Patterned inorganic layers, radiation-patterned compositions, and corresponding methods - Patents.com

Abstract

To provide a composition that provides a good patterning result so as to be used as a resist to alter organic compositions.SOLUTION: Stabilized precursor solutions can be used to form radiation inorganic coating materials. The precursor solutions generally comprise metal suboxide cations, peroxide-based ligands and polyatomic anions. Design of the precursor solutions can be performed to achieve a high level of stability of the precursor solutions. The resulting coating materials can be designed for patterning with a selected radiation, such as ultraviolet light, x-ray radiation or electron beam radiation. The radiation patterned coating material can have a high contrast with respect to material properties, so that development of a latent image can be successful to form lines with very low line-width roughness and adjacent structures with a very small pitch.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS This application claims priority to co-pending US Provisional Patent Application No. 61 / 350,103 to Stowers et al., entitled "Photopatternable Inorganic Hardmask," which is incorporated herein by reference.

[0002] Statement of Government Rights The development of the invention described herein was funded by US National Science Foundation research. and the National Science Foundation (DGE-0549503). Funded at least in part by government support under IIP-0912921 and the Federal Government The Government has certain rights in this invention.

[0003] The present invention relates to patterned inorganic layers that can be used to form device elements and / or used as resists to facilitate the patterning of other materials. The present invention further relates to radiation based methods for achieving the patterning, and precursor solutions that can be deposited to form coatings that can be patterned with extremely high resolution by radiation. [Background technology]

[0004] When forming semiconductor-based devices and other electronic devices, materials are typically patterned to incorporate structures. Thus, structures are typically formed through a repetitive process of a series of deposition and etching steps to form patterns from various materials. In this manner, a large number of devices can be formed in a small area. Some advances in the technology may include reducing the footprint of devices, which is desirable to improve performance.

[0005] The organic composition can be used as a radiation-patterned resist, in order to change the chemical structure of the organic composition corresponding to the pattern using a radiation pattern. For example, the process for patterning a semiconductor wafer requires the lithographic transfer of a desired image from a thin film of a radiation-sensitive organic material. Patterning a resist generally involves several steps, including exposing the resist to a selected energy source, for example through a mask, to record a latent image, and then developing and removing selected areas of the resist. In the case of a positive resist, the exposed areas are transformed to make such areas selectively removable, while in the case of a negative resist, the unexposed areas are more easily removable.

[0006] Typically, the pattern can be 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. However, liquid developers can be used to effectively develop the image. The substrate can be selectively etched through windows or gaps in the remaining areas of the protective resist layer. Also, desired materials can be deposited in 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. This process can be repeated to form additional layers of patterned materials. These functional inorganic materials can be deposited using chemical vapor deposition, physical vapor deposition, or other desired techniques. Additional processing steps, such as deposition of conductive materials or implantation of dopants, can be used. In the field of micro- and nano-fabrication, feature sizes in integrated circuits have become very small to achieve high integration density and improve circuit functionality. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] International Publication No. 2009 / 120169 [Patent Document 2] US Patent Application Publication No. 2005 / 0242330A [Patent Document 3] US Patent Application Publication No. 2010 / 0044698A [Patent Document 4] U.S. Patent No. 7,208,341 [Non-patent literature]

[0008] [Non-Patent Document 1] Harry J.Levinson, “Principles of Lithography” 2nd Edition, SPIE Press, Monograph Vol.PM146(2005) [Non-Patent Document 2] Cris Mack, “Fundamental Principles of Optical Lithography, The Science of Microfabrication” Willey-Interscience (2007) [Non-Patent Document 3] P.Zimmerman,J.Photopolym.Sci.Technol.,Vol.22,No.5,2009,p.625 Summary of the Invention

[0009] In a first aspect, the present invention relates to an aqueous inorganic patterning precursor solution comprising a mixture of water, metal suboxide cations, polyatomic inorganic anions, and a ligand comprising a peroxide group, the composition having a molar ratio of ligand to metal suboxide cation of at least about 2, and the resist composition being stable with respect to phase separation for at least about 2 hours without additional mixing.

[0010] In a further aspect, the present invention relates to a method of forming a radiation-sensitive inorganic coating precursor solution, the method comprising combining a first aqueous solution containing a metal suboxide cation, a complex solution comprising a ligand having a peroxide group, and a composition comprising a polyatomic inorganic anion to form the coating precursor solution, in one embodiment, the molar ratio of the ligand to the metal suboxide cation is at least about 2.

[0011] In another aspect, the invention relates to a method of patterning an inorganic material on a substrate, the method comprising forming a layer of radiation-patternable coating material to form a coated substrate, heating the coated substrate to remove at least a portion of the solvent, exposing the coated substrate to a pattern of radiation, and heating the coated substrate after irradiation. Typically the patterned coating material comprises a metal suboxide cation, a ligand comprising a peroxide group, and a polyatomic inorganic anion. Irradiation of the coated substrate can cause the coating to condense at the irradiated locations. Heating the coated substrate after irradiation can be to a temperature of at least about 45° C. before contacting the coating with a developer.

[0012] In another aspect, the invention relates to a patterned structure comprising a substrate and a patterned inorganic material on a surface of the substrate, the patterned inorganic material may comprise a patterned semiconductor material or a patterned dielectric material, and the patterned inorganic material may have edges with an average linewidth roughness of about 2.25 nm or less on a pitch of about 60 nm or less, or individual features having an average width of about 30 nm or less.

[0013] In a further aspect, the present invention relates to a method for forming a patterned structure comprising a substrate and a patterned inorganic material on a surface of the substrate, the method comprising applying a coating material to a layer of about 100 mJ / cm 2 Extreme UV with a dose of 300 μC / cm or less at 30 kV 2and contacting the irradiated layer with a developing composition to dissolve the non-irradiated material and form a patterned inorganic material, in one embodiment, the patterned inorganic material has an average pitch of about 60 nm or less, or individual features have an average width of about 30 nm or less. [Brief description of the drawings]

[0014] [Figure 1] Figure 1 is a schematic diagram showing metal cations bound to ligands, where M represents the metal atom and O represents the oxygen atom, which undergo a condensation reaction induced by absorbing energy from radiation. [Diagram 2] FIG. 2 is a schematic perspective view of a structure patterned with radiation having a latent image. [Diagram 3] FIG. 3 is a side plan view of the structure of FIG. [Figure 4] FIG. 4 is a schematic perspective view of the structure of FIG. 2 after the latent image has been developed to remove the non-irradiated coating material to form a patterned structure. [Diagram 5] FIG. 5 is a side view of the patterned structure of FIG. [Figure 6] FIG. 6 is a side plan view of the patterned structure of FIGS. 4 and 5 after etching of the underlying layers. [Figure 7] FIG. 7 is a side plan view of the structure of FIG. 6 after etching away the patterned condensed coating material. [Figure 8] Figure 8 is a side plan view of a "thermal freeze" double patterning process flow. The steps shown in Figures 2-4 are repeated after baking to make the first layer insoluble to the second layer. [Figure 9] FIG. 9 is a scanning electron microscope photograph of step coverage of a metal gate line having a step height of about 100 nm, covered with a Hf-based coating material. [Figure 10]FIG. 10 is a scanning electron micrograph of 120 nm pitch lines in a Zr-based coating material patterned by 193 nm wavelength interference lithography at a dose level of 20 mJ / cm 2 . [Figure 11] FIG. 11 is a scanning electron micrograph of 36 nm pitch lines in a Hf-based coating patterned by electron beam lithography. [Figure 12] FIG. 12 is an enlarged view of a portion of the pattern shown in FIG. [Figure 13] Figure 13A is a scanning electron micrograph of 36 nm pitch posts patterned by e-beam and developed in 2.38% TMAH, and Figure 13B is a scanning electron micrograph of 36 nm pitch posts patterned by e-beam and developed in 25% TMAH. [Figure 14] FIG. 14 is a scanning electron micrograph of a portion of the developed pattern having lines of roughness of 1.6-1.8 nm. [Figure 15] FIG. 15 is a scanning electron micrograph of a double patterned structure formed with the coating materials described herein using electron beam lithography. [Figure 16] FIG. 16 is an enlarged view of a portion of the pattern shown in FIG. [Figure 17] A scanning electron micrograph of etched silicon nanopillars 40 nm wide is shown in Figure 17. The pillars were fabricated by ion etching through a hard mask formed from a Hf-based coating material. [Figure 18] 18A-D are scanning electron micrographs of EUV lithography performed with the Hf-based coating material described herein and developed in 25% TMAH. In each case, the figure shows lines and spaces of the specified pitch, consisting of lines whose width is approximately half the specified pitch: A) 32 nm pitch lines and spaces, B) 30 nm pitch lines and spaces, C) 28 nm pitch lines and spaces, D) 26 nm pitch lines and spaces. Detailed Description of the Invention

[0015] Significant improvements in inorganic precursor solutions provide excellent direct patterning results for inorganic oxide materials comprising polyatomic ions. The precursor solutions can be used to deposit radiation-sensitive inorganic coating materials. In embodiments of particular interest, exposure to radiation converts the irradiated coating material to a condensed material that is resistant to removal by a developer composition. Selective removal of at least a portion of the non-irradiated coating material leaves a pattern that includes areas of condensed coating material and areas where the non-irradiated coating material has been removed exposing the underlying substrate. Coating materials can be designed to be sensitive to selected radiation, such as ultraviolet light and / or electron beam. The precursor solutions can further be formulated to provide suitable shelf life stability for commercial distribution.

[0016] The compositional changes to form the improved precursor solution also allow for improved image development. In particular, the irradiated coating material can result in a stable inorganic material with a high level of resistance to a developer, such as a suitable liquid for dissolving the non-irradiated coating material. Thus, the coating layer can be thinned without removing the condensed coating material during development. Compared to conventional organic resists, the inorganic materials described herein have a very high resistance to many etch chemistries for commercially available related functional layers. This allows for process simplification through avoiding intermediate sacrificial inorganic pattern transfer layers that would otherwise be used to supplement the organic resist patterned for mask functions. The coating material also allows for convenient double patterning. In particular, after thermal treatment, the condensed portion of the irradiated coating material is stable to contact with many compositions comprising additional precursor solutions. Thus, multiple patterning can be performed without prior removal of the deposited hard mask coating material.

[0017] The patterned inorganic coating material can then be removed after using the patterned material as a mask to pattern a desired functional material. Alternatively, the resulting patterned inorganic material can be incorporated into a structure as a component of a device. When the patterned inorganic coating material is incorporated into a structure, many steps in the processing procedure can be eliminated through the use of direct patterning of the material by 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 line width roughness can be reduced to very low levels to form improved patterned structures.

[0018] The formation of integrated electronic devices and the like involves the patterning of materials to form individual elements or components within the structure. This patterning generally involves different compositions coating portions of layers that interface with each other to bring out the desired functionality. Various materials can constitute semiconductors, which can have selected dopants, dielectrics, conductors, and / or other types of materials. To form high resolution patterns, radiation sensitive organic compositions can be used to introduce the pattern. The composition can be called a resist 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 using radiation to the selected pattern or the negative of the pattern to form a pattern or latent image with areas that are developer resistant and areas that are developer soluble. The radiation sensitive inorganic compositions described herein can be used to directly form the desired inorganic material structures within the device and / or as radiation patternable inorganic resists instead of organic resists. In both cases, significant process improvements can be utilized, and the structure of the patterned material can also be improved.

[0019] To form the coating material, the precursor solution is applied to a substrate surface, such as a wafer. In some embodiments, the inorganic precursor solution has a relatively low metal ion concentration such that the rheology, e.g., viscosity, of the coating composition allows for the formation of a thin coating on the substrate. The use of thinner coatings is consistent with the formation of higher resolution structures upon exposure to radiation and development of the pattern. The relatively high density and small spatial dimensions of the independently processable chemical moieties of the coating material can be exploited to reduce line width roughness, small feature sizes, and / or form structures with extremely high resolution.

[0020] The coating materials described herein can be designed for a particular type of radiation, and the precursor solutions can be correspondingly formulated to obtain the desired coating material composition. Specifically, the coating material is designed to have the desired absorption of the selected radiation, and the use of coating materials with larger radiation absorption cross-sections allows the use of correspondingly lower radiation doses. By appropriate selection of the composition, the patterning composition can be sensitive to specific wavelengths or wavelength ranges within, for example, ultraviolet, x-ray, or electron beam, as well as within each type of radiation. These specific types of radiation are desirable due to their ability to form small patterns based on short radiation wavelengths. Thus, the coating materials described herein can be used to effectively form small patterns with corresponding low line width roughness that can enhance device formation capabilities. Additionally, because the radiation-patterned coating materials are thin and have high contrast in terms of sensitivity to appropriate developers, structures can have small pitches between adjacent structures after removal of the non-irradiated coating material.

[0021] The precursor solution comprises an aqueous solution having a metal suboxide cation, a radiation sensitive ligand containing a peroxide group, and a polyatomic anion. The metal suboxide cation is a polyatomic cation having a metal element and a covalently bonded oxygen atom. Aqueous solutions of metal suboxides or hydroxides tend to be unstable with respect to gelation and / or precipitation. Specifically, these solutions become unstable upon removal of the solvent and may form an oxohydroxide network with the metal cation. However, the precipitated material may have useful properties as described below. By formulating the precursor solution with improved precipitation stability and control, radiation may be used to induce changes in the material. Specifically, peroxide-based ligands stabilize the precursor solution while also allowing controlled processing of the material.

[0022] Specifically, the precursor solution may comprise sufficient radiation-sensitive ligands such that the molar ratio of radiation-sensitive ligands to metal suboxide cations in the solution is at least about 2, and in some embodiments at least about 5. Specifically, higher peroxide-based ligand concentrations provide a surprisingly large improvement in precursor stability. Without wishing to be limited by theory, an increase in radiation-sensitive ligand concentration reduces agglomeration of metal cations and stabilizes the solution. Thus, the precursor solution can be stable without further stirring against settling of solids for at least 2 hours, and in some cases, for example, more than a month, for a significantly longer period of time. Due to the long stability time, the improved precursor increases the versatility for potential commercial applications. While hydrogen peroxide provides a desirable radiation-sensitive ligand, other inorganic peroxides may be suitable. In some embodiments, organic peroxides may be used, but generally, in some electronics applications, at least for the formation of the final product, organic compounds should be completely removed.

[0023] It has further been discovered that materials formed from metal suboxide cations and polyatomic anions can provide useful material properties that make them suitable for components such as electronic devices. Additional metal cations and anions can also be incorporated into the material to tailor the properties. These general precursor solutions are further described in US Pat. No. 5,399,363 entitled "Solution Processed Thin Films and Laminates, Devices Comprising Such Thin Films and Laminates, and Methods for the Use and Manufacture" by Keszler et al., which is incorporated herein by reference (hereinafter "Keszler PCT Application"). As described herein, significant improvements in the precursor solutions are achieved through the use of significantly higher radiation-sensitive ligand concentrations. Even more surprisingly, the significant increase in radiation-sensitive ligand concentration in the precursor solution results in coating materials with greater contrast after radiation exposure, with the surprising additional benefit that the stability of the precursor solution achieves improved patterning and shorter development times.

[0024] The metal suboxide cations can be selected to achieve the desired radiation absorption. +2 HfO based coatings have good absorption of far UV radiation at a wavelength of 193 nm. +2 The ZrO based coating material exhibits good absorption of X-ray and electron beam radiation and can impart desirable properties to the coating material, such as density and smoothness. +2 and HfO +2A blend of cations is effectively incorporated to achieve 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. Metal cations can be hydrolyzed to different degrees upon interaction with water, and the state of hydrolysis by water is generally highly dependent on pH. The metal ion concentration can be selected to obtain the desired properties of the precursor solution, with more dilute solutions generally being consistent with the formation of thinner coating materials.

[0025] Although sulfate anions are the preferred polyatomic anions for incorporation into the precursor solutions, other polyatomic anions may be desirable alternatives or additions to the sulfate anion. The concentration of the polyatomic anion has been found to correlate with the sensitivity of the coating material to various developer compositions. Some polyatomic anions contain metal atoms covalently bonded to oxygen atoms and / or hydroxyl groups, and the anion structure may also be pH dependent.

[0026] The more stable purified precursor solution also results in coating materials with the potential for greater contrast between radiation-exposed and unexposed portions of the substrate. Specifically, the exposed coating material can remain resistant to the developer composition in an appropriate manner, while the non-irradiated coating material can be relatively more easily dissolved in the appropriate developer composition. Since the non-irradiated coating material is relatively more easily dissolved in the developer compared to the irradiated coating material, the contact time with the developer can be reduced while still maintaining desirable removal of the coating composition. Specifically, the improved composition and corresponding materials reduce line width roughness to surprisingly low levels. Correspondingly, the pitch can be made very small between adjacent elements with appropriate insulation, typically electrical insulation, between the adjacent elements. The irradiated coating composition is highly resistant to the development / etching process, so that the coating composition can be made very thin without compromising the effectiveness of the development process in cleanly removing the non-irradiated coating composition while leaving appropriate portions of the irradiated patterning composition on the substrate surface. The ability to reduce developer contact time is also consistent with the use of thin coatings without damaging the exposed portions of the coating.

[0027] Typically, patterning is accomplished by applying a precursor solution to the entire surface or selected portions of the substrate. The precursor composition can be deposited on the substrate, for example, using conventional coating techniques. Prior to application of the coating material, the substrate surface can be prepared using a hydrophilic surface treatment to increase the hydrophilicity of the surface to improve wetting by the aqueous precursor solution. For example, the precursor solution can be applied onto the wafer or other substrate using spin coating, although other coating techniques, such as spray coating, knife edge coating, or other suitable techniques, can also be used. Printing techniques, such as screen printing, inkjet printing, can also be used to apply the precursor solution. However, microfeature patterning is typically achieved by radiation patterning rather than using printing. Removal of at least a portion of the solvent can stabilize the coating material for further processing. The solvent can be partially removed during the coating process itself. The substrate with the coating material can also be heated to aid in the removal of the solvent. After sufficient solvent removal, the coating material is generally relatively stable in view of the patterning and can be further processed for patterning.

[0028] Generally, the coating material is radiation sensitive such that exposure to radiation changes the composition of the coating material in the irradiated areas as a latent image. The radiation pattern can be introduced by passing or reflecting radiation through a physical mask and using appropriate optics to deliver the patterned radiation to the coating material. Additionally or alternatively, a beam of radiation can be scanned across the coating material to form a pattern in the coating material as a latent image based on exposure to radiation. Absorption of radiation causes condensation of the irradiated portions of the coating material. In other words, the energy from radiation absorption causes agglomeration of metal ions to change the properties of the irradiated material.

[0029] Without wishing to be limited by theory, it is believed that upon absorption of radiation, the peroxide functional groups break apart and the composition correspondingly condenses by forming bridging metal-oxygen bonds. The condensation reaction transfers the radiation pattern into a pattern in the coating material. Specifically, there is a pattern of the coating material that has been irradiated and condensed accordingly, and a pattern of the unirradiated coating material that remains substantially the same as its composition prior to irradiation, in which case the coating material is patterned.

[0030] It has been discovered that heating the material after irradiation can increase the contrast in material properties between the condensed and non-irradiated coating compositions. Specifically, it is found that this heating step enhances the condensation of the irradiated coating composition. Heating does not significantly alter the removal ability of the non-irradiated material in the development step.

[0031] The patterned coating composition is exposed to a developer, such as 2.38 wt % tetramethylammonium hydroxide (a standard developer in semiconductor lithography), which removes the non-irradiated portions of the coating material. Development can be accomplished in a short time by appropriate selection of the developer composition. Due to further stabilization of the condensed irradiated coating material, the condensed coating material is highly stable to the developer. The condensed coating material forms a highly hard masking material.

[0032] After patterning the coating material, additional layers of material may be applied over the pattern and / or additional etching may be performed through the windows created by removing the non-irradiated coating material to selectively remove substrate material based on the latent image in the patterned coating material. In this manner, the patterned coating material may be used to fabricate structures with further complementary patterning of various compositions. Ions may also be selectively implanted into the substrate through the windows of the patterned coating material for control of electrical properties. The compactness of this patterned inorganic coating results in a high implantation resistance compared to conventional organic patterned coatings. The patterned coating material may be directly incorporated into devices, since it is an inorganic material that can itself incorporate desirable properties into the structure. In the embodiment where the patterned coating material is directly incorporated into the structure, a significant processing advantage may be achieved, since separate steps to achieve only resist patterning and removal are avoided. These uses are detailed in the following discussion.

[0033] As mentioned above, the radiation-sensitive coating material described herein can be used as a negative resist. After developing the patterned coating material to remove the non-irradiated coating material, the pattern can be used for additional processing steps. Specifically, etching can be performed through the gaps in the patterned coating. Further, additional material can be deposited with additional material penetrating the gaps in the patterned coating material to the underlying substrate. In an embodiment, the combination of etching and / or deposition is based on the pattern in the coating material. After additional processing is performed based on the pattern in the coating material, the inorganic coating material, i.e., the inorganic resist, can be removed using a suitable etching composition or other etching process. For example, the irradiated coating material can be etched using dry BCl 3It can be removed by plasma etching or aqueous HF wet etching. The use of similar compositions as negative resists and as certain embodiments of positive resists is described in the Keseler PCT application, which is incorporated herein by reference. Compared to organic resists, this inorganic coating material offers distinct advantages in terms of absorption of selected radiation and in terms of high contrast between exposed and unexposed areas, such that high resolution can be achieved at moderate radiation doses.

[0034] The direct use of the patterned radiation-sensitive inorganic coating material allows the formation of a patterned inorganic layer without the separate use of an organic resist. The large contrast in properties between the irradiated and non-irradiated areas of the inorganic coating material allows the formation of a thin patterned layer that can be cleanly removed during the development step without significantly damaging the resistant condensed portions of the coating material. Due to the density and general etch resistance of the patterned inorganic coating material, the patterned thin coating material can be effectively used for further processing of the structure, including, for example, etching and ion implantation, guided by the patterned inorganic coating material as a mask. In some embodiments, the condensed inorganic coating material can be designed with appropriate thickness and physical properties to be directly incorporated into a device as a functional element. For example, the product metal suboxide composition can be used as a dielectric, as described in U.S. Patent Application Publication No. 2005 / 0242330A to Herman et al., entitled "Dielectric Material," which is incorporated herein by reference. Certain embodiments of the metal suboxide compositions also exhibit semiconducting properties as described in U.S. Patent Application Publication No. 2010 / 0044698A to Herman et al., entitled "Semiconductor Film Composition," which is incorporated herein by reference. Thus, the coating material may be selected to have the appropriate functionality.

[0035] The general use of lithographic techniques is well known in the electronics industry. See, for example, U.S. Patent No. 7,208,341, entitled "Method for Manufacturing Printed Circuit Boards," by Lee et al.; Harry J. Levinson, "Principles of Lithography," 2nd Edition, SPIE Press, Monograph Vol. PM146 (2005); and Cris Mack, "Fundamental Principles of Optical Lithography, The Science of Microfabrication," Willey-Interscience (2007). All three of these documents are incorporated herein by reference. The substrate is typically a single crystal silicon wafer, which may include other layers, although other substrates such as polymers may also be used. In particular, the processing temperatures of the inorganic coating materials described herein are relatively low, such that the formation of the patterned inorganic coating materials described herein can be performed with very high resolution on substrates that cannot be processed without damage at high temperatures, such as above 600°C. Suitable devices in which elements can be patterned using the inorganic coating materials described herein include, for example, integrated electronic circuits, solar cells, electronic displays, and the like.

[0036] Precursor solution The precursor solution has been formulated to achieve a very high level of stability so that the shelf life of the commercial product of the precursor solution is adequate. It has also been discovered that the formulation of the precursor solution can be designed to achieve a desired level of radiation absorption for a selected radiation based on the selection of the metal cation. The precursor solution is based on an aqueous solution of metal cations including metal oxide chemistry and polyatomic anions. The precursor solution is designed to form a coating composition upon at least partial solvent removal and ultimately an inorganic solid including the metal oxide and polyatomic anions. The control of the precursor solution is based on a high concentration of radiation sensitive ligands, specifically peroxide-based ligands, relative to the metal cations. Specifically, a more stable solution can be formed when the molar ratio of hydroxyl groups to metal cations is at least 2. A more stable precursor solution provides another advantage of a greater contrast between the final irradiated and non-irradiated coating materials.

[0037] The aqueous precursor solution generally comprises one or more metal cations. In the aqueous solution, the metal cations are hydrated due to interactions with water molecules. The nature of this interaction generally depends on the pH. Specifically, hydrolysis can occur to bond oxygen atoms to the metal ions, forming hydroxide ligands or oxo bonds with the corresponding release of hydrogen ions. As additional hydrolysis occurs, the solution becomes unstable with respect to precipitation of the metal oxide or with respect to gelation. Although it is ultimately desired to form an oxide material, the progression to this oxide is controlled as part of the procedure of first processing the solution into a coating material and then into the final metal oxide composition containing polyatomic anions. Although solvent removal can contribute to the formation of the oxide, this approach does not provide effective control of the process without the use of peroxide-based ligands as described herein. Effective control of solution processing can be achieved using peroxide-based ligands as described below.

[0038] The aqueous solution of metal cations is then ready for further processing. In particular, it is desirable to use it as an additional component of the aqueous precursor solution, i.e., a metal suboxide ready to further advance the solution toward a metal oxide composition. Typically, the precursor solution comprises about 0.01M to about 1.4M, in further embodiments about 0.05M to about 1.2M, and in additional embodiments about 0.1M to about 1.0M of metal suboxide cations. Those skilled in the art will recognize that other ranges of metal suboxides within the ranges set forth above are contemplated and are within the scope of the present disclosure. The metal suboxides can be added as appropriate salts, such as halogen salts, e.g., chlorides, fluorides, bromides, iodides, or combinations thereof. Based on the use of metal suboxide ions in the precursor solution, relatively low levels of heating can be used to form the oxides while still maintaining good control of the solution based on the use of radiation-sensitive ligands.

[0039] Various metal ions as metal suboxide cations, e.g. VO +2 , SbO + , ReO 3 + , TiO +2 , TaO +3 , TaO 2 + , Y.O. + , NbO +2 , MoO +2 , WO +4 , WO 2 +2 , AlO + , GaO + , CrO + , FeO + , BiO + , LaO + , CEO + , PrO + , NdO + , PmO + , SmO + , EuO + , GdO + , TbO + , DyO + , HoO + , ErO + , TmO + , YbO+ 、LuO + 、TiO y (OH) z (4-2y-z)+ 、TaO y (OH) z (5-2y-z)+ 、YO y (OH) z (3-2y-z)+ 、NbO y (OH) z (4-2y-z)+ 、MoO y (OH) z (4-2y-z)+ 、WO y (OH) z (6-2y-z)+ 、AlO y (OH) z (3-2y-z)+ 、GaO y (OH) z (3-2y-z)+ 、Zn(OH) + ,Nut y (OH) z (3-2y-z)+ 、FeO y (OH) z (3-2y-z)+ ,Hot y (OH) z (3-2y-z)+ 、LaO y (OH) z (3-2y-z)+ 、CeO y (OH) z (3-2y-z)+ 、PrO y (OH) z (3-2y-z)+ 、NbO y (OH) z (3-2y-z)+ 、PMO y (OH) z (3-2y-z)+ 、SmO y (OH) z (3-2y-z)+ 、EuO y (OH) z (3-2y-z)+ 、GdO y (OH) z (3-2y-z)+ 、TbO y (OH) z (3-2y-z)+ 、DyO y(OH) z (3-2y-z)+ , HoO y (OH) z (3-2y-z)+ , ErO y (OH) z (3-2y-z)+ , TmO y (OH) z (3-2y-z)+ , YbO y (OH) z (3-2y-z)+ , LuO y (OH) z (3-2y-z)+ , or combinations thereof. The parameters y and z can be selected so that the ion has a positive charge based on the particular oxidation state of the metal atom. Metal suboxide cations of particular interest include, for example, ZrO +2 , ZrOOH + , Zr(OH) 2 +2 , Zr(OH) 3 + , HfO +2 , HfOOH + , Hf(OH) 2 +2 , Hf(OH) 3 + , combinations thereof, and / or combinations with other metal suboxide cations. Additionally, the solution may contain additional metal cations, such as hafnium (Hf +4 ), Titanium (Ti +4 ), Zirconium (Zr +4 ), Cerium (Ce +4 ), Tin (Sn +4 ), Tantalum (Ta +5 ), Niobium (Nb +4 ), yttrium (Y +3 ), Molybdenum (Mo +6 ), Tungsten (W +6 ), Aluminum (Al +3 ), Gallium (Ga +3 ), Zinc (Zn +2 ), Chromium (Cr +3 ), iron (Fe +3 ), Bismuth (Bi +3 ), Scandium (Sc+3 ), Vanadium (V +4 ), Manganese (Mn +2 , Mn +3 , Mn +4 ), Cobalt (Co +2 , Co +3 ), Nickel (Ni +2 , Ni +3 ), Indium (In +3 ), Antimony (Sb +5 ), Iridium (Ir +3 , Ir +4 ), platinum (Pt +2 , Pt +4 ), Lanthanum (La +3 ), praseodymium (Pr +3 ), neodymium (Nd +3 ), Promethium (Pm +3 ), Samarium (Sm +3 ), Europium (Eu +3 ), Gadolinium (Gd +3 ), Terbium (Tb +3 ), Dysprosium (Dy +3 ), Holmium (Ho +3 ), Erbium (Eb +3 ), Thulium (Tm +3 ), Ytterbium (Yb +3 ), Lutetium (Lu +3 ), or a combination of these. As mentioned above, the state of the cations in solution is pH dependent and therefore the initial state of oxygen coordination can change in solution, but the trend is towards hydrolysis leading to the formation of oxides. Peroxide based ligands have been found to prevent the formation of metal-oxygen networks which lead to gelation and ultimately precipitation. Thus, peroxides can be used to form stable states which can rapidly condense upon breaking of the peroxide bonds.

[0040] Metal cations generally have a large effect on radiation absorption. Therefore, metal cations can be selected based on the desired radiation and absorption cross section. ZrO +2 HfO has been shown to exhibit good absorption of 193 nm wavelength ultraviolet and other far-ultraviolet radiation.+2 shows good absorption of e-beam materials and extreme ultraviolet radiation. Further tuning of the radiation absorbing composition can be adjusted based on the addition of other metal ions. For example, one or more ions (cations or anions) including titanium, zinc, calcium, indium, tin, antimony, bismuth, or combinations thereof can be added to the precursor solution to form a coating material with an absorption edge shifted to longer wavelengths, for example, to be sensitive to 248 nm wavelength ultraviolet radiation. Also, one or more ions (cations or anions) including magnesium, boron, calcium, aluminum, silicon, phosphorus, or combinations thereof can be used to increase the absorption cross section at shorter wavelengths. The absorbed energy is transferred to the peroxide ligands, which can cause the breakage of the peroxide bonds, achieving the desired control of the material properties.

[0041] The precursor solution may also comprise polyatomic anions, typically oxygen-based. Through the formation of the final inorganic oxide, the oxygen-based polyatomic anions may be carried over into the oxide in the final solid material. As with the cations, the nature of these anions may depend on the pH. Suitable oxygen-based polyatomic anions include, for example, SO 4 -2 , B.O. 3 -3 , AsO 4 -3 , MoO 4 -2 , P.O. 4 -3 , WO 4 -2 , SeO 4 -2 , SiO 4 -4, their protonated forms, and combinations thereof. Typically, the precursor solution contains a polyatomic anion concentration of about 0.5 to about 2.0 times the metal suboxide cation concentration, in other embodiments about 0.75 to about 1.5 times the metal suboxide cation concentration, and in further embodiments about 0.8 to about 1.3 times the metal suboxide cation concentration. One of ordinary skill in the art will recognize that other ranges of anion concentrations within the ranges explicitly stated above are contemplated and are within the scope of the present disclosure. The polyatomic anion can also be added as an acid if pH adjustment is appropriate, and / or the polyatomic anion can be added along with the desired metal cation. The precursor solution can generally be prepared with additional anions, such as halogen anions, which may be added along with the metal suboxide cation. The halogen anions react with the peroxide ligand to form Cl. 2 , Br 2 , or I 2 The reaction with the halogen ions reduces the peroxide concentration to a level that is moderate relative to the amount of peroxide added.

[0042] The peroxide-based ligand stabilizes the composition against condensation. Specifically, at high relative concentrations of the peroxide-based ligand, a significant amount of water can be removed from the composition without forming condensed metal oxides or metal hydroxides. Based on this stability discovery, high concentrations of radiation-sensitive ligands with good storage stability can be used to form solutions while retaining convenient processing procedures for forming coatings. A radiation-sensitive ligand of particular interest has a peroxide group -OO-. As previously mentioned in the context of FIG. 1, the energy from absorbed radiation can break this oxygen-oxygen bond. As the peroxide group breaks, the composition condenses by forming MOM bonds (where M represents a metal atom), and the corresponding stabilization is lost. Condensation can therefore be controlled by radiation. Compositions with high radiation-sensitive ligand concentrations can be extremely stable with respect to avoiding spontaneous condensation.

[0043] The chemically simplest ligand compound is hydrogen peroxide, H 2 O2 which is water soluble. Additional peroxide-based ligands may comprise, for example, organic and / or inorganic compositions. Inorganic peroxide-based ligands are desirable in some embodiments because carbon is undesirable for many devices. When inorganic peroxides are used as radiation-sensitive ligands, the risk of carbon contamination from the radiation-sensitive ligand is avoided. Suitable inorganic peroxide ligands include, for example, peroxysulfate ions (SO 5 H - ), peroxydisulfate ion (S 2 O 8 -2 ), peroxychloride ion (ClO 5 H - ), etc., and combinations thereof. The precursor compositions generally comprise a ligand concentration that is at least about 2 times the metal cation concentration, in further embodiments at least about 3 times, in other embodiments at least about 4 times, and in additional embodiments from about 5 to about 25 times the metal cation concentration.

[0044] Typically, the desired compound is dissolved to form an aqueous solution. After the components of the solution are dissolved and combined, the properties of the species may change as a result of hydration and peroxide-based ligand binding. When the composition of the solution is referred to herein, the reference is to the components added to the solution, since the properties of the species in the solution are often not well known.

[0045] In some embodiments, it may be desirable to form separate solutions that can be mixed together to form the precursor solution. Specifically, separate solutions may be formed that include one or more of the metal suboxide cations, the optional additional metal cations, the peroxide-based ligand, and the polyatomic anion. When multiple metal cations are introduced, the multiple metal cations may be introduced in the same solution and / or in separate solutions. Generally, the separate solutions may be thoroughly mixed. In some embodiments, the metal cation solution is then mixed with the peroxide-based ligand solution such that the peroxide-based ligand can conjugate with the metal cation. The resulting solution may be referred to as a stabilized metal cation solution. In some embodiments, the stabilized metal cation solution is allowed to stabilize for at least about 5 minutes, and in further embodiments, at least about 15 minutes, prior to further processing. A polymeric anion solution may be added to the stabilized metal cation solution to form a stabilized precursor solution. In some embodiments of the precursor solution, the order in which the solutions are mixed may provide more desirable results. The solutions may be mixed under appropriate mixing conditions and at an appropriate speed to achieve good mixing.

[0046] The concentration of the species in the precursor solution may be selected to achieve the desired properties of the solution. In particular, lower concentrations may provide overall desirable solution properties for some coating methods, such as spin coating, and thinner coatings may be achieved with reasonable coating parameters. In general, the concentration may be selected as appropriate for the selected coating method. A relatively large ratio of peroxide-based ligand to metal cation may be used to significantly stabilize the precursor solution, as described above. The stability of the precursor solution may be evaluated with respect to changes relative to the initial solution. In particular, the solution loses stability when phase separation occurs due to the formation of large sol particles. Based on the improvements in the stabilization techniques described herein, the solution may be stable for at least about 2 hours without additional mixing, in further embodiments for at least about 1 day, in other embodiments for at least about 5 days, and in additional embodiments for at least about 25 days. Those skilled in the art will recognize that other stabilization time ranges are contemplated and are within the scope of the present disclosure. Solutions may be formulated with sufficient stability times to allow the solution to be commercially distributed with a reasonable shelf life.

[0047] Coating Materials The coating material is formed by depositing a precursor solution onto a selected substrate. The substrate generally provides a surface onto which the coating material may be deposited, and the substrate may comprise multiple layers with the surface associated with a top layer. The substrate surface may be treated to prepare the surface for adhesion of the coating material. The surface may be cleaned and / or smoothed as necessary prior to surface preparation. Suitable substrate surfaces may comprise any reasonable material. Certain substrates of particular interest include, for example, silicon wafers, silica substrates, other inorganic materials, polymeric substrates such as organic polymers, composites thereof, and combinations thereof across the surface and / or in layers of the substrate. Wafers such as relatively thin cylindrical structures may be convenient, although structures of any reasonable shape may be used. Substrates having polymeric layers on polymeric substrates or non-polymeric structures may be desirable for certain applications based on their low cost and flexibility, and suitable polymers may be selected based on the relatively low processing temperatures that may be used to process the patternable inorganic materials described herein. Suitable polymers may include, for example, polycarbonates, polyimides, polyesters, polyalkenes, copolymers thereof, and mixtures thereof. It is generally desirable for the substrate to have a flat surface, especially for high resolution applications.

[0048] Traditional organic resists are soluble in non-polar solvents and are deposited on hydrophobic surfaces. These surfaces may be treated with compounds such as hexamethyldisilazane (HMDS) to render the surface hydrophobic and promote adhesion of the polymer resist. In contrast, the patternable inorganic materials described herein are based on aqueous solutions, which suggests that it is desirable to apply the solution to a hydrophilic surface in order to apply it to the substrate surface. If the surface is not initially as hydrophilic as desired, methods appropriate for the particular substrate composition may be used to render the surface hydrophilic. In the case of silicon substrates, methods that can be used to render the surface hydrophilic include, but are not limited to, immersion in a basic surfactant, oxygen plasma treatment, UV ozone treatment, piranha etchant (concentrated H 2 SO 4 (aqueous) and 30% by weight H 2 O 2A variety of methods can be used, including immersion in a 3:1 mixture of dimethyl sulfoxide (DMSO) and then heating at about 225° C. to about 275° C. for up to about 5 minutes.

[0049] In general, the precursor solution can be delivered to the substrate using any suitable coating method. Suitable coating techniques can include, for example, spin coating, spray coating, dip coating, knife edge coating, printing techniques such as inkjet printing and screen printing. Some of these coating techniques form a pattern of the coating material during the coating process, but the resolution currently achieved from printing is significantly lower than that achieved from radiation-based patterning as described herein. The coating material can be applied in multiple coating steps to provide greater control of the coating process. For example, multiple spin coatings can be performed to obtain a desired final coating thickness. A heating step, as described below, can be applied after each coating step or after multiple coating steps.

[0050] When patterning using radiation, spin coating is a desirable technique to provide relatively uniform substrate coverage, but edge effects may exist. In certain embodiments, the wafer may be rotated at a speed of about 500 rpm to about 10,000 rpm, in further embodiments at a speed of about 1000 rpm to about 7500 rpm, and in additional embodiments at a speed of about 2000 rpm to about 6000 rpm. The rotation speed may be adjusted to obtain the desired coating thickness. Spin coating may be performed for about 5 seconds to about 5 minutes, and in further embodiments, for about 15 seconds to about 2 minutes. An initial slow rotation speed, for example, 50 rpm to 250 rpm, may be used to provide an initial bulk spreading of the composition across the substrate. A backside rinse with water or other suitable rinse, an edge beam removal step, or the like, may be used to remove edge beads. Those skilled in the art will recognize that additional ranges of spin coating parameters within the ranges explicitly stated above are contemplated and are within the scope of the present disclosure.

[0051] The thickness of the coating is generally a function of the concentration, viscosity, and spin speed of the precursor solution. Also, for other coating methods, the thickness can generally be adjusted by selection of coating parameters. In some embodiments, it may be desirable to use thin coatings to facilitate the formation of small and highly resolved features. In some embodiments, the coating material can have an average thickness of 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 1 nm to about 40 nm, and in some embodiments about 1 nm to about 25 nm. One of ordinary skill in the art will recognize that additional ranges of thickness within the ranges explicitly stated above are contemplated and are within the scope of the present disclosure. The thickness can be evaluated using non-contact methods of X-ray reflectivity and / or ellipsometry based on the optical properties of the film.

[0052] Because many coating methods form droplets or other shapes of coating material with large surface areas and / or solution movement that promotes evaporation, the coating method itself may cause some solvent evaporation. Depletion of solvent tends to increase the viscosity of the coating material due to an increased concentration of species in the material. To further drive off the solvent and promote densification of the coating material, the coating material typically may be heated prior to radiation exposure. As a result of heat treatment and densification of the coating material, the coating material may exhibit an increase in refractive index and radiation absorption without significant loss of contrast as a result of thermal decomposition of the peroxide groups.

[0053] During the coating process, the goal is to remove enough of the solvent to stabilize the coating material for further processing. This solvent removal process cannot be quantitatively controlled with respect to the specific amount of solvent remaining in the coating material, and typically an empirical evaluation of the resulting coating material properties is performed to select effective processing conditions for the patterning process. Although heating is not required for the process to work, it may be desirable to heat the coated substrate to increase the processing rate and / or improve the reproducibility of the process. In embodiments that utilize heat to remove the solvent, the coating material may be heated to a temperature of about 45° C. to about 150° C., in further embodiments from about 50° C. to about 130° C., and in other embodiments from about 60° C. to about 110° C. Heating to remove the solvent may generally be performed 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. One of skill in the art will recognize that additional ranges of heating temperatures and times within the ranges explicitly stated above are contemplated and are within the scope of the present disclosure.

[0054] Patterned exposure and patterned coating material Radiation can be used to form fine patterns in the coating material. As mentioned 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 the radiation causes a transfer of energy that breaks the -OO- bonds of the peroxide, so that at least a portion of the peroxide-based ligands are no longer available for stabilization of the material. Absorption of a sufficient amount of radiation causes the exposed coating material to condense. Generally, the radiation is 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 areas. The irradiated areas comprise condensed coating material, and the non-irradiated areas generally comprise the as-formed coating material. Extremely sharp edges can be formed upon development of the coating material by removal of the non-irradiated coating material, as described below.

[0055] Typically, radiation is directed to the coated substrate through a mask, or a radiation beam can be controllably scanned across the substrate. Typically, the radiation can include electromagnetic radiation, an electron beam (beta radiation), or other suitable radiation. Typically, the electromagnetic radiation has a desired wavelength or range of wavelengths, such as visible light, ultraviolet light, or x-rays. The resolution that a radiation pattern can achieve generally depends on the wavelength of the radiation, with higher resolution patterns being achievable with shorter wavelength radiation. Thus, to achieve particularly high resolution patterns, it is desirable to use ultraviolet light, x-rays, or an electron beam.

[0056] According to the international standard ISO 21348 (2007), which is incorporated herein by reference, ultraviolet radiation extends between wavelengths of 100 nm and less than 400 nm. Krypton fluoride lasers can be used as a source of 248 nm ultraviolet radiation. The ultraviolet range can be subdivided in several ways under generally accepted standards, for example, into extreme ultraviolet (EUV), 10 nm and less than 121 nm, and far ultraviolet (FUV), 122 nm and less than 200 nm. The 193 nm spectral line from an argon fluoride laser can be used as a radiation source for FUV. EUV radiation is used in lithography at 13.5 nm, and is generated from Xe or Sn plasma sources excited by high-energy lasers or discharge pulses. Soft x-rays can be defined as 0.1 nm and less than 10 nm.

[0057] The amount of electromagnetic radiation can be characterized by the fluence or dose, which is given by the integrated radiant flux versus exposure time. A suitable radiation fluence is about 1 mJ / cm 2 ~Approx. 150mJ / cm 2 and in a further embodiment about 2 mJ / cm 2 ~Approx. 100mJ / cm 2 , and in further embodiments, about 3 mJ / cm 2 ~about 50mJ / cm 2A 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.

[0058] In electron beam lithography, the electron beam generally induces secondary electrons, which generally modify the material being irradiated. Resolution is a function of the range of at least some of the secondary electrons in the material, and generally higher resolution is believed to result from secondary electrons of shorter range. The range of secondary electrons in inorganic materials is limited based on the high resolution achievable by electron lithography using the inorganic coating materials described herein. The electron beam can be characterized by the energy of the beam, with suitable energies being from about 5 eV to about 200 keV, and in further embodiments, from about 7.5 eV to about 100 keV. The proximity corrected beam dose at 30 keV is about 0.1 microcoulombs per square centimeter (μC / cm 2 ) ~ Approximately 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 properties within the explicit ranges above are contemplated and are within the scope of the present disclosure.

[0059] After exposure to radiation, the coating material is patterned with irradiated and non-irradiated regions. Referring to Figures 2 and 3, 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 comprises condensed regions 110, 112, 114, 116 of the irradiated coating material, and non-condensed regions 118, 120 of the non-irradiated coating material. The patterned regions formed by the condensed regions 110, 112, 114, 116, and the non-condensed regions 118, 120 represent a latent image in the coating material.

[0060] Based on the design of the inorganic coating material, there is a large contrast in material properties between the irradiated areas with condensed coating material and the non-irradiated, non-condensed coating material. This contrast can be improved with a post-exposure heat treatment, but it has been surprisingly found that in certain embodiments, satisfactory results can be achieved without a post-exposure heat treatment. The post-exposure heat treatment appears to anneal the irradiated coating material to improve condensation without causing the non-irradiated areas of the coating material to condense less significantly due to thermal decomposition of the peroxide. For embodiments using heat treatment, the post-exposure heat treatment can be carried out at a temperature of about 45° C. to about 150° C., in additional embodiments about 50° C. to about 130° C., and in further embodiments about 60° C. to about 110° C. Heating to remove the solvent can generally be carried out for at least about 0.1 minutes, in further embodiments about 0.5 minutes to about 30 minutes, and in additional embodiments about 0.75 minutes to about 10 minutes. One of ordinary skill in the art will recognize that additional ranges of post-exposure heating temperatures and times within the ranges set forth above are contemplated and are within the scope of the present disclosure. This large contrast in material properties further facilitates the formation of sharp lines in the pattern after development, as described in the following section.

[0061] Developing and patterning structures Developing the image involves contacting the patterned coating material containing the latent image with a developer composition to remove non-irradiated coating material. With reference to Figures 4 and 5, the latent image of the structure shown in Figures 2 and 3 is developed by contacting it with a developer to form a patterned structure 130. After developing the image, the substrate 102 is exposed to light through openings 132, 134 along its top surface, which are located at the locations of the non-condensed regions 118, 120, respectively.

[0062] Generally, the developer can be an aqueous acid or base. To obtain sharper images, an aqueous base can generally be used. To reduce contamination from the developer, it may be desirable to use a developer that does not contain metal atoms. Thus, quaternary ammonium hydroxide compositions such as tetraethylammonium hydroxide, tetrapropylammonium hydroxide, tetrabutylammonium hydroxide, or combinations thereof are desirable as developers. Quaternary ammonium hydroxides of particular interest are generally represented by the formula R 4 NOH, where R=methyl, ethyl, propyl, butyl, or combinations thereof. In general, inorganic coating materials can be developed with the same developers commonly used today for polymeric resists, specifically tetramethylammonium hydroxide (TMAH). Commercially, TMAH is available at 2.38 wt %, which may be used for the processes described herein. However, in certain embodiments for developing inorganic materials, the developer may be shipped at a higher concentration, e.g., 25 wt % TMAH, than is commonly used for developing organic resists. Additionally, mixed quaternary tetraalkylammonium hydroxides may be selected based on empirical evaluation to obtain improved line edge definition. In general, the developer may include from about 2 to about 40 wt %, in further embodiments from about 3 to about 35 wt %, and in other embodiments from about 4 to about 30 wt % tetraalkylammonium hydroxide. One of ordinary skill in the art will recognize that additional ranges of developer concentrations within the ranges explicitly stated above are contemplated and are within the scope of the present disclosure.

[0063] In addition to the main developer composition, the developer may comprise additional compositions to facilitate the development process. Suitable additives include, for example, dissolved salts having cations selected from the group consisting of ammonium, d-block metal cations (hafnium, zirconium, lanthanum, etc.), f-block metal cations (cerium, lutetium, etc.), p-block metal cations (aluminum, tin, etc.), alkali metals (lithium, sodium, potassium, etc.), and combinations thereof, and dissolved salts having anions selected from the group consisting of fluorine, chlorine, bromine, iodine, nitrate, sulfate, phosphate, silicic acid, boric acid, peroxide, butoxide, formate, ethylenediamine-tetraacetic acid (EDTA), tungstic acid, molybdic acid, and the like, and combinations thereof. When these optional additives are present, the developer may comprise up to about 10% by weight of the additives, and in further embodiments up to about 5% by weight of the additives. One skilled in the art will recognize that other ranges of additive concentrations within the above-stated ranges are contemplated and are within the scope of the present disclosure. These additives may be selected to improve contrast, sensitivity, and line width roughness. The additives in the developer may also include HfO 2 / ZrO 2 Particle formation and precipitation can be suppressed.

[0064] For weaker developers, such as less concentrated developers, a higher temperature of the development step can be used to increase the process speed. For stronger developers, a lower temperature of the development step can be used to reduce and / or control the development rate. In general, the development temperature can be adjusted between the appropriate values ​​of the aqueous solvent. Furthermore, the developer containing dissolved inorganic coating material near the developer-coating interface can be ultrasonically dispersed during development.

[0065] The developer may be applied to the patterned coating material using any suitable technique. For example, the developer may be sprayed onto the patterned coating material. Spin coating may also be used. For automated processing, a puddle method may be used, which involves pouring the developer onto the coating material in a stationary mold. If desired, the development step may be completed using spin rinsing and / or spin drying. Suitable rinsing liquids include, for example, ultrapure water, methyl alcohol, ethyl alcohol, propyl alcohol, and combinations thereof. After the image is developed, the coating material is disposed on the substrate as a pattern.

[0066] After the development step is complete, the coating material can be heat treated to further condense and dehydrate the materials. This heat treatment is particularly desirable in embodiments where the inorganic coating material is incorporated into a final device, but may be desirable for some embodiments where the inorganic coating material is used as a resist and ultimately removed, if it is desired to stabilize the coating material to facilitate further patterning. Specifically, the patterned coating material can be baked under conditions where the patterned coating material exhibits a desired level of etch selectivity. In some embodiments, the patterned coating material can be heated to a temperature of about 150° C. to about 600° C., in further embodiments about 175° C. to about 500° C., and in additional embodiments about 200° C. to about 400° C. Heating can be for at least about 1 minute, in other embodiments about 2 minutes to about 1 hour, and in further embodiments about 2.5 minutes to about 25 minutes. One of ordinary skill in the art will recognize that additional ranges of temperatures and times for heat treatment within the ranges explicitly stated above are contemplated and are within the scope of the present disclosure.

[0067] For organic resists, when the aspect ratio (height divided by width) of the structures becomes very large, the structures are susceptible to pattern collapse. Pattern collapse is related to the mechanical instability of high aspect ratio structures, where forces associated with the processing steps, such as surface tension, distort the structural elements. Structures with low aspect ratios are more stable against potential deforming forces. For the patternable inorganic materials described herein, improved patterning may be achieved without the need for high aspect ratio patterned coating materials, since structures with thinner layers of coating materials can be processed more efficiently. Thus, very high resolution features are formed without the aid of high aspect ratio features in the patterned coating materials.

[0068] The resulting structures can have sharp edges with very low linewidth roughness. In addition to specifically reducing linewidth roughness, high contrast also allows for the creation of small features and spacing between features and the creation of 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 evaluated by design and verified by scanning electron microscopy (SEM), for example, by top-down imaging. Pitch, as used herein, refers to the spatial period or 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, which is generally evaluated away from corners and the like. Features can also refer to the spacing between material elements 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 can be about 2.25 nm or less, and in further embodiments, about 1.2 nm to about 2.0 nm. Linewidth roughness is quantified by analysis of top-down SEM images to derive a 3σ deviation from the average linewidth. This average includes both high 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. The pattern transfer process can smooth out the short correlation roughness during the etching process to produce much higher fidelity patterns. One of ordinary skill in the art will recognize that additional ranges of pitch, average width, and linewidth roughness within the ranges explicitly stated above are contemplated and are within the scope of the present disclosure.

[0069] Further processing of the patterned coating material After formation of the patterned coating material, the coating material may be further processed to facilitate formation of the selected device. In addition, deposition and / or patterning of additional materials may generally be performed to complete the structure. The coating material may or may not be ultimately removed. The quality of the patterned coating material may in either case be advanced toward improved devices, such as devices with smaller footprints.

[0070] The patterned coating material forms openings to the underlying substrate, for example as shown in Figures 4 and 5. As with conventional resists, the patterned coating material forms an etch mask that can be used to transfer the pattern to selectively remove the underlying thin film. Referring to Figure 6, the underlying thin film 103 is patterned leaving features 152, 154, 156 beneath condensed regions 110, 112, 114, respectively. Compared to conventional polymeric resists, the materials described herein can provide significantly greater etch resistance.

[0071] Alternatively or additionally, deposition of the further material may change the properties of the underlying structure and / or allow contact with the underlying structure. The further coating material may be selected based on the desired properties of the material. In addition, the density of the patterned inorganic coating material may provide high implantation resistance so that ions may be selectively implanted into the underlying structure. In some embodiments, the further deposition material may be a dielectric, semiconductor, conductor, or other suitable material. The further deposition material may be deposited using any suitable technique, such as solution processing, chemical vapor deposition (CVD), sputtering, physical vapor deposition (PVD), or other suitable technique.

[0072] Generally, multiple additional layers may be deposited. Additional patterning may be performed in conjunction with the deposition of multiple layers. Any additional patterning, if any, may be performed using additional amounts of coating materials described herein, polymeric resists, other patterning methods, or combinations thereof.

[0073] As discussed above, the layer of coating material after patterning may or may not be removed. If the layer is not removed, the patterned coating material is incorporated into a structure. In embodiments where the patterned coating material is incorporated into a structure, the properties of the coating material may be selected to achieve the desired patterning properties as well as the material properties within the structure.

[0074] When removal of the patterned coating material is desired, the coating material acts as a resist. This patterned coating material may be used to pattern subsequent deposited materials prior to removal of the resist / coating material and / or to selectively etch the substrate through voids in the condensed coating material. The coating material may be removed using a suitable etching method. In particular, to remove the condensed coating material, for example, BCl 3 Plasma, Cl 2 Alternatively or additionally, dry etching may be performed using a plasma such as HF (aq) or buffered HF (aq) / NH 4 The patterned coating material may be removed using a wet etch with F. Referring to Figure 7, the structure of Figure 6 is shown after removal of the coating material. The etched structure 150 comprises the substrate 102 and features 152, 154, 156.

[0075] These coating materials are particularly useful for multiple patterning using thermal freeze techniques as generally described for conventional resists in P. Zimmerman, J. Photopolym. Sci. Technol., Vol. 22, No. 5, 2009, p. 625. The process of double patterning by "thermal freeze" is outlined in FIG. 8. In a first step, the coating material is formed into a pattern 160 on a substrate 162 using lithography and development as depicted with respect to FIGS. 4 and 5. A heating step 164 is performed to dehydrate the coating material. This heating step corresponds to the post-development heating step described in the development section above. This "thermal freeze" step renders the coating material insoluble to the 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 an etching step 170, a resultant double patterned structure 172 is formed. It is noted that this process can be readily extended to multiple coating and patterning steps, and such extensions are contemplated and are 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 dehydrated by thermal baking, so that they are not water soluble and subsequent coating layers can be applied. Example 1

[0076] Preparation of precursor solutions This example describes the method used to prepare a precursor solution comprising hafnium (Hf) and / or zirconium (Zr) based metal suboxide cations.

[0077] Separate aqueous solutions of the components of the precursor solution were prepared. For ease of notation, the solutions are referred to as Part A for the suboxide cations, Part B for the peroxide-based ligand solution, and Part C for the solution containing polyatomic anions. 0.5 molar ZrOCl was mixed with 500 mL of ultrapure water (electrical resistivity 18 MΩ cm). 2 8H 2 Solution Part A1 was prepared by filtering a solution of 0.5 mol HfOClO (161.125, Alfa Aesar 99.9%) mixed with 500 mL of ultrapure water. 2 8H 2 Solution Part A2 was prepared by filtering a solution of HO (204.76 g, Alfa Aesar 98%). Part A1 was used to form a precursor solution for 193 nm lithography patterning, and Part A2 was used to form a precursor solution for 13 nm (also known as extreme UV or EUV) or electron beam lithography patterning, as described below. 2 O 2 (Aqueous) (30% w / w, Mallinckrodt Baker) diluted with ultrapure water to 6–8% w / w H 2 O 2 Solution Part B was prepared by forming a solution of 2-5M H 2 SO 4 Solution Part C, comprising (aqueous) is obtained at a certified concentration (Fischer Scientific, 10N) or as a concentrated solution (98% H 2 SO 4 , Mallinckrodt Baker) was diluted with ultrapure water.

[0078] For 193 nm lithography patterning, a Zr-based precursor solution was prepared. For EUV or e-beam lithography patterning, a Hf-based precursor solution was prepared. The methods used to prepare both precursor solutions were identical except that the Zr-based precursor solution was prepared using Part A1 and the Hf-based precursor solution was prepared using Part A2. The selected ratios of component solutions, Part A1 or Part A2, Part B, and Part C, were weighed into individual pre-cleaned polyethylene bottles. A sufficient amount of ultrapure water was added to the Part C component solution to obtain the target final metal concentration. The components in the bottle were then mixed by pouring the Part A1 or Part A2 component solution into the Part B component solution, waiting for 5 minutes, and then Part C was poured into the combined Part A1 or Part A2 and Part B, and waiting for an additional 5 minutes. This particular mixing order has been found to limit particle growth.

[0079] Using the above method, 4.8 mL of solution Part A1 (Zr) and 1.8 mL of solution Part B (H 2 O 2 ), 2.16 mL of solution Part C(H 2 SO 4 A 30 mL formulation of Zr-based precursor solution with a final zirconium concentration of 0.16 M was obtained by combining 21.24 mL of ultrapure water and 1.0 mL of Hf (aqueous). 4.5 mL of solution Part A2 (Hf), 16.875 mL of solution Part B (H 2 O 2 ), 1.8 mL of solution Part C(H 2 SO 4 (aqueous)), and 6.825 mL of ultrapure water to obtain a 30 mL formulation of Hf-based precursor solution with a final hafnium concentration of 0.15 M. Example 2

[0080] Preparation and deposition of coating materials This example describes the preparation of a substrate surface and the deposition of a patternable coating material using a precursor solution made according to Example 1.

[0081] A 5-inch silicon wafer was used as the substrate. The surface of the silicon wafer was treated with a basic surfactant, an acidic surfactant, and O 2 The wafers were pretreated with plasma, ultraviolet ozone, piranha etchant, or DMSO, followed by heating to temperatures between 225°C and 275°C to render the surface hydrophilic. The selected precursor solution was applied on a standard lithographic spin-coating track. The wafer was loaded onto the spin-coater and the precursor solution was dispensed onto the center of the wafer. The amount of dispensed precursor solution was selected based on the desired build thickness and size of the wafer. The spin-coater was spun at 100 RPM for 5 seconds to spray the resist across the wafer, then spun at 3000 RPM for 30-60 seconds to cast the resist film. The wafer was then subjected to a pre-exposure bake at 40-200°C for 0.1-5 minutes.

[0082] This method has also been used to coat wafers with steps. Figure 9 shows the coverage of Hf-based coating material on a wafer with a step of about 100 nm for thin film transistor (TFT) gate dielectric application. A film was produced from five successively deposited layers to demonstrate step coverage. Proper coverage over sharper steps was observed. Example 3

[0083] 193nm lithographic patterning of Zr-based coating materials This example describes the method used to pattern a Zr suboxide based coating material.

[0084] This coating material was prepared by the method of Example 2 using ZrO +2Zr-based coating compositions were used. The coatings were deposited to a thickness of 10-50 nm. The Zr-based coatings were irradiated with 193 nm (deep UV) light patterned with a mask or generated interference pattern using a lithography processing system with an ArF laser source. After irradiation, the wafer was returned to the wafer track and subjected to a post-exposure bake at 40°C-200°C for 1-5 minutes. The exposure to the 193 nm UV light produced a patterned coating. The patterned coating was developed with 2.38 wt % TMAH using a puddle development method. The TMAH was allowed to contact the coating for 20 seconds, and then the substrate was rinsed with water and dried. Referring to FIG. 10, highly resolved patterns were produced using this developer. FIG. 10 shows the results of 193 nm lithography with 20 mJ / cm 2 Figure 1 shows a pattern of 120 nm pitch lines (lines and spaces of approximately 60 nm) in a Zr-based coating material fabricated at a dose level of 100 nm. Example 4

[0085] Electron beam and EUV lithographic patterning of Hf-based coatings This example describes the method used to pattern a Hf suboxide based coating.

[0086] This coating material was prepared by the method of Example 2 using HfO +2 In one embodiment, the Hf-based coating composition was prepared and deposited at 30 keV and about 78 μC / cm 2 The wafer was exposed to an electron beam of 1000 Å. The resulting patterned coating material was developed in 2.38-25 wt % TMAH using a dip method. The developer was contacted with the wafer for 20 seconds. The wafer was then rinsed with water and dried. Contact with the developer produced the patterns shown in Figures 11, 12, 13A, and 13B. High resolution patterns were produced. Figure 11 shows 36 nm pitch lines in a Hf-based coating material. Another pattern with a pitch of 36 nm is shown in Figure 12. This pattern was developed using a 244 μC / cm2 This was caused by an electron beam dose of .

[0087] Figures 13A and 13B show 36 nm pitch posts in a Hf-based coating patterned by electron beam irradiation. The sample shown in Figure 13A was developed with 2.38 wt% TMAH concentration, while the sample shown in Figure 13B was developed with 25 wt% TMAH concentration. Development with 25 wt% TMAH concentration produced posts with better contours, but those samples required about 8 times higher electron beam dose. Figure 14 shows patterns with 1.6-1.8 nm linewidth roughness for a pattern with 21 nm linewidth on 60 nm pitch.

[0088] The double patterned structure is shown in Figures 15 and 16. Patterning was performed at 500 μC / cm 2 The patterning was performed with a 30 keV electron beam at a dose of 100 nm. After patterning the first layer, the coating was baked at 220° C. before applying the second coating composition. A higher magnification view is shown in FIG. 16. Well resolved and uniform 30 nm contact holes are visible in FIG. 16.

[0089] Ion etching was performed through a hard mask made of the Hf-based coating material after development as described in this example. This coating material acted as a mask for ion etching. A scanning electron micrograph of silicon nanopillars is shown in FIG. 17. The patterned structures after ion etching had a pillar width of 40 nm. This mask showed good resistance to ion etching.

[0090] EUV images were obtained using projection lithography with a numerical aperture of 0.25 operating at 13 nm. The resist was applied to a thickness of 20 nm on a silicon wafer by spin coating, followed by a post-apply bake at 50 °C. Approximately 80 mJ / cm 2 After exposure at 400° C., a post-exposure bake at 75° C. was used and then developed in 25% TMAH. The developed patterns are shown in Figures 18A-D. The patterns shown in Figure 18 have pitches of A) 32 nm, B) 30 nm, C) 28 nm, and D) 26 nm.

[0091] The above embodiments are illustrative and not limiting. Additional embodiments are within the scope of the 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 invention. All incorporation by reference of the above documents is limited so as not to incorporate any subject matter contrary to the express disclosure herein. [Explanation of symbols]

[0092] 100 Patterned Structures 102 Substrate 103 Thin Film 104 Patterned Coating Materials 110 Condensation region of irradiated coating material 112 Condensation region of irradiated coating material 114 Condensation region of irradiated coating material 116 Condensation Region of Irradiated Coating Materials 118 Non-condensed regions of non-irradiated coating materials 120 Non-condensed regions of non-irradiated coating materials 130 Patterned Structures 132 Opening 134 Opening 150 Etched Structures 152 Features 154 Features 156 Features 160 patterns 162 Substrate 164 Heating Step 166 Development Steps 168 Double Patterned Structures 170 Etching Steps 172 Double patterned structure product

Claims

1. A) exposing a layer of a radiation-sensitive coating material comprising an oxo / hydroxide network with metal ions on the surface of an underlying structure to EUV radiation in a pattern-wise manner to form a coating material bearing a latent image comprising some of the coating material that has been irradiated and some that has not been irradiated according to the pattern; B) developing the coating material bearing the latent image to remove unirradiated coating material and form a developed patterned coating material having openings to the underlying structures; C) depositing a deposited material through the opening onto the underlying structure or etching the underlying structure through the opening; and D) Repeating steps A) through C) one or more times to form a structure for a device containing semiconductor, dielectric, and / or electrical conductor features with desired functionality. A method for manufacturing a device comprising:

2. The method of claim 1 , wherein interaction of the coating material with EUV changes the chemical properties of the coating material to form structures having different dissolution rates.

3. The layer has an average thickness of about 1 nm to about 25 nm, and the EUV radiation is about 100 mJ / cm ２ 13. The method of claim 1 having a dosage of:

4. 10. The method of claim 1, wherein the underlying structure comprises a silicon wafer, a silica substrate, a polymer layer, a polymer substrate, a composite thereof, or a thin film transistor (TFT), or a combination thereof across a surface and / or within a layer.

5. The method of claim 1 , wherein the deposited material comprises an ion, a dielectric, a semiconductor, a dopant, or a conductor.

6. The method of claim 1 , wherein depositing comprises implanting ions into the underlying structure.

7. The method of claim 1 , wherein the deposition comprises chemical vapor deposition (CVD), sputtering, or physical vapor deposition (PVD).

8. The method of claim 1 further comprising performing ion etching prior to deposition to transfer the pattern to the underlying structure.

9. The method of claim 1 , wherein the developed patterned coating material comprises a metal oxide.

10. The method of claim 1 , wherein the openings have an average width of about 30 nm or less and / or an average linewidth roughness of about 2.25 nm or less.

11. 2. The method of claim 1, wherein the metal of the metal ion comprises Al, Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Zn, Y, Zr, Nb, Mo, In, Sn, Sb, Hf, Ta, W, Ir, Pt, La, Ce, Pr, Nb, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, or combinations thereof.

12. The method of claim 1 , wherein the metal of the metal ions comprises Sn.

13. The method of claim 1 , wherein the coating material before irradiation comprises a mixture of metal ions.

14. The method of claim 1 , wherein the coating material further comprises a polyatomic anion.

15. The method of claim 1, wherein the metal ion comprises a metal suboxide cation.

15. The method of claim 14, wherein in the coating material, the molar ratio of radiation-sensitive ligand to metal suboxide cation is at least 2.

16. The method of claim 1 , wherein the radiation-sensitive ligand comprises a peroxide ligand.

17. The method of claim 1, wherein the metal ion comprises a metal suboxide cation.

10. The method of claim 1, wherein the molar ratio of peroxide groups to metal suboxide cations in the coating material is at least 2.

18. The metal suboxide cation is HfO ＋２ Or ZrO ＋２ The method of claim 17, comprising at least one of:

19. The metal suboxide cation is VO ＋２ , SbO ＋ , ReO ３ ＋ , TiO ＋２ , TaO ＋３ , TaO ２ ＋ , Y.O. ＋ , NbO ＋２ , MoO ＋２ , W.O. ＋４ , W.O. ２ ＋２ , AlO ＋ , GaO ＋ , CrO ＋ , FeO ＋ , BiO ＋ , LaO ＋ , CeO ＋ , PrO ＋ , NdO ＋ , PmO ＋ , SmO ＋ , EuO ＋ , GdO ＋ , TbO ＋ , DyO ＋ , HoO ＋ , ErO ＋ , TmO ＋ , YbO ＋ , LuO ＋ or a combination thereof.

20. The coating material is aluminum (Al ＋３ ), Scandium (Sc ＋３ ), Titanium (Ti ＋４ ), Vanadium (V ＋４ ), Chromium (Cr ＋３ ), Manganese (Mn ＋２ , Mn ＋３ , Mn ＋４ ), iron (Fe ＋３ ), Cobalt (Co ＋２ , Co ＋３ ), Nickel (Ni ＋２ , Ni ＋３ ), Zinc (Zn ＋２ ), yttrium (Y ＋３ ), zirconium (Zr ＋４ ), niobium (Nb ＋４ ), Molybdenum (Mo ＋６ ), Indium (In ＋３ ), tin (Sn ＋４ ), Antimony (Sb ＋５ ), Hafnium (Hf ＋４ ), Tantalum (Ta ＋５ ), Tungsten (W ＋６ ), Iridium (Ir ＋３ , Ir ＋４ ), platinum (Pt ＋２ , Pt ＋４ ), Lanthanum (La ＋３ ), Cerium (Ce ＋４ ), praseodymium (Pr ＋３ ), neodymium (Nd ＋３ ), Promethium (Pm ＋３ ), Samarium (Sm ＋３ ), Europium (Eu ＋３ ), gadolinium (Gd ＋３ ), terbium (Tb ＋３ ), dysprosium (Dy ＋３ ), Holmium (Ho ＋３ ), Erbium (Er ＋３ ), Thulium (Tm ＋３ ), Ytterbium (Yb ＋３ ), Lutetium (Lu ＋３ ), Gallium (Ga ＋３ 20. The method of claim 18 or 19, further comprising a cation of a metal comprising:

21. The method of claim 1 , wherein the underlying structure includes a step.

22. EUV radiation is 3 mJ / cm ２ ~50mJ / cm ２ The method of claim 1 having a dose of 23. The method of claim 1, wherein the coating material having the latent image is developed with a reactive gas to remove unirradiated coating material.

24. The method of claim 1 , wherein the structures for the device comprise etched silicon nanopillars.

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