Patent Description:
Magnetic random-access memory (MRAM) devices store information utilizing magnetic materials as an information recording medium. One type of MRAM is a spin-transfer-torque magnetic random-access memory (STT-MRAM). STT-MRAM devices include a magnetic tunnel junction (MTJ) having a tunnel barrier layer stacked between a magnetic free layer and a magnetic pinned (or fixed) layer. To write to a STT-MRAM device, current is driven through the MTJ, which causes the magnetic moment of the free layer to be either aligned or anti-aligned with the magnetic moment of the pinned layer, which is unaffected by the current. To read from the STT-MRAM, a read current passes through the MTJ. However, the shared read/write path in an STT-MRAM device can impair its read reliability because the write current can impose stress on the tunnel barrier layer of the MTJ.

Another type of MRAM is spin-orbit torque magnetic random-access memory (SOT-MRAM). To write to the SOT-MRAM, the magnetization of the free magnetic layer is switched by supplying an in-plane current to a spin orbit torque (SOT) layer below the MTJ. To read from the SOT-MRAM, a read current passes through the MTJ. Accordingly, the read/write paths in a SOT-MRAM device are separate, which can improve performance.

<CIT> concerns a magnetic memory device including a spin-orbit torque (SOT) induction structure formed with a perpendicular magnetic anisotropy. A magnetic tunnel junction (MTJ) stack is disposed over the SOT induction structure. A spacer layer decouples layers between the SOT induction structure and the MTJ stack or decouples layers within the MTJ stack.

<CIT> concerns a magnetic memory including magnetic junctions and at least one spin-orbit interaction (SO) active layer. Each of the magnetic junctions includes a data storage layer that is magnetic. The SO active layer(s) are adjacent to the data storage layer of the magnetic junction. The SO active layer(s) are configured to exert a SO torque on the data storage layer due to a current passing through the at least one SO active layer in a direction substantially perpendicular to a direction between the at least one SO active layer and the data storage layer of a magnetic junction of the plurality of magnetic junctions closest to the at least one SO active layer.

<CIT> concerns a perpendicular bottom-free-layer STT-MRAM cell that includes a bottom-free-layer magnetic tunnel junction (BMTJ). The BMTJ includes a composite metal oxide seed layer, and a free layer comprising boron (B) on the composite metal oxide seed layer. The composite metal oxide seed layer includes a first metal layer; a metal oxide layer on the first metal layer; and a second metal layer on the metal oxide layer. The second metal layer has been oxygen treated.

<NPL>, discloses current-induced magnetization switching using an insulator, and that oxygen incorporation into the most widely used spintronic material, Pt, turns the heavy metal into an electrically insulating generator of the spin-orbit torques, which enables the electrical switching of perpendicular magnetization in a ferrimagnet sandwiched by insulating oxides.

<NPL> suggests that since oxidation increases the perpendicular magnetic anisotropy of a ferromagnetic (FM) layer, SOT-MRAM devices can be imagined with the FM layer sandwiched between a top MgO layer and a bottom oxidized Pt layer, resulting in enhanced SOT and perpendicular magnetic anisotropy.

The present disclosure relates to various embodiments of a spin-orbit torque magnetic random-access memory (SOT-MRAM) device. In one embodiment, the SOT-MRAM device includes a substrate, a spin orbit torque line above the substrate, a composite metal-oxide seed layer above the spin orbit torque line, and a magnetic tunnel junction above the composite metal-oxide seed layer. The magnetic tunnel junction includes a free layer on the composite metal-oxide seed layer, a main tunneling barrier layer above the free layer, and a pinned layer above the main tunneling barrier layer.

The spin orbit torque line may include tantalum, tungsten, platinum, hafnium, or combinations thereof.

The spin orbit torque line may include an alloy of two or more materials selected from tungsten, platinum, terbium, bismuth, hafnium, zirconium, silver, gold, silicon, copper, chromium, vanadium, and molybdenum.

The spin orbit torque line may include a first layer and a second layer above the first layer. The first layer and the second layer may include different materials selected from tungsten, platinum, terbium, bismuth, hafnium, zirconium, silver, gold, silicon, copper, chromium, vanadium, and molybdenum.

The spin orbit torque line may include oxidation at an interface between the first layer and the second layer.

The spin orbit torque line may include a number of layers, and each layer may be the same oxide of tungsten, platinum, terbium, bismuth, hafnium, zirconium, silver, gold, silicon, copper, chromium, vanadium, or molybdenum.

The spin orbit torque line may be a topological insulator such as bismuth telluride (BiTe), bismuth selenide (BiSe), TlBiTe, TIBiSe, SbTeS, BiTeS, BiTeSe, GeSbTe, SnSbTe, GeBiTe, SnBiTe, BiSb, or BiSbSe.

The spin orbit torque line may include iridium oxide (IrO<NUM>) or SrIrO<NUM>.

The spin orbit torque line may include a heavy metal based anti-ferromagnet or ferrimagnet.

The heavy metal based anti-ferromagnet or ferrimagnet may be AxB<NUM>-x, where A is iridium (Ir), platinum (Pt), palladium (Pd), or rhodium (Rh), where B is (Mn) or iron (Fe), and where x is a value between <NUM> and <NUM>.

The composite metal-oxide seed layer includes a first metal-oxide layer and a second metal-oxide layer.

The first metal-oxide layer may include an oxide of zirconium (Zr), niobium (Nb), tantalum (Ta), hafnium (Hf), magnesium (Mg), magnesium aluminide (MgAl), or aluminum (Al).

The second metal-oxide layer may include an oxide of nickel (Ni), iron (Fe), cobalt (Co) manganese (Mn), chromium (Cr), or vanadium (V).

The first metal-oxide layer and/or the second metal-oxide layer include a number of metal oxidation layers.

The number may be in a range from <NUM> to <NUM>.

The first metal layer and the second metal layer may each have a thickness in a range from approximately <NUM>Å to approximately <NUM>Å.

The first metal-oxide layer may be above the second metal-oxide layer.

The second metal-oxide layer may be above the first metal-oxide layer.

The pinned layer may be a synthetic antiferromagnetic pinned layer including a polarization enhancing layer (PEL) including a texture breaking layer (TBL), a bottom pinned layer above the PEL, a spacer layer above the bottom pinned layer, and a top pinned layer above the spacer layer.

The present disclosure also relates to various embodiments of manufacturing a spin-orbit torque magnetic random-access memory (SOT-MRAM) device. In one embodiment, the method includes forming a spin orbit torque line above a substrate, forming a composite metal-oxide seed layer above the spin orbit torque layer, and forming a magnetic tunnel junction above the composite metal-oxide seed layer. Forming the composite metal-oxide seed layer may include depositing a first metal layer, performing an oxygen treatment of the first metal layer, depositing a second metal layer, and performing an oxygen treatment of the second metal layer.

The first metal is zirconium (Zr), niobium (Nb), tantalum (Ta), hafnium (Hf), magnesium (Mg), magnesium aluminide (MgAl), or aluminum (Al).

The second metal may be nickel (Ni), iron (Fe), cobalt (Co), manganese (Mn), chromium (Cr), or vanadium (V).

Forming the composite metal-oxide seed layer may include repeatedly depositing the first metal layer and repeatedly performing the oxygen treatment of the first metal layer.

Forming the composite metal-oxide seed layer may include repeatedly depositing the second metal layer and repeatedly performing the oxygen treatment of the second metal layer.

Depositing the first metal layer may include depositing the first metal layer above the second metal layer.

Depositing the second metal layer may include depositing the second metal layer above the first metal layer.

This summary is provided to introduce a selection of features and concepts of embodiments of the present disclosure that are further described below in the detailed description. This summary is not intended to identify key or essential features of the claimed subject matter, nor is it intended to be used in limiting the scope of the claimed subject matter. One or more of the described features may be combined with one or more other described features to provide a workable device.

The features and advantages of embodiments of the present invention will become more apparent by reference to the following detailed description when considered in conjunction with the following drawings. In the drawings, like reference numerals are used throughout the figures to reference like features and components.

The present disclosure relates to various embodiments of a spin-orbit torque magnetic random-access memory (SOT-MRAM) device and methods of manufacturing SOT-MRAM devices. The SOT-MRAM device includes a magnetic tunnel junction (MTJ) having a magnetic free layer and a magnetic pinned (fixed) layer. In one or more embodiments, the SOT-MRAM device also includes both a spin orbit torque (SOT) line and a composite metal-oxide seed layer (CMO-SL) below the MTJ. The SOT line is configured to generate a transverse spin-current that generates a spin orbit torque (SOT) that switches a magnetization direction of the free layer. The CMO-SL is configured to provide transparency to the transverse spin-current generated by the SOT line such that the spin-current is transmitted efficiently to the free layer with minimal loss due to backscattering or dephasing. Additionally, the CMO-SL provides interface perpendicular magnetic anisotropy (PMA) to the free layer. Including both the SOT line and the CMO-SL under the free layer of the MTJ enables efficient and effective operation of the SOT-MRAM, including fast switching, low switching current/energy, and sufficient data retention in the free layer.

Hereinafter, example embodiments will be described in more detail with reference to the accompanying drawings, in which like reference numbers refer to like elements throughout. The present invention, however, may be embodied in various different forms, and should not be construed as being limited to only the illustrated embodiments herein. Rather, these embodiments are provided as examples so that this disclosure will be thorough and complete, and will fully convey the aspects and features of the present invention to those skilled in the art. Accordingly, processes, elements, and techniques that are not necessary to those having ordinary skill in the art for a complete understanding of the aspects and features of the present invention may not be described. Unless otherwise noted, like reference numerals denote like elements throughout the attached drawings and the written description, and thus, descriptions thereof may not be repeated.

In the drawings, the relative sizes of elements, layers, and regions may be exaggerated and/or simplified for clarity. Spatially relative terms, such as "beneath," "below," "lower," "under," "above," "upper," and the like, may be used herein for ease of explanation to describe one element or feature's relationship to another element(s) or feature(s) as illustrated in the figures. It will be understood that the spatially relative terms are intended to encompass different orientations of the device in use or in operation, in addition to the orientation depicted in the figures. For example, if the device in the figures is turned over, elements described as "below" or "beneath" or "under" other elements or features would then be oriented "above" the other elements or features. Thus, the example terms "below" and "under" can encompass both an orientation of above and below. The device may be otherwise oriented (e.g., rotated <NUM> degrees or at other orientations) and the spatially relative descriptors used herein should be interpreted accordingly.

It will be understood that, although the terms "first," "second," "third," etc., may be used herein to describe various elements, components, regions, layers and/or sections, these elements, components, regions, layers and/or sections should not be limited by these terms. Thus, a first element, component, region, layer or section described below could be termed a second element, component, region, layer or section, without departing from the scope of the present invention.

It will be understood that when an element or layer is referred to as being "on," "connected to," or "coupled to" another element or layer, it can be directly on, connected to, or coupled to the other element or layer, or one or more intervening elements or layers may be present. In addition, it will also be understood that when an element or layer is referred to as being "between" two elements or layers, it can be the only element or layer between the two elements or layers, or one or more intervening elements or layers may also be present.

The terminology used herein is for the purpose of describing particular embodiments and is not intended to be limiting of the present invention. It will be further understood that the terms "comprises," "comprising," "includes," and "including," when used in this specification, specify the presence of the stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof.

As used herein, the term "substantially," "about," and similar terms are used as terms of approximation and not as terms of degree, and are intended to account for the inherent variations in measured or calculated values that would be recognized by those of ordinary skill in the art. Further, the use of "may" when describing embodiments of the present invention refers to "one or more embodiments of the present invention. " As used herein, the terms "use," "using," and "used" may be considered synonymous with the terms "utilize," "utilizing," and "utilized," respectively.

The example embodiments are described in the context of particular magnetic junctions and magnetic memories having certain components. One of ordinary skill in the art will readily recognize that embodiments of the present invention are consistent with the use of magnetic junctions and magnetic memories having other and/or additional components and/or other features not inconsistent with embodiments of the present invention. The method and system are also described in the context of current understanding of spin-orbit interaction, the spin transfer phenomenon, of magnetic anisotropy, and other physical phenomena. Consequently, one of ordinary skill in the art will readily recognize that theoretical explanations of the behavior of the method and system are made based upon this current understanding of spin-orbit interaction, spin transfer, magnetic anisotropy and other physical phenomenon. However, the methods and systems described herein are not dependent upon a particular physical explanation. One of ordinary skill in the art will also readily recognize that the methods and systems are described in the context of a structure having a particular relationship to the substrate. However, one of ordinary skill in the art will readily recognize that the method and system are consistent with other structures. In addition, the method and system are described in the context of certain layers being synthetic and/or simple. However, one of ordinary skill in the art will readily recognize that the layers could have another structure. Furthermore, the method and system are described in the context of magnetic junctions, spin-orbit interaction active layers, and/or other structures having particular layers. However, one of ordinary skill in the art will readily recognize that magnetic junctions, spin-orbit interaction active layers, and/or other structures having additional and/or different layers not inconsistent with the method and system could also be used. Moreover, certain components are described as being magnetic, ferromagnetic, and ferrimagnetic. As used herein, the term magnetic could include ferromagnetic, ferrimagnetic or like structures. Thus, as used herein, the term "magnetic" or "ferromagnetic" includes, but is not limited to ferromagnets and ferrimagnets. The method and system are also described in the context of single magnetic junctions. However, one of ordinary skill in the art will readily recognize that the method and system are consistent with the use of magnetic memories having multiple magnetic junctions. Further, as used herein, "in-plane" is substantially within or parallel to the plane of one or more of the layers of a magnetic junction. Conversely, "perpendicular" corresponds to a direction that is substantially perpendicular to one or more of the layers of the magnetic junction.

For the purposes of this disclosure, expressions such as "at least one of," when preceding a list of elements, modify the entire list of elements and do not modify the individual elements of the list. For example, "at least one of X, Y, and Z," "at least one of X, Y, or Z," and "at least one selected from the group consisting of X, Y, and Z" may be construed as X only, Y only, Z only, any combination of two or more of X, Y, and Z, such as, for instance, XYZ, XYY, YZ, and ZZ, or any variation thereof. Similarly, the expression such as "at least one of A and B" may include A, B, or A and B. As used herein, "or" generally means "and/or," and the term "and/or" includes any and all combinations of one or more of the associated listed items. For example, the expression such as "A and/or B" may include A, B, or A and B.

With reference now to <FIG>, a spin-orbit torque magnetic random-access memory (SOT-MRAM) device <NUM> according to the present disclosure includes a substrate <NUM> (e.g., a silicon wafer), a spin orbit torque (SOT) line <NUM> above the substrate <NUM>, a composite metal-oxide seed layer (CMO-SL) <NUM> above the SOT line <NUM>, and a magnetic tunneling junction (MTJ) <NUM> above the CMO-SL <NUM>. In the illustrated embodiment, the MTJ <NUM> includes a free layer <NUM>, a main tunneling barrier <NUM> above the free layer <NUM>, and a synthetic antiferromagnetic pinned layer (SAF-PL) stack <NUM> above the main tunneling barrier layer <NUM>. In the illustrated embodiment, the SAF-PL stack <NUM> includes a polarization enhancing layer (PEL) <NUM> including a texture breaking layer (TBL), a bottom pinned layer <NUM> above the PEL <NUM>, a spacer layer <NUM> above the bottom pinned layer <NUM>, and a top pinned layer <NUM> above the spacer layer <NUM>. The bottom pinned layer <NUM> has a magnetization that is pinned in a first direction, and the top pinned layer <NUM> has a magnetization that is pinned in a second direction that is substantially antiparallel to the first direction. The spacer layer <NUM> provides antiferromagnetic coupling between the top pinned layer <NUM> and the bottom pinned layer <NUM>. The PEL <NUM> has a fixed magnetization configuration, and the magnetization direction of the free layer <NUM> is configured to switch such that the magnetization direction of the free layer <NUM> may be either aligned or anti-aligned with the magnetization direction of the PEL <NUM>. In this manner, the MTJ <NUM> is a bi-stable system suitable for memory storage.

In one or more embodiments, the material of the free layer <NUM> may be selected from iron boron (FeB), FeB-X, iron cobalt boron (FeCoB), FeCoB-X, iron (Fe), Fe-X, iron cobalt (FeCo), or FeCo-X, where X is selected from beryllium (Be), nickel (Ni), molybdenum (Mo), magnesium (Mg), zirconium (Zr), tantalum (Ta), vanadium (V), chromium (Cr), tungsten (W), hafnium (Hf), niobium (Nb), and terbium (Tb). In some embodiments, the free layer <NUM> may be a composite/stacked layer. For example, in one or more embodiments, the free layer <NUM> may include iron cobalt boron/iron (FeCoB/Fe).

In one or more embodiments, the main tunneling barrier layer <NUM> may include magnesium oxide (MgO). Additionally, in one or more embodiments, the PEL <NUM> may include Cobalt (Co), Iron (Fe), and/or boron (B), the bottom pinned layer <NUM> may include a ferromagnetic material (e.g., iron (Fe)), and the top pinned layer <NUM> may include a ferromagnetic material (e.g., iron (Fe)).

The SOT line <NUM> is configured to generate transverse spin-current that flows to the free layer through the CMO-SL <NUM>. The transverse spin-current flowing from the SOT line <NUM> to the free layer <NUM> generates spin orbit torque (SOT) configured to switch magnetization direction of the free layer <NUM>. In one or more embodiments, the SOT line <NUM> includes tantalum (Ta), tungsten (W), platinum (Pt), hafnium (Hf), or combinations thereof. In one or more embodiments, the SOT line <NUM> may include an alloy of two or more materials selected from tungsten, platinum, terbium, bismuth, hafnium, zirconium, silver, gold, silicon, copper, chromium, vanadium, and molybdenum. In one embodiment, the SOT line <NUM> may include an alloy of tungsten and hafnium (WHf).

In one or more embodiments, the SOT line <NUM> may include a plurality of layers. For instance, the SOT line <NUM> may include a first layer and a second layer stacked above (e.g., directly on) the first layer. The first and second layer may include different materials selected from tungsten, platinum, terbium, bismuth, hafnium, zirconium, silver, gold, silicon, copper, chromium, vanadium, and molybdenum. For instance, the first layer of the SOT line <NUM> may include gold (Au) and the second layer of the SOT line <NUM> may include silicon (Si). The SOT line <NUM> may also include oxidation at an interface between the first layer and the second layer (e.g., oxidation of an upper surface of a tungsten layer and a silicon layer on the oxidation of the tungsten layer). Providing oxidation at the interface between the first and second layers of the SOT line <NUM> increases resistivity and the spin Hall angle (SHA).

In one or more embodiments, the SOT line <NUM> may include a plurality of layers, and each layer may include a same oxide of a material selected from tungsten, platinum, terbium, bismuth, hafnium, zirconium, silver, gold, silicon, copper, chromium, vanadium, and molybdenum. For instance, in one or more embodiments, the SOT line <NUM> may include a plurality of tungsten (W) layers that were each subject to oxygen treatment (e.g., the SOT line <NUM> may include W/Ox/W/Ox/W/Ox, where Ox is oxygen treatment).

In one or more embodiments, the SOT line <NUM> may be a topological insulator, such as bismuth telluride (BiTe), bismuth selenide (BiSe), TlBiTe, TIBiSe, SbTeS, BiTeS, BiTeSe, GeSbTe, SnSbTe, GeBiTe, SnBiTe, bismuth antimonides (BiSb), or BiSbSe.

In one or more embodiments, the SOT line <NUM> may include iridium oxide (IrO<NUM>) or SrIrO<NUM>.

In one or more embodiments, the SOT line <NUM> may include a heavy metal based anti-ferromagnet or ferrimagnet. For instance, in one or more embodiments, the SOT line <NUM> may include AxB<NUM>-x, where A is iridium (Ir), platinum (Pt), palladium (Pd), or rhodium (Rh), B is manganese (Mn) or iron (Fe), and x is a value between <NUM> and <NUM>.

The CMO-SL <NUM> provides transparency to the transverse spin-current generated by the SOT line <NUM> such that the spin-current is transmitted efficiently to the free layer <NUM> with minimal loss due to backscattering or dephasing. Additionally, the CMO-SL <NUM> provides interface perpendicular magnetic anisotropy (PMA) to the free layer <NUM>, which determines the data retention by the free layer <NUM>.

The CMO-SL <NUM> includes a plurality of layers. In embodiments, the CMO-SL <NUM> includes a first metal-oxide layer (MO1) <NUM> and a second metal-oxide layer (MO2) <NUM>. The first metal-oxide layer <NUM> may be an oxide of a metal selected from zirconium (Zr), niobium (Nb), tantalum (Ta), hafnium (Hf), magnesium (Mg), magnesium aluminide (MgAl), and aluminum (Al). In one or more embodiments, the first metal-oxide layer <NUM> may include a plurality of stacked metal-oxide layers, such as from two (<NUM>) to ten (<NUM>) stacked metal-oxide layers. In one or more embodiments, the first metal-oxide layer <NUM> may include one or more stacked metal-oxide layers, such as from one (<NUM>) to ten (<NUM>) stacked metal-oxide layers, and a metal capping layer above (e.g., on top of) the one or more metal-oxide layers. In one or more embodiments, the first metal-oxide layer <NUM> may have a thickness in a range from approximately <NUM>Å to approximately <NUM>Å.

In one or more embodiments, the second metal-oxide layer <NUM> of the CMO-SL <NUM> may be an oxide of a metal selected from nickel (Ni), iron (Fe), cobalt (Co), manganese (Mn), chromium (Cr), and vanadium (V). In one or more embodiments, the second metal-oxide layer <NUM> may include a plurality of stacked metal-oxide layers, such as from two (<NUM>) to ten (<NUM>) stacked metal-oxide layers. In one or more embodiments, the second metal-oxide layer <NUM> may include one or more metal-oxide layers, such as from one (<NUM>) to ten (<NUM>) stacked metal-oxide layers, and a metal capping layer above (e.g., on top of) the one or more metal-oxide layers. In one or more embodiments, the second metal-oxide layer <NUM> may have a thickness in a range from approximately <NUM>Å to approximately <NUM>Å. In one or more embodiments, the thickness of the second metal-oxide layer <NUM> may be the same or substantially the same as the thickness of the first metal-oxide layer <NUM> (e.g., a thickness in a range from approximately <NUM>Å to approximately <NUM>Å).

Although in the illustrated embodiment the first metal-oxide layer <NUM> is stacked above the second metal-oxide layer <NUM> (e.g., the first metal-oxide layer <NUM> is directly on an upper surface of the second metal-oxide layer <NUM>), in one or more embodiments, the second metal-oxide layer <NUM> may be stacked above the first metal-oxide layer <NUM> (e.g., the second metal-oxide layer <NUM> may be directly on an upper surface of the first metal-oxide layer <NUM>).

In operation, an in-plane current is supplied to the SOT line <NUM> to write to the SOT-MRAM device <NUM>. The in-plane current supplied to the SOT line <NUM> generates a spin orbit torque (SOT) in the free layer <NUM>, which switches a magnetization direction of the free layer <NUM>. The CMO-SL <NUM> is configured to provide transparency to the transverse spin-current generated by the SOT line <NUM> such that the spin-current is transmitted efficiently to the free layer <NUM> with minimal loss due to backscattering or dephasing. Additionally, the CMO-SL <NUM> provides interface perpendicular magnetic anisotropy (PMA) to the free layer <NUM> such that free layer <NUM> exhibits sufficient data retention. Including both the SOT line <NUM> and the CMO-SL <NUM> under the free layer <NUM> of the MTJ <NUM> enables fast switching, low switching current/energy, and sufficient data retention of the SOT-MRAM device <NUM>.

To read from the SOT-MRAM device <NUM>, a read current passes through the MTJ <NUM>. According, the SOT-MRAM device <NUM> includes separate (decoupled) read and write paths, which is configured to decrease write times compared to related art spin-transfer-torque magnetic random-access memory (STT-MRAM) devices.

<FIG> is a flowchart illustrating tasks of a method <NUM> of manufacturing a spin-orbit-torque magnetic random-access memory (SOT-MRAM) device according to one embodiment of the present disclosure. In the illustrated embodiment, the method <NUM> includes a task <NUM> of forming (e.g., depositing) a spin orbit torque (SOT) line above a substrate. The SOT line formed in task <NUM> may include any of the materials described above with reference to the SOT line <NUM> depicted in <FIG>. For example, in one or more embodiments, the SOT line formed in task <NUM> may include tantalum (Ta), tungsten (W), platinum (Pt), hafnium (Hf), or combinations thereof; an alloy of two or more materials selected from tungsten, platinum, terbium, bismuth, hafnium, zirconium, silver, gold, silicon, copper, chromium, vanadium, and molybdenum (e.g., an alloy of tungsten and hafnium (WHf)); a stack of first and second layers including different materials selected from tungsten, platinum, terbium, bismuth, hafnium, zirconium, silver, gold, silicon, copper, chromium, vanadium, and molybdenum (e.g., a first layer including gold (Au) and a second layer including silicon (Si)); a topological insulator, such as bismuth telluride (BiTe), bismuth selenide (BiSe), TlBiTe, TIBiSe, SbTeS, BiTeS, BiTeSe, GeSbTe, SnSbTe, GeBiTe, SnBiTe, bismuth antimonides (BiSb), or BiSbSe; iridium oxide (lrO<NUM>); SrIrO<NUM>; or a heavy metal based anti-ferromagnet or ferrimagnet, such as AxB<NUM>-x, where A is iridium (Ir), platinum (Pt), palladium (Pd), or rhodium (Rh), B is manganese (Mn) or iron (Fe), and x is a value between <NUM> and <NUM>.

Furthermore, in one or more embodiments, the task <NUM> of forming the SOT line may include a sub-task of oxidizing one or more of the layers. For instance, in one or more embodiments, the task <NUM> may include a sub-task of performing an oxygen treatment of an upper surface of the first layer to form oxidation at an interface between the first layer and the second layer. In one or more embodiments, the task <NUM> may include a sub-task of performing an oxygen treatment of each layer deposited to achieve a plurality of layers each including a same oxide of a material selected from tungsten, platinum, terbium, bismuth, hafnium, zirconium, silver, gold, silicon, copper, chromium, vanadium, and molybdenum (e.g., a plurality of tungsten (W) layers that were each subject to oxygen treatment (W/Ox/W/Ox/W/Ox, where Ox is oxygen treatment)).

In the illustrated embodiment, the method <NUM> also includes a task <NUM> of forming a composite metal-oxide seed layer (CMO-SL) above the SOT line formed in task <NUM>. In one or more embodiments, task <NUM> may include forming the first metal-oxide layer and then forming the second metal-oxide layer above the first metal-oxide layer, or forming the second metal-oxide and then forming the first metal-oxide layer above the second metal-oxide layer.

The CMO-SL formed in task <NUM> may have the same configuration and composition as the CMO-SL <NUM> described above with reference to the embodiment depicted in <FIG>. In embodiments, the task <NUM> of forming the CMO-SL <NUM> includes a sub-task <NUM> of forming a first metal-oxide layer and a sub-task <NUM> of forming a second metal-oxide layer. In embodiments, the sub-task <NUM> of forming the first metal-oxide layer includes a sub-task <NUM>-<NUM> of depositing a metal material, being zirconium (Zr), niobium (Nb), tantalum (Ta), hafnium (Hf), magnesium (Mg), magnesium aluminide (MgAl), and/or aluminum (Al), and then a sub-task <NUM>-<NUM> of performing an oxygen treatment of the deposited metal material. In one or more embodiments, the sub-task <NUM> of forming the first metal-oxide layer may include repeatedly performing (a number (N) of times, such as from two (<NUM>) to ten (<NUM>) times) the sub-task <NUM>-<NUM> of depositing the metal material (Zr, Al, Nb, Ta, Hf, Mg, or MgAl) and the sub-task <NUM>-<NUM> of performing an oxygen treatment on the deposited metal to achieve a plurality of stacked metal-oxide layers, such as from two (<NUM>) to ten (<NUM>) stacked metal-oxide layers. Additionally, in one or more embodiments, the sub-task <NUM> of forming the first metal-oxide layer may include a sub-task <NUM>-<NUM> of depositing a metal capping layer above (e.g., on top of) the one or more metal-oxide layers formed in sub-task <NUM>. In one or more embodiments, the first metal-oxide layer formed in sub-task <NUM> may have a thickness in a range from approximately <NUM>Å to approximately <NUM>Å.

In embodiments, the sub-task <NUM> of forming the second metal-oxide layer includes a sub-task <NUM>-<NUM> of depositing a metal material, such as nickel (Ni), iron (Fe), cobalt (Co), manganese (Mn), chromium (Cr), and/or vanadium (V), and then a sub-task <NUM>-<NUM> of performing an oxygen treatment of the deposited metal material. In one or more embodiments, the sub-task <NUM> of forming the second metal-oxide layer may include repeatedly performing (a number (N) of times, such as from two (<NUM>) to ten (<NUM>) times) the sub-task <NUM>-<NUM> of depositing the metal material (e.g., Ni, Fe, Co, Mn, Cr, and/or V) and the sub-task <NUM>-<NUM> of performing an oxygen treatment on the deposited metal material to achieve a plurality of stacked metal-oxide layers, such as from two (<NUM>) to ten (<NUM>) stacked metal-oxide layers. Additionally, in one or more embodiments, the sub-task <NUM> of forming the second metal-oxide layer may include a sub-task <NUM>-<NUM> of depositing a metal capping layer above (e.g., on top of) the one or more metal-oxide layers formed in sub-task <NUM>. In one or more embodiments, the thickness of the second metal-oxide layer formed in sub-task <NUM> may be the same or substantially the same as the thickness of the first metal-oxide layer (e.g., a thickness in a range from approximately <NUM>Å to approximately <NUM>Å) formed in sub-task <NUM>.

In embodiments, the method <NUM> also includes a task <NUM> of forming a magnetic tunnel junction (MTJ) above the CMO-SL formed in task <NUM> to complete the SOT-MRAM device. The task <NUM> of forming the MTJ may include a sub-task <NUM> of forming a free layer above the CMO-SL, a sub-task <NUM> of forming a main tunneling barrier on the free layer, and a sub-task <NUM> forming a synthetic antiferromagnetic pinned layer (SAF-PL) stack above the main tunneling barrier. The configuration and composition of the free layer, the main tunneling barrier layer, and the SAF-PL stack formed in task <NUM> may be the same as the free layer <NUM>, the main tunneling barrier layer <NUM>, and the SAF-PL stack <NUM>, respectively, described above with reference to the embodiment depicted in <FIG>.

As described above, the CMO-SL is configured to provide transparency to the transverse spin-current generated by the SOT line such that the spin-current is transmitted efficiently to the free layer with minimal loss due to backscattering or dephasing, and the CMO-SL provides interface perpendicular magnetic anisotropy (PMA) to the free layer such that free layer exhibits sufficient data retention. In this manner, including both the SOT line and the CMO-SL under the free layer of the MTJ enables fast switching, low switching current/energy, and sufficient data retention of the SOT-MRAM device formed according to method <NUM>.

Claim 1:
A spin-orbit torque magnetic random-access memory, SOT-MRAM, device comprising:
a substrate (<NUM>);
a spin orbit torque line (<NUM>) above the substrate (<NUM>);
a composite metal-oxide seed layer (<NUM>) above the spin orbit torque line (<NUM>); and
a magnetic tunnel junction (<NUM>) above the composite metal-oxide seed layer (<NUM>), the magnetic tunnel junction (<NUM>) comprising:
a free layer (<NUM>) above the composite metal-oxide seed layer (<NUM>);
a main tunneling barrier layer (<NUM>) above the free layer (<NUM>); and
a pinned layer (<NUM>) above the main tunneling barrier layer (<NUM>),
wherein the composite metal-oxide seed layer (<NUM>) comprises a first metal-oxide layer (<NUM>) and a second metal-oxide layer (<NUM>), and
characterized in that
at least one of the first metal-oxide layer (<NUM>) and the second metal-oxide layer (<NUM>) comprises a number of metal oxidation layers.