KR102633125B1 - Magnetic tunnel junction device and magnetic resistance memory device - Google Patents

Abstract

The present invention includes a free layer, a fixed layer on the free layer, an insulating layer between the free layer and the fixed layer, and a spin orbit torque (SOT) generator in contact with a side of the free layer, wherein the SOT generator and the free layer This contact surface intersects the contact surface of the free layer and the insulating layer, and the SOT generator is a magnetic tunnel junction configured to allow current to flow in a direction intersecting the stacking direction of the free layer, the insulating layer, and the fixed layer. Disclosed is a magnetoresistive memory device including an element and the magnetic tunnel junction element.

Description

Magnetic tunnel junction device and magnetoresistive memory device {MAGNETIC TUNNEL JUNCTION DEVICE AND MAGNETIC RESISTANCE MEMORY DEVICE}

The present invention relates to magnetic tunnel junction devices and magnetoresistive memory devices.

Magnetoresistive elements that have a perpendicular magnetization direction and perform a read operation by the magnetoresistance effect are expected to be the next generation of memory due to their high thermal disturbance resistance due to miniaturization.

Next-generation memory includes a magnetic tunnel junction (MTJ) device having a free layer with a variable magnetization direction, a fixed layer that maintains a predetermined magnetization direction, and an insulating layer between the free layer and the fixed layer.

STT-MRAM (Spin Transfer Torque - Magnetoresistive Random Access Memory) based on such MTJ is being put into practical use. STT-MRAM has a two-terminal structure, and the paths for write current and read current are the same. Not only does STT-MRAM have low conversion efficiency from write current to spin current, but it is also difficult to achieve low current and high speed. For example, if the size of the free layer of STT-MRAM is assumed to be 10 nm wide, 10 nm long, and 1 nm thick, the number of electrons in the free layer is about 105. And, in principle, since the conversion efficiency from write current to spin current is 1 or less, injection of the same number or more electrons is required to invert the spin of electrons. Therefore, assuming the switching time when reversing the spin is 3 ns, approximately 10 μA or more is required as a write current for one MTJ device. Moreover, the margin of read current and the margin of write current are not sufficient.

International Publication No. 2016/021468 In order to solve the above-mentioned problem, a spin orbit torque (SOT) recording method has been proposed. When using the SOT recording method, in principle, the conversion efficiency from write current to spin current is likely to be 1 or more, so low current recording is possible and high speed is possible. However, in order to use SOT, the device structure must have three terminals and a horizontal (longitudinal) magnetic layer must be used instead of a vertical magnetic layer. In addition, since it was necessary to add a new magnetic field generator, there was a problem in that the device structure was complicated.

The purpose of the present invention is to provide a magnetic tunnel junction device and a magnetoresistive memory device that have a simple device structure, low recording power, fast writing speed, and high reliability.

A magnetic tunnel junction device according to embodiments of the present invention includes a free layer, a fixed layer on the free layer, an insulating layer between the free layer and the fixed layer, and a spin orbit torque (SOT) generator in contact with the side of the free layer. Including, wherein the surface in contact with the SOT generator and the free layer intersects the surface in contact with the free layer and the insulating layer, and the SOT generator intersects the stacking direction of the free layer, the insulating layer, and the fixed layer. It can be configured to allow current to flow in that direction.

Magnetoresistive memory devices according to embodiments of the present invention include a magnetic tunnel junction element and electrodes that apply a voltage to the magnetic tunnel junction element, wherein the magnetic tunnel junction element includes a free layer, a fixed layer on the free layer, and the magnetic tunnel junction element. It includes an insulating layer between a free layer and the fixed layer, and a spin orbit torque (SOT) generator in contact with a side of the free layer, and a surface in contact with the SOT generator and the free layer is a surface in contact with the free layer and the insulating layer. The SOT generator may be configured to allow current to flow in a direction intersecting the stacking direction of the free layer, the insulating layer, and the fixed layer.

According to the magnetic tunnel junction element and magnetoresistive memory device according to the present invention, the SOT generator is disposed on the side of the free layer so that current flows along the side of the SOT generator. Accordingly, a magnetic tunnel junction device and a magnetoresistive memory device having a simple device structure, low recording power, fast writing speed, and high reliability can be provided.

Figure 1 is a perspective view showing the schematic configuration of a magnetic tunnel junction element according to Embodiment 1 of the present invention.
Figure 2 is a graph showing the relationship between the structure and thermal stability of the MTJ device.
Figure 3 is a perspective view showing the schematic configuration of a magnetic tunnel junction element according to Embodiment 2 of the present invention.
Figure 4 is a perspective view showing the schematic configuration of a magnetic tunnel junction element according to Embodiment 3 of the present invention.
Figure 5 is a top view showing the schematic configuration of a magnetic tunnel junction element according to Embodiment 4 of the present invention.
Figure 6 is a top view showing the schematic configuration of a magnetic tunnel junction element according to Embodiment 5 of the present invention.
Figure 7 is a perspective view showing main parts of an example of a magnetoresistive memory device according to Embodiment 6 of the present invention.

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

(Example 1 of the present invention)

Figure 1 is a perspective view showing the schematic configuration of a magnetic tunnel junction element according to Embodiment 1 of the present invention. The magnetic tunnel junction element 10 includes a pinned layer (11), an insulating layer (12), a free layer (13), and a SOT generator (14).

Referring to FIG. 1, the fixed layer 11 is a layer with a fixed magnetization direction regardless of the flow of current. The fixed layer 11 preferably includes a material whose magnetization direction does not change easily compared to the free layer 13. That is, the fixed layer 11 preferably contains a material that has a large effective magnetic anisotropy (Kueff) and saturation magnetization (Ms) and a large magnetic relaxation constant (α).

However, the material constituting the fixed layer 11 is not particularly limited and can be selected from any material depending on various conditions. As an example, the fixed layer 11 may be composed of a layer containing CoFeB as a main component and a Co/Pt multilayer film. As another example, the fixed layer 11 may be composed of a layer containing a Heusler alloy film as a main component and a Co/Pt multilayer film. Preferably, the layer containing the Heusler alloy film as the main ingredient is a layer containing the Co-based full-Heusler alloy as the main ingredient. Specifically, the Co-based Heusler alloy may be Co2FeSi, Co2MnSi, Co2FeMnSi, Co2FeAl, or Co2CrAl. The Co/Pt multilayer film is configured to have large perpendicular magnetic anisotropy. The layer containing the Heusler alloy film as a main component is in contact with the insulating layer 12 on one side. The layer containing the Heusler alloy film as a main component is in contact with the Co/Pt multilayer film on the opposite side of the surface in contact with the insulating layer 12. By constructing the pinned layer 11 in this way, the pinned layer 11 is a single layer and can maintain the magnetization direction in a predetermined direction regardless of the flow of current. The fixed layer 11 may be called a reference layer.

The insulating layer 12 may be provided between the fixed layer 11 and the free layer 13. The insulating layer 12 is a layer containing an insulating material as its main component. As an example, the insulating layer 12 may be composed of an insulating film containing MgO or the like. The material constituting the insulating layer 12 is preferably an oxide having a NaCl structure. As another example, the material constituting the insulating layer 12 may be CaO, SrO, TiO, VO, or NbO. However, this is only an example and the material constituting the insulating layer 12 is not particularly limited. For example, the insulating layer 12 may be spinel-type MgAl2O4. And, since the voltage is applied perpendicularly to the junction surface of the fixed layer 11 and the free layer 13, current may flow in the magnetic tunnel junction element 10 due to a tunneling effect.

The free layer 13 is a layer whose magnetization direction changes due to the flow of current. For example, the free layer 13 has a magnetization easy axis perpendicular to the top surface. That is, the free layer 13 can be magnetized in a direction perpendicular to the upper surface. The easy magnetization axis refers to the axis facing the direction in which a magnetic material is easily magnetized. The magnetization direction of the free layer 13 is variable. The magnetization direction of the free layer 13 may be toward the top or bottom of the top surface. Preferably, the material constituting the free layer 13 is not particularly limited and may be selected from any material depending on various conditions. For example, the free layer 13 may include CoFeB as a main component. The free layer 13 may include a Co-based Heusler alloy. Specifically, the Co-based Heusler alloy may be Co2FeSi, Co2MnSi, Co2(Fe-Mn) Si, Co2FeAl, or Co2CrAl. The free layer 13 is also called a recording layer, a free magnetization layer, or a variable magnetization layer.

A SOT generator 14 contacting the side of the free layer 13 may be provided. As an example, the SOT generation source 14 may be in contact with the side of the free layer 13 parallel to the YZ plane. At this time, the YZ plane where the SOT generator 14 and the free layer 13 are in contact may intersect the XY plane where the insulating layer 12 and the free layer 13 are in contact. The SOT generator 14 may generate a spin-orbit torque that changes the magnetization direction of the free layer 13. However, the SOT generator 14 does not contact the fixed layer 11 and does not affect the magnetization direction of the fixed layer 11. The SOT generator 14 may be configured to allow current to flow in a direction crossing the stacking direction of the free layer 13, the insulating layer 12, and the fixed layer 11. Here, the stacking direction of the free layer 13, the insulating layer 12, and the fixed layer 11 is the Z-axis direction in FIG. 1. Current may flow through the SOT generator 14 in a direction crossing the Z-axis direction. The current flowing through the SOT generator 14 generates spin-orbit torque. Here, intersection means not parallel. That is, the direction of the current flowing through the SOT generator 14 may not be parallel to the stacking direction of the free layer 13, the insulating layer 12, and the fixed layer 11. That is, the angle at which the direction of the current flowing through the SOT generator 14 and the stacking direction of the free layer 13, the insulating layer 12, and the fixed layer 11 intersect is greater than 0° and less than 360°. In order to efficiently change the magnetization direction of the free layer 13 using the generated spin current, the intersection angle is preferably 45° or more. More preferably, the intersection angle is 80° or more. More preferably, the intersection angle may be approximately a right angle. A right angle means, for example, approximately 88° to 92°.

The SOT generator 14 includes a connection terminal 14-1, a SOT wiring 14-2, and a connection terminal 14-3. And, by the current flowing from the connection terminal 14-1 to the connection terminal 14-3 through the SOT wiring 14-2, the SOT generator 14 can generate spin-orbit torque. It is preferable that the connection terminal 14-1 and the connection terminal 14-3 are spaced apart from the free layer 13. That is, it is preferable that the length of the SOT wiring 14-2 in the Y-axis direction is the same as the length of the free layer 13 in the Y-axis direction or is greater than the length of the free layer 13 in the Y-axis direction.

The SOT generator 14 may have a structure that allows current to flow in a direction crossing the stacking direction of the free layer 13, the insulating layer 12, and the fixed layer 11. That is, the connection terminal 14-1 and the connection terminal 14-3 are a pair of electrodes spaced apart from each other in a direction crossing the stacking direction of the free layer 13, the insulating layer 12, and the fixed layer 11. You can. For example, as shown in FIG. 1, the connection terminal 14-1 and the connection terminal 14-3 are disposed at both ends of the SOT wiring 14-2 in the Y-axis direction. The connection terminal 14-1 and 14-3 may be made of a conductive material.

The SOT wiring 14-2 contains a material that allows current to flow between the connection terminal 14-1 and the connection terminal 14-3 to generate spin-orbit torque. For example, the SOT wiring 14-2 may include a topological insulator. Topological insulators are materials that are insulators on the inside but allow electric current to flow on the surface of the material. For example, the topological insulator can be the semimetallic bismuth or a bismuth compound. In particular, BiTeSb or BiSb is very suitable as a topological insulator. However, due to changes in composition, the inside of the topological insulator may become conductive. The SOT wiring 14-2 may include at least one metal among Pt, W, and Ta.

The upper surface of the SOT wiring 14-2 in the Z-axis direction of FIG. 1 may be spaced apart from the lower surface of the fixed layer 11. That is, the upper surface of the SOT wiring 14-2 may be located at a lower level than the lower surface of the fixed layer 11. Accordingly, the upper surface of the SOT wiring 14-2 may not contact the lower surface of the fixed layer 11. For example, the upper surface of the SOT wiring 14-2 may be located at substantially the same level as the lower surface of the insulating layer 12.

As described above, the magnetic tunnel junction element of Example 1 of the present invention is constructed.

Next, the thermal stability of the magnetic tunnel junction device according to Example 1 of the present invention will be explained using a comparative example. Figure 2 is a graph showing the relationship between the structure and thermal stability of an MTJ device. More specifically, it is a graph showing the value of the thermal stability factor (Δ) measured according to the combination of the thickness (t) of the MTJ element and the diameter (D) of the MTJ element. The diameter (D) of the MTJ element means, for example, the diameter of the lower surface of the MTJ element when the MTJ element has a cylindrical shape. In Figure 2, the vertical axis represents the thickness (t) of the MTJ element, and the lower horizontal axis represents the diameter (D) of the MTJ element. Additionally, in Figure 2, the upper horizontal axis represents the thermal stability factor (Δ). In Figure 2, the units of the vertical and lower horizontal axes are nm, and the units of the upper horizontal axis are unitless.

Referring to FIG. 2, an MTJ element having a combination of thickness and diameter with a high thermal stability factor (Δ) is suitable for a recording method using SOT. That is, referring to FIG. 2, a combination of thickness and diameter such that the thermal stability factor (Δ) is 40 or more is preferable. In particular, a combination of thickness and diameter such that the thermal stability factor (Δ) is 80 or more is desirable. And, the combination of thickness and diameter such that the thermal stability factor (Δ) is 120 or more is most desirable.

Referring again to FIG. 1, in the magnetic tunnel junction element 10 according to Embodiment 1 of the present invention, the SOT generator 14 is disposed on the side of the free layer 13, so that the current flows along the side of the SOT generator 14. It flows. As a result, a magnetic tunnel junction device 10 with a simple device structure, low recording power, high recording speed, and high reliability can be provided. In addition, according to the magnetic tunnel junction device 10 according to Embodiment 1 of the present invention, the free layer 13 has a long shape in the Z-axis direction, so thermal stability can be secured using shape magnetic anisotropy. Shape magnetic anisotropy is magnetic anisotropy in which the physical properties of a magnetic material depend on its shape or structure. A magnetic material with shape magnetic anisotropy is easily magnetized when a magnetic field is applied in a direction in which a deamagnetic field is not generated (for example, the in-plane direction of the thin film), but when a magnetic field is applied in a direction in which a large deamagnetic field is generated (for example, in the direction perpendicular to the film surface of the thin film). When a magnetic field is applied, it is not easily magnetized. Since the free layer 13 of the magnetic tunnel junction element 10 according to the first embodiment of the present invention has a long shape in the Z-axis direction, a demagnetizing field is not generated, and thus the perpendicular magnetization can be stable. However, a long shape in the Z-axis direction is not suitable for a conventional STT recording layer or SOT recording layer.

Additionally, the height of the free layer 13 in the Z-axis direction is preferably approximately 15 nm to 20 nm. If the height of the free layer 13 in the Z-axis direction is secured, thermal stability can be secured even if the width in the X-axis direction and the width in the Y-axis direction of the magnetic tunnel junction element 10 are each approximately 10 nm or less. High density is possible. By using SOT technology, the conversion efficiency from current to spin current is increased, enabling high-speed recording (less than 10 ns), low power consumption, high reliability, and thermal stability deterioration even over a wide operating temperature of approximately -40°C to +150°C. A magnetic tunnel junction element 10 may be provided. Additionally, the magnetic tunnel junction device 10 according to Embodiment 1 of the present invention can be realized even without an external magnetic field.

(Example 2 of the present invention)

Embodiment 2 of the present invention describes a magnetic tunnel junction device in which SOT generators are arranged on both sides of a free layer and currents in opposite directions flow through each SOT generator. Figure 3 is a perspective view showing the schematic configuration of a magnetic tunnel junction element according to Embodiment 2 of the present invention. The magnetic tunnel junction element 10 includes a fixed layer 11, an insulating layer 12, a free layer 13, a first SOT generator 14, and a second SOT generator 15. In Figure 3, the same components as in Figure 1 are assigned the same numbers and description is omitted.

Referring to FIG. 3, the configuration of the first SOT generator 14 is similar to Embodiment 1.

Additionally, the second SOT generator 15 may generate spin-orbit torque to change the magnetization direction of the free layer 13. The second SOT generator 15 includes a connection terminal 15-1, a SOT wiring 15-2, and a connection terminal 15-3. The SOT wiring 15-2 has the same configuration as the SOT wiring 14-2. The connection terminal 15-1 and the connection terminal 15-3 have the same configuration as the connection terminal 14-1 and the connection terminal 14-3, respectively.

And, the second SOT generator 15 can generate spin-orbit torque by the current flowing from the connection terminal 15-1 to the connection terminal 15-3 through the SOT wiring 15-2. Specifically, the second SOT generator 15 is configured to allow current to flow in a direction crossing the stacking direction of the free layer 13, the insulating layer 12, and the fixed layer 11, thereby generating spin-orbit torque. . Here, the stacking direction of the free layer 13, the insulating layer 12, and the fixed layer 11 is the Z-axis direction in FIG. 3. The surface of the second SOT generator 15 in contact with the free layer 13 intersects the surface of the insulating layer 12 in contact with the free layer 13.

The direction of the current flowing through the second SOT generator 15 is parallel and opposite to the direction of the current flowing through the first SOT generator 14. In order to allow current to flow in this way, the free layer 13 is located between the first SOT generator 14 and the second SOT generator 15, and the first SOT generator 14 and the second SOT generator 15 are are placed parallelly.

That is, in the first SOT generator 14, the current flows from the connection terminal 14-1 to the connection terminal 14-3 through the SOT wiring 14-2, and in the second SOT generator 15, the current flows through the SOT wiring 14-2. It flows from the connection terminal 15-1 to the connection terminal 15-3 through the wiring 15-2.

Due to the current flowing in this way, the first SOT generator 14 and the second SOT generator 15 can generate spin-orbit torque, and the spin-orbit torque in the free layer 13 does not cancel each other.

In this way, according to the magnetic tunnel junction element 10 according to the second embodiment of the present invention, the first SOT generator 14 is in contact with one side of the free layer 13, and the second SOT generator 15 is in contact with the first SOT generator 15. It is in contact with one side of the free layer 13 that is in contact with the SOT generation source 14 and the other side parallel to the other side. The first SOT generator 14 and the second SOT generator 15 may have the same composition. Since SOT can be generated on both sides of the free layer 13, approximately twice as much torque can be generated compared to the case where the SOT generator is disposed below the free layer 13. According to the magnetic tunnel junction device 10 according to the second embodiment of the present invention, the first SOT generator 14 and the second SOT generator 15 can be disposed on the side of the free layer 13. That is, a plurality of SOT generators 14 and 15 can be arranged in one free layer 13.

(Example 3 of the present invention)

Embodiment 3 of the present invention describes a magnetic tunnel junction device in which SOT generators are disposed on both sides of the free layer and current flows in the same direction to each SOT generator. Figure 4 is a perspective view showing the schematic configuration of a magnetic tunnel junction element according to Embodiment 3 of the present invention. The magnetic tunnel junction element 10 includes a fixed layer 11, an insulating layer 12, a free layer 13, a first SOT generator 14, and a third SOT generator 16. In Figure 4, the same components as in Figure 1 are given the same numbers and description is omitted.

Referring to FIG. 4, the third SOT generator 16 may generate spin-orbit torque that changes the magnetization direction of the free layer 13. The third SOT generation source 16 includes a connection terminal 16-1, a SOT wiring 16-2, and a connection terminal 16-3.

The SOT wiring 16-2 may be composed of a composition such that the direction or sign of the SOT generated by the current flowing in the SOT wiring 14-2 is opposite to that of the SOT generated by the current flowing in the SOT wiring 14-2. For example, the SOT wiring 14-2 may include Pt, and the SOT wiring 16-2 may include Ta.

The connection terminal 16-1 and the connection terminal 16-3 are configured in the same way as the connection terminal 14-1 and the connection terminal 14-3, respectively.

And, the third SOT generator 16 can generate spin-orbit torque by the current flowing from the connection terminal 16-1 to the connection terminal 16-3 through the SOT wiring 16-2. Specifically, the third SOT generator 16 generates a spin-orbit torque by flowing a current in a direction crossing the stacking direction of the free layer 13, the insulating layer 12, and the fixed layer 11. Here, the stacking direction of the free layer 13, the insulating layer 12, and the fixed layer 11 is the Z-axis direction in FIG. 4. The surface of the third SOT generator 16 in contact with the free layer 13 intersects the surface of the insulating layer 12 in contact with the free layer 13.

The direction of the current flowing through the third SOT generator 16 is parallel to and in the same direction as the direction of the current flowing through the first SOT generator 14. In order to allow current to flow in this way, the free layer 13 is located between the first SOT generator 14 and the third SOT generator 16, and the first SOT generator 14 and the third SOT generator 16 are parallel. arranged to do so.

That is, in the first SOT generator 14, the current flows from the connection terminal 14-1 to the connection terminal 14-3 through the SOT wiring 14-2, and in the third SOT generator 16, the current flows through the SOT wiring 14-2. It flows from the connection terminal 16-1 to the connection terminal 16-3 through the wiring 16-2.

Due to the current flowing in this way, the first SOT generator 14 and the second SOT generator 16 can generate spin-orbit torque, and the spin-orbit torque in the free layer 13 is not canceled.

As such, according to the magnetic tunnel junction element 10 according to the third embodiment of the present invention, the first SOT generator 14 is in contact with one side of the free layer 13, and the third SOT generator 16 is in contact with the first SOT generator 16. It is in contact with one side of the free layer 13 that is in contact with the SOT generation source 14 and the other side parallel to the other side. The first SOT generator 14 and the third SOT generator 16 may have different compositions, and as a result, the degree of freedom in the direction of the write current may increase, making magnetoresistive memory design easier.

(Example 4 of the present invention)

Embodiment 4 of the present invention describes a magnetic tunnel junction device in which a plurality of SOT generators are arranged on the side of the free layer and currents flowing through each SOT generator intersect. Figure 5 is a top view showing the schematic configuration of a magnetic tunnel junction element according to Embodiment 4 of the present invention. The magnetic tunnel junction element 10 includes a fixed layer 11, an insulating layer 12, a free layer 13, and a fourth SOT generator 17. In Figure 5, the same components as in Figure 1 are assigned the same numbers and description is omitted.

1 and 5, the fourth SOT generator 17 is configured to generate a spin-orbit torque that changes the magnetization direction of the free layer 13. The fourth SOT generation source 17 includes a connection terminal 17-1, a SOT wiring 17-2, and a connection terminal 17-3. The SOT wiring 17-2 has the same configuration as the SOT wiring 14-2 in Embodiment 1.

The connection terminal 17-1 and the connection terminal 17-3 are configured the same as the connection terminal 14-1 and the connection terminal 14-3 of Embodiment 1, respectively.

And, by the current flowing from the connection terminal 17-1 to the connection terminal 17-3 through the SOT wiring 17-2, the fourth SOT generator 17 can generate spin-orbit torque. Specifically, the fourth SOT generator 17 generates a spin-orbit torque by flowing a current in a direction crossing the stacking direction of the free layer 13, the insulating layer 12, and the fixed layer 11. Here, the stacking direction is the Z-axis direction in FIG. 5. The YZ plane and ZX plane where the fourth SOT generation source 17 is in contact with the free layer 13 intersect with the XY plane where the insulating layer 12 is in contact with the free layer 13.

The directions of the current flowing in the fourth SOT generator 17 are the X-axis direction and the Y-axis direction, as shown by the arrows in FIG. 5.

Then, a current flows from the connection terminal 17-1 to the connection terminal 17-3 through the SOT wiring 17-2. Due to the current flowing in this way, the fourth SOT generator 17 can generate spin-orbit torque, and the spin-orbit torque in the free layer 13 does not cancel each other.

In this way, according to the magnetic tunnel junction device 10 according to the fourth embodiment of the present invention, the size of the SOT can be increased compared to the case where the SOT generator is disposed below the free layer 13. According to the magnetic tunnel junction device 10 according to the fourth embodiment of the present invention, the fourth SOT generator 17 can be disposed on multiple sides of the free layer 13, and thus the size of the SOT can be increased.

(Example 5 of the present invention)

Embodiment 5 of the present invention describes a magnetic tunnel junction element in which a SOT generator is disposed on the side of the free layer and the SOT generator has a ring shape. Figure 6 is a top view showing the schematic configuration of a magnetic tunnel junction element according to Embodiment 5 of the present invention. The magnetic tunnel junction element 10 may include a fixed layer 11, an insulating layer 12, a free layer 13, and a fifth SOT generator 18. In Figure 6, the same components as in Figure 1 are given the same numbers and description is omitted.

Referring to Figures 1 and 6, in Example 5 of the present invention, the free layer 13 has a cylindrical shape extending in the Z-axis direction. And, the fifth SOT generator 18 is arranged to surround the side of the free layer 13. However, the fifth SOT generator 18 is not a completely closed ring shape, but is a shape with a portion removed from the ring shape.

The fifth SOT generator 18 is configured to generate a spin-orbit torque that changes the magnetization direction of the free layer 13. The fifth SOT generation source 18 includes a connection terminal 18-1, a SOT wiring 18-2, and a connection terminal 18-3. The SOT wiring 18-2 has the same composition as the SOT wiring 14-2 in Example 1.

The connection terminal 18-1 and the connection terminal 18-3 are each composed of the same composition as the connection terminal 14-1 and the connection terminal 14-3 of Example 1.

And, by the current flowing from the connection terminal 18-1 to the connection terminal 18-3 through the SOT wiring 18-2, the fifth SOT generator 18 can generate spin-orbit torque. Specifically, the fifth SOT generation source 18 crosses the stacking direction of the free layer 13, the insulating layer 12, and the fixed layer 11 and causes current to flow in a direction surrounding the free layer 13. , generates spin-orbit torque. Here, the stacking direction of the free layer 13, the insulating layer 12, and the fixed layer 11 is the Z-axis direction in FIG. 6. The surface of the fifth SOT generator 18 in contact with the free layer 13 intersects the surface of the insulating layer 12 in contact with the free layer 13.

In addition, the ring-shaped edge from which a portion is removed is not limited to a circular shape. For example, the ring-shaped edge may have a polygonal shape. The ring shape with a portion removed is not limited to a shape that surrounds most of the circumference of the free layer 13, and may be a shape that surrounds half of the circumference of the free layer 13, for example.

In this way, according to the magnetic tunnel junction element 10 according to the fifth embodiment of the present invention, the size of the SOT can be increased, thereby realizing lower power consumption.

(Example 6 of the present invention)

Embodiment 6 of the present invention describes a magnetoresistive memory device using the magnetic tunnel junction element of Embodiments 1 to 5 of the present invention.

Figure 7 is a perspective view showing main parts of an example of a magnetoresistive memory device according to Embodiment 6.

Referring to FIG. 7 , 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, first and second diffusion regions 33 and 34, a source line 36, a gate insulating layer 39, and a magnetic tunnel junction element 10. The illustrated magnetic tunnel junction element 10 corresponds to the magnetic tunnel junction element 10 of Embodiment 1 of the present invention, but the magnetic tunnel junction elements of Embodiments 2 to 5 of the present invention may be used.

The magnetoresistive memory device may include a plurality of memory cells 30, a plurality of bit lines 31, and a plurality of word lines 38 arranged in a matrix form.

The semiconductor substrate 32 may have first and second diffusion regions 33 and 34 on its surface. The first diffusion region 33 is arranged to be spaced apart from the second diffusion region 34. The first diffusion region 33 may function as a drain region, and the second diffusion region 34 may function as a source region. The first diffusion region 33 is connected to the magnetic tunnel junction element 10 through a contact plug 37.

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

The second diffusion region 34 is connected to the source line 36 through the contact plug 35. Source line 36 is connected to a read circuit (not shown).

The word line 38 is disposed on the semiconductor substrate 32 to vertically overlap a portion of the first diffusion region 33 and a portion of the second diffusion region 34 . The gate insulating film 39 is interposed between the word line 38 and the semiconductor substrate 32. The word line 38 and the gate insulating film 39 function as selection transistors. The word line 38 turns on the select transistor when current is supplied from a circuit not shown.

The bit line 31 of the magnetoresistive memory device reads data written into the magnetoresistive memory device from the magnetic tunnel junction element 10. When a voltage is applied between the connection terminal 14-1 and the connection terminal 14-3 of the magnetic tunnel junction element 10, the spin torque of the electrons arranged neatly in a certain direction due to the application of voltage causes the magnetization of the ferromagnetic material. change direction.

And, by changing the direction of the current, the value of data recorded in the magnetoresistive memory device can be changed.

In this way, according to the magnetoresistive memory device according to Embodiment 6 of the present invention, the SOT generation sources 14-1, 14-2, and 14-3 are disposed on the side of the free layer and are located on the side of the SOT wiring 14-2. By allowing current to flow along, it is possible to provide a magnetoresistive memory device with a simple device structure, low recording power, high recording speed, and high reliability.

In addition, the present invention is not limited to the above-mentioned embodiments of the present invention, and may be appropriately modified without departing from the spirit. For example, the magnetoresistive element of the present invention may further include other layers that are interposed between the substrate, fixed layer, insulating layer, and free layer and do not impair the function of each layer. For example, the magnetoresistive device of the present invention may further include a layer for resolving lattice mismatching between layers or a layer for resolving lattice defects. Additionally, the shape of the SOT generator (SOT wiring) may be any one of a flat shape, a thin film shape, and a line shape. In addition, the magnetoresistive element of the present invention further includes a selection transistor, so that a current selected according to data to be recorded can flow to a plurality of SOT generators.

11: fixed layer
12: insulating layer
13: Free floor
14, 15, 16, 17, 18: SOT source
14-1, 14-3, 15-1, 15-3, 16-1, 16-3, 17-1, 17-3, 18-1, 18-3: Connection terminal
14-2, 15-2, 16-2, 17-2, 18-2: SOT wiring
30: memory cell
31: bit line
32: semiconductor substrate
33, 34: Diffusion area
35, 37: contact plug
36: source line
38: word line
39: Gate insulating film

Claims (15)

free class;
a fixed layer on the free layer;
an insulating layer between the free layer and the fixed layer; and
It includes a SOT (Spin orbit torque) generator in contact with the side of the free layer,
A surface in contact between the SOT generator and the free layer intersects a surface in contact with the free layer and the insulating layer,
The SOT generator is a magnetic tunnel junction element configured to allow current to flow in a direction crossing the stacking direction of the free layer, the insulating layer, and the fixed layer. According to claim 1,
The SOT generator is a magnetic tunnel junction element including a pair of electrodes spaced apart in a direction crossing the stacking direction. According to claim 1,
A magnetic tunnel junction element wherein the SOT generator includes at least one metal selected from Pt, W, and Ta. According to claim 1,
The SOT generator is a magnetic tunnel junction device including a topological insulator. According to claim 4,
A magnetic tunnel junction device wherein the topological insulator is BiTeSb or BiSb. According to claim 1,
The free layer is provided in the shape of a polygonal pillar having a plurality of sides,
The SOT generator is a magnetic tunnel junction element in contact with one side of the free layer. According to claim 1,
The free layer is provided in the shape of a polygonal pillar having a plurality of sides,
The SOT generator is a magnetic tunnel junction element that contacts at least two of the plurality of sides of the free layer. According to claim 1,
The SOT source includes a first SOT source in contact with the first side of the free layer, and a second SOT source in contact with the second side of the free layer parallel to the first side,
The first SOT generator and the second SOT generator have the same composition. According to claim 1,
The SOT source includes a first SOT source in contact with a first side of the free layer, and a second SOT source in contact with a second side of the free layer parallel to the first side,
A magnetic tunnel junction device wherein the first SOT generator and the second SOT generator have different compositions. According to claim 1,
The SOT generator is in contact with the first side of the free layer and the second side of the free layer that intersects the first side. According to claim 1,
A magnetic tunnel junction device wherein the free layer has a thickness of 15 nm or more. According to claim 1,
The free layer has a cylindrical shape,
A magnetic tunnel junction device wherein the diameter of the lower surface of the free layer is 10 nm or less. According to claim 1,
The free layer has a cylindrical shape,
A magnetic tunnel junction device wherein the thickness of the free layer is greater than the diameter of the lower surface of the free layer. According to claim 1,
A magnetic tunnel junction element wherein the area of the surface where the free layer and the SOT generator come into contact is larger than the area of the surface where the free layer and the insulating layer come into contact. It includes a magnetic tunnel junction element and electrodes that apply a voltage to the magnetic tunnel junction element,
The magnetic tunnel junction element is:
free class;
a fixed layer on the free layer;
an insulating layer between the free layer and the fixed layer; and
It includes a spin orbit torque (SOT) generator in contact with the side of the free layer,
A surface in contact between the SOT generator and the free layer intersects a surface in contact with the free layer and the insulating layer,
The SOT generator is configured to allow current to flow in a direction crossing the stacking direction of the free layer, the insulating layer, and the fixed layer.

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