CN112652703A - Magnetic tunnel junction structure and magnetic memory thereof - Google Patents

Magnetic tunnel junction structure and magnetic memory thereof Download PDF

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CN112652703A
CN112652703A CN201910960361.3A CN201910960361A CN112652703A CN 112652703 A CN112652703 A CN 112652703A CN 201910960361 A CN201910960361 A CN 201910960361A CN 112652703 A CN112652703 A CN 112652703A
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layer
cobalt
magnetic
tunnel junction
free layer
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张云森
郭一民
陈峻
肖荣福
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Shanghai Ciyu Information Technologies Co Ltd
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Shanghai Ciyu Information Technologies Co Ltd
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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
    • H—ELECTRICITY
    • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
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    • H10N50/00—Galvanomagnetic devices
    • H10N50/10—Magnetoresistive devices
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    • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H10N—ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H10N50/00—Galvanomagnetic devices
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    • H10N50/85—Magnetic active materials

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Abstract

The application provides a magnetic tunnel junction structure and a magnetic memory thereof, wherein the magnetic tunnel junction structure comprises a free layer with a double-layer structure, a vertical anisotropy enhancement layer formed by a metal oxide layer containing a doping element between the two free layers, and a magnetic damping barrier layer arranged above the free layer. The double free layer structure with the enhanced vertical anisotropy is beneficial to improving the thermal stability by regulating and controlling the energy barrier of the free layer, and is beneficial to reducing the write current by regulating and controlling the damping coefficient.

Description

Magnetic tunnel junction structure and magnetic memory thereof
Technical Field
The present invention relates to the field of memory technologies, and in particular, to a magnetic tunnel junction structure and a magnetic memory thereof.
Background
Magnetic memory (MRAM) in a Magnetic Tunnel Junction (MTJ) having Perpendicular Anisotropy (PMA), as a free layer for storing information, there are two magnetization directions in the Perpendicular 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 present 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 density of a magnetic memory, in recent years, the Critical Dimension (Critical Dimension) of a magnetic tunnel junction is becoming smaller, and as the Dimension is further reduced, it is found that the thermal stability factor (v) of the magnetic tunnel junction is drastically deteriorated. In order to increase the thermal stability factor (v) of the ultra-small MRAM cell device, the effective perpendicular effective anisotropy energy density may be increased by reducing the thickness of the free layer, adding or changing the free layer to a material with a low saturation magnetic susceptibility, and the like, thereby maintaining a higher thermal stability factor (v), but the Tunneling Magnetoresistance Ratio (TMR) of the magnetic Tunnel junction may be reduced, thereby increasing the error rate of the memory read operation.
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 memory thereof, in which vertical anisotropy is enhanced by a double-layer free layer design and element doping.
The purpose of the application and the technical problem to be solved are realized by adopting the following technical scheme.
According to the present application, a magnetic tunnel junction structure comprises, from top to bottom, a Capping Layer (CL), a magnetic damping Barrier Layer, a Free Layer (FL), a Barrier Layer (TBL), a Reference Layer (RL), a lattice Breaking Layer (CBL), an antiferromagnetic Anti-ferromagnetic Layer (SyAF), and a Seed Layer (Seed Layer; SL), wherein the Free Layer comprises: a first free layer which is a variable magnetic polarization layer and is formed by a magnetic metal alloy; a vertical anisotropy enhancement layer disposed on the first free layer, the vertical anisotropy enhancement layer being formed of a metal oxide layer containing a doping element; a second free layer disposed on the vertical anisotropy enhancing layer, the second free layer being a variable magnetic polarization layer formed of a magnetic metal or a compound thereof; and the magnetic damping blocking layer is arranged on the second free layer and is formed by nonmagnetic metal or oxide thereof.
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 material of the first free layer is a single-layer structure selected from cobalt boride, iron boride, cobalt-iron-boron alloy, or a double-layer structure of cobalt boride/cobalt-iron-boron alloy, iron/cobalt-iron-boron alloy, or a three-layer structure of iron boride/(tungsten, molybdenum, vanadium, niobium, hafnium, titanium, zirconium, tantalum, scandium, yttrium, zinc, ruthenium, osmium, rhodium, iridium, palladium, and/or platinum)/cobalt-iron-boron alloy, cobalt-iron-boron alloy/(tungsten, molybdenum, vanadium, niobium, chromium, hafnium, titanium, zirconium, scandium, yttrium, zinc, osmium, rhodium, iridium, palladium, and/or platinum)/cobalt-iron-boron alloy, or a three-layer structure of iron/cobalt-iron-boron alloy/(tungsten, molybdenum, vanadium, niobium, chromium, hafnium, titanium, zirconium, scandium, tantalum, yttrium, zinc, ruthenium, osmium, rhodium, iridium, palladium, and/or platinum)/cobalt-iron-boron alloy, A four-layer structure of cobalt ferrite/cobalt iron boron alloy/(tungsten, molybdenum, vanadium, niobium, chromium, hafnium, titanium, zirconium, tantalum, scandium, yttrium, zinc, ruthenium, osmium, rhodium, iridium, palladium and/or platinum)/cobalt iron boron alloy; the thickness of the first free layer is between 1.2 nm and 3.0 nm.
In an embodiment of the present application, the material of the second free layer is at least one selected from iron, cobalt, nickel, cobalt ferrite, iron boride, cobalt boride, tungsten, molybdenum, vanadium, niobium, chromium, hafnium, titanium, zirconium, tantalum, scandium, yttrium, zinc, ruthenium, osmium, rhodium, iridium, palladium, platinum, and cofeb alloys.
In an embodiment of the present application, the material of the second free layer is a single-layer structure selected from cofeb, or a double-layer structure of cofeb, fe/cofeb, or a three-layer structure of (cobalt boride, iron boride, or cofeb)/(tungsten, molybdenum, vanadium, niobium, chromium, hafnium, titanium, zirconium, tantalum, scandium, yttrium, zinc, ruthenium, osmium, rhodium, iridium, palladium, and/or platinum)/(cobalt boride, iron boride, or cofeb), or an alloy of fe/cofeb/(tungsten, molybdenum, vanadium, niobium, chromium, hafnium, titanium, zirconium, tantalum, scandium, yttrium, zinc, ruthenium, osmium, rhodium, iridium, palladium, and/or platinum)/cofeb, alloy of fe/cofeb/(tungsten, molybdenum, vanadium, niobium, chromium, hafnium, titanium, zirconium, scandium, tantalum, yttrium, zinc, ruthenium, osmium, rhodium, ruthenium, osmium, rhodium, chromium, hafnium, titanium, zirconium, scandium, tantalum, yttrium, zinc, ruthenium, cobalt, vanadium, niobium, chromium, hafnium, Iridium, palladium and/or platinum)/ferrocobalt-boron alloy; the thickness of the second free layer is between 0.5 nm and 3.0 nm.
In an embodiment of the present application, the second free layer has a single-layer structure or a double-layer structure, and a non-magnetic metal is interposed between the single-layer structure and the double-layer structure, where the non-magnetic metal includes tungsten, molybdenum, vanadium, niobium, chromium, hafnium, titanium, zirconium, tantalum, scandium, yttrium, zinc, ruthenium, osmium, rhodium, iridium, palladium, and/or platinum.
In an embodiment of the present application, the second free layer has a three-layer structure, and the thickness of the first layer (cobalt boride, iron boride or cobalt-iron-boron alloy) is between 0.2 nm and 1.4 nm; the second layer (tungsten, molybdenum, vanadium, niobium, chromium, hafnium, titanium, zirconium, tantalum, scandium, yttrium, zinc, ruthenium, osmium, rhodium, iridium, palladium and/or platinum) has a thickness of between 0.1 nm and 0.6 nm; the thickness of the third layer (cobalt boride, iron boride or cobalt-iron-boron alloy) is between 0.2 nm and 1.0 nm.
In an embodiment of the present application, the second free layer has a three-layer structure of cofeb/(tungsten, molybdenum, vanadium, niobium, chromium, hafnium, titanium, zirconium, tantalum, scandium, yttrium, zinc, ruthenium, osmium, rhodium, iridium, palladium, and/or platinum)/cofeb, and in the cofeb of the first layer, the atomic ratio of cobalt to iron is 1:3 to 3:1, and the atomic percentage of boron is 15% -40%; in the third layer of the cobalt-iron-boron alloy, the atomic ratio of cobalt to iron is 1: 3-3: 1, and the atomic percentage of boron is 15% -40%.
In an embodiment of the present application, the vertical anisotropy enhancing layer is a doped metal oxide layer.
In an embodiment of the present application, in the perpendicular anisotropy enhancing layer, the metal oxide layer is magnesium oxide, zinc oxide, magnesium zinc oxide, zirconium oxide, aluminum oxide or magnesium aluminum oxide, and the total thickness thereof is between 0.3 nm and 1.5 nm.
In an embodiment of the present application, the doping element is boron, carbon, magnesium, aluminum, silicon, calcium, scandium, titanium, vanadium, chromium, manganese, iron, cobalt, nickel, copper, zinc, gallium, germanium, yttrium, zirconium, niobium, molybdenum, ruthenium, technetium, rhodium, palladium, silver, indium, hafnium, tantalum, tungsten, rhenium, osmium, iridium, platinum, or gold. The realization mode can be that the sputtering deposition is carried out on the doped oxide target material or the co-sputtering deposition is carried out on the oxide target material and the doped element target material in the PVD process cavity.
In an embodiment of the present application, the metal oxide layer containing the doping element is uniformly doped, and the doping ratio is 0.5% to 10%.
In another embodiment of the present application, the doped element-containing metal oxide layer is a metal oxide layer with a single or multiple insertion of doped element sublayers.
In another embodiment of the present application, the doping element is carbon, magnesium, aluminum, silicon, calcium, scandium, titanium, vanadium, chromium, manganese, iron, cobalt, nickel, copper, zinc, gallium, germanium, yttrium, zirconium, niobium, molybdenum, ruthenium, technetium, rhodium, palladium, silver, indium, hafnium, tantalum, tungsten, rhenium, osmium, iridium, platinum, or gold, preferably magnesium, titanium, vanadium, chromium, manganese, iron, cobalt, or nickel, and the doping element sub-layer has a thickness of not more than 0.2 nm, preferably not more than 0.1 nm.
In an embodiment of the present application, the material of the magnetic damping barrier layer is a metal selected from magnesium, zinc, aluminum, copper, calcium, titanium, vanadium, chromium, aluminum, or a metal oxide or a metal nitride thereof.
In an embodiment of the present application, the thickness of the magnetic damping barrier layer is between 0.5 nm and 3.0 nm.
It is another object of the present invention to provide a magnetic memory device, wherein the storage unit comprises any one of the above-mentioned 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.
According to the magnetic tunnel junction unit structure, the double-layer free layer is in ferromagnetic coupling, and under the condition of thermal disturbance or an external magnetic field, in order to turn over the magnetization vector of the free layer, energy larger than the sum of the energy barrier of the free layer and the energy barrier of the thermal stability enhancement layer is required to be provided, so that the thermal stability is improved; secondly, an interface anisotropy source can be additionally provided through the doped vertical anisotropy enhancement layer, so that the thermal stability is further improved; meanwhile, due to the introduction of the doping element or the conductive element, the junction Resistance Area (Resistance Area Product) can be further reduced, which is beneficial to the manufacture of a subminiature MRAM device; thirdly, the damping coefficient of the whole film structure is reduced through the magnetic damping barrier layer, so that the reduction and the stability of the read-write current are facilitated; fourthly, the tunneling magnetic resistance rate is not influenced by the addition of the second free layer; fifthly, through the design of the double-layer free layer, the whole thickness of the free layer can be increased or maintained, the reduction of the damping coefficient is facilitated, and therefore the critical write current cannot be increased.
Drawings
FIG. 1 is a schematic diagram of an exemplary magnetic memory cell structure of a magnetic memory;
FIG. 2 is a schematic diagram of a magnetic memory cell structure of a magnetic memory according to an embodiment of the present application;
FIG. 3A is a schematic illustration showing a doping structure of a vertical anisotropy enhancing layer according to an embodiment of the present application;
fig. 3B is a schematic view of a conductive via structure of a vertical anisotropic enhancement layer 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 "comprising" and "having," as well as variations thereof, such as, for example, 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 provided for a magnetic tunnel junction structure and a magnetic memory thereof according to the present invention with reference to the accompanying drawings and the embodiments.
FIG. 1 is a diagram of an exemplary magnetic memory cell structure of a magnetic memory. The magnetic memory cell structure includes a multi-layer structure formed by at least a Bottom Electrode (BE) 110, a Magnetic Tunnel Junction (MTJ)200, and a Top Electrode (Top Electrode) 310.
In some embodiments, the bottom electrode 110 is titanium (Ti), titanium nitride (TiN), tantalum (Ta), tantalum nitride (TaN), ruthenium (Ru), tungsten (W), tungsten nitride (WN), or combinations thereof; the top electrode 310 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 110 is deposited to achieve surface flatness for the magnetic tunnel junction 200.
In some embodiments, the magnetic tunnel junction 200 includes, 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 layer or a multi-layer structure of cofeb, fe/cofeb, or cofeb/(one of ta, w, mo, or hf)/cofeb. To increase the density of the magnetic 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, which is not favorable for the reading operation of the device.
FIG. 2 is a schematic diagram of a magnetic memory cell structure of a magnetic memory according to an embodiment of the present application; FIG. 3A is a schematic view of a conductive doping structure of a vertical anisotropy enhancing layer according to an embodiment of the present application; fig. 3B is a schematic view of a conductive via structure of a vertical anisotropic enhancement layer according to an embodiment of the present application. 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 200 includes a Capping Layer (CL) 290, a magnetic damping Barrier Layer 280, a Free Layer (FL) 260, a Barrier Layer (Tunneling 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 from top to bottom, wherein the Free Layer includes: a first free layer 260a which is a variable magnetic polarization layer, wherein the first free layer 260a is formed of a magnetic metal alloy; a vertical anisotropy enhancing layer 270 disposed on the first free layer 260a, the vertical anisotropy enhancing layer 270 being formed of a metal oxide layer containing a doping element; a second free layer 260b disposed on the vertical anisotropy enhancing layer 270, the second free layer 260b being a variable magnetic polarization layer and formed of a magnetic metal or a compound thereof; and the magnetic damping blocking layer 280 is disposed on the second free layer 260b, and the magnetic damping blocking layer 280 is formed of a non-magnetic metal or an oxide thereof.
In some embodiments, the magnetization vector in the second free layer 260b is always perpendicular to the first free layer 260a interface and parallel to the magnetization vector in the first free layer 260 a.
In an embodiment of the present application, the material of the first free layer 260a is a single layer structure selected from cobalt boride CoB, iron boride FeB, cobalt iron boron alloy CoFeB, or a double layer structure of cobalt boride CoFe/cobalt iron boron alloy CoFeB, iron Fe/cobalt iron boron alloy CoFeB, or a three layer structure of iron boride 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, Os, rhodium Rh, iridium Ir, palladium Pd and/or platinum Pt)/cobalt iron boron alloy CoFeB, cobalt iron boron alloy CoFeB/(tungsten W, molybdenum Mo, vanadium V, niobium Nb, chromium, hafnium Hf, titanium Ti, zirconium Zr, Ta, tantalum Sc, yttrium Y, zinc Zn, ruthenium, osmium Os, rhodium, Ir, palladium and/or platinum)/cobalt iron boron alloy, or a three layer structure of iron tungsten/cobalt iron boron/(tungsten W/Pt)/cobalt iron boron alloy, A four-layer structure of 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 alloy, cobalt iron/cobalt iron boron alloy/(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, palladium Pd and/or platinum Pt)/cobalt iron boron alloy; the thickness of the first free layer 260a is between 1.2 nm and 3.0 nm.
In an embodiment of the present application, the material of the second free layer 260b is at least one selected from Fe, Co, Ni, CoFe, FeB, CoB, W, Mo, V, Nb, Cr, Hf, Ti, Zr, Ta, Sc, Y, Zn, Ru, Os, Rh, Ir, Pd, Pt, CoFeB.
In some embodiments, the material of the second free layer 260b is a single-layer structure selected from CoFeB, or a double-layer structure of (CoFeB, FeB, CoFeB)/(W, Mo, V, Nb, Cr, Hf, Ti, Zr, Ta, Sc, Y, Zn, Ru, osos, Rh, Ir, Pd, Cr, CoFeB, or CoFeB), or a three-layer structure of Fe/CoFeB/(W, Mo, V, Nb, Cr, Hf, Ti, Zr, Ta, Sc, Y, Zn, Ru, Os, Rh, Ir, Pd, Cr, Fe, or CoFeB)/CoFeB, The cobalt ferrite/cobalt iron boron alloy 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)/cobalt iron boron alloy CoFeB.
In some embodiments, the second free layer 260b has a single-layer structure or a double-layer structure, and a single or multiple times of interposing non-magnetic metal between the layer structures, wherein the non-magnetic metal includes 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.
In some embodiments, the structure of the second free layer 260b is a three-layer structure, the thickness of the first layer (cobalt boride CoB, iron boride FeB, or cobalt iron boron alloy CoFeB) is between 0.2 nm and 1.4 nm; the second layer (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) has a thickness of between 0.1 nm and 0.6 nm; the thickness of the third layer (cobalt boride CoB, iron boride FeB or cobalt iron boron alloy CoFeB) is between 0.2 nm and 1.0 nm.
In some embodiments, the second free layer 260B has a three-layer structure of CoFeB/(W, Mo, V, Nb, Cr, Hf, Ti, Zr, Ta, Sc, Y, Zn, Ru, Os, Rh, Ir, Pd, and/or Pt) in the first layer, CoFeB in an atomic ratio of Co to Fe of 1:3 to 3:1, and B in an atomic ratio of 15% to 40%; in the third layer of CoFeB, the atomic ratio of Co to Fe is 1: 3-3: 1, and the atomic percentage of B is 15% -40%.
Further, after the second free layer 260b is deposited, a plasma process may be selected to perform surface modification or selective component removal.
Further, the total thickness of the second free layer is between 0.5 nm and 3.0 nm.
As described above, the vertical Anisotropy enhancing Layer 270 is disposed between the first free Layer 260a and the second free Layer 260b, is formed of a metal oxide Layer (also referred to as a Doped oxide Layer) containing a doping element, and may be referred to as a Doped vertical Anisotropy enhancing Layer (D-PMA-EL). In some embodiments, the perpendicular anisotropy enhancement layer 270 is used to enable magnetic coupling of the first free layer 260a with the second free layer 260 b.
In an embodiment of the present application, the metal oxide layer of the vertical anisotropy enhancing layer 270 is magnesium oxideMgOZinc oxide ZnO, magnesium zinc oxide MgZnO, zirconium oxide ZrO, aluminum oxide Al2O3Or oxides of magnesium and aluminumMgAlO，The total thickness is between 0.3 nm and 1.5 nm.
As shown in fig. 3A, in some embodiments, the metal oxide layer 271 containing doping elements is uniformly doped with a doping ratio of 0.5% to 10%. The doping elements are boron B, carbon C, magnesium Mg, aluminum Al, silicon Si, calcium Ca, scandium Sc, titanium Ti, vanadium V, chromium Cr, manganese Mn, iron Fe, cobalt Co, nickel Ni, copper Cu, zinc Zn, gallium Ga, germanium Ge, yttrium Y, zirconium Zr, niobium Nb, molybdenum Mo, ruthenium Ru, technetium Tc, rhodium Rh, palladium Pd, silver Ag, indium In, hafnium Hf, tantalum Ta, tungsten W, rhenium Re, osmium Os, iridium Ir, platinum Pt or gold Au. The realization mode can be that the sputtering deposition is carried out on the doped oxide target material or the co-sputtering deposition is carried out on the oxide target material and the doped element target material in the PVD process cavity.
As illustrated in fig. 3B, in some embodiments, the doped metal oxide layer is a single-pass or multiple-pass doped sub-layer metal oxide layer 272. The doping element is boron B, carbon C, magnesium Mg, aluminum Al, silicon Si, calcium Ca, scandium Sc, titanium Ti, vanadium V, chromium Cr, manganese Mn, iron Fe, cobalt Co, nickel Ni, copper Cu, zinc Zn, gallium Ga, germanium Ge, yttrium Y, zirconium Zr, niobium Nb, molybdenum Mo, ruthenium Ru, techneti Tc, rhodium Rh, palladium Pd, silver Ag, indium In, hafnium Hf, tantalum Ta, tungsten W, rhenium Re, osmium Os, iridium Ir, platinum Pt or gold Au, more preferably magnesium, titanium, vanadium, chromium, manganese, iron, cobalt and nickel, and the thickness of the doping element sub-layer is not more than 0.2 nm, more preferably not more than 0.1 nm.
In some embodiments, the thickness of the vertical anisotropy enhancement layer 270 is between 0.3 nm and 1.5 nm.
The vertical anisotropy enhancement layer 270 is deposited prior to the deposition of the second free layer 260b, providing a source of interfacial anisotropy, thereby increasing thermal stability.
Further, the doping layers and the oxide layers are typically implemented in a PVD process chamber, each layer having a doping element thickness of no greater than 0.3 nm. Further, a plasma process may be used to perform surface plasma treatment after or during the deposition of the vertical anisotropy enhancing layer 270 for surface modification or selective removal. The perpendicular anisotropy enhancing layer 270 has a significant effect of enhancing the thermal stability of the MRAM and further reducing the junction Resistance Area (Resistance Area Product), which is very advantageous for fabricating the ultra-small MRAM device.
In an embodiment of the present application, the material of the magnetic damping barrier layer 280 is a metal selected from Mg, Zn, Al, Cu, Ca, Ti, V, Cr, Al, or their metal oxides and metal nitrides. In some embodiments, the magnetic damping barrier layer 280 has a thickness between 0.5 nm and 3.0 nm. Further, due to the addition of the magnetic damping barrier layer 280 on the second free layer 260b, the damping coefficient of the whole film structure is effectively reduced, which is beneficial to reducing the write current.
Referring to fig. 2 to 3B, in an embodiment of the present application, a memory cell of a magnetic memory includes any one of the above-described magnetic tunnel junction 200 structures, a top electrode 310 disposed above the magnetic tunnel junction 200 structure, and a bottom electrode 110 disposed below the magnetic tunnel junction 200 structure.
In an embodiment of the present application, the material of the seed layer 210 of the magnetic tunnel junction 200 is one or a combination of Ti, TiN, Ta, TaN, W, WN, Ru, Pt, Cr, CrCo, Ni, CrNi, CoB, FeB, CoFeB, etc. 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.
An antiferromagnetic layer 220, formally known as an antiparallel ferromagnetic super-lattice (Anti-Parallel ferromagnetic super-lattice) layer 220 is also known as a Synthetic antiferromagnetic-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, Co [ Co/Pt ] Co]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 0.5 nm, 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 220 is the same or different. The antiferromagnetic layer 220 has a strong perpendicular anisotropy (PMA).
In an embodiment of the present application, the reference layer 240 has a magnetic polarization invariance under ferromagnetic coupling of the antiferromagnetic layer 220. The reference layer 240 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 0.5 nm and 1.5 nm.
Since the antiferromagnetic layer 220 has a Face Centered Cubic (FCC) crystal structure and the reference layer 240 has a Body Centered Cubic (BCC) crystal structure, the crystal lattices are not matched, in order to realize the transition and ferromagnetic coupling from the antiferromagnetic layer 220 to the reference layer 240, a lattice-blocking layer 230 is typically added between the two layers, the material of the lattice-blocking layer 230 is one or a combination of Ta, W, Mo, Hf, Fe, Co, and the thickness of the reference layer 240 is between 0.1 nm and 0.5 nm.
In some embodiments, barrier layer 250 is formed of a non-magnetic metal oxide having a thickness between 0.6 nm and 1.5 nm, including magnesium oxide MgO, magnesium zinc oxide MgZnO, zinc oxide ZnO, aluminum oxide Al2O3MgN, Mg boron oxide, Mg3B2O6Or Mg3Al2O6. Preferably, magnesium oxide MgO may be used.
In one embodiment of the present application, after deposition of all layers, an annealing process is performed on the magnetic tunnel junction 200 at a temperature between 350 ℃ and 400 ℃ for 90 minutes to change the reference layer 240, the first free layer 260a, and the second free layer 260b from an amorphous phase to a Body Centered Cubic (BCC) crystal structure.
In the magnetic tunnel junction cell structure of the present application, the magnetization vector of the second free layer 260b is always perpendicular to the interface of the first free layer 260a and parallel to the magnetization vector of the first free layer 260a, and since the second free layer 260b and the first free layer 260a exhibit ferromagnetic coupling, under the condition of thermal disturbance or external magnetic field, in order to make the magnetization vector of the first free layer 260a turn, energy larger than the sum of the energy barrier of the first free layer 260a and the energy barrier of the second free layer 260b must be provided. Further, the addition of the second free layer 260b does not affect the tunneling magnetoresistance ratio.
Further, the design of the second free layer 260b maintains or increases the overall thickness of the free layer 260, which is advantageous in reducing the damping constant (α). Also, when selecting the materials of the coupling layer and the capping layer of the first free layer 260 a/the second free layer 260b, a material having a low damping coefficient may be preferable, so that the damping coefficient may be further reduced. When writing to the device, the critical write current does not increase due to the reduced damping coefficient, despite the increased thermal stability factor.
The ability of the free layer 260 of the magnetic memory to maintain a constant magnetization direction is called Data Retention (Data Retention) or Thermal Stability (Thermal Stability). The data retention capacity can be calculated using the following formula:
Figure BDA0002228718970000101
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 (Thermal Stability factor) can then be expressed as the following equation:
Figure BDA0002228718970000102
wherein, KeffIs the effective isotropic energy density of the free layer 260, 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, KiCD is the critical dimension of the magnetic random access memory (i.e., the diameter of the free layer), A, as the interfacial anisotropy constantsK is the critical dimension of the free layer 260 switching mode transition from domain switching (i.e., Magnetization switching processed by "macro-spin" switching) to inverse domain nucleation/growth (i.e., Magnetization switching by nuclear of a reversed domain and propagation of a domain wall) for stiffness integrating exchange constants. Experiments have shown that the free layer 260 exhibits in-plane anisotropy when it has a relatively thick thickness and exhibits perpendicular anisotropy when it is relatively thinProperty, KVGenerally negligible, while the contribution of demagnetization energy to the perpendicular anisotropy is negative, so the perpendicular anisotropy comes entirely from the interfacial 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 240, in combination with the difference in the magnetization direction applied by the static magnetic Field on the free layer 260 to produce an enhancement or reduction effect.
In addition, as the volume of the magnetic free layer is reduced, the smaller the spin polarization current to be injected for writing or switching operation, and the critical current I for writing operationC0The relationship between the compound and the thermal stability is strongly related, and can be expressed as the following formula:
Figure BDA0002228718970000111
wherein alpha is a damping constant,
Figure BDA0002228718970000112
η is the spin polarizability, which is the approximate planck constant. As can be understood from the above equations, the addition of the second free layer 260b does not affect the tunneling magnetoresistance ratio. Even if the thickness of the free layer 260 is increased, the thermal stability factor can be increased by selecting a material with a low damping coefficient to lower the damping coefficient, and the critical write current will not increase.
According to the magnetic tunnel junction unit structure, the double-layer free layer is in ferromagnetic coupling, and under the condition of thermal disturbance or an external magnetic field, in order to turn over the magnetization vector of the free layer, energy larger than the sum of the energy barrier of the free layer and the energy barrier of the thermal stability enhancement layer is required to be provided, so that the thermal stability is improved; secondly, an interface anisotropy source can be additionally provided through the doped vertical anisotropy enhancement layer, so that the thermal stability is further improved; meanwhile, due to the introduction of the doping element or the conductive element, the junction Resistance Area (Resistance Area Product) can be further reduced, which is beneficial to the manufacture of a subminiature MRAM device; thirdly, the damping coefficient of the whole film structure is reduced through the magnetic damping barrier layer, so that the reduction and the stability of the read-write current are facilitated; fourthly, the tunneling magnetic resistance rate is not influenced by the addition of the second free layer; fifthly, through the design of the double-layer free layer, the whole thickness of the free layer can be increased or maintained, the reduction of the damping coefficient is facilitated, and therefore the critical write current cannot be increased.
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 memory is arranged in a magnetic random access memory unit, the magnetic tunnel junction structure comprises a covering layer, a magnetic damping barrier 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 free layer comprises:
a first free layer which is a variable magnetic polarization layer and is formed by a magnetic metal alloy; a vertical anisotropy enhancement layer disposed on the first free layer, the vertical anisotropy enhancement layer being formed of a metal oxide layer containing a doping element; a second free layer disposed on the vertical anisotropy enhancing layer, the second free layer being a variable magnetic polarization layer formed of a magnetic metal or a compound thereof; and the magnetic damping blocking layer is arranged on the second free layer and is formed by nonmagnetic metal or oxide thereof.
2. The magnetic tunnel junction structure of claim 1 wherein the material of the first free layer is a single layer structure selected from cobalt boride, iron boride, cobalt iron boron alloys, or a double layer structure of cobalt boride/cobalt iron boron alloys, iron/cobalt iron boron alloys, or a triple layer structure of iron boride/(tungsten, molybdenum, vanadium, niobium, chromium, hafnium, titanium, zirconium, tantalum, scandium, yttrium, zinc, ruthenium, osmium, rhodium, iridium, palladium and/or platinum)/cobalt iron boron alloys, cobalt iron boron alloys/(tungsten, molybdenum, vanadium, niobium, chromium, hafnium, titanium, zirconium, tantalum, scandium, yttrium, zinc, ruthenium, osmium, rhodium, iridium, palladium and/or platinum)/cobalt iron boron alloys, or iron/cobalt iron boron alloys/(tungsten, molybdenum, vanadium, niobium, chromium, hafnium, titanium, zirconium, tantalum, scandium, yttrium, zinc, ruthenium, osmium, rhodium, cobalt, and cobalt iron boron alloys, Iridium, palladium and/or platinum)/cofeb alloys, cobalt ferrite/cofeb alloys/(tungsten, molybdenum, vanadium, niobium, chromium, hafnium, titanium, zirconium, tantalum, scandium, yttrium, zinc, ruthenium, osmium, rhodium, iridium, palladium and/or platinum)/cofeb alloys; the thickness of the first free layer is between 1.2 nm and 3.0 nm.
3. The magnetic tunnel junction structure of claim 1 wherein the second free layer is made of at least one material selected from the group consisting of iron, cobalt, nickel, cobalt ferrite, iron boride, cobalt boride, tungsten, molybdenum, vanadium, niobium, chromium, hafnium, titanium, zirconium, tantalum, scandium, yttrium, zinc, ruthenium, osmium, rhodium, iridium, palladium, platinum, and cofeb alloys.
4. The magnetic tunnel junction structure of claim 1 wherein the metal oxide layer in the perpendicular anisotropy enhancement layer is magnesium oxide, zinc oxide, magnesium zinc oxide, zirconium oxide, aluminum oxide, or magnesium aluminum oxide, and has a total thickness of 0.3 nm to 1.5 nm.
5. The magnetic tunnel junction structure of claim 1, wherein the doping element is boron, carbon, magnesium, aluminum, silicon, calcium, scandium, titanium, vanadium, chromium, manganese, iron, cobalt, nickel, copper, zinc, gallium, germanium, yttrium, zirconium, niobium, molybdenum, ruthenium, technetium, rhodium, palladium, silver, indium, hafnium, tantalum, tungsten, rhenium, osmium, iridium, platinum, or gold.
6. The magnetic tunnel junction structure of claim 1 wherein the doped metal oxide layer is uniformly doped with a doping ratio of 0.5% to 10%.
7. The magnetic tunnel junction structure of claim 1 wherein the doped metal oxide layer is a single-pass or multiple-pass doped sub-layer.
8. The magnetic tunnel junction structure of claim 7, wherein the doped element sub-layer is boron, carbon, magnesium, aluminum, silicon, calcium, scandium, titanium, vanadium, chromium, manganese, iron, cobalt, nickel, copper, zinc, gallium, germanium, yttrium, zirconium, niobium, molybdenum, ruthenium, technetium, rhodium, palladium, silver, indium, hafnium, tantalum, tungsten, rhenium, osmium, iridium, platinum, or gold, preferably magnesium, titanium, vanadium, chromium, manganese, iron, cobalt, or nickel, and the doped element sub-layer has a thickness of no more than 0.2 nm, preferably no more than 0.1 nm.
9. The magnetic tunnel junction structure of claim 1 wherein the magnetic damping barrier layer is made of a material selected from the group consisting of magnesium, zinc, aluminum, copper, calcium, titanium, vanadium, chromium, aluminum, or metal oxides, metal nitrides thereof, and has a thickness of between 0.5 nm and 3.0 nm.
10. A magnetic 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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