Organometallic metal chalcogenide clusters and application to lithography

Abstract

To provide organometallic photoresist compositions and methods to form photoresist coatings and patterns using the compositions.SOLUTION: There is described patterning with UV and EUV light using organo tin sulfide (and selenide) clusters. The clusters are solids at room temperature and are soluble in organic solvents that are not too polar. Irradiation can either fragment a carbon metal bond or crosslink unsaturated organic moieties to stabilize the irradiated material. The irradiated material then resists dissolving in organic solvents so that the un-irradiated material can be contacted with an organic solvent to develop the latent image formed with the radiation. Radiation patternable layers can be formed through coating a solution or through vapor deposition. There are described corresponding precursor solutions, structures and methods.SELECTED DRAWING: None

Description

Technical Field

[0001] Cross - Reference to Related Applications This application claims priority to U.S. Provisional Patent Application No. 62 / 876,842, filed Jul. 22, 2019, by Cardineau et al., entitled “Organometallic Metal Chalcogenide Clusters and Application to Lithography”, which is incorporated herein by reference.

[0002] The present invention relates to organometallic photoresist compositions and methods of using these compositions to form photoresist coatings and patterns.

Background Art

[0003] In semiconductor manufacturing, pattern formation of materials is performed to fabricate devices and circuits. These patterned structures are generally formed by repeated photolithography processes of thin - film deposition, radiation exposure, and etching steps to form a large number of devices in a small area. Technological progress can be accompanied by an increase in device density, which may be desirable for performance improvement.

[0004] Thin - film coatings of organic and organometallic compositions can be used as radiation - sensitive photoresists. Radiation can change the chemical structure and composition of the photoresist, thereby affecting its dissolution rate in a selected solvent. The pattern of radiation can be replicated as a latent image in the photoresist coating and then as a patterned photoresist structure by selective dissolution of the unexposed and exposed regions. This patterned photoresist structure can then be transferred to a substrate, typically an active or passive device layer, by an etching process.

Summary of the Invention

Problems to be Solved by the Invention

[0005] For the development of latent images in a photoresist, a liquid developer can be particularly effective. The substrate can be selectively etched through the resulting windows or gaps in the photoresist layer, or a desired material can be deposited within the exposed windows or gaps. Functional materials such as conductors and dopants can be deposited or incorporated using chemical vapor deposition, physical vapor deposition, ion implantation, and other desired methods. Finally, the patterned photoresist, when completely removed. This process is repeated many times to form additional layers of the patterned material. In semiconductor manufacturing, EUV lithography has been introduced to obtain very small feature and device sizes for improving circuit functionality. In this type of lithography, there is a need for a new type of photoresist that effectively absorbs radiation having a wavelength of 13.5 nm.

Means for Solving the Problems

[0006] In a first aspect, the present invention relates to a formulation of (RSn)4X6 (where R is an organic group or a hydrocarbyl group and X is S or Se) in an organic solvent that can form a continuous and smooth photoresist coating. This formulation can be a pattern-forming precursor solution comprising an organic solvent and an organotin cluster composition represented by the formula (RSn)4X6 (where R is an organic ligand bonded to Sn by a metal-carbon bond and X is S or Se), and this precursor solution has a concentration of about 0.0005 M to about 1 M based on tin.

[0007] In a second aspect, the present invention relates to a coated substrate comprising a radiation-sensitive film of (RSn)4X6 having an average thickness of 1 micron or less and having a thickness variation of 25% or less from the average at any location across the film. This coating comprises a metal sulfide (selenide) network having metal cations with organic ligands by metal-carbon bonds or a metal-sulfide-oxide-hydroxide network having metal cations bonded to organic ligands via metal-carbon bonds. In some embodiments, this aspect can be described as a structure having a radiation-sensitive pattern-forming layer comprising a substrate and a radiation-sensitive layer comprising an organic tin cluster represented by the formula (RSn)4X6, where R is an organic ligand having 1 to 15 carbon atoms bonded to Sn by a metal-carbon bond, and X is S or Se, and this radiation-sensitive layer has an average thickness of about 2 nm to about 1 micron.

[0008] In a third aspect, the present invention relates to a method of patterning a radiation-sensitive coating of (RSn)4X6, comprising irradiating a coated substrate with radiation along a selected pattern to form a radiation-irradiated structure having a region of the radiation-irradiated coating and a region of the non-radiation-irradiated coating, and selectively developing the radiation-irradiated coating to remove a substantial portion of the non-radiation-irradiated region. The coated substrate generally comprises a coating comprising a metal-sulfide cluster or metal-sulfide network having a metal cation with an organic ligand by a metal-carbon bond or a metal-sulfide-oxide-hydroxide network having a metal cation bonded to an organic ligand via a metal-carbon bond. In particular, this aspect can be described as a method of patterning a coating, comprising developing a pattern from a virtual image formed by exposing a radiation-sensitive layer to a radiation pattern to form a radiation-irradiated layer. Development of the pattern can include contacting the radiation-irradiated layer with an organic solvent to substantially remove the non-radiation-irradiated portion of the radiation-irradiated layer, the radiation-sensitive layer being formed using an organotin cluster, and irradiation of the radiation-sensitive layer resulting in a material that is substantially less soluble in the organic solvent.

[0009] In a further aspect, the present invention relates to a method of forming a radiation-sensitive layer suitable for patterning on a substrate surface, comprising depositing a (RSn)4X6 cluster on the substrate, where X is S or Se, and R is a hydrocarbyl group (or organic ligand) bonded to Sn by a metal-carbon bond. The deposition step comprises 1) contacting a solution comprising a (RSn)4S6 cluster and an organic solvent with the substrate surface, and removing the solvent to form a layer of radiation-sensitive coating material, 2) volatilizing the (RSn)4X6 cluster, and collecting the volatilized cluster on the substrate surface, or 3) Performing the reactive deposition of (RSn)4X6 using the vapor and gas H2X of (RSn)4Y6, where Y is a halogen atom may be included.

Brief Description of the Drawings

[0010]

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DETAILED DESCRIPTION OF THE INVENTION

[0011] Improved properties are obtained in high-resolution radiation-based patterning with organotin clusters, and the tin tetramers described herein are suitably processable for use in EUV lithography. The clusters are formed as tetrameric species having crosslinkable thio groups and attendant alkyl groups, providing cluster stability. The tin tetramer, which is an amorphous solid at room temperature, is soluble in suitable organic liquids. The patterning formulations are described based on the dissolution of the tin tetramer in an organic solvent and the deposition of a uniform and functional coating on a suitable substrate. EUV patterning with desirable properties is demonstrated.

[0012] The manufacture of semiconductor circuits and devices has been accompanied by a regular decrease in critical dimensions over successive generations. As these dimensions decrease, new materials and methods may be required to meet the demands for processing and patterning of ever smaller feature sizes. Patterning generally involves the selective exposure of a thin layer of radiation-sensitive material (photoresist) in order to form a pattern and then transfer it to subsequent layers and functional materials. Metal-based resists exhibit good absorption of extreme UV light and electron beam radiation, while at the same time providing a particularly suitable new class of materials for obtaining very high etching contrast.

[0013] The use of alkyl-substituted metal coordination and cluster compounds that form oxohydroxo networks has been found to be a very promising patterning material in high-performance radiation-based patterning, particularly in extreme ultraviolet patterning. Alkyl metal patterning compositions are described, for example, in U.S. Patent No. 9,310,684 to Meyers, entitled "Organometallic Solution Based High Resolution Patterning Compositions", which is incorporated herein by reference. Improvements to these organometallic compositions for patterning are described in U.S. Patent No. 10,642,153 B1 to Meyers, entitled "Organometallic Solution Based High Resolution Patterning Compositions and Corresponding Methods" and U.S. Patent No. 10,228,618 B1 to Meyers, entitled "Organotin Oxide Hydroxide Patterning Compositions, Precursors, and Patterning", both of which are incorporated herein by reference. The organotin clusters described herein involve substitution of oxohydroxo ligands with sulfide ligands, and the results herein indicate that sulfide compositions can provide similarly desirable patterning results in EUV patterning.

[0014] One of the desirable organometallic precursor solutions for high-resolution EUV lithography exhibits a shelf life that supports the distribution of the product, adheres to the preferred substrates, results in a uniform and smooth thin film coating, and is highly sensitive and responsive to radiation exposure. Desirable compositions of these solutions can include metal sulfides of organometals of the (RSn)4S6 type dissolved in an organic solvent, where R is a hydrocarbyl ligand having 1 to 15 carbon atoms bonded to tin via an Sn-C bond. In particularly interesting embodiments, the organotin sulfide can be dissolved in a polar solvent such as tetrahydrofuran (THF) or a combination of THF and anisole that functions as a vehicle for uniformly coating a substrate by spin coating and related methods. In further embodiments, these coatings can be exposed to a pattern of UV light or EUV light to induce a chemical change that makes the exposed regions more resistant to dissolution in an organic developer than the unexposed regions. This behavior, where the photoresist exposed on the substrate remains after development, is characteristic of a negative-type material.

[0015] Tin clusters having alkyl and crosslinkable dianionic chalcogenides (S, Se) for forming adamantane structures have been synthesized to date. Examples of the synthesis and characterization of (RSn)4X6 (X = S or Se) can be found in the following papers (all of which are incorporated herein by reference): R = methyl, n-butyl, t-butyl, phenyl. G. A. Costa, M. C. Silva, G. M. de Lima, R. M. Logo, M. T. C. Sansiviero, Thermal decomposition of sulfur-containing organotin molecular precursors to produce pure-phase SnS. Phys. Chem. Chem. Phys. 2, 5708-5711 (2000). R = (Me3Si)3C. K. Wraage, T. Pape, R. Herbst-Irmer, M. Noltemeyer, H.-G. Schmidt, H. W. Roesky, Synthesis of (RSn)4X6 adamantanes (X = O, S, Se) in liquid ammonia in the two-phase system liquid ammonia / THF. European Journal of Inorganic Chemistry 5, 869 - 872 (1999). R = 4-(CH2=CH)-C6H4. N. Rosemann, J. P. Eussner, A. Beyer, S. W. Koch, K. Volz, S. Dehnnen, S. Chatterjee, A highly efficient directional molecular white-light emitter driven by a continuous-wave laser diode. Science 352, 1301 - 1304 (2016).

[0016] (RSn)4(S, Se)6 clusters have four metal (metalloid) atoms with one organic ligand bonded to the metal (metalloid) via a metal (metalloid)-carbon bond. Figure 1 shows the structure of one embodiment of an organotin sulfide cluster. In some embodiments, the cluster includes a dianionic chalcogen (e.g., thio) ligand shared between two Sn centers. The tin-carbon bond is sensitive to radiation-induced cleavage, which can induce different dissolution rates and enable radiation-based pattern formation as desired. Alternatively, the R group can include an unsaturated alkenyl moiety that can be crosslinked by radiation exposure. It is expected that a negative-tone lithography pattern based on the change in solubility of the radiation-irradiated material will be formed by both the initial bond cleavage and crosslinking processes. The non-aqueous solution formed using the clusters provides a promising coating composition with improved precursor solubility, coating quality, and sensitivity compared to another radiation-based organometallic pattern-forming material.

[0017] Synthesis of clusters and formation of coating solution (RSn)4S6 compositions can be prepared by the direct reaction of monoorganotin trichloride with sodium sulfide in THF. Examples describe the synthesis of derivatives where R = butyl and butenyl. The following reaction: 4RSnCl3+6Na2S=(RSn)4S6+12NaCl mixes the reagents in a 4:6 stoichiometric ratio. A solution of RSnCl3 in THF is added to a cooled solution (-78 °C) of Na2S in THF and reacted. Hydrogen sulfide (H2S) can be used instead of sodium sulfide. The precipitated solid NaCl is removed by filtration. A similar reaction can be carried out using Na2Se to form the selenide cluster compound (RSn)4Se6. The following discussion can be adapted correspondingly to the selenides as in the discussion of the sulfides and can be considered as correspondingly clearly disclosed. Next, when the solvent is evaporated, the solid (RSn)4S6 is obtained, which can then be dissolved in CH2Cl2 and passed through a silica plug to remove impurities. Subsequently, when the solvent is evaporated, a purified compound is obtained, which is triturated under pentane and recovered by filtration to obtain a free-flowing white solid. The following examples show the synthesis in the case where R = n-butyl (C4H9) or R =.n-butenyl (C4H7). Some monoorganotin trichloro precursor compounds are commercially available and others can be synthesized using available protocols, an example of which is discussed in the examples.

[0018] The R (organic) group can be a hydrocarbyl group such as a straight-chain, branched (i.e., secondary or tertiary at the metal-bonded carbon atom) or cyclic hydrocarbyl group. Each R group generally has 1 to 31 carbon atoms individually, 3 to 31 carbon atoms in the case of a secondary-bonded carbon atom, and 4 to 31 carbon atoms in the case of a tertiary-bonded carbon atom embodiment, and has, for example, methyl, ethyl, propyl, butyl and branched alkyl. In particular, R 1 R 2 R 3 CSnX3 where R 1 and R 2is, independently, an alkyl group having 1 to 10 carbon atoms, and R 3 is preferably a branched alkyl ligand that can represent the compound in another expression (wherein is hydrogen or an alkyl group having 1 to 10 carbon atoms). In some embodiments, R 1 and R 2 can form a cyclic alkyl moiety, and R3 can also be bonded to another group of the cyclic moiety. Suitable branched alkyl ligands are, for example, isopropyl (where R 1 and R 2 are methyl and R 3 is hydrogen), tert-butyl (where R 1 , R 2 and R 3 are methyl), tert-amyl (where R 1 and R 2 are methyl and R 3 is -CHCH3), sec-butyl (where R 1 is methyl, R 2 is -CHCH3 and R 3 is hydrogen), cyclohexyl, cyclopentyl, cyclobutyl and cyclopropyl. Examples of suitable cyclic groups include, for example, 1-adamantyl (-C(CH2)3(CH)3(CH2)3 or tricyclo(3.3.1.13,7)decane bonded to the metal at the tertiary carbon) and 2-adamantyl (-CH(CH)2(CH2)4(CH)2(CH2) or tricyclo(3.3.1.13,7)decane bonded to the metal at the secondary carbon). In another embodiment, the hydrocarbyl group can include an aryl group or an alkenyl group, such as a benzyl group, an allyl group or an alkynyl group. In another embodiment, the hydrocarbyl ligand R can consist of only C and H and can include any group containing 1 to 31 carbon atoms. For example, linear or branched alkyl ( i Pr, t Bu, Me, n(b) a cycloalkyl (cyclopropyl, cyclobutyl, cyclopentyl), olefin (alkenyl, aryl, allyl) or alkynyl group or a combination thereof. In a further embodiment, suitable R groups include hydrocarbon groups substituted with a heteroatom functional group such as a cyano group, thio group, silyl group, ether group, keto group, ester group or halogenated group or a combination thereof.

[0019] The solid (RSn)4S6 product can be dissolved in a suitable solvent at room temperature or by gentle heating (35 - 65 °C) to obtain a coating composition. The clusters are generally soluble in a wide range of organic solvents. These can be dissolved, for example, in organic solvents such as benzene, toluene, chlorotoluene, 1,1,2-trichloroethane, tetrahydrofuran (THF), anisole and THF-anisole mixtures, mixtures thereof, etc. Generally, the choice of organic solvent can be influenced by solubility parameters, volatility, flammability, toxicity, viscosity and chemical interaction with the substrate. In particular, THF and THF-anisole mixtures enable the deposition of smooth and uniform (RSn)4S6 coatings. As a photoresist in the case of radiation-based pattern formation, the precursor solution can generally contain from about 0.0005 M to about 1.0 M of tin atoms, in a further embodiment from about 0.00025 M to about 0.6 M of tin atoms, and in a further embodiment from about 0.01 M to about 0.40 M of tin atoms. This solution can be applied to the substrate by spin coating or other suitable techniques. Those skilled in the art will recognize that further ranges of concentrations within the explicitly stated ranges above are contemplated and that they fall within the scope of the present disclosure. Generally, the precursor solution can be thoroughly mixed using a suitable mixing device to form the appropriate amount of material. Appropriate filtration can be used to remove contaminants, small particles and other components that do not dissolve properly.

[0020] A coating material can be formed by depositing a precursor solution on a selected substrate and performing subsequent processes. The substrate generally provides a surface on which the coating material can be deposited, and the substrate can include a plurality of layers associated with the top layer in the surface. Suitable substrate surfaces can include any suitable material. Some substrates of particular interest include inorganic materials such as silicon wafers, silica substrates, other ceramics, organic polymers, their composite materials, and combinations thereof, across the surface of the substrate and / or in the layers of the substrate. Wafers such as relatively thin cylindrical structures can be convenient, but any suitable shaped structure can be used. Substrates having a polymer layer on a polymer substrate or non-polymer structure may be desirable for certain applications based on lithography performance or the cost and flexibility of the substrate, and suitable polymers can be selected based on the relatively low processing temperatures that can be used for the processing of the patternable materials described herein. Suitable polymers can include, for example, polycarbonate, polyimide, polyester, polyalkene, their copolymers, or mixtures thereof. Generally, especially for high-resolution applications, it is desirable for the substrate to have a flat surface. However, in certain embodiments, for certain pattern formation applications, the substrate can have a substantial topography where filling or planarization of features by a resist coating is intended.

[0021] Formation of coating Generally, a precursor can be supplied to a substrate using any suitable solution or vapor-phase coating method. Suitable coating methods include, for example, spin coating, spray or aerosol coating, dip coating, slot die coating, knife edge coating, printing methods such as inkjet printing and screen printing, and deposition of volatilized compounds, vapor deposition such as chemical vapor deposition (CVD) or atomic layer deposition (ALD). In some of these coating methods, a pattern of the coating material is formed during the coating process, but currently, the resolution obtained by printing, etc. is much lower than the resolution obtained by radiation-based patterning as described herein. The thickness of the layer deposited as a result can be adjusted by using coating parameters and adjusting the solution concentration. The dry coating thickness is determined by the undried coating thickness and concentration.

[0022] When pattern formation is performed by radiation-based lithography, spin coating can be a desirable method for uniformly covering a substrate, but this uniformity can be impaired by the formation of beads near the edges of the substrate. In some embodiments, the substrate can be rotated at a speed of about 500 rpm to about 10,000 rpm, in further embodiments about 1000 rpm to about 7500 rpm, and in further embodiments about 2000 rpm to about 6000 rpm. The rotation speed can be adjusted so that a desired coating thickness is obtained. Spin coating can be performed for a time of about 5 seconds to about 5 minutes, and in further embodiments about 15 seconds to about 2 minutes. An initial low-speed rotation, for example 50 to 250 rpm, can be used to first spread the entire composition across the substrate. The edge beads can be removed by performing a backside rinse, an edge bead removal step, etc. using a suitable organic solvent. Those skilled in the art will appreciate that additional ranges of spin coating parameters within the explicitly stated ranges are contemplated and that they will fall within the scope of the present disclosure. The cleaning of the bead edges of the organometallic pattern-forming material is described in U.S. Patent No. 10,627,719 to Waller et al., entitled "Methods Of Reducing Metal Residue In Edge Bead Region From Metal-Containing Resists", which is incorporated herein by reference.

[0023] Regarding vapor-based deposition, some compounds can be heated in an inert atmosphere to achieve an appropriate vapor pressure for forming a desired thin coating. The substrate surface can be placed at an appropriate close position to receive the vapor of the compound. The heating for forming the volatile compound can exceed 400 °C and can be 450 °C to 1000 °C in some embodiments. Those skilled in the art will recognize that additional ranges of temperatures within the explicitly stated ranges above are contemplated and that they fall within the scope of this disclosure. Alternatively or in addition, vapor deposition can be performed using chemical vapor deposition or atomic layer deposition. Atomic layer deposition is basically a stepwise CVD deposition in which a layer of an organotin trihalide is deposited and then reacted with a gas of hydrogen sulfide (or selenide), and then this is repeated to obtain the desired coating thickness. These reactive deposition methods can be realized using the vapor of an organotin trihalide together with a gaseous hydrogen sulfide (or hydrogen selenide). These deposition methods can be carried out in an appropriate CVD reaction chamber or the like.

[0024] The coating process itself can result in the evaporation of some of the solvent and / or the movement of the solution to stimulate evaporation, since many coating processes form droplets or other forms of the coating material over a larger surface area. As the solvent decreases, the concentration of the chemical species in the material increases, so the viscosity of the coating material tends to increase. One of the purposes during the coating process can be to remove enough solvent to stabilize the coating material for further processing. The coating species can react with air, hydrolyze, or condense during the coating or subsequent heating to form a chemically modified coating material.

[0025] To select process conditions effective for a patterning process, generally, an empirical evaluation of the properties of the resulting coating material can be performed. Although heating may not be necessary for the process to be used without problems, heating of the coated substrate may be desirable to facilitate the process and / or enhance the reproducibility of the process and / or promote the vaporization of volatile by-products. In embodiments where heat is applied to evaporate the solvent during the pre-exposure bake, the coating material can be heated to a temperature of about 45 °C to about 250 °C, and in further embodiments about 55 °C to about 225 °C. Heating for removing the solvent can generally be carried out over at least about 0.1 minute, in further embodiments about 0.5 minute to about 30 minutes, and in further embodiments about 0.75 minute to about 10 minutes. The final film thickness is determined by the baking temperature and time and the initial concentration of the precursor. In the example, a linear relationship between the film thickness and the precursor concentration is shown. Those skilled in the art will recognize that further ranges of heating temperature and time within the explicitly stated ranges above are contemplated and that they fall within the scope of the present disclosure. As a result of the heat treatment of the coating material, possible hydrolysis and densification, the coating material can exhibit an increase in refractive index and an increase in radiation absorption without substantially reducing the contrast in dissolution rate.

[0026] The undried coating thickness is determined by the deposition process. For further processing, the solvent is generally removed, leaving a solid layer as the coating on the substrate. The solution concentration and process conditions affect the dried coating thickness, and by selecting this, the desired patterning characteristics can be realized. The average dried coating thickness can be about 2 nm to about 1000 nm, in further embodiments about 3 nm to about 300 nm, and in further embodiments about 3 nm to about 80 nm. In the case of vapor deposition described later, the coating thickness can be adjusted correspondingly according to the process conditions to achieve the desired layer thickness of the coating. Those skilled in the art will recognize that further ranges of average thickness within the explicitly stated ranges above are contemplated and that they fall within the scope of the present disclosure.

[0027] Pattern formation After drying and possible hydrolysis, a fine pattern can be formed in the coating material using radiation. As described above, the composition of the precursor solution and thus the corresponding composition of the coating material can be designed so that the desired form of radiation (EUV radiation is of particular interest) is sufficiently absorbed. Absorption of the radiation provides energy that can break the bond between the metal and the alkyl ligand, such that at least some of the alkyl ligands are no longer available to stabilize the material so that tin sulfide / selenide is formed. Instead, absorption of the high-energy radiation can initiate a coupling (polymerization) reaction between the unsaturated centers in the R ligands bonded to adjacent tin sulfide / selenide clusters. Having alkyl tin ligands in the sulfide clusters may make the radiation-induced modification less distinct, but the composition is confirmed to provide good pattern formation properties. Radiation decomposition products such as alkyl ligands or other fragments may or may not diffuse from the film, depending on the process variables and the nature of such products. When a sufficient amount of radiation is absorbed, the exposed coating material condenses, i.e., forms a network with increased cross-linking, which may contain additional water absorbed from the ambient atmosphere. The radiation can generally be supplied by a selected pattern. The radiation pattern is transferred into a corresponding pattern or latent image of radiation-irradiated regions and non-radiation-irradiated regions in the coating material. The radiation-irradiated regions contain the chemically changed coating material, and the non-radiation-irradiated regions generally contain the coating material as formed. The coating material can be developed to remove the non-radiation-irradiated coating material or selectively remove the radiation-irradiated coating material to form a very smooth edge.

[0028] Radiation can generally be directed at a substrate coated through a mask or the radiation beam can be controllably scanned across the substrate. Generally, radiation can include electromagnetic radiation, an electron beam (beta rays), or other suitable radiation. Generally, electromagnetic radiation can have a desired wavelength or wavelength range such as visible light, ultraviolet light, extreme ultraviolet light, or X-ray radiation. The resolution achievable with a radiation pattern generally depends on the radiation wavelength, and higher resolution patterns can generally be achieved using shorter wavelength radiation. Thus, it may be desirable to use ultraviolet light, extreme ultraviolet light, or X-ray radiation or electron beam irradiation, particularly to achieve particularly high resolution patterns.

[0029] According to the international standard ISO 21348 (2007) incorporated herein by reference, ultraviolet light extends over wavelengths of 100 nm or more and less than 400 nm. A krypton fluoride laser can be used as a light source for 248 nm ultraviolet light. The ultraviolet range can be further divided in several ways based on approved standards, such as extreme ultraviolet (EUV) from 10 nm or more to less than 121 nm and far ultraviolet (FUV) from 122 nm or more to less than 200 nm. The 193 nm line from an argon fluoride laser can be used as a radiation source for FUV. 13.5 nm EUV light is used in lithography and this light is generated from a Xe or Sn plasma source excited using a high energy laser or a discharge pulse. Soft X-rays can be defined from 0.1 nm or more to less than 10 nm.

[0030] The amount of electromagnetic radiation can be characterized by the fluence or dose defined by the radiation flux integrated over the exposure time. Generally, a suitable EUV radiation fluence is about 1 mJ / cm 2 ~ about 175 mJ / cm 2 , and in further embodiments about 2 mJ / cm 2 ~ about 150 mJ / cm 2 , and in further embodiments about 3 mJ / cm 2 ~ about 125 mJ / cm 2It is possible. Those skilled in the art will consider further ranges of radiation fluence within the above-specified ranges and will recognize that they are within the scope of the present disclosure.

[0031] Based on the design of the coating material, a large contrast in the properties of the material can be induced between the radiation-irradiated region and the non-radiation-irradiated region of the coating material. In the case of an embodiment where post-radiation heat treatment is used, the post-radiation heat treatment can be carried out at a temperature of about 45°C to about 250°C, in a further embodiment about 50°C to about 190°C, and in a further embodiment about 60°C to about 175°C. The heating after exposure can generally be carried out over at least about 0.1 minute, in a further embodiment about 0.5 minute to about 30 minutes, and in a further embodiment about 0.75 minute to about 10 minutes. Those skilled in the art will consider further ranges of the heating temperature and time after radiation within the above-specified ranges and will recognize that they are within the scope of the present disclosure. Due to this high contrast in the properties of the material, as described in the following section, the formation of high-resolution lines with smooth edges in the pattern after development becomes easier.

[0032] In the case of negative image formation, the developer can be an organic solvent such as the solvent used for the formation of the precursor solution. Generally, the selection of the developer can be affected by the solubility parameters for both the radiation-irradiated and non-radiation-irradiated coating materials, as well as the volatility, flammability, toxicity, viscosity of the developer, and potential chemical interactions with other process materials. In particular, suitable developers include, for example, ethyl lactate, ethers (e.g., tetrahydrofuran (THF), dioxane, anisole), ketones (e.g., 2-pentanone, 3-pentanone, hexanone, 2-heptanone, octanone), etc. It is demonstrated in the examples that THF and THF-anisole mixtures are preferred developers. Development can be carried out over about 5 seconds to about 30 minutes, in a further embodiment about 8 seconds to about 15 minutes, and in a further embodiment about 10 seconds to about 10 minutes. Those skilled in the art will consider further ranges within the above-specified ranges and will recognize that they are within the scope of the present disclosure.

[0033] In addition to the main developer composition, the developer can include additives to facilitate the development process. Suitable additives can include, for example, viscosity modifiers, solubilizing aids, or other processing aids. If optional additives are present, the developer can include up to about 20 weight percent of additives, in a further embodiment up to about 10 weight percent of additives, and in a further embodiment up to about 5 weight percent of additives. Those skilled in the art will recognize that additional ranges of additive concentrations within the explicitly stated ranges above are contemplated and that they fall within the scope of this disclosure.

[0034] When using a weaker developer with a slower development rate for the coating, a higher temperature development process can be used to increase the speed of the process. When using a stronger developer, the development rate can be decreased and / or the temperature of the development process can be decreased to control the reaction rate. Generally, the development temperature can be adjusted between suitable values compatible with the volatility of the solvent. Additionally, a developer having dissolved coating material near the developer-coating interface can be dispersed using sonication during development.

[0035] The developer can be applied to the patterned coating material using any suitable method. For example, the developer can be sprayed onto the patterned coating material. Spin coating can also be used. In the case of automated processing, in a stationary mode, a paddle method involving pouring the developer onto the coating material can be used. Optionally, spin rinsing and / or drying can be used to complete the development process. Suitable rinse solutions can include, for example, ultrapure water, aqueous tetraalkylammonium hydroxide, methyl alcohol, ethyl alcohol, propyl alcohol, and combinations thereof. After development of the image, the coating material is disposed on the substrate as a pattern.

[0036] After the development step, the coating material can be heat-treated for further condensation of the material and further dehydration, densification, or removal of residual developer from the coating. This heat treatment may be particularly desirable in embodiments where the coating material is incorporated into the final device, but may also be desirable in cases where stabilization of the coating material is desired to facilitate further patterning, in some embodiments where the coating material is used as a resist and is ultimately removed. In particular, baking of the patterned coating material can be performed 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 80 °C to about 600 °C, in further embodiments about 175 °C to about 500 °C, and in further embodiments about 200 °C to about 400 °C. The heating can be carried out for at least about 1 minute, in another embodiment about 2 minutes to about 1 hour, and in further embodiments about 2.5 minutes to about 25 minutes. The heating can be carried out in air, in vacuum, or in an inert gas environment such as Ar or N2. Those skilled in the art will recognize that further ranges of heat treatment temperature and time within the explicitly stated ranges above are contemplated and are within the scope of the present disclosure. Similarly, non-thermal treatments such as blanket UV exposure or exposure to an oxidative plasma such as O2 can be used for similar purposes.

[0037] Wafer throughput is a substantial limiting factor for implementing EUV lithography in high-volume semiconductor manufacturing, which is directly related to the dose required for patterning a given feature. However, although there are chemical strategies for reducing the imaging dose, in the case of EUV photoresists at <50 nm feature sizes and pitches, a negative correlation is generally observed between the imaging dose required to print the target feature and feature size uniformity (such as LWR), thereby limiting the operability of the final device and wafer yield. The patterning ability can be represented by the dose-to-gel value. The required imaging dose can be evaluated by forming a number of exposed pads with the exposure time varying stepwise between pads to vary the exposure dose. Next, the film can be developed, and the remaining resist thickness of all pads can be evaluated, for example, using spectroscopic ellipsometry. The measured thickness can be normalized with respect to the maximum measured resist thickness and plotted against the logarithm of the exposure dose to form a characteristic curve. The maximum slope of the normalized thickness versus log dose curve is defined as the photoresist contrast (γ), and the dose value at which the tangent drawn through this point becomes 1 is defined as the photoresist dose-to-gel (Dg). D0 corresponds to the starting dose for the initial increase in the film thickness of a negative resist. The common parameters used for such photoresist characterization can be estimated according to Mack, C. (Fundamental Principles of Optical Lithography, John Wiley & Sons, Chichester, U.K; pp271-272, 2007, incorporated herein by reference).

Example

[0038] Example 1. Preparation of the precursor (C4H9Sn)4S6 This example shows the synthesis of an n-butyltin sulfide cluster composition.

[0039] Sodium sulfide (17.9 g, 230 mmol, Alfa Aesar, 95%) was added to a round-bottom flask (500 mL) equipped with a magnetic stirrer. Next, THF (150 mL, Aldrich) was added to this flask to dissolve the sodium sulfide. The resulting solution was cooled to -78 °C, and then a solution of n-butyltin trichloride (38.1 g, 135.0 mmol, Aldrich, 95%) in THF (60 mL) was added dropwise thereto. The mixed solution formed a slurry, which was stirred at room temperature for 16 h and then filtered through a short plug of Celite®. The resulting filtrate was dried under reduced pressure and subsequently dissolved in dichloromethane. The solution was filtered through a silica plug and further eluted with dichloromethane. Removal of the solvent and other volatile components under reduced pressure yielded an amorphous solid, which was triturated with pentane, collected by filtration, and dried under reduced pressure to give (C4H9)4Sn4S6 (21.02 g, 69.5%) as a white amorphous solid.

[0040] Figure 2 shows the 119 Sn{ 1 H} NMR spectrum of (C4H9Sn)4S6 in benzene-d6. This spectrum shows one peak at -144.3 ppm due to the four tin atoms in an equivalent bonding environment. The benzene-d6 solvent had a resonance at -149 MHz.

[0041] Figure 3 shows the 1The \(^1H\) NMR spectrum is shown. This spectrum shows a resonance at -1.63 ppm (\(J = 7.6\) Hz) and a septet at -1.29 ppm (\(J = 7.2\) Hz). The integration ratio is 1:1, and each resonance pattern corresponds to the eight - \(CH_2\) - hydrogens of the butyl ligand. The spectrum shows a triplet at -1.46 ppm (\(J = 7.8\) Hz), which corresponds to the - \(CH_2\) - proton closest to the tin atom, and a triplet at -0.80 ppm (\(J = 7.3\) Hz), which corresponds to the - \(CH_3\) proton. The integration ratio is 1:1.5, corresponding to a total of eight \(\alpha\) - \(CH_2\) - protons and a total of twelve - \(CH_3\) protons. The toluene - \(d_8\) solvent had resonances at -500 MHz.

[0042] Figure 4 shows the \(^{13}C\) NMR spectrum of \((C_4H_9Sn)_4S_6\) in benzene - \(d_6\). 13 The \(^{13}C\) NMR spectrum is shown. This spectrum shows singlets at -29.80 ppm, -27.43 ppm, and -26.13 ppm, corresponding to the - \(CH_2\) - carbons in the butyl ligand, respectively. This spectrum shows a singlet at -13.64 ppm, which corresponds to the - \(CH_3\) carbon. The benzene - \(d_6\) solvent had resonances at -101 MHz.

[0043] This characterization confirmed the synthesis of the purified n - butyltin cluster - composition product R1.

[0044] Example 2: Preparation of the precursor \((C_4H_7Sn)_4S_6\) This example shows the synthesis of an n - butenyltin cluster composition.

[0045] n - Butenyltin trichloride was prepared by reacting 1 part of \((C_4H_7)_4Sn\) with 3 parts of \(SnCl_4\). These procedures were adapted from the method of U.S. Patent No. 2,873,288 and Schumann, Herbert; Aksu, Yilmaz; Wassermann, Birgit C. Journal of Organometallic Chemistry 691(8), 1703 - 1712(2006).

[0046] (C 4 H 7 ) 4 Synthesis of Sn A reflux condenser and a nitrogen inlet were attached, and THF (500 ml) was added to a three-necked flask equipped with a large magnetic stir bar and freshly cut magnesium turnings (42.8 g, 1.7 mol). The solution was heated to reflux and stirred for 15 minutes. The heat source was removed, and upon addition of a small amount of 3-butenyl bromide (ca. 5 mL), the mixture refluxed. Further, 3-butenyl bromide (125 g, 0.93 mol) was added dropwise while maintaining gentle reflux. After the addition was complete, the resulting 3-butenyl Grignard solution was heated at reflux for 1 hour. The solution was cooled and then stirred at room temperature for 12 hours. Instead, a solution of SnCl4 (5.4 g, 0.22 mol) in THF (400 ml) was carefully prepared by adding SnCl4 dropwise to a cooled (-78 °C) solution of THF. (Note: A large amount of gas evolution, presumably due to the formation of HCl(g) by hydrolysis of SnCl4, can occur when SnCl4 is added to THF). The previously prepared 3-butenyl Grignard solution was added dropwise to the cooled solution of SnCl4. After the addition was complete, the solution was warmed to room temperature and stirred for 12 hours. Next, the solution was concentrated to half its volume and pentane (200 mL) was added. The resulting slurry was filtered through Celite® and concentrated under reduced pressure. The residue was placed on a short plug of silica gel (200 g) and eluted with pentane. Removal of volatiles under reduced pressure gave the desired product (C4H7)4Sn (49 g, 51%) as a colorless liquid and was confirmed by NMR as follows. 119 Sn NMR (186 MHz, chloroform-d) δ -5.64 (s, 1Sn). 1 H NMR (500 MHz, chloroform-d) δ 5.87 (ddt, J = 16.6, 10.1, 6.3 Hz, 4H, Sn-butenyl=CH), 5.01 (dq, J = 17.1, 1.8 Hz, 4H, Sn-butenyl=CH), 4.93 (dq, J = 10.1, 1.5 Hz, 4H, Sn-butenyl=CH), 2.37 - 2.18 (m, 8H, Sn-butenyl-CH2), 1.04 - 0.87 (m, 8H, Sn-butenyl-CH2).

[0047] (C 4 H 7 ) 4 Sn and SnCl 4 Synthesis of n-butenyltin trichloride by reaction of A Schlenk flask was charged with (C4H7)4Sn (10 g, 29.5 mmol) and dissolved by dropwise addition of toluene (25 ml). SnCl4 (25.13 g, 96.5 mmol) was added dropwise. The resulting mixture was stirred at room temperature for 2 hours, and then Cl2Pt(PPh3)2 (0.01 g, 0.013 mmol) was added. The mixture was then 119 The mixture was heated at 110°C for approximately 12 hours until Sn NMR spectroscopy showed complete conversion to the desired product. The mixture was cooled to room temperature and filtered through a short plug of silica, which was washed three times with 20 mL portions of toluene. The filtrate was collected and the volatiles were removed under reduced pressure. The product was distilled to give a colorless oil with a boiling point of 40-75°C and a vapor pressure of 1-0.3 torr, which corresponded to the desired product (C4H7)SnCl3 (24.71 g, 88.2 mmol, 68.5% yield), as confirmed by NMR as follows: 119 Sn NMR (149MHz, chloroform-d δ 2.71(s,1Sn). 1 H NMR (400 MHz, chloroform-d) δ 5.92 (ddt, J = 16.7, 10.1, 6.4 Hz, 1H, Sn-butenyl = CH2), 5.27 (q, J = 1.4 Hz, 1H, Sn-butenyl = CH), 5.25-5.20 (m, 1H, Sn-butenyl-CH), 2.67 (qt, J = 6.8, 1.4 Hz, 2H, Sn-butenyl-CH2), 2.45 (t, J = 7.2 Hz, 2H, Sn-butenyl-CH2).

[0048] (C 4 H 7 Sn) 4 S 6 Synthesis ofSodium sulfide (17.9 g, 230 mmol, Alfa Aesar, 95%) was added to a round-bottom flask (500 mL) equipped with a magnetic stirrer. Next, THF (150 mL) was added to this flask, and the resulting solution was cooled to -78 °C. A solution of (C4H7)SnCl3 (37.8 g, 135.0 mmol) in THF (60 mL) was added dropwise to the cooled sodium sulfide solution described above. The resulting slurry was stirred at room temperature for 16 hours and filtered through a short plug of Celite®. The filtrate was dried under reduced pressure and dissolved in dichloromethane. The resulting solution was filtered through a silica plug. This silica plug was washed with additional dichloromethane, and the resulting dichloromethane solution was mixed with the original filtrate. Removal of the solvent and volatile components under reduced pressure gave an amorphous solid, which was triturated with pentane, collected by filtration, and dried under reduced pressure to give (C4H7Sn)4S6 (18.0 g, 60.1%) as a white solid.

[0049] Figure 5 shows the 119 119Sn NMR spectrum of (C4H7Sn)4S6 in chloroform-d. This spectrum shows one peak at -141.64 ppm corresponding to four tin atoms in an equivalent bonding environment. The chloroform-d solvent had a resonance at -149 MHz.

[0050] Figure 6 shows the 1The ¹H NMR spectrum is shown. This spectrum shows a ddt pattern (J = 16.6, 10.1, 6.3 Hz) at -5.89 ppm corresponding to one of the =CH₂ hydrogens of each of the four butenyl ligands. This spectrum also shows a multiplet at -5.12 to -5.04 ppm corresponding to another =CH₂ hydrogen of each of the four butenyl ligands. This spectrum shows a quartet (J = 1.6 Hz) at -5.15 ppm corresponding to the four =CH hydrogens. This spectrum shows a multiplet and a triplet (J = 7.8 Hz) at -2.79 to -2.32 ppm where each pattern corresponds to eight -CH₂- hydrogens and shows an integration of 1:1. The chloroform-d solvent had resonances at -400 MHz.

[0051] Figure 7 shows the ¹³C NMR spectrum of (C₄H₇Sn)₄S₆ in benzene-d₆. 13 The ¹³C NMR spectrum is shown. This spectrum shows a singlet at -138.40 ppm corresponding to the =CH carbon of the butenyl ligand. The singlet at -116.05 ppm corresponds to the =CH₂ carbon. The singlets at -29.02 ppm and -28.70 ppm correspond to the bonding environments of the two -CH₂- carbons. The benzene-d₆ solvent had resonances at -101 MHz.

[0052] This characterization confirmed the synthesis of the purified n-butenyltin cluster composition product R₂.

[0053] Example 3. Preparation of Precursor Solutions of (C₄H₉Sn)₄S₆ and (C₄H₇Sn)₄S₆ This example shows the preparation of precursor solutions having either an n-butyltin cluster composition or an n-butenyltin cluster composition. These solutions were prepared using six solvents and one of a range of tin concentrations.

[0054] A photoresist precursor solution was prepared by adding 0.17 g of (C₄H₉Sn)₄S₆ of Example 1 to 20 mL of toluene. This mixture was gently heated to form a visually clear, transparent, stable, and homogeneous solution. Diagnosis 1 ¹H and119 Sn NMR resonance indicates that this solution contains the tetramer (n-butylSn)4S6. Further toluene solutions with tin concentrations of 64 - 288 mM were easily prepared by this method. Solutions using the solvents THF, chlorobenzene, 1,1,2-trichloroethane, perfluorobenzene, and pentafluorobenzene were also prepared in a similar manner. The tin concentrations in these solutions range from 1 - 150 mM.

[0055] A photoresist precursor solution was prepared by adding 0.17 g of (C4H7Sn)4S6 of Example 2 to 20 mL of toluene. This mixture was gently heated to form a clear solution. Throughout all periods of the aforementioned film deposition, the solution remained clear. Diagnosis 1 H and 119 Sn NMR resonance indicates that this solution contains the tetramer (n-butenylSn)4S6. Further toluene solutions with tin concentrations of 64 - 288 mM were easily prepared by this method. Solutions using the solvents THF, chlorobenzene, 1,1,2-trichloroethane, perfluorobenzene, and pentafluorobenzene were also prepared in a similar manner. The tin concentrations in these solutions range from 1 - 150 mM.

[0056] Example 4. Wafer Coated with a Film This example shows the fabrication of a wafer coated with a film, demonstrating that thin and smooth films can be deposited with cluster compositions of both n-butyltin and n-butenyltin.

[0057] A silicon wafer (10.2 cm in diameter) with a natural oxide surface was used as a substrate for thin film deposition. Unless otherwise indicated, a toluene-based precursor solution prepared as described in Example 3 was spin-coated onto the untreated wafer at 1500 rpm for 30 seconds to deposit a film on the untreated wafer. In some cases, the wafer was pretreated by wetting it with a casting solvent if it was useful for obtaining a good coating. In particular, a precursor solution of (C4H9Sn)4S6(R1) in toluene having a tin concentration of 75 mM was spin-coated onto the wafer at 1500 rpm for 30 seconds to prepare a film sample (F1) having a film thickness of 176 nm. A second precursor solution of (C4H7Sn)4S6(R2) in toluene having a tin concentration of 75 mM was spin-coated onto the wafer at 1500 rpm for 30 seconds to prepare a film sample having a film sample (F2) with a thickness of 188 nm. Figure 8 shows curve a of the FTIR spectrum of the powder of R1 and curve b of the FTIR spectrum of the film sample F1. The results indicate that the characteristic alkane C-H stretching absorption at 3000 - 2850 cm -1 and the deformation angle absorption at 1470 - 1450 cm-1 are maintained. However, the film shows different absorption in the range of 1600 - 500 cm -1 , suggesting a spatial change in the structure of the Sn-S cage. Figure 9 shows curve a of the FTIR spectrum of the powder of R2 and curve b of the FTIR spectrum of the film sample F2. These results indicate that the characteristic alkane and alkene C-H stretching absorptions at 3100 - 2850 cm -1 are maintained.

[0058] The wafer coated with a 23.68 nm thick film of (C4H9Sn)4S6 showed a root mean square surface roughness of 0.7 nm as measured by atomic force microscopy. Similarly, the wafer coated with a 21.1 nm thick film of (C4H7Sn)4S6 showed a surface roughness of 0.4 nm. These results indicate that a tin cluster composition can be deposited as a relatively smooth film.

[0059] A set of film samples was prepared from a precursor solution of toluene and (C4H9Sn)4S6 cluster compositions at various concentrations. Figure 10 shows the linear dependence of the film thickness on the concentration of R1. A second set of film samples was prepared from a precursor solution of toluene and (C4H7Sn)4S6 cluster compositions at various concentrations. Figure 11 shows the linear dependence of the film thickness on the concentration of R2. These results indicate that tin cluster compositions can be deposited with a well-controlled thickness on the nanometer scale.

[0060] Example 5. Negative Image Formation Using UV Exposure This example shows that UV radiation can induce a negative dissolution contrast in films made from cluster compositions of n-butyltin and n-butenyltin.

[0061] The film samples F1 and F2 prepared as described in Example 4 were placed in a box lined with aluminum foil in a glove box filled with argon. The compartments of the film samples F1 and F2 were exposed to laboratory UV light, and radiation with a wavelength of approximately 354 nm was uniformly supplied to all samples for several minutes to obtain an appropriate dose, resulting in film samples F1 and F2 having exposed and unexposed film regions, respectively. Next, the film samples were developed by immersing them in a mixture of anisole and THF for 30 seconds. For each anisole:THF mixture, the film thicknesses of the exposed and unexposed compartments of each film sample were measured using a J.A.Woollam M-2000 spectroscopic ellipsometer. The normalized film thickness was calculated by dividing the thickness of the developed compartment by the average thickness of the film before the development step.

[0062] Figure 12 shows the normalized film thickness of the unexposed section of film F1 as a function of the volume fraction of anisole in THF. This plot shows that the unexposed film of (C4H9Sn)4S6 completely dissolves in each developer composition after 30 seconds. Figure 13 shows the normalized film thickness of the UV-exposed section of film F1 as a function of the volume fraction of anisole in THF. This plot shows that more than 70% of the film thickness is maintained after 30 seconds of development. These data indicate that a change in dissolution rate occurs after UV exposure, that is, a chemical change is induced by UV exposure and a latent image is formed.

[0063] Figure 14 shows the normalized film thickness of the unexposed section of film F2 as a function of the volume fraction of anisole in THF. This plot shows that the unexposed film of (C4H7Sn)4S6 dissolves in anisole in THF from 0 to 40%. In 60 - 100 volume% of anisole, the dissolution of the unexposed R2 composition decreases with an increase in the volume percentage of anisole. Figure 15 shows the normalized film thickness of the UV-exposed section of film F2 as a function of the volume fraction of anisole in THF. This plot shows that the exposed film of (C4H7Sn)4S6 maintains 97 - 99% of its original thickness in all developer compositions tested.

[0064] All of these data indicate that UV exposure of the films of (C4H9Sn)4S6 and (C4H7Sn)4S6 causes a chemical change that alters the dissolution rate. Exposure and subsequent dissolution in a mixed solution of anisole and THF reveal that these films are negative photoresists.

[0065] Example 6. Solubility Contrast by EUV Exposure This example shows the solubility contrast of the film of Example 3 after exposure to EUV radiation.

[0066] On a silicon wafer with a diameter of 10.2 cm having a natural oxide surface, a film was deposited as described in Example 4. Precursor solutions of (C4H9Sn)4S6 and (C4H7Sn)4S6 were prepared at appropriate concentrations for the deposition of films R1 and R2 of each about 20 nm thickness. In the contrast curves shown in FIGS. 16 and 17, the film thickness was in the range of 20.6 nm to 22.9 nm.

[0067] The film was exposed on an EUV Direct Contrast Tool at Lawrence Berkeley National Laboratory. Before exposure, the film was baked at 100 °C for 2 minutes. A linear array of 50 circular exposure regions with a diameter of about 500 μm was projected onto the wafer using increasing UV exposure doses. After exposure, the film was developed with 2-heptanone, THF, a 20% (v / v) mixture of anisole in THF, or a 40% (v / v) mixture of anisole in THF. The film was developed either with or without a post-exposure bake at 100 °C for 2 minutes. The thickness of each exposed pad was evaluated with a J.A.Woollam M-2000 spectroscopic ellipsometer. The normalized thickness of each pad as a function of EUV dose is plotted in FIGS. 16 and 17 for various process conditions (curves a - k). In the unexposed and low-dose regions, the normalized film thickness is approximately 0. When each film shows the combined effect of exposure dose and developer composition on solubility contrast, the curve rises to a maximum value (dose-to-gel, D -2 exceeding 7 mJcm g ).

[0068] Table 1 summarizes the process conditions, developer composition, and the resulting values (D o , Dg, and contrast) for each composition, (C4H9Sn)4S6 (R1) and (C4H7Sn)4S6 (R2). Curves a - k are shown in FIGS. 16 and 17.

[0069]

Table 1

[0070] The results show that EUV exposure of the films of (C4H9Sn)4S6 and (C4H7Sn)4S6 causes chemical changes that alter the dissolution rate. The exposure and subsequent processing show that good solubility contrast can be achieved for compositions R1 and R2. Under the tested process conditions, the maximum contrast was achieved by developing in THF after the bake step. Without the bake step, for the R1 composition, better contrast was obtained with 20% (v / v) anisole in THF than with THF. For the R2 composition without the bake step, better contrast was obtained with the THF developer.

[0071] The above embodiments are intended to be illustrative and not limiting. Further embodiments are within the scope of the claims. Furthermore, although the 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. Any incorporation by reference of the above documents is limited so that no subject matter contrary to the disclosed disclosure is incorporated. To the extent that a particular structure, composition, and / or process is described herein within the scope with components, elements, ingredients, or other classifications, the disclosure, unless otherwise specified, includes particular embodiments, the above particular components, elements, ingredients, other classifications, or combinations thereof, and further features that do not change the basic nature of the subject matter as suggested in the discussion. It should be understood to include embodiments that consist essentially of such particular components, ingredients, or other classifications or combinations thereof.

Claims

1. A method for forming a coated substrate, the method comprising: heating an organotin composition represented by the formula (RSn) 4 X 6 to form a volatilized organotin composition; depositing the volatilized organotin composition on a surface of a substrate to form a radiation-sensitive layer on the substrate; Including, the radiation-sensitive layer has an average thickness of from 2 nm to 1 micron; R is an organic ligand having 1 to 15 carbon atoms, said organic ligand being bonded to Sn with a metal-carbon bond, and X is S or Se.

2. The method described in claim 1, wherein the radiation-sensitive layer has an average thickness of 2 nm to 200 nm.

3. The method described in claim 1, wherein the radiation-sensitive layer has an average thickness of 3 nm to 80 nm.

4. The method of claim 1, wherein the thickness of the radiation-sensitive layer at any location across the coated substrate varies by no more than 25% from the average thickness of the layer.

5. The method of claim 1, wherein the heating is carried out at a temperature above 400°C.

6. The method of claim 1, wherein the heating is carried out at a temperature of 450°C to 1000°C.

7. The method of claim 1, wherein the heating, the deposition, or both the heating and the deposition are performed in an inert atmosphere.

8. The method of claim 1, wherein R is an alkyl group, an alkenyl group, an aryl group, or a combination thereof.

9. The method of claim 1, wherein the organotin composition comprises n-butyltin sulfide, n-butenyltin sulfide, or a combination thereof.

10. The method of claim 1, wherein the metal-carbon bond is radiation sensitive.

11. The method of claim 1, wherein the deposition includes physical vapor deposition (PVD), chemical vapor deposition (CVD), or atomic layer deposition (ALD).

12. The method of claim 1, wherein the deposition is performed in a CVD reaction chamber.

13. The method of claim 1, wherein the substrate comprises a silicon wafer.

14. A method described in any one of claims 1 to 13, further comprising irradiating the radiation-sensitive layer with a pattern of EUV radiation to form a latent image comprising irradiated and non-irradiated material.

15. The method of claim 14, wherein the irradiated material comprises crosslinked organotin clusters.

16. The method of claim 14, wherein the EUV radiation has a dose of 1 mJ / cm 2 to 175 mJ / cm 2 .

17. The method of claim 14, wherein the irradiated material has substantially less solubility in organic solvents than the non-irradiated material.

18. The method of claim 14, wherein the latent image has a photoresist contrast of at least 1.5.

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