WO2019005082A1

WO2019005082A1 - Magnetic tunneling junction devices with sidewall getter

Info

Publication number: WO2019005082A1
Application number: PCT/US2017/040136
Authority: WO
Inventors: Charles C. Kuo; Sarah ATANASOV; Mark L. Doczy; Kaan OGUZ; Satyarth Suri
Original assignee: Intel Corp
Current assignee: Intel Corp
Priority date: 2017-06-29
Filing date: 2017-06-29
Publication date: 2019-01-03
Anticipated expiration: 2019-12-29

Abstract

MTJ material stacks including one or more material layers that have outdiffused one or more dopants through a layer sidewall edge, MTJ devices employing such stacks, and computing platforms employing such MTJ devices. A free magnet layer or fixed magnet layer may include a dopant, such as boron. A liner layer may be deposited over an MTJ stack, for example in close proximity to the edge of at least one of the fixed or free magnet layers. During a thermal anneal, a dopant, such as boron, may be gettered by the liner. Dopant gettering by the liner may facilitate changes with in the MTJ stack, such as development of perpendicular magnetic anisotropy within a magnet layer. Following dopant gettering, the liner may be retained, or at least partially removed as sacrificial.

Description

MAGNETIC TUNNELING JUNCTION DEVICES

WITH SIDEWALL GETTER

Non-volatile random access memory device performance and density can be improved by reducing memory cell dimensions while maintaining the ability to retain state. Magnetoresistive random-access memory (MRAM) holds the promise of significantly higher density than other technologies such as flash memory.

Some magnetic memory cell architectures utilize a phenomenon known as the tunneling magnetoresi stance (TMR) effect. For a structure including two ferromagnetic layers separated by a thin insulating barrier layer, it is more likely that electrons will tunnel through the barrier layer when magnetizations of the two magnetic layers are in a parallel orientation than if they are not (non-parallel or antiparallel orientation). As such, a magnetic tunneling junction (MTJ), typically comprising a fixed magnetic layer and a free magnetic layer separated by a barrier layer, can be switched between two states of electrical resistance, one state having a low resistance (impedance) and one state with a high resistance (impedance). The greater the differential in resistance, the higher the TMR ratio: (RAP-R_P)/R_P* 100 % where R_P and RAP are resistances for parallel and antiparallel alignment of the magnetizations, respectively. The higher the TMR ratio, the more readily a bit can be reliably stored in association with the MTJ resistive state. The TMR ratio of a given MTJ is therefore an important performance metric of an MTJ-based device.

In one MRAM technology referred to as spin transfer torque memory (STTM), current-induced magnetization switching may be used to set the bit states. Polarization states of one ferromagnetic layer can be switched relative to a fixed polarization of the second ferromagnetic layer via the spin transfer torque phenomenon, enabling states of the MTJ to be set by application of current. Angular momentum (spin) of the electrons may be polarized through one or more structures and techniques (e.g., direct current, spin-hall effect, etc.). These spin-polarized electrons can transfer their spin angular momentum to the

magnetization of the free layer and cause it to precess. As such, the magnetization of the free magnetic layer can be switched by a pulse of current (e.g., in about 1 -10 nanoseconds) exceeding a certain critical value, while magnetization of the fixed magnetic layer remains unchanged as long as the current pulse is below some higher threshold associated with the fixed layer architecture. MTJs with magnetic layers having a magnetic easy axis perpendicular (out of plane of the device footprint) have a potential for realizing higher density memory than in-plane variants. Generally, perpendicular magnetic anisotropy (PMA) can be achieved in the free and/or fixed magnet, for example through interfacial perpendicular anisotropy established by a layer adjacent to a ferromagnetic material layer. Often however, asymmetry in an MTJ material stack may favor PMA in one of the fixed and free magnets such that it is more difficult to establish PMA in the other of the fixed and free magnets. Longer or higher temperature thermal anneals may be performed in an effort to increase the degree of PMA in a ferromagnetic layer that is not optimally situated within the MTJ stack, but high temperature processing is known to have detrimental effects on the MTJ stack as well as other active devices (e.g., transistors, diodes, etc.).

BRIEF DESCRIPTION OF THE DRAWINGS

The material described herein is illustrated by way of example and not by way of limitation in the accompanying figures. For simplicity and clarity of illustration, elements illustrated in the figures are not necessarily drawn to scale. For example, the dimensions of some elements may be exaggerated relative to other elements for clarity. Further, where considered appropriate, reference labels have been repeated among the figures to indicate corresponding or analogous elements. In the figures:

FIG. 1 A is an isometric illustration of material layers of an MTJ device, in accordance with some embodiments;

FIG. IB is an isometric illustration of material layers of an MTJ device, in accordance with some alternative embodiments;

FIG. 2 is a cross-sectional view through two adjacent MTJ devices with a sidewall liner, in accordance with some embodiments; FIG. 3 is a cross-sectional view through two adjacent MTJ devices with artifacts of a sidewall liner, in accordance with some embodiments;

FIG. 4 is a cross-sectional view through two adjacent MTJ devices with a dopant concentration profile indicative of sidewall gettering, in accordance with some

embodiments; FIG. 5 is a flow diagram illustrating a method of fabricating the MTJ devices illustrated in FIG. 2-4, in accordance with some embodiments;

FIG. 6A is an isometric view of an MTJ device array, in accordance with some embodiments; FIG. 6B is a cross-sectional view of two adjacent MTJ devices, in accordance with some embodiments;

FIG. 7 A is an isometric view of an MTJ device array following deposition of a sidewall getter, in accordance with some embodiments;

FIG. 7B is cross-sectional view of two adjacent MTJ devices following deposition of a sidewall getter, in accordance with some embodiments;

FIG. 8A is an isometric view of an MTJ device array following conversion of a sidewall getter into a dielectric material, in accordance with some embodiments;

FIG. 8B is cross-sectional view of two adjacent MTJ devices following conversion of a sidewall getter into a dielectric material, in accordance with some embodiments; FIG. 9A is an isometric view of an MTJ device array following planarization with a surrounding dielectric material, in accordance with some embodiments;

FIG. 9B is cross-sectional view of two adjacent MTJ devices following planarization on a surrounding dielectric material, in accordance with some embodiments;

FIG. 10 is a cross-sectional view of two adjacent MTJ material stacks following deposition of a sidewall getter, in accordance with some embodiments;

FIG. 11 is a cross-sectional view of two adjacent MTJ material stacks following an etching of a sidewall getter, in accordance with some embodiments;

FIG. 12 is a cross-sectional view of two adjacent MTJ material stacks following planarization with a surrounding dielectric material, in accordance with some embodiments; FIG. 13 is a schematic of an MTJ-based memory cell, which includes a

perpendicular spin transfer torque element, in accordance with some embodiments; FIG. 14 is a cross-sectional view of an MTJ-based memory cell, according to some embodiments of the disclosure.

FIG. 15 is a schematic illustrating a mobile computing platform and a data server machine employing an MTJ memory device, in accordance with embodiments; and FIG. 16 is a functional block diagram illustrating an electronic computing device, in accordance with some embodiments.

DETAILED DESCRIPTION

One or more embodiments are described with reference to the enclosed figures. While specific configurations and arrangements are depicted and discussed in detail, it should be understood that this is done for illustrative purposes only. Persons skilled in the relevant art will recognize that other configurations and arrangements are possible without departing from the spirit and scope of the description. It will be apparent to those skilled in the relevant art that techniques and/or arrangements described herein may be employed in a variety of other systems and applications other than what is described in detail herein. Reference is made in the following detailed description to the accompanying drawings, which form a part hereof and illustrate exemplary embodiments. Further, it is to be understood that other embodiments may be utilized and structural and/or logical changes may be made without departing from the scope of claimed subject matter. It should also be noted that directions and references, for example, up, down, top, bottom, and so on, may be used merely to facilitate the description of features in the drawings. Therefore, the following detailed description is not to be taken in a limiting sense and the scope of claimed subject matter is defined solely by the appended claims and their equivalents.

In the following description, numerous details are set forth. However, it will be apparent to one skilled in the art, that embodiments may be practiced without these specific details. In some instances, well-known methods and devices are shown in block diagram form, rather than in detail, to avoid obscuring the embodiments. Reference throughout this specification to "an embodiment" or "one embodiment" or "some embodiments" means that a particular feature, structure, function, or characteristic described in connection with the embodiment is included in at least one embodiment. Thus, the appearances of the phrase "in an embodiment" or "in one embodiment" or "some embodiments" in various places throughout this specification are not necessarily referring to the same embodiment.

Furthermore, the particular features, structures, functions, or characteristics may be combined in any suitable manner in one or more embodiments. For example, a first embodiment may be combined with a second embodiment anywhere the particular features, structures, functions, or characteristics associated with the two embodiments are not mutually exclusive.

As used in the description and the appended claims, the singular forms "a", "an" and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will also be understood that the term "and/or" as used herein refers to and encompasses any and all possible combinations of one or more of the associated listed items.

The terms "coupled" and "connected," along with their derivatives, may be used herein to describe functional or structural relationships between components. It should be understood that these terms are not intended as synonyms for each other. Rather, in particular embodiments, "connected" may be used to indicate that two or more elements are in direct physical, optical, or electrical contact with each other. "Coupled" may be used to indicated that two or more elements are in either direct or indirect (with other intervening elements between them) physical or electrical contact with each other, and/or that the two or more elements co-operate or interact with each other (e.g., as in a cause an effect relationship).

The terms "over," "under," "between," and "on" as used herein refer to a relative position of one component or material with respect to other components or materials where such physical relationships are noteworthy. For example in the context of materials, one material or material disposed over or under another may be directly in contact or may have one or more intervening materials. Moreover, one material disposed between two materials or materials may be directly in contact with the two layers or may have one or more intervening layers. In contrast, a first material or material "on" a second material or material is in direct contact with that second material/material. Similar distinctions are to be made in the context of component assemblies.

As used throughout this description, and in the claims, a list of items joined by the term "at least one of or "one or more of can mean any combination of the listed terms. For example, the phrase "at least one of A, B or C" can mean A; B; C; A and B; A and C; B and C; or A, B and C.

MTJ material stacks including one or more material layers that have outdiffused one or more dopants through a layer sidewall edge, MTJ devices employing such stacks, and computing platforms employing such MTJ devices are described herein. A free magnet layer or fixed magnet layer may include a dopant, such as boron. A liner layer may be deposited over an MTJ stack, for example in close proximity to the edge of at least one of the fixed or free magnet layers. During a thermal anneal, a dopant, such as boron, may diffuse toward, and be gettered by, the liner. Dopant gettering by the liner may facilitate changes with in the MTJ stack, such as development of perpendicular magnetic anisotropy within a magnet layer. Following dopant gettering, the liner may be retained, or removed as sacrificial.

In some embodiments, an MTJ material stack has a fixed magnet including a layer of ferromagnetic material with perpendicular anisotropy, and a free magnet including a layer of ferromagnetic material with perpendicular anisotropy. A liner layer is adjacent to at least one of the fixed and free magnet layers in the MTJ material stack during a thermal anneal, and has a composition suitable for gettering one or more dopants from the fixed or free magnet layers through the sidewall edge of the layers. In some embodiments, the liner layer is converted to a dielectric subsequent to the thermal anneal. In some embodiments, the liner layer is at least partially removed from the MTJ stack subsequent to the thermal anneal. Exemplary MTJ material stacks having one or more of the features described herein may be employed in devices, such as, but not limited to, embedded memory, embedded non-volatile memory (eNVM), magnetic random access memory (MRAM), and non-embedded or standalone memories.

FIG. 1 illustrates an MTJ material stack 101 for an MTJ device 100, in accordance with some embodiments. In the illustrated example, MTJ device 100 is a columnar or pillar structure with material stack 101 having layers with layer thickness in a direction (e.g., z- axis) perpendicular to a plane of the device footprint (e.g., x-y axis). MTJ device 100 includes a first contact 107 (e.g., bottom contact) and a second contact 180 (e.g., top contact) with the material stack 101 there between. First contact 107 may include one or more metal layers, each layer comprising an elemental or alloyed metal. In one exemplary embodiment, contact 107 includes a layer comprising tantalum (Ta) or ruthenium (Ru). Contact 180 may also include one or more metal layers, each layer comprising an elemental or alloyed metal. In one exemplary embodiment, contact 180 includes a layer comprises tantalum (Ta), tungsten (W), or ruthenium (Ru). Although vertically oriented, material stack 101 may also extend horizontally such that the columnar structure illustrated is instead a series of material stripes across the x-y plane. MTJ device 100 is monolithic and may be built up on any substrate (not depicted) that is known to be suitable for MTJ devices.

MTJ device 100 includes a free magnet and a fixed magnet separated by an intervening barrier layer that is to filter electrons based on their Fermi wavevector. The term "free magnet" and "fixed magnet" are employed herein to emphasize that each "magnet" may be a composite structure including a plurality of material layers that together comprise a functional component of MTJ device 100. In FIG. 1 , ellipses are drawn between illustrated material layers to further emphasize that MTJ device 100 may have any number of layers, and only a selected subset of the material layers in MTJ device 100 are specifically illustrated in FIG. 1.

In the illustrated embodiment, the fixed magnet includes a fixed magnet layer 120 over contact 107. Fixed magnet layer 120 comprises a ferromagnetic material. As employed herein, the term "ferromagnetic" refers to the magnetic mechanism of the material and such a material need not be an iron alloy, although it may be. As described further below, a fixed magnet may also include material layers other than fixed magnet layer 120. A free magnet includes a free magnet layer 140 that separated from fixed magnet layer 120 by at least a barrier layer 130. Free magnet layer 140 comprises a ferromagnetic material. As described further below, a free magnet may also include material layers other than free magnet layer 140.

In some embodiments, MTJ material stack 101 is a perpendicular system. In FIG. 1 , arrows in magnet layers 120 and 140 show the magnetic easy axis as in the z-direction out of the x-y plane of material layers in MTJ material stack 101. This perpendicular magnetic anisotropy (PMA) may advantageously reduce the switching current between "high" and "low" resistance states and may improve the scalability of MTJ material stack 101. The fixed magnet may comprise any material or stack of materials suitable for maintaining a fixed magnetization direction while the free magnet is magnetically softer (i.e.

magnetization can more easily rotate to parallel and antiparallel state with respect to the fixed magnet). Ferromagnetic layers of the fixed and/or free magnets may, for example, comprise ferromagnetic metal alloys doped with one or more non-ferromagnetic constituents. The ferromagnetic metal alloy may include one or more ferromagnetic constituent while the non-ferromagnetic constituents may, for example, impart an amorphous phase to the alloy, at least in the layer's "as-deposited" state. While in the amorphous phase, PMA may be effectively absent from the alloy until long range order is imparted during a thermal anneal process. In some embodiments, ferromagnetic layers of the fixed and/or free magnets comprise one or more of cobalt (Co), iron (Fe), or nickel (Ni). In some embodiments, ferromagnetic layers of the fixed and/or free magnets comprise a Heusler alloy. Two examples of non-ferromagnetic dopants are boron or carbon, but many other elements may have a similar functional effect. In some exemplary embodiments, fixed magnet layer 120 comprises a CoFeB alloy.

In some specific examples, Fe content within the CoFeB is at least 50 at. %. Exemplary embodiments include 20-30 at. % B with one specific alloy being Co2oFe6oB2o. This iron- rich alloy has been found to achieve perpendicular magnetic anisotropy. Other embodiments with equal parts cobalt and iron are also possible (e.g., Co4oFe4oB2o), as are more iron-rich alloys.

Fixed magnet layer 120 advantageously has crystallinity associated with PMA. In some exemplary embodiments, fixed magnet layer 120 has body-centered cubic (BCC) crystal structure, which is advantageous for achieving perpendicular magnetic anisotropy in certain metal alloys comprising one or more of iron, cobalt, and nickel. Fixed magnet layer 120 may further have (001) out-of-plane texture, where texture refers to the distribution of crystallographic orientations within in fixed magnet layer 120. The inventors have found those with iron crystallize with BCC, (001) texture. Fixed magnet layer 120 may have a thickness between approximately 1.0 nm and 2.0 nm, for example.

In some exemplary embodiments, free magnet layer 140 also has body-centered cubic (BCC) crystal structure. Free magnet layer 140 may further have (001) out-of-plane texture. Free magnet layer 140 may have a thickness between approximately 1.0 nm and 2.0 nm, for example. The composition of free magnet layer 140 may be the same as that of fixed magnet layer 120 with differences in thickness or the addition of other layers within the fixed or free magnet accounting for greater magnetic softness in the free magnet. In some exemplary embodiments, free magnet layer 140 is also a CoFeB alloy. In some specific examples, Fe content within the CoFeB is at least 50 at. %. Exemplary embodiments include 20-30 at. % B with one specific alloy being Co2oFe6oB2o. Other embodiments with equal parts cobalt and iron are also possible (e.g., Co4oFe4oB2o), as are more iron-rich alloys. Free magnet layer 140 may be one of a stack of material layers (not depicted) making up the free magnet structure. A free magnet stack may, for example, include multiple ferromagnetic material layers with a coupling layer (not depicted) separating adjacent ferromagnetic layers. The alloy compositions for any of these layers may be any of those described above for free magnet layer 140. The coupling layer may comprise one or more of W, Mo, Ta, Nb, V, Hf and Cr, for example.

Barrier layer 130 may be any material or stack of materials for which current of a first (e.g., majority) spin passes more readily than does current of a second (e.g., minority) spin. Barrier layer 130 is therefore a quantum mechanical barrier, a spin filter, or spin- dependent barrier, through which electrons may tunnel according to probability that is dependent on their spin. The extent by which current of one spin is favored over the other impacts the tunneling magneto-resistance associated with MTJ material stack 101. Barrier layer 130 may further provide a crystallization template (e.g., BCC with (001) texture) for solid phase epitaxy of the free and/or fixed magnets within MTJ material layer stack 101. In some embodiments, barrier layer 130 comprises one or more metal and oxygen (i.e., a metal oxide). In some exemplary embodiments, barrier layer 130 is magnesium oxide (MgO). In some other embodiments, barrier layer 130 comprises predominantly metal or graphene, and may even be substantially oxygen-free in some embodiments. Notably, the material layers within an MTJ material stack may vary considerably without deviating from the scope of the present disclosure. For example, in FIG. 1, a cap layer 170 is between ferromagnetic material layer 140 and contact 180. In some

embodiments, cap layer 170 comprises a metal oxide (e.g., MgO, VO, WO, TaO, HfO, MoO). A cap layer may be absent for some MTJ device implementations, such as a spin-hall effect (SHE) device. As another example, in further reference to FIG. 1A, one or more intermediate material layer may be disposed between fixed magnet layer 120 and contact 107. In the illustrated embodiment, for example, MTJ material stack 101 includes an anti- ferromagnetic layer or a synthetic antiferromagnetic (SAF) structure 1 10. Such layer(s) may be useful for countering a fringing magnetic field associated with fixed magnet layer 120. Exemplary anti-ferromagnetic layers include, but are not limited to, iridium manganese (IrMn) or platinum manganese (PtMn). Exemplary SAF structures include, but are not limited to Co/Pt bilayers, Co/Pd bilayers, CoFe/Pt bilayers, or CoFe/Pd bilayers. In some exemplary embodiments, SAF structure 110 includes a first plurality of bilayers forming a superlattice of ferromagnetic material (e.g., Co, CoFe, Ni) and a nonmagnetic material (e.g., Pd, Pt, Ru). SAF structure 110 may include n bi-layers (e.g., n [Co/Pt] bilayers, or n

[CoFe/Pd] bilayers, etc.) that are separated from ap bilayers (e.g., /? [Co/Pt]) by an intervening non-magnetic spacer. The spacer may provide antiferromagnetic coupling between the bi-layers. The spacer may be a Ruthenium (Ru) layer less than 1 nm thick, for example. Other layers within SAF structure 110 may have thicknesses ranging from 0.1-0.4 nm, for example. SAF structures and/or anti-ferromagnetic layers may be considered part of a multi-layered fixed magnet. Although not depicted, one or more additional material layers may be located between SAF structure 110 and contact 107.

FIG. IB is an isometric illustration of a material stack 103 for an MTJ device 102, in accordance with some alternative embodiments. Reference number labels from FIG. 1 A are retained in FIG. IB for material layers that share any of the same properties described in the context of FIG. 1A. As shown in FIG. IB, the fixed magnet is over the free magnet with cap layer 170 more proximal to the fixed magnet than to the free magnet. Fixed magnet layer 120 and free magnet layer 140 are again separated by at least barrier layer 130. In this embodiment, free magnet layer 140 is between barrier layer 130 and first contact 107 and such an embodiment may benefit from the inclusion of one or more layers between free magnet layer 140 and first contact 107. In FIG. IB, placeholders for various intervening material layers are again represented by ellipses. As one example, a seed layer (not depicted) may be located between free magnet layer 140 and contact 107. The seed layer may be of a material having any composition and microstructure suitable to promote advantageous crystallinity in free magnet layer 140. In some embodiments, the seed layer comprises Pt and may be a substantially pure Pt (i.e. not intentionally alloyed). A Pt seed layer may have a thickness of at least 2 nm (e.g., 2-5 nm), for example. A Pt seed layer may have FCC structure unless strongly templated by an underlay er. One or more additional layers (not depicted) may be present to prevent seed layer from developing an undesirable crystal structure through interactions with contact 107.

As can be seen from the exemplary MTJ material stacks 101 (FIG 1 A) and 103 (FIG. IB), material layers proximal to fixed magnet layer 120 may be different than those proximal to free magnet layer 140. In other words, MTJ material stacks may be asymmetric with respect to ferromagnetic layers of the fixed and free magnet so interactions between the ferromagnetic layers and other proximal layers may vary between the fixed and free magnets. For example, in MTJ material stack 101 (FIG. 1A), contact 107 may interact significantly with fixed magnet layer 120 while free magnet layer 140 may not have such an interaction with contact 107, and may not experience a comparable interaction with contact 180. As another example, in MTJ material stack 103 (FIG. IB), contact 107 may interact significantly with free magnet layer 140 while fixed magnet layer 120 may not have such an interaction with contact 107, and may not experience a comparable interaction with contact 180. As such, one of magnet layers 120, 140 may more readily achieve PMA than the other, and/or may achieve PMA to a greater extent than the other. One material layer interaction subject to proximity effects is interdiffusion of alloy constituents between a ferromagnetic layer and another layer. The inventors have found that outdiffusion of constituents from a ferromagnetic layer can have a significant impact on the final composition and microstructure of a ferromagnetic alloy. In particular, outdiffusion of non-ferromagnetic constituents of the alloy may enhance crystallization of the ferromagnetic layer and/or enhance PMA within the ferromagnetic layer. For example, when an iron alloy is deposited with an amorphizing dopant, such as boron, outdiffusion of the boron during a subsequent thermal anneal is thought to enhance crystallization of the ferromagnetic layer and/or enhance PMA within the ferromagnetic layer. For example, the crystallization of the ferromagnetic layers at the interface of barrier layer 130 may achieve a better lattice match to the barrier layer crystal structure. The inventors have further found variation of such interdiffusion (and particularly outdiffusion) between ferromagnetic layers within an MTJ device may be reduced through the addition of a getter layer adjacent to sidewalls of one or more layers of the MTJ stack. The addition of a sidewall getter in accordance with embodiments herein can introduce a solid state sink of mobile dopants in close proximity to a sidewall edge of layers within the MTJ. Outdiffusion of the non-ferromagnetic constituents (e.g., boron, carbon, etc.) through the sidewall edge of the layers may therefore be promoted by the sidewall getter. Outdiffusion mechanisms may thereby become less dependent on adjacent layers within the stack for dopant sinking.

FIG. 2 is a cross-sectional view through two adjacent MTJ devices 200 with a liner layer 205, in accordance with some embodiments. Reference number labels from FIG. 1A and IB are retained in FIG. 2 for material layers that share any of the same properties described in the context of FIG. ΙΑ,ΙΒ. As shown in FIG. 2, liner layer 205 is over a sidewall of material layers 107, 120, 130, 140, 170, and 180. Liner layer 205 is located between sidewall edges of the MTJ material stack and a surrounding interlay er dielectric (ILD) 210. ILD 210 may be any conventional or low-k dielectric (e.g., SiO, SiN, SiON, SiOC(H), HSQ, MSQ, porous dielectric, etc.), for example. In the illustrated embodiment, liner layer 205 is in direct contact with each of ferromagnetic layers 120 and 140. While the direct contact between liner layer 205 and any of the material layers depicted in FIG. 2 may enhance the gettering performance of liner layer 205, one or more intervening layer may also be disposed between liner layer 205 and a sidewall of a material layer in an MTJ stack.

In exemplary embodiments, liner layer 205 getters one or more constituents from at least one of fixed and free magnet layers 120,140. As such, liner layer 205 comprises one or more constituents that are also present within fixed magnet layer 120 and/or free magnet layer 140. Advantageously, liner layer 205 comprises one or more non-ferromagnetic constituents also present within fixed magnet layer 120 and/or free magnet layer 140. For some exemplary embodiments where one or more of fixed magnet layer 120 and free magnet layer 140 comprise boron, liner layer 205 also comprises boron (i.e., liner layer 205 is a boride or boron doped) at least within the portion of liner layer 205 adjacent to sidewalls of fixed magnet layer 120 or free magnet layer 140.

Although liner layer 205 may be only nanometers thick, a scan along liner layer 205 over the z-height of the MTJ stack with an analysis technique such as single-atom electron energy loss spectroscopy (EELs) may generate a dopant profile indicative of gettering dopants from magnet layers 120, 140. For example, as shown in FIG. 2, a boron profile within liner layer 205 along the z-height of MTJ stack 101 shows boron concentration peaks adjacent to magnet layers 120 and 140. Such peaks are indicative of the outdiffusion of boron from the sidewall surfaces of magnet layers 120 and 140 into liner layer 205. The inventors have found dopant outdiffusion into a sidewall liner material is not inherent to all liners, and is instead a phenomena highly dependent on the composition of the liner layer. For example, the inventors have found no significant boron outdiffusion into liner layer 205 will occur if liner 205 is composed of silicon nitride (SiN). The inventors have however found a number of metals effectively getter boron, and therefore liner layer 205 may further comprise one or more metals, such as, but not limited to, tungsten (W), hafnium (Hi), zirconium (Zr), molybdenum (Mo), tantalum (Ta) and titanium (Ti). Other non- ferromagnetic metals may also be satisfactory dopant getters. In some exemplary embodiments, a sidewall of an MTJ stack is covered with a dielectric liner layer. As shown in Fig. 2, liner layer 205 is in direct contact with a sidewall of material layers 107, 120, 130, 140, 170, and 180, but nevertheless should not form electrical shorts across layers of the stack (e.g., short together electrodes 107 and 180). Metal borides often have significant conductivity, and so in some advantageous

embodiments where liner layer 205 includes boron and a metal, liner layer 205 further comprises an amount of oxygen that renders liner layer 205 sufficiently electrically insulative. Notably, and as described further below, a metal oxide having sufficient oxygen content to be a dielectric may not getter dopants significantly better than SiN or many other non-metallic dielectric compounds. Hence, the presence of the dopant within a dielectric liner layer is indicative of the liner layer having gettered the dopant prior the liner layer's conversion into a dielectric, for example through exposure to an oxidation process subsequent to gettering the dopant(s).

A liner layer may have any thickness. As used herein, liner layer thickness is measured along a direction normal to an edge sidewall of an MTJ material layer. The diameter of the MTJ device may impact the optimal liner layer thickness for gettering dopants from the MTJ material stack. For example, thinner liner layers may be more suitable for MTJ devices of smaller diameter. In accordance with some embodiments where an MTJ material stack has a diameter in the range of 20-30 nm, the liner layer has a thickness of 1- 10 nm. While an MTJ stack sidewall liner of greater thickness may be more capable of gettering, the liner layer thickness may be otherwise constrained, for example to ensure complete conversion of the liner layer into a dielectric so as to avoid an electrical short between separate layers of the MTJ stack. In some exemplary embodiments where liner layer 205 comprises a boron-doped metal oxide, the thickness of liner layer 205 is no more than 4 nm. Most metal layers of a few nanometers in thickness, even if of a refractory metal, can be sufficiently oxidized with known processing techniques.

In some embodiments, at least a portion of a liner layer located over a sidewall of an MTJ material stack is electrically conductive. For example, remnants of a gettering liner layer that has not been entirely converted to a dielectric may remain within an MTJ device structure. Hence, where some portions of a liner layer comprises a metal oxide and one or more gettered dopants, such as boron, other portions may include the metal and gettered dopants, but with an oxygen content that is lower than in the converted liner layer portion. Indeed, oxygen may be substantially absent in unconverted portions of a liner layer with these regions then being a metal boride, or boron-doped metal, that may have significant electrical conductivity. For embodiments having at least a portion of a liner layer that is electrically conductive, electrical shorts may be avoided by ensuring the electrically conductive portion of the liner layer does not strap across both the fixed and free magnets. For example, conductive portions of the liner layer may be allowed to extend in the z- dimension only to be adjacent to a sidewall of barrier layer 130 and underlying layers (e.g., contact 107 and fixed magnet layer 120) with the converted portion covering the sidewall over the remaining MTJ stack height H (e.g., adjacent to material layers 140, 170 and 180). In some embodiments, a gettering liner layer is at least partially sacrificial, and indeed may be entirely removed after gettering dopants from one or more MTJ material layers (e.g., after gettering boron or carbon from one or more ferromagnetic layers). For embodiments where a gettering liner layer is partially sacrificial, remnants, residue or artifacts of the layer may remain as an indication that dopants have been gettered through the MTJ material stack sidewall. FIG. 3 is a cross-sectional view through two adjacent MTJ devices 300 with gettering liner layer artifacts 305, in accordance with some embodiments. As shown, artifacts 305 appear as stringers adjacent to sidewalls of one or more material layers of MTJ devices 300. For such embodiments, because artifacts 305 are sufficiently sparse to avoid electrically shorting MTJ devices 300, artifacts 305 may themselves have electrically conductive compositions. For example, artifacts 305 may have any of the compositions described above in the context of liner artifacts 305. In some specific embodiments artifacts 305 comprise one or more metal, such as, but not limited to W, Hf, Zr, Mo, Ta, or Ti. Notably artifacts 305 may have a different composition than contact 107 and/or contact 180. Artifacts 305 may also comprise a dopant gettered from a layer within the MTJ material stacks, such as, but not limited to, boron or carbon. Artifacts 305 may also have been converted to a dielectric, for example further including oxygen, and having any of the compositions described above for liner layer 205.

FIG. 4 is a cross-sectional view through two adjacent MTJ devices 400 in accordance with some embodiments where a gettering liner layer was completely sacrificial. For such embodiments, no physical liner layer is readily evident and ILD 210, or some other non- gettering dielectric layer, is in direct contact with a sidewall of the MTJ material stack. Nevertheless, an analysis of fixed magnet layer 120 and/or free magnet layer 140 using a technique such as EELs is expected to show a dopant profile indicative of outdiffusion of dopants from the sidewall of fixed magnet layer 120 and/or free magnet layer 140. For example, as shown in FIG. 4 dopant concentration profiles 450 across free magnet layer 140 indicate boron concentration to be highest proximal to the center of the MTJ material stack and lowest at the sidewall edge (i.e., at radius RMTJ) of free magnet layer 140. Such a center- high, edge-low concentration profile is indicative of a sidewall getter. The absence of significant levels of boron within IDL 210 adjacent to free magnet layer 140 further indicates a sacrificial sidewall getter. Where MTJ material stacks have a pillar architecture, dopant concentration profiles 450 that are substantially radially symmetric about the stack centerline are also indicative of a sidewall getter. The Gaussian concentration profile in the illustrated embodiment is also indicative of boron migration via a diffusion mechanism directed toward sidewall of free magnet layer 140. In contrast diffusion of boron to an adjacent layer within the MTJ stack would likely result in a dopant profile that is less dependent on the free magnet layer 140 radius. Notably, these same dopant profiles can also be expected for MTJ devices 200, 300, and 400 as well.

MTJ material stacks in accordance with the architectures above may be fabricated by a variety of methods applying a variety of techniques and processing chamber

configurations. FIG. 5 is a flow diagram illustrating methods 501 for fabricating the MTJ devices illustrated in FIG. 2-4, in accordance with some embodiments. Methods 501 begin with receiving a substrate with MTJ structures at operation 510. Any substrate known to be suitable for microelectronic fabrication may be received, such as, but not limited to crystalline silicon substrates. Transistors (e.g., silicon-channeled FETs) and/or one or more levels of interconnect metallization may be present on the substrate as received at operation 510, for example. FIG. 6A is an isometric illustration of an MTJ device array 600 as received at operation 510, in accordance with some embodiments. MTJ device array 600 includes a plurality of MTJ devices 100 arrayed over an area (footprint) of substrate 601. MTJ devices 100 have been patterned into pillars or columnar structures. MTJ devices 100 are drawn with corner rounding and a sidewall slope to acknowledge various imperfections can be expected to exist in any manufacturing process. Hence, the MTJ device 100 illustrated in FIG. 1A may be considered an ideal structure that need not be exactly replicated during manufacture. FIG. 6B is a cross-sectional illustration of a pair of MTJ devices along the A-A' line depicted in FIG. 6A. Material layers of MTJ device 100 described above in the context of FIG. 1A are retained in FIG. 6B. At this point in the manufacture of MTJ devices 100, the ferromagnetic layers of the fixed and free magnets are substantially amorphous and have an "as-deposited" dopant concentration (e.g., boron concentration).

Returning to FIG. 5, methods 501 continue at operation 520 where a sidewall liner layer is deposited over a sidewall of an MTJ structure. The sidewall liner may be deposited at operation 520 using any technique known to be suitable for the chosen liner composition. In some embodiments, an elemental metal or metal alloy is deposited at operation 520. The metal chosen should be one capable of gettering one or more target dopants present in one or more layers of the MTJ material stack. For example, where the liner is to getter boron from one or more ferromagnetic layers, at least one of W, Hf, Zr, Mo, Ta, or Ti is deposited at operation 520. In some such embodiments, one or more metals are deposited by PVD or an ionized metal plasma (IMP) technique. Alternate deposition techniques, such as chemical vapor deposition (CVD), or atomic layer deposition (ALD), may be performed for those metals known to have suitable precursors. Depending on the slope of the MTJ sidewall and the deposition technique selected, the liner layer may be deposited conformally or non- conformally. For some embodiments where the liner layer is deposited to a nominal thickness of 1-10 nm over the sidewall of the MTJ stack. FIG. 7A is an isometric illustration of MTJ device array 600 following deposition of a gettering liner layer 705. FIG. 7B is a cross-sectional illustration of adjacent MTJ devices along the A-A' line depicted in FIG. 7 A. As shown in FIG. 7A and 7B, gettering liner layer 705 has been deposited in a substantially conformal manner, and is in direct contact with material layers 120, 130, 140, 170 as well as electrodes 107 and 180. A non-conformal deposition may result in a liner layer with less thickness uniformity.

Returning to FIG. 5, methods 501 continue at operation 530 where outdiffusion of one or more dopants from one or more material layers in the MTJ stack into the liner layer is promoted, or at least allowed to occur. In some exemplary embodiments operation 530 entails thermal process. In some examples, a thermal anneal is performed at an elevated temperature of 350 °C, or more. Such an anneal may be performed as a vacuum thermal anneal, and along with motivating dopant outdiffusion and/or gettering by the liner layer, the anneal may concurrently allow magnet layer alloys to develop a desirable dopant content, crystallinity, and/or texture from their as-deposited states (which may have been

substantially amorphous). The anneal of operation 530 may be performed under any conditions known in the art to promote solid phase epitaxy of magnet layers, for example imparting poly crystalline BCC microstructure and (001) texture. Following operation 530, the gettering liner layer will include the various dopant species gettered from the MTJ material layers during the thermal anneal. For exemplary embodiments, where the liner layer deposited at operation 520 includes one or more metals and the gettered dopants included boron, the liner layer following operation 530 may be characterized as a metal boride, or a boron-doped metal. For other embodiments, where the liner layer deposited at operation 520 includes one or more metals and the gettered dopants included carbon, the liner layer following operation 530 may be characterized as a metal carbide, or a carbon-doped metal. At operation 540, at least a portion of the gettering liner layer is converted to a dielectric, or removed. Conversion of a gettering liner layer may be incomplete, converting an amount of a conductive liner into an insulative liner that is sufficient to avoid shorts across an MTJ device. In some exemplary embodiments where the gettering liner layer deposited at operation 520 includes a metal, conversion of the gettering liner layer advantageously includes oxidizing the metal(s) to form a metal oxide. Conversion may also entail incorporation of other species, such as, but not limited to, nitrogen or silicon. An oxidation process may proceed with process conditions and a duration selected to achieve a predetermined degree of oxidation that renders the gettering liner layer sufficiently electrically insulating. In some exemplary embodiments, operation 540 is combined with operation 520. For example, a vacuum thermal anneal may be performed at operation 530 for a first anneal time during which the liner layer getter dopants, and an oxygen source gas may then be introduced for a second anneal time during which the gettering layer is oxidized. FIG. 8 A is an isometric illustration of MTJ device array 600 following conversion of gettering liner layer 705 into liner layer 205. FIG. 8B is a cross-sectional illustration of adjacent MTJ devices along the A- A' line depicted in FIG. 8 A. As shown in FIG. 8A and 8B, liner layer 205 covers MTJ devices 100.

Returning to FIG. 5, methods 501 end at operation 550 where IC processing is completed in any suitable manner, for example to interconnect the MTJ devices into functional circuitry, such as memory circuitry. In some embodiments, one or more ILD materials and damascene operations are performed to interconnect the top electrode of the MTJ devices. FIG. 9A is an isometric illustration of MTJ device array 600 following deposition of ILD 210 and planarization of ILD 210 with top contact 180. FIG. 9B is a cross-sectional illustration of adjacent MTJ devices along the A-A' line depicted in FIG. 9A. As shown in FIG. 9A and 9B, ILD 210 has been deposited with any suitable dielectric deposition process (e.g., flowable CVD, CVD, PECVD, spin-on, etc.), and planarized (e.g., with any suitable chemical/mechanical planarization process) to remove a portion of liner layer 205 and expose a surface of contact 180. Additional ILD material (not depicted) may then be deposited. Trenches and/or vias may further patterned to expose contact 180 to a subsequent interconnect metallization process (e.g., copper plating, etc.).

In other alternative embodiments where the gettering liner layer is amenable to one or more etching processes, the getting liner layer may be at least partially removed (e.g., at operation 540 in FIG. 5) as a sacrificial layer following the gettering operation (e.g., operation 530 in FIG. 5). Such an etch process may remove substantially all of the gettering liner layer (e.g., leaving no more than incidental artifacts of a liner), or may selectively remove an amount of a gettering liner layer that is sufficient to avoid shorts across an MTJ device. FIG. 10 is a cross-sectional illustration of adjacent MTJ devices along the A-A' line depicted in FIG. 7A, for example prior to a liner etch process. FIG. 11 is a cross-sectional illustration along the A-A' line during an etching of the gettering liner layer. The illustrated etch process is unmasked (i.e., a blanket-etch) that removes substantially all of gettering liner layer 705, leaving only artifacts 305. Any etch process known to be suitable for the particular gettering liner composition may be performed. In some embodiments where the gettering liner includes one or more chemically reactive metals, an isotropic wet or dry etch may be employed. In some embodiments where the gettering liner includes one or more chemically inert metals, a physical etch technique, such as a directional ion beam etch (IBE), may be employed. Notably, such a gettering liner layer etch may also be performed after a masking process, for example to leave a portion of the gettering liner layer sufficient to further serve as an interconnect between two or more MTJ devices, for example

substantially as described above in the context of converting only a portion of the liner to a dielectric. FIG. 12 is a cross-sectional illustration along the A-A' line following deposition and planarization of ILD layer 210 to arrive at MTJ device 300, substantially as described elsewhere herein. In some embodiments, the MTJ devices having one or more of the features or attributes described above function essentially as a resistor, where the resistance of an electrical path through the MTJ may exist in two resistive states, either "high" or "low," depending on the direction or orientation of magnetization in the free magnetic layer(s) and in the fixed magnetic layer(s). In the case that the spin direction is down (minority) in the free magnetic layer(s), a high resistive state exists and the directions of magnetization in the coupled free magnet and the fixed magnet are substantially opposed or anti-parallel with one another. In the case that the spin direction is up (majority) in a ferromagnetic material layer of the coupled free magnet, a low resistive state exists, and the directions of magnetization in the ferromagnetic layers of the coupled free magnet and the fixed magnet are substantially aligned or parallel with one another. The terms "low" and "high" with regard to the resistive state of the MTJ device and are relative to one another. In other words, the high resistive state is merely a detectibly higher resistance than the low resistive state, and vice versa. Thus, with a detectible difference in resistance, the low and high resistive states can represent different bits of information (i.e. a "0" or a " 1").

The direction of magnetization in the ferromagnetic layer(s) may be switched through a process called spin transfer torque ("STT") using a spin-polarized current. An electrical current is generally non-polarized (e.g. consisting of about 50% spin-up and about 50% spin-down electrons). A spin-polarized current is one with a greater number of electrons of either spin-up or spin-down. The spin-polarized current may be generated by passing a current through the fixed magnetic layer. The electrons of the spin polarized current from the fixed magnet may tunnel through the barrier layer and transfer spin angular momentum to a ferromagnetic layer of the free magnet, wherein the ferromagnetic layer will orient its magnetic direction from anti-parallel to that of the fixed magnet, or parallel.

The spin-hall effect may also be employed to generate spin-polarized current through a particular electrode material that is in contact with a free magnet. For such embodiments, the ferromagnetic material layer(s) of a free magnet may be oriented without applying current through the fixed magnet and other material layers of the MTJ device. In either implementation, the free magnetic layer may be returned to its original orientation by reversing the current. Thus, an MTJ device may store a single bit of information ("0" or "1") by its state of magnetization. The information stored in the MTJ device is sensed by driving a current through the MTJ material stack. The magnetic layer(s) of the free magnet do not require power to retain their magnetic orientations. As such, the state of the MTJ device may be preserved when power to the device is removed. Therefore, a spin transfer torque memory bit cell including the MTJ material stacks described herein are considered nonvolatile.

FIG. 13 is a schematic of an MTJ memory bit cell 1301, which includes a spin transfer torque element 1310, in accordance with some embodiments. The spin transfer torque element 1310 includes a free magnet including at least one free magnet layer 140. Element 1310 further includes first contact 107 proximate to a fixed magnet including at least one fixed magnet layer 120. At least one of ferromagnetic material layers 120 and 140 has outdiffused a dopant, such as carbon, through their sidewall edges, for example as described elsewhere herein. Barrier layer 130 is located between the free magnet and the fixed magnet. A second contact 180 is proximate to the free magnet. Second contact 180 is electrically coupled to a first metal interconnect 1392 (e.g., bit line). First contact 107 is electrically connected to a second metal interconnect 1391 (e.g., source line) through a transistor 1315. The transistor 1315 is further connected to a third metal interconnect 1393 (e.g., word line) in any manner conventional in the art. Alternatively, for example in a cross- point architecture, transistor 1315 may replaced with a two-terminal selector (e.g., diode, etc.). In SHE implementations second contact 180 may also be coupled to a fourth metal interconnect 1394 (e.g., maintained at a reference potential relative to first metal interconnect 1392).

The spin transfer torque memory bit cell 1301 may further include additional read and write circuitry (not shown), a sense amplifier (not shown), a bit line reference (not shown), and the like, as understood by those skilled in the art of solid state non-volatile memory devices. A plurality of the spin transfer torque memory bit cells 1301 may be operably connected to one another to form a memory array (not shown), and the memory array can be incorporated into a non-volatile memory device following any known techniques and architectures.

In some embodiments, transistors are formed in the front end of the line (FEOL) while an MTJ device is formed within the back end of the line (BEOL). Fig. 14 illustrates a cross-section 600 of a die layout including MTJ device 100 located in metal 3 and metal 2 layer regions, according to some embodiments of the disclosure. Elements in FIG. 14 having the same reference numbers (or names) as the elements of any other figures or description provided herein can comprise materials, operate, or function substantially as described elsewhere herein. Cross-section 1400 illustrates an active region having a transistor MN comprising diffusion region 1401 , a gate terminal 1402, drain terminal 1404, and source terminal 1403. The source terminal 1403 is coupled to SL (source line) via polysilicon or a metal via, where the SL is formed on Metal 0 (M0). In some embodiments, the drain terminal 1404 is coupled to MOa (also metal 0) through via 1405. The drain terminal 1404 is coupled to contact 107 through via 0-1 (e.g., via connecting metal 0 to metal 1 layers), metal 1 (Ml), via 1-2 (e.g., via connecting metal 1 to metal 2 layers), and Metal 2 (M2). In some embodiments, MTJ device 100 is formed in the Metal 3 (M3) region. In some embodiments, the perpendicular fixed magnet of MTJ device 100 couples to contact 107 and the perpendicular free magnet couples to the bit-line (BL) through Via 3-4 (e.g., via connecting metal 4 region to metal 4 (M4)). In this example, bit-line is formed on M4. In other embodiments, MTJ device 100 is formed in the metal 2 region and/or Via 1-2 region. In still other embodiments, MTJ device 100 is inverted with the perpendicular free magnet of MTJ device 100 coupling to contact 107 and the perpendicular fixed magnet coupling to Via 3-4 (e.g., via connecting metal 4 region to metal 4 (M4)).

FIG. 15 illustrates a system 1500 in which a mobile computing platform 1505 and/or a data server machine 1506 employs an MTJ device with an MTJ material stack including at least one ferromagnetic layer that has outdiffused a dopant, such as boron, through the layer's sidewall edge, for example into a gettering liner as described elsewhere herein. Server machine 1506 may be any commercial server, for example including any number of high-performance computing platforms disposed within a rack and networked together for electronic data processing, which in the exemplary embodiment includes data processor circuitry 1550.

The mobile computing platform 1505 may be any portable device configured for each of electronic data display, electronic data processing, wireless electronic data transmission, or the like. For example, the mobile computing platform 1505 may be any of a tablet, a smart phone, laptop computer, etc., and may include a display screen (e.g., a capacitive, inductive, resistive, or optical touchscreen), a chip-level or package-level integrated system 1510, and a battery 1515. Whether disposed within the integrated system 1510 illustrated in the expanded view

1520, or as a stand-alone packaged device within the server machine 1506, SOC 1560 includes at least an MTJ device with an MTJ material stack including at least one ferromagnetic layer that has outdiffused a dopant, such as boron, through the layer's sidewall edge, for example into a dopant gettering liner. SOC 1560 may further include memory circuitry and/or a processor circuitry 1550 (e.g., STTM, MRAM, a microprocessor, a multi-core microprocessor, graphics processor, etc.). Any of controller 1535, PMIC 1530, or RF (radio frequency) integrated circuitry (RFIC) 1525 may also be communicatively coupled to an MTJ device, such as an embedded STTM employing MTJ material stacks including one or more carbon-doped ferromagnetic layers.

As further illustrated, in the exemplary embodiment, RFIC 1525 has an output coupled to an antenna (not shown) to implement any of a number of wireless standards or protocols, including but not limited to Wi-Fi (IEEE 802.11 family), WiMAX (IEEE 802.16 family), IEEE 802.20, long term evolution (LTE), Ev-DO, HSPA+, HSDPA+, HSUPA+, EDGE, GSM, GPRS, CDMA, TDMA, DECT, Bluetooth, derivatives thereof, as well as any other wireless protocols that are designated as 3G, 4G, 5G, and beyond. In alternative implementations, each of these SoC modules may be integrated onto separate ICs coupled to a package substrate, interposer, or board.

FIG. 16 is a functional block diagram of a computing device 1600, arranged in accordance with at least some implementations of the present disclosure. Computing device 1600 may be found inside platform 1505 or server machine 1506, for example. Device 1600 further includes a motherboard 1602 hosting a number of components, such as, but not limited to, a processor 1604 (e.g., an applications processor), which may further incorporate embedded magnetic memory 1630 based on MTJ material stacks including one or more carbon-doped ferromagnetic layers, in accordance with embodiments of the present disclosure. Processor 1604 may be physically and/or electrically coupled to motherboard 1602. In some examples, processor 1604 includes an integrated circuit die packaged within the processor 1604. In general, the term "processor" or "microprocessor" may refer to any device or portion of a device that processes electronic data from registers and/or memory to transform that electronic data into other electronic data that may be further stored in registers and/or memory.

In various examples, one or more communication chips 1606 may also be physically and/or electrically coupled to the motherboard 1602. In further implementations, communication chips 1606 may be part of processor 1604. Depending on its applications, computing device 1600 may include other components that may or may not be physically and electrically coupled to motherboard 1602. These other components include, but are not limited to, volatile memory (e.g., DRAM 1632), other non-volatile memory 1635 (e.g., flash memory), a graphics processor 1622, a digital signal processor, a crypto processor, a chipset 1612, an antenna 1625, touchscreen display 1615, touchscreen controller 1675, battery 1610, audio codec, video codec, power amplifier 1621, global positioning system (GPS) device 1640, compass 1645, accelerometer, gyroscope, speaker 1620, camera 1641. Computing device 1600 may also include a mass storage device (not depicted), such as a hard disk drive, solid-state drive (SSD), compact disk (CD), digital versatile disk (DVD), or the like.

Communication chips 1606 may enable wireless communications for the transfer of data to and from the computing device 1600. The term "wireless" and its derivatives may be used to describe circuits, devices, systems, methods, techniques, communications channels, etc., that may communicate data through the use of modulated electromagnetic radiation through a non-solid medium. The term does not imply that the associated devices do not contain any wires, although in some embodiments they might not. Communication chips 1606 may implement any of a number of wireless standards or protocols, including but not limited to those described elsewhere herein. As discussed, computing device 1600 may include a plurality of communication chips 1606. For example, a first communication chip may be dedicated to shorter-range wireless communications, such as Wi-Fi and Bluetooth, and a second communication chip may be dedicated to longer-range wireless

communications such as GPS, EDGE, GPRS, CDMA, WiMAX, LTE, Ev-DO, and others.

While certain features set forth herein have been described with reference to various implementations, this description is not intended to be construed in a limiting sense. Hence, various modifications of the implementations described herein, as well as other

implementations, which are apparent to persons skilled in the art to which the present disclosure pertains are deemed to lie within the spirit and scope of the present disclosure.

It will be recognized that the disclosure is not limited to the embodiments so described, but can be practiced with modification and alteration without departing from the scope of the appended claims. For example the above embodiments may include specific combinations of features as further provided below. In one or more first examples, a magnetic tunneling junction (MTJ) device comprises a pair of contacts, each comprising one or more metals, and a material stack between the contacts. The material stack comprises a fixed magnet layer and a free magnet layer, wherein at least one of the fixed magnet layer and free magnet layer comprises a dopant having a concentration that varies as a function of distance between a center and an edge sidewall of the layer. The material stack comprises a barrier layer between the fixed magnet layer and the free magnet layer.

In one or more second examples, for any of the first examples, the dopant is nonferromagnetic and has a concentration that decreases from a maximum concentration proximal to a central axis of the stack passing through a thickness of at least one of the fixed and free magnet layers to a minimum concentration proximal to the edge sidewall. In one or more third examples, for any of the first through second examples the dopant comprises boron.

In one or more fourth examples, for any of the first through the third examples the MTJ device further comprising a sidewall liner adjacent to an edge sidewall of at least one of material layer in the MTJ stack, the liner comprising the dopant. In one or more fifth examples, for any of the fourth examples the liner is adjacent to an edge sidewall of at least one of the fixed and free magnet layers.

In one or more sixth examples, for any of the fourth through fifth examples the sidewall liner comprises one or more metal.

In one or more seventh examples, for any of the sixth examples the sidewall liner comprises at least one of W, Hf, Zr, Mo, Ta, or Ti.

In one or more eighth examples, for any of the fourth through fifth examples at least a portion of the sidewall liner further comprises oxygen.

In one or more ninth examples, for any of the fourth through eighth examples at least a portion of the sidewall liner adjacent to a sidewall edge of one the fixed and free magnet layers is a dielectric.

In one or more tenth examples, for any of the ninth examples at least a portion of the sidewall liner adjacent to a sidewall edge of both of the fixed and free magnet layers is a dielectric. In one or more eleventh examples for any of the fourth through the tenth examples the sidewall liner is adjacent to a sidewall edge of both the contacts.

In one or more twelfth example for any of the fourth through eleventh examples the sidewall liner has a thickness of 4 nm, or less. In one or more thirteenth examples, for any of the twelfth examples the sidewall liner comprises a metal oxide.

In one or more fourteenth examples for any of the first through the thirteenth examples at least one of the fixed and free magnet layers comprises a CoFeB alloy, and the barrier layer comprises MgO, VO, TaO, HfO, ZrO, WO, or TiO. In one or more fifteenth examples, a system, comprises a data processor, and a memory coupled to the processor, the memory to store data and comprising the MTJ device in any of the first through the fourteenth examples.

In one or more sixteenth examples, a magnetic random access memory (mRAM) device comprises a plurality of magnetic tunneling junction (MTJ) devices, individual ones of the MTJ devices further comprising a fixed magnet layer and a free magnet layer, wherein at least one of the fixed magnet layer and free magnet layer has and comprises a dopant, and a barrier layer between the fixed magnet layer and the free magnet layer. A liner layer is adjacent to a sidewall edge of at least one of the MTJ devices, wherein the liner layer comprises the dopant, and one or more tic metals. Bit lines and source lines are coupled to the MTJ devices.

In one or more seventeenth examples, for any of the sixteenth examples the metals comprise at least one of W, Hf, Zr, Mo, Ta, or Ti.

In one or more eighteenth examples, for any of the sixteenth through eighteenth examples the liner layer further comprises oxygen. In one or more eighteenth examples, a method of forming a magnetic tunneling junction (MTJ) device comprises forming a pair of contacts, each contact comprising one or more metals, and forming an MTJ material stack between the pair of contacts. Forming the stack further comprises forming a first of a fixed magnet layer and a free magnet layer, wherein at least one of the fixed magnet layer and free magnet layer comprises a dopant, forming a barrier layer over the first of the fixed magnet and the free magnet, and forming a second of the fixed magnet layer and the free magnet layer over the barrier layer. The method comprises depositing a liner layer over the MTJ material stack and adj acent to an edge of at least one of the fixed and free magnetic layers, and allowing at least some of the dopant to diffuse into the liner layer.

In one or more twentieth examples, for any of the nineteenth examples the method further comprises converting the liner layer into a dielectric after allowing at least some of the dopant to diffuse into the liner layer.

In one or more twenty-first examples, for any of the twentieth examples converting the liner layer in the dielectric further comprises oxidizing the metal into a metal-oxide.

In one or more twenty-second examples, for any of the nineteenth through twenty- first examples, the method comprises removing at least a portion of the liner layer after allowing at least some of the dopant to diffuse into the liner layer.

In one or more twenty -third examples, for any of the nineteenth examples allowing at least some of the dopant to diffuse into the liner layer further comprises annealing the MTJ device after depositing the liner layer over the stack.

In one or more twenty -fourth examples, for any of the nineteenth through twenty- third examples forming the fixed and free magnetic layers further comprises depositing a first layer of an alloy comprising CoFeB, depositing the barrier layer over the first layer, depositing a second layer of an alloy comprising CoFeB over the barrier layer, and annealing the MTJ stack at a temperature of at least 350 °C to diffuse boron into the liner layer and render the first and second layers poly crystalline with (001) out-of-plane texture.

In one or more twenty-fifth examples, for any of the nineteenth through twenty- fourth examples depositing the liner layer further comprises depositing at least one of W, Hf, Zr, Mo, Ta, or Ti.

In one or more twenty-sixth examples a system, comprises a data processing means, and a data storage means coupled to the processor, the data storage means comprising the MTJ device recited in any one of the first through the fourteenth examples. However, the above embodiments are not limited in this regard and, in various implementations, the above embodiments may include the undertaking only a subset of such features, undertaking a different order of such features, undertaking a different combination of such features, and/or undertaking additional features than those features explicitly listed. The scope of the disclosure should, therefore, be determined with reference to the appended claims, along with the full scope of equivalents to which such claims are entitled.

Claims

CLAIMS What is claimed is:

1. A magnetic tunneling junction (MTJ) device, comprising:

a pair of contacts, each comprising one or more metals; and

a material stack between the contacts, wherein the material stack comprises:

a fixed magnet layer and a free magnet layer, wherein at least one of the fixed

magnet layer and free magnet comprises a non-ferromagnetic dopant having a concentration that varies as a function of distance between a center and an edge sidewall of the layer; and

a barrier layer between the fixed magnet layer and the free magnet layer.

2. The MTJ device of claim 1, wherein the non-ferromagnetic dopant has a concentration that decreases from a maximum concentration proximal to a central axis of the stack passing through a thickness of at least one of the fixed and free magnet layers to a minimum concentration proximal to the edge sidewall.

3. The MTJ device of claim 1, wherein the non-ferromagnetic dopant comprises boron.

4. The MTJ device of claim 1, further comprising a sidewall liner adjacent to an edge sidewall of at least one of the layers in the stack, the liner comprising the non-ferromagnetic dopant.

5. The MTJ device of claim 4, wherein the liner is adjacent to an edge sidewall of at least one of the fixed and free magnet layers.

6. The MTJ device of claim 5, wherein the sidewall liner comprises one or more metal.

7. The MTJ device of claim 6, wherein the sidewall liner comprises at least one of W, Hf, Zr, Mo, Ta, or Ti.

8. The MTJ device of claim 6, wherein at least a portion of the sidewall liner further comprises oxygen.

9. The MTJ device of claim 8, wherein at least a portion of the sidewall liner adjacent to a sidewall edge of one the fixed and free magnet layers is a dielectric.

10. The MTJ device of claim 9, wherein at least a portion of the sidewall liner adj acent to a sidewall edge of both of the fixed and free magnet layers is a dielectric.

1 1. The MTJ device of claim 10, wherein the sidewall liner is adjacent to a sidewall edge of both the contacts.

12. The MTJ device of claim 6, wherein the sidewall liner has a thickness of 4 nm, or less.

13. The MTJ device of claim 12, wherein the sidewall liner comprises a metal oxide.

14. The MTJ device of claim 1, wherein:

at least one of the fixed and free magnet layers comprises a CoFeB alloy; and

the barrier layer comprises MgO, VO, TaO, HfO, ZrO, WO, or TiO.

15. A system, comprising:

a processor; and

a memory coupled to the processor, the memory comprising the MTJ device recited in any one of claims 1-14.

16. A magnetic random access memory (mRAM) device, comprising:

a plurality of magnetic tunneling junction (MTJ) devices, individual ones of the MTJ devices further comprising:

a fixed magnet layer and a free magnet layer, wherein at least one of the fixed

magnet layer and free magnet layer comprises a non-ferromagnetic dopant; and

a barrier layer between the fixed magnet layer and the free magnet layer;

a liner layer adjacent to a sidewall edge of at least one of the MTJ devices, wherein the liner layer comprises the non-ferromagnetic dopant, and one or more metals; and bit lines and source lines coupled to the MTJ devices.

17. The mRAM device of claim 16, wherein the metals comprise at least one of W, Hf, Zr, Mo, Ta, or Ti.

18. The mRAM device of claim 17, wherein the liner layer further comprises oxygen.

19. A method of forming a magnetic tunneling junction (MTJ) device, comprising:

forming a pair of contacts, each contact comprising one or more metals; and

forming a material stack between the pair of contacts, wherein forming the stack further comprises:

forming a first of a fixed magnet layer and a free magnet layer, wherein at least one of the fixed magnet layer and free magnet layer comprises a non- ferromagnetic dopant;

forming a barrier layer over the first of the fixed magnet and the free magnet; and forming a second of the fixed magnet layer and the free magnet layer over the barrier layer;

depositing a liner layer over the stack and adjacent to an edge of at least one of the fixed and free magnetic layers; and

allowing at least some of the non-ferromagnetic dopant to diffuse into the liner layer.

20. The method of claim 19, wherein the liner layer comprises one or more metals, and the method further comprises converting the liner layer into a dielectric after allowing at least some of the non-ferromagnetic dopant to diffuse into the liner layer.

21. The method of claim 20, wherein converting the liner layer in the dielectric further comprises oxidizing the metal into a metal-oxide.

22. The method of claim 20, further comprising removing at least a portion of the liner layer after allowing at least some of the non-ferromagnetic dopant to diffuse into the liner layer.

23. The method of claim 19, wherein allowing at least some of the non-ferromagnetic dopant to diffuse into the liner layer further comprises annealing the MTJ device after depositing the liner layer over the stack.

24. The method of claim 19, wherein forming the fixed and free magnetic layers further comprises:

depositing a first layer of an alloy comprising CoFeB;

depositing the barrier layer over the first layer;

depositing a second layer of an alloy comprising CoFeB over the barrier layer; and annealing the MTJ stack at a temperature of at least 350 °C to diffuse boron into the liner layer and render the first and second layers poly crystalline with (001) out-of-plane texture.

25. The method of claim 19, wherein depositing the liner layer further comprises depositing at least one of W, Hf, Zr, Mo, Ta, or Ti.