Patent Application
20050084613
In fabricating semiconductor integrated electrical circuits, integrated optical, magnetic and mechanical circuits, and other similarly produced devices, one method of production involves molding technology, such as embossing or nanoimprinting, step and flash imprint, and mold assisted nanolithography. While each of these methods differs in the specific method and steps, or physical principle, the methods all suffer from drawbacks in forming nano-scale patterns. Each may be generally classified as including lithography.
Embossing involves pressing a stamp into a polymer heated just above its transition temperature. While embossing generally produces a uniform pattern and provides relatively easy mold separation, embossing generally has several drawbacks with respect to the creation of nano-scaled devices. Embossing occurs at a high or at least elevated temperature, involves high pressure, acts on bulk structures, and results in limited nano-scale pattern transfer. Each of these drawbacks lessens the usefulness of embossing for creation nano-scale patterns.
Injection molding, generally, involves melting a desired polymer and forcing the melted polymer into the mold. While injection molding produces uniform patterns and provides easy mold separation, injection molding suffers from many drawbacks in creating nano-scaled device. For example, injection molding requires elevated temperatures, high pressure, bulk structures, and results in limited pattern transfer at the nano-scale. These drawbacks reduce the usefulness of injection molding in creating nano-scale patterns.
Nanoimprint lithography may generally be described as a lithographic method designed for creating ultra-fine patterns in a thin film coated on a surface. The process involves a mold being pressed into a thin film applied to a substrate, thereby creating at least one corresponding recess in the thin film. The patterns in the thin film are transferred into the substrate using a technique such as reactive ion etching (RIE) or plasma etching. While nanoimprint lithography may produce a uniform pattern of controllable thickness on the nano-scale level in a single layer, nanoimprint requires elevated temperatures and a high pressure. Thus molding equipment capable of applying the pressures and elevated temperatures in a suitable manner may be required.
Step and flash imprint generally utilizes a transparent template and a ultraviolet radiation curable material to allow pattern replication at room temperature and low pressures. This technology may provide for improved template-substrate alignment, as well as reduced magnification and distortion errors. While step and flash imprinting may be performed at room temperatures and provide easy mold separation, step and flash imprint suffers from many drawbacks with respect to nano-scale patterns. Step and flash imprint requires low to medium pressure levels and often produces a non-uniform pattern. Further, step and flash imprint operates on an imaging or transfer layer. The non-uniformity of the pattern may be sufficient to render step and flash imprinting as inapplicable for many nano-scale purposes.
Mold assisted nanolithography may be performed at room temperature with low or medium pressure with the ability to transfer nano-scale patterns to a single layer structure. But, this technology suffers from the drawback that pattern uniformity is often lacking. The non-uniform pattern is often undesirable and limits the usefulness of mold assisted nanolithography for many nano-scale purposes.
A method for replicating a nanopattern is disclosed. This method includes identifying a substrate; coating a surface of the substrate with a liquid layer with controlled thickness and good film uniformity; positioning a mold having a plurality of recesses defining a negative of the nanopattern in sufficient proximity with the coated liquid layer to cause the liquid layer to self-fill at least a portion of the plurality of recesses of the mold; and, chemically transforming the liquid layer to enable the transformed film to substantially retain the nanopattern.
Further disclosed is a liquid layer composition. This fluid film composition includes a polymerizable composite comprising a polymerizable compound and a photointiator, wherein the composition is a flowable solution for spin coating a surface of a substrate and wherein the composition is susceptible to transformation into a material for maintaining a pattern shape of a mold.
Understanding of the present invention may be facilitated by consideration of the following detailed description of the preferred embodiments of the present invention taken in conjunction with the accompanying drawings, in which like numerals refer to like parts and:
It is to be understood that the figures and descriptions of the present invention have been simplified to illustrate elements that are relevant for a clear understanding of the present invention, while eliminating, for the purpose of clarity, many other elements found in typical lithographic processes and methods of manufacturing the same. Those of ordinary skill in the art may recognize that other elements and/or steps are desirable and/or required in implementing the present invention. However, because such elements and steps are well known in the art, and because they do not facilitate a better understanding of the present invention, a discussion of such elements and steps is not provided herein.
Referring now to
Method 100 may generally include identifying a substrate 110, coating the substrate with a liquid layer 120, positioning a mold including a pattern in proximity to the liquid layer 130 to permit the liquid layer to conform to interstices in the pattern, chemically transforming the liquid layer 140 such that it retains the conformed pattern, and separating the chemically-transformed, shape retaining film from the mold 150.
Referring now also to
For example, a four-inch diameter BK7 glass wafer with multiple dielectric thin films approximately 500 microns in total thickness may be identified or selected 110 as substrate 210. Suitable thin films for use with the BK7 glass wafer may include Si3Nx, HFO2, SiO2 or Ta2O5. For example, a 500 nm to 1000 nm SiO2 layer may be provided on top of a 50 nm to 100 nm HFO2 layer, on top of a 100 nm to 300 nm SiO2 layer, on top of a 50 nm to 200 nm HFO2 layer, which is on top of 0.5 mm thick BK7 glass. On the other side, a 50 nm to 200 nm SiO2 layer may be provided on top of a 50 nm to 200 nm HFO2 layer, on top of the 0.5 mm thick BK7 glass. By way of further non-limiting example, a 500 nm to 1000 nm Silicon Nitride layer may be provided on top of a 50 nm to 200 nm HFO2 layer, on top of a 50 nm to 200 nm SiO2 layer, on top of a 50 nm to 200 nm HFO2 layer, which is on top of a 0.43 mm thick BK7 glass substrate. By way of further non-limiting example, a 500 nm to 1000 nm Silicon Nitride layer may be provided on top of a 50 nm to 150 nm Al2O3 layer, which is on top of a 430 micron thick Ohara glass substrate. On the other side, a 100 nm to 200 nm SiO2 may be provided on top of a 30 nm to 100 nm HFO2, which is on top of the 430 micron Ohara glass substrate. A further non-limiting example, a 50 nm to 250 nm Aluminum layer may be provided on top of a 10 nm to 50 nm SiO2 layer, which is on top of a 500 micron thick Polycarbonate (PC) or Polyimide plastic substrate.
Substrate 210 may be transparent, translucent or opaque to radiation, which radiation may optionally be used to aid in chemical transformation of the liquid layer into a material suitable for maintaining a patterned shape.
Still referring to
Accordingly, the substrate 210 may be coated to a thickness of approximately 50 nm-250 nm and a uniformity of better than but not limited approximately ±10 nm or 3% of the film thickness. The liquid layer coating 220 may reduce surface imperfections in substrate 210 being coated, thereby resulting in an improved flatness or roughness of the substrate/liquid layer coated composite structure. Alternatively, liquid layer coating 220 may be applied 120 at a certain thickness to substrate 210 such that some non-planaralities, imperfections or undulations in the surface of substrate 210 carry through the liquid layer, and remain in the surface of liquid layer 220.
According to an aspect of the present invention, the material used for the liquid layer preferably has certain properties. For example, it is preferably spin-coatable with controlled thickness and uniformity. Yet, it is further desirable that the fluid have suitable properties such that once it has been spin-coated onto a substrate it remains positionally stable there. To achieve such, the fluid may have an initial viscosity of about 0.001 cps to 1,000 cps at room temperature. After it has been spin coated, the material may be treated, such as by heating it sufficiently to drive off a component such as a solvent. It may thereafter have a viscosity of about 0.01 cps to 10,000 cps at room temperature. Such a viscosity may also facilitate self-conforming of the fluid to interstices of the mold, as is discussed in more detail below. Further, it may be desirable for the material to exhibit certain release characteristics associated with the mold and energy initiator, such as photo initiator, and other additives, such as photosensitizer, compatibilizer, stabilizer, viscosity controller etc. The additives, for example, may constitute 0-70% in the formula.
According to an aspect of the present invention, the use of silicon containing composites in the liquid layer may be reduced. This may advantageously render the method of the present invention, and interim products according to an aspect of the present invention, oxygen etch compliant. As will be readily understood by those possessing an ordinary skill in the pertinent arts, oxygen etching may be preferable to other forms of etching because it does not etch the substrate normally and is relatively safe and easy to use. By way of further non-limiting explanation only, when composites contain enough silicon, oxygen etching is generally realized to be inapplicable, and therefore other types of etching are often performed, involving the use of more hazardous chemicals, such a CF4 and CHF3 for example. That being said, silicon containing composites may be used in the liquid layer, if desired.
According to an aspect of the present invention, a liquid layer 220, which is a type of composition that is capable of transformation, with or without a physical treatment, into a polymer unit is provided. According to an aspect of the invention, the liquid layer 220 has a polymerizable composite so that the liquid layer 220 may be polymerized to retain the mold shape. Thus, in this aspect, it may be necessary to use a polymerizable compound or precursor of a polymer as part of the polymerizable composite of a liquid layer composition. For example, polymerizable monomers or oligomers, or a combination thereof, can be used as building blocks so that a homopolymer or a copolymer is obtained. There are a great number of polymerizable compounds known to one skilled in the art. These include, for example, organic materials (or composites) such as epoxy, methyl acrylate, acrylamide, acrylic acid, vinyl, ketene acetyl groups containing monomers, oligomers and inorganic composites such as silicon, aluminum and other metallic or semi-metallic composites. A suitable polymerizable composite may include at least one polymerizable compound or precursor and optionally a diluent and/or a solvent. A diluent is not the same as a solvent for purposes of this invention. Diluent as used herein refers to one of the reactive components which is one of the components and forms part of the final film. Solvent is not intended to be part of the final film. The solvent may be used to control the viscosity of the liquid layer composition and the use of a solvent in the final composition is optional depending on the coating process. For example, solvent may be needed to modulate the viscosity of a composition used for spin coating a substrate. Typical solvents that may be use include toluene, dimethyl formamide, chlorobenzene, xylene, dimethyl sulfoxide (DMSO), dimethyl formamide, dimethyl acetamide, dioxane, tetrahydrofuran (THF), methylene chloride, ethylene chloride, carbon tetrachloride, chloroform, lower alkyl ethers such diethyl ether and methyl ethyl ether, hexane, cyclohexane, benzene, acetone, ethyl acetate, and the like. The boiling a solvent or solvent mixture can be, for example, below 200 C. Selection of suitable solvents for a given system will be within the skill in the art and/or in view of the present disclosure.
Thus, a composition of the liquid layer in its simplest form includes a polymerizable composite (e.g., a oligomer or a monomer). For purposes of convenience, the polymerizable composite is referred to herein as a first part of the liquid layer composition of the invention. Other parts (or materials) such as, for example, second part, third part, fourth part and so on may optionally be added as part of the liquid layer composition so long as such additives do not significantly detract from the liquid layer's ability to form a polymer unit. Examples of the other parts or additives may include at least one photo-initiator and such other additives, an internal release agent and lubricants, for example.
Thus, by way of non-limiting example only, a first part of liquid layer 220 may include monomer or oligomer resins, including methyl acrylates and epoxies with mono or multi functionality, polyether, polyester, polysiloxane, and polyurethane of different molecular weights. For example, molecular weights may range from 100 to 10,000 weight average molecular weight.
The flowability of the fluid used for spin-coating a surface may depend on the components of the composition, the chemical structure of the components and the molecular weight of the components. In the composition, viscosity controllers, such as organic plasticizers or polymeric compounds may be incorporated to control the flowability. Other factors such as the flexibility of the backbone and the interaction between the backbone, the graft degree or functionality of the backbone, the chemical structure of the end reactive groups may be taken into account in adjusting the flowability. A fluid thin composition of the present invention having an initial viscosity of up to about 100 cps at room temperature is flowable for spin coating a surface.
By way of non-limiting example only, such a first part may include, aliphatic allyl urethane, nonvolatile materials, aromatic acid methacrylate, aromatic acrylic ester, acrylated polyester oligomer, acrylate monomer, polyethylene glycol dimethacrylate, lauryl methacrylate, aliphatic diacrylate, trifunctional acid ester or epoxy resin.
A second part of liquid layer 220 may include photo-initiators such as free radical or cationic species and/or photosensitizer Free-radical photoinitiators may include acetophenones, aryl glyoxalates, acylphosphine oxides, benzoin ethers, benzil ketals, thioxanthones, chloroalkyltriazines, triacylimidazoles, pyrylium compounds, sulfonium and iodonium salts, mercapto compounds, quinones, azo compounds, organic peroxides, and mixtures thereof. Cationic photoinitiators may include metallocene salts having an onium cation and a halogen-containing complex anion of a metal or metalloid as well as iodonium salts and sulfonium salts, metallocene salts having an organometallic complex cation and a halogen-containing complex anion of a metal or metalloid. Mixtures of photoinitiators may also be useful. A third part of fluid film 220 may include a viscosity controller. By way of non-limiting example, such a plasticizer may include butyl octyl phthalate, dicapryl phthalate, dicyclohexyl phthalate, diisooctyl phthalate, dimethyl sebacate and polymeric plasticizer or polymer.
A fourth part of fluid film 220 may include other materials to add certain characteristics to liquid layer 220 as desired or needed, such as, internal release agents, compatibilizer, coupling agent, lubricants and other stabilizers. By way of non-limiting example, such other materials may include a fluorinated or siloxane based structure.
A specific liquid layer 220 may include elements selected from those discussed above with respect to parts one through four. Specifically, by way of non-limiting example, the liquid layer 220 may include at least one element selected from the first part and at least one element selected from the second part. For example, the fluid film may take the form of 0.90-0.99 parts of the first part and 0.1-0.01 parts of the second part. The liquid layer may include at least one element selected from the first part, at least one element selected from the second part and at least one element selected from the third part. For example, the fluid film may take the form of 0.50-0.99 parts of the first part, 0.1-0.01 parts of the second part and 0.0-0.5 parts of the third part. Or, the fluid film may include at least one element selected from the first part, at least one element selected from the second part, at least one element selected from the third part and at least one element selected from the fourth part. For example, the fluid film may take the form of 0.50-0.99 parts of the first part, 0.1-0.01 parts of the second part, 0.0-0.50 parts of the third part and 0.1-0.01 parts of the fourth part.
By way of further example, thermal polymerization and photoinitiated polymerization generally produce chain growth or crosslinks between polymer chains. According to an aspect of the present invention, a post-added initiator suitable for reacting with an acrylate, methacrylate, allyl, epoxy, or other functional group on the polymer or oligomer to be grown or cured may be provided. The particular initiator and amount of initiator used depend upon factors known to the person skilled in the art, such as the reaction temperature, the amount and type of solvent (in the case of a solution polymerization), and so on.
The energy used to cause curing may generally be Ultraviolet (UV) in nature, or from another other radiation source. Polymerization in the reactive layer may be performed by reactive polymer or by a reaction of a coupling agent with the reactive polymer or oligomer, monomer and, alternatively, may be cured by the photo-initiated polymerization of the oligomers/monomers in the formulation. The system may use polyester, polyether, polyurethane or polyacrylate as the backbones with the structures but not limited from linear to grafted to hyperbranched to star or even to dendrimer shapes.
The physical properties of the reactive layer can be tailored by using varied mixes to make the desired film. According to an aspect of the invention, the fluid film 220 of the present invention includes at least one oligomer having an aromatic, aliphatic, or mixed aromatic and aliphatic backbone. Upon reaction, the oligomer in the fluid film 220 polymerizes to form a solid film possessing advanced properties with respect to those exhibited by the pure oligomer or the pure polymer. Alternatively, co-reactive oligomer mixes or monomer mixtures may be used instead of a pure oligomer to form cured films that include but are not limited to radom, block copolymers, polymer blends, and the compatible polymer, thereby further achieving a tailoring of properties in the desired film.
Curable species may include free-radically polymerizable or crosslinkable ethylenically-unsaturated species, for example, acrylates, methacrylates, and certain vinyl compounds such as styrenes, and cationically-polymerizable monomers and oligomers and cationically-crosslinkable polymers, for example, epoxies, vinyl ethers, cyanate esters, etc.), and the like, and mixtures.
Suitable free-radically polymerizable species may include mono-, di-, and poly-acrylates and methacrylates (for example, methyl acrylate, methyl methacrylate, ethyl acrylate, isopropyl methacrylate, stearyl acrylate, allyl acrylate, trishydroxyethyl-isocyanurate trimethacrylate, the bis-acrylates and bis-methacrylates of polyethylene glycols of molecular weight about 200-500, glycerol diacrylate, glycerol triacrylate, ethyleneglycol diacrylate, n-hexyl acrylate, diethyleneglycol diacrylate, trimethylolpropane triacrylate, 1,2,4-butanetriol trimethacrylate, 1,4-cyclohexanediol diacrylate, pentaerythritol triacrylate, pentaerythritol tetraacrylate, pentaerythritol tetramethacrylate, sorbitol hexacrylate, triethyleneglycol dimethacrylate, 1,3-propanediol diacrylate, 1,3-propanediol dimethacrylate, bis[1-(2-acryloxy)]-p-ethoxyphenyldimethylmethane, bis[1-(3-acryloxy-2-hydroxy)]-p-propoxyphenyldimethylmethane, copolymerizable mixtures of acrylated monomers, acrylated oligomers; unsaturated amides (for example, methylene bis-acrylamide, methylene bis-methacrylamide, 1,6-hexamethylene bis-acrylamide, diethylene triamine tris-acrylamide and beta-methacrylaminoethyl methacrylate); vinyl compounds (for example, styrene, diallyl phthalate, divinyl succinate, divinyl adipate, and divinyl phthalate); and the like; and mixtures thereof. Reactive polymers include polymers with pendant (meth)acrylate groups. Sarbox™ resins from Sartomer. Other polymers with hydrocarbyl backbone and pendant peptide groups with free-radically polymerizable functionality attached thereto also reactive.
Suitable cationically polymerizable species may include epoxy resins (monomeric epoxy compounds and epoxides of the polymeric type). For example, a diglycidyl ether of a polyoxyalkylene glycol, polybutadiene polyepoxide and a glycidyl methacrylate polymer or copolymer. The epoxides can be pure compounds or can be mixtures of compounds containing one, two, or more epoxy groups on different positions of the backbones. These epoxy-containing materials can vary greatly in the nature of their backbone and substituent groups. The molecular weight of the epoxy-containing materials can vary from about 58 to about 100,000 or more.
Other epoxy materials may contain cyclohexene oxide groups such as epoxycyclohexanecarboxylates, typified by 3,4-epoxycyclohexylmethyl-3,4-epoxycyclohexanecarboxylate, 3,4-epoxy-2-methylcyclohexylmethyl-3,4-epoxy-2-methylcyclohexane carboxylate, and bis(3,4-epoxy-6-methylcyclohexylmethyl)adipate.
Other epoxy-containing materials that may be useful include glycidyl ether monomers. Polymers with epoxy groups pending on the backbone or at the end of the chains are also usable for our applications.
The fluid film 220 may also contain a monomer from about 0.2 to about 8.0% by weight. The monomer may be based on an ester. The functional groups could be in different number (more than 1) with the chemical structure varied from unsaturated ester, acrylate to epoxy, for example. Examples of the polymerizable monofunctional vinyl monomers may include N-vinyl pyrrolidone, N-vinyl caprolactam, vinyl imidazole, and vinyl pyridine; (meth)acrylates containing an alicyclic structure such as isobornyl(meth)acrylate, bornyl(meth)acrylate, tricyclodecanyl(meth)acrylate, dicyclopentanyl(meth)acrylate, dicyclopentenyl(meth)acrylate, and cyclohexyl(meth)acrylate; benzyl(meth)acrylate, 4-butylcyclohexyl(meth)acrylate, acryloylmorpholine, 2-hydroxyethyl(meth)acrylate, 2-hydroxypropyl(meth)acrylate, 2-hydroxybutyl(meth)acrylate, methyl(meth)acrylate, ethyl(meth)acrylate, propyl(meth)acrylate, isopropyl(meth)acrylate, butyl(meth)acrylate, amyl(meth)acrylate, isobutyl(meth)acrylate, t-butyl(meth)acrylate, pentyl(meth)acrylate, isoamyl(meth)acrylate, hexyl(meth)acrylate, heptyl(meth)acrylate, octyl(meth)acrylate, isooctyl(meth)acrylate, 2-ethylhexyl(meth)acrylate, nonyl(meth)acrylate, decyl(meth)acrylate, isodecyl(meth)acrylate, undecyl(meth)acrylate, dodecyl(meth)acrylate, lauryl(meth)acrylate, stearyl(meth)acrylate, isostearyl(meth)acrylate, tetrahydrofurfuryl(meth)acrylate, butoxyethyl(meth)acrylate, ethoxydiethylene glycol(meth)acrylate, benzyl(meth)acrylate, phenoxyethyl(meth)acrylate, polyethylene glycol mono(meth)acrylate, polypropylene glycol mono(meth)acrylate, methoxyethylene glycol(meth)acrylate, ethoxyethyl(meth)acrylate, methoxypolyethylene glycol(meth)acrylate, methoxypropylene glycol(meth)acrylate, diacetone(meth)acrylamide, isobutoxy methyl(meth)acrylamide, N,N-dimethyl(meth)acrylamide, t-octyl(meth)acrylamide, dimethylaminoethyl(meth)acrylate, diethylaminoethyl(meth)acrylate, 7-amino-3,7-dimethyloctyl(meth)acrylate, N,N-diethyl(meth)acrylamide, N,N-dimethyl amino propyl(meth)acrylamide, hydroxy butyl vinyl ether, lauryl vinyl ether, cetyl vinyl ether, 2-ethylhexyl vinyl ether, acrylate monomers.
The fluid film 220 composition may include a photosensitizer from about 0 to about 5.0% by weight per total weight of the composition. The photosensitizer liquid layer may include one-photon or multi-photon photosensitizers. One photon photosensitizer may include ketones, coumarin dyes (for example, ketocoumarins), xanthene dyes, acridine dyes, thiazole dyes, thiazine dyes, oxazine dyes, azine dyes, aminoketone dyes, porphyrins, aromatic polycyclic hydrocarbons, p-substituted aminostyryl ketone compounds, aminotriaryl methanes, merocyanines, squarylium dyes, and pyridinium dyes. Mixtures of photosensitizers may also be utilized. For applications requiring high sensitivity, photosensitizer containing a julolidinyl moiety may be preferred.
Electron donor compounds may be used, optionally, to increase the one-photon photosensitivity of the photoinitiator system. Such electron donor compounds may include amines (including triethanolamine, hydrazine, 1,4-diazabicyclo[2.2.2]octa-ne, triphenylamine (and its triphenylphosphine and triphenylarsine analogs), aminoaldehydes, and aminosilanes), amides (including phosphoramides), ethers (including thioethers), ureas (including thioureas), sulfinic acids and their salts, salts of ferrocyanide, ascorbic acid and its salts, dithiocarbamic acid and its salts, salts of xanthates, salts of ethylene diamine tetraacetic acid, salts of (alkyl).sub.n(aryl).sub.mborates (n+m=4) (tetraalkylammonium salts preferred), various organometallic compounds such as SnR.sub.4 compounds (where each R is independently chosen from among alkyl, aralkyl, aryl, and alkaryl groups), ferrocene, and the like, and mixtures thereof. The electron donor compound may be unsubstituted or may be substituted with one or more non-interfering substituents.
Multiphoton photosensitizers may be multiphoton up-converting inorganic phosphor, for example the phosphor contain optically matched pairs of rare earth ions coordinated within a ceramic host lattice.
The fluid film 220 may also contain from about 0.01 to about 2.0% by weight a photopolymerization initiator. Both free radical and cationic species, by way of non-limiting example, may be used depending on the chemical structure of the reactive functional groups in the system. A brief list of the photoinitiators has been discussed hereinabove. More photoinitiators may include Acetophenone; 2,4,6-Trimethylbenzoyl-diphenyl phosphine; Anisoin; nthraquinone a,a-Dimethoxy-a-hydroxyacetophenone; 2-Methyl-1-(4-methylthio)phenyl-2-morpholino-propan-1-one; 1-Hydroxy-cyclohexylphenylketone; 4-(4-Methylphenylthiophenyl)-phenylmethanone; Phenyltribromomethylsulphone of 2-Isopropyl and 4-Isopropyl thioxanthone; blend of poly{2-hydroxy-2-methyl-1-[4-(1-methylvin-yl)phenyl]propan-1-one), 2,4,6-trimethylbenzoyldiphenylphosphine oxide and methylbenzophenone derivatives; Ethyl 4-(dimethylamino)benzoate; Methyl phenylglyoxylate; Blend of 4-Methylbenzophenone and benzophenone (1:1); Benzil; (Benzene) Hydroxybenzophenone; Camphorquinone; 2,2-Dimethoxy-2-phenylacetophenone; tricarbonylchromium; metallocene salts having an onium cation and a halogen-containing complex anion of a metal or metalloid; iodonium salts and sulfonium salts, as well as metallocene salts having an organometallic complex cation and a halogen-containing complex anion of a metal or metalloid.
The photopolymerization initiator may also include, for example, Irgacure 184 or 369 initiator.
The fluid film 220 may also contain from about 0 to about 2.0% by weight a coupling agent suitable for the purpose of increasing adhesion between the cured material and a material containing the cured material by producing an interaction between both materials. The coupling agent may include a silane, such as, by way of non-limiting example, a methacryloxypropyltris(vinyldimethylsiloxane)silane, methyltris(methylethylketoxime)silane, methyltris(methylisobutylketoxime)silane, methylvinyidi(methylethylketoxime)silane, aminopropyltriethoxysilane, N-.beta.-(aminoethyl)-.gamma.-aminopropyltrimethoxysilane, .gamma.-mercaptopropyltrimethoxysilane, .gamma.-mercaptopropyltriethoxysilane, .gamma.-methacryloxypropyltrimethoxysilane, N-.beta.-(N-vinylbenzylaminoethyl)-.gamma.-aminopropyl-trimethoxysilane hydrochloride, vinyltriacetoxysilane, .gamma.-chloropropyltrimethoxysilane, hexamethyldisilazane, .gamma.-anilinopropyltrimethoxysilane, octadecyidimethyl[3-(trimethoxysilyl)propyl]ammonium chloride, .gamma.-chloropropylmethyldimethoxysilane, .gamma.-mercaptopropylmethyldimethoxysilane, vinyltriethoxysilane, benzyltrimethylsilane, vinyltris(2-methoxyethoxy)silane, .gamma.-methacryloxypropyltris(2-methoxyethoxy)silane, .beta.-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, and n-octyltriethoxysilane.
The fluid film 220 may also contain from about 0.1 to about 6.0% by weight a viscosity regulating agent. The viscosity regulating agent may include a plasticizer, polymeric plasticizer, or polymer. Viscosity regulating agent may include Adipic Acid Derivatives: Dicapryl adipate; Di-(2-ethylhexyl adipate); Azelaic Acid Derivatives: Di(2-ethylhexyl azelate); Di-n-hexyl azelate; Benzoic Acid Derivatives: Diethylene glycol dibenzoate; Dipropylene glycol dibenzoate; Polyethylene glycol 200 dibenzoate; Citric Acid Devivatives: Acetyl tri-n-butyl citrate; Acetyl triethyl citrate; Dimer Acid Derivatives: Bis-(2-hydroxyethyl dimerate); Epoxy Derivatives: Epoxidized linseed oil; Epoxidized soy been oil; Fumaric Acid Derivatives: Dibutyl fumarate; Glyceryl Derivatives: Glyceryl triacetate; Isobutyrate Derivative: 2,2,4-Trimethyl-1,3-pentanediol, diisobutyrate; Isophthalic Acid Derivatives: Dimethyl isophthalate; Diphenyl isophthalate; Lauric Acid Derivatives: Methyl laurate; Linoleic Acid Derivative: Methyl linoleate; Maleic Acid Derivatives: Di-n-butyl maleate; Di(2-ethylhexyl) maleate; Mellitates: Tricapryl trimellitate; Triisodecyl trimellitate; Myristic Acid Derivatives: Isopropyl myristate; Oleic Acid Derivatives: Butyl oleate; Glycerol monooleate; Palmitic Acid Derivatives: Isopropyl palmitate; Methyl palmitate; Paraffin Derivatives: Chloroparaffin, 50% C1; Phosphoric Acid Derivatives: Isodecyl diphenyl phosphate; Tributyl phosphate; Phthalic Acid Derivatives: Butyl benzyl phthalate; Di-n-butyl phthalate; Ricinoleic Acid Derivatives: n-Butyl acetyl ricinloeate; Sebacic Acid Derivatives: Dibutyl sebacate; Stearic Acid Derivatives: Glycerol monostearate; Propylene glycol monostearate; Succinic Acid Derivatives: Diethyl succinate; Sulfonic Acid Derivatives: N-Ethyl o,p-toluenesulfonamide; o,p-toluenesulfonamide; Polymeric: EDENOL 9790; polyacrylic resin and other polymers, by way of non-limiting example only.
The fluid film 220 may also contain from about 0.01 to about 10.0% by weight a release agent. The release agents may include F or Si based compounds. For such Si based compounds, the release agent may include a polyether or polyester and other backbone modified silicone, such as, by way of non-limiting example, a polyester modified polydimethylsiloxane. Other silicones such as silsesquioxane may also be used. In addition, the F based compounds or perfluorinated compounds or polymers may also be used. The release agent could be either non-chemical reactive or chemical reactive or both.
The fluid film 220 may optionally include from about 10.0 to about 99.50% by weight a solvent. The solvent may be, by way of non-limiting example, a chlorobenzene, tetrahydrofuran, ethyl-lactate, N,N′-dimethylformamide, Toluene or Chloroform. For example, chlorobenzene can be present in the liquid layer in amounts as high as 99.5 wt % or slightly lower amounts such as from about 90.5 to 91 wt % or about 90.7 wt % of the composition. In addition to single solvents two or more solvents may also be used in the liquid layer composition. For example, xylene may be present in the range from about 0.25 wt % to 0.3 wt % or in addition to chlorobenzene. All percentages expressed herein are by weight. By “weight %” or “% by weight” is meant part by weight per total weight of liquid layer composition.
According to a first class of preferred embodiments, the composition has a monomer, at least one oligomer and a viscosity controller. The monomer can be, for example, Trimethylolpropanotriacrylate Ester. It can be present in the composition at levels as low as 0.2 wt % and as high as 10 wt %, preferably about 8.0 wt % and more preferably about 3.5-3.7 wt %. The oligomer can be, for example, low viscosity acrylic oligomer ranging from about 0.1-8.0 wt %, preferably from about 0.2-6.0 wt %, more preferably about 1.5 wt %. A second oligomer can be, for example, Methacryloxypropyltris(vinyldimethylsiloxane)silane. It can be present at levels, for example, up to about 5.0 wt %, while a low level of about 0.37 wt % is preferred. A viscosity controller may also be used in the composition. It can range from about 0.1-6.0. A preferred viscosity controller in this embodiment is Polyacrylate. It may be present at levels of about 3.0 wt %. The composition also has a release agent, for example, Polyester modified polydimethylsiloxane from about 0.01-2.0 or from about 0.05 to about 1.0 or about 0.10 wt %. It is preferred to employ a photosensitizer and a photoinitiator. For example, benzophenone can be used in amount ranging from about 0.15 wt % to about 0.20 wt %, preferably from about 0.17 to 0.18 wt %. Similar amounts of a photoinitiator may be added to the composition. Eacure 46 initiator is a preferred photoinitiator. At least one solvent is used as a primary solvent, which can constitute a bulk of the composition. Chlorobenzene can be used as a preferred solvent in amounts ranging from about 90.50-99.5 wt %. A second solvent, if used, forms only a minor part of the overall composition. For example, Xylene can be present in amounts up to about 3.0 wt %.
According to a second class of preferred embodiments, the composition has an oligomer and a surface modifier. The oligomer can be, for example, ethoxylate bisphenol-A dimethacrylate ranging from about 25 wt % to 85 wt %, preferably from about 40 wt % to about 80 wt %. Small amounts of a surface modifier, a photosensitizer and an initiator can also be added to the composition. For example, 2,2,2-trifliuoroethyl methacrylate can be added as a surface modifier. It can be present in the composition at levels as low as 0.2 wt % and as high as 5 wt %, preferably from about 0.5 wt % to about 2 wt % of total weight of the composition. Preferably, benzophenone is used as a photosensitizer and Darocure 1173 is used as a photoinitiator in the composition. For example, benzophenone can be added as a photosensitizer in amounts ranging from about 0.05 wt % to about 5 wt %, preferably from about 0.1 wt % to about 3 wt %. Similar amounts of a photoinitiator may also be added to the composition. Optionally, a monomer, a viscosity controller, and a lubricant may also be added to the composition. For example, lauryl methacrylate can be added in amounts that is up to about 45% or up to about half the amount as the oligomer. A viscosity controller may also be used in the composition. It can be present in the composition up to about 10 wt %. A preferred viscosity controller in this embodiment is diisooctyl phthalate. It may be present at levels of about 3.0 wt %. The composition may also have a lubricant. An example of a release agent used in the composition is polyester modified polydimethylsiloxane. It can be present in amounts from about 0.01-2.0 wt % or from about 0.05 wt % to about 1.0 wt % or about 0.10 wt %. A solvent is also used in the composition. An example of a preferred solvent is toluene. It can be present in amounts from about 1 to about 99 wt %.
According to a third class of preferred embodiments, the composition has an oligomer, a viscosity controller and a surface modifier. The oligomer can be, for example, ethoxylate bisphenol-A dimethacrylate ranging from about 20 wt % to 70 wt %, preferably from about 30 wt % to about 65 wt % and more preferably from about 40 wt % to 60 wt % is used in the composition. An additional oligomer such as, for example, acrylated polyester oligomer may also be used in amounts up to about 10 wt %. A first viscosity controller, for example, Poly(vinyl acetate) ranging from about 20 wt % to 50 wt %, preferably from about 25 wt % to about 40 wt % is also used in the composition. A second viscosity controller, for example, EDENOL 9672 (polymeric plasticizer) may also be added in amounts that is the same as or slightly lower than that of the first viscosity controller. The amount of second viscosity controller, for example, can range from about 1 wt % to about 30 wt %. A surface modifier such as, for example, Poly(dimethylsiloxane)graft Polyacrylate, is also used. It can range from about 1 wt % to about 15 wt %, preferably from about 2 wt % to about 10 wt %. A small amount of an initiator (e.g., Irgacure 184) also be added to the composition. The initiator can be added in amounts, for example, ranging from about 0.01 wt % to about 5 wt %, preferably from about 0.05 wt % to about 3 wt %, more preferably from about 0.1 wt % to about 2 wt %. Optionally, a coinitiator (e.g., amine coinitiator) up to about 1 wt % and a photosensitizer (e.g., benzophenone) up to about 2 wt % are also added to the composition. A solvent (e.g., N,N′-Dimethylformamide) is used in the composition in amounts from about 0 to about 99 wt %.
By way of specific, non-limiting example, a four-inch BK7 glass wafer of approximately 500 microns thickness may be spin coated with a 100-300 nm thick layer of a liquid layer composition of the first class of preferred embodiments described above.
The spin coating may be processed according to procedures known to those possessing an ordinary skill in the pertinent arts, including those set forth above, and additional steps such as baking and chemical cleaning and preparation. For example, after the liquid layer has been spun onto the substrate, the liquid layer/substrate composite may be heated to drive off solvents that were helpful to facilitate spin coating but not needed or undesirable for further processing. For example, the liquid layer/substrate composite may be heated to approximately 115 degrees C. for approximately one to four hours.
Mold 230 may be formed from materials known to those possessing an ordinary skill in the pertinent arts. Such materials include semiconductor materials, including silicon, InP, and GaAs, dielectric materials, including glass, silicon dioxide, polymer materials, including polycarbonate, or metals or metal alloys, including aluminum and nickel by way of non-limiting example only. Mold 230 may be transparent, translucent or opaque to radiation, which radiation may be used to aid in chemical transformation of the liquid layer into a material suitable for maintaining the pattern shape.
The pattern to be fashioned may form a mask layer for lithographic etching, for example. Hence, mold 230 may include recesses or interstices and protrusions that generally correspond to the desired pattern to be etched, and may be inversely related or complimentary of the pattern desired to be formed on substrate 210. That is, as will be understood by those in the pertinent arts, the etched pattern may have deeper interstices or troughs than the molded pattern itself, for example.
The surface of mold 230 may be treated, such as by coating it with a mold release agent, to reduce sticking forces between the mold and liquid layer and the chemically transformed liquid layer, to ease mold 230—film 220 separation, as discussed herein below. Suitable treatments may include siloxane or fluorinated release agents. Such treatments may be additionally applied within or to thin film 220 coated onto substrate 210. By way of specific non-limiting example, mold 230, having a negative of the desired formed pattern, may be surface treated with a mold release agent by solvent dipping, vapor evaporation and plasma based or other chemical vapor deposition, for example. The mold release agent may take the form of commercially available perfluorodecyltrichlorosilane, for example.
Mold 230 may be formed with a negative or complementarily related pattern using standard lithographic and/or other suitable techniques known to those possessing an ordinary skill in the pertinent arts, such as e-beam or holographic interference lithography. One technique that may be utilized may include starting with a silicon wafer having a thickness of approximately 0.5 mm, and then growing silicon dioxide on top of the wafer to a thickness of 150 nm. Recesses, including lines, dots, or other recesses, may be formed by etching into the silicon dioxide such that the recesses have lateral feature sizes of approximately 1 to 900 nm, or 3-300 nm, by way of non-limiting examples only.
Referring still to
The positioning of mold 230 and substrate 210 may occur at room temperature, although other temperatures such as elevated temperatures may be used. Further, the positioning of the mold 230 and substrate 210 may occur at atmospheric pressure. Further, it should be understood that the positioning need not be precisely controlled, but rather mere placement of the mold in proximity to or in partial contact with portions of the thin film may be sufficient. Of course, precisely controlled placement of the mold is by no means excluded from the scope of the present invention however.
As may be further seen in
For purposes of completeness, and as will be understood to those possessing an ordinary skill in the pertinent arts, capillary forces may be defined, generally, to be interfacial forces acting among a liquid and solid in a capillary or in a porous medium. The capillary force may determine the pressure difference (capillary pressure) across a fluid/fluid interface in a capillary or pore. Generally, an interfacial force is a force per unit length, and, as will be understood be known by those possessing an ordinary skill in the pertinent arts, includes forces such as surface tension and friction.
The critical distance represents a distance between the liquid layer and the mold that is sufficiently small such that thin film fluid self fills the mold. If the separation between the mold and the liquid layer exceeds the critical distance, no self filling of the mold will occur. Further, where the mold is not uniformly separated from the liquid layer for any of a number of reasons, if the separation of a portion of the mold and the closest portion of the liquid layer exceeds the critical distance, no self filling of that portion of the mold by the thin film fluid will occur, even though self filling of another portion of the mold may occur. The critical distance results from a number of different criteria, such as 0-200 nm. In the case of the particular formulations for the liquid layer set forth herein, the critical distance may be around 0-100 nm for example.
Non-uniform separation of the mold and liquid layer at the nano-scale may result from any of a number of causes. For example, the mold may simply not be positioned in a level manner with respect to the liquid layer. Further, and as will be understood by those possessing an ordinary skill in the pertinent arts, the surface of the mold and/or liquid layer may not be sufficiently planar at the nano-scale such that the entire mold, or that portion of the mold to be used, may be placed a uniform distance—at the nano-scale—from the liquid layer. That is, in light of the nanoscale features to be reproduced, otherwise insignificant undulations, non-planarities or imperfections in a substrate wafer or mold for example may have significant effects on the critical distances between portions of the substrate and portions of the mold. Thus, even though the mold is placed on top of and in partial contact with the liquid layer for example, portions of the mold may not be in contact with or within the critical distance from the liquid layer after being positioned, as may be desired to promote uniform mold self filling. Rather, portions of the mold may come into contact with portions of the liquid layer while other portions of the mold may remain beyond the critical distance from the film. Further exacerbating this situation, air bubbles may become trapped between the mold and liquid layer that may further serve to reduce the self filling activity.
Referring now also to row C of
For example, the mold and substrate/liquid layer composite may be placed in a deformable container having one or more openings, which container is then subjected to a decrease in pressure, such as by being placed in a vacuum chamber. Such a container may take the form of a deformable plastic bag having one or more openings therein, for example. Such a container may take the form of two PVC plastic sheets forming a quasi-bag that can be vacuumed out, as is set forth below, but that forms a sealed container when a positive pressure relative to its interior is introduced.
According to an aspect of the present invention, the mold 230 and substrate 210 may be placed within the plastic bag allowing its internal space to be evacuated when a vacuum chamber is evacuated, thereby acting to remove residual bubbles and trapped air and promote leveling of the mold with respect to the liquid layer. A vacuum may be held in the chamber for approximately one minute, for example. Vacuum treatment may serve to aid in enhancing pattern replication yield by achieving a more uniform pattern replication, particularly when using substrates of relatively large size and area, such as greater than 1 inch in diameter, for example.
After the mold and liquid layer/substrate composite have been vacuum treated they may optionally be subjected to a relatively low pressure to further promote reduction of distances between parts of the mold and parts of the liquid layer below the critical distance. Such a pressure may range from approximately 14 PSI to about 100 PSI, or even greater, by way of non-limiting example only. For example, the vacuum chamber may have 100 PSI of nitrogen gas rapidly introduced and held for approximately one minute. Where the mold and liquid layer/substrate composite have been placed within a deformable container as has been set forth, such a container may largely serve to prevent introduction of a gas used to provide the applied pressure to the mold/liquid layer/substrate composite structure due to its collapsible nature.
Thereafter, the mold and liquid layer/substrate composite structure may be removed from the vacuum chamber. It should be noted that according to an aspect of the present invention the liquid layer may not yet have been chemically transformed, and hence may not be capable of retaining the mold pattern itself. That is, those skilled in the pertinent arts may recognize that as the film is still fluid in nature, it has not yet and cannot be formed or molded but rather like any fluid merely is a continuous, amorphous substance whose molecules move freely past one another and that has the tendency to assume the shape of its container. Nonetheless, the fluid film may serve to maintain the mold and substrate proximity for some time at room temperature and pressure. For example, the liquid layer may serve to keep the mold and liquid layer/substrate composite in sufficient proximity such that the critical distance remains small enough, such that the liquid layer at least remains partially within mold interstices, recesses or grooves.
While not limiting of the present invention, it is believed interfacial forces due to the proximity of the mold, liquid layer and substrate may serve to hold the mold and liquid layer/substrate composite together for some time, such as minutes, hours, days or even a month or possibly longer, for example, even though the film is not yet formed in the shape of the mold, but rather is merely filling the mold.
Referring still to
As will be understood by those possessing an ordinary skill in the pertinent arts, the mechanism used to solidify thin film 220 may depend on the thin film used. Liquid layers and at least one relevant solidifying technique include chemical chain growth, Sol-Gel or UV crosslink processes, for example. The solidifying reaction may include at least one of the following mechanisms: cationic, free radical, or 2+2 phototcycladdition, by way of non-limiting example only.
Thereafter, if the mold/chemically transformed film/substrate sandwich has not been earlier removed from the vacuum bay, it may be. The solidified film may be formed and capable of retaining the mold features, and the mold may be removed from its position near the substrate. This solidification and the following separation are depicted in Row D of
Upon separation 150 of the solidified film 220 from the mold 230, a negative replication of mold 230 in thin film 220 may be revealed. This replicated pattern of the mold may then be used as a mask for etching the substrate 210, if desired. Such a transfer may occur by any suitable method known to those possessing an ordinary skill in the pertinent arts, such as Reactive Ion Etching (RIE), for example.
The replicated pattern may be used for other purposes as well. For example, when a phosphor containing chemical resin suitable for a pixel array is introduced into the liquid layer, the pattern may serve to provide an electro-optical device such as an organic light emitting diode (OLED) structure.
Referring now to
In view B, there is shown a 6,500×-magnification is utilized to show a larger area of the formed grating. Once again the distinct differences of the features and the darkness of the absence of features represent the accuracy and precision of the current technique.
Those of ordinary skill in the art will recognize that many modifications and variations of the present invention may be implemented without departing from the spirit or scope of the invention. Thus, it is intended that the present invention covers the modifications and variations of this invention provided they come within the scope of the appended claims and their equivalents.
This application claims priority of U.S. Patent Application Ser. No. 60/496,193, entitled SUB-MICRON-SCALE PATTERNING METHOD AND SYSTEM, filed Aug. 19, 2003, the entire disclosure of which is hereby incorporated by reference as if being set forth in its entirety herein.
| Number | Date | Country | |
|---|---|---|---|
| 60496193 | Aug 2003 | US |
