KR101956976B1 - Memory device - Google Patents

Abstract

A magnetic tunnel junction comprises an interlayer formed between two free layers, wherein a separation layer, a composite exchange ferromagnetic layer, a separation layer, a magnetic tunnel junction and a capping layer are laminated between two electrodes, At least one of the interposing layer and the capping layer is formed of a material having a bcc structure.

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 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, a capping 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, a capping 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, after the memory element is formed in this manner, a passivation process and a metal wiring process are performed, and this process is performed at a temperature of about 400 캜. However, the Ta formed by the separation layer and the capping layer is diffused into the magnetic tunnel junction, so that the vertical magnetic anisotropy of the magnetic tunnel junction is lowered, and it is difficult to realize a high MR ratio.

Korean Patent No. 10-1040163

The present invention provides a memory device capable of improving the crystallinity of a magnetic tunnel junction.

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 preventing diffusion of a separation layer and a capping layer material into a magnetic tunnel junction to improve the crystallinity of a magnetic tunnel junction.

A memory device according to one 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 formed between two electrodes, and the magnetic tunnel junction is formed by interposing At least one of the separation layer, the intercalation layer and the capping layer is formed of a material having a bcc structure.

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

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

At least one of the separation layer, the intercalation layer and the capping layer is formed of a material having a lattice constant of less than 330 pm.

At least one of the separation layer, the intercalation layer and the capping layer is formed of at least one of tungsten, vanadium, chromium, and molybdenum.

The capping layer is formed thicker than the separation layer and the insertion layer, and the separation layer and the insertion layer are formed to have the same or different thicknesses.

The capping layer is formed to a thickness of 1 nm to 6 nm, and the separation layer and the insertion layer are formed to a thickness of 0.2 nm to 0.5 nm.

A memory device according to another aspect of the present invention includes a lower electrode, a seed layer, a composite exchange ferromagnetic layer, a separation layer, a magnetic tunnel junction, a capping layer, and an upper electrode laminated on a substrate, Wherein at least one of the separation layer, the intercalation layer and the capping layer is formed of a material having a bcc structure with a lattice constant of less than 330 pm.

At least one of the separation layer, the intercalation layer and the capping layer is formed of at least one of tungsten, vanadium, chromium, and molybdenum.

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.

The present invention also relates to a method of forming a magnetic tunnel junction by forming at least one of a separation layer between a synthetic exchange semiconductive layer and a magnetic tunnel junction, an intercalation layer between double free layers, and a capping layer above a magnetic tunnel junction using a bcc structure material such as tungsten The magnetic tunnel junction can maintain the perpendicular magnetic anisotropy even at a temperature of about 400 ° C.

1 is a cross-sectional view of a memory device according to one embodiment of the present invention.
2 is a schematic diagram illustrating the lattice constant of a magnetic tunnel junction having a dual free layer according to a comparative example and an embodiment of the present invention.
FIG. 3 and FIG. 4 are diagrams showing the perpendicular magnetic anisotropy characteristics of the memory device according to the comparative example and the embodiment of the present invention after the heat treatment at 400.degree.
Figures 5 and 6 show the perpendicular magnetic anisotropy characteristics of a dual free layer after 400 < 0 > C heat treatment of a memory device according to a comparative example and an embodiment of the present invention.
7 is a diagram showing the MR ratio according to the thickness variation of the interlayer between the double free layers according to the comparative example and the embodiment 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, An isolation layer 150, a pinned layer 160, a tunnel barrier 170, a free layer 180, a second buffer layer 190, a capping layer 200, and an upper electrode 210. Here, the composite exchangeable semi-magnetic layer 140 is formed in a laminated structure of the first magnetic layer 141, the non-magnetic layer 142, and the second magnetic layer 143, and has the fixed layer 160, the tunnel barrier 170, 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 synthetic exchange semiconductive layer 140 includes a first magnetic layer 141, a nonmagnetic layer 142, and a second magnetic layer 143. That is, the first magnetic layer 141 and the second magnetic layer 143 are antiferromagnetically coupled to each other through the non-magnetic layer 142 in the synthetic exchange magnetic layer 140. At this time, the first magnetic layer 141 and the second magnetic layer 143 may have crystals in the FCC 111 direction or the HCP (001) direction. The magnetization directions of the first and second magnetic layers 141 and 143 are arranged in antiparallel. For example, the first magnetic layer 141 is magnetized upward (i.e., in the direction of the upper electrode 200) 2 The magnetic layer 143 can be magnetized in the downward direction (i.e., in the direction of the substrate 100). Conversely, the first magnetic layer 141 may be magnetized in the downward direction and the second magnetic layer 143 may be magnetized in the upward direction. The first magnetic layer 141 and the second magnetic layer 143 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 magnetic layer 141 and the second magnetic layer 143 may be formed of [Co / Pd] n, [Co / Pt] n or [CoFe / Pt] n . At this time, the first magnetic layer 141 may be formed thicker than the second magnetic layer 143. In addition, the first magnetic layer 141 may be formed of a plurality of layers, and the second magnetic layer 143 may be formed of a single layer. That is, the first magnetic layer 141 may have a structure in which a magnetic metal and a non-magnetic metal are repeatedly laminated a plurality of times, and the second magnetic layer 143 may have a structure in which a magnetic metal and a non- As shown in FIG. For example, the first and second magnetic layers 141 and 143 may be formed by stacking a plurality of the same materials having the same thickness, but the first magnetic layer 141 may be formed in a larger number of layers than the second magnetic layer 143. For example, the first magnetic layer 141 may be formed of [Co / Pt] 6 in which Co and Pt are repeatedly laminated six times, and the second magnetic layer 143 may be formed of Co / Pt] < 3 > 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 is formed between the first magnetic layer 141 and the first magnetic layer 143 and is made of a nonmagnetic material that allows the first magnetic layer 141 and the second magnetic layer 143 to perform a non- . For example, the nonmagnetic layer 142 may be formed of a single material selected from the group consisting of ruthenium (Ru), rhodium (Rh), osmium (Os), rhenium (Re), and chromium (Cr) Preferably, it may be formed of ruthenium (Ru). On the other hand, when the second magnetic layer 143 is formed as a single layered structure, that is, a single layer, the thickness of the first magnetic layer 141 can be reduced, thereby reducing the thickness of the entire memory device. That is, the sum of the magnetization value of the first magnetic layer 183 and the magnetization value of the second magnetic layer 143 and the fixed layer 160 should be the same with respect to the non-magnetic layer 142. In order to make the sum of the magnetization values of the second magnetic layer 143 and the pinned layer 160 equal to the magnetization value of the first magnetic layer 141 when the second magnetic layer 143 is formed in a plurality of laminated structures, (141) is formed by further increasing the number of repetitions than the second magnetic layer (143). However, according to the present invention, the number of times of stacking of the first magnetic layer 141 can be reduced compared to the conventional one by forming the second magnetic layer 143 in a single structure, thereby reducing the overall thickness of the memory element.

An isolation layer 150 is formed over the synthetic exchange-semiconductive layer 140. The separation layer 150 is formed so that the magnetization of the composite exchangeable semiconductive layer 140 and the pinned layer 160 are generated independently of each other. The isolation layer 150 is also formed of a material capable of improving the crystallinity of the magnetic tunnel junction including the pinned layer 160, the tunnel barrier 170 and the free layer 180. For this, the isolation layer 150 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 150 is formed of a polycrystalline material, so that the crystallinity of the magnetic tunnel junction including the pinned layer 160, the tunnel barrier 170, and the free layer 180 formed thereon can be improved. That is, when the polycrystalline separation layer 150 is formed, an amorphous magnetic tunnel junction formed on the polycrystalline separation layer 150 is grown along the crystal direction of the separation layer 150. Then, when heat treatment is performed for vertical magnetic anisotropy, The crystallinity can be improved as compared with the conventional method. Particularly, when W is used as the separation layer 150, 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 170, And the free layer 180 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. Meanwhile, the separation layer 150 may be formed to a thickness of 0.2 nm to 0.5 nm, for example. Here, the magnetization direction of the pinned layer 160 is fixed until the second magnetic layer 143 and the pinned layer 160 of the synthetic exchange ferromagnetic layer 140 are ferro-coupled, but the separation layer 150 using W The magnetization direction of the pinned layer 160 is not fixed due to the increase in the thickness of the isolation layer 150 and the same magnetization direction as that of the free layer 180 is required, The magnetization direction does not occur and the memory does not operate.

The pinned layer 160 is formed on the isolation layer 150 and is formed of a ferromagnetic material. The pinned layer 160 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 160 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 160 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 170 is formed on the pinned layer 160 to separate the pinned layer 160 and the free layer 180. The tunnel barrier 170 enables quantum mechanical tunneling between the pinned layer 160 and the free layer 180. The tunnel barrier 170 may be formed of a 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) As shown in FIG. In the embodiment of the present invention, polycrystalline magnesium oxide is used as the tunnel barrier 170. The magnesium oxide is then textured to the BCC 100 by heat treatment.

The free layer 180 is formed on the tunnel barrier 170. 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 180 may have the same (i.e., parallel) magnetization direction as the pinned layer 160 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 varying according to the magnetization arrangement of the free layer 180 and the pinned layer 160. For example, when the magnetization direction of the free layer 180 is parallel to the fixed layer 160, 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 180 is antiparallel to the pinned layer 160, the resistance value of the magnetic tunnel junction becomes large, and this case can be defined as data '1'. The free layer 180 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 nonmagnetic metal are alternately stacked, or an L10 type crystal structure Or a ferromagnetic material, e.g. On the other hand, the free layer 180 may be formed as a laminated structure of the first free layer 181, the insertion layer 182, and the second free layer 183. That is, the free layer 180 may be formed by the structure of the first and second free layers 181 and 183, which are vertically separated by the insertion layer 182. Here, the first and second free layers 181 and 183 may have magnetizations in the same direction and may have magnetizations in different directions. For example, the first and second free layers 181 and 183 may each have perpendicular magnetization, and the first free layer 181 may have vertical magnetization and the second free layer 183 may have horizontal magnetization have. Further, the insertion layer 182 can be formed of a material having a bcc structure without magnetization. That is, the first free layer 181 is vertically magnetized, the insertion layer 182 is not magnetized, and the second free layer 183 can be magnetized vertically or horizontally. The first and second free layers 181 and 183 may be formed of CoFeB and the first free layer 181 may be formed to be thinner or the same thickness as the second free layer 183. In addition, the insertion layer 182 may be formed to be thinner than the first and second free layers 183. For example, the first and second free layers 181 and 183 are formed to a thickness of 0.5 nm to 1.5 nm by using CoFeB, and the insertion layer 182 is formed of a material having a bcc structure, for example, To 0.5 nm in thickness.

A second buffer layer 190 is formed on the free layer 180. The second buffer layer 190 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 second buffer layer 190 may be formed of an oxide. In the embodiment of the present invention, polycrystalline magnesium oxide is used for the second buffer layer 190. [ This second buffer layer 190 is formed so that the free layer 180 has vertical magnetic properties. That is, the oxygen in the second buffer layer 190 diffuses into the free layer 180 and bonds with the material in the free layer 180 so that the free layer 180 has perpendicular magnetic properties. On the other hand, the second buffer layer 190 can be formed to a thickness of 0.8 nm to 1.2 nm, for example.

The capping layer 200 is formed on the second buffer layer 190. The capping layer 200 is formed of a polycrystalline material, for example, a conductive material having a bcc structure. For example, the capping layer 200 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 150 having the bcc structure, an amorphous magnetic tunnel junction is grown along the crystal direction of the isolation layer 150, and a bcc structure capping layer 200 is formed and then heat treatment is performed, the crystallinity of the magnetic tunnel junction can be further improved. In addition, the capping layer 200 serves to prevent diffusion of the upper electrode 210. The capping layer 200 may be formed to a thickness of 1 nm to 6 nm, for example.

The upper electrode 210 is formed on the capping layer 200. The upper electrode 210 may be formed using a conductive material, such as a metal, a metal oxide, a metal nitride, or the like. For example, the upper electrode 210 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. In addition, the present invention is also applicable to the case where at least one, preferably all, of the separation layer 150, the intercalation layer 182 and the capping layer 200 are formed using a material having a bcc structure such as tungsten, The magnetic tunnel junction can maintain vertical magnetic anisotropy. That is, after the upper electrode 210 is formed, a passivation process and a metal wiring process are performed at a temperature of about 400 ° C. In the conventional method using tantalum (Ta) as a separation layer or a capping layer, The perpendicular magnetic anisotropy of the junction is lowered, but the present invention can be formed of undiffused tungsten to maintain the perpendicular magnetic anisotropy of the magnetic tunnel junction.

2 is a schematic diagram showing the lattice constants of a magnetic tunnel junction having a double free layer according to a comparative example and an embodiment of the present invention. 2 (a)) in which Ta of the magnetic tunnel junction in which the MgO tunnel barrier, the CoFeB first free layer, the insertion layer, the CoFeB second free layer, and the MgO buffer layer are laminated is used as the insertion layer (Fig. 2 (b)). In a comparative example using Ta as an interlayer between the first and second free layers, the lattice constant of Ta was 330 pm and the lattice constant of the two CoFeB free layers was 286 pm, and the lattice constant between the Ta insertion layer and the first and second CoFeB free layers Are 15.3% and 13.3%, respectively. However, in the case of using W as an interlayer between the first and second free layers, the lattice constant of W is 316 pm and the lattice mismatch ratio between the W insertion layer and the first and second CoFeB free layers is -10.4 % And 9.5%. That is, W has a lower lattice structure mismatching ratio with CoFeB than Ta. The lower the mismatch rate of the lattice structure, the less diffusion occurs, so that the embodiment using W as the interlevel layer generates less diffusion of the interlevel material into the free layer than the comparative example using Ta as the interlevel layer. Thus, materials with lower lattice constants than Ta can be used as separating layers, interlayers and capping layers, which are smaller in lattice constant than Ta and are bcc materials and have 3d transition metals such as vanadium (302 pm), chromium (288 pm), molybdenum ) May be used instead of W. That is, a material having a lattice constant of less than 330 pm, for example, greater than 280 pm and less than 330 pm, can be used as a separation layer, an intercalation layer, and a capping layer material.

FIGS. 3 and 4 are diagrams showing the perpendicular magnetic anisotropy characteristics of the memory device according to the comparative example and the embodiment of the present invention after the heat treatment at 400.degree. That is, a lower electrode, a composite exchange ferromagnetic layer, a separation layer, a magnetic tunnel junction, a capping layer, and an upper electrode are laminated on a substrate, and a free layer of the magnetic tunnel junction is formed by a structure in which an interlayer is formed between the first and second free layers FIG. 3 shows perpendicular magnetic anisotropy characteristics according to a comparative example in which the separating layer, the interposing layer and the capping layer are formed of Ta, respectively, and the vertical magnetic anisotropy characteristic obtained by forming the separating layer, 4. As shown in Figs. 3 and 4, in the comparative example and the embodiment, the perpendicular magnetic properties of the fixed layer and the synthetic exchange ferromagnetic layer in the region (c region) of not less than 1.5 [kOe] (a region) or not more than -1.5 [kOe] It is almost the same. However, in the range of -500 [Oe] to 500 [Oe] (b region) representing the perpendicular magnetic properties of the double free layer for securing the tunnel magnetoresistance ratio, that is, the dual information storage layer, There is a difference. As shown in FIG. 3, in the case of the comparative example using Ta, the perpendicular magnetic properties of the double free layer are deteriorated after the heat treatment at 400 ° C., and the information storage function can not be performed. However, as shown in FIG. 4, the embodiment using W does not deteriorate the perpendicular magnetic properties of the double free layer because W is less diffused than Ta after heat treatment at 400 ° C.

Figs. 5 and 6 are diagrams showing the perpendicular magnetic anisotropy characteristics of the double free layer (region b). That is, the perpendicular magnetic properties of the double free layer, i.e., the dual information storage layer, at -500 [Oe] to 500 [Oe] are exhibited. In the comparative example using Ta, as shown in FIG. 5, the squareness showing the vertical characteristic does not appear, and the vertical magnetic amount (magnetic momet) is also 140 mu em, indicating that a low MR ratio appears after the heat treatment at 400 ° C. However, as shown in FIG. 6, in the case of the example using W, a high MR ratio was exhibited because the perpendicular magnetic susceptibility value of the double free layer was 165 em emu after almost complete squareness even after the heat treatment at 400 캜. On the other hand, the susceptibility of a single information storage layer, that is, a single CoFeB free layer, is generally about 80 to 90 mu emu.

FIG. 7 is a graph showing the MR ratio according to the thickness variation of the interlayer between the double free layers according to the comparative example and the embodiment of the present invention. That is, the thicknesses of the Ta insertion layer according to the comparative example and the W insertion layer according to the embodiment were changed from 0.2 nm to 0.7 nm, and the MR ratio was measured after the heat treatment at 400 ° C. In the comparative example, the MR ratio of 98% was maintained in the range of 0.4 nm to 0.53 nm in thickness of the Ta insertion layer. However, in the example, the MR ratio of 133% was maintained in the thickness of the W insertion layer in the range of 0.3 nm to 0.53 nm. Therefore, it can be seen that when W is used as the separation layer, the interlayer and the capping layer, the magnetic tunnel junction is not deteriorated even in the subsequent process at 400 ° C. Further, the thickness that can be used for the Ta insertion layer is 0.3 nm to 0.4 nm, whereas when the W insertion layer is used, a thickness margin of about twice to 0.3 nm to 0.5 nm can be secured.

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 exchanged semi-magnetic layer 150: Separation layer
160: Fixed layer 170: Tunnel barrier
180: free layer 190: second buffer layer
200: capping layer 210: upper electrode

Claims (9)

A seed layer, a synthetic exchange ferromagnetic layer, a separation layer, a magnetic tunnel junction and a capping layer are laminated between two electrodes,
The magnetic tunnel junction comprising a pinned layer, a tunnel barrier and a free layer,
Wherein the free layer comprises a laminated structure of a first free layer, an insertion layer and a second free layer,
Wherein at least one of the isolation layer, the interlayer, and the capping layer is formed of a material having a bcc structure.
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 an oxide layer formed between the magnetic tunnel junction and the capping layer.
The memory element according to claim 2 or 3, wherein at least one of the separation layer, the insertion layer and the capping layer is formed of a material having a lattice constant of less than 330 pm.
5. The memory element of claim 4, wherein at least one of the separation layer, the interlayer and the capping layer is formed of at least one of tungsten, vanadium, chromium, and molybdenum.
6. The memory device of claim 5, wherein the capping layer is formed thicker than the isolation layer and the insertion layer, and the isolation layer and the insertion layer are formed to have the same or different thicknesses.
The memory element according to claim 6, wherein the capping layer is formed to a thickness of 1 nm to 6 nm, and the isolation layer and the insertion layer are formed to a thickness of 0.2 nm to 0.5 nm.
A lower electrode, a seed layer, a synthetic exchange ferromagnetic layer, a separation layer, a magnetic tunnel junction, a capping layer and an upper electrode are laminated on a substrate,
The magnetic tunnel junction comprising a pinned layer, a tunnel barrier and a free layer,
Wherein the free layer comprises a laminated structure of a first free layer, an insertion layer and a second free layer,
Wherein at least one of the isolation layer, the interlayer, and the capping layer is formed of a material having a bcc structure with a lattice constant of less than 330 pm.
9. The memory element of claim 8, wherein at least one of the isolation layer, the interlevel layer, and the capping layer is formed of at least one of tungsten, vanadium, chromium, and molybdenum.

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