Alkyl quaternary ammonium hypochlorite solution, method for producing the same, and method for treating semiconductor wafers

Abstract

A quaternary alkyl ammonium hypochlorite solution, a method for producing the same, and a method for treating a semiconductor wafer. The present invention provides a method for producing a quaternary alkyl ammonium hypochlorite solution having excellent storage stability. Specifically, a method for producing a quaternary alkyl ammonium hypochlorite solution is provided, comprising: a preparation step of preparing a quaternary alkyl ammonium hydroxide solution, wherein the concentration of amines contained in the quaternary alkyl ammonium hydroxide solution is 20 mass ppm or less; and a reaction step of contacting the quaternary alkyl ammonium hydroxide solution with chlorine gas, wherein the concentration of carbon dioxide in the gas phase in the reaction step is 100 volume ppm or less, and the pH of the liquid phase in the reaction step is 10.5 or more.

Description

Technical Field

[0001] The present invention relates to a quaternary alkyl ammonium hypochlorite solution and a method for producing the same. More specifically, the present invention relates to a quaternary alkyl ammonium hypochlorite solution having excellent storage stability and a method for producing the same. In addition, the present invention relates to a quaternary alkyl ammonium hypochlorite solution suitable for cleaning semiconductor wafers / devices and having reduced metal impurities and a method for producing the same. Background Art

[0002] In recent years, as the manufacturing process of semiconductor devices has become increasingly miniaturized, the requirements for impurity management in the semiconductor device manufacturing process have become increasingly stringent. As for the impurities generated in the semiconductor device manufacturing process, since the impurities in each manufacturing process are different, it is important to identify the contamination source for each manufacturing process and then manage the concentration of the impurities that become the contamination source.

[0003] In addition, in order to improve the manufacturing efficiency of semiconductor elements, large-diameter semiconductor wafers exceeding 300 mm are used. In large-diameter semiconductor wafers, the area of ​​the end face and the back face where electronic equipment cannot be made is larger than that of small-diameter semiconductor wafers. Therefore, in the process of forming metal wiring and the process of forming barrier metal, metal wiring materials and barrier metal materials (hereinafter sometimes collectively referred to as "metal materials, etc.") are easily attached not only to the surface of the semiconductor wafer forming the semiconductor element, but also to the end face and the back face. As a result, the amount of excess metal materials, etc. attached to the end face and the back face of large-diameter semiconductor wafers increases compared to small-diameter wafers.

[0004] Excessive metal materials attached to the end face and back of semiconductor wafers may contaminate the manufacturing equipment as metal or metal oxide particles in the process after forming metal wiring and barrier metal, i.e., oxygen-based ashing process or plasma-based dry etching process, and may cause cross contamination. Therefore, it is necessary to remove the metal materials attached to the end face and back before they are carried into the subsequent process.

[0005] Among these metal materials, the noble metals represented by platinum and ruthenium are difficult to be oxidized, dissolved, and removed by the subsequent etching process and cleaning process. Therefore, these noble metals are preferably removed from the semiconductor wafer in preference to other metal materials. In particular, ruthenium is often used as a wiring material for semiconductor components with a process of less than 10nm for the reason that it can reduce the resistance value more than the case of using copper in the wiring material, and therefore, it is expected to be removed from the useless part as soon as possible.

[0006] Generally, a cleaning method using hypochlorite with high oxidizing power as a cleaning liquid for semiconductor wafers has been proposed. Specifically, a method using a sodium hypochlorite aqueous solution has been proposed (see Patent Documents 1 and 2).

[0007] However, in the method of using a sodium hypochlorite aqueous solution as a cleaning liquid, the cleaning liquid necessarily contains more sodium ions, and as a result, there is a possibility that the sodium ions are easily attached to semiconductor wafers, etc., and the production efficiency of semiconductors may be reduced.

[0008] On the other hand, cleaning solutions using hypochlorous acid solutions that do not contain sodium as an essential component (see Patent Document 3) or aqueous solutions of quaternary alkyl ammonium hypochlorous acid salts (see Patent Document 4) have also been developed.

[0009] However, cleaning solutions using these hypochlorous acid (see Patent Document 3) are used to clean substrates having metal films or metal oxide films, and their purpose is not to specifically remove noble metals. Therefore, they are not suitable for cleaning metal / metal oxide films such as noble metals.

[0010] On the other hand, the cleaning solution containing tetramethylammonium hypochlorite aqueous solution described in Patent Document 4 is also a cleaning solution used for cleaning photoresists and residues, and its cleaning target is not a metal coating layer of copper or aluminum containing ruthenium. Specifically, it is shown in the examples that the metal film is difficult to be etched.

[0011] Prior art literature

[0012] Patent Literature

[0013] Patent Document 1: Japanese Patent Application Publication No. 2002-161381

[0014] Patent Document 2: Japanese Patent Application Publication No. 2009-081247

[0015] Patent Document 3: Japanese Patent Application Publication No. 2003-119494

[0016] Patent Document 4: Japanese Patent Application Publication No. 2005-227749 Summary of the invention

[0017] Problem that the invention aims to solve

[0018] The storage stability of the tetramethylammonium hypochlorite solution of Patent Document 4 is not necessarily satisfactory. Specifically, the present inventors have found that the desired cleaning performance cannot be achieved due to a decrease in hypochlorite ions that exert an oxidizing action over time.

[0019] Furthermore, Patent Document 4 discloses that, in order to maintain the level of available halogen, for example, triazole, thiazole, tetrazole and imidazole are added to the cleaning composition as a stabilizer.

[0020] However, since the stabilizer is added, it is easy to remain as organic residue after cleaning, causing the yield of semiconductor elements to decrease. In addition, the stabilizer is easy to adsorb to a specified metal, such as triazole, it is easy to adsorb to copper, sometimes also reducing the ability to clean copper.

[0021] Therefore, a first object of the present invention is to provide a method for producing an alkyl quaternary ammonium hypochlorite solution which has little temporal change in hypochlorite ion concentration and excellent storage stability even without adding a stabilizer.

[0022] In addition, as described above, the cleaning solution containing an aqueous solution of tetramethylammonium hypochlorite described in Patent Document 4 is intended to remove photoresist / residues. Therefore, for example, it is not considered to reduce the content of metals such as sodium, aluminum and / or potassium in the cleaning solution. It is believed that when the metal content contained in the cleaning solution is low, the production efficiency of semiconductor elements can be improved.

[0023] Therefore, a second object of the present invention is to provide a solution having a reduced metal content and a method for producing the same, for a quaternary alkyl ammonium hypochlorite solution used in a process for manufacturing a semiconductor device.

[0024] Solutions for solving problems

[0025] The present inventors conducted intensive research to achieve the first object and found that the concentration of hypochlorite ions in the quaternary alkyl ammonium hypochlorite solution was reduced, and the cleaning and removal power was reduced because the pH of the quaternary alkyl ammonium hypochlorite solution during the reaction was not controlled.

[0026] That is, the concentration of hypochlorite ions varies greatly depending on the pH of the quaternary ammonium hypochlorite solution in the reaction process. Therefore, further research on the cause of the pH change in the reaction process revealed that the carbon dioxide in the gas phase of the reaction process is absorbed by the reaction solution, and the pH of the reaction solution varies greatly. By controlling the carbon dioxide concentration in the gas phase of the reaction process, an quaternary ammonium hypochlorite solution with high storage stability can be produced even without adding a stabilizer.

[0027] Furthermore, based on the above findings, the inventors have continued to study and found that even without adding a stabilizer, the storage stability of the quaternary alkyl ammonium hypochlorite solution, which can be suitably used as an oxidant and a cleaning agent, can be further improved by adjusting the pH of the quaternary alkyl ammonium hypochlorite solution.

[0028] That is, it is clear that the reaction rate of the disproportionation reaction between hypochlorous acid and hypochlorite ions varies depending on the pH of the quaternary ammonium hypochlorite solution, and there is a pH range in which the self-decomposition of hypochlorous acid and hypochlorite ions is suppressed. It is generally known that for sodium hypochlorite solutions, the disproportionation reaction between hypochlorous acid and hypochlorite ions is suppressed in alkaline conditions, for example, at pH 11 or above, but it is clear that in the case of quaternary ammonium hypochlorite solutions, the disproportionation reaction between hypochlorous acid and hypochlorite ions is specifically suppressed at a pH of 12 or above and less than 14.

[0029] For example, when the quaternary alkyl ammonium hypochlorite solution of the present invention is used for cleaning and removing metals, the optimal pH of the quaternary alkyl ammonium hypochlorite solution is greater than 7 and less than 12. However, according to the research of the present inventors, it is clear that when the quaternary alkyl ammonium hypochlorite solution is prepared and stored within such a pH range, the oxidizing power will significantly disappear in a short period of time.

[0030] In addition, according to the research of the present inventors, it is clear that ammonia and amines present in the quaternary ammonium hydroxide solution and / or the quaternary ammonium hypochlorite solution have an adverse effect on the concentration of hypochlorite ions and the stability of the quaternary ammonium hypochlorite solution. Furthermore, during the continuous research, it was found that the concentration of hypochlorite ions can be suppressed from decreasing by reducing the ammonia and amines contained in the quaternary ammonium hydroxide solution and / or the quaternary ammonium hypochlorite solution in the preparation step, the reaction step, and the storage step, thereby improving the stability of the quaternary ammonium hypochlorite solution.

[0031] Based on these findings, it was found that even without adding a stabilizer, the storage stability of the quaternary ammonium hypochlorite solution can be improved by adjusting the pH of the quaternary ammonium hypochlorite solution or reducing the ammonia and amines contained in the quaternary ammonium hydroxide solution and / or the quaternary ammonium hypochlorite solution without reducing the hypochlorite ion concentration.

[0032] Furthermore, the present inventors have conducted intensive studies to achieve the second object. First, they have conducted detailed studies on metal impurities that may be contained in the quaternary alkyl ammonium hypochlorite solution described in Patent Document 4.

[0033] Patent Document 4 aims at removing the photoresist, and therefore does not consider the necessity of reducing the metal atoms contained in the tetramethylammonium hypochlorite aqueous solution.

[0034] Specifically, in the example of Patent Document 4, a tetramethylammonium hydroxide aqueous solution is reacted with chlorine gas in a conical flask to produce a tetramethylammonium hypochlorite aqueous solution. In addition, there is no description of the flask, so it is highly likely that it is a glass container. The present inventors learned through additional experiments of this example that the obtained alkyl quaternary ammonium hypochlorite solution contains a large amount of metal atoms such as sodium.

[0035] Therefore, the inventors studied the reasons for the inclusion of metal atoms such as sodium. It is believed that one of the reasons is the materials of the quaternary alkyl ammonium hydroxide salt and the flask as raw materials. That is, it is speculated that the reason is that since the quaternary alkyl ammonium hydroxide salt is a substance showing strong alkalinity, metal atoms such as sodium are dissolved from the glass as the material of the flask. It was also found that when the quaternary alkyl ammonium hydroxide salt aqueous solution is reacted with chlorine gas, the above-mentioned problem can be solved by limiting the material of the reaction container.

[0036] That is, the configuration of the present invention is as follows.

[0037] Item 1 A method for producing a quaternary ammonium hypochlorite solution, comprising: a preparation step of preparing a quaternary ammonium hydroxide solution so that the concentration of amine contained in the quaternary ammonium hydroxide solution is 20 mass ppm or less; and a reaction step of contacting the quaternary ammonium hydroxide solution with chlorine gas, wherein the carbon dioxide concentration in the gas phase in the reaction step is 100 volume ppm or less, and the pH of the liquid phase in the reaction step is 10.5 or more.

[0038] Item 2. The method for producing a quaternary alkyl ammonium hypochlorite solution according to Item 1, wherein the chlorine gas is contacted while the concentration of the amine contained in the liquid phase in the reaction step is maintained at 100 mass ppm or less.

[0039] Item 3. The method for producing a quaternary alkyl ammonium hypochlorite solution according to Item 1 or 2, wherein the carbon dioxide concentration in the quaternary alkyl ammonium hydroxide solution is 0.001 mass ppm or more and 500 mass ppm or less.

[0040] Item 4 The method for producing a quaternary alkyl ammonium hypochlorite solution according to any one of Items 1 to 3, wherein the water content of the chlorine gas is 10 volume ppm or less.

[0041] Item 5 The method for producing a quaternary alkyl ammonium hypochlorite solution according to any one of Items 1 to 4, wherein in the reaction step, the reaction temperature is -35°C or higher and 25°C or lower.

[0042] Item 6. The method for producing a quaternary alkyl ammonium hypochlorite solution according to any one of Items 1 to 5, wherein the quaternary alkyl ammonium hydroxide solution prepared by the preparation step is a solution of a quaternary alkyl ammonium hydroxide having an alkyl group with 1 to 10 carbon atoms.

[0043] Item 7 A method for producing a quaternary ammonium hypochlorite solution according to any one of Items 1 to 6, wherein the reaction step is a step of contacting a quaternary ammonium hydroxide solution with chlorine gas in a reaction container, the surface in the reaction container with which the quaternary ammonium hydroxide solution contacts is formed of an organic polymer material, and the reaction container is shielded from light.

[0044] Item 8. The method for producing a quaternary alkyl ammonium hypochlorite solution according to Item 7, wherein the organic polymer material is a fluororesin.

[0045] Item 9 is a method for producing a quaternary alkyl ammonium hypochlorite solution according to any one of Items 1 to 8, further comprising: a filtration step of obtaining a quaternary alkyl ammonium hypochlorite solution by the production method according to any one of Items 1 to 8, and then filtering the obtained quaternary alkyl ammonium hypochlorite solution.

[0046] Item 10. The method according to Item 9, wherein the pH of the quaternary alkyl ammonium hypochlorite solution in the filtration step is 13.5 or less at 25°C.

[0047] Item 11 is a method for producing a quaternary alkyl ammonium hypochlorite solution according to any one of Items 1 to 10, comprising: a storage step, obtaining a quaternary alkyl ammonium hypochlorite solution by the production method described in any one of Items 1 to 10, and then storing the obtained quaternary alkyl ammonium hypochlorite solution under light-shielding conditions such that the pH of the quaternary alkyl ammonium hypochlorite solution at 25° C. is greater than 12.0 and less than 14.0.

[0048] Item 12. The method for producing a quaternary alkyl ammonium hypochlorite solution according to Item 11, wherein in the storage step, the quaternary alkyl ammonium hypochlorite solution is stored at a concentration of amine of 100 mass ppm or less.

[0049] Item 13 is a method for treating a semiconductor wafer, wherein the surface of the semiconductor wafer is treated using a quaternary alkyl ammonium hypochlorite solution obtained by the method described in any one of Items 1 to 12.

[0050] Item 14 is a processing method according to Item 13, wherein the aforementioned semiconductor wafer is a semiconductor wafer containing at least one selected from the group consisting of copper, tungsten, tantalum, titanium, cobalt, ruthenium, manganese, aluminum, silicon, silicon oxide and their compounds.

[0051] Effects of the Invention

[0052] According to the manufacture method of the present invention described above, even if stabilizing agents such as triazole, thiazole, tetrazole and imidazole are not added, the alkyl quaternary ammonium hypochlorite solution with high storage stability can be manufactured. In addition, the gained alkyl quaternary ammonium hypochlorite solution does not need to add a stabilizing agent that is irrelevant to the cleaning ability. Therefore, if the alkyl quaternary ammonium hypochlorite solution manufactured by the present invention is used in the semiconductor manufacturing process, it can be suitably used as a cleaning solution that the yield rate can not be reduced. And then, the alkyl quaternary ammonium hypochlorite solution with few metal contents can be obtained. Therefore, it can be suitably used as an etching solution and a cleaning solution used when manufacturing semiconductor elements.

[0053] In addition, by including the above-mentioned filtration step, the metal content contained in the quaternary alkyl ammonium hypochlorite solution can be further reduced. Furthermore, by controlling the pH during storage under light shielding, the storage stability can be further improved.

[0054] Hereinafter, the effects achieved by each embodiment of the present invention will be described in more detail. BRIEF DESCRIPTION OF THE DRAWINGS

[0055] Figure 1 This is a schematic diagram showing one form of the method for producing the quaternary alkyl ammonium hypochlorite solution according to the first embodiment.

[0056] Figure 2 This is a schematic diagram showing one form of the method for producing a quaternary alkyl ammonium hypochlorite solution according to the second embodiment.

[0057] Figure 3 This is a schematic diagram showing one embodiment of a general method for producing a quaternary alkyl ammonium hypochlorite solution.

[0058] Description of Reference Numerals

[0059] 10. Ice Water

[0060] 11 Three-necked flask

[0061] 12 Thermometer protection tube

[0062] 13 Thermocouple

[0063] 14 Rotor

[0064] 15 PFA Tubing

[0065] 16 Gas washing bottle

[0066] 17 5 mass% sodium hydroxide aqueous solution

[0067] 18 Flow Meter

[0068] 19 Water Bath

[0069] 21. Glass beaker

[0070] 22 Thermometer protection tube

[0071] 23 Thermocouple

[0072] 24 Rotor

[0073] 25 PFA Tubing

[0074] 26 Flow Meter

[0075] 27 Water Bath

[0076] 28 ice water

[0077] 31. Reaction device

[0078] 32 reaction vessel

[0079] 33 Alkyl quaternary ammonium hydroxide solution (before reaction)

[0080] 34 Inner surface of reaction vessel

[0081] 35 Thermometer

[0082] 36. Stirring motor

[0083] 37 Stirring rod

[0084] 38 Mixing blade

[0085] 39 Chlorine gas supply pipe

[0086] 40 Gas inlet pipe

[0087] 41 Nitrogen supply pipe

[0088] 42 Reaction liquid transfer tube

[0089] 43 Pump

[0090] 44 Filter

[0091] 45 Reaction liquid return pipe

[0092] 46 Chlorine gas discharge pipe

[0093] 47 Chlorine Gas Capture

[0094] 48 Reaction bath

[0095] 49 Butt Joint DETAILED DESCRIPTION

[0096] (Method for producing quaternary alkyl ammonium hypochlorite solution)

[0097] The method for producing a quaternary ammonium hypochlorite solution of the present invention is characterized in that it comprises: a preparation step of preparing a quaternary ammonium hydroxide solution, wherein the concentration of amine contained in the quaternary ammonium hydroxide solution is 20 mass ppm or less; and a reaction step of contacting the quaternary ammonium hydroxide solution with chlorine gas, wherein the concentration of carbon dioxide in the gas phase in the reaction step is 100 volume ppm or less, and the pH of the liquid phase in the reaction step is 10.5 or more. Each step is described below.

[0098] (Preparation step of preparing alkyl quaternary ammonium hydroxide solution)

[0099] The alkyl ammonium hydroxide solution can be any one of an aqueous solution obtained by dissolving the alkyl ammonium hydroxide in water or a solution obtained by dissolving in a non-aqueous solvent. The alkyl ammonium hydroxide solution can be obtained by dissolving the alkyl ammonium hydroxide in water or a non-aqueous solvent, diluting a commercially available alkyl ammonium hydroxide solution to a desired concentration, etc. As the non-aqueous solvent, known organic solvents that can dissolve the alkyl ammonium hydroxide can be listed. Specifically, alcohols and glycols can be listed, and methanol and propylene glycol are particularly preferred. Among these solvents, from the viewpoint of easy industrial acquisition and the ability to obtain a high-purity alkyl ammonium hydroxide solution, the solvent is preferably water.

[0100] The concentration of the quaternary ammonium hydroxide solution is not particularly limited. If the concentration of the quaternary ammonium hydroxide solution reaches a high concentration, the salt will precipitate to form a solid. Therefore, the concentration of the quaternary ammonium hydroxide solution is preferably 0.01 to 30% by mass, more preferably 0.05 to 27.5% by mass, and further preferably 0.1 to 25% by mass.

[0101] In the prepared alkyl ammonium hydroxide solution, carbon dioxide from the atmosphere is usually included. Carbon dioxide is present in the solution in the form of carbonate ion or bicarbonate ion. Carbon dioxide concentration is not particularly limited, converted into carbonate ion, preferably more than 0.001ppm and less than 500ppm (mass basis), more preferably more than 0.005ppm and less than 300ppm, further preferably more than 0.01ppm and less than 100ppm. By making the carbon dioxide concentration contained by the aforementioned alkyl ammonium hydroxide solution be more than 0.001ppm and less than 500ppm, the pH change of the obtained alkyl ammonium hypochlorite solution can be suppressed. As a result, the storage stability of the alkyl ammonium hypochlorite solution can be improved. The alkyl ammonium hydroxide solution of this carbon dioxide concentration can utilize commercially available products.

[0102] If ammonia and / or amines are present in the prepared quaternary alkyl ammonium hydroxide solution, the hypochlorite ions generated in the reaction step are decomposed. Generally speaking, commercially available quaternary alkyl ammonium hydroxide solutions contain amines. If such quaternary alkyl ammonium hydroxide solutions are used, the hypochlorite ions generated in the reaction step react with the amines, which causes a decrease in the hypochlorite ion concentration.

[0103] Furthermore, when the amine is a tertiary amine, the secondary amine, primary amine, and ammonia generated by the reaction with the hypochlorite ion also react with the hypochlorite ion, thereby causing a significant decrease in the hypochlorite ion concentration. In particular, the reaction of the tertiary amine with the hypochlorite ion proceeds rapidly, and even a trace amount thereof will cause a significant decrease in the hypochlorite ion concentration. For example, it is known that the commercially available tetramethylammonium hydroxide solution contains several 10 to several 100 mass ppm of trimethylamine. Trimethylamine reacts with the hypochlorite ion to generate dimethylamine and monomethylamine, so if such a tetramethylammonium hydroxide solution is used, the hypochlorite ion concentration decreases, which is not appropriate.

[0104] Therefore, the ammonia or / and amines contained in the alkyl ammonium hydroxide solution are preferably less, specifically, preferably below 20 mass ppm. If it is below 20 mass ppm, the reduction of the hypochlorite ion concentration generated in the reaction process can be alleviated, and the stability of the obtained quaternary ammonium hypochlorite solution can be improved. Therefore, the preparatory process in the manufacture method of the present invention is characterized in that the concentration of the amine contained in the alkyl ammonium hydroxide solution is below 20 mass ppm. That is, the concentration of the amine contained in the alkyl ammonium hydroxide solution after the preparatory process is below 20 mass ppm. It should be noted that in the present invention, the concentration of amine refers to the sum of the concentrations of the tertiary amine, secondary amine, primary amine and ammonia contained in the solution. The concentration of the amine in the solution can be obtained by widely known methods such as gas chromatography, liquid chromatography, colorimetry, mass spectrometry and the analytical method obtained by combining them, etc.

[0105] When the concentration of amine contained in the quaternary ammonium hydroxide solution exceeds 20 mass ppm, the method that can reduce amine concentration can be used, and the concentration of amine in this quaternary ammonium hydroxide solution is below 20 mass ppm.The quaternary ammonium hydroxide solution obtained by such operation can be suitably used for manufacture method of the present invention.

[0106] As methods for reducing the concentration of amines contained in the quaternary ammonium hydroxide solution, for example, the tetramethylammonium hydroxide solution is heated, distilled or ion exchanged to remove ammonia and / or amines; ammonia and / or amines are removed by decompression treatment, degassing treatment or inert gas circulation treatment, etc. Any method can be used as long as the concentration of amines can be reduced. The above methods for reducing the concentration of amines can be implemented alone or in combination.

[0107] Of course, the concentration of amine can be further reduced by further heating, distillation, ion exchange, decompression treatment, degassing, inert gas circulation treatment, etc. to remove ammonia and / or amines from the alkyl ammonium hydroxide solution having an amine concentration of less than 20 mass ppm. The alkyl ammonium hydroxide solution obtained by such operation can be more suitably used in the production method of the present invention.

[0108] Generally speaking, the concentration of amines contained in the tetramethylammonium hydroxide solution for semiconductor use is lower than the concentration of amines contained in the tetramethylammonium hydroxide solution for industrial use. Therefore, as the tetramethylammonium hydroxide solution used in the manufacturing method of the present invention, it is preferred to use a tetramethylammonium hydroxide solution for semiconductor use. When using such a tetramethylammonium hydroxide solution, as long as the concentration of amines in the tetramethylammonium hydroxide solution is below 20 mass ppm, the reaction process can be implemented without removing ammonia and / or amines. This situation is also included in the preparation process of the present invention.

[0109] As the solvent for preparing the quaternary ammonium hydroxide solution, water can be used as the solvent to prepare the aqueous solution, or an organic solvent can be mixed and prepared in the form of a non-aqueous solution. The solvent can be appropriately changed according to the purpose of the quaternary ammonium hypochlorite solution and the object to be cleaned. For example, when the object to be cleaned is ruthenium, the solvent can be only water to carry out sufficient cleaning, therefore, the quaternary ammonium hydroxide solution can be prepared in the form of an aqueous solution.

[0110] In the manufacturing method of the present invention, the quaternary ammonium hydroxide solution is preferably a solution of a quaternary ammonium hydroxide solution in which the carbon number of the alkyl group is 1 to 10, and more preferably a solution of a quaternary ammonium hydroxide solution in which the carbon number of the alkyl group is 1 to 5. If specific quaternary ammonium hydroxide solutions are exemplified, they are tetramethylammonium hydroxide, tetraethylammonium hydroxide, tetrapropylammonium hydroxide, tetrabutylammonium hydroxide, etc. These quaternary ammonium hydroxide solutions can be used alone or in combination of two or more. In addition, the carbon numbers of the four alkyl groups contained in the quaternary ammonium hydroxide solution can be the same or different.

[0111] In the process of making the alkyl ammonium hydroxide solution react with chlorine gas to produce the alkyl ammonium hypochlorite solution, the pH of the solution containing the alkyl ammonium hypochlorite solution generated in the reaction vessel is reduced. Considering the conditions of the filtering operation described later and the solubility of the alkyl ammonium hydroxide, in the present embodiment, the lower limit of the pH of the alkyl ammonium hydroxide solution used as the raw material is 10.5 or more, and the upper limit is determined by the concentration of the alkyl ammonium hydroxide.

[0112] In addition, in the quaternary ammonium hydroxide solution used in the manufacturing method of the present invention, the content of preferred metals, specifically sodium, potassium, aluminum, magnesium, iron, nickel, copper, silver, cadmium and lead, is respectively 0.01 ppb or more and 20 ppb or less. It should be noted that, of course, the metal content contained in the quaternary ammonium hydroxide solution used can be less than 0.01 ppb, but it is difficult to obtain such a quaternary ammonium hydroxide solution itself.

[0113] Therefore, by using the alkyl ammonium hydroxide salt solution that the above-mentioned metal content satisfies the aforementioned range, its own acquisition becomes easy, and by the manufacturing of this alkyl ammonium hypochlorite salt solution and the filtering operation after manufacturing and easily remove / reduce this metal impurity.The reason that can remove / reduce metal impurity by filtering operation is still unclear, but it can be considered that this is because: by the metal impurity of the amount of a certain degree, thereby generate the foreign particles with a certain degree of size rather than being difficult to remove by filtering the colloid, thereby can remove by filtering.Therefore, the alkyl ammonium hydroxide salt solution used in the present embodiment can remove / reduce the solid matter of metal impurity by filtering operation because pH declines, therefore, even if it is not the alkyl ammonium hydroxide salt solution of ultra-high purity, it can also be used suitably.In order to further improve this effect, especially further remove / reduce alkalinity and form the impurity of ion, the metal content of sodium, potassium, aluminum, magnesium, iron, nickel, copper, silver, cadmium and lead contained by alkyl ammonium hydroxide salt solution is more preferably respectively more than 0.01ppb and below 5ppb, more preferably more than 0.01ppb and below 2ppb.

[0114] As the above-mentioned quaternary alkyl ammonium hydroxide solution, commercial products can be used. Among them, the quaternary alkyl ammonium hydroxide solution used as a photoresist developer for semiconductor elements, which has been highly purified by electrolysis and / or by contacting it with an ion exchange resin, etc., can be suitably utilized. In addition, these commercial products can also be used after being diluted with a solvent that does not contain metal impurities, such as ultrapure water.

[0115] (Reaction step of contacting alkyl quaternary ammonium hydroxide solution with chlorine gas)

[0116] By bringing the quaternary alkyl ammonium hydroxide salt solution into contact with chlorine gas and reacting them, hydroxide ions of the quaternary alkyl ammonium hydroxide salt are replaced by hypochlorite ions generated by the chlorine gas, thereby generating a quaternary alkyl ammonium hypochlorite salt solution.

[0117] (Chlorine)

[0118] In the production method of the present invention, the chlorine gas used is not particularly limited, and a commercially available product can be used. Among them, a high-purity gas used for etching of semiconductor materials or as a raw material of semiconductor materials can be used.

[0119] Among high purity gases, it is particularly preferred that the amount of water is less, specifically, it is preferred to use a gas with a water content of less than 10 volume ppm. The reason is not clear, but it can be considered as follows. It can be considered that: for example, when manufacturing quaternary ammonium hypochlorite solution, chlorine is usually transported via piping. Therefore, if there is a large amount of water, hydrogen chloride is produced and the metal parts of piping and flowmeters, etc. are corroded, and the metal impurities corroded together with chlorine are easily introduced into the system. Therefore, it is preferred to use a gas with a water content of less than 10 volume ppm contained in chlorine. Of course, if the water content in commercially available chlorine is less than 10 volume ppm, it can be used directly, and it can also be made to contact with a drying material before being introduced into the reaction system to reduce the water content contained in chlorine. The lower limit of the water content contained in chlorine is not particularly limited, and if it is considered that it can be obtained industrially, it is 0.1 volume ppm.

[0120] The concentration of the carbon dioxide contained in the chlorine is not particularly limited, and is preferably more than 0.001 volume ppm and less than 80 volume ppm, more preferably more than 0.005 volume ppm and less than 50 volume ppm, and further preferably more than 0.01 volume ppm and less than 2 volume ppm. If the carbon dioxide concentration contained in the chlorine is more than 0.001 volume ppm and less than 80 volume ppm, the pH change of the obtained alkyl ammonium hypochlorite solution can be suppressed. As a result, the storage stability of the alkyl ammonium hypochlorite solution can be improved. The chlorine of this carbon dioxide concentration can utilize commercially available products.

[0121] The amount of chlorine (the total amount of chlorine used) is not particularly limited, and is preferably 10 to 31000 mL relative to 1 liter of quaternary ammonium hydroxide solution, according to 0°C, 1atm conversion. By using chlorine in this range, the rapid pH change in the reaction system is suppressed, and metal impurities are easily removed / reduced by filtering operation. Relative to 1 liter of quaternary ammonium hydroxide solution, the amount of chlorine can also be set to an amount exceeding 31000 mL according to 0°C, 1atm conversion, and there is a tendency that the pH of the quaternary ammonium hydroxide solution decreases / changes more, and then unreacted chlorine remains. On the other hand, when it is less than 10mL, there is a tendency that sufficient hypochlorite ions cannot be generated. Therefore, if industrial manufacturing is taken into account, the amount of chlorine is preferably in the range of 10 to 31000 mL relative to 1 liter of quaternary ammonium hydroxide solution according to 0°C, 1atm conversion. Among them, the amount of chlorine can be determined according to the pH of the resulting solution, that is, the pH of the resulting quaternary ammonium hypochlorite solution.

[0122] In addition, chlorine gas is preferably supplied to the reaction system at the following rate: From the viewpoint of preventing a sharp decrease in pH and reducing chlorine gas irrelevant to the reaction, the supply flow rate (rate) of chlorine gas is preferably 0.0034 Pa·m·s relative to 1 liter of the quaternary ammonium hydroxide solution at 0°C and 1 atm. 3 / second or more and 16.9 Pa·m 3 / sec or less. By satisfying this range, the reactivity becomes sufficient, and a sharp pH drop / change does not occur, and an alkyl ammonium hypochlorite solution can be produced. In order to further exert this effect, the amount of chlorine gas supplied to the reaction system is more preferably 0.017 Pa·m 3 / second or more and 5.1Pa·m 3 / sec or less, more preferably 0.034 Pa·m 3 / second or more and 1.7Pa·m 3 / second or less. Among them, 1Pa·m 3 / second is equivalent to 592sccm.

[0123] It should be noted that, in the production method of the present invention, the method for contacting the alkyl ammonium hydroxide solution with chlorine is not particularly limited, and a known method can be used. However, in order to prevent carbon dioxide from mixing into the reaction system, it is preferred to carry out the reaction in a closed system. For convenience, Figure 1 As shown in FIG. 1 , by blowing chlorine into the quaternary ammonium hydroxide solution prepared in the three-necked flask, a sufficient reaction can be generated, and an alkyl quaternary ammonium hypochlorite solution with excellent storage stability can be produced. In addition, although it will be described in detail later, it is possible to use Figure 2 The reaction device constructed as shown.

[0124] Furthermore, the process of contacting the alkyl ammonium hydroxide solution with chlorine is preferably carried out using a light-shielded reaction vessel. The above-mentioned chlorine present in the reaction vessel is sometimes excited by light to produce chlorine free radicals. When chlorine free radicals are produced, sometimes the alkyl ammonium hydroxide present in the reaction vessel and the above-mentioned alkyl ammonium hypochlorite generated by the reaction are affected, and decomposition occurs. An ideal mode is to shield the reaction vessel, the accompanying piping, etc.

[0125] Furthermore, the surface in contact with the quaternary ammonium hydroxide solution in the above-mentioned reaction vessel (hereinafter sometimes referred to as "the inner surface of the reaction vessel") is preferably formed by an organic polymer material. According to the research of the inventors, if a general borosilicate glass (hereinafter referred to as glass) reaction vessel is used as the reaction vessel, the quaternary ammonium hydroxide solution used as a raw material will dissolve the metal components contained in the glass, such as sodium, potassium and aluminum. It can be considered that this is because the quaternary ammonium hydroxide solution used as a raw material is alkaline. Therefore, by forming the inner surface of the reaction vessel by an organic polymer material, the mixing of impurities (metal impurities) containing the above-mentioned metals can be reduced.

[0126] In this embodiment, as the organic polymer material used, vinyl chloride resin (soft / hard vinyl chloride resin), nylon resin, silicone resin, polyolefin resin (polyethylene, polypropylene), fluorine resin, etc. can be used. Among them, if the ease of molding, solvent resistance, less impurity dissolution, etc. are taken into consideration, fluorine resin can be listed.

[0127] As the fluororesin, as long as it is a resin (polymer) containing fluorine atoms, it is not particularly limited, and known fluororesins can be used. For example, polytetrafluoroethylene, polytrifluorochloroethylene, polyvinylidene fluoride, tetrafluoroethylene-hexafluoropropylene copolymer, tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer, tetrafluoroethylene-ethylene copolymer, trifluorochloroethylene-ethylene copolymer and cyclopolymer of perfluoro (butylene vinyl ether) can be listed. Wherein, if considering the ease of acquisition of the reaction vessel itself, productivity, etc., it is preferred to use tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer.

[0128] In this embodiment, as a method of forming the inner surface of the reaction container with an organic polymer material, there are a method in which the entire reaction container is formed of an organic polymer material, a method in which only the inner surface of a glass or stainless steel reaction container is covered with an organic polymer material, and the like.

[0129] In addition, in order to prevent the metal component from dissolving out from the organic polymer material, it can also be reused after cleaning. Specifically, it is preferably fully cleaned with an acid such as high-purity nitric acid / hydrochloric acid (for example, immersing in a solution with an acid concentration of 1 mol / L for 12 hours to clean), and further cleaned with ultrapure water, etc. In addition, in order to carry out a stable reaction, it is preferred that before reacting the alkyl hydroxide quaternary ammonium salt solution with chlorine, the inner surface of the reaction vessel formed by the aforementioned organic polymer material is cleaned by the aforementioned method.

[0130] In this embodiment, if the surface in contact with the quaternary ammonium hydroxide solution in the reaction vessel is formed of an organic polymer material, the other parts may be glass, stainless steel, or stainless steel that has been passivated. In order to minimize the impact, the stirring rod and the like are preferably also formed of the same organic polymer material, but this is not necessary.

[0131] In this embodiment, when an organic solvent is used as the solvent, the reaction device is preferably made into an explosion-proof structure. Therefore, in order to make a simple device structure, the quaternary ammonium hydroxide solution is preferably made of water as the solvent.

[0132] (Liquid Phase in Reaction Process)

[0133] The amine concentration contained in the liquid phase in the reaction step is preferably maintained at 100 mass ppm or less. As described in the above (preparation step), if the quaternary alkyl ammonium hydroxide salt solution contains amine, the concentration of hypochlorite ions generated in the reaction step decreases.

[0134] In addition, the hypochlorite ions generated by the reaction react with the alkyl quaternary ammonium ions at a high pH to generate tertiary amines, so the amine concentration contained in the liquid phase increases as the reaction proceeds. That is, there is a tendency that the amine concentration contained in the liquid phase in the reaction step is higher than the amine concentration in the preparation step. However, by maintaining the amine concentration contained in the liquid phase in the reaction step at 100 mass ppm or less, the decrease in the concentration of hypochlorite ions can be alleviated, and a treatment liquid with high storage stability can be prepared.

[0135] (Gas phase in the reaction process)

[0136] The greatest feature of this embodiment is that the concentration of carbon dioxide in the gas phase during the reaction process is 100 volume ppm or less. In this embodiment, the gas phase refers to the portion occupied by the gas that contacts the quaternary ammonium hydroxide solution during the reaction process. Figure 1 The manufacturing method shown is based on the portion (upper space) occupied by the gas in the three-necked flask 11.

[0137] In the production method of the present invention, the upper limit of the carbon dioxide concentration in the gas phase is 100 volume ppm. When the carbon dioxide concentration exceeds 100 volume ppm, carbonate ions and bicarbonate ions are generated during the reaction step due to the reaction of formulas (1) and (2), and the pH of the quaternary alkyl ammonium hypochlorite solution decreases accordingly.

[0138] CO2+OH - →HCO3 - …(1)

[0139] HCO3 - +OH - →CO32- +H2O…(2)

[0140] It is presumed that when the pH is lowered by the above-mentioned chemical reaction, hypochlorite ions are decomposed during storage of the obtained quaternary alkyl ammonium hypochlorite solution, thereby deteriorating the storage stability.

[0141] In the production method of the present invention, if the carbon dioxide concentration in the gas phase is 0.001 to 100 volume ppm, preferably 0.01 to 80 volume ppm, the pH of the quaternary alkyl ammonium hypochlorite solution can be sufficiently controlled, and an alkyl ammonium hypochlorite solution having excellent storage stability can be produced.

[0142] In order to make the carbon dioxide concentration in the gas phase of the present embodiment be the above-mentioned scope, preferably use the alkyl ammonium hydroxide salt solution, chlorine etc. that the carbon dioxide amount is reduced. And, preferably in the presence of the inert gas that the carbon dioxide amount is reduced (for example, in the presence of nitrogen), react. Specifically, by using the alkyl ammonium hydroxide salt solution of the aforementioned carbon dioxide concentration and the chlorine of the aforementioned carbon dioxide concentration, and then implement the reaction process in the presence of the inert gas, the carbon dioxide concentration in the gas phase can be made to be the above-mentioned scope.

[0143] (pH of reaction process)

[0144] The pH range of the liquid phase in the reaction process is above 10.5. The upper limit is not particularly limited. If the pH in the reaction is too high, hypochlorite ions are sometimes decomposed and the effective chlorine concentration is reduced when the reaction is stored for a long time at the same pH after the reaction is completed. Therefore, the pH of the liquid phase in the reaction process is preferably less than 14, more preferably less than 13.9, and further preferably more than 11 and less than 13.8. If the pH is the aforementioned range, the decomposition of hypochlorite ions is suppressed during the storage of the obtained quaternary ammonium hypochlorite solution, and the storage stability is improved. It should be noted that even when the pH during the reaction is high, the storage stability is improved by controlling the pH during storage to a specified range as described later. On the other hand, if the pH of the reaction process is too low, the storage stability is reduced due to the chemical reaction shown in formula (3).

[0145] 2HClO+ClO - +2OH - →ClO3 - +2Cl - +2H2O…(3)

[0146] (Reaction temperature of reaction step)

[0147] The reaction temperature of the liquid phase in the reaction step of the production method of the present invention is preferably in the range of -35°C to 25°C, more preferably -15°C to 25°C, and even more preferably 0°C to 25°C. When the reaction temperature is in the above range, the quaternary alkyl ammonium hydroxide solution reacts sufficiently with chlorine gas, and a quaternary alkyl ammonium hypochlorite solution can be obtained with high generation efficiency.

[0148] It should be noted that when the reaction temperature is less than -35°C, there is a tendency that the quaternary ammonium hydroxide solution begins to solidify and the efficiency of the reaction with chlorine gas decreases. On the other hand, when the reaction temperature exceeds 25°C, there is a tendency that the hypochlorite ions generated in the quaternary ammonium hydroxide solution are thermally decomposed. In particular, when the pH during the reaction is 13.8 or more, if the reaction temperature becomes high, there is a tendency that the decomposition of the hypochlorite ions becomes significant. The reaction efficiency of the quaternary ammonium hypochlorite can be evaluated by the ratio of the number of moles of the hypochlorite ions generated to the number of moles of the chlorine molecules supplied as a raw material.

[0149] As described above, according to the production method of this embodiment, it is possible to produce an alkyl quaternary ammonium hypochlorite solution that is excellent in storage stability and that can sufficiently ensure cleaning and removal power even after 10 days have passed after production, for example.

[0150] This revealed that the quaternary alkyl ammonium hypochlorite solution obtained by the production method of the present embodiment has excellent storage stability and can be suitably used in the production process of semiconductor devices.

[0151] (Reaction device)

[0152] Next, an explanation will be given using an example of a reaction apparatus that can be preferably used in the production method of the present invention. Figure 2 A schematic diagram of the reaction device 31 is shown.

[0153] In the reaction device 31, the surface (inner surface of the reaction container) 34 of the reaction container 32 that contacts the alkyl quaternary ammonium hydroxide solution 33 is formed of the aforementioned organic polymer material. In addition, a thermometer (thermocouple) 35 capable of confirming the temperature may also be provided in the reaction device 31. In addition, in order to be able to mix the reaction system, it is preferred to have a stirring motor 36, a stirring rod 37, and a stirring blade 38. The portions of these thermometers 35, stirring rods 37, and stirring blades 38 that contact the alkyl quaternary ammonium hydroxide solution 33 are preferably formed of an organic polymer material.

[0154] In addition, the reaction device 31 is provided with a chlorine gas supply pipe 39 for supplying chlorine gas, and the chlorine gas is introduced into the reaction system through the gas introduction pipe 40 through the supply pipe 39 to contact the alkyl ammonium hydroxide solution 33. As described above, it is preferred that carbon dioxide is not contained in the reaction system, so a nitrogen gas supply pipe 41 may also be provided. Figure 2 In the embodiment, the nitrogen supply pipe 41 merges with the chlorine supply pipe 39 midway, and the nitrogen is introduced from the gas introduction pipe 40. However, the gas introduction pipe 40 can be divided into a chlorine introduction pipe / nitrogen introduction pipe. In addition, the gas introduction pipe 40 is preferably formed of the aforementioned organic polymer material because it contacts the quaternary ammonium hydroxide solution 33.

[0155] In addition, see the following description, but in the present embodiment, when chlorine is contacted with quaternary ammonium hydroxide solution to manufacture quaternary ammonium hypochlorite solution, the pH in the reaction system is sometimes reduced, and the solid matter containing the metal component is precipitated. In the present embodiment, in order to remove / reduce the solid matter by filtering, a filter may also be provided. The filter includes a reaction solution transfer pipe 42, a pump 43, a filter filter 44, and a reaction solution return pipe 45. Each component in these filters contacts the reaction solution containing quaternary ammonium hypochlorite, and is therefore preferably formed by the aforementioned organic polymer material.

[0156] The pump 43 may be a chemical diaphragm pump, a tube pump, a magnetic pump, etc. Among them, in order to prevent contamination by metal components, it is preferable to use a pump whose liquid contact portion is formed of the above-mentioned fluororesin, and in particular, considering the availability, it is preferable to use a magnetic pump.

[0157] In addition, it is preferable to use the material and form which are described in detail below for the filter 44 . Figure 2 2 shows an example in which one filter filter 44 is provided, but a plurality of filters 44 may be arranged in series and / or in parallel according to the purpose of use (to remove the intended impurities).

[0158] By providing the above-mentioned filtering device, filtering operation can also be performed during the reaction process. In addition, the supply of chlorine gas can also be stopped, and after the reaction, the solution containing the quaternary ammonium hypochlorite salt is circulated by using the pump 43, and the solid matter containing the metal component is removed / reduced by using the filter 44. It should be noted that, Figure 2 , the reaction device and the filtration device are shown as an integrated structure, but the reaction device and the filtration device may be provided separately as long as filtration is performed after the reaction.

[0159] In addition, a chlorine gas discharge pipe 46 for dissipating the supplied unreacted chlorine gas and a chlorine gas trap 47 may be provided. The chlorine gas trap 47 may be filled with, for example, an aqueous sodium hydroxide solution of about 5 mass %.

[0160] Furthermore, a reaction bath 48 for controlling the reaction temperature may be provided around the reaction container 32 .

[0161] Furthermore, the thermometer 35 , the stirring rod 37 , the gas introduction pipe 40 , the reaction liquid transfer pipe 42 , the reaction liquid return pipe 45 , and the chlorine gas discharge pipe 46 may be connected to the reaction container 32 by means of a docking joint 49 or the like.

[0162] By using such a reaction apparatus 31, the method of the present embodiment can be easily performed, and a high-purity quaternary alkyl ammonium hypochlorite solution can be produced.

[0163] (Filtration process)

[0164] If the quaternary ammonium hydroxide solution contacts chlorine and generates the quaternary ammonium hypochlorite solution, the pH of the solution in the reaction system is reduced. At this time, solids containing metal impurities may sometimes precipitate. Therefore, in order to remove / reduce these solids, it is preferred that the filtration step of filtering the obtained quaternary ammonium hypochlorite solution is also included. Furthermore, in order to prevent the hypochlorite ions from decomposing due to light, the filtration step is preferably carried out under shading. It should be noted that the filtration step can be carried out after the storage step or dilution described later.

[0165] In the filtering step, the metal components filtered out may differ depending on the pH of the quaternary ammonium hypochlorite solution. Specifically, when the pH of the quaternary ammonium hypochlorite solution is set to 13.5 or less, preferably when the pH of the solution exceeds 12.5 and is 13.5 or less, hydroxides of magnesium, iron, cadmium, etc., and oxides of nickel and silver solidify, and therefore, these impurities can also be removed / reduced by filtering.

[0166] In addition, when the pH of the quaternary ammonium hypochlorite solution is set to 12.5 or less, preferably when the pH of the solution is 9.0 or more and 12.5 or less, copper and lead oxides solidify on the basis of the above-mentioned impurities, and therefore, these impurities can also be removed / reduced by performing a filtering operation. It should be noted that the pH of the solution sometimes varies depending on the temperature. The above pH is based on the value at 25°C. The liquid temperature when the filtering process is actually implemented is not limited to 25°C, and is preferably carried out at 20 to 28°C, and more preferably at 23°C to 25°C.

[0167] Even if the purity of the quaternary alkyl ammonium hydroxide solution and chlorine gas as raw materials is increased, such solid matter of metal impurities will be generated. In particular, when the inner surface of the reaction vessel is formed of an organic polymer material, such solid matter is sometimes generated. The reason is not clear, but it can be inferred that it is because: since a highly corrosive gas such as chlorine gas is used, the metal impurities are contained in the reaction system from somewhere in the reaction device.

[0168] The filtering operation can be carried out at a pH at which the metals to be removed / reduced are solidified. Therefore, it can be carried out only once or multiple times at each pH. At this time, the filtering efficiency is further improved by preparing a plurality of filter filters with different pore sizes at each pH, ​​and filtering in sequence from the filter filter with a large pore size. Specifically, it can be implemented by removing coarse particles in the first stage and removing fine particles in the second stage. It should be noted that solids containing metal components, such as simple metal impurities, metal oxides, metal hydroxides and / or colloids, particles of 1 μm or more and 100 μm or less are sometimes referred to as "coarse particles" below. On the other hand, particles of 0.01 μm or more and less than 1 μm are sometimes referred to as "fine particles" below. It should be noted that the particle size of the solid refers to the circle equivalent diameter based on laser diffraction.

[0169] The filtering operation is not particularly limited and can be performed using a known filtering device or a filter. In order not to increase useless metal components, the surface of the filtering device that may contact the quaternary ammonium hypochlorite solution is preferably formed of an organic polymer material. The organic polymer can be the same as the organic polymer exemplified above.

[0170] As a specific filter, it is preferred to use a filter formed by an organic polymer material or an inorganic material. For example, a filter formed by polyolefin (polypropylene, polyethylene, ultra-high molecular weight polyethylene), polysulfone, cellulose acetate, polyimide, polystyrene, the aforementioned fluorine resin and / or quartz fiber can be listed. In addition, the filter preferably uses a positively charged membrane and a negatively charged membrane in combination. The reason is that a variety of metal oxides and metal hydroxides are negatively charged under an alkaline atmosphere, and metal components can be efficiently removed by electrostatic adsorption and utilizing a positively charged filter. In addition, a part of the metal components exists in a cationic state and is positively charged. Therefore, the negatively charged filter can efficiently remove ionized metal components by electrostatic adsorption.

[0171] The pore size of the filter is not particularly limited, and coarse particles can be removed using a filter or microfiltration filter with a pore size of 1 μm or more. On the other hand, fine particles can be removed using a microfiltration filter, ultrafiltration filter, or nanofiltration membrane with a pore size of 0.01 μm or more and less than 1 μm.

[0172] The above-mentioned filter can use commercial products. Specifically, the polytetrafluoroethylene "FLUOROGARD ATX filter (pore size 0.05 μm)", "Quick Change ATE filter (pore size 0.03 μm)", "Torrento ATE filter (pore size 0.02 μm)", "Quick Change ATE filter (pore size 0.03 μm)", "FLUOROLINE P-1500 (pore size 0.05 μm, 0.1 μm)" manufactured by Entegris Corporation of Japan can be used.

[0173] The above filtering operation can be implemented before the pH of the alkyl quaternary ammonium hypochlorite solution is adjusted to the scope suitable for its purpose. At this time, after the filtering operation is performed earlier, the alkyl quaternary ammonium hypochlorite solution of the target pH can be mixed with chlorine again. In addition, the alkyl quaternary ammonium hypochlorite solution of the target pH can also be mixed with alkalis such as acids such as water, hydrogen chloride and / or hydroxide tetramethyl quaternary ammonium salt aqueous solution. On the other hand, when the pH of the alkyl quaternary ammonium hypochlorite solution manufactured is the pH suitable as a cleaning solution, the solution can be filtered and directly used as the cleaning solution used when manufacturing semiconductor elements.

[0174] By carrying out this filtering operation, it is especially possible to reduce metal components such as magnesium, iron, nickel, copper, silver, cadmium and lead. Specifically, the content of magnesium, iron, nickel, copper, silver, cadmium and lead can be set to less than 1ppb (mass basis) respectively. The content of these metal components is also the value measured by the inductively coupled plasma mass spectrometry shown in the embodiment. It should be noted that the form of the metal component in the quaternary ammonium hypochlorite solution is not particularly limited, and can be included in the form of metal atoms or ions, in addition, also includes forms such as particles, complexes of oxides, hydroxides and the like.

[0175] (Save process)

[0176] In the manufacture method of the present invention, the alkyl quaternary ammonium hypochlorite solution after the above-mentioned reaction step or after the above-mentioned filtering step can be directly used for specified purposes such as cleaning fluid, and is usually used again after the preservation step (including storage and transportation). The storage stability of the alkyl quaternary ammonium hypochlorite solution when it exists alone is poor, and it is necessary to add a stabilizer such as described in patent document 4. However, stabilizers sometimes become the cause of organic residues and seek improvement. The alkyl quaternary ammonium hypochlorite solution obtained by the manufacture method of the present invention is an alkyl quaternary ammonium hypochlorite solution with excellent storage stability even if it does not contain a stabilizer.

[0177] Furthermore, the storage of the alkyl ammonium hypochlorite solution obtained by the manufacture method of the present invention is preferably a method (storage process) in which the pH of the alkyl ammonium hypochlorite solution at 25°C is 12.0 or more and less than 14.0 and is stored in a light-shielded manner. According to the storage process of the present invention, the oxidizing power of the alkyl ammonium hypochlorite solution during storage remains substantially unchanged regardless of whether the storage period is 30 days, preferably 60 days, and more preferably 90 days. Therefore, after storage, the alkyl ammonium hypochlorite solution can be used for various purposes only by diluting the solution according to the conditions of use. The longer the storage period, the more the effect of improving productivity can be expected. Below, the storage process of the present invention is described.

[0178] The concentration of the alkyl quaternary ammonium hypochlorite solution to be stored is not particularly limited. If industrial production is taken into consideration, it is preferred to specify a solution of alkyl quaternary ammonium hypochlorite with a hypochlorite ion of 0.001 to 20% by mass and an alkyl quaternary ammonium ion of 0.001 to 50% by mass at a specified pH. It should be noted that "specified pH" refers to any pH of 12.0 or more and less than 14.0 selected as the pH in the storage process. Here, "storage" means: from the time when the alkyl quaternary ammonium hypochlorite solution is stored at a pH of 12.0 or more and less than 14.0 at 25°C until the concentration and / or pH of the alkyl quaternary ammonium hypochlorite solution is adjusted. It should be noted that when the pH of the solution after the pH adjustment is 12.0 or more and less than 14.0, if the solution is further stored, it also complies with the storage of the present invention. If the pH of the quaternary alkyl ammonium hypochlorite solution is 12.0 or higher and lower than 14.0 from the beginning, the solution may be stored as it is. If the pH is lower than 12.0 or higher than 14.0, the solution may be stored after adjusting the pH to a range of 12.0 or higher and lower than 14.0.

[0179] When the pH in the storage process is less than 12.0, there is a tendency for hypochlorite ions to undergo a disproportionation reaction, hypochlorite ions to be decomposed, and the oxidizing power of the alkyl quaternary ammonium hypochlorite solution to decrease. On the other hand, when the pH is above 14.0, it can be inferred that there is a tendency for organic ions as cations to decompose. As a result, it can be inferred that the disproportionation reaction of hypochlorite ions that was hindered by the steric hindrance of organic ions proceeds again, and hypochlorite ions decompose. It is preferably stored as an alkyl quaternary ammonium hypochlorite solution having a pH of 12.0 or more and less than 13.9 at 25°C, and more preferably stored under the condition that the pH at 25°C is 12.0 or more and less than 13.8.

[0180] It should be noted that the pH of the solution sometimes changes depending on the temperature. The above pH is based on the value at 25°C. The liquid temperature when the solution is actually stored is not limited to 25°C. Therefore, the conditions during storage are not particularly limited. It is preferably stored under general storage conditions, that is, at -25 to 50°C in a known container, can, or resin storage container. It is further preferably stored in a light-shielding storage container, can or other transport container, or resin storage container filled with an inert gas at -20 to 40°C and stored in a dark place. When the storage temperature exceeds the above range, during long-term storage, hypochlorite ions may be thermally decomposed to form oxygen molecules, causing the container to swell and break.

[0181] In the storage method of the present invention, the concentration of amines contained in the quaternary ammonium hypochlorite solution is preferably 100 mass ppm or less. If the concentration of amines is 100 mass ppm or less, decomposition of the quaternary ammonium hypochlorite by amines can be suppressed, thereby enabling stable storage.

[0182] (Dilution of quaternary alkyl ammonium hypochlorite solution)

[0183] The alkyl quaternary ammonium hypochlorite solution can be appropriately diluted and used according to its purpose. The dilution method of the alkyl quaternary ammonium hypochlorite solution can be used as long as the hydrogen ion concentration contained in the alkyl quaternary ammonium hypochlorite solution can be relatively increased. The alkyl quaternary ammonium hypochlorite solution can be diluted with water, or with a solution containing an acid, or with a solution having a lower pH than the pH of the alkyl quaternary ammonium hypochlorite solution during storage. For example, as an example of a solution having a lower pH than the alkyl quaternary ammonium hypochlorite solution stored by the storage method of the present invention, an alkaline solution, for example, an alkyl quaternary ammonium hydroxide solution having a pH less than 12 can be cited.

[0184] In addition, the solution added to dilute the aforementioned quaternary alkyl ammonium hypochlorite solution may or may not contain quaternary alkyl ammonium hypochlorite. For example, when diluting with a solution containing quaternary alkyl ammonium hypochlorite, not only the pH can be adjusted, but also the concentration of the quaternary alkyl ammonium hypochlorite solution can be arbitrarily adjusted.

[0185] It should be noted that, in the present invention, the solution added in order to dilute the aforementioned quaternary ammonium hypochlorite solution is preferably diluted with a solution having a pH greater than 0 and below 7. By using an acidic solution, the reduction in the concentration of the quaternary ammonium hypochlorite accompanying the pH adjustment can be alleviated. As a specific example of a solution having a pH greater than 0 and below 7, for example, hydrochloric acid, nitric acid, sulfuric acid, phosphoric acid, boric acid, hydrofluoric acid, bromic acid, chloric acid, perchloric acid, iodic acid, periodic acid, carbonic acid, etc. can be listed if it is an inorganic acid, and formic acid, acetic acid, anhydrous acetic acid, propionic acid, citric acid, oxalic acid, malic acid, lactic acid, benzoic acid, etc. can be listed if it is an organic acid.

[0186] In addition, when the impurity concentration of the solution used for dilution is high, the use of the obtained dilution is limited, so it is preferred that the impurities of the solution used for dilution are small. For example, when the quaternary alkyl ammonium hypochlorite solution is used as a processing liquid for semiconductor wafers, since high purity is sought, it is preferred to dilute the high-purity quaternary alkyl ammonium hypochlorite solution with hydrochloric acid, sulfuric acid, etc. that can be easily purified industrially.

[0187] As the dilution method of the quaternary ammonium hypochlorite solution, there is no particular limitation, and known methods can be used to dilute. For example, the method of mixing by respectively supplying the quaternary ammonium hypochlorite solution and the solution used for dilution from two supply ports of the container and stirring with a propeller or a rotor can be used, and the method of mixing by circulating the liquid with a pump can also be adopted. In addition, the solution used for dilution can be supplied to dilute in the container storing the quaternary ammonium hypochlorite solution.

[0188] As another dilution method, the quaternary alkyl ammonium hypochlorite solution can be diluted by mixing the quaternary alkyl ammonium hypochlorite solution with a solution used for dilution at the location where the composition containing the quaternary alkyl ammonium hypochlorite solution is used. For example, if the quaternary alkyl ammonium hypochlorite solution and the solution used for dilution are respectively supplied to the application point from two nozzles, dilution can be performed at the application point. This method is particularly effective when processing semiconductor wafers.

[0189] In addition, when the diluent is used for semiconductor cleaning purposes, a method of adding an inorganic acid or an organic acid to the quaternary ammonium hypochlorite solution can be used for dilution. There is a method of diluting by merging the pipe supplying the quaternary ammonium hypochlorite solution with the pipe supplying the inorganic acid or the organic acid midway, and supplying the resulting diluent to the semiconductor wafer as the surface to be cleaned. The mixing can be carried out by the following known methods: a method of passing the liquids through a narrow passage under pressure to cause the liquids to impact and mix with each other; a method of filling the pipe with a filler such as a glass tube, and repeatedly causing the liquid flow to be split, separated and merged; a method of setting a blade driven to rotate in the pipe, etc.

[0190] As described above, the alkyl ammonium hypochlorite solution obtained by the manufacturing method of the present invention is stored in the storage step and then diluted when used, so that a diluent that stably maintains the oxidizing power can be used compared to the case where the alkyl ammonium hypochlorite solution is stored at the pH when used. Usually, when the alkyl ammonium hypochlorite solution is used as a cleaning solution, the pH is diluted to about 8 to 12, but when the alkyl ammonium hypochlorite solution is stored at this pH, the hypochlorite ion concentration decreases and the cleaning property decreases. However, by storing it after the above-mentioned storage step and then undergoing the above-mentioned dilution step, a diluent (cleaning solution) with a high hypochlorite ion concentration can be obtained.

[0191] (Semiconductor wafer processing method)

[0192] The processing method of the present invention is a processing method that can etch, clean, and remove various metals and their compounds present in semiconductor wafers without causing damage to the semiconductor wafers. The processing object is not limited thereto, and of course, it can also be used for cleaning semiconductor wafers that do not have metals on the surface, and can also be used for wet etching of metals, etc.

[0193] The object of the treatment method of the present invention is preferably a semiconductor wafer having at least one compound selected from the group consisting of copper, tungsten, tantalum, titanium, cobalt, ruthenium, manganese, aluminum, silicon, silicon oxide and these compounds. The present invention can effectively exert the strong oxidizing effect of hypochlorite ions, and therefore, it can also be suitably used for the treatment of precious metals that are not easily oxidized among the aforementioned metals. Therefore, the treatment method of the present invention can be suitably used when precious metals, especially ruthenium, are cleaned and removed. For example, if ruthenium is cleaned and removed, a known cleaning method can be used.

[0194] (Alkyl quaternary ammonium hypochlorite solution)

[0195] By manufacture method of the present invention, even if stabilizers such as triazole, thiazole, tetrazole and imidazole are not added, alkyl quaternary ammonium hypochlorite solution with high storage stability and reduced content of metal component can be manufactured. Therefore, it can be suitably used as etching solution and cleaning solution used when manufacturing semiconductor element. It should be noted that, of course, the solvent of alkyl quaternary ammonium hypochlorite solution is the same as the solvent of alkyl quaternary ammonium hydroxide solution as raw material, and other solvents can also be added in the scope that does not damage the effect of the present invention. Wherein, if considering operability, ease of handling, versatility, etc., the solvent of alkyl quaternary ammonium hypochlorite solution is preferably water. In addition, the pH of gained alkyl quaternary ammonium hypochlorite solution is not particularly limited, and it is appropriately determined according to the use purpose. For example, when pH exceeds 12.5, it can be used as photoresist remover (developer), and it can also be used for the planarization of noble metal layer when forming semiconductor element.

[0196] Among them, by making the pH value not less than 9.0 and not more than 12.5, the obtained quaternary alkyl ammonium hypochlorite solution can also be used for etching treatment of precious metals. At this time, chlorine gas can be supplied to the quaternary alkyl ammonium hydroxide solution with a high pH while making the pH value not less than 9.0 and not more than 12.5, so it is also easy to manufacture. In addition, by performing a filtering operation during or after manufacturing, the content of the metal component can also be further reduced.

[0197] In addition, the quaternary alkyl ammonium hypochlorite solution obtained by the present invention may be substantially free of triazole, thiazole, tetrazole and imidazole described as stabilizers in Patent Document 4, and preferably is free of them. Substantially free means that in the quaternary alkyl ammonium hypochlorite solution obtained by the present invention, these are below the detection limit.

[0198] In addition, in the quaternary ammonium hypochlorite solution, various additives can be compounded according to its purposes and according to expectation. For example, as additives, metal chelating agents, complexing agents, metal dissolution promoters, metal corrosion inhibitors, surfactants, acids, alkalis, etc. can be added. By adding these additives, it can be expected that when semiconductor wafers are processed, the dissolution of metals, the improvement of surface roughness, the increase in processing speed, the reduction of particle adhesion, etc. can be promoted or suppressed, and therefore, the cleaning solution comprising these additives can be suitably used for the processing of semiconductor wafers. And then, as other additives, known additives such as benzophenones, oxalylanilides and salicylates can also be compounded in the quaternary ammonium hypochlorite solution. By adding these additives, storage stability can become good.

[0199] Example

[0200] Hereinafter, the present invention will be described in more detail with reference to Examples, but the present invention is not limited to these Examples.

[0201] (pH measurement method)

[0202] The pH of 10 mL of the treatment liquid prepared in Examples and Comparative Examples was measured using a tabletop pH meter (LAQUA F-73, manufactured by Horiba, Ltd.) The pH measurement was performed after the treatment liquid was prepared and stabilized at 25°C.

[0203] (Measurement method of amine concentration)

[0204] Before the preparation process, after the preparation process, during the reaction process, immediately after the production, and after the storage process, 10 mL of each of the alkyl ammonium hydroxide solution and the alkyl ammonium hypochlorite solution was weighed and mixed with 10 mL of a 1 mol / L sodium thiosulfate solution to inactivate the hypochlorite ions in the solution. Next, diethyl ether was used to extract the amines in the solution, and a gas chromatograph-mass spectrometer (Agilent Technologies, Agilent 7890B / 5977B) was used for determination. A standard curve was prepared in advance by the standard addition method, and the amine concentration was quantified.

[0205] (Evaluation method of hypochlorite ion concentration)

[0206] In a 100 mL conical flask, 0.5 mL of the alkyl ammonium hypochlorite solution prepared in the Examples and Comparative Examples, 2 g of potassium iodide (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd., special reagent grade), 8 mL of 10% acetic acid, and 10 mL of ultrapure water were added, and the mixture was stirred until the solid matter was dissolved to obtain a brown solution.

[0207] The prepared brown solution was subjected to redox titration using a 0.02 M sodium thiosulfate solution (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd., for volumetric analysis) until the solution color changed from brown to very light yellow, and then the starch solution was added to obtain a light purple solution.

[0208] To this solution, 0.02 M sodium thiosulfate solution was further continuously added, and the point at which the solution became colorless and transparent was defined as the end point, from which the hypochlorite ion concentration was calculated.

[0209] (Calculation method of reaction efficiency)

[0210] The reaction efficiency is calculated from the ratio (%) of the number of moles of hypochlorite ions generated to the number of moles of chlorine molecules supplied. When all the added chlorine gas reacts (no decomposition occurs), the reaction efficiency reaches 100%. When the hypochlorite ions decompose during the reaction, the reaction efficiency decreases.

[0211] (Calculation method of carbon dioxide concentration in gas phase)

[0212] The carbon dioxide concentration in the gas phase during the reaction step was measured using a CO2 monitor (CO2-M1, manufactured by CUSTOM).

[0213] (Calculation method of carbon dioxide concentration in alkyl quaternary ammonium hydroxide solution)

[0214] Carbon dioxide in the alkyl ammonium hydroxide solution is in the form of carbonate ions. Its concentration is analyzed using an ion chromatography device (DIONEX INTEGRION HPLC, Thermo SCIENTIFIC company system). As eluent, KOH is used and liquid is passed through at a flow rate of 1.2 mL / min. As a column, a hydroxide-based eluent anion analysis column (AS15, Thermo SCIENTIFIC company system) is used, and the column temperature is set to 30 ° C. After removing background noise using an interference suppressor, the carbonate ion concentration is quantitatively measured using a conductivity detector, and calculated accordingly in the form of carbon dioxide concentration.

[0215] <Evaluation method of storage stability>

[0216] The alkyl quaternary ammonium hypochlorite solution was transferred to a glove box, and after the carbon dioxide concentration in the glove box reached less than 1 volume ppm, it was transferred to a PFA container and sealed. When shading was performed during storage, the PFA container was covered with a black cloth for a clean room, and when shading was not performed, the PFA container was directly stored. Then, after being stored for 10 days at 25°C and under a fluorescent lamp, the hypochlorite ion concentration of the alkyl quaternary ammonium hypochlorite solution in the PFA container was measured. The hypochlorite ion concentration ratio (concentration after 10 days / initial concentration × 100 (unit %)) was recorded as excellent when it was 60% or more and less than 100%, good when it was 30% or more and less than 60%, and unqualified when it was less than 30%.

[0217] <Calculation Method of Ruthenium Etching Rate>

[0218] An oxide film is formed on a silicon wafer using a batch thermal oxidation furnace, and a film is formed on it using a sputtering method. (±10%) of ruthenium. The sheet resistance is measured using a four-probe resistance meter (Loresta-GP, manufactured by Mitsubishi Chemical Analysis Co., Ltd.) and converted into film thickness. Prepare 30 ml of the obtained tetramethylammonium hypochlorite solution in a beaker. Next, for the tetramethylammonium hypochlorite solution with a pH exceeding 12, dilute it with an inorganic acid or an organic acid until the desired pH is reached to obtain a measurement solution. Each sample piece of a ruthenium-containing wafer cut into 10×20 mm pieces is immersed in the measurement solution for 1 minute, and the value obtained by dividing the film thickness change before and after the treatment by the immersion time is calculated as the etching rate, which is evaluated as the ruthenium etching rate. However, it can be seen that the larger the pH, the slower the etching rate. Therefore, the following operation is performed to determine the range that can be practically used at each pH. When the pH is 9.1, the ruthenium etching rate is The above evaluation is good, less than The evaluation was poor. When the pH was 9.5, The above evaluation is good, which will be less than The evaluation was poor. When the pH was 10.5, The above evaluation is good, which will be less than The evaluation was poor. When the pH was 11.0, The above evaluation is good, which will be less than Rated as bad.

[0219] <Method for Determining Metal Concentration in Alkyl Ammonium Hypochlorite Solution>

[0220] The metal concentrations in quaternary alkyl ammonium hypochlorite solutions were determined using high-resolution inductively coupled plasma mass spectrometry.

[0221] Ultrapure water and 1.25mL of high-purity nitric acid (Kanto Chemical Co., Ltd., Ultrapure-100 nitric acid) are added to the measuring bottle (AsOne company system, PFA measuring bottle) of 25mL perfluoroalkoxyalkane (PFA) system. Then, 0.25mL of hypochlorite alkyl quaternary ammonium salt solution is taken using a pipette (AsOne company system, Pipette Man P1000) and a fluororesin pipette tip (AsOne company system, fluororesin pipette tip), added to the PFA measuring bottle and stirred. Then, constant volume with ultrapure water, prepare to dilute 100 times of the determination sample. And then, using high-resolution inductively coupled plasma mass spectrometry device (ThermoFisherScientific company system, Element2), the amount of metal is quantitatively measured using a standard curve method. It should be noted that, in order to confirm the sensitivity increase and decrease caused by matrix, the sample obtained by adding impurities in the determination solution in a manner reaching 2ppb is also measured. The measurement conditions were as follows: RF output of 1500 W, argon gas flow rates of 15 L / min for plasma gas, 1.0 L / min for assist gas, and 0.7 L / min for nebulizer gas.

[0222] <Example 1>

[0223] (Manufacture of Tetramethylammonium Hypochlorite Solution)

[0224] (Preparation process)

[0225] In a 2L glass four-necked flask (manufactured by VIDTEC), 702.2 g of a 25% by mass aqueous solution of tetramethylammonium hydroxide and 397.8 g of ultrapure water were mixed to obtain 1100.0 g of a 16.0% by mass aqueous solution of tetramethylammonium hydroxide. The carbon dioxide concentration in the solution was measured and found to be less than 1 mass ppm. Furthermore, 50 g was taken out from the solution and the amine concentration was measured. The result showed that the amine concentration was 150 mass ppm. Therefore, the removal of amines was performed as described below. Into a four-necked flask were placed the above-mentioned 16.0 mass % tetramethylammonium hydroxide aqueous solution and a rotor (manufactured by AsOne, total length 30 mm×diameter 8 mm), a thermometer protection tube (manufactured by VIDTEC, bottom-sealed type) and a thermometer were placed into one opening, the other opening was connected to a chlorine gas cylinder and a nitrogen gas cylinder, and the tip of a PFA tube (manufactured by FLON INDUSTRY, F-8011-02) capable of switching the state of chlorine gas / nitrogen gas at will was immersed in the bottom of the solution, the other opening was connected to a wash bottle (manufactured by AsOne, wash bottle, model 2450 / 500) filled with a 5 mass % sodium hydroxide aqueous solution, and the remaining opening was connected to a syringe (manufactured by MonotaRO, SyringeDispo, for 10 mL) having a hole with an inner diameter of 5 mm opened in a PTFE stopper and a PTFE tube with an outer diameter of 5 mm attached.

[0226] Next, a four-necked flask and a magnetic stirrer (AsOne, C-MAG HS10) were placed in a water bath, and the mixture was heated to 40° C. and rotated and stirred at 300 rpm. A pressure of 0.289 Pa·m 3 After nitrogen gas was flowed at 400 ℃ / sec (at 0° C.) for 20 minutes to remove amines in the liquid, the amine concentration in the tetramethylammonium hydroxide aqueous solution was measured and found to be 5 mass ppm.

[0227] (Reaction process)

[0228] Thereafter, the four-necked flask was covered with a clean room black cloth (manufactured by TANIMURA, clean conductive PVC sheet / light-shielding black cloth TW-CPF-BK), and a water bath was filled with ice water to cool the outer periphery of the four-necked flask at 0.088 Pa·m 3 / second (when converted to 0°C) for 120 minutes of chlorine gas (manufactured by ADEKA, with a standard purity of 99.999% and a water content of less than 1 volume ppm), 25 g was taken out using a syringe to obtain a treated liquid in the reaction process. The carbon dioxide concentration in the gas phase in the reaction process is less than 1 volume ppm. Furthermore, the pH of the liquid phase in the reaction process is 14.0, and the pH will not be lower than 10.5 in the reaction process. Thereafter, chlorine gas is further supplied for 120 minutes to terminate the reaction process. The temperature in the reaction process is constant at 11°C. The pH of the treated liquid just after manufacture is 13.8, the amine concentration is 5 mass ppm, the hypochlorite ion concentration is 2.86 mass%, and the reaction efficiency is 99%.

[0229] (Save process)

[0230] After the reaction step was completed, the solution was transferred from the four-necked flask to a 1 L PFA container as a treatment solution immediately after production, covered with a black cloth for a clean room, and stored at room temperature for 10 days to obtain a treatment solution after storage.

[0231] (evaluate)

[0232] The pH, amine concentration, hypochlorite ion concentration, and storage stability of the treatment liquid after storage for 10 days were evaluated. The results are shown in Table 2. The storage stability was evaluated by the above-mentioned "Evaluation method of storage stability", and the hypochlorite ion concentration ratio was 100%, which was excellent.

[0233] <Examples 2 to 6, Comparative Examples 1 to 4>

[0234] In Examples 2 to 6, except that (A) the mass concentration of tetramethylammonium hydroxide (TMAH) solution and (B) the pH of TMAH solution after concentration adjustment, (C) amine removal temperature, (D) nitrogen flow rate, (E) amine removal time, (F) the amount of chlorine gas supplied and (G) the flow rate of chlorine gas, (H) reaction temperature, (I) reaction time, (J) carbon dioxide concentration in the gas phase during the reaction process, (K) light shielding during reaction, and (L) light shielding during storage were adjusted to the conditions shown in Table 1, a tetramethylammonium hypochlorite solution was prepared by the same method as in Example 1, stored, and evaluated. In addition, chlorine gas was also supplied in Comparative Examples 1 to 4, but the removal operation of amines before the reaction was not performed. The evaluation results are shown in Table 2. The pH in the reaction process of Examples 2 to 7 and Comparative Examples 1 to 4 was not lower than the pH immediately after the reaction was completed. In addition, the amine concentration in the reaction process was suppressed to less than 100 mass ppm in Examples 2 to 7, and exceeded 100 mass ppm in Comparative Examples 1 to 4. If the amine concentration in the reaction step exceeds 100 mass ppm, a decrease in reaction efficiency is observed. On the other hand, if it is 100 mass ppm or less, the reaction efficiency is high (95% or more).

[0235] <Example 7>

[0236] The same conditions as in Example 1 were used except that a tetramethylammonium hydroxide solution having an amine concentration of 15 ppm by mass was used and the amine removal operation was not performed.

[0237] When the amine concentration is low, the decomposition of hypochlorite ions generated in the reaction process can be suppressed, so the reaction efficiency becomes higher. In addition, by suppressing the decomposition of hypochlorite ions caused by amines, the hypochlorite ion concentration ratio (concentration after 10 days / initial concentration×100 (unit %)) becomes higher. In addition, it is known that shading during manufacture and storage helps to suppress the decomposition of hypochlorite ions.

[0238] [Table 1]

[0239]

[0240] [Table 2]

[0241]

[0242] <Example 8>

[0243] <Manufacturing of Tetramethylammonium Hypochlorite Solution>

[0244] In a 2L glass four-necked flask (manufactured by VIDTEC), 253 g of a 25% by mass tetramethylammonium hydroxide (TMAH) aqueous solution having a CO content of 2 mass ppm and an amine concentration of 5 mass ppm or less and 747 g of ion exchange water were mixed to obtain a 6.3% by mass TMAH aqueous solution having a CO content of 0.5 mass ppm. The pH at this time was 13.8. It should be noted that the CO concentration in the laboratory was 350 volume ppm.

[0245] Next, using the same method as in Example 1, Figure 1As shown in the figure, a rotor 14 (manufactured by AsOne, total length 30 mm×diameter 8 mm) was introduced into a four-necked flask 11, a thermometer protection tube 12 (manufactured by VIDTEC, bottom-sealed type) and a thermocouple 13 were introduced into one opening, the other opening was connected to a chlorine gas cylinder and a nitrogen gas cylinder, and the tip of a PFA tube 15 (manufactured by FLON INDUSTRY, F-8011-02) capable of switching the state of chlorine gas / nitrogen gas at will was immersed in the bottom of the solution, one opening was connected to a wash bottle 16 (manufactured by AsOne, wash bottle, model 2450 / 500) filled with a 5 mass % sodium hydroxide aqueous solution 17, and the remaining opening was connected to a syringe (manufactured by MonotaRO, Syringe Dispo, for 10 mL) having a hole with an inner diameter of 5 mm opened in a PTFE stopper and a PTFE tube with an outer diameter of 5 mm attached thereto.

[0246] Next, a four-necked flask and a magnetic stirrer (C-MAG HS10 manufactured by AsOne) were placed in a water bath, and while rotating and stirring at 300 rpm, a pressure of 0.289 Pa·m was applied from a PFA tube. 3 / second (at 0°C) for 20 minutes, nitrogen was circulated to discharge CO2 from the gas phase. At this time, the CO2 concentration in the gas phase of the flask was less than 1 volume ppm. Next, the four-necked flask was covered with a clean room black cloth (manufactured by TANIMURA, clean conductive PVC sheet / light-shielding black cloth TW-CPF-BK), and ice water was filled in a water bath. While cooling the outer periphery of the four-necked flask, the pressure was maintained at 0.088 Pa·m 3 / second (when converted to 0°C) supply chlorine gas (manufactured by ADEKA, with a standard purity of 99.999% and a water content of less than 1 volume ppm) for 90 minutes. At this time, 25 g is taken out using a syringe to obtain a treatment liquid in the reaction process. Thereafter, chlorine gas is further supplied for 90 minutes to terminate the reaction process. The liquid temperature in the reaction process is 11°C. After the reaction process is completed, 25 g of the treatment liquid is taken out from the four-necked flask as the treatment liquid just after manufacture. The four-necked flask containing the treatment liquid is placed in a glove box with a carbon dioxide concentration of less than 1 ppm so that it does not contact the atmosphere. It is then transferred to a 1L PFA container, covered with a black cloth for a clean room, and stored at room temperature for 10 days to obtain the treatment liquid after storage.

[0247] <Evaluation>

[0248] Comparison of hypochlorite ion concentration and pH before and after 10 days of storage revealed that the storage stability was evaluated to be excellent.

[0249] <Examples 9 to 14>

[0250] In Examples 9 to 14, the tetramethylammonium hypochlorite solution was prepared and evaluated by the same method as in Example 8 except that (A) the mass concentration of the TMAH solution and (B) the pH of the TMAH solution, (F) the amount of chlorine gas supplied and (G) the supply rate, (H) the reaction temperature, and (J) the carbon dioxide concentration in the gas phase were adjusted to the conditions shown in Table 3. It should be noted that in Example 14, the reaction step was not cooled, and the reaction temperature was increased from 25° C. to 35° C. In addition, the tetramethylammonium hydroxide aqueous solution used had an amine concentration of 20 mass ppm or less.

[0251] <Comparative Example 5>

[0252] In a 2L glass beaker (manufactured by AsOne), 233 g of a 25% by mass TMAH aqueous solution with a CO2 content of 2 ppm and 767 g of ion exchange water were mixed to obtain a 5.8% by mass TMAH aqueous solution. The pH at this time was 13.8. Figure 3 As shown in the figure, a rotor 24 (manufactured by AsOne, total length 30 mm×diameter 8 mm) was placed in a glass beaker 21, followed by a thermometer protection tube 22 (manufactured by VIDTEC, bottom-sealed type) and a thermocouple 23, and the tip of a PFA tube 25 (manufactured by FLONINDUSTRY, F-8011-02) connected to a chlorine gas cylinder was immersed in the bottom of the solution. At this time, the carbon dioxide concentration in the gas phase was 350 volume ppm.

[0253] Thereafter, a magnetic stirrer (AsOne, C-MAG HS10) was placed under the glass beaker and the beaker was rotated at 300 rpm while the outer periphery of the beaker was cooled with 28 g of ice water at a pressure of 0.064 Pa·m 3 Chlorine gas (manufactured by ADEKA, with a standard purity of 99.999%, a water content of 1 volume ppm or less) was supplied at 100 °C / sec (at 0 °C) for 180 minutes to obtain a tetramethylammonium hypochlorite solution. The liquid temperature during the reaction was 11 °C.

[0254] The obtained solution was placed in a glove box with a carbon dioxide concentration of 1 volume ppm or less so as not to contact the atmosphere, and then transferred to a 1L PFA container, covered with a clean room black cloth, and stored at room temperature for 10 days to obtain a treated solution after storage. The hypochlorite ion concentration and pH before and after 10 days of storage were compared to evaluate the storage stability.

[0255] <Comparative Examples 6 and 7>

[0256] In Comparative Examples 6 and 7, the tetramethylammonium hypochlorite solution was prepared and evaluated by the same method as in Comparative Example 5, except that (A) the mass concentration of the tetramethylammonium hydroxide solution, (B) the pH of the tetramethylammonium hydroxide solution, (F) the amount of chlorine gas supplied and (G) the supply rate, (H) the reaction temperature, and (J) the carbon dioxide concentration in the gas phase were prepared so as to meet the conditions shown in Table 3. In Comparative Example 7, a solution having a carbon dioxide concentration of 771 mass ppm in the tetramethylammonium hydroxide solution was used.

[0257] The evaluation results are shown in Table 4. By removing carbon dioxide, the pH in the reaction step can be maintained at 10.5 or more, and a chemical solution having excellent storage stability can be obtained.

[0258] [Table 3]

[0259]

[0260] [Table 4]

[0261]

[0262] <Example 15>

[0263] <Manufacturing of Tetramethylammonium Hypochlorite Solution>

[0264] (Preparation process)

[0265] like Figure 2 As shown in the figure, a reaction vessel 32 processed in such a way that a plurality of polytetrafluoroethylene joints 49 (AsOne, Half Female Joint I type 6φ) can be connected to a polytetrafluoroethylene reaction vessel (AsOne, reaction cylindrical vessel C type 2000cc) with a capacity of 2L is prepared, and 253g of a 25% by mass aqueous solution of tetramethylammonium hydroxide and 747g of ultrapure water are mixed in the reaction vessel 32 to obtain a 6.3% by mass aqueous solution of tetramethylammonium hydroxide, a CO2 content of 5 mass ppm, and a pH of 13.8 (25°C). The contents of sodium, potassium, aluminum, magnesium, iron, nickel, copper, silver, cadmium and lead contained in the tetramethylammonium hydroxide aqueous solution are less than 1 ppb, respectively, and the amine concentration is 5 mass ppm.

[0266] (Reaction process)

[0267] A stirring rod 37 (AsOne, made of polytetrafluoroethylene (PTFE), with a stirring rod / stirring blade, total length 450 mm × diameter 8 mm) was set in the center of the reaction container 32, and the upper part was fixed with a stirring motor 36 (Shinto Scientific Co., Ltd., Sany Electric BLh600). A thermometer 35 was set in the reaction container 32 so that the temperature during the reaction could be monitored.

[0268] The tip of a gas introduction pipe 40 made of tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer (PFA tube manufactured by FLON INDUSTRY Co., Ltd.) capable of switching between chlorine gas (chlorine gas introduction pipe 39) and nitrogen gas (nitrogen gas supply pipe 41) is immersed in the bottom of the solution (tetramethylammonium hydroxide aqueous solution 33).

[0269] Furthermore, one of the butt joints is connected to a chlorine gas trap 47 (manufactured by AsOne, a gas washing bottle) filled with a 5 mass % sodium hydroxide aqueous solution via a chlorine gas discharge pipe 46 .

[0270] In addition, a docking joint is connected to the inlet side of a magnetic pump 43 (manufactured by AsOne, a magnetic pump whose surface is covered with Teflon (registered trademark)) using a tetrafluoroethylene perfluoroalkyl vinyl ether copolymer tube (manufactured by FLON INDUSTRY, PFA tube) serving as a reaction liquid transfer tube 42, and then the outlet side is connected using a filter 44 (manufactured by Entegris Corporation of Japan, FLUOROGARD AT, pore size 0.1 μm) and a reaction liquid return tube 45 formed of the same material as the reaction liquid transfer tube 42.

[0271] Furthermore, one docking head was connected to a syringe (Syringe Dispo, manufactured by MonotaRO, for 10 mL) equipped with a PTFE tube having an outer diameter of 6 mm, and the syringe was adjusted so that the tip of the tube was located on the bottom surface of the reaction container 32 .

[0272] Next, nitrogen gas was supplied through the nitrogen supply pipe 41 and the gas supply pipe 40 (a tetrafluoroethylene perfluoroalkyl vinyl ether copolymer pipe (manufactured by FLON INDUSTRY, PFA pipe)) at a pressure of 0.29 Pa·m 3 / sec. for 20 minutes, nitrogen gas having a carbon dioxide concentration of less than 1 volume ppm was circulated, thereby exhausting carbon dioxide from the gas phase in reaction container 32.

[0273] Thereafter, the stirring motor 36 was rotated at 300 rpm, and the outer periphery of the reaction container 32 was cooled by the reaction bath 48 (ice water) while the pressure was maintained at 0.064 Pa·m 3Chlorine gas (manufactured by ADEKA, with a standard purity of 99.999% and a water content of less than 1 volume ppm) is supplied at 100 °C / sec. At this time, the carbon dioxide concentration in the gas phase of the reaction process is less than 1 volume ppm. While the reaction is being carried out while supplying chlorine gas, pump 43 is started, and a tetramethylammonium hypochlorite aqueous solution is produced while performing a filtering operation (when the pH (25°C) of the reaction solution is higher than 13.5, a filtering operation is also performed). In addition, after supplying chlorine gas for 90 minutes, 25 g is taken out using a syringe to obtain a treated liquid in the reaction process. The pH of the liquid phase in the reaction process is 13.4, and the pH will not be lower than 10.5 in the reaction process. Thereafter, gas is further supplied for 90 minutes to terminate the reaction process. The temperature in the reaction process is constant at 11°C. In addition, the pH of the treated liquid just after manufacture (at the end of the reaction process) is 13.0, the amine concentration is less than 5 mass ppb, the hypochlorite ion concentration is 1.59 mass%, and the metal amount is less than 1 mass ppb.

[0274] (Save process)

[0275] The obtained solution was transferred to a 1L PFA container in a glove box with a carbon dioxide concentration of 1 volume ppm or less without contacting the atmosphere, covered with a black cloth for a clean room, and stored at room temperature for 10 days to obtain a treated solution after storage. The hypochlorite ion concentration and pH before and after 10 days of storage were compared to evaluate the storage stability.

[0276] (evaluate)

[0277] The pH, amine concentration, hypochlorite ion concentration, and storage stability of the treatment liquid after storage for 10 days were evaluated. The results are shown in Table 6. Since the hypochlorite ion concentration ratio was 100%, the storage stability was excellent.

[0278] <Examples 16 to 18>

[0279] In Examples 16 to 18, except that the mass concentration of the (A) TMAH aqueous solution (wherein an aqueous solution having a content of less than 1 mass ppb of sodium, potassium, aluminum, magnesium, iron, nickel, copper, silver, cadmium and lead and a carbon dioxide concentration of 2 mass ppm was used) was modulated in a manner to achieve the conditions shown in Table 5, the same operation as in Example 15 was performed to produce a tetramethylammonium hypochlorite aqueous solution and its metal content was investigated.

[0280] In Example 16, after all the chlorine gas was supplied, the supply of chlorine gas was stopped, and then the pump 43 was started to perform a filtration operation for 180 minutes. The pH at the time when all the chlorine gas supply was completed was 12.0, and the pH after filtration was 12.0. This filtration operation was not performed in Example 17. In addition, in Example 18, the filtration operation was performed when the pH of the treatment liquid was between 13.8 and 13.6. The results are shown in Table 6.

[0281] <Examples 19, 20, Comparative Example 8>

[0282] As the reaction container 32, a glass reaction container (manufactured by Shibata Scientific Co., Ltd., 1L separable reaction container) having a size of 19 / 38 mm was used in combination with a 1000 mL glass reaction container, and a tetramethylammonium hypochlorite aqueous solution was produced under the conditions shown in Table 5. The results are shown in Table 6.

[0283] In Example 19, the pump 43 was started during the supply of chlorine gas to perform the filtering operation. In Example 20, the filtering operation was not performed. In Comparative Example 8, after all the chlorine gas was supplied, the supply of chlorine gas was stopped, and then the pump 43 was started to perform the filtering operation for 180 minutes. The results are shown in Table 6.

[0284] When a reaction container made of polytetrafluoroethylene is used, dissolution from the reaction container can be suppressed, thereby reducing the concentration of metal impurities such as sodium, potassium, and aluminum. In addition, it is known that magnesium, iron, nickel, copper, silver, cadmium, and lead can be removed by filtering the tetramethylammonium hypochlorite aqueous solution having a pH of 13.5 or less during the reaction step or immediately after the reaction.

[0285] [Table 5]

[0286]

[0287] [Table 6]

[0288]

[0289] <Example 21>

[0290] 100 mL of the tetramethylammonium hypochlorite aqueous solution obtained by Example 8 was put into a PFA container, shielded from light and stored in an environment of 25°C for 30 days. The pH of the tetramethylammonium hypochlorite aqueous solution after storage for 30 days was 13.0. In addition, the ratio of the hypochlorite ion concentration just after manufacture and after storage for 30 days was 100%, so the storage stability was excellent. In addition, the amine concentration was 5 mass ppm or less. 8.8 mL of 35.0 mass % high-purity hydrochloric acid was added to the tetramethylammonium hypochlorite aqueous solution after storage for 30 days, and the pH (25°C) was diluted to 9.5 (modulated in a PFA container). The contents of sodium, potassium, aluminum, magnesium, iron, nickel, copper, silver, cadmium and lead in the tetramethylammonium hypochlorite aqueous solution obtained by dilution were less than 1 ppb, respectively.

[0291] 30 mL of the tetramethylammonium hypochlorite aqueous solution with a pH of 9.5 obtained by dilution was placed in a beaker (PFA beaker), and the etching rate of ruthenium was evaluated by the above-mentioned "Calculation method of etching rate of ruthenium". The result was that the etching rate was good.

[0292] <Examples 22 to 28, Comparative Example 9>

[0293] In Examples 22 to 28 and Comparative Example 9, tetramethylammonium hypochlorite solutions were prepared and evaluated by the same method as in Example 8 except that (A) the mass concentration of tetramethylammonium hydroxide (TMAH) solution, (B) the pH after modulation, (F) the amount of chlorine gas supplied, (G) the flow rate of chlorine gas, (H) the reaction temperature, (O) the solution to be diluted, (P) the concentration of the solution to be diluted, and (Q) the amount of the solution to be diluted were changed to the conditions shown in Table 7. The pH of the tetramethylammonium hypochlorite aqueous solution obtained in Example 28 was 14.0 or more immediately after production, so 35.0% by mass of high-purity hydrochloric acid was added until the pH reached 13.0 and then stored for 30 days. The pH of the tetramethylammonium hypochlorite aqueous solution obtained in Comparative Example 9 was 10 or less after 30 days of storage, so the tetramethylammonium hypochlorite aqueous solution was not diluted. The results are shown in Table 8.

[0294] It can be seen that if the tetramethylammonium hypochlorite aqueous solution is stored under the condition of pH less than 12.0 or pH above 14.0, the decomposition of hypochlorite ions is promoted and the storage stability is reduced. In particular, it can be seen that when the pH is above 14.0, the amine concentration is likely to increase during storage, which promotes the decomposition of hypochlorite ions. Therefore, it can be seen that when the pH of the tetramethylammonium hypochlorite aqueous solution just after manufacture is above 14.0, the increase in amine concentration during storage can be suppressed by adjusting the pH to less than 14.0, the decomposition of hypochlorite ions is suppressed, and the storage stability becomes good. As a result, it can be seen that a stable Ru etching rate can be obtained.

[0295] [Table 7]

[0296]

[0297] [Table 8]

[0298]

Claims

1. A method for producing an alkyl quaternary ammonium hypochlorite solution, comprising: A preparation step of preparing a quaternary alkyl ammonium hydroxide solution so that the concentration of amine contained in the quaternary alkyl ammonium hydroxide solution is 20 mass ppm or less; as well as The reaction step is to contact the quaternary alkyl ammonium hydroxide solution with chlorine gas. The pH of the liquid phase in the reaction step is 10.5 or more and less than 14.

2. The method for producing a quaternary alkyl ammonium hypochlorite solution according to claim 1, wherein The carbon dioxide concentration in the gas phase during the reaction step is 100 volume ppm or less.

3. The method for producing a quaternary alkyl ammonium hypochlorite solution according to claim 1 or 2, wherein: The chlorine gas is contacted while the concentration of the amine contained in the liquid phase in the reaction step is maintained at 100 mass ppm or less.

4. The method for producing a quaternary alkyl ammonium hypochlorite solution according to claim 1 or 2, wherein: The carbon dioxide concentration in the quaternary alkyl ammonium hydroxide salt solution is 0.001 mass ppm or more and 500 mass ppm or less.

5. The method for producing a quaternary alkyl ammonium hypochlorite solution according to claim 1 or 2, wherein: The moisture content of the chlorine gas is 10 volume ppm or less.

6. The method for producing a quaternary alkyl ammonium hypochlorite solution according to claim 1 or 2, wherein: In the reaction step, the reaction temperature is -35°C or higher and 25°C or lower.

7. The method for producing a quaternary alkyl ammonium hypochlorite solution according to claim 1 or 2, wherein: The quaternary alkyl ammonium hydroxide salt solution prepared in the preparation step is a solution of a quaternary alkyl ammonium hydroxide salt in which the alkyl group has 1 to 10 carbon atoms.

8. The method for producing a quaternary alkyl ammonium hypochlorite solution according to claim 1 or 2, wherein: The reaction step is a step of contacting an alkyl quaternary ammonium hydroxide solution with chlorine gas in a reaction container. The surface of the reaction container in contact with the alkyl quaternary ammonium hydroxide solution is formed of an organic polymer material, and the reaction container is shielded from light.

9. The method for producing a quaternary alkyl ammonium hypochlorite solution according to claim 8, wherein: The organic polymer material is fluororesin.

10. The method for producing the quaternary alkyl ammonium hypochlorite solution according to claim 1 or 2, further comprising: The filtration step comprises obtaining a quaternary alkyl ammonium hypochlorite solution by the production method according to claim 1 or 2, and then filtering the obtained quaternary alkyl ammonium hypochlorite solution.

11. The method according to claim 10, wherein: The pH of the quaternary alkyl ammonium hypochlorite solution in the filtration step is 13.5 or less at 25°C.

12. The method for producing a quaternary alkyl ammonium hypochlorite solution according to claim 1 or 2, comprising: A storage step is to obtain a quaternary alkyl ammonium hypochlorite solution by the production method according to claim 1 or 2, and then store the quaternary alkyl ammonium hypochlorite solution under light shielding conditions at a pH of 12.0 or more and less than 14.0 at 25°C.

13. The method for producing a quaternary alkyl ammonium hypochlorite solution according to claim 12, wherein: In the storage step, the quaternary alkyl ammonium hypochlorite solution is stored so that the concentration of amine in the solution is 100 mass ppm or less.

14. A method for processing a semiconductor wafer, wherein: The surface of a semiconductor wafer is treated using the quaternary alkyl ammonium hypochlorite solution obtained by the method according to any one of claims 1 to 13.

15. The processing method according to claim 14, wherein: The semiconductor wafer is a semiconductor wafer containing at least one selected from the group consisting of copper, tungsten, tantalum, titanium, cobalt, ruthenium, manganese, aluminum, silicon, silicon oxide, and compounds thereof.

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