Classifications

• • G—PHYSICS
  • G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
  • G03F—PHOTOMECHANICAL PRODUCTION OF TEXTURED OR PATTERNED SURFACES, e.g. FOR PRINTING, FOR PROCESSING OF SEMICONDUCTOR DEVICES; MATERIALS THEREFOR; ORIGINALS THEREFOR; APPARATUS SPECIALLY ADAPTED THEREFOR
  • G03F7/00—Photomechanical, e.g. photolithographic, production of textured or patterned surfaces, e.g. printing surfaces; Materials therefor, e.g. comprising photoresists; Apparatus specially adapted therefor
  • G03F7/004—Photosensitive materials
  • G03F7/039—Macromolecular compounds which are photodegradable, e.g. positive electron resists
• • G—PHYSICS
  • G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
  • G03F—PHOTOMECHANICAL PRODUCTION OF TEXTURED OR PATTERNED SURFACES, e.g. FOR PRINTING, FOR PROCESSING OF SEMICONDUCTOR DEVICES; MATERIALS THEREFOR; ORIGINALS THEREFOR; APPARATUS SPECIALLY ADAPTED THEREFOR
  • G03F7/00—Photomechanical, e.g. photolithographic, production of textured or patterned surfaces, e.g. printing surfaces; Materials therefor, e.g. comprising photoresists; Apparatus specially adapted therefor
  • G03F7/004—Photosensitive materials
  • G03F7/09—Photosensitive materials characterised by structural details, e.g. supports, auxiliary layers
  • G03F7/091—Photosensitive materials characterised by structural details, e.g. supports, auxiliary layers characterised by antireflection means or light filtering or absorbing means, e.g. anti-halation, contrast enhancement
• • G—PHYSICS
  • G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
  • G03F—PHOTOMECHANICAL PRODUCTION OF TEXTURED OR PATTERNED SURFACES, e.g. FOR PRINTING, FOR PROCESSING OF SEMICONDUCTOR DEVICES; MATERIALS THEREFOR; ORIGINALS THEREFOR; APPARATUS SPECIALLY ADAPTED THEREFOR
  • G03F7/00—Photomechanical, e.g. photolithographic, production of textured or patterned surfaces, e.g. printing surfaces; Materials therefor, e.g. comprising photoresists; Apparatus specially adapted therefor
  • G03F7/004—Photosensitive materials
  • G03F7/039—Macromolecular compounds which are photodegradable, e.g. positive electron resists
  • G03F7/0392—Macromolecular compounds which are photodegradable, e.g. positive electron resists the macromolecular compound being present in a chemically amplified positive photoresist composition
• • G—PHYSICS
  • G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
  • G03F—PHOTOMECHANICAL PRODUCTION OF TEXTURED OR PATTERNED SURFACES, e.g. FOR PRINTING, FOR PROCESSING OF SEMICONDUCTOR DEVICES; MATERIALS THEREFOR; ORIGINALS THEREFOR; APPARATUS SPECIALLY ADAPTED THEREFOR
  • G03F7/00—Photomechanical, e.g. photolithographic, production of textured or patterned surfaces, e.g. printing surfaces; Materials therefor, e.g. comprising photoresists; Apparatus specially adapted therefor
  • G03F7/004—Photosensitive materials
  • G03F7/09—Photosensitive materials characterised by structural details, e.g. supports, auxiliary layers
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
  • Y10S—TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y10S430/00—Radiation imagery chemistry: process, composition, or product thereof
  • Y10S430/1053—Imaging affecting physical property or radiation sensitive material, or producing nonplanar or printing surface - process, composition, or product: radiation sensitive composition or product or process of making binder containing
  • Y10S430/1055—Radiation sensitive composition or product or process of making
  • Y10S430/114—Initiator containing
  • Y10S430/115—Cationic or anionic
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
  • Y10S—TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y10S438/00—Semiconductor device manufacturing: process
  • Y10S438/942—Masking
  • Y10S438/948—Radiation resist
  • Y10S438/952—Utilizing antireflective layer

Definitions

• the present invention relates to novel positive-working, photoimageable, and aqueous developable antireflective coating compositions and their use in image processing by forming a thin layer of the novel antireflective coating composition between a reflective substrate and a photoresist coating.
• Such compositions are particularly useful in the fabrication of semiconductor devices by photolithographic techniques, especially those requiring exposure with deep ultraviolet radiation. These coatings are particularly compatible for use with an edge bead remover.
• Photoresist compositions are used in microlithography processes for making miniaturized electronic components such as in the fabrication of computer chips and integrated circuits.
• a thin coating of a film of a photoresist composition is first applied to a substrate material, such as silicon wafers used for making integrated circuits.
• the coated substrate is then baked to evaporate any solvent in the photoresist composition and to fix the coating onto the substrate.
• the baked and coated surface of the substrate is next subjected to an image-wise exposure to radiation. This radiation exposure causes a chemical transformation in the exposed areas of the coated surface. Visible light, ultraviolet (UV) light, electron beam and X-ray radiant energy are radiation types commonly used today in microlithographic processes.
• the coated substrate is treated with a developer solution to dissolve and remove either the radiation-exposed or the unexposed areas of the photoresist.
• a developer solution dissolves and remove either the radiation-exposed or the unexposed areas of the photoresist.
• photoresist compositions There are two types of photoresist compositions, negative-working and positive-working.
• positive-working photoresist compositions are exposed image-wise to radiation, the areas of the photoresist composition exposed to the radiation become soluble in a developer solution while the unexposed areas of the photoresist coating remain relatively insoluble to such a solution.
• treatment of an exposed positive-working photoresist with a developer causes removal of the exposed areas of the photoresist coating and the formation of a positive image in the coating, thereby uncovering a desired portion of the underlying substrate surface on which the photoresist composition was deposited.
• Photoresists for 248 nm have typically been based on substituted polyhydroxystyrene and its copolymers.
• photoresists for 193 nm exposure require non-aromatic polymers, since aromatics are opaque at this wavelength.
• alicyclic hydrocarbons are incorporated into the polymer to replace the etch resistance lost by eliminating the aromatic functionality.
• antireflective coatings become critical.
• the use of highly absorbing antireflective coatings in photolithography is a simpler approach to diminish the problems that result from back reflection of light from highly reflective substrates.
• the bottom antireflective coating is applied on the substrate and then a layer of photoresist is applied on top of the antireflective coating.
• the photoresist is exposed imagewise and developed.
• the antireflective coating in the exposed area is then typically etched and the photoresist pattern is thus transferred to the substrate.
• Most antireflective coatings known in the prior art are designed to be dry etched.
• the etch rate of the antireflective film needs to be relatively high in comparison to the photoresist so that the antireflective film is etched without excessive loss of the resist film during the etch process.
• the novel approach of the present application is to use an absorbing, positive image-forming bottom antireflective coating that can be developed by an aqueous alkaline solution, rather than be removed by dry etching.
• Aqueous removal of the bottom antireflective coating eliminates the dry etch rate requirement of the coating, reduces the cost intensive dry etching processing steps and also prevents damage to the substrate caused by dry etching.
• the absorbing bottom antireflective coating compositions of the present invention contain a crosslinking compound and a polymer. The coating is cured and then upon exposure to light of the same wavelength as that used to expose the top positive photoresist become imageable in the same developer as that used to develop the photoresist. This process greatly simplifies the lithographic process by eliminating a large number of processing steps.
• the antireflective coating Since the antireflective coating is photosensitive, the extent of removal of the antireflective coating is defined by the latent optical image, which allows a good delineation of the remaining photoresist image in the antireflective coating.
• Bilevel photoresists are known, as in US 4,863,827, but require exposure of two different wavelengths for the top and bottom photoresists, which complicates the processing of the lithography.
• There are many patents that disclose antireflective coating compositions but these coatings are all cured to be insoluble in an aqueous developer solution and must be removed by dry etching.
• US 5,939,236 describes an antireflective coating containing a polymer, an acid or thermal acid generator, and a photoacid generator.
• Acid sensitive antireflective coatings using differing chemistries are disclosed in US 6,110,653, US 6,319,651 , US 6,054,254 and US 2004/0018451.
• the novel antireflective composition of the present invention relates to a photoimageable, aqueous alkali developable, positive-working antireflective coating.
• the antireflective coating composition of the instant invention is coated on a substrate before applying a positive photoresist layer, in order to prevent reflections in the photoresist from the substrate.
• the solid components of the antireflective coating are soluble in common photoresist solvents and capable of forming a coating, and furthermore are compatible with edge-bead remover solvents.
• Edge-bead remover solvents are used to remove the build-up on the edges of the antireflective coating formed during the spin coating process.
• This antireflective coating is photoimageable at the same wavelength of actinic radiation as the top photoresist layer applied thereupon, and is also developable with the same aqueous alkaline developing solution as that used for typically developing a photoresist.
• the combination of single exposure step and single development step greatly simplifies the lithographic process.
• an aqueous developable antireflective coating is especially desirable for imaging with photoresists that do not contain aromatic functionalities, such as those used for 193 nm and 157 nm exposures.
• the novel composition enables a good image transfer from the photoresist to the substrate, and also has good absorption characteristics to prevent reflective notching and line width variations or standing waves in the photoresist. Additionally, substantially no intermixing is present between the antireflective coating and the photoresist film.
• the antireflective coatings also have good solution stability and form thin films with good coating quality, the latter being particularly advantageous for lithography. When the antireflective coating is used with a photoresist in the imaging process, clean images are obtained, without damaging the substrate.
• the present invention relates to a positive bottom photoimageable antireflective coating composition which is capable of being developed in an aqueous alkaline developer, wherein the antireflective coating composition comprises a polymer comprising at least one recurring unit with a chromophore group and one recurring unit with a hydroxyl and/or a carboxyl group, a vinyl ether terminated crosslinking agent, and optionally, a photoacid generator.
• the invention may further comprise an acid or a thermal acid generator, preferably where the acid or the acid generated from the thermal acid generator has a pKa greater than 1.0.
• the invention further relates to a process for imaging using the antireflective composition of the present invention, especially with an edgebead removal step.
• the present invention relates to a novel absorbing, photoimageable and aqueous developable positive image-forming antireflective coating composition
• a polymer comprising at least one unit with a hydroxyl and/or carboxyl group and at least one unit with an absorbing chromophore, a vinyl ether terminated crosslinking agent, and optionally, a photoacid generator.
• the polymer is alkali-soluble and water insoluble.
• the invention further relates to a process for using such a composition, especially for irradiation from about 50 nm to about 450nm.
• the antireflective coating composition of the invention is coated on a substrate and below a positive photoresist, in order to prevent reflections in the photoresist from the substrate.
• This antireflective coating is photoimageable with the same wavelength of light as the top photoresist, and is also developable with the same aqueous alkaline developing solution as that used to typically develop the photoresist, thus forming a pattern in the antireflective coating.
• the antireflective coating composition comprises a polymer, a crosslinking agent and, optionally, a photoacid generator.
• the antireflective coating composition is coated on a reflective substrate.
• the edge bead which may form during the spinning process can then be removed using an edgebead removing solvent, since the polymer is still soluble in solvents used as edgebead removers.
• the coating is then baked to remove the solvent of the coating solution and also to crosslink the coating, in order to prevent, or minimize, the extent of intermixing between the layers and make the coating insoluble in the aqueous alkaline developer.
• a reaction takes place between the crosslinking agent, especially compounds containing vinyl ether terminal groups, and the polymer with the hydroxyl and/or a carboxyl group in the antireflective coating, to form acid labile groups within the coating.
• the antireflective coating After baking and curing the antireflective coating is essentially insoluble in both an alkaline developing solution and the solvent of the photoresist.
• a positive photoresist is then coated on top of the cured antireflective coating and baked to remove the photoresist solvent.
• the coating thickness of the photoresist is generally greater than the underlying antireflective coating.
• Prior to exposure to actinic radiation both the photoresist and the antireflective coating are insoluble in the aqueous alkaline developing solution of the photoresist.
• the bilevel system is then imagewise exposed to radiation in one single step, where an acid is then generated in both the top photoresist and the bottom antireflective coating. If a photoacid generator is present in the antireflective coating it is photolysed.
• the acid may diffuse from the photoresist into the antireflective coating.
• a subsequent baking step in the exposed regions the polymer of the antireflective coating with the crosslinked sites (acid labile groups), are decrosslinked in the presence of the photogenerated acid, thus making the polymer and hence the antireflective coating soluble in the aqueous alkaline developer.
• a subsequent developing step then dissolves the exposed regions of both the positive photoresist and the antireflective coating, thus producing a positive image, and leaving the substrate clear for further processing.
• the novel antireflective coating that is useful for the novel process of this invention comprises a crosslinking agent, a polymer, and optionally, a photoacid generator.
• the polymer comprises at least one unit with a hydroxyl and/or a carboxyl group and at least one unit with an absorbing chromophore.
• the absorbing chromophore is bound within the polymer chain, as opposed to being a free dye in the composition, in order to avoid decomposition or sublimation of the free dye during the process of baking the coating.
• the polymer of the antireflective coating of the invention contains at least one unit with hydroxyl and/or carboxyl group and at least one unit with an absorbing chromophore.
• Examples of an absorbing chromophore are hydrocarbon aromatic moieties and heterocyclic aromatic moieties with from one to four separate or fused rings, where there are 3 to 10 atoms in each ring.
• Examples of monomers with absorbing chromophores that can be polymerized with the monomers containing hydroxyl or carboxyl groups are vinyl compounds containing substituted and unsubstituted phenyl, substituted and unsubstituted anthracyl, substituted and unsubstituted phenanthryl, substituted and unsubstituted naphthyl, substituted and unsubstituted heterocyclic rings containing heteroatoms such as oxygen, nitrogen, sulfur, or combinations thereof, such as pyrrolidinyl, pyranyl, piperidinyl, acridinyl, quinolinyl.
• the substituents may be any hydrocarbyl group and may further contain heteroatoms, such as, oxygen, nitrogen, sulfur or combinations thereof.
• Examples of such groups are (C 1 -C 12 ) alkylene, esters, ethers, etc.
• Other chromophores are described in US 6,114,085, and in US 5,652,297, US 5,981 ,145, US 6,187,506, US 5,939,236, and US 5,935,760, which may also be used, and are incorporated herein by reference.
• the preferred chromophoric monomers are vinyl compounds of substituted and unsubstituted phenyl, substituted and unsubstituted anthracyl, and substituted and unsubstituted naphthyl; and more preferred monomers are styrene, hydroxystyrene, acetoxystyrene, vinyl benzoate, vinyl 4-tert-butylbenzoate, ethylene glycol phenyl ether acrylate, phenoxypropyl acrylate, N-methyl maleimide, 2-(4-benzoyl-3- hydroxyphenoxy)ethyl acrylate, 2-hydroxy-3-phenoxypropyl acrylate, phenyl methacrylate, benzyl methacrylate, 9-anthracenyl methyl methacrylate, 9- vinylanthracene, 2-vinylnaphthalene, N-vinylphthalimide, N-(3-hydroxy)phenyl methacrylamide, N-(3
• the polymer of the novel invention comprises at least one unit with a hydroxyl and/or a carboxyl group to provide alkaline solubility, and a crosslinking site.
• One function of the polymer is to provide a good coating quality and another is to enable the antireflective coating to change solubility during the imaging process.
• the hydroxyl or carboxyl groups in the polymer provide one of the components necessary for the solubility change.
• Examples of the third monomer are -CRi R2-CR 3 R 4 -, where R 1 to R 4 are independently H, (C Cio) alkyl, (C1-C10) alkoxy, nitro, halide, cyano, alkylaryl, alkenyl, dicyanovinyl, S0 2 CF 3 , COOZ, S0 3 Z, COZ, OZ, NZ 2 , SZ, S0 2 Z, NHCOZ, S0 2 NZ 2 , where Z is H, or (C C ⁇ o) alkyl, hydroxy (C C ⁇ 0 ) alkyl, (C 1 -C 10 ) alkylOCOCH2COCH 3 , or R 2 and R 4 combine to form a cyclic group such as anhydride, pyridine, or pyrollidone, or R 1 to R 3 are independently H, (C 1 -C 10 ) alkyl, (C1-C 1 0) alkoxy and R 4 is a hydrophilic group
• acid labile groups are tetrahydrofuranyl, tetrahydropyranyl, substituted or unsubstituted methoxycarbonyl, ⁇ - trialkylsilylalkyl groups (e.g. CH2-CH 2 Si(CH 3 )3, CH(-CH 2 Si(CH 3 ) 3 )2, CH 2 - CH(Si(CH 3 ) 3 )2 and the like.
• Novolak resins can also be used as suitable polymers for antireflective coatings. These resins are typically produced by conducting a condensation reaction between formaldehyde and one or more multi-substituted phenols, in the presence of an acid catalyst, such as oxalic acid, maleic acid, or maleic anhydride.
• the polymer may be synthesized using solution, emulsion, bulk, suspension polymerization, or the like.
• the polymers of this invention are polymerized to give a polymer with a weight average molecular weight from about 1 ,000 to about 1 ,000,000, preferably from about 2,000 to about 80,000, more preferably from about 6,000 to about 50,000.
• weight average molecular weight is below 1 ,000, then good film forming properties are not obtained for the antireflective coating and when the weight average molecular weight is too high, then properties such as solubility, storage stability and the like may be compromised.
• R is selected from (C 1 -C30) linear, branched or cyclic alkyl, substituted or unsubstituted (C 6 -C 4 o) aryl, or substituted or unsubstituted (C 7 -C 4 o) alicyelic hydrocarbon; and n > 2. It is believed that the terminal vinyl ether group reacts with the hydroxyl or carboxyl group of the polymer to give an acid labile acetal linkage.
• vinyl ether terminated crosslinking agents include bis(4-vinyloxy butyl) adipate; bis(4-vinyloxy butyl) succinate; bis(4-vinyloxy butyl) isophathalate; bis(4-vinyloxymethyl cyclohexylmethyl) glutarate; tris(4-vinyloxy butyl) trimellitate; bis(4-vinyloxy methyl cyclohexyl methyl) terephthalate; bis(4- vinyloxy methyl cyclohexyl methyl) isophthalate; bis(4-vinyloxy butyl) (4-methyl- 1 ,3-phenylene) biscarbamate; bis(4-vinyloxy butyl) (methylene di-4,1-phenylene) biscarbamate; and triethyleneglycol divinylether, 1 ,4-cyclohexanedimentanol divinyl ether, various Vectomer® vinyl ether monomers
• the vinyl ether terminated crosslinking agent is preferably added to the antireflective coating in a proportion which provides 0.20-2.00 mol equivalents of vinyl ether crosslinking function per reactive group on the polymer, especially preferred is 0.50-1.50 reactive equivalents per reactive group.
• the antireflective coating composition comprises a photoacid generator
• the photoacid generator in the antireflective coating and the photoacid generator in the photoresist are sensitive to the same wavelength of light, and thus the same radiant wavelength of light can cause an acid to be formed in both layers.
• the acid in the exposed areas of the antireflective coating present either through diffusion from the photoresist or through photogeneration from the photoacid generator in the antireflective film, reacts with the acid labile crosslinkages to decrosslink the polymer, thus making the exposed areas of the antireflective coating soluble in the aqueous alkaline developer.
• the photoacid generator of the antireflective coating chosen depends on the photoresist to be used.
• the onium salts are usually used in a form soluble in organic solvents, mostly as iodonium or sulfonium salts, examples of which are diphenyliodonium trifluoromethane sulfonate, diphenyliodonium nonafluorobutane sulfonate, triphenylsulfonium trifluromethane sulfonate, triphenylsulfonium nonafluorobutane sulfonate and the like.
• Other compounds that form an acid upon irradiation are triazines, oxazoles, oxadiazoles, thiazoles, substituted 2-pyrones.
• Phenolic sulfonic esters bis-sulfonylmethanes, bis- sulfonylmethanes or bis-sulfonyldiazomethanes, triphenylsulfonium tris(trifluoromethylsulfonyl)methide, triphenylsulfonium bis(trifluoromethylsulfonyl)imide, diphenyliodonium tris(trifluoromethylsulfonyl)methide, diphenyliodonium bis(trifluoromethylsulfonyl)imide and their homologues are also possible candidates. Mixtures of photoactive compounds may also be used.
• the photoacid generator can be sulfonium salts or diazonaphthoquinones, especially 2,1 ,4-diazonaphthoquinones that are capable of producing acids that can react with the acid labile groups of the polymer.
• Oxime sulfonates, substituted or unsubstituted naphthalimidyl triflates or sulfonates are also known as photoacid generators. Any photoacid generator that absorbs light at the same wavelength as the top photoresist may be used.
• Photoacid generators known in the art may be used, such as those disclosed in the US 5,731 ,386, US 5,880,169, US 5,939,236, US 5,354,643, US 5,716,756, DE 3,930,086, DE 3,930,087, German Patent Application P 4,112,967.9, F. M. Houlihan et al., J. Photopolym. Sci. Techn., 3:259 (1990); T. Yamaoka et al., J. Photopolym. Sci. Techn., 3:275 (1990)), L Schlegel et al., J. Photopolym. Sci. Techn., 3:281 (1990) or M. Shirai et al., J. Photopolym.
• any known acids or thermal acid generators may be used, exemplified without limitations, by 2,4,4,6- tetrabromocyclohexadienone, benzoin tosylate, squaric acid, 2-nitrobenzyl tosylate, chloroacetic acid, toluenesulfonic acid, methanesulfonic acid, nonaflate acid, triflic acid, other alkyl esters of organic sulfonic acids, salts of these mentioned acids.
• some acids and acids produced by thermal acid generators which have high acidity, can lead to undercutting and can prevent the desired photoimaging process from taking place.
• acids with moderate acidity i.e.
• the thermal acid be such that once the acid is generated it does not remain permanently in the coating and therefore does not facilitate the reverse reaction, but is removed from the film. It is believed that, once crosslinking takes place the acid is decomposed or volatilized by heat and the decomposition products are baked out of the film, or the acid may sublime from the coating. Thus none or very little of the free acid remains in the film after curing, and the reverse reaction causing the decomposition of the acetal linkage does not take place. Thermal acid generators which can generate an acid and then be removed prior to coating of the photoresist are preferred in some cases. Weak acids that remain in the film may also be functional, as they may not greatly hinder the decomposition of the acetal linkage.
• the acid or acid derived from the thermal acid generator is preferably removed from the antireflective coating at temperatures ranging from about 130°C to about 220°C, more preferably 150°C to about 200°C.
• the acids or thermal acid generators may be present in the antireflective composition at levels ranging from 0.1 to 25 weight% of solids, especially 0.1 to about 5 weight%.
• Typical antireflective coating compositions of the present invention may comprise up to about 15 percent by weight of the solids, preferably less than 8 percent, based on the total weight of the coating composition.
• bases are amines, ammonium hydroxide, and photosensitive bases. Particularly preferred bases are tetrabutylammonium hydroxide, triethanolamine, diethanol amine, trioctylamine, n-octylamine, trimethylsulfonium hydroxide, triphenylsulfonium hydroxide, bis(t- butylphenyl)iodonium cyclamate and tris(tert-butylphenyl)sulfonium cyclamate.
• the absorption parameter (k) of the novel composition ranges from about 0.1 to about 1.0, preferably from about 0.15 to about 0.7 as measured using ellipsometry.
• the refractive index (n) of the antireflective coating is also optimized.
• the n and k values can be calculated using an ellipsometer, such as the J. A. Woollam WVASE VU-302 TM Ellipsometer.
• the exact values of the optimum ranges for k and n are dependent on the exposure wavelength used and the type of application. Typically for 193 nm the preferred range for k is 0.1 to 0.75, for 248 nm the preferred range for k is 0.15 to 0.8, and for 365 nm the preferred range is from 0.1 to 0.8.
• the thickness of the antireflective coating is less than the thickness of the top photoresist.
• Photoresists sensitive at 193 nm that are known in the prior art are described in the following references and incorporated herein, EP 794458, WO 97/33198 and US 5,585,219, although any photoresist sensitive at 193 nm may be used on top of the antireflective composition of this invention.
• a film of photoresist is then coated on top of the cured antireflective coating and baked to substantially remove the photoresist solvent.
• the photoresist and the antireflective coating bilevel layers are then imagewise exposed to actinic radiation.
• the obtained solution was cooled down to the room temperature and tetramethylammonium hydroxide (26wt% in water) solution (7g) was added.
• the reaction temperature was raised to 40°C and was kept for 3 hours before being raised to 60°C.
• the reaction mixture was cooled down to room temperature and was acidified to pH 6 using acetic acid.
• the resultant polymer was precipitated into 600 ml of methanol and the obtained solid was filtered, washed with methanol and deionized water, and then dried.
• the precipitated polymer was redissolved in 60g of PGME and precipitated again into 600 ml of methanol.
• the solid was filtered, washed and dried at 40°C under vacuum.
• the obtained polymer represented by the structure (I)
• Synthesis Examples 2-5 Polymers with structures (II) to (V) were synthesized in the similar procedure as Synthesis Example 1 except using the different types and amount of monomers in accordance with the monomer ratio given in the structures.
• Example 1 A copolymer represented by structure (I) from Synthesis Example 1 (2.5g), tris(4-vinyloxy butyl) trimellitate (0.25g, Vectomer®5015, available from Aldrich Co.), and triphenylsulfonium nonaflate (0.05g) were dissolved in 68g propyleneglycol monomethylether acetate (PGMEA) and 29g of propyleneglycol monomethylether (PGME) to form an antireflective coating composition. The solution was filtered through a 0.1 ⁇ m filter.
• PGMEA propyleneglycol monomethylether acetate
• PGME propyleneglycol monomethylether
• Example 2 A copolymer represented by structure (I) from Synthesis Example 1 (3g), bis(4-vinyloxy butyl) adipate (0.4g, Vectomer®4060, available from Aldrich Co.), and oxalic acid (0.01 g) were dissolved in 67.6g PGMEA and 28.8g PGME to form an antireflective coating composition. The solution was filtered through a 0.1 ⁇ m filter.
• Example 3 A copolymer represented by structure (II) from Synthesis Example 2
• Example 4 A copolymer represented by structure (I) from Synthesis Example 1 (3g), triethyleneglycol divinylether (0.6g, RAPI-CURE® DVE-3, available from ISP
• Example 5 A copolymer represented by structure (III) from Synthesis Example 3 (4g), tris(4-vinyloxy butyl) trimellitate (0.5g, Vectomer®5015, available from Aldrich), and oxalic acid (0.02g) were dissolved in 70g PGMEA and 30g PGME stirring to form an antireflective coating composition. The solution was filtered through a 0.1 ⁇ m filter.
• Example 6 A copolymer represented by structure (IV) from Synthesis Example 4 (2g), tris(4-vinyloxy butyl) trimellitate (0.2g, Vectomer®5015, available from Aldrich Co.), and oxalic acid (0.01 g) were dissolved in 70g PGMEA and 30g PGME by stirring to form an antireflective coating composition. The solution was filtered through a 0.1 ⁇ m filter.
• Example 7 A copolymer represented by structure (V) from Synthesis Example 5 (2g), tris(4-vinyloxy butyl) trimellitate (0.2g, Vectomer®5015, available from Aldrich
• Example 8 The solution prepared in Example 1 was spin coated onto a 6inch silicon wafer at 2500rpm for 60 seconds and then baked on a hot plate at 170°C for 90 seconds to form a cured antireflective coating layer.
• the film thickness of the coating as determined by ellipsometry manufactured by J.A. Woollam company or by Sopra corporation, was about 700A.
• the solutions prepared in Examples 1 -8 were spin coated on 6inch silicon wafers and baked on a hot plate at different temperatures (each baking temperature 2 wafers for each sample).
• One coated wafer from each of the set of B.A.R.C coatings was puddled with PGMEA, a common photoresist solvent, and the other with developer, each for 60 seconds and then spin dried.
• No obvious film thickness change in the antireflective layer was observed on the wafers when baked above 150°C, indicating that the films were highly crosslinked and solvent- resistant, thus there would be no intermixing with the photoresist solvent when the photoresist was coated over the B.A.R.C.
• Example 9 The solutions prepared in Examples 1 -4 were spin coated on 6inch silicon wafers baked at 170°C for 90 seconds to give a thickness of 60 nanometers. Then a DUV photoresist, AZ ® DX6270P (available from Clariant (Japan) K. K.) was coated thereon and softbaked at 120°C for 90 seconds to give a thickness of 0.45 micron. The coated wafers were imagewise exposed using Cannon FPA- 3000 EX5 248 nm stepper.
• the exposed wafers were postexposure baked for 90 seconds at 130°C, followed by a puddle development of 60 seconds with AZ ® 300 MIF Developer (2.38 weight % tetramethyl ammonium hydroxide aqueous solution available from Clariant Corp.).
• AZ ® 300 MIF Developer (2.38 weight % tetramethyl ammonium hydroxide aqueous solution available from Clariant Corp.
• the secondary electron microscope results showed at 22mJ/cm 2 , both the 0.20 ⁇ m 1 :1 dense lines and 0.20 ⁇ m isolated lines was completely opened both in the photoresist layer and the antireflective coating layer. No obvious standing waves due to the reflection from the substrate were observed on the pattern profiles.
• Example 10 1.5 g of poly(hydroxystyrene-methacrylate) (55/45 molar ratio), 0.075 g of oxalic acid/triethylamine(1:1), 0.06 g of triphenylsulfonium triflate, and 0.225 g of VectomerTM5015 (available from Aldrich Corp.) were dissolved in 98.5 g of ethyl lactate to give the B.A.R.C. solution. The solution was filtered through 0.2 ⁇ m microfilter. The B.A.R.C. coating gave a refractive index (n) and absorption (k) at 193 nm of 1.59 and 0.62 respectively as measured by a J. A.
• the B.A.R.C. solution was coated on a primed silicon wafer heated on a hotplate at 200 °C for 60 seconds to give a film thickness of 35 nm.
• the B.A.R.C. wafer was coated with AZ ⁇ 1020P photoresist (available from Clariant Corp., Somerville, NJ) with a film thickness of 330 nm.
• the wafer was then baked on a hotplate for 120 °C for 60 seconds.
• the coated wafer was exposed using an ISI 193 nm ministepper for imagewise exposure.
• the exposed wafer as then post exposure baked for 90 seconds at 130 °C and followed with a 30- second puddle development at 23 °C using of AZ® 300 MIF Developer.
• 0.15 ⁇ m photoresist/B.A.R.C. lines (1 :1) were obtained at a dose of 40 mJ/cm 2 .
• Example 11 0.075 g of poly(hydroxystyrene-methacrylate) (55/45 molar ratio), 0.015 g of cyanoacetic acid, and 0.022 g of VectomerTM5015 were dissolved in 8.0 g of propylene glycol monomethyl ether. The solution was filtered through 0.2 ⁇ m microfilter. The B.A.R.C. solution was coated on a primed silicon wafer and heated on a hotplate at 175 °C for 60 seconds to give a film thickness of 293 A. The B.A.R.C.
• AZ® T430 photoresist available from Clariant Corp., Somerville, NJ
• the coated wafer was exposed using an ISI 193 nm ministepper for imagewise exposure.
• the exposed wafer was then post exposure baked for 20 seconds at 120 °C and followed with a 30-second puddle development at 23 °C using of AZ® 300 MIF Developer.
• 0.20 ⁇ m photoresist/B.A.R.C. lines (1 :1) were obtained at a dose of 20 mJ/cm2.
• Example 12 The B.A.R.C. solution from Example 10 was coated on a primed silicon wafer and baked at 175 °C for 90 seconds to give a film thickness of 499 A.
• the B.A.R.C. wafer was coated with AZ® T430 photoresist (available from Clariant Corp., Somerville, NJ), heated on a hotplate for 120 °C for 60 seconds to give a film thickness of 116 nm.
• the coated wafer was exposed using an ISI 193 nm ministepper for imagewise exposure.
• the exposed wafer was then post exposure baked for 20 seconds at 120 °C and followed with a 30-second puddle development at 23 °C using of AZ® 300 MIF Developer.
• 0.35 ⁇ m photoresist/B.A.R.C. lines (1 :1) were obtained at a dose of 21 mJ/cm2.

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