Spin-orbit torque-based magnetic tunnel junction

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 TO RELATED APPLICATIONS This application claims the benefit of priority based on Korean Patent Application No. 10-2024-0021247, filed February 14, 2024, the entire contents of which are 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 that employs a WX alloy (where W is tungsten and X includes at least one of a group IV semiconductor and a group III-V semiconductor) thin film as a spin-torque active layer, which has a structure that maintains perpendicular magnetic anisotropy (PMA) even after thin film deposition and heat treatment, and is capable of spin-orbit torque (SOT) switching, and 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 ferromagnetic material / oxide / ferromagnetic material, each of which includes a magnetic free layer (FL), a tunnel barrier (TB), and a magnetic pinned layer (PL). The positions of the magnetic free layer and the pinned layer may be interchangeable. The value of the tunnel current passing through the tunnel barrier changes depending on whether the spin directions of the magnetic free layer and the pinned layer, adjacent to each other across the tunnel barrier, are parallel or antiparallel. The resistance difference 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 current.

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

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

[0006] To achieve a high tunnel magnetoresistance ratio, high write stability, low write current, and high integration, magnetic tunnel junctions must have perpendicular magnetic anisotropy (PMA), which 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 magnetization free layer using the spin Hall effect or Rashba effect, which occurs when current flows parallel to the plane of the spin torque active layer adjacent to the magnetization free layer. This has attracted attention as a technology that can write information faster and with lower current consumption than the existing spin-transfer torque (STT) writing method.

[0008] The essential design points for a spin-orbit torque device are to form the spin torque active layer using a material structure with low resistivity and a large spin Hall angle (SHA), which is a unitless physical quantity that indicates the efficiency of spin-orbit torque.

[0009] As a result, U.S. Patent No. 11,062,752 (hereinafter referred to as the "'752 Patent") discloses a W- or Ta-based SOT magnetic tunnel junction structure. Also, 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 modifying the W deposition technique when fabricating a thin film with a W / CoFeB / MgO structure, high resistivity can be maintained even with thick W, thereby increasing the efficiency of the SOT.

[0010] However, the '752 patent and the prior art paper do not disclose maintaining perpendicular magnetic anisotropy in the structure of the alloy thin film and increasing the efficiency of the SOT with low resistivity. [Prior art documents] [Patent documents]

[0011] [Patent Document 1] U.S. Patent No. 11,062,752 (Registration date: July 13, 2021) [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” Summary of the Invention [Problem to be solved by the invention]

[0013] The present invention provides a spin-orbit torque-based magnetic tunnel junction (MTJ) that uses 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 a spin torque active layer. A device employing the MTJ is capable of spin-orbit torque switching and exhibits high spin-orbit torque efficiency with low resistivity.

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

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

[0016] The problem to be solved by the present invention 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 magnetization free layer and provides an in-plane current.

[0017] The problem to be solved by the present invention is to provide a composition range of a material that exhibits perpendicular magnetic anisotropy when a tungsten-titanium alloy layer is used as a material for MRAM.

[0018] The problem to be solved by the present invention is to provide heat treatment conditions that will produce 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 resistivity and SOT efficiency under heat treatment conditions when a tungsten-titanium alloy layer is used as a material for MRAM.

[0020] The problems to be solved by the present invention are not limited to those 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 one embodiment of the present invention includes: a spin-orbit active layer formed on a substrate; a magnetic free layer formed on the spin-torque active layer; a tunnel barrier layer formed on the magnetic free layer; and a magnetic fixed layer formed on the tunnel barrier layer, wherein the spin-torque active layer 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).

[0022] The spin torque active layer may be an electrode that contacts the free magnetization layer and provides an in-plane current.

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

[0024] The WX alloy may be a tungsten-titanium (W—Ti) alloy having a titanium content of 11.5 at % to 20.8 at %.

[0025] The spin-orbit torque-based magnetic tunnel junction may be heat-treated at a temperature of 300° C. to exhibit perpendicular magnetic anisotropy.

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

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

[0028] The substrate may include a native oxide layer on a surface in 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 pinned 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 magnetic free layer on the spin torque active layer, forming a tunnel barrier layer on the magnetic free layer, forming a magnetic fixed layer on the tunnel barrier layer, and performing a heat treatment to induce perpendicular magnetic anisotropy in the magnetic free layer and the magnetic fixed layer, wherein the step of forming the spin torque active layer on the substrate may include 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 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 may be a titanium (Ti) target, and the composition of the tungsten-titanium alloy thin film may be adjusted depending on the power of the tungsten target and the titanium target.

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

[0034] The spin-orbit torque-based magnetic tunnel junction may be heat-treated at a temperature of 300° C. to exhibit the perpendicular magnetic anisotropy.

[0035] The content of X contained in the WX alloy may be adjusted depending on the heat treatment temperature at which the perpendicular magnetic anisotropy is exhibited.

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

[0037] According to an embodiment of the present invention, by using a WX alloy thin film with large spin-orbit coupling as a spin torque active layer, it is possible to provide a spin-orbit torque-based magnetic tunnel junction that enables spin-orbit torque switching and exhibits high spin-orbit torque efficiency with low resistivity, and a manufacturing method thereof.

[0038] According to an embodiment of the present invention, it is possible to provide a spin-orbit torque-based magnetic tunnel junction in which the switching current can be controlled by adjusting the composition of X in a WX alloy, and a method for manufacturing the same.

[0039] According to an embodiment of the present invention, a spin-orbit torque-based magnetic tunnel junction and a manufacturing method thereof can be provided, in which perpendicular magnetic anisotropy (PMA) can be maintained over a range of heat treatment temperatures by using a tungsten-titanium alloy as a spin torque active layer.

[0040] According to an embodiment of the present invention, an SOT device using a tungsten-titanium alloy layer exhibits increased SOT efficiency compared to existing devices using a single W layer, while 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 drawings]

[0042] [Figure 1] 1 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] 1 is a plan view of a spin-orbit torque-based magnetic tunnel junction according to an embodiment of the present invention; [Figure 3] 1 is a flow chart illustrating a method for manufacturing a spin-orbit torque-based magnetic tunnel junction according to an embodiment of the present invention. [Figure 4] FIG. 1 shows the phase stability and spin Hall conductivity values ​​for each W-Ti composition obtained by first principles energy band calculation. [Figure 5] 1 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] 1 is a graph showing a quantitative analysis of the Ti composition by Rutherford Backscattering Spectrometry (RBS). [Figure 7] 1 is a graph showing a magnetic hysteresis loop measured by a vibrating sample magnetometer (VSM) for a thin film after heat treatment at 300° C.; [Figure 8]1 is a graph showing the spin-Hall angle of a Hall bar-shaped device measured using harmonics measurement 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 the spin-Hall angle converted into spin-Hall conductivity. [Figure 9] 1 is a graph showing the resistivity of a tungsten-titanium alloy layer having perpendicular magnetic anisotropy measured using a four-point probe method within the composition range of the alloy layer after a W-Ti5 / CoFeB0.9 / MgO1.0 / Ta2 (unit: nm) structure was heat-treated at 300°C. [Figure 10] 1 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 piece having a W-Ti5 / CoFeB0.9 / MgO1.0 / Ta2 (unit: nm) structure heat-treated at 300°C. [Figure 11] 10 is a graph showing the change in switching current density when an external magnetic field of ±300 Oe is applied to a test piece having a W-Ti5 / CoFeB0.9 / MgO1.0 / Ta2 (unit: nm) structure heat-treated at 300°C. [Figure 12] 1 is a graph showing the results of measuring the switching current (current density) while changing the magnitude of the external magnetic field for a test piece in which the titanium content of the tungsten-titanium alloy layer in a W-Ti5 / CoFeB0.9 / MgO1.0 / Ta2 (unit: nm) structure is 11.5 at%. The test piece was heat-treated at 300°C. [Figure 13] 10 is a graph showing a change in switching current density of a device to which a spin-orbit torque-based magnetic tunnel junction is applied, depending on a change in operating temperature. [Figure 14] 10 is a graph showing the change in normalized resistance of a device to which a spin-orbit torque-based magnetic tunnel junction is applied, measured by performing 100 switching operations at extreme temperatures of (a) -55°C and (b) 150°C to confirm the operating temperature stability of the device. [Figure 15]1 is a graph showing the change in current density (Jc) of a device to which a spin-orbit torque-based magnetic tunnel junction is applied depending on the driving temperature and the external magnetic field. DETAILED DESCRIPTION OF THE INVENTION

[0043] Specific structural or functional descriptions of embodiments in accordance with the inventive concepts disclosed herein are provided solely for purposes of illustrating embodiments in accordance with the inventive concepts, which may be embodied in various forms and are not limited to the embodiments described herein.

[0044] Because embodiments according to the inventive concept may be variously modified and may have various forms, the embodiments are illustrated in the drawings and described in detail herein, but it is not intended to limit the embodiments according to the inventive concept to the particular disclosed forms, and all modifications, equivalents, or alternatives within the spirit and scope of the present invention are encompassed.

[0045] Terms such as "first" or "second" may be used to describe various components, but the components should not be limited by the terms. The terms are used only to distinguish one component from another, for example, a first component may be named a second component, and similarly, a second component may be named a first component, without departing from the scope of the inventive concept.

[0046] When a component is referred to as being "coupled" or "connected" to another component, it should be understood that although the component may be directly coupled or connected to the other component, there may be other components between them. Conversely, when a component is referred to as being "directly coupled" or "directly connected" to another component, it should be understood that there are no other components between them. Expressions describing the relationship between components, such as "between," "immediately between," or "directly adjacent to," should be interpreted similarly.

[0047] The terms used in this specification are merely used to describe particular embodiments and are not intended to limit the present invention. The singular expressions include the plural expressions unless the context clearly dictates otherwise. In this specification, the terms "comprise" or "have" and the like are intended to specify the presence of stated features, numbers, steps, operations, components, parts, components, or combinations thereof, and should be understood as not precluding the presence or possibility of addition of one or more other features, numbers, steps, operations, components, parts, components, or combinations thereof.

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

[0049] The present invention will now be described more fully hereinafter with reference to the accompanying drawings, in which embodiments of the invention are shown.

[0050] FIG. 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 FIG. 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 magnetic free layer 130 formed on the spin-torque active layer 120, a tunnel barrier layer 140 formed on the magnetic free layer 130, and a magnetic fixed layer 150 formed on the tunnel barrier layer 140, where the spin-torque 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 is capable of spin-orbit torque switching by using a WX alloy with large spin-orbit coupling as the spin torque active layer 120, and can have high spin-orbit torque efficiency with low resistivity.

[0053] The spin-orbit torque-based magnetic tunnel junction according to an embodiment of the present invention includes a spin torque active layer 120 formed on a substrate 110 .

[0054] The substrate 110 can include a semiconductor substrate, which can 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 abuts the spin torque active layer 120, and the native oxide layer formed on the surface of the substrate 110 may be amorphous.

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

[0057] Thus, a seed layer and a buffer layer may 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 may be a material that facilitates crystalline growth, allowing the magnetic material to grow in a desired crystalline direction.

[0059] The seed layer may include, but is not limited to, 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 of Ta.

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

[0061] Additionally, a buffer layer may be formed to eliminate mismatches in lattice constants between layers.

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

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

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

[0065] The spin torque active layer 120 provides a spin-polarized current and applies a spin-orbit torque to the magnetic free layer 130 by the spin Hall effect or Rashba effect of the spin torque active layer 120, thereby inducing magnetization reversal of the magnetic free layer 130. In addition, the spin torque active layer 120 provides the magnetic free layer 130 with spin accumulation aligned with the magnetization direction of the spin torque active layer 120, and the spin accumulation can provide a deterministic switching effect or an effect of providing additional torque.

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

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

[0068] The spin torque active layer 120 can also facilitate switching of the magnetic field in the magnetization free layer 130, and the spin torque active layer 120 can realize 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 the embodiment of the present invention can use the spin orbit torque (SOT) to switch the magnetic free layer 130 using a spin current to operate the MRAM memory cell.

[0070] The spin-orbit torque-based magnetic tunnel junction 1 according to an embodiment of the present invention may use a WX alloy (where W is tungsten and X includes at least one of a group IV semiconductor and a group III-V semiconductor) as the spin torque active layer 120, which may maintain perpendicular magnetic anisotropy (PMA) over a range of various 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 at least one of GaAs, GaP, InP, InGaAlN, and GaN, but is not limited thereto. Preferably, in the spin-orbit torque-based magnetic tunnel junction according to an 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) is caused by the spin-Hall effect and the Rashba effect due to spin-orbit interaction, and these phenomena can become stronger in proportion to the atomic number. Therefore, research has been conducted mainly on heavy metal materials (W, Ta, Pt, etc.), and research is being conducted on alloys or insertion of various materials to further improve the properties and efficiency of single heavy metal materials.

[0073] Therefore, from the viewpoint of spintronics, tungsten is a material that excels in generating spin-orbit torque (SOT) and has a strong spin Hall effect due to spin-orbit interaction, making it suitable for use as a material for SOT-MRAM. X (Group IV and III-V groups such as Ti, Ge, and Ga-As) semiconductor materials have the spin Hall effect and Rashba effect, which are known to be the 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 high spin-orbit torque efficiency can be achieved with low resistivity.

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

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

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

[0077] In addition, electron scattering increases due to X, which partially exists as an impurity inside tungsten, so as the content of X in the tungsten composition increases, the resistivity of the WX alloy thin film can increase.

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

[0079] The content of X in the WX alloy may be 11.5 at % to 20.8 at %, but the content of X in the WX alloy is not limited thereto and can be adjusted depending on the X material.

[0080] As the content of X in the WX alloy increases, the perpendicular magnetic anisotropy may weaken, and if the content of X falls outside a specific range (e.g., 46.4 at%), the perpendicular magnetic anisotropy may be lost.

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

[0082] When the content of X in the WX alloy 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, just like when the composition is 100 at% tungsten.

[0083] When the heat treatment temperature is 300°C, if the content of X in the WX alloy exceeds 46.4 at%, not only will the perpendicular magnetic anisotropy be lost, but the magnetic layers (magnetic free layer and magnetic fixed layer) formed on the WX alloy thin film will also lose their magnetic properties, resulting in the problem that the WX alloy cannot be used 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 0.1 at%≦x≦46.4 at% when the heat treatment temperature is 300°C.

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

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

[0087] The back-end-of-line (BEOL) process, which is included in the manufacturing process of semiconductor devices, involves heat treatment at temperatures between 300°C and 400°C, so it is essential to develop devices that can maintain their magnetic properties even at these temperatures.

[0088] Therefore, in order for the spin-orbit torque-based magnetic tunnel junction 1 according to the embodiment of the present invention to exhibit perpendicular magnetic anisotropy in the CoFeB / MgO (magnetic free layer / tunnel barrier layer) structure, heat treatment must be performed at a temperature of at least 250°C to 300°C to promote crystallization of the CoFeB (magnetic free layer), and therefore the heat treatment must be performed at 300°C or higher. However, if the heat treatment temperature exceeds 500°C, the temperature goes beyond the temperature range that the CoFeB (magnetic free layer) used as the magnetic layer can withstand, resulting in a problem of losing the properties of the magnetic layer.

[0089] The spin-orbit torque-based magnetic tunnel junction according to the embodiment of the present invention can adjust the spin torque efficiency 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 spin torque active layer 120 can have the maximum spin torque efficiency when its thickness is 5 nm to 7 nm.

[0090] Preferably, in the case of W, the optimum thickness for maintaining the β (beta) phase, in which the spin torque efficiency is high, is 5 nm, so the thickness of the spin torque active layer 120 may be 5 nm.

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

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

[0093] The magnetic tunnel junction can be used as a memory element by associating information with a resistance value that changes depending on the magnetization arrangement of the magnetization free layer 130 and the magnetization fixed layer 150 .

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

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

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

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

[0098] In addition, the magnetic free layer 130 may further include at least one of non-magnetic materials such as 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 magnetic free layer 130 may include CoFe or NiFe and further include boron (B). In addition, the reference layer 126 and the magnetic free layer 130 may further include at least one of titanium (Ti), aluminum (Al), silicon (Si), magnesium (Mg), tantalum (Ta), and silicon (Si).

[0100] According to an embodiment, the magnetic free layer 130 may include at least one of a material having an L10 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 magnetization 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 to this.

[0102] The spin-orbit torque-based magnetic tunnel junction 1 according to the embodiment of the present invention includes a tunnel barrier layer 140 formed on a magnetic free layer 130 .

[0103] The tunnel barrier layer 140 separates the magnetic free layer 130 and the magnetic fixed layer 150 and enables quantum mechanical tunneling between the magnetic free layer 130 and the magnetic 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 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 to this.

[0107] The spin-orbit torque-based magnetic tunnel junction according to the embodiment of the present invention includes a pinned magnetization layer 150 formed on a tunnel barrier layer 140 .

[0108] The magnetization fixed layer 150 can have a fixed magnetic moment during a write operation of the magnetic memory element. For example, the magnetic moment of the magnetization fixed layer 150 can be unswitched by a spin-orbit torque caused by a 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] The interfacial perpendicular magnetic anisotropy is a phenomenon in which a magnetic layer having inherently horizontal magnetization characteristics has a perpendicular magnetization direction due to the influence of the interface with another adjacent layer. The magnetization pinned layer 150 can include at least one of cobalt (Co), iron (Fe), and nickel (Ni).

[0111] In addition, the magnetization fixed layer 150 may further include at least one of non-magnetic materials such as 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 include CoFe or NiFe and further include boron (B). In addition, the reference layer 126 and the magnetization free layer 130 may further include at least one of titanium (Ti), aluminum (Al), silicon (Si), magnesium (Mg), tantalum (Ta), and silicon (Si).

[0113] The pinned magnetic layer 150 may have a single layer structure. According to an embodiment, the pinned magnetic layer 150 may include a synthetic antiferromagnet having ferromagnetic layers separated by non-magnetic layers.

[0114] According to an embodiment, the magnetic pinned layer 150 may include at least one of a material having an L10 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 occur easily.

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

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

[0118] If the capping layer 160 is formed to a thickness of more than 2.2 nm, the oxidation prevention effect can be increased, but the conditions for perpendicular magnetic anisotropy (thicknesses of the magnetic free layer 130 and the tunnel barrier layer 140) must be adjusted because the capping layer 160 affects the tunnel barrier layer 140 during deposition. If the capping layer 160 is formed to a thickness of less than 1 nm, the oxidation prevention effect may be reduced.

[0119] FIG. 2 is a plan view of 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 the embodiment of the present invention, the spin torque active layer 120, the magnetization free layer 130, the tunnel barrier layer 140, and the 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 has a cross shape in a planar view, and the magnetization free layer 130, the tunnel barrier layer 140, and the magnetization fixed layer 150 can be arranged in the shape of an island in the center of the cross-shaped spin torque active layer 120.

[0122] Referring to FIG. 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 has a cross shape in a planar view, and the magnetization free layer 130, the tunnel barrier layer 140, and the magnetization fixed layer 150 are arranged in an island shape 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 depending on the magnetization direction of the magnetic layer. When all layers are cross-shaped (the spin torque active layer 120, the magnetization free layer 130, the tunnel barrier layer 140, and the magnetization fixed layer 150 are cross-shaped in plan view), the volume of the magnetic layer increases and a good signal is output, making it easier to analyze the characteristics.

[0124] On the other hand, if the spin torque active layer 120 has a cross shape in a planar view and the magnetization free layer 130, tunnel barrier layer 140, and magnetization fixed layer 150 are arranged in an island shape at the center of the cross-shaped spin torque active layer 120, this is utilized only during switching using spin-orbit torque, preventing the magnetization direction of the magnetization free layer from being changed due to domain wall propagation rather than spin-orbit torque, and magnetization reversal due to spin-orbit torque can be observed completely. Furthermore, if the magnetization free layer 130, tunnel barrier layer 140, and magnetization fixed layer 150 are arranged in an island shape, an etching step must be performed again after all layers are manufactured in a cross shape, and if the spin torque active layer 120 begins to be exposed during etching, the etching must be stopped immediately, which requires 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 cross each other.

[0126] Therefore, the magnetization switching method applies a first current (jx) of alternating current form having a first frequency to the first conductive line 121, and a second current (jy) of alternating current form having the first frequency to the second conductive line 122, so that the magnetization free layer 130 can undergo magnetization reversal.

[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 magnetization free layer 130, the tunnel barrier layer 140 and the magnetization fixed layer 150 are located.

[0128] Like the phase of the total current vector, when we look at the problem from the perspective of a rotating coordinate system, AC current becomes a DC current problem. On the other hand, in the perspective of a rotating coordinate system, a vertical effective magnetic field appears corresponding to the rotation angular velocity. That is, the effect of AC current is transformed into a DC current problem in a system with a vertical effective magnetic field. In this case, the magnetization of the free layer can be very easily reversed due to the effect of the vertical effective magnetic field.

[0129] The first conductive line 121 and the second conductive line 122 may be made of a material that induces the spin Hall effect or the Rashba effect. When a first current flows through the first conductive line 121, spin polarization perpendicular to the direction of travel of the first conductive line 121 occurs, and the spin current travels in the direction of the magnetization 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 may cross each other at one point and be connected to each other. For example, the first conductive line 121 and the second conductive line 122 may be located on the same plane (i.e., the xy plane).

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

[0133] FIG. 3 is a flow chart illustrating a method for fabricating a spin-orbit torque-based magnetic tunnel junction according to an embodiment of the present invention.

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

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

[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 embodiment, the native oxide layer may be formed by CVD, PVD, or thermal oxidation.

[0137] According to an embodiment, the method for manufacturing a spin-orbit torque-based magnetic tunnel junction according to an embodiment of the present invention may include at least one of forming a seed layer on a substrate and forming a buffer layer on a substrate before forming a spin torque active layer on the substrate.

[0138] The seed layer and the buffer layer may be formed by a method 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), a derivative CVD process including low-pressure CVD (LPCVD), ultra-high vacuum CVD (UHVCVD), or reduced-pressure CVD (RPCVD), electroplating, coating, or any combination thereof. The step of forming the spin torque 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 (where W is tungsten and X includes at least one of a group IV semiconductor and a group III-V semiconductor) thin film on the substrate disposed in the vacuum chamber.

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

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

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

[0142] The power of the W target is 0.1W to 85W (0W / cm 2 ~4.19W / cm 2If the power is less than 0.1 W, there is a problem that W is not deposited, and if the power of the W target exceeds 85 W, there is a problem that excessive energy is applied to the W target, causing cracks.

[0143] The power of the X target is 0.1W to 86.2W (0.1W / cm 2 ~4.25W / cm 2 If the power is less than 0.1 W, X may not be deposited, and if the power of the X target exceeds 86.2 W, excessive energy may be applied to the X target, causing cracks.

[0144] For example, the volume per mole (mol / cm) can be calculated using the physical properties (density, atomic weight) of each substance (W and X). 3 ) and divide it by the thickness to calculate the molar value deposited when depositing a specific thickness. Then, by fixing the thickness of the entire WX alloy thin film and adjusting the thickness of each material (W and X), the molar value of each material (W and X) is calculated, and the composition (at%) of the WX alloy thin film can be determined using this.

[0145] The power of the W target and X target was set to 50 W (2.47 W / cm ) under the assumption that the deposition power of each target is directly proportional to the deposition rate. 2 ) can be used to determine the deposition rate at which the two materials are deposited at the same power so that their deposition times are the same.

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

[0147] Therefore, the content of X in the WX alloy may be 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 is exhibited may be 0.1 at%≦x≦46.4 at% (where x is a real number) when the heat treatment temperature is 300°C.

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

[0149] The WX alloy thin film 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 includes the steps of forming a magnetic free layer on a spin torque active layer (S120), forming a tunnel barrier layer on the magnetic free layer (S130), and forming a magnetic fixed layer on the tunnel barrier layer (S140).

[0151] The magnetic free layer, the tunnel barrier layer, and the magnetic fixed layer may each be formed by a method 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), a derivative CVD process including low pressure CVD (LPCVD), ultrahigh vacuum CVD (UHVCVD) or reduced pressure CVD (RPCVD), electroplating, or any combination thereof.

[0152] In an embodiment, the method for manufacturing a spin-orbit torque-based magnetic tunnel junction according to an embodiment of the present invention may include a step of forming a capping layer on the magnetic pinned layer after performing a step (S140) of forming a magnetic pinned layer on the tunnel barrier layer.

[0153] The capping 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), derivative CVD processes including low pressure CVD (LPCVD), ultrahigh 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 the embodiment of the present invention includes a step of performing a heat treatment (S150) to cause the magnetization free layer and the magnetization fixed layer to exhibit perpendicular magnetic anisotropy.

[0155] In the method for fabricating a spin-orbit torque-based magnetic tunnel junction according to an embodiment of the present invention, as the heat treatment temperature increases, the spin torque efficiency increases, the magnitude of the uniaxial anisotropy magnetic field decreases, and therefore the switching current can be reduced. Furthermore, as the heat treatment temperature increases, X (e.g., titanium) atoms that were partially present as impurities in tungsten dissolve into the tungsten structure to form an intermetallic compound, thereby stabilizing the structure and reducing the resistivity.

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

[0157] The back-end-of-line (BEOL) process, which is included in the manufacturing process of semiconductor devices, involves heat treatment at temperatures between 300°C and 400°C, so it is essential to develop devices that can maintain their magnetic properties even at these temperatures.

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

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

[0160] <Example> Through theoretical calculations and experimental results, the present inventors have observed that when a tungsten-titanium alloy layer is used, the SOT efficiency is increased compared to devices using a single W layer.

[0161] Figure 4 shows the phase stability and spin Hall conductivity values ​​for each W-Ti composition obtained by first principles energy band calculation.

[0162] When the Ti composition was 12.5 at %, the spin Hall conductivity was -1461 S / cm, which was the largest value.

[0163] The methods used to fabricate the spin-orbit torque-based magnetic tunnel junction 1 of the present invention are direct current (dc) magnetron sputtering for depositing the metal layer and alternating current (ac) magnetron sputtering for depositing the insulator. The initial vacuum (base pressure) was 5×10 -9 The deposition was carried out in an argon (Ar) atmosphere at a pressure of less than Torr. The thickness of each layer was adjusted by adjusting the deposition time and sputtering power.

[0164] FIG. 5 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.

[0165] As shown in Figure 5, the structure of the spin-orbit torque-based magnetic tunnel junction 1 is Si / SiO2 substrate / W-Ti5 / CoFeB0.9 / MgO1 / Ta2 (thickness unit: nanometers, nm). Here, Si refers to the substrate, and the SiO2 layer is a native oxide layer formed on the substrate and is amorphous. The W-Ti layer is an electrode layer, and W-Ti refers to a tungsten-titanium alloy. The tungsten-titanium alloy was formed by simultaneously sputtering a tungsten (W) target and a titanium (Ti) target. DC magnetron sputtering was used for the tungsten and titanium targets. The composition of the tungsten-based alloy thin film was adjusted by adjusting the sputtering power of each of the co-sputtered elements with a fixed argon gas flow rate. The target used to fabricate the tungsten-titanium alloy thin film was 2 inches in diameter. The CoFeB layer is the magnetic free layer, and the sputtering target composition is CoFeB. 40 Fe 40 B 20 The MgO layer is an insulating layer, and the Ta layer is a capping layer. After the thin film deposition, the film was heat-treated at 300°C for 1 hour. The initial vacuum during the heat treatment was 10 -6During the heat treatment, an external magnetic field of 6 kOe was applied perpendicular to the thin film.

[0166] FIG. 6 is a graph showing a quantitative analysis of the Ti composition by Rutherford Backscattering Spectrometry (RBS).

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

[0168] After heat treatment at 300°C, the specimen was subjected to a photolithography process to confirm the spin-Hall angle of the specimen that maintained perpendicular magnetic anisotropy. 2 A cross-shaped Hall bar having a size of 1 μm was fabricated, and the CoFeB / MgO / Ta layer was fabricated in the shape of an island having a diameter of 6 μm.

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

[0170] Fig. 7(a) is a graph showing 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 an out-of-plane direction to the spin-orbit torque-based magnetic tunnel junction according to an embodiment of the present invention shown in Fig. 5 (hereinafter referred to as the W-Ti / CoFeB / MgO / Ta structure according to Example 1), which has been heat-treated at 300°C for 1 hour. Fig. 7(b) is a graph showing 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 an in-plane direction.

[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 exhibited when the titanium composition was from 0 at% to 46.4 at%.

[0172] FIG. 8 is a graph showing the spin-Hall angle of a Hall bar-shaped device measured using harmonics measurement 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 the spin-Hall angle converted into spin-Hall conductivity.

[0173] In FIG. 8, (a) shows the spin Hall angle as a function of titanium content, and (b) shows the spin Hall conductivity as a function of titanium content.

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

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

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

[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 piece with a W-Ti5 / CoFeB0.9 / MgO1.0 / Ta2 (unit: nm) structure heat-treated at 300°C.

[0178] Through Figure 10, it was confirmed that for all titanium compositions, switching occurred at a current smaller than that of a single layer of tungsten.

[0179] FIG. 11 is a graph showing the change in switching current density when an external magnetic field of ±300 Oe is applied to a test piece having a W-Ti5 / CoFeB0.9 / MgO1.0 / Ta2 (unit: nm) structure 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 the test piece heat-treated at 300°C, when there is no titanium, the switching current density is 35.5 MA / cm 2 When the Ti composition is 11.5 at%, it is 15.0 MA / cm 2 It decreased to.

[0181] FIG. 12 is a graph showing the results of measuring the switching current (current density) while changing the magnitude of the external magnetic field for a test piece having a W-Ti5 / CoFeB0.9 / MgO1.0 / Ta2 (unit: nm) structure in which the titanium content of the tungsten-titanium alloy layer is 11.5 at% and heat-treated at 300°C.

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

[0183] An experiment was carried out to measure the range of the operating temperature and the external magnetic field of a device to which the spin-orbit torque-based magnetic tunnel junction according to the 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, and Table 2 shows the grades of semiconductors for vehicles according to their operating temperature ranges.

[0187] FIG. 13 is a graph showing the change in switching current density of one device (Ti: 11.5%) to which a spin-orbit torque-based magnetic tunnel junction is applied, depending on the change in operating 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 is applied were measured while increasing the temperature by 25°C in the range of -55°C to 150°C.

[0189] As a result of the measurement, it was confirmed that the switching current density decreases as the temperature increases due to thermal fluctuations. At the same time, it was confirmed that the device operates normally at both high and low temperatures. This temperature corresponds to Auto-Grade-0 (automotive) in Table 2, and it was confirmed that the device employing the spin-orbit torque-based magnetic tunnel junction structure of the present invention is fully usable for automotive semiconductors. As a result, it was confirmed that the device employing the spin-orbit torque-based magnetic tunnel junction structure of the present invention corresponds to all Grades in Table 2 below and is applicable to applications in all temperature ranges.

[0190] FIG. 14 is a graph showing the change in normalized resistance of a device employing 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.

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

[0192] FIG. 15 is a graph showing the change in switching current density (Jc) of a device to which a spin-orbit torque-based magnetic tunnel junction is applied, depending on the operating temperature and the external magnetic field.

[0193] As shown in Figure 15, it was confirmed that the switching current density of the device employing the spin-orbit torque-based magnetic tunnel junction of the present invention decreased as the external magnetic field and temperature increased, which was consistent with the results of the prior art.

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

[0195] While the embodiments have been described above with reference to limited drawings, those skilled in the art will appreciate that various modifications and variations may be made from the foregoing description, including, for example, that the techniques described may be performed in a different order than described, and / or that the components of the described systems, structures, devices, circuits, etc. may be combined or combined in a different manner than described, or that other components or equivalents may be substituted or replaced, and still achieve suitable results.

[0196] Accordingly, other implementations, other embodiments, and equivalents of the claims are within the scope of the following claims. [Explanation of symbols]

[0197] 1. Magnetic tunnel junction 110 Substrate 120 Spin torque active layer 130 Magnetization free layer 140 Tunnel Barrier Layer 150 Magnetization fixed layer 160 Capping Layer

Claims

1. a spin-orbit active layer formed on a substrate; a magnetization free layer formed on the spin torque active layer; a tunnel barrier layer formed on the magnetization free layer; a magnetization fixed layer formed on the tunnel barrier layer, The spin-orbit torque-based magnetic tunnel junction, wherein the spin-torque active layer comprises a W—X alloy, where W is tungsten and X comprises at least one of a group IV semiconductor and a group III-V semiconductor.

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

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

4. 2. The spin-orbit torque-based magnetic tunnel junction of claim 1, wherein the W—X alloy is a tungsten-titanium (W—Ti) alloy with a titanium composition content of 11.5 at % to 20.8 at %.

5. 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.

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

7. The spin torque active layer is 2. The spin-orbit torque-based magnetic tunnel junction according to claim 1, which has a cross shape in a planar 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.

8. The substrate is The spin-orbit torque-based magnetic tunnel junction of claim 1 , comprising a native oxide layer on a surface in contact with the spin torque active layer.

9. The spin torque active layer is The spin-orbit torque-based magnetic tunnel junction of claim 1 , further comprising a lower buffer layer.

10. The spin-orbit torque-based magnetic tunnel junction of claim 1 , further comprising a capping layer on the magnetization pinned layer.

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