Classifications

• • G—PHYSICS
  • G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
  • G03F—PHOTOMECHANICAL PRODUCTION OF TEXTURED OR PATTERNED SURFACES, e.g. FOR PRINTING, FOR PROCESSING OF SEMICONDUCTOR DEVICES; MATERIALS THEREFOR; ORIGINALS THEREFOR; APPARATUS SPECIALLY ADAPTED THEREFOR
  • G03F7/00—Photomechanical, e.g. photolithographic, production of textured or patterned surfaces, e.g. printing surfaces; Materials therefor, e.g. comprising photoresists; Apparatus specially adapted therefor
  • G03F7/26—Processing photosensitive materials; Apparatus therefor
  • G03F7/42—Stripping or agents therefor
  • G03F7/422—Stripping or agents therefor using liquids only
  • G03F7/425—Stripping or agents therefor using liquids only containing mineral alkaline compounds; containing organic basic compounds, e.g. quaternary ammonium compounds; containing heterocyclic basic compounds containing nitrogen
• • G—PHYSICS
  • G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
  • G03F—PHOTOMECHANICAL PRODUCTION OF TEXTURED OR PATTERNED SURFACES, e.g. FOR PRINTING, FOR PROCESSING OF SEMICONDUCTOR DEVICES; MATERIALS THEREFOR; ORIGINALS THEREFOR; APPARATUS SPECIALLY ADAPTED THEREFOR
  • G03F7/00—Photomechanical, e.g. photolithographic, production of textured or patterned surfaces, e.g. printing surfaces; Materials therefor, e.g. comprising photoresists; Apparatus specially adapted therefor
  • G03F7/26—Processing photosensitive materials; Apparatus therefor
  • G03F7/42—Stripping or agents therefor

Definitions

• the present invention relates to a method for stripping a photoresist formed on a substrate having at least a copper (Cu) wiring and a low-dielectric layer thereon.
• the invention is favorably applied to a method for stripping a photoresist in a process not including a conventional O 2 plasma ashing step in the fabrication of semiconductor devices, such as ICs and LSIs.
• a photoresist is uniformly coated on an electroconductive metallic layer, an insulating layer and a low-dielectric material layer formed on a substrate, such as a silicon wafer, by CVD vapor deposition process or the like.
• the photoresist is selectively subjected to exposure and development to form a photoresist pattern.
• the electroconductive metallic layer, the insulating layer and the low-dielectric material layer formed by CVD vapor deposition are selectively etched by using the photoresist pattern as a mask to form a minute circuit, and the photoresist layer thus becoming unnecessary is then removed with a stripping solution.
• a process is used in which a Cu multilayer wiring is formed without etching Cu by using a dual damascene process, owing to the low etching resistance of Cu.
• dual damascene processes have been proposed.
• One example thereof comprises forming a Cu layer, a low-dielectric layer (e.g., SiOC layer) is accumulated as being multilayered on a substrate, then providing a photoresist layer as the uppermost layer, and thereafter selectively exposing the photoresist layer to light and developing it to form a photoresist pattern (a “first photoresist pattern”).
• the low-dielectric layer is etched, and then the first photoresist pattern is stripped away by O 2 plasma ashing treatment or the like thereby to form via holes that connect to the Cu layer on the substrate.
• another photoresist pattern (a “second photoresist pattern”) is newly formed as the uppermost layer on the remaining multilayer structure, and the remaining low-dielectric layer is partly etched by using the second photoresist pattern as a mask pattern to thereby form wiring trenches that communicate with the above-described via holes.
• the second photoresist pattern is stripped away by O 2 plasma ashing treatment or the like, and then the via holes and the trenches are filled with Cu by electrolytic plating or other method, thereby forming multilayered Cu wiring conductors.
• the substrate for use in the process may optionally be provided with a barrier layer (e.g., SiN layer, SiC layer) as an etching stopper layer between the Cu layer and the low dielectric layer.
• a barrier layer e.g., SiN layer, SiC layer
• via holes and trenches are formed, and then, while the barrier layer exposed out on the substrate is kept as such or after the barrier layer has been removed, the photoresist is stripped away and thereafter the via holes and the trenches are filled with Cu.
• Si deposition may readily occur, resulting from the low-dielectric layer, during the etching treatment and the plasma ashing treatment for forming the via holes and the trenches, and this may form Si deposits around the opening of the trenches.
• a deposition that results from photoresist may also occur. If these deposits are not completely removed, then it causes a problem in that the yield in semiconductor production may lower.
• O 2 plasma ashing treatment has been employed for removal of photoresist patterns and etching residues in conventional patterning for metal wiring.
• a material having a lower dielectric constant has become used for the low-dielectric layer to be formed on Cu wiring substrates, and at present, a process of using a low-dielectric layer that has a dielectric constant of 3 or less is being developed. It is said that the material of the type having such a low dielectric constant (low-k material) is poorly resistant to ashing or is not resistant to ashing, and when such a low-k material is used, a process not including an O 2 plasma ashing step after etching must be employed.
• the Cu layer may be kept away from direct contact with the photoresist stripping solution during the stripping treatment, and therefore, it is desirable that the stripping treatment is more efficiently attained according to it.
• JP-A-11-74180 discloses a technique of washing a semiconductor substrate having Al or the like metal wiring thereon, with a washing solution containing an oxidizing agent (hydrogen peroxide) before a photoresist is stripped away from it, and then stripping the photoresist from it by the use of a stripping solution.
• an oxidizing agent hydrogen peroxide
• Reference 1 discloses, in one line (as example listing) in its [0007], a tetramethylammonium hydroxide (TMAH)-based stripping solution such as that in JP-A-63-147168 (Patent Reference 2), along with an alkanolamine-based stripping solution and a fluorine-containing stripping solution also disclosed therein.
• TMAH tetramethylammonium hydroxide
• Patent Reference 1 only monoethanolamine-based stripping solutions are actually tested and confirmed in point of their effects, and Patent References 1 and 2 do neither describe nor suggest at all a photoresist stripping method suitable to a dual damascene process that is targeted by the present invention.
• JP-A-11-233405 discloses a method for producing semiconductor devices, which comprises dry etching a semiconductor substrate having an Al or the like metal wiring thereon, then washing a photoresist pattern with a washing solution that comprises an oxidizing agent and an organic acid, and thereafter stripping it with a resist stripping solution. Also in this publication, only monoethanolamine-based stripping solutions are actually tested and confirmed in point of their effects, and this publication does neither describe nor suggest at all the photoresist stripping method suitable to a dual damascene process that is targeted by the present invention.
• the present invention has been made in consideration of the above-mentioned situation, and its object is to provide a method for stripping a photoresist which, even when employed in a process with no O 2 plasma ashing treatment for micropatterning a substrate that has at least copper (Cu) wiring and a low-dielectric layer thereon, enables effective stripping of an etched photoresist film and an etching residue and which exhibits good corrosion resistance not having any negative influence on the dielectric constant of the low-dielectric layer.
• Cu copper
• the invention provides a method for stripping a photoresist that comprises:
• a copper (Cu) wiring is formed on a substrate such as silicon wafer, and a low-dielectric layer is formed thereon.
• a barrier layer etching stopper layer
• an insulating layer may be provided to form a multi-layered structure.
• the copper (Cu) wiring includes both wiring of pure copper, and a wiring of a copper-based alloy (e.g., Al—Si—Cu, Al—Cu).
• a copper-based alloy e.g., Al—Si—Cu, Al—Cu
• an Al-based wiring or any other metal wirings than the Cu wiring may also be used.
• the metal layer may be formed through CVD, electrolytic plating or the like.
• the barrier layer includes SiN layer, SiC layer, Ta layer, TaN layer, but is not limited to these.
• the low-dielectric layer in the invention is formed of a material having a dielectric constant of 3 or less.
• the material for the low dielectric layer examples include a low dielectric material (low-k material), for example, a carbon-doped silicon oxide (SiOC) material, such as “Black Diamond” (produced by Applied Materials, Inc.), “Coral” (produced by Novellus Systems, Inc.) and “Aurora” (produced by ASM Japan Co., Ltd.); an MSQ (methylsilsesquioxane) material, such as “OCD T-7”, “OCD T-9”, “OCD T-11”, “OCD T-31” and “OCD T-39” (all produced by Tokyo Ohka Kogyo Co., Ltd.); and an HSQ (hydroxysilsesquioxane) material, such as “OCD T-12” and “OCD T-32” (all produced by Tokyo Ohka Kogyo Co., Ltd.), but it is not limited to these examples.
• a low dielectric material for example, a carbon-doped silicon oxide (SiOC) material, such as “Black Diamond” (produced by
• the low-dielectric layer may be formed by applying the above-mentioned low-dielectric material (low-k material) on a substrate, and then baking it at a high temperature generally not lower than 350° C. for crystallizing it.
• low-k material low-dielectric material
• a photoresist composition is applied on the low-dielectric layer and dried, and then exposed to light and developed according to known photolithography to form a photoresist pattern.
• the photoresist composition is preferably any of those generally used for KrF—, ArF—, F 2 -excimer lasers or electron rays, but not limited thereto.
• the condition for exposure and development may be suitably determined, depending on the photoresist selected in accordance with the object.
• the photoresist layer may be exposed to a light source capable of emitting active rays such as UV rays, far-UV rays, excimer laser, X-rays or electron rays, such as a low-pressure mercury lamp, a high-pressure mercury lamp, an ultra-high-pressure mercury lamp or a xenon lamp, through a desired mask pattern, or the photoresist layer may be directly patterned by controlling electron rays applied thereto.
• the photoresist pattern may be further baked (post-exposure baking).
• the method of development is not also specifically defined.
• the photoresist-coated substrate is dipped in a developer for a predetermined period of time, then washed with water and dried (dip development); or a developer is dropwise applied to the surface of the photoresist-coated substrate, and then the substrate is kept as such for a predetermined period of time, then washed with water and dried (paddle development); or the photoresist surface is sprayed with a developer, then washed with water and dried (spray development).
• Various modes of development may be employed in accordance with the object.
• the low-dielectric layer is selectively etched, for example, dry-etched through the formed photoresist pattern serving as a mask, to thereby form via holes or trenches (for wiring).
• a dual damascene process is preferably employed.
• step (II) is for decomposing the photoresist pattern and the etching residue prior to the subsequent step (III).
• Ozone water for use herein is preferably one prepared by dissolving ozone gas in pure water by bubbling or the like.
• the ozone concentration is from 1 ppm to a saturation concentration.
• Aqueous hydrogen peroxide for use herein is preferably an aqueous solution having a hydrogen peroxide concentration of from 0.1 to 60% by mass or so, more preferably from 0.5 to 35% by mass or so.
• the substrate is dipped in ozone water and/or aqueous hydrogen peroxide for 5 to 60 minutes or so.
• the substrate is contacted with a photoresist stripping solution that contains at least a quaternary ammonium hydroxide to thereby remove the photoresist pattern and the etching residue.
• the quaternary ammonium hydroxide is preferably one represented by the following general formula (I): wherein R 1 , R 2 , R 3 and R 4 each independently represent an alkyl or hydroxyalkyl group having from 1 to 4 carbon atoms.
• TMAH tetramethylammonium hydroxide
• TMAH tetramethylammonium hydroxide
• tetraethylammonium hydroxide tetrapropylammonium hydroxide
• TMAH tetramethylammonium hydroxide
• tetrapropylammonium hydroxide tetrapropylammonium hydroxide
• tetrabutylammonium hydroxide methyltripropyl
• tetramethylammonium hydroxide preferred are tetramethylammonium hydroxide, tetrabutylammonium hydroxide, tetrapropylammonium hydroxide, methyltributylammonium hydroxide, methyltripropylammonium hydroxide and choline, in view of their ability to strip Cu or Si-containing residues and to strip photoresist.
• quaternary ammonium hydroxides may be used herein.
• the amount of the quaternary ammonium hydroxide to be in the photoresist stripping solution is preferably from 1 to 20% by mass or so, more preferably from 2 to 10% by mass or so.
• the photoresist stripping solution for use in the invention generally contains water and a water-soluble organic solvent, in addition to the quaternary ammonium hydroxide therein.
• the amount of water may be from 5 to 60% by mass or so, preferably from 10 to 50% by mass.
• the balance is a water-soluble organic solvent.
• dimethyl sulfoxide dimethylimidazolidinone, N-methyl-2-pyrrolidone, diethylene glycol monobutyl ether, sulforane, N,N-dimethylacetamide, and N,N-dimethylformamide.
• water-soluble organic solvents may be sued herein.
• the photoresist stripping solution may further contain a water-soluble amine, if desired.
• the water-soluble amine includes alkanolamines, such as monoethanolamine, diethanolamine, triethanolamine, 2-(2-aminoethoxy)ethanol, N,N-dimethylethanolamine, N,N-diethylethanolamine, N,N-dibutylethanolamine, N-methylethanolamine, N-ethylethanolamine, N-butylethanolamine, N-methyldiethanolamine, monoisopropanolamine, diisopropanolamine, triisopropanolamine; polyalkylene-polyamines, such as diethylenetriamine, triethylenetetramine, propylenediamine, N,N-diethylethylenediamine, 1,4-butanediamine, N-ethyl-ethylenediamine, 1,2-propanediamine, 1,3-propanediamine, 1,6-hexanediamine; aliphatic amines, such as
• a water-soluble amine is added to the photoresist stripping solution, then its amount is preferably from 10 to 50% by mass or so.
• the solution may further contain a carboxyl group-having acid compound, and a salt of hydrofluoric acid with a metal ion-free base, especially in view of their stripping abilities.
• carboxyl group-having acid compound examples include acetic acid, propionic acid, and glycolic acid.
• carboxyl group-having acid compound is added to the photoresist stripping solution, then its amount is preferably from 2 to 20% by mass or so.
• One preferred example of the salt of hydrofluoric acid with a metal ion-free base is ammonium fluoride.
• a salt of hydrofluoric acid with a metal ion-free base is added to the photoresist stripping solution, then its amount is preferably from 0.1 to 10% by mass or so.
• the substrate is not provided with a barrier layer (etching stopper layer) as an interlayer, or when the substrate is provided with such a barrier layer but is processed for stripping photoresist from it after the barrier layer is etched away, then it is desirable that at least one corrosion inhibitor selected from aromatic hydroxy compounds, benzotriazole-based compounds and mercapto group containing compounds is added to the photoresist stripping solution, for preventing Cu wirings from the corrosion.
• etching stopper layer etching stopper layer
• the benzotriazole-based compounds include the ones represented by the following general formula (II): where R 5 and R 6 are each independently a hydrogen atom, a substituted or unsubstituted hydrocarbon group of 1-10 carbon atoms, a carboxyl group, an amino group, a hydroxyl group, a cyano group, a formyl group, a sulfonylalkyl group or a sulfo group; Q is a hydrogen atom, a hydroxyl group or a substituted or unsubstituted hydrocarbon group of 1-10 carbon atoms provided that said hydrocarbon group may have an amide bond or ester bond in the structure, an aryl group or the group represented by the following formula (III): wherein R 7 represents an alkyl group of 1-6 carbon atoms; and R 8 and R 9 are each independently a hydrogen atom, a hydroxyl group or a hydroxyalkyl group or an alkoxyalkyl group of 1-6 carbon atoms.
• each of the hydrocarbon groups may be an aromatic hydrocarbon group or an aliphatic hydrocarbon group, may be saturated or unsaturated, and may be a linear group or a branched group.
• Examples of a substituted hydrocarbon group include hydroxyalkyl groups and alkoxylalkyl groups.
• Q in the above general formula (II) is a group represented by the formula (III).
• R 8 and R 9 are independently a hydroxyalkyl group or an alkoxyalkyl group of 1-6 carbon atoms.
• Q preferably forms a water-soluble group and to give specific examples, a hydrogen atom, an alkyl group of 1-3 carbon atoms (i.e., methyl, ethyl, propyl or isopropyl), a hydroxyalkyl group of 1-3 carbon atoms and a hydroxyl group are particularly preferred from the viewpoint of effective protection of inorganic material layer, such as a polysilicon film, an amorphous silicon film, etc. against corrosion.
• benzotriazole-based compounds include benzotriazole, 5,6-dimethylbenzotriazole, 1-hydroxybenzotriazole, 1-methylbenzotriazole, 1-aminobenzotriazole, 1-phenylbenzotriazole, 1-hydroxymethylbenzotriazole, 1-benzotriazole-methyl carboxylate, 5-benzotriazole-carboxylic acid, 1-methoxybenzotriazole, 1-(2,2-dihydroxyethyl)benzotriazole, 1-(2,3-dihydroxypropyl)benzotriazole, and products of “IRGAMET” series marketed from Ciba Specialty Chemicals, such as 2,2′- ⁇ [(4-methyl-1H-benzotriazol-1-yl)methyl]imino ⁇ bisethanol, 2,2′- ⁇ [(5-methyl-1H-benzotriazol-1-yl)methyl]imino ⁇ bisethanol, 2,2′- ⁇ [(4-methyl-1H-benzotriazol-1-y
• 1-(2,3-dihydroxypropyl)benzotriazole 2,2′- ⁇ [(4-methyl-1H-benzotriazol-1-yl)methyl]imino ⁇ bisethanol, 2,2′- ⁇ [(5-methyl-1H-benzotriazol-1-yl)methyl]imino ⁇ bisethanol, etc.
• the benzotriazole-based compounds may be used either individually or in combination.
• the mercapto group containing compound is preferably of such a structure that a hydroxyl group and/or a carboxyl group is present in either ⁇ -position or ⁇ -position on the carbon atom binding to the mercapto group.
• preferred examples of such compound include 1-thioglycerol, 3-(2-aminophenylthio)-2-hydroxypropylmercaptan, 3-(2-hydroxyethylthio)-2-hydroxypropylmercaptan, 2-mercaptopropionic acid and 3-mercaptopropionic acid.
• 1-thioglycerol is used with particular preference.
• Mercapto group containing compounds may be used either singly or in admixture.
• the amount of the compounds to be in the solution may vary depending on the type of the solution.
• the amount of each compound is preferably from 0.1 to 10% by mass or so, more preferably from 0.5 to 5% by mass or so.
• the uppermost limit of the total amount of the compounds is preferably at most 15% by mass or so.
• the stripping solution of the invention may further contain, as an optional component, an acetylene alcohol/alkylene oxide adduct prepared by adding an alkylene oxide to an acetylene alcohol.
• acetylene alcohol as described above, use may be preferably made of compounds represented by the following general formula (IV): wherein R 10 is a hydrogen atom or a group represented by the following formula (V): and R 11 , R 12 , R 13 and R 14 are each independently a hydrogen atom or an alkyl group having 1-6 carbon atoms.
• acetylene alcohols are commercially available under trade names of “Surfynol” and “Olfin” series (both are produced by Air Product and Chemicals Inc.). Of these commercial products, “Surfynol 104”, “Surfynol 82” or mixtures thereof are most preferred for the physical properties. Use can be also made of “Olfin B”, “Olfin P”, “Olfin Y”etc.
• alkylene oxide to be added to the acetylene alcohol as described above it is preferable to use ethylene oxide, propylene oxide or a mixture thereof.
• acetylene alcohol/alkylene oxide adduct compounds represented by the following general formula (VI): wherein R 15 is a hydrogen atom or a group represented by the following formula (VII): and R 16 , R 17 , R 18 and R 19 are each independently a hydrogen atom or an alkyl group having 1-6 carbon atoms; (n+m) is an integer of 1 to 30, which is the number of ethylene oxide molecules added. This number subtly affects the properties of the compound such as water solubility and surface tension.
• acetylene alcohol/alkylene oxide adducts per se are known as surfactants. These products are commercially available under the trade names of “Surfynol” series (products of Air Product and Chemicals Inc.) and “Acetylenol” series (products of Kawaken Fine Chemicals Co., Ltd.) and have been appropriately utilized.
• a mixture of “Acetylenol EL” with “Acetylenol EH” in a mass ratio of 2:8 to 4:6 is particularly desirable.
• acetylene alcohol/alkylene oxide adduct makes it possible to improve the penetrating properties and wetting properties of the stripping solution.
• the stripping solution according to the invention contains the acetylene alcohol/alkylene oxide adduct, the amount thereof is preferably 0.05-5% by mass, more preferably 0.1-2% by mass.
• the photoresist stripping solution of the invention can advantageously be used with all photoresists, whether negative- or positive-working, that can be developed with aqueous alkaline solutions.
• photoresists include, but are not limited to, (i) a positive-working photoresist containing a naphthoquinonediazide compound and a novolak resin, (ii) a positive-working photoresist containing a compound that generates an acid upon exposure, a compound that decomposes with an acid to have a higher solubility in aqueous alkali solutions, and an alkali-soluble resin, (iii) a positive-working photoresist containing a compound that generates an acid upon exposure and an alkali-soluble resin having a group that decomposes with an acid to have a higher solubility in aqueous alkali solutions, and (iv) a negative-working photoresist containing a compound that generates an acid upon illumination with light,
• the photoresist stripping solution is contacted with the substrate after the step (II), to thereby strip and remove the etching residues and the photoresist pattern.
• the method for their contact is not specifically defined, for which, in general, employed is any of a dip method, a paddle method or a spray method.
• the stripping time may be enough so far as the intended stripping may be attained within the period of time.
• the decomposition treatment with ozone water and/or aqueous hydrogen peroxide is carried out prior to the removing step with the stripping solution, and then the stripping treatment is effected by the use of the photoresist stripping solution that contains at least the quaternary ammonium hydroxide mentioned above.
• the method of the invention does not include O 2 plasma ashing treatment, it ensures removal of etching residues and photoresist pattern to a level of advantageous stripping effect that is comparable to or higher than the O 2 plasma ashing treatment, and, in addition, the low-dielectric layers can be protected from corrosion. Accordingly, even when a low-dielectric layer (low-k layer), which is said to have almost no resistance to ashing, is formed on a substrate, the substrate may well be treated according to the method of the invention for stripping photoresist therefrom. Any negative influences, such as changing a dielectric constant of the low-dielectric, corroding the layer, etc., are not occurred.
• the substrate may be rinsed with any conventional organic solvent, water or the like and may be dried.
• the organic solvent is preferably a lower alcohol, more preferably isopropyl alcohol.
• any known method is employable.
• herein employable are a “via-first” method where via holes are first formed and then trenches are formed; and a “trench-first” method where trenches are first formed and then via holes are formed, which, however, are not limitative.
• a low-dielectric layer is etched using a photoresist pattern (first photoresist pattern) serving as a mask to thereby form via holes that connect to the metal layer on a substrate (when the substrate is provided with a barrier layer formed thereon, then the via holes connect to the metal layer through the barrier layer), and then the substrate is contacted with the photoresist stripping solution that is used in the invention to thereby strip away the first photoresist pattern.
• second photoresist pattern is formed on the remaining low-dielectric layer, and the layer is partly etched using the photoresist pattern serving as a mask to thereby form trenches that communicate with the via holes.
• the substrate is contacted with the photoresist stripping solution that is used in the invention to thereby strip away the second photoresist pattern.
• a low-dielectric layer is etched to a predetermined depth thereof using a photoresist pattern (first photoresist pattern) serving as a mask to thereby form trenches, and then the substrate is contacted with the photoresist stripping solution that is used in the invention to thereby strip away the first photoresist pattern.
• first photoresist pattern serving as a mask
• second photoresist pattern is formed on the remaining low-dielectric layer, and using it as a mask, the low-dielectric layer is etched so as to communicate with the trenches, thereby from via holes whose lower part communicates with the Cu layer on the substrate (when a barrier layer is formed on the substrate, then the via holes reach the Cu layer on the substrate via the barrier layer).
• the substrate is contacted with the photoresist stripping solution that is used in the invention to thereby strip away the second photoresist pattern.
• the via holes and the trenches are filled, for example, electroplated with Cu to form multilayered Cu wiring.
• a substrate having a Cu wiring thereon that is overlaid with an SiOC layer (carbon-doped oxide layer; low-k layer) was used.
• a positive photoresist, TDUR-P722 (by Tokyo Ohka Kogyo Co., Ltd.) was coated on the substrate, and heated at 140° C. for 90 seconds to form a photoresist layer, and then selectively exposed to light using S-203B (by Nikon Corp.), then further heated at 140° C. for 90 seconds (post-exposure baking treatment), and developed with an aqueous 2.38 mas. % tetraammonium hydroxide (TMAH) solution to form a photoresist pattern.
• TMAH aqueous 2.38 mas. % tetraammonium hydroxide
• the substrate was contacted with ozone water for 15 minutes.
• the ozone water had been prepared by bubbling ozone gas into pure water for 15 minutes.
• the substrate was dipped (at 60° C. for 30 seconds) in a photoresist stripping solution having the composition as in Table 1 below (stripping solutions A to F).
• the substrate that had been etched in the same manner as in Examples 1 to 6 was contacted with aqueous 30 mas. % hydrogen peroxide heated at 60° C., for 30 minutes, and then dipped (at 60° C. for 30 seconds) in a photoresist stripping solution having the composition as in Table 1 below (stripping solutions A to F).
• the substrate that had been etched in the same manner as in Examples 1 to 6 was treated in the same manner as in Examples 1 to 6 except that the step of contacting it with ozone water was omitted.
• a substrate having a Cu wiring thereon that is overlaid with an SiN layer (barrier layer) and an SiOC layer (carbon-doped oxide layer; low-k layer) was used.
• a positive photoresist, TDUR-P722 (by Tokyo Ohka Kogyo Co., Ltd.) was coated on the substrate, and heated at 140° C. for 90 seconds to form a photoresist layer, and then selectively exposed to light using S-203B (by Nikon Corp.), then further heated at 140° C. for 90 seconds (post-exposure baking treatment), and developed with an aqueous 2.38 mas. % tetraammonium hydroxide (TMAH) solution to form a photoresist pattern.
• TMAH aqueous 2.38 mas. % tetraammonium hydroxide
• the substrate was contacted with ozone water for 15 minutes.
• the ozone water had been prepared by bubbling ozone gas into pure water for 15 minutes.
• the substrate was dipped (at 60° C. for 30 seconds) in a photoresist stripping solution having the composition as in Table 2 below (stripping solutions G to L).
• the substrate that had been etched in the same manner as in Examples 13 to 18 was contacted with aqueous 30 mas. % hydrogen peroxide heated at 60° C., for 30 minutes, and then dipped (at 60° C. for 30 seconds) in a photoresist stripping solution having the composition as in Table 2 below (stripping solutions G to L).
• the substrate that had been etched in the same manner as in Examples 13 to 18 was dipped (at 60° C. for 30 seconds) in a photoresist stripping solution having the composition as in Table 2 below (stripping solutions G to L), but the step of contacting it with ozone water and/or aqueous hydrogen peroxide was omitted.
• the present invention ensures advantageous effects in stripping photoresist films and etching residues even in a process that does not include O 2 plasma ashing treatment in micropatterning of a substrate having at least Cu wiring and a low-dielectric layer thereon, and, in addition, the method for stripping a photoresist of the invention does not have any negative influence on the dielectric constant of the low-dielectric layer and does not corrode the low-dielectric layer.
• the photoresist-stripping method of the invention is suitable to a dual damascene process of micropatterning a substrate that has at least Cu wiring and a low-dielectric layer thereon.
• it is favorable for stripping photoresists in a process not includeing a conventional O 2 plasma ashing step for the production of semiconductor devices such as ICs, LSIs, etc.

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