CN112652705B - Magnetic tunnel junction structure and magnetic random access memory thereof - Google Patents

Magnetic tunnel junction structure and magnetic random access memory thereof Download PDF

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CN112652705B
CN112652705B CN201910960367.0A CN201910960367A CN112652705B CN 112652705 B CN112652705 B CN 112652705B CN 201910960367 A CN201910960367 A CN 201910960367A CN 112652705 B CN112652705 B CN 112652705B
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张云森
郭一民
陈峻
肖荣福
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Shanghai Information Technologies Co ltd
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Abstract

The utility model provides a magnetic tunnel junction structure and magnetic random access memory thereof, antiferromagnetic layer in the magnetic tunnel junction structure sets up ferromagnetic superlattice layer, antiferromagnetic coupling layer and magnetic moment diluting layer's three layer construction, antiferromagnetic coupling layer realizes ferromagnetic superlattice layer and the antiferromagnetic coupling of magnetic moment diluting layer, adjusts ferromagnetic superlattice layer, the magnetic moment diluting layer with the reference layer is in saturation magnetic moment of vertical direction is in order to adjust its magnetic leakage field at the free layer, and it makes magnetic tunnel junction have the regulation and control ability of relative preferred magnetic leakage field write current, is favorable to magnetic tunnel junction unit in magnetism, electricity and the promotion of yield and the micromation of device.

Description

Magnetic tunnel junction structure and magnetic random access memory thereof
Technical Field
The present invention relates to the field of memory technology, and more particularly, to a magnetic tunnel junction structure and a magnetic random access memory thereof.
Background
Magnetic random access memory (Magnetic Random Access Memory, MRAM) has, in a magnetic tunnel junction (Magnetic Tunnel Junction; MTJ) with perpendicular anisotropy (Perpendicular Magnetic Anisotropy; PMA), as a free layer for storing information, two magnetization directions in the perpendicular direction, namely: up and down, 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 being empty; during writing, if a signal different from the existing state is input, the magnetization direction of the free layer will be flipped one hundred eighty degrees in the vertical direction. The ability of the free layer magnetization direction of the mram to remain unchanged is called Data Retention (Data Retention) or thermal stability (Thermal Stability), which is different in different applications, and for a typical Non-volatile Memory (NVM), the Data Retention is required to be able to retain Data for 10 years at 125 ℃, and the Data Retention or thermal stability is reduced when the external magnetic field is turned over, the thermal disturbance, the current disturbance, or the read/write operation is repeated. In practical applications, the data retention capability of MRAM is also strongly related to the stability of the Reference Layer (RL), which is usually pinned by an antiferromagnetic Layer (Synthetic Anti-Ferrimagnet Layer, syAF). The antiferromagnetic layer (SyAF) typically contains two superlattice ferromagnetic layers with strong perpendicular anisotropy, with one ruthenium layer to achieve antiferromagnetic coupling of the two-layer superlattice ferromagnetic layers. The design of the reference layer and the antiferromagnetic layer (SyAF) can reduce the influence of the leakage magnetic field on the free layer, however, in the current structure, the requirement of the microminiature MRAM device on the leakage magnetic field is still difficult to meet.
Disclosure of Invention
In order to solve the above technical problems, an object of the present application is to provide a magnetic tunnel junction structure and a magnetic random access memory thereof, which realize pinning of a reference layer, lattice conversion, and reduction/avoidance of the situation of "demagnetizing magnetic coupling".
The aim and the technical problems of the application are achieved by adopting the following technical scheme.
According to one proposed magnetic tunnel junction structure, the top-down structure comprises a Capping Layer (CL), a Free Layer (FL), a barrier Layer (Tunneling Barrier Layer, TBL), a Reference Layer (RL), a lattice isolating Layer (Crystal Breaking Layer, CBL), an antiferromagnetic Layer (Synthetic Anti-Ferrimagnet Layer, syAF) and a Seed Layer (Seed Layer; SL), wherein the antiferromagnetic Layer comprises: a ferromagnetic superlattice layer formed of a transition metal-bonded ferromagnetic material having a face-centered crystalline structure; an antiferromagnetically coupled layer disposed on the ferromagnetic superlattice layer and formed of a metallic material capable of forming antiferromagnetic coupling; and a magnetic moment diluting layer disposed on the antiferromagnetic coupling layer and formed of a diluted magnetic material; the antiferromagnetic coupling layer is used for realizing antiferromagnetic coupling of the ferromagnetic superlattice layer and the magnetic moment diluting layer, and adjusting the saturation magnetic moment of the ferromagnetic superlattice layer and the magnetic moment diluting layer in the vertical direction so as to adjust the leakage magnetic field of the ferromagnetic superlattice layer and the magnetic moment diluting layer in the free layer.
The technical problem of the application can be further solved by adopting the following technical measures.
In an embodiment of the present application, the ferromagnetic superlattice layer is formed of a material selected from the group consisting of cobalt/platinum] n Cobalt or [ cobalt/palladium] n Cobalt, wherein n is greater than or equal to 2.
In one embodiment of the present application, the thickness of the single layer structure of cobalt, platinum or palladium is between 0.1 nm and 1.0 nm; preferably, the platinum or palladium has a thickness of between 0.1 nm and 0.4 nm and the cobalt has a thickness of between 0.15 nm and 0.70 nm. In some embodiments, the thickness of the single layer structure of cobalt, platinum, or palladium is the same or different.
In an embodiment of the present application, the antiferromagnetic coupling layer is made of ruthenium, and the antiferromagnetic coupling layer has a thickness between 0.3 nm and 1.5 nm.
In an embodiment of the present application, the material of the antiferromagnetic coupling layer is iridium, and the thickness of the antiferromagnetic coupling layer is between 0.3 nm and 0.6 nm.
In an embodiment of the present application, the material of the magnetic moment diluting layer is [ cobalt/(platinum, iridium, palladium, magnesium oxide, aluminum oxide, zinc oxide, magnesium zinc oxide, or magnesium aluminum oxide ]] a cobalt/X] b Cobalt, wherein the thickness of platinum, iridium, palladium, magnesium oxide, aluminum oxide, zinc oxide, magnesium zinc oxide or magnesium aluminum oxide is between 0.15 nm and 1.2 nm, a=0 or 1, and b is more than or equal to 1 and less than or equal to 5; x is carbon, nitrogen, oxygen, magnesium, aluminum, silicon, gallium, scandium, titanium, vanadium, chromium, copper, zinc, germanium, strontium, yttrium, zirconium, niobium, molybdenum, technetium, ruthenium, indium, tin, antimony, hafnium, tantalum, tungsten, or a combination thereof.
In one embodiment of the present application, X has a thickness between 0 nm and 0.1 nm and cobalt has a thickness between 0.2 nm and 0.9 nm.
In one embodiment of the present application, the thickness of the single layers of cobalt and X may or may not be the same.
In an embodiment of the present application, the material of the magnetic moment diluting layer is [ cobalt/(platinum, iridium, palladium, magnesium oxide, aluminum oxide, zinc oxide, magnesium zinc oxide, or magnesium aluminum oxide ]] a /(cobalt Y compound, iron Y compound, cobalt iron Y compound, iron boron Y compound, cobalt boron Y compound or cobalt iron boron Y compound), wherein the thickness of platinum, iridium, palladium, magnesium oxide, aluminum oxide, zinc oxide, magnesium zinc oxide or magnesium aluminum oxide is between 0.15 nm and 1.2 nm, a=0 or 1; y is carbon, nitrogen, oxygen, magnesium, aluminum, silicon, gallium, scandium, titanium, vanadium, chromium, copper, zinc, germanium, strontium, yttrium, zirconium, niobium, molybdenum, technetium, ruthenium, indium, tin, antimony, hafnium, tantalum, tungsten, or a combination thereof.
In one embodiment of the present application, the cobalt Y compound, the iron Y compound, the cobalt iron Y compound, the iron boron Y compound, the cobalt boron Y compound, or the cobalt iron boron Y compound has a thickness of between 0.3 nm and 1.2 nm, and the atomic percentage of Y is not more than 30%.
In one embodiment of the present application, an annealing process is performed on the magnetic tunnel junction to cause the reference layer and the free layer to transform from an amorphous structure to a body-centered cubic stacked crystal structure under the template of a face-centered cubic crystal structure barrier layer.
Another object of the present application is to provide a magnetic random access memory, which includes a magnetic tunnel junction structure as described in any one of the above, a top electrode disposed above the magnetic tunnel junction structure, and a bottom electrode disposed below the magnetic tunnel junction structure.
The magnetic moment diluting layer of the magnetic tunnel junction and the magnetic moment of the Reference Layer (RL) are greatly reduced, so that the magnetic tunnel junction is beneficial to the adjustment of the leakage magnetic field of the reference layer, has relatively better capability of adjusting the leakage magnetic field and the write current, and is beneficial to the improvement of magnetism, electricity and yield of the magnetic random access memory and the further miniaturization of devices.
Drawings
FIG. 1 is a schematic diagram of an exemplary MRAM magnetic memory cell structure;
FIG. 2 is a schematic diagram of a magnetic memory cell structure of a magnetic random access memory according to an embodiment of the present application;
fig. 3a and 3b are schematic structural diagrams of antiferromagnetic layers according to embodiments of the present application.
Symbol description
10, a bottom electrode; a magnetic tunnel junction; a seed layer 21; an antiferromagnetic layer 22; lattice isolating layer 23; 24, a reference layer; 25, a barrier layer; 26, a free layer; a cover layer 27; 30, a top electrode; 221 ferromagnetic superlattice layer; 222 an antiferromagnetically coupling layer; 223 a second ferromagnetic superlattice layer; 224 magnetic moment diluting layer.
Detailed Description
Referring to the drawings, wherein like reference numbers refer to like elements throughout. The following description is based on the illustrated embodiments of the present application and should not be taken as limiting other embodiments not described in detail herein.
The following description of the embodiments refers to the accompanying drawings, which illustrate specific embodiments that can be used to practice the present application. The directional terms mentioned in this application, such as "up", "down", "front", "back", "left", "right", "inside", "outside", "side", etc., refer only to the directions of the attached drawings. Accordingly, directional terminology is used to describe and understand the application and is not intended to be limiting of the application.
The terms "first," second, "" third and the like in the description and in the claims of this application and in the above-described figures, if any, are used for distinguishing between similar objects and not necessarily for describing a particular sequential or chronological order. It will be appreciated that the objects so described may be interchanged under appropriate circumstances. Furthermore, the terms "comprise" and "have," as well as variations thereof, are intended to cover a non-exclusive inclusion.
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. The use of expressions in the singular encompasses plural forms of expressions unless the context clearly dictates otherwise. In this specification, it should be understood that terms such as "comprises," "comprising," "includes," and "including" are intended to specify the presence of the stated features, integers, steps, actions, or combinations thereof, disclosed in the specification, but are not intended to preclude the presence or addition of one or more other features, integers, steps, actions, or groups thereof. Like reference numerals in the drawings refer to like parts.
The drawings and description are to be regarded as illustrative in nature, and not as restrictive. In the drawings, like structural elements are denoted by like reference numerals. In addition, for the sake of understanding and convenience of description, the size and thickness of each component shown in the drawings are arbitrarily shown, but the present application is not limited thereto.
In the drawings, the scope of the arrangement of devices, systems, components, circuits, etc. is exaggerated for clarity, understanding, and convenience 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 "comprising" will be understood to mean comprising the recited component, but not excluding any other components. Further, in the specification, "above" means above or below the target assembly, and does not mean necessarily on top based on the direction of gravity.
In order to further describe the technical means and effects adopted by the present invention to achieve the preset purposes, the following description refers to a magnetic tunnel junction structure and a magnetic random access memory thereof according to the present invention, and the specific structure, characteristics and effects thereof are described in detail below with reference to the accompanying drawings and specific embodiments.
FIG. 1 is a schematic diagram of an exemplary MRAM magnetic memory cell structure. The magnetic memory cell structure comprises at least a multilayer structure formed by a bottom electrode 10, a magnetic tunnel junction 20 and a 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 a combination 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 formed by Physical Vapor Deposition (PVD), and is typically planarized after deposition to achieve surface flatness for fabricating the magnetic tunnel junction 20.
In some embodiments, the magnetic tunnel junction 20 includes, from top to bottom, a Capping Layer (CL) 27, a Free Layer (FL) 26, a barrier Layer (Tunneling Barrier Layer, TBL) 25, a Reference Layer (RL) 24, a lattice isolating Layer (Crystal Breaking Layer, CBL) 23, an antiferromagnetic Layer (Synthetic Anti-Ferrimagnet Layer, syAF) 22, and a Seed Layer (Seed Layer, SL) 21.
As shown in fig. 1, the antiferromagnetic Layer 22 includes a first superlattice ferromagnetic Layer (the 1st Ferrimagnet Supper-Lattice Layer,1st FM-SL) 221, and an antiferromagnetic coupling Layer 222 and a second superlattice ferromagnetic Layer (the 2nd Ferrimagnet Supper-Lattice Layer,2nd FM-SL) 224, respectively, from bottom to top. A ferromagnetic superlattice layer 221 formed of a transition metal-bonded ferromagnetic material having a face-centered crystal structure; an antiferromagnetically coupling layer 222 disposed on the ferromagnetic superlattice layer 221 and formed of a metallic material capable of forming antiferromagnetically coupling; a second ferromagnetic superlattice layer 223 disposed on the antiferromagnetically coupling layer 222 and formed of a transition metal-bonded ferromagnetic material having a face-centered crystalline structure; wherein the antiferromagnetic coupling layer 222 bonds the ferromagnetic superlattice layer 221 with the second ferromagnetic superlattice layer 224 for antiferromagnetic coupling of the ferromagnetic superlattice layers, the magnetic tunnel junction 20 comprising lattice switching and strong ferromagnetic coupling between the antiferromagnetic layer 22 and the reference layer 24.
In a magnetic tunnel junction 20 having perpendicular anisotropy, the free layer 26 functions to store information, possessing two magnetization directions in the perpendicular direction, namely: up and down, respectively, to "0" and "1" or "1" and "0" in the binary system. The magnetization direction of the free layer 26 remains unchanged when reading information or being empty; during writing, if a signal of a different state than that of the prior art is input, the magnetization of the free layer 26 will be reversed 180 degrees in the perpendicular direction. The ability of the free layer 26 of the magnetic random access memory to maintain the magnetization direction unchanged is called Data Retention (Data Retention) or thermal stability (Thermal Stability). The data retention capacity can be calculated using the following formula:
Figure BDA0002228719470000051
wherein τ is the time when the magnetization vector is unchanged under the thermal disturbance condition 0 For the time of attempt (typically 1 ns), E is the free layerEnergy barriers, k B Is the boltzmann constant, and T is the operating temperature.
The thermal stability factor (Thermal Stability factor) can then be expressed as follows:
Figure BDA0002228719470000052
wherein K is eff Is the effective energy density of the free layer in each direction, V is the volume of the free layer, K V For bulk anisotropy constant M s The magnetization constant in the vertical direction of Nz is the saturation magnetization of the free layer, t is the thickness of the free layer, K i CD is the critical dimension of the MRAM (i.e., diameter of free layer), A is the interfacial anisotropy constant s For stiffness integral exchange constants, k is the critical dimension for the free layer 26 switching mode transition from domain switching (i.e., magnetization switching processed by "macro-spin" switching) to the inverted domain nucleation/growth (i.e., magnetization switching processed by nucleation of a reversed domain and propagation of a domain wall) mode. Experiments have shown that the free layer exhibits in-plane anisotropy when thicker and perpendicular anisotropy, K when thinner V Is generally negligible, whereas the contribution of the demagnetizing energy to the perpendicular anisotropy is negative, so that the perpendicular anisotropy comes entirely from the interface effect (K i )。
In some embodiments, the thermal stability factor is also affected by the static magnetic Field, particularly the leakage magnetic Field (Stray Field) from the reference layer 24, in combination with the difference in the direction of magnetization imparted to the free layer 26 by the static magnetic Field, to produce an increasing or decreasing effect.
In some embodiments, the ferromagnetic superlattice layer 221 and the second ferromagnetic superlattice layer 224 both have a strong perpendicular anisotropy, and the primary material of the antiferromagnetic coupling layer 222 is ruthenium (Ru), which aids in antiferromagnetic coupling of the two ferromagnetic superlattice layers, which is known in the industry as RKKY (Ruderman-Kittel-Kasuya-Yosida) coupling. Wherein the antiferromagnetically coupling layer (SyAF) 22 has an energy density J per unit area RKKY The method comprises the following steps:
J RKKY ＝M S tH RKKY
(3)
wherein H is RKKY For RKKY antiferromagnetically coupled field, H RKKY The larger the synthetic counter magnet (SyAF) the more stable. In some embodiments, H RKKY The thickness of Ru has a strong correlation with the antiferromagnetic coupling layer 222, in the range of 0.3 nm to 2.0 nm, with two H' s RKKY Oscillation peaks.
In some embodiments, the reference layer 24 is made to have a body-centered cubic structure after annealing by the lattice isolating layer 23, and a ferromagnetic coupling of the second ferromagnetic superlattice layer 224 having a face-centered cubic structure and the reference layer 24 having a body-centered cubic structure is achieved.
Due to the presence of the synthetic antiferromagnetic layer 22, the leakage magnetic fields from the reference layer 24 and the synthetic antiferromagnetic layer 22 may partially cancel, quantitatively defining the total leakage magnetic field from the reference layer 24 and the synthetic antiferromagnetic layer 22 as H Stray ：
Figure BDA0002228719470000061
Wherein H is k eff Is a vertical effective anisotropic field, H k eff ＝2(K eff /(μ 0 M s )). Further, defining the magnetization vector perpendicular to the free layer and upward as positive, the leakage magnetic field upward perpendicular to the free layer 26 is positive. Then in the case where the magnetization vectors of the free layer 26 and the reference layer 24 are parallel or antiparallel, their thermal stability factors can be expressed as equations:
Figure BDA0002228719470000062
as the volume of the magnetic free layer 26 decreases, the smaller the spin-polarized current that needs to be injected for a write or switching operation. Critical current I for write operation c0 Is strongly related to thermal stability, which is related toThe equation can be expressed as follows:
Figure BDA0002228719470000063
wherein alpha is a damping coefficient (damping constant),
Figure BDA0002228719470000064
is about the Planck constant, η is spin polarizability. Further, the critical current can be expressed as the following expression when magnetizations are parallel and antiparallel, respectively:
Figure BDA0002228719470000065
in this case, the critical current of the mram in the parallel state and the antiparallel state can be further controlled by controlling the leakage Field (Stray Field).
In some embodiments, the magnetic tunnel junction 20, which is the core memory cell of the magnetic random access memory, must also be compatible with CMOS processing and must be capable of withstanding long-term anneals at 400 ℃.
As noted above, although the design of the double-layer superlattice ferromagnetic layer provides the magnetic tunnel junction with relatively stronger leakage field control capability, it is more difficult to control the influence of the leakage field on the free layer, and the situation of "demagnetizing coupling" still occurs.
Fig. 2 is a schematic diagram of a magnetic memory cell of the magnetic random access memory of the present application, and fig. 3a and 3b are schematic diagrams of antiferromagnetic layers of the embodiment of the present application, please refer to fig. 1 for better understanding. The magnetic tunnel junction structure comprises a cover layer 27, a free layer 26, a barrier layer 25, a reference layer 24, a lattice isolating layer 23, an antiferromagnetic layer 22 and a seed layer 21 from top to bottom, wherein the antiferromagnetic layer 22 comprises: a ferromagnetic superlattice layer 221 formed of a transition metal-bonded ferromagnetic material having a face-centered crystal structure; an antiferromagnetically coupling layer 222 disposed on the ferromagnetic superlattice layer 221 and formed of a metal material capable of forming antiferromagnetic coupling; and a magnetic moment diluting layer (Magnetic Moment Diluted Layer, MMDL) 224 disposed on the antiferromagnetic coupling layer 222 and formed of a magnetically diluted material; wherein the antiferromagnetic coupling layer 222 effects antiferromagnetic coupling of the ferromagnetic superlattice layer 221 and the moment diluting layer 224, adjusting the saturation moment of the ferromagnetic superlattice layer 221, the moment diluting layer 224 and the reference layer 24 in the vertical direction to adjust the leakage field at the free layer 26.
In one embodiment of the present application, the ferromagnetic superlattice layer 221 is formed of a material selected from the group consisting of cobalt Co/platinum Pt] n Cobalt Co or [ cobalt Co/palladium Pd ]] n A multi-layer structure of cobalt Co, wherein n is greater than or equal to 2.
In one embodiment of the present application, the thickness of the single layer structure of cobalt Co, platinum Pt or palladium Pd is between 0.1 nm and 1.0 nm; preferably, the thickness of the platinum Pt or palladium Pd is between 0.1 nm and 0.4 nm, and the thickness of the cobalt Co is between 0.15 nm and 0.70 nm. In some embodiments, the thicknesses of the single layer structures of cobalt Co, platinum Pt, or palladium Pd are the same or different.
In an embodiment of the present application, the material of the antiferromagnetic coupling layer 222 is ruthenium Ru, and the thickness of the antiferromagnetic coupling layer 222 is between 0.3 nm and 1.5 nm, and the RKKY first oscillation peak and the RKKY second oscillation peak can be selected.
In an embodiment of the present application, the material of the antiferromagnetic coupling layer 222 is iridium Ir, and the thickness of the antiferromagnetic coupling layer 222 is between 0.3 nm and 0.6 nm, which corresponds to the RKKY first oscillation peak.
In one embodiment of the present application, the material of the magnetic moment diluting layer 224 is [ cobalt Co/(platinum Pt, iridium Ir, palladium Pd, magnesium oxide MgO, aluminum oxide Al ] 2 O 3 Zinc oxide ZnO, magnesium zinc oxide MgZnO or magnesium aluminum oxide MgAlO)] a Cobalt Co/X] b Cobalt, wherein platinum Pt, iridium Ir, palladium Pd, magnesium oxide MgO, aluminum oxide Al 2 O 3 The thickness of zinc oxide ZnO, magnesium zinc oxide MgZnO or magnesium aluminum oxide MgAlO is between 0.15 nm and 1.2 nm, a=0 or 1, and b is more than or equal to 1 and less than or equal to 5; x is C, N, O, mg, al, si, ga, or scandiumSc, titanium Ti, vanadium V, chromium Cr, copper Cu, zinc Zn, germanium Ge, strontium Sr, yttrium Y, zirconium Zr, niobium Nb, molybdenum Mo, technolgy Tc, ruthenium Ru, indium In, tin Sn, antimony Sb, hafnium Hf, tantalum Ta, tungsten W, or combinations thereof. In some embodiments, X is between 0 nm and 0.1 nm thick and cobalt Co is between 0.2 nm and 0.9 nm thick; the thickness of the single layers of cobalt Co and X may be the same or different.
As shown In FIG. 3a, in some embodiments, each sub-layer of the Magnetic Moment Diluting Layer (MMDL) 224 may be formed In a PVD process chamber, X is an oxide, nitride, or oxynitride of the above-described magnesium Mg, aluminum Al, silicon Si, gallium Ga, scandium Sc, titanium Ti, vanadium V, chromium Cr, copper Cu, zinc Zn, germanium Ge, strontium Sr, yttrium Y, zirconium Zr, niobium Nb, molybdenum Mo, molybdenum Tc, ruthenium Ru, indium In, tin Sn, antimony Sb, hafnium Hf, tantalum Ta, tungsten W, and is formed by reactive ion sputtering (Reactive Ion Sputtering, RIS).
As shown in FIG. 3b, in some embodiments, the material of the magnetic moment diluting layer 224 is [ cobalt Co/(platinum Pt, iridium Ir, palladium Pd, magnesium oxide MgO, aluminum oxide Al ] 2 O 3 Zinc oxide ZnO, magnesium zinc oxide MgZnO or magnesium aluminum oxide MgAlO)] a /(cobalt Y compound, iron Y compound, cobalt iron Y compound, iron boron Y compound, cobalt boron Y compound or cobalt iron boron Y compound), wherein platinum Pt, iridium Ir, palladium Pd, magnesium oxide MgO, aluminum oxide Al 2 O 3 The thickness of zinc oxide ZnO, magnesium zinc oxide MgZnO or magnesium aluminum oxide MgAlO is between 0.15 nm and 1.2 nm, and a=0 or 1; y is C, N, O, mg, al, si, ga, sc, ti, V, cr, cu, zn, ge, sr, Y, zr, nb, mo, tc, ru, in, sn, sb, hf, ta, W or combinations thereof. In some embodiments, the thickness of Y is between 0.3 nm and 1.2 nm, and the atomic percent of Y is no greater than 30%. Wherein the substituted formula of (cobalt Y compound, iron Y compound, cobalt iron Y compound or cobalt iron boron Y compound) is (CoY, feY, coFeY, coFeBY) respectively. Co-sputtering is typically performed in a PVD process chamber.
In some embodiments, the saturation moment of the moment diluting layer 224 is controlled by adjusting the thickness and number of repeating layers of the magnetic metal, X, and the atomic percent of Y in the moment diluting layer 224.
In one embodiment of the present application, the magnetization vector of the reference layer 24 and the magnetization vector of the second ferromagnetic superlattice layer 224 are in the same direction after being initialized by the magnetic field.
In one embodiment of the present application, the saturation moment of the ferromagnetic superlattice layer 221 in the vertical direction is M S1 S 1 t 1 The saturation magnetic moment of the magnetic moment diluting layer 224 in the vertical direction is M S2 S 2 t 2 The saturation magnetic moment of the reference layer 24 in the vertical direction is M S3 S 3 t 3 By varying the saturation susceptibility (M S ) And thickness (t) to regulate the total leakage magnetic field (H) Stray ) Thereby achieving the purpose of further regulating and controlling the thermal stability factor and critical current under the parallel and anti-parallel states of magnetization vectors. To obtain better ability to read, write and store information.
In some embodiments, the saturated magnetic moment (α) of the ferromagnetic superlattice layer 221, the magnetic moment diluting layer 224, and the reference layer 24 satisfy the following relationship:
Figure BDA0002228719470000081
Figure BDA0002228719470000091
in some embodiments, alpha is less than or equal to 100%, more preferably alpha is less than or equal to 80%, in which case the use of a magnetic moment diluting layer 224 in place of the second ferromagnetic superlattice layer 223 may greatly reduce the sum of the magnetic moments of the magnetic moment diluting layer 224 and the reference layer 24, greatly facilitating the leakage of magnetic field (H Stray ) And the optimization of write current adjustment, which is very beneficial to the improvement of magnetism, electricity and yield of the magnetic random access memory and the further miniaturization of the device.
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 titanium Ti, titanium nitride TiN, tantalum Ta, tantalum nitride TaN, tungsten W, tungsten nitride WN, ruthenium Ru, palladium Pt, chromium Cr, chromium cobalt CrCo, nickel Ni, chromium nickel CrNi, cobalt boride CoB, iron boride FeB, cobalt iron boron CoFeB, and the like. In some embodiments, the seed layer 21 may be selected from one of cobalt iron boron CoFeB/tantalum Ta/platinum Pt, tantalum Ta/ruthenium Ru, tantalum Ta/platinum Pt/ruthenium Ru, cobalt iron boron CoFeB/tantalum Ta/platinum Pt/ruthenium Ru, and other multilayer structures.
In some embodiments, the reference layer 24 of the magnetic tunnel junction 20 has magnetic polarization invariance under the ferromagnetic coupling of the antiferromagnetic layer 22. The material of the reference layer 24 is one or a combination of cobalt Co, iron Fe, nickel Ni, cobalt ferrite CoFe, cobalt boride CoB, iron boride FeB, cobalt iron carbon CoFeC, cobalt iron boron CoFeB and cobalt iron boron carbon CoFeBC, and the thickness of the reference layer 24 is between 0.5 nm and 2.0 nm.
In some embodiments, since the antiferromagnetic layer 22 has a Face Centered Cubic (FCC) crystal structure and the crystal structure of the reference layer 24 is Body Centered Cubic (BCC), the crystal lattices are not matched, and in order to achieve transition and ferromagnetic coupling from the antiferromagnetic layer 22 to the reference layer 24, a layer of lattice spacing layer 23 is typically added between the two layers of materials, the material of the lattice spacing layer 23 is one selected from tantalum Ta, tungsten W, molybdenum Mo, hafnium Hf, iron Fe, cobalt Co, or a combination thereof, and the thickness of the lattice spacing layer 23 is between 0.1 nm and 0.5 nm.
In some embodiments, the barrier layer 25 of the magnetic tunnel junction 20 is formed of a non-magnetic metal oxide having a thickness of between 0.6 nm and 1.5 nm, the non-magnetic metal oxide including magnesium oxide MgO, magnesium zinc oxide MgZnO, zinc oxide ZnO, aluminum oxide Al 2 O 3 Magnesium nitride MgN, magnesium boron oxide Mg 3 B 2 O 6 Or MgAl 2 O 4 . Preferably, magnesium oxide MgO may be used.
In one embodiment of the present application, the free layer 26 of the magnetic tunnel junction 20 has a variable magnetic polarization characteristic, and the material of the free layer 26 is a single layer structure selected from cobalt boride CoB, iron boride FeB, cobalt iron boron CoFeB, or a double layer structure of cobalt boride CoFe/cobalt iron boron CoFeB, iron Fe/cobalt iron boron CoFeB, or a three layer structure of iron boron FeB/(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)/cobalt iron boron CoFeB, cobalt iron boron 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 Ir, palladium Pd and/or platinum Pt)/cobalt iron boron, or a four-layer structure of iron/cobalt-iron-boron/(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)/cobalt-iron-boron, cobalt-iron/cobalt-iron-boron/(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)/cobalt-iron-boron; the free layer 26 has a thickness of between 1.2 nm and 3.0 nm.
In an embodiment of the present application, the material of the capping layer 27 of the magnetic tunnel junction 20 is a double layer structure selected from (one of magnesium Mg, magnesium oxide MgO, magnesium zinc oxide MgZnO, magnesium boron oxide MgBO or magnesium aluminum oxide MgAlO)/(one of tungsten W, molybdenum Mo, magnesium Mg, niobium Nb, ruthenium Ru, hafnium Hf, vanadium V, chromium Cr or platinum Pt), or a three layer structure of magnesium oxide MgO/(one of tungsten W, molybdenum Mo or hafnium Hf)/ruthenium Ru, or a four layer structure of magnesium oxide/platinum/(one of tungsten, molybdenum or hafnium)/ruthenium. In some embodiments, the choice of magnesium oxide (MgO) can provide an additional source of interfacial anisotropy for the Free Layer (FL) 26, thereby increasing thermal stability.
In one embodiment of the present application, an annealing process is performed on the magnetic tunnel junction 20 at a temperature not less than 350 ℃ to cause the reference layer 24 and the free layer 26 to transform from an amorphous structure to a body-centered cubic stacked crystal structure under the template of sodium chloride (NaCl) type of the face-centered cubic crystal structure barrier layer 25.
Referring to fig. 2 to 3B, in an embodiment of the present application, a magnetic random access memory includes a plurality of memory cells, wherein each memory cell includes any one of the magnetic tunnel junction 20 structures described above, 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 one embodiment of the present application, the bottom electrode 10, the magnetic tunnel junction 20, and the top electrode 30 are all completed using a physical vapor deposition process.
The magnetic moment diluting layer of the magnetic tunnel junction and the magnetic moment of the Reference Layer (RL) are greatly reduced, so that the magnetic tunnel junction is beneficial to the adjustment of the leakage magnetic field of the reference layer, has relatively better capability of adjusting the leakage magnetic field and the write current, and is beneficial to the improvement of magnetism, electricity and yield of the magnetic random access memory and the further miniaturization of devices.
The terms "in an embodiment" and "in various embodiments" and the like are used repeatedly. This phrase generally does not refer to the same embodiment; but it may also refer to the same embodiment. The terms "comprising," "having," "including," and the like are synonymous, unless the context clearly dictates otherwise.
The foregoing description is only illustrative of the present application and is not intended to be limiting, since the present application is described in terms of specific embodiments, but rather is not intended to be limited to the details of the embodiments disclosed herein, and any and all modifications, equivalent to the above-described embodiments, may be made without departing from the scope of the present application, as long as the equivalent changes and modifications are within the scope of the present application.

Claims (6)

1. A magnetic tunnel junction structure disposed in a magnetic random access memory cell, the magnetic tunnel junction comprising, from top to bottom, a capping layer, a free layer, a barrier layer, a reference layer, a lattice barrier layer, an antiferromagnetic layer, and a seed layer, the antiferromagnetic layer comprising:
a ferromagnetic superlattice layer formed of a transition metal-bonded ferromagnetic material having a face-centered crystalline structure;
an antiferromagnetically coupled layer disposed on the ferromagnetic superlattice layer and formed of a transition metal material capable of forming antiferromagnetically coupling; and a magnetic moment diluting layer disposed on the antiferromagnetic coupling layer and formed of a diluted magnetic material; the antiferromagnetic coupling layer is used for realizing antiferromagnetic coupling of the ferromagnetic superlattice layer and the magnetic moment diluting layer, regulating the saturation magnetic moment of the ferromagnetic superlattice layer and the reference layer in the vertical direction so as to regulate the leakage magnetic field of the ferromagnetic superlattice layer and the reference layer in the free layer, wherein the antiferromagnetic coupling layer is made of ruthenium or iridium, when the antiferromagnetic coupling layer is made of ruthenium, the antiferromagnetic coupling layer is 0.3-1.5 nm thick, and when the antiferromagnetic coupling layer is made of iridium, the antiferromagnetic coupling layer is 0.3-0.6 nm thick; the magnetic moment diluting layer is made of [ cobalt/(platinum, iridium, palladium, magnesium oxide, aluminum oxide, zinc oxide, magnesium zinc oxide or magnesium aluminum oxide) ] a/[ cobalt/X ] b cobalt, wherein the thickness of the platinum, iridium, palladium, magnesium oxide, aluminum oxide, zinc oxide, magnesium zinc oxide or magnesium aluminum oxide is between 0.15 nm and 1.2 nm, a=1, and 1-b-5; x is carbon, nitrogen, oxygen, magnesium, aluminum, silicon, gallium, scandium, titanium, vanadium, copper, zinc, germanium, strontium, yttrium, zirconium, niobium, molybdenum, technetium, ruthenium, indium, tin, hafnium, tantalum, tungsten, or a combination thereof; x has a thickness of 0 nm to 0.1 nm and cobalt has a thickness of 0.2 nm to 0.9 nm.
2. The magnetic tunnel junction structure of claim 1 wherein the ferromagnetic superlattice layer material is selected from the group consisting of a multi-layer structure of [ cobalt/platinum ] ncobalt or [ cobalt/palladium ] ncobalt, wherein n is greater than or equal to 2.
3. The magnetic tunnel junction structure of claim 1 wherein the thickness of the single layers of cobalt and X may be the same or different.
4. The magnetic tunnel junction structure of claim 1 wherein the material of the magnetic moment diluting layer is [ cobalt/(platinum, iridium, palladium, magnesium oxide, aluminum oxide, zinc oxide, magnesium zinc oxide, or magnesium aluminum oxide) ] a/(cobalt Y compound, iron Y compound, cobalt iron Y compound, iron boron Y compound, cobalt boron Y compound, or cobalt iron boron Y compound), wherein the thickness of platinum, iridium, palladium, magnesium oxide, aluminum oxide, zinc oxide, magnesium zinc oxide, or magnesium aluminum oxide is between 0.2 nm and 1.2 nm, a = 0 or 1; y is carbon, nitrogen, oxygen, magnesium, aluminum, silicon, gallium, scandium, titanium, vanadium, chromium, copper, zinc, germanium, strontium, yttrium, zirconium, niobium, molybdenum, technetium, ruthenium, indium, tin, antimony, hafnium, tantalum, tungsten, or a combination thereof.
5. The magnetic tunnel junction structure of claim 4 wherein Y is between 0.3 nm and 1.2 nm thick and has an atomic percent of Y of no greater than 30%.
6. A magnetic random access memory comprising the magnetic tunnel junction structure of any one of claims 1-5, 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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