KR101898666B1 - Neuron device and method of operating the same - Google Patents

Abstract

The present invention relates to a magnetic memory device including a channel unit in which a magnetization direction is changed by accumulating a plurality of data and first and second magnetization control units for changing a magnetization direction of the channel unit according to a plurality of data formed on both ends of the channel unit, And a control unit which is formed on the channel unit between the first and second magnetization control units and which generates data accumulated in the channel unit above a threshold value, and a driving method thereof.

Description

[0001] The present invention relates to a neuron device and a driving method thereof,

The present invention relates to a neuromorphic system, and more particularly to a neuron device for integrating and firing data and a driving method thereof.

In recent years, power consumption has been greatly increased and heat problems have become serious in an integrated circuit based on the Von Neumann architecture, and many attempts have been made to imitate the animal's nervous system. Especially, in the technique imitating the animal's nervous system, it is possible to improve the recognition function and the judgment function by enabling cognitive function and learning while greatly reducing power consumption. As a result, the functions of the conventional von Neumann integrated circuit can be replaced or significantly improved, and thus interest and research are increasing.

The neuromorphic system can be implemented using the principle of nerve cell. New morphic system refers to a system that imitates brain processing of data by implementing a neuron constituting a human brain using a plurality of elements. Thus, by using a neurocompic system that includes neuron elements, data can be processed and learned in a manner similar to the brain. That is, the neuron element is connected to another neuron element through the synapse of the neuron element, and can receive data from the other neuron element through the synapse. At this time, the neuron element accumulates and integrates the received data, and if it exceeds the threshold value (Vt), it outputs the generated data. That is, the neuron element functions to integrate and fire data. In addition, the synapse device outputs selectively according to the input value. That is, the synaptic element potentiates or depresses input data and transmits it to the neuron element.

Conventionally, these neuron elements are fabricated on the basis of C-MOSFETs. The C-MOSFET-based neuron device requires a capacitor for integrating data, a comparator for generating a signal when a signal of a predetermined threshold value or more is applied, and additional circuits for securing stability and delay. . However, since the area occupied by the capacitor is considerably large, the total area of the neuron device becomes very large, and the power consumption becomes very large. These structural limitations lead to various problems such as the complexity of the configuration of the new morphic system and the limited precision.

On the other hand, Kaushik Roy et al. Have shown that the MRAM-based neuron device can reduce the power consumption to 1/100 of that of the C-MOSFET based neuron device. However, we have reported the mechanism through theoretical calculations and have not designed or manufactured MRAM-based neuron devices.

Korean Patent Publication No. 2016-0056779 Korean Patent Publication No. 2016-0019682 Korean Patent Publication No. 2016-0061966

Kaushik Roy et al. Energy-Efficient Non-Boolean Computing with Spin Neurons and Resistive Memory. 2014. 01, IEEE TRANSACTIONS ON NANOTECHNOLOGY, VOL. 13, NO. 1, pp. 23-34

The present invention provides a neuron element and a driving method thereof that can solve the problem of a C-MOSFET based neuron element.

The present invention provides a neuron element and a driving method thereof that can reduce power consumption and improve precision.

The present invention provides a magnetic tunnel junction-based neuron element and a driving method thereof.

According to an aspect of the present invention, there is provided a neuron device comprising: a channel unit in which a magnetization direction is changed by accumulating a plurality of data; First and second magnetization control units formed on the channel unit and adapted to change a magnetization direction of the channel unit according to a plurality of input data; And a control unit formed on the channel unit between the first and second magnetization control units and for igniting data accumulated in the channel unit.

The channel portion includes a substrate and a channel layer formed on the substrate and having a magnetic layer.

The channel portion further includes a buffer layer and a seed layer formed between the substrate and the channel layer, and a separation layer formed on the channel layer.

The magnetization direction of the channel layer is fixed in one direction in the initial state, and the magnetization direction is sequentially changed in the other direction opposite to the one direction as the plurality of data are sequentially inputted.

Data of the channel section is input / output through the first and second magnetization control sections.

The first and second magnetization control sections have different magnetization directions.

The first and second magnetization control sections are respectively formed in a laminated structure of a first magnetic layer, a nonmagnetic layer and a second magnetic layer on the channel section, and the thicknesses of the first and second magnetic layers are different from each other.

The initial magnetization direction of the channel section is determined by the second magnetization control section, and the magnetization direction of the channel section is sequentially changed by inputting data through the first magnetization control section.

And the data is stored in the channel section between the first magnetization control section and the control section.

The control unit includes a magnetic tunnel junction in which a free layer, a tunneling barrier and a pinned layer are stacked, a capping layer formed on the magnetic tunnel junction, and a synthetic exchange ferromagnetic layer formed on the capping layer and fixing the magnetization direction of the pinning layer do.

The magnetization direction of the pinned layer is fixed and the magnetization direction of the free layer is changed according to the magnetization direction of the channel layer.

The free layer and the pinned layer have magnetizations opposite to each other in the initial state, and when the magnetization directions of the free layer and the pinned layer are the same due to the magnetization of the channel portion, the data accumulated in the channel portion is ignited.

The control section has a width of 1/5 to 1/10 of the length of the channel section between the first and second magnetization control sections.

The accumulation amount of data is adjusted according to the length of the channel portion between the first magnetization control portion and the control portion, the width of the control portion, and the pulse width and height applied to input data.

The channel unit accumulates 2 ¹ to 2 ¹⁰ data.

According to another aspect of the present invention, there is provided a neuron device comprising: a channel unit in which a domain wall moves as a plurality of data are input and accumulated; A first magnetization control unit for moving the domain wall of the channel unit according to a plurality of input data; A second magnetization control unit having magnetization directions different from those of the first magnetization control unit and fixing the magnetization direction of the channel unit in one direction; And a control unit for causing the magnetization direction to change when at least a part of the domain wall is coupled with the channel unit, and to fire data accumulated in the channel unit when the domain wall passes the lower part.

The channel portion, the first and second magnetization control portions, and the control portion each include at least a magnetic material.

Wherein the magnetization direction of the first region is fixed and the magnetization direction of the second region below the first region is changed in accordance with the magnetization direction of the channel portion, and when the magnetization direction of the second region and the first region is the same, And the data accumulated in the portion is ignited.

According to another aspect of the present invention, there is provided a method of driving a neuron device, comprising: setting a magnetization direction of a channel portion such that a magnetization direction of a free layer and a pinned layer of a control portion are opposite; Sequentially changing a magnetization direction of the channel unit by inputting a plurality of data sequentially; And firing data accumulated in the channel portion when the magnetization direction of the channel portion overlapped with the control portion is the same as the magnetization direction of the free layer.

The width of the magnetization direction of the channel portion is adjusted according to at least one of the length of the channel portion, the width of the control portion, and the pulse width and height applied for inputting data.

The neuron device according to an embodiment of the present invention can be implemented based on MRAM. That is, a neuron device that accumulates and fires data by changing the magnetization direction and the domain wall movement by using the laminated structure and the magnetic tunnel junction structure made of the magnetic material can be manufactured. Therefore, the neuron device of the present invention can reduce energy and direct the neuron device compared to the conventional C-MOSFET based neuron device. In addition, by implementing the neuronal system using the neuron device of the present invention, it can contribute to artificial intelligence development that can learn logical thinking before data is processed.

1 is a cross-sectional view of a neuron device according to an embodiment of the present invention;
2 is a schematic cross-sectional view of a neuron device according to an embodiment of the present invention.
FIGS. 3 and 4 are graphs showing magnetization characteristics of the first and second magnetization control units of the neuron device according to an embodiment of the present invention. FIG.
5 is a graph showing magnetization characteristics of a control unit of a neuron device according to an embodiment of the present invention.
6 to 13 are schematic views for explaining a method of driving a neuron device according to an embodiment of the present invention.
FIG. 14 is an input and output waveform diagram for driving a neuron device according to an embodiment of the present invention; FIG.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. It should be understood, however, that the invention is not limited to the disclosed embodiments, but is capable of other various forms of implementation, and that these embodiments are provided so that this disclosure will be thorough and complete, It is provided to let you know completely.

FIG. 1 is a cross-sectional view of a neuron device according to an embodiment of the present invention, and FIG. 2 is a schematic cross-sectional view.

Referring to FIGS. 1 and 2, a neuron device according to an embodiment of the present invention includes a channel unit 100 having a magnetization direction changed according to input data and storing a plurality of data, First and second magnetization control units 200 and 300 that are formed on the first and second magnetization control units 200 and 300 and fix the initial magnetization direction of the channel unit 100 and input and output data, And a controller 400 that is formed on the channel unit 100 and outputs the data stored in the channel unit 100 when the data stored in the channel unit 100 is equal to or greater than a threshold value Vth.

The magnetization direction of the channel unit 100 is fixed by the first and second magnetization control units 200 and 300 and the magnetization direction is sequentially changed as a plurality of data are input, . That is, as the magnetization direction is sequentially changed, the channel unit 100 moves along the direction in which the domain wall is changed in the magnetization direction, thereby storing data. Here, domain walls are boundaries between magnetizations in different directions, and as the data is accumulated, the magnetization direction of the channel section 100 is changed to move in one direction. The first and second magnetization control units 200 and 300 have magnetizations in different directions and fix the magnetization direction of the channel unit 100 in one direction in the initial state. The first and second magnetization control units 200 and 300 may receive data from the channel unit 100 through any one of the first and second magnetization control units 200 and 300, And outputs the data. At this time, data is input through any one of the first and second magnetization control units 200 and 300 so that the magnetization direction of the channel unit 100 is changed. At least a part of the control unit 400 is coupled with the magnetization of the channel unit 100 to change its magnetization direction. When the data stored in the channel unit 100 is equal to or more than the threshold value, the magnetization direction is changed, And outputs the accumulated data. That is, the control unit 400 can output the data stored in the channel unit 100 when the magnetization direction of one region of the channel unit 100 and the region adjacent thereto overlap with the control unit 400. Therefore, the neuron device according to the present invention has a function that the channel unit 100 functions to tntegrate data, and the control unit 400 performs a fire function on the data accumulated in the channel unit 100, Driving is enabled.

One. Channel portion

The channel unit 100 stores data input through at least one of the first and second magnetization control units 200 and 300. In this case, the magnetization direction of the channel unit 100 is fixed by the first and second magnetization adjusting units 200 and 300 in an initial state before the data is input, that is, in a reset state, The magnetization direction is changed. The domain wall can be moved in one direction as the magnetization direction is changed. For example, in the initial state, the channel unit 100 has the same magnetization direction as the magnetization direction of the second magnetization control unit 300, and when the input data is accumulated, the channel unit 100 moves in the magnetization direction of the first magnetization control unit 200 Are sequentially changed along one direction, and the domain wall moves in one direction accordingly. Therefore, the channel unit 100 can determine the amount of data that can be accumulated according to the width of the channel region. Of course, the amount of data accumulated according to the width w of the controller 400 may be determined. 2, when the data is inputted through the first magnetization control unit 200, the width of the channel region where the data is accumulated is the distance between the first magnetization control unit 200 and the control unit 400 It can be defined as a). The channel unit 100 may include a channel layer 140 formed on the substrate 110 and having a magnetization direction changed according to input data. The buffer layer 120 and the seed layer 130 formed between the substrate 110 and the channel layer 140 and the separation layer 150 formed on the channel layer 140 may be further included.

The substrate 110 may be a semiconductor substrate. For example, the substrate 110 may be a silicon substrate, a gallium arsenide substrate, a silicon germanium substrate, a silicon oxide film substrate, or the like. In this embodiment, a silicon substrate is used. An insulating layer may be formed on the substrate 110. The insulating layer can be formed using an amorphous silicon oxide film (SiO ₂ ) or the like. That is, the substrate 110 may be a semiconductor substrate on which an insulating layer such as a silicon oxide film is formed.

The buffer layer 120 and the seed layer 130 may be formed under the channel layer 140 to form a vertical magnetization of the channel layer 140. That is, it is preferable that the magnetization direction is changed clearly according to the input data. To this end, the buffer layer 120 and the seed layer 130 may be formed so that the channel layer 140 has vertical magnetization. The buffer layer 120 may be formed using tantalum (Ta), for example, with a thickness of 2 nm to 10 nm. The seed layer 130 may be formed of a polycrystalline material, such as magnesium oxide (MgO), aluminum oxide (Al ₂ O _3), silicon oxide (SiO _2), tantalum oxide (Ta ₂ O _5), silicon nitride (SiNx) or aluminum nitride (AlNx). Preferably, the seed layer 130 may be formed of magnesium oxide, for example, to a thickness of 1 nm to 1.5 nm. By forming the seed layer 130 in this way, the crystallinity of the channel layer 140 formed thereon can be improved. Also, the crystallinity of the first and second magnetization control units 200 and 300 and the control unit 400 can be improved. That is, when the seed layer 130 is formed of a polycrystalline material, the amorphous channel portion 140 and the stacked structures 200, 300, and 400 formed thereon grow along the crystal direction of the seed layer 130, .

The channel layer 140 changes the magnetization direction according to data input to at least one of the first and second magnetization control units 200 and 300, thereby moving the domain wall. That is, the channel layer 140 can be changed from one direction to the opposite direction in which the magnetization is not fixed in one direction. In other words, the channel layer 140 can change the direction of magnetization in the direction of the substrate 110 (i.e., the lower direction) to the direction of the laminate (that is, the upper direction) . ≪ / RTI > Accordingly, when data is repeatedly input through at least one of the first and second magnetization controllers 200 and 300, the domain wall is shifted while the magnetization direction is sequentially changed, A plurality of data are accumulated. For example, the channel layer 140 may be magnetized in an initial state, that is, in a downward direction from a reset state, and may be magnetized from the first magnetization controller 200 according to data input through the first magnetization controller 200 The magnetization direction is changed to a predetermined width in the direction of the control unit 400, and thus the domain wall moves in the direction of the control unit 400. The channel layer 140 may be formed of a ferromagnetic material. For example, the channel layer 140 may be formed of any one of a full-Heusler semimetal alloy, an amorphous rare-earth alloy, a ferromagnetic metal and a nonmagnetic matal alternately stacked A multi-layer thin film, an alloy having an L10 type crystal structure, or a cobalt-based alloy. Examples of the alloys of the full-Hoesler semi-metal series include CoFeAl and CoFeAlSi, and amorphous rare earth element alloys include alloys such as TbFe, TbCo, TbFeCo, DyTbFeCo and GdTbCo. Co / Pt, Co / Ru, Co / Os, Co / Au, Ni / Cu, CoFeAl / Pd, and CoFeAl as the multilayered thin film in which the nonmagnetic metal and the magnetic metal are alternately stacked. / Pt, CoFeB / Pd, CoFeB / Pt, and the like. Examples of alloys having an L10 type crystal structure include Fe50Pt50, Fe50Pd50, Co50Pt50, Fe30Ni20Pt50, Co30Ni20Pt50, and the like. Examples of the cobalt-based alloys include CoCr, CoPt, CoCrPt, CoCrTa, CoCrPtTa, CoCrNb and CoFeB. Among these materials, the CoFeB monolayer can be formed thicker than the CoFeB, Co / Pt or Co / Pd multi-layer structure, and is easier to etch than metals such as Pt or Pd. The manufacturing process is easy. Therefore, the embodiment of the present invention forms a channel layer 140 using a CoFeB single layer, and CoFeB can be formed into amorphous and then textured into a BCC 100 by heat treatment.

The isolation layer 150 is formed on the channel layer 140 to magnetically isolate the channel portion 100 and the first and second magnetization control portions 200 and 300 from each other. That is, since the separation layer 150 is formed, the magnetizations of the first and second magnetization control parts 200 and 300 and the channel layer 140 are generated independently of each other. In addition, the separation layer 150 may couple at least a part of the channel section 100 and the control section 400. That is, the control unit 400 may be formed of a magnetic tunnel junction (MTJ). By forming the isolation layer 150, the free layer of the magnetic tunnel junction is coupled with the channel layer 140, The magnetization direction can be adjusted. The isolation layer 150 may be formed of a material that allows the first and second magnetization control units 200 and 300 and the control unit 400 to grow and grow. That is, the separation layer 150 allows the first and second magnetization control units 200 and 300 and the control unit 400 to grow in a desired crystal direction. For example, the separation layer 150 may facilitate crystal growth in a (111) direction of a face centered cubic (FCC) or a (001) direction of a hexagonal close-packed structure As shown in FIG. The isolation layer 150 may be formed of tantalum, ruthenium, titanium, palladium, platinum, magnesium, cobalt, aluminum and tungsten, ), Or an alloy thereof. For example, the isolation layer 150 may be formed of at least one of tantalum (Ta) and tungsten (W). That is, the isolation layer 150 may be formed of tantalum (Ta), tungsten (W), or a stacked structure of Ta / W. In an embodiment of the present invention, the isolation layer 150 is formed of tantalum. On the other hand, the separating layer 150 can be formed to a thickness of 0.3 nm to 0.6 nm. When Ta is used, the separating layer 150 can be formed to a thickness of 0.4 nm to 0.6 nm. When W is used, the separating layer 150 has a thickness of 0.35 nm to 0.55 nm .

2. 1st  And Second  The magnetization control unit

The first and second magnetization control units 200 and 300 are spaced apart from each other at both ends of the channel unit 100. That is, the first and second magnetization control units 200 and 300 may be formed to have a predetermined length in the direction of the channel unit 100 from both ends of the channel unit 100, As shown in Fig. At this time, the first and second magnetization control units 200 and 300 may be formed to have the same length and width, and may have a length and a width of 5 nm or less. For example, the first and second magnetization control units 200 and 300 may be formed to have a length and a width of 1 nm to 5 nm, and may have the same length and width, have. Also, the first and second magnetization control units 200 and 300 are formed to have magnetizations opposite to each other. For example, the first magnetization control unit 200 has magnetization in the downward direction (i.e., the substrate 110 direction) and the second magnetization control unit 200 has magnetization in the upward direction. Also, one of the first and second magnetization control units 200 and 300 inputs data and the other outputs data. That is, one of the first and second magnetization control units 200 and 300 injects electrons into the channel layer 140, and the other outputs electrons accumulated in the channel layer 140. For example, the first magnetization control unit 200 receives data and stores the data in the channel layer 140, and the second magnetization control unit 300 outputs the data stored in the channel layer 140. The first and second magnetization control units 200 and 300 may be configured such that the channel unit 100 has the magnetization in the magnetization direction of the second magnetization control unit 300 in the initial state, The channel unit 100 can sequentially have downward magnetization according to data repeatedly input through the one-magnetization control unit 200. [

The first and second magnetization controllers 200 and 300 may have the same structure. For example, the first magnetization control unit 200 may have a laminated structure of the first magnetic layer 210, the first non-magnetic layer 220 and the second magnetic layer 230 and the first electrode 240, The two-magnetization control unit 200 may have a laminated structure of the third magnetic layer 310, the second nonmagnetic layer 320, the fourth magnetic layer 330, and the second electrode 340. The first and second magnetic layers 210 and 230 are antiferromagnetically coupled through the first nonmagnetic layer 220 and the third and fourth magnetic layers 310 and 330 are coupled to the second non- As shown in FIG. The magnetization directions of the first and second magnetic layers 210 and 230 are arranged antiparallel and arranged in the magnetization direction of the third and fourth magnetic layers 310 and 330 or antiparallel to each other. For example, the first magnetic layer 210 may be magnetized in a downward direction (i.e., in the direction of the substrate 110) and the second magnetic layer 230 may be magnetized in an upward direction (i.e., in the direction of the first electrode 240) have. The third magnetic layer 310 may be magnetized in the upward direction (i.e., the second electrode 340 direction) and the fourth magnetic layer 330 may be magnetized in the downward direction (i.e., in the direction of the substrate 110) . The magnetization direction of the channel section 100 may be fixed or changed in the downward direction and the magnetization direction of the channel section 100 may be changed in the upward direction As shown in FIG.

The first and second magnetic layers 210 and 230 and the third and fourth magnetic layers 310 and 330 may be formed by alternately stacking a magnetic metal and a non-magnetic metal. As the magnetic metal, a single metal selected from the group consisting of iron (Fe), cobalt (Co) and nickel (Ni), or an alloy thereof may be used. As the nonmagnetic metal, chromium (Cr), platinum A single metal selected from the group consisting of palladium (Pd), iridium (Ir), rhodium (Rh), ruthenium (Ru), osmium (Os), rhenium (Re), gold (Au) Can be used. For example, the first and second magnetic layers 210 and 230 and the third and fourth magnetic layers 310 and 330 may be formed of [Co / Pd] n, [Co / Pt] n or [CoFe / Here, n may be an integer of 1 or more). Preferably, the first and second magnetic layers 210 and 230 and the third and fourth magnetic layers 310 and 330 may be formed of [Co / Pt] n, The magnetic layers 210 and 310 and the channel layer 140 are coupled through the separation layer 150 so that the channel layer 140 has the same magnetization direction as the first and second magnetization control portions 200 and 300. Meanwhile, the first and second magnetization controllers 200 and 300 may change the number of repetitions of [Co / Pt] n and the order of deposition so that the magnetization directions of the first and second magnetization controllers 200 and 300 are opposite to each other So that the magnetization direction in the channel section 100 can be changed. For example, the number of [Co / Pt] n repetitions of the first magnetic layer 210 is made smaller than that of the third magnetic layer 310, and the number of repetitions of [Co / Pt] n of the second magnetic layer 230 is made smaller than that of the fourth magnetic layer 330) so that the magnetization directions are opposite to each other. That is, the [Co / Pt] n repetition number of the first magnetic layer 210 is made smaller than the second magnetic layer 230, and the [Co / Pt] n repetition number of the third magnetic layer 310 is set to be the fourth magnetic layer 330 The magnetization directions of these magnetic layers can be made different from each other. For example, when the first magnetic layer 210 is formed of [Co / Pt] 3 and the second magnetic layer 230 is formed of [Co / Pt] 6 so that the first magnetic layer 210 has magnetization in the downward direction 2 magnetic layer 230 can have magnetization in the upward direction. The third magnetic layer 310 is formed of [Co / Pt] 6 and the fourth magnetic layer 330 is formed of [Co / Pt] 3 so that the third magnetic layer 310 has the magnetization in the up- (330) may have magnetization in the downward direction. Therefore, the first magnetization control unit 200 has the magnetization in the lower direction and the second magnetization control unit 300 can have the magnetization in the upper direction.

The first nonmagnetic layer 220 is formed between the first magnetic layer 210 and the second magnetic layer 230 and the second nonmagnetic layer 320 is formed between the third magnetic layer 310 and the fourth magnetic layer 330 . The first and second nonmagnetic layers 220 and 320 may be formed of a nonmagnetic material that allows the first and second magnetic layers 210 and 230 and the third and fourth magnetic layers 310 and 330 to perform a semi- . For example, the first and second nonmagnetic layers 220 and 320 may be formed of a single or a mixture of two or more of ruthenium (Ru), rhodium (Rh), osmium (Os), rhenium (Re) Alloy.

Meanwhile, the first and second electrodes 240 and 340 are formed on the second and fourth magnetic layers 230 and 330, respectively. The first and second electrodes 240 and 340 may be connected to the outside for data input / output with the outside. That is, electrons may be injected or outputted through the first and second electrodes 240 and 340. The first and second electrodes 240 and 340 may be formed using a conductive material, such as a metal, a metal oxide, a metal nitride, or the like. For example, the first and second electrodes 240 and 340 may be formed of tantalum (Ta), ruthenium (Ru), titanium (Ti), palladium (Pd), platinum (Pt), magnesium (Mg) Or a single metal selected from the group consisting of alloys thereof.

3. The control unit

The control unit 400 is formed on the channel unit 100 between the first and second magnetization control units 200 and 300. The control unit 400 may be formed to have a width narrower than the width of the first and second magnetization control units 200 and 300 in the longitudinal direction of the channel unit 100. [ The control unit 400 outputs the data stored in the channel unit 100 when the data exceeds a threshold value. That is, the controller 400 amplifies the current to a greater extent than the current applied to the channel unit 100, and outputs the current. For example, the control unit 400 may be formed to have a width w of 1/5 to 1/10 of the length L of the channel unit 100 to determine the threshold value of the current amplification according to the domain wall movement. The control unit 400 is coupled with the channel unit 100 of the region overlapping with the control unit 400 to change the magnetization direction of the channel unit 100. After the data is stored in a predetermined amount, And the data is outputted in the same direction. The number of times of data accumulation in the channel unit 100, that is, the data accumulation amount may be determined by the width of the control unit 400 and the distance between the first magnetization control unit 200 and the control unit 400. That is, as shown in FIG. 2, the length of the channel unit 100 between the first and second magnetization control units 200, that is, the channel length is L, and the first magnetization control unit 200 and the control unit 400 A + b + w, where a is the distance between the control unit 400 and the second magnetization control unit 300, b is the width of the control unit 400, and a is a 2 ¹ w or more and 2 ¹⁰ w or less. At this time, the width (w) of the control unit 400 should be such that the free layer of the vertical magnetic tunnel junction can be switched by one input pulse. If the data is inputted once through the first magnetization controller 200, the magnetization direction is changed by the width of the controller 400 and the domain wall is moved by the width of the controller 400, the amount of data accumulated according to the distance a between the first magnetization control unit 200 and the control unit 400 can be determined. Therefore, the neuron device according to the present invention can store 2 ¹ or more and 2 ¹⁰ or less data in the channel section 100. That is, two to ^ten or more of data may be accumulated in the channel section 100 between the first magnetization control section 200 and the control section 400 where data is substantially accumulated. Of course, the data accumulated in the channel unit 100 may be adjusted according to the width and the height of the pulse applied through the first magnetization control unit 200. That is, the shorter the pulse width or the lower the height, the larger the number of accumulated data. On the contrary, the longer the pulse width or the higher the height, the smaller the number of accumulated data. At this time, the width of the pulse may be 10 ns or less and the height of the pulse, that is, the voltage may be less than 1 V. On the other hand, the neuron element can be voltage-driven as described above, and can also be current-driven. In case of current driving, it can be applied to 2mA or less.

The control unit 400 may be formed of a tunnel magnetic bonding structure. That is, the control unit 400 may include a magnetic tunnel junction in which a free layer 410, a tunneling barrier 420, and a pinned layer 430 are stacked. The control unit 400 may further include a capping layer 440 formed on the magnetic tunnel junction, a composite exchange ferromagnetic layer 450, and a third electrode 460. The composite exchange semi-magnetic layer 450 may include a fifth magnetic layer 451, a third nonmagnetic layer 452 and a sixth magnetic layer 453. Particularly, the free layer 410 is formed by a tunneling barrier 420, The free layer 410 is separated from the channel layer 140 and is separated from the channel layer 140 under the channel layer 140 and the isolation layer 150 and is coupled with the magnetization direction of the channel layer 140. Accordingly, The tunneling magnetoresistance ratio (TMR) of the fixed layer 430 and the free layer 410 can be changed according to the magnetization direction of the pinned layer 430 and the free layer 410 in parallel (RP) or antiparallel (RAP) ratio, and the current can be amplified, that is, fired, when it is changed from the antiparallel state to the parallel state.

The free layer 410 is formed on the separation layer 150 and the magnetization can be changed from one direction to the opposite direction opposite thereto without being fixed in one direction. That is, the free layer 410 may have the same (or parallel) magnetization direction as the pinned layer 430 and vice versa (i.e., antiparallel). The free layer 410 may be coupled to the channel layer 140 by the isolation layer 150 to change the magnetization direction of the free layer 410 according to the magnetization direction of the channel layer 140. Therefore, if the magnetization direction of the free layer 410 is the same as the fixed layer 430 according to the magnetization direction of the channel layer 140, the data accumulated in the channel layer 140 can be amplified and output. That is, when a predetermined number of data is accumulated in the channel layer 140 to change the magnetization direction of the channel layer 140 under the control unit 400 and the magnetization direction of the free layer 410 becomes the same as the fixed layer 430, And the data stored in the layer 140 is output through the second magnetization control unit 300. The free layer 410 is formed of a ferromagnetic material, for example, a Full-Heusler semi-metal based alloy, an amorphous rare earth element alloy, a ferromagnetic metal, and a nonmagnetic metal ) Alternately stacked multilayer thin films, alloys having an L10 type crystal structure, or cobalt-based alloys. Examples of the alloys of the full-Hoesler semi-metal series include CoFeAl and CoFeAlSi, and amorphous rare earth element alloys include alloys such as TbFe, TbCo, TbFeCo, DyTbFeCo and GdTbCo. Co / Pt, Co / Ru, Co / Os, Co / Au, Ni / Cu, CoFeAl / Pd, and CoFeAl as the multilayered thin film in which the nonmagnetic metal and the magnetic metal are alternately stacked. / Pt, CoFeB / Pd, CoFeB / Pt, and the like. Examples of alloys having an L10 type crystal structure include Fe50Pt50, Fe50Pd50, Co50Pt50, Fe30Ni20Pt50, Co30Ni20Pt50, and the like. Examples of the cobalt-based alloys include CoCr, CoPt, CoCrPt, CoCrTa, CoCrPtTa, CoCrNb and CoFeB. Among these materials, the CoFeB single layer can be formed thicker than the multi-layer structure of CoFeB and Co / Pt or Co / Pd, thereby increasing the magnetoresistance ratio. In addition, since CoFeB is easier to etch than metals such as Pt or Pd, the CoFeB single layer is easier to manufacture than a multilayer structure containing Pt or Pd. Thus, an embodiment of the present invention forms a free layer 410 using a CoFeB monolayer, and the CoFeB is formed into amorphous and then textured into the BCC 100 by heat treatment.

A tunneling barrier 420 is formed on the free layer 410 to separate the free layer 410 and the pinned layer 430. The tunneling barrier 420 enables quantum mechanical tunneling between the free layer 410 and the pinned layer 430. The tunneling barrier 420 is magnesium oxide (MgO), aluminum oxide (Al ₂ O _3), silicon oxide (SiO _2), tantalum oxide (Ta ₂ O _5), silicon nitride (SiNx) or aluminum nitride (AlNx), etc. As shown in FIG. In an embodiment of the present invention, polycrystalline magnesium oxide is used as the tunneling barrier 420. The magnesium oxide is then textured to the BCC 100 by heat treatment.

The pinned layer 430 is formed on the tunnel barrier 420. The pinned layer 430 is fixed in one direction in a magnetic field in a predetermined range, and may be formed of a ferromagnetic material. For example, the magnetization may be fixed in the direction from the top to the bottom. The pinned layer 430 may be formed of, for example, a Full-Heusler semimetal alloy, an amorphous rare earth element alloy, a multilayer thin film in which a magnetic metal and a non-magnetic metal are alternately stacked, Alloy or the like. At this time, the pinned layer 430 may be formed of the same ferromagnetic material as that of the free layer 410, and may be formed of a single CoFeB layer.

The capping layer 440 is formed on the pinned layer 430 to magnetically separate the pinned layer 430 and the composite exchangeable semiconductive layer 450. By forming the capping layer 440, the magnetization of the composite exchangeable semi-magnetic layer 450 and the pinned layer 430 are generated independently of each other. The capping layer 440 may be formed in consideration of the magnetoresistance ratio of the free layer 410 and the pinned layer 430 for the operation of the magnetic tunnel junction. Such a capping layer 440 may be formed of a material that allows the synthetic exchangeable semiconductive layer 450 to undergo crystal growth. That is, the capping layer 440 allows it to grow in the crystallographic direction of the composite exchange-bismuth layer 450. For example, it may be formed of a metal that facilitates crystal growth in a (111) direction of a face centered cubic (FCC) or a (001) direction of a hexagonal close-packed structure have. The capping layer 440 may be formed of one of tantalum (Ta), ruthenium (Ru), titanium (Ti), palladium (Pd), platinum (Pt), magnesium (Mg), cobalt ), Or an alloy thereof. Preferably, the capping layer 440 may be formed of at least one of tantalum (Ta) and tungsten (W). That is, the capping layer 440 may be formed of tantalum (Ta) or tungsten (W), or may be formed of a stacked structure of Ta / W. In an embodiment of the present invention, the capping layer 440 is formed of tantalum. On the other hand, the capping layer 440 can be formed to a thickness of 0.3 nm to 0.6 nm. When Ta is used, the capping layer 440 can be formed to a thickness of 0.4 nm to 0.6 nm. When W is used, a thickness of 0.35 nm to 0.55 nm .

A composite exchangeable semi-magnetic layer 450 is formed on the capping layer 440. The composite exchangeable semi-magnetic layer 450 serves to fix the magnetization of the pinned layer 430. This composite exchangeable semi-magnetic layer 450 includes a fifth magnetic layer 451, a sixth nonmagnetic layer 452, and a sixth magnetic layer 453. In this synthetic exchange ferromagnetic layer 450, the fifth magnetic layer 451 and the sixth magnetic layer 453 are antiferromagnetically coupled via the third nonmagnetic layer 452. At this time, the magnetization directions of the fifth magnetic layer 451 and the sixth magnetic layer 453 are arranged antiparallel. For example, the fifth magnetic layer 451 may be magnetized in the downward direction (i.e., in the direction of the substrate 110) and the sixth magnetic layer 453 may be magnetized in the upward direction (i.e., in the direction of the third electrode 460) have. The fifth magnetic layer 451 and the sixth magnetic layer 453 may be formed by alternately stacking a magnetic metal and a non-magnetic metal. As the magnetic metal, a single metal selected from the group consisting of iron (Fe), cobalt (Co) and nickel (Ni), or an alloy thereof may be used. As the nonmagnetic metal, chromium (Cr), platinum A single metal selected from the group consisting of palladium (Pd), iridium (Ir), rhodium (Rh), ruthenium (Ru), osmium (Os), rhenium (Re), gold (Au) Can be used. For example, the fifth magnetic layer 451 and the sixth magnetic layer 453 may be formed of [Co / Pd] n, [Co / Pt] n or [CoFe / Pt] n . The third nonmagnetic layer 452 is formed between the fifth magnetic layer 451 and the sixth magnetic layer 453 and has a nonmagnetic property that allows the fifth magnetic layer 451 and the sixth magnetic layer 453 to perform a half- Lt; / RTI > For example, the third nonmagnetic layer 452 may be formed of a single material selected from the group consisting of ruthenium (Ru), rhodium (Rh), osmium (Os), rhenium (Re), and chromium have.

On the other hand, the third electrode 460 is formed on the sixth magnetic layer 453. The third electrode 460 may be formed using a conductive material, such as a metal, a metal oxide, a metal nitride, or the like. For example, the third electrode 460 may be selected from the group consisting of tantalum (Ta), ruthenium (Ru), titanium (Ti), palladium (Pd), platinum (Pt), magnesium (Mg) A single metal, or an alloy thereof.

As described above, the neuron device according to an embodiment of the present invention includes the first and second magnetization control units 200 and 300 spaced apart from each other by a predetermined distance on the channel unit 100, A control unit 400 including a magnetic tunnel junction is provided between the units 200 and 300. In this neuron element, the first and second magnetization control parts 200 and 300 are magnetized in directions opposite to each other, and in the initial state, the magnetization direction of the free layer 410 and the pinned layer 430 of the control part 400 are opposite to each other The magnetization direction of the channel section 100 is set. When a predetermined pulse current, that is, data, is input through the first magnetization control unit 200, the magnetization direction of the channel unit 100 is changed by the width of the controller 400, for example, (400). In this way, a plurality of currents, i.e., data, of a predetermined pulse are applied and integrated in the channel unit 100. If the magnetization direction of the channel section 100 under the control section 400 is changed and the magnetization direction of the free layer 410 becomes equal to the magnetization direction of the fixed layer 430 after the plurality of data are inputted, Are output through the second magnetization control unit 300. The second magnetization control unit 300 generates a plurality of data. That is, the current is amplified, that is, ignited and output by the control unit 400. When a predetermined current is applied between the first magnetization control unit 200 and the second magnetization control unit 300, the magnetization direction of the channel unit 100 is changed in the magnetization direction of the second magnetization control unit 300 Reset to the initial state.

In order to confirm the magnetic characteristics of the first and second magnetization control parts of the neuron device according to an embodiment of the present invention, the following structure was made. That is, SiO ₂ [Co / Pt] lower magnetic layer, a Ru nonmagnetic layer, a [Co / Pt] upper magnetic layer, and an electrode were laminated on a substrate, on which a Ta buffer layer, an MgO seed layer, a Co ₂ Fe ₆ B ₂ channel layer, a Ta separation layer, Here, iO ₂ The Ta buffer layer, the MgO seed layer, the Co ₂ Fe ₆ B ₂ channel layer, and the Ta separation layer formed on the substrate correspond to the channel portion 100. The lower magnetic layer corresponds to the first and third magnetic layers of the first and second magnetization control sections, respectively, and the upper magnetic layer corresponds to the second and fourth magnetic layers of the first and second magnetization control sections, respectively. At this time, the first and second magnetization control parts formed all the same conditions, and the thicknesses of the lower and upper magnetic layers were different. That is, in the first magnetization control part, the first magnetic layer is formed of [Co / Pt] 3 and the second magnetic layer is formed of [Co / Pt] And the fourth magnetic layer was formed of [Co / Pt] 3. That is, the first and second magnetic layers of the first magnetization control portion were formed by repeating [Co / Pt] three times and six times, and the third and fourth magnetic layers of the second magnetization controlling portion were formed by repeating [Co / And repeated three times. At this time, Co of a single layer was formed at 0.4 nm and Pt was formed at 0.3 nm.

FIGS. 3 and 4 are graphs showing the magnetization characteristics of the first and second magnetization control sections, respectively, and show magnetization characteristics and magnetization directions according to an external magnetic field. As shown in FIGS. 3 and 4, the first and second magnetization control sections represent three arrows, that is, magnetization directions. The first arrow indicates the magnetization direction of the upper magnetic layer (i.e., the second and fourth magnetic layers), the second arrow indicates the magnetization direction of the lower magnetic layer (i.e., the first and third magnetic layers) Indicates the direction of magnetization. As shown in FIG. 3, the first magnetization control portion is fixed to the lower side according to the magnetization direction of the first magnetic layer in an equilibrium state in which there is no external magnetic field, that is, at 0 kOe. However, as shown in FIG. 4, in a state where the second magnetization control unit is in an equilibrium state in which there is no external magnetic field as opposed to the first magnetization control unit, the magnetization direction of the channel layer is fixed upward according to the magnetization direction of the third magnetic layer.

As can be seen from the above, the neuron elements of the present invention can magnetize the first and second magnetization control portions in different directions, thereby changing the magnetization direction of the channel layer.

In order to confirm the magnetization characteristics of the control unit of the neuron device according to an embodiment of the present invention, the following structure was made. That is, SiO ₂ [Co / Pt] fifth magnetic layer, a third Ru layer, and a third Ru layer were formed on a substrate, and a Ta buffer layer, a MgO seed layer, a Co ₂ Fe ₆ B ₂ channel layer, a Ta separation layer, a CoFeB free layer, a MgO tunneling barrier, a CoFeB pinning layer, A non-magnetic layer, a [Co / Pt] sixth magnetic layer and an electrode were laminated. Here, SiO ₂ On the substrate, the Ta buffer layer, the MgO seed layer, the Co ₂ Fe ₆ B ₂ channel layer, the Ta separation layer correspond to the channel portion 100, the CoFeB free layer, the MgO tunneling barrier and the CoFeB fixed layer have a magnetic tunnel junction structure [ Co / Pt] fifth magnetic layer, the Ru third nonmagnetic layer, and the [Co / Pt] sixth magnetic layer are synthetic exchangeable semiconductive layers. Further, the fifth magnetic layer was formed of [Co / Pt] 3 and the sixth magnetic layer was formed of [Co / Pt] 6. That is, the fifth magnetic layer was formed by repeating [Co / Pt] three times and the sixth magnetic layer was formed by repeating [Co / Pt] six times. Of course, the fifth magnetic layer may be formed of [Co / Pt] 6 and the sixth magnetic layer may be formed of [Co / Pt] 3. The MgO seed layer serves to form the vertical spin direction of the Co ₂ Fe ₆ B ₂ channel layer and serves as an insulating film that prevents the current from leaking to the bottom. The MgO tunneling barrier is formed by the Co ₂ Fe ₆ B ₂ free layer and the fixed layer And a tunnel magnetoresistance ratio is generated in accordance with the magnetization direction.

FIG. 5A is a graph showing the magnetization characteristics of the control section, and shows magnetization characteristics and magnetization directions according to an external magnetic field. As shown in Fig. 5, arrows indicate magnetization directions of the sixth magnetic layer, the fifth magnetic layer, the pinned layer, the free layer and the channel layer from above. However, when the magnetic characteristic graph is enlarged in the interval of -500 Oe to +500 Oe, as the external magnetic field changes from + to - as shown in FIG. 5 (b) Ta separation layer so that the magnetization direction always changes in the same direction. At this time, the pinned layer is fixed by the fifth magnetic layer without changing the magnetization direction.

As can be seen from this, it can be seen that the neuron element of the present invention is changed in accordance with the magnetization direction of the channel layer by coupling the free layer of the control part with the channel layer.

A method of driving the neuron device according to an embodiment of the present invention will now be described. 6 to 13 are schematic views for explaining a method of driving a neuron device according to an embodiment of the present invention. The channel portion 100, the first and second magnetization control portions 100, (200, 300), and the control unit (400). At this time, magnetization is fixed in the downward direction of the first magnetization control unit 200, magnetization is fixed in the upward direction of the second magnetization control unit 300, data is input through the first magnetization control unit 200 Data is output through the second magnetization control unit 300. In addition, the control unit 400 is fixed in the lower direction by the composite exchange ferromagnetic layer in the magnetization direction of the pinned layer, while the lower side is the magnetization direction of the free layer and the upper side is the magnetization direction of the pinned layer. 14A and 14B show voltage pulses (FIG. 14A) and output currents (FIG. 14B) that are input at each step of the driving of the neuron elements. 14 (b) shows the current detected through the second magnetization control unit when a reading voltage of 0.1 V is applied to the control unit, which represents a current detected in a unit area, that is, an area of 1 cm 2. An example of such an embodiment is described in which the channel unit can store and store 6 pieces of data.

6 and 14, electrons are injected from the second magnetization control unit 300 to the first magnetization control unit 200 to reset the magnetization direction of the channel unit 100 (see (1) in FIG. 14 (a) ). Thus, the magnetization of the channel section 100 is fixed in the upward direction along the magnetization direction of the second magnetization control section 300, for example. At this time, when a read signal is applied through the control unit 400, a low level current is detected through the second magnetizing unit 300 as shown in FIG. 14 (b).

7 and 14, a pulse signal of, for example, 0.2 V is applied through the first magnetization control unit 200 to inject electrons once into the channel unit 100 (see (2) in FIG. 14 (a) ). That is, the data is input to the channel unit 100 through the first magnetization control unit 200 once. Therefore, the magnetization direction of the channel section 100 is partially changed. That is, the magnetization direction of the channel unit 100 is changed from the first magnetization control unit 200 to the lower direction. At this time, the domain wall 10 is between the magnetization in the lower direction and the magnetization in the upper direction, and the domain wall is moved toward the control unit 400 as the magnetization direction is changed. At this time, when a read signal is applied through the control unit 400, a low level current is detected through the second magnetization control unit 300 as shown in FIG. 14 (b).

8 and 14, a pulse signal of, for example, 0.2 V is applied through the first magnetization control unit 200 to inject electrons into the channel unit 100 twice (see (3) in FIG. 14 (a) ). That is, data is input to the channel unit 100 through the first magnetization control unit 200 twice. Therefore, the magnetization direction of the channel section 100 is changed again to the lower direction. That is, the magnetization direction is changed to a wider width than in the first data input. At this time, when a read signal is applied through the control unit 400, a low level current is detected through the second magnetization control unit 300 as shown in FIG. 14 (b).

9 to 11 and 14, a pulse signal of, for example, 0.2 V may be repeatedly applied five times through the first magnetization controller 200 (see (4), (5), ⑥). Accordingly, the magnetization direction of the channel unit 100 can be sequentially changed toward the control unit 400, and the domain wall can also be moved. However, when a read signal is applied through the control unit 400 in this state, a low level current is detected through the second magnetizing unit 300 as shown in FIG. 14 (b).

12 and 14, when a pulse signal of, for example, 0.2 V is applied for the sixth time through the first magnetization control unit 200, the magnetization direction of the channel unit 100 under the control unit 400 is shifted downward So that the magnetization direction of the free layer is changed to the lower side (⑦ in Fig. 14 (a)). That is, the free layer is coupled with the channel portion under the free layer to change the magnetization direction. The magnetization direction of the channel portion 100 under the free layer is changed to the lower side, so that the magnetization direction of the free layer also changes downward . As a result, when the magnetization direction of the free layer is changed to the lower side, the magnetization direction of the fixed layer and the free layer are maintained to be equal to each other. As a result, as shown in FIG. 14 (b) The data is ignited. That is, it is possible to amplify and output the current higher than the current applied to the channel unit 100.

13 and 14, after a plurality of data are accumulated and fired in the channel unit 100, a predetermined current is applied from the second magnetization control unit 300 so that all the magnetization directions of the channel layer 100 are all And is reset to the lower side ((8) in Fig. 14 (a)).

The present invention is not limited to the above-described embodiments, but may be embodied in various forms. In other words, the above-described embodiments are provided so that the disclosure of the present invention is complete, and those skilled in the art will fully understand the scope of the invention, and the scope of the present invention should be understood by the appended claims .

100: channel unit 200: first magnetization control unit
300: second magnetization control unit 400: control unit

Claims (20)

A channel unit in which a magnetization direction is changed by accumulating a plurality of data;
First and second magnetization control units formed on the channel unit and adapted to change a magnetization direction of the channel unit according to a plurality of input data; And
And a control unit formed on the channel unit between the first and second magnetization control units and for generating data stored in the channel unit,
Wherein the channel portion further comprises a substrate, a channel layer formed on the substrate and having a magnetic layer, a separation layer formed on the channel layer, and a buffer layer and a seed layer formed between the substrate and the channel layer. delete delete The neuron element according to claim 1, wherein the magnetization direction of the channel layer is fixed in one direction in an initial state, and the magnetization direction is sequentially changed in another direction opposite to one direction as the plurality of data are sequentially inputted. A channel unit in which a magnetization direction is changed by accumulating a plurality of data;
First and second magnetization control units formed on the channel unit to change a magnetization direction of the channel unit according to a plurality of input data; And
And a control unit formed on the channel unit between the first and second magnetization control units and for generating data stored in the channel unit,
And the data of the channel unit is input / output through the first and second magnetization control units. The neuron device of claim 5, wherein the first and second magnetization control sections have different magnetization directions. [7] The method of claim 6, wherein the first and second magnetization control portions are formed in a laminated structure of a first magnetic layer, a non-magnetic layer, and a second magnetic layer on the channel portion, device. 7. The neuron element of claim 6, wherein an initial magnetization direction of the channel section is determined by the second magnetization control section, data is input through the first magnetization control section, and the magnetization direction of the channel section is sequentially changed. The neuron element according to claim 8, wherein the data is accumulated in the channel section between the first magnetization control section and the control section. 10. The method of claim 1 or claim 9, wherein the control unit includes a magnetic tunnel junction in which a free layer, a tunneling barrier,
A capping layer formed on the magnetic tunnel junction,
And a composite exchangeable semi-magnetic layer formed on the capping layer and fixing the magnetization direction of the pinned layer. 11. The neuron element according to claim 10, wherein the magnetization direction of the pinned layer is fixed and the magnetization direction of the free layer is changed in accordance with the magnetization direction of the channel portion. 12. The method of claim 11, wherein the free layer and the pinned layer have magnetizations in opposite directions in an initial state, and when the magnetization directions of the free layer and the pinned layer are the same by the magnetization of the channel portion, Gt; The neuron device according to claim 12, wherein the control section has a width of 1/5 to 1/10 of the length of the channel section between the first and second magnetization control sections. [14] The method of claim 13, wherein the accumulation amount of data is adjusted according to at least one of a length of the channel portion between the first magnetization control portion and the control portion, a width of the control portion, and a pulse width and height applied for inputting data Neuron element. The method according to claim 14, wherein the channel portion 2 neurons device for storing data of ¹ to 2 ^10. A channel unit in which a domain wall moves as a plurality of data are input and stored;
A first magnetization control unit for moving the domain wall of the channel unit according to a plurality of input data;
A second magnetization control unit having magnetization directions different from those of the first magnetization control unit and fixing the magnetization direction of the channel unit in one direction; And
At least a part of which is coupled with the channel part to change the magnetization direction, and to fire data accumulated in the channel part when the domain wall passes the lower part. 17. The neuron device of claim 16, wherein the channel portion, the first and second magnetization control portions, and the control portion each include at least a magnetic material. [18] The method of claim 17, wherein the controller controls the magnetization direction of the first region to be fixed and the magnetization direction of the second region below the magnetization direction of the first region to be changed according to the magnetization direction of the channel portion, And the data accumulated in the channel portion is ignited when they are identical. Setting a magnetization direction of the channel portion such that the magnetization direction of the free layer and the pinned layer of the control portion are opposite to each other;
Sequentially changing a magnetization direction of the channel unit by inputting a plurality of data sequentially; And
And generating data in the channel portion when the magnetization direction of the channel portion overlapped with the control portion is the same as the magnetization direction of the free layer. The driving method of a neuron device according to claim 19, wherein a width of the magnetization direction of the channel portion is adjusted according to at least one of a length of the channel portion, a width of the control portion, and a pulse width and height applied for inputting data.

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