Tunnel junction laminated film, magnetic memory element and magnetic memory

Abstract

Provided are a tunnel junction laminated film having high thermal stability, and a magnetic memory element and a magnetic memory using a tunnel junction laminated film. A tunnel junction laminated film 1 includes a recording layer 14 having a first ferromagnetic layer 24 including boron; a tunnel junction layer 13 adjacent to the recording layer 14; and a reference layer 12 adjacent to the tunnel junction layer 13, the first ferromagnetic layer 24 and the reference layer 12 being magnetized in a direction perpendicular to the film surface, wherein the recording layer 14 has a hafnium layer 25 adjacent to the first ferromagnetic layer 24.

Description

[Technical field]

[0001] The present invention relates to a tunnel junction laminated film, a magnetic memory element, and a magnetic memory. [Background technology]

[0002] As a next-generation non-volatile magnetic memory that can achieve high speed and high rewrite resistance, MRAM (Magnetic Random Access Memory) using a magnetic tunnel junction element (Magnetic Tunnel Junction: MTJ) as a memory element is known. As a next-generation magnetic memory element to be used in MRAM, STT-MRAM (Spin Transfer Torque Random Access Memory) element (see Patent Document 1) that uses spin transfer torque to reverse the magnetization of a magnetic tunnel junction has attracted attention.

[0003] An STT-MRAM element is composed of an MTJ that includes a three-layer structure of a ferromagnetic layer (also called the recording layer), a barrier layer (also called the tunnel junction layer), and a ferromagnetic layer (also called the reference layer). An STT-MRAM element has the property that the resistance of the element is higher when the magnetization directions of the recording layer and the reference layer are in the antiparallel state, and records data by corresponding the parallel and antiparallel states to 0 and 1. When a current is passed through the MTJ in an STT-MRAM element, electron spins aligned in a certain direction flow into the recording layer, and the torque of the electron spins that flow in reverses the magnetization direction of the recording layer. This allows the STT-MRAM element to switch between the parallel and antiparallel states and record data.

[0004] Write current I for spin-transfer magnetization reversal in perpendicular magnetic anisotropy magnetic tunnel junctions (p(perpendicular)-MTJs) CO and the thermal stability index Δ(=E / k B T), the following mathematical relationship is known:

[0005]

number

[0006] The thermal stability index Δ is expressed by the following formula:

[0007]

number

[0008] where α is the damping constant, e is the elementary charge, h (h with stroke notation in the formula) is the Dirac constant, P is the spin polarizability, S is the junction area, and k B is the Boltzmann constant, t is the thickness of the recording layer, T is the absolute temperature, K eff is the effective magnetic anisotropy energy density.

[0009] From the above formula (1), it is possible to maintain a high thermal stability index Δ and a low write current I CO In order to achieve this, a high K eff Moreover, the recording layer must have a low damping constant α. It is generally known that the damping constant is large in materials with large spin-orbit coupling. It is known that the spin-orbit coupling increases with increasing atomic number. [Prior art documents] [Patent documents]

[0010] [Patent Document 1] JP 2014-179447 A Summary of the Invention [Problem to be solved by the invention]

[0011] However, as STT-MRAM elements as magnetic memory elements are miniaturized to realize high-density magnetic memories, the thermal stability of the magnetization of the recording layer decreases, making it difficult for the recording layer to maintain the recorded data, and reducing nonvolatility. Therefore, there is a demand to improve the thermal stability of the recording layer of magnetic memory elements.

[0012] Therefore, the present invention has been made in consideration of the above-mentioned problems, and has an object to provide a tunnel junction laminated film having high thermal stability, and a magnetic memory element and a magnetic memory using the tunnel junction laminated film. [Means for solving the problem]

[0013] The tunnel junction stacked film according to the present invention comprises a recording layer having a first ferromagnetic layer containing boron, a tunnel junction layer adjacent to the recording layer, and a reference layer adjacent to the tunnel junction layer, the first ferromagnetic layer and the reference layer being magnetized in a direction perpendicular to the film surface, and the recording layer has a hafnium layer adjacent to the first ferromagnetic layer.

[0014] The magnetic memory element according to the present invention comprises the above-mentioned tunnel junction stacked film, a first terminal electrically connected to the reference layer, and a second terminal electrically connected to the recording layer, and a write current flowing between the first terminal and the second terminal reverses the magnetization direction of the recording layer.

[0015] A magnetic memory according to the present invention includes the above-mentioned magnetic memory element. Effect of the Invention

[0016] According to the present invention, since the recording layer has a hafnium layer adjacent to the first ferromagnetic layer, the perpendicular magnetic anisotropy of the first ferromagnetic layer can be improved, and as a result, the thermal stability of the magnetization of the first ferromagnetic layer adjacent to the hafnium layer is improved, and the thermal stability of the recording layer is high. Therefore, it is possible to provide a tunnel junction stacked film with high thermal stability, and further to provide a magnetic memory element and a magnetic memory with high thermal stability. [Brief description of the drawings]

[0017] [Figure 1] 1 is a schematic diagram showing a cross section of a tunnel junction laminated film of the present invention. [Diagram 2] 1 is a schematic diagram showing a cross section of a tunnel-junction stacked film according to a first embodiment. [Diagram 3]1 is a schematic diagram illustrating an example of a tunnel junction stacked film according to a first embodiment. [Figure 4A] 1A to 1C are schematic cross-sectional views illustrating a method for writing data "0" to a magnetic memory element storing data "1". [Figure 4B] 1A to 1C are schematic cross-sectional views illustrating a method for writing data "0" to a magnetic memory element storing data "1". [Diagram 5] 1 is a block diagram of a magnetic memory in which a plurality of magnetic memory cell circuits each formed of a magnetic memory element according to a first embodiment are arranged. [Figure 6] FIG. 11 is a schematic diagram showing a cross section of a tunnel-junction stacked film according to a second embodiment. [Figure 7] FIG. 13 is a schematic diagram showing a cross section of a tunnel junction stacked film according to a modified example. [Figure 8] FIG. 13 is a schematic diagram showing a cross section of a tunnel junction stacked film according to a modified example. [Figure 9A] 1 is a graph showing the dependence of the magnetic anisotropy constant of a ferromagnetic layer on the Hf film thickness. [Figure 9B] 1 is a graph showing the Hf film thickness dependence of the saturation magnetization of a ferromagnetic layer. [Figure 10] FIG. 1 is a diagram showing the structure of a tunnel junction laminated film used in a verification experiment, and a graph showing the measurement results of the thickness of a magnetic dead layer of a ferromagnetic layer of the tunnel junction laminated film. [Figure 11] FIG. 11 is a schematic diagram showing a cross section of a tunnel-junction stacked film according to a third embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0018] First, the tunnel junction laminated film of the present invention will be outlined. As shown in FIG. 1, the tunnel junction laminated film 1 of the present invention is a magnetoresistance effect element including a recording layer 14, a tunnel junction layer 13 adjacent to the recording layer 14, and a reference layer 12 adjacent to the tunnel junction layer 13. The resistance value of the tunnel junction laminated film (hereinafter also referred to as MTJ film) 1 changes depending on whether the magnetization direction of the reference layer 12 and the magnetization direction of the recording layer 14 are parallel (the magnetization directions are almost the same direction) or antiparallel (the magnetization directions differ by about 180 degrees). When the MTJ film 1 is used in a magnetic memory element, data is stored by allocating 1-bit data of "0" and "1" to the parallel state and the antiparallel state by utilizing the fact that the resistance value of the MTJ film 1 differs between the parallel state and the antiparallel state. The MTJ film 1 is a perpendicular magnetization film in which the recording layer 14 and the reference layer 12 are magnetized in a direction perpendicular to the film surface.

[0019] The recording layer 14 has a first ferromagnetic layer 24 containing boron and a hafnium layer (hereinafter also referred to as an Hf layer) 25 adjacent to the first ferromagnetic layer 24. The recording layer 14 may further include a second ferromagnetic layer and a non-magnetic insertion layer, which will be described later. The recording layer 14 is configured such that the first ferromagnetic layer 24 is magnetized in a direction perpendicular to the film surface, and the magnetization direction is reversible. The reference layer 12 includes at least one or more ferromagnetic layers magnetized in a direction perpendicular to the film surface, and is configured such that the magnetization direction is fixed. In this specification, when the reference layer 12 and the recording layer 14 have multiple ferromagnetic layers, the magnetization or magnetization direction of the reference layer 12 and the recording layer 14 simply means the magnetization or magnetization direction of the ferromagnetic layer adjacent to the tunnel junction layer 13 of each layer.

[0020] FIG. 1 shows an example in which the first ferromagnetic layer 24 is magnetized vertically upward with respect to the substrate 2 (hereinafter simply referred to as upward), and the reference layer 12 is magnetized vertically downward with respect to the substrate 2 (hereinafter simply referred to as downward). Furthermore, in FIG. 1, the magnetization of the first ferromagnetic layer 24 is represented by a white arrow as magnetization 24M, and the magnetization of the reference layer 12 is represented by a filled arrow as magnetization 12M, and the direction of the arrow indicates the magnetization direction. In the example shown in FIG. 1, the direction of the magnetization 24M of the first ferromagnetic layer 24 and the direction of the magnetization 12M of the reference layer 12 are antiparallel. In this specification, when the magnetization directions are said to be antiparallel, it means that the magnetization directions are different by approximately 180 degrees. Moreover, the filled arrow means that the magnetization direction is fixed, and the filled arrow means that the magnetization direction can be reversed. In reality, the magnetization direction also includes a component that does not face the magnetization direction (the direction of the arrow). Hereinafter, when magnetization is represented by an arrow in other drawings in this specification, the same applies.

[0021] There are various variations of the tunnel junction laminated film 1 of the present invention, and various variations of the tunnel junction laminated film 1 will be described below as embodiments.

[0022] (1) First embodiment (1-1) Configuration of the tunnel junction stacked film according to the first embodiment The tunnel junction laminated film of the first embodiment is a structure in which the recording layer 14 of the tunnel junction laminated film 1 shown in FIG. 1 is configured such that the Hf layer 25 is sandwiched between ferromagnetic layers. As shown in FIG. 2, in which the same components as those in FIG. 1 are given the same numbers, the MTJ film 1a of the first embodiment includes a reference layer 12, a tunnel junction layer 13, a recording layer 14a, and a nonmagnetic layer 27 containing oxygen atoms (hereinafter simply referred to as O) adjacent to the recording layer 14a. The recording layer 14a is a multilayer film having a first ferromagnetic layer 24, an Hf layer 25, and a second ferromagnetic layer 26 containing boron and being a perpendicular magnetization film, in which the first ferromagnetic layer 24 is adjacent to the tunnel junction layer 13 and the hafnium layer 25, the hafnium layer 25 is adjacent to the second ferromagnetic layer 26, and the second ferromagnetic layer 26 is adjacent to the nonmagnetic layer 27 containing O.

[0023] The reference layer 12 is composed of a ferromagnetic layer made of a multilayer film containing a Co layer, such as a Co (cobalt) / Pt (platinum) multilayer film, a Co / Pd (palladium) multilayer film, a Co / Ni (nickel) multilayer film, or a Co / Ir (iridium) multilayer film, an ordered alloy such as Mn-Ga (manganese-gallium), Mn-Ge (germanium), or Fe (iron)-Pt, or an alloy containing Co, such as Co-Pt, Co-Pd, Co-Cr (chromium)-Pt, Co-Cr-Ta-Pt, CoFeB, FeB, and CoB, or the like.

[0024] The reference layer 12 may include a plurality of ferromagnetic layers, and may have a multi-layer structure such as a ferromagnetic layer / non-magnetic coupling layer / ferromagnetic layer. In this case, the non-magnetic coupling layer is made of a non-magnetic material such as Ru (ruthenium), Rh (rhodium), Ir (iridium), Os (osmium) and Re (rhenium). By using such a multi-layer structure, the magnetizations of the two ferromagnetic layers can be antiferromagnetically coupled by interlayer interaction, and the magnetization direction of the reference layer 12 can be fixed.

[0025] In order to generate interface magnetic anisotropy at the interface between reference layer 12 and tunnel junction layer 13 and make the magnetization direction of reference layer 12 perpendicular to the film surface, the ferromagnetic layer constituting reference layer 12 (the ferromagnetic layer adjacent to tunnel junction layer 13 when reference layer 12 has a multi-layer structure) is preferably formed of a ferromagnetic material containing B (boron), particularly CoFeB, FeB or CoB. When reference layer 12 has a multi-layer structure, reference layer 12 has a multi-layer structure such as a ferromagnetic layer / non-magnetic coupling layer / ferromagnetic layer / exchange coupling layer made of Ta (tantalum), W (tungsten) or Mo (molybdenum) / ferromagnetic layer (adjacent to tunnel junction layer 13) made of CoFeB, FeB or CoB.

[0026] In this way, by inserting an exchange coupling layer made of Ta, W or Mo, the ferromagnetic layer made of CoFeB, FeB or CoB laminated on the exchange coupling layer can be made into an amorphous ferromagnetic layer, which is more preferable. The amorphous ferromagnetic layer means a ferromagnetic layer in which amorphous is dominant, and may contain crystals in part. The number of layers and the film thickness of the reference layer 12 are appropriately adjusted according to the size of the MTJ. The thickness of the reference layer 12 is not particularly limited, but if perpendicular magnetization caused by interface magnetic anisotropy is utilized, a thickness of 5.0 nm or less is preferable, and 3.0 nm or less, and more preferably 1.6 nm or less is more preferable.

[0027] Furthermore, since stacking MgO on an amorphous layer tends to form an MgO layer dominated by single crystals oriented in the (100) direction, it is easy to form tunnel junction layer 13 made of MgO(100) adjacent to reference layer 12, so it is desirable to form the layer (e.g., the top surface) of reference layer 12 closest to tunnel junction layer 13 from CoFeB, FeB or CoB. In this way, tunnel junction layer 13 made of MgO(100) can be grown on the amorphous ferromagnetic layer as a (100) highly oriented film with large grains in the in-plane direction, improving the in-plane uniformity of the orientation of MgO(100) and making it possible to improve the uniformity of the resistance change rate (MR change rate).

[0028] Note that the magnetization direction of reference layer 12 and the orientation of magnetization 12M may be fixed to the perpendicular direction by magnetocrystalline anisotropy or shape magnetic anisotropy instead of interface magnetic anisotropy.

[0029] In this case, the reference layer 12 is preferably composed of a ferromagnetic layer made of an alloy containing at least one of Co, Fe, Ni, and Mn. Specifically, the alloy containing Co is preferably alloys such as Co-Pt, Co-Pd, Co-Cr-Pt, and Co-Cr-Ta-Pt, and in particular, it is preferable that these alloys are so-called Co-rich alloys containing more Co than other elements. The alloy containing Fe is preferably alloys such as Fe-Pt and Fe-Pd, and in particular, it is preferable that these alloys are so-called Fe-rich alloys containing more Fe than other elements. The alloy containing Co and Fe is preferably alloys such as Co-Fe, Co-Fe-Pt, and Co-Fe-Pd. The alloy containing Co and Fe may be Co-rich or Fe-rich. The alloy containing Mn is preferably alloys such as Mn-Ga and Mn-Ge. In addition, the alloy containing at least one of the above-described Co, Fe, Ni, and Mn may contain small amounts of elements such as B (boron), C (carbon), N (nitrogen), O (oxygen), P (phosphorus), Al (aluminum), and Si (silicon).

[0030] The tunnel junction layer 13 is formed adjacent to the reference layer 12. The tunnel junction layer 13 is desirably made of a nonmagnetic material containing O, such as MgO, Al2O3, AlN, or MgAlO, in particular, MgO(100). The thickness of the tunnel junction layer 13 is 0.1 nm to 2.5 nm, preferably 0.5 nm to 1.5 nm.

[0031] The recording layer 14a is a multilayer film including a first ferromagnetic layer 24 adjacent to the tunnel junction layer 13, an Hf layer 25 adjacent to the first ferromagnetic layer 24, and a second ferromagnetic layer 26 adjacent to the Hf layer 25. The recording layer 14a has a ferromagnetically coupled structure in which the magnetization 24M of the first ferromagnetic layer 24 and the magnetization 26M of the second ferromagnetic layer 26 are ferromagnetically coupled. Therefore, the magnetizations of the first ferromagnetic layer 24 and the second ferromagnetic layer 26 are ferromagnetically coupled by interlayer interaction, and the magnetization directions are parallel.

[0032] In this embodiment, the material and thickness of the first ferromagnetic layer 24 are selected so that interface magnetic anisotropy occurs at the interface between the first ferromagnetic layer 24, which is the closest to the tunnel junction layer 13 of the recording layer 14a, and the tunnel junction layer 13, and the magnetization direction of the first ferromagnetic layer 24 is perpendicular to the film surface. Therefore, the first ferromagnetic layer 24 is a perpendicular magnetization film magnetized in a direction perpendicular to the film surface. The magnetization direction of the second ferromagnetic layer 26 is parallel to that of the first ferromagnetic layer 24 due to interlayer interaction, so that the second ferromagnetic layer 26 is a perpendicular magnetization film magnetized in a direction perpendicular to the film surface. The magnetization directions of the first ferromagnetic layer 24 and the second ferromagnetic layer 26 are not fixed, and the magnetization direction can be reversed between upward and downward with respect to the substrate 2. The magnetization directions of the first ferromagnetic layer 24 and the second ferromagnetic layer 26 reverse in unison, and when the magnetization direction of the first ferromagnetic layer 24 is reversed by a spin torque, which will be described later, the magnetization direction of the second ferromagnetic layer 26 also reverses.

[0033] The first ferromagnetic layer 24 is formed of a ferromagnetic material containing B, particularly CoFeB, FeB or CoB, in order to generate interface magnetic anisotropy in the first ferromagnetic layer 24. The second ferromagnetic layer 26 is preferably formed of a ferromagnetic material containing B, such as CoFeB, FeB or CoB, like the first ferromagnetic layer 24, in order to generate interface magnetic anisotropy at the interface with the nonmagnetic layer 27 containing O, which will be described later, and to facilitate magnetization perpendicular to the film surface. Alternatively, the second ferromagnetic layer 26 is preferably a multilayer film having a layer formed of a ferromagnetic material containing B, such as CoFeB, FeB or CoB, at a position adjacent to the nonmagnetic layer 27 containing O. The second ferromagnetic layer 26 may be composed of, for example, a multilayer film containing a Co layer, such as a Co / Pt multilayer film, a Co / Pd multilayer film, and a Co / Ni multilayer film; an ordered alloy, such as Mn-Ga, Mn-Ge, and Fe-Pt; or an alloy containing Co, such as Co-Pt, Co-Pd, Co-Cr-Pt, Co-Cr-Ta-Pt, CoFeB, and CoB.

[0034] The thicknesses of the first ferromagnetic layer 24 and the second ferromagnetic layer 26 are not particularly limited, but if perpendicular magnetization resulting from interface magnetic anisotropy is utilized, the thickness is preferably 5.0 nm or less, more preferably 3.0 nm or less, and further preferably 1.6 nm or less. The thicknesses of the first ferromagnetic layer 24 and the second ferromagnetic layer 26 are particularly preferably 0.5 nm to 4.0 nm. The total thickness of the first ferromagnetic layer 24 and the second ferromagnetic layer 26 is preferably 2.0 nm or more.

[0035] The Hf layer 25 is provided adjacent to the first ferromagnetic layer 24 and the second ferromagnetic layer 26. The Hf layer 25 is a thin film made of hafnium. The Hf layer 25 functions as a non-magnetic coupling layer that makes the recording layer 14a have a ferromagnetic coupling structure (ferromagnetically coupling the magnetization 24M of the first ferromagnetic layer 24 and the magnetization 26M of the second ferromagnetic layer 26 by interlayer interaction).

[0036] Moreover, the recording layer 14a has the Hf layer 25 adjacent to the first ferromagnetic layer 24 containing boron, and thus the perpendicular magnetic anisotropy is increased, and the first ferromagnetic layer 24 can be easily magnetized in the perpendicular direction to the film surface. Furthermore, the boron of the first ferromagnetic layer 24 is less likely to diffuse into the Hf layer 25 during the heat treatment process described below, compared to the case where a non-magnetic coupling layer made of Ta, W, or an alloy thereof is used. Therefore, the use of the Hf layer 25 can suppress the diffusion of boron in the first ferromagnetic layer 24 accompanying the heat treatment, suppress the increase in the saturation magnetization Ms of the first ferromagnetic layer 24 adjacent to the Hf layer 25 due to the heat treatment, and also suppress the increase in the perpendicular demagnetizing field of the first ferromagnetic layer 24. As a result, the magnitude of the perpendicular magnetic anisotropy can be further improved by the heat treatment, and the first ferromagnetic layer 24 can be easily magnetized in the perpendicular direction, compared to the case where the Hf layer 25 is not included. Therefore, the thermal stability of the first ferromagnetic layer 24 as a perpendicular magnetization film can be improved. In addition, the first ferromagnetic layer 24 can be made thicker and have perpendicular magnetization, which further improves thermal stability. Furthermore, in the first embodiment, the second ferromagnetic layer 26 is adjacent to the surface of the Hf layer 25 that faces the surface adjacent to the first ferromagnetic layer 24, so that the same effect is also produced on the second ferromagnetic layer 26 side, which further improves thermal stability.

[0037] Moreover, compared with Ta and W, atomic diffusion of Hf atoms due to heat is less likely to occur in Hf. Therefore, by using the Hf layer 25 as a nonmagnetic coupling layer for introducing interlayer interaction, atomic diffusion of atoms constituting the nonmagnetic coupling layer from the nonmagnetic coupling layer to the first ferromagnetic layer 24 and the second ferromagnetic layer 26 due to heat treatment can be suppressed more than when a nonmagnetic coupling layer made of Ta, W or an alloy thereof is used. That is, when a Ta layer or a W layer is inserted instead of the Hf layer 25, large diffusion occurs between CoFeB (the first ferromagnetic layer 24 and the second ferromagnetic layer 26) and Ta or W. In contrast, when the Hf layer 25 is inserted, diffusion between CoFeB (the first ferromagnetic layer 24 and the second ferromagnetic layer 26) and Hf is suppressed to a small extent. In the diffusion between CoFeB and Ta, W or Hf, it is known that the damping constant becomes large when heavy metals such as W, Ta, Hf, etc., which have a larger atomic number than Co or Fe, are mixed. It is preferable to select a heavy metal that has a small diffusion amount, that is, a small magnetic dead layer. When the film thickness t of the non-magnetic coupling layer (Hf layer, Ta layer, W layer) is 0.3 nm or more, the diffusion is suppressed when the Hf layer is inserted compared to when the Ta layer or W layer is inserted, and the increase in the damping constant α of CoFeB is also suppressed. Therefore, when the Hf layer is inserted, the write current I CO becomes smaller, which is preferable.

[0038] Therefore, the recording layer 14a of the MTJ film 1a has high thermal stability, and therefore, by using such an MTJ film 1a to fabricate the magnetic memory element 100, it is possible to provide the magnetic memory element 100 with high non-volatility.

[0039] The Hf layer 25 may contain Zr (zirconium). The Hf layer 25 is preferably formed to a thickness of 0.2 nm or more and 0.9 nm or less, more preferably 0.3 nm or more and 0.7 nm or less. To form the Hf layer 25 in a layered form, a thickness of about 0.2 nm is required. By making the thickness 0.3 nm or more, the effect of preventing boron diffusion from the first ferromagnetic layer 24 is greater than that of Ta or W. Considering the etching processability of the MTJ, the thinner the total film thickness, the better. Even if the thickness of the Hf layer 25 is made thicker than 0.7 nm, the perpendicular magnetic anisotropy of the first ferromagnetic layer 24 and the second ferromagnetic layer 26 adjacent to the Hf layer 25 is not improved much, so the film thickness of the Hf layer 25 is preferably 0.7 nm or less. Considering the need to ensure the uniformity of the film thickness over the entire wafer, the film thickness of the Hf layer 25 is preferably 0.9 nm or less.

[0040] The non-magnetic layer 27 containing O is preferably made of a non-magnetic material containing oxygen, such as MgO, MgOTi, MgOTiN, Al2O3, SiO2, or MgZnO. The non-magnetic layer 27 containing O generates interface magnetic anisotropy at the interface with the adjacent recording layer 14a (the second ferromagnetic layer 26 in the first embodiment), and can easily magnetize the recording layer 14a in a direction perpendicular to the film surface. In the first embodiment, a double interface structure can be formed in which the recording layer 14a is sandwiched between the tunnel junction layer 13 containing O and the non-magnetic layer 27 containing O. This can generate interface magnetic anisotropy at each of the interface between the tunnel junction layer 13 and the recording layer 14a and the interface between the recording layer 14a and the non-magnetic layer 27 containing O, and can increase the film thickness of the recording layer 14a to improve thermal stability. The thickness of the non-magnetic layer 27 containing O is not particularly limited, but is preferably 10 nm or less, and more preferably 5 nm or less. Moreover, the nonmagnetic layer 27 containing O preferably has a thickness equal to or less than that of the tunnel junction layer 13 .

[0041] The nonmagnetic layer 27 containing O may be made of a conductive oxide film. The conductive oxide film may be, for example, (1) rutile-MoO2 type oxides such as RuO2, VO2, CrO2, NbO2, MoO2, WO2, ReO2, RhO2, OsO2, IrO2, PtO2, V3O5, and Ti3O5, (2) NaCI type oxides such as TiO, VO, NbO, LaO, NdO, SmO, EuO, SrO, BaO, and NiO, (3) spinel type oxides such as LiTi2O4, LiV2O4, and Fe3O4, (4) Perovskite-ReO3 type oxides such as ReO3, CaCrO3, SrCrO3, BaMoO3, SrMoO3, CaMoO3, LaCuO3, CaRuO3, SrVO3, BaTiO3, (5) Corundum type oxides such as Ti2O3, V2O3, Rh2O3, (6) Oxide semiconductors such as ZnO, TiO2, SnO2, Cu2O, Ag2O, In2O3, WO3, or (7) TaO2.

[0042] The MTJ film 1a is fabricated by a general film formation method such as PVD (Physical Vapor Deposition) and lithography. For example, first, an underlayer (not shown in FIG. 2) is formed on a substrate (not shown in FIG. 2) on which electrodes and the like are formed, and then a reference layer 12 is formed on the underlayer. Next, a tunnel junction layer 13 is formed on the reference layer 12. Finally, a first ferromagnetic layer 24, an Hf layer 25, and a second ferromagnetic layer 26 are formed in this order on the tunnel junction layer 13 to fabricate a recording layer 14a, and a nonmagnetic layer 27 containing O is formed on the recording layer 14a. Thereafter, the MTJ film 1a is fabricated through a heat treatment process and a molding process described later.

[0043] (1-2) An example of the tunnel junction stacked film according to the first embodiment Hereinafter, a specific example of the tunnel-junction laminated film 1a according to the first embodiment of the present invention will be described with reference to Fig. 3. In the specific example shown in Fig. 3, the tunnel-junction laminated film 1a is formed on a substrate 2, and is provided with a first terminal 10 electrically connected to a reference layer 12 and a second terminal 16 electrically connected to a recording layer 14a, and is configured as a two-terminal magnetic memory element. In addition, in the tunnel-junction laminated film 1a, an underlayer 11 is provided between the first terminal 10 and the reference layer 12, and a cap layer 15 is provided between the second terminal 16 and a nonmagnetic layer 27 containing O.

[0044] In this way, since the first terminal 10 is electrically connected to the reference layer 12 and the second terminal 16 is electrically connected to the recording layer 14a, a current can be passed through the MTJ film 1a between the first terminal 10 and the second terminal 16. Therefore, the magnetization direction of the recording layer 14a of the MTJ film 1a can be reversed by a current passed between the first terminal 10 and the second terminal 16, and the MTJ film 1a can be transitioned between a parallel state and an anti-parallel state to store data, making it possible to use the STT-MRAM element as a magnetic memory element. In addition, the reference layer 12 is disposed closer to the substrate 2 than the recording layer 14a, forming a so-called bottom-pinned structure.

[0045] The substrate 2 is, for example, a Si substrate having a SiO2 film formed on its surface, and has a structure including transistors and multiple wiring layers. The first terminal 10 is formed on the surface of the substrate 2, and the second terminal 16 is formed on the cap layer 15. The first terminal 10 and the second terminal 16 are conductive layers formed of a metal having conductivity, such as Cu (copper), Al (aluminum) and Au (gold), or a compound of these metals. The first terminal 10 has a thickness of about 20 to 50 nm, and the second terminal 16 has a thickness of about 10 to 100 nm. Although not shown in FIG. 3 for convenience, in this example, the first terminal 10 formed on the surface of the substrate 2 is connected to a field effect transistor (FET) 111 (see FIG. 4 and FIG. 5) formed on the substrate 2, and the second terminal 16 is connected to a bit line BL1 described later (see FIG. 4 and FIG. 5). The substrate 2 may also include the first terminal 10.

[0046] The underlayer 11 is formed on the first terminal 10. The underlayer 11 is a layer that serves as a base for stacking the tunnel junction stacked film 1a, and has a flat surface. The underlayer 11 is, for example, a Ta layer with a thickness of about 5 nm. The underlayer 11 may be made of a metal material such as Cu, CuN (copper nitride), Au, Ag (silver), Ru, or an alloy thereof. The underlayer 11 may have a structure in which a plurality of layers of metal materials are stacked, for example, a structure such as Ta layer / Ru layer / Ta layer. The underlayer 11 may not be formed.

[0047] The tunnel junction stacked film 1a is composed of a reference layer 12, a tunnel junction layer 13, a recording layer 14a, and a nonmagnetic layer 27 containing O, which are stacked in this order on an underlayer 11. In the example shown in FIG. 3, the reference layer 12 is composed of [Co / Pt] n / Co multilayer ferromagnetic layer / Ru non-magnetic coupling layer / [Co / Pt] m The multilayer structure is composed of a ferromagnetic layer made of a multilayered Co film, an exchange coupling layer made of Ta or W, and a ferromagnetic layer made of CoFeB. n means that the Co / Pt multilayer film is repeatedly laminated n times, [Co / Pt] n [Co / Pt] / Co multilayer film means that the bottom and top layers are Co. m The same is true for the / Co multilayer film.

[0048] In the reference layer 12, since the tunnel junction layer 13 is made of MgO as described later, the ferromagnetic layer made of CoFeB becomes a perpendicular magnetization film due to the interface magnetic anisotropy. m The ferromagnetic layer made of [Co / Pt] is magnetically coupled to the ferromagnetic layer made of CoFeB through interlayer interaction, forming a perpendicular magnetization film. m / Co multilayer ferromagnetic layer and [Co / Pt] n The magnetization of the ferromagnetic layer made of the Ru / Co multilayer film is antiferromagnetically coupled by the Ru layer, and the magnetization directions are antiparallel to each other.

[0049] The reference layer 12 is, for example, CoFeB(1.5nm) / Ta(0.4nm) / [Co(0.25nm) / Pt(0.8nm)]3 / Co(1.0nm) / Ru(0.85nm) / Co(1.0nm) / [Co(0.25nm) / Pt(0.8nm)] 13 (A Co layer (1.0 nm) is adjacent to a Pt layer (0.8 nm).)

[0050] The tunnel junction layer 13 is made of MgO and has a thickness of 1.5 nm.

[0051] The recording layer 14a is composed of a first ferromagnetic layer 24 made of CoFeB, an Hf layer 25, and a second ferromagnetic layer 26 made of CoFeB, which are stacked in this order on the tunnel junction layer 13. For example, the recording layer 14a may be CoFeB (1.0 nm) / Hf (0.7 nm) / CoFeB (1.0 nm).

[0052] The non-magnetic layer 27 containing O is made of MgO. In this example, the non-magnetic layer 27 containing O and the tunnel junction layer 13 are made of MgO, and the recording layer 14a has a double interface structure. The thickness of the non-magnetic layer 27 containing O can be, for example, 1 nm.

[0053] The cap layer 15 is formed on the nonmagnetic layer 27 containing O. The cap layer 15 is made of, for example, Ta or W, and has electrical conductivity. The thickness of the cap layer 15 may be, for example, 1.0 nm. The cap layer 15 does not necessarily have to be provided.

[0054] The magnetic memory element shown in Fig. 3 is fabricated by a general film formation method such as PVD (Physical Vapor Deposition) and lithography technology. First, the first terminal 10, the underlayer 11, the MTJ film 1a, the cap layer 15, and the second terminal 16 are laminated in this order on the surface of the substrate 2, and a multilayer film is fabricated by heat treatment at a temperature of about 300°C to 400°C. After that, the multilayer film is formed into a pillar shape by lithography technology, and the magnetic memory element 100 is fabricated. The pillar shape can be various shapes such as a cylindrical shape, a rectangular prism, or a polygonal prism.

[0055] (1-3) Methods for writing and reading data from magnetic memory elements A method of writing data to a magnetic memory element using the MTJ film 1a will be described with reference to FIGS. 4A and 4B, in which the same components as those in FIG. 2 are assigned the same numbers. As shown in FIG. 4A, the magnetic memory element 100 is a two-terminal memory including a first terminal 10 electrically connected to the reference layer 12 via an underlayer 11, and a second terminal 16 electrically connected to the recording layer 14 via a nonmagnetic layer 17 containing O and a cap layer 15. In the magnetic memory element 100, the resistance value of the MTJ film 1a changes depending on whether the magnetization directions of the recording layer 14a and the reference layer 12 are parallel or antiparallel. When the recording layer 14a and the reference layer 12 are multilayer films, the resistance value of the MTJ film 1a changes depending on whether the magnetization directions of the ferromagnetic layers adjacent to the tunnel junction layer 13 (for example, the first ferromagnetic layer 24 of the recording layer 14a and the reference layer 12) of the ferromagnetic layers of the recording layer 14a and the reference layer 12 are parallel or antiparallel.

[0056] Therefore, in this specification, when the recording layer 14a and the reference layer 12 are said to be in a parallel state, this also means that the magnetization directions of the tunnel junction layer 13 and the adjacent ferromagnetic layers are parallel, and when the recording layer 14a and the reference layer 12 are said to be in an anti-parallel state, this also means that the magnetization directions of the tunnel junction layer 13 and the adjacent ferromagnetic layers are anti-parallel.

[0057] In the magnetic memory element 100, the resistance value of the MTJ film 1a is different between the parallel state and the antiparallel state, and one bit of data, "0" and "1", is assigned to the parallel state and the antiparallel state to store data in the magnetic memory element 100. Since the magnetization direction of the recording layer 14a of the magnetic memory element 100 is reversible, the MTJ film 1a is transitioned between the parallel state and the antiparallel state by reversing the magnetization direction of the recording layer 14a, and the MTJ film 1a that has stored "0" is made to store "1" and the MTJ film 1a that has stored "1" is made to store "0". In this specification, changing the resistance value of the MTJ film 1a by reversing the magnetization direction of the recording layer 14a in this manner is also referred to as writing data.

[0058] A writing method of the magnetic memory element 100 will be described in more detail. In FIG. 4A and FIG. 4B, the first terminal 10 of the magnetic memory element 100 is connected to the drain of a field effect transistor 111, and the second terminal 16 is connected to a bit line BL1. The gate of the transistor 111 is connected to a word line WL1, and the source is connected to a source line SL1. Therefore, when a predetermined voltage is applied from the word line WL1 to the gate of the transistor 111 to turn on the transistor 111, a write current Iw can be passed through the MTJ film 1a from the first terminal 10 to the second terminal 16 or from the second terminal 16 to the first terminal 10 according to the potential difference between the bit line BL1 and the source line SL1. In FIG. 4A and FIG. 4B, the substrate 2 is omitted for convenience, but in reality, the transistor 111 is formed on the substrate 2.

[0059] First, a case where data "0" is written to the magnetic memory element 100 storing data "1" will be described. Here, as shown in Fig. 4A, the magnetic memory element 100 is in an initial state where the magnetization direction of the recording layer 14a is upward, the magnetization direction of the reference layer 12 is downward, and the MTJ film 1a is in an anti-parallel state, storing data "1". Also, the transistor 111 is turned off.

[0060] First, the bit line BL1 is set to a write voltage Vw. Then, the word line WL1 is set to a high level, and the transistor 111 is turned on. At this time, the second terminal 16 to which the write voltage Vw is applied from the bit line BL1 has a higher voltage than the first terminal 10, so that the write current Iw flows from the second terminal 16 to the first terminal 10, passing through the MTJ film 1a.

[0061] The write current Iw flows from the recording layer 14a to the reference layer 12, so that electrons flow from the reference layer 12 to the recording layer 14a. Since the magnetization directions of the reference layer 12 and the recording layer 14a are antiparallel, this flow of electrons causes spins antiparallel to the magnetization direction of the recording layer 14a to flow into the recording layer 14a. Since the spins flowing into the recording layer 14a are antiparallel to the magnetization direction of the recording layer 14a, a torque acts to reverse the magnetization direction of the recording layer 14a due to the flowing spins. This torque reverses the magnetization direction of the recording layer 14a, and the MTJ film 1a becomes parallel, so that data "0" is stored. In reality, since the recording layer 14a has a ferromagnetically coupled structure, the magnetization direction of the first ferromagnetic layer 24 adjacent to the tunnel junction layer 13 is reversed by the flowing spins, and accordingly, the magnetization 26M of the second ferromagnetic layer 26 ferromagnetically coupled to the magnetization 24M of the first ferromagnetic layer 24 is also reversed. After a predetermined time has elapsed since the transistor 111 was turned on, the word line WL1 is set to a low level to turn off the transistor 111, lower the voltage of the bit line BL1, and stop the write current Iw.

[0062] Next, a case where data "1" is written to the magnetic memory element 100 storing data "0" will be described. Here, as shown in Fig. 4B, the magnetic memory element 100 is in an initial state where the magnetization direction of the recording layer 14a is downward, the magnetization direction of the reference layer 12 is downward, and the MTJ film 1a is in a parallel state, storing data "0". Also, the transistor 111 is turned off.

[0063] First, the source line SL is set to a write voltage Vw. Then, the word line WL1 is set to a high level to turn on the transistor 111. At this time, the first terminal 10 to which the write voltage Vw is applied from the source line SL1 has a higher voltage than the second terminal 16, so that the write current Iw flows from the first terminal 10 to the second terminal 16 through the MTJ film 1a.

[0064] The write current Iw flows from the reference layer 12 to the recording layer 14a, and electrons flow from the recording layer 14a to the reference layer 12. Since the magnetization directions of the reference layer 12 and the recording layer 14a are parallel, this flow of electrons causes spins parallel to the magnetization direction of the reference layer 12 to flow into the reference layer 12. On the other hand, the recording layer 14a also has spins that are not parallel to the magnetization direction of the reference layer 12, and these spins are scattered at the interface between the tunnel junction layer 13 and the reference layer 12 and flow again into the recording layer 14a. Since the spins that have flowed back into the recording layer 14a are oriented in a direction different from the magnetization direction of the recording layer 14a, they exert a torque on the magnetization of the recording layer 14a (the magnetization 24M of the first ferromagnetic layer 24). This torque reverses the magnetization direction of the recording layer 14a, causing the MTJ film 1a to become antiparallel, and data "1" is stored. In reality, since the recording layer 14a has a ferromagnetically coupled structure, the magnetization direction of the second ferromagnetic layer 26 also reverses in accordance with the magnetization reversal of the first ferromagnetic layer 24. After a predetermined time has elapsed since the transistor 111 was turned on, the word line WL1 is set to a low level to turn off the transistor 111, lower the voltage of the source line SL1, and stop the write current Iw.

[0065] In this way, in the magnetic memory element 100, by passing a write current Iw through the MTJ film 1a between the first terminal 10 and the second terminal 16, the magnetization direction of the recording layer 14a can be reversed and data "0" or data "1" can be written.

[0066] Next, a reading method will be described. With reference to Fig. 4A, an example will be described in which data is read from the magnetic memory element 100 storing data "1". In this case, in the initial state, as shown in Fig. 4A, the magnetization direction of the recording layer 14a of the magnetic memory element 100 is upward, the magnetization direction of the reference layer 12 is downward, and the MTJ film 1a is in an anti-parallel state, storing data "1". Also, it is assumed that the transistor 111 is turned off.

[0067] First, the bit line BL1 is set to a read voltage Vr. The read voltage Vr is a voltage lower than the write voltage Vw, and is set to a voltage at which the magnetization direction of the recording layer 14a does not reverse. After that, the word line WL1 is set to a high level, and the transistor 111 is turned on. At this time, the second terminal 16 to which the read voltage Vr is applied from the bit line BL1 has a higher voltage than the first terminal 10, so that the read current Ir flows from the second terminal 16 to the first terminal 10, penetrating the MTJ film 1a. The read current Ir is detected by a current detector (not shown). The magnitude of the read current Ir changes depending on the resistance value of the MTJ, so it is possible to read out whether the MTJ is in a parallel state or an antiparallel state, that is, whether the MTJ stores data "0" or data "1", from the magnitude of the read current Ir. Therefore, data "1" can be read out from the magnitude of the read current Ir. After a predetermined time has elapsed since the transistor 111 was turned on, the word line WL1 is set to a low level to turn off the transistor 111, lowering the voltage of the bit line BL1 and stopping the read current Ir.

[0068] The same method can be used to read data from the magnetic memory element 100 that stores data "0," so a description thereof will be omitted. Similarly, when a read current Ir is passed from the first terminal 10 to the second terminal 16, the data stored in the magnetic memory element 100 can be read from the current value of the read current Ir.

[0069] (1-4) Magnetic memory equipped with the magnetic memory element of the present invention Next, a magnetic memory cell circuit using the magnetic memory element 100 having the above configuration as a memory element and a magnetic memory integrating the magnetic memory cell circuit will be described with reference to FIG. 5, in which the same components as those in FIG. 4A are given the same reference numerals. The area surrounded by the dotted line in FIG. 5 is a magnetic memory cell circuit 300 for one bit. This magnetic memory cell circuit 300 includes the magnetic memory element 100 constituting a memory cell for one bit, a bit line BL1, a source line SL1, a word line WL1, and a transistor 111. For convenience, FIG. 5 shows the magnetic memory element 100 in a schematic manner.

[0070] Next, the magnetic memory 200 will be described. The magnetic memory 200 includes a plurality of bit lines, a plurality of source lines, a plurality of word lines, a plurality of magnetic memory cell circuits 300, an X driver 203, a Y driver 202, and a controller 201. For convenience, only two bit lines BL1 and BL2, two source lines SL1 and SL2, and three word lines WL1, WL2, and WL3 are shown in FIG. 5. The magnetic memory cell circuits 300 are disposed near the intersections of the bit lines, the source lines, and the word lines.

[0071] The X driver 203 is connected to a plurality of bit lines (BL1, BL2) and a plurality of source lines (SL1, SL2), decodes an address received from the controller 201, and applies a write voltage Vw or a read voltage Vr to the bit line or source line of the row to be accessed. The X driver 203 also includes a current detector (not shown in FIG. 5) and can detect the read current Ir flowing through the magnetic memory element 100 of the selected magnetic memory cell circuit 300 and read the data stored in the magnetic memory element 100.

[0072] The Y driver 202 is connected to a plurality of word lines (WL1, WL2, WL3), decodes an address received by the controller 201, and sets the voltage of the word line of the column to be accessed to a high level or a low level.

[0073] The controller 201 controls the X driver 203 and the Y driver 202 in response to data writing or data reading. The controller 201 transmits the address of the magnetic memory cell circuit 300 to be written to the X driver 203 and the Y driver 202, and transmits a data signal representing the data to be written to the X driver. The X driver 203 selects a bit line and a source line based on the received address, and applies a write voltage Vw to either the bit line or the source line based on the received data signal. The Y driver 202 selects a word line based on the received address, and sets the voltage of the word line to a high level. By the operation of the X driver 203 and the Y driver 202, a write current Iw flows through the magnetic memory element 100 of the magnetic memory cell circuit 300 selected by the controller 201, and data is written.

[0074] The controller 201 transmits the address of the magnetic memory cell circuit 300 to be read from to the X driver 203 and the Y driver 202. The X driver 203 selects a bit line and a source line based on the received address, and applies a read voltage Vr to either the bit line or the source line. The Y driver 202 selects a word line based on the received address, and sets the voltage of the word line to a high level. By the operation of the X driver 203 and the Y driver 202, a read current Ir flows through the magnetic memory element 100 of the magnetic memory cell circuit 300 selected by the controller 201, and the read current Ir is detected by the X driver 203, and data is read out.

[0075] (1-5) Action and Effects In the above configuration, the tunnel junction stacked film 1a of the first embodiment includes a recording layer 14a having a first ferromagnetic layer 24 containing boron, a tunnel junction layer 13 adjacent to the recording layer 14a, and a reference layer 12 adjacent to the tunnel junction layer 13, the first ferromagnetic layer 24 and the reference layer 12 are magnetized in a direction perpendicular to the film surface, and the recording layer 14a is configured to have a hafnium layer 25 adjacent to the first ferromagnetic layer 24.

[0076] Therefore, in the tunnel junction laminated film 1a, since the recording layer 14a has the hafnium layer 25 adjacent to the first ferromagnetic layer 24, the perpendicular magnetic anisotropy of the first ferromagnetic layer 24 can be improved, and as a result, the thermal stability of the magnetization of the first ferromagnetic layer 24 adjacent to the hafnium layer 25 is improved, and the thermal stability of the recording layer 14a is high. Therefore, it is possible to provide the tunnel junction laminated film 1a having high thermal stability, and by using the tunnel junction laminated film 1a having high thermal stability in the magnetic memory element 100 or the magnetic memory 200, it is possible to provide the magnetic memory element 100 and the magnetic memory 200 having high non-volatility.

[0077] Furthermore, in the tunnel junction laminated film 1a, the recording layer 14a has the second ferromagnetic layer 26 containing boron, the tunnel junction layer 13 is adjacent to the first ferromagnetic layer 24, the first ferromagnetic layer 24 is adjacent to the hafnium layer 25, the hafnium layer 25 is adjacent to the second ferromagnetic layer 26, and the second ferromagnetic layer 26 is adjacent to the nonmagnetic layer 27 containing O (oxygen atoms), thereby improving the perpendicular magnetic anisotropy of the second ferromagnetic layer 26, improving the thermal stability of the second ferromagnetic layer 26, and further increasing the thermal stability of the recording layer 14. As a result, a tunnel junction laminated film 1a with higher thermal stability can be provided.

[0078] (2) Second embodiment (2-1) Tunnel Junction Stacked Film of the Second Embodiment The tunnel junction laminated film of the second embodiment differs from the tunnel junction laminated film of the first embodiment in the configuration of the recording layer. Since the other configurations and the write / read operations are the same as those of the first embodiment, the configuration of the recording layer 14 will be mainly described.

[0079] 6, in which the same components as in FIG. 1 are given the same numbers, the recording layer 14 of the tunnel junction stacked film (MTJ film) 1b of the second embodiment is composed of a first ferromagnetic layer 24 adjacent to the tunnel junction layer 13, and an Hf layer 25 adjacent to the first ferromagnetic layer 24. Furthermore, in the second embodiment, the MTJ film 1b includes a cap layer 15 adjacent to the Hf layer 25 of the recording layer 14.

[0080] The first ferromagnetic layer 24 is formed on the tunnel junction layer 13 with a thickness of about 1.0 nm to 4.0 nm, and is made of a ferromagnetic material containing B, such as CoFeB, FeB, or CoB. In the second embodiment, the first ferromagnetic layer 24 may be made of one ferromagnetic layer, or may have a multilayer structure such as a ferromagnetic layer / non-magnetic coupling layer / ferromagnetic layer, or a multilayer structure in which layers made of different materials are alternately stacked. The white arrow in FIG. 6 indicates the direction of magnetization 24M of the first ferromagnetic layer 24. In FIG. 6, the magnetization 24M is perpendicular to the film surface, indicating that the first ferromagnetic layer 24 is a perpendicular magnetization film. When the first ferromagnetic layer 24 has a multilayer structure, the magnetization 24M in FIG. 6 indicates the magnetization direction of the ferromagnetic layer adjacent to the tunnel junction layer 13.

[0081] In the second embodiment, the Hf layer 25 is disposed in the multi-layered recording layer 14 at a position farthest from the tunnel junction layer 13 adjacent to the recording layer 14, and the surface opposite to the surface adjacent to the first ferromagnetic layer 24 is adjacent to the cap layer 15. The thickness of the Hf layer 25 is preferably 0.2 nm or more and 0.9 nm or less. To form the Hf layer 25 in a layered form, a thickness of about 0.2 nm is required. By making the thickness 0.3 nm or more, the effect of preventing boron diffusion from the first ferromagnetic layer 24 is greater than that of Ta or W. In consideration of the etching processability of the MTJ, the thinner the total film thickness, the better. Even if the thickness of the Hf layer 25 is made thicker than 0.7 nm, the perpendicular magnetic anisotropy of the first ferromagnetic layer 24 adjacent to the Hf layer 25 is not improved much, so the film thickness of the Hf layer 25 is preferably 0.7 nm or less. In consideration of ensuring the uniformity of the film thickness over the entire wafer, the film thickness of the Hf layer 25 is preferably 0.9 nm or less. Furthermore, when the Hf layer 25 is disposed in the recording layer 14 at a position farthest from the tunnel junction layer 13 as in the second embodiment, the thickness of the Hf layer 25 is more preferably 0.3 nm or more and 5.0 nm or less.

[0082] Furthermore, in the second embodiment, the cap layer 15 is made of, for example, Ta, W, or an alloy thereof having electrical conductivity, so as not to increase the resistance of the MTJ film 1b. The resistance of the MTJ film 1b can be reduced more than when a nonmagnetic layer containing O is used as the cap layer.

[0083] Such an MTJ film 1b has an increased perpendicular magnetic anisotropy and can be easily magnetized in a direction perpendicular to the film surface by having the Hf layer 25 adjacent to the first ferromagnetic layer 24 containing boron. In addition, since the diffusion of B from the first ferromagnetic layer 24 to the Hf layer 25 and the cap layer 15 during heat treatment can be suppressed, an increase in the saturation magnetization Ms of the first ferromagnetic layer 24 can be suppressed, and an increase in the perpendicular demagnetizing field of the first ferromagnetic layer 24 can also be suppressed. As a result, the magnitude of the perpendicular magnetic anisotropy can be further improved, and the thermal stability of the first ferromagnetic layer 24 can be improved. Furthermore, since the MTJ film 1b has the Hf layer 25 at the interface between the first ferromagnetic layer 24 of the recording layer 14 and the cap layer 15, the diffusion of atoms constituting the cap layer 15 from the cap layer 15 to the first ferromagnetic layer 24 during heat treatment is suppressed compared to the case where a Ta layer or W layer is inserted instead of the Hf layer 25 or where the Hf layer 25 is not present, etc., so that it is possible to suppress a decrease in the saturation magnetization Ms of the first ferromagnetic layer 24 and a decrease in thermal stability. Therefore, the thermal stability of the MTJ film 1b can be further improved.

[0084] Furthermore, the Hf layer 25 adjacent to the first ferromagnetic layer 24 itself can be used as the cap layer 15. In this case as well, the perpendicular magnetic anisotropy of the first ferromagnetic layer 24 can be improved, and the thermal stability of the MTJ film can be improved. Since Hf is a metal having electrical conductivity, the resistance of the MTJ film can also be reduced by using the Hf layer 25 itself as the cap layer 15.

[0085] The recording layer 14 may have a laminated ferrimagnetic structure like the recording layer 14a of the first embodiment. For example, the recording layer 14 has a multi-layer structure of a second ferromagnetic layer / a non-magnetic coupling layer / a first ferromagnetic layer from the tunnel junction layer 13 side, and an Hf layer is inserted at the interface between the first ferromagnetic layer and the cap layer (an Hf layer 25 is provided adjacent to the first ferromagnetic layer disposed at the position farthest from the tunnel junction layer 13 in the recording layer 14 and facing the tunnel junction layer 13 with the first ferromagnetic layer sandwiched therebetween). In this case, the perpendicular magnetic anisotropy of the first ferromagnetic layer 24 can be improved.

[0086] In this way, by fabricating a magnetic memory element using the MTJ film 1b, the thermal stability of the recording layer 32 is improved and a conductive non-magnetic metal can be used for the cap layer, thereby providing a magnetic memory element that is highly non-volatile and has low resistance.

[0087] (2-2) Actions and Effects In the above configuration, the tunnel junction stacked film 1b of the second embodiment includes a recording layer 14 having a first ferromagnetic layer 24 containing boron, a tunnel junction layer 13 adjacent to the recording layer 14, and a reference layer 12 adjacent to the tunnel junction layer 13, the first ferromagnetic layer 24 and the reference layer 12 are magnetized in a direction perpendicular to the film surface, and the recording layer 14 is configured to have an Hf layer 25 adjacent to the first ferromagnetic layer 24.

[0088] Therefore, in the tunnel junction laminated film 1b, since the recording layer 14 has the Hf layer 25 adjacent to the first ferromagnetic layer 24, the perpendicular magnetic anisotropy of the first ferromagnetic layer 24 can be improved, and as a result, the thermal stability of the magnetization of the first ferromagnetic layer 24 adjacent to the Hf layer 25 is improved, and the thermal stability of the recording layer 14 is high. Therefore, it is possible to provide the tunnel junction laminated film 1b with high thermal stability, and by using the tunnel junction laminated film 1b with high thermal stability in a magnetic memory element or a magnetic memory, it is possible to provide a magnetic memory element and a magnetic memory with high non-volatility.

[0089] Furthermore, by configuring the tunnel junction stacked film 1b so that the Hf layer 25 is disposed at the farthest position from the tunnel junction layer 13 in the recording layer 14, it is possible to suppress the diffusion of atoms of the material constituting the layer adjacent to the Hf layer 25, such as the cap layer 15, into the first ferromagnetic layer 24, and to suppress the decrease in the saturation magnetization Ms of the first ferromagnetic layer 24 and the decrease in thermal stability. Therefore, the MTJ film 1b can further improve the thermal stability.

[0090] (3) Modifications It should be noted that the present invention is not limited to the above-described first and second embodiments, and various modifications are possible within the scope of the present invention.

[0091] (Variation 1) In the above first embodiment, the recording layer 14a of the MTJ film 1a has a multi-layer structure including a first ferromagnetic layer 24, an Hf layer 25, and a second ferromagnetic layer 26. However, the present invention is not limited to this. The recording layer 14c of the MTJ film 1c shown in FIG. 7 may have a multi-layer structure including a first ferromagnetic layer 24, an Hf layer 25, a nonmagnetic insertion layer 40, and a second ferromagnetic layer 26.

[0092] In the recording layer 14c of the first modification, the second ferromagnetic layer 26 is adjacent to the tunnel junction layer 13, and the first ferromagnetic layer 24 is adjacent to the nonmagnetic layer 27 containing O. In the recording layer 14c, a multilayer structure of a nonmagnetic insertion layer 40 and an Hf layer 25 is used as a nonmagnetic coupling layer to achieve a ferromagnetic coupling structure, and the nonmagnetic insertion layer 40 is adjacent to the second ferromagnetic layer 26, and the Hf layer 25 is adjacent to the first ferromagnetic layer 24. The surface of the Hf layer 25 opposite to the surface adjacent to the first ferromagnetic layer 24 is adjacent to the nonmagnetic insertion layer 40.

[0093] In the first modification, the recording layer 14c has a double interface structure sandwiched between the tunnel junction layer 13 containing O and the nonmagnetic layer 27 containing O, and an interface magnetic anisotropy is generated at each of the interface between the tunnel junction layer 13 and the recording layer 14c (second ferromagnetic layer 26) and the interface between the recording layer 14c (first ferromagnetic layer 24) and the nonmagnetic layer 27 containing O. This makes the first ferromagnetic layer 24 and the second ferromagnetic layer 26 of the recording layer 14c a perpendicular magnetization film. In the first modification, the first ferromagnetic layer 24 and the second ferromagnetic layer 26 are formed of a ferromagnetic material containing B, such as CoFeB, FeB, or CoB. The nonmagnetic insertion layer 40 is formed of Ta, W, Mo, or an alloy thereof, and has a thickness of about 0.2 to 1 nm. The first ferromagnetic layer 24 and the second ferromagnetic layer 26 may be a single layer or a multilayer.

[0094] The thickness of the Hf layer 25 is preferably 0.2 nm or more and 0.9 nm or less. To form the Hf layer 25 in a layered form, a thickness of about 0.2 nm is required. By making the thickness 0.3 nm or more, the effect of preventing boron diffusion from the first ferromagnetic layer 24 is greater than that of Ta or W. Considering the etching processability of the MTJ, the thinner the total film thickness, the better. Even if the thickness of the Hf layer 25 is made thicker than 0.7 nm, the perpendicular magnetic anisotropy of the first ferromagnetic layer 24 adjacent to the Hf layer 25 is not improved much, so the film thickness of the Hf layer 25 is preferably 0.7 nm or less. Considering the need to ensure the uniformity of the film thickness over the entire wafer, the film thickness of the Hf layer 25 is preferably 0.9 nm or less. Furthermore, as in variant example 1, when the second ferromagnetic layer 26 of the recording layer 14c is adjacent to the nonmagnetic insertion layer 40, the nonmagnetic insertion layer 40 is adjacent to the Hf layer 25, the Hf layer 25 is adjacent to the first ferromagnetic layer 24, and the first ferromagnetic layer 24 is adjacent to the nonmagnetic layer 27 containing O, it is further preferable that the thickness of the Hf layer 25 be 0.3 nm or more and 0.7 nm or less.

[0095] In this case, the first ferromagnetic layer 24 adjacent to the Hf layer 25 has its perpendicular magnetic anisotropy increased by heat treatment, and the diffusion of atoms constituting the nonmagnetic insertion layer 40 from the nonmagnetic insertion layer 40 to the first ferromagnetic layer 24 is suppressed, so that the decrease in saturation magnetization Ms of the first ferromagnetic layer 24 due to the diffusion of the atoms is small, and thermal stability can be improved.

[0096] On the other hand, in the second ferromagnetic layer 26 adjacent to the nonmagnetic insertion layer 40, since the Hf layer 25 is not inserted between the nonmagnetic insertion layer 40 and the second ferromagnetic layer 26, the atoms constituting the nonmagnetic insertion layer 40 diffuse from the nonmagnetic insertion layer 40 to the second ferromagnetic layer 26, the saturation magnetization Ms of the second ferromagnetic layer 26 decreases, the thermal stability becomes lower than that of the second ferromagnetic layer 26, and the magnetization direction becomes easier to reverse. As a result, the spin torque required for magnetization reversal of the magnetization 26M of the second ferromagnetic layer 26 decreases, and the write current Iw can be reduced. In addition, in the second ferromagnetic layer 26 adjacent to the nonmagnetic insertion layer 40, B is absorbed into the nonmagnetic insertion layer 40 due to the diffusion of B into the nonmagnetic insertion layer 40. As a result, for example, when the second ferromagnetic layer 26 is CoFeB, CoFe is formed in the second ferromagnetic layer 26, and the TMR ratio improves. In this way, as a result of B being removed from the second ferromagnetic layer 26, a ferromagnetic material not containing B is formed in a portion of the second ferromagnetic layer 26, which has the advantage of increasing the TMR ratio of the MTJ film 1c.

[0097] Therefore, in the recording layer 14c of the MTJ film 1c of the first modification example, since the second ferromagnetic layer 26, whose magnetization is reversed by spin torque, is easily reversed by spin torque, and since the first ferromagnetic layer 24 has high thermal stability, the thermal stability of the entire recording layer 14c can be improved, and further, the TMR ratio can be increased.

[0098] By using such an MTJ film 1c to fabricate a magnetic memory element, it is possible to provide a magnetic memory element that can be written with low energy, has high nonvolatility, and further has a large TMR ratio.

[0099] (Variation 2) In the above first embodiment, second embodiment, and modified example 1, a tunnel junction laminated film having a bottom-pinned structure (for example, FIG. 1) in which the reference layer is disposed closer to the substrate than the recording layer has been described as an example, but the present invention is not limited to this. A tunnel junction laminated film having a top-pinned structure in which the recording layer is disposed closer to the substrate than the reference layer may also be used, and in this case, the same effect as that of a tunnel junction laminated film having a bottom-pinned structure is also achieved. When the tunnel junction laminated film of the second embodiment has a top-pinned structure, it is preferable to insert an Hf layer so as to be adjacent to the underlayer.

[0100] (Variation 3) In the above-mentioned first embodiment and modification 1, the case where the recording layers 14a, 14c of the tunnel junction laminated films 1a, 1c have a ferromagnetic coupling structure has been described, but the present invention is not limited thereto. As in the tunnel junction laminated film 1d shown in FIG. 8, the recording layer 14d may have a laminated ferrimagnetic structure in which the magnetization 24M of the first ferromagnetic layer 24 and the magnetization 26M of the second ferromagnetic layer 26 are antiferromagnetically coupled by interlayer interaction. In the tunnel junction laminated film 1d of modification 3, the recording layer 14d is a multilayer film made of the first ferromagnetic layer 24, the Hf layer 25 adjacent to the first ferromagnetic layer 24, and the second ferromagnetic layer 26 adjacent to the Hf layer 25, as in the first embodiment. In this case, the recording layer 14d having the ferromagnetic coupling structure can be made into a laminated ferrimagnetic structure by appropriately adjusting the film thickness of the Hf layer 25 between the first ferromagnetic layer 24 and the second ferromagnetic layer 26. The other configurations are the same as those of the tunnel junction laminated film 1 of the first embodiment. Furthermore, the recording layer 14d may be a multi-layer structure of a ferromagnetic layer / non-magnetic insertion layer / Hf layer / ferromagnetic layer including B, a multi-layer structure of a ferromagnetic layer including B / Hf layer / ferromagnetic layer including B / Hf layer / ferromagnetic layer including B, or a multi-layer structure of a greater number of layers.

[0101] (Verification experiment) (Verification experiment 1) In verification experiment 1, in order to confirm the effect of the recording layer having a Hf layer adjacent to the ferromagnetic layer, Ta (7.0 nm), W-Ta alloy (3.0 nm), Hf (0.3 nm or 0.7 nm), CoFeB (1.15 nm to 1.7 nm), MgO (1.5 nm), CoFeB (0.4 nm), and Ta (1.0 nm) were sputtered in this order on a Si substrate with SiO2 formed on the surface, and then heat-treated at 400°C to fabricate a magnetic memory element. For comparison, a magnetic memory element was fabricated with the same structure as above except that it did not have a Hf layer. The magnetic anisotropy constant Keff and the effective film thickness t of the ferromagnetic layer of the fabricated magnetic memory element were measured. * The product of and the saturation magnetization Ms were evaluated using a VSM (Vibrating Sample Magnetometer).

[0102] The magnetic anisotropy constant Keff and the saturation magnetization Ms evaluated by VSM are shown in Fig. 9A and Fig. 9B. The horizontal axis of Fig. 9A is the thickness of the Hf layer, and the vertical axis is the magnetic anisotropy constant Keff vs. the thickness t * 9B, the horizontal axis is the thickness of the Hf layer, and the vertical axis is the saturation magnetization Ms. In FIG. 9B, the saturation magnetization Ms of the magnetic memory element is shown by a solid line labeled Ms(CoFeB / Hf / WTa), and the saturation magnetization Ms of bulk CoFeB is shown by a dotted line labeled Ms(CoFeB).

[0103] FIG. 9A shows that the perpendicular magnetic anisotropy is increased by having the Hf layer. Therefore, the perpendicular magnetic anisotropy of the ferromagnetic layer of the recording layer is increased by having the Hf layer, and the perpendicular magnetic film can be easily magnetized in the direction perpendicular to the film surface, and the perpendicular magnetic film can be fabricated up to a region where the ferromagnetic layer is thicker, so that it was confirmed that the thermal stability of the ferromagnetic layer can be improved. Also, FIG. 9B shows that the saturation magnetization Ms is reduced by having the Hf layer. That is, it is understood that the increase in the saturation magnetization Ms due to the heat treatment is suppressed. Therefore, the ferromagnetic layer of the recording layer can be suppressed from increasing in the saturation magnetization Ms, and as a result, the demagnetizing field in the perpendicular direction of the ferromagnetic layer can be suppressed from increasing, and the magnitude of the perpendicular magnetic anisotropy can be further improved by the heat treatment than when the Hf layer is not present, and the thermal stability can be improved. The thickness of the Hf layer is preferably 0.9 nm or less, and more preferably 0.7 nm or less. It can be seen that the diffusion of B in CoFeB can be almost suppressed by sandwiching a 0.7 nm Hf layer. Considering the etching processability of the MTJ, the thinner the total film thickness, the better, and since making the Hf layer 25 thicker than 0.7 nm does not significantly improve the perpendicular magnetic anisotropy of the first ferromagnetic layer 24 adjacent to the Hf layer 25, the film thickness of the Hf layer 25 is preferably 0.7 nm or less. Considering ensuring the uniformity of the film thickness over the entire wafer, the film thickness of the Hf layer 25 is preferably 0.9 nm or less.

[0104] (Verification experiment 2) In the verification experiment 2, a verification experiment was carried out to confirm the effect of the recording layer having the Hf layer as the non-magnetic coupling layer adjacent to the ferromagnetic layer, in particular, the effect of suppressing the atomic diffusion of the atoms constituting the non-magnetic coupling layer from the non-magnetic coupling layer to the first ferromagnetic layer 24 and the second ferromagnetic layer 26 by heat treatment, compared to the case where the non-magnetic coupling layer is made of other materials (Ta or W). Specifically, a tunnel junction laminated film having the structure shown on the left side of FIG. 10 (the numbers in parentheses in the figure indicate the layer thickness in nm) was fabricated, and the thickness of the magnetic dead layer of the ferromagnetic layer (CoFeB) was measured. The magnetic dead layer is a layer in the ferromagnetic layer (CoFeB) in the tunnel junction laminated film having the structure shown on the left side of FIG. 10 that has lost its magnetism. In verification experiment 2, in addition to the tunnel junction laminate film of the embodiment having a structure in which an Hf layer is inserted between two ferromagnetic layers, a tunnel junction laminate film having a structure in which a Ta layer is inserted between two ferromagnetic layers instead of an Hf layer and a tunnel junction laminate film having a structure in which a W layer is inserted were fabricated as comparative examples, and the thicknesses of the magnetic dead layers were similarly measured.

[0105] The tunnel junction laminated films of the examples and comparative examples were fabricated by laminating Ta (5.0 nm), CoFeB (0.4 nm), MgO (1.5 nm), CoFeB (1.0 nm), Ta, W or Hf (0-0.7 nm), CoFeB (1.0 nm), MgO (1.1 nm) and Ta (1.0 nm) in this order on a Si substrate having a SiO2 film formed on its surface, by a sputtering method, and then heat-treating at 400°C. The tunnel junction laminated films of the examples were fabricated with three Hf layers of 0.2 nm, 0.35 nm and 0.7 nm. The tunnel junction laminated films of the comparative examples were fabricated with three Hf layers of 0.2 nm, 0.35 nm and 0.7 nm, both in the case where a Ta layer was inserted and in the case where a W layer was inserted. The results are shown in the graph on the right side of FIG. 10.

[0106] In the graph on the right side of FIG. 10, the horizontal axis is the thickness t (nm) of the Hf layer, Ta layer, or W layer, and the vertical axis is the thickness (nm) of the magnetic dead layer. The solid line and black circle in the figure are the results of the W layer, the dashed line and white circle in the figure are the results of the Hf layer, and the dotted line and white square are the results of the Ta layer. From the graph, when the thickness t of the Hf layer, Ta layer, and W layer is 0.2 nm, the magnetic dead layer is very small regardless of the layer of the element inserted. It was revealed that when the thickness t of the Hf layer, Ta layer, and W layer is 0.3 nm or more, the thickness of the magnetic dead layer when the Ta layer or W layer is inserted is very large compared to the thickness of the magnetic dead layer when the Hf layer is inserted. This shows that when the Ta layer or W layer is inserted, a large diffusion occurs between CoFeB and Ta or W, whereas when the Hf layer is inserted, the diffusion between CoFeB and Hf is small and suppressed. It is known that in the diffusion between CoFeB and Ta, W, or Hf, when heavy metals with larger atomic numbers such as W, Ta, or Hf are mixed with Co or Fe, which have smaller atomic numbers, the damping constant becomes larger. It is preferable to select heavy metals that have a small amount of diffusion, that is, heavy metals that reduce the magnetic dead layer. When the thickness t of the Hf, Ta, and W layers is 0.3 nm or more, the insertion of an Hf layer suppresses diffusion compared to the insertion of a Ta or W layer, and the increase in the damping constant α of CoFeB is also suppressed. For this reason, the write current I CO The thickness of the Hf layer is preferably 0.2 nm or more, and more preferably 0.3 nm or more. To form the Hf layer in a layered form, a thickness of about 0.2 nm is necessary. In addition, by making the thickness 0.3 nm or more, the effect of preventing diffusion becomes greater compared to Ta or W.

[0107] (4) Third embodiment (4-1) Tunnel junction stacked film according to the third embodiment The tunnel junction laminated film of the third embodiment differs from the tunnel junction laminated film of the first embodiment in the configuration of the recording layer. Since the other configurations and the write / read operations are the same as those of the first embodiment, the configuration of the recording layer will be mainly described.

[0108] 11, in which the same components as those in FIG. 1 are given the same numbers, a recording layer 14e of a tunnel junction stacked film (MTJ film) 1e of the third embodiment is configured by stacking a first ferromagnetic layer 24 adjacent to the tunnel junction layer 13, a first Hf layer 25a adjacent to the first ferromagnetic layer 24, a second ferromagnetic layer 26 adjacent to the first Hf layer 25a, and a second Hf layer 25b adjacent to the second ferromagnetic layer 26, in this order. Furthermore, the MTJ film 1e includes a cap layer 15 adjacent to the second Hf layer 25b of the recording layer 14e.

[0109] The first Hf layer 25a is provided adjacent to the first ferromagnetic layer 24 and the second ferromagnetic layer 26. The first Hf layer 25a is a thin film formed of hafnium. The first Hf layer 25a functions as a non-magnetic coupling layer that makes the recording layer 14e a ferromagnetic coupling structure, and the recording layer 14e has a ferromagnetic coupling structure in which the magnetization 24M of the first ferromagnetic layer 24 and the magnetization 26M of the second ferromagnetic layer 26 are ferromagnetically coupled. The magnetizations of the first ferromagnetic layer 24 and the second ferromagnetic layer 26 are ferromagnetically coupled by interlayer interaction, and the magnetization directions are parallel. The white arrows in FIG. 11 represent the direction of the magnetization 24M of the first ferromagnetic layer 24 and the direction of the magnetization 26M of the second ferromagnetic layer 26. The magnetization 24M and the magnetization M26 are perpendicular to the film surface, indicating that the first ferromagnetic layer 24 and the second ferromagnetic layer 26 are perpendicular magnetization films.

[0110] The second Hf layer 25b is located in the multi-layered recording layer 14e at a position furthest from the tunnel junction layer 13 adjacent to the recording layer 14e, and the surface opposite to the surface adjacent to the second ferromagnetic layer 26 is adjacent to the cap layer 15.

[0111] In this embodiment, the first ferromagnetic layer 24, the first Hf layer 25a, and the second ferromagnetic layer 26 have the same configurations as the first ferromagnetic layer 24, the Hf layer 25, and the second ferromagnetic layer 26 described in the first embodiment, respectively. The second Hf layer 25b has the same configuration as the Hf layer 25 described in the second embodiment.

[0112] (4-2) Actions and Effects In the above configuration, the tunnel junction stacked film 1e of the third embodiment is configured to include a recording layer 14e having a first ferromagnetic layer 24 containing boron, a tunnel junction layer 13 adjacent to the recording layer 14e, and a reference layer 12 adjacent to the tunnel junction layer 13. Here, the recording layer 14e is configured to include the first ferromagnetic layer 24 adjacent to the tunnel junction layer 13, a first Hf layer 25a adjacent to the first ferromagnetic layer 24, a second ferromagnetic layer 26 adjacent to the first Hf layer 25a, and a second Hf layer 25b adjacent to the second ferromagnetic layer 26. It is further configured to include a cap layer 15 adjacent to the second Hf layer 25b of the recording layer 14e. The first ferromagnetic layer 24 and the reference layer 12 are configured to be magnetized in a direction perpendicular to the film surface.

[0113] The tunnel junction laminated film 1e is adjacent to the first Hf layer 25a, thereby improving the perpendicular magnetic anisotropy of the first ferromagnetic layer 24, improving the thermal stability of the magnetization of the first ferromagnetic layer 24, and increasing the thermal stability of the recording layer 14e. Therefore, the tunnel junction laminated film 1e having high thermal stability can be provided, and by using the tunnel junction laminated film 1e having high thermal stability in a magnetic memory element or a magnetic memory, a magnetic memory element and a magnetic memory having high non-volatility can be provided.

[0114] Furthermore, since the tunnel junction stacked film 1e is adjacent to the first Hf layer 25a and the second Hf layer 25b, the perpendicular magnetic anisotropy of the second ferromagnetic layer 26 can be improved, the thermal stability of the second ferromagnetic layer 26 can be improved, and the thermal stability of the recording layer 14e can be further increased, thereby providing a tunnel junction stacked film 1e with higher thermal stability.

[0115] Furthermore, by configuring the tunnel junction stacked film 1e so that the second Hf layer 25b is disposed at the position farthest from the tunnel junction layer 13 in the recording layer 14e, it is possible to suppress the diffusion of atoms of the material constituting the layer adjacent to the second Hf layer 25b, such as the cap layer 15, into the second ferromagnetic layer 26, and to suppress the decrease in saturation magnetization Ms of the second ferromagnetic layer 26 and the decrease in thermal stability. Therefore, the MTJ film 1e can further improve the thermal stability. [Explanation of symbols]

[0116] 1, 1a, 1b, 1c, 1d, 1e Tunnel junction stacked film 2. Board 14, 14a, 14c, 14d, 14e Recording layer 13 Tunnel junction layer 12, 12a reference layer 25 Hf layer 25a 1st Hf layer 25b 2nd Hf layer 27 Non-magnetic layer containing oxygen atoms 40 Non-magnetic insertion layer 100 Magnetic memory element 200 Magnetic Memory

Claims

1. A tunnel junction stacked film comprising a recording layer having a first ferromagnetic layer containing boron, a tunnel junction layer adjacent to the recording layer, and a reference layer adjacent to the tunnel junction layer, the first ferromagnetic layer and the reference layer being magnetized in a direction perpendicular to a film surface, The recording layer has a hafnium layer adjacent to the first ferromagnetic layer and having a thickness of 0.35 nm to 0.7 nm. Tunnel junction stacked film.

2. The hafnium layer is disposed at a position in the recording layer farthest from the tunnel junction layer. The tunnel junction laminated film according to claim 1 .

3. the recording layer has a second ferromagnetic layer containing boron; the tunnel junction layer is adjacent to the first ferromagnetic layer; the first ferromagnetic layer is adjacent to the hafnium layer; the hafnium layer is adjacent to the second ferromagnetic layer; The second ferromagnetic layer is adjacent to a nonmagnetic layer containing oxygen atoms. The tunnel junction laminated film according to claim 1 .

4. the recording layer has a second ferromagnetic layer containing boron; the tunnel junction layer is adjacent to the second ferromagnetic layer; the second ferromagnetic layer is adjacent to a nonmagnetic insertion layer; the nonmagnetic insertion layer is adjacent to the hafnium layer; the hafnium layer is adjacent to the first ferromagnetic layer; The first ferromagnetic layer is adjacent to a nonmagnetic layer containing oxygen atoms. The tunnel junction laminated film according to claim 1 .

5. The hafnium layer contains Zr. The tunnel junction laminated film according to any one of claims 1 to 4.

6. A tunnel junction laminated film according to any one of claims 1 to 5, A first terminal electrically connected to the reference layer; a second terminal electrically connected to the recording layer; A write current flowing between the first terminal and the second terminal reverses the magnetization direction of the recording layer. Magnetic memory element.

7. provided on one surface of the substrate, The reference layer is disposed closer to the substrate than the recording layer. The magnetic memory element according to claim 6 .

8. The magnetic memory element according to claim 6 or 7 is provided. Magnetic memory.

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