MTJ and MRAM

Abstract

The invention provides an MTJ and an MRAM (Magnetic Random Access Memory). The MTJ comprises a second tunneling layer, a first covering layer and a second covering layer, the first covering layer is located on the surface of the second tunneling layer, the first covering layer comprises a plurality of same metal layers which are sequentially stacked in the thickness direction of the second tunneling layer, and each metal layer comprises multiple layers of metal made of different materials; the second capping layer is located on a surface of the first capping layer away from the second tunneling layer. A plurality of metal layers are repeatedly arranged between the second tunneling layer and the second covering layer, and each metal layer further comprises a plurality of layers of metal made of different materials, so that external impurities are prevented from diffusing into the MTJ by taking the plurality of metal layers as diffusion barrier layers, the WER excellent performance of the MTJ is further ensured, the read-write and reliability performance of the MTJ is ensured, and the reliability of the MTJ is improved. The problem of poor performance of an MRAM (Magnetic Random Access Memory) due to high WER (Wavelet Error Rate) in the prior art is solved.

Description

Technical Field

[0001] The present application relates to the field of semiconductor memory, and in particular, to an MTJ and an MRAM. Background Art

[0002] WER (Write Error Rate) refers to the probability of MRAM (Magnetoresistive Random Access Memory) write errors under a specific current pulse. The quality of WER plays a key role in write voltage, power consumption and reliability.

[0003] Therefore, a structure is urgently needed to solve the problem of performance crossover caused by high WER of MRAM in the prior art. Summary of the invention

[0004] The main purpose of the present application is to provide an MTJ and an MRAM to solve the problem of poor performance of the MRAM in the prior art due to high WER.

[0005] In order to achieve the above-mentioned purpose, according to one aspect of the present application, an MTJ is provided, which includes: a second tunneling layer, a first covering layer and a second covering layer, wherein the first covering layer is located on the surface of the second tunneling layer, the first covering layer includes a plurality of identical metal layers stacked in sequence along the thickness direction of the second tunneling layer, and each of the metal layers includes multiple layers of metals with different materials; the second covering layer is located on the surface of the first covering layer away from the second tunneling layer.

[0006] Optionally, each of the metal layers includes a first metal sublayer and a second metal sublayer, wherein the first metal sublayer is located on the surface of the second tunneling layer; the second metal sublayer is located on the surface of the first metal sublayer away from the second tunneling layer, and the materials of the first metal sublayer and the second metal sublayer are different.

[0007] Optionally, each of the metal layers includes a third metal sublayer, a fourth metal sublayer and a fifth metal sublayer, wherein the third metal sublayer is located on the surface of the second tunneling layer; the fourth metal sublayer is located on the surface of the third metal sublayer away from the second tunneling layer; the fifth metal sublayer is located on the surface of the fourth metal sublayer away from the third metal sublayer, and the materials of the third metal sublayer, the fourth metal sublayer and the fifth metal sublayer are different.

[0008] Optionally, the structure of the first covering layer is [X / Y] nStructure, wherein the materials of X and Y include at least one of CoFeB, FeB, CoB, CoFe, Fe, Hf, Mo, W, Ta, Rh and Ir.

[0009] Optionally, the first covering layer has a thickness ranging from 2 angstroms to 20 angstroms.

[0010] Optionally, the first covering layer corresponds to [X / Y] n The value range of n is 2-6.

[0011] Optionally, the MTJ further includes a free layer, a first tunneling layer and a reference layer, wherein the free layer is located on a surface of the second tunneling layer away from the first covering layer; the first tunneling layer is located on a surface of the free layer away from the second tunneling layer; and the reference layer is located on a surface of the first tunneling layer away from the free layer.

[0012] Optionally, the MTJ also includes a first pinned layer, a coupling layer, a second pinned layer and a seed layer, wherein the first pinned layer is located on a surface of the reference layer away from the first tunneling layer; the coupling layer is located on a surface of the first pinned layer away from the reference layer; the second pinned layer is located on a surface of the coupling layer away from the first pinned layer; and the seed layer is located on a surface of the second pinned layer away from the coupling layer.

[0013] Optionally, the material of the coupling layer includes Ir, the material of the first covering layer includes MgO, and the material of the first pinning layer includes at least one of Co and Pt.

[0014] According to another aspect of the present application, an MRAM is provided, and the MRAM includes any one of the MTJs described above.

[0015] Applying the technical solution of the present application, the MTJ includes a second tunneling layer, a first covering layer and a second covering layer, wherein the first covering layer is located on the surface of the second tunneling layer, the first covering layer includes a plurality of identical metal layers stacked sequentially along the thickness direction of the second tunneling layer, and each of the metal layers includes multiple layers of metals with different materials; the second covering layer is located on the surface of the first covering layer away from the second tunneling layer. Compared with the problem of poor performance of MRAM in the prior art due to high WER, the MTJ of the present application, by setting the first covering layer between the second tunneling layer and the oxide layer corresponding to the second covering layer, and the first covering layer includes multiple identical metal layers stacked in sequence along the thickness direction of the second tunneling layer, and each of the metal layers includes multiple layers of metal with different materials, thereby ensuring that there are multiple metal layers repeatedly set between the second tunneling layer and the second covering layer, and each of the metal layers also includes multiple layers of metal with different materials, so that the multiple layers of metal layers can be used as diffusion barrier layers to prevent external impurities from diffusing into the MTJ, thereby ensuring the excellent WER performance of the MTJ, ensuring the good read, write and reliability performance of the MTJ, and solving the problem of poor performance of MRAM in the prior art due to high WER. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] The drawings constituting part of the present application are used to provide a further understanding of the present application. The illustrative embodiments and descriptions of the present application are used to explain the present application and do not constitute an improper limitation on the present application. In the drawings:

[0017] Figure 1 A schematic structural diagram of an MTJ according to an embodiment of the present application is shown;

[0018] Figure 2 A schematic diagram of the structure of a metal layer according to an embodiment of the present application is shown;

[0019] Figure 3 A schematic structural diagram of a metal layer according to another embodiment of the present application is shown;

[0020] Figure 4 A schematic diagram showing a WER test result of an MRAM in the prior art;

[0021] Figure 5 A schematic diagram showing another WER test result of an MRAM in the prior art;

[0022] Figure 6 A schematic diagram showing a WER test result of an MRAM according to an embodiment of the present application;

[0023] Figure 7A schematic diagram showing another WER test result of an MRAM according to an embodiment of the present application;

[0024] Figure 8 A schematic diagram showing a WER test result of an MRAM according to another embodiment of the present application;

[0025] Fig. 9 A schematic diagram showing another WER test result of an MRAM according to another embodiment of the present application is shown.

[0026] The above drawings include the following reference numerals:

[0027] 10. Second tunneling layer; 20. First covering layer; 30. Second covering layer; 40. Free layer; 50. First tunneling layer; 60. Reference layer; 70. First pinning layer; 80. Coupling layer; 90. Second pinning layer; 100. Seed layer; 201. Metal layer; 202. First metal sublayer; 203. Second metal sublayer; 204. Third metal sublayer; 205. Fourth metal sublayer; 206. Fifth metal sublayer. DETAILED DESCRIPTION

[0028] It should be noted that the following detailed descriptions are illustrative and are intended to provide further explanation of the present application. Unless otherwise specified, all technical and scientific terms used herein have the same meanings as those commonly understood by those skilled in the art to which the present application belongs.

[0029] It should be noted that the terms used herein are only for describing specific embodiments and are not intended to limit the exemplary embodiments according to the present application. As used herein, unless the context clearly indicates otherwise, the singular form is also intended to include the plural form. In addition, it should be understood that when the terms "comprise" and / or "include" are used in this specification, it indicates the presence of features, steps, operations, devices, components and / or combinations thereof.

[0030] It should be understood that when an element (such as a layer, film, region, or substrate) is described as being "on" another element, the element may be directly on the other element, or there may be intermediate elements. Moreover, in the specification and claims, when an element is described as being "connected" to another element, the element may be "directly connected" to the other element, or "connected" to the other element through a third element.

[0031] As introduced in the background art, the MRAM in the prior art has the problem of poor performance due to high WER. To solve the above problem, the embodiments of the present application provide an MTJ and an MRAM.

[0032] The technical solutions in the embodiments of the present invention will be described clearly and completely below in conjunction with the accompanying drawings in the embodiments of the present invention.

[0033] According to an embodiment of the present application, a MTJ is provided, such as Figures 1 to 3 As shown, the MTJ includes a second tunneling layer 10, a first covering layer 20 and a second covering layer 30, wherein the first covering layer 20 is located on the surface of the second tunneling layer 10, the first covering layer 20 includes a plurality of identical metal layers 201 stacked in sequence along the thickness direction of the second tunneling layer 10, and each of the metal layers 201 includes multiple layers of metals of different materials; the second covering layer 30 is located on the surface of the first covering layer 20 away from the second tunneling layer 10.

[0034] The above-mentioned MTJ includes a second tunneling layer, a first covering layer and a second covering layer, wherein the above-mentioned first covering layer is located on the surface of the above-mentioned second tunneling layer, the above-mentioned first covering layer includes a plurality of identical metal layers stacked in sequence along the thickness direction of the above-mentioned second tunneling layer, and each of the above-mentioned metal layers includes multiple layers of metals with different materials; the above-mentioned second covering layer is located on the surface of the above-mentioned first covering layer away from the above-mentioned second tunneling layer. Compared with the problem of poor performance of MRAM in the prior art due to high WER, the above-mentioned MTJ of the present application, by setting the above-mentioned first covering layer between the second tunneling layer and the oxide layer corresponding to the above-mentioned second covering layer, and the above-mentioned first covering layer includes multiple identical metal layers stacked in sequence along the thickness direction of the above-mentioned second tunneling layer, and each of the above-mentioned metal layers includes multiple layers of metals with different materials, thereby ensuring that there are multiple metal layers repeatedly arranged between the above-mentioned second tunneling layer and the above-mentioned second covering layer, and each of the above-mentioned metal layers also includes multiple layers of metals of different materials, so that the multiple layers of the above-mentioned metal layers can be used as diffusion barrier layers to prevent external impurities from diffusing into the above-mentioned MTJ, thereby ensuring the excellent WER performance of the above-mentioned MTJ, ensuring that the read, write and reliability performance of the above-mentioned MTJ is good, and solving the problem of poor performance of MRAM in the prior art due to high WER.

[0035] In addition, the first covering layer can also improve the crystallinity of the second covering layer, thereby ensuring that the interface PMA (Perpendicular Magnetic Anisotropy) is good, improving the Hk (perpendicular magnetic anisotropy field) and Hc (coercive force) performance of the MTJ stacking structure, ensuring that the WER performance of the MTJ is good, and ensuring that the performance of the MTJ is high.

[0036] Among them, perpendicular magnetic anisotropy is a magnetic anisotropy with a preferred orientation along a certain direction due to factors such as interface and lattice distortion. This magnetic anisotropy is very important for the function of the memory. The synchronous antiferromagnetic coupling strength refers to the exchange interaction strength between two adjacent antiferromagnetic layers. When two adjacent antiferromagnetic layers are in a synchronous state, their spin directions are complementary, that is, one spin is up and the other is down. At this time, an exchange interaction called synchronous antiferromagnetic coupling will occur. Therefore, properties such as perpendicular magnetic anisotropy and synchronous antiferromagnetic coupling strength are more important for judging the function of the memory.

[0037] Of course, the second covering layer may include a noble metal, such as tantalum (Ta) or ruthenium (Ru).

[0038] In order to further ensure the good performance of the above MTJ, Figure 2 As shown, each of the metal layers 201 includes a first metal sublayer 202 and a second metal sublayer 203, wherein the first metal sublayer 202 is located on the surface of the second tunneling layer; the second metal sublayer 203 is located on the surface of the first metal sublayer 202 away from the second tunneling layer, and the first metal sublayer 202 and the second metal sublayer 203 are made of different materials. Since each of the metal layers includes the first metal sublayer and the second metal sublayer with different materials, and the MTJ includes multiple metal layers, that is, the MTJ includes multiple metal layers in a cycle, and each of the metal layers includes two metal layers with different materials, it is ensured that the second tunneling layer and the second covering layer include multiple metal layers in which two metal materials are stacked in sequence, so that the multiple metal layers can be used as diffusion barrier layers to prevent external impurities from diffusing into the MTJ, further ensuring that the WER performance of the MTJ is good, and further ensuring that the performance of the MTJ is good.

[0039] In order to further ensure the good performance of the above MTJ, Figure 3As shown, each of the above-mentioned metal layers 201 includes a third metal sublayer 204, a fourth metal sublayer 205 and a fifth metal sublayer 206, wherein the above-mentioned third metal sublayer 204 is located on the surface of the above-mentioned second tunneling layer; the above-mentioned fourth metal sublayer 205 is located on the surface of the above-mentioned third metal sublayer 204 away from the above-mentioned second tunneling layer; the above-mentioned fifth metal sublayer 206 is located on the surface of the above-mentioned fourth metal sublayer 205 away from the above-mentioned third metal sublayer 204, and the materials of the above-mentioned third metal sublayer 204, the above-mentioned fourth metal sublayer 205 and the above-mentioned fifth metal sublayer 206 are different. Since each of the above-mentioned metal layers includes the above-mentioned third metal sublayer, the above-mentioned fourth metal sublayer and the above-mentioned fifth metal layer with different materials, and the above-mentioned MTJ includes multiple layers of the above-mentioned metal layers, that is, the above-mentioned MTJ includes multiple layers of the above-mentioned metal layers in a cycle, and each of the above-mentioned metal layers includes three layers of metal with different materials, it is ensured that the above-mentioned second tunneling layer and the above-mentioned second covering layer include multiple layers of the above-mentioned metal layers with three metal materials stacked in sequence and stacked in a cycle, so that the multiple layers of the above-mentioned metal layers can be used as diffusion barrier layers to prevent external impurities from diffusing into the above-mentioned MTJ, further ensuring that the WER performance of the above-mentioned MTJ is better, and further ensuring that the above-mentioned MTJ has better performance.

[0040] In the above implementation process, each of the above-mentioned metal layers is not limited to the two layers of metal materials corresponding to the above-mentioned first metal sublayer and the above-mentioned second metal sublayer. Of course, each of the above-mentioned metal layers is not limited to the three layers of metal materials corresponding to the above-mentioned third metal sublayer, the above-mentioned fourth metal sublayer and the above-mentioned fifth metal sublayer. Each of the above-mentioned metal layers can be two layers, three layers, four layers, five layers, six layers or more layers of metal materials, which is determined according to actual conditions. In actual application, different numbers of metal layers can be prepared, and configurations of different materials can be prepared. Then, through performance testing, the number of metal layers and materials with the best WER performance can be selected.

[0041] In a specific embodiment, the structure of the first covering layer is [X / Y] n Structure, wherein the materials of the above X and the above Y include at least one of CoFeB, FeB, CoB, CoFe, Fe, Hf, Mo, W, Ta, Rh and Ir. The materials of the above first metal sublayer, the above second metal sublayer, the above third metal sublayer, the above fourth metal sublayer and the above fifth metal sublayer include one of CoFeB, FeB, CoB, CoFe, Fe, Hf, Mo, W, Ta, Rh and Ir, ensuring that the above first covering layer can include multiple layers of the above metal layers with different materials, so that the above multiple metal layers can be used as diffusion barrier layers to prevent external impurities from diffusing into the above MTJ, further ensuring that the WER performance of the above MTJ is good, and further ensuring that the performance of the above MTJ is good.

[0042] In the above implementation process, when the WER performance of the above MTJ is poor, the write voltage and power consumption of the MRAM memory chip will increase and the reliability will decrease. The above MTJ of the present application is provided with the above first covering layer of a multilayer metal between the above second tunneling layer and the above second covering layer, and the metal material includes at least one of CoFeB, FeB, CoB, CoFe, Fe, Hf, Mo, W, Ta, Rh and Ir. Since CoFeB, FeB, CoB, CoFe, Fe, Hf, Mo, W, Ta, Rh and Ir are all anti-diffusion materials, the above metal layers can be used as diffusion barrier layers, that is, [X / Y] is introduced. n Corresponding to the multi-layer metal structure, X and Y respectively include one of CoFeB, FeB, CoB, CoFe, Fe, Hf, Mo, W, Ta, Rh and Ir, which prevents external impurities from diffusing into the above-mentioned MTJ, further ensuring that the WER performance of the above-mentioned MTJ is good. In a specific embodiment, the WER can be improved by about 18%.

[0043] In a specific embodiment, the thickness of the first covering layer is in the range of 2 angstroms to 20 angstroms. Of course, the thickness of the first covering layer is not limited to 2 angstroms to 20 angstroms, and can be determined according to actual conditions. In actual applications, samples of different thicknesses can be prepared and WER performance tests can be performed to finally determine the thickness of the first covering layer with the best performance.

[0044] In the specific implementation process, the [X / Y] corresponding to the first covering layer n The value range of the number of repetitions n is 2-6. Of course, the number of repetitions of the above metal layer is not limited to 2-6, and can be determined according to actual conditions. In actual application, samples of the above metal layer with the same number of layers can be prepared and WER performance tests can be performed to finally determine the number of layers of the above metal layer with the best performance.

[0045] In the above implementation process, the repetition number of the above metal layer is 2-6, which means that the above first covering layer includes 2-6 layers of the above repeated metal layers, and each of the above metal layers also includes metal sub-layers with different numbers of layers.

[0046] In a specific embodiment, Figure 1As shown, the MTJ further includes a free layer 40, a first tunneling layer 50 and a reference layer, wherein the free layer 40 is located on a surface of the second tunneling layer 10 away from the first cover layer 20; the first tunneling layer 50 is located on a surface of the free layer 40 away from the second tunneling layer 10; and the reference layer 60 is located on a surface of the first tunneling layer 50 away from the free layer 40. Since the MTJ further includes the free layer, the first tunneling layer and the reference layer, it is ensured that the MTJ can achieve memory performance.

[0047] In the above implementation process, the reference layer is a magnetic material with a stable polarity of constant magnetization. The reference layer can generate a magnetoresistance effect by interacting with the free layer, and determine the rotation direction of the electrons in the free layer. The free layer is a thin and movable magnetic material, which can change its magnetization state when an external field strength is applied. When the current passes through the magnetic tunnel junction, it will cause a positive or reverse rotation movement in the free region, thereby realizing data storage and reading. The second tunnel layer and the first tunnel layer are mainly metal oxides, forming an insulating medium. By adjusting the thickness and material properties of the second tunnel layer and the first tunnel layer, the energy required for electrons to cross the insulating interface between the two ferromagnets can be controlled. By greatly increasing the difference in device impedance ratio, the read sensitivity of the MRAM can be improved. In short, the reference layer, the free layer, the second tunnel layer and the first tunnel layer work together to realize the functions of data storage, reading and transmission of the memory.

[0048] In the specific implementation process, Figure 1 As shown, the MTJ further includes a first pinning layer 70, a coupling layer 80, a second pinning layer 90 and a seed layer 100, wherein the first pinning layer 70 is located on a surface of the reference layer 60 away from the first tunneling layer 50; the coupling layer 80 is located on a surface of the first pinning layer 70 away from the reference layer 60; the second pinning layer 90 is located on a surface of the coupling layer 80 away from the first pinning layer 70; and the seed layer 100 is located on a surface of the second pinning layer 90 away from the coupling layer 80. Since the MTJ further includes the first pinning layer, the coupling layer, the second pinning layer and the seed layer, the first pinning layer and the second pinning layer can be antiferromagnetically coupled according to the coupling layer, further ensuring that the MTJ can achieve memory performance.

[0049] In the above implementation process, the above coupling layer can be formed by PVD (Physical Vapor Deposition). Of course, other manufacturing methods can also be selected. In addition, the above isolation layer and other layer structures can also be obtained by PVD and other methods. In the above PVD operation process, an inert gas or a rare gas such as argon (Ar), helium (He), krypton (Kr) or xenon (Xe) is ionized into a plasma in a sputtering chamber, and the chamber is maintained in a vacuum state. In addition, the PVD processing chamber also contains at least one sputtering target, the material of the target is determined according to the material of the structure to be prepared, and the substrate is arranged to face the substantially flat surface of the sputtering target. The sputtering target is connected to a power supply so that the sputtering target is electrically driven or self-established as a cathode state in a circuit of the power supply, through plasma to ground, such as a ground part of the sputtering chamber. The substrate is arranged on a base or other structure in the sputtering chamber, and the base or other structure can be at a floating potential, connected to ground, or can be biased to form an anode in the cathode target, with a plasma to anode or ground circuit. The positively ionized portion of the inert gas atoms in the sputtering chamber is electrically attracted to the negatively biased target, causing the plasma ions to bombard the target, thereby causing the atoms in the target to be ejected and deposited on the substrate to form a thin film of the material corresponding to the target on the substrate.

[0050] In a specific embodiment, the material of the coupling layer includes Ir, the material of the first covering layer includes MgO, and the material of the first pinning layer includes at least one of Co and Pt.

[0051] In the above implementation process, the material of the first pinning layer is not limited to Co or Pt alone, and the material of the first pinning layer may include one of Co, Fe, CoFe and CoFeB.

[0052] Specifically, the seed layer is mainly used to ensure that the quality of the second pinned layer is good. The material of the seed layer includes platinum (Pt) or ruthenium (Ru). By reducing or eliminating the lattice mismatch between the subsequent structures such as the second pinned layer and the substrate, the seed layer can be used to improve the adhesion and inoculation effect of the subsequently deposited layer. Subsequently, the second pinned layer is formed on the surface of the seed layer by sputtering. Here, the second pinned layer includes a cobalt (Co) layer, and then sputtering is performed to form the coupling layer on the surface of the second pinned layer away from the seed layer. The coupling layer can be formed by iridium (Ir) sputtered from its target. Then, the first pinned layer is formed on the surface of the coupling layer away from the second pinned layer by sputtering. Since the coupling layer is located between the first pinned layer and the second pinned layer, when the MTJ is exposed to a magnetic field, the surface atoms of the first pinned layer and the second pinned layer are aligned with the surface atoms of the coupling layer, thereby pinning the orientation of the first pinned layer and the second pinned layer. The first pinned layer and the second pinned layer each exhibit similar magnetic moments, and the coupling layer maintains antiparallel alignment of the magnetic moments of the first pinned layer and the second pinned layer.

[0053] In addition, the material of the second tunneling layer is composed of metal oxides. Specifically, the second tunneling layer includes MgO, TaO x MgAlO x one of them.

[0054] The following are several main implementations of the MTJ, but the implementations of the present application are not limited thereto.

[0055] Embodiment 1, the MTJ comprises the stacked seed layer, the second pinned layer, the coupling layer, the first pinned layer, the reference layer, the first tunneling layer, the free layer, the second tunneling layer, the first capping layer and the second capping layer, wherein the first capping layer comprises a plurality of identical metal layers stacked in sequence along the thickness direction of the second tunneling layer, each of the metal layers comprises a stacked first metal sublayer and a second metal sublayer, the material of the first metal sublayer is Fe, the material of the second metal sublayer is Ir, the material of the coupling layer comprises Ir, the material of the first capping layer comprises MgO, and the material of the first pinned layer comprises Co;

[0056] Embodiment 2: The difference between Embodiment 2 and Embodiment 1 is that the material of the first metal sub-layer in Embodiment 2 is CoFeB, and the material of the second metal sub-layer is W;

[0057] Embodiment 3: The difference between Embodiment 3 and Embodiment 1 is that the material of the first metal sublayer in Embodiment 3 is Mo, and the material of the second metal sublayer is Hf.

[0058] An embodiment of the present application further provides an MRAM, and the MRAM includes any one of the above-mentioned MTJs.

[0059] The MRAM includes any of the MTJs. Compared with the MRAM in the prior art, which has the problem of poor performance due to high WER, the MRAM in the present application, by setting the first covering layer between the second tunneling layer and the oxide layer corresponding to the second covering layer, and the first covering layer includes a plurality of identical metal layers stacked in sequence along the thickness direction of the second tunneling layer, and each of the metal layers includes multiple layers of metals with different materials, ensures that there are multiple metal layers repeatedly set between the second tunneling layer and the second covering layer, and each of the metal layers also includes multiple layers of metals with different materials, so that the multiple metal layers can be used as diffusion barriers to prevent external impurities from diffusing into the MTJ, thereby ensuring the excellent WER performance of the MTJ, ensuring the good read / write and reliability performance of the MTJ, and solving the problem of poor performance of the MRAM in the prior art due to high WER.

[0060] In the above implementation process, in MRAM, the material of the coupling layer is selected as Ir, mainly because Ir has good magnetic and electrical properties, Ir can form a strong exchange coupling with ferromagnets, and has high resistivity and low magnetic leakage characteristics, which is very important for achieving high-density storage. By placing Ir between the first pinned layer and the second pinned layer, spin transfer between the two can be achieved, and an effective exchange bias field can be generated. In addition, the use of Ir in MRAM also has the advantages of increasing reading speed, reducing power consumption and increasing stability. In short, Ir plays a vital role as a coupling layer in MRAM. It not only affects basic parameters such as memory capacity and stability, but also directly determines whether the entire system can meet application requirements such as high speed and low power consumption.

[0061] Of course, the material of the coupling layer is not limited to Ir, and other materials with the same performance may also be selected, which is determined according to actual conditions.

[0062] In addition, if Figures 4 to 9 As shown, Figure 4 as well as Figure 5 FIG. 1 shows a schematic diagram of the WER test result of the MRAM when the first cover layer is not provided in the prior art. Figure 6 as well as Figure 7 FIG. 1 shows a schematic diagram of the WER test result of the MRAM when the first covering layer includes only one metal layer. Figure 8 as well as Fig. 9 The first covering layer is shown as [X / Y] nSchematic diagram of the WER test results of MRAM under the condition of Figure 4 as well as Figure 5 It can be seen that dV is 0.084, Figure 6 as well as Figure 7 The corresponding WER dV is 0.077, Figure 8 as well as Fig. 9 The corresponding WER dV is 0.69, that is, the WER performance of the MRAM provided with the first cover layer is improved by 18%.

[0063] In the above embodiments of the present invention, the description of each embodiment has its own emphasis. For parts that are not described in detail in a certain embodiment, reference can be made to the relevant descriptions of other embodiments.

[0064] From the above description, it can be seen that the above embodiments of the present application achieve the following technical effects:

[0065] 1) The MTJ of the present application includes a second tunneling layer, a first covering layer and a second covering layer, wherein the first covering layer is located on the surface of the second tunneling layer, the first covering layer includes a plurality of identical metal layers stacked in sequence along the thickness direction of the second tunneling layer, and each of the metal layers includes multiple layers of metals with different materials; the second covering layer is located on the surface of the first covering layer away from the second tunneling layer. Compared with the problem of poor performance of MRAM in the prior art due to high WER, the above-mentioned MTJ of the present application, by setting the above-mentioned first covering layer between the second tunneling layer and the oxide layer corresponding to the above-mentioned second covering layer, and the above-mentioned first covering layer includes multiple identical metal layers stacked in sequence along the thickness direction of the above-mentioned second tunneling layer, and each of the above-mentioned metal layers includes multiple layers of metals with different materials, thereby ensuring that there are multiple metal layers repeatedly arranged between the above-mentioned second tunneling layer and the above-mentioned second covering layer, and each of the above-mentioned metal layers also includes multiple layers of metals of different materials, so that the multiple layers of the above-mentioned metal layers can be used as diffusion barrier layers to prevent external impurities from diffusing into the above-mentioned MTJ, thereby ensuring the excellent WER performance of the above-mentioned MTJ, ensuring that the read, write and reliability performance of the above-mentioned MTJ is good, and solving the problem of poor performance of MRAM in the prior art due to high WER.

[0066] 2) The MRAM of the present application includes any of the above-mentioned MTJs. Compared with the problem of poor performance of the MRAM in the prior art due to the high WER, the MRAM of the present application, by setting the above-mentioned first covering layer between the second tunneling layer and the oxide layer corresponding to the above-mentioned second covering layer, and the above-mentioned first covering layer includes a plurality of identical metal layers stacked in sequence along the thickness direction of the above-mentioned second tunneling layer, and each of the above-mentioned metal layers includes a plurality of metal layers of different materials, ensures that there are a plurality of metal layers repeatedly set between the above-mentioned second tunneling layer and the above-mentioned second covering layer, and each of the above-mentioned metal layers also includes a plurality of metals of different materials, so that the plurality of metal layers can be used as diffusion barrier layers to prevent external impurities from diffusing into the above-mentioned MTJ, thereby ensuring the excellent WER performance of the above-mentioned MTJ, ensuring the good read / write and reliability performance of the above-mentioned MTJ, and solving the problem of poor performance of the MRAM in the prior art due to the high WER.

[0067] The above description is only the preferred embodiment of the present application and is not intended to limit the present application. For those skilled in the art, the present application may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. An MTJ, characterized in that: The MTJ comprises: a second tunneling layer; A first covering layer, located on the surface of the second tunneling layer, the first covering layer comprising a plurality of identical metal layers stacked in sequence along a thickness direction of the second tunneling layer, each of the metal layers comprising multiple layers of metals of different materials; The second covering layer is located on a surface of the first covering layer away from the second tunneling layer.

2. The MTJ according to claim 1, wherein: Each of the metal layers comprises: A first metal sublayer, located on a surface of the second tunneling layer; The second metal sub-layer is located on a surface of the first metal sub-layer away from the second tunneling layer, and the first metal sub-layer and the second metal sub-layer are made of different materials.

3. The MTJ according to claim 1, wherein: Each of the metal layers comprises: a third metal sublayer, located on the surface of the second tunneling layer; A fourth metal sublayer is located on a surface of the third metal sublayer away from the second tunneling layer; The fifth metal sublayer is located on a surface of the fourth metal sublayer away from the third metal sublayer, and the third metal sublayer, the fourth metal sublayer and the fifth metal sublayer are made of different materials.

4. The MTJ according to claim 1, wherein: The structure of the first covering layer is [X / Y] n Structure, wherein the materials of X and Y include at least one of CoFeB, FeB, CoB, CoFe, Fe, Hf, Mo, W, Ta, Rh and Ir.

5. The MTJ according to claim 4, characterized in that: The first covering layer corresponds to [X / Y] n The value range of n is 2-6.

6. The MTJ according to claim 1, wherein: The thickness of the first covering layer is in the range of 2 angstroms to 20 angstroms.

7. The MTJ according to claim 1, wherein: The MTJ further comprises: A free layer, located on a surface of the second tunneling layer away from the first covering layer; A first tunneling layer, located on a surface of the free layer away from the second tunneling layer; The reference layer is located on a surface of the first tunneling layer away from the free layer.

8. The MTJ according to claim 7, characterized in that: The MTJ further comprises: a first pinning layer, located on a surface of the reference layer away from the first tunneling layer; A coupling layer, located on a surface of the first pinned layer away from the reference layer; a second pinning layer, located on a surface of the coupling layer away from the first pinning layer; The seed layer is located on a surface of the second pinning layer away from the coupling layer.

9. The MTJ according to claim 8, characterized in that: The material of the coupling layer includes Ir, the material of the first capping layer includes MgO, and the material of the first pinning layer includes at least one of Co and Pt.

10. An MRAM, characterized in that: An MTJ comprising the MTJ according to any one of claims 1 to 9.

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