WO2018125089A1

WO2018125089A1 - Grating layer with variable pitch formed using directed self-assembly of multiblock copolymers

Info

Publication number: WO2018125089A1
Application number: PCT/US2016/068931
Authority: WO
Inventors: Gurpreet Singh; Eungnak Han; Florian Gstrein
Original assignee: Intel Corporation
Priority date: 2016-12-28
Filing date: 2016-12-28
Publication date: 2018-07-05

Abstract

Disclosed herein are integrated circuits incorporating grating layers with variable pitch, and methods of producing the same. In one implementation, an integrated circuit comprises a substrate and a grating layer formed above the substrate. The grating layer comprising metal regions separated from each other by dielectric spacers, having variable metal-to-metal pitch throughout the grating layer. The integrated circuit further comprises a hard mask layer formed above the grating layer, and a via formed through the hard mask layer to electrically couple a first metal region of the grating layer to an upper interconnect structure.

Description

GRATING LAYER WITH VARIABLE PITCH FORMED USING DIRECTED SELF- ASSEMBLY OF MULTIBLOCK COPOLYMERS

Background

[0001] Integrated circuits generally utilize interconnect structures that electrically couple devices of a semiconductor substrate with an external signaling medium. Multi-layer interconnect structures, in particular, often include multiple levels of planar metal regions disposed within an insulating material. Electrical couplings between interconnects on different levels are made using vias, which provide electrically conductive paths through the insulating material between the different levels.

Brief Description of the Drawings

[0002] The present disclosure described herein is illustrated by way of example and not by way of limitation in the accompanying figures. For simplicity and clarity of illustration, features illustrated in the figures are not necessarily drawn to scale. For example, the dimensions of some features may be exaggerated relative to other features for clarity. Further, where considered appropriate, reference labels have been repeated among the figures to indicate corresponding or analogous elements.

[0003] Figure 1 illustrates an exemplary multiblock copolymer.

[0004] Figure 2A is a schematic view of an exemplary structure in accordance with

implementations of the disclosure.

[0005] Figure 2B is a schematic view of another exemplary structure in accordance with implementations of the disclosure.

[0006] Figure 3 illustrates variations in pitch within a grating layer in accordance with implementations of the disclosure.

[0007] Figure 4 is a flow diagram illustrating a method for fabricating a device using directed self-assembly of multiblock copolymers according to an implementation of the disclosure.

[0008] Figure 5A illustrates a structure having a grating layer formed above a substrate according to an implementation of the disclosure.

[0009] Figure 5B illustrates polymer brushes bound to upper surfaces of metal regions of a grating layer according to an implementation of the disclosure.

[0010] Figure 5C illustrates polymer brushes bound to upper surfaces of dielectric spacers of a grating layer according to an implementation of the disclosure.

[0011] Figure 5D illustrates a pattern replication layer that includes polymer domains according to an implementation of the disclosure. [0012] Figure 5E illustrates removal of the polymer domains, exposing polymer brushes and metal regions beneath, according to an implementation of the disclosure.

[0013] Figure 5F illustrates formation of mask regions in openings formed by removal of polymer domains according to an implementation of the disclosure.

[0014] Figure 5G illustrates removal of the polymer domains, exposing polymer brushes and dielectric spacers beneath, according to an implementation of the disclosure.

[0015] Figure 5H illustrates the formation of mask regions in openings formed by removal of polymer domains according to an implementation of the disclosure.

[0016] Figure 51 illustrates the removal of a mask region to expose a metal region according to an implementation of the disclosure.

[0017] Figure 5J illustrates the formation of a via according to an implementation of the disclosure.

[0018] Figure 6 is a schematic illustrating an interposer for use with one or more of the implementations of the disclosure.

[0019] Figure 7 is a schematic illustrating a computing device built in accordance with implementations of the disclosure.

Detailed Description

[0020] Described herein are implementations of grating layers with variable pitch formed using directed self-assembly of multiblock copolymers, and methods of using directed self-assembly of multiblock copolymers to fabricate devices. In the following description, various aspects of the illustrative implementations will be described using terms commonly employed by those skilled in the art to convey the substance of their work to others skilled in the art. However, it will be apparent to those skilled in the art that the implementations of the present disclosure may be practiced with only some of the described aspects. For purposes of explanation, specific numbers, materials and configurations are set forth in order to provide a thorough understanding of the illustrative implementations. However, it will be apparent to one skilled in the art that the implementations of the present disclosure may be practiced without the specific details. In other instances, well-known features are omitted or simplified in order not to obscure the illustrative implementations .

[0021] Integrated circuits typically utilize interconnect layers to connect individual devices on a chip and for signal transmission with external devices. Interconnect layers include metal interconnect lines that couple to individual devices, and connect other interconnect lines in different layers through vias that pass through interlay er dielectric (ILD) layers that separate the interconnect layers. Metal lines and vias are typically formed using patterning techniques, such as photolithography or electron beam lithography, to define their locations and dimensions. Generally, lithographic patterning is used to position and align the vias and interconnect lines of an overlying level relative to those on the underlying level.

[0022] As interconnect lines are manufactured with smaller critical dimensions (e.g., line widths) and pitches (e.g., center-to-center line distance), it becomes increasingly difficult to properly align the vias with the desired interconnect layer. In particular, during manufacturing, the location of the via edges with respect to the interconnect layer or target line may be misaligned due to variations in the manufacturing process. If the via is misaligned and contacts the wrong metal feature, the chip may short circuit resulting in degraded electrical performance. One solution to has been to reduce the via size, for example, by fabricating the vias with narrower lateral dimensions. However, reducing the via size results in an increased electrical resistance and reduced manufacturing yield.

[0023] Directed self-assembly techniques have been utilized for via alignment by replicating critical dimensions and pitches of interlay er lines. However, these methods are highly constrained in the dimensions that can be replicated, and are unable to replicate patterns having variable pitch within an active area of a single layer or within an inactive area. The

implementations described herein overcome these limitations by utilizing multiblock

copolymers, such as triblock copolymers, to allow for pitch replication with multiple pitches in the same layer simultaneously. For example, in certain implementations, pitch and critical dimension variations of up to 60% are possible. These implementations allow for applications such as coloring and via self-alignment. Without being bound by theory, it is believed that multiblock copolymers have the ability to take on different conformations than diblock copolymers, such as forming phase- separated loops, which allow for larger spatial variations of self-assembled domains.

[0024] A block copolymer is a polymeric molecule formed from two or more subunits

("blocks") of covalently bonded monomers in a contiguous sequence, with each subunit comprising a single type of monomer and each subunit having different monomer types than its neighboring subunit(s). As used herein, a "multiblock copolymer" is a block copolymer having three or more subunits. Figure 1 illustrates an exemplary multiblock copolymer 100 for use in implementations of the present disclosure. The multiblock copolymer 100 is depicted as a triblock copolymer having a polymer block 102, a polymer block 104 covalently linked to the polymer block 102, and a polymer block 106 linked covalently linked to the polymer block 104, with X, Y, and Z representing a total number of monomers in the respective blocks. The polymer block 102 is of a polymer block type that comprises monomers of type A linked together covalently. Similarly, the polymer block 104 is of a polymer block type that comprises monomers of type B linked together covalently. The polymer block 106 is of the same polymer block type as the polymer block 102, and may differ in the overall block size (e.g., X is different than Z).

[0025] The monomers of type A and type B are representative of many different types of monomers used in block copolymers, as would be appreciated by one of ordinary skill in the art. As a non-limiting example, the monomer type A represents styrene monomers (i.e., the polymer block 102 and the polymer block 106 are both polystyrene), and the monomer type B represents methyl methacrylate monomers (i.e., the polymer block 104 is poly(methyl methacrylate)). In some implementations, the block copolymers may comprise various combinations of polymer blocks, such as polystyrene, poly(methyl methacrylate), polyethylene, polypropylene, polyacrylonitrile, polybutadiene, polyvinyl acetate, polyacetic acid, polybutyl acrylate, polylactic acid, polycaprolactone, poly(ethylene glycol), polyisoprene, or other polymer blocks. As illustrated, each block only includes one type of monomer, although in other

implementations, at least one of the blocks may include two or more different types of monomers (e.g., randomly, in alternating fashion, as graft polymers, etc.).

[0026] The multiblock copolymer 100 is depicted as having an "ABA" structure. Other multiblock copolymer structures are contemplated (e.g., ABC, ABAB, ABABA, ABCD, etc.), and may be used in various implementations.

[0027] Each of the polymer blocks of the multiblock copolymer 100 may have different chemical properties depending on the monomers contained therein. For example, the polymer block 102 and the polymer block 106 may be relatively more hydrophobic or hydrophilic than the polymer block 104. Such differences in chemical/thermodynamic properties may cause multiblock copolymer molecules to microphase separate or self-assemble into different regions, domains, or microphases. The differences in hydrophobicity, hydrophilicity, or other properties between the polymer blocks may cause a microphase separation where different polymer blocks are thermodynamically driven to "separate" from each other due to their dissimilar properties. Polymer blocks of the same type belonging to different molecules may realign/reposition themselves and segregate/agglomerate in nanoscale regions, domains, or microphases. The sizes and shapes of these domains generally depend in part upon the relative lengths of the polymer blocks.

[0028] The terms "over," "under," "between," and "on" as used herein refer to a relative position of one material layer or component with respect to other layers or components. For example, one layer disposed over or under another layer may be directly in contact with the other layer or may have one or more intervening layers. Moreover, one layer disposed between two layers may be directly in contact with the two layers or may have one or more intervening layers. In contrast, a first layer "on" a second layer is in direct contact with that second layer. Similarly, unless explicitly stated otherwise, one feature disposed between two features may be in direct contact with the adjacent features or may have one or more intervening layers.

[0029] Implementations of the disclosure may be formed or carried out on a substrate, such as a semiconductor substrate. In one implementation, the semiconductor substrate may be a crystalline substrate formed using a bulk silicon or a silicon-on-insulator substructure. In other implementations, the semiconductor substrate may be formed using alternate materials, which may or may not be combined with silicon, that include but are not limited to germanium, indium antimonide, lead telluride, indium arsenide, indium phosphide, gallium arsenide, indium gallium arsenide, gallium antimonide, or other combinations of group III-V, group IV materials, or group III- nitrides, such as gallium nitride (GaN). Although a few examples of materials from which the substrate may be formed are described here, any material that may serve as a foundation upon which a semiconductor device may be built falls within the spirit and scope of the present disclosure.

[0030] A plurality of transistors, such as metal-oxide- semiconductor field-effect transistors (MOSFET or simply MOS transistors), may be fabricated on the substrate. In various implementations of the disclosure, the MOS transistors may be planar transistors, nonplanar transistors, or a combination of both. Nonplanar transistors may include FinFET transistors such as double-gate transistors and tri-gate transistors, and wrap-around or all-around gate transistors such as nanoribbon and nanowire transistors. Although the implementations described herein may illustrate only planar transistors, it should be noted that the

implementations may also be carried out using nonplanar transistors.

[0031] Each MOS transistor includes a gate stack formed of at least two layers, a gate dielectric layer and a gate electrode layer. The gate dielectric layer may include one layer or a stack of layers. The one or more layers may include silicon oxide, silicon dioxide and/or a high-k dielectric material. The high-k dielectric material may include elements such as hafnium, silicon, oxygen, titanium, tantalum, lanthanum, aluminum, zirconium, barium, strontium, yttrium, lead, scandium, niobium, and zinc. Examples of high-k materials that may be used in the gate dielectric layer include, but are not limited to, hafnium oxide, hafnium silicon oxide, lanthanum oxide, lanthanum aluminum oxide, zirconium oxide, zirconium silicon oxide, tantalum oxide, titanium oxide, barium strontium titanium oxide, barium titanium oxide, strontium titanium oxide, yttrium oxide, aluminum oxide, lead scandium tantalum oxide, and lead zinc niobate. In some implementations, an annealing process may be carried out on the gate dielectric layer to improve its quality when a high-k material is used.

[0032] The gate electrode layer is formed on the gate dielectric layer and may consist of at least one P-type workfunction metal or N-type workfunction metal, depending on whether the transistor is to be a PMOS or an NMOS transistor. In some implementations, the gate electrode layer may consist of a stack of two or more metal layers, where one or more metal layers are workfunction metal layers and at least one metal layer is a fill metal layer. Further metal layers may be included for other purposes, such as a barrier layer.

[0033] For a PMOS transistor, metals that may be used for the gate electrode include, but are not limited to, ruthenium, palladium, platinum, cobalt, nickel, and conductive metal oxides, e.g., ruthenium oxide. A P-type metal layer will enable the formation of a PMOS gate electrode with a workfunction that is between about 4.9 eV and about 5.2 eV. For an NMOS transistor, metals that may be used for the gate electrode include, but are not limited to, hafnium, zirconium, titanium, tantalum, aluminum, alloys of these metals, and carbides of these metals such as hafnium carbide, zirconium carbide, titanium carbide, tantalum carbide, and aluminum carbide. An N-type metal layer will enable the formation of an NMOS gate electrode with a

workfunction that is between about 3.9 eV and about 4.2 eV.

[0034] In some implementations, when viewed as a cross-section of the transistor along the source-channel-drain direction, the gate electrode may consist of a "U"-shaped structure that includes a bottom portion substantially parallel to the surface of the substrate and two sidewall portions that are substantially perpendicular to the top surface of the substrate. In another implementation, at least one of the metal layers that form the gate electrode may simply be a planar layer that is substantially parallel to the top surface of the substrate and does not include sidewall portions substantially perpendicular to the top surface of the substrate. In further implementations, the gate electrode may consist of a combination of U-shaped structures and planar, non-U-shaped structures. For example, the gate electrode may consist of one or more U- shaped metal layers formed atop one or more planar, non-U-shaped layers.

[0035] In some implementations, a pair of sidewall spacers may be formed on opposing sides of the gate stack that bracket the gate stack. The sidewall spacers may be formed from a material such as silicon nitride, silicon oxide, silicon carbide, silicon nitride doped with carbon, and silicon oxynitride. Processes for forming sidewall spacers are known in the art and generally include deposition and etching. In an alternate implementation, a plurality of spacer pairs may be used, for instance, two pairs, three pairs, or four pairs of sidewall spacers may be formed on opposing sides of the gate stack. [0036] In some implementations, source and drain regions are formed within the substrate adjacent to the gate stack of each MOS transistor. The source and drain regions are generally formed using either an implantation/diffusion process or an etching/deposition process. In the former process, dopants such as boron, aluminum, antimony, phosphorous, or arsenic may be ion-implanted into the substrate to form the source and drain regions. An annealing process that activates the dopants and causes them to diffuse further into the substrate typically follows the ion implantation process. In the latter process, the substrate may first be etched to form recesses at the locations of the source and drain regions. An epitaxial deposition process may then be carried out to fill the recesses with material that is used to fabricate the source and drain regions. In some implementations, the source and drain regions may be fabricated using a silicon alloy such as silicon germanium or silicon carbide. In some implementations, the epitaxially deposited silicon alloy may be doped in situ with dopants such as boron, arsenic, or

phosphorous. In further implementations, the source and drain regions may be formed using one or more alternate semiconductor materials such as germanium or a group III-V material or alloy. In further implementations, one or more layers of metal and/or metal alloys may be used to form the source and drain regions.

[0037] One or more interlayer dielectrics (ILD) are deposited over the MOS transistors. The ILD layers may be formed using dielectric materials known for their applicability in integrated circuit structures, such as low-k dielectric materials. Examples of dielectric materials that may be used include, but are not limited to, Si0₂, carbon doped oxide (CDO), silicon nitride, organic polymers such as perfluorocyclobutane or polytetrafluoroethylene, fluorosilicate glass (FSG), and organosilicates such as silsesquioxane, siloxane, or organosilicate glass. The ILD layers may include pores or air gaps to further reduce their dielectric constant.

[0038] Figure 2A is a schematic view of an exemplary structure 200 in accordance with implementations of the disclosure. The structure 200 includes a substrate 202, which may be of any suitable material for fabricating a semiconductor device, such as those described above. In certain implementations, the substrate 202 may have one or more semiconductor devices formed thereon.

[0039] The structure 200 further includes a grating layer 210 that is patterned on the substrate 202. It is to be understood that, though not shown, one or more intervening layers and/or devices may be disposed between the grating layer 210 and the substrate 202. As used herein, a "grating layer" refers to a layer comprising two or more materials arranged within the layer in alternating fashion (e.g., interconnect lines in a single layer separated by dielectric spacers). The grating layer 210, for example, includes two types of materials: material A and material B. Material A regions 212, 216 and material B regions 214, 218 are arranged shown as being of equal size, however, one or more may vary in width (in a direction along the substrate), height (along a direction normal to the substrate), and pitch, as will be discussed with respect to Figure 3. In certain implementations, the grating layer 120 may be formed (e.g., according to a damascene process) such that upper surfaces of the materials in the layer are coplanar, and lower surfaces of the materials in the layer are also coplanar, as Figure 2A illustrates. In other implementations, one or more of the materials of the grating layer may have different thicknesses.

[0040] In certain implementations, one of the materials of the grating layer 210 may be a conductive material, such as a metal, and another one of the materials may serve as a non- conductive spacer material, such as a dielectric material. For example, the material A regions 212/216 may each be a metal, and the material B regions 214/218, may each be dielectric spacers that separate the material A regions 212/216.

[0041] The structure 200 further includes an alignment promotion layer 220 disposed above the grating layer 210. The alignment promotion layer 220 may include two or more materials that are selectively formed over the grating layer 210. For example, the alignment promotion layer 220 includes promotor materials of types A (promotor A regions 222/226) and B (promotor B regions 224/228), which may be formed over materials A and B, respectively. In certain implementations, one or more of the promoter materials may be selectively formed over their respective material regions. For example, the promoter A regions 222/226 may be selectively formed over the material A regions 212/216, respectively, and the promotor B regions 224/228 may be selectively formed over the material regions 214/218, respectively. As another example, one of the promoter materials may be selectively formed over its respective material regions in a first deposition step, and in a second deposition step, another promotor material may be formed over its respective material regions as a result of being blocked by the earlier deposited promotor material. In certain implementations, only one type of promoter material is used. For example, the promoter A regions 222/226 may be formed without forming the promoter B regions 224/228.

[0042] In certain implementations, the selectivity of the promoter materials for their respective material regions may, in practice, result in some encroachment of one type of promoter material over a different material region that it is selective for (e.g., promoter A region 222 may contain less than 10% of the promoter material B).

[0043] In certain implementations, the promoter materials may comprise polymer brushes. For example, the promoter A regions 222/226 may be formed from a first type of polymer brush that selectively, or at least preferentially, binds to materials of type A of the material A regions 212/216. In addition, or alternatively, the promoter B regions 224/228 may be formed from a second type of polymer brush that selectively, or at least preferentially, binds to materials of type B of the material B regions 214/218. In certain implementations, the first polymer brush type may react with upper surfaces of the material A regions 212/216 at a greater rate and/or to a greater extent than it reacts with upper surfaces of the material B regions 214/218, and the same may be true of the second polymer brush type. Thus, the promoter A regions 222/226 and the promoter B regions 224/228 may represent polymer brush-functionalized surfaces of the material A regions 212/216 and the material B regions 214/218, respectively. In one

implementation, the promoter A regions 222/226 may comprise poly(methyl methacrylate) polymer brushes, and the promoter B regions 224/228 may comprise polystyrene polymer brushes.

[0044] In certain implementations, a suitable polymer brush may comprise polymer having one or more reactive functional groups at or near one end of the polymer that is capable of reacting with a surface at that end. Such functional groups may include, but are not limited to, hydroxyl groups, amino groups, halo groups, or other groups that may react with metal or dielectric materials. In certain implementations, a metal or dielectric material surface may be treated to provide reactive groups (such as hydroxyl groups) for covalently binding to specific polymer brush types, thus increasing specificity of polymer brush types to different types of surfaces. A polymer brush layer is formed on a surface once the surface becomes saturated with bound polymer brushes. A "brush height" of the polymer brush layer may correspond to an average height that the polymer brushes extend above the surface, which is a function of loading density, molecular weight, and other factors (e.g., steric hindrance, hydrophobicity/hydrophilicity, etc.).

[0045] In some implementations, heat may be applied to promote the reaction between the polymer brushes and the surfaces of the material A regions and/or material B regions. For example, depending upon the particular polymer brush material and process, the temperature of the reaction may be increased to from about 160° C to about 300° C, or from about 170° C to about 270° C, without exceeding any significant thermal limits of the materials, structures, or process. The heating may be performed for a time sufficient to perform the reaction to a desired extent, which is generally on the order of tens of seconds to several minutes (e.g., hours).

[0046] The structure 200 further includes a pattern replication layer 230 formed using directed self-assembly of multiblock copolymers. To produce the pattern replication layer 230, for example, a multiblock copolymer solution is prepared by dissolving multiblock copolymers in a suitable solvent, which is then deposited onto the alignment promotion layer 220, for example, by spin coating, dip coating, immersion coating, spray coating, or any other suitable deposition technique. In certain implementations, the multiblock copolymers are all of one species type, or may include different species. In certain implementations, the multiblock copolymers comprise triblock copolymers of a single species type.

[0047] The formation of the pattern replication layer 230 is driven by the interactions between the multiblock copolymers and the promoter materials, which causes the multiblock copolymers to phase separate and self-assemble to form polymer domains at specific locations along the grating layer 210. For example, a first polymer block type of the multiblock copolymers may have an affinity for the promoter A material, and a second polymer block type of the multiblock copolymers may have an affinity for the promoter B material.

[0048] The pattern replication layer 230 includes polymer domains A 232/236 and polymer domains B 234/238. The polymer domains A 232/236 may be formed primarily from a first polymer block of type A (e.g., at least 70%), and the polymer domains B 234/238 may be formed primarily from a second polymer block of type B (e.g., at least 70%).

[0049] In certain implementations, an annealing step may be utilized after deposition of the multiblock copolymers to help initiate, accelerate, increase the quality of, or otherwise promote microphase separation and/or self-assembly. For example, the annealing may be performed by heating the substrate in an oven, heating with a thermal lamp, applying infrared radiation, or any other suitable method for increasing the temperature. The elevated temperature may provide energy to facilitate conformational freedom of the multiblock copolymer molecules. In certain implementations, the annealing is performed at a temperature from about 150° C to about 350° C, or from about 170° C to about 300° C.

[0050] Figure 2B is a schematic view of an exemplary structure 250 in accordance with implementations of the disclosure, which is similar to the structure 200 but with multiple, non- planar levels of material. For example, the material B regions 254/256 are formed on a continuous layer of material A 252. In such implementations, promoter B regions 264/268 will form on a top surface of the material B regions 254/256, and may form at least partially along sidewalls of the material B regions 254/256.

[0051] The use of multiblock copolymers to form a pattern replication layer has significant advantages over using diblock copolymers. For example, multiblock copolymers allow for variations in pitch within a grating layer, while previous methods have only allowed for a single pitch within a single layer with restraints on the pitch range. Figure 3 is a schematic illustrating variations in pitch within a grating layer 300 in accordance with implementations of the disclosure. The grating layer 300 includes material A regions 301-306 and material B regions 311-315 arranged in an alternating fashion. In certain implementations, the material A regions 301-306 comprise a metal, and the material B regions 311-315 comprise a dielectric material. The grating layer 300 is depicted as having three different pitches within the same layer, though in some implementations two or more pitches may exist. Pitch 320, pitch 330, and pitch 340 are each of different length, and may be measured from edge-to-edge or from center-to-center with respect to a single material type.

[0052] Various operations/procedures/protocols will now be described as multiple discrete operations, in turn, in a manner that is most helpful in understanding the present disclosure, however, the order of description should not be construed to imply that these

operations/procedures/protocols are necessarily order dependent. In particular, these operations need not be performed in the order of presentation.

[0053] Figure 4 is a flow diagram illustrating a method 400 for fabricating a device using directed self-assembly of multiblock copolymers according to an implementation of the disclosure. Certain elements of the method 400 may be performed in a different order, simultaneously with other elements, or with additional intermediate elements, and certain elements may be omitted in some implementations, as would be appreciated by one of ordinary skill in the art.

[0054] The method 400 begins at block 410, where a grating layer is formed above a surface of a substrate. The grating layer includes first material regions second material regions, for example, arranged in an alternating fashion. The grating layer may be formed using any suitable fabrication technique, including metal deposition, oxide growth, and planarization techniques. Figure 5A illustrates a structure 500 having a grating layer 510 formed above a substrate 502. In certain implementations, a first set of material regions (e.g., metal regions 511/513) within the grating layer (e.g., grating layer 510) are separated from each other by the second material regions (e.g., dielectric spacers 512/514) according to a first pitch (e.g., pitch 516) along an axis parallel to the surface of substrate (e.g., axis 504, which runs parallel to surface 503 of substrate 502), and a second set of the material regions (e.g., metal regions 513/515) within the grating layer are separated from each other according to a second pitch (e.g., pitch 518) along the axis. In certain implementations, one of the pitches is greater than one or more other pitches (e.g., the pitch 516 is greater than the pitch 518). In certain implementations, the first pitch and the second pitch are each independently from 10 nanometers (nm) to 100 nm (e.g., from 20 nm to 50 nm). For example, the first pitch may be from 30 nm to 50 nm, and the second pitch may be from 20 nm to 30 nm. [0055] In certain implementations, the first material regions are a metal, such as, but not limited to, ruthenium, palladium, platinum, cobalt, nickel, conductive metal oxides, or combinations thereof. In certain implementations, the second material regions are dielectric materials (i.e., dielectric spacers), such as, but not limited to, SiN, Si0₂, AlOx, or TiOx, or combinations thereof.

[0056] At block 420, polymer brushes of a first type ("first polymer brushes") are deposited onto the grating layer to bind to the first material regions of the grating layer. Figure 5B illustrates polymer brushes 521/523/525 bound to upper surfaces of the metal regions

511/513/515, respectively.

[0057] At block 430, polymer brushes of a second type ("second polymer brushes") are deposited onto the grating layer to bind to the second material regions of the grating layer.

Figure 5C illustrates polymer brushes 522/524 bound to upper surfaces of the dielectric spacers 512/514, respectively. The brushes 521-525 collectively define a brush layer 520.

[0058] In certain implementations, the first polymer brushes are deposited prior to deposition of the second polymer brushes. In certain implementations, the first polymer brushes bind selectively to the upper surfaces of the first material regions, and passivate the first material regions from the second polymer brushes. In certain implementations, the first polymer brushes are deposited simultaneously with the second polymer brushes (e.g., blocks 420 and 430 are performed simultaneously), and each of the first and second polymer brushes may bind selectively to the upper surfaces of the first and second material regions, respectively.

[0059] At block 440, multiblock copolymers are deposited onto the grating layer. In certain implementations, the multiblock copolymers comprise triblock copolymers, and the triblock copolymers each comprise an ABA structure. In certain implementations, the A corresponds to a first polymer block type, and the B corresponds to a second polymer block type. In certain implementations, the triblock copolymers comprise polystyrene-poly(methyl methacrylate)- polystyrene. In certain implementations, an average molecular weight of the triblock

copolymers is from 20 kilograms per mole (kg/mol) to 500 kg/mol, from 20 kg/mol to 200 kg/mol, from 50 kg/mol to 170 kg/mol, or from 80 kg/mol to 140 kg/mol.

[0060] At block 450, the multiblock copolymers are annealed to form a pattern replication layer. In certain implementations, the annealing is performed at a temperature from about 150° C to about 350° C, or from about 170° C to about 300° C. Figure 5D illustrates a pattern replication layer 530, which includes polymer domains 531-535, disposed above the brush layer 520. The multiblock copolymers self-assemble to form the polymer domains 531-535. The polymer domains 531/533/535 correspond to a first block type of the multiblock copolymers, and may form as a result of a greater affinity of the first block type for the polymer brushes 521/523/525 than for the polymer brushes 522/524. Similarly, the polymer domains 532/534 correspond to a second block type of the multiblock copolymers, and may form as a result of a greater affinity of the second block type for the polymer brushes 522/524 than for the polymer brushes

521/523/525.

[0061] At block 460, the first polymer domains are selectively etched (e.g., using dry etching or another suitable etching technique) to form openings, and first hard mask regions are formed in the openings. Figure 5E illustrates the removal of the polymer domains 531/533/535, exposing the polymer brushes 521/523/525 and the metal regions 511/513/515 beneath. In some implementations, the polymer brushes 521/523/525 are also etched to expose the upper surfaces of the metal regions 511/513/515. Figure 5F illustrates the formation of mask regions

531/533/535 in the openings formed by removal of the polymer domains 531/533/535.

[0062] At block 470, the second polymer domains are selectively etched (e.g., using dry etching or another suitable etching technique) to form openings, and second hard mask regions are formed in the openings. Figure 5G illustrates the removal of the polymer domains 532/534, exposing the polymer brushes 522/524 and the dielectric spacers 512/514 beneath. In some implementations, the polymer brushes 522/524 are also etched to expose the upper surfaces of the dielectric spacers 512/514. Figure 5H illustrates the formation of mask regions 542/544 in the openings formed by removal of the polymer domains 532/534. The mask regions 541-545 collectively define a hard mask layer 540. In certain implementations, planarization may be performed to planarized an upper surface of the hard mask layer 540.

[0063] At block 480, one or more of the first hard mask regions are etched to expose the first material, and one or more vias are formed to provide access to an upper interconnect structure. Figure 51 illustrates the removal of the mask region 543 and the polymer brushes 523 to expose the metal region 513. The removal of the mask region 534 may be etched in combination with a photolithographic techniques. Figure 5 J illustrates the formation of a via 550 which may be used to couple the metal region 513 to an upper level structure. In certain implementations, an interlayer dielectric (ILD) layer 560 is formed, and the via 550 may be formed through dielectric material 562 of the ILD layer 560.

[0064] Figure 6 illustrates an interposer 600 for use with one or more implementations of the disclosure. The interposer 600 is an intervening substrate used to bridge a first substrate 602 to a second substrate 604. The first substrate 602 may be, for instance, an integrated circuit die. The second substrate 604 may be, for instance, a memory module, a computer motherboard, or another integrated circuit die. Generally, the purpose of an interposer 600 is to spread a connection to a wider pitch or to reroute a connection to a different connection. For example, an interposer 600 may couple an integrated circuit die to a ball grid array (BGA) 606 that can subsequently be coupled to the second substrate 604. In some implementations, the first and second substrates 602/604 are attached to opposing sides of the interposer 600. In other implementations, the first and second substrates 602/604 are attached to the same side of the interposer 600. And in further implementations, three or more substrates are interconnected by way of the interposer 600.

[0065] The interposer 600 may be formed of an epoxy resin, a fiberglass-reinforced epoxy resin, a ceramic material, or a polymer material such as polyimide. In further implementations, the interposer may be formed of alternate rigid or flexible materials that may include the same materials described above for use in a semiconductor substrate, such as silicon, germanium, and other group III-V and group IV materials.

[0066] The interposer may include metal interconnects 608 and vias 610, including but not limited to through- silicon vias (TSVs) 612. The interposer 600 may further include embedded devices 614, including both passive and active devices. Such devices include, but are not limited to, capacitors, decoupling capacitors, resistors, inductors, fuses, diodes, transformers, sensors, and electrostatic discharge (ESD) devices. More complex devices such as radio- frequency (RF) devices, power amplifiers, power management devices, antennas, arrays, sensors, and MEMS devices may also be formed on the interposer 600.

[0067] In accordance with implementations of the disclosure, apparatuses or processes disclosed herein may be used in the fabrication of the interposer 600, and/or may be interfaced directly with the interposer 600.

[0068] Figure 7 illustrates a computing device 700 built in accordance with implementations of the disclosure. The computing device 700 may include a number of components. In one implementation, these components are attached to one or more motherboards. In an alternate implementation, some or all of these components are fabricated onto a single system-on-a-chip (SoC) die, such as an SoC used for mobile devices. The components in the computing device 700 include, but are not limited to, an integrated circuit die 702 and at least one communications logic unit 708. In some implementations the communications logic unit 708 is fabricated within the integrated circuit die 702 while in other implementations the communications logic unit 708 is fabricated in a separate integrated circuit chip that may be bonded to a substrate or

motherboard that is shared with or electronically coupled to the integrated circuit die 702. The integrated circuit die 702 may include a CPU 704 as well as on-die memory 706, often used as cache memory, that can be provided by technologies such as embedded DRAM (eDRAM), SRAM, or spin-transfer torque memory (STT-MRAM). It may be noted that, in certain implementations, the integrated circuit die 702 may include fewer elements (e.g., without the processor 704 and/or on-die memory 706) or additional elements other than the processor 704 and on-die memory 706. In one implementation, the integrated circuit die 702 may include one or more components produced using any implementations of pattern replication described herein. For example, one or more components of the integrated circuit die 702 may utilize a metal grating layer having variable pitches. In one implementation, the integrated circuit die 702 may be a part of an LED-based display device with multiple LED arrays and a thin film transistor (TFT) backplane, with or without the processor 704 and/or on-die memory 706. In another example, the integrated circuit die 702 may include some or all the elements described herein, as well as include additional elements.

[0069] Computing device 700 may include other components that may or may not be physically and electrically coupled to the motherboard or fabricated within an SoC die. These other components include, but are not limited to, volatile memory 710 (e.g., DRAM), non- volatile memory 712 (e.g., ROM or flash memory), a graphics processing unit 714 (GPU), a digital signal processor 716, a crypto processor 742 (e.g., a specialized processor that executes cryptographic algorithms within hardware), a chipset 720, at least one antenna 722 (in some implementations two or more antenna may be used), a display or a touchscreen display 724, a touchscreen controller 726, a battery 730 or other power source, a power amplifier (not shown), a voltage regulator (not shown), a global positioning system (GPS) device 728 (which may further include a compass), a motion coprocessor or sensors 732 (that may include an accelerometer, a gyroscope, and a compass), a microphone (not shown), a speaker 734, a camera 736, user input devices 738 (such as a keyboard, mouse, stylus, and touchpad), and a mass storage device 740 (such as hard disk drive, compact disk (CD), digital versatile disk (DVD), and so forth). The computing device 700 may incorporate further transmission,

telecommunication, or radio functionality not already described herein. In some

implementations, the computing device 700 includes a radio that is used to communicate over a distance by modulating and radiating electromagnetic waves in air or space. In further implementations, the computing device 700 includes a transmitter and a receiver (or a transceiver) that is used to communicate over a distance by modulating and

radiating electromagnetic waves in air or space.

[0070] The communications logic unit 708 enables wireless communications for the transfer of data to and from the computing device 700. 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 implementations they might not. The communications logic unit 708 may 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, Infrared (IR), Near Field Communication (NFC), Bluetooth, derivatives thereof, as well as any other wireless protocols that are designated as 3G, 4G, 5G, and beyond. The computing device 700 may include a plurality of communications logic units 708. For instance, a first

communications logic unit 708 may be dedicated to shorter range wireless communications such as Wi-Fi, NFC, and Bluetooth and a second communications logic unit 708 may be dedicated to longer range wireless communications such as GPS, EDGE, GPRS, CDMA, WiMAX, LTE, Ev- DO, and others.

[0071] The processor 704 of the computing device 700 includes one or more devices, such as transistors, metal interconnects, or LEDs, formed in accordance with implementations of the disclosure. The term "processor" 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 stored in registers and/or memory.

[0072] The communications logic unit 708 may also include one or more devices, such as transistors, metal interconnects, or LEDs, formed in accordance with implementations of the disclosure.

[0073] In further implementations, another component housed within the computing device 700 may contain one or more devices, such as transistors, metal interconnects, or LEDs, formed in accordance with implementations of the disclosure.

[0074] In various implementations, the computing device 700 may be a laptop computer, a netbook computer, a notebook computer, an ultrabook computer, a smartphone, a dumbphone, a tablet, a tablet/laptop hybrid, a personal digital assistant (PDA), an ultra mobile PC, a mobile phone, a desktop computer, a server, a printer, a scanner, a monitor, a set-top box, an

entertainment control unit, a digital camera, a portable music player, or a digital video recorder. In further implementations, the computing device 700 may be any other electronic device that processes data.

[0075] The following discussion provides a variety of exemplary implementations. Example 1 is an integrated circuit comprising: a substrate; a grating layer above a surface of the substrate; and a via. In certain implementations, the grating layer comprising metal regions separated from each other by dielectric spacers, wherein first metal regions within the grating layer are separated from each other according to a first pitch along an axis parallel to the substrate, wherein second metal regions within the grating layer are separated from each other according to a second pitch along the axis, and wherein the first pitch is greater than the second pitch. In certain implementations, the via is to electrically couple one of the first or second metal regions of the grating layer to an upper interconnect structure.

[0076] In Example 2, the subject matter of Example 1 can optionally provide that the first pitch and the second pitch each independently range from 10 nanometers (nm) to 100 nm.

[0077] In Example 3, the subject matter of Example 1 can optionally provide that each of the first or second metal regions comprises upper metal surfaces, wherein each of the dielectric spacers comprises upper dielectric surfaces, and wherein the upper metal surfaces and the upper dielectric surfaces are coplanar.

[0078] In Example 4, the subject matter of Example 1 can optionally provide that the integrated circuit further comprises a hard mask layer and a polymer brush layer between the grating layer and the hard mask layer. In certain implementations, the via passes through the hard mask layer.

[0079] In Example 5, the subject matter of Example 4 can optionally provide that the polymer brush layer comprises: first polymer brushes bound to upper surfaces of the first and second metal regions; and second polymer brushes bound to upper surfaces of the dielectric spacers.

[0080] In Example 6, the subject matter of Example 5 can optionally provide that the hard mask layer is formed using a pattern replication layer comprising self-assembled triblock copolymers.

[0081] In Example 7, the subject matter of Example 6 can optionally provide that the pattern replication layer comprises: first polymer domains above the first polymer brushes; and second polymer domains above the second polymer brushes.

[0082] In Example 8, the subject matter of Example 7 can optionally provide that the triblock copolymers each comprise a first polymer block type and a second polymer block type, wherein the first polymer domains comprise the first polymer block type of the triblock copolymers, and wherein the second polymer domains are formed from the second polymer block type of the triblock copolymers.

[0083] Example 9 is an apparatus comprising: a substrate; a grating layer formed above the substrate, the grating layer comprising metal regions separated from each other by dielectric spacers; a polymer brush layer disposed above the grating layer; and a pattern replication layer formed above the brush layer, the pattern replication layer comprising self-assembled triblock copolymers. [0084] In Example 10, the subject matter of Example 9 can optionally provide that first metal regions within the grating layer are separated from each other according to a first pitch along an axis parallel to a surface of the substrate, wherein second metal regions within the grating layer are separated from each other according to a second pitch along the axis, and wherein the first pitch is greater than the second pitch.

[0085] In Example 11, the subject matter of Example 10 can optionally provide that the first pitch and the second pitch each independently range from 10 nm to 100 nm.

[0086] In Example 12, the subject matter of Example 9 can optionally provide that each of the metal regions comprises upper metal surfaces, wherein each of the dielectric spacers comprises upper dielectric surfaces, and wherein the upper metal surfaces and the upper dielectric surfaces are coplanar.

[0087] In Example 13, the subject matter of Example 9 can optionally provide that the brush layer comprises: first polymer brushes bound to upper surfaces of the metal regions; and second polymer brushes bound to upper surfaces of the dielectric spacers.

[0088] In Example 14, the subject matter of Example 3 can optionally provide that the pattern replication layer comprises: first polymer domains above the first polymer brushes; and second polymer domains above the second polymer brushes.

[0089] In Example 15, the subject matter of Example 14 can optionally provide that the triblock copolymers each comprise a first polymer block type and a second polymer block type, wherein the first polymer domains comprise the first polymer block type of the triblock copolymers, and wherein the second polymer domains comprise the second polymer block type of the triblock copolymers.

[0090] In Example 16, the subject matter of Example 9 can optionally provide that each of the triblock copolymers comprises polystyrene-poly(methyl methacrylate)-polystyrene, and wherein an average molecular weight of the triblock copolymers is from 20 kilograms per mole (kg/mol) to 500 kg/mol.

[0091] Example 17 is a fabrication method comprising: depositing first polymer brushes onto a grating layer disposed above a substrate, the grating layer comprising metal regions separated by dielectric spacers, wherein the first polymer brushes bind to upper surfaces of the metal regions without binding to upper surfaces of the dielectric spacers; depositing second polymer brushes onto the grating layer, wherein the second polymer brushes bind to the upper surfaces of the dielectric spacers without binding to the upper surfaces of the metal regions; and depositing triblock copolymers onto the grating layer to form a pattern replication layer, wherein the triblock copolymers self-assemble to form the pattern replication layer, and wherein the self- assembly is driven by interactions between the triblock copolymers and the first and second polymer brushes.

[0092] In Example 18, the subject matter of Example 17 can optionally provide that the triblock copolymers each comprise a first polymer block type and a second polymer block type, and wherein pattern replication layer comprises: first polymer domains disposed above each of the metal regions, wherein the first polymer block type of the triblock copolymers interacts selectively with the first polymer brushes to form the first polymer domains; and second polymer domains disposed above each of the dielectric spacers, wherein the second polymer block type of the triblock copolymers interacts selectively with the second polymer brushes to form the second polymer domains.

[0093] In Example 19, the subject matter of Example 18 can optionally provide that the triblock copolymers each comprise an ABA structure, wherein the A corresponds to the first polymer block type, and wherein the B corresponds to the second polymer block type.

[0094] In Example 20, the subject matter of Example 18 can optionally provide that the first polymer block type comprises polystyrene and the second polymer block type comprises poly(methyl methacrylate) such that the ABA structure comprises polystyrene-poly(methyl methacrylate)-polystyrene, and wherein an average molecular weight of the triblock copolymers is from 20 kg/mol to 500 kg/mol.

[0095] In Example 21, the subject matter of Example 18 can optionally provide that the method further comprises: selectively etching the first polymer domains to expose the metal regions; forming first hard mask regions over the exposed metal regions; selectively etching the second polymer domains to expose the dielectric spacers; and forming second hard mask regions over the exposed dielectric spacers, wherein the first and second hard mask regions collectively define a hard mask layer.

[0096] In Example 22, the subject matter of Example 21 can optionally provide that the method further comprises etching through one of the first hard mask regions to expose a metal region; and forming a via to electrically couple the exposed metal region to an upper metal interconnect structure.

[0097] In Example 23, the subject matter of Example 17 can optionally provide that the first polymer brushes are deposited prior to deposition of the second polymer brushes, and the first polymer brushes bind selectively to the upper surfaces of the metal regions and passivate the metal regions from the second polymer brushes.

[0098] In Example 24, the subject matter of Example 17 can optionally provide that a first set of the metal regions within the grating layer are separated from each other according to a first pitch along an axis parallel to a surface of the substrate, wherein a second set of the metal regions within the grating layer are separated from each other according to a second pitch along the axis, and wherein the first pitch is greater than the second pitch.

[0099] In Example 25, the subject matter of Example 1248 can optionally provide that the first pitch and the second pitch are each independently from 10 nm to 100 nm.

[0100] The above description of illustrated implementations of the disclosure, including what is described in the Abstract, is not intended to be exhaustive or to limit the implementations to the precise forms disclosed. While specific implementations of, and examples for, the

implementations are described herein for illustrative purposes, various equivalent modifications are possible within the scope of the disclosure, as those skilled in the relevant art will recognize.

Claims

Claims What is claimed is:

1. An integrated circuit comprising:

a substrate;

a grating layer above a surface of the substrate, the grating layer comprising metal regions separated from each other by dielectric spacers, wherein first metal regions within the grating layer are separated from each other according to a first pitch along an axis parallel to the surface of the substrate, wherein second metal regions within the grating layer are separated from each other according to a second pitch along the axis, and wherein the first pitch is greater than the second pitch; and

a via to electrically couple one of the first or second metal regions of the grating layer to an upper interconnect structure.

2. The integrated circuit of claim 1, wherein the first pitch and the second pitch each independently range from 10 nanometers (nm) to 100 nm.

3. The integrated circuit of claim 1, wherein each of the first and second metal regions comprises upper metal surfaces, wherein each of the dielectric spacers comprises upper dielectric surfaces, and wherein the upper metal surfaces and the upper dielectric surfaces are coplanar.

4. The integrated circuit of claim 1, further comprising:

a hard mask layer, wherein the via passes through the hard mask layer; and

a polymer brush layer between the grating layer and the hard mask layer.

5. The integrated circuit of claim 4, wherein the polymer brush layer comprises:

first polymer brushes bound to upper surfaces of the first and second metal regions; and second polymer brushes bound to upper surfaces of the dielectric spacers.

6. The integrated circuit of claim 5, wherein the hard mask layer is formed using a pattern replication layer comprising self-assembled triblock copolymers.

7. The integrated circuit of claim 6, wherein the pattern replication layer comprises: first polymer domains above the first polymer brushes; and

second polymer domains above the second polymer brushes.

8. The integrated circuit of claim 7, wherein the triblock copolymers each comprise a first polymer block type and a second polymer block type, wherein the first polymer domains comprise the first polymer block type of the triblock copolymers, and wherein the second polymer domains comprise the second polymer block type of the triblock copolymers.

9. An apparatus comprising:

a substrate;

a grating layer above the substrate, the grating layer comprising metal regions separated from each other by dielectric spacers;

a polymer brush layer above the grating layer; and

a pattern replication layer above the brush layer, the pattern replication layer comprising self-assembled triblock copolymers.

10. The apparatus of claim 9, wherein first metal regions within the grating layer are separated from each other according to a first pitch along an axis parallel to a surface of the substrate, wherein second metal regions within the grating layer are separated from each other according to a second pitch along the axis, and wherein the first pitch is greater than the second pitch.

11. The apparatus of claim 10, wherein the first pitch and the second pitch each

independently range from 10 nm to 100 nm.

12. The apparatus of claim 9, wherein each of the metal regions comprises upper metal surfaces, wherein each of the dielectric spacers comprises upper dielectric surfaces, and wherein the upper metal surfaces and the upper dielectric surfaces are coplanar.

13. The apparatus of claim 9, wherein the brush layer comprises:

first polymer brushes bound to upper surfaces of the metal regions; and

second polymer brushes bound to upper surfaces of the dielectric spacers.

14. The apparatus of claim 13, wherein the pattern replication layer comprises: first polymer domains above the first polymer brushes; and

second polymer domains above the second polymer brushes.

15. The apparatus of claim 14, wherein the triblock copolymers each comprise a first polymer block type and a second polymer block type, wherein the first polymer domains comprise the first polymer block type of the triblock copolymers, and wherein the second polymer domains comprise the second polymer block type of the triblock copolymers.

16. The apparatus of claim 9, wherein each of the triblock copolymers comprises polystyrene-poly(methyl methacrylate)-polystyrene, and wherein an average molecular weight of the triblock copolymers is from 20 kilograms per mole (kg/mol) to 500 kg/mol.

17. A fabrication method comprising:

depositing first polymer brushes onto a grating layer above a substrate, the grating layer comprising metal regions separated by dielectric spacers, wherein the first polymer brushes bind to upper surfaces of the metal regions without binding to upper surfaces of the dielectric spacers;

depositing second polymer brushes onto the grating layer, wherein the second polymer brushes bind to the upper surfaces of the dielectric spacers without binding to the upper surfaces of the metal regions; and

depositing triblock copolymers onto the grating layer to form a pattern replication layer, wherein the triblock copolymers self-assemble to form the pattern replication layer, and wherein the self-assembly is driven by interactions between the triblock copolymers and the first and second polymer brushes.

18. The fabrication method of claim 17, wherein the triblock copolymers each comprise a first polymer block type and a second polymer block type, and wherein pattern replication layer comprises:

first polymer domains above each of the metal regions, wherein the first polymer block type of the triblock copolymers interacts selectively with the first polymer brushes to form the first polymer domains; and

second polymer domains above each of the dielectric spacers, wherein the second polymer block type of the triblock copolymers interacts selectively with the second polymer brushes to form the second polymer domains.

19. The fabrication method of claim 18, wherein the triblock copolymers each comprise an ABA structure, wherein the A corresponds to the first polymer block type, and wherein the B corresponds to the second polymer block type.

20. The fabrication method of claim 19, wherein the first polymer block type comprises polystyrene and the second polymer block type comprises poly(methyl methacrylate) such that the ABA structure comprises polystyrene-poly(methyl methacrylate)-polystyrene, and wherein an average molecular weight of the triblock copolymers is from 20 kg/mol to 500 kg/mol.

21. The fabrication method of claim 18, further comprising:

selectively etching the first polymer domains to expose the metal regions;

forming first hard mask regions over the exposed metal regions;

selectively etching the second polymer domains to expose the dielectric spacers; and forming second hard mask regions over the exposed dielectric spacers, wherein the first and second hard mask regions collectively define a hard mask layer.

22. The fabrication method of claim 21, further comprising:

etching through one of the first hard mask regions to expose a metal region; and forming a via to electrically couple the exposed metal region to an upper metal interconnect structure.

23. The fabrication method of claim 17, wherein the first polymer brushes are deposited prior to deposition of the second polymer brushes, and wherein the first polymer brushes bind selectively to the upper surfaces of the metal regions and passivate the metal regions from the second polymer brushes.

24. The fabrication method of claim 17, wherein first metal regions within the grating layer are separated from each other according to a first pitch along an axis parallel to a surface of the substrate, wherein second metal regions within the grating layer are separated from each other according to a second pitch along the axis, and wherein the first pitch is greater than the second pitch.

25. The fabrication method of claim 24, wherein the first pitch and the second pitch are each independently from 10 nm to 100 nm.