Stable solutions of monoalkyl tin alkoxides and their hydrolysis and condensation products

Abstract

SOLUTION: Precursor solutions for radiation patternable coatings are formed with an organic solvent and monoalkyl tin trialkoxides, where the water content of the solvent is adjusted to be within 10 percent of a selected value. Generally, the water content of the solvent is adjusted through water addition, although water removal can also be used. In some embodiments, the adjusted water content of the solvent can be from about 250 ppm by weight to about 10,000 ppm by weight.EFFECT: With the appropriate selection of ligands, the adjusted precursor solution can be stable for at least about 42 days, and in some cases at least 8 months.SELECTED DRAWING: None

Description

[Technical Field]

[0001] Related Applications This application claims priority to co-pending U.S. Provisional Patent Application No. 62 / 688,215, filed June 21, 2018, to Jiang et al., entitled "Stable Solutions Of Monoalkyl Tin Alkoxides And Their Hydrolysis And Condensation Products," which is incorporated herein by reference.

[0002] The present invention relates to stable solutions of monoalkyltin alkoxides and their hydrolysis and condensation products, and in particular to compositions of the stable solutions, and methods for making the same. [Background technology]

[0003] Organometallic photoresists, particularly monoalkyltin compositions, are high-performance materials that can produce very high-resolution structures when patterned by lithography. In addition to their high lithographic performance, the high-volume semiconductor manufacturing processes that use these materials also pose practical process requirements for the effective use of these promising materials. It would be useful to identify and resolve the relevant obstacles to achieving the effective commercialization of these materials. Summary of the Invention [Means for solving the problem]

[0004] In a first aspect, the present invention relates to a method for preparing a conditioned precursor solution for a radiation-patternable coating, the conditioned precursor solution comprising a mixture of an organic solvent and a first monoalkyltin trialkoxide (RSn(OR')3) having a tin concentration of about 0.004 M to about 1.0 M. The method generally comprises the steps of combining the organic solvent and the first monoalkyltin trialkoxide to form the conditioned precursor solution, wherein the solvent has been conditioned to have a water content to within ±15 percent of a selected value, and the conditioned water content is 10,000 ppm by weight or less. In some embodiments, the conditioned precursor solution is stable for at least 42 days.

[0005] In a further aspect, the present invention relates to a solution comprising a mixture of an alcohol having a selected water content and a first monoalkyltin trialkoxide (RSn(OR')3), wherein the solution has a tin concentration of from about 0.004 M to about 1.0 M, the selected water content is at least about 250 pm by weight, and the solution is stable for at least 42 days.

[0006] In a further aspect, the present invention relates to a method for patterning a radiation sensitive coating, the method generally comprising: forming a coating on a substrate surface with a precursor solution, the precursor solution having a uniform composition resulting from adjusting the water content of a solvent used to form the adjusted precursor solution to within about ±15% of a target value, the selected water content being between about 300 ppm by weight and about 10,000 ppm by weight; drying the coating; irradiating the dried coating to form a latent image; Includes. DETAILED DESCRIPTION OF THE INVENTION

[0007] Stable solutions of monoalkyltin trialkoxides are formed by controlling the water content of the solvents, particularly alcoholic solvents, used to form the solutions. Under certain storage conditions, monoalkyltin alkoxides and monoalkyltin hydrolysis products may form precipitates when stored for a certain period of time. Exposure to moisture and air can promote the formation of these precipitates as the alkoxides hydrolyze and condense into insoluble species. Monoalkyltin trialkoxides have been established as effective precursors for radiation-sensitive coatings that enable the patterning of fine features, for example, by extreme ultraviolet (EUV) lithography. It is generally desirable for organotin compositions to have sufficient stability, for example, in terms of long-term shelf life and performance consistency. As described herein, the stability of these precursor coating materials can be effectively enhanced by the selection of alkyl ligands and / or by controlling the water content of the solution. In addition to establishing solution stability, stabilized monoalkyltin trialkoxide solutions are expected to achieve reliable reproducibility of coating processing and patterning results. Commercially suitable coating solutions with adequate shelf life and desired reproducibility can be formed in this manner.

[0008] The use of alkylmetal coordination compounds in high performance radiation-based patterning compositions is described, for example, in U.S. Pat. No. 9,310,684 to Meyers et al., entitled "Organometallic Solution Based High Resolution Patterning Compositions" (hereinafter the '684 patent), which is incorporated herein by reference. Improvements in these organometallic compositions for patterning are described in U.S. Patent Application Publication No. 2016 / 0116839 A1 to Meyers et al., entitled "Organometallic Solution Based High Resolution Patterning Compositions and Corresponding Methods," and U.S. Patent No. 10,228,618 A1 to Meyers et al., entitled "Organotin Oxide Hydroxide Patterning Compositions, Precursors, and Patterning" (hereinafter the '618 patent), and co-pending U.S. Patent Application No. 15 / 950,286 to Edson et al., entitled "Monoalkyl Tin Compositions with Low Polyalkyl Contamination, Their Compositions and Methods" (hereinafter the '286 application), each of which is incorporated herein by reference.

[0009] Generally, these alkylmetal compounds are susceptible to gelation and precipitation from solution. For example, hydrolysis of alkoxy ligands can result in a complex distribution of the corresponding products, increasing instability. The '618 patent describes alkyltin precursor solutions that are stable for 1 to 4 weeks. These solutions were prepared by dissolving the hydrolysis and condensation products of RSnX3 (where R = alkyl group, and Sn-X is easily hydrolyzed in aqueous solution) in an organic solvent. The '684 patent describes monoalkyltin oxohydroxo compositions that can be stable for several weeks. Stability can be assessed in terms of the time until a visible solid precipitates from solution. As shown in the examples below, the compositions formulated herein can be stable for a surprising amount of time, even in the presence of some water. In some embodiments, the inventors have discovered that solutions can be prepared containing alcohol, a small amount of water, and monoalkyltin alkoxides, which are mixtures of different alkyl groups. These combinations improve the stability of the solutions to over six months (a longer period when compared to known monoalkyltin solutions exposed to air and water vapor). In some embodiments, the solutions are stable for more than one year.

[0010] The use of organometallic tin compositions as radiation resists for patterning, particularly EUV lithography patterning, is generally based on monoalkyltin oxohydroxo compounds. The oxohydroxo compounds can be prepared in solution, or they can be prepared during and / or following an in situ coating process involving water-based hydrolysis of RSnX3 compounds (where R is an alkyl group and Sn-X is a hydrolyzable group, e.g., an alkoxide group). The discussion herein focuses on precursor compositions used to form alkyltin oxohydroxo compositions that are advantageous for high-resolution patterning.

[0011] Generally, an alkyltin precursor composition is hydrolyzed with water or other suitable reagents under appropriate conditions to form an alkyltin oxohydroxypatterned composition that can be represented by the formula RSnO (1.5-(x / 2)) (OH) x (where 0 < x ≦ 3). The hydrolysis and condensation reactions that can convert a composition having a hydrolyzable Sn-X group are shown in the following reactions: RSnX3 + 3H2O → RSn(OH)3 + 3HX, RSn(OH)3 → RSnO (1.5-(x / 2)) OH x +(x / 2)H2O.

[0012] Monoalkyltin trialkoxide is a suitable precursor compound for forming a monoalkyltin oxohydroxy compound, and monoalkyltin triamide is a suitable precursor for forming monoalkyltin trialkoxide. Current best practices for using these resist compositions include forming a coating of monoalkyltin trialkoxide and hydrolyzing the trialkoxide in situ to form an oxohydroxy composition with volatile alcohol by-products that readily evaporate. The solutions described herein are stable monoalkyltin trialkoxide solutions that can be used commercially effectively to form coatings, which are hydrolyzed in situ during processing and / or in the coating to form monoalkyltin oxide hydroxide compounds for high-performance patterning.

[0013] An alkyltin trialkoxide composition has the formula RSn(OR ’)3, where R and R' are independently hydrocarbyl groups, e.g., alkyl or cycloalkyl, having 1 to 31 carbon atoms, where one or more carbon atoms are optionally substituted with one or more heteroatom functional groups containing O, N, Si, Ge, Sn, Te, and / or halogen atoms, or the alkyl or cycloalkyl is further functionalized with a phenyl or cyano group. In some embodiments, R' can contain ≦10 carbon atoms and can be, for example, methyl, ethyl, propyl, isopropyl, butyl, t-butyl, isobutyl, or t-amyl. The R group can be a linear, branched (i.e., secondary or tertiary at the metal-bonded carbon atom), or cyclic hydrocarbyl group. Each R group individually and generally has 1 to 31 carbon atoms, with 3 to 31 carbon atoms for groups having secondary bonded carbon atoms and 4 to 31 carbon atoms for groups having tertiary bonded carbon atoms. In particular, branched alkyl ligands may be desirable for some patterning compositions, where the compound is R 1 R 2 R 3 CSn(OR')3, where R 1 and R 2 are independently alkyl groups having 1 to 10 carbon atoms, and R 3 is hydrogen or an alkyl group having 1 to 10 carbon atoms. 1 and R 2 can form a cyclic alkyl moiety, R 3 may also graft other groups onto the cyclic moiety. Suitable branched alkyl ligands include, for example, isopropyl (R 1 and R 2 is methyl and R 3 is hydrogen), tert-butyl (R 1 , R 2 and R 3 is methyl), tert-amyl (R 1 and R 2 is methyl and R 3 is -CH2CH3), sec-butyl (R 1is methyl and R 2 is -CH2CH3, and R 3 is hydrogen), neopentyl (R 1 and R 2 is hydrogen and R 3 may be -C(CH3)3), cyclohexyl, cyclopentyl, cyclobutyl, and cyclopropyl. Examples of suitable cyclic groups include, for example, 1-adamantyl (bonded to the metal at a tertiary carbon, -C(CH2)3(CH)3(CH2)3 or tricyclo(3.3.1.13,7)decane) and 2-adamantyl (bonded to the metal at a secondary carbon, -CH(CH)2(CH2)4(CH)2(CH2) or tricyclo(3.3.1.13,7)decane). In other embodiments, the hydrocarbyl group may comprise an aryl or alkenyl group, such as benzyl or allyl, or an alkynyl group. In other embodiments, the hydrocarbyl ligand R may comprise any group consisting exclusively of C and H and containing 1 to 31 carbon atoms. In summary, some examples of suitable alkyl groups attached to tin include, for example, linear or branched alkyl (i-Pr((CH3)2CH-), t-Bu((CH3)3C-), Me(CH3-), n-Bu(CH3CH2CH2CH2-)), cyclo-alkyl (cyclo-propyl, cyclo-butyl, cyclo-pentyl), olefin (alkenyl, aryl, allyl), or alkynyl groups, or combinations thereof. In further embodiments, suitable R groups can include hydrocarbyl groups substituted with heteroatom functional groups, including cyano, thio, silyl, ether, keto, ester, or halogenated groups, or combinations thereof.

[0014] Although alkyltin trialkoxide precursors can be synthesized from the corresponding alkyltin triamides, other synthetic routes can be used, such as those described in the '292 application, where synthesis of monoalkyltin trialkoxides is accomplished from alkyltriamide tin compositions or by reaction of alkyltin trichloride compounds with alcohols, as described in the '618 patent for the formation of methyltin(Ot-butyl)3. Alkyltriamide tin compositions can be represented by the formula RSn(NR''COR''')3. The R groups in the formula for alkyltin triamide tin compositions can be the same R groups summarized above for alkyltin trialkoxide compositions, and the corresponding discussion of these R groups above is as if copied in its entirety in this paragraph. Monoalkyltriamide tin compositions will not be discussed further herein. An improved method for the synthesis of monoalkyltin trialkoxide compounds from monoalkyltin triamide compounds is described in the above-cited '286 application.

[0015] Monoalkyltin triamides suitable for synthesizing the corresponding alkyltin trialkoxides can be synthesized using the synthetic routes of the '292 application, which generally involve replacing the alkyl ligand in the tin tetraamide compound. After purification, the monoalkyltin triamide is reacted with an appropriate alcohol to replace the amide ligand with an alkoxide ligand. For the reaction of the triamide to form the monoalkyltin trialkoxide, the alcohol can be provided in approximately stoichiometric amounts. Since alcohol is used to replace three amide groups, three molar equivalents of alcohol is a stoichiometric amount. Generally, the amount of alcohol can be at least about 5% stoichiometric equivalent, and in further embodiments, at least approximately stoichiometric equivalent, or a large excess of alcohol can be used. To facilitate purification of the product alkyltin trialkoxide, a tetradentate ligand or chelating agent can be added to coordinate with unreacted species to form a complex that does not vaporize during distillation. For example, tris(2-aminoethyl)amine (TREN), triethylenetetramine (TRIEN), or other nonplanar tetradentate chelating agents can be used to complex unreacted species and facilitate purification. The chelating agent can be added in an amount of about 0.5 mol % to about 15 mol %, and in further embodiments, about 1.0 mol % to about 10 mol %, based on the molar amount of tin, at a selected time from the start of the reaction to any time before distillation. Those of skill in the art will recognize that additional ranges of reactant amounts within the explicit ranges above are contemplated and are within the scope of the present disclosure. If desired, fractional distillation can be performed to further purify the monoalkyltin trialkoxide from polyalkyl contaminants.

[0016] Monoalkyltin trialkoxides have two tunable features: the alkyl ligand and the alkoxide ligand. In addition to the requirement that the alkoxide ligand ultimately be hydrolyzed during coating formation and / or prior to irradiation for patterning, the choice of alkoxide ligand can be determined by other considerations, such as process convenience and precursor properties, such as melting point. Hydrolyzed alkoxide ligands form alcohols, and these alcohols should preferably have the appropriate vapor pressure and low boiling point for ready removal following hydrolysis to form patternable coatings.

[0017] As presented in the examples below, the compositions described herein have been found to be stable for well over six weeks, suggesting significantly longer-term stability. Some compositions have been stable for over eight months. These particularly stable compositions are based on monoalkyltin tri(Ot-amyl) compounds. The alkoxy ligand Ot-amyl represents O-CCH3CH3CH2CH3. While other alkoxides can be used to practice the present invention, monoalkyltin t-amyl alkoxide compounds have been found to have desirable properties with respect to preparation, purification, and subsequent manipulation and handling. Solutions containing blends of compounds with different alkoxy ligands can also be used. The selection of the appropriate alkoxy ligand may also be solvent-dependent, but it is expected that other alkoxy ligands should be able to produce at least comparable results.

[0018] The monoalkyl ligand (or monoalkyl ligands) remain attached to the tin atom in radiation-patternable coatings. The monoalkyl ligand is important for the patterning performance of the final coating, and fragmentation of the attached alkyl ligand upon radiation is believed to provide the basis for the patterning process and the high contrast in properties between irradiated and unirradiated portions of the coating. Branched alkyl ligands with secondary or tertiary carbons attached to the tin have been found to provide desirable radiation patterning with EUV light. However, the best patterning results to date have been obtained with blends of two or more alkyl ligands, at least one of which is attached at a secondary or tertiary carbon. As exemplified below, alkyl ligands also affect solution stability. Therefore, selecting the alkyl ligand composition of a solution involves balancing patterning performance and solution stability. Thus, while isopropyltin tri-tert-amyl oxide may achieve the best solution stability, it may not achieve the best patterning performance for certain patterning applications. Therefore, it is generally desirable to explore a variety of alkyl ligands and blends thereof that yield a range of suitably stable solutions while achieving desirable patterning performance.

[0019] Suitable solvents generally include alcohols that are liquid at room temperature. Typically, the solvent is at least 50 weight percent alcohol, with the remaining organic solvent liquid being soluble in the alcohol (e.g., an alkane (e.g., pentane or hexane), an aromatic hydrocarbon (e.g., toluene), an ether (e.g., diethyl ether, C2H5OC2H5), or a mixture thereof). In some embodiments, the solvent is at least 90 weight percent alcohol, and the solvent may effectively be alcohol with only trace impurities of other compounds. Suitable alcohols generally are monomeric alcohols having a melting point of about 10°C or less, such as methanol, ethanol, propanol, butanol, pentanol, hexanol, heptanol, octanol, nonanol, decanol, branched versions thereof, and mixtures thereof. For alcohols with three or more carbon atoms, numerous branched isomers are available. An example is based on branched hexanol, particularly 4-methyl-2-pentanol, which can also be referred to as methyl isobutylcarbinol. Similar results are expected with other alcohols, and although the results are not considered to be specifically alcohol-dependent, certain stabilization may have some quantitative dependence on the alcohol, which can be checked empirically based on the teachings herein.

[0020] Resist precursor compositions can be conveniently specified based on the molar concentration of tin ions. Typically, resist precursor solutions generally contain from about 0.0025 M to about 1 M tin cations, in some embodiments from about 0.004 M to about 0.9 M, and in further embodiments from about 0.005 M to about 0.75 M, and in some embodiments from about 0.01 M to about 1 M, and in further embodiments from about 0.01 M to about 0.5 M tin cations. A person of ordinary skill in the art will recognize that additional concentration ranges and values ​​within the explicit ranges above are contemplated and are within the scope of the present disclosure.

[0021] Monoalkyltin trialkoxides are generally liquid compositions at room temperature that are initially prepared in a properly purified form. For use, these liquids are dissolved in a suitable solvent. Alcoholic solvents have been found to be effective solvents for forming coatings and for forming stable solutions with commercially reasonable shelf lives. The improved solutions described herein have adjusted water levels to achieve a uniform product for commercial use. Naturally, because the compounds are water-sensitive, adjusting the water level has various ramifications that also relate to the stability of the solution.

[0022] For the preparation of a homogeneous solution, the water content is generally determined in the solvent before mixing with the tin composition. Once the mixture is formed, water may react with the tin compound, which can complicate water content assessment. Furthermore, the alkoxy groups associated with the alcohol solvent may also, to some extent, exchange with the alkoxy groups of the tin compound. Generally, the amount of water added to the relevant solution is significantly less than that required to completely hydrolyze the monoalkyltin trialkoxide compound. As long as the resulting solution is stable, there appears to be no harm in partially hydrolyzing the tin compound, which can be beneficial for processing into coatings for radiation patterning. In any case, these tin compounds may be prone to cluster formation, such as trimers and dodecamers, and alcohol solutions are generally known to be complex. The presence of some water can be expected to further exacerbate the complexity of the composition in solution, and some observations of the resulting complexity have been evaluated. As used herein, and as generally understood in the art, references to solutions of organometallic compounds are understood to refer to the corresponding solutions made with the indicated compounds, regardless of their specific form following solution formation.

[0023] For adjusting the water level in a solvent, the starting point is to estimate the water content of the initial organic compound, e.g., alcohol, solvent. An appropriate aliquot of solvent can be sampled from a stock solution of the solvent. While various methods can, in principle, be used to estimate the water content of a sample, Karl Fischer titration is an effective and practical approach. Karl Fischer titrators are commercially available for rapid, automated evaluation. Karl Fischer titrators are available from Mettler-Toledo LLC (OH, USA), Metrohm AG (Switzerland), and CSC Scientific Company (VA, USA). The measured initial water content can be used to adjust the water content of the stock solvent prior to the formation of the organometallic solution.

[0024] Commercially available stock solvents, even those sold at high purity levels, have been found to have significantly varying water contents. Examples of measured water contents are provided in the Examples below. Therefore, the water content of the solvent can be appropriately adjusted to obtain the target water content value.

[0025] In attempting to provide a uniform water content in the solvent, one option is to remove water to a uniform value. Water can be removed, for example, by using a desiccant, such as sodium benzophenone, and molecular sieve-based desiccants, such as zeolites, are considered particularly effective. See, for example, Williams et al., "Drying of Organic Solvents: Quantitative Evaluation of the Efficiency of Several Desiccants," J. Organic Chemistry 2010, 75(24), 8351-8354, incorporated herein by reference. Obtaining extremely low concentrations of water can be an expensive and time-consuming process, compared to adjusting the water content to a set value by adding water. In addition, because alcohol solvents are hygroscopic, particularly strong efforts are then required to prevent access of water from the surrounding environment. Furthermore, since monoalkyltin trialkoxide compositions generally undergo eventual hydrolysis, for example, by adding water, it seems particularly wasteful to expend effort and expense to remove water if not necessary. As discovered herein, small amounts of water can be added to achieve solution uniformity without sacrificing stability to an appropriate level, and the remainder of the discussion will focus on this approach to water content adjustment.

[0026] In this manner, a batch of stock solvent is typically obtained, and an aliquot of the batch is checked for water content. As a general matter, the selected concentration of water is chosen to exceed the range of water concentrations for the solvent grade used, so that the water content can be adjusted by adding water. However, such a selected water content should also be chosen to achieve the desired shelf life for the precursor solution, which depends on the composition of the monoalkyltin trialkoxide. Generally, the amount of water selected will also depend on the concentration of tin in the precursor solution.

[0027] The adjustment of the water level of the solvent can be achieved by adding a targeted amount of purified water to the solvent to achieve the desired water level.Alternatively, the adjustment of the water level of the solvent can be achieved by diluting a portion of the solvent with a given water content into a second portion of the solvent with a different water level from the first.For example, the solvent with a relatively high water content can be diluted into a solvent with a lower water content to achieve the solvent with the desired water content, which can be more convenient from the viewpoint of process to achieve the same result.

[0028] The stability of the precursor solution can be evaluated in terms of changes relative to the initial solution. Specifically, a solution can be described herein as having lost stability if phase separation occurs with the formation of large sol particles, or if visible fine particles are formed, as assessed in a static, unstirred solution. Based on the processing approach described herein, the solution can be stable for at least about 42 days without further mixing, in further embodiments, for at least about 3 months, and in other embodiments, for at least about 6 months. Those skilled in the art will recognize that additional ranges of stabilization times are contemplated and are within the scope of the present disclosure. Suitable solutions can generally be formulated with sufficient stabilization time, allowing the solution to be commercially distributed with a reasonable shelf life.

[0029] In some embodiments, the selected water content can be set to a selected value within a tolerance of about ±15 percent, in some embodiments ±10 percent, in further embodiments ±8%, and in other embodiments ±6%. The tolerance can be expressed as ±50 ppm, in further embodiments ±40 ppm, and in other embodiments ±25 ppm, in terms of the absolute amount of water, although for larger selected water contents, the absolute tolerance can be greater from a practical standpoint. In terms of absolute solvent water content, the solvent can be adjusted to have a water content of about 250 ppm to about 10,000 ppm by weight, in further embodiments about 275 ppm to about 6000 ppm by weight, in other embodiments about 300 ppm to about 5000 ppm by weight, in some embodiments about 300 ppm to about 4000 ppm by weight, and in further embodiments about 300 ppm to about 2500 ppm by weight. The appropriate water content may depend in part on the tin concentration in the adjusted precursor solution; thus, a 0.5 M tin solution may be stable with a water content greater than a 0.05 M tin concentration in the adjusted precursor solution. Solutions with adjusted water content have, or can be designed to have, the stability described in the previous paragraph. Those skilled in the art will recognize that additional ranges of water tolerance or water content within the values ​​set forth above are contemplated and within the scope of the present disclosure.

[0030] The adjusted solution, having the selected water content within a certain tolerance, should then be stored in a sealed container or other location to avoid exposure to ambient air that may alter the water content. With sufficient stabilization, the container of monoalkyltin trialkoxide can be dispensed in the container to a location for performing lithographic patterning.

[0031] As noted above, a monoalkyltrialkoxide solution is used to form a hydrated coating of a monoalkyltin oxohydroxo composition. Further hydrolysis to form this composition can be achieved following deposition via the addition of sufficient water during deposition by exposure to atmospheric water via the delivery of some water vapor. The hydrolyzed coating can be subjected to a drying step, which may involve heating the coating. A radiation beam, electromagnetic beam, or electron beam can generally be directed through a mask onto the dried, coated substrate, or the radiation beam can be controllably scanned across the substrate to form a latent image in the coating. Various further processing steps, such as heating and development, can be performed to pattern the coating with a positive or negative tone image. These organometallic patterning compositions offer particularly promising properties for the advancement of EUV patterning to form finer patterned features.

[0032] For the formation of thin coatings on wafers, precursor solutions with added water have been found to form more uniform coatings when applied by spin coating onto the wafer. When patterning is performed using radiation, spin coating can be a desirable approach for achieving relatively uniform substrate coverage, although edge effects can exist. In some embodiments, the wafer can be spun at speeds 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 spinning speed can be adjusted to achieve the desired coating thickness. Spin coating can be performed for a time period of about 5 seconds to about 5 minutes, and in further embodiments about 15 seconds to about 2 minutes. For example, an initial low-speed spin at 50 rpm to 250 rpm can be used to apply an initial bulk application of the composition across the entire substrate. A backside rinse, edge bead removal step, or the like can be performed with water or another suitable solvent to remove the edge bead. A person of ordinary skill in the art will recognize that additional ranges of spin-coating parameters within the explicit ranges above are contemplated and are within the present disclosure.

[0033] The coating thickness can generally be a function of the precursor solution concentration, viscosity, and spin speed for spin coating. For other coating processes, the thickness can also generally be adjusted by selection of coating parameters. In some embodiments, it may be desirable to use a thin coating that facilitates the formation of small, high-resolution features in a subsequent patterning process. For example, the coating material after drying can have an average thickness of greater than about 250 nanometers (nm), in further embodiments, from about 1 nanometer (nm) to about 50 nm, in other embodiments, from about 2 nm to about 40 nm, and in further embodiments, from about 3 nm to about 25 nm. Those of skill in the art will recognize that additional ranges within the above explicit ranges of thickness are contemplated and are within the scope of the present disclosure. Thickness can be assessed using non-contact methods of X-ray reflectivity and / or ellipsometry based on the optical properties of the film. Generally, the coating is relatively uniform, facilitating processing. In some embodiments, for example, for highly uniform coatings on moderately sized substrates, evaluation of coating uniformity or flatness can be evaluated with a 1-centimeter edge exclusion, i.e., coating uniformity is not evaluated for portions of the coating within 1 centimeter of the edge, although other appropriate edge exclusions can be selected. Stable precursor solutions with added water can be evaluated for coating flatness across the substrate to obtain a standard deviation of coating thickness. In the examples below, a 3-sigma value is reported, which is three times the standard deviation across the wafer surface. For stable precursor solutions with added water, the 3-sigma value (or 3-sigma thickness fluctuation or 3-sigma thickness variation) can be, on average, about 1.2 nanometers (nm) or less, in further embodiments about 1.1 nm or less, and in other embodiments about 1.05 nm or less. A person of ordinary skill in the art will recognize that additional ranges within the explicit ranges of thickness and flatness above are contemplated and are within the scope of the present disclosure. [Example]

[0034] Example 1 - Determination of Solvent Water Content This example provides a measurement of the water content of a commercially available alcohol sample. The alcohol was semiconductor grade 4-methyl-2-pentanol with a purity level reported as 99.9% pure.

[0035] A commercially available Karl Fischer titrator was used to measure water content. Karl Fischer titration uses a reaction with trace amounts of water to provide a very accurate measurement of residual water over a short period of time. Measurements with these instruments are generally accurate to ±5 ppm, and water adjustments can be made to this level of accuracy. Batch variations in water content were determined for 12 representative samples of semiconductor-grade commercially available 4-methyl-2-pentanol (4M2P). The water content across a series of 12 different lots of 4M2P alcohol was found to vary from 41 ppm to 166 ppm, as shown in Table 1 below.

[0036] [Table 1]

[0037] Example 2 - Solution Preparation A series of 12 solutions was prepared: 3 solutions contained a single monoalkyltin trialkoxide, and the remaining 9 solutions contained a blend of three tin compounds.

[0038] The desired solutions are generally formed from the alcoholysis of the RSn(Ot-amyl)3 (Ot-amyl = 2-methylbutane-2-oxide) precursor, synthesized by the method described in the '286 application, or the chloride, RSnCl3. A single precursor, or a binary mixture of precursors, is dissolved in 4-methyl-2-pentanol containing the indicated concentrations of water.

[0039] Three different monoalkyltin tri(Ot-amyl) compounds were prepared from the corresponding monoalkyltin trimethylamides by reaction with 2-methyl-2-butanol. The monoalkyltin trimethylamides were formed by reaction of Grignard reagents (CHMgCl, (CH)CHMgCl, or (CH)CMgCl) with tin tetramethylamide (Sn(NHCH)), to form MeSn(Ot-amyl), i-PrSn(Ot-amyl), or t-BuMeSn(Ot-amyl), respectively. The synthesis of trialkoxide compounds from trimethylamide compounds is further described in the '286 application cited above.

[0040] These three tin compounds were then used to form 12 solutions. Three solutions simply involved dilution of the purified compound in 4-methyl-2-pentanol to obtain a tin concentration of 0.05 M. To simplify the discussion below, the three solutions are labeled X for the solution with the t-BuSn(Ot-amyl)3 compound, Y for the MeSn(Ot-amyl)3 compound, and Z for the i-PrSn(Ot-amyl)3 compound.

[0041] The formation of the blends is described below. Binary mixtures are described by the mole percentage of each alkyl component and the second component relative to the total moles of Sn in each solution. For example, XY20 corresponds to a solution of 80 mole % t-BuSn(Ot-amyl)3 and 20 mole % MeSn(Ot-amyl)3; ZY75 corresponds to a solution of 25 mole % i-PrSn(Ot-amyl)3 and 75 mole % MeSn(Ot-amyl)3.

[0042] Preparation and composition of the t-Bu / Me series Three solutions were prepared with blends of t-BuSn(Ot-amyl)3 with MeSn(Ot-amyl)3. These solutions are referred to as XY solutions based on the notation for the single compound solutions above. To prepare 100 mL of a 0.05 M [Sn] solution, designated XY20, 1.619 mL of t-BuSn(Ot-amyl)3 (ρ = 1.08 g / cm3) was added. 3) and 0.356 mL of MeSn(Ot-amyl)3 (ρ = 1.11 g / cm3) were mixed in a glovebox. 4-Methyl-2-pentanol with the selected HO concentration was then cannulated into the premixed precursors on the Schlenk line to a final [Sn] of 0.05 M. The notation XY20 indicates 20 mole percent of the Y component, i.e., MeSn(Ot-amyl)3, and 80 mole percent of the t-butyl compound. Similarly, XY35 and XY50 blends were prepared with 35 mole percent and 50 mole percent of the methyl compound, respectively.

[0043] Preparation and composition of the t-Bu / i-Pr series Three solutions were prepared using blends of i-PrSn(Ot-amyl)3 and t-BuSn(Ot-amyl)3. To prepare 100 mL of a 0.05 M [Sn] solution designated XZ75, 0.506 mL of t-BuSn(Ot-amyl)3 and 1.443 mL of i-PrSn(Ot-amyl)3 (ρ = 1.10 g / cm3) were mixed in a glovebox. 4-Methyl-2-pentanol with the selected HO concentration was then cannulated into the premixed precursors on the Schlenk line to a final [Sn] of 0.05 M. The XZ75 designation indicates 75 mole percent of the Z component, i.e., i-PrSn(Ot-amyl)3, and 25 mole percent of the t-butyl compound. Similarly, XZ40 and XZ25 blends were prepared with 40 mole percent and 25 mole percent isopropyl compounds, respectively.

[0044] Preparation and composition of the i-Pr / Me series Three solutions were prepared with blends of i-PrSn(Ot-amyl)3 with MeSn(Ot-amyl)3. To prepare 100 mL of a 0.05 M [Sn] solution designated ZY50, 0.962 mL of i-PrSn(Ot-amyl)3 and 0.890 mL of MeSn(Ot-amyl)3 were mixed in a glovebox. 4-Methyl-2-pentanol with the selected HO concentration was then cannulated into the premixed precursors on the Schlenk line to a final [Sn] of 0.05 M. The ZY50 designation indicates 50 mole percent of the Y component, i.e., MeSn(Ot-amyl)3, and 50 mole percent of the isopropyl compound. Similarly, ZY25 and ZY75 blends were prepared with 25 mole percent and 75 mole percent methyl compounds, respectively.

[0045] Example 3 - Solution Stability and Results Table 2 summarizes the stability results for the 12 solutions described above, involving the dissolution of single alkyl species and binary mixtures of RSn(Ot-amyl)3 with alkyl groups R = t-butyl (X), methyl (Y), and i-Pr (Z). The water content of the 4-methyl-2-pentanol (4M2P) solvent is shown in the second column and the five middle columns of the table. The water content is adjusted by measuring the water content of a sample of 4M2P solvent and adding deionized water to obtain the desired adjusted amount of water. As noted above, various species interact in solution, and as a result, reference to the species added to the solution can be more easily assessed than the complex species formed in the mixture.

[0046] Solution stability was determined by visual observation of a precipitate in the solution, which was readily observed to form from one 24 hour period to the next.

[0047] Table 2 summarizes the time to precipitation. Specifically, Table 2 shows solution stability data for RSn(Ot-Am)3 and mixtures thereof in 4-methyl-2-pentanol (4M2P) with the indicated water content. A dash "-" represents a solution that remains clear without precipitation for the corresponding observation period (a period that is at least 148 days (21 weeks)), and "nt" represents a condition that was not tested. The observation period for each solution is presented in Table 2. Single-species solutions X and Y precipitate immediately in water-rich (5000 ppm HO) 4M2P. Single-species solution Z remains clear and stable for at least 178 days at all water addition levels. The XY solution significantly extends the stability time of the X-containing solution. XYn solutions (with n greater than or equal to about 35) are stable for at least 8 months in 2000 ppm water, and XY50 solutions are stable for at least 8 months in 5000 ppm water. ZY solutions effectively maintain and extend the stability of Z solutions, except at high doses of Y and HO (greater than about 75% Y and >4000 ppm HO), which results in precipitation within one day. Stable ZY solutions have been shown to be stable for at least 161 days. XZ solutions effectively enhance the stability of solutions containing X; measured stability extends to 8 months. It should be noted that while 8 months was the length of the observation period for XZ solutions, selected compositions are likely to be stable for significantly longer periods.

[0048] [Table 2]

[0049] Example 4 - Coating Uniformity Tables 3A and 3B summarize the film coating thicknesses produced from a series of XY20 samples deposited on 300 mm Si wafers. Film thicknesses were measured on an Aleris Ellipsometer manufactured by KLA Tencor by measuring 29 points across the wafer, and the corresponding summarized data for each sample is presented in Tables 3A and 3B.

[0050] Two types of samples were analyzed and are represented by the sample label A or B, where A represents the composition of XY20 with no additional water added to the blended solvent, and B represents the composition of XY20 with the blended solvent having an adjusted water content of 300 ppm±10 ppm. For each sample type, seven different wafers were coated and analyzed.

[0051] [Table 3]

[0052] [Table 4]

[0053] In the above table, 3-sigma thickness values ​​(i.e., the standard deviation multiplied by 3) are presented to represent a measure of variability across the wafer. As evidenced by the significantly lower 3-sigma value for Sample Type B, more consistent coating uniformity can be achieved for compositions prepared from solvents with normalized water levels.

[0054] The above-described embodiments are intended to be illustrative and not limiting. Additional embodiments are within the scope of the following claims. Moreover, while the present invention has been described with reference to specific embodiments, those skilled in the art will recognize that changes can be made in form and detail without departing from the spirit and scope of the present invention. Any incorporation by reference of the above documents is limited so as not to incorporate subject matter contrary to the explicit disclosure herein. To the extent that particular structures, compositions, and / or processes are described herein with components, elements, ingredients, or other classes, it is understood that the disclosure herein covers particular embodiments, and that the embodiments include the particular components, elements, ingredients, other classes, or combinations thereof, and that the embodiments consist essentially of such particular components, ingredients, or other classes, or combinations thereof, which may include additional features that do not alter the basic nature of the subject matter, as suggested in the discussion, unless otherwise expressly stated.

Claims

1. a first monoalkyltin trialkoxide (RSn(OR')) having a tin concentration of about 0.004 M to about 1.0 M in an organic solvent; ３ 1. A method for preparing a conditioned precursor solution for a radiation-patternable coating comprising a mixture of mixing the organic solvent and the first monoalkyltin trialkoxide to form the adjusted precursor solution, wherein the solvent is adjusted to have a water content to within ±15 percent of a selected value, and the adjusted water content is 10,000 ppm by weight or less.

2. 10. The method of claim 1, wherein the solvent having the adjusted water content is formed by a process comprising adding water to a stock solvent prior to forming the mixture with the first monoalkyltin trialkoxide.

3. 3. The method of claim 1 or claim 2, wherein the organic solvent is an alcohol having a melting point of about 10° C. or less, and the adjusted precursor solution is stable for at least 42 days.

4. The method according to claim 1 or claim 2, wherein the organic solvent is 4-methyl-2-pentanol.

5. The method of any one of claims 1 to 4, wherein the precursor solution has a tin concentration of about 0.01M to about 0.25M.

6. 6. The method of any one of claims 1 to 5, wherein the water content of the solvent is adjusted to a value of about 250 ppm to about 10,000 ppm by weight, and the adjusted precursor solution is stable for at least 42 days.

7. 6. The method of any one of claims 1 to 5, wherein the water content of the solvent is adjusted to a value of about 300 ppm to about 5,000 ppm by weight, and the adjusted precursor solution is stable for at least 148 days.

8. The first monoalkyltin trialkoxide is monoalkyltin(Ot-amyl) ３ The method according to any one of claims 1 to 5, comprising:

9. The method of any one of claims 1 to 5, wherein the first monoalkyltin trialkoxide comprises t-butyltin trialkoxide.

10. 10. The method of any one of claims 1 to 9, wherein the mixture further comprises as a component a second monoalkyltin trialkoxide separate from the first monoalkyltin trialkoxide.

11. The first monoalkyltin trialkoxide is a first monoalkyltin (Ot-amyl) ３ wherein the second monoalkyltin trialkoxide is a second monoalkyltin(Ot-amyl) ３ 11. The method of claim 10, comprising:

12. The method of any one of claims 1 to 11, wherein the adjusted precursor solution is stable for at least 6 months.

13. 10. A method of forming a radiation-patternable coating on a substrate, comprising forming a coating of a conditioned precursor solution formed by the method of claim 1, wherein the coating has an average thickness of about 45 nm or less and a 3 sigma thickness variation of about 1.15 nm or less.

14. An alcohol having a selected water content and a first monoalkyltin trialkoxide (RSn(OR') ３ ), having a stannous concentration of about 0.004M to about 1.0M, wherein the selected water content is at least about 250 ppm by weight, and the solution is stable for at least 42 days.

15. 15. The solution of claim 14, wherein the organic solvent is an alcohol having a melting point of about 10°C or less.

16. 16. The solution of claim 14 or claim 15, wherein the selected water content is adjusted to a value of about 300 ppm to about 10,000 ppm by weight.

17. The first monoalkyltin trialkoxide is monoalkyltin(Ot-amyl) ３ The solution according to any one of claims 14 to 16, comprising:

18. 17. The solution of any one of claims 14 to 16, wherein the first monoalkyltin trialkoxide comprises t-butyltin trialkoxide.

19. 19. The solution of any one of claims 14 to 18, wherein the mixture further comprises as a component a second monoalkyltin trialkoxide that is distinct from the first monoalkyltin trialkoxide.

20. The first monoalkyltin trialkoxide is monoalkyltin(Ot-amyl) ３ and the second monoalkyltin (Ot-amyl) ３ 20. The solution of claim 19, comprising:

21. The solution of any one of claims 14 to 20, wherein the solution is stable for at least 6 months.

22. 1. A method for patterning a radiation sensitive coating, comprising: forming a coating on a substrate surface with a precursor solution, the precursor solution having a uniform composition resulting from adjusting the water content of a solvent used to form the adjusted precursor solution to within about ±15% of a target value, the selected water content being from about 300 ppm by weight to about 10,000 ppm by weight; drying the coating; and irradiating the dried coating to form a latent image; A method comprising:

Images