US20030235775A1

US20030235775A1 - Photoresist composition for deep ultraviolet lithography comprising a mixture of photoactive compounds

Info

Publication number: US20030235775A1
Application number: US10/170,761
Authority: US
Inventors: Munirathna Padmanaban; Takanori Kudo; Sangho Lee; Ralph Dammel; M. Rahman
Original assignee: Clariant International Ltd
Current assignee: Clariant International Ltd
Priority date: 2002-06-13
Filing date: 2002-06-13
Publication date: 2003-12-25
Also published as: KR20050012786A; CN1659477A; MY136433A; WO2003107093A2; KR100940053B1; TW200413849A; CN100565338C; JP2005534952A; EP1516229A2; JP4403070B2; WO2003107093A3; TWI309337B; US6991888B2; US20030235782A1

Abstract

The present invention relates to a novel photoresist that can be developed with an aqueous alkaline solution, and is capable of being imaged at exposure wavelengths in the deep ultraviolet. The invention also relates to a process for imaging the novel photoresist. The novel photoresist comprises a) a polymer containing an acid labile group, and b) a novel mixture of photoactive compounds, where the mixture comprises a lower absorbing compound selected from structure 1 and 2, and a higher absorbing compound selected from structure 4 and 5,

where, R₁and R₂are independently (C₁-C₆)alkyl, cycloalkyl, cyclohexanone, R₅-R₉are independently hydrogen, hydroxyl, (C₁-C₆)alkyl, C₁-C₆)aliphatic hydrocarbon containing one or more O atoms, m=1-5, X⁻ is an anion, and Ar is selected from naphthyl, anthracyl, and structure 3,

where, R₃is hydrogen or (C₁-C₆)alkyl, R₄is independently hydrogen, (C₁-C₆)alkyl, (C₁-C₆)aliphatic hydrocarbon containing one or more O atoms, Y is a single bond or (C₁-C₆)alkyl, and n=1-4.

Description

FIELD OF INVENTION

The present invention relates to a novel photoresist composition that is particularly useful in the field of microlithography, and especially useful for imaging negative and positive patterns in the production of semiconductor devices. The photoresist composition comprises a copolymer and a photoactive component, where the photoactive component comprises a mixture of an aromatic onium salt and an alkyaryl onium salt. The novel photoresist composition provides both good photosensitivity and also significantly reduces edge roughness of the imaged photoresist profiles. Such a composition is especially useful for exposure at 193 nanometers (nm) and 157 nm. The invention further relates to a process for imaging the novel photoresist.

BACKGROUND OF THE INVENTION

Photoresist compositions are used in microlithography processes for making miniaturized electronic components such as in the fabrication of computer chips and integrated circuits. Generally, in these processes, a thin coating of 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 photoresist coated on the substrate is next subjected to an image-wise exposure to radiation.

The 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. After this image-wise exposure, the coated substrate is treated with a developer solution to dissolve and remove either the radiation exposed or the unexposed areas of the photoresist.

The trend toward the miniaturization of semiconductor devices has led to the use of new photoresists that are sensitive at lower and lower wavelengths of radiation and has also led to the use of sophisticated multilevel systems to overcome difficulties associated with such miniaturization.

There are two types of photoresist compositions: negative-working and positive-working. The type of photoresist used at a particular point in lithographic processing is determined by the design of the semiconductor device. When negative-working photoresist compositions are exposed image-wise to radiation, the areas of the photoresist composition exposed to the radiation become less soluble to a developer solution (e.g. a cross-linking reaction occurs) while the unexposed areas of the photoresist coating remain relatively soluble to such a solution. Thus, treatment of an exposed negative-working resist with a developer causes removal of the non-exposed areas of the photoresist coating and the creation of a negative image in the coating, thereby uncovering a desired portion of the underlying substrate surface on which the photoresist composition was deposited.

On the other hand, when positive-working photoresist compositions are exposed image-wise to radiation, those areas of the photoresist composition exposed to the radiation become more soluble to the developer solution (e.g. a rearrangement reaction occurs) while those areas not exposed remain relatively insoluble to the developer solution. Thus, treatment of an exposed positive-working photoresist with the developer causes removal of the exposed areas of the coating and the creation of a positive image in the photoresist coating. Again, a desired portion of the underlying surface is uncovered.

Photoresist resolution is defined as the smallest feature, which the resist composition can transfer from the photomask to the substrate with a high degree of image edge acuity after exposure and development. In many leading edge manufacturing applications today, photoresist resolution on the order of less than one-half micron are necessary. In addition, it is almost always desirable that the developed photoresist wall profiles be near vertical relative to the substrate. Such demarcations between developed and undeveloped areas of the resist coating translate into accurate pattern transfer of the mask image onto the substrate. This becomes even more critical as the push toward miniaturization reduces the critical dimensions on the devices. In cases where the photoresist dimensions have been reduced to below 150 nanometer(nm), the roughness of the photoresist patterns has become a critical issue. Edge roughness, commonly known as line edge roughness, is typically observed for line and space patterns as roughness along the photoresist line, and for contact holes as side wall roughness. Edge roughness can have adverse effects on the lithographic performance of the photoresist, especially in reducing the critical dimension latitude and also in transferring the line edge roughness of the photoresist to the substrate. Hence, photoresists that minimize edge roughness are highly desirable.

Photoresists sensitive to short wavelengths, between about 100 nm and about 300 nm are often used where subhalfmicron geometries are required. Particularly preferred are photoresists comprising non-aromatic polymers, a photoacid generator, optionally a dissolution inhibitor, and solvent.

High resolution, chemically amplified, deep ultraviolet (100-300 nm) positive and negative tone photoresists are available for patterning images with less than quarter micron geometries. To date, there are three major deep ultraviolet (uv) exposure technologies that have provided significant advancement in miniaturization, and these use lasers that emit radiation at 248 nm, 193 nm and 157 nm. Photoresists used in the deep uv typically comprise a polymer which has an acid labile group and which can deprotect in the presence of an acid, a photoactive component which generates an acid upon absorption of light, and a solvent.

Photoresists for 248 nm have typically been based on substituted polyhydroxystyrene and its copolymers, such as those described in U.S. Pat. No. 4,491,628 and U.S. Pat. No. 5,350,660. On the other hand, photoresists for 193 nm exposure require non-aromatic polymers, since aromatics are opaque at this wavelength. U.S. Pat. No. 5,843,624 and GB 2,320,718 disclose photoresists useful for 193 nm exposure. Generally, polymers containing alicyclic hydrocarbons are used for photoresists for exposure below 200 nm. Alicyclic hydrocarbons are incorporated into the polymer for many reasons, primarily since they have relatively high carbon:hydrogen ratios which improve etch resistance, they also provide transparency at low wavelengths and they have relatively high glass transition temperatures. Photoresists sensitive at 157 nm have been based on fluorinated polymers, which are known to be substantially transparent at that wavelength. Photoresists derived from polymers containing fluorinated groups are described in WO 00/67072 and WO 00/17712.

The polymers used in a photoresist are designed to be transparent to the imaging wavelength, but on the other hand, the photoactive component has been typically designed to be absorbing at the imaging wavelength to maximize photosensitivity. The photosensitivity of the photoresist is dependent on the absorption characteristics of the photoactive component, the higher the absorption the less the energy required to generate the acid and the more photosensitive the photoresist is. Aromatic photoactive compounds, such as triphenyl sulfonium salts, diphenyl iodonium salts are known to give good photosensitivity at 248 nm, but have found to be too absorbing at wavelengths below 200 nm and lead to tapered photoresist profiles. Transparent sulfonium salts based on alkyl sulfonium salts have found to be too transparent at the imaging wavelength and result in poor photosensitivity. JP 10319581, EP 1,085,377, EP 1,041,442, and U.S. Pat. No. 6,187,504 disclose alkylaryl sulfonium salts of different structures that can be used in the photoresist composition.

The inventors of this application have found that the photoactive compounds known in the prior art cause unacceptable levels of line edge roughness, or if the line edge roughness is acceptable then the photosensitivity is poor. However, the inventors of this application have also found that if a mixture of a specific alkylarylsulfonium or alkylaryliodonium salt and an arylsulfonium or aryliodonium salt is used, the line edge roughness is significantly reduced while maintaining an acceptable level of photosensitivity. EP 1,085,377 discloses that mixtures of alkylarylsulfonium salts may be used with other onium salts, diazomethane derivatives, glyoxime derivatives and many other photoactive compounds. A specific mixture of photoactive compounds is not disclosed which when formulated into a photoresist would significantly reduce line edge roughness.

The object of this invention is to provide a novel photoresist composition, which can provide good lithographic performance especially in reducing line edge roughness while maintaining good photosensitivity.

The present invention pertains to a novel photoresist composition comprising a polymer and a novel mixture of photosensitive compounds. The composition is particularly useful for imaging in the range of 100-300 nm, and more particularly for 157 nm and 193 nm.

SUMMARY OF THE INVENTION

The present invention relates to a novel photoresist composition useful for imaging in deep uv comprising a) a polymer containing an acid labile group, and, b) a novel mixture of photoactive compounds, where the mixture comprises a lower absorbing compound selected from structure 1 and 2, and a higher absorbing compound selected from structure 4 and 5,

where, R ₁and R₂are independently (C₁-C₆)alkyl, cycloalkyl, cyclohexanone, R₅-R₉are independently hydrogen, hydroxyl, (C₁-C₆)alkyl, and (C₁-C₆)aliphatic hydrocarbon containing one or more O atoms, m=1-5, X⁻ is an anion, and Ar is selected from naphthyl, anthracyl, and structure 3,

where, R ₃is hydrogen or (C₁-C₆)alkyl, R₄is independently hydrogen, (C₁-C₆)alkyl, (C₁-C₆)aliphatic hydrocarbon containing one or more 0 atoms, Y is a single bond or (C₁-C₆)alkyl, and n=1-4.

The invention also relates to a process for imaging a photoresist comprising the steps of a) forming on a substrate a photoresist coating from the novel photoresist composition, b) image-wise exposing the photoresist coating, c) optionally, postexposure baking the photoresist coating, and d) developing the photoresist coating with an aqueous alkaline solution.

DESCRIPTION OF THE INVENTION

The present invention relates to a novel photoresist that can be developed with an aqueous alkaline solution, and is capable of being imaged at exposure wavelengths below 200 nm. The invention also relates to a process for imaging the novel photoresist. The novel photoresist comprises a) a polymer containing an acid labile group, and b) a novel mixture of photoactive compounds, where the mixture comprises a higher absorbing compound selected from an aromatic sulfonium salt (structure 4) and an aromatic iodonium salt (structure 5) and a lower absorbing compound selected from structure 1 and 2.

where, R ₁and R₂are independently (C₁-C₆)alkyl, cycloalkyl, cyclohexanone, R₅-R₉are independently hydrogen, hydroxyl, (C₁-C₆)alkyl, and (C₁-C₆)aliphatic hydrocarbon containing one or more O atoms, m=1-5, X⁻ is an anion, and Ar is selected from naphthyl, anthracyl and structure 3,

where, R ₃is hydrogen or (C₁-C₆)alkyl, R₄is independently hydrogen, (C₁-C₆)alkyl, (C₁-C₆)aliphatic hydrocarbon containing one or more O atoms, Y is a single bond or (C₁-C₆)alkyl, and n=1-4.

The aromatic sulfonium salts, such as triphenyl sulfonium salt, derivatives of triphenyl sulfonium salt, diphenyl iodonium salt and derivatives of diphenyl iodonium salt, provide the higher absorbing component, while the compounds of structure 1 or 2 provide the lower absorbing component. It has unexpectedly been found that by combining a higher absorbing photoactive component with a lower absorbing photoactive component that the edge roughness of the photoresist pattern can be greatly reduced while maintaining acceptable photosensitivity. It has further been found that the optimum lithographic performance is obtained when the ratio of the higher absorbing component and the lower absorbing component is in the molar ratio 1:2 to 2:1, and preferably about 1:1. Line edge roughness improvement of greater than 20% is acceptable, greater than 35% is preferable, greater than 50% is more preferable and greater than 75% is most preferable. Acceptable levels of line edge roughness are obtained while maintaining good photosensitivity by using the components of this invention.

The higher absorbing photoactive components are aromatic iodonium and sulfonium salts of structure 4 and 5.

where, R ₅-R₉are independently hydrogen, hydroxyl, (C₁-C₆)alkyl, and (C₁-C₆)aliphatic hydrocarbon containing one or more O atoms, m=1-5, and X⁻ is an anion. Examples are diphenyliodonium salts, triphenylsulfonium salts and the like. Examples of X⁻ are trifluoromethane sulfonate (triflate), 1,1,1,2,3,3-hexafluoropropanesulfonate, perfluorobutanebutanesulfonate (nonaflate), camphor sulfonate, perfluorooctane sulfonate, benzene sulfonate and toluenesulfonate. Some examples, without limitation are, of sulfonium salts are triphenylsulfonium salts, trialkylphenylsulfonium salts, (p-tert-butoxyphenyl)triphenylsulfonium salts, bis(p-tert-butoxyphenyl)phenylsulfonium salts, and tris(p-tert-butoxyphenyl)sulfonium salts. Some examples, without limitation, of iodonium salts are diphenyliodonium salts, di(alkylphenyl)iodonium salts etc. The counter ion, X⁻, may be any ion that gives good lithographic properties, and examples of which are fluoroalkylsulfonates such as 1,1,1-trifluoromethanesulfonate and nonafluorobutanesulfonate, arylsulfonates such as tosylate, benzenesulfonate, 4-fluorobenzenesulfonate, and alkylsulfonates such as mesylate and butanesulfonate. Preferred salts are diphenyliodonium trifluoromethane sulfonate, diphenyliodonium nonafluorobutanesufonate, triphenylsulfonium trifluromethanesuflonate, and triphenylsulfonium nonafluorobutanesufonate.

The lower absorbing photoactive component is a compound of structure 1 or 2.

where, R ₁and R₂are independently (C₁-C₆)alkyl, cycloalkyl, cyclohexanone, X⁻ is an anion, and Ar is selected from naphthyl, anthracyl, and structure 3,

The alkyl group generally has up to 6 linear or branched carbon atoms and can be groups such as methyl, ethyl, propyl, butyl, pentyl, hexyl, isopropyl, and t-butyl. The (C ₁-C₆)aliphatic hydrocarbon containing one or more O atoms can be any alkyl group with linkages such as ether, keto, carboxyl, or other O based linkages. The cycloalkyl group has up to 16 carbon atoms, examples of which are cyclopentyl, cyclohexyl, cyclooctyl, norbornyl, isonorbornyl and adamantyl. The aromatic group, Ar, may be connected directly to the sulfonium ion or have a linking alkylene group with up to 6 alkyl carbon atoms. The aromatic group may be phenyl, naphthyl or anthracyl and their derivatives. The phenyl group has the structure 3, examples of which are 4-methoxyphenyl, 4-hydroxyphenyl, 3,5-dimethyl, 4-hydroxyphenyl and 3,5-dimethyl,4-methoxyphenyl. Other groups that illustrate the derivatives of the naphthyl and anthracyl functionality, but are not limited to, are alkylnaphthyl, dialkylnaphthyl, alkylanthracyl, dialkylanthracyl, alkoxynaphthyl, alkoxyanthracyl, dialkoxynaphthyl, dialkoxyanthracyl examples of which are methylnaphthyl, ethylnaphthyl, methylanthracyl, ethylanthracyl, methoxy naphthyl, ethoxynaphthyl, methoxynaphthyl, ethoxyanthracyl and others.

In one of the preferred embodiments Y is a single bond, in which, the aromatic group is connected directly to the sulfonium ion, and the aromatic group is phenyl or substituted phenyl, preferably methoxydimethylphenyl dimethyl sulfonium salts, methoxyphenyl dimethylsulfonium salts, hydroxydimethylphenyl dimethyl sulfonium salts, and hydroxyphenyl dimethylsulfonium salts.

Examples of the lower absorbing photoactive compound, without limitations, are 4-methoxyphenyl-dimethylsulfonium triflate, 3,5-dimethyl-4-hydroxyphenyl-dimethyl sulfonium triflate, 3,5-dimethyl-4-methoxyphenyl-dimethyl sulfonium triflate, 3,5-dimethyl-4-hydroxyphenyl-dimethyl sulfonium nonaflate, 3,5-dimethyl-4-methoxyphenyl-dimethyl sulfonium nonaflate, 4-methoxyphenyl-methyliodonium triflate or nonaflate, 3,5-dimethyl-4-hydroxyphenyl-methyliodonium triflate or nonaflate, and 3,5-dimethyl-4-methoxyphenyl-methyl iodonium triflate or nonaflate.

One of the preferred mixtures of photoactive compounds is a mixture of triphenylsulfonium triflate or nonaflate with 3,5-dimethyl,4-methoxyphenylsulfonium triflate or nonaflate.

The polymer of the invention is one that has acid labile groups that make the polymer insoluble in aqueous alkaline solution, but such a polymer in the presence of an acid catalytically deprotects the polymer, wherein the polymer then becomes soluble in an aqueous alkaline solution. The polymers preferably are transparent below 200 nm, and are essentially non-aromatic, and preferably are acrylates and/or cycloolefin polymers. Such polymers are, for example, but not limited to, those described in U.S. Pat. No. 5,843,624, U.S. Pat. No. 5,879,857, WO 97/33,198, EP 789,278 and GB 2,332,679. Nonaromatic polymers that are preferred for irradiation below 200 nm are substituted acrylates, cycloolefins, substituted polyethylenes, etc. Aromatic polymers based on polyhydroxystyrene and its copolymers may also be used, especially for 248 nm exposure. Preferred comonomers are methacrylates.

Polymers based on acrylates are generally based on poly(meth)acrylates with at least one unit containing pendant alicyclic groups, and with the acid labile group being pendant from the polymer backbone and/or from the alicyclic group. Examples of pendant alicyclic groups, may be adamantyl, tricyclodecyl, isobornyl, menthyl and their derivatives. Other pendant groups may also be incorporated into the polymer, such as mevalonic lactone, gamma butyrolactone, alkyloxyalkyl, etc. More preferred structures for the alicyclic group are:

The type of monomers and their ratios incorporated into the polymer are optimized to give the best lithographic performance. Such polymers are described in R. R. Dammel et al., Advances in Resist Technology and Processing, SPIE, Vol. 3333, p144, (1998). Examples of these polymers include poly(2-methyl-2-adamantane methacrylate-co-mevalonic lactone methacrylate), poly(carboxy-tetracyclododecyl methacrylate-co-tetrahydropyranylcarboxytetracyclododecyl methacrylate), poly(tricyclodecylacryl ate-co-tetrahydropyranylmethacrylate-co-methacrylicacid), poly(3-oxocyclohexyl methacrylate-co-adamantylmethacrylate).

Polymers synthesized from cycloolefins, with norbornene and tetracyclododecene derivatives, may be polymerized by ring-opening metathesis, free-radical polymerization or using metal organic catalysts. Cycloolefin derivatives may also be copolymerized with cyclic anhydrides or with maleimide or its derivatives. Examples of cyclic anhydrides are maleic anhydride and itaconic anhydride. The cycloolefin is incorporated into the backbone of the polymer and may be any substituted or unsubstituted multicyclic hydrocarbon containing an unsaturated bond. The monomer can have acid labile groups attached. The polymer may be synthesized from one or more cyclo olefin monomers having an unsaturated bond. The cyclo olefin monomers may be substituted or unsubstituted norbornene, or tetracyclododecane. The substituents on the cyclo olefin may be aliphatic or cycloaliphatic alkyls, esters, acids, hydroxyl, nitrile or alkyl derivatives. Examples of cyclo olefin monomers, without limitation, are:

Other cyclo olefin monomers which may also be used in synthesizing the polymer are:

Such polymers are described in the following reference and incorporated herein, M-D. Rahman et al, Advances in Resist Technology and Processing, SPIE, Vol. 3678, p1193, (1999). Examples of these polymers include poly((t-butyl 5-norbornene-2-carboxylate-co-2-hydroxyethyl 5-norbornene-2-carboxylate-co-5-norbornene-2-carboxylic acid-co-maleic an hydride), poly(t-butyl 5-norbornene-2-carboxylate-co-isobornyl-5-norbornene-2-carboxylate-co-2-hydroxyethyl 5-norbornene-2-carboxylate-co-5-norbornene-2-carboxylic acid-co-maleic anhydride), poly(tetracyclododecene-5-carboxylate-co-maleic anhydride), poly(t-butyl 5-norbornene-2-carboxylate-co-maleic anhydride-co-2-methyladamantyl methacrylate-co-2-mevalonic lactone methacrylate), poly(2-methyladamantyl methacrylate-co-2-mevalonic lactone methacylate) and the like.

Polymers containing mixtures of acrylate monomers, cycloolefinic monomers and cyclic anhydrides, where such monomers are described above, may also be combined into a hybrid polymer. Preferably the cyclo olefin monomer is selected from t-butyl norbornene carboxylate (BNC), hydroxyethyl norbornene carboxylate (HNC), norbornene carboxylic acid(NC), t-butyl tetracyclo[4.4.0.1. ^2,61.^7,10] dodec-8-ene-3-carboxylate, and t-butoxycarbonylmethyl tetracyclo[4.4.0.1.^2,61.^7,10] dodec-8-ene-3-carboxylate; more preferably the cyclo olefins are selected from t-butyl norbornene carboxylate (BNC), hydroxyethyl norbornene carboxylate (HNC), and norbornene carboxylic acid(NC). The preferred acrylate monomers are selected from mevaloniclactone methacrylate (MLMA), 2-methyladamantyl methacrylate (MAdMA), isoadamantyl methacrylate, 3-hydroxy-1-methacryloxyadamatane, 3,5-dihydroxy-1-methacryloxyadamantane, β-methacryloxy-γ-butyrolactone, and α-methacryloxy-γ-butyrolactone. More preferably the acrylate monomers are selected from mevaloniclactone methacrylate (MLMA) and 2-methyladamantyl methacrylate (MAdMA). The cyclic anhydride is preferably maleic anhydride.

The cyclo olefin and the cyclic anhydride monomer are believed to form an alternating polymeric structure, and the amount of the acrylate monomer incorporated into the polymer can be varied to give the optimal lithographic properties. The percentage of the acrylate monomer relative to the cyclo olefin/anhydride monomers within the polymer ranges from about 95 mole % to about 5 mole %, preferably from about 75 mole % to about 25 mole %, and most preferably from about 55 mole % to about 45 mole %.

Fluorinated non-phenolic polymers, useful for 157 nm exposure, also exhibit line edge roughness and can benefit from the use of the novel mixture of photoactive compounds described in the present invention. Such polymers are described in WO 00/17712 and WO 00/67072 and incorporated herein by reference. Example of one such polymer is poly(tetrafluoroethylene-co-norbornene-co-5-hexafluoroisopropanol-substituted 2-norbornene.

Polymers synthesized from cycloolefins and cyano containing ethylenic monomers are described in the U.S. patent application Ser. No. 09/854,312 and incorporated herein by reference, may also be used.

The molecular weight of the polymers is optimized based on the type of chemistry used and on the lithographic performance desired. Typically, the weight average molecular weight is in the range of 3,000 to 30,000 and the polydispersity is in the range 1.1 to 5, preferably 1.5 to 2.5.

The solid components of the present invention are dissolved in an organic solvent. The amount of solids in the solvent or mixture of solvents ranges from about 5 weight% to about 50 weight%. The polymer may be in the range of 5 weight% to 90 weight% of the solids and the photoacid generator may be in the range of 2 weight% to about 50 weight% of the solids. Suitable solvents for such photoresists may include propylene glycol mono-alkyl ether, propylene glycol alkyl (e.g. methyl) ether acetate, ethyl-3-ethoxypropionate, xylene, diglyme, amyl acetate, ethyl lactate, butyl acetate, 2-heptanone, ethylene glycol monoethyl ether acetate, and mixtures thereof.

Various other additives such as colorants, non-actinic dyes, anti-striation agents, plasticizers, adhesion promoters, dissolution inhibitors, coating aids, photospeed enhancers and surfactants may be added to the photoresist composition before the solution is coated onto a substrate. Surfactants that improve film thickness uniformity, such as fluorinated surfactants, can be added to the photoresist solution. A sensitizer that transfers energy from a particular range of wavelengths to a different exposure wavelength may also be added to the photoresist composition. Often bases are also added to the photoresist to prevent t-tops or bridging at the surface of the photoresist image. Examples of bases are amines, ammonium hydroxide, and photosensitive bases. Particularly preferred bases are trioctylamine, diethanolamine and tetrabutylammonium hydroxide.

The prepared photoresist composition solution can be applied to a substrate by any conventional method used in the photoresist art, including dipping, spraying, and spin coating. When spin coating, for example, the photoresist solution can be adjusted with respect to the percentage of solids content, in order to provide coating of the desired thickness, given the type of spinning equipment utilized and the amount of time allowed for the spinning process. Suitable substrates include silicon, aluminum, polymeric resins, silicon dioxide, doped silicon dioxide, silicon nitride, tantalum, copper, polysilicon, ceramics, aluminum/copper mixtures; gallium arsenide and other such Group III/V compounds. The photoresist may also be coated over antireflective coatings.

The photoresist coatings produced by the described procedure are particularly suitable for application to silicon/silicon dioxide wafers, such as are utilized in the production of microprocessors and other miniaturized integrated circuit components. An aluminum/aluminum oxide wafer can also be used. The substrate may also comprise various polymeric resins, especially transparent polymers such as polyesters.

The photoresist composition solution is then coated onto the substrate, and the substrate is treated at a temperature from about 70° C. to about 150° C. for from about 30 seconds to about 180 seconds on a hot plate or for from about 15 to about 90 minutes in a convection oven. This temperature treatment is selected in order to reduce the concentration of residual solvents in the photoresist, while not causing substantial thermal degradation of the solid components. In general, one desires to minimize the concentration of solvents and this first temperature. Treatment is conducted until substantially all of the solvents have evaporated and a thin coating of photoresist composition, on the order of half a micron (micrometer) in thickness, remains on the substrate. In a preferred embodiment the temperature is from about 95° C. to about 120° C. The treatment is conducted until the rate of change of solvent removal becomes relatively insignificant. The film thickness, temperature and time selection depends on the photoresist properties desired by the user, as well as the equipment used and commercially desired coating times. The coated substrate can then be imagewise exposed to actinic radiation, e.g., ultraviolet radiation, at a wavelength of from about 100 nm (nanometers) to about 300 nm, x-ray, electron beam, ion beam or laser radiation, in any desired pattern, produced by use of suitable masks, negatives, stencils, templates, etc.

The photoresist is then subjected to a post exposure second baking or heat treatment before development. The heating temperatures may range from about 90° C. to about 150° C., more preferably from about 100° C. to about 130° C. The heating may be conducted for from about 30 seconds to about 2 minutes, more preferably from about 60 seconds to about 90 seconds on a hot plate or about 30 to about 45 minutes by convection oven.

The exposed photoresist-coated substrates are developed to remove the image-wise exposed areas by immersion in a developing solution or developed by spray development process. The solution is preferably agitated, for example, by nitrogen burst agitation. The substrates are allowed to remain in the developer until all, or substantially all, of the photoresist coating has dissolved from the exposed areas. Developers include aqueous solutions of ammonium or alkali metal hydroxides. One preferred developer is an aqueous solution of tetramethyl ammonium hydroxide. After removal of the coated wafers from the developing solution, one may conduct an optional post-development heat treatment or bake to increase the coating's adhesion and chemical resistance to etching conditions and other substances. The post-development heat treatment can comprise the oven baking of the coating and substrate below the coating's softening point or UV hardening process. In industrial applications, particularly in the manufacture of microcircuitry units on silicon/silicon dioxide-type substrates, the developed substrates may be treated with a buffered, hydrofluoric acid base etching solution or dry etching. Prior to dry etching the photoresist may be treated to electron beam curing in order to increase the dry-etch resistance of the photoresist.

Each of the documents referred to above are incorporated herein by reference in its entirety, for all purposes. The following specific examples will provide detailed illustrations of the methods of producing and utilizing compositions of the present invention. These examples are not intended, however, to limit or restrict the scope of the invention in any way and should not be construed as providing conditions, parameters or values which must be utilized exclusively in order to practice the present invention. Unless otherwise specified, all parts and percents are by weight.

EXAMPLES

The refractive index (n) and the absorption (k) values of the photoresist in the Examples below were measured on a J. A. Woollam VASE32 ellipsometer. [0051]
The triphenyl sulfonium nonafluorobutane sulfonate used in the photoresist formulation is available from Toyo Gosei Company Ltd. Japan. [0052]
The line edge roughness (LER) was measured on a KLA8100 CD SEM tool using 600V acceleration voltage, 100K magnification and with a threshold of 50%. The length of the photoresist line measured was 1.5 μm. LER was the (3σ) value calculated using 24 data points on each side of the photoresist line. [0053]

Synthetic Example 1

Synthesis of 4-methoxyphenyl Dimethyl Sulfonium Triflate

To a 500 ml round bottomed flask equipped with a thermometer, a mechanical stirrer, and a condenser, 1-methoxy-4-(methylthio) benzene (25 g, 0.162 mole), silver triflate (42.2 g, 0.164 mole) and 300 g tetrahydrohydrofuran (THF) were added. The mixture was heated at 40° C. to dissolve all the solids. A clear solution was cooled to room temperature and iodomethane (23.5 g, 0.166 mole) was added dropwise from a dropping funnel. The precipitate formed immediately during the addition of iodomethane. An exotherm was observed and the temperature rose to 55° C. The reaction mixture was stirred for 4 hours and the precipitate was filtered out. The solution was dark and the THF was reduced under vacuum. The solution was added drop wise to one liter of ether. The precipitate was dissolved in dichloromethane (200 ml) and filtered to remove silver oxide. The filtrate was drowned in ether (1 liter) and the white precipitate was filtered and dried under vacuum at 35° C. (white crystals). The yield was 16.0 g (33%). The solid product gave the following analytical [0054] ¹H NMR(Acetone-d6) results: 3.43 (s, 6H, 2CH₃); 3.93 (s, 3H, OCH₃); 7.29 (d, 2H, aromatic); 8.13 (d, 2H, aromatic). The absorptivity was 71.21 L/g.cm.

Synthetic Example 2

4-Hydroxy-3,5-dimethyl Phenyl Dimethyl Sulphonium Chloride

61 g of dimethylphenol (0.5 mole), 39 g (0.5 mole) of dimethylsulfoxide (DMSO), and 400 ml of methanol were placed in a 1 liter round bottom flask equipped with a thermometer and a condenser. The mixture was cooled in a liquid nitrogen-isopropyl alcohol bath while hydrogen chloride gas was bubbled in at 10° C. for 6 hours. A precipitate was formed and a part of the methanol was removed by rotavap. The crystals were filtered and washed with ether several times. The solid product gave the following analytical results [0055] ¹H NMR(Acetone-d6), 2.34 (s, 6H, 2CH₃); 3.23 (s, 6H, 2CH₃); 7.80 (s, 2H, aromatic).

Synthetic Example 3

4-Hydroxy-3,5-dimethyl Phenyl Dimethyl Sulphonium Triflate

2.185 g of 4-Hydroxy-3,5-dimethyl phenyl dimethyl sulphonium chloride were placed in a flask and 10 g of water were added, followed by 2.56 g of silver trifluoro methane sulfonate in acetone. A precipitate of AgCl formed immediately. The mixture was stirred for 30 minutes and the precipitate was filtered off. The solution was extracted with dichloromethane, dried over sodium sulphate and filtered. The solution was drowned into ether and a precipitate formed which was filtered and dried in the vacuum dryer at less than 40° C. The solid product gave the following analytical results: [0056] ¹H NMR(Acetone-d6), 2.40 (s, 6H, 2CH₃); 3.10 (s, 6H, 2CH₃); 7.65 (s, 2H, aromatic).

Synthetic Example 4

4-Methoxy-3,5-dimethyl Phenyl Dimethyl Sulphonium Triflate

4-Hydroxy-3,5-dimethyl phenyl dimethyl sulphonium chloride (10.0 g, 0.054 mole) was placed in a 250 ml round bottom flask with a stirrer, a condenser and a thermowatch. Deionized water (100 ml) and 3.4 g of NaOH (50%) were added. Dimethyl sulphate (6.8 g 0.054 mole) was added with a syringe. The mixture was stirred at room temperature for 20 minutes and then heated at 55° C. for 4 hours. After neutralization the reaction mix was added to acetone, and the salt precipitated out, which was filtered. The crude product in water was treated with silver trifluoromethane sulfonate and silver chloride was precipitated out. After filtering the salt, the solution was extracted with dichloromethane. The dichloromethane layer was washed with water, dried over sodium sulphate and drowned in ether. The precipitate was filtered and washed with ether. It was dried under vacuum. The solid product gave the following analytical results: [0057] ¹H NMR(Acetone-d6), 2.40 (s, 6H, 2CH₃);3.47 (s, 6H, 2CH₃); 3.85 (s, 3H, OCH₃); 7.89 (d, 2H, aromatic).

Synthetic Example 5

4-Hydroxy-3,5-dimethyl Phenyl Dimethyl Sulphonium Nonaflate

2.185 g of 4-Hydroxy-3,5-dimethyl phenyl dimethyl sulphonium, 100 g water, and 3.38 g of potassium perflouro butane sulfonate in acetone were added in a flask. A precipitate formed immediately. The mixture was stirred for 30 minutes, the solution was extracted with dichloromethane, dried over sodium sulphate and filtered. The solution was drowned into ether, a precipitate was formed, filtered and dried in the vacuum dryer at less than 40° C. The solid product gave the following analytical results: [0058] ¹H NMR(Acetone-d6), 2.32 (s, 6H, 2CH₃); 3.4 (s, 6H, 2CH₃); 7.78 (s, 2H, aromatic). The absorptivity was 56.15 L/g.cm.

Synthetic Example 6

4-Methoxy-3,5-dimethyl Phenyl Dimethyl Sulphonium Nonaflate

5.0 g (0.023 mole) of 4-Hydroxy-3,5-dimethyl phenyl dimethyl sulphonium chloride was placed in a flask equipped with a condenser, a thermometer, and a mechanical stirrer. 45 g of water and 0.92 g of sodium hydroxide were added, and an intense color appeared. Dimethyl sulphate (2.2 ml) was added at room temperature and the mixture was heated at 60° C. for 10 minutes. The solution changed to almost colorless. The heating was stopped after 15 minutes and the solution was cooled to room temperature. 7.78 g of potassium perfluoro butane sulfonate in acetone(50 ml) was added drop wise and mixed for 2 hours. It was extracted with dichoromethane and the dicholoromethane layer was washed with water, dried over sodium sulfate, and filtered. The solution was drowned into ether, and the-precipitate formed was filtered and dried in the vacuum dryer at less than 40° C. The solid product gave the following analytical results: [0059] ¹H NMR(Acetone-d6), 2.32 (s, 6H, 2CH₃); 3.4 (s, 6H, 2CH₃); 3.85 (s, 3H, OCH₃); 7.78 (s, 2H, aromatic). The absorptivity is 32.82 L/g.cm.

Synthetic Example 7

4-Methoxy Benzyl Dimethyl Sulphonium Triflate

4-Methoxy benzyl mercaptan (25.0 g, 0.16 mole) was added to a 250 ml round bottom flask with an overhead stirrer, a condenser, and a thermometer. 50 g THF and 12.5 g of NaOH in water (50%) were added. Dimethyl sulphate (20.18 g, 0.16 mole, 15.2 ml) was added very slowly with a syringe. The mixture was stirred at room temperature for 20 minutes and then heated at 55° C. for 90 minutes. Silver trifluoromethane sulfonate (41 g, 0.16 mole) was added and the silver salt was precipitated out. After filtering the salt, the solution was diluted with acetone and water, extracted with ether, and the aqueous layer was extracted with dichloromethane. The dichloromethane layer was washed with water, dried over sodium sulphate and drowned in ether. A precipitate was formed, which was filtered and washed with ether. It was dried under vacuum. The solid product gave the following analytical results: 1H NMR(DMSO-d6), 2.75 (s, 6H, 2CH3);3.80 (s, 3H, OCH3); 4.61 (s, 2H, CH2); 6.85-7.45 (m, 4H, aromatic). [0060]

Synthetic Example 8

Poly(t-butyl Norbornene carboxylate-co-mevaloniclactone Methacrylate-co-2-methyladamantyl Methacrylate-co-maleic Anhydride)

A hybrid copolymer was synthesized by reacting 126.45 g of t-butyl norbornene carboxylate (BNC), 129.2 g of mevaloniclactone methacrylate (MLMA) and 152.73 g of 2-methyladamantyl methacrylate (MAdMA) and 191.78 g of maleic anhydride(MA) in presence of 5 weight% of AIBN in tetrahydrofuran(THF) at 50% solid. The reaction was carried out for 8 hours and the polymer was isolated from diethyl ether twice(1/10 v/v ratio). The weight average molecular weight (Mw) as measured on a Gel Permeation Chromatograph (GPC) using polystyrene standards and THF solvent, was 5780. [0061]

Synthetic Example 9

Poly(2-methyladamantyl Methacrylate-co-mevaloniclactone Methacrylate)

Polymerization was carried out using a feed of 1:1 molar ratio of [0062]
MAdMA and MLMA in tetrahydrofuran (THF) (25% solids) using AIBN initiator (10 weight% with respect to monomers) at 70° C. under nitrogen atmosphere. The reaction mixture was stirred at 70° C. for 5 hours. The polymer solution was poured into methanol after the reaction was finished. The white powder was filtered, dissolved in THF (30% solids) again and re-precipitated, filtered and dried under vacuum until constant weight was obtained. The polymerization yield was about 65%. The Mw and number average molecular weight (Mn) as measured on a GPC using polystyrene standards and THF solvent were 14000 and 8000, respectively. [0063]

Comparative Example 1

1.5222 g of poly(2-methyladamantyl methacrylate-co-2-mevalonic lactone methacrylate) of Synthetic Example 9, 0.0514 g (60 μmol/g) of triphenylsulfonium nonafluorobutanesulfonate (absorptivity 117.74 L/g.cm), 0.1444 g of 1 weight% ethyl lactate solution of diethanolamine and 0.018 g of 110 ppm ethyl lactate solution of a surfactant (FC-430, fluoroaliphatic polymeric ester, supplied by 3M Corporation, St. Paul Minn.) were dissolved in 13.26 g of ethyl lactate to give a photoresist solution. The n & k values at 193 nm for this photoresist film were 1.7287 and 0.02432, respectively. Separately, a silicon substrate coated with a bottom antireflective coating (B.A.R.C.) was prepared by spin coating the bottom anti-reflective coating solution (AZ® EXP ArF-1 B.A.R.C. available from Clariant Corporation, Somerville, N.J.) onto the silicon substrate and baking at 175° C. for 60 sec. The B.A.R.C film thickness was 39 nm. The photoresist solution was then coated on the B.A.R.C coated silicon substrate. The spin speed was adjusted such that the photoresist film thickness was 330 nm. The photoresist film was baked at 115° C. for 60 sec. The substrate was then exposed in a 193 nm ISI ministepper (numerical aperture of 0.6 and coherence of 0.7) using a chrome on quartz binary mask. After exposure, the wafer was post-exposure baked at 110° C. for 60 sec. The imaged photoresist was then developed using a 2.38 weight% aqueous solution of tetramethyl ammonium hydroxide for 60 sec. The line and space patterns were then observed on a scanning electron microscope. The photoresist had a photosensitivity of 20 mJ/cm[0064] ²and a linear resolution of 0.12 μm. The line edge roughness (3σ) as measured on a KLA8100 CD SEM for 130 nm L/S (1: 1 pitch at best focus) was 12 nm.

Comparative Example 2

26.05 g of polymer of Synthetic Example 8, 0.820 g (56 μmol/g) of triphenylsulfonium nonafluorobutanesulfonate (absorptivity 117.74 L/g.cm), 13.4g of 1 weight% propylene glycol monomethyl ether acetate (PGMEA) solution of 1,3,3-trimethyl-6-azabicyclo(3.2.1)octane and 0.24g of 10 weight% propyleneglycol monomethyether acetate (PGMEA) solution of a surfactant (FC-430, fluoroaliphatic polymeric ester, supplied by 3M corporation, Minnesota) were dissolved in 159.5 g of PGMEA. The solution was filtered using 0.2 μm filter and processed in a similar manner to that described in Comparative Example 1 except the photoresist film was baked at 110° C. for 90 sec, post-exposure baked at 130° C. for 90 sec and development was carried out for 30 sec. The n & k values at 193 nm were 1.7108 and 0.028, respectively. The photoresist had a photosensitivity of 17 mJ/cm[0065] ²and a linear resolution of 0.09 μm. The line edge roughness (3σ) as measured on a KLA8100 CD SEM for 130 nm L/S was 11 nm (130 nm, 1:2 pitch at best focus).

Comparative Example 3

43.92 g of the polymer as in Synthetic Example 8, 0.11234 g of dimethyl, p-methoxyphenyl sulfonium nonafluorobutanesulfonate (Synthesis Example 6), 1.622 g of 1% PGMEA solution of 3-trimethyl-6-azabicyclo[3.2.1]octane, and 0.036 g of 10 weight% propyleneglycol monomethyether acetate (PGMEA) solution of a surfactant (fluoroaliphatic polymeric ester, supplied by 3M corporation, Minnesota) were dissolved in 24.30 g of PGMEA. The solution was filtered using 0.2 μm filter and processed in a similar manner to that described in Comparative Example 2. The n&k values at 193 nm were 1.7158 and 0.01670 respectively. The photoresist had a sensitivity of 80 mJ/cm[0066] ²and a linear resolution of 0.09 μm. The line edge roughness (3σ) as measured on a KLA8100 CD SEM for 130 nm L/S was 5 nm (130 nm, 1:2 pitch at best focus).

Comparitive Example 4

1.544 g of poly(2-methyladamantyl methacrylate-co-2-mevalonic lactone methacrylate) as in Synthetic Example 9, 0.0295 g (60 μmol/g) of dimethyl, p-methoxyphenyl sulfon iu m nonafluorobutanesulfonate (Synthesis Example 6), 0.1461 g of 1 weight% ethyl lactate solution of diethanolamine and 0.018 g of 120 ppm ethyl lactate solution of a surfactant (FC-430, fluoroaliphatic polymeric ester, supplied by 3M Corporation, St. Paul Minn.) were dissolved in 13.26 g of ethyl lactate to give a photoresist solution. The photoresist was processed in a similar way to comparative example 1. The n& k values at 193 nm were 1.7294 and 0.012716, respectively. The photoresist had a photosensitivity of 63 mJ/cm[0067] ²and a linear resolution of 0.12 μm. The line edge roughness (3c) as measured on a KLA8100 CD SEM for 130 nm L/S (1:1 pitch, best focus) was 5 nm.

Example 1

2.5527 g of poly(2-methyladamantyl methacrylate-co-2-mevalonic lactone methacrylate) as in Synthetic Example 9, 0.0431 g (30 μmol/g) of triphenylsulfonium nonafluorobutane sulfonate, 0.0244 g (30 μmol/g) of dimethyl, p-methoxyphenyl sulfonium nonafluorobutanesulfonate, 0.4831 g of 1 weight% ethyl lactate solution of diethanolamine and 0.03 g of 10 weight% ethyl lactate solution of a surfactant (fluoroaliphatic polymeric ester, supplied by 3M Corporation, St. Paul Minn.) were dissolved in 21.887 g of ethyl lactate to give a photoresist solution. The photoresist was processed in a similar manner to comparative example 1. The photoresist had n and k values of 1.7120 and 0.017 respectively. The photoresist had a photosensitivity of 34 mJ/cm[0068] ²and a linear resolution of 0.12 μm. The line edge roughness (3σ) as measured on a KLA8100 CD SEM for 130 nm L/S was 5.5 nm, which was a 54% improvement in line edge roughness over Comparative Example 1.

Example 2

2.5506 g of the polymer as in Synthetic Example 8, 0.0430 g of triphenylsulfonium nonafluorobutanesulfonate, 0.0244 g of dimethyl, p-methoxyphenyl sulfonium nonafluorobutanesulfonate, 0.7036 g of 1% PGMEA solution of 3-trimethyl-6-azabicyclo[3.2.1]octane, and 0.03 g of 10 weight% propyleneglycol monomethyether acetate (PGMEA) solution of a surfactant (fluoroaliphatic polymeric ester, supplied by 3M corporation, Minnesota) were dissolved in 21.65 g of PGMEA. The solution was filtered using 0.2 μm filter and processed in a similar manner to that described in Comparative Example 2. The photoresist had n&k values of 1.7144 and 0.023088 respectively. The photoresist had a sensitivity of 22 mJ/cm[0069] ²and a linear resolution of 0.09 μm. The line edge roughness (3σ) as measured on a KLA8100 CD SEM for 130 nm L/S was 6.2 nm, which was a 44% improvement in line edge roughness over Comparative Example 2.

Example 3

2.7401 g of the polymer as in Synthetic Example 8, 0.0694 g of triphenylsulfonium nonafluorobutanesulfonate, 0.0523 g of dimethyl, p-methoxyphenyl sulfonium nonafluorobutanesulfonate, 1.3227 g of 1% PGMEA solution of 3-trimethyl-6-azabicyclo[3.2.1]octane, and 0.03 g of 10 weight% propyleneglycol monomethyether acetate (PGMEA) solution of a surfactant (fluoroaliphatic polymeric ester, supplied by 3M corporation, Minnesota) were dissolved in 20.78 g of PGMEA. The solution was filtered using 0.2 μm filter and processed in a similar manner to that described in Comparative Example 2. The photoresist had a photosensitivity of 21 mJ/cm[0070] ²and a linear resolution of 0.09 μm. The line edge roughness (3σ) as measured on a KLA8100 CD SEM for 130 nm L/S was 6.2 nm, which was a 46% improvement in line edge roughness over Comparative Example 2.

Example 4

2.5507 g of poly(2-methyladamantyl methacrylate-co-2-mevalonic lactone methacrylate) as in Synthesis Example 9, 0.0431 g of triphenylsulfonium nonafluorobutane sulfonate, 0.0288 g of cyclohexyl, 2-oxocyclohexyl, methyl sulfonium trifluoromethane sulfonate (absorptivity 3.32 L/g.cm), 0.2414 g of 1 weight% ethyl lactate solution of diethanolamine and 0.03 g of 10 weight% ethyl lactate solution of a surfactant (fluoroaliphatic polymeric ester, supplied by 3M Corporation, St. Paul Minn.) were dissolved in 22.1 g of ethyl lactate to give a photoresist solution. The photoresist was processed in a similar manner to comparative example 1. The photoresist had a photosensitivity of 23 mJ/cm[0071] ²and a linear resolution of 0.12 μm. The line edge roughness (3σ) as measured on a KLA8100 CD SEM for 130 nm L/S was 5.5 nm, which was a 54% improvement in line edge roughness over Comparative Example 1.

Example 5

2.5548 g of poly(2-methyladamantyl methacrylate-co-2-mevalonic lactone methacrylate), 0.0431 g of triphenylsulfonium nonafluorobutane sulfonate, 0.0288 g of bis(phenylsulfonyl)diazomethane (absorptivity 169.49 L/g.cm) from Midori Kagaku Company, 0.2417 g of 1 weight% ethyl lactate solution of diethanolamine and 0.03 g of 10 weight% ethyl lactate solution of a surfactant (fluoroaliphatic polymeric ester, supplied by 3M Corporation, St. Paul Minn.) were dissolved in 22.1 g of ethyl lactate to give a photoresist solution. The photoresist was processed in a similar manner to comparative example 1. The photoresist had a photosensitivity of 24 mJ/cm[0072] ²and a linear resolution of 0.13 μm. The line edge roughness (3σ) as measured on a KLA8100 CD SEM for 130 nm L/S was 7.0 nm, which was a 41% improvement in line edge roughness over Comparative Example 1.

Example 6

2.5496 g of poly(2-methyladamantyl methacrylate-co-2-mevalonic lactone methacrylate), 0.0430 g of triphenylsulfonium nonafluorobutane sulfonate, 0.0288 g of [bis(p-chlorophenylsulfonyl)diazomethane] (absorptivity 146.49 L/g.cm) from Midori Kagaku Company, 0.2413 g of 1 weight% ethyl lactate solution of diethanolamine and 0.03 g of 10 weight% ethyl lactate solution of a surfactant (fluoroaliphatic polymeric ester, supplied by 3M Corporation, St. Paul Minn.) were dissolved in 22.1 g of ethyl lactate to give a photoresist solution. The photoresist was processed in a similar manner to comparative example 1. The formulation had a sensitivity of 23 mJ/cm[0073] ²and a linear resolution of 0.12 μm. The line edge roughness (3σ) as measured on a KLA8100 CD SEM for 130 nm L/S was 7.5 nm, which was a 38% improvement in line edge roughness over Comparative Example 1.

Example 7

2.5556 g of poly(2-methyladamantyl methacrylate-co-2-mevalonic lactone methacrylate), 0.0431 g of triphenylsulfonium nonafluorobutane sulfonate, 0.0239 g of [5-Norbornene-2,3-trifluoromethanesulfonimide] (absorptivity 71.42 L/g.cm) from Midori Kagaku Company, 0.2418 g of 1 weight% ethyl lactate solution of diethanolamine and 0.03 g of 10 weight% ethyl lactate solution of a surfactant (fluoroaliphatic polymeric ester, supplied by 3M Corporation, St. Paul Minn.) were dissolved in 22.1 g of ethyl lactate to give a photoresist solution. The resist was processed similar to comparative example 1. The formulation had a sensitivity of 21 mJ/cm[0074] ²and a linear resolution of 0.13 μm. The line edge roughness (3σ) as measured on a KLA8100 CD SEM for 130 nm L/S was 7.8 nm, which was a 35% improvement in line edge roughness over Comparative Example 1.

Example 8

2.5512 g of poly(2-methyladamantyl methacrylate-co-2-mevalonic lactone methacrylate), 0.0430 g of triphenylsulfonium nonafluorobutane sulfonate, 0.0283 g of [4,5-dihydroxy-1-napthalene dimethylsulfonium trifluoromethane sulfonate] (absorptivity 50.62 L/g.cm)from Midori Kagaku Company, 0.2414 g of 1 weight% ethyl lactate solution of diethanolamine and 0.03 g of 10 weight% ethyl lactate solution of a surfactant (fluoroaliphatic polymeric ester, supplied by 3M Corporation, St. Paul Minn.) were dissolved in 22.1 g of ethyl lactate to give a photoresist solution. The photoresist was processed in a similar manner as comparative example 1. The photoresist had a photosensitivity of 21 mJ/cm[0075] ²and a linear resolution of 0.13 μm. The line edge roughness (3%) as measured on a KLA8100 CD SEM for 130 nm L/S was 8.0 nm, which was a 33% improvement in line edge roughness over Comparative Example 1.

Example 9

2.5512 g of poly(2-methyladamantyl methacrylate-co-2-mevalonic lactone methacrylate), 0.0430 g of triphenylsulfonium nonafluorobutane sulfonate, 0.0283 g of [4,6-dihydroxy-1-napthalene dimethylsulfonium trifluoromethane sulfonate] (absorptivity 60.34 L/g.cm) from Midori Kagaku Company, 0.2414 g of 1 weight% ethyl lactate solution of diethanolamine and 0.03 g of 10 weight% ethyl lactate solution of a surfactant (fluoroaliphatic polymeric ester, supplied by 3M Corporation, St. Paul Minn.) were dissolved in 22.1 g of ethyl lactate to give a photoresist solution. The photoresist was processed in a similar manner to comparative example 1. The photoresist had a photosensitivity of 0.22 mJ/cm[0076] ²and a linear resolution of 0.13. The line edge roughness (3σ) as measured on a KLA8100 CD SEM for 130 nm L/S was 7.5 nm, which was a 38% improvement in line edge roughness over Comparative Example 1.

Claims

1. A photoresist composition useful for imaging in deep uv comprising;

a) a polymer containing an acid labile group; and,

b) a mixture of photoactive compounds, where the mixture comprises a lower absorbing compound selected from structure 1 and 2, and a higher absorbing compound selected from structure 4 and 5,

2. The composition according to claim 1, where the compound of structure 1 is selected from a 4-methoxyphenyl-dimethylsulfonium salt, 3,5-dimethyl-4-methoxyphenyl-dimethyl sulfonium salt, 4-hydroxyphenyl-dimethyl sulfonium salt, and 3,5-dimethyl-4-hydroxyphenyl-dimethyl sulfonium salt.

3. The composition according to claim 1, where the compound of structure 2 is selected from 4-methoxyphenyl-methyliodonium salt, 3,5-dimethyl-4-hydroxyphenyl-methyliodonium salt, 4-hydroxyphenyl-methyl iodonium salt and 3,5-dimethyl-4-methoxyphenyl-methyliodonium salt.

4. The composition according to claim 1, where the compound of structure 4 is selected from a triphenyl sulfonium salt and its derivatives.

5. The composition according to claim 1, where the compound of structure 5 is selected from a diphenyl iodonium salt and its derivatives.

6. The composition according to claim 1, where the polymer is nonaromatic.

7. The composition according to claim 1, where the molar ratio of the higher absorbing compound to the lower absorbing compound is 2:1.

8. The composition according to claim 1, where the molar ratio of higher absorbing compound to the lower absorbing compound is 1:2.

9. A process for imaging a photoresist comprising the steps of:

a) forming on a substrate a photoresist coating from the photoresist composition of claim 1;

b) image-wise exposing the photoresist coating;

c) optionally, postexposure baking the photoresist coating; and

d) developing the photoresist coating with an aqueous alkaline solution.

10. The process of claim 9, where the image-wise exposure wavelength is below 200 nm.

11. The process according to claim 9, where the aqueous alkaline solution comprises tetramethylammonium hydroxide.

12. The process according to claim 9, where the aqueous alkaline solution further comprises a surfactant.

13. The process according to claim 9, where the substrate is selected from a microelectronic device and a liquid crystal display substrate.