KR20060124668A - Process for producing photonic crystals and controlled defects therein - Google Patents

Abstract

A process comprises (a) providing a substantially inorganic photoreactive composition comprising (1) at least one cationically reactive species, (2) a multi-photon photoinitiator system, and10 (3) a plurality of precondensed, inorganic nanoparticles; (b) exposing, using a multibeam interference technique involving at least three beams, at least a portion of the photoreactive composition to radiation of appropriate wavelength, spatial distribution, and intensity to produce a two- dimensional or three-dimensional periodic pattern of reacted and non- reacted portions of the photoreactive composition; (c) exposing at least a portion of the non-reacted portion of the photoreactive composition to radiation of appropriate wavelength and intensity to cause multi-photon absorption and photoreaction to form additional reacted portion; (d) removing the non-reacted portion or the reacted portion of the photoreactive composition to form interstitial void space; and (e) at least partially filling the interstitial void space with at least one material having a refractive index that is different from the refractive index of the remaining portion.

Description

How to produce photonic crystals and controlled defects in them {PROCESS FOR PRODUCING PHOTONIC CRYSTALS AND CONTROLLED DEFECTS THEREIN}

The present invention relates to a periodic dielectric structure and a method of generating defects therein.

Photon crystals, the photon homologues of traditional semiconductors, are currently the subject of intensive research for application in photonic integrated circuits. This crystal represents a photon bandgap (similar to the semiconductor electron bandgap) that determines which photon wavelengths can propagate through the crystal. By introducing specific defects within the crystal's bandgap structure, the flow of photons within the crystal can be manipulated, assembling various micrometer-scale optics.

In particular, three-dimensional (3-D) photonic crystals with appropriate line defects can cause light rays to be rotated through 90-degree bends without significant scattering losses. It is assumed to act as. Such a device would be potentially useful for increasing the density of components on optical chips and for chip-to-back plane applications. Other potential device applications include optical interconnects, optical switches, couplers, insulators, multiplexes, tunable filters, and low-threshold radiators ( use in low-threshold emitters.

Various methods were used to generate photonic crystals. Such methods include, for example, colloidal crystal self-assembly methods, self-assembly of block copolymers, semiconductor-based lithography (eg, photolithography, masking, etching, etc.). etching)), mechanical generation of the array of holes in the substrate material (or instead mechanical removal of the substrate material to form a periodic pattern of cylindrical or similar-shaped rods of the substrate material), void array in the substrate material Electrochemical generation, photofabrication using multibeam interference (MBI), or holographic lithography techniques, glancing angle deposition, and multiphoton optical fabrication. Each method has its own advantages. In general, however, all but MBI is difficult due to one or more of the following disadvantages: relatively high intrinsic structural failure or defect concentration, relatively slow deposition rate, and many essential process steps.

In contrast, MBI technology can produce photonic crystals of various different Bravais lattice structures at relatively high speed using only a few process steps. The resulting photon crystals generally exhibit exceptional regularity and structural fidelity.

In general, organic photoresists have been used for MBI, and most conventional organic photopolymers have a refractive index that is substantially less than 2, for example, often high refractive index semiconductors (generally above 500 ° C. for silicon). There is a lack of sufficient thermal stability to remain intact during the chemical vapor deposition (CVD) method used for the deposition. This lack makes it difficult or impossible to obtain high contrast ratios that can support the complete photon bandgap.

summary

Accordingly, the inventors have recognized the need for a method of producing photonic crystals (and controlled and designed defects therein) that can provide a high dielectric index periodic dielectric structure. Briefly, in one aspect, the present invention is directed to (a) (1) at least one cationic reactive material (preferably, at least one cationic curable material), (2) a multiphoton photoinitiator system (preferably multicomponent Multiphoton photoinitiator system), and (3) a substantially inorganic photoreactive composition comprising a plurality of precondensed inorganic nanoparticles; (b) wavelength, spatial distribution and intensity suitable for producing at least a portion of the photoreactive composition using a multibeam interference technique comprising at least three beams to produce two-dimensional or three-dimensional periodic patterns of the reactive and non-reactive portions of the photoreactive composition. Exposure to radiation; (c) exposing at least a portion of the non-reactive portion of the photoreactive composition to radiation of a wavelength and intensity suitable for multiphoton absorption and photoreaction to form additional reactive portions and remaining non-reactive portions; (d) removing the remaining non-reactive portion or the entire reaction portion (preferably the remaining non-reactive portion) of the photoreactive composition to form an interstitial void space; (e) at least partially filling the void spaces with at least one material having a refractive index that is different from the refractive index of the remaining non-reactive or reactive portions of the photoreactive composition.

Unlike conventional MBI methods using organic materials, the method of the present invention employs a substantially inorganic photoreactive composition, for example, a durable, highly ordered, thermally stable, durable material that withstands temperatures up to about 600 to 1300 ° C. Produce periodic dielectric structures. Thus, the refractive index contrast of this structure can be enhanced by creating air voids, for example, by semiconductor CVD followed by optional removal of the structure (eg, by hydrogen fluoride etching). The use of cationic reactive materials may allow multiple exposures without significant change in refractive index, and the use of precondensed inorganic nanoparticles may result in surprisingly reduced contraction (corresponding compositions comprising non-condensed metal oxide precursors). In comparison).

Thus, the method of the present invention not only meets the need for a method that can provide a high refractive index versus periodic dielectric structure containing defects that are tuned or designed to selectively deliver and control light propagation through the structure, Promote the optimization of optical properties. The resulting defect-containing structure can be used, for example, in a planar lightwave circuit.

These and other features, aspects, and advantages of the present invention will be better understood with reference to the following detailed description, appended claims, and accompanying drawings.

1A-1H illustrate cross-sectional views of embodiments of the method of the present invention.

These figures, which are ideally illustrated, are not drawn to scale, but merely meant to be illustrative and non-limiting.

details

Justice

As used in this patent application, "periodic dielectric structure" means a structure exhibiting a periodic spatial change in the dielectric constant; "Photon bandgap" (PBG) means a range of frequencies or wavelengths at which electromagnetic radiation cannot propagate in some ("partial photon bandgap") or all ("full photon bandgap") directions in a periodic dielectric structure; ; "Substantially inorganic photoreactive composition" means a photoreactive composition that loses less than about 80% of its original weight upon photoreaction and pyrolysis; "Precondensed" (associated with inorganic nanoparticles) means that the nanoparticles have a density substantially equal to that of the corresponding bulk material.

Substantially inorganic Photoreactivity  Composition

Photoreactive compositions useful in the methods of the present invention are substantially inorganic in nature so that they are generally thermally stable under the conditions typically used to fabricate photonic crystals (eg, temperatures up to about 600 to 1300 ° C.). Upon photoreaction and pyrolysis, such compositions lose less than about 80% (preferably less than about 60%; more preferably less than about 40%; most preferably less than about 30%) of their initial weight.

Suitable compositions include (1) at least one cationic reactive material (preferably at least one cationic curable material); (2) multiphoton photoinitiator system (preferably, multicomponent multiphoton photoinitiator system); And (3) a composition comprising a plurality of precondensed inorganic particles. This composition may optionally further comprise a non-reactive material (eg, a non-reactive polymer binder).

Preferably, the composition exhibits volume shrinkage of less than about 20% upon photoreaction. Preferably, at least a portion of the cationic reactive material used is multifunctional.

(One) Cationic  Reactive material

Suitable cationic reactive materials include curable and non-curable materials. Curable materials are generally preferred and include, for example, those whose nature is organic (eg, epoxy) or hybrid organic / inorganic (eg, glycidyloxypropyltrimethoxysilane and oligomers thereof). Useful curable materials include cationic-polymerizable monomers and oligomers and cationic-crosslinkable polymers (including, for example, epoxy, vinyl ethers, and cyanate esters), and the like. The use of cationic curable materials can enable the formation of latent images of photoacid at exposed sites without substantially changing the refractive index of the composition. This is desirable for methods involving multiple exposures before curing and developing.

Useful non-curable materials include, for example, reactive polymers that can increase their solubility in acid- or radical-derived reactions. Such reactive polymers include, for example, a number comprising ester groups that can be converted to a water soluble acid group (eg, poly (4-tert-butoxycarbonyloxystyrene)) by photogenerated acid. Insoluble polymers are included. Non-curable materials are also described in RD Allen, GM Wallraff, WD Hinsberg, and LL Simpson, "High Performance Acrylic Polymers for Chemically Amplified Photoresist Applications," J. Vac. Sci. Technol. B, 9 , 3357 (1991) Chemically-amplified photoresist, described in US Pat. The chemically-amplified photoresist concept is particularly widely used for microchip fabrication, which is characterized by less than 0.5 microns (or even 0.2 microns or less). In such photoresist systems, catalytic materials (generally hydrogen ions) can be generated by irradiation which leads to a cascade of chemical reactions. This cascade occurs when hydrogen ions amplify the rate of reaction by initiating a reaction that produces higher amounts of hydrogen ions or other acidic substances. Examples of typical acid-catalyzed chemically-amplified photoresist systems include deprotection reactions (e.g. t-butoxycarbonyloxystyrene resist, tetrahydropyran (THP) as described in US Pat. No. 4,491,628). Methacrylate-base material, THP-phenolic material as described in US Pat. No. 3,779,778, t-butyl methacryl as described in RD Allen et al., Proc. SPIE 2438 , 474 (1995) Rate-based materials, etc.); depolymerization reactions (eg, polyphthalaldehyde-based materials); and potential reactions (eg, materials based on Pinacol potential reactions).

Mixtures of various types of reactive materials can be used in the photoreactive composition. For example, mixtures of free radically-reactive materials and cationicly-reactive materials, mixtures of organic and hybrid organic / inorganic reactive materials, mixtures of curable materials and non-curable materials, and the like are also useful.

(i) organic Cationic  Reactive material

Organic cationic reactive materials can be used in the photoreactive composition. Suitable organic cationic reactive materials include cationic-curable materials. If desired, mixtures of two or more monomers, oligomers and / or reactive polymers may be used.

Suitable cationic-curable materials are described, for example, in US Pat. Nos. 5,998,495 and 6,025,406 and include epoxy resins. Such materials, broadly referred to as epoxides, include monomeric epoxy compounds and oligomer type epoxides and may be aliphatic, cycloaliphatic, aromatic or heterocyclic. These materials generally have, on average, at least one polymerizable epoxy group (preferably at least about 1.5, more preferably at least about 2) per molecule. Oligomeric epoxides include linear oligomers with terminal epoxy groups (eg, diglycidyl ethers of polyoxyalkylene glycols), oligomers with skeletal epoxy units (eg, polybutadiene polyepoxides), and pendants Oligomers having epoxy groups (eg, glycidyl methacrylate oligomers or co-oligomers) are included. Epoxides can be pure compounds or can be mixtures of compounds containing one, two or more epoxy groups per molecule. These epoxy-containing materials can vary greatly depending on the nature of their backbones and substituents. For example, the backbone may be of any type and its substituents may be any group that does not substantially inhibit cationic cure at room temperature. Examples of acceptable substituents include halogens, ester groups, ethers, sulfonate groups, siloxane groups, nitro groups, phosphate groups and the like. The molecular weight of the epoxy-containing material can vary from about 58 to about 500 or more.

Useful epoxy-containing materials include 3,4-epoxycyclohexylmethyl-3,4-epoxycyclohexanecarboxylate, 3,4-epoxy-2-methylcyclohexylmethyl-3,4-epoxy-2-methylcyclohexane carboxyl Included are materials containing cyclohexene oxide groups, such as epoxycyclohexanecarboxylate, represented by rate and bis (3,4-epoxy-6-methylcyclohexylmethyl) adipate. A more detailed list of useful epoxides of this nature is described in US Pat. No. 3,117,099.

Other epoxy-containing materials that are useful include glycidyl ether monomers of the formula:

Wherein R 'is alkyl or aryl and n is an integer from 1 to 6. Examples thereof include glycidyl ethers of polyhydric phenols obtained by reacting polyhydric phenols with excess chlorohydrin such as epichlorohydrin (eg, 2,2-bis- (2,3-epoxypropoxyphenol) Diglycidyl ether of propane). Further examples of this type of epoxide are described in US Pat. No. 3,018,262 and Handbook. of Epoxy Resins , Lee and Neville, McGraw-Hill Book Co., New York (1967).

Many commercially available epoxy resins may be used. In particular, readily available epoxides include octadecylene oxide, epichlorohydrin, styrene oxide, vinyl cyclohexene oxide, glycidol, glycidyl methacrylate, diglycidyl ether of bisphenol A (e.g. For example, the trade names EPON 828 and EPON 825 (available as Resolution Performance Products, formerly provided by Shell Chemical Co.), and trade name DER (provided by Dow Chemical Co.), vinyl Cyclohexene dioxide (for example a compound available under the trade name ERL 4206 (provided by Union Carbide Corp.)), 3,4-epoxycyclohexylmethyl-3,4-epoxycyclohexene carboxylate (for example, ERL 4221, Compound available as Cyracure UVR 6110 or UVR 6105 (provided by Union Carbide Corp.)), 3,4-epoxy-6-methylcyclohexylmethyl-3,4-epoxy -6-methyl-cyclohexene carboxylate (for example a compound available under the trade name ERL 4201 (provided by Union Carbide Corp.)), bis (3,4-epoxy-6-methylcyclohexylmethyl) adipate ( For example, a compound available under the trade name ERL 4289 (provided by Union Carbide Corp.), bis (2,3-epoxycyclopentyl) ether (e.g. under the trade name ERL 0400 (provided by Union Carbide Corp.)) Available compounds), aliphatic epoxy modified from polypropylene glycol (e.g., available under the trade names ERL 4050 and ERL 4052 (provided by Union Carbide Corp.)), dipentene dioxide (e.g., trade name ERL 4269 (compound available from Union Carbide Corp.)), epoxidized polybutadiene (e.g., compound available under the trade name Oxon 2001 (provided by FMC Corp.)), Silicone resins containing functional groups, resorcinol diglycidyl ether (e.g., a compound available under the trade name KOPOXITE (provided by Koppers Company, Inc.)), bis (3,4-epoxy Cyclohexyl) adipate (for example a compound available under the tradename ERL 4299 or UVR 6128 (provided by Union Carbide Corp.)), 2- (3,4-epoxycyclohexyl-5,5-spiro-3, 4-epoxy) cyclohexane-methdioxane (such as the compound available under the trade name ERL-4234 (provided by Union Carbide Corp.)), vinylcyclohexene monooxide, 1,2-epoxyhexadecane (e.g. For example, a compound available under the trade name UVR-6216 (provided by Union Carbide Corp.), alkyl glycidyl ethers such as alkyl C ₈ -C ₁₀ glycidyl ethers (e.g. HEROXY MODIFIER 7 from Resolution Performance Products Available), butyl glycidyl ether (e.g., a compound available under the tradename HELOXY MODIFIER 61 (provided by Solution Performance Products)), multifunctional glycidyl ether, For example, diglycidyl ether of 1,4-butanediol (e.g., the compound available under the trade name Hexoxy Modifieder 67 (provided by Solution Performance Products)), diglycidyl ether of cyclohexanedimethanol (E.g., a compound available under the trade name Hexoxy Modifiers 107 (provided by Resolution Performance Products)), trimethylol ethane triglycidyl ether (e.g. trade name Hexoxy Modifyr 44 (provided by Resolution Performance Products)) Compounds available), polyglycidyl ethers of aliphatic polyols (e. G. Compounds available from Performance Products), polyglycol diepoxides (e.g., compounds available under the tradename Hexoxy Modifier 32 (provided by Solution Performance Products)), and bisphenol F epoxides (e.g., For example, the trade names EPON 1138 (provided by Resolution Performance Products) and GY-281 (provided by Ciba-Geigy Corp.) are included.

Other useful epoxy resins include copolymers of one or more copolymerizable vinyl compounds with acrylic esters of glycidol (eg, glycidyl acrylate and glycidyl methacrylate). Examples of such copolymers are 1: 1 styrene-glycidyl methacrylate and 1: 1 methyl methacrylate-glycidyl acrylate. Other useful epoxy resins are well known and include epichlorohydrin, alkylene oxides (eg propylene oxide), styrene oxides, alkenyl oxides (eg butadiene oxide) and glycidyl esters (eg Epoxides such as, for example, ethyl glycidate).

Useful epoxy-functional polymers include epoxy-functional silicones such as those described in US Pat. No. 4,279,717, available commercially from General Electric Company. These are polydimethylsiloxanes in which 1-20 mol% of the silicon atoms are substituted by epoxyalkyl groups (preferably epoxy cyclohexylethyl) as described in US Pat. No. 5,753,346.

Blends of various epoxy-containing materials may be used. Such blends may include two or more weight average molecular weight distributions of the epoxy-containing compound (eg, low molecular weight (up to 200), medium molecular weight (about 200 to 1000) and high molecular weight (about 1000 or more)). . Alternatively or additionally, the epoxy resin may contain blends of epoxy-containing materials having different chemical properties (eg, aliphatic and aromatic) or functional groups (eg, polar and non-polar). Other cationic-reactive polymers (eg, vinyl ethers, etc.) may be further incorporated as needed.

Preferred epoxies include aromatic glycidyl epoxies (eg, EPON resins (provided by Resolution Performance Products)) and cycloaliphatic epoxies (eg ERL 4221 and ERL 4299 (provided by Union Carbide)).

Suitable cationic-curable materials also include vinyl ether monomers and oligomers such as methyl vinyl ether, ethyl vinyl ether, tert-butyl vinyl ether, isobutyl vinyl ether, triethyleneglycol divinyl ether (e.g. RAPI-CURE DVE-3 (a compound available from International Specialty Products, Wayne, NJ), trimethylolpropane trivinyl ether (e.g. trade name TMPTVE (BASF Corp., Mount Olive, Compounds available from NJ), and the trade name VECTOMER divinyl ether resin (provided from Allied Signal) (eg, Vectomer 2010, Vectomer 2020, Vectomer 4010 and Vectomer 4020, and Equivalents thereof available from other manufacturers), and mixtures thereof. Blends (in any ratio) of one or more vinyl ether resins and / or one or more epoxy resins may be used. Polyhydroxy-functional materials (such as described in US Pat. No. 5,856,373 (Kaisaki et al.), May also be used in combination with epoxy- and / or vinyl ether-functional materials. .

( ii ) hybrid  Organic / Inorganic Cationic  Reactive material

Hybrid organic / inorganic cationic reactive materials can be used in the photoreactive composition. Useful hybrid organic / inorganic cationic reactive materials include silane compounds having at least one cationic polymerizable organic group. Examples of such silanes include, for example, epoxysilane compounds (eg, glycidyloxytrimethoxysilane, bis (glycidyloxy) dimethoxysilane, β- (3,4-epoxycyclohexyl) ethyltri Methoxysilane, β- (3,4-epoxycyclohexyl) ethyltriethoxysilane, etc.), an oxetanesilane compound (for example, 3- (3-methyl-3-oxetanemethoxy) propyltrimethoxy Silane, 3- (3-methyl-3-oxetanemethoxy) propyltrimethoxysilane, etc.), a silane compound having a 6-membered ring ether structure (for example, oxacyclohexyltrimethoxysilane, oxcyclohexyl Trimethoxysilane, etc.), and other reactive silanes capable of multiphoton activated cationic photocuring. Hydrolysates of such silane compounds may also be used.

Condensates of photoreactive silane compounds and / or condensates of mixtures of reactive and non-reactive silanes (eg, polyoctaheads available from suppliers such as Hybrid Plastics, Gelest, Techneglas, and Aldrich Chemical Co.) Ral silsesquioxane and oligomeric and polymeric silsesquioxane materials), oligomeric siloxane materials (eg polydimethylsiloxane), and branched and hyperbranched silicon-containing oligomeric and polymeric materials are required In this case, it can be used in combination with the silane compound described above. Sol-gel materials (eg, silicon alkoxides) can also be used in combination with the silane compound to increase the inorganic content of the composition.

(2) Multiphoton Photoinitiator  system

The photoinitiator system may be a multiphoton photoinitiator system, since the use of such a system enables defect writing in three-dimensional periodic dielectric structures as well as enhanced contrast. Such a system is preferably a two- or three-component system comprising at least one multiphoton photosensitizer, at least one electron acceptor, and optionally, at least one electron donor. Such multicomponent systems can provide enhanced sensitivity to allow photoreactions to be performed for shorter periods of time, thereby reducing the likelihood of problems due to the movement of one or more components of the sample and / or exposure system. Let's do it.

Alternatively, the multiphoton photoinitiator system may be a one-component system comprising at least one photoinitiator. Photoinitiators useful as one-component multiphoton photoinitiator systems include stilbene derivatives having covalently attached sulfonium salt sites (see, eg, W. Zhou et al., Science 296 , 1106 (2002)). Other conventional ultraviolet (UV) cationic photoinitiators may be used, but their multiphoton photoinitiation selectivity is generally relatively low.

Multiphoton photosensitizers, electron acceptors, and electron donors useful in two- and three-component photoinitiator systems are described below.

(i) multiphoton Photosensitizer

Multiphoton photosensitizers suitable for use in photoreactive compositions can simultaneously absorb at least two photons when exposed to radiation from a suitable light source in an exposure system. Preferred multiphoton photosensitizers are larger (ie 3 ', 6'-dihydroxyspiro [isobenzofuran-1 (3H), 9'-[9H]) than fluorescein when measured at the same wavelength. Xantene] -3-one), which is greater than that of xanthene] -3-one.

In general, the two-photon absorption cross section is measured by the methods described in C. Xu and WW Webb, J. Opt. Soc. Am. B, 13, 481 (1996) and WO 98/21521. 50 × 10 ⁻⁵⁰ cm ⁴ sec / photon. This method involves comparing the two-photon fluorescence intensity of the photosensitizer with the reference compound (under the same excitation intensity and photosensitizer concentration conditions). The reference compound may be chosen to match as closely as possible the spectral range covered by the photosensitizer absorption and fluorescence. In one possible experimental set-up, the excitation beam can be split into two arms, with 50% of the excitation intensity going to the photosensitizer and 50% to the reference compound. The relative fluorescence intensity of the photosensitizer relative to the reference compound can then be measured using two photomultiplier tubes or other calibrated detectors. Finally, the fluorescence quantum efficiencies of the two compounds can be measured under single-photon excitation.

Methods of measuring fluorescence and phosphorescent quantum yields are well known in the art. In general, the area below the fluorescence (or phosphorescence) spectrum of the compound of interest is compared to the area below the fluorescence (or phosphorescence) spectrum of a standard luminescent compound having a known fluorescence (or phosphorescence) quantum yield and appropriate correction is made ( For example, consider the optical density of the composition at the excitation wavelength, the geometry of the fluorescence detector, the difference in the emission wavelength, and the response of the detector to different wavelengths). Standard methods are described, for example, in IB Berlman, Handbook. of Fluorescence Spectra of Aromatic Molecules , Second Edition, pages 24-27, Academic Press, New York (1971); JN Demas and GA Crosby, J. Phys. Chem. 75 , 991-1024 (1971); And JV Morris, MA Mahoney and JR Huber, J. Phys. Chem. 80 , 969-974 (1976).

Assuming that the emission states are the same under single- and two-photon excitation (common assumption), the two-photon absorption cross-sectional area (δ _sam ) of the photosensitizer is δ _ref Equivalent to K (I _sam / I _ref ) (Φ _sam / Φ _ref ), where δ _ref is the two-photon absorption cross-section of the reference compound, I _sam is the fluorescence intensity of the photosensitizer, and I _ref is the reference compound Is the fluorescence intensity of, φ _sam is the fluorescence quantum efficiency of the photosensitizer, Φ _ref is the fluorescence quantum efficiency of the reference compound, and K is the correction factor to explain the slight difference in optical distance and response of the two detectors. K can be determined by measuring the reaction with the same photosensitizer in both the sample and the reference arm. To ensure a valid measurement, an apparent quadratic dependence of the two-photon fluorescence intensity on the excitation force can be identified, and comparatively low concentrations of both the photosensitizer and the reference compound can be used (fluorescent material). To avoid absorption and photosensitizer aggregation effects).

If the photosensitizer is not fluorescent, the yield of the electron excited state can be measured and compared with known standards. In addition to the methods described above for measuring fluorescence yield, various methods for measuring excited state yield are known (eg, transient absorbance, phosphorescence yield, photoproduct formation, or photosensitizer (from photoreaction). Loss, etc.).

Preferably, the two-quantum absorption cross-sectional area of the photosensitizer is at least about 1.5 times greater than in the case of fluorescence (or instead of at least about 75 × 10 ⁻⁵⁰ cm ⁴ sec / photons measured by the method above); More preferably about two times or more (or instead, about 100 × 10 ⁻⁵⁰ cm ⁴ sec / photon or more) of fluorescence; Most preferably at least about 3 times as in the case of fluorescence (or instead of at least about 150 × 10 ⁻⁵⁰ cm ⁴ sec / photon); Optimally about 4 times or more (or instead, about 200 × 10 ⁻⁵⁰ cm ⁴ sec / photon or more) in the case of fluorescence.

Preferably, the multiphoton photosensitizer is soluble in the reactive material (if the reactive material is a liquid) or compatible with any binder included in the reactive material and the multiphoton reactive composition (described below). Most preferably, the photosensitizer is also used in a wavelength range that overlaps the single photon absorption spectrum (single photon absorption condition) of the photosensitizer, using the test method described in US Pat. No. 3,729,313 and outlined above. Under continuous irradiation, 2-methyl-4,6-bis (trichloromethyl) -s-triazine can be increased or decreased.

Using currently available materials, this test can be carried out as follows: Standard test solutions can be prepared with the following composition: polyvinyl with a molecular weight of 45,000-55,000 and a hydroxyl content of 9.0-13.0% in methanol 5.0 parts of a 5% solution (weight by volume) of butyral (eg, available from Monsanto under the trade name BUTVAR B76); 0.3 part of trimethylolpropane trimethacrylate; And 0.03 parts of 2-methyl-4,6-bis (trichloromethyl) -s-triazine (see Bull. Chem. Soc. Japan, 42 , 2924-2930 (1969)). To this solution can be added 0.01 part of the compound to be tested as a photosensitizer. The resulting solution can then be knife-coated on a 0.05 mm transparent polyester film using a 0.05 mm knife orifice and the coating can be air dried for about 30 minutes. The 0.05 mm of transparent polyester cover film can be carefully placed on a dry but soft, tacky coating with minimal air capture. The resulting sandwich structure then emits light in both the visible and ultraviolet ranges (eg, generated from FCH 650 W quartz-iodine lamps available from General Electric) for three minutes. Exposure to 161,000 lux incident light from a tungsten light source provided. Exposure may be through a stencil to provide exposed and non-exposed areas within the structure. After exposure, the cover film can be removed and the coating can be treated with a finely divided colored powder, such as a color toner powder of the type commonly used in xerography. If the compound tested is a photosensitizer, the trimethylolpropane trimethacrylate monomer is photo-generated by free radicals photo-generated from 2-methyl-4,6-bis (trichloromethyl) -s-triazine. Will polymerize in the exposed areas. Since the polymerized area is inherently tacky, the colored powder will selectively attach only to the tacky non-exposed areas of the coating essentially to provide a visual image corresponding to that in the stencil.

Preferably, the multiphoton photosensitizer may also be selected based in part on consideration of storage stability. Thus, the choice of a particular photosensitizer may to some extent depend on the particular reactive material used (and also on the choice of electron donor compound and / or electron acceptor).

Useful multiphoton photosensitizers include semiconductor nanoparticle quantum dots with at least one electron excited state available by absorption of two or more photons. Particularly preferred multiphoton photosensitizers include Rhodamine B (ie, N- [9- (2-carboxyphenyl) -6- (diethylamino) -3H-xanthene-3-ylidene] -N- Hexafluoroantimonate salt of ethylethaneammonium chloride and rhodamine B) and four classes of photosensitization described, for example, in Marder and Perry et al. WO 98/21521 and WO 99/53242. Additional conventional photosensitizers that exhibit a large multiphoton absorption cross-sectional area such as agent are included. Four classes can be described as follows: (a) a molecule linked to a conjugated π-electron bridge with two donors; (b) a molecule in which two donors are linked to a conjugated π-electron bridge substituted by one or more electron acceptors; (c) a molecule linked to a π-electron bridge conjugated to two receptors; And (d) a molecule wherein two receptors are linked to a conjugated π-electron bridge substituted by one or more electron donor groups, where "bridge" refers to a molecular fragment that connects two or more chemical groups, "Donor" means an atom or group of atoms with a low ionization potential that can be bonded to a conjugated π-electron bridge, and a "receptor" means a high electron affinity that can be bound to a conjugated π-electron bridge An atom or a group of atoms).

Representative examples of such photosensitizers include the following materials:

The four classes of photosensitizers described above can be prepared by reacting aldehydes with lide under standard Wittig conditions or using the McMurray reaction as described in detail in WO 98/21521. .

Other suitable compounds are described in US Pat. Nos. 6,100,405, 5,859,251 and 5,770,737 as having large multiphoton absorption cross sections, but these cross sections were measured by methods other than those described above. Representative examples of such compounds include the following compounds:

( ii A) electron acceptor compound

Electron acceptors suitable for use in photoreactive compositions can be photosensitized while producing at least one acid by accepting electrons from the electron excited state of the multiphoton photosensitizer. Such electron acceptors include iodonium salts (eg diaryliodonium salts), diazonium salts (eg phenyldiazonium salts optionally substituted by groups such as alkyl, alkoxy, halo or nitro), Sulfonium salts (eg, triarylsulfonium salts optionally substituted with alkyl or alkoxy groups and optionally having a 2,2'oxy group bridge adjacent to the aryl moiety), and mixtures thereof.

The electron acceptor is preferably soluble in the reactive material and preferably storage-stable (ie does not spontaneously promote the reaction of the reactive material when dissolved therein in the presence of photosensitizers and electron donor compounds). Thus, the choice of a particular electron acceptor may depend to some extent on the particular reactive material, photosensitizer and selected electron donor compound as described above.

Suitable iodonium salts include those described in US Pat. Nos. 5,545,676, 3,729,313, 3,741,769, 3,808,006, 4,250,053, and 4,394,403. Iodonium salts may be simple salts (for example containing anions such as Cl ^_ , Br ^_ , I ^_ or C ₄ H ₅ SO ₃ ^_ ) or metal complex salts (for example SbF ₆ ^_ , PF ₆ ^_ , BF ₄ ^_ , tetrakis (perfluorophenyl) borate, SbF ₅ OH ^_ , or AsF ₆ ^_ ). If necessary, mixtures of iodonium salts can be used.

Examples of useful aromatic iodonium complex salt electron acceptors include diphenyliodonium tetrafluoroborate; Di (4-methylphenyl) iodonium tetrafluoroborate; Phenyl-4-methylphenyliodonium tetrafluoroborate; Di (4-heptylphenyl) iodonium tetrafluoroborate; Di (3-nitrophenyl) iodonium hexafluorophosphate; Di (4-chlorophenyl) iodonium hexafluorophosphate; Di (naphthyl) iodonium tetrafluoroborate; Di (4-trifluoromethylphenyl) iodonium tetrafluoroborate; Diphenyliodonium hexafluorophosphate; Di (4-methylphenyl) iodonium hexafluorophosphate; Diphenyliodonium hexafluoroarsenate; Di (4-phenoxyphenyl) iodonium tetrafluoroborate; Phenyl-2-thienyliodonium hexafluorophosphate; 3,5-dimethylpyrazolyl-4-phenyliodonium hexafluorophosphate; Diphenyliodonium hexafluoroantimonate; 2,2'-diphenyliodonium tetrafluoroborate; Di (2,4-dichlorophenyl) iodonium hexafluorophosphate; Di (4-bromophenyl) iodonium hexafluorophosphate; Di (4-methoxyphenyl) iodonium hexafluorophosphate; Di (3-carboxyphenyl) iodonium hexafluorophosphate; Di (3-methoxycarbonylphenyl) iodonium hexafluorophosphate; Di (3-methoxysulfonylphenyl) iodonium hexafluorophosphate; Di (4-acetamidophenyl) iodonium hexafluorophosphate; Di (2-benzothienyl) iodonium hexafluorophosphate; And diphenyl iodonium hexafluoroantimonate; And mixtures thereof. Aromatic iodonium complex salts include the corresponding aromatic iodonium simple salts (eg, diphenyliodo) according to the guidelines of Breeringer et al., J. Am. Chem. Soc. 81, 342 (1959). Metal bisulfate).

Preferred iodonium salts include diphenyliodonium salts (eg, diphenyliodonium chloride, diphenyliodonium hexafluorophosphate and diphenyliodonium tetrafluoroborate), diaryliodonium Hexafluoroantimonates (such as those available under the tradename SarCAT SR 1012 from Sartomer Company), and mixtures thereof.

Sulfonic anion X ^_ suitable for the sulfonium salts (and other any other type of electron acceptors) include, for example, suited imide, methoxy, boron-centered, in-centered, antimony-centered, arsenic-centered, and aluminum-centered Anions are included.

Illustrative and non-limiting examples of suitable imide and meted anions include (C ₂ F ₅ SO ₂ ) ₂ N ^_ , (C ₄ F ₉ SO ₂ ) ₂ N ^_ , (C ₈ F ₁₇ SO ₂ ) ₃ C ^_ , (CF ₃ SO ₂ ) ₃ C ^_ , (CF ₃ SO ₂ ) ₂ N ^_ , (C ₄ F ₉ SO ₂ ) ₃ C ^_ , (CF ₃ SO ₂ ) ₂ (C ₄ F ₉ SO ₂ ) C ^_ , (CF ₃ SO ₂ ) (C ₄ F ₉ SO ₂ ) N ^_ , ((CF ₃ ) ₂ NC ₂ F ₄ SO ₂ ) ₂ N ^_ , (CF ₃ ) ₂ NC ₂ F ₄ SO ₂ C ^_ ( SO ₂ CF ₃ ) ₂ , (3,5-bis (CF ₃ ) C ₆ H ₃ ) SO ₂ ) ₂ N ^_ SO ₂ CF ₃ , C ₆ H ₅ SO ₂ C ^_ (SO ₂ CF ₃ ) ₂ , C ₆ H ₅ SO ₂ ^_ SO ₂ CF ₃ and the like. Preferred anions of this type include anions represented by the formula (R _f SO ₂ ) ₃ C ^_ , wherein R _f is a perfluoroalkyl radical having 1 to about 4 carbon atoms.

Exemplary non-limiting examples of suitable boron-centered anions include F ₄ B ^_ , (3,5-bis (CF ₃ ) C ₆ H ₃ ) ₄ B ^_ , (C ₆ F ₅ ) ₄ B ^_ , (p- CF ₃ C ₆ H ₄ ) ₄ B ^_ , (m-CF ₃ C ₆ H ₄ ) ₄ B ^_ , (p-FC ₆ H ₄ ) ₄ B ^_ , (C ₆ F ₅ ) ₃ (CH ₃ ) B ^_ , (C ₆ F ₅ ) ₃ (nC ₄ H ₉ ) B ^_ , (p-CH ₃ C ₆ H ₄ ) ₃ (C ₆ F ₅ ) B ^_ , (C ₆ F ₅ ) ₃ FB ^_ , (C ₆ H ₅ ) ₃ (C ₆ F ₅ ) B ^_ , (CH ₃ ) ₂ (p- CF ₃ C ₆ H ₄ ) ₂ B ^_ , (C ₆ F ₅ ) ₃ (nC ₁₈ H ₃₇ O) B ^_ Included. Preferred boron-centered anions generally contain three or more halogen-substituted aromatic hydrocarbon radicals attached to boron, wherein fluorine is the most preferred halogen. Exemplary non-limiting examples of preferred anions include (3,5-bis (CF ₃ ) C ₆ H ₃ ) ₄ B ^_ , (C ₆ F ₅ ) ₄ B ^_ , (C ₆ F ₅ ) ₃ (nC ₄ H ₉ ) B ^_ , (C ₆ F ₅ ) ₃ FB ^_ , and (C ₆ F ₅ ) ₃ (CH ₃ ) B ^_ .

Suitable anions containing other metal or metalloid centers include, for example, (3,5-bis (CF ₃ ) C ₆ H ₃ ) ₄ Al ^_ , (C ₆ F ₅ ) ₄ Al ^_ , (C ₆ F ₅ ) ₂ F ₄ P ^_ , (C ₆ F ₅ ) F ₅ P ^_ , F ₆ P ^_ , (C ₆ F ₅ ) F ₅ Sb ^_ , F ₆ Sb ^_ , (HO) F ₅ Sb ^_ and F ₆ As ^_ is included. Preferably, the anion X ^_ is selected from tetrafluoroborate, hexafluorophosphate, hexafluoroarsenate, hexafluoroantimonate and hydroxypentafluoroantimonate (e.g. epoxy resin For use with cationicly-curable materials, such as).

Examples of suitable sulfonium salt electron acceptors include the following compounds:

Triphenylsulfonium tetrafluoroborate

Methyldiphenylsulfonium tetrafluoroborate

Dimethylphenylsulfonium hexafluorophosphate

Triphenylsulfonium hexafluorophosphate

Triphenylsulfonium hexafluoroantimonate

Diphenylnaphthylsulfonium hexafluoroarsenate

Tritoesulfonium hexafluorophosphate

Anylsilylphenylsulfonium hexafluoroantimonate

4-butoxyphenyldiphenylsulfonium tetrafluoroborate

4-chlorophenyldiphenylsulfonium hexafluorophosphate

Tri (4-phenoxyphenyl) sulfonium hexafluorophosphate

Di (4-ethoxyphenyl) methylsulfonium hexafluoroarsenate

4-acetonylphenyldiphenylsulfonium tetrafluoroborate

4-thiomethoxyphenyldiphenylsulfonium hexafluorophosphate

Di (methoxysulfonylphenyl) methylsulfonium hexafluoroantimonate

Di (nitrophenyl) phenylsulfonium hexafluoroantimonate

Di (carbomethoxyphenyl) methylsulfonium hexafluorophosphate

4-acetamidophenyldiphenylsulfonium tetrafluoroborate

Dimethylnaphthylsulfonium hexafluorophosphate

Trifluoromethyldiphenylsulfonium tetrafluoroborate

p- (phenylthiophenyl) diphenylsulfonium hexafluoroantimonate

10-methylphenoxate hexafluorophosphate

5-methylthianthrenium hexafluorophosphate

10-phenyl-9,9-dimethylthioxatenium hexafluorophosphate

10-phenyl-9-oxothioxatenium tetrafluoroborate

5-methyl-10-oxothianthrenium tetrafluoroborate

5-methyl-10,10-dioxothioanthrenium hexafluorophosphate

Preferred sulfonium salts include triarylsulfonium hexafluoroantimonate (e.g. available under the tradename Sarcat SR 1010 from Sartomer Co.), triarylsulfonium hexafluorophosphate (e.g. Triaryl-substituted salts such as those available under the trade name Sarcat SR 1011 from the Tomer Company and triarylsulfonium hexafluorophosphates (eg, those available under the trade name Sarcat KI85 from the Sartom Company) This includes.

Preferred electron acceptors include photoacid generators such as iodonium salts (more preferably, aryliodonium salts), sulfonium salts and diazonium salts. More preferred are the aryliodonium salts.

( iii ) Electron donor compound

Electron donor compounds useful in photoreactive compositions are compounds (but not photosensitizers themselves) that can donate electrons to the electron excited state of the photosensitizer. The electron donor compound is preferably greater than zero and has an oxidation potential that is less than or equal to the oxidation potential of p-dimethoxybenzene. Preferably, the oxidation potential is between about 0.3 and 1 V as compared to a standard saturated calomel electrode ("S.C.E.").

The electron donor compound is also preferably soluble in the reactive material and is selected based in part on consideration of storage stability. Suitable donors generally can increase the curing rate and image density of the photoreactive composition by exposure to light of a desired wavelength.

When working with cationicly-reactive materials, those skilled in the art will recognize that, if the electron donor compound has significant basicity, this may adversely affect the cationic reaction (see, See, eg, US Pat. No. 6,025,406).

In general, electron donor compounds suitable for use with particular photosensitizers and electron acceptors can be selected by comparing the oxidation and reduction potentials of the three compounds (eg, as described in US Pat. No. 4,859,572). . Such dislocations can be measured experimentally (eg, by methods described in RJ Cox, Photographic Sensitivity , Chapter 15, Academic Press (1973)), or in NL Weinburg, Ed. ., Technique of Electroorganic Synthesis Part II : Techniques of Chemistry , Vol. V (1975), and CK Mann and KK Barnes, Electrochemical Reactions in Nonaqueous Systems (1970). The potential reflects the relative energy relationship and can be used in the manner described below to induce electron donor compound selection.

When the photosensitizer is in an electron excited state, the electrons at the highest occupied molecular orbital (HOMO) of the photosensitizer have a higher energy level (ie, the lowest unoccupied molecular orbital (LUMO) of the photosensitizer. ), An empty space is left behind in the molecular orbital that it occupies primarily, the electron acceptor can accept electrons from higher energy orbitals, and when certain relative energy relationships are met, the electron donor compound donates electrons You can fill space in occupied orbitals.

If the reduction potential of the electron acceptor is less negative (or more positive) than the reduction potential of the photosensitizer, this indicates an exothermic method, so that electrons at the higher energy orbital of the photosensitizer occupy the lowest occupancy of the electron acceptor from the photosensitizer. Is easily transferred to molecular orbital (LUMO). Although this method is instead a slight endothermic reaction (i.e., although the reduction potential of the photosensitizer is negative up to 0.1 volts less than the reduction potential of the electron acceptor), ambient thermal activation can easily overcome this small obstacle. have.

In a similar manner, if the oxidation potential of the electron donor compound is less positive (or more negative) than the oxidation potential of the photosensitizer, the electron transfer from the HOMO of the electron donor compound to the orbital space of the photosensitizer is lower from higher potential to lower. It is a shift to an electric potential, which in turn represents a heating method. Although this method is a slight endothermic reaction (ie, even though the oxidation potential of the photosensitizer is up to 0.1 V more positive than the oxidation potential of the electron donor compound), ambient thermal activation can easily overcome this small obstacle. .

Weak endothermic reactions in which the photosensitizer's reduction potential is negative up to 0.1 volts more than the electron acceptor's reduction potential, or the photosensitizer's oxidation potential is more positive up to 0.1 V than the electron donor compound's oxidation potential. This happens in all cases regardless of whether or not it reacts with its photosensitizer in its excited state. When an electron acceptor or electron donor compound reacts with its photosensitizer in its excited state, the reaction is preferably exothermic or only slightly endothermic. If the electron acceptor or electron donor compound reacts with the photosensitizer ion radical, an exothermic reaction is still preferred, but more endothermic reactions can be expected to occur in most cases. Thus, the reduction potential of the photosensitizer may be 0.2 V or more negative than the reduction potential of the second-to-react electron acceptor, or the oxidation potential of the photosensitizer is the secondary donor. It may be 0.2 V or more positive than the oxidation potential of the compound.

Suitable electron donor compounds are described, for example, in DF Eaton, Advances in Photochemistry , edited by B. Voman et al., Volume 13, pp. 427-488, John Wiley and Sons, New York (1986) and US patents. And those described in US Pat. Nos. 6,025,406 and 5,545,676. Such electron donor compounds include amines (including triphenylamines (and their triphenylphosphine and triphenylarcin homologues), aminoaldehydes, and aminosilanes), amides (including phosphoramides), ethers (thioethers) ), Urea (including thiourea), sulfinic acid and salts thereof, salts of ferrocyanide, ascorbic acid and salts thereof, dithiocarbamic acid and salts thereof, salts of xanthate, salts of ethylene diamine tetraacetic acid, various Organometallic compounds, eg, SnR ₄ compounds, wherein each R is independently selected from alkyl, aralkyl (especially benzyl), aryl, and alkaryl groups (eg, nC ₃ H ₇ Sn (CH ₃ ) ₃ , (allyl) Sn (CH ₃ ) ₃ and (benzyl) Sn (nC ₃ H ₇ ) ₃ ), ferrocene, and the like, and mixtures thereof. The electron donor compound may be unsubstituted or substituted by one or more non-interfering plaques. Particularly preferred electron donor compounds contain electron donor atoms (eg nitrogen, oxygen, phosphorus or sulfur atoms) and extractable hydrogen atoms bonded to carbon atoms or silicon atoms that are alpine to electron donor atoms.

Preferred amine electron donor compounds include aryl-, alkaryl- and aralkyl-amines (eg, p-N, N-dimethyl-aminophenethanol and p-N-dimethylaminobenzonitrile); Aminoaldehydes (eg, p-N, N-dimethylaminobenzaldehyde, p-N, N-diethylaminobenzaldehyde, 9-julolidine carboxaldehyde and 4-morpholinobenzaldehyde); And mixtures thereof. Tertiary aromatic alkylamines, in particular having at least one electron-withdrawing group in the aromatic ring, have been found to provide particularly good storage stability. Good storage stability is also obtained using amines that are solid at room temperature. Good photographic speed is obtained using amines containing one or more zoloridinyl moieties.

Preferred amide electron donor compounds include N, N-dimethylacetamide, N, N-diethylacetamide, N-methyl-N-phenylacetamide, hexamethylphosphoramide, hexaethylphosphoramide, hexapropylphosphoramide , Trimorpholinophosphine oxide, tripiperidinophosphine oxide and mixtures thereof.

Suitable ether electron donor compounds include 4,4'-dimethoxybiphenyl, 1,2,4-trimethoxybenzene, 1,2,4,5-tetramethoxybenzene, and the like, and mixtures thereof. Suitable urea electron donor compounds include N, N'-dimethylurea, N, N-dimethylurea, N, N'-diphenylurea, tetramethylthiourea, tetraethylthiourea, tetra-n-butylthiourea, N, N-di-n-butylthiourea, N, N'-di-n-butylthiourea, N, N-diphenylthiourea, N, N'-diphenyl-N, N'-diethylthiourea, etc. , And mixtures thereof.

Preferred electron donor compounds for acid-derived reactions include 4-dimethylaminobenzoic acid, ethyl 4-dimethylaminobenzoate, 3-dimethylaminobenzoic acid, 4-dimethylaminobenzoin, 4-dimethylaminobenzaldehyde, 4-dimethylaminobenzo Nitrile, 4-dimethylaminophenethyl alcohol and 1,2,4-trimethoxybenzene.

If desired, the electron donor, electron acceptor, or both can be bound to (eg, covalently) a multiphoton photosensitizer.

(3) inorganic nanoparticles

Particles suitable for use in the process of the present invention include particles that are precondensed and whose chemical composition is inorganic. Such precondensed particles generally have a density substantially equal to the density of the corresponding bulk material (preferably at least about 50%, more preferably at least about 50%, most preferably of the density of the corresponding bulk material). At least about 90%). When heated to a temperature of about 200 ° C., these particles generally maintain at least about 70% (preferably at least about 80%; more preferably at least about 90%) of their original weight.

The particles can be surface-treated as needed (eg, to have surface-attached organic groups). Preferably, the particles may be selected to not initiate the reaction of the cationic reactive material or may be surface treated to minimize such initiation. In general, the particles may be of the size of submicron and, when used at a concentration of at least about 10% by weight in the composition, most may be transparent at the wavelength of light used for the photoreaction of the photoreactive composition. Preferably the refractive index of the particles is substantially the same as the refractive index of the reactive material (eg within about 10%).

Suitable particles are described, for example, in US Pat. No. 5,648,407, the disclosure of which is incorporated herein by reference. Suitable particles include metal oxides (eg Al ₂ O ₃ , ZrO ₂ , TiO ₂ , ZnO, SiO ₂ , rare earth metal oxides and silicate glasses) and metal carbonates as well as other sufficiently transparent non-oxide ceramic materials (eg Particles of metal fluoride) are included, but are not limited to these. A further consideration in selecting the particle (s) may be the temperature at which the material comprising the particles can be sintered into a dense inorganic structure. Preferably, the particles can be acid etched (eg, by aqueous HF or HCl).

Colloidal silica is a preferred particle for use in the process of the invention, but other colloidal metal oxides (eg titania, alumina, zirconia, vanadia, antimony oxide, tin oxide, and the like, and mixtures thereof). May be used. The colloidal particles may essentially comprise a single oxide having sufficient transparency, such as silica, but with one type of oxide core (or core other than metal oxide) and another type of oxide deposited thereon, preferably May comprise silica. Instead, the colloidal particles can be composed of clusters of smaller particles (of similar or different composition), can be hollow, or can be porous.

In general, the particles or clusters are smaller than the wavelength of the light used to photopattern the photoreactive composition, and the size (average particle diameter, where the "diameter" is not only spherical but also non-spherical in diameter). Means the longest dimension of the particles) from about 1 nanometer to about 150 nanometers, preferably from about 5 nanometers to about 75 nanometers, more preferably from about 5 nanometers to about 30 nanometers, Most preferably from about 5 nanometers to about 20 nanometers. Incorporation of colloidal particles having a specified size range into the photoreactive composition generally yields a substantially transparent and uniform composition. Such compositions minimize scattering of light rays during the photopatterning process. Most preferably, the particles are not only this size, but also have a refractive index that is substantially the same as the refractive index of the selected reactive material.

It will be appreciated by those skilled in the art that certain types of inorganic particles can interact with components of a multiphoton photoinitiator system (eg, acting as an electron acceptor) and can interfere with multiphoton-photoinitiated photoreactions. Will be self explanatory. Combinations of inorganic particles and multiphoton photoinitiators may preferably be selected to avoid such interference.

It is also desirable that the particles remain relatively uniform in size and remain substantially non-aggregated because particle aggregation can cause precipitation, gelation, or a sharp increase in sol viscosity. Preference is given to photoreactive compositions comprising particles having a substantially monodisperse or substantially bimodal size distribution.

Thus, a particularly preferred class of particles for use in the process of the invention comprises sol of inorganic particles (eg, colloidal dispersion of inorganic particles in liquid medium), in particular sol of amorphous silica. Such sol includes, by various techniques, a hydrosol (here water acts as a liquid medium), an organic sol (here an organic liquid is used) and a mixed sol (here the liquid medium contains both water and an organic liquid). Can be prepared in a variety of forms, including, for example, the techniques and forms set forth in US Pat. Nos. 2,801,185 (Iler) and 4,522,958 (Das et al.), The disclosures of which are incorporated herein by reference. For a description, and literature (RK Iler, The Chemistry of Silica , John Wiley & Sons, New York (1979)).

Silica hydrosols are preferred for use in the process of the invention because of their surface chemistry and commercial availability. Such hydrosols are available in a variety of particle size and concentration forms (eg, Nyacol Products, Inc. in Ashland, Md .; Nalco Chemical Company in Oakbrook, Ill .; and EI Dupont de Nemours and Company in Wilmington, Del) ). Concentrations of about 10-50% by weight of silica in water are generally useful, with concentrations of about 30-50% by weight being preferred (because smaller amounts of water are removed). If necessary, the silica hydrosol may be partially dissolved, for example, with an aqueous solution of alkali metal silicate at pH about 8 or 9 (so that the sodium content of the resulting solution is less than about 1% by weight based on sodium oxide). It can be prepared by neutralizing. Other methods of preparing silica hydrosols, such as electrodialysis, ion exchange of sodium silicates, hydrolysis of silicon compounds, and dissolution of elemental silicon, are described in the above Iler literature.

Preparation of the reactive resin sol preferably includes modifying at least a portion of the surface of the inorganic particles to assist in the dispersibility of the particles in the reactive material. Such surface modification can be performed by a variety of different methods known in the art (see, eg, US Pat. Nos. 2,801,185 (Iler) and 4,522,958 (Das et al., Incorporated herein by reference). Surface deformation technology as described in Such methods include, for example, silanization, plasma treatment, corona treatment, organic acid treatment, hydrolysis, titanation and the like.

For example, silica particles can be treated with monohydric alcohols, polyols or mixtures thereof (particularly saturated primary alcohols) under conditions such that silanol groups on the surface of the particles combine with hydroxyl groups to produce surface-bonded ester groups. have. The surface of the silica (or other metal oxide) particles can also be treated with organosilanes, for example alkyl chlorosilanes, trialkoxy arylsilanes or trialkoxy alkylsilanes, or by chemical bonds (covalent or ionic) or It can adhere to the surface of the particles by strong physical bonding and can be treated with other chemical compounds, such as organotitanates, which are chemically compatible with the selected resin (s). Treatment with organosilanes is generally preferred. In the case where an aromatic resin-containing epoxy resin is used, a surface treating agent which also contains at least one aromatic ring is generally compatible with the resin and is therefore preferred. Similarly, other metal oxides can be treated with organic acids (eg, oleic acid), or organic acids can be incorporated into the photoreactive composition as dispersants.

In preparing reactive resin sols, hydrosols (eg, silica hydrosols) are generally water-miscible organic liquids (eg, alcohols, ethers, amides, ketones or nitriles), and optionally (alcohol When used as an organic liquid), it may be combined with a surface treating agent such as an organosilane or an organotitanate. Alcohols and / or surfacing agents can generally be used in an amount such that at least a portion of the surface of the particles is sufficiently modified to enable the formation of stable reactive resin sols (when combined with the reactive material). Preferably, the amount of alcohol and / or therapeutic agent is selected to provide particles that are at least 50% by weight metal oxide (eg, silica), more preferably at least about 75% by weight metal oxide. (Alcohol may be added in sufficient quantity to the alcohol acting as both a diluent and a treating agent.) The resulting mixture is then heated to remove water by distillation or by azeotropic distillation, followed by It may be maintained at 100 ° C. for a period of about 24 hours, for example, to allow alcohol and / or other surface treatment agents to react (or otherwise interact with) chemical groups on the surface of the particles. This provides an organic sol comprising particles having surface-attached or surface-bonded organic groups.

The resulting organic sol is then combined with the reactive material and the organic liquid is removed, for example by using a rotary evaporator. Preferably, the organic liquid is removed by heating to a temperature sufficient to remove even tightly-bound volatile components under vacuum. Stripping times and temperatures can generally be selected to maximize removal of volatiles while minimizing the promotion of reactive materials. Instead, reactive particles are pre-condensed using methods known in the art, such as ball milling, 3-roll milling, Brabender mixing, extrusion, or other high shear mixing methods. May be mixed with the material.

Photoreactivity  Preparation of the composition

The components of the photoreactive composition can be prepared by the method described above or by other methods known in the art, and most of them can be used as commercial products. These components may be formulated using any compounding sequence and manner under “safe light” conditions (optionally by stirring or stirring), but finally dissolving the electron acceptor (and other components). It is sometimes desirable (in view of shelf life and thermal stability) to add any heating step optionally used for this purpose). If desired, a solvent may be used, provided that the solvent is selected so that it does not react appreciably with the components of the composition. Suitable solvents include, for example, acetone, dichloromethane, and acetonitrile. The reactive material itself may also sometimes act as a solvent for other components.

The components of the photoinitiator system are demonstrated by photochemically effective amounts (ie, changes in density, viscosity, color, pH, refractive index or other physical or chemical properties, such that at least partial reaction of the reactive material under selected exposure conditions) In an amount sufficient to allow the to be carried out. Generally, the photoreactive composition comprises from about 5% to about 99.79% by weight of one or more reactive materials (or reactive and non-based) based on the total weight of the solids in the composition (ie, the total weight of components other than the solvent). Combinations of reactive substances); About 0.01% to about 10% by weight of one or more photosensitizers (preferably from about 0.1% to about 5%, more preferably from about 0.2% to about 2%); Up to about 10% by weight of one or more electron donor compounds (preferably from about 0.1% to about 10%, more preferably from about 0.1% to about 5%); And from about 0.1% to about 10% by weight of one or more electron acceptors (preferably from about 0.1% to about 5%). The photoreactive composition may generally be loaded with from about 0.01% to about 75% by volume of inorganic particles, based on the total volume of the composition.

A wide range of additives may be included in the photoreactive composition depending on the desired properties. Suitable additives include solvents, diluents, resins, binders, plasticizers, pigments, dyes, thixotropic agents, indicators, inhibitors, stabilizers, ultraviolet absorbers and the like. The amount and type of such additives and their manner of addition to the composition are well known to those skilled in the art.

As described above, it is within the scope of the present invention to include the non-reactive polymer binder in the photoreactive composition, for example, to control the viscosity or to increase the speed of light. Such polymeric binders may generally be selected to be compatible with the reactive material.

Photoreactive compositions may be applied to the substrate by any of a variety of applications. The composition may be applied by a coating method such as knife or bar coating or by a method of application such as dipping, immersion, spraying, brushing, spin coating, curtain coating, or the like. Can be applied by Instead, the composition can be applied drop-wise. The substrate may be made of any size stable material (eg, a material such as glass, fumed silica, silicon, or calcium fluoride with a softening or decomposition temperature higher than the temperature of the process steps) and may be used in certain applications. Thus it can be selected from a wide variety of films, sheets, wafers and other surfaces. Preferably, the substrate is relatively flat and preferably has a lower refractive index than that of the periodic dielectric structure produced from the process. Preferably, the substrate has an anti-reflective coating that matches the exposure wavelength. The substrate may optionally be pretreated with a primer (eg, a silane coupling agent) to enhance the adhesion of the photoreactive composition to the substrate.

The photoreactive composition may be thixotropic or may exhibit fluid behavior sensitive to both the specific surface treatment of the inorganic particles and their compatibility with other components. Thus, appropriate solvent content and shear conditions can be optimized for each particular composition and coating method to obtain a uniform film of the desired thickness. After coating, the photoreactive composition may optionally be gently baked (eg, on a hot plate or in an oven) to remove some or all of the remaining solvent. Preferably, the rheology of the resulting coated composition is such that it does not substantially sag or flow over the time scale of the exposure and development steps.

Photoreactivity  Exposure of the composition

At least a portion of the substantially inorganic photoreactive composition may be exposed to radiation of appropriate wavelength, spatial distribution and intensity using multibeam interference (MBI) technology, which includes at least three beams (preferably at least four beams). It is possible to create two-dimensional or three-dimensional (preferably three-dimensional) periodic patterns of the reactive and non-reactive portions of the photoreactive composition. Preferably, the periodic pattern may be submicron-scale. The resulting non-reactive portion (or instead of the reaction portion) of the composition is removed (e.g., by solvent development) and filled with a gap void (which is filled with other materials, for example air or solvents having different refractive indices) May be formed).

Such MBI techniques generally involve two-dimensional or three-dimensional periodic changes in irradiation intensity, where interference between radiation propagating in different directions within the sample creates a corresponding periodic pattern of the reactive and non-reactive portions of the photoreactive composition within the sample. Irradiating with the electromagnetic radiation a sample (at least a portion) of the composition to cause.

Thus, a sample of photoreactive composition is simultaneously exposed to electromagnetic radiation from multiple sources while periodically changing the intensity or dose of the radiation (determined by the interference pattern) in the sample to produce an interference pattern in the sample. You can. Irradiation of the sample can produce a pattern corresponding to the change in refractive index by inducing a photoreaction, and in some cases the accompanying change in refractive index. In cases where multiple exposures are used (eg, to fill in defects), it may be desirable to select reactive materials that have relatively minimal such changes.

Samples of the photoreactive composition may be irradiated by at least three coherent or partially-coherent sources of electromagnetic radiation. Preferably, the periodic pattern in the sample is formed by directing electromagnetic radiation from at least four coherent or partially-coherent sources to the sample to intersect and interfere with each other in the sample. The sample may be subjected to multiple exposures, each of which creates a separate interference pattern within the sample.

The scale of periodicity in the sample also depends on the scale of the periodicity of the interference pattern, which depends on the frequency of incident radiation, the refractive index of the composition, and the shape and direction of propagation of the coherent electromagnetic wavefront in the sample. . The difference between the individual wave vectors of each beam of radiation used determines the symmetry of the reciprocal lattice vector, and thus the generated periodic dielectric structure. The specific grating symmetry can also be further adjusted by independently changing the power and / or polarization state of each beam. It is possible to create three-dimensional periodicity of submicron scale in a sample without the need for costly masks. This allows the production of periodic dielectric structures for use in optical and electro-optical applications in the infrared, visible, or shorter wavelengths of the electromagnetic spectrum.

For example, three-dimensional periodic dielectric structures can be created in the following manner. Negative photoresist, in which the solubility in a suitable solvent is reduced after exposure to radiation with a wavelength of 355 nm, is a frequency-tripled Nd: YAG laser so that the beams cross each other in the layer of photoresist. Can be irradiated simultaneously by four laser beams at a wavelength of 355 nm. Interference of four beams can cause three-dimensional periodic intensity modulation in photoresist with fcc structural symmetry with a cubic unit cell size of about 0.6 μm. The photoresist can be developed to remove the less-irradiated portion of the photoresist sheet, thereby creating a three-dimensional periodic structure comprising a permeable network of irradiated photoresist and air- or solvent-filled voids.

Although in any interference pattern the intensity of the radiation generally changes slowly on the length scale of the wavelength, the resulting periodic dielectric structure may have a relatively sharply defined surface. This can be obtained as a result of phenomena in subsequent steps that can create thresholds that distinguish non-linearities in the photoreaction and the soluble and insoluble portions of the irradiated sample. This threshold may correspond to a contour of approximately constant dose. By appropriately selecting the threshold intensity, the fraction of the sample removed by development can be controlled. (For example, over-exposure can reduce the blank fraction in the resulting developed structure.) Non-linearity of the photoreaction can be further enhanced by multiphoton exposure.

Preferably, the interference pattern generated during exposure causes the portion of the sample to be removed during development to form a network to which it is connected. This ensures that these parts can be removed to create voids. In addition, the interconnection of the pores allows a material having a refractive index (or other desirable property) different from the refractive index of the photoreactive composition to be introduced into the pores. It may also be important that the removal does not destroy the periodic structure of the remainder. This can be obtained, for example, by ensuring that the portion where the interference pattern is to be removed and the portion to be left each form a continuous permeable network during development.

A single exposure using laser beams that cross at the same time can be used. Instead, multiple exposure techniques may be used.

For example, in a double exposure technique, the composition may be exposed twice, and each exposure may cause the irradiation dose due to each exposure to change periodically. Radiation that is believed to form part of one exposure may be present as radiation that is considered to form part of another exposure at the same time. The criteria used to specify the characteristics of the double exposure, and the radiation energy for one or the other exposure, differ in that the effect of the interference between the radiations from different exposures in measuring the spatial variation of the total dosage is different within the same exposure. That is reduced or eliminated with respect to the effect of interference between radiation from the source. This can be accomplished by ensuring that the degree of interference between the radiations from the two exposures is less than the amount of interference between the radiations from different sources belonging to the same exposure, or by reducing the time interval between the two exposures. Thus, the radiation at the two exposures can be derived from mutually incoherent sources, which can be, for example, the outputs of a single laser, different lasers, or sources with different frequencies.

In an alternative method using the double exposure technique, two pulses of electromagnetic radiation can be used, where the interference between the two pulses is reduced or eliminated by ensuring that the second pulse arrives later than the first. For example, a single laser pulse can be divided into two pulses, the second being delayed in time relative to the first. The first pulse can be divided into four beams that can be used to generate an initial three-dimensional interference pattern in the photoreactive composition. After the first pulse collapses (during this period the second pulse follows the delay line), the second pulse can be similarly split into four beams, which are different paths than the four beams in the first exposure. And overlap to form different three-dimensional interference patterns in the photoreactive composition.

Alternatively, the beam derived from the second pulse can substantially follow the same path as the first four beams, but can cause different relative phase delays with respect to the relative phase delay of the beam from the first pulse, thus causing an initial interference pattern. Similar to or identical to, but may form an interference pattern moved to a spatial position relative to the initial pattern. In order to generate the necessary relative phase delay, an electro-optic phase modulator may be provided over at least one of the four beam lines and adjusted during the time interval between the first and second pulses. If pulses from a frequency-triple Nd: YAG laser with a duration of about 5 ns are used, a delay line of several meters can avoid overlap in the time between two exposures and allow the phase modulator to change the state between the pulses. May provide sufficient delay.

The double exposure technique allows the shape of the dose of conto in the photoreactive composition to be precisely controlled, which can increase the ease of design and fabrication of an open but continuously-connected structure. However, as mentioned above, the photoreactive composition can be irradiated by more than two exposures. As long as no substantial photochemical change occurs at the total time of irradiation, it can be ensured that all exposures produce a periodic intensity pattern with the same periodicity or balanced periodicity. If the continuous exposure corresponds to irradiation with a laser beam along the same path, the relative phase delay between the beams may vary between each pulse from the source. This may allow three or more exposures of the composition to be performed, each producing a spatially shifted interference pattern with respect to the other interference pattern.

For some photoreactive compositions, it may be necessary to adjust the duration of the composition's exposure to electromagnetic radiation so that the intensity interference pattern is sufficiently short that the intensity interference pattern is not significantly confused by the photoinduced change in the refractive index of the composition. Short pulse exposure reduces the bond to mechanical stability of the optical component. In order to ensure that the intensity interference pattern formed in the composition is not significantly affected by the change in refractive index induced by the irradiation, most preferably the composition is not irradiated for example for about 100 ms or more. In the case of other photoreactive compositions, the major photoinduced change in refractive index does not appear during exposure, but may appear during subsequent processing (eg, during heating of the composition).

Useful MBI techniques are also described, for example, in Kondo et al., Applied Physics Letters 79 , 725 (2001); AJ Turberfield, MRS Bulletin, p. 632, August 2001; S. Yang et al., Chemistry of Materials 14 , 2831 (2002); Kondo et al., Applied Physics Letters 82 , 2759 (2003); I. Divliansky et al., Applied Physics Letters 82 , 1667 (2003); and Yu. V. Miklyaev et al., Applied Physics Letters 82 , 1284 (2003)). Such documents may include, for example, the use of diffractive masks, the use of inhibitor concentrations adjusted to enhance contrast, the use of visible light for better penetration into the thickness of the resist, and the enhancement of contrast when writing periodic structures. The use of multiphoton absorption for the purpose of, and the use of "prisms" on the photoresist to help obtain the desired light wave vector in the photoresist. The stability of the interference pattern can be further improved by using the phase locking technique described in US Pat. No. 5,142,385 (Anderson et al.).

Where defect-containing periodic dielectric structures are desired, at least a portion of the non-reactive portion of the photoreactive composition may be exposed to radiation of a wavelength and intensity suitable for causing multiphoton absorption and photoreaction to form additional reactive portions. Can be. Alternatively, defect writing can be performed before the MBI if necessary (since the order of the process steps can be changed). The multiphoton method is particularly well suited for addressing structural defects, as this method can have a resolution of less than 150 nanometers and a penetration depth that allows the generation of defects inside the structure.

Exposure system and its uses

Suitable light sources for multi-beam interference include both pulsed and continuous wave sources. Suitable continuous wave sources include argon ion lasers (eg, Innova 90 available from Coherent, Santa Clara, California) and helium cadmium lasers (eg, melis grit ( Available from Melles Griot, Caloifornia). In order to minimize the required exposure time, it may be desirable for the light source to have a relatively long interference length, a relatively good beam quality, and a relatively large power. Suitable pulsed sources are frequencyd doubled of nanosecond Nd: YAG lasers (e.g., Pro-Series 250 available from Spectra-Physics, California). Or a frequency doubled output of a tripled output and a femtosecond titanium sapphire laser (eg, Spectra-Physics May Tai). Pulse sources may be desirable to keep exposure times short and to reduce variability in patterning that may occur due to changes in optical components.

Exposure systems useful for multiphoton writing of defects include at least one light source and at least one optical element. Any light source can be used that provides sufficient intensity (to produce multiphoton absorption) at a suitable wavelength for the selected photoinitiator system. Such wavelengths may generally range from about 500 to about 1700 nm, preferably from about 600 to about 1100 nm, more preferably from about 750 to about 1000 nm. The illumination can be continuous or pulsed, or a combination thereof.

Suitable light sources for multiphoton defect writing include, for example, a femtosecond near infrared titanium sapphire oscillator (e.g. Coherent Mira Optima 900-F) pumped by an argon ion laser (e.g. Coherent Innova). Included. Such a laser operating at 76 MHz has a pulse width of less than 200 femtoseconds, can be adjusted between 700 and 980 nm, and has an average power of 1.4 watts or less. Q-switched Nd: YAG lasers (eg Spectra-Physics Quanta-Ray PRO), visible wavelength dye lasers (eg Spectra-Physics Sirah pumped by Spectra-physics Quanta-Ray PRO), And Q-switched diode pumped lasers (eg, Spectra-Physics PC bar ™) may be used. Peak intensity is generally at least about 10 ⁶ W / cm 2. The upper limit of pulse fluence is generally indicated by the ablation threshold of the photoreactive composition.

Preferred light sources for multiphoton coupled writing include near infrared pulsed lasers having a pulse length of about 10 ⁻⁸ seconds (more preferably less than about 10 ⁻⁹ seconds, most preferably less than about 10 ⁻¹¹ seconds). Other pulse lengths may be used provided they conform to the peak intensity and pulse fluence described above.

Optical elements useful in carrying out the methods of the invention include refractive optical elements (eg lenses and prisms), reflective optical elements (eg retroreflectors or focusing mirrors), diffractive optical elements (eg Diffraction gratings, phase masks and holograms, polarizing optical elements (e.g., linear polarizers and waveplates), diffusers, Pockels cells, waveguides, Waveplates, birefringent liquid crystals, and the like. Such optical elements are useful for focusing, beam delivery, beam / mode shaping, pulse shaping, and pulse timing. In general, combinations of optical elements may be used, and other suitable combinations will be appreciated by those skilled in the art. It may often be desirable to use optics with large numerical apertures to provide highly focused light rays. However, any combination of optical elements that provide the desired intensity profile (and its spatial arrangement) can be used. For example, the exposure system may include a scanning confocal microscope (BioRad MRC600) equipped with a 0.75 NA objective (Zeiss 20X Fluar).

In general, exposure of the photoreactive composition can be performed using a light source (as described above) in conjunction with an optical system as a means of adjusting the three-dimensional spatial distribution of light intensity within the composition. For example, light from a continuous wave or pulsed laser can be passed through the focusing lens in such a way that the focus is in the composition. The focus can be scanned or translated into a three-dimensional pattern corresponding to the desired shape to produce a three-dimensional image of the desired shape. The exposed or illuminated volume of the composition can be scanned by moving the composition itself or by moving the light source (eg, moving the laser beam using galvo-mirrors). The resulting exposed composition can be subjected to post-exposure heat treatment as needed.

The exposure time is generally the type of exposure system used (and the aperture coefficient, the geometry of the light intensity spatial distribution, for example the peak light intensity during the leisure pulse (the greater intensity and the shorter pulse duration are approximately the peak light). Its accompanying variable, such as intensity), as well as the nature of the exposed composition (and its concentration of photosensitizer (s), photoinitiator and electron donor compound). In general, larger peak light intensities at the site of focus allow for shorter exposure times if all else are equal. Linear imaging or “write” speeds are generally achieved using continuous wave lasers, or laser pulse durations of about 10 ⁻⁸ to 10 ⁻¹⁵ seconds (preferably about 10 ⁻¹¹ to 10 ⁻¹⁴ seconds) and per second, It may be about 5 to 100,000 microns / second using a pulsed laser having about 10 ² to 10 ⁹ pulses (preferably about 10 ³ to 10 ⁸ pulses per second).

If a photoreactive composition comprising a cationicly-curable reactive material is used, an acid is generated in the exposed portion of the composition, and any post-curing baking (eg on a hotplate or in an oven) is used. Hardening can be completed. Preferably, the gel point of the exposed portion of the composition can be reached at a low degree of cure so that large differential solubility occurs quickly between the exposed and non-exposed portions of the composition.

substitution

After selective exposure of the photoreactive composition, the void volume is removed by removing the reactive portion (e.g., using a non-curable reactive material) or non-reactive portion (preferably, non-reactive portion) of the photoreactive composition. Which may optionally be at least partially filled with one or more materials having a refractive index that is different from the refractive index of the rest of the photoreactive composition. If exposure of a portion of the photoreactive composition (eg, a low molecular weight reactive material cures to a high molecular weight material) results in a change in its solubility, the non-exposed non-reactive portion of the composition may be replaced with an appropriate solvent ( For example, it can be removed by developing using propylene glycol methyl ether acetate (PGMEA), methyl isobutyl ketone or cyclohexanone). Preferably, the developing solvent can effectively solvate both of these so that both the non-reacted reactive material and the inorganic particles can be removed essentially clean from the periodic dielectric structure.

In the case of standard resist systems, such as chemically amplified photoresists, the differential solubility (between the exposed and non-exposed portions of the photoreactive composition) can often be based on the deprotection of hydrophilic groups on the polymer backbone. Such resists can generally be developed with a basic solution to remove the exposed portions (deprotected portions). (Reference example: Introduction to Microlithography , Second Edition, edited by Larry F. Thompson, C. Grant Wilson, and Murrae J. Bowden, American Chemical Society, Washington, DC (1994).)

The development may preferably be carried out in a manner that minimizes or prevents the collapse of the photodefined pattern which may result from the stress induced by the surface tension of the solvent during drying. To minimize dry stress, the solvent used to develop the structure can instead be removed by CO ₂ supercritical extraction (see, eg, CJ Brinker and GW Scherer, Sol - Gel Science , Academic Press, New York, pp. 501-505 (1990)). In this method, a solvent-loaded structure can be placed in the extraction chamber and liquid CO ₂ completely covers the structure at temperatures below the critical point. In general, when a large amount of liquid CO ₂ is present relative to the amount of solvent, CO ₂ is almost quantitatively exchanged by the solvent inside the structure. The structure can then be heated above the critical point of CO ₂ (31.1 ° C. and P = 7.36 MPa), and the CO ₂ can be quickly discharged leaving a periodic dielectric structure that is substantially free of solvent. After development, any pyrolysis step may be performed to remove residual organic material. Additional thermal annealing or sintering may also be performed to further stabilize the inorganic structure. For example, the structure can be heated to about 600 ° C. at a rate of about 1 degree per minute, held at that temperature for about 1 hour, and then cooled slowly.

After removing the reactive or non-reactive portion of the photoreactive composition, the resulting voids of the periodic dielectric structure may be partially or fully filled with one or more materials as needed. Useful materials generally include those that are substantially non-absorbent in the wavelength range of the desired photon bandgap. Suitable materials include, for example, semiconductors (organic or inorganic), metals (for example precious metals such as tungsten and silver), or other metals exhibiting the desired properties. Preferably, the metal is a high refractive index material (eg having a refractive index greater than about 2), such as an inorganic semiconductor. Examples of useful inorganic semiconductors include ternary compounds such as silicon, germanium, selenium, gallium arsenide, indium phosphide, gallium indium phosphide and gallium indium arsenide, and the like. Doped semiconductors may also be used (eg, silicon may be doped with boron to produce an n-type semiconductor).

Filling typically includes, for example, chemical vapor deposition (CVD), melt infiltration, deposition and sintering of semiconductor nanoparticles, chemical electrodeposition, oxide formation and reduction, and the like. Can be achieved using phosphorus deposition methods (see, eg, EP 1 052 312 (Lucent Technologies Inc.) and the methods described in DJ Norris and YA Vlasov, Adv. Matter. 13 (6), 371 (2001)). ). CVD is often preferred. The conditions of the chosen deposition apparatus (eg gas flow, pressure and temperature) can preferably be adjusted to allow the periodic dielectric structure to be optimally penetrated by the material. By changing these conditions, the amount of material deposited inside the structure can be controlled. In the case of high refractive index materials, the amount of material inside the periodic dielectric structure may be an important parameter for obtaining a complete photon bandgap (see, for example, Busch et al., "Photonic Band Gap Formation in Certain Self-Organizing Systems"). , Physical Review E 58 , 3896 (1998).

After deposition, the material can be further processed, optionally by thermal annealing as is known in the art. For example, low pressure chemical vapor deposition (LPCVD) may be used primarily to fill the periodic dielectric structure partially or completely with amorphous silicon. The amorphous silicon can then be thermally annealed to form polycrystalline silicon (poly-Si). The main advantage of this latter step is the deposition of amorphous silicon with very small surface roughness to promote uniform filling. If desired, amorphous silicon can be converted to poly-Si to inherit a number of its desirable properties such as its robust mechanical properties and increased refractive index.

If desired (eg, when the ratio of the refractive index of the material to the refractive index of the remaining portion of the photoreactive composition is less than about 2), the remaining portion of the photoreactive composition may be removed to create an inverted periodic dielectric structure. Such removal can be accomplished, for example, by chemical etching using aqueous or ethanol hydrofluoric acid (HF), buffered oxide etchant or other etchant.

After removal and any filling step, the resulting structure is a periodic dielectric structure that includes arbitrarily controlled or designed defects. This structure may have sufficient periodicity of refractive index at least in two dimensions (preferably three dimensions) such that it can exhibit at least a partial photon bandgap (preferably a complete photon bandgap). Preferably, the periodicity is micron-scale periodicity (more preferably submicron-scale) such that the partial photon bandgap appears at wavelengths in the ultraviolet to infrared range (more preferably, in visible to near-infrared waves).

Periodic dielectric structures exhibiting complete photon bandgap include those based on permeable diamond-type lattice of dielectric material and air. The particular lattice structure determines the ratio of the refractive index of (dielectric material and air) required to obtain a partial or complete photon bandgap. Such structures are described, for example, in Ho et al ., Phys. Rev. Lett. 65 (25), 3152 (1990); Yablonovitch et al ., Physica B, 175 (1-3), 81 (1991); United States Patent Application Publication No. 2002/0059897 A1 (John et al .); U.S. Patent No. 5,739,796 (Jasper et al .); U.S. Patent No. 5,406,573 to Ozbay et al . ); U.S. Patent No. 5,335,240 to Ho et al .); U.S. Patent 5,600,483 to Fan et al . ); US Patent No. 5,440,421 to Fan et al . ; And SG Johnson et al ., Appl. Phys. Lett. 77 , 3490 (2000).

The resulting periodic dielectric structure is further deformed, organized, changed, processed, or patterned by additional methods known in the art (mechanical, electrical or optical) to provide optical devices (eg, optical waveguides). ) Can be generated. Such devices include those capable of inducing, attenuating, filtering and / or modulating electromagnetic radiation. Additional methods may be used, for example, to add a new layer of material (or remove material from a substrate) to a substrate (if used), or to add a new material to (or remove material from a structure) a periodic dielectric structure, The substrate can be patterned. If it is desirable to add new materials to the periodic dielectric structure, the structure can be partially or fully refilled by another material.

Controlled defect-containing three-dimensional (3-D) periodic dielectric structures, representing complete photon bandgaps, can be used as the basis for photonic integrated circuits. In one possible arrangement, the optical waveguide essentially confines the light beam completely, and in essence it can efficiently lead around sharp corners without loss of radiation. For example, a 3-D stack of logs-type periodic dielectric structures (see, eg, US Pat. No. 5,335,240 (Ho et) al .)) allows the structure to be used directly as a single-mode waveguide by substituting one log for air defects in one layer. Rays having a frequency within the photon bandgap of the structure are introduced into the waveguide (e.g., by butt coupling the optical fiber to the edge of the structure and aligning the core of the fiber parallel to the air defect). Can be. As a result of the high bondage, the light rays introduced into the waveguide can propagate with minimal loss. The optical waveguide may also be made two-dimensional if the refractive index of the two-dimensional periodic dielectric structure is high enough to bind the light beam through total internal reflection.

As described in A. Chutinan and S. Noda, Appl. Phys. Lett. 75 (24), 3739 (2002), light rays can be transmitted around a 90-degree bend. For example, a waveguide with a 90-degree bend in a stack of log-type periodic dielectric structures can be made by removing two logs that are perpendicular to each other. Optimum permeation efficiency around the bend can be obtained when the second log is in the layer just above the first log. Splitters and couplers are other optical devices that can be made using the same principle. The optimal size and shape of the adjusted defects for maximum luminous flux to the defects may depend on the particular periodic dielectric structure used. 90-degree turns are one of the most important types of defects that allow miniaturization of optical circuits.

Single point defects in periodic dielectric structures can be used as high quality microcavities. For example, a single grating point may be slightly enlarged, reduced in size, or all removed together to adjust the wavelength of the light beam to be bound in the defect. The very high effective reflection coefficient of the microcavity can change the rate of spontaneous emission. If a emitter is introduced into the point defect, ultra low threshold lasing can be achieved.

Combinations of single point and line defects can be used to produce more complex devices such as filters, wavelength division multiplexes, signal modifiers, and the like. Such an integrated circuit (or system) has maximum utility when multiple components are integrated into a single periodic dielectric structure. This can be accomplished using the method of the present invention.

If the rest of the photoreactive composition is not removed, devices such as amplifiers and high efficiency low threshold lasers can be created. The inorganic portion of the remaining photoreactive composition may be excited (any material added by charging) by radiation at a transparent wavelength to emit radiation at a wavelength within the bandgap of the periodic dielectric structure. For example, a composition containing erbium ions may be excited by 980 nm radiation to emit 1550 nm radiation, which is an ultra low threshold laser. Instead, both semiconductor nanoparticles can be incorporated into the photoreactive composition as emitters.

Desirable of method Embodiment

With reference to FIGS. 1A-1H, preferred embodiments of the process of the present invention can provide a substantially inorganic photoreactive composition 10 (optionally applied to the substrate 20) (FIG. 1A), the composition ( At least a portion of 10) forms a two-dimensional or three-dimensional periodic pattern of exposed and non-exposed portions 32 and 36 (FIG. 1C) of composition 10, respectively, and to allow photoreaction to occur in the exposed portions. ) Can be exposed using the multibeam interference device 30 (FIG. 1B). The nature and scale of the periodic pattern can be adjusted by varying the wavelength, interference angle, power and / or polarization of each of the laser beams.

The laser beam 40 can be focused on a pinpoint 42 inside the patterned structure created using the lens 44 (FIG. 1D). The location of the pinpoint can move to the desired pattern to form additional exposed portion 46 (FIG. 1E). The location of the pinpoint can be adjusted by moving the laser beam, lens or patterned structure (relative to the focused laser beam), for example using a three-axis step.

For example, the non-exposed portion 36 of the photoreactive composition 10 can be removed by development with a suitable solvent. This removal creates a void 50 (FIG. 1F), which is filled with a relatively high refractive index material 52 (eg, a semiconductor) using any of a variety of techniques (eg, chemical vapor deposition). Can be (FIG. 1G). Due to its substantially inorganic nature, at least a portion of the patterned photoreactive composition can remain intact through any process step carried out at elevated temperatures.

The resulting fill structure may optionally be exposed to an etchant (eg, HF) capable of selectively removing the remaining photoreactive composition (eg, exposed portion thereof) while keeping the high refractive index material substantially intact. . The resulting complete structure 60 includes a high refractive index material having a three-dimensional periodic air-filled void 64 and a non-periodic designed air defect 66 (FIG. 1H).

The objects and advantages of the present invention are further illustrated by the following examples, but the specific materials and amounts thereof and other conditions and details mentioned in these examples should not be understood as excessively limiting the present invention. do.

Example  1 (a)

Substantially inorganic Photoreactivity  Provision of the composition

Rhodamine  B Of hexafluoroantimonate  Produce:

A solution of 4.2 g of the chloride salt of Aldrich Chemical Co., Milwaukee, WI in 220 mL deionized water was filtered through diatomaceous earth. The filtrate was removed and 10.0 g of NaSbF ₆ (Advanced Research Chemicals, Inc., Catoosa, OK) was added with stirring. After mixing for 5 minutes, the resulting mixture was filtered and the resulting solid was washed with deionized water and dried in an oven at 50-80 ° C. overnight. A dark red solid was obtained (4.22 g), which was analyzed by infrared (IR) spectroscopy, nuclear magnetic resonance (NMR) spectroscopy, and elemental analysis for chloride. The analysis was consistent with the hexafluoroantimonate salt of Rhodamine B (structure shown below).

Surface-treated, Precondensed  Preparation of Inorganic Nanoparticles:

900 g of NALCO 2327 (dispersion of about 20 mm average diameter silica particles in water, available from ONDEO Nalco, Bedford Park, IL) was placed in a 2 liter beaker and pH under medium stirring AMBERLITE IR-120 with pre-washed until measured between 2-3 (using COLORPHAST pH paper, pH range 1-14, available from EM Science, Gibbstown, NJ) Ion exchange resin (available from Aldrich Chemical Co., Milwaukee, Wis.) Was added slowly. After stirring for 30 minutes at room temperature, the resulting mixture was filtered through a 10-micron nylon mesh fabric to remove the ion exchange resin and the solids measured 41.6%. 800 g of ion-exchanged nalco 2327 dispersions were placed in a round bottom flask and 230 g of deionized water (to prevent aggregation as pH rises) were added under medium stirring, followed by aqueous ammonium hydroxides. The pH was adjusted to between 8-9 by dropwise addition. To this mixture a pre-mixed solution of 1600 g 1-methoxy-2-propanol and 40.92 g trimethoxyphenylsilane (silica sugar, 0.62 mmol silane) was added over 5-10 minutes. The resulting non-aggregated silica dispersion was heated at 90-95 ° C. for about 22 hours. The silica solid of the dispersion was determined to be 15.4% by gravimetric analysis.

Cationic  Addition of reactive substances

390 g of 15.4% silica in a mixture of 31.5 g of ERL ™ 4221E (cycloaliphatic epoxy available from Dow Chemical, Midland, MI) and 3.5 g of 1,5-pentanediol (Aldrich Chemical Co.) Add dispersion. The components were mixed well and vacuum stripped of water and methoxy propanol with slow heating using a rotary evaporator with an aspirator and an oil bath. Final stripping temperature (using vacuum pump) was 130 ° C. for 45 minutes. 96 g of the resulting mixture were combined with 5.0 g of 3-glycidyloxypropyltrimethoxysilane (Aldrich Chemical Co.) at 100-g rated speed mixing cup (FlackTek Inc., Landrum, (Available from SC), and the resultant formulation is Flagect Inc. (FlackTek Inc.) Mix for 10 minutes at 3000 rpm using DAC 150 FVZ Speed Mixer (FlackTek Inc.). The resulting silica-epoxy sol contains 60% by weight surface-treated silica particles.

Multiphoton Photoinitiator  Addition of system

In order to prevent premature curing of the reactive material, 2.20 g of the prepared silica-epoxy sol was treated with 0.020 g of diaryliodonium hexafluoroantimonate (Sartomer, West Chester, PA) Available from), 0.010 g of Rhodamine B hexafluoroantimonate (ie, N- [9- (2-carboxyphenyl) -6- (diethylamino) -prepared essentially as described above) 3H-xanthene-3-ylidene] -N-ethylethaneammonium hexafluoroantimonate), 0.2 g tetrahydrofuran, and 0.65 g 1,2-dichloroethane. The resulting mixture is stirred for 15 minutes using a magnetic stirrer to obtain a homogeneous dispersion.

Example  1 (b)

Photoreactivity  Of composition Multi Beam  Interference ( MBI ) Impressions

A base such as triethylamine is added to the substantially inorganic composition produced in Example 1 (a), and the resulting composition is coated (e.g. dip coating, spin coating, graveur coating, Or by Meyer rod coating to a suitable substrate (eg, silicon or glass), wherein the viscosity of the composition is carefully controlled. (The base helps to mitigate nonzero-background light intensity in the "non-exposed" portion of the composition by partially neutralizing the local photoacids generated during exposure, thereby reducing the homogeneous crosslinked background. ) A heating step (eg mild baking on a hotplate) is applied prior to exposure to remove residual solvent from the composition.

The resulting coated substrate is placed at the site where the beam of light from the continuous wave (cw) laser is allowed to interfere. The coated substrate or sample is placed in an x-y linear air bearing stage equipped with a vacuum chuck to hold the sample firmly in place. Use three or four non-coplanar beams of an argon ion laser (for example, available from Coherent, Santa Clara, California) operating the sample at 488 nm for a period of about one second. Exposure to the generated interference pattern. A shutter (mechanical or acoustic-optical) is used to precisely adjust the exposure time. The beam diameter from the laser is on the order of a few millimeters. The interference angle, power and polarization of each of the laser beams are selected such that at least one of the Brave gratings of the interference pattern is parallel to the x-y plane of the stage progression.

Example  1 (c)

Photoreactivity  Of composition Multiphoton  exposure

Following the MBI exposure, the linear airborne stage is moved along its progression so that the exposed area of the sample is below the output of the second optical train. The multiphoton response of the defect structure is a diode-pumped Ti: sapphire laser (Spectra-Physics) operating at a wavelength of 800 nm, a pulse width of about 100 fs, a pulse repetition rate of 80 MHz, and a beam diameter of about 2 mm. , Mountain View, California. ”The optical train consists of a low dispersion turning mirroe, a beam expander, an optical attenuator for varying optical power, an acoustic-optic modulator for shuttering, And a 100 × oil-impregnated microscope objective mounted on a linear z-stage to focus the light into the sample The height of the microscope objective (z-axis position) on the sample is adjusted until the focal position is inside the coating. Fine tuning of the focal position is performed by monitoring multiphoton fluorescence intensities using cofocal optics and photoamplifier detectors. As photobleaching of a portion of the photosensitizer occurs, the pattern of the dark and dark areas can be identified and the focal position is placed within the desired focal plane The defect structure is in the coating by scanning the stage at a constant speed along the desired path. In order to minimize optical losses in the final device, this path is aligned with one or more grating vectors for the interference pattern.

Example  1 (d)

Photoreactivity  Removal of non-reactive portions of the composition

After exposure, the sample is heated to accelerate curing of the composition at the exposed site. The unexposed portion is then removed with a suitable solvent (eg propylene glycol methyl ether acetate) to form a gap void. The solvent is removed by supercritical drying to minimize drying stress. The resulting exposed, developed sample was pyrolyzed (e.g. by heating for 1 hour at 5 ° C / min to 600 ° C in a Vulcan oven, Model # 3-350, Degussa-Ney, Bloomfield, CT) To remove the organic content and then further heat to minimize porosity of the remaining silica. The resulting periodic dielectric structure exhibits at least a partial photon bandgap.

Example  1 (e)

Gap charge

Amorphous silicon is deposited into the gap gaps of the periodic dielectric structure using low pressure chemical vapor deposition furnaces (available from ASM, Phoenix, AZ) available commercially at about 560 ° C. Deposition conditions are chosen such that homogeneous penetration of amorphous silicon through the entire thickness of the structure is achieved. After deposition, the amorphous silicon is converted to polycrystalline silicon by annealing at 600 ° C. for 8 hours. The resulting structure is cooled to room temperature. The remaining silica is removed by etching with dilute HF solution (5-10% by weight HF in water). Silicon / air periodic dielectric structures are obtained. Periodic dielectric structures are examined using a scanning electron microscope (SEM). An air channel corresponding to the original position of the polymerized substantially inorganic photoreactive composition is observed.

The references, patents, patents, and publications cited herein are incorporated as if each were individually incorporated. Various unpredictable modifications and variations of the present invention will be apparent to those skilled in the art without departing from the scope and spirit of the present invention. It is not intended that the present invention be overly limited by the exemplary embodiments and embodiments described herein, these examples and embodiments are presented by way of example only and the scope of the invention is only set forth in the following patents. It is believed to be limited only by the claims.

Claims (35)

providing (a) a substantially inorganic photoreactive composition comprising (1) at least one cationic reactive material, (2) a multiphoton photoinitiator system, and (3) a plurality of precondensed inorganic nanoparticles; (b) wavelength, spatial distribution and intensity suitable for producing at least a portion of the photoreactive composition using a multibeam interference technique comprising at least three beams to produce two-dimensional or three-dimensional periodic patterns of the reactive and non-reactive portions of the photoreactive composition. Exposure to radiation; (c) exposing at least a portion of the non-reactive portion of the photoreactive composition to radiation of a wavelength and intensity suitable for multiphoton absorption and photoreaction to form additional reactive portions and remaining non-reactive portions; (d) removing the remaining non-reactive portion or the entire reaction portion of the photoreactive composition to form a gap void; (e) filling the gap voids at least partially with at least one material having a refractive index that is different from the refractive index of the remaining non-reactive or reactive portions of the photoreactive composition. The method of claim 1, wherein the periodic pattern is three-dimensional. The method of claim 1, wherein the periodic pattern has submicron-scale periodicity. The method of claim 1 wherein the substantially inorganic photoreactive composition loses less than about 60% of its initial weight upon photoreaction and pyrolysis. The method of claim 1 wherein the cationic reactive material is a cationic curable material. 6. The method of claim 5, wherein the cationic curable material is organic or hybrid organic / inorganic. The composition of claim 1, wherein the substantially inorganic photoreactive composition comprises a condensate of a photoreactive silane, a condensate of a mixture of reactive and non-reactive silanes, an oligomeric siloxane material, a branched silicon-containing oligomeric and polymeric material, And at least one material selected from the group consisting of sol-gel materials. The system of claim 1, wherein the multiphoton photoinitiator system comprises: (a) at least one multiphoton photosensitizer; (b) at least one electron acceptor; And (c) optionally, at least one electron donor. The method of claim 8, wherein the multiphoton photoinitiator system comprises at least one electron donor. 9. The method of claim 8, wherein the multiphoton photosensitizer has a larger two-photon absorption cross section than that of fluorescein. The method of claim 10, wherein the multiphoton photosensitizer has a two-photon absorption cross-sectional area that is about 1.5 times greater than for fluorescein. The method of claim 8, wherein the multiphoton photosensitizer is Rhodamine B, a molecule linked to a π (pi) -electron bridge conjugated with two donors, conjugated with two donors substituted by one or more electron acceptors a molecule linked to a π (pi) -electron bridge, a molecule linked to a π (pi) -electron bridge conjugated to two receptors, and a conjugated π (substituted by one or more electron donor groups Pi) -electron bridge. 13. The method of claim 12, wherein the multiphoton photosensitizer is rhodamine B. The method of claim 8, wherein the electron acceptor is selected from the group consisting of iodonium salts, diazonium salts, sulfonium salts, and mixtures thereof. 10. The method of claim 9, wherein the electron donor is an amine; amides; ether; Urea; Sulfinic acid and salts thereof; Salts of ferrocyanide, ascorbic acid and salts thereof; Dithiocarbamic acid and salts thereof; Salts of xanthate; Salts of ethylene diamine tetraacetic acid; SnR ₄ compound, wherein each R is independently selected from alkyl, aralkyl, aryl, and alkaryl groups; Ferrocene; And mixtures thereof. The method of claim 1 wherein the inorganic nanoparticles are selected from the group consisting of metal oxide nanoparticles, metal carbonate nanoparticles, metal fluoride nanoparticles, and combinations thereof. The method of claim 16, wherein the inorganic nanoparticles are metal oxide nanoparticles. 18. The method of claim 17, wherein the metal oxide is selected from the group consisting of silica, titania, alumina, zirconia, vanadia, antimony oxide, tin oxide, and mixtures thereof. The method of claim 18, wherein the metal oxide is silica. The method of claim 1, wherein the inorganic nanoparticles have an average diameter of less than about 150 nanometers. The method of claim 1 wherein the inorganic nanoparticles are surface treated. The method of claim 1, wherein the exposure is performed using a multibeam interference technique comprising at least four beams. The method of claim 1, wherein the exposure is performed by irradiating in a pulsed mode. The method of claim 1 wherein the radiation is near infrared radiation. The method of claim 1, wherein the remaining non-reactive portion of the photoreactive composition is removed to form a gap void. The method of claim 25, wherein the removal of the residual non-reactive portion of the photoreactive composition is carried out by development with a solvent. The method of claim 1 wherein the filling step comprises depositing the material by chemical vapor deposition. 27. The method of claim 25, further comprising removing residual reaction portions of the photoreactive composition. The method of claim 28, wherein the removal is by chemical etching. The method of claim 1, wherein the material has a refractive index greater than about two. The method of claim 1 wherein the material is an inorganic semiconductor. 32. The method of claim 31, wherein the inorganic semiconductor is selected from the group consisting of silicon, germanium, selenium, gallium arsenide, indium phosphide, gallium indium phosphide, and gallium indium arsenide. 33. The method of claim 32, wherein the inorganic semiconductor is silicon. The method of claim 1 further comprising sintering, pyrolysis and / or annealing. (a) (1) at least one cationic reactive material, (2) (i) at least one multiphoton photosensitizer, (ii) at least one electron acceptor and (iii) optionally, at least one electron donor A multi-photon photoinitiator system, and (3) a substantially inorganic photoreactive composition comprising a plurality of precondensed inorganic nanoparticles having an average particle diameter in the range of about 5 nanometers to about 20 nanometers; (b) a wavelength suitable for producing at least a portion of the photoreactive composition using a multibeam interference technique comprising at least four beams to generate a three dimensional, submicron-scale periodic pattern of the reactive and non-reactive portions of the photoreactive composition, Exposure to radiation of spatial distribution and intensity; (c) exposing at least a portion of the non-reactive portion of the photoreactive composition to radiation of a wavelength and intensity suitable for multiphoton absorption and photoreaction to form additional reactive portions and remaining non-reactive portions; (d) removing residual non-reactive portions of the photoreactive composition to form a gap void; (e) filling the gap voids at least partially with at least one material having a refractive index that is different from the refractive index of the remaining reactive portion of the photoreactive composition; (f) removing the remaining reaction portion of the photoreactive composition.

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