NON-CORROSIVE CLEANING COMPOSITION AND METHOD FOR REMOVING PLASMA ETCHING RESIDUES

Abstract: Non-corrosive cleaning compositions that are useful for removing photoresist and plasma etch residues from a substrate. The cleaning composition comprises, by weight: (i) 30-70 % of a hydroxy-(lower alkyl)-hydrazine; (ii) 70-30 % of a water miscible organic solvent and (iii) 0-10 % water.

Description: NON-CORROSIVE CLEANING COMPOSITION AND METHOD FOR REMOVING PLASMA ETCHING RESIDUES BACKGROUND OF THE INVENTION Field of the Invention This invention relates to a cleaning composition and method for its use in microelectronics manufacturing, and more particularly to a non- corrosive cleaning composition and method for removing photoresist and plasma etch residues on substrates Description of Art In the manufacture of microcircuits, 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 photolithography and plasma etching steps One of the steps in the microcircuit manufacturing process is the removal of the patterned photoresist films from substrates In general, this step is affected 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 consists primarily of an organic solvent and an amine However, stripper solutions 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 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 An alternative method of removing a 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 vacuum chamber and, hence, is expected to be less susceptible to airborne particulate or metallic contamination However, oxygen plasma ashing is also 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 alkaline solutions Several commercial products are now available to clean the plasma etching residues left by plasma etching followed by oxygen ashing For example, EKC 265, available from EKC Technology, Inc , is a plasma etching cleaning solution composed of water, alkanolamine, catechol and hydroxylamine Such a composition is disclosed in U S Patent No 5,279,771 to Lee ACT 935, available from Ashland Chemical, is another plasma etching cleaning solution and is composed of water, alkanolamine and hydroxylamine In both cases, hydroxylamine is used as a corrosion inhibitor R-10, 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 patternwise 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 above 11 , even in the presence of a corrosion inhibitor, they may attack certain 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 i corrosion inhibitor must not inhibit the removal of the plasma-etching residue 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 residue and the substrate metal layers Moreover, if a 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 has remained a need for a method of quickly and effectively removing the plasma etching residues without causing metal layer corrosion Several other patents in the photoresist stripper/cleaner application field exist as follows, although none of them disclose the use of the method or compositions of the present invention Japanese Patent Application No 7-028254, assigned to Kanto Kagaku, discloses a non-corrosive resist removal liquid comprising a sugar alcohol, an alcohol amine, water, and a quaternary ammonium hydroxide PCT Published Patent Application No WO 88-05813 teaches a positive or negative photoresist stripper containing butyrolactone or caprolactone, quaternary ammonium hydroxide compound, and optionally, a nonionic surfactant U S Patent No 4,239,661 to Muraoka et al discloses a surface- treating agent comprising an aqueous solution of 0 01% to 20% tnalkyl (hydroxyalkyl) ammonium hydroxide. This agent is useful in removing organic and inorganic contaminants deposited on the surface of intermediate semiconductor products. U.S. Patent No. 4,904,571 to Miyashita et al. teaches printed circuit board photoresist stripper composition containing a solvent (e.g., water, alcohols, ethers, ketones, and the like), an alkaline compound dissolved in the solvent, including quaternary ammonium hydroxide, and a borohydride compound dissolved in the solvent. U.S. Patent 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. U.S. Patent No. 5,139,607 to Ward et al. teaches positive and negative photoresist stripping composition containing: (A) tetrahydrofurfuryl alcohol; (B) a polyhydric alcohol (e.g., ethylene glycol or propylene glycol); (C) the reaction product of furfuryl alcohol and an alkylene oxide; (D) a water-soluble Bronstead base type hydroxide compound (e.g., alkali metal hydroxide, ammonium hydroxide and tetramethyl ammonium hydroxide); and (E) water. Optionally, the composition may also contain up to 1 % of a nonionic surfactant. U.S. Patent No. 5,174,816 to Aoyama et al. discloses a composition for removing chlorine remaining on the surface of an aluminum line pattern substrate after dry etching, which composition comprises an aqueous solution containing 0.01 to 15% by weight of a quaternary ammonium hydroxide, such as trimethyl (2-hydroxyethyl) ammonium hydroxide, and 0.1 to 20% by weight of sugar or sugar alcohol, such as xylitol, mannose, glucose and the like. Canadian Patent Application 2,132,768 of Schwartzkopf et al., published Aug. 4, 1995, discloses the use of 1-10% by weight of reducing agents in photoresist stripping compositions and hydrazine and its derivatives are mentioned as one of several types of reducing agents useful. The stripping compositions of Schwartzkopf et al. comprise a solvent system, alkaline compounds, such as hydroxylamines, and the reducing agent.. The present invention avoids the need to add alkanolamine to the photoresist cleaning composition since it has been found that a hydroxyalkyl hydrazine is highly effective in dissolving the photoresist. It also avoids the need to use a post-strip intermediate rinse step with an organic solvent such as isopropanol. SUMMARY OF THE INVENTION In accordance with the present invention there has been discovered a non-corrosive cleaning composition that is useful for removing photoresist and plasma etch residues from a substrate which comprises, by weight: (i) 30-70 % of a hydroxy-(lower alkyl)-hydrazine; (ii) 70-30 % of a water miscible organic solvent; and (iii) 0-10% water. The invention further contemplates a method of removing residues from a substrate comprising contacting a substrate containing residues with the above-mentioned cleaning composition. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT Suitable hydroxy-(lower alkyl)-hydrazines for use in this invention are 2- hydroxyethylhydrazine, hydroxypropyl hydrazine and hydroxybutyl hydrazine, dihydroxy-(lower alkyl)-hydrazine ,such as di-(hydroxyethyl)- hydrazine, di-(hydroxypropyl)-hydrazine, and di-(hydroxy-butyl)hydrazine), 2-hydroxyethyl hydrazine is particularly preferred. The hydrazine is present in an amount preferably in the range of 40-60% by weight, more preferably 45-55% by weight. The lower alkyl may have about 1-6 carbon atoms, and is preferably ethyl , propyl or butyl. Suitable water miscible solvents used in the stripping and cleaning composition of the invention are illustrated by N-methyl-2-pyrrolidinone (NMP), N-hydroxyethyl-2-pyrrolidinone (HEP), 1 ,3-dimethyl-2- imidazolidinone (DMI), dimethylsuifoxide (DMSO), N,N-dimethylacetamide (DMAC), diacetone alcohol, (DAAL), ethylene glycol (EG), propylene glycol (PG) or combinations thereof.. NMP and DMSO solvents are especially effective in terms of photoresist stripping power and are preferred in the present invention. The solvents are preferably present in amounts of about 60-40%, more preferably 55-45% by weight. NMP is particularly preferred, especially in a composition having about 55-45% NMP ,45-55% 2-hydroxyethyl hydrazine and no water. Water in an optional ingredient in the compositions of this invention and is used in amounts of 0-10% by weight, such as 1-10% or 5-10% by weight, but beyond about 10% corrosivity may be enhanced by the presence of water. Preferably ,a small amount of water is helpful in the removal of the plasma etch residue, such as 5-10% by weight water. A chelating agent may be optionally included in the cleaning composition. Suitable chelating agents include thethylenetetramine (hereinafter referred to as TETA); 2,2'-[[methyl-1 H-benzotriazol-1- yl)methyl]imino]bisethanol (Tradename is IRGAMET 42), (2- benzothiazolythio)succinic acid (Tradename is IRGACOR 252), tricine, bicine, and other water-soluble chelating compounds. Preferably, the chelating agent is present in the composition of the invention in the range of about 5 ppm to about 5000 ppm by weight based on the a total weight of cleaning composition. A surfactant may also be optionally included in the cleaning composition so as to enhance the power of the plasma etching residue removal from the substrate. Suitable surfactants are selected from nonionic types, cationic types and anionic types of surfactants. Preferably, a surfactant is present in the composition of the invention in the range of about 0.1 ppm to 100 ppm by weight to a total weight of the cleaning composition. Another optional agent that may be included in the cleaning composition is a corrosion inhibitor. The preferred corrosion inhibitors are lactic acid, salicyl alcohol, salicyl aldoxime, gallic acid, gallic acid esters and alizarin. This invention further contemplates the method of removing residues from a substrate comprising: applying one of the above mentioned cleaning solutions to the substrate containing residues. The cleaning method of the present invention can also be used in combination with a dry stripping process if photoresist or other polymer residues remain on the surface. Dry stripping is typically conducted prior to the present cleaning method. Any suitable dry stripping process can be used including O 2 plasma ashing, ozone gas phase-treatment, fluorine plasma treatment, hot H 2 gas treatment (described in U.S. Pat. No. 5,691 ,117), and the like. The preferred dry stripping process is O 2 plasma ashing. Furthermore, the cleaning method can also be used in combination with ozonated water, which is used to strip off photoresist and other residues. The ozonated water can be a simple mixture of ozone and ultra- pure water, e.g., Dl water. The ozone can be generated by any conventional means, e.g., an ozone generator. The mixing of the ozone and water may be achieved by any suitable method, such as jetting the ozone into the water by a gas feed nozzle, feeding the water and ozone into a spiral mixer, aspirating the gas into the flow of water, and feeding the ozone into a treatment tank regulated at a given pressure so that ozone is dissolved into the water The ozonated water can then be contacted with the substrate by any suitable method such as placing the ozonated water into a tank and submerging the substrates into the ozonated water, or by use of a spray rinse While the invention has been described above with reference to specific embodiments thereof, it is apparent that many changes, modifications and variations can be made without departing from the inventive concept disclosed herein Accordingly, it is intended to embrace all such changes, modifications and variations that fall within the spirit and broad scope of the appended claims All patent applications, patents and other publications cited herein are incorporated by reference in their entirety The invention is further illustrated by the following examples which are not to be considered as limitative of its scope EXAMPLE 1 A stripping/cleaning solution was prepared by mixing 2-hydroxyethyl hydrazιne(HEH) and N-methyl-2-pyrrolιdιnone(NMP) to prepare a mixture having 50 wt % of each component Silicon wafers having a multi-layer structure of Al-Sι-Cu/ SιO 2 /Sι were prepared by plasma deposition method and further top-coated with a positive photoresist at a film thickness of 1 0 micron by spin coating method Micropatteming was applied to the photoresist layer lithographically followed by pattern transfer onto the metal layer by plasma etching with the pre-patternized photoresist mask The wafer thus obtained contained both photoresist residues (PR) and plasma -etching photoresist residues(PER) which were a mixture of silicon and aluminum halides and/or oxides. The chemical composition of the resulting plasma- etching residues (PER) were characterized by x-ray spectroscopy but the exact composition could not be determined quantitatively. The residues-containing wafers were cut into 1 cm. by 1cm. pieces and placed in a 200 ml. beaker which contained 100 ml. of the above - prepared solution in a temperature controlled bath at 80 degrees C. The pieces of wafers were immersed in the solution with a gentle agitation (200 rpm) for 15 minutes. The wafer pieces were transferred to another beaker that contained deionized water at room temperature and gently stirred for 5 minutes. The wafer pieces were then removed from the water and dried by blowing nitrogen gas onto the surface of the wafer pieces. The wafer pieces were inspected under a scanning electron microscope (SEM) after gold sputtering. Top-down and cross-section views of the wafer SEM pictures were obtained to visualize the PR and PER on the wafer surface. In addition, the exposed metal layer surface was inspected under SEM to evaluate any corrosion of the metal surface. The SEM inspection results indicated that the formulation described above which contained 50% by weight of HEH and 50% by weight of NMP removed both PR and PER without metal corrosion even if the post-strip intermediate rinse with an organic solvent such as isopropyl alcohol (IPA) was not applied. EXAMPLES 2-5 Examples 2-5 illustrate additional compositions tested with the same type of wafers containing both PR and PER under the same conditions as described in Example 1 except that the strip time with the DMSO(dimethyl suifoxide)-based compositions was 20 minutes. Detailed formulations and test results are in Table I below. TABLE 1 Score of performance: Great>V.Good>Good>Marginal. "Marginal " means that a small amount of the residue remained but it could be removed at higher temperatures and/or for longer times.

Claims: What is claimed is: 1. A non-corrosive cleaning composition that is useful for removing photoresist and plasma etch residues from a substrate which comprises, by weight: (i) 30-70% of a hydroxy-(lower alkyl)-hydrazine, (ii) 70-30% of a water miscible organic solvent, and (iii) 0-10% water. 2. The composition of claim 1 wherein the hydroxy-(lower alkyl)- hydrazine is selected from the group consisting of 2- hydroxyethyl hydrazine, hydroxypropyl hydrazine, hydroxybutyl hydrazine, di- (hydroxyethyl)-hydrazine, di-(hydroxypropyl)-hydrazine, and di-(hydroxy- butyl)hydrazine). 3. The composition of claim 2 wherein the hydroxy-(lower alkyl)- hydrazine is 2-hydroxyethyl hydrazine. 4. The composition of claim 1 wherein the solvent is selected from the group consisting of N-methyl-2-pyrrolidinone, N-hydroxyethyl-2- pyrrolidinone, 1 ,3-dimethyl-2-imidazolidinone , dimethylsulfoxide, N,N- dimethylacetamide, diacetone alcohol, ethylene glycol, propylene glycol , or combinations thereof. 5. The composition of claim 4 wherein the solvent is N-methyl-2- pyrrolidinone or dimethyl sulfoxide. 6. The composition of claim 3 wherein there is present about 45-55% by weight of 2-hydroxyethyl hydrazine and the solvent is N-methyl-2- pyrrolidinone which is present in an amount of 55-45 % by weight. 7. The composition of claim 6 wherein there is present 1-10% by weight water. 8. The composition of claimlwhich further comprises a chelating 5 agent, surfactant or a corrosion inhibitor. 9. A method of removing from a substrate photoresist and plasma etching residues which comprises contacting a substrate containing said residues with the cleaning composition of claim 1. [ 0 10. A method of removing from a substrate photoresist and plasma etching residues which comprises contacting a substrate containing said residues the cleaning composition of claim 6. [5 11. The method of claim 10 further comprising contacting the substrate with ozonated water.

Inventors: HONDA KENJI, ROTHGERY EUGENE F, HONDA, KENJI, ROTHGERY, EUGENE, F.
Applicants: ARCH SPEC CHEM INC, ARCH SPECIALTY CHEMICALS, INC.
Application year: 1999
Main classification: B08B3
IPC codes: B08B3, C11D7, C11D11, C11D17, G03F7, H01L21