Classifications

• • C—CHEMISTRY; METALLURGY
  • C11—ANIMAL OR VEGETABLE OILS, FATS, FATTY SUBSTANCES OR WAXES; FATTY ACIDS THEREFROM; DETERGENTS; CANDLES
  • C11D—DETERGENT COMPOSITIONS; USE OF SINGLE SUBSTANCES AS DETERGENTS; SOAP OR SOAP-MAKING; RESIN SOAPS; RECOVERY OF GLYCEROL
  • C11D7/00—Compositions of detergents based essentially on non-surface-active compounds
  • C11D7/02—Inorganic compounds
  • C11D7/04—Water-soluble compounds
  • C11D7/06—Hydroxides
• • C—CHEMISTRY; METALLURGY
  • C11—ANIMAL OR VEGETABLE OILS, FATS, FATTY SUBSTANCES OR WAXES; FATTY ACIDS THEREFROM; DETERGENTS; CANDLES
  • C11D—DETERGENT COMPOSITIONS; USE OF SINGLE SUBSTANCES AS DETERGENTS; SOAP OR SOAP-MAKING; RESIN SOAPS; RECOVERY OF GLYCEROL
  • C11D7/00—Compositions of detergents based essentially on non-surface-active compounds
  • C11D7/50—Solvents
  • C11D7/5004—Organic solvents
  • C11D7/5013—Organic solvents containing nitrogen
• • C—CHEMISTRY; METALLURGY
  • C11—ANIMAL OR VEGETABLE OILS, FATS, FATTY SUBSTANCES OR WAXES; FATTY ACIDS THEREFROM; DETERGENTS; CANDLES
  • C11D—DETERGENT COMPOSITIONS; USE OF SINGLE SUBSTANCES AS DETERGENTS; SOAP OR SOAP-MAKING; RESIN SOAPS; RECOVERY OF GLYCEROL
  • C11D7/00—Compositions of detergents based essentially on non-surface-active compounds
  • C11D7/22—Organic compounds
  • C11D7/26—Organic compounds containing oxygen
  • C11D7/263—Ethers
• • C—CHEMISTRY; METALLURGY
  • C11—ANIMAL OR VEGETABLE OILS, FATS, FATTY SUBSTANCES OR WAXES; FATTY ACIDS THEREFROM; DETERGENTS; CANDLES
  • C11D—DETERGENT COMPOSITIONS; USE OF SINGLE SUBSTANCES AS DETERGENTS; SOAP OR SOAP-MAKING; RESIN SOAPS; RECOVERY OF GLYCEROL
  • C11D7/00—Compositions of detergents based essentially on non-surface-active compounds
  • C11D7/22—Organic compounds
  • C11D7/26—Organic compounds containing oxygen
  • C11D7/267—Heterocyclic compounds
• • C—CHEMISTRY; METALLURGY
  • C11—ANIMAL OR VEGETABLE OILS, FATS, FATTY SUBSTANCES OR WAXES; FATTY ACIDS THEREFROM; DETERGENTS; CANDLES
  • C11D—DETERGENT COMPOSITIONS; USE OF SINGLE SUBSTANCES AS DETERGENTS; SOAP OR SOAP-MAKING; RESIN SOAPS; RECOVERY OF GLYCEROL
  • C11D7/00—Compositions of detergents based essentially on non-surface-active compounds
  • C11D7/22—Organic compounds
  • C11D7/32—Organic compounds containing nitrogen
  • C11D7/3209—Amines or imines with one to four nitrogen atoms; Quaternized amines
• • C—CHEMISTRY; METALLURGY
  • C11—ANIMAL OR VEGETABLE OILS, FATS, FATTY SUBSTANCES OR WAXES; FATTY ACIDS THEREFROM; DETERGENTS; CANDLES
  • C11D—DETERGENT COMPOSITIONS; USE OF SINGLE SUBSTANCES AS DETERGENTS; SOAP OR SOAP-MAKING; RESIN SOAPS; RECOVERY OF GLYCEROL
  • C11D7/00—Compositions of detergents based essentially on non-surface-active compounds
  • C11D7/22—Organic compounds
  • C11D7/32—Organic compounds containing nitrogen
  • C11D7/3281—Heterocyclic compounds

Definitions

• This invention relates to improved resist stripping compositions and to processes for stripping resists from substrates using said stripping compositions and is more particularly concerned with stripping compositions com ⁇ prising a lactone or lactam as principal component and a quaternary ammonium hydroxide as minor component and with processes for stripping resists from substrates using said compositions.
• Various types of resist materials are employed to protect selected areas of a substrate, such as a wafer for microelectronics fabrication, whilst the substrate is subjected to processing such as pattern generation by techniques including etching, ion implantation, metal deposition and the like.
• processing such as pattern generation by techniques including etching, ion implantation, metal deposition and the like.
• This step is generally accomplished by the use of stripper solvent compositions. It is essen ⁇ tial that the stripper remove the resist completely i.e., without leaving any residue, and that this be done with ⁇ out the necessity for scrubbing or like abrasive techni ⁇ ques which could cause damage to the substrate. It is also necessary that the stripping composition be free of any material which could cause corrosion of the substrate or affect the latter deleteriously in any manner.
• stripper compositions have been disclosed in the prior art.
• stripper compositions have been described containing one or more components such as halogenated hydrocarbons (methylene chloride, tetrachloroethylene) , phenols and phenolic compounds. glycol ethers, ketones, (acetone, methylethyl ketone), dioxane, sulfonic acids and the like.
• halogenated hydrocarbons methylene chloride, tetrachloroethylene
• phenols and phenolic compounds glycol ethers, ketones, (acetone, methylethyl ketone), dioxane, sulfonic acids and the like.
• resists which have been subjected to pro- cessing such as high temperature post-bake or pattern generation using techniques such as ion implantation using boron ions and the like and deep ultraviolet radia ⁇ tion, are highly cross-linked and extremely resistant to dissolution " in most of the organic solvent strippers con- ventionally employed in the art.
• Extreme measures such as the use of phenolic or chlorinated hydrocarbon sol ⁇ vents at elevated temperatures have been employed hither ⁇ to in order to strip such resists. Such heroic measures are clearly undesirable since they involve considerable hazard to technicians carrying out the stripping as well as presenting potential pollution and environmental pro ⁇ blems in the disposal of the resulting waste products.
• compositions containing pyrrolidones such as N-methylpyrrolidone as active ingredient have been described.
• U.S. Patent 3,673,099 describes a stripper composition for removing cure resins such as silicones and polyvinylcinnamate from sub strates.
• the composition comprises a mixture of N-methyl 2-pyrrolidone, a strong base and optionally ethylene gly col mono-ethyl ether.
• U.S. Patent 4,276,186 discloses composition comprising N-methyl-2-pyrrolidone and a alkanolamine for cleaning substrates such as integrate circuit carriers to remove contaminants such as solde flux.
• U.S. Patent 4,428,871 describes a stripper composi ⁇ tion which is a mixture of about 55 to 80 percent b weight of pyrrolidone or certain N-substituted pyrroli ⁇ dones and about 20 to 45 percent by weight of diethylene glycol monoalkyl ether. It is specifically stated that N-methylpyrrolidone alone has proved not effective as a .stripper for certain positive resists and that the mix ⁇ tures disclosed in the patent are more effective than either of the components when used alone. The disclosure and experimental data in the patent are confined to the stripping of positive photoresists.
• the speci ⁇ fication states that the stripper compositions are effec ⁇ tive at about 75°C or less the bulk of the data was derived using stripping temperatures of 75°C with only 3 exceptions each carried out at 25°C. Of the latter 3 experiments only one resulted in 100 percent removal of photoresist. Further, all the data was derived using photoresists which had been baked at 150°C for 45 minutes to 1 hour. No data is given for photoresists baked at higher temperatures. In actual practice, the photo ⁇ resists are frequently exposed to temperatures signifi ⁇ cantly in excess of 150°C and even as high as 220°C, during the processing of a substrate to achieve pattern generation using the techniques discussed previously.
• Bendz et al U.S. Patent 4,078,102 is directed to a process for stripping resists from a substrate using an alcoholic solution of an inorganic base in admixture with an aldehyde or ketone.
• Zuber U.S. Patent 4,202,703 teaches the use of an alcoholic solution of tetramethylammonium hydroxide to strip certain types of resist.
• the resist is subjected to a pretreatment with hot (110 - 125°C) solvent and a post rinse with 1,1,1-tri- chloroethane thus indicating that treatment with the quaternary ammonium hydroxide solution alone does not suffice to achieve satisfactory stripping.
• Sizensky U.S. Patent 4,617,251 describes a process for stripping positive resists using a mixture of certain amines and an organic polar solvent which latter can be N-methylpyrrolidone. The process is said to be effective in stripping resists which have been post-baked at temper- atures above about 150 ⁇ C.
• Example 21 shows the use of aqueous tetramethylammonium hydroxide as a developer of the resist image.
• R is selected from the group consist ⁇ ing of hydrogen, lower-alkyl, cycloalkyl, and sub ⁇ stituted cycloalkyl;
• R ⁇ R 2 and R3 represent alkyl and R 4 is selected from the group consisting of alkyl, hydroxyalkyl and aralkyl;
• component (a) is the major component of the mixture and component (b) is present in an amount of about 2 to about 25 percent by weight and said composition is free from extraneously added water.
• the invention also comprises a process for stripp- ing an organic polymer photoresist from a substrate by subjecting said photoresist to the action of a photo ⁇ resist stripping composition of the invention.
• alkyl as used herein means an alkyl group of from 1 to 12 carbon atoms, inclusive, such as methyl, ethyl, propyl, butyl, pentyl, hexyl, octyl, decyl, dodecyl and isomeric forms thereof.
• lower-alkyl means those alkyl groups having from 1 to 6 carbon atoms, inclusive.
• hydroxyalkyl means alkyl as defined above substituted by a hydroxyl group.
• aralkyl as used herein means a lower- alkyl group as herein defined having at least one hydro ⁇ gen atom substituted by aryl.
• aryl e.g., benzyl, phenethyl, phenylpropyl, naphthyl-methyl, benzhydryl and the like.
• cycloalkyl as used herein means cyclo- butyl, cyclopentyl, cyclohexyl, cycloheptyl and cyclo- octyl.
• substituted cycloalkyl means cyclo ⁇ alkyl substituted by one or more polar groups such as hydroxy. While the compositions and process of the inventio can be employed to strip a wide variety of resist mater ⁇ ials from a wide variety of substrates known in the art they are particularly adapted for use in stripping posi ⁇ tive photoresists from wafers employed in fabrication of microelectronic circuitry.
• Illustrative of the latter substrates are silicon wafers whose surface has been treated to form a layer of silicon oxide, aluminum, alloys of aluminum with copper and like metals, chromium, chromium alloys, silicon nitride and the like.
• compositions of the inven ⁇ tion comprise as the principal active ingredients a quaternary ammonium hydroxide of formula (II) above and a member (a) selected from a pyrrolidone of formula (I), butyrolactone and caprolactone.
• a quaternary ammonium hydroxide of formula (II) above and a member (a) selected from a pyrrolidone of formula (I), butyrolactone and caprolactone.
• the latter compound is always the major component of the mixture while the compound of formula (II) is present in minor amount such that the ratio by weight of component (a) to component (b) generally lies within the range of about 50:1 to about 4:1.
• the member (a) is generally present in the admixture in an amount corresponding to about 70 to 98 percent by weight.
• the compound of formula (I) is present in an amount corresponding to about 2 to about 25 percent by weight.
• the remainder of the admixture, if any, is made up of minor amounts of optional components which will be discussed hereinafter.
• Illustrative of compounds having the formula (II) are tetramethylammonium hydroxide, tetraethylammonium hydroxide, tetrabutylammonium hydroxide, tetrapentyl- ammonium hydroxide, ethyl trimethylammonium hydroxide, tetrahexylammonium hydroxide, benzyltrimethylammonium hydroxide, decyl trimethylammonium hydroxide and the like. Two or more such compounds can be employed in admixture if desired.
• a preferred composition of the invention is one in which component (a) is N-methylpyrrolidone.
• a parti ⁇ cularly preferred composition of the invention is one in which component (a) is N-methylpyrrolidone and the com ⁇ pound of formula (II) is tetramethylammonium hydroxide or tetrabutylammonium hydroxide.
• the ratio by weight of N-methylpyrrolidone to compound of formula (II) is advantageously of the order of about 49:1 to about 9:1 and preferably about 25:1 to about 15:1.
• compositions of the invention there can be present various optional components including surfactants, diluents and other additives.
• the surfactants employed in the compositions of the invention are generally of the non-ionic type and can include any • of those conventionally employed in the art to increase the water rinsability of the compositions after the stripping step has been completed.
• Illustra ⁇ tive of such surfactants are poly(alkylene oxides) , poly- alkoxylated alcohols and the like of which those avail- able from Rohm and Haas under the tradename Triton X-405 and from Union Carbide Corporation under the tradename Tergitol NP 10 are typical.
• Such surfactants are generally employed in amounts in the range of about 0.1 to about 5.0 percent by weight in the compositions of the invention.
• non-ionic surfactants when employed in the compositions of the invention, also serve to increase significantly the stripping rate of the com ⁇ positions of the invention i.e. they serve to reduce markedly the total time taken to strip a resist in an given instance.
• Illustrative of surfactants which hav been found to possess this stripping rate enhancemen property are the polyalkoxylated alcohols such as th polyethoxylated alkanol which is available from Unio Carbide Corporation under the tradename Tergitol Minifoa IX.
• rate-enhancing surfactants are generall employed in amounts in the range of about 1 to about 1 percent by weight and preferably about 3 to about percent by weight, based on total weight of th composition.
• an additive which serves to minimize or inhibit any tendency of the compositions of the invention to attack metallic substrates such as copper, aluminum and the like from which resists are to be stripped.
• metal corrosion inhibitors which can be employed for this purpose are phosphate esters such as the cocoamine oxide phosphate ester which is available commercially under the tradename KCAO Jordaphas from Jordan Chemical Company, metasilicic acid (H 2 SiC"3), and the like.
• phosphate esters such as the cocoamine oxide phosphate ester which is available commercially under the tradename KCAO Jordaphas from Jordan Chemical Company, metasilicic acid (H 2 SiC"3), and the like.
• These additives are advantageously present in the compositions of the invention in an amount of about 0.1 to about 5.0 percent by weight, and preferably from about 1 to about 1.5 percent by weight, based on total weight of the compositions.
• compositions of the invention may also contain one or more diluents provided that said diluents are free from corrosive properties, do not attack the substrate, do not present any significant toxicity or environmental hazards, or interfere in any way with the efficacy of the compositions of the invention as resist strippers.
• diluents can be present in the compositions of the inven- tion in amounts up to about 85 percent by weight based on -10- total weight of the compositions of the invention. Th actual amount of such diluents employed in any give instance will vary depending on the relative ease wit which the particular resist can be stripped.
• diluents are polar organic solvents such as glycols of which ethylene glycol, pro- pylene glycol, dipropylene glycol, tripropylene glycol, tetrapropylene glycol and the like are typical; glycol mono-alkyl ethers such as the monomethyl, monoethyl, mono- propyl and mono-hexyl ethers of diethylene glycol and dipropylene glycol; glycol esters such as ethyleneglycol mono-acetate, ethyleneglycol diacetate, and the like; and glycol ether esters such as 2-ethoxyethyl acetate (cello- solve acetate), 2-butoxyethyl acetate (butylcellosolve acetate) and the like.
• These diluents can be employed alone or in mixtures of two or more provided that the total amount of diluent employed is within the above stated range.
• compositions of the invention are the mono-lower-alkyl ethers of dipropylene glycol.
• the mono-methyl ether of dipropylene glycol is a particularly preferred diluent.
• the compositions of the invention can be employed to strip any of a wide variety of resists, including both positive and negative photoresists and especially includ ⁇ ing highly cross-linked resists which are difficult to strip using conventional solvents, from a substrate after the resist has performed its protective function in respect of the substrate.
• the stripping of the resist is the final step in a process which includes the following steps.
• the substrate is first coated with a layer of the resist and an image is developed in the photoresist layer by exposure of the latter to actinic radiation via an appropriate mask followed by removal of the unexposed material (in he case of a negative resist) or the exposed material (in the case of a positi resist) using the appropriate developer.
• the substra with photoresist image formed thereon is generally su jected to a post-bake treatment at temperatures up about 220°C and or other thermal hardening techniqu known in the art as discussed above, before being expos to pattern generation by any of the procedures known the art such as etching, ion implantation doping, met deposition and the like.
• the step of pattern generati may also give rise to exposure of the resist material t elevated temperatures which can reach as high as abou 180 ⁇ C or even higher.
• the resist material i stripped from the substrate using a stripping compositio of the invention.
• this stripping can be accomplishe in many cases at temperatures approximating ambien temperature (circa 20 - 25°C) in a relatively short tim measured in minutes.
• elevate temperatures up to about 145 ⁇ C can be employed in orde that the stripping of the resist can be accomplishe completely in a short period of time i.e., of the orde of about 10 minutes.
• the exact temperature and time a which to employ the stripper composition in any give instance is principally a function of the temperature t which the resist has been exposed during post-bake and o other resist hardening techniques and or pattern genera ⁇ tion. In any event the temperature of stripping shoul be less than the flash point of the stripper composition.
• the mode of contacting the stripper composition with the resist to be stripped is not critical. Advan ⁇ tageously the resist and substrate are sprayed with or immersed in a bath of the stripper composition which is maintained at the appropriate temperature. Completion of stripping can be readily determined by visual inspection of the substrate if necessary using a microscope or like means. When the stripping operation has been completed t substrate is washed with water or dilute aqueous sol tions of surfactant in order to remove any residu stripper composition, the latter being soluble in, o miscible with, water.
• posi tive resists which generally comprise a novolak resin polyacrylamide or acrylic copolymer resin in associatio with photosensitizer such as an ester of l-oxo-2-diazo naphthoquinone-5-sulfonic acid;
• negative resists whic generally comprise polyvinylcinnamates, styrene-malei anhydride and like resins in association with a fre radical generating photoinitiator and a photosensitizer and other types of resist such as polyolefinsulfone base resins of which those described in U.S. Patent 4,513,07 are typical.
• stripper compositions of the invention ar particularly well adapted to the stripping of positiv photoresists which latter are the type of photoresis most commonly employed in fabricating high resolutio geometries in microelectronic applications.
• the stripping compositions possess a number o advantages over those hitherto employed in the art. Thu they are capable of stripping a wide variety of resist from metallic and other substrates without attacking th substrate or any circuitry or the like which may hav been generated on the substrate while the resist was i place thereon.
• the compositions .pose no significan toxicity hazard to qualified personnel handling th same.
• the compositions are miscible with water an therefore readily washed from the substrate after th stripping operation has been completed.
• Resists included ⁇ ing those which are normally resistant to stripping usin conventional solvents at ambient temperature, can b stripped in a very short t.ime, of the order of severa minutes, using bath operating temperatures of the orde of 20 - 25°C, i.e., without the need to employ elevate temperatures.
• the stripping bath is stable and can b re-used many times over a prolonged period without losin its efficacy.
• the stripper compositions of the invention are effective in most cases at temperatures at, or close to, room temperature, it is possible to use a wide range of engineering materials such as low thermal flow plastics and the like in fabricating the stripping bath and accessories such as duct work and like installa ⁇ tions.
• Stripping compositions hitherto employed in the art required higher operating temperatures which involved vaporization of solvents and led in many instances to corrosion of duct work and other equipment with conse ⁇ quent and possibly undesirable contamination of the stripping bath. Operation at temperatures which led to vaporization of stripper also caused change in composi ⁇ tion of the stripping bath where the latter contains two or more components of different volatility.
• Example 1 illustrate specific embodi ⁇ ments of the compositions and process of the invention and the best mode currently known to the inventors for carrying out the same but are not to be construed as limiting.
• Example 1 illustrate specific embodi ⁇ ments of the compositions and process of the invention and the best mode currently known to the inventors for carrying out the same but are not to be construed as limiting.
• a stripper composition of the invention was prepared by admixture of the following components.
• the photoresist image had been baked at 160°C for 1 hour following development.
• a second resist image was produced in exactly the same manner but using a silicon wafer coated with aluminum as the substrate.
• a stripper composition of the invention was pre- pared by admixture of the following components.
• Example 3 A stripper composition of the invention was pre pared using the components and proportions described i Example 2. To the mixture so obtained was added meta silicic acid in an amount corresponding to 1 g. pe gallon of the composition.
• a stripper composition of the invention was pre pared by admixture of the following components:
• Example 5 A stripper composition of the invention was pre ⁇ pared using the components and proportions set forth for the composition of Example 4. To the resulting solution was added metasilicic acid at a rate corresponding to 1 g. per gallon. Aliguots of the above composition were then employed to strip resists from duplicates of the resists (a) - (d) described in Example 1. In each in ⁇ stance the resist and substrate were immersed in a bath of the stripper composition at 75°C and the time required to completely strip the resist was determined. The times so recorded were as follows.
• composition of the invention was prepared by admixture of the following components.
• Tetrabutylammoniura hydroxide 10 . 0 N-methylpyrrolidone 82. . 5 Tergitol Minifoam IX 5. .0 Triton X405 1. .0 Jordaphos KCAO 1. . 5 100.0
• Example 7 A composition of the invention was prepared by admixture of the following components:
• Example 8 A composition of the invention was prepared admixing 5 parts by weight of tetramethylammonium hyd oxide and 95 parts by weight of N-methylpyrrolidone.
• a composition of the invention was prepared admixing 5 parts by weight of choline (trimethyl hyd oxyethyl-a monium hydroxide) and 95 parts by weight N-methylpyrrolidone.
• a composition of the invention was prepared admixing 5 parts by weight of benzyltrimethylammoni hydroxide and 95 parts by weight of N-methylpyrrolidone.
• Example 8 2 minutes 15 minutes
• Example 9 1.5 minutes 12 minutes
• Example 10 1 minute 16 minutes

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• Engineering & Computer Science (AREA)
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• Oil, Petroleum & Natural Gas (AREA)
• Wood Science & Technology (AREA)
• Organic Chemistry (AREA)
• Inorganic Chemistry (AREA)
• Exposure Of Semiconductors, Excluding Electron Or Ion Beam Exposure (AREA)
• Photosensitive Polymer And Photoresist Processing (AREA)

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• 1987
  • 1987-09-10 WO PCT/US1987/002291 patent/WO1988005813A1/en not_active Application Discontinuation
  • 1987-09-10 JP JP63501060A patent/JPH01502059A/ja active Pending
  • 1987-09-10 EP EP19880900899 patent/EP0301044A4/en not_active Withdrawn
  • 1987-09-10 AU AU11582/88A patent/AU1158288A/en not_active Abandoned
  • 1987-09-17 ZA ZA877008A patent/ZA877008B/xx unknown

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