Semiconductor processing liquid and its manufacturing method

Abstract

A semiconductor processing solution containing hypobromite ions at a concentration of 0.1 μmol / L or more but less than 0.001 mol / L. A RuO4 gas generation inhibitor comprising an onium salt composed of onium ions and bromide ions, wherein the concentration of hypobromite ions in the RuO4 gas generation inhibitor is 0.1 μmol / L or more but less than 0.001 mol / L. Furthermore, a method for manufacturing a halogen oxyacid is provided, comprising reacting a bromide salt, an organic base, and a halogen to obtain the halogen oxyacid.

Description

Technical Field

[0001] This invention relates to a semiconductor processing solution (hereinafter also referred to simply as "processing solution") containing hypobromite ions at a concentration of 0.1 μmol / L or more but less than 0.001 mol / L. Furthermore, it relates to a RuO₄ gas generation inhibitor comprising an ononium salt composed of ononium ions and bromide ions, wherein the concentration of hypobromite ions in the RuO₄ gas generation inhibitor is 0.1 μmol / L or more but less than 0.001 mol / L. Finally, it relates to a method for obtaining halogen oxyacids. Prior Technology

[0002] In recent years, the miniaturization of semiconductor device design rules has led to a trend of increased wiring resistance. This increased wiring resistance significantly hinders the high-speed operation of semiconductor devices, necessitating countermeasures. Therefore, wiring materials that offer higher resistance to electron migration and lower resistance compared to conventional materials are desirable.

[0003] Compared to conventional wiring materials such as aluminum and copper, ruthenium, tungsten, molybdenum, and chromium have attracted particular attention as wiring materials for semiconductor devices with design specifications below 10nm, due to their high resistance to electron migration. Furthermore, since ruthenium can prevent electron migration even when used in copper wiring materials, the use of ruthenium not only as a wiring material but also as a barrier metal for copper wiring is being examined.

[0004] However, in the wiring formation process of semiconductor devices, even when ruthenium, tungsten, molybdenum, or chromium is chosen as the wiring material, the wiring is formed by dry or wet etching, just like with conventional wiring materials. Furthermore, since ruthenium, tungsten, molybdenum, or chromium are difficult to remove using dry etching with etching gases or CMP polishing, more precise etching is desired; specifically, wet etching has gained attention.

[0005] In wet etching of ruthenium, tungsten, molybdenum, or chromium, the dissolution rate of these metals, i.e., the etching rate, is crucial. A faster etching rate allows the metal to dissolve in a shorter time, thus increasing the number of wafers processed per unit time.

[0006] Furthermore, when ruthenium, tungsten, molybdenum, or chromium are used as wiring materials, the stability of the etching rate becomes particularly important. A stable etching rate allows for improved machining accuracy of the metal by controlling the etching time. In particular, precision machining of ruthenium, tungsten, molybdenum, or chromium is indispensable in ultra-fine wiring. Therefore, an etching solution that exhibits excellent etching rate stability and maintains the flatness of the transition metal surface is desired, especially in the process of forming micro-wires using ruthenium, tungsten, or molybdenum.

[0007] On the other hand, in order to etch ruthenium, which is a precious metal and not easily soluble, or to etch tungsten, molybdenum, or chromium at high speed, there are cases where the etching solution contains an oxidizing agent with high oxidizing power. Even in such cases, in order to improve production efficiency and maintain processing accuracy, an etching solution with sufficient etching speed, excellent etching speed stability, and the ability to maintain the flatness of the metal surface after etching is required.

[0008] Furthermore, in the case of wet etching of ruthenium under alkaline conditions, ruthenium dissolves in the processing solution as, for example, RuO₄⁻ or RuO₄²⁻. RuO₄⁻ or RuO₄²⁻ is converted to RuO₄ in the processing solution, and a portion of it vaporizes and is released into the gas phase. Since RuO₄ is a strong oxidizing agent, it is not only harmful to the human body but also easily reduced to produce RuO₂ particles. Generally, these particles lead to reduced yields, thus becoming a significant problem in semiconductor formation. In view of this background, suppressing RuO₄ gas generation becomes crucial.

[0009] As a processing solution used for etching ruthenium from semiconductor wafers, Patent Document 1 discloses a processing solution for ruthenium-bearing wafers, which contains hypochlorite ions and a solvent, and has a pH value exceeding 7 but not exceeding 12.0 at 25°C. This processing solution contains hypochlorite ions and demonstrates the ability to remove ruthenium and tungsten adhering to the end face or back face of semiconductor wafers. Furthermore, Patent Document 1 describes a method for manufacturing an ion exchange resin as a method for manufacturing a processing solution containing hypochlorite ions.

[0010] Patent document 2 describes an etching composition for ruthenium-based metals, which is formed by adding a bromine-containing compound, an oxidant, an alkaline compound and water and mixing them together. The amount of the bromine-containing compound added is 2 to 25% by mass relative to the total mass, the amount of the oxidant added is 0.1 to 12% by mass, and the pH is 10 or higher and less than 12.

[0011] Patent document 3 discloses an etching solution for tungsten and titanium-tungsten alloys with a pH below 7, which contains hydrogen peroxide and alkaline components. This etching solution demonstrates the ability to stably etch electrodes or wirings of thin-film transistors used in semiconductor devices or liquid crystal display devices, as well as tungsten of the wirings or barrier metals of such electrodes.

[0012] Patent Document 4 discloses a method for forming wiring by processing copper and molybdenum using a solution containing an oxidant and an acid. Examples of oxidants include hydrogen peroxide, persulfate, nitric acid, hypochlorous acid, permanganate, and dichromate. Furthermore, an example is shown of using an aqueous solution containing hydrogen peroxide and carboxylic acid as the solution to etch a molybdenum film. [Previous Technical Documents] [Patent Literature]

[0013] [Patent Document 1] International Publication No. 2019 / 142788 [Patent Document 2] International Publication No. 2011 / 074601 [Patent Document 3] Japanese Patent Application Publication No. 2004-031791 [Patent Document 4] Japanese Patent Application Publication No. 2013-254946 Summary of the Invention

[0014] [The problem that the invention aims to solve]

[0015] In order to etch transition metals on semiconductor wafers using a processing solution, it is important to achieve both high etching rate and stability, while maintaining surface flatness after etching. Furthermore, in the case of wet etching of ruthenium under alkaline conditions, suppressing the generation of RuO₄ gas is crucial. Additionally, the easy and efficient production of halogen oxyacids is also important. However, based on the review of the inventors, it has been found that conventional processing solutions or compositions described in prior art documents still have room for improvement in the following aspects.

[0016] For example, as a processing solution for ruthenium-containing wafers, Patent Document 1 describes a processing solution with a pH value exceeding 7 but not exceeding 12.0. Although the processing solution described in Patent Document 1 provides a sufficient etching rate for ruthenium, the etching rate tends to decrease in stability when the oxidant concentration is high. Therefore, the processing solution for ruthenium-containing wafers described in Patent Document 1 makes it difficult to achieve both high etching rate and stable etching rate. Furthermore, it is difficult to maintain the flatness of the ruthenium surface after etching.

[0017] The etching composition described in Patent Document 2 enables the etching of ruthenium at a sufficient speed. As a method for preparing this etching composition, a method is presented for appropriately adjusting the pH to alkaline by oxidizing a bromine-containing compound with an oxidant under acidic conditions to obtain an oxide mixture with an alkaline compound. However, during additional experiments, the inventors found that the etching composition has poor solution stability, and the etching rate of ruthenium varies significantly over time. Therefore, the etching composition described in Patent Document 2 makes it difficult to achieve both high etching rate and stable etching rate. Furthermore, it is difficult to maintain the flatness of the ruthenium surface after etching, leading to an increase in the roughness of the metal surface.

[0018] The etching solution described in Patent Document 3 uses hydrogen peroxide as its main component, which leads to unstable etching rates and short solution lifespan due to the self-decomposition reaction of hydrogen peroxide. Furthermore, the etching speed is also insufficient. Therefore, the etching solution described in Patent Document 3 cannot achieve both high etching speed and stable etching speed. Additionally, it is difficult to maintain the flatness of the tungsten surface after etching, resulting in increased surface roughness.

[0019] Patent Document 4 describes a solution containing an oxidant and an acid. The oxidant disclosed in the embodiments of Patent Document 4 is only hydrogen peroxide, which, as mentioned above, leads to unstable etching rates due to self-decomposition and a short solution lifespan. Furthermore, the etching rate is also insufficient. Therefore, the solution described in Patent Document 4 cannot achieve both high etching rate and stable etching rate. Additionally, it is difficult to maintain the flatness of the molybdenum surface after etching, resulting in increased surface roughness of the metal.

[0020] Furthermore, none of the aforementioned patent documents 1-4 mention any suppression of RuO₄ gas. In fact, the processing liquids or compositions described in patent documents 1-4 cannot suppress the generation of RuO₄ gas. Moreover, there is no simple method for producing the aforementioned halogenated oxyacids with good yield.

[0021] Therefore, the present invention is based on the aforementioned prior art, and its object is to provide a semiconductor processing solution that has a sufficient etching rate, excellent etching rate stability, and can stably etch for a long time even at room temperature, while maintaining the flatness of the etched metal surface. Furthermore, it provides a RuO₄ gas generation inhibitor that can suppress the generation of RuO₄ gas during ruthenium etching. Finally, it provides a simple and high-yield method for manufacturing halogen oxyacids. [Methods used to solve problems]

[0022] The inventors have conducted careful research in order to solve the above-mentioned problems. Furthermore, it was discovered that by using a processing solution with a hypobromite ion concentration of 0.1 μmol / L or higher but less than 0.001 mol / L to process semiconductor wafers, stable etching of transition metals can be achieved at a sufficient rate even at room temperature, while maintaining the flatness of the etched metal surface. Also, it was discovered that during ruthenium etching, the generation of RuO₄ gas can be suppressed by using a RuO₄ gas generation inhibitor with a bromide ion concentration of 0.1 μmol / L or higher but less than 0.001 mol / L. Furthermore, a simple and efficient method for manufacturing halogen oxyacids was discovered, thus completing this invention.

[0023] That is, the present invention is configured as shown below.

[0024] Item 1 A semiconductor processing solution containing hypobromite ions, wherein the concentration of hypobromite ions is 0.1 μmol / L or more but less than 0.001 mol / L. Item 2 The semiconductor processing liquid of Item 1, wherein the semiconductor contains a transition metal. Item 3 The semiconductor processing solution of Item 1 or 2 further includes at least one anion selected from the group consisting of chlorate ion, chlorite ion, chloride ion, bromate ion, bromate ion and bromide ion. Item 4. Semiconductor processing solution as described in any of Items 1 to 3, wherein the aforementioned semiconductor processing solution further comprises an oxidant, the redox potential of which exceeds the redox potential of the hypobromite / bromine ion system. Item 5 The semiconductor processing solution of Item 4, wherein the aforementioned oxidant is at least one oxidant selected from the group consisting of hypochlorite ions, ozone, periodate ions, and metaperiodate ions. Item 6. Semiconductor processing solution as described in any of Items 1 to 5, further comprising tetraalkylammonium ions. Item 7. Semiconductor processing solution as described in any of Items 1 to 6, wherein the pH of the aforementioned processing solution is above 8 and below 14. Item 8 A RuO4 gas generation inhibitor comprising an onium salt composed of onium ions and bromide ions, wherein the concentration of bromide ions in the aforementioned RuO4 gas generation inhibitor is 0.1 μmol / L or more but less than 0.001 mol / L. Item 9, as in Item 8, is a RuO4 gas generation inhibitor, wherein the aforementioned onium salt is a fourth-order onium salt as shown in Formula (1) or a third-order onium salt as shown in Formula (2).

[0025]

[0026] (In formula (1), A is nitrogen or phosphorus, and R1, R2, R3, and R4 are independently alkyl, allyl, aralkyl, or aryl groups having 1 to 25 carbon atoms. However, when R1, R2, R3, and R4 are alkyl groups, at least one of the alkyl groups has 3 or more carbon atoms. Furthermore, at least one hydrogen atom in the aryl group and the aryl ring can be replaced by fluorine, chlorine, alkyl with 1 to 10 carbon atoms, alkenyl with 2 to 10 carbon atoms, alkoxy with 1 to 9 carbon atoms, or alkenoxy with 2 to 9 carbon atoms, and at least one hydrogen atom in these groups can also be replaced by fluorine or chlorine. In formula (2), A is sulfur, and R1, R2, and R3 are independently alkyl, allyl, aralkyl, or aryl groups having 1 to 25 carbon atoms. However, R 1. When R1, R2, and R3 are alkyl groups, at least one of the alkyl groups in R1, R2, and R3 has 3 or more carbon atoms. Furthermore, the aryl group in the aryl group and at least one hydrogen atom in the aryl ring can be substituted by fluorine, chlorine, an alkyl group having 1 to 10 carbon atoms, an alkenyl group having 2 to 10 carbon atoms, an alkoxy group having 1 to 9 carbon atoms, or an alkenoxy group having 2 to 9 carbon atoms, and at least one hydrogen atom in these groups can also be substituted by fluorine or chlorine. (X - represents a bromide ion.) Item 10, as in Item 9, is a RuO4 gas generation inhibitor, wherein the aforementioned fourth-order onium salt is a tetraalkylammonium salt. Item 11. The RuO4 gas generation inhibitor of any of Items 8 to 10, wherein the aforementioned bromide-containing ions are bromite ions, bromate ions, perbromate ions, hypobromate ions, or bromide ions. Item 12, such as any of items 8-11, is a RuO4 gas generation inhibitor, which further includes an oxidant. Item 13 As in Item 12, the RuO4 gas generation inhibitor, wherein the aforementioned oxidant is hypochlorite ions, and the concentration of hypochlorite ions is more than 500 ppb by mass and less than 20.0% by mass. Item 14 A method for manufacturing a halogenated oxyacid, wherein a halogenated oxyacid is obtained by reacting a bromide salt, an organic base, and a halogen. Item 15 The method for manufacturing halogenated oxyacids as described in Item 14, wherein the organic base is ium hydroxide. Item 16. Method for manufacturing halogenated oxyacids as described in Items 14 or 15, wherein the halogen is chlorine. Item 17. A method for manufacturing a halogenated oxyacid as described in any of Items 14 to 16, wherein the concentration of the aforementioned halogenated oxyacid is 0.1 μmol / L or more but less than 0.001 mol / L. [Invention Effects]

[0027] According to the semiconductor processing solution of the present invention, transition metals can be wet-etched at a sufficient speed and stably during the semiconductor formation step. Furthermore, the surface roughness of the etched transition metal can be reduced while maintaining flatness. By possessing all these effects, the processing precision of the transition metals contained in the semiconductor wafer is improved, yield is enhanced, and wafer processing efficiency per unit time is increased. Also, according to the RuO₄ gas generation inhibitor of the present invention, the generation of RuO₄ gas can be suppressed during ruthenium etching. Furthermore, according to the manufacturing method of the present invention, halogen oxyacids can be manufactured easily and with good yield. According to this manufacturing method, the metal content of the halogen oxyacids can be reduced. Simple Explanation of the Diagram

[0028] [Figure 1] shows a schematic diagram of one embodiment of the RuO4 gas measurement method according to an embodiment of the present invention. Implementation

[0029] (Semiconductor processing solution)

[0030] The semiconductor processing solution of the first embodiment of the present invention (also referred to simply as "processing solution" in this embodiment) is a semiconductor wafer processing solution, characterized by containing hypobromite ions (BrO₂⁻) at a concentration of 0.1 μmol / L or more but less than 0.001 mol / L. Hypobromite ions are oxidants with strong oxidizing properties. The processing solution of this embodiment, containing hypobromite ions at a concentration of 0.1 μmol / L or more but less than 0.001 mol / L, is a processing solution that, under alkaline conditions, can stably etch transition metals at a sufficient rate while maintaining the flatness of the etched metal surface. Furthermore, by appropriately selecting the pH, the type and concentration of the oxidant, a processing solution can suppress the generation of RuO₄ gas and simultaneously etch transition metals at a stable etching rate. It can also be used, for example, to remove poorly soluble resists or to remove residues after dry etching to remove resists. Therefore, the processing solution of this embodiment is suitable for use in semiconductor manufacturing processes such as etching, residue removal, cleaning, and CMP. Furthermore, in this embodiment, hypohalite refers to hypobromic acid, hypochlorous acid, or hypoiodic acid, and hypohalite ions refer to hypobromic acid ions, hypochlorous acid ions, and hypoiodic acid ions.

[0031] The transition metal in this embodiment includes at least one metal selected from, for example, Ru, Rh, Ti, Ta, Co, Cr, Hf, Os, Pt, Ni, Mn, Cu, Zr, La, Mo, and W. Hereinafter, the case where the transition metal is ruthenium, tungsten, molybdenum, or chromium will be described as an example. Using the processing solution of this embodiment, ruthenium, tungsten, molybdenum, or chromium adhering to the surface, end face, and back face of the semiconductor wafer can be reliably removed at a sufficient etching rate while maintaining surface flatness. In this embodiment, a sufficient etching rate refers to an etching rate of 10 Å / min or higher when the object being etched is ruthenium. For tungsten, it refers to 50 Å / min or higher; for molybdenum, it refers to 50 Å / min or higher; and for chromium, it refers to an etching rate of 50 Å / min or higher. If the etching rate of ruthenium, tungsten, molybdenum, or chromium meets the above values, it can be used in etching steps, residue removal steps, cleaning steps, CMP steps, etc.

[0032] The transition metal contained in the semiconductor wafer processed by the solution of this embodiment can be formed by any method. The film formation of the transition metal can be achieved using methods widely known in semiconductor manufacturing processes, such as CVD, ALD, sputtering, electroplating, etc. The transition metal contained in the semiconductor wafer processed by the solution of this embodiment can be of one type or multiple types. Furthermore, in this specification, "semiconductor with transition metal" means a semiconductor containing a transition metal.

[0033] In this embodiment, ruthenium refers not only to ruthenium metal, but also to any metal containing the element ruthenium. Examples include Ru, RuO 4-, RuO 4 2-, RuO 4, RuO 2, RuO 3, ruthenium complexes, ruthenium alloys, etc.

[0034] In this embodiment, tungsten refers not only to metallic tungsten, tungsten-based metals containing tungsten as a main component, and alloys of tungsten with other metals, but also to compounds that substantially contain tungsten. Examples of tungsten-based metals include tungsten oxides (WXOY), nitrides (WN), oxynitrides (WNO), and cobalt-tungsten-phosphorus compounds (CoWP). Here, tungsten oxides include tungsten dioxide (WO2), tungsten trioxide (WO3), and tungsten pentoxide (W2O5). Tungsten oxides (WXOY) also include cases where x and y cannot be represented as integers, i.e., cases with non-fixed ratios.

[0035] In this embodiment, molybdenum refers not only to metallic molybdenum, molybdenum-based metals containing molybdenum as a main component, and alloys of molybdenum with other metals, but also to compounds that substantially contain molybdenum. Examples of molybdenum-based metals include molybdenum oxides (Mo XO Y), nitrides (MoN), and acid nitrides (MoNO). Here, molybdenum oxides include molybdenum dioxide (MoO 2), molybdenum trioxide (MoO 3), and molybdenum pentoxide (Mo 2O 5). When the ratio of x to y in molybdenum oxides (Mo XO Y) cannot be expressed as integers, it also includes cases where the ratio is not fixed.

[0036] In this embodiment, chromium refers not only to metallic chromium, chromium-based metals containing chromium as a major component, and alloys of chromium with other metals, but also to compounds that substantially contain chromium. Examples of chromium-based metals include chromium oxides (CrXOY), nitrides (CrN), and acid nitrides (CrNO). Here, chromium oxides include chromium dioxide (CrO2), chromium trioxide (CrO3), and chromium pentoxide (Cr2O5). When x and y cannot be represented as integers in chromium oxides (CrXOY), it also includes cases where the ratio is not fixed.

[0037] Alloys of transition metals and other metals may contain any metal other than the transition metal itself. Examples of metals other than transition metals contained in alloys of transition metals and other metals include tantalum, silicon, copper, hafnium, zirconium, aluminum, vanadium, cobalt, nickel, manganese, gold, rhodium, palladium, titanium, ruthenium, molybdenum, tungsten, chromium, etc. They may also contain oxides, nitrides, carbides, and silicates of these metals.

[0038] These transition metals can also be intermetallic compounds, ionic compounds, or complexes. Furthermore, transition metals can be exposed on the surface of the wafer, or they can be covered by other metals, metal oxide films, insulating films, resists, etc.

[0039] Although the processing solution in this embodiment can etch ruthenium, tungsten, molybdenum, or chromium, it cannot etch metals such as copper, cobalt, titanium, platinum, titanium nitride, or tantalum nitride, or its etching rate is extremely low compared to ruthenium, tungsten, molybdenum, or chromium. Therefore, in semiconductor manufacturing processes, it can selectively etch ruthenium, tungsten, molybdenum, or chromium without damaging the substrate material containing these metals.

[0040] In this embodiment, etch rate stability means that the etch rate using a processing solution containing hypobromide ions does not change over time. Specifically, it means that when etching multiple wafers with transition metals (let the number of wafers be n) using the same processing solution, the etch rate of the transition metal on the first wafer is substantially the same as the etch rate of the transition metal on the nth wafer. Here, "substantially the same" means that the variation in the etch rate of the transition metal on the nth wafer relative to the etch rate of the first wafer, i.e., the increase or decrease in etch rate, is within ±20%. Furthermore, the time during which the etch rate of the transition metal on the nth wafer increases by within ±20% relative to the etch rate of the first wafer is defined as the etch rate stabilization time. The suitable value of the etch rate stabilization time varies depending on the conditions or manufacturing process of the processing solution used in this embodiment. For example, a processing solution with an etch rate stabilization time of 1 hour or more is suitable for use in semiconductor manufacturing processes. When considering allowing for sufficient operating time for the processing solution or the ability to flexibly set the process time, a processing solution with an etching rate stabilization time of more than 10 hours is preferred.

[0041] Processing solutions whose etching rate of transition metals does not change over time, or whose etching rate has a long stabilization time, are excellent in terms of productivity and cost because they not only enable stable etching of transition metals using the processing solution in semiconductor manufacturing processes, but also allow for reuse of the processing solution.

[0042] Furthermore, the processing solution of this embodiment is capable of maintaining the flatness of the transition metal surface after etching. In this embodiment, maintaining the flatness of the transition metal surface after etching means that the flatness of the etched transition metal surface does not substantially change before and after etching, or, even if a change occurs, it is still within a range that will not cause problems in practical application. The situation where the flatness of the transition metal surface is not maintained refers not only to situations such as pitting corrosion or uneven etching (uneven site etching) in the transition metal film due to etching, but also to situations such as an increase in the roughness (surface roughness) of the metal surface. The flatness of the transition metal surface can be easily confirmed, for example, by observing the transition metal surface using a scanning electron microscope (SEM) or by observing and measuring using an atomic force microscope (AFM). Therefore, by using the above evaluation methods, by observing and measuring the wafer surface containing the transition metal supplied for etching before and after the etching process and comparing the results, it is easy to determine whether the flatness of the metal surface after etching is maintained.

[0043] By maintaining the flatness of the transition metal surface after etching, the adhesion of other semiconductor materials, such as interlayer insulating films or other metal materials, to the etched transition metal is improved. This not only enhances the performance and reliability of the formed micro-wiring or semiconductor device but also increases the yield. The flatness of the etched transition metal surface becomes increasingly important as the wiring or device becomes finer. By using the processing solution of this embodiment, the transition metal contained in the wafer can be etched stably at a sufficient speed, and the flatness of the etched transition metal surface can be maintained. The processing solution of this embodiment is particularly suitable for applications where, for example, the wiring width used in semiconductor manufacturing is less than 10 nm.

[0044] (hypobromate ion) The hypobromide ions contained in the processing solution of this embodiment can be generated in the processing solution or added to the processing solution as hypobromate. Hypobromate, as referred to herein, means a salt containing hypobromide ions or a solution containing such salt. Generating hypobromide ions in the processing solution can be achieved, for example, by blowing bromine gas into the processing solution. In this case, from the viewpoint of efficiently generating hypobromide ions, the processing solution temperature is preferably below 50°C. If the processing solution temperature is below 50°C, not only can hypobromide ions be generated efficiently, but the generated hypobromide ions can also be stably used for etching transition metals. Furthermore, to allow more bromine to dissolve in the processing solution, the temperature of the processing solution is preferably below 30°C, and most preferably below 25°C. There is no particular limitation on the lower limit of the processing solution temperature, as long as the processing solution does not freeze. Therefore, the processing solution temperature is preferably above -35°C, more preferably above -15°C, and most preferably above 0°C. There are no particular restrictions on the pH of the treatment solution into which the bromine gas is blown in. If the pH of the treatment solution is alkaline, it can be supplied to the etching of the transition metal immediately after the generation of hypobromite ions.

[0045] Furthermore, in cases where hypobromite ions are generated by blowing bromine gas into the treatment solution, the solubility of bromine gas (Br2) increases if the treatment solution contains bromide ions (Br-). This is because Br2 dissolved in the treatment solution reacts with Br- or Br3- to form ferrite ions such as Br3- or Br5-, thereby stabilizing them in the treatment solution. Treatment solutions containing numerous Br2, Br-, Br3-, and Br5- ions generate even more hypobromite ions, making the treatment solution used in this embodiment suitable for use.

[0046] Furthermore, by oxidizing bromine-containing compounds with an oxidizing agent, hypobromite ions can also be generated in the treatment solution.

[0047] Adding hypobromide ions as a compound to the treatment solution only requires adding hypobromic acid, bromine water, and / or hypobromate. Suitable hypobromates include sodium hypobromide, potassium hypobromide, and tetraalkylammonium hypobromide. Hypobromic acid or tetraalkylammonium hypobromide is more suitable for surfaces that do not contain metal ions that could cause problems in semiconductor manufacturing.

[0048] The aforementioned tetraalkylammonium hypobromide can be easily obtained by passing bromine gas through a tetraalkylammonium hydroxide solution. Alternatively, it can be obtained by mixing hypobromic acid and a tetraalkylammonium hydroxide solution. Furthermore, tetraalkylammonium hypobromide can also be obtained by using an ion exchange resin to replace the cations contained in hypobromates such as sodium hypobromide with tetraalkylammonium ions.

[0049] In this embodiment, the concentration of hypobromite ions in the processing solution is 0.1 μmol / L or higher but less than 0.001 mol / L. If the concentration is less than 0.1 μmol / L, the etching rate of the transition metal is low, resulting in poor practicality. On the other hand, when the concentration is 0.001 mol / L or higher, the hypobromite ions are more prone to decomposition, for example, at high temperatures, making it difficult to stabilize the etching rate of the transition metal. Furthermore, if the concentration is 0.001 mol / L or higher, it tends to become difficult to maintain the flatness of the etched transition metal surface. In order to ensure stable etching of the transition metal at a sufficient rate and maintain the flatness of the etched metal surface, the concentration of hypobromate ions is preferably 0.1 μmol / L or higher but less than 0.001 mol / L, 1 μmol / L or higher but less than 0.001 mol / L, 10 μmol / L or higher but less than 0.001 mol / L is more preferred, 50 μmol / L or higher but less than 0.001 mol / L is even better, and 50 μmol / L or higher but less than 0.0005 mol / L is optimal.

[0050] The concentration of hypobromite ions in the treatment solution can be calculated based on manufacturing conditions, or it can be determined using widely known methods. For example, using ultraviolet-visible spectroscopy, the absorption caused by hypobromite ions can be easily identified, and the concentration can be determined from the intensity of its absorption peak (although it varies depending on the pH of the treatment solution or the concentration of hypobromite ions, it is generally around 330 nm). Furthermore, the concentration of hypobromite ions can also be determined by iodine titration. Alternatively, the concentration can be determined from the redox potential (ORP) or pH of the treatment solution. From the viewpoint of non-contact and continuous measurement, ultraviolet-visible spectroscopy is the best method. Moreover, when measuring the concentration of hypobromite ions using ultraviolet-visible spectroscopy, in cases where there is absorption from other chemical species, the concentration can be determined with sufficient accuracy through data processing such as spectral division or baseline correction, or by appropriate selection of the reference standard.

[0051] Since the acid dissociation constant (pKa) of hypobromic acid (HBrO) and hypobromite ions (BrO⁻) is 8.6, HBrO and BrO⁻ may coexist in the treatment solution at low pH levels, depending on the pH of the solution. When the treatment solution contains both HBrO and BrO⁻, the total concentration of HBrO and BrO⁻ can be considered the same as the concentration of hypobromite ions.

[0052] The exact mechanism by which hypobromite ions dissolve ruthenium is not fully understood, but it is speculated that in the treatment solution, hypobromite ions or hypobromic acid produced by hypobromite ions oxidize ruthenium and dissolve it in the solution as RuO₄⁻, RuO₄⁻, or RuO₄²⁻. By dissolving ruthenium as RuO₄⁻ or RuO₄²⁻, the amount of RuO₄⁻ gas produced is reduced, and the formation of RuO₂ particles is suppressed. For ruthenium to dissolve as RuO₄⁻ or RuO₄²⁻, an alkaline pH of the treatment solution is preferred, ideally between 8 and 14, even better between 12 and 14, and optimally between 12 and 13. If the pH of the processing solution is above 12 but below 13, ruthenium will dissolve in the solution as RuO₄⁻ or RuO₄²⁻, thus significantly reducing the generation of RuO₄ gas and suppressing the formation of RuO₂ particles. On the other hand, if the pH of the processing solution is below 8, ruthenium becomes more easily oxidized to RuO₂ or RuO₄, leading to an increase in the amount of RuO₂ particles and the generation of RuO₄ gas. Furthermore, if the pH exceeds 14, it becomes difficult to achieve a sufficient ruthenium etching rate due to the difficulty in ruthenium dissolution, thus reducing the production efficiency of semiconductor manufacturing. If the pH of the processing solution is between 8 and 14, ruthenium can be etched at a sufficient rate and stably, maintaining the flatness of the etched ruthenium surface and reducing the generation of RuO₄ gas.

[0053] The exact mechanism by which hypobromite ions dissolve tungsten, molybdenum, or chromium is not fully understood, but it is speculated that hypobromite ions or hypobromic acid produced by hypobromite ions oxidize tungsten, molybdenum, or chromium in the treatment solution, dissolving them in the solution by forming MO4, MO4-, or MO42- (where M represents tungsten (W), molybdenum (Mo), or chromium (Cr)). The dissolution of tungsten, molybdenum, or chromium in the treatment solution as these chemicals can suppress the precipitation of oxides onto the transition metal surface. If oxides precipitate onto the transition metal surface, the etching rate of the transition metal will change significantly, thus reducing the stability of the etching rate and deteriorating the surface flatness of the metal. Therefore, it is preferable to use tungsten, molybdenum, or chromium as these chemicals in the treatment solution. For this purpose, an alkaline pH in the treatment solution is preferred, with a pH between 8 and 14 being better, a pH between 12 and 14 being even better, and a pH between 12 and 13 being optimal.

[0054] (Anionic species) The processing solution of this embodiment may further include at least one anion selected from the group consisting of chlorate ions, chlorite ions, chloride ions, bromate ions, bromate ions, and bromide ions. It is presumed that by interacting with the metal through these anions, surface roughness will be further suppressed. That is, by including these anions, the processing solution of this embodiment makes it easier to maintain the flatness of the transition metal surface after etching. The processing solution may contain one or more of these anions. Among these, from the viewpoint of solubility, ease of acquisition, and cost, the inclusion of bromide ions is preferred. When the processing solution contains two or more anions, from the viewpoint of effectively suppressing metal surface roughness, the inclusion of anions selected from chloride ions, chlorate ions, bromide ions, or bromate ions is particularly preferred.

[0055] The anionic species used in this embodiment are generated by dissolving an acid or salt containing the anionic species in a treatment solution. Examples of acids containing anionic species include chloric acid, chlorite, hydrogen chloride, bromic acid, bromate, and hydrogen bromide. Examples of salts containing anionic species include alkali metal salts, alkaline earth metal salts, and organic salts. Specifically, examples of alkali metal salts include sodium chloride, sodium chlorate, sodium chlorite, potassium bromide, and sodium bromate; examples of organic salts include tetramethylammonium chloride, tetramethylammonium bromide, and other quaternary alkylammonium salts containing ononium ions. Furthermore, the hydrogen bromide system can also be generated by dissolving halogen gases such as bromine gas in water. Among these, considering that they do not contain metals that would cause a decrease in yield in semiconductor manufacturing, it is preferable to use acids or organic salts containing anionic species. Furthermore, considering industrial availability and ease of handling, organic salts containing onium ions, such as quaternary alkylammonium salts, are even better. Among organic salts, from the viewpoints of stability, purity, and cost, one or more from the group consisting of tetramethylammonium chloride, tetramethylammonium bromide, ethyltrimethylammonium chloride, ethyltrimethylammonium bromide, tetraethylammonium chloride, tetraethylammonium bromide, tetrapropylammonium chloride, tetrapropylammonium bromide, tetramethylammonium chlorate, tetramethylammonium bromate, tetramethylammonium chlorite, and tetramethylammonium bromate can be cited as particularly suitable for users.

[0056] The content of anions in the above-mentioned treatment solution is not particularly limited, and can be appropriately determined by considering the type or stability of anions, the concentration of hypobromite ions, the type or amount of other additives mentioned later, and etching conditions (e.g., processing time or processing temperature). Generally speaking, a longer etching time or a larger etching volume tends to deteriorate the flatness of the metal surface. This situation is mitigated by increasing the amount of anions contained in the treatment solution of this embodiment, thereby maintaining the flatness of the etched metal surface. For example, the content of anions in the treatment solution is preferably 0.01 μmol / L to 10.0 mol / L, more preferably 0.01 mmol / L to 7.00 mol / L, and even more preferably 1 mmol / L to 5.00 mol / L. The content of anions in the above-mentioned treatment solution can be measured using ion chromatography. By appropriately setting the type or conditions of the column, it is possible to both determine and quantify the anions.

[0057] (Oxidizing agents other than hypobromite ions) In the processing solution of this embodiment, hypobromite ions act as an oxidant to etch the transition metal. It is preferable that the processing solution contains an oxidant different from that of hypobromite ions. By including an oxidant, the processing solution of this embodiment achieves the effect of re-oxidizing the bromide ions (Br-) generated from the decomposition of hypobromite ions back into hypobromite ions.

[0058] When transition metals are oxidized, hypobromite ions are reduced to Br⁻. Furthermore, hypobromite ions readily decompose spontaneously in the processing solution, partially transforming into Br⁻. Moreover, the decomposition of hypobromite ions is accelerated by ultraviolet and visible light, with some transforming into Br⁻. Additionally, hypobromite ions decompose further upon heating, contact with acids, or contact with metals, also partially transforming into Br⁻. Since the Br⁻ produced by the reduction or decomposition of hypobromite ions is insoluble in transition metals, the etching rate of transition metals decreases during this reduction or decomposition. By including a suitable oxidant in the processing solution, the Br⁻ produced by reduction or decomposition can be oxidized to hypobromite ions, thereby slowing down the decrease in the etching rate of transition metals. In other words, by including hypobromite ions and a suitable oxidant in the processing solution, the stabilization time of the etching rate is extended.

[0059] The oxidant that can be included in the treatment solution is preferably one whose redox potential, generated by the reduction of the oxidant / the oxidant, exceeds that of the hypobromite ion (BrO-) / bromide ion (Br-) system. The redox potential of the hypobromite ion / bromide ion system refers to the redox potential in the following reaction formula (3), which is the potential in equilibrium between the hypobromite ions of the oxidant and the bromide ions of the reducer in the treatment. That is, the redox potential of an oxidant exceeding the redox potential of hypobromite ions / bromide ions means that the redox potential between the oxidant and the chemical species produced by the reduction of the oxidant exceeds the redox potential of the hypobromite ions and the bromide ion system produced by the reduction of the hypobromite ions. If such an oxidant is used, Br- can be oxidized to hypobromite ions. The redox potential between the oxidant and the chemical species generated by the reduction of the oxidant in the treatment solution varies depending on the concentration of the oxidant and the chemical species generated by the reduction of the oxidant, the temperature of the treatment solution, and the pH, etc. However, it is acceptable as long as the redox potential between the chemical species generated by the reduction of the oxidant exceeds the redox potential of the BrO- / Br- system, regardless of these conditions. On the other hand, there are no particular limitations on the upper limit of the redox potential between the oxidant and the chemical species generated by the reduction of the oxidant in the treatment solution, as long as it does not exceed the purpose of this invention.

[0060] From the perspective of avoiding the inclusion of metal elements that would cause problems in semiconductor manufacturing, the oxidant that can be included in the processing solution in this embodiment is preferably hypochlorite ions (ClO-), ozone, periodate ions, or metaperiodate ions. Among these, hypochlorite ions are more suitable in terms of high solubility in the processing solution, stable existence in solution, and easy adjustment of concentration.

[0061] Hypochlorite ions, ozone, periodate ions, and metaperiodate ions possess the ability to re-oxidize Br⁻ to hypobromite ions in alkaline processing solutions (pH 8 to 14). This is evident from, for example, the redox potential relative to the ClO⁻ / Cl⁻ system is 0.89 V, the redox potential relative to the ozone / oxygen system is 1.24 V, and the redox potential relative to the BrO⁻ / Br⁻ system is 0.76 V. Furthermore, the aforementioned redox potentials are values ​​relative to the standard hydrogen electrode at pH 14 (25°C). Therefore, the processing solution containing hypobromite ions and hypochlorite ions or ozone in this embodiment, by oxidizing Br⁻ to hypobromite ions, can stabilize the etching rate of transition metals by maintaining a high concentration of hypobromite ions in the processing solution.

[0062] Because the etching rate of ruthenium takes a long time to stabilize, it is particularly suitable to use a processing solution that contains both hypobromite and hypochlorite ions in the present embodiment. On the other hand, when using oxidants with weak oxidizing power under alkaline conditions, such as hydrogen peroxide, the etching rate of ruthenium is low and it is difficult to stabilize the etching rate of transition metals because Br- cannot be efficiently oxidized to hypobromite ions.

[0063] In this embodiment, the concentration of hypochlorite ions in the processing solution is not limited as long as it does not exceed the scope of the present invention, and is preferably between 0.1 μmol / L and 4 mol / L. If the concentration of hypochlorite ions is less than 0.1 μmol / L, Br- cannot be oxidized efficiently, resulting in a lower ruthenium etching rate. On the other hand, if the added amount of hypochlorite ions is greater than 4 mol / L, the stability of hypochlorite ions will decrease, which is appropriate. From the viewpoint of simultaneously suppressing RuO4 gas generation and reducing the ruthenium etching rate, the concentration of the oxidant after adding hypobromite ions and other oxidants is preferably between 1 μmol / L and 2 mol / L, and most preferably between 10 μmol / L and 2 mol / L.

[0064] On the other hand, if the ratio of hypochlorite ions to hypobromate ions is high, the reaction between hypochlorite and hypobromate ions will lead to the conversion of hypobromate ions to bromate ions, resulting in a decrease in the hypobromate ion concentration. Since a decrease in the hypobromate ion concentration leads to a decrease in the etching rate of transition metals, it is important to stabilize the hypobromate ion concentration. By controlling the ratio of hypobromate ions to hypochlorite ions in the processing solution, the hypobromate ion concentration can be stabilized.

[0065] The ratio of hypobromite ions to hypochlorite ions in the treatment solution is preferably determined by taking into account the rate of hypobromite ion reduction, or more precisely, the rate of Br- formation through the reduction and / or decomposition reactions of hypobromite ions, and the rate of the oxidation reaction from Br- to BrO- caused by hypochlorite ions. In reality, due to the complex interplay of multiple factors in these reactions, it is difficult to determine an appropriate ratio of hypobromite ions to hypochlorite ions. However, if 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, then hypochlorite ions can be used to re-oxidize Br- produced by the reduction or decomposition reactions of BrO- back to BrO-, thereby stabilizing the etching rate of the transition metal.

[0066] The methods for generating hypochlorite ions described above are not particularly limited, and hypochlorite ions generated by any method can be suitable for use in the processing solution of this embodiment. Methods for generating hypochlorite ions include, for example, adding hypochlorite or blowing in chlorine gas. Among these, adding hypochlorite to the processing solution is more suitable because it allows for easy control of the hypochlorite ion concentration, and the operation of the hypochlorite is also easy. Examples of such hypochlorites include tetraalkylammonium hypochlorite, sodium hypochlorite, potassium hypochlorite, calcium hypochlorite, magnesium hypochlorite, and hypochlorous acid. From the viewpoint that these do not contain metals that could cause problems in semiconductor manufacturing, tetraalkylammonium hypochlorite or hypochlorous acid is particularly suitable because it remains stable even at high concentrations; therefore, tetraalkylammonium hypochlorite is the most suitable.

[0067] As for the aforementioned tetraalkylammonium hypochlorite, tetraalkylammonium hypochlorite containing tetraalkylammonium ions with 1 to 20 alkyl carbons per alkyl group is suitable. Specifically, tetramethylammonium hypochlorite, ethyltrimethylammonium hypochlorite, tetraethylammonium hypochlorite, tetrapropylammonium hypochlorite, tetrabutylammonium hypochlorite, tetrapentylammonium hypochlorite, and tetrahexylammonium hypochlorite are more suitable from the viewpoint of having the most hypochlorite ions per unit weight. Tetramethylammonium hypochlorite is most suitable because high-purity products are readily available.

[0068] There are no particular limitations on the method for manufacturing tetramethylammonium hypochlorite described above, and it can be manufactured using widely known methods. For example, it is suitable to manufacture tetramethylammonium hypochlorite by blowing chlorine into tetramethylammonium hydroxide, by mixing hypochlorous acid with tetramethylammonium hydroxide, by using an ion exchange resin to replace the cations in a hypochlorite solution with tetramethylammonium, or by mixing a distillate containing a hypochlorite solution with tetramethylammonium hydroxide.

[0069] The concentration of hypohalite ions in the aforementioned treatment solution can be calculated during the manufacturing process of the treatment solution, or it can be confirmed using known methods. Specifically, as a measurement method, the absorption caused by hypohalite ions can be confirmed by ultraviolet-visible spectroscopy, and the concentration of hypohalite ions can be determined from the intensity of its absorption peak and a calibration curve prepared using a hypohalite ion solution of known concentration. Alternatively, the concentration of hypohalite ions can be determined by titration.

[0070] In this embodiment, when the processing solution contains periodate or metaperiodate ions, the concentration of periodate or metaperiodate ions is not limited as long as it does not exceed the spirit of the invention, and is preferably 0.1 μmol / L to 4 mol / L. If the concentration of periodate or metaperiodate ions is less than 0.1 μmol / L, Br- cannot be oxidized efficiently, and the ruthenium etching rate will decrease. On the other hand, if the amount of periodate or metaperiodate ions added is greater than 4 mol / L, it is inappropriate because the stability of periodate or metaperiodate ions will decrease. From the viewpoint of simultaneously suppressing RuO4 gas generation and ruthenium etching rate, even when the processing solution of this embodiment contains periodate or metaperiodate ions, the total concentration of the oxidant is preferably 1 μmol / L to 2 mol / L, and most preferably 10 μmol / L to 2 mol / L.

[0071] (pH and organic base of the treatment solution) In this embodiment, the pH of the semiconductor processing solution for the transition metal is preferably between 8 and 14, more preferably between 8 and 13, and optimally between 10 and 13. A pH between 8 and 14 allows for efficient etching of the transition metal. When the pH is below 8, hypobromite ions decompose, making etching difficult. Conversely, when the pH exceeds 14, the decomposition of the aforementioned oxidant raises concerns about inconsistent oxidation of bromine-containing compounds. This means that the etching rate of the transition metal is not constant, which complicates process control in semiconductor manufacturing and must be avoided.

[0072] To adjust the pH of the processing solution, an acid or base can be added. The acid can be any inorganic or organic acid; examples include carboxylic acids such as hydrofluoric acid, hydrochloric acid, hydrogen bromide, nitric acid, acetic acid, sulfuric acid, peroxydisulfuric acid, and formic acid. Other widely known acids used in semiconductor processing solutions can also be used without restriction. As for the base, organic bases are preferred, provided they do not contain metal ions that could cause problems in semiconductor manufacturing. An example of an organic base is tetraalkylammonium hydroxide, which is composed of tetraalkylammonium ions and hydroxide ions. Examples of tetraalkylammonium hydroxide include tetramethylammonium hydroxide, ethyltrimethylammonium hydroxide, tetraethylammonium hydroxide, tetrapropylammonium hydroxide, and tetrabutylammonium hydroxide. Since tetraalkylammonium hydroxide has a high number of hydroxide ions per unit weight and high purity is readily available, it is preferred to use tetraalkylammonium hydroxide, with tetramethylammonium hydroxide or ethyltrimethylammonium hydroxide being more suitable. Furthermore, a pH buffer may be added to the treatment solution as needed. Widely known pH buffers can be used, such as phosphoric acid, boric acid, carbonic acid, oxalic acid, and their salts.

[0073] (Tetraalkylammonium ion) To adjust the pH of the treatment solution, an acid or base can be added. As the base, an organic base is preferred, as it should not contain metal ions that could cause problems in semiconductor manufacturing. Among organic bases, onium salts containing onium ions are preferred. An example of an onium salt is tetraalkylammonium hydroxide, which is composed of tetraalkylammonium ions and hydroxide ions. The number of carbon atoms in the alkyl group of the tetraalkylammonium ion derived from this tetraalkylammonium hydroxide can be 1 to 20, preferably 1 to 10. Examples of tetraalkylammonium hydroxide include tetramethylammonium hydroxide, ethyltrimethylammonium hydroxide, tetraethylammonium hydroxide, tetrapropylammonium hydroxide, and tetrabutylammonium hydroxide. Since the number of hydroxide ions per unit weight is high and high-purity products are readily available, tetraalkylammonium hydroxide is preferred, with tetramethylammonium hydroxide or ethyltrimethylammonium hydroxide being more desirable.

[0074] The tetraalkylammonium ions contained in the treatment solution may be of one type or in combination of multiple types.

[0075] The processing solution of this embodiment may further include a RuO4 gas generation inhibitor. The inclusion of a RuO4 gas generation inhibitor in the processing solution can suppress RuO4 gas generated by ruthenium oxide dissolved in the processing solution when processing wafers containing ruthenium. As such a RuO4 gas generation inhibitor, it is preferable, for example, to be a compound having ligands that coordinate with RuO4, RuO4-, RuO42-, etc. Specifically, compounds having ligands that coordinate with RuO₄, RuO₄⁻, RuO₄²⁻, etc., include compounds with carboxyl or carbonyl groups, such as oxalic acid, dimethyl oxalate, 1,2,3,4,5,6-cyclohexanehexacarboxylic acid, succinic acid, acetic acid, butane-1,2,3,4-tetracarboxylic acid, dimethylmalonic acid, glutaric acid, diglycolic acid, citric acid, malonic acid, 1,3-adamantanedicarboxylic acid, or 2,2-bis(hydroxymethyl)propionic acid; and nitrogen-containing heterocyclic compounds, such as pyridine compounds, piperazine compounds, triazole compounds, pyrazole compounds, or imidazole compounds. Furthermore, ononium salts composed of ononium ions and bromide ions can also be cited as inhibitors of RuO₄ gas generation. From the perspective that RuO4 gas generation suppression effect is high, the metal content that would cause problems in semiconductor manufacturing is low, and it can be manufactured at a low cost in industry, the RuO4 gas generation inhibitor containing ononium salts composed of ononium ions and bromide ions, as described later, is better.

[0076] (solvent) Water is the preferred solvent for the processing solution in this embodiment. The water in the processing solution is preferably water that has been treated by distillation, ion exchange, filtration, or various adsorption processes to remove metal ions, organic impurities, or particulate matter; pure water or ultrapure water is particularly preferred. This type of water can be obtained using methods widely known in semiconductor manufacturing.

[0077] Furthermore, organic solvents can also be used as long as the hypohalite ion is stable. Examples of organic solvents include acetonitrile and cyclobutane.

[0078] Furthermore, water and organic solvents can also be used as solvents. By using water and organic solvents together, the oxidation of transition metals can proceed relatively stably, thus suppressing the oxidation of wiring in circuit forming parts. When using water and organic solvents together, the mass ratio of water to organic solvent (water / organic solvent) can be around 60 / 40 to 99.9 / 0.1.

[0079] (Other additives) The processing solution of this embodiment may be incorporated, without prejudice to the purpose of the invention, other additives conventionally used in semiconductor processing solutions. For example, other additives may include acids, metal corrosion inhibitors, water-soluble organic solvents, fluorinated compounds, oxidants, reducing agents, chelating agents, surfactants, defoamers, pH adjusters, stabilizers, etc. These additives may be added individually or in combination.

[0080] (Manufacturing method of the treatment fluid) The method for manufacturing the semiconductor processing solution of this embodiment is not particularly limited. For example, it can be manufactured by the manufacturing method described in the third embodiment of the present invention, which will be described later. Alternatively, a solvent such as water can be added to achieve the desired concentration of hypobromite ions, hypobromic acid, and / or hypobromate, and additives can be added as necessary to adjust the pH to the desired level to produce the processing solution of this embodiment. Furthermore, multiple solutions (hereinafter also referred to as "modification materials") that are separated and mixed can be prepared and mixed with these modulation materials before the processing of the semiconductor wafer to produce the processing solution of this embodiment. In the case of preparing multiple modulation materials and mixing them to produce the processing solution of this embodiment, the components contained in the modulation materials can also react after mixing to generate substances such as hypobromite ions. The processing solution of this embodiment may experience changes in pH or composition over time, leading to variations in etching performance, such as etching rate. Therefore, from the viewpoint of suppressing the decrease in etching performance due to changes over time, preparing multiple modulation materials and mixing these modulation materials before processing the semiconductor wafer to create the processing solution of this embodiment is a preferred manufacturing method. While multiple modulation materials can be prepared individually, considering operability during mixing, it is preferable to prepare two types of modulation materials.

[0081] The following details a method for manufacturing a processing liquid, which involves preparing two types of modulation materials, namely a first solution (modification material) and a second solution (modification material), mixing these modulation materials before processing a semiconductor wafer, and producing a processing liquid in the present embodiment.

[0082] (Materials for preparation) As an advantage of the two modulation materials used in the preparation of the first solution (modification material) and the second solution (modification material), for example, there is an improvement in the stability of the etching performance of the processing solution containing hypobromite ions. That is, when the processing solution is a single liquid, after the hypobromite ions are generated, the etching performance, such as the etching rate, changes over time in the semiconductor manufacturing plant until the semiconductor wafer is processed due to the decomposition of the hypobromite ions. On the other hand, by preparing the processing solution as the two modulation materials mentioned above, namely the first solution (modification material) and the second solution (modification material), and mixing the modulation materials to generate hypobromite ions, the processing solution containing hypobromite ions is prepared in the semiconductor manufacturing plant just before the semiconductor wafer is processed, thus suppressing the decomposition of hypobromite ions and exhibiting stable etching performance. In particular, when the processing solution of this embodiment is used in situations such as the etch back step, since fine machining is necessary and precise control of etching speed and surface roughness is required, it is preferable to make the above-mentioned state.

[0083] Therefore, when preparing the treatment solution as the two types of preparation materials, namely the first solution (preparation material) and the second solution (preparation material), from the viewpoint of preserving the stability of the preparation material itself and from the viewpoint of being able to stably suppress metal surface roughness, the composition of the two solutions of each preparation material is preferably made as shown below. • Solution 1 (preparation material): A solution containing at least one anion selected from bromate, bromide, and bromide ions. • Solution 2 (preparation material): A solution containing hypohalite ions

[0084] Here, in order to generate hypobromite ions by mixing the first solution (preparation material) and the second solution (preparation material) described above, it is sufficient that the first solution (preparation material) contains bromide ions and the second solution (preparation material) contains hypohalite ions with a higher oxidizing power than the bromide ions in the first solution (preparation material). Hypochlorous acid ions can be cited as such hypohalite ions. Specifically, in order to manufacture a treatment solution containing hypobromite ions, the first solution (preparation material) is prepared into a solution containing bromide ions, and the second solution (preparation material) is prepared into a solution containing hypochlorous acid ions. Since the redox potential of hypochlorite ion-chloride ion (0.89V (at 25℃, pH 14, vs. standard hydrogen electrode)) is higher than that of hypobromite ion-bromide ion (0.76V (same as above)), by mixing the first solution and the second solution, the bromide ions are oxidized due to the hypochlorite ions to generate hypobromite ions, thereby producing a treatment solution containing hypobromite ions. At this time, the hypochlorite ions are reduced to chloride ions. The bromide ions contained in the first solution (preparation material) can be added as bromide ions as described later, or they can be bromide ions generated by the decomposition of bromate ions, bromite ions, and / or hypobromite ions.

[0085] (Preparation method of the first solution (material for preparation)) In this embodiment, there are no particular limitations on the method for preparing the first solution (preparation material). Specifically, at least one anion selected from bromate ions, bromide ions, and bromide ions can be added to a solvent such as water to form the first solution (preparation material) of this embodiment. Other additives may also be added to the first solution (preparation material) as necessary. When hypobromite ions are generated by mixing the two preparation materials, the first solution (preparation material) and the second solution (preparation material), and bromide ions are present in the first solution (preparation material), these ions are obtained, for example, by dissolving a salt that generates these ions during dissolution in the solution. Examples of substances that form bromide ions include metal salts such as sodium bromide, organic salts such as tetraalkylammonium bromide, bromine gas, and hydrogen bromide. Among these, organic salts, bromine gas, and hydrogen bromide are preferred, provided they do not contain metals that would cause a decrease in yield in semiconductor manufacturing. Considering ease of industrial availability, organic salts are preferred as raw materials for bromide ions. Among these organic salts, those containing onmium ions, such as tetramethylammonium bromide, ethyltrimethylammonium bromide, tetraethylammonium bromide, and tetrapropylammonium bromide, are particularly suitable for users from the perspectives of stability, purity, and cost.

[0086] The organic salt used in this embodiment can be, for example, produced by combining tetraalkylammonium ions and bromide ions to form tetraalkylammonium bromide. Methods for producing tetraalkylammonium bromide include simply mixing an aqueous solution containing tetraalkylammonium hydroxide with an aqueous solution containing bromide ions, or dissolving it in water to produce a bromine-containing gas, such as hydrogen bromide, which generates bromide ions. Examples of tetraalkylammonium hydroxides used in the production of tetraalkylammonium bromide include tetramethylammonium hydroxide, ethyltrimethylammonium hydroxide, tetraethylammonium hydroxide, tetrapropylammonium hydroxide, and tetrabutylammonium hydroxide. Among these, tetramethylammonium hydroxide or ethyltrimethylammonium hydroxide is preferred because it produces a large number of hydroxide ions per unit weight and high purity is readily available. Examples of bromide ion sources used in the production of tetraalkylammonium bromide include hydrogen bromide, lithium bromide, sodium bromide, potassium bromide, rubidium bromide, cesium bromide, and ammonium bromide. Hydrogen bromide is the most suitable because it does not contain any metals, is readily available industrially, and can be easily obtained in high purity.

[0087] The concentration of at least one anion selected from bromate ions, bromide ions, and bromide ions contained in the first solution (preparation material) can be appropriately set in a manner that would result in the desired concentration when mixed with the second solution to form the processed solution of this embodiment. For example, if mixing the first solution (preparation material) and the second solution (preparation material) does not generate hypobromate ions, the concentration of the aforementioned anion contained in the first solution (preparation material) can be set considering the volume of the processed solution after mixing. On the other hand, if mixing the first solution (preparation material) and the second solution (preparation material) generates hypobromate ions, the concentration of bromide ions contained in the first solution (preparation material) can be set considering the amount of bromide ions consumed in generating hypobromate ions.

[0088] The pH of the first solution is not particularly limited; it can be appropriately set so that the pH of the treatment solution of this embodiment becomes the desired pH when mixed with the second solution. From the viewpoint of suppressing pH changes after mixing, a pH of 7 to 14 is ideal, and 8 to 14 is preferred. If the solution is within this pH range, the pH drop that occurs when mixed with the second solution can be reduced, and the treatment solution of this embodiment can be manufactured, stored, and used stably. If the pH of the first solution is less than 8, the pH and volume of the first solution can be adjusted so that the pH of the mixed treatment solution becomes alkaline when mixed with the second solution. As for other components included in the first solution, it is preferable to use the solvents, other additives, and pH adjusters described in the treatment solution of this embodiment.

[0089] (Preparation method of the second solution (material for preparation)) In this invention, there are no particular limitations on the method for preparing the second solution (preparation material). Specifically, the second solution (preparation material) in the cost embodiment can be prepared by adding hypohalite ions to a solvent such as water, and adding additives as necessary. Regarding the aforementioned hypohalite ions, sodium hypochlorite, sodium hypobromite, tetraalkylammonium hypochlorite, and tetraalkylammonium hypobromite can be used as the supply source, for example. Among these, from the perspective of metals that are not included in the semiconductor formation step and would cause a decrease in yield, tetraalkylammonium hypochlorite and tetraalkylammonium hypobromite are preferred. These tetraalkylammonium hypohalites can be prepared by known methods. For example, by preparing an aqueous solution of tetraalkylammonium hydroxide and blowing in chlorine or bromine, aqueous solutions containing tetraalkylammonium hypochlorite and tetraalkylammonium hypobromite can be prepared respectively. Furthermore, a method can be used to prepare a solution containing tetraalkylammonium hypochlorite or tetraalkylammonium hypobromite by contacting a tetraalkylammonium hydroxide solution with a cation exchange resin to convert the cations in the ion exchange resin into tetraalkylammonium ions, and then allowing a sodium hypochlorite solution or a sodium hypobromite solution to circulate.

[0090] The concentration of hypohalite ions in the second solution (preparation material) can be appropriately set in a way that achieves the desired concentration when mixed with the first solution to form the treatment solution of this embodiment. For example, if mixing the first solution (preparation material) and the second solution (preparation material) does not generate hypobromite ions, the concentration of hypohalite ions in the second solution (preparation material) can be set considering the volume of the mixed treatment solution. On the other hand, if mixing the first solution (preparation material) and the second solution (preparation material) generates hypobromite ions, the concentration of hypohalite ions in the second solution (preparation material) can be set considering the amount of hypohalite ions consumed in generating hypobromite ions.

[0091] The pH of the second solution is not particularly limited; it can be appropriately set so that the pH of the treatment solution of this embodiment becomes the desired pH when mixed with the first solution. From the viewpoint of suppressing pH changes after mixing, a pH of 7-14 is ideal, 10-14 is preferred, and 12-14 is particularly favorable. If the solution is within this pH range, the pH drop that occurs when mixed with the first solution can be minimized, and the treatment solution of this embodiment can be stably manufactured, stored, and used. As for other components included in the second solution, it is preferable to use the solvents, other additives, and pH adjusters described in the treatment solution of this embodiment.

[0092] Regarding the manufacture and storage of the treatment liquid and preparation materials of this embodiment, it is preferable to use low temperature, light protection, and amine-free conditions. By manufacturing and storing at low temperature, in a light-protected environment, and without amine, it is expected to inhibit the decomposition of oxidants and anionic species in the treatment liquid. Furthermore, since the treatment liquid and preparation materials are manufactured and stored using a container sealed with an inert gas, the contamination of carbon dioxide is prevented, thus maintaining the stability of the treatment liquid. Also, it is preferable that the inner surface of the container, i.e., the surface in contact with the treatment liquid, is formed of glass or an organic polymer material. This is because if the inner surface of the container is formed of glass or an organic polymer material, the contamination of impurities such as metals, metal oxides, and organic matter can be further reduced.

[0093] (Admixture of materials for preparation) In the manufacturing method of the treatment liquid of this embodiment, there is no particular limitation on the concentration of each component contained in the two preparation materials, the first solution (preparation material) and the second solution (preparation material), and they can be prepared in the manner desired when the preparation materials are mixed to form the treatment liquid.

[0094] Specifically, when preparing a treatment solution containing hypobromite ions at a concentration of 0.1 μmol / L or higher but less than 0.001 mol / L, bromide ions at a concentration of 0.01 μmol / L or higher but less than 5.0 mol / L, bromite ions at a concentration of 0.01 μmol / L or higher but less than 5.0 mol / L, and bromate ions at a concentration of 0.01 μmol / L or higher but less than 5.0 mol / L as anions, the concentration of bromide ions will be 0.22 μmol / L or higher but less than 10.002 μmol / L. A solution containing 0.02 μmol / L or more but less than 10.0 mol / L of bromate ions and 0.02 μmol / L or more but less than 10.0 mol / L of bromate ions is used as the first solution (preparation material) mentioned above. A solution containing 0.2 μmol / L to 0.002 mol / L of hypochlorite ions is used as the second solution (preparation material) mentioned above. Before processing the semiconductor wafer, these preparation materials are mixed to prepare a processing solution for the semiconductor wafer.

[0095] Alternatively, in a treatment solution containing hypohalite ions at a concentration of 0.1 μmol / L or higher but less than 0.001 mol / L, hypochlorite ions at a concentration of 0.1 μmol / L or higher but less than 4 mol / L as hypohalite ions, bromate ions at a concentration of 0.01 μmol / L or higher but less than 5.0 mol / L as an anion, and chloride ions at a concentration of 0.1 μmol / L or higher but less than 5.0 mol / L and chlorate ions at a concentration of 0.01 μmol / L or higher but less than 5.0 mol / L as other components, the solution containing 0.2 μmol / L bromide ions... A solution containing 0.002 mol / L or higher of mol / L but less than 0.002 mol / L of chloride ions but less than 9.998 mol / L of chloride ions, 0.02 μmol / L or higher of mol / L but less than 10.0 mol / L of chlorate ions, and 0.02 μmol / L or higher of mol / L but less than 10.0 mol / L of bromate ions is used as the first solution (preparation material). A solution containing 0.4 μmol / L to 8.002 mol / L of hypochlorite ions is used as the second solution (preparation material). Before processing the semiconductor wafer, these preparation materials are mixed to prepare a processing solution for the semiconductor wafer.

[0096] (Method for mixing materials for preparation) The mixing method of the first solution (preparation material) and the second solution (preparation material) is a widely known method for mixing semiconductor solutions. Suitable methods include, for example, using a mixing tank, mixing within the piping of a semiconductor manufacturing apparatus (inline mixing), and simultaneously placing multiple liquids onto a wafer for mixing. Furthermore, in cases where the first solution (preparation material) and the second solution (preparation material) are mixed to generate hypobromite ions, from the viewpoint of ensuring the reliable generation of hypobromite ions, it is preferable to pre-mix the preparation material to ensure sufficient generation of hypobromite ions before contacting it with the semiconductor wafer.

[0097] Regarding the temperature for mixing the above-mentioned conditioning materials, there are no particular restrictions as long as the mixed treatment solution becomes homogeneous; generally, a suitable temperature range of 0 to 80°C is sufficient. In cases where hypobromite ions are generated by mixing the conditioning materials, since the generation of hypobromite ions should be rapid, the mixing time should be as short as possible. To shorten the mixing time, for example, increasing the mixing temperature can be used; however, higher temperatures tend to facilitate the decomposition of hypohalite ions contained in the second solution or the mixed treatment solution. For this reason, the mixing temperature of the above-mentioned conditioning materials for generating hypobromite ions by mixing the conditioning materials is preferably 10 to 60°C, and optimally 20 to 50°C.

[0098] Furthermore, regarding the mixing time of the preparation material, if mixing the first solution (preparation material) and the second solution (preparation material) does not generate hypobromite ions, the mixing should continue until the temperature or concentration of the components in the mixed treatment solution becomes uniform; typically, a time of 30 minutes or less is suitable. On the other hand, if mixing the first solution (preparation material) and the second solution (preparation material) does generate hypobromite ions, a longer time is preferable to ensure reliable generation of hypobromite ions; from a yield perspective, a time of 60 minutes or less is suitable.

[0099] Furthermore, in the processing solution of this embodiment, the content of metals, specifically sodium, potassium, aluminum, magnesium, iron, nickel, copper, silver, cadmium, and lead, is preferably below 1 ppb. To prevent the introduction of these metals, reactors and piping with surfaces in contact with the solution formed of organic polymer materials can be used. As organic polymer materials, materials such as vinyl chloride-based resins (soft and rigid vinyl chloride resins), nylon-based resins, silicone-based resins, polyolefin-based resins (polyethylene, polypropylene), and fluorinated resins can be used. Among these, fluorinated resins are preferred considering ease of molding, solvent resistance, and minimal impurity precipitation.

[0100] The processing solution of this embodiment, and the halogen oxyacid salts, oxidants, tetraalkylammonium salts, acids, bases, water, solvents, and other additives used in the processing solution, preferably contain low levels of ammonia and amines. This is because the presence of ammonia and amines in the processing solution can react with oxidants, halogen oxyacid salts, and halogen oxyacid ions, leading to a decrease in the stability of the processing solution. For example, when tetramethylammonium hydroxide is used as a base, the ammonia and amines contained in this base compound, especially trimethylamine, can contribute to a decrease in the stability of the processing solution. Therefore, in the processing solution of this embodiment, when using tetramethylammonium hydroxide, the total amine content of the base compound is preferably, for example, below 100 ppm. If the total amine content is below 100 ppm, the impact of reactions with oxidants or bromine-containing compounds, or with the chemical species of etching transition metals generated from bromine-containing compounds, is minor and will not impair the stability of the processing solution.

[0101] In manufacturing the processing liquid of this embodiment, it is preferable to carry out the process under light protection to prevent the decomposition of halogen oxyacid ions, oxidants, and other additives due to light.

[0102] Furthermore, in the manufacturing of the processing solution of this embodiment, it is preferable to prevent carbon dioxide from dissolving in the processing solution. If the processing solution of this embodiment is alkaline, carbon dioxide will easily dissolve in the processing solution, potentially causing pH changes. Changes in the pH of the processing solution will not only cause variations in the etching rate of the transition metal, but also reduce the stability of the processing solution. The dissolution of carbon dioxide in the processing solution can be reduced by methods such as flushing the manufacturing apparatus with a flowing inert gas to prevent carbon dioxide from reacting in an inert gas environment. If the carbon dioxide concentration in the manufacturing apparatus is below 100 ppm, the effects caused by carbon dioxide dissolution can be disregarded.

[0103] (Preservation of the treatment solution) The treatment solution in this embodiment is preferably stored at low temperature and / or under light-proof conditions. By storing it at low temperature and / or under light-proof conditions, the decomposition of oxidants or hypobromite ions in the treatment solution can be expected to be inhibited. Furthermore, by storing the treatment solution in a container whose surface in contact with the solution is made of an organic polymer material, and / or using a container sealed with an inert gas, the contamination of carbon dioxide is prevented, thereby maintaining the stability of the treatment solution.

[0104] The semiconductor wafer processing solution of this embodiment can be manufactured using the above-described manufacturing method. By using the semiconductor wafer processing solution of this embodiment, not only can the wafer processing efficiency per unit time be improved, but it is also suitable for use as a processing solution in the etching process of metals in semiconductor manufacturing steps that require precise etching control of wiring materials, for example. Furthermore, since it has the same effect on metals other than ruthenium, it is not limited to ruthenium and can also be used as an etching solution for metals contained in semiconductor wafers.

[0105] (Use of the treatment solution) Using the processing solution of this embodiment, transition metals attached to the surface, end face, or back face of a semiconductor wafer can be etched stably at a sufficient etching rate. Furthermore, the flatness of the etched metal surface can be maintained. The sufficient etching rate in this embodiment refers to an etching rate at which the amount of transition metal etched can be controlled by the etching time, and the flatness of the etched surface can be maintained. In other words, it means an etching rate at which the micro-processing of transition metals can be performed within a practical timeframe in semiconductor manufacturing, and the flatness of the metal surface can be maintained. Specifically, for ruthenium, it means an etching rate of 10 Å / min or higher. For tungsten, it means 50 Å / min or higher; for molybdenum, it means 50 Å / min or higher; and for chromium, it means 50 Å / min or higher. If the etching rates of ruthenium, tungsten, molybdenum, or chromium meet the above values, they are suitable for use in etching steps, residue removal steps, cleaning steps, CMP steps, etc. In the etching of transition metals, where it is necessary to perform etching at a higher speed than those mentioned above, the appropriate selection of the following parameters for the processing solution is necessary: ​​hypobromite ion concentration, hypochlorite ion concentration, bromine-containing compound concentration, oxidant concentration, pH of the processing solution, processing temperature, and contact method between the processing solution and the wafer.

[0106] As described above, the semiconductor wafer processing solution of this embodiment not only improves the wafer processing efficiency per unit time, but is also suitable for use as a processing solution for the etching back step of metals in semiconductor manufacturing processes that require precise etching control of wiring materials. Furthermore, since it has the same effect on metals other than ruthenium, it is not limited to ruthenium and can also be used as an etching solution for metals contained in semiconductor wafers.

[0107] There are no particular limitations on the temperature when etching metal using the processing solution of this embodiment; it can be determined appropriately by considering factors such as the etching rate of the metal and the stability of the processing solution. Since the stability of the processing solution tends to deteriorate with increasing temperature, a lower processing temperature is preferable. On the other hand, the etching rate of metal tends to increase with higher temperatures. From the viewpoint of balancing the stability of the processing solution and the etching rate, the etching temperature is preferably 10℃~90℃, more preferably 15℃~70℃, and optimally 20℃~60℃.

[0108] The processing solution of this embodiment is suitable for processing substrates containing films containing transition metals. Examples of such substrates include silicon wafers, glass, plastic, and semiconductor substrates other than silicon, on which the transition metal film is deposited. By using the processing solution of this embodiment, the transition metal film present on such substrates can be etched at a sufficient speed. Therefore, by etching (dissolving) the transition metal present on the substrate to process and / or remove the metal, semiconductor device formation, wiring formation, metal film thickness control, electrode formation, etc., can be performed.

[0109] Metals contained in the semiconductor wafer to which the processing solution of this embodiment is applicable can specifically include Ru, Rh, Ti, Ta, Co, Cr, Hf, Os, Pt, Ni, Mn, Cu, Zr, La, Mo, and W. These metals can be single metal species or alloys of multiple metal species, and the processing solution is suitable for use. Metals such as Ru, Rh, Co, Cu, Mo, and W, which are useful as wiring layers, can also be used. This metal can be deposited using any method, utilizing methods widely known in semiconductor manufacturing processes, such as CVD, ALD, PVD, sputtering, and electroplating.

[0110] The aforementioned metals can also be intermetallic compounds, ionic compounds, or complexes. Furthermore, the metal system can be exposed on the wafer surface or covered by other metals, metal oxide films, insulating films, resists, etc. Even when covered by other materials, when the metal comes into contact with the processing solution of this embodiment and causes metal dissolution, it becomes possible to achieve both sufficient etching speed and surface roughness.

[0111] For example, when the processing solution of this embodiment is used in the metal wiring formation step, it will be as follows: First, a substrate made of semiconductor (e.g., Si) is prepared. An oxidation process is performed on the prepared substrate to form a silicon oxide film. Then, an interlayer insulating film made of a low-k dielectric film is formed, and via holes are formed at specified intervals. After the via holes are formed, metal is embedded into the via holes by thermal CVD, and a metal film is formed. By treating the metal film with the processing solution of this embodiment, a sufficient etching rate can be maintained and planarization can be achieved.

[0112] There are no particular limitations on the method of contacting the semiconductor wafer with the aforementioned metal layer and the processing liquid of this embodiment. For example, the semiconductor wafer can be rotated and the processing liquid of this embodiment can be discharged onto the wafer at the same time, or the semiconductor wafer can be immersed in a container filled with the processing liquid of this embodiment to achieve contact.

[0113] The etching time for metal using the processing solution of this embodiment is 0.1 to 120 minutes, preferably 0.3 to 60 minutes, and can be appropriately selected according to the etching conditions or the semiconductor device used. After using the processing solution of this embodiment, the semiconductor wafer surface that has been in contact with the processing solution can be cleaned with a rinsing solution to remove the processing solution. There are no particular limitations on the rinsing solution used after using the processing solution of this embodiment; organic solvents such as alcohols or deionized water can be used. After rinsing, the semiconductor wafer can be dried as necessary before proceeding to subsequent steps such as lamination of other wiring materials.

[0114] A second embodiment of the present invention is a RuO₄ gas generation inhibitor, which comprises an onium salt composed of onium ions and bromide ions, wherein the concentration of bromide ions in the RuO₄ gas generation inhibitor is 0.1 μmol / L or more but less than 0.001 mol / L. The RuO₄ gas generation inhibitor will be described below.

[0115] (RuO4 gas generation inhibitor) RuO4 gas generation inhibitor refers to a composition that inhibits the generation of RuO4 gas by being added to a solution used for treating ruthenium (hereinafter, it may also be described as a ruthenium treatment solution), and includes a solution containing onium salts composed of onium ions and bromide ions.

[0116] Ruthenium treatment solution refers to a liquid containing components that, upon contact with ruthenium, impart physical and chemical changes to it. Examples include solutions used in ruthenium treatment steps such as etching, residue removal, cleaning, and CMP processes in semiconductor manufacturing. It also includes solutions used in apparatus used in these semiconductor manufacturing processes for cleaning ruthenium adhering to chamber walls or piping.

[0117] All or part of the ruthenium treated by the ruthenium treatment solution is dissolved, dispersed, or precipitated in the ruthenium treatment solution, thus contributing to the generation of RuO₄ (gas) and / or RuO₂ (particles). By adding the RuO₄ gas generation inhibitor of this embodiment to the ruthenium treatment solution, anions such as RuO₄⁻ or RuO₄²⁻ (hereinafter, also described as RuO₄⁻, etc.) present in the ruthenium treatment solution and onmium ions will form ion pairs that dissolve in the ruthenium treatment solution, thereby suppressing the generation of RuO₄ gas and / or RuO₂. Furthermore, due to the bromide-containing effect of the onmium salt contained in the RuO₄ gas generation inhibitor, the formation of RuO₂ particles becomes less likely.

[0118] (Onion salt) The RuO₄ gas generation inhibitor of this embodiment contains an onium salt to suppress the generation of RuO₄ gas. This onium salt is composed of an onium ion and a bromide ion. Here, the onium ion is a polyatomic cation formed by adding an excess proton (hydrogen cation) to a monatomic anion. Specifically, it includes cations such as imidazolium ions, pyrrolidium ions, pyridinium ions, piperidinium ions, ammonium ions, phosphonium ions, fluorine ions, chloride ions, bromine ions, monium ions, oxonium ions, strontium ions, selenium ions, tellurium ions, arsenium ions, antimony ions, and bismuth ions. Among these, ammonium ions, phosphonium ions, and strontium ions are stable in alkaline solutions, and the carbon chains or functional groups contained in the onium ions can be easily modified, making it easy to control solubility, bulkiness, and charge density. Therefore, they are suitable as onium ions contained in the onium salts of this embodiment. Furthermore, bromide ions are ions containing bromine; examples include bromite ions, bromate ions, perbromate ions, hypobromate ions, or bromide ions. When the onium ions contained in the onium salt are polyvalent cations, at least one of the anions contained in the onium salt must be a bromide ion. For example, in the onium salt contained in the RuO₄ gas generation inhibitor of this embodiment, when it contains the divalent cation hexamethylammonium ion, at least one of the two paired anions must be a bromide ion.

[0119] In order to exert its ability to suppress RuO₄ gas generation, the onium salt contained in the RuO₄ gas generation inhibitor of this embodiment needs to dissociate into onium ions and bromide ions. This is because the onium ions generated by the dissociation of the onium salt interact with RuO₄⁻ and other ions, thereby inhibiting the generation of RuO₄ gas. Since onium salts containing halide ions are easily dissociated, have excellent solubility, and can stably supply onium ions, they can be used as the onium salt contained in the RuO₄ gas generation inhibitor of this embodiment. Among them, onium salts containing bromide ions are more stable and easier to synthesize than onium salts containing chloride or fluoride ions, thus high-purity products can be obtained in industrial applications. Furthermore, compared with those containing iodide ions, onium salts containing bromide ions have the advantage of having more onium ions per unit weight. Furthermore, since bromide ions interact with the ruthenium surface, anions such as RuO₄⁻ tend to move away from the ruthenium surface, making it less likely for RuO₂ particles to form. Therefore, the onium salt contained in the RuO₄⁻ gas generation inhibitor of this embodiment contains bromide ions.

[0120] In this embodiment, the concentration of bromide ions in the RuO₄ gas generation inhibitor is 0.1 μmol / L or higher but less than 0.001 mol / L. If the bromide ion concentration is less than 0.1 μmol / L, the interaction with the ruthenium surface weakens, and the effect of anions such as RuO₄⁻ moving away from the ruthenium surface becomes weaker, making it easier for RuO₂ particles to form. Furthermore, since the concentration of the bromide-containing cation, onium ions, in the ruthenium treatment solution also decreases, the effect of suppressing RuO₄ gas generation is reduced. On the other hand, if the bromide ion concentration is 0.001 mol / L or higher, there is a concern that RuO₄ reacts with the bromide ions, and RuO₄ precipitates as RuO₂ particles. The precipitation of RuO₂ particles not only reduces yield in semiconductor manufacturing but also significantly reduces the flatness of the ruthenium surface. Therefore, the bromide ion concentration in the RuO₄ gas generation inhibitor of this embodiment is preferably 0.5 μmol / L or more and less than 0.001 mol / L, and more preferably 1 μmol / L or more and less than 0.001 mol / L. This concentration range can be adjusted to achieve the above-mentioned concentration range even in a solution containing both the RuO₄ gas generation inhibitor and the ruthenium treatment solution. Furthermore, when adding onium salts, only one type can be added, or two or more types can be added in combination. Even when containing two or more types of onium salts, as long as the total bromide ion concentration in the RuO₄ gas generation inhibitor is within the above-mentioned concentration range, the generation of RuO₄ gas can be effectively suppressed. Moreover, the above-mentioned concentration range is applicable to any of the onium salts shown in formulas (1) to (2).

[0121] By including the aforementioned onium salt, the generation of RuO₄ gas from the ruthenium treatment solution is suppressed. Specifically, RuO₄⁻ and other ions generated from the dissolution of ruthenium are trapped in the ruthenium treatment solution through electrostatic interactions with onium ions. Since the trapped RuO₄⁻ and other ions exist relatively stably in the treatment solution as ion pairs, they do not easily transform into RuO₄. Therefore, the generation of RuO₄ gas and RuO₂ particles can be suppressed.

[0122] Specific examples of onium ions in onium salts include tetrapropylammonium ion, tetrabutylammonium ion, tetrapentylammonium ion, tetrahexylammonium ion, 1-butyl-2,3-dimethylimidazolium ion, 1-hexyl-3-methylimidazolium ion, 1-methyl-3-n-octylimidazolium ion, 1-butyl-1-methylpyrrolidone onium ion, 1-ethyl-1-methylpyrrolidone onium ion, 1-butyl-1-methylpiperidinium ion, 5-azoniaspiro[4,4]nonane ion, 1-methylpyridinium ion, 1-ethylpyridinium ion, 1-propylpyridinium ion, hexamethyl quaternary ammonium ion, and decamethyl quaternary ammonium ion. Onium salts are formed by combining onium ions such as ion with bromide ions such as bromite ions, bromate ions, perbromate ions, hypobromate ions, or bromide ions. Naturally, the onium salts that can be included in the RuO₄ gas generation inhibitor of this embodiment are not limited to the aforementioned onium salts.

[0123] As an onium salt that has the effect of suppressing the generation of RuO4 gas, the one shown in formula (1) or (2) below is preferred.

[0124] (In formula (1), A is nitrogen or phosphorus, and R1, R2, R3, and R4 are independently alkyl, allyl, aralkyl, or aryl groups having 1 to 25 carbon atoms. However, when R1, R2, R3, and R4 are alkyl groups, at least one of the alkyl groups has 3 or more carbon atoms. Furthermore, at least one hydrogen atom in the aryl group and the aryl ring can be replaced by fluorine, chlorine, alkyl groups having 1 to 10 carbon atoms, alkenyl groups having 2 to 10 carbon atoms, alkoxy groups having 1 to 9 carbon atoms, or alkenoxy groups having 2 to 9 carbon atoms, and at least one hydrogen atom in these groups can also be replaced by fluorine or chlorine. X - represents a bromide ion.)

[0125] (In formula (2), A is sulfur, and R1, R2, and R3 are independently alkyl, allyl, aralkyl, or aryl groups having 1 to 25 carbon atoms. However, when R1, R2, and R3 are alkyl groups, at least one of the alkyl groups has 3 or more carbon atoms. Furthermore, at least one hydrogen atom in the aryl group and the aryl ring can be replaced by fluorine, chlorine, alkyl groups having 1 to 10 carbon atoms, alkenyl groups having 2 to 10 carbon atoms, alkoxy groups having 1 to 9 carbon atoms, or alkenoxy groups having 2 to 9 carbon atoms, and at least one hydrogen atom in these groups can also be replaced by fluorine or chlorine. X- represents a bromide ion.)

[0126] In formulas (1) or (2) above, any alkyl group of R1, R2, R3, or R4 can be used without particular restriction, as long as it is an alkyl group with 1 to 25 carbon atoms. The larger the carbon number, specifically, when the carbon number is, for example, 3 or more, the stronger the interaction between the onium ion and RuO4-, the easier it is to suppress RuO4 gas. On the other hand, the larger the carbon number, the larger the volume of the onium ion, and the less soluble the ion pairs formed when it interacts electrostatically with RuO4-, etc., in the ruthenium treatment solution, thus producing precipitates. These precipitates become particles, causing a decrease in semiconductor device yield. Furthermore, the larger the carbon number, the lower the solubility in the ruthenium treatment solution, and the easier it is to generate bubbles in the treatment solution. When the solubility is high, more onium salts can dissolve in the treatment solution, thus increasing the suppression effect of RuO4 gas. Conversely, when the carbon number is small, the interaction between the onium ion and RuO4- weakens, thus weakening the RuO4 gas suppression effect. Therefore, the carbon number of the alkyl group in formula (1) or (2) is preferably 1 to 25, more preferably 2 to 10, and optimally 3 to 6. However, when R1, R2, R3, and R4 in formula (1) are alkyl groups, at least one of the alkyl groups can have 2 or more carbons, and when R1, R2, and R3 in formula (2) are alkyl groups, at least one of the alkyl groups can have 2 or more carbons. If the onium salt has an alkyl group with such a carbon number, it can suppress the generation of RuO4 gas through interaction with RuO4- and is less likely to cause precipitate formation, thus making it suitable for use as a RuO4 gas generation inhibitor.

[0127] In formula (1) or (2) above, the aryl groups of R1, R2, R3, and R4 are not only aromatic hydrocarbons, but also include heteroaryl groups containing heteroatoms, without any particular limitation, with phenyl and naphthyl being preferred. Examples of heteroatoms include nitrogen, oxygen, sulfur, phosphorus, chlorine, bromine, and iodine.

[0128] The fourth and third-order onium salts shown in formulas (1) and (2) above are salts composed of ammonium ions, phosphonium ions, or strontium ions that can stably exist in RuO₄ gas generation inhibitors or ruthenium treatment solutions. Generally, the alkyl chain length of these ions can be easily controlled, and allyl or aryl groups can also be easily introduced. In this way, the size, symmetry, hydrophilicity, hydrophobicity, stability, solubility, charge density, interfacial activity, etc. of these ions can be controlled, and the salts composed of these ions can also be controlled in the same way. Such salt systems can use the onium salts shown in formulas (1) and (2) of this embodiment. The ammonium ions contained in the fourth and third-order onium salts shown in formulas (1) and (2) above can be, for example, the same as the ammonium ions contained in the fourth-order onium bromide shown in the description of the third embodiment.

[0129] As the RuO4 gas generation inhibitor of this embodiment, the fourth-order onium salt represented by formula (1) is preferably an ammonium salt due to its high stability, ease of obtaining high-purity products industrially, and affordability. Among these, tetraalkylammonium salts are preferred because of their excellent stability and ease of synthesis. Specifically, salts composed of tetraethylammonium ions, tetrapropylammonium ions, tetrabutylammonium ions, tetrapentylammonium ions, or tetrahexylammonium ions can be cited. Inhibitors containing this onium salt are particularly effective in suppressing the generation of RuO4 gas and RuO2 particles during ruthenium treatment.

[0130] The RuO₄ gas generation inhibitor of this embodiment may further include an oxidizing agent. An oxidizing agent refers to one capable of substantially dissolving ruthenium contained in a semiconductor wafer. As an oxidizing agent, any known oxidizing agent capable of dissolving ruthenium may be used without restriction. Examples of such oxidizing agents include halogenated oxyacids, permanganate, and their salts, hydrogen peroxide, ozone, cerium(IV) salts, etc., but are not limited to these. Halogenated oxyacids or ozone are preferred as oxidizing agents, with halogenated oxyacids being more preferred. Here, halogenated oxyacids refer to hypochlorous acid, chlorite, chloric acid, perchloric acid, hypobromic acid, bromic acid, perbromic acid, hypoiodic acid, iodic acid, iodic acid, metaperiodic acid, orthoperiodic acid, or their ions. As the oxidant, hypochlorous acid, chloric acid, perchloric acid, hypobromic acid, bromic acid, perbromic acid, metaperiodic acid, orthoperiodic acid, or their ions are preferred among halogen oxyacids, with hypochlorous acid, hypobromic acid, metaperiodic acid, orthoperiodic acid, or their ions being even more preferred. Since this oxidant can dissolve ruthenium contained in the wafer, the RuO₄ gas generation inhibitor containing this oxidant and onmium salt can simultaneously dissolve ruthenium and suppress RuO₄ gas generation. Furthermore, by containing the oxidant, the dissolution of ruthenium is promoted, and the redissolution of precipitated RuO₂ particles is also promoted. Therefore, the RuO₄ gas generation inhibitor containing onmium salt and oxidant can suppress the generation of RuO₄ gas and RuO₂ particles, and simultaneously and efficiently process ruthenium-containing wafers.

[0131] Among halogenated oxyacids, hypochlorite ions have a high redox potential, so ruthenium compounds dissolved in hypochlorous acid solutions can exist relatively stably as RuO₄⁻, etc. Therefore, the RuO₄ gas generation inhibitor of this embodiment, by further including hypochlorite ions, makes it easier to maintain the interaction between RuO₄⁻ and onium ions, resulting in improved suppression of RuO₄ gas generation. Furthermore, by suppressing RuO₄ gas generation, the generation of RuO₂ particles is also suppressed. Since high-purity hypochlorite ions suitable for semiconductor manufacturing are relatively easy to obtain, they can be used as an oxidant that can be further included in the RuO₄ gas generation inhibitor of this embodiment. The concentration of hypochlorite ions included in the RuO₄ gas generation inhibitor is preferably 500 ppb by mass or more and 20.0% by mass or less. By using a ruthenium treatment solution containing a RuO4 gas generation inhibitor within the aforementioned concentration range of hypochlorite ions, it becomes possible to suppress the generation of RuO4 gas and RuO2 particles while simultaneously performing ruthenium treatment.

[0132] (pH of RuO₄ gas production inhibitor) The RuO₄ gas generation inhibitor of this embodiment is preferably set at a pH of 8 to 14 at 25°C. When the pH is below 8, ruthenium dissolves more readily, not via anions such as RuO₄⁻, but via RuO₂ or Ru(OH)₃, thus reducing the gas suppression effect of the onium salt. This RuO₂ becomes a particulate source, and a pH below 8 also leads to increased RuO₄ gas generation. Furthermore, when the pH is above 14, the redissolution of RuO₂ becomes less efficient, resulting in RuO₂ particle formation. Therefore, to fully utilize the RuO₄ gas generation suppression capability, the inhibitor is preferably set at a pH of 8 to 14, and more preferably 12 to 13. Within this pH range, since the dissolved ruthenium exists as an anion of RuO₄⁻ or RuO₄²⁻, it readily forms ion pairs with the onium ions contained in the inhibitor, thus effectively suppressing the generation of RuO₄ gas.

[0133] (Other components of RuO₄ gas generation inhibitor) The RuO4 gas generation inhibitor of this embodiment can be incorporated, without compromising the purpose of the invention, into other additives conventionally used in semiconductor processing liquids. For example, other additives may include acids, metal corrosion inhibitors, water-soluble organic solvents, fluorinated compounds, oxidants, reducing agents, chelating agents, surfactants, defoamers, pH adjusters, stabilizers, etc. These additives can be added individually or in combination.

[0134] (Methods for suppressing the generation of RuO4 gas, halogenated oxyacids) The method for suppressing RuO4 gas generation includes adding the RuO4 gas generation inhibitor of this embodiment to the ruthenium processing solution. Specifically, for example, by adding the RuO4 gas generation inhibitor of this embodiment to the ruthenium processing solution used in etching, residue removal, cleaning, and CMP steps in semiconductor manufacturing processes, the generation of RuO4 gas can be suppressed. Furthermore, in various apparatuses used in these semiconductor manufacturing processes, the generation of RuO4 gas can also be suppressed by using the RuO4 gas generation inhibitor of this embodiment when cleaning ruthenium adhering to the inner walls of chambers or piping. For example, in the maintenance of apparatuses that form Ru films using physical vapor deposition (PVD), chemical vapor deposition (CVD), atomic layer deposition (ALD), etc., by adding the RuO4 gas generation inhibitor to the cleaning solution used to remove Ru adhering to chambers or piping, the generation of RuO4 gas generated during cleaning can be suppressed. By means of this method, based on the mechanism described above, the generation of RuO4 gas can be suppressed.

[0135] For example, if the RuO4 gas generation inhibitor of this embodiment is used in the ruthenium wiring formation step, it will be as follows: First, a substrate made of semiconductor (e.g., Si) is prepared. An oxide film is formed on the prepared substrate by oxidation. Then, an interlayer insulating film made of a low-k dielectric film is formed, and vias are formed at specified intervals. After forming the vias, ruthenium is embedded in the vias by thermal CVD, and then the ruthenium film is formed. The ruthenium film is etched using a ruthenium processing solution with the RuO4 gas generation inhibitor added, thereby suppressing RuO4 gas generation and simultaneously planarizing. This allows for the formation of highly reliable ruthenium wiring with suppressed RuO2 particle generation. Furthermore, the ruthenium processing solution with the RuO4 gas generation inhibitor added can also be used to remove ruthenium adhering to the bevel of the semiconductor wafer.

[0136] The RuO4 gas generation inhibitor of this embodiment can suppress the generation of RuO4 gas not only in the ruthenium processing solution but also in the liquid after ruthenium processing (hereinafter referred to as ruthenium-containing liquid). Here, ruthenium-containing liquid means a liquid that contains ruthenium even in small amounts. The ruthenium contained in the ruthenium-containing liquid is not limited to ruthenium metal; it can be any liquid containing the element ruthenium, such as Ru, RuO4-, RuO42-, RuO4, RuO2, and ruthenium complexes. Examples of ruthenium-containing liquids include, for example, the waste liquid generated from semiconductor manufacturing steps or chamber cleaning, or the processing liquid in a gas extraction treatment device (scrubber) for capturing RuO4 gas. Even in trace amounts, ruthenium-containing liquids can generate RuO2 particles via RuO4 gas, contaminating tanks and piping, and accelerating equipment degradation due to particle oxidation. Furthermore, while the RuO4 gas generated by ruthenium-containing liquids reaches low concentrations, it still exhibits strong toxicity to humans. Therefore, given the various adverse effects of ruthenium-containing liquids on equipment and human health, it is necessary to suppress RuO4 gas generation and simultaneously handle it safely and rapidly. By adding the RuO4 gas generation inhibitor of this embodiment to ruthenium-containing liquids, RuO4 gas generation can be suppressed, enabling safe handling of ruthenium-containing liquids and reducing contamination or degradation of tanks and piping.

[0137] The amount of RuO₄ gas generation inhibitor added to the ruthenium treatment solution or ruthenium-containing solution of this embodiment can be determined after taking into account the amount of ruthenium present in such solution. There is no particular limitation on the amount of RuO₄ gas generation inhibitor added in this embodiment. For example, when the amount of ruthenium present in the ruthenium treatment solution or ruthenium-containing solution is set to 1, a weight ratio of 10 to 500,000 is preferred, 100 to 100,000 is more preferably, and 1,000 to 50,000 is even more preferably.

[0138] Furthermore, the pH of the mixture of RuO₄ gas generation inhibitor and ruthenium treatment solution or ruthenium-containing solution at 25°C is preferably 7 to 14, for example. To adjust the pH of the mixture, the acids, bases, pH buffers, and / or solvents listed above may also be added.

[0139] The third embodiment of the present invention is a method for manufacturing a halogenated oxyacid, which involves reacting a bromide salt, an organic base, and a halogen to obtain the halogenated oxyacid.

[0140] The manufacturing method of this embodiment is characterized by adding a halogen to a solution containing a bromide salt and an organic base. The halogen added to the solution containing the organic base reacts with the organic base to generate a halogenated oxyacid and a halide. This yields a halogenated oxyacid solution containing a halide. Furthermore, in this embodiment, unless otherwise defined, the halogenated oxyacid refers to hypohalous acid, halogenated acid, halogenated acid, perhalogenated acid, or ions thereof. Also, the hypohalous acid, halogenated acid, halogenated acid, or perhalogenated acid contained in the obtained halogenated oxyacid may be one type or multiple types.

[0141] (halogen) In the manufacturing method of this embodiment, halogen refers to fluorine, chlorine, bromine, or iodine. These can be added as gases to a solution containing bromide salts and organic bases, or as solutions containing halogens to a solution containing bromide salts and organic bases. Since either halogen gas or halogen-containing solution will react with bromide salts and organic bases to form halogen oxyacids, halogen oxyacids of this embodiment can be obtained. However, halogen gases that are readily available in high purity industrially and are easy to operate are preferred. Chlorine gas is particularly suitable because it can be obtained at a relatively low cost with semiconductor-grade high purity, and as described later, it readily oxidizes bromide salts directly or indirectly to obtain halogen oxyacids. The rate of halogen gas supply is not particularly limited and can be appropriately determined after considering the amount of halogen supplied or the reaction time. Furthermore, halogen gases can also be mixed with inert gases such as nitrogen or argon.

[0142] For example, when the halogen is chlorine, by adding chlorine to a solution containing a bromide salt and an organic base to allow it to react, a halogen oxyacid containing at least one of bromide salts, hypochlorous acid, chlorous acid, chloric acid, or perchloric acid, as well as a halogen oxyacid containing chloride, can be obtained. Similarly, when the halogen is bromine, by adding bromine to a solution containing a bromide salt and an organic base to allow it to react, a halogen oxyacid containing at least one of bromide salts, hypobromic acid, bromic acid, bromic acid, or perbromic acid, as well as a halogen oxyacid containing bromide, can be obtained. Likewise, when the halogen is iodine, by adding iodine to a solution containing a bromide salt and an organic base to allow it to react, a halogen oxyacid containing at least one of bromide salts, hypoiodic acid, iodic acid, iodic acid, or periodic acid, as well as a halogen oxyacid containing iodide, can be obtained.

[0143] (Organic base) In the manufacturing method of this sample, the organic base refers to an organic base composed of an organic cation and a hydroxide ion. This type of organic base does not contain metals that would cause problems in semiconductor manufacturing. Therefore, by using an organic base, the metal content in the obtained halogen oxyacid can be reduced, making it suitable for use in semiconductor manufacturing processes. An example of such an organic cation is the onium ion. Onium ions are compounds of polyatomic cations formed by the addition of an excess proton (hydrogen cation) to a monatomic anion. Specifically, examples include cations such as imidazolium ions, pyrrolidium ions, pyridinium ions, piperidinium ions, ammonium ions, phosphonium ions, fluorine ions, chloride ions, bromine ions, monium ions, oxonium ions, strontium ions, selenium ions, tellurium ions, arsenium ions, antimony ions, and bismuth ions. Among these, ammonium ions, phosphonium ions, and strontium ions are stable in alkaline solutions, and the carbon chains or functional groups contained in the onlonium ions can be easily modified. Furthermore, solubility, bulkiness, and charge density can be easily controlled, making them suitable as organic cations in the organic bases of this embodiment. From the viewpoint of being able to be manufactured in large quantities at low cost in industry, ammonium ions are more suitable. Examples of such ammonium ions include tetraalkylammonium ions, with tetramethylammonium ions, ethyltrimethylammonium ions, tetraethylammonium ions, tetrapropylammonium ions, and tetrabutylammonium ions being more suitable. Organic bases containing onlonium ions and hydroxide ions, i.e., onlonium hydroxides, are suitable as organic bases in this embodiment. Furthermore, organic bases containing ammonium ions (NH₄⁺) or 2-hydroxyethyltrimethylammonium as organic cations are also suitable as organic bases in this embodiment.

[0144] Considering the stability of halogenated oxyacids, a pH of 8 or higher but less than 14 is preferred. There are no particular restrictions on the concentration of the organic base used in the manufacturing process; the pH of the resulting halogenated oxyacid simply needs to be within the above range. This can be determined by considering the type of organic base used, and the type and amount of halogen added. For example, a concentration of 0.0001% by mass or more but less than 30% by mass would be suitable.

[0145] (bromine salt) In this embodiment, bromide salts refer to salts containing bromine atoms, such as hypobromite, bromate, perbromate, and bromide. Examples of bromides include hydrogen bromide, lithium bromide, sodium bromide, potassium bromide, rubidium bromide, cesium bromide, ammonium bromide, and onium bromide. Onium bromide, as referred to here, means a compound formed from the aforementioned onium ions and bromide ions. Furthermore, compounds that generate hypobromic acid or hypobromic acid ions in the treatment solution are also suitable as bromine-containing compounds. Examples of such compounds include bromovinyl urea, bromoisocyanuric acid, bromosulfanilamide, and bromochloroamine, but are not limited to these. More specifically, compounds such as 1-bromo-3-chloro-5,5-dimethylhydantoin, 1,3-dibromo-5,5-dimethylhydantoin, and tribromoisocyanuric acid are examples.

[0146] The aforementioned bromide system can be added as a bromide salt to a solution containing an organic base, or as a solution containing a bromide salt to a solution containing an organic base, or as bromine gas to a solution containing an organic base. Since the manufacturing process of halogen oxyacids is relatively simple, it is preferable to mix the bromide system as a bromide or a solution containing a bromide with a solution containing an organic base. The solution containing an organic base may contain one type of bromide, or a combination of two or more types. Furthermore, depending on the manufacturing process, an organic base may be added to the solution containing a bromide salt. Additionally, a solution containing both a bromide salt and an organic base may be prepared by simultaneously adding a bromide salt and an organic base to a suitable solvent. In any of these cases, a solution containing both a bromide salt and an organic base can be obtained.

[0147] In semiconductor manufacturing, the introduction of metals or metal ions can reduce yield; therefore, it is ideal for the bromide system to be metal-free. Since onium bromide is substantially metal-free, it is suitable as the bromide salt of this embodiment. Among onium bromides, quaternary onium bromide, tertiary onium bromide, or hydrogen bromide are readily available industrially and easy to handle, making them even more suitable as the bromide salt of this embodiment.

[0148] Quaternary bromide is a bromide composed of ammonium or phosphonium ions that can exist stably in a solution containing bromide and organic base. Examples of quaternary ammonium bromides 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, decamethylquaternary ammonium bromide, phenyltrimethylammonium bromide, benzyltrimethylammonium bromide, dimethylpyridineonium bromide, dimethylpiperidineonium bromide, 1-butyl-3-methylimidazolium bromide, and 1-butyl-3-methylpyridineonium bromide. Furthermore, compounds with protons added to tertiary, secondary, or primary amines can also be used. Examples of phosphonium bromide include methylamine hydrogen bromide, dimethylamine hydrogen bromide, ethylamine hydrogen bromide, diethylamine hydrogen bromide, triethylamine hydrogen bromide, 2-bromoethylamine hydrogen bromide, 2-bromoethyldiethylamine hydrogen bromide, ethylenediamine dibromide, propylamine hydrogen bromide, butylamine hydrogen bromide, tert-butylamine hydrogen bromide, neopentylamine hydrogen bromide, 3-bromo-1-propylamine hydrogen bromide, dodecylamine hydrogen bromide, cyclohexaneamine hydrogen bromide, and benzylamine hydrogen bromide. 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 strontium bromides are bromide salts composed of strontium ions that can exist stably in the treatment solution. Examples of tertiary strontium bromides include trimethylstrontium bromide, triethylstrontium bromide, tripropylstrontium bromide, tributylstrontium bromide, triphenylstrontium bromide, and (2-carboxyethyl)dimethylstrontium bromide. Among these, quaternary strontium bromides, which are bromide salts composed of ammonium ions, are preferred due to their high stability, ease of obtaining high-purity products industrially, and affordability.

[0149] The aforementioned quadratic ononium bromide system preferably includes tetraalkylammonium bromide, which exhibits excellent stability and is easily synthesized. In this tetraalkylammonium bromide, the number of carbon atoms in the alkyl groups is not particularly limited; the four alkyl groups can have the same or different carbon atoms. Tetraalkylammonium bromide with 1 to 20 carbon atoms per alkyl group is suitable as such. Since the number of bromine atoms per unit weight is high, tetraalkylammonium bromide with fewer carbon atoms in the alkyl groups is more suitable. Examples include tetramethylammonium bromide, ethyltrimethylammonium bromide, tetraethylammonium bromide, tetrapropylammonium bromide, tetrabutylammonium bromide, tetrapentylammonium bromide, and tetrahexylammonium bromide. Among these, tetramethylammonium bromide, tetraethylammonium bromide, tetrapropylammonium bromide, and tetrabutylammonium bromide are suitable, with tetramethylammonium bromide being the most suitable. The bromine-containing compound contained in the solution containing the bromide salt and organic base can be one or more.

[0150] The tetraalkylammonium bromide used in this embodiment can be either commercially available or manufactured from tetraalkylammonium ions and bromide ions. The method for manufacturing tetraalkylammonium bromide simply involves mixing an aqueous solution containing tetraalkylammonium hydroxide with an aqueous solution containing bromide ions, or using a bromine-containing gas that produces bromide ions when dissolved in water.

[0151] Examples of tetraalkylammonium hydroxides used in the manufacture of tetraalkylammonium bromide include tetramethylammonium hydroxide, ethyltrimethylammonium hydroxide, tetraethylammonium hydroxide, tetrapropylammonium hydroxide, and tetrabutylammonium hydroxide. Among these, tetramethylammonium hydroxide or ethyltrimethylammonium hydroxide are preferred because they have a higher number of hydroxide ions per unit weight and are readily available in high purity.

[0152] Examples of bromide ion sources used to generate bromide ions in the production of tetraalkylammonium bromide include hydrogen bromide, lithium bromide, sodium bromide, potassium bromide, rubidium bromide, cesium bromide, and ammonium bromide. Among these, hydrogen bromide is the most suitable because it does not contain any metals, is readily available industrially, and can be easily obtained in high purity.

[0153] (solvent) The solvent for solutions containing bromide salts and organic bases is not particularly restricted; water or organic solvents can be used. Naturally, when water is used as the solvent for solutions containing bromide salts and organic bases, the solvent for the resulting halogenated oxyacid will also become water.

[0154] Water is the preferred solvent, especially water that has been treated by distillation, ion exchange, filtration, or various adsorption processes to remove metal ions, organic impurities, or particulate matter. Pure or ultrapure water is particularly desirable. This type of water can be obtained using well-known methods widely used in semiconductor manufacturing.

[0155] Alternatively, water and an organic solvent can be used together. By using water and an organic solvent together, the oxidation of transition metals proceeds relatively stably, thus suppressing the oxidation of wiring in the circuit forming part. In the case of using water and an organic solvent together, the mass ratio of water to organic solvent (water / organic solvent) can be around 60 / 40 to 99.9 / 0.1.

[0156] (Reactions of bromide salts, organic bases, and halogens) The third embodiment of the method for producing halogen oxyacids involves the reaction of a bromide salt, an organic base, and a halogen. The halogen added to a solution containing a bromide salt and an organic base dissolves rapidly and reacts with the organic base to generate hypohalic acid and a halide. Furthermore, the hypohalic acid reacts with bromide ions, hypobromate ions, bromite ions, bromate ions, or perbromate ions contained in the bromide salt, or with bromine molecules generated from the bromide salt, to produce a new halogen oxyacid. Here, the reaction of the hypohalic acid with the aforementioned ions or bromine molecules can be a reaction that produces a new halogen oxyacid simply by adding halogen to a solution containing a bromide salt and an organic base; this reaction can be a redox reaction, a heterogeneous reaction, or a free radical reaction.

[0157] To illustrate more specifically, the reaction of the bromide, organic base, and halogen when the bromide salt is tetramethylammonium bromide, the organic base is tetramethylammonium hydroxide, and the halogen is chlorine is shown below. When chlorine gas is blown into an aqueous solution containing tetramethylammonium bromide and tetramethylammonium hydroxide, the tetramethylammonium hydroxide reacts with chlorine to produce hypochlorous acid and chloride. A portion of this hypochlorous acid reacts with the bromide ions of tetramethylammonium bromide in the solution, directly oxidizing the bromide ions to produce hypobromous acid. The result is an aqueous solution containing hypochlorous acid, hypobromous acid, chloride (tetramethylammonium chloride), unreacted tetramethylammonium bromide, and tetramethylammonium hydroxide. That is, an aqueous solution of a halogenated oxyacid containing two halogenated oxyacids (hypochlorous acid and hypobromous acid) is obtained. Furthermore, when the number of chlorine molecules is less than the number of mol of tetramethylammonium bromide in a solution containing bromide salts and organic bases, an aqueous solution containing hypobromic acid, chloride (tetramethylammonium chloride), unreacted tetramethylammonium bromide, and tetramethylammonium hydroxide is obtained.

[0158] As another specific example, if we illustrate the reaction of the bromide, organic base, and halogen when the bromide is tetramethylammonium hypobromide, the organic base is tetramethylammonium hydroxide, and the halogen is chlorine, it is as follows. When chlorine gas is blown into an aqueous solution containing tetramethylammonium hypobromide and tetramethylammonium hydroxide, the tetramethylammonium hydroxide reacts with chlorine to produce hypochlorous acid and chloride. A portion of this hypochlorous acid reacts with the hypobromous acid of the tetramethylammonium hypobromide in the solution to become chlorous acid and bromous acid, respectively. The result is an aqueous solution containing hypochlorous acid, chlorous acid, bromous acid, unreacted tetramethylammonium hypobromide, and tetramethylammonium hydroxide. That is, an aqueous solution of halogen oxyacids containing four types of halogen oxyacids (hypobromous acid, chlorous acid, bromous acid, and hypobromous acid) is obtained.

[0159] The processing solution for semiconductors containing halogen oxyacids manufactured by this method exhibits excellent solution stability, stably etches the transition metal at a sufficient etching rate, and maintains the flatness of the etched transition metal surface. In particular, a processing solution containing 0.1 μmol / L or more but less than 0.001 mol / L of hypobromite ions possesses exceptionally excellent solution stability and, as described above, stably etches the transition metal at a sufficient etching rate while maintaining the flatness of the etched transition metal surface. Therefore, as described in the first embodiment, it is suitable for use as a processing solution for semiconductor wafers containing transition metals.

[0160] Therefore, in the case where a processing solution is manufactured using onium hydroxide as an organic base, bromine as a halogen, and onium bromide as a bromide salt, bromine reacts with onium hydroxide to obtain a processing solution containing hypobromite ions and bromide ions. Furthermore, in the case where a processing solution is manufactured using onium hydroxide as an organic base, chlorine as a halogen, and onium bromide as a bromide salt, chlorine reacts with onium hydroxide to generate hypochlorous acid ions and chloride ions in the processing solution, and the hypochlorous acid ions further react with the bromide salt. This yields a processing solution containing hypobromite ions and bromide ions. The obtained processing solution can be used not only as a processing solution for semiconductor wafers but also as a RuO₄ gas generation inhibitor. Examples of bromide ion-containing compounds include those exemplified in the second embodiment.

[0161] There are no particular limitations on the concentration of the halogen oxyacid produced by this manufacturing method. For example, the concentration of hypochlorite ions or bromide ions is preferably 0.1 μmol / L or higher but less than 0.001 mol / L. If the concentration of the halogen oxyacid is within the above range, the obtained halogen oxyacid is particularly suitable for use as a processing solution for the aforementioned semiconductor wafers and / or a RuO₄ gas generation inhibitor. If the concentration of the halogen oxyacid produced by this manufacturing method is lower than the aforementioned concentration range, the concentration of the halogen oxyacid can be increased, for example, by increasing the halogen supply for reaction with the organic base or by adding halogen oxyacid salts. If the concentration of the halogen oxyacid is higher than the aforementioned concentration range, it can be diluted with a suitable solvent, for example. In order to achieve stable etching of the transition metal at a sufficient speed and maintain the flatness of the etched metal surface, the concentration of the halogen oxyacid is preferably 0.1 μmol / L or higher but less than 0.001 mol / L, more preferably 1 μmol / L or higher but less than 0.001 mol / L, even better 10 μmol / L or higher but less than 0.001 mol / L, and optimal 50 μmol / L or higher but less than 0.001 mol / L. It may contain a single type of halogenated oxyacid or multiple types. In the case of multiple types, the concentration of each halogenated oxyacid is preferably above 0.1 μmol / L and below 0.001 mol / L.

[0162] (Other additives) The halogen oxyacid produced by the method of manufacturing halogen oxyacids according to the third embodiment can, as desired and without impairing the purpose of the present invention, be incorporated with other additives conventionally used in semiconductor processing solutions. For example, other additives may include acids, metal corrosion inhibitors, water-soluble organic solvents, fluorinated compounds, oxidants, reducing agents, chelating agents, surfactants, defoamers, pH adjusters, stabilizers, etc. These additives can be added individually or in combination.

[0163] Derived from these additives, and depending on the manufacturing process of halogen oxyacids, the halogen oxyacids of this embodiment may also contain alkali metal ions, alkaline earth metal ions, etc. For example, they may contain sodium ions, potassium ions, calcium ions, etc. However, if these alkali metal ions and alkaline earth metal ions remain on the semiconductor wafer, they will have adverse effects on the semiconductor device (such as reduced semiconductor wafer yield), so their amount is preferred to be low, and in practice, it is best to contain them as little as possible. Therefore, for example, as a pH adjuster, it is preferable to use organic bases such as ammonia, amines, choline, or tetraalkylammonium hydroxide, rather than alkali metal hydroxides such as sodium hydroxide or alkaline earth metal hydroxides.

[0164] Specifically, the sum of alkali metal ions and alkaline earth metal ions is preferably below 1% by mass, better below 0.7% by mass, even better below 0.3% by mass, particularly good below 10 ppm, and best below 500 ppb.

[0165] Furthermore, when manufacturing halogen oxyacids using the manufacturing method described in this embodiment, the conditions and corresponding methods shown in the description of the semiconductor wafer processing solution or RuO4 gas generation inhibitor can be appropriately selected. For example, the aforementioned conditions and corresponding methods can be appropriately used to prevent carbon dioxide dissolution, amine contamination, metal contamination, and light-induced decomposition.

[0166] Therefore, the method for manufacturing halogen oxyacids in this embodiment is a simple and efficient method for obtaining halogen oxyacids, particularly processing solutions for semiconductor wafers containing hypobromite ions and bromide ions. Furthermore, compared to methods that use ion exchange methods to manufacture halogen oxyacids by using aqueous solutions of sodium, potassium, or calcium salts of hypohalous acids as raw materials, this method significantly reduces the amount of metal contamination, thus eliminating the need for periodic regeneration of ion exchange resins required by ion exchange methods. Moreover, this method eliminates the need for periodic regeneration of ion exchange resins required by ion exchange methods, allowing for continuous manufacturing, resulting in high productivity of the processing solution and reduced manufacturing costs. Therefore, this method for manufacturing halogen oxyacids is particularly suitable as a method for manufacturing halogen oxyacids that can be used as processing solutions for semiconductor wafers and / or as inhibitors of RuO₄ gas generation. [Example]

[0167] The present invention will be described in more detail below by way of examples, but the present invention is not limited to these examples.

[0168] (Preparation of tetramethylammonium hypochlorite ((CH3)4NClO3) or tetramethylammonium bromate ((CH3)4NBrO3)) A saturated solution was obtained by adding sodium chlorate (manufactured by Fujifilm and Koichi Chemical) or sodium bromate (manufactured by Fujifilm and Koichi Chemical) to deion-exchanged water. This solution was then stored in a cold storage for 24 hours, and the precipitated sodium bromate was recovered by filtration. The recovered sodium bromate was dissolved in ultrapure water and analyzed using an ion chromatography analyzer. Analysis of the CO₃⁻, SO₄⁻, and Br⁻ in the diluted solution confirmed a reduction in impurities such as Na₂CO₃, Na₂SO₄, and NaBr. By repeating the purification process, the concentrations of CO₃⁻, SO₄⁻, and Br⁻ were confirmed to be below 500 ppb, thus obtaining purified sodium chlorate or sodium bromate.

[0169] Next, 200 mL of a strongly acidic ion exchange resin (Organo, Amberlite IR-120BNa) was added to a glass column (AsOne Biocolumn CF-50TK) with an inner diameter of approximately 45 mm. Then, to exchange for the hydrogen form, 1 L of 1 equivalent hydrochloric acid (Fujifilm and Koichi Chemical Co., Ltd., for volumetric analysis) was passed through the ion exchange resin column, and 1 L of ultrapure water was passed through to wash the ion exchange resin. Then, 2 L of a 2.38% tetramethylammonium hydroxide solution was passed through the ion exchange resin that had been exchanged for the hydrogen form, thus exchanging the hydrogen ions for the tetramethylammonium form. After the ion exchange, 1 L of ultrapure water was passed through to wash the ion exchange resin.

[0170] 6.4 g of purified sodium chlorate or sodium bromate was placed in a fluoropolymer container, and 93.6 g of ultrapure water was added to prepare a 6.4% (w / w) sodium chlorate or sodium bromate aqueous solution. This prepared sodium chlorate or sodium bromate aqueous solution was passed through an ion exchange resin that had been converted to tetramethylammonium form. The recovered tetramethylammonium chlorate or tetramethylammonium bromate was analyzed for Na concentration using high-frequency inductively coupled plasma emission spectrometry (iCAP6500DuO, Thermo SCIENTIFIC) to confirm sufficient ion exchange. If insufficient ion exchange was observed, the above steps were repeated to obtain a 10% (w / w) tetramethylammonium chlorate or tetramethylammonium bromate solution with a Na concentration below 500 ppb. The obtained solution was then heat-treated to obtain tetramethylammonium chlorate powder or tetramethylammonium bromate powder. This tetramethylammonium chlorate or tetramethylammonium bromate powder was added to the treatment solution to generate chlorate or bromate ions.

[0171] (Other reagents) The reagents used in the examples and comparative examples are as follows. Tetramethylammonium bromide ((CH3)4NBr): Manufactured by Tokyo Chemical Industry Co., Ltd. 15wt% HCl: Manufactured by Kanto Chemical Co., Ltd. (prepared by diluting 35wt% HCl with ultrapure water) 1 mol / L Tetramethylammonium hydroxide (TMAH): Manufactured by Tokuyama Corporation (prepared by diluting 25 wt% TMAH with ultrapure water).

[0172] (Methods for measuring hypobromite and hypochlorite ion concentrations) The concentrations of hypobromite and hypochlorite ions were measured using a UV-Vis spectrophotometer (UV-2600, manufactured by Shimadzu Corporation). Calibration lines were established using aqueous solutions of hypobromite and hypochlorite ions with known concentrations to determine the concentrations of hypobromite and hypochlorite ions in the manufactured treatment solution.

[0173] (Methods for measuring the concentration of anionic species) The concentration of anions in the semiconductor wafer processing solution was measured using an ion chromatography analyzer (DIONEX INTEGRION HPLC, Thermo SCIENTIFIC). KOH was used as the precipitate, and the flow rate was 1.2 mL / min. A hydroxide-based precipitate anion exchange analysis column (AS15, Thermo SCIENTIFIC) was used, and the column temperature was set to 30°C. After background noise was removed using a suppressor, the anions in the processing solution were quantified using a conductivity detector.

[0174] (pH measurement method) The pH of 10 mL of the treatment solutions prepared in the examples and comparative examples was measured using a benchtop pH meter (LAQUA F-73, manufactured by Horiba Seisakusho). The pH measurement was performed after the treatment solutions were prepared and stabilized at 25°C.

[0175] (Preparing semiconductor wafers for evaluating the etching performance of metals) The ruthenium, molybdenum, tungsten, and chromium films used in the examples and comparative examples were formed using the following procedures. The ruthenium, molybdenum, and chromium films were formed by creating an oxide film on a silicon wafer using a batch thermal oxidation furnace, followed by sputtering to deposit 100 Å of ruthenium, 500 Å of molybdenum, or 500 Å of chromium. The tungsten film was similarly formed by thermal oxidation, and then deposited using a CVD method to create a 500 Å tungsten film. The sheet resistance was measured using a four-probe resistance meter (Loresta-GP, Mitsubishi Chemical Analysis Co., Ltd.) and converted into film thickness, which was then used as the metal film thickness before etching.

[0176] (Evaluation of the etching performance of metals) 60 mL of the processing solution from the example was prepared in a capped fluoropolymer container (AsOne Corporation, PFA container 94.0 mL). Evaluation semiconductor wafers, each 10 × 20 mm in size, were immersed in the processing solution for 1 minute at the processing temperature (30°C~50°C) listed in Table 1. The change in film thickness before and after processing was divided by the immersion time to calculate the etching rate.

[0177] (Stability evaluation of etching rate) The stability evaluation of the etching rate was conducted as follows: The etching rate of the manufactured treatment solution was evaluated every 10 hours using the "Evaluation of Etching Performance of Metals" method described above. The time during which the obtained etching rate increased or decreased by within ±20% compared to the etching rate immediately after manufacturing was defined as the stability time of the etching rate, and it was classified according to the following criteria. The stability times of the etching rate were assigned A to D in order of length, with evaluations A to C representing acceptable levels and evaluation D representing unacceptable levels. A: The etching rate stabilizes after more than 100 hours, making it particularly suitable for use. B: The etching rate stabilizes after 50 hours or more, making it suitable for use. C: The etching rate stabilizes after 10 hours or more, making it suitable for use. D: The etching rate stabilized in less than 10 hours.

[0178] (Surface evaluation after etching (flatness evaluation)) The metal surface before and after etching was observed using an electric field emission scanning electron microscope (JSM-7800F Prime, manufactured by Nippon Electron Ltd.) to confirm the presence or absence of surface roughness, and was evaluated according to the following criteria. Surface roughness was assigned from A to D in order of least roughness (flatness maintained). Evaluations A to C were acceptable, while evaluation D was unacceptable. A: No surface roughness was found. B: Some surface roughness was observed. C: Roughness was found throughout the surface, but the roughness was shallow. D: The entire surface is rough, and the roughness is deep.

[0179] (Quantitative method for metals in halogenated oxyacids) The metal concentration in halogenated oxyacids was measured using a high-energy inductively coupled plasma mass analyzer (HICP). 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). Then, 0.25 mL of the halogenated oxyacid was added to the PFA volumetric flask using a pipette (AsOne, Pipetman P1000) and a fluoropolymer pipette tip (AsOne, fluoropolymer pipette tip), and stirred. Ultrapure water was then added to the specified volume to prepare a 10- to 100-fold dilution of the sample, depending on the concentration of the halogenated oxyacid. The metal content was then quantified using a HICP apparatus (ThermoFisher Scientific, Element2) with a calibration curve method. Furthermore, to account for the sensitivity increase or decrease caused by the matrix, the measurement solution was also measured with impurities added in a manner that resulted in a concentration of 2 ppb. The measurement conditions were: RF output of 1500W, argon gas flow rate of 15 L / min (plasma gas), auxiliary gas of 1.0 L / min, and nebulizer gas of 0.7 L / min.

[0180] <Example 1> (Method for manufacturing a treatment solution containing tetramethylammonium hypobromide) (Preparation steps for solutions containing bromide salts and organic bases) Tetramethylammonium bromide (14.6 g; 0.095 mol) and tetramethylammonium hydroxide (18.2 g; 0.190 mol) were placed in a 2L glass three-necked flask (manufactured by VIDTEC), and ultrapure water was added to prepare a 1L solution containing bromide salt and organic base with pH 13.3.

[0181] (The reaction steps involving halogens with solutions containing bromide salts and organic bases) Next, a rotor (AsOne, 30mm x 8mm) was placed inside a three-necked flask. A thermometer protection tube (VIDTEC, sealed-bottom type) and a thermometer were inserted into one opening. A chlorine and nitrogen cylinder were connected to the other opening. The tip of a PFA tube (Flon Industrial Co., Ltd., F8011-02), designed to switch between chlorine and nitrogen, was immersed in the bottom of the solution. The remaining opening was connected to a gas scrubbing bottle (AsOne, model 2450 / 500), filled with a 5% (w / w) sodium hydroxide aqueous solution. Nitrogen gas was released from the PFA tube at 200 sccm for 20 minutes to remove carbon dioxide from the gas phase. Subsequently, a magnetic stirrer (AsOne, C-MAG HS10) was placed at the bottom of the three-necked flask and rotated at 300 rpm. Simultaneously, the outer circumference of the three-necked flask was cooled with ice water, and chlorine gas (Fujiox, 99.4% purity) was supplied at 200 sccm for 10.6 minutes (total chlorine supply 0.095 mol). The reaction temperature was 15°C.

[0182] A halogenated oxyacid containing 0.095 mol / L tetramethylammonium hypobromide solution (and containing 0.19 mol / L tetramethylammonium chloride and 0.01 mol / L tetramethylammonium hydroxide) was obtained by the above reaction. The halogenated oxyacid obtained by the above method was diluted to 1 / 100 with ultrapure water, 15 wt% HCl, and 1 mol / L tetramethylammonium hydroxide (TMAH) to obtain 100 mL of the treatment solution with the composition shown in Table 1.

[0183] (Evaluation of the treatment solution) The concentrations of hypohalite ions, anions, and pH in the obtained treatment solution were measured using the methods described above. Using the obtained treatment solution, the etching performance of the metal, the stability of the etching rate, and the surface finish after etching were evaluated using the methods described above. The results are shown in Tables 2 and 3.

[0184] <Examples 2~12> The concentrations of bromide salts and organic bases, as well as the supply of chlorine, were appropriately adjusted, and the process was carried out in the same manner as described in Example 1 (the method for manufacturing a treatment solution containing tetramethylammonium hypobromide) to obtain the treatment solution containing halogenated oxyacids as shown in Table 1. The obtained treatment solution was evaluated in the same manner as in Example 1. The results are shown in Tables 2 and 3.

[0185] <Examples 13-16> The concentrations of the bromide salt and organic base, as well as the supply of chlorine, were adjusted appropriately, and the process was carried out in the same manner as described in Example 1 (the method for preparing the treatment solution containing tetramethylammonium hypobromide) to obtain the halogenated oxyacid. However, in Example 15, chlorine was supplied at a liquid temperature of 45°C by heating the flask to generate bromide ions. The obtained halogenated oxyacid was diluted to 1 / 100 with a mixture of tetramethylammonium hypobromide, ultrapure water, 15 wt% HCl, and 1 mol / L TMAH to obtain 100 mL of the treatment solution with the composition described in Table 1. The obtained treatment solution was evaluated in the same manner as in Example 1. The results are shown in Tables 2 and 3.

[0186] <Example 17> (Manufacturing of a treatment solution containing tetramethylammonium hypobromide and tetramethylammonium hypochlorite) 109.4 g of tetramethylammonium hydroxide was added to a 2 L three-necked glass flask, and 0.99 L of a solution containing bromide and organic base with pH 14.1 was prepared by adding ultrapure water. Except for the chlorine gas supply time to the solution containing bromide and organic base was set to 66.6 minutes (total chlorine supply 0.595 mol), the reaction was carried out in the same manner as described in Example 1 (the reaction steps of the solution containing bromide and organic base with halogen). The reaction temperature was 15 °C.

[0187] A 0.595 mol / L tetramethylammonium hypochlorite solution (containing 0.595 mol / L tetramethylammonium chloride and 0.01 mol / L tetramethylammonium hydroxide) was obtained through the above reaction. The reaction temperature was 15°C. 14.6 g of tetramethylammonium bromide was added to the tetramethylammonium hypochlorite solution obtained by the above method, and bromide ions were oxidized by hypochlorite ions to generate 0.095 mol / L hypobromite ions. Then, by diluting with ultrapure water, 15 wt% HCl, and 1 mol / L TMAH to a concentration of 1 / 100, 100 mL of the treatment solution with the composition shown in Table 1 was obtained. The obtained treatment solution was evaluated in the same manner as in Example 1. The results are shown in Tables 2 and 3.

[0188] <Example 18> Tetramethylammonium bromide (14.6 g; 0.095 mol) and tetramethylammonium hydroxide (109.4 g; 1.20 mol) were added to a 2 L three-necked glass flask, and ultrapure water was added to prepare a 0.99 L solution containing bromide and organic base with a pH of 14.1. The reaction was carried out in the same manner as described in Example 1 (the reaction steps of the solution containing bromide and organic base with halogen) except that the chlorine gas supply time to the solution containing bromide and organic base was set to 66.6 minutes (total chlorine supply 0.595 mol). The reaction temperature was 15 °C.

[0189] The above reaction was used to prepare 0.095 mol / L tetramethyl hypobromide and 0.595 mol / L tetramethylammonium hypochlorite (containing 0.595 mol / L tetramethylammonium chloride and 0.01 mol / L tetramethylammonium hydroxide), thus obtaining a solution containing a halogenated oxyacid. The reaction temperature was 15°C. The obtained solution containing the halogenated oxyacid was diluted to 1 / 100 with tetramethylammonium hypobromide, ultrapure water, 15 wt% HCl, and 1 mol / L TMAH to obtain 100 mL of a treatment solution with the composition shown in Table 1. The obtained treatment solution was evaluated in the same manner as in Example 1. The results are shown in Tables 2 and 3.

[0190] <Comparative Examples 1-6> The treated solutions shown in Table 1 were obtained using the same method as in Example 1. However, in Comparative Example 1, chlorine was supplied to an organic base that did not contain bromide to allow the organic base to react with chlorine. In Comparative Example 4, the treated solution was obtained by dissolving a bromide in an organic base. The obtained treated solutions were evaluated in the same manner as in Example 1. The results are shown in Tables 2 and 3.

[0191]

[0192]

[0193]

[0194] The "-" in Table 1 indicates that the corresponding ion or oxidant is not present in the processing solution (the same applies to Tables 4, 6, and 8). Furthermore, "No data" in Tables 2 and 3 indicates that etching did not occur in the processing solution, therefore the stability and flatness of the etching rate could not be evaluated, and thus no data is available. As shown in Tables 2 and 3, using the processing solutions shown in Comparative Examples 1-6 did not achieve the desired effect of satisfying all requirements for etching rate, stability, and flatness. On the other hand, the processing solutions of this embodiment shown in Examples 1-16 exhibited sufficient etching rate and stability, and satisfied the surface flatness after etching.

[0195] <Examples 19-27, Comparative Examples 7-8> (Manufacturing of RuO₄ gas generation inhibitor) 30 mL of RuO₄ gas generation inhibitor with the composition described in Tables 4-7 was obtained by mixing a 0.095 mol / L tetramethylammonium hypochlorite aqueous solution, tetramethylammonium bromate powder, tetrapropylammonium chloride (Tokyo Chemicals), hexyltrimethylammonium chloride (Tokyo Chemicals), n-octyltrimethylammonium chloride (Tokyo Chemicals), hexamethyl quaternary ammonium chloride dihydrate (Tokyo Chemicals), ultrapure water, 15 wt% HCl, and 1 mol / L NaOH in a 100 mL fluoropolymer container. However, in Example 25, the flask was heated and chlorine gas was supplied at a liquid temperature of 45°C to generate bromite ions. The concentrations of hypobromite ions and hypochlorite ions, the concentration of anions, and the pH of the obtained RuO₄ gas generation inhibitor were measured using the above method.

[0196] (A solution for manufacturing ruthenium treatment) Sodium hypochlorite (NaClO; manufactured by Wako Pure Chemicals) and ultrapure water were added to a 100 mL fluoropolymer container, and the pH was adjusted to the values ​​recorded in Tables 4-7 using a 15% by mass HCl aqueous solution or a 1.0 mol / L NaOH aqueous solution, thus obtaining 30 mL of solution for ruthenium treatment.

[0197] (Quantitative Analysis of RuO4 Gas) First, 60 mL of a mixture was obtained by mixing a RuO₄ gas generation inhibitor prepared according to the above-described operational sequence with a solution for treating ruthenium. Next, 10 mL of the mixture, consisting of the compositions described in Examples 19-27 and Comparative Examples 7-8, was placed in a sealed glass container with a volume of 85 mL. A silicon wafer (5 × 5 mm, Ru film thickness 20 nm; Ru content 5.4 × 10⁻⁸ mol) with a sputtered ruthenium film was then immersed at 25°C for 15 minutes. The Ru film thickness was measured using XRF to confirm that all the Ru on the wafer had dissolved. Subsequently, nitrogen gas was circulated through a sealed container at a rate of 300 ml / min for 15 minutes. According to the schematic diagram in Figure 1, the RuO₄ gas generated during the impregnation of the ruthenium-coated silicon wafer was sequentially absorbed by gas trap liquids 4 and 5. Gas trap liquids 4 and 5 were prepared using a 1 mol / L aqueous solution of tetramethylammonium hydroxide (TMAH). Next, 10 ml of each of gas trap liquids 4 and 5 was separately aliquoted, and 20 ml of hydrochloric acid and ultrapure water were added to make a total volume of 100 ml. The solutions were then allowed to stand for 24 hours to obtain the measurement solution. The Ru in the measurement solution was quantified using ICP-MS (Agilent Technologies ICP-MS 7900, Ru detection m / z = 101). Since no Ru was detected in gas trap liquid 5, the amount of Ru absorbed by gas trap liquid 4 was used as the quantitative value of RuO₄ gas. Furthermore, the Ru amounts in Tables 5 and 7 are obtained by dividing the weight of Ru contained in the RuO4 gas absorbent by the area of ​​the Ru-attached wafer.

[0198]

[0199]

[0200]

[0201]

[0202] The results in Tables 4-7 show that adding the RuO₄ gas generation inhibitor of the present invention to the solution used for ruthenium treatment will suppress the generation of RuO₄ gas. This demonstrates that the RuO₄ gas generation inhibitor of the present invention is suitable for use in the treatment of ruthenium.

[0203] The quantification of the metal content in the manufactured halogen oxyacids was carried out as follows. The metal content in the halogen oxyacids manufactured in Examples 1, 14, 17, 18, and Reference Examples 1 and 2 below was measured using the above-described (Method for quantification of metals in halogen oxyacids). The quantification results of the metal content in the manufactured halogen oxyacids are shown in Table 8.

[0204] (Manufacturing of halogen oxyacids using ion exchange) <Pretreatment of ion exchange resins; Preparation of hydrogen-form ion exchange resins> 200 mL of sodium-form strong acid ion exchange resin (Organo, Amberlite IR-120BNa) was added to a glass column (AsOne Biocolumn CF-50TK) with an inner diameter of approximately 45 mm. Subsequently, 1 L of 1 equivalent hydrochloric acid (Wako Pure Chemical Industries, Ltd., for volumetric analysis) was passed through the ion exchange resin column to facilitate the exchange to the hydrogen form, and 1 L of ultrapure water was passed through the column to wash the ion exchange resin. <(a) Steps> Furthermore, 209 mL of the ion exchange resin, which had already been converted to the hydrogen form, was passed through 1 L of 10% tetramethylammonium hydroxide solution to convert the hydrogen form to the tetramethylammonium form. After the ion exchange, 1 L of ultrapure water was passed through the resin to wash it. <(b1) Steps> 125g of a 9% sodium hypobromite aqueous solution (Kanto Chemical, Grade 1, Shika) was placed in a 2L fluoropolymer container, and 875g of ultrapure water was added to prepare a 1.1% (w / w) sodium hypobromite aqueous solution. The prepared sodium hypobromite aqueous solution was passed through an ion exchange resin that had been converted to tetramethylammonium type in step (a) to obtain a tetramethylammonium hypobromite aqueous solution. Ultrapure water and tetramethylammonium hydroxide solution were added to the obtained halogen oxyacid to prepare a treatment solution containing 0.1 mmol / L tetramethylammonium hypobromite (pH 12.0). <(b2) Steps> 15.6 g of sodium hypochlorite pentahydrate (manufactured by Wako Pure Chemical Industries, Ltd., reagent grade) was placed in a 2 L fluoropolymer container, and 984 g of ultrapure water was added to prepare a 7.1% (w / w) sodium hypochlorite aqueous solution. The prepared sodium hypochlorite aqueous solution was passed through an ion exchange resin that had been converted to tetramethylammonium type in step (a) to obtain a tetramethylammonium hypochlorite aqueous solution. Ultrapure water and tetramethylammonium hydroxide solution were added to the obtained halogen oxyacid to prepare a treatment solution containing 0.1 mmol / L tetramethylammonium hypochlorite (pH 12.0).

[0205] <Reference Example 1> The treatment solution containing 0.1 mmol / L tetramethylammonium hypobromide (pH 12.0), prepared by step (b1) above (manufacturing of halogen oxyacids by ion exchange), and the aqueous solution of tetramethylammonium hydroxide (pH 12.0) were mixed to obtain the halogen oxyacid containing hypobromide as shown in Table 8.

[0206] <Reference Example 2> The treatment solution containing 0.1 mmol / L tetramethylammonium hypobromide (pH 12.0) produced by step (b1) above (the production of halogen oxyacids by ion exchange), the treatment solution containing 0.1 mmol / L tetramethylammonium hypobromide (pH 12.0) produced by step (b2), and the aqueous solution of tetramethylammonium hydroxide (pH 12.0) are mixed to obtain the halogen oxyacid containing hypobromide and hypochlorous acid listed in Table 8.

[0207]

[0208] The etching rates of Ru in the treatment solutions containing hypohalous acid obtained in Examples 1, 14, 17, 18, and 26 and 27 were almost identical. On the other hand, the metals (Na, K, Al) contained in the treatment solution were all less than 1 ppb in Examples 1, 14, 17, and 18, which were much larger than the values ​​in Reference Examples 1 and 2.

[0209] The above results demonstrate that the halogen oxyacid produced by the method of producing the halogen oxyacid of the third embodiment of the present invention can etch ruthenium at a sufficient rate and is a halogen oxyacid with extremely low metal content.

[0210] 1: Silicon wafers with Ru 2: Treatment liquid 3: N2 gas inlet 4: Gas trap liquid 1 5: Gas trap liquid 2 6: Exhaust pipe

Claims

1. A semiconductor processing solution containing hypobromite ions, wherein the concentration of the hypobromite ions is 0.1 μmol / L or more but less than 0.001 mol / L.

2. The semiconductor processing liquid as claimed in claim 1, wherein the semiconductor comprises a transition metal.

3. The semiconductor processing solution of claim 1 or 2 further includes at least one anion selected from the group consisting of chlorate ion, chlorite ion, chloride ion, bromate ion, bromate ion and bromide ion.

4. The semiconductor processing solution as claimed in claim 1 or 2, wherein the semiconductor processing solution further comprises an oxidant whose redox potential exceeds the redox potential of the hypobromite / bromide ion system.

5. The semiconductor processing solution of claim 4, wherein the aforementioned oxidant is at least one oxidant selected from the group consisting of hypochlorite ions, ozone, periodate ions, and metaperiodate ions.

6. The semiconductor processing solution as claimed in claim 1 or 2, further comprising tetraalkylammonium ions.

7. The semiconductor processing solution as claimed in claim 1 or 2, wherein the pH of the aforementioned processing solution is above 8 and below 14.

8. A method for manufacturing a semiconductor processing liquid, wherein the method comprises reacting a bromide salt, an organic base, and a halogen to obtain hypobromide ions, and the concentration of the hypobromide ions is 0.1 μmol / L or more but less than 0.001 mol / L.

9. The method for manufacturing a semiconductor processing liquid as described in claim 8, wherein the organic base is ium hydroxide.

10. A method for manufacturing a semiconductor processing liquid as described in claim 8 or 9, wherein the halogen is chlorine.

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