Magnetic storage device

Abstract

Embodiments provide a magnetic memory device. It includes a first ferromagnetic layer, a first ferromagnetic oxide layer including iron or cobalt, a metal layer between the first ferromagnetic layer and the first ferromagnetic oxide layer, a second ferromagnetic layer on the first ferromagnetic oxide layer, a second ferromagnetic oxide layer on the second ferromagnetic layer, a third ferromagnetic layer on the second ferromagnetic oxide layer, an insulating layer on the third ferromagnetic layer, and a fourth ferromagnetic layer on the insulating layer. The metal layer antiferromagnetically couples the first ferromagnetic layer and the first ferromagnetic oxide layer. The second ferromagnetic layer includes one of iron and cobalt included in the first ferromagnetic oxide layer and one element of a first element group. The second ferromagnetic oxide layer includes an oxide of an alloy of the one of iron and cobalt included in the second ferromagnetic layer and the first element. The first element has a standard electrode potential lower than a standard electrode potential of iron or cobalt and a standard electrode potential of the one element of the first element group included in the second ferromagnetic layer.

Description

[0001] This application enjoys priority to Japanese Patent Application No. 2021-147086 (filed September 9, 2021) and U.S. Patent Application No. 17 / 549248 (filed December 13, 2021). This application incorporates the entire contents of the basic applications by reference. Technical Field

[0002] The implementation methods generally involve magnetic storage devices. Background Technology

[0003] Magnetic storage devices are known as a type of storage device. Magnetic storage devices use storage cells to store data, and these storage cells include elements that realize the magnetoresistive effect. To improve the characteristics of magnetic storage devices, it is desirable for the storage cells to have high magnetic properties. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to provide a magnetic storage device including a high-performance storage unit.

[0005] One embodiment of a magnetic storage device includes: a first ferromagnetic layer; a first ferromagnetic oxide layer comprising iron or cobalt; a metal layer disposed between the first ferromagnetic layer and the first ferromagnetic oxide layer; a second ferromagnetic layer disposed on the surface of the first ferromagnetic oxide layer opposite to the metal layer; a second ferromagnetic oxide layer disposed on the surface of the second ferromagnetic layer opposite to the first ferromagnetic oxide layer; a third ferromagnetic layer on the second ferromagnetic oxide layer; an insulating layer on the third ferromagnetic layer; and a fourth ferromagnetic layer on the insulating layer.

[0006] The aforementioned metal layer enables antiferromagnetic coupling between the first ferromagnetic layer and the first ferromagnetic oxide layer. The second ferromagnetic layer comprises one element contained in the first ferromagnetic oxide layer (iron or cobalt) and one element from the first element group, and has an easy magnetization axis pointing toward the interface between itself and the metal layer. The second ferromagnetic oxide layer comprises an oxide of an alloy, which is an alloy of the aforementioned element contained in the second ferromagnetic layer (iron or cobalt) and the first element. The first element has a standard electrode potential lower than the standard electrode potential of iron or cobalt and the standard electrode potential of the aforementioned element contained in the second ferromagnetic layer from the first element group. Attached Figure Description

[0007] Figure 1 Functional blocks and associated elements of the magnetic storage device of the first embodiment are shown.

[0008] Figure 2This is a circuit diagram of the memory cell array according to the first embodiment.

[0009] Figure 3 This shows the structure of a portion of the cross-section of the memory cell array in the first embodiment.

[0010] Figure 4 This shows the structure of a portion of the cross-section of the memory cell array in the first embodiment.

[0011] Figure 5 A cross section showing an example of the construction of the storage cell in the first embodiment.

[0012] Figure 6 This indicates the characteristics of the layer used in the first embodiment.

[0013] Figure 7 A cross section showing an example of the construction of the storage cell in the second embodiment.

[0014] Label Explanation

[0015] 1 Magnetic storage device, 2 Storage controller, 11 Storage cell array, 12 Input / output circuit, 13 Control circuit, 14 Row selection circuit, 15 Column selection circuit, 16 Write circuit, 17 Read circuit, MC storage cell, WL word line, BL bit line, MTJ MTJ element, SE switching element, 21 Conductor, 22 Conductor, 31 Ferromagnetic layer, 32 Spacer layer, 33 Ferromagnetic layer, 34 Insulating layer, 35 Ferromagnetic layer, 331 Ferromagnetic oxide layer, 332 Ferromagnetic layer, 333 Ferromagnetic oxide layer, 334 Ferromagnetic layer. Detailed Implementation

[0016] Hereinafter, embodiments will be described with reference to the accompanying drawings. In the following description, components having substantially the same function and structure will sometimes be given the same reference numerals, and repeated descriptions will be omitted.

[0017] The accompanying drawings are schematic; the relationship between thickness and planar dimensions, and the ratio of thicknesses of each layer, may differ from reality. The drawings may also include portions with different dimensional relationships and ratios. Unless explicitly or obviously excluded, descriptions of one embodiment may be considered descriptions of other embodiments. Each embodiment exemplifies an apparatus or method for embodying the technical concept of that embodiment; the technical concept of the embodiments does not limit the materials, shapes, structures, and arrangements of the constituent components to the materials, shapes, structures, and arrangements described below.

[0018] In this specification and claims, a first element being "connected" to another second element includes the first element being directly, consistently, or selectively connected to the second element via a conductive element.

[0019] The following implementation method is described using an orthogonal xyz coordinate system. In the following description, the term "below" and its derivatives and conjunctions refer to the position of the smaller coordinate on the z-axis, and the term "above" and its derivatives and conjunctions refer to the position of the larger coordinate on the z-axis.

[0020] 1. First Implementation Method

[0021] 1.1. Structure (Composition)

[0022] 1.1.1. Overall Structure

[0023] Figure 1 Functional blocks representing the magnetic storage device of the first embodiment. For example... Figure 1 As shown, the magnetic storage device 1 is controlled by the storage controller 2. The magnetic storage device 1 is a storage device that uses ferromagnetic materials to store data. The magnetic storage device 1 includes a storage cell array 11, an input / output circuit 12, a control circuit 13, a row selection circuit 14, a column selection circuit 15, a write circuit 16, and a read circuit 17.

[0024] Memory cell array 11 is a collection of multiple memory cells MCs arranged in a row. Each memory cell MC stores data in a non-volatile manner. Multiple word lines (WLs) and multiple bit lines (BLs) are located in memory cell array 11. Each memory cell MC is connected to one word line (WL) and one bit line (BL). The word line (WL) is associated with a row. The bit line (BL) is associated with a column. A memory cell MC is determined by selecting a row and selecting a column.

[0025] Input / output circuit 12 is a circuit for inputting and outputting data and signals. Input / output circuit 12 receives control signals CNT, commands CMD, address signals ADD, and data (write data) DAT from memory controller 2. Input / output circuit 12 sends data (read data) DAT to memory controller 2.

[0026] The row selection circuit 14 receives the address signal ADD from the input / output circuit 12 and sets the word line WL associated with the row determined by the received address signal ADD to the selected state.

[0027] The column selection circuit 15 receives the address signal ADD from the input / output circuit 12 and sets one or more bit lines BL associated with the column determined by the received address signal ADD to the selected state.

[0028] Control circuit 13 receives control signal CNT and command CMD from input / output circuit 12. Based on the control signal CNT and command CMD, control circuit 13 controls write circuit 16 and read circuit 17. Specifically, during data writing to memory cell array 11, control circuit 13 supplies the voltage used in data writing to write circuit 16. Additionally, during data reading from memory cell array 11, control circuit 13 supplies the voltage used in data reading to read circuit 17.

[0029] The write circuit 16 receives write data DAT from the input / output circuit 12, and based on the control of the control circuit 13 and the write data DAT, the null selection circuit 15 supplies the voltage used in the data writing.

[0030] The readout circuit 17, based on the control of the control circuit 13, uses the voltage used in data readout to obtain the data held in the storage unit MC. The obtained data is provided to the input / output circuit 12 as readout data DAT. The readout circuit 17 includes a sense amplifier.

[0031] 1.1.2. Circuit Structure of Memory Cell Array

[0032] Figure 2 This is a circuit diagram of the memory cell array 11 according to the first embodiment. Figure 2 As shown, the memory cell array 11 has M+1 (M is a natural number) word lines WLA (WLA<0>, WLA<1>, ..., WLA<M>) and M+1 word lines WLB (WLB<0>, WLB<1>, ..., WLB<M>). Additionally, the memory cell array 11 has N+1 (N is a natural number) bit lines BL (BL<0>, BL<1>, ..., BL<N>).

[0033] Each memory cell MC (MCA and MCB) has a first node and a second node. Each memory cell MC is connected to a word line WL at the first node and to a bit line BL at the second node. More specifically, memory cell MCA includes all combinations of all cases where α is an integer greater than or equal to 0 and less than M, and all cases where β is an integer greater than or equal to 0 and less than N, including memory cell MCA<α, β>, which is connected between word line WLA<α> and bit line BL<β>. Similarly, memory cell MCB includes all combinations of all cases where α is an integer greater than or equal to 0 and less than M, and all cases where β is an integer greater than or equal to 0 and less than N, including memory cell MCB<α, β>, which is connected between word line WLB<α> and bit line BL<β>.

[0034] Each memory cell MC includes one MTJ element MTJ (MTJA or MTJB) and one switching element SE (SEA or SEB). More specifically, for all combinations of all cases where α is an integer greater than or equal to 0 and less than M, and β is an integer greater than or equal to 0 and less than N, the memory cell MCA<α, β> includes the MTJ element MTJA<α, β> and the switching element SEA<α, β>. Furthermore, for all combinations of all cases where α is greater than or equal to 0 and less than M, and β is an integer greater than or equal to 0 and less than N, the memory cell MCB<α, β> includes the MTJ element MTJB<α, β> and the switching element SEB<α, β>.

[0035] In each memory cell (MC), the MTJ element and the switching element (SE) are connected in series. The MTJ element is connected to a word line (WL), and the switching element (SE) is connected to a bit line (BL).

[0036] MTJ devices exhibit the tunneling magnetoresistance effect and are, for example, devices comprising a magnetic tunnel junction (MTJ). MTJ devices can switch between low-resistance and high-resistance states. MTJ devices can store 1 bit of data using the difference between these two resistance states.

[0037] A switching element SE is a component used to select a memory cell MC including the switching element SE. The switching element SE can be a switching element as described below. The switching element has two terminals. When a voltage less than a first threshold is applied between the two terminals in a first direction, the switching element is in a high-resistance state, for example, an electrically non-conducting state (off state). On the other hand, when a voltage greater than the first threshold is applied between the two terminals in the first direction, the switching element is in a low-resistance state, for example, an electrically conducting state (on state). Furthermore, the switching element also has the same function as the switching function between a high-resistance state and a low-resistance state based on the magnitude of the voltage applied in the first direction, in a second direction opposite to the first direction. That is, the switching element is a bidirectional switching element. By turning the switching element on or off, the presence or absence of current supply to the MTJ element MTJ connected to the switching element, i.e., the selection or non-selection of the MTJ element MTJ, can be controlled.

[0038] 1.1.3. Construction of a Storage Cell Array

[0039] Figure 3 and Figure 4 The diagram shows the structure of a portion of the cross-section of the memory cell array 11 in the first embodiment. Figure 3 This represents a cross section along the xz plane. Figure 4This represents a cross section along the yz plane.

[0040] like Figure 3 and Figure 4 As shown, a plurality of conductors 21 are disposed above a semiconductor substrate (not shown). The conductors 21 extend along the y-axis and are arranged along the x-axis. Each conductor 21 functions as a word line WL.

[0041] Each conductor 21 is connected on its upper surface to the lower surface of each of the plurality of memory cells MCBs. The memory cells MCBs have, for example, a circular shape in the xy-plane. The memory cells MCBs are arranged along the y-axis on each conductor 21, forming a matrix along the xy-plane. Each memory cell MCB includes a structure that functions as a switching element SEB and a structure that functions as an MTJ element MTJB. The structure that functions as a switching element SEB and the structure that functions as an MTJ element MTJB each include one or more layers, as described later.

[0042] Multiple conductors 22 are disposed above the memory cell MCB. The conductors 22 extend along the x-axis and are arranged along the y-axis. The lower surface of each conductor 22 contacts the upper surface of the multiple memory cells MCB arranged along the x-axis. Each conductor 22 functions as a bit line BL.

[0043] Each conductor 22 is connected on its upper surface to the lower surface of each of the plurality of memory cell MCAs. The memory cell MCAs have, for example, a circular shape in the xy-plane. The memory cell MCAs are arranged along the x-axis on each conductor 22, forming a matrix along the xy-plane. Each memory cell MCA includes a structure that functions as a switching element SEA and a structure that functions as an MTJ element MTJA. The structure that functions as a switching element SEA and the structure that functions as an MTJ element MTJA each include one or more layers, as described later.

[0044] Further conductors 21 are provided on the upper surface of each of the multiple memory cells MCA arranged along the y-axis.

[0045] 1.1.4. Construction of Storage Units

[0046] Figure 5 A cross-section showing an example of the construction of the storage cell MC in the first embodiment. For example... Figure 5 As shown, the storage cell MC includes a switching element SE and an MTJ element MTJ.

[0047] The switching element SE comprises a variable resistive material. The switching element SE may also include a lower electrode and an upper electrode. In this case, the variable resistive material is located on the upper surface of the lower electrode, and the upper electrode is located on the upper surface of the variable resistive material.

[0048] The variable resistive material is, for example, a two-terminal switching element, where the first terminal of the two terminals is one of the upper and lower surfaces of the variable resistive material, and the second terminal of the two terminals is the other of the upper and lower surfaces of the variable resistive material. When the voltage applied between the two terminals is below a threshold, the switching element is in a "high resistance" state, for example, an electrically non-conductive state. When the voltage applied between the two terminals is above the threshold, the switching element is in a "low resistance" state, for example, an electrically conductive state. The variable resistive material is formed from a material comprising an insulator, containing dopants introduced by ion implantation. The insulator, for example, comprises an oxide, or a material comprising SiO2 or substantially formed of SiO2. The dopants, for example, comprise arsenic (As) or germanium (Ge). In this specification and claims, the use of the phrase "substantially formed (constituted) of" and similar descriptions implies that the constituent elements "substantially formed" are permitted to contain unintentional impurities. Examples of unintentional impurities include elements contained in the gas used in the manufacturing process of the magnetic storage device 1, as well as other elements that diffuse from the surrounding of the constituent elements "substantially formed by" to the constituent elements "substantially formed by".

[0049] The MTJ element includes a ferromagnetic layer 31, a spacer layer 32, a ferromagnetic layer 33, an insulating layer 34, and a ferromagnetic layer 35. The ferromagnetic layer 31, spacer layer 32, ferromagnetic layer 33, insulating layer 34, and ferromagnetic layer 35 are stacked on the upper surface of the switching element SE in this order.

[0050] Ferromagnetic layers 31, 33, and 35 have an easy magnetization axis along the direction that connects the interfaces of ferromagnetic layers 31, 32, 33, 34, and 35. The easy magnetization axes of ferromagnetic layers 31, 33, and 35 have an angle of 45° or more and 90° or less relative to the interface, for example, orthogonal to the interface. Figure 5 The arrows inside the constituent elements shown indicate the magnetization direction.

[0051] The ferromagnetic layer 31, spacer layer 32, ferromagnetic layer 33, insulating layer 34, and ferromagnetic layer 35 are further described.

[0052] The ferromagnetic layer 31 is a layer of ferromagnetic material. The ferromagnetic layer 31 contains elements exhibiting ferromagnetism, or is substantially formed of elements exhibiting ferromagnetism. The ferromagnetic layer 31 contains cobalt-platinum (CoPt), cobalt-nickel (CoNi), or cobalt-palladium (CoPd), or is substantially formed of CoPt, CoNi, or CoPd. The ferromagnetic layer 31 may include, for example, a structure obtained by alternating layers of cobalt (Co) and platinum (Pt) more than once, a structure obtained by alternating layers of cobalt and nickel (Ni) more than once, or a structure obtained by alternating layers of cobalt and palladium (Pd) more than once.

[0053] Ferromagnetic layer 31 has a magnetization direction opposite to that of ferromagnetic layer 33. Ferromagnetic layer 31 suppresses the magnetic field generated by ferromagnetic layer 33 and applied to ferromagnetic layer 35, i.e., the leakage magnetic field. Ferromagnetic layer 31 functions as a so-called shift cancel layer (SCL).

[0054] Spacer layer 32 is a non-magnetic metallic layer that enables antiferromagnetic coupling between two ferromagnetic bodies sandwiched within it. Spacer layer 32 contains ruthenium (Ru) or iridium (Ir), or is substantially formed of Ru or Ir. The thickness of Ru or Ir determines whether the two ferromagnetic bodies sandwiched within the Ru or Ir layer are ferromagnetically or antiferromagnetically coupled. Spacer layer 32 has a thickness that enables antiferromagnetic coupling between ferromagnetic layer 31 and ferromagnetic layer 33 (particularly the ferromagnetic layer 332 described later included in ferromagnetic layer 33).

[0055] The ferromagnetic layer 33 is generally a stack of magnetized layers with a direction oriented through the interface of the ferromagnetic layer 33, the insulating layer 34, and the ferromagnetic layer 35. The magnetization direction of the ferromagnetic layer 33 is intended to remain unchanged whether data is read from or written to the memory cell MC. The ferromagnetic layer 33 functions as a so-called reference layer (RL).

[0056] The ferromagnetic layer 33 includes a ferromagnetic oxide layer (FMO) 331, a ferromagnetic layer 332, a ferromagnetic oxide layer 333 (FMO), and a ferromagnetic layer 334.

[0057] The ferromagnetic oxide layer 331 is a layer of alloy oxide exhibiting ferromagnetism. The alloy oxide includes, or is substantially formed by, oxides of, alloys of iron (Fe) and / or Co, and boron (B), scandium (Sc), chromium (Cr), manganese (Mn), Ni, Ru, Pd, Ir, Pt, yttrium (Y), neodymium (Nd), samarium (Sm), gadolinium (Gd), terbium (Tb), and dysprosium (Dy).

[0058] The ferromagnetic oxide layer 331 enhances the interfacial magnetic anisotropy of the ferromagnetic layer 33. Specifically, the ferromagnetic layer 332 is formed in an amorphous state and then annealed to become crystalline. The ferromagnetic layer 332 formed in the amorphous state contains impurities. Through annealing, these impurities diffuse into the ferromagnetic oxide layer 331. This diffusion increases the purity of the ferromagnetic layer 332, allowing it to crystallize in a high-purity state. Therefore, the crystallized ferromagnetic layer 332 exhibits high crystallinity. The high crystallinity of the ferromagnetic layer 332 contributes to the overall high interfacial magnetic anisotropy of the ferromagnetic layer 33. The interfacial magnetic anisotropy of the ferromagnetic layer 33 exhibited by using the ferromagnetic oxide layer 331 is higher than that of a ferromagnetic layer 33 in which a metal layer is provided instead of the ferromagnetic oxide layer 331 in the construction of the ferromagnetic layer 33.

[0059] The interfacial magnetic anisotropy of a magnetic material is related to its anisotropic energy. Therefore, a high interfacial magnetic anisotropy of the ferromagnetic layer 33 is associated with a high anisotropic energy. This high anisotropic energy is associated with a high retention characteristic of the MTJ element. Retention characteristic refers to the difficulty of reversing the resistance state of the MTJ element due to external disturbances such as thermal disturbances. The magnetization of the ferromagnetic layer 33 is intended not to reverse, but due to external influences, it may unintentionally reverse. When the magnetization of the ferromagnetic layer 33 reverses, the MTJ element cannot correctly store data.

[0060] Ferromagnetic layer 332 is a layer of ferromagnetic material. Ferromagnetic layer 332 is antiferromagnetically coupled to ferromagnetic layer 31 through spacer layer 32, and is magnetized through this antiferromagnetic coupling. The overall magnetization direction of ferromagnetic layer 33 is the same as that of ferromagnetic layer 332. The magnetization of ferromagnetic layer 332 functions as a source of anisotropic energy generating the magnetization exhibited by the entire ferromagnetic layer 33. Ferromagnetic layer 332 is the primary source of anisotropic energy generating the magnetization exhibited by the entire ferromagnetic layer 33. Ferromagnetic layer 332 is sometimes referred to as the main reference layer (MRL) based on this function.

[0061] The ferromagnetic layer 332 and the ferromagnetic oxide layer 331 have high wettability. For this purpose, the ferromagnetic layer 332 contains elements common to the ferromagnetic oxide layer 331. More specifically, the ferromagnetic layer 332 contains Fe and / or Co, including one or more elements from Fe and Co that are the same as those contained in the ferromagnetic oxide layer 331. Furthermore, the ferromagnetic layer 332 has materials and structures for exhibiting anisotropic energy. Specifically, the ferromagnetic layer 332 also contains one or more elements selected from boron (B), chromium (Cr), manganese (Mn), Ni, Ru, rhodium (Rh), Pd, Ir, and Pt. The ferromagnetic layer 332 can have a structure obtained by stacking two or more elements selected from Fe, Co, B, Cr, Mn, Ni, Ru, Rh, Pd, Ir, and Pt.

[0062] The ferromagnetic oxide layer 333 is a layer of alloy oxide exhibiting ferromagnetism. The ferromagnetic oxide layer 333 has high wettability with the ferromagnetic layer 332. For this purpose, the ferromagnetic oxide layer 333 contains elements common to the ferromagnetic layer 332. More specifically, the ferromagnetic layer 333 contains Fe and / or Co, including one or both of the elements contained in the ferromagnetic oxide layer 332.

[0063] Furthermore, the ferromagnetic oxide layer 333 is a layer of alloy oxide containing an element whose standard electrode potential is lower than that of one, multiple, or all of the elements contained in the ferromagnetic layer 332.

[0064] Based on the conditions for the alloy oxide of the ferromagnetic oxide layer 333, the alloy oxide comprises an oxide of an alloy of one or more elements selected from Fe and Co with one or more elements selected from B, Sc, Y, Nd, Sm, Gd, Tb and Dy, or is substantially formed from such an alloy oxide.

[0065] The ferromagnetic oxide layer 333 enhances the interfacial magnetic anisotropy of the ferromagnetic layer 33 through the same mechanism as that based on the ferromagnetic oxide layer 331. Specifically, through annealing the ferromagnetic layer 332 formed in an amorphous state, impurities in the ferromagnetic layer 332 diffuse into the ferromagnetic oxide layer 333. This diffusion increases the purity of the ferromagnetic layer 332, resulting in a highly crystalline ferromagnetic layer 332. This contributes to the overall high interfacial magnetic anisotropy of the ferromagnetic layer 33. The interfacial magnetic anisotropy of the ferromagnetic layer 333 exhibited by using the ferromagnetic oxide layer 333 is higher than that in a ferromagnetic layer with a metal layer replacing the ferromagnetic oxide layer 333 in its structure. Therefore, the retention characteristics of the MTJ element are also improved through the ferromagnetic oxide layer 333.

[0066] A ferromagnetic oxide layer 333 is disposed between the ferromagnetic layers 332 and 334 to suppress the influence of the crystal structure of the ferromagnetic layer 332 on the crystal structure of the ferromagnetic layer 334. Specifically, the ferromagnetic layer 334 is initially formed in an amorphous state and then crystallized through annealing to form a crystalline structure. Crystallization proceeds using the insulating layer 34 as a seed. At this point, when the amorphous ferromagnetic layer 334 comes into contact with the ferromagnetic layer 332, the crystal structure of the ferromagnetic layer 334 is affected by the crystal structure of the ferromagnetic layer 332. By presenting the ferromagnetic oxide layer 333, the influence of the crystal structure of the ferromagnetic layer 332 on the crystal structure of the ferromagnetic layer 334 is suppressed.

[0067] The ferromagnetic layer 334 is a layer of ferromagnetic material. The ferromagnetic layer 334 contains one or more elements selected from iron (Fe) and cobalt (Co). The ferromagnetic layer 334 may also contain boron (B). More specifically, for example, the ferromagnetic layer 334 contains cobalt iron boron (CoFeB) or iron boride (FeB), or is substantially formed of CoFeB or FeB.

[0068] Based on the suppression of the influence of the crystal structure of the ferromagnetic layer 332 on the crystal structure of the ferromagnetic layer 334, and the fact that the ferromagnetic layer 334 crystallizes by using the insulating layer 34 as a seed crystal, the ferromagnetic layer 334 has the same crystal structure as the insulating layer 34.

[0069] The ferromagnetic layer 334 enhances the interfacial magnetic anisotropy of the ferromagnetic layer 33 through the same mechanism used to make the ferromagnetic layer 332 highly crystalline. That is, the ferromagnetic layer 334 is formed in an amorphous state as described above and then annealed to become crystalline. Through this annealing, impurities in the ferromagnetic layer 334 diffuse into the ferromagnetic oxide layer 333. This diffusion results in high crystallinity of the ferromagnetic layer 334, which in turn contributes to the overall high interfacial magnetic anisotropy of the ferromagnetic layer 33. Therefore, the high crystallinity of the ferromagnetic layer 334 also improves the retention characteristics of the MTJ element.

[0070] Generally, a ferromagnetic material causes two ferromagnetic materials sandwiched between it to be magnetically coupled. The ferromagnetic oxide layer 333 is ferromagnetic, thus causing the ferromagnetic layers 332 and 334 sandwiched between it to be magnetically coupled. The magnetization direction of the ferromagnetic layer 334, through its ferromagnetic coupling with the magnetized ferromagnetic layer 332, is the same as the magnetization direction of the ferromagnetic layer 332. Because the ferromagnetic layers 334 and 332 are ferromagnetically coupled, they function as a single ferromagnetic layer with effectively high magnetic anisotropy energy. Through the effectively high magnetic anisotropy energy of the ferromagnetic layer 33 generated by the ferromagnetically coupled ferromagnetic layers 334 and 332, the MTJ element MTJ exhibits high retention characteristics.

[0071] 1.2. Advantages (Effects)

[0072] According to the first embodiment, as described below, it is possible to provide an MTJ element with high magnetic properties.

[0073] According to the first embodiment, the ferromagnetic oxide layer 333 comprises an alloy oxide containing one or more elements selected from Fe and Co, and an element having a standard electrode potential lower than that of the elements contained in the ferromagnetic layer 332, or is substantially formed of such an alloy oxide. That is, the ferromagnetic oxide layer 333 is substantially formed of an element having a standard electrode potential lower than that of the elements substantially constituting the ferromagnetic layers 334 and 332 that are in contact with the ferromagnetic oxide layer 333. This means that the ferromagnetic oxide layer 333 is more easily oxidized than the ferromagnetic layers 332 and 334. Therefore, the ferromagnetic oxide layer 333 retains oxygen atoms within itself with a force higher than the force required for oxygen atoms to diffuse into the ferromagnetic layers 332 and / or 334. Thus, the diffusion of oxygen atoms into the ferromagnetic layers 332 and 334 is suppressed. In the ferromagnetic layers 332 and 334, oxygen atoms are impurities. Therefore, by suppressing the diffusion of oxygen atoms into ferromagnetic layers 332 and 334, the degradation of the magnetic properties of ferromagnetic layers 332 and 334 caused by oxygen atoms in them is suppressed. That is, the degradation of the interfacial magnetic anisotropy of ferromagnetic layer 33 and the degradation of the MR ratio of the MTJ element are suppressed. This is because the MR ratio of the MTJ element depends on the properties of the ferromagnetic layers 35 and 334 in contact with the insulating layer 34, and the presence of oxygen atoms as an impurity is related to the degradation of the magnetic properties of ferromagnetic layer 334, and consequently, to the degradation of the MR ratio. The MR ratio is the ratio of the resistance of the magnetoresistive effect element (MTJ element) in its low-resistance state to its resistance in its high-resistance state.

[0074] According to the first embodiment, ferromagnetic oxide layer 331 and ferromagnetic layer 332 contain the same atoms, and ferromagnetic layer 332 and ferromagnetic oxide layer 333 contain the same atoms. The adhesion (wetting) of the interface between different materials affects the properties of these materials. This is because when the adhesion is low, pores and / or agglomeration of atoms will occur at the interface. The adhesion of the interface between different materials can be improved by having the two materials forming the interface contain the same elements. Thus, ferromagnetic oxide layer 331 and ferromagnetic layer 332 have high wettability at their interface by containing the same elements, and ferromagnetic layer 332 and ferromagnetic oxide layer 333 have high wettability at their interface by containing the same elements. Thus, ferromagnetic oxide layer 331, ferromagnetic layer 332, and ferromagnetic oxide layer 333 with high properties are provided, which helps to realize an MTJ element with high magnetic properties.

[0075] According to the first embodiment, a ferromagnetic oxide layer 331 is provided between the spacer layer 32 and the ferromagnetic layer 332. When two different materials are in contact, elements from one material diffuse into the other at the interface between the first and second materials. These diffused elements are impurities in both the first and second materials, thus degrading their properties. Sometimes, a third material is provided between the first and second materials to suppress the diffusion of impurities into them. This suppresses the interdiffusion of elements between the first and second materials, and compared to the case where the first and second materials are in contact, it reduces the amount of impurities in both materials. As a reference structure for an MTJ element, a metal layer can be provided between the spacer layer 32 and the ferromagnetic layer 332. However, the retention characteristics of such an MTJ element are still not as high as desired.

[0076] In the first embodiment, the ferromagnetic oxide layer 331 is an oxide, and therefore, it is chemically more stable than many single metallic elements, making it difficult to react with surrounding elements. Specifically, the ferromagnetic oxide layer 331 is unlikely to react with elements in the spacer layer 32 it contacts, and it is also unlikely to react with elements in the ferromagnetic layer 332 it contacts. Furthermore, for the same reason, elements in the ferromagnetic oxide layer 331 are unlikely to diffuse into the spacer layer 32 and the ferromagnetic layer 332. Thus, the diffusion of impurities into the spacer layer 32 and the ferromagnetic layer 332 is suppressed, and the property degradation of the spacer layer 32 and the ferromagnetic layer 332 caused by impurity diffusion is suppressed. The suppression of the degradation of the properties (especially the magnetic properties) of the ferromagnetic layer 332 is beneficial for the ferromagnetic layer 332 to possess high magnetic anisotropy energy. Suppressing the degradation of the properties of the spacer layer 32 is beneficial to suppressing the decrease in the strength of the antiferromagnetic coupling between the ferromagnetic layer 332 and the ferromagnetic layer 31, and thus beneficial to suppressing the degradation of the retention properties of the MTJ element. As a result, an MTJ element with high magnetic properties can be realized.

[0077] Figure 6 This describes the characteristics of the ferromagnetic oxide layer 331 in the first embodiment. More specifically, Figure 6 Regarding the MTJ element comprising spacer 32 and ferromagnetic layer 1332, which functions as a major part of the reference layer similar to ferromagnetic layer 332, the characteristics are shown in the case where a layer of different materials is disposed between spacer 32 and ferromagnetic layer 1332. Figure 6 The vertical axis represents the magnitude of the exchange interaction between the two ferromagnetic layers 31 and 332 sandwiched by the spacer layer 32. The magnitude of the exchange interaction is related to the coupling strength of the ferromagnetic layers 31 and 332, which affects the force maintaining the magnetization of the reference layer and thus the retention characteristics of the MTJ element.

[0078] Figure 6 In this example, as a first embodiment, a case is shown where a ferromagnetic oxide layer 331, substantially formed of gadolinium oxide, is provided between the spacer layer 32 and the ferromagnetic layer 332. Furthermore, Figure 6 In comparison, a case is shown where a layer substantially formed of gadolinium is provided between the spacer layer 32 and the ferromagnetic layer 1332.

[0079] like Figure 6 As shown, throughout Figure 6 Throughout the thickness range shown, the magnitude of the exchange interaction is higher in the case of gadolinium oxide than in the case of gadolinium alone. Therefore, using gadolinium oxide imparts higher retention characteristics to the MTJ element compared to using gadolinium.

[0080] 2. Second Implementation Method

[0081] The difference between the second embodiment and the first embodiment lies in the layers included in the MTJ element. Hereinafter, the differences from the first embodiment will be primarily described. For constituent elements in the second embodiment that differ from those in the first embodiment, further text or numbers are appended to the end of the reference numerals of the constituent elements in the first embodiment to distinguish them. For example, the MTJ element MTJ in the second embodiment may be referred to as the MTJ element MTJb. For points other than those described in the second embodiment, the points described in the first embodiment will be applied.

[0082] Figure 7 A cross-section showing an example of the construction of the storage cell MC in the second embodiment. For example... Figure 7 As shown, the memory cell MC includes an MTJ element MTJb. The MTJ element MTJb replaces the ferromagnetic oxide layer 333 in the first embodiment and includes a metal layer 337. The metal layer 337 is a non-magnetic metal layer, substantially formed of one or more elements selected from molybdenum (Mo), tungsten (W), and tantalum (Ta).

[0083] According to the second embodiment, advantages other than those brought by the ferromagnetic oxide layer 333, which are achieved in the first embodiment, can be obtained. Furthermore, according to the second embodiment, the ferromagnetic layer 332 is in contact with the metal layer 337. In the case of metal-to-metal contact, the wettability of these metal interfaces is high. Therefore, the ferromagnetic layer 332 and the metal layer 337 do not necessarily have a structure as in the first embodiment used to ensure high wettability between the ferromagnetic oxide layer 333 and the ferromagnetic layer 332. Thus, a layer of material that can be selected in a manner that does not consider adhesion can be provided between the ferromagnetic layer 332 and the ferromagnetic layer 334.

[0084] Several embodiments of the present invention have been described, but these embodiments are merely illustrative and not intended to limit the scope of the invention. These embodiments can be implemented in a wide variety of other ways, and various omissions, substitutions, and modifications can be made without departing from the spirit of the invention. These embodiments and their variations are included within the scope and spirit of the invention, and likewise within the scope of the invention as described in the claims and its equivalents.

Claims

1. A magnetic storage device comprising: First ferromagnetic layer; A first ferromagnetic oxide layer containing iron or cobalt; A metal layer is disposed between the first ferromagnetic layer and the first ferromagnetic oxide layer, thereby enabling the first ferromagnetic layer and the first ferromagnetic oxide layer to be antiferromagnetically coupled. The second ferromagnetic layer is disposed on the surface opposite to the metal layer in the surface of the first ferromagnetic oxide layer, and contains one element contained in the first ferromagnetic oxide layer, namely iron and cobalt, and one element in the first element group, and has an easy magnetization axis oriented toward the interface between the second ferromagnetic layer and the metal layer. The second ferromagnetic oxide layer, disposed on the surface opposite to the first ferromagnetic oxide layer, contains an oxide of an alloy, which is an alloy of iron and cobalt, the element contained in the second ferromagnetic layer, and a first element, wherein the first element has a standard electrode potential lower than the standard electrode potential of iron or cobalt and the standard electrode potential of the element contained in the second ferromagnetic layer in the first element group. The third ferromagnetic layer on the second ferromagnetic oxide layer; The insulating layer on the third ferromagnetic layer; and The fourth ferromagnetic layer on the insulating layer.

2. The magnetic storage device according to claim 1, The second ferromagnetic layer comprises iron or cobalt, and one or more elements from the first element group. The second ferromagnetic oxide layer comprises an oxide of an alloy, which is an alloy of one of the elements contained in the second ferromagnetic layer of iron and cobalt with an element having a standard electrode potential lower than that of all the elements contained in the second ferromagnetic layer of the first element group.

3. The magnetic storage device according to claim 2, The first element group includes boron, chromium, manganese, nickel, ruthenium, rhodium, palladium, iridium, and platinum.

4. The magnetic storage device according to claim 3, The first element is boron, scandium, yttrium, neodymium, samarium, gadolinium, terbium, or dysprosium.

5. The magnetic storage device according to claim 3, The second ferromagnetic oxide layer comprises an oxide of an alloy, which is an alloy of one of the elements contained in the second ferromagnetic layer of iron and cobalt with one or more of the elements selected from boron, scandium, yttrium, neodymium, samarium, gadolinium, terbium, and dysprosium.

6. The magnetic storage device according to claim 5, The metal layer contains ruthenium or iridium.

7. The magnetic storage device according to claim 6, The first ferromagnetic oxide layer comprises an oxide of an alloy, which is an alloy of iron or cobalt, and one or more elements selected from boron, scandium, chromium, manganese, nickel, ruthenium, palladium, iridium, platinum, yttrium, neodymium, samarium, gadolinium, terbium, and dysprosium.

8. The magnetic storage device according to claim 1, The first element group includes boron, chromium, manganese, nickel, ruthenium, rhodium, palladium, iridium, and platinum.

9. The magnetic storage device according to claim 8, The first element is boron, scandium, yttrium, neodymium, samarium, gadolinium, terbium, or dysprosium.

10. The magnetic storage device according to claim 8, The second ferromagnetic oxide layer comprises an oxide of an alloy, which is an alloy of one of the elements contained in the second ferromagnetic layer of iron and cobalt with one or more of the elements selected from boron, scandium, yttrium, neodymium, samarium, gadolinium, terbium, and dysprosium.

11. The magnetic storage device according to claim 10, The metal layer contains ruthenium or iridium.

12. The magnetic storage device according to claim 11, The first ferromagnetic oxide layer comprises an oxide of an alloy, which is an alloy of iron or cobalt, and one or more elements selected from boron, scandium, chromium, manganese, nickel, ruthenium, palladium, iridium, platinum, yttrium, neodymium, samarium, gadolinium, terbium, and dysprosium.

13. The magnetic storage device according to claim 1, The first element is boron, scandium, yttrium, neodymium, samarium, gadolinium, terbium, or dysprosium.

14. The magnetic storage device according to claim 1, The second ferromagnetic oxide layer comprises an oxide of an alloy, which is an alloy of one of the elements contained in the second ferromagnetic layer of iron and cobalt with one or more elements selected from boron, scandium, yttrium, neodymium, samarium, gadolinium, terbium, and dysprosium.

15. The magnetic storage device according to claim 14, The metal layer contains ruthenium or iridium.

16. The magnetic storage device according to claim 15, The first ferromagnetic oxide layer comprises an oxide of an alloy, which is an alloy of iron or cobalt, and one or more elements selected from boron, scandium, chromium, manganese, nickel, ruthenium, palladium, iridium, platinum, yttrium, neodymium, samarium, gadolinium, terbium, and dysprosium.

17. A magnetic storage device comprising: First ferromagnetic layer; A first ferromagnetic oxide layer containing iron or cobalt; A first metal layer is disposed between the first ferromagnetic layer and the first ferromagnetic oxide layer, thereby enabling the first ferromagnetic layer and the first ferromagnetic oxide layer to be antiferromagnetically coupled. The second ferromagnetic layer is disposed on the surface opposite to the first metal layer in the surface of the first ferromagnetic oxide layer, and contains one element contained in the first ferromagnetic oxide layer, namely iron and cobalt, and one element in the first element group, and has an easy magnetization axis in the direction of intersecting the interface between the second ferromagnetic layer and the first metal layer. A second metal layer is disposed on the surface of the second ferromagnetic layer opposite to the first ferromagnetic oxide layer. The third ferromagnetic layer on the second metal layer; The insulating layer on the third ferromagnetic layer; and The fourth ferromagnetic layer on the insulating layer.

18. The magnetic storage device according to claim 17, The second metal layer contains one or more elements selected from molybdenum, tungsten, and tantalum.

19. The magnetic storage device according to claim 18, The first metal layer contains ruthenium or iridium.

20. The magnetic storage device according to claim 19, The first ferromagnetic oxide layer comprises an oxide of an alloy, which is an alloy of iron or cobalt, and one or more elements selected from boron, scandium, chromium, manganese, nickel, ruthenium, palladium, iridium, platinum, yttrium, neodymium, samarium, gadolinium, terbium, and dysprosium.

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