Magnetoresistance effect element, magnetic memory, and method for manufacturing magnetoresistance effect element

Abstract

This magnetoresistance effect element comprises a wiring layer, a layered body, and a diffusion-preventing layer. The layered body is in contact with the wiring layer. The layered body is provided with a first ferromagnetic layer, a second ferromagnetic layer, a non-magnetic layer, and a non-magnetic metal layer. The second ferromagnetic layer is closer to the wiring layer than the first ferromagnetic layer. The first ferromagnetic layer is between the non-magnetic layer and the non-magnetic metal layer in the layering direction. The non-magnetic layer is between the first ferromagnetic layer and the second ferromagnetic layer in the layering direction. The diffusion-preventing layer surrounds the periphery of the first ferromagnetic layer and the non-magnetic metal layer and is not in contact with the second ferromagnetic layer.

Description

Magnetoresistive element, magnetic memory, and method of manufacturing magnetoresistive element

[0001] The present disclosure relates to a magnetoresistive element, a magnetic memory, and a method for manufacturing a magnetoresistive element.

[0002] Giant magnetoresistance (GMR) elements, which are made up of multilayer films of ferromagnetic layers and non-magnetic layers, and tunnel magnetoresistance (TMR) elements, which use an insulating layer (tunnel barrier layer or barrier layer) as the non-magnetic layer, are known as magnetoresistance effect elements. Magnetoresistance effect elements can be applied to magnetic sensors, high-frequency components, magnetic heads, and non-volatile random access memories (MRAMs).

[0003] MRAM is a memory device that integrates magnetoresistive elements. MRAM reads and writes data by utilizing the property that the resistance of a magnetoresistive element changes when the magnetization directions of two ferromagnetic layers sandwiching a nonmagnetic layer in the magnetoresistive element change. The magnetization direction of the ferromagnetic layer is controlled, for example, by using a magnetic field generated by a current. Alternatively, the magnetization direction of the ferromagnetic layer can be controlled by using spin transfer torque (STT) generated by passing a current in the stacking direction of the magnetoresistive element.

[0004] When the magnetization direction of the ferromagnetic layer is rewritten using STT, a current flows in the stacking direction of the magnetoresistive element, and the write current causes deterioration of the characteristics of the magnetoresistive element.

[0005] In recent years, attention has been focused on methods that do not require current to flow in the stacking direction of a magnetoresistive element during writing (see, for example, Patent Document 1). One such method is a writing method that utilizes spin-orbit torque (SOT). SOT is induced by spin current generated by spin-orbit interaction or the Rashba effect at the interface of different materials. The current used to induce SOT in a magnetoresistive element flows in a direction that intersects with the stacking direction of the magnetoresistive element. In other words, magnetization rotation using SOT does not require current to flow in the stacking direction of the magnetoresistive element, and is expected to extend the life of the magnetoresistive element.

[0006] Japanese Patent Application Laid-Open No. 2017-216286

[0007] When manufacturing magnetoresistive elements and magnetic memories, there are processes in which heat is applied to the magnetoresistive element. When heat is applied to the magnetoresistive element, the elements constituting the ferromagnetic layer may diffuse, which may degrade the magnetic properties of the ferromagnetic layer. Furthermore, two ferromagnetic layers constituting the magnetoresistive element may short-circuit, which may cause the resistance value of the magnetoresistive element to not change appropriately.

[0008] The present disclosure has been made in consideration of the above circumstances, and aims to provide a magnetoresistive effect element, a magnetic memory, and a method for manufacturing a magnetoresistive effect element that can suppress element diffusion from a ferromagnetic layer.

[0009] To solve the above problems, the present disclosure provides the following means.

[0010] A magnetoresistive element according to a first aspect includes a wiring layer, a stack, and a diffusion prevention layer. The stack is in contact with the wiring layer. The stack includes a first ferromagnetic layer, a second ferromagnetic layer, a non-magnetic layer, and a non-magnetic metal layer. The second ferromagnetic layer is closer to the wiring layer than the first ferromagnetic layer. The first ferromagnetic layer is located between the non-magnetic layer and the non-magnetic metal layer in the stacking direction. The non-magnetic layer is located between the first ferromagnetic layer and the second ferromagnetic layer in the stacking direction. The diffusion prevention layer surrounds the first ferromagnetic layer and the non-magnetic metal layer and does not contact the second ferromagnetic layer.

[0011] The magnetoresistive effect element and magnetic memory according to the present disclosure can suppress element diffusion from the ferromagnetic layer. The method for manufacturing a magnetoresistive effect element according to the present disclosure can easily fabricate a configuration that can suppress element diffusion from the ferromagnetic layer.

[0012] FIG. 1 is a circuit diagram of a magnetic memory according to a first embodiment. FIG. 1 is a cross-sectional view of a characteristic portion of the magnetic memory according to the first embodiment. FIG. 1 is a cross-sectional view of a magnetoresistive effect element according to the first embodiment. FIG. 2 is a plan view of the magnetoresistive effect element according to the first embodiment. FIG. 3 is an enlarged view of the vicinity of a diffusion prevention layer of the magnetoresistive effect element according to the first embodiment. FIG. 4 is a view for explaining a manufacturing method of the magnetoresistive effect element according to the first embodiment. FIG. 5 is a view for explaining a manufacturing method of the magnetoresistive effect element according to the first embodiment. FIG. 6 is a view for explaining a manufacturing method of the magnetoresistive effect element according to the first embodiment. FIG. 7 is a view for explaining a manufacturing method of the magnetoresistive effect element according to the first embodiment. FIG. 8 is an enlarged view of the vicinity of the diffusion prevention layer of the magnetoresistive effect element of the second embodiment. FIG. 9 is an enlarged view of the vicinity of the diffusion prevention layer of the magnetoresistive effect element of the third embodiment. FIG. 10 is an enlarged view of the vicinity of the diffusion prevention layer of the magnetoresistive effect element of the fourth embodiment.

[0013] The present embodiment will be described in detail below with reference to the accompanying drawings. The drawings used in the following description may show characteristic portions enlarged for ease of understanding, and the dimensional ratios of each component may differ from the actual ones. The materials, dimensions, etc. exemplified in the following description are merely examples, and the present disclosure is not limited thereto. Appropriate modifications can be made within the scope of the present disclosure.

[0014] First, directions will be defined. One direction on one surface of a substrate Sub (see FIG. 2) described later is defined as the x-direction, and the direction perpendicular to the x-direction is defined as the y-direction. The x-direction is, for example, the longitudinal direction of the spin orbit torque wiring 20. The z-direction is a direction perpendicular to the x-direction and the y-direction. The z-direction is an example of the stacking direction in which each layer is stacked. The z-direction is an example of the thickness direction. Hereinafter, the +z direction may be expressed as "up" and the -z direction as "down". Up and down do not necessarily coincide with the direction in which gravity is applied.

[0015] In this specification, "extending in the x-direction" means, for example, that the dimension in the x-direction is larger than the smallest dimension among the dimensions in the x-direction, y-direction, and z-direction. The same applies to extending in other directions. Furthermore, in this specification, "connection" is not limited to physical connection. For example, "connection" is not limited to when two layers are physically in contact with each other, but also includes when two layers are connected with another layer sandwiched between them. Furthermore, in this specification, "connection" also includes electrical connection.

[0016] 1 is a configuration diagram of a magnetic memory 200 according to a first embodiment. The magnetic memory 200 includes a plurality of magnetoresistive effect elements 100, a plurality of write wirings WL, a plurality of common wirings CL, a plurality of read wirings RL, a plurality of first switch elements Sw1, a plurality of second switch elements Sw2, and a plurality of third switch elements Sw3. In the magnetic memory 200, for example, the magnetoresistive effect elements 100 are arranged in a matrix.

[0017] Each write wiring WL electrically connects a power supply to one or more magnetoresistive effect elements 100. Each common wiring CL is a wiring used both when writing and reading data. Each common wiring CL electrically connects a reference potential to one or more magnetoresistive effect elements 100. The reference potential is, for example, ground. The common wiring CL may be provided for each of the multiple magnetoresistive effect elements 100, or may be provided across the multiple magnetoresistive effect elements 100. Each read wiring RL electrically connects a power supply to one or more magnetoresistive effect elements 100. The power supply is connected to the magnetic memory 200 during use.

[0018] Each magnetoresistive element 100 is connected to a first switch element Sw1, a second switch element Sw2, and a third switch element Sw3, respectively. The first switch element Sw1 is connected between the magnetoresistive element 100 and a write wiring WL. The second switch element Sw2 is connected between the magnetoresistive element 100 and a common wiring CL. The third switch element Sw3 is connected to a read wiring RL that spans the multiple magnetoresistive elements 100.

[0019] When predetermined first switch element Sw1 and second switch element Sw2 are turned ON, a write current flows between the write wiring WL and the common wiring CL connected to the predetermined magnetoresistive effect element 100. The flow of the write current causes data to be written to the predetermined magnetoresistive effect element 100. When predetermined second switch element Sw2 and third switch element Sw3 are turned ON, a read current flows between the common wiring CL and the read wiring RL connected to the predetermined magnetoresistive effect element 100. The flow of the read current causes data to be read from the predetermined magnetoresistive effect element 100.

[0020] The first switch element Sw1, the second switch element Sw2, and the third switch element Sw3 are elements that control the flow of current. The first switch element Sw1, the second switch element Sw2, and the third switch element Sw3 are, for example, elements that utilize a phase change of a crystal layer such as a transistor or an Ovonic Threshold Switch (OTS), elements that utilize a change in band structure such as a Metal-Insulator Transition (MIT) switch, elements that utilize a breakdown voltage such as a Zener diode or an avalanche diode, or elements that change conductivity with a change in atomic position.

[0021] 1 is shared by the magnetoresistive effect elements 100 connected to the same read wiring RL. The third switch element Sw3 may be provided in each magnetoresistive effect element 100. Alternatively, the third switch element Sw3 may be provided in each magnetoresistive effect element 100, and the first switch element Sw1 or the second switch element Sw2 may be shared by the magnetoresistive effect elements 100 connected to the same wiring.

[0022] 2 is a cross-sectional view of a characteristic portion of the magnetic memory 200 according to the first embodiment. Fig. 2 is a cross-section of the magnetoresistive element 100 taken along an xz plane passing through the center of the width in the y direction of the spin orbit torque wiring 20, which will be described later.

[0023] The first switch element Sw1 and the second switch element Sw2 shown in Fig. 2 are transistors Tr. The third switch element Sw3 is electrically connected to the read wiring RL and is located at a different position in the y direction in Fig. 2, for example. The transistor Tr is, for example, a field-effect transistor, and has a gate electrode G, a gate insulating film GI, a source S, and a drain D. The source S and the drain D are determined by the direction of current flow, and the positional relationship between the source S and the drain D may be reversed. The substrate Sub is, for example, a semiconductor substrate.

[0024] The transistor Tr and the magnetoresistive effect element 100 are electrically connected via a via wiring V, a first electrode 41, and a second electrode 42. The transistor Tr and the write wiring WL or the common wiring CL are also connected by the via wiring V. The via wiring V extends, for example, in the z direction. The read wiring RL is connected to the stack 10. The via wiring V, the first electrode 41, and the second electrode 42 contain a conductive material. The via wiring V and the first electrode 41 may be integrated. The via wiring V and the second electrode 42 may be integrated. That is, the first electrode 41 may be part of the via wiring V, and the second electrode 42 may be part of the via wiring V.

[0025] The magnetoresistive element 100 and the transistor Tr are surrounded by an insulating layer 90. The insulating layer 90 is an insulating layer that provides insulation between the wirings of the multilayer wiring and between the elements. The insulating layer 90 is made of, for example, silicon oxide (SiO ｘ ), silicon nitride (SiN ｘ ), silicon carbide (SiC), chromium nitride, silicon carbonitride (SiCN), silicon oxynitride (SiON), aluminum oxide (Al ２ O ３ ), zirconium oxide (ZrO ｘ ), magnesium oxide (MgO), aluminum nitride (AlN), etc.

[0026] Fig. 3 is a cross-sectional view of the magnetoresistive element 100. Fig. 3 is a cross-section of the magnetoresistive element 100 cut along the xz plane passing through the center of the width of the spin orbit torque wiring 20 in the y direction. Fig. 4 is a plan view of the magnetoresistive element 100 as viewed from the z direction. The read wiring RL and the insulating layer 90 are omitted in Fig. 4.

[0027] The magnetoresistive element 100 includes, for example, a stacked body 10, a spin orbit torque wiring 20, and a diffusion prevention layer 30. The spin orbit torque wiring 20 is an example of a wiring layer. The periphery of the magnetoresistive element 100 is covered with an insulating layer 90.

[0028] The magnetoresistive element 100 is a magnetic element that utilizes spin orbit torque (SOT), and may be called a spin orbit torque type magnetoresistive element, a spin injection type magnetoresistive element, or a spin current magnetoresistive element.

[0029] The magnetoresistive element 100 is an element that records and stores data. The magnetoresistive element 100 records data as the resistance value in the z direction of the stack 10. The resistance value in the z direction of the stack 10 changes when a write current is applied along the spin orbit torque wiring 20 and spins are injected into the stack 10 from the spin orbit torque wiring 20. The resistance value in the z direction of the stack 10 can be read by applying a read current in the z direction of the stack 10.

[0030] The stack 10 is in contact with the spin orbit torque wiring 20. The stack 10 is stacked on the spin orbit torque wiring 20, for example.

[0031] The resistance value in the z direction of the stack 10 changes when spins are injected from the spin orbit torque wiring 20 into the stack 10 (second ferromagnetic layer 2 ).

[0032] The stack 10 is sandwiched between the spin-orbit torque wiring 20 and the readout wiring RL in the z direction. The stack 10 is a columnar body. The stack 10 has a planar shape in the z direction, for example, a circle, an ellipse, or a rectangle. The side surface of the stack 10 is inclined with respect to the z direction, for example.

[0033] The stack 10 includes, for example, a first ferromagnetic layer 1, a second ferromagnetic layer 2, a non-magnetic layer 3, an antiferromagnetic layer 4, and a non-magnetic metal layer 5. The resistance value of the stack 10 changes depending on the difference in the relative angle of magnetization between the first ferromagnetic layer 1 and the second ferromagnetic layer 2, which sandwich the non-magnetic layer 3.

[0034] The first ferromagnetic layer 1 is located farther from the spin orbit torque wiring 20 than the second ferromagnetic layer 2. The first ferromagnetic layer 1 is located between the nonmagnetic layer 3 and the nonmagnetic metal layer 5 in the z direction. The magnetization of the first ferromagnetic layer 1 is less likely to change orientation than the magnetization of the second ferromagnetic layer 2 when a predetermined external force is applied. The first ferromagnetic layer 1 is sometimes referred to as a magnetization fixed layer or a magnetization reference layer, and the second ferromagnetic layer 2 is sometimes referred to as a magnetization free layer.

[0035] The second ferromagnetic layer 2 is, for example, in contact with the spin orbit torque wiring 20 and stacked on the spin orbit torque wiring 20. The second ferromagnetic layer 2 is closer to the spin orbit torque wiring 20 than the first ferromagnetic layer 1. Spins are injected into the second ferromagnetic layer 2 from the spin orbit torque wiring 20. The magnetization of the second ferromagnetic layer 2 is subjected to a spin orbit torque (SOT) by the injected spins, and the orientation direction of the magnetization changes.

[0036] The first ferromagnetic layer 1 and the second ferromagnetic layer 2 include a ferromagnetic material, such as a metal selected from the group consisting of Cr, Mn, Co, Fe, and Ni, an alloy containing one or more of these metals, or an alloy containing one or more of these metals and at least one of B, C, and N. Examples of the ferromagnetic material include Co—Fe, Co—Fe—B, Ni—Fe, a Co—Ho alloy, a Sm—Fe alloy, a Fe—Pt alloy, a Co—Pt alloy, and a CoCrPt alloy.

[0037] The first ferromagnetic layer 1 and the second ferromagnetic layer 2 may include a Heusler alloy. The Heusler alloy may be an XYZ or X ２ The Heusler alloy includes an intermetallic compound having a chemical composition of YZ, where X is a transition metal element or a noble metal element of the Co, Fe, Ni, or Cu group on the periodic table, Y is a transition metal element or an element species of X of the Mn, V, Cr, or Ti group, and Z is a typical element of groups III to V. The Heusler alloy is, for example, Co ２ FeSi, Co ２ FeGe, Co２ FeGa, Co ２ MnSi, Co ２ Mn １－ａ Fe ａ Al ｂ Si １－ｂ , Co ２ FeGe １－ｃ Ga ｃ etc. Heusler alloys have high spin polarization.

[0038] The nonmagnetic layer 3 is sandwiched between the first ferromagnetic layer 1 and the second ferromagnetic layer 2 in the z direction.

[0039] The non-magnetic layer 3 includes a non-magnetic material. When the non-magnetic layer 3 is an insulator (when it is a tunnel barrier layer), the material thereof is, for example, Al ２ O ３ , SiO ２ , MgO, and MgAl ２ O ４ In addition to these, materials in which a part of Al, Si, or Mg is replaced with Zn, Be, or the like can also be used for the nonmagnetic layer 3. Among these, MgO and MgAl ２ O ４ is a material that can realize coherent tunneling. When the non-magnetic layer 3 is a metal, Cu, Au, Ag, etc. can be used as the material. Furthermore, when the non-magnetic layer 3 is a semiconductor, Si, Ge, CuInSe, etc. can be used as the material. ２ , CuGaSe ２ , Cu(In,Ga)Se ２ etc. can be used.

[0040] The antiferromagnetic layer 4 is located between the first ferromagnetic layer 1 and the non-magnetic metal layer 5 in the z direction. The antiferromagnetic layer 4 strongly fixes the magnetization of the first ferromagnetic layer 1. The antiferromagnetic layer 4 is made of, for example, IrMn or PtMn. The antiferromagnetic layer 4 is not an essential component and may be omitted.

[0041] The nonmagnetic metal layer 5 is in contact with the readout wiring RL. The nonmagnetic metal layer 5 is sandwiched between the first ferromagnetic layer 1 and the readout wiring RL in the z direction. The nonmagnetic metal layer 5 also functions as a mask when manufacturing the magnetoresistive element 100. The nonmagnetic metal layer 5 is made of, for example, Al, Cu, Ta, Ti, Zr, NiCr, or a nitride (for example, TiN, TaN, or SiN). The nonmagnetic metal layer 5 may also be a laminate of NiCr and Ta.

[0042] The stack 10 may include layers other than the first ferromagnetic layer 1, the second ferromagnetic layer 2, the non-magnetic layer 3, the antiferromagnetic layer 4, and the non-magnetic metal layer 5. For example, an underlayer may be provided between the spin-orbit torque wiring 20 and the second ferromagnetic layer 2. The underlayer improves the crystallinity of each layer constituting the stack 10. Furthermore, for example, the stack 10 may include a cap layer on the top surface thereof.

[0043] The spin orbit torque wiring 20 extends in the x direction, for example, with its length in the x direction being longer than that in the y direction when viewed from the z direction. A write current flows in the x direction along the spin orbit torque wiring 20 between the first electrode 41 and the second electrode 42. The spin orbit torque wiring 20 is connected to both the first electrode 41 and the second electrode 42.

[0044] The spin-orbit torque wiring 20 generates a spin current by the spin Hall effect when a current flows, and injects spins into the second ferromagnetic layer 2. The spin-orbit torque wiring 20 applies a spin-orbit torque (SOT) to the magnetization of the second ferromagnetic layer 2 that is sufficient to reverse the magnetization of the second ferromagnetic layer 2, for example.

[0045] The spin Hall effect is a phenomenon in which, when an electric current is passed through it, a spin current is induced in a direction perpendicular to the direction of the electric current due to spin-orbit interaction. The spin Hall effect is similar to the standard Hall effect in that the direction of movement of moving charges (electrons) is bent. In the standard Hall effect, the direction of movement of charged particles moving in a magnetic field is bent by the Lorentz force. In contrast, in the spin Hall effect, the direction of spin movement is bent simply by the movement of electrons (the flow of electric current), even in the absence of a magnetic field.

[0046] For example, when a current flows through the spin-orbit torque wiring 20, the first spin polarized in one direction and the second spin polarized in the opposite direction to the first spin are bent by the spin Hall effect in a direction perpendicular to the direction of the current flow. For example, the first spin polarized in the -y direction is bent from the x direction, which is the direction of travel, to the +z direction, and the second spin polarized in the +y direction is bent from the x direction, which is the direction of travel, to the -z direction.

[0047] In non-magnetic materials (materials that are not ferromagnetic), the number of electrons with the first spin generated by the spin Hall effect is equal to the number of electrons with the second spin. In other words, the number of electrons with the first spin facing the +z direction is equal to the number of electrons with the second spin facing the -z direction. The first spins and second spins flow in a direction that eliminates the uneven distribution of spin. When the first spins and second spins move in the z direction, the flow of electric charges cancels each other out, so the amount of current is zero. Spin current that does not involve current is specifically called pure spin current.

[0048] The flow of electrons with the first spin is called J ↑ , the flow of electrons of the second spin is J ↓ , the spin current is J Ｓ Then, J Ｓ =J ↑ -J ↓ The spin current J is defined as Ｓ is generated in the z direction. The first spin is injected from the spin orbit torque wiring 20 into the second ferromagnetic layer 2.

[0049] The thickness of the spin orbit torque wire 20 is, for example, 2 nm or more. The thickness of the spin orbit torque wire 20 may be, for example, 20 nm or less.

[0050] The spin-orbit torque wiring 20 includes any of a metal, an alloy, an intermetallic compound, a metal boride, a metal carbide, a metal silicide, a metal phosphide, and a metal nitride, which has a function of generating a spin current.

[0051] The spin-orbit torque wiring 20 includes, for example, any material selected from the group consisting of heavy metals with atomic numbers equal to or greater than 39, metal oxides, metal nitrides, metal oxynitrides, and topological insulators. The spin-orbit torque wiring 20 may also include a magnetic material.

[0052] The spin orbit torque wiring 20 contains, for example, a non-magnetic heavy metal as a main component. Heavy metal means a metal having a specific gravity equal to or greater than that of yttrium (Y). Non-magnetic heavy metals are, for example, non-magnetic metals with a large atomic number equal to or greater than 39 that have d electrons or f electrons in their outermost shells. In non-magnetic heavy metals, stronger spin-orbit interaction occurs than in other metals. The spin Hall effect occurs due to spin-orbit interaction, and spins tend to be unevenly distributed in the spin orbit torque wiring 20, resulting in a spin current J. Ｓ is more likely to occur.

[0053] The diffusion prevention layer 30 surrounds the first ferromagnetic layer 1, the antiferromagnetic layer 4, and the nonmagnetic metal layer 5. The diffusion prevention layer 30 is annular when viewed in the z direction. The diffusion prevention layer 30 contacts the first ferromagnetic layer 1, the antiferromagnetic layer 4, and the nonmagnetic metal layer 5, but does not contact the second ferromagnetic layer 2. It is preferable that the diffusion prevention layer 30 does not contact the nonmagnetic layer 3. By not having the diffusion prevention layer 30 contact the second ferromagnetic layer 2, a short circuit between the first ferromagnetic layer 1 and the second ferromagnetic layer 2 via the diffusion prevention layer 30 can be prevented.

[0054] The diffusion prevention layer 30 contains, for example, the same material as the spin-orbit torque wiring 20. The diffusion prevention layer 30 contains, for example, Ta or W. When the diffusion prevention layer 30 contains a heavy metal, the diffusion of elements from the first ferromagnetic layer 1 and the antiferromagnetic layer 4 to the insulating layer 90 can be further suppressed.

[0055] The diffusion prevention layer 30 is, for example, a conductive metal. The conductivity of the diffusion prevention layer 30 is, for example, lower than the conductivity of the first ferromagnetic layer 1. When this configuration is satisfied, most of the read current can be passed through the first ferromagnetic layer 1, and the amount of the read current can be reduced.

[0056] The average thickness of the diffusion prevention layer 30 is, for example, 1 nm or more. The thickness of the diffusion prevention layer 30 is the radial thickness of the diffusion prevention layer 30 when the stacked body 10 is used as a reference. The thickness of the diffusion prevention layer 30 is, for example, the thickness of the diffusion prevention layer 30 in the x direction. The average thickness is the average value of thicknesses of the diffusion prevention layer 30 measured at five different height positions in the z direction.

[0057] The thickness of the diffusion prevention layer 30 is not constant. For example, the thickness t1 of the first portion of the diffusion prevention layer 30 is thicker than the thickness t2 of the second portion. The second portion is closer to the nonmagnetic layer 3 than the first portion. The thickness of the diffusion prevention layer 30 may increase as it moves away from the nonmagnetic layer 3. When this configuration is satisfied, the read current converges toward the nonmagnetic layer 3.

[0058] The thickness of the diffusion prevention layer 30 surrounding the antiferromagnetic layer 4 is preferably thicker than the thickness of the diffusion prevention layer 30 surrounding the first ferromagnetic layer 1. The elements constituting the antiferromagnetic layer 4 are more likely to diffuse due to heat or the like than the elements constituting the first ferromagnetic layer 1. By increasing the thickness of the diffusion prevention layer 30 in the portion where element diffusion is likely to occur, element diffusion can be further suppressed.

[0059] Next, a description will be given of a method for manufacturing the magnetoresistive effect element 100. Figures 6 to 10 are diagrams for explaining the method for manufacturing the magnetoresistive effect element according to the first embodiment.

[0060] The method for manufacturing the magnetoresistive element according to the first embodiment includes a stacking step, a masking step, a first processing step, an impurity removing step, and a second processing step.

[0061] First, an insulating layer 90 is formed so as to cover the transistor Tr. Then, openings are formed in the insulating layer 90, and the openings are filled with a conductor to form the via wiring V, the first electrode 41, and the second electrode 42. The write wiring WL and the common wiring CL are formed by laminating the insulating layer 90 to a predetermined thickness, then forming grooves in the insulating layer 90, and filling the grooves with a conductor.

[0062] Next, a lamination process is performed. In the lamination process, as shown in Fig. 6, a conductive layer 81, a second ferromagnetic layer 82, a nonmagnetic layer 83, a first ferromagnetic layer 84, and an antiferromagnetic layer 85 are sequentially formed on the insulating layer 90, the first electrode 41, and the second electrode 42. The lamination of each layer can be performed by sputtering, chemical vapor deposition (CVD), electron beam evaporation (EB evaporation), atomic laser deposition (ALD), or the like.

[0063] Next, the fabricated stack is processed to fit the outer shape of the spin orbit torque wire 20. The processing can be performed using, for example, photolithography. Through this processing, the conductive layer 81 becomes the spin orbit torque wire 20.

[0064] Next, a masking step is performed. In the masking step, as shown in FIG. 7 , a nonmagnetic metal layer 5 is formed as a mask to cover predetermined positions of the first ferromagnetic layer 84. The nonmagnetic metal layer 5 is formed, for example, on the antiferromagnetic layer 85. The nonmagnetic metal layer 5 can be formed, for example, by depositing a nonmagnetic metal through a metal mask.

[0065] Next, a first processing step is performed. In the first processing step, the first ferromagnetic layer 1 is processed into a predetermined shape. In the first processing step, as shown in FIG. 8 , a portion of the first ferromagnetic layer 84 and the antiferromagnetic layer 85 is removed down to the nonmagnetic layer 83. The first processing step is performed by, for example, dry etching or ion beam milling.

[0066] The nonmagnetic metal layer 5 functions as a mask for etching or milling. The first ferromagnetic layer 84 located below the nonmagnetic metal layer 5 is not removed and becomes the first ferromagnetic layer 1, and the antiferromagnetic layer 85 located below the nonmagnetic metal layer 5 is not removed and becomes the antiferromagnetic layer 4. When the first ferromagnetic layer 84 and the antiferromagnetic layer 85 are removed, some of the etched material re-deposits on the side surfaces of the first ferromagnetic layer 1, the antiferromagnetic layer 4, and the nonmagnetic metal layer 5.

[0067] Next, a deposit removal process is performed. In the deposit removal process, deposits adhering to the side surfaces of the nonmagnetic metal layer 5, the antiferromagnetic layer 4, and the first ferromagnetic layer 1 are removed. As described above, the deposits are etched materials that have re-adhered. The deposits can be removed by irradiating the surfaces with an ion beam from a direction oblique to the z direction.

[0068] Next, a second processing step is performed. In the second processing step, the nonmagnetic layer 83 and the second ferromagnetic layer 82 are processed into a predetermined shape. In the second processing step, the nonmagnetic metal layer 5, the antiferromagnetic layer 4, and the first ferromagnetic layer 1 are used as masks to remove portions of the nonmagnetic layer 83 and the second ferromagnetic layer 82. The second processing step is performed by, for example, dry etching or ion beam milling. After the second processing step, the nonmagnetic layer 83 becomes the nonmagnetic layer 3, and the second ferromagnetic layer 82 becomes the second ferromagnetic layer 2.

[0069] In the second processing step, when the nonmagnetic layer 83 and the second ferromagnetic layer 82 are removed, some of the etched material redeposits onto the side surfaces of the first ferromagnetic layer 1, the antiferromagnetic layer 4, and the nonmagnetic metal layer 5. These redeposits are, for example, parts of the nonmagnetic layer 83, the second ferromagnetic layer 82, and the spin-orbit torque wiring 20. The redeposits become the diffusion prevention layer 30. The shape, etc. of the diffusion prevention layer 30 can be designed by adjusting the irradiation angle, etc. of the ion beam in the second processing step.

[0070] Next, the periphery of the stacked body 10 is covered with an insulating layer 90. After that, a part of the insulating layer 90 is removed and a read wiring RL is formed, thereby fabricating the magnetoresistive effect element 100 according to this embodiment.

[0071] The magnetoresistive element 100 according to the first embodiment includes the diffusion prevention layer 30, which can prevent elements contained in the first ferromagnetic layer 1 and the antiferromagnetic layer 4 from diffusing into the insulating layer 90. If the elements contained in the first ferromagnetic layer 1 and the antiferromagnetic layer 4 diffuse to the surroundings, the compositions of the first ferromagnetic layer 1 and the antiferromagnetic layer 4 will be misaligned, reducing the stability of the magnetization of the first ferromagnetic layer 1. The magnetoresistive element 100 according to the first embodiment includes the diffusion prevention layer 30, which increases the magnetization stability of the first ferromagnetic layer 1.

[0072] The magnetoresistive element 100 stores data by utilizing a change in resistance value caused by a difference in the relative angle between the magnetizations of the first ferromagnetic layer 1 and the second ferromagnetic layer 2. The stability of the magnetization of the first ferromagnetic layer 1 is directly related to the reliability of the data stored in the magnetoresistive element 100.

[0073] 11 is a cross-sectional view of a magnetoresistive effect element 101 according to a second embodiment. The magnetoresistive effect element 101 according to the second embodiment can be replaced with the magnetoresistive effect element 100 according to the first embodiment. In the second embodiment, the same components as those in the first embodiment are denoted by the same reference numerals, and a description thereof will be omitted.

[0074] The magnetoresistive element 101 differs from the other in the shape of the diffusion prevention layer 30A. Except for the shape, the diffusion prevention layer 30A is similar to the diffusion prevention layer 30. The diffusion prevention layer 30A has a maximum thickness at a position surrounding the antiferromagnetic layer 4.

[0075] The elements constituting the antiferromagnetic layer 4 are more likely to diffuse due to heat or the like than the elements constituting the first ferromagnetic layer 1. By increasing the film thickness of the diffusion prevention layer 30A in the areas where element diffusion is likely to occur, element diffusion can be further suppressed. The shape of the diffusion prevention layer 30A can be designed by controlling the conditions of the second processing step. The magnetoresistive effect element 101 according to the second embodiment has the same effects as the magnetoresistive effect element 100 according to the first embodiment.

[0076] 12 is a cross-sectional view of a magnetoresistive effect element 102 according to a third embodiment. The magnetoresistive effect element 102 according to the third embodiment can be substituted for the magnetoresistive effect element 100 according to the first embodiment. In the third embodiment, the same components as those in the first embodiment are denoted by the same reference numerals, and a description thereof will be omitted.

[0077] The magnetoresistive element 102 differs in the configuration of the diffusion prevention layer 30B. The diffusion prevention layer 30B has a first diffusion prevention layer 31 and a second diffusion prevention layer 32. The first diffusion prevention layer 31 is located between the second diffusion prevention layer 32 and the stack 10. The first diffusion prevention layer 31 is located inside the second diffusion prevention layer 32. The first diffusion prevention layer 31 is a non-magnetic body and contains, for example, the same material as the non-magnetic layer 3. The second diffusion prevention layer 32 is a metal and contains, for example, the same material as the second ferromagnetic layer 2 and the spin orbit torque wiring 20.

[0078] The diffusion prevention layer 30B can be fabricated by controlling the conditions of the second processing step. The conditions of the second processing step are controlled so that redeposited material produced when the nonmagnetic layer 83 is etched becomes the first diffusion prevention layer 31, and so that redeposited material produced when the second ferromagnetic layer 82 is etched becomes the second diffusion prevention layer 32. The conditions of the second processing step include, for example, the irradiation angle and intensity of the ion beam.

[0079] The magnetoresistive element 102 according to the third embodiment has the same effects as the magnetoresistive element 100 according to the first embodiment. In addition, the diffusion prevention layer 30B has a two-layer structure, which further suppresses element diffusion from the first ferromagnetic layer 1 and the antiferromagnetic layer 4 to the insulating layer 90.

[0080] 13 is a cross-sectional view of a magnetoresistive effect element 103 according to a fourth embodiment. The magnetoresistive effect element 103 according to the fourth embodiment can be substituted for the magnetoresistive effect element 100 according to the first embodiment. In the fourth embodiment, the same components as those in the first embodiment are denoted by the same reference numerals, and a description thereof will be omitted.

[0081] The magnetoresistive element 103 differs in the configuration of the diffusion prevention layer 30C. The diffusion prevention layer 30C has a first diffusion prevention layer 31, a second diffusion prevention layer 32, and a third diffusion prevention layer 33. The first diffusion prevention layer 31 is located between the second diffusion prevention layer 32 and the stacked body 10. The third diffusion prevention layer 33 is located between the first diffusion prevention layer 31 and the stacked body 10. The first diffusion prevention layer 31 is located inside the second diffusion prevention layer 32. The third diffusion prevention layer 33 is located inside the first diffusion prevention layer 31.

[0082] The first diffusion prevention layer 31 is a non-magnetic material and contains, for example, the same material as the non-magnetic layer 3. The second diffusion prevention layer 32 is a metal and contains, for example, the same material as the second ferromagnetic layer 2 and the spin-orbit torque wiring 20. The third diffusion prevention layer 33 is a metal and contains, for example, the same material as the first ferromagnetic layer 1 and the antiferromagnetic layer 4.

[0083] The diffusion prevention layer 30C can be fabricated by controlling the conditions of the impurity removal step and the second processing step. In the impurity removal step, the deposits on the side surfaces of the nonmagnetic metal layer 5, the antiferromagnetic layer 4, and the first ferromagnetic layer 1 are not completely removed, thereby forming the third diffusion prevention layer 33. The first diffusion prevention layer 31 and the second diffusion prevention layer 32 can be fabricated by the same method as in the third embodiment.

[0084] The magnetoresistive element 103 according to the fourth embodiment has the same effects as the magnetoresistive element 100 according to the first embodiment. In addition, the diffusion prevention layer 30C has a three-layer structure, which further suppresses element diffusion from the first ferromagnetic layer 1 and the antiferromagnetic layer 4 to the insulating layer 90.

[0085] Although preferred aspects of the present disclosure have been described above using several exemplary embodiments, the present disclosure is not limited to these embodiments. For example, the characteristic features of each embodiment may be applied to other embodiments.

[0086] 1, 84 First ferromagnetic layer 2, 82 Second ferromagnetic layer 3, 83 Non-magnetic layer 4, 85 Antiferromagnetic layer 5 Non-magnetic metal layer 10 Stacked body 20 Spin orbit torque wiring 30, 30A, 30B, 30C Diffusion prevention layer 31 First diffusion prevention layer 32 Second diffusion prevention layer 33 Third diffusion prevention layer 41 First electrode 42 Second electrode 81 Conductive layer 90 Insulating layer 100, 101, 102, 103 Magnetoresistance effect element 200 Magnetic memory

Claims

1. A magnetoresistive effect element comprising a wiring layer, a stack, and a diffusion prevention layer, wherein the stack is in contact with the wiring layer, and the stack comprises a first ferromagnetic layer, a second ferromagnetic layer, a non-magnetic layer, and a non-magnetic metal layer, wherein the second ferromagnetic layer is closer to the wiring layer than the first ferromagnetic layer, the first ferromagnetic layer is between the non-magnetic layer and the non-magnetic metal layer in the stacking direction, and the non-magnetic layer is between the first ferromagnetic layer and the second ferromagnetic layer in the stacking direction, and the diffusion prevention layer surrounds the first ferromagnetic layer and the non-magnetic metal layer and is not in contact with the second ferromagnetic layer.

2. The magnetoresistive element according to claim 1, further comprising an antiferromagnetic layer, said antiferromagnetic layer being located between said first ferromagnetic layer and said non-magnetic metal layer in the stacking direction.

3. The magnetoresistive element according to claim 1, wherein said diffusion prevention layer is not in contact with said non-magnetic layer.

4. The magnetoresistive element according to claim 1, wherein the conductivity of said diffusion prevention layer is lower than the conductivity of said first ferromagnetic layer.

5. The magnetoresistive element according to claim 1, wherein the thickness of the first portion of said diffusion prevention layer is greater than the thickness of a second portion located closer to said nonmagnetic layer than said first portion.

6. The magnetoresistive element according to claim 1, wherein the thickness of said diffusion prevention layer increases with increasing distance from said non-magnetic layer.

7. The magnetoresistive element of claim 2, wherein the diffusion prevention layer surrounds the antiferromagnetic layer, and the thickness of the diffusion prevention layer surrounding the antiferromagnetic layer is greater than the thickness of the diffusion prevention layer surrounding the first ferromagnetic layer.

8. The magnetoresistive element according to claim 1, wherein the diffusion prevention layer has an average thickness of 1 nm or more.

9. The magnetoresistive element according to claim 1, wherein said diffusion prevention layer contains Ta or W.

10. The magnetoresistive element of claim 1, wherein the diffusion prevention layer comprises a first diffusion prevention layer and a second diffusion prevention layer, the first diffusion prevention layer is located between the second diffusion prevention layer and the stack, the first diffusion prevention layer is a non-magnetic material, and the second diffusion prevention layer is a metal.

11. A magnetic memory comprising a plurality of magnetoresistive effect elements, at least one of which is the magnetoresistive effect element according to claim 1.

12. A method for manufacturing a magnetoresistive effect element, comprising: a lamination step of laminating a second ferromagnetic layer, a non-magnetic layer, and a first ferromagnetic layer on a wiring layer; a mask step of forming a non-magnetic metal layer to serve as a mask so as to cover a predetermined position of the first ferromagnetic layer; a first processing step of processing the first ferromagnetic layer into a predetermined shape; an adhesion removal step of removing adhesions attached to the non-magnetic metal layer and around the first ferromagnetic layer that has been processed into the predetermined shape; and a second processing step of processing the non-magnetic layer and the second ferromagnetic layer into the predetermined shape.

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