Method of manufacturing integrated circuit using encapsulation during an etch process

A method of fabricating a magnetoresistive bit from a magnetoresistive stack includes etching through a first portion of the magnetoresistive stack using a first etch process to form one or more sidewalls. At least a portion of the sidewalls includes redeposited material after the etching. The method also includes modifying at least a portion of the redeposited material on the sidewalls, and etching through a second portion of the magnetoresistive stack after the modifying step. The magnetoresistive stack may include a first magnetic region, an intermediate region disposed over the first magnetic region, and a second magnetic region disposed over the intermediate region.

TECHNICAL FIELD

The present disclosure relates to, among other things, embodiments and aspects related to the manufacturing of an integrated circuit device and the devices resulting therefrom.

INTRODUCTION

There are many inventions described and illustrated herein, as well as many aspects and embodiments of those inventions. In one aspect, the present disclosure relates to methods of manufacturing an integrated circuit device and the devices resulting therefrom. To describe aspects of the disclosed method, an exemplary method of manufacturing a magnetoresistive device (for example, a magnetoresistive memory, magnetoresistive sensor/transducer, etc.) from a magnetoresistive stack/structure is described herein. However, this is only exemplary, and the disclosed method can be applied to manufacture any integrated circuit device.

There are many embodiments described and illustrated herein. The present disclosure is neither limited to any single aspect nor embodiment thereof, nor to any combinations and/or permutations of such aspects and/or embodiments. Each of the aspects of the present disclosure, and/or embodiments thereof, may be employed alone or in combination with one or more of the other aspects of the present disclosure and/or embodiments thereof. For the sake of brevity, many of those combinations and permutations are not discussed separately herein.

DETAILED DESCRIPTION

It should be noted that all numeric values disclosed herein (including all disclosed thickness values, limits, and ranges) may have a variation of ±10% (unless a different variation is specified) from the disclosed numeric value. For example, a layer disclosed as being “t” units thick can vary in thickness from (t−0.1t) to (t+0.1t) units. Further, all relative terms such as “about,” “substantially,” “approximately,” etc. are used to indicate a possible variation of ±10% (unless noted otherwise or another variation is specified). Moreover, in the claims, values, limits, and/or ranges of the thickness and atomic composition of, for example, the described layers/regions, means the value, limit, and/or range ±10%.

It should be noted that the description set forth herein is merely illustrative in nature and is not intended to limit the embodiments of the subject matter, or the application and uses of such embodiments. Any implementation described herein as exemplary is not to be construed as preferred or advantageous over other implementations. Rather, the term “exemplary” is used in the sense of example or “illustrative,” rather than “ideal.” The terms “comprise,” “include,” “have,” “with,” and any variations thereof are used synonymously to denote or describe a non-exclusive inclusion. As such, a device or a method that uses such terms does not include only those elements or steps, but may include other elements and steps not expressly listed or inherent to such device and method. Further, the terms “first,” “second,” and the like, herein do not denote any order, quantity, or importance, but rather are used to distinguish one element from another. Similarly, terms of relative orientation, such as “top,” “bottom,” etc. are used with reference to the orientation of the structure illustrated in the figures being described. Moreover, the terms “a” and “an” herein do not denote a limitation of quantity, but rather denote the presence of at least one of the referenced item.

In this disclosure, the term “region” is used generally to refer to one or more layers of material. That is, a region (as used herein) may include a single layer (or coating) of material or multiple layers or coatings of materials stacked one on top of another to form a multi-layer system. Further, although in the description below, the different regions in the disclosed stack/structure are sometimes referred to by specific names (capping layer, reference layer, transition layer, etc.), this is only for ease of description and not intended as a functional description of the layer.

As alluded to above, in one exemplary aspect, the magnetoresistive device of the present disclosure, formed from a magnetoresistive stack/structure, may be used in a magnetic tunnel junction type device (MTJ device). The MTJ device may be implemented, for example, as a spin-torque magnetoresistive random access memory (“MRAM”) element (“memory element”), a magnetoresistive sensor, a magnetoresistive transducer, etc. In such aspects, the magnetoresistive stack/structure may include an intermediate layer positioned (or sandwiched) between two ferromagnetic regions/layers. The intermediate layer may be a tunnel barrier and may include an insulating material, such as, e.g., a dielectric material. In other embodiments, the intermediate layer may be a conductive material, e.g., copper, gold, or alloys thereof. In such embodiments, where the magnetoresistive stack/structure includes a conductive material in between two ferromagnetic regions/layers, the magnetoresistive stack/structure may form a GMR or GMR-type device.

For the sake of brevity, conventional manufacturing techniques related to semiconductor processing may not be described in detail herein. The exemplary embodiments may be fabricated using known manufacturing techniques and processes, including, but not limited, lithographic processes. The fabrication of integrated circuits, microelectronic devices, micro electro mechanical devices, microfluidic devices, and photonic devices involves the creation of several layers of materials that interact in some fashion. One or more of these layers may be patterned so various regions of the layer have different electrical or other characteristics, which may be interconnected within the layer or to other layers to create electrical components and circuits. These regions may be created by selectively introducing or removing various materials. The patterns that define such regions are often created by lithographic processes. For example, a layer of photoresist is applied onto a layer overlying a wafer substrate. A photo mask (containing clear and opaque areas) is used to selectively expose the photoresist by a form of radiation, such as ultraviolet light, electrons, or x-rays. Either the photoresist exposed to the radiation, or not exposed to the radiation, is removed by the application of a developer. An etch may then be employed/applied whereby the layer not protected by the remaining resist is patterned. Alternatively, an additive process can be used in which a structure is built up using the photoresist as a template.

As noted above, in one aspect, the described embodiments relate to, among other things, methods of manufacturing a magnetoresistive device, e.g., a magnetic tunnel junction bit (MTJ bit) or a magnetic tunnel junction type device (MTJ device), from a magnetoresistive stack/structure. The magnetoresistive stack/structure may include, or may be operably coupled to, one or more electrically conductive electrodes, vias, or conductors on either side of a magnetic material stack. As described in further detail below, the magnetic material stack may include many different layers of material, where some of the layers include magnetic materials, whereas others do not. In one embodiment, the methods of manufacturing may include sequentially depositing, growing, sputtering, evaporating, and/or providing (collectively referred herein as “depositing” or other verb tense (e.g., “deposit” or “deposited”)) layers and regions which, after further processing (for example, etching) those layers form a magnetoresistive stack/structure.

The described magnetoresistive stacks/structures may be formed between a top electrode/via/line and a bottom electrode/via/line, both of which may permit access to the stack/structure by allowing for connectivity (for example, electrical) to circuitry and other elements of the magnetoresistive device. Between the electrodes/vias/lines are layers and/or regions, including at least one “fixed” magnetic region (which may include, among other things, a plurality of ferromagnetic layers), at least one “free” magnetic region (which may include, among other things, a plurality of ferromagnetic layers), and one or more intermediate layers or regions disposed between a “fixed” magnetic region and the “free” magnetic region. In some embodiments, the one or more intermediate layers or regions may be a dielectric layer or region. In other embodiments, however, the one or more intermediate layers or regions may be a conductive layer or region. In some embodiments, the top electrode (and/or the bottom electrode) may be eliminated, and the bit line may be formed on top of the magnetoresistive stack.

FIG. 1illustrates a cross-sectional view of an exemplary magnetoresistive stack/structure100(for example, an in-plane or out-of-plane magnetic anisotropy magnetoresistive stack/structure (e.g., a perpendicular magnetic anisotropy magnetoresistive stack/structure)) having multiple regions (10,20,30, etc.) formed one on top of another. For the sake of brevity, in the discussion below, the magnetoresistive stack/structure100is referred to as a “magnetoresistive stack.” It will be recognized that several other commonly-used regions (or layers) (e.g., various protective cap layers, seed layers, etc.) are not illustrated inFIG. 1(and in subsequent figures) for clarity. Each of the regions (10,20,30, etc.) of magnetoresistive stack100may comprise one or more layers of material. That is, for example, in some embodiments, region10may comprise a single layer of a material (e.g., element, a chemical composition, alloy, composite, etc.) formed on (e.g., directly on) region20, and region20may comprise multiple layers of materials (of the same or different materials) sequentially formed (one atop the other) on region30. In the discussion below, the term “region” is intended to cover both a region or a zone comprising a single layer of material (e.g., region10in the example above) and a region or zone comprising multiple layers of material (e.g., region20in the example above).

As known to one skilled in the art, the interface between the multiple regions (10,20,30, etc.) (and/or the interface between the multiple layers, if any, within a region) may, in some cases, be characterized by compositional (e.g., chemical) and/or structural changes due to intermixing between the materials (or intermetallic formation) of the adjacent regions (e.g., during deposition, post deposition anneal, etc.). For example, while the compositional profile across an ideal interface (i.e., an interface which does not undergo compositional changes) between two regions (or layers) may indicate a sharp profile (i.e., the composition abruptly changes from the composition of one region to that of the other region), the compositional profile across a typical interface of magnetoresistive stack100ofFIG. 1may indicate a different profile. For example, the profile may indicate a gradual change in chemical composition across an interface of two regions if intermixing occurs between the materials of the regions, or the profile across the interface may indicate the presence of a different composition in the vicinity of the interface if a different interfacial phase (e.g., an intermetallic) is formed at the interface.

Magnetoresistive stack100ofFIG. 1may include intermediate regions40and60(such as, for example, a dielectric layer or a conductive layer) disposed between magnetic material regions30and50, and/or magnetic material regions50and70. In a fabricated magnetoresistive device (e.g., MRAM, etc.), the magnetic material regions30,70may function as a “fixed” magnetic region, the magnetic material region50may function as a “free” magnetic region, and the intermediate regions40,60may function as tunnel barriers. As illustrated inFIG. 1, for example, regions30,40,50,60, and70may be sequentially formed between electrically conductive regions20and80. In the fabricated magnetoresistive device, regions20and80may function as electrodes. For example, region20may be a top electrode and region80may be a bottom electrode. However, those of ordinary skill in the art will recognize that the relative order of the various regions of magnetoresistive stack100may be reversed. That is, region20may function as the bottom electrode and region80may function as the top electrode.

Regions20and80may include any electrically conductive material, and may be part of (or be in physical contact with) electrically conductive interconnects (e.g., vias, traces, lines, etc.) of the magnetoresistive stack100(e.g., as shown inFIG. 8). Although any electrically conductive material may be used for regions20,80, in some embodiments, a metal such as tantalum (Ta), titanium (Ti), tungsten (W), or a composite or alloy of these elements (e.g., tantalum-nitride alloy) may be used. In some embodiments, one or both of regions20and80may be eliminated. For example, in some embodiments, region20may be eliminated by positioning the bit line (of the MRAM) on top of the stack, and region80may be eliminated by forming the stack on a conductive region of the die backend (metallization layer, redistribution layer, etc.).

As illustrated inFIG. 1, region80may be formed on a planar (or substantially planar) surface of a semiconductor substrate90(e.g., backend of an IC device, etc.), and regions80,70,60,50,40,30,20, and10may each be formed on, or above, the underlying region or regions. Each region may be formed directly on the underlying region, or may be formed on an intermediate layer (seed layer, etc.) formed, or deposited, on a surface of the underlying region. For example, although not illustrated inFIG. 1, in some embodiments, the top surface of region80(i.e., the surface of region80on which region70is formed) may include a seed layer or region. The seed layer may be formed by converting a portion of the top surface of region80into the seed layer, or the seed layer may be deposited on the top surface of region80. This seed region may facilitate the formation of region70thereon, and in some embodiments, may include one or more of nickel, chromium, cobalt, iron, and alloys thereof (for example, an alloy including nickel and/or chromium). In general, any suitable material deposition process (CVD, PVD, sputtering, plating, etc.) may be used to form an overlying region on the corresponding underlying region (e.g., region70on region80, region60on region70, etc.). Since such processes are well known in the art, they are not discussed herein.

As explained above, regions30and70may serve as a “fixed” magnetic region, and region50may serve as a “free” magnetic region of magnetoresistive stack100. That is, a magnetic moment vector in a “fixed” region30,70does not move significantly in response to applied magnetic fields (e.g., an external field) or applied currents used to switch the magnetic moment vector of “free” region50, as explained above. Regions30,50,70are illustrated as a single layer inFIG. 1only for the ease of illustration. As explained previously, in some embodiments, each of these regions (e.g., regions30,50,70) may comprise several layers of a magnetic or a ferromagnetic material formed one on top of another. In addition, regions30,50, and70may also include additional layers, including, but not limited to, an antiferromagnetic coupling layer, a reference layer, and/or a transition layer.

In some embodiments, regions30,70may include alloys that include cobalt and iron, and preferably, boron. In some embodiments, one or both of these layers may also include, for example, alloys or engineered materials with one or more of palladium, platinum, magnesium, manganese, and chromium. Additionally or alternatively, in some embodiments, one or both of the regions30,70may comprise synthetic antiferromagnetic (SAF) or synthetic ferromagnetic (SyF) structures. Since SAFs and SyFs are known to those skilled in the art, additional description is omitted for the sake of brevity. In some embodiments, one or both of the regions30,70may include one or more non-magnetic material layers. For example, ruthenium, copper, aluminum, tantalum, titanium, niobium, vanadium, zirconium, iridium, one or more alloys of these elements, and in certain embodiments, tungsten and molybdenum. In some embodiments, one or both of the regions30,70may include a multi-layer structure of cobalt and platinum or cobalt and nickel (with or without other alloying elements). For example, in embodiments where regions30and/or70comprises a multi-layer structure of cobalt and platinum, the regions30and/or70may include a cobalt layer followed by a platinum layer formed on or above a surface of the cobalt layer. In general, regions30,70may have any thickness (e.g., between approximately 8-300 Å).

Region50(which, as explained above, may function as the “free” magnetic region of the magnetoresistive stack100) may be constructed such that a magnetic vector (or moment) in this region may be moved or switched by applied magnetic fields or currents (e.g., a spin-torque current). As with conventional magnetoresistive stacks/structures, the direction of the magnetization (i.e., the magnetic vector/moment) in region50determines the resistance of magnetoresistive stack100. Similar to regions30and70, region50may also comprise one or more ferromagnetic layers. Region50may include alloys of one or more of ferromagnetic elements, such as, nickel, iron, and cobalt. In some embodiments, one or more these layers also may also include boron. In some embodiments, additional elements may be added to the alloys to provide improved magnetic, electrical, or microstructural properties.

In some embodiments, region50may comprise multiple ferromagnetic layers separated by one or more intermediate layer(s) between the ferromagnetic layers. The ferromagnetic layers may include alloys of Co, Fe, and B, and the intermediate layer(s) may include a nonmagnetic material (e.g., tantalum, tungsten, molybdenum, ruthenium, rhodium, rhenium, iridium, chromium, osmium, vanadium, zirconium, titanium, niobium, molybdenum, hafnium, manganese, and their combinations) that provides coupling (e.g., ferromagnetic or antiferromagnetic coupling) between two adjacent ferromagnetic layers. In some embodiments, the thickness and/or the configuration of the intermediate layer(s) may be selected such that it does not form a continuous layer separating (and thus breaking direct electron exchange between) the adjacent ferromagnetic layers. Instead, the intermediate layer(s) may form a non-continuous layer (e.g., areas or patches of material) between the adjacent ferromagnetic layers. In some embodiments, the material of an intermediate layer may mix with the materials of the adjacent ferromagnetic layers to form a continuous region50(e.g., having a chemical composition that varies across the thickness of the region) so that adjacent ferromagnetic layers are directly exchange coupled to each other. In general, region50may have any thickness (e.g., between approximately 7-40 Å), and the thickness of the intermediate layer (if any) may typically be less than approximately 3.5 Å.

One or more layers of region50also may include alloys or engineered materials with one or more of, for example, palladium, platinum, magnesium, manganese, and chromium. In some embodiments, similar to regions30and70, region50also may include one or more SAF or SyF structures, and one or more layers of non-magnetic materials, such as, for example, ruthenium, copper, aluminum, tantalum, titanium, niobium, vanadium, zirconium, iridium, tungsten, molybdenum, and alloys thereof. In some embodiments, one or more layers of the region50also may include ordered L10 alloys (such as, for example, Iron-Platinum (FePt), Iron-Palladium (FePd), Cobalt-Platinum (CoPt), or Iron-Nickel-Platinum (FeNiPt)), artificial multi-layered structures (such as, Cobalt/Platinum (Co/Pt), Cobalt/Palladium (Co/Pd), Cobalt-Chromium/Platinum (CoCr/Pt), Cobalt/Gold (Co/Au), or Nickel/Cobalt (Ni/Co)), and alloys of Cobalt-Iron-Boron (CoFeB). These materials may provide a strong perpendicular magnetic anisotropy (PMA) to region50and may improve the performance of magnetoresistive stack100. As explained previously, any suitable deposition process may be used to form regions30,50,70. In some embodiments, some or all of these regions (or one or more layers that make up these regions) may be deposited using a “heavy” inert gas (for example, xenon, argon, krypton, etc.), for example, at room temperature (for example, 15-40° C., and more preferably 20-30° C., and most preferably 25° C. (+/−10%)) or at a conventional/typical elevated temperature.

With continued reference toFIG. 1, an intermediate region60may be positioned between regions70and50, and an intermediate region40may be positioned between regions50and30. In some embodiments, the intermediate regions40,60may include a dielectric material, and may function as a tunnel barrier in the magnetoresistive stack100. However, it is also contemplated that, one or both of the intermediate regions40,60may include a conductive material (e.g., copper) to form a GMR-type magnetoresistive stack/structure. In general, intermediate regions40,60may be formed using any technique now known (e.g., deposition, sputtering, evaporation, etc.) or later developed. In some embodiments, one or both of intermediate regions40,60may include an oxide material, such as, for example, Magnesium Oxide (MgO) or Aluminum Oxide (AlOx) (e.g., Al2O3), and may be formed by multiple steps of material deposition and oxidation. In general, the intermediate regions40,60may have any thickness (e.g., between approximately 8.5-14.1 Å).

Although not illustrated inFIG. 1, in some embodiments, region70(and/or region50) may include one or more interfacial regions (e.g., a transition layer, a reference layer, etc.) disposed at its interface with intermediate region60(and/or region40, respectively). These interfacial regions may include one or more layers of material that, among other things, facilitate/improve growth of the intermediate region60(and/or40) during fabrication. In one embodiment, the interfacial region between regions70and60(and/or regions50and40) may include one or more layers of an amorphous alloy (e.g., CoFeB or CoFeBTa or CoFeTa) and one or more layers of a non-ferromagnetic transition metal (e.g., tantalum, titanium, tungsten, ruthenium, niobium, zirconium, and/or molybdenum). In some embodiments, during processing, a layer of iron (for example, deposited as pure or substantially pure iron) and a layer of cobalt, iron, and boron (for example, deposited as an alloy) may be deposited on the top surface (with reference toFIG. 1) of region70. After further/final processing (e.g., after annealing), the layer of iron at the interface between regions70and60may form a continuous atomic layer, or may mix with the underlying ferromagnetic alloy of region70in the final annealed structure, resulting in a high-iron concentration in region70at its interface with region60.

With continued reference toFIG. 1, region20may be provided (deposited, grown, sputtered, etc.) on or above region30, and region10may be provided on or above region20. As explained previously, region20may be formed of a material, such as, for example, tantalum, titanium, tungsten, or a composite or alloy of these elements (e.g., tantalum-nitride alloy), and in some embodiments, region20may be eliminated altogether. Region10, in some embodiments, may serve as a hard mask to assist in the subsequent processing (etching, patterning, etc.) of the magnetoresistive stack100. That is, region10may protect the underlying regions from reactive compounds and gases used in the subsequent processing (e.g., etching) of magnetoresistive stack100. Region10may be formed or deposited using any now known or later developed technique. In some embodiments, region10may include silicon oxide, silicon nitride, and/or another material that is relatively inert to the reactants used during subsequent processing.

In some embodiments, region10may include one or more metals (e.g., region10may be a metal hard mask). Suitable metals for region10may include, for example, noble metals and/or alloys thereof, for example, alloys of a noble metal with transition metals (for example, Platinum (Pt), Iridium (Ir), Molybdenum (Mo), Tungsten (W), Ruthenium (Ru), and/or an alloy of AB (where A=Pt, Ir, Mo, W, Ru and B=Fe, Ni, Manganese (Mn)). In some embodiments, region10may be comprised of materials such as, Titanium-Nitride (TiN), Platinum Manganese (PtMn), or Iridium-Manganese (IrMn). In some embodiments, region10may include multiple layers of material formed one atop another. For example, in some embodiments, region10may include TiN over PtMn and/or IrMn. In some embodiments, region10may be formed by a material harder than an ultralow K dielectric material used in the magnetoresistive stack100. In general, region10may have any thickness. In some embodiments, the thickness of region10may be in the range of approximately 5-200 Å. In some embodiments, region10may be, for example, approximately 15-150 Å thick, or preferably approximately 20-100 Å thick.

When implemented in an MTJ-like memory device, magnetoresistive stack100ofFIG. 1may be referred to as having a dual spin filter (DSF) structure with a first MTJ comprising regions70,60, and50, and a second MTJ comprising regions30,40, and50. In some embodiments of the present disclosure, a magnetoresistive stack may only include a single MTJ.FIG. 2illustrates an exemplary magnetoresistive stack200having a single MTJ comprising regions70,60, and50. The regions of magnetoresistive stack200which are similar to the regions of the MTJ formed by magnetoresistive stack/structure100(ofFIG. 1) are numbered similarly, and not described again for the sake of brevity. As illustrated inFIG. 2, in some embodiments, a interfacial region45may be provided at the interface between regions50(which, as explained above with reference toFIG. 1, may serve as the “free” region) and region20(which may be an electrode of MTJ200). Region45may serve as a capping region, and may comprise one or more layers of a dielectric material (e.g., MgO, Al2O3, etc.). In some embodiments, the interfacial region45may have a thickness between approximately 3-14 Å. Although not illustrated inFIG. 2, some embodiments of the described magnetoresistive stacks may additionally include a discontinuous layer of an insertion material at the interface between region50and the interfacial region45. This insertion material may be a dusting (e.g., non-continuous patches or areas) of any non-ferromagnetic transition metal element (e.g., Ir, Cr, etc.) having a thickness of less than one atomic layer of the material selected. The insertion material may increase the PMA of the resulting magnetoresistive stack200. Although the interfacial region45ofFIG. 2and the insertion material are not illustrated inFIG. 1, in some embodiments, magnetoresistive stack100ofFIG. 1may also include a similar interfacial region and an insertion material.

The exemplary stacks/structures100,200ofFIGS. 1 and 2, and the method of fabricating these stacks/structure are described herein as illustrative examples. Many other stacks or structures are possible. Some other exemplary magnetoresistive stacks and fabrication methods are described in U.S. Pat. Nos. 8,686,484; 8,747,680; 9,136,464; and 9,419,208, each assigned to the assignee of the current application and incorporated by reference in its entirety herein. Each of these stacks/structures may be used in connection with the current disclosure. Further, as explained previously, although a magnetoresistive stack/structure is used to describe aspects of the current disclosure, the disclosure is not limited thereto. Instead, the current disclosure may be applied in the fabrication of any integrated circuit device structure.

After the multi-layer magnetoresistive stack100ofFIG. 1(or magnetoresistive stack200ofFIG. 2) is formed, the multi-layer structure may be etched to form one or more magnetoresistive devices in a desired pattern. The magnetoresistive device may include, but are not limited to, magnetic tunnel junction bits, such as, e.g., MTJ bits120. These MTJ bits120may be further processed to form the desired magnetoresistive device, such as, e.g., an MTJ device.FIG. 3illustrates the magnetoresistive stack100ofFIG. 1etched in an exemplary pattern to form multiple MTJ bits120at a desired pitch by etching etched-regions110between the bits120. Though the MTJ bits120and/or etched-regions110depicted inFIG. 3appear to have substantially uniform vertical sidewalls, those of ordinary skill in the art that the sidewalls may include one or more irregularities. Any known (or later developed) etching process may be used to etch through the different regions of the magnetoresistive stack100(ofFIG. 1) to form the MTJ bits120ofFIG. 3. In some embodiments, after deposition of region10(e.g., the hard mask layer), a photo resist may be deposited thereon, and patterned to predetermined dimensions consistent with, or correlated to, the desired dimensions of the MTJ bits120(ofFIG. 3). The photo resist may be deposited and patterned using any now known or later developed technique (e.g., well known conventional deposition and lithographic techniques). Region10(e.g., the hard mask layer) may then be etched using a suitable etching technique (e.g., for example, physical etching, such as, sputter etching, ion beam etching or milling, reactive ion beam etching or milling, etc.) to transfer the photo resist pattern to region10(e.g., remove region10from areas above the etched-regions110). Although not required, in some embodiments, the photo resist may be removed or stripped from the magnetoresistive stack100(e.g., from above region10using conventional techniques) after region10is patterned and/or before subsequent processing of magnetoresistive stack100.

The multiple regions of the magnetoresistive stack100may then be etched with region10“protecting” or masking the areas covered by remaining portions of region10, to form, define, pattern and/or provide the MTJ bits120separated by etched-regions110(seeFIG. 3). The multiple regions (20,30,40,50,60,70,80) of the magnetoresistive stack100may be etched by any suitable process now known or developed in the future (e.g., physical etching, etc.). In some embodiments, an ion beam (comprising Argon, Krypton, Xenon, etc.) may be used to sputter etch through the multiple regions of the magnetoresistive stack100and form the etched-regions110. In some embodiments, reactive ion beam etching (ion beam of a reactive species) may be used for form the etched-regions110. During ion beam etching, as known to those of ordinary skill in the art, the magnetoresistive stack100, with selected areas covered by patterned region10, may be placed in a vacuum chamber, and exposed to an ion beam (a reactive ion beam, in some embodiments). The ion beam may be substantially normal (or perpendicular) to a surface of the magnetoresistive stack100that is being etched or may make a small angle with respect to an axis normal to the surface. For example, with reference toFIG. 3, in some embodiments, the ion beam used to etch the etched-regions110may make an angle θ between about 0 and less than about 30° (0°≤θ≤30°) or between about 0-20° (0°≤θ≤20°) with respect to a normal axis105of magnetoresistive stack100. To distinguish the etching process used to etch etched-regions110from an “angled etch” process described below, the etching process used to etch etched-regions110may be referred to as straight etching or as a “straight etch” process. As known to a person of ordinary skill in the art, during ion beam etching, the impact of the ions ablates the areas of the stack not covered by region10. In some embodiments, region10may not be patterned prior to etching the regions underlying region10. Instead, a mask (e.g., a photoresist mask) may be used to selectively etch through the multiple regions of the stack including region10.

During the etching process, a portion of the ablated material may be redeposited on the side walls of the MTJ bits120(e.g., as a veil) to form a redeposited layer130. The redeposited layer130may include nonvolatile byproducts of the multiple regions (20,30,40,50,60,70,80) that are removed (or ablated) by the etching process. The redeposited layer130may include both magnetic and non-magnetic materials from the different regions. Due to the ferromagnetic and other electrically conductive materials in some of the removed regions (e.g., regions20,30,50,70,80, etc.), the redeposited layer130may be electrically conductive and/or magnetically active. The redeposited layer130, may in some cases, also detrimentally affect the resistance and magnetic property distribution within an array of MTJ bits120. To prevent electrical shorting between the multiple regions along the thickness of MTJ bit120(e.g., regions80and20,30and70, etc.), and to preserve the magnetic property distribution in the MTJ bit array, in some embodiments, the side walls of the bits may be etched (or otherwise cleaned) to remove at least a portion of the redeposited layer130after etching the etched-regions110or portions thereof. The side walls of an MTJ bit120may be etched (or otherwise cleaned) by any suitable now-known or future-developed process.

In some embodiments, an angled etch process, (e.g., an etch process utilizing angled ion beam relative to the wafer or the wafer may be tilted with respect to the ion beam) is directed into the etched-region110(e.g., as shown inFIG. 4B) to etch away the redeposited layer130from the side walls of the MTJ bits120. In general, as illustrated inFIG. 4B, during the angled etch process, the ion beam may be tilted more with respect to normal axis105than during straight etching. That is, angle θ during angled etching may be greater than the angle θ during straight etching. For example, in some embodiments, during the angled etch process, the ion beam may be tilted at any angle θ between about 30° and less than about 90° with respect to normal axis105or (30°≤0<90°). In some embodiments, during the angled etching, θ may be greater than or equal to about 30° and less than or equal to about 60° (30°≤θ≤60°), or 30°≤θ≤70°. It should be noted that although the ion beam is described as being tilted with respect to normal axis105in the description above, this is only exemplary. In some embodiments, during angled etching, instead of (or in addition to) tilting the ion beam, the wafer with the magnetoresistive stack100may be tilted. With increasing height and/or decreasing pitch of the MTJ bits120, it may be hard to remove portions of the redeposited layer130towards the bottom of the etched-region110using such aforementioned angled etch processes (or other similar processes). In some cases, the resulting remaining redeposited layer130on the side walls may have the potential to cause electrical shorts (and/or other variations in the magnetic property distribution) of MTJ bits120. Therefore, in some embodiments, the process of etching the etched-regions110to form the MTJ bits120may be modified according to the principles described.

In some embodiments, after forming the magnetoresistive stack100(seeFIG. 1), a plurality of the regions, but less than all of the regions, of the magnetoresistive stack100may be etched to form a partially etched MTJ bit or a partial MTJ bit120′.FIG. 4Aillustrates an exemplary partial MTJ bit120′ formed by terminating the etching process at an interface of region60(which, as previously explained, may be a dielectric material that functions as a tunnel barrier in a completed MTJ device) or within region60. The partial MTJ bit120′ may be formed by any etching process. In some embodiments, the partial MTJ bit120′ may be formed by an ion beam etch process as described above with reference to MTJ bit120ofFIG. 3(e.g., a straight etch process). Any known process may be used to terminate the etch process at region60. In some embodiments, the etch process (i.e., the process used to partially etch the magnetoresistive100and form a partial etched-region110′) may be time and/or endpoint controlled or monitored. In one embodiment, the etch process may be stopped when endpoint monitoring detects the presence or absence of a predetermined material (or a combination of materials) at the bottom of the etched-region. That is, in the etch process used to etch the partial etched-region110′ ofFIG. 4A, the etch process may be terminated upon detecting the material (e.g., a dielectric material) of region60to stop the etch at the beginning of region60. The presence of region60may be detected during etching by any suitable mechanism. In some embodiments, the material of region60may be detected based on optical emission spectra (OES). That is, the etch process may be terminated when a rise in OES signal for the material of region60is detected. Here, the etch process terminates at the beginning of region60before significant etching of region60occurs. In some embodiments, however, the etch process may be terminated when a significant drop in OES signal of the material of region50(i.e., the region above region60) is detected. Here, the etch process terminates immediately above region60after substantially all of region50is etched. In some embodiments, the etch process may be continued for limited duration after etching of region60begins so as to terminate the etching process within region60. Those of ordinary skill in the art will readily recognize that the process of forming etched-regions110′ may be terminated at or within any region10,20,30,40,50,60,70, or80of magnetoresistive stack100. For example, the process of forming etched-regions110′ may be terminated at or within intermediate layer40.

As described with reference toFIG. 3, as a result of the etching process, a portion of the etched material may be redeposited on the side walls of the partial MTJ bits120′ to form a redeposited layer130′ (see, e.g.,FIG. 4A). The height of the redeposited layer130may be substantially uniform around the bits (as illustrated inFIG. 3) or may be different (as illustrated inFIG. 4A). The variability in the height of the redeposited layer130(around a bit and between different bits) may result from a variability in the spacing between the bits or variability in the underlying structure. In some embodiments, as illustrated inFIG. 4B, the redeposited layer130′ may be at least partially removed by a suitable process, such as, for example, angled ion beam etching, as described above. Due to the reduced depth of the partial etched-region110′ (as compared to etched-region110ofFIG. 3), a greater depth of the redeposited layer130can be removed from the side wall of the partial MTJ bit120′ than from the side wall of the MTJ bit120ofFIG. 3. In some embodiments, substantially all of the redeposited layer130may be removed from the side wall of the partial MTJ bit120′ by an angled ion beam etch. However, in some embodiments, as illustrated inFIG. 4B, a relatively small height of the redeposited layer130may remain on the side wall of MTJ bit120′. In some embodiments, the step of etching or otherwise “cleaning” of the side walls of MTJ bit120′ may be eliminated altogether. That is, all of the redeposited layer130formed during the formation of the partial MTJ bit120′ may remain on its side walls.

In some embodiments, in addition to removing a portion of the redeposited layer130or instead of removing any of the redeposited layer, the redeposited layer130on the side wall of the partial MTJ bit120′ may be subjected to a chemical process to render the redeposited layer130electrically nonconductive (e.g., to passivate the redeposited layer130). The partial MTJ bit120′ may be subjected to any known chemical process (e.g., oxidation, nitridization, etc.) to render the redeposited layer130nonconductive. In some embodiments, after etching partial etched-regions110′ using straight etching to form partial MTJ bits120′ with redeposited layers130on their side walls, the partial MTJ bits120′ may be plasma oxidized (or passivated) by exposing the partial MTJ bits120′ to an active oxygen plasma to oxidize the redeposited layers130and render them electrically nonconductive. In some embodiments, an angled etch process may be carried out to remove at least a portion of the redeposited layers130on the side walls of the partial MTJ bits120′ before subjecting the cleaned partial MTJ bits120′ to an oxygen plasma (or another chemical process) to render any remaining redeposited layers130on the side walls nonconductive. In some embodiments, one of the angled etch process to remove the redeposited layer130or the chemical process to make the redeposited layer130nonconductive may be eliminated.

With reference now toFIG. 4C, in some embodiments, a first encapsulant140may be deposited on the partially formed MTJ bit120′, including its side walls, and within etched-regions110′. First encapsulant140may partially, substantially, or completely fill etched-regions110′. In some embodiments, a layer of first encapsulant140may be deposited on all, or substantially all, of the exposed portions of the partially formed stack/structure. Any suitable process (e.g., CVD, ALD, etc.) may be used to deposit the first encapsulant140. The first encapsulant140may, in general, include any electrically non-conductive material. In some embodiments, silicon nitride (e.g., Si3N4, SiN, etc.) or silicon oxide (e.g., SiO2, SiOx, etc.) may be used as the first encapsulant140. However, other materials such as, for example, aluminum oxide (such as Al2O3), magnesium oxide (such as MgO), a tetraethoxysilane (TEOS), and/or one or more combinations thereof, may also be used as the first encapsulant140. In some embodiments, the first encapsulant140may be initially deposited as a conductor (for example, a metal such as aluminum or magnesium), and thereafter oxidized or nitridized to change or transform at least a portion of the material to an insulative material. In general, the first encapsulant140may have any thickness. In some embodiments, the thickness of the first encapsulant may be between about 10-500 Å, preferably between about 50-300 Å, and more preferably between about 100-300 Å.

The first encapsulant140coating on the partial MTJ bit120′ may then be used as a spacer or a mask to etch the remainder of the stack at the base of the partial etched-region110′. In some embodiments, the remainder of the stack may be etched without additional photoresist patterning (i.e., by only using the deposited first encapsulant140as a mask or guide).FIG. 4Dis a cross-sectional schematic illustration of magnetoresistive stack100after the remainder of the regions (e.g., regions60,70, and80) of the stack at the base of the partial etched-region110′ (seeFIG. 4C) have been etched to form multiple complete MTJ bits120(only one shown inFIG. 4D) separated by etched-regions110. Any suitable etch process (e.g., straight etching) may be used for the etching. In some embodiments, a physical etching process (e.g., ion beam etching, reactive ion beam etching, etc.), similar to that used to create the partial etched-region110′ (ofFIG. 4A) may be used as the etch process. During the etching, the first encapsulant140, deposited on the base of the partial etched-region110′ (seeFIG. 4C) may be first ablated and removed before the underlying regions (e.g., regions60,70, and80) at the base of the partial etched-region110′ are removed. At the end of this subsequent etching process, some (in some cases, substantially all) of the first encapsulant140covering the side walls and the top of the partial MTJ bit120′ may also be removed. However, the first encapsulant140covering the partial MTJ bit120′ during the etching may prevent significant ablation of the underlying regions of the partial MTJ bit120′. In some embodiments, the first encapsulant140at the base of the partial etched-region110′ may be removed in an optional etching or cleaning step prior to etching the regions (e.g., regions60,70, and80) of the stack100at the base of the partial etched-region110′ (i.e., prior to etching step ofFIG. 4D). Any suitable process, such as physical etching, may be used to selectively etch the first encapsulant140at the base of the partial etched-region110′. In some embodiments, this optional etching or cleaning step may be eliminated. In some embodiments, the step of depositing the first encapsulant140on the partially formed MTJ bit120′ may be eliminated, and the remainder of the stack at the base of the partial etched-region110′ may be etched without covering the partial MTJ bit120′ with first encapsulant140. For example, in some embodiments where the redeposited layer130on the side walls of the partial MTJ bits120′ are oxidized or passivated, the first encapsulant140may be eliminated since the redeposited layer130is electrically nonconductive.

As illustrated inFIG. 4D, a portion of the etched material (from the regions of the stack at the base of the partial etched-region110′) may be redeposited on the side walls of the etched-region to form a second redeposited layer130′. However, because of the lower number of regions etched (e.g., regions60,70, and80), any such redeposition may not be tall or large enough to cause electrical shorting issues, or to change the magnetic behavior of MTJ bit120. Further, the first encapsulant140layer may be configured to electrically isolate the two redeposited layers130and130′, thereby reducing the likelihood of electrical shorting amongst the various regions or layers of MTJ bit120. In embodiments where a first encapsulant140is not used (e.g., to cover the partially formed MTJ bit120′), passivating any remaining redeposited layers130on the side walls of the partial MTJ bits120′ may assist in electrically isolating the two redeposited layers130and130′. In some embodiments, some or all of the second redeposited layer130′ may be removed using any suitable process, including, but not limited to, the angled etch processes described above. In some embodiments, the second redeposited layer130′ may not be removed, and may remain on the side walls of the etched-region. In some embodiments, as an alternative to or in addition to removing the second redeposited layer130′, the MTJ bit120may be subjected to a chemical process to passivate or render the redeposited layer130′ electrically nonconductive. AlthoughFIG. 4Ddepicts that second redeposited layer130′ may extend only partially along the height of MTJ bit120, those of ordinary skill in the art will understand that second redeposited layer130′ may extend substantially along the height of MTJ bit120, including, e.g., over first encapsulant140.

Turning now toFIG. 4E, a second encapsulant150may then be deposited on the MTJ bit120to form a conformal coating over the exposed regions of the bit120(including the side walls) and the first encapsulant140. The second encapsulant150may include any electrically conductive material. In some embodiments, the second encapsulant150may include any material previously described with respect to the first encapsulant140. In some embodiments, similar to the first encapsulant, the second encapsulant may also be deposited as a conductive material that may then be converted (i.e., oxidized, nitridized, etc.) to an insulative material. In some embodiments, both the first encapsulant140and the second encapsulant150may include the same material. In general, the second encapsulant150may have any thickness. In some embodiments, the thickness of the second encapsulant150may be between about 10-500 Å, preferably between about 50-300 Å, and more preferably between about 100-300 Å. In some embodiments, the second encapsulant150may be deposited so as to only partially fill etched-regions110, as depicted inFIG. 4D. In other embodiments, second encapsulant150may completely or substantially completely fill etched-regions110in between the multiple MTJ bits120.

After the MTJ bits120are formed as described above, additional processing steps (such as, for example, polishing a top surface of the structure to expose a conductive region of the MTJ bits120, and forming a bit contact structure on the exposed regions of the MTJ bits120to make electrical contact with these MTJ bits120, etc.) may be performed to fabricate an MTJ device from the MTJ bits120. Since these additional processing steps are known to those of ordinary skill in the art, they are not described herein for the sake of brevity.

It should be noted that, although an embodiment with a single cleaning step (e.g., angled etching) is described above, this is only exemplary. In some embodiments, the method of forming MTJ bits120may include multiple etching and cleaning steps. For example, the method may include multiple alternate straight and angled etching steps to progressively etch away the regions (e.g., regions10,20,30,40, etc.) of magnetoresistive stack100and clean the redeposited material formed in the process. In some embodiments, a straight etch process may be carried out for a fixed time (e.g., 10 seconds, 20 seconds, 30 seconds, etc.) followed by an angled etch process for the same or a different fixed time. In some embodiments, the etching may be stopped based on the appearance or disappearance of some species in the plasma (e.g., in an OES signal). In some embodiments, the method may include multiple alternate straight etching and chemical processing (e.g., plasma oxidation) steps to progressively etch away regions (10,20,30,40, etc.) of magnetoresistive stack100and passivate any redeposited material formed on the side walls of the partial MTJ bit in the previous etching step. In some embodiments, after forming a partial MTJ bit by etching some regions and cleaning and/or passivating the redeposited layer formed in the process, an encapsulant (e.g., first encapsulant140) may be deposited over the cleaned partial MTJ bit before etching additional regions of the stack100.

It should be noted that, although the method of forming MTJ bits120are described with reference to magnetoresistive stack100ofFIG. 1, a similar process may also be used to form magnetoresistive bits from other exemplary magnetoresistive stacks (such as, for example, magnetoresistive stack200ofFIG. 2, the magnetoresistive stacks disclosed in U.S. Pat. Nos. 8,686,484; 8,747,680; 9,023,216; 9,136,464; and 9,419,208, the disclosures of which are incorporated by reference herein).

FIGS. 5A-5Eillustrate an exemplary process of forming magnetoresistive devices, such as, e.g., MTJ bits220, from the magnetoresistive stack200ofFIG. 2. Since manufacturing operations (etching, deposition, etc.) similar to those discussed above (i.e., with reference to the fabrication of MTJ bits120from magnetoresistive stack100) may be used to fabricate MTJ bits220, these manufacturing operations are not extensively described again below.

After forming magnetoresistive stack200ofFIG. 2, multiple regions (e.g., regions10,20,45, and50) of magnetoresistive stack200may be etched to form a plurality of partial MTJ bits220′ (only one shown inFIG. 5A) separated by partially etched-regions210′. Although in general, the etch process may be stopped at or within any region of magnetoresistive stack200, in some embodiments as illustrated inFIG. 5A, the etch process may be terminated at the beginning of region60(e.g., before significant etching of region60occurs). As described with reference toFIG. 4Aabove, the etch process may be terminated at region60when, e.g., OES monitoring begins to detect signals corresponding to the material of region60. As a result of the etching process, a portion of the etched material may be redeposited on the side walls of the partial MTJ bit220′ as a redeposited layer230. In some embodiments, as illustrated inFIG. 5B, the redeposited layer230may be at least partially removed by angled ion beam etch or another suitable process. In some embodiments, this redeposited layer removal step may be eliminated, and the redeposited layer230may be left on the side walls. In some embodiments, any remaining redeposited layer230on the side walls of the partial MTJ bit220′ may be rendered electrically nonconductive by subjecting the partial MTJ bit220′ to a suitable chemical process (such as, for example, oxidation, nitridization, etc.).

Turning now toFIG. 5C, a first encapsulant240may then be deposited to coat the partially formed MTJ bit220′, including the side walls of MTJ bit220′. The first encapsulant240may be similar in material composition and thickness to the previously described first encapsulant140. The layer of first encapsulant240on the partial MTJ bit220′ may then be used as a spacer to etch the remainder of magnetoresistive stack200(e.g., regions60,70, and80) at the base of the partial etched-region210′. As explained with reference toFIG. 4Dabove, in some embodiments, the remainder of magnetoresistive stack200may be etched without additional photoresist patterning (e.g., by only using the deposited first encapsulant240as a mask). In some embodiments, first encapsulant240may not be deposited and the remainder of magnetoresistive stack200may be etched without using first encapsulant240as a mask (e.g., by using a photoresist).

FIG. 5Dillustrates magnetoresistive stack200after the remainder of the regions (e.g., regions60,70, and80) at the base of the partial etched-region210′ have been etched to form multiple MTJ bits220separated by etched-regions210. As illustrated inFIG. 5D, a portion of the etched material (from the regions of the stack at the base of the partial etched-region210′) may be redeposited on the side walls of the etched-region to form a second redeposited layer230′. However, as discussed previously with reference to the processing of magnetoresistive stack100, the second redeposited layer230′ may not cause shorting issues and may be left on the side walls. Nevertheless, in some embodiments, the second redeposited layer230′ may be removed in an optional angled etch or another suitable process, or may be passivated by subjecting the MTJ bits220to a suitable chemical process.

Next, a second encapsulant250may be deposited on the MTJ bit220and within etched-regions210′, as illustrated inFIG. 5E, to form a conformal coating over the exposed regions of the bit220and the first encapsulant140. The second encapsulant250may be similar in material composition and thickness to the second encapsulant250. Further, the second encapsulant250may partially, substantially, or completely fill etched-regions210′.

In the description above, two etching steps (i.e., a dual etch process) are used to create MTJ bits120′ and220′. That is, in a first etching step (partial etching step), partial bits120′,220′ are formed by removing some of the regions (that is, less than all of the regions) of the described magnetoresistive stacks to form a partial etched-region110′,210′ around the partial bits120′,220′. And, in a second etching step, the remainder of the regions of the described magnetoresistive stacks are removed from the base of the partial etched-region110′,210′ to form the completed MTJ bits120,220. However, such a dual etch process is not a requirement. In general, the MTJ bits120and220may be formed using any number of etching steps, including, e.g., a single step etch process. For example, with reference to magnetoresistive stack100ofFIG. 1, in some embodiments, in a first partial etching step, only regions10,20, and30may be removed to form a plurality of partial MTJ bits120″ separated by partial etched-regions110″. That is, the first etching step may be terminated at the beginning of, or within, region40using, for example, OES signals during etching. Note that, in a completed MTJ device, region40may comprise a dielectric material that serves as a tunnel barrier. In some embodiments, any redeposited layer formed on the sidewalls may be removed or “cleaned” (using, for example, angled etch, etc.), and a first encapsulant140may be applied over the partial MTJ bits120″ to cover them. In some embodiments, the step of cleaning the redeposited layer may be eliminated.

FIG. 6Aillustrates a schematic view of the partial MTJ bits120″ covered or coated by the first encapsulant140. The first encapsulant140coating on these partial MTJ bits120″ may then be used as a spacer to etch addition regions (e.g., regions40-80) of the stack at the base of the partial etched-regions110″ in one or more additional partial etch steps. For example, as illustrated inFIG. 6B, a second etch step may be used to remove only regions40and50(i.e., by terminating the second etch at the beginning of, or within, region60) from the base of the partial etched-region110″ to form partial MTJ bits120″ separated by partial etched-regions110″. Note that, in a completed MTJ device, region60may also comprise a dielectric material that serves as a tunnel barrier. In some embodiments, regions40and50may be etched by only using the deposited first encapsulant140as a mask (i.e., etched without additional photoresist patterning).

A second encapsulant150may then be deposited on the partial MTJ bits120″ (seeFIG. 6B). The second encapsulant150may partially, substantially, or completely fill etched-regions110″. A third etch step may then be used to etch the remainder of the regions of the stack (e.g., regions60,70, and80) at the base of the partial etched-region110″ to form MTJ bits120″ separated by etched-regions110″. As illustrated inFIG. 6C, a third encapsulant160may then be used to coat the MTJ bits120. Any of the previously described materials for the first and second encapsulants may be used as the first, second, and third encapsulants140,150, and160ofFIG. 6C. As illustrated inFIGS. 6A-6C, each of the etching steps may result in some of the etched material being redeposited as a redeposited layer130,130′, or130″ on the side walls of the resulting etched structure. In some embodiments, some or all of these redeposited layers,130′, or130″ may be removed (e.g., by using an angled etch or another suitable process) prior to depositing the next encapsulant material. However, in some embodiments, these redeposited layers130,130′, or130″ may not be removed. Since a height of the redeposited layers130,130′, or130″ within an associated etched-region110″ is expected to be small, and since the redeposited layers130,130′, or130″ are electrically separated from each other by the described encapsulants, they are not expected to cause electrical shorting or magnetic issues if they are not removed from the side walls of MTJ bit120″. In some embodiments, some or all of redeposited layers130,130′, or130″ on the side walls may be rendered electrically nonconductive by subjecting the MTJ bits120″ to a suitable chemical process (such as, for example, oxidation, nitridization, etc.).

In the description above, the etching steps used to create the partial MTJ bits120′,120″, and220′ are described as being terminated at the beginning of a region (i.e., at the beginning of region60in the embodiments ofFIGS. 4A and 5A, and the beginning of regions40and60in the embodiments ofFIGS. 6A and 6B). However, this is not a requirement. In general, the etching steps may be terminated anywhere in the region. For example, as illustrated inFIG. 7A, in some embodiments, the etch step used to create the partial MTJ bits120′ ofFIG. 4Amay be stopped within region60(e.g., approximately 10%, 20%, 30%, 50%, 60%, 70%, 80%, 90%, etc. into the thickness of region60). In embodiments where OES is used to determine when to terminate the etch step, the etch step may be terminated based on the strength of the OES signals (e.g., by comparing the strength of the OES signals corresponding to the materials of region60to a threshold value, etc.). In some embodiments, as illustrated inFIG. 7B, the etch step (ofFIG. 4A) may be terminated at or proximate the end of region60. That is, for example, when OES indicates a predetermined reduction in the strength of the signals corresponding to the materials of region60. It is also contemplated that, in some embodiments, the etch step (illustrated inFIG. 7B) may only be stopped at the beginning of region70(i.e., after all of region60has been etched). As described previously, after forming the MTJ bits120,220using the above-described fabrication processes, further processes may be carried out to form MTJ devices.

It should be noted that, although the partial etch or the first etch in the embodiments described above (seeFIGS. 4A, 5A, 6B, etc.) is terminated at region60(at the beginning of region60, within region60, at the end of region60, immediately after region60, etc.), this is not a limitation. In general, the multiple etch steps described above can be terminated at any region (e.g., region50,60,70, etc.). However, when etching a multi-layer assembly comprising a plurality of electrically conductive and electrically insulating layers, terminating the partial etch at an electrically insulating layer may be advantageous because, after the magnetoresistive device (e.g., MTJ bit120ofFIG. 4E) is formed, the electrically insulating layer (e.g., region60ofFIG. 4E) separates and insulates from each other, the redeposited layers formed during the multiple etch steps and minimizes the likelihood of electrical shorting.

As explained above, in general, the partial etch step may be stopped anywhere in any region of the magnetoresistive stack. For example, in embodiments where the magnetoresistive stack is etched by subjecting the stack to alternating straight etching and angled etching (and/or chemical processing) steps (e.g., of a fixed duration), the location in the stack where the etch terminates may not be controlled. Instead, the straight etching process may be continued for a predetermined time (e.g., 10 seconds, 20 seconds, 30 seconds, 40 seconds, etc.). After straight etching for the predetermined time, the ion beam or the wafer may be tilted (e.g., such as, 30≥θ<90°, as shown inFIG. 4B), and angled etching continued for a predetermined time (the same or a different amount of time) to remove the redeposited layer on the side walls formed during the previous etching steps. Additionally or alternatively, after straight etching for a predetermined time, the wafer may be subject to a chemical process (e.g., plasma oxidation) to render the redeposited layer on the side walls electrically non-conductive. The straight etching process may then be continued by tilting the ion beam and or the wafer back such that angle θ is between about 0° and less than about 30° (seeFIG. 3).

As alluded to above, the MTJ devices (formed using MTJ bits120,220from MTJ stacks100,200) may include a sensor architecture or a memory architecture (among other architectures). For example, in an MTJ device having a memory configuration, the MTJ bits120,220may be electrically connected to an access transistor and configured to couple or connect to various conductors, which may carry one or more control signals, as shown inFIG. 8. The MTJ devices may be used in any suitable application, including, e.g., in a memory configuration. In such instances, the MTJ devices may be formed as integrated circuits comprising a discrete memory device (e.g., as shown inFIG. 9A) or an embedded memory device having a logic therein (e.g., as shown inFIG. 9B), each including MRAM, which, in one embodiment is representative of one or more arrays of MRAM having a plurality of magnetoresistive stacks/structures, according to certain aspects of certain embodiments disclosed herein.

An exemplary method of fabricating a selected embodiment of magnetoresistive device (e.g., an MTJ bit) will now be described. It should be appreciated that the described method is merely exemplary. In some embodiments, the method may include a number of additional or alternative steps, and in some embodiments, one or more of the described steps may be omitted. Any described step may be omitted or modified, or other steps added, as long as the intended functionality of the magnetoresistive device remains substantially unaltered. Although a certain order is described or implied in the described method, in general, the steps of the described method need not be performed in the illustrated and described order. Further, the described method may be incorporated into a process of fabricating an MTJ bit from the described magnetoresistive device. Since the additional steps needed to form MTJ bits are known to people skilled in the art, they are not described herein. Additionally, the described method may be incorporated into a more comprehensive procedure or process having additional functionality not described herein.

FIG. 10depicts a flow chart of an exemplary method300of fabricating a magnetoresistive device (e.g., an MTJ bit) from a magnetoresistive stack, e.g., magnetoresistive stack100described above. For the sake of brevity, the exemplary method will describe fabricating MTJ bit120(ofFIGS. 4A-4E) from magnetoresistive stack100(ofFIG. 1), referencing previously described aspects (materials, fabrication processes, dimensions, etc.) of these embodiments. A magnetoresistive stack may first be provided (step310). Providing the magnetoresistive stack may include sequentially depositing (and/or growing, sputtering, etc.) the multiple regions (of magnetoresistive stack100), and processing (e.g., annealing, etc.) the deposited regions to form magnetoresistive stack100. In some embodiments, this step may include using a magnetoresistive stack100that was previously formed. The method also includes partially etching through the thickness of the magnetoresistive stack100to form a partial magnetoresistive device, e.g., an MTJ bit (step320). In some embodiments, this step may include using known lithographic techniques (photoresist, photolithography, etc.) to expose selected regions of the magnetoresistive stack100, and etching through multiple regions of the stack (e.g., less than all the regions) to form a plurality of partial magnetoresistive devices, e.g., MTJ bits120′, separated by partial etched-regions110′ (seeFIG. 4A). Etching may be performed using any suitable technique (for example, straight etching using physical etching such as ion beam etching, reactive ion beam etching, etc.). In some embodiments, the partial etch of step320may be terminated at the beginning of region60, for example, by monitoring OES signals during the etching. However, as described previously, in other embodiments, the partial etch of step320may be terminated at other locations (e.g., other regions of the stack, other locations of regions60(such as, within region60, at the end of region60, immediately after region60, etc.)).

In some embodiments, the redeposited layer130formed on the side walls of the partial MTJ bits120′ (after the partial etch step of320) may then be removed (step330) (seeFIG. 4B). Any known process, such as, for example, an angled ion beam etch, may be used to remove at least a portion of this redeposited layer130. In some embodiments, step330may be omitted. In some embodiments, instead of step300or in addition to step330(before or after step330), any redeposited layer130on the side walls of the partial MTJ bits120′ may be rendered electrically nonconductive by subjecting the MTJ bits120′ to a suitable chemical process (e.g., oxidation, nitridization, etc.). A first encapsulant140may be deposited on the partial MTJ bits120′ to cover the bits120′, including their side walls (step340) (seeFIG. 4C). Any suitable process (CVD, ALD, etc.) may be used to deposit the first encapsulant140on the partially etched magnetoresistive stack100. The first encapsulant140may then be used as a spacer to continue etching the remaining regions of the magnetoresistive stack100at the base of the partial etched-region110′ to convert the partial MTJ bits120′ to MTJ bits120(step350) (seeFIG. 4D). In some embodiments, step340may be eliminated and step350may be carried out without the first encapsulant140covering the partial MTJ bits120′. The etching may be performed using any suitable technique (for example, physical etching such as ion beam etching, reactive ion beam etching, etc.). In some embodiments, a second redeposited layer130′ formed on the side walls of the MTJ bits120′ after step350may then be removed (e.g., by angled etching). However, in some embodiments, this step may be omitted. In some embodiments, any remaining second redeposited layer130′ on the side walls of the MTJ bits120′ (before or after angled etching) may be rendered nonconductive by exposing the MTJ bits120′ to a suitable chemical process (e.g., oxidation, nitridization, etc.). A second encapsulant150may then be deposited on the MTJ bits120′ (step360) (seeFIG. 4E). Further processing (polishing to expose the MTJ bits, forming bit contact structures to make electrical contact with the bits, etc.) may then be carried out to fabricate an MTJ device using the MTJ bits120′.

In one embodiment, a method of fabricating a magnetoresistive bit from a magnetoresistive stack including (i) a first magnetic region, (ii) an intermediate region disposed over the first magnetic region, and (iii) a second magnetic region disposed over the intermediate region, is disclosed. The method may include etching through a first portion of the magnetoresistive stack using a first etch process to form one or more sidewalls, wherein at least a portion of the sidewalls includes redeposited material after the etching. The method may also include modifying at least a portion of the redeposited material on the sidewalls, and etching through a second portion of the magnetoresistive stack after the modifying step.

Various embodiments of the disclosed method may alternatively or additionally include one or more of the following aspects: the modifying step may include removing at least a portion of the redeposited material on the sidewalls using a second etch process; the modifying step may include removing at least a portion of the redeposited material on the sidewalls using a second etch process, and wherein the first etch process and the second etch process include using an ion beam for etching; the modifying step may include removing at least a portion of the redeposited material on the sidewalls using a second etch process, and wherein the first etch process and the second etch process include using an ion beam for etching, and (a) in the first etch process, the ion beams are inclined at an angle between about 0° and less than about 30° with respect to an axis normal to a surface of the magnetoresistive stack, and (b) in the second etch process, the ion beams are inclined at an angle between about 30° and less than 90° with respect to the axis; the modifying step includes rendering at least a portion of the redeposited material on the sidewalls electrically-nonconductive; the modifying step may include rendering at least a portion of the redeposited material on the sidewalls electrically-nonconductive by subjecting the magnetoresistive stack to a chemical process to convert the portion of the redeposited material to an electrically-nonconductive material; the modifying step may include rendering at least a portion of the redeposited material on the sidewalls electrically-nonconductive by subjecting the magnetoresistive stack to one of oxidation or nitridization; the modifying step may include rendering at least a portion of the redeposited material on the sidewalls electrically-nonconductive by subjecting the magnetoresistive stack to plasma oxidation; etching through the first portion may include subjecting the magnetoresistive stack to the first etch process for a first predetermined amount of time, and the modifying step may include subjecting the magnetoresistive stack to a modification process for a second predetermined amount of time after the first etch process to modify the portion of the redeposited material; and the intermediate material includes a dielectric material.

In one embodiment, a method of fabricating a magnetoresistive bit from a magnetoresistive stack including (i) a first magnetic region, (ii) a dielectric region disposed over the first magnetic region, and (iii) a second magnetic region disposed over the dielectric region, is disclosed. The method may include using a first etch process to etch a first portion of the magnetoresistive stack and form one or more sidewalls. At least a portion of the sidewalls may include redeposited material after the first etch process. The method may also include using a second etch process to etch at least a portion of the redeposited material from the sidewalls after etching the first portion. And, etching through a second portion of the magnetoresistive stack using the first etch process after the second etch process.

Various embodiments of the disclosed method may alternatively or additionally include one or more of the following aspects: both the first etch process and the second etch process may use ion beams for etching, and wherein (a) in the first etch process, the ion beams are inclined at an angle between about 0° and less than about 30° with respect to an axis normal to a surface of the magnetoresistive stack, and (b) in the second etch process, the ion beams are inclined at an angle between about 30° and less than 90° with respect to the axis; the method may further include depositing a first encapsulant on the sidewalls after etching at least a portion of the redeposited material from the sidewalls using the second etch process; the method may further include (a) depositing a first encapsulant on the sidewalls after etching at least a portion of the redeposited material from the sidewalls using the second etch process, and (b) depositing a second encapsulant on the magnetoresistive stack after etching through the second portion, the first encapsulant being the same as, or different from, the second encapsulant; the first portion may include substantially an entire thickness of the second magnetic region and at least a portion of the dielectric region; using the first etch process may include subjecting the magnetoresistive stack to the first etch process for a first predetermined amount of time, and using the second etch process includes subjecting the magnetoresistive stack to the second etch process for a second predetermined amount of time; the first predetermined amount of time being the same as, or different from, the second predetermined amount of time.

In one embodiment, a method of fabricating a magnetoresistive bit from a magnetoresistive stack including (i) a first magnetic region, (ii) a dielectric region disposed over the first magnetic region, and (iii) a second magnetic region disposed over the dielectric region, is disclosed. The method may include using a first etch process to etch a first portion of the magnetoresistive stack and form one or more sidewalls, wherein at least a portion of the sidewalls includes redeposited material after the first etch process. The method may also include exposing the magnetoresistive stack to a chemical process to render at least a portion of the redeposited material on the sidewalls electrically nonconductive after etching the first portion. The method may further include etching through a second portion of the magnetoresistive stack after exposing the magnetoresistive stack to the chemical process.

Various embodiments of the disclosed method may alternatively or additionally include one or more of the following aspects: the first etch process may include using ion beams for etching and the chemical process may include one of oxidation or nitridization; the chemical process may include plasma oxidation; the method may further include depositing a first encapsulant on the sidewalls after exposing the magnetoresistive stack to the chemical process.

Although various embodiments of the present disclosure have been illustrated and described in detail, it will be readily apparent to those skilled in the art that various modifications may be made without departing from the present disclosure or from the scope of the appended claims.