A high particle loaded thin film for use as a reactive ion etching mask and methods thereof

Abstract

Described herein is mask for reaction ion etching silicon substrates, wherein the mask comprises a thin film comprising at least 60% by weight of inorganic nanoparticles. The thin film is coated over a patterned replication resin, which is disposed onto top of an amorphous silicon layer. A method is described wherein patterning a replication resin is disposed on an amorphous silicon layer, wherein the replication resin comprises a nanostructured surface. A thin film comprising at least 60% by weight of inorganic nanoparticles is disposed onto the nanostructured surface. The articles can then be etched by reactive ion etching to pattern the amorphous silicon layer.

Description

A HIGH PARTICLE LOADED THIN FILM FOR USE AS A REACTIVE ION ETCHING MASK AND METHODS THEREOF U.S. GOVERNMENT RIGHTS This disclosure was made with Government support under Grant Number FA8650-22-D-5406 awarded by DOD. The Government has certain rights in this disclosure. TECHNICAL FIELD

[0001] A thin film comprising a high percentage of inorganic nanoparticles is described. The thin film can be used as a mask for the reactive ion etching of silicon. Also disclosed are methods of making and using the masks. BRIEF DESCRIPTION OF DRAWINGS

[0002] Unless otherwise noted, the schematic drawings below are for illustrative purposes only and are not drawn to scale.

[0003] Figs.1A-1G are schematic cross-sectional views illustrating the making of an article according to one embodiment of the present disclosure.

[0004] Fig.2 is an SEM image of Example 5. SUMMARY

[0005] Conventional approaches to creating micro- and nanoscale patterns used in the semiconductor and other industries are based on the processing of substrates using optical lithography and photoresist technology in batch processing techniques (e.g., as discrete units), generally using rigid (silicon, glass, quartz, etc.) substrates. The conventional batch processes are well suited to ultra-high resolution / high- density devices on rigid substrates, but are less than optimal for use with devices requiring large substrates, high throughputs, and / or lower cost manufacturing.

[0006] There is interest in developing a continuous (or roll-to-roll)-type process, wherein webs of silicon can be patterned resulting in higher part volumes, larger part sizes, and flexible substrates. New technologies, such as mask compositions that have good selectivity are needed to enable roll-to-roll processing. Masks are used to create a pattern on an underlying layer by selectively blocking or masking the removal of the underlying layer. Often the masking materials considered for continuous-type processes generally lack sufficient etch resistance. Thus, the masks are etched along with the underlying layer, resulting in among other things, thick masking layers, undercutting, etc. Thus, there is a need to identify improved masking materials for continuous type manufacturing, and / or improved methods for making amorphous silicon substrates having nanostructured features.

[0007] In one aspect, an article is described comprising the following layers in order: (i) a base substrate; (ii) an amorphous silicon layer; (iii) a patterned replication resin comprising a nanostructured surface; and(iv) a thin film disposed on the nanostructured surface wherein the thin film comprises at least 60 % by weight of inorganic nanoparticles.

[0008] In another aspect, a method is described. The method comprising: (a) providing an amorphous silicon layer on a base substrate; (b) patterning a replication resin disposed on the amorphous silicon layer, wherein the replication resin comprises a nanostructured surface; and (c) disposing a thin film onto the nanostructured surface, wherein the thin film comprises at least 60% by weight of inorganic nanoparticles.

[0009] In some embodiments, the method further comprises: (d) planarly removing the thin film until reaching the nanostructured surface; followed by (e) removing any exposed replication resin to form a masked substrate. The masked substrate can then be exposed to reactive ion etching to etch the amorphous silicon, thereby forming a patterned amorphous silicon article.

[0010] The above summary is not intended to describe each embodiment. The details of one or more embodiments of the invention are also set forth in the description below. Other features, objects, and advantages will be apparent from the description and from the claims. DETAILED DESCRIPTION

[0011] As used herein and in the appended claims, the singular forms “a,” “an,” and “the” include plural referents unless the context clearly dictates otherwise. Thus, for example, reference to “a” or “the” component may include one or more of the components and equivalents thereof known to those skilled in the art. Further, the term “and / or” means one or all the listed elements or a combination of any two or more of the listed elements.

[0012] Relative terms such as top, bottom, side, upper, lower, horizontal, vertical, and the like may be used herein and, if so, are from the perspective observed in the drawing. These terms are used only to simplify the description, however, and not to limit the scope of the invention in any way.

[0013] Reference throughout this specification to “one embodiment,” “certain embodiments,” “one or more embodiments” or “an embodiment” means that a particular feature, structure, material, or characteristic described in connection with the embodiment is included in at least one embodiment of the invention. Thus, the appearances of the phrases such as “in one or more embodiments,” “in certain embodiments,” “in some embodiments” or “in one embodiment” in various places throughout this specification are not necessarily referring to the same embodiment of the invention.

[0014] As used herein, the term “plasma” means a partially ionized gaseous or fluid state of matter containing reactive species which include electrons, ions, neutral molecules, free radicals, and other excited state atoms and molecules. Visible light and other radiation are typically emitted from the plasma as the species forming the plasma relax from various excited states to lower, or ground, states. The plasma usually appears as a colored cloud in the reaction chamber.

[0015] "Primary particle size" refers to the median diameter of a single (non-aggregate, non- agglomerate) particle. "Agglomerate” refers to a weak association between primary particles which may be held together by charge or polarity and can be broken down into smaller entities. As used herein“aggregate” with respect to particles refers to strongly bonded or fused particles where the resulting external surface area may be significantly smaller than the sum of calculated surface areas of the individual components. The forces holding an aggregate together are strong forces, for example covalent bonds, or those resulting from sintering or complex physical entanglement. Although agglomerated nanoparticles can be broken down into smaller entities such as discrete primary particles such as by application of a surface treatment; the application of a surface treatment to an aggregate simply results in a surface treated aggregate. In some embodiments, a majority of the nanoparticles (i.e. at least 50%) are present as discrete unagglomerated nanoparticles. For example, at least 70%, 80% or 90% of the nanoparticles (e.g. in the thin film) are present as discrete unagglomerated nanoparticles.

[0016] As used herein, the term “or” is generally employed in its sense including “and / or” unless the content clearly dictates otherwise. The phrase “and / or” is used to indicate one or both stated cases may occur, for example A and / or B includes, (A and B) and (A or B).

[0017] As used herein, recitation of ranges by endpoints includes all numbers subsumed within that range (e.g., 1 to 10 includes 1.4, 1.9, 2.33, 5.75, 9.98, etc.).

[0018] As used herein, recitation of “at least one” includes all numbers of one and greater (e.g., at least 2, at least 4, at least 6, at least 8, at least 10, at least 25, at least 50, at least 100, etc.).

[0019] As used herein the phrase “(meth)acryl” refers to compounds containing either an acryl (CH2=CHCOO-) or a methacryl (CH2=CCH3COO-) structure or combinations thereof.

[0020] As used herein, “comprises at least one of” A, B, and C refers to element A by itself, element B by itself, element C by itself, A and B, A and C, B and C, and a combination of all three.

[0021] The present disclosure may be understood by reference to Figs.1A-1F, which depicts one embodiment of a process for making the articles of the present disclosure. Fig.1A depicts amorphous silicon layer 12 disposed on top of base substrate 10.

[0022] The amorphous silicon layer may comprise pure silicon, doped silicon, or hydrogenated silicon. As used herein, amorphous refers to the silicon lacking long range order and crystalline structure. Amorphous silicon does not have a measurable Tg and / or lacks grain structure as determined by electron microscopy.

[0023] Dopants for silicon can include boron, phosphorous, aluminum, nitrogen, indium, and gallium. Typically, the dopants are used in small amounts, generally no more than 0.2, 0.1, 0.05, or even 0.01 wt% based on the weight of the amorphous silicon. In some embodiments, the amorphous silicon layer comprises bulk silicon with an epitaxial layer that is lightly doped.

[0024] In some embodiments, the amorphous silicon layer comprises a hydrogenated amorphous silicon, which comprises silicon and hydrogen.

[0025] The amorphous silicon may be deposited onto a base substrate by plasma enhanced chemical vapor deposition. For example, an amorphous silicon thin film can be grown on a base substrate through a plasma deposition process. One suitable type of plasma reactor provides a reaction chamber having a capacitively-coupled system with at least one electrode powered by a radiofrequency (RF) source and at least one grounded electrode. Regardless of the specific type, such a chamber may provide anenvironment which allows for the control of, among other things, pressure, the flow of various inert and reactive gases, voltage supplied to the powered electrode, strength of the electric field across an ion sheath formed in the chamber, formation of a plasma containing reactive species, intensity of ion bombardment, rate of deposition, and the like.

[0026] In order to perform the plasma treatment, the base substrate may be placed in, or passed through, the reaction chamber. Plasma, created from a gas or gas mixture within the chamber, may be generated and sustained by supplying power (for example, from an RF generator) to at least one electrode, as will be well understood. Various ancillary components (power sources, oscillators, and so on, are often used in such systems, again as will be well understood). The pressure in the reaction chamber may be maintained at any pressure that is conducive to the formation of a suitable plasma. Often, the plasma reaction chamber may be maintained at a reduced pressure. However, in some embodiments, so called atmospheric pressure plasma treatment may be performed.

[0027] In some embodiments, a mode of plasma enhanced chemical vapor deposition may be used that involves the positioning of at least the base substrate within an ion sheath that is established within the reaction chamber of the plasma reactor. Such a mode may provide for example, enhanced attachment of plasma-reactive species to the patterned surface, enhanced coverage of such species over the area of the surface, enhanced durability of the plasma treatment, and the like. Methods of establishing such an ion sheath and of positioning a substrate within such an ion sheath, are described in detail in U.S. Pat. Nos. 7,125,603 (David et al.) and 7,387,081 (David et al).

[0028] The plasma treatment environment may be composed of any desired gas or gas-phase mixture with an appropriate applied power to initiate a plasma, thereby depositing a covalently bound thin film with a desirable surface energy. The plasma treatment environment may include one or more suitable silane or organosilane constituents. The silicon-containing thin film may be deposited from an organosilane or a silane precursor gas. In some embodiments, the silicon-containing precursor gas is reacted with other gases such as nitrogen (N2), oxygen (O2), or combinations thereof. Suitable silicon containing precursor gases include, but are not limited to, silanes such as SiH4, Si2H6, tetramethylsilane (TMS), tetraethylorthosilicate (TEOS), hexamethyldisiloxane (HMDSO), silane, etc. as described for example in U.S. Pat. No.6,696,157 (David et al.).

[0029] In some embodiments, the plasma treatment environment may comprise a mixture of an oxygen, argon, hydrogen, or helium containing constituent and a silane constituent at any suitable ratio. In certain exemplary embodiments, a mixture of argon and silane may be used. In further embodiments a volumetric ratio of silane to argon ratio of about 1:5, 1:10, 1:20, or 1:50 may be used.

[0030] In some embodiments, the amorphous silicon layer is disposed on a base substrate layer. In these embodiments, the base substrate can be a material providing mechanical support to the amorphous silicon layer during processing and / or is a material that is more resistant to etching than the amorphous silicon, which can act as a backstop to the etching process. Exemplary support materials include polyolefins (such as polyethylene, polypropylene, cyclic olefin copolymers, etc.), polyesters (such as polyethylene terephthalate (PET)), polystyrene, acrylonitrile butadiene styrene, polyvinyl chloride, polyvinylidenechloride, polycarbonate, polyacrylates, thermoplastic polyurethanes, polyvinyl acetate, polyamide, polyimide, poly(methylmethacrylate), polyethylene naphthalate, polystyrene acrylonitrile, triacetate cellulose, nylon, silicone-polyoxamide polymers, fluoropolymers, and thermoplastic elastomers.

[0031] In some embodiments, the base substrate is flexible, enabling the base substrate along with the amorphous silicon layer to be processed in a continuous, roll-to-roll process, passing around rollers and through nips. In some embodiments, the base substrate is a web with a given width and an indefinite length, such that the base substrate may be processed in a roll-to-roll fashion. In some embodiment, an indefinite length refers to a length of greater than 2, 5, 10, 50, 100, 500, 1000, or even 2000 meters.

[0032] In some embodiments, the thickness of the amorphous silicon layer to be etched can be at least 200, 300, or even 400 nm and at most 5000, 4000, 3000, 2000, 1500, 1000, or even 500 nm. In some embodiments, the amorphous silicon layer is etched through its thickness down to a base substrate.

[0033] Although not shown in Fig.1A, in some embodiments, a metal layer comprising a metal or metal oxide is disposed between the amorphous silicon layer and the base substrate. Exemplary metals or metal oxides include Al, Al2O3, Cr, Cr2O3, or combinations thereof. In some embodiments, the metal layer has a thickness of less than 150, 100, 80, 50, 30, 20, or even 10 nm.

[0034] As shown in Fig.1B, patterned replication resin 14 then is disposed onto amorphous silicon layer 12. The replication resin can be any material, but is typically an organic resin, optionally comprising inorganic particles. The replication resin is patterned, having a nanostructured surface as shown in Fig. 1B, which is used to pattern the amorphous silicon layer. The patterned replication resin can be made using techniques known in the art including lithography such as photolithography or nanoimprint lithography. Photolithography and nanoimprint lithography are known in the art and have feature sizes less 3, 2, or even 1 micrometers.

[0035] In some embodiments, the patterned replication resin is made via a nanoimprint lithography process on top of the amorphous silicon layer. These replication resins can be made from organic materials such as (meth)acrylates, silicone (meth)acrylates, urethane (meth)acrylates, urethanes, polyvinyl alcohol, polyvinyl butyral, or combinations thereof. In some embodiments, the replication resin is substantially free of metals, for example comprising less than 5, 4, 3, 2, 1, or even 0.5 % by weight of a metal. In some embodiments, the replication resin comprises a plurality of inorganic particles such as metal oxides including SiO2, Al2O3, Sb2O5, ZrO2, HfO7, TiO2, ZnO2, and mixtures thereof. If inorganic particles are present in the replication resin, they are typically present in an amount of at least 5, 8, or even 10% by weight and at most 15, 20, 30, 40, or even 50% by weight. Higher loading of inorganic nanoparticles in masks can provide improved etching resistance of the masks. However, high particle loadings in these resins tend to not effectively transfer patterns due to the brittle nature of the composite. Thus, in the present disclosure it has been discovered that a replication resin with less etch resistance can be used to provide the pattern for etching and then the replication resin can be coated with a more etch resistant material, such as the thin films disclosed herein, to provide for good pattern transfer enabling higher aspect ratios in the resulting patterned amorphous silicon article.

[0036] In one embodiment, the patterned replication resin is a (meth)acrylate based resin derived from multifunctional acrylates such as a resin derived from a urethane acrylate oligomer (e.g., urethane acrylate oligomer available under the trade designation “Photomer 6210” from IGM Resins, Charlotte, NC), a diol diacrylate (e.g., SR238, 1,6-hpexandiol diacrylate available from Sartomer Americas, Exton, PA), a multifunctional acrylate (e.g., SR351, trimethylopropane triacrylate available from Sartomer Americas), and an initiator (e.g., Diphenyl(2,4,6- trimethylbenzoyl)phosphine oxide available under the trade designation “IRGACURE TPO” from BASF, Florham Park, NJ).

[0037] In one embodiment, the patterned replication resin is a (meth)acrylate-functionalized silicone which comprises an ethylenically unsaturated compound comprising at least one (meth)acryl moiety and a plurality of repeating siloxane units, wherein a siloxane unit is for example, -(O-SiR2)-, where R is a monovalent organic group, such as methyl, ethyl, acryl, or methacryl. Exemplary (meth)acrylate- functionalized silicone compositions are disclosed in U.S. Pat. Appl. No.63 / 677439, herein incorporated by reference. Exemplary (meth)acrylate-functionalized silicones are commercially available from Gelest, Morrisville, PA, or from Evonik Industries AG, Essen, Germany under the trade designation “TEGO” and “TEGO RAD” series such products include TEGO RC 702, TEGO RC 902, TEGO Rad, TEGO Rad 2100, TEGO Rad 2200 N, TEGO Rad 2250, TEGO Rad 2300, TEGO Rad 2330, TEGO Rad 2500, TEGO Rad 2550, TEGO Rad 2650, TEGO Rad 2700, TEGO Rad 2800.

[0038] As shown in the Example Section below, these replication resins are not completely resistant to reactive ion etching (RIE) etching. Often, the thickness of the replication resin is selected to withstand each RIE process that is performed so that the top surface of the amorphous silicon layer covered by the patterned replication resin remains protected from etchant materials throughout the etching process. In some embodiments, the thickness of the patterned replication resin can be twice as thick as the amorphous silicon to be etched.

[0039] In the present disclosure, it has been discovered that a replication resin can be used to introduce the pattern onto the article to be etched and then the replication resin can be coated with a protective thin film that is more resistant to RIE etching. Thus, lower aspect ratios (height to span) of the patterned replication resin may be used, which is advantageous for manufacture and quality.

[0040] The patterned replication resin comprises a plurality of openings patterned to provide a desired geometry. Exemplary openings may include: circles, squares, rectangles, quadrilaterals, or other designs. In some embodiments, the mask has at least some openings that are less than 5, 4, 3, 2, 1.5, 1, 0.9, 0.8, 0.5, 0.2, or even 0.1 micrometers in one dimension (in other words, length, width, diameter, etc.). Based on the technique used to make the mask, the openings are generally at least 50 nm in dimension.

[0041] After applying the replication resin, thin film 16 is deposited thereon as shown in Fig.1C. The thin film comprises a high percentage (or loading) of inorganic nanoparticles, for example, wherein the thin film layer comprises at least 60, 70, 75, 80, 85, 90, 92, 95, 97, 98, or even 99 % by weight and at most 100 % by weight of inorganic nanoparticles.

[0042] Typically, the inorganic nanoparticles have an average particle diameter which is smaller than the feature size of the patterned replication resin. For example, in some embodiments, the inorganicnanoparticles have an average primary particle size of at least 1, 2, 5, 10, 20, 25, or even 45 nm and at most 50, 55, 75, 100, 150, 200, 250, 300, 350, 400, 450, or even 500 nm. Particle size can be measured using techniques known in the art such as particle size analyzers (such as a Malvern Zetasizer) using calibrated standards or microscopy (e.g., scanning electron microscopy).

[0043] Methods known in the art to form high loading inorganic nanoparticle coatings may be used to generate the thin film. In some embodiments, the thin film is made by a layer-by-layer process which is a self-assembly process known in the art. This process is commonly used to assemble films or coatings of oppositely charged materials electrostatically, but other functionalities such as hydrogen bond donor / acceptors, metal ions / ligands, and covalent bonding moieties can be the driving force for film assembly. “Polyelectrolyte” means a polymer or compound with multiple ionic groups capable of electrostatic interaction. “Strong polyelectrolytes” possess permanent charges across a wide range of pH (e.g., polymers containing quaternary ammonium groups or sulfonic acid groups). “Weak polyelectrolytes” possess a pH-dependent level of charge (e.g. polymers containing primary, secondary, or tertiary amines, or carboxylic acids). Typically, this deposition process involves exposing the substrate having a surface charge, to a series of liquid solutions, or baths. This can be accomplished by immersion of the substrate into liquid baths (also referred to as dip coating), spraying, spin coating, roll coating, inkjet printing, and the like. Exposure to the first polyion (e.g. polyelectrolyte bath) liquid solution, which has charge opposite that of the substrate, results in charged species near the substrate surface adsorbing quickly, establishing a concentration gradient, and drawing more polyelectrolyte from the bulk solution to the surface. Further adsorption occurs until a sufficient layer has developed to mask the underlying charge and reverse the net charge of the substrate surface. In order for mass transfer and adsorption to occur, this exposure time is typically on the order of minutes. The substrate is then removed from the first polyion (e.g. bath) liquid solution, and is then exposed to a series of water rinse baths to remove any physically entangled or loosely bound polyelectrolyte. Following these rinse (e.g. bath) liquid solutions, the substrate is then exposed to a second polyion (e.g. bath) liquid solution, which has charge opposite that of the first polyion (e.g. bath) liquid solution. Once again adsorption occurs, since the surface charge of the substrate is opposite that of the second (e.g. bath) liquid solution. Continued exposure to the second polyion (e.g. bath) liquid solution then results in a reversal of the surface charge of the substrate. A subsequent rinsing can be performed to complete the cycle. This sequence of steps is said to build up one layer pair, also referred to herein as a “bi-layer” of deposition and can be repeated as desired to add further layer pairs to the substrate.

[0044] Some examples of suitable layer-by-layer processes include those described in U.S. Pat. Nos. 8,234,998 (Krogman et al.) and 8,313,798 (Nogueira et al.); and U.S. Pat. Publ. No.2011 / 0064936 (Hammond-Cunningham et al.). Layer-by layer dip coating can be conducted using, for example, a StratoSequence VI (nanoStrata Inc., Tallahassee, FL) dip coating robot.

[0045] In some embodiments, the plurality of layers deposited by layer-by-layer self-assembly is a polyelectrolyte stack comprising an organic polymeric polyion (e.g. cation) and counterion (e.g. anion) comprising a plurality of nanoparticles. In some embodiments, the plurality of layers deposited by layer-by-layer self-assembly is a polyelectrolyte stack comprising inorganic nanoparticles (e.g. cation) and counterion (e.g. anion) comprising a plurality of nanoparticles.

[0046] The thickness of a bi-layer and the number of bi-layers are selected to achieve the desired etch resistance. In some embodiments, the thickness of a bi-layer, the number of bi-layers are selected to achieve the desired (e.g., etch rate) etch resistance using the minimum total thickness of self-assembled layers and / or the minimum number of layer-by-layer deposition steps. The thickness of each bi-layer typically ranges from at least 5, 10, 25, or even 50 nm to at most 15, 20, 25, 50, 75, 100, 150, 200, 150, 300, 500, 800, 1000, or even 2000 nm. Generally, the number of bi-layers will be based on the harshness of the process, thickness of the inorganic layers, and / or replication resin used. The number of bi-layers is typically at least 5, 6, 7, 8, 9, or 10. In some embodiments, the number of bilayers per stack is no greater than 150, 100, 80, 50, or even 25. It should be appreciated that individual bi-layers layer-by-layer thin film may not be distinguishable from each other by common methods in the art such as scanning electron microscopy (SEM) or transmission electron microscopy (TEM).

[0047] Various polyelectrolytes can be utilized including inorganic compounds, such as silica or silicate, as well as various phosphonocarboxylic acids and salts thereof (some of which are described in WO2015 / 095317; incorporated herein by reference.) Due to their resistance to reactive ion etching, at least one of the polyions (e.g. the polyanion or polycation) in the layer-by-layer thin film is an inorganic nanoparticle. Exemplary inorganics nanoparticles include metals and metal oxides, such as SiO2, Al2O3, Sb2O5, ZrO2, HfO7, TiO2, ZnO2, and mixtures thereof. Typically, unmodified inorganic nanoparticles, such as silica have a negative surface charge. However, surface modification of the inorganic nanoparticles and / or adjustment of the pH of the solution the inorganic nanoparticles are dispersed in can render them with a positive charge. In some embodiments, the surface treatment compound is anionic, such as in the case of sulfonate or carboxylate.

[0048] Exemplary inorganic nanoparticles include those commercially available under the trade designation “NALCO 1056” and “NALCO 2329” available from Ecolab, St. Paul, MN.

[0049] The surface charge of the inorganic nanoparticles can be adjusted by adjusting the pH to above or below the isoelectric point to achieve the desired surface charge. For example, the surface charge on a silica nanoparticle has an isoelectric point of around 2. By adjusting the dispersion to a pH greater than 2, the silica nanoparticles can be made to have a negative surface charge. In some embodiments, the inorganic nanoparticles can be surface treated or coated to produce cationic materials. For example, alumina has an isoelectric point of around 9 and can be used to thinly coat inorganic nanoparticles. By adjusting the pH of a dispersion comprising the alumina coated inorganic nanoparticles to less than 9, this would result in the inorganic nanoparticles having an overall positive charge.

[0050] Polyelectrolyte organic polymers tend to be more easily removed by reactive ion etching than inorganic materials.

[0051] Suitable polycationic organic polymers include, but are not limited to, linear and branched poly(ethylenimine) (PEI), poly(allylamine hydrochloride), polyvinylamine, chitosan, polyaniline, polyamidoamine, poly(vinylbenzyltriamethylamine), polydiallyldimethylammonium chloride (PDAC),poly(dimethylaminoethyl methacrylate), poly(methacryloylamino)propyl-trimethylammonium chloride, and combinations thereof including copolymers thereof.

[0052] Suitable polyanionic organic polymers include, but are not limited to, poly(vinyl sulfate), poly(vinyl sulfonate), poly(acrylic acid) (PAA), poly(methacrylic acid), poly(styrene sulfonate), dextran sulfate, heparin, hyaluronic acid, carrageenan, carboxymethylcellulose, alginate, sulfonated tetrafluoroethylene based fluoropolymers such as those available under the trade designation NAFION, poly(vinylphosphoric acid), poly(vinylphosphonic acid) , and combinations thereof including copolymers thereof.

[0053] The molecular weight of the polyelectrolyte polymers can vary, ranging from about 1,000 g / mole to about 1,000,000 g / mole; from 50,000 g / mole to 150,000 g / mole; 50,000 g / mole to 300,000 g / mole; or even from 10,000 g / mole to 50,000 g / mole depending on the type of polyelectrolyte polymer selected.

[0054] The inorganic nanoparticles are applied to the surface as a dispersion. In favored embodiments, the polyelectrolyte is prepared and applied to the patterned replication resin surface as an aqueous solution. The term "aqueous" means that the liquid of the coating contains at least 85 percent by weight of water. It may contain a higher amount of water such as, for example, at least 90, 95, or even at least 99 percent by weight of water or more. The aqueous liquid medium may comprise a mixture of water and one or more water-soluble organic cosolvent(s), in amounts such that the aqueous liquid medium forms a single phase. Examples of water-soluble organic cosolvents include methanol, ethanol, isopropanol, 2- methoxyethanol, 3-methoxypropanol, 1-methoxy-2-propanol, tetrahydrofuran, and ketone or ester solvents. The amount of organic cosolvent typically does not exceed 15 wt% of the total liquids of the coating composition. The aqueous polyelectrolyte composition for use in layer-by-layer self-assembly typically comprises at least 0.01, 0.05, or even 0.1 wt% of polyelectrolyte and typically no greater than 5, 4, 3, 2, or even 1 wt%.

[0055] In some embodiments, the aqueous solutions further comprise a "screening agent", an additive that promotes even and reproducible deposition by increasing ionic strength and reducing interparticle electrostatic repulsion. Suitable screening agents include any low molecular weight salts such as halide salts, sulfate salts, nitrate salts, phosphate salts, fluorophosphate salts, and the like. Examples of halide salts include chloride salts such as LiCl, NaCl, KCl, CaCl2, MgCl2, NH4Cl and the like, bromide salts such as LiBr, NaBr, KBr, CaBr2, MgBr2, and the like, iodide salts such as LiI, NaI, KI, CaI2, MgI2, and the like, and fluoride salts such as, NaF, KF, and the like. Examples of sulfate salts include Li2SO4, Na2SO4, K2SO4, (NH4)2SO4, MgSO4, CoSO4, CuSO4, ZnSO4, SrSO4, Al2(SO4)3, and Fe2(SO4)3. Organic salts such as (CH3)3CCl, (C2H5)3CCl, and the like are also suitable screening agents.

[0056] Suitable screening agent concentrations can vary with the ionic strength of the salt. In some embodiments, the aqueous solution comprises (e.g. NaCl) screening agent at a concentration ranging from 0.01 M to 0.1M. The absorptive regions may contain trace amounts of screening agent.

[0057] The layer-by-layer thin film may be sequentially coated, layer-by-layer, onto the patterned replication resin atop the amorphous silicon layer. The patterned replication resin may comprise a patternof holes and the layer-by-layer thin film fills the crevasses (or holes) of patterned replication resin 14, creating a pattern of posts, when the exposed replication resin is removed.

[0058] As shown in Fig.1C, when the layer-by-layer thin film is coated over the patterned replication resin, the layer-by-layer thin film covers the features of the patterned replication resin. After applying and drying the thin film on the patterned replication resin, the thin film is then removed from the top portions of the patterned replication resin 14 (e.g. protrusions) resulting in Fig.1D. Any suitable method can be used to selectively remove the layer-by-layer thin film from the top surface of the protrusions (e.g., patterned replication resin). Typically, since the layer-by-layer thin film has good resistance to etching, a strong etching process is needed. In one embodiment, the layer-by-layer thin film is removed by reactive ion etching. Reactive ion etching (RIE) is a directional etching process utilizing ion bombardment to remove material. RIE systems are used to remove organic or inorganic material by etching surfaces orthogonal to the direction of the ion bombardment. The most notable difference between reactive ion etching and isotropic plasma etching is the etch direction. Reactive ion etching is characterized by a ratio of the vertical etch rate to the lateral etch rate which is greater than 1. Systems for reactive ion etching are built around a durable vacuum chamber. Before beginning the etching process, the chamber is evacuated to a base pressure lower than 1 Torr, 100 mTorr, 20 mTorr, 10 mTorr, or even 1 mTorr. An electrode holds the materials to be treated and is electrically isolated from the vacuum chamber. The electrode may be a rotatable electrode in a cylindrical shape. A counter electrode is also provided within the chamber and may be comprised of the vacuum reactor walls. Gas comprising an etchant enters the chamber through a control valve. The process pressure is maintained by continuously evacuating chamber gases through a vacuum pump. The type of gas used varies depending on the etch process. Carbon tetrafluoride (CF4), sulfur hexafluoride (SF6), octafluoropropane (C3F8), fluoroform (CHF3), boron trichloride (BCl3), hydrogen bromide (HBr), chlorine, argon, and oxygen are commonly used for etching. RF power is applied to the electrode to generate a plasma. Samples can be conveyed on the electrode through plasma for a controlled time period to achieve a specified etch depth. Reactive ion etching is known in the art and further described in US 8,460,568 (David et al.); incorporated herein by reference.

[0059] In some embodiments, the top of the substrate is etched with a fluorine (such as NF3and / or SF6), chlorine, or bromine gas to remove planarly the top surface just until the apex of the patterned replication resin is exposed. Then another process is used to selectively remove exposed replication resin 14, exposing the underlying amorphous silicon layer 12 as shown in Fig.1E. In some embodiments, a less aggressive etching gas is used, such as O2, which would be more selective for etching the replication resin. After removal of the exposed replication resin, the article of Fig.1E results, wherein the layer-by- layer thin film is disposed on the patterned replication resin and areas of the amorphous silicon are exposed. The substrate of Fig.1E can then be exposed (again) to reactive ion etching to remove the exposed amorphous silicon resulting in Fig.1F. The reactive ion etching step can be any dry etching technique wherein a chemically reactive plasma is generated by an electromagnetic field, which accelerates high-energy plasma ions towards the main surface of the masked substrate. The high-energyplasma ions collide with the exposed portions of the amorphous silicon layer, and thus remove the silicon material through the first set of openings on the mask.

[0060] For example, the reaction chamber is filled with an etching gas to etch the amorphous silicon layer. Exemplary etching gases include fluorine-containing gases such as SF6, CF4, CHF3, C4F8, C3F8, C6F14, and NF3. In some embodiments, an inert gas, such as argon, is passed through the reaction chamber during etching. In some embodiments, oxygen or hydrogen gas may be mixed with the fluorine- containing gas during etching.

[0061] The flow rate of the gas, process pressure, and amount of time the masked substrate is exposed to the reaction gas will vary depending on the desired etching.

[0062] In some embodiments, the pressure range in the etching process is 1 to 400 millitorr, radio- frequency power density is 0.25 to 1 W / cm2, and a RF (radio frequency) frequency of 13.56 megahertz.

[0063] In some embodiments, the masked substrate is held at a temperature of at least 20°C to at most 150°C during the etching process.

[0064] After etching the layer of amorphous silicon to the desired depth, as shown in Fig.1F, at least portion of the layer-by-layer thin film and patterned replication resin may remain on top of the amorphous silicon layer. Any remaining, undesired layer-by-layer thin film and / or patterned replication resin remaining may be removed using conventional processes, such as stripping with tape, leaving the etched amorphous silicon substrate as shown in Fig.1G. Although the above description refers to a tooling comprising holes, which results in a patterned mask comprising posts, various configurations of holes or posts can be used on the patterned replication resin to result in the desired etching of the amorphous silicon.

[0065] The patterned replication resin comprises a plurality of openings or features, patterned to provide a desired geometry, which is used to pattern the amorphous silicon layer. Generally, the patterned replication resin comprises a nanostructured surface having tall (or post) features and low (or open) features. Exemplary features include circles, squares, rectangles, quadrilaterals, or other designs. In some embodiments, the patterned mask has at least some features that are less than 5, 4, 3, 2, 1.5, 1, 0.9, 0.8, 0.5, 0.2, or even 0.1 micrometers in one dimension (in other words, length, width, diameter, etc.). Based on the technique used to make the patterned replication resin, the features are generally at least 50 nm in dimension.

[0066] Following the desired etching of the amorphous silicon, the replication resin and patterned layer- by-layer thin film can be removed resulting in Fig.1G, which is an article comprising a structured, or patterned, amorphous silicon surface.

[0067] The masking (or protection) of certain portions of the amorphous silicon layer is accomplished primarily by the layer-by-layer thin film which rests upon the patterned replication resin, which is used to create the nanostructured pattern. The patterned mask is used to protect covered areas of the amorphous silicon, while the uncovered areas can be etched (or removed) thereby transferring the pattern to the amorphous silicon layer. Due to the harsh conditions of plasma etching, generally, the patterned mask is etched along with the amorphous silicon during the etching process. Thus, either the mask needs to bethick enough to withstand the entire etching of the amorphous silicon and / or, more preferably, the composition of the mask etches at a similar or slower rate than the amorphous silicon.

[0068] The thickness of the layer-by-layer thin film is selected to withstand each reactive ion etching process that is performed so that the top surface of the amorphous silicon layer (shown by arrow 15 in Fig.1F) remains protected from etchant materials throughout the etching process. The thickness of the layer-by-layer thin film is dependent upon, among other things, the selectivity of the materials (in other words the etch rate of the mask versus the etch rate of the amorphous silicon layer). In some embodiments, the layer-by-layer thin film can have a thickness of at least 100, 150, 200, or even 400 nm and at most 500, 800, 1000, 1500, 2000, 3000, 4000, or even 5000 nm.

[0069] Ideally, the layer-by-layer thin film has good selectivity between the layer-by-layer thin film and the amorphous silicon to be etched. In other words, the composition of the layer-by-layer thin film is etched away at rate similar to, or less than, the etch rate of the amorphous silicon. In some embodiments, the selectivity of layer-by-layer thin film etch rate to the amorphous silicon layer etch rate of at most 2.5, 2.2, 2.0, 1.8, 1.6, 1.4, 1.2, 1.0, 0.8. or even 0.6. The layer-by-layer thin film is etched away at a rate smaller the patterned replication resin.

[0070] The patterned replication resin with the layer-by-layer thin film thereon comprises nanosized features (e.g., holes, posts, etc.) and results in an etched amorphous silicon layer having nanosized features. As used herein “nanometer sized” refers to a feature having an average dimension of at least 1, 2, 5, 10, 20, 25, or even 50 nm (nanometer) and at most 0.1, 0.2, 0.5, 0.8, 0.9, 1, 2, 3, 4, or even 5 micrometers. Ideally, the present disclosure is directed toward nanostructured surfaces, wherein the smallest dimension of an etched feature (in other words, length or width) is nanometer sized. Pitch, p, refers to the distance between features (center to center).

[0071] In some embodiments, the height, h, of the etched features of the amorphous silicon layer is on average at least 10, 25, 50, 100, 150, or even 200 nm; and at most 0.5, 0.8, 1, 1.5, 2, 2.5, 3, 4, or even 5 µm (micrometers). In some embodiments, the resulting feature, which was masked during the process has a width at the top of the feature (wt) of at least 10, 25, 50, 100, 150, or even 200 nm; and at most 0.5, 0.8, 1, 1.5, 2, 2.5, 3, 4, or even 5 µm. In some embodiments, the resulting feature, which was masked during the process has a length at the top of the feature (lt) of at least 10, 25, 50, 100, 150, or even 200 nm; and at most 0.5, 0.8, 1, 1.5, 2, 2.5, 3, 4, or even 5 µm. Ideally, the etched amorphous silicon layer has etched features with vertical sidewalls. For example, width at feature top versus width at feature bottom (wt / wb) (or length at top versus length at bottom, lt / lb) = 0.9 or even more preferably 1. In certain embodiments, the features have an aspect ratio of height (h) to span at the top of the feature at least 0.25, 0.5, 0.75, or even 1 and at most 1.5, 2, 2.5, 3, 4, 5, 6, 8, or even 10. By “span” is meant the shortest dimension at the top of the feature orthogonal to the height. Thus, span can refer to wtor lt. The features may comprise shapes including, but are not limited to, rectangular, triangular and trapezoidal prisms; fins, cylindrical and truncated-cone shaped pillars, etc. The features may be placed with regular or randomized pitch, orientation, and shapes, dependent on application-functionality and determined article design. The pitch is the distance between adjacent features (center-to-center). In some cases, the features have a pitch thatis less than half of a predetermined wavelength of electromagnetic radiation (such as visible light, IR, etc.).

[0072] In some embodiments, the layer-by-layer thin film of the present disclosure enables improved dimensional stability. During etching, the plasma etches the exposed amorphous silicon perpendicular to the major surface of the amorphous silicon layer. However, as is known in the art, the plasma can etch amorphous silicon under the mask, in a process referred to as “undercutting”. In some embodiments, the resulting patterned features on the etched amorphous silicon have a % change from the initial of less than 15, 10, 8, 6, 4, or even 2.

[0073] In some embodiments, the structured amorphous silicon layers of the present disclosure may be used in infrared (IR) metasurfaces. IR metasurfaces are planar devices composed of subwavelength structures (i.e., meta-atoms) and can steer the polarization, phase, and amplitude of electromagnetic waves at the wavelengths between 0.700 micrometers and 300 micrometers. Their ability to control the properties of electromagnetic waves, particularly polarization, in the longer IR wavelength region allows these materials to play an important role for various applications including optical sensing, thermal imaging, and free-space wireless communication. EXAMPLES

[0074] Unless otherwise noted, all parts, percentages, ratios, etc. in the examples and the rest of the specification are by weight, and all reagents used in the examples were obtained, or are available, from general chemical suppliers such as, for example, Sigma-Aldrich Company, Saint Louis, Missouri, or may be synthesized by conventional methods.

[0075] Unless otherwise noted, all parts, percentages, ratios, etc. in the examples and the rest of the specification are by weight, and all reagents used in the examples were obtained, or are available, from general chemical suppliers such as, for example, Sigma-Aldrich Company, Saint Louis, Missouri, or may be synthesized by conventional methods.

[0076] These abbreviations are used in the following examples: °C = degree Celsius, cc = cubic centimeter, cP =CentiPoise, cm = centimeter, gsm = grams per square meter, ft = feet, fpm = feet per minute kHz = kilohertz, kW = kilowatt, µm= micrometer, m = meter, min = minute, mm = millimeter, MHz = megahertz, MPa = megapascal, mtorr = milli Torr, sccm = standard cubic centimeters per minute, s = second, W = Watts, and wt = weight. Table 1. Materials List Name Description TEGO RC 702 Solvent-free, UV-curing silicone acrylate release obtained under the trade designation “Tego RC 702” from Evonik Industries, Essen, Germany Omnirad 819 Bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide, UV / Visible photoinitiator obtained from GM Resins, Waalwijk, The Netherlands MIBK Methyl isobutyl ketone obtained from Alfa Aesar, Haverhill, MAIPA Isopropyl alcohol obtained from VWR, Radnor, PA MIBK-ST Colloidal silica nanoparticles, 31 wt % dispersed in methyl isobutyl ketone obtained from Nissan Chemical Industries, Ltd, Tokyo, Japan TOL-ST Colloidal silica nanoparticles, 31 wt % dispersed in toluene obtained from Nissan Chemical Industries, Ltd, Tokyo, Japan SR238 1,6-hexandiol diacrylate obtained from Sartomer Americas, Exton, PA SR351 trimethylopropane triacrylate obtained from Sartomer Americas Nalco 1056 Colloidal dispersion of 20 nm-diameter alumina-coated silica nanoparticles in water at 30% wt solids concentration obtained from Nalco Chemical Co., Naperville, IL Nalco 2329 Colloidal dispersion of 75 nm-diameter silica nanoparticles in water at 40% wt solids concentration obtained from Nalco Chemical Co. PDAC Poly(diallyldimethylammonium chloride) at 40 wt % solids content under the trade designation Dehyquart CC 6 polymer obtained from BASF co., Ludwigshafen, Germany TiO214 wt % stock TiO2nanoparticle solution obtained from 3M Co., St. Paul, MN TMACl Tetramethylammonium Chloride, 50 wt % aqueous solution obtained from SACHEM Americas, Austin, TX TMAOH Tetramethylammonium Hydroxide, 2.38 wt % aqueous solution obtained from Alfa Aesar Silicon wafer 100 mm Silicon wafers, N-type doped with P, <100> Res 0-100, 500 um thick, SSP, Test-Grade obtained from University Wafer, Boston, MA NF3 nitrogen trifluoride (ultra-high purity grade) obtained from Airgas, St. Paul, MN Argon argon (ultra-high purity grade) obtained from Airgas SF6 Sulfur hexafluoride obtained from Scott Specialty Gases, Plumsteadville, PA SiH4 / Ar mixture silane (2% in argon) obtained from Airgas aSi Amorphous boron-doped silicon (sputter target), 99.999% obtained from ProTech Materials, Hayward, CA ST504 PET heat-stabilized polyester film, 500-gauge (127 µm) thickness, single-side primed obtained under the trade designation “MELINEX ST504” from DuPont Teijin Films, Chester, VA ST505 PET heat-stabilized polyester film, 500-gauge (127 µm) thickness, double- side primed obtained under the trade designation “MELINEX ST505” DuPont Teijin Films

[0077] Preparation of amorphous silicon samples A-C

[0078] Preparation of amorphous silicon layer on ST504 PET. A custom-built Mill Lane Engineering roll-to-roll sputter coating system using aSi sputter targets disposed on the sputter sources in an argon atmosphere was used. The sputter sources are 5 in (127 mm) x 15 in (381 mm) magnetron sources from Material Science (Canton, MI). There are multiple sputter sources (three total) surrounding a cooled drum that cools the ST504 PET when performing the sputter deposition. The sputtering process was as follows: the chamber was pumped to a base pressure of less than 2x10-6Torr, and Argon was introduced into the sputter chamber at a flow rate of 200 sccm. Pumping was then throttled by closing off various cryopumps to achieve a process pressure of 3 mTorr. A 20 kHz pulsed DC power supply was used for the sputtering process at an applied power of 4 kW. The deposition time (correlated to thickness) was controlled by translating the film over the cooled drum and through the sputter zone(s) at 3 ft / min (0.91 m / min) for the designated machine passes until the desired thickness was achieved. Following the sputter depositionprocess, the process gas flow, applied power, and film translation were stopped, and the chamber was returned to atmospheric pressure. Shown in Table 2 below is the number of machine passes used for each sample. Table 2 Amorphous Silicon Sample Machine passes A 14 B 24 C 36

[0079] Preparation of amorphous silicon sample D

[0080] Preparation of a hydrogenated amorphous silicon layer on ST505 PET. Plasma enhanced chemical vapor deposition (PECVD) was performed in a home-built parallel plate capacitively coupled plasma reactor. The chamber had a central cylindrical powered electrode with a surface area of 1.24 m2. After placing ST505 PET on the powered electrode, the reactor chamber was pumped down to a base pressure of less than 1 mTorr. SiH4 / Ar mixture was introduced into the chamber at a flow rate of 4000 sccm. Deposition was carried out by coupling RF power into the reactor at a frequency of 13.56 MHz and an applied power of 6500 watts with a deposition time of 67 min. During deposition, the powered electrode was rotated at a linear speed of 1 fpm (0.3 m / min) to simulate a roll-to-roll process. Following deposition, the RF power and the gas supply were stopped, and the chamber was returned to atmospheric pressure. Additional information regarding materials and processes for applying cylindrical PECVD and further details around this kind of reactor can be found in U.S. Pat. No.8,460,568 (David et al.).

[0081] Tooling

[0082] The tooling film was generated as follows:

[0083] A nickel master comprised a nanostructured nickel surface that had nanostructured patterns which were attached to a steel roller. The nickel master comprised a plurality of posts (post diameter of 1233 nm and height of 1250 nm), which when replicated generated a tooling comprising a plurality of holes.

[0084] Resin A was prepared by combining and mixing PHOTOMER 6210, SR351, SR238 and IRGACURE TPO in respective weight ratios of 60 / 20 / 20 / 0.5. After all components were added, the resin composition was blended by warming to approximately 50 °C and mixing for 12 hours on a roller mixer, resulting in a homogeneous mixture.

[0085] Resin A was then die coated onto ST505 PET for form a coated film. Resin A on the coated film then was pressed against the nickel master described above. Resin A fully wet the nickel surface and formed a rolling bead of Resin A as the coated film was pressed against the nickel surface. Resin A was exposed to radiation from two UV lamp systems (obtained under the trade designation “F600” from Fusion UV Systems, Gaithersburg, MD) fitted with D bulbs both operating at 142 W / cm, while in contact with the nickel master to gel Resin A. The resulting nanostructured gelled Resin A was peeled from the master tooling and then further exposed to radiation from a UV lamp system (obtained under the trade designation “F600” from Fusion UV Systems) fitted with a D bulb operating at 142 W / cm to generate thetooling. This tooling was corona treated for 5 passes prior to use to aid in adhesion of the layer-by-layer coating.

[0086] Methods to determine coating thickness

[0087] Method 1-Spectroscopic Ellipsometry (SE) Method

[0088] SE measurements were collected with a dual-rotating compensator ellipsometer (RC2 from J.A. Woollam Co., Lincoln, NE) at 790 wavelengths between 200-1000 nm. Measurements were collected in reflection at angles of 65, 70, 75 and 80°, unless otherwise noted. The resulting data was analyzed or modeled in CompleteEase software available from J.A. Woollam Co. The samples were modeled using a biaxial description (multiple B-spline functions) of PET as measured from a reference substrate (ST504 PET). The deposited coatings were modeled using oscillator models. Prior to measurement of each sample, reference points on the sample measurement stage were marked on the sample such that the sample could be registered for measurement before and after etching, minimizing any error from sample thickness non-uniformity.

[0089] Method 2- Reflectance Spectroscopy Method

[0090] Reflectance spectroscopy measurements were collected with a visible wavelength spectrum fiber optic spectrometer purchased from tec5USA Inc. (Plainview, NY). The spectrometer was interfaced with proprietary spectral analysis software to calculate coating thickness based on the reflectance spectra and fixed refractive index input. Unless otherwise noted, a refractive index of 1.45 was used. Prior to measurement of each sample, reference points on the sample measurement stage were marked on the sample such that the sample could be registered for measurement before and after etching, minimizing any error from sample thickness non-uniformity.

[0091] Method 3- Wavelength Dispersive X-ray Fluorescence (WDXRF) Spectroscopy Method

[0092] WDXRF measurements were collected with a Supermini200 WDXRF instrument from Rigaku Corporation (Woodlands, TX). Samples were measured in vacuum using the manufacturer-standard settings to measure the net intensity of the silicon k-alpha peak. A calibration curve was constructed using physical thickness measurements from scanning electron microscopy (SEM) images and silicon k-alpha intensity values for samples of varying known thickness. Linear regression analysis of the data with a zero intercept was used to generate the calibration curve. The WDXRF measurements for the samples were converted to a physical thickness using the constructed calibration curve.

[0093] Test Method 4- Scanning Electron Microscopy (SEM) Imaging

[0094] Samples were mounted on aluminum examination stubs and coated with AuPd by DC sputtering in a Denton Vacuum Desk IV coater to ensure conductivity. Examinations were performed in Field Emission Scanning Electron Microscope (Hitachi high-Tech, Schaumburg, IL). Where applicable, feature dimensions were measured in ImageJ using the reference scale bar generated by the microscope.

[0095] Test Method 5- Profilometry

[0096] The coating thickness was measured with a Dektak XT stylus profilometer (Bruker Nano Inc., Tucson, Arizona) after scratching the surface with a razor blade.

[0097] Reactive Ion Etching (RIE) Method

[0098] RIE was performed in a custom-built parallel plate capacitively coupled plasma reactor. The chamber had a central cylindrical powered electrode with a surface area of about 1.70 m2. After loading the rolled material into the chamber, the reactor chamber was pumped down to a base pressure of less than 1 mtorr. Process gas was introduced into the chamber at the flow rates detailed below. RIE was performed by coupling RF power into the reactor at a frequency of 13.56 MHz and an applied power of 7500 watts (about 0.44 W / cm2). The treatment time was controlled by translating the film samples through the reaction zone at the designated speeds and operating pressures. Following the treatment(s), the process gas flow, applied power, and film translation were stopped, and the chamber was returned to atmospheric pressure. Additional information regarding materials and processes for applying cylindrical RIE and further details around the reactor used can be found in U.S. Pat. No.8,460,568.

[0099] Preparative Examples 1-4 (PE-1 to PE-4)

[0100] PE-1, which is an aqueous coating solution composed of Nalco 1056 diluted at 1 wt% concentration and has an adjusted pH of 3, was prepared by first adding 16.67 g of the 30% Nalco 1056 stock solution in a 16 oz. plastic jug with stir bar. Deionized (DI) water was then added to an approximate mass of 350 g then the pH of the solution was adjusted to 3.0 by gradually adding 1N HCl and optionally adjusting with 1N NaOH. Afterwards, additional DI water was added to reach a total mass of 500 g and the resulting solution was stirred for at least 10 min before use.

[0101] PE-2, which is an aqueous coating solution composed of Nalco 2329 diluted at 1 wt% concentration and has an adjusted pH of 3, was prepared by first adding 12.5 g of the 40% Nalco 2329 stock solution in a 16 oz. plastic jug with stir bar. Deionized (DI) water was then added to an approximate mass of 350 g then the pH of the solution was adjusted to 3.0 by gradually adding 1N HCl and optionally adjusting with 1N NaOH. Afterwards, additional DI water was added to reach a total mass of 500 g and the resulting solution was stirred for at least 10 min before use.

[0102] PE-3, which is an aqueous coating solution composed of PDAC at 1 wt% concentration and has an adjusted pH of 12 using TMAOH, was prepared by first adding ~300 g of deionized water and 0.71 g of TMAOH onto a 16 oz. plastic jar with stir bar. Additional amounts of TMAOH were added to set the pH to 12. Afterwards, 4.14 g of PDAC was added. Lastly, additional DI water was added to reach a total mass of 500 g and the resulting solution as stirred for at least 10 min before use.

[0103] PE-4, which is an aqueous coating solution composed of TiO2nanoparticles at 1 wt% concentration and has an adjusted pH of 12 using the TMAOH, was prepared by first adding ~300 g of deionized water, 6.93 g of 50.4 % TMACl solution, and 8.6 g of TMAOH onto a 16 ounce plastic jar with stir bar. Additional amounts of TMAOH were added to set the pH to 12. Afterwards, 35.71 g of the 14% TiO2stock solution (3M) was added. Lastly, additional DI water was added to reach a total mass of 500 g and the resulting solution was stirred for at least 10 min before use.

[0104] Preparative Examples 5-10 (PE-5 to PE-10)

[0105] Polymerizable mixtures were prepared by using the amounts listed in Table 4. First, appropriate amounts of Omnirad 819 and TEGO RC 702 were weighed onto an amber glass jar with a stir bar. Solvent was then added, and the resulting mixture was stirred for at least 5 minutes until thephotoinitiator and oligomer were visibly dissolved. Afterwards, if used, the silica dispersion (TOL-ST or MIBK-ST) was added, and the resulting solutions were stirred once more. Table 4 PE-5 PE-6 PE-7 PE-8 PE-9 PE-10 Total Amount of 100 10 Mixture (g) % Total Solids 15% 20% Composition %Initiator of based on % none 1% Polymerizable Solids Mixture % Silica based on % 0 10% 20% 30% 40% 50% Solids Silica Used none TOL- ST MIBK-ST Solvent IPA / MIBK (80:20) MIBK Omnirad 819 none 0.02 Actual TEGO RC 702 15 1.8 1.6 1.4 1.2 1 Amounts (g) Used Solvent 85 7.353 6.706 6.058 5.411 4.764 Silica Dispersion none 0.647 1.294 1.942 2.589 3.236

[0106] Each of the polymerizable solutions were coated onto ST504 PET using a #3 wire-wound rod and cured using a UV processor equipped with an H-type bulb (500 W, Heraeus Noblelight America / Fusion UV Systems, Hanau, Germany) at 100% power under nitrogen purge at 30 ft / min (9.1 m / min). The apparent loss of tackiness of the resulting coating indicated that the coating successfully cured.

[0107] Comparative Example Set 1 (CE-1)

[0108] The etch rate of Amorphous Silicon Substrates B and D were studied by testing each sample according to the RIE Method using varying flow rates of NF3. The thickness of the amorphous silicon was measured using Method 3 both before and after etching to determine the etch rate and is reported in Table 7.

[0109] PE-5 to PE-10 were studied by testing each sample according to the RIE Method using varying flow rates of NF3. The thickness of the amorphous silicon was measured using Method 1 and / or Method 2 both before and after etching to determine the etch rate and is reported in Table 7.Table 7 Sample % SiO2 NF3 etch rate (nm / min) 125 sccm 250 sccm B 0 90 145 D 0 96 170 PE-5 0 344 408 PE-6 10 335 331 PE-7 20 318 335 PE-8 30 303 316 PE-9 40 263 283 PE-10 50 230 276

[0110] Using the data from Table 7, the selectivity ratio of PE-5 to PE-10 versus Sample B and Sample D were calculated, for example by dividing the etch rate of PE-5 by the etch rate of B. The results are shown in Table 8. Table 8 NF3Selectivity Ratio NF3Selectivity Ratio of Coatings Compared of Coatings Compared Input Sample to Substrate B to Substrate D 125 sccm 250 sccm 125 sccm 250 sccm PE-5 3.82 2.81 3.58 2.40 PE-6 3.72 2.28 3.49 1.95 PE-7 3.53 2.31 3.31 1.97 PE-8 3.37 2.18 3.16 1.86 PE-9 2.92 1.95 2.74 1.66 PE-10 2.56 1.90 2.40 1.62

[0111] Example 1

[0112] Layer-by-layer constructions were prepared on silicon wafer as follows. The silicon wafer as initially rinsed with isopropyl alcohol, dried with nitrogen and plasma cleaned for 5 min. The silicon wafer was then mounted on the sample holder of a robotic dip coater like the system reported in Gamboa, et al., Review of Scientific Instruments 51, 036103 (2010). The automatic dip coater can be programmed to alternately immerse the silicon wafer in the designated coating solutions. The coater was equipped with spray nozzles to rinse the silicon wafer with deionized water immediately after immersion in the coating solution and separate nozzles with compressed air to dry the substrates. The total dwell time for each immersion was 24 seconds.

[0113] The silicon wafer was immersed in an aqueous dispersion / solution of PE-1 washed with water and dried with nitrogen. Afterwards, it was then immersed in a PE-2, washed with water, and driedwith nitrogen. This sequence, which corresponds to 1 bilayer, was repeated until the 35 bilayers were deposited. Method 5 was used to determine the thickness of the SiO2coating on the silicon wafer and was measured to be 1220 ± 35 nm.

[0114] Example 2

[0115] Layer-by-layer constructions were prepared on ST505PET film as follows. A sheet of ST505PET film was cut into a 4 in × 4 in (10.2 centimeters (cm) x 10.2 cm) piece and adhered at the edges on a 4 in × 4.75 in (10.2 cm x 12.0 cm) glass plate with epoxy (Scotch-Weld epoxy adhesive obtained as DP100 CLEAR, 3M Company, St. Paul, MN, USA). The ST505PET adhered to the glass plate was corona treated by hand using a BD-20AC Laboratory Corona Treater (Electro-Technic Products, Chicago, IL, USA). Then, the automatic dip coater was used to coat 35 bilayers of PE-1 and PE-2 as described in Example 1.

[0116] Example 3

[0117] Example 3 was prepared similarly to Example 1 except that PE-3 was used instead of PE- 1 and PE-4 was used instead of PE-2. Method 5 was used to determine the thickness of the TiO2coating on the silicon wafer and was measured to be 389 ± 6 nm.

[0118] Example 4 was prepared similarly to Example 2 except that PE-3 was used instead of PE- 1 and PE-4 was used instead of PE-2. Based on the amounts used and the depositing conditions, the thin film contained 90.6 wt% of TiO2and 9.4 wt% of PDAC.

[0119] REI was performed on Examples 2 and 4 at two different flow rates of NF3(i.e., 125 and 250 sccm). The amount of material etched was calculated by Method 1 before and after exposure to the NF3plasma for multiple exposure times ranging from 60 to 200 s. The etch rate was then calculated and the results are shown in Table 9. Table 9 Sample NF3etch rate (nm / min) 125 sccm 250 sccm EX 2 146 187 EX 4 142 >260

[0120] Using the data from Table 9, the selectivity ratio of EX 2 and EX 4 versus Sample B and Sample D were calculated and the results are shown in Table 10. Table 10 NF3Selectivity Ratio of Coatings Compared to NF3Selectivity Ratio of Coatings Sample Substrate B Compared to Substrate D 125 sccm 250 sccm 125 sccm 250 sccm EX 2 1.62 1.29 1.52 1.10 EX 4 1.58 1.79 1.48 1.53

[0121] Example 5

[0122] Example 5 was prepared similar to Example 1 except that the layer-by-layer composition was formed on a corona-treating Tooling instead of a silicon wafer. Shown in Fig.5 is an SEM image of a cross-section of Example 5 showing layer-by-layer composition 26 overcoating Tooling 22 and filling the cavities of the tooling.

[0123] Foreseeable modifications and alterations of this invention will be apparent to those skilled in the art without departing from the scope and spirit of this invention. This invention should not be restricted to the embodiments that are set forth in this application for illustrative purposes. To the extent that there is any conflict or discrepancy between this specification as written and the disclosure in any document mentioned or incorporated by reference herein, this specification as written will prevail.

Claims

What is claimed is:

1. An article comprising the following layers in order: a base substrate; an amorphous silicon layer; a patterned replication resin comprising a nanostructured surface; and a thin film disposed on the nanostructured surface, wherein the thin film comprises at least 60 % by weight of inorganic nanoparticles.

2. An article according to claim 1, wherein the thin film comprises at least 85 % by weight of inorganic nanoparticles.

3. An article according to claim 1, wherein the thin film comprises at least 95 % by weight of inorganic nanoparticles.

4. The article of any one of the previous claims, wherein the thin film has a thickness of at least 50 nm and at most 2 micrometers.

5. The article of any one of the previous claims, wherein the inorganic nanoparticle comprises SiO2, Al2O3, Sb2O5, ZrO2, HfO7, TiO2, ZnO2, or mixtures thereof.

6. The article of any one of the previous claims, wherein the inorganic nanoparticles have an average diameter of 5 nm to 500 nm.

7. The article according to any one of the previous claims, wherein the thin film comprises a polyelectrolyte organic polymer.

8. The article of claim 7, wherein the polyelectrolyte organic polymer is a polycationic organic polymer.

9. The article of claim 8, wherein the polycationic organic polymer comprises a linear and branched poly(ethylenimine) (PEI), poly(allylamine hydrochloride), polyvinylamine, chitosan, polyaniline, polyamidoamine, poly(vinylbenzyltriamethylamine), polydiallyldimethylammonium chloride (PDAC), poly(dimethylaminoethyl methacrylate), poly(methacryloylamino)propyl- trimethylammonium chloride, or combinations thereof including copolymers thereof.

10. The article of claim 7, wherein the polyelectrolyte organic polymer is a polyanionic organic polymer.

11. The article of claim 10, wherein the polyanionic organic polymer comprises poly(vinyl sulfate), poly(vinyl sulfonate), poly(acrylic acid) (PAA), poly(methacrylic acid), poly(styrene sulfonate), dextran sulfate, heparin, hyaluronic acid, carrageenan, carboxymethylcellulose, alginate, sulfonated tetrafluoroethylene based fluoropolymers, poly(vinylphosphoric acid), poly(vinylphosphonic acid), or combinations thereof including copolymers thereof.

12. The article according to any one of the previous claims, wherein the patterned replication resin is derived from a (meth)acrylate or a (meth)acrylate-functionalized silicone.

13. The article of any one of the previous claims, wherein the patterned replication resin has an aspect ratio of at most 5.

14. The article of any one of the previous claims, wherein the patterned replication resin comprises a plurality of features, wherein the plurality of features has an average height of between 10 nm and 5 micrometers, inclusive.

15. The article of any one of the previous claims, wherein the patterned replication resin comprises a plurality of features, wherein the plurality of features has an average length and / or width between 10 nm and 5 micrometers, inclusive.

16. The article of any one of the previous claims, wherein the base substrate comprises polyethylene terephthalate (PET), polyethylene terephthalate glycol (PETg), polyethylene napthalate (PEN), heat stabilized PET, heat stabilized PEN, polyoxymethylene, polyvinylnaphthalene, polyetheretherketone, a fluoropolymer, polycarbonate, polymethylmeth(meth)acrylate, poly α- methyl styrene, polysulfone, polyphenylene oxide, polyetherimide, polyethersulfone, polyamideimide, polyimide, polyphthalamide, cyclic olefin polymer (COP), cyclic olefin copolymer (COC), triacetate cellulose (TAC), or combinations thereof.

17. The article of any one of the previous claims, wherein the base substrate has an indefinite length.

18. The article of any one of the previous claims, wherein the amorphous silicon layer comprises doped silicon, a hydrogenated silicon, or combinations thereof.

19. The article of any one of the previous claims, wherein the thickness of the amorphous silicon layer is at least 100 nm to at most 5 micrometers.

20. The article of any one of the previous claims, further comprising a layer disposed between the amorphous silicon layer and the base substrate, wherein the layer comprises metal or metal oxide.

21. The article of claim 20 wherein the metal or metal oxide layer is comprised of Al, Al2O3, Cr, Cr2O3, or combinations thereof.

22. The article of claim 20 or claim 21 wherein the layer disposed between the amorphous silicon and the base substrate is less than 150 nm thick.

23. A method comprising: (a) providing an amorphous silicon layer on a base substrate; (b) patterning a replication resin disposed on the amorphous silicon layer; and (c) depositing a thin film onto the replication resin, wherein the thin film comprises at least 60% by weight of inorganic nanoparticles.

24. The method of claim 23, wherein the thin film is a layer-by-layer film formed by depositing a first layer comprising positive polyelectrolyte and a second layer comprising a negative polyelectrolyte wherein at least one of the positive or negative polyelectrolytes is an inorganic nanoparticle.

25. The method of claim 24, wherein the thin film comprises at least 3 and no more than 100 bi- layers, wherein one bi-layer includes a first layer and a second layer.

26. The method of any one of claims 23-25, further comprising (d) planarly removing the thin film until reaching the replication resin.

27. The method of claim 26, wherein fluorine, chlorine, or bromine etching is used to planarly remove the layer-by-layer thin film.

28. The method of any one of claims 26-27, further comprising (e) removing any exposed replication resin to form a masked substrate.

29. The method of claim 28, wherein oxygen etching is used to remove the exposed replication resin.

30. The method of any one of claims 28-29, further comprising exposing the masked substrate to reactive ion etching.

31. The method of claim 30, wherein the reactive ion etching comprises fluorine containing gases.

32. The method of any one of claims 30-31, further comprising removing the patterned layer following reactive ion etching.

33. The method of any one of claims 23-32, wherein the amorphous silicon layer is deposited by plasma enhanced chemical vapor deposition.

34. The method of any one of claims 23-33, wherein the method is run in a continuous roll-to-roll fashion.

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