Semiconductor wafer processing solution

Abstract

A processing solution for etching transition metals on semiconductor wafers and a method for producing the same are provided. [Solution] The method etches the transition metal by contacting the semiconductor wafer treatment solution with a transition metal used in the semiconductor formation process, the transition metal containing hypohalite ions or periodate ions and an alkylammonium salt represented by the following formula (1): TIFF2022153481000015.tif47115 In the formula, a is an integer of 6 to 20, and R 1 , R 2 , R 3 are independently a hydrogen atom or an alkyl group having 1 to 20 carbon atoms, and X - is a bromine-containing ion.

Description

[Technical Field]

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

[0002] In recent years, the design rules for semiconductor devices have become increasingly finer, leading to an increase in wiring resistance. As a result of the increase in wiring resistance, it has become apparent that the high-speed operation of semiconductor devices is being hindered, and countermeasures are therefore required. Therefore, wiring materials with improved electromigration resistance and reduced resistance compared to conventional wiring materials are desired.

[0003] Compared to the conventional wiring materials of aluminum and copper, ruthenium, tungsten, molybdenum, or chromium (hereinafter, tungsten, molybdenum, and chromium may be collectively referred to as Group 6 metals) has high electromigration resistance and can reduce the resistance value of wiring, and therefore is attracting attention as a wiring material, particularly for semiconductor device design rules of 10 nm or less.In addition to wiring materials, ruthenium can prevent electromigration even when copper is used as the wiring material, so its use as a barrier metal for copper wiring is also being considered.

[0004] In the wiring formation process for semiconductor devices, even when ruthenium, tungsten, molybdenum, or chromium is selected as the wiring material, wiring is formed by dry etching or wet etching, as with conventional wiring materials. However, when dry etching these metals, there are problems such as in-plane nonuniformity due to plasma distribution and the etching rate varying depending on the flux or energy of reactive species and ions, making precise etching difficult. Therefore, wet etching has attracted attention as a method that can etch these metals more precisely.

[0005] Microfabrication of semiconductor devices requires microfabrication of ruthenium, tungsten, molybdenum, or chromium using wet etching. To achieve microfabrication of ruthenium, tungsten, molybdenum, or chromium, precise control of the etching rate of these metals is required. Furthermore, to achieve multilayer wiring, flatness of each metal layer is essential, and flatness of the metal surface after etching is also desired.

[0006] Patent Document 1 proposes a method for etching a ruthenium film using a chemical solution having a pH of 12 or higher and a standard oxidation-reduction potential of 300 mV vs. SHE (standard hydrogen electrode) or higher, specifically a solution containing a halogen oxyacid salt such as hypochlorite, chlorite, or bromate.

[0007] Patent Document 2 proposes a method of oxidizing, dissolving, and removing ruthenium using an aqueous solution containing orthoperiodic acid and having a pH of 11 or higher. Patent Document 3 also proposes a ruthenium metal treatment solution containing a bromine-containing compound, an oxidizing agent, a base compound, and water, having a pH of 10 or higher but lower than 12.

[0008] Additionally, Patent Document 4 proposes a cleaning method in which ruthenium is oxidized, dissolved, and removed using a remover solution prepared by adding a strong acid such as nitric acid to cerium (IV) ammonium nitrate.

[0009] Patent Document 5 proposes a treatment liquid for wafers containing ruthenium and tungsten, which contains hypochlorite ions and a solvent and has a pH of more than 7 and less than 12.0 at 25° C., as a treatment liquid used to etch tungsten from semiconductor wafers. It is disclosed that this treatment liquid contains hypochlorite ions and can remove ruthenium and tungsten adhering to the edge surface and back surface of the semiconductor wafer.

[0010] Patent Document 6 proposes a tungsten metal remover containing orthoperiodic acid and water. It has been shown that this remover can stably remove unwanted tungsten metal formed on or attached to a semiconductor substrate.

[0011] Patent Document 7 discloses a method for forming wiring by processing copper and molybdenum with a chemical solution containing an oxidizing agent and an acid. Examples of the oxidizing agent include hydrogen peroxide, persulfuric acid, nitric acid, hypochlorous acid, permanganic acid, and dichromate. It also shows an example of etching a molybdenum film using an aqueous solution containing hydrogen peroxide and a carboxylic acid as the chemical solution. [Prior art documents] [Patent documents]

[0012] [Patent Document 1] Japanese Patent Application Laid-Open No. 2002-161381 [Patent Document 2] International Publication No. 2016 / 068183 [Patent Document 3] International Publication No. 2011 / 074601 [Patent Document 4] Japanese Patent Application Laid-Open No. 2001-234373 [Patent Document 5] International Publication No. 2019 / 142788 [Patent Document 6] Japanese Patent Application Laid-Open No. 2005-166924 [Patent Document 7] Japanese Patent Application Laid-Open No. 2013-254946 Summary of the Invention [Problem to be solved by the invention]

[0013] However, according to the investigations of the present inventors, it has been found that the conventional processing solutions described in the prior art documents have room for improvement in the following respects.

[0014] For example, the ruthenium etching methods described in Patent Documents 1 and 4 are intended to remove ruthenium residues adhering to the backside or bevel of a semiconductor substrate, and although they are capable of dissolving and removing ruthenium, they do not disclose precise etching of ruthenium, making it difficult to achieve. Furthermore, with the treatment solutions described in Patent Documents 1 and 4, it is difficult to maintain the flatness of the ruthenium surface after etching, which is desired in the wiring process. Furthermore, with these treatment solutions, it is difficult to accurately control the etching rate of ruthenium, making it difficult to perform precise etching of ruthenium. Therefore, the methods described in Patent Documents 1 and 4 are difficult to use as treatment solutions for ruthenium in the process of forming wiring for semiconductor elements.

[0015] Furthermore, the treatment solution described in Patent Document 2, like Patent Document 1, is a treatment solution targeted at etching residues containing ruthenium, and it is difficult to maintain the flatness of the ruthenium surface after etching, and it is also difficult to accurately control the etching rate of ruthenium, making it difficult to perform precise etching of ruthenium. Therefore, it is difficult to use it in a wiring formation process that requires precise etching of ruthenium.

[0016] In addition, the processing solution described in Patent Document 3 is described as etching ruthenium used in the manufacturing process of semiconductor elements, wiring, and barrier metals that are configured on substrates such as semiconductor wafers. However, like Patent Documents 1 and 4, the purpose is to clean substrates such as semiconductor wafers, and not for precision etching. Therefore, the processing solution described in Patent Document 3 When ruthenium was etched with the above-described treatment solution, the flatness of the ruthenium surface after etching was not maintained, and accurate control of the etching rate was difficult. Therefore, it was difficult to use the treatment solution described in Patent Document 3 in a wiring formation process that required precise etching of ruthenium, and there was room for further improvement.

[0017] Furthermore, the tungsten treatment solution described in Patent Document 5 is intended to remove tungsten adhering to the edge or back surface of a semiconductor wafer, but is not intended for precision etching. Similarly, the removal solution described in Patent Document 6 is intended to stably remove unwanted tungsten metal deposited or attached to a semiconductor substrate, but is not intended for precision etching. Therefore, when tungsten is etched with the treatment solution described in Patent Document 5 or Patent Document 6, the flatness of the tungsten surface after etching is not maintained, and accurate control of the etching rate is difficult. Therefore, it is difficult to use the treatment solution described in Patent Document 5 or Patent Document 6 in a wiring formation process that requires precise etching of tungsten, and further improvement is needed.

[0018] The chemical solution for etching molybdenum described in Patent Document 7 contains an oxidizing agent and an acid. The oxidizing agent disclosed in the examples of Patent Document 7 is hydrogen peroxide alone, which has the problem of a short solution life due to a self-decomposition reaction and an unstable etching rate. Another problem is that the flatness of the molybdenum after treatment is not maintained. Therefore, it is difficult to use the treatment solution described in Patent Document 7 in a wiring formation process that requires precise etching of molybdenum, and further improvement is needed.

[0019] Therefore, an object of the present invention is to provide a treatment liquid suitable for precision processing of transition metals, which can etch transition metals present on semiconductor wafers at an accurate etching rate and maintain the flatness of the transition metal surface after etching. [Means for solving the problem]

[0020] The present inventors have conducted extensive research to solve the above-mentioned problems. It is difficult to accurately control the etching rate with a treatment solution containing only hypohalite ions, and the smoothness of the transition metal surface after etching cannot be maintained. Therefore, the inventors have investigated components to be added to the treatment solution. As a result, they have found that adding a specific alkylammonium salt makes it possible to maintain the smoothness of the transition metal surface after etching and to control the etching rate, thereby completing the present invention.

[0021] That is, the present invention is configured as follows. Item 1: A processing solution for etching transition metals on a semiconductor wafer, (A) hypohalite ion or periodate ion, (B) an alkylammonium salt represented by the following formula (1): A processing solution for semiconductor wafers comprising:

[0022] [ka] (wherein a is an integer of 6 to 20, and R 1 , R 2 , R 3 are independently a hydrogen atom or an alkyl group having 1 to 20 carbon atoms, and X - is a bromine-containing ion. Item 2. The semiconductor wafer treating solution according to Item 1, wherein the (A) hypohalite ions or periodate ions are hypohalite ions. Item 3. The semiconductor wafer treating solution according to Item 1 or 2, wherein the hypohalite ions are hypobromite ions, and the concentration of the hypobromite ions is 0.0096 to 1.92 mass %. Item 4. The semiconductor wafer treatment solution according to Item 1 or 2, wherein the hypohalite ions are hypochlorite ions and hypobromite ions, the concentration of the hypochlorite ions is 0.05 to 20.0 mass %, and the concentration of the hypobromite ions is 0.0096 to 1.92 mass %. Item 5. The semiconductor wafer treating liquid according to any one of Items 1 to 4, wherein the concentration of the alkylammonium salt represented by the formula (1) (B) is 0.0001 to 10 mass %. Item 6. The semiconductor wafer treatment solution according to any one of Items 1 to 5, further comprising (C) at least one ammonium ion selected from the group consisting of tetramethylammonium ion, ethyltrimethylammonium ion, tetraethylammonium ion, tetrapropylammonium ion, and tetrabutylammonium ion. Item 7. The treatment solution for semiconductor wafers according to any one of Items 1 to 6, wherein the (A) hypohalite ions or periodate ions are hypohalite ions, and the pH at 25° C. is greater than 7 and less than 14.0. Item 8. The semiconductor wafer treating solution according to any one of Items 1 to 7, wherein the transition metal on the semiconductor wafer is a Group 6 metal or ruthenium. Item 9. The treating solution for semiconductor wafers according to any one of Items 1 to 8, further comprising chloride ions. Item 10. The semiconductor wafer treating solution according to any one of Items 1 to 9, further comprising chlorate ions. Item 11. The semiconductor wafer processing solution according to any one of Items 1 to 10, wherein the concentration of metals contained in the semiconductor wafer processing solution is 1 ppb or less by mass. Item 12. An etching method comprising the step of contacting a semiconductor wafer with the treating solution for semiconductor wafers according to any one of items 1 to 10. Item 13: A chemical solution for semiconductor wafers, comprising the following (A), (B), and (C): (A) at least one ammonium salt selected from the group consisting of tetramethylammonium bromide, ethyltrimethylammonium bromide, tetraethylammonium bromide, tetrapropylammonium bromide, and tetrabutylammonium bromide; (B) an alkylammonium salt represented by the following formula (1): (C) Metals with a concentration of 1 ppb or less by mass [ka] (wherein a is an integer of 6 to 20, and R 1 , R 2 , R 3 are independently a hydrogen atom or an alkyl group having 1 to 20 carbon atoms, and X - is a bromine-containing ion. Item 14 (A) A chemical solution containing at least one ammonium salt selected from the group consisting of tetramethylammonium bromide, ethyltrimethylammonium bromide, tetraethylammonium bromide, tetrapropylammonium bromide, and tetrabutylammonium bromide; (B) A method for producing a chemical solution for semiconductor wafers, comprising the step of mixing an alkylammonium salt represented by the following formula (1): [ka] (wherein a is an integer of 6 to 20, and R 1 , R 2 , R 3 are independently a hydrogen atom or an alkyl group having 1 to 20 carbon atoms, and X - is a bromine-containing ion. Item 15. The method for producing a chemical solution for semiconductor wafers according to Item 14, wherein the chemical solution for semiconductor wafers contains (C) a metal having a concentration of 1 ppb or less by mass. Item 16. A method for producing a solution containing tetramethylammonium bromide, ethyltrimethylammonium bromide, tetraethylammonium bromide, tetrapropylammonium bromide, or tetrabutylammonium bromide by mixing tetramethylammonium hydroxide, ethyltrimethylammonium hydroxide, tetraethylammonium hydroxide, tetrapropylammonium hydroxide, or tetrabutylammonium hydroxide with a solution containing bromide ions or a bromine-containing gas that generates bromide ions when dissolved in water. Item 16. A method for producing a treatment solution for semiconductor wafers, comprising the step of mixing the chemical solution for semiconductor wafers according to Item 13 with a solution containing hypochlorite ions. [Effects of the Invention]

[0023] The semiconductor wafer treatment solution of the present invention enables wet etching of transition metals in the process of forming semiconductor devices. Furthermore, the flatness of the transition metal surface after etching is maintained (surface roughness is reduced), and the etching rate of the transition metal can be accurately controlled by adjusting the oxidizing agent concentration, pH, and the type and / or concentration of the alkylammonium salt. Therefore, the semiconductor wafer treatment solution of the present invention is suitable for use in forming semiconductor devices having a multilayer wiring structure in which flatness of each layer is required.

[0024] The semiconductor wafer processing solution of the present invention provides excellent smoothness to the surface of transition metals after etching, and therefore can uniformly etch the surface of transition metals that come into contact with the processing solution without unevenness. In particular, the processing solution is suitable for semiconductor manufacturing, which requires precise etching of ruthenium at the level of several nanometers, and can be suitably used, for example, in the formation of semiconductor elements having wiring structures of 10 nm or less.

[0025] The mechanism by which the treatment solution of the present invention maintains the surface flatness of transition metals, particularly ruthenium or Group 6 metals, after etching is not entirely clear, but the following is thought to be the case. While the case where the transition metal is ruthenium will be described as an example, it is presumed that the surface flatness of other transition metals is maintained by a similar mechanism. That is, the alkylammonium ions contained in the alkylammonium salt contained in the treatment solution preferentially adsorb to areas of the ruthenium surface that are more susceptible to etching, forming a protective layer. This protective layer prevents contact with hypohalite ions, which oxidize and dissolve ruthenium, thereby reducing the etching rate of areas that are more susceptible to etching, and as a result, it is thought that ruthenium dissolution occurs more uniformly. Therefore, it is thought that it is possible to maintain the surface flatness of the ruthenium after etching compared to etching with a treatment solution containing only hypohalite ions. Furthermore, since the adsorption of alkylammonium ions onto the surface of ruthenium partially suppresses the etching of ruthenium, it is thought that the amount of alkylammonium ions adsorbed can be controlled by adjusting the type and concentration of alkylammonium ions, making it possible to accurately control the etching rate of ruthenium.

[0026] Furthermore, the semiconductor wafer processing solution of the present invention is capable of etching ruthenium at an etching rate of 10 Å / min or more. Furthermore, by controlling the oxidizing agent concentration, pH, and the type and / or concentration of alkylammonium salt, the etching rate of ruthenium can be adjusted as desired, and the etching amount can be controlled to a desired value. In other words, the processing solution of the present invention is a processing solution that can be suitably used for precision etching of ruthenium. [Brief explanation of the drawings]

[0027] [Figure 1] 1 is a schematic cross-sectional view showing an example of a wiring formation process in which the treatment liquid of the present invention can be suitably used. [Figure 2] 1 is a schematic cross-sectional view showing an example of a wiring formation process after treatment with the treatment liquid of the present invention. [Figure 3] 1 is a photograph (a drawing-substitute photograph) of the ruthenium surface after the etching treatment shown in Example 1, observed with an electron microscope at 100,000 magnifications. DETAILED DESCRIPTION OF THE INVENTION

[0028] (Semiconductor wafer processing liquid) The semiconductor wafer treatment liquid of the present invention (hereinafter also referred to as "treatment liquid") is a treatment liquid that maintains the flatness of the transition metal, particularly ruthenium or Group 6 metal, surface after etching treatment and enables accurate control of the etching rate of the transition metal, particularly ruthenium or Group 6 metal. Therefore, it is a treatment liquid that can be suitably used in semiconductor manufacturing processes, and more suitably used in wiring formation processes.

[0029] The transition metal to which the treatment solution of the present invention is applied may be a film formed by any method, but for example, in the semiconductor manufacturing process, a transition metal is formed on a semiconductor wafer by a known method such as CVD, ALD, sputtering, etc. The formed transition metal is etched with the treatment solution to form semiconductor wiring.

[0030] The transition metal contained in the wafer treated with the treatment solution of the present invention is not particularly limited, but examples of the transition metal include Ru, Rh, Ti, Ta, Co, Cr, Hf, Os, Pt, Ni, Mn, Cu, Zr, La, Mo, and W. Among these, Ru, W, Mo, and Cr are preferably used because treatment with the treatment solution of the present invention allows precise etching to be achieved and a surface with excellent flatness can be obtained.

[0031] In this specification, ruthenium (also referred to as Ru) is not limited to ruthenium metal, but may be any metal containing ruthenium. That is, ruthenium metal, ruthenium alloy, ruthenium oxide, etc. are referred to as ruthenium. In addition, tungsten (also referred to as W) is not limited to tungsten metal, but may be any metal containing tungsten. That is, tungsten metal, tungsten alloy, tungsten oxide, etc. are referred to as tungsten. In addition, molybdenum (also referred to as Mo) is not limited to molybdenum metal, but may be any metal containing molybdenum. That is, molybdenum metal, molybdenum alloy, molybdenum oxide, etc. are referred to as molybdenum. In addition, chromium (also referred to as Cr) is not limited to chromium metal, but may be any metal containing chromium. That is, chromium metal, chromium alloy, chromium oxide, etc. are referred to as chromium. In addition, in this specification, Group 6 metal refers to tungsten, molybdenum, and chromium.

[0032] Furthermore, the treatment solution of the present invention is capable of maintaining the flatness of the transition metal surface after etching. In the present invention, "the flatness of the transition metal surface is maintained after etching" means that the flatness of the etched transition metal surface does not substantially change before and after etching, or if it does change, it is within a range that is not problematic for practical use. Examples of cases in which the flatness of the transition metal surface is not maintained include cases in which etching causes pitting corrosion in the transition metal film or uneven etching (local unevenness), as well as cases in which the surface roughness of the metal surface increases. The flatness of the transition metal surface can be easily confirmed, for example, by observing and measuring the transition metal surface with a scanning electron microscope (SEM) or an atomic force microscope (AFM). Therefore, by observing and measuring the surface of a transition metal-containing wafer to be etched before and after the etching process using the above-mentioned evaluation method and comparing the results, it is possible to easily determine whether the flatness of the metal surface after etching is maintained.

[0033] 1 and 2 show an example of the wiring formation process. The wiring formation process will be explained using an example in which the transition metal is ruthenium or a Group 6 metal.

[0034] First, a substrate 1 made of a semiconductor (e.g., Si) is prepared. The prepared substrate is subjected to an oxidation process to form a silicon oxide film on the substrate. Then, an interlayer insulating film 2 made of a low-dielectric constant (Low-k) film is formed, and via holes are formed at predetermined intervals. After formation, a transition metal 3 is filled into the via holes by thermal CVD, and a transition metal film is then formed (Figure 1). This is then wet-etched using a processing solution to etch the transition metal film, forming transition metal wiring (Figure 2).

[0035] The treatment liquid of the present invention contains (A) hypohalite ions or periodate ions, and (B) an alkylammonium salt represented by the following formula (1).

[0036] [ka]

[0037] (wherein a is an integer of 6 to 20, and R 1 , R 2 , R 3 are independently a hydrogen atom or an alkyl group having 1 to 20 carbon atoms, and X - is a bromine-containing ion.

[0038] (A) Hypohalite ion, periodate ion In the present invention, hypohalite ions refer to hypochlorite ions, hypobromite ions, and hypoiodite ions. These may be used alone or in combination. Hypohalite ions etch transition metals as an oxidizing agent. The hypohalite ions used in the present invention may be added to the treatment solution by any method, but for example, hypohalite ions can be generated in the treatment solution by dissolving a hypohalite in a solvent. That is, hypochlorite ions can be generated by dissolving a hypochlorite in a solvent, and hypobromite ions can be generated by dissolving a hypobromite in a solvent. In addition, hypochlorite ions and hypobromite ions can be generated by blowing chlorine gas or bromine gas into the treatment solution, respectively. In addition, Hypochlorite ions or hypobromite ions can also be added to the treatment solution of the present invention by adding chlorine water or bromine water to the solvent.

[0039] In the present invention, periodate ions refer to orthoperiodate ions, metaperiodate ions, etc. Periodate ions act as an oxidizing agent to etch transition metals. The periodate ions used in the present invention may be added to the treatment solution by any method. These ions may be used alone or in combination. Counterions (cations) for the hypohalite ions and periodate ions are alkali metal ions, alkaline earth metal ions, and organic cations. Since alkali metal ions and alkaline earth metal ions, if remaining on semiconductor wafers, can adversely affect the semiconductor wafers (e.g., reducing the yield of semiconductor wafers), their incorporation ratio is preferably low, and in fact, they are preferably not present at all. Therefore, organic cations are preferred as counterions. Considering industrial production, the organic cation is preferably at least one ammonium ion selected from tetramethylammonium ion, tetraethylammonium ion, tetrapropylammonium ion, tetrabutylammonium ion, and ethyltrimethylammonium ion, with tetramethylammonium ion or ethyltrimethylammonium ion being particularly preferred. Therefore, by selecting tetramethylammonium ion or ethyltrimethylammonium ion as the counterion, sodium ion and calcium ion in the treatment solution can be reduced, and therefore, it is preferred that the treatment solution contain tetramethylammonium ion or ethyltrimethylammonium ion.

[0040] In the present invention, when the hypohalite ions are hypochlorite ions or hypoiodite ions, the hypochlorite ion concentration range or periodate ion concentration range is preferably 0.05 to 20 mass% relative to the total amount of the treatment solution. Within these ranges, the decrease in concentration due to decomposition of hypochlorite ions or periodate ions in the treatment solution is suppressed (hereinafter, the effect of suppressing the decomposition reaction of hypohalite ions or periodate ions in the treatment solution and suppressing the decrease in the hypohalite ion or periodate ion concentration is sometimes referred to as "good storage stability"). Transition metals can be etched at a high etching rate. If the hypochlorite ion, hypoiodite ion, or periodate ion concentration is greater than 20 mass%, storage stability may be impaired. Furthermore, if the hypochlorite ion or periodate ion concentration is less than 0.05 mass%, the transition metal etching rate tends to be slow, resulting in reduced production efficiency. Within the above concentration ranges, from the viewpoint of the etching rate of the transition metal and the storage stability of the treatment liquid, the concentration of hypochlorite ions, hypoiodite ions, or periodate ions is preferably 0.05 to 20 mass%, more preferably 0.1 to 15 mass%, more preferably 0.3 to 10 mass%, even more preferably 0.5 to 6 mass%, and particularly preferably 0.5 to 4 mass%. When the hypohalite ion is a hypobromite ion, the concentration range is preferably 0.0096 to 1.92 mass% relative to the total amount of the treatment solution. Within this range, a decrease in concentration due to decomposition of the hypobromite ion in the treatment solution can be suppressed, enabling transition metals to be etched at a high etching rate. If the hypobromite ion concentration is greater than 1.92 mass%, storage stability may deteriorate. Furthermore, if the hypobromite ion concentration is less than 0.0096 mass%, the etching rate of the transition metal tends to slow, resulting in a decrease in production efficiency. Within the above concentration range, from the viewpoints of the etching rate of the transition metal and the storage stability of the treatment solution, the hypobromite ion concentration is preferably 0.0096 to 1.92 mass%, more preferably 0.048 to 1.92 mass%, and even more preferably 0.096 to 0.96 mass%.

[0041] The concentration of hypohalite ions or periodate ions in the processing solution of the present invention can be calculated when the processing solution is produced, or can be confirmed by directly analyzing the processing solution. Examples of methods for directly analyzing the treatment solution include iodometric titration and methods for determining the concentration of hypohalite ions or periodate ions from the absorption spectrum of hypohalite ions or periodate ions measured with a spectrophotometer.

[0042] The treatment solution of the present invention containing hypohalite ions preferably has a pH greater than 7 and less than 14.0. If the pH of the treatment solution is less than 7, the hypohalite ion decomposition reaction is more likely to occur, resulting in a decrease in the hypohalite ion concentration. Therefore, to achieve storage stability of the treatment solution and stable and controllable transition metal etching rates, the pH of the treatment solution is preferably greater than 7 and less than 14.0, more preferably between 8 and 14.0, even more preferably between 8 and 13, and most preferably between 9 and 12.5. From the viewpoints of being stable within the above pH range, achieving a high transition metal etching rate, and facilitating the production of high-purity products suitable for semiconductor manufacturing, the hypohalite ions are preferably hypochlorite ions or hypobromite ions. For example, within the above range, the hypochlorite ion concentration is less likely to decrease during storage, and the treatment solution can exhibit sufficient transition metal etching performance even after storage for 15 days at 23°C in a dark place under an inert gas atmosphere. In the case of a treatment solution containing periodate ions, the pH is preferably 1 or more and 14.0 or less. The preferred pH range of the treatment solution containing periodate ions varies depending on the transition metal to be treated: when the transition metal is ruthenium, the pH is preferably 1 or more and 9 or less; when the transition metal is tungsten, the pH is preferably 4 or more and 14 or less; when the transition metal is molybdenum, the pH is preferably 6 or more and 14 or less; and when the transition metal is chromium, the pH is preferably 4 or more and 14 or less. In this specification, pH is the value at 25°C.

[0043] (B) Alkylammonium salt The treatment liquid of the present invention contains an alkylammonium salt.

[0044] The mechanism by which the treatment solution of the present invention can maintain the flatness of a transition metal surface after etching is thought to be as follows. Specifically, it is thought that the cations (alkylammonium ions) of the alkylammonium salt contained in the treatment solution are adsorbed on the transition metal surface at the polar group portion centered on the nitrogen atom. The alkyl group, which is the nonpolar group of the adsorbed cation, is positioned away from the transition metal surface, forming a hydrophobic protective layer on the transition metal surface. The formed protective layer prevents contact between the transition metal and the hypohalite ions or periodate ions contained in the treatment solution, resulting in a uniform, even etching of the transition metal, and it is thought that the flatness of the transition metal surface after etching is maintained.

[0045] The alkylammonium salt contained in the treatment liquid of the present invention is an alkylammonium salt represented by the following formula (1).

[0046] [ka] (wherein a is an integer of 6 to 20, and R 1 , R 2 , R 3are independently a hydrogen atom or an alkyl group having 1 to 20 carbon atoms, and X - is a bromine-containing ion.

[0047] The integer a in the above formula (1) represents the number of methylene groups. As long as the integer a is 6 to 20, it is not particularly limited and can be used. However, the integer a is preferably 6 to 15, and even more preferably 8 to 15. Alkylammonium salts having methylene groups within the aforementioned range are suitable for use because they adsorb to the transition metal surface and form an appropriate protective layer. Furthermore, the larger the integer a of the alkylammonium salt, the greater the amount of alkylammonium ions adsorbed to the transition metal surface, which tends to decrease the transition metal etching rate. Furthermore, a large integer a of the alkylammonium salt reduces the water solubility of the alkylammonium salt, which can cause particle generation in the processing solution and reduce the yield of semiconductor devices. On the other hand, the smaller the integer a of the alkylammonium salt, the less adsorbed to the transition metal surface, which tends to prevent the formation of an appropriate protective layer on the transition metal surface and prevent the transition metal surface from maintaining flatness after etching.

[0048] In addition, R in the above formula (1) 1 , R 2 , R 3 are independently a hydrogen atom or an alkyl group having 1 to 20 carbon atoms, and may be the same or different. 1 , R 2 , R 3 is preferably an alkyl group having 1 to 20 carbon atoms. 1 , R 2 , R 3 The number of carbon atoms in each of R is preferably equal to or smaller than the integer a. 1 , R 2 , R 3 It is more preferable that any one of the groups R is a methyl group. 1 , R 2 , R 3By using a methyl group for either of the above, a more uniform and dense protective layer is formed on the transition metal surface, and the flatness of the transition metal surface can be maintained after etching.

[0049] The alkylammonium salt represented by formula (1) contains bromine-containing ions. Here, the bromine-containing ions are ions containing bromine, such as bromite ions, bromate ions, perbromate ions, hypobromite ions, and bromide ions. The inclusion of an alkylammonium salt containing bromine-containing ions in the treatment solution improves the smoothness of the transition metal surface after etching. While the reason for this is not entirely clear, it is thought to be as follows: The alkylammonium salt dissociates partially or completely in the treatment solution, resulting in the presence of bromine-containing ions in the treatment solution. It is presumed that these bromine-containing ions are present to a certain extent on the transition metal surface in the treatment solution, and therefore it is presumed that it is possible to control to some extent the etching rate of the transition metal by hypohalite ions or periodate ions. It is presumed that reducing the etching rate of the transition metal can suppress surface roughness caused by etching.

[0050] Alkylammonium salts containing bromine-containing ions are more stable and easier to synthesize than alkylammonium salts containing chlorine-containing ions or fluorine-containing ions, making them industrially available at low cost and high purity. Furthermore, alkylammonium salts containing bromine-containing ions have the advantage of containing more alkylammonium ions per unit weight than those containing iodine-containing ions. Therefore, the alkylammonium salt contained in the treatment solution of the present invention contains bromine-containing ions.

[0051] Specific examples of alkylammonium salts represented by formula (1) that can be suitably used in the present invention include bromides such as n-octyltrimethylammonium bromide, decyltrimethylammonium bromide, dodecyltrimethylammonium bromide, tetradecyltrimethylammonium bromide, hexadecyltrimethylammonium bromide, octadecyltrimethylammonium bromide, didecyldimethylammonium bromide, didodecyldimethylammonium bromide, and ethyltrimethylammonium bromide ion; n-octyltrimethylammonium hypobromite, decyltrimethylammonium hypobromite, and dodecyltrimethylammonium hypobromite; hypobromite salts such as ammonium, tetradecyltrimethylammonium hypobromite, hexadecyltrimethylammonium hypobromite, octadecyltrimethylammonium hypobromite, didecyldimethylammonium hypobromite, and didodecyldimethylammonium hypobromite; Bromites such as n-octyltrimethylammonium bromite, decyltrimethylammonium bromite, dodecyltrimethylammonium bromite, tetradecyltrimethylammonium bromite, hexadecyltrimethylammonium bromite, octadecyltrimethylammonium bromite, didecyldimethylammonium bromite, and didodecyldimethylammonium bromite; n-octyltrimethylammonium bromate, decyltrimethylammonium bromate, dodecyltrimethylammonium bromate, tetradecyltrimethylammonium bromate, and hexadecyltrimethylammonium bromate; Examples include bromates such as decyltrimethylammonium, octadecyltrimethylammonium bromate, didecyldimethylammonium bromate, and didodecyldimethylammonium bromate; and perbromates such as n-octyltrimethylammonium perbromate, decyltrimethylammonium perbromate, dodecyltrimethylammonium perbromate, tetradecyltrimethylammonium perbromate, hexadecyltrimethylammonium perbromate, octadecyltrimethylammonium perbromate, didecyldimethylammonium perbromate, and didodecyldimethylammonium perbromate.

[0052] The amount of alkylammonium salt added is preferably in the range of 0.0001 to 10% by mass based on the total treatment solution. When the amount of alkylammonium salt added is within this range, the amount of adsorption of alkylammonium ions can be controlled by adjusting the type and concentration of alkylammonium ions, enabling accurate control of the transition metal etching rate. Furthermore, by adjusting the type and concentration of alkylammonium ions, a sufficient protective layer can be formed on the transition metal surface, maintaining the smoothness of the transition metal surface after etching. When alkylammonium salts are added, only one type may be added, or two or more types may be added. Even when multiple types of alkylammonium salts are added, accurate control of the transition metal etching rate is possible as long as the total amount of alkylammonium salts added is within the above range. The treatment solution of the present invention may contain metals (or metal ions, hereinafter, including metal ions) due to the addition of alkylammonium salts or the manufacturing process of the treatment solution. Specific examples of metals include lithium, sodium, potassium, aluminum, magnesium, calcium, chromium, manganese, iron, nickel, cobalt, copper, silver, cadmium, barium, zinc, and lead, as well as their ions. However, because these metals affect the stability of the alkylammonium salt, it is preferable that their presence be low. While the reason for this is unclear, it is thought that the metals act as catalysts to promote the decomposition reaction of alkyl groups in alkali. On the other hand, while a low metal content in the treatment solution is preferable, the presence of some metals makes it possible to maintain the flatness of the metal surface after etching (preventing surface roughness). Therefore, the metal content of any one metal selected from lithium, sodium, potassium, aluminum, magnesium, calcium, chromium, manganese, iron, nickel, cobalt, copper, silver, cadmium, barium, zinc, and lead is preferably 0.01 ppt to 1 ppb by mass, more preferably 1 ppt to 1 ppb, even more preferably 10 ppt to 500 ppt, and most preferably 100 ppt to 200 ppt. Furthermore, if these metals remain on semiconductor wafers, they have adverse effects on the semiconductor wafers (such as adverse effects on reduced semiconductor wafer yields). If the metal content exceeds 1 ppb, it is possible to reduce the metal content to 1 ppb or less by filtration, distillation, ion exchange, or other methods.

[0053] In the treatment liquid of the present invention, (A) hypohalite ions or periodate ions, (B The remainder, other than the alkylammonium salt represented by formula (1), (C) ammonium ions described in detail below, and other additives, is water. The water contained in the treatment solution of the present invention is preferably water from which metal ions, organic impurities, particles, etc. have been removed by distillation, ion exchange treatment, filtration, various adsorption treatments, etc., with pure water being more preferred and ultrapure water being most preferred. Such water can be suitably produced by methods widely known in the semiconductor manufacturing industry.

[0054] (C) Ammonium ion In the treatment liquid of the present invention, when hypohalite ions are added to the treatment liquid by, for example, dissolving a hypohalite in water, the counter ions of the hypohalite ions contained in the hypohalite will be contained in the treatment liquid.

[0055] Here, when the hypohalite is sodium hypochlorite, sodium ions are contained as counter ions in the treatment solution; when the hypohalite is calcium hypochlorite, calcium ions are contained as counter ions. The alkali metal ions and alkaline earth metal ions, such as sodium ions and calcium ions, have adverse effects on semiconductor wafers (such as reduced semiconductor wafer yield) if they remain on the semiconductor wafer. Therefore, it is preferable that they be present in small amounts in the treatment solution, and in fact, it is preferable that they are not contained at all. Therefore, organic ions are preferred as counter ions to hypohalite ions. In consideration of industrial production, the ammonium ion (C) that may be contained in the treatment solution of the present invention is preferably at least one ammonium ion selected from the group consisting of tetramethylammonium ion, ethyltrimethylammonium ion, tetraethylammonium ion, tetrapropylammonium ion, and tetrabutylammonium ion. Among these, tetramethylammonium ion and ethyltrimethylammonium ion are more preferred, with tetramethylammonium ion being particularly preferred because high-purity products are readily available industrially. Therefore, by selecting tetramethylammonium ion as the counter ion, sodium ions and calcium ions in the treatment solution can be reduced, so it is preferable that the treatment solution contains tetramethylammonium ion. Alternatively, tetramethylammonium ion may be separately contained as tetramethylammonium hydroxide. As mentioned above, tetramethylammonium ion and ethyltrimethylammonium ion are preferred as ammonium ions, but ethyltrimethylammonium ion is preferred from the viewpoint of safety in handling.

[0056] The (C) ammonium ion may also be a counter ion of the organic alkali added to the treatment liquid of the present invention. For example, when the organic alkali is tetramethylammonium hydroxide, ethyltrimethylammonium hydroxide, tetraethylammonium hydroxide, tetrapropylammonium hydroxide, or tetrabutylammonium hydroxide, the (C) ammonium ion will be any of the cations contained in the organic alkali, namely, tetramethylammonium ion, ethyltrimethylammonium ion, tetraethylammonium ion, tetrapropylammonium ion, and tetrabutylammonium ion.

[0057] In the present invention, the concentration of the ammonium ions is preferably in the range of 0.001 to 30% by mass based on the total mass of the processing solution. By ensuring that the concentration of ammonium ions falls within this range, the processing solution can be made to have excellent long-term storage stability. To further improve storage stability, the concentration of ammonium ions is more preferably 0.005 to 20% by mass, even more preferably 0.01 to 15% by mass, and particularly preferably 0.05 to 8% by mass.

[0058] In the present invention, for example, the tetramethylammonium ion is tetramethylammonium hydroxide. The ion exchange resin is prepared by passing an aqueous solution of hypochlorite ions through the ion exchange resin to exchange the ions into the tetramethylammonium ion type. Then, a solution containing hypochlorite ions is brought into contact with the ion exchange resin to exchange the cations contained in the solution for tetramethylammonium ions, thereby allowing the treatment solution to contain tetramethylammonium ions.

[0059] (anionic species) The treatment solution of the present invention may contain at least one anion species selected from halide ions, halite ions, and halide ions. Specific examples of the anion species include ClO3 - , BrO3 - , IO3 - Halide ions such as ClO2 - , BrO2- , IO2 - Haloid ions such as Cl - , Br - , I - The treatment solution may contain one or more of these anion species. When two or more anion species are contained, it is possible to use either a case where ions having the same oxidation number of halogen atoms are contained, such as two types of halide ions, or a case where ions having different oxidation numbers of halogen atoms are contained, such as one type of halite ion and one type of halide ion. The inclusion of anionic species in the processing solution can improve the stability of the alkylammonium bromide contained in the processing solution. Although the reason for this is unclear, when alkylammonium bromide is dissolved, bromide ions exist as counterions to the alkylammonium ions. Due to insufficient solubility, alkylammonium bromide may precipitate during storage. Therefore, adding anionic species that exchange with bromide ions as counterions is thought to be effective in stabilizing the alkylammonium ions in the processing solution. Among these, from the viewpoints of solubility in the treatment solution, ease of availability, cost, etc., it is preferable that the anion species contain halate ions and / or halide ions, and it is more preferable that the anion species contain chlorate ions and / or chloride ions.

[0060] The anion species used in the present invention can be generated by dissolving an acid or salt containing the anion species in the treatment solution. Examples of acids containing anion species include halogen acids such as chloric acid, bromic acid, and iodic acid; halogenous acids such as chlorous acid, bromous acid, and iodous acid; and hydrogen halides such as hydrogen chloride, hydrogen bromide, and hydrogen iodide. Examples of salts containing anion species include alkali metal salts, alkaline earth metal salts, and organic salts. Specific examples of alkali metal salts include potassium chloride, sodium chlorite, potassium bromide, sodium bromite, potassium iodide, and sodium iodite. Examples of organic salts include organic salts containing onium ions, such as quaternary alkylammonium salts such as tetramethylammonium chloride, tetramethylammonium bromide, and tetramethylammonium iodide. The hydrogen halides can also be generated by dissolving halogen gases such as chlorine gas, bromine gas, and iodine gas in water. Among these, it is preferable to use acids and organic salts containing anionic species because they do not contain metals that can reduce yields in semiconductor manufacturing, and even more preferable are organic salts containing onium ions such as quaternary alkylammonium salts in terms of industrial availability and ease of handling. Among organic salts, those that can be particularly preferably used in terms of stability, purity, and cost include tetramethylammonium chloride, tetramethylammonium bromide, tetramethylammonium iodide, ethyltrimethylammonium chloride, ethyltrimethylammonium bromide, ethyltrimethylammonium iodide, tetraethylammonium chloride, tetraethylammonium bromide, tetraethylammonium iodide, tetrapropylammonium chloride, tetrapropylammonium bromide, and tetrapropylammonium iodide.

[0061] The acid or salt containing the anion species used to generate the anion species in the treatment solution may be an industrially available salt, or may be prepared by a known method. A quaternary alkylammonium salt containing an anion species can be prepared by preparing an aqueous solution of tetramethylammonium hydroxide and blowing in chlorine, bromine, etc. Alternatively, a solution containing the quaternary alkylammonium salt of the anion species can also be prepared by contacting a tetramethylammonium hydroxide solution with a cation-exchange ion-exchange resin to convert the cations in the ion-exchange resin into tetramethylammonium ions, and then passing a halogen acid such as hydrochloric acid, bromic acid, or iodic acid through the resin to exchange the ions.

[0062] (anion species content) In the treatment solution of the present invention, the content of at least one of the anion species is 1 ppm by mass to 20% by mass. When the treatment solution of the present invention contains only one anion species, the content of that anion species in the treatment solution must be 1 ppm by mass to 20% by mass. When the treatment solution contains two or more anion species, the content of at least one of the anion species must be 1 ppm by mass to 20% by mass. By containing anion species in the treatment solution within the above range, the stability of the alkylammonium bromide contained in the treatment solution can be improved. The concentration of the anion species needs only to be sufficient to exchange counterions with bromide ions and stabilize the alkylammonium ions in the treatment solution. The concentration of the anion species is preferably 1 ppm by mass to 20% by mass, more preferably 10 ppm by mass to 10% by mass, even more preferably 0.1% by mass to 10% by mass, and most preferably 1% by mass to 10% by mass. When two or more of the above anion species are contained in the treatment solution, from the viewpoint of achieving both a sufficient etching rate, smoothness, and stability of the alkylammonium ions in the treatment solution, the anion species contained at a concentration of 1 ppm by mass to 20% by mass are preferably halide ions or halide ions. Furthermore, when two or more of the above anion species are contained, the content of other anion species other than the anion species within the above concentration range is not particularly limited and may be set appropriately depending on the type of metal species to be etched and the etching site, and the content of the other anion species may also be 1 ppm by mass to 20% by mass. If the content of the above anion species is too high, the etching rate tends to decrease and the effect of improving stability tends to decrease. Therefore, when two or more anion species are contained, the total content of the anion species is preferably 20% by mass or less, more preferably 10% by mass or less, and most preferably 5% by mass or less. The content of anionic species in the treated solution can be measured by ion chromatography, which allows identification and quantification of anionic species by appropriately selecting the type of column and conditions.

[0063] (Other additives) If desired, the processing solution of the present invention may contain other additives conventionally used in semiconductor processing solutions, provided that the addition does not impair the object of the present invention. For example, such additives may include acids, alkalis, metal corrosion inhibitors, water-soluble organic solvents, fluorine compounds, oxidizing agents, reducing agents, complexing agents, chelating agents, surfactants, antifoaming agents, and pH adjusters.

[0064] (Method of manufacturing the treatment liquid) The treatment solution of the present invention containing hypohalite ions can be produced by adding and mixing an alkylammonium salt with a hypohalite solution or an aqueous solution of a hypohalite salt containing hypohalite ions. The aqueous solution of hypohalite can be produced by dissolving a commercially available hypochlorite, such as sodium hypochlorite, calcium hypochlorite, or sodium hypobromite, in water, or by blowing chlorine or bromine gas into an aqueous alkaline solution, such as a sodium hydroxide solution or a tetramethylammonium hydroxide solution. Alternatively, for example, the counter ions of the hypohalite ions can be exchanged for tetramethylammonium ions by contacting an aqueous solution of sodium hypochlorite or sodium hypobromite with a tetramethylammonium-type ion exchange resin.

[0065] The treatment liquid of the present invention containing periodate ions can be produced by adding an alkylammonium salt to a periodic acid solution or an aqueous periodate solution containing periodate ions and mixing them together. The aqueous periodate solution can be produced by dissolving a commercially available periodate such as orthoperiodic acid, sodium orthoperiodate, potassium orthoperiodate, or sodium metaperiodate in water.

[0066] Hereinafter, the method for producing the treatment liquid of the present invention will be described in detail using the treatment liquid containing the hypochlorite aqueous solution in which the counter ions of hypochlorite ions are exchanged using ion exchange resin as an example.Specifically, the method is a method for producing the treatment liquid of the present invention by converting the sodium hypochlorite aqueous solution into the tetramethylammonium hypochlorite aqueous solution by ion exchange.

[0067] First, an aqueous solution containing tetramethylammonium ions, specifically an aqueous solution of tetramethylammonium hydroxide, is brought into contact with an ion exchange resin to prepare a tetramethylammonium-type ion exchange resin. The ion exchange resin used can be any known cation exchange resin without any particular limitation. For example, either a hydrogen-type ion exchange resin or a sodium-type ion exchange resin can be used. Among these, a hydrogen-type ion exchange resin, which is less likely to be contaminated with sodium, is preferred. Furthermore, even among hydrogen-type ion exchange resins, weakly acidic or strongly acidic ion exchange resins can be used without any particular limitation.

[0068] After preparing the tetramethylammonium-type ion exchange resin, an aqueous solution of tetramethylammonium hypochlorite can be produced by contacting the ion exchange resin with an aqueous solution of hypochlorite, for example, an aqueous solution of sodium hypochlorite. The aqueous sodium hypochlorite solution can be prepared by dissolving sodium hypochlorite in water.In addition, sodium hypochlorite is used here because it has good storage stability and easy handling, but calcium hypochlorite or the like can also be used as long as it is commercially available and easily available.Furthermore, it is more preferable to use sodium hypochlorite with a low sodium chloride content, since this can further reduce the amount of sodium mixed into the treatment solution after ion exchange.Such sodium hypochlorite is generally commercially available as low-salt sodium hypochlorite.

[0069] The ion exchange step may be repeated. By repeating the ion exchange step, it is possible to reduce metal ions such as sodium and calcium, which serve as counter ions of hypochlorite ions contained in the aqueous tetramethylammonium hypochlorite solution. The treatment liquid of the present invention containing tetramethylammonium ions can be produced by mixing and dissolving an alkylammonium salt and, if necessary, other additives in the obtained aqueous tetramethylammonium hypochlorite solution.

[0070] The hypobromite ions contained in the treatment solution of the present invention may be generated in the treatment solution. One method for generating hypobromite ions in the treatment solution is to oxidize a bromine-containing compound with an oxidizing agent. The ratio of the amount of the bromine-containing compound to the amount of the oxidizing agent contained in the treatment solution is determined based on the stoichiometric ratio and reaction rate when the bromine-containing compound reacts with the oxidizing agent to generate hypobromite ions, and the amount of Br contained in the treatment solution. - It is preferable to determine the ratio of the bromine-containing compound to the oxidizing agent in consideration of the stoichiometric ratio and reaction rate when the bromine-containing compound reacts with the oxidizing agent to generate hypobromite ions. However, in reality, since multiple factors have a complex influence on these reactions, it is difficult to determine an appropriate ratio of the bromine-containing compound to the oxidizing agent. However, if the ratio of the concentration of the bromine-containing compound divided by the chemical equivalent (molar equivalent) of the bromine-containing compound to the concentration of the oxidizing agent divided by the chemical equivalent (molar equivalent) of the bromine-containing compound is in the range of 0.001 to 100, the oxidizing agent can convert the bromine-containing compound to BrO. - Not only can it efficiently generate BrO - Br produced by the reduction or decomposition reaction of - Re Degrees BrO - Since the transition metal can be oxidized to a stable state, the etching rate of the transition metal is stabilized. For example, when the bromine-containing compound is tetramethylammonium bromide and the oxidizing agent is tetramethylammonium hypochlorite, the reaction equivalent (molar equivalent) of the bromine-containing compound is equal to the chemical equivalent (molar equivalent) of the oxidizing agent, and therefore the ratio of the molar concentration of the bromine-containing compound to the concentration of the oxidizing agent may be in the range of 0.001 to 100.

[0071] The ratio of hypobromite ions to hypochlorite ions contained in the treatment solution is determined by the rate of reduction of hypobromite ions, or more precisely, the rate of reduction and / or decomposition of hypobromite ions. - The rate at which Br is produced and the rate at which Br is produced by hypochlorite ions - From BrO -However, in reality, since these reactions are affected by a number of factors in a complex manner, it is difficult to determine an appropriate ratio of hypobromite ions to hypochlorite ions. However, if the ratio of the molar concentration of hypobromite ions to the molar concentration of hypochlorite ions (molar concentration of hypobromite ions / molar concentration of hypochlorite ions) is in the range of 0.001 to 100, BrO - Br produced by the reduction or decomposition reaction of - is converted again to BrO by hypochlorite ions. - This stabilizes the etching rate of the transition metal.

[0072] (bromine-containing compounds) The bromine-containing compound used in the treatment solution of the present invention may be any compound that contains a bromine atom and is oxidized by an oxidizing agent (described below) to produce bromine, hypobromous acid, hypobromite ions, bromous acid, bromite ions, bromic acid, bromate ions, perbromic acid, perbromate ions, or bromide ions. For example, it is preferable to use at least one compound selected from the group consisting of bromine salts and hydrogen bromide. The hydrogen bromide referred to here may be hydrogen bromide gas or hydrobromic acid, which is an aqueous solution of hydrogen bromide. Examples of bromine salts include lithium bromide, sodium bromide, potassium bromide, rubidium bromide, cesium bromide, ammonium bromide, and onium bromide. The onium bromide referred to here is a compound formed from an onium ion and a bromide ion. An onium ion is a polyatomic cation formed by the addition of an excess proton (hydrogen cation) to a monoatomic anion. Specific examples of cations include imidazolium ions, pyrrolidinium ions, pyridinium ions, piperidinium ions, ammonium ions, phosphonium ions, fluoronium ions, chloronium ions, bromonium ions, iodonium ions, oxonium ions, sulfonium ions, selenonium ions, telluronium ions, arsonium ions, stibonium ions, and bismuthonium ions. Compounds that generate hypobromous acid or hypobromous acid ions in the treatment solution can also be used as bromine-containing compounds. Examples of such compounds include, but are not limited to, bromohydantoins, bromoisocyanuric acids, bromosulfamic acids, and bromochloramines. More specific examples of compounds include 1-bromo-3-chloro-5,5-dimethylhydantoin, 1,3-dibromo-5,5-dimethylhydantoin, and tribromoisocyanuric acid.

[0073] The bromine-containing compound may be added to the treatment solution as hydrogen bromide or a bromine salt, as a solution containing a bromine salt, or as bromine gas. For ease of handling in the semiconductor manufacturing process, the bromine-containing compound is preferably mixed with other treatment solutions as a bromine salt, a solution containing a bromine salt, or hydrogen bromide. The treatment solution may contain one type of bromine-containing compound, or two or more types may be used in combination. In semiconductor manufacturing, contamination with metals or metal ions causes a decrease in yield, so it is desirable that the bromine-containing compound does not contain metals. Among bromine gas, hydrogen bromide, and bromine salts, onium bromide is substantially free of metals and can therefore be suitably used as the bromine-containing compound of the present invention. Among onium bromides, quaternary onium bromides and bromine salts are particularly preferred. Tertiary onium compounds and hydrogen bromide are more suitable as the bromine-containing compound of the present invention because they are easily available industrially and are easy to handle.

[0074] The quaternary onium bromide is a bromide salt consisting of an ammonium ion or a phosphonium ion that can exist stably in the treatment solution. Examples of the quaternary onium bromide include tetramethylammonium bromide, ethyltrimethylammonium bromide, tetraethylammonium bromide, tetrapropylammonium bromide, tetrabutylammonium bromide, tetrapentylammonium bromide, tetrahexylammonium bromide, methyltriethylammonium bromide, diethyldimethylammonium bromide, trimethylpropylammonium bromide, butyltrimethylammonium bromide, trimethylnonylammonium bromide, decyltrimethylammonium bromide, tetradecyltrimethylammonium bromide, hexadecyltrimethylammonium bromide, trimethylstearylammonium bromide, decamesonium bromide, phenyltrimethylammonium bromide, benzyltrimethylammonium bromide, dimethylpyrrolidinium bromide, dimethylpiperidium bromide, 1-butyl-3-methylimidazolium bromide, and 1-butyl-3-methylpyridinium bromide. Compounds in which a proton is added to a tertiary amine, secondary amine, or primary amine can also be used. Examples include methylamine hydrobromide, dimethylamine hydrobromide, ethylamine hydrobromide, diethylamine hydrobromide, triethylamine hydrobromide, 2-bromoethylamine hydrobromide, 2-bromoethyldiethylamine hydrobromide, ethylenediamine dihydrobromide, propylamine hydrobromide, butylamine hydrobromide, tert-butylamine hydrobromide, neopentylamine hydrobromide, 3-bromo-1-propylamine hydrobromide, dodecylamine hydrobromide, cyclohexanamine hydrobromide, and benzylamine hydrobromide. Examples of quaternary phosphonium bromides include tetramethylphosphonium bromide, tetraethylphosphonium bromide, tetrapropylphosphonium bromide, tetrabutylphosphonium bromide, tetraphenylphosphonium bromide, methyltriphenylphosphonium bromide, phenyltrimethylphosphonium bromide, and methoxycarbonylmethyl(triphenyl)phosphonium bromide. Tertiary onium bromides are bromine salts consisting of sulfonium ions that can exist stably in the treatment solution.Examples of tertiary sulfonium bromides include trimethylsulfonium bromide, triethylsulfonium bromide, tripropylsulfonium bromide, tributylsulfonium bromide, triphenylsulfonium bromide, and (2-carboxyethyl)dimethylsulfonium bromide. Among these, quaternary onium bromides, which are bromide salts consisting of ammonium ions, are preferred because they are highly stable, highly pure products are readily available industrially, and are inexpensive.

[0075] The quaternary onium bromide is preferably a tetraalkylammonium bromide, which is particularly stable and can be easily synthesized. In the tetraalkylammonium bromide, the number of carbon atoms in the alkyl group is not particularly limited, and the four alkyl groups may have the same or different carbon atoms. As such alkylammonium bromides, tetraalkylammonium bromides having 1 to 20 carbon atoms per alkyl group are preferably used. Among these, tetraalkylammonium bromides having a small number of carbon atoms in the alkyl group are more preferably used because they have a large number of bromine atoms per weight. Examples include tetramethylammonium bromide, tetraethylammonium bromide, tetrapropylammonium bromide, tetrabutylammonium bromide, tetrapentylammonium bromide, and tetrahexylammonium bromide. Among these, tetramethylammonium bromide, tetraethylammonium bromide, tetrapropylammonium bromide, and tetrabutylammonium bromide are preferred, with tetramethylammonium bromide being the most preferred. The treatment solution may contain one or more bromine-containing compounds.

[0076] The tetraalkylammonium bromide used in the present invention may be a commercially available tetraalkylammonium bromide, or a mixture of tetraalkylammonium and bromide ions. Tetraalkylammonium bromide can be produced by mixing an aqueous solution containing tetraalkylammonium hydroxide with an aqueous solution containing bromide ions or a bromine-containing gas that generates bromide ions when dissolved in water. Examples of tetraalkylammonium hydroxides used to produce tetraalkylammonium bromide include tetramethylammonium hydroxide, tetraethylammonium hydroxide, tetrapropylammonium hydroxide, tetrabutylammonium hydroxide, etc. Among these, tetramethylammonium hydroxide is more preferred because it has a large number of hydroxide ions per unit weight and is readily available as a high-purity product. Examples of bromide ion sources that generate bromide ions used to produce tetraalkylammonium bromide include hydrogen bromide, lithium bromide, sodium bromide, potassium bromide, rubidium bromide, cesium bromide, and ammonium bromide. Among these, hydrogen bromide is preferred because it is substantially free of metals, is readily available industrially, and high-purity products are readily available. Examples of bromine-containing gases that generate bromide ions when dissolved in water include hydrogen bromide gas.

[0077] The amount of the bromine-containing compound added is not particularly limited, and may be determined in consideration of the etching rate of the transition metal, the stability of the treatment solution, the solubility of the bromine-containing compound, cost, etc. The bromine-containing compound added to the treatment solution is oxidized by an oxidizing agent described later to produce chemical species effective for etching the transition metal, specifically, bromine, hypobromous acid (HBrO), hypobromite ion (BrO - ), bromous acid (HBrO2), bromous acid ion (BrO2 - ), bromic acid (HBrO3), bromate ion (BrO3 - ), perbromic acid (HBrO4), perbromate ion (BrO4 - ), bromide ion (Br - ) Among the chemical species effective for etching the above transition metals, HBrO, BrO -, HBrO2, BrO2 - , HBrO3, BrO3 - Since the etching rate of transition metals is high in a treatment solution containing these chemical species, it is preferable that the treatment solution contains these chemical species. - (Hereinafter, BrO - A treatment solution containing a large amount of transition metals (sometimes referred to as "transition metals") is more preferable in that it can shorten the treatment time because it has a particularly high etching rate for transition metals. Therefore, when the bromine-containing compound is oxidized with an oxidizing agent, the bromine atoms contained in the bromine-containing compound are oxidized with an oxidizing agent such as HBrO, BrO - , HBrO2, BrO2 - , HBrO3, BrO3 - It is preferred to oxidize it to BrO - It is preferable to oxidize it to the above.

[0078] When the treatment solution of the present invention contains a bromine-containing compound, an oxidizing agent, a base compound, and water, the treatment solution may be a single solution, or may be a mixture of two or more treatment solutions or chemical solutions. When the treatment solution is a single solution, it contains all of the bromine-containing compound, the oxidizing agent, the base compound, and the alkylammonium salt represented by formula (1). The treatment solution may be produced by mixing two or more treatment solutions or chemical solutions. When the treatment solution or chemical solution is two or more solutions, the treatment solution or chemical solution contains at least one of the bromine-containing compound, the oxidizing agent, the base compound, and water. It may also contain other components, as described below. Whether the treatment solution is a single solution or a mixture of two or more treatment solutions or chemical solutions, the simultaneous presence of the bromine-containing compound, the oxidizing agent, and the base compound in the treatment solution allows the bromine-containing compound to be oxidized by the oxidizing agent, generating chemical species that etch transition metals. When preparing a treatment solution by mixing two or more treatment solutions or chemical solutions, it is preferable to separate the chemical solution containing the bromine-containing compound and the alkylammonium salt from the treatment solution containing the oxidizing agent. By separating the bromine-containing compound and the alkylammonium salt from the oxidizing agent, oxidation of the bromine-containing compound and the alkylammonium salt by the oxidizing agent can be prevented, and the treatment solution of the present invention can be stored stably.

[0079] The chemical solution and the processing solution are mixed by a method widely known as a method for mixing semiconductor chemical solutions. For example, a method using a mixing tank, a method of mixing within the piping of a semiconductor manufacturing device (in-line mixing), a method of mixing by simultaneously pouring a plurality of liquids onto a wafer, etc. can be suitably used. When preparing a treatment solution by mixing a chemical solution and a treatment solution, the chemical solution and treatment solution can be mixed at any time. If the oxidation of the bromine-containing compound requires time, the chemical solution and treatment solution can be mixed before etching the transition metal, allowing time for the generation of chemical species that etch the transition metal. In this case, if the oxidation of the bromine-containing compound requires time, it can become a bottleneck in the production line, resulting in reduced throughput. For these reasons, the shorter the time required for oxidation, the better, and preferably one hour or less. The time required for oxidation of the bromine-containing compound can be controlled by appropriately selecting the oxidizing agent concentration, the bromine-containing compound concentration, the pH of the treatment solution, the temperature of the treatment solution, the stirring method of the treatment solution, and the like. Furthermore, if the concentration of the chemical species that etch the transition metal is low, the lifetime of the treatment solution may be short, making it difficult to control the production process. In such cases, it is preferable to mix the chemical solution and treatment solution immediately before transition metal etching. Therefore, when mixing a chemical solution and a treatment solution, it is preferable to mix a solution (treatment solution) containing an oxidizing agent and a basic compound with a chemical solution containing a bromine-containing compound and an alkylammonium salt, and it is more preferable to mix a solution (treatment solution) containing hypochlorite ions and a basic compound with a chemical solution containing a bromine-containing compound and an alkylammonium salt.The solution (treatment solution) containing hypochlorite ions and a basic compound is preferably alkaline. In the mixing of the chemical solution and the treatment solution of the present invention, the pH of the treatment solution after mixing is preferably alkaline. Specifically, the pH of the treatment solution is preferably greater than 7 and less than 14. If the pH of the chemical solution or treatment solution before mixing is lower than 7, the concentrations of the basic compound and / or water are adjusted so that the pH of the treatment solution (containing the bromine-containing compound, oxidizing agent, basic compound, and water) after mixing is greater than 7 and less than 14. In this way, by maintaining the pH of the treatment solution after mixing at greater than 7 and less than 14, the bromine-containing compound is rapidly converted by the oxidizing agent into a chemical species that etches the transition metal, enabling stable and sufficient etching of the transition metal film.

[0080] When a chemical solution and a treatment solution are mixed to generate chemical species that etch transition metals, the pH of the mixed chemical solution and treatment solution may be the same or different. When the pH of the chemical solution and treatment solution is the same, the pH of the treatment solution after mixing does not change significantly, and the treatment solution can be suitably used as an etching solution for transition metals. When a chemical solution and a treatment solution are mixed to generate chemical species that etch transition metals, the composition after mixing (bromine-containing compound concentration, oxidizing agent concentration, basic compound concentration, pH) should be within the above-mentioned ranges, and the mixing method, such as the mixing ratio and mixing order of the chemical solution and treatment solution to be mixed, is not particularly limited. However, for example, when an alkaline solution containing a hypochlorous acid compound is mixed with an acidic solution containing a bromine-containing compound and an alkylammonium salt, there is a risk that the decomposition of the hypochlorous acid compound will progress locally. In this case, it is preferable to mix an acidic solution containing a bromine-containing compound and an alkylammonium salt with an alkaline solution containing a hypochlorous acid compound. The chemical species that etch transition metals, which are produced when bromine-containing compounds are oxidized by an oxidizing agent, vary depending on the pH and oxidation-reduction potential (ORP) of the treatment solution, but are mainly bromine, bromide ions, hypobromous acid, bromous acid, bromic acid, perbromic acid, and their ions.

[0081] (oxidizing agent) The oxidizing agent used in the treatment solution of the present invention has the function of oxidizing bromine-containing compounds and generating chemical species effective for etching transition metals. Specific examples of oxidizing agents include nitric acid, sulfuric acid, persulfuric acid, peroxodisulfuric acid, hypochlorous acid, chlorous acid, chloric acid, perchloric acid, hypobromous acid, bromous acid, bromic acid, perbromic acid, hypoiodous acid, iodous acid, iodic acid, periodic acid, salts thereof, and ions generated by dissociation of these salts, as well as hydrogen peroxide, ozone, fluorine, chlorine, bromine, iodine, permanganate, chromate, dichromate, and cerium salts. These oxidizing agents may be used alone or in combination. When adding these oxidizing agents to the treatment solution of the present invention, a suitable oxidizing agent may be selected from solid, liquid, and gaseous forms depending on the properties of the oxidizing agent used. Of the above oxidizing agents, hypochlorous acid, chlorous acid, chloric acid, perchloric acid, hypobromous acid, bromous acid, bromic acid, perbromic acid, hypoiodous acid, iodous acid, iodic acid, periodic acid, salts thereof, ions generated by dissociation of these salts, ozone, or hydrogen peroxide are preferred because they can exist stably even in alkaline conditions; hypochlorous acid, chlorous acid, chloric acid, perchloric acid, hypobromous acid, bromous acid, bromic acid, perbromic acid, salts thereof, ions generated by dissociation of these salts, ozone, or hydrogen peroxide are more preferred; hypochlorite ion or ozone are even more preferred; and hypochlorite ion is most preferred. The use of hypochlorous acid, its salt tetraalkylammonium hypochlorite, or ozone as the oxidizing agent can substantially prevent metal contamination, making it suitable as a processing solution for semiconductor manufacturing. Among these, tetraalkylammonium hypochlorite is particularly suitable because it exists stably even in an alkaline solution and can efficiently oxidize the bromine-containing compounds.

[0082] The concentration of the oxidizing agent is not particularly limited, and it is sufficient to add an amount that can oxidize the bromine-containing compound to a chemical species that is effective in etching transition metals. The amount of the oxidizing agent added is preferably 0.1 ppm by mass or more and 10% by mass or less. If the amount of the oxidizing agent added is less than 0.1 ppm by mass, the bromine-containing compound cannot be efficiently oxidized, and the etching rate of the transition metal decreases. That is, a composition without the oxidizing agent will have a low etching rate. On the other hand, if the amount of the oxidizing agent added is more than 10% by mass, the stability of the oxidizing agent decreases, which is not appropriate. When the transition metal is ruthenium, from the viewpoint of suppressing the generation of RuO4 gas and increasing the etching rate of ruthenium, the concentration of the oxidizing agent is more preferably 1 ppm by mass or more and 5% by mass or less, and most preferably 0.5% by mass or more and 4% by mass or less. The pH of the solution containing an oxidizing agent is not particularly limited, but is preferably greater than 7 and less than 14, and more preferably between 10 and 13. A solution within this pH range can minimize the decrease in pH that occurs when the solution containing the bromine-containing compound and the solution containing the oxidizing agent are mixed, making it possible to stably produce, store, and use the treatment solution of the present invention. When the pH of the solution containing an oxidizing agent is set to less than 8, the pH and volume of the solution containing the oxidizing agent can be adjusted so that the pH of the treatment solution after mixing the solution containing the bromine-containing compound and the solution containing the oxidizing agent becomes alkaline.

[0083] (Method of manufacturing chemical solution) The chemical solution containing the bromine-containing compound and alkylammonium salt can be produced by adding and mixing an alkylammonium salt with an aqueous solution containing tetramethylammonium bromide, ethyltrimethylammonium bromide, tetraethylammonium bromide, tetrapropylammonium bromide, or tetrabutylammonium bromide. An aqueous solution containing tetramethylammonium bromide, ethyltrimethylammonium bromide, tetraethylammonium bromide, tetrapropylammonium bromide, or tetrabutylammonium bromide can be produced by dissolving commercially available tetramethylammonium bromide, tetraethylammonium bromide, tetrapropylammonium bromide, or tetrabutylammonium bromide in water, or by adding an aqueous solution of tetramethylammonium hydroxide, ethyltrimethylammonium hydroxide, tetraethylammonium hydroxide, tetrapropylammonium hydroxide, or tetrabutylammonium hydroxide to hydrobromic acid. Among these, adding an aqueous solution of tetramethylammonium hydroxide to hydrobromic acid to produce tetramethylammonium bromide is more preferred because high-purity products are readily available.

[0084] (Transition Metal Etching Method) The conditions for using the treatment solution of the present invention may be appropriately determined according to the etching conditions of the etching device to be used, etc. For example, the treatment temperature may be 10 to 80°C, and more preferably in the range of 20 to 70°C.

[0085] Furthermore, the etching rate of transition metals varies depending on the temperature. Therefore, to improve the etching rate of transition metals, a temperature of 40 to 70°C should be selected from the above temperature range. A temperature range of 40 to 70°C allows for a high etching rate and allows for easy operation even with a simple device.

[0086] The time for using the treatment solution of the present invention is 0.1 to 120 minutes, preferably 0.5 to 60 minutes, and can be appropriately selected depending on the etching conditions and the semiconductor device used. After using the treatment solution of the present invention, an organic solvent such as alcohol can be used as a rinse solution, but simply rinsing with deionized water is sufficient. If alkylammonium salt remains on the wafer surface after the rinsing, it is preferable to clean it with an acid such as hydrochloric acid, formic acid, acetic acid, sulfuric acid, nitric acid, hydrofluoric acid, citric acid, or oxalic acid, or a mixture of ammonia water and hydrogen peroxide, a mixture of hydrochloric acid and hydrogen peroxide, ozone water, a mixture of sulfuric acid and hydrogen peroxide, or a mixture of hydrofluoric acid and ammonium fluoride. These cleaning methods may also be used in combination. Alternatively, the alkylammonium salt can be removed by heating the wafer to a temperature at which it evaporates.

[0087] As described above, the treatment solution of the present invention can achieve an etching rate of transition metals of 10 Å / min or more, preferably 30 Å / min or more, and can provide excellent smoothness of the transition metal surface after etching. The treatment solution of the present invention can be suitably used when a transition metal, particularly ruthenium, tungsten, molybdenum, or chromium, is used in a semiconductor device formation process. [Example]

[0088] The present invention will be explained in more detail below with reference to examples, but the present invention is not limited to these examples.

[0089] (pH measurement method) 30 mL of the treatment solution prepared in the examples and comparative examples was measured using a tabletop pH meter (LAQUA F The pH was measured using a pH analyzer (Horiba, Ltd.) after the treatment solution was prepared and stabilized at 25°C.

[0090] (Calculation method for hypohalite ion concentration and periodate ion concentration) The hypohalite ion concentration or periodate ion concentration was measured using an ultraviolet-visible spectrophotometer (UV-2600, manufactured by Shimadzu Corporation). A calibration curve was prepared using an aqueous solution of hypohalite ion or periodate ion with a known concentration, and the concentration of hypohalite ion or periodate ion in the produced treatment solution was determined.

[0091] (Calculation method for tetramethylammonium ion concentration) The tetramethylammonium ion concentration in the treatment solution of the examples and comparative examples was calculated from the pH, hypochlorite ion concentration, and sodium ion concentration, which was measured by ICP-MS (inductively coupled plasma mass spectrometry).

[0092] (Calculation method of etching rate of transition metal) An oxide film was formed on a silicon wafer using a batch-type thermal oxidation furnace, and a transition metal film was then formed on the oxide film using a sputtering method. When the transition metal was ruthenium, the ruthenium was deposited to a thickness of 1200 Å (±10%). When the transition metal was ruthenium dioxide, the ruthenium dioxide was deposited to a thickness of 100 A film of 0 Å (±10%) was formed. When the transition metal was tungsten, a tungsten film of 8000 Å (±10%) was formed. When the transition metal was molybdenum, a molybdenum film of 1000 Å (±10%) was formed. When the transition metal was chromium, a chromium film of 1000 Å (±10%) was formed. The sheet resistance was measured using a four-probe resistance meter (Loresta-GP, Mitsubishi Chemical Analytech Co., Ltd.) and converted to film thickness. After the etching process, the sheet resistance was also measured using the four-probe resistance meter and converted to film thickness, which was used as the film thickness of the transition metal after the etching process. The difference in film thickness of the transition metal after the etching process and the film thickness before the etching process was used as the film thickness change before and after the etching process.

[0093] 30 mL of the treatment solution from the Examples and Comparative Examples was prepared in a fluororesin container with a lid (manufactured by AsOne, PFA container 94.0 mL), and each sample piece measuring 10 × 20 mm was immersed in the treatment solution at 23°C for 1 minute. The etching rate was calculated by dividing the change in film thickness before and after treatment by the immersion time.

[0094] The time required to etch the transition metal by 50 ű10 Šwas calculated from the calculated etching rate, and after etching the transition metal film for that time, the transition metal surface was observed using a field emission scanning electron microscope (FE-SEM) at 100,000x magnification. If surface roughness was observed, the result was rated as poor (C), if slight surface roughness was observed, it was rated as good (B), and if no surface roughness was observed, it was rated as excellent (A).

[0095] Example 1 (Manufacturing of processing liquid) <Pretreatment of ion exchange resin: Preparation of hydrogen-type ion exchange resin> 200 mL of sodium-type strongly acidic ion exchange resin (Amberlite IR-120BNa, Organo Corporation) was placed in a glass column (AsOne Biocolumn CF-50TK) with an inner diameter of approximately 45 mm. Then, 1 L of 1N hydrochloric acid (Wako Pure Chemical Industries, Ltd., for volumetric analysis) was passed through the ion exchange resin column to exchange it for hydrogen type, and 1 L of ultrapure water was passed through to wash the ion exchange resin.

[0096] <(a) Process> Furthermore, 1 L of 10% by mass tetramethylammonium hydroxide solution was passed through 209 mL of the hydrogen-type ion exchange resin to exchange the hydrogen-type ion into the tetramethylammonium type. After the ion exchange, 1 L of ultrapure water was passed through the ion exchange resin to wash it.

[0097] <(b) Process> 69 g of sodium hypochlorite pentahydrate (Wako Pure Chemical Industries, Ltd., special grade reagent) was placed in a 2 L fluororesin container, and 931 g of ultrapure water was added to prepare a 3.11 mass % sodium hypochlorite aqueous solution. The prepared sodium hypochlorite aqueous solution was passed through an ion exchange resin exchanged to a tetramethylammonium form, yielding 1,000 g of tetramethylammonium hypochlorite aqueous solution. 100 mg of tetradecyltrimethylammonium bromide (Tokyo Chemical Industry Co., Ltd., purity >98%) was added to 999.9 g of the obtained tetramethylammonium hypochlorite aqueous solution, yielding a treatment solution with the composition listed in Table 1.

[0098] <Evaluation> The pH of the treatment solution immediately after production, the etching rate of ruthenium, and the concentration of hypochlorite ions were evaluated. The evaluation of the etching rate of ruthenium was carried out using the above-mentioned "Method for calculating the etching rate of transition metals." From the calculated etching rate, the time required to etch ruthenium to 50 ű10 Šwas calculated, and a ruthenium film treated for the time required to etch 50 ű10 Šwas prepared as a ruthenium film for surface observation. The surface of the ruthenium film for surface observation was measured using a 1000 The results are shown in Figure 3.

[0099] <Example 2> In Example 1, the amount of ion exchange resin in step (a) was 564 mL, the amount of 10% by mass tetramethylammonium hydroxide solution passed through was 2 L, and the concentration of the sodium hypochlorite aqueous solution in step (b) was 8.39% by mass to obtain a tetramethylammonium hypochlorite aqueous solution. Furthermore, in the pH adjustment step (c), a 25% by mass tetramethylammonium hydroxide (TMAH) solution was added to the tetramethylammonium hypochlorite aqueous solution until the pH reached 11. 1 g of decyltrimethylammonium bromide (manufactured by Tokyo Chemical Industry Co., Ltd., purity >99%) was added to 999 g of the obtained tetramethylammonium hypochlorite aqueous solution to obtain a treatment solution with the composition shown in Table 1. The evaluation results are shown in Table 2.

[0100] Example 3 In Example 3, a treatment solution was prepared in the same manner as in Example 2 so as to have the composition shown in Table 1, except that dodecyltrimethylammonium bromide (manufactured by Tokyo Chemical Industry Co., Ltd., purity >98%) was used as the alkylammonium salt represented by formula (1), and evaluation was carried out using a ruthenium film (sample piece) prepared in the same manner as in Example 1.

[0101] Example 4 In Example 4, a treatment solution was prepared in the same manner as in Example 2 so as to have the composition shown in Table 1, except that octadecyltrimethylammonium bromide (manufactured by Tokyo Chemical Industry Co., Ltd., purity >98%) was used as the alkylammonium salt represented by formula (1), and evaluation was carried out using a ruthenium film (sample piece) prepared in the same manner as in Example 1.

[0102] <Example 5> In Example 5, a treatment solution was prepared in the same manner as in Example 1 so as to have the composition shown in Table 1, except that n-octyltrimethylammonium bromide (manufactured by Tokyo Chemical Industry Co., Ltd., purity >98%) was used as the alkylammonium salt represented by formula (1), and evaluation was carried out using a ruthenium film (sample piece) prepared in the same manner as in Example 2.

[0103] Example 6 The same procedure as in Example 1 was carried out to obtain an aqueous solution of tetramethylammonium hypochlorite. Then, as a pH adjustment step (c), a glass column filled with 50 mL of a strongly acidic sodium-type ion exchange resin (Amberlite IR-120BNa, manufactured by Organo Corporation) was used. The tetramethylammonium hypochlorite aqueous solution was passed through a filter. 100 mg of tetradecyltrimethylammonium bromide was added to 999.9 g of the obtained tetramethylammonium hypochlorite aqueous solution to obtain a treatment liquid having the composition shown in Table 1. The evaluation results are shown in Table 2.

[0104] Example 7 In Example 7, a treatment solution was prepared in the same manner as in Example 2 so as to have the composition shown in Table 1, except that hexadecyltrimethylammonium bromide (manufactured by Tokyo Chemical Industry Co., Ltd., purity >98%) was used as the alkylammonium salt represented by formula (1), and evaluation was carried out using a ruthenium film (sample piece) prepared in the same manner as in Example 1.

[0105] Example 8 In Example 8, water and 25% by mass tetramethylammonium hydroxide were added to sodium hypochlorite pentahydrate (Wako Pure Chemical Industries, Ltd., special grade reagent) so that the hypochlorite ion concentration was 2.15% by mass. 1 g of tetradecyltrimethylammonium bromide was added to 999 g of the resulting aqueous sodium hypochlorite solution, yielding a treatment solution with the composition shown in Table 1. The evaluation results are shown in Table 2.

[0106] Example 9 In Example 9, a treatment solution was prepared in the same manner as in Example 1 so as to have the composition shown in Table 1, except that didecyldimethylammonium bromide (manufactured by Tokyo Chemical Industry Co., Ltd., purity >98%) was used as the alkylammonium salt represented by formula (1), and evaluation was carried out using a ruthenium film (sample piece) prepared in the same manner as in Example 1.

[0107] Example 10 In Example 10, a treatment solution was prepared in the same manner as in Example 1 so as to have the composition shown in Table 1, except that didodecyldimethylammonium bromide (manufactured by Tokyo Chemical Industry Co., Ltd., purity >98%) was used as the alkylammonium salt represented by formula (1), and evaluation was carried out using a ruthenium film (sample piece) prepared in the same manner as in Example 1.

[0108] Example 11 Hexadecyltrimethylammonium bromate was precipitated by mixing an aqueous solution of hexadecyltrimethylammonium bromide and an aqueous solution of sodium bromate. The mixture was filtered, and the precipitated hexadecyltrimethylammonium bromate was separated and washed three times with ultrapure water. A treatment solution having the composition shown in Table 1 was obtained in the same manner as in Example 1, except that tetradecyltrimethylammonium bromide was replaced with hexadecyltrimethylammonium bromate. Evaluation was carried out using a ruthenium film (sample piece) prepared in the same manner as in Example 1.

[0109] Example 12 In Example 12, a treatment solution was prepared in the same manner as in Example 6 so as to have the composition shown in Table 1, except that decyltrimethylammonium bromide was used as the alkylammonium salt represented by formula (1), and evaluation was carried out using a ruthenium film (sample piece) prepared in the same manner as in Example 1. <Comparative Example 1> A treatment liquid was prepared in the same manner as in Example 1, except that the alkylammonium salt represented by formula (1) was not added, and evaluations were carried out in the same manner as in Example 1. <Comparative Example 2> In Comparative Example 2, a treatment solution was prepared in the same manner as in Example 1 so as to have the composition shown in Table 1, except that tetrapropylammonium bromide (manufactured by Tokyo Chemical Industry Co., Ltd., purity >98%) was used as the alkylammonium salt represented by formula (1), and evaluation was carried out using a ruthenium film (sample piece) prepared in the same manner as in Example 1.

[0110] Example 13 Orthoperiodic acid (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd., content >98.5%) was mixed with a 25 mass% aqueous solution of tetramethylammonium hydroxide, ultrapure water, and tetradecyltrimethylammonium bromide to obtain a treatment solution with the composition shown in Table 1. Evaluation was carried out using a ruthenium film (sample piece) prepared in the same manner as in Example 1.

[0111] Example 14 In Example 14, a treatment solution was prepared in the same manner as in Example 6, with the exception that n-octyltrimethylammonium bromide was used as the alkylammonium salt represented by formula (1), so as to have the composition shown in Table 1. Using a wafer on which a ruthenium oxide film had been formed, the etching rate was evaluated according to the above-mentioned "Method for calculating the etching rate of a transition metal." From the calculated etching rate, the time required to etch ruthenium oxide to 50 ű10 Šwas calculated, and a ruthenium oxide film treated for the time required to etch 50 ű10 Šwas prepared, and this was used as a ruthenium oxide film for surface observation. The surface of the ruthenium oxide film for surface observation was observed using an electron microscope at 100,000x magnification.

[0112] <Comparative Example 3> In Comparative Example 3, a treatment liquid was prepared in the same manner as in Example 14, except that the alkylammonium salt represented by formula (1) was not added, and evaluations were carried out in the same manner as in Example 14.

[0113] Example 15 In Example 15, a treatment solution was prepared in the same manner as in Example 6, with the exception that decyltrimethylammonium bromide was used as the alkylammonium salt represented by formula (1), so as to have the composition shown in Table 1. Using a wafer with a tungsten film formed thereon, the etching rate was evaluated according to the "Method for Calculating the Etching Rate of Transition Metals" described above. From the calculated etching rate, the time required to etch tungsten to 50 ű10 Šwas calculated, and a tungsten film treated for the time required to etch 50 ű10 Šwas prepared and used as a tungsten film for surface observation. The surface of the tungsten film for surface observation was observed using an electron microscope at 100,000x magnification.

[0114] <Comparative Example 4> In Comparative Example 4, a treatment liquid was prepared in the same manner as in Example 15, except that the alkylammonium salt represented by formula (1) was not added, and evaluations were carried out in the same manner as in Example 15.

[0115] Example 16 In Example 16, a treatment solution was prepared in the same manner as in Example 2, with the exception that dodecyltrimethylammonium bromide was used as the alkylammonium salt represented by formula (1), so as to have the composition shown in Table 1. Using a wafer with a molybdenum film formed thereon, the etching rate was evaluated according to the above-mentioned "Method for Calculating the Etching Rate of a Transition Metal." From the calculated etching rate, the time required to etch molybdenum to 50 ű10 Šwas calculated, and a molybdenum film treated for the time required to etch 50 ű10 Šwas prepared and used as a molybdenum film for surface observation. The surface of the molybdenum film for surface observation was observed using an electron microscope at 100,000x magnification.

[0116] <Comparative Example 5> In Comparative Example 5, a treatment liquid was prepared in the same manner as in Example 16, except that the alkylammonium salt represented by formula (1) was not added, and evaluations were carried out in the same manner as in Example 16.

[0117] Example 17 In Example 17, a treatment solution was prepared in the same manner as in Example 1, with the exception that decyltrimethylammonium bromide was used as the alkylammonium salt represented by formula (1), so as to have the composition shown in Table 1. Using a wafer on which a chromium film had been formed, the etching rate was evaluated according to the above-mentioned "Method for Calculating the Etching Rate of Transition Metals." From the calculated etching rate, the time required to etch 50 ű10 Šof chromium was calculated, and a chromium film treated for the time required to etch 50 ű10 Šwas prepared and used as the chromium film for surface observation. The surface of the chromium film for surface observation was observed using an electron microscope at 100,000x magnification.

[0118] <Comparative Example 6> In Comparative Example 6, a treatment liquid was prepared in the same manner as in Example 17, except that the alkylammonium salt represented by formula (1) was not added, and evaluations were carried out in the same manner as in Example 17. The compositions of the treatment solutions prepared in the above Examples and Comparative Examples are shown in Table 1, and the results obtained are shown in Table 2. [Table 1] [Table 2]

[0119] Example 18 A 0.1 mol / L tetramethylammonium hypochlorite aqueous solution with a pH of 12.0 was prepared in the same manner as in Example 2. A 0.1 mol / L tetramethylammonium bromide aqueous solution with a pH of 12.0 was prepared by adding a 25% by mass tetramethylammonium hydroxide aqueous solution and ultrapure water to tetramethylammonium bromide (Tokyo Chemical Industry Co., Ltd., purity >97%). 2 g of hexadecyltrimethylammonium bromide was added to 998 g of the resulting tetramethylammonium bromide aqueous solution to prepare a chemical solution containing a bromine-containing compound. 500 g of the 0.1 mol / L tetramethylammonium hypochlorite aqueous solution and 500 g of the chemical solution containing a bromine-containing compound were mixed to obtain a treatment solution with the composition listed in Table 4. Evaluation was performed using a ruthenium film (sample piece) prepared in the same manner as in Example 1.

[0120] Example 19 A tetramethylammonium hypochlorite aqueous solution of pH 13.0 and 0.2 mol / L was prepared in the same manner as in Example 2. Also, a tetramethylammonium hypochlorite aqueous solution of pH 13.0 and 0. A 2 mol / L aqueous solution of tetramethylammonium bromide was prepared. 200 mg of dimethyldioctylammonium bromide (Tokyo Chemical Industry Co., Ltd., purity >97%) was added to 999.8 g of the obtained aqueous solution of tetramethylammonium bromide to prepare a chemical solution containing a bromine-containing compound. 500 g of the above 0.2 mol / L aqueous solution of tetramethylammonium hypochlorite and 500 g of the chemical solution containing a bromine-containing compound were mixed to obtain a treatment solution with the composition listed in Table 4. Evaluation was performed using a ruthenium film (sample piece) prepared in the same manner as in Example 1.

[0121] Example 20 A 0.1 mol / L tetramethylammonium hypochlorite aqueous solution with a pH of 12.0 was prepared in the same manner as in Example 2. A 0.1 mol / L tetrapropylammonium bromide aqueous solution with a pH of 12.0 was prepared by adding 25% by mass tetramethylammonium hydroxide aqueous solution and ultrapure water to tetrapropylammonium bromide (Tokyo Chemical Industry Co., Ltd., purity >97%). 200 mg of tetradecyltrimethylammonium bromide was added to 999.8 g of the resulting tetrapropylammonium bromide aqueous solution to prepare a chemical solution containing a bromine-containing compound with the composition listed in Table 3. 500 g of the 0.1 mol / L tetramethylammonium hypochlorite aqueous solution and 500 g of the chemical solution containing a bromine-containing compound were mixed to obtain a treatment solution with the composition listed in Table 4. Evaluation was performed using a ruthenium film (sample piece) prepared in the same manner as in Example 1.

[0122] <Example 21> A 0.4 mol / L tetramethylammonium hypochlorite aqueous solution was prepared using the same method as in Example 2. A 0.4 mol / L tetramethylammonium bromide aqueous solution was prepared using the same method as in Example 18. 2 mg of tetraheptylammonium bromide (Tokyo Chemical Industry Co., Ltd., purity >98%) was added to 999.998 g of the resulting tetramethylammonium bromide aqueous solution to prepare a chemical solution containing a bromine-containing compound with the composition listed in Table 3. 500 g of the 0.4 mol / L tetramethylammonium hypochlorite aqueous solution and 500 g of the chemical solution containing a bromine-containing compound were mixed to obtain a treatment solution with the composition listed in Table 4. Evaluation was performed using a ruthenium film (sample piece) prepared in the same manner as in Example 1.

[0123] <Example 22> A 0.002 mol / L tetramethylammonium hypochlorite aqueous solution was prepared using the same method as in Example 2. A 0.002 mol / L tetramethylammonium bromide aqueous solution was prepared using the same method as in Example 18. 200 mg of hexyldimethyloctyl bromide (Tokyo Chemical Industry Co., Ltd., purity >97%) was added to 999.8 g of the resulting tetramethylammonium bromide aqueous solution to prepare a chemical solution containing a bromine-containing compound with the composition listed in Table 3. 500 g of the 0.002 mol / L tetramethylammonium hypochlorite aqueous solution and 500 g of the chemical solution containing a bromine-containing compound were mixed to obtain a treatment solution with the composition listed in Table 4. Evaluation was performed using a ruthenium film (sample piece) prepared in the same manner as in Example 1.

[0124] Example 23 A 0.19 mol / L tetramethylammonium hypochlorite aqueous solution was prepared in the same manner as in Example 2. A 0.1 mol / L tetramethylammonium bromide aqueous solution was prepared in the same manner as in Example 18. 2 g of dodecyltrimethylammonium bromide was added to 998 g of the resulting tetramethylammonium bromide aqueous solution to prepare a chemical solution containing a bromine-containing compound with the composition listed in Table 3. 500 g of the 0.19 mol / L tetramethylammonium hypochlorite aqueous solution and 500 g of the chemical solution containing a bromine-containing compound were mixed to obtain a treatment solution with the composition listed in Table 4. Evaluation was performed using a ruthenium film (sample piece) prepared in the same manner as in Example 1.

[0125] Example 24 In Example 24, a 0.1 mol / L tetramethylammonium hypochlorite aqueous solution with a pH of 12.0 was prepared in the same manner as in Example 2. Furthermore, a chemical solution containing a bromine-containing compound was prepared by mixing an ethyltrimethylammonium hydroxide aqueous solution and a hydrobromic acid aqueous solution to obtain the composition shown in Table 3, and then mixing n-octyltrimethylammonium bromide with the resulting solution. 500 g of the 0.1 mol / L tetramethylammonium hypochlorite aqueous solution and 500 g of the chemical solution containing the bromine-containing compound were mixed to obtain a treatment solution with the composition shown in Table 4. Evaluation was performed using a ruthenium film (sample piece) prepared in the same manner as in Example 1.

[0126] Example 25 In Example 25, a 0.1 mol / L tetramethylammonium hypochlorite aqueous solution was prepared using the same method as in Example 2. A 0.1 mol / L tetramethylammonium bromide aqueous solution was prepared using the same method as in Example 18. 20 mg of hexadecyltrimethylammonium bromide was added to 999.98 g of the resulting tetramethylammonium bromide aqueous solution to prepare a chemical solution containing a bromine-containing compound with the composition listed in Table 3. 500 g of the 0.1 mol / L tetramethylammonium hypochlorite aqueous solution and 500 g of the chemical solution containing a bromine-containing compound were mixed to obtain a treatment solution with the composition listed in Table 4. Evaluation was performed using a ruthenium oxide film (sample piece) prepared in the same manner as in Example 14. Example 26 In Example 26, a treatment solution was prepared in the same manner as in Example 18 so as to have the composition shown in Table 3, except that tetradecyltrimethylammonium bromide was used as the alkylammonium salt represented by formula (1). Evaluation was carried out using a tungsten film (sample piece) prepared in the same manner as in Example 14.

[0127] Example 27 In Example 27, a treatment solution was prepared in the same manner as in Example 18 so as to have the composition shown in Tables 3 and 4, except that dodecyltrimethylammonium bromide was used as the alkylammonium salt represented by formula (1). Evaluation was carried out using a molybdenum film (sample piece) prepared in the same manner as in Example 15.

[0128] Example 28 In Example 28, a treatment solution was prepared in the same manner as in Example 18 so as to have the composition shown in Tables 3 and 4, except that decyltrimethylammonium bromide was used as the alkylammonium salt represented by formula (1). Evaluation was carried out using a chromium film (sample piece) prepared in the same manner as in Example 16.

[0129] <Comparative Examples 7 to 11> In Comparative Examples 7 to 11, the treatment solution was prepared in the same manner as in Example 18, except that the alkylammonium salt represented by formula (1) was not added. Comparative Example 7 was evaluated using a ruthenium film (sample piece) prepared in the same manner as in Example 1. Comparative Example 8 was evaluated using a ruthenium dioxide film (sample piece) prepared in the same manner as in Example 14. Comparative Example 9 was evaluated using a tungsten film (sample piece) prepared in the same manner as in Example 15. Comparative Example 10 was evaluated using a molybdenum film (sample piece) prepared in the same manner as in Example 16. Comparative Example 11 was evaluated using a chromium film (sample piece) prepared in the same manner as in Example 17. The compositions of the treatment solutions prepared in the above Examples and Comparative Examples are shown in Tables 3 and 4, and the results obtained are shown in Table 4.

[0130] [Table 3] [Table 4]

[0131] Example 29 (Preparation of tetramethylammonium chlorate ((CH3)4NClO3)) A saturated solution was obtained by adding sodium chlorate (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) to ion-exchanged water and storing it in a refrigerator for 24 hours. The precipitated sodium chlorate was collected by filtration. The collected sodium chlorate was diluted with ultrapure water and analyzed using an ion chromatography analyzer. The CO3 - , SO4 - , Cl- By analyzing It was confirmed that the amount of Na2CO3, Na2SO4, and NaCl in the water was reduced. - , SO4 - , Cl - are each 500 ppb or less The result was purified sodium chlorate. Next, a strong acid ion exchange resin (Amberlite IR-120BNa, Organo Corporation) was placed in a glass column (AsOne Corporation, Biocolumn CF-50TK) with an inner diameter of approximately 45 mm. 0 mL was added. Subsequently, 1 L of 1 N hydrochloric acid (Fujifilm Wako Pure Chemical Industries, Ltd., for volumetric analysis) was passed through the ion exchange resin column to exchange the ion exchange resin into the hydrogen form, and 1 L of ultrapure water was passed through to wash the ion exchange resin. Furthermore, 2 L of 2.38% tetramethylammonium hydroxide solution was passed through the ion exchange resin that had been exchanged into the hydrogen form, and the ion exchange from the hydrogen form to the tetramethylammonium form was performed. After the ion exchange, 1 L of ultrapure water was passed through to wash the ion exchange resin. 6.4 g of purified sodium chlorate was placed in a fluororesin container, and 93.6 g of ultrapure water was added to prepare a 6.4 mass% sodium chlorate aqueous solution. The prepared sodium chlorate aqueous solution was passed through an ion exchange resin that had been converted to a tetramethylammonium form. The recovered tetramethylammonium chlorate was analyzed for Na concentration using high-frequency inductively coupled plasma atomic emission spectroscopy (iCAP6500DuO, Thermo Scientific) to confirm that ion exchange had been sufficiently carried out. If the ion exchange was insufficient, the above procedure was repeated to obtain a 10 mass% tetramethylammonium chlorate solution with a Na concentration of 500 ppb or less. The resulting solution was heat-treated to obtain tetramethylammonium chlorate powder. To a treatment liquid prepared in the same manner as in Example 4, tetramethylammonium chlorate was added so as to obtain the composition shown in Table 5.

[0132] <Stability evaluation> The resulting treatment solution was stored in a 30 mL fluororesin container and kept in a dark place at 25°C for 30 days. The presence or absence of precipitation of alkylammonium salt was checked visually. If precipitation was found, it was rated C. If no precipitation was found, it was kept in a dark place for a further 15 days, and the presence or absence of precipitation was checked visually. If no precipitation was found, it was rated A, and if precipitation was found, it was rated B.

[0133] Example 30 Tetramethylammonium chloride (Tokyo Chemical Industry Co., Ltd., purity >98%) was added to a treatment solution prepared using the same method as in Example 18 to obtain the composition shown in Table 5. The stability of the treatment solution obtained using the same method as in Example 29 was evaluated.

[0134] Example 31 Tetramethylammonium chloride was added to a treatment solution prepared in the same manner as in Example 18 to obtain the composition shown in Table 5. The stability of the treatment solution obtained in the same manner as in Example 29 was evaluated.

[0135] The compositions of the treatment solutions prepared in the above examples and the results obtained are shown in Table 5.

[0136] [Table 5]

[0137] Example 32 47% hydrobromic acid (ultrapure hydrobromic acid, manufactured by Tama Chemicals Co., Ltd.) was mixed with SD-25 (ultrapure tetramethylammonium hydroxide aqueous solution, manufactured by Tokuyama Corporation) and ultrapure water to prepare a 0.1 mol / L tetramethylammonium bromide aqueous solution with a pH of 12.0. 1 g of decyltrimethylammonium bromide was added to 999 g of the resulting tetramethylammonium bromide aqueous solution to obtain a chemical solution with the composition listed in Table 6. The resulting chemical solution was circulated and filtered using a filter (manufactured by Nippon Entegris Co., Ltd., made of polytetrafluoroethylene, pore size 20 nm) until the metal impurity concentration in the chemical solution reached 1 ppb or less.

[0138] (Method for measuring metal impurity concentration in chemical solutions) Ultrapure water and 1.25 ml of high-purity nitric acid (Ultrapure-100 nitric acid, Kanto Chemical Co., Ltd.) were added to a 25 ml polyfluoroalkyl ether (PFA) volumetric flask (AsOne, PFA volumetric flask). Next, 0.25 ml of the solution was collected using a pipette (AsOne, Pipetman P1000) and a fluororesin pipette tip (AsOne, fluororesin pipette tip), added to the PFA volumetric flask, and stirred. The solution was then diluted 100-fold with ultrapure water to prepare a measurement sample. Metal atoms were then quantified using a calibration curve method using a high-resolution inductively coupled plasma mass spectrometer (ThermoFisher Scientific, Element 2).

[0139] (Stability evaluation of alkylammonium bromide) The resulting solution was stored in a 30 mL fluororesin container at 80°C for 15 days. The alkylammonium salt concentration in the solution after 15 days of storage was measured, and a ratio of the alkylammonium salt concentration after 15 days of storage to the alkylammonium salt concentration before storage of 0.5 or more was rated as A, and a ratio of less than 0.5 was rated as B. The alkylammonium salt concentration was measured using a liquid chromatograph mass spectrometer (Xevo QT of MS, manufactured by Waters).

[0140] Example 33 47% hydrobromic acid (ultrapure hydrobromic acid, manufactured by Tama Chemical Industries, Ltd.) was mixed with SD-25 (ultrapure tetramethylammonium hydroxide aqueous solution, manufactured by Tokuyama Corporation), sodium nitrate (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd., purity 99.9%), potassium nitrate (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd., purity 99.9%), and ultrapure water to obtain the composition shown in Table 6. The stability of the treatment solution obtained was evaluated in the same manner as in Example 32.

[0141] Example 34 47% hydrobromic acid (ultrapure hydrobromic acid, manufactured by Tama Chemical Industries Co., Ltd.) was mixed with SD-25 (ultrapure tetramethylammonium hydroxide aqueous solution, manufactured by Tokuyama Corporation), magnesium nitrate hexahydrate (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd., purity 99.999%), calcium nitrate tetrahydrate (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd., purity 99.98%), and ultrapure water to obtain the composition shown in Table 6. The stability of the treatment solution obtained was evaluated in the same manner as in Example 32.

[0142] Example 35 47% hydrobromic acid (ultrapure hydrobromic acid, manufactured by Tama Chemicals Co., Ltd.) was mixed with SD-25 (ultrapure tetramethylammonium hydroxide aqueous solution, manufactured by Tokuyama Corporation), aluminum nitrate nonahydrate (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd., purity 99.999%), and ultrapure water to obtain the composition shown in Table 6. The stability of the treatment solution obtained was evaluated in the same manner as in Example 32.

[0143] Example 36 47% hydrobromic acid (ultrapure hydrobromic acid, manufactured by Tama Chemicals Co., Ltd.) was mixed with SD-25 (ultrapure tetramethylammonium hydroxide aqueous solution, manufactured by Tokuyama Corporation), iron nitrate nonahydrate (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd., purity 99.999%), and ultrapure water to obtain the composition shown in Table 6. The stability of the treatment solution obtained was evaluated in the same manner as in Example 32.

[0144] Example 37 47% hydrobromic acid (ultrapure hydrobromic acid, manufactured by Tama Chemical Industries, Ltd.) was mixed with SD-25 (ultrapure tetramethylammonium hydroxide aqueous solution, manufactured by Tokuyama Corporation), nickel nitrate hexahydrate (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd., purity 99.9985%), cobalt nitrate hexahydrate (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd., purity 99.999%), and ultrapure water to obtain the composition shown in Table 6. The stability of the treatment solution obtained was evaluated in the same manner as in Example 32.

[0145] Example 38 47% hydrobromic acid (ultrapure hydrobromic acid, manufactured by Tama Chemical Industries Co., Ltd.) was mixed with SD-25 (ultrapure tetramethylammonium hydroxide aqueous solution, manufactured by Tokuyama Corporation), copper (II) nitrate trihydrate (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd., purity 99.999%), and ultrapure water to obtain the composition shown in Table 6. The stability of the treatment solution obtained was evaluated in the same manner as in Example 32.

[0146] Example 39 47% hydrobromic acid (ultrapure hydrobromic acid, manufactured by Tama Chemical Industries Co., Ltd.) was mixed with SD-25 (ultrapure tetramethylammonium hydroxide aqueous solution, manufactured by Tokuyama Corporation), silver nitrate (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd., purity 99.9995%), and ultrapure water to obtain the composition shown in Table 6. The stability of the treatment solution obtained was evaluated in the same manner as in Example 32.

[0147] <Example 40> 47% hydrobromic acid (ultrapure hydrobromic acid, manufactured by Tama Chemical Industries Co., Ltd.) was mixed with SD-25 (ultrapure tetramethylammonium hydroxide aqueous solution, manufactured by Tokuyama Corporation), cadmium nitrate tetrahydrate (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd., purity 99.9%), and ultrapure water to obtain the composition shown in Table 6. The stability of the treatment solution obtained was evaluated in the same manner as in Example 32.

[0148] <Example 41> 47% hydrobromic acid (ultrapure hydrobromic acid, manufactured by Tama Chemical Industries Co., Ltd.) was mixed with SD-25 (ultrapure tetramethylammonium hydroxide aqueous solution, manufactured by Tokuyama Corporation), barium nitrate (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd., purity 99.999%), and ultrapure water to obtain the composition shown in Table 6. The stability of the treatment solution obtained was evaluated in the same manner as in Example 32.

[0149] <Example 42> 47% hydrobromic acid (ultrapure hydrobromic acid, manufactured by Tama Chemical Industries Co., Ltd.) was mixed with SD-25 (ultrapure tetramethylammonium hydroxide aqueous solution, manufactured by Tokuyama Corporation), lead nitrate (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd., purity 99.999%), and ultrapure water to obtain the composition shown in Table 6. The stability of the treatment solution obtained was evaluated in the same manner as in Example 32. [Table 6]

[0150] As shown in Tables 2 and 4, in Examples 1 to 28 in which the treatment solution of the present invention was applied, the smoothness of the transition metal surface was maintained after etching. Furthermore, as is clear from Examples 1 to 28, it was shown that the etching rate of the transition metal can be controlled to a desired value by adjusting the oxidizing agent concentration, pH, and the type and / or concentration of the alkylammonium salt. Thus, the treatment solution of the present invention can be suitably used as a treatment solution for semiconductor manufacturing.

[0151] In Comparative Examples 1 and 3 to 11, no alkylammonium salt was added, so surface roughness was observed after etching and flatness was reduced compared to Examples 1 to 28. In Comparative Example 2, in which an alkylammonium salt was added, surface roughness was observed after etching and flatness was reduced compared to the Examples due to the influence of the smaller number of carbon atoms in the alkyl group. As shown in Table 5, the precipitation of alkylammonium bromide can be suppressed by further adding chloride ions or chlorate ions to the treatment solution of the present invention. As shown in Table 6, by reducing the amount of metal impurities in the chemical solution of the present invention to 1 ppb or less, the stability of alkylammonium bromide can be improved. [Explanation of symbols]

[0152] 1 Base 2. Interlayer insulating film 3. Ruthenium

Claims

[Claim 1] A method for producing a solution containing tetraalkylammonium bromide by mixing tetraalkylammonium hydroxide with a solution containing bromide ions or a bromine-containing gas that generates bromide ions when dissolved in water, wherein the alkyl group of the tetraalkylammonium bromide has 1 to 20 carbon atoms, and the bromide ion source that generates bromide ions in the bromide ion-containing solution is hydrogen bromide, lithium bromide, sodium bromide, potassium bromide, rubidium bromide, cesium bromide, or ammonium bromide.

Images