EP1631863A2 - Photoresist composition for deep uv and imaging process thereof - Google Patents

Photoresist composition for deep uv and imaging process thereof

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Publication number
EP1631863A2
EP1631863A2 EP04731579A EP04731579A EP1631863A2 EP 1631863 A2 EP1631863 A2 EP 1631863A2 EP 04731579 A EP04731579 A EP 04731579A EP 04731579 A EP04731579 A EP 04731579A EP 1631863 A2 EP1631863 A2 EP 1631863A2
Authority
EP
European Patent Office
Prior art keywords
photoresist
mole
photoresist composition
polymer
coating
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Withdrawn
Application number
EP04731579A
Other languages
German (de)
French (fr)
Inventor
Sangho Lee
Dalil M. Rahman
Douglas Mckenzie
Woo-Kyu Kim
Munirathna Padmanaban
Joseph E. Oberlander
Medhat A. Toukhy
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
EMD Performance Materials Corp
Original Assignee
AZ Electronic Materials USA Corp
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Filing date
Publication date
Application filed by AZ Electronic Materials USA Corp filed Critical AZ Electronic Materials USA Corp
Publication of EP1631863A2 publication Critical patent/EP1631863A2/en
Withdrawn legal-status Critical Current

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Classifications

    • GPHYSICS
    • G03PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
    • G03FPHOTOMECHANICAL PRODUCTION OF TEXTURED OR PATTERNED SURFACES, e.g. FOR PRINTING, FOR PROCESSING OF SEMICONDUCTOR DEVICES; MATERIALS THEREFOR; ORIGINALS THEREFOR; APPARATUS SPECIALLY ADAPTED THEREFOR
    • G03F7/00Photomechanical, e.g. photolithographic, production of textured or patterned surfaces, e.g. printing surfaces; Materials therefor, e.g. comprising photoresists; Apparatus specially adapted therefor
    • G03F7/004Photosensitive materials
    • G03F7/039Macromolecular compounds which are photodegradable, e.g. positive electron resists
    • G03F7/0392Macromolecular compounds which are photodegradable, e.g. positive electron resists the macromolecular compound being present in a chemically amplified positive photoresist composition
    • G03F7/0395Macromolecular compounds which are photodegradable, e.g. positive electron resists the macromolecular compound being present in a chemically amplified positive photoresist composition the macromolecular compound having a backbone with alicyclic moieties
    • GPHYSICS
    • G03PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
    • G03FPHOTOMECHANICAL PRODUCTION OF TEXTURED OR PATTERNED SURFACES, e.g. FOR PRINTING, FOR PROCESSING OF SEMICONDUCTOR DEVICES; MATERIALS THEREFOR; ORIGINALS THEREFOR; APPARATUS SPECIALLY ADAPTED THEREFOR
    • G03F7/00Photomechanical, e.g. photolithographic, production of textured or patterned surfaces, e.g. printing surfaces; Materials therefor, e.g. comprising photoresists; Apparatus specially adapted therefor
    • G03F7/004Photosensitive materials
    • G03F7/0048Photosensitive materials characterised by the solvents or agents facilitating spreading, e.g. tensio-active agents
    • GPHYSICS
    • G03PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
    • G03FPHOTOMECHANICAL PRODUCTION OF TEXTURED OR PATTERNED SURFACES, e.g. FOR PRINTING, FOR PROCESSING OF SEMICONDUCTOR DEVICES; MATERIALS THEREFOR; ORIGINALS THEREFOR; APPARATUS SPECIALLY ADAPTED THEREFOR
    • G03F7/00Photomechanical, e.g. photolithographic, production of textured or patterned surfaces, e.g. printing surfaces; Materials therefor, e.g. comprising photoresists; Apparatus specially adapted therefor
    • G03F7/004Photosensitive materials
    • G03F7/039Macromolecular compounds which are photodegradable, e.g. positive electron resists
    • G03F7/0392Macromolecular compounds which are photodegradable, e.g. positive electron resists the macromolecular compound being present in a chemically amplified positive photoresist composition
    • G03F7/0397Macromolecular compounds which are photodegradable, e.g. positive electron resists the macromolecular compound being present in a chemically amplified positive photoresist composition the macromolecular compound having an alicyclic moiety in a side chain

Definitions

  • the present invention relates to- a photoresist composition sensitive to radiation in the deep ultraviolet, particularly a positive working photoresist sensitive in the range of 100-300 nanometers(nm).
  • the present invention also relates to a process for imaging the photoresist composition of this invention.
  • valerolactone a solvent for a photoresist composition is also disclosed, which is particularly useful for the photoresist of the present invention.
  • 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 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.
  • UV light ultraviolet
  • 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.
  • the trend towards the miniaturization of semiconductor devices has led to the use of new photoresists that are sensitive to lower and lower wavelengths of radiation and has also led to the use of sophisticated multilevel systems to overcome difficulties associated with such miniaturization.
  • photoresist compositions negative-working and positive-working.
  • 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 manufacturing applications today, resist resolution on the order of less than one 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.
  • Photoresists sensitive to short wavelengths between about 100 nm and about 300nm can also be used where subhalfmicron geometries are required. Particularly preferred are photoresists comprising non-aromatic polymers, a photoacid generator, optionally a solubility 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.
  • Chemically amplified resists in which a single photo generated proton catalytically cleaves several acid labile groups, are used in photolithography applicable to sub quarter-micron design rules.
  • the sensitivity of the resulting resist is quite high compared to the conventional novolak-diazonaphthoquinone resists.
  • uv deep ultraviolet
  • Photoresists for 248nm have typically been based on substituted polyhydroxystyrene and its copolymers.
  • photoresists for 193nm 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 the absence of aromatics.
  • Photoresists based on chemical amplification mechanism are employed for 248 and 193 nm applications.
  • the photoresist materials applicable for 248 nm cannot be used at 193 nm due to the high absorption of the poly(4- hydroxystyrene) based polymers used for 248 nm applications.
  • 193 nm applications typically require non-aromatic compounds.
  • Open-chain aliphatic resins cannot be used due to the very high etch rates of these materials.
  • Polymers possessing annelated structures in the side chains such as tricyclododecyl and adamantane or cycloolefins in the main chain are shown to provide etch resistance close to poly(4-hydroxystyrene) polymers [Nakano et al. Proc. SPIE 3333, 43 (1998), Nozaki et al., Wallow et al. Proc. SPIE 3333, 92 (1998), and J.C. Jung et al. Proc. SPIE 3333, 11 , (1998)].
  • Houlihan et al disclose a polymer for photoresist application, which is a polymer made from a cyclic olefin, maleic anhydride and a substituted or unsubstituted acrylate.
  • the patent describes the substituted acrylate as one where the substituent is acid labile and includes t-butyl, t-amyl, 1- methylcyclohexyl, 3-oxocyclohexyl, and bis(2-trimethylsilyl)ethyl.
  • the present invention relates to a chemically amplified system, which is sensitive to wavelengths between 300 nm and 100 nm, and comprises a) a polymer that is insoluble in an aqueous alkaline solution and comprises at least one acid labile group, and, b) a compound capable of producing an acid upon radiation.
  • the present invention comprises a polymer that is made from at least one nonaromatic cyclo olefin, at least one cyclic anhydride, at least one acrylic ester of a cyclic lactone, and at least one acrylate with a pendant nonlactone aliphatic hydrocarbon moiety, preferably the pendant hydrocarbon moeity is multicyclic since these groups offer good etch resistance.
  • the nonaromatic cyclo olefin is present at less than 20 mole%
  • the cyclic anhydride is present at less than 20 mole%
  • the acrylic ester of the lactone is present in the range of about 20 mole% to about 60 mole%
  • acrylate with a pendant hydrocarbon moiety is present in the range of about 20 mole% to about 60 mole%.
  • the polymer is inhibited from dissolving in water or the alkaline developer by having acid labile groups within the polymer.
  • the objective of the invention is to have a photoresist comprising a polymer with reduced absorbance at the exposure wavelength and yet maintaining an acceptable level of dry etch resistance.
  • cyclo olefin ratio in the polymer is reduced to less than 20 mole% and also reducing the cyclic anhydride concentration to less than 20 mole%, while at the same time increasing the concentration of the acrylic ester of a cyclic lactone to be greater than 20 mole% but less than 60 mole%, and increasing the concentration of the acrylate with the pendant hydrocarbon moiety to be greater than 20 mole% but less than 60 mole%.
  • acrylate polymers are transparent resins at 193 nm, but lack the necessary etch resistance.
  • polymers derived from cycloolefins and cyclic anhydrides are absorbing at wavelengths less than 200 nm.
  • both monomers are necessary for free radical polymerization, and cycloolefins are necessary for etch resistance.
  • the acrylates and the cycloolefin/cyclo anhydride monomers polymerize in a 1:1 ratio, resulting in a minimum of 25 mole% each of the cycloolefin and anhydride monomers, which can result in polymers with excessive absorbance at the exposure wavelength.
  • concentration of the cycloolefin/anhydride can be significantly reduced to give a more transparent polymer, better adhesion and improved resolution, and hence resulting in an improvement in the lithographic properties of the photoresist.
  • the transparency of the polymer must also increase. It is the objective of the present invention to provide for a photoresist with greater transparency at the exposure wavelength.
  • Photoresists comprising polymers containing mixtures of cycloelefins and acrylates, in particular acrylates of cyclic lactones are known and examples of such disclosure are US 6,447,980, 6,087,063, 6,225,476, 6,517,994, 2001/0044070, 2002/0009666, and 2002/0064727, and are incorporated herein by reference. However, the requirement of the specific combination of monomers and their ratios within the polymer to give a photoresist with the desired lithographic properties is not disclosed.
  • valerolactone As a new photoresist solvent, valerolactone, although itself known, has not been used as a solvent for photoresists in the semiconductor technology, particularly in deep uv photoresists, and especially as a mixture with other photoresist solvents. It is an objective of the present invention to provide for a new solvent which has improved solubilizing properties and also improves the lithographic properties of photoresists.
  • the present invention relates to a novel photoresist composition sensitive to radiation in the deep ultraviolet, particularly a positive working photoresist sensitive in the range of 100-300 nm.
  • the photoresist composition comprises a) a polymer that is insoluble in an aqueous alkaline solution and comprises at least one acid labile group, and further where the polymer comprises at least one alicyclic hydrocarbon unit, at least one cyclic anhydride, at least one acrylate unit with the structure 1 , and at least one acrylate unit with structure 2:
  • R and R' are independently H or (CrC4)alkyl; Ri is a pendant cyclic lactone, and, R 2 is a pendant nonlactone aliphatic hydrocarbon moiety, b) a compound or a mixture of compounds capable of producing acid upon irradiation.
  • the alicyclic hydrocarbon unit is present at less than 20 mole%, the cyclic anhydride is present at less than 20 mole%, the acrylate unit of structure 1 is present in the range of about 20 mole% to about 60 mole% and the acrylate unit of structure 2 is present in the range of about 20 mole% to about 60 mole%.
  • the photoresist is irradiated preferably with wavelength of light at 193 nm or 157 nm.
  • the lactone is not a acid labile group.
  • the lactone is a 5-membered ring, and in another embodiment the nonlactone hydrocarbon moiety is alicyclic.
  • the invention also relates to a process of imaging the novel positive photoresist composition comprising the steps of a) coating a substrate with the novel photoresist composition, b) baking the substrate to substantially remove the solvent, c) imagewise irradiating the photoresist film, d) baking the photoresist, and e) developing the irradiated film using an alkali developer.
  • the invention further relates to a photoresist composition
  • a photoresist composition comprising a polymer that is insoluble in an aqueous alkaline solution and comprises at least one acid labile group, a compound or a mixture of compounds capable of producing acid upon irradiation, and, a solvent comprising valerolactone.
  • the solvent is gamma valerolactone.
  • the solvent may be in a mixture with other photoresist solvent or solvents.
  • the present invention relates to a chemically amplified system, which is sensitive to wavelengths between 300 nm and 100 nm, and comprises a) a polymer that is insoluble in an aqueous alkaline solution and comprises at least one acid labile group, and b) a compound capable of producing an acid upon irradiation.
  • the polymer of the present invention comprises at least one alicyclic hydrocarbon unit, at least one cyclic anhydride, at least one acrylate unit with the structure 1 , and at least one acrylate unit with structure 2:
  • R and R' are independently H or (C1-C4) alkyl
  • Ri is a pendant cyclic lactone
  • R 2 is a pendant nonlactone aliphatic hydrocarbon moiety
  • the alicyclic hydrocarbon unit is present at less than about 20 mole%
  • the cyclic anhydride is present at less than about 20 mole%
  • the acrylate unit of structure 1 is present in the range of about 20 mole% to about 60 mole%
  • the acrylate unit of structure 2 is present in the range of about 10 mole% to about 60 moIe%.
  • alicyclic is defined as essentially a nonaromatic carbon/hydrogen cyclic system, which may comprise small amounts of heteroatoms as functional groups, such as oxygen, nitrogen or sulfur, as pendant from the cyclic system.
  • groups such as alkyl (linear or branched) groups, may also be present.
  • Functional groups such as ethers, esters, acids, nitrile, hydroxyl, alcohols etc. are some of the commonly known groups.
  • Aliphatic hydrocarbon in this application, refers to a predominantly carbon/hydrogen chain which may be linear or cyclic. The chain may be unsubstituted or substituted with alkyl groups or with any known functional groups described above.
  • the alicyclic hydrocarbon unit is derived from a cyclo olefin monomer which is incorporated into the backbone of the polymer and may be any substituted or unsubstituted multicyclic hydrocarbon containing an unsaturated bond.
  • 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 norbomene, or tetracyclododecane.
  • substituents on the cyclo olefin may be (CrC ⁇ Jalkyl, halogen, such as fluorine and chlorine, carboxylic acid, (CrCio)alkylOCOalkyl, cyano(CN), (C 1 -C 10 ) secondary or tertiary carboxylate, substituted pinacol, adjacent substituents may be linked to form a cyclic non-aromatic structure (such as lactone or anhydride), fluoroalkyl, acid or base labile group, and W(CF 3 ) 2 OH, where W is (C ⁇ -C 6 )alkyl or (C C 6 )alkyl ether.
  • cyclo olefin monomers examples are:
  • cyclo olefin monomers which may also be used in synthesizing the polymer are:
  • 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. 2,6 1. 7,1 ° ] dodec-8-ene-3-carboxylate, and t-butoxycarbonylmethyl tetracyclo[4.4.0.1. 2,6 1.
  • the cyclo olefins are selected from t-butyl norbornene carboxylate (BNC), hydroxyethyl norbornene carboxylate (HNC), and norbornene carboxylic acid(NC).
  • the cyclic anhydride unit is any unsaturated cyclic aliphatic anhydride, and is preferably derived from monomers such as maleic anhydride or itaconic anhydride.
  • acrylate unit containing the cyclic lactone of structure 1 used in the synthesis of the polymer are of the following structure, furthermore, acrylate as referred to in this application refers generally to alkyl substituted or unsubstituted monomers, such as methacrylate, ethacrylate, etc.:
  • R is independently H or (C ⁇ -C4)alkyl; and, Ri is a pendant cyclic hydrocarbon lactone.
  • the cyclic lactone may be a mono or poly cyclic lactone, which is linked directly to the oxygen of the ester group or through an aliphatic linking group, for example, a (C1-C4) alkyl group.
  • the cyclic lactone is preferably a 5-membered ring, which leads to a polymer of lower absorptivity by reducing the cyclic anhydride content of the polymer.
  • the pendant cyclic lactone may be described by the following structures:
  • R 3 - R 11 are selected from hydrogen, (C 1 -C14) alkyl and substituted alkyl.
  • cyclic lactones in the polymer are derived from monomers, such as, ⁇ -methacryloxy- ⁇ -butyrolactone, ⁇ -methacryloxy- ⁇ - butyrolactone, methacryloyloxy-norbornane-butyrolactone, 3-oxo-4- oxatricyclo[5.2.1.02, 6]decan-8-yl methacrylate, or mixtures thereof.
  • the lactone does not cleave during the imaging process.
  • Some lactones, such as 2-mevalonic lactone are known to cleave, and can change the dissolution properties of the photoresist.
  • mixtures of lactones can further enhance the lithographic properties of the photoresist, in particular mixtures of ⁇ -methacryloxy- ⁇ -butyrolactone, or ⁇ -methacryloxy- ⁇ -butyrolactone, methacryloyloxy-norbomane-butyrolactone and ⁇ -methacryloxy- ⁇ -butyrolactone, or ⁇ -methacryloxy- ⁇ -butyrolactone, 3-oxo-4-oxatricyclo[5.2.1.02, 6]decan-8-yl methacrylate.
  • the acrylate unit (structure 2) with the pendant cyclic hydrocarbon moiety, further where the pendant cyclic moiety is not a cyclic lactone, is a group containing an aliphatic hydrocarbon moiety which may be connected directly to the oxygen of the acrylic ester or through a connecting group, such as an (C1-C4) alkyl group.
  • R' is independently H or (C ⁇ -C 4 )alkyl; and, R 2 is a pendant nonlactone aliphatic hydrocarbon moiety.
  • the nonlactone aliphatic hydrocarbon moiety may be linear, branched or cyclic hydrocarbons, which may be unsubstituted or be substituted with known functional groups described previously.
  • the moiety is cyclic, and more preferably multicyclic.
  • the moiety is an acid labile group, which when removed in the presence of an acid, increases the solubility of the polymer in the developer. Examples of the cyclic aliphatic moiety are,
  • the preferred acrylate monomers are selected from 2-methyladamantyl methacrylate (MAdMA), isoadamantyl methacrylate, 3-hydroxy-1- methacryloxyadamatane, and 3,5-dihydroxy-1 -methacryloxyadamantane.
  • MAdMA 2-methyladamantyl methacrylate
  • isoadamantyl methacrylate 3-hydroxy-1- methacryloxyadamatane
  • 3,5-dihydroxy-1 -methacryloxyadamantane 3,5-dihydroxy-1 -methacryloxyadamantane.
  • the cyclo olefin and the cyclic anhydride monomer are believed to form an alternating polymeric structure and their individual concentrations are kept below 20 mole%. Additionally, the concentration of the acrylate lactone is varied such that its concentration is greater than the individual concentrations of the cyclo olefin and the cyclic anhydride monomers incorporated into the polymer.
  • the cyclo olefin concentration is less than about 20 mole% and preferably less than 15 mole%; the cyclic anhydride concentration is less than 20 mole%, and preferably less than 15 mole%; the acrylate lactone concentration is greater than about 20 mole%, more preferably greater than 30 mole%, and even more preferably more than 35 mole%; and the concentration of the acrylate with the pendant hydrocarbon moiety is greater than about 20 mole%, preferably greater than 30 mole%, and even more preferably greater than 35 mole%.
  • the acrylate lactone concentration is less than about 60 mole% and more preferably less than 50 mole%.
  • the acrylate with the pendant hydrocarbon moiety is present at a concentration of less than 60 mole%, and more preferably less than 50 mole%.
  • the cyclo olefin concentration is less than 20 mole%
  • the cyclic anhydride concentration is less than 20 mole%
  • the acrylate lactone concentration is in the range of about 30 mole% to about 50 mole%
  • the acrylate with the pendant hydrocarbon moiety is incorporated into the polymer at a concentration range from about 30 mole% to about 50 mole%.
  • the concentration of the cycloolefin and the cyclic anhydride in the polymer is at or greater than about 25 mole%, the absorptivity of the polymer in the photoresist system is relatively high, thus giving reduced lithographic performance compared to the polymer of the present invention.
  • a certain minimum amount of the cycloolefin is required to give the desired dry etch resistance, thus the concentration is preferably greater than 5 mole% and more preferably greater than 10 mole%.
  • Acid labile groups may be attached to any one of the monomers, preferably the cyclo olefin or the acrylate with the pendant hydrocarbon moeity. These groups make the polymer insoluble in the aqueous alkaline developer, but upon exposure the photoacid generated removes the acid labile group, thus making the polymer in the exposed regions soluble.
  • the acid labile group is preferably attached to the cyclo olefin and/or the acrylate with the pendant hydrocarbon cyclic moiety.
  • Examples of monomers containing acid labile groups that can be used in the polymers are methacrylate ester of methyladamantane, 3-hydroxy-1-adamantyl methacrylate, t-butyl norbomyl carboxylate, t-butyl methyl adamantyl methacryate, methyl adamantyl acrylate, t-butyl acrylate and t-butyl methacrylate.
  • the acid labile group that may be attached to the alicyclic olefin or be present in the acrylate of structure 2.
  • acid labile functionalities are - (CO)O-A, -O-A, -0(CO)0-A, -C(CF 3 ) 2 O-A, -C(CF 3 )2 ⁇ (CO)O-A, and - C(CF 3 ) 2 (COOA), where A is alkyl, cycloalkyl, substituted cycloalkyl, oxocyclohexyl, benzyl, silyl, alkyl silyl, substituted benzyl, alkoxy alkyl such as ethoxy ethyl or methoxy ethoxy ethyl, acetoxyalkoxy alkyl such as acetoxy ethoxy ethyl, tetrahydrofuranyl, menthyl, and tetrahydropyranyl.
  • Examples of specific groups for A are t-butoxycarbonyl tricyclo(5.3.2.0) decanyl, 2-methyl-2-adamantyl, isobomyl, norbomyl, adamantyloxyethoxy ethyl, menthyl, tertiary butyl, tetrahydropyranyl and 3-oxocyclohexyl.
  • A is tert-butyl, 3-hydroxy-1 -adamantyl, and 2-methyl- 2-adamantyl.
  • the polymer of this invention can be synthesized using techniques known in the art.
  • the polymer of this invention may be synthesized by free radical polymerization technique using, for example, 2,2'-azobisisobutyronitrile (AIBN) as initiator.
  • AIBN 2,2'-azobisisobutyronitrile
  • a mixture of monomers is added to a reaction vessel together with a solvent, e.g. tetrahydrofuran, and AIBN is added.
  • the reaction is carried out at a suitable temperature for a suitable amount of time to give a polymer with desired properties.
  • the reaction may also be carried out without a solvent.
  • the temperature may range from about 35°C to about 150°C, preferably 50°C to 90°C for about 5 to 25 hours.
  • the reaction may be carried out at atmospheric pressure or at higher pressures.
  • the polymer may be isolated from any suitable solvent, such as, diethyl ether, hexane or mixture of both hexane and ether. Other polymerization techniques may be used to obtain a polymer with the desired chemical and physical properties.
  • the optimum molecular weight of the polymer is dependant on the monomers incorporated into the polymer, the photoactive compound and any other chemical components used, and on the lithographic performance desired.
  • the weight average molecular weight is in the range of 3,000 to 50,000, preferably 5,000 to 25000, more preferably 7,000 to 20000, the number average molecular weight is in the range from about 1500 to about 10,000, and the polydispersity is in the range 1.1 to 5, preferably 1.5 to 2.5.
  • Suitable examples, without limitation, of the acid generating photosensitive compound include onium-salts, such as, diazonium salts, iodonium salts, sulfonium salts, halides and esters, although any photosensitive compound that produces an acid upon irradiation may be used.
  • onium-salts such as, diazonium salts, iodonium salts, sulfonium salts, halides and esters, although any photosensitive compound that produces an acid upon irradiation may 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 diphenyliodoinum trifluoromethane sulfonate, diphenyliodoinum nonafluorobutanesulfonate, triphenylsulfonium trifluromethanesuflonate, triphenylsulfonium nonafluorobutanesufonate and the like.
  • Other compounds that form an acid upon irradiation may be used, such as triazines, oxazoles, oxadiazoles, thiazoles, substituted 2-pyrones.
  • Phenolic sulfonic esters bis-sulfonylmethanes, bis-sulfonylmethanes or bis- sulfonyldiazomethanes, are also preferred.
  • Other preferred embodiments are mixtures of phenyl onium salts and essentially aliphatic onium salts, such photosensitive compounds, and which are incorporated by reference, are described in the application of serial no. 10/170,760, Attorney Docket No. 2002US307CIP entitled 'Photoresist Composition for Deep Ultraviolet Lithography Comprising a Mixture of Photoactive Compounds' filed May 16, 2003; and Attorney Docket No. 2003US308 entitled 'Photoactive Compounds' filed May 16, 2003.
  • 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 (e.g. methyl) ether, propylene glycol alkyl (e.g.
  • valerolactone especially gamma valerolactone
  • a solvent mixture comprising valerolactone has been unexpectedly found to improve the solubility of certain polymers, which may otherwise not be soluble in standard photoresist solvents.
  • Valerolactone, alone or as a mixture with other solvents may also be used in formulations comprising various polymers and photoactive compounds which are used as coatings in the semiconductor technologies. These coatings could be used as photoresists, insulating coatings, photoimageable antireflective coatings used under a photoresist coating, etc., such as disclosed in applications 10/042,532 and 10/322,239 filed January 9, 2002, herein incorporated by reference.
  • Valerolactone, gamma or delta valerolactone may be combined with other photoresist solvents, particularly those described above in levels ranging from about 0.5 weight% to about 15 weight percent, preferably 1 weight% to 10 weight%, more preferably 2 weight% to about 5 weight%, although any combination of one or more solvents may be combined with valerolactone to form the solvent mixture.
  • the cosolvent is particularly suitable for photoresists, especially deep uv photoresists, as described in the present application.
  • the photoresist comprises polymers, which may be selected from cycloolefin/maleic anhydride polymers, acrylate polymers, cycloolefin/maleic anhydride/acrylate polymers, and phenolic polymers.
  • valerolactone as a solvent has been found to be especially useful for polymers that are difficult to dissolve in standard photoresist solvents, particularly for polymers containing more than one lactone acrylate of structure 1. It has also been unexpectedly found that the cosolvent, valerolactone, assists also in improving the line edge roughness and stability of the photoresist pattern.
  • the polymers comprising monomers derived from mixtures of ⁇ -methacryloyloxy- ⁇ - butyrolactone, 3-oxo-4-oxatricyclo[5.2.1.02, 6]decan-8-yl, and methacryloyloxy- norbornane-butyrolactone particularly benefit from the use of the cosolvent, valerolactone, particularly, gamma valerolactone.
  • the photoactive compounds useful in the photoresist may be those described previously in this application.
  • Preferred solvent mixtures are gamma valerolactone, propylene glycol monomethy ether acetate (PGMEA) and propylene glycol monomethy ether (PGME), where the ratio of PGMEA:PGME can range from 9:1 to 1 :1 , and preferably 8:2 to 7:3.
  • Additives such as colorants, non-actinic dyes, anti-striation agents, plasticizers, adhesion promoters, coating aids, speed enhancers and surfactants may be added to the photoresist composition before the solution is coated onto a substrate.
  • a sensitizer that transfers energy from a particular range of wavelengths to a different exposure wavelength may also be added to the photoresist composition.
  • bases or photobases may be added to the photoresist composition.
  • bases are known to those skilled in the art and some of which are described the following references: US 5,525,453 and US serial number 09/455872.
  • Bases which do not absorb or do not absorb significantly, at the wavelength of light used to expose the photoresist, are preferred.
  • Bases such as dimethyliodonium hydroxide, trimethylsulfonium hydroxide and 1 ,3,3-trimethyl-6-azabicyclo[3.2.1]octane are preferred.
  • the prepared photoresist composition solution can be applied to a substrate by any conventional method used in the photoresist art, including dipping, spraying, whirling and spin coating.
  • spin coating for example, the resist 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 lll/V compounds.
  • the photoresist may also be coated over an antireflective coating.
  • the photoresist coatings produced by the described procedure are particularly suitable for application to metal/metal oxide coated wafers, especially these coated with an antireflective coating, such as are utilized in the production of microprocessors and other miniaturized integrated circuit components.
  • a silicon/silicon dioxide 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.
  • 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.
  • 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) or less in thickness, remains on the substrate.
  • 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 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 coating substrate can then be imagewise exposed to actinic radiation, e.g., ultraviolet radiation, at a wavelength of from about 100 nm 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.
  • actinic radiation e.g., ultraviolet radiation
  • 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.
  • Surfactants may be added to the developer. 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.
  • the developed substrates may be treated with a buffered, hydrofluoric acid base etching solution or dry etching.
  • the photoresist compositions of the present invention are resistant to acid-base etching solutions and provide effective protection for the unexposed photoresist- coating areas of the substrate. Metal deposition or dry etching are some of the other important processes that can be applied.
  • LER line edge roughness
  • a copolymer was synthesized by reacting 94.25 g of t-butyl norbornene carboxylate (BNC, 15 mole%), 192.67 g of ⁇ -methacryloyloxy- ⁇ -butyrolactone (GBLMA, 35 mole%) and 265.5 g of 2-methyladamantyl methacrylate (MAdMA, 35 mole%) and 47.59 g of maleic anhydride (MA, 15 mole%) in the 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 twice from diethyl ether (1/10 v/v ratio), giving a 64% yield.
  • the weight average molecular weight (Mw) as measured on a Gel Permeation Chromatograph (GPC) using polystyrene standards and THF solvent was 12, 638.
  • 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, NJ) 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 240 nm.
  • the photoresist film was baked at 115°C for 90 sec.
  • the substrate was then exposed in a 193 nm ISI ministepper (numerical aperture of 0.6 and coherence of 0.3/0.7, Annular Illumination) using a chrome on quartz binary mask. After exposure, the wafer was post-exposure baked at 130°C for 90 sec.
  • the imaged photoresist was then developed for 60 seconds using a 2.38 weight% aqueous solution of tetramethyl ammonium hydroxide. The line and space patterns were then observed on a scanning electron microscope.
  • the photoresist had a photosensitivity of 21 mJ/cm 2 and a linear resolution of 0.09 ⁇ m.
  • the line edge roughness (3 ⁇ ) as measured on a KLA8100 CD SEM for 130 nm L/S (1 : 2 pitch at best focus) was 8 nm.
  • a copolymer was synthesized by reacting 5.09 g of t-butyl norbornene carboxylate (BNC, 10 mole%), 17.81 g of - ⁇ -methacryloyloxy- ⁇ -butyrolactone (GBLMA, 40 mole%) and 24.58 g of 2-methyladamantyl methacrylate (MAdMA, 40 mole%) and 2.57 g of maleic anhydride (MA, 10 mole%) 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 twice from diethyl ether (1/10 v/v ratio) giving a yield of 74%.
  • the weight average molecular weight (Mw) as measured on a Gel Permeation Chromatograph (GPC) using polystyrene standards and THF solvent was 15, 567.
  • 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, NJ) 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 90 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 130°C for 90 sec.
  • the imaged photoresist was then developed for 60 sec using a 2.38 weight% aqueous solution of tetramethyl ammonium hydroxide. The line and space patterns were then observed on a scanning electron microscope.
  • the photoresist had a photosensitivity of 20mJ/cm 2 and a linear resolution of 0.08 ⁇ m.
  • the line edge roughness (3 ⁇ ) as measured on a KLA8100 CD SEM for 130 nm L/S (1 : 1 pitch at best focus) was 5.0 nm.
  • a copolymer was synthesized by reacting 29.62 g of t-butyl norbornene carboxylate (BNC, 5 mole%), 467.06 g of - ⁇ -methacryloyloxy- ⁇ -butyrolactone (GBLMA, 45 mole%) and 321.91 g of 2-methyladamantyl methacrylate (MAdMA, 45 mole%) and 15.01 g of maleic anhydride (MA, 5 mole%) 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 twice from diethyl ether (1/10 v/v ratio) giving a yield of 75%. The weight average molecular weight (Mw) as measured on a Gel Permeation Chromatograph (GPC) using polystyrene standards and THF solvent was 16,997. Lithographic Example 6
  • 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, NJ) 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 90 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 130°C for 90 sec.
  • the imaged photoresist was then developed for 60 sec using a 2.38 weight% aqueous solution of tetramethyl ammonium hydroxide.
  • the line and space patterns were then observed on a scanning electron microscope.
  • the photoresist had a photosensitivity of 20 mJ/cm 2 and a linear resolution of 0.12 ⁇ m.
  • the line edge roughness (3 ⁇ ) as measured on a KLA8100 CD SEM for 130 nm L/S (1: 1 pitch at best focus) was 5.0 nm.
  • the reaction was carried out for 8 hours and the polymer was isolated from diethyl ether twice (1/10 v/v ratio) giving a yield of 76%.
  • the weight average molecular weight (Mw) as measured on a Gel Permeation Chromatograph (GPC) using polystyrene standards and THF solvent was 16,110.
  • 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, NJ) onto the silicon substrate and baking at 175°C for 60 sec.
  • the B.A.R.C film thickness was 37 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 210 nm.
  • the photoresist film was baked at 115°C for 90 sec.
  • the substrate was then exposed in a 193 nm ISI ministepper (numerical aperture of 0.6 and coherence of 0.3/0.7, Annular Illumination). After exposure, the wafer was post-exposure baked at 130°C for 90 sec.
  • the imaged photoresist was then developed for 30 sec using a 2.38 weight% aqueous solution of tetramethyl ammonium hydroxide. The line and space patterns were then observed on a scanning electron microscope.
  • the photoresist had a photosensitivity of 20 mJ/cm 2 and a linear resolution of 0.08 ⁇ m.
  • the line edge roughness (3 ⁇ ) as measured on a KLA8100 CD SEM for 130 nm L/S (1 : 2 pitch at best focus) was 5 nm.
  • a copolymer was synthesized by reacting 29.47 g t-butyl norbornene carboxylate (BNC, 10 mole% ), 77.44 g of ⁇ -methacryloyloxy- ⁇ -butyrolactone (GBLMA, 30 mole%), 142.35 g of 2-methyladamantyl methacrylate (MAdMA, 40 mole%), 35.89 g of 3-oxo-4-oxatricyclo[5.2.1.02, 6]decan-8-yl (10 mole%) and 15.02 g of maleic anhydride (MA, 10 mole%) in presence of 5 weight% of AIBN in tetrahydrofuran (THF) at 50% solid.
  • BNC t-butyl norbornene carboxylate
  • GBLMA ⁇ -methacryloyloxy- ⁇ -butyrolactone
  • MAdMA 2-methyladamantyl methacrylate
  • MAdMA 3-oxo-4-oxatricycl
  • the reaction was carried out for 8 hours and the polymer was isolated from diethyl ether twice (1/10 v/v ratio), giving a yield of 75%o.
  • the weight average molecular weight (Mw) as measured on a Gel Permeation Chromatograph (GPC) using polystyrene standards and THF solvent was 14,904.
  • 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, NJ) onto the silicon substrate and baking at 175°C for 60 sec.
  • the B.A.R.C film thickness was 37 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 210 nm.
  • the photoresist film was baked at 115°C for 90 sec.
  • the substrate was then exposed in a 193 nm ISI ministepper (numerical aperture of 0.6 and coherence of 0.3/0.7, Annular Illumination). After exposure, the wafer was post-exposure baked at 130°C for 90 sec. The imaged photoresist was then developed using a 2.38 weight% aqueous solution of tetramethyl ammonium hydroxide for 30 sec. The line and space patterns were then observed on a scanning electron microscope. The photoresist had a photosensitivity of 18 mJ/cm 2 and a linear resolution of 0.09 ⁇ m. The line edge roughness (3 ⁇ ) as measured on a KLA8100 CD SEM for 130 nm L/S (1 : 2 pitch at best focus) was 5 nm.
  • 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, NJ) 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 coated on the B.A.R.C coated silicon substrate.
  • the spin speed was adjusted such that the photoresist film thickness was 210 nm.
  • the photoresist film was baked at 115°C for 90 sec.
  • the substrate was then exposed in a 193 nm ISI mini stepper (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 130°C for 90 sec. The imaged photoresist was then developed using a 2.38 weight% aqueous solution of tetramethyl ammonium hydroxide for 30 sec. The line and space patterns were then observed on a scanning electron microscope. The photoresist had a photosensitivity of 13.0 mJ/cm 2 and a linear resolution of 0.08 ⁇ m.
  • 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, NJ) 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 coated on the B.A.R.C coated silicon substrate.
  • the spin speed was adjusted such that the photoresist film thickness was 210 nm.
  • the photoresist film was baked at 115°C for 90 sec.
  • the substrate was then exposed in a 193 nm ISI mini stepper (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 130°C for 90 sec. The imaged photoresist was then developed using a 2.38 weight% aqueous solution of tetramethyl ammonium hydroxide for 30 sec. The line and space patterns were then observed on a scanning electron microscope. The photoresist had a photosensitivity of 13.0 mJ/cm 2 and a linear resolution of 0.09 ⁇ m.
  • 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, NJ) 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 coated on the B.A.R.C coated silicon substrate.
  • the spin speed was adjusted such that the photoresist film thickness was 240 nm.
  • the photoresist film was baked at 115°C for 90 sec.
  • the substrate was then exposed in a 193 nm ISI mini stepper (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 130°C for 90 sec. The imaged photoresist was then developed using a 2.38 weight% aqueous solution of tetramethyl ammonium hydroxide for 30 sec. The line and space patterns were then observed on a scanning electron microscope. The photoresist had a photosensitivity of 18.0 mJ/cm 2 and a linear resolution of 0.08 ⁇ m. Comparative Example 1
  • BNC t-butyl norbornene carboxylate
  • GBLMA 73.12 g
  • MNBL methacryloyloxy-norbornane-butyrolactone
  • MA maleic anhydride
  • a copolymer was synthesized by reacting 20.25 g t-butyl norbornene carboxylate (BNC, 16.66 mo!e% ), 24.47 g of 2-methyladamantyl methacrylate (MAdMA, 16.66 mole%), 24.6 g (16.66 mole%) of hydroxyadamantyl methacrylate and 30.9 g of maleic anhydride (MA, 50 mole%) 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 10,526.
  • BNC t-butyl norbornene carboxylate
  • MAdMA 2-methyladamantyl methacrylate
  • MA hydroxyadamantyl me
  • Comparartive Lithographic Example 3 1.6935 g of Poly(t-butyl norbornene carboxylate-co-2-methyiadamantyl methacrylate-co- hydroxyadamantyl methacrylate-co-maleic anhydride) from comparative example 2, 0.0286 g (30 ⁇ mol/g) of triphenylsulfonium nonafluorobutanesulfonate (absorptivity 117.74 L/g.cm), 0.2946 g of 1 weight% PGMEA solution of N-(1 -adamantyl) acetamide and 0.0180 g of 120 ppm of a surfactant, FC-4430, in PGMEA, (fluoroaliphatic polymeric ester, supplied by 3M Corporation, St. Paul Minnesota) was dissolved in 12.9653 g of PGMEA.
  • 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, NJ) onto the silicon substrate and baking at 175°C for 60 sec.
  • the B.A.R.C film thickness was 37 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 90 sec.
  • the substrate was then exposed in a 193 nm ISI ministepper (numerical aperture of 0.6 and coherence of 0.7). After exposure, the wafer was post-exposure baked at 130°C for 90 sec. The imaged photoresist was then developed using a 2.38 weight% aqueous solution of tetramethyl ammonium hydroxide for 30 sec. The dose clear was found to be too high for effective processing.

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Abstract

The present invention relates to a novel photoresist composition sensitive to radiation in the deep ultraviolet, particularly a positive working photoresist sensitive in the range of 100-300 nm, and a process for using it. The photoresist composition comprises: a) a polymer that is insoluble in an aqueous alkaline solution and comprises at least one acid labile group, and further where the polymer comprises at least one alicyclic hydrocarbon unit, at least one cyclic anhydride, at least one acrylate unit with the structure (1), and at least one acrylate unit with structure (2): where, R’ and R are independently H or (C1-C4)alkyl; R1 is a pendant cyclic lactone, and, R2 is a pendant nonlactone aliphatic hydrocarbon moiety, b) a compound or a mixture of compounds capable of producing acid upon irradiation. The invention further relates to the use of a solvent comprising valerolactone as a solvent for photosensitive materials. Preferably, the solvent is gamma valerolactone. The solvent may be in a mixture with another photoresist solvent or solvents.

Description

Description Photoresist Composition for Deep UV and Process Thereof
Field of Invention
The present invention relates to- a photoresist composition sensitive to radiation in the deep ultraviolet, particularly a positive working photoresist sensitive in the range of 100-300 nanometers(nm). The present invention also relates to a process for imaging the photoresist composition of this invention. Furthermore, valerolactone, a solvent for a photoresist composition is also disclosed, which is particularly useful for the photoresist of the present invention.
Background of 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 towards the miniaturization of semiconductor devices has led to the use of new photoresists that are sensitive to 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. When negative- working photoresist compositions are exposed image-wise to radiation, the areas of the resist 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 manufacturing applications today, resist resolution on the order of less than one 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.
Photoresists sensitive to short wavelengths, between about 100 nm and about 300nm can also be used where subhalfmicron geometries are required. Particularly preferred are photoresists comprising non-aromatic polymers, a photoacid generator, optionally a solubility 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. Chemically amplified resists, in which a single photo generated proton catalytically cleaves several acid labile groups, are used in photolithography applicable to sub quarter-micron design rules. As a result of the catalytic reaction, the sensitivity of the resulting resist is quite high compared to the conventional novolak-diazonaphthoquinone resists. To date, there are three major deep ultraviolet (uv) exposure technologies that have provided significant advancement in miniaturization, and these are lasers that emit radiation at 248 nm, 193 nm and 157 nm. Examples of such photoresists are given in the following patents and incorporated herein by reference, US 4,491 ,628, US 5,350,660, and US 5,843,624 Photoresists for 248nm have typically been based on substituted polyhydroxystyrene and its copolymers. On the other hand, photoresists for 193nm exposure require non-aromatic polymers, since aromatics are opaque at this wavelength. Generally, alicyclic hydrocarbons are incorporated into the polymer to replace the etch resistance lost by the absence of aromatics.
Photoresists based on chemical amplification mechanism are employed for 248 and 193 nm applications. However, the photoresist materials applicable for 248 nm cannot be used at 193 nm due to the high absorption of the poly(4- hydroxystyrene) based polymers used for 248 nm applications. 193 nm applications typically require non-aromatic compounds. Open-chain aliphatic resins cannot be used due to the very high etch rates of these materials. Polymers possessing annelated structures in the side chains such as tricyclododecyl and adamantane or cycloolefins in the main chain are shown to provide etch resistance close to poly(4-hydroxystyrene) polymers [Nakano et al. Proc. SPIE 3333, 43 (1998), Nozaki et al., Wallow et al. Proc. SPIE 3333, 92 (1998), and J.C. Jung et al. Proc. SPIE 3333, 11 , (1998)].
Houlihan et al (US 5,843,624), disclose a polymer for photoresist application, which is a polymer made from a cyclic olefin, maleic anhydride and a substituted or unsubstituted acrylate. The patent describes the substituted acrylate as one where the substituent is acid labile and includes t-butyl, t-amyl, 1- methylcyclohexyl, 3-oxocyclohexyl, and bis(2-trimethylsilyl)ethyl.
The present invention relates to a chemically amplified system, which is sensitive to wavelengths between 300 nm and 100 nm, and comprises a) a polymer that is insoluble in an aqueous alkaline solution and comprises at least one acid labile group, and, b) a compound capable of producing an acid upon radiation. The present invention comprises a polymer that is made from at least one nonaromatic cyclo olefin, at least one cyclic anhydride, at least one acrylic ester of a cyclic lactone, and at least one acrylate with a pendant nonlactone aliphatic hydrocarbon moiety, preferably the pendant hydrocarbon moeity is multicyclic since these groups offer good etch resistance. Furthermore, in the polymer, the nonaromatic cyclo olefin is present at less than 20 mole%, the cyclic anhydride is present at less than 20 mole%, the acrylic ester of the lactone is present in the range of about 20 mole% to about 60 mole%, and acrylate with a pendant hydrocarbon moiety is present in the range of about 20 mole% to about 60 mole%. The polymer is inhibited from dissolving in water or the alkaline developer by having acid labile groups within the polymer. The objective of the invention is to have a photoresist comprising a polymer with reduced absorbance at the exposure wavelength and yet maintaining an acceptable level of dry etch resistance. This is achieved in the present invention by reducing the cyclo olefin ratio in the polymer to less than 20 mole% and also reducing the cyclic anhydride concentration to less than 20 mole%, while at the same time increasing the concentration of the acrylic ester of a cyclic lactone to be greater than 20 mole% but less than 60 mole%, and increasing the concentration of the acrylate with the pendant hydrocarbon moiety to be greater than 20 mole% but less than 60 mole%. It is known that acrylate polymers are transparent resins at 193 nm, but lack the necessary etch resistance. It is also known that polymers derived from cycloolefins and cyclic anhydrides are absorbing at wavelengths less than 200 nm. Furthermore, both monomers are necessary for free radical polymerization, and cycloolefins are necessary for etch resistance. Typically the acrylates and the cycloolefin/cyclo anhydride monomers polymerize in a 1:1 ratio, resulting in a minimum of 25 mole% each of the cycloolefin and anhydride monomers, which can result in polymers with excessive absorbance at the exposure wavelength. It has been unexpectedly found that by using the acrylic ester of a cyclic lactone the concentration of the cycloolefin/anhydride can be significantly reduced to give a more transparent polymer, better adhesion and improved resolution, and hence resulting in an improvement in the lithographic properties of the photoresist. As the demand to print smaller and smaller images increases, the transparency of the polymer must also increase. It is the objective of the present invention to provide for a photoresist with greater transparency at the exposure wavelength.
Photoresists comprising polymers containing mixtures of cycloelefins and acrylates, in particular acrylates of cyclic lactones are known and examples of such disclosure are US 6,447,980, 6,087,063, 6,225,476, 6,517,994, 2001/0044070, 2002/0009666, and 2002/0064727, and are incorporated herein by reference. However, the requirement of the specific combination of monomers and their ratios within the polymer to give a photoresist with the desired lithographic properties is not disclosed.
As a new photoresist solvent, valerolactone, although itself known, has not been used as a solvent for photoresists in the semiconductor technology, particularly in deep uv photoresists, and especially as a mixture with other photoresist solvents. It is an objective of the present invention to provide for a new solvent which has improved solubilizing properties and also improves the lithographic properties of photoresists.
Summary of Invention
The present invention relates to a novel photoresist composition sensitive to radiation in the deep ultraviolet, particularly a positive working photoresist sensitive in the range of 100-300 nm. The photoresist composition comprises a) a polymer that is insoluble in an aqueous alkaline solution and comprises at least one acid labile group, and further where the polymer comprises at least one alicyclic hydrocarbon unit, at least one cyclic anhydride, at least one acrylate unit with the structure 1 , and at least one acrylate unit with structure 2:
(1 ) (2)
where,
R and R' are independently H or (CrC4)alkyl; Ri is a pendant cyclic lactone, and, R2 is a pendant nonlactone aliphatic hydrocarbon moiety, b) a compound or a mixture of compounds capable of producing acid upon irradiation.
Furthermore, in the polymer the alicyclic hydrocarbon unit is present at less than 20 mole%, the cyclic anhydride is present at less than 20 mole%, the acrylate unit of structure 1 is present in the range of about 20 mole% to about 60 mole% and the acrylate unit of structure 2 is present in the range of about 20 mole% to about 60 mole%. The photoresist is irradiated preferably with wavelength of light at 193 nm or 157 nm. Preferably the lactone is not a acid labile group. In one embodiment the lactone is a 5-membered ring, and in another embodiment the nonlactone hydrocarbon moiety is alicyclic.
The invention also relates to a process of imaging the novel positive photoresist composition comprising the steps of a) coating a substrate with the novel photoresist composition, b) baking the substrate to substantially remove the solvent, c) imagewise irradiating the photoresist film, d) baking the photoresist, and e) developing the irradiated film using an alkali developer.
The invention further relates to a photoresist composition comprising a polymer that is insoluble in an aqueous alkaline solution and comprises at least one acid labile group, a compound or a mixture of compounds capable of producing acid upon irradiation, and, a solvent comprising valerolactone. Preferably, the solvent is gamma valerolactone. The solvent may be in a mixture with other photoresist solvent or solvents.
Detail description of the Invention
The present invention relates to a chemically amplified system, which is sensitive to wavelengths between 300 nm and 100 nm, and comprises a) a polymer that is insoluble in an aqueous alkaline solution and comprises at least one acid labile group, and b) a compound capable of producing an acid upon irradiation. The polymer of the present invention comprises at least one alicyclic hydrocarbon unit, at least one cyclic anhydride, at least one acrylate unit with the structure 1 , and at least one acrylate unit with structure 2:
(1 ) (2)
where, R and R' are independently H or (C1-C4) alkyl;
Ri is a pendant cyclic lactone, and, R2 is a pendant nonlactone aliphatic hydrocarbon moiety, Furthermore, in the polymer of the present invention, the alicyclic hydrocarbon unit is present at less than about 20 mole%, the cyclic anhydride is present at less than about 20 mole%, the acrylate unit of structure 1 is present in the range of about 20 mole% to about 60 mole% and the acrylate unit of structure 2 is present in the range of about 10 mole% to about 60 moIe%.
Throughout the present application alicyclic is defined as essentially a nonaromatic carbon/hydrogen cyclic system, which may comprise small amounts of heteroatoms as functional groups, such as oxygen, nitrogen or sulfur, as pendant from the cyclic system. Other groups, such as alkyl (linear or branched) groups, may also be present. Functional groups such as ethers, esters, acids, nitrile, hydroxyl, alcohols etc. are some of the commonly known groups. Aliphatic hydrocarbon, in this application, refers to a predominantly carbon/hydrogen chain which may be linear or cyclic. The chain may be unsubstituted or substituted with alkyl groups or with any known functional groups described above.
In the present polymer the alicyclic hydrocarbon unit is derived from a cyclo olefin monomer which is incorporated into the backbone of the polymer and may be any substituted or unsubstituted multicyclic hydrocarbon containing an unsaturated bond. 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 norbomene, or tetracyclododecane. Examples of substituents on the cyclo olefin may be (CrCβJalkyl, halogen, such as fluorine and chlorine, carboxylic acid, (CrCio)alkylOCOalkyl, cyano(CN), (C1-C10) secondary or tertiary carboxylate, substituted pinacol, adjacent substituents may be linked to form a cyclic non-aromatic structure (such as lactone or anhydride), fluoroalkyl, acid or base labile group, and W(CF3)2OH, where W is (Cι-C6)alkyl or (C C6)alkyl ether.
Examples of cyclo olefin monomers, without limitation, are:
Other cyclo olefin monomers which may also be used in synthesizing the polymer are:
°π
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. 7,1° ] dodec-8-ene-3-carboxylate, and t-butoxycarbonylmethyl tetracyclo[4.4.0.1.2,61. 7,1° ] 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 cyclic anhydride unit is any unsaturated cyclic aliphatic anhydride, and is preferably derived from monomers such as maleic anhydride or itaconic anhydride.
The acrylate unit containing the cyclic lactone of structure 1 , used in the synthesis of the polymer are of the following structure, furthermore, acrylate as referred to in this application refers generally to alkyl substituted or unsubstituted monomers, such as methacrylate, ethacrylate, etc.:
(1 ) where,
R is independently H or (Cι-C4)alkyl; and, Ri is a pendant cyclic hydrocarbon lactone. The cyclic lactone may be a mono or poly cyclic lactone, which is linked directly to the oxygen of the ester group or through an aliphatic linking group, for example, a (C1-C4) alkyl group. In one embodiment the cyclic lactone is preferably a 5-membered ring, which leads to a polymer of lower absorptivity by reducing the cyclic anhydride content of the polymer. The pendant cyclic lactone may be described by the following structures:
where, n=1-4,
X=O, CH2 or N, and,
R3 - R11 are selected from hydrogen, (C1-C14) alkyl and substituted alkyl.
Specific examples of the cyclic lactones in the polymer are derived from monomers, such as, β-methacryloxy-γ-butyrolactone, α-methacryloxy-γ- butyrolactone, methacryloyloxy-norbornane-butyrolactone, 3-oxo-4- oxatricyclo[5.2.1.02, 6]decan-8-yl methacrylate, or mixtures thereof. Preferably, the lactone does not cleave during the imaging process. Some lactones, such as 2-mevalonic lactone, are known to cleave, and can change the dissolution properties of the photoresist. It has been found that using mixtures of lactones can further enhance the lithographic properties of the photoresist, in particular mixtures of β-methacryloxy-γ-butyrolactone, or α-methacryloxy-γ-butyrolactone, methacryloyloxy-norbomane-butyrolactone and β-methacryloxy-γ-butyrolactone, or α-methacryloxy-γ-butyrolactone, 3-oxo-4-oxatricyclo[5.2.1.02, 6]decan-8-yl methacrylate.
The acrylate unit (structure 2) with the pendant cyclic hydrocarbon moiety, further where the pendant cyclic moiety is not a cyclic lactone, is a group containing an aliphatic hydrocarbon moiety which may be connected directly to the oxygen of the acrylic ester or through a connecting group, such as an (C1-C4) alkyl group.
(2) where,
R' is independently H or (Cι-C4)alkyl; and, R2 is a pendant nonlactone aliphatic hydrocarbon moiety. The nonlactone aliphatic hydrocarbon moiety may be linear, branched or cyclic hydrocarbons, which may be unsubstituted or be substituted with known functional groups described previously. Preferably the moiety is cyclic, and more preferably multicyclic. In one preferred embodiment the moiety is an acid labile group, which when removed in the presence of an acid, increases the solubility of the polymer in the developer. Examples of the cyclic aliphatic moiety are,
,0 alkyl
The preferred acrylate monomers are selected from 2-methyladamantyl methacrylate (MAdMA), isoadamantyl methacrylate, 3-hydroxy-1- methacryloxyadamatane, and 3,5-dihydroxy-1 -methacryloxyadamantane.
The cyclo olefin and the cyclic anhydride monomer are believed to form an alternating polymeric structure and their individual concentrations are kept below 20 mole%. Additionally, the concentration of the acrylate lactone is varied such that its concentration is greater than the individual concentrations of the cyclo olefin and the cyclic anhydride monomers incorporated into the polymer. The cyclo olefin concentration is less than about 20 mole% and preferably less than 15 mole%; the cyclic anhydride concentration is less than 20 mole%, and preferably less than 15 mole%; the acrylate lactone concentration is greater than about 20 mole%, more preferably greater than 30 mole%, and even more preferably more than 35 mole%; and the concentration of the acrylate with the pendant hydrocarbon moiety is greater than about 20 mole%, preferably greater than 30 mole%, and even more preferably greater than 35 mole%. Preferably the acrylate lactone concentration is less than about 60 mole% and more preferably less than 50 mole%. Preferably the acrylate with the pendant hydrocarbon moiety is present at a concentration of less than 60 mole%, and more preferably less than 50 mole%. In a particularly preferred embodiment the cyclo olefin concentration is less than 20 mole%, the cyclic anhydride concentration is less than 20 mole%, the acrylate lactone concentration is in the range of about 30 mole% to about 50 mole%, and the acrylate with the pendant hydrocarbon moiety is incorporated into the polymer at a concentration range from about 30 mole% to about 50 mole%.
It has been found that when the individual concentration of the cycloolefin and the cyclic anhydride in the polymer is at or greater than about 25 mole%, the absorptivity of the polymer in the photoresist system is relatively high, thus giving reduced lithographic performance compared to the polymer of the present invention. Yet, a certain minimum amount of the cycloolefin is required to give the desired dry etch resistance, thus the concentration is preferably greater than 5 mole% and more preferably greater than 10 mole%.
Acid labile groups may be attached to any one of the monomers, preferably the cyclo olefin or the acrylate with the pendant hydrocarbon moeity. These groups make the polymer insoluble in the aqueous alkaline developer, but upon exposure the photoacid generated removes the acid labile group, thus making the polymer in the exposed regions soluble. The acid labile group is preferably attached to the cyclo olefin and/or the acrylate with the pendant hydrocarbon cyclic moiety.
Examples of monomers containing acid labile groups that can be used in the polymers are methacrylate ester of methyladamantane, 3-hydroxy-1-adamantyl methacrylate, t-butyl norbomyl carboxylate, t-butyl methyl adamantyl methacryate, methyl adamantyl acrylate, t-butyl acrylate and t-butyl methacrylate.
The acid labile group that may be attached to the alicyclic olefin or be present in the acrylate of structure 2. Examples of acid labile functionalities are - (CO)O-A, -O-A, -0(CO)0-A, -C(CF3)2O-A, -C(CF3)2θ(CO)O-A, and - C(CF3)2(COOA), where A is alkyl, cycloalkyl, substituted cycloalkyl, oxocyclohexyl, benzyl, silyl, alkyl silyl, substituted benzyl, alkoxy alkyl such as ethoxy ethyl or methoxy ethoxy ethyl, acetoxyalkoxy alkyl such as acetoxy ethoxy ethyl, tetrahydrofuranyl, menthyl, and tetrahydropyranyl. Examples of specific groups for A are t-butoxycarbonyl tricyclo(5.3.2.0) decanyl, 2-methyl-2-adamantyl, isobomyl, norbomyl, adamantyloxyethoxy ethyl, menthyl, tertiary butyl, tetrahydropyranyl and 3-oxocyclohexyl. Preferably A is tert-butyl, 3-hydroxy-1 -adamantyl, and 2-methyl- 2-adamantyl.
The polymer of this invention can be synthesized using techniques known in the art. The polymer of this invention may be synthesized by free radical polymerization technique using, for example, 2,2'-azobisisobutyronitrile (AIBN) as initiator. A mixture of monomers is added to a reaction vessel together with a solvent, e.g. tetrahydrofuran, and AIBN is added. The reaction is carried out at a suitable temperature for a suitable amount of time to give a polymer with desired properties. The reaction may also be carried out without a solvent. The temperature may range from about 35°C to about 150°C, preferably 50°C to 90°C for about 5 to 25 hours. The reaction may be carried out at atmospheric pressure or at higher pressures. It has been found that a reaction carried out under a pressure of from about 48,000 Pascals to about 250,000 Pascals gives a polymer with more consistent properties, where examples of such desirable properties are molecular weight, dark film loss, yield, etc. Dark film loss is a measure of the solubility of the unexposed photoresist film in the developing solution, and a minimal film loss is preferred. The polymer may be isolated from any suitable solvent, such as, diethyl ether, hexane or mixture of both hexane and ether. Other polymerization techniques may be used to obtain a polymer with the desired chemical and physical properties.
The optimum molecular weight of the polymer is dependant on the monomers incorporated into the polymer, the photoactive compound and any other chemical components used, and on the lithographic performance desired. Typically, the weight average molecular weight is in the range of 3,000 to 50,000, preferably 5,000 to 25000, more preferably 7,000 to 20000, the number average molecular weight is in the range from about 1500 to about 10,000, and the polydispersity is in the range 1.1 to 5, preferably 1.5 to 2.5. Suitable examples, without limitation, of the acid generating photosensitive compound include onium-salts, such as, diazonium salts, iodonium salts, sulfonium salts, halides and esters, although any photosensitive compound that produces an acid upon irradiation may 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 diphenyliodoinum trifluoromethane sulfonate, diphenyliodoinum nonafluorobutanesulfonate, triphenylsulfonium trifluromethanesuflonate, triphenylsulfonium nonafluorobutanesufonate and the like. Other compounds that form an acid upon irradiation may be used, such as triazines, oxazoles, oxadiazoles, thiazoles, substituted 2-pyrones. Phenolic sulfonic esters, bis-sulfonylmethanes, bis-sulfonylmethanes or bis- sulfonyldiazomethanes, are also preferred. Other preferred embodiments are mixtures of phenyl onium salts and essentially aliphatic onium salts, such photosensitive compounds, and which are incorporated by reference, are described in the application of serial no. 10/170,760, Attorney Docket No. 2002US307CIP entitled 'Photoresist Composition for Deep Ultraviolet Lithography Comprising a Mixture of Photoactive Compounds' filed May 16, 2003; and Attorney Docket No. 2003US308 entitled 'Photoactive Compounds' filed May 16, 2003.
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 (e.g. methyl) 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.
Particularly useful is a cosolvent, valerolactone, especially gamma valerolactone, since a solvent mixture comprising valerolactone has been unexpectedly found to improve the solubility of certain polymers, which may otherwise not be soluble in standard photoresist solvents. Valerolactone, alone or as a mixture with other solvents, may also be used in formulations comprising various polymers and photoactive compounds which are used as coatings in the semiconductor technologies. These coatings could be used as photoresists, insulating coatings, photoimageable antireflective coatings used under a photoresist coating, etc., such as disclosed in applications 10/042,532 and 10/322,239 filed January 9, 2002, herein incorporated by reference. Valerolactone, gamma or delta valerolactone, may be combined with other photoresist solvents, particularly those described above in levels ranging from about 0.5 weight% to about 15 weight percent, preferably 1 weight% to 10 weight%, more preferably 2 weight% to about 5 weight%, although any combination of one or more solvents may be combined with valerolactone to form the solvent mixture. The cosolvent is particularly suitable for photoresists, especially deep uv photoresists, as described in the present application. The photoresist comprises polymers, which may be selected from cycloolefin/maleic anhydride polymers, acrylate polymers, cycloolefin/maleic anhydride/acrylate polymers, and phenolic polymers. The use of valerolactone as a solvent has been found to be especially useful for polymers that are difficult to dissolve in standard photoresist solvents, particularly for polymers containing more than one lactone acrylate of structure 1. It has also been unexpectedly found that the cosolvent, valerolactone, assists also in improving the line edge roughness and stability of the photoresist pattern. The polymers comprising monomers derived from mixtures of β-methacryloyloxy-γ- butyrolactone, 3-oxo-4-oxatricyclo[5.2.1.02, 6]decan-8-yl, and methacryloyloxy- norbornane-butyrolactone particularly benefit from the use of the cosolvent, valerolactone, particularly, gamma valerolactone. The photoactive compounds useful in the photoresist may be those described previously in this application. Preferred solvent mixtures are gamma valerolactone, propylene glycol monomethy ether acetate (PGMEA) and propylene glycol monomethy ether (PGME), where the ratio of PGMEA:PGME can range from 9:1 to 1 :1 , and preferably 8:2 to 7:3. Additives such as colorants, non-actinic dyes, anti-striation agents, plasticizers, adhesion promoters, coating aids, speed enhancers and surfactants may be added to the photoresist composition before the solution is coated onto a substrate. A sensitizer that transfers energy from a particular range of wavelengths to a different exposure wavelength may also be added to the photoresist composition.
In order to improve the stability of the photoresist image after exposure, bases or photobases may be added to the photoresist composition. These bases are known to those skilled in the art and some of which are described the following references: US 5,525,453 and US serial number 09/455872. Bases, which do not absorb or do not absorb significantly, at the wavelength of light used to expose the photoresist, are preferred. Bases such as dimethyliodonium hydroxide, trimethylsulfonium hydroxide and 1 ,3,3-trimethyl-6-azabicyclo[3.2.1]octane are preferred.
The prepared photoresist composition solution can be applied to a substrate by any conventional method used in the photoresist art, including dipping, spraying, whirling and spin coating. When spin coating, for example, the resist 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 lll/V compounds. The photoresist may also be coated over an antireflective coating.
The photoresist coatings produced by the described procedure are particularly suitable for application to metal/metal oxide coated wafers, especially these coated with an antireflective coating, such as are utilized in the production of microprocessors and other miniaturized integrated circuit components. A silicon/silicon dioxide 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. 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) or less 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 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 coating substrate can then be imagewise exposed to actinic radiation, e.g., ultraviolet radiation, at a wavelength of from about 100 nm 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. Surfactants may be added to the developer. 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. The photoresist compositions of the present invention are resistant to acid-base etching solutions and provide effective protection for the unexposed photoresist- coating areas of the substrate. Metal deposition or dry etching are some of the other important processes that can be applied.
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. The triphenyl sulfonium nonafluorobutane sulfonate used in the photoresist formulation is available commercially.
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.
Synthetic Example 1 : Polv(t-butyl norbornene carboxylate-co-β-methacryloyloxy-γ-butyrolactone -co-2- methyladamantyl methacrylate-co-maleic anhydride)
A copolymer was synthesized by reacting 94.25 g of t-butyl norbornene carboxylate (BNC, 15 mole%), 192.67 g of β-methacryloyloxy-γ-butyrolactone (GBLMA, 35 mole%) and 265.5 g of 2-methyladamantyl methacrylate (MAdMA, 35 mole%) and 47.59 g of maleic anhydride (MA, 15 mole%) in the 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 twice from diethyl ether (1/10 v/v ratio), giving a 64% yield. The weight average molecular weight (Mw) as measured on a Gel Permeation Chromatograph (GPC) using polystyrene standards and THF solvent was 12, 638.
Lithographic Example 2
27.77 g of poly(t-butyl norbornene carboxylate-co-β-methacryloyloxy-γ- butyrolactone -co-2-methyladamantyl methacrylate-co-maleic anhydride) of Synthetic Example 1, 0.469 g (30 μmol/g) of triphenylsulfonium nonafluorobutanesulfonate (absorptivity 117.74 L/g.cm), 0.414 g (30μmol/g) of dimethyl, p-methoxyphenyl sulfonium nonafluorobutanesulfonate, 9.66 g of 1 weight% propylene glycol monomethyl ether acetate (PGMEA) solution of N-(1- adamantyl) acetamide and 0.30 g of 120 ppm of a surfactant, FC-4430, in PGMEA, (fluoroaliphatic polymeric ester, supplied by 3M Corporation, St. Paul Minnesota), were dissolved in 211.38 g of PGMEA to give a photoresist solution which was filtered through 0.2μm Teflon filter. The n & k values at 193 nm for this photoresist film were 1.7120 and 0.020607, 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, NJ) 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 240 nm. The photoresist film was baked at 115°C for 90 sec. The substrate was then exposed in a 193 nm ISI ministepper (numerical aperture of 0.6 and coherence of 0.3/0.7, Annular Illumination) using a chrome on quartz binary mask. After exposure, the wafer was post-exposure baked at 130°C for 90 sec. The imaged photoresist was then developed for 60 seconds using a 2.38 weight% aqueous solution of tetramethyl ammonium hydroxide. The line and space patterns were then observed on a scanning electron microscope. The photoresist had a photosensitivity of 21 mJ/cm2 and a linear resolution of 0.09 μm. The line edge roughness (3σ) as measured on a KLA8100 CD SEM for 130 nm L/S (1 : 2 pitch at best focus) was 8 nm.
Synthetic Example 3
Polv(t-butyl norbornene carboxylate-co-β-methacryloyloxy-γ-butyrolactone -co-2- methyladamantyl methacrylate-co-maleic anhydride)
A copolymer was synthesized by reacting 5.09 g of t-butyl norbornene carboxylate (BNC, 10 mole%), 17.81 g of -β-methacryloyloxy-γ-butyrolactone (GBLMA, 40 mole%) and 24.58 g of 2-methyladamantyl methacrylate (MAdMA, 40 mole%) and 2.57 g of maleic anhydride (MA, 10 mole%) 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 twice from diethyl ether (1/10 v/v ratio) giving a yield of 74%. The weight average molecular weight (Mw) as measured on a Gel Permeation Chromatograph (GPC) using polystyrene standards and THF solvent was 15, 567.
Lithographic Example 4
1.52 g of poly(t-butyl norbornene carboxylate-co-β-methacryloyloxy-γ- butyrolactone -co-2-methyladamantyl methacrylate-co-maleic anhydride) of Synthetic Example 3, 0.026 g (30 μmol/g) of triphenylsulfonium nonafluorobutanesulfonate (absorptivity 117.74 L/g.cm), 0.023g (30μmol/g) of dimethyl, p-methoxyphenyl sulfonium nonafluoromethanesulfonate, 0.529 g of 1 weight% PGMEA solution of N-adamantyl-1-acetamide and 0.0180 g of 120 ppm of a surfactant, FC-4430, in PGMEA, (fluoroaliphatic polymeric ester, supplied by 3M Corporation, St. Paul Minnesota), were dissolved in 12.88 g of PGMEA to give a photoresist solution, which was filtered through 0.2μm Teflon filter. The n & k values at 193 nm for this photoresist film were 1.7111 and 0.017288, 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, NJ) 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 90 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 130°C for 90 sec. The imaged photoresist was then developed for 60 sec using a 2.38 weight% aqueous solution of tetramethyl ammonium hydroxide. The line and space patterns were then observed on a scanning electron microscope. The photoresist had a photosensitivity of 20mJ/cm2 and a linear resolution of 0.08 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 5.0 nm.
Synthetic Example 5
Poly(t-butyl norbornene carboxylate-co-β-methacryloyloxy-γ-butyrolactone -co-2- methyladamantyl methacrylate-co-maleic anhydride)
A copolymer was synthesized by reacting 29.62 g of t-butyl norbornene carboxylate (BNC, 5 mole%), 467.06 g of -β-methacryloyloxy-γ-butyrolactone (GBLMA, 45 mole%) and 321.91 g of 2-methyladamantyl methacrylate (MAdMA, 45 mole%) and 15.01 g of maleic anhydride (MA, 5 mole%) 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 twice from diethyl ether (1/10 v/v ratio) giving a yield of 75%. The weight average molecular weight (Mw) as measured on a Gel Permeation Chromatograph (GPC) using polystyrene standards and THF solvent was 16,997. Lithographic Example 6
1.6663 g of poly(t-butyl norbornene carboxylate-co-β-methacryloyloxy-γ- butyrolactone -co-2-methyladamantyl methacrylate-co-maleic anhydride) of Synthetic Example 5, 0.0281 g (30 μmol/g) of triphenylsulfonium nonafluorobutanesulfonate (absorptivity 117.74 L/g.cm), 0.0248g (30μmol/g) of dimethyl, p-methoxyphenyl sulfonium nonafluoromethanesulfonate, 0.5797 g of 1 weight% PGMEA solution of N-(1 -adamantyl) acetamide and 0.0180 g of 120 ppm of a surfactant, FC-4430, in PGMEA, (fluoroaliphatic polymeric ester, supplied by 3M Corporation, St. Paul Minnesota), were dissolved in 12.6831 g of PGMEA to give a photoresist solution. The n & k values at 193 nm for this photoresist film were 1.7111 and 0.017288, 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, NJ) 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 90 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 130°C for 90 sec. The imaged photoresist was then developed for 60 sec using a 2.38 weight% aqueous solution of tetramethyl ammonium hydroxide. The line and space patterns were then observed on a scanning electron microscope. The photoresist had a photosensitivity of 20 mJ/cm2 and 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 5.0 nm.
Synthetic Example 7: Polvft-butyl norbornene carboxylate-co-β-methacryloyloxy-γ-butyrolactone -co-2- methyladamantyl methacrylate-co- methacryloyloxy-norbornane-butyrolactone-co- maleic anhydride) A copolymer was synthesized by reacting 9.92 g t-butyl norbornene carboxylate (BNC, 10 mole% ), 26 g of β-methacryloyloxy-γ-butyrolactone (GBLMA, 30 mole%), 47.78 g of 2-methyladamantyl methacrylate (MAdMA, 40 mole%), 11.32 g of methacryloyloxy-norbomane-butyrolactone (MNBL, 10 mole%) and 5.01 g of maleic anhydride (MA, 10 moie%) 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) giving a yield of 76%. The weight average molecular weight (Mw) as measured on a Gel Permeation Chromatograph (GPC) using polystyrene standards and THF solvent was 16,110.
Lithographic Example 8
5.751 g of poly(t-butyl norbornene carboxylate-co-β-methacryloyloxy-γ- butyrolactone -co-2-methyladamantyl methacrylate-co- methacryloyloxy- norbomane-butyrolactone-co-maleic anhydride of Synthetic Example 7, 0.098 g (30 μmol/g) of triphenylsulfonium nonafluorobutanesulfonate (absorptivity 117.74 L/g.cm), 0.085 g (30μmol/g) of dimethyl, p-methoxyphenyl sulfonium nonafluorobutanesulfonate, 1.663 g of 1 weight% PGMEA solution of N-(1- adamantyl) acetamide and 0.0.083 g of 120 ppm of a surfactant, FC-4430, in PGMEA, (fluoroaliphatic polymeric ester, supplied by 3M Corporation, St. Paul Minnesota) was dissolved in 61.00 g of PGMEA, and 1.29 g of gamma valerolactone to give a photoresist solution. The n & k values at 193 nm for this photoresist film were 1.7120 and 0.020607, 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, NJ) onto the silicon substrate and baking at 175°C for 60 sec. The B.A.R.C film thickness was 37 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 210 nm. The photoresist film was baked at 115°C for 90 sec. The substrate was then exposed in a 193 nm ISI ministepper (numerical aperture of 0.6 and coherence of 0.3/0.7, Annular Illumination). After exposure, the wafer was post-exposure baked at 130°C for 90 sec. The imaged photoresist was then developed for 30 sec using a 2.38 weight% aqueous solution of tetramethyl ammonium hydroxide. The line and space patterns were then observed on a scanning electron microscope. The photoresist had a photosensitivity of 20 mJ/cm2 and a linear resolution of 0.08 μm. The line edge roughness (3σ) as measured on a KLA8100 CD SEM for 130 nm L/S (1 : 2 pitch at best focus) was 5 nm.
Synthetic Example 9: Polv(t-butyl norbornene carboxylate-co-β-methacryloyloxy-γ-butyrolactone -co-2- methyladamantyl methacrylate-co- 3-oxo-4-oxatricvclof5.2.1.02. 61decan-8-yl methacrylate-co-maleic anhydride)
A copolymer was synthesized by reacting 29.47 g t-butyl norbornene carboxylate (BNC, 10 mole% ), 77.44 g of β-methacryloyloxy-γ-butyrolactone (GBLMA, 30 mole%), 142.35 g of 2-methyladamantyl methacrylate (MAdMA, 40 mole%), 35.89 g of 3-oxo-4-oxatricyclo[5.2.1.02, 6]decan-8-yl (10 mole%) and 15.02 g of maleic anhydride (MA, 10 mole%) 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), giving a yield of 75%o. The weight average molecular weight (Mw) as measured on a Gel Permeation Chromatograph (GPC) using polystyrene standards and THF solvent was 14,904.
Lithographic Example 10
2.22 g of poly(t-butyl norbornene carboxylate-co-β-methacryloyloxy-γ- butyrolactone -co-2-methyladamantyl methacrylate-co- 3-oxo-4- oxatricyclo[5.2.1.02, 6]decan-8-yl methacrylate-co-maleic anhydride) from Synthetic Example 9, 0.0375 g (30 μmol/g) of triphenylsulfonium nonafluorobutanesulfonate (absorptivity 117.74 L/g.cm), 0.0331 g (30μmol/g) of dimethyl, p-methoxyphenyl sulfonium trifluoromethanesulfonate, 0.644 g of 1 weight% PGMEA solution of N-(1 -adamantyl) acetamide and 0.024 g of 120 ppm of a surfactant, FC-4430, in PGMEA, (fluoroaliphatic polymeric ester, supplied by 3M Corporation, St. Paul Minnesota) was dissolved in 16.68 g of PGMEA, and 0.354 g of gamma valerolactone to give a photoresist solution. The n & k values at 193 nm for this photoresist film were 1.7120 and 0.020607, 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, NJ) onto the silicon substrate and baking at 175°C for 60 sec. The B.A.R.C film thickness was 37 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 210 nm. The photoresist film was baked at 115°C for 90 sec. The substrate was then exposed in a 193 nm ISI ministepper (numerical aperture of 0.6 and coherence of 0.3/0.7, Annular Illumination). After exposure, the wafer was post-exposure baked at 130°C for 90 sec. The imaged photoresist was then developed using a 2.38 weight% aqueous solution of tetramethyl ammonium hydroxide for 30 sec. The line and space patterns were then observed on a scanning electron microscope. The photoresist had a photosensitivity of 18 mJ/cm2 and a linear resolution of 0.09 μm. The line edge roughness (3σ) as measured on a KLA8100 CD SEM for 130 nm L/S (1 : 2 pitch at best focus) was 5 nm.
Lithographic Example 11
8.2086 g of poly(BNC/MA MAdMA/GBLMA/MNBL) from Synthetic Example 7, 0.1385 g (30 μmol/g) of triphenylsulfonium nonafluorobutane sulfonate, 0.1290 g (30 μmol/g) of 4-acetoxy-3,5-dimethyl phenyl dimethyl sulphonium nonaflate, 2.38 g of 1 weight% propylene glycol monomethyl ether acetate solution of N-(1- adamantyl) acetamide, 0.12 g of 10 weight% propylene glycol monomethyl ether acetate solution of a surfactant (FC-430 fluoroaliphatic polymeric ester, supplied by 3M Corporation, St. Paul Minnesota) and 1.83 g of gamma valerolactone were dissolved in 87.1938 g of propylene glycol monomethyl ether acetate to give a photoresist solution; the photoresist solution was filtered through 0.2 μm filter.
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, NJ) 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 coated on the B.A.R.C coated silicon substrate. The spin speed was adjusted such that the photoresist film thickness was 210 nm. The photoresist film was baked at 115°C for 90 sec. The substrate was then exposed in a 193 nm ISI mini stepper (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 130°C for 90 sec. The imaged photoresist was then developed using a 2.38 weight% aqueous solution of tetramethyl ammonium hydroxide for 30 sec. The line and space patterns were then observed on a scanning electron microscope. The photoresist had a photosensitivity of 13.0 mJ/cm2and a linear resolution of 0.08 μm.
Lithographic Example 12
16.2755 g of poly(BNC/MA/MAdMA/GBLMA/MNBL) from Synthetic Example 7, 0.2746 g (30 μmol/g) of triphenylsulfonium nonafluorobutane sulfonate, 0.3838 g (45 μmol/g) of 4-acetoxy-3,5-dimethyl phenyl dimethyl sulphonium nonaflate, 6.6064 g of 1 weight% propylene glycol monomethyl ether acetate solution of N-(1 -Adamantyl) acetamide, 0.24 g of 10 weight% propylene glycol monomethyl ether acetate solution of a surfactant (fluoroaliphatic polymeric ester, supplied by 3M Corporation, St. Paul Minnesota) and 3.66 g of gamma valerolactone were dissolved in 172.56 g of propylene glycol monomethyl ether acetate to give a photoresist solution; the photoresist solution was filtered through 0.2 μm filter.
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, NJ) 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 coated on the B.A.R.C coated silicon substrate. The spin speed was adjusted such that the photoresist film thickness was 210 nm. The photoresist film was baked at 115°C for 90 sec. The substrate was then exposed in a 193 nm ISI mini stepper (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 130°C for 90 sec. The imaged photoresist was then developed using a 2.38 weight% aqueous solution of tetramethyl ammonium hydroxide for 30 sec. The line and space patterns were then observed on a scanning electron microscope. The photoresist had a photosensitivity of 13.0 mJ/cm2 and a linear resolution of 0.09 μm.
Lithographic Example 13
1.6419 g of poly(BNC/MA/MAdMA/GBLMA/MNBL) from Synthetic Example
7, 0.0280 g (30 μmol/g) of triphenylsulfonium nonafluorobutane sulfonate, 0.0258 g (30 μmol/g) of 4-acetoxy-3,5-dimethyl phenyl dimethyl sulphonium nonaflate, 0.4801 g of 1 weight% propylene glycol monomethyl ether acetate solution of N-(1- adamantyl) acetamide, 0.0261 g of 10 weight% propylene glycol monomethyl ether acetate solution of a surfactant (fluoroaliphatic polymeric ester, supplied by 3M Corporation, St. Paul Minnesota) and 0.3655 g of gamma valerolactone were dissolved in 17.4374 g of propylene glycol monomethyl ether acetate to give a photoresist solution; the photoresist solution was filtered through 0.2 μm filter.
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, NJ) 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 coated on the B.A.R.C coated silicon substrate. The spin speed was adjusted such that the photoresist film thickness was 240 nm. The photoresist film was baked at 115°C for 90 sec. The substrate was then exposed in a 193 nm ISI mini stepper (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 130°C for 90 sec. The imaged photoresist was then developed using a 2.38 weight% aqueous solution of tetramethyl ammonium hydroxide for 30 sec. The line and space patterns were then observed on a scanning electron microscope. The photoresist had a photosensitivity of 18.0 mJ/cm2and a linear resolution of 0.08 μm. Comparative Example 1
Polvft-butyl norbornene carboxylate-co-methacryloyloxy--butyrolactone -co- methacryloyloxy-norbomane-butyrolactone-co-maleic anhydride
10.49 g t-butyl norbornene carboxylate (BNC), 73.12 g of -methacryloyloxy-- butyolactone (GBLMA), 47.74 g of methacryloyloxy-norbornane-butyrolactone (MNBL) and 5.27g of maleic anhydride (MA) was mixed in the presence of 5 weight% of AIBN in tetrahydrofuran (THF) at 50% solid. A gel was formed which was completely insoluble in THF.
Comparative Example 2:
Polv(t-butyl norbornene carboxylate-co-2-methyladamantyl methacrylate-co- hvdroxyadamantyl methacrylate-co-maleic anhydride)
A copolymer was synthesized by reacting 20.25 g t-butyl norbornene carboxylate (BNC, 16.66 mo!e% ), 24.47 g of 2-methyladamantyl methacrylate (MAdMA, 16.66 mole%), 24.6 g (16.66 mole%) of hydroxyadamantyl methacrylate and 30.9 g of maleic anhydride (MA, 50 mole%) 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 10,526.
Comparartive Lithographic Example 3 1.6935 g of Poly(t-butyl norbornene carboxylate-co-2-methyiadamantyl methacrylate-co- hydroxyadamantyl methacrylate-co-maleic anhydride) from comparative example 2, 0.0286 g (30 μmol/g) of triphenylsulfonium nonafluorobutanesulfonate (absorptivity 117.74 L/g.cm), 0.2946 g of 1 weight% PGMEA solution of N-(1 -adamantyl) acetamide and 0.0180 g of 120 ppm of a surfactant, FC-4430, in PGMEA, (fluoroaliphatic polymeric ester, supplied by 3M Corporation, St. Paul Minnesota) was dissolved in 12.9653 g of PGMEA.
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, NJ) onto the silicon substrate and baking at 175°C for 60 sec. The B.A.R.C film thickness was 37 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 90 sec. The substrate was then exposed in a 193 nm ISI ministepper (numerical aperture of 0.6 and coherence of 0.7). After exposure, the wafer was post-exposure baked at 130°C for 90 sec. The imaged photoresist was then developed using a 2.38 weight% aqueous solution of tetramethyl ammonium hydroxide for 30 sec. The dose clear was found to be too high for effective processing.

Claims

Claims
1. A photoresist composition comprising an admixture of; a) polymer that is insoluble in an aqueous alkaline solution and comprises at least one acid labile group and further where the polymer comprises at least one alicyclic hydrocarbon unit, at least one cyclic anhydride, at least one acrylate unit with the structure 1 , and at least one acrylate unit with structure 2:
(1) (2)
where,
R and R' are independently H or (Cι-C4)alkyl;
Ri is a pendant lactone,
R2 is pendant nonlactone aliphatic hydrocarbon moiety; and, b) a compound or a mixture of compounds capable of producing acid upon irradiation.
2. The photoresist composition according to claim 1 , where the alicyclic hydrocarbon unit is present at less than 20 mole%, the cyclic anhydride is present at less than 20 mole%, the acrylate unit of structure (1 ) is present in the range of 20 mole% to 60 mole% and the acrylate unit of structure (2) is present in the range of 20 mole% to 60 mole% .
3. The photoresist composition according to claim 1 , where the polymer comprises a mixture of 2 or more acrylate units of structure (1).
4. The photoresist composition according to claim 1 , where R2 is a pendant polycyclic moeity.
5. The photoresist composition according to claim 1 , where the alicyclic hydrocarbon is selected from norbornene, substituted norbornene, tetracyclodecene and substituted tetracyclodecene.
6. The photoresist composition according to claim 1 , where lactone is not cleavable by acid.
7. The photoresist composition according to claim 1 , where the lactone is a 5 membered ring.
8. The photoresist composition according to claim 1 , where the alicyclic hydrocarbon unit has an acid labile group.
9. The photoresist composition according to claim 1 , where the anhydride unit is derived from a maleic anhydride monomer.
10. The photoresist composition according to claim 1 , where the pendant hydrocarbon moiety is acid labile.
11. The photoresist composition according to claim 1 , where the compound capable of producing an acid upon irradiation is selected from sulphonium salts, iodoinum salts, triazines, oxazoles, oxadiazoles, thiazoles, substituted
2-pyrones, phenol sulfonic esters, bis-sulfonylmethanes, bis- sulfonylmethanes, bis-sulfonyldiazomethanes, and mixtures thereof.
12. The photoresist composition according to claim 1 , where the composition further comprises a base.
13. The process of imaging a positive photoresist composition comprising the steps of: a) forming a coating on a substrate of a photoresist film from a photoresist composition of claim 1 ; b) imagewise irradiating the photoresist film; c) baking the photoresist film; and, d) developing the irradiated photoresist film using an alkali developer.
14. The process according to claim 13, further comprising coating an antireflective film on the substrate prior to coating the photoresist.
15. The process according to claim 13, further where the antireflective coating is sensitive at 193 nm.
16. The process according to claim 13, wherein the photoresist film is imagewise irradiated with light of wavelength in the range of 100nm to
300nm.
17. The process according to claim 13, wherein the alkali developer comprises an aqueous solution of tetramethyl ammonium hydroxide.
18. A photosensitive composition comprising, a) polymer that is insoluble in an aqueous alkaline solution and comprises at least one acid labile group, b) a compound or a mixture of compounds capable of producing acid upon irradiation, and, c) a solvent comprising valerolactone.
19. The photosensitive composition of claim 18, where the composition further comprises a solvent selected from propyleneglycol alkyl ether acetate, propyleneglycol alkyl ether, ethyl lactate and mixtures thereof.
20. The photosensitive composition of claim 18, where the solvent is gamma valerolactone.
21. The photosensitive composition of claim 18, where the polymer is selected from cycloolefin/maleic anhydride polymers, acrylate polymers, cycloolefin/maleic anhydride/acrylate polymers, and phenolic polymers.
22. The photosensitive composition of claim 18, where the coating is a photoresist coating or an antireflective coating.
EP04731579A 2003-05-16 2004-05-07 Photoresist composition for deep uv and imaging process thereof Withdrawn EP1631863A2 (en)

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