(12) INTERNATIONAL APPLICATION PUBLISHED UNDER THE PATENT COOPERATION TREATY (PCT)
`
`(19) World Intellectual Property Organization
`International Bureau
`
`1111111111111111 IIIIII 111111111111111111111111111111 lllll lllll 11111111111111111111111
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`(43) International Publication Date
`6 November 2003 (06.11.2003)
`
`PCT
`
`(10) International Publication Number
`WO 03/091376 Al
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`(51) International Patent Classification 7: CllD 3/20, 7/26,
`3/30, 7/32, G03F 7/42, H0lL 21/00
`
`(21) International Application Number: PCT/US03/13019
`
`(22) International Filing Date:
`
`24 April 2003 (24.04.2003)
`
`(25) Filing Language:
`
`(26) Publication Language:
`
`English
`
`English
`
`(30) Priority Data:
`60/374,819
`
`24 April 2002 (24.04.2002) US
`
`(71) Applicant: EKC TECHNOLOGY, INC. [US/US]; 2520
`Barrington Court, Hayward, CA 94545-1163 (US).
`
`(72) Inventors: LEE, Shihying; 925 Arrowtail Terrace, Fre(cid:173)
`mont, CA 94536 (US). SMALL, Robert, J.; 11418 Ram(cid:173)
`part DRive, Dublin , CA 94568 (US).
`
`(81) Designated States (national): AE, AG, AL, AM, AT, AU,
`AZ, BA, BB, BG, BR, BY, BZ, CA, CH, CN, CO, CR, CU,
`CZ, DE, DK, DM, DZ, EC, EE, ES, Fl, GB, GD, GE, GH,
`GM, HR, HU, ID, IL, IN, IS, JP, KE, KG, KP, KR, KZ, LC,
`LK, LR, LS, LT, LU, LV, MA, MD, MG, MK, MN, MW,
`MX, MZ, NO, NZ, OM, PH, PL, PT, RO, RU, SC, SD, SE,
`SG, SK, SL, TJ, TM, TN, TR, TT, TZ, UA, UG, UZ, VC,
`VN, YU, ZA, ZM, ZW.
`
`(84) Designated States (regional): ARIPO patent (GH, GM,
`KE, LS, MW, MZ, SD, SL, SZ, TZ, UG, ZM, ZW),
`Eurasian patent (AM, AZ, BY, KG, KZ, MD, RU, TJ, TM),
`European patent (AT, BE, BG, CH, CY, CZ, DE, DK, EE,
`ES, Fl, FR, GB, GR, HU, IE, IT, LU, MC, NL, PT, RO,
`SE, SI, SK, TR), OAPI patent (BF, BJ, CF, CG, CI, CM,
`GA, GN, GQ, GW, ML, MR, NE, SN, TD, TG).
`
`Published:
`with international search report
`before the expiration of the time limit for amending the
`claims and to be republished in the event of receipt of
`amendments
`
`(74) Agents: BALANCIA, Victor, N. et al.; Pennie & Ed(cid:173)
`monds LLP, 1155 Avenue of the Americas, New York, NY
`10036 (US).
`
`For two-letter codes and other abbreviations, refer to the "Guid(cid:173)
`ance Notes on Codes and Abbreviations" appearing at the begin(cid:173)
`ning of each regular issue of the PCT Gazette.
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`0\ (54) Title: OXALIC ACID AS A CLEANING PRODUCT FOR ALUMINIUM, COPPER AND DIELECTRIC SURFACES
`
`TOK Ex. 1014
`PGR Petition
`
`Q ---~ (57) Abstract: THE PRESENT INVENTION PROVIDES A SEMIACQUEOUS CLEANING COMPOSITION FOR USE WITH
`0 1 % TO ABOUT 30% OXALIC ACID DIHYDRATE, BETWEEN ABOUT 0.1 % AND ABOUT 30% OF AN AMINE, AND WA(cid:173)
`> TER, WHEREIN THE CLEANING COMPOSITION CONTAINS LESS THAN ABOUT 0.5% FLUORINE-CONTAINING COM(cid:173)
`
`ALUMINIUM, COPPER, AND LOW-K SUBSTRATES, THE CLEANING COMPOSITION COMPRISING BETWEEN ABOUT
`
`; , POUNDS AND LESS THAN 0.5% PEROXIDES.
`
`

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`WO 03/091376
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`PCT/0S03/13019
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`OXALIC ACID AS A CLEANING PRODUCT FOR ALUMINIUM,
`
`COPPER AND DIELECTRIC SURFACES
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`5
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`BACKGROUND OF THE INVENTION
`
`1. Field of the Invention
`This invention relates to semi-aqueous stripping and cleaning compositions that are
`1 O particularly useful for stripping photoresists and cleaning organic and inorganic compounds
`from a semiconductor substrate, particularly including post etch, post ash residues on
`oxygen plasma treated substrates, and on copper and low-k dielectric wafers. The cleaning
`solutions contain oxalic acid dihydrate and optionally include acids, amines, corrosion
`inhibitors, chelating agents, and surfactants. The invention also relates to a method of using
`15 h
`. .
`b
`t e composition on su strates.
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`25
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`2. Description of Related Art
`During the fabrication of microcircuits, the precise positioning of a number of
`appropriately doped regions on a slice of semiconductor is typically followed by the
`20 positioning of one or more interconnection patterns on the semiconductor. Positively doped
`resists have been extensively used as masking materials to delineate patterns onto a
`substrate so that the patterns can be subsequently etched into, or otherwise defined in, the
`substrate. The final steps in preparing the substrate then involve removing the unexposed
`resist material and any etching residue, if etching was used, from the substrate. It is critical
`that as much as possible of the residue and resist be removed to provide a wafer having
`sufficient integrity for subsequent use of the wafer in microcircuitry.
`A semiconductor integrated circuit has very fine structures. The fine circuits are
`generally fabricated by: uniformly coating a photoresist on an insulating film or a
`conductive film (such as an oxide film, an Cu film, or Al alloy film) coated on a substrate;
`exposing and developing the photoresist to form a certain pattern; etching the substrate, or
`depositing a film thereon, by using the patterned photoresist as a mask; and thereafter
`removing the unnecessary photoresist. Positive photoresists are used as an intermediate
`mask for transferring an original mask pattern of a reticle onto wafer substrates by means of
`a series of photo lithography and plasma etching steps. The etchant gases selectively attack
`the unprotected area of the substrate. Liquid or wet etching chemistries have been used
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`extensively over the years to etch metals, oxides and dielectrics. These chemistries can be
`very aggressive and can result in isotropic etching (etching equally in all directions).
`Increasingly, plasma etching, reactive ion etching or ion milling are used, and such
`etching processes produce undesirable by-products from the interaction of the plasma gases,
`reacted species and the photoresist. The composition of such by-products is generally made
`up of the etched substrates, underlying substrate, photoresist and etching gases. The
`formation of such by-products is influenced by the type of etching equipment, process
`conditions and substrates utilized. These by-products are generally referred to as "sidewall
`polymer," "veil" or "fences" and cannot be removed completely by either oxygen plasma or
`10 conventional solvents.
`One of the steps in the microcircuit manufacturing process is the subsequent
`removal of the patterned photoresist films from substrates. In general, this step is conducted
`by one of two methods. One method involves a wet stripping step in which the
`photoresist-covered substrate is brought into contact with a photoresist stripper solution that
`15 consists primarily of an organic solvent and an amine.
`Stripper solutions, however, cannot completely and reliably remove the photoresist
`films, especially if the photoresist films have been exposed to UV radiation and plasma
`treatments during fabrication. Some photoresist films become highly cross-linked by such
`treatments and are more difficult to dissolve in the stripper solution. In addition, the
`20 chemicals used in these conventional wet stripping methods are sometimes ineffective for
`removing inorganic residual materials formed during the plasma etching of metal or oxide
`layers with halogen-containing gases.
`Sidewall residues have been removed with either acidic organic solvents or alkaline
`organic solvents. The acidic solvents are generally composed of phenolic compounds or
`25 chloro-solvent and/or an aromatic hydrocarbon and/or alkylbenzenesulfonic acids. These
`formulations generally need to be used at temperatures up to and beyond 100°C. These
`chemistries normally need to be rinsed with isopropanol.
`Known photoresist stripper compositions containing a combination of a polar
`solvent and an amine compound include:
`30 1.
`U.S. Pat. No. 4,403,029 describes alkaline/solvent mixtures useful as photoresist
`strippers, but not necessarily cleaners, that include dimethylacetamide or
`dimethylformamide and alkanolamines.
`2.
`U.S. Pat. Nos. 4,428,871, 4,401,747, and 4,395,479 describe cleaners containing
`2-pyrrolidone, dialkylsulfone and alkanolamines.
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`U.S. Pat. No. 4,744,834 describes cleaners containing 2-pyrrolidone and
`3.
`tetramethylammonium hydroxide.
`4.
`U.S. Pat. No. 4,617,251 teaches a pos!tive photoresist stripping composition
`containing (A) a selected amine compound (e.g., 2-(2-aminoethoxy)-ethanol;
`5 2-(2-aminoethylamino )-ethanol; or a mixture thereof) and (B) selected polar solvents ( e.g.,
`N-methyl-2-pyrolidinone, tetrahydrofurfuryl alcohol, isophorone, dimethyl sulfoxide,
`dimethyl adipate, dimethyl glutarate, sulfolane, gamma-butyrolactone,
`N,N-dimethylacetamide or mixtures thereof). The reference further teaches that water as
`well as dyes or colorants, wetting agents, surfactants and antifoamers may be added into this
`l O composition.
`5.
`U.S. Pat. No. 4,770,713 teaches a positive photoresist stripping composition
`containing (A) a selected amide (e.g., N,N-dimethyl acetamide; N-methyl acetamide;
`N,N-diethyl acetamide; N,N-dipropyl acetamide; N,N-dimethyl propionamide; N,N-diethyl
`butyramide or N-methyl-N-ethyl propionamide) and (B) a selected amine compound (e.g.,
`15 monoethanolamine, monopropanolamine, or methyl-aminoethanol). The patent also teaches
`this stripper may optionally contain a water miscible nonionic detergent ( e.g., alkylene
`oxide condensates, amides or semi-polar nonionics).
`6.
`U.S. Pat. No. 4,824,763 teaches positive-working photoresist stripping composition
`containing (A) triamine (e.g., diethylene-triamine) and (B) a polar solvent (e.g.,
`20 N-methyl-2-pyrrolidone, dimethylfonnamide, butyrolactone, aliphatic hydrocarbons,
`aromatic hydrocarbons, or chlorinated hydrocarbons).
`7.
`U.S. Pat. No. 4,904,571 teaches printed circuit board photoresist stripper
`composition containing (A) a solvent ( e.g., water, alcohols, ethers, ketones, chlorinated
`hydrocarbons or aromatic hydrocarbons); (B) an alkaline compound dissolved in said
`25 solvent (e.g., primary amines, secondary amines, tertiary amines, cyclic amines, polyamines,
`quaternary ammonium amines, sulfoniumhydroxides, alkali hydroxides, alkali carbonates,
`alkali phosphates or alkali pyrophosphates); and (C) a borohydride compound dissolved in
`said solvent ( e.g., sodium borohydride, lithium borohydride, dimethyl amine borone,
`trimethyl amine borone, pyridane borone, tert-butyl amine borone, triethyl amine borone, or
`30 morpholine borone).
`8.
`U.S. Pat. No. 5,102,777 teaches a positive photoresist stripper composition
`comprising (A) a solvent (e.g., a pyrrolidone compound, a diethylene glycol monoalkyl
`ether, a sulfur oxide compound, a sulfolane compound or a mixture thereof); (B) an amine
`(e.g., alkanolamine); and (C) a fatty acid (e.g., capric acid, lauric acid, talmitric acid,
`35 caprylic acid, myristic acid, oleic acid, stearic acid, linoleic acid, linolic acid, buthylic acid,
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`abietic acid, isooctoic acid, isohexadecanoic acid, isostearic acid, behenic acid, undecylenic
`acid, hydroxystearic acid, chipanodonic acid, arachidonic acid, oleostearic acid, or
`2-ethylhexadecanilic acid).
`U.S. Pat. No. 5,279,791 teaches a stripping composition for removing resists from
`9.
`substrates containing (A) hydroxylamine; (B) at least one alkanolamine; and optionally (C)
`at least one polar solvent.
`U.S. Pat. No. 5,308,745 teaches an alkaline-containing photoresist stripping
`10.
`composition comprising (A) a stripping solvent ( e.g., 2-pyrrolidinone,
`1-methyl-2-pyrrolidinone, 1-ethyl-2-pyrrolidinone, 1-propyl-2-pyrrolidinone,
`10 1-hydroxyethyl-2-pyrolidinone, 1-hydroxypropyl-2-pyrrolidinone, diethylene glycol
`monoalkyl ethers, dialkyl sulfones, dimethyl sulfoxide, tetrahydrothiophene-1, I-dioxides,
`polyethylene glycol, dimethylacetamide or dimethylformamide; (B) a nucleophilic amine
`( e.g., 1-amino-2-propanol, 2-(2-aminoethoxy) ethanol, 2-aminoethanol,
`2-(2-aminoethylamino)-ethanol or 2-(2-aminoethylamino) ethylamine); and (C) a
`15 non-nitrogen containing weak acid (e.g., acetic acid, phthalic acid, 2-mercaptobenzoic acid,
`2-mercaptoethanol, 1,3,5-trihydroxybenzene, pyrogallol, resorcinol, 4-tert-butylcatechol,
`carbonic acid or hydrofluoric acid).
`11. U.S. Pat. No. 5,334,332 teaches a photoresist resist stripping and cleaning
`composition comprising (A) hydroxylamine; (B) at least one alkanolamine; (C) water; (D)
`20 optionally, at least one polar solvent; and (E) optionally, a chelating reagent ( e.g.,
`thiophenol, ethylenediamine tetraacetic acid or 1,2-dihydroxybenzene) to reduce the surface
`metal contamination on wafers.
`12.
`U.S. Pat. No. 5,399,464 teaches a stripping composition for removing positive
`organic photoresist from a substrate comprising (A) a triamine (e.g., diethylene triamine);
`25 (B) a nonpolar or polar organic solvent (e.g., N-methyl pyrrolidone).
`13.
`U.S. Pat. No. 5,417,802 teaches a material useful for photoresist removal or
`post-metal etch clean up that comprises (A) a primary or secondary amine; (B) a solvent
`(e.g., dimethyl sulphoxide or dimethylacetylamide); and (C) organic ligands such as crown
`ethers or cyclodextrines.
`30 14.
`Japanese Patent Application No. 63-2.08043 teaches a positive-working photoresist
`stripper composition containing (A) 1,3-dimethyl-2-imidazolidinone; (B) a water-soluble
`organic amine ( e.g., monoethanolamine, 2-(2-aminoethoxy)-ethanol, or
`triethylenetetramine ). The application also teaches a surfactant may be added to the
`stripper.
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`Japanese Patent Application No. 64-081949 teaches a positive-working photoresist
`15.
`stripper composition containing (A) a solvent (e.g., gamma-butyrolactone,
`N-methyl-formamide, N,N-dimethylfonnamide, N,N-dimethyl-acetamide or
`N-methylpyrrolidone); (B) an amino alcohol (e.g., N-butyl-ethanolamine or
`5 N-ethyldiethanolamine); and (C) water.
`16.
`Japanese Patent Application No. 4-350660 teaches a stripper for positive
`photoresists comprising (A) 1,3-dimethyl-2-imiclazolidinone (DMI), (B) dimethylsulfoxide
`(DMSO}, and (C) a water-soluble amine (e.g., monoethanolamine or
`2-(2-amino-ethoxy)ethanol), wherein the amount of the water-soluble amine is 7-30% by
`10 weight.
`17.
`Japanese Patent Application No. 1999-197523 describes a stripper composition for
`photoresist used in manufacture of liquid crystal display device that includes 5-15 weight%
`of alkanolamine, 35-55% sulfoxide or sulfone compound, and 35-55 wt.% glycol ether.
`18.
`Japanese Patent Application No. 08087118 describes a stripper composition that
`15 includes 50-90 weight% of alkanolamine, and 50-10% dimethyl sulfoxide or
`N-methyl-2-pyrrolidone.
`19.
`Japanese Patent Application No. 03227009 describes a stripper composition that
`includes ethanolamine and dimethyl sulfoxide.
`20.
`Japanese Patent Application No. 07069619 describes a stripper composition that
`20 includes alkanolamine, dimethyl sulfoxide, and water.
`21.
`U.S. Pat. No. 5,480,585 and Japanese Patent Hei. 5-181753 disclose organic
`strippers comprising alkanolamine, a sulfone compound or a sulfoxide compound, and a
`hydroxyl compound.
`22.
`The Japanese Laid-open Patent No. 4-124668 discloses a photoresist stripping
`25 composition including 20-90% by weight of an organic amine, 0.1-20% by weight of
`phosphoric ester surfactant, 0.1-20% by weight of2-butyne-1,4-diol, and the remainder
`glycol monoalkylether and/or an aprotic polar solvent.
`23.
`The Japanese Laid-open Patent Sho. 64-42653 discloses a photoresist stripping
`composition comprising over 50% by weight of dimethylsulfoxide (more desirably over
`30 70% by weight), 1 to 50% by weight of a solvent such as diethyleneglycol monoalkylether,
`diethyleneglycol dialkylether, gamma-butyrolactone or l,3-dimethyl-2imidazoledinone, and
`0.1-5% by weight of a nitrogen-including organic hydroxyl compound, such as
`monoethanolamine. The reference recites that the amount of dimethylsulfoxide less than
`50% by weight causes great reduction in stripping force, while the amount of
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`nitrogen-including organic hydroxyl compound solvent over 5% by weight corrodes the
`metal ( e.g., aluminum) film.
`24.
`U.S. Pat. No. 5,091,103 to Dean et al. teaches a positive photoresist stripping
`composition containing: (A) N-alkyl-2-pyrrolidone; (B) 1,2-propanediol; and (C)
`tetraalkylammonium hydroxide.
`25.
`Japanese Patent Application No. 10028482 describes a cleaning composition that
`includes an oxidizing agent, for example a peroxide, and an organic acid, for example
`formic acid, acetic acid, oxalic acid, or maleic acid. After cleaning, residual resist are
`removed with a stripper.
`10 26.
`Japanese Patent Application No. 08050018 describes a cleaning composition that
`includes a chelating agent, for example citric acid, oxalic acid, or EDTA, and a
`photocatalyst, for example titanium oxide, SnO2, WO3, or SiO2.
`27.
`Japanese Patent Application No. 06056109 describes a method of preparing
`electrolysis water that includes adding at most 0.08 moles per liter of an organic salt, for
`15 example ammonium oxalate.
`28.
`Japanese Patent Application No. 0901475 filed July 28, 1997, describes a cleaning
`composition for semiconductors that includes a fluorine-containing compound, a water(cid:173)
`soluble organic solvent, an organic or inorganic acid, and optionally an organic acid
`ammonium salt to clean ashed resist from a semiconductor.
`20 29.
`U.S. Patent No. 5,780,406 describes a non-corrosive cleaning composition for
`removing plasma etching residues that includes water; an hydroxylammonium compound,
`for example bi- or triethylamine compound, bi- or triethanolamine and the like; a basic
`compound selected from amines and quaternary ammonium hydroxides, and optionally a
`chelating agent and/or surfactant, wherein the pH is between 2 and 6.
`25 30.
`U.S. Patent No. 5,630,904 describes a cleaning composition for removing dry
`etching photoresist residues that includes 5% to 50% of an organocarboxylic ammonium
`salt or amine carboxylate, and from 0.5% to 15% of a fluorine compound.
`31. WO - 09800244 describes a wafer cleaning composition that has 2-98% of a
`chelating agent, for example malonic acid, oxalic acid, or tetrafluoroacetic acid; and 2-98%
`30 of a solvent, such as water, NMP, or BLO.
`32.
`EP 00474053 Bl describes a cleaner having from 51 % to 95% of a liquid
`hydrocarbon solvent, excluding terpene; 1 to 25% of a nonionic ethoxylate emulsifier; and 1
`to 25% of a dibasic ester of dicarboxylic acids, for example oxalic acid, malonic acid, adipic
`acid, and the like.
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`U.S. Patent 6,030,932 describes a cleaning composition for removing photoresist,
`33.
`plasma etch, and CMP residue that includes an hydroxylamine or an amine, a fluorine(cid:173)
`containing c.ompound, and water.
`34.
`U.S. Patent No. 5,800,726 describes a etching composition that includes 10-25
`5 grams EDTA, 15-3 5 grams of a salt of phosphoric acid, 25-45 grams oxalic acid, and a liter
`of 30% hydrogen peroxide.
`Such stripping compositions, however, have only proven successful in cleaning
`"sidewall polymer" from the contact openings and metal line etching in simple microcircuit
`manufacturing involving a single layer of metal process when the metal structure involves
`IO mainly Al--Si or Al--Si--Cu and the "sidewall polymer" residue contains only an
`organometallic compound with aluminum. Many of the stripping and cleaning compounds
`are incompatable with, i.e., cause excessive etching, swelling, or change in the refractive
`index (RI) of copper, copper-ER, or a variety oflow-k substrates.
`Depending on the constituents of the compositions and the ratio thereof, the
`15 aforementioned stripping compositions exhibit greatly different characteristics in
`photoresist stripping force, metal corrosion properties, the complexities of a rinsing process
`following the stripping, environmental safety, workability and price.
`If etching residue is not removed from the substrate, the residue can interfere with
`subsequent processes involving the substrate. The need to effectively remove etching
`20 residue and photoresist from a substrate becomes more critical as the industry progresses
`into submicron processing techniques. The requirement for cleaning solutions that remove
`all types of residue generated as a result of plasma etching of various types of metals, such
`as aluminum, aluminum/silicon/copper, titanium, titanium nitride, titanium/tungsten,
`tungsten, silicon oxide, polysilicon crystal, etc., while not corroding the underlying metal
`25 presents a need for more effective chemistry in the processing area. The effect of poor
`cleaning results in low device yield, low device reliability, and low device performance.
`Also, if the components in these residues are not removed or neutralized in some
`manner then the residues will absorb moisture and fonn acidic species that can corrode the
`metal structures. The resultant acid corrodes wiring materials to bring about an adverse
`30 effect such as an increase in electrical resistance and wire disconnection. Such problems
`frequently occur, in particular in aluminum and aluminum alloys generally used as wiring
`material. The wafer substrate in contact with acidic materials, if not controlled, can destroy
`the metal structures. Following completion of the etching operation it is necessary that the
`post-etch resist mask be removed from the protective surface to permit finishing operations.
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`An alternative method of removing photoresist film involves exposing a
`photoresist-coated wafer to oxygen plasma in order to burn the resist film from the substrate
`surface in a process known as oxygen plasma ashing. Oxygen plasma ashing has become
`more popular in the microcircuit manufacturing process because it is carried out in a
`5 vacuum chamber and, hence, is expected to be less susceptible to airborne particulate or
`metallic contamination. Oxygen plasma ashing, however, is not fully effective in removing
`plasma-etching residues noted above. Instead, removal of these plasma-etching residues
`must be accomplished by subsequently exposing the photoresist film to certain solutions.
`Generally, this exposure at least consists of first rinsing the substrate with an organic
`10 solvent (most commonly isopropyl alcohol) followed by a second rinsing operation with
`deionized water. Besides isopropyl alcohol, specific teachings of alternative organic solvent
`rinse solutions are described in U.S. Pat. Nos. 4,786,578 (Neisius et al.) (an organic base
`such as triethanolamine in combination with a non:ionic surfactant); 4,824,762 (Kobayashi
`et al.) (an ether and optionally, an amine compound such as monoethanolamine); and
`15 5,174,816 (Aoyama et al.) (an aqueous solution of a quarternary ammonium hydroxide in
`combination with a sugar or sugar alcohol). The use of such organic solvent-containing
`rinses, however, are not necessarily desirable because they add complexity to the photoresist
`removal operation and generate additional solvent waste.
`Other commercial products are also available to clean the post-etch residues left by
`20 plasma etching followed by oxygen ashing. For example, EKC 265 {TM), available from
`EKC Technology, Inc., is a plasma etching cleaning solution composed of water,
`alkanolamine, catechol and hydroxylamine. Catechol is not very effective under acidic
`conditions. Therefore, EKC 265 can badly corrode copper especially when used with low K
`films. Such a composition is disclosed in U.S. Pat. No. 5,279,771 to Lee. ACT 935 (TM),
`25 available from Ashland Chemical, is another plasma etching cleaning solution and is
`composed of water, alkanolamine and hydroxylamine. In both cases, hydroxylamine may
`be used as a corrosion inhibitor. R-10 (TM), a post-strip rinse available from Mitsubishi
`Gas Chemical, is composed of water, alkanolamine and a sugar alcohol, wherein the sugar
`alcohol acts as a corrosion inhibitor.
`Although these commercial products can effectively dissolve plasma-etching
`residues, the combination of water and alkanolamine contained therein can also attack the
`metallic layers deposited pattemwise on the substrate. The addition of a corrosion inhibitor
`to these products can mitigate to a certain extent the unwanted attack on the metallic layers
`and oxide layers deposited on the substrate. However, since these products have a pH
`35 above 11, even in the presence of a corrosion inhibitor, they may attack certain
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`corrosion-sensitive metal layers. Particularly, metal layers such as aluminum or aluminum
`alloys ( e.g., Al Cu Si), titanium nitride, titanium tungsten and the like are particularly
`corrosion sensitive. Furthermore, while the addition of a suitable corrosion inhibitor is
`essential to prevent corrosion of the substrate metal layers, the corrosion inhibitor must not
`inhibit the removal of the plasma-etching residue.
`Commercial cleaning solutions were tested on an oxide/SiLK wafer after
`delamination was observed in SiLK CMP when commercial products were utilized. Cleaved
`sample pieces were immersed in the solutions for two minutes at room temperature, and
`extensive delamination was somewhat visible.
`It is difficult to balance effective plasma etching residue removal and corrosion
`inhibition because chemical compositions of the plasma etching residues are generally
`similar to those of the metal layers or oxide layers on the substrate. The alkanolamine used
`in the prior art cleaning compositions was oftentimes found to attack both the plasma
`etching residues and the substrate metal layers in the presence of water. Moreover, if a
`15 post-cleaner rinse (such as isopropyl alcohol) was not used, the corrosion could be very
`severe. In addition, some types of the corrosion inhibitors have been found to retard plasma
`etching residue removal. There has also always been a tradeoff between speed of plasma
`etching residue removal and substrate metal layer corrosion inhibition. Accordingly, there
`remains a need for a method of quickly and effectively removing the cured photoresist and
`20 plasma etching residues without causing metal layer corrosion.
`The demand for new wafer cleaning technology for use after etching and resist
`removal increases as the industry enters into submicron processing techniques. The
`requirem~nt for a cleaning solution to remove all types of residue generated as a result of
`plasma etching of various types of metals (e.g., aluminum, aluminum/silicon/copper,
`25 titanium, titanium nitride, titanium/tungsten, tungsten, silicon oxide, polysilicon crystal,
`etc.) presents a need for more effective chemistry in the processing area. It is believed that
`the present invention offers a solution to that need.
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`30
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`SUMMARY OF THE INVENTION
`Accordingly, the present invention is directed to semiaqueous cleaning compositions
`including oxalic acid and water for use in removing post-etch residues remaining on
`substrate surfaces after oxygen plasma treatment, and a method of using the compositions to
`remove photoresist, .
`The compositions alternatively, additionally, or optionally include: other acids, e.g.,
`35 dicarboxylic, monocarboxylic, hydroxy-carboxylic, amino-carboxylic, sulfano-carboxylic,
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`amino-sulfano, and inorganic acids; amines, e.g., primary/secondary/tertiary amines, and
`hydroxylamines, alkanolamines.
`Specific examples of compounds advantageously included include:maleic, ascorbic,
`glycolic, and sulfamic acids; monoethanolamine (MEA), diethanolamine, propylamine,
`5 choline hydroxide, ammonium hydroxide.
`Other optional components include: corrosion inhibitors, e.g., benzotriazole,
`thiourea, ammonium bisulfite, choline bisulfite, propylene glycol, glycerol, sorbitol,
`gelatine, starch, phosphoric acid, silicic acid polyethylene oxide, and polyethylene imine;
`chelating agents, e.g., dicarboxylic acids, hydroxy-carboxylic acids, amino-carboxylic acids,
`10 diamine, polyalcohol, polyethylene oxide and polyamine/imine; and surfactants, e.g.,
`polyvinyl alcohol, polyethylene oxide, polyethylene imine, polyalcohol, polyether, and
`polyamine/imine.
`The invention further contemplates a method of using semiaqueous cleaning
`compositions including oxalic acid and water to remove post-etch residues from substrates
`15 including, but not limited to, conventional aluminum metal line/pad or oxide wafers,
`aluminum/low-k dielectric wafers, advanced copper/low-k dielectric wafers, and advanced
`compound semiconductor wafers such as gallium arsenide {GaAs) or indium phosphide
`(InP).
`
`One embodiment includes a semiaqueous cleaning composition for use with
`20 aluminum, copper, and low-k substrates, the cleaning composition comprising between
`abo_ut 1 % to about 30% oxalic acid dihydrate, between about 0.1 % and about 30% of an
`amine, and water, wherein the cleaning composition contains essentially no, i.e., less than
`about 0.5%, preferably less than 0.1 %, of fluorine-containing compounds and less than
`0.5% peroxides. Another embodiment includes a semiaqueous cleaning composition which
`25 additionally comprising a second organic acid, an inorganic acid, or mixture thereof,
`wherein the pH of the composition is between about 2 and 12. The organic acid is selected
`from dicarboxylic, monocarboxylic, hydroxy-carboxylic, amino-carboxylic, sulfano(cid:173)
`carboxylic, and amino-sulfano acids.
`Another embodiment includes a cleaning composition comprising between about
`30 1 % to about 30% oxalic acid dihydrate, between about 0.1 % and about 30% of an amine,
`and water, wherein the cleaning composition contains less than about 0.5%
`fluorine-_containing compounds and less than 0.5% peroxides, and additionally comprising
`at least one hydroxylamine.
`Another embodiment includes a cleaning composition comprising between about
`35 1 % to about 30% oxalic acid dihydrate, between about 0.1 % and about 30% of an amine,
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`and water, wherein the cleaning composition contains less than about 0.5%
`fluorine-containing compounds and less than 0.5% peroxides, additionally comprising
`benzotriazole, thiourea, ammonium bisulfite, choline bisulfite, propylene glycol, glycerol,
`sorbitol, gelatine, starch, phosphoric acid, silicic acid polyethylene oxide, polyethylene
`imine, or mixture thereof in an amount sufficient to reduce etching of the substrate
`contacting the cleaner.
`Another embodiment includes a cleaning composition comprising between about
`1 % to about 30% oxalic acid dihydrate, between about 0.1 % and about 30% of an amine,
`and water, wherein the cleaning composition contains less than about 0.5%
`10 fluorine-containing compounds, less than about 0.1 % of organic solvents, and less than
`0.5% peroxides, and additionally comprising at least one chelating agent.. The chelating
`agent may be selected from dicarboxylic acids, hydroxy-carboxylic acids, amino-carboxylic
`acids, diamine, polyalcohol, polyethylene oxide and polyamine/imine.
`The semiaqueous cleaning compositions of this invention may additionally include
`15 between 0.01 % and 1 % of polyvinyl alcohol, polyethylene oxide, polyethylene imine,
`polyalcohol, polyether, polyamine/imine, or mixture thereof.
`In a preferred embodiment the semiaqueous cleaning composition will further
`comprising between about 0.01 % ·and about 10% of an oxygen scavenger, for example a
`sulfite.
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`20
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`In a preferred embodiment the oxalic acid dihydrate concentration is between about
`2% and about 20%, and the pH is between about 4 and 7.
`Advantageously, the semiaqueous cleaning composition further comprising a second
`organic acid, for example citric acid, formic acid, or a mixture thereof, wherein the total
`organic acid concentration is less than about 20% total organic acids, and wherein the oxalic
`25 acid dihydrate concentration is between about 4% and about 12%.
`In some embodiments the semiaqueous cleaning composition this invention may
`additionally include between about 0.01 % and about 6% of an inorganic acid.
`In one embodiment, the amine is one or more alkanolamines in am amount ranging
`from about 1 % and about 15%.
`A preferred semiaqueous cleaning composition includes between about 3% and
`about 15% of oxalic acid; between about 3% and about 20% of a second organic acid;
`between about 3% and about 30% of an amine; and betw