Magnetic storage device

Abstract

In one embodiment, a magnetic storage device is provided. The magnetic storage device includes: a free layer structure having a variable magnetization direction. The free layer structure includes: a first free layer which is a first Heusler alloy; a coupling layer located on the first free layer, the coupling layer including a metal oxide layer; and a second free layer located on the metal oxide layer, the second free layer being a second Heusler alloy different from the first Heusler alloy. The magnetic storage device may further include: a pinned layer structure having a fixed magnetization direction; and a tunnel barrier layer located between the pinned layer structure and the free layer structure.

Description

[0001] Cross - reference to related applications

[0002] This application claims priority and all benefits arising therefrom to Korean Patent Application No. 10 - 2019 - 0013435, filed on February 1, 2019, the disclosure of which is incorporated herein by reference in its entirety. Technical field

[0003] The present inventive concept relates to a magnetic tunnel junction and a magnetic storage device including the magnetic tunnel junction. Background art

[0004] With higher speeds and lower power consumption of electronic devices, it is desirable that storage devices embedded in electronic devices also have fast read / write operations and low operating voltages. As such a storage device, magnetic storage devices have been studied. Since magnetic storage devices are non - volatile and can operate at high speeds, magnetic storage devices are attracting attention as next - generation memories.

[0005] Meanwhile, as magnetic storage elements are becoming increasingly highly integrated, magnetic random access memories (MRAMs) that store information by utilizing the spin - transfer torque (STT) phenomenon have been studied. STT - MRAM can store information by directly applying a current to a magnetic tunnel junction to cause magnetization reversal. Highly integrated STT - MRAM is expected to have high - speed operation and low - current operation. Summary of the invention

[0006] At least one embodiment relates to a magnetic storage device.

[0007] In one embodiment, the magnetic storage device includes: a free layer structure having a variable magnetization direction. The free layer structure includes: a first free layer which is a first Heusler alloy; a coupling layer located on the first free layer, the coupling layer including a metal oxide layer; and a second free layer located on the metal oxide layer, the second free layer being a second Heusler alloy different from the first Heusler alloy. The magnetic storage device may further include: a pinned layer structure having a fixed magnetization direction; and a tunnel barrier layer located between the pinned layer structure and the free layer structure. The free layer structure includes: a first free layer which is a first Heusler alloy and has a cubic structure; a metal oxide layer located on the first free layer; and a second free layer located on the metal oxide layer, the second free layer being a second Heusler alloy having a tetragonal structure. The magnetic storage device may further include: a pinned layer structure having a fixed magnetization direction; and a tunnel barrier layer located between the pinned layer structure and the free layer structure.

[0008] In another embodiment, the magnetic storage device includes: a pinned layer structure and a free layer structure. The pinned layer structure has a fixed magnetization direction. The pinned layer structure includes a first pinned layer, a non-magnetic layer, and a second pinned layer, the first pinned layer and the second pinned layer having antiparallel magnetization directions. The free layer structure has a variable magnetization direction. The free layer structure includes a first free layer, a metal oxide layer located on the first free layer, and a second free layer located on the metal oxide layer. The first free layer is a first Heusler alloy having a cubic structure and a first saturation magnetization. The second free layer is a second Heusler alloy having a tetragonal structure and a second saturation magnetization. The second saturation magnetization is less than the first saturation magnetization, and the magnetic coupling strength between the first free layer and the second free layer is 0.05 - 1 erg / cm 2 . The magnetic storage device includes a tunnel barrier layer located between the pinned layer structure and the free layer structure.

[0009] In another embodiment, the magnetic storage device includes a free layer structure having a variable magnetization direction. The free layer structure includes: a first free layer that is an ordered ferroalloy; a metal oxide layer located on the first free layer; and a second free layer located on the metal oxide layer, the second free layer being a Heusler alloy and having a tetragonal structure. The magnetic storage device includes: a pinned layer structure having a fixed magnetization direction; and a tunnel barrier layer located between the pinned layer structure and the free layer structure.

[0010] At least one embodiment relates to a method of manufacturing a magnetic storage device.

[0011] In one embodiment, the method includes: forming a first layer having a first material; annealing the first material to form a first free layer that is a first Heusler alloy; forming a metal oxide layer on the first free layer; forming a second layer having a second material on the metal oxide; and annealing the second material to form a second free layer on the metal oxide layer, the second free layer being a second Heusler alloy that is different from the first Heusler alloy.

[0012] In another embodiment, the method includes: forming a first layer having a first material; forming a metal oxide layer on the first layer; forming a second layer having a second material on the metal oxide; and annealing the first material and the second material to form a first free layer and a second free layer, respectively, with the metal oxide layer located between the first free layer and the second free layer, the first free layer being a first Heusler alloy and the second free layer being a second Heusler alloy that is different from the first Heusler alloy.

[0013] In another embodiment, the magnetic storage device includes a magnetic tunnel junction. The magnetic tunnel junction includes: a pinned layer having a fixed magnetization direction; a free layer having a variable magnetization direction and including an exchange-coupled composite material that includes a first Heusler alloy and a second Heusler alloy separated by a metal oxide layer; and a tunnel barrier layer located between the pinned layer and the free layer. The magnetic storage device includes: a selection element electrically connected to the magnetic tunnel junction; and control logic configured to control the selection element to write data to the magnetic tunnel junction using a write current of less than 150 μA within a time of less than or equal to 10 ns. Description of the Drawings

[0014] The above and other aspects and features of the inventive concept will become more apparent by describing exemplary embodiments of the inventive concept in detail with reference to the accompanying drawings, in which:

[0015] Figure 1 is a block diagram of a magnetic storage device according to some embodiments of the inventive concept.

[0016] Figure 2 is a circuit diagram of a cell array of a magnetic storage device according to some embodiments of the inventive concept.

[0017] Figure 3 is a conceptual diagram illustrating a unit storage cell of a magnetic storage device according to some embodiments of the inventive concept.

[0018] Figure 4 is a schematic cross-sectional view illustrating a magnetic tunnel junction of a magnetic storage device according to some embodiments of the inventive concept.

[0019] Figure 5 is a view illustrating magnetic exchange coupling of a magnetic storage device according to some embodiments of the inventive concept.

[0020] Figure 6 is a schematic cross-sectional view illustrating a magnetic tunnel junction of a magnetic storage device according to some embodiments of the inventive concept.

[0021] Figure 7 is a schematic cross-sectional view illustrating a magnetic tunnel junction of a magnetic storage device according to some embodiments of the inventive concept.

[0022] Figure 8 is a schematic cross-sectional view illustrating a magnetic tunnel junction of a magnetic storage device according to some embodiments of the inventive concept.

[0023] Figure 9 is a schematic cross-sectional view illustrating a magnetic tunnel junction of a magnetic storage device according to some embodiments of the inventive concept.

[0024] Figure 10 is a conceptual diagram for explaining a unit storage cell of a magnetic storage device according to some embodiments of the inventive concept.

[0025] Figure 11 is a schematic cross-sectional view of a magnetic storage device according to some embodiments of the inventive concept.

[0026] Figure 12 is a cross-sectional view of a magnetic storage device according to some embodiments of the inventive concept. DETAILED DESCRIPTION

[0027] Hereinafter, with reference to Figures 1 to 12Describe a magnetic tunnel junction and a magnetic storage device according to some embodiments of the inventive concept.

[0028] Figure 1 is a block diagram of a magnetic storage device according to some embodiments of the inventive concept.

[0029] Referring to Figure 1 , the magnetic storage device includes a cell array 1, a row decoder 2, a column decoder 3, a read / write circuit 4, and a control logic 5.

[0030] The cell array 1 may include a plurality of word lines and a plurality of bit lines. Memory cells may be connected to points where the word lines and the bit lines intersect. The cell array 1 will be described in more detail below with reference to Figure 2 is described in more detail.

[0031] The row decoder 2 may be connected to the cell array 1 through the word lines. The row decoder 2 may decode an address input from the outside and select one word line among the plurality of word lines.

[0032] The column decoder 3 may be connected to the cell array 1 through the bit lines. The column decoder 3 may decode an address input from the outside and select one bit line among the plurality of bit lines. The bit line selected by the column decoder 3 may be connected to the read / write circuit 4.

[0033] The read / write circuit 4 may provide a bit line bias for accessing the selected memory cell under the control of the control logic 5. For example, the read / write circuit 4 may provide a bit line bias to the selected bit line to write input data into the memory cell or read input data from the memory cell.

[0034] The control logic 5 may output a control signal for controlling the magnetic storage device according to a command signal provided from the outside. The control signal output from the control logic 5 may control the read / write circuit 4.

[0035] Figure 2 is a circuit diagram of a cell array of a magnetic storage device according to some embodiments of the inventive concept. Figure 3 is a conceptual diagram illustrating a unit memory cell of a magnetic storage device according to some embodiments of the inventive concept.

[0036] Referring to Figure 2 , the cell array 1 includes a plurality of bit lines BL, a plurality of word lines WL, and a plurality of unit memory cells MC.

[0037] The word line WL can extend in a first direction, and the bit line BL can extend in a second direction intersecting the first direction. The unit memory cell MC can be arranged two-dimensionally or three-dimensionally. Each unit memory cell MC can be connected to the intersection point between the word line WL and the bit line BL that intersect each other. Thus, each unit memory cell MC connected to the word line WL can be connected to the read / write circuit (e.g., Figure 1 4 in

[0038] Referring to Figure 3 , in a magnetic storage device according to some embodiments, the unit memory cell MC includes a magnetic tunnel junction 100 and a selection element 200. As a reference, Figure 3 the magnetic storage device is shown as an STT-MRAM.

[0039] The magnetic tunnel junction 100 can be connected between the bit line BL and the selection element 200. The selection element 200 can be connected between the magnetic tunnel junction 100 and the word line WL. The magnetic tunnel junction 100 can include a pinned layer 110, a free layer 120, and a tunnel barrier layer 130.

[0040] The pinned layer 110 can have a fixed magnetization direction. For example, regardless of the programming current flowing through the pinned layer, the magnetization direction of the pinned layer 110 can be fixed. The pinned layer 110 can have perpendicular magnetic anisotropy (PMA). That is, the pinned layer 110 can have an easy magnetization axis in a direction perpendicular to the stretching direction of the pinned layer 110. In the pinned layer 110, Figure 3 the unidirectional arrow A indicates that the magnetization direction of the pinned layer 110 is vertically fixed.

[0041] The pinned layer 110 can include a ferromagnetic material. For example, the pinned layer 110 can include at least one of an amorphous rare earth element alloy, a multilayer thin film in which ferromagnetic metals (FM) and non-magnetic metals (NM) are alternately stacked, an alloy having an L10-type crystal structure, a cobalt alloy, or a combination thereof. The amorphous rare earth element alloy can include, for example, alloys such as TbFe, TbCo, TbFeCo, DyTbFeCo, and / or GdTbCo. The multilayer thin film in which ferromagnetic metals and non-magnetic metals are alternately stacked can include, for example, multilayer thin films such as Co / Pt, Co / Pd, CoCr / Pt, Co / Ru, Co / Os, Co / Au, and / or Ni / Cu. The alloy having an L10-type crystal structure can include, for example, alloys such as Fe 50 Pt 50 Fe 50 Pd 50 Co 50 Pt 50 Fe 30 Ni20 Pt 50 and / or Co 30 Ni 20 Pt 50 alloys. Cobalt alloys may include, for example, alloys such as CoCr, CoPt, CoCrPt, CoCrTa, CoCrPtTa, CoCrNb, and / or CoFeB. In some embodiments, the pinned layer 110 may also include a single CoFeB layer.

[0042] The free layer 120 may have a variable magnetization direction. For example, the magnetization direction of the free layer 120 may vary according to the programming current flowing through the free layer 120. The free layer 120 may have perpendicular magnetic anisotropy (PMA). That is, the free layer 120 may have an easy magnetization axis in a direction perpendicular to the stretching direction of the free layer 120. Figure 3 The double-headed arrow B indicates that the magnetization direction of the free layer 120 is parallel or antiparallel to the magnetization direction of the pinned layer 110. In some embodiments, the magnetization direction of the free layer 120 may vary with spin transfer torque (STT). The free layer 120 will be described in more detail later with reference to Figure 4 and Figure 5 more specifically.

[0043] The tunnel barrier layer 130 may be interposed between the pinned layer 110 and the free layer 120. The tunnel barrier layer 130 may be used as an insulating tunnel barrier that generates a quantum mechanical tunneling effect between the pinned layer 110 and the free layer 120.

[0044] The tunnel barrier layer 130 may include, for example, but not limited to, at least one of magnesium oxide (MgO), aluminum oxide (Al2O3), silicon dioxide (SiO2), tantalum oxide (Ta2O5), silicon nitride (SiN), aluminum nitride (AlN), or a combination thereof. In some embodiments, the tunnel barrier layer 130 may include magnesium oxide having a sodium chloride (NaCl) crystal structure.

[0045] In some embodiments, based on the tunnel barrier layer 130, the pinned layer 110 may be connected to the word line WL, and the free layer 120 may be connected to the bit line BL. For example, the pinned layer 110 may be interposed between the lower electrode BE and the tunnel barrier layer 130, and the free layer 120 may be interposed between the tunnel barrier layer 130 and the upper electrode TE. However, Figure 3 the arrangement of the pinned layer 110 and the free layer 120 is only an example, and the present disclosure is not limited thereto. For example, the positions of the pinned layer 110 and the free layer 120 may be interchanged based on the tunnel barrier layer 130.

[0046] The select element 200 may be configured to selectively control the flow of charge through the magnetic tunnel junction 100. For example, the select element 200 may include at least one of a diode, a PNP bipolar transistor, an NPN bipolar transistor, an NMOS field-effect transistor, or a PMOS field-effect transistor. In the case where the select element 200 is constituted by a bipolar transistor or a MOS field-effect transistor as a three-terminal element, additional wiring (e.g., a source line) may be connected to the select element 200.

[0047] In some embodiments, the unit memory cell MC may further include a bottom electrode BE interposed between the magnetic tunnel junction 100 and the select element 200. In some embodiments, the unit memory cell MC may further include a top electrode TE interposed between the magnetic tunnel junction 100 and the bit line BL.

[0048] The magnetic tunnel junction 100 may be used as a variable resistance element that can be switched to two resistance states by an electrical signal applied thereto. For example, when the magnetization directions of the pinned layer 110 and the free layer 120 are parallel to each other, the magnetic tunnel junction 100 has a low resistance value, and the low resistance value may represent data "0" and thus may store data "0". Conversely, when the magnetization directions of the pinned layer 110 and the free layer 120 are antiparallel to each other, the magnetic tunnel junction 100 has a high resistance value, and the high resistance value may represent data "1" and thus store data "1".

[0049] Figure 4 is a schematic cross-sectional view of a magnetic tunnel junction of a magnetic storage device according to some embodiments of the inventive concept. For ease of explanation, the same reference numerals are used for the same elements described previously Figures 1 to 3 and the description of these elements will be briefly described or omitted.

[0050] Referring to Figure 4 , a magnetic storage device according to some embodiments includes a substrate 10, a pinned layer 110, a free layer 120, and a tunnel barrier layer 130.

[0051] The pinned layer 110, the free layer 120, and the tunnel barrier layer 130 may be formed on the substrate 10. The substrate 10 may be, for example, but not limited to, a silicon substrate, a gallium arsenide substrate, a silicon germanium substrate, a ceramic substrate, a quartz substrate, a display glass substrate, etc., and may be a SOI (semiconductor-on-insulator) substrate.

[0052] In a magnetic storage device according to some embodiments, the free layer 120 may include a first magnetic layer 122 (e.g., a first free layer), a second magnetic layer 124 (e.g., a second free layer), and a coupling layer 126 that form an exchange-coupled composite (ECC).

[0053] The first magnetic layer 122 may have perpendicular magnetic anisotropy (PMA). The first magnetic layer 122 may have, for example, a first perpendicular magnetic anisotropy energy. The first magnetic layer 122 may have a first magnetization amount. For example, the first magnetic layer 122 may have a first saturation magnetization intensity (M s ) of 1200 emu / cc or less. In one embodiment, the first magnetic layer 122 may have a first saturation magnetization intensity of 500 - 1200 emu / cc. In some embodiments, the relative change rate of TMR (tunneling magnetoresistance relative change rate) of the first magnetic layer 122 at room temperature (e.g., about 20 to 25 degrees Celsius, typically 23 degrees Celsius) is greater than 100%. The thickness of the first magnetic layer 122 may be 5 nm or less. For example, the first magnetic layer 122 of CoFeB may be 2 nm thick.

[0054] The first magnetic layer 122 may include a Heusler alloy. The first magnetic layer 122 may include, for example, a first Heusler alloy. In some embodiments, the first Heusler alloy has a cubic structure (cubic lattice structure). In some embodiments, the first Heusler alloy has a structure X2YZ, where X = manganese (Mn), iron (Fe), cobalt (Co), nickel (Ni), copper (Cu), ruthenium (Ru), rhodium (Rh), palladium (Pd), silver (Ag), cadmium (Cd), iridium (Ir), platinum (Pt), gold (Au), or magnesium (Mg); Y = beryllium (Be), scandium (Sc), titanium (Ti), vanadium (V), chromium (Cr), manganese (Mn), iron (Fe), cobalt (Co), nickel (Ni), zinc (Zn), yttrium (Y), zirconium (Zr), niobium (Nb), molybdenum (Mo), hafnium (Hf), tungsten (W), lanthanum (La), cerium (Ce), praseodymium (Pr), neodymium (Nd), samarium (Sm), gadolinium (Gd), terbium (Tb), dysprosium (Dy), holmium (Ho), erbium (Er), thulium (Tm), ytterbium (Yb), or lutetium (Lu); and Z = magnesium (Mg), boron (B), aluminum (Al), silicon (Si), zinc (Zn), gallium (Ga), germanium (Ge), arsenic (As), indium (In), tin (Sn), antimony (Sb), lead (Pb), or bismuth (Bi).

[0055] For example, the first Heusler alloy may include a Co2-based full Heusler alloy. For example, the first Heusler alloy may include at least one of Co2MnSi or Co2FeAl. Since the Co2-based full Heusler alloy has a lower magnetization amount, the operation speed of the magnetic storage device can be increased, and it has the advantage of a high relative change rate of TMR.

[0056] In an alternative embodiment, the first magnetic layer 122 may be an ordered ferroalloy. For example, the first magnetic layer 122 may be FeX, where X is one of Al, Si, Ge, or Ga.

[0057] In some embodiments, the first Heusler alloy may have in-plane magnetic anisotropy (IMA). However, due to the strong perpendicular magnetic anisotropy of the second magnetic layer 124, which will be described later, and the magnetic exchange coupling between the first magnetic layer 122 and the second magnetic layer 124, the perpendicular magnetic anisotropy of the first magnetic layer 122 can be ensured.

[0058] The second magnetic layer 124 and the tunnel barrier layer 130 may be separated by the first magnetic layer 122 interposed therebetween. The second magnetic layer 124 may have a stronger perpendicular magnetic anisotropy than the first magnetic layer 122. For example, the second magnetic layer 124 may have a second perpendicular magnetic anisotropy energy greater than the first perpendicular magnetic anisotropy energy.

[0059] In some embodiments, the magnetization of the second magnetic layer 124 may be less than the magnetization of the first magnetic layer 122. For example, the second saturation magnetization of the second magnetic layer 124 may be less than the first saturation magnetization. For example, the second magnetic layer 124 may have a second saturation magnetization of 500 emu / cc or less. In some embodiments, the thickness of the second magnetic layer 124 is 10 nm or less.

[0060] In some embodiments, the second magnetic layer 124 may include a Heusler alloy having perpendicular magnetic anisotropy. For example, the second magnetic layer 124 may include a second Heusler alloy different from the first Heusler alloy. In some embodiments, the second Heusler alloy has a tetragonal structure (tetragonal lattice structure).

[0061] The second magnetic layer 124 or the second Heusler alloy may include a material having strong perpendicular magnetic anisotropy. For example, the second magnetic layer 124 or the second Heusler alloy may include at least one of cobalt (Co), nickel (Ni), iron (Fe), Mn3X (where X is a metal selected from the group including germanium (Ge), gallium (Ga), antimony (Sb), or aluminum (Al)), and combinations thereof. The second Heusler alloy may include, for example, but not limited to, at least one of Mn3Ga, Mn3Ge, or combinations thereof.

[0062] In another embodiment, the second magnetic layer or the second Heusler alloy includes a multilayer film such as Co / Pt, Co / Ni, or a rare earth metal alloy. In another embodiment, the second magnetic layer or the second Heusler alloy includes a rare earth metal.

[0063] The coupling layer 126 may be interposed between the first magnetic layer 122 and the second magnetic layer 124. Accordingly, the first magnetic layer 122 may be interposed between the tunnel barrier layer 130 and the coupling layer 126. The thickness of the coupling layer 126 may be 1.5 nm or less. The first magnetic layer 122 and the second magnetic layer 124 may form a magnetic exchange coupling through the coupling layer 126. In some embodiments, the exchange energy (J ex ) or the magnetic coupling strength of the magnetic exchange coupling may be in the range of 0.05 erg / cm 2 to 1.0 erg / cm 2 .

[0064] The coupling layer 126 may have a material composition different from those of the first magnetic layer 122 and the second magnetic layer 124. The coupling layer 126 may include, for example, a metal layer. For example, the coupling layer 126 may include at least one of cobalt (Co), nickel (Ni), iron (Fe), tantalum (Ta), niobium (No), tungsten (W), ruthenium (Ru), or a combination thereof.

[0065] In some embodiments, the coupling layer 126 may include a metal oxide layer. The metal oxide layer may include, for example, at least one of magnesium oxide (MgO), magnesium aluminum oxide (MgAlO), hafnium oxide (HfO), tantalum pentoxide (Ta2O5), niobium pentoxide (Nb2O5), zirconium oxide (ZrO), aluminum oxide (AlO), or a combination thereof.

[0066] In some embodiments, the coupling layer 126 may include a material that induces interfacial perpendicular magnetic anisotropy (PMA) at the interface with the first magnetic layer 122. Interfacial perpendicular magnetic anisotropy refers to the phenomenon in which a magnetic layer having in-plane magnetic anisotropy (IMA) inside is affected by the interface with another adjacent layer and thus has perpendicular magnetic anisotropy (PMA). For example, when the coupling layer 126 contains a metal oxide, the oxygen atoms of the coupling layer 126 bond to the metal atoms of the first magnetic layer 122 and may induce interfacial perpendicular magnetic anisotropy in the first magnetic layer 122.

[0067] In an embodiment, the free layer 120 may be formed by forming a first layer having a first material and annealing the first material to form the first magnetic layer 122. Any of the materials discussed above for the first magnetic layer 122 may be used to form the first magnetic layer 122. The free layer is further formed by forming a metal oxide layer (coupling layer 126) on the first magnetic layer 122, forming a second layer having a second material on the metal oxide, and annealing the second material to form the second magnetic layer 124 on the metal oxide layer 126. Any of the materials discussed above for the metal oxide layer 126 may be used to form the metal oxide layer 126, and any of the materials discussed above for the second magnetic layer 124 may be used to form the second magnetic layer 124.

[0068] In another embodiment, the free layer 120 can be formed by forming a first layer of a first material, forming a metal oxide layer on the first layer, forming a second layer of a second material on the metal oxide layer, and annealing the first material and the second material to form a first magnetic layer 122 and a second magnetic layer 124, respectively, wherein the metal oxide layer 126 is located between the first magnetic layer 122 and the second magnetic layer 124. Similarly, any of the materials discussed above can be used to form these layers.

[0069] In some embodiments, based on the tunnel barrier layer 130, the pinned layer 110 can be disposed below the free layer 120. For example, as shown, the pinned layer 110, the tunnel barrier layer 130, and the free layer 120 can be stacked on the substrate 10 in this order. In this case, the first magnetic layer 122, the coupling layer 126, and the second magnetic layer 124 can be stacked on the substrate 10 in this order.

[0070] The magnetic storage device according to some embodiments may further include a capping layer 140. The capping layer 140 and the tunnel barrier layer 130 can be spaced apart by the free layer 120 therebetween. For example, as shown, when the pinned layer 110 is disposed below the free layer 120 based on the tunnel barrier layer 130, the capping layer 140 can be disposed above the second magnetic layer 124. The capping layer 140 can protect the characteristics of the free layer 120.

[0071] The capping layer 140 can include, for example, a metal layer or a metal oxide layer. The metal layer can include, for example, but not limited to, at least one of cobalt (Co), nickel (Ni), iron (Fe), tantalum (Ta), tungsten (W), ruthenium (Ru), or a combination thereof. The metal oxide layer can include, for example, but not limited to, at least one of magnesium oxide (MgO), magnesium aluminum oxide (MgAlO), hafnium oxide (HfO), zirconium oxide (ZrO), aluminum oxide (AlO), or a combination thereof.

[0072] Figure 5 is a schematic diagram illustrating magnetic exchange coupling of a magnetic storage device according to some embodiments of the inventive concept. For ease of explanation, the repeated portions of the description provided will be briefly described or omitted. Figures 1 to 4 portions of the description provided.

[0073] For reference, Figure 5An example is shown where a write current is applied to the magnetic tunnel junction 100 such that the magnetization direction of the free layer 120 changes from an antiparallel state to a parallel state with respect to the magnetization direction of the pinned layer 110. However, the following description can of course be similarly applied to the case where a write current is applied to the magnetic tunnel junction 100 such that the magnetization direction of the free layer 120 changes from a parallel state to an antiparallel state with respect to the magnetization direction of the pinned layer 110. That is, the direction in which the write current flows controls the change from the parallel to the antiparallel state, and vice versa.

[0074] For example, when the magnetization direction of the free layer 120 is antiparallel to the magnetization direction of the pinned layer 110, electrons (e - ) can flow in the direction from the pinned layer 110 to the free layer 120. Accordingly, the magnetization direction of the free layer 120 can be reversed by the spin transfer torque (STT) generated from the pinned layer 110.

[0075] At this time, the spin transfer torque generated from the pinned layer 110 can first reverse the first magnetic layer 122 having a low magnetization amount. Subsequently, due to the magnetic exchange coupling formed by the first magnetic layer 122 and the second magnetic layer 124, the magnetization direction of the second magnetic layer 124 can be reversed until the magnetization direction of the entire free layer 120 is reversed. That is, the second magnetic layer 124 can be easily reversed by the magnetic exchange coupling formed by the first magnetic layer 122 and the second magnetic layer 124. Accordingly, the operation current applied to the magnetic tunnel junction 100 can be reduced, and a magnetic storage device capable of performing low-current operation can be provided.

[0076] In some embodiments, the exchange energy (J ex ) of the magnetic exchange coupling can be in the range of 0.05 erg / cm 2 to 1.0 erg / cm 2 . When the exchange energy (J ex ) is less than 0.05 erg / cm 2 , a magnetic exchange coupling may not be formed between the first magnetic layer 122 and the second magnetic layer 124. When the exchange energy (J ex ) is greater than 1.0 erg / cm 2 , the operation current applied to the magnetic tunnel junction 100 may increase.

[0077] In a magnetic storage device according to some embodiments, since the free layer 120 can ensure sufficient perpendicular magnetic anisotropy, a magnetic storage device having improved thermal stability can be provided. For example, since the free layer 120 includes a second magnetic layer 124 having strong perpendicular magnetic anisotropy, sufficient perpendicular magnetic anisotropy can be ensured. In a magnetic storage device according to some embodiments, since the free layer 120 includes a coupling layer 126 that induces interfacial perpendicular magnetic anisotropy (interfacial PMA), perpendicular magnetic anisotropy can be additionally ensured.

[0078] In addition, in a magnetic storage device according to some embodiments, since the first magnetic layer 122 includes a Co2-based full Heusler alloy, a magnetic storage device having a high TMR relative change rate (tunneling magnetoresistance relative change rate) can be provided.

[0079] Figure 6 FIG. is a schematic cross-sectional view of a magnetic tunnel junction of a magnetic storage device according to some embodiments of the inventive concept. For ease of explanation, repeated parts of the description provided will be briefly described or omitted. Figures 1 to 5 The repeated parts of the description provided.

[0080] Referring to Figure 6 , in a magnetic storage device according to some embodiments, the pinned layer 110 includes a third magnetic layer 112, a fourth magnetic layer 114, and a first non-magnetic layer 116 that form a synthetic antiferromagnetic (SAF) structure.

[0081] Due to the RKKY (Ruderman-Kittel-Kasuya-Yosida) interaction, the synthetic antiferromagnetic (SAF) structure can exhibit, for example, antiferromagnetic coupling (AFC) characteristics. For example, as shown, the magnetization directions of the third magnetic layer 112 and the fourth magnetic layer 114 are arranged antiparallel to minimize the total magnetization of the pinned layer 110. Since the third magnetic layer 112 and the fourth magnetic layer 114 constitute the pinned layer 110, they can have fixed magnetization directions.

[0082] The third magnetic layer 112 and the fourth magnetic layer 114 may include ferromagnetic materials. For example, the third magnetic layer 112 and the fourth magnetic layer 114 may include at least one of, for example, an amorphous rare earth element alloy, a multilayer thin film in which ferromagnetic metal (FM) and non-magnetic metal (NM) are alternately stacked, an alloy having an L10-type crystal structure, a cobalt alloy, or a combination thereof.

[0083] The first non-magnetic layer 116 may be interposed between the third magnetic layer 112 and the fourth magnetic layer 114. The third magnetic layer 112 and the fourth magnetic layer 114 may form an antiferromagnetic coupling (AFC) through the first non-magnetic layer 116. The first non-magnetic layer 116 may include a non-magnetic material. The first non-magnetic layer 116 may include at least one of, for example, ruthenium (Ru), chromium (Cr), platinum (Pt), palladium (Pd), iridium (Ir), rhodium (Rh), osmium (Os), rhenium (Re), gold (Au), copper (Cu), or a combination thereof.

[0084] Figure 7 is a schematic cross-sectional view of a magnetic tunnel junction in a magnetic storage device illustrating some embodiments according to the inventive concept. For ease of explanation, repeated portions of the description provided will be briefly described or omitted. Figures 1 to 6 The

[0085] Referring Figure 7 , a magnetic storage device according to some embodiments further includes a seed layer 160.

[0086] The seed layer 160 may be disposed below the pinned layer 110 or the free layer 120. The seed layer 160 may be formed by sputtering and annealing. As shown, when the pinned layer 110 is disposed below the free layer 120 based on the tunnel barrier layer 130, the seed layer 160 may be disposed below the pinned layer 110. The seed layer 160 enhances the perpendicular magnetic anisotropy of the pinned layer 110 and may fix the magnetization direction of the pinned layer 110.

[0087] The seed layer 160 may include at least one of, for example, tantalum (Ta), ruthenium (Ru), titanium (Ti), palladium (Pd), platinum (Pt), magnesium (Mg), aluminum (Al), or a combination thereof. In some embodiments, the seed layer 160 may be composed of a multi-layer thin film stacked with different non-magnetic metals. For example, the seed layer 160 may include a second non-magnetic layer 162 and a third non-magnetic layer 164 stacked in sequence. The second non-magnetic layer 162 may include, for example, but not limited to, tantalum (Ta). The third non-magnetic layer 164 may include, for example, but not limited to, platinum (Pt).

[0088] Figure 8 is a schematic cross-sectional view of a magnetic tunnel junction of a magnetic storage device illustrating some embodiments according to the inventive concept. For ease of explanation, repeated portions of the description provided will be briefly described or omitted. Figures 1 to 7 The

[0089] Referring Figure 8 , a magnetic storage device according to some embodiments further includes a polarization enhancement layer 150.

[0090] The polarization enhancement layer 150 may be interposed between the tunnel barrier layer 130 and the free layer 120. The polarization enhancement layer 150 may increase the spin polarization rate of the free layer 120. In some embodiments, the magnetization direction of the polarization enhancement layer 150 may be parallel to the magnetization direction of the fourth magnetic layer 114.

[0091] The polarization enhancement layer 150 may include a ferromagnetic material. The polarization enhancement layer 150 may include a material having a high spin polarization and a low damping constant. For example, the polarization enhancement layer 150 may include at least one of cobalt (Co), nickel (Ni), iron (Fe), or a combination thereof. In some embodiments, the polarization enhancement layer 150 may include CoFeB. In some embodiments, the polarization enhancement layer 150 may further include a non-magnetic material. For example, the polarization enhancement layer 150 may further include at least one of boron (B), zinc (Zn), ruthenium (Ru), silver (Ag), gold (Au), copper (Cu), carbon (C), nitrogen (N), or a combination thereof.

[0092] Figure 9 is a schematic cross-sectional view of a magnetic tunnel junction of a magnetic storage device according to some embodiments of the inventive concept. For ease of explanation, repeated portions of the description provided will be briefly described or omitted. Figures 1 to 8 portions of the description provided.

[0093] Referring to Figure 9 , a magnetic storage device according to some embodiments further includes an amorphous layer 170.

[0094] The amorphous layer 170 may be disposed below the tunnel barrier layer 130. For example, as shown, the amorphous layer 170 may be interposed between the tunnel barrier layer 130 and the pinned layer 110.

[0095] The amorphous layer 170 may prevent the elements constituting the pinned layer 110 from diffusing to protect the characteristics of the tunnel barrier layer 130. For example, when the fourth magnetic layer 114 includes a crystalline substance of cobalt (Co) or a cobalt (Co) alloy, the amorphous layer 170 may include a CoFeB-based amorphous substance to prevent the elements constituting the fourth magnetic layer 114 from diffusing.

[0096] Figure 10 is a conceptual diagram of a unit storage cell of a magnetic storage device according to some embodiments of the inventive concept. Figure 11 is a schematic cross-sectional view of a magnetic storage device according to some embodiments of the inventive concept. For ease of explanation, repeated portions of the description provided will be briefly described or omitted. Figures 1 to 5 portions of the description provided.

[0097] Referring to Figure 10, in a magnetic storage device according to some embodiments, based on the tunnel barrier layer 130, the pinned layer 110 can be connected to the bit line BL, and the free layer 120 can be connected to the word line WL. For example, the pinned layer 110 can be interposed between the upper electrode TE and the tunnel barrier layer 130, and the free layer 120 can be interposed between the tunnel barrier layer 130 and the lower electrode BE.

[0098] Referring to Figure 11 , in a magnetic storage device according to some embodiments, based on the tunnel barrier layer 130, the pinned layer 110 can be disposed above the free layer 120. For example, as shown in the figure, the free layer 120, the tunnel barrier layer 130, and the pinned layer 110 can be stacked on the substrate 10 in this order. In this case, the second magnetic layer 124, the coupling layer 126, and the first magnetic layer 122 can be stacked on the substrate 10 in this order.

[0099] In some embodiments, the capping layer 140 and the tunnel barrier layer 130 can be spaced apart by the free layer 120 interposed therebetween. For example, as shown in the figure, the capping layer 140 can be interposed between the substrate 10 and the second magnetic layer 124.

[0100] Figure 12 is a cross-sectional view of a magnetic storage device according to some embodiments of the inventive concept. For ease of explanation, the repeated portions of the description provided will be briefly described or omitted. By way of reference, Figures 1 to 11 the repeated portions of the description provided. By way of reference, Figure 12 illustrates a magnetic storage device constituting an STT-MRAM.

[0101] Referring to Figure 12 , a magnetic storage device according to some embodiments includes a substrate 10, select elements 12, 13, 21, and 22, and a magnetic tunnel junction 100. By way of reference, although the select elements 12, 13, 21, and 22 are illustrated as MOS field effect transistors, this is merely an example, and the present disclosure is not limited thereto. For example, different from the illustrated case, a diode or a bipolar transistor may also constitute a select element.

[0102] The substrate 10 may be, for example, but not limited to, a silicon substrate, a gallium arsenide substrate, a silicon germanium substrate, a ceramic substrate, a quartz substrate, a display glass substrate, etc., and may be a SOI (semiconductor on insulator) substrate.

[0103] The select elements 12, 13, 21, and 22 may include a source region 13, a drain region 12, a gate electrode 22, and a gate insulating film 21. The source region 13 and the drain region 12 may be formed in the substrate 10 spaced apart from each other. The gate electrode 22 may be formed on the substrate 10 between the source region 13 and the drain region 12. The gate electrode 22 may extend, for example, across the upper surface of the substrate 10 and serve as a word line (e.g., Figure 2 andFigure 3 WL). The gate electrode 22 can be insulated from the substrate 10 through the gate insulating film 21.

[0104] The first interlayer insulating film 20 covering the selection elements 12, 13, 21, and 22 can be formed on the substrate 10. The source line 32 can be formed on a desired (or, predetermined) region of the first interlayer insulating film 20 corresponding to the source region 13. For example, the source line 32 can be formed to extend in the same direction as the gate electrode 22. In Figure 12 , the adjacent selection elements 12, 13, 21, and 22 are illustrated as sharing the source region 13, but the present disclosure is not limited thereto. For example, the adjacent selection elements 12, 13, 21, and 22 may not share the source region 13 and the drain region 12.

[0105] The source line contact 24 and the landing contact 23 can be formed in the first interlayer insulating film 20. The source line contact 24 can electrically connect the source line 32 and the source region 13. The landing contact 23 is formed on the drain region 12 and can be electrically connected to the drain region 12.

[0106] The second interlayer insulating film 30 can be formed on the first interlayer insulating film 20. The lower electrode contact 31 electrically connected to the landing contact 23 can be formed in the second interlayer insulating film 30.

[0107] The magnetic tunnel junction 100 according to some embodiments of the inventive concept can be disposed on the second interlayer insulating film 30. Since the magnetic tunnel junction 100 is the same as the magnetic tunnel junction described using Figures 1 to 11 , a detailed description will not be provided below.

[0108] The magnetic tunnel junction 100 can be electrically connected to the drain region 12 through, for example, the lower electrode BE, the lower electrode contact 31, and the landing contact 23.

[0109] The third interlayer insulating film 40 can be formed on the second interlayer insulating film 30. The bit line 50 (e.g., Figure 2 and Figure 3 BL) can be formed on the third interlayer insulating film 40. The bit line 50 can extend to intersect, for example, the gate electrode 22. The bit line 50 can be electrically connected to the magnetic tunnel junction 100 through, for example, the upper electrode contact 41.

[0110] The first interlayer insulating film 20, the second interlayer insulating film 30, and the third interlayer insulating film 40 can include, but are not limited to, insulating materials such as silicon oxide or silicon oxynitride. The landing contact 23, the source line contact 24, the source line 32, the lower electrode contact 31, the upper electrode contact 41, and the bit line 50 can include, for example, but are not limited to, conductive materials such as tungsten (W), ruthenium (Ru), tantalum (Ta), copper (Cu), aluminum (Al), doped polysilicon, etc.

[0111] In some embodiments, metal wirings electrically connected to a circuit of a peripheral circuit unit (not shown) may also be formed on the bit line 50.

[0112] Due to the magnetic tunnel junctions of one or more example embodiments, with reference to Figure 1 , the control logic 5 may be configured to control the row decoder 2 and the read / write circuit 4 such that a write current of less than 150 μA is used to write data into the memory cell MC in a time of less than or equal to 10 ns.

[0113] In summarizing the detailed description, those skilled in the art will understand that some changes and modifications may be made to the preferred embodiments without substantially departing from the principles of the inventive concept. Therefore, the preferred embodiments of the present invention disclosed are for general and descriptive purposes only and not for the purpose of limitation.

Claims

1. A magnetic storage device, comprising: A free layer structure having a variable magnetization direction, the free layer structure comprising: A first free layer which is a first Heusler alloy, A coupling layer located on the first free layer, the coupling layer comprising a metal oxide layer, the coupling layer being configured to induce interfacial perpendicular magnetic anisotropy in the first free layer, and A second free layer located on the metal oxide layer, the second free layer being a second Heusler alloy different from the first Heusler alloy; A pinned layer structure having a fixed magnetization direction; and A tunneling barrier layer located between the pinned layer structure and the free layer structure.

2. The magnetic storage device according to claim 1, wherein, The magnetic coupling strength between the first free layer and the second free layer is 0.05 - 1 erg / cm 2 .

3. The magnetic storage device according to claim 2, wherein, The thickness of the metal oxide layer is less than or equal to 1.5 nm.

4. The magnetic storage device according to claim 3, wherein The metal oxide layer contains Mg, Al, Hf, Zr, Ta, Nb or a combination thereof.

5. The magnetic storage device according to claim 1, wherein, The thickness of the metal oxide layer is less than or equal to 1.5 nm.

6. The magnetic storage device according to claim 5, wherein, The metal oxide layer contains Mg, Al, Hf, Zr, Ta, Nb or a combination thereof.

7. The magnetic storage device according to claim 1, wherein, The first free layer has a cubic structure.

8. The magnetic storage device according to claim 1, wherein, The first free layer has a saturation magnetization of 1200 emu / cc or less.

9. The magnetic storage device according to claim 1, wherein, The first free layer has a saturation magnetization of 500 - 1200 emu / cc.

10. The magnetic storage device according to claim 1, wherein, The relative change rate of tunneling magnetoresistance of the first free layer at room temperature is greater than 100%.

11. The magnetic storage device according to claim 1, wherein, The thickness of the first free layer is 5 nm or less.

12. The magnetic storage device according to claim 1, wherein, The first free layer has a structure X2YZ, where X = Mn, Fe, Co, Ni, Cu, Ru, Rh, Pd, Ag, Cd, Ir, Pt, Au or Mg; Y = Be, Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Zn, Y, Zr, Nb, Mo, Hf, W, La, Ce, Pr, Nd, Sm, Gd, Tb, Dy, Ho, Er, Tm, Yb or Lu; and Z = Mg, B, Al, Si, Zn, Ga, Ge, As, In, Sn, Sb, Pb or Bi.

13. The magnetic storage device according to claim 1, wherein, The first free layer contains cobalt.

14. The magnetic storage device according to claim 1, wherein, The second free layer has a tetragonal structure.

15. The magnetic storage device according to claim 1, wherein, The second free layer has a saturation magnetization of 500 emu / cc or less.

16. The magnetic storage device according to claim 1, wherein, The thickness of the second free layer is 10 nm or less.

17. The magnetic storage device according to claim 1, wherein, The second free layer contains one of cobalt, nickel, iron, manganese or a combination thereof.

18. The magnetic storage device according to claim 17, wherein, The second free layer is Mn3X, where X = Ge, Ga, Sb, Al or a combination thereof.

19. A magnetic storage device, comprising: A pinned layer structure having a fixed magnetization direction, the pinned layer structure comprising: A first pinned layer, A non - magnetic layer, and A second pinned layer, the first pinned layer and the second pinned layer having antiparallel magnetization directions; A free layer structure having a variable magnetization direction, the free layer structure comprising: A first free layer which is a first Heusler alloy, having a cubic structure and having a first saturation magnetization, A metal oxide layer, the metal oxide layer being located on the first free layer, the metal oxide layer being configured to induce interfacial perpendicular magnetic anisotropy in the first free layer, and A second free layer, the second free layer being located on the metal oxide layer, the second free layer being a second Heusler alloy, having a tetragonal structure and having a second saturation magnetization, the second saturation magnetization being less than the first saturation magnetization, and a magnetic coupling strength between the first free layer and the second free layer being 0.05 - 1 erg / cm 2 ; and A tunnel barrier layer, the tunnel barrier layer being located between the pinned layer structure and the free layer structure.

Images