Spin-orbit torque-based magnetic tunnel junctions

Abstract

To provide a spin-orbit torque-based magnetic tunnel junction capable of spin-orbit torque switching and exhibiting a high spin-orbit torque efficiency with a low specific resistance; and to provide a manufacturing method of the same.SOLUTION: A spin-orbit torque (SOT)-based magnetic tunnel junction 1 includes: a spin-orbit active layer formed on a substrate; a magnetization-free layer formed on the spin-orbit active layer; a tunnel barrier layer formed on the magnetization free layer; and a magnetization--pinned layer formed on the tunnel barrier layer. The spin torque active layer comprises a W-X alloy (in which W is tungsten and X comprises at least one of a group IV semiconductor and a group III-V semiconductor).SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] [Cross-reference with related applications] This application claims priority under Korean Patent Application No. 10-2024-0021247 dated February 14, 2024, and all content disclosed in the said Korean Patent Application is incorporated herein by reference.

[0002] The present invention relates to a spin-orbit torque-based magnetic tunnel junction, and more particularly to a spin-orbit torque-based magnetic tunnel junction in which a thin film of a WX alloy (where W is tungsten and X is at least one of a group IV semiconductor and a group III-V semiconductor) is applied as a spin-orbit active layer, which maintains perpendicular magnetic anisotropy (PMA) even after thin film deposition and heat treatment, and has a structure that enables spin-orbit torque switching, and has a composition that has low resistivity and high spin-orbit torque efficiency. [Background technology]

[0003] A magnetic tunnel junction basically consists of a three-layer structure of ferromagnet / oxide / ferromagnet, including a magnetized free layer (FL), a tunnel barrier (TB), and a magnetized pinned layer (PL), respectively. The positions of the magnetized free layer and pinned layer may be interchangeable. The value of the tunnel current passing through the tunnel barrier changes depending on whether the spin directions of adjacent magnetized free layers and pinned layers separated by the tunnel barrier are aligned parallel or antiparallel. The difference in resistance at this time is called the tunnel magnetoresistance (TMR) ratio. The spin direction of the pinned layer is fixed, and information can be input by manipulating the spin direction of the free layer by applying a magnetic field or electric current.

[0004] The magnetic tunnel junction (MTJ) structure, which is the core element of conventional spin-orbit torque (SOT) switching-based MRAM (magnetic random access memory), can be composed of a non-magnetic spin torque generating layer (hereinafter referred to as the spin torque active layer), a first magnetic layer (magnetization free layer), a tunnel barrier layer, and a second magnetic layer (magnetization fixed layer).

[0005] The aforementioned magnetic tunnel junction structure reads information using the tunneling magnetoresistance (TMR) phenomenon, in which the electrical resistance of the tunnel current passing through the insulating layer changes depending on the relative magnetization direction of the magnetized free layer and the stationary layer.

[0006] To achieve a high tunnel magnetoresistance ratio, high write stability, low write current, and high integration, magnetic tunnel junctions must always possess perpendicular magnetic anisotropy (PMA). Perpendicular magnetic anisotropy means that the magnetization direction of the magnetic layer is perpendicular to the magnetic layer plane.

[0007] Recently, a spin-orbit torque phenomenon has been discovered that induces switching of the magnetized free layer using the spin Hall effect or Rashba effect, which occurs when current flows in a parallel direction within the plane of a spin-torque active layer adjacent to the magnetized free layer. This is attracting attention as a technology that enables information writing at higher speeds and with lower current consumption than existing spin-transfer torque (STT) writing methods.

[0008] Essential design considerations for spin-orbit torque elements include forming the spin-torque active layer with a material structure that has low resistivity and a large spin Hall angle (SHA), which is a physical quantity (without units) that indicates the efficiency of spin-orbit torque.

[0009] As a result, U.S. Patent No. 11062752 (hereinafter referred to as the "752 patent") discloses a SOT magnetic tunnel junction structure based on W or Ta. Furthermore, Physical Review B 98, 134411 (2018), “Temperature study of the giant spin Hall effect in the bulk limit of β-W” (hereinafter referred to as the "prior paper") discloses that by changing the W deposition technique when fabricating a thin film of the W / CoFeB / MgO structure, it is possible to maintain high resistivity even with a thick W and increase the efficiency of the SOT.

[0010] However, the "752 patent" and the "prior papers" do not disclose how to maintain perpendicular magnetic anisotropy in the structure of an alloy thin film, or how to increase the efficiency of SOT with low resistivity. [Prior art documents] [Patent Documents]

[0011] [Patent Document 1] U.S. Patent No. 11062752 (Registration Date: 2021.07.13.) [Non-patent literature]

[0012] [Non-Patent Document 1] Physical Review B 98, 134411(2018), “Temperature study of the giant spin Hall effect in the bulk limit of β-W” [Overview of the project] [Problems that the invention aims to solve]

[0013] The problem that the present invention aims to solve is to provide a spin-orbit torque-based magnetic tunnel junction using a thin film of a WX alloy (where W is tungsten and X includes at least one of a group IV semiconductor and a group III-V semiconductor) with high spin-orbit coupling as the spin-torque active layer. A device to which this spin-orbit torque-based magnetic tunnel junction is applied is capable of spin-orbit torque switching and can exhibit high spin-orbit torque efficiency with low resistivity.

[0014] Another objective of the present invention is to provide a spin-orbit torque-based magnetic tunnel junction and a method for manufacturing the same, which have a structure that allows the switching current to be controlled by adjusting the composition of X in the WX alloy.

[0015] Another objective of the present invention is to provide a spin-orbit torque-based magnetic tunnel junction in which perpendicular magnetic anisotropy (PMA) can be maintained even after heat treatment by using a tungsten-titanium alloy as the spin torque active layer.

[0016] The problem that this invention aims to solve is to maintain perpendicular magnetic anisotropy, enhance the spin-orbit torque effect of SOT-MRAM, and reduce the operating current by using a tungsten-titanium alloy layer as a conductor layer that contacts the magnetized free layer and provides in-plane current.

[0017] The problem that this invention aims to solve is to provide a range of material compositions in which perpendicular magnetic anisotropy is exhibited when a tungsten-titanium alloy layer is used as a material for MRAM.

[0018] The problem that this invention aims to solve is to provide heat treatment conditions that result in perpendicular magnetic anisotropy when a tungsten-titanium alloy layer is used as a material for MRAM.

[0019] The problem to be solved by the present invention is to provide the resistivity according to heat treatment conditions and the SOT efficiency at that time when a tungsten-titanium alloy layer is used as a material for MRAM.

[0020] The problem to be solved by the present invention is not limited to the problems mentioned above, and other problems not mentioned will be clearly understood by those skilled in the art from the following description.

Means for Solving the Problem

[0021] A spin-orbit torque (SOT)-based magnetic tunnel junction according to an embodiment of the present invention includes a spin-orbit active layer formed on a substrate; a free magnetization layer formed on the spin-orbit active layer; a tunnel barrier layer formed on the free magnetization layer; and a fixed magnetization layer formed on the tunnel barrier layer, and the spin-orbit active layer can include a W-X alloy (where W is tungsten and X includes at least one of a group-IV semiconductor and a group-III-V semiconductor).

[0022] The spin-orbit active layer may be an electrode that contacts the free magnetization layer to provide an in-plane current.

[0023] As the content of X included in the W-X alloy increases, the switching current can decrease.

[0024] The W-X alloy may be a tungsten-titanium (W-Ti) alloy in which the content of the titanium composition is 11.5 at% to 20.8 at%.

[0025] The heat treatment temperature at which perpendicular magnetic anisotropy appears in the spin-orbit torque-based magnetic tunnel junction may be 300°C.

[0026] The content of X in the WX alloy may be adjusted depending on the heat treatment temperature at which perpendicular magnetic anisotropy occurs.

[0027] The spin torque active layer has a cross shape in plan view, and the magnetization free layer, the tunnel barrier layer, and the magnetization fixed layer may be arranged in an island-like manner at the center of the cross-shaped spin torque active layer.

[0028] The substrate may include a native oxide layer on the surface that comes into contact with the spin torque active layer.

[0029] The spin torque active layer may further include a buffer layer below it.

[0030] The spin-orbit torque-based magnetic tunnel junction may further include a capping layer on the magnetization fixed layer.

[0031] A method for manufacturing a spin-orbit torque-based magnetic tunnel junction according to an embodiment of the present invention includes the steps of forming a spin-torque active layer on a substrate, forming a magnetization free layer on the spin-torque active layer, forming a tunnel barrier layer on the magnetization free layer, forming a magnetization fixed layer on the tunnel barrier layer, and performing heat treatment on the magnetization free layer and the magnetization fixed layer to induce perpendicular magnetic anisotropy, wherein the step of forming the spin-torque active layer on the substrate may involve simultaneously sputtering a W target and an X target in a vacuum chamber to form a WX alloy thin film (wherein W is tungsten and X includes at least one of a group IV semiconductor and a group III-V semiconductor) on the substrate placed in the vacuum chamber.

[0032] The X target is a titanium (Ti) target, and the composition of the tungsten-titanium alloy thin film may be adjusted according to the power of the tungsten target and the titanium target.

[0033] The compositional content of X contained in the WX alloy may be 11.5 at% to 20.8 at%.

[0034] The spin-orbit torque-based magnetic tunnel junction may have a heat treatment temperature of 300°C at which the perpendicular magnetic anisotropy manifests.

[0035] Depending on the heat treatment temperature at which the aforementioned perpendicular magnetic anisotropy manifests, the content of X in the composition of the WX alloy may be adjusted.

[0036] The step of forming a spin torque active layer on the substrate may further include the step of patterning the tungsten-titanium alloy thin film in a cross shape. [Effects of the Invention]

[0037] According to embodiments of the present invention, by using a WX alloy thin film with high spin-orbit coupling as the spin-torque active layer, spin-orbit torque switching is possible, and a spin-orbit torque-based magnetic tunnel junction and a method for manufacturing the same that exhibits high spin-orbit torque efficiency with low resistivity can be provided.

[0038] According to embodiments of the present invention, a spin-orbit torque-based magnetic tunnel junction and a method for manufacturing the same can be provided, which allows for control of the switching current by adjusting the composition of X in the WX alloy.

[0039] According to embodiments of the present invention, by using a tungsten-titanium alloy as the spin torque active layer, it is possible to provide a spin-orbit torque-based magnetic tunnel junction and a method for manufacturing the same, in which perpendicular magnetic anisotropy (PMA) can be maintained over a wide range of heat treatment temperatures.

[0040] According to embodiments of the present invention, SOT elements using a tungsten-titanium alloy layer exhibit increased SOT efficiency compared to existing elements using a single W layer, while simultaneously maintaining low resistivity and perpendicular magnetic anisotropy.

[0041] The effects of the present invention are not limited to those mentioned above, and other effects not mentioned will be clearly understood by those skilled in the art from the following description. [Brief explanation of the drawing]

[0042] [Figure 1] This is a cross-sectional view of a spin-orbit torque-based magnetic tunnel junction 1 according to an embodiment of the present invention. [Figure 2] This is a plan view showing a spin-orbit torque-based magnetic tunnel junction according to an embodiment of the present invention. [Figure 3] This is a flowchart illustrating a method for manufacturing a spin-orbit torque-based magnetic tunnel junction according to an embodiment of the present invention. [Figure 4] This figure shows the results obtained from first-principles energy band calculations for different W-Ti compositions, specifically for phase stability and spin Hall conductivity. [Figure 5] This is a cross-sectional view showing a structure for measuring the spin-orbit torque efficiency of a spin-orbit torque-based magnetic tunnel junction according to an embodiment of the present invention. [Figure 6] This graph shows the quantitative analysis of the Ti composition using Rutherford backscattering spectrometry (RBS). [Figure 7] This graph shows the magnetic hysteresis curve measured using a vibrating sample magnetometer (VSM) for a thin film after heat treatment at 300°C. [Figure 8]This graph shows the spin Hall angle of a Hall bar-shaped element measured using the harmonic measurement method within the composition range of a tungsten-titanium alloy layer with perpendicular magnetic anisotropy, after heat treatment of a W-Ti5 / CoFeB0.9 / MgO1.0 / Ta2 (unit: nm) structure at 300°C, and its conversion to spin Hall conductivity. [Figure 9] This graph shows the resistivity of an alloy layer measured using the four-point probe method within the composition range of a tungsten-titanium alloy layer with perpendicular magnetic anisotropy, after heat treatment of a W-Ti5 / CoFeB0.9 / MgO1.0 / Ta2 (unit: nm) structure at 300°C. [Figure 10] This graph shows the spin-orbit torque switching characteristics of the tungsten-titanium alloy layer when an external magnetic field of ±300 Oe is applied to a test specimen with a W-Ti5 / CoFeB0.9 / MgO1.0 / Ta2 (unit: nm) structure that has been heat-treated at 300°C. [Figure 11] This graph shows the change in switching current density when an external magnetic field of ±300 Oe is applied to a test specimen with a W-Ti5 / CoFeB0.9 / MgO1.0 / Ta2 (unit: nm) structure that has been heat-treated at 300°C. [Figure 12] This graph shows the measurement results of switching current (current density) while varying the magnitude of the external magnetic field for a test specimen with a tungsten-titanium alloy layer containing 11.5 at% titanium in a W-Ti5 / CoFeB0.9 / MgO1.0 / Ta2 (unit: nm) structure, after heat treatment at 300°C. [Figure 13] This graph shows the change in switching current density of a device using a spin-orbit torque-based magnetic tunnel junction due to a change in driving temperature. [Figure 14] This graph shows the normalized resistance change of a device using a spin-orbit torque-based magnetic tunnel junction, measured by performing 100 switching cycles at extreme temperatures of (a) -55°C and (b) 150°C to confirm the device's operating temperature stability. [Figure 15]This graph shows the change in current density (Jc) of a device using a spin-orbit torque-based magnetic tunnel junction, depending on the driving temperature and external magnetic field. [Modes for carrying out the invention]

[0043] The specific structural or functional descriptions of embodiments of the concept of the present invention disclosed herein are merely illustrative for the purpose of illustrating embodiments of the concept of the present invention, and embodiments of the concept of the present invention can be implemented in various forms and are not limited to those described herein.

[0044] Embodiments of the concept of the present invention can be modified in various ways and may take on various forms; such embodiments are illustrated in the drawings and described in detail herein. However, this is not intended to limit embodiments of the concept of the present invention to any particular disclosure, but rather to include modifications, equivalents, or substitutions that fall within the spirit and technical scope of the present invention.

[0045] Terms such as "first" or "second" can be used to describe various components, but the components should not be limited by such terms. The terms are used solely for the purpose of distinguishing one component from another; for example, without departing from the scope of rights under the concept of the present invention, the first component may be named the second component, and similarly, the second component may be named the first component.

[0046] When it is mentioned that one component is "linked" or "connected" to another, it must be understood that this may mean that it is directly linked or connected to the other component, but that there may also be other components between those components. Conversely, when it is mentioned that one component is "directly linked" or "directly connected" to another, it must be understood that there are no other components between those components. Expressions describing the relationship between components, such as "between," "immediately between," or "directly adjacent to," must be interpreted in the same way.

[0047] The terms used herein are used solely to describe specific embodiments and are not intended to limit the invention. Singular expressions include plural expressions unless the context clearly indicates otherwise. In this specification, terms such as “includes” or “having” are intended to specify the existence of a described feature, figure, stage, operation, component, part, component, or combination thereof, and should not be understood to preemptively exclude the existence or possibility of adding one or more other features, figures, stages, operations, components, parts, components, or combination thereof.

[0048] Unless otherwise defined, all terms used herein, including technical or scientific terms, have the same meaning as those generally understood by a person of ordinary skill in the art to which this invention pertains. Terms as defined in commonly used dictionaries should be interpreted as having the meaning consistent with their meaning in the context of the relevant art, and not as ideal or overly formal unless explicitly defined herein.

[0049] The present invention will be described in more detail below with reference to the attached drawings showing embodiments of the present invention.

[0050] Figure 1 is a cross-sectional view of a spin-orbit torque-based magnetic tunnel junction 1 according to an embodiment of the present invention.

[0051] As shown in Figure 1, a spin-orbit torque (SOT) based magnetic tunnel junction according to an embodiment of the present invention includes a spin-orbit active layer 120 formed on a substrate 110, a magnetization free layer 130 formed on the spin-orbit active layer 120, a tunnel barrier layer 140 formed on the magnetization free layer 130, and a magnetization fixed layer 150 formed on the tunnel barrier layer 140, wherein the spin-orbit active layer 120 includes a WX alloy (where W is tungsten and X includes at least one of a group IV semiconductor and a group III-V semiconductor).

[0052] Therefore, the spin-orbit torque-based magnetic tunnel junction 1 according to the embodiment of the present invention enables spin-orbit torque switching by using a WX alloy with high spin-orbit coupling as the spin-torque active layer 120, and can have high spin-orbit torque efficiency with low resistivity.

[0053] An embodiment of the present invention includes a spin-torque active layer 120 formed on a substrate 110, which is part of a spin-orbit torque-based magnetic tunnel junction.

[0054] The substrate 110 may include a semiconductor substrate, which may include silicon (Si), silicon-on-insulator (SOI), silicon germanium (SiGe), germanium (Ge), gallium arsenide (GaAs), and the like.

[0055] The substrate 110 may include a native oxide layer on the surface that contacts the spin torque active layer 120, and the native oxide layer formed on the surface of the substrate 110 may be amorphous.

[0056] In the embodiment, the substrate 110 may further include at least one of a seed layer and a buffer layer.

[0057] Therefore, the seed layer and buffer layer can be formed between the substrate 110 and the spin torque active layer 120.

[0058] The seed layer may be formed on the substrate 110 or on the spin-torque active layer 120. The seed layer is a material that enables crystal growth, allowing the magnetic material to grow in a desired crystal direction.

[0059] The seed layer may, but is not limited to, contain at least one of tantalum (Ta), ruthenium (Ru), titanium (Ti), palladium (Pd), platinum (Pt), magnesium (Mg), cobalt (Co), aluminum (Al), and tungsten (W). Preferably, the seed layer may be 5 nm thick Ta.

[0060] The buffer layer can be formed below the spin-torque active layer 120, and the formation of the buffer layer below the spin-torque active layer 120 can improve the crystallinity of the spin-torque active layer 120.

[0061] Furthermore, buffer layers may be formed to resolve mismatches in lattice constants between layers.

[0062] Furthermore, the seed layer and buffer layer may be formed as a single layer without being separated from each other. For example, the buffer layer may also include the function of the seed layer.

[0063] The buffer layer may, but is not limited to, include at least one of Ta, W, and Pd. Preferably, the buffer layer may be 10 nm Pd or 2 nm Ta.

[0064] The spin torque active layer 120 can be used as an electrode that contacts the magnetized free layer 130 and provides an in-plane current, thereby inducing the spin Hall effect or the Rashba effect.

[0065] The spin torque active layer 120 provides a spin polarization current and can apply a spin orbit torque to the magnetized free layer 130 through the spin Hall effect or Rashba effect of the spin torque active layer 120, thereby inducing magnetization reversal of the magnetized free layer 130. Furthermore, the spin torque active layer 120 provides a spin accumulation in the magnetized free layer 130 aligned with the magnetization direction of the spin torque active layer 120, and this spin accumulation can provide a deterministic switching effect or an additional torque effect.

[0066] Furthermore, the current driven in-plane through the spin-torque active layer 120 and the accompanying spin-orbit interaction can give rise to a spin-orbit magnetic field (H). This spin-orbit magnetic field (H) is equivalent to the spin-orbit torque (T) on magnetization. Therefore, torque and magnetic field may be interchangeably referred to as spin-orbit magnetic field and spin-orbit torque. This reflects the fact that spin-orbit interaction is the source of spin-orbit torque and spin-orbit magnetic field. Spin-orbit torque can be generated for current driven in the plane of the spin-torque active layer 120 and spin-orbit interaction.

[0067] The spin-torque active layer 120 has a strong spin-orbit interaction and can be used as an electrode when switching the magnetic moment of the magnetized free layer 130.

[0068] Furthermore, the spin torque active layer 120 can easily switch the magnetic field within the magnetization free layer 130, and the spin torque active layer 120 can realize a spin orbit torque memory by changing the direction of the polarity of the magnetic field in the magnetization free layer 130.

[0069] Therefore, the spin-orbit torque-based magnetic tunnel junction 1 according to an embodiment of the present invention can use spin orbit torque (SOT) to switch the magnetized free layer 130 using spin current in order to operate the MRAM memory cell.

[0070] In the spin-orbit torque-based magnetic tunnel junction 1 according to an embodiment of the present invention, a WX alloy (where W is tungsten and X includes at least one of a group IV semiconductor and a group III-V semiconductor) can be used as the spin torque active layer 120, thereby enabling the maintenance of perpendicular magnetic anisotropy (PMA) over a wide range of heat treatment temperatures.

[0071] Preferably, the group IV semiconductor may include at least one of titanium (Ti), zirconium (Zr), hafnium (Hf), and alloys thereof, and the group III-V semiconductor may include, but is not limited to, at least one of GaAs, GaP, InP, InGaAlN, and GaN. Preferably, in the spin-orbit torque-based magnetic tunnel junction according to the embodiment of the present invention, a tungsten (W)-titanium (Ti) alloy may be used as the spin torque active layer 120.

[0072] More specifically, spin-orbit torque (SOT) arises from the spin-Hall effect and Rashba effect due to spin-orbit interaction, and these phenomena can be stronger in proportion to the atomic number. Therefore, conventional research has focused on heavy metal materials (W, Ta, Pt, etc.), and research is being conducted on alloys or insertions of various materials to further improve the properties and efficiency of single heavy metal materials.

[0073] Therefore, from a spintronics perspective, tungsten is a material that excels at generating spin-orbit torque (SOT), and because it exhibits a strong spin Hall effect due to spin-orbit interaction, it is easy to use as a material for SOT-MRAM. X (Group IV and III-V semiconductor materials such as Ti, Ge, and Ga-As) also exhibit the spin Hall effect and Rashba effect, which are known causes of spin-orbit torque. Therefore, when a WX alloy is used as the spin torque active layer 120, spin-orbit torque switching is possible, and it is possible to have high spin-orbit torque efficiency with low resistivity.

[0074] Preferably, tungsten (W) and titanium (Ti) are essential materials for semiconductor processes, and W-Ti alloys also have low contact resistance when heat-treated at high temperatures and are very compatible with semiconductor processes; therefore, W-Ti alloys can be used as the spin torque active layer 120.

[0075] The element X contained in the spin torque active layer 120 of the spin-orbit torque-based magnetic tunnel junction according to an embodiment of the present invention is a semiconductor material, and the element X can exhibit the extrinsic spin Hall effect.

[0076] Therefore, due to the extrinsic spin Hall effect of X, which is partially present as an impurity within tungsten, the spin Hall angle, also known as the spin-orbit torque efficiency, can increase as the compositional content of X (e.g., titanium) in tungsten increases.

[0077] Furthermore, the presence of X as a partial impurity within the tungsten increases electron scattering, and as the X content in the tungsten composition increases, the resistivity of the WX alloy thin film can be increased.

[0078] In the spin-orbit torque-based magnetic tunnel junction according to an embodiment of the present invention, the switching current can be reduced as the compositional content of X in the WX alloy increases.

[0079] Furthermore, the content of X in the WX alloy may be between 11.5 at% and 20.8 at%. However, the content of X in the WX alloy is not limited to this and can be adjusted according to the X substance.

[0080] In WX alloys, as the content of X increases, the perpendicular magnetic anisotropy may weaken, and outside a specific compositional content range (e.g., 46.4 at%), there is a problem in that the perpendicular magnetic anisotropy is lost altogether.

[0081] Preferably, the composition of X in the WX alloy can be adjusted according to the temperature of the subsequent heat treatment. When the heat treatment temperature is 300°C, perpendicular magnetic anisotropy can be exhibited when the composition of X is between 0.1 at% and 46.4 at%. However, the content of X in the composition of the WX alloy depending on the heat treatment temperature is not limited to this and can be adjusted according to the X material.

[0082] In WX alloys, if the X content is less than 11.5 at%, the spin-orbit torque efficiency may decrease, as it is a conventional tungsten-based spin-orbit torque material that does not contain X, similar to the case with a 100 at% tungsten composition.

[0083] When the heat treatment temperature is 300°C, if the X content in the WX alloy exceeds 46.4 at%, not only is perpendicular magnetic anisotropy lost, but the magnetic layer (magnetized free layer and magnetized fixed layer) formed on the WX alloy thin film also loses its magnetic properties, making it unusable as a magnetic tunnel junction element.

[0084] For example, when a tungsten (W)-titanium (Ti) alloy is used as the spin torque active layer 120, the titanium composition ratio at which perpendicular magnetic anisotropy is exhibited may be such that, when the heat treatment temperature is 300°C, the titanium composition ratio (x) (where x is a real number) is 0.1 at% ≤ x ≤ 46.4 at%.

[0085] In the spin-orbit torque-based magnetic tunnel junction according to an embodiment of the present invention, the switching current can be reduced as the heat treatment temperature at which perpendicular magnetic anisotropy appears increases.

[0086] The heat treatment temperature at which perpendicular magnetic anisotropy appears may be 300°C.

[0087] The BEOL (Back End Of Line) process, which is included in the semiconductor device manufacturing process, involves heat treatment at 300°C to 400°C. Therefore, it is essential to develop devices that can maintain their magnetic properties even at this temperature.

[0088] Therefore, in the spin-orbit torque-based magnetic tunnel junction 1 according to the embodiment of the present invention, in order for perpendicular magnetic anisotropy to be exhibited in the CoFeB / MgO (magnetized free layer / tunnel barrier layer) structure, heat treatment of at least 250°C to 300°C is required to promote crystallization of the CoFeB (magnetized free layer), and thus heat treatment must be performed at 300°C or higher. However, if the heat treatment temperature exceeds 500°C, it falls outside the temperature range that the CoFeB (magnetized free layer) used as the magnetic layer can withstand, resulting in the loss of the magnetic layer's properties.

[0089] In the spin-orbit torque-based magnetic tunnel junction according to an embodiment of the present invention, the spin torque efficiency can be adjusted according to the thickness of the spin torque active layer 120. As the thickness of the spin torque active layer 120 increases from 1 nm, the spin torque efficiency increases and then saturates, so the maximum spin torque efficiency can be obtained when the thickness of the spin torque active layer 120 is 5 nm to 7 nm.

[0090] Preferably, in the case of W, the thickness of the spin torque active layer 120 can be 5 nm, as an optimal thickness of 5 nm can be maintained in order to maintain the β (beta) phase with high spin torque efficiency.

[0091] An embodiment of the present invention includes a spin-orbit torque-based magnetic tunnel junction comprising a magnetization-free layer 130 formed on a spin-torque active layer 120.

[0092] The magnetization of the magnetization free layer 130 is not fixed in one direction, but can change from one direction to the opposite direction. The magnetization direction of the magnetization free layer 130 may be the same as (i.e., parallel to) that of the magnetization fixed layer 150, or it may be opposite (i.e., antiparallel).

[0093] A magnetic tunnel junction can be used as a memory element by associating information with the resistance value, which changes according to the magnetization arrangement of the magnetized free layer 130 and the magnetized fixed layer 150.

[0094] For example, when the magnetization direction of the magnetized free layer 130 is parallel to the magnetized fixed layer 150, the resistance value of the magnetic tunnel junction becomes small, and this case can be defined as data '0'. Conversely, when the magnetization direction of the magnetized free layer 130 is antiparallel to the magnetized fixed layer 150, the resistance value of the magnetic tunnel junction becomes large, and this case can be defined as data '1'.

[0095] In the spin-orbit torque-based magnetic tunnel junction according to an embodiment of the present invention, the magnetization free layer 130 can have perpendicular magnetic anisotropy (PMA).

[0096] For example, if the magnetization direction of the magnetized free layer 130 is in the negative z-axis direction, the rotation direction of the current can be clockwise in order to reverse the magnetization in the positive z-axis direction. The torque applied to the magnetic moment of the magnetized free layer 130 due to the in-plane current can be named the spin-orbit torque.

[0097] The magnetized free layer 130 may include a material exhibiting interface perpendicular magnetic anisotropy. Interface perpendicular magnetic anisotropy refers to the phenomenon in which a magnetic layer having intrinsic horizontal magnetization properties acquires a perpendicular magnetization direction due to the influence of the interface with other adjacent layers. The magnetized free layer 130 may include at least one of cobalt (Co), iron (Fe), and nickel (Ni).

[0098] Furthermore, the magnetization free layer 130 may further contain at least one of the following nonmagnetic materials: boron (B), zinc (Zn), aluminum (Al), titanium (Ti), ruthenium (Ru), tantalum (Ta), silicon (Si), silver (Ag), gold (Au), copper (Cu), carbon (C), and nitrogen (N).

[0099] For example, the magnetization free layer 130 may contain CoFe or NiFe and further contain boron (B). In addition, the reference layer 126 and the magnetization free layer 130 may further contain at least one of titanium (Ti), aluminum (Al), silicon (Si), magnesium (Mg), tantalum (Ta), and silicon (Si).

[0100] In some examples, the magnetization free layer 130 may include at least one of a material having an L10 type crystal structure, a material having a hexagonal close-packed lattice (HCP), and an amorphous RE-TM (Rare-Earth Transition Metal) alloy.

[0101] The thickness of the magnetized free layer 130 may be 0.8 to 1 nm, preferably 0.9 nm, in order to exhibit perpendicular magnetic anisotropy, but is not limited thereto.

[0102] An embodiment of the present invention includes a spin-orbit torque-based magnetic tunnel junction 1, which includes a tunnel barrier layer 140 formed on a magnetization-free layer 130.

[0103] The tunnel barrier layer 140 separates the magnetized free layer 130 from the magnetized fixed layer 150, enabling quantum mechanical tunneling between the magnetized free layer 130 and the magnetized fixed layer 150.

[0104] The tunnel barrier layer 140 can be interposed between the magnetization free layer 130 and the magnetization fixed layer 150.

[0105] The tunnel barrier layer 140 may include at least one of the following: magnesium (Mg) oxide, titanium (Ti) oxide, aluminum (Al) oxide, magnesium-zinc (MgZn) oxide, magnesium-boron (MgB) oxide, titanium (Ti) nitride, and vanadium (V) nitride. For example, the tunnel barrier layer 140 may include crystalline magnesium oxide (MgO).

[0106] The thickness of the tunnel barrier layer 140 may be 0.9 to 1.1 nm, preferably 1.0 nm, in order to exhibit perpendicular magnetic anisotropy, but is not limited thereto.

[0107] An embodiment of the present invention includes a spin-orbit torque-based magnetic tunnel junction comprising a magnetization fixed layer 150 formed on a tunnel barrier layer 140.

[0108] The magnetization fixed layer 150 can have a fixed magnetic moment during the writing operation of the magnetic memory element. For example, the magnetic moment of the magnetization fixed layer 150 can not be switched by the spin orbit torque caused by the current flowing through the spin torque active layer 120.

[0109] The magnetization fixed layer 150 may include a material having interface perpendicular magnetic anisotropy.

[0110] Interfacial perpendicular magnetic anisotropy refers to the phenomenon in which a magnetic layer having intrinsic horizontal magnetization properties acquires a perpendicular magnetization direction due to the influence from the interface with other adjacent layers. The magnetization-fixing layer 150 may contain at least one of cobalt (Co), iron (Fe), and nickel (Ni).

[0111] Furthermore, the magnetization fixed layer 150 may further contain at least one of the following nonmagnetic materials: boron (B), zinc (Zn), aluminum (Al), titanium (Ti), ruthenium (Ru), tantalum (Ta), silicon (Si), silver (Ag), gold (Au), copper (Cu), carbon (C), and nitrogen (N).

[0112] For example, the magnetization fixed layer 150 may contain CoFe or NiFe and further contain boron (B). In addition, the reference layer 126 and the magnetization free layer 130 may further contain at least one of titanium (Ti), aluminum (Al), silicon (Si), magnesium (Mg), tantalum (Ta), and silicon (Si).

[0113] The magnetization fixed layer 150 may have a single-layer structure. In some embodiments, the magnetization fixed layer 150 may include a synthetic antiferromagnet having a ferromagnetic layer separated by a non-magnetic layer.

[0114] In some examples, the magnetization fixed layer 150 may include at least one of a material having an L10 type crystal structure, a material having a hexagonal close-packed lattice (HCP), and an amorphous RE-TM (Rare-Earth Transition Metal) alloy.

[0115] The magnetization fixed layer 150 can be formed to be thicker than the magnetization free layer 130 so that switching does not easily occur.

[0116] The spin-orbit torque-based magnetic tunnel junction 1 may further include a capping layer 160 on the magnetization fixed layer 150, preferably using Ta for the capping layer 160.

[0117] The capping layer 160 can be used as an anti-oxidation film and may be deposited with a thickness of 1 to 2.2 nm, preferably 2 nm, to prevent the properties of the magnetic layer (magnetized free layer 130 and magnetized fixed layer 150) from being reduced by natural oxidation.

[0118] If the capping layer 160 is formed with a thickness greater than 2.2 nm, the antioxidant effect can be increased. However, since the deposition of the capping layer 160 affects the tunnel barrier layer 140, the conditions for perpendicular magnetic anisotropy (thickness of the magnetization free layer 130 and the tunnel barrier layer 140) must be adjusted. If the capping layer 160 is formed with a thickness less than 1 nm, the antioxidant effect may decrease.

[0119] Figure 2 is a plan view showing a spin-orbit torque-based magnetic tunnel junction 1 according to an embodiment of the present invention.

[0120] In the spin-orbit torque-based magnetic tunnel junction 1 according to an embodiment of the present invention, the spin torque active layer 120, magnetization free layer 130, tunnel barrier layer 140, and magnetization fixed layer 150 may have a cross shape in plan view.

[0121] Furthermore, the spin torque active layer 120 of the spin-orbit torque-based magnetic tunnel junction 1 according to an embodiment of the present invention is cross-shaped in plan view, and the magnetization free layer 130, tunnel barrier layer 140, and magnetization fixed layer 150 may be arranged in an island-like manner at the center of the cross-shaped spin torque active layer 120.

[0122] Referring to Figure 2, a spin-orbit torque-based magnetic tunnel junction 1 according to an embodiment of the present invention will be described in detail, in which the spin torque active layer 120 is cross-shaped in plan view, and the magnetization free layer 130, tunnel barrier layer 140, and magnetization fixed layer 150 are arranged in an island-like manner at the center of the cross-shaped spin torque active layer 120.

[0123] The spin-orbit torque-based magnetic tunnel junction 1 electrically measures the change in resistance due to the magnetization direction of the magnetic layer. If all layers are cross-shaped (the spin-torque active layer 120, magnetization free layer 130, tunnel barrier layer 140, and magnetization fixed layer 150 are cross-shaped in plan view), the volume of the magnetic layer becomes large and the signal is well-defined, making it easier to analyze the characteristics.

[0124] On the other hand, if the spin torque active layer 120 is cross-shaped in plan view, and the magnetization free layer 130, tunnel barrier layer 140, and magnetization fixed layer 150 are arranged in an island-like manner in the center of the cross-shaped spin torque active layer 120, by utilizing them only during switching using spin orbit torque, it is possible to prevent the magnetization direction of the magnetization free layer from changing due to domain wall propagation rather than spin orbit torque, and to observe magnetization reversal completely due to spin orbit torque. Furthermore, if the magnetization free layer 130, tunnel barrier layer 140, and magnetization fixed layer 150 are arranged in an island-like manner, the etching step must be performed again after manufacturing all layers in a cross shape, and if the spin torque active layer 120 begins to be exposed during etching, the etching must be stopped immediately, thus requiring know-how for device fabrication.

[0125] The cross-shaped spin torque active layer 120 may include a first conductive line 121 and a second conductive line 122, and the first conductive line 121 and the second conductive line 122 may be formed to intersect each other.

[0126] Therefore, the magnetization switching method applies a first current (jx) in AC form having a first frequency to the first conductive line 121, and a second current (jy) in AC form having a first frequency to the second conductive line 122, thereby enabling the magnetization of the free layer 130 to reverse.

[0127] When a first current having a first angular frequency (ω) is injected into the first conductive line 121 and a second current having a first angular frequency (ω) is injected into the second conductive line 122, the total current vector can rotate over time at the positions where the magnetized free layer 130, tunnel barrier layer 140, and magnetized fixed layer 150 are arranged.

[0128] When viewing the problem from the perspective of a rotating coordinate system, such as the phase of the total current vector, the AC current problem transforms into a DC current problem. On the other hand, from the perspective of a rotating coordinate system, a vertical effective magnetic field corresponding to the rotational angular velocity appears. That is, the effect of the AC current is transformed into a DC current problem in a system with a vertical effective magnetic field. In this case, due to the effect of the vertical effective magnetic field, the magnetization of the free layer can be reversed very easily.

[0129] The first conductive line 121 and the second conductive line 122 may be made of materials that induce the spin Hall effect or the Rashba effect. When a first current flows through the first conductive line 121, a spin polarization perpendicular to the direction of propagation of the first conductive line 121 occurs, and the spin current propagates in the direction of the magnetized free layer (z-axis direction).

[0130] The first conductive line 121 may have a line shape extending along the x-direction. The second conductive line 122 may have a line shape intersecting the first conductive line 121. For example, the second conductive line 122 may have a line shape extending along the y-direction.

[0131] The first conductive line 121 and the second conductive line 122 can intersect each other at a single point and can be connected to each other. For example, the first conductive line 121 and the second conductive line 122 can be located on the same plane (i.e., the xy-plane).

[0132] In the spin-orbit torque-based magnetic tunnel junction according to an embodiment of the present invention, the spin torque active layer 120 can be patterned in a cross shape, allowing for the electrical measurement of characteristics due to the spin Hall effect, and the movement of magnetization due to spin torque can be measured by voltage in a direction perpendicular to the current injection direction.

[0133] Figure 3 is a flowchart showing a method for manufacturing a spin-orbit torque-based magnetic tunnel junction according to an embodiment of the present invention.

[0134] Since it contains the same components as the spin-orbit torque-based magnetic tunnel junction 1 according to an embodiment of the present invention, a description of the same components will be omitted.

[0135] First, the method for manufacturing a spin-orbit torque-based magnetic tunnel junction according to an embodiment of the present invention involves the step of forming a spin torque active layer on a substrate (S110).

[0136] The substrate may be a silicon substrate, and a native oxide layer may be formed on the surface of the silicon substrate. Depending on the example, the native oxide layer may be formed by CVD, PVD, or thermal oxidation.

[0137] As demonstrated by the embodiments, the method for manufacturing a spin-orbit torque-based magnetic tunnel junction according to the embodiments of the present invention can perform at least one of the following steps before forming a spin-torque active layer on the substrate: forming a seed layer on the substrate and forming a buffer layer on the substrate.

[0138] The seed layer and buffer layer may be formed by methods including physical vapor deposition (PVD), molecular beam epitaxy (MBE), pulsed laser deposition (PLD), atomic layer deposition (ALD), electron beam epitaxy (e-beam), chemical vapor deposition (CVD), low-pressure CVD (LPCVD), ultra-high vacuum CVD (UHVCVD), or reduced-pressure CVD (RPCVD), electroplating, coating, or any combination thereof. The step of forming a spintorque active layer on the substrate (S110) involves simultaneously sputtering a W target and an X target in a vacuum chamber to form a WX alloy thin film (where W is tungsten and X is at least one of a group IV semiconductor and a group III-V semiconductor) on the substrate placed in the vacuum chamber.

[0139] Preferably, a tungsten-titanium alloy thin film can be formed on a substrate placed in a vacuum chamber by a co-deposition method in which a W target and an X target are sputtered simultaneously in a vacuum chamber.

[0140] In the spin-orbit torque-based magnetic tunnel junction manufacturing method according to embodiments of the present invention, the composition of the WX alloy thin film can be adjusted according to the power and thickness of the W target and X target.

[0141] First, the composition of the WX alloy thin film can be adjusted according to the power of the W target and the X target.

[0142] The power of the W target is 0.1W to 85W (0W / cm²). 2 ~4.19 W / cm² 2) is also acceptable, but if it is less than 0.1W, there is a problem that W will not be deposited, and if the power of the W target exceeds 85W, there is a problem that excessive energy will be applied to the W target and cracks will occur.

[0143] The X-Target's power range is 0.1W to 86.2W (0.1W / cm²). 2 ~4.25W / cm 2 ) is also acceptable, but if it is less than 0.1W, there is a problem that X will not be deposited, and if the power of the X target exceeds 86.2W, there is a problem that excessive energy will be applied to the X target and cracks will occur.

[0144] For example, using the physical properties (density, atomic weight) of each substance (W and X), we can calculate the volume per mole (mol / cm³). 3 When a specific thickness is deposited by calculating the molar value of the deposited material, and then by fixing the total thickness of the WX alloy thin film and adjusting the thickness of each material (W and X), the molar value of each material (W and X) can be calculated, and this can be used to determine the composition (at%) of the WX alloy thin film.

[0145] The power of the W target and X target is 50W (2.47W / cm²), assuming that the deposition power and deposition rate of each target are directly proportional. 2 By using the deposition rate when depositing with ), it is possible to deposit two materials at a power that results in the same deposition time for each material.

[0146] The initial vacuum level of the sputtering chamber is 5 × 10⁻⁶. -9 The pressure may be Torr, and when 39 sccm of argon is flowing, the working pressure may be 1.4 mTorr.

[0147] Therefore, the compositional content of X in the WX alloy may range from 0.1 at% to 46.4 at%. For example, when a tungsten (W)-titanium (Ti) alloy is used as the WX alloy, the titanium composition ratio at which perpendicular magnetic anisotropy occurs may be 0.1 at% ≤ x ≤ 46.4 at% when the heat treatment temperature is 300°C.

[0148] The step of forming a spin-torque active layer on a substrate may further include the step of patterning a WX alloy thin film in a cross shape.

[0149] WX alloy thin films can be patterned into a cross shape by photolithography and etching.

[0150] A method for manufacturing a spin-orbit torque-based magnetic tunnel junction according to an embodiment of the present invention involves the steps of forming a magnetized free layer on a spin-torque active layer (S120), forming a tunnel barrier layer on the magnetized free layer (S130), and forming a magnetized fixed layer on the tunnel barrier layer (S140).

[0151] The magnetized free layer, tunnel barrier layer, and magnetized fixed layer may be formed by methods including physical vapor deposition (PVD) including sputtering, molecular beam epitaxy (MBE), pulsed laser deposition (PLD), atomic layer deposition (ALD), electron beam (e-beam) epitaxy, chemical vapor deposition (CVD), low-pressure CVD (LPCVD), ultra-high vacuum CVD (UHVCVD), or reduced-pressure CVD (RPCVD), electroplating, or any combination thereof.

[0152] In the embodiment, the method for manufacturing a spin-orbit torque-based magnetic tunnel junction according to the embodiment of the present invention can perform the step of forming a magnetized fixed layer on the tunnel barrier layer (S140), and then the step of forming a capping layer on the magnetized fixed layer.

[0153] The capping layer may be formed by methods including physical vapor deposition (PVD), molecular beam epitaxy (MBE), pulsed laser deposition (PLD), atomic layer deposition (ALD), electron beam epitaxy (e-beam), chemical vapor deposition (CVD), low-pressure CVD (LPCVD), ultra-high vacuum CVD (UHVCVD), or reduced-pressure CVD (RPCVD), electroplating, coating, or any combination thereof.

[0154] The method for manufacturing a spin-orbit torque-based magnetic tunnel junction according to an embodiment of the present invention involves a step (S150) of performing heat treatment to induce perpendicular magnetic anisotropy in the magnetized free layer and the magnetized fixed layer.

[0155] In the spin-orbit torque-based magnetic tunnel junction manufacturing method according to an embodiment of the present invention, the spin torque efficiency increases and the magnitude of the uniaxial anisotropic magnetic field decreases as the heat treatment temperature increases, thus reducing the switching current. Furthermore, as the heat treatment temperature increases, X (e.g., titanium) atoms that were partially present as impurities inside the tungsten dissolve into the tungsten structure and form intermetallic compounds, thereby stabilizing the structure and reducing the resistivity.

[0156] The heat treatment temperature at which perpendicular magnetic anisotropy appears may be 300°C.

[0157] The BEOL (Back End Of Line) process, which is included in the semiconductor device manufacturing process, involves heat treatment at 300°C to 400°C. Therefore, it is essential to develop devices that can maintain their magnetic properties even at this temperature.

[0158] Therefore, in the spin-orbit torque-based magnetic tunnel junction manufacturing method according to the embodiment of the present invention, in order for perpendicular magnetic anisotropy to be exhibited in the CoFeB / MgO (magnetized free layer / tunnel barrier layer) structure, heat treatment at least 250°C to 300°C is required to promote crystallization of the CoFeB (magnetized free layer). This means that heat treatment must be performed at 300°C or higher, and if the heat treatment temperature exceeds 500°C, it will fall outside the temperature range that the CoFeB (magnetized free layer) used as the magnetic layer can withstand, resulting in the loss of the magnetic layer's properties.

[0159] By using a tungsten (W) and titanium (Ti) alloy thin film (hereinafter referred to as the tungsten-titanium alloy layer) in the spin torque active layer that contacts the magnetized free layer and provides an in-plane current, perpendicular magnetic anisotropy is maintained, and the spin orbit torque effect of the SOT-MRAM is increased with low resistivity.

[0160] <Examples> Through theoretical calculations and experimental results, this invention has been observed to show increased SOT efficiency when using a tungsten-titanium alloy layer compared to devices using a single W layer.

[0161] Figure 4 shows the results obtained from first-principles energy band calculations for different W-Ti compositions, specifically for phase stability and spin Hall conductivity.

[0162] The spin Hall conductivity of Ti with a composition of 12.5 at% was -1461 S / cm, which was the highest value observed.

[0163] The method used to fabricate the spin-orbit torque-based magnetic tunnel junction 1 of the present invention is DC (direct current) magnetron sputtering when depositing metal layers and AC (alternating current) magnetron sputtering when depositing insulators. The base pressure was -9 5×10 Torr or less, respectively, and deposition was carried out in an argon (Ar) atmosphere. The thickness of each layer was adjusted using the deposition time and sputtering power.

[0164] FIG. 5 is a cross-sectional view showing the structure for measuring the spin-orbit torque efficiency of the spin-orbit torque-based magnetic tunnel junction according to an embodiment of the present invention.

[0165] As shown in FIG. 5, the structure of the spin-orbit torque-based magnetic tunnel junction 1 is Si / SiO2 substrate / W-Ti5 / CoFeB0.9 / MgO1 / Ta2 (unit of thickness: nanometer, nm). Here, Si means the substrate, and the SiO2 layer is a natural oxide layer formed on the substrate and is amorphous. The W-Ti layer is an electrode layer, and W-Ti means a tungsten-titanium alloy. The tungsten-titanium alloy was formed by sputtering a tungsten (W) target and simultaneously sputtering a titanium (Ti) target. The tungsten target and the titanium target were sputtered using DC magnetron sputtering. By adjusting the sputtering power of each element sputtered simultaneously while fixing the flow rate of the argon gas, the composition of the tungsten-based alloy thin film was adjusted. The size of the target used for fabricating the tungsten-titanium alloy thin film was 2 inches in diameter. The CoFeB layer is a magnetic free layer, and the composition of the sputtering target is Co 40 Fe 40 B 20 (at%). The MgO layer is an insulating layer, and the Ta layer is a capping layer. After thin film deposition, heat treatment was carried out at a temperature of 300°C for 1 hour. The initial vacuum during heat treatment was 10 -6The sample was in the Torr band, and during the heat treatment, an external magnetic field of 6 kOe was applied perpendicular to the thin film.

[0166] Figure 6 is a graph showing the quantitative analysis of the Ti composition using Rutherford backscattering spectrometry (RBS).

[0167] In the W-Ti / CoFeB / MgO / Ta structure, the composition of Ti was quantitatively confirmed by Rutherford backscattering analysis, as shown in Figure 6.

[0168] After heat treatment at 300°C, the spin Hall angle was confirmed using a 5 × 35 μm photolithography process on a specimen in which perpendicular magnetic anisotropy was maintained. 2 A cross-shaped hall bar of a certain size was fabricated, and the CoFeB / MgO / Ta layer was created in the form of an island with a diameter of 6 μm.

[0169] Figure 7 is a graph showing the magnetic hysteresis curve measured with a vibrating sample magnetometer (VSM) for a thin film after heat treatment at 300°C.

[0170] Figure 7(a) is a graph showing the magnetic hysteresis curves depending on the titanium content (11.5 at% to 20.8 at%) of the spin-orbit torque-based magnetic tunnel junction according to an embodiment of the present invention shown in Figure 5 (hereinafter referred to as the W-Ti / CoFeB / MgO / Ta structure according to Example 1) when a magnetic field is applied in the out-of-plane direction perpendicular to the thin film surface. Figure 7(b) is a graph showing the magnetic hysteresis curves depending on the titanium content (11.5 at% to 20.8 at%) of the spin-torque active layer when a magnetic field is applied in the in-plane direction of the thin film surface.

[0171] The results showed that in the W-Ti / CoFeB / MgO / Ta structure, when the thickness of the tungsten-titanium alloy was fixed at 5 nm, perpendicular magnetic anisotropy was observed in the titanium composition from 0 at% to 46.4 at%.

[0172] Figure 8 shows the spin Hall angles of a Hall bar-shaped element measured using the harmonic measurement method within the composition range of a tungsten-titanium alloy layer with perpendicular magnetic anisotropy, after heat treatment of a W-Ti5 / CoFeB0.9 / MgO1.0 / Ta2 (unit: nm) structure at 300°C, and a graph showing the spin Hall conductivity converted from these angles.

[0173] In Figure 8, (a) shows the spin Hall angle depending on the titanium content, and (b) shows the spin Hall conductivity depending on the titanium content.

[0174] As shown in Figure 8(a), when a tungsten-titanium alloy layer was heat-treated at 300°C, it was confirmed that the spin Hall angle increased compared to when a single layer of tungsten was used (30%) for titanium compositions of 11.5 to 20.8 at%. In particular, when the Ti composition was 11.5 at%, it was confirmed that the spin Hall angle was 0.55, which was approximately 83% higher than that of a single layer of tungsten.

[0175] Figure 9 is a graph showing the resistivity of the alloy layer measured using the four-point probe method within the composition range of the tungsten-titanium alloy layer with perpendicular magnetic anisotropy after heat treatment of the W-Ti5 / CoFeB0.9 / MgO1.0 / Ta2 (unit: nm) structure at 300°C.

[0176] Figure 9 shows the results of calculating the resistivity of W-Ti by performing parallel resistance calculations on the electrode layer W-Ti and the magnetic free layer CoFeB (ρ=170μΩ·cm), based on the assumption that no current flows through the tunnel barrier layer (MgO) 140, the magnetization fixed layer (Ta) 150, and the capping layer (Ta) 160 when current is passed through the structure.

[0177] Figure 10 is a graph showing the spin-orbit torque switching characteristics depending on the composition of the tungsten-titanium alloy layer when an external magnetic field of ±300 Oe is applied to a test specimen with a W-Ti5 / CoFeB0.9 / MgO1.0 / Ta2 (unit: nm) structure that has been heat-treated at 300°C.

[0178] Figure 10 confirms that switching occurs with a smaller current than that required for a single layer of tungsten for all titanium compositions.

[0179] Figure 11 is a graph showing the change in switching current density when an external magnetic field of ±300 Oe is applied to a test specimen with a W-Ti5 / CoFeB0.9 / MgO1.0 / Ta2 (unit: nm) structure that has been heat-treated at 300°C.

[0180] As shown in Figure 11, it was confirmed that the switching current decreases as the titanium composition increases. In the case of a test specimen heat-treated at 300°C, the switching current density was 35.5 MA / cm² when titanium was absent. 2 Therefore, when the Ti composition is 11.5 at%, the concentration is 15.0 MA / cm². 2 It decreased to that point.

[0181] Figure 12 is a graph showing the measurement results of switching current (current density) while varying the magnitude of the external magnetic field for a test specimen with a tungsten-titanium alloy layer containing 11.5 at% titanium in a W-Ti5 / CoFeB0.9 / MgO1.0 / Ta2 (unit: nm) structure, after heat treatment at 300°C.

[0182] As shown in Figure 12, we confirmed that the value of the switching current required for magnetization reversal decreased in response to the applied external magnetic field, which was increased in magnitude from 10 Oe to 100 Oe, and observed the spin-orbit torque switching phenomenon under all applied external magnetic fields.

[0183] Experiments were conducted to measure the driving temperature and external magnetic field range of an element to which a spin-orbit torque-based magnetic tunnel junction according to an embodiment of the present invention is applied.

[0184] [Table 1]

[0185] [Table 2]

[0186] Table 1 shows the operating temperature ranges for commercial, industrial, automotive, and military applications, while Table 2 shows the grades of automotive semiconductors based on their operating temperature ranges.

[0187] Figure 13 is a graph showing the change in switching current density of one element (Ti: 11.5%) to which a spin-orbit torque-based magnetic tunnel junction is applied, due to a change in driving temperature.

[0188] As shown in Figure 13, to confirm the operating temperature resilience, the switching current density and resistance of the device to which the spin-orbit torque-based magnetic tunnel junction was applied were measured while increasing the temperature by 25°C in the range of -55°C to 150°C.

[0189] Measurement results confirmed that the switching current density decreases as the temperature rises due to thermal fluctuation. Simultaneously, it was confirmed that the element operates normally at both high and low temperatures. This temperature corresponds to Auto-Grade-0 (automotive) in Table 2, confirming that the element to which the spin-orbit torque-based magnetic tunnel junction structure of the present invention is applied is fully suitable for automotive semiconductors. Consequently, it was confirmed that the element to which the spin-orbit torque-based magnetic tunnel junction structure of the present invention is applied corresponds to all Grades in Table 2 below, and is applicable to applications across all temperature ranges.

[0190] Figure 14 is a graph showing the normalized resistance change of a device to which a spin-orbit torque-based magnetic tunnel junction is applied, measured by performing 100 switching cycles at extreme temperatures of (a) -55°C and (b) 150°C to confirm the operating temperature stability of the device.

[0191] As shown in Figure 14, the normalized resistance change of the element to which the spin-orbit torque-based magnetic tunnel junction is applied was measured by performing 100 switching cycles at the extreme temperatures of (a) -55°C and (b) 150°C, and it was confirmed that the change was uniform within a certain range. This confirmed that the element to which the spin-orbit torque-based magnetic tunnel junction structure of the present invention is applied has operating temperature stability even at extreme temperatures.

[0192] Figure 15 is a graph showing the change in switching current density (Jc) of a device using a spin-orbit torque-based magnetic tunnel junction due to driving temperature and external magnetic field.

[0193] As shown in Figure 15, it was confirmed that the switching current density of the element to which the spin-orbit torque-based magnetic tunnel junction of the present invention is applied decreases as the external magnetic field and temperature increase. This result was consistent with the prior art.

[0194] As a result, referring to Tables 1 and 2, and Figures 13 and 14, it was confirmed that the element to which the spin-orbit torque-based magnetic tunnel junction of the present invention is applied has temperature-dependent driving stability in the range of -55°C to 150°C. Therefore, the element to which the spin-orbit torque-based magnetic tunnel junction of the present invention is applied has temperature-dependent driving stability in the range of -55°C to 150°C and is applicable to various industrial applications.

[0195] As described above, the embodiments have been illustrated with limited drawings, but any person with ordinary skill in the art can make various modifications and variations from the above description. For example, the described technique may be performed in a different order than described, and / or the components of the described system, structure, apparatus, circuit, etc. may be combined or assembled in a different manner than described, or substituted or replaced by other components or equivalents, and the appropriate results may be achieved.

[0196] Therefore, other embodiments, other embodiments and equivalents of the claims also fall within the scope of the attached claims. [Explanation of Symbols]

[0197] 1. Magnetic tunnel junction 110 circuit boards 120 Spin Torque Active Layer 130 Magnetization free layer 140 Tunnel barrier layer 150 Magnetization fixed layer 160 capping layers

Claims

1. A spin-orbit active layer formed on the substrate, A magnetization free layer formed on the spin torque active layer, A tunnel barrier layer formed on the magnetization free layer, The tunnel barrier layer includes a magnetization fixing layer formed on the tunnel barrier layer, The spin torque active layer comprises a W-X alloy (where W is tungsten), The W-X alloy is a tungsten-titanium (W-Ti) alloy with a titanium content of 11.5 at% to 20.8 at%, and is a spin-orbit torque-based magnetic tunnel junction.

2. The spin-orbit torque-based magnetic tunnel junction according to claim 1, wherein the spin-torque active layer is an electrode that contacts the magnetization free layer to provide an in-plane current.

3. The spin-orbit torque-based magnetic tunnel junction according to claim 1, wherein the switching current decreases as the content of X in the W-X alloy increases.

4. The spin-orbit torque-based magnetic tunnel junction according to claim 1, wherein the heat treatment temperature at which perpendicular magnetic anisotropy is exhibited is 300°C.

5. The spin-orbit torque-based magnetic tunnel junction according to claim 1, wherein the content of X in the W-X alloy is adjusted according to the heat treatment temperature at which perpendicular magnetic anisotropy is exhibited.

6. The aforementioned spin torque active layer is The spin-orbit torque-based magnetic tunnel junction according to claim 1, wherein the junction has a cross shape in plan view, and the magnetization free layer, the tunnel barrier layer, and the magnetization fixed layer are arranged in an island shape at the center of the cross-shaped spin torque active layer.

7. The aforementioned substrate is The spin-orbit torque-based magnetic tunnel junction according to claim 1, wherein the surface in contact with the spin torque active layer includes a native oxide layer.

8. The aforementioned spin torque active layer is The spin-orbit torque-based magnetic tunnel junction according to claim 1, further comprising a buffer layer in the lower stage.

9. The spin-orbit torque-based magnetic tunnel junction according to claim 1, further comprising a capping layer on the magnetization fixed layer.

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