Magnetic tunnel junction device and method of manufacturing the same

Abstract

The application provides a magnetic tunnel junction device, comprising: a reference layer, a barrier layer, a free layer and a cap layer which are stacked, the reference layer has a fixed magnetization which is substantially perpendicular to the plane of the reference layer, the free layer has a magnetization which is substantially perpendicular to the plane of the free layer and can be switched between parallel or anti-parallel to the magnetization direction of the reference layer, and the magnetic damping coefficient of the free layer is less than 0.003. The application can reduce the critical switching current of the magnetic tunnel junction device.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of magnetic random access memory technology, and in particular to a magnetic tunnel junction device and a manufacturing method thereof. BACKGROUND

[0002] Magnetic random access memory (MRAM) is a new type of solid-state non-volatile memory. The core unit of MRAM is a magnetic tunnel junction (MTJ) device, which is composed of a free layer, a reference layer, and a barrier layer sandwiched between the two. Among them, the magnetization direction of the reference layer is fixed and does not occur during device operation. The magnetization direction of the free layer is collinear (parallel or antiparallel) with the reference layer. By using the spin torque of electrons, the magnetization direction of the free layer is flipped to realize the parallel (low resistance) or antiparallel (high resistance) of the magnetization direction of the reference layer and the free layer, so as to realize the writing of "0" or "1".

[0003] For a magnetic tunnel junction device, the size of the write current directly affects the power consumption of the device. The larger the write current, the greater the power consumption of the device. Therefore, in order to reduce the power consumption of the device, it is necessary to propose a magnetic tunnel junction device with lower critical switching current. SUMMARY

[0004] To solve the above problems, the present application provides a magnetic tunnel junction device, which reduces the magnetic damping coefficient of the device, thereby reducing the critical switching current of the device.

[0005] In a first aspect, the present application provides a magnetic tunnel junction device, comprising: a reference layer, a barrier layer, a free layer and a cap layer which are stacked, the reference layer has a fixed magnetization which is substantially perpendicular to the plane of the reference layer, the free layer has a magnetization which is substantially perpendicular to the plane of the free layer and can be converted between parallel or antiparallel to the magnetization direction of the reference layer, and the magnetic damping coefficient of the free layer is less than 0.003.

[0006] Optionally, the free layer is a ferromagnetic layer containing boron (B).

[0007] Optionally, the free layer has a composite structure, and the free layer comprises:

[0008] a first ferromagnetic layer, which is disposed adjacent to the barrier layer, and the magnetic damping coefficient of the first ferromagnetic layer is less than 0.004;

[0009] a second ferromagnetic layer, which is disposed on the side of the first ferromagnetic layer away from the barrier layer, and the magnetic damping coefficient of the second ferromagnetic layer is less than 0.002.

[0010] Optionally, the first ferromagnetic layer is a ferromagnetic layer having a first boron content, the first boron content being between 15% and 30%.

[0011] The second ferromagnetic layer is a ferromagnetic layer having a second boron content, the second boron content being greater than the first boron content.

[0012] Optionally, the material of the first ferromagnetic layer is selected from any one of Co, Fe, Ni, CoB, FeB, NiB, CoFe, NiFe, CoNi and CoFeB.

[0013] The material of the second ferromagnetic layer is selected from one of Fe2CoSi, Fe2CoSiB, Co2MnSi, Co2MnGe, Fe2Cr (1-x) Co x Si and Co (2-x) Fe (1+x) Si, wherein x is between 0.5 and 0.75.

[0014] Optionally, the free layer includes an insertion layer, the insertion layer being located between the first ferromagnetic layer and the second ferromagnetic layer.

[0015] In a second aspect, the present application provides a method for manufacturing a magnetic tunnel junction device, comprising:

[0016] forming a reference layer film;

[0017] forming a barrier layer film on the reference layer film;

[0018] depositing a free layer film on the barrier layer film;

[0019] performing high-temperature annealing on the free layer film to form a free layer film with large grains;

[0020] filling the grain boundaries of the free layer film with boron element;

[0021] performing photolithography and etching on the formed reference layer film, barrier layer film and free layer film.

[0022] Optionally, wherein depositing a free layer film comprises:

[0023] depositing a ferromagnetic layer film containing boron (B).

[0024] Optionally, wherein depositing a free layer film comprises:

[0025] depositing a first ferromagnetic layer film having a first boron content, the first boron content being between 15% and 30%;

[0026] depositing a second ferromagnetic layer film on the first ferromagnetic layer film, the second ferromagnetic layer film having a second boron content, the second boron content being greater than the first boron content.

[0027] Optionally, wherein the free layer film is deposited, comprising:

[0028] depositing a first ferromagnetic layer film, the first ferromagnetic layer film having a material selected from any one of Co, Fe, Ni, CoB, FeB, NiB, CoFe, NiFe, CoNi and CoFeB;

[0029] depositing a second ferromagnetic layer film on the first ferromagnetic layer film, the second ferromagnetic layer film having a material selected from Fe2CoSi, Fe2CoSiB, Co2MnSi, Co2MnGe, Fe2Cr (1-x) Co x Si and Co (2-x) Fe (1+x) Si, wherein x is between 0.5 and 0.75.

[0030] In a third aspect, the present application provides a magnetic tunnel junction device, comprising the magnetic tunnel junction device according to the first aspect.

[0031] The magnetic tunnel junction device provided by the present application improves the free layer structure, the free layer has a low magnetic damping coefficient less than 0.003, reduces the magnetic damping coefficient of the whole MTJ device, thereby reducing the critical switching current of the device and reducing the power consumption of the device. BRIEF DESCRIPTION OF DRAWINGS

[0032] Figure 1 a structure diagram of the magnetic tunnel junction device provided by an embodiment of the present application;

[0033] Figure 2 a structure diagram of the magnetic tunnel junction device provided by an embodiment of the present application. DETAILED DESCRIPTION

[0034] In order to make the purpose, technical scheme and advantages of the embodiments of the present application clearer, the technical scheme of the embodiments of the present application will be described clearly and completely below with reference to the drawings in the embodiments of the present application, but it should be understood that these descriptions are only exemplary and are not intended to limit the scope of the present disclosure. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative labor fall within the scope of the present application. In addition, in the following description, the description of well-known structures and technologies is omitted to avoid unnecessary confusion of the concepts of the present disclosure.

[0035] Various structural diagrams according to embodiments of the present disclosure are shown in the drawings. These diagrams are not drawn to scale in which certain details are shown exaggerated for clarity and others omitted. The shapes and relative sizes of the various regions, layers, and the relative positions of these in the drawings are shown for example only and can deviate in actual implementation due to manufacturing tolerances or technical limitations, and regions / layers with different shapes, sizes, relative positions can be additionally designed according to actual needs by those skilled in the art.

[0036] In the context of the present disclosure, when a layer / element is referred to as being located "on" another layer / element, the layer / element can be directly on the other layer / element, or there can be an intervening layer / element therebetween. In addition, if a layer / element is located "on" another layer / element in one orientation, it can be located "under" the other layer / element when the orientation is reversed.

[0037] It is known that to cause the free layer of a magnetic tunnel junction to flip, a write current needs to exceed the critical flipping current I c0 of the magnetic tunnel junction device, the critical flipping current I c0 is larger, the corresponding power consumption of the device is also larger. Therefore, it is necessary to appropriately reduce the critical flipping current of the device. Research shows that the critical flipping current I c0 is positively correlated with the magnetic damping coefficient α of the device, so the critical flipping current of the device can be reduced by reducing the magnetic damping coefficient α of the device.

[0038] Figure 1 A cross-sectional structural diagram of a magnetic tunnel junction device 100 provided by an embodiment of the present disclosure is shown. As shown in Figure 1 , the embodiment of the present disclosure provides a magnetic tunnel junction device 100, which includes, from bottom to top, a reference layer 101, a barrier layer 102, a free layer 103, and a cap layer 104. The cap layer 104 is a layer of heavy metal, such as Ta, which can play a protective role. The reference layer 101 has a fixed magnetization substantially perpendicular to the reference layer plane, the free layer 103 has a magnetization substantially perpendicular to the free layer plane and capable of switching between parallel or antiparallel to the magnetization direction of the reference layer 101, and the magnetic damping coefficient of the free layer 103 is less than 0.003.

[0039] In the embodiment of the present disclosure, in order to make the magnetic damping coefficient of the free layer 103 less than 0.003, the following several ways can be implemented.

[0040] 1. The crystalline grains of the free layer can be improved, and the increase of the magnetic damping coefficient caused by the grain boundary can be reduced. This can be achieved by layer-by-layer growth and subsequent high-temperature annealing. Typically, in order to achieve layer-by-layer growth of the free layer, the deposition rate can be reduced, the energy of atoms reaching the wafer during magnetron sputtering can be reduced, such as increasing the distance between the wafer and the target, increasing the pressure during deposition, etc. The temperature of the wafer can also be controlled, so that the deposited film is amorphous, and the growth of the grains is completely formed by subsequent high-temperature annealing, which is conducive to the formation of large grains while meeting the lattice matching requirements.

[0041] 2. The grain boundary can be filled with light elements (such as B), which can inhibit the diffusion of heavy metals in the cap layer to the interface and reduce the pump effect. The free layer 103 formed is a ferromagnetic layer containing boron (B), which can be a CoFeB alloy, for example.

[0042] 3. As shown in FIG. 1, the free layer 103 can adopt a layered composite structure, including a first ferromagnetic layer 1031 adjacent to the barrier layer 102 and a second ferromagnetic layer 1033 disposed on the side of the first ferromagnetic layer 1031 away from the barrier layer 102. In this embodiment, the magnetic damping coefficient of the first ferromagnetic layer 1031 is less than 0.004, and the magnetic damping coefficient of the second ferromagnetic layer 1033 is less than 0.002. Figure 2 As an implementation, the first ferromagnetic layer 1031 adopts a lower concentration of boron, and the second ferromagnetic layer 1033 far away from the barrier layer 102 adopts a higher concentration of boron, so that it diffuses to the grain boundary and reduces the pump effect. For example, the boron content of the first ferromagnetic layer 1031 is between 15% and 30%, and the boron content of the second ferromagnetic layer 1033 is between 20% and 60%, ensuring that the boron content of the second ferromagnetic layer 1033 is greater than that of the first ferromagnetic layer 1031. The free layer formed can include two layers of CoFeB alloy with different boron contents.

[0043] As an implementation, the second ferromagnetic layer 1033 can adopt a material with a lower magnetic damping coefficient to effectively reduce the damping coefficient α. For example, the material of the second ferromagnetic layer 1033 is selected from one of Fe2CoSi, Fe2CoSiB, Co2MnSi, Co2MnGe, Fe2Cr (1-x) Co x Si and Co (2-x) Fe (1+x) Si, where x is between 0.5 and 0.75. The first ferromagnetic layer 1031 also adopts a conventional material, such as any one of Co, Fe, Ni, CoB, FeB, NiB, CoFe, NiFe, CoNi, and CoFeB.

[0044]

[0045] ​Further, a non-magnetic insertion layer 1032 can be included between the first ferromagnetic layer 1031 and the second ferromagnetic layer 1033, which is preferably a heavy metal material that can absorb boron (B) and is relatively light, and can be, for example, Ta, Mo, W, Hf, Nb, V, Y, Cr, Ru, etc.

[0046] The magnetic tunnel junction device provided by the above embodiment has a free layer with a low magnetic damping coefficient of less than 0.003, which reduces the overall magnetic damping coefficient of the MTJ device, thereby reducing the critical switching current of the device and reducing the power consumption of the device.

[0047] The embodiment of the present application provides a manufacturing method of a magnetic tunnel junction device, which can be used to manufacture the magnetic tunnel junction device with a low magnetic damping coefficient in the above embodiment, and specifically includes the following steps:

[0048] Step 301: forming a reference layer film.

[0049] Step 302: forming a barrier layer film on the reference layer film.

[0050] Step 303: depositing a free layer film on the barrier layer film.

[0051] Step 304: performing high-temperature annealing treatment on the free layer film to form a free layer film with large grains.

[0052] Step 305: filling the grain boundaries of the free layer film with boron elements.

[0053] Step 306: performing photolithography and etching on the formed reference layer film, barrier layer film and free layer film.

[0054] Specifically, in step 303, since the free layer film with a low magnetic damping coefficient is to be formed, the deposition process is improved. First, the free layer film is deposited on the barrier layer film, a lower deposition speed is used to reduce the energy of atoms reaching the wafer during magnetron sputtering, a higher gas pressure is used, for example, between 15-25mtorr, and then high-temperature annealing treatment is performed on the deposited free layer film to form a free layer film with large grains; finally, the grain boundaries of the free layer film are filled with boron (B) elements.

[0055] In the embodiment, a ferromagnetic layer film containing boron (B) can be deposited, for example, CoFeB. Alternatively, the free layer film can be deposited in layers, a first ferromagnetic layer film with a first boron content is first deposited on the barrier layer film, and then a second ferromagnetic layer film with a second boron content is deposited on the first ferromagnetic layer film, the second boron content being greater than the first boron content. The first boron content is generally between 15% and 30%, and the second boron content is generally between 20% and 60%. The two ferromagnetic layer films can be CoFeB.

[0056] As another embodiment, the material of the two ferromagnetic layers can be changed, and the material of the second ferromagnetic layer can be selected to have a lower magnetic damping coefficient, so as to effectively reduce the damping coefficient α. For example, the material of the second ferromagnetic layer is selected from Fe2CoSi, Fe2CoSiB, Co2MnSi, Co2MnGe, Fe2Cr (1-x) Co x Si and Co (2-x) Fe (1+x) Si, where x is between 0.5 and 0.75. The first ferromagnetic layer can be made of a conventional material, such as any one of Co, Fe, Ni, CoB, FeB, NiB, CoFe, NiFe, CoNi, and CoFeB.

[0057] The manufacturing method provided by the above embodiments can be used to manufacture a magnetic tunnel junction device with a low magnetic damping coefficient, so as to reduce the critical switching current of the device.

[0058] Further, the embodiments of the present application also provide a magnetoresistive random access memory, which comprises the above magnetic tunnel junction device.

[0059] In the above description, the technical details of patterning, etching, etc. of each layer are not described in detail. However, those skilled in the art should understand that the layers, regions, etc. with the desired shape can be formed by various technical means. In addition, those skilled in the art can also design methods that are not exactly the same as the above-described methods in order to form the same structure. In addition, although each embodiment is described separately above, this does not mean that the measures in each embodiment cannot be used advantageously in combination.

[0060] The above merely provides a specific embodiment of the present application, but the protection scope of the present application is not limited thereto. Any changes or replacements within the technical scope disclosed by the present application can be easily thought of by those skilled in the art, and should be covered within the protection scope of the present application. Therefore, the protection scope of the present application should be subject to the protection scope of the claims.

Claims

1. A magnetic tunnel junction device, characterized in that, include: A reference layer, a barrier layer, a free layer, and a capping layer are stacked sequentially. The reference layer has a fixed magnetization that is approximately perpendicular to the plane of the reference layer. The free layer has a magnetization that is approximately perpendicular to the plane of the free layer and can switch between being parallel or antiparallel to the magnetization direction of the reference layer. The magnetic damping coefficient of the free layer is less than 0.

003. The capping layer is a heavy metal layer; The free layer has a composite structure, and the free layer includes: A first ferromagnetic layer is disposed adjacent to the barrier layer, and the magnetic damping coefficient of the first ferromagnetic layer is less than 0.

004. The second ferromagnetic layer is disposed on the side of the first ferromagnetic layer away from the barrier layer and adjacent to the capping layer. The magnetic damping coefficient of the second ferromagnetic layer is less than 0.

002. The first ferromagnetic layer uses a lower concentration of boron, while the second ferromagnetic layer, which is farther from the barrier layer, uses a higher concentration of boron. The boron content of the first ferromagnetic layer is between 15% and 30%, and the boron content of the second ferromagnetic layer is between 20% and 60%, ensuring that the boron content of the second ferromagnetic layer is greater than that of the first ferromagnetic layer.

2. The magnetic tunnel junction device according to claim 1, characterized in that, The free layer includes an insertion layer located between the first ferromagnetic layer and the second ferromagnetic layer.

3. A method for manufacturing a magnetic tunnel junction device, characterized in that, include: Form a reference layer thin film; A barrier layer film is formed on the reference layer film; Depositing a free layer film on the barrier layer film specifically includes: firstly depositing a first ferromagnetic layer film with a first boron content between 15% and 30% on the barrier layer film; then depositing a second ferromagnetic layer film with a second boron content between 20% and 60% on the first ferromagnetic layer film, ensuring that the boron content of the second ferromagnetic layer is greater than the boron content of the first ferromagnetic layer. The free layer film is subjected to high-temperature annealing to form a free layer film with large grains; By filling the particle boundaries of the free layer film with boron, the magnetic damping coefficient of the first ferromagnetic layer film is ultimately guaranteed to be less than 0.004, and the magnetic damping coefficient of the second ferromagnetic layer film is less than 0.

002. The reference layer film, barrier layer film, and free layer film are subjected to photolithography and etching.

4. A magnetoresistive random access memory, characterized in that, Includes the magnetic tunnel junction device as described in claim 1 or 2.

Images