WO2000011107A1 - Ito etching composition - Google Patents
Ito etching composition Download PDFInfo
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- WO2000011107A1 WO2000011107A1 PCT/KR1999/000459 KR9900459W WO0011107A1 WO 2000011107 A1 WO2000011107 A1 WO 2000011107A1 KR 9900459 W KR9900459 W KR 9900459W WO 0011107 A1 WO0011107 A1 WO 0011107A1
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- WIPO (PCT)
- Prior art keywords
- etching
- aqueous solution
- etchant composition
- etchant
- per liter
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- 238000005530 etching Methods 0.000 title claims abstract description 148
- 239000000203 mixture Substances 0.000 title claims abstract description 96
- MUBZPKHOEPUJKR-UHFFFAOYSA-N Oxalic acid Chemical compound OC(=O)C(O)=O MUBZPKHOEPUJKR-UHFFFAOYSA-N 0.000 claims abstract description 134
- VSCWAEJMTAWNJL-UHFFFAOYSA-K aluminium trichloride Chemical compound Cl[Al](Cl)Cl VSCWAEJMTAWNJL-UHFFFAOYSA-K 0.000 claims abstract description 44
- 235000006408 oxalic acid Nutrition 0.000 claims abstract description 44
- 150000003839 salts Chemical class 0.000 claims abstract description 18
- 239000004094 surface-active agent Substances 0.000 claims abstract description 18
- JRKICGRDRMAZLK-UHFFFAOYSA-L peroxydisulfate Chemical compound [O-]S(=O)(=O)OOS([O-])(=O)=O JRKICGRDRMAZLK-UHFFFAOYSA-L 0.000 claims abstract description 17
- 239000007864 aqueous solution Substances 0.000 claims description 71
- 229920006395 saturated elastomer Polymers 0.000 claims description 14
- CIWBSHSKHKDKBQ-JLAZNSOCSA-N Ascorbic acid Chemical group OC[C@H](O)[C@H]1OC(=O)C(O)=C1O CIWBSHSKHKDKBQ-JLAZNSOCSA-N 0.000 claims description 12
- 239000003638 chemical reducing agent Substances 0.000 claims description 11
- ROOXNKNUYICQNP-UHFFFAOYSA-N ammonium persulfate Chemical group [NH4+].[NH4+].[O-]S(=O)(=O)OOS([O-])(=O)=O ROOXNKNUYICQNP-UHFFFAOYSA-N 0.000 claims description 10
- 239000002211 L-ascorbic acid Substances 0.000 claims description 6
- 235000000069 L-ascorbic acid Nutrition 0.000 claims description 6
- 229960005070 ascorbic acid Drugs 0.000 claims description 6
- 229910001870 ammonium persulfate Inorganic materials 0.000 claims description 5
- RZMWTGFSAMRLQH-UHFFFAOYSA-L disodium;2,2-dihexyl-3-sulfobutanedioate Chemical group [Na+].[Na+].CCCCCCC(C([O-])=O)(C(C([O-])=O)S(O)(=O)=O)CCCCCC RZMWTGFSAMRLQH-UHFFFAOYSA-L 0.000 claims description 4
- VEXZGXHMUGYJMC-UHFFFAOYSA-M Chloride anion Chemical compound [Cl-] VEXZGXHMUGYJMC-UHFFFAOYSA-M 0.000 claims description 3
- VBIXEXWLHSRNKB-UHFFFAOYSA-N ammonium oxalate Chemical group [NH4+].[NH4+].[O-]C(=O)C([O-])=O VBIXEXWLHSRNKB-UHFFFAOYSA-N 0.000 claims description 3
- 230000000694 effects Effects 0.000 abstract description 12
- 239000003795 chemical substances by application Substances 0.000 abstract description 2
- 231100001261 hazardous Toxicity 0.000 abstract description 2
- 238000000034 method Methods 0.000 description 26
- 239000000758 substrate Substances 0.000 description 21
- 229940063656 aluminum chloride Drugs 0.000 description 19
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Chemical compound O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 18
- 229910001868 water Inorganic materials 0.000 description 16
- 230000000052 comparative effect Effects 0.000 description 15
- 239000000243 solution Substances 0.000 description 15
- 239000011521 glass Substances 0.000 description 13
- 238000005259 measurement Methods 0.000 description 11
- VEXZGXHMUGYJMC-UHFFFAOYSA-N Hydrochloric acid Chemical compound Cl VEXZGXHMUGYJMC-UHFFFAOYSA-N 0.000 description 10
- QZPSXPBJTPJTSZ-UHFFFAOYSA-N aqua regia Chemical compound Cl.O[N+]([O-])=O QZPSXPBJTPJTSZ-UHFFFAOYSA-N 0.000 description 9
- 230000007423 decrease Effects 0.000 description 9
- 229920002120 photoresistant polymer Polymers 0.000 description 8
- AJGPQPPJQDDCDA-UHFFFAOYSA-N azanium;hydron;oxalate Chemical compound N.OC(=O)C(O)=O AJGPQPPJQDDCDA-UHFFFAOYSA-N 0.000 description 7
- 238000006243 chemical reaction Methods 0.000 description 6
- 239000000463 material Substances 0.000 description 6
- 230000001603 reducing effect Effects 0.000 description 6
- FBAFATDZDUQKNH-UHFFFAOYSA-M iron chloride Chemical compound [Cl-].[Fe] FBAFATDZDUQKNH-UHFFFAOYSA-M 0.000 description 5
- 238000004519 manufacturing process Methods 0.000 description 5
- XOLBLPGZBRYERU-UHFFFAOYSA-N tin dioxide Chemical compound O=[Sn]=O XOLBLPGZBRYERU-UHFFFAOYSA-N 0.000 description 5
- GRYLNZFGIOXLOG-UHFFFAOYSA-N Nitric acid Chemical compound O[N+]([O-])=O GRYLNZFGIOXLOG-UHFFFAOYSA-N 0.000 description 4
- 238000000354 decomposition reaction Methods 0.000 description 4
- PJXISJQVUVHSOJ-UHFFFAOYSA-N indium(III) oxide Inorganic materials [O-2].[O-2].[O-2].[In+3].[In+3] PJXISJQVUVHSOJ-UHFFFAOYSA-N 0.000 description 4
- 239000000126 substance Substances 0.000 description 4
- 230000010757 Reduction Activity Effects 0.000 description 3
- 230000003247 decreasing effect Effects 0.000 description 3
- 230000003628 erosive effect Effects 0.000 description 3
- 239000003517 fume Substances 0.000 description 3
- 229910017604 nitric acid Inorganic materials 0.000 description 3
- CSCPPACGZOOCGX-UHFFFAOYSA-N Acetone Chemical compound CC(C)=O CSCPPACGZOOCGX-UHFFFAOYSA-N 0.000 description 2
- NLXLAEXVIDQMFP-UHFFFAOYSA-N Ammonia chloride Chemical compound [NH4+].[Cl-] NLXLAEXVIDQMFP-UHFFFAOYSA-N 0.000 description 2
- 229910021578 Iron(III) chloride Inorganic materials 0.000 description 2
- 229910004205 SiNX Inorganic materials 0.000 description 2
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N Silicium dioxide Chemical compound O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 description 2
- -1 alkyl sulfonic acid Chemical class 0.000 description 2
- 229910045601 alloy Inorganic materials 0.000 description 2
- 239000000956 alloy Substances 0.000 description 2
- 229910052782 aluminium Inorganic materials 0.000 description 2
- 229910021417 amorphous silicon Inorganic materials 0.000 description 2
- 239000000470 constituent Substances 0.000 description 2
- 230000000254 damaging effect Effects 0.000 description 2
- 239000008367 deionised water Substances 0.000 description 2
- 229910021641 deionized water Inorganic materials 0.000 description 2
- 238000007598 dipping method Methods 0.000 description 2
- 229910052736 halogen Inorganic materials 0.000 description 2
- 150000002367 halogens Chemical class 0.000 description 2
- RBTARNINKXHZNM-UHFFFAOYSA-K iron trichloride Chemical compound Cl[Fe](Cl)Cl RBTARNINKXHZNM-UHFFFAOYSA-K 0.000 description 2
- SHXXPRJOPFJRHA-UHFFFAOYSA-K iron(iii) fluoride Chemical compound F[Fe](F)F SHXXPRJOPFJRHA-UHFFFAOYSA-K 0.000 description 2
- 229910001092 metal group alloy Inorganic materials 0.000 description 2
- 229910052750 molybdenum Inorganic materials 0.000 description 2
- 150000007524 organic acids Chemical class 0.000 description 2
- 239000002245 particle Substances 0.000 description 2
- 239000007921 spray Substances 0.000 description 2
- 238000004544 sputter deposition Methods 0.000 description 2
- 238000003860 storage Methods 0.000 description 2
- 230000001988 toxicity Effects 0.000 description 2
- 231100000419 toxicity Toxicity 0.000 description 2
- LCPVQAHEFVXVKT-UHFFFAOYSA-N 2-(2,4-difluorophenoxy)pyridin-3-amine Chemical compound NC1=CC=CN=C1OC1=CC=C(F)C=C1F LCPVQAHEFVXVKT-UHFFFAOYSA-N 0.000 description 1
- XFXPMWWXUTWYJX-UHFFFAOYSA-N Cyanide Chemical compound N#[C-] XFXPMWWXUTWYJX-UHFFFAOYSA-N 0.000 description 1
- BDAGIHXWWSANSR-UHFFFAOYSA-N Formic acid Chemical compound OC=O BDAGIHXWWSANSR-UHFFFAOYSA-N 0.000 description 1
- 229910021626 Tin(II) chloride Inorganic materials 0.000 description 1
- 239000002253 acid Substances 0.000 description 1
- 150000007513 acids Chemical class 0.000 description 1
- JGDITNMASUZKPW-UHFFFAOYSA-K aluminium trichloride hexahydrate Chemical compound O.O.O.O.O.O.Cl[Al](Cl)Cl JGDITNMASUZKPW-UHFFFAOYSA-K 0.000 description 1
- 229940009861 aluminum chloride hexahydrate Drugs 0.000 description 1
- 235000019270 ammonium chloride Nutrition 0.000 description 1
- MSMNVXKYCPHLLN-UHFFFAOYSA-N azane;oxalic acid;hydrate Chemical compound N.N.O.OC(=O)C(O)=O MSMNVXKYCPHLLN-UHFFFAOYSA-N 0.000 description 1
- 238000009835 boiling Methods 0.000 description 1
- 239000002894 chemical waste Substances 0.000 description 1
- 229910052681 coesite Inorganic materials 0.000 description 1
- 239000002131 composite material Substances 0.000 description 1
- 229910052906 cristobalite Inorganic materials 0.000 description 1
- 230000000779 depleting effect Effects 0.000 description 1
- 238000000151 deposition Methods 0.000 description 1
- 230000007613 environmental effect Effects 0.000 description 1
- 238000003912 environmental pollution Methods 0.000 description 1
- 229910052731 fluorine Inorganic materials 0.000 description 1
- 239000011737 fluorine Substances 0.000 description 1
- 235000019253 formic acid Nutrition 0.000 description 1
- 229940093915 gynecological organic acid Drugs 0.000 description 1
- GPRLSGONYQIRFK-UHFFFAOYSA-N hydron Chemical compound [H+] GPRLSGONYQIRFK-UHFFFAOYSA-N 0.000 description 1
- APFVFJFRJDLVQX-UHFFFAOYSA-N indium atom Chemical compound [In] APFVFJFRJDLVQX-UHFFFAOYSA-N 0.000 description 1
- 229910003437 indium oxide Inorganic materials 0.000 description 1
- AMGQUBHHOARCQH-UHFFFAOYSA-N indium;oxotin Chemical compound [In].[Sn]=O AMGQUBHHOARCQH-UHFFFAOYSA-N 0.000 description 1
- 238000009434 installation Methods 0.000 description 1
- 150000002500 ions Chemical class 0.000 description 1
- 239000004973 liquid crystal related substance Substances 0.000 description 1
- 229910044991 metal oxide Inorganic materials 0.000 description 1
- 150000004706 metal oxides Chemical class 0.000 description 1
- 238000002156 mixing Methods 0.000 description 1
- 229910052758 niobium Inorganic materials 0.000 description 1
- 235000005985 organic acids Nutrition 0.000 description 1
- 239000007800 oxidant agent Substances 0.000 description 1
- 230000003647 oxidation Effects 0.000 description 1
- 238000007254 oxidation reaction Methods 0.000 description 1
- 230000000149 penetrating effect Effects 0.000 description 1
- 229910021420 polycrystalline silicon Inorganic materials 0.000 description 1
- USHAGKDGDHPEEY-UHFFFAOYSA-L potassium persulfate Chemical compound [K+].[K+].[O-]S(=O)(=O)OOS([O-])(=O)=O USHAGKDGDHPEEY-UHFFFAOYSA-L 0.000 description 1
- 239000000376 reactant Substances 0.000 description 1
- 238000011946 reduction process Methods 0.000 description 1
- 239000000377 silicon dioxide Substances 0.000 description 1
- CHQMHPLRPQMAMX-UHFFFAOYSA-L sodium persulfate Substances [Na+].[Na+].[O-]S(=O)(=O)OOS([O-])(=O)=O CHQMHPLRPQMAMX-UHFFFAOYSA-L 0.000 description 1
- 229910052682 stishovite Inorganic materials 0.000 description 1
- 239000010409 thin film Substances 0.000 description 1
- 229910001887 tin oxide Inorganic materials 0.000 description 1
- AXZWODMDQAVCJE-UHFFFAOYSA-L tin(II) chloride (anhydrous) Chemical compound [Cl-].[Cl-].[Sn+2] AXZWODMDQAVCJE-UHFFFAOYSA-L 0.000 description 1
- 229910052905 tridymite Inorganic materials 0.000 description 1
- 238000009834 vaporization Methods 0.000 description 1
- 230000008016 vaporization Effects 0.000 description 1
Classifications
-
- C—CHEMISTRY; METALLURGY
- C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
- C09K—MATERIALS FOR MISCELLANEOUS APPLICATIONS, NOT PROVIDED FOR ELSEWHERE
- C09K13/00—Etching, surface-brightening or pickling compositions
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
- H01L21/00—Processes or apparatus adapted for the manufacture or treatment of semiconductor or solid state devices or of parts thereof
- H01L21/02—Manufacture or treatment of semiconductor devices or of parts thereof
- H01L21/04—Manufacture or treatment of semiconductor devices or of parts thereof the devices having potential barriers, e.g. a PN junction, depletion layer or carrier concentration layer
- H01L21/18—Manufacture or treatment of semiconductor devices or of parts thereof the devices having potential barriers, e.g. a PN junction, depletion layer or carrier concentration layer the devices having semiconductor bodies comprising elements of Group IV of the Periodic Table or AIIIBV compounds with or without impurities, e.g. doping materials
- H01L21/30—Treatment of semiconductor bodies using processes or apparatus not provided for in groups H01L21/20 - H01L21/26
- H01L21/31—Treatment of semiconductor bodies using processes or apparatus not provided for in groups H01L21/20 - H01L21/26 to form insulating layers thereon, e.g. for masking or by using photolithographic techniques; After treatment of these layers; Selection of materials for these layers
- H01L21/3205—Deposition of non-insulating-, e.g. conductive- or resistive-, layers on insulating layers; After-treatment of these layers
- H01L21/321—After treatment
- H01L21/3213—Physical or chemical etching of the layers, e.g. to produce a patterned layer from a pre-deposited extensive layer
- H01L21/32133—Physical or chemical etching of the layers, e.g. to produce a patterned layer from a pre-deposited extensive layer by chemical means only
- H01L21/32134—Physical or chemical etching of the layers, e.g. to produce a patterned layer from a pre-deposited extensive layer by chemical means only by liquid etching only
Definitions
- the present invention relates to an etchant composition, and more particularly to an ITO etchant composition for etching Indium Tin Oxide (In 2 O 3 - SnO 3 ) layers, a composite of indium and tin oxide (hereinafter referred to as ITO), formed on various electronic substrates for achieving a transparent electrode.
- ITO Indium Tin Oxide
- a composition of In 2 O 3 and SnO 3 are deposited on a glass substrate in layers by a conventional sputtering technique.
- the deposited ITO layer is then coated with a photoresist to be exposed and developed for a desired pattern. Once the photoresist pattern is formed, the ITO layer is etched by using the photoresist pattern as an etching mask, to thereby fabricate a transparent electrode.
- Aqua regia is economical in terms of cost, but the etchant composition is somewhat unstable and tend to volatilize into hydrochloric and nitric acids, and a large amount is etched in side-way pattern etching. Similar to aqua regia, iron fluoride etchant composition is also unstable and easily decompose into hydrochloric acid, a main constituent in the etchant composition. HBr and HI have fast etching rates and a low side-way pattern etching ability, but because of its cost, toxicity, and erosive effect, its commercial use in the manufacture of electronic substrates is limited.
- an etchant composition having an etching layer selectivity, an improved rate of reproductivity. a less toxicity, a less erosive effect, and a less fuming effect for use in ITO layer etching.
- the present invention provides an ITO etchant composition comprising oxalic acid and its salts in aqueous solution, at a concentration range of from about 1.5g per liter of auqueous solution to its saturated concentration, to be used in certain temperatures.
- the present invention also provides an ITO etchant composition comprising aluminum chloride in aqueous solution, at a concentration range of from about 80g per liter of aquous solution to its saturated concentration, to be used in certain temperatures.
- aqueous solution of oxalic acid and its salts and aqueous solution of aluminum chloride can further comprise a persulfate.
- aqueous solution of oxalic acid and its salts and aqueous solution of aluminum chloride may further include about 0.01 to about 2 weight % of surfactant.
- the etchant composition of the present invention due to the less fuming effects and stableness of the etchant composition of the present invention, environmentally hazardous effects can be minimized, while the etchant composition also provides decreased side-etching activity for obtaining micro-patterns.
- a first preferred etchant composition comprises oxalic acid and its salts in aqueous solution.
- Oxalic acid and its salts are strong reducing agents, and when in aqueous solution, oxalic acid exhibit chemical stability which makes it possible to store in room temperature for a significant duration of time (for more than a year in cold and dark storage) without decomposing. Because of strong reducing properties of both oxalic acid and its salts, they are commonly utilized as a reducing agent for reducing oxides.
- oxalic acid aqueous solution In presence of light, in high temperatures, or when combined with other materials, oxalic acid aqueous solution decomposes and yields a reducing agent which reduces metal oxides, as shown below.
- H 2 C 2 O 4 HCOOH + 2CO 2 + CO +H 2 O (1)
- the CO from the above is a reducing agent and it react with ITO, as shown by below reaction, for etching ITO layer.
- the concentration of oxalic acid is from about 1.5g per liter of water to its saturated concentration, preferably from of about 2 to 350g per liter of water.
- oxalic acid is preferably used due to its strong reducing property, and additionally, oxalic salts in aqueous solution which decompose into oxalic acid can also be used.
- oxalic salt nonmetallic oxalic salts such as ammonium oxalate may be mentioned.
- Persulfates in aqueous solution function as an uniform oxidizing agent. Its reaction in aqueous solution is show below.
- an amount of persulfate is from about 1 to 250g per liter of water, preferably from of about 5 to 150g per liter of water.
- ammonium persulfate sodium persulfate, potassium persulfate, etc. may be mentioned.
- ammonium persulfate is selectively used.
- An ITO etchant of the present invention may further comprise a surfactant.
- Surfactants when used in etching process decrease the surface tension of etchant, which increases the penetrating ability of the etchant, making it possible for the etchant to easily penetrate photoresist layers of micro-patterns. Surfactants also facilitate the removal of reactants from substrate layers, while increasing wettability of the substrate surface. As a result, surfactants decreases the etching time.
- surfactants are used in an amount less than about O. lg per liter of water, its ability to decrease the surface tension of etchant composition decreases, and more, its characteristic effects fail to realize in an amount excess of 20g, and there also a possibility it may interfere with reduction activity. Accordingly, it is preferable to use an amount of surfactant from about 0.1 to 20g per liter of water, more preferably from about 0.5 to 5g per liter of water.
- Surfactant of the present invention is sodium dihexylsulfosuccinate or similar salts of alkyl sulfonic acid.
- the ITO etchant composition comprising oxalic acid and its salts do not include halogen, the etchant composition is environmental friendly.
- an ITO etchant composition comprising a nonferrous metallic chloride such as aluminum chloride and a surfactant is provided.
- A1C1 3 etchant composition in aqueous solution, with In 2 O 3 and SnO 3 is shown below.
- the above aluminum chloride is used in an amount of about 80g per liter of water, its etching rate in ITO layers is slow, and if the amount exceed the saturation concentration, the aluminum chloride crystallizes, accordingly, it is preferable to use an amount of about 80g per liter of water to its saturated concentration, more preferably from about 100 to 350g per liter of water.
- An ITO etchant composition comprising ammonium chloride as its main constituent includes a surfactant in an amount of about from O. lg to 20g per liter of aqueous solution, more preferably in an amount of from about 0.5 to 5g per liter of aqueous solution.
- Persulfate should be added in an amount of about 1 to 250g per liter of aqueous solution, and preferably in an amount of from about 5 to 150g per liter of aqueous solution.
- an ITO etchant composition comprising an organic acid, for performing the functions of reducing agent, and aluminum chloride is also provided.
- organic acids which is used in the present invention as a reducing agent, oxalic acid, L-ascorbic acid, etc. may be mentioned.
- TFT-LCDs Thin film transistor-Liquid crystal display
- Al layer, Mo layer or their metallic alloy layer, a-Si layer, poly-Si layer, SiN x layer, SiO 2 layer, Cr layer, ITO layer are conventionally used. It is common during the etching process, there is a risk of damaging lower gate wirings or sour/drain wirings made from Al, Mo or their alloys.
- a majority of conventional etchants used for etching TFT-LCDs comprise chloride ions, fluorine ions from the halogen elements and cyanide ions. Etchants comprising these ions tend to erode metallic wirings made from the materials as mentioned above. In order to deal with this problem, metallic layers to be etched are made much thicker than its desired thickness.
- An ITO etchant composition of the present invention comprising oxalic acid or its salts overcomes the damaging effects of the above problem by not eroding the neighboring and supporting layers and layers made from Al, Mo or their metallic alloy composition during the etching process.
- aluminum chloride ITO etchant composition of the present invention aluminum chloride dissolve in aqueous solution and exists as a salt as opposed to naturally occurring acids similar to hydrochloric acid, thus fuming effects which is common in the conventional etchants can be drastically eliminated.
- the etchant compositions of the present invention be under heat in order to accelerate the etching rate.
- an ' etching temperature is from about room temperature to the boiling point of each ITO etchant composition, and more preferably from about 35 °C to 85 °C.
- Etchant composition of the present invention can be accomplished with dipping, spray, water turbulence, and ultrasonic methods. Further implementation of the etchant composition is also possible with other methods for realizing the present invention.
- the etchant compositions of the present invention is used in aqueous solution
- the composition may be separated into solute particles for storage and transportation, and dissolved into an aqueous solution prior to use.
- an additional solute particles can be added to the aqueous composition for extending the life of the etchant composition.
- 0.7mm thickness for LCD was prepared by depositing ITO into a bare glass by sputtering method until 500 angstroms of ITO layer thickness was obtained.
- ammonium oxalate monohydrate and aluminum chloride hexahydrate was respectively used for ammonium oxalate and aluminum chloride of the present invention.
- a bare glass substrate test-piece with 0.7mm thickness for LCD having 500 angstroms of ITO layer was prepared.
- Aqueous solution from each respective Examples 1-7 was used to etch the test-piece at a temperature of about 60 °C to 80 °C until etching was completed.
- Etching time for completing etching process in each of Examples 1-7 was measured and shown in the following Table 1.
- Example 5 when the temperature of the aqueous solution was raised to 100 °C, the time it took for oxalic acid aqueous solution to etch ITO layer was measured to be 1 minute.
- An etchant composition was prepared by adding L-ascorbic acid, in an amount shown for each respective Examples 8-16 in Table 2, to the aqueous solution of Example 4 (oxalic acid aqueous solution in concentration of 150g/l) for respective Examples 8-16.
- a bare glass substrate test-piece with 0.7mm thickness for LCD having 500 angstroms of ITO layer was prepared.
- Aqueous solution from each respective Examples 8-16 was used to etch the test-piece at a temperature of about 60 °C to 80 °C until etching was completed.
- Etching time for completing etching process in each of Examples 8-16 was measured and shown in the following Table 2.
- Example 2 compared to etching rate in Example 5 in which aqueous solution containing only oxalic acid composition at concentration of 150 g/L at a temperature of about 60 °C and 80 °C took 15 and 8.5 minutes, respectively, to complete the etching process, while the aqueous solution further comprising L-ascorbic acid in addition to oxalic acid, as in Examples 8-16, showed enhanced etching rate and took significantly less time to complete the etching process.
- An etchant composition as shown in Table 3, comprising oxalic acid and ammonium persulfate was prepared by mixing in a ratio of about 1 : 1 by weight and dissolving into aqueous solution.
- An etchant composition as shown in Table 4, comprising oxalic acid and H 2 O 2 (35 %), which were mixed in a ratio of about 1 : 1 by weight and dissolved into aqueous solution, was prepared.
- a bare glass substrate test-piece with 0.7mm thickness for LCD having 500 angstroms of ITO layer was prepared.
- Aqueous solution from each respective Examples 23-27 was used to etch the test-piece at a temperature of about 60 °C until etching was completed.
- Etching time for each Examples 23-27 was measured and shown in the following Table 4.
- the etching rate is decreased at a low oxalic acid concentration, but beyond oxalic acid concentration of about 150g/l in aqueous solution, it can be observed that the etching rate increases. Similar to the effects seen in Examples 17-22 having persulfate included therein to the oxalic acid composition, at a low concentration of oxalic acid the etchant composition having H 2 O 2 is unsuitable, while at high concentrations of oxalic acid the etchant composition can be used as a suitable etchant for etching ITO layer.
- An etchant composition was prepared by adding ammonium oxalic acid to aqueous solution in an amount shown for each respective Examples in Table 5.
- Etching rate measurements As described above, a bare glass substrate test-piece with 0.7mm thickness for LCD having 500 angstroms of ITO layer was prepared. Aqueous solution from each respective Examples 28-31 was used to etch the test-piece at a temperature of about 60 °C, 80 °C and 100 °C until etching was completed. Etching time for completing the etching process in each of Examples 28-31 was measured and shown in the following Table 5. Table 5
- the etching effect of ammonium oxalic acid decreases at a lower temperature of about 60 °C, and at a higher temperature above 70 °C the ammonium oxalic acid aqueous solution can be used as an ITO layer etchant.
- Examples 32-34 An etchant composition was prepared by adding aluminum chloride and L- ascorbic acid, both having same concentration, to aqueous solution.
- a bare glass substrate test-piece with 0.7mm thickness for LCD having 500 angstroms of ITO layer was prepared.
- Aqueous solution from each respective Examples 32-34 was used to etch the test-piece at a temperature of
- An etchant composition was prepared by dissolving aluminum chloride and oxalic acid into aqueous solution in an amount shown for each respective Examples in Table 7.
- a bare glass substrate test-piece with 0.7mm thickness for LCD having 500 angstroms of ITO layer was prepared.
- Aqueous solution from each respective Examples 35-37 was used to etch the test-piece at a temperature of 80 °C until etching was completed.
- Etching time for completing the etching process in each of Examples 35-37 was measured and shown in the following Table 7.
- An etchant composition was prepared by dissolving aluminum chloride into aqueous solution in an amount shown for each respective Examples in Table 8.
- a bare glass substrate test-piece with 0.7mm thickness for LCD having 500 angstroms of ITO layer was prepared.
- Aqueous solution from each respective Comparative Examples 1-6 was used to etch the test-piece at a temperature of about 60 °C, 80 °C and 100 °C until etching was completed.
- Etching time for completing the etching process in each of Comparative Examples 1-7 was measured and shown in the following Table 8.
- the etching rate of etchant composition comprising only aluminum chloride in aqueous solution is comparatively faster at high temperatures and high concentrations; however, at lower temperatures and concentrations, the etching rate is much too slow for it to be practically applied as an etchant composition for etching ITO layers.
- the etching time for the etchant composition in Comparative Example 4 having only aluminum chloride in aqueous solution was measured to 25 minutes at 80 °C, comparatively, by adding a reducing agent L-ascorbic acid to the composition solution, a faster etching rate was observed. Accordingly, in presence of a reducing agent, an increase of etching rates can be seen at comparatively lower temperatures, allowing the etchant composition comprising aluminum chloride to be applied as an etchant composition for etching ITO layers.
- a bare glass substrate test-piece with 0.7mm thickness for LCD having 500 angstroms of ITO layer was prepared.
- Aqueous solution from Example 4 and Comparative Example 6 was respectively used to etch the test-piece at a temperature of about 55 °C, 45 °C and 40 °C until etching was completed.
- Etching time for completing the etching process for the respective etchant composition was measured and shown in the following Table 9.
- the respective etchant compositions from Example 4 comprising oxalic acid and Comparative Example 6 comprising aluminum chloride exhibited decrease of etching rate in lower temperatures below 60 °C.
- the etchant composition comprising aluminum chloride of Comparative Example 6 showed inadequate etching rate for it to be used as an etchant composition for etching ITO layers.
- Examples 38 and 39 An etchant composition comprising oxalic acid and an etchant composition comprising ammonium oxalic acid for the respective Examples 38 and 39 was prepared by dissolving oxalic acid and ammonium oxalic acid into their respective aqueous solution at about 80 °C in a saturated amount shown for each respective Examples 38 and 39 in Table 10.
- a bare glass substrate test-piece with 0.7mm thickness for LCD having 500 angstroms of ITO layer was prepared.
- Aqueous solution from Examples 38 and 39 was respectively used to etch the test-piece at a temperature of about 80 °C until etching was completed.
- Etching time for the respective etchant composition was measured and shown in the following Table 10.
- an etchant composition comprising oxalic acid and an etchant composition comprising ammonium oxalic acid in their respective saturated concentration showed excellent etching rates for them to be applied as an etchant composition for etching ITO layers.
- a conventional aqua regia used for etching ITO layers was prepared by adding HCl (35 %) and HNO 3 (65 %) into deionized water (D.I.W) in 53 : 7 : 40 ratio by volume.
- a conventional iron chloride used for etching ITO layers was prepared by adding FeCl 3 , HCl (35 %) and HNO 3 (65 %) into deionized water (D.I.W) in 20 : 50 : 2 : 28 ratio by weight.
- D.I.W deionized water
- An etchant composition was prepared by adding a surfactant sodium dihexylsulfosuccinate into the respective aqueous etchant solution of Example 30 and Comparative Example 5.
- a test-piece was prepared by forming 500 angstroms of ITO layers onto 0.7mm bare glass. On the ITO layer, a 5 micro-meters of photoresist pattern was formed. Etchant solutions from Comparative Examples 7 and 8 and from Examples 3, 19, 40, and 41 was respectively used to etch the ITO layers of the test-piece at a temperature and time parameters set forth in Table 10. Then, for measuring the ITO layer line-width of the test-piece, acetone was used to remove photoresist and the line-width of the patterned ITO layer was measured.
- the resulting line-width of ITO layer after etching was in a range of about 4.72 to 4.76 micro-meters for the conventional etchants, while the etchants of the present invention yielded a much more superior result with ITO layer line-width of about 4.76 to 4.80 micro-meters.
- an additional etching was carried out for 2 minutes after the completion of above etching process.
- the etchants of the present invention provided a better result with ITO layer line- width of about 4.68 to 4.74 micro-meters, while the line-width of ITO layer after the additional etching was in a range of about 4.20 to 4.26 micro-meters for the conventional etchants.
- etching ratio an appropriate photoresist can be selected, thus etching can be carried out by controlling the etchant concentrations and temperatures more appropriately.
- a high selectivity of the etchant composition of the present invention was also determined, as the etchants showed an etching ratio of about 11 % to 33 % with Al-Nb.
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Abstract
An etchant composition for etching an ITO layer deposited on various electronic parts is disclosed. The etchant composition includes oxalic acid and its salts or aluminum chloride as its main components. For etching parameters which vary and as the needs may occur, the composition may appropriately comprise a persulfate or a surfactant. Due to its stable property as a composition and its characteristics of lessening the fuming effect prevalent with the conventional etchants, the etchant composition markedly reduces environmentally hazardous agents. The etchant composition has minimizing effects of side-etching, thus micropatterns can be more efficiently and accurately achieved.
Description
ITO ETCHING COMPOSITION
TECHNICAL FIELD The present invention relates to an etchant composition, and more particularly to an ITO etchant composition for etching Indium Tin Oxide (In2O3- SnO3) layers, a composite of indium and tin oxide (hereinafter referred to as ITO), formed on various electronic substrates for achieving a transparent electrode.
BACKGROUND ART In general, to obtain a transparent electrode on various electronic substrates, a composition of In2O3 and SnO3, in appropriate ratio, are deposited on a glass substrate in layers by a conventional sputtering technique. The deposited ITO layer is then coated with a photoresist to be exposed and developed for a desired pattern. Once the photoresist pattern is formed, the ITO layer is etched by using the photoresist pattern as an etching mask, to thereby fabricate a transparent electrode.
Due to an inherent chemical resistance of ITO, it is well known in the art that etching ITO layers chemically is a difficult process, and conventionally, three types of etchant are commonly used: aqua regia (HCl+HNO3+H2O), iron fluoride
(FeCl3+HCl), HBr, and HI. Aqua regia is economical in terms of cost, but the etchant composition is somewhat unstable and tend to volatilize into hydrochloric and nitric acids, and a large amount is etched in side-way pattern etching. Similar to aqua regia, iron fluoride etchant composition is also unstable and easily decompose into hydrochloric acid, a main constituent in the etchant composition. HBr and HI have fast etching rates and a low side-way pattern etching ability, but because of its cost, toxicity, and erosive effect, its commercial use in the manufacture of electronic substrates is limited.
Additionally, conventional ITO etchants due to their strong chemical activity tend to damage other substrates made of materials possessing weak chemical resistance, such as Al. Mo, and its alloy layers. This proposes a problem when fabricating electronic substrates requiring various muti-layer etching materials, for example as in TFT-LCD. and as a result, conventional etchants complicates the
manufacturing process by necessitating the need to use various selection of etching layers made from different types of materials; that is, materials with a significant etching rate difference to obtain a higher etching selectivity.
Further, conventional ITO etchants, because of its fuming characteristic, are agents of environmental pollution, as such, appropriate safety measures and installation of additional facilities is needed to properly dispose the fumes from the etchant. More, it is difficult to obtain a high rate of etching reproductivity with the conventional etchants due to the unstable characteristic of their composition, and in high temperatures the unstableness increases. Hence, the etchant must be frequently replaced or a fresh etchant is added to depleting ethchant to obtain a satisfactory rate of reproductivity, thus further increasing chemical waste to be disposed.
DISCLOSURE OF INVENTION In view of the foregoing, it is an object of the present invention to provide an etchant composition having an etching layer selectivity, an improved rate of reproductivity. a less toxicity, a less erosive effect, and a less fuming effect for use in ITO layer etching.
In order to achieve the above object, the present invention provides an ITO etchant composition comprising oxalic acid and its salts in aqueous solution, at a concentration range of from about 1.5g per liter of auqueous solution to its saturated concentration, to be used in certain temperatures.
The present invention also provides an ITO etchant composition comprising aluminum chloride in aqueous solution, at a concentration range of from about 80g per liter of aquous solution to its saturated concentration, to be used in certain temperatures.
The above aqueous solution of oxalic acid and its salts and aqueous solution of aluminum chloride can further comprise a persulfate.
As necessary, the above aqueous solution of oxalic acid and its salts and aqueous solution of aluminum chloride may further include about 0.01 to about 2 weight % of surfactant.
Accordingly, due to the less fuming effects and stableness of the etchant composition of the present invention, environmentally hazardous effects can be
minimized, while the etchant composition also provides decreased side-etching activity for obtaining micro-patterns.
BEST MODE FOR CARRYING OUT THE INVENTION The present invention will now be described in detail below.
A first preferred etchant composition comprises oxalic acid and its salts in aqueous solution.
Oxalic acid and its salts are strong reducing agents, and when in aqueous solution, oxalic acid exhibit chemical stability which makes it possible to store in room temperature for a significant duration of time (for more than a year in cold and dark storage) without decomposing. Because of strong reducing properties of both oxalic acid and its salts, they are commonly utilized as a reducing agent for reducing oxides.
In presence of light, in high temperatures, or when combined with other materials, oxalic acid aqueous solution decomposes and yields a reducing agent which reduces metal oxides, as shown below.
H2C2O4 = HCOOH + 2CO2 + CO +H2O (1)
H2C2O4 = CO2 + CO +H2O (2)
Here, the CO from the above is a reducing agent and it react with ITO, as shown by below reaction, for etching ITO layer.
In2O3 + 3CO = 2In + 3CO2 (3)
SnO2 + 2CO = Sn + 2CO2 (4)
Because the etching rate is slow for the above oxalic acid in concentration of less than 1.5g per liter of water (or aquous solution), and it crystallizes above its saturated concentration, accordingly, the concentration of oxalic acid is from about 1.5g per liter of water to its saturated concentration, preferably from of about 2 to 350g per liter of water.
Preferably, as an etchant, oxalic acid is preferably used due to its strong reducing property, and additionally, oxalic salts in aqueous solution which decompose into oxalic acid can also be used. As such oxalic salt, nonmetallic oxalic salts such as ammonium oxalate may be mentioned.
Persulfates in aqueous solution function as an uniform oxidizing agent. Its reaction in aqueous solution is show below.
S2O8 2- + 2e" = 2SO4 2- E=2.01V (5)
S2O8 2- + 2H2 = 2S04 2- + O2 + 4H+ (6)
Further, as the temperature of the aqueous solution increases, the following reaction is observed.
S2O8 2- + 4H20 = 2SO4 2- + H2O2 + 2H+ (7)
Although oxalic acid and its salts play a crucial role in reducing ITO oxide composition, in presence of persulfates an additional reduction activity can be observed when hydrogen ion is released by the above reaction formula (7), thus the presence of persulfates in aqueous solution further enhances the reducing activity of oxalic acid and its salts. It can be determined that the ITO layer to be removed by the etching process, during reduction process, closely react with each other in a complex oxidation/reduction.
Since the reduction activity for the above persulfate is not adequate in concentration of less than lg per liter of water (or aquous solution), and its reducing effect diminishes in an amount excess of 250g, an amount of persulfate is from about 1 to 250g per liter of water, preferably from of about 5 to 150g per liter of water.
As persulfate which can be used in the present invention, ammonium persulfate, sodium persulfate, potassium persulfate, etc. may be mentioned. Preferably ammonium persulfate is selectively used.
An ITO etchant of the present invention may further comprise a surfactant. Surfactants when used in etching process decrease the surface tension of etchant,
which increases the penetrating ability of the etchant, making it possible for the etchant to easily penetrate photoresist layers of micro-patterns. Surfactants also facilitate the removal of reactants from substrate layers, while increasing wettability of the substrate surface. As a result, surfactants decreases the etching time. When surfactants are used in an amount less than about O. lg per liter of water, its ability to decrease the surface tension of etchant composition decreases, and more, its characteristic effects fail to realize in an amount excess of 20g, and there also a possibility it may interfere with reduction activity. Accordingly, it is preferable to use an amount of surfactant from about 0.1 to 20g per liter of water, more preferably from about 0.5 to 5g per liter of water.
Surfactant of the present invention is sodium dihexylsulfosuccinate or similar salts of alkyl sulfonic acid.
Since, the ITO etchant composition comprising oxalic acid and its salts do not include halogen, the etchant composition is environmental friendly. According to another aspect of the present invention, an ITO etchant composition comprising a nonferrous metallic chloride such as aluminum chloride and a surfactant is provided.
The reaction of A1C13 etchant composition, in aqueous solution, with In2O3 and SnO3 is shown below.
In2O3 + A1C13 = In2Cl3 + l/2Al2O3 + 3/2O2 (1) SnO2 + AICI3 = SnCl2 + l/2Al2O3 + l/2O2 (2)
According to Examples of the present invention, it was found that aluminum chloride alone does not effectively etches the ITO layers, however, in conjunction with a surfactant or a reducing agent, it can be used for etching ITO layers.
If the above aluminum chloride is used in an amount of about 80g per liter of water, its etching rate in ITO layers is slow, and if the amount exceed the saturation concentration, the aluminum chloride crystallizes, accordingly, it is preferable to use an amount of about 80g per liter of water to its saturated concentration, more preferably from about 100 to 350g per liter of water.
An ITO etchant composition comprising ammonium chloride as its main
constituent includes a surfactant in an amount of about from O. lg to 20g per liter of aqueous solution, more preferably in an amount of from about 0.5 to 5g per liter of aqueous solution.
At this time, by adding a persulfate selected from a group already mentioned above, the etching rate increases. Persulfate should be added in an amount of about 1 to 250g per liter of aqueous solution, and preferably in an amount of from about 5 to 150g per liter of aqueous solution.
According to yet another aspect of the present invention, an ITO etchant composition comprising an organic acid, for performing the functions of reducing agent, and aluminum chloride is also provided.
As organic acids which is used in the present invention as a reducing agent, oxalic acid, L-ascorbic acid, etc. may be mentioned.
For TFT-LCDs (Thin film transistor-Liquid crystal display), Al layer, Mo layer or their metallic alloy layer, a-Si layer, poly-Si layer, SiNx layer, SiO2 layer, Cr layer, ITO layer are conventionally used. It is common during the etching process, there is a risk of damaging lower gate wirings or sour/drain wirings made from Al, Mo or their alloys.
A majority of conventional etchants used for etching TFT-LCDs comprise chloride ions, fluorine ions from the halogen elements and cyanide ions. Etchants comprising these ions tend to erode metallic wirings made from the materials as mentioned above. In order to deal with this problem, metallic layers to be etched are made much thicker than its desired thickness.
An ITO etchant composition of the present invention comprising oxalic acid or its salts overcomes the damaging effects of the above problem by not eroding the neighboring and supporting layers and layers made from Al, Mo or their metallic alloy composition during the etching process.
More, in aluminum chloride ITO etchant composition of the present invention, aluminum chloride dissolve in aqueous solution and exists as a salt as opposed to naturally occurring acids similar to hydrochloric acid, thus fuming effects which is common in the conventional etchants can be drastically eliminated.
It is preferable that the etchant compositions of the present invention be under heat in order to accelerate the etching rate. Preferably an 'etching temperature
is from about room temperature to the boiling point of each ITO etchant composition, and more preferably from about 35 °C to 85 °C.
Etchant composition of the present invention can be accomplished with dipping, spray, water turbulence, and ultrasonic methods. Further implementation of the etchant composition is also possible with other methods for realizing the present invention.
Although, the etchant compositions of the present invention is used in aqueous solution, the composition may be separated into solute particles for storage and transportation, and dissolved into an aqueous solution prior to use. During use, an additional solute particles can be added to the aqueous composition for extending the life of the etchant composition.
The examples of the present invention will be described in detail below. The following examples are provided to further illustrate the invention and are not intended to limit the scope of the present invention. For the following Examples and Comparative Examples, a test-piece of
0.7mm thickness for LCD was prepared by depositing ITO into a bare glass by sputtering method until 500 angstroms of ITO layer thickness was obtained.
Commercially available ammonium oxalate monohydrate and aluminum chloride hexahydrate was respectively used for ammonium oxalate and aluminum chloride of the present invention.
Examples 1-7
For the respective Examples, an oxalic acid in aqueous solution in concentration as shown in Table 1 was prepared. Etching rate measurements
A bare glass substrate test-piece with 0.7mm thickness for LCD having 500 angstroms of ITO layer was prepared. Aqueous solution from each respective Examples 1-7 was used to etch the test-piece at a temperature of about 60 °C to 80 °C until etching was completed. Etching time for completing etching process in each of Examples 1-7 was measured and shown in the following Table 1.
Table 1
As it can be determined from Table 1 , as the concentration and etching temperature of oxalic acid increases, the etching rate of oxalic acid increases, decreasing the time it takes to etch ITO layer.
In Example 5, when the temperature of the aqueous solution was raised to 100 °C, the time it took for oxalic acid aqueous solution to etch ITO layer was measured to be 1 minute.
Examples 8-16
An etchant composition was prepared by adding L-ascorbic acid, in an amount shown for each respective Examples 8-16 in Table 2, to the aqueous solution of Example 4 (oxalic acid aqueous solution in concentration of 150g/l) for respective Examples 8-16.
Etching rate measurements
As described above, a bare glass substrate test-piece with 0.7mm thickness for LCD having 500 angstroms of ITO layer was prepared. Aqueous solution from each respective Examples 8-16 was used to etch the test-piece at a temperature of about 60 °C to 80 °C until etching was completed. Etching time for completing etching process in each of Examples 8-16 was measured and shown in the following Table 2.
Table 2
As it can be determined from Table 2, compared to etching rate in Example 5 in which aqueous solution containing only oxalic acid composition at concentration of 150 g/L at a temperature of about 60 °C and 80 °C took 15 and 8.5 minutes, respectively, to complete the etching process, while the aqueous solution further comprising L-ascorbic acid in addition to oxalic acid, as in Examples 8-16, showed enhanced etching rate and took significantly less time to complete the etching process.
Examples 17-22
An etchant composition, as shown in Table 3, comprising oxalic acid and ammonium persulfate was prepared by mixing in a ratio of about 1 : 1 by weight and dissolving into aqueous solution.
Etching rate measurements
As described above, a bare glass substrate test-piece with 0.7mm thickness for LCD having 500 angstroms of ITO layer was prepared. Aqueous solution from each respective Examples 17-22 was used to etch the test-piece at a temperature of about 60 °C until etching was completed. Etching time for each Examples 17-22 was measured and shown in the following Table 3.
Table 3
As it can be determined from Table 3, although persulfate is not directly involved in the chemical reaction, its presence in the aqueous solution when the amount of oxalic acid is up to lOOg per liter of solution, as observed from the etching time in Examples 17-22, increases the etching rate.
Examples 23-27
An etchant composition, as shown in Table 4, comprising oxalic acid and H2O2 (35 %), which were mixed in a ratio of about 1 : 1 by weight and dissolved into aqueous solution, was prepared.
Etching rate measurements
As described above, a bare glass substrate test-piece with 0.7mm thickness for LCD having 500 angstroms of ITO layer was prepared. Aqueous solution from each respective Examples 23-27 was used to etch the test-piece at a temperature of about 60 °C until etching was completed. Etching time for each Examples 23-27 was measured and shown in the following Table 4.
Table 4
- min* (inapplicable for etching process)
As it can be determined from Table 4, when H2O2 is added to the oxalic acid aqueous solution, the etching rate is decreased at a low oxalic acid concentration, but beyond oxalic acid concentration of about 150g/l in aqueous solution, it can be observed that the etching rate increases. Similar to the effects seen in Examples 17-22 having persulfate included therein to the oxalic acid composition, at a low concentration of oxalic acid the etchant composition having H2O2 is unsuitable, while at high concentrations of oxalic acid the etchant composition can be used as a suitable etchant for etching ITO layer.
Examples 28-31
An etchant composition was prepared by adding ammonium oxalic acid to aqueous solution in an amount shown for each respective Examples in Table 5.
Etching rate measurements As described above, a bare glass substrate test-piece with 0.7mm thickness for LCD having 500 angstroms of ITO layer was prepared. Aqueous solution from each respective Examples 28-31 was used to etch the test-piece at a temperature of
about 60 °C, 80 °C and 100 °C until etching was completed. Etching time for completing the etching process in each of Examples 28-31 was measured and shown in the following Table 5. Table 5
- min* (inapplicable for etching process)
As it can be determined from Table 5, the etching effect of ammonium oxalic acid decreases at a lower temperature of about 60 °C, and at a higher temperature above 70 °C the ammonium oxalic acid aqueous solution can be used as an ITO layer etchant.
Examples 32-34 An etchant composition was prepared by adding aluminum chloride and L- ascorbic acid, both having same concentration, to aqueous solution.
Etching rate measurements
As described above, a bare glass substrate test-piece with 0.7mm thickness for LCD having 500 angstroms of ITO layer was prepared. Aqueous solution from each respective Examples 32-34 was used to etch the test-piece at a temperature of
80 °C until etching was completed. Etching time for completing the etching process
in each of Examples 32-34 was measured and shown in the following Table 6.
Table 6
Examples 35-37
An etchant composition was prepared by dissolving aluminum chloride and oxalic acid into aqueous solution in an amount shown for each respective Examples in Table 7.
Etching rate measurements
As described above, a bare glass substrate test-piece with 0.7mm thickness for LCD having 500 angstroms of ITO layer was prepared. Aqueous solution from each respective Examples 35-37 was used to etch the test-piece at a temperature of 80 °C until etching was completed. Etching time for completing the etching process in each of Examples 35-37 was measured and shown in the following Table 7.
Table 7
Comparative Examples 1-6
An etchant composition was prepared by dissolving aluminum chloride into aqueous solution in an amount shown for each respective Examples in Table 8.
Etching rate measurements
As described above, a bare glass substrate test-piece with 0.7mm thickness for LCD having 500 angstroms of ITO layer was prepared. Aqueous solution from each respective Comparative Examples 1-6 was used to etch the test-piece at a temperature of about 60 °C, 80 °C and 100 °C until etching was completed. Etching time for completing the etching process in each of Comparative Examples 1-7 was measured and shown in the following Table 8.
Table 8.
-minutes* (for etching time more than 80 minutes, an insufficient etching is observed)
As it can be determined from Table 8, the etching rate of etchant composition comprising only aluminum chloride in aqueous solution is comparatively faster at high temperatures and high concentrations; however, at lower temperatures and concentrations, the etching rate is much too slow for it to be practically applied as an etchant composition for etching ITO layers.
Although, as it can seen from Table 7, the etching time for the etchant composition in Comparative Example 4 having only aluminum chloride in aqueous solution was measured to 25 minutes at 80 °C, comparatively, by adding a reducing agent L-ascorbic acid to the composition solution, a faster etching rate was observed. Accordingly, in presence of a reducing agent, an increase of etching rates can be seen at comparatively lower temperatures, allowing the etchant composition comprising aluminum chloride to be applied as an etchant composition for etching ITO layers.
Measurement of etching rate below 60 °C
As described above, a bare glass substrate test-piece with 0.7mm thickness for LCD having 500 angstroms of ITO layer was prepared. Aqueous solution from Example 4 and Comparative Example 6 was respectively used to etch the test-piece at a temperature of about 55 °C, 45 °C and 40 °C until etching was completed.
Etching time for completing the etching process for the respective etchant composition was measured and shown in the following Table 9.
Table 9
-minutes* (for etching time more than 80 minutes, an insufficient etching is observed)
As it can be determined from Table 9, the respective etchant compositions from Example 4 comprising oxalic acid and Comparative Example 6 comprising aluminum chloride exhibited decrease of etching rate in lower temperatures below 60 °C. Particularly, the etchant composition comprising aluminum chloride of Comparative Example 6 showed inadequate etching rate for it to be used as an etchant composition for etching ITO layers.
Measurements of etching rates of oxalic acid and ammonium oxalic acid in their respective saturated concentration under same temperature
Examples 38 and 39 An etchant composition comprising oxalic acid and an etchant composition comprising ammonium oxalic acid for the respective Examples 38 and 39 was prepared by dissolving oxalic acid and ammonium oxalic acid into their respective aqueous solution at about 80 °C in a saturated amount shown for each respective
Examples 38 and 39 in Table 10.
As described earlier, a bare glass substrate test-piece with 0.7mm thickness for LCD having 500 angstroms of ITO layer was prepared. Aqueous solution from Examples 38 and 39 was respectively used to etch the test-piece at a temperature of about 80 °C until etching was completed. Etching time for the respective etchant composition was measured and shown in the following Table 10.
Table 10
As it can be determined from the Table 10, an etchant composition comprising oxalic acid and an etchant composition comprising ammonium oxalic acid in their respective saturated concentration showed excellent etching rates for them to be applied as an etchant composition for etching ITO layers.
Comparative Example 7
A conventional aqua regia used for etching ITO layers was prepared by adding HCl (35 %) and HNO3 (65 %) into deionized water (D.I.W) in 53 : 7 : 40 ratio by volume.
Comparative Example 8
A conventional iron chloride used for etching ITO layers was prepared by adding FeCl3, HCl (35 %) and HNO3 (65 %) into deionized water (D.I.W) in 20 : 50 : 2 : 28 ratio by weight.
Examples 40 and 41
An etchant composition was prepared by adding a surfactant sodium dihexylsulfosuccinate into the respective aqueous etchant solution of Example 30 and Comparative Example 5.
Measurements in decrease in line-width by etchants
For measuring the decrease in line-width by etchants, a test-piece was prepared by forming 500 angstroms of ITO layers onto 0.7mm bare glass. On the ITO layer, a 5 micro-meters of photoresist pattern was formed. Etchant solutions from Comparative Examples 7 and 8 and from Examples 3, 19, 40, and 41 was respectively used to etch the ITO layers of the test-piece at a temperature and time parameters set forth in Table 10. Then, for measuring the ITO layer line-width of the test-piece, acetone was used to remove photoresist and the line-width of the patterned ITO layer was measured.
The conventional etchants of Comparative Examples 7 an 8, because they have a common tendency to fume and decompose in high temperatures during the etching process, the test was carried out in a conventional etching temperature of 40 °C used in manufacturing line.
The etchants of Examples 3, 9, 40, and 41 , because they do not have a tendency to fume and decompose in temperatures above 60 °C during the etching process, and also in consideration of their etching rates, the test was carried out in temperatures above 60 °C.
Etching times and line-widths of ITO layers with a pattern were measured and shown in below Table 11.
Table 11
As it can be determined from the above table, the resulting line-width of ITO layer after etching was in a range of about 4.72 to 4.76 micro-meters for the conventional etchants, while the etchants of the present invention yielded a much more superior result with ITO layer line-width of about 4.76 to 4.80 micro-meters.
In view of LCD manufacturing process for a LCD having a large surface area, an additional etching was carried out for 2 minutes after the completion of above etching process. Again, the etchants of the present invention provided a better result with ITO layer line- width of about 4.68 to 4.74 micro-meters, while the line-width of ITO layer after the additional etching was in a range of about 4.20 to 4.26 micro-meters for the conventional etchants.
Conventional etchants compared to the etchants composition of the present invention accomplish etching in a shorter time. However, in order to obtain substrates uniformity, there is a drawback with the conventional etchants in that only spray method can be implemented. In contrast, the etchant composition of present invention makes it possible to etch tens of panels inserted into a cassette simultaneously, hence the comparison of etching rates obtained by the present invention to the etching rates in the conventional etchants becomes less significant. Rather, in view of more important factors to be considered for etching process, such as the accuracy of circuit patterns and minimization of circuit line-width, one can appreciate the advantageous effects of the etchant composition provided by the present invention.
Further, with respect to etching ratio, an appropriate photoresist can be selected, thus etching can be carried out by controlling the etchant concentrations and temperatures more appropriately.
Additionally, because of existence of different response time to a single
etchant when etching a large-scale substrate comprising a wide-array of layers to be etched, there is a need to increase the etching time to completely etch portions not covered by photoresist pattern. With this regard, as shown in the above Table 10, a further etching was carried out for 2 additional minutes, and a notable difference in line-width decrease rate between the etchant compositions of the present invention and the conventional etchants was observed. Hence, it was determined that a difficulty would arise when conventional etchant are used for obtaining micro line- width etching product.
Comparison of selectivity of etchant solutions
Six substrate test-pieces having Al-Nb layer with thickness of 500 A, Mo-W layer with thickness of 5000 A. Cr layer with thickness of 1500 A, a-Si layer with thickness of 1500 A, SiNx layer with thickness of 3000 A, and ITO layer with thickness of 500 A, respectively, was prepared. Aqueous solution from Comparative Examples 7 and 8 and Examples 3, 19, 40, and 41 was respectively used to etch the test-pieces at a certain temperature by dipping until etching was completed. Etching selectivity of the etchant compositions for the different layers was observed and shown in the following Table 12.
Table 12
As can be seen from the above table, a conventional aqua regia etchant, while etching 500 A of ITO layer also etched into the layers of Al-Nb and Mo-W. In contrast, the etchant compositions of the present invention left Mo-W layer intact.
A high selectivity of the etchant composition of the present invention was also determined, as the etchants showed an etching ratio of about 11 % to 33 % with Al-Nb.
To increase the etching selectivity between ITO and Al-Nb layers, an additional test was carried out with the aqueous solution of Example 4 for about 25 minutes at about 60 °C. ITO layer showed 100% etching while only 2% of Al-Nb layer was etched.
Comparison of decomposition of etchant solutions To measure decomposition, conventional etchants aqua regia and iron chloride utilized for Comparative Examples 7 and 8, respectively, and the etchant solutions of Examples 3, 19, and 41 were placed in 200ml beaker, respectively. Aqua regia and iron chloride etchant solutions were allowed stand in their respective beakers at their conventional application temperature of about 40 °C for a predetermined time shown in the following Table 13, while the etchant solutions of the present invention were allowed to stand in their respective beakers at a preferred etching temperature of about 60 °C for a predetermined time, prior to being used for etching. ITO layer was etched with the above etchant solutions and etching times were measured and shown in the below Table 13.
Table 13
As can be seen from the above table, there is a notable difference in etching time for both conventional aqua regia and iron chloride etchants when the etchant solutions were allowed to stand in beaker prior to use, as opposed to directly applying the etchants for the etching process. This is mainly attributed by vaporization of hydrochloric acid, which occupy most of both aqua regia and iron chloride etchants contents, when the etchants decompose during the waiting period prior to being applied for the etching process. On the other hand, the etchant compositions of the present invention is determined to exhibit a little or no decomposition during the specified waiting time, as the etching time showed a minimal or inappreciable difference. This result is significantly an important factor for obtaining reproductivity, as less decomposition of etchants lead to a higher reproductivity in the manufacture of devices.
While the present invention has been particularly shown and described with reference to particular Examples thereof, it will be understood by those skilled in the art that various changes in form and details may be effected therein without departing from the spirit and scope of the invention as defined by the appended claims.
Claims
1. An etchant composition for etching ITO layers comprising oxalic acid and its salts in aqueous solution, at a concentration range from about 1.5g per liter of the aqueous solution to its saturated concentration, to be used in certain temperatures.
2. An etchant composition for etching ITO layers as claimed in claim 1 , wherein the oxalic salt is ammonium oxalate.
3. An etchant composition for etching ITO layers as claimed in claim 1 , wherein the etchant composition further comprises a persulfate in an amount of about lg to about 250g per liter of aqueous solution.
4. An etchant composition for etching ITO layers as claimed in claim
3, wherein the persulfate is ammonium persulfate.
5. An etchant composition for etching ITO layers as claimed in claim 1 , wherein the etchant composition further comprises a surfactant in an amount of about O. lg to about 20g per liter of aqueous solution.
6. An etchant composition for etching ITO layers as claimed in claim 5, wherein the surfactant is sodium dihexylsulfosuccinate.
7. An etchant composition for etching ITO layers as claimed in claim
1 , wherein the etchant composition further comprises a nonferrous metallic chloride in an amount of from about 50g per liter of aqueous solution to its saturated concentration.
8. An etchant composition for etching ITO layers comprising oxalic acid in aqueous solution, at a concentration range from about 0.1 weight % to its saturated concentration, to be used in certain temperatures; wherein the etchant composition further comprises a persulfate in an amount of from about lg to about 250g per liter of aqueous solution.
9. An etchant composition for etching ITO layers as claimed in claim
8, wherein the persulfate is ammonium persulfate.
10. An etchant composition for etching ITO layers comprising: oxalic acid in aqueous solution, at a concentration range from about 1.5g per liter of aqueous solution to its saturated concentration, to be used in certain temperatures; and a surfactant in an amount of from about O. lg to about 20g per liter of aqueous solution.
11. An etchant composition for etching ITO layers as claimed in claim
10, wherein the surfactant is sodium dihexylsulfosuccinate.
12. An etchant composition for etching ITO layers comprising: aluminum chloride in aqueous solution, at a concentration range from about 820g per liter of aqueous solution to its saturated concentration, to be used in certain temperatures; and a surfactant in an amount of from about O. lg to about 20g per liter of aqueous solution.
13. An etchant composition for etching ITO layers as claimed in claim
12, wherein the etchant composition further comprises a persulfate in an amount of about lg to about 250g per liter of aqueous solution.
14. An etchant composition for etching ITO layers comprising: aluminum chloride in aqueous solution, at a concentration range from about
80g per liter of aqueous solution to its saturated concentration, to be used in certain temperatures; and a reducing agent in an amount of from about 0.5g to about lOOg per liter of aqueous solution.
15. An etchant composition for etching ITO layers as claimed in claim 14, wherein the reducing agent is L-ascorbic acid or oxalic acid.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| KR19980033377 | 1998-08-18 | ||
| KR1998/33377 | 1998-08-18 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| WO2000011107A1 true WO2000011107A1 (en) | 2000-03-02 |
Family
ID=19547495
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| PCT/KR1999/000459 WO2000011107A1 (en) | 1998-08-18 | 1999-08-18 | Ito etching composition |
Country Status (1)
| Country | Link |
|---|---|
| WO (1) | WO2000011107A1 (en) |
Cited By (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| SG89419A1 (en) * | 2000-09-08 | 2002-06-18 | Kanto Kagaku | Etching liquid composition |
| WO2007003255A1 (en) * | 2005-07-04 | 2007-01-11 | Merck Patent Gmbh | Medium for etching oxidic transparent conductive layers |
| CN102585832A (en) * | 2011-12-30 | 2012-07-18 | 江阴江化微电子材料股份有限公司 | Low-tension ITO (Indium Tin Oxide) etching liquid and preparation method thereof |
| CN105087009A (en) * | 2014-04-30 | 2015-11-25 | 王丽 | Process for etching ITO film |
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| DD258698A1 (en) * | 1985-02-21 | 1988-07-27 | Akad Wissenschaften Ddr | METHOD FOR PRODUCING ELECTRICALLY CONDUCTIVE INDIUM TIN OXIDE PATTERN ON INSULATING SUPPORTS |
| JPH07141932A (en) * | 1993-11-18 | 1995-06-02 | Kanto Chem Co Inc | Etching liquid composition for transparent conductive film |
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| DD258698A1 (en) * | 1985-02-21 | 1988-07-27 | Akad Wissenschaften Ddr | METHOD FOR PRODUCING ELECTRICALLY CONDUCTIVE INDIUM TIN OXIDE PATTERN ON INSULATING SUPPORTS |
| DD253512A1 (en) * | 1986-10-21 | 1988-01-20 | Werk Fernsehelektronik Veb | METHOD FOR STRUCTURING TRANSPARENT CONDUCTIVE METAL OXIDE LAYERS |
| JPH07141932A (en) * | 1993-11-18 | 1995-06-02 | Kanto Chem Co Inc | Etching liquid composition for transparent conductive film |
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Cited By (7)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| SG89419A1 (en) * | 2000-09-08 | 2002-06-18 | Kanto Kagaku | Etching liquid composition |
| US6914039B2 (en) | 2000-09-08 | 2005-07-05 | Kanto Kagaku Kabushiki Kaisha | Etching liquid composition |
| US7507350B2 (en) | 2000-09-08 | 2009-03-24 | Kanto Kagaku Kabushiki Kaisha | Etching liquid composition |
| WO2007003255A1 (en) * | 2005-07-04 | 2007-01-11 | Merck Patent Gmbh | Medium for etching oxidic transparent conductive layers |
| CN102585832A (en) * | 2011-12-30 | 2012-07-18 | 江阴江化微电子材料股份有限公司 | Low-tension ITO (Indium Tin Oxide) etching liquid and preparation method thereof |
| CN105087009A (en) * | 2014-04-30 | 2015-11-25 | 王丽 | Process for etching ITO film |
| CN105087009B (en) * | 2014-04-30 | 2017-06-30 | 东莞市钜升金属科技有限公司 | A kind of technique for ito film etching |
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