Processing solution for semiconductor wafers containing hypobromite ions and pH buffer.

Abstract

The present invention provides a processing liquid for processing a semiconductor wafer in a semiconductor formation process, said processing liquid containing (A) hypobromite ions, (B) a pH buffering agent and (C) onium ions represented by formula (1). (In the formula, each of R1, R2, R3 and R4 independently represents an alkyl group having from 1 to 25 carbon atoms.)

Description

[Technical Field]

[0001] The present invention relates to a novel processing solution for etching ruthenium present on a semiconductor wafer, used in the manufacturing process of semiconductor devices. [Background technology]

[0002] In recent years, the miniaturization of semiconductor device design rules has progressed, leading to an increase in wiring resistance. This increased wiring resistance is significantly hindering the high-speed operation of semiconductor devices, necessitating countermeasures. Therefore, wiring materials with improved electromigration resistance and reduced resistance compared to conventional materials are desired.

[0003] Compared to conventional wiring materials such as aluminum and copper, ruthenium is attracting attention as a wiring material, particularly for semiconductor devices with design rules of 10 nm or less, due to its high resistance to electromigration and its ability to reduce wiring resistance. In addition to being used as a wiring material, ruthenium can also prevent electromigration even when copper is used as the wiring material, so its use as a barrier metal for copper wiring is also being considered.

[0004] Incidentally, even when ruthenium is selected as the wiring material in the wiring formation process for semiconductor devices, the wiring is formed by dry or wet etching, similar to conventional wiring materials. However, when dry etching ruthenium, in-plane non-uniformity occurs due to the plasma distribution, and the etching rate increases or decreases depending on the flux or energy of the reactant species and ions, making precise etching difficult. For this reason, wet etching is attracting attention as a method that can etch ruthenium more precisely.

[0005] When using ruthenium as a wiring material or barrier metal in semiconductor device design rules of 10 nm or less, precise processing of the ruthenium is required during wet etching. In other words, if the amount of ruthenium etching is not controlled, other wiring materials may be exposed due to excessive etching of the ruthenium. Furthermore, if multilayer wiring is formed with wiring materials other than ruthenium exposed, current will leak from the exposed wiring materials, preventing the semiconductor device from functioning correctly. Therefore, a semiconductor processing solution capable of achieving precise processing of ruthenium is desired.

[0006] Patent Document 1 proposes an etching solution for semiconductors used to etch ruthenium, which is characterized by the addition and mixing of a bromine-containing compound, an oxidizing agent, a base compound, and water, wherein the amount of the bromine-containing compound added is 2 to 25% by mass as the amount of bromine element, the amount of the oxidizing agent added is 0.1 to 12% by mass, and the pH is 10 or higher and less than 12. [Prior art documents] [Patent Documents]

[0007] [Patent Document 1] International Publication No. 2011 / 074601 [Overview of the project] [Problems that the invention aims to solve]

[0008] The processing solution described in Patent Document 1 is useful in that it has a high etching rate for ruthenium. However, according to the inventors' research, it has been found that the conventional processing solution described in Patent Document 1 has room for improvement in the following respects.

[0009] In other words, the processing solution described in Patent Document 1 is described as being used in the semiconductor wafer manufacturing process for semiconductor elements, wiring, and barrier metals. However, the purpose of this processing solution is to remove ruthenium adhering to substrates such as semiconductor wafers, and it is not intended for precise etching. Therefore, when ruthenium is etched using the processing solution described in Patent Document 1, there is a problem in that it is difficult to control the etching rate. Furthermore, because the processing solution is not stable, there is a problem in the stability of the etching rate. As a result, with the processing solution described in Patent Document 1, precise control of the amount of ruthenium etched is not possible, and there is room for further improvement. [Means for solving the problem]

[0010] The inventors diligently studied to solve the above problems. They hypothesized that in a treatment solution containing only hypobromite ions, the etching rate of ruthenium would be unstable due to large fluctuations in the pH of the treatment solution and the concentration of hypobromite ions, making it difficult to control the amount of ruthenium etched. Therefore, they investigated the components to be added to the treatment solution. As a result, they found that by adding onium ions and a pH buffer to a treatment solution containing hypobromite ions, fluctuations in the pH of the treatment solution and the concentration of hypobromite ions could be suppressed, and the etching rate of ruthenium could be controlled, thereby enabling precise control of the etching amount. Furthermore, they found that by including specific anions such as bromite ions and / or bromate ions in the treatment solution, the concentration of hypobromite ions in the treatment solution could be kept constant, improving the stability of the treatment solution. This led to the discovery that the stability of the etching rate of ruthenium could be improved, and thus the present invention was completed.

[0011] In other words, the present invention includes the following items. Item 1 A semiconductor processing solution comprising (A), (B), and (C) below. (A) Hypobromite ions (B) pH buffering agent (C) Onium Ion Item 2: Furthermore, the semiconductor processing solution according to Item 1, further comprising (D) bromide ions. Item 3: The semiconductor processing solution according to item 1 or 2, further comprising (E) bromite ions and / or bromate ions. Item 4 The total concentration of (E) bromite ions and bromate ions is 3.3 × 10 -6 mol / L or more 5.0×10 -1 A semiconductor processing solution described in any one of items 1 to 3, having a concentration of mol / L or less. Item 5 The semiconductor processing solution according to any one of items 1 to 4, wherein the semiconductor processing solution further contains an oxidizing agent, and the oxidation-reduction potential of the oxidizing agent exceeds the oxidation-reduction potential of the hypobromite ion / bromide ion. Item 6 The semiconductor processing solution according to Item 5, wherein the oxidizing agent contained in the semiconductor processing solution is hypochlorite ions or ozone. Item 7: A semiconductor processing solution according to any one of items 1 to 6, further comprising (F) one or more chlorine-containing ions selected from the group consisting of chlorite ions, chlorate ions, and chloride ions. Item 8 A semiconductor processing solution according to any one of items 1 to 7, wherein the hypobromite ion concentration is 0.001 mol / L or more and 0.20 mol / L or less. Item 9 The semiconductor processing solution according to any one of items 1 to 8, wherein the concentration of the (B) pH buffer is 0.00001 to 1.0 mol / L. Item 10 The semiconductor processing solution according to any one of items 1 to 9, wherein the (B) pH buffer is at least one selected from the group consisting of carbonic acid, boric acid, phosphoric acid, trishydroxymethylaminomethane (tris), ammonia, pyrophosphate, p-phenolsulfonic acid, diethanolamine, ethanolamine, triethanolamine, 5,5-diethylbarbituric acid, glycine, glycylglycine, imidazole, N,N-bis(2-hydroxyethyl)-2-aminoethanesulfonic acid, 3-morpholinopropanesulfonic acid, N-tris(hydroxymethyl)methyl-2-aminoethanesulfonic acid, 2-[4-(2-hydroxyethyl)-1-piperazinyl]ethanesulfonic acid, 4-(2-hydroxyethyl)-1-piperazinepropanesulfonic acid, tricine, N,N-di(2-hydroxyethyl)glycine, 2-cyclohexylaminoethanesulfonic acid, hydroxyproline, phenol, and ethylenediaminetetraacetic acid.

[0012] Item 11 The semiconductor processing solution according to any one of items 1 to 10, wherein the (C) onium ion is a quaternary ammonium ion or quaternary phosphonium ion represented by the following formula (1), a tertiary ammonium ion or tertiary sulfonium ion represented by the following formula (2), an ammonium ion, pyrrolidinium ion, piperidinium ion, imidazolium ion, or sulfonium ion represented by the following formula (3), or an ammonium ion or phosphonium ion represented by the following formula (4).

[0013] [ka]

[0014] [ka]

[0015] [ka]

[0016] [Chemical formula]

[0017] (In formula (1), A is nitrogen or phosphorus, and R 1 , R 2 , R 3 , R 4 are independently an alkyl group having 1 to 25 carbon atoms, an allyl group having 1 to 25 carbon atoms, an aralkyl group which may have a substituent on the aryl group, or an aryl group. However, when R 1 , R 2 , R 3 , R 4 is an alkyl group, at least one of the alkyl groups of R 1 , R 2 , R 3 , R 4 has 2 or more carbon atoms.

[0018] In formula (2), A is nitrogen or sulfur, and R 1 , R 2 , R 3 are independently an alkyl group having 1 to 25 carbon atoms, an allyl group, an aralkyl group having an alkyl group having 1 to 25 carbon atoms, or an aryl group. However, when R 1 , R 2 , R 3 is an alkyl group, at least one of the alkyl groups of R 1 , R 2 , R 3 has 2 or more carbon atoms. Also, at least one hydrogen in the aryl group and the ring of the aryl group in the aralkyl group may be replaced by fluorine, chlorine, an alkyl group having 1 to 10 carbon atoms, an alkenyl group having 2 to 10 carbon atoms, an alkoxy group having 1 to 9 carbon atoms, or an alkenyloxy group having 2 to 9 carbon atoms, and in these groups, at least one hydrogen may be replaced by fluorine or chlorine.

[0019] In formula (3), Z is an aromatic group or alicyclic group which may contain nitrogen, sulfur, or oxygen atoms, and in the aromatic group or alicyclic group, at least one hydrogen to which carbon or nitrogen is bonded may be replaced with chlorine, bromine, fluorine, iodine, at least one C1-C15 alkyl group, at least one C2-C9 alkenyloxy group, an aromatic group which may be substituted with at least one C1-C15 alkyl group, or an alicyclic group which may be substituted with at least one C1-C15 alkyl group. A is nitrogen or sulfur. R is chlorine, bromine, fluorine, iodine, a C1-C15 alkyl group, an allyl group, an aromatic group which may be substituted with at least one C1-C15 alkyl group, or an alicyclic group which may be substituted with at least one C1-C15 alkyl group. n is an integer of 1 or 2 and indicates the number of R. When n is 2, R may be the same or different and may form a ring.

[0020] In formula (4), A is independently nitrogen or phosphorus, and R 1 , R 2 , R 3 , R 4 , R 5 , R 6 These are independently a C1-C25 alkyl group, an allyl group, an aralkyl group having a C1-C25 alkyl group, or an aryl group. In the aralkyl group, at least one hydrogen atom in the aryl group and the ring of the aryl group may be replaced with fluorine, chlorine, a C1-C10 alkyl group, a C2-C10 alkenyl group, a C1-C9 alkoxy group, or a C2-C9 alkenyloxy group, and in these groups, at least one hydrogen atom may be replaced with fluorine or chlorine. Item 12 A semiconductor processing solution according to any one of items 1 to 11, wherein the pH at 25°C is 8 or higher and 14 or lower. Item 13 An etching method comprising the step of bringing a semiconductor wafer into contact with a processing solution described in any one of items 1 to 12. Item 14 The etching method according to item 13, wherein the metal on the semiconductor wafer is ruthenium or tungsten, and the ruthenium or tungsten is etched. Item 15. A RuO4-containing gas generation inhibitor comprising (A), (B), and (C) below. (A) Hypobromite ions (B) pH buffering agent (C) Onium Ion Item 16. Furthermore, a RuO4-containing gas generation inhibitor as described in Item 15, comprising (D) bromide ions. Item 17. A RuO4-containing gas generation inhibitor according to item 15 or 16, further comprising (E) bromite ions and / or bromate ions. Item 18. A RuO4-containing gas generation inhibitor according to any one of items 15 to 17, further comprising (F) one or more chlorine-containing ions selected from the group consisting of chlorite ions, chlorate ions, and chloride ions. Item 19 Treatment agent for ruthenium-containing wastewater, comprising (A), (B), and (C) below. (A) Hypobromite ions (B) pH buffering agent (C) Onium Ion Item 20: Furthermore, a treatment agent for ruthenium-containing wastewater as described in Item 19, comprising (D) bromide ions. Item 21 (E) A treatment agent for ruthenium-containing wastewater as described in Item 19 or 20, comprising bromite ions and / or bromate ions. Item 22. A ruthenium-containing wastewater treatment agent according to any one of items 19 to 21, further comprising (F) one or more chlorine-containing ions selected from the group consisting of chlorite ions, chlorate ions, and chloride ions. [Effects of the Invention]

[0021] The processing solution of the present invention can suppress pH changes associated with the ruthenium etching reaction and carbon dioxide gas absorption when etching ruthenium. Furthermore, it can suppress changes in etching rate due to the decomposition of hypobromite ions during storage. This makes it possible to maintain a constant etching rate during use, providing a processing solution that enables stable precision machining. Moreover, by adding bromite ions, bromate ions, chlorite ions, chloride ions, and other ions to the processing solution, a processing solution with suppressed hypobromite ion decomposition can be provided. [Brief explanation of the drawing]

[0022] [Figure 1] This is a schematic cross-sectional view showing an example of a wiring formation process in which the processing liquid of the present invention can be suitably used. [Figure 2] This is a schematic cross-sectional view showing an example of a wiring formation process after treatment with the processing solution of the present invention. [Modes for carrying out the invention]

[0023] (Processing solution for semiconductors) The processing solution of the present invention is capable of etching ruthenium present on a semiconductor wafer without damaging the semiconductor wafer, and is capable of etching ruthenium at an etching rate with little fluctuation. Therefore, the processing solution of the present invention is suitable for use in the wiring formation process in the semiconductor manufacturing process.

[0024] The ruthenium to which the processing solution of the present invention is applied may be formed by any method, but for example, in semiconductor manufacturing processes, it is formed on a semiconductor wafer by known methods such as CVD, ALD, and sputtering. By etching the formed ruthenium with the processing solution, semiconductor wiring is formed. In this specification, ruthenium (also written as Ru) is not limited to ruthenium metal, but may contain the element ruthenium. That is, ruthenium metal, ruthenium alloy, ruthenium oxide, etc. are all referred to as ruthenium. Figures 1 and 2 show an example of the wiring formation process. An interlayer insulating film 2 made of a silicon oxide film, a low dielectric constant film, etc. is placed on a lower substrate 1, and a ruthenium film 3 is formed on top of it. By etching the ruthenium as shown in Figure 2, wiring using ruthenium as the wiring material is formed.

[0025] As described above, the processing solution of the present invention can be suitably used for etching ruthenium. The processing solution contains (A) hypobromite ions, (B) a pH buffer, and (C) onium ions. The following is a step-by-step explanation.

[0026] (A) Hypobromite ions The hypobromite ions used in this invention are added to oxidize ruthenium and dissolve it in the treatment solution. The hypobromite ions may be added to the treatment solution by any method, such as generating them in the treatment solution or adding a salt containing hypobromite ions. To generate hypobromite ions in the treatment solution, bromine can be supplied to the treatment solution. In this case, from the viewpoint of efficiently generating hypobromite ions, the treatment solution temperature is preferably 50°C or lower. If the treatment solution temperature is 50°C or lower, not only can hypobromite ions be efficiently generated, but the generated hypobromite ions can also be stably used for etching ruthenium. Furthermore, in order to dissolve more bromine in the treatment solution, the temperature of the treatment solution is more preferably 30°C or lower, and most preferably 25°C or lower. There is no particular lower limit to the temperature of the treatment solution, but it is preferable that the treatment solution does not freeze. Therefore, the treatment solution temperature is preferably -35°C or higher, more preferably -15°C or higher, and most preferably 0°C or higher. The pH of the treatment solution supplied with bromine is not particularly limited, but if the pH of the treatment solution is alkaline, it can be immediately subjected to ruthenium etching after the generation of hypobromite ions.

[0027] When generating hypobromite ions by supplying bromine to the treatment solution, bromide ions (Br) are added to the treatment solution. - The presence of ) improves the solubility of bromine (Br2). The Br2 dissolved in the treatment solution is Br - Ya Br3 - And it reacted, Br3 - Ya Br5 - This is because it forms complex ions such as Br2 and Br2, which stabilize in the treatment solution. - , Br3 - , Br5 - A treatment solution containing a large amount of this substance can generate a larger amount of hypobromite ions, and therefore can be suitably used as the treatment solution of the present invention.

[0028] As a method for generating hypobromite ions in the treatment solution, one method is to oxidize a bromine-containing compound with an oxidizing agent. The bromine-containing compound can be any compound that contains a bromine atom and, when oxidized by an oxidizing agent other than the hypobromite ion described later, produces bromine, hypobromite acid, or hypobromite ions. The bromine produced from the bromine-containing compound changes into hypobromite ions as described above. In addition, some or all of the hypobromite produced from the bromine-containing compound also changes into hypobromite ions, etching the ruthenium. As an example of the bromine-containing compound, it is preferable to use at least one selected from the group consisting of bromine salts and hydrogen bromide. Here, hydrogen bromide may be hydrogen bromide gas or hydrobromic acid, which is an aqueous solution of hydrogen bromide. Examples of bromine salts include lithium bromide, sodium bromide, potassium bromide, rubidium bromide, cesium bromide, ammonium bromide, onium bromide, etc. The term "onium bromide" as used here refers to a compound formed from an onium ion and a bromide ion. An onium ion is a polyatomic cation compound formed by the addition of an excess proton (hydrogen cation) to a monatomic anion. Specifically, these include cations such as imidazolium ion, pyrrolidinium ion, pyridinium ion, piperidinium ion, ammonium ion, phosphonium ion, fluoronium ion, chloronium ion, bromonium ion, iodonium ion, oxonium ion, sulfonium ion, selenonium ion, tellonium ion, arsonium ion, stivonium ion, and bismuthonium ion. Compounds that generate hypobromous acid or hypobromous acid ions in the treatment solution can also be suitably used as bromine-containing compounds. Examples of such compounds include, but are not limited to, bromohydantoins, bromoisocyanurates, bromusulfamic acids, and bromochloramines. More specifically, examples of such compounds include 1-bromo-3-chloro-5,5-dimethylhydantoin, 1,3-dibromo-5,5-dimethylhydantoin, and tribromoisocyanuric acid.

[0029] To add hypobromite ions as a compound to the treatment solution, hypobromite, bromine water, hypobromite salts, etc., can be added. Suitable hypobromite salts include sodium hypobromite, potassium hypobromite, and tetraalkylammonium hypobromite. Hypobromite or tetraalkylammonium hypobromite are even more suitable because they allow for control of the amount of metal ions, which is a problem in semiconductor manufacturing.

[0030] Tetraalkylammonium hypobromite can be easily obtained by passing bromine gas through a solution of tetraalkylammonium hydroxide. It can also be obtained by mixing hypobromite and a solution of tetraalkylammonium hydroxide. Furthermore, tetraalkylammonium hypobromite can be obtained by replacing the cations contained in hypobromite salts such as sodium hypobromite with tetraalkylammonium ions using an ion exchange resin.

[0031] The concentration of hypobromite ions in the processing solution of the present invention is not particularly limited as long as it does not deviate from the purpose of the present invention, but is preferably 0.001 mol / L or more and 0.20 mol / L or less as the amount of bromine element contained in the hypobromite ions. Below 0.001 mol / L, the etching rate of ruthenium is small and impractical. On the other hand, if it exceeds 0.20 mol / L, decomposition of the hypobromite ions is likely to occur, making it difficult to stabilize the etching rate of ruthenium. In order to stably etch ruthenium at a sufficient rate, the concentration of hypobromite ions is preferably 0.001 mol / L or more and 0.20 mol / L or less, more preferably 0.005 mol / L or more and 0.20 mol / L or less, and most preferably 0.01 mol / L or more and 0.10 mol / L or less.

[0032] The concentration of hypobromite ions in the treatment solution can be confirmed using widely known methods. For example, using ultraviolet-visible spectrophotometry, absorption due to hypobromite ions can be easily confirmed, and the hypobromite ion concentration can be determined from the intensity of the absorption peak (generally around 330 nm, depending on the pH and hypobromite ion concentration of the treatment solution). Furthermore, the hypobromite ion concentration can also be determined by iodine titration. In addition, the hypobromite ion concentration can be determined from the oxidation-reduction potential (ORP) and pH of the treatment solution. From the viewpoint of being non-contact and allowing for continuous measurement, measurement by ultraviolet-visible spectrophotometry is the most preferred method. When measuring the hypobromite ion concentration by ultraviolet-visible spectrophotometry, if there is absorption by other chemical species, the hypobromite ion concentration can be determined with sufficient accuracy by performing data processing such as spectral splitting and baseline correction, and by appropriately selecting a reference.

[0033] Hypobromous acid (HBrO) and hypobromous acid ion (BrO) - The acid dissociation constant (pK) of ) a ) is 8.6, therefore, when the pH is low, the amount of HBrO and BrO depends on the pH of the treatment solution. - They may coexist. HBrO and BrO - If it contains HBrO and BrO - The total concentration of these can be treated as the concentration of the hypobromite ion mentioned above.

[0034] The detailed mechanism by which hypobromite ions dissolve ruthenium is not entirely clear, but it is believed that in the treatment solution, hypobromite ions or hypobromite generated from hypobromite ions oxidize ruthenium, resulting in RuO4, RuO4 - or RuO4 2- It is presumed that the ruthenium is dissolved in the processing solution. - or RuO4 2- By dissolving it as Ruthenium, it is possible to reduce the amount of RuO4 gas generated and suppress the generation of RuO2 particles. - or RuO4 2-For dissolution, the pH of the treatment solution is preferably alkaline, more preferably 8 to 14, even more preferably 12 to 14, and most preferably 12 to less than 13. If the pH of the treatment solution is 12 to less than 13, ruthenium will dissolve as RuO4. - or RuO4 2- Because it dissolves in the processing solution, the amount of RuO4 gas generated can be significantly reduced, and the generation of RuO2 particles can be suppressed. On the other hand, if the pH of the processing solution is less than 8, ruthenium is more easily oxidized to RuO2 or RuO4, so the amount of RuO2 particles tends to increase, and the amount of RuO4 gas generated also tends to increase.

[0035] (B) pH buffering agent The pH buffer used in this invention is a combination of a weak acid and a conjugate base, and is added to the treatment solution for the purpose of suppressing fluctuations in hydrogen ions in the treatment solution.

[0036] The mechanism by which the processing solution of the present invention enables precise control of the etching rate of ruthenium is thought to be as follows: Even if the pH of the processing solution fluctuates, the conjugate base of the pH buffer present in the processing solution reacts with hydrogen ions to neutralize the fluctuation in the pH of the processing solution, thereby suppressing the pH fluctuation and enabling constant control of the etching rate of ruthenium.

[0037] As a pH buffer, any substance with pH buffering capacity, and any combination of a weak acid and a conjugate base, can be used without particular limitations. In the present invention, suitable cationic pH buffers include, specifically, carbonic acid, boric acid, phosphoric acid, trishydroxymethylaminomethane (tris), ammonia, pyrophosphate, p-phenolsulfonic acid, diethanolamine, ethanolamine, triethanolamine, 5,5-diethylbarbituric acid, glycine, glycylglycine, imidazole, N,N-bis(2-hydroxyethyl)-2-aminoethanesulfonic acid, 3-morpholinopropanesulfonic acid, N-tris(hydroxymethyl)methyl-2-aminoethanesulfonic acid, 2-[4-(2-hydroxyethyl)-1-piperazinyl]ethanesulfonic acid, 4-(2-hydroxyethyl)-1-piperazinepropanesulfonic acid, tricine, N,N-di(2-hydroxyethyl)glycine, 2-cyclohexylaminoethanesulfonic acid, hydroxyproline, phenol, ethylenediaminetetraacetic acid, and the like.

[0038] In this invention, only one type of pH buffer may be added, or two or more types of pH buffers may be added in combination. By combining two or more types of pH buffers, pH fluctuations can be suppressed over a wide pH range. In this specification, pH is expressed as the value at 25°C.

[0039] In this invention, it is preferable to use at least one pH buffer selected from the group consisting of boric acid, carbonic acid, and phosphoric acid. In particular, when using boric acid, a desirable pH buffering capacity can be expected when the pH of the treatment solution is 8.2 to 10.2; when using carbonic acid, when the pH of the treatment solution is 9.3 to 11.3; and when using phosphoric acid, when the pH of the treatment solution is 11.4 to 13.4. These pH buffers may be used individually or in combination. Furthermore, when etching ruthenium, it is preferable to use a pH buffer that does not adsorb to the surface of ruthenium.

[0040] In the present invention, the concentration of the pH buffer in the treatment solution is preferably 0.0001 to 1.0 mol / L, more preferably 0.0001 to 0.8 mol / L, and even more preferably 0.001 to 0.6 mol / L.

[0041] A pH buffer content in the processing solution of the present invention is preferable if it is in the range of 0.0001 to 1.0 mol / L, as this allows for stabilization of the pH of the processing solution and suppression of an increase in the viscosity of the processing solution. When the processing solution contains multiple pH buffers, it is preferable that the concentration of each pH buffer is in the range of 0.0001 to 1.0 mol / L. A high viscosity of the processing solution tends to make it difficult to apply to miniaturized wiring processes, so a pH buffer content within the above range is preferable. Furthermore, within the above range, the pH buffer is sufficiently dissolved in the processing solution, which is preferable because it prevents contamination of the etching target by reprecipitation of the pH buffer.

[0042] The mechanism by which the processing solution of the present invention can suppress fluctuations in the etching rate of ruthenium by adding a pH buffer is thought to be as follows: Even if the pH of the processing solution fluctuates, the conjugate base of the pH buffer present in the processing solution reacts with hydrogen ions, thereby suppressing fluctuations in the pH of the processing solution caused by disturbances such as the absorption of carbon dioxide contained in the ambient air and etching reactions. As a result, it is thought that fluctuations in the etching rate of ruthenium can be suppressed.

[0043] (C) Onium Ion In the present invention, onium ions represented by the following formulas (1) to (4) are included in the treatment solution to adjust the pH of the treatment solution.

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[0048] (In formula (1), A + R is an ammonium ion or a phosphonium ion, 1 , R 2 , R 3 , R 4 R is independently an alkyl group having 1 to 25 carbon atoms, an allyl group, an aralkyl group which may have an aryl group substituent, or an aryl group. However, R 1 , R 2 , R 3 , R 4 If R is an alkyl group, 1 , R 2 , R 3 , R 4 At least one alkyl group has two or more carbon atoms. Furthermore, the aryl group in the aralkyl group and at least one hydrogen atom in the ring of the aryl group may be replaced with fluorine, chlorine, an alkyl group having 1 to 10 carbon atoms, an alkenyl group having 2 to 10 carbon atoms, an alkoxy group having 1 to 9 carbon atoms, or an alkenyloxy group having 2 to 9 carbon atoms. In these groups, at least one hydrogen atom may be replaced with fluorine or chlorine, and it is preferable that the alkyl group in the aralkyl group has 1 to 25 carbon atoms.

[0049] In formula (2), A + R is a sulfonium ion, 1 , R 2 , R 3 R is independently an alkyl group having 1 to 25 carbon atoms, an allyl group, an aralkyl group having an alkyl group having 1 to 25 carbon atoms, or an aryl group. However, R 1 , R 2 , R 3 If R is an alkyl group, 1 , R 2 , R3 At least one alkyl group has two or more carbon atoms. In addition, at least one hydrogen atom in the aryl group and the ring of the aryl group in the aralkyl group may be replaced with fluorine, chlorine, an alkyl group having 1 to 10 carbon atoms, an alkenyl group having 2 to 10 carbon atoms, an alkoxy group having 1 to 9 carbon atoms, or an alkenyloxy group having 2 to 9 carbon atoms, and in these groups, at least one hydrogen atom may be replaced with fluorine or chlorine.

[0050] In formula (3), Z is an aromatic group or alicyclic group which may contain nitrogen, sulfur, or oxygen atoms, and in the aromatic group or alicyclic group, at least one hydrogen to which carbon or nitrogen is bonded may be replaced with chlorine, bromine, fluorine, iodine, at least one C1-C15 alkyl group, at least one C2-C9 alkenyloxy group, an aromatic group which may be substituted with at least one C1-C15 alkyl group, or an alicyclic group which may be substituted with at least one C1-C15 alkyl group. A is nitrogen or sulfur. R is chlorine, bromine, fluorine, iodine, a C1-C15 alkyl group, an allyl group, an aromatic group which may be substituted with at least one C1-C15 alkyl group, or an alicyclic group which may be substituted with at least one C1-C15 alkyl group. n is an integer of 1 or 2 and indicates the number of R. When n is 2, R may be the same or different and may form a ring.

[0051] In formula (4), A + R is independently an ammonium ion or a phosphonium ion, 1 , R 2 , R 3 , R 4 , R 5 , R 6These are independently a C1-C25 alkyl group, an allyl group, an aralkyl group having a C1-C25 alkyl group, or an aryl group. In the aralkyl group, at least one hydrogen atom in the aryl group and the ring of the aryl group may be replaced with fluorine, chlorine, a C1-C10 alkyl group, a C2-C10 alkenyl group, a C1-C9 alkoxy group, or a C2-C9 alkenyloxy group, and in these groups, at least one hydrogen atom may be replaced with fluorine or chlorine. In the processing solution according to the embodiment of the present invention, the concentration range of onium ions is preferably 0.000001 to 5.0 mol / L. By satisfying this concentration range of onium ions, ruthenium can be etched. As a result, stable etching can be performed, and the processing solution can be made to have excellent long-term storage stability. To further exhibit this effect, the concentration of onium ions is more preferably 0.00001 to 3.0 mol / L, and even more preferably 0.00001 to 2.0 mol / L. The concentration range, preferred concentration range, and even more preferred concentration range mentioned above are applicable to any specific example of onium ions represented by formulas (1) to (4), such as the tetramethylammonium ion. In this specification, "may be substituted" means that both "substituted" and "not substituted" are included.

[0052] The (C) onium ions contained in the processing solution have the effect of suppressing surface roughness of ruthenium after etching. The reason for this is not clear, but it is thought that the bulky onium ions adsorb onto the ruthenium surface through electrostatic interaction, slowing down the reaction between hypobromite ions and ruthenium, and allowing for uniform surface etching.

[0053] (pH adjuster) The pH adjusting agent of the present invention is an acid or alkali, different from the onium ions and pH buffers described above. For example, it is an acid such as hydrochloric acid, sulfuric acid, or nitric acid, or an alkali such as alkylammonium hydroxide, for example, tetramethylammonium hydroxide, or choline.

[0054] In this invention, when a pH buffer is included in the treatment solution, the range in which the pH can stably exist is determined by the combination of the pH adjusting agent and the pH buffer in the treatment solution. For example, when an aqueous solution of tetramethylammonium hydroxide is used as the pH adjusting agent and boric acid is used as the pH buffer, the pH of the treatment solution can be stabilized at 8.2 to 10.2, thereby suppressing fluctuations in the etching rate of ruthenium. Furthermore, since no alkali metal compounds such as potassium hydroxide or sodium hydroxide are used as pH adjusting agents, no alkali metal contamination such as potassium or sodium is observed on the semiconductor substrate surface after etching, making it suitable for use.

[0055] (Oxidizing agent) The treatment solution of the present invention preferably contains an oxidizing agent other than hypobromite ions. When the oxidizing agent is included in the treatment solution of the present invention, the hypobromite ions decompose to produce bromide ions (Br - The oxidizing agent plays a role in oxidizing the hypobromite ion back to the hypobromite ion. Therefore, it is preferable that the oxidation-reduction potential between the oxidizing agent and the chemical species produced by the reduction of the oxidizing agent exceeds the oxidation-reduction potential of the hypobromite ion / bromide ion system. Using such an oxidizing agent, bromide ions can be oxidized to hypobromite ions. The oxidation-reduction potential of the hypobromite ion / bromide ion system is the oxidation-reduction potential in the following reaction equation (5), and means the potential in the equilibrium state between the hypobromite ion, which is the oxidized form, and the bromide ion, which is the reduced form, present in the solution. BrO - + 2H2O + 2e - → Br - + 2OH - (5) In other words, when the redox potential of an oxidizing agent exceeds the redox potential of hypobromite ions / bromide ions, it means that the redox potential between the oxidizing agent and the chemical species produced when the oxidizing agent is reduced exceeds the redox potential between the hypobromite ion and the bromide ion system produced when the hypobromite ion is reduced. The redox potential between an oxidizing agent that may be present in the treatment solution and the chemical species produced by the reduction of the oxidizing agent varies depending on the concentration of the oxidizing agent and the chemical species produced by its reduction, the temperature and pH of the solution, etc. However, regardless of these conditions, it is sufficient that the redox potential between the oxidizing agent and the chemical species produced by its reduction exceeds the redox potential of the hypobromite ion / bromide ion system in the treatment solution. The redox potentials of these redox species may be determined by measuring them as potentials relative to a reference electrode (e.g., a standard hydrogen electrode (SHE) or a silver / silver chloride electrode), or they may be calculated using standard redox potentials listed in a database (e.g., "Electrochemical Handbook, 6th Edition," edited by the Electrochemical Society, Maruzen Publishing, 2013, pp. 92-95, or "CRC Handbook of Chemistry and Physics, 87th edition," David R. Lide ed., CRC Press, pp. 8-20 to 8-30, etc.), taking into account the concentration of the redox species, pH, temperature, etc.

[0056] On the other hand, the upper limit of the redox potential between the oxidizing agent and the chemical species produced by the reduction of the oxidizing agent, which may be included in the processing solution, is not particularly limited as long as it does not deviate from the purpose of the present invention. However, when processing a semiconductor wafer containing ruthenium with the processing solution of the present invention containing an oxidizing agent, the redox potential is RuO4 - If the redox potential of the RuO4 system is higher than that of the RuO4 system (1.0V vs. SHE), then the RuO4 dissolved in the treatment solution... - The oxidizing agent can oxidize the oxidizing agent to RuO4, potentially increasing the amount of RuO4 gas generated. In such cases, the amount of oxidizing agent added to the treatment solution and the timing of its addition can be adjusted accordingly. - It is possible to suppress the oxidation from to RuO4 and control the amount of RuO4 gas generated.

[0057] Specific examples of such oxidizing agents include nitric acid, sulfuric acid, persulfuric acid, peroxodisulfuric acid, hypochlorous acid, chlorous acid, chloric acid, perchloric acid, bromic acid, bromate, perbromic acid, hypoiodic acid, iodic acid, iodic acid, periodic acid, their salts, and ions produced by the dissociation of these salts. Furthermore, hydrogen peroxide, ozone, fluorine, chlorine, bromine, iodine, permanganate, chromate, dichromate, cerium salts, and the like can be used. These oxidizing agents may be used individually or in combination. When adding these oxidizing agents to the treatment solution of the present invention, a suitable solid, liquid, or gaseous form may be selected depending on the properties of the oxidizing agent used.

[0058] Of the above oxidizing agents, hypochlorous acid, chlorous acid, chloric acid, perchloric acid, bromous acid, bromate, perbromate, hypoiodic acid, iodous acid, iodic acid, periodic acid, and their salts, as well as the ions produced by the dissociation of these salts, ozone, or hydrogen peroxide are preferred because they can exist stably even in alkaline conditions. More preferably, hypochlorous acid, chlorous acid, chloric acid, perchloric acid, bromous acid, bromate, perbromate, and their salts, as well as the ions produced by the dissociation of these salts, ozone, or hydrogen peroxide are preferred. Even more preferably, hypochlorite ions or ozone are preferred, and hypochlorite ions are most preferred.

[0059] Hypochlorite ions and ozone have the ability to reoxidize bromide ions to hypobromite ions in alkaline treatment solutions (pH between 8 and 14). This is evident from the fact that the oxidation-reduction potential of the hypochlorite ion / chloride ion system is 0.89V, the oxidation-reduction potential of the ozone / oxygen system is 1.24V, while the oxidation-reduction potential of the hypobromite ion / bromide ion system is 0.76V. Note that the above oxidation-reduction potentials are values ​​relative to a standard hydrogen electrode at pH 14 (25°C).

[0060] Using hypochlorous acid, its salt tetraalkylammonium hypochlorite, or ozone as the oxidizing agent allows for substantially control over the amount of metal, making it suitable as a processing solution for semiconductor manufacturing. Among these, tetraalkylammonium hypochlorite is particularly preferred because it is stable even in alkaline environments and can efficiently oxidize bromide ions and / or the bromine-containing compounds mentioned above.

[0061] The concentration of the oxidizing agent is not particularly limited; only an amount sufficient to oxidize the bromide ions and / or the bromine-containing compound to a chemical species effective for etching ruthenium should be added. The amount of oxidizing agent added is preferably 21 μmol / L or more and 2.0 mol / L or less. If the amount of oxidizing agent added is less than 21 μmol / L, the bromide ions and / or the bromine-containing compound cannot be efficiently oxidized, and the etching rate of ruthenium decreases. In other words, the etching rate is low in compositions without the oxidizing agent. On the other hand, if the amount of oxidizing agent added is greater than 2.0 mol / L, the stability of the oxidizing agent decreases, which is unsuitable. From the viewpoint of stabilizing the etching rate of ruthenium over a long period of time, the concentration of the oxidizing agent is more preferably 21 μmol / L or more and 2.0 mol / L or less, and most preferably 100 μmol / L or more and 1.0 mol / L or less.

[0062] (D) Bromide ions The bromide ions used in this invention are added to the treatment solution to improve its stability.

[0063] As for the bromide ion, any solution containing bromide salts or bromide ions can be used without particular limitations. In the present invention, bromide ions that can be preferably used include tetraalkylammonium bromide, hydrobromic acid, sodium bromide, potassium bromide, calcium bromide, and magnesium bromide, with tetraalkylammonium bromide or hydrobromic acid being even more preferred.

[0064] In the processing liquid according to the embodiment of the present invention, the concentration range of bromide ions is preferably 0.001 mol / L or more and 2.0 mol / L or less. By satisfying this range of the concentration of bromide ions, the liquid life of the processing liquid can be extended. As a result, etching can be stably performed, and a processing liquid excellent in long-term storage stability can be obtained. To further exert this effect, the concentration of bromide ions is more preferably 0.001 mol / L or more and 1.5 mol / L or less, still more preferably 0.005 mol / L or more and 1.0 mol / L or less, and particularly preferably 0.01 mol / L or more and 0.5 mol / L or less.

[0065] By adding bromide ions to the processing liquid of the present invention, the concentration of the etching component in the processing liquid can be kept constant, and the stability of the processing liquid can be improved. The mechanism regarding this improvement in stability is not necessarily clear, but the following can be considered. That is, when hypobromite ions in the processing liquid decompose by disproportionation reaction, bromide ions are generated as one of the decomposition products. Therefore, it is considered that by previously adding bromide ions, the rate of the disproportionation reaction of hypobromite ions can be reduced. As a result, the change in the concentration of hypobromite ions, which is the chemical species that etches ruthenium, becomes small, not only the etching rate of ruthenium is stabilized, but also the storage stability of the processing liquid is improved, and the liquid life of the processing liquid can be extended.

[0066] (E) Bromite ions, bromate ions The total concentration range of bromite ions and bromate ions used in the present invention is 3.3×10 -6 mol / L or more and 5.0×10 -1It is preferable that the concentration is mol / L or less. Bromite ions and bromate ions can be added to the treatment solution to improve its stability. The bromite ions used in this invention may be commercially available bromite salts, or those produced using a disproportionation reaction of hypobromite ions. To obtain a bromite salt free of metal impurities, a sodium bromite solution obtained by a disproportionation reaction of sodium hypobromite may be passed through an ion exchange resin substituted with tetramethylammonium ions to purify and use a tetramethylammonium bromite solution. Furthermore, any solution containing bromate salts or bromate can be used without particular restriction as the bromate ions. In this invention, suitably usable bromate ions include sodium bromate, potassium bromate, and tetraalkylammonium bromate, with tetramethylammonium bromate being even more preferred.

[0067] By adding bromite ions and / or bromate ions to the treatment solution of the present invention, the concentration of etching components in the treatment solution can be kept constant, and the stability of the treatment solution can be improved. The mechanism for this improvement in stability is not entirely clear, but the following is considered possible: When hypobromite ions in the treatment solution decompose in a disproportionation reaction, bromite ions and / or bromate ions are produced as decomposition products. Therefore, it is thought that by adding these ions in advance, the rate of the disproportionation reaction of hypobromite ions can be reduced. As a result, the concentration change of hypobromite ions, which are the chemical species that etch ruthenium, becomes smaller, which not only stabilizes the etching rate of ruthenium but also improves the storage stability of the treatment solution and extends its lifespan.

[0068] (F) Chlorite ions, chlorate ions, chloride ions, sulfate ions The total concentration range of chlorite ions, chlorate ions, chloride ions, and sulfate ions used in this invention is preferably 10 μmol / L or more and 2.0 mol / L or less. Chlorite ions, chlorate ions, chloride ions, and sulfate ions can be added to the treatment solution to improve its stability. As for the chlorite ions used in this invention, any solution containing chlorite salts or chlorous acid can be used without particular limitations. In this invention, suitably usable chlorite ions include sodium chlorite, potassium chlorite, and tetraalkylammonium chlorite, with tetramethylammonium chlorite being even more preferred. Furthermore, as for chlorate ions, any solution containing chlorate salts or chlorous acid can be used without particular limitations. In this invention, suitably usable chlorate ions include sodium chlorate, potassium chlorate, and tetraalkylammonium chlorate, with tetramethylammonium chlorate being even more preferred. Furthermore, as for chloride ions, any solution containing chloride salts or hydrochloric acid can be used without particular limitations. In the present invention, suitable chloride ions include hydrochloric acid, sodium chloride, potassium chloride, and tetraalkylammonium chloride, with hydrochloric acid and tetramethylammonium chloride being more preferred. Furthermore, as sulfate ions, any solution containing sulfates or sulfuric acid can be used without particular limitation. Suitable sulfate ions in the present invention include sulfuric acid, sodium sulfate, sodium bisulfate, potassium sulfate, potassium bisulfate, barium sulfate, potassium sulfate, and strontium sulfate, with sulfuric acid and tetramethylammonium sulfate being more preferred. By adding one or more ions selected from the group consisting of chlorite ions, chlorate ions, chloride ions, and sulfate ions to the treatment solution of the present invention, the concentration of etching components in the treatment solution can be kept constant, and the stability of the treatment solution can be improved. The mechanism for this improvement in stability is not entirely clear, but the following is considered possible.In other words, when hypobromite ions in the treatment solution decompose through a disproportionation reaction, bromite ions and / or bromate ions and / or bromide ions are produced as decomposition products. Therefore, it is thought that the rate of the disproportionation reaction of hypobromite ions can be reduced by adding one or more ions selected from the group consisting of chlorite ions, chlorate ions, and chloride ions beforehand. That is, chlorite ions, chlorate ions, and chloride ions exhibit the same effect as the above-mentioned bromite ions, bromate ions, and bromide ions. As a result, the concentration change of hypobromite ions, which are the chemical species that etch ruthenium, becomes smaller, the etching rate of ruthenium is stabilized, and the storage stability of the treatment solution is improved, extending the lifespan of the treatment solution.

[0069] The processing solution of the present invention may contain metals (or metal ions; hereinafter, "metals" also refers to metal ions) due to the manufacturing process of the processing solution. Specific examples of metals that may be included include lithium, sodium, potassium, aluminum, magnesium, calcium, chromium, manganese, iron, nickel, cobalt, copper, silver, cadmium, barium, zinc, and lead, as well as their ions. If these metals remain on the semiconductor wafer, they can have adverse effects on the semiconductor wafer (such as a decrease in semiconductor wafer yield). Therefore, it is preferable to have a low metal content in the processing solution, but including a small amount of metal makes it possible to maintain the flatness of the metal surface after etching (preventing surface roughness). Therefore, the metal content in the treatment solution is preferably 0.01 ppt to 1 ppb by mass of any one metal selected from lithium, sodium, potassium, aluminum, magnesium, calcium, chromium, manganese, iron, nickel, cobalt, copper, silver, cadmium, barium, zinc, and lead, more preferably 1 ppt to 1 ppb, even more preferably 10 ppt to 500 ppt, and most preferably 100 ppt to 200 ppt. If the metal content exceeds 1 ppb, it is possible to reduce the metal content to 1 ppb or less through filtration, distillation, ion exchange, etc.

[0070] (Storage stability of the treatment solution) The storage conditions for the processing solution of the present invention are not particularly limited, but general storage conditions are preferred, namely, storage at -25 to 50°C in a known container, canister, or resin storage container, and it is even more preferable to store it at -20 to 40°C in a light-shielding storage container, transport container such as a canister, or resin storage container filled with an inert gas in a dark place. If the storage temperature exceeds the above range, the container may expand and break due to the evaporation of moisture during long-term storage.

[0071] When the treatment solution of the present invention contains at least one ion selected from the group consisting of bromide ions, bromite ions, bromate ions, chlorite ions, chlorate ions, chloride ions, and sulfate ions, the rate of the disproportionation reaction of hypobromite ions decreases, thereby further reducing the change in the concentration of hypobromite ions. Therefore, the treatment solution of the present invention containing these anions can be used without a significant change in etching rate even after storage, and stable etching can be performed.

[0072] According to the storage method of the present invention, the oxidizing power of the treatment solution containing hypobromite ions remains virtually unchanged even after a storage period of 3 days, or more preferably 7 days. Therefore, it can be used for various purposes after storage. The longer the storage period, the greater the expected improvement in productivity.

[0073] (solvent) In the treatment solution of the present invention, in addition to components (A), (B), (C), (D), (E), and (F), the residue other than the bromine-containing compound, oxidizing agent, pH adjuster, and other additives described later is a solvent. The residue can be adjusted with a solvent to achieve the concentrations of each component by adjusting (A), (B), (C), (D), (E), (F), the bromine-containing compound, oxidizing agent, pH adjuster, and other additives.

[0074] In the present invention, the solvent is not particularly limited, and organic solvents, water, etc., can be used. The solvent may also be a mixture of water and an organic solvent. When using an organic solvent, it is preferable to use an organic solvent that is stable even in the presence of hypobromite ions present in the treatment solution, such as acetonitrile and sulfolane. When using water, it is preferable to use water from which metal ions, organic impurities, and particle particles have been removed by distillation, ion exchange treatment, filtration treatment, or various adsorption treatments, and pure water and ultrapure water are particularly preferred. Such water can be easily obtained by methods for producing ultrapure water that are widely used in semiconductor manufacturing.

[0075] (pH of the treatment solution) The pH of the processing solution of the present invention can be between 8 and 14. If the pH of the processing solution of the present invention is 14 or less, even if ruthenium is oxidized, dissolved, or removed, the pH of the processing solution will not fluctuate significantly, and fluctuations in the concentration of hypobromite ions can be suppressed. Therefore, fluctuations in the etching rate of ruthenium can be suppressed, and ruthenium can be etched stably. If the pH of the processing solution is higher than 14, the etching rate of ruthenium decreases significantly. If the pH is less than 8, the decomposition reaction of hypobromite ions contained in the processing solution tends to occur more easily. Therefore, considering the etching rate and high-precision etching rate control, the pH of the processing solution is preferably between 8 and 14, more preferably between 12 and 14, and even more preferably between 12 and less than 13. As a preferred upper limit for the pH of the processing solution, for example, when boric acid is used as a pH buffer, a value of less than 10 can also be exemplified.

[0076] (Other additives) In addition, the processing solution of the present invention may optionally contain additives that have been conventionally used in semiconductor processing solutions, as long as they do not impair the objectives of the present invention. For example, acids, alkalis, metal corrosion inhibitors, water-soluble organic solvents, fluorine compounds, oxidizing agents, reducing agents, chelating agents, surfactants, defoaming agents, and the like can be added as additives.

[0077] (Ruthenium etching method) The processing solution of the present invention can be used to suitably etch ruthenium present on a semiconductor wafer. The processing of a ruthenium-containing wafer with the processing solution of the present invention may be done by single-wafer processing or immersion processing. Furthermore, the method of processing a semiconductor wafer with the processing solution of the present invention is not limited to wet etching, but can also be suitably used as a processing solution for cleaning or residue removal, or as a component of a CMP slurry.

[0078] The conditions for using the processing solution of the present invention can be appropriately determined according to the etching conditions of the etching apparatus used. For example, the processing temperature can be 10 to 80°C, and more preferably in the range of 20 to 70°C.

[0079] When processing a wafer using the processing solution of the present invention, the processing time is in the range of 0.1 to 120 minutes, preferably 0.5 to 60 minutes, and can be appropriately determined depending on the etching conditions and the semiconductor element used. Furthermore, while an organic solvent such as alcohol can be used as the rinsing solution after using the processing solution of the present invention, rinsing with deionized water alone is sufficient.

[0080] As described above, the processing solution of the present invention can achieve an etching rate of 20 Å / min or more, preferably 50 Å / min or more, for precious metals, particularly ruthenium, and by suppressing pH fluctuations, even if the pH of the processing solution fluctuates due to disturbances, for example, the fluctuation rate of the ruthenium etching rate can be suppressed to 30% or less. As is clear from this, the processing solution of the present invention can be suitably used as a processing solution for etching ruthenium when ruthenium is used in the semiconductor device formation process.

[0081] The processing solution of the present invention also has the function of suppressing the generation of RuO4 gas. The mechanism is presumed to be as follows: In an alkaline processing solution, RuO4 gas is generated by the dissolution of ruthenium. - Ya RuO4 2- Anions like this (hereinafter referred to as RuO4) -(Sometimes written as etc.) interacts electrostatically with (C) onium ions contained in the processing solution, and some of them become stable as ion pairs. As a result, RuO4 - The conversion from these substances to RuO4 is inhibited, and as a result, the generation of RuO4 gas is suppressed. Furthermore, since the generation of RuO4 is inhibited, it is presumed that the generation of RuO2 particles, which are produced by the reduction of RuO4, is also suppressed. Since the generation of RuO4 and RuO2 depends on pH, it is preferable that the pH of the treatment solution containing ruthenium does not fluctuate. By including a pH buffer in the treatment solution, the pH fluctuation of the treatment solution can be suppressed, and the generation of RuO4 and RuO2 is suppressed. From the viewpoint of generating RuO4 and RuO2, an oxidizing agent capable of etching ruthenium in the alkaline range of pH 8 to 12 is preferred, and hypobromite ions are superior to hypochlorite ions, orthoperiodate ions, and metaperiodate ions in that they have a faster etching rate of ruthenium in the alkaline range.

[0082] In the processing solution of the present invention, the RuO4 gas suppression effect achieved by adding onium ions represented by formulas (1) to (4) is not limited to the type and concentration of hypobromite ions, pH buffers, oxidizing agents other than hypobromite ions, and other additives contained in the processing solution, nor is it limited to the processing method or processing conditions. For example, regardless of the concentration of hypobromite ions contained in the processing solution of the present invention, the RuO4 gas suppression effect can be obtained by the onium ions represented by formulas (1) to (4) contained in the processing solution. Furthermore, the temperature of the processing solution is not particularly limited, and the RuO4 gas suppression effect can be achieved at any processing temperature by the onium ions represented by formulas (1) to (4) contained in the processing solution. The RuO4 gas suppression effect of the processing solution of the present invention is not limited to when used in wet etching, but is also effective when the processing solution of the present invention is used for cleaning, residue removal, or as a component of a CMP slurry. For example, if the processing solution of the present invention is used in CMP polishing, it is possible to suppress the generation of RuO4 gas even in the CMP polishing process.

[0083] (Ruthenium-containing gas generation inhibitor) A ruthenium-containing gas (RuO4-containing gas) generation inhibitor is an agent that suppresses the generation of ruthenium-containing gas by being added to a solution for processing ruthenium, and refers to a solution containing (A) hypobromite ions, (B) a pH buffer, and (C) onium ions. The pH buffer may be any agent that has pH buffering capacity, but the pH buffer used in the semiconductor processing solution of the present invention can be suitably used. Furthermore, the onium ions are preferably onium ions represented by formulas (1) to (4). The ruthenium-containing gas generation inhibitor may further contain (D) bromide ions, (E) bromite ions and / or bromate ions, and (F) one or more chlorine-containing ions selected from the group consisting of chlorite ions, chlorate ions, and chloride ions.

[0084] The solution for treating ruthenium can be any solution that contains components that come into contact with the ruthenium and cause physical and chemical changes to it, for example, a solution containing an oxidizing agent. Examples of such oxidizing agents include those exemplified in the above description and hypobromite ions. When ruthenium is treated with the solution, all or part of it dissolves, disperses, or precipitates in the solution, causing the formation of RuO4 (gas) and / or RuO2 (particles). Since the formation of RuO4 (solution) and RuO2 (particles) is pH-dependent, it is preferable that the pH of the ruthenium-containing solution does not fluctuate. By including a pH buffer in the ruthenium-containing gas generation inhibitor, the pH fluctuation of the solution for treating ruthenium to which the ruthenium-containing gas generation inhibitor has been added can be suppressed. This suppresses the generation of RuO4-containing gas from the solution for treating ruthenium. Any pH buffer, as exemplified in the above description, can be used without any limitations as the pH buffer. In a liquid containing a liquid for processing ruthenium and the ruthenium-containing gas generation inhibitor of the present invention (also referred to as a processing liquid containing the gas generation inhibitor), RuO4 present in the processing liquid -The onium ions and other elements form ion pairs that dissolve in the treatment solution, thereby suppressing the generation of RuO4 gas and RuO2 (particles).

[0085] In the ruthenium-containing gas generation inhibitor, the conditions such as the hypobromite ion content, the type and content of the pH buffer, the type and content of the onium ion, other components and their content, and pH should be set appropriately so as to suppress the generation of ruthenium-containing gas from the processing solution containing the gas generation inhibitor. For example, the same conditions described in the description of semiconductor processing solutions can be applied. For example, the concentration of hypobromite ions in the ruthenium-containing gas generation inhibitor is preferably 0.001 mol / L or more and 0.20 mol / L or less in terms of the amount of bromine element contained in the hypobromite ions. Furthermore, it is preferable to include boric acid, carbonic acid, or phosphoric acid as a pH buffer. In particular, when using boric acid, a desirable pH buffering capacity can be expected when the pH of the treatment solution containing the gas generation inhibitor is 8.2 to 10.2; when using carbonic acid, when the pH of the treatment solution containing the gas generation inhibitor is 9.3 to 11.3; and when using phosphoric acid, when the pH of the treatment solution containing the gas generation inhibitor is 11.4 to 13.4. These pH buffers may be used individually or in combination. Furthermore, the concentration of the pH buffer in the ruthenium-containing gas generation inhibitor is preferably 0.0001 to 1.0 mol / L, and more preferably 0.001 to 0.8 mol / L. Within the range of 0.001 to 0.8 mol / L, pH fluctuations in the treatment solution containing the gas generation inhibitor are suppressed, and a sufficient ruthenium-containing gas generation suppression effect can be obtained. In addition to the above conditions, for example, the content of onium ions represented by formulas (1) to (4) above in the ruthenium-containing gas generation inhibitor is preferably 0.000001 to 5.0 mol / L, more preferably 0.00001 to 3.0 mol / L, and even more preferably 0.00001 to 2.0 mol / L. Furthermore, the same pH adjuster as described above may be added to the ruthenium-containing gas generation inhibitor as appropriate. The content of the pH adjuster can be adjusted so that the pH of the treatment solution containing the gas generation inhibitor falls within a predetermined range. For example, the content of the pH adjuster in the ruthenium-containing gas generation inhibitor only needs to be an effective amount, and specifically, 0.000001 to 1.0 mol / L can be exemplified. The pH of the treatment solution containing the gas generation inhibitor is preferably 8 to 14.

[0086] As explained above, the processing solution of the present invention contains hypobromite ions, onium ions, and a pH buffer, and is therefore a processing solution that can process semiconductor wafers containing ruthenium without generating RuO4 gas. Thus, the processing solution of the present invention is both a solution for processing ruthenium and a gas suppressant for ruthenium-containing gas generation.

[0087] (Method for suppressing the generation of ruthenium-containing gas) The present invention relates to a method for suppressing the generation of ruthenium-containing gas, which includes the step of adding the above-mentioned ruthenium-containing gas generation inhibitor to a liquid used for processing ruthenium. Specifically, for example, by adding the ruthenium-containing gas generation inhibitor of the present invention to a liquid used in processes that process ruthenium, such as etching, residue removal, cleaning, and CMP in semiconductor manufacturing (these correspond to liquids used for processing ruthenium), the generation of ruthenium-containing gas can be suppressed. Furthermore, when cleaning ruthenium adhering to the inner walls of chambers, piping, etc., in each of the devices used in these semiconductor manufacturing processes, the generation of ruthenium-containing gas can be suppressed by using a liquid containing the ruthenium-containing gas generation inhibitor. For example, in the maintenance of equipment that forms ruthenium using physical vapor deposition (PVD) or chemical vapor deposition (CVD), by adding the ruthenium-containing gas generation inhibitor of the present invention to the cleaning liquid used to remove ruthenium adhering to chambers, piping, etc., it is possible to suppress the generation of ruthenium-containing gas during cleaning. According to this method, the generation of ruthenium-containing gas can be suppressed by the mechanism described above.

[0088] In the method for suppressing the generation of ruthenium-containing gas, it is preferable to adjust the concentration of the onium salt in the ruthenium-containing gas generation suppressor and the amount added so that the concentrations of the pH buffer and onium ions in the mixture of the ruthenium-containing gas generation suppressor and the liquid for treating ruthenium are, respectively, 10 μmol / L to 5.0 mol / L. Furthermore, in the case of a ruthenium-containing gas generation inhibitor, the same pH adjuster as described above may be added to the ruthenium-containing gas generation inhibitor as appropriate. The amount of pH adjuster contained in the ruthenium-containing gas generation inhibitor should be adjusted as appropriate so that the pH of the mixture obtained by mixing the ruthenium treatment solution and the ruthenium-containing gas generation inhibitor is, for example, between 8 and 14. Also, the amount of ruthenium-containing gas generation inhibitor added to the ruthenium treatment solution should be adjusted as appropriate so that the pH of the mixture obtained by mixing the two solutions is, for example, between 8 and 14. The amount of ruthenium-containing gas generation inhibitor added to the ruthenium treatment solution depends on the amount of ruthenium dissolved in the treatment solution containing the gas generation inhibitor. The amount of ruthenium-containing gas generation inhibitor to add is not particularly limited, but for example, when the amount of ruthenium dissolved in the ruthenium treatment solution is set to 1, the weight ratio is preferably 10 to 500,000, more preferably 100 to 100,000, and even more preferably 1,000 to 50,000. The ruthenium-containing gas generation inhibitor and the ruthenium treatment solution can be mixed at any time, but it is more preferable to mix them before treating the ruthenium with the ruthenium treatment solution, as this can reduce the generation of ruthenium-containing gas.

[0089] (Treatment agent for ruthenium-containing wastewater) The ruthenium-containing waste liquid treatment agent of the present invention refers to a liquid that suppresses the generation of ruthenium-containing gas by being added to a ruthenium-containing waste liquid, and refers to a liquid containing hypobromite ion, a pH buffer, and an onium ion. The pH buffer may be any substance as long as it has a pH buffering ability, but the pH buffer used in the treatment liquid for semiconductors of the present invention can be preferably used. Further, as the onium ion, it is preferably an onium ion represented by the above formulas (1) to (4). The ruthenium-containing waste liquid treatment agent may further contain (D) bromide ion, may contain (E) hypobromite ion or / and bromate ion, and may contain one or more ions selected from the group consisting of chlorite ion, chlorate ion, chloride ion, and sulfate ion. Since the treatment liquid for semiconductors of the present invention and the inhibitor for suppressing the generation of RuO4-containing gas are liquids containing hypobromite ion, a pH buffer, and an onium ion, they can also be used as the ruthenium-containing waste liquid treatment agent of the present invention.

[0090] Here, the ruthenium-containing waste liquid means a solution containing ruthenium even in a small amount. Here, ruthenium is not limited to ruthenium metal, and it may contain ruthenium element. For example, Ru, RuO4 - , RuO4 2- , RuO4, RuO2, etc. may be mentioned. For example, the liquid after performing the etching treatment of a semiconductor wafer containing ruthenium using a treatment liquid different from the treatment liquid of the present invention, or the liquid after performing the treatment using the treatment liquid for the semiconductor wafer of the present invention, etc. can be mentioned. Further, not limited to the etching of semiconductor wafers, ruthenium-containing liquids generated by semiconductor manufacturing processes, chamber cleaning, etc., as described in the above method for suppressing the generation of ruthenium-containing gas, are also an example thereof.

[0091] Even trace amounts of ruthenium in wastewater can generate RuO2 particles via RuO4 gas, contaminating tanks and piping, and accelerating equipment deterioration through the oxidation of these particles. Furthermore, RuO4 gas generated from wastewater is highly toxic to humans even at low concentrations. Thus, ruthenium-containing wastewater has various adverse effects on equipment and human health, and therefore, it is necessary to treat it promptly to suppress the generation of RuO4 gas. By adding the ruthenium-containing wastewater treatment agent of the present invention to ruthenium-containing wastewater, fluctuations in the pH of the ruthenium-containing wastewater and the resulting increase in RuO4 gas and RuO2 particles can be suppressed. For example, if the ruthenium-containing wastewater is alkaline, the pH of the ruthenium-containing wastewater will decrease due to the inclusion of carbon dioxide, acid, etc., and the amount of RuO4 gas and RuO2 particles will increase. However, by adding the ruthenium-containing wastewater treatment agent of the present invention to the ruthenium-containing wastewater, pH fluctuations are suppressed, and the amount of RuO4 gas and RuO2 particles generated can be kept low. Furthermore, the onium ions contained in the ruthenium-containing wastewater treatment agent and the RuO4 contained in the ruthenium-containing wastewater - These substances form ion pairs that dissolve in the wastewater, thereby suppressing the generation of RuO4 gas and RuO2 (particles).

[0092] In the ruthenium-containing wastewater treatment agent of the present invention, the conditions such as the hypobromite ion content, the type and content of the pH buffer, the type and content of the onium ion, other components and their content, and pH should be set appropriately so as to suppress the generation of ruthenium-containing gas from the ruthenium-containing wastewater. For example, the same conditions as those described in the description of semiconductor treatment solutions can be applied.

[0093] In addition to these conditions, for example, the onium ion content represented by formulas (1) to (4) above in the ruthenium-containing wastewater treatment agent can be 10 μmol / L to 5.0 mol / L. This concentration can be adjusted so that the concentration of onium ions represented by formulas (1) to (4) in the mixture when mixed with the ruthenium-containing wastewater reaches a predetermined amount. Furthermore, the same pH adjusting agent as described above may be added to the ruthenium-containing wastewater treatment agent as appropriate. The pH adjusting agent content can be adjusted so that the pH of the mixture when mixed with the ruthenium-containing wastewater reaches a predetermined range. For example, the pH adjusting agent content in the ruthenium-containing wastewater treatment agent can be any effective amount, specifically 0.000001 to 1.0 mol / L.

[0094] Furthermore, it is preferable to include boric acid, carbonic acid, or phosphoric acid as a pH buffer. In particular, when using boric acid, a desirable pH buffering capacity can be expected when the pH of the ruthenium-containing wastewater treatment agent is 8.2 to 10.2; when using carbonic acid, when the pH of the ruthenium-containing wastewater treatment agent is 9.3 to 11.3; and when using phosphoric acid, when the pH of the ruthenium-containing wastewater treatment agent is 11.4 to 13.4. These pH buffers may be used individually or in combination. The concentration of each pH buffer in the ruthenium-containing wastewater treatment agent is preferably 0.0001 to 1.0 mol / L, more preferably 0.0001 to 0.8 mol / L, and even more preferably 0.001 to 0.6 mol / L. Within the range of 0.001 to 0.6 mol / L, fluctuations in the pH of the ruthenium-containing wastewater treatment agent can be suppressed, and a sufficient effect of suppressing the generation of ruthenium-containing gas can be obtained.

[0095] (Method for treating ruthenium-containing waste liquid) The present invention relates to a method for treating ruthenium-containing wastewater, which includes the step of adding the above-mentioned ruthenium-containing wastewater treatment agent to the ruthenium-containing wastewater. According to this method, ruthenium-containing gas generated from the ruthenium-containing wastewater can be suppressed by the mechanism described in the above-mentioned explanation of the ruthenium-containing gas generation suppressor. As a result, not only is the handling of ruthenium-containing wastewater made easier, but exhaust equipment and pollution control equipment can be simplified, and the costs associated with treating ruthenium-containing gas can be reduced. Furthermore, the risk of workers being exposed to highly toxic ruthenium-containing gas is reduced, and safety is greatly improved.

[0096] Furthermore, in the method for treating ruthenium-containing wastewater, it is preferable to adjust the concentrations of the pH buffer and the onium ions represented by formulas (1) to (4) in the ruthenium-containing wastewater treatment agent and the amount added so that the concentrations of the onium ions and pH buffer represented by formulas (1) to (4) in the mixture of the ruthenium-containing wastewater and the ruthenium-containing wastewater are, for example, 10 μmol / L to 5.0 mol / L, respectively. Furthermore, in the method for treating ruthenium-containing wastewater, the same pH adjusting agent as described above may be added to the treatment agent for ruthenium-containing wastewater as appropriate. The amount of pH adjusting agent contained in the treatment agent for ruthenium-containing wastewater should be adjusted as appropriate so that the pH of the mixture obtained by mixing the treatment agent for ruthenium-containing wastewater with the ruthenium-containing wastewater is, for example, between 8 and 14. Also, the amount of treatment agent for ruthenium-containing wastewater added to the ruthenium-containing wastewater should be adjusted as appropriate so that the pH of the mixture obtained by mixing the two liquids is, for example, between 8 and 14.

[0097] The amount of ruthenium-containing wastewater treatment agent added to the ruthenium-containing wastewater depends on the amount of ruthenium in the wastewater, but is not particularly limited. For example, when the amount of ruthenium in the wastewater is set to 1, the weight ratio is preferably 10 to 500,000, more preferably 100 to 100,000, and even more preferably 1,000 to 50,000. [Examples]

[0098] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples.

[0099] (pH measurement method) After preparing 30 mL of the treatment solutions from Examples 1-68 and Comparative Examples 1-11, the pH was measured using a benchtop pH meter (LAQUA F-73, manufactured by Horiba, Ltd.). The pH measurement was performed after the temperature of the treatment solution had stabilized at 25°C.

[0100] (Method for calculating the concentrations of hypobromite ions, bromite ions, and hypochlorite ions) The concentrations of hypobromite ions, bromite ions, and hypochlorite ions in the treatment solutions of Examples 1-68 and Comparative Examples 1-11 were measured using a UV-Vis spectrophotometer (UV-2600, Shimadzu Corporation). Calibration curves were created using aqueous solutions of hypobromite ions, bromite ions, and hypochlorite ions with known concentrations, and the concentrations of hypobromite ions, bromite ions, and hypochlorite ions in the prepared treatment solutions were determined. The concentrations of hypobromite ions, bromite ions, and hypochlorite ions were obtained from measurement data when the absorption spectrum was stable, and spectral splitting was performed as necessary.

[0101] (Method for calculating the concentrations of bromide ions, bromate ions, chlorite ions, chlorate ions, and sulfate ions) The concentrations of bromide ions, bromate ions, chlorite ions, chlorate ions, and sulfate ions in the treatment solutions of Examples 1-68 and Comparative Examples 1-11 were analyzed using an ion chromatography analyzer (DIONEX INTEGRION HPLC, Thermo SCIENTIFIC). KOH was used as the eluent and passed through at a flow rate of 1.2 mL / min. The column temperature was 30°C. After removing background noise with a suppressor, the concentrations of bromide ions, bromate ions, chlorite ions, chlorate ions, and sulfate ions were quantified using an electrical conductivity detector.

[0102] (Method for calculating chloride ion concentration) After obtaining the treatment solutions for Examples 1-68 and Comparative Examples 1-11, 0.5 mL of each treatment solution was transferred to a 100 mL Erlenmeyer flask. Then, approximately 50 mL of ultrapure water was added, followed by 5 mL of 34% by mass hydrogen peroxide solution (manufactured by Fujifilm Wako Pure Chemical Industries, reagent grade). An electrode (GE-101B / AGR-811) attached to an automatic titrator (manufactured by Hiranuma Sangyo, Hiranuma Automatic Titrator COM Series) was immersed in the solution, and titration was performed with 0.1 mol / L nitric acid standard solution to obtain a pH of 2-3. Next, titration was performed with 0.2 mol / L silver nitrate standard solution. The chloride ion concentration was quantified by reducing the concentrations of hypobromite ions, bromite ions, bromate ions, bromide ions, hypochlorite ions, chlorite ions, and chlorate ions.

[0103] (Method for calculating onium ion concentration) The onium ion concentrations in the treatment solutions of Examples 1-68 and Comparative Examples 1-11 were calculated from the pH and the concentrations of hypobromite ions, bromite ions, bromate ions, bromide ions, hypochlorite ions, chlorite ions, chlorate ions, and chloride ions.

[0104] (Method for calculating buffer concentration) The buffer concentration was analyzed using an ion chromatography analyzer (DIONEX INTEGRION HPLC, Thermo SCIENTIFIC). KOH was used as the eluent and passed through at a flow rate of 1.2 mL / min. A hydroxide-based anion analysis column (AS15, Thermo SCIENTIFIC) was used as the column, and the column temperature was set to 30°C. After removing background noise with a suppressor, the boric acid concentration, carbonic acid concentration, and phosphoric acid concentration were quantified using an electrical conductivity detector.

[0105] (Method for calculating the etching rate of ruthenium) An oxide film was formed on a silicon wafer using a batch-type thermal oxidation furnace, and then a ruthenium film of 1200 Å (±10%) was deposited on top of it using the sputtering method. The sheet resistance was measured using a four-probe resistance meter (Loresta-GP, manufactured by Mitsubishi Chemical Analytec Co., Ltd.) and converted to film thickness.

[0106] For each of the Examples 1-68 and Comparative Examples 1-11, 40 ml of the treatment solution was prepared in a lidded fluororesin container (AsOne, 94.0 mL PFA container). The containers were then immersed in a water bath while being stirred at 800 rpm using a stirrer (AsOne CHPS-170DF) and stabilized at the temperatures shown in Tables 1, 2, and 4. Each sample piece, measuring 10 × 20 mm, was immersed in these treatment solutions for 1 minute, and the etching rate was calculated by dividing the change in film thickness before and after treatment by the immersion time.

[0107] (pH stability) After preparing 49.5 mL of the treatment solution for Examples 1-68 and Comparative Examples 1-11, 0.5 mL of 1% by mass hydrochloric acid was added to Examples 1-20, 51-54, and Comparative Example 3, and the mixture was stirred for 5 minutes. The pH was then measured using a benchtop pH meter. For Examples 21-50, 55-60, and Comparative Examples 1, 2, and 4, 0.5 mL of 5% by mass hydrochloric acid was added, and the mixture was stirred for 5 minutes. The pH was then measured using a benchtop pH meter.

[0108] (Stability of etching rate after acid addition) The etching rate stability was evaluated using the treatment solution prepared as described above. The etching rate was measured before and after the addition of hydrochloric acid. The etching rate fluctuation rate after acid addition was calculated using the following formula. Etching rate change rate after acid addition (%) = (Etching rate after acid addition - Etching rate before acid addition) / Etching rate before acid addition × 100

[0109] (Method for evaluating storage stability) The storage stability of Examples 57-60, 67, 68, and Comparative Example 11 was evaluated as follows: 50 mL of the treatment solution was transferred to a PFA bottle and stored for 7 days under conditions where the carbon dioxide concentration in the gas phase was 1 ppm or less and the storage temperature was 23°C. After that, the hypobromite ion concentration and pH of the treatment solution were evaluated. The storage stability of Examples 61-66, and Comparative Examples 9 and 10 was evaluated as follows: 50 mL of the treatment solution was transferred to a PFA bottle and stored for 7 days under conditions where the carbon dioxide concentration in the gas phase was 1 ppm or less and the storage temperature was 5°C. After that, the hypobromite ion concentration and pH of the treatment solution were evaluated.

[0110] (Stability of etching rate after storage) As described above, the stability of the etching rate was evaluated using the treatment solution stored for 7 days. The etching rate was measured immediately before the start of storage and after 7 days of storage. The rate of change in the etching rate after storage was calculated using the following formula. Etching rate fluctuation rate after storage (%) = (Etching rate immediately before storage - Etching rate after 7 days of storage) (Etching rate after the initial etching) / Etching rate immediately before storage begins × 100

[0111] (Quantitative analysis of RuO4 gas) The amount of RuO4 gas generated was measured using ICP-OES. 5 mL of the treatment solution was placed in a sealed container, and a 10 × 20 mm silicon wafer with a 1200 Å ruthenium film was immersed in it for 60 minutes at the temperature shown in Table 4. The weight of the ruthenium after complete dissolution was 0.000298 g. Subsequently, air was flowed into the sealed container, and the gas phase inside the container was bubbled into a container of absorbent solution (1 mol / L NaOH) to trap the RuO4 gas generated during immersion. The amount of ruthenium in this absorbent solution was measured using ICP-OES, and the amount of ruthenium in the generated RuO4 gas was determined. The complete dissolution of ruthenium on the silicon wafer immersed in the treatment solution was confirmed by measuring the sheet resistance before and after immersion using a four-probe resistance meter (Loresta-GP, Mitsubishi Chemical Analytec Co., Ltd.) and converting the results to film thickness.

[0112] <Example 1> (Preparation of the sample to be etched) A silicon wafer with a cleaned surface was prepared, and a thermal oxide film of a predetermined thickness was formed on it. Ruthenium was then deposited onto the resulting silicon wafer by sputtering to prepare a sample in which ruthenium was layered with a thickness of 1200 Å. (Preparation of tetramethylammonium bromite aqueous solution) An aqueous solution of sodium hypobromite (manufactured by Kanto Chemical Co., Ltd., Grade 1, concentration 9% or higher) was concentrated and dried while being cooled to 0°C using an evaporator to obtain yellow crude crystals. The obtained crude crystals were recrystallized six times in a 2N sodium hydroxide solution to obtain yellow needle-shaped crystals of bromite trihydrate. These were vacuum-dried at 20°C or below under approximately 5 mmHg for 72 hours to obtain anhydrous sodium bromite.

[0113] Next, 200 mL of strongly acidic ion exchange resin (Organo Corporation, Amberlite IR-120BNa) was added to a glass column with an inner diameter of approximately 45 mm (AsOne Corporation, Bio Column CF-50TK). Then, to convert to the hydrogen type, 1 L of 1 N hydrochloric acid (Fujifilm Wako Pure Chemical Industries, for volumetric analysis) was passed through the ion exchange resin column, and 1 L of ultrapure water was passed through to wash the ion exchange resin.

[0114] Furthermore, 2 L of a 2.38% tetramethylammonium hydroxide solution was passed through the ion exchange resin, which had been converted to the hydrogen type, to exchange ions from the hydrogen type back to the tetramethylammonium type. After ion exchange, 1 L of ultrapure water was passed through the ion exchange resin to wash it.

[0115] 54.0 g of purified sodium bromite was placed in a fluororesin container, and then 946 g of ultrapure water was added to prepare a 5.4% by mass (0.40 mol / L) aqueous solution of sodium bromite. The prepared aqueous solution of sodium bromite was passed through an ion exchange resin that had been converted to a tetramethylammonium type. The recovered tetramethylammonium bromite was analyzed for Na concentration using high-frequency inductively coupled plasma atomic emission spectrometry (iCAP6500DuO, Thermo SCIENTIFIC) to confirm that sufficient ion exchange had occurred. If the exchange was insufficient, the above procedure was repeated to obtain a 7.4% by mass (0.40 mol / L) tetramethylammonium bromite solution with a Na concentration of 500 ppb or less. (Preparation of tetramethylammonium bromate aqueous solution) 60.4 g of sodium bromate (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd., Wako Special Grade) was placed in a fluororesin container, and then 939.6 g of ultrapure water was added to prepare a 6.0% by mass (0.40 mol / L) aqueous solution of sodium bromate. The prepared aqueous solution of sodium bromate was passed through an ion exchange resin that had been converted to the tetramethylammonium type, using the same method as for preparing the aqueous solution of tetramethylammonium bromate. The recovered tetramethylammonium bromate was analyzed for Na concentration using high-frequency inductively coupled plasma atomic emission spectrometry (iCAP6500DuO, Thermo SCIENTIFIC) to confirm that sufficient ion exchange had occurred. If insufficient, the above procedure was repeated to obtain an 8.1% by mass (0.40 mol / L) tetramethylammonium bromate solution with a Na concentration of 500 ppb or less. (Preparation of tetramethylammonium bromide) Tetramethylammonium bromide (manufactured by Tokyo Chemical Industry Co., Ltd., purity 97.0% or higher) was added to deionized water until saturated. The saturated aqueous solution of tetramethylammonium bromide was stored in a refrigerator overnight. The precipitated tetramethylammonium bromide was recovered by filtration. The recovered tetramethylammonium bromide was diluted with ultrapure water and analyzed using an ion chromatography analyzer. CO3 in the diluted solution - SO4 - Cl -By analyzing the solution, we confirmed that the amount of impurities Na2CO3, Na2SO4, and NaCl had decreased. By repeating the above purification process, the amount of CO3 - SO4 - Cl - After confirming that each of the concentrations was 500 ppb or less, purified tetramethylammonium bromide was obtained.

[0116] (Preparation of tetramethylammonium hypochlorite aqueous solution) 98.7 g of sodium hypobromite pentahydrate (manufactured by Nippon Light Metal Co., Ltd., Nikkei Diasote® pentahydrate) was dissolved in 901.3 g of ultrapure water to obtain a 4.5% by mass (0.60 mol / L) sodium hypochlorite aqueous solution. The prepared sodium hypochlorite aqueous solution was passed through an ion exchange resin that had been converted to tetramethylammonium type, using the same method as for the preparation of the tetramethylammonium bromite aqueous solution. The recovered tetramethylammonium hypochlorite solution was analyzed for Na concentration using high-frequency inductively coupled plasma atomic emission spectrometry (iCAP6500DuO, Thermo SCIENTIFIC) to confirm that sufficient ion exchange had occurred. If insufficient, the above procedure was repeated to obtain a 7.5% by mass (0.60 mol / L) tetramethylammonium hypochlorite solution with a Na concentration of 500 ppb or less.

[0117] (Preparation of tetramethylammonium chlorate aqueous solution) Sodium chlorate (Alfa Aesar) was added to deionized water until saturated. The saturated sodium chlorate solution was stored in a refrigerator overnight. The precipitated sodium chlorate was recovered by filtration. The recovered sodium chlorate was diluted with ultrapure water and analyzed using an ion chromatography analyzer. CO3 in the diluted solution - SO4 - Cl - By analyzing the solution, we confirmed that the amount of impurities Na2CO3, Na2SO4, and NaCl had decreased. By repeating the above purification process, the amount of CO3 - SO4 - Cl -We confirmed that each of the concentrations was below 500 ppb and obtained purified sodium chlorate.

[0118] After placing 11 g of purified sodium chlorate into a fluororesin container, 989 g of ultrapure water was added to prepare a 1.1% by mass (0.1 mol / L) sodium chlorate aqueous solution. The prepared sodium chlorate aqueous solution was passed through an ion exchange resin converted to tetramethylammonium type, using the same method as for preparing the tetramethylammonium bromite aqueous solution. The recovered tetramethylammonium chlorate was analyzed for Na concentration using inductively coupled plasma atomic emission spectrometry (iCAP6500DuO, Thermo SCIENTIFIC) to confirm that sufficient ion exchange had occurred. If insufficient, the above procedure was repeated to obtain a 1.6% by mass (0.1 mol / L) tetramethylammonium chlorate aqueous solution with a Na concentration of 500 ppb or less.

[0119] (Preparation of tetramethylammonium chloride) Tetramethylammonium chloride (manufactured by Tokyo Chemical Industry Co., Ltd., purity 98.0% or higher) was added to deionized water until saturated. The saturated aqueous solution of tetramethylammonium chloride was stored in a refrigerator overnight. The precipitated tetramethylammonium chloride was recovered by filtration. The recovered tetramethylammonium chloride was diluted with ultrapure water and analyzed using an ion chromatography analyzer. CO3 in the diluted solution - SO4 - By analyzing the solution, it was confirmed that the amount of impurities Na2CO3 and Na2SO4 had decreased. By repeating the above purification process, the amount of CO3 - SO4 - After confirming that each of the concentrations was 500 ppb or less, purified tetramethylammonium chloride was obtained.

[0120] (Preparation of quaternary alkylammonium hypobromite aqueous solution) 7.2 g of a 25% by mass aqueous solution of tetramethylammonium hydroxide and 992.8 g of ultrapure water were mixed in a 2 L glass four-necked flask (manufactured by Cosmosbead Co., Ltd.) to obtain a 0.18% by mass aqueous solution of tetramethylammonium hydroxide with a CO2 content of 0.5 ppm. The pH at this time was 12.3.

[0121] Next, a rotor (AsOne, 30mm total length x 8mm diameter) was placed inside a four-necked flask. A thermometer protection tube (Cosmosbead, bottom sealed type) and a thermometer were inserted into one opening. The end of a PFA tube (F-8011-02, manufactured by Flon Industries Co., Ltd.) connected to a nitrogen gas cylinder was placed above the liquid surface at another opening. The third opening was connected to a gas washing bottle (AsOne, model 2450 / 500) filled with a 5% sodium hydroxide aqueous solution. The remaining opening was connected to a PFA tube for supplying bromine using a liquid transfer pump. Next, nitrogen gas with a carbon dioxide concentration of less than 1 ppm was flowed through the PFA tube at 200 ccm (25°C) for 20 minutes to expel the carbon dioxide from the gas phase. At this time, the carbon dioxide concentration in the gas phase was less than 1 ppm. Subsequently, a magnetic stirrer (AsOne, C-MAG HS10) was placed at the bottom of the four-necked flask and rotated at 300 rpm for stirring. While cooling the outer circumference of the four-necked flask with ice water, bromine (Fujifilm Wako Pure Chemical Industries, 99% purity) was supplied at a rate of 1.6 g / min for 1 minute to obtain a 1.6 mass% (0.01 mol / L) aqueous solution of tetramethylammonium hypobromite. At this time, the liquid temperature during the reaction was 11°C.

[0122] (Manufacturing of processing solution) The obtained solution was transferred from a four-necked glass flask to a glove bag to prevent contact with the atmosphere. After the carbon dioxide concentration in the glove bag fell below 1 ppm, it was transferred to a 1 L PFA container. 0.77 g of tetramethylammonium bromide, 5.0 g of aqueous tetramethylammonium bromitite, 5.0 g of aqueous tetramethylammonium bromate, 16.7 g of aqueous tetramethylammonium hypochlorite, 1.2 g of tetramethylammonium chloride, 3 g of aqueous tetramethylammonium chlorate, and 22.3 g of boric acid (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd., reagent grade) were dissolved in 976.2 g of the obtained solution to obtain treatment solutions with the compositions shown in Tables 1-4.

[0123] (evaluation) The pH of the obtained treatment solution, the concentrations of hypobromite ions, bromite ions, bromate ions, bromide ions, and onium ions, and the pH buffer concentration were evaluated. Furthermore, the ruthenium etching rate, the pH after acid addition, the ruthenium etching rate after acid addition, and the etching rate before and after acid addition were evaluated. The results are shown in Tables 5 and 6. The effect of acid addition was evaluated by forcibly changing the pH of the treatment solution to the acidic side by adding hydrochloric acid, and then examining the rate of change in etching rate before and after acid addition.

[0124] <Examples 2-10, 51, 52, Comparative Examples 1, 2> Examples 2-10, 51, 52, and Comparative Examples 1 and 2 were prepared using the same method as in Example 1, with the concentrations and pH of (A) hypobromite ions, (B) pH buffer, (C) onium ions, (D) bromide ions, (E) bromite ions, bromate ions, (F) chlorite ions, chlorate ions, chloride ions, and hypochlorite ions being as shown in Table 1-4. The treatment solutions were then evaluated.

[0125] <Example 11> (Preparation of carbonate buffer) A PFA beaker containing 500 g of a 25% by mass tetramethylammonium hydroxide aqueous solution was placed inside a glove bag. After adjusting the carbon dioxide concentration inside the glove bag to 1 ppm, 30.7 L (at 0°C) of high-purity carbon dioxide (manufactured by Showa Denko Gas Products, specification purity 99.99% or higher) was supplied, and the bag was sealed overnight to obtain a carbonate buffer. The buffer concentration was calculated using an ion chromatography analyzer and the method described above.

[0126] (Preparation of quaternary alkylammonium hypobromite solution) 22 g of a 25% by mass aqueous solution of tetramethylammonium hydroxide and 978 g of ultrapure water were mixed in a 2 L glass four-necked flask (manufactured by Cosmosbead Co., Ltd.) to obtain a 0.55% by mass (0.06 mol / L) aqueous solution of tetramethylammonium hydroxide with a CO2 content of 0.5 ppm. The pH at this time was 12.8.

[0127] Next, a rotor (AsOne, 30mm total length x 8mm diameter) was placed in a four-necked flask. A thermometer protection tube (Cosmosbead, bottom sealed type) and a thermometer were inserted into one opening. The end of a PFA tube (F-8011-02, manufactured by Flon Industries Co., Ltd.) connected to a nitrogen gas cylinder was placed above the liquid surface at another opening. The third opening was connected to a gas washing bottle (AsOne, model 2450 / 500) filled with a 5% sodium hydroxide aqueous solution. The remaining opening was connected to a PFA tube for supplying bromine using a liquid transfer pump. Next, nitrogen gas with a carbon dioxide concentration of less than 1 ppm was flowed through the PFA tube at 200 ccm (25°C) for 20 minutes to expel the carbon dioxide from the gas phase. At this time, the carbon dioxide concentration in the gas phase was less than 1 ppm.

[0128] Subsequently, a magnetic stirrer (AsOne, C-MAG HS10) was placed at the bottom of the four-necked flask and rotated at 300 rpm for stirring. While cooling the outer circumference of the four-necked flask with ice water, bromine (Fujifilm Wako Pure Chemical Industries, 99% purity) was supplied at a rate of 1.6 g / min for 3 minutes to obtain an aqueous solution of tetramethylammonium hypobromite (equivalent to 0.51% by mass, 0.03 mol / L). At this time, the liquid temperature during the reaction was 11°C.

[0129] (Manufacturing of processing solution) The obtained aqueous solution was placed in a four-necked glass flask and then transferred to a glove bag to prevent contact with the atmosphere. After the carbon dioxide concentration in the glove bag fell to 1 ppm or less, it was transferred to a 1 L PFA container. 300 g of buffer was dissolved in 600 g of the obtained solution, and the following substances were dissolved to obtain a treatment solution with the compositions shown in Tables 1-4: tetramethylammonium bromide, tetramethylammonium bromitite aqueous solution, tetramethylammonium bromate aqueous solution, tetramethylammonium hypochlorite aqueous solution, tetramethylammonium chloride, and tetramethylammonium chlorate aqueous solution. The treatment solution was then evaluated.

[0130] <Examples 12-20, 53, 54, Comparative Examples 3-5> Examples 12-20, 53, 54, and Comparative Examples 3-5 were prepared using the same method as in Example 11, with the concentrations and pH of (A) hypobromite ions, (B) pH buffer, (C) onium ions, (D) bromide ions, (E) bromite ions, bromate ions, (F) chlorite ions, chlorate ions, chloride ions, and hypochlorite ions being as shown in Tables 1-4. The treatment solutions were then evaluated.

[0131] <Example 21> (Preparation of phosphate buffer) 500 g of a 25% by mass aqueous solution of tetramethylammonium hydroxide was placed in a PFA container, and 60.3 g of phosphoric acid (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd., specified purity 85%) was added thereto while cooling with ice water to obtain a phosphate buffer. The buffer concentration was calculated using an ion chromatography analyzer and the method described above.

[0132] (Preparation of tetramethylammonium chlorite aqueous solution) Sodium chlorite (manufactured by Alfa Aesar) was added to deionized water until saturated. The saturated sodium chlorite solution was stored in a refrigerator overnight. The precipitated sodium chlorite was recovered by filtration. The recovered sodium chlorite was diluted with ultrapure water and analyzed using an ion chromatography analyzer. CO3 in the diluted solution - SO4 - Cl - By analyzing the solution, we confirmed that the amount of impurities Na2CO3, Na2SO4, and NaCl had decreased. By repeating the above purification process, the amount of CO3 - SO4 - Cl - We confirmed that each of the concentrations was below 500 ppb and obtained purified sodium chlorite. 9.0 g of purified sodium chlorite was placed in a fluororesin container, and then 991 g of ultrapure water was added to prepare a 0.9% by mass (0.1 mol / L) sodium chlorite aqueous solution. The prepared sodium chlorite aqueous solution was passed through an ion exchange resin that had been converted to tetramethylammonium type, using the same method as for preparing the tetramethylammonium bromitite aqueous solution. The recovered tetramethylammonium chlorate was analyzed for Na concentration using high-frequency inductively coupled plasma atomic emission spectrometry (iCAP6500DuO, Thermo SCIENTIFIC) to confirm that sufficient ion exchange had occurred. If insufficient, the above procedure was repeated to obtain a 1.4% by mass (0.1 mol / L) tetramethylammonium chlorite aqueous solution with a Na concentration of 500 ppb or less.

[0133] (Preparation of tetramethylammonium hypobromite aqueous solution) 58 g of a 25% by mass aqueous solution of tetramethylammonium hydroxide and 942 g of ultrapure water were mixed in a 2 L glass four-necked flask (manufactured by Cosmosbead Co., Ltd.) to obtain a 0.82% by mass (0.09 mol / L) aqueous solution of tetramethylammonium hydroxide with a CO2 content of 0.5 ppm. The pH at this time was 13.0.

[0134] Next, a rotor (AsOne, 30mm total length x 8mm diameter) was placed inside a four-necked flask. A thermometer protection tube (Cosmosbead, bottom sealed type) and a thermometer were inserted into one opening. The end of a PFA tube (F-8011-02, manufactured by Flon Industries Co., Ltd.) connected to a nitrogen gas cylinder was placed above the liquid surface at another opening. The third opening was connected to a gas washing bottle (AsOne, model 2450 / 500) filled with a 5% sodium hydroxide aqueous solution. The remaining opening was connected to a PFA tube for supplying bromine using a liquid transfer pump. Next, nitrogen gas with a carbon dioxide concentration of less than 1 ppm was flowed through the PFA tube at 200 ccm (25°C) for 20 minutes to expel the carbon dioxide from the gas phase. At this time, the carbon dioxide concentration in the gas phase was less than 1 ppm.

[0135] Subsequently, a magnetic stirrer (AsOne, C-MAG HS10) was placed at the bottom of the four-necked flask and rotated at 300 rpm for stirring. While cooling the outer circumference of the four-necked flask with ice water, bromine (Fujifilm Wako Pure Chemical Industries, 99% purity) was supplied at a rate of 2.4 g / min for 1 minute to obtain an aqueous solution of tetramethylammonium hypobromite (equivalent to 2.4% by mass, 0.015 mol / L). At this time, the liquid temperature during the reaction was 11°C.

[0136] (Manufacturing of processing solution) The obtained solution was placed in a four-necked glass flask and then transferred to a glove bag to prevent contact with the atmosphere. After the carbon dioxide concentration in the glove bag fell to 1 ppm or less, it was transferred to a 1 L PFA container. 300 g of buffer was dissolved in 600 g of the obtained solution, and the following substances were dissolved to obtain a treatment solution with the composition shown in Table 1-4: tetramethylammonium bromide, tetramethylammonium bromitate aqueous solution, tetramethylammonium bromate aqueous solution, tetramethylammonium hypochlorite aqueous solution, tetramethylammonium chloride, tetramethylammonium chlorate aqueous solution, and tetramethylammonium chlorite aqueous solution. The treatment solution was then evaluated.

[0137] <Examples 22-44, 47-50, 55, 56, Comparative Examples 6-8> Examples 22-44, 47-50, 55, 56, and Comparative Examples 6-8 were prepared and evaluated in the same manner as in Example 21, with the concentrations and pH of (A) hypobromite ions, (B) pH buffer, (C) onium ions, (D) bromide ions, (E) bromite ions, bromate ions, (F) chlorite ions, chlorate ions, chloride ions, and hypochlorite ions being as shown in Tables 1-4.

[0138] <Examples 45, 46> For Examples 45 and 46, treatment solutions were prepared and evaluated in the same manner as in Example 21, with (A) hypobromite ions, (B) pH buffer, (C) onium ions, and (F) chloride ions having the compositions shown in Table 3. For (C) onium ions, tetrapropylammonium aqueous solution (manufactured by Tokyo Chemical Industry Co., Ltd., 40% by mass) was used.

[0139] The compositions of the prepared treatment solutions are shown in Tables 1, 2, 3, and 4, and the results obtained are shown in Tables 5 and 6. It was confirmed that the treatment solution in this embodiment exhibited excellent etching rate stability due to its ability to suppress pH fluctuations.

[0140] [Table 1] [Table 2] [Table 3] [Table 4] [Table 5] [Table 6]

[0141] <Examples 51, 52> For Examples 51 and 52, treatment solutions were prepared and evaluated in the same manner as in Example 1, with (A) hypobromite ions, (B) pH buffer, and (C) onium ions having the compositions shown in Table 7. For (C) onium ions, tetrapropylammonium aqueous solution (manufactured by Tokyo Chemical Industry Co., Ltd., 40% by mass) was used.

[0142] <Examples 53, 54> For Examples 53 and 54, treatment solutions were prepared and evaluated in the same manner as in Example 11, with (A) hypobromite ions, (B) pH buffer, and (C) onium ions having the compositions shown in Table 7. For (C) onium ions, tetrapropylammonium aqueous solution (manufactured by Tokyo Chemical Industry Co., Ltd., 40% by mass) was used.

[0143] <Examples 55, 56> For Examples 55 and 56, treatment solutions were prepared and evaluated in the same manner as in Example 21, with (A) hypobromite ions, (B) pH buffer, and (C) onium ions having the compositions shown in Table 7. For (C) onium ions, tetrapropylammonium aqueous solution (manufactured by Tokyo Chemical Industry Co., Ltd., 40% by mass) was used.

[0144] <Example 57> As Example 57, a treatment solution was prepared and evaluated in the same manner as in Example 21, with (A) hypobromite ions, (B) pH buffer, and (C) onium ions having the compositions shown in Table 7. For (C) onium ions, n-octyltrimethylammonium chloride (manufactured by Tokyo Chemical Industry Co., Ltd., purity >98%) was used.

[0145] <Example 58> As Example 58, a treatment solution was prepared and evaluated in the same manner as in Example 21, with (A) hypobromite ions, (B) pH buffer, and (C) onium ions having the compositions shown in Table 7. For (C) onium ions, hexadecyltrimethylammonium chloride (manufactured by Tokyo Chemical Industry Co., Ltd., purity >95%) was used.

[0146] <Example 59> As Example 59, a treatment solution was prepared and evaluated in the same manner as in Example 21, with (A) hypobromite ions, (B) pH buffer, and (C) onium ions having the compositions shown in Table 7. For (C) onium ions, 5-azonia spiro[4.4]nonane chloride (manufactured by Tokyo Chemical Industry Co., Ltd., purity >98%) was used.

[0147] <Example 60> As Example 60, a treatment solution was prepared and evaluated in the same manner as in Example 21, with (A) hypobromite ions, (B) pH buffer, and (C) onium ions having the compositions shown in Table 7. For (C) onium ions, hexamethonium bromide (manufactured by Tokyo Chemical Industry Co., Ltd., purity >98%) was used.

[0148] <Rating> The pH and hypobromite ion concentration of the obtained treatment solution were evaluated, and the onium ion concentration, ruthenium etching rate, pH after hydrochloric acid addition, ruthenium etching rate after acid addition, etching variability before and after hydrochloric acid addition, and quantitative analysis of RuO4 gas were evaluated. The results are shown in Table 8. From the results in Table 8, it was possible to keep the etching rate variability low even when two types of onium ions, as shown in equation (1), were present.

[0149] [Table 7]

[0150] [Table 8]

[0151] <Examples 61-64, Comparative Example 11> Examples 61-64 and Comparative Example 11 were prepared and evaluated in the same manner as in Example 21, with the concentrations and pH of (A) hypobromite ions, (B) pH buffer, (C) onium ions, (D) bromide ions, (E) bromite ions, (F) chlorite ions, chlorate ions, chloride ions, and hypochlorite ions being as shown in Tables 9 and 10.

[0152] <Examples 65-67, Comparative Example 9> Examples 65-67 and Comparative Example 9 were prepared and evaluated in the same manner as in Example 1, with the concentrations and pH of (A) hypobromite ions, (B) pH buffer, (C) onium ions, (D) bromide ions, (E) bromite ions, (F) chlorite ions, chlorate ions, chloride ions, and hypochlorite ions being as shown in Tables 9 and 10.

[0153] <Examples 68-70, Comparative Example 10> Examples 68-70 and Comparative Example 10 were prepared and evaluated in the same manner as in Example 11, with the concentrations and pH of (A) hypobromite ions, (B) pH buffer, (C) onium ions, (D) bromide ions, (E) bromite ions, (F) chlorite ions, chlorate ions, chloride ions, and hypochlorite ions being as shown in Tables 9 and 10.

[0154] <Example 71> (Preparation of tetramethylammonium sulfate aqueous solution) Tetramethylammonium sulfate (manufactured by Tokyo Chemical Industry Co., Ltd.) was added to deionized water until saturated. The saturated aqueous solution of tetramethylammonium sulfate was stored in a refrigerator overnight. The precipitated tetramethylammonium sulfate was recovered by filtration. The recovered tetramethylammonium sulfate was diluted with ultrapure water and analyzed using an ion chromatography analyzer. CO3 in the diluted solution - Cl - By analyzing it, the CO3 contained as an impurity - Cl -We confirmed that the amount of CO3 decreased. By repeating the above purification process, - Cl - After confirming that each of the concentrations was 500 ppb or less, purified tetramethylammonium sulfate was obtained. 24.4 g of purified tetramethylammonium sulfate was placed in a fluororesin container, and then 975.6 g of ultrapure water was prepared. The sodium concentration was analyzed using inductively coupled plasma emission spectroscopy (iCAP6500DuO, Thermo SCIENTIFIC) to confirm that the purification was sufficient. If the purification was insufficient, the above procedure was repeated to obtain a 2.4 mass% (0.1 mol / L) aqueous solution of tetramethylammonium sulfate with a sodium concentration of 500 ppb or less.

[0155] (Manufacturing of processing solution) Using the obtained solution, Example 71 was prepared and evaluated in the same manner as in Example 21, so that the concentrations and pH of (A) hypobromite ions, (B) pH buffer, (C) onium ions, (D) bromide ions, (E) bromite ions, bromate ions, and (F) sulfate ions were as shown in Tables 9 and 10. <Rating> The obtained treatment solution was stored for 7 days at a storage temperature of 23°C, and the hypobromite ion concentration and pH of the solution were evaluated. Furthermore, the rate of change in the etching rate after storage was calculated, using the etching rate before storage as a baseline. The results are shown in Table 11. From the results in Table 11, it was possible to keep the rate of change in the etching rate low even after storage.

[0156] <Example 72> In Example 72, a treatment solution was prepared in the same manner as in Example 71, with the concentrations and pH of (A) hypobromite ions, (B) pH buffer, (C) onium ions, (D) bromide ions, (E) bromite ions, bromate ions, and (F) sulfate ions as shown in Tables 9-11, and the solution was evaluated. [Table 9] [Table 10] [Table 11]

[0157] <Example 73> In Example 73, a treatment solution was prepared in the same manner as in Example 21 so that (A) hypobromite ions, (B) pH buffer, (C) onium ions, and pH were as shown in Tables 12 and 13, and then evaluated.

[0158] <Comparative Example 12> 209 g of a 25% by mass aqueous solution of tetramethylammonium hydroxide and 791 g of ultrapure water were mixed in a 2 L glass three-necked flask (manufactured by Cosmosbead Co., Ltd.) to obtain a 5.2% by mass aqueous solution of tetramethylammonium hydroxide with a CO2 content of 0.5 ppm. The pH at this time was 13.8. Next, a rotor (AsOne, 30mm total length x 8mm diameter) was placed inside a three-necked flask. A thermometer protection tube (Cosmosbead, bottom sealed type) and a thermometer were inserted into one opening. A PFA tube (F-8011-02, manufactured by Fluorocarbon Industries Co., Ltd.), connected to a chlorine gas cylinder and a nitrogen gas cylinder, allowing for switching between chlorine and nitrogen gas, had its tip immersed in the bottom of the solution. The remaining opening was connected to a gas washing bottle (AsOne, model 2450 / 500) filled with a 5% sodium hydroxide aqueous solution. Next, nitrogen gas with a carbon dioxide concentration of less than 1 ppm was introduced through the PFA tube at 0.289 Pa·m. 3 The carbon dioxide in the gas phase was expelled by flowing the mixture at a rate of 1 ppm / second (at 0°C) for 20 minutes. At this time, the carbon dioxide concentration in the gas phase was less than 1 ppm. Subsequently, a magnetic stirrer (AsOne, C-MAG HS10) was placed at the bottom of the three-necked flask and rotated at 300 rpm for stirring. While cooling the outer circumference of the three-necked flask with ice water, chlorine gas (Fujiox, specified purity 99.4%) was added at 0.059 Pa·m. 3The mixture was supplied at a rate of / second (at 0°C) for 180 minutes to obtain a mixed solution of aqueous tetramethylammonium hypochlorite (oxidizing agent; equivalent to 3.51% by mass, 0.28 mol / L) and tetramethylammonium hydroxide (equivalent to 0.09% by mass, 0.0097 mol / L). The liquid temperature during the reaction was 11°C. Boric acid, hydrochloric acid, and ultrapure water were added to the obtained tetramethylammonium hypochlorite aqueous solution to obtain treatment solutions with the compositions shown in Tables 12 and 13. These solutions were evaluated in the same manner as in Example 21. In Comparative Example 12, the ruthenium was not etched by the treatment solution.

[0159] <Comparative Example 13> Comparative Example 13 was prepared using the same method as in Comparative Example 12, so that the composition was as shown in Tables 12 and 13. The obtained treatment solution was evaluated using the same method as in Example 21.

[0160] [Table 12] [Table 13]

[0161] The processing solution of the present invention was able to suppress pH changes associated with the ruthenium etching reaction and carbon dioxide gas absorption during ruthenium etching. Furthermore, the processing solution of the present invention was able to suppress the rate of fluctuation in the ruthenium etching rate during semiconductor device formation. [Explanation of Symbols]

[0162] 1 Base Two-layer insulating film 3 Ruthenium

Claims

1. The following (A), (B), (C), and (E) are included, and the concentration of (E) bromate ions is 3.3 × 10 －６ mol / L or more 5.0×10 －１ An etching solution of ruthenium or tungsten with a concentration of mol / L or less. (A) Hypobromite ions (B) pH buffer (C) Onium Ion (E) Bromate ion

2. Furthermore, the etching solution according to claim 1, further comprising (D) bromide ions.

3. The etching solution according to claim 1 or 2, wherein the etching solution further contains an oxidizing agent, and the oxidation-reduction potential of the oxidizing agent exceeds the oxidation-reduction potential of the hypobromite ion / bromide ion system.

4. The etching solution according to claim 3, wherein the oxidizing agent contained in the etching solution is one or more oxidizing agents selected from the group consisting of hypochlorite ions and ozone.

5. Furthermore, the etching solution according to any one of claims 1 to 4, comprising (F) one or more chlorine-containing ions selected from the group consisting of chlorite ions, chlorate ions, and chloride ions.

6. The etching solution according to any one of claims 1 to 5, wherein the hypobromite ion concentration is 0.001 mol / L or more and 0.20 mol / L or less.

7. The etching solution according to any one of claims 1 to 6, wherein the concentration of the (B) pH buffer is 0.00001 to 1.0 mol / L.

8. The (B) pH buffering agent is carbonate, boric acid, phosphoric acid, trishydroxymethylaminomethane (tris), ammonia, pyrophosphate, p-phenolsulfonic acid, diethanolamine Min, ethanolamine, triethanolamine, 5,5-diethylbarbituric acid, glycine, glycylglycine, imidazole, N,N-bis(2-hydroxyethyl)-2-aminoethanesulfonic acid, 3-morpholinopropanesulfonic acid, N-tris(hydroxy) Methyl)methyl-2-aminoethanesulfonic acid, 2-[4-(2-hydroxyethyl)- The etching solution according to any one of claims 1 to 7, wherein the etching solution is at least one selected from the group consisting of 1-piperazinyl]ethanesulfonic acid, 4-(2-hydroxyethyl)-1-piperazinepropanesulfonic acid, tricine, N,N-di(2-hydroxyethyl)glycine, 2-cyclohexylaminoethanesulfonic acid, hydroxyproline, phenol, and ethylenediaminetetraacetic acid.

9. The etching solution according to any one of claims 1 to 8, wherein the (C) onium ion is a quaternary ammonium ion or quaternary phosphonium ion represented by the following formula (1), a tertiary ammonium ion or tertiary sulfonium ion represented by the following formula (2), an ammonium ion, pyrrolidinium ion, piperidinium ion, imidazolium ion, or sulfonium ion represented by the following formula (3), or an annium ion or phosphonium ion represented by the following formula (4). 【Chemistry 1】 【Chemistry 2】 【Transformation 3】 【Chemistry 4】 In formula (1), A is nitrogen or phosphorus, and R １ , R ２ , R ３ , R ４ are each independently an alkyl group having 1 to 25 carbon atoms, an allyl group, an aralkyl group which may have a substituent, or an aryl group. However, when R １ , R ２ , R ３ , R ４ are alkyl groups, at least one of the alkyl groups of R １ , R ２ , R ３ , R ４ has 2 or more carbon atoms. In formula (2), A ＋ is nitrogen or sulfur, and R １ , R ２ , R ３ R is independently an alkyl group having 1 to 25 carbon atoms, an allyl group, an aralkyl group having an alkyl group having 1 to 25 carbon atoms, or an aryl group. However, R １ , R ２ , R ３ If R is an alkyl group, １ , R ２ , R ３ At least one alkyl group has two or more carbon atoms. In addition, the aryl group in the aralkyl group and at least one hydrogen atom in the aryl ring may be replaced with fluorine, chlorine, an alkyl group having 1 to 10 carbon atoms, an alkenyl group having 2 to 10 carbon atoms, an alkoxy group having 1 to 9 carbon atoms, or an alkenyloxy group having 2 to 9 carbon atoms, and in these groups, at least one hydrogen atom may be replaced with fluorine or chlorine. In formula (3), Z is an aromatic group or alicyclic group which may contain nitrogen, sulfur, or oxygen atoms, and in the aromatic group or alicyclic group, at least one hydrogen to which carbon or nitrogen is bonded may be replaced with chlorine, bromine, fluorine, iodine, at least one C1-C15 alkyl group, at least one C2-C9 alkenyloxy group, an aromatic group which may be substituted with at least one C1-C15 alkyl group, or an alicyclic group which may be substituted with at least one C1-C15 alkyl group. A is nitrogen or sulfur. R is chlorine, bromine, fluorine, iodine, a C1-C15 alkyl group, an allyl group, an aromatic group which may be substituted with at least one C1-C15 alkyl group, or an alicyclic group which may be substituted with at least one C1-C15 alkyl group. n is an integer of 1 or 2 and indicates the number of R. When n is 2, R may be the same or different, and may form a ring. In formula (4), A is independently nitrogen or sulfur, and R １ , R ２ , R ３ , R ４ , R ５ , R ６ These are independently a C1-C25 alkyl group, an allyl group, an aralkyl group having a C1-C25 alkyl group, or an aryl group. The aryl group in the aralkyl group and at least one hydrogen atom in the ring of the aryl group may be replaced with fluorine, chlorine, a C1-C10 alkyl group, a C2-C10 alkenyl group, a C1-C9 alkoxy group, or a C2-C9 alkenyloxy group, and in these groups, at least one hydrogen atom may be replaced with fluorine or chlorine.

10. An etching solution according to any one of claims 1 to 9, wherein the pH at 25°C is 8 or higher and 14 or lower.

11. An etching method comprising the step of bringing an etching solution according to any one of claims 1 to 10 into contact with a semiconductor wafer, wherein the metal on the semiconductor wafer is ruthenium or tungsten.

12. RuO ４ A gas generation inhibitor comprising (C) an onium ion, wherein the (C) onium ion is a quaternary ammonium ion or a quaternary ammonium ion represented by the following formula (1). RuO containing quaternary phosphonium ions ４ A gas suppressant that inhibits the generation of contained gases. (A) Hypobromite ions (B) pH buffer (C) Onium Ion 【Transformation 5】 (In formula (1), A is nitrogen or phosphorus, and R １ , R ２ , R ３ , R ４ R is independently an alkyl group having 1 to 25 carbon atoms, an allyl group, an aralkyl group which may have an aryl group substituent, or an aryl group. However, R １ , R ２ , R ３ , R ４ If R is an alkyl group, １ , R ２ , R ３ , R ４ (At least one of the alkyl groups has two or more carbon atoms.)

13. Furthermore, (D) RuO according to claim 12, which contains bromide ions. ４ A gas suppressant that inhibits the generation of contained gases.

14. Furthermore, the RuO according to claim 12 or 13 comprises (E) one or more ions selected from the group consisting of bromite ions and bromate ions. ４ A gas suppressant that inhibits the generation of contained gases.

15. Furthermore, (F) the RuO according to any one of claims 12 to 14, comprising one or more chlorine-containing ions selected from the group consisting of chlorite ions, chlorate ions, and chloride ions. ４ A gas suppressant that inhibits the generation of contained gases.

16. A treatment agent for ruthenium-containing wastewater, comprising (A), (B), and (C) below. (A) Hypobromite ions (B) pH buffer (C) Onium Ion

17. Furthermore, the ruthenium-containing wastewater treatment agent according to claim 16, further comprising (D) bromide ions.

18. (E) A ruthenium-containing wastewater treatment agent according to claim 16 or 17, comprising one or more ions selected from the group consisting of bromite ions and bromate ions.

19. Furthermore, the ruthenium-containing wastewater treatment agent according to any one of claims 16 to 18, comprising (F) one or more chlorine-containing ions selected from the group consisting of chlorite ions, chlorate ions, and chloride ions.

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