treatment, and provides another source of interfacial anisotropy between the first capping layer and the second capping layer; the third capping layer prevents at least one of a material and atoms of the fourth capping layer from diffusing into the first capping layer and the second capping layer during a process.

2. The magnetic tunnel junction structure of the magnetic random access memory of claim 1 wherein the first capping layer has a total thickness of 0.4nm to 2.0nm and is formed of MgO, ZnO, Al₂O₃，MgAl₂O₄，Mg₃B₂O₆，SiMg₂O₄，SiZn₂O₄，SiAl₂O₄，MgZnO₄Or a combination thereof.

3. The magnetic tunnel junction structure of claim 1 wherein the first cladding layer is formed by sputter deposition directly on a metal oxide target or by sputter deposition of a metal target followed by oxidation to convert the deposited metal to metal oxide.

4. The magnetic tunnel junction structure of claim 3 wherein the first capping layer is a bilayer of MgO/MgO_xStructure, x<1，MgO_xFirstly, sputtering deposition is carried out on a Mg metal target material, and then, the sputtering deposited Mg film is oxidized to form MgO_xIs realized in the following manner.

5. The magnetic tunnel junction structure of claim 1 wherein the first cladding layer is formed and then heat treated using infrared, microwave or laser as a radiation source and cooled to room temperature or ultra-low temperature to form a NaCl crystal face-centered cubic lattice structure.

6. The magnetic tunnel junction structure of claim 1 wherein the second capping layer has a thickness of no greater than 0.6nm and is comprised of CoFeB, FeB, CoB, CoC, FeC, CoFeC or combinations thereof, and the second capping layer is used to adjust the coercivity and the perpendicular anisotropy field of the free layer.

7. The magnetic tunnel junction structure of claim 6 wherein the fourth cladding layer has a total thickness of 0.1nm to 4.0nm and is formed of Zr, Nb, Ti, V, Cr, Ta, W, Hf, Mo or a combination thereof, and the fourth cladding layer is configured to absorb at least one of B and C of the second cladding layer.

8. The magnetic tunnel junction structure of claim 1 wherein the third cladding layer has a total thickness of 0nm to 0.5nm and is formed of Ru, Rh, Pd, Ag, Re, Os, Ir, Pt, Au or combinations thereof.

9. The magnetic tunnel junction structure of claim 1, wherein the material of the fifth cladding layer is a single-layer or multi-layer metal or alloy of at least one of Ru and Ir, and the total thickness of the fifth cladding layer is 1.0nm to 10.0 nm.

10. A magnetic random access memory comprising the magnetic tunnel junction structure of any of claims 1-9, a top electrode disposed above the magnetic tunnel junction structure, and a bottom electrode disposed below the magnetic tunnel junction structure.

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