Use of a liquid composition for stripping photoresists

Abstract: A photoresist stripping liquid composition effective for removing resist residues after dry etching and resist ashing in the manufacturing processes of semiconductor devices, which does not corrode the different metallic materials, and wherein are comprised, as active component, one or more polycarboxylic acids and/or their salts selected from the group consisting of aliphatic polycarboxylic acids and their salts as well as aminopolycarboxylic acids and their salts.

Description: FIELD OF THE INVENTION The present invention relates to the use of a liquid composition for stripping photoresists, and more specifically relates to the use of a photoresist stripping liquid composition for removing resist residues remaining after dry etching insulating films, wiring materials, capacitors and electrode materials in the manufacture of semiconductor devices. BACKGROUND OF THE INVENTION Dry etching is the most important technology for patterning insulating films, wiring materials, etc. in the manufacture of semiconductor devices. In the dry etching process a pattern is formed on a substrate, deposited by sputtering, CVD, spin coating, etc., by applying, exposing and developing a photoresist; after which the insulating film and the wiring pattern are formed by dry etching using a reactive gas and said photoresist as mask. After this patterning, ashing is performed, and the resist residues, which still remain in part after the photoresist used as mask has been removed by ashing, are typically removed by a stripping liquid. However, the photoresist residues which remain after dry etching cannot be completely removed by the combination of an organic solvent with alkanolamine generally used as conventional stripping liquid (e.g. , JP, A, 5-281753; US Patent 5,480,585). It is thought that the reason for this is that, together with the etched material, part of the resist residues remaining after ashing becomes inorganic. Therefore, stripping liquids containing fluorine compounds (JP, A, 7-201794; EP, A, 662705), hydroxylamine (US Patent 5,334,332) and quarternary ammonium compounds (JP, A, 8-262746; US Patent 5,567,574) have been proposed for removing photoresist residues after dry etching. However, since these stripping liquids corrode the wiring material, it is necessary to rinse with isopropyl alcohol or another organic solvent and to perform the treatment at a high temperature to remove resist residues completely. Moreover, the impact of organic compounds on the environment has to be taken into consideration, since these stripping liquids are prepared from some 10 % to 100 % of organic compounds and since rinsing with organic solvents is also necessary. On the other hand, together with the diversification of materials used for semiconductor devices in recent years, brought about by the use of new metallic materials such as barrier metals, ferroelectrics, etc. as wiring materials, etc., a diversification of the contents of the photoresist residue remaining after dry etching has also taken place. What is required of the removing liquid is that it be effective in removing photoresist residues and that it does not corrode the surrounding materials. Also, the use of the before-mentioned fluorine compounds and inorganic acids is subject to limitation, since they possess the characteristic of etching lead zirconium titanate (PZT) , which is a ferroelectric material. Moreover, removing methods using strongly alkaline liquids, such as tetramethylammonium hydroxide (TMAH) , etc., have also been proposed (JP, A, 8-222574) ; however, alkaline liquids cannot be used with titanium nitride, one of the barrier metals which is easily etched on the alkaline side, nor with hydrogen silsesquioxane (HSQ), which recently received much attention as interlayer insulating film because of its low dielectric constant, since there is the danger of film degradation (increase of the dielectric constant when the Si-H group changes to Si-OH). I.e., TMAH cannot be used with semiconductor devices in which PZT occurs together with titanium nitride or HSQ. Thus, considering that the stripping liquids of the prior art are limited depending on their intended purpose, there is a need in the future for combining stripping liquids corresponding to the properties of the different materials used in the manufacturing processes of semiconductor devices. Therefore, when treating laminated films in which different materials are stacked, a different stripping liquid tank is required for each material; however, from the point of view of the manufacturing processes, production line planning and operating costs, this is a very negative factor. Moreover, a related invention is mentioned in JP, A, 10-256210; however, the publication date of this application is September 25, 1998, which is after the filing date of February 27, 1998 of Japanese Patent Application Hei. 10-62031 which is the application on which the priority rights of the present application are based. Moreover, related inventions are mentioned in WO-A-9800244, FR-A-2455076, FR-A-2455075, WO-A-9845399 and EP-A-0827188. The publications of WO-A-9800244, FR-A-2455076 and FR-A-2455075 respectively antedate the priority date of the present application, that is the filing date of February 27, 1998 of Japanese Patent Application Hei. 10-62031, on which the priority rights of the present application are based. Accordingly, they form a part of the state of the art according to Article 54(2). The publication data of WO-A-9845399 and EP-A-0827188, October 15, 1998 and March 4, 1998 respectively, are after the priority date of the present application, and their priority data, April 4, 1997 and August 9, 1996 respectively, are before the priority date of the present application. Accordingly, they form a part of the state of the art according to Article 54(3). WO-A-9800244 discloses semiconductor wafer cleaning formulations comprising a chelating agent, such as malonic acid, oxalic acid etc. FR-A-2455076 and FR-A-2455075 disclose compositions for eliminating photoresistant resins comprising an add such as oxalic acid, citric acid etc. WO-A-9845399 discloses a photoresist residue cleaning composition comprising ethylenediaminetetraacetic acid(EDTA) or a mono-, di-, tri or tetraammonium salt thereof in amounts of 1 to 50% by weight, optionally an organic polar solvent, optionally an organic or inorganic ammonium salt in amounts of 0.15 to 10% in addition to EDTA ammonium salts, e.g. ammonium tartrate, ammonium citrate etc. and optionally an additional chelating agent such as catechol or gallic acid. EP-A-0827188 relates to cleaning liquids for producing semiconductor devices, comprising a fluorine-containing compound, a water-soluble or water-miscible organic solvent, an inorganic and/or organic acid, such as oxalic acid, malonic acid, succinic acid etc., a quaternary ammonium salt or an organic carboxylic acid ammonium salt and/or an organic carboxylic acid amine salt, such as derivatives of oxalic acid, malonic acid etc." OBJECT OF THE INVENTION Accordingly, the present invention relates to the use of a stripping liquid composition which is excellent for removing photoresist residues remaining after dry etching in the manufacturing processes of semiconductor devices using different metallic materials, does not corrode wiring materials, etc. and can be rinsed with water. SUMMARY OF THE INVENTION The inventors of the present invention, as a result of having made diligent efforts to achieve this object, accomplished the present invention by discovering that the use of a stripping liquid composition as set out in present claim 1 is excellent for removing photoresist residues, and does not corrode metallic materials such as wiring materials, barrier metals, etc. Moreover, the liquid composition can be rinsed with water after treatment. I.e., the present invention relates to the above-mentioned use of a photoresist stripping liquid composition comprising, as active component, one or more polycarboxylic acids and/or their salts selected from the group consisting of aliphatic polycarboxylic acids and their salts as well as aminopolycarboxylic acids and their salts with the proviso that (i) in the use the photoresist stripping liquid composition comprise a combination of (a) one or more ethylenediaminetetraacetic acid and or salt thereof and (b) an amine or an alkanolamine, than the concentration of ethylenediaminetetraacetic acid and/or salt thereof is not in the range of 1-50 wt%, (ii) the solvent is water and the liquid composition comprises no fluorine containing compound. Through the present invention, it has been possible to provide the use of a photoresist stripping liquid composition which is far more effective for removing photoresist residues remaining after dry etching than the stripping liquids of the prior art, does not corrode metallic materials and does not have an impact on the environment caused by organic solvents. One embodiment of the present invention is the use of a photoresist stripping liquid composition, as set out in present claim 2, comprising, as active component, one or more aliphatic polycarboxylic acids and/or their salts selected from the group consisting of oxalic acid, malonic acid, tartaric acid, malic acid, succinic acid and citric acid. Another embodiment of the present invention is the use of a photoresist stripping liquid composition as set out in present claim 3, comprising, as active component, one or more aminopolycarboxylic acids and/or their salts selected from the group consisting of ethylenediaminetetraacetic acid, ethylenediaminetetraacetic acid diammonium salt or N-(2-hydroxyethyl)-N,N',N'-ethylenediaminetriacetic acid. Still another embodiment of the present invention relates to the use of the above mentioned photoresist stripping liquid composition for removing resist residues from wiring material made of Al-Si-Cu or from ferroelectrics made of lead zirconium titanate (PZT). Yet another embodiment of the present invention relates to the use of the above mentioned photoresist stripping liquid composition for removing deposited polymers after ashing treatment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The below is to explain the embodiments of the present invention in greater detail and is not intended to limit the scope of the invention. As preferred aliphatic polycarboxylic acids used in the stripping liquid composition dicarboxylic acids such as oxalic acid, malonic acid and succinic acid; and dicarboxylic or tricarboxylic acids having a hydroxyl group such as tartaric acid, malic acid and citric acid can be mentioned. Further, the salts of the aliphatic polycarboxylic acids can also be used; however, in the manufacture of semiconductor devices, where metallic salts are not desirable, ammonium salts are typically used. As aminopolycarboxylic acids and their salts, compounds of ethylenediaminetetraacetic acid (EDTA), ethylenediaminetetraacetic acid diammonium salt, trans-1,2-cyclohexanediaminetetraacetic acid (CyDTA), nitrilotriacetic acid (NTA), diethylenetriaminepentaacetic acid (DTPA), N-(2-hydroxyethyl)-N,N',N'-ethylenediaminetriacetic acid (EDTA-OH) , etc. and their salts can be mentioned. As aliphatic polycarboxylic acids, compounds of oxalic acid and malonic acid are particularly preferred because they have excellent removing properties at low temperature. These aliphatic polycarboxylic acids are different from hydrochloric acid and other inorganic acids in that they have very little corrosive effect on metal; also it is thought that the reason why they possess excellent solubilizing power in regard to metal oxides is that they have 2 or more carboxylic groups. The photoresist residues remaining after dry etching are mainly oxides produced during ashing by oxygen plasma treatment of the reaction products which are produced during etching between the wiring material etc. and the gas; therefore, these photoresist residues, which are mainly oxides, can be advantageously removed by the use of polycarboxylic acids and their salts. The concentration of aliphatic polycarboxylic acids or their salts is in the range between 0.01 wt % and 30 wt %, and preferably between 0.1 wt % and 10 wt %. On the other hand, the concentration of aminopolycarboxylic acids or their salts is in the range between 0.0001 wt % and 10 wt %, and preferably between 0.001 wt % and 1 wt %. The concentration of aliphatic polycarboxylic acids and aminopolycarboxylic acids is determined in consideration of the desired stripping power, the economy of use and whether or not crystallization takes place. Aliphatic polycarboxylic acids and aminopolycarboxylic acids can be used on their own or in combination of a plurality thereof. In particular, oxalic acid exhibits excellent removing properties on its own; but a stripping liquid in which oxalic acid is combined with ethylenediaminetetraacetic acid has even better stripping power, and since it can be used at low temperatures, it is a preferred embodiment of the present invention. The stripping liquid compositions, whose object is the removal of the residues remaining after dry etching, are aqueous solutions. The present invention can be applied to photoresist residues on wiring materials, ferroelectrics, electrode materials, barrier metals, etc. that have been treated by etching, ashing, etc.; however, it is most effective in removing sidewall polymers after ashing treatment. The photoresist stripping liquid composition can be applied to a wide range of metallic materials including Al-Si-Cu, Al-Cu, W and other wiring materials, lead zirconium titanate (PZT), lead lanthanum zirconium titanate (PLZT), strontium bismuth tantalate (SBT) and other ferroelectrics, iridium, iridium oxide, ruthenium, ruthenium oxide and other electrode materials; and, without intending to limit its use, it is particularly suitable for removing resist residues from wiring materials made of Al-Si-Cu and ferroelectrics made of lead zirconium titanate (PZT). Moreover, aliphatic carboxylic acids with only one carboxylic group, such as formic acid, acetic acid, etc. and aromatic polycarboxylic acids such as phthalic acid, etc. do not exhibit any properties for removing photoresist residues. The examples and comparative examples given next are to explain the present invention in even greater detail and are not intended to limit the scope of the invention. 1) Stripping liquid evaluation test 1 (Al-Si-Cu wiring) The resist residues on a silicon wafer or on an Al-Si-Cu wiring pattern formed on a silicon wafer by dry etching with a photoresist as mask were treated, after removal of the resist by oxygen plasma, for 20 min. at different temperatures with the stripping liquids shown in Tables 1 and 2; and the Al-Si-Cu corrosion and the removal of the photoresist residues were examined by means of an electron microscope after rinsing (with isopropyl alcohol and/or water) and drying. The results are shown in Table 3. Composition of the Comparative Examples Comparative Example Stripping liquid Rinsing 1 Stripping liquid 105 (manufactured by Tokyo Ohka Kogyo Co., Ltd.) 2 times with isopropyl alcohol, water 2 Stripping liquid 105 (manufactured by Tokyo Ohka Kogyo Co., Ltd.) water only 3 aqueous solution of 3.4 wt % acetic acid water only 4 aqueous solution of 3 .4 wt % formic acid water only Composition of Examples Example Stripping liquid composition (wt %) Aliphatic polycarboxylic acids Water Dimethylsulfoxide 1 3.4 Oxalic acid 96.6 2 3.4 Malonic acid 96.6 3 3.4 Succinic acid 96.6 4 3.4 Tartaric acid 96.6 5 3.4 Malic acid 96.6 6 3.4 Citric acid 96.6 7 3.4 Ammonium oxalate 96.6 8 0.34 Oxalic acid 99.66 9 3.4 Oxalic acid 96.59 0.01 ethylenediaminetetraacetic acid diammonium salt Resist residues removal Al-Si-Cu corrosion Temp. (°C) 20 25 30 40 50 60 70 80 20 25 30 40 50 60 70 80 Comp. Example 1 - - - - - X X X - - - - - O O O 2 - - - - - X X X - - - - - X X X 3 - - - - - X X X - - - - - O O O 4 - - - - - X X X - - - - - O O O Example 1 X O O O - - - - O O O O - - - - 2 X X X O O O - - O O O O O O - - 3 X X X X X O O O O O O O O O - - 4 X X X X X O O O O O O O O O - - 5 X X X X X O O O O O O O O O - - 6 X X X X X O O O O O O O O O - - 7 X X X O O O - - O O O O O O - - 8 X X X O O O - - O O O O O O - - 9 O O O O - - - - O O O O - - - - Note: Removing properties O : removal of resist residues X : no removal of resist residues Al-Si-Cu corrosion O : no corrosion X : corrosion - : no evaluation With conventional stripping liquids (Comparative Examples) the removal of the resist residues was incomplete, and corrosion, appearing as a result, of the rinsing with water, was observed. Monocarboxylic acids such as acetic acid and formic acids did not remove the resist residues. In contrast, the stripping liquid compositions related to the present invention, as can be seen from the different examples, exhibit good removal properties, and the oxalic acid stripping liquid exhibits good removing properties even when used at room temperature. Moreover, no corrosion of the wiring material was noted with any of these stripping liquids. (0019) 2) Stripping liquid evaluation test 2 (ferroelectric material: PZT) A wafer, on which a lead zirconium titanate (PZT) pattern was dry etched with a photoresist as mask on Pt electrodes formed on a silicon wafer, was treated, after removal of the photoresist by oxygen plasma ashing, for 20 min. at different temperatures with the stripping liquids shown in Tables 4 and 5; and the PZT corrosion and the removal of the photoresist residues on the wafer surface were examined by means of an electron microscope after rinsing (with isopropyl alcohol and/or water) and drying. The evaluation results are compiled in Table 6. Composition of Comparative Examples Comparative Example Stripping liquid Rinsing 5 Stripping liquid 105 (manufactured by Tokyo Ohka Kogyo Co., Ltd.) 2 times with isopropyl alcohol, water 6 ELM-C30 (manufactured by Mitsubishi Gas Chemical Company, Inc.) water only 7 aqueous solution of 3.4 wt % acetic acid water only 8 aqueous solution of 3.4 wt % ophthalic acid water only Composition of Examples Example Stripping liquid composition (wt %) Polycarboxylic acids / aminopolycarboxylic acids Water 12 3.4 Oxalic acid 96.6 13 0.34 Oxalic acid 99.66 14 0.1 ethylenediaminetetraacetic acid diammonium salt 99.9 15 0.1 N-(2-hydroxyethyl)-N,N',N'-ethylenediaminetriacetic acid 99.9 16 3.4 Oxalic acid 96.59 0.01 ethylenediaminetetraacetic acid diammonium salt Note: Only water was used for rinsing in the different Examples. Resist residues removal PZT corrosion Temp. (°C) 25 30 40 50 60 70 80 25 30 40 50 60 70 80 Comp. Example 5 - - - - X X X - - - - ○ ○ ○ 6 - - - - X X X - - - - X X X 7 - - - - X X X - - - - ○ ○ ○ 8 - - - - X X X - - - - ○ ○ ○ Example 12 X ○ ○ - - - - ○ ○ ○ - - - - 13 X X X ○ ○ - - ○ ○ ○ ○ ○ - - 14 X X X X X ○ ○ ○ ○ ○ ○ ○ ○ ○ 15 X X X X X ○ ○ ○ ○ ○ ○ ○ ○ ○ 16 ○ ○ ○ - - - - ○ ○ ○ - - - - Note: Removing properties O : removal of resist residues X : no removal of resist residues Al-Si-Cu corrosion O : no corrosion X : corrosion - : no evaluation As is clear from Table 6, it was not possible to remove the resist residues remaining after dry etching of a ferroelectric material (PZT) with conventional stripping liquids, monocarboxylic acids or aromatic carboxylic acids; but the stripping liquids related to the present invention effectively removed the resist residues without corroding the PZT. An effect was also noted with the combined use of polycarboxylic acids and aminopolycarboxylic acids.

Claims: The use of a stripping liquid composition, for stripping photoresists, wherein the composition comprises as an active component, one or more polycarboxylic acids and/or salts thereof selected from the group consisting of aliphatic polycarboxylic acids and salts thereof as well as aminopolycarboxylic acids and salts thereof, with the proviso that (i) in the case the photoresist stripping liquid composition comprises a combination of (a) one or more ethylenediaminetetraacetic acid and/or salt thereof and (b) an amine or an alkanolamine, then the concentration of ethylenediaminetetraacetic acid and/or salt is not in the range of 1 - 50 wt%, (ii) the solvent is water and the liquid composition comprises no fluorine-containing compound. The use according to claim 1, wherein the aliphatic polycarboxylic acids are selected from the group consisting of oxalic acid, malonic acid, tartaric acid, malic acid, succinic acid and citric acid. The use according to claim 1, wherein the aminopolycarboxylic acids are selected from the group consisting of ethylenediaminetetraacetic acid, ethylenediaminetraacetic acid diammonium salt and N-(2-hydroxyethyl)-N,N',N'-ethylenediamine-triacetic acid. The use according to claim 1, wherein the aliphatic polycarboxylic acid is oxalic acid, the salt of the aliphatic polycarboxylic acid is ammonium oxalate, the aminopolycarboxylic acid is ethylenediaminetetraacetic acid and the salt of the aminopolycarboxylic acid is ethylenediaminetetraacetic acid diammonium salt. The use according to claim 4, wherein the photoresist stripping liquid composition is selected from the group consisting of an aqueous solution of oxalic acid, an aqueous solution of ammonium oxalate and an aqueous solution of a combination of ethylenediaminetetraacetic acid and/or ethylenediaminetetraacetic acid diammonium salt, and oxalic acid. Use according to any one of claims 1 to 5 wherein residues from wiring material made of Al-Si-Cu or from ferroelectrics made of lead zirconium titanate (PZT), are removed. Use according to any one of claims 1 to 5 wherein deposited polymers after ashing treatment, are removed. Process for removing resist residues from wiring material made of Al-Si-Cu or from ferroelectrics made of lead zirconium titanate (PZT), comprising (a) treating the resist residues for 20 minutes with the photoresist stripping liquid composition which consists of water and, as an active component, a compound selected from the group consisting of oxalic acid, malonic acid, tartaric acid, malic acid, succinic acid, citric acid, ammonium oxalate, ethylenediaminetetraacetic acid diammonium salt and N-(2-hydroxyethyl)-N,N',N'-ethylenediamine-triacetic acid or a pair of compounds of oxalic acid and ethylenediaminetetraacetic acid diammonium salt, and (b) rinsing with isopropyl alcohol and/or water and drying.

Inventors: ISHIKAWA NORIO, MORI KIYOTO, SUGA MASANORI, ISHIKAWA, NORIO, MORI, KIYOTO, SUGA, MASANORI, Ishikawa, Norio, c/o Kanto Kagaku K.K., Mori, Kiyoto c/o Kanto Kagaku K.K., Suga, Masanori c/o Kanto Kagaku K.K.
Applicants: KANTO KAGAKU, KANTO KAGAKU KABUSHIKI KAISHA
Application year: 1999
Main classification: G03F7
IPC codes: G03F7