Patent Application
20240199658
The invention relates to versatile synthesis methods for forming organotin trialkoxide compounds involving the direct alkylation of tin alkoxides that avoid hydrolysable ligand replacement. The synthesis methods involve the use of an alkali metal tin trialkoxide or a di-tin tetraalkoxide starting material, which both exemplify a high mono-organo specificity. The invention further relates to polytin compounds with bridging organo ligands forming C—Sn bonds to each of the tin atoms.
Organometallic compounds provide metal ions in solution and vapor forms for deposition of thin films. Organotin compounds provide high EUV absorption and radiation sensitive tin-ligand bonds that can be used to lithographically pattern thin films. The manufacture of semiconductor devices at ever shrinking dimensions with EUV radiation requires new materials with wide process latitude to achieve required patterning resolutions and low defect densities.
In one aspect, the invention pertains to a method for synthesizing a monoorgano tin trialkoxide comprises reacting MSn(OR′)3 with RXn to form R[Sn(OR′)3]n, wherein M is Li, Na, K, Rb, or Cs; X is Cl, Br, or I; and n≥1. R is an organo group with 1 to 31 carbon atoms and forming a C—Sn bond. R′ is an organo group with 1 to 10 carbon atoms. The organo groups can optionally comprise hetero-atoms and/or unsaturated bonds.
In another aspect, the invention pertains to a method for synthesizing a monoorgano tin trialkoxide comprising reacting Sn2(OR′)4 with RX under ultraviolet light to form RSn(OR′)3, where X is Cl, Br or I. R is an organo group with 1 to 31 carbon atoms and forming a C—Sn bond. R′ is an organo group with 1 to 10 carbon atoms. The organo groups can optionally comprise hetero-atoms and/or unsaturated bonds.
In another aspect, the invention pertains to an organometallic compound represented by the formula ((R′O)3Sn)n—R, where n≥3; R′ is an organo group with 1 to 10 carbon atoms; and R is an organo group with 5 to 31 carbon atoms and forms a C—Sn bond with each Sn atom.
In another aspect, the invention pertains to a method for forming a fluorinated organometallic compound represented by the formula (CF3)RSn(OR′)3, where R is an organo group with 1 to 31 carbon atoms and forming a C—Sn bond; and R′ is an organo group with 1 to 10 carbon atoms. The method comprises reacting (CF3)RX with Sn2(OR′)4 or MSn(OR′)3 under visible or ultraviolet light where X is Cl, Br or I.
In another aspect, the invention pertains to a fluorinated organometallic compound represented by the formula (CF3)2R1C—R0Sn(OR′)3, where R0 is an organo group with 1 to 31 carbon atoms and forming a C—Sn bond; R1 is hydrogen, a halogen atom or an organo group with 1 to 10 carbon atoms; and R1 is an organo group with 1 to 10 carbon atoms.
New synthetic routes to organotin trialkoxide compositions have been discovered based on oxidative stannylation starting from Sn(II) alkoxide, and the methods offer high selectivity and efficiency. In some embodiments, the new synthesis methods are based on reaction of tin (II) alkoxide with a potassium alkoxide to form an intermediate bimetallic alkali metal tin trialkoxide, such as potassium tin(II) trialkoxide, composition, followed by subsequent reaction of the intermediate bimetallic composition with an alkyl halide to form a monoalkyltin trialkoxide composition. In other embodiments, effective synthesis methods are based on the reaction of di-tin tetraalkoxide with an organohalide under UV light to directly synthesize the organotin trialkoxide, and tin halide alkoxide by-products are readily separated. The methods described herein can provide for high selectivity and yield and enable the preparation of monoalkyltin trialkoxide compositions without the need to perform ligand exchange or conversion reactions, for example, conversion of a monoalkyltin triamide to a monoalkyltin trialkoxide. The reactions described herein can be useful for preparing monoalkyltin trialkoxides having primary or secondary Sn—C bonds. In some embodiments, an organo group, such as an aromatic group, can be a bridging organic ligand with direct C—Sn bonds to a plurality of Sn atoms, such as two, three or more tin. Furthermore, the reactions described herein can be useful in preparing organotin compounds with fluorinated organic groups, e.g., RFSnL3 compounds where RF is an alkyl group substituted with one or more fluorine atoms, especially with a plurality of trifluoromethyl (F3C—) groups. The resulting organotin trialkoxides can be desirable precursors for radiation based patterning compositions, especially for effective EUV patterning. As used herein, and as generally consistent with usage in this field, “organotin,” “hydrocarbyl tin” and “alkyl tin” terms can be used interchangeably, and likewise “monoalkyl” can be used interchangeably with “monoorgano” or “monohydrocarbyl”. The “alkyl” ligands suggest bonding to the tin with carbon (generally sp3 or sp2 hybridized) to form a bond that is generally not hydrolysable through contact with water. The “alkyl” group can also have internal unsaturated bonds and hetero-atoms, i.e., distinct from carbon and hydrogen, that are not involved in bonding with the tin. Similarly, a reference to alkoxide groups refers to group bound at an oxygen atom with an organo substituent on the oxygen. New synthesis methods described herein yield monoalkyl tin trialkoxides in high yield and with low (non-tin) metal and polyalkyl (i.e., polyhydrocarbyl) contaminants following straightforward purification. The synthesis approaches are amenable for efficient scale up for commercial production, and the reactions are straightforward and can be performed as a single pot synthesis.
Organotin compounds, particularly monoalkyltin trialkoxide and triamide compounds, have found use as precursors for high-performance photoresists for EUV lithography. The use of alkyl tin 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,” incorporated herein by reference. Refinements of these organometallic compositions for patterning are described in U.S. Pat. No. 10,642,153 to Meyers et al., entitled “Organometallic Solution Based High Resolution Patterning Compositions and Corresponding Methods,” and U.S. Pat. No. 10,228,618 to Meyers et al. (hereinafter the '618 patent), entitled “Organotin Oxide Hydroxide Patterning Compositions, Precursors, and Patterning,” both of which are incorporated herein by reference.
The compositions synthesized herein can be effective precursors for forming the alkyl tin oxo-hydroxo compositions that are advantageous for high resolution patterning, for example in extreme ultraviolet (EUV), ultraviolet (UV), electron-beam lithography. The alkyl tin precursor compositions comprise a group that can be hydrolyzed with water or other suitable reagent under appropriate conditions to form the monoorgano tin oxo-hydroxo patterning compositions, which, when fully hydrolyzed, can be represented by the formula RSnO(1.5-(x/2))(OH)x where 0<x≤3. It can be convenient to perform the hydrolysis to form the oxo-hydroxo compositions in situ, such as during deposition and/or following initial coating formation. While organo tin triamides and organo tin triacetylides described, for example, in the above-referenced '618 patent, can be used under hydrolyzing conditions for forming radiation sensitive coatings for patterning, it can be desirable to use organo tin trialkoxides as part of the film-forming compositions. Direct synthesis of organo tin trialkoxides are described herein.
Monoorgano tin compositions can generally be represented by the formula RSnL3, where R is an alkyl group and L is a hydrolysable ligand. For processing to form radiation patternable coatings, L is generally hydrolysed before or during (e.g., in-situ) deposition to result in a coating comprising a polymeric organotin oxo-hydroxo composition on a substrate wherein the Sn—R bonds remain substantially intact. As a result, a radiation patternable coating having radiation-sensitive Sn—R (Sn—C) bonds can be realized.
The new syntheses described herein are advantageous for efficient formation of R—Sn bonds with a wide selection of R groups having heteroatom(s) that can offer improvements in thermal and/or photosensitivity over R groups having non-substituted alkyl groups. While not wanting to be limited by theory, it is generally believed that the presence of R ligands hinders extended network formation and condensing of the organotin film, and irradiation of the material can result in the cleavage of Sn—C bonds which, in turn, allows for subsequent processing to condense and/or densify the film.
At the time of radiation patterning, hydrolysable ligands have generally been substantially removed to form the ultimate patterning composition from the precursor compositions. In general, organometallic radiation sensitive resists have been developed based on organo tin compositions, such as alkyltin oxide hydroxide, approximately represented by the formula RzSnO(2-z/2-x/2)(OH)x, where 0<x<3, 0<z≤2, x+z≤4, and R is a hydrocarbyl or organo group forming a carbon bond with the tin atom. Particularly effective forms of these compositions are mono-organotin oxide hydroxide, in which z=1 in the above formula, and the mono-organotin compositions are the focus herein. In particular, R can be a moiety with 1-31 carbon atoms with one or more carbon atoms optionally substituted with one of more heteroatom functional groups, such as groups containing O, N, Si, Ge, Sn, Te, and/or halogen atoms, or an alkyl, or a cycloalkyl further functionalized with a phenyl, or cyano group. In some embodiments, R can comprise ≤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 from 1 to 31 carbon atoms with 3 to 31 carbon atoms for the group with a secondary-bonded carbon atom and 4 to 31 carbon atoms for the group with a tertiary-bonded carbon atom, optionally with unsaturated or aromatic carbon bonds. In particular, branched alkyl ligands can be desirable for some patterning compositions. The formation of the oxo-hydroxo coating material can comprise deposition of a tin composition with hydrolysable bonds, such as RSnL3, where L is a hydrolysable ligand, such as an alkoxide, a dialkyl amine, an acetylide or other suitable hydrolysable ligand. The hydrolysable ligands can be hydrolyzed to form the oxo-hydroxo network during deposition of the coating and/or in the coating following deposition, i.e., completing the hydrolysis after deposition. Applicant has developed methodologies to efficiently and effectively form a wide range of patterning compositions with different R groups, optionally with various hetero atoms, with C—Sn bonds, as described further in published U.S. patent application 2022/00064192 to Edson et al., entitled “Methods to Produce Organotin Compositions With Convenient Ligand Providing Reactants,” incorporated herein by reference.
The stability of the Sn—C bond can generally depend on the substitution of the alpha carbon (the C bound to the Sn), and the stability generally increases as the alpha carbon substitution decreases. For example, Sn—R bonds with primary alpha carbons are generally more stable than secondary alpha carbons which are in turn more stable than tertiary alpha carbons. Also, some unsaturated alpha carbons, such as an alkynyl C bound to Sn (e.g., Sn—C≡C), may hydrolyze during processing, so they may not be suitable for reliance on their radiation sensitivity. Stability of Sn—C bonds can correlate with dose sensitivity and/or thermal stability such that lower stability Sn—C bonds require less energy to cleave, and therefore may be expected to correlate with lower doses needed to form a pattern. Additionally, thermal stability of the Sn—C bonds can depend on alpha carbon substitution in the same way where increasing substitution of the alpha carbon can lead to generally undesirable tradeoffs between lower thermal stability and higher dose sensitivity. It is therefore desirable for new organotin compositions to have both high thermal stability and high dose sensitivity.
Processing of the organotin precursor compositions to afford organotin oxo-hydroxo coatings generally involves hydrolysis of the RSnL3 composition(s) to afford the related organotin oxo-hydroxo composition(s). Hydrolysis can be performed prior to the deposition process to yield soluble organotin oxo-hydroxo species (i.e., clusters, oligomeric species, etc.) These soluble organotin oxo-hydroxo species can then be dissolved and/or dispersed into a suitable solvent to form an organotin photoresist solution that can then be used to form radiation-patternable organotin oxo-hydroxo coatings. Alternatively, the organotin precursor compositions can be directly dissolved in a suitable solvent to form a photoresist solution that can then be used to form radiation-patternable organotin oxo-hydroxo coatings. The organotin compositions can also be hydrolysed in-situ with water, which can be ambient water vapor, during the substrate coating process, such as during solution deposition or during vapor deposition. Various processing options are described further in the '684 and '618 patents referenced above.
For organotin photoresist precursor compositions wherein the organotin compound(s) dissolved into a solvent for spin-coating, organotin trialkoxides (RSnL3, L=OR′) can be desirable for use over other RSnL3 compositions (e.g, organotin triamides, L=NR′2). Some advantages to organotin trialkoxide compositions are, for example, the production of more benign side-products, e.g., alcohols, that are relatively innocuous compared to the production of gaseous products (e.g., amines) which may cause contamination, environmental health and safety (EHS), and similar concerns within the wafer track and/or wafer fab. Organotin trialkoxides also possess appreciable vapor pressures and low melting points which makes them attractive compounds for use in vapor deposition methods to prepare radiation patternable coatings.
Synthesis of organotin trialkoxide compounds have been previously described, such as in previous patent applications by Applicant. However, these reactions offering monoalkyltin trialkoxides as products generally involve conversion of a non-alkoxide alkyl tin compound into an alkyl tin alkoxide rather than a direct synthesis. In other words, organotin trialkoxides have generally been synthesized through ligand replacement reactions. For example, organotin trialkoxides can be prepared from the corresponding organotin trichlorides by reaction with an alkali metal alkoxide, e.g., KOR′, NaOR′, and the like, according to the following reaction:
RSnCl3+3MOR′→RSn(OR′)3+3MCl, (1)
Using this synthetic scheme, the potential product space for organotin trialkoxides therefore has practical constraints based on the access to and purity of the corresponding organotin trichloride. Organotin trichlorides are generally synthesized through the well-known Kocheskov Reaction where a tetraalkyl tin, R4Sn, serves as a starting material for the synthesis of other organotin halides that are generated through redistribution reaction with SnCl4. This reaction is known to be non-selective and highly sensitive to stoichiometry, and generally results in some distribution of off-target and undesired RnSnCl4−n products. For example, to synthesize RSnCl3, a mixture of SnCl4 and R4Sn are reacted in a 3 to 1 ratio to target RSnCl3 as the major product, but the reaction produces significant amounts of R2SnCl2 and R3SnCl as side products. For semiconductor applications where high purity compounds are required for low defect processing and for commercial viability, one or more purification steps can be necessary to further purify and/or isolate the RSnCl3 compound prior to its conversion to a trialkoxide, and the purification itself can involve significant effort. The synthetic methods described herein alleviate the need for a high-purity organotin trichloride starting material in the synthesis of an organotin trialkoxide.
Other methods of preparing organotin trialkoxides involve conversion of an organotin triamide to an organotin trialkoxide via the following reaction:
RSn(NR2″)3+3HOR′→RSn(OR′)3+3HNR″2.tm (2)
While this reaction is relatively straightforward, application of the method can be constrained by factors such as it being exothermic and can potentially lead to decomposition of the reactants and/or products, and high cost because of the necessity of first synthesizing the corresponding organotin triamide. While Applicant has previously described synthesis techniques for preparation of a wide variety of organotin triamides, there remains a desire for access to methods to directly synthesize organotin trialkoxides without the need to first obtain an organotin starting material with the desired R ligand identity. A direct synthesis of a target organotin trialkoxide, RSn(OR′)3, is desirable and is described herein.
Two related synthesis techniques are described for the direct synthesis of organo tin trialkoxides. As exemplified, both methods involve the reaction of an organohalide, such as an alkyl halide (RX), with a tin alkoxide compound to form a Sn—R bond. The tin alkoxide can be a di-tin tetraalkoxide (Sn2(OR′)4) or an alkali metal tin alkoxide, e.g., MSn(OR′)3. In a first approach, the di-tin tertaalkoxides are reacted with an organohalide, generally in the presence of UV or monochromatic visible light, to form a monoalkyl tin trialkoxide, RSn(OR′)3. In a second approach, the alkali metal tin trialkoxide is reacted with an organohalide to form the corresponding organo tin trialkoxide with low tin contaminant production.
The di-tin tetralkoxide (Sn2(OR′)4) and alkali metal tin alkoxide (MSn(OR′)3) can be prepared using methods known in literature, for example, in an article by Veith et al. (hereinafter the Veith article), entitled “Alkoxistannate, II Tri(rerr-butoxi)alkalistannates(II): Synthesis and Structures,” Z. Naturforsch. 41b, 1071-1080 (1986), incorporated herein by reference. The Veith article does not suggest specific reactions using Sn2(OR′)4 or MSn(OtBu)3 as a further reactants to form alkyltin trialkoxides, e.g., RSn(OtBu)3. The Veith article discloses the synthesis of MSn(OtBu)3 using Sn2(OtBu)4. As exemplified herein, MSn(OtBu)3 is synthesized in a two-step reaction from SnCl2 and M(OtBu). After the first step, precipitated MCl (KCl) removed, but no further purification is needed.
As descried herein and in the Examples below, monoalkyltin trialkoxides can be synthesized by the following overall reaction:
MSn(OR′)3+RX→RSn(OR′)3, (3)
where M is generally an alkali metal, such as Li, K, Na, Cs, or Rb. R′ is generally an organo group with ≤10 carbon atoms, and OR′ can generally be selected for desirable properties of the product monoalkyltin trialkoxide, RSn(OR′)3, such as stability, melting point, solubility, case of purification, and so forth. In some embodiments, M is K. In some embodiments, OR′ is tert-butoxide (OtBu). In some embodiments, OR′ is tert-amyloxide (OtAm). The RX compounds are selected to provide the desired organo ligands, R, for the mono-organotin products. The wide availability of RX compounds as reactants as well as the broad reactivity of the compounds in the corresponding reaction provides an ability to introduce a wide range of alkyl ligands into the product monoalkyl tin products. X can generally be a halide chosen from I, Br, or Cl.
The reaction of Eq. (3) can be generalized for the synthesis of poly-tin products with bridging organo ligands,
n MSn(OR′)3+RXn→R(Sn(OR′)3)n, (4)
where n≥1, such as 1, 2, 3, 4, or more than 4 and M is generally an alkali metal as described above. In general, as long as reasonable polyhalide reactants are available, there are not clear limits on the number of tin atoms that can be bridged in this way. In some embodiments, n can be from 2 to about 12. R, X and R′are as specified in the previous paragraph. For the mono-tin or poly-tin embodiments, a plurality of different R′ groups can be used if desired.
For the reactions described herein, primary and secondary R groups (i.e., R groups that have a 1° or 2° C. atom that forms the C—Sn bond) can be particularly effective at forming the desired RSn(OR′)3 compositions via the synthetic routes described herein. In general, R ligands are organo ligands with 1-31 carbon atoms with one or more carbon atoms optionally substituted with one of more heteroatom functional groups containing O, N, Si, and/or halogen atoms or an alkyl or a cycloalkyl further functionalized with a phenyl or cyano group with optional unsaturated carbon-carbon or heteroatom bonds. In particular, olefinic R ligands having unsaturated carbon bonds can also be prepared, such as R ligands having one or more C═C bonds, as shown in the examples herein. Additionally, polytin compounds having two, three or more Sn atoms bridged by a shared R group can also be prepared via the new synthetic methods described herein using polyhalide reactants. In some embodiments, it can be desirable for a catalyst to be present during the reaction to form the monoalkyltin trialkoxide, as described further below.
In some embodiments, the R ligands can comprise heteroatom functional groups containing O, N, Si, and/or halogen atoms. In some embodiments, the R ligands are fluorinated. Fluorine atoms can be desirable to substitute for H atoms within the R ligands due to their higher EUV absorption. Additionally, the presence of F atoms within the R ligand can increase the hydrophobicity of the ligand, thus improving the developer contrast between irradiated and non-irradiated areas of the film.
In some embodiments, the fluorinated R ligands can comprise 2 to 10 carbon atoms and two or more —CF3 groups, such as in the hexafluorobutyl (HFB) compound described in the Examples herein. In some embodiments, the R ligands can comprise a tertiary carbon having a C—F bond, e.g. —CFR2 wherein R is a hydrocarbyl group having 1 to 10 carbon atoms, such as in the HFP compound described in the Examples herein.
In some embodiments, the R ligands can comprise bridging hydrocarbyl groups shared between two, three or more Sn atoms. The bridging R ligands can generally include lincar, branched, cyclic, and/or aromatic hydrocarbyl groups having from 1 to 31 carbon atoms.
The alkali tin trialkoxide intermediate, MSn(OR′)3, a bimetallic alkoxide of Sn(II), has been discovered to be a useful reagent for forming organotin trialkoxides, and can be prepared according to the following reaction:
SnCl2+3MOR′→MSn(OR′)3+2MCl. (4)
The alkali metal M can generally be chosen from Li, Na, K, Cs, or Rb. In some embodiments, M is K. In some embodiments, M is Li or Na. The MSn(OR′)3 compound can be isolated, purified, and used as a solid reagent in the syntheses, and its preparation is included in the Examples herein. When reacted with an organohalide at modest temperatures and conditions, an oxidative addition reaction can occur wherein a carbon tin bond is formed with rapid formation of potassium halide and RSn(OR′)3. As exemplified below, the reaction is performed in two steps with 2 equivalents of MOR′ added first to precipitate the MCl, which can then be removed. A further amount of MOR′ is added, and a somewhat less than an equivalent can be added in view of losses from the filtering for removal of the precipitated MCl. Generally, the precipitated alkali halide, such as potassium halide, salt can be alternatively filtered away, and/or the RSn(OR′)3 product can be purified and collected, such as via distillation.
For some R groups, such as fluorinated alkyl groups, it has been discovered that the corresponding RFSn(OR′)3 composition can be synthesized without the use of the alkali tin alkoxide composition, i.e., directly from Sn(OR)2 ([Sn(OR′)2]2) in the presence of UV light or visible light according to the following reaction:
[Sn(OR′)2]2+RFX→RFSn(OR′)3+½Sn2X2(OR′)2, (5)
The ditin by-product (Sn2X2(OR′)2) is generally formed as a solid precipitate, which can be separated by filtration or other suitable technique. While noted as a reaction for fluorinated organo ligands, this reaction can be more generally applied as desired.
In the Examples herein, synthesis of fluorinated alkyltin trialkoxides wherein RF=trifluoroethyl (TFE, CF3CH2—), R′=tert-butyl, and X=halide (Cl, Br, I) are described. While not wanting to be limited by theory, it is believed that the reaction with fluorinated alkyl groups involves a radical mechanism that can be promoted via irradiation with suitable UV or visible light. Notably, the reaction can be performed under UV or visible irradiation without the presence of a bimetallic tin(II) alkoxide. These reactions can also be performed with alkali metal tin trialkoxides, and these reactions are also facilitated with visible or UV irradiation. Suitable light sources can be used to provide UV and/or visible light to the reaction vessel, for example, LEDs, lasers, bulbs, and the like. The light source can generally provide light with a wavelength from between 200 nm and 700 nm, and it can generally be desirable for the selected wavelength to have sufficient transmission through the reaction vessel(s) (i.e., glassware) to enable sufficient absorption by the species in the reaction medium. In some embodiments, the light source can be monochromatic.
The reactions are generally performed in dry organic solvents under an oxygen free or depleted atmosphere, such as a nitrogen purged atmosphere. Solvents can be selected to result in the solubility of the various components. Due to interactions of the solvent with the metal ions, selection of solvents can be based at least in part on reaction rates in the selected solvents, which can be evaluated empirically. If different solvents are selected, they are generally miscible. Both aprotic polar and non-polar solvents are generally useful, such as alkanes (for example, hexane, pentane), ethers (for example, dimethyl ether, diethyl ether), tetrahydrofuran (THF), acetone, toluene, acetonitrile, and mixtures thereof. The solvents should generally be selected to be inert with respect to the reactants, intermediates, and products. If multiple solvents are used, for example to introduce distinct reactants, the solvents should generally be miscible with respect to each other.
A catalyst comprising a halide can be present during the reaction of the bimetallic MSn(OR′)3 compound and the alkylhalide RX compound. The catalyst can generally comprise a tetraalkyl (quaternary) ammonium salt, a tetraalkyl phosphonium salt or a mixture thereof, such as tetrabutylammonium iodide, tetrabutylammonium bromide, tetrabutylammonium hexafluorophosphate, and/or tetraphenylphosphonium chloride. Since the catalyst is not consumed, the amount of catalyst can be selected to influence the reaction rate as desired. Generally, the amount of catalyst is a fraction of a stoichiometric amount.
The reactions using MSn(OR′)3 as a starting material can generally be performed in a single pot without any intermediate steps, such as separation, purification, transfer, and the like. Following the reaction between the bimetallic alkoxide MSn(OR′)3 and the alkyl halide, the desired organotin alkoxide product can be obtained in pure form via filtration and/or distillation. Using polyhalide organic reactants, bridging organo groups can be formed, R(Sn(OR′)3)n, where n>1, and wherein the organo group, R, has Sn—C bonds to n number of Sn atoms, and a tri-tin product is exemplified.
The reactions described herein are highly selective towards formation of a mono-organo tin trialkoxide compound, and the organohalide can generally be present as a reactant in a molar excess of the MSn(OR′)3 composition. But for the formation of poly-tin product with bridging ligands, then a stoichiometric amount of the polyhalide organo reactant can be used. Similarly, for the reactions involving the Sn2(OR′)4 for the direct formation of the organotin trialkoxide indicated in Eq. (5) above, this reaction is also very specific for the mono-organo products. In some embodiments, the organohalide can be present up to about 2 mol. equivalents to the MSn(OR′)3 (or Sn2(OR′)4) compound, up to about 1.6 mol. equivalents to the MSn(OR′)3 (or Sn2(OR′)4) compound in other embodiments, up to about 1.3 mol. equivalents MSn(OR′)3 (or Sn2(OR′)4) compound in other embodiments, and up to about 1.1 mol. equivalents to the MSn(OR′)3 (or Sn2(OR′)4) compound in further embodiments. In some embodiments, the organohalide and the MSn(OR′)3 (or Sn2(OR′)4) compound can be present in roughly stoichiometric amounts. Note with the reactions based on Sn2(OR′)4, the generation of an Sn by-product that is removed results in a limit of 50% yield based on tin, which is not a constraint for the reactions involving MSn(OR′)3 reactant. A person of ordinary skill in the art will recognize that additional ranges of relative reactant amounts within the explicit ranges above are contemplated and are within the present disclosure.
In some embodiments, the reactions can generally be performed at temperatures less than about 100° C., less than about 80° C. in other embodiments, and less than 60° C. in further embodiments. In some embodiments, the reactions can be performed at room temperature. In some embodiments, the reaction can be performed under UV irradiation. In embodiments wherein UV irradiation is performed during reaction, the reaction may or may not be heated. In some embodiments, the reaction can be cooled and performed at temperatures from about −80° C. to about −60° C., from about −60° C. to about −40° C. in some embodiments, from about −40° C. to about −20° C. in other embodiments, and from about −20° C. to about 20° C. in other embodiments. In some embodiments, the UV irradiation can be conducted with a wavelength of 365 nm. In some embodiments, the UV irradiation can be conducted with a wavelength on 254 nm. In some embodiments, the reaction can be performed under monochromatic visible irradiation. The irradiation provided during the reaction can generally be performed at a wavelength suitably transparent to the reaction apparatus (e.g., glassware, vessels, etc.) such that appreciable absorption can occur to drive the reaction. The reactions are generally stirred for the duration of the reaction. Efficacy of the reaction can be monitored by analyzing the reaction mixture via 1H and/or 119Sn NMR to determine when the reaction has reached sufficient completion. In some embodiments, the reactions can be performed for about 5 days, for about 3 days in other embodiments, for about 1 day in other embodiments, and for about 1 hour in further embodiments. A person of ordinary skill in the art will recognize that additional ranges of time and temperature within the explicit ranges above are contemplated and are within the present disclosure. Desirable reaction times and temperatures can generally depend on the identity of the organohalide (RX). Reactivity of the organohalide generally follows in the order of X=I>Br>Cl, and in the order of the carbon forming the C—X bond as 1°>2°>>3°. Suitable reaction times and temperatures can be determined through routine experimentation based on the teachings herein. The reactions are generally performed under an inert atmosphere, such as N2 or Ar. A person of ordinary skill in the art will recognize that additional ranges of process conditions within the explicit ranges above are contemplated and are within the present disclosure.
Once the product is formed, the organotin trialkoxides can be purified. The purification depends on the nature of the product, but generally involves the separation of the desired product from by products and potentially any unreacted reagents. Purification can generally be achieved by methods known in the art. Typical means of purification can comprise filtration, recrystallization, extraction, distillation, sublimation, combinations thereof, and the like. Filtration is typically performed on a crude product mixture using commercial filters to remove insoluble contaminants and/or by products, for example, metal halide salts such as KI, from the solution containing the desired product. Recrystallization methods can be useful to purify solid compounds by forming, via heating, a saturated solution that then is allowed to cool. Extraction techniques can comprise, for example, liquid-liquid extractions wherein two non-miscible solvents with different densities are used to separate the desired compounds based on their relative solubilities. Purification can also comprise removal of any volatile compounds including solvents from the product mixture by drying with heat and/or exposure to vacuum. For products with significant vapor pressures, it can be desirable to purify the product through vacuum distillation or, if desired, fractional distillation designed to achieve high purity. See published U.S. patent application 2020/0241413 to Clark et al., entitled “Monoalkyl Tin Trialkoxides and/or Monoalkyl Tin Triamides With Low Metal Contamination and/or Particulate Contamination and Corresponding Methods,” incorporated herein by reference. In some cases, products can be purified through sublimation techniques wherein the crude product mixture is heated and/or subject to reduced pressure to result in collection of a solid product that can be purified by sublimation of the solid product, which can be collected by depositing on a target surface, such as a cold finger. Purification of a ditin compound via sublimation is described in the Examples herein.
The organotin trialkoxides, RSnL3 (L=OR′), described herein can be further processed to form corresponding organotin compounds with different hydrolysable ligands, L. In one example, the alkoxide ligands can be replaced with different alkoxide ligands, such as replacing one or more OR′ ligands for OR″ ligands via solvolysis and/or alcoholysis. The organotin trialkoxides can also be converted to organotin triamides (RSnL3, L=NR″2), such as via reaction of the organotin trialkoxide with LiNR″2 or similar metal amide. In other examples, the alkoxide ligands can be replaced by acetylide, amidinate, carboxylate, and so forth.
The hydrolysable ligand can generally be chosen for handling or use-case considerations, such as for use in a desired mode of processing the RSnL3 composition into a radiation patternable film. For example, while organotin trialkoxides (RSn(OR′)3, L=OR′) can be desirable for the formation of resist solutions, organotin triamides (RSn(NR″2)3) can be particularly desirable for use vapor deposition applications because of their generally high vapor pressures and high reactivity. In either case, i.e.,L=OR′ or L=NR″, the hydrolysis and condensation reactions that occur during the deposition process result in the formation of similar organotin oxide hydroxide film compositions wherein the Sn—C bonds are conserved and Sn—O—Sn and Sn—OH bonds are formed from hydrolysis of the Sn-L bonds.
The organotin precursor compositions described herein can be effectively used for radiation patterning, especially EUV patterning. The ability to have greater flexibility for R ligand selection allows for further improvements in patterning results as well as designing ligands to be particularly effective for specific applications. In general, any suitable coating process can be used to deliver the precursor solution to a substrate. Suitable coating approaches can include, for example, solution deposition techniques such as spin coating, spray coating, dip coating, knife edge coating, printing, such as inkjet printing and screen printing, and the like. Many of the precursors are also suitable for vapor deposition onto a substrate as discussed in the '618 patent cited above. For some R ligand compositions and/or specific process considerations, vapor deposition may be useful for preparation of radiation sensitive coatings.
After preparation of the desired organotin precursor, the precursor can be dissolved in an appropriate solvent to prepare a precursor solution, such as an organic solvent, e.g., alcohols, aromatic and aliphatic hydrocarbons, esters or combinations thereof. In particular, suitable solvents include, for example, aromatic compounds (e.g., xylenes, toluene), ethers (anisole, tetrahydrofuran), esters (propylene glycol monomethyl ether acetate, ethyl acetate, ethyl lactate), alcohols (e.g., 4-methyl-2-pentanol, 1-pentanol, 1-butanol, methanol, isopropyl alcohol, 1-propanol), ketones (e.g., methyl ethyl ketone), mixtures thereof, and the like. In general, organic solvent selection can be influenced by solubility parameters, volatility, flammability, toxicity, viscosity and potential chemical interactions with other processing materials.
The organotin precursor(s) can also generally be dissolved in mixtures of solvents to prepare precursor solutions. Some solvent mixtures useful for forming organotin photoresist solutions have been described in published U.S. Patent Application 2023/0143592 to Jiang et al., entitled “Stability-Enhanced Organotin Photoresist Compositions”, incorporated herein by reference. It can be desirable for the organotin precursor(s) to be dissolved in a solvent mixture comprising a primary alcohol. In some embodiments, the solvent can comprise a primary alcohol, such as methanol, ethanol, 1-propanol, 1-butanol, 1-pentanol, 1-hexanol, and the like. In some embodiments, the solvent can comprise a mixture of two alcohols. In other embodiments the solvent can comprise a mixture of an alcohol and an ester. After the components of the solution are dissolved and combined, the character of the species may change as a result of partial in-situ hydrolysis, hydration, and/or condensation.
The organotin precursors can be dissolved in the solvent at concentrations to afford concentrations of Sn suitable for forming coatings of appropriate thickness for processing. The concentrations of the species in the precursor solutions can be selected to achieve desired physical properties of the solution. In particular, lower concentrations overall can result in desirable properties of the solution for certain coating approaches, such as spin coating, that can achieve thinner coatings using reasonable coating parameters. It can be desirable to use thinner coatings to achieve ultrafine patterning as well as to reduce material costs. In general, the concentration can be selected to be appropriate for the selected coating approach. Coating properties are described further below. In general, tin concentrations comprise from about 0.005 M to about 1.4 M, in further embodiments from about 0.02 M to about 1.2 M, and in additional embodiments from about 0.1 M to about 1.0 M. A person of ordinary skill in the art will recognize that additional ranges of tin concentrations within the explicit ranges above are contemplated and are within the present disclosure.
In some embodiments, improved photosensitive precursor compositions can be present in a blended solution with one or more organotin compositions, such as RnSnL4−nand its hydrolysates, where R is chosen from the various moieties described in detail herein and elaborated on explicitly above. Such blended solutions can be tuned for optimization of various performance considerations, such as solution stability, coating uniformity, and patterning performance. In some embodiments, the improved photosensitive composition can comprise at least 1% by mol. Sn of a desired component in the blended solution, in further embodiments at least 10% by mol. Sn of the blended solution, in further embodiments at least 20% by mol. Sn of the blended solution, and in further embodiments at least 50% by mol. Sn of a specific desired component of the blended solution. Additional ranges of mol % of the improved photosensitive composition within the explicit ranges of the blended solution are contemplated and within the present disclosure. The hydrolysable ligands L can be hydrolyzed during deposition or following deposition, such as through hydrolysis with water vapor.
Owing generally to their high vapor pressures, the organotin compositions described herein can be useful as precursors for forming coatings via vapor deposition. Vapor deposition methods generally include chemical vapor deposition (CVD), physical vapor deposition (PVD), atomic layer deposition (ALD), and modifications thereof. In a typical vapor deposition process, the organotin composition can be reacted with small molecule gas-phase reagents such as H2O, O2, H2O2, O3, CH3OH, HCOOH, CH3COOH, and the like, which serve as O and H sources for production of radiation sensitive organotin oxide and oxide hydroxide coatings. Water vapor can be provided from ambient air, delivered in vapor form, or otherwise provided in a suitable liquid or vapor composition. Specific apparatuses for vapor deposition of radiation patternable organotin coatings has been described by Wu et. al in PCT Application # PCT/US2019/031618 entitled “Methods for Making EUV Patternable Hard Masks”, incorporated herein by reference. Production of radiation sensitive organotin coatings can generally be achieved by reacting the volatile organotin precursor RSnL3 with a small gas-phase molecule. The reactions can include hydrolysis/condensation of the organotin precursor to hydrolyze the hydrolysable ligands while leaving the Sn—C bonds substantially intact. In some embodiments, two or more distinct RSnL3 compounds having different R and/or L ligands can be used to form a final film that comprises a mixture of the RSn species.
Whether deposited by solution deposition or vapor deposition, hydrolysis of the hydrolysable ligands can result in formation of an oxo-hydroxo network represented by RSnOxOH3-2x. Generally, radiation exposure and patterning is performed with the hydrolyzed coating.
With respect to an outline of a representative process for a radiation-based patterning, e.g., an extreme ultraviolet (EUV) lithographic process, photoresist material is deposited or coated as a thin film on a substrate, pre-exposure baked, exposed with a pattern of radiation to create a latent image, post-exposure baked, and then developed with a liquid, typically an organic solvent, to produce a developed pattern of the resist. Fewer steps can be used if desired, and additional steps can be used to remove residue to improve pattern fidelity.
The thickness of the radiation patternable coating can depend on the desired process. For use in single-patterning EUV lithography, coating thicknesses are generally chosen to yield patterns with low defectivity and reproducibility of the patterning. In some embodiments, suitable coating thickness can from between 0.1 nm and 100 nm, in further embodiments from about 1 nm to 50 nm, and in further embodiments from about 2 nm to 25 nm. Those of ordinary skill in the art will understand that additional ranges of coating thickness are contemplated and are within the present disclosure.
Coating thickness for radiation patternable coatings prepared by vapor deposition techniques can generally be controlled through appropriate selection of reaction time or cycles of the process. The thickness of the radiation patternable coating can depend on the desired process. For use in single-patterning EUV lithography, coating thicknesses are generally chosen to yield patterns with low defectivity and reproducibility of the patterning. In some embodiments, suitable coating thickness can from between 0.1 nm and 100 nm, in further embodiments from about 1 nm to 50 nm, and in further embodiments from about 2 nm to 25 nm. Those of ordinary skill in the art will understand that additional ranges of coating thickness are contemplated and are within the present disclosure.
The substrate generally presents a surface onto which the coating material can be deposited, and it may comprise a plurality of layers in which the surface relates to an upper most layer. The substrate is not particularly limited and can comprise any reasonable material such as silicon, silica, other inorganic materials, such as ceramics, and polymer materials.
After deposition and formation of the radiation patternable coating, further processing can be employed prior to exposure with radiation. In some embodiments, the coating can be heated from between 30° C. and 300° C., in further embodiments from between 50° C. and 200° C., and in further embodiments from between 80° C. and 150° C. The heating can be performed, in some embodiments for about 10 seconds to about 10 minutes, in further embodiments from about 30 seconds to about 5 minutes, and in further embodiments from about 45 seconds to about 2 minutes. Additional ranges for temperatures and heating durations within the above explicit ranges are anticipated and envisioned.
Radiation generally can be directed to the coated substrate through a mask or a radiation beam can be controllably scanned across the substrate. In general, the radiation can comprise electromagnetic radiation, an electron-beam (beta radiation), or other suitable radiation. In general, electromagnetic radiation can have a desired wavelength or range of wavelengths, such as visible radiation, ultraviolet radiation, or X-ray radiation. The resolution achievable for the radiation pattern is generally dependent on the radiation wavelength, and a higher resolution pattern generally can be achieved with shorter wavelength radiation. Thus, it can be desirable to use ultraviolet light, X-ray radiation, or an electron-beam to achieve particularly high-resolution patterns.
Following International Standard ISO 21348 (2007) incorporated herein by reference, ultraviolet light extends between wavelengths of greater than or equal to 100 nm and less than 400 nm. A krypton fluoride laser can be used as a source for 248 nm ultraviolet light. The ultraviolet range can be subdivided in several ways under accepted Standards, such as extreme ultraviolet (EUV) from greater than or equal 10 nm to less than 121 nm and far ultraviolet (FUV) from greater than or equal to 122 nm to less than 200 nm. A 193 nm line from an argon fluoride laser can be used as a radiation source in the FUV. EUV light at 13.5 nm has been used for lithography, and this light is generated from a Xe or Sn plasma source excited using high energy lasers or discharge pulses. Soft x-rays can be defined from greater than or equal to 0.1 nm to less than 10 nm.
Based on the design of the coating material, there can be a large contrast of material properties between the irradiated regions that have condensed coating material and the unirradiated, coating material with substantially intact Sn—C bonds. For embodiments in which a post irradiation heat treatment is used, the post-irradiation heat treatment can be performed at temperatures from about 45° C. to about 250° C., in additional embodiments from about 50° C. to about 190° C. and in further embodiments from about 60° C. to about 175° C. The post exposure heating can generally be performed for at least about 0.1 minute, in further embodiments from about 0.5 minutes to about 30 minutes and in additional embodiments from about 0.75 minutes to about 10 minutes. A person of ordinary skill in the art will recognize that additional ranges of post-irradiation heating temperature and times within the explicit ranges above are contemplated and are within the present disclosure. This high contrast in material properties further facilitates the formation of high-resolution lines with smooth edges in the pattern following development as described in the following section.
For the negative tone imaging, the developer can be an organic solvent, such as the solvents used to form the precursor solutions. In general, developer selection can be influenced by solubility parameters with respect to the coating material, both irradiated and non-irradiated, as well as developer volatility, flammability, toxicity, viscosity and potential chemical interactions with other process material. In particular, suitable developers include, for example, alcohols (e.g., 4-methyl-2-pentanol, 1-butanol, isopropanol, 1-propanol, methanol), ethyl lactate, ethers (e.g., tetrahydrofuran, dioxane, anisole), esters (propylene glycol monomethyl ether acetate, ethyl acetate, ethyl lactate), ketones (pentanone, hexanone, 2-heptanone, octanone), and the like, and mixtures thereof. Suitable developers are further described in published U.S. Patent Application No. 2020/0326627 to Jiang et. al, entitled “Organometallic photoresist developer compositions and processing methods”, incorporated herein by reference, and such developers may generally include solvent blends of ketone, alcohol, ether, ester and water, glycol ether, pyrrolidone, lactone, carboxylic acid, or combinations thereof. The development can be performed for about 5 seconds to about 30 minutes, in further embodiments from about 8 seconds to about 15 minutes and in additional embodiments from about 10 seconds to about 10 minutes. A person of ordinary skill in the art will recognize that additional ranges within the explicit ranges above are contemplated and are within the present disclosure.
With a weaker developer, e.g., diluted organic developer or compositions in which the coating has a lower development rate, a higher temperature development process can be used to increase the rate of the process. With a stronger developer, the temperature of the development process can be lower to reduce the rate and/or control the kinetics of the development. In general, the temperature of the development can be adjusted between the appropriate values consistent with the volatility of the solvents. Additionally, developer with dissolved coating material near the developer-coating interface can be dispersed with ultrasonication during development. The developer can be applied to the patterned coating material using any reasonable approach. For example, the developer can be sprayed onto the patterned coating material. Also, spin coating can be used. For automated processing, a puddle method can be used involving the pouring of the developer onto the coating material in a stationary format. If desired spin rinsing and/or drying can be used to complete the development process. Suitable rinsing solutions include, for example, ultrapure water, aqueous tetraalkyl ammonium hydroxide, methyl alcohol, ethyl alcohol, propyl alcohol and combinations thereof. After the image is developed, the coating material is disposed on the substrate as a pattern.
In some embodiments, a solventless (dry) development process may be conducted through the use of an appropriate thermal development or plasma development process, such as those described by Tan et. al in PCT Pat App. No: PCT/US2020/039615 entitled “Photoresist Development With Halide Chemistries”, incorporated herein by reference. For organotin photoresist coatings, dry development can be conducted through the use of halogen-containing plasmas and gases, for example HBr and BCl3. In some cases, dry development may offer advantages over wet development such as reduced pattern collapse, deceased scum, and fine control over developer compositions, i.e. the plasma and/or etch gases.
After completion of the development step, the coating materials can be heat treated to further condense the material and to further dehydrate, densify, or remove residual developer from the material. This heat treatment can be particularly desirable for embodiments in which the oxide coating material is incorporated into the ultimate device, although it may be desirable to perform the heat treatment for some embodiments in which the coating material is used as a resist and ultimately removed if the stabilization of the coating material is desirable to facilitate further patterning. In particular, the bake of the patterned coating material can be performed under conditions in which the patterned coating material exhibits desired levels of etch selectivity. In some embodiments, the patterned coating material can be heated to a temperature from about 100° C. to about 600° C., in further embodiments from about 175° C. to about 500° C. and in additional embodiments from about 200° C. to about 400° C. The heating can be performed for at least about 1 minute, in other embodiment for about 2 minutes to about 1 hour, in further embodiments from about 2.5 minutes to about 25 minutes. The heating may be performed in air, vacuum, or an inert gas ambient, such as Ar or N2. A person of ordinary skill in the art will recognize that additional ranges of temperatures and time for the heat treatment within the explicit ranges above are contemplated and are within the present disclosure. Likewise, non-thermal treatments, including blanket UV exposure, or exposure to an oxidizing plasma such as O2 may also be employed for similar purposes.
This example describes a method for the one-pot, direct synthesis of an organo tin trialkoxide. The method is based on the following two reactions, with the second reaction performed at room temperature and employing a tetraalkyl (quaternary) ammonium salt as a catalyst. Experiments described in all of the examples are performed under oxygen depleted inert atmospheres, such as nitrogen, argon or other inert atmospheres.
SnCl2+K(OtBu)→KSn(OtBu)3 (1)
KSn(OtBu)3+CH3I→MeSn(OtBu)3 (2)
(1) Tin dichloride and anhydrous tetrahydrofuran were added to a reaction vessel under inert atmosphere to form a solution having a concentration of approximately 0.07 g SnCl2/ml THF. The solution was mixed for while cooling to 4° C. Then 2.0 molar equivalents of potassium tert-butyl oxide relative to the initial tin dichloride amount was added slowly. The reaction mixture was maintained at a temperature below 60° C. Upon completion of the addition step, the reaction mixture was stirred for 1 hour. The resulting white precipitate was removed by filtration over a bed of celite and the filtrate was collected. Additional potassium tert-butyl oxide (0.9 molar equivalents relative to the initial tin dichloride amount) was added slowly to the filtrate. In view of processing practicalities, the 0.9 molar equivalents relative to initial tin is roughly a molar equivalent relative to persistent tin. The reaction mixture was maintained at a temperature below 60° C. Volatiles were removed under vacuum and the product was recrystallized from a 1:1 mixture of THF/Toluene (˜2 mL/g product) at −20° C. to afford KSn(OtBu)3 as a white crystalline solid.
(2) The KSn(OtBu)3 product from (1) (one molar equivalent) was mixed with, 0.5 molar equivalents of tetrabutylammonium iodide ((n-Bu)4N(I)) as a catalyst, and toluene were added to the reaction vessel under inert atmosphere to form a solution having a concentration of approximately 0.10 g KSn(OtBu)3/ml toluene. The solution was mixed for at room temperature. Then 1.5 molar equivalents of methyl iodide (CH3I) relative to the KSn(OtBu)3 amount was added slowly and the reaction was stirred for 1 hour at room temperature. Volatiles were removed under vacuum and the remaining residue was filtered over a bed of celite with pentane. The filtrate was pumped down and distilled to afford MeSn(OtBu)3 as a clear yellow liquid.
This example demonstrates a two-step, one-pot method for directly synthesizing an organotin trialkoxide having primary Sn—C bonds with high mono-organo specificity. The method uses commercially available tin dichloride, alkali alkoxide, and alkyl halide reagents.
This example describes a method for the one-pot, direct synthesis of an organo tin trialkoxide. The method is based on the following reaction. The reaction is performed with the addition of heat and a tetraalkyl (quaternary) ammonium salt as a catalyst.
KSn(OtBu)3+(CH3)2CH2I→iPrSn(OtBu)3
The KSn(OtBu)3 product from Example 1, 0.67 molar equivalents (referenced to 1 molar equivalent of tin) of tetrabutylammonium iodide ((n-Bu)4N(I)) as a catalyst, and toluene were added to a reaction vessel under inert atmosphere and mixed to form a solution having a concentration of approximately 0.10 g KSn(OtBu)3/ml toluene. The solution was mixed for at room temperature. Then 1.5 molar equivalents of 2-iodopropane ((CH3)2CH2I) relative to the KSn(OtBu)3 amount was added slowly with stirring. Then the reaction mixture was heated to 80° C. and stirred for 2 days. Afterwards, volatiles were removed under vacuum and the remaining residue was filtered over a bed of celite with pentane. The filtrate was pumped down and distilled to afford 2-propyltin tris(tert-butyl oxide) (iPrSn(OtBu)3) as a clear yellow liquid.
This example demonstrates a method for directly synthesizing an organotin trialkoxide having secondary Sn—C bonds with high mono-organo specificity.
This example describes two methods that use different alkylhalides (RX) for the one-pot, direct synthesis of an organo tin trialkoxide. The methods are based on the following reaction, with RX being nPrI in Method A and nPrBr in Method B. The reactions were performed with the addition of heat and a tetraalkyl (quaternary) ammonium salt as a catalyst.
KSn(OtBu)3+RX→nPrSn(OtBu)3
Method A. The KSn(OtBu)3 product from Example 1, 0.5 molar equivalents (referenced to 1 molar equivalent of tin) of tetrabutylammonium iodide ((n-Bu)4N(I)) as a catalyst, and toluene were added to a reaction vessel under inert atmosphere and mixed to form a solution having a concentration of approximately 0.10 g KSn(OtBu)3/ml toluene. The solution was mixed for at room temperature. Then 1.3 molar equivalents of 1-iodopropane (nPrI) relative to the KSn(OtBu)3 amount was added slowly with stirring. Then the reaction mixture was heated to 45° C. and stirred for 1 day. Afterwards, volatiles were removed under vacuum and the remaining residue was filtered over a bed of celite with pentane. The filtrate was pumped down and distilled to afford 1-propyltin tris(tert-butyl oxide) (nPrSn(OtBu)3) as a clear yellow liquid.
Method B. The procedure of Method A was repeated with two exceptions: 0.4 molar equivalents of tetrabutylammonium iodide were used as a catalyst and 1.3 molar equivalents of 1-bromopropane (nPrBr) relative to the KSn(OtBu)3 amount was used as the alkylhalide reagent. The filtrate was distilled to afford 1-propyltin tris(tert-butyl oxide) (nPrSn(OtBu)3) as a clear yellow liquid.
This example demonstrates that different halide groups can be used in the direct synthesis of organotin trialkoxides having high mono-organo specificity.
This example describes a method for the one-pot, direct synthesis of an unsaturated organo tin trialkoxide. The method is based on the following reaction. The reaction is performed with the addition of heat and a tetraalkyl (quaternary) ammonium salt as a catalyst.
KSn(OtBu)3+(CH3)(H)C═C(H)(CH2Cl),→(CH3)(H)C═C(H)(CH2)Sn(OtBu)3
The KSn(OtBu)3 product from Example 1, 0.1 molar equivalents (referenced to 1 molar equivalent of tin) of tetrabutylammonium iodide ((n-Bu)4N(I)) as a catalyst, and toluene were added to a reaction vessel under inert atmosphere and mixed to form a solution having a concentration of approximately 0.10 g KSn(OtBu)3/ml toluene. The solution was mixed for at room temperature. Then 1.2 molar equivalents of 1-chloro-2-butene ((CH3)(H)C═C(H)(CH2Cl) (mixture of trans- and cis- and isomers, in an approximate ratio of 70:30) relative to the KSn(OtBu)3 amount was added slowly with stirring. Then the reaction mixture was heated to 45° C. and stirred for 3 days. Afterwards, volatiles were removed under vacuum and the remaining residue was filtered over a bed of celite with pentane. The filtrate was pumped down and distilled to afford the product (CH3)(H)C═C(H)(CH2)Sn(OtBu)3 (1-but-3-enyltin tris(tert-butyl oxide) or MAL) as a mixture of trans- and cis-isomers. The product was a clear yellow liquid.
This example demonstrates a method for directly synthesizing an unsaturated organotin trialkoxide with high mono-organo specificity. This example also demonstrates that the method proceeds with both the trans- and cis-isomers of an olefinic halide reagent.
This example describes a method for the one-pot, direct synthesis of a fluorinated organo tin trialkoxide under UV light. The method is based on the following reaction.
Sn2(OtBu)4+CF3CH2I→CF3CH2Sn(OtBu)3
Sn2(OtBu)4, 1.3 molar equivalents (referenced to 1 molar equivalent of ditin reactant) of 2,2,2-trifluoroiodoethane (CF3CH2I), and pentane were added to a reaction vessel under inert atmosphere and mixed to form a solution having a concentration of approximately 0.33 g Sn2(OtBu)4/ml pentane. The solution was mixed for at room temperature. Then the solution was irradiated with ultraviolet light (40 W LED; 365 nm) overnight (approximately 15 hours). Afterwards, the reaction mixture was filtered over a bed of celite and the volatiles of the filtrate were removed under vacuum. The resulting filtrate was distilled to afford the final product CF3CH2Sn(OtBu)3 (2,2,2-trifluoroethyltin tris(tert-butyl oxide) or TFE). The product was a clear yellow liquid.
The NMR results indicate that there are no identified tin by-products in the conversion of KSn(OtBu)3 to CF3CH2Sn(OtBu)3.
This example demonstrates a photochemical method for directly synthesizing a fluorinated organotin trialkoxide with high mono-organo specificity.
This example describes a photochemical method for the one-pot, direct synthesis of a fluorinated organo tin trialkoxide under visible (LED) light. The method is based on the following reaction.
KSn(OtBu)3+CF3CH2I→CF3CH2Sn(OtBu)3
The KSn(OtBu)3 product from Example 1, 1.1 molar equivalents (referenced to 1 molar equivalent of tin) of 2,2,2-trifluoroiodoethane (CF3CH2I), and acetonitrile were added to a reaction vessel under inert atmosphere and mixed to form a solution having a concentration of approximately 0.25 g KSn(OtBu)3/ml acetonitrile. The solution was mixed for at room temperature. Then, while stirring, the solution was irradiated with visible light for 1 day. The visible light was provided via a 100 W LED and was either purple light (approximately 400 nm) or blue light (approximately 460 nm). The external temperature of the reaction vessel was maintained below 30° C. with the use of a fan. Afterwards, the reaction solvent was removed under reduced pressure and the remaining residue was filtered over a bed of celite with pentane. Volatiles of the filtrate were removed under vacuum and the resulting oil was distilled to afford the final product CF3CH2Sn(OtBu)3 (2,2,2-trifluoroethyltin tris(tert-butyl oxide) or TFE). The product was a clear yellow liquid.
A solution was prepared according to Part 1 with the exception that the solution was provided in a sealed NMR tube (under inert atmosphere) instead in a reaction vessel. The NMR tube was irradiated for 3 hours with a 100 W green LED (approximately 530 nm). Conversion to the product CF3CH2Sn(OtBu)3 was confirmed by the disappearance of the KSn(OtBu)3 signal in 119Sn NMR (δ −188 ppm), as shown in
An additional experiment was performed to study the effect of the LED light on the method. A solution of KSn(OtBu)3. 1.5 molar equivalents (referenced to 1 molar equivalent of tin) of CF3CH2I, and acetonitrile were added to a reaction vessel under inert atmosphere and mixed to form a solution having a concentration of approximately 0.33 g KSn(OtBu)3/ml acetonitrile (Solution A). Another solution in the same way as Solution A except 0.4 molar equivalents of tetrabutylammonium iodide relative to the KSn(OtBu)3 amount was also added (Solution B). Solution A and Solution B were each heated to 80° C. and stirred for 2 days. Afterwards, NMR analyses were performed for each of the samples. The results showed that CF3CH2Sn(OtBu)3 was not formed for either sample, indicating that more photons than standard ambient light provides is needed to form the fluorinated trialkoxy product. The results of this study are in contrast to the results shown in Example 2 in which a non-fluorinated trialkoxy product was prepared with the same reagents and the same heating conditions as used with Solution B.
This example demonstrates a photochemical method for directly synthesizing a fluorinated organotin trialkoxide with high mono-organo specificity and high yield. This example also demonstrates that the method is effective with visible light of various wavelengths. This example further demonstrates that the reaction to form the fluorinated trialkoxy product is photochemically driven.
This example describes a method for the direct synthesis of the organo di-tin trialkoxide represented by Formula 1. The method is based on the following reaction. The reaction is performed with the addition of heat and a tetraalkyl (quaternary) ammonium salt as a catalyst and the product is purified via sublimation.
The KSn(OtBu)3 product from Example 1 (2.1 molar equivalents), tetrabutylammonium iodide ((n-Bu)4N(I)) (0.21 molar equivalents) as a catalyst, and toluene) were added to a reaction vessel under inert atmosphere and mixed to form a solution having a concentration of approximately 0.5 mmol KSn(OtBu)3/ml toluene. The solution was mixed for at room temperature. Then 1.0 molar equivalent of 1,4-diiodobutane (CH2I)CH2)2CH2I, Ambeed) was added slowly with stirring. The reaction mixture was heated to 60° C. and stirred overnight (approximately 15 hours). Afterwards, volatiles were removed under vacuum and the remaining residue was dissolved into pentane. The pentane mixture was then filtered over a bed of celite. The filtrate was pumped down under reduced pressure to afford a colorless solid. The colorless solid was then stirred in acetonitrile (5 mL/g solid) overnight under inert atmosphere. Following stirring, the solids were recollected via filtration with a medium porosity fritted glass filter and washed with minimal acetonitrile. The collected solids were then dissolved into acetonitrile (10 mL/g solids) by heating at 50° C., followed by filtering the heated solution over Celite into a sealed flask, and then cooling the sealed flask at −20 ° C. to form crystals over the course of about 12 hours. After removing the mother liquor via decanting and evaporation, the crystalline solids were subjected to sublimation under vacuum (60 mTorr) to yield colorless crystals of the product (C4H8Sn2(OtBu)6, Formula 1).
This example demonstrates a method for directly synthesizing an organo di-tin trialkoxide having the general formula L3Sn—R—SnL3. This example also demonstrates that sublimation can be used effectively to purify the di-tin compositions.
This example describes a method for the direct synthesis of the organo tri-tin trialkoxide, represented by Formula 2. The method is based on the following reaction. The reaction is performed with the addition of heat and a tetraalkyl (quaternary) ammonium salt as a catalyst.
KSn(OtBu)3+C9H9Br3→C6H3(CH2Sn(OtBu)3)3 (Formula 2)
The KSn(OtBu)3 product from Example 1, 0.1 molar equivalents (referenced to 1 molar equivalent of tin) of tetrabutylammonium iodide ((n-Bu)4N(I)) as a catalyst, and toluene were added to a reaction vessel under inert atmosphere and mixed to form a solution having a concentration of approximately 0.10 g KSn(OtBu)3/ml toluene. The solution was mixed for at room temperature. Then 0.3 molar equivalents of 1,3,5-tris-(bromomethyl)benzene (C9H9Br3) relative to the KSn(OtBu)3 amount was added slowly with stirring. Then the reaction mixture was heated to 45° C. and stirred overnight (approximately 15 hours). Afterwards, volatiles were removed under vacuum and the remaining residue was filtered over a bed of celite with pentane. The filtrate was pumped down and washed with MeCN to obtain a white solid.
This example demonstrates a method for directly synthesizing an organo tri-tin trialkoxide and suggests that other organo polytin trialkoxides could be similarly prepared.
This example describes a method for the one-pot, direct synthesis of a fluorinated organo tin trialkoxide under UV light. The method is based on the following reaction.
Sn2(OtBu)4 was mixed with pentane in a reaction vessel under inert atmosphere to form a solution having a concentration of approximately 0.33 g Sn2(OtBu)4/ml pentane. The mixture was cooled to −40° C. Then 1.3 molar equivalents (referenced to 1 molar equivalent of ditin reactant) of (CF3)2CHCH2I was added to a reaction vessel with stirring. The solution was irradiated with ultraviolet light (40 W LED; 365 nm) for approximately 12 hours with mixing while maintain a reaction temperature below −30° C. The reaction mixture was then further diluted in pentane (5 mL pentane/1 mL mixture) to form a diluted crude mixture that was then held at −20° C. for 24 hours. The reaction mixture was then filtered over a bed of celite and the volatiles of the filtrate were removed under vacuum. The resulting filtrate was distilled to afford the final product (CF3)2CHCH2Sn(OtBu)3 (3,3,3,4,4,4-hexafluoroisobuyltin tris(tert-butyl oxide) or HFB), as represented by Formula 3. The product was a clear yellow liquid.
This example demonstrates a photochemical method for directly synthesizing a polyfluorinated organotin trialkoxide with high mono-organo specificity.
This example describes a method for the one-pot, direct synthesis of a fluorinated organo tin trialkoxide under UV light. The method is based on the following reaction.
The method of Example 9 is followed with the exception of performing the reaction with (CF3)2CF(CH2)2I instead of (CF3)2CHCH2I. The resulting filtrate is distilled to afford the final product (CF3)2CF(CH2)2Sn(OtBu)3 (4,5,5,5,6,6,6-heptafluoropentyltin tris(tert-butyl oxide) or HFP), as represented by Formula 4.
This example describes a photochemical method for directly synthesizing a polyfluorinated organotin trialkoxide with an expected high mono-organo specificity.
The embodiments above are intended to be illustrative and not limiting. Additional embodiments are within the claims. In addition, although the present invention has been described with reference to particular 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 invention. Any incorporation by reference of documents above is limited such that no subject matter is incorporated that is contrary to the explicit disclosure herein. To the extent that specific structures, compositions and/or processes are described herein with components, elements, ingredients or other partitions, it is to be understand that the disclosure herein covers the specific embodiments, embodiments comprising the specific components, elements, ingredients, other partitions or combinations thereof as well as embodiments consisting essentially of such specific components, ingredients or other partitions or combinations thereof that can include additional features that do not change the fundamental nature of the subject matter, as suggested in the discussion, unless otherwise specifically indicated. The use of the term “about” herein refers to expected uncertainties in the associated values as would be understood in the particular context by a person of ordinary skill in the art.
This application claims priority to copending U.S. provisional patent application 63/429,261 filed Dec. 1, 2022 to Jilek et al., entitled “Direct Synthesis of Organotin Alkoxides,” incorporated herein by reference.
| Number | Date | Country | |
|---|---|---|---|
| 63429261 | Dec 2022 | US |
