Magnetic tunnel junction device

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, the free layer comprises a first ferromagnetic layer and a second ferromagnetic layer which are stacked, the first ferromagnetic layer is arranged adjacent to the barrier layer and has a high saturation magnetization. The application can reduce the 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 particularly relates to a magnetic tunnel junction device. 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 flip 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 the MTJ device, the size of the write current directly affects the power consumption of the device, and the larger the write current, the greater the power consumption of the device. Therefore, in order to reduce the power consumption of the MTJ device, it is necessary to propose a MTJ device with lower flip current. SUMMARY

[0004] To solve the above problems, the present application provides a magnetic tunnel junction device, which improves the saturation magnetization of the MTJ device, thereby reducing the flip 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 sequentially 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, wherein the free layer comprises:

[0006] A first ferromagnetic layer is disposed adjacent to the barrier layer, the first ferromagnetic layer has a high saturation magnetization, and the saturation magnetization is greater than 800 emu / cc;

[0007] A second ferromagnetic layer is disposed on the side of the first ferromagnetic layer away from the barrier layer, and the second ferromagnetic layer has a saturation magnetization smaller than that of the first ferromagnetic layer.

[0008] Optionally, the first ferromagnetic layer is a single-layer magnetic layer structure, the first ferromagnetic layer adopts Fe, Co x Fe (1-x) CoFe alloy in the form of CoFe or (Co x Fe(1-x) ) y B (1-y) CoFeB alloy in the form of CoxFeyB1-y, where the subscript denotes the atomic fraction, 0.3≤x≤0.5, 0.7≤y≤0.85.

[0009] Optionally, the first ferromagnetic layer is a multi-layer composite structure, and the first ferromagnetic layer comprises:

[0010] a first sub-layer, disposed adjacent to the barrier layer, having a high saturation magnetization, the saturation magnetization being greater than 800 emu / cc;

[0011] a second sub-layer, disposed on a side of the first sub-layer away from the barrier layer, having a saturation magnetization between the first sub-layer and the second ferromagnetic layer;

[0012] an adjusting layer, disposed between the first sub-layer and the second sub-layer, causing the first sub-layer and the second sub-layer to form a ferromagnetic coupling.

[0013] Optionally, the first sub-layer is made of Fe, Co x Fe (1-x) CoFe alloy in the form of CoxFey, where the subscript denotes the atomic fraction, 0.7≤y≤0.85. x Fe (1-x) ) y B (1-y) CoFeB alloy in the form of CoxFeyB1-y, where the subscript denotes the atomic fraction, 0.3≤x≤0.5, 0.7≤y≤0.85.

[0014] Optionally, the material of the second sub-layer has the same elemental composition as the material of the first sub-layer, but has different atomic proportions.

[0015] Optionally, the adjusting layer is a layer of non-magnetic metal, or a layer of weak magnetic or paramagnetic, or a discontinuous layer or interface.

[0016] Optionally, the material of the second ferromagnetic layer is (Co x Fe (1-x) ) y B (1-y) , 0.3≤x≤0.5, y≤0.7.

[0017] Optionally, the free layer further comprises an insertion layer, the insertion layer being disposed between the first ferromagnetic layer and the second ferromagnetic layer.

[0018] Optionally, the material of the insertion layer is selected from any one of Ta, Mo, W, Hf, Nb, V, Y, Cr, Ru.

[0019] In a second aspect, the present application provides a magnetoresistive random access memory, comprising the magnetic tunnel junction device provided in the first aspect.

[0020] The magnetic tunnel junction device provided by the present application improves the free layer structure, the free layer has high saturation magnetization, improves the overall saturation magnetization of the MTJ device, and further reduces the switching current of the MTJ device, and reduces the power consumption of the device. BRIEF DESCRIPTION OF DRAWINGS

[0021] Figure 1 A structural schematic diagram of the magnetic tunnel junction device provided by an embodiment of the present application is shown in the figure.

[0022] Figure 2 A structural schematic diagram of the magnetic tunnel junction device provided by an embodiment of the present application is shown in the figure. DETAILED DESCRIPTION

[0023] 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 known structures and technologies is omitted to avoid unnecessary confusion of the concepts of the present disclosure.

[0024] Various structural schematic diagrams according to the embodiments of the present disclosure are shown in the drawings. These figures are not drawn to scale, in which certain details are exaggerated for the purpose of clarity and certain details can be omitted. The shapes of various regions, layers and their relative sizes and positional relationships shown in the figures are only exemplary, and in actuality, there can be deviations due to manufacturing tolerances or technical limitations, and those skilled in the art can additionally design regions / layers with different shapes, sizes and relative positions according to actual needs.

[0025] 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 located on the other layer / element, or there can be an intervening layer / element between them. 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.

[0026] It is known that to cause the free layer of the magnetic tunnel junction to switch, the write current needs to exceed the critical switching current I c0 of the magnetic tunnel junction device, the critical switching current I c0The larger the device is, the larger the power consumption of the device is. Therefore, it is necessary to properly reduce the switching current of the device. The applicant finds through research that when the thermal stability factor Δ is constant, the saturation magnetization Ms of the device is increased, and the switching current I c of the device is reduced. Therefore, the application provides a magnetic tunnel junction device with high saturation magnetization, so that a low switching current can be achieved.

[0027] Figure 1 A cross-sectional structure diagram of a magnetic tunnel junction device 100 is shown. As Figure 1 shown, the magnetic tunnel junction device 100 provided by the embodiment of the application includes a reference layer 101, a barrier layer 102, a free layer 103, and a cap layer 104 stacked in sequence from bottom to top. The cap layer 104 is a heavy metal layer, for example, Ta, which can play a protective role. The reference layer 101 has a fixed magnetization substantially perpendicular to the plane of the reference layer 101. The free layer 103 has a magnetization substantially perpendicular to the plane of the free layer 103 and capable of switching between parallel or antiparallel to the magnetization direction of the reference layer 101. The barrier layer 102 can be a magnesium oxide MgO layer. In order to improve the saturation magnetization Ms of the device while not affecting the thermal stability factor Δ of the device, in the embodiment of the application, the free layer 103 adopts a layered structure, and the free layer 103 includes a first ferromagnetic layer 1031 and a second ferromagnetic layer 1033. The first ferromagnetic layer 1031 is arranged adjacent to the barrier layer 102, and has a relatively high saturation magnetization Ms, generally greater than 800 emu / cc. The second ferromagnetic layer 1033 is arranged on the side of the first ferromagnetic layer 1031 away from the barrier layer 102, and has a saturation magnetization Ms smaller than that of the first ferromagnetic layer 1031. Such a structure has a small overall demagnetizing field, and can maintain a high thermal stability factor Δ. During the switching process of the free layer, the magnetic moment of the first ferromagnetic layer 1031 close to the barrier layer 102 is switched first, and then drives the magnetic moment of the second ferromagnetic layer 1033 to switch.

[0028] Further, referring to Figure 1 , a non-magnetic insertion layer 1032 can be inserted between the first ferromagnetic layer 1031 and the second ferromagnetic layer 1033. Preferably, the non-magnetic insertion layer 1032 is a heavy metal material that can absorb boron (B) and is relatively light. Typical materials can include Ta, Mo, W, Hf, Nb, V, Y, Cr, Ru, etc., so that the two ferromagnetic layers are ferromagnetically coupled.

[0029] As an implementation, the first ferromagnetic layer 1031 can be a single-layer magnetic layer structure, and a magnetic material with high saturation magnetization Ms and high spin polarization rate after matching with the barrier layer MgO (so as to achieve high STT switching efficiency and high TMR) is used. Typical materials include Fe, Cox Fe (1-x) CoFe alloys or (Co) x Fe (1-x) ) y B (1-y) CoFeB alloys in the form of subscripts indicating the proportion of atoms, 0.3≤x≤0.5, Ms is maximum near x=0.4, 0.7≤y≤0.85.

[0030] As another implementation method, such as Figure 2 As shown, the first ferromagnetic layer 1031 may further include a first sublayer 10311, a regulating layer 10312, and a second sublayer 10313. The first sublayer 10311 is disposed adjacent to the barrier layer 102 and has a high saturation magnetization, which is greater than 800 emu / cc. Its material selection is mainly based on high Ms and high spin polarization after matching with the MgO of the barrier layer (thereby achieving high STT switching efficiency and high TMR). Typical materials include Fe and Co. x Fe (1-x) CoFe alloys or (Co) x Fe (1-x) ) y B (1-y) CoFeB alloys are in the form where the subscripts indicate the proportion of atoms, with 0.3 ≤ x ≤ 0.5, Ms being the largest near x = 0.4, and 0.7 ≤ y ≤ 0.85. The thickness is generally a few molecular layers, not exceeding 1 nm.

[0031] The second sublayer 10313 is located on the side of the first sublayer 10311 away from the barrier layer 102, and its saturation magnetization is between that of the first sublayer 10311 and the second ferromagnetic layer 1033. The structure of the second sublayer 10313 matches that of the first sublayer 10311, and it can have the same elemental composition but different atomic ratios. Typically, it can be (Co... x Fe (1-x) ) y B (1-y) CoFeB alloys in the form of materials, but with different compositions x and y.

[0032] The second sublayer 10313 can be obtained in several ways, such as adjusting the Fe and Co ratio in CoFeB, or doping CoFeB with other non-magnetic materials, or inserting other non-magnetic metal layers into CoFeB, such as Mg, Al, B, Ca, Ba, Sr, Ta, Si, Mn, Ti, Zr, Hf, etc., or using other low Ms materials, such as Fe, Ni, Co and their alloys.

[0033] The adjusting layer 10312 can be a metal layer, a simple interface, a discontinuous layer such as a B-absorbing layer of Mo, W, Ta, Ir, Mg, or a weakly magnetic or paramagnetic layer, so as to form ferromagnetic coupling between the first sub-layer 10311 and the second sub-layer 10313.

[0034] The second ferromagnetic layer 1033 is generally made of a low Ms material, which can be the same as the material of the second sub-layer 10313, for example, can be (Co x Fe (1-x) ) y B (1-y) 0.3≤x≤0.5, y≤0.7, which can improve the anisotropy field and meet the lattice matching of the barrier layer MgO, so as to form strong interface perpendicular magnetic anisotropy (PMA).

[0035] The magnetic tunnel junction device provided by the embodiment of the present application has a layered structure for the free layer, and the part close to the barrier layer has a high saturation magnetization, which can improve the overall saturation magnetization of the MTJ device, thereby reducing the switching current of the device, reducing the power consumption of the device, and improving the durability of the device.

[0036] Further, the embodiment of the present application further provides a magnetoresistive random access memory, which comprises the above magnetic tunnel junction device.

[0037] In the above description, the patterning, etching and other technical details of each layer are not described in detail. However, those skilled in the art should understand that the layers, regions and the like with the required 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.

[0038] The above is only a specific embodiment of the present application, but the protection scope of the present application is not limited thereto, and any changes or replacements within the technical range disclosed by the present application can be easily thought of by those skilled in the art, which 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, comprising: Comprising: a reference layer, a barrier layer, a free layer and a cap layer stacked in sequence, the reference layer having a fixed magnetization substantially perpendicular to a plane of the reference layer, the free layer having a magnetization substantially perpendicular to a plane of the free layer and capable of switching between parallel or anti-parallel to a magnetization direction of the reference layer, wherein the free layer comprises: a first ferromagnetic layer disposed adjacent to the barrier layer, the first ferromagnetic layer having a high saturation magnetization, a saturation magnetization greater than 800 emu / cc; a second ferromagnetic layer disposed on a side of the first ferromagnetic layer away from the barrier layer, the second ferromagnetic layer disposed adjacent to the cap layer, the second ferromagnetic layer having a saturation magnetization less than the first ferromagnetic layer; during a switching of the free layer, the first ferromagnetic layer near the barrier layer has its magnetic moment switched first, then the second ferromagnetic layer has its magnetic moment switched; wherein the first ferromagnetic layer is a multi-layer composite structure, the first ferromagnetic layer comprises: a first sub-layer disposed adjacent to the barrier layer, having a high saturation magnetization, a saturation magnetization greater than 800 emu / cc, the first sub-layer material selected from (Co x Fe （1-x） ) y B （1-y） CoFeB alloy in the form of CoFeB, where the subscripts represent atomic number fractions, 0.3 < x < 0.5, 0.7 < y < 0.85; a second sub-layer disposed on a side of the first sub-layer away from the barrier layer, the second sub-layer having a saturation magnetization between the first sub-layer and the second ferromagnetic layer; an adjustment layer disposed between the first sub-layer and the second sub-layer, the adjustment layer causing the first sub-layer and the second sub-layer to form a ferromagnetic coupling; The second ferromagnetic layer is the same as the second sublayer material, using material is (Co x Fe （1-x） ) y B （1-y） , 0.3≤x≤0.5, y≤0.

7.

2. The magnetic tunnel junction device of claim 1, wherein, the second sub-layer has a same elemental composition as the first sub-layer but has a different atomic ratio.

3. The magnetic tunnel junction device of claim 1, wherein, the adjustment layer is a non-magnetic metal layer, or a weakly magnetic or paramagnetic layer, or a discontinuous layer or interface.

4. The magnetic tunnel junction device of claim 1, wherein, the free layer further comprises an insertion layer disposed between the first ferromagnetic layer and the second ferromagnetic layer.

5. The magnetic tunnel junction device of claim 4, wherein, the insertion layer is selected from any one of Ta, Mo, W, Hf, Nb, V, Y, Cr, Ru.

6. A magnetoresistive random access memory, characterized by, A magnetic tunnel junction device as claimed in any one of claims 1 to 5.

Images