Nanoparticle-filled masks for reactive ion etching silicon and methods thereof

Abstract

Described herein is patterned mask for reaction ion etching silicon substrates, wherein the patterned mask is derived from a (meth)acrylate-functionalized silicone and a plurality of inorganic nanoparticles.

Description

NANOPARTICLE-FILLED MASKS FOR REACTIVE ION ETCHING SILICON 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 mask derived from (meth)acrylate-functionalized silicone and inorganic nanoparticles is described that can be used for reactive ion etching of silicon as well as methods of making and using the masks. BRIEF DESCRIPTION OF DRAWINGS

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

[0003] Figs.1A-1C is a schematic cross-sectional view of an article at various steps during construction according to one embodiment of the present disclosure.

[0004] Fig.1D is an isometric view of an etched feature in the patterned silicon layer.

[0005] Fig. 2 is a schematic of a roll-to-roll process to make an article according to one embodiment of the present disclosure. SUMMARY

[0006] 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.

[0007] Thus, 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.

[0008] In one aspect, an article is described comprising (i) a base substrate; (ii) a patterned mask having an outwardly facing nanostructured surface, wherein the patterned mask is derived from a (meth)acrylate- functionalized silicone and inorganic nanoparticles; and (iii) an amorphous silicon layer disposed between the base substrate and the patterned mask.

[0009] In another aspect, a method is described. The method comprising: (a) providing amorphous silicon layer on a base substrate; (b) disposing a second layer derived from a (meth)acrylate-functionalized silicone, inorganic nanoparticles, and an initiator onto the amorphous silicon layer; and (c) disposing a patterned layer on the second layer and curing the second layer to form a patterned mask.

[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] 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).

[0016] 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.).

[0017] 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.).

[0018] As used herein “(meth)acryl” refers to compounds containing either an acryl (CH2=CHCOO-) or a methacryl (CH2=CCH3COO-) structure or combinations thereof.

[0019] 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.

[0020] The present disclosure may be understood by reference to Figs.1A-1C, which depicts cross- sectional views of one embodiment of the article of the present disclosure being constructed. Shown in Fig.1A is article 10 comprising base substrate 16 and patterned mask 12A with amorphous silicon layer 14A disposed therebetween. As shown in Fig.1 A, patterned mask 12A comprises an outwardly facing nanostructured surface. In other words, the patterned surface of the patterned mask is located on the opposing surface from the amorphous silicon layer. Article 10 is exposed to an etching process, going through Fig.1B, wherein amorphous silicon layer 14B and a portion of the patterned mask 12B are removed, ultimately resulting in etched article 30 of Fig.1C, comprising patterned silicon layer 14C disposed on base substrate 16. In some embodiments, the article comprises a metal layer comprising a metal or metal oxide 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.

[0021] 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 be thick 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.

[0022] The patterned mask is a composite derived from a polymerizable composition comprising a (meth)acrylate-functionalized silicone and a plurality of inorganic nanoparticles. The (meth)acrylate- functionalized silicone provides easy removal of the mask from the tooling during manufacture and acts as a matrix for the inorganic nanoparticles. As shown in the examples, the inorganic nanoparticles help to decrease the etch rate of the mask.

[0023] The (meth)acrylate-functionalized silicone is an ethylenically unsaturated compound comprising a plurality of repeating siloxane units and at least one (meth)acryl moiety. A siloxane unit is for example, -(O-SiR2)-, where each R is a monovalent organic group, such as methyl, ethyl, acryl, or methacryl.

[0024] In some embodiments, the (meth)acrylate-functionalized silicone is terminated by two (meth)acryl moieties. For example, in some embodiments, the (meth)acrylate-functionalized silicone comprises a (meth)acryloxyalkyl-terminated polydimethylsiloxane such as according to Formula Iselected from 5 to at most 50. In some embodiments, n and m are integers independently selected from at least 5, 8, 10, 12, 15, 18, 20, or even 25 and at most 50, 45, 40, 35, or even 30.

[0025] In some embodiments, the (meth)acrylate-functionalized silicone comprises a (meth)acryloxyalkoxy-terminated polydimethylsiloxane such as according to Formula IIost 50. In some embod ments, n and m are ntegers ndependent y se ected rom at east 5, 8, 10, 12, 15, 18, 20, or even 25 and at most 50, 45, 40, 35, or even 30.

[0026] In some embodiments, the (meth)acrylate-functionalized silicone comprises more than two (meth)acryl moieties, for example, in some embodiments, the (meth)acrylate-functionalized silicone is a random copolymer comprising repeat siloxane groups and repeat (meth)acryl modified siloxane group. In some embodiments, the (meth)acrylate-functionalized silicone is a [(meth)acryloxyalkyl]methylsiloxane dialkyl siloxane such as according to Formula III 2, 3, 4, or 5, and p and q are independently selected fromintegers from 5 to at most 50. In some embodiments, p and q are integers independently selected from at least 5, 8, 10, 12, 15, 18, 20, or even 25 and at most 50, 45, 40, 35, or even 30. An exemplary (meth)acrylate-functionalized silicone is represented by Formula IV: Wherein X is H orat most 50. In some embodiments, p and q are integers independently selected from at least 5, 8, 10, 12, 15, 18, 20, or even 25 and at most 50, 45, 40, 35, or even 30.

[0027] Generally, the (meth)acrylate-functionalized silicone has a smaller molecular weight to enable ease of coating and ability to completely fill the tooling. In some embodiments, the (meth)acrylate- functionalized silicone has a molecular weight of at least 500, 750, 1000, 1200, 1500, or even 1800 Daltons; and at most 3000, 2800, 2500, 2200, or even 2000 Daltons.

[0028] Exemplary (meth)acrylate-functionalized silicone may be synthesized using techniques known in the art or 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.

[0029] In some embodiments, the polymerizable composition comprises 5, 10, 15, 20, 25, 30, 35, 40, 50, 55, 60, 65, 70, 75, 80, 85, 90, or even 95 % by weight of (meth)acrylate silicone based on total solids, wherein total solids is the amount of material remaining after any volatile components (such as solvents) are removed from the polymerizable composition.

[0030] The polymerizable composition further comprises a plurality of inorganic nanoparticles. Exemplary inorganics include metals and metal oxides, such as SiO2, Al2O3, Sb2O5, ZrO2, HfO7, TiO2, ZnO2, and mixtures thereof.

[0031] The inorganic particles are nanometer-sized, meaning that the largest dimension (e.g., diameter) has an average dimension of less than 100, 90, 80,70, 60 or even 50 nanometers (nm). In some embodiments, the particles have an average particle diameter of at least 1, 2, 5, 8, 10, 12, 15, 20, 25, 30, 35, 40, or even 45 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).

[0032] In some embodiments, the inorganic nanoparticles used in the present disclosure are spherical or substantially spherical in shape. In other embodiments, the inorganic nanoparticle may be rod-like in appearance.

[0033] The inorganic nanoparticles used in the present disclosure are typically un-aggregated and / or unagglomerated. If the unmodified inorganic nanoparticles are an aggregation of primary particles, then the maximum cross-sectional dimension of the aggregated nanoparticle is within the range of range of about 3 nm to about 100 nm, about 3 nm to about 50 nm, about 3 nm to about 20 nm, or even about 3nm to about 10nm.

[0034] In some embodiments, the surface of the inorganic nanoparticles of the present disclosure is unmodified, such as silica have a negative surface charge.

[0035] In another embodiment, the surface of the inorganic nanoparticles may be associated with an organic compound via ionic bonding, hydrogen bonding, Van der waals forces, etc. For example, organic compounds with an acid end group, (e.g., a carboxylate salt, a carboxylic acid, a phosphonate, a phosphonic acid, or a hydroxylamine) may ionically bond to the surface of the inorganic nanoparticle. For example, inorganic nanoparticles may be surface treated through adsorption of acidic or basic compounds onto the nanoparticle’s surface. Inorganic particles such as zirconia, alumina, or titania may be treated with an acidic compound, such as with carboxylic acids, phosphonic acids, and sulfonic acids or an acidic function derived from oxyacids of boron, carbon, phosphorus, and sulfur. In some embodiments, the inorganic nanoparticles are hydrophobically modified with organic compounds using the surfacetreatments. Exemplary organic compounds that may be non-covalently bonded to the inorganic nanoparticles include: acetic acid or short chain organic molecules comprising an acidic end group such as polyalkyleneoxide, a polyol or a hydroxyl-substituted moiety having a carboxylate salt, carboxylic acid, phosphoniate, phosphonic acid, hydroxyamine end group. The organic compounds may include hydrocarbon moieties, including alkyl chains and or tert-butyl groups, optionally comprising catenated oxygen (i.e., ether), nitrogen (i.e, amine), and / or sulfur (i.e., thiol) atoms, which result in the inorganic nanoparticles having a hydrophobic character. Exemplary surface treatment agents include N-(3- triethoxysilylpropyl) methoxyethoxyethoxyethyl carbamate, N-(3-triethoxysilylpropyl) methoxyethoxyethoxyethyl carbamate, 3-(methacryloyloxy)propyltrimethoxysilane, 3- acryloxypropyltrimethoxysilane, 3-(methacryloyloxy)propyltriethoxysilane, 3-(methacryloyloxy) propylmethyldimethoxysilane, 3-(acryloyloxypropyl) methyldimethoxysilane, 3- (methacryloyloxy)propyldimethylethoxysilane, 3-(methacryloyloxy) propyldimethylethoxysilane, vinyldimethylethoxysilane, phenyltrimethoxysilane, n-octyltrimethoxysilane, dodecyltrimethoxysilane, octadecyltrimethoxysilane, propyltrimethoxysilane, hexyltrimethoxysilane, vinylmethyldiacetoxysilane, vinylmethyldiethoxysilane, vinyltriacetoxysilane, vinyltriethoxysilane, vinyltriisopropoxysilane, vinyltrimethoxysilane, vinyltriphenoxysilane, vinyltri-t-butoxysilane, vinyltris-isobutoxysilane, vinyltriisopropenoxysilane, vinyltris(2-methoxyethoxy)silane, styrylethyltrimethoxysilane, mercaptopropyltrimethoxysilane, 3-glycidoxypropyltrimethoxysilane, acrylic acid, methacrylic acid, oleic acid, stearic acid, dodecanoic acid, 2-[2-(2-methoxyethoxy)ethoxy]acetic acid (MEEAA), beta- carboxyethylacrylate (BCEA), 2-(2-methoxyethoxy)acetic acid, methoxyphenyl acetic acid, and mixtures thereof.

[0036] The inorganic nanoparticles are typically homogeneously dispersed within the patterned mask. In some embodiments, the polymerizable composition comprises at least 20, 25, 30, or even 35 wt % of inorganic nanoparticles based on total solids weight. In some embodiments, the polymeriziable composition comprises at most 55, 50, 45, or even 40 wt % of inorganic nanoparticles based on total solids weight. This would result in the patterned mask having at least 20, 25, 30, or even 35 wt %; and at most 55, 50, 45, or even 40 wt % of the inorganic nanoparticles.

[0037] In some embodiments, the polymerizable composition further comprises a solvent used to dispose the polymerizable composition on a surface. The term "solvent" refers both to water and to conventional organic solvents used in the industry which are volatilized in the process. Suitable solvents include water, alcohols such as isopropyl alcohol (IPA) or ethanol; ketones such as methyl ethyl ketone, methyl isobutyl ketone (MIBK), diisobutyl ketone (DEBK); cyclohexanone, or acetone; aromatic hydrocarbons such as toluene; isophorone; butyrolactone; N-methylpyrrolidone; tetrahydrofuran; esters such as lactates, acetates, including propylene glycol monomethyl ether acetate (PM acetate), diethylene glycol ethyl ether acetate (DE acetate), ethylene glycol butyl ether acetate (EB acetate), dipropylene glycol monomethyl acetate (DPM acetate); iso-alkyl esters such as isohexyl acetate, isoheptyl acetate, isooctyl acetate, isononyl acetate, isodecyl acetate, isododecyl acetate, isotridecyl acetate or other iso-alkyl esters;combinations of these, and the like. In some embodiments, the amount of solvent used is at least about 5% to at most 30 or even 25 % by weight in the polymerizable composition.

[0038] In some embodiments, the polymerizable composition further comprises an initiator, such as a photoinitiator or thermal initiator which is used to polymerize the (meth)acrylate-functionalized silicone. The type of initiator used depends on the polymerization process. In a preferred embodiment, photoinitiators that may be useful include benzoin ethers such as benzoin methyl ether or benzoin isopropyl ether, substituted benzoin ethers such as 2-methyl-2-hydroxypropiophenone, aromatic sulfonyl chlorides such as 2-naphthalenesulfonyl chloride, and photoactive oxides such as 1-phenyl-1,2- propanedione-2-(o-ethoxycarbonyl)oxime, and diphenyl(2,4,6- trimethylbenzoyl)phosphine oxide. Exemplary initiators include benzoin ethers such as benzoin methyl ether and benzoin isopropyl ether; substituted acetophenones such as 2, 2-dimethoxyacetophenone, available under the trade designation “IRGACURE 651” photoinitiator (BASF), 2,2 dimethoxy-2-phenyl-l-phenylethanone, available under the trade designation “ESACURE KB-1” photoinitiator (Sartomer Co.; West Chester, PA), 1-[4-(2- hydroxyethoxy)phenyl]-2-hydroxy-2-methyl-1-propan-1-one, available under the trade designation “IRGACURE 2959” (BASF), and dimethoxyhydroxyacetophenone; substituted a-ketols such as 2- methyl-2-hydroxy propiophenone; aromatic sulfonyl chlorides such as 2-naphthalene-sulfonyl chloride; and photoactive oximes such as 1-phenyl-1,2-propanedione-2-(O-ethoxy-carbonyl)oxime. Generally, the photoinitiator is present in an amount of about 0.005 to 2 weight percent based on the weight of the polymerizable components such as (meth)acrylate-functionalized silicone and additional monomers. In another embodiment, a thermal initiator may be used, such as for example, AIBN (azobisisobutyronitrile) and / or peroxides. The initiators can be used in amounts from about 0.001 part by weight to about 15 parts, preferably from about 0.5 to about 5 parts, by weight based on 100 parts total polymerizable components.

[0039] In some embodiments, the polymerizable composition further comprises an additional monomer. The additional monomers may be (meth)acrylate monomers, which are different from the (meth)acrylate- functionalized silicone and may be used as a binder and / or provide mechanical robustness to the resulting patterned mask to enable separation of the mask from the tooling. Exemplary types of additional monomer include: a C1 to C12 (meth)acrylate ester monomers. In some embodiments, the (meth)acrylate ester monomer comprises 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, or 12 carbon atoms. Exemplary second (meth)acrylate monomers include, methyl (meth)acrylate, ethyl (meth)acrylate, n-propyl (meth)acrylate, isopropyl (meth)acrylate, 2-methylbutyl acrylate, n-butyl acrylate, isobutyl acrylate, tert-butyl (meth)acrylate, n-pentyl (meth)acrylate, iso-pentyl (meth)acrylate, n-hexyl (meth)acrylate, iso-hexyl (meth)acrylate, cyclohexyl (meth)acrylate, phenyl (meth)acrylate, n-octyl (meth)acrylate, iso-octyl (meth)acrylate, 2-octyl(meth)acrylate, 2-ethylhexyl (meth)acrylate, decyl (meth)acrylate, lauryl (meth)acrylate, 2-propylheptyl (meth)acrylate, isobornyl (meth)acrylate, benzyl (meth)acrylate, nonyl acrylate, isophoryl (meth)acrylate, dodecyl (meth)acrylate, and any combinations or mixtures thereof. In some embodiments, the (meth)acrylate monomer is a polar monomer, such as acid or non-acid functional polar monomers such as acrylic acid, hydroxyethyl acrylate, N-methyl acrylamide, or any monomerhaving a sidechain containing at least one of the following: alcohol, carboxylic acid, amine, amide, imide, thiol, ester, phosphate, and combinations thereof. Exemplary polar monomers include: acrylic acid, methacrylic acid, itaconic acid, fumaric acid, crotonic acid, citraconic acid, and maleic acid, hydroxyalkyl acrylates, acrylamides and substituted acrylamides (such as N,N-dialkylaminoalkyl (meth)acrylates or tert-octylacrylamide), acrylamines and substituted acrylamines, lactams and substituted lactams, β- carboxyethylacrylate, N-vinyl-2-pyrrolidone, N-vinyl caprolactam, acrylonitrile, and any combinations or mixtures thereof. In some embodiments, the additional monomer is a non-polar ethylenically unsaturated monomer selected from monomers comprising a hydrocarbon sidechain. Examples of non-polar comonomers include 3,3,5-trimethylcyclohexyl acrylate, cyclohexyl acrylate, t-butyl acrylate, methyl methacrylate, ethyl methacrylate, and combinations thereof.

[0040] Typically, the amount of these additional monomers would be kept low to ensure good release properties of the patterned mask and may be used to assist with dispersion of the inorganic nanoparticles, physical properties of the polymerizable composition, and / or mechanical properties of the resulting patterned mask. In some embodiments, the polymerizable composition comprises at least 0.5, 1, 2, or even 2.5 %wt and at most 10, 8, 6, 5, 4, or even 3 %wt by solids of these additional monomers.

[0041] In some embodiments, the polymerizable composition further comprises a cross-linking agent. A cross-linking agent is used to create a three-dimensional polymer network and can create high internal strength of the patterned mask. Useful cross-linking agents include photosensitive cross-linking agents, which are activated by ultraviolet (UV) light. Useful cross-linking agents include: multifunctional (meth)acrylates, triazines, and combinations thereof. Exemplary crosslinking agents include substituted triazines such as 2,4,-bis(trichloromethyl)-6-(4-methoxy phenyl)-s-triazine, 2,4-bis(trichloromethyl)-6- (3,4-dimethoxyphenyl)-s-triazine, and the chromophore-substituted halo-s-triazines disclosed in U.S. Pat. Nos.4,329,384 and 4,330,590 (Vesley). Other useful crosslinking agents include multifunctional alkyl acrylate monomers such as trimetholpropane triacrylate, pentaerythritol tetra-acrylate, 1,2 ethylene glycol diacrylate, 1,4 butanediol diacrylate, 1,6 hexanediol diacrylate, and 1,12 dodecanol diacrylate. Various other crosslinking agents with different molecular weights between (meth)acrylate functionality may also be useful. In some embodiments, the polymerizable composition comprises at least 0.1, 0.5, 1, 2, or even 2.5 % wt and at most 10, 8, 6, 5, 4, or even 3 % wt by solids of these cross-linking agents.

[0042] In some embodiments, the curable composition consists essentially of (or consists of) the (meth)acrylate-functionalized silicone, a plurality of inorganic nanoparticles, an initiator, and solvent.

[0043] In an embodiment of the disclosure, the polymeric nanoparticles are blended with a (meth)acrylic syrup, which is derived from the (meth)acrylate-functionalized silicone. As used herein, a syrup refers to a mixture that has been thickened to a coatable viscosity, i.e., preferably between about 300 and 10,000 centipoise or higher depending upon the coating method used, and includes mixtures in which the (meth)acrylate-functionalized silicone or monomers are partially polymerized to form the syrup.

[0044] The polymerizable composition is coated onto an amorphous silicon layer. Conventional coating techniques known in the art can be used, including but not limited to, dip coating, roll coating, spray coating, knife coating, gravure coating, extrusion, die-coating, and the like. Preferably if a roll-to-rolltechnique is used, the polymerizable composition is overcoated to insure high fidelity between the tooling and the patterned mask. Shown in Fig.2 is an exemplary process for making an article according to the present disclosure, wherein the patterned mask is made via a nanoimprint lithography process on top of the amorphous silicon layer. Nanoimprint lithography is known in the art and has feature sizes less 3, 2, or even 1 micrometers. Polymerizable composition 23 is applied via coater 230 onto amorphous silicon layer 24, which is disposed on a substrate. The web then travels to section 250, wherein the polymerizable composition is contacted with tooling 21. Tooling 21, comprising a pattern of holes, is brought into contact with polymerizable composition 23. The polymerizable composition fills the crevasses (or holes) of tooling 21, creating a pattern of posts when the tooling is separated from the polymerized composition. The web passes through activator 260, wherein the polymerizable composition is polymerized (or cured) via radiation (e.g., photoradiation or thermal radiation depending on the initiator used to polymerize the polymerizable composition). Following the gelling of the polymerizable composition, the tooling is separated, and the web and the web is optionally further treated at station 270 (via additional radiation) resulting in patterned mask 22 atop amorphous silicon 24. The web is then treated at station 280 by reactive ion etching, which etches the article, resulting in an etched amorphous silicon layer 24C. In some embodiments, following etching, a portion of the patterned mask remains atop the amorphous silicon layer. Any remaining, undesired patterned mask remaining may be removed using conventional processes, such as stripping with tape. 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 tooling and / or patterned mask to result in the desired etching of the amorphous silicon.

[0045] Radiation at station 260 and optional station 270 may be applied using a conventional ultraviolet radiation (UV) such as may be provided by excimer lamp or other UV emitting lamp. Irradiation is generally conducted using a UV lamp with an intensity in the range of from 100 to 700 watts per inch (“W / in”), preferably in the range of from 400 to 600 W / in for 0.1 seconds to 15 minutes or more, with the distance between the UV lamp and the substrate being 2 to 30 centimeters.

[0046] The temperature during photo irradiation is not critical and may be done at room temperature.

[0047] Although thermal processes are not preferred, thermal polymerization is possible. In the case of a continuous process, the web may be passed through a dryer, such as an infrared (“IR”), through air or the like. The polymerization temperature can vary depending on the thickness of the substrate, the concentration of monomer, the type of solvent used, and the type and amount of thermal initiator used in the blend. The polymerization is typically in the range of from 0° C to 150° C and preferably in the range of from 10° C to 100° C, and more preferably in the range of 20°C to 50°C. The polymerization time depends on the polymerization temperature and the identity of the initiator, but is typically several seconds to 2 hours and preferably several seconds to 10 minutes. Preferred initiators for thermal processes are redox initiators, many of which are well known in the art.

[0048] 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.

[0049] 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.

[0050] In some embodiments, the amorphous silicon layer comprises a hydrogenated amorphous silicon, which comprises silicon and hydrogen.

[0051] In some embodiments, the amorphous silicon is deposited by plasma enhanced chemical vapor deposition. For example, an a-Si:H 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 an environment 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.

[0052] 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.

[0053] 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 e.g., enhanced attachment of plasma- reactive species to the patterned surface, may provide enhanced coverage of such species over the area of the surface, may provide 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).

[0054] 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 siliconcontaining 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.).

[0055] 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.

[0056] 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, polyvinylidene chloride, polycarbonate, polyacrylates, thermoplastic polyurethanes, polyvinyl acetate, polyamide, polyimide, poly(methylmethacrylate), polyethylene naphthalate, polystyrene acrylonitrile, triacetate cellulose, nylon, silicone-polyoxamide polymers, fluoropolymers, and thermoplastic elastomers. 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.

[0057] In some embodiments, the thickness of the amorphous silicon layer to be etched can be at least 100, 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.

[0058] After providing the patterned mask atop the amorphous silicon layer, the masked substrate (comprising the patterned mask, the amorphous silicon layer, and optional base substrate) is then exposed to reaction ion etching (RIE), which is a process known in the art. 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- energy plasma 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.

[0059] For example, the reaction chamber is filled with an etching gas to etch the amorphous silicon layer. In some embodiments, the mask may comprise a thin layer of material, which is first etched away before etching the amorphous silicon. Exemplary etching gases include fluorine-containing gases such as SF6, CF4, CHF3, C6F14, C4F8, C3F8, and NF3. In some embodiments, an inert gas, such as argon, is passed through reaction chamber during etching. In some embodiments, oxygen or hydrogen gas may be mixed with the fluorine-containing gas during etching.

[0060] 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.

[0061] 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 frequency of 13.56 megahertz.

[0062] 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.

[0063] After etching the layer of amorphous silicon to the desired depth, the patterned mask is removed, leaving the etched substrate comprising a series of features which were covered by the patterned mask.

[0064] The patterned mask 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 mask 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 mask, the features are generally at least 50 nm in dimension. In some embodiments, a small amount of mask material is present between the feature to be etched and amorphous silicon layer as shown by arrow 13 in Fig.1 A. During RIE, this sacrificial layer of material is etched away, exposing the underlying silicon, which is continued to be etched.

[0065] The thickness of the patterned mask is selected to withstand each reactive ion etching process that is performed so that the top surface of the amorphous silicon layer remains protected from etchant materials throughout the etching process. This necessary thickness of the patterned mask 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 mask can be at least twice as thick as the depth the amorphous silicon layer is etched.

[0066] Ideally, the mask composition has good selectivity between the mask and the amorphous silicon to be etched. In other words, the composition of the patterned mask is etched away at rate similar to or less than the etch rate of the amorphous silicon. In some embodiments, the selectivity of mask etch rate to the amorphous silicon layer etch rate of at most 3, 2.5, 2.2, 2.0, 1.8, 1.6, 1.4, 1.2, 1.0, 0.8. or even 0.6.

[0067] The patterned mask of the present disclosure comprises nanosized features 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 5, 4, 3, 2, 1, 0.9, 0.8, 0.5, 0.2, or even 0.1 µm (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). Shown in Fig.1C is the pitch (p) and height (h) for the etched features. Fig.1D is an isometric view of an etched feature of Fig.1C, which is an etched post in silicon layer 14C atop base substrate 16. The etched post has an oval cross-section with width at the top of the feature (wt) and a length at the top of thefeature (lt) as shown in Fig.1D. The etched post has an oval cross-section with width at the bottom of the feature (wb) and a length at the bottom of the feature (lb) as shown in Fig.1D.

[0068] 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 5, 4, 3, 2.5, 2, 1.5, 1, 0.8, or even 0.5 µm. 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 5, 4, 3, 2.5, 2, 1.5, 1, 0.8, or even 0.5 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 5, 4, 3, 2.5, 2, 1.5, 1, 0.8, or even 0.5 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 10, 8, 6, 5, 4, 3, 2.5, 2, or even 1.5. 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 that is less than half of a predetermined wavelength of electromagnetic radiation (such as visible light, infrared, etc.).

[0069] In some embodiments, the patterned mask 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 patterned 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.

[0070] 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

[0071] 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, fromgeneral chemical suppliers such as, for example, Sigma-Aldrich Company, Saint Louis, Missouri, or may be synthesized by conventional methods.

[0072] These abbreviations are used in the following examples: °C = degree Celsius, cm= centimeter, ft = feet, fpm = feet per minute, in = inch, 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, 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 IGM Resins, Waalwijk, The Netherlands MIBK Methyl isobutyl ketone obtained from Alfa Aesar, Haverhill, MA IPA 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,m SR238 1,6-hexandiol diacrylate obtained from Sartomer Americas, Exton, PA SR351 trimethylopropane triacrylate obtained from Sartomer Americas PHOTOMER 6210 Urethane acrylate oligomer obtained under the trade designation “PHOTOMER 6210” from IGM Resins, Charlotte, NC IRGACURE TPO Diphenyl(2,4,6- trimethylbenzoyl)phosphine oxide obtained under the trade designation “IRGACURE TPO” from BASF, Florham Park, NJ Silicon wafer 100 mm silicon wafer, 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 O2 Oxygen (ultra-high purity grade) gas obtained from Airgas, St. Paul, MN HMDSO Hexamethyldisiloxane (98%) obtained from Geleste, Morrisville, PA a-Si 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

[0073] Preparation of amorphous silicon samples A-C

[0074] Preparation of amorphous silicon layer on ST504 PET. A custom-built Mill Lane Engineering roll-to-roll sputter coating system using a-Si sputter targets disposed on the sputter sources in an argonatmosphere 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 fpm (0.91 m / min) for the designated machine passes until the desired thickness was achieved. Following the sputter deposition process, the process gas flow, applied power, and substrate 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

[0075] Preparation of amorphous silicon sample D

[0076] 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. The substrate was passed through the plasma 11 times to achieve the desired a-SiH thickness. 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.).

[0077] Tooling

[0078] The tooling to generate the patterned mask was made as follows:

[0079] A nickel master comprised a nanostructured nickel surface that had nanostructured patterns attached to a steel roller. The nickel master comprised a plurality of posts, which when replicated generated a tooling comprising a plurality of holes. Shown in Table 3 below are the resulting pattern features of Tooling I and II.

[0080] 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 resincomposition was blended by warming to approximately 50 °C and mixing for 12 hours on a roller mixer, resulting in a homogeneous mixture.

[0081] Resin A was then die coated onto ST505 PET to 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 the tooling. Table 3 Tooling Pattern Type of Pattern in Type of Resulting Pitch Height Tooling Replicated Pattern (micrometer) (micrometer) I 1 Holes Posts 1.86 μm 1.2 μm II 2 Holes Posts 1.86 μm 2.7 μm

[0082] The patterned side of the tooling was then treated to facilitate release from the patterned mask as follows. Plasma enhanced chemical vapor deposition (PECVD) was performed in a home-built parallel plate capacitively coupled plasma reactor. The chamber has a central cylindrical powered electrode with a surface area of 18.3 ft2(1.7 m2). After placing the micro-structured film on the powered electrode, the reactor chamber was pumped down to a base pressure of less than 1.3 Pa (2 mTorr). Oxygen was introduced into the chamber at a flow rate of 1000 sccm, resulting in a chamber pressure of approximately 7 mTorr. Treatment was carried out by coupling RF power into the reactor at a frequency of 13.56 MHz and an applied power of 2000 watts. Treatment time was controlled by moving the microstructured film through the reaction zone at rate of 30 fpm (9.1 m / min). A second step resulting in a deposited thin film on the structured surface was accomplished by stopping the flow of oxygen and evaporating and transporting HMDSO into the system to sustain an operating pressure of approximately 6.3 mTorr. Treatment was carried out using a PECVD method by coupling RF power into the reactor at a frequency of 13.56 MHz and an applied power of 1000 watts. Treatment time was controlled by moving the microstructured film back through the reaction zone at rate of 30 fpm (9.1 m / min). Following the treatment, the RF power and the gas supply were stopped and the chamber was returned to atmospheric pressure. This tooling was then used in the samples below. Additional information regarding materials and processes for applying cylindrical PECVD and further details around the reactor used can be found in U.S. Pat. No.8,460,568.

[0083] Methods to determine coating thickness

[0084] Method 1-Spectroscopic Ellipsometry (SE) Method

[0085] 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 inreflection 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.

[0086] Method 2- Reflectance Spectroscopy Method

[0087] 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.

[0088] Method 3- Wavelength Dispersive X-ray Fluorescence (WDXRF) Spectroscopy Method

[0089] 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.

[0090] Test Method 4- Scanning Electron Microscopy (SEM) Imaging

[0091] Samples were mounted on aluminum examination stubs and coated with AuPd by DC sputtering in a Denton Vacuum Desk IV coater (Moorestown, NJ) 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.

[0092] Reactive Ion Etching (RIE) Method

[0093] 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 toatmospheric 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.

[0094] PREPARATIVE EXAMPLES

[0095] PREPARATIVE EXAMPLES 1-7 (PE-1 to PE-7)

[0096] The polymerizable mixtures were prepared by using the components and 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 the photoinitiator and (meth)acrylate-functionalized silicone 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-1 PE-2 PE-3 PE-4 PE-5 PE-6 PE-7 Total Amount of 100 10 100 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% 40% Solids Silica Used none TOL- ST MIBK-ST Solvent IPA / MIBK (80:20) MIBK Omnirad 819 none 0.02 0.2 Actual TEGO RC 15 1.8 1.6 1.4 1.2 1 12 Amounts (g) 702 Used Solvent 85 7.353 6.706 6.058 5.411 4.764 54.110 Silica Dispersion none 0.647 1.294 1.942 2.589 3.236 25.890

[0097] PREPARATIVE EXAMPLES 8 – 12

[0098] Each of PE-2 to PE-6 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 fpm (9.1 m / min) as shown in Table 5. The apparent loss of tackiness of the resulting coating indicated that the coating successfully cured. Table 5 Sample Polymerizable % Silica Mixture PE-8 PE-2 10% PE-9 PE-3 20% PE-10 PE-4 30% PE-11 PE-5 40%PE-12 PE-6 50%

[0099] COMPARATIVE

[0100] PE-1 was coated 15.3 cm wide on ST504 PET with a 0.127 mm shim and pumped with a Harvard syringe pump at a rate of 3.8 sccm. The coating was dried at ambient conditions for 4 min. The solution was feed at a rate of 4 cc / min with a line speed of 10 fpm (3 m / min) through a fusion D bulb to polymerize the coating.

[0101] EXAMPLE SET 2

[0102] The etch rate the polymerized mixtures of PE-8 to PE12 and CE-1 were examined. PE-8 to PE-12 and CE-1 were etched using the RIE Method using NF3and different exposure times. The thickness of the polymerized resin was measured using Method 1 or Method 2 disclosed above both before and after etching and the measured thickness change was divided by the etching time to determine the etch rate. The results are shown in Table 6. Table 6 Sample % SiO2NF3etch rate (nm / min) 125 sccm 250 sccm 500 sccm CE-1 0% 344 408 489 PE-8 10% 335 331 443 PE-9 20% 318 335 410 PE-10 30% 303 316 354 PE-11 40% 263 283 345 PE-12 50% 230 276 329

[0103] As shown above, for the various flow rates, the calculated etch rates steadily decreased with increasing amounts of incorporated silica nanoparticles in the polymerizable mixture. Decreased etch rate (vertical) will improve the selectivity and can enable taller silicon feature heights before the mask material has been removed.

[0104] COMPARATIVE EXAMPLE SET 3

[0105] The etch rate of Amorphous Silicon Samples B and D were studied by testing each sample according to the RIE Method using varying flow rates of NF3and SF6gas. The thickness of the amorphous silicon was measured using the method designated in Table 7 both before and after etching and the etch rate was calculated and is reported in Table 7. Table 7 Amorphous Thickness NF3etch rate (nm / min) SF6etch rate (nm / min) Silicon test method 125 250 500 50 100 200 Sample used sccm sccm sccm sccm sccm sccm B 3 90 145 211 109 233 507 D 3 96 170 253 116 260 602

[0106] EXAMPLES 3-6

[0107] Formation of patterned mask on amorphous silicon layer. PE-7 was coated 15.3 cm wide with a 0.127 mm shim and pumped with a Harvard syringe pump at a rate of 3.8 sccm onto tooling I or II as designated in Table 8 below. The coating was dried at ambient conditions for 4 min, then laminated in a nip to the designated amorphous silicon layer. The nip consisted of a 90-durometer rubber roll and a steel roll set at 54 °C. The nip was engaged by two Bimba air cylinders (IMI Bimba, University Park,IL) pressed by 0.27 MPa. The films remain in contact for approximately 1.5 m, where they were cured with a fusion D bulb, and subsequently the patterned mask atop the amorphous silicon layer was peeled from the tooling. Table 1. Example Amorphous Silicon Sample Tooling 3 A I 4 B I 5 B II 6 C II

[0108] Example 6 and Comparative Example 1 were etched using the RIE Method above and the etch rate was measured for varying flow rates of NF3and SF6gas. For Example 6, the etch rate was conducted on a planar section of film on an edge of the patterned mask outside of the patterned area. The amount of material etched was calculated by Method 1 before and after exposure to a NF3or SF6plasma for multiple exposure times and the etch rate is reported in Table 9.

[0109] The data in Table 9 can be used along with etch rates of the amorphous silicon of B and D in Table 7 to calculate the selectivity between the mask material and the silicon material (selectivity = etch rate (mask) / etch rate (silicon)). The selectivity is reported in the table 10 below, where the etch rate of Example 6 is compared to the etch rate of Amorphous Silicon Sample B (Ex 6 / B) and compared to the etch rate of Amorphous Silicon Sample D (Ex 6 / D), and the etch rate of Comparative Example 1 is compared to the etch rate of Amorphous Silicon Sample B (CE-1 / B) and compared to the etch rate of Amorphous Silicon Sample D (CE-1 / D). Table 9 Sample Thickness NF3etch rate (nm / min) SF6etch rate (nm / min) test method 125 250 500 50 100 200 used sccm sccm sccm sccm sccm sccm Example 6 1 194 274 342 239 277 320 CE-1 1 344 408 489 292 384 522Table 10 Sample NF3selectivity SF6selectivity 125 250 500 50 100 200 sccm sccm sccm sccm sccm sccm Ex 6 / B 2.2 1.9 1.6 2.2 1.2 0.6 Ex 6 / D 2.0 1.6 1.4 2.1 1.1 0.5 CE-1 / B 3.8 2.8 2.3 2.2 1.2 0.6 CE-1 / D 2.0 1.6 1.4 2.1 1.1 0.5

[0110] COMPARATIVE EXAMPLE 7

[0111] The same process for creating a patterned mask was followed as described in Example 3 except that the polymerizable mixture used was PE-1, and Tooling I and Amorphous Silicon Sample B were used.

[0112] EXAMPLE SET 8

[0113] Comparative Example 7 and Example 3 were etched following the RIE Method above by exposure to a NF3 plasma for multiple exposure times. Samples at each time point were analyzed by Test Method 4 and image processing software (ImageJ) to determine the etch rate (vertical) and dimensional stability (lateral) of the patterned mask, with results shown in Table 11. The dimensional stability can also be calculated as the relative change in post diameter. The % change was calculated as (initial diameter-etched diameter)x100% / initial diameter. Table 11 % % change Sample NF3Patterned change Post of post flow Etch mask Post top of post bottom bottom rate Time thickness diameter top from diameter from (sccm) (sec) (nm)1(nm) initial (nm) initial Initial NA 0 1971 889 NA 1017 NA i 125 60 1673 841 5.4 960 5.6 ii 125 100 1453 825 7.2 965 5.1 Comparative Example 7 iii 125 150 1243 695 21.8 865 14.9 iv 500 60 1567 817 8.1 991 2.6 v 500 100 1208 810 8.9 870 14.4 vi 500 150 728 700 21.2 690 32.2 Initial NA 0 1545 920 NA 1051 NA i 125 60 1028 891 3.2 998 5.0 ii 125 100 993 887 3.6 951 9.5 Example 3 iii 125 150 947 904 1.7 899 14.5 iv 500 60 1054 908 1.3 978 6.9 v 500 100 1009 899 2.3 988 6.0 vi 500 150 987 885 3.8 989 5.9 1total thickness (includes post height and land thickness) NA = not applicable

[0114] EXAMPLE SET 8

[0115] Example 4 was etched following the RIE Method above by exposure to NF3plasma for multiple exposure times. Samples at each time point were analyzed by Test Method 4 and image processing software (ImageJ) to determine the etch rate (vertical) and dimensional stability (lateral) of the patterned mask with results shown in Table 12. For Example 4, the a-Si film was considerably thicker (about 1 micron) than Example 3, and the plasma exposure time was longer to demonstrate dimensional stability of the mask material loaded with silica nanoparticles for etch times relevant to real world applications. Shown in Table 12 are the % changes observed in the posts during the etch. Table 12 3 % % NF Etch Patterned Post t Post change e flo op change Sampl w mask bottom of post rate Time thickness diameter of post diameter botto m) (sec) (nm) (nm) t m (scc1op from initial (nm) from initial Example Initial NA 0 3269 1020 NA 1387 NA 4 i 250 100 2780 972 4.7 1325 4.5 ii 250 200 2138 957 6.2 1200 13.5 iii 250 300 1785 1100 -7.8 1243 10.4 iv 250 400 1419 1015 0.5 1141 17.7 1 total thickness including the mask post height and mask land thickness NA = not applicable

[0116] 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 a base substrate; a patterned mask having an outwardly facing nanostructured surface, wherein the patterned mask is derived from a (meth)acrylate-functionalized silicone and inorganic nanoparticles; and an amorphous silicon layer disposed between the base substrate and the patterned mask.

2. The article of claim 1, wherein the (meth)acrylate-functionalized silicone is of formula I where X from 5 to at most 50.

3. The article of claim 1, wherein the (meth)acrylate-functionalized silicone is of formula II where50.

4. The article of claim 1, wherein the (meth)acrylate-functionalized silicone is a random copolymer comprising a plurality of repeating siloxane groups and repeating (meth)acryl modified siloxane groups.

5. The article of claim 4, wherein the random copolymer is according to Formula III Whereand p and q are independently selected from integers from 5 to at most 50.

6. The article of claim 4, wherein the random copolymer is Formula IV:wherein X is H or CH most 50.

7. The article of any one of the previous claims, wherein the (meth)acrylate-functionalized silicone has a molecular weight of at least 500 to at most 3000 Daltons.

8. The article of any one of the previous claims, wherein the patterned mask is further derived from an initiator.

9. The article of claim 8, wherein the initiator comprises a photoinitiator or a thermal initiator.

10. The article of any one of the previous claims, wherein the patterned mask is further derived from a second (meth)acrylate monomer.

11. The article of any one of the previous claims, wherein the patterned mask comprises at least 5% and at most 95% by weight of (meth)acrylate-functionalized silicone.

12. The article of any one of the previous claims, wherein the inorganic nanoparticles are comprised of SiO2, Al2O3, Sb2O5, ZrO2, HfO7, TiO2, ZnO2, and mixtures thereof.

13. The article of any one of the previous claims, wherein the inorganic nanoparticles have an average diameter of at least 1 nm to at most 100 nm.

14. The article of any one of the previous claims, wherein the inorganic nanoparticles are hydrophobically modified.

15. The article of any one of the previous claims, wherein the patterned mask comprises at least 25 and at most 50% by solids weight of the inorganic nanoparticles.

16. The article of any one of the previous claims, wherein the nanostructured surface comprises a plurality of features, wherein the plurality of features has an average height of between 10 nm and 5 micrometers, inclusive.

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

18. The article of any one of the previous claims, wherein the patterned mask further comprises a crosslinking agent.

19. 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.

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

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

22. 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.

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

24. The article of claim 23, wherein the layer is comprised of Al, Al2O3, Cr, Cr2O3, or combinations thereof.

25. The article of claim 23 or claim 24 wherein the layer disposed between the amorphous silicon and the base substrate is less than 150 nm thick.

26. A method comprising: providing an amorphous silicon layer on a base substrate; disposing a second layer onto the amorphous silicon layer, wherein the second layer is derived from a (meth)acrylate-functionalized silicone, inorganic nanoparticles, and an initiator; anddisposing a patterned layer on the second layer and curing the second layer to form a patterned mask, wherein the patterned mask has an outwardly facing nanostructured surface.

27. The method of claim 26, further comprising exposing the patterned mask to reactive ion etching.

28. The method of claim 27, wherein the reactive ion etching comprises fluorine containing gases.

29. The method of any one of claims 27-28, further comprising removing the patterned mask following reactive ion etching.

30. The method of any one of claims 26-29, wherein a metal layer comprising metal or metal oxide is disposed between the base substrate and the amorphous silicon.

31. The method of any one of claims 26-30, wherein the amorphous silicon layer is deposited by plasma enhanced chemical vapor deposition.

32. The method of any one of claims 26-31, wherein the method is run in a continuous roll-to-roll fashion.

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