Top-coating composition for photoresist and process for forming fine pattern using the same

[0001] 1. Field of the Invention

[0002] The present invention relates to a top-coating composition, for a photolithography process, and a process for forming a pattern using the same.

[0003] 2. Description of the Background Art

[0004] Chemical amplification-type DUV photoresists have been used to achieve high sensitivity in minute image formation processes for preparing semiconductor devices. Such photoresists are prepared by blending a photoacid generator and a matrix resin polymer having an acid labile group.

[0005] It is believed that when a photoresist (sometimes referred to as PR) composition is illuminated by an appropriate light source the photoacid generator generates acid. The resin (i.e., polymer) which is present in the photoresist decomposes or becomes cross-linked when reacted with the generated acid. This change in the resin results in the solubility differences in the developing solution between the exposed portion and the unexposed portion. Thus, by using an appropriate mask, one can form a predetermined pattern using the photoresist composition.

[0006] In a lithography process, the image resolution generally depends on the wavelength of the light source, e.g., a shorter wavelength allows a more minute image pattern formation.

[0007] Lithography processes employing light sources having a wavelength below 250 nm have been recently investigated. In particular, there have been a lot of interests directed to a polymer containing alicyclic derivatives in its main or branched chain as a suitable photoresist polymer. However, utilizing these alicyclic polymers to a semiconductor fabrication process has many disadvantages. For example, chemical properties of the alicyclic polymer vary. In addition, the generated acid may be neutralized by environmental amine compounds during the time between the exposure and the post exposure baking (i.e., post exposure delay effect). As a result, a desired resolution are often not obtained and/or the pattern can be T-shaped (i.e., T-topping). One or more of these problems are especially acute when the concentration of environmental amine is over 30 ppb, which in some instances may lead to no pattern formation.

[0008] In order to overcome the aforementioned disadvantages, the following methods have been suggested in the prior art:

[0009] (1) An annealing method whereby the PR resin is baked over its glass transition temperature (Tg) after the PR is coated see W. D. Hinsberg, S. A. MacDonald, N. J. Clecak, C. D. Snyder, and H. Ito, Proc. SPIE, 1925, (1993) 43; H. Ito, W. P. England, R. Soornyakumaran, N. J. Clecak, G. Breyta, W. D. Hinsberg, H. Lee, and D. Y. Yoon, J. Photopolymer Sci. and Technol., 6, (1993) 547; G. Breyta, D. C. Hofer, H. Ito, D. Seeger, K. Petrillo, H. Moritz, and T. Fischer, J. Photopolymer Sci. and Technol., 7, (1994) 449; H. Ito, G. Breyta, D. Hofer, R. Sooriyakumaran, K. Petrillo, and D. Seeger, J. Photopolymer Sci. and Technol., 7, (1994) 433; H. Ito, G. Breyta, R. Sooriyakumaran, and D. Hofer, J. Photopolymer Sci. and Technol., 8, (1995) 505;

[0010] (2) Adding an amine compound to the PR see Y. Kawai, A. Otaka, J. Nakamura, A. Tanaka, and T. Matsuda, J. Photopolymer Sci. and Technol., 8, (1995) 535; S. Saito, N. Kihara, T. Naito, M. Nakase, T. Nakasugi, and Y. Kat. Photopolymer Sci. and Technol., 9, (1996) 677; S. Funato, Y. Kinoshita, T. Kuto, S. Masuda, H. Okazaki, M. Padmanaban, K. J. Przybilla, N. Suehiro, and G. Pawlowski, J. Photopolymer Sci. and Technol., 8, (1995) 543; and

[0011] (3) Adding a top-coating to the upper portion of the PR to protect it against an environmental amine contamination, after the PR coating step and the baking step see J. Nakamura, H. Ban, Y. Kawai, and A. Tanaka, J. Photopolymer Sci. and Technol., 8, (1995) 555; A. Oikawa, Y. Hatakenaka, Y. Ikeda, Y. Kokubo, S. Miyata, N. Santoh, and N. Abe, J. Photopolymer Sci. and Technol., 8, (1995) 519.

[0012] Even using one or more of these techniques it is difficult to form an ultrafine pattern. In addition, the above methods have other disadvantages, such as adding complication or additional steps to a lithography process.

[0013] Accordingly, an object of the present invention is to provide a top-coating composition containing an amine contamination-protecting compound that can solve the above-mentioned problems, and a process for forming a photoresist pattern using the same.

[0014] FIGS. 1 and 2 are SEM photographs showing a conventional photoresist pattern; and

[0015] FIGS. 3 to 20 are SEM photographs showing a photoresist pattern in accordance with a preferred example of the present invention.

[0016] The present invention provides a top-coating composition, which is useful in a photolithography process, and a process for forming a pattern using the same. In particular, the present invention provides a top-coating composition for protecting amine-contamination and a method for forming a fine pattern by using the same. Compositions and methods of the present invention are particularly useful in a photolithography process utilizing a light sources having an ultrashort wavelength below 250 nm.

[0017] Specifically, the present invention provides an amine contamination-protecting top-coating composition comprising a top-coating material and an amine contamination-protecting compound which has a basic or weakly basic property (i.e., a basic compound). The present invention also provides a method for forming a fine pattern by using the same.

[0018] Any of the commercially available top-coating compositions for producing semiconductor devices can be used in the present invention. Such top-coating compositions are well known to one skilled in the art. Examples of such top-coating compositions are sold under the designations NFC 540 by Japan Synthetic Rubber in Japan, and Aquatar by Clariant Inc. in Switzerland.

[0019] The amine contamination-protecting compound of the present invention is a basic compound, preferably weakly basic compound, more preferably a water-soluble compound including cyclic and acyclic nitrogen-containing compounds. Exemplary nitrogen-containing compounds which are useful in the present invention include amine derivatives; amino acid derivatives; amide derivatives; urethane derivatives; urea derivatives; and salts thereof. The amount of amine contamination-protecting compound present in the composition of the present invention is preferably from about 0.015 to about 0.5 weight % relative to the amount of top-coating composition.

[0020] Preferably, the conjugate acid (i.e., a protonated form) of the basic compound has pKa of about 8 or less.

[0021] In one particular embodiment, the amine contamination-protecting compound is a compound of formula I:

[0022] where each of R₁, R₂ and R₃ is independently H or C₁-C₂₀ alkyl. Alkyl groups according to the present invention are aliphatic hydrocarbons which can be straight or branched chain groups. Alkyl groups optionally can be substituted with one or more substituents, such as a halogen, alkenyl, alkynyl, aryl, hydroxy, amino, thio, alkoxy, carboxy, oxo or cycloalkyl. There may be optionally inserted along the alkyl group one or more oxygen, sulfur or substituted or unsubstituted nitrogen atoms. Preferred alkyl groups include unsubstituted alkyl groups and substituted alkyl groups containing one or more hydroxy, amine, and/or carbonyl (such as ketone, carboxylic acid, and ester) groups, i.e., straight or branched C₁-C₂₀ alkyl, straight or branched C₁-C₂₀ alcohol (OH), straight or branched C₁-C₂₀ carboxylic acid, straight or branched C₁-C₂₀ amine, straight or branched C₁-C₂₀ ketone, or straight or branched C₁-C₂₀ ester.

[0023] In one aspect of the present invention, the amine contamination-protecting compound comprises an amino acid, in particular L-proline (i.e., compound of formula II), triethanolamine (i.e., compound of formula III), and mixtures thereof. Preferably, the amine contamination-protecting compound comprises triethanolamine.

[0024] In another embodiment, the amine contamination-protecting compound is preferably selected from the group consisting of aniline, p-nitroaniline, p-aminotoluene, 3-amino-1-propanesulfonic acid, 4-aminotoluene-5-sulfonic acid, 4-aminosalicyclic acid, 4-aminophenol, 2-amino-2-norbornanecarboxylic acid, 2-aminonicotinic acid, 2-aminobutyric acid, alanine, aspartic acid, cysteine, glutamine, serine and mixtures thereof.

[0025] It has been discovered by the present inventors, that when a top-coating step is carried out using the amine contamination-protecting top-coating composition of the present invention, an ultrafine pattern having an excellent profile can be formed. Without being bound by any theory, it is believed that the amine contamination-protecting top-coating composition of the present invention effectively intercepts environmental amine contamination during the post exposure delay (hereinafter, referred to as PED), and prevents acid, which is generated by the light exposure, from diffusing into an unexposed area. That is, when an amine contamination-protecting compound of the present invention is added to a conventional top-coating composition, the resulting amine contamination-protecting top-coating composition has a suitable basic property to act as a buffer to prevent the acid generated at the exposed area from being contaminated by the environmental amine compounds. In addition, the amine contamination-protecting top-coating composition of the present invention is coated at the upper portion of the PR. It is believed that the amine contamination-protecting compound contained in the amine contamination-protecting top-coating composition of the present invention restricts acid diffusion on the PR surface, thereby providing a superior pattern (i.e., image having a vertical profile).

[0026] Additional objects, advantages, and novel features of this invention will become apparent to those skilled in the art upon examination of the following examples thereof, which are not intended to be limiting.

[0027] In order to confirm the effects of the top-coating composition according to the present invention, a PR pattern is formed in the following Examples by employing a top-coating process which comprises:

[0028] (a) coating a photoresist composition on a substrate to form a photoresist film;

[0029] (b) coating a top-coating composition on the upper portion of the photoresist film to form a top-coating;

[0030] (c) exposing the resultant coated substrate to light using an exposer; and

[0031] (d) developing the resultant product.

[0032] The PR composition used above is prepared by dissolving (i) poly(2-hydroxyethyl 5-norbornene-2-carboxylic acid/tert-butyl 5-norbornene-2-carboxylate/5-norbornene-2-carboxylic acid/maleic anhydride), (ii) a photoacid generator and (iii) certain other optional additives in (iv) propylene glycol methyl ether acetate (PGMEA) solvent see J. C. Jung, C. K. Bok, and K. H. Baik, J. Photopolymer Sci. and Technol., 10, (1997) 529; J. C. Jung, C. K. Bok, and K. H. Baik, Proc. SPIE, 3333, (1998)11; J. C. Jung, M. H. Jung, and K. H. Baik, J. Photopolymer Sci. and Technol., 11, (1998) 481.

[0033] The amine contamination-protecting top-coating composition in the Invention Examples is prepared by adding the amine contamination-protecting compound to a conventional top-coating composition.

[0034] All the pattern formation experiments are performed under a condition having the environmental amine concentration of over 15 parts per billion (ppb).

[0035] At an environmental amine concentration of 15 ppb, the PR composition is coated on the substrate, baked at 110 C. for 90 seconds, and cooled at 23 C.

[0036] Thereafter, an NFC 540 top-coating material manufactured by Japan Synthetic Rubber in Japan (hereinafter, referred to as JSR) is coated as a top-coating composition on the upper portion of the PR coating, baked at 60 C. for 60 seconds and cooled.

[0037] The resultant product is exposed to light by an ArF exposer, baked at 110 C. for 90 seconds, and developed in 2.38 wt % TMAH solution, thereby obtaining the 150 mn pattern shown in FIG. 1.

[0038] As shown in FIG. 1, the upper portion of the pattern is considerably damaged, and the vertical profile thereof is not complete. It is believed that this results from acid diffusion to the unexposed area during the PED.

[0039] At an environmental amine concentration of 15 ppb, the PR composition is coated on the substrate, baked at 110 C. for 90 seconds, and cooled at 23 C.

[0040] Thereafter, an Aquatar top-coating material manufactured by Clariant Inc. in Switzerland is coated on the upper portion of the PR coating, baked at 60 C. for 60 seconds and cooled.

[0041] The resultant product is exposed to light by the ArF exposer, baked at 110 C. for 90 seconds, and developed in the 2.38 wt % TMAH solution, thereby obtaining the 150 nm pattern shown in FIG. 2.

[0042] As illustrated in FIG. 2, the upper portion of the pattern is considerably damaged as in FIG. 1, and the developing state of the exposed area is not complete.

[0043] A novel amine contamination-protecting top-coating composition of the present invention is first prepared by blending 20 g of NFC 540 (a top-coating material manufactured by JSR) and 0.016 g of L-proline.

[0044] The PR pattern is formed by repeating the procedure of Comparative Example 1 but using the above-described composition as the amine contamination-protecting top-coating composition. Briefly, at the environmental amine concentration of about 15 ppb, the PR composition is coated on the substrate, baked at 110 C. for 90 seconds, and cooled at 23 C.

[0045] Thereafter, the amine contamination-protecting top-coating composition is coated on the upper portion of the PR coating baked at 60 C. for 60 seconds and cooled.

[0046] The resultant product is exposed to light by the ArF exposer, baked at 110 C. for 90 seconds, and developed in the 2.38 wt % TMAH solution, to produce the 150 nm pattern shown in FIG. 3.

[0047] Compared to FIG. 1, the upper portion of the pattern in FIG. 3 is significantly less damaged and shows a significantly improved vertical profile.

[0048] A novel amine contamination-protecting top-coating composition of the present invention is prepared by blending 20 g of Aquatar (a top-coating material manufactured by Clariant Inc.) and 0.016 g of L-proline.

[0049] The top-coating process is performed by repeating the procedure of Comparative Example 2 but using the aforementioned amine contamination-protecting top-coating composition. The lithography process described in Comparative Example 2 produced the 150 nm PR pattern shown in FIG. 4. Compared to FIG. 2, the upper portion of the pattern of FIG. 4 is significantly less damaged, and the vertical profile thereof is significantly improved.

[0050] A novel amine contamination-protecting top-coating composition of the present invention is prepared by blending 20 g of Aquatar (a top-coating material manufactured by Clariant Inc.) and 0.020 g of triethanolamine.

[0051] The top-coating process is performed by repeating the procedure of Comparative Example 2 but using the aforementioned amine contamination-protecting top-coating composition to produce the 150 nm PR pattern shown in FIG. 5. Compared to FIG. 2, the upper portion of the pattern in FIG. 5 is significantly less damaged, and the vertical profile thereof is significantly improved.

[0052] A novel amine contamination-protecting top-coating composition of the present invention is prepared by blending 200 g of NFC 540 (a top-coating material manufactured by JSR) and 0.113 g of aniline.

[0053] The lithography process is carried out in the same manner as Comparative Example 1 using the above-described amine contamination-protecting top-coating composition to produce the 150 mn pattern depicted in FIG. 6.

[0054] Compared to FIG. 1, the upper portion of the pattern in FIG. 6 is significantly less damaged and shows a significantly improved vertical profile.

[0055] A novel amine contamination-protecting top-coating composition of the present invention is prepared by blending 200 g of NFC 540 (a top-coating material manufactured by JSR) and 0.17 g of p-nitroaniline.

[0056] The lithography process is carried out in the same manner as Comparative Example 1 using the above-described amine contamination-protecting top-coating composition to produce the 150 nm pattern depicted in FIG. 7.

[0057] Compared to FIG. 1, the upper portion of the pattern in FIG. 7 is significantly less damaged and shows a significantly improved vertical profile.

[0058] A novel amine contamination-protecting top-coating composition of the present invention is prepared by blending 200 g of NFC 540 (a top-coating material manufactured by JSR) and 0.131 g of p-aminotoluene.

[0059] The lithography process is carried out in the same manner as Comparative Example 1 using the above-described amine contamination-protecting top-coating composition to produce the 150 nm pattern depicted in FIG. 8.

[0060] Compared to FIG. 1, the upper portion of the pattern in FIG. 8 is significantly less damaged and shows a significantly improved vertical profile.

[0061] A novel amine contamination-protecting top-coating composition of the present invention is prepared by blending 200 g of NFC 540 (a top-coating material manufactured by JSR) and 0.17 g of 3-amino-1-propanesulfonic acid.

[0062] The lithography process is carried out in the same manner as Comparative Example 1 using the above-described amine contamination-protecting top-coating composition to produce the 150 nm pattern depicted in FIG. 9.

[0063] Compared to FIG. 1, the upper portion of the pattern in FIG. 9 is significantly less damaged and shows a significantly improved vertical profile.

[0064] A novel amine contamination-protecting top-coating composition of the present invention is prepared by blending 200 g of NFC 540 (a top-coating material manufactured by JSR) and 0.23 g of 4-aminotoluene-5-sulfonic acid.

[0065] The lithography process is carried out in the same manner as Comparative Example 1 using the above-described amine contamination-protecting top-coating composition to produce the 150 nm pattern depicted in FIG. 10.

[0066] Compared to FIG. 1, the upper portion of the pattern in FIG. 10 is significantly less damaged and shows a significantly improved vertical profile.

[0067] A novel amine contamination-protecting top-coating composition of the present invention is prepared by blending 200 g of NFC 540 (a top-coating material manufactured by JSR) and 0.19 g of 4-aminosalicyclic acid.

[0068] The lithography process is carried out in the same manner as Comparative Example 1 using the above-described amine contamination-protecting top-coating composition to produce the 150 nm pattern depicted in FIG. 11.

[0069] Compared to FIG. 1, the upper portion of the pattern in FIG. 11 is significantly less damaged and shows a significantly improved vertical profile.

[0070] A novel amine contamination-protecting top-coating composition of the present invention is prepared by blending 200 g of NFC 540 (a top-coating material manufactured by JSR) and 0.13 g of 4-aminophenol.

[0071] The lithography process is carried out in the same manner as Comparative Example 1 using the above-described amine contamination-protecting top-coating composition to produce the 150 nm pattern depicted in FIG. 12.

[0072] Compared to FIG. 1, the upper portion of the pattern in FIG. 12 is significantly less damaged and shows a significantly improved vertical profile.

[0073] A novel amine contamination-protecting top-coating composition of the present invention is prepared by blending 200 g of NFC 540 (a top-coating material manufactured by JSR) and 0.19 g of 2-amino-2-norbornanecarboxylic acid.

[0074] The lithography process is carried out in the same manner as Comparative Example 1 using the above-described amine contamination-protecting top-coating composition to produce the 150 nm pattern depicted in FIG. 13.

[0075] Compared to FIG. 1, the upper portion of the pattern in FIG. 13 is significantly less damaged and shows a significantly improved vertical profile.

[0076] A novel amine contamination-protecting top-coating composition of the present invention is prepared by blending 200 g of NFC 540 (a top-coating material manufactured by JSR) and 0.17 g of 2-aminonicotinic acid.

[0077] The lithography process is carried out in the same manner as Comparative Example 1 using the above-described amine contamination-protecting top-coating composition to produce the 150 nm pattern depicted in FIG. 14.

[0078] Compared to FIG. 1, the upper portion of the pattern in FIG. 14 is significantly less damaged and shows a significantly improved vertical profile.

[0079] A novel amine contamination-protecting top-coating composition of the present invention is prepared by blending 200 g of NFC 540 (a top-coating material manufactured by JSR) and 0.13 g of 2-aminobutyric acid.

[0080] The lithography process is carried out in the same manner as Comparative Example 1 using the above-described amine contamination-protecting top-coating composition to produce the 150 nm pattern depicted in FIG. 15.

[0081] Compared to FIG. 1, the upper portion of the pattern in FIG. 15 is significantly less damaged and shows a significantly improved vertical profile.

[0082] A novel amine contamination-protecting top-coating composition of the present invention is prepared by blending 200 g of NFC 540 (a top-coating material manufactured by JSR) and 0.108 g of alanine.

[0083] The lithography process is carried out in the same manner as Comparative Example 1 using the above-described amine contamination-protecting top-coating composition to produce the 150 nm pattern depicted in FIG. 16.

[0084] Compared to FIG. 1, the upper portion of the pattern in FIG. 16 is significantly less damaged and shows a significantly improved vertical profile.

[0085] A novel amine contamination-protecting top-coating composition of the present invention is prepared by blending 200 g of NFC 540 (a top-coating material manufactured by JSR) and 0.162 g of aspartic acid.

[0086] The lithography process is carried out in the same manner as Comparative Example 1 using the above-described amine contamination-protecting top-coating composition to produce the 150 nm pattern depicted in FIG. 17.

[0087] Compared to FIG. 1, the upper portion of the pattern in FIG. 17 is significantly less damaged and shows a significantly improved vertical profile.

[0088] A novel amine contamination-protecting top-coating composition of the present invention is prepared by blending 200 g of NFC 540 (a top-coating material manufactured by JSR) and 0.147 g of cysteine.

[0089] The lithography process is carried out in the same manner as Comparative Example 1 using the above-described amine contamination-protecting top-coating composition to produce the 150 nm pattern depicted in FIG. 18.

[0090] Compared to FIG. 1, the upper portion of the pattern in FIG. 18 is significantly less damaged and shows a significantly improved vertical profile.

[0091] A novel amine contamination-protecting top-coating composition of the present invention is prepared by blending 200 g of NFC 540 (a top-coating material manufactured by JSR) and 0.18 g of glutamine.

[0092] The lithography process is carried out in the same manner as Comparative Example 1 using the above-described amine contamination-protecting top-coating composition to produce the 150 nm pattern depicted in FIG. 19.

[0093] Compared to FIG. 1, the upper portion of the pattern in FIG. 19 is significantly less damaged and shows a significantly improved vertical profile.

[0094] A novel amine contamination-protecting top-coating composition of the present invention is prepared by blending 200 g of NFC 540 (a top-coating material manufactured by JSR) and 0.128 g of serine.

[0095] The lithography process is carried out in the same manner as Comparative Example 1 using the above-described amine contamination-protecting top-coating composition to produce the 150 nm pattern depicted in FIG. 20.

[0096] Compared to FIG. 1, the upper portion of the pattern in FIG. 20 is significantly less damaged and shows a significantly improved vertical profile.

[0097] While Invention Examples 1-18 describe using ArF radiation as the exposure light source, other light sources, including the ultrashort wavelength light sources such as KrF (248 nm), F₂(157 nm), E-beam, ion beam and extremely ultraviolet (EUV), can also be employed.

[0098] In addition to the above-described PR composition, other conventional PR compositions known to one of ordinary skill in the art can also be used. Lithography conditions used in the Examples may vary, if necessary.

[0099] The results obtained from the above Examples show that amine contamination during PED and pattern deformation on the top surface of the PR layer because of acid diffusion can be significantly reduced or prevented by adding an amine contamination-protecting compound to a conventional top-coating composition in accordance with the present invention.

[0100] The foregoing discussion of the invention has been presented for purposes of illustration and description. The foregoing is not intended to limit the invention to the form or forms disclosed herein. Although the description of the invention has included description of one or more embodiments and certain variations and modifications, other variations and modifications are within the scope of the invention, e.g., as may be within the skill and knowledge of those in the art, after understanding the present disclosure. It is intended to obtain rights which include alternative embodiments to the extent permitted, including alternate, interchangeable and/or equivalent structures, functions, ranges or steps to those claimed, whether or not such alternate, interchangeable and/or equivalent structures, functions, ranges or steps are disclosed herein, and without intending to publicly dedicate any patentable subject matter.