KR20180045302A - Spin Synapse Device using Spin Orbit Torque and Method of operating the same - Google Patents

Abstract

The present invention relates to a structure for a spin synapse device using the movement of a magnetic domain wall by a spin orbital torque, and an operation method. It is possible to invert the magnetization of the free layer of a device at a low current by using the spin orbital torque and to facilitate manufacture because the structure of the device is simpler than that of a conventional CMOS. In addition, since a low-power memory is manufactured by a simple process, it is easy to be applied to a highly integrated neurocomputer computer device. The spin synapse device includes an electrode, a tunnel barrier layer, a space layer and first and second pinned layers.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a spin synapse device using a spin-orbit torque and a spin-

BACKGROUND OF THE INVENTION Field of the Invention [0001] The present invention relates to a structure and an operation method of a spin synapse element, and more particularly, to a structure and an operation method of a spin synapse element using a magnetic domain wall movement with a spin orbital torque.

Among the nonvolatile memories that have been recently proposed, there is magnetoresistive random access memory (MRAM) using tunneling magnetoresistance (TMR) as a magnetic memory. Until now, the driving of the MRAM using the spin transfer torque was made by using the method of writing 0 and 1 using the resistance change according to the magnetization direction of the magnetic layer. MRAM is a memory that stores information in a memory cell in accordance with the magnetization state of a magnetoresistive element exhibiting a magnetoresistive effect.

Usually, the magnetoresistive element includes a magnetization variable layer and a magnetization fixed layer. When the magnetization direction of the magnetization variable layer and the magnetization fixed layer are parallel, a low resistance state appears. When the magnetization directions are opposite to each other, a high resistance state appears. Which can be used to store information.

Conventional MRAM devices have only two values, a high resistance state and a low resistance state. Meanwhile, in 2014, IBM created a CMOS neurópic synapse and neuron to show the possibility of a real newcomer computer.

However, in order to realize synaptic behavior in an organism through a CMOS-based device, weighting can be given, but conventional MRAM devices have a problem that it is difficult to implement.

Further, when the size of the MR element is reduced by reducing the size of the magnetoresistive element, the coercive force (Hc) in the magnetoresistive element is increased, so that the current required for writing increases. For this reason, there is a problem that it is very difficult to drive a reduced cell driven with a low current value for a large capacity of 256 Mbits or more.

In order to increase the recording density of the MRAM, it is necessary to reduce the size of the magnetic tunneling junction element. The problem is that when the width of the element element is reduced to several tens of nanometers (nm) or less, the stray field The strength greatly increases, which may adversely affect switching (i.e., magnetization inversion) characteristics of the free layer. Therefore, a problem of switching asymmetry of the free layer occurs, which can be a serious problem in the operation of the memory device (MRAM).

Further, in the case of the spin transfer torque memory, the power consumption is relatively large, and the device is affected by the current required in the read operation, and there is a stability problem.

Further, if a current is flowed by applying a voltage to the element in order to read the resistance value of the magnetic material layer of the spin transfer torque memory, the magnetization direction is interfered by the current, and the resistance value of the magnetic material layer of the memory is read incorrectly And the stability of the device is lowered.

Also, in the case of a CMOS synapse, the size of a device required to make one synapse element is large, and the process is complicated compared to other devices.

US patent application No. US13 / 318119 (filed on April 30, 2010) discloses a memory including a non-magnetic body and performing a storage function by movement of a magnetic wall by a spin transfer torque. However, There is a problem in that direct driving of the device is limited because the driving power is large when the memory is manufactured.

US patent application No. US13 / 318119 (filed October 21, 2008) discloses a structure in which an insulating thin film is formed between magnetic thin films, and a device is controlled using a spin orbital torque. In addition, it relates to a low current multi-step current-switching magnetic memory, which applies a magnetic tunneling junction and uses a torque generated by an electron polarized spin to move the free layer domain will be. Such a device has a problem in that its fabrication structure is complicated and it is difficult to direct the device.

In US patent application No. 12/118499 (filed on May 29, 2008), in a two-pillar structure, a magnetization state of the free layer is reset from 1 to 0 by varying the magnetic wall of the ferromagnetic layer by applying current to one terminal Is a spin RAM that uses bi-directional currents, and is a technique for improving its driving characteristics. Further, the magnetic memory of the multilayer structure is a device whose domain is controlled by the spin transfer torque, and a barrier layer is used between the magnetic thin films. In addition, this structure has a problem in that direct drive of the device is limited because the drive power is large at the time of memory fabrication using the spin transfer torque.

A first aspect of the present invention is to provide a spin synapse device including a free layer in which a magnetic domain wall movement occurs according to a spin orbital torque.

According to a second aspect of the present invention, there is provided a method of operating a spin synapse device to achieve the first technical object.

According to an aspect of the present invention, there is provided a magnetoresistance effect element comprising: an electrode formed on a substrate; a free layer formed on the electrode, the free layer generating a magnetic domain wall movement according to a spin orbital torque; A tunnel barrier layer, a spin synapse element formed on the tunnel barrier layer and including a first pinning layer having a fixed magnetization direction, a spacer layer formed on the first pinning layer, and a second pinning layer formed on the spacer layer .

Wherein the free layer is a spin synapse element made of a metal alloy containing at least any one selected from the group consisting of Co, Fe, Pd, Ni, Mn, and a metal alloy thereof.

The metal alloy may have at least one selected from the group consisting of CoFeB, CoNi, and CoPd.

The tunnel barrier layer may be a metal oxide, and the metal oxide may have at least one selected from the group consisting of HfO ₂ , ZrO ₂ , AlO _x , SiO ₂ , MgO, and Ta ₂ O ₃ .

The first pinned layer and the second pinned layer may have at least one selected from the group consisting of Co, Fe, Pd, Ni, Mn and their alloys.

The spacer layer may have at least one selected from the group consisting of Ta, Cu, Ru, and W.

According to another aspect of the present invention, there is provided a semiconductor device comprising: an electrode formed on a substrate and composed of heavy metal; a free layer formed on the electrode; a tunnel barrier layer formed on the free layer; 1. A spin synapse device comprising a first pinned layer, a spacer layer formed on the first pinned layer, and a second pinned layer formed on the spacer layer, the spin synaptic device comprising: applying a magnetic field in the major axis direction of the electrode; A step of gradually increasing the magnetoresistance value of the spin synapse element due to the movement of the magnetic domain wall in a stepwise manner by the pulse power and the magnetoresistance value being saturated, The magnetization direction of the spin synapse element being formed in a direction opposite to the magnetization direction of the spin synapse element There.

Applying a pulse power in a direction of a magnetic field applied to the spin synapse element after the magnetoresistance value reaches a maximum and a magnetization direction of the free layer is formed in a direction opposite to a magnetization direction of the pinned layer; The step of decreasing the magnetoresistive value of the spin synapse element in a stepwise manner due to the movement of the magnetic domain wall in a stepwise manner by the movement of the magnetization direction of the free layer, The method comprising the steps of: forming a spin synapse element on a substrate;

And confirming the magnetoresistance value of the spin synapse device in order to confirm the accumulation of the pulse power.

According to the present invention described above, there is an effect that the magnetization inversion of the free layer can be reversed with a lower current than the magnetic element using the spin transfer torque.

In addition, since the structure of the device is simpler than that of the conventional CMOS, it is easy to manufacture.

Further, there is an effect that a nonvolatile memory of low power consumption and high integration can be manufactured.

In addition, since it is possible to manufacture a low-power memory by a simple process, it is easy to apply to a highly integrated neurocomputer computer device.

1 is a cross-sectional view of a device structure driven using a spin orbital torque according to a preferred embodiment of the present invention.
2 is a schematic diagram showing a magnetic domain wall state that is moved according to the intensity of a magnetic field applied to a device according to a preferred embodiment of the present invention.
FIG. 3 is a schematic diagram showing a moving state of a magnetic domain wall according to the accumulation or conversion of a pulse signal according to a preferred embodiment of the present invention.
FIG. 4 is a graph showing a change in magnetoresistance value (MR) according to movement of a magnetic domain wall due to movement of a magnetic domain wall as a pulse progresses according to a preferred embodiment of the present invention.
FIG. 5 is a graph illustrating two operations of a long-term potentiation (LTP) and a long-term depression (LTD) according to a preferred embodiment of the present invention.

The present invention is capable of various modifications and various forms, and specific embodiments are illustrated in the drawings and described in detail in the text. It should be understood, however, that the invention is not intended to be limited to the particular forms disclosed, but includes all modifications, equivalents, and alternatives falling within the spirit and scope of the invention. Like reference numerals are used for like elements in describing each drawing.

Unless defined otherwise, all terms used herein, including technical or scientific terms, have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. Terms such as those defined in commonly used dictionaries are to be interpreted as having a meaning consistent with the contextual meaning of the related art and are to be interpreted as either ideal or overly formal in the sense of the present application Do not.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings.

The present invention is a synaptic element for use in a neuromotion computer or the like, and is a synapse element that implements a synapse behavior similar to a living body by using the magnetic wall movement of a magnetic layer caused by a spin-orbital torque.

In general, when a CMOS synapse device is manufactured, the size of the CMOS synapse device is large, and integration is difficult and the manufacturing process is complicated, resulting in a high production cost. The best way to solve such a problem is to use a spin-orbit torque and to manufacture a device capable of controlling the magnetic domain wall by using the spin-orbit torque.

1 is a cross-sectional view of a device structure driven using a spin orbital torque according to a preferred embodiment of the present invention.

Referring to FIG. 1, an electrode 20 is formed on a substrate 10. The electrode 20 is made of a heavy metal material and a free layer 30 is formed on the electrode 20 and a tunnel barrier layer 40 is formed on the free layer 30. The first pinned layer 50 is formed on the tunnel barrier layer 40 and the spacer layer 60 is formed on the first pinned layer 50 and the second pinned layer 70 is formed on the spacer layer 60.

When a current is supplied to the electrode 20 composed of a heavy metal disposed directly under the free layer 30, spin-orbit torque is generated by the Rashba effect or the spin Hall effect. As a result, spin pumping occurs in the free layer 30 and a spin current flows. The magnetization reversal of the free layer 30 occurs due to the spin current. In this case, since the direct current is not applied to the free layer 30, the consumed current is low. In addition, since the write line and the read line are separated from each other in the memory using the spin orbital torque, the stability of the element operation can be easily ensured.

Because CMOS synapses are designed to require multiple gates and channels, the size of a CMOS synapse becomes larger, but synapses based on spin-orbit torque are constructed using a single device, The device can be manufactured with a smaller size.

It is easy to fabricate because the structure of the device using the spin-orbit torque that can reverse the magnetization with lower current than the existing spin transfer torque is simpler than the conventional CMOS.

The electrode 20 is a non-magnetic metal, and the metal used as the electrode 20 is Ta and can provide a spin orbital torque. A spin orbit torque is generated from the accumulation of spin-polarized electrons at the interface between the electrode 20 and the free layer 20. The polarization direction is different from the direction of magnetism and is determined by the current direction.

The free layer 20 can move the magnetic domain wall by the current in the electrode 20 that is in contact. The material used for the free layer 20 is CoFeB, Co / Ni, Co / Pd, CoFe, and Co.

The material used for the tunnel barrier layer 40 is an oxide, and oxides mainly used are MgO and AlO _x .

The first pinned layer 50 and the second pinned layer 70 may be made of any one of Co, Fe, Pd, Ni, Mn, Fe, Co, Ni, Cr, permalloy, heusler alloy, GaMnAs, It is mainly used.

The second pinning layer 70 is provided to prevent the magnetization direction of the first pinning layer 50 from changing when the magnetic domain wall is moved. That is, the second pinning layer 70 has the same magnetization direction as the first pinning layer 50, and the magnetization of the first pinning layer 50 is affected by the movement of the magnetic domain wall of the free layer 20 or the change of magnetization ≪ / RTI >

The spacer layer 60 is a non-magnetic layer, and is mainly made of Ta, Ru, or Cu.

FIG. 2 is a schematic view showing a state of a magnetic domain wall moving according to a magnitude of a current value applied to a device according to a preferred embodiment of the present invention. FIG.

Referring to FIGS. 2 (a), 2 (b) and 2 (c), a current flows in the electrode 100 in the major axis direction.

2 (a), pulse power is continuously applied in the major axis direction of the electrode 100 so that the magnetic domain walls in the free layer 120 can be maximally moved.

In addition, since the magnetization direction of the pinned layer 140 and the main magnetization direction of the free layer 120 are opposite to each other, the magnetoresistance in the vertical direction of the magnetic element can be a high value or a maximum value.

Referring to FIG. 2 (b), the ratio of the magnetic domain wall of the free layer 120 in the spin direction is controlled by the current value flowing through the electrode 100 regardless of the direction of the applied external magnetic field Can be seen.

Further, since the magnetization direction of the pinned layer 140 is equal to the ratio of the magnetic domain wall of the free layer 120, the magnetoresistance in the vertical direction of the device can have an intermediate value among the entire magnetoresistance values.

Referring to FIG. 2 (c), the pulse power is continuously applied in the longitudinal direction of the heavy metal layer 100 so that the magnetic domain walls in the free layer 120 can be maximally moved.

In addition, since the magnetization direction of the pinned layer 140 and the main magnetization direction of the free layer 120 are the same, the magnetoresistance in the vertical direction of the device can be a low value or a minimum value.

Referring to FIGS. 2 (a), 2 (b) and 2 (c), the region of the magnetic domain wall in the same spin direction in the free layer 120 can be adjusted by controlling the pulse power in the long axis direction of the electrode 100.

FIG. 3 is a schematic diagram showing a magnetic domain wall movement state of a free layer as a pulse signal is accumulated or converted according to a preferred embodiment of the present invention.

3 (a) and 3 (b), FIG. 3 (a) shows the progress of the pulse power, FIG. 3 (b) shows the magnetic domain wall movement state of the free layer 120 as the pulse power progresses have.

Referring to FIG. 3, the current value corresponding to the first pulse flows through the electrode 110, and the current flows in the direction of the ground of the electrode 110. At this time, since the magnetization direction of the main region of the free layer 120 is opposite to the magnetization direction of the pinned layer 140, the magnetoresistance value in the vertical direction of the device can show a high value.

Then, the second pulse is applied, and since the free layer 120 is composed of a magnetic domain wall of the same size as the magnetization direction of the opposite direction, the magnetization resistance of the free layer 120 becomes smaller than that of the first pulse.

Then, the third pulse is applied, and the magnetic domain wall of the free layer 120 moves, so that the magnetic domain wall region in the same direction as the magnetization direction of the fixed layer 140 increases. Therefore, the magnetoresistance of the device is reduced.

 Next, the fourth pulse, which is phase-inverted from the third pulse, is applied, and the magnetic domain wall in the free layer 120 moves in the opposite direction unlike the case where the third pulse is applied, so that the domain state of the magnetic domain wall of the free layer 110 Becomes the same state as when the second pulse is applied.

Subsequently, when the fifth pulse is applied, the magnetic domain wall in the free layer 120 moves further so that the domain wall region opposite to the magnetization state of the pinned layer 140 increases, and the magnetoresistance of the element is the same as that when the first pulse is applied State.

In the case of the magnetic domain wall movement using the spin orbital torque, the magnetic domain wall moves in a direction perpendicular to the direction in which the current flows. The current required for the magnetic domain wall movement due to the spin orbital current is about 10% of the current required for the magnetic domain wall movement due to the spin transfer torque.

FIG. 4 is a graph illustrating a change in magnetoresistance due to movement of a magnetic domain wall as a pulse progresses according to a preferred embodiment of the present invention. FIG.

Referring to FIG. 4, the initial state of the device is a state in which the magnetization direction of the free layer 120 is the same as the magnetization direction of the pinned layer 140, and the magnetoresistance value of the device is minimum.

  If the magnetization direction of the free layer 120 of the device is in the same state as the magnetization direction of the pinned layer 140, the magnetoresistance in the vertical direction of the device can be minimized.

By applying pulse power stepwise to the device, a spin orbital current is generated due to the current flowing to the electrode 100, and the magnetic domain wall in the free layer 120 is moved.

In the initial state of the device, a reverse pulse power as in No. 4 of FIG. 3 is applied to move the magnetic domain wall of the free layer 120. The magnetoresistance of the device increases with the increase of the domain wall region having the magnetization direction opposite to the magnetization direction of the pinned layer 140. [ The magnetic domain wall is further moved due to the applied reverse pulse and the magnetic domain wall region having the magnetization direction opposite to the magnetization direction of the pinned layer 140 becomes the maximum, so that the magnetoresistance of the device becomes maximum.

Subsequently, the same pulse power as the first pulse of FIG. 3 is applied to change the moving direction of the magnetic domain wall. The area of the magnetic domain wall of the free layer 120 having the magnetization direction in the same direction as the magnetization direction of the pinned layer 140 is increased by the movement of the magnetic domain wall and the magnetoresistance of the device is decreased.

Subsequently, when the pulse power is further applied, the subsequent magnetic domain wall movement causes the domain wall free region having the magnetization direction in the same direction as the magnetization direction of the pinned layer 140 to be the maximum, and the magnetoresistive value of the device is minimized.

That is, the magnetoresistance value of the device can be adjusted by changing the region having the same magnetization direction due to the magnetic domain wall movement of the free layer 120, and the magnetic domain wall of the free layer 120 moves according to the progress of the pulse power , The magnetoresistance value of the device can be adjusted in steps.

 FIG. 5 is a graph illustrating two operations of a long-term potentiation (LTP) and a long-term depression (LTD) according to a preferred embodiment of the present invention.

Referring to FIG. 5, biological synapses perform two operations, Long-Term Potentiation (LTP) and Long-Term Depression (LTD). LTP is a synapse between two neurons that is stimulated with a long cycle, which means that the signal transmission between the neurons is gradually improved. This means that the signaling ability of the synapse is improved. LTD, on the contrary, means that signaling between neurons is getting weaker. It is said that the control of the improvement and weakening of the signal transduction regulates the weight of the synapse. It can be seen that the operation of the biological synapse is similar to the adjustment of the magnetoresistance value according to the movement of the magnetic domain wall in FIG.

In the present invention, in the case of the spin synapse, it can be implemented in a similar manner by changing the magnetoresistance through the magnetic domain wall movement operation as in the operation of the biological synapse LTP, LTD.

Example 1

For experimental investigation, the device is fabricated with the following structure. Si is used as a substrate, and SiO ₂ is formed to a thickness of 120 nm on Si as a substrate. Subsequently, Ta was formed to 2 nm as the electrode 100, and then the free layer 120 was formed of Co _0.4 Fe _0.55 B _0.05 on the electrode 100.

Further, MgO 2 nm was formed as a tunnel barrier layer 130, and 4 nm of Fe was formed as a fixed layer 140 on the free layer 120 in order.

Evaluation example 1

The devices fabricated in Example 1 were evaluated. Pulse power was applied to the electrode 100 in the major axis direction to cause a current to flow. The magnetic domain wall in the free layer 120 moved according to the pulse power, and the direction of movement of the domain wall moved in the direction perpendicular to the current flow. Pulse power was applied to change the current flowing to the electrode 100 in the range of 5.0 ⁶ 10 ⁶ A / Cm ² to 6.4 ⁶ 10 ⁶ A / Cm ² .

When the pulse power is continuously applied in the same phase, the magnetic domain wall of the free layer 120 moves in one direction, and the spin directions of the free layer 120 are all the same. At this time, the magnetization direction of the free layer 120 became the same as the magnetization direction of the fixed layer 140, and the magnetoresistance value of the device reached a maximum value.

10: substrate 20: electrode
30: free layer 40: tunnel barrier layer
50: first fixing layer 60: spacer layer
70: second fixed layer 100: current direction
110: electrode 120: free layer
130: tunnel barrier layer 140: fixed layer

Claims (10)

An electrode formed on a substrate;
A free layer formed on the electrode and generating a magnetic domain wall movement in accordance with a spin orbit torque;
A tunnel barrier layer which is a nonmagnetic material formed on the free layer;
A first pinned layer formed on the tunnel barrier layer and having a fixed magnetization direction;
A spacer layer formed on the first pinning layer; And
And a second pinning layer formed on the spacer layer. The method according to claim 1,
Wherein the free layer comprises at least one selected from the group consisting of Co, Fe, Pd, Ni, Mn, and alloys thereof. 3. The method of claim 2,
Wherein the free layer is at least one selected from the group consisting of CoFeB, CoNi, and CoPd. The method according to claim 1,
Wherein the tunnel barrier layer is a metal oxide and the metal oxide is at least one selected from the group consisting of HfO ₂ , ZrO ₂ , AlOx, SiO ₂ , MgO, and Ta ₂ O ₃ . The method according to claim 1,
Wherein the first pinned layer and the second pinned layer comprise at least one selected from the group consisting of Co, Fe, Pd, Ni, Mn, and alloys thereof. The method according to claim 1,
Wherein the spacer layer is at least one selected from the group consisting of Ta, Cu, Ru, and W. A free layer formed on the electrode, a tunnel barrier layer formed on the free layer, a first pinning layer formed on the tunnel barrier layer, a spacer layer formed on the first pinning layer, and a spacer layer formed on the spacer layer, A spin synapse device comprising a second pinning layer formed on a layer,
Applying a magnetic field in a longitudinal direction of the electrode;
Applying pulse power in a direction opposite to the direction of the magnetic field;
The magnetoresistance value of the spin synapse element is increased stepwise due to the stepwise movement of the magnetic domain wall by the pulse power; And
Wherein the magnetoresistance value is saturated and the magnetization direction of the free layer is formed in a direction opposite to the magnetization direction of the pinned layer. The method of claim 7, further comprising the step of confirming the magneto-resistance value of the spin synapse device for confirming the accumulation state of the pulse power after the step of gradually increasing the magneto-resistance value A method of operating a spin synapse device. 8. The method of claim 7,
After the step of setting the magnetization direction of the free layer in a direction opposite to the magnetization direction of the pinned layer,
Applying a magnetic field to the spin synapse device in the same direction as the direction of the pulse power;
The magnetoresistance value of the spin synapse element is gradually decreased due to the movement of the magnetic domain wall by a magnetic field applied in the same direction as the pulse power; And
The magnetoresistance value is minimized and the magnetization direction of the free layer is formed in the same direction as the magnetization direction of the pinned layer. The method of claim 9, further comprising the step of confirming the magneto-resistance value of the spin synapse device for confirmation of the accumulated state of the pulse power after the step of decreasing the magnetoresistance value stepwise A method of operating a spin synapse device.

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