Magnetic resistance effect element and method for manufacturing magnetic resistance effect element

Abstract

A magnetic resistance effect element and a manufacturing method of the magnetic resistance effect element are provided. The magnetic resistance effect element includes a first ferromagnetic layer, a second ferromagnetic layer, and a nonmagnetic layer. The nonmagnetic layer is located between the first ferromagnetic layer and the second ferromagnetic layer. The nonmagnetic layer includes a first central region and a first outer peripheral region located outward of the first central region. A maximum thickness of the first outer peripheral region is thicker than an average thickness of the first central region.

Description

Technical Field

[0001] This invention relates to magnetoresistive elements and methods for manufacturing magnetoresistive elements. Background Technology

[0002] A magnetoresistive element is a device whose resistance varies along its stacking direction due to the magnetoresistive effect. A magnetoresistive element consists of two ferromagnetic layers and a non-magnetic layer sandwiched between them. A magnetoresistive element that uses a conductor in the non-magnetic layer is called a giant magnetoresistive (GMR) element, while a magnetoresistive element that uses an insulating layer (tunnel barrier layer, barrier layer) in the non-magnetic layer is called a tunnel magnetoresistive (TMR) element.

[0003] Magnetoresistive elements can be applied to various applications such as magnetic sensors, high-frequency components, magnetic heads, and non-volatile random access memory (MRAM) (e.g., Patent Documents 1 and 2). For example, Patent Document 3 describes a method for controlling the direction of magnetization using spin-transmitted torque (STT) generated by current flowing through the stacking direction of the magnetoresistive elements. This method is called spin-injected magnetization reversal.

[0004] Existing technical documents

[0005] Patent documents

[0006] Patent Document 1: Japanese Patent No. 5586028.

[0007] Patent Document 2: Japanese Patent No. 5988019.

[0008] Patent document 3: Japanese Patent Application Publication No. 2015-156501. Summary of the Invention

[0009] The resistance of a magnetoresistive element varies with the relative angle between the magnetization of the first and second ferromagnetic layers. When the first and second ferromagnetic layers are short-circuited, an unexpected current path is formed, requiring significant energy to reverse the magnetization of the ferromagnetic layers. Furthermore, a short circuit between the first and second ferromagnetic layers reduces the reliability of the magnetoresistive element.

[0010] This disclosure was made in view of the above circumstances, and its purpose is to provide a magnetoresistive element with excellent reliability.

[0011] To address the aforementioned issues, this disclosure provides the following solutions.

[0012] (1) The magnetoresistive element of the first aspect comprises a first ferromagnetic layer, a second ferromagnetic layer, and a non-magnetic layer. The non-magnetic layer is located between the first ferromagnetic layer and the second ferromagnetic layer. The non-magnetic layer comprises a first central region and a first peripheral region located outside the first central region. The maximum thickness of the first peripheral region is greater than the average thickness of the first central region.

[0013] The magnetoresistive element of this invention has excellent reliability. Attached Figure Description

[0014] Figure 1 This is a circuit diagram of the magnetic storage device according to the first embodiment.

[0015] Figure 2 This is a cross-sectional view of a characteristic portion of the magnetic storage device according to the first embodiment.

[0016] Figure 3 This is a cross-sectional view of the magnetoresistive effect element according to the first embodiment.

[0017] Figure 4 This is a top view of the magnetoresistive effect element of the first embodiment.

[0018] Figure 5 This is an enlarged view of the characteristic portion of the magnetoresistive effect element in the first embodiment.

[0019] Figure 6 This is a cross-sectional view of a magnetoresistive element in the second real mode.

[0020] Figure 7 This is an enlarged view of the characteristic part of the magnetoresistive effect element in the second real mode.

[0021] Figure 8 The results of Examples 1-4 and Comparative Example 1 are shown.

[0022] Figure 9 This is an enlarged view of the characteristic part of the magnetoresistive effect element in the first modified example. Detailed Implementation

[0023] Hereinafter, this embodiment will be described in detail with appropriate reference to the accompanying drawings. In the drawings used in the following description, for ease of understanding, some parts of the features are sometimes shown as enlarged for convenience, and the dimensions and proportions of each component may sometimes differ from the actual dimensions. The materials, dimensions, etc., illustrated in the following description are examples, and the present invention is not limited to these; it can be appropriately modified and implemented within the scope of achieving the effects of the present invention.

[0024] First, the orientation is defined. The substrate Sub (refer to...) will be described later. Figure 2Let one direction of one side of the structure be the x-direction, and the direction orthogonal to the x-direction be the y-direction. The z-direction is the direction orthogonal to both the x and y directions. The z-direction is an example of the stacking direction of each layer. Hereinafter, the +z direction may sometimes be represented as "up," and the -z direction must be represented as "down." Up and down are not necessarily consistent with the direction of applied gravity.

[0025] In this specification, "connection" is not limited to physical connections. For example, it is not limited to the case of two layers being physically connected; the case of two layers connected with other layers sandwiched between them is also included in the term "connection." In addition, "connection" in this specification also includes electrical connections.

[0026] [First Implementation Method]

[0027] Figure 1 This is a structural diagram of the magnetic memory 100 according to the first embodiment. The magnetic memory 100 includes a plurality of magnetoresistive elements 10, a plurality of source lines SL, a plurality of bit lines BL, and a plurality of first switching elements Sw1.

[0028] The magnetoresistive elements 10 are arranged in a matrix, for example. Each magnetoresistive element 10 is connected to a source line SL and a bit line BL. The source line SL electrically connects a power supply and one or more magnetoresistive elements 10. The bit line BL electrically connects a reference potential and one or more magnetoresistive elements 10. The reference potential is, for example, grounded. The power supply is connected to the magnetic memory 100 during use.

[0029] The flow of current to the magnetoresistive element 10 is controlled by a first switching element Sw1. For example, when a specific first switching element Sw1 is turned on, data is written to and read from the magnetoresistive element 10 connected to that first switching element Sw1. The magnetoresistive element 10 writes data by using spin-transmitted torque through the current flowing in the stacking direction.

[0030] The first switching element Sw1 is a component that controls the flow of current. The first switching element Sw1 can be, for example, a transistor, an Ovonic Threshold Switch (OTS) that utilizes a phase transition of the crystal layer, a metal-insulator transition (MIT) switch that utilizes a change in the band structure, a Zener diode or an avalanche diode that utilizes a breakdown voltage, or a component whose conductivity changes with the position of atoms.

[0031] Figure 2 This is a cross-sectional view of a characteristic portion of the magnetic storage 100 according to the first embodiment. Figure 2The first switching element Sw1 shown is a transistor Tr. Transistor Tr is, for example, a field-effect transistor, having a gate electrode G, a gate insulating film GI, a source electrode S, and a drain electrode D formed on a substrate Sub. The source electrode S and the drain electrode D are defined according to the direction of current flow, and they are the same region. The positional relationship between the source electrode S and the drain electrode D can also be reversed. The substrate Sub is, for example, a semiconductor substrate.

[0032] Transistor Tr and magnetoresistive element 10 are electrically connected via via wiring V and electrode E1. Additionally, transistor Tr and bit line BL are connected via via wiring V. Via wiring V extends, for example, along the z-direction. Source line SL is connected to magnetoresistive element 10 via electrode E2. Via wiring V, electrode E1, and electrode E2 contain conductive material. Via wiring V and electrode E1 can also be integrated. Furthermore, source line SL and electrode E2 can also be integrated. That is, electrode E1 can be part of via wiring V, and electrode E2 can be part of source line SL.

[0033] The magnetoresistive element 10 is surrounded by an insulating layer 90. The insulating layer 90 is used to insulate between wirings and components in multilayer wiring. The insulating layer 90 is, for example, silicon oxide (SiO2). x Silicon nitride (SiN) x Silicon carbide (SiC), chromium nitride, silicon carbonitride (SiCN), silicon oxynitride (SiON), aluminum oxide (Al2O3), zirconium oxide (ZrO2) x Magnesium oxide (MgO), aluminum nitride (AlN), etc.

[0034] Figure 3 This is a cross-sectional view of the magnetoresistive element 10. Figure 3 The cross section is obtained by cutting the magnetoresistive element 10 with the xz plane passing through the center of the magnetoresistive element 10. Figure 4 This is a top view of the magnetoresistive element 10 viewed from the z-axis. Figure 3 and Figure 4 The diagram also shows an insulating layer 90 covering the magnetoresistive effect element 10.

[0035] The magnetoresistive element 10 is a data recording and storage element. The magnetoresistive element 10 records data with its resistance value in the z-direction. The resistance value of the magnetoresistive element 10 in the z-direction changes when a write current is applied in the z-direction. The resistance value of the magnetoresistive element 10 in the z-direction can be read out by applying a read current in the z-direction of the magnetoresistive element 10.

[0036] The magnetoresistive element 10 comprises a first ferromagnetic layer 1, a second ferromagnetic layer 2, and a non-magnetic layer 3. The non-magnetic layer 3 is located between the first ferromagnetic layer 1 and the second ferromagnetic layer 2. In addition, the magnetoresistive element 10 may also include a buffer layer 4, a seed layer 5, a ferromagnetic layer 6, a spacer layer 7, and a magnetic induction layer 8. The buffer layer 4, seed layer 5, ferromagnetic layer 6, and spacer layer 7 are located between the first ferromagnetic layer 1 and electrode E1, and the magnetic induction layer 8 is located between the second ferromagnetic layer 2 and electrode E2.

[0037] The magnetoresistive element 10 is a columnar stack. The top-view shape of the magnetoresistive element 10 viewed from the z-direction is not particularly limited. For example, it could be... Figure 2 The circle shown can also be elliptical, oblong, or rectangular. The width of the magnetoresistive element 10 is, for example, 10 nm to 2000 nm, preferably 30 nm to 500 nm.

[0038] The first ferromagnetic layer 1 and the second ferromagnetic layer 2 are, for example, vertically magnetized films having an easy magnetization axis in the z-direction. The first ferromagnetic layer 1 and the second ferromagnetic layer 2 can also be in-plane magnetized films having an easy magnetization axis in any direction within the xy-plane.

[0039] The first ferromagnetic layer 1 and the second ferromagnetic layer 2 each contain a ferromagnetic material. The magnetization of the first ferromagnetic layer 1 is, for example, more difficult to move than the magnetization of the second ferromagnetic layer 2. Under a given external force, the magnetization direction of the first ferromagnetic layer 1 remains unchanged (fixed), while the magnetization direction of the second ferromagnetic layer 2 changes. The first ferromagnetic layer 1 is referred to as the magnetization-fixed layer. The second ferromagnetic layer 2 is referred to as the magnetization-free layer. Figure 3 The magnetization fixed layer of the magnetoresistive element 10 shown is located closer to the substrate Sub than the magnetization free layer, and is referred to as a bottom pin structure. The positional relationship between the first ferromagnetic layer 1 and the second ferromagnetic layer 2 can also be reversed. The resistance value of the magnetoresistive element 10 varies according to the relative angle between the magnetization of the first ferromagnetic layer 1 and the magnetization of the second ferromagnetic layer 2.

[0040] The first ferromagnetic layer 1 and the second ferromagnetic layer 2 are, for example, metals selected from Cr, Mn, Co, Fe, and Ni, alloys containing one or more of these metals, or alloys containing these metals and at least one of the elements B, C, and N. The first ferromagnetic layer 1 and the second ferromagnetic layer 2 are, for example, Co-Fe, Co-Fe-B, Ni-Fe, Co-Ho alloys, Sm-Fe alloys, Fe-Pt alloys, Co-Pt alloys, and CoCrPt alloys.

[0041] The first ferromagnetic layer 1 and the second ferromagnetic layer 2 may also contain Whistler alloys. Whistler alloys contain intermetallic compounds with a chemical composition of XYZ or X2YZ. X is a transition metal or noble metal element from the Co, Fe, Ni, or Cu group in the periodic table; Y is a transition metal from the Mn, V, Cr, or Ti group, or an element of X; and Z is a typical element from Groups III to V. Examples of Whistler alloys include Co2FeSi, Co2FeGe, Co2FeGa, Co2MnSi, and Co2Mn. 1－a Fe a Al b Si 1－b Co2FeGe 1一c Ga c Etc. Whistler alloys have high spin polarization.

[0042] Figure 5 This is an enlarged view of the characteristic portion of the magnetoresistive effect element 10 in the first embodiment.

[0043] The first ferromagnetic layer 1 includes a central region 11 and an outer peripheral region 12. The outer peripheral region 12 is located outside the central region 11. The outer peripheral region 12 is, for example, a region within 10% of the width of the first ferromagnetic layer 1 in the xy direction.

[0044] The average thickness of the central region 11 is greater than the average thickness of the outer peripheral region 12. The average thickness is the average of the thicknesses measured at five different points in the xy plane. The thickness can be measured using scanning electron microscopy (SEM) or transmission electron microscopy (TEM).

[0045] The thickness of the central region 11 is approximately constant in the xy plane. The outer peripheral region 12 narrows outward from the interface between the central region 11 and the outer peripheral region 12. That is, the outer peripheral region 12 becomes thinner towards the insulating layer 90 from the interface between the central region 11 and the outer peripheral region 12.

[0046] The central region 11 is, for example, made of the material constituting the first ferromagnetic layer 1. The outer peripheral region 12, for example, contains nitrogen in addition to the material constituting the first ferromagnetic layer 1. The nitrogen concentration in the outer peripheral region 12 is, for example, lower as it approaches the central region 11.

[0047] Similarly, the second ferromagnetic layer 2 includes a central region 21 and an outer peripheral region 22. The central region 21 is an example of a third central region. The outer peripheral region 22 is an example of a third outer peripheral region. The outer peripheral region 22 is located outside the central region 21. The outer peripheral region 22 is, for example, a region within 10% of the width of the second ferromagnetic layer 2 in the xy direction.

[0048] The average thickness of the central region 21 is greater than the average thickness of the outer peripheral region 22. The thickness of the central region 21 is approximately constant in the xy plane. The outer peripheral region 22 narrows outward from the interface between the central region 21 and the outer peripheral region 22. That is, the outer peripheral region 22 becomes thinner towards the insulating layer 90 from the interface between the central region 21 and the outer peripheral region 22.

[0049] The central region 21 is, for example, made of the material constituting the second ferromagnetic layer 2. The outer peripheral region 22, for example, contains nitrogen in addition to the material constituting the second ferromagnetic layer 2. The nitrogen concentration in the outer peripheral region 22 is, for example, lower as it approaches the central region 21.

[0050] The non-magnetic layer 3 comprises a non-magnetic material. When the non-magnetic layer 3 is an insulator (as a tunneling barrier layer), materials such as Al₂O₃, SiO₂, MgO, and MgAl₂O₄ can be used. Alternatively, materials in which some of the Al, Si, and Mg are replaced by Zn, Be, etc., can also be used. Among these, MgO and MgAl₂O₄ are materials capable of coherent tunneling, thus enabling efficient spin injection. When the non-magnetic layer 3 is a metal, materials such as Cu, Au, and Ag can be used. Furthermore, when the non-magnetic layer 3 is a semiconductor, materials such as Si, Ge, CuInSe₂, CuGaSe₂, and Cu(In,Ga)Se₂ can be used.

[0051] The non-magnetic layer 3 may contain MgO or Mg-Al-O as the main component. The main component refers to the component that constitutes the largest proportion of the molecules in the non-magnetic layer 3, for example, accounting for more than 80% of the non-magnetic layer 3. Mg-Al-O is an oxide of magnesium and aluminum, and the ratio of Mg to Al can be freely designed.

[0052] The non-magnetic layer 3 may contain, for example, one or more elements selected from Ti, Si, Ga, In, Fe, Co, N, and Ta. These elements may be included as elements other than the aforementioned main components. These elements alter the lattice constant of the non-magnetic layer 3, improving the lattice matching between the first ferromagnetic layer 1 and the non-magnetic layer 3, or between the second ferromagnetic layer 2 and the non-magnetic layer 3. If the lattice matching of these interfaces is high, electron scattering at the interfaces can be suppressed, and the MR ratio of the magnetoresistive effect element 10 is improved.

[0053] The non-magnetic layer 3 includes a central region 31 and an outer peripheral region 32. The central region 31 is an example of a first central region. The outer peripheral region 32 is an example of a first outer peripheral region. The outer peripheral region 32 is located outside the central region 31. The outer peripheral region 32 is, for example, a region within 10% of the width of the non-magnetic layer 3 in the xy direction.

[0054] The average thickness t of the central region 31 31The maximum thickness t of the outer perimeter region is 32. 32 Thin. Maximum thickness t 32 For example, it is the maximum thickness in the z-direction of the xz section. The thickness of the central region 31 is approximately constant in the xy plane.

[0055] The outer peripheral region 32 extends outward from the interface between the central region 31 and the outer peripheral region 32. That is, the outer peripheral region 32 becomes thicker towards the insulating layer 90 from the interface between the central region 31 and the outer peripheral region 32. The first surface 3A and the second surface 3B of the non-magnetic layer 3 are further outward from the outer peripheral region 32.

[0056] The central region 31 is, for example, made of the material constituting the non-magnetic layer 3. The outer peripheral region 32, for example, contains nitrogen in addition to the material constituting the non-magnetic layer 3. The nitrogen concentration in the outer peripheral region 32 is, for example, lower as it approaches the central region 31.

[0057] The magnetic induction layer 8 enhances the magnetic anisotropy of the second ferromagnetic layer 2. For example, the magnetic induction layer 8 enhances the perpendicular magnetic anisotropy of the second ferromagnetic layer 2. The magnetic induction layer 8 is, for example, magnesium oxide, W, Ta, Mo, etc. When the magnetic induction layer 8 is magnesium oxide, it is preferable to have magnesium oxide that is oxygen-deficient in order to improve conductivity. The average film thickness of the magnetic induction layer 8 is, for example, 0.5 nm or more and 5.0 nm or less.

[0058] The magnetic induction layer 8 includes a central region 81 and an outer peripheral region 82. The central region 81 is an example of a second central region. The outer peripheral region 82 is an example of a second outer peripheral region. The outer peripheral region 82 is located outside the central region 81. The outer peripheral region 82 is, for example, a region within 10% of the outer edge of the width of the magnetic induction layer 8 in the xy direction.

[0059] The average thickness t of the central region 81 81 The maximum thickness t of the outer perimeter region is 82. 82 Thin. The thickness of the central region 81 is approximately constant in the xy plane. The outer peripheral region 82 extends outward from the interface between the central region 81 and the outer peripheral region 82. That is, the outer peripheral region 82 becomes thicker towards the insulating layer 90 from the interface between the central region 81 and the outer peripheral region 82. The first surface 8A and the second surface 8B of the magnetic induction layer are further outward from the outer peripheral region 82.

[0060] The central region 81 is, for example, made of the material constituting the magnetic induction layer 8. The outer peripheral region 82, for example, contains nitrogen in addition to the material constituting the magnetic induction layer 8. The nitrogen concentration in the outer peripheral region 82 is, for example, lower as it approaches the central region 81.

[0061] The outer peripheral region 32 of the non-magnetic layer 3 and the outer peripheral region 82 of the magnetic induction layer 8, for example, cover the side surface of the second ferromagnetic layer 2. The second ferromagnetic layer 2 may also be a structure that is not directly in contact with the insulating layer 90. In this case, there is an outer peripheral region 32 of the non-magnetic layer 3 or an outer peripheral region 82 of the magnetic induction layer 8 between the insulating layer 90 and the second ferromagnetic layer 2.

[0062] Buffer layer 4 and seed layer 5 are referred to as the base layer. Buffer layer 4 is a layer that mitigates lattice mismatch between different crystals. Buffer layer 4 is, for example, a metal containing at least one element selected from Ta, Ti, Zr, and Cr, or a nitride containing at least one element selected from Ta, Ti, Zr, and Cu. More specifically, buffer layer 4 is, for example, Ta (monomer), TaN (tantalum nitride), CuN (copper nitride), TiN (titanium nitride), or NiAl (nickel-aluminum). The film thickness of buffer layer 4 is, for example, 1 nm to 5 nm. Buffer layer 4 is, for example, amorphous. Buffer layer 4 is, for example, located between seed layer 5 and electrode E1, and is in contact with electrode E1. Buffer layer 4 suppresses the influence of the crystal structure of electrode E1 on the crystal structure of the first ferromagnetic layer 1.

[0063] Seed layer 5 enhances the crystallinity of the layers stacked on top of it. Seed layer 5 is, for example, located between buffer layer 4 and ferromagnetic layer 6, and on top of buffer layer 4. In the absence of ferromagnetic layer 6 and spacer layer 7, seed layer 5 is, for example, located between buffer layer 4 and first ferromagnetic layer 1. Seed layer 5 is, for example, a compound with a (001) oriented NaCl structure. Seed layer 5 is, for example, Pt, Ru, Zr, NiCr alloy, or NiFeCr. The film thickness of seed layer 5 is, for example, 1 nm or more and 5 nm or less.

[0064] Ferromagnetic layer 6 is magnetically coupled to, for example, the first ferromagnetic layer 1. This magnetic coupling is, for example, antiferromagnetic coupling, generated through RKKY interactions. The magnetization directions of the first ferromagnetic layer 1 and the ferromagnetic layer 6 are antiparallel. The material constituting the ferromagnetic layer 6 is, for example, the same as that of the first ferromagnetic layer 1. The ferromagnetic layer 6, the spacer layer 7, and the first ferromagnetic layer 1 form a synthetic antiferromagnetic structure (SAF structure). The synthetic antiferromagnetic structure consists of two magnetic layers sandwiching a non-magnetic layer. Through the antiferromagnetic coupling between the first ferromagnetic layer 1 and the ferromagnetic layer 6, the coercivity of the first ferromagnetic layer 1 is increased compared to the case without the ferromagnetic layer 6.

[0065] Spacer layer 7 is located between the first ferromagnetic layer 1 and the ferromagnetic layer 6. Spacer layer 7 is also called magnetic coupling layer. Spacer layer 7 is, for example, Ru, Ir, etc.

[0066] An insulating layer 90 covers the periphery of the magnetoresistive element 10. The insulating layer 90 may have multiple layers starting from one side adjacent to the side of the magnetoresistive element 10. The side of the insulating layer 90 in contact with the laminate may, for example, contain nitrogen. The insulating layer 90 may also have a nitride layer in contact with the side of the magnetoresistive element 10 and an oxide layer sandwiching the nitride layer together with the magnetoresistive element 10. For example, the nitride layer may be silicon nitride, and the oxide layer may be silicon oxide.

[0067] Next, the manufacturing method of the magnetoresistive element 10 will be described. The manufacturing method of the magnetoresistive element 10 includes a lamination process, a processing process, an exposure process, an insulating layer formation process, and an annealing process.

[0068] In the lamination process, the layers that form the magnetoresistive element 10 are stacked. For example, starting from the side closest to the substrate Sub, the buffer layer 4, seed layer 5, ferromagnetic layer 6, spacer layer 7, first ferromagnetic layer 1, nonmagnetic layer 3, second ferromagnetic layer 2, and magnetic induction layer 8 are stacked sequentially. The stacking of each layer can be performed using sputtering, chemical vapor deposition (CVD), electron beam evaporation (EB evaporation), atomic laser deposition, etc.

[0069] In the lamination process, at least a laminated film comprising a first ferromagnetic layer 1, a non-magnetic layer 3, and a second ferromagnetic layer 2 is formed. When the non-magnetic layer 3 and the magnetic induction layer 8 are oxide films, these layers can also be made into an oxygen-deficient state; when the non-magnetic layer 3 and the magnetic induction layer 8 are nitride films, these layers can also be made into a nitrogen-deficient state.

[0070] Next, in the processing steps, the laminated films are processed into a specified shape. The processing of each layer can be performed, for example, using photolithography or etching. Etching can be performed, for example, using an ion beam or argon gas. The laminated films become a columnar stack.

[0071] Next, in the exposure process, the sides of the laminate are exposed to an oxygen or nitrogen atmosphere. The lamination and processing steps are generally carried out in a vacuum; therefore, oxygen or nitrogen is supplied into the furnace. The oxygen or nitrogen adheres to the sides of the laminate.

[0072] Next, in the insulating layer formation process, the sides of the laminate are covered with an insulating layer. The insulating layer can be fabricated by sputtering, chemical vapor deposition (CVD), electron beam evaporation (EB evaporation), atomic laser deposition, etc.

[0073] Next, in the annealing process, the laminate and the insulating layer are annealed. After annealing, oxygen or nitrogen adhering to the non-magnetic layer 3 and the magnetic induction layer 8 is absorbed into the interior of the non-magnetic layer 3 and the magnetic induction layer 8. When oxygen or nitrogen is absorbed into the non-magnetic layer 3 and the magnetic induction layer 8, the lattice constant of the portion with absorbed oxygen or nitrogen increases, and the volume increases. As a result, a shape is formed in which the outer peripheral region expands relative to the central region. If the non-magnetic layer 3 and the magnetic induction layer 8 are in a defective state, oxygen or nitrogen is easily absorbed into the interior.

[0074] In the magnetoresistive element 10 of this embodiment, the non-magnetic layer 3 covers a portion of the side surface of the second ferromagnetic layer 2. Therefore, it is difficult for the first ferromagnetic layer 1 and the second ferromagnetic layer 2 to short-circuit. The first ferromagnetic layer 1 and the second ferromagnetic layer 2 may sometimes short-circuit, for example, due to the re-attachment of a portion of the ferromagnetic layer removed during manufacturing or on the wiring.

[0075] When the first ferromagnetic layer 1 and the second ferromagnetic layer 2 are short-circuited, a current path is formed that does not pass through the non-magnetic layer 3. In this case, data may be accidentally written or the recorded data may be accidentally erased, reducing the reliability of the magnetoresistive element 10. The magnetoresistive element 10 of this embodiment has excellent reliability because the first ferromagnetic layer 1 and the second ferromagnetic layer 2 are difficult to short-circuit.

[0076] Furthermore, in this embodiment, when the magnetoresistive effect element 10 has a magnetic induction layer 8 and the magnetic induction layer 8 and the non-magnetic layer 3 cover the side of the second ferromagnetic layer 2, it is difficult for the first ferromagnetic layer 1 and the second ferromagnetic layer 2 to short-circuit.

[0077] In addition, the magnetoresistive effect element 10 of this embodiment can avoid energy loss due to the current path not passing through the non-magnetic layer 3, and can suppress the reverse current density used to reverse the magnetization of the ferromagnetic layer.

[0078] [Second Implementation Method]

[0079] Figure 6 This is a cross-sectional view of the magnetoresistive effect element 10' according to the second embodiment. Figure 6 It is the cross section obtained by cutting the magnetoresistive element 10 with the xz plane passing through the center of the magnetoresistive element 10'.

[0080] The magnetoresistive element 10' comprises a first ferromagnetic layer 1', a second ferromagnetic layer 2', and a nonmagnetic layer 3'. In addition, the magnetoresistive element 10' may also have a buffer layer 4', a seed layer 5', a ferromagnetic layer 6', a spacer layer 7', and a magnetic induction layer 8'.

[0081] The first ferromagnetic layer 1' corresponds to the first ferromagnetic layer 1 in the first embodiment. The second ferromagnetic layer 2' corresponds to the second ferromagnetic layer 2 in the first embodiment. The non-magnetic layer 3' corresponds to the non-magnetic layer 3 in the first embodiment. The buffer layer 4' corresponds to the buffer layer 4 in the first embodiment. The seed layer 5' corresponds to the seed layer 5 in the first embodiment. The ferromagnetic layer 6' corresponds to the ferromagnetic layer 6 in the first embodiment. The spacer layer 7' corresponds to the spacer layer 7 in the first embodiment. The magnetic induction layer 8' corresponds to the magnetic induction layer 8 in the first embodiment. In the structure of each layer, the structure that is the same as the corresponding layer in the first embodiment is omitted from the description. That is, each of the first ferromagnetic layer 1', the second ferromagnetic layer 2', the non-magnetic layer 3', the buffer layer 4', the seed layer 5', the ferromagnetic layer 6', the spacer layer 7', and the magnetic induction layer 8' can be selected from the structure of the first embodiment.

[0082] Figure 7 This is an enlarged view of a characteristic portion of the magnetoresistive effect element 10' in the second real mode. The non-magnetic layer 3' undulates relative to a reference plane S1. The reference plane S1 is a plane extending in an xy plane orthogonal to the stacking direction, passing through the midpoint between the highest and lowest points in the z-direction of the non-magnetic layer 3'. The undulation relative to the reference plane S1 means that upward and downward convex portions are alternately arranged in one direction relative to the reference plane S1. The upper surface of the non-magnetic layer 3' alternately has upward and downward convex portions, and the lower surface of the non-magnetic layer 3' also alternately has upward and downward convex portions. The non-magnetic layer 3' has a first central region and a first peripheral region located outside the first central region, the maximum thickness of the first peripheral region being thicker than the average thickness of the first central region.

[0083] The non-magnetic layer 3' has, for example, upward and downward convex portions relative to the reference plane S1 arranged periodically in one direction. The period p of the undulations of the non-magnetic layer 3' is preferably 30% or less of the width W1 of the non-magnetic layer 3'. The period p of the undulations of the non-magnetic layer 3' is preferably, for example, 30 nm or less. If this condition is met, the reversal current density required to reverse the magnetization of the second ferromagnetic layer 2' can be reduced.

[0084] The period p can be calculated as the average distance between the vertices of the convex protrusions projecting upward relative to the reference plane S1. The average distance between the vertices of the convex protrusions is calculated by taking the distance between each of the vertices 2T of adjacent convex protrusions and calculating their average. The distance between the vertices 3T of adjacent convex protrusions can be determined, for example, by a scanning electron microscope. The period p can also be calculated as the average distance between the vertices 3B of the convex protrusions projecting downward relative to the reference plane S1.

[0085] The nonmagnetic layer 3' has undulations of at least two periods in any direction within the xy plane. For example, the width W1 of the nonmagnetic layer 3' is preferably at least two periods (2p) of undulations. The width along the major axis of the nonmagnetic layer 3' when viewed from above is preferably at least two periods (2p) of undulations. If this condition is met, the reversal current density required to reverse the magnetization of the second ferromagnetic layer 2' can be particularly reduced.

[0086] The height difference h between the highest and lowest points of the nonmagnetic layer 3' is, for example, less than twice the film thickness t of the nonmagnetic layer 3'. The height difference h is the height of a vertical line extending downwards from the highest point in the z-direction through the lowest point in the z-direction into the xy-plane. The film thickness t of the nonmagnetic layer 3' is the average film thickness measured at 10 different points in the xy-plane. The height difference h between the highest and lowest points of the nonmagnetic layer 3' and the film thickness t of the nonmagnetic layer 3' can be measured using a scanning electron microscope. The film thickness t of the nonmagnetic layer 3' is, for example, between 0.5 nm and 10.0 nm, and between 1.0 nm and 5.0 nm.

[0087] If the height of the undulation of the non-magnetic layer 3' is within the above range, then the degree of tilt of the magnetization M2 of the second ferromagnetic layer 2' relative to the z direction is within the specified range. If the tilt of the magnetization M2 of the second ferromagnetic layer 2' is within the specified range, then the decrease in the MR ratio of the magnetoresistive element 10' can be suppressed.

[0088] In the magnetoresistive element 10', each layer other than the non-magnetic layer 3' can also undulate relative to the surface parallel to the reference plane S1 in the same way as the non-magnetic layer 3'.

[0089] For example, the first ferromagnetic layer 1' and the second ferromagnetic layer 2' can be undulated relative to a surface parallel to the reference plane S1. The period of the undulation of the first ferromagnetic layer 1' and the second ferromagnetic layer 2' is approximately the same as the period of the undulation of the non-magnetic layer 3'. The height of the undulation of the first ferromagnetic layer 1' and the second ferromagnetic layer 2' is approximately the same as the height of the undulation of the non-magnetic layer 3'. The first ferromagnetic layer 1' and the second ferromagnetic layer 2', for example, reflect the shape of the non-magnetic layer 3'.

[0090] Additionally, for example, layers located between the base layer (buffer layer 4' and seed layer 5') and the first ferromagnetic layer 1' (e.g., ferromagnetic layer 6' and spacer layer 7') may also undulate relative to a surface parallel to the reference plane S1. The period of these undulations is approximately the same as the period of the undulations of the nonmagnetic layer 3'. These layers, for example, reflect the shape of the nonmagnetic layer 3'.

[0091] The undulations of the non-magnetic layer 3' are formed by creating unevenness on the surface of the buffer layer 4', and by forming each film layer in a manner that follows this unevenness. Unevenness can be formed on the surface of the buffer layer 4' by controlling the conditions of chemical mechanical polishing (CMP). The conditions of CMP vary depending on the CMP pressure, CMP time, type of abrasive, materials constituting the buffer layer 4', and materials constituting the insulating layer 90. The period, height, and other characteristics of the unevenness formed on the buffer layer 4' can be adjusted by changing these conditions.

[0092] The conditions for CMP polishing vary depending on the equipment, the type of abrasive, the materials constituting the buffer layer 4', the materials constituting the insulating layer 90, the polishing pressure, and the polishing time. Therefore, the CMP polishing conditions can be determined in advance through multiple condition proposals and feedback processes. The CMP polishing conditions are determined by conducting preliminary studies using samples prepared under identical conditions and varying their parameters. When CMP polishing is performed on samples prepared under identical conditions, the surface condition of the buffer layer 4' can be reproducibly controlled.

[0093] Furthermore, a seed layer 5', a ferromagnetic layer 6', a spacer layer 7', a first ferromagnetic layer 1', a non-magnetic layer 3', a second ferromagnetic layer 2', and a magnetic induction layer 8' are sequentially formed on the buffer layer 4', which has undergone CMP polishing. Each of these layers follows the surface shape of the buffer layer 4'. As a result, each of these layers has a shape that is undulating relative to a flat surface extending in the in-plane direction.

[0094] The magnetoresistive element 10' in the second embodiment is similar to that in the first embodiment, the outer side of the non-magnetic layer 3 is thicker than the inner side, making it less prone to short circuits between the first ferromagnetic layer 1 and the second ferromagnetic layer 2. Therefore, the magnetoresistive element 10' has excellent reliability.

[0095] Furthermore, the magnetoresistive effect element 10' in the second embodiment can reduce the reversing current density required to reverse the magnetization of the second ferromagnetic layer 2' due to the undulation of the nonmagnetic layer 3'. This is believed to be because the magnetization of the second ferromagnetic layer 2' is slightly inclined along the surface of the nonmagnetic layer 3'.

[0096] like Figure 7 As shown, the magnetization M2 of the second ferromagnetic layer 2' is orthogonally oriented relative to the surface of the non-magnetic layer 3'. The magnetization M2 is tilted relative to the z-direction. When spin is injected from the first ferromagnetic layer 1', the magnetization M2 undergoes precession and reverses. When the magnetization M2 is tilted in its initial state, it readily undergoes precession for magnetization reversal, reducing the energy required for reversal. As a result, the magnetoresistive effect element 10' in this embodiment can reduce the reversal current density required to reverse the magnetization of the second ferromagnetic layer 2'.

[0097] Figure 8 The results of Examples 1 to 4 and Comparative Example 1 used to confirm the above-mentioned hypothesis are shown.

[0098]

Example 1

[0099] A magnetoresistive element with a diameter of 100 nm was fabricated. Starting from the side closest to the substrate, the magnetoresistive element sequentially comprises a buffer layer (TiN), a seed layer (NiCr alloy), a ferromagnetic layer (CoFe alloy), a magnetic coupling layer (Ru), a first ferromagnetic layer (CoFe alloy), a non-magnetic layer (MgO), a second ferromagnetic layer (CoFe alloy), and a magnetic induction layer (MgO). After the buffer layer was formed, the surface was CMP-polished to create an uneven surface. The non-magnetic layer was undulated according to the unevenness of the buffer layer. The period of the undulations in the non-magnetic layer was 20 nm.

[0100] The reversal current density was measured using the magnetoresistive element of Example 1. The reversal current density of Example 1 was 5.15 mA / cm². 2 .

[0101]

Examples 2-4

[0102] The difference between Examples 2-4 and Example 1 lies in the alteration of the undulation period of the non-magnetic layer. This alteration was achieved by changing the conditions during CMP polishing of the buffer layer. The undulation period in Example 2 was 30 nm, in Example 3 it was 40 nm, and in Example 4 it was 60 nm. Furthermore, the reversing current density was measured using the respective magnetoresistive effect elements of Examples 2-4.

[0103]

Comparative Example 1

[0104] The difference between Comparative Example 1 and Example 1 is that the non-magnetic layer is flat. By changing the conditions during CMP polishing of the buffer layer, the surface of the buffer layer is made flat, thereby making the non-magnetic layer flat. The reverse current density was measured using the magnetoresistive effect element of Comparative Example 1.

[0105] exist Figure 8 In Comparative Example 1, since there are no undulations, the distance of the convex portion is expressed as the width of the magnetoresistive element (100 nm). For example... Figure 8 As shown, the reverse current density of the magnetoresistive element decreases when the non-magnetic layer 3' undulates. Furthermore, the reverse current density of the magnetoresistive element decreases particularly when the undulation period is less than 30% of the width of the magnetoresistive element.

[0106] The above shows an example of the magnetoresistive effect element 10 of the first embodiment and the magnetoresistive effect element 10' of the second embodiment, but without departing from the spirit of the present invention, additions, omissions, substitutions and other changes to the structure can be made.

[0107] For example, Figure 9 This is an enlarged view of the characteristic part of the magnetoresistive effect element in the first modified example. Figure 9 yes Figure 5 A variation of the above. Figure 9 The first variant is similar in that the second ferromagnetic layer 2 is disposed on the inner side of the upper surface of the magnetoresistive element 10 when viewed from the z-direction. Figure 5 The first embodiment differs from the second embodiment. By disposing the second ferromagnetic layer 2 inside the magnetoresistive element 10, short circuits between the second ferromagnetic layer 2 and the first ferromagnetic layer 1 or the electrode E2 can be further prevented. In the second embodiment, the second ferromagnetic layer 2 can also be disposed further inside the magnetoresistive element 10'.

[0108] This illustration shows an example of applying magnetoresistive element 10 or magnetoresistive element 10' to magnetic memory 100, but is not limited to this example. For example, magnetoresistive element 10 or magnetoresistive element 10' can also be used in magnetic heads, magnetic sensors, etc.

[0109] Explanation of reference numerals in the attached figures

[0110] 1, 1'… First ferromagnetic layer, 2, 2'… Second ferromagnetic layer, 3, 3'… Non-magnetic layer, 3A, 8A… First surface, 3B, 8B… Second surface, 4, 4'… Buffer layer, 5, 5'… Seed layer, 6, 6'… Ferromagnetic layer, 7, 7'… Spacer layer, 8, 8'… Magnetic induction layer, 10, 10'… Magnetoresistive effect element, 11, 21, 31, 81… Central region, 12, 22, 32, 82… Outer peripheral region, 90… Insulating layer, 100… Magnetic memory.

Claims

1. A magnetoresistive effect element comprising a first ferromagnetic layer, a second ferromagnetic layer, and a nonmagnetic layer, The non-magnetic layer is located between the first ferromagnetic layer and the second ferromagnetic layer. The non-magnetic layer has a first central region and a first peripheral region located outside the first central region. The maximum thickness of the first peripheral region is greater than the average thickness of the first central region. The non-magnetic layer contains MgO or Mg-Al-O as the main component. The first peripheral region contains nitrogen. The nitrogen concentration in the first peripheral region is lower as it gets closer to the first central region.

2. The magnetoresistive effect element according to claim 1, wherein, The thickness of the first peripheral region increases as it moves outward from the interface between the first central region and the first peripheral region.

3. The magnetoresistive effect element according to claim 1, wherein, It also has a magnetic induction layer. The magnetic induction layer and the non-magnetic layer sandwich the second ferromagnetic layer. The magnetic induction layer has a second central region and a second peripheral region located outside the second central region. The maximum thickness of the second peripheral region is greater than the average thickness of the second central region.

4. The magnetoresistive effect element according to claim 3, wherein, The second peripheral region becomes thicker as it moves outward from the interface between the second central region and the second peripheral region.

5. The magnetoresistive effect element according to claim 3, wherein, The second peripheral region contains nitrogen.

6. The magnetoresistive effect element according to claim 1, wherein, The second ferromagnetic layer has a third central region and a third peripheral region located outside the third central region. The average thickness of the third peripheral region is thinner than the average thickness of the third central region.

7. The magnetoresistive effect element according to claim 6, wherein, The third peripheral region becomes thinner as it moves outward from the interface between the third central region and the third peripheral region.

8. The magnetoresistive effect element according to claim 1, wherein, It also includes an insulating layer covering the sides of the laminate comprising the first ferromagnetic layer, the second ferromagnetic layer, and the non-magnetic layer. The insulating layer contains nitrogen in the region where it is in contact with the laminate.

9. The magnetoresistive effect element according to claim 8, wherein, The non-magnetic layer contains one or more elements selected from Ti, Si, Ga, In, Fe, Co, N, and Ta.

10. The magnetoresistive effect element according to claim 1, wherein, The non-magnetic layer undulates relative to a reference plane orthogonal to the stacking direction.

11. The magnetoresistive effect element according to claim 10, wherein, The average distance between the vertices of the protrusions projecting upward relative to the reference surface is less than 30% of the width of the non-magnetic layer.

12. The magnetoresistive effect element according to claim 10, wherein, The average distance between the vertices of the protrusions projecting upward relative to the reference surface is less than 30 nm.

13. The magnetoresistive effect element according to claim 10, wherein, The width of the non-magnetic layer in the in-plane direction is more than twice the period of the undulation of the non-magnetic layer.

14. The magnetoresistive effect element according to claim 10, wherein, The difference between the highest and lowest points of the non-magnetic layer is less than twice the thickness of the non-magnetic layer.

15. The magnetoresistive effect element according to claim 1, wherein, It also has a spacer layer and a third ferromagnetic layer. The spacer layer is in contact with the first ferromagnetic layer. The first ferromagnetic layer and the third ferromagnetic layer sandwich the spacer layer.

16. The magnetoresistive effect element according to claim 1, wherein, It also has a basal layer. The layer located between the substrate layer and the non-magnetic layer undulates relative to a reference plane orthogonal to the stacking direction.

17. A method for manufacturing a magnetoresistive effect element, comprising the method for manufacturing the magnetoresistive effect element according to any one of claims 1 to 16, wherein, This manufacturing method has the following characteristics: The process of forming a laminated film consisting of a first ferromagnetic layer, a nonmagnetic layer containing MgO or Mg-Al-O as the main component, and a second ferromagnetic layer stacked sequentially. The process of processing the laminated film into a laminate of a specified shape; The process of exposing the sides of the laminate to a nitrogen atmosphere; The process of forming an insulating layer covering the sides; and The process of annealing the laminate and the insulating layer.

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