Anhydrous hexane

Example 1

This example is directed to the formation of organotin amido compounds that are suitable for in situ hydrolysis to form coatings of organotin oxide hydroxides.

The precursor, tert-butyl tris(diethylamido)tin, (tBuSn(NEt₂)₃, hereinafter P-1) was synthesized after the method reported in Hänssgen, D.; Puff, H.; Beckerman, N. J. Organomet. Chem. 1985, 293, 191, incorporated herein by reference. Tetrakis(diethylamido)tin and tBuLi reagents were purchased from Sigma-Aldrich and used without further purification. Reagents were reacted in stoichiometric quantities at −78° C. in anhydrous hexanes (Sigma-Aldrich). Precipitated lithium amide salts were removed via filtration and the product rinsed with hexanes, and the solvent stripped under vacuum. The crude product was distilled under vacuum (˜0.3 torr at 95° C.).

A solution was prepared in an Ar-filled glove box by weighing 1.177 g (3.0 mmol) of P-1 in a 30-mL amber glass vial and then adding 15 mL of anhydrous 4-methyl-2-pentanol (dried 24 h over 3 A molecular sieves). The vial was capped and agitated. This stock solution was diluted 1 part in 2.85 parts (volume) anhydrous 4-methyl-2-pentanol prior to coating.

The precursor, isopropyl tris(dimethylamido)tin, (iPrSn(NMe₂)₃, hereinafter P-2) was synthesized under inert atmosphere and subsequently dissolved in toluene to form a resist precursor solution. Under argon, a 1-L Schlenk-adapted round bottom flask was charged with LiNMe₂ (81.75 g, 1.6 mol, Sigma-Aldrich) and anhydrous hexanes (700 mL, Sigma-Aldrich) to form a slurry. A large stir bar was added and the vessel sealed. An addition funnel under positive argon pressure was charged with iPrSnCl₃ (134.3 g, 0.5 mol, Gelest) via syringe and then attached to the reaction flask. The reaction flask was cooled to −78° C. and the iPrSnCl₃ was then added dropwise over a period of 2 hours. The reaction was warmed to room temperature overnight while stirring. The reaction produces a by-product solid. After settling, the solid was filtered under positive argon pressure through an in-line cannula filter. The solvent was then removed under vacuum, and the residue distilled under reduced pressure (50-52° C., 1.4 mmHg) to give a pale yellow liquid (110 g, 75% yield). ¹H and ¹¹⁹Sn NMR spectra of the distillate in a C₆D₆ solvent were collected on a Bruker DPX-400 (400 MHz, BBO probe) spectrometer. Observed ¹H resonances (s, 2.82 ppm, —N(CH₃)₂; d 1.26 ppm, —CH₃; m, 1.60 ppm, —CH) match the predicted spectrum for iPrSn(NMe₂)₃. The primary ¹¹⁹Sn resonance at −65.4 ppm is consistent with a major product having a single tin environment; the chemical shift is comparable to reported monoalkyl tris(dialkylamido)tin compounds.

A solution was prepared in an Ar-filled glove box by weighing 0.662 g (2.25 mmol) of P-2 in a 30 mL amber glass vial. A 15-mL volume of anhydrous toluene (dried 24 h over 3 A molecular sieves) were then added to make a stock solution (SOL-2). The vial was then capped and agitated. This stock solution was diluted 1 part in 3 parts (volume) anhydrous toluene prior to coating.

Example 2

This example demonstrates the successful in situ hydrolysis of coatings formed from the compositions of Example 1 and the subsequent EUV patterning.

Thin films were deposited on silicon wafers (100-mm diameter) with a native-oxide surface. The Si wafers were treated with a hexamethyldisilazane (HMDS) vapor prime prior to deposition of the amido precursor. Solutions of P-1 in 4-methyl-2-pentanol were spin-coated on substrates in air at 1500 rpm and baked on a hotplate in air for 2 min at 100° C. to evaporate residual solvent and volatile hydrolysis products. Film thickness following coating and baking was measured via ellipsometry to be ˜31 nm.

The coated substrates were exposed to extreme ultraviolet radiation (Lawrence Berkeley National Laboratory Micro Exposure Tool). A pattern of 17-nm lines on a 34-nm pitch was projected onto the wafer using 13.5-nm wavelength radiation, dipole illumination, and a numerical aperture of 0.3. The patterned resists and substrates were then subjected to a post-exposure bake (PEB) on a hotplate for 2 min at 170° C. in air. The exposed film was then dipped in 2-heptanone for 15 seconds, then rinsed an additional 15 seconds with the same developer to form a negative tone image, i.e., unexposed portions of the coating were removed. A final 5-min hotplate bake at 150° C. in air was performed after development. FIG. 7 exhibits an SEM image of 16.7-nm resist lines produced from P-1 cast from 4-methyl-2-pentanol on a 34-nm pitch at a EUV dose of 56 mJ/cm² with a calculated LWR of 2.6 nm.

A second film was cast from the solution of P-2 in toluene using identical coating and bake conditions as above. A linear array of 50 circular pads ˜500 um in diameter were projected on the wafer using EUV light. Pad exposure times were modulated to step the delivered EUV dose for each pad from 1.38 to 37.99 mJ cm⁻² with an exponential 7% step. Following the PEB, development, and final bake processes described above, a J. A. Woollam M-2000 Spectroscopic ellipsometer was used to measure the residual thickness of the exposed pads. The thickness of each pad is plotted as a function of delivered EUV dose in FIG. 8. The resulting curve clearly illustrates the negative tone contrast generated on exposure, as residual film thickness starts at ˜0 and reaches a maximum (dose to gel, D_g) at approximately 15.8 mJ cm⁻² delivered dose.

Example 4

This example describes formation of mixed hydrolysable precursor compounds to provide for control of the stoichiometry of radiation sensitive ligands relative to metal in the radiation sensitive coatings.

Tert-butyl tris(diethylamido)tin was synthesized as described in Example 1. Tetrakis(dimethylamido)tin, (Sn(NMe₂)₄, FW=295.01) was purchased from Sigma-Aldrich and used without further purification.

Tin (IV) tert-butoxide, (Sn(O^tBu)₄, FW=411.16, hereinafter P-5) was prepared after the method of Hampden-Smith et al. Canadian Journal of Chemistry, 1991, 69, 121, incorporated herein by reference: Stannous chloride (152 g/0.8 mol) and pentane (1 L) were added to a 3-L oven-dried round-bottom flask equipped with a magnetic stir-bar and purged with nitrogen. A 1-L pressure-equalizing addition funnel fitted with a nitrogen pressure inlet was charged with diethylamine (402 mL/3.9 mol) and pentane (600 mL) and then attached to the flask, and the flask submerged in an ice bath. The amine solution was then added dropwise such that a gentle reflux was maintained. Upon completion of the amine addition, 2-methyl-2-propanol (290 g/3.9 mol) in pentane (50 mL) was added to the addition funnel and thence dropwise to the flask. After stirring for 18 hours, the slurry was transferred into an air-free fritted filter flask and precipitated salts removed. The solvent was removed under reduced pressure and the target compound distilled (B.P.=60-62 C @ 1 torr). ¹H NMR (C₆D₆): 1.45 ppm (s); ¹¹⁹Sn NMR (C₆D₆): −371.4 ppm (s).

Stock solutions of P-1 (^tBuSn(NEt₂)₃, hereinafter S-1), P-4 (Sn(NMe₂)₄, hereinafter S-2), and P-5 (Sn(O^tBu)₄, hereinafter S-3) were prepared by transferring each of the corresponding compounds via cannula into separate flasks containing anhydrous 4-methyl-2-pentanol (dried 24 h over 4 A molecular sieves). Additional dry 4-methyl-2-pentanol was then added to dilute the solutions to 0.25 M (Sn) final concentration.

A further stock solution, S-4, was prepared by cannulating 41 g of P-1 into a round bottom flask immersed in an iso-propanol/dry ice bath and containing 250 mL of methanol while stirring on a magnetic stir plate. After the transfer of the ^tBuSn(NEt₂)₃ aliquot, the flask containing the mixture was removed from the ice bath and allowed to reach room temperature. Next, the flask containing the mixture was brought to 50° C. in a water bath attached to a rotary evaporator and the solvent stripped at reduced pressure (10 mtorr) until solvent evaporation was substantially complete and a viscous yellow oil obtained. Finally, the yellow oil was dissolved in 1.0 L of 4-methy-2-pentanol. The resulting solution was determined to have a molarity of 0.097 M [Sn] based on the residual mass of the solution following solvent evaporation and subsequent thermal decomposition of the residual solids to SnO₂.

Precursor coating solutions CS-a, CS-b, and CS-c were prepared by mixing stock solution S-1 with S-2 in 0, 5:1, and 9:1 volume ratios to produce coating solutions where 0 (a), 10 (b), and 20 (c) mol % of the total Sn concentration in the mixture was derived from Sn(NMe₂)₄. These solutions were then further diluted with 4-methyl-2-pentanol to 0.070 M (total Sn) prior to spin coating. For example, to prepare 200 mL of CS-b, 5.6 mL of the stock solution prepared from Sn(NMe₂)₄ (S-2) was added to 50.4 mL of the solution prepared from ^tBuSn(NEt₂)₃ (S-1), mixed vigorously, and diluted to 200 mL total volume with dry 4-methyl-2-pentanol. A summary of precursor coating solutions, concentrations, and compositions is presented in Table 2.

Precursor coating solutions CS-e-h were prepared with a total Sn concentration of 0.044 M by mixing stock solution S-4 with stock solutions S-2 and S-3 in appropriate volume ratios such that 10 and 20 mol % of the total Sn concentration was derived from Sn(NMe₂)₄ (CS-e, CS-f, respectively), and Sn(O^tBu)₄ (CS-g, CS-h) and diluting with dry 4-methyl-2-pentanol. Precursor coating solution CS-d was prepared by directly diluting stock solution S-4 with dry 4-methyl-2-pentanol to a final concentration of 0.042 M Sn. As an example, 200 mL of precursor coating solution CS-e is prepared by mixing 72.6 mL of S-4 with 7.04 mL of S-3, and diluting to 200 mL total volume with dry 4-methyl-2-pentanol.

Precursor coating solution CS-i was prepared by mixing a methanol solution containing a pre-hydrolysed t-butyl tin oxide hydroxide hydrolysate with a 4-methyl-2-pentanol solution of a prehydrolysed i-propyl tin oxide hydroxide hydrolysate, and diluting the resulting mixture to 0.03 M [Sn] with pure solvents as described in the '839 application. The resulting solutions are characterized as a blend of ⁱPrSnO_{(3/2−(x/2))}(OH)_x and tBuSnO_{(3/2−(x/2))}(OH)_x hydrolysates, where the fraction of t-BuSnO_{(3/2−(x/2))}(OH)_x is 40% relative to the total moles of Sn.

Example 5

This example presents results obtain by patterning of coatings formed with the coating solutions prepared as described in Example 4 demonstrating improved patterning with lower radiation doses.

Tert-butyltin oxide hydroxide photoresist films were deposited from precursor coating solutions from Example 4 prepared from ^tBuSn(NEt₂)₃ and, for some coating solutions, Sn(NMe₂)₄ or Sn(O^tBu)₄, and then exposed with EUV radiation. Thin films for EUV contrast curves were deposited on silicon wafers (100-mm diameter) with a native-oxide surface. The Si wafers were treated with a hexamethyldisilazane (HMDS) vapor prime prior to deposition. Precursor coating solutions CS-a, CS-b, and CS-c (0.070 M Sn) prepared according to specification in Table 1 from ^tBuSn(NEt₂)₃ and 0, 10, and 20 mol % Sn(NMe₂)₄ were spin-coated the Si substrates in air at 1500 rpm and baked on a hotplate in air for 2 min at 100° C. to eliminate residual solvent and volatile hydrolysis products. Film thicknesses following coating and baking were measured via ellipsometry to be ˜25-28 nm.

A linear array of 50 circular pads ˜500 m in diameter were exposed on each wafer with EUV light using the Lawrence Berkeley National Laboratory Micro Exposure Tool. Pad exposure times were modulated to step the delivered EUV dose for each pad from 1.38 to 37.99 mJ cm⁻² with an exponential 7% step. After exposure, wafers were subjected to a post-exposure bake (PEB) on a hotplate in air at 170° C. for 2 min. The exposed film was then dipped in 2-heptanone for 15 seconds and rinsed an additional 15 seconds with the same developer to form a negative tone image, i.e., unexposed portions of the coating were removed. A final 5-min hotplate bake at 150° C. in air was performed after development. A J. A. Woollam M-2000 spectroscopic ellipsometer was used to measure the residual thickness of the exposed pads. The measured thicknesses were normalized to the maximum measured resist thickness and plotted versus the logarithm of exposure dose to form characteristic curves for each resist at a series of post exposure bake temperatures. See FIG. 10. The maximum slope of the normalized thickness vs log dose curve is defined as the photoresist contrast (γ) and the dose value at which a tangent line drawn through this point equals 1 is defined as the photoresist dose-to-gel, (D_g). In this way common parameters used for photoresist characterization may be approximated following Mack, C. Fundamental Principles of Optical Lithography, John Wiley & Sons, Chichester, U.K; pp 271-272, 2007.

The resulting curves clearly illustrate the negative-tone contrast generated on exposure, as residual pad thickness for each resist film starts at ˜0 and reaches a maximum near D_g. The dose required to initiate the development rate change is clearly observed to decrease as the mol fraction of Sn in the precursor coating solutions corresponding to Sn(NMe₂)₄ is increased from 0 (D_g=13.8 mJ cm⁻²), to 10% (D_g=10.6 mJ cm⁻²), and finally 20% (D_g=5.8 mJ cm⁻².

High-resolution line-space patterns were likewise printed using a EUV scanner and tert-butyltin oxide hydroxide photoresist films cast from precursor coating solutions CS-d, CS-e, and CS-f. Silicon wafers (300-mm diameter) with a native-oxide surface were used as substrates without additional surface treatment. Precursor coating solutions CS-d-h prepared from ^tBuSn(NEt₂)₃ and 0, 10, or 20 mol % Sn(NMe₂)₄ or Sn(O^tBu)₄ as described above, as well as CS-i, were spin-coated on the Si substrates in air at 1000 or 1500 rpm (CS-d only) and baked on a hotplate in air for 2 min at 100° C.

The coated substrates were exposed to extreme ultraviolet radiation using a NXE:3300B EUV scanner with dipole 60× illumination and a numerical aperture of 0.33. A pattern of 16-nm lines on a 32-nm pitch was projected on the coated wafer following 2 minute, 100° C. post-apply bake (PAB). The exposed resist films and substrates were then subjected to a PEB on a hotplate for 2 min at 170° C. in air. The exposed films were then developed in 2-heptanone for 15 seconds, then rinsed an additional 15 seconds with the same developer to form a negative tone image, i.e., unexposed portions of the coating were removed. A final 5-min hotplate bake at 150° C. in air was performed after development. FIG. 11 exhibits SEM images of the resulting resist lines developed from tert-butyltin oxide hydroxide photoresist films. The imaging dose, critical dimension, and line-width roughness are shown for each film cast from precursor coating solutions prepared from ^tBuSn(NEt₂)₃ (CS-d), and 10 or 20 mol % Sn(NMe₂)₄ (CS-e, CS-f, respectively), or Sn(O^tBu)₄ (CS-g, CS-h). Again, imaging dose is observed to decrease with increasing fraction of SnX₄ added to the precursor coating solution. The imaging dose required to achieve a critical dimension of 16 nm is plotted versus the calculated LWR each film cast from precursor coating solutions d-i is plotted in FIG. 12. Significantly, a >30% reduction in the required imaging dose in is obtained for the films cast from CS-e and -f, relative to -i without a concomitant increase in line-width-roughness (LWR), indicating a substantial improvement over the pre-hydrolysed mixed alkyl ligand formulation and an important circumvention (over that dose range) of the commonly observed inverse relationship between patterning dose and LWR.

Example 6

Pattering performance is evaluated for coatings prepared with a mixture of tert-butyl and methyl radiation sensitive ligands.

Specifically, precursor solution preparation, film coating, and lithographic performance were examined in the context of organotin oxide hydroxide photoresist films comprising a mixture of ^tBuSnO_{(3/2−(x/2))}(OH)_x and MeSnO_{(3/2−(x/2))}(OH)_x prepared via in situ hydrolysis of a precursor solution comprising ^tBuSnX₃ and MeSnX₃ compounds.

MeSn(O^tBu)₃ (FW=353.1, hereinafter P-6) was synthesized as follows from MeSnCl₃ (Gelest), an oven-dried RBF equipped with an addition funnel and magnetic stir-bar was charged with 0.8 M MeSnCl₃ in pentane. While cooling with an ice bath, 4 molar equivalents of diethylamine in pentane (5.5 M) were added dropwise through the addition funnel. Upon complete addition, 4 molar equivalents of tert-butyl alcohol mixed 3.25:1 (vol) in pentane were added, and the solution is allowed to stir at room temperature for 30 min. The reaction mixture was then filtered and volatiles removed under vacuum leaving a product as a light oil. The product was then distilled at 55-60° C. at ˜0.1 torr.

A stock solution of P-6 was prepared by dissolution in dry 4-methyl-2-pentanol. This solution of MeSn(O^tBu)₃ was mixed at various volume ratios with a second stock solution of prepared from ^tBuSn(NEt₂)₃ in 4-methyl-2-pentanol in an identical manner to solution S-4 above and diluted with the same solvent to achieve a total Sn concentration of 0.05 M. By this method a series of precursor solutions were prepared with a range of 0-60 mol % of the total alkyl-Sn concentration added as MeSn(OtBu)₃. These precursor solutions were coated on 100-mm Si substrates, baked at 100° C., and then exposed to EUV radiation at varying doses creating a contrast array as previously described.

Following exposure the coated wafers were baked at 170° C. in air and developed for 15 s in 2-heptanone, rinsed for 15 s with a wash-bottle containing the same solvent, then dried under N₂ and baked in air at 150° C. for 5 min. The residual thickness of each exposure pad was measured and plotted as a function of dose in FIG. 13. Extracted resist metrics (see Example 5) are tabulated in Table 3. It is observed from FIG. 13 that Dg decreases markedly as the mol % of MeSn(OtBu)₃ in the precursor solution increases, while the contrast remains high, even at relatively low values of D_g. Importantly, the residual thickness <<D_g is consistently near zero, indicating the resist is cleared in the unexposed region with minimal residue (scum).

A pattern of 18-nm lines on a 36-nm pitch was exposed on similarly processed wafers, using the Lawrence Berkeley National Laboratory Micro Exposure Tool using 13.5-nm wavelength radiation, dipole illumination, and a numerical aperture of 0.3. The line width (CD) measured with a SEM and plotted versus imaging dose in FIG. 14. Again the imaging dose required to achieve a given line-width is found to strongly decrease as the mol-fraction of MeSn(O^tBu)₃ in the precursor solution is increased. Representative SEM images from the same wafers are shown in Figure FIG. 15 for precursor solutions containing a) 20%, b) 40%, and c) 60% P-6.

The embodiments above are intended to be illustrative and not limiting. Additional embodiments are within the claims and additional inventive concepts. 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.

Example 21

Isosorbide (98.0%) was purchased from Fisher Scientific. Ethanox 330 was purchased from SI group. Acetic acid (99.0%), Amberlyst 15 dry resin, reagent grade (99%), methacrylic acid, acrylated epoxidized soybean oil (4,000 ppm inhibitor), N,N-dimethylformamide (DMF) anhydrous (99.8%), hexane (anhydrous) (95.0%), 2-phenyl-2-propyl benzodithioate (99% HPLC grade), and 2,2′-azobis(2-methylpropionitrile) (98%) were purchased from Sigma-Aldrich. All chemicals except the AIBN were used without further purification. AIBN was recrystallized in methanol.