Magnetization Rotation Element, Magnetoresistive Element, and Magnetic Memory

Abstract

To provide a magnetization rotation element, a magnetoresistance effect element and a magnetic memory which can generate a highly efficient spin flow.SOLUTION: A magnetization rotation element includes spin orbit torque wiring, and a first ferromagnetic layer connected to the spin orbit torque wiring, wherein the spin orbit torque wiring has a first layer and a second layer, the first layer is closer to the first ferromagnetic layer than the second layer, and an average grain size of the first layer is larger than an average grain size of the second layer.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a magnetization rotation element, a magnetoresistive element, and a magnetic memory.

Background Art

[0002] A giant magnetoresistive (GMR) element composed of a multilayer film of a ferromagnetic layer and a nonmagnetic layer, and a tunnel magnetoresistive (TMR) element using an insulating layer (tunnel barrier layer, barrier layer) in the nonmagnetic layer are known as magnetoresistive elements. Magnetoresistive elements can be applied to magnetic sensors, high-frequency components, magnetic heads, and nonvolatile random access memories (MRAMs).

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

[0004] When rewriting the direction of magnetization of a ferromagnetic layer using STT, an electric current is passed in the stacking direction of the magnetoresistive element. The write current causes deterioration of the characteristics of the magnetoresistive element.

[0005] In recent years, attention has been focused on a method that does not require passing an electric current in the stacking direction of a magnetoresistive element during writing (for example, Patent Document 1). One such method is a writing method using spin orbit torque (SOT). SOT is induced by a spin current generated by spin orbit interaction or by the Rashba effect at the interface of different materials. The current for inducing SOT in the magnetoresistive element flows in a direction intersecting the stacking direction of the magnetoresistive element. That is, it is not necessary to pass an electric current in the stacking direction of the magnetoresistive element, and a long life of the magnetoresistive element is expected.

Prior Art Documents

Patent Document

[0006]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0007] In a magnetoresistive element using SOT, data is written by flowing a current along a spin-orbit torque wiring. The data is stored in the magnetization direction of the ferromagnetic layer. The magnetization direction of the ferromagnetic layer is rewritten by the spin injected from the spin-orbit torque wiring. In order to increase the amount of spin from the spin-orbit torque wiring to the ferromagnetic layer, there is a demand for a magnetization rotation element, a magnetoresistive element, and a magnetic memory that can generate a spin current with high efficiency.

[0008] The present invention has been made in view of the above circumstances, and an object thereof is to provide a magnetization rotation element, a magnetoresistive element, and a magnetic memory that can generate a highly efficient spin current.

Means for Solving the Problems

[0009] In order to solve the above problems, the present invention provides the following means.

[0010] (1) The magnetization rotation element according to the first aspect includes a spin-orbit torque wiring and a first ferromagnetic layer connected to the spin-orbit torque wiring. The spin-orbit torque wiring has a first layer and a second layer. The first layer is closer to the first ferromagnetic layer than the second layer. The average grain size of the first layer is larger than the average grain size of the second layer.

[0011] (2) In the magnetization rotation element according to the above aspect, the average grain size of the first layer may be larger than 1 times and smaller than 2 times the average grain size of the second layer.

[0012] (3) In the magnetization rotation element according to the above aspect, the second layer may contain any one of boron, oxygen, nitrogen, and carbon.

[0013] (4) In the magnetization rotation element according to the above aspect, the spin-orbit torque wiring may further include a third layer. The third layer is closer to the first ferromagnetic layer than the first layer and the second layer. The average grain size of the third layer is smaller than the average grain size of the first layer.

[0014] (5) In the magnetization rotation element according to the above aspect, the average grain size of the third layer may be smaller than the average grain size of the second layer.

[0015] (6) In the magnetization rotation element according to the above aspect, the third layer may contain any one of boron, oxygen, nitrogen, and carbon. The total content ratio of boron, oxygen, nitrogen, and carbon in the third layer is higher than that in the second layer.

[0016] (7) The magnetization rotation element according to the above aspect may further include an amorphous layer between the first ferromagnetic layer and the spin-orbit torque wiring.

[0017] (8) In the magnetization rotation element according to the above aspect, the thickness of the amorphous layer may be 1 nm or less.

[0018] (9) The magnetoresistive effect element according to the second aspect includes the magnetization rotation element according to the above aspect, a non-magnetic layer, and a second ferromagnetic layer. The non-magnetic layer is sandwiched between the first ferromagnetic layer and the second ferromagnetic layer. The first ferromagnetic layer is closer to the spin-orbit torque wiring than the second ferromagnetic layer.

[0019] (10) The magnetic memory according to the third aspect includes a plurality of the magnetoresistive effect elements according to the above aspect.

Advantages of the Invention

[0020] The magnetization rotation element, magnetoresistive element, and magnetic memory according to the present invention can generate a highly efficient spin current.

Brief Description of the Drawings

[0021]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Figure 9

Figure 10

Embodiments for Carrying Out the Invention

[0022] Hereinafter, the present embodiment will be described in detail with appropriate reference to the drawings. In the drawings used in the following description, in some cases, parts considered to be characteristic are enlarged for easy understanding of the features, and the dimensional ratios of the respective components may be different from the actual ones. The materials, dimensions, etc. exemplified in the following description are merely examples, and the present invention is not limited thereto, and can be appropriately modified and implemented within the scope where the effects of the present invention are achieved.

[0023] First, define the directions. One direction on one side of the substrate Sub (see FIG. 2) described later is defined as the x direction, and the direction orthogonal 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 the direction orthogonal to the x direction and the y direction. The z direction is an example of the stacking direction in which the respective layers are stacked. Hereinafter, the +z direction may be expressed as "up" and the -z direction may be expressed as "down". The up and down do not necessarily coincide with the direction in which gravity acts.

[0024] In this specification, "extending in the x direction" means, for example, that the dimension in the x direction is larger than the minimum dimension among the dimensions in the x direction, y direction, and z direction. The same applies to the case of extending in other directions. Also, in this specification, "connection" is not limited to physically connected cases. For example, it is not limited to the case where two layers are physically in contact, and the case where two layers are connected with other layers sandwiched therebetween is also included in "connection". Also, "connection" in this specification includes electrical connection.

[0025] "First Embodiment" FIG. 1 is a configuration diagram of a magnetic memory 200 according to the 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 switching elements Sw1, a plurality of second switching elements Sw2, and a plurality of third switching elements Sw3. In the magnetic memory 200, for example, the magnetoresistive effect elements 100 are arranged in an array.

[0026] Each write wiring WL electrically connects a power supply and one or more magnetoresistive elements 100. Each common wiring CL is a wiring used both during data writing and reading. Each common wiring CL electrically connects a reference potential and one or more magnetoresistive elements 100. The reference potential is, for example, ground. The common wiring CL may be provided for each of the plurality of magnetoresistive elements 100, or may be provided across the plurality of magnetoresistive elements 100. Each read wiring RL electrically connects a power supply and one or more magnetoresistive elements 100. The power supply is connected to the magnetic memory 200 during use.

[0027] Each magnetoresistive element 100 is connected to each of a first switching element Sw1, a second switching element Sw2, and a third switching element Sw3. The first switching element Sw1 is connected between the magnetoresistive element 100 and the write wiring WL. The second switching element Sw2 is connected between the magnetoresistive element 100 and the common wiring CL. The third switching element Sw3 is connected to a read wiring RL extending across the plurality of magnetoresistive elements 100.

[0028] When a predetermined first switching element Sw1 and a second switching element Sw2 are turned on, a write current flows between the write wiring WL and the common wiring CL connected to a predetermined magnetoresistive element 100. When the write current flows, data is written to the predetermined magnetoresistive element 100. When a predetermined second switching element Sw2 and a third switching element Sw3 are turned on, a read current flows between the common wiring CL and the read wiring RL connected to a predetermined magnetoresistive element 100. When the read current flows, data is read from the predetermined magnetoresistive element 100.

[0029] The first switching element Sw1, the second switching element Sw2, and the third switching element Sw3 are elements that control the flow of current. The first switching element Sw1, the second switching element Sw2, and the third switching element Sw3 are, for example, transistors, elements that utilize the phase change of a crystal layer such as an ovonic threshold switch (OTS), elements that utilize the change in the band structure such as a metal-insulator transition (MIT) switch, elements that utilize the breakdown voltage such as a Zener diode and an avalanche diode, and elements whose conductivity changes with the change in the atomic position.

[0030] In the magnetic memory 200 shown in FIG. 1, the magnetoresistive effect elements 100 connected to the same read wiring RL share the third switching element Sw3. The third switching element Sw3 may be provided for each magnetoresistive effect element 100. Also, the third switching element Sw3 may be provided for each magnetoresistive effect element 100, and the first switching element Sw1 or the second switching element Sw2 may be shared by the magnetoresistive effect elements 100 connected to the same wiring.

[0031] FIG. 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 taken along the xz plane passing through the center of the width in the y direction of the spin-orbit torque wiring 20 described later for the magnetoresistive effect element 100.

[0032] The first switching element Sw1 and the second switching element Sw2 shown in FIG. 2 are transistors Tr. The third switching element Sw3 is electrically connected to the read wiring RL and is, for example, at different positions in the x direction in FIG. 2. The transistor Tr is, for example, a field effect transistor and has a gate electrode G, a gate insulating film GI, and a source S and a drain D formed on a substrate Sub. The source S and the drain D are defined by the direction of the current flow, and these are in the same region. The positional relationship between the source S and the drain D may be reversed. The substrate Sub is, for example, a semiconductor substrate.

[0033] The transistor Tr and the magnetoresistive element 100 are electrically connected via the via wiring V, the first wiring 31, and the second wiring 32. The transistor Tr is also connected to the write wiring WL or the common wiring CL via the via wiring V. The via wiring V extends, for example, in the z direction. The read wiring RL is connected to the laminate 10 via the electrode E. The via wiring V and the electrode E contain a conductive material. The via wiring V and the first wiring 31 may be integrated. Also, the via wiring V and the second wiring 32 may be integrated. That is, the first wiring 31 may be part of the via wiring V, and the second wiring 32 may be part of the via wiring V.

[0034] The periphery of the magnetoresistive element 100 and the transistor Tr is covered with an insulating layer In. The insulating layer In is an insulating layer that insulates between wirings and between elements in multilayer wiring. The insulating layer In is, for example, silicon oxide (SiO x ), silicon nitride (SiN x ), silicon carbide (SiC), chromium nitride, silicon carbonitride (SiCN), silicon oxynitride (SiON), aluminum oxide (Al2O3), zirconium oxide (ZrO x ), magnesium oxide (MgO), aluminum nitride (AlN), or the like.

[0035] FIG. 3 is a cross-sectional view of the magnetoresistive element 100. FIG. 3 is a cross-section obtained by cutting the magnetoresistive element 100 in 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.

[0036] The magnetoresistive element 100 includes, for example, a laminate 10, a spin-orbit torque wiring 20, a first wiring 31, and a second wiring 32. The laminate 10 has a first ferromagnetic layer 1, a second ferromagnetic layer 2, and a nonmagnetic layer 3. The periphery of the magnetoresistive element 100 is covered with, for example, a first insulating layer 91, a second insulating layer 92, and a third insulating layer 93. The first insulating layer 91, the second insulating layer 92, and the third insulating layer 93 are part of the above-described insulating layer In.

[0037] The first insulating layer 91 is in the same layer as the spin-orbit torque wiring 20. The first insulating layer 91 extends, for example, in the xy plane. The first insulating layer 91 surrounds the spin-orbit torque wiring 20 when viewed in plan from the z direction. The second insulating layer 92 is in the same layer as the first wiring 31 and the second wiring 32. The second insulating layer 92 extends, for example, in the xy plane. The second insulating layer 92 surrounds the first wiring 31 and the second wiring 32 when viewed in plan from the z direction. The third insulating layer 93 is in the same layer as the laminate 10. The third insulating layer 93 extends, for example, in the xy plane. The third insulating layer 93 surrounds the laminate 10 when viewed in plan from the z direction. The third insulating layer 93 is in contact with the laminate 10, for example.

[0038] The magnetoresistive element 100 is a magnetic element that utilizes spin-orbit torque (SOT), and may be referred to as a spin-orbit torque type magnetoresistive element, a spin injection type magnetoresistive element, or a spin current magnetoresistive element.

[0039] The magnetoresistive element 100 is an element for recording data. The magnetoresistive element 100 records data with the resistance value in the z direction of the laminate 10. The resistance value in the z direction of the laminate 10 changes by applying a write current along the spin-orbit torque wiring 20 and injecting spins from the spin-orbit torque wiring 20 into the laminate 10. The resistance value in the z direction of the laminate 10 can be read by applying a read current in the z direction of the laminate 10.

[0040] The first wiring 31 and the second wiring 32 are connected to the spin-orbit torque wiring 20 at positions sandwiching the first ferromagnetic layer 1 when viewed from the z direction. Other layers may be provided between the first wiring 31 and the spin-orbit torque wiring 20, and between the second wiring 32 and the spin-orbit torque wiring 20.

[0041] The first wiring 31 and the second wiring 32 are, for example, conductors that electrically connect the switching element and the magnetoresistive element 100. Both the first wiring 31 and the second wiring 32 have conductivity. The first wiring 31 and the second wiring 32 contain, for example, any one selected from the group consisting of Ti, Cr, Cu, Mo, Ru, Ta, and W.

[0042] The spin-orbit torque wiring 20, for example, has a length in the x direction that is longer than the y direction when viewed from the z direction and extends in the x direction. The write current flows in the x direction along the spin-orbit torque wiring 20 between the first wiring 31 and the second wiring 32. The spin-orbit torque wiring 20 is connected to each of the first wiring 31 and the second wiring 32.

[0043] The spin-orbit torque wiring 20 generates a spin current by the spin Hall effect when a current flows, and injects the spin into the first ferromagnetic layer 1. The spin-orbit torque wiring 20, for example, gives a spin-orbit torque (SOT) to the magnetization of the first ferromagnetic layer 1 that is sufficient to reverse the magnetization of the first ferromagnetic layer 1.

[0044] The spin Hall effect is a phenomenon in which a spin current is induced in a direction orthogonal to the direction of current flow based on the spin-orbit interaction when a current flows. The spin Hall effect is common to the ordinary Hall effect in that the moving (traveling) charge (electron) is bent in the direction of motion (travel). In the ordinary Hall effect, the direction of motion of charged particles moving in a magnetic field is bent by the Lorentz force. In contrast, in the spin Hall effect, even in the absence of a magnetic field, the direction of spin movement is bent only by the movement of electrons (only when a current flows).

[0045] The spin current is generated by eliminating the spin polarization. For example, when a current flows through the wiring, spins (for example, + spins) oriented in the first direction are polarized on the first surface of the wiring, and spins (for example, - spins) oriented in the direction opposite to the first direction are polarized on the second surface facing the first surface. In order to eliminate this spin polarization, a spin current is generated from the first surface toward the second surface or from the second surface toward the first surface. Since both + spins and - spins are electrons and the flows of charges cancel each other out, no current is generated between the first surface and the second surface.

[0046] The spin-orbit torque wiring 20 includes a first layer 21 and a second layer 22. The first layer 21 is closer to the first ferromagnetic layer 1 than the second layer 22. The first layer 21 and the second layer 22 are in direct contact, for example. The first layer 21 and the second layer 22 each extend in the x direction. A part of the first layer 21 and a part of the second layer 22 overlap with the first wiring 31 and the second wiring 32, respectively, when viewed in the z direction.

[0047] The first layer 21 and the second layer 22 include any one of a metal, an alloy, an intermetallic compound, a metal boride, a metal carbide, a metal silicide, a metal phosphide, and a metal nitride that has a function of generating a pure spin current by the spin Hall effect when current flows. The first layer 21 and the second layer have different constituent elements or composition ratios.

[0048] The first layer 21 and the second layer 22 may include, for example, a nonmagnetic heavy metal. Here, the heavy metal means a metal having a specific gravity of yttrium or more. The nonmagnetic heavy metal is, for example, a nonmagnetic metal having a large atomic number of 39 or more having d electrons or f electrons in the outermost shell. These nonmagnetic metals have a large spin-orbit interaction that causes the spin Hall effect. The first layer 21 and the second layer 22 include, for example, Hf, Ta, and W.

[0049] Also, the first layer 21 may include, for example, any one of boron, oxygen, nitrogen, and carbon. Also, the second layer 22 may include, for example, any one of boron, oxygen, nitrogen, and carbon. The first layer 21 and the second layer 22 may be, for example, any one of a boride, an oxide, a nitride, and a carbide of the metal constituting the layer. Boron, oxygen, nitrogen, and carbon may be combined with the metal element constituting the layer or may be present between the metals constituting the layer without being combined. The metal element constituting the layer in this case is not limited to a heavy metal and may be a light metal element having an atomic number of 38 or less. For example, at least one of the first layer 21 and the second layer 22 includes, for example, tantalum nitride (TaN) and titanium nitride (TiN).

[0050] For example, the total content rate of boron, oxygen, nitrogen, and carbon in the first layer 21 is lower than that in the second layer 22. In each of the first layer 21 and the second layer 22, the content rates of boron, oxygen, nitrogen, and carbon are preferably all 50 atm% or less. Further, the content rate of boron, oxygen, nitrogen, or carbon contained in the second layer 22 is preferably, for example, 30 atm% or more. The content rates of these elements can be calculated by performing composition mapping on the spin-orbit torque wiring 20 thinned to 20 nm or less in the Y direction using energy-dispersive X-ray spectroscopy (EDS) or electron energy loss spectroscopy (EELS) of a transmission electron microscope (TEM). Boron, oxygen, nitrogen, and carbon reduce the average grain size of crystal grains.

[0051] FIG. 5 is an enlarged cross-sectional view of a characteristic portion of the spin-orbit torque wiring 20 according to the first embodiment. The first layer 21 has a plurality of crystal grains 21G that have grown in grains. The second layer 22 has a plurality of crystal grains 22G that have grown in grains. The average grain size S1 of the crystal grains 21G constituting the first layer 21 is larger than the average grain size S2 of the crystal grains 22G constituting the second layer 22.

[0052] By laminating layers with different grain sizes, electrons flowing through the spin-orbit torque wiring 20 are more likely to be diffused, and the generation efficiency of the spin current is increased. Further, since the average grain size S1 of the first layer 21 is larger than the average grain size S2 of the second layer 22, it becomes easier to flatten the surface on which the laminate 10 is laminated.

[0053] The average grain sizes S1 and S2 of the crystal grains 21G and 22G can be measured using a transmission electron microscope (TEM). For example, when determining the average grain size S1 of the crystal grains 21G, the cross-section of the spin-orbit torque wiring 20 is measured with a transmission electron microscope, and any 10 crystal grains 21G in the cross-sectional image are extracted. Then, the particle size of each of the 10 crystal grains 21G is measured, and the average is obtained. When the crystal grains 21G are amorphous, the length in the x-direction is taken as the particle size. The average of this particle size is the average grain size S1. The average grain size S2 of the crystal grains 22G can also be measured in the same procedure.

[0054] Also, when the surfaces of the first layer 21 and the second layer 22 can be measured, the average grain sizes of the crystal grains 21G and 22G may be measured with an atomic force microscope (AFM). The surface of each layer is measured with an AFM, particle size analysis is performed, and the average grain sizes S1 and S2 of the crystal grains 21G and 22G may be obtained.

[0055] The average grain size S1 of the crystal grains 21G constituting the first layer 21 is, for example, greater than 1 times and less than 2 times the average grain size S2 of the second layer 22. Since the average grain size S1 is not an integer multiple of the average grain size S2, a shift occurs between the period of the crystal grains 21G in the first layer 21 and the period of the crystal grains 22G in the second layer 22. That is, the positions in the x-direction of the grain boundaries between the crystal grains 21G and the grain boundaries between the crystal grains 22G are shifted. When the positions in the x-direction of these grain boundaries are shifted, the number of interfaces as seen from the electrons flowing in the x-direction increases. As a result, the electrons flowing through the spin-orbit torque wiring 20 are more likely to be diffused, and the generation efficiency of the spin current increases.

[0056] The thickness of the first layer 21 may be, for example, equal to or less than the spin diffusion length of the material constituting the first layer 21. When this condition is satisfied, the spin generated in the second layer 22 passes through the first layer 21 and reaches the first ferromagnetic layer 1. That is, the amount of spin injected into the first ferromagnetic layer 1 increases, and the magnetization of the first ferromagnetic layer 1 is more likely to be reversed during writing. The thickness of the first layer 21 is, for example, 2 nm or more. The thickness of the first layer 21 may be, for example, 20 nm or less.

[0057] The thickness of the second layer 22 is, for example, 2 nm or more and 20 nm or less. Further, since the writing current is divided between the first layer 21 and the second layer 22, when mainly using the spin generated in the first layer 21, the second layer 22 is preferably thinner than the first layer 21.

[0058] The resistivity of the spin-orbit torque wiring 20 is, for example, 1 mΩ·cm or more. Also, the resistivity of the spin-orbit torque wiring 20 is, for example, 10 mΩ·cm or less. When the resistivity of the spin-orbit torque wiring 20 is high, a high voltage can be applied to the spin-orbit torque wiring 20. When the potential of the spin-orbit torque wiring 20 becomes high, spin can be efficiently supplied from the spin-orbit torque wiring 20 to the first ferromagnetic layer 1. Also, since the spin-orbit torque wiring 20 has conductivity equal to or higher than a certain level, a current path flowing along the spin-orbit torque wiring 20 can be secured, and a spin current associated with the spin Hall effect can be efficiently generated. The resistivity of the first wiring 31 and the second wiring 32 is preferably lower than the resistivity of the spin-orbit torque wiring 20.

[0059] In addition, the spin-orbit torque wiring 20 may contain a magnetic metal or may contain a topological insulator. A topological insulator is a substance in which the interior of the substance is an insulator or a high-resistance body, but a spin-polarized metallic state is generated on its surface.

[0060] The laminate 10 is connected to the spin-orbit torque wiring 20. For example, the laminate 10 is laminated on the spin-orbit torque wiring 20. Another layer may be provided between the laminate 10 and the spin-orbit torque wiring 20.

[0061] The resistance value of the laminate 10 in the z direction changes when spin is injected from the spin-orbit torque wiring 20 into the laminate 10 (the first ferromagnetic layer 1).

[0062] The laminate 10 is sandwiched in the z direction between the spin-orbit torque wiring 20 and the electrode E (see FIG. 2). The laminate 10 is a columnar body. The planar shape of the laminate 10 as viewed from the z direction is, for example, circular, elliptical, or rectangular. The side surface of the laminate 10 is inclined with respect to the z direction, for example.

[0063] The laminate 10 has, for example, a first ferromagnetic layer 1, a second ferromagnetic layer 2, and a nonmagnetic layer 3. The first ferromagnetic layer 1 is in contact with the spin-orbit torque wiring 20, for example, and is laminated on the spin-orbit torque wiring 20. Spin is injected into the first ferromagnetic layer 1 from the spin-orbit torque wiring 20. The magnetization of the first ferromagnetic layer 1 receives a spin-orbit torque (SOT) from the injected spin, and the orientation direction changes. The first ferromagnetic layer 1 and the second ferromagnetic layer 2 sandwich the nonmagnetic layer 3 in the z direction.

[0064] The first ferromagnetic layer 1 and the second ferromagnetic layer 2 each have magnetization. When a predetermined external force is applied, the magnetization of the second ferromagnetic layer 2 is less likely to change in the orientation direction than the magnetization of the first ferromagnetic layer 1. The first ferromagnetic layer 1 is called a magnetization-free layer, and the second ferromagnetic layer 2 may be called a magnetization-fixed layer or a magnetization-reference layer. In the laminate 10 shown in FIG. 3, the magnetization-fixed layer is on the side away from the substrate Sub and is called a top-pin structure. The resistance value of the laminate 10 changes according to the difference in the relative angle of magnetization between the first ferromagnetic layer 1 and the second ferromagnetic layer 2 sandwiching the nonmagnetic layer 3.

[0065]

[0066] ​The first ferromagnetic layer 1 and the second ferromagnetic layer 2 may contain a Heusler alloy. The Heusler alloy contains an intermetallic compound having a chemical composition of XYZ or X2YZ. X is a transition metal element or a noble metal element of the Co, Fe, Ni, or Cu group in the periodic table, Y is a transition metal of the Mn, V, Cr, or Ti group or an element species of X, and Z is a typical element from Group III to Group V. The Heusler alloy is, for example, Co2FeSi, Co2FeGe, Co2FeGa, Co2MnSi, Co2Mn 1-a Fe a Al b Si 1-b , Co2FeGe 1-c Ga c and the like. The Heusler alloy has a high spin polarization rate.

[0067] The non-magnetic layer 3 contains a non-magnetic material. When the non-magnetic layer 3 is an insulator (when it is a tunnel barrier layer), materials such as Al2O3, SiO2, MgO, and MgAl2O4 can be used as the material. In addition to these, materials in which a part of Al, Si, and Mg is replaced by Zn, Be, etc. can also be used. Among these, MgO and MgAl2O4 are materials in which coherent tunneling can be realized, so spin can be efficiently injected. When the non-magnetic layer 3 is a metal, materials such as Cu, Au, and Ag can be used. Further, when the non-magnetic layer 3 is a semiconductor, materials such as Si, Ge, CuInSe2, CuGaSe2, and Cu(In,Ga)Se2 can be used.

[0068] The laminate 10 may have layers other than the first ferromagnetic layer 1, the second ferromagnetic layer 2, and the non-magnetic layer 3. For example, an underlayer may be provided between the spin-orbit torque wiring 20 and the first ferromagnetic layer 1. The underlayer enhances the crystallinity of each layer constituting the laminate 10. Also, for example, a cap layer may be provided on the uppermost surface of the laminate 10.

[0069] Further, a ferromagnetic layer may be provided via a spacer layer on the surface of the laminate 10 opposite to the nonmagnetic layer 3 of the second ferromagnetic layer 2. The second ferromagnetic layer 2, the spacer layer, and the ferromagnetic layer form a synthetic antiferromagnetic structure (SAF structure). The synthetic antiferromagnetic structure consists of two magnetic layers sandwiching a nonmagnetic layer. By the antiferromagnetic coupling between the second ferromagnetic layer 2 and the ferromagnetic layer, the coercive force of the second ferromagnetic layer 2 becomes larger than when there is no ferromagnetic layer. The ferromagnetic layer is, for example, IrMn, PtMn, etc. The spacer layer contains, for example, at least one selected from the group consisting of Ru, Ir, and Rh.

[0070] Next, a method for manufacturing the magnetoresistive element 100 will be described. The magnetoresistive element 100 is formed by a lamination process for each layer and a processing process for processing a part of each layer into a predetermined shape. For the lamination of each layer, a sputtering method, a chemical vapor deposition (CVD) method, an electron beam evaporation method (EB evaporation method), an atomic laser deposition method, etc. can be used. The processing of each layer can be performed using photolithography or the like.

[0071] First, impurities are doped at a predetermined position on the substrate Sub to form the source S and the drain D. Next, a gate insulating film GI and a gate electrode G are formed between the source S and the drain D. The source S, the drain D, the gate insulating film GI, and the gate electrode G form the transistor Tr. As the substrate Sub, a commercially available semiconductor circuit substrate on which the transistor Tr is formed may be used.

[0072] Next, an insulating layer In is formed so as to cover the transistor Tr. Further, an opening is formed in the insulating layer In, and a conductor is filled in the opening to form the via wiring V, the first wiring 31, and the second wiring 32. The write wiring WL and the common wiring CL are formed by laminating the insulating layer In to a predetermined thickness and then forming a groove in the insulating layer In and filling the groove with a conductor.

[0073] Next, a layer to be the second layer 22 and a layer to be the first layer 21 are sequentially stacked on one surface of the insulating layer In, the first wiring 31, and the second wiring 32. The average grain sizes of the first layer 21 and the second layer 22 can be adjusted, for example, by changing the energy of ions irradiated to the target during sputtering. When the sputtering energy is large, the atoms attached to the film formation surface can move, and grain growth is likely to occur. Also, the average grain sizes of the first layer 21 and the second layer 22 may be changed by adjusting the content rates of boron, oxygen, nitrogen, and carbon. When the content rates of boron, oxygen, nitrogen, and carbon increase, the average grain size tends to become smaller.

[0074] Next, a ferromagnetic layer, a nonmagnetic layer, a ferromagnetic layer, and a hard mask layer are sequentially stacked on the layer to be the second layer 22. Next, the hard mask layer is processed into a predetermined shape. The predetermined shape is, for example, the outer shape of the spin-orbit torque wiring 20. Next, through the hard mask layer, the layer to be the spin-orbit torque wiring 20, the ferromagnetic layer, the nonmagnetic layer, and the ferromagnetic layer are processed into a predetermined shape at once.

[0075] Next, unnecessary portions of the hard mask layer in the x direction are removed. The hard mask layer becomes the outer shape of the laminate 10. Next, through the hard mask layer, unnecessary portions of the laminate formed on the spin-orbit torque wiring 20 in the x direction are removed. The laminate 10 is processed into a predetermined shape and becomes the laminate 10. The hard mask layer becomes the electrode E. Next, the periphery of the laminate 10 and the spin-orbit torque wiring 20 is filled with the insulating layer In, and the magnetoresistive effect element 100 is obtained.

[0076] The magnetoresistive effect element 100 according to the first embodiment has layers with different grain sizes in the spin-orbit torque wiring 20. Since the spin-orbit torque wiring 20 has layers with different grain sizes, electrons flowing through the spin-orbit torque wiring 20 are likely to be diffused, and the generation efficiency of the spin current is increased. Also, since the average grain size S1 of the first layer 21 is larger than the average grain size S2 of the second layer 22, the surface on which the laminate 10 is stacked is easily flattened. When the stacked surface of the laminate 10 becomes flat, the magnetoresistance change rate (MR ratio) of the laminate 10 becomes large.

[0077] As described above, an example of the magnetoresistive element 100 according to the first embodiment has been shown. However, additions, omissions, substitutions, and other modifications can be made without departing from the spirit of the present invention.

[0078] (First Modification Example) FIG. 6 is a cross-sectional view of the magnetoresistive element 101 according to the first modification example. FIG. 6 is an xz cross-section passing through the center of the spin-orbit torque wiring 25 in the y direction. In FIG. 6, the same components as those in FIG. 3 are denoted by the same reference numerals, and the description thereof is omitted.

[0079] In the magnetoresistive element 101 according to the first modification example, the configuration of the spin-orbit torque wiring 25 is different from that of the spin-orbit torque wiring 20 of the magnetoresistive element 100.

[0080] The spin-orbit torque wiring 25 includes a first layer 21, a second layer 22, and a third layer 23. The third layer 23 is closer to the first ferromagnetic layer 1 than the first layer 21 and the second layer 22. The third layer 23 is, for example, on the first layer 21. The third layer 23 has different constituent elements or composition ratios from those of the first layer 21. The third layer 23 may have different constituent elements or composition ratios from those of the second layer 22.

[0081] The third layer 23 includes any one of a metal, an alloy, an intermetallic compound, a metal boride, a metal carbide, a metal silicide, a metal phosphide, and a metal nitride that has a function of generating a pure spin current by the spin Hall effect when a current flows.

[0082] The third layer 23 may contain, for example, a non-magnetic heavy metal. The third layer 23 may also contain, for example, any one of boron, oxygen, nitrogen, and carbon. When the third layer 23 contains any one of boron, oxygen, nitrogen, and carbon, the metal element constituting the layer is not limited to a heavy metal, and may be a light metal element having an atomic number of 38 or less. For example, the third layer 23 has a higher total content rate of boron, oxygen, nitrogen, and carbon than the first layer 21. The third layer 23 may also have a higher total content rate of boron, oxygen, nitrogen, and carbon than the second layer 22. The content rates of boron, oxygen, nitrogen, and carbon in the third layer 23 are preferably all 50 atm% or less. Also, the content rate of boron, oxygen, nitrogen, or carbon contained in the third layer 23 is preferably, for example, 30 atm% or more.

[0083] FIG. 7 is an enlarged cross-sectional view of a characteristic portion of the spin-orbit torque wiring 25 according to the first modification. The third layer 23 has a plurality of crystallites 23G that have grown in grains. The average grain size S3 of the crystallites 23G constituting the third layer 23 is smaller than the average grain size S1 of the crystallites 21G constituting the first layer 21. The average grain size S3 of the crystallites 23G constituting the third layer 23 may be smaller than the average grain size S2 of the crystallites 22G constituting the second layer 22.

[0084] When the grain size becomes smaller, the interface resistance of the layer increases, and the generation efficiency of the spin current accompanying the spin-orbit interaction increases. The presence of a layer (the third layer 23) with a high spin current generation efficiency near the first ferromagnetic layer 1 increases the spin injection efficiency into the first ferromagnetic layer 1. Also, the crystallites 23G fill the unevenness remaining on the laminated surface flattened by the first layer 21, so that the surface on which the laminate 10 is laminated can be made flatter.

[0085] The average grain size S3 of the crystallites 23G can be measured in the same manner as the crystallites 21G and the crystallites 22G. The average grain size S1 of the crystallites 21G constituting the first layer 21 is, for example, larger than 1 times and smaller than 2 times the average grain size S2 of the third layer 23.

[0086] The thickness of the third layer 23 is, for example, 0.5 nm or more and 10 nm or less. Also, it is preferably thinner than the first layer 21. When it becomes thick, grain growth progresses and the grain size becomes large.

[0087] The magnetoresistive effect element 101 according to the first modification has the same effect as the magnetoresistive effect element 100 according to the first embodiment. Also, since the spin-orbit torque wiring 25 has the third layer 23, the spin injection efficiency into the first ferromagnetic layer 1 can be increased. Further, when there is the third layer 23, the interfaces of different layers in the spin-orbit torque wiring 25 increase. When the interfaces of different layers increase, the amount of spin injected from the spin-orbit torque wiring 25 into the first ferromagnetic layer 1 increases due to the Rashba effect.

[0088] (Second Modification) FIG. 8 is a cross-sectional view of the magnetoresistive effect element 102 according to the second modification. FIG. 8 is an xz cross-section passing through the center in the y direction of the spin-orbit torque wiring 20. In FIG. 8, the same components as those in FIG. 3 are denoted by the same reference numerals, and the description thereof is omitted.

[0089] The magnetoresistive effect element 102 according to the second modification is different from the spin-orbit torque wiring 20 of the magnetoresistive effect element 100 in that it further includes an amorphous layer 40 between the spin-orbit torque wiring 20 and the first ferromagnetic layer 1.

[0090] The amorphous layer 40 improves the flatness of the laminated surface of the laminate 10. The film thickness of the amorphous layer 40 is, for example, 1 nm or less. When the thickness of the amorphous layer 40 is sufficiently thin, the spin from the spin-orbit torque wiring 20 to the first ferromagnetic layer 1 is difficult to diffuse.

[0091] The amorphous layer 40 may have a non-magnetic element. The amorphous layer 40 is, for example, Ta or W. The amorphous layer 40 may contain a ferromagnetic element. When the amorphous layer 40 is sufficiently thin at 1 nm or less, the ferromagnetic element does not exhibit magnetization. Therefore, even if the amorphous layer 40 contains a ferromagnetic element, the spin from the spin-orbit torque wiring 20 to the first ferromagnetic layer 1 is not largely diffused.

[0092] The magnetoresistive element 102 according to the second modification example can obtain the same effects as the magnetoresistive element 100 according to the first embodiment. Further, since the magnetoresistive element 102 has the amorphous layer 40, the laminated surface of the laminate 10 is flattened. When the laminated surface of the laminate 10 becomes flat, the magnetoresistance change rate (MR ratio) of the laminate 10 increases.

[0093] (Third Modification Example) FIG. 9 is a cross-sectional view of the magnetoresistive element 103 according to the third modification example. FIG. 9 is an xz cross-section passing through the center of the spin-orbit torque wiring 26 in the y direction. In FIG. 9, the same components as those in FIG. 3 are denoted by the same reference numerals, and the description thereof is omitted.

[0094] The laminate 10 shown in FIG. 9 has a bottom pin structure in which the magnetization fixed layer (second ferromagnetic layer 2) is near the substrate Sub. When the magnetization fixed layer is on the substrate Sub side, the stability of the magnetization of the magnetization fixed layer is enhanced, and the MR ratio of the magnetoresistive element 103 increases. The spin-orbit torque wiring 26 is, for example, on the laminate 10. The first layer 21 is closer to the first ferromagnetic layer 1 than the second layer 22, and the second layer 22 is on the first layer 21. The first wiring 31 and the second wiring 32 are on the spin-orbit torque wiring 26.

[0095] The magnetoresistive element 103 according to the third modification example has only a different positional relationship of each component, and the same effects as the magnetoresistive element 100 according to the first embodiment can be obtained.

[0096] "Second Embodiment" FIG. 10 is a cross-sectional view of the magnetization rotation element 110 according to the second embodiment. In FIG. 1, the magnetization rotation element 110 is replaced with the magnetoresistive element 100 according to the first embodiment.

[0097] The magnetization rotation element 110, for example, irradiates light onto the first ferromagnetic layer 1 and evaluates the light reflected by the first ferromagnetic layer 1. When the orientation direction of magnetization changes due to the magneto - Kerr effect, the deflection state of the reflected light changes. The magnetization rotation element 110 can be used, for example, as an optical element such as a video display device that utilizes the difference in the deflection state of light.

[0098] In addition, the magnetization rotation element 110 can be used alone as an anisotropic magnetic sensor, an optical element utilizing the magneto - Faraday effect, etc.

[0099] The spin - orbit torque wiring 20 of the magnetization rotation element 110 has a first layer 21 and a second layer 22. The average grain size S1 of the first layer 21 is larger than the average grain size S2 of the second layer 22.

[0100] The magnetization rotation element 110 according to the second embodiment is only obtained by removing the non - magnetic layer 3 and the second ferromagnetic layer 2 from the magnetoresistive effect element 100, and the same effects as those of the magnetoresistive effect element 100 according to the first embodiment can be obtained.

[0101] So far, based on the first embodiment, the second embodiment, and the modification examples, the preferred embodiments of the present invention have been exemplified, but the present invention is not limited to these embodiments. For example, the characteristic configurations in each of the embodiments and modification examples may be applied to other embodiments and modification examples.

Explanation of Reference Numerals

[0102] 1... First ferromagnetic layer, 2... Second ferromagnetic layer, 3... Non - magnetic layer, 10... Stacked body, 20... Spin - orbit torque wiring, 21... First layer, 22... Second layer, 23... Third layer, 21G, 22G, 23G... Crystal grains, 31... First wiring, 32... Second wiring, 91... First insulating layer, 92... Second insulating layer, 93... Third insulating layer, 100, 101, 102... Magnetoresistive effect elements, 110... Magnetization rotation element, 200... Magnetic memory, CL... Common wiring, RL... Read - out wiring, WL... Write - in wiring, In... Insulating layer, S1, S2, S3... Average grain size

Claims

1. A spin-orbit torque wiring, and a first ferromagnetic layer connected to the spin-orbit torque wiring, comprising: The spin-orbit torque wiring has a first layer and a second layer, The first layer is closer to the first ferromagnetic layer than the second layer, A magnetization rotation element in which an average grain size of the first layer is larger than an average grain size of the second layer.

2. The magnetization rotation element according to claim 1, wherein the average grain size of the first layer is not an integral multiple of the average grain size of the second layer.

3. The magnetization rotation element according to claim 1, wherein the average grain size of the first layer is larger than 1 times and smaller than 2 times the average grain size of the second layer.

4. The magnetization rotation element according to any one of claims 1 to 3, wherein the second layer contains any one of boron, oxygen, nitrogen, and carbon.

5. The spin-orbit torque wiring further includes a third layer, The third layer is closer to the first ferromagnetic layer than the first layer and the second layer, The magnetization rotation element according to any one of claims 1 to 4, wherein an average grain size of the third layer is smaller than an average grain size of the first layer.

6. The magnetization rotation element according to claim 5, wherein the average grain size of the third layer is smaller than the average grain size of the second layer.

7. The third layer contains any one of boron, oxygen, nitrogen, and carbon, The magnetization rotation element according to claim 5 or 6, wherein a total content ratio of boron, oxygen, nitrogen, and carbon in the third layer is larger than that in the second layer.

8. The magnetization rotation element according to any one of claims 1 to 7, further comprising an amorphous layer between the first ferromagnetic layer and the spin-orbit torque wiring.

9. The magnetization rotation element according to claim 8, wherein the amorphous layer has a film thickness of 1 nm or less.

10. A magnetoresistive effect element comprising the magnetization rotation element according to any one of claims 1 to 9, a non-magnetic layer, and a second ferromagnetic layer, The non-magnetic layer is sandwiched between the first ferromagnetic layer and the second ferromagnetic layer, The first ferromagnetic layer is closer to the spin-orbit torque wiring than the second ferromagnetic layer.

11. A magnetic memory including a plurality of the magnetoresistive effect elements according to claim 10.

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