A spin-orbit magnetic memory and its fabrication method

Abstract

This invention discloses a spin-orbit-moment (SOT-MRAM) magnetic memory and its fabrication method, relating to the field of electronics. The SOT-MRAM comprises a composite heavy metal layer and a magnetic tunnel junction disposed on the composite heavy metal layer. The composite metal layer includes at least two thin-film structures: a first heavy metal layer structure and a second heavy metal layer structure, where either of the at least two thin-film structures is made of a β-phase material. It is evident that selecting a β-phase material for the original heavy metal layer is advantageous because the β-phase material itself possesses a large spin Hall angle, which can enable the SOT-MRAM to have a higher switching efficiency. Furthermore, compared to other materials with the same spin conductivity, the β-phase material has a lower resistivity, which can reduce losses caused by resistivity during device operation.

Description

TECHNICAL FIELD

[0001] The embodiment of the application relates to the electronic field, in particular to a preparation method of a magnetic random memory. BACKGROUND

[0002] With the continuous development of emerging memory research and development process, spin orbit torque magnetic memory (SOT-MRAM, Spin Orbit Torque - Magnetic Access Memory) is more and more widely used. SOT-MRAM can produce a strong spin orbit coupling (Spain Orbit Coupling, SOC) effect of the spin orbit torque effect heavy metal layer, so the SOT is often required to have a large spin-charge conversion efficiency to improve the flip efficiency of the SOT-MRAM; and is required to have a large spin conductivity to reduce the power loss caused by the large resistivity of the SOT-MRAM device during use.

[0003] Therefore, in the actual preparation and application process, for the SOT-MRAM, improving the flip efficiency and reducing the resistivity become the common technical research direction in the field. SUMMARY

[0004] The embodiment of the application provides a spin orbit torque magnetic memory and a preparation method thereof, which can improve the flip efficiency of the SOT-MRAM device and reduce the loss caused by the resistivity.

[0005] In order to solve the above problems, the first aspect of the application provides a spin orbit torque magnetic memory, which comprises: a composite heavy metal layer and a magnetic tunnel junction arranged above the composite heavy metal layer,

[0006] The composite metal layer comprises at least two thin film structures: a first heavy metal layer structure and a second heavy metal layer structure, and the first heavy metal layer structure is arranged below the second heavy metal layer structure.

[0007] Any one of the at least two thin film structures is obtained by a beta phase structure material. In some embodiments, the spin orbit torque magnetic memory, the beta phase structure material at least comprises beta tungsten beta-W, beta tantalum beta-Ta and beta A3B compound,

[0008] For the beta A3B compound, the A element selection range at least includes vanadium, niobium, tantalum and the sixth period transition metal element;

[0009] The B element selection range at least includes the fifth subgroup element and the sixth subgroup element;

[0010] The sixth period transition metal elements at least include hafnium, tantalum, tungsten, rhenium, osmium, iridium, platinum and gold;

[0011] The fifth subgroup elements at least include vanadium, niobium, tantalum and technetium;

[0012] The sixth subgroup elements at least include chromium, molybdenum, tungsten and rutherfordium.

[0013] In some embodiments, the composite heavy metal layer is 1-10 layers, and the thickness of the composite metal layer is 1-10 nm.

[0014] In some embodiments, the magnetic tunnel junction includes a free layer, a non-magnetic barrier layer and a fixed layer, wherein the free layer is disposed on the composite heavy metal layer, the non-magnetic barrier layer is disposed on the free layer, and the fixed layer is disposed on the non-magnetic barrier layer.

[0015] In some embodiments, the free layer and / or the fixed layer can be obtained from at least one of the following materials, including cobalt-iron-boron alloy, cobaltized iron alloy and cobalt,

[0016] The atomic ratio of the cobalt-iron-boron alloy at least includes one of Co 20 Fe 60 B 20 , Co 40 Fe 40 B 20 and Co 60 Fe 20 B 20 ;

[0017] The atomic ratio of the cobalt-iron-boron alloy at least includes one of Co 70 Fe 30 , Co 75 Fe 25 and Co 85 Fe 15 ;

[0018] The non-magnetic barrier layer can be obtained from at least one of the following materials, including magnesium oxide and aluminum trioxide.

[0019] In some embodiments, the thickness of the free layer and / or the fixed layer is selected from the range of 0.5 nm to 5 nm.

[0020] In the second aspect of the present application, a preparation method of a spin-orbit torque magnetic memory is also provided,

[0021] The spin-orbit torque magnetic memory includes a composite heavy metal layer, and the method includes:

[0022] building a composite heavy metal layer on the bottom electrode layer;

[0023] building a magnetic tunnel junction on the bottom heavy metal layer;

[0024] building a capping layer on the magnetic tunnel junction.

[0025] In some embodiments, the composite heavy metal layer comprises a first heavy metal layer and a second heavy metal layer, and the building a first heavy metal layer on the bottom electrode layer comprises:

[0026] building the first heavy metal layer on the bottom electrode layer by sputtering;

[0027] building the second heavy metal layer on the first heavy metal layer by sputtering.

[0028] In some embodiments, the number of the composite heavy metal layers is 1-10, and the thickness of the composite heavy metal layer is 1-10 nm.

[0029] In some embodiments, the first heavy metal layer and the second heavy metal layer are obtained by sputtering of a β-phase structure material,

[0030] The β-phase structure material at least comprises beta-tungsten β-W, beta-tantalum β-Ta, and a βA3B compound,

[0031] For the βA3B compound, the A element is selected from at least: vanadium, niobium, tantalum, and a sixth period transition metal element;

[0032] The B element is selected from at least: a fifth subgroup element and a sixth subgroup element;

[0033] The sixth period transition metal element at least comprises hafnium, tantalum, tungsten, rhenium, osmium, iridium, platinum, and gold;

[0034] The fifth subgroup element at least comprises vanadium, niobium, tantalum, and rutherfordium;

[0035] The sixth subgroup element at least comprises chromium, molybdenum, tungsten, and seaborgium.

[0036] In some embodiments, the process of processing the magnetic tunnel junction film layer structure into a magnetic tunnel junction can be built by three ways: gluing, developing, and etching.

[0037] The embodiment of the present application provides a composite heavy metal layer structure SOT-MRAM and a preparation method thereof, the multi-layer design of the heavy metal layer of the SOT-MRAM structure, the change of the single-layer structure of the original heavy metal layer into a multi-layer thin film structure can reduce the yield caused by the precision error of the subsequent etching process on the device, and the heavy metal layer prepared by applying the beta phase structure material has a large spin Hall angle due to the large spin Hall angle of the beta phase structure material itself, so that the SOT-MRAM has a large flip efficiency, and the beta phase structure material has a smaller resistivity than other materials with the same spin conductivity, so that the loss caused by the resistivity during the operation of the device can be reduced. BRIEF DESCRIPTION OF DRAWINGS

[0038] In order to more clearly illustrate the technical solutions of the embodiments of the present application or the prior art, the drawings needed to be used in the embodiments or the prior art description will be briefly introduced. Obviously, the drawings in the following description are only some embodiments of the present application.

[0039] Figure 1 It is a structure schematic diagram of the SOT-MRAM according to the conventional technology of the present application.

[0040] Figure 2 It is a magnetic tunnel junction structure schematic diagram of the composite heavy metal layer structure according to an embodiment of the present application.

[0041] Figure 3 It is a beta phase structure material unit cell structure schematic diagram according to an embodiment of the present application.

[0042] Figure 4 It is a resistivity distribution schematic diagram of different sputtering ratios of Ta in W3Ta according to an embodiment of the present application.

[0043] Figure 5 It is a different beta phase structure material spin conductivity data diagram according to an embodiment of the present application.

[0044] Figure 6 It is a magnetic tunnel junction structure schematic diagram with a multi-layer composite heavy metal layer according to an embodiment of the present application. DETAILED DESCRIPTION

[0045] In order to make the purposes, characteristics and advantages of the present application more obvious and easy to understand, the technical solutions in the embodiments of the present application will be described clearly and completely in combination with the drawings in the embodiments of the present application. Obviously, the described embodiments are only some embodiments of the present application, but not all embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor are within the scope of protection of the present application.

[0046] Those skilled in the art can understand that the terms "first", "second" and the like in the present application are only used to distinguish different devices, modules or parameters, and do not represent any specific technical meaning, nor indicate their logical order.

[0047] As shown in Figure 1 The core structure of the conventional SOT-MRAM includes, from bottom to top, a heavy metal layer, a free layer, a non-magnetic barrier layer, a fixed layer, an anti-ferromagnetic coupling layer, a pinning layer and a cover layer. The heavy metal layer generates a spin Hall effect. Spin is an angular momentum inherent to electrons, and the spin Hall effect refers to the movement of spin-up and spin-down electrons in opposite directions when a non-polarized current is injected under the condition of no external magnetic field. However, the number of charges moving upwards and downwards is equal, so there is no net current flowing. The main cause of the spin Hall effect is based on the electron spin-orbit coupling (SOC) in the material, that is, the interaction between the "spin angular momentum" and the "orbital angular momentum" of the electron. Therefore, the degree of spin Hall effect result is strongly related to the selection of the sample material used. In the application of SOT-MRAM, SOT-MRAM generates a non-equilibrium spin accumulation by passing an in-plane current through the heavy metal layer, thereby forming a spin current perpendicular to the current direction. The spin-polarized current entering the free layer rapidly interacts with the local magnetic moment to generate a spin-orbit torque (or a field), which can induce the magnetic moment to flip if the critical current is reached. The SOT-MRAM can generate a flip due to the strong spin-orbit coupling of the heavy metal layer, and the spin source often has a certain spin conversion efficiency, that is, the spin Hall angle (SHA),

[0048] Generally, the larger the spin Hall angle, the greater the spin conversion rate, and the more likely the device to flip.

[0049] Generally, the fixed layer has a magnetic moment fixed in one direction and is not easily changed by external stimulation, while the magnetic moment direction of the free layer can be changed by the spin current induced by the SOT current, thereby switching in the two directions of the easy magnetization axis. The change in direction represents the high and low resistance states of the MTJ, which can be used to represent the storage data "1" or "0" state in the row storage field.

[0050] Generally, there are some problems in the use of SOT-MRAM in actual devices, such as insufficient spin conversion rate causing flip difficulty, or large device resistivity due to material selection or structure design, resulting in large power loss during operation.

[0051] In an embodiment of the present application, the composite heavy metal layer is used to construct the SOT-MRAM to ensure the switching efficiency of the magnetic tunnel junction in use and reduce the loss caused by the resistivity.

[0052] As shown in the magnetic tunnel junction structure diagram with a composite heavy metal layer structure, Figure 2

[0053] The spin-orbit torque magnetic memory includes a composite heavy metal layer and a magnetic tunnel junction disposed on the composite heavy metal layer.

[0054] The composite metal layer includes at least two thin film structures: a first heavy metal layer structure and a second heavy metal layer structure.

[0055] Any one of the at least two thin film structures is made of a β-phase structure material.

[0056] Compared with the materials (Pt, Ta, W, Hf, Cu, Ir, and PtMn) widely used to prepare the heavy metal layer in the prior art, the β-phase structure material (for example, β-W) has a larger self-Hall angle (about -0.3), and thus has a larger self-rotation rate. The β-phase structure material has a body-centered cubic crystal system, as shown in the figure, each lattice point and body center contains one atom, and each surface of the body-centered cubic has two atoms. The material with such a structure has a larger self-rotation rate. Figure 3

[0057] In addition, due to the composite structure, the thickness of the composite heavy metal layer is larger than that of the single-layer structure in the prior art. Therefore, in the etching process, the etching error has a smaller impact on the multi-layer heavy metal layer structure than on the conventional heavy metal layer under the same etching process capability. Therefore, the composite heavy metal layer has a larger adjustment range of etching thickness and etching time than the conventional heavy metal layer, that is, has a larger upper and lower limit of product specifications. In other words, the introduction of the composite heavy metal layer strengthens the ability of the product itself to resist the abnormal impact of etching precision, thereby reducing the risk of product failure caused by etching precision abnormality.

[0058] In an embodiment of the present application, the construction material of the composite heavy metal layer is selected and limited to improve the spin rotation rate of the SOT-MRAM and reduce the loss caused by the resistivity.

[0059] Optionally, the β-phase structure material at least includes β-W, β-Ta, and a β-phase A3B compound.

[0060] ​​For the β-phase A3B compound, the range of elements A includes at least: vanadium (V), niobium (Nb), tantalum (Ta), silicon (Si), and transition metal elements from the sixth period;

[0061] The selection range for element B includes at least: elements of subgroup 5 and elements of subgroup 6;

[0062] The sixth-period transition metal elements include at least: hafnium (Hf), tantalum, tungsten (W), rhenium (Re), osmium (Os), iridium (Ir), platinum (Pt), and gold (Au);

[0063] The fifth subgroup elements include at least: vanadium, niobium, tantalum, and argon (Db);

[0064] The sixth subgroup elements include at least: chromium, molybdenum, tungsten, and sg (Sg).

[0065] The β-phase A3B compound includes at least: W3Ta, W3W, Ta3Sb, Cr3Ir, Nb3Au, W3Re, Ta3Ta, and W3Si.

[0066] In one embodiment of this application, the formation of the β-phase A3B compound is typically achieved by sputtering both element A and element B materials together, resulting in a target molar ratio of A:B = 3:1, thus forming the β-phase A3B compound.

[0067] Optionally, during the co-sputtering process, to ensure a higher probability of generating a β-phase A3B compound structure, the sputtering ratio can be controlled by adjusting the sputtering rate.

[0068] For example, taking W3Ta as an example, to obtain the β-phase structure, the resistivity range of the β-phase W3Ta structure is 100 μΩcm to 300 μΩcm. In actual testing, as shown... Figure 4 As shown, the proportion of Ta is changed by adjusting the co-sputtering rate of W and Ta:

[0069] When the proportion of Ta is less than or equal to 30%, resistivity is tested and the resistivity meets the range of β-phase resistivity.

[0070] When the proportion of Ta is greater than 30%, the resistivity decreases and exceeds the resistivity range of the β phase (i.e., the structure is not a β phase structure at this time).

[0071] Therefore, for W3Ta, the proportion of Ta can be selected from 0% to 30%, and the same applies to other materials, which will not be elaborated here.

[0072] For example, the spin conductivity results of β-phase A3B compounds in different materials were calculated as follows: Figure 5 As shown, it can be seen that W3Ta has the largest absolute value of spin conductivity compared to the listed materials. Since resistivity and spin conductivity are inversely proportional, W3Ta has a larger spin Hall angle and the smallest resistivity (that is, the device prepared by using this material to prepare SOT-MRAM has less loss during operation than the device prepared by other materials in the table).

[0073] Optionally, the number of composite heavy metal layers is 1 to 10, and the thickness of the composite metal layer is 1 to 10 nm. In this way, the introduction of the composite heavy metal layer enhances the product's ability to resist the influence of abnormal etching precision, thereby reducing the risk of product defects caused by abnormal etching precision.

[0074] Optionally, the magnetic tunnel junction includes: a free layer, a non-magnetic barrier layer, and a fixed layer, wherein the free layer is disposed on the composite heavy metal layer, the non-magnetic barrier layer is disposed on the free layer, and the fixed layer is disposed on the non-magnetic barrier layer.

[0075] Optionally, the free layer and / or fixed layer may be obtained from at least one of the following materials: cobalt-iron-boron alloy, cobalt-iron alloy, and cobalt.

[0076] The atomic ratio of the cobalt-iron-boron alloy includes at least one of the following: Co 20 Fe 60 B 20 Co 40 Fe 40 B 20 and Co 60 Fe 20 B 20 ;

[0077] The atomic ratio of the cobalt-iron alloy includes at least one of the following: Co 70 Fe 30 Co 75 Fe 25 and Co 85 Fe 15 ;

[0078] The non-magnetic barrier layer can be obtained from at least one of the following materials: magnesium oxide and aluminum oxide.

[0079] Optionally, the thickness of the free layer and / or the fixed layer may be selected within the range of 0.5 nm to 5 nm.

[0080] Specifically, such as Figure 6Taking an antiferromagnetically coupled in-plane tunneling magnetoresistance as an example, from bottom to top, the layers are: bottom electrode, composite heavy metal layer, free layer, non-magnetic barrier layer, fixed layer, ferromagnetic layer, pinning layer and capping layer.

[0081] The bottom electrode is made of silicon or silicon dioxide.

[0082] The composite heavy metal layer adopts a 4-layer heavy metal layer structure, specifically including: β-W (i.e., the first heavy metal layer structure), β-W3Ta (i.e., the second heavy metal layer structure), β-W (i.e., the third heavy metal layer structure) and β-Ta (i.e., the fourth heavy metal layer structure) disposed on β-W3Ta.

[0083] Free layer material selection: cobalt-iron-boron alloy;

[0084] Non-magnetic barrier layer material selection: magnesium oxide;

[0085] The fixing layer material is selected as: cobalt iron boron alloy or cobalt iron alloy;

[0086] Antiferromagnetic layer material selection: Ruthenium;

[0087] Pinning layer material selection: cobalt iron alloy or iridium manganese;

[0088] The coating material is ruthenium.

[0089] Optionally, for the composite heavy metal layer, an annealing operation is performed after sputtering. The annealing conditions include: temperature 300℃, magnetic field strength 1T, and annealing time 1h.

[0090] Optionally, the annealing direction is perpendicular to the current direction in the heavy metal layer.

[0091] Optionally, the produced film stack can be further processed by coating, developing, etching, and other operations to obtain a complete device.

[0092] In another embodiment of this application, a method for fabricating a spin-orbit magnetic memory is also described, applicable to spin-orbit magnetic memories, wherein the spin-orbit magnetic memory includes a composite heavy metal layer, and the method includes:

[0093] A composite heavy metal layer is constructed on top of the bottom electrode layer;

[0094] A magnetic tunnel junction is constructed on top of the bottom heavy metal layer;

[0095] A capping layer is constructed on top of the magnetic tunnel junction.

[0096] Optionally, the composite heavy metal layer includes a first heavy metal layer and a second heavy metal layer, and constructing the first heavy metal layer on the bottom electrode layer includes:

[0097] The first heavy metal layer is constructed on top of the bottom electrode layer by sputtering;

[0098] The second heavy metal layer is constructed on top of the first heavy metal layer by sputtering.

[0099] Sputtering is a process in which particles (particles or neutral atoms or molecules) of a certain energy bombard a solid surface, so that the atoms or molecules near the solid surface gain enough energy to eventually escape from the solid surface. Sputtering can only be carried out under certain vacuum conditions. The hybrid heavy metal layer growth and construction described here can be carried out using sputtering, but is not limited to this scheme. Other modes are also applicable.

[0100] Optionally, the number of composite heavy metal layers is 1 to 10, and the thickness of the composite metal layer is 1 to 10 nm.

[0101] Optionally, the first heavy metal layer and the second heavy metal layer are obtained by sputtering a β-phase structure material.

[0102] The β-phase structural material includes at least: beta-tungsten β-W, beta-tantalum β-Ta, and β-phase A3B type compounds.

[0103] For the β-phase A3B compound, the range of elements A includes at least: vanadium, niobium, tantalum, and transition metal elements from the sixth period;

[0104] The selection range for element B includes at least: elements of subgroup 5 and elements of subgroup 6;

[0105] The sixth-period transition metal elements include at least: hafnium, tantalum, tungsten, rhenium, osmium, iridium, platinum, and gold;

[0106] The fifth subgroup elements include at least: vanadium, niobium, tantalum, and argon;

[0107] The sixth subgroup elements include at least: chromium, molybdenum, tungsten, and tungsten.

[0108] This invention provides a composite heavy metal layer structure for SOT-MRAM and its fabrication method. By designing a multilayer heavy metal layer in the SOT-MRAM structure, the original single-layer heavy metal layer structure is changed to a multilayer thin film structure, which can reduce the defect rate of the device caused by precision errors in the subsequent etching process. Furthermore, the heavy metal layer prepared by using a β-phase structure material has a large spin Hall angle, which can make the SOT-MRAM have a large flipping efficiency. At the same time, compared with other materials with the same spin conductivity, the β-phase structure material has a lower resistivity, which can reduce the loss caused by resistivity during device operation.

[0109] The above description is merely a preferred embodiment of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A spin-orbit torque magnetic memory, comprising: The spin-orbit torque magnetic memory comprises a composite heavy metal layer and a magnetic tunnel junction disposed above the composite heavy metal layer, The composite heavy metal layer comprises at least two thin film structures: a first heavy metal layer structure and a second heavy metal layer structure, the first heavy metal layer structure is disposed below the second heavy metal layer structure; Each thin film structure in the composite heavy metal layer is obtained from a beta phase structure material; The materials of adjacent two thin film structures are different.

2. The spin orbit torque magnetic memory of claim 1, wherein, The beta phase structure material at least comprises: beta tungsten β-W, beta tantalum β-Ta and a beta phase A3B compound, For the beta phase A3B compound, the selection range of A element at least includes: vanadium, niobium, tantalum, silicon and the sixth period transition metal element; The selection range of B element at least includes: the fifth subgroup element and the sixth subgroup element; The sixth period transition metal element at least includes: hafnium, tantalum, tungsten, rhenium, osmium, iridium, platinum and gold; The fifth subgroup element at least includes: vanadium, niobium, tantalum and rhenium; The sixth subgroup element at least includes: chromium, molybdenum, tungsten and rhenium.

3. The spin orbit torque magnetic memory of claim 1, wherein, The number of layers of the composite heavy metal layer is 2-10, and the thickness of the composite heavy metal layer is 1-10 nm.

4. The spin orbit torque magnetic memory of claim 1, wherein, The magnetic tunnel junction comprises: a free layer, a non-magnetic barrier layer and a fixed layer, wherein the free layer is disposed above the composite heavy metal layer, the non-magnetic barrier layer is disposed above the free layer, and the fixed layer is disposed above the non-magnetic barrier layer.

5. The spin orbit torque magnetic memory of claim 4, wherein, The free layer and / or the fixed layer is obtained from at least one of the following materials, including: cobalt iron boron alloy, cobalt iron alloy and cobalt, The atomic ratio of the cobalt-iron-boron alloy includes at least one of: Co 20 Fe 60 B 20 , Co 40 Fe 40 B 20 , and Co 60 Fe 20 B 20 ; The atomic ratio of the cobaltized iron alloy includes at least one of Co 70 Fe 30 , Co 75 Fe 25 , and Co 85 Fe 15 ; The non-magnetic barrier layer is obtained from at least one of the following materials, including: magnesium oxide and aluminum oxide.

6. The spin orbit torque magnetic memory of claim 4 or 5, wherein, The thickness of the free layer and / or the fixed layer is selected from the range of 0.5 nm to 5 nm.

7. A method of fabricating a spin orbit torque magnetic memory, comprising: The method is suitable for spin-orbit torque magnetic memory, the spin-orbit torque magnetic memory comprises a composite heavy metal layer, and the method comprises: Building a composite heavy metal layer above a bottom electrode layer; Building a magnetic tunnel junction above the composite heavy metal layer; Building a cover layer above the magnetic tunnel junction; The composite heavy metal layer comprises at least two thin film structures: a first heavy metal layer and a second heavy metal layer, the first heavy metal layer is built below the second heavy metal layer; Each thin film structure in the composite heavy metal layer is obtained from a beta phase structure material; The materials of adjacent two thin film structures are different.

8. The method of claim 7, wherein, The building of the composite heavy metal layer above the bottom electrode layer comprises: Building a first heavy metal layer above a bottom electrode layer by sputtering; Building the second heavy metal layer above the first heavy metal layer by sputtering.

9. The method of claim 7, wherein, The number of layers of the composite heavy metal layer is 2-10, and the thickness of the composite heavy metal layer is 1-10 nm.

10. The method of claim 7, wherein, Any one layer in the composite heavy metal layer is obtained by sputtering a beta phase structure material, The beta phase structure material at least comprises: beta tungsten β-W, beta tantalum β-Ta and a beta phase A3B compound, For the beta phase A3B compound, the selection range of A element at least includes: vanadium, niobium, tantalum and the sixth period transition metal element; The B element is selected from at least: a fifth subgroup element and a sixth subgroup element; The sixth period transition metal element includes at least: hafnium, tantalum, tungsten, rhenium, osmium, iridium, platinum and gold; The fifth subgroup element includes at least: vanadium, niobium, tantalum and technetium; The sixth subgroup element includes at least: chromium, molybdenum, tungsten and rutherfordium.

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