KR101956977B1

KR101956977B1 - Memory device

Info

Publication number: KR101956977B1
Application number: KR1020160015154A
Authority: KR
Inventors: 박재근; 이승은
Original assignee: 한양대학교 산학협력단
Priority date: 2016-02-05
Filing date: 2016-02-05
Publication date: 2019-03-11
Also published as: KR20170093576A

Abstract

The present invention discloses a memory device in which a seed layer, a synthetic exchange ferromagnetic layer, a separation layer, a magnetic tunnel junction and a capping layer are laminated between two electrodes, and a synthetic exchange ferromagnetic layer has one magnetic layer and a non-magnetic layer, respectively .

Description

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a memory device, and more particularly, to a magnetic memory device using a magnetic tunnel junction (MTJ).

Studies are being made on a next generation nonvolatile memory device having a lower power consumption and higher integration than a flash memory device. These next generation non-volatile memory devices include a phase change memory (PRAM) that utilizes a state change of a phase change material such as a chalcogenide alloy, a magnetic tunnel junction (PMR) according to a magnetization state of a ferromagnetic material, (MRAM) using resistance change of MTJ, ferroelectric RAM using polarization of ferroelectric material, resistance change RAM (ReRAM) using resistance change of variable resistance material, etc. .

An STT-MRAM (Spin-Transfer Torque Magnetic Random Access Memory) device for inverting magnetization by using a spin transfer torque (STT) phenomenon by electron injection as a magnetic memory and discriminating the difference in resistance before and after magnetization inversion . The STT-MRAM devices each include a pinned layer and a free layer formed of a ferromagnetic material, and a magnetic tunnel junction formed with a tunnel barrier therebetween. If the magnetization directions of the free layer and the pinned layer are the same (i.e., parallel), the magnetic tunnel junction has a low resistance state due to easy current flow, and if the magnetization directions are different (i.e., anti parallel) Resistance state. In addition, since the magnetization direction of the magnetic tunnel junction must change only in the direction perpendicular to the substrate, the free layer and the pinned layer must have perpendicular magnetization values. The vertical magnetic anisotropy (PMA) is superior when the vertical magnetization value is symmetrical with respect to zero according to the intensity and direction of the magnetic field and the shape of the squareness (S) becomes clear (S = 1) . These STT-MRAM devices can theoretically be cycled at 10 ¹⁵ or more, and can be switched at a speed as high as nanoseconds (ns). In particular, the vertical magnetization type STT-MRAM device has no scaling limit in theory, and the current density of the driving current can be lowered as the scaling progresses. Therefore, the research is being actively conducted as a next generation memory device that can replace the DRAM device . On the other hand, an example of an STT-MRAM device is disclosed in Korean Patent No. 10-1040163.

In the STT-MRAM device, a seed layer is formed under the free layer, a separation layer is formed on the fixed layer, and a synthetic exchange ferromagnetic layer and an upper electrode are formed on the separation layer. In the STT-MRAM device, a silicon oxide film is formed on a silicon substrate, and then a seed layer and a magnetic tunnel junction are formed thereon. A selection element such as a transistor may be formed on the silicon substrate, and a silicon oxide film may be formed so as to cover the selection element. Therefore, the STT-MRAM device has a stacked structure of a silicon oxide film, a seed layer, a free layer, a tunnel barrier, a fixed layer, a separation layer, a synthetic exchange ferromagnetic layer and an upper electrode on a silicon substrate on which a selection element is formed. Here, the separating layer and the capping layer are formed using tantalum (Ta), and the synthetic exchange ferromagnetic layer includes a lower magnetic layer and an upper magnetic layer in which magnetic metal and nonmagnetic metal are alternately stacked, and a structure in which a nonmagnetic layer is formed therebetween . That is, a magnetic tunnel junction is formed on the lower side of the substrate, and a composite exchangeable semi-magnetic layer is formed on the upper side.

However, since the synthetic exchange ferromagnetic layer of fcc (111) is formed on the magnetic tunnel junction textured in the bcc (100) direction, the fcc (111) structure diffuses into the magnetic tunnel junction when forming the synthetic exchange ferromagnetic layer, ) Decision. That is, when forming the composite exchangeable semi-magnetic layer, a part of the material diffuses into the magnetic tunnel junction, which may deteriorate the crystallinity of the magnetic tunnel junction. Therefore, the magnetization direction of the magnetic tunnel junction can not be changed suddenly, so that the operation speed of the memory may decrease or the operation may not be performed.

Further, the synthetic exchangeable semiconductive layer is mainly composed of a laminate of a first magnetic layer having a multilayer structure, a non-magnetic layer, and a second magnetic layer having a multilayer structure. For example, the first magnetic layer is formed by laminating Co and Pt repeatedly at least six times, and the second magnetic layer is formed by laminating Co and Pt repeatedly at least three times. Since the first and second magnetic layers are each formed in a multi-layered structure, the thickness of the memory element becomes thick. In addition, since rare-earth is often used for the first and second magnetic layers, the process cost is also increased.

Korean Patent No. 10-1040163

The present invention provides a memory device capable of preventing the diffusion of a synthetic exchange-semiconductive layer material to a magnetic tunnel junction to improve the crystallinity of a magnetic tunnel junction.

The present invention provides a memory device capable of reducing the thickness of the synthetic exchange ferromagnetic layer to reduce the process cost and reduce the overall thickness.

A memory device according to an aspect of the present invention includes a seed layer, a composite exchange ferromagnetic layer, a separation layer, a magnetic tunnel junction and a capping layer laminated between two electrodes, and the synthetic exchange ferromagnetic layer has a single magnetic layer and a non- Respectively.

A magnetic tunnel junction is formed on the composite exchange-ferromagnetic layer.

And a buffer layer provided between the composite exchangeable semiconductive layer and the separation layer.

The buffer layer has a single layer formed of a magnetic material, and is formed to be thinner than the magnetic layer of the synthetic exchange-ferromagnetic layer.

And an oxide layer formed between the magnetic tunnel junction and the capping layer.

The memory element according to another aspect of the present invention is characterized in that the magnetic tunnel junction comprises a pinned layer, a tunnel barrier and a free layer, wherein the free layer comprises first and second free layers and an interposed layer formed therebetween.

The first and second free layers are formed of a material including CoFeB, and the first free layer is formed to be thinner or the same thickness as the second free layer.

The isolation layer is formed of a material having a bcc structure and is formed to a thickness of 0.1 nm to 0.5 nm.

In the present invention, the lower electrode is formed of a polycrystalline material, and a synthetic exchange ferromagnetic layer is formed on the lower electrode, followed by formation of a magnetic tunnel junction. Therefore, since the fcc (111) structure of the composite exchange ferromagnetic layer is not diffused into the magnetic tunnel junction, the bcc (100) crystal of the magnetic tunnel junction can be conserved and the magnetization direction of the magnetic tunnel junction can be rapidly changed The operating speed of the memory can be improved.

Furthermore, by forming the composite exchangeable semi-magnetic layer so as to have one magnetic layer and a nonmagnetic layer, respectively, the thickness of the composite exchangeable semi-magnetic layer can be reduced, and the thickness of the entire memory device can be reduced. In addition, the amount of material used for forming the composite exchangeable semiconductive layer can be reduced to reduce the process cost.

1 is a cross-sectional view of a memory device according to one embodiment of the present invention.
2 is a view showing a magnetoresistive ratio of a comparative example according to a thickness of a separation layer and an embodiment of the present invention.
3 is a diagram showing the tunnel magnetoresistance ratio according to the position of the composite exchange-ferromagnetic layer and the thickness of the separation layer in the embodiments of the present invention.

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.

1 is a cross-sectional view of a memory device according to an embodiment of the present invention, and is a cross-sectional view of an STT-MRAM device.

1, a memory device according to an embodiment of the present invention includes a lower electrode 110 formed on a substrate 100, a first buffer layer 120, a seed layer 130, a synthetic exchange ferromagnetic layer 140, A second buffer layer 150, an isolation layer 160, a pinned layer 170, a tunnel barrier 180, a free layer 190, a second buffer layer 200, a capping layer 210, and an upper electrode 220 . Here, the composite exchangeable semi-magnetic layer 140 is formed in a laminated structure of the magnetic layer 141 and the non-magnetic layer 142, and the pinned layer 160, the tunnel barrier 170, and the free layer 180 form a magnetic tunnel junction. That is, in the memory device according to the present invention, a composite exchangeable semi-magnetic layer 140 is first formed on a substrate 100, and a magnetic tunnel junction is formed thereon.

The substrate 100 may be a semiconductor substrate. For example, the substrate 100 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. Further, on the substrate 100, a selection device including a transistor may be formed. On the other hand, an insulating layer (not shown) may be formed on the substrate 100. That is, the insulating layer may be formed to cover a predetermined structure such as a selection element, and the insulating layer may be provided with a contact hole exposing at least a part of the selection element. Such an insulating layer can be formed using an amorphous silicon oxide (SiO ₂ ) film or the like.

A lower electrode 110 is formed on the substrate 100. The lower electrode 110 may be formed using a conductive material such as a metal, a metal nitride, or the like. In addition, the lower electrode 110 of the present invention may be formed of at least one layer. That is, the lower electrode 110 may be formed as a single layer or may be formed of two or more layers. When the lower electrode 110 is formed as a single layer, it may be formed of a metal nitride such as a titanium nitride (TiN) film. In addition, the lower electrode 110 may be formed as a double structure of, for example, first and second lower electrodes. Here, the first lower electrode may be formed on the substrate 100, and the second lower electrode may be formed on the first lower electrode. On the other hand, when an insulating layer is formed on the substrate 100, the first lower electrode may be formed on the insulating layer, and may be formed in the insulating layer, thereby being connected to the selection element formed on the substrate 100 It is possible. The lower electrode 110 may be formed of polycrystalline conductive material. That is, the first and second lower electrodes may be formed of a conductive material having a bcc structure. For example, the first lower electrode may be formed of a metal such as tungsten (W), and the second lower electrode may be formed of a metal nitride such as a titanium nitride film (TiN).

The first buffer layer 120 is formed on the lower electrode 110. The first buffer layer 120 may be formed of a material having excellent compatibility with the lower electrode 110 to eliminate lattice constant mismatch between the lower electrode 110 and the seed layer 130. For example, when the lower electrode 110 or the second lower electrode is formed of TiN, the first buffer layer 120 may be formed using tantalum (Ta) excellent in lattice matching with TiN. Since Ta is amorphous, since the lower electrode 110 is polycrystalline, the amorphous first buffer layer 120 can be grown along the crystal direction of the polycrystalline lower electrode 110, and then the crystallinity is improved by the heat treatment . Meanwhile, the first buffer layer 120 may be formed to a thickness of 2 nm to 10 nm, for example.

A seed layer (130) is formed on the first buffer layer (120). The seed layer 130 may be formed of a material that allows the synthetic exchangeable semiconductive layer 140 to undergo crystal growth. That is, the seed layer 130 allows the first and second magnetic layers 141 and 143 of the synthetic exchangeable semiconductive layer 140 to grow in a desired crystal orientation. 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 seed layer 130 may be formed of tantalum (Ta), ruthenium (Ru), titanium (Ti), palladium (Pd), platinum (Pt), magnesium (Mg), cobalt ), Or an alloy thereof. Preferably, the seed layer 130 may be formed of platinum (Pt), and may be formed to a thickness of 1 nm to 3 nm.

A composite exchangeable semi-magnetic layer 140 is formed on the seed layer 130. The composite exchangeable semi-magnetic layer 140 serves to fix the magnetization of the pinned layer 160. The composite exchangeable semiconductive layer 140 includes a magnetic layer 141 and a nonmagnetic layer 142. That is, the composite exchangeable semi-magnetic layers of the present invention each comprise one magnetic layer and a non-magnetic layer. At this time, the magnetic layer 141 may have crystals in the FCC 111 direction or the HCP (001) direction. The magnetic layer 141 may be magnetized in an upward direction (i.e., in the direction of the upper electrode 220) or in a downward direction (i.e., in the direction of the substrate 100). The magnetic layer 141 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 magnetic layer 141 may be formed of [Co / Pd] n, [Co / Pt] n or [CoFe / Pt] n (where n is an integer of 1 or more). That is, the magnetic layer 141 may have a structure in which a magnetic metal and a non-magnetic metal are repeatedly laminated a plurality of times. For example, the magnetic layer 141 may be formed of [Co / Pt] 3 in which Co and Pt are repeatedly laminated three times. At this time, Co may be formed to a thickness of 0.3 nm to 0.5 nm, for example, and Pt may be formed to be thinner or equal to Co, for example, a thickness of 0.2 nm to 0.4 nm. The nonmagnetic layer 142 may be formed of a nonmagnetic material and may be formed of a material selected from the group consisting of ruthenium (Ru), rhodium (Rh), osmium (Os), rhenium (Re) , And may be formed of ruthenium (Ru). For example, the nonmagnetic layer 141 may be formed of a Co / Ru / Co structure. In this way, a single magnetic layer 141 can be formed to form the composite exchangeable semi-magnetic layer 140, thereby reducing the thickness of the composite exchangeable semi-magnetic layer 140, thereby reducing the thickness of the entire memory device.

A second buffer layer 150 is formed on the composite exchange-bismuth layer 140. That is, the second buffer layer 150 is formed on the non-magnetic layer 142. The second buffer layer 150 may be formed of a magnetic layer having a single layer structure. Also, the second buffer layer 150 may have a crystal orientation in the FCC 111 direction or the HCP (001) direction. Thus, the second buffer layer 150 is antiferromagnetically coupled to the magnetic layer 141 of the synthetic exchangeable semiconductive layer 140 via the nonmagnetic layer 142. For example, the magnetic layer 141 is magnetized in the upward direction (that is, in the direction of the upper electrode 220), and the second buffer layer 150 is magnetized in the second buffer layer 150. In this case, The substrate 150 may be magnetized in the downward direction (i.e., in the direction of the substrate 100). Conversely, the magnetic layer 141 may be magnetized in the downward direction, and the second buffer layer 150 may be magnetized in the upward direction. The second buffer layer 150 may be formed of a stacked structure of 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 second buffer layer 150 may be formed of Co / Pd, Co / Pt, or CoFe / Pt. That is, the second buffer layer 150 may be formed by stacking a magnetic metal and a non-magnetic metal once, that is, a single stacked structure. At this time, Co may be formed to a thickness of 0.3 nm to 0.5 nm, for example, and Pt may be formed to be thinner or equal to Co, for example, a thickness of 0.2 nm to 0.4 nm. Here, the sum of the magnetization value of the magnetic layer 141 and the magnetization value of the second buffer layer 150 and the fixed layer 170 should be the same with respect to the non-magnetic layer 142.

The separation layer 160 is formed on the second buffer layer 150. The separation layer 160 is formed so that the magnetization of the composite exchangeable semiconductive layer 140 and the pinned layer 170 is generated independently of each other. The isolation layer 160 is also formed of a material that can enhance the crystallinity of the magnetic tunnel junction including the pinned layer 170, the tunnel barrier 180, and the free layer 190. For this purpose, the isolation layer 160 may be formed of a polycrystalline material, for example, a conductive material having a bcc structure, and may be formed of tungsten (W). The isolation layer 160 is formed of a polycrystalline material to improve the crystallinity of the magnetic tunnel junction including the pinned layer 170, the tunnel barrier 180, and the free layer 190 formed on the isolation layer 160. That is, when the polycrystalline separation layer 160 is formed, an amorphous magnetic tunnel junction formed on the polycrystalline separation layer 160 is grown along the crystal direction of the separation layer 160. Then, when heat treatment is performed for perpendicular magnetic anisotropy, The crystallinity can be improved as compared with the conventional method. Particularly, when W is used as the separation layer 160, it is crystallized after a high-temperature heat treatment at 400 ° C or higher, for example, 400 ° C to 500 ° C, thereby suppressing diffusion of dissimilar materials into the tunnel barrier 180, And the free layer 190 can be crystallized to maintain the perpendicular magnetic anisotropy of the magnetic tunnel junction. That is, when the crystallinity of the magnetic tunnel junction is improved, the magnetization becomes larger when the magnetic field is applied, and the current flowing through the magnetic tunnel junction becomes larger in the parallel state. Therefore, application of such a magnetic tunnel junction to a memory device can improve the operating speed and reliability of the device. On the other hand, the separation layer 160 may be formed to a thickness of 0.2 nm to 0.5 nm, for example. Here, the magnetization direction of the pinned layer 170 is fixed until the composite exchange magnetic layer 140 and the pinned layer 170 are ferro-coupled to each other. However, since the separation layer 160 using W has a thickness exceeding 0.5 nm The magnetization direction of the fixed layer 170 is not fixed and the same magnetization direction as that of the free layer 190 does not occur so that the same magnetization direction and other magnetization directions required in the MRAM device do not occur, .

The pinned layer 170 is formed on the isolation layer 160 and is formed of a ferromagnetic material. The pinned layer 170 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 pinning layer 170 may be formed of, for example, a full-Heusler semimetal alloy, an amorphous rare earth element alloy, a multi-layered structure in which a ferromagnetic metal and a nonmagnetic metal are alternately stacked A 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 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. In addition, CoFeB can have horizontal magnetization as well as vertical magnetization by controlling the thickness. Thus, an embodiment of the present invention forms a pinned layer 170 using a CoFeB single layer, and the CoFeB is formed into amorphous and then textured into the BCC 100 by heat treatment.

The tunnel barrier 180 is formed on the pinned layer 170 to separate the pinned layer 170 and the free layer 190. The tunnel barrier 180 enables quantum mechanical tunneling between the pinned layer 170 and the free layer 190. The tunnel barrier 180 may be 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 the embodiment of the present invention, polycrystalline magnesium oxide is used as the tunnel barrier 180. [ The magnesium oxide is then textured to the BCC 100 by heat treatment.

A free layer 190 is formed on the tunnel barrier 180. This free layer 180 can be changed in one direction and in the opposite direction in which magnetization is not fixed in one direction. That is, the free layer 190 may have the same (i.e., parallel) magnetization direction as the pinned layer 170 and vice versa (i.e., antiparallel). The magnetic tunnel junction can be utilized as a memory element by mapping information of '0' or '1' to a resistance value that varies depending on the magnetization arrangement of the free layer 190 and the pinned layer 170. For example, when the magnetization direction of the free layer 190 is parallel to the fixed layer 170, the resistance value of the magnetic tunnel junction becomes small, and this case can be defined as data '0'. In addition, when the magnetization direction of the free layer 190 is antiparallel to the pinned layer 170, the resistance value of the magnetic tunnel junction increases, and this case can be defined as data '1'. The free layer 190 may be formed of, for example, a Full-Heusler semi-metal series alloy, an amorphous rare earth element alloy, a multilayer thin film in which a magnetic metal and a non-magnetic metal are alternately stacked or an L10 type crystal structure Or a ferromagnetic material, e.g. Meanwhile, the free layer 190 may be formed as a laminated structure of the first free layer 191, the insertion layer 192, and the second free layer 193. That is, the free layer 190 may be formed by the structure of the first and second free layers 191 and 193 which are vertically separated by the insertion layer 192. Here, the first and second free layers 191 and 193 may have magnetizations in the same direction and magnetizations in different directions. For example, the first and second free layers 191 and 193 may each have perpendicular magnetization, and the first free layer 191 may have vertical magnetization and the second free layer 193 may have horizontal magnetization have. Further, the insertion layer 192 can be formed of a material having a bcc structure without magnetization. That is, the first free layer 191 is vertically magnetized, the insertion layer 192 is not magnetized, and the second free layer 193 can be magnetized vertically or horizontally. At this time, the first and second free layers 191 and 193 may be formed of CoFeB, and the first free layer 191 may be thinner or the same thickness as the second free layer 193. In addition, the insertion layer 192 may be formed to be thinner than the first and second free layers 193. For example, the first and second free layers 191 and 193 are formed to a thickness of 0.5 nm to 1.5 nm by using CoFeB, and the insert layer 192 is formed of a material having a bcc structure, for example, To 0.5 nm in thickness.

A third buffer layer 200 is formed on the free layer 190. The third buffer layer 200 may be formed of magnesium oxide (MgO), aluminum oxide (Al ₂ O ₃ ), silicon oxide (SiO ₂ ), tantalum oxide (Ta ₂ O ₅ ), or the like. That is, the third buffer layer 200 may be formed of an oxide. In the embodiment of the present invention, the polycrystalline magnesium oxide is used as the third buffer layer 200. This third buffer layer 200 is formed so that the free layer 190 has perpendicular magnetic properties. That is, the oxygen in the third buffer layer 200 diffuses into the free layer 190 and bonds with the material in the free layer 190 so that the free layer 190 has perpendicular magnetic properties. On the other hand, the third buffer layer 200 can be formed to a thickness of 0.8 nm to 1.2 nm, for example.

The capping layer 210 is formed on the third buffer layer 200. The capping layer 210 is formed of a polycrystalline material, for example, a conductive material having a bcc structure. For example, the capping layer 210 may be formed of tungsten (W). As the capping layer 210 is formed of a polycrystalline material, the crystallinity of the magnetic tunnel junction below the capping layer 210 can be improved. That is, when an amorphous magnetic tunnel junction is formed on the isolation layer 160 having the bcc structure, an amorphous magnetic tunnel junction is grown along the crystal direction of the isolation layer 160, and a bcc structure capping layer 210 are formed and then heat treatment is performed, the crystallinity of the magnetic tunnel junction can be further improved. In addition, the capping layer 210 serves to prevent diffusion of the upper electrode 220. The capping layer 210 may be formed to a thickness of 1 nm to 6 nm, for example.

The upper electrode 220 is formed on the capping layer 210. The upper electrode 220 may be formed of a conductive material, such as a metal, a metal oxide, a metal nitride, or the like. For example, the upper electrode 220 may be a single electrode selected from the group consisting of tantalum (Ta), ruthenium (Ru), titanium (Ti), palladium (Pd), platinum (Pt), magnesium (Mg) Metal, or an alloy thereof.

As described above, in the memory device according to the embodiments of the present invention, the lower electrode 110 is formed of a polycrystalline material, and a synthetic exchangeable semi-magnetic layer 140 is formed thereon, and then a magnetic tunnel junction is formed. Thus, since the fcc (111) structure of the composite exchange antiferromagnetic layer 140 is not diffused into the magnetic tunnel junction, it is possible to preserve the bcc (100) crystal of the magnetic tunnel junction and thus the magnetization direction of the magnetic tunnel junction rapidly changes So that the operating speed of the memory can be improved. Further, the thickness of the synthetic exchangeable semiconductive layer 140 can be reduced by reducing the thickness of the entire memory device by forming the synthetic exchange semiconductive layer 140 with the structure of the magnetic layer 141 and the nonmagnetic layer 142. [ That is, while the composite exchangeable semi-magnetic layer 140 is conventionally formed of a nonmagnetic layer structure between two magnetic layers, the present invention is formed of one magnetic layer and one nonmagnetic layer. Therefore, the time can be shortened in a subsequent etching process or the like, and the width and height ratio of the device after etching can be lowered, thereby enabling a stable process. Also, the amount of material used can be reduced to reduce the process cost in order to form the synthesis-exchange semiconductive layer 140 such as a rare earth material.

FIG. 2 is a view showing a comparative example according to the thickness of the separation layer and a magnetic resistance (MR) ratio of the embodiment of the present invention. That is, a magnetic tunnel junction including a lower electrode, a seed layer, a synthetic exchange ferromagnetic layer, a separation layer, a free layer of a dual structure, a capping layer and an upper electrode are laminated from a substrate, Magnetic layer, a nonmagnetic layer, and a second magnetic layer, and the examples were formed by the structure of the magnetic exchange layer and the nonmagnetic layer in the synthetic exchangeable semiconductive layer. In the comparative example, the first magnetic layer was formed of [Co / Pt] 6 and the second magnetic layer was formed of [Co / Pt] 3. In this example, the magnetic layer was formed of [Co / Pt] 3. In addition, the embodiment formed a buffer layer of Co / Pt between the synthetic exchangeable semiconductive layer and the separation layer. The separation layer was formed using W, and the thickness was varied from 0.1 nm to 0.5 nm. As shown in Fig. 2, in the comparative example (A), the magnetoresistance ratio of the separation layer is 0.2% to 0.3 nm, which is the maximum at about 160%. Incidentally, in the embodiment, the magnetoresistive ratio of the (B) separating layer is 0.2 nm to 0.3 nm and the maximum is shown by about 179%. Therefore, it can be seen that the embodiment of the present invention has a magnetoresistance ratio as high as about 20% as compared with the comparative example. This is because the amount of metal diffused into the magnetic tunnel junction decreases as the thickness of the composite exchange-bismuth layer decreases.

FIG. 3 is a diagram showing the tunnel magnetoresistance ratio according to the position of the composite exchangeable semi-magnetic layer and the thickness of the separation layer. FIG. That is, the magnetoresistive ratio in the case where the composite exchangeable semi-magnetic layer having one magnetic layer and the non-magnetic layer are located on the upper side of the tunnel magnetic junction (Example 1) and the case where the composite exchange magnetic domain is located on the lower side of the tunnel magnetic junction Respectively. Example 1 is a lamination of a tunneling magnetic junction having a lower electrode, a seed layer, a double free layer, a separation layer, a composite exchangeable semiconductive layer according to the present invention, a capping layer and an upper electrode on a substrate, A tunneling magnetic junction having a lower electrode, a seed layer, a composite exchangeable semiconductive layer according to the present invention, a separation layer, a double free layer, a capping layer, and an upper electrode were laminated on the substrate. As shown in FIG. 3, in the case of Example 1 (C), the magnetoresistance ratio of the isolation layer at 0.55 nm is the maximum at about 158%. Incidentally, in Example 2 (D), the magnetoresistance ratio of the separation layer at the thickness of 0.2 nm to 0.3 nm is the maximum at about 179%. Therefore, it can be seen that the magneto-resistance ratio of Example 2 of the present invention is higher than that of Comparative Example 2 by about 20%. This is because the material of the synthetic exchange ferromagnetic layer diffuses into the magnetic tunnel junction when the synthetic exchange ferromagnetic layer is formed on the upper side of the magnetic tunnel junction, but when the synthetic exchange ferromagnetic layer is formed below the magnetic tunnel junction, Because it does not diffuse into the tunnel junction.

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it is to be understood that the invention is not limited to the disclosed exemplary embodiments. It will be apparent to those skilled in the art that various modifications and variations can be made in the present invention without departing from the spirit and scope of the invention.

100: substrate 110: lower electrode
120: first buffer layer 130: seed layer
140: synthetic exchange ferromagnetic layer 150: second buffer layer
160: separation layer 170: fixed layer
180: tunnel barrier 190: free layer
200: third buffer layer 210: capping layer
220: upper electrode

Claims

A seed layer, a synthetic exchange ferromagnetic layer, a separation layer, a magnetic tunnel junction and a capping layer are laminated between two electrodes,
Wherein the composite exchangeable semi-magnetic layer has one magnetic layer and one non-magnetic layer,
Wherein the one magnetic layer is formed of a structure in which a magnetic metal and a non-magnetic metal are repeatedly laminated a plurality of times.

2. The memory element of claim 1, wherein a magnetic tunnel junction is formed on the synthetic exchange ferromagnetic layer.

3. The memory element of claim 2, further comprising a buffer layer disposed between the composite exchangeable semiconductive layer and the isolation layer.

4. The memory element of claim 3, wherein the buffer layer is formed of a magnetic material with a single layer, and is thinner than the magnetic layer of the synthetic exchange ferromagnetic layer.

4. The memory element of claim 3, further comprising an oxide layer formed between the magnetic tunnel junction and the capping layer.

The magnetic tunnel junction of claim 1, wherein the magnetic tunnel junction comprises a pinned layer, a tunnel barrier and a free layer,
Wherein the free layer comprises first and second free layers and an interposed layer formed therebetween.

7. The memory device of claim 6, wherein the first and second free layers are formed of a material containing CoFeB, and the first free layer is thinner or the same thickness as the second free layer.

The memory element of claim 1, wherein the isolation layer is formed of a material having a bcc structure.

The memory element according to claim 8, wherein the isolation layer is formed to a thickness of 0.1 nm to 0.5 nm.