WO2024189676A1

WO2024189676A1 - Domain wall displacement element and magnetic array

Info

Publication number: WO2024189676A1
Application number: PCT/JP2023/009321
Authority: WO
Inventors: 心人市川; 祥吾米村; 章悟山田; 竜雄柴田
Original assignee: Tdk株式会社
Priority date: 2023-03-10
Filing date: 2023-03-10
Publication date: 2024-09-19

Abstract

This domain wall displacement element comprises: a first ferromagnetic layer having a domain wall inside; a second ferromagnetic layer; a nonmagnetic layer sandwiched between the first ferromagnetic layer and the second ferromagnetic layer; a first magnetization fixed section connected to the first ferromagnetic layer; a second magnetization fixed section connected to the first ferromagnetic layer at a position apart, in a first direction, from the first magnetization fixed section; and an insulating layer sandwiched between the first magnetization fixed section and the second magnetization fixed section in the first direction as viewed from the lamination direction. The insulating layer includes a first region containing an added metal different from a main element forming the insulating layer or an added metal nitride.

Description

Domain wall motion element and magnetic array

The present invention relates to a domain wall motion element and a magnetic array.

Magnetoresistance effect elements are known that utilize a change in resistance value (magnetoresistance change) based on a change in the relative angle between the magnetizations of two ferromagnetic layers. For example, the domain wall motion type magnetoresistance effect element (hereinafter referred to as domain wall motion element) described in Patent Document 1 is one example of a magnetoresistance effect element. In domain wall motion elements, the resistance value in the stacking direction changes depending on the position of the domain wall, and data can be recorded in multi-value or analog form.

The magnetic domain wall motion element can be used in neuromorphic devices that mimic the functions of the brain, as described in Patent Document 2, for example.

Patent No. 5441005 JP 2020-053660 A

The domain wall motion element writes signals by applying a write current. The write current is one of the causes of heat generation in the domain wall motion element. Heat generation in the domain wall motion element reduces the stability of magnetization within the domain wall motion element, and reduces the reliability of the domain wall motion element. Furthermore, if the domain wall motion element is subjected to excessive heat, the domain wall motion element may be damaged.

This disclosure has been made in consideration of the above problems, and aims to provide a domain wall motion element and magnetic array that can efficiently dissipate heat.

The domain wall motion element according to the first aspect includes a first ferromagnetic layer, a second ferromagnetic layer, a non-magnetic layer, a first magnetization fixed portion, a second magnetization fixed portion, and an insulating layer. The first ferromagnetic layer has a domain wall therein. The non-magnetic layer is sandwiched between the first ferromagnetic layer and the second ferromagnetic layer. The first magnetization fixed portion is connected to the first ferromagnetic layer. The second magnetization fixed portion is connected to the first ferromagnetic layer at a position spaced apart from the first magnetization fixed portion in the first direction. The insulating layer is sandwiched in the first direction between the first magnetization fixed portion and the second magnetization fixed portion when viewed from the stacking direction. The insulating layer includes a first region to which a metal or metal nitride different from the main element constituting the insulating layer is added.

FIG. 2 is a block diagram of a magnetic array according to the first embodiment. FIG. 2 is a circuit diagram of an integrated region of the magnetic array according to the first embodiment. 3 is a cross-sectional view of the vicinity of a domain wall motion element of the magnetic array according to the first embodiment. FIG. 1 is a cross-sectional view of a domain wall motion element according to a first embodiment. FIG. 2 is a plan view of the domain wall motion element according to the first embodiment. FIG. 2 is a plan view of an insulating layer of the domain wall motion element according to the first embodiment. FIG. 13 is a plan view of a domain wall motion element according to a first modified example. FIG. 13 is a plan view of an insulating layer of a domain wall motion element according to a second modified example. FIG. 11 is a cross-sectional view of a domain wall motion element according to a third modified example. FIG. 13 is a cross-sectional view of a domain wall motion element according to a fourth modified example.

The present embodiment will now be described in detail with reference to the drawings as appropriate. The drawings used in the following description may show enlarged characteristic parts for the sake of convenience in order to make the features of the present invention easier to understand, 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 invention is not limited to them. Appropriate modifications can be made within the scope of the effects of the present invention.

First, the directions are defined. The x and y directions are substantially parallel to one surface of the substrate Sub (see FIG. 3), which will be described later. The x direction is the direction in which the first ferromagnetic layer, which will be described later, extends. The x direction is an example of a first direction. The y direction is a direction perpendicular to the x direction. The y direction is an example of a second direction. The z direction is a direction from the substrate, which will be described later, to the domain wall motion element. The z direction is an example of a stacking direction. In this specification, the +z direction may be expressed as "up" and the -z direction as "down", but these expressions are for convenience and do not define the direction of gravity. 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.

[First embodiment]
1 is a block diagram of a magnetic array MA according to a first embodiment. The magnetic array MA has an integration region 1 and a peripheral region 2. The magnetic array MA can be used for, for example, a magnetic memory, a multiply-and-accumulate calculator, a neuromorphic device, a spin memristor, or a magneto-optical element.

The accumulation region 1 is an area where multiple domain wall motion elements are accumulated. When the magnetic array MA is used as a memory, data is stored in the accumulation region 1. When the magnetic array MA is used as a neuromorphic device, learning and inference are performed in the accumulation region 1.

The peripheral region 2 is an area in which a control element that controls the operation of the domain wall motion element in the integration region 1 is implemented. The peripheral region 2 includes, for example, a pulse application device 3, a resistance detection device 4, and an output section 5.

The pulse application device 3 is configured to apply a pulse to at least one of the multiple domain wall motion elements in the accumulation region 1. The pulse application device 3 has, for example, a control unit 6 and a power supply 7.

The control unit 6 has, for example, a processor and a memory. The processor is, for example, a CPU (Central Processing Unit). The processor operates based on an operating program stored in the memory. The control unit 6 controls, for example, the address of the domain wall motion element to which a pulse is applied, the magnitude of the pulse (voltage, pulse length) to be applied to a specific domain wall motion element, etc. The control unit 6 may also have a clock, a counter, a random number generator, etc. The clock is an indicator of the timing for applying the pulse, and the counter counts the number of times the pulse is applied, etc. The power supply 7 applies a pulse to the domain wall motion element according to instructions from the control unit 6.

The resistance detection device 4 is configured to detect the resistance value of the domain wall motion elements in the integration region 1. The resistance detection device 4 may detect the resistance of each domain wall motion element in the integration region 1, or may detect the total resistance of domain wall motion elements belonging to the same column, for example. The resistance detection device 4 has, for example, a comparator that compares the magnitude of the detected resistance values. The comparator may, for example, compare the detected resistance values with each other, or may compare the detected resistance value with a preset reference resistance value.

The output unit 5 is connected to the resistance detection device 4. The output unit 5 has, for example, a processor, an output capacitor, an amplifier, a converter, etc. When the magnetic array MA is used as a neuromorphic device, the output unit 5 may perform a calculation to substitute the detection result of the resistance detection device 4 into an activation function. The calculation is performed, for example, by a processor. The output unit 5 outputs the calculation result to the outside. When the magnetic array MA is used as a neuromorphic device, for example, the output unit 5 may perform an operation such as outputting the calculation result as an input signal for another magnetic array, or may perform an operation such as outputting the calculation result to the outside as a discrimination rate. The output unit 5 may also feed back the calculation result to the pulse application device 3.

FIG. 2 is a circuit diagram of the integrated region 1 according to the first embodiment. The integrated region 1 includes a plurality of domain wall motion 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, and a plurality of second switching elements SW2. The third switching element SW3 may belong to, for example, the pulse application device 3 in the peripheral region 2.

The multiple domain wall motion elements 100 are arranged, for example, in a matrix. The multiple domain wall motion elements 100 are not limited to elements arranged in a matrix in the actual device, but may be arranged in a matrix in a circuit diagram.

Each of the write wirings WL is used when writing data. Each of the write wirings WL electrically connects the pulse application device 3 to one or more domain wall motion elements 100. Each of the common wirings CL is used when both writing and reading data. Each of the common wirings CL is connected to, for example, a resistance detection device 4. The common wiring CL may be provided for each of the multiple domain wall motion elements 100, or may be provided across the multiple domain wall motion elements 100. Each of the read wirings RL is used when reading data. Each of the read wirings RL electrically connects the pulse application device 3 to one or more domain wall motion elements 100.

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, elements that utilize a phase change in 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, and elements whose conductivity changes with a change in atomic position.

The first switching element SW1 and the second switching element SW2 are connected, for example, to each domain wall motion element 100. The first switching element SW1 is connected, for example, between the domain wall motion element 100 and the write wiring WL. The second switching element SW2 is connected, for example, between the domain wall motion element 100 and the common wiring CL. The third switching element SW3 is connected, for example, across multiple domain wall motion elements 100. The third switching element SW3 is connected, for example, to the read wiring RL.

The positional relationship between the first switching element SW1, the second switching element SW2, and the third switching element SW3 is not limited to that shown in FIG. 2. For example, the first switching element SW1 may be connected across multiple domain wall motion elements 100 and located upstream of the write wiring WL. Also, for example, the second switching element SW2 may be connected across multiple domain wall motion elements 100 and located upstream of the common wiring CL. Also, for example, the third switching element SW3 may be connected to each domain wall motion element 100 one by one.

FIG. 3 is a cross-sectional view of the vicinity of the domain wall motion element 100 in the accumulation region 1 according to the first embodiment. FIG. 3 is a cross-section of one domain wall motion element 100 in FIG. 2 cut along the xz plane passing through the center of the width of the first ferromagnetic layer 10 in the y direction.

The first switching element SW1 and the second switching element SW2 shown in FIG. 3 are transistors Tr. The transistor Tr 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 determined by the direction of current flow, and are both semiconductor active regions. FIG. 3 shows only one example, and the positional relationship between the source S and the drain D may be reversed. The substrate Sub is, for example, a semiconductor substrate. The third switching element SW3 is electrically connected to the read wiring RL, and is, for example, shifted in the y direction in FIG. 3.

The transistor Tr, write wiring WL, common wiring CL, read wiring RL, and domain wall motion element 100 are connected by via wiring Vw extending in the z direction or in-plane wiring IPw extending in any direction within the xy plane. The via wiring Vw and in-plane wiring IPw contain a conductive material. An insulating layer 90 is formed between different layers in the z direction, except for the via wiring Vw.

The insulating layer 90 is an insulating layer that insulates between wirings of a multilayer wiring and between elements. The domain wall motion element 100 and the transistor Tr are electrically isolated by the insulating layer 90, except for the via wiring Vw. The insulating layer 90 is, 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 ), or the like.

FIG. 4 is a cross-sectional view of the domain wall motion element 100 cut in the xz plane passing through the center of the first ferromagnetic layer 10 in the y direction. The arrows in the figure are an example of the orientation direction of the magnetization of the ferromagnetic material. FIG. 5 is a plan view of the domain wall motion element 100 as seen from the z direction.

The domain wall motion element 100 includes, for example, a first ferromagnetic layer 10, a non-magnetic layer 20, a second ferromagnetic layer 30, a first magnetization fixed layer 40, a second magnetization fixed layer 50, an insulating layer 60, a first wiring W1, a second wiring W2, and a third wiring W3. At least one of the multiple domain wall motion elements included in the integration region 1 is the domain wall motion element 100 shown in Figures 4 and 5.

The first ferromagnetic layer 10 extends in the x direction. When viewed from the z direction, the length of the first ferromagnetic layer 10 in the x direction is longer than the length in the y direction. The first ferromagnetic layer 10 has two magnetic domains inside, and a domain wall DW at the boundary between the two magnetic domains. The first ferromagnetic layer 10 is, for example, a layer capable of magnetically recording information by changing the magnetic state. The first ferromagnetic layer 10 is also called an analog layer, a magnetic recording layer, or a domain wall displacement layer.

The first ferromagnetic layer 10 has a first magnetization region A1, a second magnetization region A2, and a third magnetization region A3.

The first magnetization region A1 is a region in which the orientation direction of the magnetization M _A1 is fixed in one direction. The magnetization being fixed means that the magnetization does not reverse during normal operation of the domain wall motion element 100 (when no external force exceeding the expected value is applied). The first magnetization region A1 is, for example, a region of the first ferromagnetic layer 10 that overlaps with the first magnetization fixed layer 40 when viewed from the z direction. The magnetization M _A1 of the first magnetization region A1 is fixed by, for example, the magnetization M ₄₀ of the first magnetization fixed layer 40.

The second magnetization region A2 is a region in which the orientation direction of the magnetization M _A2 is fixed in one direction. The orientation direction of the magnetization M _A2 of the second magnetization region A2 is different from the orientation direction of the magnetization M _A1 of the first magnetization region A1. The orientation direction of the magnetization M _A2 of the second magnetization region A2 is, for example, opposite to the orientation direction of the magnetization M _A1 of the first magnetization region A1. The second magnetization region A2 is, for example, a region of the first ferromagnetic layer 10 that overlaps with the second magnetization fixed layer 50 when viewed from the z direction. The magnetization M _A2 of the second magnetization region A2 is, for example, fixed by the magnetization M ₅₀ of the second magnetization fixed layer 50.

The third magnetization region A3 is a region other than the first magnetization region A1 and the second magnetization region A2 of the first ferromagnetic layer 10. The third magnetization region A3 is, for example, a region sandwiched between the first magnetization region A1 and the second magnetization region A2 in the x direction.

The third magnetized region A3 is a region where the magnetization direction changes and the domain wall DW can move. The third magnetized region A3 is called a domain wall movable region. The third magnetized region A3 has a first magnetic domain A31 and a second magnetic domain A32. The first magnetic domain A31 and the second magnetic domain A32 have magnetization orientation directions opposite to each other. The boundary between the first magnetic domain A31 and the second magnetic domain A32 is the domain wall DW. The magnetization M _A31 of the first magnetic domain A31 is oriented in the same direction as the magnetization M _A1 of the first magnetized region A1, for example. The magnetization M _A32 of the second magnetic domain A32 is oriented in the same direction as the magnetization M _A2 of the adjacent second magnetized region A2, for example. In principle, the domain wall DW moves within the third magnetized region A3 and does not invade the first magnetized region A1 and the second magnetized region A2.

When the volume ratio between the first magnetic domain A31 and the second magnetic domain A32 in the third magnetized region A3 changes, the domain wall DW moves. The domain wall DW moves by applying a write current in the x direction of the third magnetized region A3. For example, when a write current (e.g., a current pulse) in the +x direction is applied to the third magnetized region A3, electrons flow in the -x direction opposite to the current, and the domain wall DW moves in the -x direction. When a current flows from the first magnetic domain A31 to the second magnetic domain A32, the electrons spin-polarized in the second magnetic domain A32 reverse the magnetization M _A31 of the first magnetic domain A31. When the magnetization M _A31 of the first magnetic domain A31 is reversed, the domain wall DW moves in the -x direction.

The first ferromagnetic layer 10 is composed of a magnetic material. The first ferromagnetic layer 10 may be a ferromagnetic material, a ferrimagnetic material, or a combination of these with an antiferromagnetic material whose magnetic state can be changed by a current. The first ferromagnetic layer 10 preferably contains at least one element selected from the group consisting of Co, Ni, Fe, Pt, Pd, Gd, Tb, Mn, Ge, and Ga.

Examples of materials used for the first ferromagnetic layer 10 include a laminated film of Co and Ni, a laminated film of Co and Pt, a laminated film of Co and Pd, a laminated film of Co _x Fe _1-x B (0≦x≦1) and a material similar to the non-magnetic layer 20 described later, MnGa-based materials, GdCo-based materials, and TbCo-based materials. Ferrimagnetic materials such as MnGa-based materials, GdCo-based materials, and TbCo-based materials have small saturation magnetization, and the threshold current required to move the domain wall DW is small. In addition, the laminated film of Co and Ni, the laminated film of Co and Pt, and the laminated film of Co and Pd have large coercive force, and the moving speed of the domain wall DW is slow. Examples of antiferromagnetic materials include Mn ₃ X (X is Sn, Ge, Ga, Pt, Ir, etc.), CuMnAs, and Mn ₂ Au. The first ferromagnetic layer 10 may be made of the same material as the second ferromagnetic layer 30 described later. A laminate of two or more types of films or materials may also be used.

The nonmagnetic layer 20 is sandwiched between the first ferromagnetic layer 10 and the second ferromagnetic layer 30. The nonmagnetic layer 20 inhibits magnetic coupling between the first ferromagnetic layer 10 and the second ferromagnetic layer 30. The nonmagnetic layer 20 is stacked on one side of the second ferromagnetic layer 30.

The nonmagnetic layer 20 is made of, for example, a nonmagnetic insulator, semiconductor, or metal. The nonmagnetic layer 20 is preferably, for example, a nonmagnetic insulator. The nonmagnetic insulator is, for example, Al ₂ O ₃ , SiO ₂ , MgO, MgAl ₂ O ₄ , and materials in which a part of Al, Si, and Mg is replaced with Zn, Be, Ga, Ti, or the like. These materials have a large band gap and excellent insulating properties. The nonmagnetic insulator is, for example, an oxide containing Mg or Al. When the nonmagnetic layer 20 is made of a nonmagnetic insulator, the nonmagnetic layer 20 is a tunnel barrier layer. The nonmagnetic metal is, for example, Cu, Au, Ag, or the like. The nonmagnetic semiconductor is, for example, Si, Ge, CuInSe ₂ , CuGaSe ₂ , Cu(In,Ga)Se ₂ , or the like.

The thickness of the nonmagnetic layer 20 is, for example, 20 Å or more, and may be 25 Å or more.

The second ferromagnetic layer 30, together with the first ferromagnetic layer 10, sandwiches the nonmagnetic layer 20. The second ferromagnetic layer 30 is positioned so that at least a portion of it overlaps with the third magnetization region A3 in the z direction. The second ferromagnetic layer 30 is, for example, closer to the substrate Sub than the first ferromagnetic layer 10.

The magnetization _M30 of the second ferromagnetic layer 30 is more difficult to reverse than the magnetization of the third magnetization region A3 of the first ferromagnetic layer 10. The magnetization _M30 of the second ferromagnetic layer 30 is fixed and does not change direction when an external force strong enough to reverse the magnetization of the third magnetization region A3 is applied. The second ferromagnetic layer 30 may also be called a fixed layer or a reference layer.

The second ferromagnetic layer 30 includes a ferromagnetic material. The second ferromagnetic layer 30 includes, for example, a material that is easy to obtain a coherent tunnel effect between the first ferromagnetic layer 10 and the second ferromagnetic layer 30. The second ferromagnetic layer 30 includes, for example, a metal selected from the group consisting of Cr, Mn, Co, Fe, and Ni, an alloy containing one or more of these metals, an alloy containing these metals and at least one of the elements B, C, and N, etc. The second ferromagnetic layer 30 is, for example, Co-Fe, Co-Fe-B, or Ni-Fe. Also, a laminated film of Co and Ni, a laminated film of Co and Pt, or a laminated film of Co and Pd may be used as part of the second ferromagnetic layer 30.

The second ferromagnetic layer 30 may be, for example, a Heusler alloy. The Heusler alloy is a half metal and has a high spin polarization. The Heusler alloy is an intermetallic compound having a chemical composition of XYZ or X ₂ 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 type of X of the Mn, V, Cr, or Ti group, and Z is a typical element of groups III to V. Examples of Heusler alloys include Co ₂ FeSi, Co ₂ FeGe, Co ₂ FeGa, Co ₂ MnSi, Co ₂ Mn _1-a Fe _a Al _b Si _1-b , and Co ₂ FeGe _1-c Ga _c .

The second ferromagnetic layer 30 may have multiple layers and may be a synthetic antiferromagnetic structure (SAF structure). The synthetic antiferromagnetic structure is made up of two magnetic layers sandwiching a nonmagnetic spacer layer. The magnetic layers include, for example, a ferromagnetic material, and may include an antiferromagnetic material such as IrMn or PtMn. The spacer layer includes, for example, at least one selected from the group consisting of Ru, Ir, and Rh.

Each of the second ferromagnetic layer 30 and the non-magnetic layer 20 is, for example, longer in the x direction than the third magnetization region A3. The portion where the second ferromagnetic layer 30 and the third magnetization region A3 face each other with the non-magnetic layer 20 in between is responsible for the resistance change of the domain wall motion element 100. If the length in the x direction of the second ferromagnetic layer 30 and the non-magnetic layer 20 is longer than the length in the x direction of the third region, it becomes easier to divide the resistance change width of the domain wall motion element 100 into multiple values.

The second ferromagnetic layer 30 is, for example, longer than the first ferromagnetic layer 10 in the x direction. When the second ferromagnetic layer 30 overlaps the entire first ferromagnetic layer 10 as viewed in the z direction, the heat dissipation of the first ferromagnetic layer 10 is improved. As a result, the stability of the magnetization of the first magnetization region A1 and the magnetization of the second magnetization region A2 is increased, and the reliability of the data of the domain wall motion element 100 is improved.

The first magnetization fixed layer 40 is connected to the first ferromagnetic layer 10. The first magnetization fixed layer 40 is an example of a first magnetization fixed portion. The first magnetization fixed layer 40 is connected to the first magnetization region A1 of the first ferromagnetic layer 10. The magnetization _M40 of the first magnetization fixed layer 40 fixes the magnetization of the first magnetization region A1. The first magnetization fixed layer 40 is a write electrode used when applying a write current to the domain wall motion element 100. The write current flows between the first magnetization fixed layer 40 and the second magnetization fixed layer 50.

The first magnetization pinned layer 40 is, for example, a ferromagnetic material. The first magnetization pinned layer 40 can be made of, for example, the same material as the first ferromagnetic layer 10 or the second ferromagnetic layer 30.

The first magnetization pinned layer 40 may have multiple layers and may be a synthetic antiferromagnetic structure (SAF structure). The synthetic antiferromagnetic structure is made up of two magnetic layers sandwiching a nonmagnetic spacer layer. The magnetic layers include, for example, a ferromagnetic material, and may include an antiferromagnetic material such as IrMn or PtMn. The spacer layer includes, for example, at least one selected from the group consisting of Ru, Ir, and Rh.

Furthermore, the first magnetization pinned layer 40 is not limited to a ferromagnetic material. If the first magnetization pinned layer 40 is not a ferromagnetic material, the current density of the current flowing through the first ferromagnetic layer 10 changes suddenly in the region overlapping with the first magnetization pinned layer 40, thereby restricting the movement of the domain wall DW and pinning the magnetization of the first magnetization region A1.

The second magnetization fixed layer 50 is connected to the first ferromagnetic layer 10 at a position spaced apart from the first magnetization fixed layer 40 in the x-direction. The second magnetization fixed layer 50 is an example of a second magnetization fixed section. The second magnetization fixed layer 50 is connected to the second magnetization region A2 of the first ferromagnetic layer 10. The magnetization _M50 of the second magnetization fixed layer 50 fixes the magnetization of the second magnetization region A2. The second magnetization fixed layer 50 is a common electrode used when applying a write current to the domain wall motion element 100 and when applying a read current to the domain wall motion element 100.

The second magnetization pinned layer 50 may be made of the same material as the first magnetization pinned layer 40. The second magnetization pinned layer 50 may be a synthetic antiferromagnetic structure (SAF structure).

The film thickness of the second magnetization pinned layer 50 may be different from that of the first magnetization pinned layer 40, for example. The film thickness of the second magnetization pinned layer 50 is, for example, thinner than that of the first magnetization pinned layer 40. If the film thickness of the second magnetization pinned layer 50 and the film thickness of the first magnetization pinned layer 40 are different, a difference in the coercive force between the second magnetization pinned layer 50 and the first magnetization pinned layer 40 is likely to occur. If there is a difference in the coercive force between the second magnetization pinned layer 50 and the first magnetization pinned layer 40, it becomes easier to set the orientation direction of the magnetization _M50 of the second magnetization pinned layer 50 and the orientation direction of the magnetization _M40 of the first magnetization pinned layer 40 to different directions at the time of manufacture.

The first wiring W1 is connected to the first magnetization fixed layer 40. The second wiring W2 is connected to the second magnetization fixed layer 50. The third wiring W3 is connected to the second ferromagnetic layer 30. Each of the first wiring W1, the second wiring W2, and the third wiring W3 includes a material having electrical conductivity. Each of the first wiring W1, the second wiring W2, and the third wiring W3 may be a via wiring extending in the z direction.

When viewed from the z direction, the insulating layer 60 is sandwiched in the x direction between the first magnetization fixed layer 40 and the second magnetization fixed layer 50. The insulating layer 60 is a part of the insulating layer 90. The main elements constituting the insulating layer 60 are, 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 ), etc.

The insulating layer 60 includes a first region 61. The first region 61 is formed by adding a metal or metal nitride different from the main element constituting the insulating layer 60 to the material constituting the insulating layer 60.

For example, if the insulating layer 60 is a silicon compound, the metal or metal nitride different from the main element constituting the insulating layer 60 is a metal or metal nitride other than Si. For example, if the insulating layer 60 is aluminum oxide, the metal or metal nitride different from the main element constituting the insulating layer 60 is a metal or metal nitride other than Al. For example, if the insulating layer 60 is zirconium oxide, the metal or metal nitride different from the main element constituting the insulating layer 60 is a metal or metal nitride other than Zr.

The first region 61 has better heat dissipation properties than the insulating layer 60 because a metal or metal nitride is added to it. Even though the first region 61 contains a metal or metal nitride, it is still an insulator overall.

The metal or metal nitride contained in the first region 61 is, for example, any one selected from the group consisting of Ti, Ta, Ru, Ni, Cr, Fe, TiN, and TaN. The first region 61 may contain two or more types of metals or metal nitrides. If the first region 61 contains two or more types of metals or metal nitrides, the diffusion of these metals or metal nitrides can be suppressed.

The concentration of the metal or metal nitride in the first region 61 is, for example, 0.1 atm% or more. The concentration of the metal or metal nitride in the first region 61 is, for example, 5 atm% or less.

The concentration of the metal or metal nitride in the first region 61 may be lower, for example, in the z direction, closer to the first ferromagnetic layer 10. By increasing the insulation on the side closer to the first ferromagnetic layer 10, insulation failure of the domain wall motion element 100 can be more effectively prevented. In addition, by increasing the concentration of the metal or metal nitride at a position away from the first ferromagnetic layer 10, heat can be dissipated to a position away from the first ferromagnetic layer 10.

FIG. 6 is a plan view of the first region 61 of the domain wall motion element 100 according to the first embodiment. When viewed from the z direction, the first region 61 extends in the xy plane between the first magnetization fixed layer 40 or the first wiring W1 and the second magnetization fixed layer 50 or the second wiring W2.

The first region 61 is connected to, for example, the second wiring W2. The first region 61 may also be connected to the first wiring W1. Most of the heat generated in the domain wall motion element 100 is dissipated via the first wiring W1, the second wiring W2, and the third wiring W3, so the first region 61 being in contact with these wirings increases the efficiency of dissipating heat from the domain wall motion element 100.

The first region 61 includes, for example, a second region 62 and a third region 63. The second region 62 is a region that includes the above-mentioned metal or metal nitride. The third region 63 is a region that does not include the above-mentioned metal or metal nitride. The third region 63 has the same structure as the insulating layer 60. The second region 62 and the third region 63 are insulators.

The second region 62 may be discontinuous in the x direction. That is, the third region 63 is present between the second regions 62 in the x direction. By having the second region 62 containing a metal or metal nitride be discontinuous in the x direction, it is possible to suppress a decrease in the breakdown voltage between the first wiring W1 and the second wiring W2.

The second region 62 may be continuous in the y direction. By having the second region 62 continuous in the y direction, heat can be dissipated in the y direction.

The domain wall motion element 100 may have layers other than those described above. For example, a magnetic layer may be provided on the surface of the second ferromagnetic layer 30 opposite the nonmagnetic layer 20, via a spacer layer. The second ferromagnetic layer 30, the spacer layer, and the magnetic layer form a synthetic antiferromagnetic structure (SAF structure). Also, a base layer may be provided on the surface of the magnetic layer opposite the spacer layer.

The magnetization direction of each layer of the domain wall motion element 100 can be confirmed, for example, by measuring the magnetization curve. The magnetization curve can be measured, for example, using MOKE (Magneto Optical Kerr Effect). Measurement using MOKE is a measurement method in which linearly polarized light is incident on the object being measured, and the magneto-optical effect (magnetic Kerr effect) is used to cause the polarization direction to rotate, etc.

The domain wall motion element 100 is formed by a process of stacking each layer and a process of processing a part of each layer into a predetermined shape. The layers can be stacked using sputtering, chemical vapor deposition (CVD), electron beam evaporation (EB evaporation), atomic laser deposition, etc. The layers can be processed using photolithography and etching (e.g., Ar etching), etc.

The first region 61 can be created by filling the gap between the first magnetization pinned layer 40 and the second magnetization pinned layer 50 with an insulating layer 60, and then adding a metal or metal nitride. For example, the metal or metal nitride may be ion-implanted into the insulating layer 60. Alternatively, for example, a layer of metal or metal nitride may be formed on the insulating layer 60, and these elements may be diffused into the insulating layer 60 by annealing. In this case, the metal or metal nitride layer is removed after annealing.

Next, the operation of writing a signal to the magnetic array MA and the operation of reading a signal from the magnetic array MA will be explained.

First, the operation of writing a signal to the magnetic array MA will be described. The write operation is performed, for example, by a processor executing an operation program stored in the control unit 6.

First, the pulse application device 3 selects the domain wall motion element 100 to which a pulse is to be applied in accordance with the operating program. When the magnetic array MA is used as a magnetic memory, the domain wall motion element 100 to which a pulse is applied is an element that stores data. When the magnetic array MA is used as a neural network, the domain wall motion element 100 to which a pulse is applied is an element that changes the weight in response to learning.

The control unit 6 controls which of the multiple domain wall motion elements 100 to apply a pulse to. The control unit 6 turns ON the first switching element SW1 and second switching element SW2 connected to the domain wall motion element 100 to which the pulse is applied, and turns OFF the third switching element SW3. The control unit 6 also turns OFF at least one of the first switching element SW1 and second switching element SW2 connected to the domain wall motion element 100 to which the pulse is not applied.

Then, the pulse application device 3 outputs a write pulse to the domain wall motion element 100 according to the operating program. The write pulse is applied between the first magnetization fixed layer 40 and the second magnetization fixed layer 50 along the first ferromagnetic layer 10 of the domain wall motion element 100. The write pulse may be a square wave, a spike wave, or a wave of another waveform. By changing the number of write pulses, the magnitude, etc., the position of the domain wall DW changes, and a signal is written to a specific domain wall motion element 100.

Next, the operation of reading signals from the magnetic array MA will be described. The reading operation is performed, for example, by the processor executing an operation program stored in the control unit 6.

First, the pulse application device 3 selects the domain wall motion element 100 to which the read pulse is to be applied in accordance with the operating program. When the magnetic array MA is used as a magnetic memory, the domain wall motion element 100 to which the read pulse is applied is an element that reads out data. When the magnetic array MA is used as a neural network, the application of a read pulse to a specific domain wall motion element 100 corresponds to a multiplication operation of the input and the weight. In other words, when the magnetic array MA is used as a neural network, the read operation is an identification operation of the neural network.

The control unit 6 controls which of the multiple domain wall motion elements 100 to apply a pulse to. The control unit 6 turns ON the third switching element SW3 and second switching element SW2 connected to the domain wall motion element 100 to which the pulse is applied, and turns OFF the first switching element SW1. The control unit 6 also turns OFF at least one of the third switching element SW3 and second switching element SW2 connected to the domain wall motion element 100 to which the pulse is not applied.

Then, the pulse application device 3 applies a read pulse to a specific domain wall motion element 100 according to the operation program. The read pulse is applied, for example, between the third wiring W3 and the second magnetization fixed layer 50. The voltage of the read pulse is a voltage that obtains a current density less than the critical current density required to move the domain wall DW of the first ferromagnetic layer 10. In other words, the read pulse does not move the domain wall DW.

The resistance detection device 4 detects the resistance value of the domain wall motion element 100 to which the read pulse has been applied. The output unit 5, for example, outputs the calculation result to the outside. In this manner, a signal can be read out from a specific domain wall motion element 100.

In the domain wall motion element 100 according to this embodiment, a metal or metal nitride is added to a portion of the insulating layer 60. The metal or metal nitride has a higher thermal conductivity than the main element that constitutes the insulating layer 60. Therefore, the heat generated in the domain wall motion element 100 can be efficiently dissipated to the first wiring W1 and the second wiring W2 via the first region 61 of the insulating layer 60.

The above describes in detail a preferred embodiment of the present invention, but the present invention is not limited to this embodiment. For example, characteristic configurations of the embodiments may be combined, and parts may be modified without changing the gist of the invention.

FIG. 7 is a plan view of a domain wall motion element according to a first modified example. FIG. 5 shows an example in which the first magnetization fixed layer 40 and the second magnetization fixed layer 50 have a rectangular shape in plan view, but the shape of the first magnetization fixed layer 40 and the second magnetization fixed layer 50 is not particularly important. For example, as shown in FIG. 7, the first magnetization fixed layer 40 and the second magnetization fixed layer 50 may have a circular shape in plan view. The first magnetization fixed layer 40 and the second magnetization fixed layer 50 may have a rectangular, circular, elliptical, or other shape in plan view.

FIG. 8 is a plan view of a first region 61 of a domain wall motion element according to a second modified example. The first region 61 shown in FIG. 8 is made of a second region 62 containing the above-mentioned metal or metal nitride. Although the second region 62 contains a metal or metal nitride, it is an insulator overall, so that even with this configuration, short circuits do not fundamentally occur.

FIG. 9 is a cross-sectional view of a domain wall motion element according to a third modified example. The domain wall motion element 101 shown in FIG. 9 differs from the domain wall motion element 100 in that the first magnetization fixed portion is made up of a first magnetization fixed layer 40 and an intermediate layer 41, and the second magnetization fixed portion is made up of a second magnetization fixed layer 50 and an intermediate layer 51.

The intermediate layer 41 and the intermediate layer 51 are, for example, Ru, Ir, or Rh. The first magnetization fixed layer 40 and the first magnetization region A1 are magnetically coupled via the intermediate layer 41. The second magnetization fixed layer 50 and the second magnetization region A2 are magnetically coupled via the intermediate layer 51. As shown in FIG. 9, the first magnetization fixed portion and the second magnetization fixed portion may be made of multiple layers. Also, the first magnetization fixed layer 40 and the second magnetization fixed layer 50 may each be made of multiple layers.

FIG. 10 is a cross-sectional view of a domain wall motion element according to a fourth modified example. The domain wall motion element 102 shown in FIG. 10 differs from the domain wall motion element 100 in that the second ferromagnetic layer 30 is located farther from the substrate Sub than the first ferromagnetic layer 10. The domain wall motion element 102 is said to have a top pin structure. The domain wall motion element 100 is said to have a bottom pin structure, in that the second ferromagnetic layer 30 is closer to the substrate Sub than the first ferromagnetic layer 10. The top pin structure shown in the domain wall motion element 102 also provides the same effects as the bottom pin structure.

The above first to fourth modified examples also provide the same effects as the domain wall motion element 100 according to the first embodiment. The characteristic configurations of these modified examples may also be combined.

1...integration region, 2...peripheral region, 3...pulse application device, 4...resistance detection device, 5...output section, 6...control section, 7...power supply, 10...first ferromagnetic layer, 20...non-magnetic layer, 30...second ferromagnetic layer, 40...first magnetization fixed layer, 50...second magnetization fixed layer, 41, 51...intermediate layer, 60...insulating layer, 61...first region, 62...second region, 63...third region, 90...insulating layer, 100, 101, 102, 103...domain wall motion element, A1...first magnetization region, A2...second magnetization region, A3...third magnetization region, WL...write wiring, CL...common wiring, RL...read wiring, DW...domain wall, MA...magnetic array, W1...first wiring, W2...second wiring, W3...third wiring

Claims

a first ferromagnetic layer having a magnetic domain wall therein;
A second ferromagnetic layer;
a nonmagnetic layer sandwiched between the first ferromagnetic layer and the second ferromagnetic layer;
a first magnetization fixed unit connected to the first ferromagnetic layer;
a second magnetization fixed unit connected to the first ferromagnetic layer at a position spaced apart from the first magnetization fixed unit in a first direction;
an insulating layer sandwiched in the first direction between the first magnetization fixed part and the second magnetization fixed part as viewed from a stacking direction,
The insulating layer includes a first region to which a metal or a metal nitride different from a main element constituting the insulating layer is added.
The domain wall motion element according to claim 1, wherein the concentration of the metal or metal nitride in the first region is lower in the stacking direction closer to the first ferromagnetic layer.
the first region has a second region containing the metal or the metal nitride and a third region not containing the metal or the metal nitride,
The domain wall motion element according to claim 1 , wherein the second region is discontinuous in the first direction.
the first region has a second region containing the metal or the metal nitride and a third region not containing the metal or the metal nitride,
The domain wall motion element according to claim 1 , wherein the second region is continuous in a second direction perpendicular to the first direction in a plane substantially parallel to one surface of the substrate.
A first wiring connected to the first magnetization fixed portion;
A second wiring connected to the second magnetization fixed portion,
The domain wall motion element according to claim 1 , wherein the first region is connected to the first wiring or the second wiring.
The domain wall motion element of claim 1, wherein the concentration of the metal or metal nitride in the first region is 0.1 atm % or more.
The domain wall motion element according to claim 1, wherein the metal or metal nitride is selected from the group consisting of Ti, Ta, Ru, Ni, Cr, Fe, TiN, and TaN.
The domain wall motion element according to claim 1, wherein the first region contains two or more types of the metal or metal nitride.
A magnetic array including the domain wall motion element according to claim 1.