US 20150.048053A1 (19) United States (12) Patent Application Publication (10) Pub. No.: US 2015/0048053 A1 Cordonier et al. (43) Pub. Date: Feb. 19, 2015
(54) SELECTIVEETCHING METHOD Publication Classification (51) Int. C. (75) Inventors: Christopher Cordonier, Kanagawa C09K I3/02 (2006.01) (JP); Mitsuhiro Nabeshima, Kanagawa C23F L/40 (2006.01) (JP); Shingo Kumagai, Kanagawa (JP); C23F I/44 (2006.01) Naoki Takahashi, Kanagawa (JP) C23F I/38 (2006.01) (52) U.S. C. CPC. C09K 13/02 (2013.01); C23H 1/38 (2013.01); (73) Assignee: JCUCORPORATION, Tokyo (JP) C23F I/40 (2013.01); C23H I/44 (2013.01) USPC ...... 216/97: 216/99: 216/105: 216/100; (21) Appl. No.: 14/385,007 252/79.5; 562/476; 562/584; 562/477; 562/585 (22) PCT Fled: Sep. 3, 2012 (57) ABSTRACT A layer of a metal selected from titanium, niobium, tungsten, (86) PCT NO.: PCT/UP2012/072301 molybdenum, ruthenium, rhodium, arsenic, aluminum and S371 (c)(1), gallium, an oxide of the metal, a nitride of the metal, silicon (2), (4) Date: Sep. 12, 2014 nitride, hafnium nitride, tantalum nitride, or an alloy of these metals, the layer being provided on an underlying base mate (30) Foreign Application Priority Data rial selected from glass, silicon, copper and nickel, is selec tively etched with an alkaline etching solution containing a Mar. 12, 2012 (JP) ...... PCT/JP2012/056315 predefined complexing agent. Patent Application Publication Feb. 19, 2015 Sheet 1 of 2 US 2015/0048053 A1
Patent Application Publication Feb. 19, 2015 Sheet 2 of 2 US 2015/0048053 A1
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US 2015/0048053 A1 Feb. 19, 2015
SELECTIVE ETCHING METHOD glass, silicon, copper and nickel, and the present inventors completed the present invention. TECHNICAL FIELD 0009 Specifically, the present invention relates to an etch 0001. The present invention relates to a method for selec ing method, including: bringing a layer of a metal selected tively etching a layer of a metal selected from titanium, nio from titanium, niobium, tungsten, molybdenum, ruthenium, bium, tungsten, molybdenum, ruthenium, rhodium, arsenic, rhodium, arsenic, aluminum and gallium, an oxide of the aluminum and gallium, an oxide of the metal, a nitride of the metal, a nitride of the metal, silicon nitride, hafnium nitride, metal, silicon nitride, hafnium nitride, tantalum nitride, oran tantalum nitride, or an alloy of these metals, the layer being alloy of these metals, the layer being provided on an under provided on an underlying base material selected from glass, lying base material selected from glass, silicon, copper and silicon, copper and nickel, into contact with an etching solu nickel, in preference to the underlying base material. tion which consists essentially of at least one complexing agent selected from compounds shown by Formulas (I) and BACKGROUND ART (II) and which is alkaline, thereby selectively etching the 0002. In general, when etching of titanium is carried out, a metal selected from titanium, niobium, tungsten, molybde hydrofluoric acid-based etching solution is used. However, num, ruthenium, rhodium, arsenic, aluminum and gallium, when Such a hydrofluoric acid-based etching solution is used, the oxide of the metal, the nitride of the metal, silicon nitride, the underlying base material will also be etched in cases hafnium nitride, tantalum nitride, or the alloy of these metals, where the underlying base material is nickel or glass. 0003. Furthermore, when etching of titanium is carried out, a sodium hydroxide solution may be used. However, Chemical Formula 1 titanium will hardly be etched with such an etching solution (I) alone, and the etching rate is very slow even when hydrogen peroxide is combined with the etching solution to improve the etching rate. Therefore, this etching solution is impracticable. R2 OH 0004. In recent years, as for etching solutions for titanium, a method in which EDTA is used as a complexing agent has been known, and, specifically, a method in which an alkaline etching solution containing EDTA and hydrogen peroxide is used has been known (Patent Document 1). wherein R' to R may be identical to or different from one 0005. However, while titanium deposited on lithium nio another, and are -R, OR, OOR, COOR, bate (LiNbO) can be selectively etched by this method, there COOOR, CHCOOR, CHCOOOR3, CRO or is a problem of slow etching rate. Furthermore, in this —CHCHCH, where R to R' may be identical to or different method, Some Substances (metals) cannot be etched, and the from one another, and are hydrogen, a C1 to C10 Saturated underlying base material may be adversely affected depend aliphatic group, a C1 to C10 unsaturated aliphatic group, oran ing on the type of the underlying base material. For example, aryl group, and since the etching rate of titanium is slower than the etching rate of nickel, the underlying base material is dissolved prior Chemical Formula 2) to dissolution of titanium. (II) PRIOR ART DOCUMENT
Patent Document 0006 Patent Document 1: U.S. Pat. No. 4,554,050 SUMMARY OF THE INVENTION
Problems that the Invention is to Solve 0007 An objective of the present invention is to provide a wherein R* to R' may be identical to or different from one method for selectively etching not only titanium but also another, and are - R, OR, OOR, COOR', other metals at practical speed in preference to the underlying COOOR", CHCOOR", CHCOOOR, CRPO, base material. —CH2CHCH. —CN, NC, NO. —F. —Cl, —Br. —I, or -SOR where R to R may be identical to or different Means for Solving the Problems from one another, and are hydrogen, a C1 to C10 Saturated 0008. The present inventors conducted intensive studies to aliphatic group, a C1 to C10 unsaturated aliphatic group, oran solve the above-described problem. Consequently, the aryl group, and X is -OH,-COOH or -COOOH. present inventors found that an alkaline etching Solution con 0010 Furthermore, the present invention relates to an taining a specific complexing agent can selectively etch a etching Solution for a metal selected from titanium, niobium, metal selected from titanium, niobium, tungsten, molybde tungsten, molybdenum, ruthenium, rhodium, arsenic, alumi num, ruthenium, rhodium, arsenic, aluminum and gallium, an num and gallium, an oxide of the metal, a nitride of the metal, oxide of the metal, a nitride of the metal, silicon nitride, silicon nitride, hafnium nitride, tantalum nitride, or an alloy hafnium nitride, tantalum nitride, or an alloy of these metals, of these metals, provided on an underlying base material in preference to the underlying base material selected from selected from glass, silicon, copper and nickel, the etching US 2015/0048053 A1 Feb. 19, 2015
Solution consisting essentially of at least one complexing 0014 FIG. 2 shows SPM photos and Ra values of samples agent selected from compounds shown by Formulas (I) and which were etched under etching conditions of 80° C. and 5 (II) minutes by using the etching Solution of Example 6 in Test Example 4. (In this figure. (A) refers to the surface of Sample A: (B) refers to the surface of Sample B: (C) refers to the Chemical Formula 3 surface of Sample B which was subjected to etching; and (D) refers to the surface of Sample A which was subjected to (I) etching.) (0015 FIG.3 shows SEM photos (upside) and SPM photos (downside) of samples which were etched under etching con R2 OH ditions of 80° C. and 40 minutes by using the etching solution of Example 6 in Test Example 5. (In this figure, (A) refers to the surface of Sample A; (B) refers to the surface of Sample B: and (C) refers to the surface of Sample B which was subjected wherein R' to R may be identical to or different from one to etching.) another, and are -R, OR, —OOR, COOR, (0016 FIG. 4 shows SEM photos (upside) and SPM photos COOOR, CHCOOR, CHCOOOR3, CRO or (downside) of samples which were etched under etching con —CHCHCH, where R to R' may be identical to ordifferent ditions of 80° C. and 25 seconds by using the etching solution from one another, and are hydrogen, a C1 to C10 Saturated of Example 6 in Test Example 6. (In this figure, (A) refers to aliphatic group, a C1 to C10 unsaturated aliphatic group, oran the surface of Sample A; (B) refers to the surface of Sample B: aryl group, and and (C) refers to the surface of Sample B which was subjected to etching.)
Chemical Formula 4 MODE FOR CARRYING OUT THE INVENTION (II) 0017. The method for selectively etching a metal selected from titanium, niobium, tungsten, molybdenum, ruthenium, rhodium, arsenic, aluminum and gallium, an oxide of the metal, a nitride of the metal, silicon nitride, hafnium nitride, tantalum nitride, or an alloy of these metals according to the present invention (hereinafter, simply referred to as “the method of the present invention') is carried out by bringing a layer of a metal selected from titanium, niobium, tungsten, molybdenum, ruthenium, rhodium, arsenic, aluminum and wherein R* to R' may be identical to or different from one gallium, an oxide of the metal, a nitride of the metal, silicon another, and are - R', -OR, —OOR', -COOR', nitride, hafnium nitride, tantalum nitride, or an alloy of these COOOR", CHCOOR", CHCOOOR, CRPO, metals, the layer being provided on an underlying base mate —CH2CHCH. —CN, NC, NO. —F. —Cl, —Br. —I, rial selected from glass, silicon, copper and nickel, into con or - SOR where R to R may be identical to or different tact with an etching solution which consists essentially of at from one another, and are hydrogen, a C1 to C10 Saturated least one complexing agent selected from compounds shown aliphatic group, a C1 to C10 unsaturated aliphatic group, oran by Formulas (I) and (II) and which is alkaline. aryl group, and X is —OH, -COOH or COOOH, wherein the etching Solution is alkaline. Chemical Formula 5 Advantage of the Invention (I) OH O 0011. According to the present invention, a metal selected R3 from titanium, niobium, tungsten, molybdenum, ruthenium, rhodium, arsenic, aluminum and gallium, an oxide of the R2 OH metal, a nitride of the metal, silicon nitride, hafnium nitride, RI tantalum nitride, or an alloy of these metals can be etched at practical speed in preference to the underlying base material Chemical Formula 6 selected from glass, silicon, copper and nickel. 4 (II) 0012. Furthermore, the present invention can be utilized R not only for the above-described etching but also for recycling R X of the underlying base material selected from glass, silicon, copper and nickel, or for recovery of the above-described metal, oxide of the metal, nitride of the metal, silicon nitride, R6 OH hafnium nitride, tantalum nitride, or alloy of these metals. R7 BRIEF DESCRIPTION OF THE DRAWINGS 0013 FIG. 1 shows a photo of the appearance of a sample Additionally, in the present specification, "consisting (con which was etched under etching conditions of 80°C. and 30 sist) essentially of means that any Substances which are other seconds by using the etching Solution of Example 6 in Test than the Substance referred to by "consisting (consist) essen Example 1. tially of and which influence the effects of the invention US 2015/0048053 A1 Feb. 19, 2015
should be excluded (in other words, any substances which do 0023 The content of the above-described complexing not influence the effects of the invention can be included), and agents in the etching solution is 0.001 mol/L or more, pref preferably means that any substances which are other than the erably 0.1 to 1 mol/L. substance referred to by “consisting (consist) essentially of 0024. The pH of the etching solution used in the method of are not at all included (in other words, only the substance the present invention is not particularly limited as long as the referred to by “consisting (consist) essentially of is etching solution is alkaline. However, since the higher the pH included). of the etching Solution is, the higher the etching rate becomes, 0018. As to the compound shown by Formula (I) among the pH of the etching solution may be adjusted to preferably complexing agents used in the method of the present inven 9 or higher, more preferably 10 to 14, particularly preferably tion, R' to R may be identical to or different from one 11 to 14, more particularly preferably 12 to 14. The method another, and are -R, OR, OOR, COOR, for making the etching Solution alkaline is not particularly COOOR, CHCOOR, CHCOOOR3, CRO or limited, and an alkaline material Such as Sodium hydroxide or —CHCHCH (where R to R' may be identical to or differ potassium hydroxide may be used. ent from one another, and are hydrogen, a C1 to C10 Saturated 0025. It is preferable that the etching solution used for the aliphatic group, a C1 to C10 unsaturated aliphatic group, oran method of the present invention further contains an oxidizing aryl group). R' to Rare preferably —H, -OH,-COOH or agent. By having Such an oxidizing agent contained in the etching solution, the etching rate will increase. A type of the CHCOOH. oxidizing agent is not particularly limited. However, an oxi 0019. As specific examples of the compound shown by dizing agent which itself does not corrode the underlying base Formula (I), 3-hydroxypropionic acid, tartaric acid, citric material is preferable. As examples of such an oxidizing agent acid, malic acid, malonic acid, galacturonic acid, galactaric which does not corrode the underlying basematerial, oxygen, acid, gluconic acid, hydroxybutyric acid, 2.2-bis(hydroxym hydrogen peroxide, OZone, and percarboxylic acids Such as ethyl)butyric acid, hydroxypivalic acid, and B-hydroxyisova peracetic acid and perbenzoic acid can be mentioned. Among leric acid can be mentioned. Among them, tartaric acid or these oxidizing agents, oxygen, hydrogen peroxide and OZone citric acid is preferable. In addition, the compound shown by that do not cause any byproduct are preferable. The content of Formula (I) also includes those which are in a form of an the oxidizing agent in the etching solution is 0.001% to 10% alkali metal salt (e.g. a lithium salt, Sodium salt or potassium by mass (hereinafter, simply referred to as “%), preferably salt) or an ammonium salt and which exhibit the same behav 0.1% to 3%. In addition, in cases where the oxidizing agent is iors as the above-described compounds in the etching solu a gas such as oxygen or OZone, the gas may be introduced into tion. the etching Solution by bubbling and the like of the gas, such 0020. As to the compound shown by Formula (II) among that the concentration of the gas in the etching Solution falls complexing agents used in the method of the present inven within the above-mentioned ranges. tion, R to R' may be identical to or different from one 0026. Additionally, surfactants generally used in etching another, and are - R', -OR, —OOR', -COOR', Solutions may be added to the etching Solution used in the COOOR", CHCOOR", CHCOOOR, CRPO, method of the present invention in Such a manner that the —CH2CHCH. —CN, NC, NO. —F. —Cl, —Br. —I, surfactants do not impair the effects of the present invention. or -SOR7 (where R to R may be identical to or different By addition of such surfactants, uniformity of etching will be from one another and are hydrogen, a C1 to C10 saturated improved. As examples of preferable Surfactants, liquid poly aliphatic group, a C1 to C10 unsaturated aliphatic group, oran ethylene glycols such as PEG-200 can be mentioned. aryl group). R* to R are preferably -H, -COOH, or 0027. As one preferable example of the etching solution CHCOOH. used in the method of the present invention, an etching solu 0021. Furthermore, Xin the compound shown by Formula tion which consists essentially of the above-described com (II) is -OH, -COOH or -COOOH, and is preferably plexing agent and which is alkaline can be mentioned. OH or COOH. 0028. As another preferable example of the etching solu tion used in the method of the present invention, an etching 0022. As specific examples of the compound shown by solution which consists essentially of the above-described Formula (II), protocatechuic acid, ethyl protocatechuate, sali complexing agent and the oxidizing agent and which is alka cylic acid, 2,3-dihydroxybenzoic acid, 5-chlorosalicylic acid, line can be mentioned. cresotinic acid, resorcylic acid, naphtholic acid, 3.5-dihy 0029. Furthermore, as yet another preferable example of droxy-2-naphthoic acid, 1,4-dihydroxy-2-naphthoic acid, the etching solution used in the method of the present inven 1-hydroxy-2-naphthoic acid, 2,6-dihydroxy-4-methylben tion, an etching Solution which consists essentially of the Zoic acid, 2,5-dihydroxyterephthalic acid, methylene disali above-described complexing agent, the oxidizing agent, and cylic acid, nitrosalicylic acid, 2,4,6-trihydroxybenzoic acid, the Surfactant and which is alkaline can be mentioned. 5-sulfosalicylic acid, Mordant Blue 1, chrome yellow, 4-tert 0030. As a preferable composition for the etching solution butylcatechol, 4-methylcatechol, catechol, bromocatechol, used in the method of the present invention, a composition chlorocatechol, iodocatechol, fluorocatechol, nitrocatechol, containing: cyanocatechol, alizarin, esculetin, gallic acid, ethyl gallate, and 3,4-dihydroxybenzaldehyde can be mentioned. Among 0031 0.1 to 0.4 mol/L of salicylic acid, or an alkali metal them, protocatechuic acid or salicylic acid is preferable. In salt or ammonium salt thereof, and/or addition, the compound shown by Formula (II) also includes 0032 0.1 to 0.4 mol/L of tartaric acid, or an alkali metal those which are in a form of an alkali metal salt (e.g. a lithium salt or ammonium salt thereof, and/or salt, Sodium salt or potassium salt) or an ammonium salt and 0033 0.1 to 0.4 mol/L of citric acid, or an alkali metal salt which exhibit the same behaviors as the above-described or ammonium salt thereof, and compounds in the etching solution. 0034 0.3% to 3% of hydrogen peroxide, wherein US 2015/0048053 A1 Feb. 19, 2015
0035 the pH of the composition is 11 or higher, preferably nitride of the metal, silicon nitride, hafnium nitride, tantalum 12 to 14, more preferably 13 to 14, nitride, or an alloy of these metals, the layer being provided can be mentioned, and as a more specific composition for the on the above-described underlying base material, is not par etching Solution, a composition, containing: ticularly limited. For example, a method in which the under 0036 0.1 to 0.4 mol/L of sodium salicylate; and lying base material where the layer has been provided is 0037 0.1 to 0.4 mol/L of potassium sodium tartarate immersed in the etching solution; a method in which the (Rochelle salt); and etching Solution is sprayed onto the layer, and a method in 0038 0.1 to 0.4 mol/L of torisodium citrate; and which the etching Solution is applied onto the layer can be 0039 0.1 to 0.4 mol/L of sodium hydroxide; and mentioned. 0040. 0.3% to 3% of hydrogen peroxide, can be mentioned. 0045 Also, conditions for etching in the method of the 0041 As examples of the metal selected from titanium, present invention are not particularly limited. However, for niobium, tungsten, molybdenum, ruthenium, rhodium, example, the temperature of the etching solution is 20° C. to arsenic, aluminum and gallium, the oxide of the metal, the 100° C., preferably 40°C. to 80°C., and the treating time is nitride of the metal, silicon nitride, hafnium nitride, tantalum 0.1 to 200 minutes, preferably 1 to 20 minutes. Additionally, nitride, or the alloy of these metals that is a target to be etched the etching rate in the method of the present invention can be by the method of the present invention, titanium, titanium properly controlled by a person skilled in the art based on the oxide (II), titanium oxide (III), titanium oxide (IV), titanium concentrations of compounds of Formulas (I) and (II) nitride, niobium, niobium oxide (II), niobium oxide (III), included in the etching solution, the pH of the etching solu niobium oxide (IV), niobium oxide (V), niobium nitride, tion, the temperature of the etching solution and the treating tungsten, molybdenum, ruthenium, rhodium, arsenic, alumi time. num, aluminum oxide, aluminum nitride, gallium, gallium oxide, gallium nitride, silicon nitride, hafnium nitride, tanta 0046. Furthermore, in the method of the present invention, lum nitride, or alloys of combinations of one or more of these it is preferable that the etching solution be stirred with a materials (e.g. niobium titanium, and gallium arsenide) can stirring bar or by bubbling during etching. By stirring of the be mentioned. Among these materials, titanium, titanium etching solution, uniformity of etching may be improved, or oxide (II), titanium oxide (III), titanium oxide (IV), titanium redeposition of metals or the like removed by etching onto the nitride, niobium, niobium oxide (II), niobium oxide (III), underlying base material may not occur. niobium oxide (IV), niobium oxide (V), niobium nitride, 10047. Because, in the above-described method of the tantalum nitride, silicon nitride, aluminum, aluminum oxide, present invention, the layer of a metal selected from titanium, aluminum nitride, gallium, gallium oxide, gallium nitride, niobium, tungsten, molybdenum, ruthenium, rhodium, and an aluminum nitride/aluminum alloy are preferable. arsenic, aluminum and gallium, an oxide of the metal, a 0042. As to the underlying base material used in the nitride of the metal, silicon nitride, hafnium nitride, tantalum method of the present invention, the glass includes silicate nitride, or an alloy of these metals dissolves, in preference to glass, quartz, Pyrex, TEMPAX, soda-lime glass, borosilicate the underlying base material selected from glass, silicon, glass and the like; the silicon includes monocrystalline sili copper and nickel in the above-described way, the layer can con, boron-doped silicon, phosphorus-doped silicon, arsenic be selectively removed from the underlying base material. doped silicon, antimony-doped silicon, polycrystalline sili con and the like; the copper includes a pure copper metal, 0048. As preferable examples of combinations of the met copper-containing alloys and the like; and the nickel includes als or the like which can be selectively removed by the a pure nickel metal, nickel-containing alloys and the like. method of the present invention and the underlying base Furthermore, as for the underlying base material, those materials, the following combinations can be mentioned. including the metal selected from titanium, niobium, tung Sten, molybdenum, ruthenium, rhodium, arsenic, aluminum (Underlying and gallium, the oxide of the metal, the nitride of the metal, base material) (Metal or the like) silicon nitride, hafnium nitride, tantalum nitride, or the alloy Glass Titanium and or niobium and for their of these metals that is a target to be etched are excluded oxides and/or nitrides therefrom. In addition, the shape of the above-described Nickel Titanium and/or titanium oxide andfor underlying base material is not particularly limited, and any titanium nitride and/or silicon form Such as a form of a plate, circle, sphere or combination nitride of these shapes may be adopted. Silicon Tantalum nitride and/or titanium and/or titanium nitride and/or 0043 Moreover, a method for providing on the above titanium oxide and/or aluminum and/or described underlying base material the layer of a metal aluminum oxide and/or aluminum nitride selected from titanium, niobium, tungsten, molybdenum, and/or gallium and/or gallium oxide and/or gallium nitride ruthenium, rhodium, arsenic, aluminum and gallium, an Copper Aluminum and/or aluminum nitride oxide of the metal, a nitride of the metal, silicon nitride, and/or gallium and/or gallium nitride hafnium nitride, tantalum nitride, or an alloy of these metals is not particularly limited, and the layer may be provided thereon by Sputtering, vapor deposition, plating or the like which has been generally performed. EXAMPLES 0044. A method for bringing the etching solution into contact with the layer of a metal selected from titanium, 0049. Hereinafter, the present invention will be described niobium, tungsten, molybdenum, ruthenium, rhodium, in detail with reference to Examples. However, the present arsenic, aluminum and gallium, an oxide of the metal, a invention is not to be considered limited to the Examples. US 2015/0048053 A1 Feb. 19, 2015
Example 1 Comparative Example 3 Etching Solution Etching Solution 0050) 1.54 g of protocatechuic acid and 1.2 g of sodium 0.058 1.38g of salicylic acid, 1 mL of hydrogen peroxide hydroxide were dissolved in 100 mL of water. The pH of this (30%) and 0.4 g of sodium hydroxide were dissolved in 100 etching Solution was 14. mL of water. The pH of this etching solution was 5. Example 2 Comparative Example 4 Etching Solution Etching Solution 0051 1.92 g of citric acid and 1.2 g of sodium hydroxide 0059) 1.4 g of ethyl maltol and 0.8g of sodium hydroxide were dissolved in 100 mL of water. The pH of this etching were dissolved in 100 mL of water. The pH of this etching Solution was 14. Solution was 14. Example 3 Comparative Example 5 Etching Solution Etching Solution 0052 1.38g of salicylic acid, 1 mL of hydrogen peroxide 0060) 1.0 g of acetylacetone and 0.8g of sodium hydrox (30%) and 0.8g of sodium hydroxide were dissolved in 100 ide were dissolved in 100 mL of water. The pH of this etching mL of water. The pH of this etching solution was 14. Solution was 14. Example 4 Comparative Example 6 Etching Solution Etching Solution 0053 1.50 g of tartaric acid, 1 mL of hydrogen peroxide 0061 0.6 g of glycol and 0.8g of sodium hydroxide were (30%) and 1.2 g of sodium hydroxide were dissolved in 100 dissolved in 100 mL of water. The pH of this etching solution mL of water. The pH of this etching solution was 14. was 14. Example 5 Comparative Example 7 Etching Solution Etching Solution 0054 1.92 g of citric acid, 1 mL of hydrogen peroxide 0062 1.76 g of ascorbic acid, 1 mL of hydrogen peroxide (30%) and 1.6 g of sodium hydroxide were dissolved in 100 (30%) and 1.2 g of sodium hydroxide were dissolved in 100 mL of water. The pH of this etching solution was 14. mL of water. The pH of this etching solution was 14. Example 6 Comparative Example 8 Etching Solution Etching Solution 0055 1.38g of salicylic acid, 1.50 g of tartaric acid, 1.92 0063 1.54 g of protocatechuic acid was dissolved in 100 g of citric acid, 3 mL of hydrogen peroxide (30%) and 3.6 g of mL of water. The pH of this etching solution was 5. sodium hydroxide were dissolved in 300 mL of water. The pH of this etching Solution was 14. Test Example 1 Comparative Example 1 Etching Test Etching Solution 0064. Titanium was deposited onto the inside of each glass cylinder at a thickness of 100 nm by sputtering, and the 0056 1 mL of hydrogen peroxide (30%) and 1.2 g of resulting glass cylinders were used as samples. The samples sodium hydroxide were dissolved in 100 mL of water. The pH were each immersed in the etching Solutions prepared in of this etching Solution was 14. Examples 1 to 6 and Comparative Examples 1 to 8 under the conditions described in Table 1, while stirring the etching Comparative Example 2 Solutions with stirring bars, thereby carrying out the etching test. Appearances of the samples after the etching test were Etching Solution evaluated based on the following evaluation criteria. The results are also shown in Table 1. Additionally, a photo of 0057 4.16 g of EDTA'4Na, 1 mL of hydrogen peroxide appearance of a sample which was etched under the condi (30%) and 0.4 g of sodium hydroxide were dissolved in 100 tions of 80°C. and 30 seconds by using the etching solution mL of water. The pH of this etching solution was 14. of Example 6 is shown in FIG. 1. US 2015/0048053 A1 Feb. 19, 2015
(Evaluation) (Contents) (Evaluation) (Contents) -- Glass was not dissolved. 8 Titanium oxide, titanium, silicon nitride, and Glass was dissolved. titanium nitride were completely dissolved. O Most of titanium oxide, titanium, silicon nitride and titanium nitride were dissolved. A Most of titanium oxide, titanium, silicon nitride and TABLE 1. titanium nitride were not dissolved. X No titanium oxide, titanium, silicon nitride and Etching Titanium Glass titanium nitride were dissolved. Etching solution conditions dissolution dissolution Example 1 80° C., 60 min. 8 --
Test Example 3 solution prepared in Example 6 under the conditions of 80°C. and 5 minutes, while stirring the etching Solution with a Etching Test stirring bar, thereby carrying out the etching test. With respect 0072 Tantalum nitride was deposited on one side of each to the samples before and after the etching test, the surface silicon wafer at 50 um by sputtering, and the silicon wafers shape and the Surface roughness (Ra values) were observed were used as samples. The samples were each immersed in with a scanning probe microscope (SPM). The results are the etching solutions prepared in Examples 1 and 3-6 and shown in FIG. 2. Comparative Examples 1-3 under the conditions described in 0077. From the results of the SPM observation and the Ra Table 3, while stirring the etching solutions with stirring bars, measurement, it was revealed that, as titanium oxide, tita thereby carrying out the etching test. Appearances of the nium, silicon nitride, and titanium nitride were dissolved by samples after the etching test were evaluated based on the the etching Solution of the present invention in preference to following evaluation criteria. The results are also shown in the underlying base material of nickel, these materials could Table 3. be selectively removed from the underlying base material of nickel.
Dissolution Etching Test Etching of tantalum Silicon Etching solution conditions nitride dissolution 0080 A product obtained through deposition of titanium nitride and titanium oxide in that order on one side of a silicon Example 3 80° C., 60 min. 8 -- wafer (Sample A) at 50 um each by Sputtering was designated Example 4 80° C., 60 min. s -- Example 5 80°C., 40 min. 6 -- as Sample B. Sample B was immersed in the etching solution Example 6 80°C., 40 min. (8) -- prepared in Example 6 under the conditions of 80°C. and 25 Comparative Example 1 80° C., 60 min. X -- seconds, while stirring the etching Solution with a stirring bar, Comparative Example 2 80° C., 30 min. s thereby carrying out the etching test, and the resulting silicon Comparative Example 3 80° C., 60 min. X -- wafer was designated as Sample C. These samples were Sub jected to observations with a SEM and an SPM. The results 0075 Based on the above results, it was revealed that, as are shown in FIG. 4. tantalum nitride was dissolved by the etching solutions of the 0081 From the results of the SEM and SPM observations, present invention in preference to the underlying base mate it was revealed that, as titanium nitride and titanium oxide rial of silicon, this material could be selectively removed from were dissolved by the etching solution of the present inven the underlying base material of silicon. tion in preference to the underlying base material of silicon, these materials could be selectively removed from the under Test Example 4 lying base material of silicon. Etching Test Test Example 7 0076. A brass plate, one side of which was nickel-plated, was designated as Sample A. Additionally, that obtained by Selection of Etching Conditions depositing titanium oxide, titanium, Silicon nitride, titanium I0082 An etching solution which included 0.334 mol/L of nitride, silicon nitride and titanium nitride in that order at 10 salicylic acid, 0.333 mol/L of tartaric acid, 0.333 mol/L of nm, 70 nm, 45 nm, 85 nm, 80 nm and 10 nm, respectively, by citric acid, and 1 mol/L of hydrogen peroxide, and the pH of sputtering, on the above brass plate was designated as Sample which was adjusted to 11 or higher with sodium hydroxide B. Each of Samples A and B was immersed in the etching was used as a basic composition, and this basic composition US 2015/0048053 A1 Feb. 19, 2015
was diluted as described in Table 4 below to prepare the conventional etching solution. As to the etching solution of etching Solutions. The same sample as that used in Test the present invention, titanium was 5 mg/L while silicon was Example 1 (glass cylinder) and the same sample as that used 36.1 mg/L and nickel was not detected. On the other hand, as in Test Example 2 (ring) were subjected to etching under the to the conventional etching solution, titanium was 1 mg/L conditions described in Table 4 with these etching solutions, while silicon and nickel were 23.5 mg/L and 8.5 mg/L, while stirring the etching solutions with tirring bars. In addi respectively. It was considered that, in comparison with the tion, the etching-termination time corresponds to a time quantity of titanium in the conventional etching solution, the required for removal of each sputtering film which was visu excessive silicon was dissolved from the silicon wafer sub ally confirmed. strate while nickel was dissolved from the nickel-plated sub strate. It was revealed that the complexing agent used in the TABLE 4 present invention exhibited selectivity in dissolution of tita nium and the nitride. Concen- Concen- Glass Ring tration of tration of Bath cylinder (titanium complexing oxidizing temper- (titanium) oxide, etc.) Test Example 9 agent agent ature etching-termination (mol/L) (mol/L) pH (° C.) time (s) Measurement of the Etching Rate O.O1 O.1 11 or 50 1SOO 7200 higher O.1 O.1 11 or 50 270 900 (1) Measurement of the Etching Rate of Titanium higher O.S O.S 11 or 50 15 240 I0086 Titanium was deposited on each glass at 100 nm by higher sputtering, the resulting samples were each immersed in the 1.O 1.O 11 or 50 10 18O higher etching solutions described in Table 6 which had been heated 1.O 1.O 11 or 35 50 to 80° C., while stirring the etching solutions with stirring higher bars, and each etching rate was calculated from the etching 1.O 1.O 11 or 25 150 higher time, the quantity of titanium dissolved therein and the area O.S O.S 11 or 25 600 which came into contact with the etching solution. The results higher are shown in Table 6. —; untested TABLE 6 0.083 Based on the above results, correlations between the Etching rate concentration of complexing agent or the bath temperature Etching solution (nms) and the etching rate were confirmed. It was revealed that, as Example 1 O.O28 the concentration of complexing agent and the bath tempera Example 2 O.O24 ture were increased, the etching rate became higher. Example 3 1.667 Example 4 1.667 Test Example 8 Example 5 1O.OO Example 6 S.OOO Comparative Example 1 O.167 Elemental Analysis on an Etching Solution Used Comparative Example 2 O.833 0084. By using the etching solution of Example 6, the same sample as that used in Test Example 1 (glass cylinder) was etched at 80°C. for 30 seconds, the same sample as that (2) Measurement of the Etching Rate of Titanium used in Test Example 2 (ring) was etched at 80° C. for 5 Oxide/Titanium Nitride minutes, and the same sample as that used in Test Example 6 (the product obtained by depositing titanium nitride and tita I0087 Titanium oxide and titanium nitride were deposited nium oxide on a silicon wafer (Sample B)) was etched at 80° in that order on each silicon wafer at 50 nm each by sputter C. for 25 seconds. The etching solutions after the etching ing, the resulting samples were each immersed in the etching treatments were Subjected to an elemental analysis with an solutions described in Table 7 which had been heated to 80° ICP-AES. Additionally, for comparison, same samples were C., while stirring the etching Solutions with stirring bars, and each etched by using the etching solution of Comparative each etching rate was calculated from the etching time, the Example 2, and the etching Solutions remained after the etch quantity of titanium oxide/titanium nitride dissolved therein ing treatments were also Subjected to the elemental analysis. and the area which came into contact with the etching solu The results of the analysis are shown in Table 5. tion. The results are shown in Table 7.
TABLE 5 TABLE 7 Example 6 Comparative Example 2 Etching rate Silicon 36.1 mg/L. 23.5 mg/L Etching solution (nms) Titanium About 5 mg/L About 1 mg/L. Example 3 S.OOO Nickel Not detected 8.5 mg/L Example 4 O.833 Example 5 3.333 Example 6 4.OOO 0085. From the above results, it was revealed that titanium Comparative Example 2 O.833 was dissolved by the etching solution of the present invention in preference to nickel and silicon, as compared with the US 2015/0048053 A1 Feb. 19, 2015
(3) Measurement of the Etching Rate of Niobium (2) Measurement of the Etching Rate of Silicon 0088 Niobium was deposited on each glass at 200 nm by 0091 Silicon wafers were each immersed in the etching sputtering, the resulting samples were each immersed in the solutions described in Table 11 which had been heated to 80° etching solutions described in Table 8 which had been heated C., while stirring the etching Solutions with stirring bars, and to 80° C., while stirring the etching solutions with stirring each etching rate was calculated from the etching time, the bars, and each etching rate was calculated from the etching quantity of silicondissolved therein and the weight difference time, the quantity of niobium dissolved therein and the area of the silicon wafer between before and after etching with which came into contact with the etching solution. The results respect to the area of the silicon wafer which came into are shown in Table 8. contact with the etching Solution. The results are shown in Table 11. TABLE 8 TABLE 11 Etching rate Etching solution (nms) Etching rate Example 3 1.667 Etching solution (nms) Example 4 1.667 Example 6 O.007 Example 5 1.667 Comparative Example 2 O418 Example 6 1.667 Comparative Example 2 O.667 (3) Measurement of the Etching Rate of Nickel (4) Measurement of the Etching Rate of Tantalum Nitride 0092 Brass plates (front sides of which were nickel 0089 Tantalum nitride was deposited on each silicon plated) were each immersed in the etching solutions wafer at 50 nm by sputtering, the resulting samples were each described in Table 12 which had been heated to 80°C., while immersed in the etching solutions described in Table 9 which stirring the etching Solutions with stirring bars, and each had been heated to 80°C., while stirring the etching solutions etching rate was calculated from the etching time, the quan with stirring bars, and each etching rate was calculated from tity of nickel dissolved therein and the weight difference of the etching time, the quantity of tantalum nitride dissolved the brass plate having a nickel-plated front side between therein and the area which came into contact with the etching before and after etching with respect to the area of the brass solution. The results are shown in Table 9. plate which came into contact with the etching Solution. The results are shown in Table 12. TABLE 9 TABLE 12 Etching rate Etching solution (nms) Etching rate Etching solution (nms) Example 3 O.O14 Example 4 O.O14 Example 3 O.OO60 Example 5 O.O21 Example 4 O.OOO3 Example 6 O.O21 Example 5 O.OO3S Comparative Example 2 O.O28 Example 6 O.OO77 Comparative Example 2 O.2454
Test Example 10 0093. From the above results, it was shown that, as to the etching Solutions of the present invention, the etching rates of Measurement of the Etching Rate glass, silicon and nickel which served as underlying base materials were slower than the etching rates of titanium, (1) Measurement of the Etching Rate of Glass titanium oxide, titanium nitride, niobium and tantalum 0090 Glass plates were each immersed in the etching nitride. Therefore, it was shown that titanium, titanium oxide, solutions described in Table 10 which had been heated to 80° titanium nitride, niobium and tantalum nitride were dissolved C., while stirring the etching Solutions with stirring bars, and by the etching Solutions of the present invention in preference each etching rate was calculated from the etching time, the to the underlying base materials. On the other hand, it was quantity of glass dissolved therein and the weight difference shown that the etching solutions using EDTA exhibited quite of the glass plate between before and after etching with faster etching rates of the underlying base materials than the respect to the area of the glass plate which came into contact etching solutions of the present invention. with the etching solution. The results are shown in Table 10. Test Example 11 TABLE 10 Etching Test Etching rate Etching solution (nms) 0094. When a strip of a gallium arsenide wafer was Example 6 O.OO2 immersed in the etching solution prepared in Example 6 Comparative Example 2 O.OO7 which had been heated to 80°C., the strip of gallium arsenide was dissolved therein soon. From this result, it was revealed that arsenic, gallium, and gallium arsenide could be selec US 2015/0048053 A1 Feb. 19, 2015
tively etched by the etching solution of the present invention TABLE 13-continued in the same manner as titanium or the like. Etching time (s Test Example 12 Glass cylinder Ring Etching Test pH (titanium) (titanium oxide, etc.) 11 360 1200 0095. When a test piece oftungsten, molybdenum, ruthe 12 120 S4O nium or rhodium was immersed in the etching solution pre 13 15 18O pared in Example 6 that had been heated to 80°C., the test 14 10 18O piece was dissolved soon. From the results, it was revealed that tungsten, molybdenum, ruthenium or rhodium could be (0099. This test revealed that the higher the pH of the etch selectively etched by the etching solution of the present ing solution was, the more the etching rate increased. In invention in the same manner as titanium or the like. particular, the etching rate increased about twice or even higher in each of pH ranges of 11 or higher, 12 or higher, and Test Example 13 13 to 14, compared with a case where the pH is below each pH Recycling Test range. 0.096 Titanium oxide, titanium, silicon nitride, titanium Example 8 nitride, silicon nitride and titanium nitride were deposited in that order at 10 nm, 70 nm, 45 nm, 85 nm, 80 nm and 10 nm, Etching Solution respectively, on a hairline-finished brass ring, the both sides 0100 129 g of sodium citrate, 0.1 mL of PEG-200, and 50 of which were nickel-plated, by Sputtering, and the resulting mL of hydrogen peroxide (34%) were dissolved in 1,000 mL ring was used as a sample. The sample was immersed in the of water. The pH of this etching solution was 13. etching Solution prepared in Example 6 that had been heated to 80° C., for 5 minutes, and the titanium oxide, titanium, Test Example 15 silicon nitride and titanium nitride deposited by Sputtering were completely etched. After that, this sample was dried, and Etching Test further, the above Sputtering was again carried out. Conse 0101. An aluminum or copper plate of 5x5x0.1 cm was quently, the same appearance as that of the sample before immersed in the etching Solution prepared in Example 8 that etching was obtained. This test showed that recycling of had been heated to 50° C., and the etching rate was measured samples is possible. in the same manner as Test Example 10. It was revealed that the etching rate of the aluminum plate was 130 nm/s while the Example 7 etching rate of the copper plate was 0.142 mm/s. Etching Solution Test Example 16 0097. 23 g of salicylic acid, 47 g of Rochelle salt, 43 g of sodium citrate, 1 mL of PEG-200, 50 mL of hydrogen perox Etching Test ide (34%) and 10 g of sodium hydroxide were dissolved in 0102. When a test piece of aluminum oxide was immersed 1,000 mL of water. The pH of this etching solution was 12.7. in the etching solution prepared in Example 8 that had been heated to 60°C., the test piece was dissolved soon. From this Test Example 14 result, it was revealed that aluminum oxide could also be selectively etched by the etching solution of the present Etching Test invention in the same manner as titanium or the like. 0098. The pH of the etching solutions prepared along with Example 7 were each adjusted to pH values described in Table Test Example 17 13 by using sodium hydroxide or sulfuric acid. The same sample as that used in Test Example 1 (glass cylinder) and the Etching Test same sample as that used in Test Example 2 (ring) were each 0103) When a test piece obtained through lamination of immersed in the etching solutions which had been heated to aluminum nitride and gallium nitride onto a silicon wafer in 50° C., and a time required for complete removal of each that order by Sputtering was immersed in the etching Solution sputtering film, which was visually confirmed, was measured. prepared in Example 8 that had been heated to 60° C., the The results are shown in Table 13. layers of aluminum nitride and gallium nitride were dissolved soon. From this result, it was revealed that aluminum nitride TABLE 13 or gallium nitride could also be selectively etched by the Etching time (s etching Solution of the present invention in the same manner as titanium or the like. Glass cylinder Ring 0104. The principle of etching in the method of the present pH (titanium) (titanium oxide, etc.) invention described above is presumed as follows. 7 2100 4200 8 1200 24OO (1) a Role of the Complexing Agent: 9 1200 2100 10 1200 2100 0105. The selected complexing agent chelates metals on the surface (a) to thereby make it easier for the metals on the US 2015/0048053 A1 Feb. 19, 2015 surface to receive nucleophilic attacks and (b) to thereby metals, said layer being provided on an underlying base make it easier for generated metal complexes to be dissolved material selected from the group consisting of glass, in the etching solution. That is, the ligand of the selected silicon, copper and nickel, into contact with an etching complexing agent selectively chelates metals (e.g. titanium Solution which consists essentially of at least one com and niobium) that are Suited to the shape, orbital alignment plexing agent selected from by Formulas (I) and (II) and and electronic properties of metal atoms subjected to etching, wherein the pH of said etching solution is 11 or higher, and thus, it becomes possible to etch only specific metals. thereby selectively etching said metal; However, when EDTA or the like which is a generally used complexing agent, are used. Such a complexing agent strongly chelates many types of metals, and therefore, the (I) selectivity is low. That is, the complexing agent selected in the present invention serves as one factor which specify the selec tivity against metals to be etched. R2 OH 0106 The complexing capability or selectivity of a com plexing agent is determined depending on the coordination number, coordination species nitrogen (e.g. nitrogen included in amines or nitriles), oxygen (e.g. oxygen included wherein R' to R may be identical to or different from one in hydroxyls, carboxylic acids or carbonyls), phosphorus, or another, and are selected from the group consisting of Sulfur (e.g. Sulfur included in mercaptos or thiocarbonyls). R, OR, OOR, COOR, COOOR, coordination properties, electronic properties, and the dis CHCOOR, -CHCOOOR3, CRO and tancefalignment of ligand-ligand in case of a higher coordi —CHCHCH, where R to R' may be identical to or nation number. In the present invention, a molecule which has different from one another, and are selected from the two or three coordinating oxygen atoms separated by three group consisting of hydrogen, a C1 to C10 Saturated carbons and which has a hydroxyl for one coordination spe aliphatic group, a C1 to C10 unsaturated aliphatic group, cies and a carboxylic acid or benzenediol for the other coor and an aryl group, and dination species is considered optimal. (In case of three coor dinating oxygen atoms, another coordination species may also be oxygen-based one, preferably.) For example, when (II) nitrogen is present in coordination species, nickel is also etched although titanium or niobium should be etched, and therefore, such a complexing agent is inconsistent with the purpose of the present invention. (2) a Role of the Base: 0107 The base makes nucleophilic attacks against che lated metals (e.g. hydroxides). (3) a Role of the Oxidizing Agent: wherein R* to R' may be identical to or different from one another, and are selected from the group consisting of 0108. When binding with each metal (M) within a metal R, OR, OOR, COOR, COOOR", oxide, metal nitride or metal complex, the oxidizing agent CHCOOR", CHCOOOR, CRPO, causes oxidative decomposition of bonds with metals, and - CHCHCH-CN, NC, NO, F - C1, Br, destroys the lattice or non-lattice bonds. —I, and —SOR where R to R may be identical to or (e.g. M-O-M->M-O-O-M->2M=O) different from one another, and are selected from the 0109. In case of metal etching, a metal or metal complex is group consisting of hydrogen, a C1 to C10 Saturated oxidized. aliphatic group, a C1 to C10 unsaturated aliphatic group, (e.g. M->Mn", or ligand-Mn->ligand-M) and an aryl group, and X is —OH, -COOH or COOOH INDUSTRIAL APPLICABILITY 2. The etching method according to claim 1, wherein the 0110. The method of the present invention can be utilized etching solution further comprises an oxidizing agent. for etching of a metal selected from titanium, niobium, tung 3. (canceled) Sten, molybdenum, ruthenium, rhodium, arsenic, aluminum and gallium, an oxide of the metal, a nitride of the metal, 4. An etching solution for a metal, silicon nitride, hafnium nitride, tantalum nitride, or an alloy wherein the metal is selected from the group consisting of of these metals, as well as for recycling of the underlying base titanium, niobium, tungsten, molybdenum, ruthenium, material or for recovery of the above metal, the oxide of the rhodium, arsenic, aluminum and gallium, an oxide of the metal, the nitride of the metal, silicon nitride, hafnium nitride, metal, a nitride of the metal, silicon nitride, hafnium tantalum nitride, or the alloy of these metals. nitride, tantalum nitride, and an alloy of these metals, 1. An etching method, comprising: and bringing a layer of a metal selected from the group con said metal is provided on an underlying base material sisting of titanium, niobium, tungsten, molybdenum, Selected from the group consisting of glass, silicon, cop ruthenium, rhodium, arsenic, aluminum and gallium, an per and nickel, oxide of the metal, a nitride of the metal, silicon nitride, said etching Solution consisting essentially of at least one hafnium nitride, tantalum nitride, and an alloy of these complexing agent selected from Formulas (I) and (II) US 2015/0048053 A1 Feb. 19, 2015 12
wherein R* to R' may be identical to or different from one (I) another, and are selected from the group consisting of R3 R, OR, OOR, COOR, COOOR", CHCOOR", CHCOOOR, CRPO, R2 OH —CHCHCH, CN, NC, NO,-F, - C1, —Br. —I, and —SOR where R to R may be identical to or different from one another, and are selected from the ... t) l 3. group consisting of hydrogen, a C1 to C10 Saturated wherein R' to R may be identical to or different from O aliphatic group, a C1 to C10 unsaturated aliphatic group, another, and are selected from the group consisting of and an aryl group, and X is —OH, -COOH or R, OR, OOR, COOR, COOOR CHCOOR,s s -CHCOOOR3,s s CRO ands 11 COOOH,or higher wnereinWh theune pH of saidsa1d etchetcning soluuonlut 1s —CHCHCH, where R to R' may be identical to or different from one another, and are selected from the 5. The etching solution for a metal according to claim 4. group consisting of hydrogen, a C1 to C10 Saturated wherein said etching solution further comprises an oxidizing aliphatic group, a C1 to C10 unsaturated aliphatic group, agent. and an aryl group, and 6. (canceled) 7. The etching method according to claim 1, wherein the (II) pH is from 12 to 14. R4 8. The etching method according to claim 2, wherein the R X pH is from 12 to 14. 9. The etching solution for metal according to claim 4. R6 OH wherein the pH is from 12 to 14. R7 10. The etching solution for metal according to claim 5, wherein the pH is from 12 to 14. k k k k k