Paramagnetic hexagonal metallic phase bonded spacer

Abstract

A top fixed SAF-containing magnetic tunnel junction structure is provided containing a coupling spacer composed of a paramagnetic hexagonal metal phase material with a stoichiometry of Me3X or Me2X, where Me is a magnetic metal having a magnetic moment and X is a metal that alloys with Me in the hexagonal phase and dilutes the magnetic moment of Me. In an embodiment where a Me3X coupling spacer is present, Me is cobalt (Co) and X is vanadium, niobium, tantalum, molybdenum or tungsten. In an embodiment where a Me2X coupling spacer is present, Me is iron and X is tantalum or tungsten. The coupling spacer is formed by constructing a material stack including a multilayer structure formed by at least a precursor paramagnetic hexagonal metal phase material including alternating layers of magnetic metal Me and metal X, and then thermally soaking the material stack.

Description

[Technical field]

[0001] The present application relates to memory structures, and more particularly to a top fixed synthetic antiferromagnet-containing magnetic tunnel junction (MTJ) structure that includes a platinum layer and a paramagnetic hexagonal metallic phase coupled spacer. [Background technology]

[0002] MRAM is a non-volatile random access memory technology in which data is stored by magnetic storage elements. These elements are typically formed from two ferromagnetic plates, each capable of holding a magnetization, separated by a thin dielectric layer (i.e., a tunnel barrier layer). One of the two plates (i.e., the magnetic reference or pinned layer) is a magnet with its magnetic moment direction set in a particular direction, while the magnetization of the other plate (i.e., the magnetic free layer) can change to at least two different directions, representing different digital states such as 0 and 1 for memory applications. In MRAM, such elements are sometimes referred to as magnetic tunnel junction (MTJ) structures. In a typical MTJ structure, the magnetization of the magnetic reference layer is fixed in one direction (e.g., pointing up), while the orientation of the magnetic free layer can be "switched" by some external force, such as a magnetic field or a charging current that generates a spin transfer torque. The current used to read the device resistance, which depends on the relative orientation of the magnetizations of the magnetic free and magnetic reference layers, can be small (of either polarity). Typically, the resistance is high when the magnetizations are antiparallel and low when they are parallel (although this can be reversed for some materials).

[0003] MTJ structures can be classified as bottom pinned MTJ structures, where the magnetic reference layer is located at the bottom of the MTJ structure, or top pinned MTJ structures, where the magnetic reference layer is located at the top of the MTJ structure. A top pinned MTJ structure containing a synthetic antiferromagnetic (SAF) coupling layer (hereafter top pinned SAF-containing MTJ) is required for certain MRAM applications, mainly spin-orbit torque (SOT) MRAM, which has the advantage of independent read and write current paths. In top pinned SAF-containing MTJ, the SAF coupling layer is located in a multi-layer structure containing a top magnetic reference layer and a bottom magnetic reference layer. It is not easy to form the SAF coupling layer in the top pinned MTJ structure because there is no seed layer to grow the SAF coupling layer. Also, since the SAF coupling layer must be in direct contact with the magnetic reference layer of the top pinned MTJ structure, it is very difficult to form the correct texture to form a working SAF coupling layer. Although platinum helps to form the required texture, having a platinum layer close to the magnetic free layer or diffusing platinum into the magnetic free layer tends to degrade the perpendicular magnetic anisotropy (PMA) of the magnetic free layer. It is not easy to insert a platinum diffusion barrier layer, as used in conventional bottom-fixed SAF-containing MTJ structures, into a top-fixed SAF-containing MTJ structure because such a layer requires a suitable texture. Summary of the Invention

[0004] A top-fixed SAF-containing magnetic tunnel junction structure for memory applications is provided, including a platinum layer and a coupling spacer. The coupling spacer is composed of a paramagnetic hexagonal metal phase material with a stoichiometry of Me3X or Me2X, where Me is a magnetic metal having a moment, and X is a metal that alloys with Me in the hexagonal phase and dilutes the magnetic moment of Me. In an embodiment where a Me3X coupling spacer is present, Me is cobalt (Co) and X is vanadium (V), niobium (Nb), tantalum (Ta), molybdenum (Mo) or tungsten (W). In another embodiment where a Me2X coupling spacer is present, Me is iron (Fe) and X is tantalum (Ta) or tungsten (W). The paramagnetic hexagonal metal phase material is formed by constructing a material stack including a multilayer structure formed by at least a precursor paramagnetic hexagonal metal phase material including alternating layers of magnetic metal Me and metal X, and then hot-dipping the material stack.

[0005] In one aspect of the present application, a memory structure is provided. In one aspect of the present application, the memory structure includes an upper fixed magnetic tunnel junction structure including a multi-layer magnetic reference structure including, from bottom to top, a magnetic free layer, a tunnel barrier layer, a paramagnetic hexagonal metallic phase coupling spacer, a platinum layer, and a synthetic antiferromagnetic (SAF) coupling layer located between a lower magnetic reference layer and an upper magnetic reference layer.

[0006] In an embodiment of the present application, the paramagnetic hexagonal metallic phase binding spacer is comprised of a material having the formula Me3X, where Me is cobalt (Co) and X is vanadium (V), niobium (Nb), tantalum (Ta), molybdenum (Mo) or tungsten (W). In such an embodiment, X can be Nb or V, resulting in Co3Nb or Co3V. In other embodiments, X can be W or Mo. In yet other embodiments, the paramagnetic hexagonal metallic phase binding spacer is comprised of a material having the formula Me2X, where Me is iron (Fe) and X is tantalum (Ta) or tungsten (W), resulting in Fe2Ta or Fe2W.

[0007] In an embodiment of the present application, the paramagnetic hexagonal metallic phase bonding spacer has a magnetic moment. In such an embodiment, the magnetic moment per area of ​​the paramagnetic hexagonal metallic phase bonding spacer is between 0 and 0.1 memu / cm. 2 where the term "emu" stands for electromagnetic units. In an embodiment of the present application, the paramagnetic hexagonal metallic phase coupling spacer is a thick layer having a thickness of 0.2 nm to 3 nm. In an embodiment of the present application, the paramagnetic hexagonal metallic phase coupling spacer has a thickness that inhibits the diffusion of platinum into the magnetic free layer. In an embodiment, the platinum layer is a thin layer having a thickness of 0.2 nm to 3 nm. In an embodiment, the SAF coupling layer has a coupling field plateau of 4000 Oe to 6000 Oe. In an embodiment, the multilayer magnetic reference structure has a hexagonal crystal structure.

[0008] In embodiments of the present application, the SAF coupling layer is a non-magnetic material that couples the lower and upper magnetic reference layers in an anti-parallel manner. In such embodiments, the SAF coupling layer comprises ruthenium (Ru), iridium (Ir), rhodium (Rh), or alloys of Ru, Ir, or Rh with each other (e.g., RuIr with a Ru or Ir composition of 0 to 100%).

[0009] In an embodiment of the present application, the memory structure further includes a polarization enhancement layer and a non-magnetic spacer located between the tunnel barrier layer and the paramagnetic hexagonal metallic phase bonded spacer.

[0010] In another aspect of the present application, a method is provided for forming a paramagnetic hexagonal metallic phase material coupling spacer in a top fixed SAF-containing MTJ structure. In one embodiment, the method includes forming a material stack including a magnetic free layer, a tunnel barrier layer, and a precursor paramagnetic hexagonal metallic phase material multilayer structure including alternating layers of a magnetic metal Me having a magnetic moment and a metal X that alloys with Me in the hexagonal phase and dilutes the magnetic moment of Me. The alternating layers have the "right" thickness (atomic ratio) to facilitate the formation of Me3X or Me2X phases. The material stack can be thermally immersed, for example, in a UHV deposition system to convert the precursor paramagnetic hexagonal metallic phase material multilayer structure into a paramagnetic hexagonal metallic phase material coupling spacer. A multilayer magnetic reference structure including a platinum layer and a synthetic antiferromagnetic (SAF) coupling layer located between a lower magnetic reference layer and an upper magnetic reference layer is then formed on the paramagnetic hexagonal metallic phase material coupling spacer.

[0011] In an embodiment, the precursor paramagnetic hexagonal metallic phase material forms a multilayer structure formed by co-sputtering from a magnetic metal containing target Me and from a metal containing target X. In an embodiment, the precursor paramagnetic hexagonal metallic phase material forms a multilayer structure having a thickness or atomic ratio of Me and X that constitutes a paramagnetic hexagonal metallic phase material bond spacer.

[0012] In an embodiment, the heat soak is performed at a temperature of 300° C. to 450° C. In an embodiment, the heat soak is performed in a vacuum or inert atmosphere.

[0013] In some embodiments, the method includes forming a material stack including a magnetic reference layer, a tunnel barrier layer, a precursor paramagnetic hexagonal metallic phase material multilayer structure, a platinum layer, and a multilayer magnetic reference structure, the precursor paramagnetic hexagonal metallic phase material multilayer structure including alternating layers of a magnetic metal Me having a magnetic moment and a metal X, where X is a metal that alloys with Me in the hexagonal phase and dilutes the magnetic moment of Me. The alternating layers have the "right" thickness (atomic ratio) to facilitate the formation of Me3X or Me2X phases. The material stack is then hot-soaked to convert the precursor paramagnetic hexagonal metallic phase material multilayer structure into a paramagnetic hexagonal metallic phase material bond spacer.

[0014] In either method embodiment, Me is cobalt (Co) and X may be vanadium (V), niobium (Nb), tantalum (Ta), molybdenum (Mo) or tungsten (W), and the paramagnetic hexagonal metallic phase material bond spacer has the formula MeX.

[0015] Alternatively, in any method embodiment, Me may be iron (Fe) and X may be tantalum (Ta) or tungsten (W), and the paramagnetic hexagonal metallic phase material bond spacer has the formula Me2X. [Brief description of the drawings]

[0016] [Figure 1] 1 is a cross-sectional view of an exemplary memory structure according to one embodiment of the present application. [Figure 2A] 2A-2C are cross-sectional views illustrating basic processing steps that may be employed in forming the exemplary memory structure shown in FIG. 1 according to embodiments of the present application. [Figure 2B] 4A to 4C are cross-sectional views illustrating the above processing steps. [Diagram 3] 2 is a cross-sectional view of an exemplary material stack that may be used in constructing the exemplary memory structure shown in FIG. 1 according to another embodiment of the present application. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0017] The present application will now be described in more detail with reference to the following discussion and the drawings that accompany this application. It should be noted that the drawings in this application are provided for illustrative purposes only and are not drawn to scale. Also, like corresponding elements are referred to with like reference numerals.

[0018] In the following description, numerous specific details are set forth, such as specific structures, components, materials, dimensions, processing steps and techniques, in order to understand various embodiments of the present application. However, those skilled in the art will appreciate that various embodiments of the present application can be practiced without these specific details. In other instances, well-known structures or processing steps have not been described in detail to avoid obscuring the present application.

[0019] When an element is referred to as being "on" or "on" another element as a layer, region, or substrate, it is understood that it can be directly on the other element, or that intervening elements may be present. In contrast, when an element is referred to as being "directly on" or "directly on" another element, there are no intervening elements present. Also, when an element is referred to as being "below" or "under" another element, it is understood that the element is under or directly under the other element, or that intervening elements may be present. In contrast, when an element is referred to as being "directly under" or "directly under" another element, there are no intervening elements present.

[0020] The present application provides a memory structure including a top fixed magnetic tunnel junction structure as shown in FIG. 1 of the present application. The top fixed magnetic tunnel junction structure includes a multi-layer magnetic reference structure 22S containing, from bottom to top, a magnetic free layer 10, a tunnel barrier layer 12, a paramagnetic hexagonal metallic phase coupling spacer 18, a platinum layer 20, and a synthetic antiferromagnetic (SAF) coupling layer 26 located between a bottom magnetic reference layer 24 and a top magnetic reference layer 28. In an embodiment, the top fixed magnetic tunnel junction structure further includes a polarization enhancing layer 14 and a non-magnetic spacer 16 located between the tunnel barrier layer 12 and the paramagnetic hexagonal metallic phase coupling spacer 18. In some embodiments, the polarization enhancing layer 14 and the non-magnetic spacer 16 may be omitted from the top fixed magnetic tunnel junction structure of the present application.

[0021] Although not shown in the present application, the top fixed magnetic tunnel junction structure is located between the bottom electrode and the top electrode. The bottom electrode would be located under the magnetic free layer 10 and the top electrode would be located above the multi-layer magnetic reference structure 22S. The bottom electrode and the top electrode described above may be composed of a conductive material such as, for example, Ta, TaN, Ti, TiN, Ru, RuN, RuTa, RuTaN, Co, CoWP, CoN, W, WN, or any combination thereof. In some embodiments, the conductive material that comprises the bottom electrode may be compositionally different from the conductive material that comprises the top electrode. In other embodiments, the conductive material that comprises the bottom electrode may be compositionally the same as the conductive material that comprises the top electrode. The bottom electrode and the top electrode may be formed using techniques including deposition processes that are well known to those skilled in the art.

[0022] In an embodiment, the bottom electrode is located on a surface of a conductive structure embedded in an interconnect dielectric material layer of one interconnect level of a multi-layer interconnect structure. One interconnect level including the conductive structure may be located above at least one underlying metal level (not shown) and a front-end (FEOL) of the level, also not shown. In some embodiments, the metal level may be a mid-line (MOL) level. In other embodiments, the metal level may be at least one lower interconnect level of a multi-level interconnect structure. In further embodiments, the metal level may be a combination of a MOL level and at least one lower interconnect level of a multi-level interconnect structure. The metal level may include a conductive structure embedded in a dielectric material layer. The FEOL may include a semiconductor substrate having one or more semiconductor devices (e.g., transistors, etc.) formed thereon. The metal level and the FEOL may be formed utilizing materials and techniques well known to those skilled in the art. Therefore, in order not to obscure the memory structure of the present application, the materials and techniques used in constructing the interconnect level including the conductive structure, the metal level and the FEOL are not described in the present application.

[0023] The magnetic free layer 10 of the top fixed magnetic tunnel junction structure of the present application has a magnetization that can be changed in orientation relative to the magnetization orientation of the multi-layer magnetic reference structure 20S. The magnetic free layer 10 may have a thickness of 0.3 nm to 3 nm, although other thicknesses are possible and may be used as the thickness of the magnetic free layer 10. The magnetic free layer 10 may be composed of a magnetic material or a stack of magnetic materials well known to those skilled in the art. In some embodiments, the magnetic free layer 10 includes alloys and multilayers of cobalt (Co), iron (Fe), alloys of cobalt and iron, nickel (Ni), alloys of nickel and iron, and alloys of cobalt, iron and boron. In other embodiments, the magnetic free layer 10 is composed of an ordered magnetic alloy. "Ordered magnetic alloy" refers to a magnetic alloy having a lattice structure in which atoms of one element occupy certain sites and atoms of at least one other element occupy other sites. In one embodiment, the ordered magnetic alloy that composes the magnetic free layer is a Heusler alloy. The term "Heusler alloy" is used herein to denote an intermetallic ternary compound of formula A2BA having a Heusler half-Heusler crystal structure. Exemplary Heusler alloys that can be used in this application include, but are not limited to, Mn3Ge, Mn3Ga, Co2MnSi, Mn3Sn, or Mn3Sb. In another embodiment, the ordered magnetic alloy that constitutes the magnetic free layer 10 is an L10 alloy. The term "L10 alloy" refers to an intermetallic compound having a body-centered tetragonal crystal structure with one element occupying the corner of the lattice cell and the other element occupying the body center. Exemplary L10 alloys that can be used in this application include, but are not limited to, MnAl or CoFe. An ordered magnetic alloy requires a seed layer located under the ordered magnetic alloy.

[0024] The tunnel barrier layer 12 of the top fixed magnetic tunnel junction structure of the present application is composed of an insulating material and formed to a thickness sufficient to provide a suitable tunneling resistance. Exemplary insulating materials for the tunnel barrier layer 12 include, but are not limited to, magnesium oxide, aluminum oxide, and titanium oxide, or higher electrical tunneling conductance materials such as semiconductors and low band gap insulators. The thickness of the tunnel barrier layer 12 depends on the material selected. In one example, the tunnel barrier layer 12 may have a thickness of 0.5 nm to 1.5 nm, although other thicknesses are possible as long as the thickness of the tunnel barrier layer 12 provides a suitable tunneling resistance.

[0025] As mentioned above, and in some embodiments, the upper fixed magnetic tunnel junction structure of the present application may further include a polarization facilitating layer 14. When present, the polarization facilitating layer 14 has at least one surface that forms an interface with a surface of the tunnel barrier layer 12. The polarization facilitating layer 14 is used in embodiments where a substantially large tunnel magnetoresistance (TMR) is required. The polarization facilitating layer 14 may include an iron (Fe) layer, an Fe-based alloy layer having a body-centered cubic (bcc) structure, a cobalt iron boride (CoFeB)-based amorphous alloy layer, an L21 Heusler alloy layer (e.g., Co2MnSi, etc.), or a combination thereof. The polarization facilitating layer 14 may have a thickness of 0.2 nm to 2 nm, although other thicknesses are contemplated and may be used in the present application for the thickness of the polarization facilitating layer 14.

[0026] As mentioned above, and in some embodiments, the top fixed magnetic tunnel junction structure of the present application may further include a non-magnetic spacer 16, which is used in conjunction with the polarization facilitating layer 14. In embodiments, the non-magnetic spacer 16 has a first surface that interfaces with a surface of the polarization facilitating layer 14 opposite the surface of the polarization facilitating layer 14 that interfaces with the tunnel barrier layer 12, and a second surface that is opposite the first surface that interfaces with the coupling spacer 18. The non-magnetic spacer 16 may be comprised of tungsten (W), magnesium (Mg), aluminum (Al), copper (Cu), vanadium (V), titanium (Ti), chromium (Cr), manganese (Mn), tantalum (Ta), molybdenum (Mo), hafnium (Hf), rhenium (Re), or any combination thereof. The non-magnetic spacer 16 may have a thickness of 0.1 nm to 0.5 nm, although other thicknesses are contemplated and may be used in the present application as the thickness of the non-magnetic spacer 16.

[0027] In some embodiments, the paramagnetic hexagonal metallic phase coupling spacer 18 that can interface with the nonmagnetic spacer 16 or with the tunnel barrier layer 12 is comprised of a material having the formula Me3X, where Me is cobalt (Co) and X is vanadium (V), niobium (Nb), tantalum (Ta), molybdenum (Mo) or tungsten (W), such material having a paramagnetic hexagonal metallic phase. In some embodiments, the paramagnetic hexagonal metallic phase coupling spacer 18 may be one of Co3W, Co3Mo, Co3V, Co3Nb or Co3Ta. In other embodiments, the paramagnetic hexagonal metallic phase coupling spacer 18 that can interface with the nonmagnetic spacer 16 or with the tunnel barrier layer 12 is comprised of a material having the formula Me2X, where Me is iron (Fe) and X is tantalum (Ta) or tungsten (W). In such embodiments, the paramagnetic hexagonal metallic phase coupling spacer 18 may be comprised of Fe2W or Fe2Ta. It should be noted that the paramagnetic hexagonal metallic phase bonding spacer 18 has a stoichiometry of Me3X or Me2X.

[0028] The paramagnetic hexagonal metallic phase bonding spacer 18 has a magnetic moment that allows for the use of a thick paramagnetic hexagonal metallic phase bonding spacer 18. In one example, the paramagnetic hexagonal metallic phase bonding spacer 18 has a magnetic moment of 0 to 0.1 memu / cm 2 may have a magnetic moment of

[0029] The paramagnetic hexagonal metallic phase bonding spacer 18 may have a thickness of 0.2 nm to 3 nm, although other thicknesses are contemplated and may be used in this application for the thickness of the paramagnetic hexagonal metallic phase bonding spacer 18. The paramagnetic hexagonal metallic phase bonding spacer 18 allows for the use of a thin layer of platinum 20 (formed later) to act as a texture layer (in replacing the seed layer used in the lower SAF device) and as a platinum diffusion barrier. In some embodiments, the paramagnetic hexagonal metallic phase bonding spacer 18 may act as a seed / template for the platinum layer 20 and the multi-layer magnetic reference structure 22S to be formed later. Due to the presence of the paramagnetic hexagonal metallic phase bonding spacer 18, the SAF bonding layer 26 of the multi-layer magnetic reference structure 22S may have a bonding field plateau of 4000 Oe to 6000 Oe.

[0030] The platinum layer 20, located between the paramagnetic hexagonal metallic phase bonding spacer 18 and the multi-layered magnetic reference structure 22S, has a seed surface that allows the formation of the multi-layered magnetic reference structure 22S having a hexagonal phase due to the presence of the paramagnetic hexagonal metallic phase bonding spacer 18. The platinum layer is a thin layer having a thickness of 0.2 nm to 2 nm. It should be noted that such a thickness is less than that of the lower fixed SAF-containing structure.

[0031] The multilayer magnetic reference structure 22S includes a lower magnetic reference layer 24, a synthetic antiferromagnetic coupling layer 26, and an upper magnetic reference layer 28. Although the present application describes and illustrates the multilayer magnetic reference structure 22S including one stack of the lower magnetic reference layer 24, the synthetic antiferromagnetic coupling layer 26, and the upper magnetic reference layer 28, the present application also contemplates embodiments in which the multilayer magnetic reference structure 22S includes multiple alternating stacks of the lower magnetic reference layer 24, the synthetic antiferromagnetic coupling layer 26, and the upper magnetic reference layer 28 stacked one on top of the other.

[0032] The lower magnetic reference layer 24 may be comprised of a magnetic metal or magnetic metal alloy including iron (Fe), nickel (Ni), cobalt (Co), chromium (Cr), boron (B), or manganese (Mn). Exemplary magnetic metal alloys may include the magnetic metals exemplified above for the lower magnetic reference layer 24. In another embodiment, the lower magnetic reference layer 24 may be a multi-layer arrangement having (1) high spin polarization regions formed of metals and / or metal alloys using the metals described above, and (2) regions composed of one or more materials exhibiting strong perpendicular magnetic anisotropy (strong PMA). Exemplary materials having strong PMA that may be used include metals such as cobalt, nickel, platinum, palladium, iridium, ruthenium, etc., and may be arranged as alternating layers. The strong PMA region may also include alloys exhibiting strong intrinsic or bulk (as opposed to interfacial) PMA, with exemplary alloys including cobalt iron terbium, cobalt iron gadolinium, cobalt chromium platinum, cobalt platinum, cobalt palladium, iron platinum, and iron palladium, or an alloy including any of these. The alloys may be arranged as alternating layers. In one embodiment, the lower magnetic reference layer 24 may have a thickness of 1 nm to 15 nm, although other thicknesses are possible and may be used as the thickness of the lower magnetic reference layer 24.

[0033] The synthetic antiferromagnetic coupling layer 26 may be comprised of a non-magnetic material capable of antiparallel coupling the bottom magnetic layer 24 and the top magnetic layer 28 of the multi-layer magnetic reference structure 22S. Exemplary non-magnetic materials that may be used as the synthetic antiferromagnetic coupling layer 26 include, but are not limited to, ruthenium (Ru), iridium (Ir), or rhodium (Rh), or alloys of Ru, Ir, or Rh with each other (e.g., RuIr with a composition of 0 to 100% Ru or Ir). In one embodiment, the synthetic antiferromagnetic coupling layer 26 may have a thickness of 0.2 nm to 1.2 nm, although other thicknesses are possible and may be used as the thickness of the synthetic antiferromagnetic coupling layer 26.

[0034] The top magnetic reference layer 28 may be composed of one of the magnetic materials described above for the bottom magnetic reference layer 24. In some embodiments, the magnetic material that comprises the top magnetic reference layer 28 is the same in composition as the magnetic material that comprises the bottom magnetic reference layer 24. In other embodiments, the magnetic material that comprises the top magnetic reference layer 28 is different in composition from the magnetic material that comprises the bottom magnetic reference layer 24. In one embodiment, the top magnetic reference layer 28 may have a thickness of 1 nm to 15 nm, although other thicknesses are possible and may be used as the thickness of the top magnetic reference layer 28.

[0035] In the illustrated embodiment, the top magnetic reference layer 28 and the bottom magnetic reference layer 24 of the multilayer magnetic reference structure 22S are both comprised of Co, and the synthetic antiferromagnetic coupling layer 26 is comprised of Ir.

[0036] In some embodiments (not shown), a layer of MTJ capping material may be formed on the top surface of the multi-layer magnetic reference structure 22S. If present, the MTJ capping material may include, but is not limited to, Nb, NbN, W, WN, Ta, TaN, Ti, TiN, Ru, Mo, Cr, V, Pd, Pt, Rh, Sc, Al, or other refractory metals or conductive metal nitrides. In some embodiments, no separate MTJ cap is formed, and the lower portion of the top electrode described above can function as the capping layer. The layer of MTJ capping material may be 2 nm to 25 nm thick, although other thicknesses are possible and may be used in this application as the thickness of the MTJ capping material.

[0037] Reference is now made to Figures 2A and 2B, which illustrate basic processing steps that may be used in the present application in forming the exemplary memory structure shown in Figure 1. Referring first to Figure 2A, a first step of forming a material stack including, from bottom to top, a magnetic free layer 10, a tunnel barrier layer 12, and a multilayer structure 30 formed by a precursor paramagnetic hexagonal metallic phase material is shown. The material stack may also include a tunnel barrier layer 12 and a non-magnetic spacer 16 located between the tunnel barrier layer 12 and the multilayer structure 30 formed by the precursor paramagnetic hexagonal metallic phase material. The magnetic free layer 10, the tunnel barrier layer 12, the polarization enhancement layer 14, and the non-magnetic spacer 16 include materials and have thicknesses as described above in describing the exemplary memory structure shown in Figure 1. The magnetic reference layer 10, tunnel barrier layer 12, polarization enhancement layer 14 and non-magnetic spacer 16 of the material stack shown in FIG. 2A may be formed using one or more deposition processes, including, but not limited to, chemical vapor deposition (CVD), plasma enhanced chemical vapor deposition (PECVD), physical vapor deposition (PVD), atomic layer deposition (ALD) or sputtering.

[0038] The material stack shown in FIG. 2A also includes a multilayer structure 30 formed by the precursor paramagnetic hexagonal metal phase material. In an embodiment, the multilayer structure 30 formed by the precursor paramagnetic hexagonal metal phase material includes alternating layers of magnetic metal Me and metal X, where Me and X are as defined above. Each layer of magnetic metal Me may be referred to as a magnetic material layer 32, and each layer of metal X may be referred to herein as an X-containing metal layer 34. It is noted that each X-containing metal layer 34 includes a metal that alloys with Me in the hexagonal phase and dilutes the magnetic moment of Me. In the multilayer structure 30 formed by the precursor paramagnetic hexagonal metal phase material, each X-containing metal layer 34 is sandwiched between a lower magnetic material layer 32 and an upper magnetic material layer 32 such that the multilayer structure 30 formed by the precursor paramagnetic hexagonal metal phase material includes n number of X-containing metal layers 34 and n+1 number of magnetic material layers 32, where n is an integer equal to or greater than 1. As an example, the precursor paramagnetic hexagonal metallic phase material shown in FIG. 2A forms a multilayer structure 30 including two X-containing metal layers 34 and three magnetic material layers 32. It is noted that the precursor paramagnetic hexagonal metallic phase material forms a multilayer structure 30 designed to configure an appropriate ratio of Me and X so that a hexagonal metallic phase material can be subsequently formed. In one example, the precursor paramagnetic hexagonal metallic phase material forms a multilayer structure 30 designed to have a Me / X ratio of 5:2. In such an embodiment, a Co3W or Co3Nb bonded spacer having a hexagonal metallic phase is subsequently formed.

[0039] In some embodiments, the precursor paramagnetic hexagonal metallic phase material multilayer structure 30 is formed by co-sputtering from a magnetic metal containing target Me and from a metal containing target X. In other embodiments, any of the deposition processes described above may be used to form the precursor paramagnetic hexagonal metallic phase material multilayer structure 30.

[0040] The material stack illustrated in FIG. 2A may then be subjected to a hot soak process to convert the precursor paramagnetic hexagonal metallic phase material 30 (including the various magnetic material layers 32 and the X-containing metal layer 34) into a paramagnetic hexagonal metallic phase material bonding spacer 18, which has the formula Me3X, where Me is Co and X is a metal (i.e., V, Nb, Ta, Mo, or W) that alloys with Co in the hexagonal phase and dilutes the magnetic moment of Co. Alternatively, the formed paramagnetic hexagonal metallic phase material bonding spacer 18 has the formula Me2X, where Me is Fe and X is a metal (i.e., Ta or W) that alloys with Fe in the hexagonal phase and dilutes the magnetic moment of Fe. The formed material stack after the hot soak process step is shown in FIG. 2B. The paramagnetic hexagonal metallic phase material bonding spacer 18 constitutes a seed / template for the subsequent formation of a platinum layer.

[0041] In embodiments, the heat soak may be performed at a temperature of 300° C. to 450° C. In embodiments, the heat soak is performed in a vacuum or inert atmosphere. The heat soak converts the precursor paramagnetic hexagonal metallic phase material 30 into the paramagnetic hexagonal metallic phase material bond spacer 18 as described above. In some embodiments, the heat soak may be performed in a UHV deposition system.

[0042] Next, a platinum layer 20 and a multi-layer magnetic reference structure 22S are formed on the paramagnetic hexagonal metallic phase material coupling spacer 18 shown in Figure 2B to form the exemplary material stack shown in Figure 1. The multi-layer magnetic reference structure 22S includes a synthetic antiferromagnetic (SAF) coupling layer 26 as described above located between a lower magnetic reference layer 24 as described above and an upper magnetic reference layer 28 as described above. The platinum layer 20 and the multi-layer magnetic reference structure 22S may be formed using one or more deposition processes including, but not limited to, CVD, PECVD, PVD, ALD or sputtering.

[0043] In some embodiments, the exemplary structure shown in Figure 1 may be formed by first constructing the exemplary material stack shown in Figure 2A. After constructing such a material stack, a platinum layer 20 and a multi-layered magnetic reference structure 22S are formed over the precursor paramagnetic hexagonal metallic phase material 30 to form the material stack shown in Figure 3. After forming such a material stack, the precursor paramagnetic hexagonal metallic phase material 30 shown in Figure 3 may be converted into a paramagnetic hexagonal metallic phase material bond spacer 18 as shown in Figure 1 by performing the heat soak described above.

[0044] In some embodiments, after forming the material stack shown in Figure 1, the material stack may be patterned to form pillar-shaped structures. Patterning may be performed by lithography and etching. In embodiments, patterning may be performed on the structure shown in Figure 2A or the structure shown in Figure 2B.

[0045] While the present application has been particularly shown and described with respect to preferred embodiments, it will be understood by those skilled in the art that changes in form and detail, such as those described above, may be made without departing from the spirit and scope of the present application. It is therefore intended that the present application not be limited to the exact forms and details described and illustrated, but fall within the scope of the appended claims.

Claims

1. A memory structure comprising an upper fixed magnetic tunnel junction structure including a multi-layer magnetic reference structure containing, from bottom to top, a magnetic free layer, a tunnel barrier layer, a paramagnetic hexagonal metallic phase coupling spacer, a platinum layer, and a synthetic antiferromagnetic (SAF) coupling layer located between a lower magnetic reference layer and an upper magnetic reference layer.

2. The paramagnetic hexagonal metallic phase bonding spacer has the formula Me ３ 2. The memory structure of claim 1, composed of a material having X, where Me is cobalt (Co) and X is vanadium (V), niobium (Nb), tantalum (Ta), molybdenum (Mo) or tungsten (W).

3. 3. The memory structure of claim 2, wherein X is niobium (Nb) or vanadium (V).

4. The paramagnetic hexagonal metallic phase bonding spacer has the formula Me ２ 10. The memory structure of claim 1, composed of a material having X, where Me is iron (Fe) and X is tantalum (Ta) or tungsten (W).

5. 5. The memory structure of claim 4, wherein X is tantalum (Ta).

6. 2. The memory structure of claim 1, wherein said paramagnetic hexagonal metallic phase bonded spacer has a magnetic moment.

7. The magnetic moment of the paramagnetic hexagonal metallic phase bonded spacer is between 0 and 0.1 memu / cm ２ 7. The memory structure of claim 6, wherein:

8. 7. The memory structure of claim 6, wherein said paramagnetic hexagonal metallic phase bonded spacer has a thickness of 0.2 nm to 3 nm.

9. 2. The memory structure of claim 1, wherein said paramagnetic hexagonal metallic phase bond spacer has a thickness that inhibits platinum diffusion into said magnetic free layer.

10. 10. The memory structure of claim 9, wherein said platinum layer has a thickness of 0.2 nm to 2 nm.

11. 10. The memory structure of claim 1, wherein the SAF coupling layer has a coupling field plateau of 4000 to 6000 Oe.

12. The memory structure of claim 1 , wherein the multi-layer magnetic reference structure has a hexagonal crystal structure.

13. 10. The memory structure of claim 1, wherein the SAF coupling layer is a non-magnetic material that couples the lower magnetic reference layer and the upper magnetic reference layer in an anti-parallel manner.

14. 14. The memory structure of claim 13, wherein the SAF bonding layer comprises ruthenium (Ru), iridium (Ir), rhodium (Rh) or alloys of Ir, Ru or Rh with each other.

15. 2. The memory structure of claim 1 further comprising at least one of a polarization enhancement layer and a non-magnetic spacer located between said tunnel barrier layer and said paramagnetic hexagonal metallic phase bonded spacer.

16. forming a material stack including a magnetic reference layer, a tunnel barrier layer, and a multilayer structure formed by a precursor paramagnetic hexagonal metallic phase material, the multilayer structure comprising alternating layers of a magnetic metal Me having a magnetic moment and a metal X, where X is a metal that alloys with Me in the hexagonal phase and dilutes the magnetic moment of Me; hot soaking the stack of materials to convert the precursor paramagnetic hexagonal metallic phase material formed multilayer structure into a paramagnetic hexagonal metallic phase material bond spacer; forming a platinum layer and a multi-layer magnetic reference structure on the paramagnetic hexagonal metallic phase material coupling spacer, the multi-layer magnetic reference structure including a synthetic antiferromagnetic (SAF) coupling layer located between a lower magnetic reference layer and an upper magnetic reference layer.

17. 17. The method of claim 16, wherein the precursor paramagnetic hexagonal metallic phase material forms a multilayer structure by co-sputtering from a magnetic metal Me containing target and from a metal X containing target.

18. 17. The method of claim 16, wherein the precursor paramagnetic hexagonal metallic phase material forms a multilayer structure having a thickness or atomic ratio of Me and X that constitute the paramagnetic hexagonal metallic phase material bonding spacer.

19. 17. The method of claim 16, wherein the heat soaking is performed at a temperature of from 300°C to 450°C.

20. Me is cobalt (Co) and X is vanadium (V), niobium (Nb), tantalum (Ta), molybdenum (Mo) or tungsten (W), and the paramagnetic hexagonal metallic phase material coupling spacer has the formula Me ３ The method of claim 16 , wherein X is

21. Me is iron (Fe) and X is tantalum (Ta) or tungsten (W), and the paramagnetic hexagonal metallic phase material coupling spacer has the formula Me ２ The method of claim 16 , wherein X is

22. 17. The method of claim 16, wherein the material stack further comprises a polarization enhancement layer and a non-magnetic spacer positioned between the tunnel barrier layer and the multilayer structure formed by the precursor paramagnetic hexagonal metallic phase material.

23. forming a material stack including a magnetic reference layer, a tunnel barrier layer, a multilayer structure formed by a precursor paramagnetic hexagonal metallic phase material, a platinum layer, and a multilayer magnetic reference structure, the multilayer structure formed by the precursor paramagnetic hexagonal metallic phase material including alternating layers of a magnetic metal Me having a magnetic moment and a metal X, where X is a metal that alloys with Me in the hexagonal phase and dilutes the magnetic moment of Me; and hot soaking the stack of materials to convert the precursor paramagnetic hexagonal metallic phase material formed multilayer structure into a paramagnetic hexagonal metallic phase material bond spacer.

24. 24. The method of claim 23, wherein the precursor paramagnetic hexagonal metallic phase material forms a multilayer structure by co-sputtering from a magnetic metal Me containing target and from a metal X containing target.

25. 24. The method of claim 23, wherein the precursor paramagnetic hexagonal metallic phase material forms a multilayer structure having a thickness or atomic ratio of Me and X that constitute the paramagnetic hexagonal metallic phase material bonding spacer.

26. Me is cobalt (Co) and X is vanadium (V), niobium (Nb), tantalum (Ta), molybdenum (Mo) or tungsten (W), and the paramagnetic hexagonal metallic phase material coupling spacer has the formula Me ３ 24. The method of claim 23, wherein X is

27. Me is iron (Fe) and X is tantalum (Ta) or tungsten (W), and the paramagnetic hexagonal metallic phase material coupling spacer has the formula Me ２ 24. The method of claim 23, wherein X is

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