KR20200019557A - Magnetic Tunnel Junction Device and Magnetic Resistance Memory Device - Google Patents

Abstract

Provided is a magnetic tunnel junction element which can simplify a structure of a fixed layer of a magnetic tunnel junction element and reduce the number of stacked layers of the magnetic tunnel junction element. The magnetic tunnel junction element comprises: a free layer of which with the magnetization direction is variable; a fixed layer formed of a single layer while maintaining the magnetization direction in a predetermined direction; and an insulating layer laminated between the free layer and the fixed layer. At least one of the free layer and the fixed layer is an L1_1 type magnetic alloy film, and the insulating layer has a texture of (111).

Description

Magnetic tunnel junction element and magnetoresistive memory device {Magnetic TunnelunJunction Device and Magnetic Resistance Memory Device}

The present invention relates to a magnetic tunnel junction element and a magnetoresistive memory device.

Magnetoresistive elements having perpendicular magnetization can be read by the magnetoresistive effect and have high resistance to thermal disturbance due to miniaturization, and are expected to be the next generation of memories.

This next-generation memory has a free layer (also called a memory layer) having a variable magnetization direction, a fixed layer (also called a reference layer) maintaining a predetermined magnetization direction, and an insulating layer (tunnel barrier) disposed between the free layer and the fixed layer. It includes a magnetic tunnel junction (MTJ) element.

The spin polarization magnetic layer that basically constitutes such a next-generation memory requires a ferromagnetic material having high perpendicular magnetic anisotropy and high spin polarization rate. However, few materials have their own perpendicular magnetic anisotropy and experimentally high spin polarization. In addition, the material having perpendicular magnetic anisotropy and high spin polarization is only CoFeB alloy using interfacial magnetic anisotropy, and the material selection range is very narrow.

Currently, CoFeB alloy is being researched and developed as a spin polarized magnetic layer. Patent document 1 discloses a magnetic tunnel junction element in which a spacer layer having a lattice constant smaller than a spin polarization magnetic layer is brought into contact with a spin polarization magnetic layer to reduce the crystal lattice of the spin polarization magnetic layer in the x-axis and y-axis directions.

However, since the material itself does not have a large perpendicular magnetic anisotropy, Patent Document 1 uses a fixed layer in which a vertical magnetization holding layer is bonded. In many studies, the vertical magnetization retaining layer is a L1 ₀ type FePd, FePt, CoPd, or CoPt, Co / Pd multilayer (Co and Pd layered in the (001) axial direction) with a (001) texture. Or a Co / Pt multilayer film (a film in which Co and Pt are laminated in the (001) axial direction), and the easy magnetization axis is made of a ferromagnetic material directed in a direction perpendicular to the film surface.

In addition, the pinned layer may be configured by combining with a perpendicular magnetization holding layer and CoFeB, a ferromagnetic material having a high spin polarization rate. In addition, the magnetic tunnel junction element having a free layer and a fixed layer composed of CoFeB alloy has a (001) texture so as to obtain a high tunnel magneto resistance (TMR) effect from the relationship of the band structure with the insulating layer. Has

For example, an MgO film having a (001) texture is used as the insulating layer of the magnetic tunnel junction, and the base layer which improves the orientation of the vertical magnetization holding layer may also have a (001) texture. That is, the magnetic tunnel junction has a (001) texture by default.

[Patent Document 1] Japanese Unexamined Patent Publication (20) 10-238769

As described above, the magnetic tunnel junction element described in Patent Document 1 has a problem in that the structure of the fixed layer is complicated and the thickness becomes large.

In addition, due to the weak perpendicular magnetic anisotropy of the free layer, there is a problem in thermal stability and high density. On the other hand, Mn-Ge materials themselves, such as MnGa and MnGe, have been studied for magnetic materials having large perpendicular magnetic anisotropy. However, there was a problem that a high tunnel magnetoresistance effect could not be obtained in an experiment.

The magnetic tunnel junction element according to an embodiment includes a free layer having a variable magnetization direction, a fixed layer composed of a single layer while maintaining the magnetization direction in a predetermined direction, and an insulating layer laminated between the free layer and the fixed layer. at least one of the free layer and the fixed layer is the L1 ₁ type magnetic alloy film, the insulating layer has a texture (texture) of 111.

The magnetic tunnel junction element according to an embodiment does not include a vertical magnetization holding layer and a spacer layer, and may maintain a magnetization direction in a predetermined direction with a single spin polarization magnetic layer. Therefore, since the magnetic tunnel junction element has a simple fixed layer structure, the number of stacks of the magnetic tunnel junction element can be reduced.

Preferably, the insulating layer of the magnetic tunnel junction device according to an embodiment includes MgO, MgAl ₂ O ₄ , MgGa ₂ O ₄ , ZnAl ₂ O ₄ or ZnGa ₂ O ₄ having a texture of 111. can do.

The magnetic tunnel junction element according to an embodiment may have a large tunnel magnetoresistance effect and high perpendicular magnetic anisotropy.

The magnetic tunnel junction element according to an embodiment may preferably further include a base layer having a texture of (111).

According to the magnetic tunnel junction element according to the embodiment, since the (111) plane has more coordination number (coordination number) than the (001) plane, the bond in the plane becomes stronger, so that the crystal structure is stable and consequently, Atom diffusion can be suppressed.

Preferably, the pinned layer of the magnetic tunnel junction element according to an embodiment may not include a vertical magnetization holding layer and a spacer layer.

According to the magnetic tunnel junction element according to an embodiment, the thickness of the magnetic tunnel junction element may be thinner.

In an embodiment, a magnetoresistive memory device may include a magnetic tunnel junction element, and an electrode for applying a voltage to the magnetic tunnel junction element. The magnetic tunnel junction element includes a free layer having a variable magnetization direction, a fixed layer composed of a single layer while maintaining a predetermined direction in the magnetization direction, and an insulating layer laminated between the free layer and the fixed layer. and at least one of the fixed bed is a type ₁ L1 a magnetic alloy film, the insulating layer can have a texture (texture) of 111.

The magnetoresistive memory device according to an embodiment may not include a vertical magnetization sustaining layer and a spacer layer, and may maintain a magnetization direction in a predetermined direction with a single spin polarization magnetic layer. Therefore, since the magnetic tunnel junction element has a simple fixed layer structure, the number of stacks of the magnetic tunnel junction element can be reduced.

According to the magnetic tunnel junction element and the magnetoresistive memory device of the present invention, the structure of the fixed layer of the magnetic tunnel junction element can be provided, and the magnetic tunnel junction element can be provided in which the number of magnetic tunnel junction elements is reduced.

1 is a sectional view showing a schematic configuration of a magnetic tunnel junction element according to the first embodiment.
2 is a sectional view showing a schematic configuration of a reference example of a magnetic tunnel junction element.
3 is a graph showing a band structure of NiPt used in the spin polarization magnetic layer (fixed layer) of the magnetic tunnel junction element according to Example 1. FIG.
4 is a graph showing a band structure of MgAl ₂ O ₄ used in the barrier layer of the magnetic tunnel junction element according to Example 2. FIG.
FIG. 5 is a perspective view showing an essential part of an example of the magnetoresistive memory device according to the third embodiment. FIG.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.

(Example 1)

1 is a cross-sectional view showing a schematic configuration of a magnetic tunnel junction element according to the first embodiment. The magnetic tunnel junction element 10 includes a substrate 11, a buffer layer 12, a pinned layer 13, an insulating layer 14, a free layer 15, and a cap layer 16.

The substrate 11 may be a silicon (Si) substrate. For example, the substrate 11 is preferably a (111) substrate. The substrate 11 may be a silicon (Si) substrate or a silicon (Si) single crystal substrate having a thermal oxide film.

The buffer layer 12 is a stabilization layer formed on the substrate 11. In detail, the buffer layer 12 may include Ru.

The pinned layer 13 is a layer which keeps a magnetization direction in a predetermined direction. A fixed bed (13) is preferably in the L1 ₁ type magnetic alloy film. The pinned layer 13 is preferably selected from materials in which the magnetization direction does not change easily with respect to the free layer 15. However, the material constituting the pinned layer 13 is not particularly limited and may be selected from any material.

For example, the fixed layer 13 may be composed of L1 ₁ alloy. In particular, the fixed bed 13 may be of a type L1 ₁ (Co-Ni) alloy, Pt. Specifically, the fixed bed 13 can be composed of L1 ₁ alloy of Ni _0.5 Co _0.5 Pt. The pinned layer 13 is Fe _{0 . 5} Ni _{0 . 5} Pt, Co _0.5 Fe _0.5 Pt, NiPt, FePt, or CoPt. The atomic ratio in the alloy can vary. By configuring the pinned layer 13 as described above, the pinned layer 13 can maintain the magnetization direction in a predetermined direction as a single layer. The pinned layer 13 is also called a reference layer.

The insulating layer 14 is a layer containing an insulating material as a main component. In addition, the insulating layer 14 may have a texture of 111. The insulating layer 14 is laminated between the pinned layer 13 and the free layer 15 having ferromagnetic properties. The insulating layer 14 is preferably composed of an insulating film of MgO or MgAl ₂ O ₄ . When a voltage is applied perpendicularly to the junction surfaces of the fixed layer 13 and the free layer 15, current flows in the magnetic tunnel junction element 10 due to the tunnel effect.

The free layer 15 is a layer in which the magnetization direction changes. The free layer 15 is preferably in the magnetic alloy film type L1 _1. For example, the free layer 15 may be of a type ₁ rule L1 alloy (ordered alloy). In particular, the free layer 15 may be of a type L1 ₁ (Co-Ni) alloy, Pt rule. Specifically, the free layer 15 is Co _{0 . 5} Ni _{0 .} L1 may be of a type _{1 5} alloy of Pt. In addition, the free layer 15 is Fe _{0 . 5} Ni _{0 . 5} Pt, Co _{0 . 5} Fe _{0 . 5} Pt, NiPt, FePt, or CoPt. In addition, the atomic ratio in the alloy can be changed. By configuring the free layer 15 as described above, the free layer 15 can be a layer in which the magnetization direction changes to a single layer. The free layer 15 is also called a memory layer.

The cap layer 16 is a stabilization layer formed on the free layer 15. For example, the cap layer 16 preferably contains Ru.

As described above, the magnetic tunnel junction element 10 of the first embodiment is configured. Next, the structure of the conventional magnetic tunnel junction element and the first embodiment will be compared. 2 is a sectional view showing a schematic configuration of a reference example of the magnetic tunnel junction element.

Referring to FIG. 2, the magnetic tunnel junction element 20 may include a substrate 21, a buffer layer 22, a high spin polarization magnetic layer 23A, and a perpendicular magnetization preserving layer 23B. , An insulating layer 24, a free layer 25, and a cap layer 26. The pinned layer 23 is formed of a high spin polarized magnetic layer 23A and a vertical magnetization holding layer 23B. The high spin polarized magnetic layer 23A is made of a Co-based Hoisler alloy or the like, but the material itself does not have perpendicular magnetic anisotropy. Therefore, the high spin polarized magnetic layer 23A may be combined with the vertical magnetization holding layer 23B to function as a fixed layer of the magnetic tunnel junction element 20.

Note in the example, and a magnetic tunnel junction element 10 of Example 1 as compared to, a fixed bed 13 as by utilizing film L1 ₁ type magnetic alloy, the fixed bed 13 is high with high spin polarizability of a single layer It may have perpendicular magnetic anisotropy. Therefore, in the magnetic tunnel junction element 10 of the first embodiment, the pinned layer 23 is formed of a multilayer of the high spin polarized magnetic layer 23A and the vertical magnetization holding layer 23B like the magnetic tunnel junction element 20 of the reference example. There is no need to do it.

Next, the band structure of the magnetic tunnel junction element 10 of the first embodiment will be described.

3 is a graph illustrating a band structure of NiPt used in a spin polarization magnetic layer (eg, the pinned layer 13) of the magnetic tunnel junction element 10 according to the first embodiment. In FIG. 3, the vertical axis represents the energy level (eV), and the horizontal axis represents the wave vector (k) of electrons. 3 shows a band structure of the Example ₁ using the L1-type magnetic alloy NiPt as a fixed bed (13).

3 shows a band structure of the L1 ₁ type magnetic alloy NiPt. The first principle is the result of research by calculation, L1 ₁ type magnetic alloy NiPt the 111 direction, that is, half metal (Half metallic, that is, the spin polarization rate of 100%) between the G-Z of Figure 3, high tunnel magneto A resistance effect can be expected. In addition, L1 ₁ type magnetic alloy NiPt represents a high perpendicular magnetic anisotropy of 10 ⁶ J / m ^3.

As described above, the magnetic tunnel junction element 10 of Example 1 has a large perpendicular magnetic anisotropy and at the same time obtains a high spin polarization rate.

In addition, in order to construct a magnetic tunnel junction element, it is desirable to consider matching of lattice constants. Table 1 is a table showing the lattice mismatch by the lattice constant of the alloy. In Table 1, the lattice mismatch (Misfit) represents a ratio divided by the lattice constant of Ru, MgO, or MgAl ₂ O ₄ lattice with L1 ₁ structure of NiPt the difference in lattice constant, L1 ₁ NiPt alloy structure of the alloy.

 TABLE 1

As shown in Table 1, the size of the mismatch is small enough to deposit L1 ₁ NiPt on Ru, MgO or MgAl ₂ O ₄ .

In this way, the embodiment according to the first magnetic tunnel junction element 10 of, thereby forming a fixing layer 13 in the L1 ₁ type magnetic alloy film, the insulating layer 14 in a layer having a texture (texture) of 111 By forming, the pinned layer 13 can maintain a magnetization direction in a predetermined direction by a single layer.

In addition, according to the magnetic tunnel junction element 10 of the first embodiment, the pinned layer 13 can maintain the magnetization direction in a predetermined direction without a vertical magnetization holding layer as a single layer. Therefore, since the structure of the pinned layer 13 can be simplified in the magnetic tunnel junction element 10 of the first embodiment, the number of stacked layers of the magnetic tunnel junction element 10 can be reduced. In addition, according to the magnetic tunnel junction element 10 of the first embodiment, the thickness of the magnetic tunnel junction element 10 can be further reduced.

Further, according to the magnetic tunnel junction element 10 of the first embodiment, formed in a layer having a texture (texture) of forming a free layer 15 in the L1 ₁ type magnetic alloy film and the insulating layer 14 (111) By doing so, the free layer 15 can be a layer in which the magnetization direction changes to a single layer.

Further, in the embodiment according to the first magnetic tunnel junction element 10 of the free layer 15 and the fixed layer 13, at least either the L1 ₁ type formed in a magnetic alloy film and the insulating layer 14, 111 of the By forming a layer having a texture, the magnetic tunnel junction element 10 can be configured with a smaller stacking number, and the crystal structure of the magnetic tunnel junction element 10 can be stabilized. As a result, atomic diffusion in the magnetic tunnel junction element 10 can be suppressed.

In addition, the magnetic tunnel junction element 10 of Embodiment 1 may have good thermal stability and may be densified.

In addition, according to the magnetic tunnel junction element 10 of the first embodiment, by controlling the amounts of Ni and Co, Ms (saturated magnetization) can be reduced, and the magnetization direction can be changed at high speed.

(Example 2)

In Example 2, a description will be given of the example using the MgAl ₂ O ₄ with an insulating layer (14).

4 is a graph showing a band structure of MgAl ₂ O ₄ used in the barrier layer of the magnetic tunnel junction element 10 according to the second embodiment. In FIG. 4, the vertical axis represents the energy level (eV) and the horizontal axis represents the wave number vector k of the electron. Figure 4 shows a band structure in the example with a MgAl ₂ O ₄ with an insulating layer (14).

As shown in FIG. 4, MgAl ₂ O ₄ is a direct gap insulator at point G, and filters only electrons perpendicular to the insulating layer 14, ie, traveling in the (111) direction. Accordingly, the magnetic tunnel junction element 10 using MgAl ₂ O ₄ as the insulating layer 14 spins a half metallic material in the (111) direction, as shown in FIG. 3 of the first embodiment. By using it as a polarization layer, a high tunnel magnetoresistance effect and a high spin polarization rate can be obtained.

As described above, according to the magnetic tunnel junction element 10 of the second embodiment, since the lattice mismatch can be reduced, a new large tunnel magnetoresistance effect can be expected.

(Example 3)

In Embodiment 3, a magnetoresistive memory device using the magnetic tunnel junction element 10 of Embodiment 1 or Embodiment 2 will be described.

FIG. 5 is a perspective view showing an essential part of an example of the magnetoresistive memory device according to the third embodiment. FIG.

Referring to FIG. 5, the magnetoresistive memory device includes a memory cell 30, a bit line 31, contact plugs 35 and 37, and a word line 38.

The memory cell 30 includes a semiconductor substrate 32, diffusion regions 33 and 34, a source line 36, a gate insulating layer 39, and a magnetic tunnel junction element 10. The magnetic tunnel junction element 10 corresponds to the magnetic tunnel junction element 10 of the first embodiment, but may also be the magnetic tunnel junction element 10 of the second embodiment.

The magnetoresistive memory device is formed by arranging a plurality of memory cells 30 in a matrix form and connecting them to each other using a plurality of bit lines 31 and a plurality of word lines 38. The MRAM executes a data write process using the spin torque injection method.

The semiconductor substrate 32 has diffusion regions 33 and 34 on its surface. The diffusion region 33 is disposed spaced apart from the diffusion region 34 by a predetermined interval. The diffusion region 33 functions as a drain region, and the diffusion region 34 functions as a source region. The diffusion region 33 is connected to the magnetic tunnel junction element 10 via the contact plug 37.

The bit line 31 is disposed above the semiconductor substrate 32 and is connected to the magnetic tunnel junction element 10. The bit line 31 is connected to a write circuit (not shown) and a read circuit (not shown).

The diffusion region 34 is connected to the source line 36 via the contact plug 35. The source line 36 is connected to a write circuit (not shown) and a read circuit (not shown).

The word line 38 is adjacent to the diffusion region 33 and the diffusion region 34 and is disposed on the semiconductor substrate 32 via the gate insulating film 39. The word line 38 and the gate insulating film 39 function as selection transistors. When a current is supplied from a circuit not shown, the select transistor is turned on.

When voltage is applied to the magnetic tunnel junction element 10 using the bit line 31 and the diffusion region 33 as electrodes, the spin torque of electrons aligned in a predetermined direction changes the magnetization direction of the ferromagnetic layer. By changing the current direction, the value of data written to the magnetoresistive memory device can be changed.

As described above, according to the magnetoresistive memory device of the third embodiment, the magnetization direction can be maintained in a predetermined direction by a single layer without including the vertical magnetization holding layer. Therefore, the magnetoresistive memory device according to the embodiment can simplify the structure of the pinned layer and can reduce the number of stacked layers of the magnetic tunnel junction element 10.

In addition, according to the magnetoresistive memory device of the third embodiment, the thermal stability of the magnetic tunnel junction element 10 is good, and the magnetoresistive memory device can be densified.

In addition, this invention is not limited to the above-mentioned embodiment, It is possible to change suitably in the range which does not deviate from the meaning. For example, in the magnetic tunnel junction element 10, a (111) plane junction may be between one of the pinned layer 13 or the free layer 15 and the insulating layer 14. In the magnetic tunnel junction element 10, both the fixed layer 13 and the insulating layer 14, and the free layer 15 and the insulating layer 14 may both be (111) plane junctions. The insulating layer 14 may be MgGa ₂ O ₄ , ZnAl ₂ O _4, or ZnGa ₂ O ₄ having the texture of 111.

10, 20 magnetic tunnel junction element
11, 21 boards
12, 22 buffer layer
13, 23 fixed bed
14, 24 insulation layer
15, 25 free layer
16, 26 cap layers
23A high spin polarized magnetic layer
23B Vertical Magnetized Retention Layer
30 memory cells
31 bit lines
32 semiconductor substrate
33, 34 diffusion zone
35, 37 contact plug
36 source lines
38 word lines
39 gate insulating film

Claims (8)

A free layer having a variable magnetization direction;
A pinned layer which maintains the magnetization direction in a predetermined direction and is formed of a single layer; And
An insulating layer laminated between the free layer and the fixed layer,
At least one of the free layer and the fixed layer is a magnetic alloy film type L1 _1,
And the insulating layer has a texture of (111). The method according to claim 1,
And the insulating layer comprises MgO, MgAl ₂ O ₄ , MgGa ₂ O ₄ , ZnAl ₂ O _4, or ZnGa ₂ O ₄ having a texture of (111). The method according to claim 2,
A magnetic tunnel junction element further comprising a base layer having a texture of (111). The method according to claim 3,
And the pinned layer does not include a vertical magnetization holding layer. The method according to claim 2,
And the pinned layer does not include a vertical magnetization holding layer. The method according to claim 1,
A magnetic tunnel junction element further comprising a base layer having a texture of (111). The method according to claim 1,
And the pinned layer does not include a vertical magnetization holding layer. A free layer having a variable magnetization direction, a fixed layer formed of a single layer while maintaining the magnetization direction in a predetermined direction, and an insulating layer laminated between the free layer and the fixed layer, wherein at least one of the free layer and the fixed layer a magnetic tunnel junction device having a texture (texture) of a type ₁ L1 a magnetic alloy film, the insulating layer 111; And
And a electrode for applying a voltage to the magnetic tunnel junction element.

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