High resolution patterning compositions based on organometallic solutions

Abstract

To provide high-resolution patterning based on radiation using a thin coating.SOLUTION: Patterning can include irradiating the coated surface with a selected pattern and developing the pattern with a developer to form a developed image. The patternable coating may be susceptible to positive patterning or negative patterning based on the use of an organic developer or an aqueous acid or base developer. The radiation sensitive coating can include a metal oxo / hydroxo network with organic ligands. The precursor solution can include an organic liquid and metal polynuclear oxo-hydroxo cations with organic ligands having metal-carbon bonds and / or metal carboxylate bonds.SELECTED DRAWING: None

Description

[Technical Field]

[0001] STATEMENT OF GOVERNMENT RIGHTS Development of the invention described herein was funded at least in part with government support under US National Science Foundation Grant IIP-0912921, and the US government has certain rights in this invention.

[0002] The present invention relates to a radiation-based method for patterning materials using organometallic coating compositions. The invention further relates to precursor solutions that can be applied to form organometallic coatings that can be patterned with very high resolution by radiation, and to coated substrates and coatings formed with the precursor solutions before and after patterning. [Background technology]

[0003] When forming semiconductor-based devices and other electronic devices or other complex microstructures, materials are typically patterned to integrate the structures. Thus, the structures are typically formed by an iterative process of sequential deposition and etching steps in which patterns are formed from various materials. In this manner, multiple devices can be formed in a small area. Some technological advances can include reducing the footprint of the devices, which can be desirable for improved performance.

[0004] Organic compositions can be used as radiation-patterned resists, such that a radiation pattern is used to change the chemical structure of the organic composition in response to the pattern. For example, a process for patterning a semiconductor wafer may require lithographic transfer of a desired image from a thin film of radiation-sensitive organic material. Patterning a resist generally involves several steps, including exposing the resist to a selected energy source (e.g., through a mask) to record a latent image, and then developing and removing selected areas of the resist. In the case of a positive-tone resist, the exposed areas are altered to make such areas selectively removable, while in the case of a negative-tone resist, the unexposed areas are more easily removable.

[0005] Typically, the pattern is developed with radiation, reactive gases, or solutions to remove selectively sensitive portions of the resist, while other portions of the resist act as a protective, etch-resistant layer. Liquid developers can be particularly effective for developing the image. The substrate can be selectively etched through windows or gaps in the remaining areas of the protective resist layer. Alternatively, a desired material can be deposited on the exposed areas of the underlying substrate through the developed windows or gaps in the remaining areas of the protective resist layer. Finally, the protective resist layer is removed. The process can be repeated to form additional layers of patterned material. Functional inorganic materials can be deposited using chemical vapor deposition, physical vapor deposition, or other desired means. Additional processing steps, such as the deposition of conductive materials or the implantation of dopants, can be used. In the field of micro- and nano-fabrication, feature sizes within integrated circuits are becoming increasingly smaller to achieve high integration densities and improve circuit functionality. Summary of the Invention [Means for solving the problem]

[0006] In a first aspect, the present invention relates to a method for patterning a substrate with radiation, the method comprising the steps of irradiating a coated substrate along a selected pattern to form an irradiated structure having areas of irradiated coating and areas of non-irradiated coating, and selectively developing the irradiated structure to remove most of the irradiated or non-irradiated coating to form a patterned substrate. The coated substrate generally comprises a coating comprising a metal oxo-hydroxo network with organic ligands through metal-carbon and / or metal-carboxylate bonds.

[0007] In a further aspect, the present invention relates to a coated substrate comprising a radiation-sensitive coating having an average thickness of about 10 microns or less and a thickness variation of about 50% or less from the average at any point along the coating, the coating comprising a metal oxo-hydroxo network having metal cations with organic ligands through metal carbon and / or metal carboxylate bonds.

[0008] In another aspect, the present invention relates to a patterned substrate comprising a substrate having a surface and a first coating present in selected regions along the surface and absent in other regions along the surface. Generally, the first coating comprises a metal oxo-hydroxo network and organic ligands, wherein the metal cations are linked to the organic ligands by metal-carbon and / or metal-carboxylate bonds. Alternatively, the first coating is soluble in at least some organic liquids, or the first coating is soluble in aqueous base solutions.

[0009] In an additional aspect, the present invention relates to a precursor solution comprising an organic liquid and about 0.01 M to about 1.4 M of a metal polynuclear oxo / hydroxo cation having organic ligands with metal-carbon and / or metal carboxylate bonds, the precursor solution having a viscosity of about 0.5 centipoise (cP) to about 150 cP. The organic liquid may have a flash point of at least 10°C and a vapor pressure of less than about 10 kPa at 20°C. [Brief explanation of the drawings]

[0010] [Figure 1] 1 is a schematic perspective view of a radiation patterning structure having a latent image. [Figure 2] FIG. 2 is a side plan view of the structure of FIG. 1. [Figure 3] 2 is a schematic perspective view of the structure of FIG. 1 after the latent image has been developed and the unirradiated coating material has been removed to form a patterned structure. [Figure 4] FIG. 4 is a side view of the patterned structure of FIG. [Figure 5] 2 is a schematic perspective view of the structure of FIG. 1 after the latent image has been developed and the radiation coating material has been removed to form a patterned structure. [Figure 6] FIG. 6 is a side view of the patterned structure of FIG. [Figure 7] FIG. 5 is a side plan view of the patterned structure of FIGS. 3 and 4 after etching the underlying layer. [Figure 8] 8 is a side plan view of the structure of FIG. 7 after etching away the patterned condensed coating material. [Figure 9] 1-3 are side plan views of the process flow for "thermal freeze" double patterning. The process shown in Figures 1-3 is repeated after baking to make the first layer insoluble to the second layer. [Figure 10A] 1 is a plot of autocorrelated scattered intensity decay versus time for a precursor solution with monobutyltin oxide hydrate. [Figure 10B] 1 is a histogram of the calculated mass-average particle size distribution of a precursor solution containing monobutyltin oxide hydrate in 4-methyl-2-pentanol. [Figure 11A] Scanning electron micrograph of a negative-tone patterned coating with 18 nm wide lines on a 36 nm pitch in the coating material formed with monobutyltin oxide hydrate after irradiation with a 30 kV electron beam at a dose of 1191 μC / cm and development in 4-methyl-2-pentanol. [Figure 11B]Scanning electron micrograph of a negative-tone patterned coating with 18 nm wide lines on a 36 nm pitch in a coating material formed with monobutyltin oxide hydrate after irradiation with a 30 kV electron beam at a dose of 1191 μC / cm and development in ethyl lactate. [Figure 11C] Scanning electron micrograph of a negative-tone patterned coating with 18 nm wide lines on a 36 nm pitch in the coating material formed with monobutyltin oxide hydrate after irradiation with a 30 kV electron beam at a dose of 1191 μC / cm and development in propylene glycol monomethyl ether (PGMEA). [Figure 11D] Scanning electron micrograph of a negative-tone patterned coating with 18 nm wide lines on a 36 nm pitch in the coating material formed with monobutyltin oxide hydrate after irradiation with a 30 kV electron beam at a dose of 1191 μC / cm and development in n-butyl acetate. [Figure 12A] Scanning electron micrograph of a negative-tone patterned coating with 22 nm wide lines on a 44 nm pitch in the coating material formed with monobutyltin oxide hydrate after exposure to 13.5 nm radiation at a dose of 101 mJ cm using EUV projection lithography and development with PGMEA. [Figure 12B] Scanning electron micrograph of a negative-tone patterned coating with 18 nm wide lines on a 36 nm pitch in the coating material formed with monobutyltin oxide hydrate after exposure to 13.5 nm radiation at a dose of 101 mJ cm using EUV projection lithography and development with PGMEA. [Figure 13] 1 is a plot of relative hydrocarbon concentration versus electron beam dose as calculated from FTIR transmission measurements of absorbance of the C-H stretching mode of a coating material formed with monobutyltin oxide hydrate. [Figure 14]Scanning electron micrograph of a positive-tone patterned coating with 30 nm wide lines and 60 nm pitch in the coating material formed with monobutyltin oxide hydrate after irradiation with a 30 kV electron beam at a dose of 511 μC / cm and development with 2.38% TMAH. [Figure 15A] Scanning electron micrograph of a negative-tone patterned coating with 18 nm wide lines on a 36 nm pitch and a line width roughness (LWR) of 2.78 nm in the coating material formed with monobutyltin oxide hydrate after irradiation of a film deposited from a freshly prepared precursor solution and immediately exposed and developed in PGMEA with a dose of 1191 μC / cm2 by a 30 kV electron beam. [Figure 15B] Scanning electron micrograph of a negative-tone patterned coating with 18 nm wide lines on a 36 nm pitch and a 2.87 nm LWR in the coating material formed with monobutyltin oxide hydrate after irradiation with a 30 kV electron beam at a dose of 1191 μC / cm of a film deposited from a precursor solution aged at room temperature for 39 days and immediately exposed and developed in PGMEA. [Figure 15C] Scanning electron micrograph of a negative-tone patterned coating with 18 nm wide lines on a 36 nm pitch and a 2.68 nm LWR in the coating material formed with monobutyltin oxide hydrate after irradiating a resist film deposited from a freshly prepared precursor solution, aged as a coating at room temperature for 39 days, and exposed and developed in PGMEA with a 30 kV electron beam at a dose of 1191 μC / cm. [Figure 16] FIG. 1 is a scanning electron micrograph of a negative-tone patterned coating with 100 nm pitch lines in the coating material formed using a divinyltin hydroxide / oxide coating material after irradiation with a 30 kV electron beam at a dose of 75 μC / cm and development in PGMEA. [Figure 17]1 is a plot of relative vinyl (C-H stretch) absorbance versus dose as calculated from FTIR transmission spectra of coatings formed using divinyltin hydroxide / oxide coating materials exposed to a 30 kV electron beam. [Figure 18] FIG. 1 is a scanning electron micrograph of a negative-tone patterned coating with 32 nm pitch lines in the coating material formed using dibutyltin oxo-carboxylate coating material after irradiation with a 30 kV electron beam at a dose of 1500 μC / cm and development in PGMEA. [Figure 19] FTIR transmission spectra in comparative transmission mode of a dibutyltin oxo-carboxylate film in the unexposed state and after exposure to a 30 kV electron beam at a dose of 800 μC / cm 2 . DETAILED DESCRIPTION OF THE INVENTION

[0011] Desirable organometallic precursor solutions generally have non-aqueous solvents and ligand structures that provide high-resolution patterning, and the solutions have a high degree of stability for the formation of radiation-patternable coatings with good radiation sensitivity. Desirable ligands for forming metal oxo / hydroxo complexes can include M-C or M-O-C bonds, where M is the selected metal atom. Particularly desirable results can be obtained when M is tin, indium, antimony, or a combination thereof. A desirable feature of coatings formed using organometallic precursor solutions is that they provide excellent direct patterning for forming patterned metal oxide coatings. In particularly interesting embodiments, exposure to radiation converts the irradiated coating material into a material that is resistant to removal by a developer composition, or the exposure sufficiently changes the polarity of the coating material so that it is selectively removed. Thus, in some embodiments, coatings can be either negatively or positively patterned using the same coating. Selective removal of at least a portion of the coating material can leave a pattern in which areas of the coating are removed to expose the underlying substrate. After irradiation and subsequent development of the coating, the patterned oxide material can be used to facilitate processing in device formation due to its excellent pattern resolution. The coating material can be designed to be sensitive to selected radiation, such as extreme ultraviolet, ultraviolet, and / or electron beam. Furthermore, the precursor solution can be formulated to be stable and have an adequate shelf life for commercial distribution.

[0012] For ease of discussion herein, metal ions having M-C and / or M-OC ligand bonds can be referred to as organically stabilized metal ions. In addition to the organic ligands, the metal ions are also typically further bound to one or more oxo (i.e., MO) and / or hydroxo (i.e., MOH) ligands. The organically stabilized and oxo / hydroxo ligands provide desirable characteristics for precursor solutions and corresponding coatings by providing significant control over the condensation process to metal oxides, resulting in significant processing advantages. While the use of organic solvents supports solution stability, surprisingly, nonaqueous solution-based processing preserves the ability to selectively develop the resulting coatings after formation of latent images with excellent development rate contrast for both positive and negative patterning. Desirable precursor solutions containing dissolved organically stabilized metal ions provide convenient solution-based deposition for forming coatings that may have high radiation sensitivity and excellent contrast with respect to etch resistance to enable the formation of microstructures. The design of the precursor composition can provide for the formation of a coating composition that has high sensitivity to a particular radiation type and / or energy / wavelength.

[0013] Radiation-sensitive coating materials can be used as either positive or negative radiation patterning coatings. In negative patterning, exposure to radiation converts the irradiated coating material into a material that is more resistant to removal by a developer composition compared to the non-irradiated coating material. In positive patterning, exposure sufficiently changes (e.g., increases) the polarity of the exposed coating material so that it can be selectively removed by an aqueous or other highly polar solvent. Selective removal of at least a portion of the coating material leaves a pattern in which areas are removed to expose the underlying substrate.

[0014] The formation of integrated electronic devices and the like typically involves patterning materials to form individual elements or components within the structure. This patterning can involve covering selected portions of stacked layers with different compositions, which interact with each other vertically and / or horizontally to induce desired functionality. The various materials can include semiconductors, dielectrics, conductors, and / or other types of materials, which may have selected dopants. To form high-resolution patterns, patterns can be introduced using radiation-sensitive organic compositions, which can be called resists because portions of the composition can be processed to be resistant to development / etching so that selective material removal can be used to introduce the selected pattern. The resist can be exposed to radiation with a selected pattern or the negative of the pattern to form a pattern or latent image with developer-resistant and developer-soluble regions. The radiation-sensitive organometallic compositions described herein can be used to directly form desired inorganic material structures within devices and / or as radiation-patternable inorganic resists, an alternative to organic resists. In either case, significant processing improvements can be utilized, and the structure of the patterned material can also be improved.

[0015] Specifically, the precursor solution can contain sufficient radiation-sensitive organic ligands so that the solution has a molar concentration ratio of radiation-sensitive ligand to metal cation of about 0.1 to about 3. The coating formed from the precursor solution is influenced by the ligand structure of the ions in the precursor solution, and upon drying, the ligand structure around the metal may remain the same, or the ligand structure may change during the coating and / or drying process. In particular, the organic ligand concentration provides a surprisingly large improvement in precursor stability and control of network formation with solutions formed in organic solvents (generally polar organic solvents). While not wishing to be limited by theory, increasing the radiation-sensitive ligand concentration apparently reduces agglomeration of metal cations with the corresponding oxo-ligands and / or hydroxo-ligands, stabilizing the solution. Thus, the precursor solution can be stable against solid settling for at least one week, and possibly significantly longer (e.g., more than one month), without further agitation. Due to the long stability time, the improved precursor offers increased versatility for potential commercial applications. The overall molar concentration can be selected to achieve the desired coating thickness and desired coating properties consistent with the desired stability level. Ligands having metal-carbon or metal-carboxylate bonds provide desirable radiation-sensitive ligands, and specific ligands include, for example, alkyl groups (e.g., methyl, ethyl, propyl, butyl, t-butyl), aryl groups (e.g., phenyl, benzyl), alkenyl groups (e.g., vinyl, allyl), carboxylate (e.g., acetate, propanoate, butanoate, benzoate) groups, or combinations thereof.

[0016] Polyatomic metal oxo / hydroxo cations with organic ligands can be selected to achieve the desired radiation absorption. In particular, indium- and tin-based coating materials exhibit good absorption in the far UV at 193 nm and the extreme UV at 13.5 nm. Table 1 lists the optical constants (n = refractive index and k = extinction coefficient) at selected wavelengths for coating materials formed from monobutyltin oxide hydrate and baked at 100°C.

[0017] [Table 1]

[0018] Some precursor solutions effectively incorporate a blend of additional metals to provide the desired overall properties of the coating material. The precursor solution can contain additional metal cations to increase absorption of some radiation wavelengths important for lithography. The metal ion concentration can be selected to provide the precursor solution with the desired properties, with thinner solutions generally being consistent with the formation of thinner coating materials, although coating properties also depend on the deposition technique.

[0019] The ligand structure of the precursor composition is believed to provide desirable precursor solution stability and radiation patterning functionality. In particular, it is believed that absorption of radiation can provide bond breaking between the metal and organic ligands, resulting in compositional differentiation in irradiated and non-irradiated portions of the coating material. Therefore, modifying the composition to form an improved precursor solution also provides improved image development. In particular, radiation coating materials can yield stable inorganic metal oxide materials with tunable developer response, for example, by selecting an appropriate developer capable of developing either positive or negative images. In some embodiments, suitable developers include, for example, 2.38% TMAH (i.e., semiconductor industry standard). Coating layers can be thinned without pattern loss during development due to removal of coating material from areas where it is intended to remain after development. Compared to conventional organic resists, the materials described herein have extremely high resistance to many commercially relevant etch chemistries for functional layers. This allows for process simplification by avoiding intermediate sacrificial inorganic pattern transfer layers that might otherwise be used to supplement patterned organic resists for masking functions. The coating material can also provide convenient double patterning. Specifically, after thermal treatment, the patterned portions of the coating material are stable with respect to contact with multiple compositions, including additional precursor solutions. Thus, multiple patterning can be performed without removing previously deposited hard mask or resist coating materials.

[0020] After using the patterned material as a mask to pattern a desired functional material, the patterned coating material can be subsequently removed. Alternatively, the resulting patterned material can be incorporated into a structure as a component of a final device after appropriate stabilization by at least some condensation into an inorganic metal oxide material. When the patterned inorganic coating material is incorporated into a structure, for example as a stable dielectric layer, many steps in the processing procedure can be eliminated by using direct patterning of the material with radiation. Alternatively, it has been found that very high-resolution structures can be formed using thin inorganic coating materials exposed with short-wavelength electromagnetic radiation and / or electron beams, and linewidth roughness can be reduced to very low levels to form improved patterned structures.

[0021] The precursor solution contains a polynuclear metal oxo / hydroxo cation and an organic ligand. Polynuclear metal oxo / hydroxo cations, also known as metal suboxide cations, are polyatomic cations having a metal element and a covalently bonded oxygen atom. Metal suboxide cations with peroxide-based ligands are described in U.S. Pat. No. 8,415,000 (Stowers et al.) ('000 patent), entitled "Patterned Inorganic Layers, Radiation-Based Patterning Compositions and Corresponding Methods," which is incorporated herein by reference. Aqueous solutions of metal suboxides or hydroxides can be prone to instability with respect to gelation and / or precipitation. In particular, the solution is unstable when the solvent is removed, and oxo-hydroxide networks can form with the metal cations. Incorporation of radiation-sensitive ligands, such as peroxides, into such solutions can improve stability, but background instability associated with network formation can persist. This uncontrolled network formation effectively reduces the radiation sensitivity and / or development rate contrast of the coating material by providing a development rate determining pathway independent of irradiation.

[0022] The new precursor solutions have been formulated with improved stability and control of network formation and precipitation compared to inorganic resist materials with peroxide-based ligands. In this case, the characterization of the ligand as radiation-sensitive refers to the instability of the metal-ligand bond after absorption of radiation, allowing radiation to be used to induce chemical changes in the material. In particular, the organic ligand stabilizes the precursor solution but also provides control over the processing of the material, and the selection of the ratio of organic ligand to metal ion can be adjusted to control the properties of the solution and the resulting coating. In particular, a molar ratio of organic ligand to metal cation between about 0.1 and about 3 generally results in a more stable solution. Because radiation can be used to rupture the organic ligand-metal bond, improving the development rate contrast in the latent image-bearing coating material, the more stable precursor solution offers the added benefit of greater contrast between the final irradiated and unirradiated coating material.

[0023] Purified precursor solutions with greater stability also provide coating materials with the potential for greater development rate contrast between radiation-exposed and non-exposed portions of a substrate, which, surprisingly, can be achieved simultaneously using either positive or negative patterning. Specifically, the irradiated or non-irradiated coating material can be dissolved relatively more easily by an appropriate developer composition. Therefore, using the improved compositions and corresponding materials, positive or negative image formation can be achieved by selecting an appropriate developer. At the same time, very small pitches can be achieved between adjacent elements, along with adequate insulation, typically electrical insulation, between adjacent elements. The irradiated coating composition can be very sensitive to the subsequent development / etching process, so that the coating composition can be very thinned without compromising the effectiveness of the development process for selectively and cleanly removing the coating composition while leaving appropriate portions of the irradiated patterning composition on the surface of the substrate. The ability to shorten exposure times to the developer is further consistent with the use of thin coatings without damaging the patterned portions of the coating.

[0024] The precursor solution can generally be applied by any reasonable coating or printing technique, as further described below. The coating is generally dried, and heat can be applied to stabilize the coating before irradiation. Generally, the coating is thin, e.g., having an average thickness of less than 10 microns; very thin, submicron coatings may be desired for patterning very small features. The dried coating can be exposed to appropriate radiation, e.g., extreme ultraviolet, electron beam, or ultraviolet light, to form a latent image within the coating. The latent image is contacted with a developer to form a physical image, i.e., a patterned coating. The patterned coating can be further heated to stabilize the remaining coating patterned on the surface. The patterned coating can be used as a physical mask to perform further processing, e.g., etching of the substrate and / or deposition of additional materials, according to the pattern. At the appropriate point in processing, the remaining patterned coating can be removed, but the patterned coating can also be incorporated into the final structure. Very fine features can be effectively achieved with the patterning compositions described herein.

[0025] Precursor solution Precursor solutions for forming resist coatings typically contain metal cations with suitable organic stabilizing ligands in an organic solvent (typically an organic solvent). The precursor solution and final resist coating are based on metal oxide chemistry, and organic solutions of metal polycations with organic ligands provide stable solutions with good resist properties. The ligands provide radiation sensitivity, and the specific selection of ligands can affect radiation sensitivity. In particular, precursor solutions can be designed to achieve a desired level of radiation absorption for a selected radiation based on the selection of metal cations and associated ligands. The concentration of ligand-stabilizing metal cations in the solution can be selected to provide appropriate solution properties for a particular deposition method (e.g., spin coating, etc.). Metals that are particularly effective in terms of stability and processing effectiveness are those in groups 13, 14, and 15. Correspondingly, it is desirable to include Sn, In, and Sb metals in the precursor solution to provide high absorption of radiation commonly used for patterning, but these metals can also be combined with other metals to tailor properties, particularly radiation absorption. The precursor solution is formulated to achieve a very high level of stability, so that it has an adequate shelf life for commercial use. As described in the following sections, the precursor solution can be applied to a substrate surface, dried, and further processed to form an effective radiation resist. The precursor solution is designed to form a coating composition upon at least partial solvent removal, and ultimately, the inorganic solids become predominantly metal oxides upon irradiation and / or thermal treatment, exposure to plasma, or similar treatment.

[0026] Precursor solutions typically contain one or more metal cations. In aqueous solutions, the metal cations are hydrated due to interactions with water molecules, and hydrolysis occurs, attaching oxygen atoms to the metal ions to form hydroxide ligands or oxo bonds, with the corresponding release of hydrogen ions. The nature of the interaction is generally pH-dependent. As additional hydrolysis occurs in aqueous solutions, the solution may become unstable with respect to precipitation of the metal oxide or gelation. While the eventual formation of an oxide material is desired, this progression can be better controlled using precursor solutions based on organic solvents with organic ligand-stabilized metal cations. With precursor solutions based on organic stabilizing ligands and organic solvents, the progression to the oxide can be controlled as part of the procedure for first processing the solution into a coating material and then into the final metal oxide composition with organic ligands. As described herein, organic ligands can be used to provide significant control over the processing of the solution into an effective radiation resist composition.

[0027] In this manner, the solution of metal cations is ready for further processing. In particular, it may be desirable to use polynuclear metal oxo / hydroxo cations as additional components of the precursor solution, which can further prepare the solution for metal oxide compositions. Generally, the precursor solution contains about 0.01 M to about 1.4 M, in further embodiments about 0.05 M to about 1.2 M, and in additional embodiments about 0.1 M to about 1.0 M metal polynuclear oxo / hydroxo cations. One of ordinary skill in the art will recognize that additional ranges of metal polynuclear oxo / hydroxo cations within the explicit ranges above are contemplated and are within the scope of the present disclosure.

[0028] Tin, antimony, and / or indium are particularly suitable metals for forming the polynuclear metal oxo / hydroxocations of the precursor solutions described herein. Tin, in particular, has desirable chemical properties based on organic ligands. Additional metals, including, for example, Ti, Zr, Hf, V, Co, Mo, W, Al, Ga, Si, Ge, P, As, Y, La, Ce, Lu, or combinations thereof, can be provided to generate more complex polynuclear metal oxo / hydroxocation formulations. The additional metals can be provided as a replacement for, or in addition to, tin ions, antimony ions, and / or indium ions (tin / antimony / indium ions). When a blend of metal ions is used, in some embodiments, the molar ratio of tin / antimony / indium to the additional metal ions is up to about 1 non-tin / antimony / indium metal ion per tin / antimony / indium ion, and in further embodiments, from about 0.1 to about 0.75 non-tin / indium metal ions per tin / antimony / indium metal ion. When a blend of metal ions is used, the metal ions can be in complex multi-metal oxo-hydroxo clusters or in separate metal oxo-hydroxo clusters in solution. The exact cluster morphology in solution may or may not be known, and the resulting coating can generally provide the desired functionality regardless of whether the cluster structure in solution is known. As noted above, because the state of cations in solution is pH-dependent, the initial state of oxygen coordination can vary in solution, but the tendency is toward hydrolysis and condensation, leading to oxide formation. It has been found that organic ligands can interfere with the formation of the metal-oxygen network, which leads to gelation and ultimately precipitation. Thus, organic ligands can be used to form stable states ready to be converted to oxides by selective radiation exposure. The use of organic ligands also expands the choice of precursor solvents and developers to include both aqueous and organic solvents.

[0029] Metals generally have a significant effect on radiation absorption. Therefore, metal cations can be selected based on the desired radiation and absorption cross-section. Indium and tin provide strong absorption of extreme ultraviolet radiation at 13.5 nm. In combination with organic ligands, they also provide good absorption of ultraviolet radiation at 193 nm wavelength. Hf also provides good absorption of electron beam materials and extreme ultraviolet radiation. Further tuning of the composition for radiation absorption can be achieved by adding other metal ions. For example, one or more metal compositions containing Ti, V, Mo, or W, or combinations thereof, can be added to the precursor solution to form coating materials with absorption edges shifted to longer wavelengths, providing sensitivity to ultraviolet radiation at, for example, 248 nm wavelength. The absorbed energy is regulated by metal-organic interactions, which can result in metal-ligand scission and desired control over material properties.

[0030] Organic-based ligands stabilize compositions against condensation. In particular, when the relative concentration of organic-based ligands is high, the formation of condensed metal oxides or hydroxides is very slow, even if condensation occurs spontaneously at room temperature. Based on the discovery of this stabilizing property, solutions can be formed using high concentrations of radiation-sensitive ligands with good storage stability while maintaining convenient processing for forming coatings. Radiation-sensitive ligands include carboxylates and organic moieties that form metal-carbon bonds, such as tin-carbon bonds. Energy from absorbed radiation can break metal-organic ligand bonds. When these bonds are broken, the corresponding stabilization against condensation is reduced or lost. The composition can be transformed by forming M--OH or by condensing to form M--O--M bonds, where M represents the metal atom. Thus, chemical changes can be controlled by radiation. Compositions with high radiation-sensitive ligand concentrations can be highly stable with respect to avoiding the spontaneous formation of hydroxides and condensates. Some suitable metal compositions with desired ligand structures can be purchased from commercial sources such as Alfa Aesar (MA, USA) and TCI America (OR, USA) (see Examples below), while other metal-ligand compositions can be synthesized as described below.

[0031] The organic ligand can be, for example, alkyl (e.g., methyl, ethyl, propyl, butyl, t-butyl, aryl (phenyl, benzyl)), alkenyl (e.g., vinyl, allyl), and carboxylate (acetate, propanoate, butanoate, benzoate). The precursor composition generally comprises a ligand concentration from about 0.25 times to about 4 times the metal cation concentration, in further embodiments from about 0.5 times to about 3.5 times, in additional embodiments from about 0.75 times to about 3 times, and in other embodiments from about 1 time to about 2.75 times the metal cation concentration. A person of ordinary skill in the art will recognize that additional ranges of ligand concentration within the explicit ranges above are contemplated and are within the present disclosure.

[0032] With regard to oxo / hydroxo ligands for metal ions, these ligands can be formed during processing by hydrolysis. In some embodiments, hydrolysis can involve displacement of halide ligands in a basic aqueous solution, followed by transfer to an organic solvent. Specific examples are provided below. Essentially, a composition containing an organic stabilizing ligand and a metal ion bearing a halide ligand is dissolved in an organic solvent, which is then contacted with a basic aqueous solution, where displacement of the halide ligand with a hydroxo ligand can occur. After allowing sufficient time for the hydroxo ligand to form, the aqueous solution can be separated from the organic phase, assuming the organic liquid is not soluble in the aqueous liquid. In some embodiments, the oxo / hydroxo ligands can be formed by hydrolysis from atmospheric water. Hydrolyzable metal ion compositions can be heated in the presence of atmospheric moisture so that the oxo / hydroxo ligands form directly within the coating material, which can be relatively easy due to the high surface area. An example of hydrolysis from atmospheric water is also described below.

[0033] Regarding the formation of organic stabilizing ligands, these can also be formed in solution to form the desired composition. For carboxylate ligands, the corresponding carboxylic acid or its salt can be dissolved in a solution containing a metal cation. If desired, the pH of the solution can be adjusted to facilitate binding of the carboxylate group to the metal, and heat can be applied to further drive the process. Generally, the reaction is carried out in an aqueous solvent and then transferred to an organic solvent, or can be carried out directly in an organic solvent. MC bonds can also be formed in a solution-phase displacement reaction. The following reaction is a representative example of a suitable displacement reaction to form Sn-C bonds; similar reactions occur for other metal ions. nRCl+Sn→R n SnCl 4-n +Residue 4RMgBr+SnCl4→R4Sn+4MgBrCl 3SnCl4+4R3Al → 3R4Sn+4AlCl3 R4Sn+SnCl4→2R2SnCl2 In the formula, R represents an organic ligand. Generally, different suitable halides can be substituted in the above reaction. The reaction can be carried out in a suitable organic solvent in which the reactants have reasonable solubility.

[0034] Generally, the desired compound can be dissolved in an organic solvent, such as an alcohol, an ester, or a combination thereof. In particular, suitable solvents include, for example, aromatic compounds (e.g., xylene, toluene), esters (propylene glycol monomethyl ether acetate, ethyl acetate, ethyl lactate), alcohols (e.g., 4-methyl-2-propanol, 1-butanol, anisole), ketones (e.g., methyl ethyl ketone), and the like. Generally, the choice of organic solvent can be influenced by solubility parameters, volatility, flammability, toxicity, viscosity, and potential chemical interactions with other processing materials. After dissolving and combining the components of the solution, the properties of the species can change as a result of partial hydration and condensation, especially during the coating process. When the composition of a solution is referred to herein, the reference is to the components added to the solution, as complex formulations can result in polynuclear metal species in the solution that cannot be fully characterized. For certain applications, it is desirable for the organic solvent to have a flash point of about 10° C. or greater, in further embodiments about 20° C. or greater, and in further embodiments about 25° C. or greater, and a vapor pressure of about 10 kPa or less, in some embodiments about 8 kPa or less, and in further embodiments about 6 kPa or less at 20° C. A person of ordinary skill in the art will recognize that additional ranges of flash point and vapor pressure within the explicit ranges above are contemplated and are within the present disclosure.

[0035] Generally, the precursor solution is thoroughly mixed using appropriate mixing equipment appropriate for the volume of material to be formed. Appropriate filtration can be used to remove any contaminants or other components that do not dissolve properly. In some embodiments, it may be desirable to form separate solutions that can be combined to form the combined precursor solution. Specifically, separate solutions can be formed containing one or more of the following: metal polynuclear oxo / hydroxo cations, optional additional metal cations, and organic ligands. When multiple metal cations are introduced, the multiple metal cations can be introduced in the same solution and / or separate solutions. Generally, the separate or combined solutions can be thoroughly mixed. In some embodiments, the metal cation solution is then mixed with an organic-based ligand solution so that the organic-based ligands can bond with the metal cations. The resulting solution can be referred to as a stabilized metal cation solution. In some embodiments, the stabilized metal cation solution is allowed to react for an appropriate time to provide stable ligand formation, which may or may not involve cluster formation within the solution, regardless of whether mixed metal ions are introduced. In some embodiments, the reaction or stabilization time of the solution may be at least about 5 minutes, in other embodiments at least about 1 hour, and in further embodiments from about 2 hours to about 48 hours prior to further processing. A person of ordinary skill in the art will recognize that additional ranges of stabilization periods are contemplated and are within the scope of the present disclosure.

[0036] The concentration of the species in the precursor solution can be selected to achieve the desired physical properties of the solution. In particular, a lower concentration can result in desirable solution properties for certain coating procedures, such as spin coating, which can achieve thinner coatings overall with reasonable coating parameters. It may be desirable to use thinner coatings to achieve ultrafine patterning and reduce material costs. In general, the concentration can be selected to be appropriate for the selected coating procedure. Coating properties are further described below.

[0037] As noted above, a relatively large ratio of organic-based ligands to metal cations can be used to make the precursor solution highly stable. The stability of a precursor solution can be evaluated in terms of changes relative to the initial solution. Specifically, a solution is unstable if phase separation occurs with the formation of large sol particles or if the solution loses its ability to perform the desired pattern formation. Based on the improved stabilization measures described herein, the solution can be stable without further mixing for at least about one week, in further embodiments at least about two weeks, and in other embodiments at least about four weeks. Those skilled in the art will recognize that additional ranges of stabilization times are contemplated and fall within the scope of the present disclosure. Solutions with sufficient stabilization times can be formulated and commercially distributed with appropriate shelf lives.

[0038] Coating materials Coating materials are formed by depositing a precursor solution on a selected substrate and subsequent processing. A substrate generally refers to a surface onto which a coating material can be applied, and the substrate may include multiple layers, with the surface being related to the top layer. In some embodiments, the substrate surface can be treated to prepare the surface for adhesion of the coating material. The surface can also be cleaned and / or smoothed as needed. Suitable substrate surfaces can comprise any reasonable material. Some substrates of particular interest include, for example, silicon wafers, silica substrates, other inorganic materials, polymeric substrates (e.g., organic polymers), composites thereof, and combinations thereof across the surface and / or within the layers of the substrate. While wafers, such as relatively thin cylindrical structures, can be convenient, any reasonably shaped structure can be used. Polymeric substrates or substrates having a polymer layer on a non-polymeric structure can be desirable for certain applications based on their low cost and flexibility, and suitable polymers can be selected based on the relatively low processing temperatures that can be used for processing the patternable materials described herein. Suitable polymers can include, for example, polycarbonates, polyimides, polyesters, polyalkenes, copolymers thereof, and mixtures thereof. In general, it is desirable for the substrate to have a flat surface, especially for high resolution applications.

[0039] Generally, any suitable coating process can be used to deliver the precursor solution to the substrate. Suitable coating means can include, for example, spin coating, spray coating, dip coating, knife-edge coating, printing means (e.g., inkjet printing and screen printing), and the like. While some of these coating means form a pattern of the coating material during the coating process, the resolution currently available from printing and the like has a significantly lower level of resolution than that available from the radiation-based patterning described herein. To provide greater control over the coating process, the coating material can be applied in multiple coating steps. For example, multiple spin coatings can be performed to achieve the desired final coating thickness. The heat treatment described below can be applied after each coating step or after multiple coating steps.

[0040] When patterning is performed using radiation, spin coating can be a desirable means for achieving a relatively uniform coating of the substrate, although edge effects may exist. In some embodiments, the wafer can be spun at a speed of about 500 rpm to about 10,000 rpm, in further embodiments about 1000 rpm to about 7500 rpm, and in additional embodiments about 2000 rpm to about 6000 rpm. The rotation speed can be adjusted to achieve the desired coating thickness. Spin coating can be performed for a time period of about 5 seconds to about 5 minutes, and in further embodiments about 15 seconds to about 2 minutes. An initial slow rotation speed (e.g., 50 rpm to 250 rpm) can be used to apply an initial bulk application of the composition across the entire substrate. To remove any edge bead, a backside rinse, edge bead removal step, or the like, using water or other suitable solvent can be performed. A person of ordinary skill in the art will recognize that additional ranges of spin coating parameters within the explicit ranges above are contemplated and are within the scope of the present disclosure.

[0041] The thickness of the coating can generally be a function of the concentration and viscosity of the precursor solution and the spin-coating rotation speed. For other coating processes, the thickness can also generally be adjusted by selection of coating parameters. In some embodiments, it may be desirable to use a thin coating to facilitate the formation of small and highly modified features in a subsequent patterning process. For example, the coating material after drying can have an average thickness of about 10 microns or less, in other embodiments about 1 micron or less, in further embodiments about 250 nanometers (nm) or less, in additional embodiments about 1 nanometer (nm) to about 50 nm, in other embodiments about 2 nm to about 40 nm, and in some embodiments about 3 nm to about 25 nm. One of ordinary skill in the art will recognize that additional ranges of thickness within the explicit ranges above are contemplated and are within the scope of the present disclosure. Thickness can be evaluated using non-contact methods of x-ray reflectivity and / or ellipsometry based on the optical properties of the film. Generally, the coating is relatively uniform to facilitate processing. In some embodiments, the coating thickness varies by no more than ±50% from the average coating thickness, in further embodiments by no more than ±40%, and in additional embodiments by no more than about 25% relative to the average coating thickness. In some embodiments, such as highly uniform coatings on larger substrates, evaluation of coating uniformity may be evaluated using a one centimeter edge exclusion. That is, coating uniformity is not evaluated within one centimeter of the coating edge. A person of ordinary skill in the art will recognize that additional ranges within the explicit ranges above are contemplated and are within the present disclosure.

[0042] Because many coating processes form coating materials in droplets or other forms with larger surface areas and / or solvent migration to stimulate evaporation, the coating process itself may result in the evaporation of some of the solvent. Solvent loss tends to increase the viscosity of the coating material as the concentration of species in the material increases. The goal during the coating process may be to remove enough solvent to stabilize the coating material for further processing. The coating material may generally be heated prior to radiation exposure to further drive off the solvent and promote densification of the coating material. The dried coating material may generally form a polymeric metal-oxo / hydroxo network based on oxo-hydroxo ligands to the metal, where the metal also has some organic ligands, or a molecular solid composed of polynuclear metal-oxo / hydroxo species with organic ligands.

[0043] The solvent removal process may or may not be quantitatively controlled with respect to the specific amount of solvent remaining in the coating material, and empirical evaluation of the resulting coating material properties can generally be performed to select processing conditions that are effective for the patterning process. While heating is not required for successful process application, it may be desirable to heat the coated substrate to accelerate processing and / or increase process reproducibility. In embodiments where heating is applied to remove solvent, the coating material may be heated to a temperature of from about 45°C to about 250°C, and in further embodiments, from about 55°C to about 225°C. Heating for solvent removal may generally be carried out for at least about 0.1 minutes, in further embodiments, from about 0.5 minutes to about 30 minutes, and in additional embodiments, from about 0.75 minutes to about 10 minutes. Those skilled in the art will recognize that additional ranges of heating temperature and time within the explicit ranges above are contemplated and are within the scope of the present disclosure. As a result of heat treatment and densification of the coating material, the coating material can exhibit an increase in refractive index and radiation absorption without a significant loss of contrast.

[0044] Patterned Exposure and Patterned Coating Materials Coating materials can be micropatterned using radiation. As described above, the composition of the precursor solution, and therefore the corresponding coating material, can be designed to sufficiently absorb the desired form of radiation. Absorption of radiation generates energy capable of breaking bonds between the metal and organic ligands, such that at least a portion of the organic-based ligands are no longer available to stabilize the material. Upon absorption of a sufficient amount of radiation, the exposed coating material condenses, i.e., forms an enhanced metal oxo / hydroxo network, which may include water absorbed from the surrounding atmosphere. The radiation can generally be delivered according to a selected pattern. The radiation pattern is transferred to a corresponding pattern or latent image in the coating material, having irradiated and non-irradiated regions. The irradiated regions comprise chemically altered coating material, while the non-irradiated regions generally comprise as-formed coating material. As described below, very sharp edges can be formed upon development of the coating material by removal of the non-irradiated coating material or selective removal of the irradiated coating material.

[0045] The radiation may generally be directed to the coated substrate through a mask, or the radiation beam may be controllably scanned across the substrate. Generally, the radiation may include electromagnetic radiation, an electron beam (beta radiation), or other suitable radiation. Generally, the electromagnetic radiation may have a desired wavelength or range of wavelengths, such as visible light, ultraviolet light, or x-rays. The achievable resolution of a radiation pattern generally depends on the wavelength of the radiation, with higher resolution patterns generally being achievable with shorter wavelength radiation. Therefore, it may be desirable to use ultraviolet light, x-rays, or an electron beam to achieve particularly high resolution patterns.

[0046] According to International Standard ISO 21348 (2007), incorporated herein by reference, ultraviolet radiation spans the wavelength range from 100 nm to less than 400 nm. A krypton fluoride laser can be used as a 248 nm ultraviolet source. The ultraviolet range can be subdivided in several ways under accepted standards, such as extreme ultraviolet (EUV), which is from 10 nm to less than 121 nm, and far ultraviolet (FUV), which is from 122 nm to less than 200 nm. The 193 nm line from an argon fluoride laser can be used as a radiation source in the FUV range. EUV light is used for lithography at 13.5 nm, and this light is generated from Xe or Sn plasma sources excited using high-energy lasers or discharge pulses. Soft x-rays can be defined as from 0.1 nm to less than 10 nm.

[0047] The amount of electromagnetic radiation can be characterized by the fluence or dose, which is the integrated radiant flux over the exposure time. A suitable radiation fluence is approximately 1 mJ / cm. 2 ~Approx. 150mJ / cm 2 and in a further embodiment about 2 mJ / cm 2 ~Approx. 100mJ / cm 2 , and in a further embodiment about 3 mJ / cm 2 ~about 50mJ / cm 2 A person of ordinary skill in the art will recognize that additional ranges of radiation fluence within the explicit ranges above are contemplated and are within the present disclosure.

[0048] In electron beam lithography, the electron beam typically induces secondary electrons, which typically alter the irradiated material. Resolution can be, at least in part, a function of the range of the secondary electrons within the material, where it is believed that higher resolution generally results from shorter-range secondary electrons. Based on the high resolution achievable by electron lithography using the inorganic coating materials described herein, the range of secondary electrons in inorganic materials is limited. Electron beams can be characterized by the energy of the beam, with suitable energies ranging from about 5 V to about 200 kV (kilovolts), and in further embodiments, from about 7.5 V to about 100 kV. At 30 kV, the proximity-corrected beam dose ranges from about 0.1 microcoulombs per square centimeter to about 5 millicoulombs per square centimeter (mC / cm). 2 ), and in a further embodiment, about 0.5 μC / cm 2 ~about 1mC / cm 2 , and in other embodiments, about 1 μC / cm 2 ~about 100μC / cm 2 A person of ordinary skill in the art will be able to calculate corresponding doses at other beam energies based on the teachings herein and will recognize that additional ranges of electron beam characteristics within the explicit ranges above are contemplated and are within the scope of the present disclosure.

[0049] Based on the design of the coating material, a large contrast in material properties exists between the irradiated regions with condensed coating material and the non-irradiated coating material with the organic ligands substantially unchanged. While this contrast can be improved by a post-irradiation heat treatment, it has been found that in some embodiments, satisfactory results can be obtained without a post-irradiation heat treatment. The post-irradiation heat treatment appears to anneal the irradiated coating material, increasing its condensation without significantly condensing the non-irradiated regions of the coating material due to thermal disruption of the organic ligand-metal bond. For embodiments in which a post-irradiation heat treatment is used, the post-irradiation heat treatment may be carried out at a temperature of from about 45°C to about 250°C, from about 50°C to about 190°C in additional embodiments, and from about 60°C to about 175°C in further embodiments. The post-exposure heat treatment may generally be carried out for at least about 0.1 minutes, from about 0.5 minutes to about 30 minutes in further embodiments, and from about 0.75 minutes to about 10 minutes in additional embodiments. A person of ordinary skill in the art will recognize that additional ranges of post-irradiation heat temperatures and times within the explicit ranges above are contemplated and are within the scope of the present disclosure. This high contrast in material properties further facilitates the formation of sharp lines in the developed patterns described in the following section.

[0050] After exposure to radiation, the coating material becomes patterned with irradiated and non-irradiated regions. Referring to Figures 1 and 2, a patterned structure 100 is shown that includes a substrate 102, a thin film 103, and a patterned coating material 104. The patterned coating material 104 includes regions 110, 112, 114, 116 of irradiated coating material and non-condensed regions 118, 120, 122 of non-irradiated coating material. The patterned structure formed by the condensed regions 110, 112, 114, 116 and non-condensed regions 118, 120, 122 represents a latent image in the coating material, the development of which is described in the following section.

[0051] Developing and patterning structures Developing the image involves contacting the patterned coating material containing the latent image with a developer composition to either remove the non-irradiated coating material to form a negative image or remove the irradiated coating to form a positive image. Using the resist materials described herein, effective negative or positive patterning with desired resolution can be achieved using an appropriate developer solution, generally based on the same coating. In particular, the irradiated areas are at least partially condensed to enhance their metal oxide properties, such that the irradiated material is resistant to dissolution by organic solvents, while the non-irradiated composition remains soluble in organic solvents. References to condensed coating material refer to at least partial condensation in the sense that the oxide properties of the material are enhanced relative to the initial material. Meanwhile, the non-irradiated material is insoluble in weak base or aqueous acid solutions due to its hydrophobic nature; therefore, for positive patterning, an aqueous base solution can be used to remove the irradiated material while retaining the non-irradiated material.

[0052] Coating compositions with organic stabilizing ligands produce materials that are inherently relatively hydrophobic. Irradiation to break at least some of the organometallic bonds converts the material to a less hydrophobic, i.e., more hydrophilic, material. This change in properties provides a significant contrast between irradiated and non-irradiated coatings, allowing both positive-tone and negative-tone patterning to be achieved using the same resist composition. Specifically, while irradiated coating materials condense to some extent to metal oxide-rich compositions, the degree of condensation is generally moderate without significant heating, making the irradiated materials relatively straightforward to development with conventional developers. In contrast, inorganic resist materials based on metal oxo-hydroxo chemistry with peroxide-stabilizing ligands are inherently more hydrophilic prior to irradiation, as described in the '000 patent, and irradiated peroxide-based coatings can condense to a greater extent upon irradiation, resulting in non-irradiated resists that can be removed with mild acids or bases, while irradiated peroxide-based coatings can be developed similarly to metal oxide materials.

[0053] For negative-tone imaging, with reference to FIGS. 3 and 4, the latent image of the structure shown in FIGS. 1 and 2 is developed by contact with a developer to form patterned structure 130. After image development, substrate 102 is exposed along its upper surface through openings 132 and 134. Openings 132, 134, and 135 are located at the locations of non-condensed regions 118, 120, and 122, respectively. For positive-tone imaging, with reference to FIGS. 5 and 6, the latent image of the structure shown in FIGS. 1 and 2 is developed to form patterned structure 140. Patterned structure 140 has a conjugate image of patterned structure 130 of FIG. 3. Patterned structure 140 has substrate 102 exposed in the locations of irradiated regions 110, 112, 114, and 116 of FIGS. 1-4 (which are developed to form openings 142, 144, 146, and 148). The non-condensing regions 118, 120, and 122 are retained.

[0054] For negative-tone imaging, the developer can be an organic solvent, such as the solvent used to form the precursor solution. Generally, the choice of developer can be influenced by the solubility parameters of the coating material (both irradiated and non-irradiated), as well as the developer's volatility, flammability, toxicity, viscosity, and potential chemical interactions with other process materials. In particular, suitable developers include, for example, aromatic compounds (e.g., benzene, xylene, toluene), esters (e.g., propylene glycol monomethyl ester acetate, ethyl acetate, ethyl lactate, n-butyl acetate, butyrolactone), alcohols (e.g., 4-methyl-2-propanol, 1-butanol, isopropanol, anisole), ketones (e.g., methyl ethyl ketone, acetone, cyclohexanone), ethers (e.g., tetrahydrofuran, dioxane), and the like. Development can be carried out for about 5 seconds to about 30 minutes, in further embodiments from about 8 seconds to about 15 minutes, and in additional embodiments from about 10 seconds to about 10 minutes. A person of ordinary skill in the art will recognize that additional ranges within the explicit ranges above are contemplated and are within the present disclosure.

[0055] For positive-tone imaging, the developer can generally be an aqueous acid or base solution. In some embodiments, an aqueous base can be used to obtain sharper images. To reduce contamination from the developer, it may be desirable to use a developer that does not contain metal atoms. Therefore, quaternary ammonium hydroxide compositions, such as tetraethylammonium hydroxide, tetrapropylammonium hydroxide, tetrabutylammonium hydroxide, or combinations thereof, are desirable developers. Quaternary ammonium hydroxides of particular interest generally can be represented by the formula R4NOH (where R = methyl, ethyl, propyl, butyl, or combinations thereof). The coating materials described herein can generally be developed with the same developers currently commonly used for polymer resists, specifically tetramethylammonium hydroxide (TMAH). Commercially available TMAH is available at 2.38 weight percent, and this concentration can be used for the processes described herein. Additionally, mixed quaternary tetraalkylammonium hydroxides can be used. Generally, the developer may contain from about 0.5 to about 30 weight percent, and in further embodiments from about 1 to about 25 weight percent, and in other embodiments from about 1.25 to about 20 weight percent of the tetraalkylammonium hydroxide or similar quaternary ammonium hydroxide. A person of ordinary skill in the art will recognize that additional ranges of developer concentrations within the explicit ranges above are contemplated and are within the present disclosure.

[0056] In addition to the main developer composition, the developer can contain additional components to facilitate the development process. Suitable additives include, for example, dissolved salts having a cation selected from the group consisting of ammonium, d-block metal cations (e.g., hafnium, zirconium, lanthanum), f-block metal cations (e.g., cerium, lutetium), p-block metal cations (e.g., aluminum, tin), alkali metals (e.g., lithium, sodium, potassium), and combinations thereof, and an anion selected from the group consisting of fluorine, chlorine, bromine, iodine, nitrate, sulfate, phosphate, silicate, borate, peroxide, butoxide, formate, ethylenediamine-tetraacetic acid (EDTA), tungstate, molybdate, and the like, and combinations thereof. Other potentially useful additives include, for example, molecular chelating agents, such as polyamines, alcoholamines, amino acids, or combinations thereof. When optional additives are present, the developer can contain up to about 10 weight percent of the additives, and in further embodiments, up to about 5 weight percent of the additives. A person of ordinary skill in the art will recognize that additional ranges of additive concentrations within the explicit ranges above are contemplated and are within the present disclosure. Additives can be selected to improve contrast, sensitivity, and linewidth roughness. Additives in the developer can also suppress metal oxide particle formation and precipitation.

[0057] For weaker developers, such as less concentrated aqueous developers, diluted organic developers, or compositions (where the coating has a lower development rate), a higher temperature development process can be used to increase the process speed. For stronger developers, the temperature of the development process can be lowered to slow down the rate of development and / or control the development kinetics. In general, the development temperature can be adjusted between appropriate values ​​consistent with the volatility of the solvent. Furthermore, the developer containing dissolved coating material near the developer-coating interface can be dispersed by ultrasonic treatment during development.

[0058] The developer can be applied to the patterned coating material using any reasonable means. For example, the developer can be sprayed onto the patterned coating material. Spin coating can also be used. For automated processing, a puddle method can be used, which involves statically pouring the developer onto the coating material. If desired, spin rinsing and / or drying can be used to complete the development process. Suitable rinsing solutions include, for example, ultrapure water, methyl alcohol, ethyl alcohol, propyl alcohol, and combinations thereof in the case of negative patterning, and ultrapure water in the case of positive patterning. After the image is developed, the coating material is disposed on the substrate as a pattern.

[0059] Once the development step is complete, the coating material may be heat-treated to further condense and dehydrate the material. While this heat treatment may be particularly desirable for embodiments in which an oxide coating material is incorporated into the final device, it may also be desirable to perform the heat treatment for some embodiments in which the coating material is used as a resist and ultimately removed if stabilization of the coating material is desired to facilitate further patterning. In particular, baking the patterned coating material may be performed under conditions that result in the patterned coating material exhibiting a desired level of etch selectivity. In some embodiments, the patterned coating material may be heated to a temperature of about 100°C to about 600°C, from about 175°C to about 500°C in further embodiments, and from about 200°C to about 400°C in additional embodiments. Heating may be performed for at least about 1 minute, from about 2 minutes to about 1 hour in other embodiments, and from about 2.5 minutes to about 25 minutes in further embodiments. Heating may be performed in air, vacuum, or an inert gas atmosphere, such as Ar or N2. A person of ordinary skill in the art will recognize that additional ranges of temperature and time for heat treatment within the explicit ranges above are contemplated and are within the scope of the present disclosure.

[0060] In conventional organic resists, when the aspect ratio (height divided by width) of a structure becomes very large, the structure becomes susceptible to pattern collapse. Pattern collapse can be related to the mechanical instability of high aspect ratio structures, where forces associated with the processing step, such as surface tension, deform the structural elements. Low aspect ratio structures are more stable with respect to potential deformation forces. Using the patternable coating materials described herein, improved patterning can be achieved without the need for high aspect ratio patterned coating materials, because structures with thinner coating material layers can be effectively processed. Thus, very high-resolution features are formed without relying on high aspect ratio features in the patterned coating material.

[0061] The resulting structures can have sharp edges with very low linewidth roughness. In particular, in addition to reducing linewidth roughness, high contrast also enables the creation of small features and spaces between features, as well as the ability to create very well-resolved two-dimensional patterns (e.g., sharp corners). Thus, in some embodiments, adjacent linear portions of adjacent structures can have an average pitch of about 60 nm or less, in some embodiments about 50 nm or less, and in further embodiments about 40 nm or less. Pitch can be assessed by design and confirmed by scanning electron microscopy (SEM), e.g., top-down imaging. As used herein, pitch refers to the spatial periodicity, i.e., center-to-center distance, of repeating structural elements. Feature dimensions of a pattern can also be expressed in terms of the average width of features, typically assessed away from corners, etc. Features can also refer to gaps between and / or material elements. In some embodiments, the average width can be about 30 nm or less, in further embodiments about 25 nm or less, and in additional embodiments about 20 nm or less. The average linewidth roughness may be about 3.0 nm or less, and in further embodiments, about 1.5 nm to about 2.5 nm. Linewidth roughness assessment is performed by deriving the 3σ deviation from the average linewidth through analysis of top-down SEM images. The average contains both high-frequency and low-frequency roughness, i.e., short and long correlation lengths, respectively. While the linewidth roughness of organic resists is primarily characterized by long correlation lengths, the inorganic coating materials of the present invention exhibit significantly shorter correlation lengths. In the pattern transfer process, the short correlation roughness can be smoothed during the etching process, producing much higher fidelity patterns. A person of ordinary skill in the art will recognize that additional ranges of pitch, average width, and linewidth roughness within the explicit ranges above are contemplated and are within the scope of the present disclosure.

[0062] Further processing of the patterned coating material After forming the patterned coating material, the coating material can be further processed to facilitate the formation of a selected device. Furthermore, deposition, etching, and / or patterning of additional materials can typically be performed to complete the structure. The coating material may or may not be ultimately removed. In either case, the quality of the patterned coating material can be advanced to form improved devices (e.g., devices with smaller footprints, etc.).

[0063] The patterned coating material forms openings to the underlying substrate, as shown, for example, in FIGS. 3 and 4. Similar to conventional resists, the patterned coating material forms an etch mask that can be used to transfer patterns and selectively remove the underlying thin film. Referring to FIG. 7, the lower thin film 103 in FIG. 1 is patterned, leaving features 152, 154, and 156 above the substrate 102 and below the condensation regions 110, 112, and 114, respectively. Compared to conventional polymer resists, the materials described herein can offer significantly greater etch resistance. Similar processing can be performed using the mask patterns shown in FIGS. 5 and 6, with patterned structures resulting directly from alternative mask patterns varying accordingly.

[0064] Alternatively or additionally, deposition of additional material according to a mask pattern can modify the properties of the underlying structure and / or provide contact with the underlying structure. The additional coating material can be selected based on the desired material properties. In addition, the density of the patterned inorganic coating material can provide a high implant resistance, so that ions can be selectively implanted into the underlying structure through the openings in the mask. In some embodiments, the additionally deposited material can be a dielectric, semiconductor, conductor, or other suitable material. The additionally deposited material can be deposited using any suitable means, such as solution-based procedures, chemical vapor deposition (CVD), sputtering, physical vapor deposition (PVD), or other suitable means.

[0065] Generally, multiple additional layers can be deposited. Additional patterning can be performed in conjunction with the deposition of multiple layers. If desired, any additional patterning can be performed using additional amounts of the coating materials described herein, polymer-based resists, other patterning means, or combinations thereof.

[0066] As noted above, the layer of coating (resist) material after patterning may or may not be removed. If the layer is not removed, the patterned coating (resist) material is incorporated into the structure. For embodiments in which the patterned coating (resist) material is incorporated into the structure, the properties of the coating (resist) material can be selected to provide not only the desired patterning properties, but also the properties of the material within the structure.

[0067] If removal of the patterned coating material is desired, the coating material functions as a conventional resist. The patterned coating material is used to pattern subsequently deposited materials and / or to selectively etch the substrate through spaces within the condensed coating material prior to removal of the resist / coating material. The condensed coating material can be removed using an appropriate etching process. Specifically, to remove the condensed coating material, dry etching can be performed using, for example, BCl3 plasma, Cl2 plasma, HBr plasma, Ar plasma, or other suitable process gas plasma. Alternatively or additionally, wet etching can be used to remove the patterned coating material, for example, using an aqueous acid or base solution, HF (water), or buffered HF (water) / NH4F or oxalic acid. Referring to Figure 8, the structure of Figure 8 is shown after removal of the coating material. The etched structure 150 includes the substrate 102 and features 152, 154, and 156.

[0068] Metal oxo / hydroxo-based coating materials are particularly useful for performing multiple patterning using a thermal freeze process, as generally described for conventional resists in P. Zimmerman, J. Photopolym. Sci. Technol., Vol. 22, No. 5, 2009, p. 625. The "thermal freeze" double patterning process is outlined in FIG. 9. In the first step, a coating material is formed into a pattern 160 on a substrate 162 using a lithography process and development, as described with respect to FIGS. 3 and 4. A heating step 164 is performed to remove solvent and condense the coating material, which may or may not result in the formation of a complete oxide. This heating step is equivalent to the post-development heating step described in the development section above. This "thermal freeze" process renders the coating material insoluble for subsequent deposition of a second layer of coating material. A second lithography and development step 166 is performed to form a double-patterned structure 168 on the substrate 162. After the etching step 170, a product double-patterned structure 172 is formed. Note that this process can be readily extended to multiple coating and patterning steps, and such extensions are contemplated and within the scope of the present disclosure. With respect to multiple patterning, a notable difference between the inorganic coating materials described herein and conventional organic resists is that the organic resists remain soluble in conventional resist casting solvents even after thermal baking. The resist materials described herein can be condensed by thermal baking, so that they are not soluble in organic solvents and subsequent coating layers can be applied. [Example]

[0069] Example 1 - Preparation of precursor solution This example described the preparation of a precursor solution for depositing a tin-based organometallic composition to form a radiation resist coating.

[0070] A resist precursor solution was prepared by adding 0.209 g of monobutyltin oxide hydrate (BuSnOOH) powder (TCI America) to 10 mL of 4-methyl-2-pentanol. The solution was placed in a closed vial and allowed to stir for 24 h. The resulting mixture was centrifuged at 4000 rpm for 15 min and filtered through a 0.45 μm PTFE syringe filter to remove insoluble material. Evaporation of the solvent and calcination of this sample at 600 °C revealed a tin concentration of 0.093 M based on the SnO2 residual mass. Dynamic light scattering (DLS) analysis of the precursor solution using a Moebius instrument (Wyatt Technology) (Figures 10A and 10B) was consistent with a unimodal distribution of particles with an average diameter of approximately 2 nm, consistent with the diameter reported for the dodecamer butyltin hydroxide oxide polyatomic cation (Eychenne-Baron et al., Organometallics, 19, 1940-1949 (2000)). The results are therefore consistent with cluster formation in non-aqueous solutions.

[0071] Example 2 - Resist Coating, Film Processing, Negative Imaging This example demonstrates the formation of a resist pattern based on negative imaging, based on electron beam exposure or extreme ultraviolet light exposure.

[0072] Silicon wafers (25 × 25 mm square) with native oxide surfaces were used as substrates for thin film deposition. Prior to deposition, the Si substrates were treated in a UV-ozone cleaning system for a 10-minute cycle. The resist precursor solution from Example 1 was then spin-coated onto the substrate at 4500 rpm for 30 seconds and baked on a hotplate at 100°C for 2 minutes to remove residual solvent. The film thickness after coating and baking was measured to be approximately 22 nm by ellipsometry.

[0073] The first substrate coated with the resist film was exposed to 1100 μC / cm 2The resist was exposed to a 30 kV electron beam rastered to form a pattern at a dose of 1000 kV. The patterned resist and substrate were then subjected to a post-exposure bake (PEB) at 150 °C for 2 min. The exposed film was then immersed in a polar organic solvent for 30 s and rinsed with DI H2O, forming a negative image in which the unexposed portions of the coating were removed. Finally, a hotplate bake at 200 °C for 5 min was performed after development. Figures 11A-11D show SEM images of 18 nm lines at a 36 nm pitch in resist films developed in 4-methyl-2-pentanol (A), ethyl lactate (B), propylene glycol monomethyl ether (PGMEA) (C), and n-butyl acetate (D).

[0074] Another substrate was prepared using the same precursor solution and exposed to extreme UV light, which is also suitable for high-resolution patterning, after a coating / baking process: patterns of 22 and 18 nm lines at 44 and 36 nm pitch, respectively, were fabricated using a 13.5 nm wavelength and 101 mJ / cm. 2 The resist was exposed using a projection with a 0.3 aperture operating at an imaging dose of 1000 nm. After a 2-minute hotplate PEB at 165°C, the film was developed by immersion in PGMEA, rinsed with DI H2O, and finally baked at 200°C for 5 minutes. Negative images of well-resolved line-space patterns are shown in Figures 12A and 12B.

[0075] The chemical contrast generated upon radiation exposure to induce a polarity change is manifested in the development rate contrast, and the imaging performance of the resist is clearly demonstrated using Fourier transform infrared (FTIR) spectroscopy. Transmission mode FTIR spectra of butyltin hydroxide oxide resist films spin-coated onto undoped silicon wafers from tetrahydrofuran (THF) solvent were collected as a function of exposure dose with a 30 kV electron beam. The FTIR spectra ranged from 2800 to 2900 cm. -1 Analysis of several absorption peaks corresponding to alkyl C-H stretching modes from shows a consistent decrease in alkyl ligand concentration as a function of dose (Figure 13).

[0076] Example 3 - Positive Imaging This example demonstrates the formation of a positive image using the resist solution from Example 1.

[0077] Another substrate was coated with a resist film deposited from the same precursor solution from Example 1 and baked on a hotplate at 150°C for 2 minutes. The base wafer with the resist coating was then heated to 511 μC / cm 2 The resist was exposed to a 30 kV electron beam with a dose of 0.01 μm, followed by a post-exposure bake at 150°C for 2 minutes. Positive imaging was achieved by developing the exposed resist film in an aqueous base solution, e.g., 2.38% tetramethylammonium hydroxide (TMAH). Immersion in 2.38% TMAH etched the exposed resist, developing 30 nm (60 nm pitch) lines, as shown in the SEM image in Figure 14.

[0078] Example 4 - Resist Stability This example demonstrates the stability of the resist precursor by the consistent imaging performance of the resist precursor solution and the coated film after aging.

[0079] A resist precursor solution prepared as described in Example 1 was applied to a pair of wafer substrates by spin coating and baked on a hotplate at 100°C for 2 minutes. A portion of the precursor solution was kept in a sealed vial and stored in the dark with one of the coated substrates (the first substrate) at uncontrolled room temperature (20-30°C) under atmospheric conditions. Immediately after coating, the second substrate bearing the resist film was subsequently patterned using a 30 kV electron beam, baked at 150°C for 2 minutes, developed in PGMEA for 30 seconds, rinsed, and hard-baked at 200°C for 2 minutes. An SEM image of the resulting patterned second substrate is shown in Figure 15A. This exposure and development process was repeated on the first substrate bearing the stored resist film after 39 days. An SEM image of the patterned first substrate is shown in Figure 15B. Similarly, the retained portion of the original precursor solution was used on the same day after 39 days of storage to coat a third wafer substrate with a resist film, which was immediately processed, exposed, and developed in the same manner as the first two substrates. An SEM image of the patterned third substrate is shown in Figure 15C. The imaging performance of the three resist films at the same 36 nm pitch and 18 nm line width was functionally identical, showing no observable degradation in image fidelity, line width write, or sensitivity after aging of the coated resist film or precursor solution over the 39-day period.

[0080] Example 5 - Modulation of radiosensitivity based on organic ligand selection This example demonstrates that tuning of the radiation sensitivity of the resist can be observed by selecting the appropriate organic ligand.

[0081] Divinyltin dichloride (Alpha Aesar) was dissolved in PGMEA to a concentration of 0.1 M. A 15 mL quantity of this solution was placed in a separatory funnel, to which 7.31 mL of 0.4 M NaOH (aqueous) was added. Immediately after the NaOH addition, the vessel was shaken thoroughly for approximately 1 minute, and the resulting emulsion was allowed to separate for approximately 24 hours. During this period, light aggregates formed at the phase interface between the two media were observed to disappear, resulting in two clear phases. The lower aqueous phase was removed from the separatory funnel, and the upper PGMEA phase was shaken over 4A molecular sieves (Mallinkrodt, Grade 514) for approximately 5 minutes to remove residual water. Evaporation of the solvent and calcination of an aliquot of the sieved composition revealed a tin concentration of 0.1 M based on the residual mass of SnO2.

[0082] After separation and sieving, the divinyltin hydroxide solution in PGMEA was spin-cast directly onto a silicon wafer at 1250 rpm and hot-plate baked at 100 °C for 2 minutes. Ellipsometry measurements after baking showed a resist film thickness of approximately 16 nm. A 30 kV electron beam was used to measure the resist thickness at 75 μC / cm. 2 The resist film was exposed to a dose of 100 nm, followed by a second hotplate bake at 100° C. and development in PGMEA. An SEM image of the negative line / space pattern at 100 nm pitch is shown in FIG. 16. Note that the electron beam dose used to generate FIG. 16 was significantly lower than that used in Examples 2 and 3.

[0083] Transmission mode FTIR spectra were collected on similar resist films deposited from ethyl acetate solvent on undoped silicon wafers as a function of dose. The relative IR absorption as a function of electron beam dose is plotted in Figure 17. Based on analysis of the area of ​​the absorption peak corresponding to the vinyl C-H stretch centered at approximately 3055 1 / cm, the decrease in area indicates the loss of vinyl groups as tin ligands upon exposure, which is much more rapid and comprehensive with respect to dose than the loss of alkyl ligands for butyltin hydroxide oxide shown in Figure 13.

[0084] Example 6 - Organotin oxo-carboxylate resist This example demonstrates the effectiveness of radiation resists formed with alkyl and carboxylate ligands for tin ions.

[0085] A resist precursor solution was prepared by dissolving dibutyltin diacetate (Alfa-Aesar) in n-propanol to a final concentration of 0.025 M. The solution was then filtered through a 0.45 μm PTFE syringe filter and spin-cast onto a silicon wafer substrate spun at 3000 rpm for 30 seconds. The coated film was then baked at 60 °C for 2 minutes to remove residual solvent. During casting and baking, the dibutyltin diacetate is partially hydrolyzed by atmospheric water, converting it from a volatile liquid carboxylate to a solid organotin oxocarboxylate. Ellipsometry measurements indicated a resist film thickness of approximately 22 nm.

[0086] Then 1500μC / cm 2 Subsequent exposure of the film to a 30 kV electron beam raster-scanned to form a pattern at a dose of 100 nm was followed by a hotplate PEB at 60 °C and a 30-second immersion in PGMEA to develop the pattern by etching the unexposed material. A final hard bake at 100 °C for 5 minutes was performed before SEM imaging. Figure 18 contains an electron micrograph of the resulting negative line / space pattern at 32 nm pitch.

[0087] The creation of chemical contrast in the material upon radiation exposure by the electron beam can be observed by transmission FTIR spectroscopy, as shown in Figure 19. 30 kV electron beam (800 μC / cm 2 Transmission spectra were collected for organotin oxo-carboxylate thin films deposited on undoped silicon wafers and baked at 50 °C for 2 min before and after exposure to 1000 kJ / cm . Similar to simple organotin oxohydroxides, absorption peaks assigned to hydrocarbon CH stretching and bending modes (2957, 2924, 2858, 1391, and 1331 cm ) were observed.-1 A strong decrease in the peak energy of the carboxylate ligands was observed, confirming the loss of alkyl ligands upon exposure. -1 The significant decrease in absorbance centered around and the concomitant reduction in the carbonyl C=O absorbance are readily apparent and are characteristic of carboxylates.

[0088] The above-described embodiments are illustrative and not intended to be limiting. Additional embodiments are within the scope of the following claims. Moreover, while the present invention has been described with reference to specific embodiments, those skilled in the art will recognize that changes in form and detail may be made without departing from the spirit and scope of the present invention. Any incorporation by reference of the above documents is limited such that no subject matter contrary to the explicit disclosure herein is incorporated.

Claims

1. 1. A method for patterning a substrate with radiation, comprising: irradiating the coated substrate along a selected pattern to form an irradiated structure having areas of irradiated coating and areas of non-irradiated coating, said coated substrate comprising a coating comprising a metal oxo-hydroxo network having organic ligands with metal carbon and / or metal carboxylate bonds; selectively developing the irradiated structure to remove a majority of the irradiated coating or the non-irradiated coating to form a patterned substrate; A method comprising:

2. 10. The method of claim 1, wherein the irradiated structure has an irradiated coating that is soluble in an aqueous base and a non-irradiated coating that is soluble in an organic solvent, such that the irradiated structure can alternatively undergo positive or negative imaging.

3. 3. The method of claim 1, wherein the developing is carried out with an organic solvent to remove the non-irradiated coating.

4. 3. The method of claim 1, wherein the selective development is carried out using an aqueous base solution.

5. The method of any one of claims 1 to 4, wherein the irradiation is carried out with an electron beam, ultraviolet light, extreme ultraviolet light, irradiation from an ArF laser, irradiation from a KrF laser, or a UV lamp.

6. The method of any one of claims 1 to 5, wherein the etched pattern comprises features having an average pitch of about 60 nm or less.

7. 7. The method of any one of claims 1 to 6, wherein the non-irradiated coating has a molar ratio between organic ligands and metal cations that is from about 0.1 to about 4, and has an average coating thickness of about 1 micron or less.

8. 8. The method of any one of claims 1 to 7, wherein the metal comprises tin ions, antimony ions, indium ions, or a combination thereof; the organic ligand forms a metal carbon bond, and the ligand forming the metal carbon bond comprises an alkyl ligand, an alkenyl ligand, an aryl ligand, or a combination thereof, each ligand containing 1 to 16 carbon atoms; and / or the organic ligand forms a metal-carboxyl bond, and the metal-carboxyl bond is formed by an alkyl carboxylate ligand, an alkenyl carboxylate ligand, an aryl carboxylate ligand, or a combination thereof, each ligand having 1 to 16 carbon atoms.

9. The method of any one of claims 1 to 8, further comprising forming the coating by depositing a liquid precursor solution and evaporating the solvent to solidify the coating.

10. 1. A coated substrate comprising a radiation-sensitive coating having an average thickness of about 10 microns or less and a thickness variation at any point along the coating that is about 50% or less from the average, wherein the coating comprises a metal oxo-hydroxo network having metal cations with organic ligands through metal carbon and / or metal carboxylate bonds.

11. The coated substrate of claim 10, wherein the molar ratio between the organic ligand and the metal cation is from about 0.1 to about 4.

12. The coated substrate of claim 10, wherein the molar ratio between the organic ligand and the metal cation is from about 0.5 to about 3.

13. The coated substrate of any one of claims 10 to 12, having an average coating thickness of about 1 micron or less.

14. The coated substrate of any one of claims 10 to 12, having an average thickness of from about 5 nm to about 200 nm.

15. The coated substrate of any one of claims 10 to 14, wherein the metal ions comprise tin ions, antimony ions, indium ions, or a combination thereof.

16. 16. The coated substrate of claim 15, wherein the metal cations further comprise cations of additional metal and / or metalloid elements that are up to about 50 mole % of the total metal and metalloid content.

17. 17. The coated substrate of any one of claims 10 to 16, wherein the organic ligands form a metal carbon bond, and the ligands forming the metal carbon bond comprise alkyl ligands, alkenyl ligands, aryl ligands, or combinations thereof, each containing from 1 to 16 carbon atoms.

18. 17. The coated substrate of any one of claims 10 to 16, wherein the organic ligands form a metal carboxyl bond, and the metal carboxyl bond is formed by alkyl carboxylate ligands, alkenyl carboxylate ligands, aryl carboxylate ligands, or combinations thereof, each having 1 to 16 carbon atoms.

19. 1. A patterned substrate comprising a substrate having a surface and a first coating present in selected areas along the surface and absent in other areas along the surface, wherein the first coating comprises a metal oxo-hydroxo network and an organic ligand, wherein metal cations are bonded to the organic ligands by metal carbon bonds and / or metal carboxylate bonds, and alternatively, the first coating is soluble in at least some organic liquids or the first coating is soluble in aqueous base solutions.

20. 20. The patterned substrate of claim 19, wherein the substrate surface is exposed in areas of the substrate where the coating is not present.

21. 21. The patterned substrate of claim 19 or 20, wherein the coating is effectively soluble in at least some organic liquids and further comprises a second coating along the surface in areas where the first coating is absent, the second coating being soluble in aqueous base.

22. The patterned substrate of any one of claims 19 to 21, wherein the patterned coating comprises features having an average pitch of about 60 nm or less.

23. 1. A precursor solution comprising an organic liquid and about 0.01 M to about 1.4 M of a metal polynuclear oxo / hydroxo cation having organic ligands with metal-carbon and / or metal-carboxylate bonds, wherein the precursor solution has a viscosity of about 0.5 centipoise (cP) to about 150 cP, and the organic liquid has a flash point of at least 10° C. and a vapor pressure of less than about 10 kPa at 20° C.

24. 24. The precursor solution of claim 23, wherein the metal comprises tin and the organic liquid is an alcohol.

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